1 \input texinfo @c -*-texinfo-*-
4 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
6 @c GNAT DOCUMENTATION o
10 @c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o
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14 @setfilename gnat_ugn.info
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 1.2 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
49 @c @smallexample commands, and preprocess the texi file with the
50 @c ada2texi tool (which generates appropriate highlighting):
51 @c @smallexample @c ada
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
71 @c cause the document build to fail.
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
75 @c lead to large, ugly patches of empty space on a page.
77 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
78 @c or the unw flag set. The unw flag covers topics for both Unix and
81 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
84 @c This flag is used where the text refers to conditions that exist when the
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
111 @settitle @value{EDITION} User's Guide @value{PLATFORM}
112 @dircategory GNU Ada tools
114 * @value{EDITION} User's Guide: (gnat_ugn). @value{PLATFORM}
117 @include gcc-common.texi
119 @setchapternewpage odd
124 @title @value{EDITION} User's Guide
128 @titlefont{@i{@value{PLATFORM}}}
134 @subtitle GNAT, The GNU Ada Compiler
139 @vskip 0pt plus 1filll
146 @node Top, About This Guide, (dir), (dir)
147 @top @value{EDITION} User's Guide
150 @value{EDITION} User's Guide @value{PLATFORM}
153 GNAT, The GNU Ada Compiler@*
154 GCC version @value{version-GCC}@*
161 * Getting Started with GNAT::
162 * The GNAT Compilation Model::
163 * Compiling Using gcc::
164 * Binding Using gnatbind::
165 * Linking Using gnatlink::
166 * The GNAT Make Program gnatmake::
167 * Improving Performance::
168 * Renaming Files Using gnatchop::
169 * Configuration Pragmas::
170 * Handling Arbitrary File Naming Conventions Using gnatname::
171 * GNAT Project Manager::
172 * The Cross-Referencing Tools gnatxref and gnatfind::
173 * The GNAT Pretty-Printer gnatpp::
174 * The GNAT Metric Tool gnatmetric::
175 * File Name Krunching Using gnatkr::
176 * Preprocessing Using gnatprep::
178 * The GNAT Run-Time Library Builder gnatlbr::
180 * The GNAT Library Browser gnatls::
181 * Cleaning Up Using gnatclean::
183 * GNAT and Libraries::
184 * Using the GNU make Utility::
186 * Memory Management Issues::
187 * Stack Related Facilities::
188 * Verifying Properties Using gnatcheck::
189 * Creating Sample Bodies Using gnatstub::
190 * Generating Ada Bindings for C and C++ headers::
191 * Other Utility Programs::
192 * Running and Debugging Ada Programs::
194 * Code Coverage and Profiling::
197 * Compatibility with HP Ada::
199 * Platform-Specific Information for the Run-Time Libraries::
200 * Example of Binder Output File::
201 * Elaboration Order Handling in GNAT::
202 * Conditional Compilation::
204 * Compatibility and Porting Guide::
206 * Microsoft Windows Topics::
208 * GNU Free Documentation License::
211 --- The Detailed Node Listing ---
215 * What This Guide Contains::
216 * What You Should Know before Reading This Guide::
217 * Related Information::
220 Getting Started with GNAT
223 * Running a Simple Ada Program::
224 * Running a Program with Multiple Units::
225 * Using the gnatmake Utility::
227 * Editing with Emacs::
230 * Introduction to GPS::
233 The GNAT Compilation Model
235 * Source Representation::
236 * Foreign Language Representation::
237 * File Naming Rules::
238 * Using Other File Names::
239 * Alternative File Naming Schemes::
240 * Generating Object Files::
241 * Source Dependencies::
242 * The Ada Library Information Files::
243 * Binding an Ada Program::
244 * Mixed Language Programming::
246 * Building Mixed Ada & C++ Programs::
247 * Comparison between GNAT and C/C++ Compilation Models::
249 * Comparison between GNAT and Conventional Ada Library Models::
251 * Placement of temporary files::
254 Foreign Language Representation
257 * Other 8-Bit Codes::
258 * Wide Character Encodings::
260 Compiling Ada Programs With gcc
262 * Compiling Programs::
264 * Search Paths and the Run-Time Library (RTL)::
265 * Order of Compilation Issues::
270 * Output and Error Message Control::
271 * Warning Message Control::
272 * Debugging and Assertion Control::
273 * Validity Checking::
276 * Using gcc for Syntax Checking::
277 * Using gcc for Semantic Checking::
278 * Compiling Different Versions of Ada::
279 * Character Set Control::
280 * File Naming Control::
281 * Subprogram Inlining Control::
282 * Auxiliary Output Control::
283 * Debugging Control::
284 * Exception Handling Control::
285 * Units to Sources Mapping Files::
286 * Integrated Preprocessing::
291 Binding Ada Programs With gnatbind
294 * Switches for gnatbind::
295 * Command-Line Access::
296 * Search Paths for gnatbind::
297 * Examples of gnatbind Usage::
299 Switches for gnatbind
301 * Consistency-Checking Modes::
302 * Binder Error Message Control::
303 * Elaboration Control::
305 * Binding with Non-Ada Main Programs::
306 * Binding Programs with No Main Subprogram::
308 Linking Using gnatlink
311 * Switches for gnatlink::
313 The GNAT Make Program gnatmake
316 * Switches for gnatmake::
317 * Mode Switches for gnatmake::
318 * Notes on the Command Line::
319 * How gnatmake Works::
320 * Examples of gnatmake Usage::
322 Improving Performance
323 * Performance Considerations::
324 * Text_IO Suggestions::
325 * Reducing Size of Ada Executables with gnatelim::
326 * Reducing Size of Executables with unused subprogram/data elimination::
328 Performance Considerations
329 * Controlling Run-Time Checks::
330 * Use of Restrictions::
331 * Optimization Levels::
332 * Debugging Optimized Code::
333 * Inlining of Subprograms::
334 * Other Optimization Switches::
335 * Optimization and Strict Aliasing::
337 * Coverage Analysis::
340 Reducing Size of Ada Executables with gnatelim
343 * Correcting the List of Eliminate Pragmas::
344 * Making Your Executables Smaller::
345 * Summary of the gnatelim Usage Cycle::
347 Reducing Size of Executables with unused subprogram/data elimination
348 * About unused subprogram/data elimination::
349 * Compilation options::
351 Renaming Files Using gnatchop
353 * Handling Files with Multiple Units::
354 * Operating gnatchop in Compilation Mode::
355 * Command Line for gnatchop::
356 * Switches for gnatchop::
357 * Examples of gnatchop Usage::
359 Configuration Pragmas
361 * Handling of Configuration Pragmas::
362 * The Configuration Pragmas Files::
364 Handling Arbitrary File Naming Conventions Using gnatname
366 * Arbitrary File Naming Conventions::
368 * Switches for gnatname::
369 * Examples of gnatname Usage::
374 * Examples of Project Files::
375 * Project File Syntax::
376 * Objects and Sources in Project Files::
377 * Importing Projects::
378 * Project Extension::
379 * Project Hierarchy Extension::
380 * External References in Project Files::
381 * Packages in Project Files::
382 * Variables from Imported Projects::
385 * Stand-alone Library Projects::
386 * Switches Related to Project Files::
387 * Tools Supporting Project Files::
388 * An Extended Example::
389 * Project File Complete Syntax::
391 The Cross-Referencing Tools gnatxref and gnatfind
393 * gnatxref Switches::
394 * gnatfind Switches::
395 * Project Files for gnatxref and gnatfind::
396 * Regular Expressions in gnatfind and gnatxref::
397 * Examples of gnatxref Usage::
398 * Examples of gnatfind Usage::
400 The GNAT Pretty-Printer gnatpp
402 * Switches for gnatpp::
405 The GNAT Metrics Tool gnatmetric
407 * Switches for gnatmetric::
409 File Name Krunching Using gnatkr
414 * Examples of gnatkr Usage::
416 Preprocessing Using gnatprep
417 * Preprocessing Symbols::
419 * Switches for gnatprep::
420 * Form of Definitions File::
421 * Form of Input Text for gnatprep::
424 The GNAT Run-Time Library Builder gnatlbr
427 * Switches for gnatlbr::
428 * Examples of gnatlbr Usage::
431 The GNAT Library Browser gnatls
434 * Switches for gnatls::
435 * Examples of gnatls Usage::
437 Cleaning Up Using gnatclean
439 * Running gnatclean::
440 * Switches for gnatclean::
441 @c * Examples of gnatclean Usage::
447 * Introduction to Libraries in GNAT::
448 * General Ada Libraries::
449 * Stand-alone Ada Libraries::
450 * Rebuilding the GNAT Run-Time Library::
452 Using the GNU make Utility
454 * Using gnatmake in a Makefile::
455 * Automatically Creating a List of Directories::
456 * Generating the Command Line Switches::
457 * Overcoming Command Line Length Limits::
460 Memory Management Issues
462 * Some Useful Memory Pools::
463 * The GNAT Debug Pool Facility::
468 Stack Related Facilities
470 * Stack Overflow Checking::
471 * Static Stack Usage Analysis::
472 * Dynamic Stack Usage Analysis::
474 Some Useful Memory Pools
476 The GNAT Debug Pool Facility
482 * Switches for gnatmem::
483 * Example of gnatmem Usage::
486 Verifying Properties Using gnatcheck
488 * Format of the Report File::
489 * General gnatcheck Switches::
490 * gnatcheck Rule Options::
491 * Adding the Results of Compiler Checks to gnatcheck Output::
492 * Project-Wide Checks::
495 Sample Bodies Using gnatstub
498 * Switches for gnatstub::
500 Other Utility Programs
502 * Using Other Utility Programs with GNAT::
503 * The External Symbol Naming Scheme of GNAT::
504 * Converting Ada Files to html with gnathtml::
507 Code Coverage and Profiling
509 * Code Coverage of Ada Programs using gcov::
510 * Profiling an Ada Program using gprof::
513 Running and Debugging Ada Programs
515 * The GNAT Debugger GDB::
517 * Introduction to GDB Commands::
518 * Using Ada Expressions::
519 * Calling User-Defined Subprograms::
520 * Using the Next Command in a Function::
523 * Debugging Generic Units::
524 * GNAT Abnormal Termination or Failure to Terminate::
525 * Naming Conventions for GNAT Source Files::
526 * Getting Internal Debugging Information::
534 Compatibility with HP Ada
536 * Ada Language Compatibility::
537 * Differences in the Definition of Package System::
538 * Language-Related Features::
539 * The Package STANDARD::
540 * The Package SYSTEM::
541 * Tasking and Task-Related Features::
542 * Pragmas and Pragma-Related Features::
543 * Library of Predefined Units::
545 * Main Program Definition::
546 * Implementation-Defined Attributes::
547 * Compiler and Run-Time Interfacing::
548 * Program Compilation and Library Management::
550 * Implementation Limits::
551 * Tools and Utilities::
553 Language-Related Features
555 * Integer Types and Representations::
556 * Floating-Point Types and Representations::
557 * Pragmas Float_Representation and Long_Float::
558 * Fixed-Point Types and Representations::
559 * Record and Array Component Alignment::
561 * Other Representation Clauses::
563 Tasking and Task-Related Features
565 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
566 * Assigning Task IDs::
567 * Task IDs and Delays::
568 * Task-Related Pragmas::
569 * Scheduling and Task Priority::
571 * External Interrupts::
573 Pragmas and Pragma-Related Features
575 * Restrictions on the Pragma INLINE::
576 * Restrictions on the Pragma INTERFACE::
577 * Restrictions on the Pragma SYSTEM_NAME::
579 Library of Predefined Units
581 * Changes to DECLIB::
585 * Shared Libraries and Options Files::
589 Platform-Specific Information for the Run-Time Libraries
591 * Summary of Run-Time Configurations::
592 * Specifying a Run-Time Library::
593 * Choosing the Scheduling Policy::
594 * Solaris-Specific Considerations::
595 * Linux-Specific Considerations::
596 * AIX-Specific Considerations::
597 * Irix-Specific Considerations::
599 Example of Binder Output File
601 Elaboration Order Handling in GNAT
604 * Checking the Elaboration Order::
605 * Controlling the Elaboration Order::
606 * Controlling Elaboration in GNAT - Internal Calls::
607 * Controlling Elaboration in GNAT - External Calls::
608 * Default Behavior in GNAT - Ensuring Safety::
609 * Treatment of Pragma Elaborate::
610 * Elaboration Issues for Library Tasks::
611 * Mixing Elaboration Models::
612 * What to Do If the Default Elaboration Behavior Fails::
613 * Elaboration for Access-to-Subprogram Values::
614 * Summary of Procedures for Elaboration Control::
615 * Other Elaboration Order Considerations::
617 Conditional Compilation
618 * Use of Boolean Constants::
619 * Debugging - A Special Case::
620 * Conditionalizing Declarations::
621 * Use of Alternative Implementations::
626 * Basic Assembler Syntax::
627 * A Simple Example of Inline Assembler::
628 * Output Variables in Inline Assembler::
629 * Input Variables in Inline Assembler::
630 * Inlining Inline Assembler Code::
631 * Other Asm Functionality::
633 Compatibility and Porting Guide
635 * Compatibility with Ada 83::
636 * Compatibility between Ada 95 and Ada 2005::
637 * Implementation-dependent characteristics::
639 @c This brief section is only in the non-VMS version
640 @c The complete chapter on HP Ada issues is in the VMS version
641 * Compatibility with HP Ada 83::
643 * Compatibility with Other Ada Systems::
644 * Representation Clauses::
646 * Transitioning to 64-Bit GNAT for OpenVMS::
650 Microsoft Windows Topics
652 * Using GNAT on Windows::
653 * CONSOLE and WINDOWS subsystems::
655 * Mixed-Language Programming on Windows::
656 * Windows Calling Conventions::
657 * Introduction to Dynamic Link Libraries (DLLs)::
658 * Using DLLs with GNAT::
659 * Building DLLs with GNAT::
660 * GNAT and Windows Resources::
662 * Setting Stack Size from gnatlink::
663 * Setting Heap Size from gnatlink::
670 @node About This Guide
671 @unnumbered About This Guide
675 This guide describes the use of @value{EDITION},
676 a compiler and software development toolset for the full Ada
677 programming language, implemented on OpenVMS for HP's Alpha and
678 Integrity server (I64) platforms.
681 This guide describes the use of @value{EDITION},
682 a compiler and software development
683 toolset for the full Ada programming language.
685 It documents the features of the compiler and tools, and explains
686 how to use them to build Ada applications.
688 @value{EDITION} implements Ada 95 and Ada 2005, and it may also be invoked in
689 Ada 83 compatibility mode.
690 By default, @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
691 but you can override with a compiler switch
692 (@pxref{Compiling Different Versions of Ada})
693 to explicitly specify the language version.
694 Throughout this manual, references to ``Ada'' without a year suffix
695 apply to both the Ada 95 and Ada 2005 versions of the language.
699 For ease of exposition, ``@value{EDITION}'' will be referred to simply as
700 ``GNAT'' in the remainder of this document.
707 * What This Guide Contains::
708 * What You Should Know before Reading This Guide::
709 * Related Information::
713 @node What This Guide Contains
714 @unnumberedsec What This Guide Contains
717 This guide contains the following chapters:
721 @ref{Getting Started with GNAT}, describes how to get started compiling
722 and running Ada programs with the GNAT Ada programming environment.
724 @ref{The GNAT Compilation Model}, describes the compilation model used
728 @ref{Compiling Using gcc}, describes how to compile
729 Ada programs with @command{gcc}, the Ada compiler.
732 @ref{Binding Using gnatbind}, describes how to
733 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
737 @ref{Linking Using gnatlink},
738 describes @command{gnatlink}, a
739 program that provides for linking using the GNAT run-time library to
740 construct a program. @command{gnatlink} can also incorporate foreign language
741 object units into the executable.
744 @ref{The GNAT Make Program gnatmake}, describes @command{gnatmake}, a
745 utility that automatically determines the set of sources
746 needed by an Ada compilation unit, and executes the necessary compilations
750 @ref{Improving Performance}, shows various techniques for making your
751 Ada program run faster or take less space.
752 It discusses the effect of the compiler's optimization switch and
753 also describes the @command{gnatelim} tool and unused subprogram/data
757 @ref{Renaming Files Using gnatchop}, describes
758 @code{gnatchop}, a utility that allows you to preprocess a file that
759 contains Ada source code, and split it into one or more new files, one
760 for each compilation unit.
763 @ref{Configuration Pragmas}, describes the configuration pragmas
767 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
768 shows how to override the default GNAT file naming conventions,
769 either for an individual unit or globally.
772 @ref{GNAT Project Manager}, describes how to use project files
773 to organize large projects.
776 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
777 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
778 way to navigate through sources.
781 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
782 version of an Ada source file with control over casing, indentation,
783 comment placement, and other elements of program presentation style.
786 @ref{The GNAT Metric Tool gnatmetric}, shows how to compute various
787 metrics for an Ada source file, such as the number of types and subprograms,
788 and assorted complexity measures.
791 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
792 file name krunching utility, used to handle shortened
793 file names on operating systems with a limit on the length of names.
796 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
797 preprocessor utility that allows a single source file to be used to
798 generate multiple or parameterized source files by means of macro
803 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
804 a tool for rebuilding the GNAT run time with user-supplied
805 configuration pragmas.
809 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
810 utility that displays information about compiled units, including dependences
811 on the corresponding sources files, and consistency of compilations.
814 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
815 to delete files that are produced by the compiler, binder and linker.
819 @ref{GNAT and Libraries}, describes the process of creating and using
820 Libraries with GNAT. It also describes how to recompile the GNAT run-time
824 @ref{Using the GNU make Utility}, describes some techniques for using
825 the GNAT toolset in Makefiles.
829 @ref{Memory Management Issues}, describes some useful predefined storage pools
830 and in particular the GNAT Debug Pool facility, which helps detect incorrect
833 It also describes @command{gnatmem}, a utility that monitors dynamic
834 allocation and deallocation and helps detect ``memory leaks''.
838 @ref{Stack Related Facilities}, describes some useful tools associated with
839 stack checking and analysis.
842 @ref{Verifying Properties Using gnatcheck}, discusses @code{gnatcheck},
843 a utility that checks Ada code against a set of rules.
846 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
847 a utility that generates empty but compilable bodies for library units.
850 @ref{Generating Ada Bindings for C and C++ headers}, describes how to
851 generate automatically Ada bindings from C and C++ headers.
854 @ref{Other Utility Programs}, discusses several other GNAT utilities,
855 including @code{gnathtml}.
859 @ref{Code Coverage and Profiling}, describes how to perform a structural
860 coverage and profile the execution of Ada programs.
864 @ref{Running and Debugging Ada Programs}, describes how to run and debug
869 @ref{Compatibility with HP Ada}, details the compatibility of GNAT with
870 HP Ada 83 @footnote{``HP Ada'' refers to the legacy product originally
871 developed by Digital Equipment Corporation and currently supported by HP.}
872 for OpenVMS Alpha. This product was formerly known as DEC Ada,
875 historical compatibility reasons, the relevant libraries still use the
880 @ref{Platform-Specific Information for the Run-Time Libraries},
881 describes the various run-time
882 libraries supported by GNAT on various platforms and explains how to
883 choose a particular library.
886 @ref{Example of Binder Output File}, shows the source code for the binder
887 output file for a sample program.
890 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
891 you deal with elaboration order issues.
894 @ref{Conditional Compilation}, describes how to model conditional compilation,
895 both with Ada in general and with GNAT facilities in particular.
898 @ref{Inline Assembler}, shows how to use the inline assembly facility
902 @ref{Compatibility and Porting Guide}, contains sections on compatibility
903 of GNAT with other Ada development environments (including Ada 83 systems),
904 to assist in porting code from those environments.
908 @ref{Microsoft Windows Topics}, presents information relevant to the
909 Microsoft Windows platform.
913 @c *************************************************
914 @node What You Should Know before Reading This Guide
915 @c *************************************************
916 @unnumberedsec What You Should Know before Reading This Guide
918 @cindex Ada 95 Language Reference Manual
919 @cindex Ada 2005 Language Reference Manual
921 This guide assumes a basic familiarity with the Ada 95 language, as
922 described in the International Standard ANSI/ISO/IEC-8652:1995, January
924 It does not require knowledge of the new features introduced by Ada 2005,
925 (officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1
927 Both reference manuals are included in the GNAT documentation
930 @node Related Information
931 @unnumberedsec Related Information
934 For further information about related tools, refer to the following
939 @xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, GNAT
940 Reference Manual}, which contains all reference material for the GNAT
941 implementation of Ada.
945 @cite{Using the GNAT Programming Studio}, which describes the GPS
946 Integrated Development Environment.
949 @cite{GNAT Programming Studio Tutorial}, which introduces the
950 main GPS features through examples.
954 @cite{Ada 95 Reference Manual}, which contains reference
955 material for the Ada 95 programming language.
958 @cite{Ada 2005 Reference Manual}, which contains reference
959 material for the Ada 2005 programming language.
962 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
964 in the GNU:[DOCS] directory,
966 for all details on the use of the GNU source-level debugger.
969 @xref{Top,, The extensible self-documenting text editor, emacs,
972 located in the GNU:[DOCS] directory if the EMACS kit is installed,
974 for full information on the extensible editor and programming
981 @unnumberedsec Conventions
983 @cindex Typographical conventions
986 Following are examples of the typographical and graphic conventions used
991 @code{Functions}, @command{utility program names}, @code{standard names},
995 @option{Option flags}
998 @file{File names}, @samp{button names}, and @samp{field names}.
1001 @code{Variables}, @env{environment variables}, and @var{metasyntactic
1008 @r{[}optional information or parameters@r{]}
1011 Examples are described by text
1013 and then shown this way.
1018 Commands that are entered by the user are preceded in this manual by the
1019 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
1020 uses this sequence as a prompt, then the commands will appear exactly as
1021 you see them in the manual. If your system uses some other prompt, then
1022 the command will appear with the @code{$} replaced by whatever prompt
1023 character you are using.
1026 Full file names are shown with the ``@code{/}'' character
1027 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
1028 If you are using GNAT on a Windows platform, please note that
1029 the ``@code{\}'' character should be used instead.
1032 @c ****************************
1033 @node Getting Started with GNAT
1034 @chapter Getting Started with GNAT
1037 This chapter describes some simple ways of using GNAT to build
1038 executable Ada programs.
1040 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
1041 show how to use the command line environment.
1042 @ref{Introduction to GPS}, provides a brief
1043 introduction to the GNAT Programming Studio, a visually-oriented
1044 Integrated Development Environment for GNAT.
1045 GPS offers a graphical ``look and feel'', support for development in
1046 other programming languages, comprehensive browsing features, and
1047 many other capabilities.
1048 For information on GPS please refer to
1049 @cite{Using the GNAT Programming Studio}.
1054 * Running a Simple Ada Program::
1055 * Running a Program with Multiple Units::
1056 * Using the gnatmake Utility::
1058 * Editing with Emacs::
1061 * Introduction to GPS::
1066 @section Running GNAT
1069 Three steps are needed to create an executable file from an Ada source
1074 The source file(s) must be compiled.
1076 The file(s) must be bound using the GNAT binder.
1078 All appropriate object files must be linked to produce an executable.
1082 All three steps are most commonly handled by using the @command{gnatmake}
1083 utility program that, given the name of the main program, automatically
1084 performs the necessary compilation, binding and linking steps.
1086 @node Running a Simple Ada Program
1087 @section Running a Simple Ada Program
1090 Any text editor may be used to prepare an Ada program.
1092 used, the optional Ada mode may be helpful in laying out the program.)
1094 program text is a normal text file. We will assume in our initial
1095 example that you have used your editor to prepare the following
1096 standard format text file:
1098 @smallexample @c ada
1100 with Ada.Text_IO; use Ada.Text_IO;
1103 Put_Line ("Hello WORLD!");
1109 This file should be named @file{hello.adb}.
1110 With the normal default file naming conventions, GNAT requires
1112 contain a single compilation unit whose file name is the
1114 with periods replaced by hyphens; the
1115 extension is @file{ads} for a
1116 spec and @file{adb} for a body.
1117 You can override this default file naming convention by use of the
1118 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1119 Alternatively, if you want to rename your files according to this default
1120 convention, which is probably more convenient if you will be using GNAT
1121 for all your compilations, then the @code{gnatchop} utility
1122 can be used to generate correctly-named source files
1123 (@pxref{Renaming Files Using gnatchop}).
1125 You can compile the program using the following command (@code{$} is used
1126 as the command prompt in the examples in this document):
1133 @command{gcc} is the command used to run the compiler. This compiler is
1134 capable of compiling programs in several languages, including Ada and
1135 C. It assumes that you have given it an Ada program if the file extension is
1136 either @file{.ads} or @file{.adb}, and it will then call
1137 the GNAT compiler to compile the specified file.
1140 The @option{-c} switch is required. It tells @command{gcc} to only do a
1141 compilation. (For C programs, @command{gcc} can also do linking, but this
1142 capability is not used directly for Ada programs, so the @option{-c}
1143 switch must always be present.)
1146 This compile command generates a file
1147 @file{hello.o}, which is the object
1148 file corresponding to your Ada program. It also generates
1149 an ``Ada Library Information'' file @file{hello.ali},
1150 which contains additional information used to check
1151 that an Ada program is consistent.
1152 To build an executable file,
1153 use @code{gnatbind} to bind the program
1154 and @command{gnatlink} to link it. The
1155 argument to both @code{gnatbind} and @command{gnatlink} is the name of the
1156 @file{ALI} file, but the default extension of @file{.ali} can
1157 be omitted. This means that in the most common case, the argument
1158 is simply the name of the main program:
1166 A simpler method of carrying out these steps is to use
1168 a master program that invokes all the required
1169 compilation, binding and linking tools in the correct order. In particular,
1170 @command{gnatmake} automatically recompiles any sources that have been
1171 modified since they were last compiled, or sources that depend
1172 on such modified sources, so that ``version skew'' is avoided.
1173 @cindex Version skew (avoided by @command{gnatmake})
1176 $ gnatmake hello.adb
1180 The result is an executable program called @file{hello}, which can be
1188 assuming that the current directory is on the search path
1189 for executable programs.
1192 and, if all has gone well, you will see
1199 appear in response to this command.
1201 @c ****************************************
1202 @node Running a Program with Multiple Units
1203 @section Running a Program with Multiple Units
1206 Consider a slightly more complicated example that has three files: a
1207 main program, and the spec and body of a package:
1209 @smallexample @c ada
1212 package Greetings is
1217 with Ada.Text_IO; use Ada.Text_IO;
1218 package body Greetings is
1221 Put_Line ("Hello WORLD!");
1224 procedure Goodbye is
1226 Put_Line ("Goodbye WORLD!");
1243 Following the one-unit-per-file rule, place this program in the
1244 following three separate files:
1248 spec of package @code{Greetings}
1251 body of package @code{Greetings}
1254 body of main program
1258 To build an executable version of
1259 this program, we could use four separate steps to compile, bind, and link
1260 the program, as follows:
1264 $ gcc -c greetings.adb
1270 Note that there is no required order of compilation when using GNAT.
1271 In particular it is perfectly fine to compile the main program first.
1272 Also, it is not necessary to compile package specs in the case where
1273 there is an accompanying body; you only need to compile the body. If you want
1274 to submit these files to the compiler for semantic checking and not code
1275 generation, then use the
1276 @option{-gnatc} switch:
1279 $ gcc -c greetings.ads -gnatc
1283 Although the compilation can be done in separate steps as in the
1284 above example, in practice it is almost always more convenient
1285 to use the @command{gnatmake} tool. All you need to know in this case
1286 is the name of the main program's source file. The effect of the above four
1287 commands can be achieved with a single one:
1290 $ gnatmake gmain.adb
1294 In the next section we discuss the advantages of using @command{gnatmake} in
1297 @c *****************************
1298 @node Using the gnatmake Utility
1299 @section Using the @command{gnatmake} Utility
1302 If you work on a program by compiling single components at a time using
1303 @command{gcc}, you typically keep track of the units you modify. In order to
1304 build a consistent system, you compile not only these units, but also any
1305 units that depend on the units you have modified.
1306 For example, in the preceding case,
1307 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1308 you edit @file{greetings.ads}, you must recompile both
1309 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1310 units that depend on @file{greetings.ads}.
1312 @code{gnatbind} will warn you if you forget one of these compilation
1313 steps, so that it is impossible to generate an inconsistent program as a
1314 result of forgetting to do a compilation. Nevertheless it is tedious and
1315 error-prone to keep track of dependencies among units.
1316 One approach to handle the dependency-bookkeeping is to use a
1317 makefile. However, makefiles present maintenance problems of their own:
1318 if the dependencies change as you change the program, you must make
1319 sure that the makefile is kept up-to-date manually, which is also an
1320 error-prone process.
1322 The @command{gnatmake} utility takes care of these details automatically.
1323 Invoke it using either one of the following forms:
1326 $ gnatmake gmain.adb
1327 $ gnatmake ^gmain^GMAIN^
1331 The argument is the name of the file containing the main program;
1332 you may omit the extension. @command{gnatmake}
1333 examines the environment, automatically recompiles any files that need
1334 recompiling, and binds and links the resulting set of object files,
1335 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1336 In a large program, it
1337 can be extremely helpful to use @command{gnatmake}, because working out by hand
1338 what needs to be recompiled can be difficult.
1340 Note that @command{gnatmake}
1341 takes into account all the Ada rules that
1342 establish dependencies among units. These include dependencies that result
1343 from inlining subprogram bodies, and from
1344 generic instantiation. Unlike some other
1345 Ada make tools, @command{gnatmake} does not rely on the dependencies that were
1346 found by the compiler on a previous compilation, which may possibly
1347 be wrong when sources change. @command{gnatmake} determines the exact set of
1348 dependencies from scratch each time it is run.
1351 @node Editing with Emacs
1352 @section Editing with Emacs
1356 Emacs is an extensible self-documenting text editor that is available in a
1357 separate VMSINSTAL kit.
1359 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1360 click on the Emacs Help menu and run the Emacs Tutorial.
1361 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1362 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1364 Documentation on Emacs and other tools is available in Emacs under the
1365 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1366 use the middle mouse button to select a topic (e.g.@: Emacs).
1368 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1369 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1370 get to the Emacs manual.
1371 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1374 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1375 which is sufficiently extensible to provide for a complete programming
1376 environment and shell for the sophisticated user.
1380 @node Introduction to GPS
1381 @section Introduction to GPS
1382 @cindex GPS (GNAT Programming Studio)
1383 @cindex GNAT Programming Studio (GPS)
1385 Although the command line interface (@command{gnatmake}, etc.) alone
1386 is sufficient, a graphical Interactive Development
1387 Environment can make it easier for you to compose, navigate, and debug
1388 programs. This section describes the main features of GPS
1389 (``GNAT Programming Studio''), the GNAT graphical IDE.
1390 You will see how to use GPS to build and debug an executable, and
1391 you will also learn some of the basics of the GNAT ``project'' facility.
1393 GPS enables you to do much more than is presented here;
1394 e.g., you can produce a call graph, interface to a third-party
1395 Version Control System, and inspect the generated assembly language
1397 Indeed, GPS also supports languages other than Ada.
1398 Such additional information, and an explanation of all of the GPS menu
1399 items. may be found in the on-line help, which includes
1400 a user's guide and a tutorial (these are also accessible from the GNAT
1404 * Building a New Program with GPS::
1405 * Simple Debugging with GPS::
1408 @node Building a New Program with GPS
1409 @subsection Building a New Program with GPS
1411 GPS invokes the GNAT compilation tools using information
1412 contained in a @emph{project} (also known as a @emph{project file}):
1413 a collection of properties such
1414 as source directories, identities of main subprograms, tool switches, etc.,
1415 and their associated values.
1416 See @ref{GNAT Project Manager} for details.
1417 In order to run GPS, you will need to either create a new project
1418 or else open an existing one.
1420 This section will explain how you can use GPS to create a project,
1421 to associate Ada source files with a project, and to build and run
1425 @item @emph{Creating a project}
1427 Invoke GPS, either from the command line or the platform's IDE.
1428 After it starts, GPS will display a ``Welcome'' screen with three
1433 @code{Start with default project in directory}
1436 @code{Create new project with wizard}
1439 @code{Open existing project}
1443 Select @code{Create new project with wizard} and press @code{OK}.
1444 A new window will appear. In the text box labeled with
1445 @code{Enter the name of the project to create}, type @file{sample}
1446 as the project name.
1447 In the next box, browse to choose the directory in which you
1448 would like to create the project file.
1449 After selecting an appropriate directory, press @code{Forward}.
1451 A window will appear with the title
1452 @code{Version Control System Configuration}.
1453 Simply press @code{Forward}.
1455 A window will appear with the title
1456 @code{Please select the source directories for this project}.
1457 The directory that you specified for the project file will be selected
1458 by default as the one to use for sources; simply press @code{Forward}.
1460 A window will appear with the title
1461 @code{Please select the build directory for this project}.
1462 The directory that you specified for the project file will be selected
1463 by default for object files and executables;
1464 simply press @code{Forward}.
1466 A window will appear with the title
1467 @code{Please select the main units for this project}.
1468 You will supply this information later, after creating the source file.
1469 Simply press @code{Forward} for now.
1471 A window will appear with the title
1472 @code{Please select the switches to build the project}.
