1 \input texinfo @c -*-texinfo-*-
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6 @c GNAT DOCUMENTATION o
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17 Copyright @copyright{} 1995-2009 Free Software Foundation,
20 Permission is granted to copy, distribute and/or modify this document
21 under the terms of the GNU Free Documentation License, Version 1.3 or
22 any later version published by the Free Software Foundation; with no
23 Invariant Sections, with no Front-Cover Texts and with no Back-Cover
24 Texts. A copy of the license is included in the section entitled
25 ``GNU Free Documentation License''.
28 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
30 @c GNAT_UGN Style Guide
32 @c 1. Always put a @noindent on the line before the first paragraph
33 @c after any of these commands:
45 @c 2. DO NOT use @example. Use @smallexample instead.
46 @c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample
47 @c context. These can interfere with the readability of the texi
48 @c source file. Instead, use one of the following annotated
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50 @c ada2texi tool (which generates appropriate highlighting):
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52 @c @smallexample @c adanocomment
53 @c @smallexample @c projectfile
54 @c b) The "@c ada" markup will result in boldface for reserved words
55 @c and italics for comments
56 @c c) The "@c adanocomment" markup will result only in boldface for
57 @c reserved words (comments are left alone)
58 @c d) The "@c projectfile" markup is like "@c ada" except that the set
59 @c of reserved words include the new reserved words for project files
61 @c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
62 @c command must be preceded by two empty lines
64 @c 4. The @item command should be on a line of its own if it is in an
65 @c @itemize or @enumerate command.
67 @c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
70 @c 6. DO NOT put trailing spaces at the end of a line. Such spaces will
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73 @c 7. DO NOT use @cartouche for examples that are longer than around 10 lines.
74 @c This command inhibits page breaks, so long examples in a @cartouche can
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77 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
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85 @c text was entered into the document but which may change over time.
86 @c Update the setting for the flag, and (if necessary) the text surrounding,
87 @c the references to the flag, on future doc revisions:
88 @c search for @value{NOW}.
92 @set DEFAULTLANGUAGEVERSION Ada 2005
93 @set NONDEFAULTLANGUAGEVERSION Ada 95
100 @set PLATFORM OpenVMS
105 @c The ARG is an optional argument. To be used for macro arguments in
106 @c their documentation (@defmac).
108 @r{[}@var{\varname\}@r{]}@c
110 @c Status as of November 2009:
111 @c Unfortunately texi2pdf and texi2html treat the trailing "@c"
112 @c differently, and faulty output is produced by one or the other
113 @c depending on whether the "@c" is present or absent.
114 @c As a result, the @ovar macro is not used, and all invocations
115 @c of the @ovar macro have been expanded inline.
118 @settitle @value{EDITION} User's Guide @value{PLATFORM}
119 @dircategory GNU Ada tools
121 * @value{EDITION} User's Guide: (gnat_ugn). @value{PLATFORM}
124 @include gcc-common.texi
126 @setchapternewpage odd
131 @title @value{EDITION} User's Guide
135 @titlefont{@i{@value{PLATFORM}}}
141 @subtitle GNAT, The GNU Ada Compiler
146 @vskip 0pt plus 1filll
153 @node Top, About This Guide, (dir), (dir)
154 @top @value{EDITION} User's Guide
157 @value{EDITION} User's Guide @value{PLATFORM}
160 GNAT, The GNU Ada Compiler@*
161 GCC version @value{version-GCC}@*
168 * Getting Started with GNAT::
169 * The GNAT Compilation Model::
170 * Compiling Using gcc::
171 * Binding Using gnatbind::
172 * Linking Using gnatlink::
173 * The GNAT Make Program gnatmake::
174 * Improving Performance::
175 * Renaming Files Using gnatchop::
176 * Configuration Pragmas::
177 * Handling Arbitrary File Naming Conventions Using gnatname::
178 * GNAT Project Manager::
179 * Tools Supporting Project Files::
180 * The Cross-Referencing Tools gnatxref and gnatfind::
181 * The GNAT Pretty-Printer gnatpp::
182 * The GNAT Metric Tool gnatmetric::
183 * File Name Krunching Using gnatkr::
184 * Preprocessing Using gnatprep::
185 * The GNAT Library Browser gnatls::
186 * Cleaning Up Using gnatclean::
188 * GNAT and Libraries::
189 * Using the GNU make Utility::
191 * Memory Management Issues::
192 * Stack Related Facilities::
193 * Verifying Properties Using gnatcheck::
194 * Creating Sample Bodies Using gnatstub::
195 * Generating Ada Bindings for C and C++ headers::
196 * Other Utility Programs::
197 * Running and Debugging Ada Programs::
199 * Code Coverage and Profiling::
202 * Compatibility with HP Ada::
204 * Platform-Specific Information for the Run-Time Libraries::
205 * Example of Binder Output File::
206 * Elaboration Order Handling in GNAT::
207 * Conditional Compilation::
209 * Compatibility and Porting Guide::
211 * Microsoft Windows Topics::
213 * GNU Free Documentation License::
216 --- The Detailed Node Listing ---
220 * What This Guide Contains::
221 * What You Should Know before Reading This Guide::
222 * Related Information::
225 Getting Started with GNAT
228 * Running a Simple Ada Program::
229 * Running a Program with Multiple Units::
230 * Using the gnatmake Utility::
232 * Editing with Emacs::
235 * Introduction to GPS::
238 The GNAT Compilation Model
240 * Source Representation::
241 * Foreign Language Representation::
242 * File Naming Rules::
243 * Using Other File Names::
244 * Alternative File Naming Schemes::
245 * Generating Object Files::
246 * Source Dependencies::
247 * The Ada Library Information Files::
248 * Binding an Ada Program::
249 * Mixed Language Programming::
251 * Building Mixed Ada & C++ Programs::
252 * Comparison between GNAT and C/C++ Compilation Models::
254 * Comparison between GNAT and Conventional Ada Library Models::
256 * Placement of temporary files::
259 Foreign Language Representation
262 * Other 8-Bit Codes::
263 * Wide Character Encodings::
265 Compiling Ada Programs With gcc
267 * Compiling Programs::
269 * Search Paths and the Run-Time Library (RTL)::
270 * Order of Compilation Issues::
275 * Output and Error Message Control::
276 * Warning Message Control::
277 * Debugging and Assertion Control::
278 * Validity Checking::
281 * Using gcc for Syntax Checking::
282 * Using gcc for Semantic Checking::
283 * Compiling Different Versions of Ada::
284 * Character Set Control::
285 * File Naming Control::
286 * Subprogram Inlining Control::
287 * Auxiliary Output Control::
288 * Debugging Control::
289 * Exception Handling Control::
290 * Units to Sources Mapping Files::
291 * Integrated Preprocessing::
296 Binding Ada Programs With gnatbind
299 * Switches for gnatbind::
300 * Command-Line Access::
301 * Search Paths for gnatbind::
302 * Examples of gnatbind Usage::
304 Switches for gnatbind
306 * Consistency-Checking Modes::
307 * Binder Error Message Control::
308 * Elaboration Control::
310 * Binding with Non-Ada Main Programs::
311 * Binding Programs with No Main Subprogram::
313 Linking Using gnatlink
316 * Switches for gnatlink::
318 The GNAT Make Program gnatmake
321 * Switches for gnatmake::
322 * Mode Switches for gnatmake::
323 * Notes on the Command Line::
324 * How gnatmake Works::
325 * Examples of gnatmake Usage::
327 Improving Performance
328 * Performance Considerations::
329 * Text_IO Suggestions::
330 * Reducing Size of Ada Executables with gnatelim::
331 * Reducing Size of Executables with unused subprogram/data elimination::
333 Performance Considerations
334 * Controlling Run-Time Checks::
335 * Use of Restrictions::
336 * Optimization Levels::
337 * Debugging Optimized Code::
338 * Inlining of Subprograms::
339 * Other Optimization Switches::
340 * Optimization and Strict Aliasing::
342 * Coverage Analysis::
345 Reducing Size of Ada Executables with gnatelim
348 * Processing Precompiled Libraries::
349 * Correcting the List of Eliminate Pragmas::
350 * Making Your Executables Smaller::
351 * Summary of the gnatelim Usage Cycle::
353 Reducing Size of Executables with unused subprogram/data elimination
354 * About unused subprogram/data elimination::
355 * Compilation options::
357 Renaming Files Using gnatchop
359 * Handling Files with Multiple Units::
360 * Operating gnatchop in Compilation Mode::
361 * Command Line for gnatchop::
362 * Switches for gnatchop::
363 * Examples of gnatchop Usage::
365 Configuration Pragmas
367 * Handling of Configuration Pragmas::
368 * The Configuration Pragmas Files::
370 Handling Arbitrary File Naming Conventions Using gnatname
372 * Arbitrary File Naming Conventions::
374 * Switches for gnatname::
375 * Examples of gnatname Usage::
377 The Cross-Referencing Tools gnatxref and gnatfind
379 * Switches for gnatxref::
380 * Switches for gnatfind::
381 * Project Files for gnatxref and gnatfind::
382 * Regular Expressions in gnatfind and gnatxref::
383 * Examples of gnatxref Usage::
384 * Examples of gnatfind Usage::
386 The GNAT Pretty-Printer gnatpp
388 * Switches for gnatpp::
391 The GNAT Metrics Tool gnatmetric
393 * Switches for gnatmetric::
395 File Name Krunching Using gnatkr
400 * Examples of gnatkr Usage::
402 Preprocessing Using gnatprep
403 * Preprocessing Symbols::
405 * Switches for gnatprep::
406 * Form of Definitions File::
407 * Form of Input Text for gnatprep::
409 The GNAT Library Browser gnatls
412 * Switches for gnatls::
413 * Examples of gnatls Usage::
415 Cleaning Up Using gnatclean
417 * Running gnatclean::
418 * Switches for gnatclean::
419 @c * Examples of gnatclean Usage::
425 * Introduction to Libraries in GNAT::
426 * General Ada Libraries::
427 * Stand-alone Ada Libraries::
428 * Rebuilding the GNAT Run-Time Library::
430 Using the GNU make Utility
432 * Using gnatmake in a Makefile::
433 * Automatically Creating a List of Directories::
434 * Generating the Command Line Switches::
435 * Overcoming Command Line Length Limits::
438 Memory Management Issues
440 * Some Useful Memory Pools::
441 * The GNAT Debug Pool Facility::
446 Stack Related Facilities
448 * Stack Overflow Checking::
449 * Static Stack Usage Analysis::
450 * Dynamic Stack Usage Analysis::
452 Some Useful Memory Pools
454 The GNAT Debug Pool Facility
460 * Switches for gnatmem::
461 * Example of gnatmem Usage::
464 Verifying Properties Using gnatcheck
466 Sample Bodies Using gnatstub
469 * Switches for gnatstub::
471 Other Utility Programs
473 * Using Other Utility Programs with GNAT::
474 * The External Symbol Naming Scheme of GNAT::
475 * Converting Ada Files to html with gnathtml::
478 Code Coverage and Profiling
480 * Code Coverage of Ada Programs using gcov::
481 * Profiling an Ada Program using gprof::
484 Running and Debugging Ada Programs
486 * The GNAT Debugger GDB::
488 * Introduction to GDB Commands::
489 * Using Ada Expressions::
490 * Calling User-Defined Subprograms::
491 * Using the Next Command in a Function::
494 * Debugging Generic Units::
495 * Remote Debugging using gdbserver::
496 * GNAT Abnormal Termination or Failure to Terminate::
497 * Naming Conventions for GNAT Source Files::
498 * Getting Internal Debugging Information::
506 Compatibility with HP Ada
508 * Ada Language Compatibility::
509 * Differences in the Definition of Package System::
510 * Language-Related Features::
511 * The Package STANDARD::
512 * The Package SYSTEM::
513 * Tasking and Task-Related Features::
514 * Pragmas and Pragma-Related Features::
515 * Library of Predefined Units::
517 * Main Program Definition::
518 * Implementation-Defined Attributes::
519 * Compiler and Run-Time Interfacing::
520 * Program Compilation and Library Management::
522 * Implementation Limits::
523 * Tools and Utilities::
525 Language-Related Features
527 * Integer Types and Representations::
528 * Floating-Point Types and Representations::
529 * Pragmas Float_Representation and Long_Float::
530 * Fixed-Point Types and Representations::
531 * Record and Array Component Alignment::
533 * Other Representation Clauses::
535 Tasking and Task-Related Features
537 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
538 * Assigning Task IDs::
539 * Task IDs and Delays::
540 * Task-Related Pragmas::
541 * Scheduling and Task Priority::
543 * External Interrupts::
545 Pragmas and Pragma-Related Features
547 * Restrictions on the Pragma INLINE::
548 * Restrictions on the Pragma INTERFACE::
549 * Restrictions on the Pragma SYSTEM_NAME::
551 Library of Predefined Units
553 * Changes to DECLIB::
557 * Shared Libraries and Options Files::
561 Platform-Specific Information for the Run-Time Libraries
563 * Summary of Run-Time Configurations::
564 * Specifying a Run-Time Library::
565 * Choosing the Scheduling Policy::
566 * Solaris-Specific Considerations::
567 * Linux-Specific Considerations::
568 * AIX-Specific Considerations::
569 * Irix-Specific Considerations::
570 * RTX-Specific Considerations::
571 * HP-UX-Specific Considerations::
573 Example of Binder Output File
575 Elaboration Order Handling in GNAT
578 * Checking the Elaboration Order::
579 * Controlling the Elaboration Order::
580 * Controlling Elaboration in GNAT - Internal Calls::
581 * Controlling Elaboration in GNAT - External Calls::
582 * Default Behavior in GNAT - Ensuring Safety::
583 * Treatment of Pragma Elaborate::
584 * Elaboration Issues for Library Tasks::
585 * Mixing Elaboration Models::
586 * What to Do If the Default Elaboration Behavior Fails::
587 * Elaboration for Access-to-Subprogram Values::
588 * Summary of Procedures for Elaboration Control::
589 * Other Elaboration Order Considerations::
591 Conditional Compilation
592 * Use of Boolean Constants::
593 * Debugging - A Special Case::
594 * Conditionalizing Declarations::
595 * Use of Alternative Implementations::
600 * Basic Assembler Syntax::
601 * A Simple Example of Inline Assembler::
602 * Output Variables in Inline Assembler::
603 * Input Variables in Inline Assembler::
604 * Inlining Inline Assembler Code::
605 * Other Asm Functionality::
607 Compatibility and Porting Guide
609 * Compatibility with Ada 83::
610 * Compatibility between Ada 95 and Ada 2005::
611 * Implementation-dependent characteristics::
613 @c This brief section is only in the non-VMS version
614 @c The complete chapter on HP Ada issues is in the VMS version
615 * Compatibility with HP Ada 83::
617 * Compatibility with Other Ada Systems::
618 * Representation Clauses::
620 * Transitioning to 64-Bit GNAT for OpenVMS::
624 Microsoft Windows Topics
626 * Using GNAT on Windows::
627 * CONSOLE and WINDOWS subsystems::
629 * Mixed-Language Programming on Windows::
630 * Windows Calling Conventions::
631 * Introduction to Dynamic Link Libraries (DLLs)::
632 * Using DLLs with GNAT::
633 * Building DLLs with GNAT::
634 * GNAT and Windows Resources::
636 * Setting Stack Size from gnatlink::
637 * Setting Heap Size from gnatlink::
644 @node About This Guide
645 @unnumbered About This Guide
649 This guide describes the use of @value{EDITION},
650 a compiler and software development toolset for the full Ada
651 programming language, implemented on OpenVMS for HP's Alpha and
652 Integrity server (I64) platforms.
655 This guide describes the use of @value{EDITION},
656 a compiler and software development
657 toolset for the full Ada programming language.
659 It documents the features of the compiler and tools, and explains
660 how to use them to build Ada applications.
662 @value{EDITION} implements Ada 95 and Ada 2005, and it may also be invoked in
663 Ada 83 compatibility mode.
664 By default, @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
665 but you can override with a compiler switch
666 (@pxref{Compiling Different Versions of Ada})
667 to explicitly specify the language version.
668 Throughout this manual, references to ``Ada'' without a year suffix
669 apply to both the Ada 95 and Ada 2005 versions of the language.
673 For ease of exposition, ``@value{EDITION}'' will be referred to simply as
674 ``GNAT'' in the remainder of this document.
681 * What This Guide Contains::
682 * What You Should Know before Reading This Guide::
683 * Related Information::
687 @node What This Guide Contains
688 @unnumberedsec What This Guide Contains
691 This guide contains the following chapters:
695 @ref{Getting Started with GNAT}, describes how to get started compiling
696 and running Ada programs with the GNAT Ada programming environment.
698 @ref{The GNAT Compilation Model}, describes the compilation model used
702 @ref{Compiling Using gcc}, describes how to compile
703 Ada programs with @command{gcc}, the Ada compiler.
706 @ref{Binding Using gnatbind}, describes how to
707 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
711 @ref{Linking Using gnatlink},
712 describes @command{gnatlink}, a
713 program that provides for linking using the GNAT run-time library to
714 construct a program. @command{gnatlink} can also incorporate foreign language
715 object units into the executable.
718 @ref{The GNAT Make Program gnatmake}, describes @command{gnatmake}, a
719 utility that automatically determines the set of sources
720 needed by an Ada compilation unit, and executes the necessary compilations
724 @ref{Improving Performance}, shows various techniques for making your
725 Ada program run faster or take less space.
726 It discusses the effect of the compiler's optimization switch and
727 also describes the @command{gnatelim} tool and unused subprogram/data
731 @ref{Renaming Files Using gnatchop}, describes
732 @code{gnatchop}, a utility that allows you to preprocess a file that
733 contains Ada source code, and split it into one or more new files, one
734 for each compilation unit.
737 @ref{Configuration Pragmas}, describes the configuration pragmas
741 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
742 shows how to override the default GNAT file naming conventions,
743 either for an individual unit or globally.
746 @ref{GNAT Project Manager}, describes how to use project files
747 to organize large projects.
750 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
751 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
752 way to navigate through sources.
755 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
756 version of an Ada source file with control over casing, indentation,
757 comment placement, and other elements of program presentation style.
760 @ref{The GNAT Metric Tool gnatmetric}, shows how to compute various
761 metrics for an Ada source file, such as the number of types and subprograms,
762 and assorted complexity measures.
765 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
766 file name krunching utility, used to handle shortened
767 file names on operating systems with a limit on the length of names.
770 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
771 preprocessor utility that allows a single source file to be used to
772 generate multiple or parameterized source files by means of macro
776 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
777 utility that displays information about compiled units, including dependences
778 on the corresponding sources files, and consistency of compilations.
781 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
782 to delete files that are produced by the compiler, binder and linker.
786 @ref{GNAT and Libraries}, describes the process of creating and using
787 Libraries with GNAT. It also describes how to recompile the GNAT run-time
791 @ref{Using the GNU make Utility}, describes some techniques for using
792 the GNAT toolset in Makefiles.
796 @ref{Memory Management Issues}, describes some useful predefined storage pools
797 and in particular the GNAT Debug Pool facility, which helps detect incorrect
800 It also describes @command{gnatmem}, a utility that monitors dynamic
801 allocation and deallocation and helps detect ``memory leaks''.
805 @ref{Stack Related Facilities}, describes some useful tools associated with
806 stack checking and analysis.
809 @ref{Verifying Properties Using gnatcheck}, discusses @code{gnatcheck},
810 a utility that checks Ada code against a set of rules.
813 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
814 a utility that generates empty but compilable bodies for library units.
817 @ref{Generating Ada Bindings for C and C++ headers}, describes how to
818 generate automatically Ada bindings from C and C++ headers.
821 @ref{Other Utility Programs}, discusses several other GNAT utilities,
822 including @code{gnathtml}.
826 @ref{Code Coverage and Profiling}, describes how to perform a structural
827 coverage and profile the execution of Ada programs.
831 @ref{Running and Debugging Ada Programs}, describes how to run and debug
836 @ref{Compatibility with HP Ada}, details the compatibility of GNAT with
837 HP Ada 83 @footnote{``HP Ada'' refers to the legacy product originally
838 developed by Digital Equipment Corporation and currently supported by HP.}
839 for OpenVMS Alpha. This product was formerly known as DEC Ada,
842 historical compatibility reasons, the relevant libraries still use the
847 @ref{Platform-Specific Information for the Run-Time Libraries},
848 describes the various run-time
849 libraries supported by GNAT on various platforms and explains how to
850 choose a particular library.
853 @ref{Example of Binder Output File}, shows the source code for the binder
854 output file for a sample program.
857 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
858 you deal with elaboration order issues.
861 @ref{Conditional Compilation}, describes how to model conditional compilation,
862 both with Ada in general and with GNAT facilities in particular.
865 @ref{Inline Assembler}, shows how to use the inline assembly facility
869 @ref{Compatibility and Porting Guide}, contains sections on compatibility
870 of GNAT with other Ada development environments (including Ada 83 systems),
871 to assist in porting code from those environments.
875 @ref{Microsoft Windows Topics}, presents information relevant to the
876 Microsoft Windows platform.
880 @c *************************************************
881 @node What You Should Know before Reading This Guide
882 @c *************************************************
883 @unnumberedsec What You Should Know before Reading This Guide
885 @cindex Ada 95 Language Reference Manual
886 @cindex Ada 2005 Language Reference Manual
888 This guide assumes a basic familiarity with the Ada 95 language, as
889 described in the International Standard ANSI/ISO/IEC-8652:1995, January
891 It does not require knowledge of the new features introduced by Ada 2005,
892 (officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1
894 Both reference manuals are included in the GNAT documentation
897 @node Related Information
898 @unnumberedsec Related Information
901 For further information about related tools, refer to the following
906 @xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, GNAT
907 Reference Manual}, which contains all reference material for the GNAT
908 implementation of Ada.
912 @cite{Using the GNAT Programming Studio}, which describes the GPS
913 Integrated Development Environment.
916 @cite{GNAT Programming Studio Tutorial}, which introduces the
917 main GPS features through examples.
921 @cite{Ada 95 Reference Manual}, which contains reference
922 material for the Ada 95 programming language.
925 @cite{Ada 2005 Reference Manual}, which contains reference
926 material for the Ada 2005 programming language.
929 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
931 in the GNU:[DOCS] directory,
933 for all details on the use of the GNU source-level debugger.
936 @xref{Top,, The extensible self-documenting text editor, emacs,
939 located in the GNU:[DOCS] directory if the EMACS kit is installed,
941 for full information on the extensible editor and programming
948 @unnumberedsec Conventions
950 @cindex Typographical conventions
953 Following are examples of the typographical and graphic conventions used
958 @code{Functions}, @command{utility program names}, @code{standard names},
962 @option{Option flags}
965 @file{File names}, @samp{button names}, and @samp{field names}.
968 @code{Variables}, @env{environment variables}, and @var{metasyntactic
975 @r{[}optional information or parameters@r{]}
978 Examples are described by text
980 and then shown this way.
985 Commands that are entered by the user are preceded in this manual by the
986 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
987 uses this sequence as a prompt, then the commands will appear exactly as
988 you see them in the manual. If your system uses some other prompt, then
989 the command will appear with the @code{$} replaced by whatever prompt
990 character you are using.
993 Full file names are shown with the ``@code{/}'' character
994 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
995 If you are using GNAT on a Windows platform, please note that
996 the ``@code{\}'' character should be used instead.
999 @c ****************************
1000 @node Getting Started with GNAT
1001 @chapter Getting Started with GNAT
1004 This chapter describes some simple ways of using GNAT to build
1005 executable Ada programs.
1007 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
1008 show how to use the command line environment.
1009 @ref{Introduction to GPS}, provides a brief
1010 introduction to the GNAT Programming Studio, a visually-oriented
1011 Integrated Development Environment for GNAT.
1012 GPS offers a graphical ``look and feel'', support for development in
1013 other programming languages, comprehensive browsing features, and
1014 many other capabilities.
1015 For information on GPS please refer to
1016 @cite{Using the GNAT Programming Studio}.
1021 * Running a Simple Ada Program::
1022 * Running a Program with Multiple Units::
1023 * Using the gnatmake Utility::
1025 * Editing with Emacs::
1028 * Introduction to GPS::
1033 @section Running GNAT
1036 Three steps are needed to create an executable file from an Ada source
1041 The source file(s) must be compiled.
1043 The file(s) must be bound using the GNAT binder.
1045 All appropriate object files must be linked to produce an executable.
1049 All three steps are most commonly handled by using the @command{gnatmake}
1050 utility program that, given the name of the main program, automatically
1051 performs the necessary compilation, binding and linking steps.
1053 @node Running a Simple Ada Program
1054 @section Running a Simple Ada Program
1057 Any text editor may be used to prepare an Ada program.
1059 used, the optional Ada mode may be helpful in laying out the program.)
1061 program text is a normal text file. We will assume in our initial
1062 example that you have used your editor to prepare the following
1063 standard format text file:
1065 @smallexample @c ada
1067 with Ada.Text_IO; use Ada.Text_IO;
1070 Put_Line ("Hello WORLD!");
1076 This file should be named @file{hello.adb}.
1077 With the normal default file naming conventions, GNAT requires
1079 contain a single compilation unit whose file name is the
1081 with periods replaced by hyphens; the
1082 extension is @file{ads} for a
1083 spec and @file{adb} for a body.
1084 You can override this default file naming convention by use of the
1085 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1086 Alternatively, if you want to rename your files according to this default
1087 convention, which is probably more convenient if you will be using GNAT
1088 for all your compilations, then the @code{gnatchop} utility
1089 can be used to generate correctly-named source files
1090 (@pxref{Renaming Files Using gnatchop}).
1092 You can compile the program using the following command (@code{$} is used
1093 as the command prompt in the examples in this document):
1100 @command{gcc} is the command used to run the compiler. This compiler is
1101 capable of compiling programs in several languages, including Ada and
1102 C. It assumes that you have given it an Ada program if the file extension is
1103 either @file{.ads} or @file{.adb}, and it will then call
1104 the GNAT compiler to compile the specified file.
1107 The @option{-c} switch is required. It tells @command{gcc} to only do a
1108 compilation. (For C programs, @command{gcc} can also do linking, but this
1109 capability is not used directly for Ada programs, so the @option{-c}
1110 switch must always be present.)
1113 This compile command generates a file
1114 @file{hello.o}, which is the object
1115 file corresponding to your Ada program. It also generates
1116 an ``Ada Library Information'' file @file{hello.ali},
1117 which contains additional information used to check
1118 that an Ada program is consistent.
1119 To build an executable file,
1120 use @code{gnatbind} to bind the program
1121 and @command{gnatlink} to link it. The
1122 argument to both @code{gnatbind} and @command{gnatlink} is the name of the
1123 @file{ALI} file, but the default extension of @file{.ali} can
1124 be omitted. This means that in the most common case, the argument
1125 is simply the name of the main program:
1133 A simpler method of carrying out these steps is to use
1135 a master program that invokes all the required
1136 compilation, binding and linking tools in the correct order. In particular,
1137 @command{gnatmake} automatically recompiles any sources that have been
1138 modified since they were last compiled, or sources that depend
1139 on such modified sources, so that ``version skew'' is avoided.
1140 @cindex Version skew (avoided by @command{gnatmake})
1143 $ gnatmake hello.adb
1147 The result is an executable program called @file{hello}, which can be
1155 assuming that the current directory is on the search path
1156 for executable programs.
1159 and, if all has gone well, you will see
1166 appear in response to this command.
1168 @c ****************************************
1169 @node Running a Program with Multiple Units
1170 @section Running a Program with Multiple Units
1173 Consider a slightly more complicated example that has three files: a
1174 main program, and the spec and body of a package:
1176 @smallexample @c ada
1179 package Greetings is
1184 with Ada.Text_IO; use Ada.Text_IO;
1185 package body Greetings is
1188 Put_Line ("Hello WORLD!");
1191 procedure Goodbye is
1193 Put_Line ("Goodbye WORLD!");
1210 Following the one-unit-per-file rule, place this program in the
1211 following three separate files:
1215 spec of package @code{Greetings}
1218 body of package @code{Greetings}
1221 body of main program
1225 To build an executable version of
1226 this program, we could use four separate steps to compile, bind, and link
1227 the program, as follows:
1231 $ gcc -c greetings.adb
1237 Note that there is no required order of compilation when using GNAT.
1238 In particular it is perfectly fine to compile the main program first.
1239 Also, it is not necessary to compile package specs in the case where
1240 there is an accompanying body; you only need to compile the body. If you want
1241 to submit these files to the compiler for semantic checking and not code
1242 generation, then use the
1243 @option{-gnatc} switch:
1246 $ gcc -c greetings.ads -gnatc
1250 Although the compilation can be done in separate steps as in the
1251 above example, in practice it is almost always more convenient
1252 to use the @command{gnatmake} tool. All you need to know in this case
1253 is the name of the main program's source file. The effect of the above four
1254 commands can be achieved with a single one:
1257 $ gnatmake gmain.adb
1261 In the next section we discuss the advantages of using @command{gnatmake} in
1264 @c *****************************
1265 @node Using the gnatmake Utility
1266 @section Using the @command{gnatmake} Utility
1269 If you work on a program by compiling single components at a time using
1270 @command{gcc}, you typically keep track of the units you modify. In order to
1271 build a consistent system, you compile not only these units, but also any
1272 units that depend on the units you have modified.
1273 For example, in the preceding case,
1274 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1275 you edit @file{greetings.ads}, you must recompile both
1276 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1277 units that depend on @file{greetings.ads}.
1279 @code{gnatbind} will warn you if you forget one of these compilation
1280 steps, so that it is impossible to generate an inconsistent program as a
1281 result of forgetting to do a compilation. Nevertheless it is tedious and
1282 error-prone to keep track of dependencies among units.
1283 One approach to handle the dependency-bookkeeping is to use a
1284 makefile. However, makefiles present maintenance problems of their own:
1285 if the dependencies change as you change the program, you must make
1286 sure that the makefile is kept up-to-date manually, which is also an
1287 error-prone process.
1289 The @command{gnatmake} utility takes care of these details automatically.
1290 Invoke it using either one of the following forms:
1293 $ gnatmake gmain.adb
1294 $ gnatmake ^gmain^GMAIN^
1298 The argument is the name of the file containing the main program;
1299 you may omit the extension. @command{gnatmake}
1300 examines the environment, automatically recompiles any files that need
1301 recompiling, and binds and links the resulting set of object files,
1302 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1303 In a large program, it
1304 can be extremely helpful to use @command{gnatmake}, because working out by hand
1305 what needs to be recompiled can be difficult.
1307 Note that @command{gnatmake}
1308 takes into account all the Ada rules that
1309 establish dependencies among units. These include dependencies that result
1310 from inlining subprogram bodies, and from
1311 generic instantiation. Unlike some other
1312 Ada make tools, @command{gnatmake} does not rely on the dependencies that were
1313 found by the compiler on a previous compilation, which may possibly
1314 be wrong when sources change. @command{gnatmake} determines the exact set of
1315 dependencies from scratch each time it is run.
1318 @node Editing with Emacs
1319 @section Editing with Emacs
1323 Emacs is an extensible self-documenting text editor that is available in a
1324 separate VMSINSTAL kit.
1326 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1327 click on the Emacs Help menu and run the Emacs Tutorial.
1328 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1329 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1331 Documentation on Emacs and other tools is available in Emacs under the
1332 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1333 use the middle mouse button to select a topic (e.g.@: Emacs).
1335 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1336 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1337 get to the Emacs manual.
1338 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1341 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1342 which is sufficiently extensible to provide for a complete programming
1343 environment and shell for the sophisticated user.
1347 @node Introduction to GPS
1348 @section Introduction to GPS
1349 @cindex GPS (GNAT Programming Studio)
1350 @cindex GNAT Programming Studio (GPS)
1352 Although the command line interface (@command{gnatmake}, etc.) alone
1353 is sufficient, a graphical Interactive Development
1354 Environment can make it easier for you to compose, navigate, and debug
1355 programs. This section describes the main features of GPS
1356 (``GNAT Programming Studio''), the GNAT graphical IDE.
1357 You will see how to use GPS to build and debug an executable, and
1358 you will also learn some of the basics of the GNAT ``project'' facility.
1360 GPS enables you to do much more than is presented here;
1361 e.g., you can produce a call graph, interface to a third-party
1362 Version Control System, and inspect the generated assembly language
1364 Indeed, GPS also supports languages other than Ada.
1365 Such additional information, and an explanation of all of the GPS menu
1366 items. may be found in the on-line help, which includes
1367 a user's guide and a tutorial (these are also accessible from the GNAT
1371 * Building a New Program with GPS::
1372 * Simple Debugging with GPS::
1375 @node Building a New Program with GPS
1376 @subsection Building a New Program with GPS
1378 GPS invokes the GNAT compilation tools using information
1379 contained in a @emph{project} (also known as a @emph{project file}):
1380 a collection of properties such
1381 as source directories, identities of main subprograms, tool switches, etc.,
1382 and their associated values.
1383 See @ref{GNAT Project Manager} for details.
1384 In order to run GPS, you will need to either create a new project
1385 or else open an existing one.
1387 This section will explain how you can use GPS to create a project,
1388 to associate Ada source files with a project, and to build and run
1392 @item @emph{Creating a project}
1394 Invoke GPS, either from the command line or the platform's IDE.
1395 After it starts, GPS will display a ``Welcome'' screen with three
1400 @code{Start with default project in directory}
1403 @code{Create new project with wizard}
1406 @code{Open existing project}
1410 Select @code{Create new project with wizard} and press @code{OK}.
1411 A new window will appear. In the text box labeled with
1412 @code{Enter the name of the project to create}, type @file{sample}
1413 as the project name.
1414 In the next box, browse to choose the directory in which you
1415 would like to create the project file.
1416 After selecting an appropriate directory, press @code{Forward}.
1418 A window will appear with the title
1419 @code{Version Control System Configuration}.
1420 Simply press @code{Forward}.
1422 A window will appear with the title
1423 @code{Please select the source directories for this project}.
1424 The directory that you specified for the project file will be selected
1425 by default as the one to use for sources; simply press @code{Forward}.
1427 A window will appear with the title
1428 @code{Please select the build directory for this project}.
1429 The directory that you specified for the project file will be selected
1430 by default for object files and executables;
1431 simply press @code{Forward}.
1433 A window will appear with the title
1434 @code{Please select the main units for this project}.
1435 You will supply this information later, after creating the source file.
1436 Simply press @code{Forward} for now.
1438 A window will appear with the title
1439 @code{Please select the switches to build the project}.
1440 Press @code{Apply}. This will create a project file named
1441 @file{sample.prj} in the directory that you had specified.
1443 @item @emph{Creating and saving the source file}
1445 After you create the new project, a GPS window will appear, which is
1446 partitioned into two main sections:
1450 A @emph{Workspace area}, initially greyed out, which you will use for
1451 creating and editing source files
1454 Directly below, a @emph{Messages area}, which initially displays a
1455 ``Welcome'' message.
1456 (If the Messages area is not visible, drag its border upward to expand it.)
1460 Select @code{File} on the menu bar, and then the @code{New} command.
1461 The Workspace area will become white, and you can now
1462 enter the source program explicitly.
1463 Type the following text
1465 @smallexample @c ada
1467 with Ada.Text_IO; use Ada.Text_IO;
1470 Put_Line("Hello from GPS!");
1476 Select @code{File}, then @code{Save As}, and enter the source file name
1478 The file will be saved in the same directory you specified as the
1479 location of the default project file.
1481 @item @emph{Updating the project file}
1483 You need to add the new source file to the project.
1485 the @code{Project} menu and then @code{Edit project properties}.
1486 Click the @code{Main files} tab on the left, and then the
1488 Choose @file{hello.adb} from the list, and press @code{Open}.
1489 The project settings window will reflect this action.
1492 @item @emph{Building and running the program}
1494 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1495 and select @file{hello.adb}.
1496 The Messages window will display the resulting invocations of @command{gcc},
1497 @command{gnatbind}, and @command{gnatlink}
1498 (reflecting the default switch settings from the
1499 project file that you created) and then a ``successful compilation/build''
1502 To run the program, choose the @code{Build} menu, then @code{Run}, and
1503 select @command{hello}.
1504 An @emph{Arguments Selection} window will appear.
1505 There are no command line arguments, so just click @code{OK}.
1507 The Messages window will now display the program's output (the string
1508 @code{Hello from GPS}), and at the bottom of the GPS window a status
1509 update is displayed (@code{Run: hello}).
1510 Close the GPS window (or select @code{File}, then @code{Exit}) to
1511 terminate this GPS session.
1514 @node Simple Debugging with GPS
1515 @subsection Simple Debugging with GPS
1517 This section illustrates basic debugging techniques (setting breakpoints,
1518 examining/modifying variables, single stepping).
1521 @item @emph{Opening a project}
1523 Start GPS and select @code{Open existing project}; browse to
1524 specify the project file @file{sample.prj} that you had created in the
1527 @item @emph{Creating a source file}
1529 Select @code{File}, then @code{New}, and type in the following program:
1531 @smallexample @c ada
1533 with Ada.Text_IO; use Ada.Text_IO;
1534 procedure Example is
1535 Line : String (1..80);
1538 Put_Line("Type a line of text at each prompt; an empty line to exit");
1542 Put_Line (Line (1..N) );
1550 Select @code{File}, then @code{Save as}, and enter the file name
1553 @item @emph{Updating the project file}
1555 Add @code{Example} as a new main unit for the project:
1558 Select @code{Project}, then @code{Edit Project Properties}.
1561 Select the @code{Main files} tab, click @code{Add}, then
1562 select the file @file{example.adb} from the list, and
1564 You will see the file name appear in the list of main units
1570 @item @emph{Building/running the executable}
1572 To build the executable
1573 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1575 Run the program to see its effect (in the Messages area).
1576 Each line that you enter is displayed; an empty line will
1577 cause the loop to exit and the program to terminate.
1579 @item @emph{Debugging the program}
1581 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1582 which are required for debugging, are on by default when you create
1584 Thus unless you intentionally remove these settings, you will be able
1585 to debug any program that you develop using GPS.
1588 @item @emph{Initializing}
1590 Select @code{Debug}, then @code{Initialize}, then @file{example}
1592 @item @emph{Setting a breakpoint}
1594 After performing the initialization step, you will observe a small
1595 icon to the right of each line number.
1596 This serves as a toggle for breakpoints; clicking the icon will
1597 set a breakpoint at the corresponding line (the icon will change to
1598 a red circle with an ``x''), and clicking it again
1599 will remove the breakpoint / reset the icon.
1601 For purposes of this example, set a breakpoint at line 10 (the
1602 statement @code{Put_Line@ (Line@ (1..N));}
1604 @item @emph{Starting program execution}
1606 Select @code{Debug}, then @code{Run}. When the
1607 @code{Program Arguments} window appears, click @code{OK}.
1608 A console window will appear; enter some line of text,
1609 e.g.@: @code{abcde}, at the prompt.
1610 The program will pause execution when it gets to the
1611 breakpoint, and the corresponding line is highlighted.
1613 @item @emph{Examining a variable}
1615 Move the mouse over one of the occurrences of the variable @code{N}.
1616 You will see the value (5) displayed, in ``tool tip'' fashion.
1617 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1618 You will see information about @code{N} appear in the @code{Debugger Data}
1619 pane, showing the value as 5.
1621 @item @emph{Assigning a new value to a variable}
1623 Right click on the @code{N} in the @code{Debugger Data} pane, and
1624 select @code{Set value of N}.
1625 When the input window appears, enter the value @code{4} and click
1627 This value does not automatically appear in the @code{Debugger Data}
1628 pane; to see it, right click again on the @code{N} in the
1629 @code{Debugger Data} pane and select @code{Update value}.
1630 The new value, 4, will appear in red.
1632 @item @emph{Single stepping}
1634 Select @code{Debug}, then @code{Next}.
1635 This will cause the next statement to be executed, in this case the
1636 call of @code{Put_Line} with the string slice.
1637 Notice in the console window that the displayed string is simply
1638 @code{abcd} and not @code{abcde} which you had entered.
1639 This is because the upper bound of the slice is now 4 rather than 5.
1641 @item @emph{Removing a breakpoint}
1643 Toggle the breakpoint icon at line 10.
1645 @item @emph{Resuming execution from a breakpoint}
1647 Select @code{Debug}, then @code{Continue}.
1648 The program will reach the next iteration of the loop, and
1649 wait for input after displaying the prompt.
1650 This time, just hit the @kbd{Enter} key.
1651 The value of @code{N} will be 0, and the program will terminate.
1652 The console window will disappear.
1657 @node The GNAT Compilation Model
1658 @chapter The GNAT Compilation Model
1659 @cindex GNAT compilation model
1660 @cindex Compilation model
1663 * Source Representation::
1664 * Foreign Language Representation::
1665 * File Naming Rules::
1666 * Using Other File Names::
1667 * Alternative File Naming Schemes::
1668 * Generating Object Files::
1669 * Source Dependencies::
1670 * The Ada Library Information Files::
1671 * Binding an Ada Program::
1672 * Mixed Language Programming::
1674 * Building Mixed Ada & C++ Programs::
1675 * Comparison between GNAT and C/C++ Compilation Models::
1677 * Comparison between GNAT and Conventional Ada Library Models::
1679 * Placement of temporary files::
1684 This chapter describes the compilation model used by GNAT. Although
1685 similar to that used by other languages, such as C and C++, this model
1686 is substantially different from the traditional Ada compilation models,
1687 which are based on a library. The model is initially described without
1688 reference to the library-based model. If you have not previously used an
1689 Ada compiler, you need only read the first part of this chapter. The
1690 last section describes and discusses the differences between the GNAT
1691 model and the traditional Ada compiler models. If you have used other
1692 Ada compilers, this section will help you to understand those
1693 differences, and the advantages of the GNAT model.
1695 @node Source Representation
1696 @section Source Representation
1700 Ada source programs are represented in standard text files, using
1701 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1702 7-bit ASCII set, plus additional characters used for
1703 representing foreign languages (@pxref{Foreign Language Representation}
1704 for support of non-USA character sets). The format effector characters
1705 are represented using their standard ASCII encodings, as follows:
1710 Vertical tab, @code{16#0B#}
1714 Horizontal tab, @code{16#09#}
1718 Carriage return, @code{16#0D#}
1722 Line feed, @code{16#0A#}
1726 Form feed, @code{16#0C#}
1730 Source files are in standard text file format. In addition, GNAT will
1731 recognize a wide variety of stream formats, in which the end of
1732 physical lines is marked by any of the following sequences:
1733 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1734 in accommodating files that are imported from other operating systems.
1736 @cindex End of source file
1737 @cindex Source file, end
1739 The end of a source file is normally represented by the physical end of
1740 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1741 recognized as signalling the end of the source file. Again, this is
1742 provided for compatibility with other operating systems where this
1743 code is used to represent the end of file.
1745 Each file contains a single Ada compilation unit, including any pragmas
1746 associated with the unit. For example, this means you must place a
1747 package declaration (a package @dfn{spec}) and the corresponding body in
1748 separate files. An Ada @dfn{compilation} (which is a sequence of
1749 compilation units) is represented using a sequence of files. Similarly,
1750 you will place each subunit or child unit in a separate file.
1752 @node Foreign Language Representation
1753 @section Foreign Language Representation
1756 GNAT supports the standard character sets defined in Ada as well as
1757 several other non-standard character sets for use in localized versions
1758 of the compiler (@pxref{Character Set Control}).
1761 * Other 8-Bit Codes::
1762 * Wide Character Encodings::
1770 The basic character set is Latin-1. This character set is defined by ISO
1771 standard 8859, part 1. The lower half (character codes @code{16#00#}
1772 @dots{} @code{16#7F#)} is identical to standard ASCII coding, but the upper
1773 half is used to represent additional characters. These include extended letters
1774 used by European languages, such as French accents, the vowels with umlauts
1775 used in German, and the extra letter A-ring used in Swedish.
1777 @findex Ada.Characters.Latin_1
1778 For a complete list of Latin-1 codes and their encodings, see the source
1779 file of library unit @code{Ada.Characters.Latin_1} in file
1780 @file{a-chlat1.ads}.
1781 You may use any of these extended characters freely in character or
1782 string literals. In addition, the extended characters that represent
1783 letters can be used in identifiers.
1785 @node Other 8-Bit Codes
1786 @subsection Other 8-Bit Codes
1789 GNAT also supports several other 8-bit coding schemes:
1792 @item ISO 8859-2 (Latin-2)
1795 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1798 @item ISO 8859-3 (Latin-3)
1801 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1804 @item ISO 8859-4 (Latin-4)
1807 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1810 @item ISO 8859-5 (Cyrillic)
1813 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1814 lowercase equivalence.
1816 @item ISO 8859-15 (Latin-9)
1819 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1820 lowercase equivalence
1822 @item IBM PC (code page 437)
1823 @cindex code page 437
1824 This code page is the normal default for PCs in the U.S. It corresponds
1825 to the original IBM PC character set. This set has some, but not all, of
1826 the extended Latin-1 letters, but these letters do not have the same
1827 encoding as Latin-1. In this mode, these letters are allowed in
1828 identifiers with uppercase and lowercase equivalence.
1830 @item IBM PC (code page 850)
1831 @cindex code page 850
1832 This code page is a modification of 437 extended to include all the
1833 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1834 mode, all these letters are allowed in identifiers with uppercase and
1835 lowercase equivalence.
1837 @item Full Upper 8-bit
1838 Any character in the range 80-FF allowed in identifiers, and all are
1839 considered distinct. In other words, there are no uppercase and lowercase
1840 equivalences in this range. This is useful in conjunction with
1841 certain encoding schemes used for some foreign character sets (e.g.,
1842 the typical method of representing Chinese characters on the PC).
1845 No upper-half characters in the range 80-FF are allowed in identifiers.
1846 This gives Ada 83 compatibility for identifier names.
1850 For precise data on the encodings permitted, and the uppercase and lowercase
1851 equivalences that are recognized, see the file @file{csets.adb} in
1852 the GNAT compiler sources. You will need to obtain a full source release
1853 of GNAT to obtain this file.
1855 @node Wide Character Encodings
1856 @subsection Wide Character Encodings
1859 GNAT allows wide character codes to appear in character and string
1860 literals, and also optionally in identifiers, by means of the following
1861 possible encoding schemes:
1866 In this encoding, a wide character is represented by the following five
1874 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1875 characters (using uppercase letters) of the wide character code. For
1876 example, ESC A345 is used to represent the wide character with code
1878 This scheme is compatible with use of the full Wide_Character set.
1880 @item Upper-Half Coding
1881 @cindex Upper-Half Coding
1882 The wide character with encoding @code{16#abcd#} where the upper bit is on
1883 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
1884 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1885 character, but is not required to be in the upper half. This method can
1886 be also used for shift-JIS or EUC, where the internal coding matches the
1889 @item Shift JIS Coding
1890 @cindex Shift JIS Coding
1891 A wide character is represented by a two-character sequence,
1893 @code{16#cd#}, with the restrictions described for upper-half encoding as
1894 described above. The internal character code is the corresponding JIS
1895 character according to the standard algorithm for Shift-JIS
1896 conversion. Only characters defined in the JIS code set table can be
1897 used with this encoding method.
1901 A wide character is represented by a two-character sequence
1903 @code{16#cd#}, with both characters being in the upper half. The internal
1904 character code is the corresponding JIS character according to the EUC
1905 encoding algorithm. Only characters defined in the JIS code set table
1906 can be used with this encoding method.
1909 A wide character is represented using
1910 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1911 10646-1/Am.2. Depending on the character value, the representation
1912 is a one, two, or three byte sequence:
1917 16#0000#-16#007f#: 2#0@var{xxxxxxx}#
1918 16#0080#-16#07ff#: 2#110@var{xxxxx}# 2#10@var{xxxxxx}#
1919 16#0800#-16#ffff#: 2#1110@var{xxxx}# 2#10@var{xxxxxx}# 2#10@var{xxxxxx}#
1924 where the @var{xxx} bits correspond to the left-padded bits of the
1925 16-bit character value. Note that all lower half ASCII characters
1926 are represented as ASCII bytes and all upper half characters and
1927 other wide characters are represented as sequences of upper-half
1928 (The full UTF-8 scheme allows for encoding 31-bit characters as
1929 6-byte sequences, but in this implementation, all UTF-8 sequences
1930 of four or more bytes length will be treated as illegal).
1931 @item Brackets Coding
1932 In this encoding, a wide character is represented by the following eight
1940 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1941 characters (using uppercase letters) of the wide character code. For
1942 example, [``A345''] is used to represent the wide character with code
1943 @code{16#A345#}. It is also possible (though not required) to use the
1944 Brackets coding for upper half characters. For example, the code
1945 @code{16#A3#} can be represented as @code{[``A3'']}.
1947 This scheme is compatible with use of the full Wide_Character set,
1948 and is also the method used for wide character encoding in the standard
1949 ACVC (Ada Compiler Validation Capability) test suite distributions.
1954 Note: Some of these coding schemes do not permit the full use of the
1955 Ada character set. For example, neither Shift JIS, nor EUC allow the
1956 use of the upper half of the Latin-1 set.
1958 @node File Naming Rules
1959 @section File Naming Rules
1962 The default file name is determined by the name of the unit that the
1963 file contains. The name is formed by taking the full expanded name of
1964 the unit and replacing the separating dots with hyphens and using
1965 ^lowercase^uppercase^ for all letters.
1967 An exception arises if the file name generated by the above rules starts
1968 with one of the characters
1970 @samp{A}, @samp{G}, @samp{I}, or @samp{S},
1973 @samp{a}, @samp{g}, @samp{i}, or @samp{s},
1975 and the second character is a
1976 minus. In this case, the character ^tilde^dollar sign^ is used in place
1977 of the minus. The reason for this special rule is to avoid clashes with
1978 the standard names for child units of the packages System, Ada,
1979 Interfaces, and GNAT, which use the prefixes
1981 @samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},
1984 @samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},
1988 The file extension is @file{.ads} for a spec and
1989 @file{.adb} for a body. The following list shows some
1990 examples of these rules.
1997 @item arith_functions.ads
1998 Arith_Functions (package spec)
1999 @item arith_functions.adb
2000 Arith_Functions (package body)
2002 Func.Spec (child package spec)
2004 Func.Spec (child package body)
2006 Sub (subunit of Main)
2007 @item ^a~bad.adb^A$BAD.ADB^
2008 A.Bad (child package body)
2012 Following these rules can result in excessively long
2013 file names if corresponding
2014 unit names are long (for example, if child units or subunits are
2015 heavily nested). An option is available to shorten such long file names
2016 (called file name ``krunching''). This may be particularly useful when
2017 programs being developed with GNAT are to be used on operating systems
2018 with limited file name lengths. @xref{Using gnatkr}.
2020 Of course, no file shortening algorithm can guarantee uniqueness over
2021 all possible unit names; if file name krunching is used, it is your
2022 responsibility to ensure no name clashes occur. Alternatively you
2023 can specify the exact file names that you want used, as described
2024 in the next section. Finally, if your Ada programs are migrating from a
2025 compiler with a different naming convention, you can use the gnatchop
2026 utility to produce source files that follow the GNAT naming conventions.
2027 (For details @pxref{Renaming Files Using gnatchop}.)
2029 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2030 systems, case is not significant. So for example on @code{Windows XP}
2031 if the canonical name is @code{main-sub.adb}, you can use the file name
2032 @code{Main-Sub.adb} instead. However, case is significant for other
2033 operating systems, so for example, if you want to use other than
2034 canonically cased file names on a Unix system, you need to follow
2035 the procedures described in the next section.
2037 @node Using Other File Names
2038 @section Using Other File Names
2042 In the previous section, we have described the default rules used by
2043 GNAT to determine the file name in which a given unit resides. It is
2044 often convenient to follow these default rules, and if you follow them,
2045 the compiler knows without being explicitly told where to find all
2048 However, in some cases, particularly when a program is imported from
2049 another Ada compiler environment, it may be more convenient for the
2050 programmer to specify which file names contain which units. GNAT allows
2051 arbitrary file names to be used by means of the Source_File_Name pragma.
2052 The form of this pragma is as shown in the following examples:
2053 @cindex Source_File_Name pragma
2055 @smallexample @c ada
2057 pragma Source_File_Name (My_Utilities.Stacks,
2058 Spec_File_Name => "myutilst_a.ada");
2059 pragma Source_File_name (My_Utilities.Stacks,
2060 Body_File_Name => "myutilst.ada");
2065 As shown in this example, the first argument for the pragma is the unit
2066 name (in this example a child unit). The second argument has the form
2067 of a named association. The identifier
2068 indicates whether the file name is for a spec or a body;
2069 the file name itself is given by a string literal.
2071 The source file name pragma is a configuration pragma, which means that
2072 normally it will be placed in the @file{gnat.adc}
2073 file used to hold configuration
2074 pragmas that apply to a complete compilation environment.
2075 For more details on how the @file{gnat.adc} file is created and used
2076 see @ref{Handling of Configuration Pragmas}.
2077 @cindex @file{gnat.adc}
2080 GNAT allows completely arbitrary file names to be specified using the
2081 source file name pragma. However, if the file name specified has an
2082 extension other than @file{.ads} or @file{.adb} it is necessary to use
2083 a special syntax when compiling the file. The name in this case must be
2084 preceded by the special sequence @option{-x} followed by a space and the name
2085 of the language, here @code{ada}, as in:
2088 $ gcc -c -x ada peculiar_file_name.sim
2093 @command{gnatmake} handles non-standard file names in the usual manner (the
2094 non-standard file name for the main program is simply used as the
2095 argument to gnatmake). Note that if the extension is also non-standard,
2096 then it must be included in the @command{gnatmake} command, it may not
2099 @node Alternative File Naming Schemes
2100 @section Alternative File Naming Schemes
2101 @cindex File naming schemes, alternative
2104 In the previous section, we described the use of the @code{Source_File_Name}
2105 pragma to allow arbitrary names to be assigned to individual source files.
2106 However, this approach requires one pragma for each file, and especially in
2107 large systems can result in very long @file{gnat.adc} files, and also create
2108 a maintenance problem.
2110 GNAT also provides a facility for specifying systematic file naming schemes
2111 other than the standard default naming scheme previously described. An
2112 alternative scheme for naming is specified by the use of
2113 @code{Source_File_Name} pragmas having the following format:
2114 @cindex Source_File_Name pragma
2116 @smallexample @c ada
2117 pragma Source_File_Name (
2118 Spec_File_Name => FILE_NAME_PATTERN
2119 @r{[},Casing => CASING_SPEC@r{]}
2120 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2122 pragma Source_File_Name (
2123 Body_File_Name => FILE_NAME_PATTERN
2124 @r{[},Casing => CASING_SPEC@r{]}
2125 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2127 pragma Source_File_Name (
2128 Subunit_File_Name => FILE_NAME_PATTERN
2129 @r{[},Casing => CASING_SPEC@r{]}
2130 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2132 FILE_NAME_PATTERN ::= STRING_LITERAL
2133 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2137 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2138 It contains a single asterisk character, and the unit name is substituted
2139 systematically for this asterisk. The optional parameter
2140 @code{Casing} indicates
2141 whether the unit name is to be all upper-case letters, all lower-case letters,
2142 or mixed-case. If no
2143 @code{Casing} parameter is used, then the default is all
2144 ^lower-case^upper-case^.
2146 The optional @code{Dot_Replacement} string is used to replace any periods
2147 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2148 argument is used then separating dots appear unchanged in the resulting
2150 Although the above syntax indicates that the
2151 @code{Casing} argument must appear
2152 before the @code{Dot_Replacement} argument, but it
2153 is also permissible to write these arguments in the opposite order.
2155 As indicated, it is possible to specify different naming schemes for
2156 bodies, specs, and subunits. Quite often the rule for subunits is the
2157 same as the rule for bodies, in which case, there is no need to give
2158 a separate @code{Subunit_File_Name} rule, and in this case the
2159 @code{Body_File_name} rule is used for subunits as well.
2161 The separate rule for subunits can also be used to implement the rather
2162 unusual case of a compilation environment (e.g.@: a single directory) which
2163 contains a subunit and a child unit with the same unit name. Although
2164 both units cannot appear in the same partition, the Ada Reference Manual
2165 allows (but does not require) the possibility of the two units coexisting
2166 in the same environment.
2168 The file name translation works in the following steps:
2173 If there is a specific @code{Source_File_Name} pragma for the given unit,
2174 then this is always used, and any general pattern rules are ignored.
2177 If there is a pattern type @code{Source_File_Name} pragma that applies to
2178 the unit, then the resulting file name will be used if the file exists. If
2179 more than one pattern matches, the latest one will be tried first, and the
2180 first attempt resulting in a reference to a file that exists will be used.
2183 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2184 for which the corresponding file exists, then the standard GNAT default
2185 naming rules are used.
2190 As an example of the use of this mechanism, consider a commonly used scheme
2191 in which file names are all lower case, with separating periods copied
2192 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2193 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2196 @smallexample @c ada
2197 pragma Source_File_Name
2198 (Spec_File_Name => "*.1.ada");
2199 pragma Source_File_Name
2200 (Body_File_Name => "*.2.ada");
2204 The default GNAT scheme is actually implemented by providing the following
2205 default pragmas internally:
2207 @smallexample @c ada
2208 pragma Source_File_Name
2209 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2210 pragma Source_File_Name
2211 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2215 Our final example implements a scheme typically used with one of the
2216 Ada 83 compilers, where the separator character for subunits was ``__''
2217 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2218 by adding @file{.ADA}, and subunits by
2219 adding @file{.SEP}. All file names were
2220 upper case. Child units were not present of course since this was an
2221 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2222 the same double underscore separator for child units.
2224 @smallexample @c ada
2225 pragma Source_File_Name
2226 (Spec_File_Name => "*_.ADA",
2227 Dot_Replacement => "__",
2228 Casing = Uppercase);
2229 pragma Source_File_Name
2230 (Body_File_Name => "*.ADA",
2231 Dot_Replacement => "__",
2232 Casing = Uppercase);
2233 pragma Source_File_Name
2234 (Subunit_File_Name => "*.SEP",
2235 Dot_Replacement => "__",
2236 Casing = Uppercase);
2239 @node Generating Object Files
2240 @section Generating Object Files
2243 An Ada program consists of a set of source files, and the first step in
2244 compiling the program is to generate the corresponding object files.
2245 These are generated by compiling a subset of these source files.
2246 The files you need to compile are the following:
2250 If a package spec has no body, compile the package spec to produce the
2251 object file for the package.
2254 If a package has both a spec and a body, compile the body to produce the
2255 object file for the package. The source file for the package spec need
2256 not be compiled in this case because there is only one object file, which
2257 contains the code for both the spec and body of the package.
2260 For a subprogram, compile the subprogram body to produce the object file
2261 for the subprogram. The spec, if one is present, is as usual in a
2262 separate file, and need not be compiled.
2266 In the case of subunits, only compile the parent unit. A single object
2267 file is generated for the entire subunit tree, which includes all the
2271 Compile child units independently of their parent units
2272 (though, of course, the spec of all the ancestor unit must be present in order
2273 to compile a child unit).
2277 Compile generic units in the same manner as any other units. The object
2278 files in this case are small dummy files that contain at most the
2279 flag used for elaboration checking. This is because GNAT always handles generic
2280 instantiation by means of macro expansion. However, it is still necessary to
2281 compile generic units, for dependency checking and elaboration purposes.
2285 The preceding rules describe the set of files that must be compiled to
2286 generate the object files for a program. Each object file has the same
2287 name as the corresponding source file, except that the extension is
2290 You may wish to compile other files for the purpose of checking their
2291 syntactic and semantic correctness. For example, in the case where a
2292 package has a separate spec and body, you would not normally compile the
2293 spec. However, it is convenient in practice to compile the spec to make
2294 sure it is error-free before compiling clients of this spec, because such
2295 compilations will fail if there is an error in the spec.
2297 GNAT provides an option for compiling such files purely for the
2298 purposes of checking correctness; such compilations are not required as
2299 part of the process of building a program. To compile a file in this
2300 checking mode, use the @option{-gnatc} switch.
2302 @node Source Dependencies
2303 @section Source Dependencies
2306 A given object file clearly depends on the source file which is compiled
2307 to produce it. Here we are using @dfn{depends} in the sense of a typical
2308 @code{make} utility; in other words, an object file depends on a source
2309 file if changes to the source file require the object file to be
2311 In addition to this basic dependency, a given object may depend on
2312 additional source files as follows:
2316 If a file being compiled @code{with}'s a unit @var{X}, the object file
2317 depends on the file containing the spec of unit @var{X}. This includes
2318 files that are @code{with}'ed implicitly either because they are parents
2319 of @code{with}'ed child units or they are run-time units required by the
2320 language constructs used in a particular unit.
2323 If a file being compiled instantiates a library level generic unit, the
2324 object file depends on both the spec and body files for this generic
2328 If a file being compiled instantiates a generic unit defined within a
2329 package, the object file depends on the body file for the package as
2330 well as the spec file.
2334 @cindex @option{-gnatn} switch
2335 If a file being compiled contains a call to a subprogram for which
2336 pragma @code{Inline} applies and inlining is activated with the
2337 @option{-gnatn} switch, the object file depends on the file containing the
2338 body of this subprogram as well as on the file containing the spec. Note
2339 that for inlining to actually occur as a result of the use of this switch,
2340 it is necessary to compile in optimizing mode.
2342 @cindex @option{-gnatN} switch
2343 The use of @option{-gnatN} activates inlining optimization
2344 that is performed by the front end of the compiler. This inlining does
2345 not require that the code generation be optimized. Like @option{-gnatn},
2346 the use of this switch generates additional dependencies.
2348 When using a gcc-based back end (in practice this means using any version
2349 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
2350 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
2351 Historically front end inlining was more extensive than the gcc back end
2352 inlining, but that is no longer the case.
2355 If an object file @file{O} depends on the proper body of a subunit through
2356 inlining or instantiation, it depends on the parent unit of the subunit.
2357 This means that any modification of the parent unit or one of its subunits
2358 affects the compilation of @file{O}.
2361 The object file for a parent unit depends on all its subunit body files.
2364 The previous two rules meant that for purposes of computing dependencies and
2365 recompilation, a body and all its subunits are treated as an indivisible whole.
2368 These rules are applied transitively: if unit @code{A} @code{with}'s
2369 unit @code{B}, whose elaboration calls an inlined procedure in package
2370 @code{C}, the object file for unit @code{A} will depend on the body of
2371 @code{C}, in file @file{c.adb}.
2373 The set of dependent files described by these rules includes all the
2374 files on which the unit is semantically dependent, as dictated by the
2375 Ada language standard. However, it is a superset of what the
2376 standard describes, because it includes generic, inline, and subunit
2379 An object file must be recreated by recompiling the corresponding source
2380 file if any of the source files on which it depends are modified. For
2381 example, if the @code{make} utility is used to control compilation,
2382 the rule for an Ada object file must mention all the source files on
2383 which the object file depends, according to the above definition.
2384 The determination of the necessary
2385 recompilations is done automatically when one uses @command{gnatmake}.
2388 @node The Ada Library Information Files
2389 @section The Ada Library Information Files
2390 @cindex Ada Library Information files
2391 @cindex @file{ALI} files
2394 Each compilation actually generates two output files. The first of these
2395 is the normal object file that has a @file{.o} extension. The second is a
2396 text file containing full dependency information. It has the same
2397 name as the source file, but an @file{.ali} extension.
2398 This file is known as the Ada Library Information (@file{ALI}) file.
2399 The following information is contained in the @file{ALI} file.
2403 Version information (indicates which version of GNAT was used to compile
2404 the unit(s) in question)
2407 Main program information (including priority and time slice settings,
2408 as well as the wide character encoding used during compilation).
2411 List of arguments used in the @command{gcc} command for the compilation
2414 Attributes of the unit, including configuration pragmas used, an indication
2415 of whether the compilation was successful, exception model used etc.
2418 A list of relevant restrictions applying to the unit (used for consistency)
2422 Categorization information (e.g.@: use of pragma @code{Pure}).
2425 Information on all @code{with}'ed units, including presence of
2426 @code{Elaborate} or @code{Elaborate_All} pragmas.
2429 Information from any @code{Linker_Options} pragmas used in the unit
2432 Information on the use of @code{Body_Version} or @code{Version}
2433 attributes in the unit.
2436 Dependency information. This is a list of files, together with
2437 time stamp and checksum information. These are files on which
2438 the unit depends in the sense that recompilation is required
2439 if any of these units are modified.
2442 Cross-reference data. Contains information on all entities referenced
2443 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2444 provide cross-reference information.
2449 For a full detailed description of the format of the @file{ALI} file,
2450 see the source of the body of unit @code{Lib.Writ}, contained in file
2451 @file{lib-writ.adb} in the GNAT compiler sources.
2453 @node Binding an Ada Program
2454 @section Binding an Ada Program
2457 When using languages such as C and C++, once the source files have been
2458 compiled the only remaining step in building an executable program
2459 is linking the object modules together. This means that it is possible to
2460 link an inconsistent version of a program, in which two units have
2461 included different versions of the same header.
2463 The rules of Ada do not permit such an inconsistent program to be built.
2464 For example, if two clients have different versions of the same package,
2465 it is illegal to build a program containing these two clients.
2466 These rules are enforced by the GNAT binder, which also determines an
2467 elaboration order consistent with the Ada rules.
2469 The GNAT binder is run after all the object files for a program have
2470 been created. It is given the name of the main program unit, and from
2471 this it determines the set of units required by the program, by reading the
2472 corresponding ALI files. It generates error messages if the program is
2473 inconsistent or if no valid order of elaboration exists.
2475 If no errors are detected, the binder produces a main program, in Ada by
2476 default, that contains calls to the elaboration procedures of those
2477 compilation unit that require them, followed by
2478 a call to the main program. This Ada program is compiled to generate the
2479 object file for the main program. The name of
2480 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2481 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2484 Finally, the linker is used to build the resulting executable program,
2485 using the object from the main program from the bind step as well as the
2486 object files for the Ada units of the program.
2488 @node Mixed Language Programming
2489 @section Mixed Language Programming
2490 @cindex Mixed Language Programming
2493 This section describes how to develop a mixed-language program,
2494 specifically one that comprises units in both Ada and C.
2497 * Interfacing to C::
2498 * Calling Conventions::
2501 @node Interfacing to C
2502 @subsection Interfacing to C
2504 Interfacing Ada with a foreign language such as C involves using
2505 compiler directives to import and/or export entity definitions in each
2506 language---using @code{extern} statements in C, for instance, and the
2507 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
2508 A full treatment of these topics is provided in Appendix B, section 1
2509 of the Ada Reference Manual.
2511 There are two ways to build a program using GNAT that contains some Ada
2512 sources and some foreign language sources, depending on whether or not
2513 the main subprogram is written in Ada. Here is a source example with
2514 the main subprogram in Ada:
2520 void print_num (int num)
2522 printf ("num is %d.\n", num);
2528 /* num_from_Ada is declared in my_main.adb */
2529 extern int num_from_Ada;
2533 return num_from_Ada;
2537 @smallexample @c ada
2539 procedure My_Main is
2541 -- Declare then export an Integer entity called num_from_Ada
2542 My_Num : Integer := 10;
2543 pragma Export (C, My_Num, "num_from_Ada");
2545 -- Declare an Ada function spec for Get_Num, then use
2546 -- C function get_num for the implementation.
2547 function Get_Num return Integer;
2548 pragma Import (C, Get_Num, "get_num");
2550 -- Declare an Ada procedure spec for Print_Num, then use
2551 -- C function print_num for the implementation.
2552 procedure Print_Num (Num : Integer);
2553 pragma Import (C, Print_Num, "print_num");
2556 Print_Num (Get_Num);
2562 To build this example, first compile the foreign language files to
2563 generate object files:
2565 ^gcc -c file1.c^gcc -c FILE1.C^
2566 ^gcc -c file2.c^gcc -c FILE2.C^
2570 Then, compile the Ada units to produce a set of object files and ALI
2573 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2577 Run the Ada binder on the Ada main program:
2579 gnatbind my_main.ali
2583 Link the Ada main program, the Ada objects and the other language
2586 gnatlink my_main.ali file1.o file2.o
2590 The last three steps can be grouped in a single command:
2592 gnatmake my_main.adb -largs file1.o file2.o
2595 @cindex Binder output file
2597 If the main program is in a language other than Ada, then you may have
2598 more than one entry point into the Ada subsystem. You must use a special
2599 binder option to generate callable routines that initialize and
2600 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2601 Calls to the initialization and finalization routines must be inserted
2602 in the main program, or some other appropriate point in the code. The
2603 call to initialize the Ada units must occur before the first Ada
2604 subprogram is called, and the call to finalize the Ada units must occur
2605 after the last Ada subprogram returns. The binder will place the
2606 initialization and finalization subprograms into the
2607 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2608 sources. To illustrate, we have the following example:
2612 extern void adainit (void);
2613 extern void adafinal (void);
2614 extern int add (int, int);
2615 extern int sub (int, int);
2617 int main (int argc, char *argv[])
2623 /* Should print "21 + 7 = 28" */
2624 printf ("%d + %d = %d\n", a, b, add (a, b));
2625 /* Should print "21 - 7 = 14" */
2626 printf ("%d - %d = %d\n", a, b, sub (a, b));
2632 @smallexample @c ada
2635 function Add (A, B : Integer) return Integer;
2636 pragma Export (C, Add, "add");
2640 package body Unit1 is
2641 function Add (A, B : Integer) return Integer is
2649 function Sub (A, B : Integer) return Integer;
2650 pragma Export (C, Sub, "sub");
2654 package body Unit2 is
2655 function Sub (A, B : Integer) return Integer is
2664 The build procedure for this application is similar to the last
2665 example's. First, compile the foreign language files to generate object
2668 ^gcc -c main.c^gcc -c main.c^
2672 Next, compile the Ada units to produce a set of object files and ALI
2675 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2676 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2680 Run the Ada binder on every generated ALI file. Make sure to use the
2681 @option{-n} option to specify a foreign main program:
2683 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2687 Link the Ada main program, the Ada objects and the foreign language
2688 objects. You need only list the last ALI file here:
2690 gnatlink unit2.ali main.o -o exec_file
2693 This procedure yields a binary executable called @file{exec_file}.
2697 Depending on the circumstances (for example when your non-Ada main object
2698 does not provide symbol @code{main}), you may also need to instruct the
2699 GNAT linker not to include the standard startup objects by passing the
2700 @option{^-nostartfiles^/NOSTART_FILES^} switch to @command{gnatlink}.
2702 @node Calling Conventions
2703 @subsection Calling Conventions
2704 @cindex Foreign Languages
2705 @cindex Calling Conventions
2706 GNAT follows standard calling sequence conventions and will thus interface
2707 to any other language that also follows these conventions. The following
2708 Convention identifiers are recognized by GNAT:
2711 @cindex Interfacing to Ada
2712 @cindex Other Ada compilers
2713 @cindex Convention Ada
2715 This indicates that the standard Ada calling sequence will be
2716 used and all Ada data items may be passed without any limitations in the
2717 case where GNAT is used to generate both the caller and callee. It is also
2718 possible to mix GNAT generated code and code generated by another Ada
2719 compiler. In this case, the data types should be restricted to simple
2720 cases, including primitive types. Whether complex data types can be passed
2721 depends on the situation. Probably it is safe to pass simple arrays, such
2722 as arrays of integers or floats. Records may or may not work, depending
2723 on whether both compilers lay them out identically. Complex structures
2724 involving variant records, access parameters, tasks, or protected types,
2725 are unlikely to be able to be passed.
2727 Note that in the case of GNAT running
2728 on a platform that supports HP Ada 83, a higher degree of compatibility
2729 can be guaranteed, and in particular records are layed out in an identical
2730 manner in the two compilers. Note also that if output from two different
2731 compilers is mixed, the program is responsible for dealing with elaboration
2732 issues. Probably the safest approach is to write the main program in the
2733 version of Ada other than GNAT, so that it takes care of its own elaboration
2734 requirements, and then call the GNAT-generated adainit procedure to ensure
2735 elaboration of the GNAT components. Consult the documentation of the other
2736 Ada compiler for further details on elaboration.
2738 However, it is not possible to mix the tasking run time of GNAT and
2739 HP Ada 83, All the tasking operations must either be entirely within
2740 GNAT compiled sections of the program, or entirely within HP Ada 83
2741 compiled sections of the program.
2743 @cindex Interfacing to Assembly
2744 @cindex Convention Assembler
2746 Specifies assembler as the convention. In practice this has the
2747 same effect as convention Ada (but is not equivalent in the sense of being
2748 considered the same convention).
2750 @cindex Convention Asm
2753 Equivalent to Assembler.
2755 @cindex Interfacing to COBOL
2756 @cindex Convention COBOL
2759 Data will be passed according to the conventions described
2760 in section B.4 of the Ada Reference Manual.
2763 @cindex Interfacing to C
2764 @cindex Convention C
2766 Data will be passed according to the conventions described
2767 in section B.3 of the Ada Reference Manual.
2769 A note on interfacing to a C ``varargs'' function:
2770 @findex C varargs function
2771 @cindex Interfacing to C varargs function
2772 @cindex varargs function interfaces
2776 In C, @code{varargs} allows a function to take a variable number of
2777 arguments. There is no direct equivalent in this to Ada. One
2778 approach that can be used is to create a C wrapper for each
2779 different profile and then interface to this C wrapper. For
2780 example, to print an @code{int} value using @code{printf},
2781 create a C function @code{printfi} that takes two arguments, a
2782 pointer to a string and an int, and calls @code{printf}.
2783 Then in the Ada program, use pragma @code{Import} to
2784 interface to @code{printfi}.
2787 It may work on some platforms to directly interface to
2788 a @code{varargs} function by providing a specific Ada profile
2789 for a particular call. However, this does not work on
2790 all platforms, since there is no guarantee that the
2791 calling sequence for a two argument normal C function
2792 is the same as for calling a @code{varargs} C function with
2793 the same two arguments.
2796 @cindex Convention Default
2801 @cindex Convention External
2808 @cindex Interfacing to C++
2809 @cindex Convention C++
2810 @item C_Plus_Plus (or CPP)
2811 This stands for C++. For most purposes this is identical to C.
2812 See the separate description of the specialized GNAT pragmas relating to
2813 C++ interfacing for further details.
2817 @cindex Interfacing to Fortran
2818 @cindex Convention Fortran
2820 Data will be passed according to the conventions described
2821 in section B.5 of the Ada Reference Manual.
2824 This applies to an intrinsic operation, as defined in the Ada
2825 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
2826 this means that the body of the subprogram is provided by the compiler itself,
2827 usually by means of an efficient code sequence, and that the user does not
2828 supply an explicit body for it. In an application program, the pragma may
2829 be applied to the following sets of names:
2833 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
2834 Shift_Right_Arithmetic. The corresponding subprogram declaration must have
2835 two formal parameters. The
2836 first one must be a signed integer type or a modular type with a binary
2837 modulus, and the second parameter must be of type Natural.
2838 The return type must be the same as the type of the first argument. The size
2839 of this type can only be 8, 16, 32, or 64.
2842 Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
2843 The corresponding operator declaration must have parameters and result type
2844 that have the same root numeric type (for example, all three are long_float
2845 types). This simplifies the definition of operations that use type checking
2846 to perform dimensional checks:
2848 @smallexample @c ada
2849 type Distance is new Long_Float;
2850 type Time is new Long_Float;
2851 type Velocity is new Long_Float;
2852 function "/" (D : Distance; T : Time)
2854 pragma Import (Intrinsic, "/");
2858 This common idiom is often programmed with a generic definition and an
2859 explicit body. The pragma makes it simpler to introduce such declarations.
2860 It incurs no overhead in compilation time or code size, because it is
2861 implemented as a single machine instruction.
2864 General subprogram entities, to bind an Ada subprogram declaration to
2865 a compiler builtin by name with back-ends where such interfaces are
2866 available. A typical example is the set of ``__builtin'' functions
2867 exposed by the GCC back-end, as in the following example:
2869 @smallexample @c ada
2870 function builtin_sqrt (F : Float) return Float;
2871 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
2874 Most of the GCC builtins are accessible this way, and as for other
2875 import conventions (e.g. C), it is the user's responsibility to ensure
2876 that the Ada subprogram profile matches the underlying builtin
2884 @cindex Convention Stdcall
2886 This is relevant only to Windows XP/2000/NT implementations of GNAT,
2887 and specifies that the @code{Stdcall} calling sequence will be used,
2888 as defined by the NT API. Nevertheless, to ease building
2889 cross-platform bindings this convention will be handled as a @code{C} calling
2890 convention on non-Windows platforms.
2893 @cindex Convention DLL
2895 This is equivalent to @code{Stdcall}.
2898 @cindex Convention Win32
2900 This is equivalent to @code{Stdcall}.
2904 @cindex Convention Stubbed
2906 This is a special convention that indicates that the compiler
2907 should provide a stub body that raises @code{Program_Error}.
2911 GNAT additionally provides a useful pragma @code{Convention_Identifier}
2912 that can be used to parameterize conventions and allow additional synonyms
2913 to be specified. For example if you have legacy code in which the convention
2914 identifier Fortran77 was used for Fortran, you can use the configuration
2917 @smallexample @c ada
2918 pragma Convention_Identifier (Fortran77, Fortran);
2922 And from now on the identifier Fortran77 may be used as a convention
2923 identifier (for example in an @code{Import} pragma) with the same
2927 @node Building Mixed Ada & C++ Programs
2928 @section Building Mixed Ada and C++ Programs
2931 A programmer inexperienced with mixed-language development may find that
2932 building an application containing both Ada and C++ code can be a
2933 challenge. This section gives a few
2934 hints that should make this task easier. The first section addresses
2935 the differences between interfacing with C and interfacing with C++.
2937 looks into the delicate problem of linking the complete application from
2938 its Ada and C++ parts. The last section gives some hints on how the GNAT
2939 run-time library can be adapted in order to allow inter-language dispatching
2940 with a new C++ compiler.
2943 * Interfacing to C++::
2944 * Linking a Mixed C++ & Ada Program::
2945 * A Simple Example::
2946 * Interfacing with C++ constructors::
2947 * Interfacing with C++ at the Class Level::
2950 @node Interfacing to C++
2951 @subsection Interfacing to C++
2954 GNAT supports interfacing with the G++ compiler (or any C++ compiler
2955 generating code that is compatible with the G++ Application Binary
2956 Interface ---see http://www.codesourcery.com/archives/cxx-abi).
2959 Interfacing can be done at 3 levels: simple data, subprograms, and
2960 classes. In the first two cases, GNAT offers a specific @code{Convention
2961 C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}.
2962 Usually, C++ mangles the names of subprograms. To generate proper mangled
2963 names automatically, see @ref{Generating Ada Bindings for C and C++ headers}).
2964 This problem can also be addressed manually in two ways:
2968 by modifying the C++ code in order to force a C convention using
2969 the @code{extern "C"} syntax.
2972 by figuring out the mangled name (using e.g. @command{nm}) and using it as the
2973 Link_Name argument of the pragma import.
2977 Interfacing at the class level can be achieved by using the GNAT specific
2978 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
2979 gnat_rm, GNAT Reference Manual}, for additional information.
2981 @node Linking a Mixed C++ & Ada Program
2982 @subsection Linking a Mixed C++ & Ada Program
2985 Usually the linker of the C++ development system must be used to link
2986 mixed applications because most C++ systems will resolve elaboration
2987 issues (such as calling constructors on global class instances)
2988 transparently during the link phase. GNAT has been adapted to ease the
2989 use of a foreign linker for the last phase. Three cases can be
2994 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
2995 The C++ linker can simply be called by using the C++ specific driver
2998 Note that if the C++ code uses inline functions, you will need to
2999 compile your C++ code with the @code{-fkeep-inline-functions} switch in
3000 order to provide an existing function implementation that the Ada code can
3004 $ g++ -c -fkeep-inline-functions file1.C
3005 $ g++ -c -fkeep-inline-functions file2.C
3006 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
3010 Using GNAT and G++ from two different GCC installations: If both
3011 compilers are on the @env{PATH}, the previous method may be used. It is
3012 important to note that environment variables such as
3013 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3014 @env{GCC_ROOT} will affect both compilers
3015 at the same time and may make one of the two compilers operate
3016 improperly if set during invocation of the wrong compiler. It is also
3017 very important that the linker uses the proper @file{libgcc.a} GCC
3018 library -- that is, the one from the C++ compiler installation. The
3019 implicit link command as suggested in the @command{gnatmake} command
3020 from the former example can be replaced by an explicit link command with
3021 the full-verbosity option in order to verify which library is used:
3024 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3026 If there is a problem due to interfering environment variables, it can
3027 be worked around by using an intermediate script. The following example
3028 shows the proper script to use when GNAT has not been installed at its
3029 default location and g++ has been installed at its default location:
3037 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3041 Using a non-GNU C++ compiler: The commands previously described can be
3042 used to insure that the C++ linker is used. Nonetheless, you need to add
3043 a few more parameters to the link command line, depending on the exception
3046 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3047 to the libgcc libraries are required:
3052 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3053 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3056 Where CC is the name of the non-GNU C++ compiler.
3058 If the @code{zero cost} exception mechanism is used, and the platform
3059 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3060 paths to more objects are required:
3065 CC `gcc -print-file-name=crtbegin.o` $* \
3066 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3067 `gcc -print-file-name=crtend.o`
3068 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3071 If the @code{zero cost} exception mechanism is used, and the platform
3072 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3073 Tru64 or AIX), the simple approach described above will not work and
3074 a pre-linking phase using GNAT will be necessary.
3078 Another alternative is to use the @command{gprbuild} multi-language builder
3079 which has a large knowledge base and knows how to link Ada and C++ code
3080 together automatically in most cases.
3082 @node A Simple Example
3083 @subsection A Simple Example
3085 The following example, provided as part of the GNAT examples, shows how
3086 to achieve procedural interfacing between Ada and C++ in both
3087 directions. The C++ class A has two methods. The first method is exported
3088 to Ada by the means of an extern C wrapper function. The second method
3089 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3090 a limited record with a layout comparable to the C++ class. The Ada
3091 subprogram, in turn, calls the C++ method. So, starting from the C++
3092 main program, the process passes back and forth between the two
3096 Here are the compilation commands:
3098 $ gnatmake -c simple_cpp_interface
3101 $ gnatbind -n simple_cpp_interface
3102 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++
3103 -lstdc++ ex7.o cpp_main.o
3107 Here are the corresponding sources:
3115 void adainit (void);
3116 void adafinal (void);
3117 void method1 (A *t);
3139 class A : public Origin @{
3141 void method1 (void);
3142 void method2 (int v);
3152 extern "C" @{ void ada_method2 (A *t, int v);@}
3154 void A::method1 (void)
3157 printf ("in A::method1, a_value = %d \n",a_value);
3161 void A::method2 (int v)
3163 ada_method2 (this, v);
3164 printf ("in A::method2, a_value = %d \n",a_value);
3171 printf ("in A::A, a_value = %d \n",a_value);
3175 @smallexample @c ada
3177 package body Simple_Cpp_Interface is
3179 procedure Ada_Method2 (This : in out A; V : Integer) is
3185 end Simple_Cpp_Interface;
3188 package Simple_Cpp_Interface is
3191 Vptr : System.Address;
3195 pragma Convention (C, A);
3197 procedure Method1 (This : in out A);
3198 pragma Import (C, Method1);
3200 procedure Ada_Method2 (This : in out A; V : Integer);
3201 pragma Export (C, Ada_Method2);
3203 end Simple_Cpp_Interface;
3206 @node Interfacing with C++ constructors
3207 @subsection Interfacing with C++ constructors
3210 In order to interface with C++ constructors GNAT provides the
3211 @code{pragma CPP_Constructor} (@xref{Interfacing to C++,,,
3212 gnat_rm, GNAT Reference Manual}, for additional information).
3213 In this section we present some common uses of C++ constructors
3214 in mixed-languages programs in GNAT.
3216 Let us assume that we need to interface with the following
3224 @b{virtual} int Get_Value ();
3225 Root(); // Default constructor
3226 Root(int v); // 1st non-default constructor
3227 Root(int v, int w); // 2nd non-default constructor
3231 For this purpose we can write the following package spec (further
3232 information on how to build this spec is available in
3233 @ref{Interfacing with C++ at the Class Level} and
3234 @ref{Generating Ada Bindings for C and C++ headers}).
3236 @smallexample @c ada
3237 with Interfaces.C; use Interfaces.C;
3239 type Root is tagged limited record
3243 pragma Import (CPP, Root);
3245 function Get_Value (Obj : Root) return int;
3246 pragma Import (CPP, Get_Value);
3248 function Constructor return Root;
3249 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
3251 function Constructor (v : Integer) return Root;
3252 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
3254 function Constructor (v, w : Integer) return Root;
3255 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
3259 On the Ada side the constructor is represented by a function (whose
3260 name is arbitrary) that returns the classwide type corresponding to
3261 the imported C++ class. Although the constructor is described as a
3262 function, it is typically a procedure with an extra implicit argument
3263 (the object being initialized) at the implementation level. GNAT
3264 issues the appropriate call, whatever it is, to get the object
3265 properly initialized.
3267 Constructors can only appear in the following contexts:
3271 On the right side of an initialization of an object of type @var{T}.
3273 On the right side of an initialization of a record component of type @var{T}.
3275 In an Ada 2005 limited aggregate.
3277 In an Ada 2005 nested limited aggregate.
3279 In an Ada 2005 limited aggregate that initializes an object built in
3280 place by an extended return statement.
3284 In a declaration of an object whose type is a class imported from C++,
3285 either the default C++ constructor is implicitly called by GNAT, or
3286 else the required C++ constructor must be explicitly called in the
3287 expression that initializes the object. For example:
3289 @smallexample @c ada
3291 Obj2 : Root := Constructor;
3292 Obj3 : Root := Constructor (v => 10);
3293 Obj4 : Root := Constructor (30, 40);
3296 The first two declarations are equivalent: in both cases the default C++
3297 constructor is invoked (in the former case the call to the constructor is
3298 implicit, and in the latter case the call is explicit in the object
3299 declaration). @code{Obj3} is initialized by the C++ non-default constructor
3300 that takes an integer argument, and @code{Obj4} is initialized by the
3301 non-default C++ constructor that takes two integers.
3303 Let us derive the imported C++ class in the Ada side. For example:
3305 @smallexample @c ada
3306 type DT is new Root with record
3307 C_Value : Natural := 2009;
3311 In this case the components DT inherited from the C++ side must be
3312 initialized by a C++ constructor, and the additional Ada components
3313 of type DT are initialized by GNAT. The initialization of such an
3314 object is done either by default, or by means of a function returning
3315 an aggregate of type DT, or by means of an extension aggregate.
3317 @smallexample @c ada
3319 Obj6 : DT := Function_Returning_DT (50);
3320 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
3323 The declaration of @code{Obj5} invokes the default constructors: the
3324 C++ default constructor of the parent type takes care of the initialization
3325 of the components inherited from Root, and GNAT takes care of the default
3326 initialization of the additional Ada components of type DT (that is,
3327 @code{C_Value} is initialized to value 2009). The order of invocation of
3328 the constructors is consistent with the order of elaboration required by
3329 Ada and C++. That is, the constructor of the parent type is always called
3330 before the constructor of the derived type.
3332 Let us now consider a record that has components whose type is imported
3333 from C++. For example:
3335 @smallexample @c ada
3336 type Rec1 is limited record
3337 Data1 : Root := Constructor (10);
3338 Value : Natural := 1000;
3341 type Rec2 (D : Integer := 20) is limited record
3343 Data2 : Root := Constructor (D, 30);
3347 The initialization of an object of type @code{Rec2} will call the
3348 non-default C++ constructors specified for the imported components.
3351 @smallexample @c ada
3355 Using Ada 2005 we can use limited aggregates to initialize an object
3356 invoking C++ constructors that differ from those specified in the type
3357 declarations. For example:
3359 @smallexample @c ada
3360 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
3365 The above declaration uses an Ada 2005 limited aggregate to
3366 initialize @code{Obj9}, and the C++ constructor that has two integer
3367 arguments is invoked to initialize the @code{Data1} component instead
3368 of the constructor specified in the declaration of type @code{Rec1}. In
3369 Ada 2005 the box in the aggregate indicates that unspecified components
3370 are initialized using the expression (if any) available in the component
3371 declaration. That is, in this case discriminant @code{D} is initialized
3372 to value @code{20}, @code{Value} is initialized to value 1000, and the
3373 non-default C++ constructor that handles two integers takes care of
3374 initializing component @code{Data2} with values @code{20,30}.
3376 In Ada 2005 we can use the extended return statement to build the Ada
3377 equivalent to C++ non-default constructors. For example:
3379 @smallexample @c ada
3380 function Constructor (V : Integer) return Rec2 is
3382 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
3385 -- Further actions required for construction of
3386 -- objects of type Rec2
3392 In this example the extended return statement construct is used to
3393 build in place the returned object whose components are initialized
3394 by means of a limited aggregate. Any further action associated with
3395 the constructor can be placed inside the construct.
3397 @node Interfacing with C++ at the Class Level
3398 @subsection Interfacing with C++ at the Class Level
3400 In this section we demonstrate the GNAT features for interfacing with
3401 C++ by means of an example making use of Ada 2005 abstract interface
3402 types. This example consists of a classification of animals; classes
3403 have been used to model our main classification of animals, and
3404 interfaces provide support for the management of secondary
3405 classifications. We first demonstrate a case in which the types and
3406 constructors are defined on the C++ side and imported from the Ada
3407 side, and latter the reverse case.
3409 The root of our derivation will be the @code{Animal} class, with a
3410 single private attribute (the @code{Age} of the animal) and two public
3411 primitives to set and get the value of this attribute.
3416 @b{virtual} void Set_Age (int New_Age);
3417 @b{virtual} int Age ();
3423 Abstract interface types are defined in C++ by means of classes with pure
3424 virtual functions and no data members. In our example we will use two
3425 interfaces that provide support for the common management of @code{Carnivore}
3426 and @code{Domestic} animals:
3429 @b{class} Carnivore @{
3431 @b{virtual} int Number_Of_Teeth () = 0;
3434 @b{class} Domestic @{
3436 @b{virtual void} Set_Owner (char* Name) = 0;
3440 Using these declarations, we can now say that a @code{Dog} is an animal that is
3441 both Carnivore and Domestic, that is:
3444 @b{class} Dog : Animal, Carnivore, Domestic @{
3446 @b{virtual} int Number_Of_Teeth ();
3447 @b{virtual} void Set_Owner (char* Name);
3449 Dog(); // Constructor
3456 In the following examples we will assume that the previous declarations are
3457 located in a file named @code{animals.h}. The following package demonstrates
3458 how to import these C++ declarations from the Ada side:
3460 @smallexample @c ada
3461 with Interfaces.C.Strings; use Interfaces.C.Strings;
3463 type Carnivore is interface;
3464 pragma Convention (C_Plus_Plus, Carnivore);
3465 function Number_Of_Teeth (X : Carnivore)
3466 return Natural is abstract;
3468 type Domestic is interface;
3469 pragma Convention (C_Plus_Plus, Set_Owner);
3471 (X : in out Domestic;
3472 Name : Chars_Ptr) is abstract;
3474 type Animal is tagged record
3477 pragma Import (C_Plus_Plus, Animal);
3479 procedure Set_Age (X : in out Animal; Age : Integer);
3480 pragma Import (C_Plus_Plus, Set_Age);
3482 function Age (X : Animal) return Integer;
3483 pragma Import (C_Plus_Plus, Age);
3485 type Dog is new Animal and Carnivore and Domestic with record
3486 Tooth_Count : Natural;
3487 Owner : String (1 .. 30);
3489 pragma Import (C_Plus_Plus, Dog);
3491 function Number_Of_Teeth (A : Dog) return Integer;
3492 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3494 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3495 pragma Import (C_Plus_Plus, Set_Owner);
3497 function New_Dog return Dog;
3498 pragma CPP_Constructor (New_Dog);
3499 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3503 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3504 interfacing with these C++ classes is easy. The only requirement is that all
3505 the primitives and components must be declared exactly in the same order in
3508 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3509 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3510 the arguments to the called primitives will be the same as for C++. For the
3511 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3512 to indicate that they have been defined on the C++ side; this is required
3513 because the dispatch table associated with these tagged types will be built
3514 in the C++ side and therefore will not contain the predefined Ada primitives
3515 which Ada would otherwise expect.
3517 As the reader can see there is no need to indicate the C++ mangled names
3518 associated with each subprogram because it is assumed that all the calls to
3519 these primitives will be dispatching calls. The only exception is the
3520 constructor, which must be registered with the compiler by means of
3521 @code{pragma CPP_Constructor} and needs to provide its associated C++
3522 mangled name because the Ada compiler generates direct calls to it.
3524 With the above packages we can now declare objects of type Dog on the Ada side
3525 and dispatch calls to the corresponding subprograms on the C++ side. We can
3526 also extend the tagged type Dog with further fields and primitives, and
3527 override some of its C++ primitives on the Ada side. For example, here we have
3528 a type derivation defined on the Ada side that inherits all the dispatching
3529 primitives of the ancestor from the C++ side.
3532 @b{with} Animals; @b{use} Animals;
3533 @b{package} Vaccinated_Animals @b{is}
3534 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3535 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3536 @b{end} Vaccinated_Animals;
3539 It is important to note that, because of the ABI compatibility, the programmer
3540 does not need to add any further information to indicate either the object
3541 layout or the dispatch table entry associated with each dispatching operation.
3543 Now let us define all the types and constructors on the Ada side and export
3544 them to C++, using the same hierarchy of our previous example:
3546 @smallexample @c ada
3547 with Interfaces.C.Strings;
3548 use Interfaces.C.Strings;
3550 type Carnivore is interface;
3551 pragma Convention (C_Plus_Plus, Carnivore);
3552 function Number_Of_Teeth (X : Carnivore)
3553 return Natural is abstract;
3555 type Domestic is interface;
3556 pragma Convention (C_Plus_Plus, Set_Owner);
3558 (X : in out Domestic;
3559 Name : Chars_Ptr) is abstract;
3561 type Animal is tagged record
3564 pragma Convention (C_Plus_Plus, Animal);
3566 procedure Set_Age (X : in out Animal; Age : Integer);
3567 pragma Export (C_Plus_Plus, Set_Age);
3569 function Age (X : Animal) return Integer;
3570 pragma Export (C_Plus_Plus, Age);
3572 type Dog is new Animal and Carnivore and Domestic with record
3573 Tooth_Count : Natural;
3574 Owner : String (1 .. 30);
3576 pragma Convention (C_Plus_Plus, Dog);
3578 function Number_Of_Teeth (A : Dog) return Integer;
3579 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3581 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3582 pragma Export (C_Plus_Plus, Set_Owner);
3584 function New_Dog return Dog'Class;
3585 pragma Export (C_Plus_Plus, New_Dog);
3589 Compared with our previous example the only difference is the use of
3590 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3591 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3592 nothing else to be done; as explained above, the only requirement is that all
3593 the primitives and components are declared in exactly the same order.
3595 For completeness, let us see a brief C++ main program that uses the
3596 declarations available in @code{animals.h} (presented in our first example) to
3597 import and use the declarations from the Ada side, properly initializing and
3598 finalizing the Ada run-time system along the way:
3601 @b{#include} "animals.h"
3602 @b{#include} <iostream>
3603 @b{using namespace} std;
3605 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3606 void Check_Domestic (Domestic *obj) @{@dots{}@}
3607 void Check_Animal (Animal *obj) @{@dots{}@}
3608 void Check_Dog (Dog *obj) @{@dots{}@}
3611 void adainit (void);
3612 void adafinal (void);
3618 Dog *obj = new_dog(); // Ada constructor
3619 Check_Carnivore (obj); // Check secondary DT
3620 Check_Domestic (obj); // Check secondary DT
3621 Check_Animal (obj); // Check primary DT
3622 Check_Dog (obj); // Check primary DT
3627 adainit (); test(); adafinal ();
3632 @node Comparison between GNAT and C/C++ Compilation Models
3633 @section Comparison between GNAT and C/C++ Compilation Models
3636 The GNAT model of compilation is close to the C and C++ models. You can
3637 think of Ada specs as corresponding to header files in C. As in C, you
3638 don't need to compile specs; they are compiled when they are used. The
3639 Ada @code{with} is similar in effect to the @code{#include} of a C
3642 One notable difference is that, in Ada, you may compile specs separately
3643 to check them for semantic and syntactic accuracy. This is not always
3644 possible with C headers because they are fragments of programs that have
3645 less specific syntactic or semantic rules.
3647 The other major difference is the requirement for running the binder,
3648 which performs two important functions. First, it checks for
3649 consistency. In C or C++, the only defense against assembling
3650 inconsistent programs lies outside the compiler, in a makefile, for
3651 example. The binder satisfies the Ada requirement that it be impossible
3652 to construct an inconsistent program when the compiler is used in normal
3655 @cindex Elaboration order control
3656 The other important function of the binder is to deal with elaboration
3657 issues. There are also elaboration issues in C++ that are handled
3658 automatically. This automatic handling has the advantage of being
3659 simpler to use, but the C++ programmer has no control over elaboration.
3660 Where @code{gnatbind} might complain there was no valid order of
3661 elaboration, a C++ compiler would simply construct a program that
3662 malfunctioned at run time.
3665 @node Comparison between GNAT and Conventional Ada Library Models
3666 @section Comparison between GNAT and Conventional Ada Library Models
3669 This section is intended for Ada programmers who have
3670 used an Ada compiler implementing the traditional Ada library
3671 model, as described in the Ada Reference Manual.
3673 @cindex GNAT library
3674 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3675 source files themselves acts as the library. Compiling Ada programs does
3676 not generate any centralized information, but rather an object file and
3677 a ALI file, which are of interest only to the binder and linker.
3678 In a traditional system, the compiler reads information not only from
3679 the source file being compiled, but also from the centralized library.
3680 This means that the effect of a compilation depends on what has been
3681 previously compiled. In particular:
3685 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3686 to the version of the unit most recently compiled into the library.
3689 Inlining is effective only if the necessary body has already been
3690 compiled into the library.
3693 Compiling a unit may obsolete other units in the library.
3697 In GNAT, compiling one unit never affects the compilation of any other
3698 units because the compiler reads only source files. Only changes to source
3699 files can affect the results of a compilation. In particular:
3703 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3704 to the source version of the unit that is currently accessible to the
3709 Inlining requires the appropriate source files for the package or
3710 subprogram bodies to be available to the compiler. Inlining is always
3711 effective, independent of the order in which units are complied.
3714 Compiling a unit never affects any other compilations. The editing of
3715 sources may cause previous compilations to be out of date if they
3716 depended on the source file being modified.
3720 The most important result of these differences is that order of compilation
3721 is never significant in GNAT. There is no situation in which one is
3722 required to do one compilation before another. What shows up as order of
3723 compilation requirements in the traditional Ada library becomes, in
3724 GNAT, simple source dependencies; in other words, there is only a set
3725 of rules saying what source files must be present when a file is
3729 @node Placement of temporary files
3730 @section Placement of temporary files
3731 @cindex Temporary files (user control over placement)
3734 GNAT creates temporary files in the directory designated by the environment
3735 variable @env{TMPDIR}.
3736 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3737 for detailed information on how environment variables are resolved.
3738 For most users the easiest way to make use of this feature is to simply
3739 define @env{TMPDIR} as a job level logical name).
3740 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3741 for compiler temporary files, then you can include something like the
3742 following command in your @file{LOGIN.COM} file:
3745 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3749 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3750 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3751 designated by @env{TEMP}.
3752 If none of these environment variables are defined then GNAT uses the
3753 directory designated by the logical name @code{SYS$SCRATCH:}
3754 (by default the user's home directory). If all else fails
3755 GNAT uses the current directory for temporary files.
3758 @c *************************
3759 @node Compiling Using gcc
3760 @chapter Compiling Using @command{gcc}
3763 This chapter discusses how to compile Ada programs using the @command{gcc}
3764 command. It also describes the set of switches
3765 that can be used to control the behavior of the compiler.