1473 Press @code{Apply}. This will create a project file named
1474 @file{sample.prj} in the directory that you had specified.
1476 @item @emph{Creating and saving the source file}
1478 After you create the new project, a GPS window will appear, which is
1479 partitioned into two main sections:
1483 A @emph{Workspace area}, initially greyed out, which you will use for
1484 creating and editing source files
1487 Directly below, a @emph{Messages area}, which initially displays a
1488 ``Welcome'' message.
1489 (If the Messages area is not visible, drag its border upward to expand it.)
1493 Select @code{File} on the menu bar, and then the @code{New} command.
1494 The Workspace area will become white, and you can now
1495 enter the source program explicitly.
1496 Type the following text
1498 @smallexample @c ada
1500 with Ada.Text_IO; use Ada.Text_IO;
1503 Put_Line("Hello from GPS!");
1509 Select @code{File}, then @code{Save As}, and enter the source file name
1511 The file will be saved in the same directory you specified as the
1512 location of the default project file.
1514 @item @emph{Updating the project file}
1516 You need to add the new source file to the project.
1518 the @code{Project} menu and then @code{Edit project properties}.
1519 Click the @code{Main files} tab on the left, and then the
1521 Choose @file{hello.adb} from the list, and press @code{Open}.
1522 The project settings window will reflect this action.
1525 @item @emph{Building and running the program}
1527 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1528 and select @file{hello.adb}.
1529 The Messages window will display the resulting invocations of @command{gcc},
1530 @command{gnatbind}, and @command{gnatlink}
1531 (reflecting the default switch settings from the
1532 project file that you created) and then a ``successful compilation/build''
1535 To run the program, choose the @code{Build} menu, then @code{Run}, and
1536 select @command{hello}.
1537 An @emph{Arguments Selection} window will appear.
1538 There are no command line arguments, so just click @code{OK}.
1540 The Messages window will now display the program's output (the string
1541 @code{Hello from GPS}), and at the bottom of the GPS window a status
1542 update is displayed (@code{Run: hello}).
1543 Close the GPS window (or select @code{File}, then @code{Exit}) to
1544 terminate this GPS session.
1547 @node Simple Debugging with GPS
1548 @subsection Simple Debugging with GPS
1550 This section illustrates basic debugging techniques (setting breakpoints,
1551 examining/modifying variables, single stepping).
1554 @item @emph{Opening a project}
1556 Start GPS and select @code{Open existing project}; browse to
1557 specify the project file @file{sample.prj} that you had created in the
1560 @item @emph{Creating a source file}
1562 Select @code{File}, then @code{New}, and type in the following program:
1564 @smallexample @c ada
1566 with Ada.Text_IO; use Ada.Text_IO;
1567 procedure Example is
1568 Line : String (1..80);
1571 Put_Line("Type a line of text at each prompt; an empty line to exit");
1575 Put_Line (Line (1..N) );
1583 Select @code{File}, then @code{Save as}, and enter the file name
1586 @item @emph{Updating the project file}
1588 Add @code{Example} as a new main unit for the project:
1591 Select @code{Project}, then @code{Edit Project Properties}.
1594 Select the @code{Main files} tab, click @code{Add}, then
1595 select the file @file{example.adb} from the list, and
1597 You will see the file name appear in the list of main units
1603 @item @emph{Building/running the executable}
1605 To build the executable
1606 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1608 Run the program to see its effect (in the Messages area).
1609 Each line that you enter is displayed; an empty line will
1610 cause the loop to exit and the program to terminate.
1612 @item @emph{Debugging the program}
1614 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1615 which are required for debugging, are on by default when you create
1617 Thus unless you intentionally remove these settings, you will be able
1618 to debug any program that you develop using GPS.
1621 @item @emph{Initializing}
1623 Select @code{Debug}, then @code{Initialize}, then @file{example}
1625 @item @emph{Setting a breakpoint}
1627 After performing the initialization step, you will observe a small
1628 icon to the right of each line number.
1629 This serves as a toggle for breakpoints; clicking the icon will
1630 set a breakpoint at the corresponding line (the icon will change to
1631 a red circle with an ``x''), and clicking it again
1632 will remove the breakpoint / reset the icon.
1634 For purposes of this example, set a breakpoint at line 10 (the
1635 statement @code{Put_Line@ (Line@ (1..N));}
1637 @item @emph{Starting program execution}
1639 Select @code{Debug}, then @code{Run}. When the
1640 @code{Program Arguments} window appears, click @code{OK}.
1641 A console window will appear; enter some line of text,
1642 e.g.@: @code{abcde}, at the prompt.
1643 The program will pause execution when it gets to the
1644 breakpoint, and the corresponding line is highlighted.
1646 @item @emph{Examining a variable}
1648 Move the mouse over one of the occurrences of the variable @code{N}.
1649 You will see the value (5) displayed, in ``tool tip'' fashion.
1650 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1651 You will see information about @code{N} appear in the @code{Debugger Data}
1652 pane, showing the value as 5.
1654 @item @emph{Assigning a new value to a variable}
1656 Right click on the @code{N} in the @code{Debugger Data} pane, and
1657 select @code{Set value of N}.
1658 When the input window appears, enter the value @code{4} and click
1660 This value does not automatically appear in the @code{Debugger Data}
1661 pane; to see it, right click again on the @code{N} in the
1662 @code{Debugger Data} pane and select @code{Update value}.
1663 The new value, 4, will appear in red.
1665 @item @emph{Single stepping}
1667 Select @code{Debug}, then @code{Next}.
1668 This will cause the next statement to be executed, in this case the
1669 call of @code{Put_Line} with the string slice.
1670 Notice in the console window that the displayed string is simply
1671 @code{abcd} and not @code{abcde} which you had entered.
1672 This is because the upper bound of the slice is now 4 rather than 5.
1674 @item @emph{Removing a breakpoint}
1676 Toggle the breakpoint icon at line 10.
1678 @item @emph{Resuming execution from a breakpoint}
1680 Select @code{Debug}, then @code{Continue}.
1681 The program will reach the next iteration of the loop, and
1682 wait for input after displaying the prompt.
1683 This time, just hit the @kbd{Enter} key.
1684 The value of @code{N} will be 0, and the program will terminate.
1685 The console window will disappear.
1690 @node The GNAT Compilation Model
1691 @chapter The GNAT Compilation Model
1692 @cindex GNAT compilation model
1693 @cindex Compilation model
1696 * Source Representation::
1697 * Foreign Language Representation::
1698 * File Naming Rules::
1699 * Using Other File Names::
1700 * Alternative File Naming Schemes::
1701 * Generating Object Files::
1702 * Source Dependencies::
1703 * The Ada Library Information Files::
1704 * Binding an Ada Program::
1705 * Mixed Language Programming::
1707 * Building Mixed Ada & C++ Programs::
1708 * Comparison between GNAT and C/C++ Compilation Models::
1710 * Comparison between GNAT and Conventional Ada Library Models::
1712 * Placement of temporary files::
1717 This chapter describes the compilation model used by GNAT. Although
1718 similar to that used by other languages, such as C and C++, this model
1719 is substantially different from the traditional Ada compilation models,
1720 which are based on a library. The model is initially described without
1721 reference to the library-based model. If you have not previously used an
1722 Ada compiler, you need only read the first part of this chapter. The
1723 last section describes and discusses the differences between the GNAT
1724 model and the traditional Ada compiler models. If you have used other
1725 Ada compilers, this section will help you to understand those
1726 differences, and the advantages of the GNAT model.
1728 @node Source Representation
1729 @section Source Representation
1733 Ada source programs are represented in standard text files, using
1734 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1735 7-bit ASCII set, plus additional characters used for
1736 representing foreign languages (@pxref{Foreign Language Representation}
1737 for support of non-USA character sets). The format effector characters
1738 are represented using their standard ASCII encodings, as follows:
1743 Vertical tab, @code{16#0B#}
1747 Horizontal tab, @code{16#09#}
1751 Carriage return, @code{16#0D#}
1755 Line feed, @code{16#0A#}
1759 Form feed, @code{16#0C#}
1763 Source files are in standard text file format. In addition, GNAT will
1764 recognize a wide variety of stream formats, in which the end of
1765 physical lines is marked by any of the following sequences:
1766 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1767 in accommodating files that are imported from other operating systems.
1769 @cindex End of source file
1770 @cindex Source file, end
1772 The end of a source file is normally represented by the physical end of
1773 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1774 recognized as signalling the end of the source file. Again, this is
1775 provided for compatibility with other operating systems where this
1776 code is used to represent the end of file.
1778 Each file contains a single Ada compilation unit, including any pragmas
1779 associated with the unit. For example, this means you must place a
1780 package declaration (a package @dfn{spec}) and the corresponding body in
1781 separate files. An Ada @dfn{compilation} (which is a sequence of
1782 compilation units) is represented using a sequence of files. Similarly,
1783 you will place each subunit or child unit in a separate file.
1785 @node Foreign Language Representation
1786 @section Foreign Language Representation
1789 GNAT supports the standard character sets defined in Ada as well as
1790 several other non-standard character sets for use in localized versions
1791 of the compiler (@pxref{Character Set Control}).
1794 * Other 8-Bit Codes::
1795 * Wide Character Encodings::
1803 The basic character set is Latin-1. This character set is defined by ISO
1804 standard 8859, part 1. The lower half (character codes @code{16#00#}
1805 @dots{} @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1806 is used to represent additional characters. These include extended letters
1807 used by European languages, such as French accents, the vowels with umlauts
1808 used in German, and the extra letter A-ring used in Swedish.
1810 @findex Ada.Characters.Latin_1
1811 For a complete list of Latin-1 codes and their encodings, see the source
1812 file of library unit @code{Ada.Characters.Latin_1} in file
1813 @file{a-chlat1.ads}.
1814 You may use any of these extended characters freely in character or
1815 string literals. In addition, the extended characters that represent
1816 letters can be used in identifiers.
1818 @node Other 8-Bit Codes
1819 @subsection Other 8-Bit Codes
1822 GNAT also supports several other 8-bit coding schemes:
1825 @item ISO 8859-2 (Latin-2)
1828 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1831 @item ISO 8859-3 (Latin-3)
1834 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1837 @item ISO 8859-4 (Latin-4)
1840 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1843 @item ISO 8859-5 (Cyrillic)
1846 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1847 lowercase equivalence.
1849 @item ISO 8859-15 (Latin-9)
1852 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1853 lowercase equivalence
1855 @item IBM PC (code page 437)
1856 @cindex code page 437
1857 This code page is the normal default for PCs in the U.S. It corresponds
1858 to the original IBM PC character set. This set has some, but not all, of
1859 the extended Latin-1 letters, but these letters do not have the same
1860 encoding as Latin-1. In this mode, these letters are allowed in
1861 identifiers with uppercase and lowercase equivalence.
1863 @item IBM PC (code page 850)
1864 @cindex code page 850
1865 This code page is a modification of 437 extended to include all the
1866 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1867 mode, all these letters are allowed in identifiers with uppercase and
1868 lowercase equivalence.
1870 @item Full Upper 8-bit
1871 Any character in the range 80-FF allowed in identifiers, and all are
1872 considered distinct. In other words, there are no uppercase and lowercase
1873 equivalences in this range. This is useful in conjunction with
1874 certain encoding schemes used for some foreign character sets (e.g.,
1875 the typical method of representing Chinese characters on the PC).
1878 No upper-half characters in the range 80-FF are allowed in identifiers.
1879 This gives Ada 83 compatibility for identifier names.
1883 For precise data on the encodings permitted, and the uppercase and lowercase
1884 equivalences that are recognized, see the file @file{csets.adb} in
1885 the GNAT compiler sources. You will need to obtain a full source release
1886 of GNAT to obtain this file.
1888 @node Wide Character Encodings
1889 @subsection Wide Character Encodings
1892 GNAT allows wide character codes to appear in character and string
1893 literals, and also optionally in identifiers, by means of the following
1894 possible encoding schemes:
1899 In this encoding, a wide character is represented by the following five
1907 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1908 characters (using uppercase letters) of the wide character code. For
1909 example, ESC A345 is used to represent the wide character with code
1911 This scheme is compatible with use of the full Wide_Character set.
1913 @item Upper-Half Coding
1914 @cindex Upper-Half Coding
1915 The wide character with encoding @code{16#abcd#} where the upper bit is on
1916 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
1917 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1918 character, but is not required to be in the upper half. This method can
1919 be also used for shift-JIS or EUC, where the internal coding matches the
1922 @item Shift JIS Coding
1923 @cindex Shift JIS Coding
1924 A wide character is represented by a two-character sequence,
1926 @code{16#cd#}, with the restrictions described for upper-half encoding as
1927 described above. The internal character code is the corresponding JIS
1928 character according to the standard algorithm for Shift-JIS
1929 conversion. Only characters defined in the JIS code set table can be
1930 used with this encoding method.
1934 A wide character is represented by a two-character sequence
1936 @code{16#cd#}, with both characters being in the upper half. The internal
1937 character code is the corresponding JIS character according to the EUC
1938 encoding algorithm. Only characters defined in the JIS code set table
1939 can be used with this encoding method.
1942 A wide character is represented using
1943 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1944 10646-1/Am.2. Depending on the character value, the representation
1945 is a one, two, or three byte sequence:
1950 16#0000#-16#007f#: 2#0@var{xxxxxxx}#
1951 16#0080#-16#07ff#: 2#110@var{xxxxx}# 2#10@var{xxxxxx}#
1952 16#0800#-16#ffff#: 2#1110@var{xxxx}# 2#10@var{xxxxxx}# 2#10@var{xxxxxx}#
1957 where the @var{xxx} bits correspond to the left-padded bits of the
1958 16-bit character value. Note that all lower half ASCII characters
1959 are represented as ASCII bytes and all upper half characters and
1960 other wide characters are represented as sequences of upper-half
1961 (The full UTF-8 scheme allows for encoding 31-bit characters as
1962 6-byte sequences, but in this implementation, all UTF-8 sequences
1963 of four or more bytes length will be treated as illegal).
1964 @item Brackets Coding
1965 In this encoding, a wide character is represented by the following eight
1973 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1974 characters (using uppercase letters) of the wide character code. For
1975 example, [``A345''] is used to represent the wide character with code
1976 @code{16#A345#}. It is also possible (though not required) to use the
1977 Brackets coding for upper half characters. For example, the code
1978 @code{16#A3#} can be represented as @code{[``A3'']}.
1980 This scheme is compatible with use of the full Wide_Character set,
1981 and is also the method used for wide character encoding in the standard
1982 ACVC (Ada Compiler Validation Capability) test suite distributions.
1987 Note: Some of these coding schemes do not permit the full use of the
1988 Ada character set. For example, neither Shift JIS, nor EUC allow the
1989 use of the upper half of the Latin-1 set.
1991 @node File Naming Rules
1992 @section File Naming Rules
1995 The default file name is determined by the name of the unit that the
1996 file contains. The name is formed by taking the full expanded name of
1997 the unit and replacing the separating dots with hyphens and using
1998 ^lowercase^uppercase^ for all letters.
2000 An exception arises if the file name generated by the above rules starts
2001 with one of the characters
2003 @samp{A}, @samp{G}, @samp{I}, or @samp{S},
2006 @samp{a}, @samp{g}, @samp{i}, or @samp{s},
2008 and the second character is a
2009 minus. In this case, the character ^tilde^dollar sign^ is used in place
2010 of the minus. The reason for this special rule is to avoid clashes with
2011 the standard names for child units of the packages System, Ada,
2012 Interfaces, and GNAT, which use the prefixes
2014 @samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},
2017 @samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},
2021 The file extension is @file{.ads} for a spec and
2022 @file{.adb} for a body. The following list shows some
2023 examples of these rules.
2030 @item arith_functions.ads
2031 Arith_Functions (package spec)
2032 @item arith_functions.adb
2033 Arith_Functions (package body)
2035 Func.Spec (child package spec)
2037 Func.Spec (child package body)
2039 Sub (subunit of Main)
2040 @item ^a~bad.adb^A$BAD.ADB^
2041 A.Bad (child package body)
2045 Following these rules can result in excessively long
2046 file names if corresponding
2047 unit names are long (for example, if child units or subunits are
2048 heavily nested). An option is available to shorten such long file names
2049 (called file name ``krunching''). This may be particularly useful when
2050 programs being developed with GNAT are to be used on operating systems
2051 with limited file name lengths. @xref{Using gnatkr}.
2053 Of course, no file shortening algorithm can guarantee uniqueness over
2054 all possible unit names; if file name krunching is used, it is your
2055 responsibility to ensure no name clashes occur. Alternatively you
2056 can specify the exact file names that you want used, as described
2057 in the next section. Finally, if your Ada programs are migrating from a
2058 compiler with a different naming convention, you can use the gnatchop
2059 utility to produce source files that follow the GNAT naming conventions.
2060 (For details @pxref{Renaming Files Using gnatchop}.)
2062 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2063 systems, case is not significant. So for example on @code{Windows XP}
2064 if the canonical name is @code{main-sub.adb}, you can use the file name
2065 @code{Main-Sub.adb} instead. However, case is significant for other
2066 operating systems, so for example, if you want to use other than
2067 canonically cased file names on a Unix system, you need to follow
2068 the procedures described in the next section.
2070 @node Using Other File Names
2071 @section Using Other File Names
2075 In the previous section, we have described the default rules used by
2076 GNAT to determine the file name in which a given unit resides. It is
2077 often convenient to follow these default rules, and if you follow them,
2078 the compiler knows without being explicitly told where to find all
2081 However, in some cases, particularly when a program is imported from
2082 another Ada compiler environment, it may be more convenient for the
2083 programmer to specify which file names contain which units. GNAT allows
2084 arbitrary file names to be used by means of the Source_File_Name pragma.
2085 The form of this pragma is as shown in the following examples:
2086 @cindex Source_File_Name pragma
2088 @smallexample @c ada
2090 pragma Source_File_Name (My_Utilities.Stacks,
2091 Spec_File_Name => "myutilst_a.ada");
2092 pragma Source_File_name (My_Utilities.Stacks,
2093 Body_File_Name => "myutilst.ada");
2098 As shown in this example, the first argument for the pragma is the unit
2099 name (in this example a child unit). The second argument has the form
2100 of a named association. The identifier
2101 indicates whether the file name is for a spec or a body;
2102 the file name itself is given by a string literal.
2104 The source file name pragma is a configuration pragma, which means that
2105 normally it will be placed in the @file{gnat.adc}
2106 file used to hold configuration
2107 pragmas that apply to a complete compilation environment.
2108 For more details on how the @file{gnat.adc} file is created and used
2109 see @ref{Handling of Configuration Pragmas}.
2110 @cindex @file{gnat.adc}
2113 GNAT allows completely arbitrary file names to be specified using the
2114 source file name pragma. However, if the file name specified has an
2115 extension other than @file{.ads} or @file{.adb} it is necessary to use
2116 a special syntax when compiling the file. The name in this case must be
2117 preceded by the special sequence @option{-x} followed by a space and the name
2118 of the language, here @code{ada}, as in:
2121 $ gcc -c -x ada peculiar_file_name.sim
2126 @command{gnatmake} handles non-standard file names in the usual manner (the
2127 non-standard file name for the main program is simply used as the
2128 argument to gnatmake). Note that if the extension is also non-standard,
2129 then it must be included in the @command{gnatmake} command, it may not
2132 @node Alternative File Naming Schemes
2133 @section Alternative File Naming Schemes
2134 @cindex File naming schemes, alternative
2137 In the previous section, we described the use of the @code{Source_File_Name}
2138 pragma to allow arbitrary names to be assigned to individual source files.
2139 However, this approach requires one pragma for each file, and especially in
2140 large systems can result in very long @file{gnat.adc} files, and also create
2141 a maintenance problem.
2143 GNAT also provides a facility for specifying systematic file naming schemes
2144 other than the standard default naming scheme previously described. An
2145 alternative scheme for naming is specified by the use of
2146 @code{Source_File_Name} pragmas having the following format:
2147 @cindex Source_File_Name pragma
2149 @smallexample @c ada
2150 pragma Source_File_Name (
2151 Spec_File_Name => FILE_NAME_PATTERN
2152 @r{[},Casing => CASING_SPEC@r{]}
2153 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2155 pragma Source_File_Name (
2156 Body_File_Name => FILE_NAME_PATTERN
2157 @r{[},Casing => CASING_SPEC@r{]}
2158 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2160 pragma Source_File_Name (
2161 Subunit_File_Name => FILE_NAME_PATTERN
2162 @r{[},Casing => CASING_SPEC@r{]}
2163 @r{[},Dot_Replacement => STRING_LITERAL@r{]});
2165 FILE_NAME_PATTERN ::= STRING_LITERAL
2166 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2170 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2171 It contains a single asterisk character, and the unit name is substituted
2172 systematically for this asterisk. The optional parameter
2173 @code{Casing} indicates
2174 whether the unit name is to be all upper-case letters, all lower-case letters,
2175 or mixed-case. If no
2176 @code{Casing} parameter is used, then the default is all
2177 ^lower-case^upper-case^.
2179 The optional @code{Dot_Replacement} string is used to replace any periods
2180 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2181 argument is used then separating dots appear unchanged in the resulting
2183 Although the above syntax indicates that the
2184 @code{Casing} argument must appear
2185 before the @code{Dot_Replacement} argument, but it
2186 is also permissible to write these arguments in the opposite order.
2188 As indicated, it is possible to specify different naming schemes for
2189 bodies, specs, and subunits. Quite often the rule for subunits is the
2190 same as the rule for bodies, in which case, there is no need to give
2191 a separate @code{Subunit_File_Name} rule, and in this case the
2192 @code{Body_File_name} rule is used for subunits as well.
2194 The separate rule for subunits can also be used to implement the rather
2195 unusual case of a compilation environment (e.g.@: a single directory) which
2196 contains a subunit and a child unit with the same unit name. Although
2197 both units cannot appear in the same partition, the Ada Reference Manual
2198 allows (but does not require) the possibility of the two units coexisting
2199 in the same environment.
2201 The file name translation works in the following steps:
2206 If there is a specific @code{Source_File_Name} pragma for the given unit,
2207 then this is always used, and any general pattern rules are ignored.
2210 If there is a pattern type @code{Source_File_Name} pragma that applies to
2211 the unit, then the resulting file name will be used if the file exists. If
2212 more than one pattern matches, the latest one will be tried first, and the
2213 first attempt resulting in a reference to a file that exists will be used.
2216 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2217 for which the corresponding file exists, then the standard GNAT default
2218 naming rules are used.
2223 As an example of the use of this mechanism, consider a commonly used scheme
2224 in which file names are all lower case, with separating periods copied
2225 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2226 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2229 @smallexample @c ada
2230 pragma Source_File_Name
2231 (Spec_File_Name => "*.1.ada");
2232 pragma Source_File_Name
2233 (Body_File_Name => "*.2.ada");
2237 The default GNAT scheme is actually implemented by providing the following
2238 default pragmas internally:
2240 @smallexample @c ada
2241 pragma Source_File_Name
2242 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2243 pragma Source_File_Name
2244 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2248 Our final example implements a scheme typically used with one of the
2249 Ada 83 compilers, where the separator character for subunits was ``__''
2250 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2251 by adding @file{.ADA}, and subunits by
2252 adding @file{.SEP}. All file names were
2253 upper case. Child units were not present of course since this was an
2254 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2255 the same double underscore separator for child units.
2257 @smallexample @c ada
2258 pragma Source_File_Name
2259 (Spec_File_Name => "*_.ADA",
2260 Dot_Replacement => "__",
2261 Casing = Uppercase);
2262 pragma Source_File_Name
2263 (Body_File_Name => "*.ADA",
2264 Dot_Replacement => "__",
2265 Casing = Uppercase);
2266 pragma Source_File_Name
2267 (Subunit_File_Name => "*.SEP",
2268 Dot_Replacement => "__",
2269 Casing = Uppercase);
2272 @node Generating Object Files
2273 @section Generating Object Files
2276 An Ada program consists of a set of source files, and the first step in
2277 compiling the program is to generate the corresponding object files.
2278 These are generated by compiling a subset of these source files.
2279 The files you need to compile are the following:
2283 If a package spec has no body, compile the package spec to produce the
2284 object file for the package.
2287 If a package has both a spec and a body, compile the body to produce the
2288 object file for the package. The source file for the package spec need
2289 not be compiled in this case because there is only one object file, which
2290 contains the code for both the spec and body of the package.
2293 For a subprogram, compile the subprogram body to produce the object file
2294 for the subprogram. The spec, if one is present, is as usual in a
2295 separate file, and need not be compiled.
2299 In the case of subunits, only compile the parent unit. A single object
2300 file is generated for the entire subunit tree, which includes all the
2304 Compile child units independently of their parent units
2305 (though, of course, the spec of all the ancestor unit must be present in order
2306 to compile a child unit).
2310 Compile generic units in the same manner as any other units. The object
2311 files in this case are small dummy files that contain at most the
2312 flag used for elaboration checking. This is because GNAT always handles generic
2313 instantiation by means of macro expansion. However, it is still necessary to
2314 compile generic units, for dependency checking and elaboration purposes.
2318 The preceding rules describe the set of files that must be compiled to
2319 generate the object files for a program. Each object file has the same
2320 name as the corresponding source file, except that the extension is
2323 You may wish to compile other files for the purpose of checking their
2324 syntactic and semantic correctness. For example, in the case where a
2325 package has a separate spec and body, you would not normally compile the
2326 spec. However, it is convenient in practice to compile the spec to make
2327 sure it is error-free before compiling clients of this spec, because such
2328 compilations will fail if there is an error in the spec.
2330 GNAT provides an option for compiling such files purely for the
2331 purposes of checking correctness; such compilations are not required as
2332 part of the process of building a program. To compile a file in this
2333 checking mode, use the @option{-gnatc} switch.
2335 @node Source Dependencies
2336 @section Source Dependencies
2339 A given object file clearly depends on the source file which is compiled
2340 to produce it. Here we are using @dfn{depends} in the sense of a typical
2341 @code{make} utility; in other words, an object file depends on a source
2342 file if changes to the source file require the object file to be
2344 In addition to this basic dependency, a given object may depend on
2345 additional source files as follows:
2349 If a file being compiled @code{with}'s a unit @var{X}, the object file
2350 depends on the file containing the spec of unit @var{X}. This includes
2351 files that are @code{with}'ed implicitly either because they are parents
2352 of @code{with}'ed child units or they are run-time units required by the
2353 language constructs used in a particular unit.
2356 If a file being compiled instantiates a library level generic unit, the
2357 object file depends on both the spec and body files for this generic
2361 If a file being compiled instantiates a generic unit defined within a
2362 package, the object file depends on the body file for the package as
2363 well as the spec file.
2367 @cindex @option{-gnatn} switch
2368 If a file being compiled contains a call to a subprogram for which
2369 pragma @code{Inline} applies and inlining is activated with the
2370 @option{-gnatn} switch, the object file depends on the file containing the
2371 body of this subprogram as well as on the file containing the spec. Note
2372 that for inlining to actually occur as a result of the use of this switch,
2373 it is necessary to compile in optimizing mode.
2375 @cindex @option{-gnatN} switch
2376 The use of @option{-gnatN} activates inlining optimization
2377 that is performed by the front end of the compiler. This inlining does
2378 not require that the code generation be optimized. Like @option{-gnatn},
2379 the use of this switch generates additional dependencies.
2381 When using a gcc-based back end (in practice this means using any version
2382 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
2383 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
2384 Historically front end inlining was more extensive than the gcc back end
2385 inlining, but that is no longer the case.
2388 If an object file @file{O} depends on the proper body of a subunit through
2389 inlining or instantiation, it depends on the parent unit of the subunit.
2390 This means that any modification of the parent unit or one of its subunits
2391 affects the compilation of @file{O}.
2394 The object file for a parent unit depends on all its subunit body files.
2397 The previous two rules meant that for purposes of computing dependencies and
2398 recompilation, a body and all its subunits are treated as an indivisible whole.
2401 These rules are applied transitively: if unit @code{A} @code{with}'s
2402 unit @code{B}, whose elaboration calls an inlined procedure in package
2403 @code{C}, the object file for unit @code{A} will depend on the body of
2404 @code{C}, in file @file{c.adb}.
2406 The set of dependent files described by these rules includes all the
2407 files on which the unit is semantically dependent, as dictated by the
2408 Ada language standard. However, it is a superset of what the
2409 standard describes, because it includes generic, inline, and subunit
2412 An object file must be recreated by recompiling the corresponding source
2413 file if any of the source files on which it depends are modified. For
2414 example, if the @code{make} utility is used to control compilation,
2415 the rule for an Ada object file must mention all the source files on
2416 which the object file depends, according to the above definition.
2417 The determination of the necessary
2418 recompilations is done automatically when one uses @command{gnatmake}.
2421 @node The Ada Library Information Files
2422 @section The Ada Library Information Files
2423 @cindex Ada Library Information files
2424 @cindex @file{ALI} files
2427 Each compilation actually generates two output files. The first of these
2428 is the normal object file that has a @file{.o} extension. The second is a
2429 text file containing full dependency information. It has the same
2430 name as the source file, but an @file{.ali} extension.
2431 This file is known as the Ada Library Information (@file{ALI}) file.
2432 The following information is contained in the @file{ALI} file.
2436 Version information (indicates which version of GNAT was used to compile
2437 the unit(s) in question)
2440 Main program information (including priority and time slice settings,
2441 as well as the wide character encoding used during compilation).
2444 List of arguments used in the @command{gcc} command for the compilation
2447 Attributes of the unit, including configuration pragmas used, an indication
2448 of whether the compilation was successful, exception model used etc.
2451 A list of relevant restrictions applying to the unit (used for consistency)
2455 Categorization information (e.g.@: use of pragma @code{Pure}).
2458 Information on all @code{with}'ed units, including presence of
2459 @code{Elaborate} or @code{Elaborate_All} pragmas.
2462 Information from any @code{Linker_Options} pragmas used in the unit
2465 Information on the use of @code{Body_Version} or @code{Version}
2466 attributes in the unit.
2469 Dependency information. This is a list of files, together with
2470 time stamp and checksum information. These are files on which
2471 the unit depends in the sense that recompilation is required
2472 if any of these units are modified.
2475 Cross-reference data. Contains information on all entities referenced
2476 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2477 provide cross-reference information.
2482 For a full detailed description of the format of the @file{ALI} file,
2483 see the source of the body of unit @code{Lib.Writ}, contained in file
2484 @file{lib-writ.adb} in the GNAT compiler sources.
2486 @node Binding an Ada Program
2487 @section Binding an Ada Program
2490 When using languages such as C and C++, once the source files have been
2491 compiled the only remaining step in building an executable program
2492 is linking the object modules together. This means that it is possible to
2493 link an inconsistent version of a program, in which two units have
2494 included different versions of the same header.
2496 The rules of Ada do not permit such an inconsistent program to be built.
2497 For example, if two clients have different versions of the same package,
2498 it is illegal to build a program containing these two clients.
2499 These rules are enforced by the GNAT binder, which also determines an
2500 elaboration order consistent with the Ada rules.
2502 The GNAT binder is run after all the object files for a program have
2503 been created. It is given the name of the main program unit, and from
2504 this it determines the set of units required by the program, by reading the
2505 corresponding ALI files. It generates error messages if the program is
2506 inconsistent or if no valid order of elaboration exists.
2508 If no errors are detected, the binder produces a main program, in Ada by
2509 default, that contains calls to the elaboration procedures of those
2510 compilation unit that require them, followed by
2511 a call to the main program. This Ada program is compiled to generate the
2512 object file for the main program. The name of
2513 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2514 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2517 Finally, the linker is used to build the resulting executable program,
2518 using the object from the main program from the bind step as well as the
2519 object files for the Ada units of the program.
2521 @node Mixed Language Programming
2522 @section Mixed Language Programming
2523 @cindex Mixed Language Programming
2526 This section describes how to develop a mixed-language program,
2527 specifically one that comprises units in both Ada and C.
2530 * Interfacing to C::
2531 * Calling Conventions::
2534 @node Interfacing to C
2535 @subsection Interfacing to C
2537 Interfacing Ada with a foreign language such as C involves using
2538 compiler directives to import and/or export entity definitions in each
2539 language---using @code{extern} statements in C, for instance, and the
2540 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
2541 A full treatment of these topics is provided in Appendix B, section 1
2542 of the Ada Reference Manual.
2544 There are two ways to build a program using GNAT that contains some Ada
2545 sources and some foreign language sources, depending on whether or not
2546 the main subprogram is written in Ada. Here is a source example with
2547 the main subprogram in Ada:
2553 void print_num (int num)
2555 printf ("num is %d.\n", num);
2561 /* num_from_Ada is declared in my_main.adb */
2562 extern int num_from_Ada;
2566 return num_from_Ada;
2570 @smallexample @c ada
2572 procedure My_Main is
2574 -- Declare then export an Integer entity called num_from_Ada
2575 My_Num : Integer := 10;
2576 pragma Export (C, My_Num, "num_from_Ada");
2578 -- Declare an Ada function spec for Get_Num, then use
2579 -- C function get_num for the implementation.
2580 function Get_Num return Integer;
2581 pragma Import (C, Get_Num, "get_num");
2583 -- Declare an Ada procedure spec for Print_Num, then use
2584 -- C function print_num for the implementation.
2585 procedure Print_Num (Num : Integer);
2586 pragma Import (C, Print_Num, "print_num");
2589 Print_Num (Get_Num);
2595 To build this example, first compile the foreign language files to
2596 generate object files:
2598 ^gcc -c file1.c^gcc -c FILE1.C^
2599 ^gcc -c file2.c^gcc -c FILE2.C^
2603 Then, compile the Ada units to produce a set of object files and ALI
2606 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2610 Run the Ada binder on the Ada main program:
2612 gnatbind my_main.ali
2616 Link the Ada main program, the Ada objects and the other language
2619 gnatlink my_main.ali file1.o file2.o
2623 The last three steps can be grouped in a single command:
2625 gnatmake my_main.adb -largs file1.o file2.o
2628 @cindex Binder output file
2630 If the main program is in a language other than Ada, then you may have
2631 more than one entry point into the Ada subsystem. You must use a special
2632 binder option to generate callable routines that initialize and
2633 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2634 Calls to the initialization and finalization routines must be inserted
2635 in the main program, or some other appropriate point in the code. The
2636 call to initialize the Ada units must occur before the first Ada
2637 subprogram is called, and the call to finalize the Ada units must occur
2638 after the last Ada subprogram returns. The binder will place the
2639 initialization and finalization subprograms into the
2640 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2641 sources. To illustrate, we have the following example:
2645 extern void adainit (void);
2646 extern void adafinal (void);
2647 extern int add (int, int);
2648 extern int sub (int, int);
2650 int main (int argc, char *argv[])
2656 /* Should print "21 + 7 = 28" */
2657 printf ("%d + %d = %d\n", a, b, add (a, b));
2658 /* Should print "21 - 7 = 14" */
2659 printf ("%d - %d = %d\n", a, b, sub (a, b));
2665 @smallexample @c ada
2668 function Add (A, B : Integer) return Integer;
2669 pragma Export (C, Add, "add");
2673 package body Unit1 is
2674 function Add (A, B : Integer) return Integer is
2682 function Sub (A, B : Integer) return Integer;
2683 pragma Export (C, Sub, "sub");
2687 package body Unit2 is
2688 function Sub (A, B : Integer) return Integer is
2697 The build procedure for this application is similar to the last
2698 example's. First, compile the foreign language files to generate object
2701 ^gcc -c main.c^gcc -c main.c^
2705 Next, compile the Ada units to produce a set of object files and ALI
2708 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2709 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2713 Run the Ada binder on every generated ALI file. Make sure to use the
2714 @option{-n} option to specify a foreign main program:
2716 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2720 Link the Ada main program, the Ada objects and the foreign language
2721 objects. You need only list the last ALI file here:
2723 gnatlink unit2.ali main.o -o exec_file
2726 This procedure yields a binary executable called @file{exec_file}.
2730 Depending on the circumstances (for example when your non-Ada main object
2731 does not provide symbol @code{main}), you may also need to instruct the
2732 GNAT linker not to include the standard startup objects by passing the
2733 @option{^-nostartfiles^/NOSTART_FILES^} switch to @command{gnatlink}.
2735 @node Calling Conventions
2736 @subsection Calling Conventions
2737 @cindex Foreign Languages
2738 @cindex Calling Conventions
2739 GNAT follows standard calling sequence conventions and will thus interface
2740 to any other language that also follows these conventions. The following
2741 Convention identifiers are recognized by GNAT:
2744 @cindex Interfacing to Ada
2745 @cindex Other Ada compilers
2746 @cindex Convention Ada
2748 This indicates that the standard Ada calling sequence will be
2749 used and all Ada data items may be passed without any limitations in the
2750 case where GNAT is used to generate both the caller and callee. It is also
2751 possible to mix GNAT generated code and code generated by another Ada
2752 compiler. In this case, the data types should be restricted to simple
2753 cases, including primitive types. Whether complex data types can be passed
2754 depends on the situation. Probably it is safe to pass simple arrays, such
2755 as arrays of integers or floats. Records may or may not work, depending
2756 on whether both compilers lay them out identically. Complex structures
2757 involving variant records, access parameters, tasks, or protected types,
2758 are unlikely to be able to be passed.
2760 Note that in the case of GNAT running
2761 on a platform that supports HP Ada 83, a higher degree of compatibility
2762 can be guaranteed, and in particular records are layed out in an identical
2763 manner in the two compilers. Note also that if output from two different
2764 compilers is mixed, the program is responsible for dealing with elaboration
2765 issues. Probably the safest approach is to write the main program in the
2766 version of Ada other than GNAT, so that it takes care of its own elaboration
2767 requirements, and then call the GNAT-generated adainit procedure to ensure
2768 elaboration of the GNAT components. Consult the documentation of the other
2769 Ada compiler for further details on elaboration.
2771 However, it is not possible to mix the tasking run time of GNAT and
2772 HP Ada 83, All the tasking operations must either be entirely within
2773 GNAT compiled sections of the program, or entirely within HP Ada 83
2774 compiled sections of the program.
2776 @cindex Interfacing to Assembly
2777 @cindex Convention Assembler
2779 Specifies assembler as the convention. In practice this has the
2780 same effect as convention Ada (but is not equivalent in the sense of being
2781 considered the same convention).
2783 @cindex Convention Asm
2786 Equivalent to Assembler.
2788 @cindex Interfacing to COBOL
2789 @cindex Convention COBOL
2792 Data will be passed according to the conventions described
2793 in section B.4 of the Ada Reference Manual.
2796 @cindex Interfacing to C
2797 @cindex Convention C
2799 Data will be passed according to the conventions described
2800 in section B.3 of the Ada Reference Manual.
2802 A note on interfacing to a C ``varargs'' function:
2803 @findex C varargs function
2804 @cindex Interfacing to C varargs function
2805 @cindex varargs function interfaces
2809 In C, @code{varargs} allows a function to take a variable number of
2810 arguments. There is no direct equivalent in this to Ada. One
2811 approach that can be used is to create a C wrapper for each
2812 different profile and then interface to this C wrapper. For
2813 example, to print an @code{int} value using @code{printf},
2814 create a C function @code{printfi} that takes two arguments, a
2815 pointer to a string and an int, and calls @code{printf}.
2816 Then in the Ada program, use pragma @code{Import} to
2817 interface to @code{printfi}.
2820 It may work on some platforms to directly interface to
2821 a @code{varargs} function by providing a specific Ada profile
2822 for a particular call. However, this does not work on
2823 all platforms, since there is no guarantee that the
2824 calling sequence for a two argument normal C function
2825 is the same as for calling a @code{varargs} C function with
2826 the same two arguments.
2829 @cindex Convention Default
2834 @cindex Convention External
2841 @cindex Interfacing to C++
2842 @cindex Convention C++
2843 @item C_Plus_Plus (or CPP)
2844 This stands for C++. For most purposes this is identical to C.
2845 See the separate description of the specialized GNAT pragmas relating to
2846 C++ interfacing for further details.
2850 @cindex Interfacing to Fortran
2851 @cindex Convention Fortran
2853 Data will be passed according to the conventions described
2854 in section B.5 of the Ada Reference Manual.
2857 This applies to an intrinsic operation, as defined in the Ada
2858 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
2859 this means that the body of the subprogram is provided by the compiler itself,
2860 usually by means of an efficient code sequence, and that the user does not
2861 supply an explicit body for it. In an application program, the pragma may
2862 be applied to the following sets of names:
2866 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right,
2867 Shift_Right_Arithmetic. The corresponding subprogram declaration must have
2868 two formal parameters. The
2869 first one must be a signed integer type or a modular type with a binary
2870 modulus, and the second parameter must be of type Natural.
2871 The return type must be the same as the type of the first argument. The size
2872 of this type can only be 8, 16, 32, or 64.
2875 Binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
2876 The corresponding operator declaration must have parameters and result type
2877 that have the same root numeric type (for example, all three are long_float
2878 types). This simplifies the definition of operations that use type checking
2879 to perform dimensional checks:
2881 @smallexample @c ada
2882 type Distance is new Long_Float;
2883 type Time is new Long_Float;
2884 type Velocity is new Long_Float;
2885 function "/" (D : Distance; T : Time)
2887 pragma Import (Intrinsic, "/");
2891 This common idiom is often programmed with a generic definition and an
2892 explicit body. The pragma makes it simpler to introduce such declarations.
2893 It incurs no overhead in compilation time or code size, because it is
2894 implemented as a single machine instruction.
2897 General subprogram entities, to bind an Ada subprogram declaration to
2898 a compiler builtin by name with back-ends where such interfaces are
2899 available. A typical example is the set of ``__builtin'' functions
2900 exposed by the GCC back-end, as in the following example:
2902 @smallexample @c ada
2903 function builtin_sqrt (F : Float) return Float;
2904 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
2907 Most of the GCC builtins are accessible this way, and as for other
2908 import conventions (e.g. C), it is the user's responsibility to ensure
2909 that the Ada subprogram profile matches the underlying builtin
2917 @cindex Convention Stdcall
2919 This is relevant only to Windows XP/2000/NT implementations of GNAT,
2920 and specifies that the @code{Stdcall} calling sequence will be used,
2921 as defined by the NT API. Nevertheless, to ease building
2922 cross-platform bindings this convention will be handled as a @code{C} calling
2923 convention on non-Windows platforms.
2926 @cindex Convention DLL
2928 This is equivalent to @code{Stdcall}.
2931 @cindex Convention Win32
2933 This is equivalent to @code{Stdcall}.
2937 @cindex Convention Stubbed
2939 This is a special convention that indicates that the compiler
2940 should provide a stub body that raises @code{Program_Error}.
2944 GNAT additionally provides a useful pragma @code{Convention_Identifier}
2945 that can be used to parametrize conventions and allow additional synonyms
2946 to be specified. For example if you have legacy code in which the convention
2947 identifier Fortran77 was used for Fortran, you can use the configuration
2950 @smallexample @c ada
2951 pragma Convention_Identifier (Fortran77, Fortran);
2955 And from now on the identifier Fortran77 may be used as a convention
2956 identifier (for example in an @code{Import} pragma) with the same
2960 @node Building Mixed Ada & C++ Programs
2961 @section Building Mixed Ada and C++ Programs
2964 A programmer inexperienced with mixed-language development may find that
2965 building an application containing both Ada and C++ code can be a
2966 challenge. This section gives a few
2967 hints that should make this task easier. The first section addresses
2968 the differences between interfacing with C and interfacing with C++.
2970 looks into the delicate problem of linking the complete application from
2971 its Ada and C++ parts. The last section gives some hints on how the GNAT
2972 run-time library can be adapted in order to allow inter-language dispatching
2973 with a new C++ compiler.
2976 * Interfacing to C++::
2977 * Linking a Mixed C++ & Ada Program::
2978 * A Simple Example::
2979 * Interfacing with C++ constructors::
2980 * Interfacing with C++ at the Class Level::
2983 @node Interfacing to C++
2984 @subsection Interfacing to C++
2987 GNAT supports interfacing with the G++ compiler (or any C++ compiler
2988 generating code that is compatible with the G++ Application Binary
2989 Interface ---see http://www.codesourcery.com/archives/cxx-abi).
2992 Interfacing can be done at 3 levels: simple data, subprograms, and
2993 classes. In the first two cases, GNAT offers a specific @code{Convention
2994 C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}.
2995 Usually, C++ mangles the names of subprograms. To generate proper mangled
2996 names automatically, see @ref{Generating Ada Bindings for C and C++ headers}).
2997 This problem can also be addressed manually in two ways:
3001 by modifying the C++ code in order to force a C convention using
3002 the @code{extern "C"} syntax.
3005 by figuring out the mangled name (using e.g. @command{nm}) and using it as the
3006 Link_Name argument of the pragma import.
3010 Interfacing at the class level can be achieved by using the GNAT specific
3011 pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,,
3012 gnat_rm, GNAT Reference Manual}, for additional information.
3014 @node Linking a Mixed C++ & Ada Program
3015 @subsection Linking a Mixed C++ & Ada Program
3018 Usually the linker of the C++ development system must be used to link
3019 mixed applications because most C++ systems will resolve elaboration
3020 issues (such as calling constructors on global class instances)
3021 transparently during the link phase. GNAT has been adapted to ease the
3022 use of a foreign linker for the last phase. Three cases can be
3027 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3028 The C++ linker can simply be called by using the C++ specific driver
3031 Note that if the C++ code uses inline functions, you will need to
3032 compile your C++ code with the @code{-fkeep-inline-functions} switch in
3033 order to provide an existing function implementation that the Ada code can
3037 $ g++ -c -fkeep-inline-functions file1.C
3038 $ g++ -c -fkeep-inline-functions file2.C
3039 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
3043 Using GNAT and G++ from two different GCC installations: If both
3044 compilers are on the @env{PATH}, the previous method may be used. It is
3045 important to note that environment variables such as
3046 @env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and
3047 @env{GCC_ROOT} will affect both compilers
3048 at the same time and may make one of the two compilers operate
3049 improperly if set during invocation of the wrong compiler. It is also
3050 very important that the linker uses the proper @file{libgcc.a} GCC
3051 library -- that is, the one from the C++ compiler installation. The
3052 implicit link command as suggested in the @command{gnatmake} command
3053 from the former example can be replaced by an explicit link command with
3054 the full-verbosity option in order to verify which library is used:
3057 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3059 If there is a problem due to interfering environment variables, it can
3060 be worked around by using an intermediate script. The following example
3061 shows the proper script to use when GNAT has not been installed at its
3062 default location and g++ has been installed at its default location:
3070 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3074 Using a non-GNU C++ compiler: The commands previously described can be
3075 used to insure that the C++ linker is used. Nonetheless, you need to add
3076 a few more parameters to the link command line, depending on the exception
3079 If the @code{setjmp/longjmp} exception mechanism is used, only the paths
3080 to the libgcc libraries are required:
3085 CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a`
3086 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3089 Where CC is the name of the non-GNU C++ compiler.
3091 If the @code{zero cost} exception mechanism is used, and the platform
3092 supports automatic registration of exception tables (e.g.@: Solaris or IRIX),
3093 paths to more objects are required:
3098 CC `gcc -print-file-name=crtbegin.o` $* \
3099 `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \
3100 `gcc -print-file-name=crtend.o`
3101 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3104 If the @code{zero cost} exception mechanism is used, and the platform
3105 doesn't support automatic registration of exception tables (e.g.@: HP-UX,
3106 Tru64 or AIX), the simple approach described above will not work and
3107 a pre-linking phase using GNAT will be necessary.
3111 Another alternative is to use the @command{gprbuild} multi-language builder
3112 which has a large knowledge base and knows how to link Ada and C++ code
3113 together automatically in most cases.
3115 @node A Simple Example
3116 @subsection A Simple Example
3118 The following example, provided as part of the GNAT examples, shows how
3119 to achieve procedural interfacing between Ada and C++ in both
3120 directions. The C++ class A has two methods. The first method is exported
3121 to Ada by the means of an extern C wrapper function. The second method
3122 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3123 a limited record with a layout comparable to the C++ class. The Ada
3124 subprogram, in turn, calls the C++ method. So, starting from the C++
3125 main program, the process passes back and forth between the two
3129 Here are the compilation commands:
3131 $ gnatmake -c simple_cpp_interface
3134 $ gnatbind -n simple_cpp_interface
3135 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++
3136 -lstdc++ ex7.o cpp_main.o
3140 Here are the corresponding sources:
3148 void adainit (void);
3149 void adafinal (void);
3150 void method1 (A *t);
3172 class A : public Origin @{
3174 void method1 (void);
3175 void method2 (int v);
3185 extern "C" @{ void ada_method2 (A *t, int v);@}
3187 void A::method1 (void)
3190 printf ("in A::method1, a_value = %d \n",a_value);
3194 void A::method2 (int v)
3196 ada_method2 (this, v);
3197 printf ("in A::method2, a_value = %d \n",a_value);
3204 printf ("in A::A, a_value = %d \n",a_value);
3208 @smallexample @c ada
3210 package body Simple_Cpp_Interface is
3212 procedure Ada_Method2 (This : in out A; V : Integer) is
3218 end Simple_Cpp_Interface;
3221 package Simple_Cpp_Interface is
3224 Vptr : System.Address;
3228 pragma Convention (C, A);
3230 procedure Method1 (This : in out A);
3231 pragma Import (C, Method1);
3233 procedure Ada_Method2 (This : in out A; V : Integer);
3234 pragma Export (C, Ada_Method2);
3236 end Simple_Cpp_Interface;
3239 @node Interfacing with C++ constructors
3240 @subsection Interfacing with C++ constructors
3243 In order to interface with C++ constructors GNAT provides the
3244 @code{pragma CPP_Constructor} (@xref{Interfacing to C++,,,
3245 gnat_rm, GNAT Reference Manual}, for additional information).
3246 In this section we present some common uses of C++ constructors
3247 in mixed-languages programs in GNAT.
3249 Let us assume that we need to interface with the following
3257 @b{virtual} int Get_Value ();
3258 Root(); // Default constructor
3259 Root(int v); // 1st non-default constructor
3260 Root(int v, int w); // 2nd non-default constructor
3264 For this purpose we can write the following package spec (further
3265 information on how to build this spec is available in
3266 @ref{Interfacing with C++ at the Class Level} and
3267 @ref{Generating Ada Bindings for C and C++ headers}).
3269 @smallexample @c ada
3270 with Interfaces.C; use Interfaces.C;
3272 type Root is tagged limited record
3276 pragma Import (CPP, Root);
3278 function Get_Value (Obj : Root) return int;
3279 pragma Import (CPP, Get_Value);
3281 function Constructor return Root'Class;
3282 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
3284 function Constructor (v : Integer) return Root'Class;
3285 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
3287 function Constructor (v, w : Integer) return Root'Class;
3288 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
3292 On the Ada side the constructor is represented by a function (whose
3293 name is arbitrary) that returns the classwide type corresponding to
3294 the imported C++ class. Although the constructor is described as a
3295 function, it is typically a procedure with an extra implicit argument
3296 (the object being initialized) at the implementation level. GNAT
3297 issues the appropriate call, whatever it is, to get the object
3298 properly initialized.
3300 Constructors can only appear in the following contexts:
3304 On the right side of an initialization of an object of type @var{T}.
3306 On the right side of an initialization of a record component of type @var{T}.
3308 In an Ada 2005 limited aggregate.
3310 In an Ada 2005 nested limited aggregate.
3312 In an Ada 2005 limited aggregate that initializes an object built in
3313 place by an extended return statement.
3317 In a declaration of an object whose type is a class imported from C++,
3318 either the default C++ constructor is implicitly called by GNAT, or
3319 else the required C++ constructor must be explicitly called in the
3320 expression that initializes the object. For example:
3322 @smallexample @c ada
3324 Obj2 : Root := Constructor;
3325 Obj3 : Root := Constructor (v => 10);
3326 Obj4 : Root := Constructor (30, 40);
3329 The first two declarations are equivalent: in both cases the default C++
3330 constructor is invoked (in the former case the call to the constructor is
3331 implicit, and in the latter case the call is explicit in the object
3332 declaration). @code{Obj3} is initialized by the C++ non-default constructor
3333 that takes an integer argument, and @code{Obj4} is initialized by the
3334 non-default C++ constructor that takes two integers.
3336 Let us derive the imported C++ class in the Ada side. For example:
3338 @smallexample @c ada
3339 type DT is new Root with record
3340 C_Value : Natural := 2009;
3344 In this case the components DT inherited from the C++ side must be
3345 initialized by a C++ constructor, and the additional Ada components
3346 of type DT are initialized by GNAT. The initialization of such an
3347 object is done either by default, or by means of a function returning
3348 an aggregate of type DT, or by means of an extension aggregate.
3350 @smallexample @c ada
3352 Obj6 : DT := Function_Returning_DT (50);
3353 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
3356 The declaration of @code{Obj5} invokes the default constructors: the
3357 C++ default constructor of the parent type takes care of the initialization
3358 of the components inherited from Root, and GNAT takes care of the default
3359 initialization of the additional Ada components of type DT (that is,
3360 @code{C_Value} is initialized to value 2009). The order of invocation of
3361 the constructors is consistent with the order of elaboration required by
3362 Ada and C++. That is, the constructor of the parent type is always called
3363 before the constructor of the derived type.
3365 Let us now consider a record that has components whose type is imported
3366 from C++. For example:
3368 @smallexample @c ada
3369 type Rec1 is limited record
3370 Data1 : Root := Constructor (10);
3371 Value : Natural := 1000;
3374 type Rec2 (D : Integer := 20) is limited record
3376 Data2 : Root := Constructor (D, 30);
3380 The initialization of an object of type @code{Rec2} will call the
3381 non-default C++ constructors specified for the imported components.
3384 @smallexample @c ada
3388 Using Ada 2005 we can use limited aggregates to initialize an object
3389 invoking C++ constructors that differ from those specified in the type
3390 declarations. For example:
3392 @smallexample @c ada
3393 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
3398 The above declaration uses an Ada 2005 limited aggregate to
3399 initialize @code{Obj9}, and the C++ constructor that has two integer
3400 arguments is invoked to initialize the @code{Data1} component instead
3401 of the constructor specified in the declaration of type @code{Rec1}. In
3402 Ada 2005 the box in the aggregate indicates that unspecified components
3403 are initialized using the expression (if any) available in the component
3404 declaration. That is, in this case discriminant @code{D} is initialized
3405 to value @code{20}, @code{Value} is initialized to value 1000, and the
3406 non-default C++ constructor that handles two integers takes care of
3407 initializing component @code{Data2} with values @code{20,30}.
3409 In Ada 2005 we can use the extended return statement to build the Ada
3410 equivalent to C++ non-default constructors. For example:
3412 @smallexample @c ada
3413 function Constructor (V : Integer) return Rec2 is
3415 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
3418 -- Further actions required for construction of
3419 -- objects of type Rec2
3425 In this example the extended return statement construct is used to
3426 build in place the returned object whose components are initialized
3427 by means of a limited aggregate. Any further action associated with
3428 the constructor can be placed inside the construct.
3430 @node Interfacing with C++ at the Class Level
3431 @subsection Interfacing with C++ at the Class Level
3433 In this section we demonstrate the GNAT features for interfacing with
3434 C++ by means of an example making use of Ada 2005 abstract interface
3435 types. This example consists of a classification of animals; classes
3436 have been used to model our main classification of animals, and
3437 interfaces provide support for the management of secondary
3438 classifications. We first demonstrate a case in which the types and
3439 constructors are defined on the C++ side and imported from the Ada
3440 side, and latter the reverse case.
3442 The root of our derivation will be the @code{Animal} class, with a
3443 single private attribute (the @code{Age} of the animal) and two public
3444 primitives to set and get the value of this attribute.
3449 @b{virtual} void Set_Age (int New_Age);
3450 @b{virtual} int Age ();
3456 Abstract interface types are defined in C++ by means of classes with pure
3457 virtual functions and no data members. In our example we will use two
3458 interfaces that provide support for the common management of @code{Carnivore}
3459 and @code{Domestic} animals:
3462 @b{class} Carnivore @{
3464 @b{virtual} int Number_Of_Teeth () = 0;
3467 @b{class} Domestic @{
3469 @b{virtual void} Set_Owner (char* Name) = 0;
3473 Using these declarations, we can now say that a @code{Dog} is an animal that is
3474 both Carnivore and Domestic, that is:
3477 @b{class} Dog : Animal, Carnivore, Domestic @{
3479 @b{virtual} int Number_Of_Teeth ();
3480 @b{virtual} void Set_Owner (char* Name);
3482 Dog(); // Constructor
3489 In the following examples we will assume that the previous declarations are
3490 located in a file named @code{animals.h}. The following package demonstrates
3491 how to import these C++ declarations from the Ada side:
3493 @smallexample @c ada
3494 with Interfaces.C.Strings; use Interfaces.C.Strings;
3496 type Carnivore is interface;
3497 pragma Convention (C_Plus_Plus, Carnivore);
3498 function Number_Of_Teeth (X : Carnivore)
3499 return Natural is abstract;
3501 type Domestic is interface;
3502 pragma Convention (C_Plus_Plus, Set_Owner);
3504 (X : in out Domestic;
3505 Name : Chars_Ptr) is abstract;
3507 type Animal is tagged record
3510 pragma Import (C_Plus_Plus, Animal);
3512 procedure Set_Age (X : in out Animal; Age : Integer);
3513 pragma Import (C_Plus_Plus, Set_Age);
3515 function Age (X : Animal) return Integer;
3516 pragma Import (C_Plus_Plus, Age);
3518 type Dog is new Animal and Carnivore and Domestic with record
3519 Tooth_Count : Natural;
3520 Owner : String (1 .. 30);
3522 pragma Import (C_Plus_Plus, Dog);
3524 function Number_Of_Teeth (A : Dog) return Integer;
3525 pragma Import (C_Plus_Plus, Number_Of_Teeth);
3527 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3528 pragma Import (C_Plus_Plus, Set_Owner);
3530 function New_Dog return Dog'Class;
3531 pragma CPP_Constructor (New_Dog);
3532 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
3536 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
3537 interfacing with these C++ classes is easy. The only requirement is that all
3538 the primitives and components must be declared exactly in the same order in
3541 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
3542 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
3543 the arguments to the called primitives will be the same as for C++. For the
3544 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
3545 to indicate that they have been defined on the C++ side; this is required
3546 because the dispatch table associated with these tagged types will be built
3547 in the C++ side and therefore will not contain the predefined Ada primitives
3548 which Ada would otherwise expect.
3550 As the reader can see there is no need to indicate the C++ mangled names
3551 associated with each subprogram because it is assumed that all the calls to
3552 these primitives will be dispatching calls. The only exception is the
3553 constructor, which must be registered with the compiler by means of
3554 @code{pragma CPP_Constructor} and needs to provide its associated C++
3555 mangled name because the Ada compiler generates direct calls to it.
3557 With the above packages we can now declare objects of type Dog on the Ada side
3558 and dispatch calls to the corresponding subprograms on the C++ side. We can
3559 also extend the tagged type Dog with further fields and primitives, and
3560 override some of its C++ primitives on the Ada side. For example, here we have
3561 a type derivation defined on the Ada side that inherits all the dispatching
3562 primitives of the ancestor from the C++ side.
3565 @b{with} Animals; @b{use} Animals;
3566 @b{package} Vaccinated_Animals @b{is}
3567 @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record};
3568 @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean;
3569 @b{end} Vaccinated_Animals;
3572 It is important to note that, because of the ABI compatibility, the programmer
3573 does not need to add any further information to indicate either the object
3574 layout or the dispatch table entry associated with each dispatching operation.
3576 Now let us define all the types and constructors on the Ada side and export
3577 them to C++, using the same hierarchy of our previous example:
3579 @smallexample @c ada
3580 with Interfaces.C.Strings;
3581 use Interfaces.C.Strings;
3583 type Carnivore is interface;
3584 pragma Convention (C_Plus_Plus, Carnivore);
3585 function Number_Of_Teeth (X : Carnivore)
3586 return Natural is abstract;
3588 type Domestic is interface;
3589 pragma Convention (C_Plus_Plus, Set_Owner);
3591 (X : in out Domestic;
3592 Name : Chars_Ptr) is abstract;
3594 type Animal is tagged record
3597 pragma Convention (C_Plus_Plus, Animal);
3599 procedure Set_Age (X : in out Animal; Age : Integer);
3600 pragma Export (C_Plus_Plus, Set_Age);
3602 function Age (X : Animal) return Integer;
3603 pragma Export (C_Plus_Plus, Age);
3605 type Dog is new Animal and Carnivore and Domestic with record
3606 Tooth_Count : Natural;
3607 Owner : String (1 .. 30);
3609 pragma Convention (C_Plus_Plus, Dog);
3611 function Number_Of_Teeth (A : Dog) return Integer;
3612 pragma Export (C_Plus_Plus, Number_Of_Teeth);
3614 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
3615 pragma Export (C_Plus_Plus, Set_Owner);
3617 function New_Dog return Dog'Class;
3618 pragma Export (C_Plus_Plus, New_Dog);
3622 Compared with our previous example the only difference is the use of
3623 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
3624 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
3625 nothing else to be done; as explained above, the only requirement is that all
3626 the primitives and components are declared in exactly the same order.
3628 For completeness, let us see a brief C++ main program that uses the
3629 declarations available in @code{animals.h} (presented in our first example) to
3630 import and use the declarations from the Ada side, properly initializing and
3631 finalizing the Ada run-time system along the way:
3634 @b{#include} "animals.h"
3635 @b{#include} <iostream>
3636 @b{using namespace} std;
3638 void Check_Carnivore (Carnivore *obj) @{@dots{}@}
3639 void Check_Domestic (Domestic *obj) @{@dots{}@}
3640 void Check_Animal (Animal *obj) @{@dots{}@}
3641 void Check_Dog (Dog *obj) @{@dots{}@}
3644 void adainit (void);
3645 void adafinal (void);
3651 Dog *obj = new_dog(); // Ada constructor
3652 Check_Carnivore (obj); // Check secondary DT
3653 Check_Domestic (obj); // Check secondary DT
3654 Check_Animal (obj); // Check primary DT
3655 Check_Dog (obj); // Check primary DT
3660 adainit (); test(); adafinal ();
3665 @node Comparison between GNAT and C/C++ Compilation Models
3666 @section Comparison between GNAT and C/C++ Compilation Models
3669 The GNAT model of compilation is close to the C and C++ models. You can
3670 think of Ada specs as corresponding to header files in C. As in C, you
3671 don't need to compile specs; they are compiled when they are used. The
3672 Ada @code{with} is similar in effect to the @code{#include} of a C
3675 One notable difference is that, in Ada, you may compile specs separately
3676 to check them for semantic and syntactic accuracy. This is not always
3677 possible with C headers because they are fragments of programs that have
3678 less specific syntactic or semantic rules.
3680 The other major difference is the requirement for running the binder,
3681 which performs two important functions. First, it checks for
3682 consistency. In C or C++, the only defense against assembling
3683 inconsistent programs lies outside the compiler, in a makefile, for
3684 example. The binder satisfies the Ada requirement that it be impossible
3685 to construct an inconsistent program when the compiler is used in normal
3688 @cindex Elaboration order control
3689 The other important function of the binder is to deal with elaboration
3690 issues. There are also elaboration issues in C++ that are handled
3691 automatically. This automatic handling has the advantage of being
3692 simpler to use, but the C++ programmer has no control over elaboration.
3693 Where @code{gnatbind} might complain there was no valid order of
3694 elaboration, a C++ compiler would simply construct a program that
3695 malfunctioned at run time.
3698 @node Comparison between GNAT and Conventional Ada Library Models
3699 @section Comparison between GNAT and Conventional Ada Library Models
3702 This section is intended for Ada programmers who have
3703 used an Ada compiler implementing the traditional Ada library
3704 model, as described in the Ada Reference Manual.
3706 @cindex GNAT library
3707 In GNAT, there is no ``library'' in the normal sense. Instead, the set of
3708 source files themselves acts as the library. Compiling Ada programs does
3709 not generate any centralized information, but rather an object file and
3710 a ALI file, which are of interest only to the binder and linker.
3711 In a traditional system, the compiler reads information not only from
3712 the source file being compiled, but also from the centralized library.
3713 This means that the effect of a compilation depends on what has been
3714 previously compiled. In particular:
3718 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3719 to the version of the unit most recently compiled into the library.
3722 Inlining is effective only if the necessary body has already been
3723 compiled into the library.
3726 Compiling a unit may obsolete other units in the library.
3730 In GNAT, compiling one unit never affects the compilation of any other
3731 units because the compiler reads only source files. Only changes to source
3732 files can affect the results of a compilation. In particular:
3736 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3737 to the source version of the unit that is currently accessible to the
3742 Inlining requires the appropriate source files for the package or
3743 subprogram bodies to be available to the compiler. Inlining is always
3744 effective, independent of the order in which units are complied.
3747 Compiling a unit never affects any other compilations. The editing of
3748 sources may cause previous compilations to be out of date if they
3749 depended on the source file being modified.
3753 The most important result of these differences is that order of compilation
3754 is never significant in GNAT. There is no situation in which one is
3755 required to do one compilation before another. What shows up as order of
3756 compilation requirements in the traditional Ada library becomes, in
3757 GNAT, simple source dependencies; in other words, there is only a set
3758 of rules saying what source files must be present when a file is
3762 @node Placement of temporary files
3763 @section Placement of temporary files
3764 @cindex Temporary files (user control over placement)
3767 GNAT creates temporary files in the directory designated by the environment
3768 variable @env{TMPDIR}.
3769 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3770 for detailed information on how environment variables are resolved.
3771 For most users the easiest way to make use of this feature is to simply
3772 define @env{TMPDIR} as a job level logical name).
3773 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3774 for compiler temporary files, then you can include something like the
3775 following command in your @file{LOGIN.COM} file:
3778 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3782 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3783 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3784 designated by @env{TEMP}.
3785 If none of these environment variables are defined then GNAT uses the
3786 directory designated by the logical name @code{SYS$SCRATCH:}
3787 (by default the user's home directory). If all else fails
3788 GNAT uses the current directory for temporary files.
3791 @c *************************
3792 @node Compiling Using gcc
3793 @chapter Compiling Using @command{gcc}
3796 This chapter discusses how to compile Ada programs using the @command{gcc}
3797 command. It also describes the set of switches
3798 that can be used to control the behavior of the compiler.