3767 * Compiling Programs::
3768 * Switches for gcc::
3769 * Search Paths and the Run-Time Library (RTL)::
3770 * Order of Compilation Issues::
3774 @node Compiling Programs
3775 @section Compiling Programs
3778 The first step in creating an executable program is to compile the units
3779 of the program using the @command{gcc} command. You must compile the
3784 the body file (@file{.adb}) for a library level subprogram or generic
3788 the spec file (@file{.ads}) for a library level package or generic
3789 package that has no body
3792 the body file (@file{.adb}) for a library level package
3793 or generic package that has a body
3798 You need @emph{not} compile the following files
3803 the spec of a library unit which has a body
3810 because they are compiled as part of compiling related units. GNAT
3812 when the corresponding body is compiled, and subunits when the parent is
3815 @cindex cannot generate code
3816 If you attempt to compile any of these files, you will get one of the
3817 following error messages (where @var{fff} is the name of the file you
3821 cannot generate code for file @var{fff} (package spec)
3822 to check package spec, use -gnatc
3824 cannot generate code for file @var{fff} (missing subunits)
3825 to check parent unit, use -gnatc
3827 cannot generate code for file @var{fff} (subprogram spec)
3828 to check subprogram spec, use -gnatc
3830 cannot generate code for file @var{fff} (subunit)
3831 to check subunit, use -gnatc
3835 As indicated by the above error messages, if you want to submit
3836 one of these files to the compiler to check for correct semantics
3837 without generating code, then use the @option{-gnatc} switch.
3839 The basic command for compiling a file containing an Ada unit is
3842 @c $ gcc -c @ovar{switches} @file{file name}
3843 @c Expanding @ovar macro inline (explanation in macro def comments)
3844 $ gcc -c @r{[}@var{switches}@r{]} @file{file name}
3848 where @var{file name} is the name of the Ada file (usually
3850 @file{.ads} for a spec or @file{.adb} for a body).
3853 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3855 The result of a successful compilation is an object file, which has the
3856 same name as the source file but an extension of @file{.o} and an Ada
3857 Library Information (ALI) file, which also has the same name as the
3858 source file, but with @file{.ali} as the extension. GNAT creates these
3859 two output files in the current directory, but you may specify a source
3860 file in any directory using an absolute or relative path specification
3861 containing the directory information.
3864 @command{gcc} is actually a driver program that looks at the extensions of
3865 the file arguments and loads the appropriate compiler. For example, the
3866 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3867 These programs are in directories known to the driver program (in some
3868 configurations via environment variables you set), but need not be in
3869 your path. The @command{gcc} driver also calls the assembler and any other
3870 utilities needed to complete the generation of the required object
3873 It is possible to supply several file names on the same @command{gcc}
3874 command. This causes @command{gcc} to call the appropriate compiler for
3875 each file. For example, the following command lists three separate
3876 files to be compiled:
3879 $ gcc -c x.adb y.adb z.c
3883 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3884 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3885 The compiler generates three object files @file{x.o}, @file{y.o} and
3886 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3887 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3890 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3893 @node Switches for gcc
3894 @section Switches for @command{gcc}
3897 The @command{gcc} command accepts switches that control the
3898 compilation process. These switches are fully described in this section.
3899 First we briefly list all the switches, in alphabetical order, then we
3900 describe the switches in more detail in functionally grouped sections.
3902 More switches exist for GCC than those documented here, especially
3903 for specific targets. However, their use is not recommended as
3904 they may change code generation in ways that are incompatible with
3905 the Ada run-time library, or can cause inconsistencies between
3909 * Output and Error Message Control::
3910 * Warning Message Control::
3911 * Debugging and Assertion Control::
3912 * Validity Checking::
3915 * Using gcc for Syntax Checking::
3916 * Using gcc for Semantic Checking::
3917 * Compiling Different Versions of Ada::
3918 * Character Set Control::
3919 * File Naming Control::
3920 * Subprogram Inlining Control::
3921 * Auxiliary Output Control::
3922 * Debugging Control::
3923 * Exception Handling Control::
3924 * Units to Sources Mapping Files::
3925 * Integrated Preprocessing::
3926 * Code Generation Control::
3935 @cindex @option{-b} (@command{gcc})
3936 @item -b @var{target}
3937 Compile your program to run on @var{target}, which is the name of a
3938 system configuration. You must have a GNAT cross-compiler built if
3939 @var{target} is not the same as your host system.
3942 @cindex @option{-B} (@command{gcc})
3943 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3944 from @var{dir} instead of the default location. Only use this switch
3945 when multiple versions of the GNAT compiler are available.
3946 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3947 GNU Compiler Collection (GCC)}, for further details. You would normally
3948 use the @option{-b} or @option{-V} switch instead.
3951 @cindex @option{-c} (@command{gcc})
3952 Compile. Always use this switch when compiling Ada programs.
3954 Note: for some other languages when using @command{gcc}, notably in
3955 the case of C and C++, it is possible to use
3956 use @command{gcc} without a @option{-c} switch to
3957 compile and link in one step. In the case of GNAT, you
3958 cannot use this approach, because the binder must be run
3959 and @command{gcc} cannot be used to run the GNAT binder.
3963 @cindex @option{-fno-inline} (@command{gcc})
3964 Suppresses all inlining, even if other optimization or inlining
3965 switches are set. This includes suppression of inlining that
3966 results from the use of the pragma @code{Inline_Always}.
3967 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
3968 are ignored, and @option{-gnatn} and @option{-gnatN} have no
3969 effect if this switch is present.
3971 @item -fno-inline-functions
3972 @cindex @option{-fno-inline-functions} (@command{gcc})
3973 Suppresses automatic inlining of subprograms, which is enabled
3974 if @option{-O3} is used.
3976 @item -fno-inline-small-functions
3977 @cindex @option{-fno-inline-small-functions} (@command{gcc})
3978 Suppresses automatic inlining of small subprograms, which is enabled
3979 if @option{-O2} is used.
3981 @item -fno-inline-functions-called-once
3982 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
3983 Suppresses inlining of subprograms local to the unit and called once
3984 from within it, which is enabled if @option{-O1} is used.
3987 @cindex @option{-fno-ivopts} (@command{gcc})
3988 Suppresses high-level loop induction variable optimizations, which are
3989 enabled if @option{-O1} is used. These optimizations are generally
3990 profitable but, for some specific cases of loops with numerous uses
3991 of the iteration variable that follow a common pattern, they may end
3992 up destroying the regularity that could be exploited at a lower level
3993 and thus producing inferior code.
3995 @item -fno-strict-aliasing
3996 @cindex @option{-fno-strict-aliasing} (@command{gcc})
3997 Causes the compiler to avoid assumptions regarding non-aliasing
3998 of objects of different types. See
3999 @ref{Optimization and Strict Aliasing} for details.
4002 @cindex @option{-fstack-check} (@command{gcc})
4003 Activates stack checking.
4004 See @ref{Stack Overflow Checking} for details.
4007 @cindex @option{-fstack-usage} (@command{gcc})
4008 Makes the compiler output stack usage information for the program, on a
4009 per-subprogram basis. See @ref{Static Stack Usage Analysis} for details.
4011 @item -fcallgraph-info@r{[}=su@r{]}
4012 @cindex @option{-fcallgraph-info} (@command{gcc})
4013 Makes the compiler output callgraph information for the program, on a
4014 per-file basis. The information is generated in the VCG format. It can
4015 be decorated with stack-usage per-node information.
4018 @cindex @option{^-g^/DEBUG^} (@command{gcc})
4019 Generate debugging information. This information is stored in the object
4020 file and copied from there to the final executable file by the linker,
4021 where it can be read by the debugger. You must use the
4022 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
4025 @cindex @option{-gnat83} (@command{gcc})
4026 Enforce Ada 83 restrictions.
4029 @cindex @option{-gnat95} (@command{gcc})
4030 Enforce Ada 95 restrictions.
4033 @cindex @option{-gnat05} (@command{gcc})
4034 Allow full Ada 2005 features.
4037 @cindex @option{-gnat2005} (@command{gcc})
4038 Allow full Ada 2005 features (same as @option{-gnat05})
4041 @cindex @option{-gnat12} (@command{gcc})
4044 @cindex @option{-gnat2012} (@command{gcc})
4045 Allow full Ada 2012 features (same as @option{-gnat12})
4048 @cindex @option{-gnata} (@command{gcc})
4049 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
4050 activated. Note that these pragmas can also be controlled using the
4051 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
4052 It also activates pragmas @code{Check}, @code{Precondition}, and
4053 @code{Postcondition}. Note that these pragmas can also be controlled
4054 using the configuration pragma @code{Check_Policy}.
4057 @cindex @option{-gnatA} (@command{gcc})
4058 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
4062 @cindex @option{-gnatb} (@command{gcc})
4063 Generate brief messages to @file{stderr} even if verbose mode set.
4066 @cindex @option{-gnatB} (@command{gcc})
4067 Assume no invalid (bad) values except for 'Valid attribute use
4068 (@pxref{Validity Checking}).
4071 @cindex @option{-gnatc} (@command{gcc})
4072 Check syntax and semantics only (no code generation attempted).
4075 @cindex @option{-gnatC} (@command{gcc})
4076 Generate CodePeer information (no code generation attempted).
4077 This switch will generate an intermediate representation suitable for
4078 use by CodePeer (@file{.scil} files). This switch is not compatible with
4079 code generation (it will, among other things, disable some switches such
4080 as -gnatn, and enable others such as -gnata).
4083 @cindex @option{-gnatd} (@command{gcc})
4084 Specify debug options for the compiler. The string of characters after
4085 the @option{-gnatd} specify the specific debug options. The possible
4086 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
4087 compiler source file @file{debug.adb} for details of the implemented
4088 debug options. Certain debug options are relevant to applications
4089 programmers, and these are documented at appropriate points in this
4094 @cindex @option{-gnatD[nn]} (@command{gcc})
4097 @item /XDEBUG /LXDEBUG=nnn
4099 Create expanded source files for source level debugging. This switch
4100 also suppress generation of cross-reference information
4101 (see @option{-gnatx}).
4103 @item -gnatec=@var{path}
4104 @cindex @option{-gnatec} (@command{gcc})
4105 Specify a configuration pragma file
4107 (the equal sign is optional)
4109 (@pxref{The Configuration Pragmas Files}).
4111 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
4112 @cindex @option{-gnateD} (@command{gcc})
4113 Defines a symbol, associated with @var{value}, for preprocessing.
4114 (@pxref{Integrated Preprocessing}).
4117 @cindex @option{-gnateE} (@command{gcc})
4118 Generate extra information in exception messages. In particular, display
4119 extra column information and the value and range associated with index and
4120 range check failures, and extra column information for access checks.
4121 In cases where the compiler is able to determine at compile time that
4122 a check will fail, it gives a warning, and the extra information is not
4123 produced at run time.
4126 @cindex @option{-gnatef} (@command{gcc})
4127 Display full source path name in brief error messages.
4130 @cindex @option{-gnateG} (@command{gcc})
4131 Save result of preprocessing in a text file.
4133 @item -gnatem=@var{path}
4134 @cindex @option{-gnatem} (@command{gcc})
4135 Specify a mapping file
4137 (the equal sign is optional)
4139 (@pxref{Units to Sources Mapping Files}).
4141 @item -gnatep=@var{file}
4142 @cindex @option{-gnatep} (@command{gcc})
4143 Specify a preprocessing data file
4145 (the equal sign is optional)
4147 (@pxref{Integrated Preprocessing}).
4150 @cindex @option{-gnateP} (@command{gcc})
4151 Turn categorization dependency errors into warnings.
4152 Ada requires that units that WITH one another have compatible categories, for
4153 example a Pure unit cannot WITH a Preelaborate unit. If this switch is used,
4154 these errors become warnings (which can be ignored, or suppressed in the usual
4155 manner). This can be useful in some specialized circumstances such as the
4156 temporary use of special test software.
4158 @cindex @option{-gnateS} (@command{gcc})
4159 Generate SCO (Source Coverage Obligation) information in the ALI
4160 file. This information is used by advanced coverage tools. See
4161 unit @file{SCOs} in the compiler sources for details in files
4162 @file{scos.ads} and @file{scos.adb}.
4165 @cindex @option{-gnatE} (@command{gcc})
4166 Full dynamic elaboration checks.
4169 @cindex @option{-gnatf} (@command{gcc})
4170 Full errors. Multiple errors per line, all undefined references, do not
4171 attempt to suppress cascaded errors.
4174 @cindex @option{-gnatF} (@command{gcc})
4175 Externals names are folded to all uppercase.
4177 @item ^-gnatg^/GNAT_INTERNAL^
4178 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
4179 Internal GNAT implementation mode. This should not be used for
4180 applications programs, it is intended only for use by the compiler
4181 and its run-time library. For documentation, see the GNAT sources.
4182 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
4183 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
4184 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
4185 so that all standard warnings and all standard style options are turned on.
4186 All warnings and style messages are treated as errors.
4190 @cindex @option{-gnatG[nn]} (@command{gcc})
4193 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
4195 List generated expanded code in source form.
4197 @item ^-gnath^/HELP^
4198 @cindex @option{^-gnath^/HELP^} (@command{gcc})
4199 Output usage information. The output is written to @file{stdout}.
4201 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
4202 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
4203 Identifier character set
4205 (@var{c}=1/2/3/4/8/9/p/f/n/w).
4207 For details of the possible selections for @var{c},
4208 see @ref{Character Set Control}.
4210 @item ^-gnatI^/IGNORE_REP_CLAUSES^
4211 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
4212 Ignore representation clauses. When this switch is used,
4213 representation clauses are treated as comments. This is useful
4214 when initially porting code where you want to ignore rep clause
4215 problems, and also for compiling foreign code (particularly
4216 for use with ASIS). The representation clauses that are ignored
4217 are: enumeration_representation_clause, record_representation_clause,
4218 and attribute_definition_clause for the following attributes:
4219 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
4220 Object_Size, Size, Small, Stream_Size, and Value_Size.
4221 Note that this option should be used only for compiling -- the
4222 code is likely to malfunction at run time.
4225 @cindex @option{-gnatjnn} (@command{gcc})
4226 Reformat error messages to fit on nn character lines
4228 @item -gnatk=@var{n}
4229 @cindex @option{-gnatk} (@command{gcc})
4230 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4233 @cindex @option{-gnatl} (@command{gcc})
4234 Output full source listing with embedded error messages.
4237 @cindex @option{-gnatL} (@command{gcc})
4238 Used in conjunction with -gnatG or -gnatD to intersperse original
4239 source lines (as comment lines with line numbers) in the expanded
4242 @item -gnatm=@var{n}
4243 @cindex @option{-gnatm} (@command{gcc})
4244 Limit number of detected error or warning messages to @var{n}
4245 where @var{n} is in the range 1..999999. The default setting if
4246 no switch is given is 9999. If the number of warnings reaches this
4247 limit, then a message is output and further warnings are suppressed,
4248 but the compilation is continued. If the number of error messages
4249 reaches this limit, then a message is output and the compilation
4250 is abandoned. The equal sign here is optional. A value of zero
4251 means that no limit applies.
4254 @cindex @option{-gnatn} (@command{gcc})
4255 Activate inlining for subprograms for which
4256 pragma @code{Inline} is specified. This inlining is performed
4257 by the GCC back-end.
4260 @cindex @option{-gnatN} (@command{gcc})
4261 Activate front end inlining for subprograms for which
4262 pragma @code{Inline} is specified. This inlining is performed
4263 by the front end and will be visible in the
4264 @option{-gnatG} output.
4266 When using a gcc-based back end (in practice this means using any version
4267 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4268 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4269 Historically front end inlining was more extensive than the gcc back end
4270 inlining, but that is no longer the case.
4273 @cindex @option{-gnato} (@command{gcc})
4274 Enable numeric overflow checking (which is not normally enabled by
4275 default). Note that division by zero is a separate check that is not
4276 controlled by this switch (division by zero checking is on by default).
4279 @cindex @option{-gnatp} (@command{gcc})
4280 Suppress all checks. See @ref{Run-Time Checks} for details. This switch
4281 has no effect if cancelled by a subsequent @option{-gnat-p} switch.
4284 @cindex @option{-gnat-p} (@command{gcc})
4285 Cancel effect of previous @option{-gnatp} switch.
4288 @cindex @option{-gnatP} (@command{gcc})
4289 Enable polling. This is required on some systems (notably Windows NT) to
4290 obtain asynchronous abort and asynchronous transfer of control capability.
4291 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4295 @cindex @option{-gnatq} (@command{gcc})
4296 Don't quit. Try semantics, even if parse errors.
4299 @cindex @option{-gnatQ} (@command{gcc})
4300 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4303 @cindex @option{-gnatr} (@command{gcc})
4304 Treat pragma Restrictions as Restriction_Warnings.
4306 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4307 @cindex @option{-gnatR} (@command{gcc})
4308 Output representation information for declared types and objects.
4311 @cindex @option{-gnats} (@command{gcc})
4315 @cindex @option{-gnatS} (@command{gcc})
4316 Print package Standard.
4319 @cindex @option{-gnatt} (@command{gcc})
4320 Generate tree output file.
4322 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4323 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4324 All compiler tables start at @var{nnn} times usual starting size.
4327 @cindex @option{-gnatu} (@command{gcc})
4328 List units for this compilation.
4331 @cindex @option{-gnatU} (@command{gcc})
4332 Tag all error messages with the unique string ``error:''
4335 @cindex @option{-gnatv} (@command{gcc})
4336 Verbose mode. Full error output with source lines to @file{stdout}.
4339 @cindex @option{-gnatV} (@command{gcc})
4340 Control level of validity checking (@pxref{Validity Checking}).
4342 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4343 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4345 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4346 the exact warnings that
4347 are enabled or disabled (@pxref{Warning Message Control}).
4349 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4350 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4351 Wide character encoding method
4353 (@var{e}=n/h/u/s/e/8).
4356 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4360 @cindex @option{-gnatx} (@command{gcc})
4361 Suppress generation of cross-reference information.
4364 @cindex @option{-gnatX} (@command{gcc})
4365 Enable GNAT implementation extensions and latest Ada version.
4367 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4368 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4369 Enable built-in style checks (@pxref{Style Checking}).
4371 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4372 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4373 Distribution stub generation and compilation
4375 (@var{m}=r/c for receiver/caller stubs).
4378 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4379 to be generated and compiled).
4382 @item ^-I^/SEARCH=^@var{dir}
4383 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4385 Direct GNAT to search the @var{dir} directory for source files needed by
4386 the current compilation
4387 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4389 @item ^-I-^/NOCURRENT_DIRECTORY^
4390 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4392 Except for the source file named in the command line, do not look for source
4393 files in the directory containing the source file named in the command line
4394 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4398 @cindex @option{-mbig-switch} (@command{gcc})
4399 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4400 This standard gcc switch causes the compiler to use larger offsets in its
4401 jump table representation for @code{case} statements.
4402 This may result in less efficient code, but is sometimes necessary
4403 (for example on HP-UX targets)
4404 @cindex HP-UX and @option{-mbig-switch} option
4405 in order to compile large and/or nested @code{case} statements.
4408 @cindex @option{-o} (@command{gcc})
4409 This switch is used in @command{gcc} to redirect the generated object file
4410 and its associated ALI file. Beware of this switch with GNAT, because it may
4411 cause the object file and ALI file to have different names which in turn
4412 may confuse the binder and the linker.
4416 @cindex @option{-nostdinc} (@command{gcc})
4417 Inhibit the search of the default location for the GNAT Run Time
4418 Library (RTL) source files.
4421 @cindex @option{-nostdlib} (@command{gcc})
4422 Inhibit the search of the default location for the GNAT Run Time
4423 Library (RTL) ALI files.
4427 @c Expanding @ovar macro inline (explanation in macro def comments)
4428 @item -O@r{[}@var{n}@r{]}
4429 @cindex @option{-O} (@command{gcc})
4430 @var{n} controls the optimization level.
4434 No optimization, the default setting if no @option{-O} appears
4437 Normal optimization, the default if you specify @option{-O} without
4438 an operand. A good compromise between code quality and compilation
4442 Extensive optimization, may improve execution time, possibly at the cost of
4443 substantially increased compilation time.
4446 Same as @option{-O2}, and also includes inline expansion for small subprograms
4450 Optimize space usage
4454 See also @ref{Optimization Levels}.
4459 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4460 Equivalent to @option{/OPTIMIZE=NONE}.
4461 This is the default behavior in the absence of an @option{/OPTIMIZE}
4464 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4465 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4466 Selects the level of optimization for your program. The supported
4467 keywords are as follows:
4470 Perform most optimizations, including those that
4472 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4473 without keyword options.
4476 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4479 Perform some optimizations, but omit ones that are costly.
4482 Same as @code{SOME}.
4485 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4486 automatic inlining of small subprograms within a unit
4489 Try to unroll loops. This keyword may be specified together with
4490 any keyword above other than @code{NONE}. Loop unrolling
4491 usually, but not always, improves the performance of programs.
4494 Optimize space usage
4498 See also @ref{Optimization Levels}.
4502 @item -pass-exit-codes
4503 @cindex @option{-pass-exit-codes} (@command{gcc})
4504 Catch exit codes from the compiler and use the most meaningful as
4508 @item --RTS=@var{rts-path}
4509 @cindex @option{--RTS} (@command{gcc})
4510 Specifies the default location of the runtime library. Same meaning as the
4511 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4514 @cindex @option{^-S^/ASM^} (@command{gcc})
4515 ^Used in place of @option{-c} to^Used to^
4516 cause the assembler source file to be
4517 generated, using @file{^.s^.S^} as the extension,
4518 instead of the object file.
4519 This may be useful if you need to examine the generated assembly code.
4521 @item ^-fverbose-asm^/VERBOSE_ASM^
4522 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4523 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4524 to cause the generated assembly code file to be annotated with variable
4525 names, making it significantly easier to follow.
4528 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4529 Show commands generated by the @command{gcc} driver. Normally used only for
4530 debugging purposes or if you need to be sure what version of the
4531 compiler you are executing.
4535 @cindex @option{-V} (@command{gcc})
4536 Execute @var{ver} version of the compiler. This is the @command{gcc}
4537 version, not the GNAT version.
4540 @item ^-w^/NO_BACK_END_WARNINGS^
4541 @cindex @option{-w} (@command{gcc})
4542 Turn off warnings generated by the back end of the compiler. Use of
4543 this switch also causes the default for front end warnings to be set
4544 to suppress (as though @option{-gnatws} had appeared at the start of
4550 @c Combining qualifiers does not work on VMS
4551 You may combine a sequence of GNAT switches into a single switch. For
4552 example, the combined switch
4554 @cindex Combining GNAT switches
4560 is equivalent to specifying the following sequence of switches:
4563 -gnato -gnatf -gnati3
4568 The following restrictions apply to the combination of switches
4573 The switch @option{-gnatc} if combined with other switches must come
4574 first in the string.
4577 The switch @option{-gnats} if combined with other switches must come
4578 first in the string.
4582 ^^@option{/DISTRIBUTION_STUBS=},^
4583 @option{-gnatzc} and @option{-gnatzr} may not be combined with any other
4584 switches, and only one of them may appear in the command line.
4587 The switch @option{-gnat-p} may not be combined with any other switch.
4591 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4592 switch), then all further characters in the switch are interpreted
4593 as style modifiers (see description of @option{-gnaty}).
4596 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4597 switch), then all further characters in the switch are interpreted
4598 as debug flags (see description of @option{-gnatd}).
4601 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4602 switch), then all further characters in the switch are interpreted
4603 as warning mode modifiers (see description of @option{-gnatw}).
4606 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4607 switch), then all further characters in the switch are interpreted
4608 as validity checking options (@pxref{Validity Checking}).
4611 Option ``em'', ``ec'', ``ep'', ``l='' and ``R'' must be the last options in
4612 a combined list of options.
4616 @node Output and Error Message Control
4617 @subsection Output and Error Message Control
4621 The standard default format for error messages is called ``brief format''.
4622 Brief format messages are written to @file{stderr} (the standard error
4623 file) and have the following form:
4626 e.adb:3:04: Incorrect spelling of keyword "function"
4627 e.adb:4:20: ";" should be "is"
4631 The first integer after the file name is the line number in the file,
4632 and the second integer is the column number within the line.
4634 @code{GPS} can parse the error messages
4635 and point to the referenced character.
4637 The following switches provide control over the error message
4643 @cindex @option{-gnatv} (@command{gcc})
4646 The v stands for verbose.
4648 The effect of this setting is to write long-format error
4649 messages to @file{stdout} (the standard output file.
4650 The same program compiled with the
4651 @option{-gnatv} switch would generate:
4655 3. funcion X (Q : Integer)
4657 >>> Incorrect spelling of keyword "function"
4660 >>> ";" should be "is"
4665 The vertical bar indicates the location of the error, and the @samp{>>>}
4666 prefix can be used to search for error messages. When this switch is
4667 used the only source lines output are those with errors.
4670 @cindex @option{-gnatl} (@command{gcc})
4672 The @code{l} stands for list.
4674 This switch causes a full listing of
4675 the file to be generated. In the case where a body is
4676 compiled, the corresponding spec is also listed, along
4677 with any subunits. Typical output from compiling a package
4678 body @file{p.adb} might look like:
4680 @smallexample @c ada
4684 1. package body p is
4686 3. procedure a is separate;
4697 2. pragma Elaborate_Body
4721 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4722 standard output is redirected, a brief summary is written to
4723 @file{stderr} (standard error) giving the number of error messages and
4724 warning messages generated.
4726 @item ^-gnatl^/OUTPUT_FILE^=file
4727 @cindex @option{^-gnatl^/OUTPUT_FILE^=fname} (@command{gcc})
4728 This has the same effect as @option{-gnatl} except that the output is
4729 written to a file instead of to standard output. If the given name
4730 @file{fname} does not start with a period, then it is the full name
4731 of the file to be written. If @file{fname} is an extension, it is
4732 appended to the name of the file being compiled. For example, if
4733 file @file{xyz.adb} is compiled with @option{^-gnatl^/OUTPUT_FILE^=.lst},
4734 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4737 @cindex @option{-gnatU} (@command{gcc})
4738 This switch forces all error messages to be preceded by the unique
4739 string ``error:''. This means that error messages take a few more
4740 characters in space, but allows easy searching for and identification
4744 @cindex @option{-gnatb} (@command{gcc})
4746 The @code{b} stands for brief.
4748 This switch causes GNAT to generate the
4749 brief format error messages to @file{stderr} (the standard error
4750 file) as well as the verbose
4751 format message or full listing (which as usual is written to
4752 @file{stdout} (the standard output file).
4754 @item -gnatm=@var{n}
4755 @cindex @option{-gnatm} (@command{gcc})
4757 The @code{m} stands for maximum.
4759 @var{n} is a decimal integer in the
4760 range of 1 to 999999 and limits the number of error or warning
4761 messages to be generated. For example, using
4762 @option{-gnatm2} might yield
4765 e.adb:3:04: Incorrect spelling of keyword "function"
4766 e.adb:5:35: missing ".."
4767 fatal error: maximum number of errors detected
4768 compilation abandoned
4772 The default setting if
4773 no switch is given is 9999. If the number of warnings reaches this
4774 limit, then a message is output and further warnings are suppressed,
4775 but the compilation is continued. If the number of error messages
4776 reaches this limit, then a message is output and the compilation
4777 is abandoned. A value of zero means that no limit applies.
4780 Note that the equal sign is optional, so the switches
4781 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4784 @cindex @option{-gnatf} (@command{gcc})
4785 @cindex Error messages, suppressing
4787 The @code{f} stands for full.
4789 Normally, the compiler suppresses error messages that are likely to be
4790 redundant. This switch causes all error
4791 messages to be generated. In particular, in the case of
4792 references to undefined variables. If a given variable is referenced
4793 several times, the normal format of messages is
4795 e.adb:7:07: "V" is undefined (more references follow)
4799 where the parenthetical comment warns that there are additional
4800 references to the variable @code{V}. Compiling the same program with the
4801 @option{-gnatf} switch yields
4804 e.adb:7:07: "V" is undefined
4805 e.adb:8:07: "V" is undefined
4806 e.adb:8:12: "V" is undefined
4807 e.adb:8:16: "V" is undefined
4808 e.adb:9:07: "V" is undefined
4809 e.adb:9:12: "V" is undefined
4813 The @option{-gnatf} switch also generates additional information for
4814 some error messages. Some examples are:
4818 Details on possibly non-portable unchecked conversion
4820 List possible interpretations for ambiguous calls
4822 Additional details on incorrect parameters
4826 @cindex @option{-gnatjnn} (@command{gcc})
4827 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4828 with continuation lines are treated as though the continuation lines were
4829 separate messages (and so a warning with two continuation lines counts as
4830 three warnings, and is listed as three separate messages).
4832 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4833 messages are output in a different manner. A message and all its continuation
4834 lines are treated as a unit, and count as only one warning or message in the
4835 statistics totals. Furthermore, the message is reformatted so that no line
4836 is longer than nn characters.
4839 @cindex @option{-gnatq} (@command{gcc})
4841 The @code{q} stands for quit (really ``don't quit'').
4843 In normal operation mode, the compiler first parses the program and
4844 determines if there are any syntax errors. If there are, appropriate
4845 error messages are generated and compilation is immediately terminated.
4847 GNAT to continue with semantic analysis even if syntax errors have been
4848 found. This may enable the detection of more errors in a single run. On
4849 the other hand, the semantic analyzer is more likely to encounter some
4850 internal fatal error when given a syntactically invalid tree.
4853 @cindex @option{-gnatQ} (@command{gcc})
4854 In normal operation mode, the @file{ALI} file is not generated if any
4855 illegalities are detected in the program. The use of @option{-gnatQ} forces
4856 generation of the @file{ALI} file. This file is marked as being in
4857 error, so it cannot be used for binding purposes, but it does contain
4858 reasonably complete cross-reference information, and thus may be useful
4859 for use by tools (e.g., semantic browsing tools or integrated development
4860 environments) that are driven from the @file{ALI} file. This switch
4861 implies @option{-gnatq}, since the semantic phase must be run to get a
4862 meaningful ALI file.
4864 In addition, if @option{-gnatt} is also specified, then the tree file is
4865 generated even if there are illegalities. It may be useful in this case
4866 to also specify @option{-gnatq} to ensure that full semantic processing
4867 occurs. The resulting tree file can be processed by ASIS, for the purpose
4868 of providing partial information about illegal units, but if the error
4869 causes the tree to be badly malformed, then ASIS may crash during the
4872 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4873 being in error, @command{gnatmake} will attempt to recompile the source when it
4874 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4876 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4877 since ALI files are never generated if @option{-gnats} is set.
4881 @node Warning Message Control
4882 @subsection Warning Message Control
4883 @cindex Warning messages
4885 In addition to error messages, which correspond to illegalities as defined
4886 in the Ada Reference Manual, the compiler detects two kinds of warning
4889 First, the compiler considers some constructs suspicious and generates a
4890 warning message to alert you to a possible error. Second, if the
4891 compiler detects a situation that is sure to raise an exception at
4892 run time, it generates a warning message. The following shows an example
4893 of warning messages:
4895 e.adb:4:24: warning: creation of object may raise Storage_Error
4896 e.adb:10:17: warning: static value out of range
4897 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4901 GNAT considers a large number of situations as appropriate
4902 for the generation of warning messages. As always, warnings are not
4903 definite indications of errors. For example, if you do an out-of-range
4904 assignment with the deliberate intention of raising a
4905 @code{Constraint_Error} exception, then the warning that may be
4906 issued does not indicate an error. Some of the situations for which GNAT
4907 issues warnings (at least some of the time) are given in the following
4908 list. This list is not complete, and new warnings are often added to
4909 subsequent versions of GNAT. The list is intended to give a general idea
4910 of the kinds of warnings that are generated.
4914 Possible infinitely recursive calls
4917 Out-of-range values being assigned
4920 Possible order of elaboration problems
4923 Assertions (pragma Assert) that are sure to fail
4929 Address clauses with possibly unaligned values, or where an attempt is
4930 made to overlay a smaller variable with a larger one.
4933 Fixed-point type declarations with a null range
4936 Direct_IO or Sequential_IO instantiated with a type that has access values
4939 Variables that are never assigned a value
4942 Variables that are referenced before being initialized
4945 Task entries with no corresponding @code{accept} statement
4948 Duplicate accepts for the same task entry in a @code{select}
4951 Objects that take too much storage
4954 Unchecked conversion between types of differing sizes
4957 Missing @code{return} statement along some execution path in a function
4960 Incorrect (unrecognized) pragmas
4963 Incorrect external names
4966 Allocation from empty storage pool
4969 Potentially blocking operation in protected type
4972 Suspicious parenthesization of expressions
4975 Mismatching bounds in an aggregate
4978 Attempt to return local value by reference
4981 Premature instantiation of a generic body
4984 Attempt to pack aliased components
4987 Out of bounds array subscripts
4990 Wrong length on string assignment
4993 Violations of style rules if style checking is enabled
4996 Unused @code{with} clauses
4999 @code{Bit_Order} usage that does not have any effect
5002 @code{Standard.Duration} used to resolve universal fixed expression
5005 Dereference of possibly null value
5008 Declaration that is likely to cause storage error
5011 Internal GNAT unit @code{with}'ed by application unit
5014 Values known to be out of range at compile time
5017 Unreferenced labels and variables
5020 Address overlays that could clobber memory
5023 Unexpected initialization when address clause present
5026 Bad alignment for address clause
5029 Useless type conversions
5032 Redundant assignment statements and other redundant constructs
5035 Useless exception handlers
5038 Accidental hiding of name by child unit
5041 Access before elaboration detected at compile time
5044 A range in a @code{for} loop that is known to be null or might be null
5049 The following section lists compiler switches that are available
5050 to control the handling of warning messages. It is also possible
5051 to exercise much finer control over what warnings are issued and
5052 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
5053 gnat_rm, GNAT Reference manual}.
5058 @emph{Activate most optional warnings.}
5059 @cindex @option{-gnatwa} (@command{gcc})
5060 This switch activates most optional warning messages. See the remaining list
5061 in this section for details on optional warning messages that can be
5062 individually controlled. The warnings that are not turned on by this
5064 @option{-gnatwd} (implicit dereferencing),
5065 @option{-gnatwh} (hiding),
5066 @option{-gnatw.h} (holes (gaps) in record layouts)
5067 @option{-gnatwl} (elaboration warnings),
5068 @option{-gnatw.o} (warn on values set by out parameters ignored)
5069 and @option{-gnatwt} (tracking of deleted conditional code).
5070 All other optional warnings are turned on.
5073 @emph{Suppress all optional errors.}
5074 @cindex @option{-gnatwA} (@command{gcc})
5075 This switch suppresses all optional warning messages, see remaining list
5076 in this section for details on optional warning messages that can be
5077 individually controlled.
5080 @emph{Activate warnings on failing assertions.}
5081 @cindex @option{-gnatw.a} (@command{gcc})
5082 @cindex Assert failures
5083 This switch activates warnings for assertions where the compiler can tell at
5084 compile time that the assertion will fail. Note that this warning is given
5085 even if assertions are disabled. The default is that such warnings are
5089 @emph{Suppress warnings on failing assertions.}
5090 @cindex @option{-gnatw.A} (@command{gcc})
5091 @cindex Assert failures
5092 This switch suppresses warnings for assertions where the compiler can tell at
5093 compile time that the assertion will fail.
5096 @emph{Activate warnings on bad fixed values.}
5097 @cindex @option{-gnatwb} (@command{gcc})
5098 @cindex Bad fixed values
5099 @cindex Fixed-point Small value
5101 This switch activates warnings for static fixed-point expressions whose
5102 value is not an exact multiple of Small. Such values are implementation
5103 dependent, since an implementation is free to choose either of the multiples
5104 that surround the value. GNAT always chooses the closer one, but this is not
5105 required behavior, and it is better to specify a value that is an exact
5106 multiple, ensuring predictable execution. The default is that such warnings
5110 @emph{Suppress warnings on bad fixed values.}
5111 @cindex @option{-gnatwB} (@command{gcc})
5112 This switch suppresses warnings for static fixed-point expressions whose
5113 value is not an exact multiple of Small.
5116 @emph{Activate warnings on biased representation.}
5117 @cindex @option{-gnatw.b} (@command{gcc})
5118 @cindex Biased representation
5119 This switch activates warnings when a size clause, value size clause, component
5120 clause, or component size clause forces the use of biased representation for an
5121 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
5122 to represent 10/11). The default is that such warnings are generated.
5125 @emph{Suppress warnings on biased representation.}
5126 @cindex @option{-gnatwB} (@command{gcc})
5127 This switch suppresses warnings for representation clauses that force the use
5128 of biased representation.
5131 @emph{Activate warnings on conditionals.}
5132 @cindex @option{-gnatwc} (@command{gcc})
5133 @cindex Conditionals, constant
5134 This switch activates warnings for conditional expressions used in
5135 tests that are known to be True or False at compile time. The default
5136 is that such warnings are not generated.
5137 Note that this warning does
5138 not get issued for the use of boolean variables or constants whose
5139 values are known at compile time, since this is a standard technique
5140 for conditional compilation in Ada, and this would generate too many
5141 false positive warnings.
5143 This warning option also activates a special test for comparisons using
5144 the operators ``>='' and`` <=''.
5145 If the compiler can tell that only the equality condition is possible,
5146 then it will warn that the ``>'' or ``<'' part of the test
5147 is useless and that the operator could be replaced by ``=''.
5148 An example would be comparing a @code{Natural} variable <= 0.
5150 This warning option also generates warnings if
5151 one or both tests is optimized away in a membership test for integer
5152 values if the result can be determined at compile time. Range tests on
5153 enumeration types are not included, since it is common for such tests
5154 to include an end point.
5156 This warning can also be turned on using @option{-gnatwa}.
5159 @emph{Suppress warnings on conditionals.}
5160 @cindex @option{-gnatwC} (@command{gcc})
5161 This switch suppresses warnings for conditional expressions used in
5162 tests that are known to be True or False at compile time.
5165 @emph{Activate warnings on missing component clauses.}
5166 @cindex @option{-gnatw.c} (@command{gcc})
5167 @cindex Component clause, missing
5168 This switch activates warnings for record components where a record
5169 representation clause is present and has component clauses for the
5170 majority, but not all, of the components. A warning is given for each
5171 component for which no component clause is present.
5173 This warning can also be turned on using @option{-gnatwa}.
5176 @emph{Suppress warnings on missing component clauses.}
5177 @cindex @option{-gnatwC} (@command{gcc})
5178 This switch suppresses warnings for record components that are
5179 missing a component clause in the situation described above.
5182 @emph{Activate warnings on implicit dereferencing.}
5183 @cindex @option{-gnatwd} (@command{gcc})
5184 If this switch is set, then the use of a prefix of an access type
5185 in an indexed component, slice, or selected component without an
5186 explicit @code{.all} will generate a warning. With this warning
5187 enabled, access checks occur only at points where an explicit
5188 @code{.all} appears in the source code (assuming no warnings are
5189 generated as a result of this switch). The default is that such
5190 warnings are not generated.
5191 Note that @option{-gnatwa} does not affect the setting of
5192 this warning option.
5195 @emph{Suppress warnings on implicit dereferencing.}
5196 @cindex @option{-gnatwD} (@command{gcc})
5197 @cindex Implicit dereferencing
5198 @cindex Dereferencing, implicit
5199 This switch suppresses warnings for implicit dereferences in
5200 indexed components, slices, and selected components.
5203 @emph{Treat warnings and style checks as errors.}
5204 @cindex @option{-gnatwe} (@command{gcc})
5205 @cindex Warnings, treat as error
5206 This switch causes warning messages and style check messages to be
5208 The warning string still appears, but the warning messages are counted
5209 as errors, and prevent the generation of an object file. Note that this
5210 is the only -gnatw switch that affects the handling of style check messages.
5213 @emph{Activate every optional warning}
5214 @cindex @option{-gnatw.e} (@command{gcc})
5215 @cindex Warnings, activate every optional warning
5216 This switch activates all optional warnings, including those which
5217 are not activated by @code{-gnatwa}.
5220 @emph{Activate warnings on unreferenced formals.}
5221 @cindex @option{-gnatwf} (@command{gcc})
5222 @cindex Formals, unreferenced
5223 This switch causes a warning to be generated if a formal parameter
5224 is not referenced in the body of the subprogram. This warning can
5225 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
5226 default is that these warnings are not generated.
5229 @emph{Suppress warnings on unreferenced formals.}
5230 @cindex @option{-gnatwF} (@command{gcc})
5231 This switch suppresses warnings for unreferenced formal
5232 parameters. Note that the
5233 combination @option{-gnatwu} followed by @option{-gnatwF} has the
5234 effect of warning on unreferenced entities other than subprogram
5238 @emph{Activate warnings on unrecognized pragmas.}
5239 @cindex @option{-gnatwg} (@command{gcc})
5240 @cindex Pragmas, unrecognized
5241 This switch causes a warning to be generated if an unrecognized
5242 pragma is encountered. Apart from issuing this warning, the
5243 pragma is ignored and has no effect. This warning can
5244 also be turned on using @option{-gnatwa}. The default
5245 is that such warnings are issued (satisfying the Ada Reference
5246 Manual requirement that such warnings appear).
5249 @emph{Suppress warnings on unrecognized pragmas.}
5250 @cindex @option{-gnatwG} (@command{gcc})
5251 This switch suppresses warnings for unrecognized pragmas.
5254 @emph{Activate warnings on hiding.}
5255 @cindex @option{-gnatwh} (@command{gcc})
5256 @cindex Hiding of Declarations
5257 This switch activates warnings on hiding declarations.
5258 A declaration is considered hiding
5259 if it is for a non-overloadable entity, and it declares an entity with the
5260 same name as some other entity that is directly or use-visible. The default
5261 is that such warnings are not generated.
5262 Note that @option{-gnatwa} does not affect the setting of this warning option.
5265 @emph{Suppress warnings on hiding.}
5266 @cindex @option{-gnatwH} (@command{gcc})
5267 This switch suppresses warnings on hiding declarations.
5270 @emph{Activate warnings on holes/gaps in records.}
5271 @cindex @option{-gnatw.h} (@command{gcc})
5272 @cindex Record Representation (gaps)
5273 This switch activates warnings on component clauses in record
5274 representation clauses that leave holes (gaps) in the record layout.
5275 If this warning option is active, then record representation clauses
5276 should specify a contiguous layout, adding unused fill fields if needed.
5277 Note that @option{-gnatwa} does not affect the setting of this warning option.
5280 @emph{Suppress warnings on holes/gaps in records.}
5281 @cindex @option{-gnatw.H} (@command{gcc})
5282 This switch suppresses warnings on component clauses in record
5283 representation clauses that leave holes (haps) in the record layout.
5286 @emph{Activate warnings on implementation units.}
5287 @cindex @option{-gnatwi} (@command{gcc})
5288 This switch activates warnings for a @code{with} of an internal GNAT
5289 implementation unit, defined as any unit from the @code{Ada},
5290 @code{Interfaces}, @code{GNAT},
5291 ^^@code{DEC},^ or @code{System}
5292 hierarchies that is not
5293 documented in either the Ada Reference Manual or the GNAT
5294 Programmer's Reference Manual. Such units are intended only
5295 for internal implementation purposes and should not be @code{with}'ed
5296 by user programs. The default is that such warnings are generated
5297 This warning can also be turned on using @option{-gnatwa}.
5300 @emph{Disable warnings on implementation units.}
5301 @cindex @option{-gnatwI} (@command{gcc})
5302 This switch disables warnings for a @code{with} of an internal GNAT
5303 implementation unit.
5306 @emph{Activate warnings on overlapping actuals.}
5307 @cindex @option{-gnatw.i} (@command{gcc})
5308 This switch enables a warning on statically detectable overlapping actuals in
5309 a subprogram call, when one of the actuals is an in-out parameter, and the
5310 types of the actuals are not by-copy types. The warning is off by default,
5311 and is not included under -gnatwa.
5314 @emph{Disable warnings on overlapping actuals.}
5315 @cindex @option{-gnatw.I} (@command{gcc})
5316 This switch disables warnings on overlapping actuals in a call..
5319 @emph{Activate warnings on obsolescent features (Annex J).}
5320 @cindex @option{-gnatwj} (@command{gcc})
5321 @cindex Features, obsolescent
5322 @cindex Obsolescent features
5323 If this warning option is activated, then warnings are generated for
5324 calls to subprograms marked with @code{pragma Obsolescent} and
5325 for use of features in Annex J of the Ada Reference Manual. In the
5326 case of Annex J, not all features are flagged. In particular use
5327 of the renamed packages (like @code{Text_IO}) and use of package
5328 @code{ASCII} are not flagged, since these are very common and
5329 would generate many annoying positive warnings. The default is that
5330 such warnings are not generated. This warning is also turned on by
5331 the use of @option{-gnatwa}.
5333 In addition to the above cases, warnings are also generated for
5334 GNAT features that have been provided in past versions but which
5335 have been superseded (typically by features in the new Ada standard).
5336 For example, @code{pragma Ravenscar} will be flagged since its
5337 function is replaced by @code{pragma Profile(Ravenscar)}.
5339 Note that this warning option functions differently from the
5340 restriction @code{No_Obsolescent_Features} in two respects.
5341 First, the restriction applies only to annex J features.
5342 Second, the restriction does flag uses of package @code{ASCII}.
5345 @emph{Suppress warnings on obsolescent features (Annex J).}
5346 @cindex @option{-gnatwJ} (@command{gcc})
5347 This switch disables warnings on use of obsolescent features.
5350 @emph{Activate warnings on variables that could be constants.}
5351 @cindex @option{-gnatwk} (@command{gcc})
5352 This switch activates warnings for variables that are initialized but
5353 never modified, and then could be declared constants. The default is that
5354 such warnings are not given.
5355 This warning can also be turned on using @option{-gnatwa}.
5358 @emph{Suppress warnings on variables that could be constants.}
5359 @cindex @option{-gnatwK} (@command{gcc})
5360 This switch disables warnings on variables that could be declared constants.
5363 @emph{Activate warnings for elaboration pragmas.}
5364 @cindex @option{-gnatwl} (@command{gcc})
5365 @cindex Elaboration, warnings
5366 This switch activates warnings on missing
5367 @code{Elaborate_All} and @code{Elaborate} pragmas.
5368 See the section in this guide on elaboration checking for details on
5369 when such pragmas should be used. In dynamic elaboration mode, this switch
5370 generations warnings about the need to add elaboration pragmas. Note however,
5371 that if you blindly follow these warnings, and add @code{Elaborate_All}
5372 warnings wherever they are recommended, you basically end up with the
5373 equivalent of the static elaboration model, which may not be what you want for
5374 legacy code for which the static model does not work.
5376 For the static model, the messages generated are labeled "info:" (for
5377 information messages). They are not warnings to add elaboration pragmas,
5378 merely informational messages showing what implicit elaboration pragmas
5379 have been added, for use in analyzing elaboration circularity problems.
5381 Warnings are also generated if you
5382 are using the static mode of elaboration, and a @code{pragma Elaborate}
5383 is encountered. The default is that such warnings
5385 This warning is not automatically turned on by the use of @option{-gnatwa}.
5388 @emph{Suppress warnings for elaboration pragmas.}
5389 @cindex @option{-gnatwL} (@command{gcc})
5390 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5391 See the section in this guide on elaboration checking for details on
5392 when such pragmas should be used.
5395 @emph{Activate warnings on modified but unreferenced variables.}
5396 @cindex @option{-gnatwm} (@command{gcc})
5397 This switch activates warnings for variables that are assigned (using
5398 an initialization value or with one or more assignment statements) but
5399 whose value is never read. The warning is suppressed for volatile
5400 variables and also for variables that are renamings of other variables
5401 or for which an address clause is given.
5402 This warning can also be turned on using @option{-gnatwa}.
5403 The default is that these warnings are not given.
5406 @emph{Disable warnings on modified but unreferenced variables.}
5407 @cindex @option{-gnatwM} (@command{gcc})
5408 This switch disables warnings for variables that are assigned or
5409 initialized, but never read.
5412 @emph{Activate warnings on suspicious modulus values.}
5413 @cindex @option{-gnatw.m} (@command{gcc})
5414 This switch activates warnings for modulus values that seem suspicious.
5415 The cases caught are where the size is the same as the modulus (e.g.
5416 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
5417 with no size clause. The guess in both cases is that 2**x was intended
5418 rather than x. The default is that these warnings are given.
5421 @emph{Disable warnings on suspicious modulus values.}
5422 @cindex @option{-gnatw.M} (@command{gcc})
5423 This switch disables warnings for suspicious modulus values.
5426 @emph{Set normal warnings mode.}
5427 @cindex @option{-gnatwn} (@command{gcc})
5428 This switch sets normal warning mode, in which enabled warnings are
5429 issued and treated as warnings rather than errors. This is the default
5430 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5431 an explicit @option{-gnatws} or
5432 @option{-gnatwe}. It also cancels the effect of the
5433 implicit @option{-gnatwe} that is activated by the
5434 use of @option{-gnatg}.
5437 @emph{Activate warnings on address clause overlays.}
5438 @cindex @option{-gnatwo} (@command{gcc})
5439 @cindex Address Clauses, warnings
5440 This switch activates warnings for possibly unintended initialization
5441 effects of defining address clauses that cause one variable to overlap
5442 another. The default is that such warnings are generated.
5443 This warning can also be turned on using @option{-gnatwa}.
5446 @emph{Suppress warnings on address clause overlays.}
5447 @cindex @option{-gnatwO} (@command{gcc})
5448 This switch suppresses warnings on possibly unintended initialization
5449 effects of defining address clauses that cause one variable to overlap
5453 @emph{Activate warnings on modified but unreferenced out parameters.}
5454 @cindex @option{-gnatw.o} (@command{gcc})
5455 This switch activates warnings for variables that are modified by using
5456 them as actuals for a call to a procedure with an out mode formal, where
5457 the resulting assigned value is never read. It is applicable in the case
5458 where there is more than one out mode formal. If there is only one out
5459 mode formal, the warning is issued by default (controlled by -gnatwu).
5460 The warning is suppressed for volatile
5461 variables and also for variables that are renamings of other variables
5462 or for which an address clause is given.
5463 The default is that these warnings are not given. Note that this warning
5464 is not included in -gnatwa, it must be activated explicitly.
5467 @emph{Disable warnings on modified but unreferenced out parameters.}
5468 @cindex @option{-gnatw.O} (@command{gcc})
5469 This switch suppresses warnings for variables that are modified by using
5470 them as actuals for a call to a procedure with an out mode formal, where
5471 the resulting assigned value is never read.
5474 @emph{Activate warnings on ineffective pragma Inlines.}
5475 @cindex @option{-gnatwp} (@command{gcc})
5476 @cindex Inlining, warnings
5477 This switch activates warnings for failure of front end inlining
5478 (activated by @option{-gnatN}) to inline a particular call. There are
5479 many reasons for not being able to inline a call, including most
5480 commonly that the call is too complex to inline. The default is
5481 that such warnings are not given.
5482 This warning can also be turned on using @option{-gnatwa}.
5483 Warnings on ineffective inlining by the gcc back-end can be activated
5484 separately, using the gcc switch -Winline.
5487 @emph{Suppress warnings on ineffective pragma Inlines.}
5488 @cindex @option{-gnatwP} (@command{gcc})
5489 This switch suppresses warnings on ineffective pragma Inlines. If the
5490 inlining mechanism cannot inline a call, it will simply ignore the
5494 @emph{Activate warnings on parameter ordering.}
5495 @cindex @option{-gnatw.p} (@command{gcc})
5496 @cindex Parameter order, warnings
5497 This switch activates warnings for cases of suspicious parameter
5498 ordering when the list of arguments are all simple identifiers that
5499 match the names of the formals, but are in a different order. The
5500 warning is suppressed if any use of named parameter notation is used,
5501 so this is the appropriate way to suppress a false positive (and
5502 serves to emphasize that the "misordering" is deliberate). The
5504 that such warnings are not given.
5505 This warning can also be turned on using @option{-gnatwa}.
5508 @emph{Suppress warnings on parameter ordering.}
5509 @cindex @option{-gnatw.P} (@command{gcc})
5510 This switch suppresses warnings on cases of suspicious parameter
5514 @emph{Activate warnings on questionable missing parentheses.}
5515 @cindex @option{-gnatwq} (@command{gcc})
5516 @cindex Parentheses, warnings
5517 This switch activates warnings for cases where parentheses are not used and
5518 the result is potential ambiguity from a readers point of view. For example
5519 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5520 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5521 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5522 follow the rule of always parenthesizing to make the association clear, and
5523 this warning switch warns if such parentheses are not present. The default
5524 is that these warnings are given.
5525 This warning can also be turned on using @option{-gnatwa}.
5528 @emph{Suppress warnings on questionable missing parentheses.}
5529 @cindex @option{-gnatwQ} (@command{gcc})
5530 This switch suppresses warnings for cases where the association is not
5531 clear and the use of parentheses is preferred.
5534 @emph{Activate warnings on redundant constructs.}
5535 @cindex @option{-gnatwr} (@command{gcc})
5536 This switch activates warnings for redundant constructs. The following
5537 is the current list of constructs regarded as redundant:
5541 Assignment of an item to itself.
5543 Type conversion that converts an expression to its own type.
5545 Use of the attribute @code{Base} where @code{typ'Base} is the same
5548 Use of pragma @code{Pack} when all components are placed by a record
5549 representation clause.
5551 Exception handler containing only a reraise statement (raise with no
5552 operand) which has no effect.
5554 Use of the operator abs on an operand that is known at compile time
5557 Comparison of boolean expressions to an explicit True value.
5560 This warning can also be turned on using @option{-gnatwa}.
5561 The default is that warnings for redundant constructs are not given.
5564 @emph{Suppress warnings on redundant constructs.}
5565 @cindex @option{-gnatwR} (@command{gcc})
5566 This switch suppresses warnings for redundant constructs.
5569 @emph{Activate warnings for object renaming function.}
5570 @cindex @option{-gnatw.r} (@command{gcc})
5571 This switch activates warnings for an object renaming that renames a
5572 function call, which is equivalent to a constant declaration (as
5573 opposed to renaming the function itself). The default is that these
5574 warnings are given. This warning can also be turned on using
5578 @emph{Suppress warnings for object renaming function.}
5579 @cindex @option{-gnatwT} (@command{gcc})
5580 This switch suppresses warnings for object renaming function.
5583 @emph{Suppress all warnings.}
5584 @cindex @option{-gnatws} (@command{gcc})
5585 This switch completely suppresses the
5586 output of all warning messages from the GNAT front end.
5587 Note that it does not suppress warnings from the @command{gcc} back end.
5588 To suppress these back end warnings as well, use the switch @option{-w}
5589 in addition to @option{-gnatws}. Also this switch has no effect on the
5590 handling of style check messages.
5593 @emph{Activate warnings on overridden size clauses.}
5594 @cindex @option{-gnatw.s} (@command{gcc})
5595 @cindex Record Representation (component sizes)
5596 This switch activates warnings on component clauses in record
5597 representation clauses where the length given overrides that
5598 specified by an explicit size clause for the component type. A
5599 warning is similarly given in the array case if a specified
5600 component size overrides an explicit size clause for the array
5602 Note that @option{-gnatwa} does not affect the setting of this warning option.
5605 @emph{Suppress warnings on overridden size clauses.}
5606 @cindex @option{-gnatw.S} (@command{gcc})
5607 This switch suppresses warnings on component clauses in record
5608 representation clauses that override size clauses, and similar
5609 warnings when an array component size overrides a size clause.
5612 @emph{Activate warnings for tracking of deleted conditional code.}
5613 @cindex @option{-gnatwt} (@command{gcc})
5614 @cindex Deactivated code, warnings
5615 @cindex Deleted code, warnings
5616 This switch activates warnings for tracking of code in conditionals (IF and
5617 CASE statements) that is detected to be dead code which cannot be executed, and
5618 which is removed by the front end. This warning is off by default, and is not
5619 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5620 useful for detecting deactivated code in certified applications.
5623 @emph{Suppress warnings for tracking of deleted conditional code.}
5624 @cindex @option{-gnatwT} (@command{gcc})
5625 This switch suppresses warnings for tracking of deleted conditional code.
5628 @emph{Activate warnings on unused entities.}
5629 @cindex @option{-gnatwu} (@command{gcc})
5630 This switch activates warnings to be generated for entities that
5631 are declared but not referenced, and for units that are @code{with}'ed
5633 referenced. In the case of packages, a warning is also generated if
5634 no entities in the package are referenced. This means that if the package
5635 is referenced but the only references are in @code{use}
5636 clauses or @code{renames}
5637 declarations, a warning is still generated. A warning is also generated
5638 for a generic package that is @code{with}'ed but never instantiated.
5639 In the case where a package or subprogram body is compiled, and there
5640 is a @code{with} on the corresponding spec
5641 that is only referenced in the body,
5642 a warning is also generated, noting that the
5643 @code{with} can be moved to the body. The default is that
5644 such warnings are not generated.
5645 This switch also activates warnings on unreferenced formals
5646 (it includes the effect of @option{-gnatwf}).
5647 This warning can also be turned on using @option{-gnatwa}.
5650 @emph{Suppress warnings on unused entities.}
5651 @cindex @option{-gnatwU} (@command{gcc})
5652 This switch suppresses warnings for unused entities and packages.
5653 It also turns off warnings on unreferenced formals (and thus includes
5654 the effect of @option{-gnatwF}).
5657 @emph{Activate warnings on unordered enumeration types.}
5658 @cindex @option{-gnatw.u} (@command{gcc})
5659 This switch causes enumeration types to be considered as conceptually
5660 unordered, unless an explicit pragma @code{Ordered} is given for the type.
5661 The effect is to generate warnings in clients that use explicit comparisons
5662 or subranges, since these constructs both treat objects of the type as
5663 ordered. (A @emph{client} is defined as a unit that is other than the unit in
5664 which the type is declared, or its body or subunits.) Please refer to
5665 the description of pragma @code{Ordered} in the
5666 @cite{@value{EDITION} Reference Manual} for further details.
5669 @emph{Deactivate warnings on unordered enumeration types.}
5670 @cindex @option{-gnatw.U} (@command{gcc})
5671 This switch causes all enumeration types to be considered as ordered, so
5672 that no warnings are given for comparisons or subranges for any type.
5675 @emph{Activate warnings on unassigned variables.}
5676 @cindex @option{-gnatwv} (@command{gcc})
5677 @cindex Unassigned variable warnings
5678 This switch activates warnings for access to variables which
5679 may not be properly initialized. The default is that
5680 such warnings are generated.
5681 This warning can also be turned on using @option{-gnatwa}.
5684 @emph{Suppress warnings on unassigned variables.}
5685 @cindex @option{-gnatwV} (@command{gcc})
5686 This switch suppresses warnings for access to variables which
5687 may not be properly initialized.
5688 For variables of a composite type, the warning can also be suppressed in
5689 Ada 2005 by using a default initialization with a box. For example, if
5690 Table is an array of records whose components are only partially uninitialized,
5691 then the following code:
5693 @smallexample @c ada
5694 Tab : Table := (others => <>);
5697 will suppress warnings on subsequent statements that access components
5701 @emph{Activate warnings on wrong low bound assumption.}
5702 @cindex @option{-gnatww} (@command{gcc})
5703 @cindex String indexing warnings
5704 This switch activates warnings for indexing an unconstrained string parameter
5705 with a literal or S'Length. This is a case where the code is assuming that the
5706 low bound is one, which is in general not true (for example when a slice is
5707 passed). The default is that such warnings are generated.
5708 This warning can also be turned on using @option{-gnatwa}.
5711 @emph{Suppress warnings on wrong low bound assumption.}
5712 @cindex @option{-gnatwW} (@command{gcc})
5713 This switch suppresses warnings for indexing an unconstrained string parameter
5714 with a literal or S'Length. Note that this warning can also be suppressed
5715 in a particular case by adding an
5716 assertion that the lower bound is 1,
5717 as shown in the following example.
5719 @smallexample @c ada
5720 procedure K (S : String) is
5721 pragma Assert (S'First = 1);
5726 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5727 @cindex @option{-gnatw.w} (@command{gcc})
5728 @cindex Warnings Off control
5729 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5730 where either the pragma is entirely useless (because it suppresses no
5731 warnings), or it could be replaced by @code{pragma Unreferenced} or
5732 @code{pragma Unmodified}.The default is that these warnings are not given.
5733 Note that this warning is not included in -gnatwa, it must be
5734 activated explicitly.
5737 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5738 @cindex @option{-gnatw.W} (@command{gcc})
5739 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5742 @emph{Activate warnings on Export/Import pragmas.}
5743 @cindex @option{-gnatwx} (@command{gcc})
5744 @cindex Export/Import pragma warnings
5745 This switch activates warnings on Export/Import pragmas when
5746 the compiler detects a possible conflict between the Ada and
5747 foreign language calling sequences. For example, the use of
5748 default parameters in a convention C procedure is dubious
5749 because the C compiler cannot supply the proper default, so
5750 a warning is issued. The default is that such warnings are
5752 This warning can also be turned on using @option{-gnatwa}.
5755 @emph{Suppress warnings on Export/Import pragmas.}
5756 @cindex @option{-gnatwX} (@command{gcc})
5757 This switch suppresses warnings on Export/Import pragmas.
5758 The sense of this is that you are telling the compiler that
5759 you know what you are doing in writing the pragma, and it
5760 should not complain at you.
5763 @emph{Activate warnings for No_Exception_Propagation mode.}
5764 @cindex @option{-gnatwm} (@command{gcc})
5765 This switch activates warnings for exception usage when pragma Restrictions
5766 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5767 explicit exception raises which are not covered by a local handler, and for
5768 exception handlers which do not cover a local raise. The default is that these
5769 warnings are not given.
5772 @emph{Disable warnings for No_Exception_Propagation mode.}
5773 This switch disables warnings for exception usage when pragma Restrictions
5774 (No_Exception_Propagation) is in effect.
5777 @emph{Activate warnings for Ada 2005 compatibility issues.}
5778 @cindex @option{-gnatwy} (@command{gcc})
5779 @cindex Ada 2005 compatibility issues warnings
5780 For the most part Ada 2005 is upwards compatible with Ada 95,
5781 but there are some exceptions (for example the fact that
5782 @code{interface} is now a reserved word in Ada 2005). This
5783 switch activates several warnings to help in identifying
5784 and correcting such incompatibilities. The default is that
5785 these warnings are generated. Note that at one point Ada 2005
5786 was called Ada 0Y, hence the choice of character.
5787 This warning can also be turned on using @option{-gnatwa}.
5790 @emph{Disable warnings for Ada 2005 compatibility issues.}
5791 @cindex @option{-gnatwY} (@command{gcc})
5792 @cindex Ada 2005 compatibility issues warnings
5793 This switch suppresses several warnings intended to help in identifying
5794 incompatibilities between Ada 95 and Ada 2005.
5797 @emph{Activate warnings on unchecked conversions.}
5798 @cindex @option{-gnatwz} (@command{gcc})
5799 @cindex Unchecked_Conversion warnings
5800 This switch activates warnings for unchecked conversions
5801 where the types are known at compile time to have different
5803 is that such warnings are generated. Warnings are also
5804 generated for subprogram pointers with different conventions,
5805 and, on VMS only, for data pointers with different conventions.
5806 This warning can also be turned on using @option{-gnatwa}.
5809 @emph{Suppress warnings on unchecked conversions.}
5810 @cindex @option{-gnatwZ} (@command{gcc})
5811 This switch suppresses warnings for unchecked conversions
5812 where the types are known at compile time to have different
5813 sizes or conventions.
5815 @item ^-Wunused^WARNINGS=UNUSED^
5816 @cindex @option{-Wunused}
5817 The warnings controlled by the @option{-gnatw} switch are generated by
5818 the front end of the compiler. The @option{GCC} back end can provide
5819 additional warnings and they are controlled by the @option{-W} switch.
5820 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5821 warnings for entities that are declared but not referenced.
5823 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5824 @cindex @option{-Wuninitialized}
5825 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5826 the back end warning for uninitialized variables. This switch must be
5827 used in conjunction with an optimization level greater than zero.
5829 @item -Wstack-usage=@var{len}
5830 @cindex @option{-Wstack-usage}
5831 Warn if the stack usage of a subprogram might be larger than @var{len} bytes.
5832 See @ref{Static Stack Usage Analysis} for details.
5834 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5835 @cindex @option{-Wall}
5836 This switch enables most warnings from the @option{GCC} back end.
5837 The code generator detects a number of warning situations that are missed
5838 by the @option{GNAT} front end, and this switch can be used to activate them.
5839 The use of this switch also sets the default front end warning mode to
5840 @option{-gnatwa}, that is, most front end warnings activated as well.
5842 @item ^-w^/NO_BACK_END_WARNINGS^
5844 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5845 The use of this switch also sets the default front end warning mode to
5846 @option{-gnatws}, that is, front end warnings suppressed as well.
5852 A string of warning parameters can be used in the same parameter. For example:
5859 will turn on all optional warnings except for elaboration pragma warnings,
5860 and also specify that warnings should be treated as errors.
5862 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5887 @node Debugging and Assertion Control
5888 @subsection Debugging and Assertion Control
5892 @cindex @option{-gnata} (@command{gcc})
5898 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5899 are ignored. This switch, where @samp{a} stands for assert, causes
5900 @code{Assert} and @code{Debug} pragmas to be activated.
5902 The pragmas have the form:
5906 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5907 @var{static-string-expression}@r{]})
5908 @b{pragma} Debug (@var{procedure call})
5913 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5914 If the result is @code{True}, the pragma has no effect (other than
5915 possible side effects from evaluating the expression). If the result is
5916 @code{False}, the exception @code{Assert_Failure} declared in the package
5917 @code{System.Assertions} is
5918 raised (passing @var{static-string-expression}, if present, as the
5919 message associated with the exception). If no string expression is
5920 given the default is a string giving the file name and line number
5923 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5924 @code{pragma Debug} may appear within a declaration sequence, allowing
5925 debugging procedures to be called between declarations.
5928 @item /DEBUG@r{[}=debug-level@r{]}
5930 Specifies how much debugging information is to be included in
5931 the resulting object file where 'debug-level' is one of the following:
5934 Include both debugger symbol records and traceback
5936 This is the default setting.
5938 Include both debugger symbol records and traceback in
5941 Excludes both debugger symbol records and traceback
5942 the object file. Same as /NODEBUG.
5944 Includes only debugger symbol records in the object
5945 file. Note that this doesn't include traceback information.
5950 @node Validity Checking
5951 @subsection Validity Checking
5952 @findex Validity Checking
5955 The Ada Reference Manual defines the concept of invalid values (see
5956 RM 13.9.1). The primary source of invalid values is uninitialized
5957 variables. A scalar variable that is left uninitialized may contain
5958 an invalid value; the concept of invalid does not apply to access or
5961 It is an error to read an invalid value, but the RM does not require
5962 run-time checks to detect such errors, except for some minimal
5963 checking to prevent erroneous execution (i.e. unpredictable
5964 behavior). This corresponds to the @option{-gnatVd} switch below,
5965 which is the default. For example, by default, if the expression of a
5966 case statement is invalid, it will raise Constraint_Error rather than
5967 causing a wild jump, and if an array index on the left-hand side of an
5968 assignment is invalid, it will raise Constraint_Error rather than
5969 overwriting an arbitrary memory location.
5971 The @option{-gnatVa} may be used to enable additional validity checks,
5972 which are not required by the RM. These checks are often very
5973 expensive (which is why the RM does not require them). These checks
5974 are useful in tracking down uninitialized variables, but they are
5975 not usually recommended for production builds.
5977 The other @option{-gnatV^@var{x}^^} switches below allow finer-grained
5978 control; you can enable whichever validity checks you desire. However,
5979 for most debugging purposes, @option{-gnatVa} is sufficient, and the
5980 default @option{-gnatVd} (i.e. standard Ada behavior) is usually
5981 sufficient for non-debugging use.
5983 The @option{-gnatB} switch tells the compiler to assume that all
5984 values are valid (that is, within their declared subtype range)
5985 except in the context of a use of the Valid attribute. This means
5986 the compiler can generate more efficient code, since the range
5987 of values is better known at compile time. However, an uninitialized
5988 variable can cause wild jumps and memory corruption in this mode.
5990 The @option{-gnatV^@var{x}^^} switch allows control over the validity
5991 checking mode as described below.
5993 The @code{x} argument is a string of letters that
5994 indicate validity checks that are performed or not performed in addition
5995 to the default checks required by Ada as described above.
5998 The options allowed for this qualifier
5999 indicate validity checks that are performed or not performed in addition
6000 to the default checks required by Ada as described above.
6006 @emph{All validity checks.}
6007 @cindex @option{-gnatVa} (@command{gcc})
6008 All validity checks are turned on.
6010 That is, @option{-gnatVa} is
6011 equivalent to @option{gnatVcdfimorst}.
6015 @emph{Validity checks for copies.}
6016 @cindex @option{-gnatVc} (@command{gcc})
6017 The right hand side of assignments, and the initializing values of
6018 object declarations are validity checked.
6021 @emph{Default (RM) validity checks.}
6022 @cindex @option{-gnatVd} (@command{gcc})
6023 Some validity checks are done by default following normal Ada semantics
6025 A check is done in case statements that the expression is within the range
6026 of the subtype. If it is not, Constraint_Error is raised.
6027 For assignments to array components, a check is done that the expression used
6028 as index is within the range. If it is not, Constraint_Error is raised.
6029 Both these validity checks may be turned off using switch @option{-gnatVD}.
6030 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
6031 switch @option{-gnatVd} will leave the checks turned on.
6032 Switch @option{-gnatVD} should be used only if you are sure that all such
6033 expressions have valid values. If you use this switch and invalid values
6034 are present, then the program is erroneous, and wild jumps or memory
6035 overwriting may occur.
6038 @emph{Validity checks for elementary components.}
6039 @cindex @option{-gnatVe} (@command{gcc})
6040 In the absence of this switch, assignments to record or array components are
6041 not validity checked, even if validity checks for assignments generally
6042 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
6043 require valid data, but assignment of individual components does. So for
6044 example, there is a difference between copying the elements of an array with a
6045 slice assignment, compared to assigning element by element in a loop. This
6046 switch allows you to turn off validity checking for components, even when they
6047 are assigned component by component.
6050 @emph{Validity checks for floating-point values.}
6051 @cindex @option{-gnatVf} (@command{gcc})
6052 In the absence of this switch, validity checking occurs only for discrete
6053 values. If @option{-gnatVf} is specified, then validity checking also applies
6054 for floating-point values, and NaNs and infinities are considered invalid,
6055 as well as out of range values for constrained types. Note that this means
6056 that standard IEEE infinity mode is not allowed. The exact contexts
6057 in which floating-point values are checked depends on the setting of other
6058 options. For example,
6059 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
6060 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
6061 (the order does not matter) specifies that floating-point parameters of mode
6062 @code{in} should be validity checked.
6065 @emph{Validity checks for @code{in} mode parameters}
6066 @cindex @option{-gnatVi} (@command{gcc})
6067 Arguments for parameters of mode @code{in} are validity checked in function
6068 and procedure calls at the point of call.
6071 @emph{Validity checks for @code{in out} mode parameters.}
6072 @cindex @option{-gnatVm} (@command{gcc})
6073 Arguments for parameters of mode @code{in out} are validity checked in
6074 procedure calls at the point of call. The @code{'m'} here stands for
6075 modify, since this concerns parameters that can be modified by the call.
6076 Note that there is no specific option to test @code{out} parameters,
6077 but any reference within the subprogram will be tested in the usual
6078 manner, and if an invalid value is copied back, any reference to it
6079 will be subject to validity checking.
6082 @emph{No validity checks.}
6083 @cindex @option{-gnatVn} (@command{gcc})
6084 This switch turns off all validity checking, including the default checking
6085 for case statements and left hand side subscripts. Note that the use of
6086 the switch @option{-gnatp} suppresses all run-time checks, including
6087 validity checks, and thus implies @option{-gnatVn}. When this switch
6088 is used, it cancels any other @option{-gnatV} previously issued.
6091 @emph{Validity checks for operator and attribute operands.}
6092 @cindex @option{-gnatVo} (@command{gcc})
6093 Arguments for predefined operators and attributes are validity checked.
6094 This includes all operators in package @code{Standard},
6095 the shift operators defined as intrinsic in package @code{Interfaces}
6096 and operands for attributes such as @code{Pos}. Checks are also made
6097 on individual component values for composite comparisons, and on the
6098 expressions in type conversions and qualified expressions. Checks are
6099 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
6102 @emph{Validity checks for parameters.}
6103 @cindex @option{-gnatVp} (@command{gcc})
6104 This controls the treatment of parameters within a subprogram (as opposed
6105 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
6106 of parameters on a call. If either of these call options is used, then
6107 normally an assumption is made within a subprogram that the input arguments
6108 have been validity checking at the point of call, and do not need checking
6109 again within a subprogram). If @option{-gnatVp} is set, then this assumption
6110 is not made, and parameters are not assumed to be valid, so their validity
6111 will be checked (or rechecked) within the subprogram.
6114 @emph{Validity checks for function returns.}
6115 @cindex @option{-gnatVr} (@command{gcc})
6116 The expression in @code{return} statements in functions is validity
6120 @emph{Validity checks for subscripts.}
6121 @cindex @option{-gnatVs} (@command{gcc})
6122 All subscripts expressions are checked for validity, whether they appear
6123 on the right side or left side (in default mode only left side subscripts
6124 are validity checked).
6127 @emph{Validity checks for tests.}
6128 @cindex @option{-gnatVt} (@command{gcc})
6129 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
6130 statements are checked, as well as guard expressions in entry calls.
6135 The @option{-gnatV} switch may be followed by
6136 ^a string of letters^a list of options^
6137 to turn on a series of validity checking options.
6139 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
6140 specifies that in addition to the default validity checking, copies and
6141 function return expressions are to be validity checked.
6142 In order to make it easier
6143 to specify the desired combination of effects,
6145 the upper case letters @code{CDFIMORST} may
6146 be used to turn off the corresponding lower case option.
6149 the prefix @code{NO} on an option turns off the corresponding validity
6152 @item @code{NOCOPIES}
6153 @item @code{NODEFAULT}
6154 @item @code{NOFLOATS}
6155 @item @code{NOIN_PARAMS}
6156 @item @code{NOMOD_PARAMS}
6157 @item @code{NOOPERANDS}
6158 @item @code{NORETURNS}
6159 @item @code{NOSUBSCRIPTS}
6160 @item @code{NOTESTS}
6164 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
6165 turns on all validity checking options except for
6166 checking of @code{@b{in out}} procedure arguments.
6168 The specification of additional validity checking generates extra code (and
6169 in the case of @option{-gnatVa} the code expansion can be substantial).
6170 However, these additional checks can be very useful in detecting
6171 uninitialized variables, incorrect use of unchecked conversion, and other
6172 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
6173 is useful in conjunction with the extra validity checking, since this
6174 ensures that wherever possible uninitialized variables have invalid values.
6176 See also the pragma @code{Validity_Checks} which allows modification of
6177 the validity checking mode at the program source level, and also allows for
6178 temporary disabling of validity checks.
6180 @node Style Checking
6181 @subsection Style Checking
6182 @findex Style checking
6185 The @option{-gnaty^x^(option,option,@dots{})^} switch
6186 @cindex @option{-gnaty} (@command{gcc})
6187 causes the compiler to
6188 enforce specified style rules. A limited set of style rules has been used
6189 in writing the GNAT sources themselves. This switch allows user programs
6190 to activate all or some of these checks. If the source program fails a
6191 specified style check, an appropriate message is given, preceded by
6192 the character sequence ``(style)''. This message does not prevent
6193 successful compilation (unless the @option{-gnatwe} switch is used).
6195 Note that this is by no means intended to be a general facility for
6196 checking arbitrary coding standards. It is simply an embedding of the
6197 style rules we have chosen for the GNAT sources. If you are starting
6198 a project which does not have established style standards, you may
6199 find it useful to adopt the entire set of GNAT coding standards, or
6200 some subset of them. If you already have an established set of coding
6201 standards, then it may be that selected style checking options do
6202 indeed correspond to choices you have made, but for general checking
6203 of an existing set of coding rules, you should look to the gnatcheck
6204 tool, which is designed for that purpose.
6207 @code{(option,option,@dots{})} is a sequence of keywords
6210 The string @var{x} is a sequence of letters or digits
6212 indicating the particular style
6213 checks to be performed. The following checks are defined:
6218 @emph{Specify indentation level.}
6219 If a digit from 1-9 appears
6220 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
6221 then proper indentation is checked, with the digit indicating the
6222 indentation level required. A value of zero turns off this style check.
6223 The general style of required indentation is as specified by
6224 the examples in the Ada Reference Manual. Full line comments must be
6225 aligned with the @code{--} starting on a column that is a multiple of
6226 the alignment level, or they may be aligned the same way as the following
6227 non-blank line (this is useful when full line comments appear in the middle
6231 @emph{Check attribute casing.}
6232 Attribute names, including the case of keywords such as @code{digits}
6233 used as attributes names, must be written in mixed case, that is, the
6234 initial letter and any letter following an underscore must be uppercase.
6235 All other letters must be lowercase.
6237 @item ^A^ARRAY_INDEXES^
6238 @emph{Use of array index numbers in array attributes.}
6239 When using the array attributes First, Last, Range,
6240 or Length, the index number must be omitted for one-dimensional arrays
6241 and is required for multi-dimensional arrays.
6244 @emph{Blanks not allowed at statement end.}
6245 Trailing blanks are not allowed at the end of statements. The purpose of this
6246 rule, together with h (no horizontal tabs), is to enforce a canonical format
6247 for the use of blanks to separate source tokens.
6249 @item ^B^BOOLEAN_OPERATORS^
6250 @emph{Check Boolean operators.}
6251 The use of AND/OR operators is not permitted except in the cases of modular
6252 operands, array operands, and simple stand-alone boolean variables or
6253 boolean constants. In all other cases AND THEN/OR ELSE are required.
6256 @emph{Check comments.}
6257 Comments must meet the following set of rules:
6262 The ``@code{--}'' that starts the column must either start in column one,
6263 or else at least one blank must precede this sequence.
6266 Comments that follow other tokens on a line must have at least one blank
6267 following the ``@code{--}'' at the start of the comment.
6270 Full line comments must have at least two blanks following the
6271 ``@code{--}'' that starts the comment, with the following exceptions.
6274 A line consisting only of the ``@code{--}'' characters, possibly preceded
6275 by blanks is permitted.
6278 A comment starting with ``@code{--x}'' where @code{x} is a special character
6280 This allows proper processing of the output generated by specialized tools
6281 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
6283 language (where ``@code{--#}'' is used). For the purposes of this rule, a
6284 special character is defined as being in one of the ASCII ranges
6285 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
6286 Note that this usage is not permitted
6287 in GNAT implementation units (i.e., when @option{-gnatg} is used).
6290 A line consisting entirely of minus signs, possibly preceded by blanks, is
6291 permitted. This allows the construction of box comments where lines of minus
6292 signs are used to form the top and bottom of the box.
6295 A comment that starts and ends with ``@code{--}'' is permitted as long as at
6296 least one blank follows the initial ``@code{--}''. Together with the preceding
6297 rule, this allows the construction of box comments, as shown in the following
6300 ---------------------------
6301 -- This is a box comment --
6302 -- with two text lines. --
6303 ---------------------------
6307 @item ^d^DOS_LINE_ENDINGS^
6308 @emph{Check no DOS line terminators present.}
6309 All lines must be terminated by a single ASCII.LF
6310 character (in particular the DOS line terminator sequence CR/LF is not
6314 @emph{Check end/exit labels.}
6315 Optional labels on @code{end} statements ending subprograms and on
6316 @code{exit} statements exiting named loops, are required to be present.
6319 @emph{No form feeds or vertical tabs.}
6320 Neither form feeds nor vertical tab characters are permitted
6324 @emph{GNAT style mode}
6325 The set of style check switches is set to match that used by the GNAT sources.
6326 This may be useful when developing code that is eventually intended to be
6327 incorporated into GNAT. For further details, see GNAT sources.
6330 @emph{No horizontal tabs.}
6331 Horizontal tab characters are not permitted in the source text.
6332 Together with the b (no blanks at end of line) check, this
6333 enforces a canonical form for the use of blanks to separate
6337 @emph{Check if-then layout.}
6338 The keyword @code{then} must appear either on the same
6339 line as corresponding @code{if}, or on a line on its own, lined
6340 up under the @code{if} with at least one non-blank line in between
6341 containing all or part of the condition to be tested.
6344 @emph{check mode IN keywords}
6345 Mode @code{in} (the default mode) is not
6346 allowed to be given explicitly. @code{in out} is fine,
6347 but not @code{in} on its own.
6350 @emph{Check keyword casing.}
6351 All keywords must be in lower case (with the exception of keywords
6352 such as @code{digits} used as attribute names to which this check
6356 @emph{Check layout.}
6357 Layout of statement and declaration constructs must follow the
6358 recommendations in the Ada Reference Manual, as indicated by the
6359 form of the syntax rules. For example an @code{else} keyword must
6360 be lined up with the corresponding @code{if} keyword.
6362 There are two respects in which the style rule enforced by this check
6363 option are more liberal than those in the Ada Reference Manual. First
6364 in the case of record declarations, it is permissible to put the
6365 @code{record} keyword on the same line as the @code{type} keyword, and
6366 then the @code{end} in @code{end record} must line up under @code{type}.
6367 This is also permitted when the type declaration is split on two lines.
6368 For example, any of the following three layouts is acceptable:
6370 @smallexample @c ada
6393 Second, in the case of a block statement, a permitted alternative
6394 is to put the block label on the same line as the @code{declare} or
6395 @code{begin} keyword, and then line the @code{end} keyword up under
6396 the block label. For example both the following are permitted:
6398 @smallexample @c ada
6416 The same alternative format is allowed for loops. For example, both of
6417 the following are permitted:
6419 @smallexample @c ada
6421 Clear : while J < 10 loop
6432 @item ^Lnnn^MAX_NESTING=nnn^
6433 @emph{Set maximum nesting level}
6434 The maximum level of nesting of constructs (including subprograms, loops,
6435 blocks, packages, and conditionals) may not exceed the given value
6436 @option{nnn}. A value of zero disconnects this style check.
6438 @item ^m^LINE_LENGTH^
6439 @emph{Check maximum line length.}
6440 The length of source lines must not exceed 79 characters, including
6441 any trailing blanks. The value of 79 allows convenient display on an
6442 80 character wide device or window, allowing for possible special
6443 treatment of 80 character lines. Note that this count is of
6444 characters in the source text. This means that a tab character counts
6445 as one character in this count but a wide character sequence counts as
6446 a single character (however many bytes are needed in the encoding).
6448 @item ^Mnnn^MAX_LENGTH=nnn^
6449 @emph{Set maximum line length.}
6450 The length of lines must not exceed the
6451 given value @option{nnn}. The maximum value that can be specified is 32767.
6453 @item ^n^STANDARD_CASING^
6454 @emph{Check casing of entities in Standard.}
6455 Any identifier from Standard must be cased
6456 to match the presentation in the Ada Reference Manual (for example,
6457 @code{Integer} and @code{ASCII.NUL}).
6460 @emph{Turn off all style checks}
6461 All style check options are turned off.
6463 @item ^o^ORDERED_SUBPROGRAMS^
6464 @emph{Check order of subprogram bodies.}
6465 All subprogram bodies in a given scope
6466 (e.g.@: a package body) must be in alphabetical order. The ordering
6467 rule uses normal Ada rules for comparing strings, ignoring casing
6468 of letters, except that if there is a trailing numeric suffix, then
6469 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6472 @item ^O^OVERRIDING_INDICATORS^
6473 @emph{Check that overriding subprograms are explicitly marked as such.}
6474 The declaration of a primitive operation of a type extension that overrides
6475 an inherited operation must carry an overriding indicator.
6478 @emph{Check pragma casing.}
6479 Pragma names must be written in mixed case, that is, the
6480 initial letter and any letter following an underscore must be uppercase.
6481 All other letters must be lowercase.
6483 @item ^r^REFERENCES^
6484 @emph{Check references.}
6485 All identifier references must be cased in the same way as the
6486 corresponding declaration. No specific casing style is imposed on
6487 identifiers. The only requirement is for consistency of references
6490 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6491 @emph{Check no statements after THEN/ELSE.}
6492 No statements are allowed
6493 on the same line as a THEN or ELSE keyword following the
6494 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6495 and a special exception allows a pragma to appear after ELSE.
6498 @emph{Check separate specs.}
6499 Separate declarations (``specs'') are required for subprograms (a
6500 body is not allowed to serve as its own declaration). The only
6501 exception is that parameterless library level procedures are
6502 not required to have a separate declaration. This exception covers
6503 the most frequent form of main program procedures.
6506 @emph{Check token spacing.}
6507 The following token spacing rules are enforced:
6512 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6515 The token @code{=>} must be surrounded by spaces.
6518 The token @code{<>} must be preceded by a space or a left parenthesis.
6521 Binary operators other than @code{**} must be surrounded by spaces.
6522 There is no restriction on the layout of the @code{**} binary operator.
6525 Colon must be surrounded by spaces.
6528 Colon-equal (assignment, initialization) must be surrounded by spaces.
6531 Comma must be the first non-blank character on the line, or be
6532 immediately preceded by a non-blank character, and must be followed
6536 If the token preceding a left parenthesis ends with a letter or digit, then
6537 a space must separate the two tokens.
6540 if the token following a right parenthesis starts with a letter or digit, then
6541 a space must separate the two tokens.
6544 A right parenthesis must either be the first non-blank character on
6545 a line, or it must be preceded by a non-blank character.
6548 A semicolon must not be preceded by a space, and must not be followed by
6549 a non-blank character.
6552 A unary plus or minus may not be followed by a space.
6555 A vertical bar must be surrounded by spaces.
6558 @item ^u^UNNECESSARY_BLANK_LINES^
6559 @emph{Check unnecessary blank lines.}
6560 Unnecessary blank lines are not allowed. A blank line is considered
6561 unnecessary if it appears at the end of the file, or if more than
6562 one blank line occurs in sequence.
6564 @item ^x^XTRA_PARENS^
6565 @emph{Check extra parentheses.}
6566 Unnecessary extra level of parentheses (C-style) are not allowed
6567 around conditions in @code{if} statements, @code{while} statements and
6568 @code{exit} statements.
6570 @item ^y^ALL_BUILTIN^
6571 @emph{Set all standard style check options}
6572 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6573 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6574 @option{-gnatyS}, @option{-gnatyLnnn},
6575 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6579 @emph{Remove style check options}
6580 This causes any subsequent options in the string to act as canceling the
6581 corresponding style check option. To cancel maximum nesting level control,
6582 use @option{L} parameter witout any integer value after that, because any
6583 digit following @option{-} in the parameter string of the @option{-gnaty}
6584 option will be threated as canceling indentation check. The same is true
6585 for @option{M} parameter. @option{y} and @option{N} parameters are not
6586 allowed after @option{-}.
6589 This causes any subsequent options in the string to enable the corresponding
6590 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6596 @emph{Removing style check options}
6597 If the name of a style check is preceded by @option{NO} then the corresponding
6598 style check is turned off. For example @option{NOCOMMENTS} turns off style
6599 checking for comments.
6604 In the above rules, appearing in column one is always permitted, that is,
6605 counts as meeting either a requirement for a required preceding space,
6606 or as meeting a requirement for no preceding space.
6608 Appearing at the end of a line is also always permitted, that is, counts
6609 as meeting either a requirement for a following space, or as meeting
6610 a requirement for no following space.
6613 If any of these style rules is violated, a message is generated giving
6614 details on the violation. The initial characters of such messages are
6615 always ``@code{(style)}''. Note that these messages are treated as warning
6616 messages, so they normally do not prevent the generation of an object
6617 file. The @option{-gnatwe} switch can be used to treat warning messages,
6618 including style messages, as fatal errors.
6622 @option{-gnaty} on its own (that is not
6623 followed by any letters or digits), then the effect is equivalent
6624 to the use of @option{-gnatyy}, as described above, that is all
6625 built-in standard style check options are enabled.
6629 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6630 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6631 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6641 clears any previously set style checks.
6643 @node Run-Time Checks
6644 @subsection Run-Time Checks
6645 @cindex Division by zero
6646 @cindex Access before elaboration
6647 @cindex Checks, division by zero
6648 @cindex Checks, access before elaboration
6649 @cindex Checks, stack overflow checking
6652 By default, the following checks are suppressed: integer overflow
6653 checks, stack overflow checks, and checks for access before
6654 elaboration on subprogram calls. All other checks, including range
6655 checks and array bounds checks, are turned on by default. The
6656 following @command{gcc} switches refine this default behavior.
6661 @cindex @option{-gnatp} (@command{gcc})
6662 @cindex Suppressing checks
6663 @cindex Checks, suppressing
6665 This switch causes the unit to be compiled
6666 as though @code{pragma Suppress (All_checks)}
6667 had been present in the source. Validity checks are also eliminated (in
6668 other words @option{-gnatp} also implies @option{-gnatVn}.
6669 Use this switch to improve the performance
6670 of the code at the expense of safety in the presence of invalid data or
6673 Note that when checks are suppressed, the compiler is allowed, but not
6674 required, to omit the checking code. If the run-time cost of the
6675 checking code is zero or near-zero, the compiler will generate it even
6676 if checks are suppressed. In particular, if the compiler can prove
6677 that a certain check will necessarily fail, it will generate code to
6678 do an unconditional ``raise'', even if checks are suppressed. The
6679 compiler warns in this case. Another case in which checks may not be
6680 eliminated is when they are embedded in certain run time routines such
6681 as math library routines.
6683 Of course, run-time checks are omitted whenever the compiler can prove
6684 that they will not fail, whether or not checks are suppressed.
6686 Note that if you suppress a check that would have failed, program
6687 execution is erroneous, which means the behavior is totally
6688 unpredictable. The program might crash, or print wrong answers, or
6689 do anything else. It might even do exactly what you wanted it to do
6690 (and then it might start failing mysteriously next week or next
6691 year). The compiler will generate code based on the assumption that
6692 the condition being checked is true, which can result in disaster if
6693 that assumption is wrong.
6695 The @option{-gnatp} switch has no effect if a subsequent
6696 @option{-gnat-p} switch appears.
6699 @cindex @option{-gnat-p} (@command{gcc})
6700 @cindex Suppressing checks
6701 @cindex Checks, suppressing
6703 This switch cancels the effect of a previous @option{gnatp} switch.
6706 @cindex @option{-gnato} (@command{gcc})
6707 @cindex Overflow checks
6708 @cindex Check, overflow
6709 Enables overflow checking for integer operations.
6710 This causes GNAT to generate slower and larger executable
6711 programs by adding code to check for overflow (resulting in raising
6712 @code{Constraint_Error} as required by standard Ada
6713 semantics). These overflow checks correspond to situations in which
6714 the true value of the result of an operation may be outside the base
6715 range of the result type. The following example shows the distinction:
6717 @smallexample @c ada
6718 X1 : Integer := "Integer'Last";
6719 X2 : Integer range 1 .. 5 := "5";
6720 X3 : Integer := "Integer'Last";
6721 X4 : Integer range 1 .. 5 := "5";
6722 F : Float := "2.0E+20";
6731 Note that if explicit values are assigned at compile time, the
6732 compiler may be able to detect overflow at compile time, in which case
6733 no actual run-time checking code is required, and Constraint_Error
6734 will be raised unconditionally, with or without
6735 @option{-gnato}. That's why the assigned values in the above fragment
6736 are in quotes, the meaning is "assign a value not known to the
6737 compiler that happens to be equal to ...". The remaining discussion
6738 assumes that the compiler cannot detect the values at compile time.
6740 Here the first addition results in a value that is outside the base range
6741 of Integer, and hence requires an overflow check for detection of the
6742 constraint error. Thus the first assignment to @code{X1} raises a
6743 @code{Constraint_Error} exception only if @option{-gnato} is set.
6745 The second increment operation results in a violation of the explicit
6746 range constraint; such range checks are performed by default, and are
6747 unaffected by @option{-gnato}.
6749 The two conversions of @code{F} both result in values that are outside
6750 the base range of type @code{Integer} and thus will raise
6751 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6752 The fact that the result of the second conversion is assigned to
6753 variable @code{X4} with a restricted range is irrelevant, since the problem
6754 is in the conversion, not the assignment.
6756 Basically the rule is that in the default mode (@option{-gnato} not
6757 used), the generated code assures that all integer variables stay
6758 within their declared ranges, or within the base range if there is
6759 no declared range. This prevents any serious problems like indexes
6760 out of range for array operations.
6762 What is not checked in default mode is an overflow that results in
6763 an in-range, but incorrect value. In the above example, the assignments
6764 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6765 range of the target variable, but the result is wrong in the sense that
6766 it is too large to be represented correctly. Typically the assignment
6767 to @code{X1} will result in wrap around to the largest negative number.
6768 The conversions of @code{F} will result in some @code{Integer} value
6769 and if that integer value is out of the @code{X4} range then the
6770 subsequent assignment would generate an exception.
6772 @findex Machine_Overflows
6773 Note that the @option{-gnato} switch does not affect the code generated
6774 for any floating-point operations; it applies only to integer
6776 For floating-point, GNAT has the @code{Machine_Overflows}
6777 attribute set to @code{False} and the normal mode of operation is to
6778 generate IEEE NaN and infinite values on overflow or invalid operations
6779 (such as dividing 0.0 by 0.0).
6781 The reason that we distinguish overflow checking from other kinds of
6782 range constraint checking is that a failure of an overflow check, unlike
6783 for example the failure of a range check, can result in an incorrect
6784 value, but cannot cause random memory destruction (like an out of range
6785 subscript), or a wild jump (from an out of range case value). Overflow
6786 checking is also quite expensive in time and space, since in general it
6787 requires the use of double length arithmetic.
6789 Note again that @option{-gnato} is off by default, so overflow checking is
6790 not performed in default mode. This means that out of the box, with the
6791 default settings, GNAT does not do all the checks expected from the
6792 language description in the Ada Reference Manual. If you want all constraint
6793 checks to be performed, as described in this Manual, then you must
6794 explicitly use the -gnato switch either on the @command{gnatmake} or
6795 @command{gcc} command.
6798 @cindex @option{-gnatE} (@command{gcc})
6799 @cindex Elaboration checks
6800 @cindex Check, elaboration
6801 Enables dynamic checks for access-before-elaboration
6802 on subprogram calls and generic instantiations.
6803 Note that @option{-gnatE} is not necessary for safety, because in the
6804 default mode, GNAT ensures statically that the checks would not fail.
6805 For full details of the effect and use of this switch,
6806 @xref{Compiling Using gcc}.
6809 @cindex @option{-fstack-check} (@command{gcc})
6810 @cindex Stack Overflow Checking
6811 @cindex Checks, stack overflow checking
6812 Activates stack overflow checking. For full details of the effect and use of
6813 this switch see @ref{Stack Overflow Checking}.
6818 The setting of these switches only controls the default setting of the
6819 checks. You may modify them using either @code{Suppress} (to remove
6820 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6823 @node Using gcc for Syntax Checking
6824 @subsection Using @command{gcc} for Syntax Checking
6827 @cindex @option{-gnats} (@command{gcc})
6831 The @code{s} stands for ``syntax''.
6834 Run GNAT in syntax checking only mode. For
6835 example, the command
6838 $ gcc -c -gnats x.adb
6842 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6843 series of files in a single command
6845 , and can use wild cards to specify such a group of files.
6846 Note that you must specify the @option{-c} (compile
6847 only) flag in addition to the @option{-gnats} flag.
6850 You may use other switches in conjunction with @option{-gnats}. In
6851 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6852 format of any generated error messages.
6854 When the source file is empty or contains only empty lines and/or comments,
6855 the output is a warning:
6858 $ gcc -c -gnats -x ada toto.txt
6859 toto.txt:1:01: warning: empty file, contains no compilation units
6863 Otherwise, the output is simply the error messages, if any. No object file or
6864 ALI file is generated by a syntax-only compilation. Also, no units other
6865 than the one specified are accessed. For example, if a unit @code{X}
6866 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6867 check only mode does not access the source file containing unit
6870 @cindex Multiple units, syntax checking
6871 Normally, GNAT allows only a single unit in a source file. However, this
6872 restriction does not apply in syntax-check-only mode, and it is possible
6873 to check a file containing multiple compilation units concatenated
6874 together. This is primarily used by the @code{gnatchop} utility
6875 (@pxref{Renaming Files Using gnatchop}).
6878 @node Using gcc for Semantic Checking
6879 @subsection Using @command{gcc} for Semantic Checking
6882 @cindex @option{-gnatc} (@command{gcc})
6886 The @code{c} stands for ``check''.
6888 Causes the compiler to operate in semantic check mode,
6889 with full checking for all illegalities specified in the
6890 Ada Reference Manual, but without generation of any object code
6891 (no object file is generated).
6893 Because dependent files must be accessed, you must follow the GNAT
6894 semantic restrictions on file structuring to operate in this mode:
6898 The needed source files must be accessible
6899 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6902 Each file must contain only one compilation unit.
6905 The file name and unit name must match (@pxref{File Naming Rules}).
6908 The output consists of error messages as appropriate. No object file is
6909 generated. An @file{ALI} file is generated for use in the context of
6910 cross-reference tools, but this file is marked as not being suitable
6911 for binding (since no object file is generated).
6912 The checking corresponds exactly to the notion of
6913 legality in the Ada Reference Manual.
6915 Any unit can be compiled in semantics-checking-only mode, including
6916 units that would not normally be compiled (subunits,
6917 and specifications where a separate body is present).
6920 @node Compiling Different Versions of Ada
6921 @subsection Compiling Different Versions of Ada
6924 The switches described in this section allow you to explicitly specify
6925 the version of the Ada language that your programs are written in.
6926 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6927 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6928 indicate Ada 83 compatibility mode.
6931 @cindex Compatibility with Ada 83
6933 @item -gnat83 (Ada 83 Compatibility Mode)
6934 @cindex @option{-gnat83} (@command{gcc})
6935 @cindex ACVC, Ada 83 tests
6939 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6940 specifies that the program is to be compiled in Ada 83 mode. With
6941 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6942 semantics where this can be done easily.
6943 It is not possible to guarantee this switch does a perfect
6944 job; some subtle tests, such as are
6945 found in earlier ACVC tests (and that have been removed from the ACATS suite
6946 for Ada 95), might not compile correctly.
6947 Nevertheless, this switch may be useful in some circumstances, for example
6948 where, due to contractual reasons, existing code needs to be maintained
6949 using only Ada 83 features.
6951 With few exceptions (most notably the need to use @code{<>} on
6952 @cindex Generic formal parameters
6953 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6954 reserved words, and the use of packages
6955 with optional bodies), it is not necessary to specify the
6956 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6957 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6958 a correct Ada 83 program is usually also a correct program
6959 in these later versions of the language standard.
6960 For further information, please refer to @ref{Compatibility and Porting Guide}.
6962 @item -gnat95 (Ada 95 mode)
6963 @cindex @option{-gnat95} (@command{gcc})
6967 This switch directs the compiler to implement the Ada 95 version of the
6969 Since Ada 95 is almost completely upwards
6970 compatible with Ada 83, Ada 83 programs may generally be compiled using
6971 this switch (see the description of the @option{-gnat83} switch for further
6972 information about Ada 83 mode).
6973 If an Ada 2005 program is compiled in Ada 95 mode,
6974 uses of the new Ada 2005 features will cause error
6975 messages or warnings.
6977 This switch also can be used to cancel the effect of a previous
6978 @option{-gnat83}, @option{-gnat05/2005}, or @option{-gnat12/2012}
6979 switch earlier in the command line.
6981 @item -gnat05 or -gnat2005 (Ada 2005 mode)
6982 @cindex @option{-gnat05} (@command{gcc})
6983 @cindex @option{-gnat2005} (@command{gcc})
6984 @cindex Ada 2005 mode
6987 This switch directs the compiler to implement the Ada 2005 version of the
6988 language, as documented in the official Ada standards document.
6989 Since Ada 2005 is almost completely upwards
6990 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6991 may generally be compiled using this switch (see the description of the
6992 @option{-gnat83} and @option{-gnat95} switches for further
6996 Note that even though Ada 2005 is the current official version of the
6997 language, GNAT still compiles in Ada 95 mode by default, so if you are
6998 using Ada 2005 features in your program, you must use this switch (or
6999 the equivalent Ada_05 or Ada_2005 configuration pragmas).