3800 * Compiling Programs::
3801 * Switches for gcc::
3802 * Search Paths and the Run-Time Library (RTL)::
3803 * Order of Compilation Issues::
3807 @node Compiling Programs
3808 @section Compiling Programs
3811 The first step in creating an executable program is to compile the units
3812 of the program using the @command{gcc} command. You must compile the
3817 the body file (@file{.adb}) for a library level subprogram or generic
3821 the spec file (@file{.ads}) for a library level package or generic
3822 package that has no body
3825 the body file (@file{.adb}) for a library level package
3826 or generic package that has a body
3831 You need @emph{not} compile the following files
3836 the spec of a library unit which has a body
3843 because they are compiled as part of compiling related units. GNAT
3845 when the corresponding body is compiled, and subunits when the parent is
3848 @cindex cannot generate code
3849 If you attempt to compile any of these files, you will get one of the
3850 following error messages (where @var{fff} is the name of the file you compiled):
3853 cannot generate code for file @var{fff} (package spec)
3854 to check package spec, use -gnatc
3856 cannot generate code for file @var{fff} (missing subunits)
3857 to check parent unit, use -gnatc
3859 cannot generate code for file @var{fff} (subprogram spec)
3860 to check subprogram spec, use -gnatc
3862 cannot generate code for file @var{fff} (subunit)
3863 to check subunit, use -gnatc
3867 As indicated by the above error messages, if you want to submit
3868 one of these files to the compiler to check for correct semantics
3869 without generating code, then use the @option{-gnatc} switch.
3871 The basic command for compiling a file containing an Ada unit is
3874 $ gcc -c @ovar{switches} @file{file name}
3878 where @var{file name} is the name of the Ada file (usually
3880 @file{.ads} for a spec or @file{.adb} for a body).
3883 @option{-c} switch to tell @command{gcc} to compile, but not link, the file.
3885 The result of a successful compilation is an object file, which has the
3886 same name as the source file but an extension of @file{.o} and an Ada
3887 Library Information (ALI) file, which also has the same name as the
3888 source file, but with @file{.ali} as the extension. GNAT creates these
3889 two output files in the current directory, but you may specify a source
3890 file in any directory using an absolute or relative path specification
3891 containing the directory information.
3894 @command{gcc} is actually a driver program that looks at the extensions of
3895 the file arguments and loads the appropriate compiler. For example, the
3896 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3897 These programs are in directories known to the driver program (in some
3898 configurations via environment variables you set), but need not be in
3899 your path. The @command{gcc} driver also calls the assembler and any other
3900 utilities needed to complete the generation of the required object
3903 It is possible to supply several file names on the same @command{gcc}
3904 command. This causes @command{gcc} to call the appropriate compiler for
3905 each file. For example, the following command lists three separate
3906 files to be compiled:
3909 $ gcc -c x.adb y.adb z.c
3913 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3914 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3915 The compiler generates three object files @file{x.o}, @file{y.o} and
3916 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3917 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3920 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3923 @node Switches for gcc
3924 @section Switches for @command{gcc}
3927 The @command{gcc} command accepts switches that control the
3928 compilation process. These switches are fully described in this section.
3929 First we briefly list all the switches, in alphabetical order, then we
3930 describe the switches in more detail in functionally grouped sections.
3932 More switches exist for GCC than those documented here, especially
3933 for specific targets. However, their use is not recommended as
3934 they may change code generation in ways that are incompatible with
3935 the Ada run-time library, or can cause inconsistencies between
3939 * Output and Error Message Control::
3940 * Warning Message Control::
3941 * Debugging and Assertion Control::
3942 * Validity Checking::
3945 * Using gcc for Syntax Checking::
3946 * Using gcc for Semantic Checking::
3947 * Compiling Different Versions of Ada::
3948 * Character Set Control::
3949 * File Naming Control::
3950 * Subprogram Inlining Control::
3951 * Auxiliary Output Control::
3952 * Debugging Control::
3953 * Exception Handling Control::
3954 * Units to Sources Mapping Files::
3955 * Integrated Preprocessing::
3956 * Code Generation Control::
3965 @cindex @option{-b} (@command{gcc})
3966 @item -b @var{target}
3967 Compile your program to run on @var{target}, which is the name of a
3968 system configuration. You must have a GNAT cross-compiler built if
3969 @var{target} is not the same as your host system.
3972 @cindex @option{-B} (@command{gcc})
3973 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3974 from @var{dir} instead of the default location. Only use this switch
3975 when multiple versions of the GNAT compiler are available.
3976 @xref{Directory Options,, Options for Directory Search, gcc, Using the
3977 GNU Compiler Collection (GCC)}, for further details. You would normally
3978 use the @option{-b} or @option{-V} switch instead.
3981 @cindex @option{-c} (@command{gcc})
3982 Compile. Always use this switch when compiling Ada programs.
3984 Note: for some other languages when using @command{gcc}, notably in
3985 the case of C and C++, it is possible to use
3986 use @command{gcc} without a @option{-c} switch to
3987 compile and link in one step. In the case of GNAT, you
3988 cannot use this approach, because the binder must be run
3989 and @command{gcc} cannot be used to run the GNAT binder.
3993 @cindex @option{-fno-inline} (@command{gcc})
3994 Suppresses all back-end inlining, even if other optimization or inlining
3996 This includes suppression of inlining that results
3997 from the use of the pragma @code{Inline_Always}.
3998 Any occurrences of pragma @code{Inline} or @code{Inline_Always}
3999 are ignored, and @option{-gnatn} and @option{-gnatN} have no
4000 effect if this switch is present.
4002 @item -fno-inline-functions
4003 @cindex @option{-fno-inline-functions} (@command{gcc})
4004 Suppresses automatic inlining of simple subprograms, which is enabled
4005 if @option{-O3} is used.
4007 @item -fno-inline-small-functions
4008 @cindex @option{-fno-inline-small-functions} (@command{gcc})
4009 Suppresses automatic inlining of small subprograms, which is enabled
4010 if @option{-O2} is used.
4012 @item -fno-inline-functions-called-once
4013 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
4014 Suppresses inlining of subprograms local to the unit and called once
4015 from within it, which is enabled if @option{-O1} is used.
4018 @cindex @option{-fno-ivopts} (@command{gcc})
4019 Suppresses high-level loop induction variable optimizations, which are
4020 enabled if @option{-O1} is used. These optimizations are generally
4021 profitable but, for some specific cases of loops with numerous uses
4022 of the iteration variable that follow a common pattern, they may end
4023 up destroying the regularity that could be exploited at a lower level
4024 and thus producing inferior code.
4026 @item -fno-strict-aliasing
4027 @cindex @option{-fno-strict-aliasing} (@command{gcc})
4028 Causes the compiler to avoid assumptions regarding non-aliasing
4029 of objects of different types. See
4030 @ref{Optimization and Strict Aliasing} for details.
4033 @cindex @option{-fstack-check} (@command{gcc})
4034 Activates stack checking.
4035 See @ref{Stack Overflow Checking} for details.
4038 @cindex @option{-fstack-usage} (@command{gcc})
4039 Makes the compiler output stack usage information for the program, on a
4040 per-function basis. See @ref{Static Stack Usage Analysis} for details.
4042 @item -fcallgraph-info@r{[}=su@r{]}
4043 @cindex @option{-fcallgraph-info} (@command{gcc})
4044 Makes the compiler output callgraph information for the program, on a
4045 per-file basis. The information is generated in the VCG format. It can
4046 be decorated with stack-usage per-node information.
4049 @cindex @option{^-g^/DEBUG^} (@command{gcc})
4050 Generate debugging information. This information is stored in the object
4051 file and copied from there to the final executable file by the linker,
4052 where it can be read by the debugger. You must use the
4053 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
4056 @cindex @option{-gnat83} (@command{gcc})
4057 Enforce Ada 83 restrictions.
4060 @cindex @option{-gnat95} (@command{gcc})
4061 Enforce Ada 95 restrictions.
4064 @cindex @option{-gnat05} (@command{gcc})
4065 Allow full Ada 2005 features.
4068 @cindex @option{-gnata} (@command{gcc})
4069 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
4070 activated. Note that these pragmas can also be controlled using the
4071 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
4072 It also activates pragmas @code{Check}, @code{Precondition}, and
4073 @code{Postcondition}. Note that these pragmas can also be controlled
4074 using the configuration pragma @code{Check_Policy}.
4077 @cindex @option{-gnatA} (@command{gcc})
4078 Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present,
4082 @cindex @option{-gnatb} (@command{gcc})
4083 Generate brief messages to @file{stderr} even if verbose mode set.
4086 @cindex @option{-gnatB} (@command{gcc})
4087 Assume no invalid (bad) values except for 'Valid attribute use.
4090 @cindex @option{-gnatc} (@command{gcc})
4091 Check syntax and semantics only (no code generation attempted).
4094 @cindex @option{-gnatd} (@command{gcc})
4095 Specify debug options for the compiler. The string of characters after
4096 the @option{-gnatd} specify the specific debug options. The possible
4097 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
4098 compiler source file @file{debug.adb} for details of the implemented
4099 debug options. Certain debug options are relevant to applications
4100 programmers, and these are documented at appropriate points in this
4105 @cindex @option{-gnatD[nn]} (@command{gcc})
4108 @item /XDEBUG /LXDEBUG=nnn
4110 Create expanded source files for source level debugging. This switch
4111 also suppress generation of cross-reference information
4112 (see @option{-gnatx}).
4114 @item -gnatec=@var{path}
4115 @cindex @option{-gnatec} (@command{gcc})
4116 Specify a configuration pragma file
4118 (the equal sign is optional)
4120 (@pxref{The Configuration Pragmas Files}).
4122 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
4123 @cindex @option{-gnateD} (@command{gcc})
4124 Defines a symbol, associated with @var{value}, for preprocessing.
4125 (@pxref{Integrated Preprocessing}).
4128 @cindex @option{-gnatef} (@command{gcc})
4129 Display full source path name in brief error messages.
4132 @cindex @option{-gnateG} (@command{gcc})
4133 Save result of preprocessing in a text file.
4135 @item -gnatem=@var{path}
4136 @cindex @option{-gnatem} (@command{gcc})
4137 Specify a mapping file
4139 (the equal sign is optional)
4141 (@pxref{Units to Sources Mapping Files}).
4143 @item -gnatep=@var{file}
4144 @cindex @option{-gnatep} (@command{gcc})
4145 Specify a preprocessing data file
4147 (the equal sign is optional)
4149 (@pxref{Integrated Preprocessing}).
4152 @cindex @option{-gnatE} (@command{gcc})
4153 Full dynamic elaboration checks.
4156 @cindex @option{-gnatf} (@command{gcc})
4157 Full errors. Multiple errors per line, all undefined references, do not
4158 attempt to suppress cascaded errors.
4161 @cindex @option{-gnatF} (@command{gcc})
4162 Externals names are folded to all uppercase.
4164 @item ^-gnatg^/GNAT_INTERNAL^
4165 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
4166 Internal GNAT implementation mode. This should not be used for
4167 applications programs, it is intended only for use by the compiler
4168 and its run-time library. For documentation, see the GNAT sources.
4169 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
4170 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
4171 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
4172 so that all standard warnings and all standard style options are turned on.
4173 All warnings and style error messages are treated as errors.
4177 @cindex @option{-gnatG[nn]} (@command{gcc})
4180 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
4182 List generated expanded code in source form.
4184 @item ^-gnath^/HELP^
4185 @cindex @option{^-gnath^/HELP^} (@command{gcc})
4186 Output usage information. The output is written to @file{stdout}.
4188 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
4189 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
4190 Identifier character set
4192 (@var{c}=1/2/3/4/8/9/p/f/n/w).
4194 For details of the possible selections for @var{c},
4195 see @ref{Character Set Control}.
4197 @item ^-gnatI^/IGNORE_REP_CLAUSES^
4198 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
4199 Ignore representation clauses. When this switch is used,
4200 representation clauses are treated as comments. This is useful
4201 when initially porting code where you want to ignore rep clause
4202 problems, and also for compiling foreign code (particularly
4203 for use with ASIS). The representation clauses that are ignored
4204 are: enumeration_representation_clause, record_representation_clause,
4205 and attribute_definition_clause for the following attributes:
4206 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
4207 Object_Size, Size, Small, Stream_Size, and Value_Size.
4208 Note that this option should be used only for compiling -- the
4209 code is likely to malfunction at run time.
4212 @cindex @option{-gnatjnn} (@command{gcc})
4213 Reformat error messages to fit on nn character lines
4215 @item -gnatk=@var{n}
4216 @cindex @option{-gnatk} (@command{gcc})
4217 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4220 @cindex @option{-gnatl} (@command{gcc})
4221 Output full source listing with embedded error messages.
4224 @cindex @option{-gnatL} (@command{gcc})
4225 Used in conjunction with -gnatG or -gnatD to intersperse original
4226 source lines (as comment lines with line numbers) in the expanded
4229 @item -gnatm=@var{n}
4230 @cindex @option{-gnatm} (@command{gcc})
4231 Limit number of detected error or warning messages to @var{n}
4232 where @var{n} is in the range 1..999999. The default setting if
4233 no switch is given is 9999. If the number of warnings reaches this
4234 limit, then a message is output and further warnings are suppressed,
4235 but the compilation is continued. If the number of error messages
4236 reaches this limit, then a message is output and the compilation
4237 is abandoned. The equal sign here is optional. A value of zero
4238 means that no limit applies.
4241 @cindex @option{-gnatn} (@command{gcc})
4242 Activate inlining for subprograms for which
4243 pragma @code{inline} is specified. This inlining is performed
4244 by the GCC back-end.
4247 @cindex @option{-gnatN} (@command{gcc})
4248 Activate front end inlining for subprograms for which
4249 pragma @code{Inline} is specified. This inlining is performed
4250 by the front end and will be visible in the
4251 @option{-gnatG} output.
4253 When using a gcc-based back end (in practice this means using any version
4254 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4255 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4256 Historically front end inlining was more extensive than the gcc back end
4257 inlining, but that is no longer the case.
4260 @cindex @option{-gnato} (@command{gcc})
4261 Enable numeric overflow checking (which is not normally enabled by
4262 default). Note that division by zero is a separate check that is not
4263 controlled by this switch (division by zero checking is on by default).
4266 @cindex @option{-gnatp} (@command{gcc})
4267 Suppress all checks. See @ref{Run-Time Checks} for details.
4270 @cindex @option{-gnatP} (@command{gcc})
4271 Enable polling. This is required on some systems (notably Windows NT) to
4272 obtain asynchronous abort and asynchronous transfer of control capability.
4273 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4277 @cindex @option{-gnatq} (@command{gcc})
4278 Don't quit. Try semantics, even if parse errors.
4281 @cindex @option{-gnatQ} (@command{gcc})
4282 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4285 @cindex @option{-gnatr} (@command{gcc})
4286 Treat pragma Restrictions as Restriction_Warnings.
4288 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4289 @cindex @option{-gnatR} (@command{gcc})
4290 Output representation information for declared types and objects.
4293 @cindex @option{-gnats} (@command{gcc})
4297 @cindex @option{-gnatS} (@command{gcc})
4298 Print package Standard.
4301 @cindex @option{-gnatt} (@command{gcc})
4302 Generate tree output file.
4304 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4305 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4306 All compiler tables start at @var{nnn} times usual starting size.
4309 @cindex @option{-gnatu} (@command{gcc})
4310 List units for this compilation.
4313 @cindex @option{-gnatU} (@command{gcc})
4314 Tag all error messages with the unique string ``error:''
4317 @cindex @option{-gnatv} (@command{gcc})
4318 Verbose mode. Full error output with source lines to @file{stdout}.
4321 @cindex @option{-gnatV} (@command{gcc})
4322 Control level of validity checking. See separate section describing
4325 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4326 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4328 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4329 the exact warnings that
4330 are enabled or disabled (@pxref{Warning Message Control}).
4332 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4333 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4334 Wide character encoding method
4336 (@var{e}=n/h/u/s/e/8).
4339 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4343 @cindex @option{-gnatx} (@command{gcc})
4344 Suppress generation of cross-reference information.
4346 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4347 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4348 Enable built-in style checks (@pxref{Style Checking}).
4350 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4351 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4352 Distribution stub generation and compilation
4354 (@var{m}=r/c for receiver/caller stubs).
4357 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4358 to be generated and compiled).
4361 @item ^-I^/SEARCH=^@var{dir}
4362 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4364 Direct GNAT to search the @var{dir} directory for source files needed by
4365 the current compilation
4366 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4368 @item ^-I-^/NOCURRENT_DIRECTORY^
4369 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4371 Except for the source file named in the command line, do not look for source
4372 files in the directory containing the source file named in the command line
4373 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4377 @cindex @option{-mbig-switch} (@command{gcc})
4378 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4379 This standard gcc switch causes the compiler to use larger offsets in its
4380 jump table representation for @code{case} statements.
4381 This may result in less efficient code, but is sometimes necessary
4382 (for example on HP-UX targets)
4383 @cindex HP-UX and @option{-mbig-switch} option
4384 in order to compile large and/or nested @code{case} statements.
4387 @cindex @option{-o} (@command{gcc})
4388 This switch is used in @command{gcc} to redirect the generated object file
4389 and its associated ALI file. Beware of this switch with GNAT, because it may
4390 cause the object file and ALI file to have different names which in turn
4391 may confuse the binder and the linker.
4395 @cindex @option{-nostdinc} (@command{gcc})
4396 Inhibit the search of the default location for the GNAT Run Time
4397 Library (RTL) source files.
4400 @cindex @option{-nostdlib} (@command{gcc})
4401 Inhibit the search of the default location for the GNAT Run Time
4402 Library (RTL) ALI files.
4406 @cindex @option{-O} (@command{gcc})
4407 @var{n} controls the optimization level.
4411 No optimization, the default setting if no @option{-O} appears
4414 Normal optimization, the default if you specify @option{-O} without
4415 an operand. A good compromise between code quality and compilation
4419 Extensive optimization, may improve execution time, possibly at the cost of
4420 substantially increased compilation time.
4423 Same as @option{-O2}, and also includes inline expansion for small subprograms
4427 Optimize space usage
4431 See also @ref{Optimization Levels}.
4436 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4437 Equivalent to @option{/OPTIMIZE=NONE}.
4438 This is the default behavior in the absence of an @option{/OPTIMIZE}
4441 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4442 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4443 Selects the level of optimization for your program. The supported
4444 keywords are as follows:
4447 Perform most optimizations, including those that
4449 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4450 without keyword options.
4453 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4456 Perform some optimizations, but omit ones that are costly.
4459 Same as @code{SOME}.
4462 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4463 automatic inlining of small subprograms within a unit
4466 Try to unroll loops. This keyword may be specified together with
4467 any keyword above other than @code{NONE}. Loop unrolling
4468 usually, but not always, improves the performance of programs.
4471 Optimize space usage
4475 See also @ref{Optimization Levels}.
4479 @item -pass-exit-codes
4480 @cindex @option{-pass-exit-codes} (@command{gcc})
4481 Catch exit codes from the compiler and use the most meaningful as
4485 @item --RTS=@var{rts-path}
4486 @cindex @option{--RTS} (@command{gcc})
4487 Specifies the default location of the runtime library. Same meaning as the
4488 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4491 @cindex @option{^-S^/ASM^} (@command{gcc})
4492 ^Used in place of @option{-c} to^Used to^
4493 cause the assembler source file to be
4494 generated, using @file{^.s^.S^} as the extension,
4495 instead of the object file.
4496 This may be useful if you need to examine the generated assembly code.
4498 @item ^-fverbose-asm^/VERBOSE_ASM^
4499 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4500 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4501 to cause the generated assembly code file to be annotated with variable
4502 names, making it significantly easier to follow.
4505 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4506 Show commands generated by the @command{gcc} driver. Normally used only for
4507 debugging purposes or if you need to be sure what version of the
4508 compiler you are executing.
4512 @cindex @option{-V} (@command{gcc})
4513 Execute @var{ver} version of the compiler. This is the @command{gcc}
4514 version, not the GNAT version.
4517 @item ^-w^/NO_BACK_END_WARNINGS^
4518 @cindex @option{-w} (@command{gcc})
4519 Turn off warnings generated by the back end of the compiler. Use of
4520 this switch also causes the default for front end warnings to be set
4521 to suppress (as though @option{-gnatws} had appeared at the start of
4527 @c Combining qualifiers does not work on VMS
4528 You may combine a sequence of GNAT switches into a single switch. For
4529 example, the combined switch
4531 @cindex Combining GNAT switches
4537 is equivalent to specifying the following sequence of switches:
4540 -gnato -gnatf -gnati3
4545 The following restrictions apply to the combination of switches
4550 The switch @option{-gnatc} if combined with other switches must come
4551 first in the string.
4554 The switch @option{-gnats} if combined with other switches must come
4555 first in the string.
4559 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4560 may not be combined with any other switches.
4564 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4565 switch), then all further characters in the switch are interpreted
4566 as style modifiers (see description of @option{-gnaty}).
4569 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4570 switch), then all further characters in the switch are interpreted
4571 as debug flags (see description of @option{-gnatd}).
4574 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4575 switch), then all further characters in the switch are interpreted
4576 as warning mode modifiers (see description of @option{-gnatw}).
4579 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4580 switch), then all further characters in the switch are interpreted
4581 as validity checking options (see description of @option{-gnatV}).
4585 @node Output and Error Message Control
4586 @subsection Output and Error Message Control
4590 The standard default format for error messages is called ``brief format''.
4591 Brief format messages are written to @file{stderr} (the standard error
4592 file) and have the following form:
4595 e.adb:3:04: Incorrect spelling of keyword "function"
4596 e.adb:4:20: ";" should be "is"
4600 The first integer after the file name is the line number in the file,
4601 and the second integer is the column number within the line.
4603 @code{GPS} can parse the error messages
4604 and point to the referenced character.
4606 The following switches provide control over the error message
4612 @cindex @option{-gnatv} (@command{gcc})
4615 The v stands for verbose.
4617 The effect of this setting is to write long-format error
4618 messages to @file{stdout} (the standard output file.
4619 The same program compiled with the
4620 @option{-gnatv} switch would generate:
4624 3. funcion X (Q : Integer)
4626 >>> Incorrect spelling of keyword "function"
4629 >>> ";" should be "is"
4634 The vertical bar indicates the location of the error, and the @samp{>>>}
4635 prefix can be used to search for error messages. When this switch is
4636 used the only source lines output are those with errors.
4639 @cindex @option{-gnatl} (@command{gcc})
4641 The @code{l} stands for list.
4643 This switch causes a full listing of
4644 the file to be generated. In the case where a body is
4645 compiled, the corresponding spec is also listed, along
4646 with any subunits. Typical output from compiling a package
4647 body @file{p.adb} might look like:
4649 @smallexample @c ada
4653 1. package body p is
4655 3. procedure a is separate;
4666 2. pragma Elaborate_Body
4690 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4691 standard output is redirected, a brief summary is written to
4692 @file{stderr} (standard error) giving the number of error messages and
4693 warning messages generated.
4695 @item -^gnatl^OUTPUT_FILE^=file
4696 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4697 This has the same effect as @option{-gnatl} except that the output is
4698 written to a file instead of to standard output. If the given name
4699 @file{fname} does not start with a period, then it is the full name
4700 of the file to be written. If @file{fname} is an extension, it is
4701 appended to the name of the file being compiled. For example, if
4702 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4703 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4706 @cindex @option{-gnatU} (@command{gcc})
4707 This switch forces all error messages to be preceded by the unique
4708 string ``error:''. This means that error messages take a few more
4709 characters in space, but allows easy searching for and identification
4713 @cindex @option{-gnatb} (@command{gcc})
4715 The @code{b} stands for brief.
4717 This switch causes GNAT to generate the
4718 brief format error messages to @file{stderr} (the standard error
4719 file) as well as the verbose
4720 format message or full listing (which as usual is written to
4721 @file{stdout} (the standard output file).
4723 @item -gnatm=@var{n}
4724 @cindex @option{-gnatm} (@command{gcc})
4726 The @code{m} stands for maximum.
4728 @var{n} is a decimal integer in the
4729 range of 1 to 999999 and limits the number of error or warning
4730 messages to be generated. For example, using
4731 @option{-gnatm2} might yield
4734 e.adb:3:04: Incorrect spelling of keyword "function"
4735 e.adb:5:35: missing ".."
4736 fatal error: maximum number of errors detected
4737 compilation abandoned
4741 The default setting if
4742 no switch is given is 9999. If the number of warnings reaches this
4743 limit, then a message is output and further warnings are suppressed,
4744 but the compilation is continued. If the number of error messages
4745 reaches this limit, then a message is output and the compilation
4746 is abandoned. A value of zero means that no limit applies.
4749 Note that the equal sign is optional, so the switches
4750 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4753 @cindex @option{-gnatf} (@command{gcc})
4754 @cindex Error messages, suppressing
4756 The @code{f} stands for full.
4758 Normally, the compiler suppresses error messages that are likely to be
4759 redundant. This switch causes all error
4760 messages to be generated. In particular, in the case of
4761 references to undefined variables. If a given variable is referenced
4762 several times, the normal format of messages is
4764 e.adb:7:07: "V" is undefined (more references follow)
4768 where the parenthetical comment warns that there are additional
4769 references to the variable @code{V}. Compiling the same program with the
4770 @option{-gnatf} switch yields
4773 e.adb:7:07: "V" is undefined
4774 e.adb:8:07: "V" is undefined
4775 e.adb:8:12: "V" is undefined
4776 e.adb:8:16: "V" is undefined
4777 e.adb:9:07: "V" is undefined
4778 e.adb:9:12: "V" is undefined
4782 The @option{-gnatf} switch also generates additional information for
4783 some error messages. Some examples are:
4787 Full details on entities not available in high integrity mode
4789 Details on possibly non-portable unchecked conversion
4791 List possible interpretations for ambiguous calls
4793 Additional details on incorrect parameters
4797 @cindex @option{-gnatjnn} (@command{gcc})
4798 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4799 with continuation lines are treated as though the continuation lines were
4800 separate messages (and so a warning with two continuation lines counts as
4801 three warnings, and is listed as three separate messages).
4803 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4804 messages are output in a different manner. A message and all its continuation
4805 lines are treated as a unit, and count as only one warning or message in the
4806 statistics totals. Furthermore, the message is reformatted so that no line
4807 is longer than nn characters.
4810 @cindex @option{-gnatq} (@command{gcc})
4812 The @code{q} stands for quit (really ``don't quit'').
4814 In normal operation mode, the compiler first parses the program and
4815 determines if there are any syntax errors. If there are, appropriate
4816 error messages are generated and compilation is immediately terminated.
4818 GNAT to continue with semantic analysis even if syntax errors have been
4819 found. This may enable the detection of more errors in a single run. On
4820 the other hand, the semantic analyzer is more likely to encounter some
4821 internal fatal error when given a syntactically invalid tree.
4824 @cindex @option{-gnatQ} (@command{gcc})
4825 In normal operation mode, the @file{ALI} file is not generated if any
4826 illegalities are detected in the program. The use of @option{-gnatQ} forces
4827 generation of the @file{ALI} file. This file is marked as being in
4828 error, so it cannot be used for binding purposes, but it does contain
4829 reasonably complete cross-reference information, and thus may be useful
4830 for use by tools (e.g., semantic browsing tools or integrated development
4831 environments) that are driven from the @file{ALI} file. This switch
4832 implies @option{-gnatq}, since the semantic phase must be run to get a
4833 meaningful ALI file.
4835 In addition, if @option{-gnatt} is also specified, then the tree file is
4836 generated even if there are illegalities. It may be useful in this case
4837 to also specify @option{-gnatq} to ensure that full semantic processing
4838 occurs. The resulting tree file can be processed by ASIS, for the purpose
4839 of providing partial information about illegal units, but if the error
4840 causes the tree to be badly malformed, then ASIS may crash during the
4843 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4844 being in error, @command{gnatmake} will attempt to recompile the source when it
4845 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4847 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4848 since ALI files are never generated if @option{-gnats} is set.
4852 @node Warning Message Control
4853 @subsection Warning Message Control
4854 @cindex Warning messages
4856 In addition to error messages, which correspond to illegalities as defined
4857 in the Ada Reference Manual, the compiler detects two kinds of warning
4860 First, the compiler considers some constructs suspicious and generates a
4861 warning message to alert you to a possible error. Second, if the
4862 compiler detects a situation that is sure to raise an exception at
4863 run time, it generates a warning message. The following shows an example
4864 of warning messages:
4866 e.adb:4:24: warning: creation of object may raise Storage_Error
4867 e.adb:10:17: warning: static value out of range
4868 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4872 GNAT considers a large number of situations as appropriate
4873 for the generation of warning messages. As always, warnings are not
4874 definite indications of errors. For example, if you do an out-of-range
4875 assignment with the deliberate intention of raising a
4876 @code{Constraint_Error} exception, then the warning that may be
4877 issued does not indicate an error. Some of the situations for which GNAT
4878 issues warnings (at least some of the time) are given in the following
4879 list. This list is not complete, and new warnings are often added to
4880 subsequent versions of GNAT. The list is intended to give a general idea
4881 of the kinds of warnings that are generated.
4885 Possible infinitely recursive calls
4888 Out-of-range values being assigned
4891 Possible order of elaboration problems
4894 Assertions (pragma Assert) that are sure to fail
4900 Address clauses with possibly unaligned values, or where an attempt is
4901 made to overlay a smaller variable with a larger one.
4904 Fixed-point type declarations with a null range
4907 Direct_IO or Sequential_IO instantiated with a type that has access values
4910 Variables that are never assigned a value
4913 Variables that are referenced before being initialized
4916 Task entries with no corresponding @code{accept} statement
4919 Duplicate accepts for the same task entry in a @code{select}
4922 Objects that take too much storage
4925 Unchecked conversion between types of differing sizes
4928 Missing @code{return} statement along some execution path in a function
4931 Incorrect (unrecognized) pragmas
4934 Incorrect external names
4937 Allocation from empty storage pool
4940 Potentially blocking operation in protected type
4943 Suspicious parenthesization of expressions
4946 Mismatching bounds in an aggregate
4949 Attempt to return local value by reference
4952 Premature instantiation of a generic body
4955 Attempt to pack aliased components
4958 Out of bounds array subscripts
4961 Wrong length on string assignment
4964 Violations of style rules if style checking is enabled
4967 Unused @code{with} clauses
4970 @code{Bit_Order} usage that does not have any effect
4973 @code{Standard.Duration} used to resolve universal fixed expression
4976 Dereference of possibly null value
4979 Declaration that is likely to cause storage error
4982 Internal GNAT unit @code{with}'ed by application unit
4985 Values known to be out of range at compile time
4988 Unreferenced labels and variables
4991 Address overlays that could clobber memory
4994 Unexpected initialization when address clause present
4997 Bad alignment for address clause
5000 Useless type conversions
5003 Redundant assignment statements and other redundant constructs
5006 Useless exception handlers
5009 Accidental hiding of name by child unit
5012 Access before elaboration detected at compile time
5015 A range in a @code{for} loop that is known to be null or might be null
5020 The following section lists compiler switches that are available
5021 to control the handling of warning messages. It is also possible
5022 to exercise much finer control over what warnings are issued and
5023 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
5024 gnat_rm, GNAT Reference manual}.
5029 @emph{Activate all optional errors.}
5030 @cindex @option{-gnatwa} (@command{gcc})
5031 This switch activates most optional warning messages, see remaining list
5032 in this section for details on optional warning messages that can be
5033 individually controlled. The warnings that are not turned on by this
5035 @option{-gnatwd} (implicit dereferencing),
5036 @option{-gnatwh} (hiding),
5037 @option{-gnatwl} (elaboration warnings),
5038 @option{-gnatw.o} (warn on values set by out parameters ignored)
5039 and @option{-gnatwt} (tracking of deleted conditional code).
5040 All other optional warnings are turned on.
5043 @emph{Suppress all optional errors.}
5044 @cindex @option{-gnatwA} (@command{gcc})
5045 This switch suppresses all optional warning messages, see remaining list
5046 in this section for details on optional warning messages that can be
5047 individually controlled.
5050 @emph{Activate warnings on failing assertions.}
5051 @cindex @option{-gnatw.a} (@command{gcc})
5052 @cindex Assert failures
5053 This switch activates warnings for assertions where the compiler can tell at
5054 compile time that the assertion will fail. Note that this warning is given
5055 even if assertions are disabled. The default is that such warnings are
5059 @emph{Suppress warnings on failing assertions.}
5060 @cindex @option{-gnatw.A} (@command{gcc})
5061 @cindex Assert failures
5062 This switch suppresses warnings for assertions where the compiler can tell at
5063 compile time that the assertion will fail.