7002 @item -gnat12 or -gnat2012 (Ada 2012 mode)
7003 @cindex @option{-gnat12} (@command{gcc})
7004 @cindex @option{-gnat2012} (@command{gcc})
7005 @cindex Ada 2012 mode
7008 This switch directs the compiler to implement the Ada 2012 version of the
7010 Since Ada 2012 is almost completely upwards
7011 compatible with Ada 2005 (and thus also with Ada 83, and Ada 95),
7012 Ada 83 and Ada 95 programs
7013 may generally be compiled using this switch (see the description of the
7014 @option{-gnat83}, @option{-gnat95}, and @option{-gnat05/2005} switches
7015 for further information).
7017 For information about the approved ``Ada Issues'' that have been incorporated
7018 into Ada 2012, see @url{http://www.ada-auth.org/ais.html}.
7019 Included with GNAT releases is a file @file{features-ada12} that describes
7020 the set of implemented Ada 2012 features.
7022 @item -gnatX (Enable GNAT Extensions)
7023 @cindex @option{-gnatX} (@command{gcc})
7024 @cindex Ada language extensions
7025 @cindex GNAT extensions
7028 This switch directs the compiler to implement the latest version of the
7029 language (currently Ada 2012) and also to enable certain GNAT implementation
7030 extensions that are not part of any Ada standard. For a full list of these
7031 extensions, see the GNAT reference manual.
7035 @node Character Set Control
7036 @subsection Character Set Control
7038 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
7039 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
7042 Normally GNAT recognizes the Latin-1 character set in source program
7043 identifiers, as described in the Ada Reference Manual.
7045 GNAT to recognize alternate character sets in identifiers. @var{c} is a
7046 single character ^^or word^ indicating the character set, as follows:
7050 ISO 8859-1 (Latin-1) identifiers
7053 ISO 8859-2 (Latin-2) letters allowed in identifiers
7056 ISO 8859-3 (Latin-3) letters allowed in identifiers
7059 ISO 8859-4 (Latin-4) letters allowed in identifiers
7062 ISO 8859-5 (Cyrillic) letters allowed in identifiers
7065 ISO 8859-15 (Latin-9) letters allowed in identifiers
7068 IBM PC letters (code page 437) allowed in identifiers
7071 IBM PC letters (code page 850) allowed in identifiers
7073 @item ^f^FULL_UPPER^
7074 Full upper-half codes allowed in identifiers
7077 No upper-half codes allowed in identifiers
7080 Wide-character codes (that is, codes greater than 255)
7081 allowed in identifiers
7084 @xref{Foreign Language Representation}, for full details on the
7085 implementation of these character sets.
7087 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
7088 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
7089 Specify the method of encoding for wide characters.
7090 @var{e} is one of the following:
7095 Hex encoding (brackets coding also recognized)
7098 Upper half encoding (brackets encoding also recognized)
7101 Shift/JIS encoding (brackets encoding also recognized)
7104 EUC encoding (brackets encoding also recognized)
7107 UTF-8 encoding (brackets encoding also recognized)
7110 Brackets encoding only (default value)
7112 For full details on these encoding
7113 methods see @ref{Wide Character Encodings}.
7114 Note that brackets coding is always accepted, even if one of the other
7115 options is specified, so for example @option{-gnatW8} specifies that both
7116 brackets and UTF-8 encodings will be recognized. The units that are
7117 with'ed directly or indirectly will be scanned using the specified
7118 representation scheme, and so if one of the non-brackets scheme is
7119 used, it must be used consistently throughout the program. However,
7120 since brackets encoding is always recognized, it may be conveniently
7121 used in standard libraries, allowing these libraries to be used with
7122 any of the available coding schemes.
7125 If no @option{-gnatW?} parameter is present, then the default
7126 representation is normally Brackets encoding only. However, if the
7127 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
7128 byte order mark or BOM for UTF-8), then these three characters are
7129 skipped and the default representation for the file is set to UTF-8.
7131 Note that the wide character representation that is specified (explicitly
7132 or by default) for the main program also acts as the default encoding used
7133 for Wide_Text_IO files if not specifically overridden by a WCEM form
7137 @node File Naming Control
7138 @subsection File Naming Control
7141 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
7142 @cindex @option{-gnatk} (@command{gcc})
7143 Activates file name ``krunching''. @var{n}, a decimal integer in the range
7144 1-999, indicates the maximum allowable length of a file name (not
7145 including the @file{.ads} or @file{.adb} extension). The default is not
7146 to enable file name krunching.
7148 For the source file naming rules, @xref{File Naming Rules}.
7151 @node Subprogram Inlining Control
7152 @subsection Subprogram Inlining Control
7157 @cindex @option{-gnatn} (@command{gcc})
7159 The @code{n} here is intended to suggest the first syllable of the
7162 GNAT recognizes and processes @code{Inline} pragmas. However, for the
7163 inlining to actually occur, optimization must be enabled. To enable
7164 inlining of subprograms specified by pragma @code{Inline},
7165 you must also specify this switch.
7166 In the absence of this switch, GNAT does not attempt
7167 inlining and does not need to access the bodies of
7168 subprograms for which @code{pragma Inline} is specified if they are not
7169 in the current unit.
7171 If you specify this switch the compiler will access these bodies,
7172 creating an extra source dependency for the resulting object file, and
7173 where possible, the call will be inlined.
7174 For further details on when inlining is possible
7175 see @ref{Inlining of Subprograms}.
7178 @cindex @option{-gnatN} (@command{gcc})
7179 This switch activates front-end inlining which also
7180 generates additional dependencies.
7182 When using a gcc-based back end (in practice this means using any version
7183 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
7184 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
7185 Historically front end inlining was more extensive than the gcc back end
7186 inlining, but that is no longer the case.
7189 @node Auxiliary Output Control
7190 @subsection Auxiliary Output Control
7194 @cindex @option{-gnatt} (@command{gcc})
7195 @cindex Writing internal trees
7196 @cindex Internal trees, writing to file
7197 Causes GNAT to write the internal tree for a unit to a file (with the
7198 extension @file{.adt}.
7199 This not normally required, but is used by separate analysis tools.
7201 these tools do the necessary compilations automatically, so you should
7202 not have to specify this switch in normal operation.
7203 Note that the combination of switches @option{-gnatct}
7204 generates a tree in the form required by ASIS applications.
7207 @cindex @option{-gnatu} (@command{gcc})
7208 Print a list of units required by this compilation on @file{stdout}.
7209 The listing includes all units on which the unit being compiled depends
7210 either directly or indirectly.
7213 @item -pass-exit-codes
7214 @cindex @option{-pass-exit-codes} (@command{gcc})
7215 If this switch is not used, the exit code returned by @command{gcc} when
7216 compiling multiple files indicates whether all source files have
7217 been successfully used to generate object files or not.
7219 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
7220 exit status and allows an integrated development environment to better
7221 react to a compilation failure. Those exit status are:
7225 There was an error in at least one source file.
7227 At least one source file did not generate an object file.
7229 The compiler died unexpectedly (internal error for example).
7231 An object file has been generated for every source file.
7236 @node Debugging Control
7237 @subsection Debugging Control
7241 @cindex Debugging options
7244 @cindex @option{-gnatd} (@command{gcc})
7245 Activate internal debugging switches. @var{x} is a letter or digit, or
7246 string of letters or digits, which specifies the type of debugging
7247 outputs desired. Normally these are used only for internal development
7248 or system debugging purposes. You can find full documentation for these
7249 switches in the body of the @code{Debug} unit in the compiler source
7250 file @file{debug.adb}.
7254 @cindex @option{-gnatG} (@command{gcc})
7255 This switch causes the compiler to generate auxiliary output containing
7256 a pseudo-source listing of the generated expanded code. Like most Ada
7257 compilers, GNAT works by first transforming the high level Ada code into
7258 lower level constructs. For example, tasking operations are transformed
7259 into calls to the tasking run-time routines. A unique capability of GNAT
7260 is to list this expanded code in a form very close to normal Ada source.
7261 This is very useful in understanding the implications of various Ada
7262 usage on the efficiency of the generated code. There are many cases in
7263 Ada (e.g.@: the use of controlled types), where simple Ada statements can
7264 generate a lot of run-time code. By using @option{-gnatG} you can identify
7265 these cases, and consider whether it may be desirable to modify the coding
7266 approach to improve efficiency.
7268 The optional parameter @code{nn} if present after -gnatG specifies an
7269 alternative maximum line length that overrides the normal default of 72.
7270 This value is in the range 40-999999, values less than 40 being silently
7271 reset to 40. The equal sign is optional.
7273 The format of the output is very similar to standard Ada source, and is
7274 easily understood by an Ada programmer. The following special syntactic
7275 additions correspond to low level features used in the generated code that
7276 do not have any exact analogies in pure Ada source form. The following
7277 is a partial list of these special constructions. See the spec
7278 of package @code{Sprint} in file @file{sprint.ads} for a full list.
7280 If the switch @option{-gnatL} is used in conjunction with
7281 @cindex @option{-gnatL} (@command{gcc})
7282 @option{-gnatG}, then the original source lines are interspersed
7283 in the expanded source (as comment lines with the original line number).
7286 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
7287 Shows the storage pool being used for an allocator.
7289 @item at end @var{procedure-name};
7290 Shows the finalization (cleanup) procedure for a scope.
7292 @item (if @var{expr} then @var{expr} else @var{expr})
7293 Conditional expression equivalent to the @code{x?y:z} construction in C.
7295 @item @var{target}^^^(@var{source})
7296 A conversion with floating-point truncation instead of rounding.
7298 @item @var{target}?(@var{source})
7299 A conversion that bypasses normal Ada semantic checking. In particular
7300 enumeration types and fixed-point types are treated simply as integers.
7302 @item @var{target}?^^^(@var{source})
7303 Combines the above two cases.
7305 @item @var{x} #/ @var{y}
7306 @itemx @var{x} #mod @var{y}
7307 @itemx @var{x} #* @var{y}
7308 @itemx @var{x} #rem @var{y}
7309 A division or multiplication of fixed-point values which are treated as
7310 integers without any kind of scaling.
7312 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
7313 Shows the storage pool associated with a @code{free} statement.
7315 @item [subtype or type declaration]
7316 Used to list an equivalent declaration for an internally generated
7317 type that is referenced elsewhere in the listing.
7319 @c @item freeze @var{type-name} @ovar{actions}
7320 @c Expanding @ovar macro inline (explanation in macro def comments)
7321 @item freeze @var{type-name} @r{[}@var{actions}@r{]}
7322 Shows the point at which @var{type-name} is frozen, with possible
7323 associated actions to be performed at the freeze point.
7325 @item reference @var{itype}
7326 Reference (and hence definition) to internal type @var{itype}.
7328 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
7329 Intrinsic function call.
7331 @item @var{label-name} : label
7332 Declaration of label @var{labelname}.
7334 @item #$ @var{subprogram-name}
7335 An implicit call to a run-time support routine
7336 (to meet the requirement of H.3.1(9) in a
7339 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
7340 A multiple concatenation (same effect as @var{expr} & @var{expr} &
7341 @var{expr}, but handled more efficiently).
7343 @item [constraint_error]
7344 Raise the @code{Constraint_Error} exception.
7346 @item @var{expression}'reference
7347 A pointer to the result of evaluating @var{expression}.
7349 @item @var{target-type}!(@var{source-expression})
7350 An unchecked conversion of @var{source-expression} to @var{target-type}.
7352 @item [@var{numerator}/@var{denominator}]
7353 Used to represent internal real literals (that) have no exact
7354 representation in base 2-16 (for example, the result of compile time
7355 evaluation of the expression 1.0/27.0).
7359 @cindex @option{-gnatD} (@command{gcc})
7360 When used in conjunction with @option{-gnatG}, this switch causes
7361 the expanded source, as described above for
7362 @option{-gnatG} to be written to files with names
7363 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
7364 instead of to the standard output file. For
7365 example, if the source file name is @file{hello.adb}, then a file
7366 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
7367 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
7368 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
7369 you to do source level debugging using the generated code which is
7370 sometimes useful for complex code, for example to find out exactly
7371 which part of a complex construction raised an exception. This switch
7372 also suppress generation of cross-reference information (see
7373 @option{-gnatx}) since otherwise the cross-reference information
7374 would refer to the @file{^.dg^.DG^} file, which would cause
7375 confusion since this is not the original source file.
7377 Note that @option{-gnatD} actually implies @option{-gnatG}
7378 automatically, so it is not necessary to give both options.
7379 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
7381 If the switch @option{-gnatL} is used in conjunction with
7382 @cindex @option{-gnatL} (@command{gcc})
7383 @option{-gnatDG}, then the original source lines are interspersed
7384 in the expanded source (as comment lines with the original line number).
7386 The optional parameter @code{nn} if present after -gnatD specifies an
7387 alternative maximum line length that overrides the normal default of 72.
7388 This value is in the range 40-999999, values less than 40 being silently
7389 reset to 40. The equal sign is optional.
7392 @cindex @option{-gnatr} (@command{gcc})
7393 @cindex pragma Restrictions
7394 This switch causes pragma Restrictions to be treated as Restriction_Warnings
7395 so that violation of restrictions causes warnings rather than illegalities.
7396 This is useful during the development process when new restrictions are added
7397 or investigated. The switch also causes pragma Profile to be treated as
7398 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
7399 restriction warnings rather than restrictions.
7402 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
7403 @cindex @option{-gnatR} (@command{gcc})
7404 This switch controls output from the compiler of a listing showing
7405 representation information for declared types and objects. For
7406 @option{-gnatR0}, no information is output (equivalent to omitting
7407 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
7408 so @option{-gnatR} with no parameter has the same effect), size and alignment
7409 information is listed for declared array and record types. For
7410 @option{-gnatR2}, size and alignment information is listed for all
7411 declared types and objects. Finally @option{-gnatR3} includes symbolic
7412 expressions for values that are computed at run time for
7413 variant records. These symbolic expressions have a mostly obvious
7414 format with #n being used to represent the value of the n'th
7415 discriminant. See source files @file{repinfo.ads/adb} in the
7416 @code{GNAT} sources for full details on the format of @option{-gnatR3}
7417 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
7418 the output is to a file with the name @file{^file.rep^file_REP^} where
7419 file is the name of the corresponding source file.
7422 @item /REPRESENTATION_INFO
7423 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
7424 This qualifier controls output from the compiler of a listing showing
7425 representation information for declared types and objects. For
7426 @option{/REPRESENTATION_INFO=NONE}, no information is output
7427 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
7428 @option{/REPRESENTATION_INFO} without option is equivalent to
7429 @option{/REPRESENTATION_INFO=ARRAYS}.
7430 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
7431 information is listed for declared array and record types. For
7432 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
7433 is listed for all expression information for values that are computed
7434 at run time for variant records. These symbolic expressions have a mostly
7435 obvious format with #n being used to represent the value of the n'th
7436 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7437 @code{GNAT} sources for full details on the format of
7438 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7439 If _FILE is added at the end of an option
7440 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7441 then the output is to a file with the name @file{file_REP} where
7442 file is the name of the corresponding source file.
7444 Note that it is possible for record components to have zero size. In
7445 this case, the component clause uses an obvious extension of permitted
7446 Ada syntax, for example @code{at 0 range 0 .. -1}.
7448 Representation information requires that code be generated (since it is the
7449 code generator that lays out complex data structures). If an attempt is made
7450 to output representation information when no code is generated, for example
7451 when a subunit is compiled on its own, then no information can be generated
7452 and the compiler outputs a message to this effect.
7455 @cindex @option{-gnatS} (@command{gcc})
7456 The use of the switch @option{-gnatS} for an
7457 Ada compilation will cause the compiler to output a
7458 representation of package Standard in a form very
7459 close to standard Ada. It is not quite possible to
7460 do this entirely in standard Ada (since new
7461 numeric base types cannot be created in standard
7462 Ada), but the output is easily
7463 readable to any Ada programmer, and is useful to
7464 determine the characteristics of target dependent
7465 types in package Standard.
7468 @cindex @option{-gnatx} (@command{gcc})
7469 Normally the compiler generates full cross-referencing information in
7470 the @file{ALI} file. This information is used by a number of tools,
7471 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7472 suppresses this information. This saves some space and may slightly
7473 speed up compilation, but means that these tools cannot be used.
7476 @node Exception Handling Control
7477 @subsection Exception Handling Control
7480 GNAT uses two methods for handling exceptions at run-time. The
7481 @code{setjmp/longjmp} method saves the context when entering
7482 a frame with an exception handler. Then when an exception is
7483 raised, the context can be restored immediately, without the
7484 need for tracing stack frames. This method provides very fast
7485 exception propagation, but introduces significant overhead for
7486 the use of exception handlers, even if no exception is raised.
7488 The other approach is called ``zero cost'' exception handling.
7489 With this method, the compiler builds static tables to describe
7490 the exception ranges. No dynamic code is required when entering
7491 a frame containing an exception handler. When an exception is
7492 raised, the tables are used to control a back trace of the
7493 subprogram invocation stack to locate the required exception
7494 handler. This method has considerably poorer performance for
7495 the propagation of exceptions, but there is no overhead for
7496 exception handlers if no exception is raised. Note that in this
7497 mode and in the context of mixed Ada and C/C++ programming,
7498 to propagate an exception through a C/C++ code, the C/C++ code
7499 must be compiled with the @option{-funwind-tables} GCC's
7502 The following switches may be used to control which of the
7503 two exception handling methods is used.
7509 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7510 This switch causes the setjmp/longjmp run-time (when available) to be used
7511 for exception handling. If the default
7512 mechanism for the target is zero cost exceptions, then
7513 this switch can be used to modify this default, and must be
7514 used for all units in the partition.
7515 This option is rarely used. One case in which it may be
7516 advantageous is if you have an application where exception
7517 raising is common and the overall performance of the
7518 application is improved by favoring exception propagation.
7521 @cindex @option{--RTS=zcx} (@command{gnatmake})
7522 @cindex Zero Cost Exceptions
7523 This switch causes the zero cost approach to be used
7524 for exception handling. If this is the default mechanism for the
7525 target (see below), then this switch is unneeded. If the default
7526 mechanism for the target is setjmp/longjmp exceptions, then
7527 this switch can be used to modify this default, and must be
7528 used for all units in the partition.
7529 This option can only be used if the zero cost approach
7530 is available for the target in use, otherwise it will generate an error.
7534 The same option @option{--RTS} must be used both for @command{gcc}
7535 and @command{gnatbind}. Passing this option to @command{gnatmake}
7536 (@pxref{Switches for gnatmake}) will ensure the required consistency
7537 through the compilation and binding steps.
7539 @node Units to Sources Mapping Files
7540 @subsection Units to Sources Mapping Files
7544 @item -gnatem=@var{path}
7545 @cindex @option{-gnatem} (@command{gcc})
7546 A mapping file is a way to communicate to the compiler two mappings:
7547 from unit names to file names (without any directory information) and from
7548 file names to path names (with full directory information). These mappings
7549 are used by the compiler to short-circuit the path search.
7551 The use of mapping files is not required for correct operation of the
7552 compiler, but mapping files can improve efficiency, particularly when
7553 sources are read over a slow network connection. In normal operation,
7554 you need not be concerned with the format or use of mapping files,
7555 and the @option{-gnatem} switch is not a switch that you would use
7556 explicitly. It is intended primarily for use by automatic tools such as
7557 @command{gnatmake} running under the project file facility. The
7558 description here of the format of mapping files is provided
7559 for completeness and for possible use by other tools.
7561 A mapping file is a sequence of sets of three lines. In each set, the
7562 first line is the unit name, in lower case, with @code{%s} appended
7563 for specs and @code{%b} appended for bodies; the second line is the
7564 file name; and the third line is the path name.
7570 /gnat/project1/sources/main.2.ada
7573 When the switch @option{-gnatem} is specified, the compiler will
7574 create in memory the two mappings from the specified file. If there is
7575 any problem (nonexistent file, truncated file or duplicate entries),
7576 no mapping will be created.
7578 Several @option{-gnatem} switches may be specified; however, only the
7579 last one on the command line will be taken into account.
7581 When using a project file, @command{gnatmake} creates a temporary
7582 mapping file and communicates it to the compiler using this switch.
7586 @node Integrated Preprocessing
7587 @subsection Integrated Preprocessing
7590 GNAT sources may be preprocessed immediately before compilation.
7591 In this case, the actual
7592 text of the source is not the text of the source file, but is derived from it
7593 through a process called preprocessing. Integrated preprocessing is specified
7594 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7595 indicates, through a text file, the preprocessing data to be used.
7596 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7599 Note that when integrated preprocessing is used, the output from the
7600 preprocessor is not written to any external file. Instead it is passed
7601 internally to the compiler. If you need to preserve the result of
7602 preprocessing in a file, then you should use @command{gnatprep}
7603 to perform the desired preprocessing in stand-alone mode.
7606 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7607 used when Integrated Preprocessing is used. The reason is that preprocessing
7608 with another Preprocessing Data file without changing the sources will
7609 not trigger recompilation without this switch.
7612 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7613 always trigger recompilation for sources that are preprocessed,
7614 because @command{gnatmake} cannot compute the checksum of the source after
7618 The actual preprocessing function is described in details in section
7619 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7620 preprocessing is triggered and parameterized.
7624 @item -gnatep=@var{file}
7625 @cindex @option{-gnatep} (@command{gcc})
7626 This switch indicates to the compiler the file name (without directory
7627 information) of the preprocessor data file to use. The preprocessor data file
7628 should be found in the source directories.
7631 A preprocessing data file is a text file with significant lines indicating
7632 how should be preprocessed either a specific source or all sources not
7633 mentioned in other lines. A significant line is a nonempty, non-comment line.
7634 Comments are similar to Ada comments.
7637 Each significant line starts with either a literal string or the character '*'.
7638 A literal string is the file name (without directory information) of the source
7639 to preprocess. A character '*' indicates the preprocessing for all the sources
7640 that are not specified explicitly on other lines (order of the lines is not
7641 significant). It is an error to have two lines with the same file name or two
7642 lines starting with the character '*'.
7645 After the file name or the character '*', another optional literal string
7646 indicating the file name of the definition file to be used for preprocessing
7647 (@pxref{Form of Definitions File}). The definition files are found by the
7648 compiler in one of the source directories. In some cases, when compiling
7649 a source in a directory other than the current directory, if the definition
7650 file is in the current directory, it may be necessary to add the current
7651 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7652 the compiler would not find the definition file.
7655 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7656 be found. Those ^switches^switches^ are:
7661 Causes both preprocessor lines and the lines deleted by
7662 preprocessing to be replaced by blank lines, preserving the line number.
7663 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7664 it cancels the effect of @option{-c}.
7667 Causes both preprocessor lines and the lines deleted
7668 by preprocessing to be retained as comments marked
7669 with the special string ``@code{--! }''.
7671 @item -Dsymbol=value
7672 Define or redefine a symbol, associated with value. A symbol is an Ada
7673 identifier, or an Ada reserved word, with the exception of @code{if},
7674 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7675 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7676 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7677 same name defined in a definition file.
7680 Causes a sorted list of symbol names and values to be
7681 listed on the standard output file.
7684 Causes undefined symbols to be treated as having the value @code{FALSE}
7686 of a preprocessor test. In the absence of this option, an undefined symbol in
7687 a @code{#if} or @code{#elsif} test will be treated as an error.
7692 Examples of valid lines in a preprocessor data file:
7695 "toto.adb" "prep.def" -u
7696 -- preprocess "toto.adb", using definition file "prep.def",
7697 -- undefined symbol are False.
7700 -- preprocess all other sources without a definition file;
7701 -- suppressed lined are commented; symbol VERSION has the value V101.
7703 "titi.adb" "prep2.def" -s
7704 -- preprocess "titi.adb", using definition file "prep2.def";
7705 -- list all symbols with their values.
7708 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7709 @cindex @option{-gnateD} (@command{gcc})
7710 Define or redefine a preprocessing symbol, associated with value. If no value
7711 is given on the command line, then the value of the symbol is @code{True}.
7712 A symbol is an identifier, following normal Ada (case-insensitive)
7713 rules for its syntax, and value is any sequence (including an empty sequence)
7714 of characters from the set (letters, digits, period, underline).
7715 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7716 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7719 A symbol declared with this ^switch^switch^ on the command line replaces a
7720 symbol with the same name either in a definition file or specified with a
7721 ^switch^switch^ -D in the preprocessor data file.
7724 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7727 When integrated preprocessing is performed and the preprocessor modifies
7728 the source text, write the result of this preprocessing into a file
7729 <source>^.prep^_prep^.
7733 @node Code Generation Control
7734 @subsection Code Generation Control
7738 The GCC technology provides a wide range of target dependent
7739 @option{-m} switches for controlling
7740 details of code generation with respect to different versions of
7741 architectures. This includes variations in instruction sets (e.g.@:
7742 different members of the power pc family), and different requirements
7743 for optimal arrangement of instructions (e.g.@: different members of
7744 the x86 family). The list of available @option{-m} switches may be
7745 found in the GCC documentation.
7747 Use of these @option{-m} switches may in some cases result in improved
7750 The GNAT Pro technology is tested and qualified without any
7751 @option{-m} switches,
7752 so generally the most reliable approach is to avoid the use of these
7753 switches. However, we generally expect most of these switches to work
7754 successfully with GNAT Pro, and many customers have reported successful
7755 use of these options.
7757 Our general advice is to avoid the use of @option{-m} switches unless
7758 special needs lead to requirements in this area. In particular,
7759 there is no point in using @option{-m} switches to improve performance
7760 unless you actually see a performance improvement.
7764 @subsection Return Codes
7765 @cindex Return Codes
7766 @cindex @option{/RETURN_CODES=VMS}
7769 On VMS, GNAT compiled programs return POSIX-style codes by default,
7770 e.g.@: @option{/RETURN_CODES=POSIX}.
7772 To enable VMS style return codes, use GNAT BIND and LINK with the option
7773 @option{/RETURN_CODES=VMS}. For example:
7776 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7777 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7781 Programs built with /RETURN_CODES=VMS are suitable to be called in
7782 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7783 are suitable for spawning with appropriate GNAT RTL routines.
7787 @node Search Paths and the Run-Time Library (RTL)
7788 @section Search Paths and the Run-Time Library (RTL)
7791 With the GNAT source-based library system, the compiler must be able to
7792 find source files for units that are needed by the unit being compiled.
7793 Search paths are used to guide this process.
7795 The compiler compiles one source file whose name must be given
7796 explicitly on the command line. In other words, no searching is done
7797 for this file. To find all other source files that are needed (the most
7798 common being the specs of units), the compiler examines the following
7799 directories, in the following order:
7803 The directory containing the source file of the main unit being compiled
7804 (the file name on the command line).
7807 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7808 @command{gcc} command line, in the order given.
7811 @findex ADA_PRJ_INCLUDE_FILE
7812 Each of the directories listed in the text file whose name is given
7813 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7816 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7817 driver when project files are used. It should not normally be set
7821 @findex ADA_INCLUDE_PATH
7822 Each of the directories listed in the value of the
7823 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7825 Construct this value
7826 exactly as the @env{PATH} environment variable: a list of directory
7827 names separated by colons (semicolons when working with the NT version).
7830 Normally, define this value as a logical name containing a comma separated
7831 list of directory names.
7833 This variable can also be defined by means of an environment string
7834 (an argument to the HP C exec* set of functions).
7838 DEFINE ANOTHER_PATH FOO:[BAG]
7839 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7842 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7843 first, followed by the standard Ada
7844 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7845 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7846 (Text_IO, Sequential_IO, etc)
7847 instead of the standard Ada packages. Thus, in order to get the standard Ada
7848 packages by default, ADA_INCLUDE_PATH must be redefined.
7852 The content of the @file{ada_source_path} file which is part of the GNAT
7853 installation tree and is used to store standard libraries such as the
7854 GNAT Run Time Library (RTL) source files.
7856 @ref{Installing a library}
7861 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7862 inhibits the use of the directory
7863 containing the source file named in the command line. You can still
7864 have this directory on your search path, but in this case it must be
7865 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7867 Specifying the switch @option{-nostdinc}
7868 inhibits the search of the default location for the GNAT Run Time
7869 Library (RTL) source files.
7871 The compiler outputs its object files and ALI files in the current
7874 Caution: The object file can be redirected with the @option{-o} switch;
7875 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7876 so the @file{ALI} file will not go to the right place. Therefore, you should
7877 avoid using the @option{-o} switch.
7881 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7882 children make up the GNAT RTL, together with the simple @code{System.IO}
7883 package used in the @code{"Hello World"} example. The sources for these units
7884 are needed by the compiler and are kept together in one directory. Not
7885 all of the bodies are needed, but all of the sources are kept together
7886 anyway. In a normal installation, you need not specify these directory
7887 names when compiling or binding. Either the environment variables or
7888 the built-in defaults cause these files to be found.
7890 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7891 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7892 consisting of child units of @code{GNAT}. This is a collection of generally
7893 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7894 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7896 Besides simplifying access to the RTL, a major use of search paths is
7897 in compiling sources from multiple directories. This can make
7898 development environments much more flexible.
7900 @node Order of Compilation Issues
7901 @section Order of Compilation Issues
7904 If, in our earlier example, there was a spec for the @code{hello}
7905 procedure, it would be contained in the file @file{hello.ads}; yet this
7906 file would not have to be explicitly compiled. This is the result of the
7907 model we chose to implement library management. Some of the consequences
7908 of this model are as follows:
7912 There is no point in compiling specs (except for package
7913 specs with no bodies) because these are compiled as needed by clients. If
7914 you attempt a useless compilation, you will receive an error message.
7915 It is also useless to compile subunits because they are compiled as needed
7919 There are no order of compilation requirements: performing a
7920 compilation never obsoletes anything. The only way you can obsolete
7921 something and require recompilations is to modify one of the
7922 source files on which it depends.
7925 There is no library as such, apart from the ALI files
7926 (@pxref{The Ada Library Information Files}, for information on the format
7927 of these files). For now we find it convenient to create separate ALI files,
7928 but eventually the information therein may be incorporated into the object
7932 When you compile a unit, the source files for the specs of all units
7933 that it @code{with}'s, all its subunits, and the bodies of any generics it
7934 instantiates must be available (reachable by the search-paths mechanism
7935 described above), or you will receive a fatal error message.
7942 The following are some typical Ada compilation command line examples:
7945 @item $ gcc -c xyz.adb
7946 Compile body in file @file{xyz.adb} with all default options.
7949 @item $ gcc -c -O2 -gnata xyz-def.adb
7952 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7955 Compile the child unit package in file @file{xyz-def.adb} with extensive
7956 optimizations, and pragma @code{Assert}/@code{Debug} statements
7959 @item $ gcc -c -gnatc abc-def.adb
7960 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7964 @node Binding Using gnatbind
7965 @chapter Binding Using @code{gnatbind}
7969 * Running gnatbind::
7970 * Switches for gnatbind::
7971 * Command-Line Access::
7972 * Search Paths for gnatbind::
7973 * Examples of gnatbind Usage::
7977 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7978 to bind compiled GNAT objects.
7980 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7981 driver (see @ref{The GNAT Driver and Project Files}).
7983 The @code{gnatbind} program performs four separate functions:
7987 Checks that a program is consistent, in accordance with the rules in
7988 Chapter 10 of the Ada Reference Manual. In particular, error
7989 messages are generated if a program uses inconsistent versions of a
7993 Checks that an acceptable order of elaboration exists for the program
7994 and issues an error message if it cannot find an order of elaboration
7995 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7998 Generates a main program incorporating the given elaboration order.
7999 This program is a small Ada package (body and spec) that
8000 must be subsequently compiled
8001 using the GNAT compiler. The necessary compilation step is usually
8002 performed automatically by @command{gnatlink}. The two most important
8003 functions of this program
8004 are to call the elaboration routines of units in an appropriate order
8005 and to call the main program.
8008 Determines the set of object files required by the given main program.
8009 This information is output in the forms of comments in the generated program,
8010 to be read by the @command{gnatlink} utility used to link the Ada application.
8013 @node Running gnatbind
8014 @section Running @code{gnatbind}
8017 The form of the @code{gnatbind} command is
8020 @c $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
8021 @c Expanding @ovar macro inline (explanation in macro def comments)
8022 $ gnatbind @r{[}@var{switches}@r{]} @var{mainprog}@r{[}.ali@r{]} @r{[}@var{switches}@r{]}
8026 where @file{@var{mainprog}.adb} is the Ada file containing the main program
8027 unit body. @code{gnatbind} constructs an Ada
8028 package in two files whose names are
8029 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
8030 For example, if given the
8031 parameter @file{hello.ali}, for a main program contained in file
8032 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
8033 and @file{b~hello.adb}.
8035 When doing consistency checking, the binder takes into consideration
8036 any source files it can locate. For example, if the binder determines
8037 that the given main program requires the package @code{Pack}, whose
8039 file is @file{pack.ali} and whose corresponding source spec file is
8040 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
8041 (using the same search path conventions as previously described for the
8042 @command{gcc} command). If it can locate this source file, it checks that
8044 or source checksums of the source and its references to in @file{ALI} files
8045 match. In other words, any @file{ALI} files that mentions this spec must have
8046 resulted from compiling this version of the source file (or in the case
8047 where the source checksums match, a version close enough that the
8048 difference does not matter).
8050 @cindex Source files, use by binder
8051 The effect of this consistency checking, which includes source files, is
8052 that the binder ensures that the program is consistent with the latest
8053 version of the source files that can be located at bind time. Editing a
8054 source file without compiling files that depend on the source file cause
8055 error messages to be generated by the binder.
8057 For example, suppose you have a main program @file{hello.adb} and a
8058 package @code{P}, from file @file{p.ads} and you perform the following
8063 Enter @code{gcc -c hello.adb} to compile the main program.
8066 Enter @code{gcc -c p.ads} to compile package @code{P}.
8069 Edit file @file{p.ads}.
8072 Enter @code{gnatbind hello}.
8076 At this point, the file @file{p.ali} contains an out-of-date time stamp
8077 because the file @file{p.ads} has been edited. The attempt at binding
8078 fails, and the binder generates the following error messages:
8081 error: "hello.adb" must be recompiled ("p.ads" has been modified)
8082 error: "p.ads" has been modified and must be recompiled
8086 Now both files must be recompiled as indicated, and then the bind can
8087 succeed, generating a main program. You need not normally be concerned
8088 with the contents of this file, but for reference purposes a sample
8089 binder output file is given in @ref{Example of Binder Output File}.
8091 In most normal usage, the default mode of @command{gnatbind} which is to
8092 generate the main package in Ada, as described in the previous section.
8093 In particular, this means that any Ada programmer can read and understand
8094 the generated main program. It can also be debugged just like any other
8095 Ada code provided the @option{^-g^/DEBUG^} switch is used for
8096 @command{gnatbind} and @command{gnatlink}.
8098 @node Switches for gnatbind
8099 @section Switches for @command{gnatbind}
8102 The following switches are available with @code{gnatbind}; details will
8103 be presented in subsequent sections.
8106 * Consistency-Checking Modes::
8107 * Binder Error Message Control::
8108 * Elaboration Control::
8110 * Dynamic Allocation Control::
8111 * Binding with Non-Ada Main Programs::
8112 * Binding Programs with No Main Subprogram::
8119 @cindex @option{--version} @command{gnatbind}
8120 Display Copyright and version, then exit disregarding all other options.
8123 @cindex @option{--help} @command{gnatbind}
8124 If @option{--version} was not used, display usage, then exit disregarding
8128 @cindex @option{-a} @command{gnatbind}
8129 Indicates that, if supported by the platform, the adainit procedure should
8130 be treated as an initialisation routine by the linker (a constructor). This
8131 is intended to be used by the Project Manager to automatically initialize
8132 shared Stand-Alone Libraries.
8134 @item ^-aO^/OBJECT_SEARCH^
8135 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
8136 Specify directory to be searched for ALI files.
8138 @item ^-aI^/SOURCE_SEARCH^
8139 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8140 Specify directory to be searched for source file.
8142 @item ^-A^/ALI_LIST^@r{[=}@var{filename}@r{]}
8143 @cindex @option{^-A^/ALI_LIST^} (@command{gnatbind})
8144 Output ALI list (to standard output or to the named file).
8146 @item ^-b^/REPORT_ERRORS=BRIEF^
8147 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
8148 Generate brief messages to @file{stderr} even if verbose mode set.
8150 @item ^-c^/NOOUTPUT^
8151 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
8152 Check only, no generation of binder output file.
8154 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8155 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
8156 This switch can be used to change the default task stack size value
8157 to a specified size @var{nn}, which is expressed in bytes by default, or
8158 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8160 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
8161 in effect, to completing all task specs with
8162 @smallexample @c ada
8163 pragma Storage_Size (nn);
8165 When they do not already have such a pragma.
8167 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8168 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
8169 This switch can be used to change the default secondary stack size value
8170 to a specified size @var{nn}, which is expressed in bytes by default, or
8171 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8174 The secondary stack is used to deal with functions that return a variable
8175 sized result, for example a function returning an unconstrained
8176 String. There are two ways in which this secondary stack is allocated.
8178 For most targets, the secondary stack is growing on demand and is allocated
8179 as a chain of blocks in the heap. The -D option is not very
8180 relevant. It only give some control over the size of the allocated
8181 blocks (whose size is the minimum of the default secondary stack size value,
8182 and the actual size needed for the current allocation request).
8184 For certain targets, notably VxWorks 653,
8185 the secondary stack is allocated by carving off a fixed ratio chunk of the
8186 primary task stack. The -D option is used to define the
8187 size of the environment task's secondary stack.
8189 @item ^-e^/ELABORATION_DEPENDENCIES^
8190 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
8191 Output complete list of elaboration-order dependencies.
8193 @item ^-E^/STORE_TRACEBACKS^
8194 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
8195 Store tracebacks in exception occurrences when the target supports it.
8197 @c The following may get moved to an appendix
8198 This option is currently supported on the following targets:
8199 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
8201 See also the packages @code{GNAT.Traceback} and
8202 @code{GNAT.Traceback.Symbolic} for more information.
8204 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
8205 @command{gcc} option.
8208 @item ^-F^/FORCE_ELABS_FLAGS^
8209 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
8210 Force the checks of elaboration flags. @command{gnatbind} does not normally
8211 generate checks of elaboration flags for the main executable, except when
8212 a Stand-Alone Library is used. However, there are cases when this cannot be
8213 detected by gnatbind. An example is importing an interface of a Stand-Alone
8214 Library through a pragma Import and only specifying through a linker switch
8215 this Stand-Alone Library. This switch is used to guarantee that elaboration
8216 flag checks are generated.
8219 @cindex @option{^-h^/HELP^} (@command{gnatbind})
8220 Output usage (help) information
8222 @item ^-H32^/32_MALLOC^
8223 @cindex @option{^-H32^/32_MALLOC^} (@command{gnatbind})
8224 Use 32-bit allocations for @code{__gnat_malloc} (and thus for access types).
8225 For further details see @ref{Dynamic Allocation Control}.
8227 @item ^-H64^/64_MALLOC^
8228 @cindex @option{^-H64^/64_MALLOC^} (@command{gnatbind})
8229 Use 64-bit allocations for @code{__gnat_malloc} (and thus for access types).
8230 @cindex @code{__gnat_malloc}
8231 For further details see @ref{Dynamic Allocation Control}.
8234 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8235 Specify directory to be searched for source and ALI files.
8237 @item ^-I-^/NOCURRENT_DIRECTORY^
8238 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
8239 Do not look for sources in the current directory where @code{gnatbind} was
8240 invoked, and do not look for ALI files in the directory containing the
8241 ALI file named in the @code{gnatbind} command line.
8243 @item ^-l^/ORDER_OF_ELABORATION^
8244 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
8245 Output chosen elaboration order.
8247 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
8248 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
8249 Bind the units for library building. In this case the adainit and
8250 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
8251 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
8252 ^@var{xxx}final^@var{XXX}FINAL^.
8253 Implies ^-n^/NOCOMPILE^.
8255 (@xref{GNAT and Libraries}, for more details.)
8258 On OpenVMS, these init and final procedures are exported in uppercase
8259 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
8260 the init procedure will be "TOTOINIT" and the exported name of the final
8261 procedure will be "TOTOFINAL".
8264 @item ^-Mxyz^/RENAME_MAIN=xyz^
8265 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
8266 Rename generated main program from main to xyz. This option is
8267 supported on cross environments only.
8269 @item ^-m^/ERROR_LIMIT=^@var{n}
8270 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
8271 Limit number of detected errors or warnings to @var{n}, where @var{n} is
8272 in the range 1..999999. The default value if no switch is
8273 given is 9999. If the number of warnings reaches this limit, then a
8274 message is output and further warnings are suppressed, the bind
8275 continues in this case. If the number of errors reaches this
8276 limit, then a message is output and the bind is abandoned.
8277 A value of zero means that no limit is enforced. The equal
8281 Furthermore, under Windows, the sources pointed to by the libraries path
8282 set in the registry are not searched for.
8286 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8290 @cindex @option{-nostdinc} (@command{gnatbind})
8291 Do not look for sources in the system default directory.
8294 @cindex @option{-nostdlib} (@command{gnatbind})
8295 Do not look for library files in the system default directory.
8297 @item --RTS=@var{rts-path}
8298 @cindex @option{--RTS} (@code{gnatbind})
8299 Specifies the default location of the runtime library. Same meaning as the
8300 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
8302 @item ^-o ^/OUTPUT=^@var{file}
8303 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
8304 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
8305 Note that if this option is used, then linking must be done manually,
8306 gnatlink cannot be used.
8308 @item ^-O^/OBJECT_LIST^@r{[=}@var{filename}@r{]}
8309 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
8310 Output object list (to standard output or to the named file).
8312 @item ^-p^/PESSIMISTIC_ELABORATION^
8313 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
8314 Pessimistic (worst-case) elaboration order
8317 @cindex @option{^-P^/CODEPEER^} (@command{gnatbind})
8318 Generate binder file suitable for CodePeer.
8321 @cindex @option{^-R^-R^} (@command{gnatbind})
8322 Output closure source list.
8324 @item ^-s^/READ_SOURCES=ALL^
8325 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
8326 Require all source files to be present.
8328 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
8329 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
8330 Specifies the value to be used when detecting uninitialized scalar
8331 objects with pragma Initialize_Scalars.
8332 The @var{xxx} ^string specified with the switch^option^ may be either
8334 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
8335 @item ``@option{^lo^LOW^}'' for the lowest possible value
8336 @item ``@option{^hi^HIGH^}'' for the highest possible value
8337 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
8338 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
8341 In addition, you can specify @option{-Sev} to indicate that the value is
8342 to be set at run time. In this case, the program will look for an environment
8343 @cindex GNAT_INIT_SCALARS
8344 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
8345 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
8346 If no environment variable is found, or if it does not have a valid value,
8347 then the default is @option{in} (invalid values).
8351 @cindex @option{-static} (@code{gnatbind})
8352 Link against a static GNAT run time.
8355 @cindex @option{-shared} (@code{gnatbind})
8356 Link against a shared GNAT run time when available.
8359 @item ^-t^/NOTIME_STAMP_CHECK^
8360 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8361 Tolerate time stamp and other consistency errors
8363 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
8364 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
8365 Set the time slice value to @var{n} milliseconds. If the system supports
8366 the specification of a specific time slice value, then the indicated value
8367 is used. If the system does not support specific time slice values, but
8368 does support some general notion of round-robin scheduling, then any
8369 nonzero value will activate round-robin scheduling.
8371 A value of zero is treated specially. It turns off time
8372 slicing, and in addition, indicates to the tasking run time that the
8373 semantics should match as closely as possible the Annex D
8374 requirements of the Ada RM, and in particular sets the default
8375 scheduling policy to @code{FIFO_Within_Priorities}.
8377 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
8378 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
8379 Enable dynamic stack usage, with @var{n} results stored and displayed
8380 at program termination. A result is generated when a task
8381 terminates. Results that can't be stored are displayed on the fly, at
8382 task termination. This option is currently not supported on Itanium
8383 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
8385 @item ^-v^/REPORT_ERRORS=VERBOSE^
8386 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8387 Verbose mode. Write error messages, header, summary output to
8392 @cindex @option{-w} (@code{gnatbind})
8393 Warning mode (@var{x}=s/e for suppress/treat as error)
8397 @item /WARNINGS=NORMAL
8398 @cindex @option{/WARNINGS} (@code{gnatbind})
8399 Normal warnings mode. Warnings are issued but ignored
8401 @item /WARNINGS=SUPPRESS
8402 @cindex @option{/WARNINGS} (@code{gnatbind})
8403 All warning messages are suppressed
8405 @item /WARNINGS=ERROR
8406 @cindex @option{/WARNINGS} (@code{gnatbind})
8407 Warning messages are treated as fatal errors
8410 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8411 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8412 Override default wide character encoding for standard Text_IO files.
8414 @item ^-x^/READ_SOURCES=NONE^
8415 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
8416 Exclude source files (check object consistency only).
8419 @item /READ_SOURCES=AVAILABLE
8420 @cindex @option{/READ_SOURCES} (@code{gnatbind})
8421 Default mode, in which sources are checked for consistency only if
8425 @item ^-y^/ENABLE_LEAP_SECONDS^
8426 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
8427 Enable leap seconds support in @code{Ada.Calendar} and its children.
8429 @item ^-z^/ZERO_MAIN^
8430 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8436 You may obtain this listing of switches by running @code{gnatbind} with
8440 @node Consistency-Checking Modes
8441 @subsection Consistency-Checking Modes
8444 As described earlier, by default @code{gnatbind} checks
8445 that object files are consistent with one another and are consistent
8446 with any source files it can locate. The following switches control binder
8451 @item ^-s^/READ_SOURCES=ALL^
8452 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8453 Require source files to be present. In this mode, the binder must be
8454 able to locate all source files that are referenced, in order to check
8455 their consistency. In normal mode, if a source file cannot be located it
8456 is simply ignored. If you specify this switch, a missing source
8459 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8460 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8461 Override default wide character encoding for standard Text_IO files.
8462 Normally the default wide character encoding method used for standard
8463 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8464 the main source input (see description of switch
8465 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8466 use of this switch for the binder (which has the same set of
8467 possible arguments) overrides this default as specified.
8469 @item ^-x^/READ_SOURCES=NONE^
8470 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8471 Exclude source files. In this mode, the binder only checks that ALI
8472 files are consistent with one another. Source files are not accessed.
8473 The binder runs faster in this mode, and there is still a guarantee that
8474 the resulting program is self-consistent.
8475 If a source file has been edited since it was last compiled, and you
8476 specify this switch, the binder will not detect that the object
8477 file is out of date with respect to the source file. Note that this is the
8478 mode that is automatically used by @command{gnatmake} because in this
8479 case the checking against sources has already been performed by
8480 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8483 @item /READ_SOURCES=AVAILABLE
8484 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8485 This is the default mode in which source files are checked if they are
8486 available, and ignored if they are not available.
8490 @node Binder Error Message Control
8491 @subsection Binder Error Message Control
8494 The following switches provide control over the generation of error
8495 messages from the binder:
8499 @item ^-v^/REPORT_ERRORS=VERBOSE^
8500 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8501 Verbose mode. In the normal mode, brief error messages are generated to
8502 @file{stderr}. If this switch is present, a header is written
8503 to @file{stdout} and any error messages are directed to @file{stdout}.
8504 All that is written to @file{stderr} is a brief summary message.
8506 @item ^-b^/REPORT_ERRORS=BRIEF^
8507 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8508 Generate brief error messages to @file{stderr} even if verbose mode is
8509 specified. This is relevant only when used with the
8510 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8514 @cindex @option{-m} (@code{gnatbind})
8515 Limits the number of error messages to @var{n}, a decimal integer in the
8516 range 1-999. The binder terminates immediately if this limit is reached.
8519 @cindex @option{-M} (@code{gnatbind})
8520 Renames the generated main program from @code{main} to @code{xxx}.
8521 This is useful in the case of some cross-building environments, where
8522 the actual main program is separate from the one generated
8526 @item ^-ws^/WARNINGS=SUPPRESS^
8527 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8529 Suppress all warning messages.
8531 @item ^-we^/WARNINGS=ERROR^
8532 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8533 Treat any warning messages as fatal errors.
8536 @item /WARNINGS=NORMAL
8537 Standard mode with warnings generated, but warnings do not get treated
8541 @item ^-t^/NOTIME_STAMP_CHECK^
8542 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8543 @cindex Time stamp checks, in binder
8544 @cindex Binder consistency checks
8545 @cindex Consistency checks, in binder
8546 The binder performs a number of consistency checks including:
8550 Check that time stamps of a given source unit are consistent
8552 Check that checksums of a given source unit are consistent
8554 Check that consistent versions of @code{GNAT} were used for compilation
8556 Check consistency of configuration pragmas as required
8560 Normally failure of such checks, in accordance with the consistency
8561 requirements of the Ada Reference Manual, causes error messages to be
8562 generated which abort the binder and prevent the output of a binder
8563 file and subsequent link to obtain an executable.
8565 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8566 into warnings, so that
8567 binding and linking can continue to completion even in the presence of such
8568 errors. The result may be a failed link (due to missing symbols), or a
8569 non-functional executable which has undefined semantics.
8570 @emph{This means that
8571 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8575 @node Elaboration Control
8576 @subsection Elaboration Control
8579 The following switches provide additional control over the elaboration
8580 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8583 @item ^-p^/PESSIMISTIC_ELABORATION^
8584 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8585 Normally the binder attempts to choose an elaboration order that is
8586 likely to minimize the likelihood of an elaboration order error resulting
8587 in raising a @code{Program_Error} exception. This switch reverses the
8588 action of the binder, and requests that it deliberately choose an order
8589 that is likely to maximize the likelihood of an elaboration error.
8590 This is useful in ensuring portability and avoiding dependence on
8591 accidental fortuitous elaboration ordering.
8593 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8595 elaboration checking is used (@option{-gnatE} switch used for compilation).
8596 This is because in the default static elaboration mode, all necessary
8597 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8598 These implicit pragmas are still respected by the binder in
8599 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8600 safe elaboration order is assured.
8603 @node Output Control
8604 @subsection Output Control
8607 The following switches allow additional control over the output
8608 generated by the binder.
8613 @item ^-c^/NOOUTPUT^
8614 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8615 Check only. Do not generate the binder output file. In this mode the
8616 binder performs all error checks but does not generate an output file.
8618 @item ^-e^/ELABORATION_DEPENDENCIES^
8619 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8620 Output complete list of elaboration-order dependencies, showing the
8621 reason for each dependency. This output can be rather extensive but may
8622 be useful in diagnosing problems with elaboration order. The output is
8623 written to @file{stdout}.
8626 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8627 Output usage information. The output is written to @file{stdout}.
8629 @item ^-K^/LINKER_OPTION_LIST^
8630 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8631 Output linker options to @file{stdout}. Includes library search paths,
8632 contents of pragmas Ident and Linker_Options, and libraries added
8635 @item ^-l^/ORDER_OF_ELABORATION^
8636 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8637 Output chosen elaboration order. The output is written to @file{stdout}.
8639 @item ^-O^/OBJECT_LIST^
8640 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8641 Output full names of all the object files that must be linked to provide
8642 the Ada component of the program. The output is written to @file{stdout}.
8643 This list includes the files explicitly supplied and referenced by the user
8644 as well as implicitly referenced run-time unit files. The latter are
8645 omitted if the corresponding units reside in shared libraries. The
8646 directory names for the run-time units depend on the system configuration.
8648 @item ^-o ^/OUTPUT=^@var{file}
8649 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8650 Set name of output file to @var{file} instead of the normal
8651 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8652 binder generated body filename.
8653 Note that if this option is used, then linking must be done manually.
8654 It is not possible to use gnatlink in this case, since it cannot locate
8657 @item ^-r^/RESTRICTION_LIST^
8658 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8659 Generate list of @code{pragma Restrictions} that could be applied to
8660 the current unit. This is useful for code audit purposes, and also may
8661 be used to improve code generation in some cases.
8665 @node Dynamic Allocation Control
8666 @subsection Dynamic Allocation Control
8669 The heap control switches -- @option{-H32} and @option{-H64} --
8670 determine whether dynamic allocation uses 32-bit or 64-bit memory.
8671 They only affect compiler-generated allocations via @code{__gnat_malloc};
8672 explicit calls to @code{malloc} and related functions from the C
8673 run-time library are unaffected.
8677 Allocate memory on 32-bit heap
8680 Allocate memory on 64-bit heap. This is the default
8681 unless explicitly overridden by a @code{'Size} clause on the access type.
8686 See also @ref{Access types and 32/64-bit allocation}.
8690 These switches are only effective on VMS platforms.
8694 @node Binding with Non-Ada Main Programs
8695 @subsection Binding with Non-Ada Main Programs
8698 In our description so far we have assumed that the main
8699 program is in Ada, and that the task of the binder is to generate a
8700 corresponding function @code{main} that invokes this Ada main
8701 program. GNAT also supports the building of executable programs where
8702 the main program is not in Ada, but some of the called routines are
8703 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8704 The following switch is used in this situation:
8708 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8709 No main program. The main program is not in Ada.
8713 In this case, most of the functions of the binder are still required,
8714 but instead of generating a main program, the binder generates a file
8715 containing the following callable routines:
8720 You must call this routine to initialize the Ada part of the program by
8721 calling the necessary elaboration routines. A call to @code{adainit} is
8722 required before the first call to an Ada subprogram.
8724 Note that it is assumed that the basic execution environment must be setup
8725 to be appropriate for Ada execution at the point where the first Ada
8726 subprogram is called. In particular, if the Ada code will do any
8727 floating-point operations, then the FPU must be setup in an appropriate
8728 manner. For the case of the x86, for example, full precision mode is
8729 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8730 that the FPU is in the right state.
8734 You must call this routine to perform any library-level finalization
8735 required by the Ada subprograms. A call to @code{adafinal} is required
8736 after the last call to an Ada subprogram, and before the program
8741 If the @option{^-n^/NOMAIN^} switch
8742 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8743 @cindex Binder, multiple input files
8744 is given, more than one ALI file may appear on
8745 the command line for @code{gnatbind}. The normal @dfn{closure}
8746 calculation is performed for each of the specified units. Calculating
8747 the closure means finding out the set of units involved by tracing
8748 @code{with} references. The reason it is necessary to be able to
8749 specify more than one ALI file is that a given program may invoke two or
8750 more quite separate groups of Ada units.
8752 The binder takes the name of its output file from the last specified ALI
8753 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8754 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8755 The output is an Ada unit in source form that can be compiled with GNAT.
8756 This compilation occurs automatically as part of the @command{gnatlink}
8759 Currently the GNAT run time requires a FPU using 80 bits mode
8760 precision. Under targets where this is not the default it is required to
8761 call GNAT.Float_Control.Reset before using floating point numbers (this
8762 include float computation, float input and output) in the Ada code. A
8763 side effect is that this could be the wrong mode for the foreign code
8764 where floating point computation could be broken after this call.
8766 @node Binding Programs with No Main Subprogram
8767 @subsection Binding Programs with No Main Subprogram
8770 It is possible to have an Ada program which does not have a main
8771 subprogram. This program will call the elaboration routines of all the
8772 packages, then the finalization routines.
8774 The following switch is used to bind programs organized in this manner:
8777 @item ^-z^/ZERO_MAIN^
8778 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8779 Normally the binder checks that the unit name given on the command line
8780 corresponds to a suitable main subprogram. When this switch is used,
8781 a list of ALI files can be given, and the execution of the program
8782 consists of elaboration of these units in an appropriate order. Note
8783 that the default wide character encoding method for standard Text_IO
8784 files is always set to Brackets if this switch is set (you can use
8786 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8789 @node Command-Line Access
8790 @section Command-Line Access
8793 The package @code{Ada.Command_Line} provides access to the command-line
8794 arguments and program name. In order for this interface to operate
8795 correctly, the two variables
8807 are declared in one of the GNAT library routines. These variables must
8808 be set from the actual @code{argc} and @code{argv} values passed to the
8809 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8810 generates the C main program to automatically set these variables.
8811 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8812 set these variables. If they are not set, the procedures in
8813 @code{Ada.Command_Line} will not be available, and any attempt to use
8814 them will raise @code{Constraint_Error}. If command line access is
8815 required, your main program must set @code{gnat_argc} and
8816 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8819 @node Search Paths for gnatbind
8820 @section Search Paths for @code{gnatbind}
8823 The binder takes the name of an ALI file as its argument and needs to
8824 locate source files as well as other ALI files to verify object consistency.
8826 For source files, it follows exactly the same search rules as @command{gcc}
8827 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8828 directories searched are:
8832 The directory containing the ALI file named in the command line, unless
8833 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8836 All directories specified by @option{^-I^/SEARCH^}
8837 switches on the @code{gnatbind}
8838 command line, in the order given.
8841 @findex ADA_PRJ_OBJECTS_FILE
8842 Each of the directories listed in the text file whose name is given
8843 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8846 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8847 driver when project files are used. It should not normally be set
8851 @findex ADA_OBJECTS_PATH
8852 Each of the directories listed in the value of the
8853 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8855 Construct this value
8856 exactly as the @env{PATH} environment variable: a list of directory
8857 names separated by colons (semicolons when working with the NT version
8861 Normally, define this value as a logical name containing a comma separated
8862 list of directory names.
8864 This variable can also be defined by means of an environment string
8865 (an argument to the HP C exec* set of functions).
8869 DEFINE ANOTHER_PATH FOO:[BAG]
8870 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8873 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8874 first, followed by the standard Ada
8875 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8876 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8877 (Text_IO, Sequential_IO, etc)
8878 instead of the standard Ada packages. Thus, in order to get the standard Ada
8879 packages by default, ADA_OBJECTS_PATH must be redefined.
8883 The content of the @file{ada_object_path} file which is part of the GNAT
8884 installation tree and is used to store standard libraries such as the
8885 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8888 @ref{Installing a library}
8893 In the binder the switch @option{^-I^/SEARCH^}
8894 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8895 is used to specify both source and
8896 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8897 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8898 instead if you want to specify
8899 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8900 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8901 if you want to specify library paths
8902 only. This means that for the binder
8903 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8904 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8905 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8906 The binder generates the bind file (a C language source file) in the
8907 current working directory.
8913 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8914 children make up the GNAT Run-Time Library, together with the package
8915 GNAT and its children, which contain a set of useful additional
8916 library functions provided by GNAT. The sources for these units are
8917 needed by the compiler and are kept together in one directory. The ALI
8918 files and object files generated by compiling the RTL are needed by the
8919 binder and the linker and are kept together in one directory, typically
8920 different from the directory containing the sources. In a normal
8921 installation, you need not specify these directory names when compiling
8922 or binding. Either the environment variables or the built-in defaults
8923 cause these files to be found.
8925 Besides simplifying access to the RTL, a major use of search paths is
8926 in compiling sources from multiple directories. This can make
8927 development environments much more flexible.
8929 @node Examples of gnatbind Usage
8930 @section Examples of @code{gnatbind} Usage
8933 This section contains a number of examples of using the GNAT binding
8934 utility @code{gnatbind}.
8937 @item gnatbind hello
8938 The main program @code{Hello} (source program in @file{hello.adb}) is
8939 bound using the standard switch settings. The generated main program is
8940 @file{b~hello.adb}. This is the normal, default use of the binder.
8943 @item gnatbind hello -o mainprog.adb
8946 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8948 The main program @code{Hello} (source program in @file{hello.adb}) is
8949 bound using the standard switch settings. The generated main program is
8950 @file{mainprog.adb} with the associated spec in
8951 @file{mainprog.ads}. Note that you must specify the body here not the
8952 spec. Note that if this option is used, then linking must be done manually,
8953 since gnatlink will not be able to find the generated file.
8956 @c ------------------------------------
8957 @node Linking Using gnatlink
8958 @chapter Linking Using @command{gnatlink}
8959 @c ------------------------------------
8963 This chapter discusses @command{gnatlink}, a tool that links
8964 an Ada program and builds an executable file. This utility
8965 invokes the system linker ^(via the @command{gcc} command)^^
8966 with a correct list of object files and library references.
8967 @command{gnatlink} automatically determines the list of files and
8968 references for the Ada part of a program. It uses the binder file
8969 generated by the @command{gnatbind} to determine this list.
8971 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8972 driver (see @ref{The GNAT Driver and Project Files}).
8975 * Running gnatlink::
8976 * Switches for gnatlink::
8979 @node Running gnatlink
8980 @section Running @command{gnatlink}
8983 The form of the @command{gnatlink} command is
8986 @c $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8987 @c @ovar{non-Ada objects} @ovar{linker options}
8988 @c Expanding @ovar macro inline (explanation in macro def comments)
8989 $ gnatlink @r{[}@var{switches}@r{]} @var{mainprog}@r{[}.ali@r{]}
8990 @r{[}@var{non-Ada objects}@r{]} @r{[}@var{linker options}@r{]}
8995 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8997 or linker options) may be in any order, provided that no non-Ada object may
8998 be mistaken for a main @file{ALI} file.
8999 Any file name @file{F} without the @file{.ali}
9000 extension will be taken as the main @file{ALI} file if a file exists
9001 whose name is the concatenation of @file{F} and @file{.ali}.
9004 @file{@var{mainprog}.ali} references the ALI file of the main program.
9005 The @file{.ali} extension of this file can be omitted. From this
9006 reference, @command{gnatlink} locates the corresponding binder file
9007 @file{b~@var{mainprog}.adb} and, using the information in this file along
9008 with the list of non-Ada objects and linker options, constructs a
9009 linker command file to create the executable.
9011 The arguments other than the @command{gnatlink} switches and the main
9012 @file{ALI} file are passed to the linker uninterpreted.
9013 They typically include the names of
9014 object files for units written in other languages than Ada and any library
9015 references required to resolve references in any of these foreign language
9016 units, or in @code{Import} pragmas in any Ada units.
9018 @var{linker options} is an optional list of linker specific
9020 The default linker called by gnatlink is @command{gcc} which in
9021 turn calls the appropriate system linker.
9023 One useful option for the linker is @option{-s}: it reduces the size of the
9024 executable by removing all symbol table and relocation information from the
9027 Standard options for the linker such as @option{-lmy_lib} or
9028 @option{-Ldir} can be added as is.
9029 For options that are not recognized by
9030 @command{gcc} as linker options, use the @command{gcc} switches
9031 @option{-Xlinker} or @option{-Wl,}.
9033 Refer to the GCC documentation for
9036 Here is an example showing how to generate a linker map:
9039 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
9042 Using @var{linker options} it is possible to set the program stack and
9045 See @ref{Setting Stack Size from gnatlink} and
9046 @ref{Setting Heap Size from gnatlink}.
9049 @command{gnatlink} determines the list of objects required by the Ada
9050 program and prepends them to the list of objects passed to the linker.
9051 @command{gnatlink} also gathers any arguments set by the use of
9052 @code{pragma Linker_Options} and adds them to the list of arguments
9053 presented to the linker.
9056 @command{gnatlink} accepts the following types of extra files on the command
9057 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
9058 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
9059 handled according to their extension.
9062 @node Switches for gnatlink
9063 @section Switches for @command{gnatlink}
9066 The following switches are available with the @command{gnatlink} utility:
9072 @cindex @option{--version} @command{gnatlink}
9073 Display Copyright and version, then exit disregarding all other options.
9076 @cindex @option{--help} @command{gnatlink}
9077 If @option{--version} was not used, display usage, then exit disregarding
9080 @item ^-f^/FORCE_OBJECT_FILE_LIST^
9081 @cindex Command line length
9082 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
9083 On some targets, the command line length is limited, and @command{gnatlink}
9084 will generate a separate file for the linker if the list of object files
9086 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
9087 to be generated even if
9088 the limit is not exceeded. This is useful in some cases to deal with
9089 special situations where the command line length is exceeded.
9092 @cindex Debugging information, including
9093 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
9094 The option to include debugging information causes the Ada bind file (in
9095 other words, @file{b~@var{mainprog}.adb}) to be compiled with
9096 @option{^-g^/DEBUG^}.
9097 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
9098 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
9099 Without @option{^-g^/DEBUG^}, the binder removes these files by
9100 default. The same procedure apply if a C bind file was generated using
9101 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
9102 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
9104 @item ^-n^/NOCOMPILE^
9105 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
9106 Do not compile the file generated by the binder. This may be used when
9107 a link is rerun with different options, but there is no need to recompile
9111 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
9112 Causes additional information to be output, including a full list of the
9113 included object files. This switch option is most useful when you want
9114 to see what set of object files are being used in the link step.
9116 @item ^-v -v^/VERBOSE/VERBOSE^
9117 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
9118 Very verbose mode. Requests that the compiler operate in verbose mode when
9119 it compiles the binder file, and that the system linker run in verbose mode.
9121 @item ^-o ^/EXECUTABLE=^@var{exec-name}
9122 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
9123 @var{exec-name} specifies an alternate name for the generated
9124 executable program. If this switch is omitted, the executable has the same
9125 name as the main unit. For example, @code{gnatlink try.ali} creates
9126 an executable called @file{^try^TRY.EXE^}.
9129 @item -b @var{target}
9130 @cindex @option{-b} (@command{gnatlink})
9131 Compile your program to run on @var{target}, which is the name of a
9132 system configuration. You must have a GNAT cross-compiler built if
9133 @var{target} is not the same as your host system.
9136 @cindex @option{-B} (@command{gnatlink})
9137 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
9138 from @var{dir} instead of the default location. Only use this switch
9139 when multiple versions of the GNAT compiler are available.
9140 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
9141 for further details. You would normally use the @option{-b} or
9142 @option{-V} switch instead.
9145 When linking an executable, create a map file. The name of the map file
9146 has the same name as the executable with extension ".map".
9149 When linking an executable, create a map file. The name of the map file is
9152 @item --GCC=@var{compiler_name}
9153 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
9154 Program used for compiling the binder file. The default is
9155 @command{gcc}. You need to use quotes around @var{compiler_name} if
9156 @code{compiler_name} contains spaces or other separator characters.
9157 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
9158 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
9159 inserted after your command name. Thus in the above example the compiler
9160 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
9161 A limitation of this syntax is that the name and path name of the executable
9162 itself must not include any embedded spaces. If the compiler executable is
9163 different from the default one (gcc or <prefix>-gcc), then the back-end
9164 switches in the ALI file are not used to compile the binder generated source.
9165 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
9166 switches will be used for @option{--GCC="gcc -gnatv"}. If several
9167 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
9168 is taken into account. However, all the additional switches are also taken
9170 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9171 @option{--GCC="bar -x -y -z -t"}.
9173 @item --LINK=@var{name}
9174 @cindex @option{--LINK=} (@command{gnatlink})
9175 @var{name} is the name of the linker to be invoked. This is especially
9176 useful in mixed language programs since languages such as C++ require
9177 their own linker to be used. When this switch is omitted, the default
9178 name for the linker is @command{gcc}. When this switch is used, the
9179 specified linker is called instead of @command{gcc} with exactly the same
9180 parameters that would have been passed to @command{gcc} so if the desired
9181 linker requires different parameters it is necessary to use a wrapper
9182 script that massages the parameters before invoking the real linker. It
9183 may be useful to control the exact invocation by using the verbose
9189 @item /DEBUG=TRACEBACK
9190 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
9191 This qualifier causes sufficient information to be included in the
9192 executable file to allow a traceback, but does not include the full
9193 symbol information needed by the debugger.
9195 @item /IDENTIFICATION="<string>"
9196 @code{"<string>"} specifies the string to be stored in the image file
9197 identification field in the image header.
9198 It overrides any pragma @code{Ident} specified string.
9200 @item /NOINHIBIT-EXEC
9201 Generate the executable file even if there are linker warnings.
9203 @item /NOSTART_FILES
9204 Don't link in the object file containing the ``main'' transfer address.
9205 Used when linking with a foreign language main program compiled with an
9209 Prefer linking with object libraries over sharable images, even without
9215 @node The GNAT Make Program gnatmake
9216 @chapter The GNAT Make Program @command{gnatmake}
9220 * Running gnatmake::
9221 * Switches for gnatmake::
9222 * Mode Switches for gnatmake::
9223 * Notes on the Command Line::
9224 * How gnatmake Works::
9225 * Examples of gnatmake Usage::
9228 A typical development cycle when working on an Ada program consists of
9229 the following steps:
9233 Edit some sources to fix bugs.
9239 Compile all sources affected.
9249 The third step can be tricky, because not only do the modified files
9250 @cindex Dependency rules
9251 have to be compiled, but any files depending on these files must also be
9252 recompiled. The dependency rules in Ada can be quite complex, especially
9253 in the presence of overloading, @code{use} clauses, generics and inlined
9256 @command{gnatmake} automatically takes care of the third and fourth steps
9257 of this process. It determines which sources need to be compiled,
9258 compiles them, and binds and links the resulting object files.
9260 Unlike some other Ada make programs, the dependencies are always
9261 accurately recomputed from the new sources. The source based approach of
9262 the GNAT compilation model makes this possible. This means that if
9263 changes to the source program cause corresponding changes in
9264 dependencies, they will always be tracked exactly correctly by
9267 @node Running gnatmake
9268 @section Running @command{gnatmake}
9271 The usual form of the @command{gnatmake} command is
9274 @c $ gnatmake @ovar{switches} @var{file_name}
9275 @c @ovar{file_names} @ovar{mode_switches}
9276 @c Expanding @ovar macro inline (explanation in macro def comments)
9277 $ gnatmake @r{[}@var{switches}@r{]} @var{file_name}
9278 @r{[}@var{file_names}@r{]} @r{[}@var{mode_switches}@r{]}
9282 The only required argument is one @var{file_name}, which specifies
9283 a compilation unit that is a main program. Several @var{file_names} can be
9284 specified: this will result in several executables being built.
9285 If @code{switches} are present, they can be placed before the first
9286 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
9287 If @var{mode_switches} are present, they must always be placed after
9288 the last @var{file_name} and all @code{switches}.
9290 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
9291 extension may be omitted from the @var{file_name} arguments. However, if
9292 you are using non-standard extensions, then it is required that the
9293 extension be given. A relative or absolute directory path can be
9294 specified in a @var{file_name}, in which case, the input source file will
9295 be searched for in the specified directory only. Otherwise, the input
9296 source file will first be searched in the directory where
9297 @command{gnatmake} was invoked and if it is not found, it will be search on
9298 the source path of the compiler as described in
9299 @ref{Search Paths and the Run-Time Library (RTL)}.
9301 All @command{gnatmake} output (except when you specify
9302 @option{^-M^/DEPENDENCIES_LIST^}) is to
9303 @file{stderr}. The output produced by the
9304 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
9307 @node Switches for gnatmake
9308 @section Switches for @command{gnatmake}
9311 You may specify any of the following switches to @command{gnatmake}:
9317 @cindex @option{--version} @command{gnatmake}
9318 Display Copyright and version, then exit disregarding all other options.
9321 @cindex @option{--help} @command{gnatmake}
9322 If @option{--version} was not used, display usage, then exit disregarding
9326 @item --GCC=@var{compiler_name}
9327 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
9328 Program used for compiling. The default is `@command{gcc}'. You need to use
9329 quotes around @var{compiler_name} if @code{compiler_name} contains
9330 spaces or other separator characters. As an example @option{--GCC="foo -x
9331 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
9332 compiler. A limitation of this syntax is that the name and path name of
9333 the executable itself must not include any embedded spaces. Note that
9334 switch @option{-c} is always inserted after your command name. Thus in the
9335 above example the compiler command that will be used by @command{gnatmake}
9336 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
9337 used, only the last @var{compiler_name} is taken into account. However,
9338 all the additional switches are also taken into account. Thus,
9339 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9340 @option{--GCC="bar -x -y -z -t"}.
9342 @item --GNATBIND=@var{binder_name}
9343 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
9344 Program used for binding. The default is `@code{gnatbind}'. You need to
9345 use quotes around @var{binder_name} if @var{binder_name} contains spaces
9346 or other separator characters. As an example @option{--GNATBIND="bar -x
9347 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
9348 binder. Binder switches that are normally appended by @command{gnatmake}
9349 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
9350 A limitation of this syntax is that the name and path name of the executable
9351 itself must not include any embedded spaces.
9353 @item --GNATLINK=@var{linker_name}
9354 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
9355 Program used for linking. The default is `@command{gnatlink}'. You need to
9356 use quotes around @var{linker_name} if @var{linker_name} contains spaces
9357 or other separator characters. As an example @option{--GNATLINK="lan -x
9358 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
9359 linker. Linker switches that are normally appended by @command{gnatmake} to
9360 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
9361 A limitation of this syntax is that the name and path name of the executable
9362 itself must not include any embedded spaces.
9366 @item ^--subdirs^/SUBDIRS^=subdir
9367 Actual object directory of each project file is the subdirectory subdir of the
9368 object directory specified or defaulted in the project file.
9370 @item ^--single-compile-per-obj-dir^/SINGLE_COMPILE_PER_OBJ_DIR^
9371 Disallow simultaneous compilations in the same object directory when
9372 project files are used.
9374 @item ^--unchecked-shared-lib-imports^/UNCHECKED_SHARED_LIB_IMPORTS^
9375 By default, shared library projects are not allowed to import static library
9376 projects. When this switch is used on the command line, this restriction is
9379 @item ^--source-info=<source info file>^/SRC_INFO=source-info-file^
9380 Specify a source info file. This switch is active only when project files
9381 are used. If the source info file is specified as a relative path, then it is
9382 relative to the object directory of the main project. If the source info file
9383 does not exist, then after the Project Manager has successfully parsed and
9384 processed the project files and found the sources, it creates the source info
9385 file. If the source info file already exists and can be read successfully,
9386 then the Project Manager will get all the needed information about the sources
9387 from the source info file and will not look for them. This reduces the time
9388 to process the project files, especially when looking for sources that take a
9389 long time. If the source info file exists but cannot be parsed successfully,
9390 the Project Manager will attempt to recreate it. If the Project Manager fails
9391 to create the source info file, a message is issued, but gnatmake does not
9392 fail. @command{gnatmake} "trusts" the source info file. This means that
9393 if the source files have changed (addition, deletion, moving to a different
9394 source directory), then the source info file need to be deleted and recreated.
9397 @item --create-map-file
9398 When linking an executable, create a map file. The name of the map file
9399 has the same name as the executable with extension ".map".
9401 @item --create-map-file=mapfile
9402 When linking an executable, create a map file. The name of the map file is
9407 @item ^-a^/ALL_FILES^
9408 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
9409 Consider all files in the make process, even the GNAT internal system
9410 files (for example, the predefined Ada library files), as well as any
9411 locked files. Locked files are files whose ALI file is write-protected.
9413 @command{gnatmake} does not check these files,
9414 because the assumption is that the GNAT internal files are properly up
9415 to date, and also that any write protected ALI files have been properly
9416 installed. Note that if there is an installation problem, such that one
9417 of these files is not up to date, it will be properly caught by the
9419 You may have to specify this switch if you are working on GNAT
9420 itself. The switch @option{^-a^/ALL_FILES^} is also useful
9421 in conjunction with @option{^-f^/FORCE_COMPILE^}
9422 if you need to recompile an entire application,
9423 including run-time files, using special configuration pragmas,
9424 such as a @code{Normalize_Scalars} pragma.
9427 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
9430 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
9433 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
9436 @item ^-b^/ACTIONS=BIND^
9437 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
9438 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
9439 compilation and binding, but no link.
9440 Can be combined with @option{^-l^/ACTIONS=LINK^}
9441 to do binding and linking. When not combined with
9442 @option{^-c^/ACTIONS=COMPILE^}
9443 all the units in the closure of the main program must have been previously
9444 compiled and must be up to date. The root unit specified by @var{file_name}
9445 may be given without extension, with the source extension or, if no GNAT
9446 Project File is specified, with the ALI file extension.
9448 @item ^-c^/ACTIONS=COMPILE^
9449 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
9450 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
9451 is also specified. Do not perform linking, except if both
9452 @option{^-b^/ACTIONS=BIND^} and
9453 @option{^-l^/ACTIONS=LINK^} are also specified.
9454 If the root unit specified by @var{file_name} is not a main unit, this is the
9455 default. Otherwise @command{gnatmake} will attempt binding and linking
9456 unless all objects are up to date and the executable is more recent than
9460 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
9461 Use a temporary mapping file. A mapping file is a way to communicate
9462 to the compiler two mappings: from unit names to file names (without
9463 any directory information) and from file names to path names (with
9464 full directory information). A mapping file can make the compiler's
9465 file searches faster, especially if there are many source directories,
9466 or the sources are read over a slow network connection. If
9467 @option{^-P^/PROJECT_FILE^} is used, a mapping file is always used, so
9468 @option{^-C^/MAPPING^} is unnecessary; in this case the mapping file
9469 is initially populated based on the project file. If
9470 @option{^-C^/MAPPING^} is used without
9471 @option{^-P^/PROJECT_FILE^},
9472 the mapping file is initially empty. Each invocation of the compiler
9473 will add any newly accessed sources to the mapping file.
9475 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
9476 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
9477 Use a specific mapping file. The file, specified as a path name (absolute or
9478 relative) by this switch, should already exist, otherwise the switch is
9479 ineffective. The specified mapping file will be communicated to the compiler.
9480 This switch is not compatible with a project file
9481 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9482 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9484 @item ^-d^/DISPLAY_PROGRESS^
9485 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9486 Display progress for each source, up to date or not, as a single line
9489 completed x out of y (zz%)
9492 If the file needs to be compiled this is displayed after the invocation of
9493 the compiler. These lines are displayed even in quiet output mode.
9495 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9496 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9497 Put all object files and ALI file in directory @var{dir}.
9498 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9499 and ALI files go in the current working directory.
9501 This switch cannot be used when using a project file.
9505 @cindex @option{-eL} (@command{gnatmake})
9506 @cindex symbolic links
9507 Follow all symbolic links when processing project files.
9508 This should be used if your project uses symbolic links for files or
9509 directories, but is not needed in other cases.
9511 @cindex naming scheme
9512 This also assumes that no directory matches the naming scheme for files (for
9513 instance that you do not have a directory called "sources.ads" when using the
9514 default GNAT naming scheme).
9516 When you do not have to use this switch (i.e.@: by default), gnatmake is able to
9517 save a lot of system calls (several per source file and object file), which
9518 can result in a significant speed up to load and manipulate a project file,
9519 especially when using source files from a remote system.
9523 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9524 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9525 Output the commands for the compiler, the binder and the linker
9526 on ^standard output^SYS$OUTPUT^,
9527 instead of ^standard error^SYS$ERROR^.
9529 @item ^-f^/FORCE_COMPILE^
9530 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9531 Force recompilations. Recompile all sources, even though some object
9532 files may be up to date, but don't recompile predefined or GNAT internal
9533 files or locked files (files with a write-protected ALI file),
9534 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9536 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9537 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9538 When using project files, if some errors or warnings are detected during
9539 parsing and verbose mode is not in effect (no use of switch
9540 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9541 file, rather than its simple file name.
9544 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9545 Enable debugging. This switch is simply passed to the compiler and to the
9548 @item ^-i^/IN_PLACE^
9549 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9550 In normal mode, @command{gnatmake} compiles all object files and ALI files
9551 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9552 then instead object files and ALI files that already exist are overwritten
9553 in place. This means that once a large project is organized into separate
9554 directories in the desired manner, then @command{gnatmake} will automatically
9555 maintain and update this organization. If no ALI files are found on the
9556 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9557 the new object and ALI files are created in the
9558 directory containing the source being compiled. If another organization
9559 is desired, where objects and sources are kept in different directories,
9560 a useful technique is to create dummy ALI files in the desired directories.
9561 When detecting such a dummy file, @command{gnatmake} will be forced to
9562 recompile the corresponding source file, and it will be put the resulting
9563 object and ALI files in the directory where it found the dummy file.
9565 @item ^-j^/PROCESSES=^@var{n}
9566 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9567 @cindex Parallel make
9568 Use @var{n} processes to carry out the (re)compilations. On a
9569 multiprocessor machine compilations will occur in parallel. In the
9570 event of compilation errors, messages from various compilations might
9571 get interspersed (but @command{gnatmake} will give you the full ordered
9572 list of failing compiles at the end). If this is problematic, rerun
9573 the make process with n set to 1 to get a clean list of messages.
9575 @item ^-k^/CONTINUE_ON_ERROR^
9576 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9577 Keep going. Continue as much as possible after a compilation error. To
9578 ease the programmer's task in case of compilation errors, the list of
9579 sources for which the compile fails is given when @command{gnatmake}
9582 If @command{gnatmake} is invoked with several @file{file_names} and with this
9583 switch, if there are compilation errors when building an executable,
9584 @command{gnatmake} will not attempt to build the following executables.
9586 @item ^-l^/ACTIONS=LINK^
9587 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9588 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9589 and linking. Linking will not be performed if combined with
9590 @option{^-c^/ACTIONS=COMPILE^}
9591 but not with @option{^-b^/ACTIONS=BIND^}.
9592 When not combined with @option{^-b^/ACTIONS=BIND^}
9593 all the units in the closure of the main program must have been previously
9594 compiled and must be up to date, and the main program needs to have been bound.
9595 The root unit specified by @var{file_name}
9596 may be given without extension, with the source extension or, if no GNAT
9597 Project File is specified, with the ALI file extension.
9599 @item ^-m^/MINIMAL_RECOMPILATION^
9600 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9601 Specify that the minimum necessary amount of recompilations
9602 be performed. In this mode @command{gnatmake} ignores time
9603 stamp differences when the only
9604 modifications to a source file consist in adding/removing comments,
9605 empty lines, spaces or tabs. This means that if you have changed the
9606 comments in a source file or have simply reformatted it, using this
9607 switch will tell @command{gnatmake} not to recompile files that depend on it
9608 (provided other sources on which these files depend have undergone no
9609 semantic modifications). Note that the debugging information may be
9610 out of date with respect to the sources if the @option{-m} switch causes
9611 a compilation to be switched, so the use of this switch represents a
9612 trade-off between compilation time and accurate debugging information.
9614 @item ^-M^/DEPENDENCIES_LIST^
9615 @cindex Dependencies, producing list
9616 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9617 Check if all objects are up to date. If they are, output the object
9618 dependences to @file{stdout} in a form that can be directly exploited in
9619 a @file{Makefile}. By default, each source file is prefixed with its
9620 (relative or absolute) directory name. This name is whatever you
9621 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9622 and @option{^-I^/SEARCH^} switches. If you use
9623 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9624 @option{^-q^/QUIET^}
9625 (see below), only the source file names,
9626 without relative paths, are output. If you just specify the
9627 @option{^-M^/DEPENDENCIES_LIST^}
9628 switch, dependencies of the GNAT internal system files are omitted. This
9629 is typically what you want. If you also specify
9630 the @option{^-a^/ALL_FILES^} switch,
9631 dependencies of the GNAT internal files are also listed. Note that
9632 dependencies of the objects in external Ada libraries (see switch
9633 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9636 @item ^-n^/DO_OBJECT_CHECK^
9637 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9638 Don't compile, bind, or link. Checks if all objects are up to date.
9639 If they are not, the full name of the first file that needs to be
9640 recompiled is printed.
9641 Repeated use of this option, followed by compiling the indicated source
9642 file, will eventually result in recompiling all required units.
9644 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9645 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9646 Output executable name. The name of the final executable program will be
9647 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9648 name for the executable will be the name of the input file in appropriate form
9649 for an executable file on the host system.
9651 This switch cannot be used when invoking @command{gnatmake} with several
9654 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9655 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9656 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9657 automatically missing object directories, library directories and exec
9660 @item ^-P^/PROJECT_FILE=^@var{project}
9661 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9662 Use project file @var{project}. Only one such switch can be used.
9663 @xref{gnatmake and Project Files}.
9666 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9667 Quiet. When this flag is not set, the commands carried out by
9668 @command{gnatmake} are displayed.
9670 @item ^-s^/SWITCH_CHECK/^
9671 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9672 Recompile if compiler switches have changed since last compilation.
9673 All compiler switches but -I and -o are taken into account in the
9675 orders between different ``first letter'' switches are ignored, but
9676 orders between same switches are taken into account. For example,
9677 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9678 is equivalent to @option{-O -g}.
9680 This switch is recommended when Integrated Preprocessing is used.
9683 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9684 Unique. Recompile at most the main files. It implies -c. Combined with
9685 -f, it is equivalent to calling the compiler directly. Note that using
9686 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9687 (@pxref{Project Files and Main Subprograms}).
9689 @item ^-U^/ALL_PROJECTS^
9690 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9691 When used without a project file or with one or several mains on the command
9692 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9693 on the command line, all sources of all project files are checked and compiled
9694 if not up to date, and libraries are rebuilt, if necessary.
9697 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9698 Verbose. Display the reason for all recompilations @command{gnatmake}
9699 decides are necessary, with the highest verbosity level.
9701 @item ^-vl^/LOW_VERBOSITY^
9702 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9703 Verbosity level Low. Display fewer lines than in verbosity Medium.
9705 @item ^-vm^/MEDIUM_VERBOSITY^
9706 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9707 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9709 @item ^-vh^/HIGH_VERBOSITY^
9710 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9711 Verbosity level High. Equivalent to ^-v^/REASONS^.
9713 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9714 Indicate the verbosity of the parsing of GNAT project files.
9715 @xref{Switches Related to Project Files}.
9717 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9718 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9719 Indicate that sources that are not part of any Project File may be compiled.
9720 Normally, when using Project Files, only sources that are part of a Project
9721 File may be compile. When this switch is used, a source outside of all Project
9722 Files may be compiled. The ALI file and the object file will be put in the
9723 object directory of the main Project. The compilation switches used will only
9724 be those specified on the command line. Even when
9725 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9726 command line need to be sources of a project file.
9728 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9729 Indicate that external variable @var{name} has the value @var{value}.
9730 The Project Manager will use this value for occurrences of
9731 @code{external(name)} when parsing the project file.
9732 @xref{Switches Related to Project Files}.
9735 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9736 No main subprogram. Bind and link the program even if the unit name
9737 given on the command line is a package name. The resulting executable
9738 will execute the elaboration routines of the package and its closure,
9739 then the finalization routines.
9744 @item @command{gcc} @asis{switches}
9746 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9747 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9750 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9751 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9752 automatically treated as a compiler switch, and passed on to all
9753 compilations that are carried out.
9758 Source and library search path switches:
9762 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9763 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9764 When looking for source files also look in directory @var{dir}.
9765 The order in which source files search is undertaken is
9766 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9768 @item ^-aL^/SKIP_MISSING=^@var{dir}
9769 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9770 Consider @var{dir} as being an externally provided Ada library.
9771 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9772 files have been located in directory @var{dir}. This allows you to have
9773 missing bodies for the units in @var{dir} and to ignore out of date bodies
9774 for the same units. You still need to specify
9775 the location of the specs for these units by using the switches
9776 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9777 or @option{^-I^/SEARCH=^@var{dir}}.
9778 Note: this switch is provided for compatibility with previous versions
9779 of @command{gnatmake}. The easier method of causing standard libraries
9780 to be excluded from consideration is to write-protect the corresponding
9783 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9784 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9785 When searching for library and object files, look in directory
9786 @var{dir}. The order in which library files are searched is described in
9787 @ref{Search Paths for gnatbind}.
9789 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9790 @cindex Search paths, for @command{gnatmake}
9791 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9792 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9793 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9795 @item ^-I^/SEARCH=^@var{dir}
9796 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9797 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9798 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9800 @item ^-I-^/NOCURRENT_DIRECTORY^
9801 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9802 @cindex Source files, suppressing search
9803 Do not look for source files in the directory containing the source
9804 file named in the command line.
9805 Do not look for ALI or object files in the directory
9806 where @command{gnatmake} was invoked.
9808 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9809 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9810 @cindex Linker libraries
9811 Add directory @var{dir} to the list of directories in which the linker
9812 will search for libraries. This is equivalent to
9813 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9815 Furthermore, under Windows, the sources pointed to by the libraries path
9816 set in the registry are not searched for.
9820 @cindex @option{-nostdinc} (@command{gnatmake})
9821 Do not look for source files in the system default directory.
9824 @cindex @option{-nostdlib} (@command{gnatmake})
9825 Do not look for library files in the system default directory.
9827 @item --RTS=@var{rts-path}
9828 @cindex @option{--RTS} (@command{gnatmake})
9829 Specifies the default location of the runtime library. GNAT looks for the
9831 in the following directories, and stops as soon as a valid runtime is found
9832 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9833 @file{ada_object_path} present):
9836 @item <current directory>/$rts_path
9838 @item <default-search-dir>/$rts_path
9840 @item <default-search-dir>/rts-$rts_path
9844 The selected path is handled like a normal RTS path.
9848 @node Mode Switches for gnatmake
9849 @section Mode Switches for @command{gnatmake}
9852 The mode switches (referred to as @code{mode_switches}) allow the
9853 inclusion of switches that are to be passed to the compiler itself, the
9854 binder or the linker. The effect of a mode switch is to cause all
9855 subsequent switches up to the end of the switch list, or up to the next
9856 mode switch, to be interpreted as switches to be passed on to the
9857 designated component of GNAT.
9861 @item -cargs @var{switches}
9862 @cindex @option{-cargs} (@command{gnatmake})
9863 Compiler switches. Here @var{switches} is a list of switches
9864 that are valid switches for @command{gcc}. They will be passed on to
9865 all compile steps performed by @command{gnatmake}.
9867 @item -bargs @var{switches}
9868 @cindex @option{-bargs} (@command{gnatmake})
9869 Binder switches. Here @var{switches} is a list of switches
9870 that are valid switches for @code{gnatbind}. They will be passed on to
9871 all bind steps performed by @command{gnatmake}.
9873 @item -largs @var{switches}
9874 @cindex @option{-largs} (@command{gnatmake})
9875 Linker switches. Here @var{switches} is a list of switches
9876 that are valid switches for @command{gnatlink}. They will be passed on to
9877 all link steps performed by @command{gnatmake}.
9879 @item -margs @var{switches}
9880 @cindex @option{-margs} (@command{gnatmake})
9881 Make switches. The switches are directly interpreted by @command{gnatmake},
9882 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9886 @node Notes on the Command Line
9887 @section Notes on the Command Line
9890 This section contains some additional useful notes on the operation
9891 of the @command{gnatmake} command.
9895 @cindex Recompilation, by @command{gnatmake}
9896 If @command{gnatmake} finds no ALI files, it recompiles the main program
9897 and all other units required by the main program.
9898 This means that @command{gnatmake}
9899 can be used for the initial compile, as well as during subsequent steps of
9900 the development cycle.
9903 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9904 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9905 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9909 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9910 is used to specify both source and
9911 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9912 instead if you just want to specify
9913 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9914 if you want to specify library paths
9918 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9919 This may conveniently be used to exclude standard libraries from
9920 consideration and in particular it means that the use of the
9921 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9922 unless @option{^-a^/ALL_FILES^} is also specified.
9925 @command{gnatmake} has been designed to make the use of Ada libraries
9926 particularly convenient. Assume you have an Ada library organized
9927 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9928 of your Ada compilation units,
9929 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9930 specs of these units, but no bodies. Then to compile a unit
9931 stored in @code{main.adb}, which uses this Ada library you would just type
9935 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9938 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9939 /SKIP_MISSING=@i{[OBJ_DIR]} main
9944 Using @command{gnatmake} along with the
9945 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9946 switch provides a mechanism for avoiding unnecessary recompilations. Using
9948 you can update the comments/format of your
9949 source files without having to recompile everything. Note, however, that
9950 adding or deleting lines in a source files may render its debugging
9951 info obsolete. If the file in question is a spec, the impact is rather
9952 limited, as that debugging info will only be useful during the
9953 elaboration phase of your program. For bodies the impact can be more
9954 significant. In all events, your debugger will warn you if a source file
9955 is more recent than the corresponding object, and alert you to the fact
9956 that the debugging information may be out of date.
9959 @node How gnatmake Works
9960 @section How @command{gnatmake} Works
9963 Generally @command{gnatmake} automatically performs all necessary
9964 recompilations and you don't need to worry about how it works. However,
9965 it may be useful to have some basic understanding of the @command{gnatmake}
9966 approach and in particular to understand how it uses the results of
9967 previous compilations without incorrectly depending on them.
9969 First a definition: an object file is considered @dfn{up to date} if the
9970 corresponding ALI file exists and if all the source files listed in the
9971 dependency section of this ALI file have time stamps matching those in
9972 the ALI file. This means that neither the source file itself nor any
9973 files that it depends on have been modified, and hence there is no need
9974 to recompile this file.
9976 @command{gnatmake} works by first checking if the specified main unit is up
9977 to date. If so, no compilations are required for the main unit. If not,
9978 @command{gnatmake} compiles the main program to build a new ALI file that
9979 reflects the latest sources. Then the ALI file of the main unit is
9980 examined to find all the source files on which the main program depends,
9981 and @command{gnatmake} recursively applies the above procedure on all these
9984 This process ensures that @command{gnatmake} only trusts the dependencies
9985 in an existing ALI file if they are known to be correct. Otherwise it
9986 always recompiles to determine a new, guaranteed accurate set of
9987 dependencies. As a result the program is compiled ``upside down'' from what may
9988 be more familiar as the required order of compilation in some other Ada
9989 systems. In particular, clients are compiled before the units on which
9990 they depend. The ability of GNAT to compile in any order is critical in
9991 allowing an order of compilation to be chosen that guarantees that
9992 @command{gnatmake} will recompute a correct set of new dependencies if
9995 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9996 imported by several of the executables, it will be recompiled at most once.
9998 Note: when using non-standard naming conventions
9999 (@pxref{Using Other File Names}), changing through a configuration pragmas
10000 file the version of a source and invoking @command{gnatmake} to recompile may
10001 have no effect, if the previous version of the source is still accessible
10002 by @command{gnatmake}. It may be necessary to use the switch
10003 ^-f^/FORCE_COMPILE^.
10005 @node Examples of gnatmake Usage
10006 @section Examples of @command{gnatmake} Usage
10009 @item gnatmake hello.adb
10010 Compile all files necessary to bind and link the main program
10011 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
10012 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
10014 @item gnatmake main1 main2 main3
10015 Compile all files necessary to bind and link the main programs
10016 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
10017 (containing unit @code{Main2}) and @file{main3.adb}
10018 (containing unit @code{Main3}) and bind and link the resulting object files
10019 to generate three executable files @file{^main1^MAIN1.EXE^},
10020 @file{^main2^MAIN2.EXE^}
10021 and @file{^main3^MAIN3.EXE^}.
10024 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
10028 @item gnatmake Main_Unit /QUIET
10029 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
10030 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
10032 Compile all files necessary to bind and link the main program unit
10033 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
10034 be done with optimization level 2 and the order of elaboration will be
10035 listed by the binder. @command{gnatmake} will operate in quiet mode, not
10036 displaying commands it is executing.
10039 @c *************************
10040 @node Improving Performance
10041 @chapter Improving Performance
10042 @cindex Improving performance
10045 This chapter presents several topics related to program performance.
10046 It first describes some of the tradeoffs that need to be considered
10047 and some of the techniques for making your program run faster.
10048 It then documents the @command{gnatelim} tool and unused subprogram/data
10049 elimination feature, which can reduce the size of program executables.
10051 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
10052 driver (see @ref{The GNAT Driver and Project Files}).
10056 * Performance Considerations::
10057 * Text_IO Suggestions::
10058 * Reducing Size of Ada Executables with gnatelim::
10059 * Reducing Size of Executables with unused subprogram/data elimination::
10063 @c *****************************
10064 @node Performance Considerations
10065 @section Performance Considerations
10068 The GNAT system provides a number of options that allow a trade-off
10073 performance of the generated code
10076 speed of compilation
10079 minimization of dependences and recompilation
10082 the degree of run-time checking.
10086 The defaults (if no options are selected) aim at improving the speed
10087 of compilation and minimizing dependences, at the expense of performance
10088 of the generated code:
10095 no inlining of subprogram calls
10098 all run-time checks enabled except overflow and elaboration checks
10102 These options are suitable for most program development purposes. This
10103 chapter describes how you can modify these choices, and also provides
10104 some guidelines on debugging optimized code.
10107 * Controlling Run-Time Checks::
10108 * Use of Restrictions::
10109 * Optimization Levels::
10110 * Debugging Optimized Code::
10111 * Inlining of Subprograms::
10112 * Other Optimization Switches::
10113 * Optimization and Strict Aliasing::
10116 * Coverage Analysis::
10120 @node Controlling Run-Time Checks
10121 @subsection Controlling Run-Time Checks
10124 By default, GNAT generates all run-time checks, except integer overflow
10125 checks, stack overflow checks, and checks for access before elaboration on
10126 subprogram calls. The latter are not required in default mode, because all
10127 necessary checking is done at compile time.
10128 @cindex @option{-gnatp} (@command{gcc})
10129 @cindex @option{-gnato} (@command{gcc})
10130 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
10131 be modified. @xref{Run-Time Checks}.
10133 Our experience is that the default is suitable for most development
10136 We treat integer overflow specially because these
10137 are quite expensive and in our experience are not as important as other
10138 run-time checks in the development process. Note that division by zero
10139 is not considered an overflow check, and divide by zero checks are
10140 generated where required by default.
10142 Elaboration checks are off by default, and also not needed by default, since
10143 GNAT uses a static elaboration analysis approach that avoids the need for
10144 run-time checking. This manual contains a full chapter discussing the issue
10145 of elaboration checks, and if the default is not satisfactory for your use,
10146 you should read this chapter.
10148 For validity checks, the minimal checks required by the Ada Reference
10149 Manual (for case statements and assignments to array elements) are on
10150 by default. These can be suppressed by use of the @option{-gnatVn} switch.
10151 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
10152 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
10153 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
10154 are also suppressed entirely if @option{-gnatp} is used.
10156 @cindex Overflow checks
10157 @cindex Checks, overflow
10160 @cindex pragma Suppress
10161 @cindex pragma Unsuppress
10162 Note that the setting of the switches controls the default setting of
10163 the checks. They may be modified using either @code{pragma Suppress} (to
10164 remove checks) or @code{pragma Unsuppress} (to add back suppressed
10165 checks) in the program source.
10167 @node Use of Restrictions
10168 @subsection Use of Restrictions
10171 The use of pragma Restrictions allows you to control which features are
10172 permitted in your program. Apart from the obvious point that if you avoid
10173 relatively expensive features like finalization (enforceable by the use
10174 of pragma Restrictions (No_Finalization), the use of this pragma does not
10175 affect the generated code in most cases.
10177 One notable exception to this rule is that the possibility of task abort
10178 results in some distributed overhead, particularly if finalization or
10179 exception handlers are used. The reason is that certain sections of code
10180 have to be marked as non-abortable.
10182 If you use neither the @code{abort} statement, nor asynchronous transfer
10183 of control (@code{select @dots{} then abort}), then this distributed overhead
10184 is removed, which may have a general positive effect in improving
10185 overall performance. Especially code involving frequent use of tasking
10186 constructs and controlled types will show much improved performance.
10187 The relevant restrictions pragmas are
10189 @smallexample @c ada
10190 pragma Restrictions (No_Abort_Statements);
10191 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
10195 It is recommended that these restriction pragmas be used if possible. Note
10196 that this also means that you can write code without worrying about the
10197 possibility of an immediate abort at any point.
10199 @node Optimization Levels
10200 @subsection Optimization Levels
10201 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
10204 Without any optimization ^option,^qualifier,^
10205 the compiler's goal is to reduce the cost of
10206 compilation and to make debugging produce the expected results.
10207 Statements are independent: if you stop the program with a breakpoint between
10208 statements, you can then assign a new value to any variable or change
10209 the program counter to any other statement in the subprogram and get exactly
10210 the results you would expect from the source code.
10212 Turning on optimization makes the compiler attempt to improve the
10213 performance and/or code size at the expense of compilation time and
10214 possibly the ability to debug the program.
10216 If you use multiple
10217 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
10218 the last such option is the one that is effective.
10221 The default is optimization off. This results in the fastest compile
10222 times, but GNAT makes absolutely no attempt to optimize, and the
10223 generated programs are considerably larger and slower than when
10224 optimization is enabled. You can use the
10226 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
10227 @option{-O2}, @option{-O3}, and @option{-Os})
10230 @code{OPTIMIZE} qualifier
10232 to @command{gcc} to control the optimization level:
10235 @item ^-O0^/OPTIMIZE=NONE^
10236 No optimization (the default);
10237 generates unoptimized code but has
10238 the fastest compilation time.