5066 @emph{Activate warnings on bad fixed values.}
5067 @cindex @option{-gnatwb} (@command{gcc})
5068 @cindex Bad fixed values
5069 @cindex Fixed-point Small value
5071 This switch activates warnings for static fixed-point expressions whose
5072 value is not an exact multiple of Small. Such values are implementation
5073 dependent, since an implementation is free to choose either of the multiples
5074 that surround the value. GNAT always chooses the closer one, but this is not
5075 required behavior, and it is better to specify a value that is an exact
5076 multiple, ensuring predictable execution. The default is that such warnings
5080 @emph{Suppress warnings on bad fixed values.}
5081 @cindex @option{-gnatwB} (@command{gcc})
5082 This switch suppresses warnings for static fixed-point expressions whose
5083 value is not an exact multiple of Small.
5086 @emph{Activate warnings on biased representation.}
5087 @cindex @option{-gnatw.b} (@command{gcc})
5088 @cindex Biased representation
5089 This switch activates warnings when a size clause, value size clause, component
5090 clause, or component size clause forces the use of biased representation for an
5091 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
5092 to represent 10/11). The default is that such warnings are generated.
5095 @emph{Suppress warnings on biased representation.}
5096 @cindex @option{-gnatwB} (@command{gcc})
5097 This switch suppresses warnings for representation clauses that force the use
5098 of biased representation.
5101 @emph{Activate warnings on conditionals.}
5102 @cindex @option{-gnatwc} (@command{gcc})
5103 @cindex Conditionals, constant
5104 This switch activates warnings for conditional expressions used in
5105 tests that are known to be True or False at compile time. The default
5106 is that such warnings are not generated.
5107 Note that this warning does
5108 not get issued for the use of boolean variables or constants whose
5109 values are known at compile time, since this is a standard technique
5110 for conditional compilation in Ada, and this would generate too many
5111 false positive warnings.
5113 This warning option also activates a special test for comparisons using
5114 the operators ``>='' and`` <=''.
5115 If the compiler can tell that only the equality condition is possible,
5116 then it will warn that the ``>'' or ``<'' part of the test
5117 is useless and that the operator could be replaced by ``=''.
5118 An example would be comparing a @code{Natural} variable <= 0.
5120 This warning option also generates warnings if
5121 one or both tests is optimized away in a membership test for integer
5122 values if the result can be determined at compile time. Range tests on
5123 enumeration types are not included, since it is common for such tests
5124 to include an end point.
5126 This warning can also be turned on using @option{-gnatwa}.
5129 @emph{Suppress warnings on conditionals.}
5130 @cindex @option{-gnatwC} (@command{gcc})
5131 This switch suppresses warnings for conditional expressions used in
5132 tests that are known to be True or False at compile time.
5135 @emph{Activate warnings on missing component clauses.}
5136 @cindex @option{-gnatw.c} (@command{gcc})
5137 @cindex Component clause, missing
5138 This switch activates warnings for record components where a record
5139 representation clause is present and has component clauses for the
5140 majority, but not all, of the components. A warning is given for each
5141 component for which no component clause is present.
5143 This warning can also be turned on using @option{-gnatwa}.
5146 @emph{Suppress warnings on missing component clauses.}
5147 @cindex @option{-gnatwC} (@command{gcc})
5148 This switch suppresses warnings for record components that are
5149 missing a component clause in the situation described above.
5152 @emph{Activate warnings on implicit dereferencing.}
5153 @cindex @option{-gnatwd} (@command{gcc})
5154 If this switch is set, then the use of a prefix of an access type
5155 in an indexed component, slice, or selected component without an
5156 explicit @code{.all} will generate a warning. With this warning
5157 enabled, access checks occur only at points where an explicit
5158 @code{.all} appears in the source code (assuming no warnings are
5159 generated as a result of this switch). The default is that such
5160 warnings are not generated.
5161 Note that @option{-gnatwa} does not affect the setting of
5162 this warning option.
5165 @emph{Suppress warnings on implicit dereferencing.}
5166 @cindex @option{-gnatwD} (@command{gcc})
5167 @cindex Implicit dereferencing
5168 @cindex Dereferencing, implicit
5169 This switch suppresses warnings for implicit dereferences in
5170 indexed components, slices, and selected components.
5173 @emph{Treat warnings as errors.}
5174 @cindex @option{-gnatwe} (@command{gcc})
5175 @cindex Warnings, treat as error
5176 This switch causes warning messages to be treated as errors.
5177 The warning string still appears, but the warning messages are counted
5178 as errors, and prevent the generation of an object file.
5181 @emph{Activate every optional warning}
5182 @cindex @option{-gnatw.e} (@command{gcc})
5183 @cindex Warnings, activate every optional warning
5184 This switch activates all optional warnings, including those which
5185 are not activated by @code{-gnatwa}.
5188 @emph{Activate warnings on unreferenced formals.}
5189 @cindex @option{-gnatwf} (@command{gcc})
5190 @cindex Formals, unreferenced
5191 This switch causes a warning to be generated if a formal parameter
5192 is not referenced in the body of the subprogram. This warning can
5193 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
5194 default is that these warnings are not generated.
5197 @emph{Suppress warnings on unreferenced formals.}
5198 @cindex @option{-gnatwF} (@command{gcc})
5199 This switch suppresses warnings for unreferenced formal
5200 parameters. Note that the
5201 combination @option{-gnatwu} followed by @option{-gnatwF} has the
5202 effect of warning on unreferenced entities other than subprogram
5206 @emph{Activate warnings on unrecognized pragmas.}
5207 @cindex @option{-gnatwg} (@command{gcc})
5208 @cindex Pragmas, unrecognized
5209 This switch causes a warning to be generated if an unrecognized
5210 pragma is encountered. Apart from issuing this warning, the
5211 pragma is ignored and has no effect. This warning can
5212 also be turned on using @option{-gnatwa}. The default
5213 is that such warnings are issued (satisfying the Ada Reference
5214 Manual requirement that such warnings appear).
5217 @emph{Suppress warnings on unrecognized pragmas.}
5218 @cindex @option{-gnatwG} (@command{gcc})
5219 This switch suppresses warnings for unrecognized pragmas.
5222 @emph{Activate warnings on hiding.}
5223 @cindex @option{-gnatwh} (@command{gcc})
5224 @cindex Hiding of Declarations
5225 This switch activates warnings on hiding declarations.
5226 A declaration is considered hiding
5227 if it is for a non-overloadable entity, and it declares an entity with the
5228 same name as some other entity that is directly or use-visible. The default
5229 is that such warnings are not generated.
5230 Note that @option{-gnatwa} does not affect the setting of this warning option.
5233 @emph{Suppress warnings on hiding.}
5234 @cindex @option{-gnatwH} (@command{gcc})
5235 This switch suppresses warnings on hiding declarations.
5238 @emph{Activate warnings on implementation units.}
5239 @cindex @option{-gnatwi} (@command{gcc})
5240 This switch activates warnings for a @code{with} of an internal GNAT
5241 implementation unit, defined as any unit from the @code{Ada},
5242 @code{Interfaces}, @code{GNAT},
5243 ^^@code{DEC},^ or @code{System}
5244 hierarchies that is not
5245 documented in either the Ada Reference Manual or the GNAT
5246 Programmer's Reference Manual. Such units are intended only
5247 for internal implementation purposes and should not be @code{with}'ed
5248 by user programs. The default is that such warnings are generated
5249 This warning can also be turned on using @option{-gnatwa}.
5252 @emph{Disable warnings on implementation units.}
5253 @cindex @option{-gnatwI} (@command{gcc})
5254 This switch disables warnings for a @code{with} of an internal GNAT
5255 implementation unit.
5258 @emph{Activate warnings on obsolescent features (Annex J).}
5259 @cindex @option{-gnatwj} (@command{gcc})
5260 @cindex Features, obsolescent
5261 @cindex Obsolescent features
5262 If this warning option is activated, then warnings are generated for
5263 calls to subprograms marked with @code{pragma Obsolescent} and
5264 for use of features in Annex J of the Ada Reference Manual. In the
5265 case of Annex J, not all features are flagged. In particular use
5266 of the renamed packages (like @code{Text_IO}) and use of package
5267 @code{ASCII} are not flagged, since these are very common and
5268 would generate many annoying positive warnings. The default is that
5269 such warnings are not generated. This warning is also turned on by
5270 the use of @option{-gnatwa}.
5272 In addition to the above cases, warnings are also generated for
5273 GNAT features that have been provided in past versions but which
5274 have been superseded (typically by features in the new Ada standard).
5275 For example, @code{pragma Ravenscar} will be flagged since its
5276 function is replaced by @code{pragma Profile(Ravenscar)}.
5278 Note that this warning option functions differently from the
5279 restriction @code{No_Obsolescent_Features} in two respects.
5280 First, the restriction applies only to annex J features.
5281 Second, the restriction does flag uses of package @code{ASCII}.
5284 @emph{Suppress warnings on obsolescent features (Annex J).}
5285 @cindex @option{-gnatwJ} (@command{gcc})
5286 This switch disables warnings on use of obsolescent features.
5289 @emph{Activate warnings on variables that could be constants.}
5290 @cindex @option{-gnatwk} (@command{gcc})
5291 This switch activates warnings for variables that are initialized but
5292 never modified, and then could be declared constants. The default is that
5293 such warnings are not given.
5294 This warning can also be turned on using @option{-gnatwa}.
5297 @emph{Suppress warnings on variables that could be constants.}
5298 @cindex @option{-gnatwK} (@command{gcc})
5299 This switch disables warnings on variables that could be declared constants.
5302 @emph{Activate warnings for elaboration pragmas.}
5303 @cindex @option{-gnatwl} (@command{gcc})
5304 @cindex Elaboration, warnings
5305 This switch activates warnings on missing
5306 @code{Elaborate_All} and @code{Elaborate} pragmas.
5307 See the section in this guide on elaboration checking for details on
5308 when such pragmas should be used. In dynamic elaboration mode, this switch
5309 generations warnings about the need to add elaboration pragmas. Note however,
5310 that if you blindly follow these warnings, and add @code{Elaborate_All}
5311 warnings wherever they are recommended, you basically end up with the
5312 equivalent of the static elaboration model, which may not be what you want for
5313 legacy code for which the static model does not work.
5315 For the static model, the messages generated are labeled "info:" (for
5316 information messages). They are not warnings to add elaboration pragmas,
5317 merely informational messages showing what implicit elaboration pragmas
5318 have been added, for use in analyzing elaboration circularity problems.
5320 Warnings are also generated if you
5321 are using the static mode of elaboration, and a @code{pragma Elaborate}
5322 is encountered. The default is that such warnings
5324 This warning is not automatically turned on by the use of @option{-gnatwa}.
5327 @emph{Suppress warnings for elaboration pragmas.}
5328 @cindex @option{-gnatwL} (@command{gcc})
5329 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5330 See the section in this guide on elaboration checking for details on
5331 when such pragmas should be used.
5334 @emph{Activate warnings on modified but unreferenced variables.}
5335 @cindex @option{-gnatwm} (@command{gcc})
5336 This switch activates warnings for variables that are assigned (using
5337 an initialization value or with one or more assignment statements) but
5338 whose value is never read. The warning is suppressed for volatile
5339 variables and also for variables that are renamings of other variables
5340 or for which an address clause is given.
5341 This warning can also be turned on using @option{-gnatwa}.
5342 The default is that these warnings are not given.
5345 @emph{Disable warnings on modified but unreferenced variables.}
5346 @cindex @option{-gnatwM} (@command{gcc})
5347 This switch disables warnings for variables that are assigned or
5348 initialized, but never read.
5351 @emph{Set normal warnings mode.}
5352 @cindex @option{-gnatwn} (@command{gcc})
5353 This switch sets normal warning mode, in which enabled warnings are
5354 issued and treated as warnings rather than errors. This is the default
5355 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5356 an explicit @option{-gnatws} or
5357 @option{-gnatwe}. It also cancels the effect of the
5358 implicit @option{-gnatwe} that is activated by the
5359 use of @option{-gnatg}.
5362 @emph{Activate warnings on address clause overlays.}
5363 @cindex @option{-gnatwo} (@command{gcc})
5364 @cindex Address Clauses, warnings
5365 This switch activates warnings for possibly unintended initialization
5366 effects of defining address clauses that cause one variable to overlap
5367 another. The default is that such warnings are generated.
5368 This warning can also be turned on using @option{-gnatwa}.
5371 @emph{Suppress warnings on address clause overlays.}
5372 @cindex @option{-gnatwO} (@command{gcc})
5373 This switch suppresses warnings on possibly unintended initialization
5374 effects of defining address clauses that cause one variable to overlap
5378 @emph{Activate warnings on modified but unreferenced out parameters.}
5379 @cindex @option{-gnatw.o} (@command{gcc})
5380 This switch activates warnings for variables that are modified by using
5381 them as actuals for a call to a procedure with an out mode formal, where
5382 the resulting assigned value is never read. It is applicable in the case
5383 where there is more than one out mode formal. If there is only one out
5384 mode formal, the warning is issued by default (controlled by -gnatwu).
5385 The warning is suppressed for volatile
5386 variables and also for variables that are renamings of other variables
5387 or for which an address clause is given.
5388 The default is that these warnings are not given. Note that this warning
5389 is not included in -gnatwa, it must be activated explicitly.
5392 @emph{Disable warnings on modified but unreferenced out parameters.}
5393 @cindex @option{-gnatw.O} (@command{gcc})
5394 This switch suppresses warnings for variables that are modified by using
5395 them as actuals for a call to a procedure with an out mode formal, where
5396 the resulting assigned value is never read.
5399 @emph{Activate warnings on ineffective pragma Inlines.}
5400 @cindex @option{-gnatwp} (@command{gcc})
5401 @cindex Inlining, warnings
5402 This switch activates warnings for failure of front end inlining
5403 (activated by @option{-gnatN}) to inline a particular call. There are
5404 many reasons for not being able to inline a call, including most
5405 commonly that the call is too complex to inline. The default is
5406 that such warnings are not given.
5407 This warning can also be turned on using @option{-gnatwa}.
5408 Warnings on ineffective inlining by the gcc back-end can be activated
5409 separately, using the gcc switch -Winline.
5412 @emph{Suppress warnings on ineffective pragma Inlines.}
5413 @cindex @option{-gnatwP} (@command{gcc})
5414 This switch suppresses warnings on ineffective pragma Inlines. If the
5415 inlining mechanism cannot inline a call, it will simply ignore the
5419 @emph{Activate warnings on parameter ordering.}
5420 @cindex @option{-gnatw.p} (@command{gcc})
5421 @cindex Parameter order, warnings
5422 This switch activates warnings for cases of suspicious parameter
5423 ordering when the list of arguments are all simple identifiers that
5424 match the names of the formals, but are in a different order. The
5425 warning is suppressed if any use of named parameter notation is used,
5426 so this is the appropriate way to suppress a false positive (and
5427 serves to emphasize that the "misordering" is deliberate). The
5429 that such warnings are not given.
5430 This warning can also be turned on using @option{-gnatwa}.
5433 @emph{Suppress warnings on parameter ordering.}
5434 @cindex @option{-gnatw.P} (@command{gcc})
5435 This switch suppresses warnings on cases of suspicious parameter
5439 @emph{Activate warnings on questionable missing parentheses.}
5440 @cindex @option{-gnatwq} (@command{gcc})
5441 @cindex Parentheses, warnings
5442 This switch activates warnings for cases where parentheses are not used and
5443 the result is potential ambiguity from a readers point of view. For example
5444 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5445 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5446 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5447 follow the rule of always parenthesizing to make the association clear, and
5448 this warning switch warns if such parentheses are not present. The default
5449 is that these warnings are given.
5450 This warning can also be turned on using @option{-gnatwa}.
5453 @emph{Suppress warnings on questionable missing parentheses.}
5454 @cindex @option{-gnatwQ} (@command{gcc})
5455 This switch suppresses warnings for cases where the association is not
5456 clear and the use of parentheses is preferred.
5459 @emph{Activate warnings on redundant constructs.}
5460 @cindex @option{-gnatwr} (@command{gcc})
5461 This switch activates warnings for redundant constructs. The following
5462 is the current list of constructs regarded as redundant:
5466 Assignment of an item to itself.
5468 Type conversion that converts an expression to its own type.
5470 Use of the attribute @code{Base} where @code{typ'Base} is the same
5473 Use of pragma @code{Pack} when all components are placed by a record
5474 representation clause.
5476 Exception handler containing only a reraise statement (raise with no
5477 operand) which has no effect.
5479 Use of the operator abs on an operand that is known at compile time
5482 Comparison of boolean expressions to an explicit True value.
5485 This warning can also be turned on using @option{-gnatwa}.
5486 The default is that warnings for redundant constructs are not given.
5489 @emph{Suppress warnings on redundant constructs.}
5490 @cindex @option{-gnatwR} (@command{gcc})
5491 This switch suppresses warnings for redundant constructs.
5494 @emph{Activate warnings for object renaming function.}
5495 @cindex @option{-gnatw.r} (@command{gcc})
5496 This switch activates warnings for an object renaming that renames a
5497 function call, which is equivalent to a constant declaration (as
5498 opposed to renaming the function itself). The default is that these
5499 warnings are given. This warning can also be turned on using
5503 @emph{Suppress warnings for object renaming function.}
5504 @cindex @option{-gnatwT} (@command{gcc})
5505 This switch suppresses warnings for object renaming function.
5508 @emph{Suppress all warnings.}
5509 @cindex @option{-gnatws} (@command{gcc})
5510 This switch completely suppresses the
5511 output of all warning messages from the GNAT front end.
5512 Note that it does not suppress warnings from the @command{gcc} back end.
5513 To suppress these back end warnings as well, use the switch @option{-w}
5514 in addition to @option{-gnatws}.
5517 @emph{Activate warnings for tracking of deleted conditional code.}
5518 @cindex @option{-gnatwt} (@command{gcc})
5519 @cindex Deactivated code, warnings
5520 @cindex Deleted code, warnings
5521 This switch activates warnings for tracking of code in conditionals (IF and
5522 CASE statements) that is detected to be dead code which cannot be executed, and
5523 which is removed by the front end. This warning is off by default, and is not
5524 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5525 useful for detecting deactivated code in certified applications.
5528 @emph{Suppress warnings for tracking of deleted conditional code.}
5529 @cindex @option{-gnatwT} (@command{gcc})
5530 This switch suppresses warnings for tracking of deleted conditional code.
5533 @emph{Activate warnings on unused entities.}
5534 @cindex @option{-gnatwu} (@command{gcc})
5535 This switch activates warnings to be generated for entities that
5536 are declared but not referenced, and for units that are @code{with}'ed
5538 referenced. In the case of packages, a warning is also generated if
5539 no entities in the package are referenced. This means that if the package
5540 is referenced but the only references are in @code{use}
5541 clauses or @code{renames}
5542 declarations, a warning is still generated. A warning is also generated
5543 for a generic package that is @code{with}'ed but never instantiated.
5544 In the case where a package or subprogram body is compiled, and there
5545 is a @code{with} on the corresponding spec
5546 that is only referenced in the body,
5547 a warning is also generated, noting that the
5548 @code{with} can be moved to the body. The default is that
5549 such warnings are not generated.
5550 This switch also activates warnings on unreferenced formals
5551 (it includes the effect of @option{-gnatwf}).
5552 This warning can also be turned on using @option{-gnatwa}.
5555 @emph{Suppress warnings on unused entities.}
5556 @cindex @option{-gnatwU} (@command{gcc})
5557 This switch suppresses warnings for unused entities and packages.
5558 It also turns off warnings on unreferenced formals (and thus includes
5559 the effect of @option{-gnatwF}).
5562 @emph{Activate warnings on unassigned variables.}
5563 @cindex @option{-gnatwv} (@command{gcc})
5564 @cindex Unassigned variable warnings
5565 This switch activates warnings for access to variables which
5566 may not be properly initialized. The default is that
5567 such warnings are generated.
5568 This warning can also be turned on using @option{-gnatwa}.
5571 @emph{Suppress warnings on unassigned variables.}
5572 @cindex @option{-gnatwV} (@command{gcc})
5573 This switch suppresses warnings for access to variables which
5574 may not be properly initialized.
5575 For variables of a composite type, the warning can also be suppressed in
5576 Ada 2005 by using a default initialization with a box. For example, if
5577 Table is an array of records whose components are only partially uninitialized,
5578 then the following code:
5580 @smallexample @c ada
5581 Tab : Table := (others => <>);
5584 will suppress warnings on subsequent statements that access components
5588 @emph{Activate warnings on wrong low bound assumption.}
5589 @cindex @option{-gnatww} (@command{gcc})
5590 @cindex String indexing warnings
5591 This switch activates warnings for indexing an unconstrained string parameter
5592 with a literal or S'Length. This is a case where the code is assuming that the
5593 low bound is one, which is in general not true (for example when a slice is
5594 passed). The default is that such warnings are generated.
5595 This warning can also be turned on using @option{-gnatwa}.
5598 @emph{Suppress warnings on wrong low bound assumption.}
5599 @cindex @option{-gnatwW} (@command{gcc})
5600 This switch suppresses warnings for indexing an unconstrained string parameter
5601 with a literal or S'Length. Note that this warning can also be suppressed
5602 in a particular case by adding an
5603 assertion that the lower bound is 1,
5604 as shown in the following example.
5606 @smallexample @c ada
5607 procedure K (S : String) is
5608 pragma Assert (S'First = 1);
5613 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5614 @cindex @option{-gnatw.w} (@command{gcc})
5615 @cindex Warnings Off control
5616 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5617 where either the pragma is entirely useless (because it suppresses no
5618 warnings), or it could be replaced by @code{pragma Unreferenced} or
5619 @code{pragma Unmodified}.The default is that these warnings are not given.
5620 Note that this warning is not included in -gnatwa, it must be
5621 activated explicitly.
5624 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5625 @cindex @option{-gnatw.W} (@command{gcc})
5626 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5629 @emph{Activate warnings on Export/Import pragmas.}
5630 @cindex @option{-gnatwx} (@command{gcc})
5631 @cindex Export/Import pragma warnings
5632 This switch activates warnings on Export/Import pragmas when
5633 the compiler detects a possible conflict between the Ada and
5634 foreign language calling sequences. For example, the use of
5635 default parameters in a convention C procedure is dubious
5636 because the C compiler cannot supply the proper default, so
5637 a warning is issued. The default is that such warnings are
5639 This warning can also be turned on using @option{-gnatwa}.
5642 @emph{Suppress warnings on Export/Import pragmas.}
5643 @cindex @option{-gnatwX} (@command{gcc})
5644 This switch suppresses warnings on Export/Import pragmas.
5645 The sense of this is that you are telling the compiler that
5646 you know what you are doing in writing the pragma, and it
5647 should not complain at you.
5650 @emph{Activate warnings for No_Exception_Propagation mode.}
5651 @cindex @option{-gnatwm} (@command{gcc})
5652 This switch activates warnings for exception usage when pragma Restrictions
5653 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5654 explicit exception raises which are not covered by a local handler, and for
5655 exception handlers which do not cover a local raise. The default is that these
5656 warnings are not given.
5659 @emph{Disable warnings for No_Exception_Propagation mode.}
5660 This switch disables warnings for exception usage when pragma Restrictions
5661 (No_Exception_Propagation) is in effect.
5664 @emph{Activate warnings for Ada 2005 compatibility issues.}
5665 @cindex @option{-gnatwy} (@command{gcc})
5666 @cindex Ada 2005 compatibility issues warnings
5667 For the most part Ada 2005 is upwards compatible with Ada 95,
5668 but there are some exceptions (for example the fact that
5669 @code{interface} is now a reserved word in Ada 2005). This
5670 switch activates several warnings to help in identifying
5671 and correcting such incompatibilities. The default is that
5672 these warnings are generated. Note that at one point Ada 2005
5673 was called Ada 0Y, hence the choice of character.
5674 This warning can also be turned on using @option{-gnatwa}.
5677 @emph{Disable warnings for Ada 2005 compatibility issues.}
5678 @cindex @option{-gnatwY} (@command{gcc})
5679 @cindex Ada 2005 compatibility issues warnings
5680 This switch suppresses several warnings intended to help in identifying
5681 incompatibilities between Ada 95 and Ada 2005.
5684 @emph{Activate warnings on unchecked conversions.}
5685 @cindex @option{-gnatwz} (@command{gcc})
5686 @cindex Unchecked_Conversion warnings
5687 This switch activates warnings for unchecked conversions
5688 where the types are known at compile time to have different
5690 is that such warnings are generated. Warnings are also
5691 generated for subprogram pointers with different conventions,
5692 and, on VMS only, for data pointers with different conventions.
5693 This warning can also be turned on using @option{-gnatwa}.
5696 @emph{Suppress warnings on unchecked conversions.}
5697 @cindex @option{-gnatwZ} (@command{gcc})
5698 This switch suppresses warnings for unchecked conversions
5699 where the types are known at compile time to have different
5700 sizes or conventions.
5702 @item ^-Wunused^WARNINGS=UNUSED^
5703 @cindex @option{-Wunused}
5704 The warnings controlled by the @option{-gnatw} switch are generated by
5705 the front end of the compiler. The @option{GCC} back end can provide
5706 additional warnings and they are controlled by the @option{-W} switch.
5707 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5708 warnings for entities that are declared but not referenced.
5710 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5711 @cindex @option{-Wuninitialized}
5712 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5713 the back end warning for uninitialized variables. This switch must be
5714 used in conjunction with an optimization level greater than zero.
5716 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5717 @cindex @option{-Wall}
5718 This switch enables all the above warnings from the @option{GCC} back end.
5719 The code generator detects a number of warning situations that are missed
5720 by the @option{GNAT} front end, and this switch can be used to activate them.
5721 The use of this switch also sets the default front end warning mode to
5722 @option{-gnatwa}, that is, most front end warnings activated as well.
5724 @item ^-w^/NO_BACK_END_WARNINGS^
5726 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5727 The use of this switch also sets the default front end warning mode to
5728 @option{-gnatws}, that is, front end warnings suppressed as well.
5734 A string of warning parameters can be used in the same parameter. For example:
5741 will turn on all optional warnings except for elaboration pragma warnings,
5742 and also specify that warnings should be treated as errors.
5744 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5769 @node Debugging and Assertion Control
5770 @subsection Debugging and Assertion Control
5774 @cindex @option{-gnata} (@command{gcc})
5780 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5781 are ignored. This switch, where @samp{a} stands for assert, causes
5782 @code{Assert} and @code{Debug} pragmas to be activated.
5784 The pragmas have the form:
5788 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5789 @var{static-string-expression}@r{]})
5790 @b{pragma} Debug (@var{procedure call})
5795 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5796 If the result is @code{True}, the pragma has no effect (other than
5797 possible side effects from evaluating the expression). If the result is
5798 @code{False}, the exception @code{Assert_Failure} declared in the package
5799 @code{System.Assertions} is
5800 raised (passing @var{static-string-expression}, if present, as the
5801 message associated with the exception). If no string expression is
5802 given the default is a string giving the file name and line number
5805 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5806 @code{pragma Debug} may appear within a declaration sequence, allowing
5807 debugging procedures to be called between declarations.
5810 @item /DEBUG@r{[}=debug-level@r{]}
5812 Specifies how much debugging information is to be included in
5813 the resulting object file where 'debug-level' is one of the following:
5816 Include both debugger symbol records and traceback
5818 This is the default setting.
5820 Include both debugger symbol records and traceback in
5823 Excludes both debugger symbol records and traceback
5824 the object file. Same as /NODEBUG.
5826 Includes only debugger symbol records in the object
5827 file. Note that this doesn't include traceback information.
5832 @node Validity Checking
5833 @subsection Validity Checking
5834 @findex Validity Checking
5837 The Ada Reference Manual has specific requirements for checking
5838 for invalid values. In particular, RM 13.9.1 requires that the
5839 evaluation of invalid values (for example from unchecked conversions),
5840 not result in erroneous execution. In GNAT, the result of such an
5841 evaluation in normal default mode is to either use the value
5842 unmodified, or to raise Constraint_Error in those cases where use
5843 of the unmodified value would cause erroneous execution. The cases
5844 where unmodified values might lead to erroneous execution are case
5845 statements (where a wild jump might result from an invalid value),
5846 and subscripts on the left hand side (where memory corruption could
5847 occur as a result of an invalid value).
5849 The @option{-gnatB} switch tells the compiler to assume that all
5850 values are valid (that is, within their declared subtype range)
5851 except in the context of a use of the Valid attribute. This means
5852 the compiler can generate more efficient code, since the range
5853 of values is better known at compile time.
5855 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5858 The @code{x} argument is a string of letters that
5859 indicate validity checks that are performed or not performed in addition
5860 to the default checks described above.
5863 The options allowed for this qualifier
5864 indicate validity checks that are performed or not performed in addition
5865 to the default checks described above.
5871 @emph{All validity checks.}
5872 @cindex @option{-gnatVa} (@command{gcc})
5873 All validity checks are turned on.
5875 That is, @option{-gnatVa} is
5876 equivalent to @option{gnatVcdfimorst}.
5880 @emph{Validity checks for copies.}
5881 @cindex @option{-gnatVc} (@command{gcc})
5882 The right hand side of assignments, and the initializing values of
5883 object declarations are validity checked.
5886 @emph{Default (RM) validity checks.}
5887 @cindex @option{-gnatVd} (@command{gcc})
5888 Some validity checks are done by default following normal Ada semantics
5890 A check is done in case statements that the expression is within the range
5891 of the subtype. If it is not, Constraint_Error is raised.
5892 For assignments to array components, a check is done that the expression used
5893 as index is within the range. If it is not, Constraint_Error is raised.
5894 Both these validity checks may be turned off using switch @option{-gnatVD}.
5895 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5896 switch @option{-gnatVd} will leave the checks turned on.
5897 Switch @option{-gnatVD} should be used only if you are sure that all such
5898 expressions have valid values. If you use this switch and invalid values
5899 are present, then the program is erroneous, and wild jumps or memory
5900 overwriting may occur.
5903 @emph{Validity checks for elementary components.}
5904 @cindex @option{-gnatVe} (@command{gcc})
5905 In the absence of this switch, assignments to record or array components are
5906 not validity checked, even if validity checks for assignments generally
5907 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5908 require valid data, but assignment of individual components does. So for
5909 example, there is a difference between copying the elements of an array with a
5910 slice assignment, compared to assigning element by element in a loop. This
5911 switch allows you to turn off validity checking for components, even when they
5912 are assigned component by component.
5915 @emph{Validity checks for floating-point values.}
5916 @cindex @option{-gnatVf} (@command{gcc})
5917 In the absence of this switch, validity checking occurs only for discrete
5918 values. If @option{-gnatVf} is specified, then validity checking also applies
5919 for floating-point values, and NaNs and infinities are considered invalid,
5920 as well as out of range values for constrained types. Note that this means
5921 that standard IEEE infinity mode is not allowed. The exact contexts
5922 in which floating-point values are checked depends on the setting of other
5923 options. For example,
5924 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5925 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5926 (the order does not matter) specifies that floating-point parameters of mode
5927 @code{in} should be validity checked.
5930 @emph{Validity checks for @code{in} mode parameters}
5931 @cindex @option{-gnatVi} (@command{gcc})
5932 Arguments for parameters of mode @code{in} are validity checked in function
5933 and procedure calls at the point of call.
5936 @emph{Validity checks for @code{in out} mode parameters.}
5937 @cindex @option{-gnatVm} (@command{gcc})
5938 Arguments for parameters of mode @code{in out} are validity checked in
5939 procedure calls at the point of call. The @code{'m'} here stands for
5940 modify, since this concerns parameters that can be modified by the call.
5941 Note that there is no specific option to test @code{out} parameters,
5942 but any reference within the subprogram will be tested in the usual
5943 manner, and if an invalid value is copied back, any reference to it
5944 will be subject to validity checking.
5947 @emph{No validity checks.}
5948 @cindex @option{-gnatVn} (@command{gcc})
5949 This switch turns off all validity checking, including the default checking
5950 for case statements and left hand side subscripts. Note that the use of
5951 the switch @option{-gnatp} suppresses all run-time checks, including
5952 validity checks, and thus implies @option{-gnatVn}. When this switch
5953 is used, it cancels any other @option{-gnatV} previously issued.
5956 @emph{Validity checks for operator and attribute operands.}
5957 @cindex @option{-gnatVo} (@command{gcc})
5958 Arguments for predefined operators and attributes are validity checked.
5959 This includes all operators in package @code{Standard},
5960 the shift operators defined as intrinsic in package @code{Interfaces}
5961 and operands for attributes such as @code{Pos}. Checks are also made
5962 on individual component values for composite comparisons, and on the
5963 expressions in type conversions and qualified expressions. Checks are
5964 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
5967 @emph{Validity checks for parameters.}
5968 @cindex @option{-gnatVp} (@command{gcc})
5969 This controls the treatment of parameters within a subprogram (as opposed
5970 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5971 of parameters on a call. If either of these call options is used, then
5972 normally an assumption is made within a subprogram that the input arguments
5973 have been validity checking at the point of call, and do not need checking
5974 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5975 is not made, and parameters are not assumed to be valid, so their validity
5976 will be checked (or rechecked) within the subprogram.
5979 @emph{Validity checks for function returns.}
5980 @cindex @option{-gnatVr} (@command{gcc})
5981 The expression in @code{return} statements in functions is validity
5985 @emph{Validity checks for subscripts.}
5986 @cindex @option{-gnatVs} (@command{gcc})
5987 All subscripts expressions are checked for validity, whether they appear
5988 on the right side or left side (in default mode only left side subscripts
5989 are validity checked).