10240 Note that many other compilers do fairly extensive optimization
10241 even if ``no optimization'' is specified. With gcc, it is
10242 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
10243 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
10244 really does mean no optimization at all. This difference between
10245 gcc and other compilers should be kept in mind when doing
10246 performance comparisons.
10248 @item ^-O1^/OPTIMIZE=SOME^
10249 Moderate optimization;
10250 optimizes reasonably well but does not
10251 degrade compilation time significantly.
10253 @item ^-O2^/OPTIMIZE=ALL^
10255 @itemx /OPTIMIZE=DEVELOPMENT
10258 generates highly optimized code and has
10259 the slowest compilation time.
10261 @item ^-O3^/OPTIMIZE=INLINING^
10262 Full optimization as in @option{-O2};
10263 also uses more aggressive automatic inlining of subprograms within a unit
10264 (@pxref{Inlining of Subprograms}) and attempts to vectorize loops.
10266 @item ^-Os^/OPTIMIZE=SPACE^
10267 Optimize space usage (code and data) of resulting program.
10271 Higher optimization levels perform more global transformations on the
10272 program and apply more expensive analysis algorithms in order to generate
10273 faster and more compact code. The price in compilation time, and the
10274 resulting improvement in execution time,
10275 both depend on the particular application and the hardware environment.
10276 You should experiment to find the best level for your application.
10278 Since the precise set of optimizations done at each level will vary from
10279 release to release (and sometime from target to target), it is best to think
10280 of the optimization settings in general terms.
10281 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
10282 the GNU Compiler Collection (GCC)}, for details about
10283 ^the @option{-O} settings and a number of @option{-f} options that^how to^
10284 individually enable or disable specific optimizations.
10286 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
10287 been tested extensively at all optimization levels. There are some bugs
10288 which appear only with optimization turned on, but there have also been
10289 bugs which show up only in @emph{unoptimized} code. Selecting a lower
10290 level of optimization does not improve the reliability of the code
10291 generator, which in practice is highly reliable at all optimization
10294 Note regarding the use of @option{-O3}: The use of this optimization level
10295 is generally discouraged with GNAT, since it often results in larger
10296 executables which may run more slowly. See further discussion of this point
10297 in @ref{Inlining of Subprograms}.
10299 @node Debugging Optimized Code
10300 @subsection Debugging Optimized Code
10301 @cindex Debugging optimized code
10302 @cindex Optimization and debugging
10305 Although it is possible to do a reasonable amount of debugging at
10307 nonzero optimization levels,
10308 the higher the level the more likely that
10311 @option{/OPTIMIZE} settings other than @code{NONE},
10312 such settings will make it more likely that
10314 source-level constructs will have been eliminated by optimization.
10315 For example, if a loop is strength-reduced, the loop
10316 control variable may be completely eliminated and thus cannot be
10317 displayed in the debugger.
10318 This can only happen at @option{-O2} or @option{-O3}.
10319 Explicit temporary variables that you code might be eliminated at
10320 ^level^setting^ @option{-O1} or higher.
10322 The use of the @option{^-g^/DEBUG^} switch,
10323 @cindex @option{^-g^/DEBUG^} (@command{gcc})
10324 which is needed for source-level debugging,
10325 affects the size of the program executable on disk,
10326 and indeed the debugging information can be quite large.
10327 However, it has no effect on the generated code (and thus does not
10328 degrade performance)
10330 Since the compiler generates debugging tables for a compilation unit before
10331 it performs optimizations, the optimizing transformations may invalidate some
10332 of the debugging data. You therefore need to anticipate certain
10333 anomalous situations that may arise while debugging optimized code.
10334 These are the most common cases:
10338 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
10340 the PC bouncing back and forth in the code. This may result from any of
10341 the following optimizations:
10345 @i{Common subexpression elimination:} using a single instance of code for a
10346 quantity that the source computes several times. As a result you
10347 may not be able to stop on what looks like a statement.
10350 @i{Invariant code motion:} moving an expression that does not change within a
10351 loop, to the beginning of the loop.
10354 @i{Instruction scheduling:} moving instructions so as to
10355 overlap loads and stores (typically) with other code, or in
10356 general to move computations of values closer to their uses. Often
10357 this causes you to pass an assignment statement without the assignment
10358 happening and then later bounce back to the statement when the
10359 value is actually needed. Placing a breakpoint on a line of code
10360 and then stepping over it may, therefore, not always cause all the
10361 expected side-effects.
10365 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
10366 two identical pieces of code are merged and the program counter suddenly
10367 jumps to a statement that is not supposed to be executed, simply because
10368 it (and the code following) translates to the same thing as the code
10369 that @emph{was} supposed to be executed. This effect is typically seen in
10370 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
10371 a @code{break} in a C @code{^switch^switch^} statement.
10374 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
10375 There are various reasons for this effect:
10379 In a subprogram prologue, a parameter may not yet have been moved to its
10383 A variable may be dead, and its register re-used. This is
10384 probably the most common cause.
10387 As mentioned above, the assignment of a value to a variable may
10391 A variable may be eliminated entirely by value propagation or
10392 other means. In this case, GCC may incorrectly generate debugging
10393 information for the variable
10397 In general, when an unexpected value appears for a local variable or parameter
10398 you should first ascertain if that value was actually computed by
10399 your program, as opposed to being incorrectly reported by the debugger.
10401 array elements in an object designated by an access value
10402 are generally less of a problem, once you have ascertained that the access
10404 Typically, this means checking variables in the preceding code and in the
10405 calling subprogram to verify that the value observed is explainable from other
10406 values (one must apply the procedure recursively to those
10407 other values); or re-running the code and stopping a little earlier
10408 (perhaps before the call) and stepping to better see how the variable obtained
10409 the value in question; or continuing to step @emph{from} the point of the
10410 strange value to see if code motion had simply moved the variable's
10415 In light of such anomalies, a recommended technique is to use @option{-O0}
10416 early in the software development cycle, when extensive debugging capabilities
10417 are most needed, and then move to @option{-O1} and later @option{-O2} as
10418 the debugger becomes less critical.
10419 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
10420 a release management issue.
10422 Note that if you use @option{-g} you can then use the @command{strip} program
10423 on the resulting executable,
10424 which removes both debugging information and global symbols.
10427 @node Inlining of Subprograms
10428 @subsection Inlining of Subprograms
10431 A call to a subprogram in the current unit is inlined if all the
10432 following conditions are met:
10436 The optimization level is at least @option{-O1}.
10439 The called subprogram is suitable for inlining: It must be small enough
10440 and not contain something that @command{gcc} cannot support in inlined
10444 @cindex pragma Inline
10446 Any one of the following applies: @code{pragma Inline} is applied to the
10447 subprogram and the @option{^-gnatn^/INLINE^} switch is specified; the
10448 subprogram is local to the unit and called once from within it; the
10449 subprogram is small and optimization level @option{-O2} is specified;
10450 optimization level @option{-O3}) is specified.
10454 Calls to subprograms in @code{with}'ed units are normally not inlined.
10455 To achieve actual inlining (that is, replacement of the call by the code
10456 in the body of the subprogram), the following conditions must all be true.
10460 The optimization level is at least @option{-O1}.
10463 The called subprogram is suitable for inlining: It must be small enough
10464 and not contain something that @command{gcc} cannot support in inlined
10468 The call appears in a body (not in a package spec).
10471 There is a @code{pragma Inline} for the subprogram.
10474 The @option{^-gnatn^/INLINE^} switch is used on the command line.
10477 Even if all these conditions are met, it may not be possible for
10478 the compiler to inline the call, due to the length of the body,
10479 or features in the body that make it impossible for the compiler
10480 to do the inlining.
10482 Note that specifying the @option{-gnatn} switch causes additional
10483 compilation dependencies. Consider the following:
10485 @smallexample @c ada
10505 With the default behavior (no @option{-gnatn} switch specified), the
10506 compilation of the @code{Main} procedure depends only on its own source,
10507 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10508 means that editing the body of @code{R} does not require recompiling
10511 On the other hand, the call @code{R.Q} is not inlined under these
10512 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10513 is compiled, the call will be inlined if the body of @code{Q} is small
10514 enough, but now @code{Main} depends on the body of @code{R} in
10515 @file{r.adb} as well as on the spec. This means that if this body is edited,
10516 the main program must be recompiled. Note that this extra dependency
10517 occurs whether or not the call is in fact inlined by @command{gcc}.
10519 The use of front end inlining with @option{-gnatN} generates similar
10520 additional dependencies.
10522 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10523 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10524 can be used to prevent
10525 all inlining. This switch overrides all other conditions and ensures
10526 that no inlining occurs. The extra dependences resulting from
10527 @option{-gnatn} will still be active, even if
10528 this switch is used to suppress the resulting inlining actions.
10530 @cindex @option{-fno-inline-functions} (@command{gcc})
10531 Note: The @option{-fno-inline-functions} switch can be used to prevent
10532 automatic inlining of subprograms if @option{-O3} is used.
10534 @cindex @option{-fno-inline-small-functions} (@command{gcc})
10535 Note: The @option{-fno-inline-small-functions} switch can be used to prevent
10536 automatic inlining of small subprograms if @option{-O2} is used.
10538 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10539 Note: The @option{-fno-inline-functions-called-once} switch
10540 can be used to prevent inlining of subprograms local to the unit
10541 and called once from within it if @option{-O1} is used.
10543 Note regarding the use of @option{-O3}: There is no difference in inlining
10544 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10545 pragma @code{Inline} assuming the use of @option{-gnatn}
10546 or @option{-gnatN} (the switches that activate inlining). If you have used
10547 pragma @code{Inline} in appropriate cases, then it is usually much better
10548 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10549 in this case only has the effect of inlining subprograms you did not
10550 think should be inlined. We often find that the use of @option{-O3} slows
10551 down code by performing excessive inlining, leading to increased instruction
10552 cache pressure from the increased code size. So the bottom line here is
10553 that you should not automatically assume that @option{-O3} is better than
10554 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10555 it actually improves performance.
10557 @node Other Optimization Switches
10558 @subsection Other Optimization Switches
10559 @cindex Optimization Switches
10561 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10562 @command{gcc} optimization switches are potentially usable. These switches
10563 have not been extensively tested with GNAT but can generally be expected
10564 to work. Examples of switches in this category are
10565 @option{-funroll-loops} and
10566 the various target-specific @option{-m} options (in particular, it has been
10567 observed that @option{-march=pentium4} can significantly improve performance
10568 on appropriate machines). For full details of these switches, see
10569 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10570 the GNU Compiler Collection (GCC)}.
10572 @node Optimization and Strict Aliasing
10573 @subsection Optimization and Strict Aliasing
10575 @cindex Strict Aliasing
10576 @cindex No_Strict_Aliasing
10579 The strong typing capabilities of Ada allow an optimizer to generate
10580 efficient code in situations where other languages would be forced to
10581 make worst case assumptions preventing such optimizations. Consider
10582 the following example:
10584 @smallexample @c ada
10587 type Int1 is new Integer;
10588 type Int2 is new Integer;
10589 type Int1A is access Int1;
10590 type Int2A is access Int2;
10597 for J in Data'Range loop
10598 if Data (J) = Int1V.all then
10599 Int2V.all := Int2V.all + 1;
10608 In this example, since the variable @code{Int1V} can only access objects
10609 of type @code{Int1}, and @code{Int2V} can only access objects of type
10610 @code{Int2}, there is no possibility that the assignment to
10611 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10612 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10613 for all iterations of the loop and avoid the extra memory reference
10614 required to dereference it each time through the loop.
10616 This kind of optimization, called strict aliasing analysis, is
10617 triggered by specifying an optimization level of @option{-O2} or
10618 higher or @option{-Os} and allows @code{GNAT} to generate more efficient code
10619 when access values are involved.
10621 However, although this optimization is always correct in terms of
10622 the formal semantics of the Ada Reference Manual, difficulties can
10623 arise if features like @code{Unchecked_Conversion} are used to break
10624 the typing system. Consider the following complete program example:
10626 @smallexample @c ada
10629 type int1 is new integer;
10630 type int2 is new integer;
10631 type a1 is access int1;
10632 type a2 is access int2;
10637 function to_a2 (Input : a1) return a2;
10640 with Unchecked_Conversion;
10642 function to_a2 (Input : a1) return a2 is
10644 new Unchecked_Conversion (a1, a2);
10646 return to_a2u (Input);
10652 with Text_IO; use Text_IO;
10654 v1 : a1 := new int1;
10655 v2 : a2 := to_a2 (v1);
10659 put_line (int1'image (v1.all));
10665 This program prints out 0 in @option{-O0} or @option{-O1}
10666 mode, but it prints out 1 in @option{-O2} mode. That's
10667 because in strict aliasing mode, the compiler can and
10668 does assume that the assignment to @code{v2.all} could not
10669 affect the value of @code{v1.all}, since different types
10672 This behavior is not a case of non-conformance with the standard, since
10673 the Ada RM specifies that an unchecked conversion where the resulting
10674 bit pattern is not a correct value of the target type can result in an
10675 abnormal value and attempting to reference an abnormal value makes the
10676 execution of a program erroneous. That's the case here since the result
10677 does not point to an object of type @code{int2}. This means that the
10678 effect is entirely unpredictable.
10680 However, although that explanation may satisfy a language
10681 lawyer, in practice an applications programmer expects an
10682 unchecked conversion involving pointers to create true
10683 aliases and the behavior of printing 1 seems plain wrong.
10684 In this case, the strict aliasing optimization is unwelcome.
10686 Indeed the compiler recognizes this possibility, and the
10687 unchecked conversion generates a warning:
10690 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10691 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10692 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10696 Unfortunately the problem is recognized when compiling the body of
10697 package @code{p2}, but the actual "bad" code is generated while
10698 compiling the body of @code{m} and this latter compilation does not see
10699 the suspicious @code{Unchecked_Conversion}.
10701 As implied by the warning message, there are approaches you can use to
10702 avoid the unwanted strict aliasing optimization in a case like this.
10704 One possibility is to simply avoid the use of @option{-O2}, but
10705 that is a bit drastic, since it throws away a number of useful
10706 optimizations that do not involve strict aliasing assumptions.
10708 A less drastic approach is to compile the program using the
10709 option @option{-fno-strict-aliasing}. Actually it is only the
10710 unit containing the dereferencing of the suspicious pointer
10711 that needs to be compiled. So in this case, if we compile
10712 unit @code{m} with this switch, then we get the expected
10713 value of zero printed. Analyzing which units might need
10714 the switch can be painful, so a more reasonable approach
10715 is to compile the entire program with options @option{-O2}
10716 and @option{-fno-strict-aliasing}. If the performance is
10717 satisfactory with this combination of options, then the
10718 advantage is that the entire issue of possible "wrong"
10719 optimization due to strict aliasing is avoided.
10721 To avoid the use of compiler switches, the configuration
10722 pragma @code{No_Strict_Aliasing} with no parameters may be
10723 used to specify that for all access types, the strict
10724 aliasing optimization should be suppressed.
10726 However, these approaches are still overkill, in that they causes
10727 all manipulations of all access values to be deoptimized. A more
10728 refined approach is to concentrate attention on the specific
10729 access type identified as problematic.
10731 First, if a careful analysis of uses of the pointer shows
10732 that there are no possible problematic references, then
10733 the warning can be suppressed by bracketing the
10734 instantiation of @code{Unchecked_Conversion} to turn
10737 @smallexample @c ada
10738 pragma Warnings (Off);
10740 new Unchecked_Conversion (a1, a2);
10741 pragma Warnings (On);
10745 Of course that approach is not appropriate for this particular
10746 example, since indeed there is a problematic reference. In this
10747 case we can take one of two other approaches.
10749 The first possibility is to move the instantiation of unchecked
10750 conversion to the unit in which the type is declared. In
10751 this example, we would move the instantiation of
10752 @code{Unchecked_Conversion} from the body of package
10753 @code{p2} to the spec of package @code{p1}. Now the
10754 warning disappears. That's because any use of the
10755 access type knows there is a suspicious unchecked
10756 conversion, and the strict aliasing optimization
10757 is automatically suppressed for the type.
10759 If it is not practical to move the unchecked conversion to the same unit
10760 in which the destination access type is declared (perhaps because the
10761 source type is not visible in that unit), you may use pragma
10762 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10763 same declarative sequence as the declaration of the access type:
10765 @smallexample @c ada
10766 type a2 is access int2;
10767 pragma No_Strict_Aliasing (a2);
10771 Here again, the compiler now knows that the strict aliasing optimization
10772 should be suppressed for any reference to type @code{a2} and the
10773 expected behavior is obtained.
10775 Finally, note that although the compiler can generate warnings for
10776 simple cases of unchecked conversions, there are tricker and more
10777 indirect ways of creating type incorrect aliases which the compiler
10778 cannot detect. Examples are the use of address overlays and unchecked
10779 conversions involving composite types containing access types as
10780 components. In such cases, no warnings are generated, but there can
10781 still be aliasing problems. One safe coding practice is to forbid the
10782 use of address clauses for type overlaying, and to allow unchecked
10783 conversion only for primitive types. This is not really a significant
10784 restriction since any possible desired effect can be achieved by
10785 unchecked conversion of access values.
10787 The aliasing analysis done in strict aliasing mode can certainly
10788 have significant benefits. We have seen cases of large scale
10789 application code where the time is increased by up to 5% by turning
10790 this optimization off. If you have code that includes significant
10791 usage of unchecked conversion, you might want to just stick with
10792 @option{-O1} and avoid the entire issue. If you get adequate
10793 performance at this level of optimization level, that's probably
10794 the safest approach. If tests show that you really need higher
10795 levels of optimization, then you can experiment with @option{-O2}
10796 and @option{-O2 -fno-strict-aliasing} to see how much effect this
10797 has on size and speed of the code. If you really need to use
10798 @option{-O2} with strict aliasing in effect, then you should
10799 review any uses of unchecked conversion of access types,
10800 particularly if you are getting the warnings described above.
10803 @node Coverage Analysis
10804 @subsection Coverage Analysis
10807 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10808 the user to determine the distribution of execution time across a program,
10809 @pxref{Profiling} for details of usage.
10813 @node Text_IO Suggestions
10814 @section @code{Text_IO} Suggestions
10815 @cindex @code{Text_IO} and performance
10818 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10819 the requirement of maintaining page and line counts. If performance
10820 is critical, a recommendation is to use @code{Stream_IO} instead of
10821 @code{Text_IO} for volume output, since this package has less overhead.
10823 If @code{Text_IO} must be used, note that by default output to the standard
10824 output and standard error files is unbuffered (this provides better
10825 behavior when output statements are used for debugging, or if the
10826 progress of a program is observed by tracking the output, e.g. by
10827 using the Unix @command{tail -f} command to watch redirected output.
10829 If you are generating large volumes of output with @code{Text_IO} and
10830 performance is an important factor, use a designated file instead
10831 of the standard output file, or change the standard output file to
10832 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10836 @node Reducing Size of Ada Executables with gnatelim
10837 @section Reducing Size of Ada Executables with @code{gnatelim}
10841 This section describes @command{gnatelim}, a tool which detects unused
10842 subprograms and helps the compiler to create a smaller executable for your
10847 * Running gnatelim::
10848 * Processing Precompiled Libraries::
10849 * Correcting the List of Eliminate Pragmas::
10850 * Making Your Executables Smaller::
10851 * Summary of the gnatelim Usage Cycle::
10854 @node About gnatelim
10855 @subsection About @code{gnatelim}
10858 When a program shares a set of Ada
10859 packages with other programs, it may happen that this program uses
10860 only a fraction of the subprograms defined in these packages. The code
10861 created for these unused subprograms increases the size of the executable.
10863 @code{gnatelim} tracks unused subprograms in an Ada program and
10864 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10865 subprograms that are declared but never called. By placing the list of
10866 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10867 recompiling your program, you may decrease the size of its executable,
10868 because the compiler will not generate the code for 'eliminated' subprograms.
10869 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10870 information about this pragma.
10872 @code{gnatelim} needs as its input data the name of the main subprogram.
10874 If a set of source files is specified as @code{gnatelim} arguments, it
10875 treats these files as a complete set of sources making up a program to
10876 analyse, and analyses only these sources.
10878 After a full successful build of the main subprogram @code{gnatelim} can be
10879 called without specifying sources to analyse, in this case it computes
10880 the source closure of the main unit from the @file{ALI} files.
10882 The following command will create the set of @file{ALI} files needed for
10886 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10889 Note that @code{gnatelim} does not need object files.
10891 @node Running gnatelim
10892 @subsection Running @code{gnatelim}
10895 @code{gnatelim} has the following command-line interface:
10898 $ gnatelim [@var{switches}] ^-main^?MAIN^=@var{main_unit_name} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
10902 @var{main_unit_name} should be a name of a source file that contains the main
10903 subprogram of a program (partition).
10905 Each @var{filename} is the name (including the extension) of a source
10906 file to process. ``Wildcards'' are allowed, and
10907 the file name may contain path information.
10909 @samp{@var{gcc_switches}} is a list of switches for
10910 @command{gcc}. They will be passed on to all compiler invocations made by
10911 @command{gnatelim} to generate the ASIS trees. Here you can provide
10912 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
10913 use the @option{-gnatec} switch to set the configuration file,
10914 use the @option{-gnat05} switch if sources should be compiled in
10917 @code{gnatelim} has the following switches:
10921 @item ^-files^/FILES^=@var{filename}
10922 @cindex @option{^-files^/FILES^} (@code{gnatelim})
10923 Take the argument source files from the specified file. This file should be an
10924 ordinary text file containing file names separated by spaces or
10925 line breaks. You can use this switch more than once in the same call to
10926 @command{gnatelim}. You also can combine this switch with
10927 an explicit list of files.
10930 @cindex @option{^-log^/LOG^} (@command{gnatelim})
10931 Duplicate all the output sent to @file{stderr} into a log file. The log file
10932 is named @file{gnatelim.log} and is located in the current directory.
10934 @item ^-log^/LOGFILE^=@var{filename}
10935 @cindex @option{^-log^/LOGFILE^} (@command{gnatelim})
10936 Duplicate all the output sent to @file{stderr} into a specified log file.
10938 @cindex @option{^--no-elim-dispatch^/NO_DISPATCH^} (@command{gnatelim})
10939 @item ^--no-elim-dispatch^/NO_DISPATCH^
10940 Do not generate pragmas for dispatching operations.
10942 @item ^--ignore^/IGNORE^=@var{filename}
10943 @cindex @option{^--ignore^/IGNORE^} (@command{gnatelim})
10944 Do not generate pragmas for subprograms declared in the sources
10945 listed in a specified file
10947 @cindex @option{^-o^/OUTPUT^} (@command{gnatelim})
10948 @item ^-o^/OUTPUT^=@var{report_file}
10949 Put @command{gnatelim} output into a specified file. If this file already exists,
10950 it is overridden. If this switch is not used, @command{gnatelim} outputs its results
10954 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10955 Quiet mode: by default @code{gnatelim} outputs to the standard error
10956 stream the number of program units left to be processed. This option turns
10959 @cindex @option{^-t^/TIME^} (@command{gnatelim})
10961 Print out execution time.
10963 @item ^-v^/VERBOSE^
10964 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10965 Verbose mode: @code{gnatelim} version information is printed as Ada
10966 comments to the standard output stream. Also, in addition to the number of
10967 program units left @code{gnatelim} will output the name of the current unit
10970 @item ^-wq^/WARNINGS=QUIET^
10971 @cindex @option{^-wq^/WARNINGS=QUIET^} (@command{gnatelim})
10972 Quiet warning mode - some warnings are suppressed. In particular warnings that
10973 indicate that the analysed set of sources is incomplete to make up a
10974 partition and that some subprogram bodies are missing are not generated.
10977 @node Processing Precompiled Libraries
10978 @subsection Processing Precompiled Libraries
10981 If some program uses a precompiled Ada library, it can be processed by
10982 @code{gnatelim} in a usual way. @code{gnatelim} will newer generate an
10983 Eliminate pragma for a subprogram if the body of this subprogram has not
10984 been analysed, this is a typical case for subprograms from precompiled
10985 libraries. Switch @option{^-wq^/WARNINGS=QUIET^} may be used to suppress
10986 warnings about missing source files and non-analyzed subprogram bodies
10987 that can be generated when processing precompiled Ada libraries.
10989 @node Correcting the List of Eliminate Pragmas
10990 @subsection Correcting the List of Eliminate Pragmas
10993 In some rare cases @code{gnatelim} may try to eliminate
10994 subprograms that are actually called in the program. In this case, the
10995 compiler will generate an error message of the form:
10998 main.adb:4:08: cannot reference subprogram "P" eliminated at elim.out:5
11002 You will need to manually remove the wrong @code{Eliminate} pragmas from
11003 the configuration file indicated in the error message. You should recompile
11004 your program from scratch after that, because you need a consistent
11005 configuration file(s) during the entire compilation.
11007 @node Making Your Executables Smaller
11008 @subsection Making Your Executables Smaller
11011 In order to get a smaller executable for your program you now have to
11012 recompile the program completely with the configuration file containing
11013 pragmas Eliminate generated by gnatelim. If these pragmas are placed in
11014 @file{gnat.adc} file located in your current directory, just do:
11017 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
11021 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
11022 recompile everything
11023 with the set of pragmas @code{Eliminate} that you have obtained with
11024 @command{gnatelim}).
11026 Be aware that the set of @code{Eliminate} pragmas is specific to each
11027 program. It is not recommended to merge sets of @code{Eliminate}
11028 pragmas created for different programs in one configuration file.
11030 @node Summary of the gnatelim Usage Cycle
11031 @subsection Summary of the @code{gnatelim} Usage Cycle
11034 Here is a quick summary of the steps to be taken in order to reduce
11035 the size of your executables with @code{gnatelim}. You may use
11036 other GNAT options to control the optimization level,
11037 to produce the debugging information, to set search path, etc.
11041 Create a complete set of @file{ALI} files (if the program has not been
11045 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
11049 Generate a list of @code{Eliminate} pragmas in default configuration file
11050 @file{gnat.adc} in the current directory
11053 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
11056 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
11061 Recompile the application
11064 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
11069 @node Reducing Size of Executables with unused subprogram/data elimination
11070 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
11071 @findex unused subprogram/data elimination
11074 This section describes how you can eliminate unused subprograms and data from
11075 your executable just by setting options at compilation time.
11078 * About unused subprogram/data elimination::
11079 * Compilation options::
11080 * Example of unused subprogram/data elimination::
11083 @node About unused subprogram/data elimination
11084 @subsection About unused subprogram/data elimination
11087 By default, an executable contains all code and data of its composing objects
11088 (directly linked or coming from statically linked libraries), even data or code
11089 never used by this executable.
11091 This feature will allow you to eliminate such unused code from your
11092 executable, making it smaller (in disk and in memory).
11094 This functionality is available on all Linux platforms except for the IA-64
11095 architecture and on all cross platforms using the ELF binary file format.
11096 In both cases GNU binutils version 2.16 or later are required to enable it.
11098 @node Compilation options
11099 @subsection Compilation options
11102 The operation of eliminating the unused code and data from the final executable
11103 is directly performed by the linker.
11105 In order to do this, it has to work with objects compiled with the
11107 @option{-ffunction-sections} @option{-fdata-sections}.
11108 @cindex @option{-ffunction-sections} (@command{gcc})
11109 @cindex @option{-fdata-sections} (@command{gcc})
11110 These options are usable with C and Ada files.
11111 They will place respectively each
11112 function or data in a separate section in the resulting object file.
11114 Once the objects and static libraries are created with these options, the
11115 linker can perform the dead code elimination. You can do this by setting
11116 the @option{-Wl,--gc-sections} option to gcc command or in the
11117 @option{-largs} section of @command{gnatmake}. This will perform a
11118 garbage collection of code and data never referenced.
11120 If the linker performs a partial link (@option{-r} ld linker option), then you
11121 will need to provide one or several entry point using the
11122 @option{-e} / @option{--entry} ld option.
11124 Note that objects compiled without the @option{-ffunction-sections} and
11125 @option{-fdata-sections} options can still be linked with the executable.
11126 However, no dead code elimination will be performed on those objects (they will
11129 The GNAT static library is now compiled with -ffunction-sections and
11130 -fdata-sections on some platforms. This allows you to eliminate the unused code
11131 and data of the GNAT library from your executable.
11133 @node Example of unused subprogram/data elimination
11134 @subsection Example of unused subprogram/data elimination
11137 Here is a simple example:
11139 @smallexample @c ada
11148 Used_Data : Integer;
11149 Unused_Data : Integer;
11151 procedure Used (Data : Integer);
11152 procedure Unused (Data : Integer);
11155 package body Aux is
11156 procedure Used (Data : Integer) is
11161 procedure Unused (Data : Integer) is
11163 Unused_Data := Data;
11169 @code{Unused} and @code{Unused_Data} are never referenced in this code
11170 excerpt, and hence they may be safely removed from the final executable.
11175 $ nm test | grep used
11176 020015f0 T aux__unused
11177 02005d88 B aux__unused_data
11178 020015cc T aux__used
11179 02005d84 B aux__used_data
11181 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
11182 -largs -Wl,--gc-sections
11184 $ nm test | grep used
11185 02005350 T aux__used
11186 0201ffe0 B aux__used_data
11190 It can be observed that the procedure @code{Unused} and the object
11191 @code{Unused_Data} are removed by the linker when using the
11192 appropriate options.
11194 @c ********************************
11195 @node Renaming Files Using gnatchop
11196 @chapter Renaming Files Using @code{gnatchop}
11200 This chapter discusses how to handle files with multiple units by using
11201 the @code{gnatchop} utility. This utility is also useful in renaming
11202 files to meet the standard GNAT default file naming conventions.
11205 * Handling Files with Multiple Units::
11206 * Operating gnatchop in Compilation Mode::
11207 * Command Line for gnatchop::
11208 * Switches for gnatchop::
11209 * Examples of gnatchop Usage::
11212 @node Handling Files with Multiple Units
11213 @section Handling Files with Multiple Units
11216 The basic compilation model of GNAT requires that a file submitted to the
11217 compiler have only one unit and there be a strict correspondence
11218 between the file name and the unit name.
11220 The @code{gnatchop} utility allows both of these rules to be relaxed,
11221 allowing GNAT to process files which contain multiple compilation units
11222 and files with arbitrary file names. @code{gnatchop}
11223 reads the specified file and generates one or more output files,
11224 containing one unit per file. The unit and the file name correspond,
11225 as required by GNAT.
11227 If you want to permanently restructure a set of ``foreign'' files so that
11228 they match the GNAT rules, and do the remaining development using the
11229 GNAT structure, you can simply use @command{gnatchop} once, generate the
11230 new set of files and work with them from that point on.
11232 Alternatively, if you want to keep your files in the ``foreign'' format,
11233 perhaps to maintain compatibility with some other Ada compilation
11234 system, you can set up a procedure where you use @command{gnatchop} each
11235 time you compile, regarding the source files that it writes as temporary
11236 files that you throw away.
11238 Note that if your file containing multiple units starts with a byte order
11239 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
11240 will each start with a copy of this BOM, meaning that they can be compiled
11241 automatically in UTF-8 mode without needing to specify an explicit encoding.
11243 @node Operating gnatchop in Compilation Mode
11244 @section Operating gnatchop in Compilation Mode
11247 The basic function of @code{gnatchop} is to take a file with multiple units
11248 and split it into separate files. The boundary between files is reasonably
11249 clear, except for the issue of comments and pragmas. In default mode, the
11250 rule is that any pragmas between units belong to the previous unit, except
11251 that configuration pragmas always belong to the following unit. Any comments
11252 belong to the following unit. These rules
11253 almost always result in the right choice of
11254 the split point without needing to mark it explicitly and most users will
11255 find this default to be what they want. In this default mode it is incorrect to
11256 submit a file containing only configuration pragmas, or one that ends in
11257 configuration pragmas, to @code{gnatchop}.
11259 However, using a special option to activate ``compilation mode'',
11261 can perform another function, which is to provide exactly the semantics
11262 required by the RM for handling of configuration pragmas in a compilation.
11263 In the absence of configuration pragmas (at the main file level), this
11264 option has no effect, but it causes such configuration pragmas to be handled
11265 in a quite different manner.
11267 First, in compilation mode, if @code{gnatchop} is given a file that consists of
11268 only configuration pragmas, then this file is appended to the
11269 @file{gnat.adc} file in the current directory. This behavior provides
11270 the required behavior described in the RM for the actions to be taken
11271 on submitting such a file to the compiler, namely that these pragmas
11272 should apply to all subsequent compilations in the same compilation
11273 environment. Using GNAT, the current directory, possibly containing a
11274 @file{gnat.adc} file is the representation
11275 of a compilation environment. For more information on the
11276 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
11278 Second, in compilation mode, if @code{gnatchop}
11279 is given a file that starts with
11280 configuration pragmas, and contains one or more units, then these
11281 configuration pragmas are prepended to each of the chopped files. This
11282 behavior provides the required behavior described in the RM for the
11283 actions to be taken on compiling such a file, namely that the pragmas
11284 apply to all units in the compilation, but not to subsequently compiled
11287 Finally, if configuration pragmas appear between units, they are appended
11288 to the previous unit. This results in the previous unit being illegal,
11289 since the compiler does not accept configuration pragmas that follow
11290 a unit. This provides the required RM behavior that forbids configuration
11291 pragmas other than those preceding the first compilation unit of a
11294 For most purposes, @code{gnatchop} will be used in default mode. The
11295 compilation mode described above is used only if you need exactly
11296 accurate behavior with respect to compilations, and you have files
11297 that contain multiple units and configuration pragmas. In this
11298 circumstance the use of @code{gnatchop} with the compilation mode
11299 switch provides the required behavior, and is for example the mode
11300 in which GNAT processes the ACVC tests.
11302 @node Command Line for gnatchop
11303 @section Command Line for @code{gnatchop}
11306 The @code{gnatchop} command has the form:
11309 @c $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11310 @c @ovar{directory}
11311 @c Expanding @ovar macro inline (explanation in macro def comments)
11312 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11313 @r{[}@var{directory}@r{]}
11317 The only required argument is the file name of the file to be chopped.
11318 There are no restrictions on the form of this file name. The file itself
11319 contains one or more Ada units, in normal GNAT format, concatenated
11320 together. As shown, more than one file may be presented to be chopped.
11322 When run in default mode, @code{gnatchop} generates one output file in
11323 the current directory for each unit in each of the files.
11325 @var{directory}, if specified, gives the name of the directory to which
11326 the output files will be written. If it is not specified, all files are
11327 written to the current directory.
11329 For example, given a
11330 file called @file{hellofiles} containing
11332 @smallexample @c ada
11337 with Text_IO; use Text_IO;
11340 Put_Line ("Hello");
11350 $ gnatchop ^hellofiles^HELLOFILES.^
11354 generates two files in the current directory, one called
11355 @file{hello.ads} containing the single line that is the procedure spec,
11356 and the other called @file{hello.adb} containing the remaining text. The
11357 original file is not affected. The generated files can be compiled in
11361 When gnatchop is invoked on a file that is empty or that contains only empty
11362 lines and/or comments, gnatchop will not fail, but will not produce any
11365 For example, given a
11366 file called @file{toto.txt} containing
11368 @smallexample @c ada
11380 $ gnatchop ^toto.txt^TOT.TXT^
11384 will not produce any new file and will result in the following warnings:
11387 toto.txt:1:01: warning: empty file, contains no compilation units
11388 no compilation units found
11389 no source files written
11392 @node Switches for gnatchop
11393 @section Switches for @code{gnatchop}
11396 @command{gnatchop} recognizes the following switches:
11402 @cindex @option{--version} @command{gnatchop}
11403 Display Copyright and version, then exit disregarding all other options.
11406 @cindex @option{--help} @command{gnatchop}
11407 If @option{--version} was not used, display usage, then exit disregarding
11410 @item ^-c^/COMPILATION^
11411 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
11412 Causes @code{gnatchop} to operate in compilation mode, in which
11413 configuration pragmas are handled according to strict RM rules. See
11414 previous section for a full description of this mode.
11417 @item -gnat@var{xxx}
11418 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
11419 used to parse the given file. Not all @var{xxx} options make sense,
11420 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
11421 process a source file that uses Latin-2 coding for identifiers.
11425 Causes @code{gnatchop} to generate a brief help summary to the standard
11426 output file showing usage information.
11428 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
11429 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
11430 Limit generated file names to the specified number @code{mm}
11432 This is useful if the
11433 resulting set of files is required to be interoperable with systems
11434 which limit the length of file names.
11436 If no value is given, or
11437 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
11438 a default of 39, suitable for OpenVMS Alpha
11439 Systems, is assumed
11442 No space is allowed between the @option{-k} and the numeric value. The numeric
11443 value may be omitted in which case a default of @option{-k8},
11445 with DOS-like file systems, is used. If no @option{-k} switch
11447 there is no limit on the length of file names.
11450 @item ^-p^/PRESERVE^
11451 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
11452 Causes the file ^modification^creation^ time stamp of the input file to be
11453 preserved and used for the time stamp of the output file(s). This may be
11454 useful for preserving coherency of time stamps in an environment where
11455 @code{gnatchop} is used as part of a standard build process.
11458 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
11459 Causes output of informational messages indicating the set of generated
11460 files to be suppressed. Warnings and error messages are unaffected.
11462 @item ^-r^/REFERENCE^
11463 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
11464 @findex Source_Reference
11465 Generate @code{Source_Reference} pragmas. Use this switch if the output
11466 files are regarded as temporary and development is to be done in terms
11467 of the original unchopped file. This switch causes
11468 @code{Source_Reference} pragmas to be inserted into each of the
11469 generated files to refers back to the original file name and line number.
11470 The result is that all error messages refer back to the original
11472 In addition, the debugging information placed into the object file (when
11473 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
11475 also refers back to this original file so that tools like profilers and
11476 debuggers will give information in terms of the original unchopped file.
11478 If the original file to be chopped itself contains
11479 a @code{Source_Reference}
11480 pragma referencing a third file, then gnatchop respects
11481 this pragma, and the generated @code{Source_Reference} pragmas
11482 in the chopped file refer to the original file, with appropriate
11483 line numbers. This is particularly useful when @code{gnatchop}
11484 is used in conjunction with @code{gnatprep} to compile files that
11485 contain preprocessing statements and multiple units.
11487 @item ^-v^/VERBOSE^
11488 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
11489 Causes @code{gnatchop} to operate in verbose mode. The version
11490 number and copyright notice are output, as well as exact copies of
11491 the gnat1 commands spawned to obtain the chop control information.
11493 @item ^-w^/OVERWRITE^
11494 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
11495 Overwrite existing file names. Normally @code{gnatchop} regards it as a
11496 fatal error if there is already a file with the same name as a
11497 file it would otherwise output, in other words if the files to be
11498 chopped contain duplicated units. This switch bypasses this
11499 check, and causes all but the last instance of such duplicated
11500 units to be skipped.
11503 @item --GCC=@var{xxxx}
11504 @cindex @option{--GCC=} (@code{gnatchop})
11505 Specify the path of the GNAT parser to be used. When this switch is used,
11506 no attempt is made to add the prefix to the GNAT parser executable.
11510 @node Examples of gnatchop Usage
11511 @section Examples of @code{gnatchop} Usage
11515 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
11518 @item gnatchop -w hello_s.ada prerelease/files
11521 Chops the source file @file{hello_s.ada}. The output files will be
11522 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
11524 files with matching names in that directory (no files in the current
11525 directory are modified).
11527 @item gnatchop ^archive^ARCHIVE.^
11528 Chops the source file @file{^archive^ARCHIVE.^}
11529 into the current directory. One
11530 useful application of @code{gnatchop} is in sending sets of sources
11531 around, for example in email messages. The required sources are simply
11532 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11534 @command{gnatchop} is used at the other end to reconstitute the original
11537 @item gnatchop file1 file2 file3 direc
11538 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11539 the resulting files in the directory @file{direc}. Note that if any units
11540 occur more than once anywhere within this set of files, an error message
11541 is generated, and no files are written. To override this check, use the
11542 @option{^-w^/OVERWRITE^} switch,
11543 in which case the last occurrence in the last file will
11544 be the one that is output, and earlier duplicate occurrences for a given
11545 unit will be skipped.
11548 @node Configuration Pragmas
11549 @chapter Configuration Pragmas
11550 @cindex Configuration pragmas
11551 @cindex Pragmas, configuration
11554 Configuration pragmas include those pragmas described as
11555 such in the Ada Reference Manual, as well as
11556 implementation-dependent pragmas that are configuration pragmas.
11557 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11558 for details on these additional GNAT-specific configuration pragmas.
11559 Most notably, the pragma @code{Source_File_Name}, which allows
11560 specifying non-default names for source files, is a configuration
11561 pragma. The following is a complete list of configuration pragmas
11562 recognized by GNAT:
11572 Assume_No_Invalid_Values
11577 Compile_Time_Warning
11579 Component_Alignment
11580 Convention_Identifier
11583 Default_Storage_Pool
11589 External_Name_Casing
11592 Float_Representation
11605 Priority_Specific_Dispatching
11608 Propagate_Exceptions
11611 Restricted_Run_Time
11613 Restrictions_Warnings
11615 Short_Circuit_And_Or
11617 Source_File_Name_Project
11620 Suppress_Exception_Locations
11621 Task_Dispatching_Policy
11627 Wide_Character_Encoding
11632 * Handling of Configuration Pragmas::
11633 * The Configuration Pragmas Files::
11636 @node Handling of Configuration Pragmas
11637 @section Handling of Configuration Pragmas
11639 Configuration pragmas may either appear at the start of a compilation
11640 unit, in which case they apply only to that unit, or they may apply to
11641 all compilations performed in a given compilation environment.
11643 GNAT also provides the @code{gnatchop} utility to provide an automatic
11644 way to handle configuration pragmas following the semantics for
11645 compilations (that is, files with multiple units), described in the RM.
11646 See @ref{Operating gnatchop in Compilation Mode} for details.
11647 However, for most purposes, it will be more convenient to edit the
11648 @file{gnat.adc} file that contains configuration pragmas directly,
11649 as described in the following section.
11651 @node The Configuration Pragmas Files
11652 @section The Configuration Pragmas Files
11653 @cindex @file{gnat.adc}
11656 In GNAT a compilation environment is defined by the current
11657 directory at the time that a compile command is given. This current
11658 directory is searched for a file whose name is @file{gnat.adc}. If
11659 this file is present, it is expected to contain one or more
11660 configuration pragmas that will be applied to the current compilation.
11661 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11664 Configuration pragmas may be entered into the @file{gnat.adc} file
11665 either by running @code{gnatchop} on a source file that consists only of
11666 configuration pragmas, or more conveniently by
11667 direct editing of the @file{gnat.adc} file, which is a standard format
11670 In addition to @file{gnat.adc}, additional files containing configuration
11671 pragmas may be applied to the current compilation using the switch
11672 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11673 contains only configuration pragmas. These configuration pragmas are
11674 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11675 is present and switch @option{-gnatA} is not used).
11677 It is allowed to specify several switches @option{-gnatec}, all of which
11678 will be taken into account.
11680 If you are using project file, a separate mechanism is provided using
11681 project attributes, see @ref{Specifying Configuration Pragmas} for more
11685 Of special interest to GNAT OpenVMS Alpha is the following
11686 configuration pragma:
11688 @smallexample @c ada
11690 pragma Extend_System (Aux_DEC);
11695 In the presence of this pragma, GNAT adds to the definition of the
11696 predefined package SYSTEM all the additional types and subprograms that are
11697 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11700 @node Handling Arbitrary File Naming Conventions Using gnatname
11701 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11702 @cindex Arbitrary File Naming Conventions
11705 * Arbitrary File Naming Conventions::
11706 * Running gnatname::
11707 * Switches for gnatname::
11708 * Examples of gnatname Usage::
11711 @node Arbitrary File Naming Conventions
11712 @section Arbitrary File Naming Conventions
11715 The GNAT compiler must be able to know the source file name of a compilation
11716 unit. When using the standard GNAT default file naming conventions
11717 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11718 does not need additional information.
11721 When the source file names do not follow the standard GNAT default file naming
11722 conventions, the GNAT compiler must be given additional information through
11723 a configuration pragmas file (@pxref{Configuration Pragmas})
11725 When the non-standard file naming conventions are well-defined,
11726 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11727 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11728 if the file naming conventions are irregular or arbitrary, a number
11729 of pragma @code{Source_File_Name} for individual compilation units
11731 To help maintain the correspondence between compilation unit names and
11732 source file names within the compiler,
11733 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11736 @node Running gnatname
11737 @section Running @code{gnatname}
11740 The usual form of the @code{gnatname} command is
11743 @c $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11744 @c @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11745 @c Expanding @ovar macro inline (explanation in macro def comments)
11746 $ gnatname @r{[}@var{switches}@r{]} @var{naming_pattern} @r{[}@var{naming_patterns}@r{]}
11747 @r{[}--and @r{[}@var{switches}@r{]} @var{naming_pattern} @r{[}@var{naming_patterns}@r{]}@r{]}
11751 All of the arguments are optional. If invoked without any argument,
11752 @code{gnatname} will display its usage.
11755 When used with at least one naming pattern, @code{gnatname} will attempt to
11756 find all the compilation units in files that follow at least one of the
11757 naming patterns. To find these compilation units,
11758 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11762 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11763 Each Naming Pattern is enclosed between double quotes (or single
11764 quotes on Windows).
11765 A Naming Pattern is a regular expression similar to the wildcard patterns
11766 used in file names by the Unix shells or the DOS prompt.
11769 @code{gnatname} may be called with several sections of directories/patterns.
11770 Sections are separated by switch @code{--and}. In each section, there must be
11771 at least one pattern. If no directory is specified in a section, the current
11772 directory (or the project directory is @code{-P} is used) is implied.
11773 The options other that the directory switches and the patterns apply globally
11774 even if they are in different sections.
11777 Examples of Naming Patterns are
11786 For a more complete description of the syntax of Naming Patterns,
11787 see the second kind of regular expressions described in @file{g-regexp.ads}
11788 (the ``Glob'' regular expressions).
11791 When invoked with no switch @code{-P}, @code{gnatname} will create a
11792 configuration pragmas file @file{gnat.adc} in the current working directory,
11793 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11796 @node Switches for gnatname
11797 @section Switches for @code{gnatname}
11800 Switches for @code{gnatname} must precede any specified Naming Pattern.
11803 You may specify any of the following switches to @code{gnatname}:
11809 @cindex @option{--version} @command{gnatname}
11810 Display Copyright and version, then exit disregarding all other options.
11813 @cindex @option{--help} @command{gnatname}
11814 If @option{--version} was not used, display usage, then exit disregarding
11818 Start another section of directories/patterns.
11820 @item ^-c^/CONFIG_FILE=^@file{file}
11821 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11822 Create a configuration pragmas file @file{file} (instead of the default
11825 There may be zero, one or more space between @option{-c} and
11828 @file{file} may include directory information. @file{file} must be
11829 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11830 When a switch @option{^-c^/CONFIG_FILE^} is
11831 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11833 @item ^-d^/SOURCE_DIRS=^@file{dir}
11834 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11835 Look for source files in directory @file{dir}. There may be zero, one or more
11836 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11837 When a switch @option{^-d^/SOURCE_DIRS^}
11838 is specified, the current working directory will not be searched for source
11839 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11840 or @option{^-D^/DIR_FILES^} switch.
11841 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11842 If @file{dir} is a relative path, it is relative to the directory of
11843 the configuration pragmas file specified with switch
11844 @option{^-c^/CONFIG_FILE^},
11845 or to the directory of the project file specified with switch
11846 @option{^-P^/PROJECT_FILE^} or,
11847 if neither switch @option{^-c^/CONFIG_FILE^}
11848 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11849 current working directory. The directory
11850 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11852 @item ^-D^/DIRS_FILE=^@file{file}
11853 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11854 Look for source files in all directories listed in text file @file{file}.
11855 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11857 @file{file} must be an existing, readable text file.
11858 Each nonempty line in @file{file} must be a directory.
11859 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11860 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11863 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11864 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11865 Foreign patterns. Using this switch, it is possible to add sources of languages
11866 other than Ada to the list of sources of a project file.
11867 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11870 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11873 will look for Ada units in all files with the @file{.ada} extension,
11874 and will add to the list of file for project @file{prj.gpr} the C files
11875 with extension @file{.^c^C^}.
11878 @cindex @option{^-h^/HELP^} (@code{gnatname})
11879 Output usage (help) information. The output is written to @file{stdout}.
11881 @item ^-P^/PROJECT_FILE=^@file{proj}
11882 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11883 Create or update project file @file{proj}. There may be zero, one or more space
11884 between @option{-P} and @file{proj}. @file{proj} may include directory
11885 information. @file{proj} must be writable.
11886 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11887 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11888 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11890 @item ^-v^/VERBOSE^
11891 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11892 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11893 This includes name of the file written, the name of the directories to search
11894 and, for each file in those directories whose name matches at least one of
11895 the Naming Patterns, an indication of whether the file contains a unit,
11896 and if so the name of the unit.
11898 @item ^-v -v^/VERBOSE /VERBOSE^
11899 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11900 Very Verbose mode. In addition to the output produced in verbose mode,
11901 for each file in the searched directories whose name matches none of
11902 the Naming Patterns, an indication is given that there is no match.
11904 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11905 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11906 Excluded patterns. Using this switch, it is possible to exclude some files
11907 that would match the name patterns. For example,
11909 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11912 will look for Ada units in all files with the @file{.ada} extension,
11913 except those whose names end with @file{_nt.ada}.
11917 @node Examples of gnatname Usage
11918 @section Examples of @code{gnatname} Usage
11922 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11928 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11933 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11934 and be writable. In addition, the directory
11935 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11936 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11939 Note the optional spaces after @option{-c} and @option{-d}.
11944 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11945 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11948 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11949 /EXCLUDED_PATTERN=*_nt_body.ada
11950 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11951 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11955 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11956 even in conjunction with one or several switches
11957 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11958 are used in this example.
11960 @c *****************************************
11961 @c * G N A T P r o j e c t M a n a g e r *
11962 @c *****************************************
11964 @c ------ macros for projects.texi
11965 @c These macros are needed when building the gprbuild documentation, but
11966 @c should have no effect in the gnat user's guide
11968 @macro CODESAMPLE{TXT}
11976 @macro PROJECTFILE{TXT}
11980 @c simulates a newline when in a @CODESAMPLE
11991 @macro TIPHTML{TXT}
11995 @macro IMPORTANT{TXT}
12010 @include projects.texi
12012 @c *****************************************
12013 @c * Cross-referencing tools
12014 @c *****************************************
12016 @node The Cross-Referencing Tools gnatxref and gnatfind
12017 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
12022 The compiler generates cross-referencing information (unless
12023 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
12024 This information indicates where in the source each entity is declared and
12025 referenced. Note that entities in package Standard are not included, but
12026 entities in all other predefined units are included in the output.
12028 Before using any of these two tools, you need to compile successfully your
12029 application, so that GNAT gets a chance to generate the cross-referencing
12032 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
12033 information to provide the user with the capability to easily locate the
12034 declaration and references to an entity. These tools are quite similar,
12035 the difference being that @code{gnatfind} is intended for locating
12036 definitions and/or references to a specified entity or entities, whereas
12037 @code{gnatxref} is oriented to generating a full report of all
12040 To use these tools, you must not compile your application using the
12041 @option{-gnatx} switch on the @command{gnatmake} command line
12042 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
12043 information will not be generated.
12045 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
12046 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
12049 * Switches for gnatxref::
12050 * Switches for gnatfind::
12051 * Project Files for gnatxref and gnatfind::
12052 * Regular Expressions in gnatfind and gnatxref::
12053 * Examples of gnatxref Usage::
12054 * Examples of gnatfind Usage::
12057 @node Switches for gnatxref
12058 @section @code{gnatxref} Switches
12061 The command invocation for @code{gnatxref} is:
12063 @c $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
12064 @c Expanding @ovar macro inline (explanation in macro def comments)
12065 $ gnatxref @r{[}@var{switches}@r{]} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
12074 identifies the source files for which a report is to be generated. The
12075 ``with''ed units will be processed too. You must provide at least one file.
12077 These file names are considered to be regular expressions, so for instance
12078 specifying @file{source*.adb} is the same as giving every file in the current
12079 directory whose name starts with @file{source} and whose extension is
12082 You shouldn't specify any directory name, just base names. @command{gnatxref}
12083 and @command{gnatfind} will be able to locate these files by themselves using
12084 the source path. If you specify directories, no result is produced.
12089 The switches can be:
12093 @cindex @option{--version} @command{gnatxref}
12094 Display Copyright and version, then exit disregarding all other options.
12097 @cindex @option{--help} @command{gnatxref}
12098 If @option{--version} was not used, display usage, then exit disregarding
12101 @item ^-a^/ALL_FILES^
12102 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
12103 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
12104 the read-only files found in the library search path. Otherwise, these files
12105 will be ignored. This option can be used to protect Gnat sources or your own
12106 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
12107 much faster, and their output much smaller. Read-only here refers to access
12108 or permissions status in the file system for the current user.
12111 @cindex @option{-aIDIR} (@command{gnatxref})
12112 When looking for source files also look in directory DIR. The order in which
12113 source file search is undertaken is the same as for @command{gnatmake}.
12116 @cindex @option{-aODIR} (@command{gnatxref})
12117 When searching for library and object files, look in directory
12118 DIR. The order in which library files are searched is the same as for
12119 @command{gnatmake}.
12122 @cindex @option{-nostdinc} (@command{gnatxref})
12123 Do not look for sources in the system default directory.
12126 @cindex @option{-nostdlib} (@command{gnatxref})
12127 Do not look for library files in the system default directory.
12129 @item --ext=@var{extension}
12130 @cindex @option{--ext} (@command{gnatxref})
12131 Specify an alternate ali file extension. The default is @code{ali} and other
12132 extensions (e.g. @code{sli} for SPARK library files) may be specified via this
12133 switch. Note that if this switch overrides the default, which means that only
12134 the new extension will be considered.
12136 @item --RTS=@var{rts-path}
12137 @cindex @option{--RTS} (@command{gnatxref})
12138 Specifies the default location of the runtime library. Same meaning as the
12139 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
12141 @item ^-d^/DERIVED_TYPES^
12142 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
12143 If this switch is set @code{gnatxref} will output the parent type
12144 reference for each matching derived types.
12146 @item ^-f^/FULL_PATHNAME^
12147 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
12148 If this switch is set, the output file names will be preceded by their
12149 directory (if the file was found in the search path). If this switch is
12150 not set, the directory will not be printed.
12152 @item ^-g^/IGNORE_LOCALS^
12153 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
12154 If this switch is set, information is output only for library-level
12155 entities, ignoring local entities. The use of this switch may accelerate
12156 @code{gnatfind} and @code{gnatxref}.
12159 @cindex @option{-IDIR} (@command{gnatxref})
12160 Equivalent to @samp{-aODIR -aIDIR}.
12163 @cindex @option{-pFILE} (@command{gnatxref})
12164 Specify a project file to use @xref{GNAT Project Manager}.
12165 If you need to use the @file{.gpr}
12166 project files, you should use gnatxref through the GNAT driver
12167 (@command{gnat xref -Pproject}).
12169 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
12170 project file in the current directory.
12172 If a project file is either specified or found by the tools, then the content
12173 of the source directory and object directory lines are added as if they
12174 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
12175 and @samp{^-aO^OBJECT_SEARCH^}.
12177 Output only unused symbols. This may be really useful if you give your
12178 main compilation unit on the command line, as @code{gnatxref} will then
12179 display every unused entity and 'with'ed package.
12183 Instead of producing the default output, @code{gnatxref} will generate a
12184 @file{tags} file that can be used by vi. For examples how to use this
12185 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
12186 to the standard output, thus you will have to redirect it to a file.
12192 All these switches may be in any order on the command line, and may even
12193 appear after the file names. They need not be separated by spaces, thus
12194 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
12195 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
12197 @node Switches for gnatfind
12198 @section @code{gnatfind} Switches
12201 The command line for @code{gnatfind} is:
12204 @c $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
12205 @c @r{[}@var{file1} @var{file2} @dots{}]
12206 @c Expanding @ovar macro inline (explanation in macro def comments)
12207 $ gnatfind @r{[}@var{switches}@r{]} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
12208 @r{[}@var{file1} @var{file2} @dots{}@r{]}
12216 An entity will be output only if it matches the regular expression found
12217 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
12219 Omitting the pattern is equivalent to specifying @samp{*}, which
12220 will match any entity. Note that if you do not provide a pattern, you
12221 have to provide both a sourcefile and a line.
12223 Entity names are given in Latin-1, with uppercase/lowercase equivalence
12224 for matching purposes. At the current time there is no support for
12225 8-bit codes other than Latin-1, or for wide characters in identifiers.
12228 @code{gnatfind} will look for references, bodies or declarations
12229 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
12230 and column @var{column}. See @ref{Examples of gnatfind Usage}
12231 for syntax examples.
12234 is a decimal integer identifying the line number containing
12235 the reference to the entity (or entities) to be located.
12238 is a decimal integer identifying the exact location on the
12239 line of the first character of the identifier for the
12240 entity reference. Columns are numbered from 1.
12242 @item file1 file2 @dots{}
12243 The search will be restricted to these source files. If none are given, then
12244 the search will be done for every library file in the search path.
12245 These file must appear only after the pattern or sourcefile.
12247 These file names are considered to be regular expressions, so for instance
12248 specifying @file{source*.adb} is the same as giving every file in the current
12249 directory whose name starts with @file{source} and whose extension is
12252 The location of the spec of the entity will always be displayed, even if it
12253 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
12254 occurrences of the entity in the separate units of the ones given on the
12255 command line will also be displayed.
12257 Note that if you specify at least one file in this part, @code{gnatfind} may
12258 sometimes not be able to find the body of the subprograms.
12263 At least one of 'sourcefile' or 'pattern' has to be present on
12266 The following switches are available:
12270 @cindex @option{--version} @command{gnatfind}
12271 Display Copyright and version, then exit disregarding all other options.
12274 @cindex @option{--help} @command{gnatfind}
12275 If @option{--version} was not used, display usage, then exit disregarding
12278 @item ^-a^/ALL_FILES^
12279 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
12280 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
12281 the read-only files found in the library search path. Otherwise, these files
12282 will be ignored. This option can be used to protect Gnat sources or your own
12283 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
12284 much faster, and their output much smaller. Read-only here refers to access
12285 or permission status in the file system for the current user.
12288 @cindex @option{-aIDIR} (@command{gnatfind})
12289 When looking for source files also look in directory DIR. The order in which
12290 source file search is undertaken is the same as for @command{gnatmake}.
12293 @cindex @option{-aODIR} (@command{gnatfind})
12294 When searching for library and object files, look in directory
12295 DIR. The order in which library files are searched is the same as for
12296 @command{gnatmake}.
12299 @cindex @option{-nostdinc} (@command{gnatfind})
12300 Do not look for sources in the system default directory.
12303 @cindex @option{-nostdlib} (@command{gnatfind})
12304 Do not look for library files in the system default directory.
12306 @item --ext=@var{extension}
12307 @cindex @option{--ext} (@command{gnatfind})
12308 Specify an alternate ali file extension. The default is @code{ali} and other
12309 extensions (e.g. @code{sli} for SPARK library files) may be specified via this
12310 switch. Note that if this switch overrides the default, which means that only
12311 the new extension will be considered.
12313 @item --RTS=@var{rts-path}
12314 @cindex @option{--RTS} (@command{gnatfind})
12315 Specifies the default location of the runtime library. Same meaning as the
12316 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
12318 @item ^-d^/DERIVED_TYPE_INFORMATION^
12319 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
12320 If this switch is set, then @code{gnatfind} will output the parent type
12321 reference for each matching derived types.
12323 @item ^-e^/EXPRESSIONS^
12324 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
12325 By default, @code{gnatfind} accept the simple regular expression set for
12326 @samp{pattern}. If this switch is set, then the pattern will be
12327 considered as full Unix-style regular expression.
12329 @item ^-f^/FULL_PATHNAME^
12330 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
12331 If this switch is set, the output file names will be preceded by their
12332 directory (if the file was found in the search path). If this switch is
12333 not set, the directory will not be printed.
12335 @item ^-g^/IGNORE_LOCALS^
12336 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
12337 If this switch is set, information is output only for library-level
12338 entities, ignoring local entities. The use of this switch may accelerate
12339 @code{gnatfind} and @code{gnatxref}.
12342 @cindex @option{-IDIR} (@command{gnatfind})
12343 Equivalent to @samp{-aODIR -aIDIR}.
12346 @cindex @option{-pFILE} (@command{gnatfind})
12347 Specify a project file (@pxref{GNAT Project Manager}) to use.
12348 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
12349 project file in the current directory.
12351 If a project file is either specified or found by the tools, then the content
12352 of the source directory and object directory lines are added as if they
12353 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
12354 @samp{^-aO^/OBJECT_SEARCH^}.
12356 @item ^-r^/REFERENCES^
12357 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
12358 By default, @code{gnatfind} will output only the information about the
12359 declaration, body or type completion of the entities. If this switch is
12360 set, the @code{gnatfind} will locate every reference to the entities in
12361 the files specified on the command line (or in every file in the search
12362 path if no file is given on the command line).
12364 @item ^-s^/PRINT_LINES^
12365 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
12366 If this switch is set, then @code{gnatfind} will output the content
12367 of the Ada source file lines were the entity was found.
12369 @item ^-t^/TYPE_HIERARCHY^
12370 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
12371 If this switch is set, then @code{gnatfind} will output the type hierarchy for
12372 the specified type. It act like -d option but recursively from parent
12373 type to parent type. When this switch is set it is not possible to
12374 specify more than one file.
12379 All these switches may be in any order on the command line, and may even
12380 appear after the file names. They need not be separated by spaces, thus
12381 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
12382 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
12384 As stated previously, gnatfind will search in every directory in the
12385 search path. You can force it to look only in the current directory if
12386 you specify @code{*} at the end of the command line.
12388 @node Project Files for gnatxref and gnatfind
12389 @section Project Files for @command{gnatxref} and @command{gnatfind}
12392 Project files allow a programmer to specify how to compile its
12393 application, where to find sources, etc. These files are used
12395 primarily by GPS, but they can also be used
12398 @code{gnatxref} and @code{gnatfind}.
12400 A project file name must end with @file{.gpr}. If a single one is
12401 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
12402 extract the information from it. If multiple project files are found, none of
12403 them is read, and you have to use the @samp{-p} switch to specify the one
12406 The following lines can be included, even though most of them have default
12407 values which can be used in most cases.
12408 The lines can be entered in any order in the file.
12409 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
12410 each line. If you have multiple instances, only the last one is taken into
12415 [default: @code{"^./^[]^"}]
12416 specifies a directory where to look for source files. Multiple @code{src_dir}
12417 lines can be specified and they will be searched in the order they
12421 [default: @code{"^./^[]^"}]
12422 specifies a directory where to look for object and library files. Multiple
12423 @code{obj_dir} lines can be specified, and they will be searched in the order
12426 @item comp_opt=SWITCHES
12427 [default: @code{""}]
12428 creates a variable which can be referred to subsequently by using
12429 the @code{$@{comp_opt@}} notation. This is intended to store the default
12430 switches given to @command{gnatmake} and @command{gcc}.
12432 @item bind_opt=SWITCHES
12433 [default: @code{""}]
12434 creates a variable which can be referred to subsequently by using
12435 the @samp{$@{bind_opt@}} notation. This is intended to store the default
12436 switches given to @command{gnatbind}.
12438 @item link_opt=SWITCHES
12439 [default: @code{""}]
12440 creates a variable which can be referred to subsequently by using
12441 the @samp{$@{link_opt@}} notation. This is intended to store the default
12442 switches given to @command{gnatlink}.
12444 @item main=EXECUTABLE
12445 [default: @code{""}]
12446 specifies the name of the executable for the application. This variable can
12447 be referred to in the following lines by using the @samp{$@{main@}} notation.
12450 @item comp_cmd=COMMAND
12451 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
12454 @item comp_cmd=COMMAND
12455 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
12457 specifies the command used to compile a single file in the application.
12460 @item make_cmd=COMMAND
12461 [default: @code{"GNAT MAKE $@{main@}
12462 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
12463 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
12464 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
12467 @item make_cmd=COMMAND
12468 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
12469 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
12470 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
12472 specifies the command used to recompile the whole application.
12474 @item run_cmd=COMMAND
12475 [default: @code{"$@{main@}"}]
12476 specifies the command used to run the application.
12478 @item debug_cmd=COMMAND
12479 [default: @code{"gdb $@{main@}"}]
12480 specifies the command used to debug the application
12485 @command{gnatxref} and @command{gnatfind} only take into account the
12486 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
12488 @node Regular Expressions in gnatfind and gnatxref
12489 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
12492 As specified in the section about @command{gnatfind}, the pattern can be a
12493 regular expression. Actually, there are to set of regular expressions
12494 which are recognized by the program:
12497 @item globbing patterns
12498 These are the most usual regular expression. They are the same that you
12499 generally used in a Unix shell command line, or in a DOS session.
12501 Here is a more formal grammar:
12508 term ::= elmt -- matches elmt
12509 term ::= elmt elmt -- concatenation (elmt then elmt)
12510 term ::= * -- any string of 0 or more characters
12511 term ::= ? -- matches any character
12512 term ::= [char @{char@}] -- matches any character listed
12513 term ::= [char - char] -- matches any character in range
12517 @item full regular expression
12518 The second set of regular expressions is much more powerful. This is the
12519 type of regular expressions recognized by utilities such a @file{grep}.
12521 The following is the form of a regular expression, expressed in Ada
12522 reference manual style BNF is as follows
12529 regexp ::= term @{| term@} -- alternation (term or term @dots{})
12531 term ::= item @{item@} -- concatenation (item then item)
12533 item ::= elmt -- match elmt
12534 item ::= elmt * -- zero or more elmt's
12535 item ::= elmt + -- one or more elmt's
12536 item ::= elmt ? -- matches elmt or nothing
12539 elmt ::= nschar -- matches given character
12540 elmt ::= [nschar @{nschar@}] -- matches any character listed
12541 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
12542 elmt ::= [char - char] -- matches chars in given range
12543 elmt ::= \ char -- matches given character
12544 elmt ::= . -- matches any single character
12545 elmt ::= ( regexp ) -- parens used for grouping
12547 char ::= any character, including special characters
12548 nschar ::= any character except ()[].*+?^^^
12552 Following are a few examples:
12556 will match any of the two strings @samp{abcde} and @samp{fghi},
12559 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
12560 @samp{abcccd}, and so on,
12563 will match any string which has only lowercase characters in it (and at
12564 least one character.
12569 @node Examples of gnatxref Usage
12570 @section Examples of @code{gnatxref} Usage
12572 @subsection General Usage
12575 For the following examples, we will consider the following units:
12577 @smallexample @c ada
12583 3: procedure Foo (B : in Integer);
12590 1: package body Main is
12591 2: procedure Foo (B : in Integer) is
12602 2: procedure Print (B : Integer);
12611 The first thing to do is to recompile your application (for instance, in
12612 that case just by doing a @samp{gnatmake main}, so that GNAT generates
12613 the cross-referencing information.
12614 You can then issue any of the following commands:
12616 @item gnatxref main.adb
12617 @code{gnatxref} generates cross-reference information for main.adb
12618 and every unit 'with'ed by main.adb.
12620 The output would be:
12628 Decl: main.ads 3:20
12629 Body: main.adb 2:20
12630 Ref: main.adb 4:13 5:13 6:19
12633 Ref: main.adb 6:8 7:8
12643 Decl: main.ads 3:15
12644 Body: main.adb 2:15
12647 Body: main.adb 1:14
12650 Ref: main.adb 6:12 7:12
12654 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
12655 its body is in main.adb, line 1, column 14 and is not referenced any where.
12657 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
12658 is referenced in main.adb, line 6 column 12 and line 7 column 12.
12660 @item gnatxref package1.adb package2.ads
12661 @code{gnatxref} will generates cross-reference information for
12662 package1.adb, package2.ads and any other package 'with'ed by any
12668 @subsection Using gnatxref with vi
12670 @code{gnatxref} can generate a tags file output, which can be used
12671 directly from @command{vi}. Note that the standard version of @command{vi}
12672 will not work properly with overloaded symbols. Consider using another
12673 free implementation of @command{vi}, such as @command{vim}.
12676 $ gnatxref -v gnatfind.adb > tags
12680 will generate the tags file for @code{gnatfind} itself (if the sources
12681 are in the search path!).
12683 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
12684 (replacing @var{entity} by whatever you are looking for), and vi will
12685 display a new file with the corresponding declaration of entity.
12688 @node Examples of gnatfind Usage
12689 @section Examples of @code{gnatfind} Usage
12693 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
12694 Find declarations for all entities xyz referenced at least once in
12695 main.adb. The references are search in every library file in the search
12698 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
12701 The output will look like:
12703 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
12704 ^directory/^[directory]^main.adb:24:10: xyz <= body
12705 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
12709 that is to say, one of the entities xyz found in main.adb is declared at
12710 line 12 of main.ads (and its body is in main.adb), and another one is
12711 declared at line 45 of foo.ads
12713 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
12714 This is the same command as the previous one, instead @code{gnatfind} will
12715 display the content of the Ada source file lines.
12717 The output will look like:
12720 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
12722 ^directory/^[directory]^main.adb:24:10: xyz <= body
12724 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
12729 This can make it easier to find exactly the location your are looking
12732 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
12733 Find references to all entities containing an x that are
12734 referenced on line 123 of main.ads.
12735 The references will be searched only in main.ads and foo.adb.
12737 @item gnatfind main.ads:123
12738 Find declarations and bodies for all entities that are referenced on
12739 line 123 of main.ads.
12741 This is the same as @code{gnatfind "*":main.adb:123}.
12743 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
12744 Find the declaration for the entity referenced at column 45 in
12745 line 123 of file main.adb in directory mydir. Note that it
12746 is usual to omit the identifier name when the column is given,
12747 since the column position identifies a unique reference.
12749 The column has to be the beginning of the identifier, and should not
12750 point to any character in the middle of the identifier.
12754 @c *********************************
12755 @node The GNAT Pretty-Printer gnatpp
12756 @chapter The GNAT Pretty-Printer @command{gnatpp}
12758 @cindex Pretty-Printer
12761 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
12762 for source reformatting / pretty-printing.
12763 It takes an Ada source file as input and generates a reformatted
12765 You can specify various style directives via switches; e.g.,
12766 identifier case conventions, rules of indentation, and comment layout.
12768 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
12769 tree for the input source and thus requires the input to be syntactically and
12770 semantically legal.
12771 If this condition is not met, @command{gnatpp} will terminate with an
12772 error message; no output file will be generated.
12774 If the source files presented to @command{gnatpp} contain
12775 preprocessing directives, then the output file will
12776 correspond to the generated source after all
12777 preprocessing is carried out. There is no way
12778 using @command{gnatpp} to obtain pretty printed files that
12779 include the preprocessing directives.
12781 If the compilation unit
12782 contained in the input source depends semantically upon units located
12783 outside the current directory, you have to provide the source search path
12784 when invoking @command{gnatpp}, if these units are contained in files with
12785 names that do not follow the GNAT file naming rules, you have to provide
12786 the configuration file describing the corresponding naming scheme;
12787 see the description of the @command{gnatpp}
12788 switches below. Another possibility is to use a project file and to
12789 call @command{gnatpp} through the @command{gnat} driver
12791 The @command{gnatpp} command has the form
12794 @c $ gnatpp @ovar{switches} @var{filename}
12795 @c Expanding @ovar macro inline (explanation in macro def comments)
12796 $ gnatpp @r{[}@var{switches}@r{]} @var{filename} @r{[}-cargs @var{gcc_switches}@r{]}
12803 @var{switches} is an optional sequence of switches defining such properties as
12804 the formatting rules, the source search path, and the destination for the
12808 @var{filename} is the name (including the extension) of the source file to
12809 reformat; ``wildcards'' or several file names on the same gnatpp command are
12810 allowed. The file name may contain path information; it does not have to
12811 follow the GNAT file naming rules
12814 @samp{@var{gcc_switches}} is a list of switches for
12815 @command{gcc}. They will be passed on to all compiler invocations made by
12816 @command{gnatelim} to generate the ASIS trees. Here you can provide
12817 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
12818 use the @option{-gnatec} switch to set the configuration file,
12819 use the @option{-gnat05} switch if sources should be compiled in
12824 * Switches for gnatpp::
12825 * Formatting Rules::
12828 @node Switches for gnatpp
12829 @section Switches for @command{gnatpp}
12832 The following subsections describe the various switches accepted by
12833 @command{gnatpp}, organized by category.
12836 You specify a switch by supplying a name and generally also a value.
12837 In many cases the values for a switch with a given name are incompatible with
12839 (for example the switch that controls the casing of a reserved word may have
12840 exactly one value: upper case, lower case, or
12841 mixed case) and thus exactly one such switch can be in effect for an
12842 invocation of @command{gnatpp}.
12843 If more than one is supplied, the last one is used.
12844 However, some values for the same switch are mutually compatible.
12845 You may supply several such switches to @command{gnatpp}, but then
12846 each must be specified in full, with both the name and the value.
12847 Abbreviated forms (the name appearing once, followed by each value) are
12849 For example, to set
12850 the alignment of the assignment delimiter both in declarations and in
12851 assignment statements, you must write @option{-A2A3}
12852 (or @option{-A2 -A3}), but not @option{-A23}.
12856 In many cases the set of options for a given qualifier are incompatible with
12857 each other (for example the qualifier that controls the casing of a reserved
12858 word may have exactly one option, which specifies either upper case, lower
12859 case, or mixed case), and thus exactly one such option can be in effect for
12860 an invocation of @command{gnatpp}.
12861 If more than one is supplied, the last one is used.
12862 However, some qualifiers have options that are mutually compatible,
12863 and then you may then supply several such options when invoking
12867 In most cases, it is obvious whether or not the
12868 ^values for a switch with a given name^options for a given qualifier^
12869 are compatible with each other.
12870 When the semantics might not be evident, the summaries below explicitly
12871 indicate the effect.
12874 * Alignment Control::
12876 * Construct Layout Control::
12877 * General Text Layout Control::
12878 * Other Formatting Options::
12879 * Setting the Source Search Path::
12880 * Output File Control::
12881 * Other gnatpp Switches::
12884 @node Alignment Control
12885 @subsection Alignment Control
12886 @cindex Alignment control in @command{gnatpp}
12889 Programs can be easier to read if certain constructs are vertically aligned.
12890 By default all alignments are set ON.
12891 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
12892 OFF, and then use one or more of the other
12893 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
12894 to activate alignment for specific constructs.
12897 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
12901 Set all alignments to ON
12904 @item ^-A0^/ALIGN=OFF^
12905 Set all alignments to OFF
12907 @item ^-A1^/ALIGN=COLONS^
12908 Align @code{:} in declarations
12910 @item ^-A2^/ALIGN=DECLARATIONS^
12911 Align @code{:=} in initializations in declarations
12913 @item ^-A3^/ALIGN=STATEMENTS^
12914 Align @code{:=} in assignment statements
12916 @item ^-A4^/ALIGN=ARROWS^
12917 Align @code{=>} in associations
12919 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
12920 Align @code{at} keywords in the component clauses in record
12921 representation clauses
12925 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
12928 @node Casing Control
12929 @subsection Casing Control
12930 @cindex Casing control in @command{gnatpp}
12933 @command{gnatpp} allows you to specify the casing for reserved words,
12934 pragma names, attribute designators and identifiers.
12935 For identifiers you may define a
12936 general rule for name casing but also override this rule
12937 via a set of dictionary files.
12939 Three types of casing are supported: lower case, upper case, and mixed case.
12940 Lower and upper case are self-explanatory (but since some letters in
12941 Latin1 and other GNAT-supported character sets
12942 exist only in lower-case form, an upper case conversion will have no
12944 ``Mixed case'' means that the first letter, and also each letter immediately
12945 following an underscore, are converted to their uppercase forms;
12946 all the other letters are converted to their lowercase forms.
12949 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
12950 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
12951 Attribute designators are lower case
12953 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
12954 Attribute designators are upper case
12956 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
12957 Attribute designators are mixed case (this is the default)
12959 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
12960 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
12961 Keywords (technically, these are known in Ada as @emph{reserved words}) are
12962 lower case (this is the default)
12964 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
12965 Keywords are upper case
12967 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
12968 @item ^-nD^/NAME_CASING=AS_DECLARED^
12969 Name casing for defining occurrences are as they appear in the source file
12970 (this is the default)
12972 @item ^-nU^/NAME_CASING=UPPER_CASE^
12973 Names are in upper case
12975 @item ^-nL^/NAME_CASING=LOWER_CASE^
12976 Names are in lower case
12978 @item ^-nM^/NAME_CASING=MIXED_CASE^
12979 Names are in mixed case
12981 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
12982 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
12983 Pragma names are lower case
12985 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
12986 Pragma names are upper case
12988 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
12989 Pragma names are mixed case (this is the default)
12991 @item ^-D@var{file}^/DICTIONARY=@var{file}^
12992 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
12993 Use @var{file} as a @emph{dictionary file} that defines
12994 the casing for a set of specified names,
12995 thereby overriding the effect on these names by
12996 any explicit or implicit
12997 ^-n^/NAME_CASING^ switch.
12998 To supply more than one dictionary file,
12999 use ^several @option{-D} switches^a list of files as options^.
13002 @option{gnatpp} implicitly uses a @emph{default dictionary file}
13003 to define the casing for the Ada predefined names and
13004 the names declared in the GNAT libraries.
13006 @item ^-D-^/SPECIFIC_CASING^
13007 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
13008 Do not use the default dictionary file;
13009 instead, use the casing
13010 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
13015 The structure of a dictionary file, and details on the conventions
13016 used in the default dictionary file, are defined in @ref{Name Casing}.
13018 The @option{^-D-^/SPECIFIC_CASING^} and
13019 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
13022 @node Construct Layout Control
13023 @subsection Construct Layout Control
13024 @cindex Layout control in @command{gnatpp}
13027 This group of @command{gnatpp} switches controls the layout of comments and
13028 complex syntactic constructs. See @ref{Formatting Comments} for details
13032 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
13033 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
13034 All the comments remain unchanged
13036 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
13037 GNAT-style comment line indentation (this is the default).
13039 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
13040 Reference-manual comment line indentation.
13042 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
13043 GNAT-style comment beginning
13045 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
13046 Reformat comment blocks
13048 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
13049 Keep unchanged special form comments
13051 Reformat comment blocks
13053 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
13054 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
13055 GNAT-style layout (this is the default)
13057 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
13060 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
13063 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
13065 All the VT characters are removed from the comment text. All the HT characters
13066 are expanded with the sequences of space characters to get to the next tab
13069 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
13070 @item ^--no-separate-is^/NO_SEPARATE_IS^
13071 Do not place the keyword @code{is} on a separate line in a subprogram body in
13072 case if the spec occupies more then one line.
13074 @cindex @option{^--separate-label^/SEPARATE_LABEL^} (@command{gnatpp})
13075 @item ^--separate-label^/SEPARATE_LABEL^
13076 Place statement label(s) on a separate line, with the following statement
13079 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
13080 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
13081 Place the keyword @code{loop} in FOR and WHILE loop statements and the
13082 keyword @code{then} in IF statements on a separate line.
13084 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
13085 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
13086 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
13087 keyword @code{then} in IF statements on a separate line. This option is
13088 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
13090 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
13091 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
13092 Start each USE clause in a context clause from a separate line.
13094 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
13095 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
13096 Use a separate line for a loop or block statement name, but do not use an extra
13097 indentation level for the statement itself.
13103 The @option{-c1} and @option{-c2} switches are incompatible.
13104 The @option{-c3} and @option{-c4} switches are compatible with each other and
13105 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
13106 the other comment formatting switches.
13108 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
13113 For the @option{/COMMENTS_LAYOUT} qualifier:
13116 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
13118 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
13119 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
13123 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
13124 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
13127 @node General Text Layout Control
13128 @subsection General Text Layout Control
13131 These switches allow control over line length and indentation.
13134 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
13135 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
13136 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
13138 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
13139 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
13140 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
13142 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
13143 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
13144 Indentation level for continuation lines (relative to the line being
13145 continued), @var{nnn} from 1@dots{}9.
13147 value is one less then the (normal) indentation level, unless the
13148 indentation is set to 1 (in which case the default value for continuation
13149 line indentation is also 1)
13152 @node Other Formatting Options
13153 @subsection Other Formatting Options
13156 These switches control the inclusion of missing end/exit labels, and
13157 the indentation level in @b{case} statements.
13160 @item ^-e^/NO_MISSED_LABELS^
13161 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
13162 Do not insert missing end/exit labels. An end label is the name of
13163 a construct that may optionally be repeated at the end of the
13164 construct's declaration;
13165 e.g., the names of packages, subprograms, and tasks.
13166 An exit label is the name of a loop that may appear as target
13167 of an exit statement within the loop.
13168 By default, @command{gnatpp} inserts these end/exit labels when
13169 they are absent from the original source. This option suppresses such
13170 insertion, so that the formatted source reflects the original.
13172 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
13173 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
13174 Insert a Form Feed character after a pragma Page.
13176 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
13177 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
13178 Do not use an additional indentation level for @b{case} alternatives
13179 and variants if there are @var{nnn} or more (the default
13181 If @var{nnn} is 0, an additional indentation level is
13182 used for @b{case} alternatives and variants regardless of their number.
13185 @node Setting the Source Search Path
13186 @subsection Setting the Source Search Path
13189 To define the search path for the input source file, @command{gnatpp}
13190 uses the same switches as the GNAT compiler, with the same effects.
13193 @item ^-I^/SEARCH=^@var{dir}
13194 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
13195 The same as the corresponding gcc switch
13197 @item ^-I-^/NOCURRENT_DIRECTORY^
13198 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
13199 The same as the corresponding gcc switch
13201 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
13202 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
13203 The same as the corresponding gcc switch
13205 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
13206 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
13207 The same as the corresponding gcc switch
13211 @node Output File Control
13212 @subsection Output File Control
13215 By default the output is sent to the file whose name is obtained by appending
13216 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
13217 (if the file with this name already exists, it is unconditionally overwritten).
13218 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
13219 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
13221 The output may be redirected by the following switches:
13224 @item ^-pipe^/STANDARD_OUTPUT^
13225 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
13226 Send the output to @code{Standard_Output}
13228 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
13229 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
13230 Write the output into @var{output_file}.
13231 If @var{output_file} already exists, @command{gnatpp} terminates without
13232 reading or processing the input file.
13234 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
13235 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
13236 Write the output into @var{output_file}, overwriting the existing file
13237 (if one is present).
13239 @item ^-r^/REPLACE^
13240 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
13241 Replace the input source file with the reformatted output, and copy the
13242 original input source into the file whose name is obtained by appending the
13243 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
13244 If a file with this name already exists, @command{gnatpp} terminates without
13245 reading or processing the input file.
13247 @item ^-rf^/OVERRIDING_REPLACE^
13248 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
13249 Like @option{^-r^/REPLACE^} except that if the file with the specified name
13250 already exists, it is overwritten.
13252 @item ^-rnb^/REPLACE_NO_BACKUP^
13253 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
13254 Replace the input source file with the reformatted output without
13255 creating any backup copy of the input source.
13257 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
13258 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
13259 Specifies the format of the reformatted output file. The @var{xxx}
13260 ^string specified with the switch^option^ may be either
13262 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
13263 @item ``@option{^crlf^CRLF^}''
13264 the same as @option{^crlf^CRLF^}
13265 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
13266 @item ``@option{^lf^LF^}''
13267 the same as @option{^unix^UNIX^}
13270 @item ^-W^/RESULT_ENCODING=^@var{e}
13271 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
13272 Specify the wide character encoding method used to write the code in the
13274 @var{e} is one of the following:
13282 Upper half encoding
13284 @item ^s^SHIFT_JIS^
13294 Brackets encoding (default value)
13300 Options @option{^-pipe^/STANDARD_OUTPUT^},
13301 @option{^-o^/OUTPUT^} and
13302 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
13303 contains only one file to reformat.
13305 @option{^--eol^/END_OF_LINE^}
13307 @option{^-W^/RESULT_ENCODING^}
13308 cannot be used together
13309 with @option{^-pipe^/STANDARD_OUTPUT^} option.
13311 @node Other gnatpp Switches
13312 @subsection Other @code{gnatpp} Switches
13315 The additional @command{gnatpp} switches are defined in this subsection.
13318 @item ^-files @var{filename}^/FILES=@var{filename}^
13319 @cindex @option{^-files^/FILES^} (@code{gnatpp})
13320 Take the argument source files from the specified file. This file should be an
13321 ordinary text file containing file names separated by spaces or
13322 line breaks. You can use this switch more than once in the same call to
13323 @command{gnatpp}. You also can combine this switch with an explicit list of
13326 @item ^-v^/VERBOSE^
13327 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
13329 @command{gnatpp} generates version information and then
13330 a trace of the actions it takes to produce or obtain the ASIS tree.
13332 @item ^-w^/WARNINGS^
13333 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
13335 @command{gnatpp} generates a warning whenever it cannot provide
13336 a required layout in the result source.
13339 @node Formatting Rules
13340 @section Formatting Rules
13343 The following subsections show how @command{gnatpp} treats ``white space'',
13344 comments, program layout, and name casing.
13345 They provide the detailed descriptions of the switches shown above.
13348 * White Space and Empty Lines::
13349 * Formatting Comments::
13350 * Construct Layout::
13354 @node White Space and Empty Lines
13355 @subsection White Space and Empty Lines
13358 @command{gnatpp} does not have an option to control space characters.
13359 It will add or remove spaces according to the style illustrated by the
13360 examples in the @cite{Ada Reference Manual}.
13362 The only format effectors
13363 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
13364 that will appear in the output file are platform-specific line breaks,
13365 and also format effectors within (but not at the end of) comments.
13366 In particular, each horizontal tab character that is not inside
13367 a comment will be treated as a space and thus will appear in the
13368 output file as zero or more spaces depending on
13369 the reformatting of the line in which it appears.
13370 The only exception is a Form Feed character, which is inserted after a
13371 pragma @code{Page} when @option{-ff} is set.
13373 The output file will contain no lines with trailing ``white space'' (spaces,
13376 Empty lines in the original source are preserved
13377 only if they separate declarations or statements.
13378 In such contexts, a
13379 sequence of two or more empty lines is replaced by exactly one empty line.
13380 Note that a blank line will be removed if it separates two ``comment blocks''
13381 (a comment block is a sequence of whole-line comments).
13382 In order to preserve a visual separation between comment blocks, use an
13383 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
13384 Likewise, if for some reason you wish to have a sequence of empty lines,
13385 use a sequence of empty comments instead.
13387 @node Formatting Comments
13388 @subsection Formatting Comments
13391 Comments in Ada code are of two kinds:
13394 a @emph{whole-line comment}, which appears by itself (possibly preceded by
13395 ``white space'') on a line
13398 an @emph{end-of-line comment}, which follows some other Ada lexical element
13403 The indentation of a whole-line comment is that of either
13404 the preceding or following line in
13405 the formatted source, depending on switch settings as will be described below.
13407 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
13408 between the end of the preceding Ada lexical element and the beginning
13409 of the comment as appear in the original source,
13410 unless either the comment has to be split to
13411 satisfy the line length limitation, or else the next line contains a
13412 whole line comment that is considered a continuation of this end-of-line
13413 comment (because it starts at the same position).
13415 cases, the start of the end-of-line comment is moved right to the nearest
13416 multiple of the indentation level.
13417 This may result in a ``line overflow'' (the right-shifted comment extending
13418 beyond the maximum line length), in which case the comment is split as
13421 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
13422 (GNAT-style comment line indentation)
13423 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
13424 (reference-manual comment line indentation).
13425 With reference-manual style, a whole-line comment is indented as if it
13426 were a declaration or statement at the same place
13427 (i.e., according to the indentation of the preceding line(s)).
13428 With GNAT style, a whole-line comment that is immediately followed by an
13429 @b{if} or @b{case} statement alternative, a record variant, or the reserved
13430 word @b{begin}, is indented based on the construct that follows it.
13433 @smallexample @c ada
13445 Reference-manual indentation produces:
13447 @smallexample @c ada
13459 while GNAT-style indentation produces:
13461 @smallexample @c ada
13473 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
13474 (GNAT style comment beginning) has the following
13479 For each whole-line comment that does not end with two hyphens,
13480 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
13481 to ensure that there are at least two spaces between these hyphens and the
13482 first non-blank character of the comment.
13486 For an end-of-line comment, if in the original source the next line is a
13487 whole-line comment that starts at the same position
13488 as the end-of-line comment,
13489 then the whole-line comment (and all whole-line comments
13490 that follow it and that start at the same position)
13491 will start at this position in the output file.
13494 That is, if in the original source we have:
13496 @smallexample @c ada
13499 A := B + C; -- B must be in the range Low1..High1
13500 -- C must be in the range Low2..High2
13501 --B+C will be in the range Low1+Low2..High1+High2
13507 Then in the formatted source we get
13509 @smallexample @c ada
13512 A := B + C; -- B must be in the range Low1..High1
13513 -- C must be in the range Low2..High2
13514 -- B+C will be in the range Low1+Low2..High1+High2
13520 A comment that exceeds the line length limit will be split.
13522 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
13523 the line belongs to a reformattable block, splitting the line generates a
13524 @command{gnatpp} warning.
13525 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
13526 comments may be reformatted in typical
13527 word processor style (that is, moving words between lines and putting as
13528 many words in a line as possible).
13531 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
13532 that has a special format (that is, a character that is neither a letter nor digit
13533 not white space nor line break immediately following the leading @code{--} of
13534 the comment) should be without any change moved from the argument source
13535 into reformatted source. This switch allows to preserve comments that are used
13536 as a special marks in the code (e.g.@: SPARK annotation).
13538 @node Construct Layout
13539 @subsection Construct Layout
13542 In several cases the suggested layout in the Ada Reference Manual includes
13543 an extra level of indentation that many programmers prefer to avoid. The
13544 affected cases include:
13548 @item Record type declaration (RM 3.8)
13550 @item Record representation clause (RM 13.5.1)
13552 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
13554 @item Block statement in case if a block has a statement identifier (RM 5.6)
13558 In compact mode (when GNAT style layout or compact layout is set),
13559 the pretty printer uses one level of indentation instead
13560 of two. This is achieved in the record definition and record representation
13561 clause cases by putting the @code{record} keyword on the same line as the
13562 start of the declaration or representation clause, and in the block and loop
13563 case by putting the block or loop header on the same line as the statement
13567 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
13568 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
13569 layout on the one hand, and uncompact layout
13570 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
13571 can be illustrated by the following examples:
13575 @multitable @columnfractions .5 .5
13576 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
13579 @smallexample @c ada
13586 @smallexample @c ada
13595 @smallexample @c ada
13597 a at 0 range 0 .. 31;
13598 b at 4 range 0 .. 31;
13602 @smallexample @c ada
13605 a at 0 range 0 .. 31;
13606 b at 4 range 0 .. 31;
13611 @smallexample @c ada
13619 @smallexample @c ada
13629 @smallexample @c ada
13630 Clear : for J in 1 .. 10 loop
13635 @smallexample @c ada
13637 for J in 1 .. 10 loop
13648 GNAT style, compact layout Uncompact layout
13650 type q is record type q is
13651 a : integer; record
13652 b : integer; a : integer;
13653 end record; b : integer;
13656 for q use record for q use
13657 a at 0 range 0 .. 31; record
13658 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
13659 end record; b at 4 range 0 .. 31;
13662 Block : declare Block :
13663 A : Integer := 3; declare
13664 begin A : Integer := 3;
13666 end Block; Proc (A, A);
13669 Clear : for J in 1 .. 10 loop Clear :
13670 A (J) := 0; for J in 1 .. 10 loop
13671 end loop Clear; A (J) := 0;
13678 A further difference between GNAT style layout and compact layout is that
13679 GNAT style layout inserts empty lines as separation for
13680 compound statements, return statements and bodies.
13682 Note that the layout specified by
13683 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
13684 for named block and loop statements overrides the layout defined by these
13685 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
13686 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
13687 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
13690 @subsection Name Casing
13693 @command{gnatpp} always converts the usage occurrence of a (simple) name to
13694 the same casing as the corresponding defining identifier.
13696 You control the casing for defining occurrences via the
13697 @option{^-n^/NAME_CASING^} switch.
13699 With @option{-nD} (``as declared'', which is the default),
13702 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
13704 defining occurrences appear exactly as in the source file
13705 where they are declared.
13706 The other ^values for this switch^options for this qualifier^ ---
13707 @option{^-nU^UPPER_CASE^},
13708 @option{^-nL^LOWER_CASE^},
13709 @option{^-nM^MIXED_CASE^} ---
13711 ^upper, lower, or mixed case, respectively^the corresponding casing^.
13712 If @command{gnatpp} changes the casing of a defining
13713 occurrence, it analogously changes the casing of all the
13714 usage occurrences of this name.
13716 If the defining occurrence of a name is not in the source compilation unit
13717 currently being processed by @command{gnatpp}, the casing of each reference to
13718 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
13719 switch (subject to the dictionary file mechanism described below).
13720 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
13722 casing for the defining occurrence of the name.
13724 Some names may need to be spelled with casing conventions that are not
13725 covered by the upper-, lower-, and mixed-case transformations.
13726 You can arrange correct casing by placing such names in a
13727 @emph{dictionary file},
13728 and then supplying a @option{^-D^/DICTIONARY^} switch.
13729 The casing of names from dictionary files overrides
13730 any @option{^-n^/NAME_CASING^} switch.
13732 To handle the casing of Ada predefined names and the names from GNAT libraries,
13733 @command{gnatpp} assumes a default dictionary file.
13734 The name of each predefined entity is spelled with the same casing as is used
13735 for the entity in the @cite{Ada Reference Manual}.
13736 The name of each entity in the GNAT libraries is spelled with the same casing
13737 as is used in the declaration of that entity.
13739 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
13740 default dictionary file.
13741 Instead, the casing for predefined and GNAT-defined names will be established
13742 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
13743 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
13744 will appear as just shown,
13745 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
13746 To ensure that even such names are rendered in uppercase,
13747 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
13748 (or else, less conveniently, place these names in upper case in a dictionary
13751 A dictionary file is
13752 a plain text file; each line in this file can be either a blank line
13753 (containing only space characters and ASCII.HT characters), an Ada comment
13754 line, or the specification of exactly one @emph{casing schema}.
13756 A casing schema is a string that has the following syntax:
13760 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
13762 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
13767 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
13768 @var{identifier} lexical element and the @var{letter_or_digit} category.)
13770 The casing schema string can be followed by white space and/or an Ada-style
13771 comment; any amount of white space is allowed before the string.
13773 If a dictionary file is passed as
13775 the value of a @option{-D@var{file}} switch
13778 an option to the @option{/DICTIONARY} qualifier
13781 simple name and every identifier, @command{gnatpp} checks if the dictionary
13782 defines the casing for the name or for some of its parts (the term ``subword''
13783 is used below to denote the part of a name which is delimited by ``_'' or by
13784 the beginning or end of the word and which does not contain any ``_'' inside):
13788 if the whole name is in the dictionary, @command{gnatpp} uses for this name
13789 the casing defined by the dictionary; no subwords are checked for this word
13792 for every subword @command{gnatpp} checks if the dictionary contains the
13793 corresponding string of the form @code{*@var{simple_identifier}*},
13794 and if it does, the casing of this @var{simple_identifier} is used
13798 if the whole name does not contain any ``_'' inside, and if for this name
13799 the dictionary contains two entries - one of the form @var{identifier},
13800 and another - of the form *@var{simple_identifier}*, then the first one
13801 is applied to define the casing of this name
13804 if more than one dictionary file is passed as @command{gnatpp} switches, each
13805 dictionary adds new casing exceptions and overrides all the existing casing
13806 exceptions set by the previous dictionaries
13809 when @command{gnatpp} checks if the word or subword is in the dictionary,
13810 this check is not case sensitive
13814 For example, suppose we have the following source to reformat:
13816 @smallexample @c ada
13819 name1 : integer := 1;
13820 name4_name3_name2 : integer := 2;
13821 name2_name3_name4 : Boolean;
13824 name2_name3_name4 := name4_name3_name2 > name1;
13830 And suppose we have two dictionaries:
13847 If @command{gnatpp} is called with the following switches:
13851 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
13854 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
13859 then we will get the following name casing in the @command{gnatpp} output:
13861 @smallexample @c ada
13864 NAME1 : Integer := 1;
13865 Name4_NAME3_Name2 : Integer := 2;
13866 Name2_NAME3_Name4 : Boolean;
13869 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
13874 @c *********************************
13875 @node The GNAT Metric Tool gnatmetric
13876 @chapter The GNAT Metric Tool @command{gnatmetric}
13878 @cindex Metric tool
13881 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
13882 for computing various program metrics.
13883 It takes an Ada source file as input and generates a file containing the
13884 metrics data as output. Various switches control which
13885 metrics are computed and output.
13887 @command{gnatmetric} generates and uses the ASIS
13888 tree for the input source and thus requires the input to be syntactically and
13889 semantically legal.
13890 If this condition is not met, @command{gnatmetric} will generate
13891 an error message; no metric information for this file will be
13892 computed and reported.
13894 If the compilation unit contained in the input source depends semantically
13895 upon units in files located outside the current directory, you have to provide
13896 the source search path when invoking @command{gnatmetric}.
13897 If it depends semantically upon units that are contained
13898 in files with names that do not follow the GNAT file naming rules, you have to
13899 provide the configuration file describing the corresponding naming scheme (see
13900 the description of the @command{gnatmetric} switches below.)
13901 Alternatively, you may use a project file and invoke @command{gnatmetric}
13902 through the @command{gnat} driver.
13904 The @command{gnatmetric} command has the form
13907 @c $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
13908 @c Expanding @ovar macro inline (explanation in macro def comments)
13909 $ gnatmetric @r{[}@var{switches}@r{]} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
13916 @var{switches} specify the metrics to compute and define the destination for
13920 Each @var{filename} is the name (including the extension) of a source
13921 file to process. ``Wildcards'' are allowed, and
13922 the file name may contain path information.
13923 If no @var{filename} is supplied, then the @var{switches} list must contain
13925 @option{-files} switch (@pxref{Other gnatmetric Switches}).
13926 Including both a @option{-files} switch and one or more
13927 @var{filename} arguments is permitted.
13930 @samp{@var{gcc_switches}} is a list of switches for
13931 @command{gcc}. They will be passed on to all compiler invocations made by
13932 @command{gnatmetric} to generate the ASIS trees. Here you can provide
13933 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
13934 and use the @option{-gnatec} switch to set the configuration file,
13935 use the @option{-gnat05} switch if sources should be compiled in
13940 * Switches for gnatmetric::
13943 @node Switches for gnatmetric
13944 @section Switches for @command{gnatmetric}
13947 The following subsections describe the various switches accepted by
13948 @command{gnatmetric}, organized by category.
13951 * Output Files Control::
13952 * Disable Metrics For Local Units::
13953 * Specifying a set of metrics to compute::
13954 * Other gnatmetric Switches::
13955 * Generate project-wide metrics::
13958 @node Output Files Control
13959 @subsection Output File Control
13960 @cindex Output file control in @command{gnatmetric}
13963 @command{gnatmetric} has two output formats. It can generate a
13964 textual (human-readable) form, and also XML. By default only textual
13965 output is generated.
13967 When generating the output in textual form, @command{gnatmetric} creates
13968 for each Ada source file a corresponding text file
13969 containing the computed metrics, except for the case when the set of metrics
13970 specified by gnatmetric parameters consists only of metrics that are computed
13971 for the whole set of analyzed sources, but not for each Ada source.
13972 By default, this file is placed in the same directory as where the source
13973 file is located, and its name is obtained
13974 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
13977 All the output information generated in XML format is placed in a single
13978 file. By default this file is placed in the current directory and has the
13979 name ^@file{metrix.xml}^@file{METRIX$XML}^.
13981 Some of the computed metrics are summed over the units passed to
13982 @command{gnatmetric}; for example, the total number of lines of code.
13983 By default this information is sent to @file{stdout}, but a file
13984 can be specified with the @option{-og} switch.