5992 @emph{Validity checks for tests.}
5993 @cindex @option{-gnatVt} (@command{gcc})
5994 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
5995 statements are checked, as well as guard expressions in entry calls.
6000 The @option{-gnatV} switch may be followed by
6001 ^a string of letters^a list of options^
6002 to turn on a series of validity checking options.
6004 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
6005 specifies that in addition to the default validity checking, copies and
6006 function return expressions are to be validity checked.
6007 In order to make it easier
6008 to specify the desired combination of effects,
6010 the upper case letters @code{CDFIMORST} may
6011 be used to turn off the corresponding lower case option.
6014 the prefix @code{NO} on an option turns off the corresponding validity
6017 @item @code{NOCOPIES}
6018 @item @code{NODEFAULT}
6019 @item @code{NOFLOATS}
6020 @item @code{NOIN_PARAMS}
6021 @item @code{NOMOD_PARAMS}
6022 @item @code{NOOPERANDS}
6023 @item @code{NORETURNS}
6024 @item @code{NOSUBSCRIPTS}
6025 @item @code{NOTESTS}
6029 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
6030 turns on all validity checking options except for
6031 checking of @code{@b{in out}} procedure arguments.
6033 The specification of additional validity checking generates extra code (and
6034 in the case of @option{-gnatVa} the code expansion can be substantial).
6035 However, these additional checks can be very useful in detecting
6036 uninitialized variables, incorrect use of unchecked conversion, and other
6037 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
6038 is useful in conjunction with the extra validity checking, since this
6039 ensures that wherever possible uninitialized variables have invalid values.
6041 See also the pragma @code{Validity_Checks} which allows modification of
6042 the validity checking mode at the program source level, and also allows for
6043 temporary disabling of validity checks.
6045 @node Style Checking
6046 @subsection Style Checking
6047 @findex Style checking
6050 The @option{-gnaty^x^(option,option,@dots{})^} switch
6051 @cindex @option{-gnaty} (@command{gcc})
6052 causes the compiler to
6053 enforce specified style rules. A limited set of style rules has been used
6054 in writing the GNAT sources themselves. This switch allows user programs
6055 to activate all or some of these checks. If the source program fails a
6056 specified style check, an appropriate warning message is given, preceded by
6057 the character sequence ``(style)''.
6059 @code{(option,option,@dots{})} is a sequence of keywords
6062 The string @var{x} is a sequence of letters or digits
6064 indicating the particular style
6065 checks to be performed. The following checks are defined:
6070 @emph{Specify indentation level.}
6071 If a digit from 1-9 appears
6072 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
6073 then proper indentation is checked, with the digit indicating the
6074 indentation level required. A value of zero turns off this style check.
6075 The general style of required indentation is as specified by
6076 the examples in the Ada Reference Manual. Full line comments must be
6077 aligned with the @code{--} starting on a column that is a multiple of
6078 the alignment level, or they may be aligned the same way as the following
6079 non-blank line (this is useful when full line comments appear in the middle
6083 @emph{Check attribute casing.}
6084 Attribute names, including the case of keywords such as @code{digits}
6085 used as attributes names, must be written in mixed case, that is, the
6086 initial letter and any letter following an underscore must be uppercase.
6087 All other letters must be lowercase.
6089 @item ^A^ARRAY_INDEXES^
6090 @emph{Use of array index numbers in array attributes.}
6091 When using the array attributes First, Last, Range,
6092 or Length, the index number must be omitted for one-dimensional arrays
6093 and is required for multi-dimensional arrays.
6096 @emph{Blanks not allowed at statement end.}
6097 Trailing blanks are not allowed at the end of statements. The purpose of this
6098 rule, together with h (no horizontal tabs), is to enforce a canonical format
6099 for the use of blanks to separate source tokens.
6102 @emph{Check comments.}
6103 Comments must meet the following set of rules:
6108 The ``@code{--}'' that starts the column must either start in column one,
6109 or else at least one blank must precede this sequence.
6112 Comments that follow other tokens on a line must have at least one blank
6113 following the ``@code{--}'' at the start of the comment.
6116 Full line comments must have two blanks following the ``@code{--}'' that
6117 starts the comment, with the following exceptions.
6120 A line consisting only of the ``@code{--}'' characters, possibly preceded
6121 by blanks is permitted.
6124 A comment starting with ``@code{--x}'' where @code{x} is a special character
6126 This allows proper processing of the output generated by specialized tools
6127 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
6129 language (where ``@code{--#}'' is used). For the purposes of this rule, a
6130 special character is defined as being in one of the ASCII ranges
6131 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
6132 Note that this usage is not permitted
6133 in GNAT implementation units (i.e., when @option{-gnatg} is used).
6136 A line consisting entirely of minus signs, possibly preceded by blanks, is
6137 permitted. This allows the construction of box comments where lines of minus
6138 signs are used to form the top and bottom of the box.
6141 A comment that starts and ends with ``@code{--}'' is permitted as long as at
6142 least one blank follows the initial ``@code{--}''. Together with the preceding
6143 rule, this allows the construction of box comments, as shown in the following
6146 ---------------------------
6147 -- This is a box comment --
6148 -- with two text lines. --
6149 ---------------------------
6153 @item ^d^DOS_LINE_ENDINGS^
6154 @emph{Check no DOS line terminators present.}
6155 All lines must be terminated by a single ASCII.LF
6156 character (in particular the DOS line terminator sequence CR/LF is not
6160 @emph{Check end/exit labels.}
6161 Optional labels on @code{end} statements ending subprograms and on
6162 @code{exit} statements exiting named loops, are required to be present.
6165 @emph{No form feeds or vertical tabs.}
6166 Neither form feeds nor vertical tab characters are permitted
6170 @emph{GNAT style mode}
6171 The set of style check switches is set to match that used by the GNAT sources.
6172 This may be useful when developing code that is eventually intended to be
6173 incorporated into GNAT. For further details, see GNAT sources.
6176 @emph{No horizontal tabs.}
6177 Horizontal tab characters are not permitted in the source text.
6178 Together with the b (no blanks at end of line) check, this
6179 enforces a canonical form for the use of blanks to separate
6183 @emph{Check if-then layout.}
6184 The keyword @code{then} must appear either on the same
6185 line as corresponding @code{if}, or on a line on its own, lined
6186 up under the @code{if} with at least one non-blank line in between
6187 containing all or part of the condition to be tested.
6190 @emph{check mode IN keywords}
6191 Mode @code{in} (the default mode) is not
6192 allowed to be given explicitly. @code{in out} is fine,
6193 but not @code{in} on its own.
6196 @emph{Check keyword casing.}
6197 All keywords must be in lower case (with the exception of keywords
6198 such as @code{digits} used as attribute names to which this check
6202 @emph{Check layout.}
6203 Layout of statement and declaration constructs must follow the
6204 recommendations in the Ada Reference Manual, as indicated by the
6205 form of the syntax rules. For example an @code{else} keyword must
6206 be lined up with the corresponding @code{if} keyword.
6208 There are two respects in which the style rule enforced by this check
6209 option are more liberal than those in the Ada Reference Manual. First
6210 in the case of record declarations, it is permissible to put the
6211 @code{record} keyword on the same line as the @code{type} keyword, and
6212 then the @code{end} in @code{end record} must line up under @code{type}.
6213 This is also permitted when the type declaration is split on two lines.
6214 For example, any of the following three layouts is acceptable:
6216 @smallexample @c ada
6239 Second, in the case of a block statement, a permitted alternative
6240 is to put the block label on the same line as the @code{declare} or
6241 @code{begin} keyword, and then line the @code{end} keyword up under
6242 the block label. For example both the following are permitted:
6244 @smallexample @c ada
6262 The same alternative format is allowed for loops. For example, both of
6263 the following are permitted:
6265 @smallexample @c ada
6267 Clear : while J < 10 loop
6278 @item ^Lnnn^MAX_NESTING=nnn^
6279 @emph{Set maximum nesting level}
6280 The maximum level of nesting of constructs (including subprograms, loops,
6281 blocks, packages, and conditionals) may not exceed the given value
6282 @option{nnn}. A value of zero disconnects this style check.
6284 @item ^m^LINE_LENGTH^
6285 @emph{Check maximum line length.}
6286 The length of source lines must not exceed 79 characters, including
6287 any trailing blanks. The value of 79 allows convenient display on an
6288 80 character wide device or window, allowing for possible special
6289 treatment of 80 character lines. Note that this count is of
6290 characters in the source text. This means that a tab character counts
6291 as one character in this count but a wide character sequence counts as
6292 a single character (however many bytes are needed in the encoding).
6294 @item ^Mnnn^MAX_LENGTH=nnn^
6295 @emph{Set maximum line length.}
6296 The length of lines must not exceed the
6297 given value @option{nnn}. The maximum value that can be specified is 32767.
6299 @item ^n^STANDARD_CASING^
6300 @emph{Check casing of entities in Standard.}
6301 Any identifier from Standard must be cased
6302 to match the presentation in the Ada Reference Manual (for example,
6303 @code{Integer} and @code{ASCII.NUL}).
6306 @emph{Turn off all style checks}
6307 All style check options are turned off.
6309 @item ^o^ORDERED_SUBPROGRAMS^
6310 @emph{Check order of subprogram bodies.}
6311 All subprogram bodies in a given scope
6312 (e.g.@: a package body) must be in alphabetical order. The ordering
6313 rule uses normal Ada rules for comparing strings, ignoring casing
6314 of letters, except that if there is a trailing numeric suffix, then
6315 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6318 @item ^O^OVERRIDING_INDICATORS^
6319 @emph{Check that overriding subprograms are explicitly marked as such.}
6320 The declaration of a primitive operation of a type extension that overrides
6321 an inherited operation must carry an overriding indicator.
6324 @emph{Check pragma casing.}
6325 Pragma names must be written in mixed case, that is, the
6326 initial letter and any letter following an underscore must be uppercase.
6327 All other letters must be lowercase.
6329 @item ^r^REFERENCES^
6330 @emph{Check references.}
6331 All identifier references must be cased in the same way as the
6332 corresponding declaration. No specific casing style is imposed on
6333 identifiers. The only requirement is for consistency of references
6336 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6337 @emph{Check no statements after THEN/ELSE.}
6338 No statements are allowed
6339 on the same line as a THEN or ELSE keyword following the
6340 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6341 and a special exception allows a pragma to appear after ELSE.
6344 @emph{Check separate specs.}
6345 Separate declarations (``specs'') are required for subprograms (a
6346 body is not allowed to serve as its own declaration). The only
6347 exception is that parameterless library level procedures are
6348 not required to have a separate declaration. This exception covers
6349 the most frequent form of main program procedures.
6352 @emph{Check token spacing.}
6353 The following token spacing rules are enforced:
6358 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6361 The token @code{=>} must be surrounded by spaces.
6364 The token @code{<>} must be preceded by a space or a left parenthesis.
6367 Binary operators other than @code{**} must be surrounded by spaces.
6368 There is no restriction on the layout of the @code{**} binary operator.
6371 Colon must be surrounded by spaces.
6374 Colon-equal (assignment, initialization) must be surrounded by spaces.
6377 Comma must be the first non-blank character on the line, or be
6378 immediately preceded by a non-blank character, and must be followed
6382 If the token preceding a left parenthesis ends with a letter or digit, then
6383 a space must separate the two tokens.
6386 A right parenthesis must either be the first non-blank character on
6387 a line, or it must be preceded by a non-blank character.
6390 A semicolon must not be preceded by a space, and must not be followed by
6391 a non-blank character.
6394 A unary plus or minus may not be followed by a space.
6397 A vertical bar must be surrounded by spaces.
6400 @item ^u^UNNECESSARY_BLANK_LINES^
6401 @emph{Check unnecessary blank lines.}
6402 Unnecessary blank lines are not allowed. A blank line is considered
6403 unnecessary if it appears at the end of the file, or if more than
6404 one blank line occurs in sequence.
6406 @item ^x^XTRA_PARENS^
6407 @emph{Check extra parentheses.}
6408 Unnecessary extra level of parentheses (C-style) are not allowed
6409 around conditions in @code{if} statements, @code{while} statements and
6410 @code{exit} statements.
6412 @item ^y^ALL_BUILTIN^
6413 @emph{Set all standard style check options}
6414 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6415 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6416 @option{-gnatyS}, @option{-gnatyLnnn},
6417 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6421 @emph{Remove style check options}
6422 This causes any subsequent options in the string to act as canceling the
6423 corresponding style check option. To cancel maximum nesting level control,
6424 use @option{L} parameter witout any integer value after that, because any
6425 digit following @option{-} in the parameter string of the @option{-gnaty}
6426 option will be threated as canceling indentation check. The same is true
6427 for @option{M} parameter. @option{y} and @option{N} parameters are not
6428 allowed after @option{-}.
6431 This causes any subsequent options in the string to enable the corresponding
6432 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6438 @emph{Removing style check options}
6439 If the name of a style check is preceded by @option{NO} then the corresponding
6440 style check is turned off. For example @option{NOCOMMENTS} turns off style
6441 checking for comments.
6446 In the above rules, appearing in column one is always permitted, that is,
6447 counts as meeting either a requirement for a required preceding space,
6448 or as meeting a requirement for no preceding space.
6450 Appearing at the end of a line is also always permitted, that is, counts
6451 as meeting either a requirement for a following space, or as meeting
6452 a requirement for no following space.
6455 If any of these style rules is violated, a message is generated giving
6456 details on the violation. The initial characters of such messages are
6457 always ``@code{(style)}''. Note that these messages are treated as warning
6458 messages, so they normally do not prevent the generation of an object
6459 file. The @option{-gnatwe} switch can be used to treat warning messages,
6460 including style messages, as fatal errors.
6464 @option{-gnaty} on its own (that is not
6465 followed by any letters or digits), then the effect is equivalent
6466 to the use of @option{-gnatyy}, as described above, that is all
6467 built-in standard style check options are enabled.
6471 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6472 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6473 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6485 clears any previously set style checks.
6487 @node Run-Time Checks
6488 @subsection Run-Time Checks
6489 @cindex Division by zero
6490 @cindex Access before elaboration
6491 @cindex Checks, division by zero
6492 @cindex Checks, access before elaboration
6493 @cindex Checks, stack overflow checking
6496 By default, the following checks are suppressed: integer overflow
6497 checks, stack overflow checks, and checks for access before
6498 elaboration on subprogram calls. All other checks, including range
6499 checks and array bounds checks, are turned on by default. The
6500 following @command{gcc} switches refine this default behavior.
6505 @cindex @option{-gnatp} (@command{gcc})
6506 @cindex Suppressing checks
6507 @cindex Checks, suppressing
6509 Suppress all run-time checks as though @code{pragma Suppress (All_checks)}
6510 had been present in the source. Validity checks are also suppressed (in
6511 other words @option{-gnatp} also implies @option{-gnatVn}.
6512 Use this switch to improve the performance
6513 of the code at the expense of safety in the presence of invalid data or
6516 Note that when checks are suppressed, the compiler is allowed, but not
6517 required, to omit the checking code. If the run-time cost of the
6518 checking code is zero or near-zero, the compiler will generate it even
6519 if checks are suppressed. In particular, if the compiler can prove
6520 that a certain check will necessarily fail, it will generate code to
6521 do an unconditional ``raise'', even if checks are suppressed. The
6522 compiler warns in this case.
6524 Of course, run-time checks are omitted whenever the compiler can prove
6525 that they will not fail, whether or not checks are suppressed.
6527 Note that if you suppress a check that would have failed, program
6528 execution is erroneous, which means the behavior is totally
6529 unpredictable. The program might crash, or print wrong answers, or
6530 do anything else. It might even do exactly what you wanted it to do
6531 (and then it might start failing mysteriously next week or next
6532 year). The compiler will generate code based on the assumption that
6533 the condition being checked is true, which can result in disaster if
6534 that assumption is wrong.
6537 @cindex @option{-gnato} (@command{gcc})
6538 @cindex Overflow checks
6539 @cindex Check, overflow
6540 Enables overflow checking for integer operations.
6541 This causes GNAT to generate slower and larger executable
6542 programs by adding code to check for overflow (resulting in raising
6543 @code{Constraint_Error} as required by standard Ada
6544 semantics). These overflow checks correspond to situations in which
6545 the true value of the result of an operation may be outside the base
6546 range of the result type. The following example shows the distinction:
6548 @smallexample @c ada
6549 X1 : Integer := "Integer'Last";
6550 X2 : Integer range 1 .. 5 := "5";
6551 X3 : Integer := "Integer'Last";
6552 X4 : Integer range 1 .. 5 := "5";
6553 F : Float := "2.0E+20";
6562 Note that if explicit values are assigned at compile time, the
6563 compiler may be able to detect overflow at compile time, in which case
6564 no actual run-time checking code is required, and Constraint_Error
6565 will be raised unconditionally, with or without
6566 @option{-gnato}. That's why the assigned values in the above fragment
6567 are in quotes, the meaning is "assign a value not known to the
6568 compiler that happens to be equal to ...". The remaining discussion
6569 assumes that the compiler cannot detect the values at compile time.
6571 Here the first addition results in a value that is outside the base range
6572 of Integer, and hence requires an overflow check for detection of the
6573 constraint error. Thus the first assignment to @code{X1} raises a
6574 @code{Constraint_Error} exception only if @option{-gnato} is set.
6576 The second increment operation results in a violation of the explicit
6577 range constraint; such range checks are performed by default, and are
6578 unaffected by @option{-gnato}.
6580 The two conversions of @code{F} both result in values that are outside
6581 the base range of type @code{Integer} and thus will raise
6582 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6583 The fact that the result of the second conversion is assigned to
6584 variable @code{X4} with a restricted range is irrelevant, since the problem
6585 is in the conversion, not the assignment.
6587 Basically the rule is that in the default mode (@option{-gnato} not
6588 used), the generated code assures that all integer variables stay
6589 within their declared ranges, or within the base range if there is
6590 no declared range. This prevents any serious problems like indexes
6591 out of range for array operations.
6593 What is not checked in default mode is an overflow that results in
6594 an in-range, but incorrect value. In the above example, the assignments
6595 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6596 range of the target variable, but the result is wrong in the sense that
6597 it is too large to be represented correctly. Typically the assignment
6598 to @code{X1} will result in wrap around to the largest negative number.
6599 The conversions of @code{F} will result in some @code{Integer} value
6600 and if that integer value is out of the @code{X4} range then the
6601 subsequent assignment would generate an exception.
6603 @findex Machine_Overflows
6604 Note that the @option{-gnato} switch does not affect the code generated
6605 for any floating-point operations; it applies only to integer
6607 For floating-point, GNAT has the @code{Machine_Overflows}
6608 attribute set to @code{False} and the normal mode of operation is to
6609 generate IEEE NaN and infinite values on overflow or invalid operations
6610 (such as dividing 0.0 by 0.0).
6612 The reason that we distinguish overflow checking from other kinds of
6613 range constraint checking is that a failure of an overflow check, unlike
6614 for example the failure of a range check, can result in an incorrect
6615 value, but cannot cause random memory destruction (like an out of range
6616 subscript), or a wild jump (from an out of range case value). Overflow
6617 checking is also quite expensive in time and space, since in general it
6618 requires the use of double length arithmetic.
6620 Note again that @option{-gnato} is off by default, so overflow checking is
6621 not performed in default mode. This means that out of the box, with the
6622 default settings, GNAT does not do all the checks expected from the
6623 language description in the Ada Reference Manual. If you want all constraint
6624 checks to be performed, as described in this Manual, then you must
6625 explicitly use the -gnato switch either on the @command{gnatmake} or
6626 @command{gcc} command.
6629 @cindex @option{-gnatE} (@command{gcc})
6630 @cindex Elaboration checks
6631 @cindex Check, elaboration
6632 Enables dynamic checks for access-before-elaboration
6633 on subprogram calls and generic instantiations.
6634 Note that @option{-gnatE} is not necessary for safety, because in the
6635 default mode, GNAT ensures statically that the checks would not fail.
6636 For full details of the effect and use of this switch,
6637 @xref{Compiling Using gcc}.
6640 @cindex @option{-fstack-check} (@command{gcc})
6641 @cindex Stack Overflow Checking
6642 @cindex Checks, stack overflow checking
6643 Activates stack overflow checking. For full details of the effect and use of
6644 this switch see @ref{Stack Overflow Checking}.
6649 The setting of these switches only controls the default setting of the
6650 checks. You may modify them using either @code{Suppress} (to remove
6651 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6654 @node Using gcc for Syntax Checking
6655 @subsection Using @command{gcc} for Syntax Checking
6658 @cindex @option{-gnats} (@command{gcc})
6662 The @code{s} stands for ``syntax''.
6665 Run GNAT in syntax checking only mode. For
6666 example, the command
6669 $ gcc -c -gnats x.adb
6673 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6674 series of files in a single command
6676 , and can use wild cards to specify such a group of files.
6677 Note that you must specify the @option{-c} (compile
6678 only) flag in addition to the @option{-gnats} flag.
6681 You may use other switches in conjunction with @option{-gnats}. In
6682 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6683 format of any generated error messages.
6685 When the source file is empty or contains only empty lines and/or comments,
6686 the output is a warning:
6689 $ gcc -c -gnats -x ada toto.txt
6690 toto.txt:1:01: warning: empty file, contains no compilation units
6694 Otherwise, the output is simply the error messages, if any. No object file or
6695 ALI file is generated by a syntax-only compilation. Also, no units other
6696 than the one specified are accessed. For example, if a unit @code{X}
6697 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6698 check only mode does not access the source file containing unit
6701 @cindex Multiple units, syntax checking
6702 Normally, GNAT allows only a single unit in a source file. However, this
6703 restriction does not apply in syntax-check-only mode, and it is possible
6704 to check a file containing multiple compilation units concatenated
6705 together. This is primarily used by the @code{gnatchop} utility
6706 (@pxref{Renaming Files Using gnatchop}).
6709 @node Using gcc for Semantic Checking
6710 @subsection Using @command{gcc} for Semantic Checking
6713 @cindex @option{-gnatc} (@command{gcc})
6717 The @code{c} stands for ``check''.
6719 Causes the compiler to operate in semantic check mode,
6720 with full checking for all illegalities specified in the
6721 Ada Reference Manual, but without generation of any object code
6722 (no object file is generated).
6724 Because dependent files must be accessed, you must follow the GNAT
6725 semantic restrictions on file structuring to operate in this mode:
6729 The needed source files must be accessible
6730 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6733 Each file must contain only one compilation unit.
6736 The file name and unit name must match (@pxref{File Naming Rules}).
6739 The output consists of error messages as appropriate. No object file is
6740 generated. An @file{ALI} file is generated for use in the context of
6741 cross-reference tools, but this file is marked as not being suitable
6742 for binding (since no object file is generated).
6743 The checking corresponds exactly to the notion of
6744 legality in the Ada Reference Manual.
6746 Any unit can be compiled in semantics-checking-only mode, including
6747 units that would not normally be compiled (subunits,
6748 and specifications where a separate body is present).
6751 @node Compiling Different Versions of Ada
6752 @subsection Compiling Different Versions of Ada
6755 The switches described in this section allow you to explicitly specify
6756 the version of the Ada language that your programs are written in.
6757 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6758 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6759 indicate Ada 83 compatibility mode.
6762 @cindex Compatibility with Ada 83
6764 @item -gnat83 (Ada 83 Compatibility Mode)
6765 @cindex @option{-gnat83} (@command{gcc})
6766 @cindex ACVC, Ada 83 tests
6770 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6771 specifies that the program is to be compiled in Ada 83 mode. With
6772 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6773 semantics where this can be done easily.
6774 It is not possible to guarantee this switch does a perfect
6775 job; some subtle tests, such as are
6776 found in earlier ACVC tests (and that have been removed from the ACATS suite
6777 for Ada 95), might not compile correctly.
6778 Nevertheless, this switch may be useful in some circumstances, for example
6779 where, due to contractual reasons, existing code needs to be maintained
6780 using only Ada 83 features.
6782 With few exceptions (most notably the need to use @code{<>} on
6783 @cindex Generic formal parameters
6784 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6785 reserved words, and the use of packages
6786 with optional bodies), it is not necessary to specify the
6787 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6788 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6789 a correct Ada 83 program is usually also a correct program
6790 in these later versions of the language standard.
6791 For further information, please refer to @ref{Compatibility and Porting Guide}.
6793 @item -gnat95 (Ada 95 mode)
6794 @cindex @option{-gnat95} (@command{gcc})
6798 This switch directs the compiler to implement the Ada 95 version of the
6800 Since Ada 95 is almost completely upwards
6801 compatible with Ada 83, Ada 83 programs may generally be compiled using
6802 this switch (see the description of the @option{-gnat83} switch for further
6803 information about Ada 83 mode).
6804 If an Ada 2005 program is compiled in Ada 95 mode,
6805 uses of the new Ada 2005 features will cause error
6806 messages or warnings.
6808 This switch also can be used to cancel the effect of a previous
6809 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6811 @item -gnat05 (Ada 2005 mode)
6812 @cindex @option{-gnat05} (@command{gcc})
6813 @cindex Ada 2005 mode
6816 This switch directs the compiler to implement the Ada 2005 version of the
6818 Since Ada 2005 is almost completely upwards
6819 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6820 may generally be compiled using this switch (see the description of the
6821 @option{-gnat83} and @option{-gnat95} switches for further
6824 For information about the approved ``Ada Issues'' that have been incorporated
6825 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6826 Included with GNAT releases is a file @file{features-ada0y} that describes
6827 the set of implemented Ada 2005 features.
6831 @node Character Set Control
6832 @subsection Character Set Control
6834 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6835 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6838 Normally GNAT recognizes the Latin-1 character set in source program
6839 identifiers, as described in the Ada Reference Manual.
6841 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6842 single character ^^or word^ indicating the character set, as follows:
6846 ISO 8859-1 (Latin-1) identifiers
6849 ISO 8859-2 (Latin-2) letters allowed in identifiers
6852 ISO 8859-3 (Latin-3) letters allowed in identifiers
6855 ISO 8859-4 (Latin-4) letters allowed in identifiers
6858 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6861 ISO 8859-15 (Latin-9) letters allowed in identifiers
6864 IBM PC letters (code page 437) allowed in identifiers
6867 IBM PC letters (code page 850) allowed in identifiers
6869 @item ^f^FULL_UPPER^
6870 Full upper-half codes allowed in identifiers
6873 No upper-half codes allowed in identifiers
6876 Wide-character codes (that is, codes greater than 255)
6877 allowed in identifiers
6880 @xref{Foreign Language Representation}, for full details on the
6881 implementation of these character sets.
6883 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6884 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6885 Specify the method of encoding for wide characters.
6886 @var{e} is one of the following:
6891 Hex encoding (brackets coding also recognized)
6894 Upper half encoding (brackets encoding also recognized)
6897 Shift/JIS encoding (brackets encoding also recognized)
6900 EUC encoding (brackets encoding also recognized)
6903 UTF-8 encoding (brackets encoding also recognized)
6906 Brackets encoding only (default value)
6908 For full details on these encoding
6909 methods see @ref{Wide Character Encodings}.
6910 Note that brackets coding is always accepted, even if one of the other
6911 options is specified, so for example @option{-gnatW8} specifies that both
6912 brackets and UTF-8 encodings will be recognized. The units that are
6913 with'ed directly or indirectly will be scanned using the specified
6914 representation scheme, and so if one of the non-brackets scheme is
6915 used, it must be used consistently throughout the program. However,
6916 since brackets encoding is always recognized, it may be conveniently
6917 used in standard libraries, allowing these libraries to be used with
6918 any of the available coding schemes.
6921 If no @option{-gnatW?} parameter is present, then the default
6922 representation is normally Brackets encoding only. However, if the
6923 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6924 byte order mark or BOM for UTF-8), then these three characters are
6925 skipped and the default representation for the file is set to UTF-8.
6927 Note that the wide character representation that is specified (explicitly
6928 or by default) for the main program also acts as the default encoding used
6929 for Wide_Text_IO files if not specifically overridden by a WCEM form
6933 @node File Naming Control
6934 @subsection File Naming Control
6937 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6938 @cindex @option{-gnatk} (@command{gcc})
6939 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6940 1-999, indicates the maximum allowable length of a file name (not
6941 including the @file{.ads} or @file{.adb} extension). The default is not
6942 to enable file name krunching.
6944 For the source file naming rules, @xref{File Naming Rules}.
6947 @node Subprogram Inlining Control
6948 @subsection Subprogram Inlining Control
6953 @cindex @option{-gnatn} (@command{gcc})
6955 The @code{n} here is intended to suggest the first syllable of the
6958 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6959 inlining to actually occur, optimization must be enabled. To enable
6960 inlining of subprograms specified by pragma @code{Inline},
6961 you must also specify this switch.
6962 In the absence of this switch, GNAT does not attempt
6963 inlining and does not need to access the bodies of
6964 subprograms for which @code{pragma Inline} is specified if they are not
6965 in the current unit.
6967 If you specify this switch the compiler will access these bodies,
6968 creating an extra source dependency for the resulting object file, and
6969 where possible, the call will be inlined.
6970 For further details on when inlining is possible
6971 see @ref{Inlining of Subprograms}.
6974 @cindex @option{-gnatN} (@command{gcc})
6975 This switch activates front-end inlining which also
6976 generates additional dependencies.
6978 When using a gcc-based back end (in practice this means using any version
6979 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
6980 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
6981 Historically front end inlining was more extensive than the gcc back end
6982 inlining, but that is no longer the case.
6985 @node Auxiliary Output Control
6986 @subsection Auxiliary Output Control
6990 @cindex @option{-gnatt} (@command{gcc})
6991 @cindex Writing internal trees
6992 @cindex Internal trees, writing to file
6993 Causes GNAT to write the internal tree for a unit to a file (with the
6994 extension @file{.adt}.
6995 This not normally required, but is used by separate analysis tools.
6997 these tools do the necessary compilations automatically, so you should
6998 not have to specify this switch in normal operation.
6999 Note that the combination of switches @option{-gnatct} generates a tree
7000 in the form required by ASIS applications.
7003 @cindex @option{-gnatu} (@command{gcc})
7004 Print a list of units required by this compilation on @file{stdout}.
7005 The listing includes all units on which the unit being compiled depends
7006 either directly or indirectly.
7009 @item -pass-exit-codes
7010 @cindex @option{-pass-exit-codes} (@command{gcc})
7011 If this switch is not used, the exit code returned by @command{gcc} when
7012 compiling multiple files indicates whether all source files have
7013 been successfully used to generate object files or not.
7015 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
7016 exit status and allows an integrated development environment to better
7017 react to a compilation failure. Those exit status are:
7021 There was an error in at least one source file.
7023 At least one source file did not generate an object file.
7025 The compiler died unexpectedly (internal error for example).
7027 An object file has been generated for every source file.
7032 @node Debugging Control
7033 @subsection Debugging Control
7037 @cindex Debugging options
7040 @cindex @option{-gnatd} (@command{gcc})
7041 Activate internal debugging switches. @var{x} is a letter or digit, or
7042 string of letters or digits, which specifies the type of debugging
7043 outputs desired. Normally these are used only for internal development
7044 or system debugging purposes. You can find full documentation for these
7045 switches in the body of the @code{Debug} unit in the compiler source
7046 file @file{debug.adb}.
7050 @cindex @option{-gnatG} (@command{gcc})
7051 This switch causes the compiler to generate auxiliary output containing
7052 a pseudo-source listing of the generated expanded code. Like most Ada
7053 compilers, GNAT works by first transforming the high level Ada code into
7054 lower level constructs. For example, tasking operations are transformed
7055 into calls to the tasking run-time routines. A unique capability of GNAT
7056 is to list this expanded code in a form very close to normal Ada source.
7057 This is very useful in understanding the implications of various Ada
7058 usage on the efficiency of the generated code. There are many cases in
7059 Ada (e.g.@: the use of controlled types), where simple Ada statements can
7060 generate a lot of run-time code. By using @option{-gnatG} you can identify
7061 these cases, and consider whether it may be desirable to modify the coding
7062 approach to improve efficiency.
7064 The optional parameter @code{nn} if present after -gnatG specifies an
7065 alternative maximum line length that overrides the normal default of 72.
7066 This value is in the range 40-999999, values less than 40 being silently
7067 reset to 40. The equal sign is optional.
7069 The format of the output is very similar to standard Ada source, and is
7070 easily understood by an Ada programmer. The following special syntactic
7071 additions correspond to low level features used in the generated code that
7072 do not have any exact analogies in pure Ada source form. The following
7073 is a partial list of these special constructions. See the spec
7074 of package @code{Sprint} in file @file{sprint.ads} for a full list.
7076 If the switch @option{-gnatL} is used in conjunction with
7077 @cindex @option{-gnatL} (@command{gcc})
7078 @option{-gnatG}, then the original source lines are interspersed
7079 in the expanded source (as comment lines with the original line number).
7082 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
7083 Shows the storage pool being used for an allocator.
7085 @item at end @var{procedure-name};
7086 Shows the finalization (cleanup) procedure for a scope.
7088 @item (if @var{expr} then @var{expr} else @var{expr})
7089 Conditional expression equivalent to the @code{x?y:z} construction in C.
7091 @item @var{target}^^^(@var{source})
7092 A conversion with floating-point truncation instead of rounding.
7094 @item @var{target}?(@var{source})
7095 A conversion that bypasses normal Ada semantic checking. In particular
7096 enumeration types and fixed-point types are treated simply as integers.
7098 @item @var{target}?^^^(@var{source})
7099 Combines the above two cases.
7101 @item @var{x} #/ @var{y}
7102 @itemx @var{x} #mod @var{y}
7103 @itemx @var{x} #* @var{y}
7104 @itemx @var{x} #rem @var{y}
7105 A division or multiplication of fixed-point values which are treated as
7106 integers without any kind of scaling.
7108 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
7109 Shows the storage pool associated with a @code{free} statement.
7111 @item [subtype or type declaration]
7112 Used to list an equivalent declaration for an internally generated
7113 type that is referenced elsewhere in the listing.
7115 @item freeze @var{type-name} @ovar{actions}
7116 Shows the point at which @var{type-name} is frozen, with possible
7117 associated actions to be performed at the freeze point.
7119 @item reference @var{itype}
7120 Reference (and hence definition) to internal type @var{itype}.
7122 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
7123 Intrinsic function call.
7125 @item @var{label-name} : label
7126 Declaration of label @var{labelname}.
7128 @item #$ @var{subprogram-name}
7129 An implicit call to a run-time support routine
7130 (to meet the requirement of H.3.1(9) in a
7133 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
7134 A multiple concatenation (same effect as @var{expr} & @var{expr} &
7135 @var{expr}, but handled more efficiently).
7137 @item [constraint_error]
7138 Raise the @code{Constraint_Error} exception.
7140 @item @var{expression}'reference
7141 A pointer to the result of evaluating @var{expression}.
7143 @item @var{target-type}!(@var{source-expression})
7144 An unchecked conversion of @var{source-expression} to @var{target-type}.
7146 @item [@var{numerator}/@var{denominator}]
7147 Used to represent internal real literals (that) have no exact
7148 representation in base 2-16 (for example, the result of compile time
7149 evaluation of the expression 1.0/27.0).
7153 @cindex @option{-gnatD} (@command{gcc})
7154 When used in conjunction with @option{-gnatG}, this switch causes
7155 the expanded source, as described above for
7156 @option{-gnatG} to be written to files with names
7157 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
7158 instead of to the standard output file. For
7159 example, if the source file name is @file{hello.adb}, then a file
7160 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
7161 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
7162 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
7163 you to do source level debugging using the generated code which is
7164 sometimes useful for complex code, for example to find out exactly
7165 which part of a complex construction raised an exception. This switch
7166 also suppress generation of cross-reference information (see
7167 @option{-gnatx}) since otherwise the cross-reference information
7168 would refer to the @file{^.dg^.DG^} file, which would cause
7169 confusion since this is not the original source file.
7171 Note that @option{-gnatD} actually implies @option{-gnatG}
7172 automatically, so it is not necessary to give both options.
7173 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
7175 If the switch @option{-gnatL} is used in conjunction with
7176 @cindex @option{-gnatL} (@command{gcc})
7177 @option{-gnatDG}, then the original source lines are interspersed
7178 in the expanded source (as comment lines with the original line number).
7180 The optional parameter @code{nn} if present after -gnatD specifies an
7181 alternative maximum line length that overrides the normal default of 72.
7182 This value is in the range 40-999999, values less than 40 being silently
7183 reset to 40. The equal sign is optional.
7186 @cindex @option{-gnatr} (@command{gcc})
7187 @cindex pragma Restrictions
7188 This switch causes pragma Restrictions to be treated as Restriction_Warnings
7189 so that violation of restrictions causes warnings rather than illegalities.
7190 This is useful during the development process when new restrictions are added
7191 or investigated. The switch also causes pragma Profile to be treated as
7192 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
7193 restriction warnings rather than restrictions.
7196 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
7197 @cindex @option{-gnatR} (@command{gcc})
7198 This switch controls output from the compiler of a listing showing
7199 representation information for declared types and objects. For
7200 @option{-gnatR0}, no information is output (equivalent to omitting
7201 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
7202 so @option{-gnatR} with no parameter has the same effect), size and alignment
7203 information is listed for declared array and record types. For
7204 @option{-gnatR2}, size and alignment information is listed for all
7205 declared types and objects. Finally @option{-gnatR3} includes symbolic
7206 expressions for values that are computed at run time for
7207 variant records. These symbolic expressions have a mostly obvious
7208 format with #n being used to represent the value of the n'th
7209 discriminant. See source files @file{repinfo.ads/adb} in the
7210 @code{GNAT} sources for full details on the format of @option{-gnatR3}
7211 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
7212 the output is to a file with the name @file{^file.rep^file_REP^} where
7213 file is the name of the corresponding source file.
7216 @item /REPRESENTATION_INFO
7217 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
7218 This qualifier controls output from the compiler of a listing showing
7219 representation information for declared types and objects. For
7220 @option{/REPRESENTATION_INFO=NONE}, no information is output
7221 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
7222 @option{/REPRESENTATION_INFO} without option is equivalent to
7223 @option{/REPRESENTATION_INFO=ARRAYS}.
7224 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
7225 information is listed for declared array and record types. For
7226 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
7227 is listed for all expression information for values that are computed
7228 at run time for variant records. These symbolic expressions have a mostly
7229 obvious format with #n being used to represent the value of the n'th
7230 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7231 @code{GNAT} sources for full details on the format of
7232 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7233 If _FILE is added at the end of an option
7234 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7235 then the output is to a file with the name @file{file_REP} where
7236 file is the name of the corresponding source file.
7238 Note that it is possible for record components to have zero size. In
7239 this case, the component clause uses an obvious extension of permitted
7240 Ada syntax, for example @code{at 0 range 0 .. -1}.
7242 Representation information requires that code be generated (since it is the
7243 code generator that lays out complex data structures). If an attempt is made
7244 to output representation information when no code is generated, for example
7245 when a subunit is compiled on its own, then no information can be generated
7246 and the compiler outputs a message to this effect.
7249 @cindex @option{-gnatS} (@command{gcc})
7250 The use of the switch @option{-gnatS} for an
7251 Ada compilation will cause the compiler to output a
7252 representation of package Standard in a form very
7253 close to standard Ada. It is not quite possible to
7254 do this entirely in standard Ada (since new
7255 numeric base types cannot be created in standard
7256 Ada), but the output is easily
7257 readable to any Ada programmer, and is useful to
7258 determine the characteristics of target dependent
7259 types in package Standard.
7262 @cindex @option{-gnatx} (@command{gcc})
7263 Normally the compiler generates full cross-referencing information in
7264 the @file{ALI} file. This information is used by a number of tools,
7265 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7266 suppresses this information. This saves some space and may slightly
7267 speed up compilation, but means that these tools cannot be used.
7270 @node Exception Handling Control
7271 @subsection Exception Handling Control
7274 GNAT uses two methods for handling exceptions at run-time. The
7275 @code{setjmp/longjmp} method saves the context when entering
7276 a frame with an exception handler. Then when an exception is
7277 raised, the context can be restored immediately, without the
7278 need for tracing stack frames. This method provides very fast
7279 exception propagation, but introduces significant overhead for
7280 the use of exception handlers, even if no exception is raised.
7282 The other approach is called ``zero cost'' exception handling.
7283 With this method, the compiler builds static tables to describe
7284 the exception ranges. No dynamic code is required when entering
7285 a frame containing an exception handler. When an exception is
7286 raised, the tables are used to control a back trace of the
7287 subprogram invocation stack to locate the required exception
7288 handler. This method has considerably poorer performance for
7289 the propagation of exceptions, but there is no overhead for
7290 exception handlers if no exception is raised. Note that in this
7291 mode and in the context of mixed Ada and C/C++ programming,
7292 to propagate an exception through a C/C++ code, the C/C++ code
7293 must be compiled with the @option{-funwind-tables} GCC's
7296 The following switches may be used to control which of the
7297 two exception handling methods is used.
7303 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7304 This switch causes the setjmp/longjmp run-time (when available) to be used
7305 for exception handling. If the default
7306 mechanism for the target is zero cost exceptions, then
7307 this switch can be used to modify this default, and must be
7308 used for all units in the partition.
7309 This option is rarely used. One case in which it may be
7310 advantageous is if you have an application where exception
7311 raising is common and the overall performance of the
7312 application is improved by favoring exception propagation.
7315 @cindex @option{--RTS=zcx} (@command{gnatmake})
7316 @cindex Zero Cost Exceptions
7317 This switch causes the zero cost approach to be used
7318 for exception handling. If this is the default mechanism for the
7319 target (see below), then this switch is unneeded. If the default
7320 mechanism for the target is setjmp/longjmp exceptions, then
7321 this switch can be used to modify this default, and must be
7322 used for all units in the partition.
7323 This option can only be used if the zero cost approach
7324 is available for the target in use, otherwise it will generate an error.
7328 The same option @option{--RTS} must be used both for @command{gcc}
7329 and @command{gnatbind}. Passing this option to @command{gnatmake}
7330 (@pxref{Switches for gnatmake}) will ensure the required consistency
7331 through the compilation and binding steps.
7333 @node Units to Sources Mapping Files
7334 @subsection Units to Sources Mapping Files
7338 @item -gnatem^^=^@var{path}
7339 @cindex @option{-gnatem} (@command{gcc})
7340 A mapping file is a way to communicate to the compiler two mappings:
7341 from unit names to file names (without any directory information) and from
7342 file names to path names (with full directory information). These mappings
7343 are used by the compiler to short-circuit the path search.
7345 The use of mapping files is not required for correct operation of the
7346 compiler, but mapping files can improve efficiency, particularly when
7347 sources are read over a slow network connection. In normal operation,
7348 you need not be concerned with the format or use of mapping files,
7349 and the @option{-gnatem} switch is not a switch that you would use
7350 explicitly. it is intended only for use by automatic tools such as
7351 @command{gnatmake} running under the project file facility. The
7352 description here of the format of mapping files is provided
7353 for completeness and for possible use by other tools.
7355 A mapping file is a sequence of sets of three lines. In each set,
7356 the first line is the unit name, in lower case, with ``@code{%s}''
7358 specs and ``@code{%b}'' appended for bodies; the second line is the
7359 file name; and the third line is the path name.
7365 /gnat/project1/sources/main.2.ada
7368 When the switch @option{-gnatem} is specified, the compiler will create
7369 in memory the two mappings from the specified file. If there is any problem
7370 (nonexistent file, truncated file or duplicate entries), no mapping will
7373 Several @option{-gnatem} switches may be specified; however, only the last
7374 one on the command line will be taken into account.
7376 When using a project file, @command{gnatmake} create a temporary mapping file
7377 and communicates it to the compiler using this switch.
7381 @node Integrated Preprocessing
7382 @subsection Integrated Preprocessing
7385 GNAT sources may be preprocessed immediately before compilation.
7386 In this case, the actual
7387 text of the source is not the text of the source file, but is derived from it
7388 through a process called preprocessing. Integrated preprocessing is specified
7389 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7390 indicates, through a text file, the preprocessing data to be used.
7391 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7394 Note that when integrated preprocessing is used, the output from the
7395 preprocessor is not written to any external file. Instead it is passed
7396 internally to the compiler. If you need to preserve the result of
7397 preprocessing in a file, then you should use @command{gnatprep}
7398 to perform the desired preprocessing in stand-alone mode.
7401 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7402 used when Integrated Preprocessing is used. The reason is that preprocessing
7403 with another Preprocessing Data file without changing the sources will
7404 not trigger recompilation without this switch.
7407 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7408 always trigger recompilation for sources that are preprocessed,
7409 because @command{gnatmake} cannot compute the checksum of the source after
7413 The actual preprocessing function is described in details in section
7414 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7415 preprocessing is triggered and parameterized.
7419 @item -gnatep=@var{file}
7420 @cindex @option{-gnatep} (@command{gcc})
7421 This switch indicates to the compiler the file name (without directory
7422 information) of the preprocessor data file to use. The preprocessor data file
7423 should be found in the source directories.
7426 A preprocessing data file is a text file with significant lines indicating
7427 how should be preprocessed either a specific source or all sources not
7428 mentioned in other lines. A significant line is a nonempty, non-comment line.
7429 Comments are similar to Ada comments.
7432 Each significant line starts with either a literal string or the character '*'.
7433 A literal string is the file name (without directory information) of the source
7434 to preprocess. A character '*' indicates the preprocessing for all the sources
7435 that are not specified explicitly on other lines (order of the lines is not
7436 significant). It is an error to have two lines with the same file name or two
7437 lines starting with the character '*'.
7440 After the file name or the character '*', another optional literal string
7441 indicating the file name of the definition file to be used for preprocessing
7442 (@pxref{Form of Definitions File}). The definition files are found by the
7443 compiler in one of the source directories. In some cases, when compiling
7444 a source in a directory other than the current directory, if the definition
7445 file is in the current directory, it may be necessary to add the current
7446 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7447 the compiler would not find the definition file.
7450 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7451 be found. Those ^switches^switches^ are:
7456 Causes both preprocessor lines and the lines deleted by
7457 preprocessing to be replaced by blank lines, preserving the line number.
7458 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7459 it cancels the effect of @option{-c}.
7462 Causes both preprocessor lines and the lines deleted
7463 by preprocessing to be retained as comments marked
7464 with the special string ``@code{--! }''.
7466 @item -Dsymbol=value
7467 Define or redefine a symbol, associated with value. A symbol is an Ada
7468 identifier, or an Ada reserved word, with the exception of @code{if},
7469 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7470 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7471 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7472 same name defined in a definition file.
7475 Causes a sorted list of symbol names and values to be
7476 listed on the standard output file.
7479 Causes undefined symbols to be treated as having the value @code{FALSE}
7481 of a preprocessor test. In the absence of this option, an undefined symbol in
7482 a @code{#if} or @code{#elsif} test will be treated as an error.
7487 Examples of valid lines in a preprocessor data file:
7490 "toto.adb" "prep.def" -u
7491 -- preprocess "toto.adb", using definition file "prep.def",
7492 -- undefined symbol are False.
7495 -- preprocess all other sources without a definition file;
7496 -- suppressed lined are commented; symbol VERSION has the value V101.
7498 "titi.adb" "prep2.def" -s
7499 -- preprocess "titi.adb", using definition file "prep2.def";
7500 -- list all symbols with their values.
7503 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7504 @cindex @option{-gnateD} (@command{gcc})
7505 Define or redefine a preprocessing symbol, associated with value. If no value
7506 is given on the command line, then the value of the symbol is @code{True}.
7507 A symbol is an identifier, following normal Ada (case-insensitive)
7508 rules for its syntax, and value is any sequence (including an empty sequence)
7509 of characters from the set (letters, digits, period, underline).
7510 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7511 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7514 A symbol declared with this ^switch^switch^ on the command line replaces a
7515 symbol with the same name either in a definition file or specified with a
7516 ^switch^switch^ -D in the preprocessor data file.
7519 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7522 When integrated preprocessing is performed and the preprocessor modifies
7523 the source text, write the result of this preprocessing into a file
7524 <source>^.prep^_prep^.
7528 @node Code Generation Control
7529 @subsection Code Generation Control
7533 The GCC technology provides a wide range of target dependent
7534 @option{-m} switches for controlling
7535 details of code generation with respect to different versions of
7536 architectures. This includes variations in instruction sets (e.g.@:
7537 different members of the power pc family), and different requirements
7538 for optimal arrangement of instructions (e.g.@: different members of
7539 the x86 family). The list of available @option{-m} switches may be
7540 found in the GCC documentation.
7542 Use of these @option{-m} switches may in some cases result in improved
7545 The GNAT Pro technology is tested and qualified without any
7546 @option{-m} switches,
7547 so generally the most reliable approach is to avoid the use of these
7548 switches. However, we generally expect most of these switches to work
7549 successfully with GNAT Pro, and many customers have reported successful
7550 use of these options.
7552 Our general advice is to avoid the use of @option{-m} switches unless
7553 special needs lead to requirements in this area. In particular,
7554 there is no point in using @option{-m} switches to improve performance
7555 unless you actually see a performance improvement.
7559 @subsection Return Codes
7560 @cindex Return Codes
7561 @cindex @option{/RETURN_CODES=VMS}
7564 On VMS, GNAT compiled programs return POSIX-style codes by default,
7565 e.g.@: @option{/RETURN_CODES=POSIX}.
7567 To enable VMS style return codes, use GNAT BIND and LINK with the option
7568 @option{/RETURN_CODES=VMS}. For example:
7571 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7572 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7576 Programs built with /RETURN_CODES=VMS are suitable to be called in
7577 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7578 are suitable for spawning with appropriate GNAT RTL routines.
7582 @node Search Paths and the Run-Time Library (RTL)
7583 @section Search Paths and the Run-Time Library (RTL)
7586 With the GNAT source-based library system, the compiler must be able to
7587 find source files for units that are needed by the unit being compiled.
7588 Search paths are used to guide this process.
7590 The compiler compiles one source file whose name must be given
7591 explicitly on the command line. In other words, no searching is done
7592 for this file. To find all other source files that are needed (the most
7593 common being the specs of units), the compiler examines the following
7594 directories, in the following order:
7598 The directory containing the source file of the main unit being compiled
7599 (the file name on the command line).
7602 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7603 @command{gcc} command line, in the order given.
7606 @findex ADA_PRJ_INCLUDE_FILE
7607 Each of the directories listed in the text file whose name is given
7608 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7611 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7612 driver when project files are used. It should not normally be set
7616 @findex ADA_INCLUDE_PATH
7617 Each of the directories listed in the value of the
7618 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7620 Construct this value
7621 exactly as the @env{PATH} environment variable: a list of directory
7622 names separated by colons (semicolons when working with the NT version).
7625 Normally, define this value as a logical name containing a comma separated
7626 list of directory names.
7628 This variable can also be defined by means of an environment string
7629 (an argument to the HP C exec* set of functions).
7633 DEFINE ANOTHER_PATH FOO:[BAG]
7634 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7637 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7638 first, followed by the standard Ada
7639 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7640 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7641 (Text_IO, Sequential_IO, etc)
7642 instead of the standard Ada packages. Thus, in order to get the standard Ada
7643 packages by default, ADA_INCLUDE_PATH must be redefined.
7647 The content of the @file{ada_source_path} file which is part of the GNAT
7648 installation tree and is used to store standard libraries such as the
7649 GNAT Run Time Library (RTL) source files.
7651 @ref{Installing a library}
7656 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7657 inhibits the use of the directory
7658 containing the source file named in the command line. You can still
7659 have this directory on your search path, but in this case it must be
7660 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7662 Specifying the switch @option{-nostdinc}
7663 inhibits the search of the default location for the GNAT Run Time
7664 Library (RTL) source files.
7666 The compiler outputs its object files and ALI files in the current
7669 Caution: The object file can be redirected with the @option{-o} switch;
7670 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7671 so the @file{ALI} file will not go to the right place. Therefore, you should
7672 avoid using the @option{-o} switch.
7676 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7677 children make up the GNAT RTL, together with the simple @code{System.IO}
7678 package used in the @code{"Hello World"} example. The sources for these units
7679 are needed by the compiler and are kept together in one directory. Not
7680 all of the bodies are needed, but all of the sources are kept together
7681 anyway. In a normal installation, you need not specify these directory
7682 names when compiling or binding. Either the environment variables or
7683 the built-in defaults cause these files to be found.
7685 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7686 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7687 consisting of child units of @code{GNAT}. This is a collection of generally
7688 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7689 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7691 Besides simplifying access to the RTL, a major use of search paths is
7692 in compiling sources from multiple directories. This can make
7693 development environments much more flexible.
7695 @node Order of Compilation Issues
7696 @section Order of Compilation Issues
7699 If, in our earlier example, there was a spec for the @code{hello}
7700 procedure, it would be contained in the file @file{hello.ads}; yet this
7701 file would not have to be explicitly compiled. This is the result of the
7702 model we chose to implement library management. Some of the consequences
7703 of this model are as follows:
7707 There is no point in compiling specs (except for package
7708 specs with no bodies) because these are compiled as needed by clients. If
7709 you attempt a useless compilation, you will receive an error message.
7710 It is also useless to compile subunits because they are compiled as needed
7714 There are no order of compilation requirements: performing a
7715 compilation never obsoletes anything. The only way you can obsolete
7716 something and require recompilations is to modify one of the
7717 source files on which it depends.
7720 There is no library as such, apart from the ALI files
7721 (@pxref{The Ada Library Information Files}, for information on the format
7722 of these files). For now we find it convenient to create separate ALI files,
7723 but eventually the information therein may be incorporated into the object
7727 When you compile a unit, the source files for the specs of all units
7728 that it @code{with}'s, all its subunits, and the bodies of any generics it
7729 instantiates must be available (reachable by the search-paths mechanism
7730 described above), or you will receive a fatal error message.
7737 The following are some typical Ada compilation command line examples:
7740 @item $ gcc -c xyz.adb
7741 Compile body in file @file{xyz.adb} with all default options.
7744 @item $ gcc -c -O2 -gnata xyz-def.adb
7747 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7750 Compile the child unit package in file @file{xyz-def.adb} with extensive
7751 optimizations, and pragma @code{Assert}/@code{Debug} statements
7754 @item $ gcc -c -gnatc abc-def.adb
7755 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7759 @node Binding Using gnatbind
7760 @chapter Binding Using @code{gnatbind}
7764 * Running gnatbind::
7765 * Switches for gnatbind::
7766 * Command-Line Access::
7767 * Search Paths for gnatbind::
7768 * Examples of gnatbind Usage::
7772 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7773 to bind compiled GNAT objects.
7775 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7776 driver (see @ref{The GNAT Driver and Project Files}).
7778 The @code{gnatbind} program performs four separate functions:
7782 Checks that a program is consistent, in accordance with the rules in
7783 Chapter 10 of the Ada Reference Manual. In particular, error
7784 messages are generated if a program uses inconsistent versions of a
7788 Checks that an acceptable order of elaboration exists for the program
7789 and issues an error message if it cannot find an order of elaboration
7790 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7793 Generates a main program incorporating the given elaboration order.
7794 This program is a small Ada package (body and spec) that
7795 must be subsequently compiled
7796 using the GNAT compiler. The necessary compilation step is usually
7797 performed automatically by @command{gnatlink}. The two most important
7798 functions of this program
7799 are to call the elaboration routines of units in an appropriate order
7800 and to call the main program.
7803 Determines the set of object files required by the given main program.
7804 This information is output in the forms of comments in the generated program,
7805 to be read by the @command{gnatlink} utility used to link the Ada application.
7808 @node Running gnatbind
7809 @section Running @code{gnatbind}
7812 The form of the @code{gnatbind} command is
7815 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7819 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7820 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7821 package in two files whose names are
7822 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7823 For example, if given the
7824 parameter @file{hello.ali}, for a main program contained in file
7825 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7826 and @file{b~hello.adb}.
7828 When doing consistency checking, the binder takes into consideration
7829 any source files it can locate. For example, if the binder determines
7830 that the given main program requires the package @code{Pack}, whose
7832 file is @file{pack.ali} and whose corresponding source spec file is
7833 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7834 (using the same search path conventions as previously described for the
7835 @command{gcc} command). If it can locate this source file, it checks that
7837 or source checksums of the source and its references to in @file{ALI} files
7838 match. In other words, any @file{ALI} files that mentions this spec must have
7839 resulted from compiling this version of the source file (or in the case
7840 where the source checksums match, a version close enough that the
7841 difference does not matter).
7843 @cindex Source files, use by binder
7844 The effect of this consistency checking, which includes source files, is
7845 that the binder ensures that the program is consistent with the latest
7846 version of the source files that can be located at bind time. Editing a
7847 source file without compiling files that depend on the source file cause
7848 error messages to be generated by the binder.
7850 For example, suppose you have a main program @file{hello.adb} and a
7851 package @code{P}, from file @file{p.ads} and you perform the following
7856 Enter @code{gcc -c hello.adb} to compile the main program.
7859 Enter @code{gcc -c p.ads} to compile package @code{P}.
7862 Edit file @file{p.ads}.
7865 Enter @code{gnatbind hello}.
7869 At this point, the file @file{p.ali} contains an out-of-date time stamp
7870 because the file @file{p.ads} has been edited. The attempt at binding
7871 fails, and the binder generates the following error messages:
7874 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7875 error: "p.ads" has been modified and must be recompiled
7879 Now both files must be recompiled as indicated, and then the bind can
7880 succeed, generating a main program. You need not normally be concerned
7881 with the contents of this file, but for reference purposes a sample
7882 binder output file is given in @ref{Example of Binder Output File}.
7884 In most normal usage, the default mode of @command{gnatbind} which is to
7885 generate the main package in Ada, as described in the previous section.
7886 In particular, this means that any Ada programmer can read and understand
7887 the generated main program. It can also be debugged just like any other
7888 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7889 @command{gnatbind} and @command{gnatlink}.
7891 However for some purposes it may be convenient to generate the main
7892 program in C rather than Ada. This may for example be helpful when you
7893 are generating a mixed language program with the main program in C. The
7894 GNAT compiler itself is an example.
7895 The use of the @option{^-C^/BIND_FILE=C^} switch
7896 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7897 be generated in C (and compiled using the gnu C compiler).
7899 @node Switches for gnatbind
7900 @section Switches for @command{gnatbind}
7903 The following switches are available with @code{gnatbind}; details will
7904 be presented in subsequent sections.
7907 * Consistency-Checking Modes::
7908 * Binder Error Message Control::
7909 * Elaboration Control::
7911 * Binding with Non-Ada Main Programs::
7912 * Binding Programs with No Main Subprogram::
7919 @cindex @option{--version} @command{gnatbind}
7920 Display Copyright and version, then exit disregarding all other options.
7923 @cindex @option{--help} @command{gnatbind}
7924 If @option{--version} was not used, display usage, then exit disregarding
7928 @cindex @option{-a} @command{gnatbind}
7929 Indicates that, if supported by the platform, the adainit procedure should
7930 be treated as an initialisation routine by the linker (a constructor). This
7931 is intended to be used by the Project Manager to automatically initialize
7932 shared Stand-Alone Libraries.
7934 @item ^-aO^/OBJECT_SEARCH^
7935 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7936 Specify directory to be searched for ALI files.
7938 @item ^-aI^/SOURCE_SEARCH^
7939 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7940 Specify directory to be searched for source file.
7942 @item ^-A^/BIND_FILE=ADA^
7943 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7944 Generate binder program in Ada (default)
7946 @item ^-b^/REPORT_ERRORS=BRIEF^
7947 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
7948 Generate brief messages to @file{stderr} even if verbose mode set.
7950 @item ^-c^/NOOUTPUT^
7951 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
7952 Check only, no generation of binder output file.
7954 @item ^-C^/BIND_FILE=C^
7955 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
7956 Generate binder program in C
7958 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7959 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
7960 This switch can be used to change the default task stack size value
7961 to a specified size @var{nn}, which is expressed in bytes by default, or
7962 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7964 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
7965 in effect, to completing all task specs with
7966 @smallexample @c ada
7967 pragma Storage_Size (nn);
7969 When they do not already have such a pragma.
7971 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
7972 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
7973 This switch can be used to change the default secondary stack size value
7974 to a specified size @var{nn}, which is expressed in bytes by default, or
7975 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
7978 The secondary stack is used to deal with functions that return a variable
7979 sized result, for example a function returning an unconstrained
7980 String. There are two ways in which this secondary stack is allocated.
7982 For most targets, the secondary stack is growing on demand and is allocated
7983 as a chain of blocks in the heap. The -D option is not very
7984 relevant. It only give some control over the size of the allocated
7985 blocks (whose size is the minimum of the default secondary stack size value,
7986 and the actual size needed for the current allocation request).
7988 For certain targets, notably VxWorks 653,
7989 the secondary stack is allocated by carving off a fixed ratio chunk of the
7990 primary task stack. The -D option is used to define the
7991 size of the environment task's secondary stack.
7993 @item ^-e^/ELABORATION_DEPENDENCIES^
7994 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
7995 Output complete list of elaboration-order dependencies.
7997 @item ^-E^/STORE_TRACEBACKS^
7998 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
7999 Store tracebacks in exception occurrences when the target supports it.
8000 This is the default with the zero cost exception mechanism.
8002 @c The following may get moved to an appendix
8003 This option is currently supported on the following targets:
8004 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
8006 See also the packages @code{GNAT.Traceback} and
8007 @code{GNAT.Traceback.Symbolic} for more information.
8009 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
8010 @command{gcc} option.
8013 @item ^-F^/FORCE_ELABS_FLAGS^
8014 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
8015 Force the checks of elaboration flags. @command{gnatbind} does not normally
8016 generate checks of elaboration flags for the main executable, except when
8017 a Stand-Alone Library is used. However, there are cases when this cannot be
8018 detected by gnatbind. An example is importing an interface of a Stand-Alone
8019 Library through a pragma Import and only specifying through a linker switch
8020 this Stand-Alone Library. This switch is used to guarantee that elaboration
8021 flag checks are generated.
8024 @cindex @option{^-h^/HELP^} (@command{gnatbind})
8025 Output usage (help) information
8028 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8029 Specify directory to be searched for source and ALI files.
8031 @item ^-I-^/NOCURRENT_DIRECTORY^
8032 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
8033 Do not look for sources in the current directory where @code{gnatbind} was
8034 invoked, and do not look for ALI files in the directory containing the
8035 ALI file named in the @code{gnatbind} command line.
8037 @item ^-l^/ORDER_OF_ELABORATION^
8038 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
8039 Output chosen elaboration order.
8041 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
8042 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
8043 Bind the units for library building. In this case the adainit and
8044 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
8045 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
8046 ^@var{xxx}final^@var{XXX}FINAL^.
8047 Implies ^-n^/NOCOMPILE^.
8049 (@xref{GNAT and Libraries}, for more details.)
8052 On OpenVMS, these init and final procedures are exported in uppercase
8053 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
8054 the init procedure will be "TOTOINIT" and the exported name of the final
8055 procedure will be "TOTOFINAL".
8058 @item ^-Mxyz^/RENAME_MAIN=xyz^
8059 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
8060 Rename generated main program from main to xyz. This option is
8061 supported on cross environments only.
8063 @item ^-m^/ERROR_LIMIT=^@var{n}
8064 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
8065 Limit number of detected errors or warnings to @var{n}, where @var{n} is
8066 in the range 1..999999. The default value if no switch is
8067 given is 9999. If the number of warnings reaches this limit, then a
8068 message is output and further warnings are suppressed, the bind
8069 continues in this case. If the number of errors reaches this
8070 limit, then a message is output and the bind is abandoned.
8071 A value of zero means that no limit is enforced. The equal
8075 Furthermore, under Windows, the sources pointed to by the libraries path
8076 set in the registry are not searched for.
8080 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8084 @cindex @option{-nostdinc} (@command{gnatbind})
8085 Do not look for sources in the system default directory.
8088 @cindex @option{-nostdlib} (@command{gnatbind})
8089 Do not look for library files in the system default directory.
8091 @item --RTS=@var{rts-path}
8092 @cindex @option{--RTS} (@code{gnatbind})
8093 Specifies the default location of the runtime library. Same meaning as the
8094 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
8096 @item ^-o ^/OUTPUT=^@var{file}
8097 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
8098 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
8099 Note that if this option is used, then linking must be done manually,
8100 gnatlink cannot be used.
8102 @item ^-O^/OBJECT_LIST^
8103 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
8106 @item ^-p^/PESSIMISTIC_ELABORATION^
8107 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
8108 Pessimistic (worst-case) elaboration order
8111 @cindex @option{^-R^-R^} (@command{gnatbind})
8112 Output closure source list.
8114 @item ^-s^/READ_SOURCES=ALL^
8115 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
8116 Require all source files to be present.
8118 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
8119 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
8120 Specifies the value to be used when detecting uninitialized scalar
8121 objects with pragma Initialize_Scalars.
8122 The @var{xxx} ^string specified with the switch^option^ may be either
8124 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
8125 @item ``@option{^lo^LOW^}'' for the lowest possible value
8126 @item ``@option{^hi^HIGH^}'' for the highest possible value
8127 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
8128 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
8131 In addition, you can specify @option{-Sev} to indicate that the value is
8132 to be set at run time. In this case, the program will look for an environment
8133 @cindex GNAT_INIT_SCALARS
8134 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
8135 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
8136 If no environment variable is found, or if it does not have a valid value,
8137 then the default is @option{in} (invalid values).
8141 @cindex @option{-static} (@code{gnatbind})
8142 Link against a static GNAT run time.
8145 @cindex @option{-shared} (@code{gnatbind})
8146 Link against a shared GNAT run time when available.
8149 @item ^-t^/NOTIME_STAMP_CHECK^
8150 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8151 Tolerate time stamp and other consistency errors
8153 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
8154 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
8155 Set the time slice value to @var{n} milliseconds. If the system supports
8156 the specification of a specific time slice value, then the indicated value
8157 is used. If the system does not support specific time slice values, but
8158 does support some general notion of round-robin scheduling, then any
8159 nonzero value will activate round-robin scheduling.
8161 A value of zero is treated specially. It turns off time
8162 slicing, and in addition, indicates to the tasking run time that the
8163 semantics should match as closely as possible the Annex D
8164 requirements of the Ada RM, and in particular sets the default
8165 scheduling policy to @code{FIFO_Within_Priorities}.