13986 The following switches control the @command{gnatmetric} output:
13989 @cindex @option{^-x^/XML^} (@command{gnatmetric})
13991 Generate the XML output
13993 @cindex @option{^-xs^/XSD^} (@command{gnatmetric})
13995 Generate the XML output and the XML schema file that describes the structure
13996 of the XML metric report, this schema is assigned to the XML file. The schema
13997 file has the same name as the XML output file with @file{.xml} suffix replaced
14000 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
14001 @item ^-nt^/NO_TEXT^
14002 Do not generate the output in text form (implies @option{^-x^/XML^})
14004 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
14005 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
14006 Put text files with detailed metrics into @var{output_dir}
14008 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
14009 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
14010 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
14011 in the name of the output file.
14013 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
14014 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
14015 Put global metrics into @var{file_name}
14017 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
14018 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
14019 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
14021 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
14022 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
14023 Use ``short'' source file names in the output. (The @command{gnatmetric}
14024 output includes the name(s) of the Ada source file(s) from which the metrics
14025 are computed. By default each name includes the absolute path. The
14026 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
14027 to exclude all directory information from the file names that are output.)
14031 @node Disable Metrics For Local Units
14032 @subsection Disable Metrics For Local Units
14033 @cindex Disable Metrics For Local Units in @command{gnatmetric}
14036 @command{gnatmetric} relies on the GNAT compilation model @minus{}
14038 unit per one source file. It computes line metrics for the whole source
14039 file, and it also computes syntax
14040 and complexity metrics for the file's outermost unit.
14042 By default, @command{gnatmetric} will also compute all metrics for certain
14043 kinds of locally declared program units:
14047 subprogram (and generic subprogram) bodies;
14050 package (and generic package) specs and bodies;
14053 task object and type specifications and bodies;
14056 protected object and type specifications and bodies.
14060 These kinds of entities will be referred to as
14061 @emph{eligible local program units}, or simply @emph{eligible local units},
14062 @cindex Eligible local unit (for @command{gnatmetric})
14063 in the discussion below.
14065 Note that a subprogram declaration, generic instantiation,
14066 or renaming declaration only receives metrics
14067 computation when it appear as the outermost entity
14070 Suppression of metrics computation for eligible local units can be
14071 obtained via the following switch:
14074 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
14075 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
14076 Do not compute detailed metrics for eligible local program units
14080 @node Specifying a set of metrics to compute
14081 @subsection Specifying a set of metrics to compute
14084 By default all the metrics are computed and reported. The switches
14085 described in this subsection allow you to control, on an individual
14086 basis, whether metrics are computed and
14087 reported. If at least one positive metric
14088 switch is specified (that is, a switch that defines that a given
14089 metric or set of metrics is to be computed), then only
14090 explicitly specified metrics are reported.
14093 * Line Metrics Control::
14094 * Syntax Metrics Control::
14095 * Complexity Metrics Control::
14096 * Object-Oriented Metrics Control::
14099 @node Line Metrics Control
14100 @subsubsection Line Metrics Control
14101 @cindex Line metrics control in @command{gnatmetric}
14104 For any (legal) source file, and for each of its
14105 eligible local program units, @command{gnatmetric} computes the following
14110 the total number of lines;
14113 the total number of code lines (i.e., non-blank lines that are not comments)
14116 the number of comment lines
14119 the number of code lines containing end-of-line comments;
14122 the comment percentage: the ratio between the number of lines that contain
14123 comments and the number of all non-blank lines, expressed as a percentage;
14126 the number of empty lines and lines containing only space characters and/or
14127 format effectors (blank lines)
14130 the average number of code lines in subprogram bodies, task bodies, entry
14131 bodies and statement sequences in package bodies (this metric is only computed
14132 across the whole set of the analyzed units)
14137 @command{gnatmetric} sums the values of the line metrics for all the
14138 files being processed and then generates the cumulative results. The tool
14139 also computes for all the files being processed the average number of code
14142 You can use the following switches to select the specific line metrics
14143 to be computed and reported.
14146 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
14149 @cindex @option{--no-lines@var{x}}
14152 @item ^--lines-all^/LINE_COUNT_METRICS=ALL^
14153 Report all the line metrics
14155 @item ^--no-lines-all^/LINE_COUNT_METRICS=NONE^
14156 Do not report any of line metrics
14158 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES^
14159 Report the number of all lines
14161 @item ^--no-lines^/LINE_COUNT_METRICS=NOALL_LINES^
14162 Do not report the number of all lines
14164 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES^
14165 Report the number of code lines
14167 @item ^--no-lines-code^/LINE_COUNT_METRICS=NOCODE_LINES^
14168 Do not report the number of code lines
14170 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES^
14171 Report the number of comment lines
14173 @item ^--no-lines-comment^/LINE_COUNT_METRICS=NOCOMMENT_LINES^
14174 Do not report the number of comment lines
14176 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES^
14177 Report the number of code lines containing
14178 end-of-line comments
14180 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=NOCODE_COMMENT_LINES^
14181 Do not report the number of code lines containing
14182 end-of-line comments
14184 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE^
14185 Report the comment percentage in the program text
14187 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=NOCOMMENT_PERCENTAGE^
14188 Do not report the comment percentage in the program text
14190 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES^
14191 Report the number of blank lines
14193 @item ^--no-lines-blank^/LINE_COUNT_METRICS=NOBLANK_LINES^
14194 Do not report the number of blank lines
14196 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES^
14197 Report the average number of code lines in subprogram bodies, task bodies,
14198 entry bodies and statement sequences in package bodies. The metric is computed
14199 and reported for the whole set of processed Ada sources only.
14201 @item ^--no-lines-average^/LINE_COUNT_METRICS=NOAVERAGE_BODY_LINES^
14202 Do not report the average number of code lines in subprogram bodies,
14203 task bodies, entry bodies and statement sequences in package bodies.
14207 @node Syntax Metrics Control
14208 @subsubsection Syntax Metrics Control
14209 @cindex Syntax metrics control in @command{gnatmetric}
14212 @command{gnatmetric} computes various syntactic metrics for the
14213 outermost unit and for each eligible local unit:
14216 @item LSLOC (``Logical Source Lines Of Code'')
14217 The total number of declarations and the total number of statements
14219 @item Maximal static nesting level of inner program units
14221 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
14222 package, a task unit, a protected unit, a
14223 protected entry, a generic unit, or an explicitly declared subprogram other
14224 than an enumeration literal.''
14226 @item Maximal nesting level of composite syntactic constructs
14227 This corresponds to the notion of the
14228 maximum nesting level in the GNAT built-in style checks
14229 (@pxref{Style Checking})
14233 For the outermost unit in the file, @command{gnatmetric} additionally computes
14234 the following metrics:
14237 @item Public subprograms
14238 This metric is computed for package specs. It is the
14239 number of subprograms and generic subprograms declared in the visible
14240 part (including the visible part of nested packages, protected objects, and
14243 @item All subprograms
14244 This metric is computed for bodies and subunits. The
14245 metric is equal to a total number of subprogram bodies in the compilation
14247 Neither generic instantiations nor renamings-as-a-body nor body stubs
14248 are counted. Any subprogram body is counted, independently of its nesting
14249 level and enclosing constructs. Generic bodies and bodies of protected
14250 subprograms are counted in the same way as ``usual'' subprogram bodies.
14253 This metric is computed for package specs and
14254 generic package declarations. It is the total number of types
14255 that can be referenced from outside this compilation unit, plus the
14256 number of types from all the visible parts of all the visible generic
14257 packages. Generic formal types are not counted. Only types, not subtypes,
14261 Along with the total number of public types, the following
14262 types are counted and reported separately:
14269 Root tagged types (abstract, non-abstract, private, non-private). Type
14270 extensions are @emph{not} counted
14273 Private types (including private extensions)
14284 This metric is computed for any compilation unit. It is equal to the total
14285 number of the declarations of different types given in the compilation unit.
14286 The private and the corresponding full type declaration are counted as one
14287 type declaration. Incomplete type declarations and generic formal types
14289 No distinction is made among different kinds of types (abstract,
14290 private etc.); the total number of types is computed and reported.
14295 By default, all the syntax metrics are computed and reported. You can use the
14296 following switches to select specific syntax metrics.
14300 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
14303 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
14306 @item ^--syntax-all^/SYNTAX_METRICS=ALL^
14307 Report all the syntax metrics
14309 @item ^--no-syntax-all^/SYNTAX_METRICS=NONE^
14310 Do not report any of syntax metrics
14312 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS^
14313 Report the total number of declarations
14315 @item ^--no-declarations^/SYNTAX_METRICS=NODECLARATIONS^
14316 Do not report the total number of declarations
14318 @item ^--statements^/SYNTAX_METRICS=STATEMENTS^
14319 Report the total number of statements
14321 @item ^--no-statements^/SYNTAX_METRICS=NOSTATEMENTS^
14322 Do not report the total number of statements
14324 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS^
14325 Report the number of public subprograms in a compilation unit
14327 @item ^--no-public-subprograms^/SYNTAX_METRICS=NOPUBLIC_SUBPROGRAMS^
14328 Do not report the number of public subprograms in a compilation unit
14330 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS^
14331 Report the number of all the subprograms in a compilation unit
14333 @item ^--no-all-subprograms^/SYNTAX_METRICS=NOALL_SUBPROGRAMS^
14334 Do not report the number of all the subprograms in a compilation unit
14336 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES^
14337 Report the number of public types in a compilation unit
14339 @item ^--no-public-types^/SYNTAX_METRICS=NOPUBLIC_TYPES^
14340 Do not report the number of public types in a compilation unit
14342 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES^
14343 Report the number of all the types in a compilation unit
14345 @item ^--no-all-types^/SYNTAX_METRICS=NOALL_TYPES^
14346 Do not report the number of all the types in a compilation unit
14348 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING^
14349 Report the maximal program unit nesting level
14351 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
14352 Do not report the maximal program unit nesting level
14354 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING^
14355 Report the maximal construct nesting level
14357 @item ^--no-construct-nesting^/SYNTAX_METRICS=NOCONSTRUCT_NESTING^
14358 Do not report the maximal construct nesting level
14362 @node Complexity Metrics Control
14363 @subsubsection Complexity Metrics Control
14364 @cindex Complexity metrics control in @command{gnatmetric}
14367 For a program unit that is an executable body (a subprogram body (including
14368 generic bodies), task body, entry body or a package body containing
14369 its own statement sequence) @command{gnatmetric} computes the following
14370 complexity metrics:
14374 McCabe cyclomatic complexity;
14377 McCabe essential complexity;
14380 maximal loop nesting level;
14383 extra exit points (for subprograms);
14387 The McCabe cyclomatic complexity metric is defined
14388 in @url{http://www.mccabe.com/pdf/mccabe-nist235r.pdf}
14390 According to McCabe, both control statements and short-circuit control forms
14391 should be taken into account when computing cyclomatic complexity. For each
14392 body, we compute three metric values:
14396 the complexity introduced by control
14397 statements only, without taking into account short-circuit forms,
14400 the complexity introduced by short-circuit control forms only, and
14404 cyclomatic complexity, which is the sum of these two values.
14409 The origin of cyclomatic complexity metric is the need to estimate the number
14410 of independent paths in the control flow graph that in turn gives the number
14411 of tests needed to satisfy paths coverage testing completeness criterion.
14412 Considered from the testing point of view, a static Ada @code{loop} (that is,
14413 the @code{loop} statement having static subtype in loop parameter
14414 specification) does not add to cyclomatic complexity. By providing
14415 @option{^--no-static-loop^NO_STATIC_LOOP^} option a user
14416 may specify that such loops should not be counted when computing the
14417 cyclomatic complexity metric
14419 The Ada essential complexity metric is a McCabe cyclomatic complexity metric
14420 counted for the code that is reduced by excluding all the pure structural Ada
14421 control statements. An compound statement is considered as a non-structural
14422 if it contains a @code{raise} or @code{return} statement as it subcomponent,
14423 or if it contains a @code{goto} statement that transfers the control outside
14424 the operator. A selective accept statement with @code{terminate} alternative
14425 is considered as non-structural statement. When computing this metric,
14426 @code{exit} statements are treated in the same way as @code{goto}
14427 statements unless @option{^-ne^NO_EXITS_AS_GOTOS^} option is specified.
14429 The Ada essential complexity metric defined here is intended to quantify
14430 the extent to which the software is unstructured. It is adapted from
14431 the McCabe essential complexity metric defined in
14432 http://www.mccabe.com/pdf/nist235r.pdf but is modified to be more
14433 suitable for typical Ada usage. For example, short circuit forms
14434 are not penalized as unstructured in the Ada essential complexity metric.
14436 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
14437 the code in the exception handlers and in all the nested program units.
14439 By default, all the complexity metrics are computed and reported.
14440 For more fine-grained control you can use
14441 the following switches:
14444 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
14447 @cindex @option{--no-complexity@var{x}}
14450 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL^
14451 Report all the complexity metrics
14453 @item ^--no-complexity-all^/COMPLEXITY_METRICS=NONE^
14454 Do not report any of complexity metrics
14456 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC^
14457 Report the McCabe Cyclomatic Complexity
14459 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=NOCYCLOMATIC^
14460 Do not report the McCabe Cyclomatic Complexity
14462 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL^
14463 Report the Essential Complexity
14465 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=NOESSENTIAL^
14466 Do not report the Essential Complexity
14468 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
14469 Report maximal loop nesting level
14471 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=NOLOOP_NESTING^
14472 Do not report maximal loop nesting level
14474 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY^
14475 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
14476 task bodies, entry bodies and statement sequences in package bodies.
14477 The metric is computed and reported for whole set of processed Ada sources
14480 @item ^--no-complexity-average^/COMPLEXITY_METRICS=NOAVERAGE_COMPLEXITY^
14481 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
14482 bodies, task bodies, entry bodies and statement sequences in package bodies
14484 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
14485 @item ^-ne^/NO_EXITS_AS_GOTOS^
14486 Do not consider @code{exit} statements as @code{goto}s when
14487 computing Essential Complexity
14489 @cindex @option{^--no-static-loop^/NO_STATIC_LOOP^} (@command{gnatmetric})
14490 @item ^--no-static-loop^/NO_STATIC_LOOP^
14491 Do not consider static loops when computing cyclomatic complexity
14493 @item ^--extra-exit-points^/EXTRA_EXIT_POINTS^
14494 Report the extra exit points for subprogram bodies. As an exit point, this
14495 metric counts @code{return} statements and raise statements in case when the
14496 raised exception is not handled in the same body. In case of a function this
14497 metric subtracts 1 from the number of exit points, because a function body
14498 must contain at least one @code{return} statement.
14500 @item ^--no-extra-exit-points^/NOEXTRA_EXIT_POINTS^
14501 Do not report the extra exit points for subprogram bodies
14505 @node Object-Oriented Metrics Control
14506 @subsubsection Object-Oriented Metrics Control
14507 @cindex Object-Oriented metrics control in @command{gnatmetric}
14510 @cindex Coupling metrics (in in @command{gnatmetric})
14511 Coupling metrics are object-oriented metrics that measure the
14512 dependencies between a given class (or a group of classes) and the
14513 ``external world'' (that is, the other classes in the program). In this
14514 subsection the term ``class'' is used in its
14515 traditional object-oriented programming sense
14516 (an instantiable module that contains data and/or method members).
14517 A @emph{category} (of classes)
14518 is a group of closely related classes that are reused and/or
14521 A class @code{K}'s @emph{efferent coupling} is the number of classes
14522 that @code{K} depends upon.
14523 A category's efferent coupling is the number of classes outside the
14524 category that the classes inside the category depend upon.
14526 A class @code{K}'s @emph{afferent coupling} is the number of classes
14527 that depend upon @code{K}.
14528 A category's afferent coupling is the number of classes outside the
14529 category that depend on classes belonging to the category.
14531 Ada's implementation of the object-oriented paradigm does not use the
14532 traditional class notion, so the definition of the coupling
14533 metrics for Ada maps the class and class category notions
14534 onto Ada constructs.
14536 For the coupling metrics, several kinds of modules -- a library package,
14537 a library generic package, and a library generic package instantiation --
14538 that define a tagged type or an interface type are
14539 considered to be a class. A category consists of a library package (or
14540 a library generic package) that defines a tagged or an interface type,
14541 together with all its descendant (generic) packages that define tagged
14542 or interface types. For any package counted as a class,
14543 its body and subunits (if any) are considered
14544 together with its spec when counting the dependencies, and coupling
14545 metrics are reported for spec units only. For dependencies
14546 between classes, the Ada semantic dependencies are considered.
14547 For coupling metrics, only dependencies on units that are considered as
14548 classes, are considered.
14550 When computing coupling metrics, @command{gnatmetric} counts only
14551 dependencies between units that are arguments of the gnatmetric call.
14552 Coupling metrics are program-wide (or project-wide) metrics, so to
14553 get a valid result, you should call @command{gnatmetric} for
14554 the whole set of sources that make up your program. It can be done
14555 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
14556 option (see See @ref{The GNAT Driver and Project Files} for details.
14558 By default, all the coupling metrics are disabled. You can use the following
14559 switches to specify the coupling metrics to be computed and reported:
14564 @cindex @option{--package@var{x}} (@command{gnatmetric})
14565 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
14566 @cindex @option{--category@var{x}} (@command{gnatmetric})
14567 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
14571 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
14574 @item ^--coupling-all^/COUPLING_METRICS=ALL^
14575 Report all the coupling metrics
14577 @item ^--no-coupling-all^/COUPLING_METRICS=NONE^
14578 Do not report any of metrics
14580 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT^
14581 Report package efferent coupling
14583 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=NOPACKAGE_EFFERENT^
14584 Do not report package efferent coupling
14586 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT^
14587 Report package afferent coupling
14589 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=NOPACKAGE_AFFERENT^
14590 Do not report package afferent coupling
14592 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT^
14593 Report category efferent coupling
14595 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=NOCATEGORY_EFFERENT^
14596 Do not report category efferent coupling
14598 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT^
14599 Report category afferent coupling
14601 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=NOCATEGORY_AFFERENT^
14602 Do not report category afferent coupling
14606 @node Other gnatmetric Switches
14607 @subsection Other @code{gnatmetric} Switches
14610 Additional @command{gnatmetric} switches are as follows:
14613 @item ^-files @var{filename}^/FILES=@var{filename}^
14614 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
14615 Take the argument source files from the specified file. This file should be an
14616 ordinary text file containing file names separated by spaces or
14617 line breaks. You can use this switch more than once in the same call to
14618 @command{gnatmetric}. You also can combine this switch with
14619 an explicit list of files.
14621 @item ^-v^/VERBOSE^
14622 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
14624 @command{gnatmetric} generates version information and then
14625 a trace of sources being processed.
14628 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
14632 @node Generate project-wide metrics
14633 @subsection Generate project-wide metrics
14635 In order to compute metrics on all units of a given project, you can use
14636 the @command{gnat} driver along with the @option{-P} option:
14642 If the project @code{proj} depends upon other projects, you can compute
14643 the metrics on the project closure using the @option{-U} option:
14645 gnat metric -Pproj -U
14649 Finally, if not all the units are relevant to a particular main
14650 program in the project closure, you can generate metrics for the set
14651 of units needed to create a given main program (unit closure) using
14652 the @option{-U} option followed by the name of the main unit:
14654 gnat metric -Pproj -U main
14658 @c ***********************************
14659 @node File Name Krunching Using gnatkr
14660 @chapter File Name Krunching Using @code{gnatkr}
14664 This chapter discusses the method used by the compiler to shorten
14665 the default file names chosen for Ada units so that they do not
14666 exceed the maximum length permitted. It also describes the
14667 @code{gnatkr} utility that can be used to determine the result of
14668 applying this shortening.
14672 * Krunching Method::
14673 * Examples of gnatkr Usage::
14677 @section About @code{gnatkr}
14680 The default file naming rule in GNAT
14681 is that the file name must be derived from
14682 the unit name. The exact default rule is as follows:
14685 Take the unit name and replace all dots by hyphens.
14687 If such a replacement occurs in the
14688 second character position of a name, and the first character is
14689 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
14690 then replace the dot by the character
14691 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
14692 instead of a minus.
14694 The reason for this exception is to avoid clashes
14695 with the standard names for children of System, Ada, Interfaces,
14696 and GNAT, which use the prefixes
14697 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
14700 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
14701 switch of the compiler activates a ``krunching''
14702 circuit that limits file names to nn characters (where nn is a decimal
14703 integer). For example, using OpenVMS,
14704 where the maximum file name length is
14705 39, the value of nn is usually set to 39, but if you want to generate
14706 a set of files that would be usable if ported to a system with some
14707 different maximum file length, then a different value can be specified.
14708 The default value of 39 for OpenVMS need not be specified.
14710 The @code{gnatkr} utility can be used to determine the krunched name for
14711 a given file, when krunched to a specified maximum length.
14714 @section Using @code{gnatkr}
14717 The @code{gnatkr} command has the form
14721 @c $ gnatkr @var{name} @ovar{length}
14722 @c Expanding @ovar macro inline (explanation in macro def comments)
14723 $ gnatkr @var{name} @r{[}@var{length}@r{]}
14729 $ gnatkr @var{name} /COUNT=nn
14734 @var{name} is the uncrunched file name, derived from the name of the unit
14735 in the standard manner described in the previous section (i.e., in particular
14736 all dots are replaced by hyphens). The file name may or may not have an
14737 extension (defined as a suffix of the form period followed by arbitrary
14738 characters other than period). If an extension is present then it will
14739 be preserved in the output. For example, when krunching @file{hellofile.ads}
14740 to eight characters, the result will be hellofil.ads.
14742 Note: for compatibility with previous versions of @code{gnatkr} dots may
14743 appear in the name instead of hyphens, but the last dot will always be
14744 taken as the start of an extension. So if @code{gnatkr} is given an argument
14745 such as @file{Hello.World.adb} it will be treated exactly as if the first
14746 period had been a hyphen, and for example krunching to eight characters
14747 gives the result @file{hellworl.adb}.
14749 Note that the result is always all lower case (except on OpenVMS where it is
14750 all upper case). Characters of the other case are folded as required.
14752 @var{length} represents the length of the krunched name. The default
14753 when no argument is given is ^8^39^ characters. A length of zero stands for
14754 unlimited, in other words do not chop except for system files where the
14755 implied crunching length is always eight characters.
14758 The output is the krunched name. The output has an extension only if the
14759 original argument was a file name with an extension.
14761 @node Krunching Method
14762 @section Krunching Method
14765 The initial file name is determined by the name of the unit that the file
14766 contains. The name is formed by taking the full expanded name of the
14767 unit and replacing the separating dots with hyphens and
14768 using ^lowercase^uppercase^
14769 for all letters, except that a hyphen in the second character position is
14770 replaced by a ^tilde^dollar sign^ if the first character is
14771 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
14772 The extension is @code{.ads} for a
14773 spec and @code{.adb} for a body.
14774 Krunching does not affect the extension, but the file name is shortened to
14775 the specified length by following these rules:
14779 The name is divided into segments separated by hyphens, tildes or
14780 underscores and all hyphens, tildes, and underscores are
14781 eliminated. If this leaves the name short enough, we are done.
14784 If the name is too long, the longest segment is located (left-most
14785 if there are two of equal length), and shortened by dropping
14786 its last character. This is repeated until the name is short enough.
14788 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
14789 to fit the name into 8 characters as required by some operating systems.
14792 our-strings-wide_fixed 22
14793 our strings wide fixed 19
14794 our string wide fixed 18
14795 our strin wide fixed 17
14796 our stri wide fixed 16
14797 our stri wide fixe 15
14798 our str wide fixe 14
14799 our str wid fixe 13
14805 Final file name: oustwifi.adb
14809 The file names for all predefined units are always krunched to eight
14810 characters. The krunching of these predefined units uses the following
14811 special prefix replacements:
14815 replaced by @file{^a^A^-}
14818 replaced by @file{^g^G^-}
14821 replaced by @file{^i^I^-}
14824 replaced by @file{^s^S^-}
14827 These system files have a hyphen in the second character position. That
14828 is why normal user files replace such a character with a
14829 ^tilde^dollar sign^, to
14830 avoid confusion with system file names.
14832 As an example of this special rule, consider
14833 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
14836 ada-strings-wide_fixed 22
14837 a- strings wide fixed 18
14838 a- string wide fixed 17
14839 a- strin wide fixed 16
14840 a- stri wide fixed 15
14841 a- stri wide fixe 14
14842 a- str wide fixe 13
14848 Final file name: a-stwifi.adb
14852 Of course no file shortening algorithm can guarantee uniqueness over all
14853 possible unit names, and if file name krunching is used then it is your
14854 responsibility to ensure that no name clashes occur. The utility
14855 program @code{gnatkr} is supplied for conveniently determining the
14856 krunched name of a file.
14858 @node Examples of gnatkr Usage
14859 @section Examples of @code{gnatkr} Usage
14866 $ gnatkr very_long_unit_name.ads --> velounna.ads
14867 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
14868 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
14869 $ gnatkr grandparent-parent-child --> grparchi
14871 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
14872 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
14875 @node Preprocessing Using gnatprep
14876 @chapter Preprocessing Using @code{gnatprep}
14880 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
14882 Although designed for use with GNAT, @code{gnatprep} does not depend on any
14883 special GNAT features.
14884 For further discussion of conditional compilation in general, see
14885 @ref{Conditional Compilation}.
14888 * Preprocessing Symbols::
14890 * Switches for gnatprep::
14891 * Form of Definitions File::
14892 * Form of Input Text for gnatprep::
14895 @node Preprocessing Symbols
14896 @section Preprocessing Symbols
14899 Preprocessing symbols are defined in definition files and referred to in
14900 sources to be preprocessed. A Preprocessing symbol is an identifier, following
14901 normal Ada (case-insensitive) rules for its syntax, with the restriction that
14902 all characters need to be in the ASCII set (no accented letters).
14904 @node Using gnatprep
14905 @section Using @code{gnatprep}
14908 To call @code{gnatprep} use
14911 @c $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
14912 @c Expanding @ovar macro inline (explanation in macro def comments)
14913 $ gnatprep @r{[}@var{switches}@r{]} @var{infile} @var{outfile} @r{[}@var{deffile}@r{]}
14920 is an optional sequence of switches as described in the next section.
14923 is the full name of the input file, which is an Ada source
14924 file containing preprocessor directives.
14927 is the full name of the output file, which is an Ada source
14928 in standard Ada form. When used with GNAT, this file name will
14929 normally have an ads or adb suffix.
14932 is the full name of a text file containing definitions of
14933 preprocessing symbols to be referenced by the preprocessor. This argument is
14934 optional, and can be replaced by the use of the @option{-D} switch.
14938 @node Switches for gnatprep
14939 @section Switches for @code{gnatprep}
14944 @item ^-b^/BLANK_LINES^
14945 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
14946 Causes both preprocessor lines and the lines deleted by
14947 preprocessing to be replaced by blank lines in the output source file,
14948 preserving line numbers in the output file.
14950 @item ^-c^/COMMENTS^
14951 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
14952 Causes both preprocessor lines and the lines deleted
14953 by preprocessing to be retained in the output source as comments marked
14954 with the special string @code{"--! "}. This option will result in line numbers
14955 being preserved in the output file.
14957 @item ^-C^/REPLACE_IN_COMMENTS^
14958 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
14959 Causes comments to be scanned. Normally comments are ignored by gnatprep.
14960 If this option is specified, then comments are scanned and any $symbol
14961 substitutions performed as in program text. This is particularly useful
14962 when structured comments are used (e.g., when writing programs in the
14963 SPARK dialect of Ada). Note that this switch is not available when
14964 doing integrated preprocessing (it would be useless in this context
14965 since comments are ignored by the compiler in any case).
14967 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
14968 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
14969 Defines a new preprocessing symbol, associated with value. If no value is given
14970 on the command line, then symbol is considered to be @code{True}. This switch
14971 can be used in place of a definition file.
14975 @cindex @option{/REMOVE} (@command{gnatprep})
14976 This is the default setting which causes lines deleted by preprocessing
14977 to be entirely removed from the output file.
14980 @item ^-r^/REFERENCE^
14981 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
14982 Causes a @code{Source_Reference} pragma to be generated that
14983 references the original input file, so that error messages will use
14984 the file name of this original file. The use of this switch implies
14985 that preprocessor lines are not to be removed from the file, so its
14986 use will force @option{^-b^/BLANK_LINES^} mode if
14987 @option{^-c^/COMMENTS^}
14988 has not been specified explicitly.
14990 Note that if the file to be preprocessed contains multiple units, then
14991 it will be necessary to @code{gnatchop} the output file from
14992 @code{gnatprep}. If a @code{Source_Reference} pragma is present
14993 in the preprocessed file, it will be respected by
14994 @code{gnatchop ^-r^/REFERENCE^}
14995 so that the final chopped files will correctly refer to the original
14996 input source file for @code{gnatprep}.
14998 @item ^-s^/SYMBOLS^
14999 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
15000 Causes a sorted list of symbol names and values to be
15001 listed on the standard output file.
15003 @item ^-u^/UNDEFINED^
15004 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
15005 Causes undefined symbols to be treated as having the value FALSE in the context
15006 of a preprocessor test. In the absence of this option, an undefined symbol in
15007 a @code{#if} or @code{#elsif} test will be treated as an error.
15013 Note: if neither @option{-b} nor @option{-c} is present,
15014 then preprocessor lines and
15015 deleted lines are completely removed from the output, unless -r is
15016 specified, in which case -b is assumed.
15019 @node Form of Definitions File
15020 @section Form of Definitions File
15023 The definitions file contains lines of the form
15030 where symbol is a preprocessing symbol, and value is one of the following:
15034 Empty, corresponding to a null substitution
15036 A string literal using normal Ada syntax
15038 Any sequence of characters from the set
15039 (letters, digits, period, underline).
15043 Comment lines may also appear in the definitions file, starting with
15044 the usual @code{--},
15045 and comments may be added to the definitions lines.
15047 @node Form of Input Text for gnatprep
15048 @section Form of Input Text for @code{gnatprep}
15051 The input text may contain preprocessor conditional inclusion lines,
15052 as well as general symbol substitution sequences.
15054 The preprocessor conditional inclusion commands have the form
15059 #if @i{expression} @r{[}then@r{]}
15061 #elsif @i{expression} @r{[}then@r{]}
15063 #elsif @i{expression} @r{[}then@r{]}
15074 In this example, @i{expression} is defined by the following grammar:
15076 @i{expression} ::= <symbol>
15077 @i{expression} ::= <symbol> = "<value>"
15078 @i{expression} ::= <symbol> = <symbol>
15079 @i{expression} ::= <symbol> 'Defined
15080 @i{expression} ::= not @i{expression}
15081 @i{expression} ::= @i{expression} and @i{expression}
15082 @i{expression} ::= @i{expression} or @i{expression}
15083 @i{expression} ::= @i{expression} and then @i{expression}
15084 @i{expression} ::= @i{expression} or else @i{expression}
15085 @i{expression} ::= ( @i{expression} )
15088 The following restriction exists: it is not allowed to have "and" or "or"
15089 following "not" in the same expression without parentheses. For example, this
15096 This should be one of the following:
15104 For the first test (@i{expression} ::= <symbol>) the symbol must have
15105 either the value true or false, that is to say the right-hand of the
15106 symbol definition must be one of the (case-insensitive) literals
15107 @code{True} or @code{False}. If the value is true, then the
15108 corresponding lines are included, and if the value is false, they are
15111 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
15112 the symbol has been defined in the definition file or by a @option{-D}
15113 switch on the command line. Otherwise, the test is false.
15115 The equality tests are case insensitive, as are all the preprocessor lines.
15117 If the symbol referenced is not defined in the symbol definitions file,
15118 then the effect depends on whether or not switch @option{-u}
15119 is specified. If so, then the symbol is treated as if it had the value
15120 false and the test fails. If this switch is not specified, then
15121 it is an error to reference an undefined symbol. It is also an error to
15122 reference a symbol that is defined with a value other than @code{True}
15125 The use of the @code{not} operator inverts the sense of this logical test.
15126 The @code{not} operator cannot be combined with the @code{or} or @code{and}
15127 operators, without parentheses. For example, "if not X or Y then" is not
15128 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
15130 The @code{then} keyword is optional as shown
15132 The @code{#} must be the first non-blank character on a line, but
15133 otherwise the format is free form. Spaces or tabs may appear between
15134 the @code{#} and the keyword. The keywords and the symbols are case
15135 insensitive as in normal Ada code. Comments may be used on a
15136 preprocessor line, but other than that, no other tokens may appear on a
15137 preprocessor line. Any number of @code{elsif} clauses can be present,
15138 including none at all. The @code{else} is optional, as in Ada.
15140 The @code{#} marking the start of a preprocessor line must be the first
15141 non-blank character on the line, i.e., it must be preceded only by
15142 spaces or horizontal tabs.
15144 Symbol substitution outside of preprocessor lines is obtained by using
15152 anywhere within a source line, except in a comment or within a
15153 string literal. The identifier
15154 following the @code{$} must match one of the symbols defined in the symbol
15155 definition file, and the result is to substitute the value of the
15156 symbol in place of @code{$symbol} in the output file.
15158 Note that although the substitution of strings within a string literal
15159 is not possible, it is possible to have a symbol whose defined value is
15160 a string literal. So instead of setting XYZ to @code{hello} and writing:
15163 Header : String := "$XYZ";
15167 you should set XYZ to @code{"hello"} and write:
15170 Header : String := $XYZ;
15174 and then the substitution will occur as desired.
15176 @node The GNAT Library Browser gnatls
15177 @chapter The GNAT Library Browser @code{gnatls}
15179 @cindex Library browser
15182 @code{gnatls} is a tool that outputs information about compiled
15183 units. It gives the relationship between objects, unit names and source
15184 files. It can also be used to check the source dependencies of a unit
15185 as well as various characteristics.
15187 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
15188 driver (see @ref{The GNAT Driver and Project Files}).
15192 * Switches for gnatls::
15193 * Examples of gnatls Usage::
15196 @node Running gnatls
15197 @section Running @code{gnatls}
15200 The @code{gnatls} command has the form
15203 $ gnatls switches @var{object_or_ali_file}
15207 The main argument is the list of object or @file{ali} files
15208 (@pxref{The Ada Library Information Files})
15209 for which information is requested.
15211 In normal mode, without additional option, @code{gnatls} produces a
15212 four-column listing. Each line represents information for a specific
15213 object. The first column gives the full path of the object, the second
15214 column gives the name of the principal unit in this object, the third
15215 column gives the status of the source and the fourth column gives the
15216 full path of the source representing this unit.
15217 Here is a simple example of use:
15221 ^./^[]^demo1.o demo1 DIF demo1.adb
15222 ^./^[]^demo2.o demo2 OK demo2.adb
15223 ^./^[]^hello.o h1 OK hello.adb
15224 ^./^[]^instr-child.o instr.child MOK instr-child.adb
15225 ^./^[]^instr.o instr OK instr.adb
15226 ^./^[]^tef.o tef DIF tef.adb
15227 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
15228 ^./^[]^tgef.o tgef DIF tgef.adb
15232 The first line can be interpreted as follows: the main unit which is
15234 object file @file{demo1.o} is demo1, whose main source is in
15235 @file{demo1.adb}. Furthermore, the version of the source used for the
15236 compilation of demo1 has been modified (DIF). Each source file has a status
15237 qualifier which can be:
15240 @item OK (unchanged)
15241 The version of the source file used for the compilation of the
15242 specified unit corresponds exactly to the actual source file.
15244 @item MOK (slightly modified)
15245 The version of the source file used for the compilation of the
15246 specified unit differs from the actual source file but not enough to
15247 require recompilation. If you use gnatmake with the qualifier
15248 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
15249 MOK will not be recompiled.
15251 @item DIF (modified)
15252 No version of the source found on the path corresponds to the source
15253 used to build this object.
15255 @item ??? (file not found)
15256 No source file was found for this unit.
15258 @item HID (hidden, unchanged version not first on PATH)
15259 The version of the source that corresponds exactly to the source used
15260 for compilation has been found on the path but it is hidden by another
15261 version of the same source that has been modified.
15265 @node Switches for gnatls
15266 @section Switches for @code{gnatls}
15269 @code{gnatls} recognizes the following switches:
15273 @cindex @option{--version} @command{gnatls}
15274 Display Copyright and version, then exit disregarding all other options.
15277 @cindex @option{--help} @command{gnatls}
15278 If @option{--version} was not used, display usage, then exit disregarding
15281 @item ^-a^/ALL_UNITS^
15282 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
15283 Consider all units, including those of the predefined Ada library.
15284 Especially useful with @option{^-d^/DEPENDENCIES^}.
15286 @item ^-d^/DEPENDENCIES^
15287 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
15288 List sources from which specified units depend on.
15290 @item ^-h^/OUTPUT=OPTIONS^
15291 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
15292 Output the list of options.
15294 @item ^-o^/OUTPUT=OBJECTS^
15295 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
15296 Only output information about object files.
15298 @item ^-s^/OUTPUT=SOURCES^
15299 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
15300 Only output information about source files.
15302 @item ^-u^/OUTPUT=UNITS^
15303 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
15304 Only output information about compilation units.
15306 @item ^-files^/FILES^=@var{file}
15307 @cindex @option{^-files^/FILES^} (@code{gnatls})
15308 Take as arguments the files listed in text file @var{file}.
15309 Text file @var{file} may contain empty lines that are ignored.
15310 Each nonempty line should contain the name of an existing file.
15311 Several such switches may be specified simultaneously.
15313 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
15314 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
15315 @itemx ^-I^/SEARCH=^@var{dir}
15316 @itemx ^-I-^/NOCURRENT_DIRECTORY^
15318 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
15319 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
15320 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
15321 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
15322 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
15323 flags (@pxref{Switches for gnatmake}).
15325 @item --RTS=@var{rts-path}
15326 @cindex @option{--RTS} (@code{gnatls})
15327 Specifies the default location of the runtime library. Same meaning as the
15328 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15330 @item ^-v^/OUTPUT=VERBOSE^
15331 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
15332 Verbose mode. Output the complete source, object and project paths. Do not use
15333 the default column layout but instead use long format giving as much as
15334 information possible on each requested units, including special
15335 characteristics such as:
15338 @item Preelaborable
15339 The unit is preelaborable in the Ada sense.
15342 No elaboration code has been produced by the compiler for this unit.
15345 The unit is pure in the Ada sense.
15347 @item Elaborate_Body
15348 The unit contains a pragma Elaborate_Body.
15351 The unit contains a pragma Remote_Types.
15353 @item Shared_Passive
15354 The unit contains a pragma Shared_Passive.
15357 This unit is part of the predefined environment and cannot be modified
15360 @item Remote_Call_Interface
15361 The unit contains a pragma Remote_Call_Interface.
15367 @node Examples of gnatls Usage
15368 @section Example of @code{gnatls} Usage
15372 Example of using the verbose switch. Note how the source and
15373 object paths are affected by the -I switch.
15376 $ gnatls -v -I.. demo1.o
15378 GNATLS 5.03w (20041123-34)
15379 Copyright 1997-2004 Free Software Foundation, Inc.
15381 Source Search Path:
15382 <Current_Directory>
15384 /home/comar/local/adainclude/
15386 Object Search Path:
15387 <Current_Directory>
15389 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
15391 Project Search Path:
15392 <Current_Directory>
15393 /home/comar/local/lib/gnat/
15398 Kind => subprogram body
15399 Flags => No_Elab_Code
15400 Source => demo1.adb modified
15404 The following is an example of use of the dependency list.
15405 Note the use of the -s switch
15406 which gives a straight list of source files. This can be useful for
15407 building specialized scripts.
15410 $ gnatls -d demo2.o
15411 ./demo2.o demo2 OK demo2.adb
15417 $ gnatls -d -s -a demo1.o
15419 /home/comar/local/adainclude/ada.ads
15420 /home/comar/local/adainclude/a-finali.ads
15421 /home/comar/local/adainclude/a-filico.ads
15422 /home/comar/local/adainclude/a-stream.ads
15423 /home/comar/local/adainclude/a-tags.ads
15426 /home/comar/local/adainclude/gnat.ads
15427 /home/comar/local/adainclude/g-io.ads
15429 /home/comar/local/adainclude/system.ads
15430 /home/comar/local/adainclude/s-exctab.ads
15431 /home/comar/local/adainclude/s-finimp.ads
15432 /home/comar/local/adainclude/s-finroo.ads
15433 /home/comar/local/adainclude/s-secsta.ads
15434 /home/comar/local/adainclude/s-stalib.ads
15435 /home/comar/local/adainclude/s-stoele.ads
15436 /home/comar/local/adainclude/s-stratt.ads
15437 /home/comar/local/adainclude/s-tasoli.ads
15438 /home/comar/local/adainclude/s-unstyp.ads
15439 /home/comar/local/adainclude/unchconv.ads
15445 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
15447 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
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15451 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
15455 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
15456 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
15458 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
15459 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
15460 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
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15463 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
15464 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
15465 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
15466 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
15467 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
15468 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
15472 @node Cleaning Up Using gnatclean
15473 @chapter Cleaning Up Using @code{gnatclean}
15475 @cindex Cleaning tool
15478 @code{gnatclean} is a tool that allows the deletion of files produced by the
15479 compiler, binder and linker, including ALI files, object files, tree files,
15480 expanded source files, library files, interface copy source files, binder
15481 generated files and executable files.
15484 * Running gnatclean::
15485 * Switches for gnatclean::
15486 @c * Examples of gnatclean Usage::
15489 @node Running gnatclean
15490 @section Running @code{gnatclean}
15493 The @code{gnatclean} command has the form:
15496 $ gnatclean switches @var{names}
15500 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
15501 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
15502 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
15505 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
15506 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
15507 the linker. In informative-only mode, specified by switch
15508 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
15509 normal mode is listed, but no file is actually deleted.
15511 @node Switches for gnatclean
15512 @section Switches for @code{gnatclean}
15515 @code{gnatclean} recognizes the following switches:
15519 @cindex @option{--version} @command{gnatclean}
15520 Display Copyright and version, then exit disregarding all other options.
15523 @cindex @option{--help} @command{gnatclean}
15524 If @option{--version} was not used, display usage, then exit disregarding
15527 @item ^--subdirs^/SUBDIRS^=subdir
15528 Actual object directory of each project file is the subdirectory subdir of the
15529 object directory specified or defaulted in the project file.
15531 @item ^--unchecked-shared-lib-imports^/UNCHECKED_SHARED_LIB_IMPORTS^
15532 By default, shared library projects are not allowed to import static library
15533 projects. When this switch is used on the command line, this restriction is
15536 @item ^-c^/COMPILER_FILES_ONLY^
15537 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
15538 Only attempt to delete the files produced by the compiler, not those produced
15539 by the binder or the linker. The files that are not to be deleted are library
15540 files, interface copy files, binder generated files and executable files.
15542 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
15543 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
15544 Indicate that ALI and object files should normally be found in directory
15547 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
15548 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
15549 When using project files, if some errors or warnings are detected during
15550 parsing and verbose mode is not in effect (no use of switch
15551 ^-v^/VERBOSE^), then error lines start with the full path name of the project
15552 file, rather than its simple file name.
15555 @cindex @option{^-h^/HELP^} (@code{gnatclean})
15556 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
15558 @item ^-n^/NODELETE^
15559 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
15560 Informative-only mode. Do not delete any files. Output the list of the files
15561 that would have been deleted if this switch was not specified.
15563 @item ^-P^/PROJECT_FILE=^@var{project}
15564 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
15565 Use project file @var{project}. Only one such switch can be used.
15566 When cleaning a project file, the files produced by the compilation of the
15567 immediate sources or inherited sources of the project files are to be
15568 deleted. This is not depending on the presence or not of executable names
15569 on the command line.
15572 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
15573 Quiet output. If there are no errors, do not output anything, except in
15574 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
15575 (switch ^-n^/NODELETE^).
15577 @item ^-r^/RECURSIVE^
15578 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
15579 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
15580 clean all imported and extended project files, recursively. If this switch
15581 is not specified, only the files related to the main project file are to be
15582 deleted. This switch has no effect if no project file is specified.
15584 @item ^-v^/VERBOSE^
15585 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
15588 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
15589 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
15590 Indicates the verbosity of the parsing of GNAT project files.
15591 @xref{Switches Related to Project Files}.
15593 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
15594 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
15595 Indicates that external variable @var{name} has the value @var{value}.
15596 The Project Manager will use this value for occurrences of
15597 @code{external(name)} when parsing the project file.
15598 @xref{Switches Related to Project Files}.
15600 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
15601 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
15602 When searching for ALI and object files, look in directory
15605 @item ^-I^/SEARCH=^@var{dir}
15606 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
15607 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
15609 @item ^-I-^/NOCURRENT_DIRECTORY^
15610 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
15611 @cindex Source files, suppressing search
15612 Do not look for ALI or object files in the directory
15613 where @code{gnatclean} was invoked.
15617 @c @node Examples of gnatclean Usage
15618 @c @section Examples of @code{gnatclean} Usage
15621 @node GNAT and Libraries
15622 @chapter GNAT and Libraries
15623 @cindex Library, building, installing, using
15626 This chapter describes how to build and use libraries with GNAT, and also shows
15627 how to recompile the GNAT run-time library. You should be familiar with the
15628 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
15632 * Introduction to Libraries in GNAT::
15633 * General Ada Libraries::
15634 * Stand-alone Ada Libraries::
15635 * Rebuilding the GNAT Run-Time Library::
15638 @node Introduction to Libraries in GNAT
15639 @section Introduction to Libraries in GNAT
15642 A library is, conceptually, a collection of objects which does not have its
15643 own main thread of execution, but rather provides certain services to the
15644 applications that use it. A library can be either statically linked with the
15645 application, in which case its code is directly included in the application,
15646 or, on platforms that support it, be dynamically linked, in which case
15647 its code is shared by all applications making use of this library.
15649 GNAT supports both types of libraries.
15650 In the static case, the compiled code can be provided in different ways. The
15651 simplest approach is to provide directly the set of objects resulting from
15652 compilation of the library source files. Alternatively, you can group the
15653 objects into an archive using whatever commands are provided by the operating
15654 system. For the latter case, the objects are grouped into a shared library.
15656 In the GNAT environment, a library has three types of components:
15662 @xref{The Ada Library Information Files}.
15664 Object files, an archive or a shared library.
15668 A GNAT library may expose all its source files, which is useful for
15669 documentation purposes. Alternatively, it may expose only the units needed by
15670 an external user to make use of the library. That is to say, the specs
15671 reflecting the library services along with all the units needed to compile
15672 those specs, which can include generic bodies or any body implementing an
15673 inlined routine. In the case of @emph{stand-alone libraries} those exposed
15674 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
15676 All compilation units comprising an application, including those in a library,
15677 need to be elaborated in an order partially defined by Ada's semantics. GNAT
15678 computes the elaboration order from the @file{ALI} files and this is why they
15679 constitute a mandatory part of GNAT libraries.
15680 @emph{Stand-alone libraries} are the exception to this rule because a specific
15681 library elaboration routine is produced independently of the application(s)
15684 @node General Ada Libraries
15685 @section General Ada Libraries
15688 * Building a library::
15689 * Installing a library::
15690 * Using a library::
15693 @node Building a library
15694 @subsection Building a library
15697 The easiest way to build a library is to use the Project Manager,
15698 which supports a special type of project called a @emph{Library Project}
15699 (@pxref{Library Projects}).
15701 A project is considered a library project, when two project-level attributes
15702 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
15703 control different aspects of library configuration, additional optional
15704 project-level attributes can be specified:
15707 This attribute controls whether the library is to be static or dynamic
15709 @item Library_Version
15710 This attribute specifies the library version; this value is used
15711 during dynamic linking of shared libraries to determine if the currently
15712 installed versions of the binaries are compatible.
15714 @item Library_Options
15716 These attributes specify additional low-level options to be used during
15717 library generation, and redefine the actual application used to generate
15722 The GNAT Project Manager takes full care of the library maintenance task,
15723 including recompilation of the source files for which objects do not exist
15724 or are not up to date, assembly of the library archive, and installation of
15725 the library (i.e., copying associated source, object and @file{ALI} files
15726 to the specified location).
15728 Here is a simple library project file:
15729 @smallexample @c ada
15731 for Source_Dirs use ("src1", "src2");
15732 for Object_Dir use "obj";
15733 for Library_Name use "mylib";
15734 for Library_Dir use "lib";
15735 for Library_Kind use "dynamic";
15740 and the compilation command to build and install the library:
15742 @smallexample @c ada
15743 $ gnatmake -Pmy_lib
15747 It is not entirely trivial to perform manually all the steps required to
15748 produce a library. We recommend that you use the GNAT Project Manager
15749 for this task. In special cases where this is not desired, the necessary
15750 steps are discussed below.
15752 There are various possibilities for compiling the units that make up the
15753 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
15754 with a conventional script. For simple libraries, it is also possible to create
15755 a dummy main program which depends upon all the packages that comprise the
15756 interface of the library. This dummy main program can then be given to
15757 @command{gnatmake}, which will ensure that all necessary objects are built.
15759 After this task is accomplished, you should follow the standard procedure
15760 of the underlying operating system to produce the static or shared library.
15762 Here is an example of such a dummy program:
15763 @smallexample @c ada
15765 with My_Lib.Service1;
15766 with My_Lib.Service2;
15767 with My_Lib.Service3;
15768 procedure My_Lib_Dummy is
15776 Here are the generic commands that will build an archive or a shared library.
15779 # compiling the library
15780 $ gnatmake -c my_lib_dummy.adb
15782 # we don't need the dummy object itself
15783 $ rm my_lib_dummy.o my_lib_dummy.ali
15785 # create an archive with the remaining objects
15786 $ ar rc libmy_lib.a *.o
15787 # some systems may require "ranlib" to be run as well
15789 # or create a shared library
15790 $ gcc -shared -o libmy_lib.so *.o
15791 # some systems may require the code to have been compiled with -fPIC
15793 # remove the object files that are now in the library
15796 # Make the ALI files read-only so that gnatmake will not try to
15797 # regenerate the objects that are in the library
15802 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
15803 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
15804 be accessed by the directive @option{-l@var{xxx}} at link time.
15806 @node Installing a library
15807 @subsection Installing a library
15808 @cindex @code{ADA_PROJECT_PATH}
15809 @cindex @code{GPR_PROJECT_PATH}
15812 If you use project files, library installation is part of the library build
15813 process (@pxref{Installing a library with project files}).
15815 When project files are not an option, it is also possible, but not recommended,
15816 to install the library so that the sources needed to use the library are on the
15817 Ada source path and the ALI files & libraries be on the Ada Object path (see
15818 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
15819 administrator can place general-purpose libraries in the default compiler
15820 paths, by specifying the libraries' location in the configuration files
15821 @file{ada_source_path} and @file{ada_object_path}. These configuration files
15822 must be located in the GNAT installation tree at the same place as the gcc spec
15823 file. The location of the gcc spec file can be determined as follows:
15829 The configuration files mentioned above have a simple format: each line
15830 must contain one unique directory name.
15831 Those names are added to the corresponding path
15832 in their order of appearance in the file. The names can be either absolute
15833 or relative; in the latter case, they are relative to where theses files
15836 The files @file{ada_source_path} and @file{ada_object_path} might not be
15838 GNAT installation, in which case, GNAT will look for its run-time library in
15839 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
15840 objects and @file{ALI} files). When the files exist, the compiler does not
15841 look in @file{adainclude} and @file{adalib}, and thus the
15842 @file{ada_source_path} file
15843 must contain the location for the GNAT run-time sources (which can simply
15844 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
15845 contain the location for the GNAT run-time objects (which can simply
15848 You can also specify a new default path to the run-time library at compilation
15849 time with the switch @option{--RTS=rts-path}. You can thus choose / change
15850 the run-time library you want your program to be compiled with. This switch is
15851 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
15852 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
15854 It is possible to install a library before or after the standard GNAT
15855 library, by reordering the lines in the configuration files. In general, a
15856 library must be installed before the GNAT library if it redefines
15859 @node Using a library
15860 @subsection Using a library
15862 @noindent Once again, the project facility greatly simplifies the use of
15863 libraries. In this context, using a library is just a matter of adding a
15864 @code{with} clause in the user project. For instance, to make use of the
15865 library @code{My_Lib} shown in examples in earlier sections, you can
15868 @smallexample @c projectfile
15875 Even if you have a third-party, non-Ada library, you can still use GNAT's
15876 Project Manager facility to provide a wrapper for it. For example, the
15877 following project, when @code{with}ed by your main project, will link with the
15878 third-party library @file{liba.a}:
15880 @smallexample @c projectfile
15883 for Externally_Built use "true";
15884 for Source_Files use ();
15885 for Library_Dir use "lib";
15886 for Library_Name use "a";
15887 for Library_Kind use "static";
15891 This is an alternative to the use of @code{pragma Linker_Options}. It is
15892 especially interesting in the context of systems with several interdependent
15893 static libraries where finding a proper linker order is not easy and best be
15894 left to the tools having visibility over project dependence information.
15897 In order to use an Ada library manually, you need to make sure that this
15898 library is on both your source and object path
15899 (see @ref{Search Paths and the Run-Time Library (RTL)}
15900 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
15901 in an archive or a shared library, you need to specify the desired
15902 library at link time.
15904 For example, you can use the library @file{mylib} installed in
15905 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
15908 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
15913 This can be expressed more simply:
15918 when the following conditions are met:
15921 @file{/dir/my_lib_src} has been added by the user to the environment
15922 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
15923 @file{ada_source_path}
15925 @file{/dir/my_lib_obj} has been added by the user to the environment
15926 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
15927 @file{ada_object_path}
15929 a pragma @code{Linker_Options} has been added to one of the sources.
15932 @smallexample @c ada
15933 pragma Linker_Options ("-lmy_lib");
15937 @node Stand-alone Ada Libraries
15938 @section Stand-alone Ada Libraries
15939 @cindex Stand-alone library, building, using
15942 * Introduction to Stand-alone Libraries::
15943 * Building a Stand-alone Library::
15944 * Creating a Stand-alone Library to be used in a non-Ada context::
15945 * Restrictions in Stand-alone Libraries::
15948 @node Introduction to Stand-alone Libraries
15949 @subsection Introduction to Stand-alone Libraries
15952 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
15954 elaborate the Ada units that are included in the library. In contrast with
15955 an ordinary library, which consists of all sources, objects and @file{ALI}
15957 library, a SAL may specify a restricted subset of compilation units
15958 to serve as a library interface. In this case, the fully
15959 self-sufficient set of files will normally consist of an objects
15960 archive, the sources of interface units' specs, and the @file{ALI}
15961 files of interface units.
15962 If an interface spec contains a generic unit or an inlined subprogram,
15964 source must also be provided; if the units that must be provided in the source
15965 form depend on other units, the source and @file{ALI} files of those must
15968 The main purpose of a SAL is to minimize the recompilation overhead of client
15969 applications when a new version of the library is installed. Specifically,
15970 if the interface sources have not changed, client applications do not need to
15971 be recompiled. If, furthermore, a SAL is provided in the shared form and its
15972 version, controlled by @code{Library_Version} attribute, is not changed,
15973 then the clients do not need to be relinked.
15975 SALs also allow the library providers to minimize the amount of library source
15976 text exposed to the clients. Such ``information hiding'' might be useful or
15977 necessary for various reasons.
15979 Stand-alone libraries are also well suited to be used in an executable whose
15980 main routine is not written in Ada.
15982 @node Building a Stand-alone Library
15983 @subsection Building a Stand-alone Library
15986 GNAT's Project facility provides a simple way of building and installing
15987 stand-alone libraries; see @ref{Stand-alone Library Projects}.
15988 To be a Stand-alone Library Project, in addition to the two attributes
15989 that make a project a Library Project (@code{Library_Name} and
15990 @code{Library_Dir}; see @ref{Library Projects}), the attribute
15991 @code{Library_Interface} must be defined. For example:
15993 @smallexample @c projectfile
15995 for Library_Dir use "lib_dir";
15996 for Library_Name use "dummy";
15997 for Library_Interface use ("int1", "int1.child");
16002 Attribute @code{Library_Interface} has a non-empty string list value,
16003 each string in the list designating a unit contained in an immediate source
16004 of the project file.
16006 When a Stand-alone Library is built, first the binder is invoked to build
16007 a package whose name depends on the library name
16008 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
16009 This binder-generated package includes initialization and
16010 finalization procedures whose
16011 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
16013 above). The object corresponding to this package is included in the library.
16015 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
16016 calling of these procedures if a static SAL is built, or if a shared SAL
16018 with the project-level attribute @code{Library_Auto_Init} set to
16021 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
16022 (those that are listed in attribute @code{Library_Interface}) are copied to
16023 the Library Directory. As a consequence, only the Interface Units may be
16024 imported from Ada units outside of the library. If other units are imported,
16025 the binding phase will fail.
16027 The attribute @code{Library_Src_Dir} may be specified for a
16028 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
16029 single string value. Its value must be the path (absolute or relative to the
16030 project directory) of an existing directory. This directory cannot be the
16031 object directory or one of the source directories, but it can be the same as
16032 the library directory. The sources of the Interface
16033 Units of the library that are needed by an Ada client of the library will be
16034 copied to the designated directory, called the Interface Copy directory.
16035 These sources include the specs of the Interface Units, but they may also
16036 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
16037 are used, or when there is a generic unit in the spec. Before the sources
16038 are copied to the Interface Copy directory, an attempt is made to delete all
16039 files in the Interface Copy directory.
16041 Building stand-alone libraries by hand is somewhat tedious, but for those
16042 occasions when it is necessary here are the steps that you need to perform:
16045 Compile all library sources.
16048 Invoke the binder with the switch @option{-n} (No Ada main program),
16049 with all the @file{ALI} files of the interfaces, and
16050 with the switch @option{-L} to give specific names to the @code{init}
16051 and @code{final} procedures. For example:
16053 gnatbind -n int1.ali int2.ali -Lsal1
16057 Compile the binder generated file:
16063 Link the dynamic library with all the necessary object files,
16064 indicating to the linker the names of the @code{init} (and possibly
16065 @code{final}) procedures for automatic initialization (and finalization).
16066 The built library should be placed in a directory different from
16067 the object directory.
16070 Copy the @code{ALI} files of the interface to the library directory,
16071 add in this copy an indication that it is an interface to a SAL
16072 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
16073 with letter ``P'') and make the modified copy of the @file{ALI} file
16078 Using SALs is not different from using other libraries
16079 (see @ref{Using a library}).
16081 @node Creating a Stand-alone Library to be used in a non-Ada context
16082 @subsection Creating a Stand-alone Library to be used in a non-Ada context
16085 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
16088 The only extra step required is to ensure that library interface subprograms
16089 are compatible with the main program, by means of @code{pragma Export}
16090 or @code{pragma Convention}.
16092 Here is an example of simple library interface for use with C main program:
16094 @smallexample @c ada
16095 package My_Package is
16097 procedure Do_Something;
16098 pragma Export (C, Do_Something, "do_something");
16100 procedure Do_Something_Else;
16101 pragma Export (C, Do_Something_Else, "do_something_else");
16107 On the foreign language side, you must provide a ``foreign'' view of the
16108 library interface; remember that it should contain elaboration routines in
16109 addition to interface subprograms.
16111 The example below shows the content of @code{mylib_interface.h} (note
16112 that there is no rule for the naming of this file, any name can be used)
16114 /* the library elaboration procedure */
16115 extern void mylibinit (void);
16117 /* the library finalization procedure */
16118 extern void mylibfinal (void);
16120 /* the interface exported by the library */
16121 extern void do_something (void);
16122 extern void do_something_else (void);
16126 Libraries built as explained above can be used from any program, provided
16127 that the elaboration procedures (named @code{mylibinit} in the previous
16128 example) are called before the library services are used. Any number of
16129 libraries can be used simultaneously, as long as the elaboration
16130 procedure of each library is called.
16132 Below is an example of a C program that uses the @code{mylib} library.
16135 #include "mylib_interface.h"
16140 /* First, elaborate the library before using it */
16143 /* Main program, using the library exported entities */
16145 do_something_else ();
16147 /* Library finalization at the end of the program */
16154 Note that invoking any library finalization procedure generated by
16155 @code{gnatbind} shuts down the Ada run-time environment.
16157 finalization of all Ada libraries must be performed at the end of the program.
16158 No call to these libraries or to the Ada run-time library should be made
16159 after the finalization phase.
16161 @node Restrictions in Stand-alone Libraries
16162 @subsection Restrictions in Stand-alone Libraries
16165 The pragmas listed below should be used with caution inside libraries,
16166 as they can create incompatibilities with other Ada libraries:
16168 @item pragma @code{Locking_Policy}
16169 @item pragma @code{Queuing_Policy}
16170 @item pragma @code{Task_Dispatching_Policy}
16171 @item pragma @code{Unreserve_All_Interrupts}
16175 When using a library that contains such pragmas, the user must make sure
16176 that all libraries use the same pragmas with the same values. Otherwise,
16177 @code{Program_Error} will
16178 be raised during the elaboration of the conflicting
16179 libraries. The usage of these pragmas and its consequences for the user
16180 should therefore be well documented.
16182 Similarly, the traceback in the exception occurrence mechanism should be
16183 enabled or disabled in a consistent manner across all libraries.
16184 Otherwise, Program_Error will be raised during the elaboration of the
16185 conflicting libraries.
16187 If the @code{Version} or @code{Body_Version}
16188 attributes are used inside a library, then you need to
16189 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
16190 libraries, so that version identifiers can be properly computed.
16191 In practice these attributes are rarely used, so this is unlikely
16192 to be a consideration.
16194 @node Rebuilding the GNAT Run-Time Library
16195 @section Rebuilding the GNAT Run-Time Library
16196 @cindex GNAT Run-Time Library, rebuilding
16197 @cindex Building the GNAT Run-Time Library
16198 @cindex Rebuilding the GNAT Run-Time Library
16199 @cindex Run-Time Library, rebuilding
16202 It may be useful to recompile the GNAT library in various contexts, the
16203 most important one being the use of partition-wide configuration pragmas
16204 such as @code{Normalize_Scalars}. A special Makefile called
16205 @code{Makefile.adalib} is provided to that effect and can be found in
16206 the directory containing the GNAT library. The location of this
16207 directory depends on the way the GNAT environment has been installed and can
16208 be determined by means of the command:
16215 The last entry in the object search path usually contains the
16216 gnat library. This Makefile contains its own documentation and in
16217 particular the set of instructions needed to rebuild a new library and
16220 @node Using the GNU make Utility
16221 @chapter Using the GNU @code{make} Utility
16225 This chapter offers some examples of makefiles that solve specific
16226 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
16227 make, make, GNU @code{make}}), nor does it try to replace the
16228 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
16230 All the examples in this section are specific to the GNU version of
16231 make. Although @command{make} is a standard utility, and the basic language
16232 is the same, these examples use some advanced features found only in
16236 * Using gnatmake in a Makefile::
16237 * Automatically Creating a List of Directories::
16238 * Generating the Command Line Switches::
16239 * Overcoming Command Line Length Limits::
16242 @node Using gnatmake in a Makefile
16243 @section Using gnatmake in a Makefile
16248 Complex project organizations can be handled in a very powerful way by
16249 using GNU make combined with gnatmake. For instance, here is a Makefile
16250 which allows you to build each subsystem of a big project into a separate
16251 shared library. Such a makefile allows you to significantly reduce the link
16252 time of very big applications while maintaining full coherence at
16253 each step of the build process.
16255 The list of dependencies are handled automatically by
16256 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
16257 the appropriate directories.
16259 Note that you should also read the example on how to automatically
16260 create the list of directories
16261 (@pxref{Automatically Creating a List of Directories})
16262 which might help you in case your project has a lot of subdirectories.
16267 @font@heightrm=cmr8
16270 ## This Makefile is intended to be used with the following directory
16272 ## - The sources are split into a series of csc (computer software components)
16273 ## Each of these csc is put in its own directory.
16274 ## Their name are referenced by the directory names.
16275 ## They will be compiled into shared library (although this would also work
16276 ## with static libraries
16277 ## - The main program (and possibly other packages that do not belong to any
16278 ## csc is put in the top level directory (where the Makefile is).
16279 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
16280 ## \_ second_csc (sources) __ lib (will contain the library)
16282 ## Although this Makefile is build for shared library, it is easy to modify
16283 ## to build partial link objects instead (modify the lines with -shared and
16286 ## With this makefile, you can change any file in the system or add any new
16287 ## file, and everything will be recompiled correctly (only the relevant shared
16288 ## objects will be recompiled, and the main program will be re-linked).
16290 # The list of computer software component for your project. This might be
16291 # generated automatically.
16294 # Name of the main program (no extension)
16297 # If we need to build objects with -fPIC, uncomment the following line
16300 # The following variable should give the directory containing libgnat.so
16301 # You can get this directory through 'gnatls -v'. This is usually the last
16302 # directory in the Object_Path.
16305 # The directories for the libraries
16306 # (This macro expands the list of CSC to the list of shared libraries, you
16307 # could simply use the expanded form:
16308 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
16309 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
16311 $@{MAIN@}: objects $@{LIB_DIR@}
16312 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
16313 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
16316 # recompile the sources
16317 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
16319 # Note: In a future version of GNAT, the following commands will be simplified
16320 # by a new tool, gnatmlib
16322 mkdir -p $@{dir $@@ @}
16323 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
16324 cd $@{dir $@@ @} && cp -f ../*.ali .
16326 # The dependencies for the modules
16327 # Note that we have to force the expansion of *.o, since in some cases
16328 # make won't be able to do it itself.
16329 aa/lib/libaa.so: $@{wildcard aa/*.o@}
16330 bb/lib/libbb.so: $@{wildcard bb/*.o@}
16331 cc/lib/libcc.so: $@{wildcard cc/*.o@}
16333 # Make sure all of the shared libraries are in the path before starting the
16336 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
16339 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
16340 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
16341 $@{RM@} $@{CSC_LIST:%=%/*.o@}
16342 $@{RM@} *.o *.ali $@{MAIN@}
16345 @node Automatically Creating a List of Directories
16346 @section Automatically Creating a List of Directories
16349 In most makefiles, you will have to specify a list of directories, and
16350 store it in a variable. For small projects, it is often easier to
16351 specify each of them by hand, since you then have full control over what
16352 is the proper order for these directories, which ones should be
16355 However, in larger projects, which might involve hundreds of
16356 subdirectories, it might be more convenient to generate this list
16359 The example below presents two methods. The first one, although less
16360 general, gives you more control over the list. It involves wildcard
16361 characters, that are automatically expanded by @command{make}. Its
16362 shortcoming is that you need to explicitly specify some of the
16363 organization of your project, such as for instance the directory tree
16364 depth, whether some directories are found in a separate tree, @enddots{}
16366 The second method is the most general one. It requires an external
16367 program, called @command{find}, which is standard on all Unix systems. All
16368 the directories found under a given root directory will be added to the
16374 @font@heightrm=cmr8
16377 # The examples below are based on the following directory hierarchy:
16378 # All the directories can contain any number of files
16379 # ROOT_DIRECTORY -> a -> aa -> aaa
16382 # -> b -> ba -> baa
16385 # This Makefile creates a variable called DIRS, that can be reused any time
16386 # you need this list (see the other examples in this section)
16388 # The root of your project's directory hierarchy
16392 # First method: specify explicitly the list of directories
16393 # This allows you to specify any subset of all the directories you need.
16396 DIRS := a/aa/ a/ab/ b/ba/
16399 # Second method: use wildcards
16400 # Note that the argument(s) to wildcard below should end with a '/'.
16401 # Since wildcards also return file names, we have to filter them out
16402 # to avoid duplicate directory names.
16403 # We thus use make's @code{dir} and @code{sort} functions.
16404 # It sets DIRs to the following value (note that the directories aaa and baa
16405 # are not given, unless you change the arguments to wildcard).
16406 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
16409 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
16410 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
16413 # Third method: use an external program
16414 # This command is much faster if run on local disks, avoiding NFS slowdowns.
16415 # This is the most complete command: it sets DIRs to the following value:
16416 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
16419 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
16423 @node Generating the Command Line Switches
16424 @section Generating the Command Line Switches
16427 Once you have created the list of directories as explained in the
16428 previous section (@pxref{Automatically Creating a List of Directories}),
16429 you can easily generate the command line arguments to pass to gnatmake.
16431 For the sake of completeness, this example assumes that the source path
16432 is not the same as the object path, and that you have two separate lists
16436 # see "Automatically creating a list of directories" to create
16441 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
16442 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
16445 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
16448 @node Overcoming Command Line Length Limits
16449 @section Overcoming Command Line Length Limits
16452 One problem that might be encountered on big projects is that many
16453 operating systems limit the length of the command line. It is thus hard to give
16454 gnatmake the list of source and object directories.
16456 This example shows how you can set up environment variables, which will
16457 make @command{gnatmake} behave exactly as if the directories had been
16458 specified on the command line, but have a much higher length limit (or
16459 even none on most systems).
16461 It assumes that you have created a list of directories in your Makefile,
16462 using one of the methods presented in
16463 @ref{Automatically Creating a List of Directories}.
16464 For the sake of completeness, we assume that the object
16465 path (where the ALI files are found) is different from the sources patch.
16467 Note a small trick in the Makefile below: for efficiency reasons, we
16468 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
16469 expanded immediately by @code{make}. This way we overcome the standard
16470 make behavior which is to expand the variables only when they are
16473 On Windows, if you are using the standard Windows command shell, you must
16474 replace colons with semicolons in the assignments to these variables.
16479 @font@heightrm=cmr8
16482 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH.
16483 # This is the same thing as putting the -I arguments on the command line.
16484 # (the equivalent of using -aI on the command line would be to define
16485 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH).
16486 # You can of course have different values for these variables.
16488 # Note also that we need to keep the previous values of these variables, since
16489 # they might have been set before running 'make' to specify where the GNAT
16490 # library is installed.
16492 # see "Automatically creating a list of directories" to create these
16498 space:=$@{empty@} $@{empty@}
16499 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
16500 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
16501 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
16502 ADA_OBJECTS_PATH += $@{OBJECT_LIST@}
16503 export ADA_INCLUDE_PATH
16504 export ADA_OBJECTS_PATH
16511 @node Memory Management Issues
16512 @chapter Memory Management Issues
16515 This chapter describes some useful memory pools provided in the GNAT library
16516 and in particular the GNAT Debug Pool facility, which can be used to detect
16517 incorrect uses of access values (including ``dangling references'').
16519 It also describes the @command{gnatmem} tool, which can be used to track down
16524 * Some Useful Memory Pools::
16525 * The GNAT Debug Pool Facility::
16527 * The gnatmem Tool::
16531 @node Some Useful Memory Pools
16532 @section Some Useful Memory Pools
16533 @findex Memory Pool
16534 @cindex storage, pool
16537 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
16538 storage pool. Allocations use the standard system call @code{malloc} while
16539 deallocations use the standard system call @code{free}. No reclamation is
16540 performed when the pool goes out of scope. For performance reasons, the
16541 standard default Ada allocators/deallocators do not use any explicit storage
16542 pools but if they did, they could use this storage pool without any change in
16543 behavior. That is why this storage pool is used when the user
16544 manages to make the default implicit allocator explicit as in this example:
16545 @smallexample @c ada
16546 type T1 is access Something;
16547 -- no Storage pool is defined for T2
16548 type T2 is access Something_Else;
16549 for T2'Storage_Pool use T1'Storage_Pool;
16550 -- the above is equivalent to
16551 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
16555 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
16556 pool. The allocation strategy is similar to @code{Pool_Local}'s
16557 except that the all
16558 storage allocated with this pool is reclaimed when the pool object goes out of
16559 scope. This pool provides a explicit mechanism similar to the implicit one
16560 provided by several Ada 83 compilers for allocations performed through a local
16561 access type and whose purpose was to reclaim memory when exiting the
16562 scope of a given local access. As an example, the following program does not
16563 leak memory even though it does not perform explicit deallocation:
16565 @smallexample @c ada
16566 with System.Pool_Local;
16567 procedure Pooloc1 is
16568 procedure Internal is
16569 type A is access Integer;
16570 X : System.Pool_Local.Unbounded_Reclaim_Pool;
16571 for A'Storage_Pool use X;
16574 for I in 1 .. 50 loop
16579 for I in 1 .. 100 loop
16586 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
16587 @code{Storage_Size} is specified for an access type.
16588 The whole storage for the pool is
16589 allocated at once, usually on the stack at the point where the access type is
16590 elaborated. It is automatically reclaimed when exiting the scope where the
16591 access type is defined. This package is not intended to be used directly by the
16592 user and it is implicitly used for each such declaration:
16594 @smallexample @c ada
16595 type T1 is access Something;
16596 for T1'Storage_Size use 10_000;
16599 @node The GNAT Debug Pool Facility
16600 @section The GNAT Debug Pool Facility
16602 @cindex storage, pool, memory corruption
16605 The use of unchecked deallocation and unchecked conversion can easily
16606 lead to incorrect memory references. The problems generated by such
16607 references are usually difficult to tackle because the symptoms can be
16608 very remote from the origin of the problem. In such cases, it is
16609 very helpful to detect the problem as early as possible. This is the
16610 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
16612 In order to use the GNAT specific debugging pool, the user must
16613 associate a debug pool object with each of the access types that may be
16614 related to suspected memory problems. See Ada Reference Manual 13.11.
16615 @smallexample @c ada
16616 type Ptr is access Some_Type;
16617 Pool : GNAT.Debug_Pools.Debug_Pool;
16618 for Ptr'Storage_Pool use Pool;
16622 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
16623 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
16624 allow the user to redefine allocation and deallocation strategies. They
16625 also provide a checkpoint for each dereference, through the use of
16626 the primitive operation @code{Dereference} which is implicitly called at
16627 each dereference of an access value.
16629 Once an access type has been associated with a debug pool, operations on
16630 values of the type may raise four distinct exceptions,
16631 which correspond to four potential kinds of memory corruption:
16634 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
16636 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
16638 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
16640 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
16644 For types associated with a Debug_Pool, dynamic allocation is performed using
16645 the standard GNAT allocation routine. References to all allocated chunks of
16646 memory are kept in an internal dictionary. Several deallocation strategies are
16647 provided, whereupon the user can choose to release the memory to the system,
16648 keep it allocated for further invalid access checks, or fill it with an easily
16649 recognizable pattern for debug sessions. The memory pattern is the old IBM
16650 hexadecimal convention: @code{16#DEADBEEF#}.
16652 See the documentation in the file g-debpoo.ads for more information on the
16653 various strategies.
16655 Upon each dereference, a check is made that the access value denotes a
16656 properly allocated memory location. Here is a complete example of use of
16657 @code{Debug_Pools}, that includes typical instances of memory corruption:
16658 @smallexample @c ada
16662 with Gnat.Io; use Gnat.Io;
16663 with Unchecked_Deallocation;
16664 with Unchecked_Conversion;
16665 with GNAT.Debug_Pools;
16666 with System.Storage_Elements;
16667 with Ada.Exceptions; use Ada.Exceptions;
16668 procedure Debug_Pool_Test is
16670 type T is access Integer;
16671 type U is access all T;
16673 P : GNAT.Debug_Pools.Debug_Pool;
16674 for T'Storage_Pool use P;
16676 procedure Free is new Unchecked_Deallocation (Integer, T);
16677 function UC is new Unchecked_Conversion (U, T);
16680 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
16690 Put_Line (Integer'Image(B.all));
16692 when E : others => Put_Line ("raised: " & Exception_Name (E));
16697 when E : others => Put_Line ("raised: " & Exception_Name (E));
16701 Put_Line (Integer'Image(B.all));
16703 when E : others => Put_Line ("raised: " & Exception_Name (E));
16708 when E : others => Put_Line ("raised: " & Exception_Name (E));
16711 end Debug_Pool_Test;
16715 The debug pool mechanism provides the following precise diagnostics on the
16716 execution of this erroneous program:
16719 Total allocated bytes : 0
16720 Total deallocated bytes : 0
16721 Current Water Mark: 0
16725 Total allocated bytes : 8
16726 Total deallocated bytes : 0
16727 Current Water Mark: 8
16730 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
16731 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
16732 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
16733 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
16735 Total allocated bytes : 8
16736 Total deallocated bytes : 4
16737 Current Water Mark: 4
16742 @node The gnatmem Tool
16743 @section The @command{gnatmem} Tool
16747 The @code{gnatmem} utility monitors dynamic allocation and
16748 deallocation activity in a program, and displays information about
16749 incorrect deallocations and possible sources of memory leaks.
16750 It is designed to work in association with a static runtime library
16751 only and in this context provides three types of information:
16754 General information concerning memory management, such as the total
16755 number of allocations and deallocations, the amount of allocated
16756 memory and the high water mark, i.e.@: the largest amount of allocated
16757 memory in the course of program execution.
16760 Backtraces for all incorrect deallocations, that is to say deallocations
16761 which do not correspond to a valid allocation.
16764 Information on each allocation that is potentially the origin of a memory
16769 * Running gnatmem::
16770 * Switches for gnatmem::
16771 * Example of gnatmem Usage::
16774 @node Running gnatmem
16775 @subsection Running @code{gnatmem}
16778 @code{gnatmem} makes use of the output created by the special version of
16779 allocation and deallocation routines that record call information. This
16780 allows to obtain accurate dynamic memory usage history at a minimal cost to
16781 the execution speed. Note however, that @code{gnatmem} is not supported on
16782 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
16783 Solaris and Windows NT/2000/XP (x86).
16786 The @code{gnatmem} command has the form
16789 @c $ gnatmem @ovar{switches} user_program
16790 @c Expanding @ovar macro inline (explanation in macro def comments)
16791 $ gnatmem @r{[}@var{switches}@r{]} @var{user_program}
16795 The program must have been linked with the instrumented version of the
16796 allocation and deallocation routines. This is done by linking with the
16797 @file{libgmem.a} library. For correct symbolic backtrace information,
16798 the user program should be compiled with debugging options
16799 (see @ref{Switches for gcc}). For example to build @file{my_program}:
16802 $ gnatmake -g my_program -largs -lgmem
16806 As library @file{libgmem.a} contains an alternate body for package
16807 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
16808 when an executable is linked with library @file{libgmem.a}. It is then not
16809 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
16812 When @file{my_program} is executed, the file @file{gmem.out} is produced.
16813 This file contains information about all allocations and deallocations
16814 performed by the program. It is produced by the instrumented allocations and
16815 deallocations routines and will be used by @code{gnatmem}.
16817 In order to produce symbolic backtrace information for allocations and
16818 deallocations performed by the GNAT run-time library, you need to use a
16819 version of that library that has been compiled with the @option{-g} switch
16820 (see @ref{Rebuilding the GNAT Run-Time Library}).
16822 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
16823 examine. If the location of @file{gmem.out} file was not explicitly supplied by
16824 @option{-i} switch, gnatmem will assume that this file can be found in the
16825 current directory. For example, after you have executed @file{my_program},
16826 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
16829 $ gnatmem my_program
16833 This will produce the output with the following format:
16835 *************** debut cc
16837 $ gnatmem my_program
16841 Total number of allocations : 45
16842 Total number of deallocations : 6
16843 Final Water Mark (non freed mem) : 11.29 Kilobytes
16844 High Water Mark : 11.40 Kilobytes
16849 Allocation Root # 2
16850 -------------------
16851 Number of non freed allocations : 11
16852 Final Water Mark (non freed mem) : 1.16 Kilobytes
16853 High Water Mark : 1.27 Kilobytes
16855 my_program.adb:23 my_program.alloc
16861 The first block of output gives general information. In this case, the
16862 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
16863 Unchecked_Deallocation routine occurred.
16866 Subsequent paragraphs display information on all allocation roots.
16867 An allocation root is a specific point in the execution of the program
16868 that generates some dynamic allocation, such as a ``@code{@b{new}}''
16869 construct. This root is represented by an execution backtrace (or subprogram
16870 call stack). By default the backtrace depth for allocations roots is 1, so
16871 that a root corresponds exactly to a source location. The backtrace can
16872 be made deeper, to make the root more specific.
16874 @node Switches for gnatmem
16875 @subsection Switches for @code{gnatmem}
16878 @code{gnatmem} recognizes the following switches:
16883 @cindex @option{-q} (@code{gnatmem})
16884 Quiet. Gives the minimum output needed to identify the origin of the
16885 memory leaks. Omits statistical information.
16888 @cindex @var{N} (@code{gnatmem})
16889 N is an integer literal (usually between 1 and 10) which controls the
16890 depth of the backtraces defining allocation root. The default value for
16891 N is 1. The deeper the backtrace, the more precise the localization of
16892 the root. Note that the total number of roots can depend on this
16893 parameter. This parameter must be specified @emph{before} the name of the
16894 executable to be analyzed, to avoid ambiguity.
16897 @cindex @option{-b} (@code{gnatmem})
16898 This switch has the same effect as just depth parameter.
16900 @item -i @var{file}
16901 @cindex @option{-i} (@code{gnatmem})
16902 Do the @code{gnatmem} processing starting from @file{file}, rather than
16903 @file{gmem.out} in the current directory.
16906 @cindex @option{-m} (@code{gnatmem})
16907 This switch causes @code{gnatmem} to mask the allocation roots that have less
16908 than n leaks. The default value is 1. Specifying the value of 0 will allow to
16909 examine even the roots that didn't result in leaks.
16912 @cindex @option{-s} (@code{gnatmem})
16913 This switch causes @code{gnatmem} to sort the allocation roots according to the
16914 specified order of sort criteria, each identified by a single letter. The
16915 currently supported criteria are @code{n, h, w} standing respectively for
16916 number of unfreed allocations, high watermark, and final watermark
16917 corresponding to a specific root. The default order is @code{nwh}.
16921 @node Example of gnatmem Usage
16922 @subsection Example of @code{gnatmem} Usage
16925 The following example shows the use of @code{gnatmem}
16926 on a simple memory-leaking program.
16927 Suppose that we have the following Ada program:
16929 @smallexample @c ada
16932 with Unchecked_Deallocation;
16933 procedure Test_Gm is
16935 type T is array (1..1000) of Integer;
16936 type Ptr is access T;
16937 procedure Free is new Unchecked_Deallocation (T, Ptr);
16940 procedure My_Alloc is
16945 procedure My_DeAlloc is
16953 for I in 1 .. 5 loop
16954 for J in I .. 5 loop
16965 The program needs to be compiled with debugging option and linked with
16966 @code{gmem} library:
16969 $ gnatmake -g test_gm -largs -lgmem
16973 Then we execute the program as usual:
16980 Then @code{gnatmem} is invoked simply with
16986 which produces the following output (result may vary on different platforms):
16991 Total number of allocations : 18
16992 Total number of deallocations : 5
16993 Final Water Mark (non freed mem) : 53.00 Kilobytes
16994 High Water Mark : 56.90 Kilobytes
16996 Allocation Root # 1
16997 -------------------
16998 Number of non freed allocations : 11
16999 Final Water Mark (non freed mem) : 42.97 Kilobytes
17000 High Water Mark : 46.88 Kilobytes
17002 test_gm.adb:11 test_gm.my_alloc
17004 Allocation Root # 2
17005 -------------------
17006 Number of non freed allocations : 1
17007 Final Water Mark (non freed mem) : 10.02 Kilobytes
17008 High Water Mark : 10.02 Kilobytes
17010 s-secsta.adb:81 system.secondary_stack.ss_init
17012 Allocation Root # 3
17013 -------------------
17014 Number of non freed allocations : 1
17015 Final Water Mark (non freed mem) : 12 Bytes
17016 High Water Mark : 12 Bytes
17018 s-secsta.adb:181 system.secondary_stack.ss_init
17022 Note that the GNAT run time contains itself a certain number of
17023 allocations that have no corresponding deallocation,
17024 as shown here for root #2 and root
17025 #3. This is a normal behavior when the number of non-freed allocations
17026 is one, it allocates dynamic data structures that the run time needs for
17027 the complete lifetime of the program. Note also that there is only one
17028 allocation root in the user program with a single line back trace:
17029 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
17030 program shows that 'My_Alloc' is called at 2 different points in the
17031 source (line 21 and line 24). If those two allocation roots need to be
17032 distinguished, the backtrace depth parameter can be used:
17035 $ gnatmem 3 test_gm
17039 which will give the following output:
17044 Total number of allocations : 18
17045 Total number of deallocations : 5
17046 Final Water Mark (non freed mem) : 53.00 Kilobytes
17047 High Water Mark : 56.90 Kilobytes
17049 Allocation Root # 1
17050 -------------------
17051 Number of non freed allocations : 10
17052 Final Water Mark (non freed mem) : 39.06 Kilobytes
17053 High Water Mark : 42.97 Kilobytes
17055 test_gm.adb:11 test_gm.my_alloc
17056 test_gm.adb:24 test_gm
17057 b_test_gm.c:52 main
17059 Allocation Root # 2
17060 -------------------
17061 Number of non freed allocations : 1
17062 Final Water Mark (non freed mem) : 10.02 Kilobytes
17063 High Water Mark : 10.02 Kilobytes
17065 s-secsta.adb:81 system.secondary_stack.ss_init
17066 s-secsta.adb:283 <system__secondary_stack___elabb>
17067 b_test_gm.c:33 adainit
17069 Allocation Root # 3
17070 -------------------
17071 Number of non freed allocations : 1
17072 Final Water Mark (non freed mem) : 3.91 Kilobytes
17073 High Water Mark : 3.91 Kilobytes
17075 test_gm.adb:11 test_gm.my_alloc
17076 test_gm.adb:21 test_gm
17077 b_test_gm.c:52 main
17079 Allocation Root # 4
17080 -------------------
17081 Number of non freed allocations : 1
17082 Final Water Mark (non freed mem) : 12 Bytes
17083 High Water Mark : 12 Bytes
17085 s-secsta.adb:181 system.secondary_stack.ss_init
17086 s-secsta.adb:283 <system__secondary_stack___elabb>
17087 b_test_gm.c:33 adainit
17091 The allocation root #1 of the first example has been split in 2 roots #1
17092 and #3 thanks to the more precise associated backtrace.
17096 @node Stack Related Facilities
17097 @chapter Stack Related Facilities
17100 This chapter describes some useful tools associated with stack
17101 checking and analysis. In
17102 particular, it deals with dynamic and static stack usage measurements.
17105 * Stack Overflow Checking::
17106 * Static Stack Usage Analysis::
17107 * Dynamic Stack Usage Analysis::
17110 @node Stack Overflow Checking
17111 @section Stack Overflow Checking
17112 @cindex Stack Overflow Checking
17113 @cindex -fstack-check
17116 For most operating systems, @command{gcc} does not perform stack overflow
17117 checking by default. This means that if the main environment task or
17118 some other task exceeds the available stack space, then unpredictable
17119 behavior will occur. Most native systems offer some level of protection by
17120 adding a guard page at the end of each task stack. This mechanism is usually
17121 not enough for dealing properly with stack overflow situations because
17122 a large local variable could ``jump'' above the guard page.
17123 Furthermore, when the
17124 guard page is hit, there may not be any space left on the stack for executing
17125 the exception propagation code. Enabling stack checking avoids
17128 To activate stack checking, compile all units with the gcc option
17129 @option{-fstack-check}. For example:
17132 gcc -c -fstack-check package1.adb
17136 Units compiled with this option will generate extra instructions to check
17137 that any use of the stack (for procedure calls or for declaring local
17138 variables in declare blocks) does not exceed the available stack space.
17139 If the space is exceeded, then a @code{Storage_Error} exception is raised.
17141 For declared tasks, the stack size is controlled by the size
17142 given in an applicable @code{Storage_Size} pragma or by the value specified
17143 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
17144 the default size as defined in the GNAT runtime otherwise.
17146 For the environment task, the stack size depends on
17147 system defaults and is unknown to the compiler. Stack checking
17148 may still work correctly if a fixed
17149 size stack is allocated, but this cannot be guaranteed.
17151 To ensure that a clean exception is signalled for stack
17152 overflow, set the environment variable
17153 @env{GNAT_STACK_LIMIT} to indicate the maximum
17154 stack area that can be used, as in:
17155 @cindex GNAT_STACK_LIMIT
17158 SET GNAT_STACK_LIMIT 1600
17162 The limit is given in kilobytes, so the above declaration would
17163 set the stack limit of the environment task to 1.6 megabytes.
17164 Note that the only purpose of this usage is to limit the amount
17165 of stack used by the environment task. If it is necessary to
17166 increase the amount of stack for the environment task, then this
17167 is an operating systems issue, and must be addressed with the
17168 appropriate operating systems commands.
17171 To have a fixed size stack in the environment task, the stack must be put
17172 in the P0 address space and its size specified. Use these switches to
17176 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
17180 The quotes are required to keep case. The number after @samp{STACK=} is the
17181 size of the environmental task stack in pagelets (512 bytes). In this example
17182 the stack size is about 2 megabytes.
17185 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
17186 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
17187 more details about the @option{/p0image} qualifier and the @option{stack}
17191 @node Static Stack Usage Analysis
17192 @section Static Stack Usage Analysis
17193 @cindex Static Stack Usage Analysis
17194 @cindex -fstack-usage
17197 A unit compiled with @option{-fstack-usage} will generate an extra file
17199 the maximum amount of stack used, on a per-function basis.
17200 The file has the same
17201 basename as the target object file with a @file{.su} extension.
17202 Each line of this file is made up of three fields:
17206 The name of the function.
17210 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
17213 The second field corresponds to the size of the known part of the function
17216 The qualifier @code{static} means that the function frame size
17218 It usually means that all local variables have a static size.
17219 In this case, the second field is a reliable measure of the function stack
17222 The qualifier @code{dynamic} means that the function frame size is not static.
17223 It happens mainly when some local variables have a dynamic size. When this
17224 qualifier appears alone, the second field is not a reliable measure
17225 of the function stack analysis. When it is qualified with @code{bounded}, it
17226 means that the second field is a reliable maximum of the function stack
17229 A unit compiled with @option{-Wstack-usage} will issue a warning for each
17230 subprogram whose stack usage might be larger than the specified amount of
17231 bytes. The wording is in keeping with the qualifier documented above.
17233 @node Dynamic Stack Usage Analysis
17234 @section Dynamic Stack Usage Analysis
17237 It is possible to measure the maximum amount of stack used by a task, by
17238 adding a switch to @command{gnatbind}, as:
17241 $ gnatbind -u0 file
17245 With this option, at each task termination, its stack usage is output on
17247 It is not always convenient to output the stack usage when the program
17248 is still running. Hence, it is possible to delay this output until program
17249 termination. for a given number of tasks specified as the argument of the
17250 @option{-u} option. For instance:
17253 $ gnatbind -u100 file
17257 will buffer the stack usage information of the first 100 tasks to terminate and
17258 output this info at program termination. Results are displayed in four
17262 Index | Task Name | Stack Size | Stack Usage
17269 is a number associated with each task.
17272 is the name of the task analyzed.
17275 is the maximum size for the stack.
17278 is the measure done by the stack analyzer. In order to prevent overflow, the stack
17279 is not entirely analyzed, and it's not possible to know exactly how
17280 much has actually been used.
17285 The environment task stack, e.g., the stack that contains the main unit, is
17286 only processed when the environment variable GNAT_STACK_LIMIT is set.
17289 The package @code{GNAT.Task_Stack_Usage} provides facilities to get
17290 stack usage reports at run-time. See its body for the details.
17292 @c *********************************
17294 @c *********************************
17295 @node Verifying Properties Using gnatcheck
17296 @chapter Verifying Properties Using @command{gnatcheck}
17298 @cindex @command{gnatcheck}
17301 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
17302 of Ada source files according to a given set of semantic rules.
17305 In order to check compliance with a given rule, @command{gnatcheck} has to
17306 semantically analyze the Ada sources.
17307 Therefore, checks can only be performed on
17308 legal Ada units. Moreover, when a unit depends semantically upon units located
17309 outside the current directory, the source search path has to be provided when
17310 calling @command{gnatcheck}, either through a specified project file or
17311 through @command{gnatcheck} switches.
17313 For full details, refer to @cite{GNATcheck Reference Manual} document.
17316 @c *********************************
17317 @node Creating Sample Bodies Using gnatstub
17318 @chapter Creating Sample Bodies Using @command{gnatstub}
17322 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
17323 for library unit declarations.
17325 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
17326 driver (see @ref{The GNAT Driver and Project Files}).
17328 To create a body stub, @command{gnatstub} has to compile the library
17329 unit declaration. Therefore, bodies can be created only for legal
17330 library units. Moreover, if a library unit depends semantically upon
17331 units located outside the current directory, you have to provide
17332 the source search path when calling @command{gnatstub}, see the description
17333 of @command{gnatstub} switches below.
17335 By default, all the program unit body stubs generated by @code{gnatstub}
17336 raise the predefined @code{Program_Error} exception, which will catch
17337 accidental calls of generated stubs. This behavior can be changed with
17338 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
17341 * Running gnatstub::
17342 * Switches for gnatstub::
17345 @node Running gnatstub
17346 @section Running @command{gnatstub}
17349 @command{gnatstub} has the command-line interface of the form
17352 @c $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
17353 @c Expanding @ovar macro inline (explanation in macro def comments)
17354 $ gnatstub @r{[}@var{switches}@r{]} @var{filename} @r{[}@var{directory}@r{]} @r{[}-cargs @var{gcc_switches}@r{]}
17361 is the name of the source file that contains a library unit declaration
17362 for which a body must be created. The file name may contain the path
17364 The file name does not have to follow the GNAT file name conventions. If the
17366 does not follow GNAT file naming conventions, the name of the body file must
17368 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
17369 If the file name follows the GNAT file naming
17370 conventions and the name of the body file is not provided,
17373 of the body file from the argument file name by replacing the @file{.ads}
17375 with the @file{.adb} suffix.
17378 indicates the directory in which the body stub is to be placed (the default
17382 @item @samp{@var{gcc_switches}} is a list of switches for
17383 @command{gcc}. They will be passed on to all compiler invocations made by
17384 @command{gnatelim} to generate the ASIS trees. Here you can provide
17385 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17386 use the @option{-gnatec} switch to set the configuration file,
17387 use the @option{-gnat05} switch if sources should be compiled in
17391 is an optional sequence of switches as described in the next section
17394 @node Switches for gnatstub
17395 @section Switches for @command{gnatstub}
17401 @cindex @option{^-f^/FULL^} (@command{gnatstub})
17402 If the destination directory already contains a file with the name of the
17404 for the argument spec file, replace it with the generated body stub.
17406 @item ^-hs^/HEADER=SPEC^
17407 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
17408 Put the comment header (i.e., all the comments preceding the
17409 compilation unit) from the source of the library unit declaration
17410 into the body stub.
17412 @item ^-hg^/HEADER=GENERAL^
17413 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
17414 Put a sample comment header into the body stub.
17416 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
17417 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
17418 Use the content of the file as the comment header for a generated body stub.
17422 @cindex @option{-IDIR} (@command{gnatstub})
17424 @cindex @option{-I-} (@command{gnatstub})
17427 @item /NOCURRENT_DIRECTORY
17428 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
17430 ^These switches have ^This switch has^ the same meaning as in calls to
17432 ^They define ^It defines ^ the source search path in the call to
17433 @command{gcc} issued
17434 by @command{gnatstub} to compile an argument source file.
17436 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
17437 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
17438 This switch has the same meaning as in calls to @command{gcc}.
17439 It defines the additional configuration file to be passed to the call to
17440 @command{gcc} issued
17441 by @command{gnatstub} to compile an argument source file.
17443 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
17444 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
17445 (@var{n} is a non-negative integer). Set the maximum line length in the
17446 body stub to @var{n}; the default is 79. The maximum value that can be
17447 specified is 32767. Note that in the special case of configuration
17448 pragma files, the maximum is always 32767 regardless of whether or
17449 not this switch appears.
17451 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
17452 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
17453 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
17454 the generated body sample to @var{n}.
17455 The default indentation is 3.
17457 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
17458 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
17459 Order local bodies alphabetically. (By default local bodies are ordered
17460 in the same way as the corresponding local specs in the argument spec file.)
17462 @item ^-i^/INDENTATION=^@var{n}
17463 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
17464 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
17466 @item ^-k^/TREE_FILE=SAVE^
17467 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
17468 Do not remove the tree file (i.e., the snapshot of the compiler internal
17469 structures used by @command{gnatstub}) after creating the body stub.
17471 @item ^-l^/LINE_LENGTH=^@var{n}
17472 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
17473 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
17475 @item ^--no-exception^/NO_EXCEPTION^
17476 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
17477 void raising PROGRAM_ERROR in the generated bodies of program unit stubs.
17478 This is not always possible for function stubs.
17480 @item ^--no-local-header^/NO_LOCAL_HEADER^
17481 @cindex @option{^--no-local-header^/NO_LOCAL_HEADER^} (@command{gnatstub})
17482 Do not place local comment header with unit name before body stub for a
17485 @item ^-o ^/BODY=^@var{body-name}
17486 @cindex @option{^-o^/BODY^} (@command{gnatstub})
17487 Body file name. This should be set if the argument file name does not
17489 the GNAT file naming
17490 conventions. If this switch is omitted the default name for the body will be
17492 from the argument file name according to the GNAT file naming conventions.
17495 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
17496 Quiet mode: do not generate a confirmation when a body is
17497 successfully created, and do not generate a message when a body is not
17501 @item ^-r^/TREE_FILE=REUSE^
17502 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
17503 Reuse the tree file (if it exists) instead of creating it. Instead of
17504 creating the tree file for the library unit declaration, @command{gnatstub}
17505 tries to find it in the current directory and use it for creating
17506 a body. If the tree file is not found, no body is created. This option
17507 also implies @option{^-k^/SAVE^}, whether or not
17508 the latter is set explicitly.
17510 @item ^-t^/TREE_FILE=OVERWRITE^
17511 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
17512 Overwrite the existing tree file. If the current directory already
17513 contains the file which, according to the GNAT file naming rules should
17514 be considered as a tree file for the argument source file,
17516 will refuse to create the tree file needed to create a sample body
17517 unless this option is set.
17519 @item ^-v^/VERBOSE^
17520 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
17521 Verbose mode: generate version information.
17525 @c *********************************
17526 @node Generating Ada Bindings for C and C++ headers
17527 @chapter Generating Ada Bindings for C and C++ headers
17531 GNAT now comes with a binding generator for C and C++ headers which is
17532 intended to do 95% of the tedious work of generating Ada specs from C
17533 or C++ header files.
17535 Note that this capability is not intended to generate 100% correct Ada specs,
17536 and will is some cases require manual adjustments, although it can often
17537 be used out of the box in practice.
17539 Some of the known limitations include:
17542 @item only very simple character constant macros are translated into Ada
17543 constants. Function macros (macros with arguments) are partially translated
17544 as comments, to be completed manually if needed.
17545 @item some extensions (e.g. vector types) are not supported
17546 @item pointers to pointers or complex structures are mapped to System.Address
17547 @item identifiers with identical name (except casing) will generate compilation
17548 errors (e.g. @code{shm_get} vs @code{SHM_GET}).
17551 The code generated is using the Ada 2005 syntax, which makes it
17552 easier to interface with other languages than previous versions of Ada.
17555 * Running the binding generator::
17556 * Generating bindings for C++ headers::
17560 @node Running the binding generator
17561 @section Running the binding generator
17564 The binding generator is part of the @command{gcc} compiler and can be
17565 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
17566 spec files for the header files specified on the command line, and all
17567 header files needed by these files transitively. For example:
17570 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
17571 $ gcc -c -gnat05 *.ads
17574 will generate, under GNU/Linux, the following files: @file{time_h.ads},
17575 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
17576 correspond to the files @file{/usr/include/time.h},
17577 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
17578 mode these Ada specs.
17580 The @code{-C} switch tells @command{gcc} to extract comments from headers,
17581 and will attempt to generate corresponding Ada comments.
17583 If you want to generate a single Ada file and not the transitive closure, you
17584 can use instead the @option{-fdump-ada-spec-slim} switch.
17586 Note that we recommend when possible to use the @command{g++} driver to
17587 generate bindings, even for most C headers, since this will in general
17588 generate better Ada specs. For generating bindings for C++ headers, it is
17589 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
17590 is equivalent in this case. If @command{g++} cannot work on your C headers
17591 because of incompatibilities between C and C++, then you can fallback to
17592 @command{gcc} instead.
17594 For an example of better bindings generated from the C++ front-end,
17595 the name of the parameters (when available) are actually ignored by the C
17596 front-end. Consider the following C header:
17599 extern void foo (int variable);
17602 with the C front-end, @code{variable} is ignored, and the above is handled as:
17605 extern void foo (int);
17608 generating a generic:
17611 procedure foo (param1 : int);
17614 with the C++ front-end, the name is available, and we generate:
17617 procedure foo (variable : int);
17620 In some cases, the generated bindings will be more complete or more meaningful
17621 when defining some macros, which you can do via the @option{-D} switch. This
17622 is for example the case with @file{Xlib.h} under GNU/Linux:
17625 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
17628 The above will generate more complete bindings than a straight call without
17629 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
17631 In other cases, it is not possible to parse a header file in a stand alone
17632 manner, because other include files need to be included first. In this
17633 case, the solution is to create a small header file including the needed
17634 @code{#include} and possible @code{#define} directives. For example, to
17635 generate Ada bindings for @file{readline/readline.h}, you need to first
17636 include @file{stdio.h}, so you can create a file with the following two
17637 lines in e.g. @file{readline1.h}:
17641 #include <readline/readline.h>
17644 and then generate Ada bindings from this file:
17647 $ g++ -c -fdump-ada-spec readline1.h
17650 @node Generating bindings for C++ headers
17651 @section Generating bindings for C++ headers
17654 Generating bindings for C++ headers is done using the same options, always
17655 with the @command{g++} compiler.
17657 In this mode, C++ classes will be mapped to Ada tagged types, constructors
17658 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
17659 multiple inheritance of abstract classes will be mapped to Ada interfaces
17660 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
17661 information on interfacing to C++).
17663 For example, given the following C++ header file:
17670 virtual int Number_Of_Teeth () = 0;
17675 virtual void Set_Owner (char* Name) = 0;
17681 virtual void Set_Age (int New_Age);
17684 class Dog : Animal, Carnivore, Domestic @{
17689 virtual int Number_Of_Teeth ();
17690 virtual void Set_Owner (char* Name);
17698 The corresponding Ada code is generated:
17700 @smallexample @c ada
17703 package Class_Carnivore is
17704 type Carnivore is limited interface;
17705 pragma Import (CPP, Carnivore);
17707 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
17709 use Class_Carnivore;
17711 package Class_Domestic is
17712 type Domestic is limited interface;
17713 pragma Import (CPP, Domestic);
17715 procedure Set_Owner
17716 (this : access Domestic;
17717 Name : Interfaces.C.Strings.chars_ptr) is abstract;
17719 use Class_Domestic;
17721 package Class_Animal is
17722 type Animal is tagged limited record
17723 Age_Count : aliased int;
17725 pragma Import (CPP, Animal);
17727 procedure Set_Age (this : access Animal; New_Age : int);
17728 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
17732 package Class_Dog is
17733 type Dog is new Animal and Carnivore and Domestic with record
17734 Tooth_Count : aliased int;
17735 Owner : Interfaces.C.Strings.chars_ptr;
17737 pragma Import (CPP, Dog);
17739 function Number_Of_Teeth (this : access Dog) return int;
17740 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
17742 procedure Set_Owner
17743 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
17744 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
17746 function New_Dog return Dog;
17747 pragma CPP_Constructor (New_Dog);
17748 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
17759 @item -fdump-ada-spec
17760 @cindex @option{-fdump-ada-spec} (@command{gcc})
17761 Generate Ada spec files for the given header files transitively (including
17762 all header files that these headers depend upon).
17764 @item -fdump-ada-spec-slim
17765 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
17766 Generate Ada spec files for the header files specified on the command line
17770 @cindex @option{-C} (@command{gcc})
17771 Extract comments from headers and generate Ada comments in the Ada spec files.
17774 @node Other Utility Programs
17775 @chapter Other Utility Programs
17778 This chapter discusses some other utility programs available in the Ada
17782 * Using Other Utility Programs with GNAT::
17783 * The External Symbol Naming Scheme of GNAT::
17784 * Converting Ada Files to html with gnathtml::
17785 * Installing gnathtml::
17792 @node Using Other Utility Programs with GNAT
17793 @section Using Other Utility Programs with GNAT
17796 The object files generated by GNAT are in standard system format and in
17797 particular the debugging information uses this format. This means
17798 programs generated by GNAT can be used with existing utilities that
17799 depend on these formats.
17802 In general, any utility program that works with C will also often work with
17803 Ada programs generated by GNAT. This includes software utilities such as
17804 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
17808 @node The External Symbol Naming Scheme of GNAT
17809 @section The External Symbol Naming Scheme of GNAT
17812 In order to interpret the output from GNAT, when using tools that are
17813 originally intended for use with other languages, it is useful to
17814 understand the conventions used to generate link names from the Ada
17817 All link names are in all lowercase letters. With the exception of library
17818 procedure names, the mechanism used is simply to use the full expanded
17819 Ada name with dots replaced by double underscores. For example, suppose
17820 we have the following package spec:
17822 @smallexample @c ada
17833 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
17834 the corresponding link name is @code{qrs__mn}.
17836 Of course if a @code{pragma Export} is used this may be overridden:
17838 @smallexample @c ada
17843 pragma Export (Var1, C, External_Name => "var1_name");
17845 pragma Export (Var2, C, Link_Name => "var2_link_name");
17852 In this case, the link name for @var{Var1} is whatever link name the
17853 C compiler would assign for the C function @var{var1_name}. This typically
17854 would be either @var{var1_name} or @var{_var1_name}, depending on operating
17855 system conventions, but other possibilities exist. The link name for
17856 @var{Var2} is @var{var2_link_name}, and this is not operating system
17860 One exception occurs for library level procedures. A potential ambiguity
17861 arises between the required name @code{_main} for the C main program,
17862 and the name we would otherwise assign to an Ada library level procedure
17863 called @code{Main} (which might well not be the main program).
17865 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
17866 names. So if we have a library level procedure such as
17868 @smallexample @c ada
17871 procedure Hello (S : String);
17877 the external name of this procedure will be @var{_ada_hello}.
17880 @node Converting Ada Files to html with gnathtml
17881 @section Converting Ada Files to HTML with @code{gnathtml}
17884 This @code{Perl} script allows Ada source files to be browsed using
17885 standard Web browsers. For installation procedure, see the section
17886 @xref{Installing gnathtml}.
17888 Ada reserved keywords are highlighted in a bold font and Ada comments in
17889 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
17890 switch to suppress the generation of cross-referencing information, user
17891 defined variables and types will appear in a different color; you will
17892 be able to click on any identifier and go to its declaration.
17894 The command line is as follow:
17896 @c $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
17897 @c Expanding @ovar macro inline (explanation in macro def comments)
17898 $ perl gnathtml.pl @r{[}@var{^switches^options^}@r{]} @var{ada-files}
17902 You can pass it as many Ada files as you want. @code{gnathtml} will generate
17903 an html file for every ada file, and a global file called @file{index.htm}.
17904 This file is an index of every identifier defined in the files.
17906 The available ^switches^options^ are the following ones:
17910 @cindex @option{-83} (@code{gnathtml})
17911 Only the Ada 83 subset of keywords will be highlighted.
17913 @item -cc @var{color}
17914 @cindex @option{-cc} (@code{gnathtml})
17915 This option allows you to change the color used for comments. The default
17916 value is green. The color argument can be any name accepted by html.
17919 @cindex @option{-d} (@code{gnathtml})
17920 If the Ada files depend on some other files (for instance through
17921 @code{with} clauses, the latter files will also be converted to html.
17922 Only the files in the user project will be converted to html, not the files
17923 in the run-time library itself.
17926 @cindex @option{-D} (@code{gnathtml})
17927 This command is the same as @option{-d} above, but @command{gnathtml} will
17928 also look for files in the run-time library, and generate html files for them.
17930 @item -ext @var{extension}
17931 @cindex @option{-ext} (@code{gnathtml})
17932 This option allows you to change the extension of the generated HTML files.
17933 If you do not specify an extension, it will default to @file{htm}.
17936 @cindex @option{-f} (@code{gnathtml})
17937 By default, gnathtml will generate html links only for global entities
17938 ('with'ed units, global variables and types,@dots{}). If you specify
17939 @option{-f} on the command line, then links will be generated for local
17942 @item -l @var{number}
17943 @cindex @option{-l} (@code{gnathtml})
17944 If this ^switch^option^ is provided and @var{number} is not 0, then
17945 @code{gnathtml} will number the html files every @var{number} line.
17948 @cindex @option{-I} (@code{gnathtml})
17949 Specify a directory to search for library files (@file{.ALI} files) and
17950 source files. You can provide several -I switches on the command line,
17951 and the directories will be parsed in the order of the command line.
17954 @cindex @option{-o} (@code{gnathtml})
17955 Specify the output directory for html files. By default, gnathtml will
17956 saved the generated html files in a subdirectory named @file{html/}.
17958 @item -p @var{file}
17959 @cindex @option{-p} (@code{gnathtml})
17960 If you are using Emacs and the most recent Emacs Ada mode, which provides
17961 a full Integrated Development Environment for compiling, checking,
17962 running and debugging applications, you may use @file{.gpr} files
17963 to give the directories where Emacs can find sources and object files.
17965 Using this ^switch^option^, you can tell gnathtml to use these files.
17966 This allows you to get an html version of your application, even if it
17967 is spread over multiple directories.
17969 @item -sc @var{color}
17970 @cindex @option{-sc} (@code{gnathtml})
17971 This ^switch^option^ allows you to change the color used for symbol
17973 The default value is red. The color argument can be any name accepted by html.
17975 @item -t @var{file}
17976 @cindex @option{-t} (@code{gnathtml})
17977 This ^switch^option^ provides the name of a file. This file contains a list of
17978 file names to be converted, and the effect is exactly as though they had
17979 appeared explicitly on the command line. This
17980 is the recommended way to work around the command line length limit on some
17985 @node Installing gnathtml
17986 @section Installing @code{gnathtml}
17989 @code{Perl} needs to be installed on your machine to run this script.
17990 @code{Perl} is freely available for almost every architecture and
17991 Operating System via the Internet.
17993 On Unix systems, you may want to modify the first line of the script
17994 @code{gnathtml}, to explicitly tell the Operating system where Perl
17995 is. The syntax of this line is:
17997 #!full_path_name_to_perl
18001 Alternatively, you may run the script using the following command line:
18004 @c $ perl gnathtml.pl @ovar{switches} @var{files}
18005 @c Expanding @ovar macro inline (explanation in macro def comments)
18006 $ perl gnathtml.pl @r{[}@var{switches}@r{]} @var{files}
18015 The GNAT distribution provides an Ada 95 template for the HP Language
18016 Sensitive Editor (LSE), a component of DECset. In order to
18017 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
18024 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
18025 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
18026 the collection phase with the /DEBUG qualifier.
18029 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
18030 $ DEFINE LIB$DEBUG PCA$COLLECTOR
18031 $ RUN/DEBUG <PROGRAM_NAME>
18037 @c ******************************
18038 @node Code Coverage and Profiling
18039 @chapter Code Coverage and Profiling
18040 @cindex Code Coverage
18044 This chapter describes how to use @code{gcov} - coverage testing tool - and
18045 @code{gprof} - profiler tool - on your Ada programs.
18048 * Code Coverage of Ada Programs using gcov::
18049 * Profiling an Ada Program using gprof::
18052 @node Code Coverage of Ada Programs using gcov
18053 @section Code Coverage of Ada Programs using gcov
18055 @cindex -fprofile-arcs
18056 @cindex -ftest-coverage
18058 @cindex Code Coverage
18061 @code{gcov} is a test coverage program: it analyzes the execution of a given
18062 program on selected tests, to help you determine the portions of the program
18063 that are still untested.
18065 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
18066 User's Guide. You can refer to this documentation for a more complete
18069 This chapter provides a quick startup guide, and
18070 details some Gnat-specific features.
18073 * Quick startup guide::
18077 @node Quick startup guide
18078 @subsection Quick startup guide
18080 In order to perform coverage analysis of a program using @code{gcov}, 3
18085 Code instrumentation during the compilation process
18087 Execution of the instrumented program
18089 Execution of the @code{gcov} tool to generate the result.
18092 The code instrumentation needed by gcov is created at the object level:
18093 The source code is not modified in any way, because the instrumentation code is
18094 inserted by gcc during the compilation process. To compile your code with code
18095 coverage activated, you need to recompile your whole project using the
18097 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
18098 @code{-fprofile-arcs}.
18101 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
18102 -largs -fprofile-arcs
18105 This compilation process will create @file{.gcno} files together with
18106 the usual object files.
18108 Once the program is compiled with coverage instrumentation, you can
18109 run it as many times as needed - on portions of a test suite for
18110 example. The first execution will produce @file{.gcda} files at the
18111 same location as the @file{.gcno} files. The following executions
18112 will update those files, so that a cumulative result of the covered
18113 portions of the program is generated.
18115 Finally, you need to call the @code{gcov} tool. The different options of
18116 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
18118 This will create annotated source files with a @file{.gcov} extension:
18119 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
18121 @node Gnat specifics
18122 @subsection Gnat specifics
18124 Because Ada semantics, portions of the source code may be shared among
18125 several object files. This is the case for example when generics are
18126 involved, when inlining is active or when declarations generate initialisation
18127 calls. In order to take
18128 into account this shared code, you need to call @code{gcov} on all
18129 source files of the tested program at once.
18131 The list of source files might exceed the system's maximum command line
18132 length. In order to bypass this limitation, a new mechanism has been
18133 implemented in @code{gcov}: you can now list all your project's files into a
18134 text file, and provide this file to gcov as a parameter, preceded by a @@
18135 (e.g. @samp{gcov @@mysrclist.txt}).
18137 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
18138 not supported as there can be unresolved symbols during the final link.
18140 @node Profiling an Ada Program using gprof
18141 @section Profiling an Ada Program using gprof
18147 This section is not meant to be an exhaustive documentation of @code{gprof}.
18148 Full documentation for it can be found in the GNU Profiler User's Guide
18149 documentation that is part of this GNAT distribution.
18151 Profiling a program helps determine the parts of a program that are executed
18152 most often, and are therefore the most time-consuming.
18154 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
18155 better handle Ada programs and multitasking.
18156 It is currently supported on the following platforms
18161 solaris sparc/sparc64/x86
18167 In order to profile a program using @code{gprof}, 3 steps are needed:
18171 Code instrumentation, requiring a full recompilation of the project with the
18174 Execution of the program under the analysis conditions, i.e. with the desired
18177 Analysis of the results using the @code{gprof} tool.
18181 The following sections detail the different steps, and indicate how
18182 to interpret the results:
18184 * Compilation for profiling::
18185 * Program execution::
18187 * Interpretation of profiling results::
18190 @node Compilation for profiling
18191 @subsection Compilation for profiling
18195 In order to profile a program the first step is to tell the compiler
18196 to generate the necessary profiling information. The compiler switch to be used
18197 is @code{-pg}, which must be added to other compilation switches. This
18198 switch needs to be specified both during compilation and link stages, and can
18199 be specified once when using gnatmake:
18202 gnatmake -f -pg -P my_project
18206 Note that only the objects that were compiled with the @samp{-pg} switch will
18207 be profiled; if you need to profile your whole project, use the @samp{-f}
18208 gnatmake switch to force full recompilation.
18210 @node Program execution
18211 @subsection Program execution
18214 Once the program has been compiled for profiling, you can run it as usual.
18216 The only constraint imposed by profiling is that the program must terminate
18217 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
18220 Once the program completes execution, a data file called @file{gmon.out} is
18221 generated in the directory where the program was launched from. If this file
18222 already exists, it will be overwritten.
18224 @node Running gprof
18225 @subsection Running gprof
18228 The @code{gprof} tool is called as follow:
18231 gprof my_prog gmon.out
18242 The complete form of the gprof command line is the following:
18245 gprof [^switches^options^] [executable [data-file]]
18249 @code{gprof} supports numerous ^switch^options^. The order of these
18250 ^switch^options^ does not matter. The full list of options can be found in
18251 the GNU Profiler User's Guide documentation that comes with this documentation.
18253 The following is the subset of those switches that is most relevant:
18257 @item --demangle[=@var{style}]
18258 @itemx --no-demangle
18259 @cindex @option{--demangle} (@code{gprof})
18260 These options control whether symbol names should be demangled when
18261 printing output. The default is to demangle C++ symbols. The
18262 @code{--no-demangle} option may be used to turn off demangling. Different
18263 compilers have different mangling styles. The optional demangling style
18264 argument can be used to choose an appropriate demangling style for your
18265 compiler, in particular Ada symbols generated by GNAT can be demangled using
18266 @code{--demangle=gnat}.
18268 @item -e @var{function_name}
18269 @cindex @option{-e} (@code{gprof})
18270 The @samp{-e @var{function}} option tells @code{gprof} not to print
18271 information about the function @var{function_name} (and its
18272 children@dots{}) in the call graph. The function will still be listed
18273 as a child of any functions that call it, but its index number will be
18274 shown as @samp{[not printed]}. More than one @samp{-e} option may be
18275 given; only one @var{function_name} may be indicated with each @samp{-e}
18278 @item -E @var{function_name}
18279 @cindex @option{-E} (@code{gprof})
18280 The @code{-E @var{function}} option works like the @code{-e} option, but
18281 execution time spent in the function (and children who were not called from
18282 anywhere else), will not be used to compute the percentages-of-time for
18283 the call graph. More than one @samp{-E} option may be given; only one
18284 @var{function_name} may be indicated with each @samp{-E} option.
18286 @item -f @var{function_name}
18287 @cindex @option{-f} (@code{gprof})
18288 The @samp{-f @var{function}} option causes @code{gprof} to limit the
18289 call graph to the function @var{function_name} and its children (and
18290 their children@dots{}). More than one @samp{-f} option may be given;
18291 only one @var{function_name} may be indicated with each @samp{-f}
18294 @item -F @var{function_name}
18295 @cindex @option{-F} (@code{gprof})
18296 The @samp{-F @var{function}} option works like the @code{-f} option, but
18297 only time spent in the function and its children (and their
18298 children@dots{}) will be used to determine total-time and
18299 percentages-of-time for the call graph. More than one @samp{-F} option
18300 may be given; only one @var{function_name} may be indicated with each
18301 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
18305 @node Interpretation of profiling results
18306 @subsection Interpretation of profiling results
18310 The results of the profiling analysis are represented by two arrays: the
18311 'flat profile' and the 'call graph'. Full documentation of those outputs
18312 can be found in the GNU Profiler User's Guide.
18314 The flat profile shows the time spent in each function of the program, and how
18315 many time it has been called. This allows you to locate easily the most
18316 time-consuming functions.
18318 The call graph shows, for each subprogram, the subprograms that call it,
18319 and the subprograms that it calls. It also provides an estimate of the time
18320 spent in each of those callers/called subprograms.
18323 @c ******************************
18324 @node Running and Debugging Ada Programs
18325 @chapter Running and Debugging Ada Programs
18329 This chapter discusses how to debug Ada programs.
18331 It applies to GNAT on the Alpha OpenVMS platform;
18332 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
18333 since HP has implemented Ada support in the OpenVMS debugger on I64.
18336 An incorrect Ada program may be handled in three ways by the GNAT compiler:
18340 The illegality may be a violation of the static semantics of Ada. In
18341 that case GNAT diagnoses the constructs in the program that are illegal.
18342 It is then a straightforward matter for the user to modify those parts of
18346 The illegality may be a violation of the dynamic semantics of Ada. In
18347 that case the program compiles and executes, but may generate incorrect
18348 results, or may terminate abnormally with some exception.
18351 When presented with a program that contains convoluted errors, GNAT
18352 itself may terminate abnormally without providing full diagnostics on
18353 the incorrect user program.
18357 * The GNAT Debugger GDB::
18359 * Introduction to GDB Commands::
18360 * Using Ada Expressions::
18361 * Calling User-Defined Subprograms::
18362 * Using the Next Command in a Function::
18365 * Debugging Generic Units::
18366 * Remote Debugging using gdbserver::
18367 * GNAT Abnormal Termination or Failure to Terminate::
18368 * Naming Conventions for GNAT Source Files::
18369 * Getting Internal Debugging Information::
18370 * Stack Traceback::
18376 @node The GNAT Debugger GDB
18377 @section The GNAT Debugger GDB
18380 @code{GDB} is a general purpose, platform-independent debugger that
18381 can be used to debug mixed-language programs compiled with @command{gcc},
18382 and in particular is capable of debugging Ada programs compiled with
18383 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
18384 complex Ada data structures.
18386 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
18388 located in the GNU:[DOCS] directory,
18390 for full details on the usage of @code{GDB}, including a section on
18391 its usage on programs. This manual should be consulted for full
18392 details. The section that follows is a brief introduction to the
18393 philosophy and use of @code{GDB}.
18395 When GNAT programs are compiled, the compiler optionally writes debugging
18396 information into the generated object file, including information on
18397 line numbers, and on declared types and variables. This information is
18398 separate from the generated code. It makes the object files considerably
18399 larger, but it does not add to the size of the actual executable that
18400 will be loaded into memory, and has no impact on run-time performance. The
18401 generation of debug information is triggered by the use of the
18402 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
18403 used to carry out the compilations. It is important to emphasize that
18404 the use of these options does not change the generated code.
18406 The debugging information is written in standard system formats that
18407 are used by many tools, including debuggers and profilers. The format
18408 of the information is typically designed to describe C types and
18409 semantics, but GNAT implements a translation scheme which allows full
18410 details about Ada types and variables to be encoded into these
18411 standard C formats. Details of this encoding scheme may be found in
18412 the file exp_dbug.ads in the GNAT source distribution. However, the
18413 details of this encoding are, in general, of no interest to a user,
18414 since @code{GDB} automatically performs the necessary decoding.
18416 When a program is bound and linked, the debugging information is
18417 collected from the object files, and stored in the executable image of
18418 the program. Again, this process significantly increases the size of
18419 the generated executable file, but it does not increase the size of
18420 the executable program itself. Furthermore, if this program is run in
18421 the normal manner, it runs exactly as if the debug information were
18422 not present, and takes no more actual memory.
18424 However, if the program is run under control of @code{GDB}, the
18425 debugger is activated. The image of the program is loaded, at which
18426 point it is ready to run. If a run command is given, then the program
18427 will run exactly as it would have if @code{GDB} were not present. This
18428 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
18429 entirely non-intrusive until a breakpoint is encountered. If no
18430 breakpoint is ever hit, the program will run exactly as it would if no
18431 debugger were present. When a breakpoint is hit, @code{GDB} accesses
18432 the debugging information and can respond to user commands to inspect
18433 variables, and more generally to report on the state of execution.
18437 @section Running GDB
18440 This section describes how to initiate the debugger.
18441 @c The above sentence is really just filler, but it was otherwise
18442 @c clumsy to get the first paragraph nonindented given the conditional
18443 @c nature of the description
18446 The debugger can be launched from a @code{GPS} menu or
18447 directly from the command line. The description below covers the latter use.
18448 All the commands shown can be used in the @code{GPS} debug console window,
18449 but there are usually more GUI-based ways to achieve the same effect.
18452 The command to run @code{GDB} is
18455 $ ^gdb program^GDB PROGRAM^
18459 where @code{^program^PROGRAM^} is the name of the executable file. This
18460 activates the debugger and results in a prompt for debugger commands.
18461 The simplest command is simply @code{run}, which causes the program to run
18462 exactly as if the debugger were not present. The following section
18463 describes some of the additional commands that can be given to @code{GDB}.
18465 @c *******************************
18466 @node Introduction to GDB Commands
18467 @section Introduction to GDB Commands
18470 @code{GDB} contains a large repertoire of commands. @xref{Top,,
18471 Debugging with GDB, gdb, Debugging with GDB},
18473 located in the GNU:[DOCS] directory,
18475 for extensive documentation on the use
18476 of these commands, together with examples of their use. Furthermore,
18477 the command @command{help} invoked from within GDB activates a simple help
18478 facility which summarizes the available commands and their options.
18479 In this section we summarize a few of the most commonly
18480 used commands to give an idea of what @code{GDB} is about. You should create
18481 a simple program with debugging information and experiment with the use of
18482 these @code{GDB} commands on the program as you read through the
18486 @item set args @var{arguments}
18487 The @var{arguments} list above is a list of arguments to be passed to
18488 the program on a subsequent run command, just as though the arguments
18489 had been entered on a normal invocation of the program. The @code{set args}
18490 command is not needed if the program does not require arguments.
18493 The @code{run} command causes execution of the program to start from
18494 the beginning. If the program is already running, that is to say if
18495 you are currently positioned at a breakpoint, then a prompt will ask
18496 for confirmation that you want to abandon the current execution and
18499 @item breakpoint @var{location}
18500 The breakpoint command sets a breakpoint, that is to say a point at which
18501 execution will halt and @code{GDB} will await further
18502 commands. @var{location} is
18503 either a line number within a file, given in the format @code{file:linenumber},
18504 or it is the name of a subprogram. If you request that a breakpoint be set on
18505 a subprogram that is overloaded, a prompt will ask you to specify on which of
18506 those subprograms you want to breakpoint. You can also
18507 specify that all of them should be breakpointed. If the program is run
18508 and execution encounters the breakpoint, then the program
18509 stops and @code{GDB} signals that the breakpoint was encountered by
18510 printing the line of code before which the program is halted.
18512 @item catch exception @var{name}
18513 This command causes the program execution to stop whenever exception
18514 @var{name} is raised. If @var{name} is omitted, then the execution is
18515 suspended when any exception is raised.
18517 @item print @var{expression}
18518 This will print the value of the given expression. Most simple
18519 Ada expression formats are properly handled by @code{GDB}, so the expression
18520 can contain function calls, variables, operators, and attribute references.
18523 Continues execution following a breakpoint, until the next breakpoint or the
18524 termination of the program.
18527 Executes a single line after a breakpoint. If the next statement
18528 is a subprogram call, execution continues into (the first statement of)
18529 the called subprogram.
18532 Executes a single line. If this line is a subprogram call, executes and
18533 returns from the call.
18536 Lists a few lines around the current source location. In practice, it
18537 is usually more convenient to have a separate edit window open with the
18538 relevant source file displayed. Successive applications of this command
18539 print subsequent lines. The command can be given an argument which is a
18540 line number, in which case it displays a few lines around the specified one.
18543 Displays a backtrace of the call chain. This command is typically
18544 used after a breakpoint has occurred, to examine the sequence of calls that
18545 leads to the current breakpoint. The display includes one line for each
18546 activation record (frame) corresponding to an active subprogram.
18549 At a breakpoint, @code{GDB} can display the values of variables local
18550 to the current frame. The command @code{up} can be used to
18551 examine the contents of other active frames, by moving the focus up
18552 the stack, that is to say from callee to caller, one frame at a time.
18555 Moves the focus of @code{GDB} down from the frame currently being
18556 examined to the frame of its callee (the reverse of the previous command),
18558 @item frame @var{n}
18559 Inspect the frame with the given number. The value 0 denotes the frame
18560 of the current breakpoint, that is to say the top of the call stack.
18565 The above list is a very short introduction to the commands that
18566 @code{GDB} provides. Important additional capabilities, including conditional
18567 breakpoints, the ability to execute command sequences on a breakpoint,
18568 the ability to debug at the machine instruction level and many other
18569 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
18570 Debugging with GDB}. Note that most commands can be abbreviated
18571 (for example, c for continue, bt for backtrace).
18573 @node Using Ada Expressions
18574 @section Using Ada Expressions
18575 @cindex Ada expressions
18578 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
18579 extensions. The philosophy behind the design of this subset is
18583 That @code{GDB} should provide basic literals and access to operations for
18584 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18585 leaving more sophisticated computations to subprograms written into the
18586 program (which therefore may be called from @code{GDB}).
18589 That type safety and strict adherence to Ada language restrictions
18590 are not particularly important to the @code{GDB} user.
18593 That brevity is important to the @code{GDB} user.
18597 Thus, for brevity, the debugger acts as if there were
18598 implicit @code{with} and @code{use} clauses in effect for all user-written
18599 packages, thus making it unnecessary to fully qualify most names with
18600 their packages, regardless of context. Where this causes ambiguity,
18601 @code{GDB} asks the user's intent.
18603 For details on the supported Ada syntax, see @ref{Top,, Debugging with
18604 GDB, gdb, Debugging with GDB}.
18606 @node Calling User-Defined Subprograms
18607 @section Calling User-Defined Subprograms
18610 An important capability of @code{GDB} is the ability to call user-defined
18611 subprograms while debugging. This is achieved simply by entering
18612 a subprogram call statement in the form:
18615 call subprogram-name (parameters)
18619 The keyword @code{call} can be omitted in the normal case where the
18620 @code{subprogram-name} does not coincide with any of the predefined
18621 @code{GDB} commands.
18623 The effect is to invoke the given subprogram, passing it the
18624 list of parameters that is supplied. The parameters can be expressions and
18625 can include variables from the program being debugged. The
18626 subprogram must be defined
18627 at the library level within your program, and @code{GDB} will call the
18628 subprogram within the environment of your program execution (which
18629 means that the subprogram is free to access or even modify variables
18630 within your program).
18632 The most important use of this facility is in allowing the inclusion of
18633 debugging routines that are tailored to particular data structures
18634 in your program. Such debugging routines can be written to provide a suitably
18635 high-level description of an abstract type, rather than a low-level dump
18636 of its physical layout. After all, the standard
18637 @code{GDB print} command only knows the physical layout of your
18638 types, not their abstract meaning. Debugging routines can provide information
18639 at the desired semantic level and are thus enormously useful.
18641 For example, when debugging GNAT itself, it is crucial to have access to
18642 the contents of the tree nodes used to represent the program internally.
18643 But tree nodes are represented simply by an integer value (which in turn
18644 is an index into a table of nodes).
18645 Using the @code{print} command on a tree node would simply print this integer
18646 value, which is not very useful. But the PN routine (defined in file
18647 treepr.adb in the GNAT sources) takes a tree node as input, and displays
18648 a useful high level representation of the tree node, which includes the
18649 syntactic category of the node, its position in the source, the integers
18650 that denote descendant nodes and parent node, as well as varied
18651 semantic information. To study this example in more detail, you might want to
18652 look at the body of the PN procedure in the stated file.
18654 @node Using the Next Command in a Function
18655 @section Using the Next Command in a Function
18658 When you use the @code{next} command in a function, the current source
18659 location will advance to the next statement as usual. A special case
18660 arises in the case of a @code{return} statement.
18662 Part of the code for a return statement is the ``epilog'' of the function.
18663 This is the code that returns to the caller. There is only one copy of
18664 this epilog code, and it is typically associated with the last return
18665 statement in the function if there is more than one return. In some
18666 implementations, this epilog is associated with the first statement
18669 The result is that if you use the @code{next} command from a return
18670 statement that is not the last return statement of the function you
18671 may see a strange apparent jump to the last return statement or to
18672 the start of the function. You should simply ignore this odd jump.
18673 The value returned is always that from the first return statement
18674 that was stepped through.
18676 @node Ada Exceptions
18677 @section Stopping when Ada Exceptions are Raised
18681 You can set catchpoints that stop the program execution when your program
18682 raises selected exceptions.
18685 @item catch exception
18686 Set a catchpoint that stops execution whenever (any task in the) program
18687 raises any exception.
18689 @item catch exception @var{name}
18690 Set a catchpoint that stops execution whenever (any task in the) program
18691 raises the exception @var{name}.
18693 @item catch exception unhandled
18694 Set a catchpoint that stops executing whenever (any task in the) program
18695 raises an exception for which there is no handler.
18697 @item info exceptions
18698 @itemx info exceptions @var{regexp}
18699 The @code{info exceptions} command permits the user to examine all defined
18700 exceptions within Ada programs. With a regular expression, @var{regexp}, as
18701 argument, prints out only those exceptions whose name matches @var{regexp}.
18709 @code{GDB} allows the following task-related commands:
18713 This command shows a list of current Ada tasks, as in the following example:
18720 ID TID P-ID Thread Pri State Name
18721 1 8088000 0 807e000 15 Child Activation Wait main_task
18722 2 80a4000 1 80ae000 15 Accept/Select Wait b
18723 3 809a800 1 80a4800 15 Child Activation Wait a
18724 * 4 80ae800 3 80b8000 15 Running c
18728 In this listing, the asterisk before the first task indicates it to be the
18729 currently running task. The first column lists the task ID that is used
18730 to refer to tasks in the following commands.
18732 @item break @var{linespec} task @var{taskid}
18733 @itemx break @var{linespec} task @var{taskid} if @dots{}
18734 @cindex Breakpoints and tasks
18735 These commands are like the @code{break @dots{} thread @dots{}}.
18736 @var{linespec} specifies source lines.
18738 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
18739 to specify that you only want @code{GDB} to stop the program when a
18740 particular Ada task reaches this breakpoint. @var{taskid} is one of the
18741 numeric task identifiers assigned by @code{GDB}, shown in the first
18742 column of the @samp{info tasks} display.
18744 If you do not specify @samp{task @var{taskid}} when you set a
18745 breakpoint, the breakpoint applies to @emph{all} tasks of your
18748 You can use the @code{task} qualifier on conditional breakpoints as
18749 well; in this case, place @samp{task @var{taskid}} before the
18750 breakpoint condition (before the @code{if}).
18752 @item task @var{taskno}
18753 @cindex Task switching
18755 This command allows to switch to the task referred by @var{taskno}. In
18756 particular, This allows to browse the backtrace of the specified
18757 task. It is advised to switch back to the original task before
18758 continuing execution otherwise the scheduling of the program may be
18763 For more detailed information on the tasking support,
18764 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
18766 @node Debugging Generic Units
18767 @section Debugging Generic Units
18768 @cindex Debugging Generic Units
18772 GNAT always uses code expansion for generic instantiation. This means that
18773 each time an instantiation occurs, a complete copy of the original code is
18774 made, with appropriate substitutions of formals by actuals.
18776 It is not possible to refer to the original generic entities in
18777 @code{GDB}, but it is always possible to debug a particular instance of
18778 a generic, by using the appropriate expanded names. For example, if we have
18780 @smallexample @c ada
18785 generic package k is
18786 procedure kp (v1 : in out integer);
18790 procedure kp (v1 : in out integer) is
18796 package k1 is new k;
18797 package k2 is new k;
18799 var : integer := 1;
18812 Then to break on a call to procedure kp in the k2 instance, simply
18816 (gdb) break g.k2.kp
18820 When the breakpoint occurs, you can step through the code of the
18821 instance in the normal manner and examine the values of local variables, as for
18824 @node Remote Debugging using gdbserver
18825 @section Remote Debugging using gdbserver
18826 @cindex Remote Debugging using gdbserver
18829 On platforms where gdbserver is supported, it is possible to use this tool
18830 to debug your application remotely. This can be useful in situations
18831 where the program needs to be run on a target host that is different
18832 from the host used for development, particularly when the target has
18833 a limited amount of resources (either CPU and/or memory).
18835 To do so, start your program using gdbserver on the target machine.
18836 gdbserver then automatically suspends the execution of your program
18837 at its entry point, waiting for a debugger to connect to it. The
18838 following commands starts an application and tells gdbserver to
18839 wait for a connection with the debugger on localhost port 4444.
18842 $ gdbserver localhost:4444 program
18843 Process program created; pid = 5685
18844 Listening on port 4444
18847 Once gdbserver has started listening, we can tell the debugger to establish
18848 a connection with this gdbserver, and then start the same debugging session
18849 as if the program was being debugged on the same host, directly under
18850 the control of GDB.
18854 (gdb) target remote targethost:4444
18855 Remote debugging using targethost:4444
18856 0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so.
18858 Breakpoint 1 at 0x401f0c: file foo.adb, line 3.
18862 Breakpoint 1, foo () at foo.adb:4
18866 It is also possible to use gdbserver to attach to an already running
18867 program, in which case the execution of that program is simply suspended
18868 until the connection between the debugger and gdbserver is established.
18870 For more information on how to use gdbserver, @ref{Top, Server, Using
18871 the gdbserver Program, gdb, Debugging with GDB}. GNAT Pro provides support
18872 for gdbserver on x86-linux, x86-windows and x86_64-linux.
18874 @node GNAT Abnormal Termination or Failure to Terminate
18875 @section GNAT Abnormal Termination or Failure to Terminate
18876 @cindex GNAT Abnormal Termination or Failure to Terminate
18879 When presented with programs that contain serious errors in syntax
18881 GNAT may on rare occasions experience problems in operation, such
18883 segmentation fault or illegal memory access, raising an internal
18884 exception, terminating abnormally, or failing to terminate at all.
18885 In such cases, you can activate
18886 various features of GNAT that can help you pinpoint the construct in your
18887 program that is the likely source of the problem.
18889 The following strategies are presented in increasing order of
18890 difficulty, corresponding to your experience in using GNAT and your
18891 familiarity with compiler internals.
18895 Run @command{gcc} with the @option{-gnatf}. This first
18896 switch causes all errors on a given line to be reported. In its absence,
18897 only the first error on a line is displayed.
18899 The @option{-gnatdO} switch causes errors to be displayed as soon as they
18900 are encountered, rather than after compilation is terminated. If GNAT
18901 terminates prematurely or goes into an infinite loop, the last error
18902 message displayed may help to pinpoint the culprit.
18905 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
18906 mode, @command{gcc} produces ongoing information about the progress of the
18907 compilation and provides the name of each procedure as code is
18908 generated. This switch allows you to find which Ada procedure was being
18909 compiled when it encountered a code generation problem.
18912 @cindex @option{-gnatdc} switch
18913 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
18914 switch that does for the front-end what @option{^-v^VERBOSE^} does
18915 for the back end. The system prints the name of each unit,
18916 either a compilation unit or nested unit, as it is being analyzed.
18918 Finally, you can start
18919 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
18920 front-end of GNAT, and can be run independently (normally it is just
18921 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
18922 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
18923 @code{where} command is the first line of attack; the variable
18924 @code{lineno} (seen by @code{print lineno}), used by the second phase of
18925 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
18926 which the execution stopped, and @code{input_file name} indicates the name of
18930 @node Naming Conventions for GNAT Source Files
18931 @section Naming Conventions for GNAT Source Files
18934 In order to examine the workings of the GNAT system, the following
18935 brief description of its organization may be helpful:
18939 Files with prefix @file{^sc^SC^} contain the lexical scanner.
18942 All files prefixed with @file{^par^PAR^} are components of the parser. The
18943 numbers correspond to chapters of the Ada Reference Manual. For example,
18944 parsing of select statements can be found in @file{par-ch9.adb}.
18947 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
18948 numbers correspond to chapters of the Ada standard. For example, all
18949 issues involving context clauses can be found in @file{sem_ch10.adb}. In
18950 addition, some features of the language require sufficient special processing
18951 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
18952 dynamic dispatching, etc.
18955 All files prefixed with @file{^exp^EXP^} perform normalization and
18956 expansion of the intermediate representation (abstract syntax tree, or AST).
18957 these files use the same numbering scheme as the parser and semantics files.
18958 For example, the construction of record initialization procedures is done in
18959 @file{exp_ch3.adb}.
18962 The files prefixed with @file{^bind^BIND^} implement the binder, which
18963 verifies the consistency of the compilation, determines an order of
18964 elaboration, and generates the bind file.
18967 The files @file{atree.ads} and @file{atree.adb} detail the low-level
18968 data structures used by the front-end.
18971 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
18972 the abstract syntax tree as produced by the parser.
18975 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
18976 all entities, computed during semantic analysis.
18979 Library management issues are dealt with in files with prefix
18985 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
18986 defined in Annex A.
18991 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
18992 defined in Annex B.
18996 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
18997 both language-defined children and GNAT run-time routines.
19001 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
19002 general-purpose packages, fully documented in their specs. All
19003 the other @file{.c} files are modifications of common @command{gcc} files.
19006 @node Getting Internal Debugging Information
19007 @section Getting Internal Debugging Information
19010 Most compilers have internal debugging switches and modes. GNAT
19011 does also, except GNAT internal debugging switches and modes are not
19012 secret. A summary and full description of all the compiler and binder
19013 debug flags are in the file @file{debug.adb}. You must obtain the
19014 sources of the compiler to see the full detailed effects of these flags.
19016 The switches that print the source of the program (reconstructed from
19017 the internal tree) are of general interest for user programs, as are the
19019 the full internal tree, and the entity table (the symbol table
19020 information). The reconstructed source provides a readable version of the
19021 program after the front-end has completed analysis and expansion,
19022 and is useful when studying the performance of specific constructs.
19023 For example, constraint checks are indicated, complex aggregates
19024 are replaced with loops and assignments, and tasking primitives
19025 are replaced with run-time calls.
19027 @node Stack Traceback
19028 @section Stack Traceback
19030 @cindex stack traceback
19031 @cindex stack unwinding
19034 Traceback is a mechanism to display the sequence of subprogram calls that
19035 leads to a specified execution point in a program. Often (but not always)
19036 the execution point is an instruction at which an exception has been raised.
19037 This mechanism is also known as @i{stack unwinding} because it obtains
19038 its information by scanning the run-time stack and recovering the activation
19039 records of all active subprograms. Stack unwinding is one of the most
19040 important tools for program debugging.
19042 The first entry stored in traceback corresponds to the deepest calling level,
19043 that is to say the subprogram currently executing the instruction
19044 from which we want to obtain the traceback.
19046 Note that there is no runtime performance penalty when stack traceback
19047 is enabled, and no exception is raised during program execution.
19050 * Non-Symbolic Traceback::
19051 * Symbolic Traceback::
19054 @node Non-Symbolic Traceback
19055 @subsection Non-Symbolic Traceback
19056 @cindex traceback, non-symbolic
19059 Note: this feature is not supported on all platforms. See
19060 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
19064 * Tracebacks From an Unhandled Exception::
19065 * Tracebacks From Exception Occurrences (non-symbolic)::
19066 * Tracebacks From Anywhere in a Program (non-symbolic)::
19069 @node Tracebacks From an Unhandled Exception
19070 @subsubsection Tracebacks From an Unhandled Exception
19073 A runtime non-symbolic traceback is a list of addresses of call instructions.
19074 To enable this feature you must use the @option{-E}
19075 @code{gnatbind}'s option. With this option a stack traceback is stored as part
19076 of exception information. You can retrieve this information using the
19077 @code{addr2line} tool.
19079 Here is a simple example:
19081 @smallexample @c ada
19087 raise Constraint_Error;
19102 $ gnatmake stb -bargs -E
19105 Execution terminated by unhandled exception
19106 Exception name: CONSTRAINT_ERROR
19108 Call stack traceback locations:
19109 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
19113 As we see the traceback lists a sequence of addresses for the unhandled
19114 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
19115 guess that this exception come from procedure P1. To translate these
19116 addresses into the source lines where the calls appear, the
19117 @code{addr2line} tool, described below, is invaluable. The use of this tool
19118 requires the program to be compiled with debug information.
19121 $ gnatmake -g stb -bargs -E
19124 Execution terminated by unhandled exception
19125 Exception name: CONSTRAINT_ERROR
19127 Call stack traceback locations:
19128 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
19130 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
19131 0x4011f1 0x77e892a4
19133 00401373 at d:/stb/stb.adb:5
19134 0040138B at d:/stb/stb.adb:10
19135 0040139C at d:/stb/stb.adb:14
19136 00401335 at d:/stb/b~stb.adb:104
19137 004011C4 at /build/@dots{}/crt1.c:200
19138 004011F1 at /build/@dots{}/crt1.c:222
19139 77E892A4 in ?? at ??:0
19143 The @code{addr2line} tool has several other useful options:
19147 to get the function name corresponding to any location
19149 @item --demangle=gnat
19150 to use the gnat decoding mode for the function names. Note that
19151 for binutils version 2.9.x the option is simply @option{--demangle}.
19155 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
19156 0x40139c 0x401335 0x4011c4 0x4011f1
19158 00401373 in stb.p1 at d:/stb/stb.adb:5
19159 0040138B in stb.p2 at d:/stb/stb.adb:10
19160 0040139C in stb at d:/stb/stb.adb:14
19161 00401335 in main at d:/stb/b~stb.adb:104
19162 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
19163 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
19167 From this traceback we can see that the exception was raised in
19168 @file{stb.adb} at line 5, which was reached from a procedure call in
19169 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
19170 which contains the call to the main program.
19171 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
19172 and the output will vary from platform to platform.
19174 It is also possible to use @code{GDB} with these traceback addresses to debug
19175 the program. For example, we can break at a given code location, as reported
19176 in the stack traceback:
19182 Furthermore, this feature is not implemented inside Windows DLL. Only
19183 the non-symbolic traceback is reported in this case.
19186 (gdb) break *0x401373
19187 Breakpoint 1 at 0x401373: file stb.adb, line 5.
19191 It is important to note that the stack traceback addresses
19192 do not change when debug information is included. This is particularly useful
19193 because it makes it possible to release software without debug information (to
19194 minimize object size), get a field report that includes a stack traceback
19195 whenever an internal bug occurs, and then be able to retrieve the sequence
19196 of calls with the same program compiled with debug information.
19198 @node Tracebacks From Exception Occurrences (non-symbolic)
19199 @subsubsection Tracebacks From Exception Occurrences
19202 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
19203 The stack traceback is attached to the exception information string, and can
19204 be retrieved in an exception handler within the Ada program, by means of the
19205 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
19207 @smallexample @c ada
19209 with Ada.Exceptions;
19214 use Ada.Exceptions;
19222 Text_IO.Put_Line (Exception_Information (E));
19236 This program will output:
19241 Exception name: CONSTRAINT_ERROR
19242 Message: stb.adb:12
19243 Call stack traceback locations:
19244 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
19247 @node Tracebacks From Anywhere in a Program (non-symbolic)
19248 @subsubsection Tracebacks From Anywhere in a Program
19251 It is also possible to retrieve a stack traceback from anywhere in a
19252 program. For this you need to
19253 use the @code{GNAT.Traceback} API. This package includes a procedure called
19254 @code{Call_Chain} that computes a complete stack traceback, as well as useful
19255 display procedures described below. It is not necessary to use the
19256 @option{-E gnatbind} option in this case, because the stack traceback mechanism
19257 is invoked explicitly.
19260 In the following example we compute a traceback at a specific location in
19261 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
19262 convert addresses to strings:
19264 @smallexample @c ada
19266 with GNAT.Traceback;
19267 with GNAT.Debug_Utilities;
19273 use GNAT.Traceback;
19276 TB : Tracebacks_Array (1 .. 10);
19277 -- We are asking for a maximum of 10 stack frames.
19279 -- Len will receive the actual number of stack frames returned.
19281 Call_Chain (TB, Len);
19283 Text_IO.Put ("In STB.P1 : ");
19285 for K in 1 .. Len loop
19286 Text_IO.Put (Debug_Utilities.Image (TB (K)));
19307 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
19308 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
19312 You can then get further information by invoking the @code{addr2line}
19313 tool as described earlier (note that the hexadecimal addresses
19314 need to be specified in C format, with a leading ``0x'').
19316 @node Symbolic Traceback
19317 @subsection Symbolic Traceback
19318 @cindex traceback, symbolic
19321 A symbolic traceback is a stack traceback in which procedure names are
19322 associated with each code location.
19325 Note that this feature is not supported on all platforms. See
19326 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
19327 list of currently supported platforms.
19330 Note that the symbolic traceback requires that the program be compiled
19331 with debug information. If it is not compiled with debug information
19332 only the non-symbolic information will be valid.
19335 * Tracebacks From Exception Occurrences (symbolic)::
19336 * Tracebacks From Anywhere in a Program (symbolic)::
19339 @node Tracebacks From Exception Occurrences (symbolic)
19340 @subsubsection Tracebacks From Exception Occurrences
19342 @smallexample @c ada
19344 with GNAT.Traceback.Symbolic;
19350 raise Constraint_Error;
19367 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
19372 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
19375 0040149F in stb.p1 at stb.adb:8
19376 004014B7 in stb.p2 at stb.adb:13
19377 004014CF in stb.p3 at stb.adb:18
19378 004015DD in ada.stb at stb.adb:22
19379 00401461 in main at b~stb.adb:168
19380 004011C4 in __mingw_CRTStartup at crt1.c:200
19381 004011F1 in mainCRTStartup at crt1.c:222
19382 77E892A4 in ?? at ??:0
19386 In the above example the ``.\'' syntax in the @command{gnatmake} command
19387 is currently required by @command{addr2line} for files that are in
19388 the current working directory.
19389 Moreover, the exact sequence of linker options may vary from platform
19391 The above @option{-largs} section is for Windows platforms. By contrast,
19392 under Unix there is no need for the @option{-largs} section.
19393 Differences across platforms are due to details of linker implementation.
19395 @node Tracebacks From Anywhere in a Program (symbolic)
19396 @subsubsection Tracebacks From Anywhere in a Program
19399 It is possible to get a symbolic stack traceback
19400 from anywhere in a program, just as for non-symbolic tracebacks.
19401 The first step is to obtain a non-symbolic
19402 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
19403 information. Here is an example:
19405 @smallexample @c ada
19407 with GNAT.Traceback;
19408 with GNAT.Traceback.Symbolic;
19413 use GNAT.Traceback;
19414 use GNAT.Traceback.Symbolic;
19417 TB : Tracebacks_Array (1 .. 10);
19418 -- We are asking for a maximum of 10 stack frames.
19420 -- Len will receive the actual number of stack frames returned.
19422 Call_Chain (TB, Len);
19423 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
19436 @c ******************************
19438 @node Compatibility with HP Ada
19439 @chapter Compatibility with HP Ada
19440 @cindex Compatibility
19445 @cindex Compatibility between GNAT and HP Ada
19446 This chapter compares HP Ada (formerly known as ``DEC Ada'')
19447 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
19448 GNAT is highly compatible
19449 with HP Ada, and it should generally be straightforward to port code
19450 from the HP Ada environment to GNAT. However, there are a few language
19451 and implementation differences of which the user must be aware. These
19452 differences are discussed in this chapter. In
19453 addition, the operating environment and command structure for the
19454 compiler are different, and these differences are also discussed.
19456 For further details on these and other compatibility issues,
19457 see Appendix E of the HP publication
19458 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
19460 Except where otherwise indicated, the description of GNAT for OpenVMS
19461 applies to both the Alpha and I64 platforms.
19463 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
19464 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
19466 The discussion in this chapter addresses specifically the implementation
19467 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
19468 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
19469 GNAT always follows the Alpha implementation.
19471 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
19472 attributes are recognized, although only a subset of them can sensibly
19473 be implemented. The description of pragmas in
19474 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
19475 indicates whether or not they are applicable to non-VMS systems.
19478 * Ada Language Compatibility::
19479 * Differences in the Definition of Package System::
19480 * Language-Related Features::
19481 * The Package STANDARD::
19482 * The Package SYSTEM::
19483 * Tasking and Task-Related Features::
19484 * Pragmas and Pragma-Related Features::
19485 * Library of Predefined Units::
19487 * Main Program Definition::
19488 * Implementation-Defined Attributes::
19489 * Compiler and Run-Time Interfacing::
19490 * Program Compilation and Library Management::
19492 * Implementation Limits::
19493 * Tools and Utilities::
19496 @node Ada Language Compatibility
19497 @section Ada Language Compatibility
19500 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
19501 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
19502 with Ada 83, and therefore Ada 83 programs will compile
19503 and run under GNAT with
19504 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
19505 provides details on specific incompatibilities.
19507 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
19508 as well as the pragma @code{ADA_83}, to force the compiler to
19509 operate in Ada 83 mode. This mode does not guarantee complete
19510 conformance to Ada 83, but in practice is sufficient to
19511 eliminate most sources of incompatibilities.
19512 In particular, it eliminates the recognition of the
19513 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
19514 in Ada 83 programs is legal, and handles the cases of packages
19515 with optional bodies, and generics that instantiate unconstrained
19516 types without the use of @code{(<>)}.
19518 @node Differences in the Definition of Package System
19519 @section Differences in the Definition of Package @code{System}
19522 An Ada compiler is allowed to add
19523 implementation-dependent declarations to package @code{System}.
19525 GNAT does not take advantage of this permission, and the version of
19526 @code{System} provided by GNAT exactly matches that defined in the Ada
19529 However, HP Ada adds an extensive set of declarations to package
19531 as fully documented in the HP Ada manuals. To minimize changes required
19532 for programs that make use of these extensions, GNAT provides the pragma
19533 @code{Extend_System} for extending the definition of package System. By using:
19534 @cindex pragma @code{Extend_System}
19535 @cindex @code{Extend_System} pragma
19537 @smallexample @c ada
19540 pragma Extend_System (Aux_DEC);
19546 the set of definitions in @code{System} is extended to include those in
19547 package @code{System.Aux_DEC}.
19548 @cindex @code{System.Aux_DEC} package
19549 @cindex @code{Aux_DEC} package (child of @code{System})
19550 These definitions are incorporated directly into package @code{System},
19551 as though they had been declared there. For a
19552 list of the declarations added, see the spec of this package,
19553 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
19554 @cindex @file{s-auxdec.ads} file
19555 The pragma @code{Extend_System} is a configuration pragma, which means that
19556 it can be placed in the file @file{gnat.adc}, so that it will automatically
19557 apply to all subsequent compilations. See @ref{Configuration Pragmas},
19558 for further details.
19560 An alternative approach that avoids the use of the non-standard
19561 @code{Extend_System} pragma is to add a context clause to the unit that
19562 references these facilities:
19564 @smallexample @c ada
19566 with System.Aux_DEC;
19567 use System.Aux_DEC;
19572 The effect is not quite semantically identical to incorporating
19573 the declarations directly into package @code{System},
19574 but most programs will not notice a difference
19575 unless they use prefix notation (e.g.@: @code{System.Integer_8})
19576 to reference the entities directly in package @code{System}.
19577 For units containing such references,
19578 the prefixes must either be removed, or the pragma @code{Extend_System}
19581 @node Language-Related Features
19582 @section Language-Related Features
19585 The following sections highlight differences in types,
19586 representations of types, operations, alignment, and
19590 * Integer Types and Representations::
19591 * Floating-Point Types and Representations::
19592 * Pragmas Float_Representation and Long_Float::
19593 * Fixed-Point Types and Representations::
19594 * Record and Array Component Alignment::
19595 * Address Clauses::
19596 * Other Representation Clauses::
19599 @node Integer Types and Representations
19600 @subsection Integer Types and Representations
19603 The set of predefined integer types is identical in HP Ada and GNAT.
19604 Furthermore the representation of these integer types is also identical,
19605 including the capability of size clauses forcing biased representation.
19608 HP Ada for OpenVMS Alpha systems has defined the
19609 following additional integer types in package @code{System}:
19626 @code{LARGEST_INTEGER}
19630 In GNAT, the first four of these types may be obtained from the
19631 standard Ada package @code{Interfaces}.
19632 Alternatively, by use of the pragma @code{Extend_System}, identical
19633 declarations can be referenced directly in package @code{System}.
19634 On both GNAT and HP Ada, the maximum integer size is 64 bits.
19636 @node Floating-Point Types and Representations
19637 @subsection Floating-Point Types and Representations
19638 @cindex Floating-Point types
19641 The set of predefined floating-point types is identical in HP Ada and GNAT.
19642 Furthermore the representation of these floating-point
19643 types is also identical. One important difference is that the default
19644 representation for HP Ada is @code{VAX_Float}, but the default representation
19647 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
19648 pragma @code{Float_Representation} as described in the HP Ada
19650 For example, the declarations:
19652 @smallexample @c ada
19654 type F_Float is digits 6;
19655 pragma Float_Representation (VAX_Float, F_Float);
19660 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
19662 This set of declarations actually appears in @code{System.Aux_DEC},
19664 the full set of additional floating-point declarations provided in
19665 the HP Ada version of package @code{System}.
19666 This and similar declarations may be accessed in a user program
19667 by using pragma @code{Extend_System}. The use of this
19668 pragma, and the related pragma @code{Long_Float} is described in further
19669 detail in the following section.
19671 @node Pragmas Float_Representation and Long_Float
19672 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
19675 HP Ada provides the pragma @code{Float_Representation}, which
19676 acts as a program library switch to allow control over
19677 the internal representation chosen for the predefined
19678 floating-point types declared in the package @code{Standard}.
19679 The format of this pragma is as follows:
19681 @smallexample @c ada
19683 pragma Float_Representation(VAX_Float | IEEE_Float);
19688 This pragma controls the representation of floating-point
19693 @code{VAX_Float} specifies that floating-point
19694 types are represented by default with the VAX system hardware types
19695 @code{F-floating}, @code{D-floating}, @code{G-floating}.
19696 Note that the @code{H-floating}
19697 type was available only on VAX systems, and is not available
19698 in either HP Ada or GNAT.
19701 @code{IEEE_Float} specifies that floating-point
19702 types are represented by default with the IEEE single and
19703 double floating-point types.
19707 GNAT provides an identical implementation of the pragma
19708 @code{Float_Representation}, except that it functions as a
19709 configuration pragma. Note that the
19710 notion of configuration pragma corresponds closely to the
19711 HP Ada notion of a program library switch.
19713 When no pragma is used in GNAT, the default is @code{IEEE_Float},
19715 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
19716 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
19717 advisable to change the format of numbers passed to standard library
19718 routines, and if necessary explicit type conversions may be needed.
19720 The use of @code{IEEE_Float} is recommended in GNAT since it is more
19721 efficient, and (given that it conforms to an international standard)
19722 potentially more portable.
19723 The situation in which @code{VAX_Float} may be useful is in interfacing
19724 to existing code and data that expect the use of @code{VAX_Float}.
19725 In such a situation use the predefined @code{VAX_Float}
19726 types in package @code{System}, as extended by
19727 @code{Extend_System}. For example, use @code{System.F_Float}
19728 to specify the 32-bit @code{F-Float} format.
19731 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
19732 to allow control over the internal representation chosen
19733 for the predefined type @code{Long_Float} and for floating-point
19734 type declarations with digits specified in the range 7 .. 15.
19735 The format of this pragma is as follows:
19737 @smallexample @c ada
19739 pragma Long_Float (D_FLOAT | G_FLOAT);
19743 @node Fixed-Point Types and Representations
19744 @subsection Fixed-Point Types and Representations
19747 On HP Ada for OpenVMS Alpha systems, rounding is
19748 away from zero for both positive and negative numbers.
19749 Therefore, @code{+0.5} rounds to @code{1},
19750 and @code{-0.5} rounds to @code{-1}.
19752 On GNAT the results of operations
19753 on fixed-point types are in accordance with the Ada
19754 rules. In particular, results of operations on decimal
19755 fixed-point types are truncated.
19757 @node Record and Array Component Alignment
19758 @subsection Record and Array Component Alignment
19761 On HP Ada for OpenVMS Alpha, all non-composite components
19762 are aligned on natural boundaries. For example, 1-byte
19763 components are aligned on byte boundaries, 2-byte
19764 components on 2-byte boundaries, 4-byte components on 4-byte
19765 byte boundaries, and so on. The OpenVMS Alpha hardware
19766 runs more efficiently with naturally aligned data.
19768 On GNAT, alignment rules are compatible
19769 with HP Ada for OpenVMS Alpha.
19771 @node Address Clauses
19772 @subsection Address Clauses
19775 In HP Ada and GNAT, address clauses are supported for
19776 objects and imported subprograms.
19777 The predefined type @code{System.Address} is a private type
19778 in both compilers on Alpha OpenVMS, with the same representation
19779 (it is simply a machine pointer). Addition, subtraction, and comparison
19780 operations are available in the standard Ada package
19781 @code{System.Storage_Elements}, or in package @code{System}
19782 if it is extended to include @code{System.Aux_DEC} using a
19783 pragma @code{Extend_System} as previously described.
19785 Note that code that @code{with}'s both this extended package @code{System}
19786 and the package @code{System.Storage_Elements} should not @code{use}
19787 both packages, or ambiguities will result. In general it is better
19788 not to mix these two sets of facilities. The Ada package was
19789 designed specifically to provide the kind of features that HP Ada
19790 adds directly to package @code{System}.
19792 The type @code{System.Address} is a 64-bit integer type in GNAT for
19793 I64 OpenVMS. For more information,
19794 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
19796 GNAT is compatible with HP Ada in its handling of address
19797 clauses, except for some limitations in
19798 the form of address clauses for composite objects with
19799 initialization. Such address clauses are easily replaced
19800 by the use of an explicitly-defined constant as described
19801 in the Ada Reference Manual (13.1(22)). For example, the sequence
19804 @smallexample @c ada
19806 X, Y : Integer := Init_Func;
19807 Q : String (X .. Y) := "abc";
19809 for Q'Address use Compute_Address;
19814 will be rejected by GNAT, since the address cannot be computed at the time
19815 that @code{Q} is declared. To achieve the intended effect, write instead:
19817 @smallexample @c ada
19820 X, Y : Integer := Init_Func;
19821 Q_Address : constant Address := Compute_Address;
19822 Q : String (X .. Y) := "abc";
19824 for Q'Address use Q_Address;
19830 which will be accepted by GNAT (and other Ada compilers), and is also
19831 compatible with Ada 83. A fuller description of the restrictions
19832 on address specifications is found in @ref{Top, GNAT Reference Manual,
19833 About This Guide, gnat_rm, GNAT Reference Manual}.
19835 @node Other Representation Clauses
19836 @subsection Other Representation Clauses
19839 GNAT implements in a compatible manner all the representation
19840 clauses supported by HP Ada. In addition, GNAT
19841 implements the representation clause forms that were introduced in Ada 95,
19842 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
19844 @node The Package STANDARD
19845 @section The Package @code{STANDARD}
19848 The package @code{STANDARD}, as implemented by HP Ada, is fully
19849 described in the @cite{Ada Reference Manual} and in the
19850 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
19851 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
19853 In addition, HP Ada supports the Latin-1 character set in
19854 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
19855 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
19856 the type @code{WIDE_CHARACTER}.
19858 The floating-point types supported by GNAT are those
19859 supported by HP Ada, but the defaults are different, and are controlled by
19860 pragmas. See @ref{Floating-Point Types and Representations}, for details.
19862 @node The Package SYSTEM
19863 @section The Package @code{SYSTEM}
19866 HP Ada provides a specific version of the package
19867 @code{SYSTEM} for each platform on which the language is implemented.
19868 For the complete spec of the package @code{SYSTEM}, see
19869 Appendix F of the @cite{HP Ada Language Reference Manual}.
19871 On HP Ada, the package @code{SYSTEM} includes the following conversion
19874 @item @code{TO_ADDRESS(INTEGER)}
19876 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
19878 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
19880 @item @code{TO_INTEGER(ADDRESS)}
19882 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
19884 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
19885 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
19889 By default, GNAT supplies a version of @code{SYSTEM} that matches
19890 the definition given in the @cite{Ada Reference Manual}.
19892 is a subset of the HP system definitions, which is as
19893 close as possible to the original definitions. The only difference
19894 is that the definition of @code{SYSTEM_NAME} is different:
19896 @smallexample @c ada
19898 type Name is (SYSTEM_NAME_GNAT);
19899 System_Name : constant Name := SYSTEM_NAME_GNAT;
19904 Also, GNAT adds the Ada declarations for
19905 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
19907 However, the use of the following pragma causes GNAT
19908 to extend the definition of package @code{SYSTEM} so that it
19909 encompasses the full set of HP-specific extensions,
19910 including the functions listed above:
19912 @smallexample @c ada
19914 pragma Extend_System (Aux_DEC);
19919 The pragma @code{Extend_System} is a configuration pragma that
19920 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
19921 Extend_System,,, gnat_rm, GNAT Reference Manual}, for further details.
19923 HP Ada does not allow the recompilation of the package
19924 @code{SYSTEM}. Instead HP Ada provides several pragmas
19925 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
19926 to modify values in the package @code{SYSTEM}.
19927 On OpenVMS Alpha systems, the pragma
19928 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
19929 its single argument.
19931 GNAT does permit the recompilation of package @code{SYSTEM} using
19932 the special switch @option{-gnatg}, and this switch can be used if
19933 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
19934 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
19935 or @code{MEMORY_SIZE} by any other means.
19937 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
19938 enumeration literal @code{SYSTEM_NAME_GNAT}.
19940 The definitions provided by the use of
19942 @smallexample @c ada
19943 pragma Extend_System (AUX_Dec);
19947 are virtually identical to those provided by the HP Ada 83 package
19948 @code{SYSTEM}. One important difference is that the name of the
19950 function for type @code{UNSIGNED_LONGWORD} is changed to
19951 @code{TO_ADDRESS_LONG}.
19952 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual}, for a
19953 discussion of why this change was necessary.
19956 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
19958 an extension to Ada 83 not strictly compatible with the reference manual.
19959 GNAT, in order to be exactly compatible with the standard,
19960 does not provide this capability. In HP Ada 83, the
19961 point of this definition is to deal with a call like:
19963 @smallexample @c ada
19964 TO_ADDRESS (16#12777#);
19968 Normally, according to Ada 83 semantics, one would expect this to be
19969 ambiguous, since it matches both the @code{INTEGER} and
19970 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
19971 However, in HP Ada 83, there is no ambiguity, since the
19972 definition using @i{universal_integer} takes precedence.
19974 In GNAT, since the version with @i{universal_integer} cannot be supplied,
19976 not possible to be 100% compatible. Since there are many programs using
19977 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
19979 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
19980 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
19982 @smallexample @c ada
19983 function To_Address (X : Integer) return Address;
19984 pragma Pure_Function (To_Address);
19986 function To_Address_Long (X : Unsigned_Longword) return Address;
19987 pragma Pure_Function (To_Address_Long);
19991 This means that programs using @code{TO_ADDRESS} for
19992 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
19994 @node Tasking and Task-Related Features
19995 @section Tasking and Task-Related Features
19998 This section compares the treatment of tasking in GNAT
19999 and in HP Ada for OpenVMS Alpha.
20000 The GNAT description applies to both Alpha and I64 OpenVMS.
20001 For detailed information on tasking in
20002 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
20003 relevant run-time reference manual.
20006 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
20007 * Assigning Task IDs::
20008 * Task IDs and Delays::
20009 * Task-Related Pragmas::
20010 * Scheduling and Task Priority::
20012 * External Interrupts::
20015 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
20016 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
20019 On OpenVMS Alpha systems, each Ada task (except a passive
20020 task) is implemented as a single stream of execution
20021 that is created and managed by the kernel. On these
20022 systems, HP Ada tasking support is based on DECthreads,
20023 an implementation of the POSIX standard for threads.
20025 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
20026 code that calls DECthreads routines can be used together.
20027 The interaction between Ada tasks and DECthreads routines
20028 can have some benefits. For example when on OpenVMS Alpha,
20029 HP Ada can call C code that is already threaded.
20031 GNAT uses the facilities of DECthreads,
20032 and Ada tasks are mapped to threads.
20034 @node Assigning Task IDs
20035 @subsection Assigning Task IDs
20038 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
20039 the environment task that executes the main program. On
20040 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
20041 that have been created but are not yet activated.
20043 On OpenVMS Alpha systems, task IDs are assigned at
20044 activation. On GNAT systems, task IDs are also assigned at
20045 task creation but do not have the same form or values as
20046 task ID values in HP Ada. There is no null task, and the
20047 environment task does not have a specific task ID value.
20049 @node Task IDs and Delays
20050 @subsection Task IDs and Delays
20053 On OpenVMS Alpha systems, tasking delays are implemented
20054 using Timer System Services. The Task ID is used for the
20055 identification of the timer request (the @code{REQIDT} parameter).
20056 If Timers are used in the application take care not to use
20057 @code{0} for the identification, because cancelling such a timer
20058 will cancel all timers and may lead to unpredictable results.
20060 @node Task-Related Pragmas
20061 @subsection Task-Related Pragmas
20064 Ada supplies the pragma @code{TASK_STORAGE}, which allows
20065 specification of the size of the guard area for a task
20066 stack. (The guard area forms an area of memory that has no
20067 read or write access and thus helps in the detection of
20068 stack overflow.) On OpenVMS Alpha systems, if the pragma
20069 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
20070 area is created. In the absence of a pragma @code{TASK_STORAGE},
20071 a default guard area is created.
20073 GNAT supplies the following task-related pragmas:
20076 @item @code{TASK_INFO}
20078 This pragma appears within a task definition and
20079 applies to the task in which it appears. The argument
20080 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
20082 @item @code{TASK_STORAGE}
20084 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
20085 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
20086 @code{SUPPRESS}, and @code{VOLATILE}.
20088 @node Scheduling and Task Priority
20089 @subsection Scheduling and Task Priority
20092 HP Ada implements the Ada language requirement that
20093 when two tasks are eligible for execution and they have
20094 different priorities, the lower priority task does not
20095 execute while the higher priority task is waiting. The HP
20096 Ada Run-Time Library keeps a task running until either the
20097 task is suspended or a higher priority task becomes ready.
20099 On OpenVMS Alpha systems, the default strategy is round-
20100 robin with preemption. Tasks of equal priority take turns
20101 at the processor. A task is run for a certain period of
20102 time and then placed at the tail of the ready queue for
20103 its priority level.
20105 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
20106 which can be used to enable or disable round-robin
20107 scheduling of tasks with the same priority.
20108 See the relevant HP Ada run-time reference manual for
20109 information on using the pragmas to control HP Ada task
20112 GNAT follows the scheduling rules of Annex D (Real-Time
20113 Annex) of the @cite{Ada Reference Manual}. In general, this
20114 scheduling strategy is fully compatible with HP Ada
20115 although it provides some additional constraints (as
20116 fully documented in Annex D).
20117 GNAT implements time slicing control in a manner compatible with
20118 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
20119 are identical to the HP Ada 83 pragma of the same name.
20120 Note that it is not possible to mix GNAT tasking and
20121 HP Ada 83 tasking in the same program, since the two run-time
20122 libraries are not compatible.
20124 @node The Task Stack
20125 @subsection The Task Stack
20128 In HP Ada, a task stack is allocated each time a
20129 non-passive task is activated. As soon as the task is
20130 terminated, the storage for the task stack is deallocated.
20131 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
20132 a default stack size is used. Also, regardless of the size
20133 specified, some additional space is allocated for task
20134 management purposes. On OpenVMS Alpha systems, at least
20135 one page is allocated.
20137 GNAT handles task stacks in a similar manner. In accordance with
20138 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
20139 an alternative method for controlling the task stack size.
20140 The specification of the attribute @code{T'STORAGE_SIZE} is also
20141 supported in a manner compatible with HP Ada.
20143 @node External Interrupts
20144 @subsection External Interrupts
20147 On HP Ada, external interrupts can be associated with task entries.
20148 GNAT is compatible with HP Ada in its handling of external interrupts.
20150 @node Pragmas and Pragma-Related Features
20151 @section Pragmas and Pragma-Related Features
20154 Both HP Ada and GNAT supply all language-defined pragmas
20155 as specified by the Ada 83 standard. GNAT also supplies all
20156 language-defined pragmas introduced by Ada 95 and Ada 2005.
20157 In addition, GNAT implements the implementation-defined pragmas
20161 @item @code{AST_ENTRY}
20163 @item @code{COMMON_OBJECT}
20165 @item @code{COMPONENT_ALIGNMENT}
20167 @item @code{EXPORT_EXCEPTION}
20169 @item @code{EXPORT_FUNCTION}
20171 @item @code{EXPORT_OBJECT}
20173 @item @code{EXPORT_PROCEDURE}
20175 @item @code{EXPORT_VALUED_PROCEDURE}
20177 @item @code{FLOAT_REPRESENTATION}
20181 @item @code{IMPORT_EXCEPTION}
20183 @item @code{IMPORT_FUNCTION}
20185 @item @code{IMPORT_OBJECT}
20187 @item @code{IMPORT_PROCEDURE}
20189 @item @code{IMPORT_VALUED_PROCEDURE}
20191 @item @code{INLINE_GENERIC}
20193 @item @code{INTERFACE_NAME}
20195 @item @code{LONG_FLOAT}
20197 @item @code{MAIN_STORAGE}
20199 @item @code{PASSIVE}
20201 @item @code{PSECT_OBJECT}
20203 @item @code{SHARE_GENERIC}
20205 @item @code{SUPPRESS_ALL}
20207 @item @code{TASK_STORAGE}
20209 @item @code{TIME_SLICE}
20215 These pragmas are all fully implemented, with the exception of @code{TITLE},
20216 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
20217 recognized, but which have no
20218 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
20219 use of Ada protected objects. In GNAT, all generics are inlined.
20221 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
20222 a separate subprogram specification which must appear before the
20225 GNAT also supplies a number of implementation-defined pragmas including the
20229 @item @code{ABORT_DEFER}
20231 @item @code{ADA_83}
20233 @item @code{ADA_95}
20235 @item @code{ADA_05}
20237 @item @code{Ada_2005}
20239 @item @code{Ada_12}
20241 @item @code{Ada_2012}
20243 @item @code{ANNOTATE}
20245 @item @code{ASSERT}
20247 @item @code{C_PASS_BY_COPY}
20249 @item @code{CPP_CLASS}
20251 @item @code{CPP_CONSTRUCTOR}
20253 @item @code{CPP_DESTRUCTOR}
20257 @item @code{EXTEND_SYSTEM}
20259 @item @code{LINKER_ALIAS}
20261 @item @code{LINKER_SECTION}
20263 @item @code{MACHINE_ATTRIBUTE}
20265 @item @code{NO_RETURN}
20267 @item @code{PURE_FUNCTION}
20269 @item @code{SOURCE_FILE_NAME}
20271 @item @code{SOURCE_REFERENCE}
20273 @item @code{TASK_INFO}
20275 @item @code{UNCHECKED_UNION}
20277 @item @code{UNIMPLEMENTED_UNIT}
20279 @item @code{UNIVERSAL_DATA}
20281 @item @code{UNSUPPRESS}
20283 @item @code{WARNINGS}
20285 @item @code{WEAK_EXTERNAL}
20289 For full details on these and other GNAT implementation-defined pragmas,
20290 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
20294 * Restrictions on the Pragma INLINE::
20295 * Restrictions on the Pragma INTERFACE::
20296 * Restrictions on the Pragma SYSTEM_NAME::
20299 @node Restrictions on the Pragma INLINE
20300 @subsection Restrictions on Pragma @code{INLINE}
20303 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
20305 @item Parameters cannot have a task type.
20307 @item Function results cannot be task types, unconstrained
20308 array types, or unconstrained types with discriminants.
20310 @item Bodies cannot declare the following:
20312 @item Subprogram body or stub (imported subprogram is allowed)
20316 @item Generic declarations
20318 @item Instantiations
20322 @item Access types (types derived from access types allowed)
20324 @item Array or record types
20326 @item Dependent tasks
20328 @item Direct recursive calls of subprogram or containing
20329 subprogram, directly or via a renaming
20335 In GNAT, the only restriction on pragma @code{INLINE} is that the
20336 body must occur before the call if both are in the same
20337 unit, and the size must be appropriately small. There are
20338 no other specific restrictions which cause subprograms to
20339 be incapable of being inlined.
20341 @node Restrictions on the Pragma INTERFACE
20342 @subsection Restrictions on Pragma @code{INTERFACE}
20345 The following restrictions on pragma @code{INTERFACE}
20346 are enforced by both HP Ada and GNAT:
20348 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
20349 Default is the default on OpenVMS Alpha systems.
20351 @item Parameter passing: Language specifies default
20352 mechanisms but can be overridden with an @code{EXPORT} pragma.
20355 @item Ada: Use internal Ada rules.
20357 @item Bliss, C: Parameters must be mode @code{in}; cannot be
20358 record or task type. Result cannot be a string, an
20359 array, or a record.
20361 @item Fortran: Parameters cannot have a task type. Result cannot
20362 be a string, an array, or a record.
20367 GNAT is entirely upwards compatible with HP Ada, and in addition allows
20368 record parameters for all languages.
20370 @node Restrictions on the Pragma SYSTEM_NAME
20371 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
20374 For HP Ada for OpenVMS Alpha, the enumeration literal
20375 for the type @code{NAME} is @code{OPENVMS_AXP}.
20376 In GNAT, the enumeration
20377 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
20379 @node Library of Predefined Units
20380 @section Library of Predefined Units
20383 A library of predefined units is provided as part of the
20384 HP Ada and GNAT implementations. HP Ada does not provide
20385 the package @code{MACHINE_CODE} but instead recommends importing
20388 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
20389 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
20391 The HP Ada Predefined Library units are modified to remove post-Ada 83
20392 incompatibilities and to make them interoperable with GNAT
20393 (@pxref{Changes to DECLIB}, for details).
20394 The units are located in the @file{DECLIB} directory.
20396 The GNAT RTL is contained in
20397 the @file{ADALIB} directory, and
20398 the default search path is set up to find @code{DECLIB} units in preference
20399 to @code{ADALIB} units with the same name (@code{TEXT_IO},
20400 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
20403 * Changes to DECLIB::
20406 @node Changes to DECLIB
20407 @subsection Changes to @code{DECLIB}
20410 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
20411 compatibility are minor and include the following:
20414 @item Adjusting the location of pragmas and record representation
20415 clauses to obey Ada 95 (and thus Ada 2005) rules
20417 @item Adding the proper notation to generic formal parameters
20418 that take unconstrained types in instantiation
20420 @item Adding pragma @code{ELABORATE_BODY} to package specs
20421 that have package bodies not otherwise allowed
20423 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
20424 ``@code{PROTECTD}''.
20425 Currently these are found only in the @code{STARLET} package spec.
20427 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
20428 where the address size is constrained to 32 bits.
20432 None of the above changes is visible to users.
20438 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
20441 @item Command Language Interpreter (CLI interface)
20443 @item DECtalk Run-Time Library (DTK interface)
20445 @item Librarian utility routines (LBR interface)
20447 @item General Purpose Run-Time Library (LIB interface)
20449 @item Math Run-Time Library (MTH interface)
20451 @item National Character Set Run-Time Library (NCS interface)
20453 @item Compiled Code Support Run-Time Library (OTS interface)
20455 @item Parallel Processing Run-Time Library (PPL interface)
20457 @item Screen Management Run-Time Library (SMG interface)
20459 @item Sort Run-Time Library (SOR interface)
20461 @item String Run-Time Library (STR interface)
20463 @item STARLET System Library
20466 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
20468 @item X Windows Toolkit (XT interface)
20470 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
20474 GNAT provides implementations of these HP bindings in the @code{DECLIB}
20475 directory, on both the Alpha and I64 OpenVMS platforms.
20477 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
20479 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
20480 A pragma @code{Linker_Options} has been added to packages @code{Xm},
20481 @code{Xt}, and @code{X_Lib}
20482 causing the default X/Motif sharable image libraries to be linked in. This
20483 is done via options files named @file{xm.opt}, @file{xt.opt}, and
20484 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
20486 It may be necessary to edit these options files to update or correct the
20487 library names if, for example, the newer X/Motif bindings from
20488 @file{ADA$EXAMPLES}
20489 had been (previous to installing GNAT) copied and renamed to supersede the
20490 default @file{ADA$PREDEFINED} versions.
20493 * Shared Libraries and Options Files::
20494 * Interfaces to C::
20497 @node Shared Libraries and Options Files
20498 @subsection Shared Libraries and Options Files
20501 When using the HP Ada
20502 predefined X and Motif bindings, the linking with their sharable images is
20503 done automatically by @command{GNAT LINK}.
20504 When using other X and Motif bindings, you need
20505 to add the corresponding sharable images to the command line for
20506 @code{GNAT LINK}. When linking with shared libraries, or with
20507 @file{.OPT} files, you must
20508 also add them to the command line for @command{GNAT LINK}.
20510 A shared library to be used with GNAT is built in the same way as other
20511 libraries under VMS. The VMS Link command can be used in standard fashion.
20513 @node Interfaces to C
20514 @subsection Interfaces to C
20518 provides the following Ada types and operations:
20521 @item C types package (@code{C_TYPES})
20523 @item C strings (@code{C_TYPES.NULL_TERMINATED})
20525 @item Other_types (@code{SHORT_INT})
20529 Interfacing to C with GNAT, you can use the above approach
20530 described for HP Ada or the facilities of Annex B of
20531 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
20532 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
20533 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
20535 The @option{-gnatF} qualifier forces default and explicit
20536 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
20537 to be uppercased for compatibility with the default behavior
20538 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
20540 @node Main Program Definition
20541 @section Main Program Definition
20544 The following section discusses differences in the
20545 definition of main programs on HP Ada and GNAT.
20546 On HP Ada, main programs are defined to meet the
20547 following conditions:
20549 @item Procedure with no formal parameters (returns @code{0} upon
20552 @item Procedure with no formal parameters (returns @code{42} when
20553 an unhandled exception is raised)
20555 @item Function with no formal parameters whose returned value
20556 is of a discrete type
20558 @item Procedure with one @code{out} formal of a discrete type for
20559 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
20564 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
20565 a main function or main procedure returns a discrete
20566 value whose size is less than 64 bits (32 on VAX systems),
20567 the value is zero- or sign-extended as appropriate.
20568 On GNAT, main programs are defined as follows:
20570 @item Must be a non-generic, parameterless subprogram that
20571 is either a procedure or function returning an Ada
20572 @code{STANDARD.INTEGER} (the predefined type)
20574 @item Cannot be a generic subprogram or an instantiation of a
20578 @node Implementation-Defined Attributes
20579 @section Implementation-Defined Attributes
20582 GNAT provides all HP Ada implementation-defined
20585 @node Compiler and Run-Time Interfacing
20586 @section Compiler and Run-Time Interfacing
20589 HP Ada provides the following qualifiers to pass options to the linker
20592 @item @option{/WAIT} and @option{/SUBMIT}
20594 @item @option{/COMMAND}
20596 @item @option{/@r{[}NO@r{]}MAP}
20598 @item @option{/OUTPUT=@var{file-spec}}
20600 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
20604 To pass options to the linker, GNAT provides the following
20608 @item @option{/EXECUTABLE=@var{exec-name}}
20610 @item @option{/VERBOSE}
20612 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
20616 For more information on these switches, see
20617 @ref{Switches for gnatlink}.
20618 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
20619 to control optimization. HP Ada also supplies the
20622 @item @code{OPTIMIZE}
20624 @item @code{INLINE}
20626 @item @code{INLINE_GENERIC}
20628 @item @code{SUPPRESS_ALL}
20630 @item @code{PASSIVE}
20634 In GNAT, optimization is controlled strictly by command
20635 line parameters, as described in the corresponding section of this guide.
20636 The HP pragmas for control of optimization are
20637 recognized but ignored.
20639 Note that in GNAT, the default is optimization off, whereas in HP Ada
20640 the default is that optimization is turned on.
20642 @node Program Compilation and Library Management
20643 @section Program Compilation and Library Management
20646 HP Ada and GNAT provide a comparable set of commands to
20647 build programs. HP Ada also provides a program library,
20648 which is a concept that does not exist on GNAT. Instead,
20649 GNAT provides directories of sources that are compiled as
20652 The following table summarizes
20653 the HP Ada commands and provides
20654 equivalent GNAT commands. In this table, some GNAT
20655 equivalents reflect the fact that GNAT does not use the
20656 concept of a program library. Instead, it uses a model
20657 in which collections of source and object files are used
20658 in a manner consistent with other languages like C and
20659 Fortran. Therefore, standard system file commands are used
20660 to manipulate these elements. Those GNAT commands are marked with
20662 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
20665 @multitable @columnfractions .35 .65
20667 @item @emph{HP Ada Command}
20668 @tab @emph{GNAT Equivalent / Description}
20670 @item @command{ADA}
20671 @tab @command{GNAT COMPILE}@*
20672 Invokes the compiler to compile one or more Ada source files.
20674 @item @command{ACS ATTACH}@*
20675 @tab [No equivalent]@*
20676 Switches control of terminal from current process running the program
20679 @item @command{ACS CHECK}
20680 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
20681 Forms the execution closure of one
20682 or more compiled units and checks completeness and currency.
20684 @item @command{ACS COMPILE}
20685 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
20686 Forms the execution closure of one or
20687 more specified units, checks completeness and currency,
20688 identifies units that have revised source files, compiles same,
20689 and recompiles units that are or will become obsolete.
20690 Also completes incomplete generic instantiations.
20692 @item @command{ACS COPY FOREIGN}
20694 Copies a foreign object file into the program library as a
20697 @item @command{ACS COPY UNIT}
20699 Copies a compiled unit from one program library to another.
20701 @item @command{ACS CREATE LIBRARY}
20702 @tab Create /directory (*)@*
20703 Creates a program library.
20705 @item @command{ACS CREATE SUBLIBRARY}
20706 @tab Create /directory (*)@*
20707 Creates a program sublibrary.
20709 @item @command{ACS DELETE LIBRARY}
20711 Deletes a program library and its contents.
20713 @item @command{ACS DELETE SUBLIBRARY}
20715 Deletes a program sublibrary and its contents.
20717 @item @command{ACS DELETE UNIT}
20718 @tab Delete file (*)@*
20719 On OpenVMS systems, deletes one or more compiled units from
20720 the current program library.
20722 @item @command{ACS DIRECTORY}
20723 @tab Directory (*)@*
20724 On OpenVMS systems, lists units contained in the current
20727 @item @command{ACS ENTER FOREIGN}
20729 Allows the import of a foreign body as an Ada library
20730 spec and enters a reference to a pointer.
20732 @item @command{ACS ENTER UNIT}
20734 Enters a reference (pointer) from the current program library to
20735 a unit compiled into another program library.
20737 @item @command{ACS EXIT}
20738 @tab [No equivalent]@*
20739 Exits from the program library manager.
20741 @item @command{ACS EXPORT}
20743 Creates an object file that contains system-specific object code
20744 for one or more units. With GNAT, object files can simply be copied
20745 into the desired directory.
20747 @item @command{ACS EXTRACT SOURCE}
20749 Allows access to the copied source file for each Ada compilation unit
20751 @item @command{ACS HELP}
20752 @tab @command{HELP GNAT}@*
20753 Provides online help.
20755 @item @command{ACS LINK}
20756 @tab @command{GNAT LINK}@*
20757 Links an object file containing Ada units into an executable file.
20759 @item @command{ACS LOAD}
20761 Loads (partially compiles) Ada units into the program library.
20762 Allows loading a program from a collection of files into a library
20763 without knowing the relationship among units.
20765 @item @command{ACS MERGE}
20767 Merges into the current program library, one or more units from
20768 another library where they were modified.
20770 @item @command{ACS RECOMPILE}
20771 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
20772 Recompiles from external or copied source files any obsolete
20773 unit in the closure. Also, completes any incomplete generic
20776 @item @command{ACS REENTER}
20777 @tab @command{GNAT MAKE}@*
20778 Reenters current references to units compiled after last entered
20779 with the @command{ACS ENTER UNIT} command.
20781 @item @command{ACS SET LIBRARY}
20782 @tab Set default (*)@*
20783 Defines a program library to be the compilation context as well
20784 as the target library for compiler output and commands in general.
20786 @item @command{ACS SET PRAGMA}
20787 @tab Edit @file{gnat.adc} (*)@*
20788 Redefines specified values of the library characteristics
20789 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
20790 and @code{Float_Representation}.
20792 @item @command{ACS SET SOURCE}
20793 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
20794 Defines the source file search list for the @command{ACS COMPILE} command.
20796 @item @command{ACS SHOW LIBRARY}
20797 @tab Directory (*)@*
20798 Lists information about one or more program libraries.
20800 @item @command{ACS SHOW PROGRAM}
20801 @tab [No equivalent]@*
20802 Lists information about the execution closure of one or
20803 more units in the program library.
20805 @item @command{ACS SHOW SOURCE}
20806 @tab Show logical @code{ADA_INCLUDE_PATH}@*
20807 Shows the source file search used when compiling units.
20809 @item @command{ACS SHOW VERSION}
20810 @tab Compile with @option{VERBOSE} option
20811 Displays the version number of the compiler and program library
20814 @item @command{ACS SPAWN}
20815 @tab [No equivalent]@*
20816 Creates a subprocess of the current process (same as @command{DCL SPAWN}
20819 @item @command{ACS VERIFY}
20820 @tab [No equivalent]@*
20821 Performs a series of consistency checks on a program library to
20822 determine whether the library structure and library files are in
20829 @section Input-Output
20832 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
20833 Management Services (RMS) to perform operations on
20837 HP Ada and GNAT predefine an identical set of input-
20838 output packages. To make the use of the
20839 generic @code{TEXT_IO} operations more convenient, HP Ada
20840 provides predefined library packages that instantiate the
20841 integer and floating-point operations for the predefined
20842 integer and floating-point types as shown in the following table.
20844 @multitable @columnfractions .45 .55
20845 @item @emph{Package Name} @tab Instantiation
20847 @item @code{INTEGER_TEXT_IO}
20848 @tab @code{INTEGER_IO(INTEGER)}
20850 @item @code{SHORT_INTEGER_TEXT_IO}
20851 @tab @code{INTEGER_IO(SHORT_INTEGER)}
20853 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
20854 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
20856 @item @code{FLOAT_TEXT_IO}
20857 @tab @code{FLOAT_IO(FLOAT)}
20859 @item @code{LONG_FLOAT_TEXT_IO}
20860 @tab @code{FLOAT_IO(LONG_FLOAT)}
20864 The HP Ada predefined packages and their operations
20865 are implemented using OpenVMS Alpha files and input-output
20866 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
20867 Familiarity with the following is recommended:
20869 @item RMS file organizations and access methods
20871 @item OpenVMS file specifications and directories
20873 @item OpenVMS File Definition Language (FDL)
20877 GNAT provides I/O facilities that are completely
20878 compatible with HP Ada. The distribution includes the
20879 standard HP Ada versions of all I/O packages, operating
20880 in a manner compatible with HP Ada. In particular, the
20881 following packages are by default the HP Ada (Ada 83)
20882 versions of these packages rather than the renamings
20883 suggested in Annex J of the Ada Reference Manual:
20885 @item @code{TEXT_IO}
20887 @item @code{SEQUENTIAL_IO}
20889 @item @code{DIRECT_IO}
20893 The use of the standard child package syntax (for
20894 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
20896 GNAT provides HP-compatible predefined instantiations
20897 of the @code{TEXT_IO} packages, and also
20898 provides the standard predefined instantiations required
20899 by the @cite{Ada Reference Manual}.
20901 For further information on how GNAT interfaces to the file
20902 system or how I/O is implemented in programs written in
20903 mixed languages, see @ref{Implementation of the Standard I/O,,,
20904 gnat_rm, GNAT Reference Manual}.
20905 This chapter covers the following:
20907 @item Standard I/O packages
20909 @item @code{FORM} strings
20911 @item @code{ADA.DIRECT_IO}
20913 @item @code{ADA.SEQUENTIAL_IO}
20915 @item @code{ADA.TEXT_IO}
20917 @item Stream pointer positioning
20919 @item Reading and writing non-regular files
20921 @item @code{GET_IMMEDIATE}
20923 @item Treating @code{TEXT_IO} files as streams
20930 @node Implementation Limits
20931 @section Implementation Limits
20934 The following table lists implementation limits for HP Ada
20936 @multitable @columnfractions .60 .20 .20
20938 @item @emph{Compilation Parameter}
20943 @item In a subprogram or entry declaration, maximum number of
20944 formal parameters that are of an unconstrained record type
20949 @item Maximum identifier length (number of characters)
20954 @item Maximum number of characters in a source line
20959 @item Maximum collection size (number of bytes)
20964 @item Maximum number of discriminants for a record type
20969 @item Maximum number of formal parameters in an entry or
20970 subprogram declaration
20975 @item Maximum number of dimensions in an array type
20980 @item Maximum number of library units and subunits in a compilation.
20985 @item Maximum number of library units and subunits in an execution.
20990 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
20991 or @code{PSECT_OBJECT}
20996 @item Maximum number of enumeration literals in an enumeration type
21002 @item Maximum number of lines in a source file
21007 @item Maximum number of bits in any object
21012 @item Maximum size of the static portion of a stack frame (approximate)
21017 @node Tools and Utilities
21018 @section Tools and Utilities
21021 The following table lists some of the OpenVMS development tools
21022 available for HP Ada, and the corresponding tools for
21023 use with @value{EDITION} on Alpha and I64 platforms.
21024 Aside from the debugger, all the OpenVMS tools identified are part
21025 of the DECset package.
21028 @c Specify table in TeX since Texinfo does a poor job
21032 \settabs\+Language-Sensitive Editor\quad
21033 &Product with HP Ada\quad
21036 &\it Product with HP Ada
21037 & \it Product with GNAT Pro\cr
21039 \+Code Management System
21043 \+Language-Sensitive Editor
21045 & emacs or HP LSE (Alpha)\cr
21055 & OpenVMS Debug (I64)\cr
21057 \+Source Code Analyzer /
21074 \+Coverage Analyzer
21078 \+Module Management
21080 & Not applicable\cr
21090 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
21091 @c the TeX version above for the printed version
21093 @c @multitable @columnfractions .3 .4 .4
21094 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
21096 @tab @i{Tool with HP Ada}
21097 @tab @i{Tool with @value{EDITION}}
21098 @item Code Management@*System
21101 @item Language-Sensitive@*Editor
21103 @tab emacs or HP LSE (Alpha)
21112 @tab OpenVMS Debug (I64)
21113 @item Source Code Analyzer /@*Cross Referencer
21117 @tab HP Digital Test@*Manager (DTM)
21119 @item Performance and@*Coverage Analyzer
21122 @item Module Management@*System
21124 @tab Not applicable
21131 @c **************************************
21132 @node Platform-Specific Information for the Run-Time Libraries
21133 @appendix Platform-Specific Information for the Run-Time Libraries
21134 @cindex Tasking and threads libraries
21135 @cindex Threads libraries and tasking
21136 @cindex Run-time libraries (platform-specific information)
21139 The GNAT run-time implementation may vary with respect to both the
21140 underlying threads library and the exception handling scheme.
21141 For threads support, one or more of the following are supplied:
21143 @item @b{native threads library}, a binding to the thread package from
21144 the underlying operating system
21146 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
21147 POSIX thread package
21151 For exception handling, either or both of two models are supplied:
21153 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
21154 Most programs should experience a substantial speed improvement by
21155 being compiled with a ZCX run-time.
21156 This is especially true for
21157 tasking applications or applications with many exception handlers.}
21158 @cindex Zero-Cost Exceptions
21159 @cindex ZCX (Zero-Cost Exceptions)
21160 which uses binder-generated tables that
21161 are interrogated at run time to locate a handler
21163 @item @b{setjmp / longjmp} (``SJLJ''),
21164 @cindex setjmp/longjmp Exception Model
21165 @cindex SJLJ (setjmp/longjmp Exception Model)
21166 which uses dynamically-set data to establish
21167 the set of handlers
21171 This appendix summarizes which combinations of threads and exception support
21172 are supplied on various GNAT platforms.
21173 It then shows how to select a particular library either
21174 permanently or temporarily,
21175 explains the properties of (and tradeoffs among) the various threads
21176 libraries, and provides some additional
21177 information about several specific platforms.
21180 * Summary of Run-Time Configurations::
21181 * Specifying a Run-Time Library::
21182 * Choosing the Scheduling Policy::
21183 * Solaris-Specific Considerations::
21184 * Linux-Specific Considerations::
21185 * AIX-Specific Considerations::
21186 * Irix-Specific Considerations::
21187 * RTX-Specific Considerations::
21188 * HP-UX-Specific Considerations::
21191 @node Summary of Run-Time Configurations
21192 @section Summary of Run-Time Configurations
21194 @multitable @columnfractions .30 .70
21195 @item @b{alpha-openvms}
21196 @item @code{@ @ }@i{rts-native (default)}
21197 @item @code{@ @ @ @ }Tasking @tab native VMS threads
21198 @item @code{@ @ @ @ }Exceptions @tab ZCX
21200 @item @b{alpha-tru64}
21201 @item @code{@ @ }@i{rts-native (default)}
21202 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
21203 @item @code{@ @ @ @ }Exceptions @tab ZCX
21205 @item @code{@ @ }@i{rts-sjlj}
21206 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
21207 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21209 @item @b{ia64-hp_linux}
21210 @item @code{@ @ }@i{rts-native (default)}
21211 @item @code{@ @ @ @ }Tasking @tab pthread library
21212 @item @code{@ @ @ @ }Exceptions @tab ZCX
21214 @item @b{ia64-hpux}
21215 @item @code{@ @ }@i{rts-native (default)}
21216 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
21217 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21219 @item @b{ia64-openvms}
21220 @item @code{@ @ }@i{rts-native (default)}
21221 @item @code{@ @ @ @ }Tasking @tab native VMS threads
21222 @item @code{@ @ @ @ }Exceptions @tab ZCX
21224 @item @b{ia64-sgi_linux}
21225 @item @code{@ @ }@i{rts-native (default)}
21226 @item @code{@ @ @ @ }Tasking @tab pthread library
21227 @item @code{@ @ @ @ }Exceptions @tab ZCX
21229 @item @b{mips-irix}
21230 @item @code{@ @ }@i{rts-native (default)}
21231 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
21232 @item @code{@ @ @ @ }Exceptions @tab ZCX
21235 @item @code{@ @ }@i{rts-native (default)}
21236 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
21237 @item @code{@ @ @ @ }Exceptions @tab ZCX
21239 @item @code{@ @ }@i{rts-sjlj}
21240 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
21241 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21244 @item @code{@ @ }@i{rts-native (default)}
21245 @item @code{@ @ @ @ }Tasking @tab native AIX threads
21246 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21248 @item @b{ppc-darwin}
21249 @item @code{@ @ }@i{rts-native (default)}
21250 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
21251 @item @code{@ @ @ @ }Exceptions @tab ZCX
21253 @item @b{sparc-solaris} @tab
21254 @item @code{@ @ }@i{rts-native (default)}
21255 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
21256 @item @code{@ @ @ @ }Exceptions @tab ZCX
21258 @item @code{@ @ }@i{rts-pthread}
21259 @item @code{@ @ @ @ }Tasking @tab pthread library
21260 @item @code{@ @ @ @ }Exceptions @tab ZCX
21262 @item @code{@ @ }@i{rts-sjlj}
21263 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
21264 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21266 @item @b{sparc64-solaris} @tab
21267 @item @code{@ @ }@i{rts-native (default)}
21268 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
21269 @item @code{@ @ @ @ }Exceptions @tab ZCX
21271 @item @b{x86-linux}
21272 @item @code{@ @ }@i{rts-native (default)}
21273 @item @code{@ @ @ @ }Tasking @tab pthread library
21274 @item @code{@ @ @ @ }Exceptions @tab ZCX
21276 @item @code{@ @ }@i{rts-sjlj}
21277 @item @code{@ @ @ @ }Tasking @tab pthread library
21278 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21281 @item @code{@ @ }@i{rts-native (default)}
21282 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
21283 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21285 @item @b{x86-solaris}
21286 @item @code{@ @ }@i{rts-native (default)}
21287 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
21288 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21290 @item @b{x86-windows}
21291 @item @code{@ @ }@i{rts-native (default)}
21292 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
21293 @item @code{@ @ @ @ }Exceptions @tab ZCX
21295 @item @code{@ @ }@i{rts-sjlj (default)}
21296 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
21297 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21299 @item @b{x86-windows-rtx}
21300 @item @code{@ @ }@i{rts-rtx-rtss (default)}
21301 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
21302 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21304 @item @code{@ @ }@i{rts-rtx-w32}
21305 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
21306 @item @code{@ @ @ @ }Exceptions @tab ZCX
21308 @item @b{x86_64-linux}
21309 @item @code{@ @ }@i{rts-native (default)}
21310 @item @code{@ @ @ @ }Tasking @tab pthread library
21311 @item @code{@ @ @ @ }Exceptions @tab ZCX
21313 @item @code{@ @ }@i{rts-sjlj}
21314 @item @code{@ @ @ @ }Tasking @tab pthread library
21315 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21319 @node Specifying a Run-Time Library
21320 @section Specifying a Run-Time Library
21323 The @file{adainclude} subdirectory containing the sources of the GNAT
21324 run-time library, and the @file{adalib} subdirectory containing the
21325 @file{ALI} files and the static and/or shared GNAT library, are located
21326 in the gcc target-dependent area:
21329 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
21333 As indicated above, on some platforms several run-time libraries are supplied.
21334 These libraries are installed in the target dependent area and
21335 contain a complete source and binary subdirectory. The detailed description
21336 below explains the differences between the different libraries in terms of
21337 their thread support.
21339 The default run-time library (when GNAT is installed) is @emph{rts-native}.
21340 This default run time is selected by the means of soft links.
21341 For example on x86-linux:
21347 +--- adainclude----------+
21349 +--- adalib-----------+ |
21351 +--- rts-native | |
21353 | +--- adainclude <---+
21355 | +--- adalib <----+
21366 If the @i{rts-sjlj} library is to be selected on a permanent basis,
21367 these soft links can be modified with the following commands:
21371 $ rm -f adainclude adalib
21372 $ ln -s rts-sjlj/adainclude adainclude
21373 $ ln -s rts-sjlj/adalib adalib
21377 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
21378 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
21379 @file{$target/ada_object_path}.
21381 Selecting another run-time library temporarily can be
21382 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
21383 @cindex @option{--RTS} option
21385 @node Choosing the Scheduling Policy
21386 @section Choosing the Scheduling Policy
21389 When using a POSIX threads implementation, you have a choice of several
21390 scheduling policies: @code{SCHED_FIFO},
21391 @cindex @code{SCHED_FIFO} scheduling policy
21393 @cindex @code{SCHED_RR} scheduling policy
21394 and @code{SCHED_OTHER}.
21395 @cindex @code{SCHED_OTHER} scheduling policy
21396 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
21397 or @code{SCHED_RR} requires special (e.g., root) privileges.
21399 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
21401 @cindex @code{SCHED_FIFO} scheduling policy
21402 you can use one of the following:
21406 @code{pragma Time_Slice (0.0)}
21407 @cindex pragma Time_Slice
21409 the corresponding binder option @option{-T0}
21410 @cindex @option{-T0} option
21412 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
21413 @cindex pragma Task_Dispatching_Policy
21417 To specify @code{SCHED_RR},
21418 @cindex @code{SCHED_RR} scheduling policy
21419 you should use @code{pragma Time_Slice} with a
21420 value greater than @code{0.0}, or else use the corresponding @option{-T}
21423 @node Solaris-Specific Considerations
21424 @section Solaris-Specific Considerations
21425 @cindex Solaris Sparc threads libraries
21428 This section addresses some topics related to the various threads libraries
21432 * Solaris Threads Issues::
21435 @node Solaris Threads Issues
21436 @subsection Solaris Threads Issues
21439 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
21440 library based on POSIX threads --- @emph{rts-pthread}.
21441 @cindex rts-pthread threads library
21442 This run-time library has the advantage of being mostly shared across all
21443 POSIX-compliant thread implementations, and it also provides under
21444 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
21445 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
21446 and @code{PTHREAD_PRIO_PROTECT}
21447 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
21448 semantics that can be selected using the predefined pragma
21449 @code{Locking_Policy}
21450 @cindex pragma Locking_Policy (under rts-pthread)
21452 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
21453 @cindex @code{Inheritance_Locking} (under rts-pthread)
21454 @cindex @code{Ceiling_Locking} (under rts-pthread)
21456 As explained above, the native run-time library is based on the Solaris thread
21457 library (@code{libthread}) and is the default library.
21459 When the Solaris threads library is used (this is the default), programs
21460 compiled with GNAT can automatically take advantage of
21461 and can thus execute on multiple processors.
21462 The user can alternatively specify a processor on which the program should run
21463 to emulate a single-processor system. The multiprocessor / uniprocessor choice
21465 setting the environment variable @env{GNAT_PROCESSOR}
21466 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
21467 to one of the following:
21471 Use the default configuration (run the program on all
21472 available processors) - this is the same as having @code{GNAT_PROCESSOR}
21476 Let the run-time implementation choose one processor and run the program on
21479 @item 0 .. Last_Proc
21480 Run the program on the specified processor.
21481 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
21482 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
21485 @node Linux-Specific Considerations
21486 @section Linux-Specific Considerations
21487 @cindex Linux threads libraries
21490 On GNU/Linux without NPTL support (usually system with GNU C Library
21491 older than 2.3), the signal model is not POSIX compliant, which means
21492 that to send a signal to the process, you need to send the signal to all
21493 threads, e.g.@: by using @code{killpg()}.
21495 @node AIX-Specific Considerations
21496 @section AIX-Specific Considerations
21497 @cindex AIX resolver library
21500 On AIX, the resolver library initializes some internal structure on
21501 the first call to @code{get*by*} functions, which are used to implement
21502 @code{GNAT.Sockets.Get_Host_By_Name} and
21503 @code{GNAT.Sockets.Get_Host_By_Address}.
21504 If such initialization occurs within an Ada task, and the stack size for
21505 the task is the default size, a stack overflow may occur.
21507 To avoid this overflow, the user should either ensure that the first call
21508 to @code{GNAT.Sockets.Get_Host_By_Name} or
21509 @code{GNAT.Sockets.Get_Host_By_Addrss}
21510 occurs in the environment task, or use @code{pragma Storage_Size} to
21511 specify a sufficiently large size for the stack of the task that contains
21514 @node Irix-Specific Considerations
21515 @section Irix-Specific Considerations
21516 @cindex Irix libraries
21519 The GCC support libraries coming with the Irix compiler have moved to
21520 their canonical place with respect to the general Irix ABI related
21521 conventions. Running applications built with the default shared GNAT
21522 run-time now requires the LD_LIBRARY_PATH environment variable to
21523 include this location. A possible way to achieve this is to issue the
21524 following command line on a bash prompt:
21528 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
21532 @node RTX-Specific Considerations
21533 @section RTX-Specific Considerations
21534 @cindex RTX libraries
21537 The Real-time Extension (RTX) to Windows is based on the Windows Win32
21538 API. Applications can be built to work in two different modes:
21542 Windows executables that run in Ring 3 to utilize memory protection
21543 (@emph{rts-rtx-w32}).
21546 Real-time subsystem (RTSS) executables that run in Ring 0, where
21547 performance can be optimized with RTSS applications taking precedent
21548 over all Windows applications (@emph{rts-rtx-rtss}). This mode requires
21549 the Microsoft linker to handle RTSS libraries.
21553 @node HP-UX-Specific Considerations
21554 @section HP-UX-Specific Considerations
21555 @cindex HP-UX Scheduling
21558 On HP-UX, appropriate privileges are required to change the scheduling
21559 parameters of a task. The calling process must have appropriate
21560 privileges or be a member of a group having @code{PRIV_RTSCHED} access to
21561 successfully change the scheduling parameters.
21563 By default, GNAT uses the @code{SCHED_HPUX} policy. To have access to the
21564 priority range 0-31 either the @code{FIFO_Within_Priorities} or the
21565 @code{Round_Robin_Within_Priorities} scheduling policies need to be set.
21567 To specify the @code{FIFO_Within_Priorities} scheduling policy you can use
21568 one of the following:
21572 @code{pragma Time_Slice (0.0)}
21573 @cindex pragma Time_Slice
21575 the corresponding binder option @option{-T0}
21576 @cindex @option{-T0} option
21578 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
21579 @cindex pragma Task_Dispatching_Policy
21583 To specify the @code{Round_Robin_Within_Priorities}, scheduling policy
21584 you should use @code{pragma Time_Slice} with a
21585 value greater than @code{0.0}, or use the corresponding @option{-T}
21586 binder option, or set the @code{pragma Task_Dispatching_Policy
21587 (Round_Robin_Within_Priorities)}.
21589 @c *******************************
21590 @node Example of Binder Output File
21591 @appendix Example of Binder Output File
21594 This Appendix displays the source code for @command{gnatbind}'s output
21595 file generated for a simple ``Hello World'' program.
21596 Comments have been added for clarification purposes.
21598 @smallexample @c adanocomment
21602 -- The package is called Ada_Main unless this name is actually used
21603 -- as a unit name in the partition, in which case some other unique
21607 package ada_main is
21609 Elab_Final_Code : Integer;
21610 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
21612 -- The main program saves the parameters (argument count,
21613 -- argument values, environment pointer) in global variables
21614 -- for later access by other units including
21615 -- Ada.Command_Line.
21617 gnat_argc : Integer;
21618 gnat_argv : System.Address;
21619 gnat_envp : System.Address;
21621 -- The actual variables are stored in a library routine. This
21622 -- is useful for some shared library situations, where there
21623 -- are problems if variables are not in the library.
21625 pragma Import (C, gnat_argc);
21626 pragma Import (C, gnat_argv);
21627 pragma Import (C, gnat_envp);
21629 -- The exit status is similarly an external location
21631 gnat_exit_status : Integer;
21632 pragma Import (C, gnat_exit_status);
21634 GNAT_Version : constant String :=
21635 "GNAT Version: 6.0.0w (20061115)";
21636 pragma Export (C, GNAT_Version, "__gnat_version");
21638 -- This is the generated adafinal routine that performs
21639 -- finalization at the end of execution. In the case where
21640 -- Ada is the main program, this main program makes a call
21641 -- to adafinal at program termination.
21643 procedure adafinal;
21644 pragma Export (C, adafinal, "adafinal");
21646 -- This is the generated adainit routine that performs
21647 -- initialization at the start of execution. In the case
21648 -- where Ada is the main program, this main program makes
21649 -- a call to adainit at program startup.
21652 pragma Export (C, adainit, "adainit");
21654 -- This routine is called at the start of execution. It is
21655 -- a dummy routine that is used by the debugger to breakpoint
21656 -- at the start of execution.
21658 procedure Break_Start;
21659 pragma Import (C, Break_Start, "__gnat_break_start");
21661 -- This is the actual generated main program (it would be
21662 -- suppressed if the no main program switch were used). As
21663 -- required by standard system conventions, this program has
21664 -- the external name main.
21668 argv : System.Address;
21669 envp : System.Address)
21671 pragma Export (C, main, "main");
21673 -- The following set of constants give the version
21674 -- identification values for every unit in the bound
21675 -- partition. This identification is computed from all
21676 -- dependent semantic units, and corresponds to the
21677 -- string that would be returned by use of the
21678 -- Body_Version or Version attributes.
21680 type Version_32 is mod 2 ** 32;
21681 u00001 : constant Version_32 := 16#7880BEB3#;
21682 u00002 : constant Version_32 := 16#0D24CBD0#;
21683 u00003 : constant Version_32 := 16#3283DBEB#;
21684 u00004 : constant Version_32 := 16#2359F9ED#;
21685 u00005 : constant Version_32 := 16#664FB847#;
21686 u00006 : constant Version_32 := 16#68E803DF#;
21687 u00007 : constant Version_32 := 16#5572E604#;
21688 u00008 : constant Version_32 := 16#46B173D8#;
21689 u00009 : constant Version_32 := 16#156A40CF#;
21690 u00010 : constant Version_32 := 16#033DABE0#;
21691 u00011 : constant Version_32 := 16#6AB38FEA#;
21692 u00012 : constant Version_32 := 16#22B6217D#;
21693 u00013 : constant Version_32 := 16#68A22947#;
21694 u00014 : constant Version_32 := 16#18CC4A56#;
21695 u00015 : constant Version_32 := 16#08258E1B#;
21696 u00016 : constant Version_32 := 16#367D5222#;
21697 u00017 : constant Version_32 := 16#20C9ECA4#;
21698 u00018 : constant Version_32 := 16#50D32CB6#;
21699 u00019 : constant Version_32 := 16#39A8BB77#;
21700 u00020 : constant Version_32 := 16#5CF8FA2B#;
21701 u00021 : constant Version_32 := 16#2F1EB794#;
21702 u00022 : constant Version_32 := 16#31AB6444#;
21703 u00023 : constant Version_32 := 16#1574B6E9#;
21704 u00024 : constant Version_32 := 16#5109C189#;
21705 u00025 : constant Version_32 := 16#56D770CD#;
21706 u00026 : constant Version_32 := 16#02F9DE3D#;
21707 u00027 : constant Version_32 := 16#08AB6B2C#;
21708 u00028 : constant Version_32 := 16#3FA37670#;
21709 u00029 : constant Version_32 := 16#476457A0#;
21710 u00030 : constant Version_32 := 16#731E1B6E#;
21711 u00031 : constant Version_32 := 16#23C2E789#;
21712 u00032 : constant Version_32 := 16#0F1BD6A1#;
21713 u00033 : constant Version_32 := 16#7C25DE96#;
21714 u00034 : constant Version_32 := 16#39ADFFA2#;
21715 u00035 : constant Version_32 := 16#571DE3E7#;
21716 u00036 : constant Version_32 := 16#5EB646AB#;
21717 u00037 : constant Version_32 := 16#4249379B#;
21718 u00038 : constant Version_32 := 16#0357E00A#;
21719 u00039 : constant Version_32 := 16#3784FB72#;
21720 u00040 : constant Version_32 := 16#2E723019#;
21721 u00041 : constant Version_32 := 16#623358EA#;
21722 u00042 : constant Version_32 := 16#107F9465#;
21723 u00043 : constant Version_32 := 16#6843F68A#;
21724 u00044 : constant Version_32 := 16#63305874#;
21725 u00045 : constant Version_32 := 16#31E56CE1#;
21726 u00046 : constant Version_32 := 16#02917970#;
21727 u00047 : constant Version_32 := 16#6CCBA70E#;
21728 u00048 : constant Version_32 := 16#41CD4204#;
21729 u00049 : constant Version_32 := 16#572E3F58#;
21730 u00050 : constant Version_32 := 16#20729FF5#;
21731 u00051 : constant Version_32 := 16#1D4F93E8#;
21732 u00052 : constant Version_32 := 16#30B2EC3D#;
21733 u00053 : constant Version_32 := 16#34054F96#;
21734 u00054 : constant Version_32 := 16#5A199860#;
21735 u00055 : constant Version_32 := 16#0E7F912B#;
21736 u00056 : constant Version_32 := 16#5760634A#;
21737 u00057 : constant Version_32 := 16#5D851835#;
21739 -- The following Export pragmas export the version numbers
21740 -- with symbolic names ending in B (for body) or S
21741 -- (for spec) so that they can be located in a link. The
21742 -- information provided here is sufficient to track down
21743 -- the exact versions of units used in a given build.
21745 pragma Export (C, u00001, "helloB");
21746 pragma Export (C, u00002, "system__standard_libraryB");
21747 pragma Export (C, u00003, "system__standard_libraryS");
21748 pragma Export (C, u00004, "adaS");
21749 pragma Export (C, u00005, "ada__text_ioB");
21750 pragma Export (C, u00006, "ada__text_ioS");
21751 pragma Export (C, u00007, "ada__exceptionsB");
21752 pragma Export (C, u00008, "ada__exceptionsS");
21753 pragma Export (C, u00009, "gnatS");
21754 pragma Export (C, u00010, "gnat__heap_sort_aB");
21755 pragma Export (C, u00011, "gnat__heap_sort_aS");
21756 pragma Export (C, u00012, "systemS");
21757 pragma Export (C, u00013, "system__exception_tableB");
21758 pragma Export (C, u00014, "system__exception_tableS");
21759 pragma Export (C, u00015, "gnat__htableB");
21760 pragma Export (C, u00016, "gnat__htableS");
21761 pragma Export (C, u00017, "system__exceptionsS");
21762 pragma Export (C, u00018, "system__machine_state_operationsB");
21763 pragma Export (C, u00019, "system__machine_state_operationsS");
21764 pragma Export (C, u00020, "system__machine_codeS");
21765 pragma Export (C, u00021, "system__storage_elementsB");
21766 pragma Export (C, u00022, "system__storage_elementsS");
21767 pragma Export (C, u00023, "system__secondary_stackB");
21768 pragma Export (C, u00024, "system__secondary_stackS");
21769 pragma Export (C, u00025, "system__parametersB");
21770 pragma Export (C, u00026, "system__parametersS");
21771 pragma Export (C, u00027, "system__soft_linksB");
21772 pragma Export (C, u00028, "system__soft_linksS");
21773 pragma Export (C, u00029, "system__stack_checkingB");
21774 pragma Export (C, u00030, "system__stack_checkingS");
21775 pragma Export (C, u00031, "system__tracebackB");
21776 pragma Export (C, u00032, "system__tracebackS");
21777 pragma Export (C, u00033, "ada__streamsS");
21778 pragma Export (C, u00034, "ada__tagsB");
21779 pragma Export (C, u00035, "ada__tagsS");
21780 pragma Export (C, u00036, "system__string_opsB");
21781 pragma Export (C, u00037, "system__string_opsS");
21782 pragma Export (C, u00038, "interfacesS");
21783 pragma Export (C, u00039, "interfaces__c_streamsB");
21784 pragma Export (C, u00040, "interfaces__c_streamsS");
21785 pragma Export (C, u00041, "system__file_ioB");
21786 pragma Export (C, u00042, "system__file_ioS");
21787 pragma Export (C, u00043, "ada__finalizationB");
21788 pragma Export (C, u00044, "ada__finalizationS");
21789 pragma Export (C, u00045, "system__finalization_rootB");
21790 pragma Export (C, u00046, "system__finalization_rootS");
21791 pragma Export (C, u00047, "system__finalization_implementationB");
21792 pragma Export (C, u00048, "system__finalization_implementationS");
21793 pragma Export (C, u00049, "system__string_ops_concat_3B");
21794 pragma Export (C, u00050, "system__string_ops_concat_3S");
21795 pragma Export (C, u00051, "system__stream_attributesB");
21796 pragma Export (C, u00052, "system__stream_attributesS");
21797 pragma Export (C, u00053, "ada__io_exceptionsS");
21798 pragma Export (C, u00054, "system__unsigned_typesS");
21799 pragma Export (C, u00055, "system__file_control_blockS");
21800 pragma Export (C, u00056, "ada__finalization__list_controllerB");
21801 pragma Export (C, u00057, "ada__finalization__list_controllerS");
21803 -- BEGIN ELABORATION ORDER
21806 -- gnat.heap_sort_a (spec)
21807 -- gnat.heap_sort_a (body)
21808 -- gnat.htable (spec)
21809 -- gnat.htable (body)
21810 -- interfaces (spec)
21812 -- system.machine_code (spec)
21813 -- system.parameters (spec)
21814 -- system.parameters (body)
21815 -- interfaces.c_streams (spec)
21816 -- interfaces.c_streams (body)
21817 -- system.standard_library (spec)
21818 -- ada.exceptions (spec)
21819 -- system.exception_table (spec)
21820 -- system.exception_table (body)
21821 -- ada.io_exceptions (spec)
21822 -- system.exceptions (spec)
21823 -- system.storage_elements (spec)
21824 -- system.storage_elements (body)
21825 -- system.machine_state_operations (spec)
21826 -- system.machine_state_operations (body)
21827 -- system.secondary_stack (spec)
21828 -- system.stack_checking (spec)
21829 -- system.soft_links (spec)
21830 -- system.soft_links (body)
21831 -- system.stack_checking (body)
21832 -- system.secondary_stack (body)
21833 -- system.standard_library (body)
21834 -- system.string_ops (spec)
21835 -- system.string_ops (body)
21838 -- ada.streams (spec)
21839 -- system.finalization_root (spec)
21840 -- system.finalization_root (body)
21841 -- system.string_ops_concat_3 (spec)
21842 -- system.string_ops_concat_3 (body)
21843 -- system.traceback (spec)
21844 -- system.traceback (body)
21845 -- ada.exceptions (body)
21846 -- system.unsigned_types (spec)
21847 -- system.stream_attributes (spec)
21848 -- system.stream_attributes (body)
21849 -- system.finalization_implementation (spec)
21850 -- system.finalization_implementation (body)
21851 -- ada.finalization (spec)
21852 -- ada.finalization (body)
21853 -- ada.finalization.list_controller (spec)
21854 -- ada.finalization.list_controller (body)
21855 -- system.file_control_block (spec)
21856 -- system.file_io (spec)
21857 -- system.file_io (body)
21858 -- ada.text_io (spec)
21859 -- ada.text_io (body)
21861 -- END ELABORATION ORDER
21865 -- The following source file name pragmas allow the generated file
21866 -- names to be unique for different main programs. They are needed
21867 -- since the package name will always be Ada_Main.
21869 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
21870 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
21872 -- Generated package body for Ada_Main starts here
21874 package body ada_main is
21876 -- The actual finalization is performed by calling the
21877 -- library routine in System.Standard_Library.Adafinal
21879 procedure Do_Finalize;
21880 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
21887 procedure adainit is
21889 -- These booleans are set to True once the associated unit has
21890 -- been elaborated. It is also used to avoid elaborating the
21891 -- same unit twice.
21894 pragma Import (Ada, E040, "interfaces__c_streams_E");
21897 pragma Import (Ada, E008, "ada__exceptions_E");
21900 pragma Import (Ada, E014, "system__exception_table_E");
21903 pragma Import (Ada, E053, "ada__io_exceptions_E");
21906 pragma Import (Ada, E017, "system__exceptions_E");
21909 pragma Import (Ada, E024, "system__secondary_stack_E");
21912 pragma Import (Ada, E030, "system__stack_checking_E");
21915 pragma Import (Ada, E028, "system__soft_links_E");
21918 pragma Import (Ada, E035, "ada__tags_E");
21921 pragma Import (Ada, E033, "ada__streams_E");
21924 pragma Import (Ada, E046, "system__finalization_root_E");
21927 pragma Import (Ada, E048, "system__finalization_implementation_E");
21930 pragma Import (Ada, E044, "ada__finalization_E");
21933 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
21936 pragma Import (Ada, E055, "system__file_control_block_E");
21939 pragma Import (Ada, E042, "system__file_io_E");
21942 pragma Import (Ada, E006, "ada__text_io_E");
21944 -- Set_Globals is a library routine that stores away the
21945 -- value of the indicated set of global values in global
21946 -- variables within the library.
21948 procedure Set_Globals
21949 (Main_Priority : Integer;
21950 Time_Slice_Value : Integer;
21951 WC_Encoding : Character;
21952 Locking_Policy : Character;
21953 Queuing_Policy : Character;
21954 Task_Dispatching_Policy : Character;
21955 Adafinal : System.Address;
21956 Unreserve_All_Interrupts : Integer;
21957 Exception_Tracebacks : Integer);
21958 @findex __gnat_set_globals
21959 pragma Import (C, Set_Globals, "__gnat_set_globals");
21961 -- SDP_Table_Build is a library routine used to build the
21962 -- exception tables. See unit Ada.Exceptions in files
21963 -- a-except.ads/adb for full details of how zero cost
21964 -- exception handling works. This procedure, the call to
21965 -- it, and the two following tables are all omitted if the
21966 -- build is in longjmp/setjmp exception mode.
21968 @findex SDP_Table_Build
21969 @findex Zero Cost Exceptions
21970 procedure SDP_Table_Build
21971 (SDP_Addresses : System.Address;
21972 SDP_Count : Natural;
21973 Elab_Addresses : System.Address;
21974 Elab_Addr_Count : Natural);
21975 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
21977 -- Table of Unit_Exception_Table addresses. Used for zero
21978 -- cost exception handling to build the top level table.
21980 ST : aliased constant array (1 .. 23) of System.Address := (
21982 Ada.Text_Io'UET_Address,
21983 Ada.Exceptions'UET_Address,
21984 Gnat.Heap_Sort_A'UET_Address,
21985 System.Exception_Table'UET_Address,
21986 System.Machine_State_Operations'UET_Address,
21987 System.Secondary_Stack'UET_Address,
21988 System.Parameters'UET_Address,
21989 System.Soft_Links'UET_Address,
21990 System.Stack_Checking'UET_Address,
21991 System.Traceback'UET_Address,
21992 Ada.Streams'UET_Address,
21993 Ada.Tags'UET_Address,
21994 System.String_Ops'UET_Address,
21995 Interfaces.C_Streams'UET_Address,
21996 System.File_Io'UET_Address,
21997 Ada.Finalization'UET_Address,
21998 System.Finalization_Root'UET_Address,
21999 System.Finalization_Implementation'UET_Address,
22000 System.String_Ops_Concat_3'UET_Address,
22001 System.Stream_Attributes'UET_Address,
22002 System.File_Control_Block'UET_Address,
22003 Ada.Finalization.List_Controller'UET_Address);
22005 -- Table of addresses of elaboration routines. Used for
22006 -- zero cost exception handling to make sure these
22007 -- addresses are included in the top level procedure
22010 EA : aliased constant array (1 .. 23) of System.Address := (
22011 adainit'Code_Address,
22012 Do_Finalize'Code_Address,
22013 Ada.Exceptions'Elab_Spec'Address,
22014 System.Exceptions'Elab_Spec'Address,
22015 Interfaces.C_Streams'Elab_Spec'Address,
22016 System.Exception_Table'Elab_Body'Address,
22017 Ada.Io_Exceptions'Elab_Spec'Address,
22018 System.Stack_Checking'Elab_Spec'Address,
22019 System.Soft_Links'Elab_Body'Address,
22020 System.Secondary_Stack'Elab_Body'Address,
22021 Ada.Tags'Elab_Spec'Address,
22022 Ada.Tags'Elab_Body'Address,
22023 Ada.Streams'Elab_Spec'Address,
22024 System.Finalization_Root'Elab_Spec'Address,
22025 Ada.Exceptions'Elab_Body'Address,
22026 System.Finalization_Implementation'Elab_Spec'Address,
22027 System.Finalization_Implementation'Elab_Body'Address,
22028 Ada.Finalization'Elab_Spec'Address,
22029 Ada.Finalization.List_Controller'Elab_Spec'Address,
22030 System.File_Control_Block'Elab_Spec'Address,
22031 System.File_Io'Elab_Body'Address,
22032 Ada.Text_Io'Elab_Spec'Address,
22033 Ada.Text_Io'Elab_Body'Address);
22035 -- Start of processing for adainit
22039 -- Call SDP_Table_Build to build the top level procedure
22040 -- table for zero cost exception handling (omitted in
22041 -- longjmp/setjmp mode).
22043 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
22045 -- Call Set_Globals to record various information for
22046 -- this partition. The values are derived by the binder
22047 -- from information stored in the ali files by the compiler.
22049 @findex __gnat_set_globals
22051 (Main_Priority => -1,
22052 -- Priority of main program, -1 if no pragma Priority used
22054 Time_Slice_Value => -1,
22055 -- Time slice from Time_Slice pragma, -1 if none used
22057 WC_Encoding => 'b',
22058 -- Wide_Character encoding used, default is brackets
22060 Locking_Policy => ' ',
22061 -- Locking_Policy used, default of space means not
22062 -- specified, otherwise it is the first character of
22063 -- the policy name.
22065 Queuing_Policy => ' ',
22066 -- Queuing_Policy used, default of space means not
22067 -- specified, otherwise it is the first character of
22068 -- the policy name.
22070 Task_Dispatching_Policy => ' ',
22071 -- Task_Dispatching_Policy used, default of space means
22072 -- not specified, otherwise first character of the
22075 Adafinal => System.Null_Address,
22076 -- Address of Adafinal routine, not used anymore
22078 Unreserve_All_Interrupts => 0,
22079 -- Set true if pragma Unreserve_All_Interrupts was used
22081 Exception_Tracebacks => 0);
22082 -- Indicates if exception tracebacks are enabled
22084 Elab_Final_Code := 1;
22086 -- Now we have the elaboration calls for all units in the partition.
22087 -- The Elab_Spec and Elab_Body attributes generate references to the
22088 -- implicit elaboration procedures generated by the compiler for
22089 -- each unit that requires elaboration.
22092 Interfaces.C_Streams'Elab_Spec;
22096 Ada.Exceptions'Elab_Spec;
22099 System.Exception_Table'Elab_Body;
22103 Ada.Io_Exceptions'Elab_Spec;
22107 System.Exceptions'Elab_Spec;
22111 System.Stack_Checking'Elab_Spec;
22114 System.Soft_Links'Elab_Body;
22119 System.Secondary_Stack'Elab_Body;
22123 Ada.Tags'Elab_Spec;
22126 Ada.Tags'Elab_Body;
22130 Ada.Streams'Elab_Spec;
22134 System.Finalization_Root'Elab_Spec;
22138 Ada.Exceptions'Elab_Body;
22142 System.Finalization_Implementation'Elab_Spec;
22145 System.Finalization_Implementation'Elab_Body;
22149 Ada.Finalization'Elab_Spec;
22153 Ada.Finalization.List_Controller'Elab_Spec;
22157 System.File_Control_Block'Elab_Spec;
22161 System.File_Io'Elab_Body;
22165 Ada.Text_Io'Elab_Spec;
22168 Ada.Text_Io'Elab_Body;
22172 Elab_Final_Code := 0;
22180 procedure adafinal is
22189 -- main is actually a function, as in the ANSI C standard,
22190 -- defined to return the exit status. The three parameters
22191 -- are the argument count, argument values and environment
22194 @findex Main Program
22197 argv : System.Address;
22198 envp : System.Address)
22201 -- The initialize routine performs low level system
22202 -- initialization using a standard library routine which
22203 -- sets up signal handling and performs any other
22204 -- required setup. The routine can be found in file
22207 @findex __gnat_initialize
22208 procedure initialize;
22209 pragma Import (C, initialize, "__gnat_initialize");
22211 -- The finalize routine performs low level system
22212 -- finalization using a standard library routine. The
22213 -- routine is found in file a-final.c and in the standard
22214 -- distribution is a dummy routine that does nothing, so
22215 -- really this is a hook for special user finalization.
22217 @findex __gnat_finalize
22218 procedure finalize;
22219 pragma Import (C, finalize, "__gnat_finalize");
22221 -- We get to the main program of the partition by using
22222 -- pragma Import because if we try to with the unit and
22223 -- call it Ada style, then not only do we waste time
22224 -- recompiling it, but also, we don't really know the right
22225 -- switches (e.g.@: identifier character set) to be used
22228 procedure Ada_Main_Program;
22229 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
22231 -- Start of processing for main
22234 -- Save global variables
22240 -- Call low level system initialization
22244 -- Call our generated Ada initialization routine
22248 -- This is the point at which we want the debugger to get
22253 -- Now we call the main program of the partition
22257 -- Perform Ada finalization
22261 -- Perform low level system finalization
22265 -- Return the proper exit status
22266 return (gnat_exit_status);
22269 -- This section is entirely comments, so it has no effect on the
22270 -- compilation of the Ada_Main package. It provides the list of
22271 -- object files and linker options, as well as some standard
22272 -- libraries needed for the link. The gnatlink utility parses
22273 -- this b~hello.adb file to read these comment lines to generate
22274 -- the appropriate command line arguments for the call to the
22275 -- system linker. The BEGIN/END lines are used for sentinels for
22276 -- this parsing operation.
22278 -- The exact file names will of course depend on the environment,
22279 -- host/target and location of files on the host system.
22281 @findex Object file list
22282 -- BEGIN Object file/option list
22285 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
22286 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
22287 -- END Object file/option list
22293 The Ada code in the above example is exactly what is generated by the
22294 binder. We have added comments to more clearly indicate the function
22295 of each part of the generated @code{Ada_Main} package.
22297 The code is standard Ada in all respects, and can be processed by any
22298 tools that handle Ada. In particular, it is possible to use the debugger
22299 in Ada mode to debug the generated @code{Ada_Main} package. For example,
22300 suppose that for reasons that you do not understand, your program is crashing
22301 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
22302 you can place a breakpoint on the call:
22304 @smallexample @c ada
22305 Ada.Text_Io'Elab_Body;
22309 and trace the elaboration routine for this package to find out where
22310 the problem might be (more usually of course you would be debugging
22311 elaboration code in your own application).
22313 @node Elaboration Order Handling in GNAT
22314 @appendix Elaboration Order Handling in GNAT
22315 @cindex Order of elaboration
22316 @cindex Elaboration control
22319 * Elaboration Code::
22320 * Checking the Elaboration Order::
22321 * Controlling the Elaboration Order::
22322 * Controlling Elaboration in GNAT - Internal Calls::
22323 * Controlling Elaboration in GNAT - External Calls::
22324 * Default Behavior in GNAT - Ensuring Safety::
22325 * Treatment of Pragma Elaborate::
22326 * Elaboration Issues for Library Tasks::
22327 * Mixing Elaboration Models::
22328 * What to Do If the Default Elaboration Behavior Fails::
22329 * Elaboration for Access-to-Subprogram Values::
22330 * Summary of Procedures for Elaboration Control::
22331 * Other Elaboration Order Considerations::
22335 This chapter describes the handling of elaboration code in Ada and
22336 in GNAT, and discusses how the order of elaboration of program units can
22337 be controlled in GNAT, either automatically or with explicit programming
22340 @node Elaboration Code
22341 @section Elaboration Code
22344 Ada provides rather general mechanisms for executing code at elaboration
22345 time, that is to say before the main program starts executing. Such code arises
22349 @item Initializers for variables.
22350 Variables declared at the library level, in package specs or bodies, can
22351 require initialization that is performed at elaboration time, as in:
22352 @smallexample @c ada
22354 Sqrt_Half : Float := Sqrt (0.5);
22358 @item Package initialization code
22359 Code in a @code{BEGIN-END} section at the outer level of a package body is
22360 executed as part of the package body elaboration code.
22362 @item Library level task allocators
22363 Tasks that are declared using task allocators at the library level
22364 start executing immediately and hence can execute at elaboration time.
22368 Subprogram calls are possible in any of these contexts, which means that
22369 any arbitrary part of the program may be executed as part of the elaboration
22370 code. It is even possible to write a program which does all its work at
22371 elaboration time, with a null main program, although stylistically this
22372 would usually be considered an inappropriate way to structure
22375 An important concern arises in the context of elaboration code:
22376 we have to be sure that it is executed in an appropriate order. What we
22377 have is a series of elaboration code sections, potentially one section
22378 for each unit in the program. It is important that these execute
22379 in the correct order. Correctness here means that, taking the above
22380 example of the declaration of @code{Sqrt_Half},
22381 if some other piece of
22382 elaboration code references @code{Sqrt_Half},
22383 then it must run after the
22384 section of elaboration code that contains the declaration of
22387 There would never be any order of elaboration problem if we made a rule
22388 that whenever you @code{with} a unit, you must elaborate both the spec and body
22389 of that unit before elaborating the unit doing the @code{with}'ing:
22391 @smallexample @c ada
22395 package Unit_2 is @dots{}
22401 would require that both the body and spec of @code{Unit_1} be elaborated
22402 before the spec of @code{Unit_2}. However, a rule like that would be far too
22403 restrictive. In particular, it would make it impossible to have routines
22404 in separate packages that were mutually recursive.
22406 You might think that a clever enough compiler could look at the actual
22407 elaboration code and determine an appropriate correct order of elaboration,
22408 but in the general case, this is not possible. Consider the following
22411 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
22413 the variable @code{Sqrt_1}, which is declared in the elaboration code
22414 of the body of @code{Unit_1}:
22416 @smallexample @c ada
22418 Sqrt_1 : Float := Sqrt (0.1);
22423 The elaboration code of the body of @code{Unit_1} also contains:
22425 @smallexample @c ada
22428 if expression_1 = 1 then
22429 Q := Unit_2.Func_2;
22436 @code{Unit_2} is exactly parallel,
22437 it has a procedure @code{Func_2} that references
22438 the variable @code{Sqrt_2}, which is declared in the elaboration code of
22439 the body @code{Unit_2}:
22441 @smallexample @c ada
22443 Sqrt_2 : Float := Sqrt (0.1);
22448 The elaboration code of the body of @code{Unit_2} also contains:
22450 @smallexample @c ada
22453 if expression_2 = 2 then
22454 Q := Unit_1.Func_1;
22461 Now the question is, which of the following orders of elaboration is
22486 If you carefully analyze the flow here, you will see that you cannot tell
22487 at compile time the answer to this question.
22488 If @code{expression_1} is not equal to 1,
22489 and @code{expression_2} is not equal to 2,
22490 then either order is acceptable, because neither of the function calls is
22491 executed. If both tests evaluate to true, then neither order is acceptable
22492 and in fact there is no correct order.
22494 If one of the two expressions is true, and the other is false, then one
22495 of the above orders is correct, and the other is incorrect. For example,
22496 if @code{expression_1} /= 1 and @code{expression_2} = 2,
22497 then the call to @code{Func_1}
22498 will occur, but not the call to @code{Func_2.}
22499 This means that it is essential
22500 to elaborate the body of @code{Unit_1} before
22501 the body of @code{Unit_2}, so the first
22502 order of elaboration is correct and the second is wrong.
22504 By making @code{expression_1} and @code{expression_2}
22505 depend on input data, or perhaps
22506 the time of day, we can make it impossible for the compiler or binder
22507 to figure out which of these expressions will be true, and hence it
22508 is impossible to guarantee a safe order of elaboration at run time.
22510 @node Checking the Elaboration Order
22511 @section Checking the Elaboration Order
22514 In some languages that involve the same kind of elaboration problems,
22515 e.g.@: Java and C++, the programmer is expected to worry about these
22516 ordering problems himself, and it is common to
22517 write a program in which an incorrect elaboration order gives
22518 surprising results, because it references variables before they
22520 Ada is designed to be a safe language, and a programmer-beware approach is
22521 clearly not sufficient. Consequently, the language provides three lines
22525 @item Standard rules
22526 Some standard rules restrict the possible choice of elaboration
22527 order. In particular, if you @code{with} a unit, then its spec is always
22528 elaborated before the unit doing the @code{with}. Similarly, a parent
22529 spec is always elaborated before the child spec, and finally
22530 a spec is always elaborated before its corresponding body.
22532 @item Dynamic elaboration checks
22533 @cindex Elaboration checks
22534 @cindex Checks, elaboration
22535 Dynamic checks are made at run time, so that if some entity is accessed
22536 before it is elaborated (typically by means of a subprogram call)
22537 then the exception (@code{Program_Error}) is raised.
22539 @item Elaboration control
22540 Facilities are provided for the programmer to specify the desired order
22544 Let's look at these facilities in more detail. First, the rules for
22545 dynamic checking. One possible rule would be simply to say that the
22546 exception is raised if you access a variable which has not yet been
22547 elaborated. The trouble with this approach is that it could require
22548 expensive checks on every variable reference. Instead Ada has two
22549 rules which are a little more restrictive, but easier to check, and
22553 @item Restrictions on calls
22554 A subprogram can only be called at elaboration time if its body
22555 has been elaborated. The rules for elaboration given above guarantee
22556 that the spec of the subprogram has been elaborated before the
22557 call, but not the body. If this rule is violated, then the
22558 exception @code{Program_Error} is raised.
22560 @item Restrictions on instantiations
22561 A generic unit can only be instantiated if the body of the generic
22562 unit has been elaborated. Again, the rules for elaboration given above
22563 guarantee that the spec of the generic unit has been elaborated
22564 before the instantiation, but not the body. If this rule is
22565 violated, then the exception @code{Program_Error} is raised.
22569 The idea is that if the body has been elaborated, then any variables
22570 it references must have been elaborated; by checking for the body being
22571 elaborated we guarantee that none of its references causes any
22572 trouble. As we noted above, this is a little too restrictive, because a
22573 subprogram that has no non-local references in its body may in fact be safe
22574 to call. However, it really would be unsafe to rely on this, because
22575 it would mean that the caller was aware of details of the implementation
22576 in the body. This goes against the basic tenets of Ada.
22578 A plausible implementation can be described as follows.
22579 A Boolean variable is associated with each subprogram
22580 and each generic unit. This variable is initialized to False, and is set to
22581 True at the point body is elaborated. Every call or instantiation checks the
22582 variable, and raises @code{Program_Error} if the variable is False.
22584 Note that one might think that it would be good enough to have one Boolean
22585 variable for each package, but that would not deal with cases of trying
22586 to call a body in the same package as the call
22587 that has not been elaborated yet.
22588 Of course a compiler may be able to do enough analysis to optimize away
22589 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
22590 does such optimizations, but still the easiest conceptual model is to
22591 think of there being one variable per subprogram.
22593 @node Controlling the Elaboration Order
22594 @section Controlling the Elaboration Order
22597 In the previous section we discussed the rules in Ada which ensure
22598 that @code{Program_Error} is raised if an incorrect elaboration order is
22599 chosen. This prevents erroneous executions, but we need mechanisms to
22600 specify a correct execution and avoid the exception altogether.
22601 To achieve this, Ada provides a number of features for controlling
22602 the order of elaboration. We discuss these features in this section.
22604 First, there are several ways of indicating to the compiler that a given
22605 unit has no elaboration problems:
22608 @item packages that do not require a body
22609 A library package that does not require a body does not permit
22610 a body (this rule was introduced in Ada 95).
22611 Thus if we have a such a package, as in:
22613 @smallexample @c ada
22616 package Definitions is
22618 type m is new integer;
22620 type a is array (1 .. 10) of m;
22621 type b is array (1 .. 20) of m;
22629 A package that @code{with}'s @code{Definitions} may safely instantiate
22630 @code{Definitions.Subp} because the compiler can determine that there
22631 definitely is no package body to worry about in this case
22634 @cindex pragma Pure
22636 Places sufficient restrictions on a unit to guarantee that
22637 no call to any subprogram in the unit can result in an
22638 elaboration problem. This means that the compiler does not need
22639 to worry about the point of elaboration of such units, and in
22640 particular, does not need to check any calls to any subprograms
22643 @item pragma Preelaborate
22644 @findex Preelaborate
22645 @cindex pragma Preelaborate
22646 This pragma places slightly less stringent restrictions on a unit than
22648 but these restrictions are still sufficient to ensure that there
22649 are no elaboration problems with any calls to the unit.
22651 @item pragma Elaborate_Body
22652 @findex Elaborate_Body
22653 @cindex pragma Elaborate_Body
22654 This pragma requires that the body of a unit be elaborated immediately
22655 after its spec. Suppose a unit @code{A} has such a pragma,
22656 and unit @code{B} does
22657 a @code{with} of unit @code{A}. Recall that the standard rules require
22658 the spec of unit @code{A}
22659 to be elaborated before the @code{with}'ing unit; given the pragma in
22660 @code{A}, we also know that the body of @code{A}
22661 will be elaborated before @code{B}, so
22662 that calls to @code{A} are safe and do not need a check.
22667 unlike pragma @code{Pure} and pragma @code{Preelaborate},
22669 @code{Elaborate_Body} does not guarantee that the program is
22670 free of elaboration problems, because it may not be possible
22671 to satisfy the requested elaboration order.
22672 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
22674 marks @code{Unit_1} as @code{Elaborate_Body},
22675 and not @code{Unit_2,} then the order of
22676 elaboration will be:
22688 Now that means that the call to @code{Func_1} in @code{Unit_2}
22689 need not be checked,
22690 it must be safe. But the call to @code{Func_2} in
22691 @code{Unit_1} may still fail if
22692 @code{Expression_1} is equal to 1,
22693 and the programmer must still take
22694 responsibility for this not being the case.
22696 If all units carry a pragma @code{Elaborate_Body}, then all problems are
22697 eliminated, except for calls entirely within a body, which are
22698 in any case fully under programmer control. However, using the pragma
22699 everywhere is not always possible.
22700 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
22701 we marked both of them as having pragma @code{Elaborate_Body}, then
22702 clearly there would be no possible elaboration order.
22704 The above pragmas allow a server to guarantee safe use by clients, and
22705 clearly this is the preferable approach. Consequently a good rule
22706 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
22707 and if this is not possible,
22708 mark them as @code{Elaborate_Body} if possible.
22709 As we have seen, there are situations where neither of these
22710 three pragmas can be used.
22711 So we also provide methods for clients to control the
22712 order of elaboration of the servers on which they depend:
22715 @item pragma Elaborate (unit)
22717 @cindex pragma Elaborate
22718 This pragma is placed in the context clause, after a @code{with} clause,
22719 and it requires that the body of the named unit be elaborated before
22720 the unit in which the pragma occurs. The idea is to use this pragma
22721 if the current unit calls at elaboration time, directly or indirectly,
22722 some subprogram in the named unit.
22724 @item pragma Elaborate_All (unit)
22725 @findex Elaborate_All
22726 @cindex pragma Elaborate_All
22727 This is a stronger version of the Elaborate pragma. Consider the
22731 Unit A @code{with}'s unit B and calls B.Func in elab code
22732 Unit B @code{with}'s unit C, and B.Func calls C.Func
22736 Now if we put a pragma @code{Elaborate (B)}
22737 in unit @code{A}, this ensures that the
22738 body of @code{B} is elaborated before the call, but not the
22739 body of @code{C}, so
22740 the call to @code{C.Func} could still cause @code{Program_Error} to
22743 The effect of a pragma @code{Elaborate_All} is stronger, it requires
22744 not only that the body of the named unit be elaborated before the
22745 unit doing the @code{with}, but also the bodies of all units that the
22746 named unit uses, following @code{with} links transitively. For example,
22747 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
22749 not only that the body of @code{B} be elaborated before @code{A},
22751 body of @code{C}, because @code{B} @code{with}'s @code{C}.
22755 We are now in a position to give a usage rule in Ada for avoiding
22756 elaboration problems, at least if dynamic dispatching and access to
22757 subprogram values are not used. We will handle these cases separately
22760 The rule is simple. If a unit has elaboration code that can directly or
22761 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
22762 a generic package in a @code{with}'ed unit,
22763 then if the @code{with}'ed unit does not have
22764 pragma @code{Pure} or @code{Preelaborate}, then the client should have
22765 a pragma @code{Elaborate_All}
22766 for the @code{with}'ed unit. By following this rule a client is
22767 assured that calls can be made without risk of an exception.
22769 For generic subprogram instantiations, the rule can be relaxed to
22770 require only a pragma @code{Elaborate} since elaborating the body
22771 of a subprogram cannot cause any transitive elaboration (we are
22772 not calling the subprogram in this case, just elaborating its
22775 If this rule is not followed, then a program may be in one of four
22779 @item No order exists
22780 No order of elaboration exists which follows the rules, taking into
22781 account any @code{Elaborate}, @code{Elaborate_All},
22782 or @code{Elaborate_Body} pragmas. In
22783 this case, an Ada compiler must diagnose the situation at bind
22784 time, and refuse to build an executable program.
22786 @item One or more orders exist, all incorrect
22787 One or more acceptable elaboration orders exist, and all of them
22788 generate an elaboration order problem. In this case, the binder
22789 can build an executable program, but @code{Program_Error} will be raised
22790 when the program is run.
22792 @item Several orders exist, some right, some incorrect
22793 One or more acceptable elaboration orders exists, and some of them
22794 work, and some do not. The programmer has not controlled
22795 the order of elaboration, so the binder may or may not pick one of
22796 the correct orders, and the program may or may not raise an
22797 exception when it is run. This is the worst case, because it means
22798 that the program may fail when moved to another compiler, or even
22799 another version of the same compiler.
22801 @item One or more orders exists, all correct
22802 One ore more acceptable elaboration orders exist, and all of them
22803 work. In this case the program runs successfully. This state of
22804 affairs can be guaranteed by following the rule we gave above, but
22805 may be true even if the rule is not followed.
22809 Note that one additional advantage of following our rules on the use
22810 of @code{Elaborate} and @code{Elaborate_All}
22811 is that the program continues to stay in the ideal (all orders OK) state
22812 even if maintenance
22813 changes some bodies of some units. Conversely, if a program that does
22814 not follow this rule happens to be safe at some point, this state of affairs
22815 may deteriorate silently as a result of maintenance changes.
22817 You may have noticed that the above discussion did not mention
22818 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
22819 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
22820 code in the body makes calls to some other unit, so it is still necessary
22821 to use @code{Elaborate_All} on such units.
22823 @node Controlling Elaboration in GNAT - Internal Calls
22824 @section Controlling Elaboration in GNAT - Internal Calls
22827 In the case of internal calls, i.e., calls within a single package, the
22828 programmer has full control over the order of elaboration, and it is up
22829 to the programmer to elaborate declarations in an appropriate order. For
22832 @smallexample @c ada
22835 function One return Float;
22839 function One return Float is
22848 will obviously raise @code{Program_Error} at run time, because function
22849 One will be called before its body is elaborated. In this case GNAT will
22850 generate a warning that the call will raise @code{Program_Error}:
22856 2. function One return Float;
22858 4. Q : Float := One;
22860 >>> warning: cannot call "One" before body is elaborated
22861 >>> warning: Program_Error will be raised at run time
22864 6. function One return Float is
22877 Note that in this particular case, it is likely that the call is safe, because
22878 the function @code{One} does not access any global variables.
22879 Nevertheless in Ada, we do not want the validity of the check to depend on
22880 the contents of the body (think about the separate compilation case), so this
22881 is still wrong, as we discussed in the previous sections.
22883 The error is easily corrected by rearranging the declarations so that the
22884 body of @code{One} appears before the declaration containing the call
22885 (note that in Ada 95 and Ada 2005,
22886 declarations can appear in any order, so there is no restriction that
22887 would prevent this reordering, and if we write:
22889 @smallexample @c ada
22892 function One return Float;
22894 function One return Float is
22905 then all is well, no warning is generated, and no
22906 @code{Program_Error} exception
22908 Things are more complicated when a chain of subprograms is executed:
22910 @smallexample @c ada
22913 function A return Integer;
22914 function B return Integer;
22915 function C return Integer;
22917 function B return Integer is begin return A; end;
22918 function C return Integer is begin return B; end;
22922 function A return Integer is begin return 1; end;
22928 Now the call to @code{C}
22929 at elaboration time in the declaration of @code{X} is correct, because
22930 the body of @code{C} is already elaborated,
22931 and the call to @code{B} within the body of
22932 @code{C} is correct, but the call
22933 to @code{A} within the body of @code{B} is incorrect, because the body
22934 of @code{A} has not been elaborated, so @code{Program_Error}
22935 will be raised on the call to @code{A}.
22936 In this case GNAT will generate a
22937 warning that @code{Program_Error} may be
22938 raised at the point of the call. Let's look at the warning:
22944 2. function A return Integer;
22945 3. function B return Integer;
22946 4. function C return Integer;
22948 6. function B return Integer is begin return A; end;
22950 >>> warning: call to "A" before body is elaborated may
22951 raise Program_Error
22952 >>> warning: "B" called at line 7
22953 >>> warning: "C" called at line 9
22955 7. function C return Integer is begin return B; end;
22957 9. X : Integer := C;
22959 11. function A return Integer is begin return 1; end;
22969 Note that the message here says ``may raise'', instead of the direct case,
22970 where the message says ``will be raised''. That's because whether
22972 actually called depends in general on run-time flow of control.
22973 For example, if the body of @code{B} said
22975 @smallexample @c ada
22978 function B return Integer is
22980 if some-condition-depending-on-input-data then
22991 then we could not know until run time whether the incorrect call to A would
22992 actually occur, so @code{Program_Error} might
22993 or might not be raised. It is possible for a compiler to
22994 do a better job of analyzing bodies, to
22995 determine whether or not @code{Program_Error}
22996 might be raised, but it certainly
22997 couldn't do a perfect job (that would require solving the halting problem
22998 and is provably impossible), and because this is a warning anyway, it does
22999 not seem worth the effort to do the analysis. Cases in which it
23000 would be relevant are rare.
23002 In practice, warnings of either of the forms given
23003 above will usually correspond to
23004 real errors, and should be examined carefully and eliminated.
23005 In the rare case where a warning is bogus, it can be suppressed by any of
23006 the following methods:
23010 Compile with the @option{-gnatws} switch set
23013 Suppress @code{Elaboration_Check} for the called subprogram
23016 Use pragma @code{Warnings_Off} to turn warnings off for the call
23020 For the internal elaboration check case,
23021 GNAT by default generates the
23022 necessary run-time checks to ensure
23023 that @code{Program_Error} is raised if any
23024 call fails an elaboration check. Of course this can only happen if a
23025 warning has been issued as described above. The use of pragma
23026 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
23027 some of these checks, meaning that it may be possible (but is not
23028 guaranteed) for a program to be able to call a subprogram whose body
23029 is not yet elaborated, without raising a @code{Program_Error} exception.
23031 @node Controlling Elaboration in GNAT - External Calls
23032 @section Controlling Elaboration in GNAT - External Calls
23035 The previous section discussed the case in which the execution of a
23036 particular thread of elaboration code occurred entirely within a
23037 single unit. This is the easy case to handle, because a programmer
23038 has direct and total control over the order of elaboration, and
23039 furthermore, checks need only be generated in cases which are rare
23040 and which the compiler can easily detect.
23041 The situation is more complex when separate compilation is taken into account.
23042 Consider the following:
23044 @smallexample @c ada
23048 function Sqrt (Arg : Float) return Float;
23051 package body Math is
23052 function Sqrt (Arg : Float) return Float is
23061 X : Float := Math.Sqrt (0.5);
23074 where @code{Main} is the main program. When this program is executed, the
23075 elaboration code must first be executed, and one of the jobs of the
23076 binder is to determine the order in which the units of a program are
23077 to be elaborated. In this case we have four units: the spec and body
23079 the spec of @code{Stuff} and the body of @code{Main}).
23080 In what order should the four separate sections of elaboration code
23083 There are some restrictions in the order of elaboration that the binder
23084 can choose. In particular, if unit U has a @code{with}
23085 for a package @code{X}, then you
23086 are assured that the spec of @code{X}
23087 is elaborated before U , but you are
23088 not assured that the body of @code{X}
23089 is elaborated before U.
23090 This means that in the above case, the binder is allowed to choose the
23101 but that's not good, because now the call to @code{Math.Sqrt}
23102 that happens during
23103 the elaboration of the @code{Stuff}
23104 spec happens before the body of @code{Math.Sqrt} is
23105 elaborated, and hence causes @code{Program_Error} exception to be raised.
23106 At first glance, one might say that the binder is misbehaving, because
23107 obviously you want to elaborate the body of something you @code{with}
23109 that is not a general rule that can be followed in all cases. Consider
23111 @smallexample @c ada
23114 package X is @dots{}
23116 package Y is @dots{}
23119 package body Y is @dots{}
23122 package body X is @dots{}
23128 This is a common arrangement, and, apart from the order of elaboration
23129 problems that might arise in connection with elaboration code, this works fine.
23130 A rule that says that you must first elaborate the body of anything you
23131 @code{with} cannot work in this case:
23132 the body of @code{X} @code{with}'s @code{Y},
23133 which means you would have to
23134 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
23136 you have to elaborate the body of @code{X} first, but @dots{} and we have a
23137 loop that cannot be broken.
23139 It is true that the binder can in many cases guess an order of elaboration
23140 that is unlikely to cause a @code{Program_Error}
23141 exception to be raised, and it tries to do so (in the
23142 above example of @code{Math/Stuff/Spec}, the GNAT binder will
23144 elaborate the body of @code{Math} right after its spec, so all will be well).
23146 However, a program that blindly relies on the binder to be helpful can
23147 get into trouble, as we discussed in the previous sections, so
23149 provides a number of facilities for assisting the programmer in
23150 developing programs that are robust with respect to elaboration order.
23152 @node Default Behavior in GNAT - Ensuring Safety
23153 @section Default Behavior in GNAT - Ensuring Safety
23156 The default behavior in GNAT ensures elaboration safety. In its
23157 default mode GNAT implements the
23158 rule we previously described as the right approach. Let's restate it:
23162 @emph{If a unit has elaboration code that can directly or indirectly make a
23163 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
23164 package in a @code{with}'ed unit, then if the @code{with}'ed unit
23165 does not have pragma @code{Pure} or
23166 @code{Preelaborate}, then the client should have an
23167 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
23169 @emph{In the case of instantiating a generic subprogram, it is always
23170 sufficient to have only an @code{Elaborate} pragma for the
23171 @code{with}'ed unit.}
23175 By following this rule a client is assured that calls and instantiations
23176 can be made without risk of an exception.
23178 In this mode GNAT traces all calls that are potentially made from
23179 elaboration code, and puts in any missing implicit @code{Elaborate}
23180 and @code{Elaborate_All} pragmas.
23181 The advantage of this approach is that no elaboration problems
23182 are possible if the binder can find an elaboration order that is
23183 consistent with these implicit @code{Elaborate} and
23184 @code{Elaborate_All} pragmas. The
23185 disadvantage of this approach is that no such order may exist.
23187 If the binder does not generate any diagnostics, then it means that it has
23188 found an elaboration order that is guaranteed to be safe. However, the binder
23189 may still be relying on implicitly generated @code{Elaborate} and
23190 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
23193 If it is important to guarantee portability, then the compilations should
23196 (warn on elaboration problems) switch. This will cause warning messages
23197 to be generated indicating the missing @code{Elaborate} and
23198 @code{Elaborate_All} pragmas.
23199 Consider the following source program:
23201 @smallexample @c ada
23206 m : integer := k.r;
23213 where it is clear that there
23214 should be a pragma @code{Elaborate_All}
23215 for unit @code{k}. An implicit pragma will be generated, and it is
23216 likely that the binder will be able to honor it. However, if you want
23217 to port this program to some other Ada compiler than GNAT.
23218 it is safer to include the pragma explicitly in the source. If this
23219 unit is compiled with the
23221 switch, then the compiler outputs a warning:
23228 3. m : integer := k.r;
23230 >>> warning: call to "r" may raise Program_Error
23231 >>> warning: missing pragma Elaborate_All for "k"
23239 and these warnings can be used as a guide for supplying manually
23240 the missing pragmas. It is usually a bad idea to use this warning
23241 option during development. That's because it will warn you when
23242 you need to put in a pragma, but cannot warn you when it is time
23243 to take it out. So the use of pragma @code{Elaborate_All} may lead to
23244 unnecessary dependencies and even false circularities.
23246 This default mode is more restrictive than the Ada Reference
23247 Manual, and it is possible to construct programs which will compile
23248 using the dynamic model described there, but will run into a
23249 circularity using the safer static model we have described.
23251 Of course any Ada compiler must be able to operate in a mode
23252 consistent with the requirements of the Ada Reference Manual,
23253 and in particular must have the capability of implementing the
23254 standard dynamic model of elaboration with run-time checks.
23256 In GNAT, this standard mode can be achieved either by the use of
23257 the @option{-gnatE} switch on the compiler (@command{gcc} or
23258 @command{gnatmake}) command, or by the use of the configuration pragma:
23260 @smallexample @c ada
23261 pragma Elaboration_Checks (DYNAMIC);
23265 Either approach will cause the unit affected to be compiled using the
23266 standard dynamic run-time elaboration checks described in the Ada
23267 Reference Manual. The static model is generally preferable, since it
23268 is clearly safer to rely on compile and link time checks rather than
23269 run-time checks. However, in the case of legacy code, it may be
23270 difficult to meet the requirements of the static model. This
23271 issue is further discussed in
23272 @ref{What to Do If the Default Elaboration Behavior Fails}.
23274 Note that the static model provides a strict subset of the allowed
23275 behavior and programs of the Ada Reference Manual, so if you do
23276 adhere to the static model and no circularities exist,
23277 then you are assured that your program will
23278 work using the dynamic model, providing that you remove any
23279 pragma Elaborate statements from the source.
23281 @node Treatment of Pragma Elaborate
23282 @section Treatment of Pragma Elaborate
23283 @cindex Pragma Elaborate
23286 The use of @code{pragma Elaborate}
23287 should generally be avoided in Ada 95 and Ada 2005 programs,
23288 since there is no guarantee that transitive calls
23289 will be properly handled. Indeed at one point, this pragma was placed
23290 in Annex J (Obsolescent Features), on the grounds that it is never useful.
23292 Now that's a bit restrictive. In practice, the case in which
23293 @code{pragma Elaborate} is useful is when the caller knows that there
23294 are no transitive calls, or that the called unit contains all necessary
23295 transitive @code{pragma Elaborate} statements, and legacy code often
23296 contains such uses.
23298 Strictly speaking the static mode in GNAT should ignore such pragmas,
23299 since there is no assurance at compile time that the necessary safety
23300 conditions are met. In practice, this would cause GNAT to be incompatible
23301 with correctly written Ada 83 code that had all necessary
23302 @code{pragma Elaborate} statements in place. Consequently, we made the
23303 decision that GNAT in its default mode will believe that if it encounters
23304 a @code{pragma Elaborate} then the programmer knows what they are doing,
23305 and it will trust that no elaboration errors can occur.
23307 The result of this decision is two-fold. First to be safe using the
23308 static mode, you should remove all @code{pragma Elaborate} statements.
23309 Second, when fixing circularities in existing code, you can selectively
23310 use @code{pragma Elaborate} statements to convince the static mode of
23311 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
23314 When using the static mode with @option{-gnatwl}, any use of
23315 @code{pragma Elaborate} will generate a warning about possible
23318 @node Elaboration Issues for Library Tasks
23319 @section Elaboration Issues for Library Tasks
23320 @cindex Library tasks, elaboration issues
23321 @cindex Elaboration of library tasks
23324 In this section we examine special elaboration issues that arise for
23325 programs that declare library level tasks.
23327 Generally the model of execution of an Ada program is that all units are
23328 elaborated, and then execution of the program starts. However, the
23329 declaration of library tasks definitely does not fit this model. The
23330 reason for this is that library tasks start as soon as they are declared
23331 (more precisely, as soon as the statement part of the enclosing package
23332 body is reached), that is to say before elaboration
23333 of the program is complete. This means that if such a task calls a
23334 subprogram, or an entry in another task, the callee may or may not be
23335 elaborated yet, and in the standard
23336 Reference Manual model of dynamic elaboration checks, you can even
23337 get timing dependent Program_Error exceptions, since there can be
23338 a race between the elaboration code and the task code.
23340 The static model of elaboration in GNAT seeks to avoid all such
23341 dynamic behavior, by being conservative, and the conservative
23342 approach in this particular case is to assume that all the code
23343 in a task body is potentially executed at elaboration time if
23344 a task is declared at the library level.
23346 This can definitely result in unexpected circularities. Consider
23347 the following example
23349 @smallexample @c ada
23355 type My_Int is new Integer;
23357 function Ident (M : My_Int) return My_Int;
23361 package body Decls is
23362 task body Lib_Task is
23368 function Ident (M : My_Int) return My_Int is
23376 procedure Put_Val (Arg : Decls.My_Int);
23380 package body Utils is
23381 procedure Put_Val (Arg : Decls.My_Int) is
23383 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
23390 Decls.Lib_Task.Start;
23395 If the above example is compiled in the default static elaboration
23396 mode, then a circularity occurs. The circularity comes from the call
23397 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
23398 this call occurs in elaboration code, we need an implicit pragma
23399 @code{Elaborate_All} for @code{Utils}. This means that not only must
23400 the spec and body of @code{Utils} be elaborated before the body
23401 of @code{Decls}, but also the spec and body of any unit that is
23402 @code{with'ed} by the body of @code{Utils} must also be elaborated before
23403 the body of @code{Decls}. This is the transitive implication of
23404 pragma @code{Elaborate_All} and it makes sense, because in general
23405 the body of @code{Put_Val} might have a call to something in a
23406 @code{with'ed} unit.
23408 In this case, the body of Utils (actually its spec) @code{with's}
23409 @code{Decls}. Unfortunately this means that the body of @code{Decls}
23410 must be elaborated before itself, in case there is a call from the
23411 body of @code{Utils}.
23413 Here is the exact chain of events we are worrying about:
23417 In the body of @code{Decls} a call is made from within the body of a library
23418 task to a subprogram in the package @code{Utils}. Since this call may
23419 occur at elaboration time (given that the task is activated at elaboration
23420 time), we have to assume the worst, i.e., that the
23421 call does happen at elaboration time.
23424 This means that the body and spec of @code{Util} must be elaborated before
23425 the body of @code{Decls} so that this call does not cause an access before
23429 Within the body of @code{Util}, specifically within the body of
23430 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
23434 One such @code{with}'ed package is package @code{Decls}, so there
23435 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
23436 In fact there is such a call in this example, but we would have to
23437 assume that there was such a call even if it were not there, since
23438 we are not supposed to write the body of @code{Decls} knowing what
23439 is in the body of @code{Utils}; certainly in the case of the
23440 static elaboration model, the compiler does not know what is in
23441 other bodies and must assume the worst.
23444 This means that the spec and body of @code{Decls} must also be
23445 elaborated before we elaborate the unit containing the call, but
23446 that unit is @code{Decls}! This means that the body of @code{Decls}
23447 must be elaborated before itself, and that's a circularity.
23451 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
23452 the body of @code{Decls} you will get a true Ada Reference Manual
23453 circularity that makes the program illegal.
23455 In practice, we have found that problems with the static model of
23456 elaboration in existing code often arise from library tasks, so
23457 we must address this particular situation.
23459 Note that if we compile and run the program above, using the dynamic model of
23460 elaboration (that is to say use the @option{-gnatE} switch),
23461 then it compiles, binds,
23462 links, and runs, printing the expected result of 2. Therefore in some sense
23463 the circularity here is only apparent, and we need to capture
23464 the properties of this program that distinguish it from other library-level
23465 tasks that have real elaboration problems.
23467 We have four possible answers to this question:
23472 Use the dynamic model of elaboration.
23474 If we use the @option{-gnatE} switch, then as noted above, the program works.
23475 Why is this? If we examine the task body, it is apparent that the task cannot
23477 @code{accept} statement until after elaboration has been completed, because
23478 the corresponding entry call comes from the main program, not earlier.
23479 This is why the dynamic model works here. But that's really giving
23480 up on a precise analysis, and we prefer to take this approach only if we cannot
23482 problem in any other manner. So let us examine two ways to reorganize
23483 the program to avoid the potential elaboration problem.
23486 Split library tasks into separate packages.
23488 Write separate packages, so that library tasks are isolated from
23489 other declarations as much as possible. Let us look at a variation on
23492 @smallexample @c ada
23500 package body Decls1 is
23501 task body Lib_Task is
23509 type My_Int is new Integer;
23510 function Ident (M : My_Int) return My_Int;
23514 package body Decls2 is
23515 function Ident (M : My_Int) return My_Int is
23523 procedure Put_Val (Arg : Decls2.My_Int);
23527 package body Utils is
23528 procedure Put_Val (Arg : Decls2.My_Int) is
23530 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
23537 Decls1.Lib_Task.Start;
23542 All we have done is to split @code{Decls} into two packages, one
23543 containing the library task, and one containing everything else. Now
23544 there is no cycle, and the program compiles, binds, links and executes
23545 using the default static model of elaboration.
23548 Declare separate task types.
23550 A significant part of the problem arises because of the use of the
23551 single task declaration form. This means that the elaboration of
23552 the task type, and the elaboration of the task itself (i.e.@: the
23553 creation of the task) happen at the same time. A good rule
23554 of style in Ada is to always create explicit task types. By
23555 following the additional step of placing task objects in separate
23556 packages from the task type declaration, many elaboration problems
23557 are avoided. Here is another modified example of the example program:
23559 @smallexample @c ada
23561 task type Lib_Task_Type is
23565 type My_Int is new Integer;
23567 function Ident (M : My_Int) return My_Int;
23571 package body Decls is
23572 task body Lib_Task_Type is
23578 function Ident (M : My_Int) return My_Int is
23586 procedure Put_Val (Arg : Decls.My_Int);
23590 package body Utils is
23591 procedure Put_Val (Arg : Decls.My_Int) is
23593 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
23599 Lib_Task : Decls.Lib_Task_Type;
23605 Declst.Lib_Task.Start;
23610 What we have done here is to replace the @code{task} declaration in
23611 package @code{Decls} with a @code{task type} declaration. Then we
23612 introduce a separate package @code{Declst} to contain the actual
23613 task object. This separates the elaboration issues for
23614 the @code{task type}
23615 declaration, which causes no trouble, from the elaboration issues
23616 of the task object, which is also unproblematic, since it is now independent
23617 of the elaboration of @code{Utils}.
23618 This separation of concerns also corresponds to
23619 a generally sound engineering principle of separating declarations
23620 from instances. This version of the program also compiles, binds, links,
23621 and executes, generating the expected output.
23624 Use No_Entry_Calls_In_Elaboration_Code restriction.
23625 @cindex No_Entry_Calls_In_Elaboration_Code
23627 The previous two approaches described how a program can be restructured
23628 to avoid the special problems caused by library task bodies. in practice,
23629 however, such restructuring may be difficult to apply to existing legacy code,
23630 so we must consider solutions that do not require massive rewriting.
23632 Let us consider more carefully why our original sample program works
23633 under the dynamic model of elaboration. The reason is that the code
23634 in the task body blocks immediately on the @code{accept}
23635 statement. Now of course there is nothing to prohibit elaboration
23636 code from making entry calls (for example from another library level task),
23637 so we cannot tell in isolation that
23638 the task will not execute the accept statement during elaboration.
23640 However, in practice it is very unusual to see elaboration code
23641 make any entry calls, and the pattern of tasks starting
23642 at elaboration time and then immediately blocking on @code{accept} or
23643 @code{select} statements is very common. What this means is that
23644 the compiler is being too pessimistic when it analyzes the
23645 whole package body as though it might be executed at elaboration
23648 If we know that the elaboration code contains no entry calls, (a very safe
23649 assumption most of the time, that could almost be made the default
23650 behavior), then we can compile all units of the program under control
23651 of the following configuration pragma:
23654 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
23658 This pragma can be placed in the @file{gnat.adc} file in the usual
23659 manner. If we take our original unmodified program and compile it
23660 in the presence of a @file{gnat.adc} containing the above pragma,
23661 then once again, we can compile, bind, link, and execute, obtaining
23662 the expected result. In the presence of this pragma, the compiler does
23663 not trace calls in a task body, that appear after the first @code{accept}
23664 or @code{select} statement, and therefore does not report a potential
23665 circularity in the original program.
23667 The compiler will check to the extent it can that the above
23668 restriction is not violated, but it is not always possible to do a
23669 complete check at compile time, so it is important to use this
23670 pragma only if the stated restriction is in fact met, that is to say
23671 no task receives an entry call before elaboration of all units is completed.
23675 @node Mixing Elaboration Models
23676 @section Mixing Elaboration Models
23678 So far, we have assumed that the entire program is either compiled
23679 using the dynamic model or static model, ensuring consistency. It
23680 is possible to mix the two models, but rules have to be followed
23681 if this mixing is done to ensure that elaboration checks are not
23684 The basic rule is that @emph{a unit compiled with the static model cannot
23685 be @code{with'ed} by a unit compiled with the dynamic model}. The
23686 reason for this is that in the static model, a unit assumes that
23687 its clients guarantee to use (the equivalent of) pragma
23688 @code{Elaborate_All} so that no elaboration checks are required
23689 in inner subprograms, and this assumption is violated if the
23690 client is compiled with dynamic checks.
23692 The precise rule is as follows. A unit that is compiled with dynamic
23693 checks can only @code{with} a unit that meets at least one of the
23694 following criteria:
23699 The @code{with'ed} unit is itself compiled with dynamic elaboration
23700 checks (that is with the @option{-gnatE} switch.
23703 The @code{with'ed} unit is an internal GNAT implementation unit from
23704 the System, Interfaces, Ada, or GNAT hierarchies.
23707 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
23710 The @code{with'ing} unit (that is the client) has an explicit pragma
23711 @code{Elaborate_All} for the @code{with'ed} unit.
23716 If this rule is violated, that is if a unit with dynamic elaboration
23717 checks @code{with's} a unit that does not meet one of the above four
23718 criteria, then the binder (@code{gnatbind}) will issue a warning
23719 similar to that in the following example:
23722 warning: "x.ads" has dynamic elaboration checks and with's
23723 warning: "y.ads" which has static elaboration checks
23727 These warnings indicate that the rule has been violated, and that as a result
23728 elaboration checks may be missed in the resulting executable file.
23729 This warning may be suppressed using the @option{-ws} binder switch
23730 in the usual manner.
23732 One useful application of this mixing rule is in the case of a subsystem
23733 which does not itself @code{with} units from the remainder of the
23734 application. In this case, the entire subsystem can be compiled with
23735 dynamic checks to resolve a circularity in the subsystem, while
23736 allowing the main application that uses this subsystem to be compiled
23737 using the more reliable default static model.
23739 @node What to Do If the Default Elaboration Behavior Fails
23740 @section What to Do If the Default Elaboration Behavior Fails
23743 If the binder cannot find an acceptable order, it outputs detailed
23744 diagnostics. For example:
23750 error: elaboration circularity detected
23751 info: "proc (body)" must be elaborated before "pack (body)"
23752 info: reason: Elaborate_All probably needed in unit "pack (body)"
23753 info: recompile "pack (body)" with -gnatwl
23754 info: for full details
23755 info: "proc (body)"
23756 info: is needed by its spec:
23757 info: "proc (spec)"
23758 info: which is withed by:
23759 info: "pack (body)"
23760 info: "pack (body)" must be elaborated before "proc (body)"
23761 info: reason: pragma Elaborate in unit "proc (body)"
23767 In this case we have a cycle that the binder cannot break. On the one
23768 hand, there is an explicit pragma Elaborate in @code{proc} for
23769 @code{pack}. This means that the body of @code{pack} must be elaborated
23770 before the body of @code{proc}. On the other hand, there is elaboration
23771 code in @code{pack} that calls a subprogram in @code{proc}. This means
23772 that for maximum safety, there should really be a pragma
23773 Elaborate_All in @code{pack} for @code{proc} which would require that
23774 the body of @code{proc} be elaborated before the body of
23775 @code{pack}. Clearly both requirements cannot be satisfied.
23776 Faced with a circularity of this kind, you have three different options.
23779 @item Fix the program
23780 The most desirable option from the point of view of long-term maintenance
23781 is to rearrange the program so that the elaboration problems are avoided.
23782 One useful technique is to place the elaboration code into separate
23783 child packages. Another is to move some of the initialization code to
23784 explicitly called subprograms, where the program controls the order
23785 of initialization explicitly. Although this is the most desirable option,
23786 it may be impractical and involve too much modification, especially in
23787 the case of complex legacy code.
23789 @item Perform dynamic checks
23790 If the compilations are done using the
23792 (dynamic elaboration check) switch, then GNAT behaves in a quite different
23793 manner. Dynamic checks are generated for all calls that could possibly result
23794 in raising an exception. With this switch, the compiler does not generate
23795 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
23796 exactly as specified in the @cite{Ada Reference Manual}.
23797 The binder will generate
23798 an executable program that may or may not raise @code{Program_Error}, and then
23799 it is the programmer's job to ensure that it does not raise an exception. Note
23800 that it is important to compile all units with the switch, it cannot be used
23803 @item Suppress checks
23804 The drawback of dynamic checks is that they generate a
23805 significant overhead at run time, both in space and time. If you
23806 are absolutely sure that your program cannot raise any elaboration
23807 exceptions, and you still want to use the dynamic elaboration model,
23808 then you can use the configuration pragma
23809 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
23810 example this pragma could be placed in the @file{gnat.adc} file.
23812 @item Suppress checks selectively
23813 When you know that certain calls or instantiations in elaboration code cannot
23814 possibly lead to an elaboration error, and the binder nevertheless complains
23815 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
23816 elaboration circularities, it is possible to remove those warnings locally and
23817 obtain a program that will bind. Clearly this can be unsafe, and it is the
23818 responsibility of the programmer to make sure that the resulting program has no
23819 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
23820 used with different granularity to suppress warnings and break elaboration
23825 Place the pragma that names the called subprogram in the declarative part
23826 that contains the call.
23829 Place the pragma in the declarative part, without naming an entity. This
23830 disables warnings on all calls in the corresponding declarative region.
23833 Place the pragma in the package spec that declares the called subprogram,
23834 and name the subprogram. This disables warnings on all elaboration calls to
23838 Place the pragma in the package spec that declares the called subprogram,
23839 without naming any entity. This disables warnings on all elaboration calls to
23840 all subprograms declared in this spec.
23842 @item Use Pragma Elaborate
23843 As previously described in section @xref{Treatment of Pragma Elaborate},
23844 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
23845 that no elaboration checks are required on calls to the designated unit.
23846 There may be cases in which the caller knows that no transitive calls
23847 can occur, so that a @code{pragma Elaborate} will be sufficient in a
23848 case where @code{pragma Elaborate_All} would cause a circularity.
23852 These five cases are listed in order of decreasing safety, and therefore
23853 require increasing programmer care in their application. Consider the
23856 @smallexample @c adanocomment
23858 function F1 return Integer;
23863 function F2 return Integer;
23864 function Pure (x : integer) return integer;
23865 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
23866 -- pragma Suppress (Elaboration_Check); -- (4)
23870 package body Pack1 is
23871 function F1 return Integer is
23875 Val : integer := Pack2.Pure (11); -- Elab. call (1)
23878 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
23879 -- pragma Suppress(Elaboration_Check); -- (2)
23881 X1 := Pack2.F2 + 1; -- Elab. call (2)
23886 package body Pack2 is
23887 function F2 return Integer is
23891 function Pure (x : integer) return integer is
23893 return x ** 3 - 3 * x;
23897 with Pack1, Ada.Text_IO;
23900 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
23903 In the absence of any pragmas, an attempt to bind this program produces
23904 the following diagnostics:
23910 error: elaboration circularity detected
23911 info: "pack1 (body)" must be elaborated before "pack1 (body)"
23912 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
23913 info: recompile "pack1 (body)" with -gnatwl for full details
23914 info: "pack1 (body)"
23915 info: must be elaborated along with its spec:
23916 info: "pack1 (spec)"
23917 info: which is withed by:
23918 info: "pack2 (body)"
23919 info: which must be elaborated along with its spec:
23920 info: "pack2 (spec)"
23921 info: which is withed by:
23922 info: "pack1 (body)"
23925 The sources of the circularity are the two calls to @code{Pack2.Pure} and
23926 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
23927 F2 is safe, even though F2 calls F1, because the call appears after the
23928 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
23929 remove the warning on the call. It is also possible to use pragma (2)
23930 because there are no other potentially unsafe calls in the block.
23933 The call to @code{Pure} is safe because this function does not depend on the
23934 state of @code{Pack2}. Therefore any call to this function is safe, and it
23935 is correct to place pragma (3) in the corresponding package spec.
23938 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
23939 warnings on all calls to functions declared therein. Note that this is not
23940 necessarily safe, and requires more detailed examination of the subprogram
23941 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
23942 be already elaborated.
23946 It is hard to generalize on which of these four approaches should be
23947 taken. Obviously if it is possible to fix the program so that the default
23948 treatment works, this is preferable, but this may not always be practical.
23949 It is certainly simple enough to use
23951 but the danger in this case is that, even if the GNAT binder
23952 finds a correct elaboration order, it may not always do so,
23953 and certainly a binder from another Ada compiler might not. A
23954 combination of testing and analysis (for which the warnings generated
23957 switch can be useful) must be used to ensure that the program is free
23958 of errors. One switch that is useful in this testing is the
23959 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
23962 Normally the binder tries to find an order that has the best chance
23963 of avoiding elaboration problems. However, if this switch is used, the binder
23964 plays a devil's advocate role, and tries to choose the order that
23965 has the best chance of failing. If your program works even with this
23966 switch, then it has a better chance of being error free, but this is still
23969 For an example of this approach in action, consider the C-tests (executable
23970 tests) from the ACVC suite. If these are compiled and run with the default
23971 treatment, then all but one of them succeed without generating any error
23972 diagnostics from the binder. However, there is one test that fails, and
23973 this is not surprising, because the whole point of this test is to ensure
23974 that the compiler can handle cases where it is impossible to determine
23975 a correct order statically, and it checks that an exception is indeed
23976 raised at run time.
23978 This one test must be compiled and run using the
23980 switch, and then it passes. Alternatively, the entire suite can
23981 be run using this switch. It is never wrong to run with the dynamic
23982 elaboration switch if your code is correct, and we assume that the
23983 C-tests are indeed correct (it is less efficient, but efficiency is
23984 not a factor in running the ACVC tests.)
23986 @node Elaboration for Access-to-Subprogram Values
23987 @section Elaboration for Access-to-Subprogram Values
23988 @cindex Access-to-subprogram
23991 Access-to-subprogram types (introduced in Ada 95) complicate
23992 the handling of elaboration. The trouble is that it becomes
23993 impossible to tell at compile time which procedure
23994 is being called. This means that it is not possible for the binder
23995 to analyze the elaboration requirements in this case.
23997 If at the point at which the access value is created
23998 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
23999 the body of the subprogram is
24000 known to have been elaborated, then the access value is safe, and its use
24001 does not require a check. This may be achieved by appropriate arrangement
24002 of the order of declarations if the subprogram is in the current unit,
24003 or, if the subprogram is in another unit, by using pragma
24004 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
24005 on the referenced unit.
24007 If the referenced body is not known to have been elaborated at the point
24008 the access value is created, then any use of the access value must do a
24009 dynamic check, and this dynamic check will fail and raise a
24010 @code{Program_Error} exception if the body has not been elaborated yet.
24011 GNAT will generate the necessary checks, and in addition, if the
24013 switch is set, will generate warnings that such checks are required.
24015 The use of dynamic dispatching for tagged types similarly generates
24016 a requirement for dynamic checks, and premature calls to any primitive
24017 operation of a tagged type before the body of the operation has been
24018 elaborated, will result in the raising of @code{Program_Error}.
24020 @node Summary of Procedures for Elaboration Control
24021 @section Summary of Procedures for Elaboration Control
24022 @cindex Elaboration control
24025 First, compile your program with the default options, using none of
24026 the special elaboration control switches. If the binder successfully
24027 binds your program, then you can be confident that, apart from issues
24028 raised by the use of access-to-subprogram types and dynamic dispatching,
24029 the program is free of elaboration errors. If it is important that the
24030 program be portable, then use the
24032 switch to generate warnings about missing @code{Elaborate} or
24033 @code{Elaborate_All} pragmas, and supply the missing pragmas.
24035 If the program fails to bind using the default static elaboration
24036 handling, then you can fix the program to eliminate the binder
24037 message, or recompile the entire program with the
24038 @option{-gnatE} switch to generate dynamic elaboration checks,
24039 and, if you are sure there really are no elaboration problems,
24040 use a global pragma @code{Suppress (Elaboration_Check)}.
24042 @node Other Elaboration Order Considerations
24043 @section Other Elaboration Order Considerations
24045 This section has been entirely concerned with the issue of finding a valid
24046 elaboration order, as defined by the Ada Reference Manual. In a case
24047 where several elaboration orders are valid, the task is to find one
24048 of the possible valid elaboration orders (and the static model in GNAT
24049 will ensure that this is achieved).
24051 The purpose of the elaboration rules in the Ada Reference Manual is to
24052 make sure that no entity is accessed before it has been elaborated. For
24053 a subprogram, this means that the spec and body must have been elaborated
24054 before the subprogram is called. For an object, this means that the object
24055 must have been elaborated before its value is read or written. A violation
24056 of either of these two requirements is an access before elaboration order,
24057 and this section has been all about avoiding such errors.
24059 In the case where more than one order of elaboration is possible, in the
24060 sense that access before elaboration errors are avoided, then any one of
24061 the orders is ``correct'' in the sense that it meets the requirements of
24062 the Ada Reference Manual, and no such error occurs.
24064 However, it may be the case for a given program, that there are
24065 constraints on the order of elaboration that come not from consideration
24066 of avoiding elaboration errors, but rather from extra-lingual logic
24067 requirements. Consider this example:
24069 @smallexample @c ada
24070 with Init_Constants;
24071 package Constants is
24076 package Init_Constants is
24077 procedure P; -- require a body
24078 end Init_Constants;
24081 package body Init_Constants is
24082 procedure P is begin null; end;
24086 end Init_Constants;
24090 Z : Integer := Constants.X + Constants.Y;
24094 with Text_IO; use Text_IO;
24097 Put_Line (Calc.Z'Img);
24102 In this example, there is more than one valid order of elaboration. For
24103 example both the following are correct orders:
24106 Init_Constants spec
24109 Init_Constants body
24114 Init_Constants spec
24115 Init_Constants body
24122 There is no language rule to prefer one or the other, both are correct
24123 from an order of elaboration point of view. But the programmatic effects
24124 of the two orders are very different. In the first, the elaboration routine
24125 of @code{Calc} initializes @code{Z} to zero, and then the main program
24126 runs with this value of zero. But in the second order, the elaboration
24127 routine of @code{Calc} runs after the body of Init_Constants has set
24128 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
24131 One could perhaps by applying pretty clever non-artificial intelligence
24132 to the situation guess that it is more likely that the second order of
24133 elaboration is the one desired, but there is no formal linguistic reason
24134 to prefer one over the other. In fact in this particular case, GNAT will
24135 prefer the second order, because of the rule that bodies are elaborated
24136 as soon as possible, but it's just luck that this is what was wanted
24137 (if indeed the second order was preferred).
24139 If the program cares about the order of elaboration routines in a case like
24140 this, it is important to specify the order required. In this particular
24141 case, that could have been achieved by adding to the spec of Calc:
24143 @smallexample @c ada
24144 pragma Elaborate_All (Constants);
24148 which requires that the body (if any) and spec of @code{Constants},
24149 as well as the body and spec of any unit @code{with}'ed by
24150 @code{Constants} be elaborated before @code{Calc} is elaborated.
24152 Clearly no automatic method can always guess which alternative you require,
24153 and if you are working with legacy code that had constraints of this kind
24154 which were not properly specified by adding @code{Elaborate} or
24155 @code{Elaborate_All} pragmas, then indeed it is possible that two different
24156 compilers can choose different orders.
24158 However, GNAT does attempt to diagnose the common situation where there
24159 are uninitialized variables in the visible part of a package spec, and the
24160 corresponding package body has an elaboration block that directly or
24161 indirectly initialized one or more of these variables. This is the situation
24162 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
24163 a warning that suggests this addition if it detects this situation.
24165 The @code{gnatbind}
24166 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
24167 out problems. This switch causes bodies to be elaborated as late as possible
24168 instead of as early as possible. In the example above, it would have forced
24169 the choice of the first elaboration order. If you get different results
24170 when using this switch, and particularly if one set of results is right,
24171 and one is wrong as far as you are concerned, it shows that you have some
24172 missing @code{Elaborate} pragmas. For the example above, we have the
24176 gnatmake -f -q main
24179 gnatmake -f -q main -bargs -p
24185 It is of course quite unlikely that both these results are correct, so
24186 it is up to you in a case like this to investigate the source of the
24187 difference, by looking at the two elaboration orders that are chosen,
24188 and figuring out which is correct, and then adding the necessary
24189 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
24193 @c *******************************
24194 @node Conditional Compilation
24195 @appendix Conditional Compilation
24196 @c *******************************
24197 @cindex Conditional compilation
24200 It is often necessary to arrange for a single source program
24201 to serve multiple purposes, where it is compiled in different
24202 ways to achieve these different goals. Some examples of the
24203 need for this feature are
24206 @item Adapting a program to a different hardware environment
24207 @item Adapting a program to a different target architecture
24208 @item Turning debugging features on and off
24209 @item Arranging for a program to compile with different compilers
24213 In C, or C++, the typical approach would be to use the preprocessor
24214 that is defined as part of the language. The Ada language does not
24215 contain such a feature. This is not an oversight, but rather a very
24216 deliberate design decision, based on the experience that overuse of
24217 the preprocessing features in C and C++ can result in programs that
24218 are extremely difficult to maintain. For example, if we have ten
24219 switches that can be on or off, this means that there are a thousand
24220 separate programs, any one of which might not even be syntactically
24221 correct, and even if syntactically correct, the resulting program
24222 might not work correctly. Testing all combinations can quickly become
24225 Nevertheless, the need to tailor programs certainly exists, and in
24226 this Appendix we will discuss how this can
24227 be achieved using Ada in general, and GNAT in particular.
24230 * Use of Boolean Constants::
24231 * Debugging - A Special Case::
24232 * Conditionalizing Declarations::
24233 * Use of Alternative Implementations::
24237 @node Use of Boolean Constants
24238 @section Use of Boolean Constants
24241 In the case where the difference is simply which code
24242 sequence is executed, the cleanest solution is to use Boolean
24243 constants to control which code is executed.
24245 @smallexample @c ada
24247 FP_Initialize_Required : constant Boolean := True;
24249 if FP_Initialize_Required then
24256 Not only will the code inside the @code{if} statement not be executed if
24257 the constant Boolean is @code{False}, but it will also be completely
24258 deleted from the program.
24259 However, the code is only deleted after the @code{if} statement
24260 has been checked for syntactic and semantic correctness.
24261 (In contrast, with preprocessors the code is deleted before the
24262 compiler ever gets to see it, so it is not checked until the switch
24264 @cindex Preprocessors (contrasted with conditional compilation)
24266 Typically the Boolean constants will be in a separate package,
24269 @smallexample @c ada
24272 FP_Initialize_Required : constant Boolean := True;
24273 Reset_Available : constant Boolean := False;
24280 The @code{Config} package exists in multiple forms for the various targets,
24281 with an appropriate script selecting the version of @code{Config} needed.
24282 Then any other unit requiring conditional compilation can do a @code{with}
24283 of @code{Config} to make the constants visible.
24286 @node Debugging - A Special Case
24287 @section Debugging - A Special Case
24290 A common use of conditional code is to execute statements (for example
24291 dynamic checks, or output of intermediate results) under control of a
24292 debug switch, so that the debugging behavior can be turned on and off.
24293 This can be done using a Boolean constant to control whether the code
24296 @smallexample @c ada
24299 Put_Line ("got to the first stage!");
24307 @smallexample @c ada
24309 if Debugging and then Temperature > 999.0 then
24310 raise Temperature_Crazy;
24316 Since this is a common case, there are special features to deal with
24317 this in a convenient manner. For the case of tests, Ada 2005 has added
24318 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
24319 @cindex pragma @code{Assert}
24320 on the @code{Assert} pragma that has always been available in GNAT, so this
24321 feature may be used with GNAT even if you are not using Ada 2005 features.
24322 The use of pragma @code{Assert} is described in
24323 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
24324 example, the last test could be written:
24326 @smallexample @c ada
24327 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
24333 @smallexample @c ada
24334 pragma Assert (Temperature <= 999.0);
24338 In both cases, if assertions are active and the temperature is excessive,
24339 the exception @code{Assert_Failure} will be raised, with the given string in
24340 the first case or a string indicating the location of the pragma in the second
24341 case used as the exception message.
24343 You can turn assertions on and off by using the @code{Assertion_Policy}
24345 @cindex pragma @code{Assertion_Policy}
24346 This is an Ada 2005 pragma which is implemented in all modes by
24347 GNAT, but only in the latest versions of GNAT which include Ada 2005
24348 capability. Alternatively, you can use the @option{-gnata} switch
24349 @cindex @option{-gnata} switch
24350 to enable assertions from the command line (this is recognized by all versions
24353 For the example above with the @code{Put_Line}, the GNAT-specific pragma
24354 @code{Debug} can be used:
24355 @cindex pragma @code{Debug}
24357 @smallexample @c ada
24358 pragma Debug (Put_Line ("got to the first stage!"));
24362 If debug pragmas are enabled, the argument, which must be of the form of
24363 a procedure call, is executed (in this case, @code{Put_Line} will be called).
24364 Only one call can be present, but of course a special debugging procedure
24365 containing any code you like can be included in the program and then
24366 called in a pragma @code{Debug} argument as needed.
24368 One advantage of pragma @code{Debug} over the @code{if Debugging then}
24369 construct is that pragma @code{Debug} can appear in declarative contexts,
24370 such as at the very beginning of a procedure, before local declarations have
24373 Debug pragmas are enabled using either the @option{-gnata} switch that also
24374 controls assertions, or with a separate Debug_Policy pragma.
24375 @cindex pragma @code{Debug_Policy}
24376 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
24377 in Ada 95 and Ada 83 programs as well), and is analogous to
24378 pragma @code{Assertion_Policy} to control assertions.
24380 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
24381 and thus they can appear in @file{gnat.adc} if you are not using a
24382 project file, or in the file designated to contain configuration pragmas
24384 They then apply to all subsequent compilations. In practice the use of
24385 the @option{-gnata} switch is often the most convenient method of controlling
24386 the status of these pragmas.
24388 Note that a pragma is not a statement, so in contexts where a statement
24389 sequence is required, you can't just write a pragma on its own. You have
24390 to add a @code{null} statement.
24392 @smallexample @c ada
24395 @dots{} -- some statements
24397 pragma Assert (Num_Cases < 10);
24404 @node Conditionalizing Declarations
24405 @section Conditionalizing Declarations
24408 In some cases, it may be necessary to conditionalize declarations to meet
24409 different requirements. For example we might want a bit string whose length
24410 is set to meet some hardware message requirement.
24412 In some cases, it may be possible to do this using declare blocks controlled
24413 by conditional constants:
24415 @smallexample @c ada
24417 if Small_Machine then
24419 X : Bit_String (1 .. 10);
24425 X : Large_Bit_String (1 .. 1000);
24434 Note that in this approach, both declarations are analyzed by the
24435 compiler so this can only be used where both declarations are legal,
24436 even though one of them will not be used.
24438 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word},
24439 or Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
24440 that are parameterized by these constants. For example
24442 @smallexample @c ada
24445 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
24451 If @code{Bits_Per_Word} is set to 32, this generates either
24453 @smallexample @c ada
24456 Field1 at 0 range 0 .. 32;
24462 for the big endian case, or
24464 @smallexample @c ada
24467 Field1 at 0 range 10 .. 32;
24473 for the little endian case. Since a powerful subset of Ada expression
24474 notation is usable for creating static constants, clever use of this
24475 feature can often solve quite difficult problems in conditionalizing
24476 compilation (note incidentally that in Ada 95, the little endian
24477 constant was introduced as @code{System.Default_Bit_Order}, so you do not
24478 need to define this one yourself).
24481 @node Use of Alternative Implementations
24482 @section Use of Alternative Implementations
24485 In some cases, none of the approaches described above are adequate. This
24486 can occur for example if the set of declarations required is radically
24487 different for two different configurations.
24489 In this situation, the official Ada way of dealing with conditionalizing
24490 such code is to write separate units for the different cases. As long as
24491 this does not result in excessive duplication of code, this can be done
24492 without creating maintenance problems. The approach is to share common
24493 code as far as possible, and then isolate the code and declarations
24494 that are different. Subunits are often a convenient method for breaking
24495 out a piece of a unit that is to be conditionalized, with separate files
24496 for different versions of the subunit for different targets, where the
24497 build script selects the right one to give to the compiler.
24498 @cindex Subunits (and conditional compilation)
24500 As an example, consider a situation where a new feature in Ada 2005
24501 allows something to be done in a really nice way. But your code must be able
24502 to compile with an Ada 95 compiler. Conceptually you want to say:
24504 @smallexample @c ada
24507 @dots{} neat Ada 2005 code
24509 @dots{} not quite as neat Ada 95 code
24515 where @code{Ada_2005} is a Boolean constant.
24517 But this won't work when @code{Ada_2005} is set to @code{False},
24518 since the @code{then} clause will be illegal for an Ada 95 compiler.
24519 (Recall that although such unreachable code would eventually be deleted
24520 by the compiler, it still needs to be legal. If it uses features
24521 introduced in Ada 2005, it will be illegal in Ada 95.)
24523 So instead we write
24525 @smallexample @c ada
24526 procedure Insert is separate;
24530 Then we have two files for the subunit @code{Insert}, with the two sets of
24532 If the package containing this is called @code{File_Queries}, then we might
24536 @item @file{file_queries-insert-2005.adb}
24537 @item @file{file_queries-insert-95.adb}
24541 and the build script renames the appropriate file to
24544 file_queries-insert.adb
24548 and then carries out the compilation.
24550 This can also be done with project files' naming schemes. For example:
24552 @smallexample @c project
24553 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
24557 Note also that with project files it is desirable to use a different extension
24558 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
24559 conflict may arise through another commonly used feature: to declare as part
24560 of the project a set of directories containing all the sources obeying the
24561 default naming scheme.
24563 The use of alternative units is certainly feasible in all situations,
24564 and for example the Ada part of the GNAT run-time is conditionalized
24565 based on the target architecture using this approach. As a specific example,
24566 consider the implementation of the AST feature in VMS. There is one
24574 which is the same for all architectures, and three bodies:
24578 used for all non-VMS operating systems
24579 @item s-asthan-vms-alpha.adb
24580 used for VMS on the Alpha
24581 @item s-asthan-vms-ia64.adb
24582 used for VMS on the ia64
24586 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
24587 this operating system feature is not available, and the two remaining
24588 versions interface with the corresponding versions of VMS to provide
24589 VMS-compatible AST handling. The GNAT build script knows the architecture
24590 and operating system, and automatically selects the right version,
24591 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
24593 Another style for arranging alternative implementations is through Ada's
24594 access-to-subprogram facility.
24595 In case some functionality is to be conditionally included,
24596 you can declare an access-to-procedure variable @code{Ref} that is initialized
24597 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
24599 In some library package, set @code{Ref} to @code{Proc'Access} for some
24600 procedure @code{Proc} that performs the relevant processing.
24601 The initialization only occurs if the library package is included in the
24603 The same idea can also be implemented using tagged types and dispatching
24607 @node Preprocessing
24608 @section Preprocessing
24609 @cindex Preprocessing
24612 Although it is quite possible to conditionalize code without the use of
24613 C-style preprocessing, as described earlier in this section, it is
24614 nevertheless convenient in some cases to use the C approach. Moreover,
24615 older Ada compilers have often provided some preprocessing capability,
24616 so legacy code may depend on this approach, even though it is not
24619 To accommodate such use, GNAT provides a preprocessor (modeled to a large
24620 extent on the various preprocessors that have been used
24621 with legacy code on other compilers, to enable easier transition).
24623 The preprocessor may be used in two separate modes. It can be used quite
24624 separately from the compiler, to generate a separate output source file
24625 that is then fed to the compiler as a separate step. This is the
24626 @code{gnatprep} utility, whose use is fully described in
24627 @ref{Preprocessing Using gnatprep}.
24628 @cindex @code{gnatprep}
24630 The preprocessing language allows such constructs as
24634 #if DEBUG or PRIORITY > 4 then
24635 bunch of declarations
24637 completely different bunch of declarations
24643 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
24644 defined either on the command line or in a separate file.
24646 The other way of running the preprocessor is even closer to the C style and
24647 often more convenient. In this approach the preprocessing is integrated into
24648 the compilation process. The compiler is fed the preprocessor input which
24649 includes @code{#if} lines etc, and then the compiler carries out the
24650 preprocessing internally and processes the resulting output.
24651 For more details on this approach, see @ref{Integrated Preprocessing}.
24654 @c *******************************
24655 @node Inline Assembler
24656 @appendix Inline Assembler
24657 @c *******************************
24660 If you need to write low-level software that interacts directly
24661 with the hardware, Ada provides two ways to incorporate assembly
24662 language code into your program. First, you can import and invoke
24663 external routines written in assembly language, an Ada feature fully
24664 supported by GNAT@. However, for small sections of code it may be simpler
24665 or more efficient to include assembly language statements directly
24666 in your Ada source program, using the facilities of the implementation-defined
24667 package @code{System.Machine_Code}, which incorporates the gcc
24668 Inline Assembler. The Inline Assembler approach offers a number of advantages,
24669 including the following:
24672 @item No need to use non-Ada tools
24673 @item Consistent interface over different targets
24674 @item Automatic usage of the proper calling conventions
24675 @item Access to Ada constants and variables
24676 @item Definition of intrinsic routines
24677 @item Possibility of inlining a subprogram comprising assembler code
24678 @item Code optimizer can take Inline Assembler code into account
24681 This chapter presents a series of examples to show you how to use
24682 the Inline Assembler. Although it focuses on the Intel x86,
24683 the general approach applies also to other processors.
24684 It is assumed that you are familiar with Ada
24685 and with assembly language programming.
24688 * Basic Assembler Syntax::
24689 * A Simple Example of Inline Assembler::
24690 * Output Variables in Inline Assembler::
24691 * Input Variables in Inline Assembler::
24692 * Inlining Inline Assembler Code::
24693 * Other Asm Functionality::
24696 @c ---------------------------------------------------------------------------
24697 @node Basic Assembler Syntax
24698 @section Basic Assembler Syntax
24701 The assembler used by GNAT and gcc is based not on the Intel assembly
24702 language, but rather on a language that descends from the AT&T Unix
24703 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
24704 The following table summarizes the main features of @emph{as} syntax
24705 and points out the differences from the Intel conventions.
24706 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
24707 pre-processor) documentation for further information.
24710 @item Register names
24711 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
24713 Intel: No extra punctuation; for example @code{eax}
24715 @item Immediate operand
24716 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
24718 Intel: No extra punctuation; for example @code{4}
24721 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
24723 Intel: No extra punctuation; for example @code{loc}
24725 @item Memory contents
24726 gcc / @emph{as}: No extra punctuation; for example @code{loc}
24728 Intel: Square brackets; for example @code{[loc]}
24730 @item Register contents
24731 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
24733 Intel: Square brackets; for example @code{[eax]}
24735 @item Hexadecimal numbers
24736 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
24738 Intel: Trailing ``h''; for example @code{A0h}
24741 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
24744 Intel: Implicit, deduced by assembler; for example @code{mov}
24746 @item Instruction repetition
24747 gcc / @emph{as}: Split into two lines; for example
24753 Intel: Keep on one line; for example @code{rep stosl}
24755 @item Order of operands
24756 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
24758 Intel: Destination first; for example @code{mov eax, 4}
24761 @c ---------------------------------------------------------------------------
24762 @node A Simple Example of Inline Assembler
24763 @section A Simple Example of Inline Assembler
24766 The following example will generate a single assembly language statement,
24767 @code{nop}, which does nothing. Despite its lack of run-time effect,
24768 the example will be useful in illustrating the basics of
24769 the Inline Assembler facility.
24771 @smallexample @c ada
24773 with System.Machine_Code; use System.Machine_Code;
24774 procedure Nothing is
24781 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
24782 here it takes one parameter, a @emph{template string} that must be a static
24783 expression and that will form the generated instruction.
24784 @code{Asm} may be regarded as a compile-time procedure that parses
24785 the template string and additional parameters (none here),
24786 from which it generates a sequence of assembly language instructions.
24788 The examples in this chapter will illustrate several of the forms
24789 for invoking @code{Asm}; a complete specification of the syntax
24790 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
24793 Under the standard GNAT conventions, the @code{Nothing} procedure
24794 should be in a file named @file{nothing.adb}.
24795 You can build the executable in the usual way:
24799 However, the interesting aspect of this example is not its run-time behavior
24800 but rather the generated assembly code.
24801 To see this output, invoke the compiler as follows:
24803 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
24805 where the options are:
24809 compile only (no bind or link)
24811 generate assembler listing
24812 @item -fomit-frame-pointer
24813 do not set up separate stack frames
24815 do not add runtime checks
24818 This gives a human-readable assembler version of the code. The resulting
24819 file will have the same name as the Ada source file, but with a @code{.s}
24820 extension. In our example, the file @file{nothing.s} has the following
24825 .file "nothing.adb"
24827 ___gnu_compiled_ada:
24830 .globl __ada_nothing
24842 The assembly code you included is clearly indicated by
24843 the compiler, between the @code{#APP} and @code{#NO_APP}
24844 delimiters. The character before the 'APP' and 'NOAPP'
24845 can differ on different targets. For example, GNU/Linux uses '#APP' while
24846 on NT you will see '/APP'.
24848 If you make a mistake in your assembler code (such as using the
24849 wrong size modifier, or using a wrong operand for the instruction) GNAT
24850 will report this error in a temporary file, which will be deleted when
24851 the compilation is finished. Generating an assembler file will help
24852 in such cases, since you can assemble this file separately using the
24853 @emph{as} assembler that comes with gcc.
24855 Assembling the file using the command
24858 as @file{nothing.s}
24861 will give you error messages whose lines correspond to the assembler
24862 input file, so you can easily find and correct any mistakes you made.
24863 If there are no errors, @emph{as} will generate an object file
24864 @file{nothing.out}.
24866 @c ---------------------------------------------------------------------------
24867 @node Output Variables in Inline Assembler
24868 @section Output Variables in Inline Assembler
24871 The examples in this section, showing how to access the processor flags,
24872 illustrate how to specify the destination operands for assembly language
24875 @smallexample @c ada
24877 with Interfaces; use Interfaces;
24878 with Ada.Text_IO; use Ada.Text_IO;
24879 with System.Machine_Code; use System.Machine_Code;
24880 procedure Get_Flags is
24881 Flags : Unsigned_32;
24884 Asm ("pushfl" & LF & HT & -- push flags on stack
24885 "popl %%eax" & LF & HT & -- load eax with flags
24886 "movl %%eax, %0", -- store flags in variable
24887 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24888 Put_Line ("Flags register:" & Flags'Img);
24893 In order to have a nicely aligned assembly listing, we have separated
24894 multiple assembler statements in the Asm template string with linefeed
24895 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
24896 The resulting section of the assembly output file is:
24903 movl %eax, -40(%ebp)
24908 It would have been legal to write the Asm invocation as:
24911 Asm ("pushfl popl %%eax movl %%eax, %0")
24914 but in the generated assembler file, this would come out as:
24918 pushfl popl %eax movl %eax, -40(%ebp)
24922 which is not so convenient for the human reader.
24924 We use Ada comments
24925 at the end of each line to explain what the assembler instructions
24926 actually do. This is a useful convention.
24928 When writing Inline Assembler instructions, you need to precede each register
24929 and variable name with a percent sign. Since the assembler already requires
24930 a percent sign at the beginning of a register name, you need two consecutive
24931 percent signs for such names in the Asm template string, thus @code{%%eax}.
24932 In the generated assembly code, one of the percent signs will be stripped off.
24934 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
24935 variables: operands you later define using @code{Input} or @code{Output}
24936 parameters to @code{Asm}.
24937 An output variable is illustrated in
24938 the third statement in the Asm template string:
24942 The intent is to store the contents of the eax register in a variable that can
24943 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
24944 necessarily work, since the compiler might optimize by using a register
24945 to hold Flags, and the expansion of the @code{movl} instruction would not be
24946 aware of this optimization. The solution is not to store the result directly
24947 but rather to advise the compiler to choose the correct operand form;
24948 that is the purpose of the @code{%0} output variable.
24950 Information about the output variable is supplied in the @code{Outputs}
24951 parameter to @code{Asm}:
24953 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24956 The output is defined by the @code{Asm_Output} attribute of the target type;
24957 the general format is
24959 Type'Asm_Output (constraint_string, variable_name)
24962 The constraint string directs the compiler how
24963 to store/access the associated variable. In the example
24965 Unsigned_32'Asm_Output ("=m", Flags);
24967 the @code{"m"} (memory) constraint tells the compiler that the variable
24968 @code{Flags} should be stored in a memory variable, thus preventing
24969 the optimizer from keeping it in a register. In contrast,
24971 Unsigned_32'Asm_Output ("=r", Flags);
24973 uses the @code{"r"} (register) constraint, telling the compiler to
24974 store the variable in a register.
24976 If the constraint is preceded by the equal character (@strong{=}), it tells
24977 the compiler that the variable will be used to store data into it.
24979 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
24980 allowing the optimizer to choose whatever it deems best.
24982 There are a fairly large number of constraints, but the ones that are
24983 most useful (for the Intel x86 processor) are the following:
24989 global (i.e.@: can be stored anywhere)
25007 use one of eax, ebx, ecx or edx
25009 use one of eax, ebx, ecx, edx, esi or edi
25012 The full set of constraints is described in the gcc and @emph{as}
25013 documentation; note that it is possible to combine certain constraints
25014 in one constraint string.
25016 You specify the association of an output variable with an assembler operand
25017 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
25019 @smallexample @c ada
25021 Asm ("pushfl" & LF & HT & -- push flags on stack
25022 "popl %%eax" & LF & HT & -- load eax with flags
25023 "movl %%eax, %0", -- store flags in variable
25024 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
25028 @code{%0} will be replaced in the expanded code by the appropriate operand,
25030 the compiler decided for the @code{Flags} variable.
25032 In general, you may have any number of output variables:
25035 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
25037 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
25038 of @code{Asm_Output} attributes
25042 @smallexample @c ada
25044 Asm ("movl %%eax, %0" & LF & HT &
25045 "movl %%ebx, %1" & LF & HT &
25047 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
25048 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
25049 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
25053 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
25054 in the Ada program.
25056 As a variation on the @code{Get_Flags} example, we can use the constraints
25057 string to direct the compiler to store the eax register into the @code{Flags}
25058 variable, instead of including the store instruction explicitly in the
25059 @code{Asm} template string:
25061 @smallexample @c ada
25063 with Interfaces; use Interfaces;
25064 with Ada.Text_IO; use Ada.Text_IO;
25065 with System.Machine_Code; use System.Machine_Code;
25066 procedure Get_Flags_2 is
25067 Flags : Unsigned_32;
25070 Asm ("pushfl" & LF & HT & -- push flags on stack
25071 "popl %%eax", -- save flags in eax
25072 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
25073 Put_Line ("Flags register:" & Flags'Img);
25079 The @code{"a"} constraint tells the compiler that the @code{Flags}
25080 variable will come from the eax register. Here is the resulting code:
25088 movl %eax,-40(%ebp)
25093 The compiler generated the store of eax into Flags after
25094 expanding the assembler code.
25096 Actually, there was no need to pop the flags into the eax register;
25097 more simply, we could just pop the flags directly into the program variable:
25099 @smallexample @c ada
25101 with Interfaces; use Interfaces;
25102 with Ada.Text_IO; use Ada.Text_IO;
25103 with System.Machine_Code; use System.Machine_Code;
25104 procedure Get_Flags_3 is
25105 Flags : Unsigned_32;
25108 Asm ("pushfl" & LF & HT & -- push flags on stack
25109 "pop %0", -- save flags in Flags
25110 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
25111 Put_Line ("Flags register:" & Flags'Img);
25116 @c ---------------------------------------------------------------------------
25117 @node Input Variables in Inline Assembler
25118 @section Input Variables in Inline Assembler
25121 The example in this section illustrates how to specify the source operands
25122 for assembly language statements.
25123 The program simply increments its input value by 1:
25125 @smallexample @c ada
25127 with Interfaces; use Interfaces;
25128 with Ada.Text_IO; use Ada.Text_IO;
25129 with System.Machine_Code; use System.Machine_Code;
25130 procedure Increment is
25132 function Incr (Value : Unsigned_32) return Unsigned_32 is
25133 Result : Unsigned_32;
25136 Inputs => Unsigned_32'Asm_Input ("a", Value),
25137 Outputs => Unsigned_32'Asm_Output ("=a", Result));
25141 Value : Unsigned_32;
25145 Put_Line ("Value before is" & Value'Img);
25146 Value := Incr (Value);
25147 Put_Line ("Value after is" & Value'Img);
25152 The @code{Outputs} parameter to @code{Asm} specifies
25153 that the result will be in the eax register and that it is to be stored
25154 in the @code{Result} variable.
25156 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
25157 but with an @code{Asm_Input} attribute.
25158 The @code{"="} constraint, indicating an output value, is not present.
25160 You can have multiple input variables, in the same way that you can have more
25161 than one output variable.
25163 The parameter count (%0, %1) etc, now starts at the first input
25164 statement, and continues with the output statements.
25165 When both parameters use the same variable, the
25166 compiler will treat them as the same %n operand, which is the case here.
25168 Just as the @code{Outputs} parameter causes the register to be stored into the
25169 target variable after execution of the assembler statements, so does the
25170 @code{Inputs} parameter cause its variable to be loaded into the register
25171 before execution of the assembler statements.
25173 Thus the effect of the @code{Asm} invocation is:
25175 @item load the 32-bit value of @code{Value} into eax
25176 @item execute the @code{incl %eax} instruction
25177 @item store the contents of eax into the @code{Result} variable
25180 The resulting assembler file (with @option{-O2} optimization) contains:
25183 _increment__incr.1:
25196 @c ---------------------------------------------------------------------------
25197 @node Inlining Inline Assembler Code
25198 @section Inlining Inline Assembler Code
25201 For a short subprogram such as the @code{Incr} function in the previous
25202 section, the overhead of the call and return (creating / deleting the stack
25203 frame) can be significant, compared to the amount of code in the subprogram
25204 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
25205 which directs the compiler to expand invocations of the subprogram at the
25206 point(s) of call, instead of setting up a stack frame for out-of-line calls.
25207 Here is the resulting program:
25209 @smallexample @c ada
25211 with Interfaces; use Interfaces;
25212 with Ada.Text_IO; use Ada.Text_IO;
25213 with System.Machine_Code; use System.Machine_Code;
25214 procedure Increment_2 is
25216 function Incr (Value : Unsigned_32) return Unsigned_32 is
25217 Result : Unsigned_32;
25220 Inputs => Unsigned_32'Asm_Input ("a", Value),
25221 Outputs => Unsigned_32'Asm_Output ("=a", Result));
25224 pragma Inline (Increment);
25226 Value : Unsigned_32;
25230 Put_Line ("Value before is" & Value'Img);
25231 Value := Increment (Value);
25232 Put_Line ("Value after is" & Value'Img);
25237 Compile the program with both optimization (@option{-O2}) and inlining
25238 (@option{-gnatn}) enabled.
25240 The @code{Incr} function is still compiled as usual, but at the
25241 point in @code{Increment} where our function used to be called:
25246 call _increment__incr.1
25251 the code for the function body directly appears:
25264 thus saving the overhead of stack frame setup and an out-of-line call.
25266 @c ---------------------------------------------------------------------------
25267 @node Other Asm Functionality
25268 @section Other @code{Asm} Functionality
25271 This section describes two important parameters to the @code{Asm}
25272 procedure: @code{Clobber}, which identifies register usage;
25273 and @code{Volatile}, which inhibits unwanted optimizations.
25276 * The Clobber Parameter::
25277 * The Volatile Parameter::
25280 @c ---------------------------------------------------------------------------
25281 @node The Clobber Parameter
25282 @subsection The @code{Clobber} Parameter
25285 One of the dangers of intermixing assembly language and a compiled language
25286 such as Ada is that the compiler needs to be aware of which registers are
25287 being used by the assembly code. In some cases, such as the earlier examples,
25288 the constraint string is sufficient to indicate register usage (e.g.,
25290 the eax register). But more generally, the compiler needs an explicit
25291 identification of the registers that are used by the Inline Assembly
25294 Using a register that the compiler doesn't know about
25295 could be a side effect of an instruction (like @code{mull}
25296 storing its result in both eax and edx).
25297 It can also arise from explicit register usage in your
25298 assembly code; for example:
25301 Asm ("movl %0, %%ebx" & LF & HT &
25303 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
25304 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
25308 where the compiler (since it does not analyze the @code{Asm} template string)
25309 does not know you are using the ebx register.
25311 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
25312 to identify the registers that will be used by your assembly code:
25316 Asm ("movl %0, %%ebx" & LF & HT &
25318 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
25319 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
25324 The Clobber parameter is a static string expression specifying the
25325 register(s) you are using. Note that register names are @emph{not} prefixed
25326 by a percent sign. Also, if more than one register is used then their names
25327 are separated by commas; e.g., @code{"eax, ebx"}
25329 The @code{Clobber} parameter has several additional uses:
25331 @item Use ``register'' name @code{cc} to indicate that flags might have changed
25332 @item Use ``register'' name @code{memory} if you changed a memory location
25335 @c ---------------------------------------------------------------------------
25336 @node The Volatile Parameter
25337 @subsection The @code{Volatile} Parameter
25338 @cindex Volatile parameter
25341 Compiler optimizations in the presence of Inline Assembler may sometimes have
25342 unwanted effects. For example, when an @code{Asm} invocation with an input
25343 variable is inside a loop, the compiler might move the loading of the input
25344 variable outside the loop, regarding it as a one-time initialization.
25346 If this effect is not desired, you can disable such optimizations by setting
25347 the @code{Volatile} parameter to @code{True}; for example:
25349 @smallexample @c ada
25351 Asm ("movl %0, %%ebx" & LF & HT &
25353 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
25354 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
25360 By default, @code{Volatile} is set to @code{False} unless there is no
25361 @code{Outputs} parameter.
25363 Although setting @code{Volatile} to @code{True} prevents unwanted
25364 optimizations, it will also disable other optimizations that might be
25365 important for efficiency. In general, you should set @code{Volatile}
25366 to @code{True} only if the compiler's optimizations have created
25368 @c END OF INLINE ASSEMBLER CHAPTER
25369 @c ===============================
25371 @c ***********************************
25372 @c * Compatibility and Porting Guide *
25373 @c ***********************************
25374 @node Compatibility and Porting Guide
25375 @appendix Compatibility and Porting Guide
25378 This chapter describes the compatibility issues that may arise between
25379 GNAT and other Ada compilation systems (including those for Ada 83),
25380 and shows how GNAT can expedite porting
25381 applications developed in other Ada environments.
25384 * Compatibility with Ada 83::
25385 * Compatibility between Ada 95 and Ada 2005::
25386 * Implementation-dependent characteristics::
25387 * Compatibility with Other Ada Systems::
25388 * Representation Clauses::
25390 @c Brief section is only in non-VMS version
25391 @c Full chapter is in VMS version
25392 * Compatibility with HP Ada 83::
25395 * Transitioning to 64-Bit GNAT for OpenVMS::
25399 @node Compatibility with Ada 83
25400 @section Compatibility with Ada 83
25401 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
25404 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
25405 particular, the design intention was that the difficulties associated
25406 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
25407 that occur when moving from one Ada 83 system to another.
25409 However, there are a number of points at which there are minor
25410 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
25411 full details of these issues,
25412 and should be consulted for a complete treatment.
25414 following subsections treat the most likely issues to be encountered.
25417 * Legal Ada 83 programs that are illegal in Ada 95::
25418 * More deterministic semantics::
25419 * Changed semantics::
25420 * Other language compatibility issues::
25423 @node Legal Ada 83 programs that are illegal in Ada 95
25424 @subsection Legal Ada 83 programs that are illegal in Ada 95
25426 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
25427 Ada 95 and thus also in Ada 2005:
25430 @item Character literals
25431 Some uses of character literals are ambiguous. Since Ada 95 has introduced
25432 @code{Wide_Character} as a new predefined character type, some uses of
25433 character literals that were legal in Ada 83 are illegal in Ada 95.
25435 @smallexample @c ada
25436 for Char in 'A' .. 'Z' loop @dots{} end loop;
25440 The problem is that @code{'A'} and @code{'Z'} could be from either
25441 @code{Character} or @code{Wide_Character}. The simplest correction
25442 is to make the type explicit; e.g.:
25443 @smallexample @c ada
25444 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
25447 @item New reserved words
25448 The identifiers @code{abstract}, @code{aliased}, @code{protected},
25449 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
25450 Existing Ada 83 code using any of these identifiers must be edited to
25451 use some alternative name.
25453 @item Freezing rules
25454 The rules in Ada 95 are slightly different with regard to the point at
25455 which entities are frozen, and representation pragmas and clauses are
25456 not permitted past the freeze point. This shows up most typically in
25457 the form of an error message complaining that a representation item
25458 appears too late, and the appropriate corrective action is to move
25459 the item nearer to the declaration of the entity to which it refers.
25461 A particular case is that representation pragmas
25464 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
25466 cannot be applied to a subprogram body. If necessary, a separate subprogram
25467 declaration must be introduced to which the pragma can be applied.
25469 @item Optional bodies for library packages
25470 In Ada 83, a package that did not require a package body was nevertheless
25471 allowed to have one. This lead to certain surprises in compiling large
25472 systems (situations in which the body could be unexpectedly ignored by the
25473 binder). In Ada 95, if a package does not require a body then it is not
25474 permitted to have a body. To fix this problem, simply remove a redundant
25475 body if it is empty, or, if it is non-empty, introduce a dummy declaration
25476 into the spec that makes the body required. One approach is to add a private
25477 part to the package declaration (if necessary), and define a parameterless
25478 procedure called @code{Requires_Body}, which must then be given a dummy
25479 procedure body in the package body, which then becomes required.
25480 Another approach (assuming that this does not introduce elaboration
25481 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
25482 since one effect of this pragma is to require the presence of a package body.
25484 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
25485 In Ada 95, the exception @code{Numeric_Error} is a renaming of
25486 @code{Constraint_Error}.
25487 This means that it is illegal to have separate exception handlers for
25488 the two exceptions. The fix is simply to remove the handler for the
25489 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
25490 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
25492 @item Indefinite subtypes in generics
25493 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
25494 as the actual for a generic formal private type, but then the instantiation
25495 would be illegal if there were any instances of declarations of variables
25496 of this type in the generic body. In Ada 95, to avoid this clear violation
25497 of the methodological principle known as the ``contract model'',
25498 the generic declaration explicitly indicates whether
25499 or not such instantiations are permitted. If a generic formal parameter
25500 has explicit unknown discriminants, indicated by using @code{(<>)} after the
25501 type name, then it can be instantiated with indefinite types, but no
25502 stand-alone variables can be declared of this type. Any attempt to declare
25503 such a variable will result in an illegality at the time the generic is
25504 declared. If the @code{(<>)} notation is not used, then it is illegal
25505 to instantiate the generic with an indefinite type.
25506 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
25507 It will show up as a compile time error, and
25508 the fix is usually simply to add the @code{(<>)} to the generic declaration.
25511 @node More deterministic semantics
25512 @subsection More deterministic semantics
25516 Conversions from real types to integer types round away from 0. In Ada 83
25517 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
25518 implementation freedom was intended to support unbiased rounding in
25519 statistical applications, but in practice it interfered with portability.
25520 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
25521 is required. Numeric code may be affected by this change in semantics.
25522 Note, though, that this issue is no worse than already existed in Ada 83
25523 when porting code from one vendor to another.
25526 The Real-Time Annex introduces a set of policies that define the behavior of
25527 features that were implementation dependent in Ada 83, such as the order in
25528 which open select branches are executed.
25531 @node Changed semantics
25532 @subsection Changed semantics
25535 The worst kind of incompatibility is one where a program that is legal in
25536 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
25537 possible in Ada 83. Fortunately this is extremely rare, but the one
25538 situation that you should be alert to is the change in the predefined type
25539 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
25542 @item Range of type @code{Character}
25543 The range of @code{Standard.Character} is now the full 256 characters
25544 of Latin-1, whereas in most Ada 83 implementations it was restricted
25545 to 128 characters. Although some of the effects of
25546 this change will be manifest in compile-time rejection of legal
25547 Ada 83 programs it is possible for a working Ada 83 program to have
25548 a different effect in Ada 95, one that was not permitted in Ada 83.
25549 As an example, the expression
25550 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
25551 delivers @code{255} as its value.
25552 In general, you should look at the logic of any
25553 character-processing Ada 83 program and see whether it needs to be adapted
25554 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
25555 character handling package that may be relevant if code needs to be adapted
25556 to account for the additional Latin-1 elements.
25557 The desirable fix is to
25558 modify the program to accommodate the full character set, but in some cases
25559 it may be convenient to define a subtype or derived type of Character that
25560 covers only the restricted range.
25564 @node Other language compatibility issues
25565 @subsection Other language compatibility issues
25568 @item @option{-gnat83} switch
25569 All implementations of GNAT provide a switch that causes GNAT to operate
25570 in Ada 83 mode. In this mode, some but not all compatibility problems
25571 of the type described above are handled automatically. For example, the
25572 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
25573 as identifiers as in Ada 83.
25575 in practice, it is usually advisable to make the necessary modifications
25576 to the program to remove the need for using this switch.
25577 See @ref{Compiling Different Versions of Ada}.
25579 @item Support for removed Ada 83 pragmas and attributes
25580 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
25581 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
25582 compilers are allowed, but not required, to implement these missing
25583 elements. In contrast with some other compilers, GNAT implements all
25584 such pragmas and attributes, eliminating this compatibility concern. These
25585 include @code{pragma Interface} and the floating point type attributes
25586 (@code{Emax}, @code{Mantissa}, etc.), among other items.
25590 @node Compatibility between Ada 95 and Ada 2005
25591 @section Compatibility between Ada 95 and Ada 2005
25592 @cindex Compatibility between Ada 95 and Ada 2005
25595 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
25596 a number of incompatibilities. Several are enumerated below;
25597 for a complete description please see the
25598 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
25599 @cite{Rationale for Ada 2005}.
25602 @item New reserved words.
25603 The words @code{interface}, @code{overriding} and @code{synchronized} are
25604 reserved in Ada 2005.
25605 A pre-Ada 2005 program that uses any of these as an identifier will be
25608 @item New declarations in predefined packages.
25609 A number of packages in the predefined environment contain new declarations:
25610 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
25611 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
25612 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
25613 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
25614 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
25615 If an Ada 95 program does a @code{with} and @code{use} of any of these
25616 packages, the new declarations may cause name clashes.
25618 @item Access parameters.
25619 A nondispatching subprogram with an access parameter cannot be renamed
25620 as a dispatching operation. This was permitted in Ada 95.
25622 @item Access types, discriminants, and constraints.
25623 Rule changes in this area have led to some incompatibilities; for example,
25624 constrained subtypes of some access types are not permitted in Ada 2005.
25626 @item Aggregates for limited types.
25627 The allowance of aggregates for limited types in Ada 2005 raises the
25628 possibility of ambiguities in legal Ada 95 programs, since additional types
25629 now need to be considered in expression resolution.
25631 @item Fixed-point multiplication and division.
25632 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
25633 were legal in Ada 95 and invoked the predefined versions of these operations,
25635 The ambiguity may be resolved either by applying a type conversion to the
25636 expression, or by explicitly invoking the operation from package
25639 @item Return-by-reference types.
25640 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
25641 can declare a function returning a value from an anonymous access type.
25645 @node Implementation-dependent characteristics
25646 @section Implementation-dependent characteristics
25648 Although the Ada language defines the semantics of each construct as
25649 precisely as practical, in some situations (for example for reasons of
25650 efficiency, or where the effect is heavily dependent on the host or target
25651 platform) the implementation is allowed some freedom. In porting Ada 83
25652 code to GNAT, you need to be aware of whether / how the existing code
25653 exercised such implementation dependencies. Such characteristics fall into
25654 several categories, and GNAT offers specific support in assisting the
25655 transition from certain Ada 83 compilers.
25658 * Implementation-defined pragmas::
25659 * Implementation-defined attributes::
25661 * Elaboration order::
25662 * Target-specific aspects::
25665 @node Implementation-defined pragmas
25666 @subsection Implementation-defined pragmas
25669 Ada compilers are allowed to supplement the language-defined pragmas, and
25670 these are a potential source of non-portability. All GNAT-defined pragmas
25671 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
25672 Reference Manual}, and these include several that are specifically
25673 intended to correspond to other vendors' Ada 83 pragmas.
25674 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
25675 For compatibility with HP Ada 83, GNAT supplies the pragmas
25676 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
25677 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
25678 and @code{Volatile}.
25679 Other relevant pragmas include @code{External} and @code{Link_With}.
25680 Some vendor-specific
25681 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
25683 avoiding compiler rejection of units that contain such pragmas; they are not
25684 relevant in a GNAT context and hence are not otherwise implemented.
25686 @node Implementation-defined attributes
25687 @subsection Implementation-defined attributes
25689 Analogous to pragmas, the set of attributes may be extended by an
25690 implementation. All GNAT-defined attributes are described in
25691 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
25692 Manual}, and these include several that are specifically intended
25693 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
25694 the attribute @code{VADS_Size} may be useful. For compatibility with HP
25695 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
25699 @subsection Libraries
25701 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
25702 code uses vendor-specific libraries then there are several ways to manage
25703 this in Ada 95 or Ada 2005:
25706 If the source code for the libraries (specs and bodies) are
25707 available, then the libraries can be migrated in the same way as the
25710 If the source code for the specs but not the bodies are
25711 available, then you can reimplement the bodies.
25713 Some features introduced by Ada 95 obviate the need for library support. For
25714 example most Ada 83 vendors supplied a package for unsigned integers. The
25715 Ada 95 modular type feature is the preferred way to handle this need, so
25716 instead of migrating or reimplementing the unsigned integer package it may
25717 be preferable to retrofit the application using modular types.
25720 @node Elaboration order
25721 @subsection Elaboration order
25723 The implementation can choose any elaboration order consistent with the unit
25724 dependency relationship. This freedom means that some orders can result in
25725 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
25726 to invoke a subprogram its body has been elaborated, or to instantiate a
25727 generic before the generic body has been elaborated. By default GNAT
25728 attempts to choose a safe order (one that will not encounter access before
25729 elaboration problems) by implicitly inserting @code{Elaborate} or
25730 @code{Elaborate_All} pragmas where
25731 needed. However, this can lead to the creation of elaboration circularities
25732 and a resulting rejection of the program by gnatbind. This issue is
25733 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
25734 In brief, there are several
25735 ways to deal with this situation:
25739 Modify the program to eliminate the circularities, e.g.@: by moving
25740 elaboration-time code into explicitly-invoked procedures
25742 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
25743 @code{Elaborate} pragmas, and then inhibit the generation of implicit
25744 @code{Elaborate_All}
25745 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
25746 (by selectively suppressing elaboration checks via pragma
25747 @code{Suppress(Elaboration_Check)} when it is safe to do so).
25750 @node Target-specific aspects
25751 @subsection Target-specific aspects
25753 Low-level applications need to deal with machine addresses, data
25754 representations, interfacing with assembler code, and similar issues. If
25755 such an Ada 83 application is being ported to different target hardware (for
25756 example where the byte endianness has changed) then you will need to
25757 carefully examine the program logic; the porting effort will heavily depend
25758 on the robustness of the original design. Moreover, Ada 95 (and thus
25759 Ada 2005) are sometimes
25760 incompatible with typical Ada 83 compiler practices regarding implicit
25761 packing, the meaning of the Size attribute, and the size of access values.
25762 GNAT's approach to these issues is described in @ref{Representation Clauses}.
25764 @node Compatibility with Other Ada Systems
25765 @section Compatibility with Other Ada Systems
25768 If programs avoid the use of implementation dependent and
25769 implementation defined features, as documented in the @cite{Ada
25770 Reference Manual}, there should be a high degree of portability between
25771 GNAT and other Ada systems. The following are specific items which
25772 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
25773 compilers, but do not affect porting code to GNAT@.
25774 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
25775 the following issues may or may not arise for Ada 2005 programs
25776 when other compilers appear.)
25779 @item Ada 83 Pragmas and Attributes
25780 Ada 95 compilers are allowed, but not required, to implement the missing
25781 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
25782 GNAT implements all such pragmas and attributes, eliminating this as
25783 a compatibility concern, but some other Ada 95 compilers reject these
25784 pragmas and attributes.
25786 @item Specialized Needs Annexes
25787 GNAT implements the full set of special needs annexes. At the
25788 current time, it is the only Ada 95 compiler to do so. This means that
25789 programs making use of these features may not be portable to other Ada
25790 95 compilation systems.
25792 @item Representation Clauses
25793 Some other Ada 95 compilers implement only the minimal set of
25794 representation clauses required by the Ada 95 reference manual. GNAT goes
25795 far beyond this minimal set, as described in the next section.
25798 @node Representation Clauses
25799 @section Representation Clauses
25802 The Ada 83 reference manual was quite vague in describing both the minimal
25803 required implementation of representation clauses, and also their precise
25804 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
25805 minimal set of capabilities required is still quite limited.
25807 GNAT implements the full required set of capabilities in
25808 Ada 95 and Ada 2005, but also goes much further, and in particular
25809 an effort has been made to be compatible with existing Ada 83 usage to the
25810 greatest extent possible.
25812 A few cases exist in which Ada 83 compiler behavior is incompatible with
25813 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
25814 intentional or accidental dependence on specific implementation dependent
25815 characteristics of these Ada 83 compilers. The following is a list of
25816 the cases most likely to arise in existing Ada 83 code.
25819 @item Implicit Packing
25820 Some Ada 83 compilers allowed a Size specification to cause implicit
25821 packing of an array or record. This could cause expensive implicit
25822 conversions for change of representation in the presence of derived
25823 types, and the Ada design intends to avoid this possibility.
25824 Subsequent AI's were issued to make it clear that such implicit
25825 change of representation in response to a Size clause is inadvisable,
25826 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
25827 Reference Manuals as implementation advice that is followed by GNAT@.
25828 The problem will show up as an error
25829 message rejecting the size clause. The fix is simply to provide
25830 the explicit pragma @code{Pack}, or for more fine tuned control, provide
25831 a Component_Size clause.
25833 @item Meaning of Size Attribute
25834 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
25835 the minimal number of bits required to hold values of the type. For example,
25836 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
25837 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
25838 some 32 in this situation. This problem will usually show up as a compile
25839 time error, but not always. It is a good idea to check all uses of the
25840 'Size attribute when porting Ada 83 code. The GNAT specific attribute
25841 Object_Size can provide a useful way of duplicating the behavior of
25842 some Ada 83 compiler systems.
25844 @item Size of Access Types
25845 A common assumption in Ada 83 code is that an access type is in fact a pointer,
25846 and that therefore it will be the same size as a System.Address value. This
25847 assumption is true for GNAT in most cases with one exception. For the case of
25848 a pointer to an unconstrained array type (where the bounds may vary from one
25849 value of the access type to another), the default is to use a ``fat pointer'',
25850 which is represented as two separate pointers, one to the bounds, and one to
25851 the array. This representation has a number of advantages, including improved
25852 efficiency. However, it may cause some difficulties in porting existing Ada 83
25853 code which makes the assumption that, for example, pointers fit in 32 bits on
25854 a machine with 32-bit addressing.
25856 To get around this problem, GNAT also permits the use of ``thin pointers'' for
25857 access types in this case (where the designated type is an unconstrained array
25858 type). These thin pointers are indeed the same size as a System.Address value.
25859 To specify a thin pointer, use a size clause for the type, for example:
25861 @smallexample @c ada
25862 type X is access all String;
25863 for X'Size use Standard'Address_Size;
25867 which will cause the type X to be represented using a single pointer.
25868 When using this representation, the bounds are right behind the array.
25869 This representation is slightly less efficient, and does not allow quite
25870 such flexibility in the use of foreign pointers or in using the
25871 Unrestricted_Access attribute to create pointers to non-aliased objects.
25872 But for any standard portable use of the access type it will work in
25873 a functionally correct manner and allow porting of existing code.
25874 Note that another way of forcing a thin pointer representation
25875 is to use a component size clause for the element size in an array,
25876 or a record representation clause for an access field in a record.
25880 @c This brief section is only in the non-VMS version
25881 @c The complete chapter on HP Ada is in the VMS version
25882 @node Compatibility with HP Ada 83
25883 @section Compatibility with HP Ada 83
25886 The VMS version of GNAT fully implements all the pragmas and attributes
25887 provided by HP Ada 83, as well as providing the standard HP Ada 83
25888 libraries, including Starlet. In addition, data layouts and parameter
25889 passing conventions are highly compatible. This means that porting
25890 existing HP Ada 83 code to GNAT in VMS systems should be easier than
25891 most other porting efforts. The following are some of the most
25892 significant differences between GNAT and HP Ada 83.
25895 @item Default floating-point representation
25896 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
25897 it is VMS format. GNAT does implement the necessary pragmas
25898 (Long_Float, Float_Representation) for changing this default.
25901 The package System in GNAT exactly corresponds to the definition in the
25902 Ada 95 reference manual, which means that it excludes many of the
25903 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
25904 that contains the additional definitions, and a special pragma,
25905 Extend_System allows this package to be treated transparently as an
25906 extension of package System.
25909 The definitions provided by Aux_DEC are exactly compatible with those
25910 in the HP Ada 83 version of System, with one exception.
25911 HP Ada provides the following declarations:
25913 @smallexample @c ada
25914 TO_ADDRESS (INTEGER)
25915 TO_ADDRESS (UNSIGNED_LONGWORD)
25916 TO_ADDRESS (@i{universal_integer})
25920 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
25921 an extension to Ada 83 not strictly compatible with the reference manual.
25922 In GNAT, we are constrained to be exactly compatible with the standard,
25923 and this means we cannot provide this capability. In HP Ada 83, the
25924 point of this definition is to deal with a call like:
25926 @smallexample @c ada
25927 TO_ADDRESS (16#12777#);
25931 Normally, according to the Ada 83 standard, one would expect this to be
25932 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
25933 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
25934 definition using @i{universal_integer} takes precedence.
25936 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
25937 is not possible to be 100% compatible. Since there are many programs using
25938 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
25939 to change the name of the function in the UNSIGNED_LONGWORD case, so the
25940 declarations provided in the GNAT version of AUX_Dec are:
25942 @smallexample @c ada
25943 function To_Address (X : Integer) return Address;
25944 pragma Pure_Function (To_Address);
25946 function To_Address_Long (X : Unsigned_Longword)
25948 pragma Pure_Function (To_Address_Long);
25952 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
25953 change the name to TO_ADDRESS_LONG@.
25955 @item Task_Id values
25956 The Task_Id values assigned will be different in the two systems, and GNAT
25957 does not provide a specified value for the Task_Id of the environment task,
25958 which in GNAT is treated like any other declared task.
25962 For full details on these and other less significant compatibility issues,
25963 see appendix E of the HP publication entitled @cite{HP Ada, Technical
25964 Overview and Comparison on HP Platforms}.
25966 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
25967 attributes are recognized, although only a subset of them can sensibly
25968 be implemented. The description of pragmas in @ref{Implementation
25969 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
25970 indicates whether or not they are applicable to non-VMS systems.
25974 @node Transitioning to 64-Bit GNAT for OpenVMS
25975 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
25978 This section is meant to assist users of pre-2006 @value{EDITION}
25979 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
25980 the version of the GNAT technology supplied in 2006 and later for
25981 OpenVMS on both Alpha and I64.
25984 * Introduction to transitioning::
25985 * Migration of 32 bit code::
25986 * Taking advantage of 64 bit addressing::
25987 * Technical details::
25990 @node Introduction to transitioning
25991 @subsection Introduction
25994 64-bit @value{EDITION} for Open VMS has been designed to meet
25999 Providing a full conforming implementation of Ada 95 and Ada 2005
26002 Allowing maximum backward compatibility, thus easing migration of existing
26006 Supplying a path for exploiting the full 64-bit address range
26010 Ada's strong typing semantics has made it
26011 impractical to have different 32-bit and 64-bit modes. As soon as
26012 one object could possibly be outside the 32-bit address space, this
26013 would make it necessary for the @code{System.Address} type to be 64 bits.
26014 In particular, this would cause inconsistencies if 32-bit code is
26015 called from 64-bit code that raises an exception.
26017 This issue has been resolved by always using 64-bit addressing
26018 at the system level, but allowing for automatic conversions between
26019 32-bit and 64-bit addresses where required. Thus users who
26020 do not currently require 64-bit addressing capabilities, can
26021 recompile their code with only minimal changes (and indeed
26022 if the code is written in portable Ada, with no assumptions about
26023 the size of the @code{Address} type, then no changes at all are necessary).
26025 this approach provides a simple, gradual upgrade path to future
26026 use of larger memories than available for 32-bit systems.
26027 Also, newly written applications or libraries will by default
26028 be fully compatible with future systems exploiting 64-bit
26029 addressing capabilities.
26031 @ref{Migration of 32 bit code}, will focus on porting applications
26032 that do not require more than 2 GB of
26033 addressable memory. This code will be referred to as
26034 @emph{32-bit code}.
26035 For applications intending to exploit the full 64-bit address space,
26036 @ref{Taking advantage of 64 bit addressing},
26037 will consider further changes that may be required.
26038 Such code will be referred to below as @emph{64-bit code}.
26040 @node Migration of 32 bit code
26041 @subsection Migration of 32-bit code
26045 * Access types and 32/64-bit allocation::
26046 * Unchecked conversions::
26047 * Predefined constants::
26048 * Interfacing with C::
26049 * 32/64-bit descriptors::
26050 * Experience with source compatibility::
26053 @node Address types
26054 @subsubsection Address types
26057 To solve the problem of mixing 64-bit and 32-bit addressing,
26058 while maintaining maximum backward compatibility, the following
26059 approach has been taken:
26063 @code{System.Address} always has a size of 64 bits
26064 @cindex @code{System.Address} size
26065 @cindex @code{Address} size
26068 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
26069 @cindex @code{System.Short_Address} size
26070 @cindex @code{Short_Address} size
26074 Since @code{System.Short_Address} is a subtype of @code{System.Address},
26075 a @code{Short_Address}
26076 may be used where an @code{Address} is required, and vice versa, without
26077 needing explicit type conversions.
26078 By virtue of the Open VMS parameter passing conventions,
26080 and exported subprograms that have 32-bit address parameters are
26081 compatible with those that have 64-bit address parameters.
26082 (See @ref{Making code 64 bit clean} for details.)
26084 The areas that may need attention are those where record types have
26085 been defined that contain components of the type @code{System.Address}, and
26086 where objects of this type are passed to code expecting a record layout with
26089 Different compilers on different platforms cannot be
26090 expected to represent the same type in the same way,
26091 since alignment constraints
26092 and other system-dependent properties affect the compiler's decision.
26093 For that reason, Ada code
26094 generally uses representation clauses to specify the expected
26095 layout where required.
26097 If such a representation clause uses 32 bits for a component having
26098 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
26099 will detect that error and produce a specific diagnostic message.
26100 The developer should then determine whether the representation
26101 should be 64 bits or not and make either of two changes:
26102 change the size to 64 bits and leave the type as @code{System.Address}, or
26103 leave the size as 32 bits and change the type to @code{System.Short_Address}.
26104 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
26105 required in any code setting or accessing the field; the compiler will
26106 automatically perform any needed conversions between address
26109 @node Access types and 32/64-bit allocation
26110 @subsubsection Access types and 32/64-bit allocation
26111 @cindex 32-bit allocation
26112 @cindex 64-bit allocation
26115 By default, objects designated by access values are always allocated in
26116 the 64-bit address space, and access values themselves are represented
26117 in 64 bits. If these defaults are not appropriate, and 32-bit allocation
26118 is required (for example if the address of an allocated object is assigned
26119 to a @code{Short_Address} variable), then several alternatives are available:
26123 A pool-specific access type (ie, an @w{Ada 83} access type, whose
26124 definition is @code{access T} versus @code{access all T} or
26125 @code{access constant T}), may be declared with a @code{'Size} representation
26126 clause that establishes the size as 32 bits.
26127 In such circumstances allocations for that type will
26128 be from the 32-bit heap. Such a clause is not permitted
26129 for a general access type (declared with @code{access all} or
26130 @code{access constant}) as values of such types must be able to refer
26131 to any object of the designated type, including objects residing outside
26132 the 32-bit address range. Existing @w{Ada 83} code will not contain such
26133 type definitions, however, since general access types were introduced
26137 Switches for @command{GNAT BIND} control whether the internal GNAT
26138 allocation routine @code{__gnat_malloc} uses 64-bit or 32-bit allocations.
26139 @cindex @code{__gnat_malloc}
26140 The switches are respectively @option{-H64} (the default) and
26142 @cindex @option{-H32} (@command{gnatbind})
26143 @cindex @option{-H64} (@command{gnatbind})
26146 The environment variable (logical name) @code{GNAT$NO_MALLOC_64}
26147 @cindex @code{GNAT$NO_MALLOC_64} environment variable
26148 may be used to force @code{__gnat_malloc} to use 32-bit allocation.
26149 If this variable is left
26150 undefined, or defined as @code{"DISABLE"}, @code{"FALSE"}, or @code{"0"},
26151 then the default (64-bit) allocation is used.
26152 If defined as @code{"ENABLE"}, @code{"TRUE"}, or @code{"1"},
26153 then 32-bit allocation is used. The gnatbind qualifiers described above
26154 override this logical name.
26157 A ^gcc switch^gcc switch^ for OpenVMS, @option{-mno-malloc64}, operates
26158 @cindex @option{-mno-malloc64} (^gcc^gcc^)
26159 at a low level to convert explicit calls to @code{malloc} and related
26160 functions from the C run-time library so that they perform allocations
26161 in the 32-bit heap.
26162 Since all internal allocations from GNAT use @code{__gnat_malloc},
26163 this switch is not required unless the program makes explicit calls on
26164 @code{malloc} (or related functions) from interfaced C code.
26168 @node Unchecked conversions
26169 @subsubsection Unchecked conversions
26172 In the case of an @code{Unchecked_Conversion} where the source type is a
26173 64-bit access type or the type @code{System.Address}, and the target
26174 type is a 32-bit type, the compiler will generate a warning.
26175 Even though the generated code will still perform the required
26176 conversions, it is highly recommended in these cases to use
26177 respectively a 32-bit access type or @code{System.Short_Address}
26178 as the source type.
26180 @node Predefined constants
26181 @subsubsection Predefined constants
26184 The following table shows the correspondence between pre-2006 versions of
26185 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
26188 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
26189 @item @b{Constant} @tab @b{Old} @tab @b{New}
26190 @item @code{System.Word_Size} @tab 32 @tab 64
26191 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
26192 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
26193 @item @code{System.Address_Size} @tab 32 @tab 64
26197 If you need to refer to the specific
26198 memory size of a 32-bit implementation, instead of the
26199 actual memory size, use @code{System.Short_Memory_Size}
26200 rather than @code{System.Memory_Size}.
26201 Similarly, references to @code{System.Address_Size} may need
26202 to be replaced by @code{System.Short_Address'Size}.
26203 The program @command{gnatfind} may be useful for locating
26204 references to the above constants, so that you can verify that they
26207 @node Interfacing with C
26208 @subsubsection Interfacing with C
26211 In order to minimize the impact of the transition to 64-bit addresses on
26212 legacy programs, some fundamental types in the @code{Interfaces.C}
26213 package hierarchy continue to be represented in 32 bits.
26214 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
26215 This eases integration with the default HP C layout choices, for example
26216 as found in the system routines in @code{DECC$SHR.EXE}.
26217 Because of this implementation choice, the type fully compatible with
26218 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
26219 Depending on the context the compiler will issue a
26220 warning or an error when type @code{Address} is used, alerting the user to a
26221 potential problem. Otherwise 32-bit programs that use
26222 @code{Interfaces.C} should normally not require code modifications
26224 The other issue arising with C interfacing concerns pragma @code{Convention}.
26225 For VMS 64-bit systems, there is an issue of the appropriate default size
26226 of C convention pointers in the absence of an explicit size clause. The HP
26227 C compiler can choose either 32 or 64 bits depending on compiler options.
26228 GNAT chooses 32-bits rather than 64-bits in the default case where no size
26229 clause is given. This proves a better choice for porting 32-bit legacy
26230 applications. In order to have a 64-bit representation, it is necessary to
26231 specify a size representation clause. For example:
26233 @smallexample @c ada
26234 type int_star is access Interfaces.C.int;
26235 pragma Convention(C, int_star);
26236 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
26239 @node 32/64-bit descriptors
26240 @subsubsection 32/64-bit descriptors
26243 By default, GNAT uses a 64-bit descriptor mechanism. For an imported
26244 subprogram (i.e., a subprogram identified by pragma @code{Import_Function},
26245 @code{Import_Procedure}, or @code{Import_Valued_Procedure}) that specifies
26246 @code{Short_Descriptor} as its mechanism, a 32-bit descriptor is used.
26247 @cindex @code{Short_Descriptor} mechanism for imported subprograms
26249 If the configuration pragma @code{Short_Descriptors} is supplied, then
26250 all descriptors will be 32 bits.
26251 @cindex pragma @code{Short_Descriptors}
26253 @node Experience with source compatibility
26254 @subsubsection Experience with source compatibility
26257 The Security Server and STARLET on I64 provide an interesting ``test case''
26258 for source compatibility issues, since it is in such system code
26259 where assumptions about @code{Address} size might be expected to occur.
26260 Indeed, there were a small number of occasions in the Security Server
26261 file @file{jibdef.ads}
26262 where a representation clause for a record type specified
26263 32 bits for a component of type @code{Address}.
26264 All of these errors were detected by the compiler.
26265 The repair was obvious and immediate; to simply replace @code{Address} by
26266 @code{Short_Address}.
26268 In the case of STARLET, there were several record types that should
26269 have had representation clauses but did not. In these record types
26270 there was an implicit assumption that an @code{Address} value occupied
26272 These compiled without error, but their usage resulted in run-time error
26273 returns from STARLET system calls.
26274 Future GNAT technology enhancements may include a tool that detects and flags
26275 these sorts of potential source code porting problems.
26277 @c ****************************************
26278 @node Taking advantage of 64 bit addressing
26279 @subsection Taking advantage of 64-bit addressing
26282 * Making code 64 bit clean::
26283 * Allocating memory from the 64 bit storage pool::
26284 * Restrictions on use of 64 bit objects::
26285 * STARLET and other predefined libraries::
26288 @node Making code 64 bit clean
26289 @subsubsection Making code 64-bit clean
26292 In order to prevent problems that may occur when (parts of) a
26293 system start using memory outside the 32-bit address range,
26294 we recommend some additional guidelines:
26298 For imported subprograms that take parameters of the
26299 type @code{System.Address}, ensure that these subprograms can
26300 indeed handle 64-bit addresses. If not, or when in doubt,
26301 change the subprogram declaration to specify
26302 @code{System.Short_Address} instead.
26305 Resolve all warnings related to size mismatches in
26306 unchecked conversions. Failing to do so causes
26307 erroneous execution if the source object is outside
26308 the 32-bit address space.
26311 (optional) Explicitly use the 32-bit storage pool
26312 for access types used in a 32-bit context, or use
26313 generic access types where possible
26314 (@pxref{Restrictions on use of 64 bit objects}).
26318 If these rules are followed, the compiler will automatically insert
26319 any necessary checks to ensure that no addresses or access values
26320 passed to 32-bit code ever refer to objects outside the 32-bit
26322 Any attempt to do this will raise @code{Constraint_Error}.
26324 @node Allocating memory from the 64 bit storage pool
26325 @subsubsection Allocating memory from the 64-bit storage pool
26328 By default, all allocations -- for both pool-specific and general
26329 access types -- use the 64-bit storage pool. To override
26330 this default, for an individual access type or globally, see
26331 @ref{Access types and 32/64-bit allocation}.
26333 @node Restrictions on use of 64 bit objects
26334 @subsubsection Restrictions on use of 64-bit objects
26337 Taking the address of an object allocated from a 64-bit storage pool,
26338 and then passing this address to a subprogram expecting
26339 @code{System.Short_Address},
26340 or assigning it to a variable of type @code{Short_Address}, will cause
26341 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
26342 (@pxref{Making code 64 bit clean}), or checks are suppressed,
26343 no exception is raised and execution
26344 will become erroneous.
26346 @node STARLET and other predefined libraries
26347 @subsubsection STARLET and other predefined libraries
26350 All code that comes as part of GNAT is 64-bit clean, but the
26351 restrictions given in @ref{Restrictions on use of 64 bit objects},
26352 still apply. Look at the package
26353 specs to see in which contexts objects allocated
26354 in 64-bit address space are acceptable.
26356 @node Technical details
26357 @subsection Technical details
26360 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
26361 Ada standard with respect to the type of @code{System.Address}. Previous
26362 versions of GNAT Pro have defined this type as private and implemented it as a
26365 In order to allow defining @code{System.Short_Address} as a proper subtype,
26366 and to match the implicit sign extension in parameter passing,
26367 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
26368 visible (i.e., non-private) integer type.
26369 Standard operations on the type, such as the binary operators ``+'', ``-'',
26370 etc., that take @code{Address} operands and return an @code{Address} result,
26371 have been hidden by declaring these
26372 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
26373 ambiguities that would otherwise result from overloading.
26374 (Note that, although @code{Address} is a visible integer type,
26375 good programming practice dictates against exploiting the type's
26376 integer properties such as literals, since this will compromise
26379 Defining @code{Address} as a visible integer type helps achieve
26380 maximum compatibility for existing Ada code,
26381 without sacrificing the capabilities of the 64-bit architecture.
26384 @c ************************************************
26386 @node Microsoft Windows Topics
26387 @appendix Microsoft Windows Topics
26393 This chapter describes topics that are specific to the Microsoft Windows
26394 platforms (NT, 2000, and XP Professional).
26397 * Using GNAT on Windows::
26398 * Using a network installation of GNAT::
26399 * CONSOLE and WINDOWS subsystems::
26400 * Temporary Files::
26401 * Mixed-Language Programming on Windows::
26402 * Windows Calling Conventions::
26403 * Introduction to Dynamic Link Libraries (DLLs)::
26404 * Using DLLs with GNAT::
26405 * Building DLLs with GNAT Project files::
26406 * Building DLLs with GNAT::
26407 * Building DLLs with gnatdll::
26408 * GNAT and Windows Resources::
26409 * Debugging a DLL::
26410 * Setting Stack Size from gnatlink::
26411 * Setting Heap Size from gnatlink::
26414 @node Using GNAT on Windows
26415 @section Using GNAT on Windows
26418 One of the strengths of the GNAT technology is that its tool set
26419 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
26420 @code{gdb} debugger, etc.) is used in the same way regardless of the
26423 On Windows this tool set is complemented by a number of Microsoft-specific
26424 tools that have been provided to facilitate interoperability with Windows
26425 when this is required. With these tools:
26430 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
26434 You can use any Dynamically Linked Library (DLL) in your Ada code (both
26435 relocatable and non-relocatable DLLs are supported).
26438 You can build Ada DLLs for use in other applications. These applications
26439 can be written in a language other than Ada (e.g., C, C++, etc). Again both
26440 relocatable and non-relocatable Ada DLLs are supported.
26443 You can include Windows resources in your Ada application.
26446 You can use or create COM/DCOM objects.
26450 Immediately below are listed all known general GNAT-for-Windows restrictions.
26451 Other restrictions about specific features like Windows Resources and DLLs
26452 are listed in separate sections below.
26457 It is not possible to use @code{GetLastError} and @code{SetLastError}
26458 when tasking, protected records, or exceptions are used. In these
26459 cases, in order to implement Ada semantics, the GNAT run-time system
26460 calls certain Win32 routines that set the last error variable to 0 upon
26461 success. It should be possible to use @code{GetLastError} and
26462 @code{SetLastError} when tasking, protected record, and exception
26463 features are not used, but it is not guaranteed to work.
26466 It is not possible to link against Microsoft libraries except for
26467 import libraries. Interfacing must be done by the mean of DLLs.
26470 When the compilation environment is located on FAT32 drives, users may
26471 experience recompilations of the source files that have not changed if
26472 Daylight Saving Time (DST) state has changed since the last time files
26473 were compiled. NTFS drives do not have this problem.
26476 No components of the GNAT toolset use any entries in the Windows
26477 registry. The only entries that can be created are file associations and
26478 PATH settings, provided the user has chosen to create them at installation
26479 time, as well as some minimal book-keeping information needed to correctly
26480 uninstall or integrate different GNAT products.
26483 @node Using a network installation of GNAT
26484 @section Using a network installation of GNAT
26487 Make sure the system on which GNAT is installed is accessible from the
26488 current machine, i.e., the install location is shared over the network.
26489 Shared resources are accessed on Windows by means of UNC paths, which
26490 have the format @code{\\server\sharename\path}
26492 In order to use such a network installation, simply add the UNC path of the
26493 @file{bin} directory of your GNAT installation in front of your PATH. For
26494 example, if GNAT is installed in @file{\GNAT} directory of a share location
26495 called @file{c-drive} on a machine @file{LOKI}, the following command will
26498 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
26500 Be aware that every compilation using the network installation results in the
26501 transfer of large amounts of data across the network and will likely cause
26502 serious performance penalty.
26504 @node CONSOLE and WINDOWS subsystems
26505 @section CONSOLE and WINDOWS subsystems
26506 @cindex CONSOLE Subsystem
26507 @cindex WINDOWS Subsystem
26511 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
26512 (which is the default subsystem) will always create a console when
26513 launching the application. This is not something desirable when the
26514 application has a Windows GUI. To get rid of this console the
26515 application must be using the @code{WINDOWS} subsystem. To do so
26516 the @option{-mwindows} linker option must be specified.
26519 $ gnatmake winprog -largs -mwindows
26522 @node Temporary Files
26523 @section Temporary Files
26524 @cindex Temporary files
26527 It is possible to control where temporary files gets created by setting
26528 the @env{TMP} environment variable. The file will be created:
26531 @item Under the directory pointed to by the @env{TMP} environment variable if
26532 this directory exists.
26534 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
26535 set (or not pointing to a directory) and if this directory exists.
26537 @item Under the current working directory otherwise.
26541 This allows you to determine exactly where the temporary
26542 file will be created. This is particularly useful in networked
26543 environments where you may not have write access to some
26546 @node Mixed-Language Programming on Windows
26547 @section Mixed-Language Programming on Windows
26550 Developing pure Ada applications on Windows is no different than on
26551 other GNAT-supported platforms. However, when developing or porting an
26552 application that contains a mix of Ada and C/C++, the choice of your
26553 Windows C/C++ development environment conditions your overall
26554 interoperability strategy.
26556 If you use @command{gcc} to compile the non-Ada part of your application,
26557 there are no Windows-specific restrictions that affect the overall
26558 interoperability with your Ada code. If you do want to use the
26559 Microsoft tools for your non-Ada code, you have two choices:
26563 Encapsulate your non-Ada code in a DLL to be linked with your Ada
26564 application. In this case, use the Microsoft or whatever environment to
26565 build the DLL and use GNAT to build your executable
26566 (@pxref{Using DLLs with GNAT}).
26569 Or you can encapsulate your Ada code in a DLL to be linked with the
26570 other part of your application. In this case, use GNAT to build the DLL
26571 (@pxref{Building DLLs with GNAT Project files}) and use the Microsoft
26572 or whatever environment to build your executable.
26575 @node Windows Calling Conventions
26576 @section Windows Calling Conventions
26580 This section pertain only to Win32. On Win64 there is a single native
26581 calling convention. All convention specifiers are ignored on this
26585 * C Calling Convention::
26586 * Stdcall Calling Convention::
26587 * Win32 Calling Convention::
26588 * DLL Calling Convention::
26592 When a subprogram @code{F} (caller) calls a subprogram @code{G}
26593 (callee), there are several ways to push @code{G}'s parameters on the
26594 stack and there are several possible scenarios to clean up the stack
26595 upon @code{G}'s return. A calling convention is an agreed upon software
26596 protocol whereby the responsibilities between the caller (@code{F}) and
26597 the callee (@code{G}) are clearly defined. Several calling conventions
26598 are available for Windows:
26602 @code{C} (Microsoft defined)
26605 @code{Stdcall} (Microsoft defined)
26608 @code{Win32} (GNAT specific)
26611 @code{DLL} (GNAT specific)
26614 @node C Calling Convention
26615 @subsection @code{C} Calling Convention
26618 This is the default calling convention used when interfacing to C/C++
26619 routines compiled with either @command{gcc} or Microsoft Visual C++.
26621 In the @code{C} calling convention subprogram parameters are pushed on the
26622 stack by the caller from right to left. The caller itself is in charge of
26623 cleaning up the stack after the call. In addition, the name of a routine
26624 with @code{C} calling convention is mangled by adding a leading underscore.
26626 The name to use on the Ada side when importing (or exporting) a routine
26627 with @code{C} calling convention is the name of the routine. For
26628 instance the C function:
26631 int get_val (long);
26635 should be imported from Ada as follows:
26637 @smallexample @c ada
26639 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26640 pragma Import (C, Get_Val, External_Name => "get_val");
26645 Note that in this particular case the @code{External_Name} parameter could
26646 have been omitted since, when missing, this parameter is taken to be the
26647 name of the Ada entity in lower case. When the @code{Link_Name} parameter
26648 is missing, as in the above example, this parameter is set to be the
26649 @code{External_Name} with a leading underscore.
26651 When importing a variable defined in C, you should always use the @code{C}
26652 calling convention unless the object containing the variable is part of a
26653 DLL (in which case you should use the @code{Stdcall} calling
26654 convention, @pxref{Stdcall Calling Convention}).
26656 @node Stdcall Calling Convention
26657 @subsection @code{Stdcall} Calling Convention
26660 This convention, which was the calling convention used for Pascal
26661 programs, is used by Microsoft for all the routines in the Win32 API for
26662 efficiency reasons. It must be used to import any routine for which this
26663 convention was specified.
26665 In the @code{Stdcall} calling convention subprogram parameters are pushed
26666 on the stack by the caller from right to left. The callee (and not the
26667 caller) is in charge of cleaning the stack on routine exit. In addition,
26668 the name of a routine with @code{Stdcall} calling convention is mangled by
26669 adding a leading underscore (as for the @code{C} calling convention) and a
26670 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
26671 bytes) of the parameters passed to the routine.
26673 The name to use on the Ada side when importing a C routine with a
26674 @code{Stdcall} calling convention is the name of the C routine. The leading
26675 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
26676 the compiler. For instance the Win32 function:
26679 @b{APIENTRY} int get_val (long);
26683 should be imported from Ada as follows:
26685 @smallexample @c ada
26687 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26688 pragma Import (Stdcall, Get_Val);
26689 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
26694 As for the @code{C} calling convention, when the @code{External_Name}
26695 parameter is missing, it is taken to be the name of the Ada entity in lower
26696 case. If instead of writing the above import pragma you write:
26698 @smallexample @c ada
26700 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26701 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
26706 then the imported routine is @code{_retrieve_val@@4}. However, if instead
26707 of specifying the @code{External_Name} parameter you specify the
26708 @code{Link_Name} as in the following example:
26710 @smallexample @c ada
26712 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26713 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
26718 then the imported routine is @code{retrieve_val}, that is, there is no
26719 decoration at all. No leading underscore and no Stdcall suffix
26720 @code{@@}@code{@var{nn}}.
26723 This is especially important as in some special cases a DLL's entry
26724 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
26725 name generated for a call has it.
26728 It is also possible to import variables defined in a DLL by using an
26729 import pragma for a variable. As an example, if a DLL contains a
26730 variable defined as:
26737 then, to access this variable from Ada you should write:
26739 @smallexample @c ada
26741 My_Var : Interfaces.C.int;
26742 pragma Import (Stdcall, My_Var);
26747 Note that to ease building cross-platform bindings this convention
26748 will be handled as a @code{C} calling convention on non-Windows platforms.
26750 @node Win32 Calling Convention
26751 @subsection @code{Win32} Calling Convention
26754 This convention, which is GNAT-specific is fully equivalent to the
26755 @code{Stdcall} calling convention described above.
26757 @node DLL Calling Convention
26758 @subsection @code{DLL} Calling Convention
26761 This convention, which is GNAT-specific is fully equivalent to the
26762 @code{Stdcall} calling convention described above.
26764 @node Introduction to Dynamic Link Libraries (DLLs)
26765 @section Introduction to Dynamic Link Libraries (DLLs)
26769 A Dynamically Linked Library (DLL) is a library that can be shared by
26770 several applications running under Windows. A DLL can contain any number of
26771 routines and variables.
26773 One advantage of DLLs is that you can change and enhance them without
26774 forcing all the applications that depend on them to be relinked or
26775 recompiled. However, you should be aware than all calls to DLL routines are
26776 slower since, as you will understand below, such calls are indirect.
26778 To illustrate the remainder of this section, suppose that an application
26779 wants to use the services of a DLL @file{API.dll}. To use the services
26780 provided by @file{API.dll} you must statically link against the DLL or
26781 an import library which contains a jump table with an entry for each
26782 routine and variable exported by the DLL. In the Microsoft world this
26783 import library is called @file{API.lib}. When using GNAT this import
26784 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
26785 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
26787 After you have linked your application with the DLL or the import library
26788 and you run your application, here is what happens:
26792 Your application is loaded into memory.
26795 The DLL @file{API.dll} is mapped into the address space of your
26796 application. This means that:
26800 The DLL will use the stack of the calling thread.
26803 The DLL will use the virtual address space of the calling process.
26806 The DLL will allocate memory from the virtual address space of the calling
26810 Handles (pointers) can be safely exchanged between routines in the DLL
26811 routines and routines in the application using the DLL.
26815 The entries in the jump table (from the import library @file{libAPI.dll.a}
26816 or @file{API.lib} or automatically created when linking against a DLL)
26817 which is part of your application are initialized with the addresses
26818 of the routines and variables in @file{API.dll}.
26821 If present in @file{API.dll}, routines @code{DllMain} or
26822 @code{DllMainCRTStartup} are invoked. These routines typically contain
26823 the initialization code needed for the well-being of the routines and
26824 variables exported by the DLL.
26828 There is an additional point which is worth mentioning. In the Windows
26829 world there are two kind of DLLs: relocatable and non-relocatable
26830 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
26831 in the target application address space. If the addresses of two
26832 non-relocatable DLLs overlap and these happen to be used by the same
26833 application, a conflict will occur and the application will run
26834 incorrectly. Hence, when possible, it is always preferable to use and
26835 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
26836 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
26837 User's Guide) removes the debugging symbols from the DLL but the DLL can
26838 still be relocated.
26840 As a side note, an interesting difference between Microsoft DLLs and
26841 Unix shared libraries, is the fact that on most Unix systems all public
26842 routines are exported by default in a Unix shared library, while under
26843 Windows it is possible (but not required) to list exported routines in
26844 a definition file (@pxref{The Definition File}).
26846 @node Using DLLs with GNAT
26847 @section Using DLLs with GNAT
26850 * Creating an Ada Spec for the DLL Services::
26851 * Creating an Import Library::
26855 To use the services of a DLL, say @file{API.dll}, in your Ada application
26860 The Ada spec for the routines and/or variables you want to access in
26861 @file{API.dll}. If not available this Ada spec must be built from the C/C++
26862 header files provided with the DLL.
26865 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
26866 mentioned an import library is a statically linked library containing the
26867 import table which will be filled at load time to point to the actual
26868 @file{API.dll} routines. Sometimes you don't have an import library for the
26869 DLL you want to use. The following sections will explain how to build
26870 one. Note that this is optional.
26873 The actual DLL, @file{API.dll}.
26877 Once you have all the above, to compile an Ada application that uses the
26878 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
26879 you simply issue the command
26882 $ gnatmake my_ada_app -largs -lAPI
26886 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
26887 tells the GNAT linker to look for an import library. The linker will
26888 look for a library name in this specific order:
26891 @item @file{libAPI.dll.a}
26892 @item @file{API.dll.a}
26893 @item @file{libAPI.a}
26894 @item @file{API.lib}
26895 @item @file{libAPI.dll}
26896 @item @file{API.dll}
26899 The first three are the GNU style import libraries. The third is the
26900 Microsoft style import libraries. The last two are the actual DLL names.
26902 Note that if the Ada package spec for @file{API.dll} contains the
26905 @smallexample @c ada
26906 pragma Linker_Options ("-lAPI");
26910 you do not have to add @option{-largs -lAPI} at the end of the
26911 @command{gnatmake} command.
26913 If any one of the items above is missing you will have to create it
26914 yourself. The following sections explain how to do so using as an
26915 example a fictitious DLL called @file{API.dll}.
26917 @node Creating an Ada Spec for the DLL Services
26918 @subsection Creating an Ada Spec for the DLL Services
26921 A DLL typically comes with a C/C++ header file which provides the
26922 definitions of the routines and variables exported by the DLL. The Ada
26923 equivalent of this header file is a package spec that contains definitions
26924 for the imported entities. If the DLL you intend to use does not come with
26925 an Ada spec you have to generate one such spec yourself. For example if
26926 the header file of @file{API.dll} is a file @file{api.h} containing the
26927 following two definitions:
26939 then the equivalent Ada spec could be:
26941 @smallexample @c ada
26944 with Interfaces.C.Strings;
26949 function Get (Str : C.Strings.Chars_Ptr) return C.int;
26952 pragma Import (C, Get);
26953 pragma Import (DLL, Some_Var);
26960 Note that a variable is
26961 @strong{always imported with a DLL convention}. A function
26962 can have @code{C} or @code{Stdcall} convention.
26963 (@pxref{Windows Calling Conventions}).
26965 @node Creating an Import Library
26966 @subsection Creating an Import Library
26967 @cindex Import library
26970 * The Definition File::
26971 * GNAT-Style Import Library::
26972 * Microsoft-Style Import Library::
26976 If a Microsoft-style import library @file{API.lib} or a GNAT-style
26977 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
26978 with @file{API.dll} you can skip this section. You can also skip this
26979 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
26980 as in this case it is possible to link directly against the
26981 DLL. Otherwise read on.
26983 @node The Definition File
26984 @subsubsection The Definition File
26985 @cindex Definition file
26989 As previously mentioned, and unlike Unix systems, the list of symbols
26990 that are exported from a DLL must be provided explicitly in Windows.
26991 The main goal of a definition file is precisely that: list the symbols
26992 exported by a DLL. A definition file (usually a file with a @code{.def}
26993 suffix) has the following structure:
26998 @r{[}LIBRARY @var{name}@r{]}
26999 @r{[}DESCRIPTION @var{string}@r{]}
27009 @item LIBRARY @var{name}
27010 This section, which is optional, gives the name of the DLL.
27012 @item DESCRIPTION @var{string}
27013 This section, which is optional, gives a description string that will be
27014 embedded in the import library.
27017 This section gives the list of exported symbols (procedures, functions or
27018 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
27019 section of @file{API.def} looks like:
27033 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
27034 (@pxref{Windows Calling Conventions}) for a Stdcall
27035 calling convention function in the exported symbols list.
27038 There can actually be other sections in a definition file, but these
27039 sections are not relevant to the discussion at hand.
27041 @node GNAT-Style Import Library
27042 @subsubsection GNAT-Style Import Library
27045 To create a static import library from @file{API.dll} with the GNAT tools
27046 you should proceed as follows:
27050 Create the definition file @file{API.def} (@pxref{The Definition File}).
27051 For that use the @code{dll2def} tool as follows:
27054 $ dll2def API.dll > API.def
27058 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
27059 to standard output the list of entry points in the DLL. Note that if
27060 some routines in the DLL have the @code{Stdcall} convention
27061 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
27062 suffix then you'll have to edit @file{api.def} to add it, and specify
27063 @option{-k} to @command{gnatdll} when creating the import library.
27066 Here are some hints to find the right @code{@@}@var{nn} suffix.
27070 If you have the Microsoft import library (.lib), it is possible to get
27071 the right symbols by using Microsoft @code{dumpbin} tool (see the
27072 corresponding Microsoft documentation for further details).
27075 $ dumpbin /exports api.lib
27079 If you have a message about a missing symbol at link time the compiler
27080 tells you what symbol is expected. You just have to go back to the
27081 definition file and add the right suffix.
27085 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
27086 (@pxref{Using gnatdll}) as follows:
27089 $ gnatdll -e API.def -d API.dll
27093 @code{gnatdll} takes as input a definition file @file{API.def} and the
27094 name of the DLL containing the services listed in the definition file
27095 @file{API.dll}. The name of the static import library generated is
27096 computed from the name of the definition file as follows: if the
27097 definition file name is @var{xyz}@code{.def}, the import library name will
27098 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
27099 @option{-e} could have been removed because the name of the definition
27100 file (before the ``@code{.def}'' suffix) is the same as the name of the
27101 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
27104 @node Microsoft-Style Import Library
27105 @subsubsection Microsoft-Style Import Library
27108 With GNAT you can either use a GNAT-style or Microsoft-style import
27109 library. A Microsoft import library is needed only if you plan to make an
27110 Ada DLL available to applications developed with Microsoft
27111 tools (@pxref{Mixed-Language Programming on Windows}).
27113 To create a Microsoft-style import library for @file{API.dll} you
27114 should proceed as follows:
27118 Create the definition file @file{API.def} from the DLL. For this use either
27119 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
27120 tool (see the corresponding Microsoft documentation for further details).
27123 Build the actual import library using Microsoft's @code{lib} utility:
27126 $ lib -machine:IX86 -def:API.def -out:API.lib
27130 If you use the above command the definition file @file{API.def} must
27131 contain a line giving the name of the DLL:
27138 See the Microsoft documentation for further details about the usage of
27142 @node Building DLLs with GNAT Project files
27143 @section Building DLLs with GNAT Project files
27144 @cindex DLLs, building
27147 There is nothing specific to Windows in the build process.
27148 @pxref{Library Projects}.
27151 Due to a system limitation, it is not possible under Windows to create threads
27152 when inside the @code{DllMain} routine which is used for auto-initialization
27153 of shared libraries, so it is not possible to have library level tasks in SALs.
27155 @node Building DLLs with GNAT
27156 @section Building DLLs with GNAT
27157 @cindex DLLs, building
27160 This section explain how to build DLLs using the GNAT built-in DLL
27161 support. With the following procedure it is straight forward to build
27162 and use DLLs with GNAT.
27166 @item building object files
27168 The first step is to build all objects files that are to be included
27169 into the DLL. This is done by using the standard @command{gnatmake} tool.
27171 @item building the DLL
27173 To build the DLL you must use @command{gcc}'s @option{-shared} and
27174 @option{-shared-libgcc} options. It is quite simple to use this method:
27177 $ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o @dots{}
27180 It is important to note that in this case all symbols found in the
27181 object files are automatically exported. It is possible to restrict
27182 the set of symbols to export by passing to @command{gcc} a definition
27183 file, @pxref{The Definition File}. For example:
27186 $ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o @dots{}
27189 If you use a definition file you must export the elaboration procedures
27190 for every package that required one. Elaboration procedures are named
27191 using the package name followed by "_E".
27193 @item preparing DLL to be used
27195 For the DLL to be used by client programs the bodies must be hidden
27196 from it and the .ali set with read-only attribute. This is very important
27197 otherwise GNAT will recompile all packages and will not actually use
27198 the code in the DLL. For example:
27202 $ copy *.ads *.ali api.dll apilib
27203 $ attrib +R apilib\*.ali
27208 At this point it is possible to use the DLL by directly linking
27209 against it. Note that you must use the GNAT shared runtime when using
27210 GNAT shared libraries. This is achieved by using @option{-shared} binder's
27214 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
27217 @node Building DLLs with gnatdll
27218 @section Building DLLs with gnatdll
27219 @cindex DLLs, building
27222 * Limitations When Using Ada DLLs from Ada::
27223 * Exporting Ada Entities::
27224 * Ada DLLs and Elaboration::
27225 * Ada DLLs and Finalization::
27226 * Creating a Spec for Ada DLLs::
27227 * Creating the Definition File::
27232 Note that it is preferred to use GNAT Project files
27233 (@pxref{Building DLLs with GNAT Project files}) or the built-in GNAT
27234 DLL support (@pxref{Building DLLs with GNAT}) or to build DLLs.
27236 This section explains how to build DLLs containing Ada code using
27237 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
27238 remainder of this section.
27240 The steps required to build an Ada DLL that is to be used by Ada as well as
27241 non-Ada applications are as follows:
27245 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
27246 @code{Stdcall} calling convention to avoid any Ada name mangling for the
27247 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
27248 skip this step if you plan to use the Ada DLL only from Ada applications.
27251 Your Ada code must export an initialization routine which calls the routine
27252 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
27253 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
27254 routine exported by the Ada DLL must be invoked by the clients of the DLL
27255 to initialize the DLL.
27258 When useful, the DLL should also export a finalization routine which calls
27259 routine @code{adafinal} generated by @command{gnatbind} to perform the
27260 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
27261 The finalization routine exported by the Ada DLL must be invoked by the
27262 clients of the DLL when the DLL services are no further needed.
27265 You must provide a spec for the services exported by the Ada DLL in each
27266 of the programming languages to which you plan to make the DLL available.
27269 You must provide a definition file listing the exported entities
27270 (@pxref{The Definition File}).
27273 Finally you must use @code{gnatdll} to produce the DLL and the import
27274 library (@pxref{Using gnatdll}).
27278 Note that a relocatable DLL stripped using the @code{strip}
27279 binutils tool will not be relocatable anymore. To build a DLL without
27280 debug information pass @code{-largs -s} to @code{gnatdll}. This
27281 restriction does not apply to a DLL built using a Library Project.
27282 @pxref{Library Projects}.
27284 @node Limitations When Using Ada DLLs from Ada
27285 @subsection Limitations When Using Ada DLLs from Ada
27288 When using Ada DLLs from Ada applications there is a limitation users
27289 should be aware of. Because on Windows the GNAT run time is not in a DLL of
27290 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
27291 each Ada DLL includes the services of the GNAT run time that are necessary
27292 to the Ada code inside the DLL. As a result, when an Ada program uses an
27293 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
27294 one in the main program.
27296 It is therefore not possible to exchange GNAT run-time objects between the
27297 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
27298 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
27301 It is completely safe to exchange plain elementary, array or record types,
27302 Windows object handles, etc.
27304 @node Exporting Ada Entities
27305 @subsection Exporting Ada Entities
27306 @cindex Export table
27309 Building a DLL is a way to encapsulate a set of services usable from any
27310 application. As a result, the Ada entities exported by a DLL should be
27311 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
27312 any Ada name mangling. As an example here is an Ada package
27313 @code{API}, spec and body, exporting two procedures, a function, and a
27316 @smallexample @c ada
27319 with Interfaces.C; use Interfaces;
27321 Count : C.int := 0;
27322 function Factorial (Val : C.int) return C.int;
27324 procedure Initialize_API;
27325 procedure Finalize_API;
27326 -- Initialization & Finalization routines. More in the next section.
27328 pragma Export (C, Initialize_API);
27329 pragma Export (C, Finalize_API);
27330 pragma Export (C, Count);
27331 pragma Export (C, Factorial);
27337 @smallexample @c ada
27340 package body API is
27341 function Factorial (Val : C.int) return C.int is
27344 Count := Count + 1;
27345 for K in 1 .. Val loop
27351 procedure Initialize_API is
27353 pragma Import (C, Adainit);
27356 end Initialize_API;
27358 procedure Finalize_API is
27359 procedure Adafinal;
27360 pragma Import (C, Adafinal);
27370 If the Ada DLL you are building will only be used by Ada applications
27371 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
27372 convention. As an example, the previous package could be written as
27375 @smallexample @c ada
27379 Count : Integer := 0;
27380 function Factorial (Val : Integer) return Integer;
27382 procedure Initialize_API;
27383 procedure Finalize_API;
27384 -- Initialization and Finalization routines.
27390 @smallexample @c ada
27393 package body API is
27394 function Factorial (Val : Integer) return Integer is
27395 Fact : Integer := 1;
27397 Count := Count + 1;
27398 for K in 1 .. Val loop
27405 -- The remainder of this package body is unchanged.
27412 Note that if you do not export the Ada entities with a @code{C} or
27413 @code{Stdcall} convention you will have to provide the mangled Ada names
27414 in the definition file of the Ada DLL
27415 (@pxref{Creating the Definition File}).
27417 @node Ada DLLs and Elaboration
27418 @subsection Ada DLLs and Elaboration
27419 @cindex DLLs and elaboration
27422 The DLL that you are building contains your Ada code as well as all the
27423 routines in the Ada library that are needed by it. The first thing a
27424 user of your DLL must do is elaborate the Ada code
27425 (@pxref{Elaboration Order Handling in GNAT}).
27427 To achieve this you must export an initialization routine
27428 (@code{Initialize_API} in the previous example), which must be invoked
27429 before using any of the DLL services. This elaboration routine must call
27430 the Ada elaboration routine @code{adainit} generated by the GNAT binder
27431 (@pxref{Binding with Non-Ada Main Programs}). See the body of
27432 @code{Initialize_Api} for an example. Note that the GNAT binder is
27433 automatically invoked during the DLL build process by the @code{gnatdll}
27434 tool (@pxref{Using gnatdll}).
27436 When a DLL is loaded, Windows systematically invokes a routine called
27437 @code{DllMain}. It would therefore be possible to call @code{adainit}
27438 directly from @code{DllMain} without having to provide an explicit
27439 initialization routine. Unfortunately, it is not possible to call
27440 @code{adainit} from the @code{DllMain} if your program has library level
27441 tasks because access to the @code{DllMain} entry point is serialized by
27442 the system (that is, only a single thread can execute ``through'' it at a
27443 time), which means that the GNAT run time will deadlock waiting for the
27444 newly created task to complete its initialization.
27446 @node Ada DLLs and Finalization
27447 @subsection Ada DLLs and Finalization
27448 @cindex DLLs and finalization
27451 When the services of an Ada DLL are no longer needed, the client code should
27452 invoke the DLL finalization routine, if available. The DLL finalization
27453 routine is in charge of releasing all resources acquired by the DLL. In the
27454 case of the Ada code contained in the DLL, this is achieved by calling
27455 routine @code{adafinal} generated by the GNAT binder
27456 (@pxref{Binding with Non-Ada Main Programs}).
27457 See the body of @code{Finalize_Api} for an
27458 example. As already pointed out the GNAT binder is automatically invoked
27459 during the DLL build process by the @code{gnatdll} tool
27460 (@pxref{Using gnatdll}).
27462 @node Creating a Spec for Ada DLLs
27463 @subsection Creating a Spec for Ada DLLs
27466 To use the services exported by the Ada DLL from another programming
27467 language (e.g.@: C), you have to translate the specs of the exported Ada
27468 entities in that language. For instance in the case of @code{API.dll},
27469 the corresponding C header file could look like:
27474 extern int *_imp__count;
27475 #define count (*_imp__count)
27476 int factorial (int);
27482 It is important to understand that when building an Ada DLL to be used by
27483 other Ada applications, you need two different specs for the packages
27484 contained in the DLL: one for building the DLL and the other for using
27485 the DLL. This is because the @code{DLL} calling convention is needed to
27486 use a variable defined in a DLL, but when building the DLL, the variable
27487 must have either the @code{Ada} or @code{C} calling convention. As an
27488 example consider a DLL comprising the following package @code{API}:
27490 @smallexample @c ada
27494 Count : Integer := 0;
27496 -- Remainder of the package omitted.
27503 After producing a DLL containing package @code{API}, the spec that
27504 must be used to import @code{API.Count} from Ada code outside of the
27507 @smallexample @c ada
27512 pragma Import (DLL, Count);
27518 @node Creating the Definition File
27519 @subsection Creating the Definition File
27522 The definition file is the last file needed to build the DLL. It lists
27523 the exported symbols. As an example, the definition file for a DLL
27524 containing only package @code{API} (where all the entities are exported
27525 with a @code{C} calling convention) is:
27540 If the @code{C} calling convention is missing from package @code{API},
27541 then the definition file contains the mangled Ada names of the above
27542 entities, which in this case are:
27551 api__initialize_api
27556 @node Using gnatdll
27557 @subsection Using @code{gnatdll}
27561 * gnatdll Example::
27562 * gnatdll behind the Scenes::
27567 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
27568 and non-Ada sources that make up your DLL have been compiled.
27569 @code{gnatdll} is actually in charge of two distinct tasks: build the
27570 static import library for the DLL and the actual DLL. The form of the
27571 @code{gnatdll} command is
27575 @c $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
27576 @c Expanding @ovar macro inline (explanation in macro def comments)
27577 $ gnatdll @r{[}@var{switches}@r{]} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
27582 where @var{list-of-files} is a list of ALI and object files. The object
27583 file list must be the exact list of objects corresponding to the non-Ada
27584 sources whose services are to be included in the DLL. The ALI file list
27585 must be the exact list of ALI files for the corresponding Ada sources
27586 whose services are to be included in the DLL. If @var{list-of-files} is
27587 missing, only the static import library is generated.
27590 You may specify any of the following switches to @code{gnatdll}:
27593 @c @item -a@ovar{address}
27594 @c Expanding @ovar macro inline (explanation in macro def comments)
27595 @item -a@r{[}@var{address}@r{]}
27596 @cindex @option{-a} (@code{gnatdll})
27597 Build a non-relocatable DLL at @var{address}. If @var{address} is not
27598 specified the default address @var{0x11000000} will be used. By default,
27599 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
27600 advise the reader to build relocatable DLL.
27602 @item -b @var{address}
27603 @cindex @option{-b} (@code{gnatdll})
27604 Set the relocatable DLL base address. By default the address is
27607 @item -bargs @var{opts}
27608 @cindex @option{-bargs} (@code{gnatdll})
27609 Binder options. Pass @var{opts} to the binder.
27611 @item -d @var{dllfile}
27612 @cindex @option{-d} (@code{gnatdll})
27613 @var{dllfile} is the name of the DLL. This switch must be present for
27614 @code{gnatdll} to do anything. The name of the generated import library is
27615 obtained algorithmically from @var{dllfile} as shown in the following
27616 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
27617 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
27618 by option @option{-e}) is obtained algorithmically from @var{dllfile}
27619 as shown in the following example:
27620 if @var{dllfile} is @code{xyz.dll}, the definition
27621 file used is @code{xyz.def}.
27623 @item -e @var{deffile}
27624 @cindex @option{-e} (@code{gnatdll})
27625 @var{deffile} is the name of the definition file.
27628 @cindex @option{-g} (@code{gnatdll})
27629 Generate debugging information. This information is stored in the object
27630 file and copied from there to the final DLL file by the linker,
27631 where it can be read by the debugger. You must use the
27632 @option{-g} switch if you plan on using the debugger or the symbolic
27636 @cindex @option{-h} (@code{gnatdll})
27637 Help mode. Displays @code{gnatdll} switch usage information.
27640 @cindex @option{-I} (@code{gnatdll})
27641 Direct @code{gnatdll} to search the @var{dir} directory for source and
27642 object files needed to build the DLL.
27643 (@pxref{Search Paths and the Run-Time Library (RTL)}).
27646 @cindex @option{-k} (@code{gnatdll})
27647 Removes the @code{@@}@var{nn} suffix from the import library's exported
27648 names, but keeps them for the link names. You must specify this
27649 option if you want to use a @code{Stdcall} function in a DLL for which
27650 the @code{@@}@var{nn} suffix has been removed. This is the case for most
27651 of the Windows NT DLL for example. This option has no effect when
27652 @option{-n} option is specified.
27654 @item -l @var{file}
27655 @cindex @option{-l} (@code{gnatdll})
27656 The list of ALI and object files used to build the DLL are listed in
27657 @var{file}, instead of being given in the command line. Each line in
27658 @var{file} contains the name of an ALI or object file.
27661 @cindex @option{-n} (@code{gnatdll})
27662 No Import. Do not create the import library.
27665 @cindex @option{-q} (@code{gnatdll})
27666 Quiet mode. Do not display unnecessary messages.
27669 @cindex @option{-v} (@code{gnatdll})
27670 Verbose mode. Display extra information.
27672 @item -largs @var{opts}
27673 @cindex @option{-largs} (@code{gnatdll})
27674 Linker options. Pass @var{opts} to the linker.
27677 @node gnatdll Example
27678 @subsubsection @code{gnatdll} Example
27681 As an example the command to build a relocatable DLL from @file{api.adb}
27682 once @file{api.adb} has been compiled and @file{api.def} created is
27685 $ gnatdll -d api.dll api.ali
27689 The above command creates two files: @file{libapi.dll.a} (the import
27690 library) and @file{api.dll} (the actual DLL). If you want to create
27691 only the DLL, just type:
27694 $ gnatdll -d api.dll -n api.ali
27698 Alternatively if you want to create just the import library, type:
27701 $ gnatdll -d api.dll
27704 @node gnatdll behind the Scenes
27705 @subsubsection @code{gnatdll} behind the Scenes
27708 This section details the steps involved in creating a DLL. @code{gnatdll}
27709 does these steps for you. Unless you are interested in understanding what
27710 goes on behind the scenes, you should skip this section.
27712 We use the previous example of a DLL containing the Ada package @code{API},
27713 to illustrate the steps necessary to build a DLL. The starting point is a
27714 set of objects that will make up the DLL and the corresponding ALI
27715 files. In the case of this example this means that @file{api.o} and
27716 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
27721 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
27722 the information necessary to generate relocation information for the
27728 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
27733 In addition to the base file, the @command{gnatlink} command generates an
27734 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
27735 asks @command{gnatlink} to generate the routines @code{DllMain} and
27736 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
27737 is loaded into memory.
27740 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
27741 export table (@file{api.exp}). The export table contains the relocation
27742 information in a form which can be used during the final link to ensure
27743 that the Windows loader is able to place the DLL anywhere in memory.
27747 $ dlltool --dllname api.dll --def api.def --base-file api.base \
27748 --output-exp api.exp
27753 @code{gnatdll} builds the base file using the new export table. Note that
27754 @command{gnatbind} must be called once again since the binder generated file
27755 has been deleted during the previous call to @command{gnatlink}.
27760 $ gnatlink api -o api.jnk api.exp -mdll
27761 -Wl,--base-file,api.base
27766 @code{gnatdll} builds the new export table using the new base file and
27767 generates the DLL import library @file{libAPI.dll.a}.
27771 $ dlltool --dllname api.dll --def api.def --base-file api.base \
27772 --output-exp api.exp --output-lib libAPI.a
27777 Finally @code{gnatdll} builds the relocatable DLL using the final export
27783 $ gnatlink api api.exp -o api.dll -mdll
27788 @node Using dlltool
27789 @subsubsection Using @code{dlltool}
27792 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
27793 DLLs and static import libraries. This section summarizes the most
27794 common @code{dlltool} switches. The form of the @code{dlltool} command
27798 @c $ dlltool @ovar{switches}
27799 @c Expanding @ovar macro inline (explanation in macro def comments)
27800 $ dlltool @r{[}@var{switches}@r{]}
27804 @code{dlltool} switches include:
27807 @item --base-file @var{basefile}
27808 @cindex @option{--base-file} (@command{dlltool})
27809 Read the base file @var{basefile} generated by the linker. This switch
27810 is used to create a relocatable DLL.
27812 @item --def @var{deffile}
27813 @cindex @option{--def} (@command{dlltool})
27814 Read the definition file.
27816 @item --dllname @var{name}
27817 @cindex @option{--dllname} (@command{dlltool})
27818 Gives the name of the DLL. This switch is used to embed the name of the
27819 DLL in the static import library generated by @code{dlltool} with switch
27820 @option{--output-lib}.
27823 @cindex @option{-k} (@command{dlltool})
27824 Kill @code{@@}@var{nn} from exported names
27825 (@pxref{Windows Calling Conventions}
27826 for a discussion about @code{Stdcall}-style symbols.
27829 @cindex @option{--help} (@command{dlltool})
27830 Prints the @code{dlltool} switches with a concise description.
27832 @item --output-exp @var{exportfile}
27833 @cindex @option{--output-exp} (@command{dlltool})
27834 Generate an export file @var{exportfile}. The export file contains the
27835 export table (list of symbols in the DLL) and is used to create the DLL.
27837 @item --output-lib @var{libfile}
27838 @cindex @option{--output-lib} (@command{dlltool})
27839 Generate a static import library @var{libfile}.
27842 @cindex @option{-v} (@command{dlltool})
27845 @item --as @var{assembler-name}
27846 @cindex @option{--as} (@command{dlltool})
27847 Use @var{assembler-name} as the assembler. The default is @code{as}.
27850 @node GNAT and Windows Resources
27851 @section GNAT and Windows Resources
27852 @cindex Resources, windows
27855 * Building Resources::
27856 * Compiling Resources::
27857 * Using Resources::
27861 Resources are an easy way to add Windows specific objects to your
27862 application. The objects that can be added as resources include:
27871 @item string tables
27881 @item version information
27884 For example, a version information resource can be defined as follow and
27885 embedded into an executable or DLL:
27887 A version information resource can be used to embed information into an
27888 executable or a DLL. These information can be viewed using the file properties
27889 from the Windows Explorer. Here is an example of a version information
27895 FILEVERSION 1,0,0,0
27896 PRODUCTVERSION 1,0,0,0
27898 BLOCK "StringFileInfo"
27902 VALUE "CompanyName", "My Company Name"
27903 VALUE "FileDescription", "My application"
27904 VALUE "FileVersion", "1.0"
27905 VALUE "InternalName", "my_app"
27906 VALUE "LegalCopyright", "My Name"
27907 VALUE "OriginalFilename", "my_app.exe"
27908 VALUE "ProductName", "My App"
27909 VALUE "ProductVersion", "1.0"
27913 BLOCK "VarFileInfo"
27915 VALUE "Translation", 0x809, 1252
27921 The value @code{0809} (langID) is for the U.K English language and
27922 @code{04E4} (charsetID), which is equal to @code{1252} decimal, for
27926 This section explains how to build, compile and use resources. Note that this
27927 section does not cover all resource objects, for a complete description see
27928 the corresponding Microsoft documentation.
27930 @node Building Resources
27931 @subsection Building Resources
27932 @cindex Resources, building
27935 A resource file is an ASCII file. By convention resource files have an
27936 @file{.rc} extension.
27937 The easiest way to build a resource file is to use Microsoft tools
27938 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
27939 @code{dlgedit.exe} to build dialogs.
27940 It is always possible to build an @file{.rc} file yourself by writing a
27943 It is not our objective to explain how to write a resource file. A
27944 complete description of the resource script language can be found in the
27945 Microsoft documentation.
27947 @node Compiling Resources
27948 @subsection Compiling Resources
27951 @cindex Resources, compiling
27954 This section describes how to build a GNAT-compatible (COFF) object file
27955 containing the resources. This is done using the Resource Compiler
27956 @code{windres} as follows:
27959 $ windres -i myres.rc -o myres.o
27963 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
27964 file. You can specify an alternate preprocessor (usually named
27965 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
27966 parameter. A list of all possible options may be obtained by entering
27967 the command @code{windres} @option{--help}.
27969 It is also possible to use the Microsoft resource compiler @code{rc.exe}
27970 to produce a @file{.res} file (binary resource file). See the
27971 corresponding Microsoft documentation for further details. In this case
27972 you need to use @code{windres} to translate the @file{.res} file to a
27973 GNAT-compatible object file as follows:
27976 $ windres -i myres.res -o myres.o
27979 @node Using Resources
27980 @subsection Using Resources
27981 @cindex Resources, using
27984 To include the resource file in your program just add the
27985 GNAT-compatible object file for the resource(s) to the linker
27986 arguments. With @command{gnatmake} this is done by using the @option{-largs}
27990 $ gnatmake myprog -largs myres.o
27993 @node Debugging a DLL
27994 @section Debugging a DLL
27995 @cindex DLL debugging
27998 * Program and DLL Both Built with GCC/GNAT::
27999 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
28003 Debugging a DLL is similar to debugging a standard program. But
28004 we have to deal with two different executable parts: the DLL and the
28005 program that uses it. We have the following four possibilities:
28009 The program and the DLL are built with @code{GCC/GNAT}.
28011 The program is built with foreign tools and the DLL is built with
28014 The program is built with @code{GCC/GNAT} and the DLL is built with
28019 In this section we address only cases one and two above.
28020 There is no point in trying to debug
28021 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
28022 information in it. To do so you must use a debugger compatible with the
28023 tools suite used to build the DLL.
28025 @node Program and DLL Both Built with GCC/GNAT
28026 @subsection Program and DLL Both Built with GCC/GNAT
28029 This is the simplest case. Both the DLL and the program have @code{GDB}
28030 compatible debugging information. It is then possible to break anywhere in
28031 the process. Let's suppose here that the main procedure is named
28032 @code{ada_main} and that in the DLL there is an entry point named
28036 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
28037 program must have been built with the debugging information (see GNAT -g
28038 switch). Here are the step-by-step instructions for debugging it:
28041 @item Launch @code{GDB} on the main program.
28047 @item Start the program and stop at the beginning of the main procedure
28054 This step is required to be able to set a breakpoint inside the DLL. As long
28055 as the program is not run, the DLL is not loaded. This has the
28056 consequence that the DLL debugging information is also not loaded, so it is not
28057 possible to set a breakpoint in the DLL.
28059 @item Set a breakpoint inside the DLL
28062 (gdb) break ada_dll
28069 At this stage a breakpoint is set inside the DLL. From there on
28070 you can use the standard approach to debug the whole program
28071 (@pxref{Running and Debugging Ada Programs}).
28074 @c This used to work, probably because the DLLs were non-relocatable
28075 @c keep this section around until the problem is sorted out.
28077 To break on the @code{DllMain} routine it is not possible to follow
28078 the procedure above. At the time the program stop on @code{ada_main}
28079 the @code{DllMain} routine as already been called. Either you can use
28080 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
28083 @item Launch @code{GDB} on the main program.
28089 @item Load DLL symbols
28092 (gdb) add-sym api.dll
28095 @item Set a breakpoint inside the DLL
28098 (gdb) break ada_dll.adb:45
28101 Note that at this point it is not possible to break using the routine symbol
28102 directly as the program is not yet running. The solution is to break
28103 on the proper line (break in @file{ada_dll.adb} line 45).
28105 @item Start the program
28114 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
28115 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
28118 * Debugging the DLL Directly::
28119 * Attaching to a Running Process::
28123 In this case things are slightly more complex because it is not possible to
28124 start the main program and then break at the beginning to load the DLL and the
28125 associated DLL debugging information. It is not possible to break at the
28126 beginning of the program because there is no @code{GDB} debugging information,
28127 and therefore there is no direct way of getting initial control. This
28128 section addresses this issue by describing some methods that can be used
28129 to break somewhere in the DLL to debug it.
28132 First suppose that the main procedure is named @code{main} (this is for
28133 example some C code built with Microsoft Visual C) and that there is a
28134 DLL named @code{test.dll} containing an Ada entry point named
28138 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
28139 been built with debugging information (see GNAT -g option).
28141 @node Debugging the DLL Directly
28142 @subsubsection Debugging the DLL Directly
28146 Find out the executable starting address
28149 $ objdump --file-header main.exe
28152 The starting address is reported on the last line. For example:
28155 main.exe: file format pei-i386
28156 architecture: i386, flags 0x0000010a:
28157 EXEC_P, HAS_DEBUG, D_PAGED
28158 start address 0x00401010
28162 Launch the debugger on the executable.
28169 Set a breakpoint at the starting address, and launch the program.
28172 $ (gdb) break *0x00401010
28176 The program will stop at the given address.
28179 Set a breakpoint on a DLL subroutine.
28182 (gdb) break ada_dll.adb:45
28185 Or if you want to break using a symbol on the DLL, you need first to
28186 select the Ada language (language used by the DLL).
28189 (gdb) set language ada
28190 (gdb) break ada_dll
28194 Continue the program.
28201 This will run the program until it reaches the breakpoint that has been
28202 set. From that point you can use the standard way to debug a program
28203 as described in (@pxref{Running and Debugging Ada Programs}).
28208 It is also possible to debug the DLL by attaching to a running process.
28210 @node Attaching to a Running Process
28211 @subsubsection Attaching to a Running Process
28212 @cindex DLL debugging, attach to process
28215 With @code{GDB} it is always possible to debug a running process by
28216 attaching to it. It is possible to debug a DLL this way. The limitation
28217 of this approach is that the DLL must run long enough to perform the
28218 attach operation. It may be useful for instance to insert a time wasting
28219 loop in the code of the DLL to meet this criterion.
28223 @item Launch the main program @file{main.exe}.
28229 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
28230 that the process PID for @file{main.exe} is 208.
28238 @item Attach to the running process to be debugged.
28244 @item Load the process debugging information.
28247 (gdb) symbol-file main.exe
28250 @item Break somewhere in the DLL.
28253 (gdb) break ada_dll
28256 @item Continue process execution.
28265 This last step will resume the process execution, and stop at
28266 the breakpoint we have set. From there you can use the standard
28267 approach to debug a program as described in
28268 (@pxref{Running and Debugging Ada Programs}).
28270 @node Setting Stack Size from gnatlink
28271 @section Setting Stack Size from @command{gnatlink}
28274 It is possible to specify the program stack size at link time. On modern
28275 versions of Windows, starting with XP, this is mostly useful to set the size of
28276 the main stack (environment task). The other task stacks are set with pragma
28277 Storage_Size or with the @command{gnatbind -d} command.
28279 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
28280 reserve size of individual tasks, the link-time stack size applies to all
28281 tasks, and pragma Storage_Size has no effect.
28282 In particular, Stack Overflow checks are made against this
28283 link-time specified size.
28285 This setting can be done with
28286 @command{gnatlink} using either:
28290 @item using @option{-Xlinker} linker option
28293 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
28296 This sets the stack reserve size to 0x10000 bytes and the stack commit
28297 size to 0x1000 bytes.
28299 @item using @option{-Wl} linker option
28302 $ gnatlink hello -Wl,--stack=0x1000000
28305 This sets the stack reserve size to 0x1000000 bytes. Note that with
28306 @option{-Wl} option it is not possible to set the stack commit size
28307 because the coma is a separator for this option.
28311 @node Setting Heap Size from gnatlink
28312 @section Setting Heap Size from @command{gnatlink}
28315 Under Windows systems, it is possible to specify the program heap size from
28316 @command{gnatlink} using either:
28320 @item using @option{-Xlinker} linker option
28323 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
28326 This sets the heap reserve size to 0x10000 bytes and the heap commit
28327 size to 0x1000 bytes.
28329 @item using @option{-Wl} linker option
28332 $ gnatlink hello -Wl,--heap=0x1000000
28335 This sets the heap reserve size to 0x1000000 bytes. Note that with
28336 @option{-Wl} option it is not possible to set the heap commit size
28337 because the coma is a separator for this option.
28343 @c **********************************
28344 @c * GNU Free Documentation License *
28345 @c **********************************
28347 @c GNU Free Documentation License
28349 @node Index,,GNU Free Documentation License, Top
28355 @c Put table of contents at end, otherwise it precedes the "title page" in
28356 @c the .txt version
28357 @c Edit the pdf file to move the contents to the beginning, after the title