8167 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
8168 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
8169 Enable dynamic stack usage, with @var{n} results stored and displayed
8170 at program termination. A result is generated when a task
8171 terminates. Results that can't be stored are displayed on the fly, at
8172 task termination. This option is currently not supported on Itanium
8173 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
8175 @item ^-v^/REPORT_ERRORS=VERBOSE^
8176 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8177 Verbose mode. Write error messages, header, summary output to
8182 @cindex @option{-w} (@code{gnatbind})
8183 Warning mode (@var{x}=s/e for suppress/treat as error)
8187 @item /WARNINGS=NORMAL
8188 @cindex @option{/WARNINGS} (@code{gnatbind})
8189 Normal warnings mode. Warnings are issued but ignored
8191 @item /WARNINGS=SUPPRESS
8192 @cindex @option{/WARNINGS} (@code{gnatbind})
8193 All warning messages are suppressed
8195 @item /WARNINGS=ERROR
8196 @cindex @option{/WARNINGS} (@code{gnatbind})
8197 Warning messages are treated as fatal errors
8200 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8201 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8202 Override default wide character encoding for standard Text_IO files.
8204 @item ^-x^/READ_SOURCES=NONE^
8205 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
8206 Exclude source files (check object consistency only).
8209 @item /READ_SOURCES=AVAILABLE
8210 @cindex @option{/READ_SOURCES} (@code{gnatbind})
8211 Default mode, in which sources are checked for consistency only if
8215 @item ^-y^/ENABLE_LEAP_SECONDS^
8216 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
8217 Enable leap seconds support in @code{Ada.Calendar} and its children.
8219 @item ^-z^/ZERO_MAIN^
8220 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8226 You may obtain this listing of switches by running @code{gnatbind} with
8230 @node Consistency-Checking Modes
8231 @subsection Consistency-Checking Modes
8234 As described earlier, by default @code{gnatbind} checks
8235 that object files are consistent with one another and are consistent
8236 with any source files it can locate. The following switches control binder
8241 @item ^-s^/READ_SOURCES=ALL^
8242 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8243 Require source files to be present. In this mode, the binder must be
8244 able to locate all source files that are referenced, in order to check
8245 their consistency. In normal mode, if a source file cannot be located it
8246 is simply ignored. If you specify this switch, a missing source
8249 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8250 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8251 Override default wide character encoding for standard Text_IO files.
8252 Normally the default wide character encoding method used for standard
8253 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8254 the main source input (see description of switch
8255 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8256 use of this switch for the binder (which has the same set of
8257 possible arguments) overrides this default as specified.
8259 @item ^-x^/READ_SOURCES=NONE^
8260 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8261 Exclude source files. In this mode, the binder only checks that ALI
8262 files are consistent with one another. Source files are not accessed.
8263 The binder runs faster in this mode, and there is still a guarantee that
8264 the resulting program is self-consistent.
8265 If a source file has been edited since it was last compiled, and you
8266 specify this switch, the binder will not detect that the object
8267 file is out of date with respect to the source file. Note that this is the
8268 mode that is automatically used by @command{gnatmake} because in this
8269 case the checking against sources has already been performed by
8270 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8273 @item /READ_SOURCES=AVAILABLE
8274 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8275 This is the default mode in which source files are checked if they are
8276 available, and ignored if they are not available.
8280 @node Binder Error Message Control
8281 @subsection Binder Error Message Control
8284 The following switches provide control over the generation of error
8285 messages from the binder:
8289 @item ^-v^/REPORT_ERRORS=VERBOSE^
8290 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8291 Verbose mode. In the normal mode, brief error messages are generated to
8292 @file{stderr}. If this switch is present, a header is written
8293 to @file{stdout} and any error messages are directed to @file{stdout}.
8294 All that is written to @file{stderr} is a brief summary message.
8296 @item ^-b^/REPORT_ERRORS=BRIEF^
8297 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8298 Generate brief error messages to @file{stderr} even if verbose mode is
8299 specified. This is relevant only when used with the
8300 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8304 @cindex @option{-m} (@code{gnatbind})
8305 Limits the number of error messages to @var{n}, a decimal integer in the
8306 range 1-999. The binder terminates immediately if this limit is reached.
8309 @cindex @option{-M} (@code{gnatbind})
8310 Renames the generated main program from @code{main} to @code{xxx}.
8311 This is useful in the case of some cross-building environments, where
8312 the actual main program is separate from the one generated
8316 @item ^-ws^/WARNINGS=SUPPRESS^
8317 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8319 Suppress all warning messages.
8321 @item ^-we^/WARNINGS=ERROR^
8322 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8323 Treat any warning messages as fatal errors.
8326 @item /WARNINGS=NORMAL
8327 Standard mode with warnings generated, but warnings do not get treated
8331 @item ^-t^/NOTIME_STAMP_CHECK^
8332 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8333 @cindex Time stamp checks, in binder
8334 @cindex Binder consistency checks
8335 @cindex Consistency checks, in binder
8336 The binder performs a number of consistency checks including:
8340 Check that time stamps of a given source unit are consistent
8342 Check that checksums of a given source unit are consistent
8344 Check that consistent versions of @code{GNAT} were used for compilation
8346 Check consistency of configuration pragmas as required
8350 Normally failure of such checks, in accordance with the consistency
8351 requirements of the Ada Reference Manual, causes error messages to be
8352 generated which abort the binder and prevent the output of a binder
8353 file and subsequent link to obtain an executable.
8355 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8356 into warnings, so that
8357 binding and linking can continue to completion even in the presence of such
8358 errors. The result may be a failed link (due to missing symbols), or a
8359 non-functional executable which has undefined semantics.
8360 @emph{This means that
8361 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8365 @node Elaboration Control
8366 @subsection Elaboration Control
8369 The following switches provide additional control over the elaboration
8370 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8373 @item ^-p^/PESSIMISTIC_ELABORATION^
8374 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8375 Normally the binder attempts to choose an elaboration order that is
8376 likely to minimize the likelihood of an elaboration order error resulting
8377 in raising a @code{Program_Error} exception. This switch reverses the
8378 action of the binder, and requests that it deliberately choose an order
8379 that is likely to maximize the likelihood of an elaboration error.
8380 This is useful in ensuring portability and avoiding dependence on
8381 accidental fortuitous elaboration ordering.
8383 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8385 elaboration checking is used (@option{-gnatE} switch used for compilation).
8386 This is because in the default static elaboration mode, all necessary
8387 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8388 These implicit pragmas are still respected by the binder in
8389 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8390 safe elaboration order is assured.
8393 @node Output Control
8394 @subsection Output Control
8397 The following switches allow additional control over the output
8398 generated by the binder.
8403 @item ^-A^/BIND_FILE=ADA^
8404 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8405 Generate binder program in Ada (default). The binder program is named
8406 @file{b~@var{mainprog}.adb} by default. This can be changed with
8407 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8409 @item ^-c^/NOOUTPUT^
8410 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8411 Check only. Do not generate the binder output file. In this mode the
8412 binder performs all error checks but does not generate an output file.
8414 @item ^-C^/BIND_FILE=C^
8415 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8416 Generate binder program in C. The binder program is named
8417 @file{b_@var{mainprog}.c}.
8418 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8421 @item ^-e^/ELABORATION_DEPENDENCIES^
8422 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8423 Output complete list of elaboration-order dependencies, showing the
8424 reason for each dependency. This output can be rather extensive but may
8425 be useful in diagnosing problems with elaboration order. The output is
8426 written to @file{stdout}.
8429 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8430 Output usage information. The output is written to @file{stdout}.
8432 @item ^-K^/LINKER_OPTION_LIST^
8433 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8434 Output linker options to @file{stdout}. Includes library search paths,
8435 contents of pragmas Ident and Linker_Options, and libraries added
8438 @item ^-l^/ORDER_OF_ELABORATION^
8439 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8440 Output chosen elaboration order. The output is written to @file{stdout}.
8442 @item ^-O^/OBJECT_LIST^
8443 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8444 Output full names of all the object files that must be linked to provide
8445 the Ada component of the program. The output is written to @file{stdout}.
8446 This list includes the files explicitly supplied and referenced by the user
8447 as well as implicitly referenced run-time unit files. The latter are
8448 omitted if the corresponding units reside in shared libraries. The
8449 directory names for the run-time units depend on the system configuration.
8451 @item ^-o ^/OUTPUT=^@var{file}
8452 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8453 Set name of output file to @var{file} instead of the normal
8454 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8455 binder generated body filename. In C mode you would normally give
8456 @var{file} an extension of @file{.c} because it will be a C source program.
8457 Note that if this option is used, then linking must be done manually.
8458 It is not possible to use gnatlink in this case, since it cannot locate
8461 @item ^-r^/RESTRICTION_LIST^
8462 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8463 Generate list of @code{pragma Restrictions} that could be applied to
8464 the current unit. This is useful for code audit purposes, and also may
8465 be used to improve code generation in some cases.
8469 @node Binding with Non-Ada Main Programs
8470 @subsection Binding with Non-Ada Main Programs
8473 In our description so far we have assumed that the main
8474 program is in Ada, and that the task of the binder is to generate a
8475 corresponding function @code{main} that invokes this Ada main
8476 program. GNAT also supports the building of executable programs where
8477 the main program is not in Ada, but some of the called routines are
8478 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8479 The following switch is used in this situation:
8483 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8484 No main program. The main program is not in Ada.
8488 In this case, most of the functions of the binder are still required,
8489 but instead of generating a main program, the binder generates a file
8490 containing the following callable routines:
8495 You must call this routine to initialize the Ada part of the program by
8496 calling the necessary elaboration routines. A call to @code{adainit} is
8497 required before the first call to an Ada subprogram.
8499 Note that it is assumed that the basic execution environment must be setup
8500 to be appropriate for Ada execution at the point where the first Ada
8501 subprogram is called. In particular, if the Ada code will do any
8502 floating-point operations, then the FPU must be setup in an appropriate
8503 manner. For the case of the x86, for example, full precision mode is
8504 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8505 that the FPU is in the right state.
8509 You must call this routine to perform any library-level finalization
8510 required by the Ada subprograms. A call to @code{adafinal} is required
8511 after the last call to an Ada subprogram, and before the program
8516 If the @option{^-n^/NOMAIN^} switch
8517 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8518 @cindex Binder, multiple input files
8519 is given, more than one ALI file may appear on
8520 the command line for @code{gnatbind}. The normal @dfn{closure}
8521 calculation is performed for each of the specified units. Calculating
8522 the closure means finding out the set of units involved by tracing
8523 @code{with} references. The reason it is necessary to be able to
8524 specify more than one ALI file is that a given program may invoke two or
8525 more quite separate groups of Ada units.
8527 The binder takes the name of its output file from the last specified ALI
8528 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8529 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8530 The output is an Ada unit in source form that can
8531 be compiled with GNAT unless the -C switch is used in which case the
8532 output is a C source file, which must be compiled using the C compiler.
8533 This compilation occurs automatically as part of the @command{gnatlink}
8536 Currently the GNAT run time requires a FPU using 80 bits mode
8537 precision. Under targets where this is not the default it is required to
8538 call GNAT.Float_Control.Reset before using floating point numbers (this
8539 include float computation, float input and output) in the Ada code. A
8540 side effect is that this could be the wrong mode for the foreign code
8541 where floating point computation could be broken after this call.
8543 @node Binding Programs with No Main Subprogram
8544 @subsection Binding Programs with No Main Subprogram
8547 It is possible to have an Ada program which does not have a main
8548 subprogram. This program will call the elaboration routines of all the
8549 packages, then the finalization routines.
8551 The following switch is used to bind programs organized in this manner:
8554 @item ^-z^/ZERO_MAIN^
8555 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8556 Normally the binder checks that the unit name given on the command line
8557 corresponds to a suitable main subprogram. When this switch is used,
8558 a list of ALI files can be given, and the execution of the program
8559 consists of elaboration of these units in an appropriate order. Note
8560 that the default wide character encoding method for standard Text_IO
8561 files is always set to Brackets if this switch is set (you can use
8563 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8566 @node Command-Line Access
8567 @section Command-Line Access
8570 The package @code{Ada.Command_Line} provides access to the command-line
8571 arguments and program name. In order for this interface to operate
8572 correctly, the two variables
8584 are declared in one of the GNAT library routines. These variables must
8585 be set from the actual @code{argc} and @code{argv} values passed to the
8586 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8587 generates the C main program to automatically set these variables.
8588 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8589 set these variables. If they are not set, the procedures in
8590 @code{Ada.Command_Line} will not be available, and any attempt to use
8591 them will raise @code{Constraint_Error}. If command line access is
8592 required, your main program must set @code{gnat_argc} and
8593 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8596 @node Search Paths for gnatbind
8597 @section Search Paths for @code{gnatbind}
8600 The binder takes the name of an ALI file as its argument and needs to
8601 locate source files as well as other ALI files to verify object consistency.
8603 For source files, it follows exactly the same search rules as @command{gcc}
8604 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8605 directories searched are:
8609 The directory containing the ALI file named in the command line, unless
8610 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8613 All directories specified by @option{^-I^/SEARCH^}
8614 switches on the @code{gnatbind}
8615 command line, in the order given.
8618 @findex ADA_PRJ_OBJECTS_FILE
8619 Each of the directories listed in the text file whose name is given
8620 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8623 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8624 driver when project files are used. It should not normally be set
8628 @findex ADA_OBJECTS_PATH
8629 Each of the directories listed in the value of the
8630 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8632 Construct this value
8633 exactly as the @env{PATH} environment variable: a list of directory
8634 names separated by colons (semicolons when working with the NT version
8638 Normally, define this value as a logical name containing a comma separated
8639 list of directory names.
8641 This variable can also be defined by means of an environment string
8642 (an argument to the HP C exec* set of functions).
8646 DEFINE ANOTHER_PATH FOO:[BAG]
8647 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8650 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8651 first, followed by the standard Ada
8652 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8653 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8654 (Text_IO, Sequential_IO, etc)
8655 instead of the standard Ada packages. Thus, in order to get the standard Ada
8656 packages by default, ADA_OBJECTS_PATH must be redefined.
8660 The content of the @file{ada_object_path} file which is part of the GNAT
8661 installation tree and is used to store standard libraries such as the
8662 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8665 @ref{Installing a library}
8670 In the binder the switch @option{^-I^/SEARCH^}
8671 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8672 is used to specify both source and
8673 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8674 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8675 instead if you want to specify
8676 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8677 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8678 if you want to specify library paths
8679 only. This means that for the binder
8680 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8681 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8682 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8683 The binder generates the bind file (a C language source file) in the
8684 current working directory.
8690 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8691 children make up the GNAT Run-Time Library, together with the package
8692 GNAT and its children, which contain a set of useful additional
8693 library functions provided by GNAT. The sources for these units are
8694 needed by the compiler and are kept together in one directory. The ALI
8695 files and object files generated by compiling the RTL are needed by the
8696 binder and the linker and are kept together in one directory, typically
8697 different from the directory containing the sources. In a normal
8698 installation, you need not specify these directory names when compiling
8699 or binding. Either the environment variables or the built-in defaults
8700 cause these files to be found.
8702 Besides simplifying access to the RTL, a major use of search paths is
8703 in compiling sources from multiple directories. This can make
8704 development environments much more flexible.
8706 @node Examples of gnatbind Usage
8707 @section Examples of @code{gnatbind} Usage
8710 This section contains a number of examples of using the GNAT binding
8711 utility @code{gnatbind}.
8714 @item gnatbind hello
8715 The main program @code{Hello} (source program in @file{hello.adb}) is
8716 bound using the standard switch settings. The generated main program is
8717 @file{b~hello.adb}. This is the normal, default use of the binder.
8720 @item gnatbind hello -o mainprog.adb
8723 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8725 The main program @code{Hello} (source program in @file{hello.adb}) is
8726 bound using the standard switch settings. The generated main program is
8727 @file{mainprog.adb} with the associated spec in
8728 @file{mainprog.ads}. Note that you must specify the body here not the
8729 spec, in the case where the output is in Ada. Note that if this option
8730 is used, then linking must be done manually, since gnatlink will not
8731 be able to find the generated file.
8734 @item gnatbind main -C -o mainprog.c -x
8737 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8739 The main program @code{Main} (source program in
8740 @file{main.adb}) is bound, excluding source files from the
8741 consistency checking, generating
8742 the file @file{mainprog.c}.
8745 @item gnatbind -x main_program -C -o mainprog.c
8746 This command is exactly the same as the previous example. Switches may
8747 appear anywhere in the command line, and single letter switches may be
8748 combined into a single switch.
8752 @item gnatbind -n math dbase -C -o ada-control.c
8755 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8757 The main program is in a language other than Ada, but calls to
8758 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8759 to @code{gnatbind} generates the file @file{ada-control.c} containing
8760 the @code{adainit} and @code{adafinal} routines to be called before and
8761 after accessing the Ada units.
8764 @c ------------------------------------
8765 @node Linking Using gnatlink
8766 @chapter Linking Using @command{gnatlink}
8767 @c ------------------------------------
8771 This chapter discusses @command{gnatlink}, a tool that links
8772 an Ada program and builds an executable file. This utility
8773 invokes the system linker ^(via the @command{gcc} command)^^
8774 with a correct list of object files and library references.
8775 @command{gnatlink} automatically determines the list of files and
8776 references for the Ada part of a program. It uses the binder file
8777 generated by the @command{gnatbind} to determine this list.
8779 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8780 driver (see @ref{The GNAT Driver and Project Files}).
8783 * Running gnatlink::
8784 * Switches for gnatlink::
8787 @node Running gnatlink
8788 @section Running @command{gnatlink}
8791 The form of the @command{gnatlink} command is
8794 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8795 @ovar{non-Ada objects} @ovar{linker options}
8799 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8801 or linker options) may be in any order, provided that no non-Ada object may
8802 be mistaken for a main @file{ALI} file.
8803 Any file name @file{F} without the @file{.ali}
8804 extension will be taken as the main @file{ALI} file if a file exists
8805 whose name is the concatenation of @file{F} and @file{.ali}.
8808 @file{@var{mainprog}.ali} references the ALI file of the main program.
8809 The @file{.ali} extension of this file can be omitted. From this
8810 reference, @command{gnatlink} locates the corresponding binder file
8811 @file{b~@var{mainprog}.adb} and, using the information in this file along
8812 with the list of non-Ada objects and linker options, constructs a
8813 linker command file to create the executable.
8815 The arguments other than the @command{gnatlink} switches and the main
8816 @file{ALI} file are passed to the linker uninterpreted.
8817 They typically include the names of
8818 object files for units written in other languages than Ada and any library
8819 references required to resolve references in any of these foreign language
8820 units, or in @code{Import} pragmas in any Ada units.
8822 @var{linker options} is an optional list of linker specific
8824 The default linker called by gnatlink is @command{gcc} which in
8825 turn calls the appropriate system linker.
8826 Standard options for the linker such as @option{-lmy_lib} or
8827 @option{-Ldir} can be added as is.
8828 For options that are not recognized by
8829 @command{gcc} as linker options, use the @command{gcc} switches
8830 @option{-Xlinker} or @option{-Wl,}.
8831 Refer to the GCC documentation for
8832 details. Here is an example showing how to generate a linker map:
8835 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8838 Using @var{linker options} it is possible to set the program stack and
8841 See @ref{Setting Stack Size from gnatlink} and
8842 @ref{Setting Heap Size from gnatlink}.
8845 @command{gnatlink} determines the list of objects required by the Ada
8846 program and prepends them to the list of objects passed to the linker.
8847 @command{gnatlink} also gathers any arguments set by the use of
8848 @code{pragma Linker_Options} and adds them to the list of arguments
8849 presented to the linker.
8852 @command{gnatlink} accepts the following types of extra files on the command
8853 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8854 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8855 handled according to their extension.
8858 @node Switches for gnatlink
8859 @section Switches for @command{gnatlink}
8862 The following switches are available with the @command{gnatlink} utility:
8868 @cindex @option{--version} @command{gnatlink}
8869 Display Copyright and version, then exit disregarding all other options.
8872 @cindex @option{--help} @command{gnatlink}
8873 If @option{--version} was not used, display usage, then exit disregarding
8876 @item ^-A^/BIND_FILE=ADA^
8877 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8878 The binder has generated code in Ada. This is the default.
8880 @item ^-C^/BIND_FILE=C^
8881 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8882 If instead of generating a file in Ada, the binder has generated one in
8883 C, then the linker needs to know about it. Use this switch to signal
8884 to @command{gnatlink} that the binder has generated C code rather than
8887 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8888 @cindex Command line length
8889 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8890 On some targets, the command line length is limited, and @command{gnatlink}
8891 will generate a separate file for the linker if the list of object files
8893 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8894 to be generated even if
8895 the limit is not exceeded. This is useful in some cases to deal with
8896 special situations where the command line length is exceeded.
8899 @cindex Debugging information, including
8900 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8901 The option to include debugging information causes the Ada bind file (in
8902 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8903 @option{^-g^/DEBUG^}.
8904 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8905 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8906 Without @option{^-g^/DEBUG^}, the binder removes these files by
8907 default. The same procedure apply if a C bind file was generated using
8908 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8909 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8911 @item ^-n^/NOCOMPILE^
8912 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8913 Do not compile the file generated by the binder. This may be used when
8914 a link is rerun with different options, but there is no need to recompile
8918 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8919 Causes additional information to be output, including a full list of the
8920 included object files. This switch option is most useful when you want
8921 to see what set of object files are being used in the link step.
8923 @item ^-v -v^/VERBOSE/VERBOSE^
8924 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8925 Very verbose mode. Requests that the compiler operate in verbose mode when
8926 it compiles the binder file, and that the system linker run in verbose mode.
8928 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8929 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8930 @var{exec-name} specifies an alternate name for the generated
8931 executable program. If this switch is omitted, the executable has the same
8932 name as the main unit. For example, @code{gnatlink try.ali} creates
8933 an executable called @file{^try^TRY.EXE^}.
8936 @item -b @var{target}
8937 @cindex @option{-b} (@command{gnatlink})
8938 Compile your program to run on @var{target}, which is the name of a
8939 system configuration. You must have a GNAT cross-compiler built if
8940 @var{target} is not the same as your host system.
8943 @cindex @option{-B} (@command{gnatlink})
8944 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8945 from @var{dir} instead of the default location. Only use this switch
8946 when multiple versions of the GNAT compiler are available.
8947 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
8948 for further details. You would normally use the @option{-b} or
8949 @option{-V} switch instead.
8951 @item --GCC=@var{compiler_name}
8952 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
8953 Program used for compiling the binder file. The default is
8954 @command{gcc}. You need to use quotes around @var{compiler_name} if
8955 @code{compiler_name} contains spaces or other separator characters.
8956 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
8957 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
8958 inserted after your command name. Thus in the above example the compiler
8959 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
8960 A limitation of this syntax is that the name and path name of the executable
8961 itself must not include any embedded spaces. If the compiler executable is
8962 different from the default one (gcc or <prefix>-gcc), then the back-end
8963 switches in the ALI file are not used to compile the binder generated source.
8964 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
8965 switches will be used for @option{--GCC="gcc -gnatv"}. If several
8966 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
8967 is taken into account. However, all the additional switches are also taken
8969 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8970 @option{--GCC="bar -x -y -z -t"}.
8972 @item --LINK=@var{name}
8973 @cindex @option{--LINK=} (@command{gnatlink})
8974 @var{name} is the name of the linker to be invoked. This is especially
8975 useful in mixed language programs since languages such as C++ require
8976 their own linker to be used. When this switch is omitted, the default
8977 name for the linker is @command{gcc}. When this switch is used, the
8978 specified linker is called instead of @command{gcc} with exactly the same
8979 parameters that would have been passed to @command{gcc} so if the desired
8980 linker requires different parameters it is necessary to use a wrapper
8981 script that massages the parameters before invoking the real linker. It
8982 may be useful to control the exact invocation by using the verbose
8988 @item /DEBUG=TRACEBACK
8989 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
8990 This qualifier causes sufficient information to be included in the
8991 executable file to allow a traceback, but does not include the full
8992 symbol information needed by the debugger.
8994 @item /IDENTIFICATION="<string>"
8995 @code{"<string>"} specifies the string to be stored in the image file
8996 identification field in the image header.
8997 It overrides any pragma @code{Ident} specified string.
8999 @item /NOINHIBIT-EXEC
9000 Generate the executable file even if there are linker warnings.
9002 @item /NOSTART_FILES
9003 Don't link in the object file containing the ``main'' transfer address.
9004 Used when linking with a foreign language main program compiled with an
9008 Prefer linking with object libraries over sharable images, even without
9014 @node The GNAT Make Program gnatmake
9015 @chapter The GNAT Make Program @command{gnatmake}
9019 * Running gnatmake::
9020 * Switches for gnatmake::
9021 * Mode Switches for gnatmake::
9022 * Notes on the Command Line::
9023 * How gnatmake Works::
9024 * Examples of gnatmake Usage::
9027 A typical development cycle when working on an Ada program consists of
9028 the following steps:
9032 Edit some sources to fix bugs.
9038 Compile all sources affected.
9048 The third step can be tricky, because not only do the modified files
9049 @cindex Dependency rules
9050 have to be compiled, but any files depending on these files must also be
9051 recompiled. The dependency rules in Ada can be quite complex, especially
9052 in the presence of overloading, @code{use} clauses, generics and inlined
9055 @command{gnatmake} automatically takes care of the third and fourth steps
9056 of this process. It determines which sources need to be compiled,
9057 compiles them, and binds and links the resulting object files.
9059 Unlike some other Ada make programs, the dependencies are always
9060 accurately recomputed from the new sources. The source based approach of
9061 the GNAT compilation model makes this possible. This means that if
9062 changes to the source program cause corresponding changes in
9063 dependencies, they will always be tracked exactly correctly by
9066 @node Running gnatmake
9067 @section Running @command{gnatmake}
9070 The usual form of the @command{gnatmake} command is
9073 $ gnatmake @ovar{switches} @var{file_name}
9074 @ovar{file_names} @ovar{mode_switches}
9078 The only required argument is one @var{file_name}, which specifies
9079 a compilation unit that is a main program. Several @var{file_names} can be
9080 specified: this will result in several executables being built.
9081 If @code{switches} are present, they can be placed before the first
9082 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
9083 If @var{mode_switches} are present, they must always be placed after
9084 the last @var{file_name} and all @code{switches}.
9086 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
9087 extension may be omitted from the @var{file_name} arguments. However, if
9088 you are using non-standard extensions, then it is required that the
9089 extension be given. A relative or absolute directory path can be
9090 specified in a @var{file_name}, in which case, the input source file will
9091 be searched for in the specified directory only. Otherwise, the input
9092 source file will first be searched in the directory where
9093 @command{gnatmake} was invoked and if it is not found, it will be search on
9094 the source path of the compiler as described in
9095 @ref{Search Paths and the Run-Time Library (RTL)}.
9097 All @command{gnatmake} output (except when you specify
9098 @option{^-M^/DEPENDENCIES_LIST^}) is to
9099 @file{stderr}. The output produced by the
9100 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
9103 @node Switches for gnatmake
9104 @section Switches for @command{gnatmake}
9107 You may specify any of the following switches to @command{gnatmake}:
9113 @cindex @option{--version} @command{gnatmake}
9114 Display Copyright and version, then exit disregarding all other options.
9117 @cindex @option{--help} @command{gnatmake}
9118 If @option{--version} was not used, display usage, then exit disregarding
9122 @item --GCC=@var{compiler_name}
9123 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
9124 Program used for compiling. The default is `@command{gcc}'. You need to use
9125 quotes around @var{compiler_name} if @code{compiler_name} contains
9126 spaces or other separator characters. As an example @option{--GCC="foo -x
9127 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
9128 compiler. A limitation of this syntax is that the name and path name of
9129 the executable itself must not include any embedded spaces. Note that
9130 switch @option{-c} is always inserted after your command name. Thus in the
9131 above example the compiler command that will be used by @command{gnatmake}
9132 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
9133 used, only the last @var{compiler_name} is taken into account. However,
9134 all the additional switches are also taken into account. Thus,
9135 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9136 @option{--GCC="bar -x -y -z -t"}.
9138 @item --GNATBIND=@var{binder_name}
9139 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
9140 Program used for binding. The default is `@code{gnatbind}'. You need to
9141 use quotes around @var{binder_name} if @var{binder_name} contains spaces
9142 or other separator characters. As an example @option{--GNATBIND="bar -x
9143 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
9144 binder. Binder switches that are normally appended by @command{gnatmake}
9145 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
9146 A limitation of this syntax is that the name and path name of the executable
9147 itself must not include any embedded spaces.
9149 @item --GNATLINK=@var{linker_name}
9150 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
9151 Program used for linking. The default is `@command{gnatlink}'. You need to
9152 use quotes around @var{linker_name} if @var{linker_name} contains spaces
9153 or other separator characters. As an example @option{--GNATLINK="lan -x
9154 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
9155 linker. Linker switches that are normally appended by @command{gnatmake} to
9156 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
9157 A limitation of this syntax is that the name and path name of the executable
9158 itself must not include any embedded spaces.
9162 @item ^-a^/ALL_FILES^
9163 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
9164 Consider all files in the make process, even the GNAT internal system
9165 files (for example, the predefined Ada library files), as well as any
9166 locked files. Locked files are files whose ALI file is write-protected.
9168 @command{gnatmake} does not check these files,
9169 because the assumption is that the GNAT internal files are properly up
9170 to date, and also that any write protected ALI files have been properly
9171 installed. Note that if there is an installation problem, such that one
9172 of these files is not up to date, it will be properly caught by the
9174 You may have to specify this switch if you are working on GNAT
9175 itself. The switch @option{^-a^/ALL_FILES^} is also useful
9176 in conjunction with @option{^-f^/FORCE_COMPILE^}
9177 if you need to recompile an entire application,
9178 including run-time files, using special configuration pragmas,
9179 such as a @code{Normalize_Scalars} pragma.
9182 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
9185 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
9188 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
9191 @item ^-b^/ACTIONS=BIND^
9192 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
9193 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
9194 compilation and binding, but no link.
9195 Can be combined with @option{^-l^/ACTIONS=LINK^}
9196 to do binding and linking. When not combined with
9197 @option{^-c^/ACTIONS=COMPILE^}
9198 all the units in the closure of the main program must have been previously
9199 compiled and must be up to date. The root unit specified by @var{file_name}
9200 may be given without extension, with the source extension or, if no GNAT
9201 Project File is specified, with the ALI file extension.
9203 @item ^-c^/ACTIONS=COMPILE^
9204 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
9205 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
9206 is also specified. Do not perform linking, except if both
9207 @option{^-b^/ACTIONS=BIND^} and
9208 @option{^-l^/ACTIONS=LINK^} are also specified.
9209 If the root unit specified by @var{file_name} is not a main unit, this is the
9210 default. Otherwise @command{gnatmake} will attempt binding and linking
9211 unless all objects are up to date and the executable is more recent than
9215 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
9216 Use a temporary mapping file. A mapping file is a way to communicate to the
9217 compiler two mappings: from unit names to file names (without any directory
9218 information) and from file names to path names (with full directory
9219 information). These mappings are used by the compiler to short-circuit the path
9220 search. When @command{gnatmake} is invoked with this switch, it will create
9221 a temporary mapping file, initially populated by the project manager,
9222 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
9223 Each invocation of the compiler will add the newly accessed sources to the
9224 mapping file. This will improve the source search during the next invocation
9227 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
9228 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
9229 Use a specific mapping file. The file, specified as a path name (absolute or
9230 relative) by this switch, should already exist, otherwise the switch is
9231 ineffective. The specified mapping file will be communicated to the compiler.
9232 This switch is not compatible with a project file
9233 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9234 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9236 @item ^-d^/DISPLAY_PROGRESS^
9237 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9238 Display progress for each source, up to date or not, as a single line
9241 completed x out of y (zz%)
9244 If the file needs to be compiled this is displayed after the invocation of
9245 the compiler. These lines are displayed even in quiet output mode.
9247 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9248 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9249 Put all object files and ALI file in directory @var{dir}.
9250 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9251 and ALI files go in the current working directory.
9253 This switch cannot be used when using a project file.
9257 @cindex @option{-eL} (@command{gnatmake})
9258 Follow all symbolic links when processing project files.
9261 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9262 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9263 Output the commands for the compiler, the binder and the linker
9264 on ^standard output^SYS$OUTPUT^,
9265 instead of ^standard error^SYS$ERROR^.
9267 @item ^-f^/FORCE_COMPILE^
9268 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9269 Force recompilations. Recompile all sources, even though some object
9270 files may be up to date, but don't recompile predefined or GNAT internal
9271 files or locked files (files with a write-protected ALI file),
9272 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9274 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9275 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9276 When using project files, if some errors or warnings are detected during
9277 parsing and verbose mode is not in effect (no use of switch
9278 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9279 file, rather than its simple file name.
9282 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9283 Enable debugging. This switch is simply passed to the compiler and to the
9286 @item ^-i^/IN_PLACE^
9287 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9288 In normal mode, @command{gnatmake} compiles all object files and ALI files
9289 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9290 then instead object files and ALI files that already exist are overwritten
9291 in place. This means that once a large project is organized into separate
9292 directories in the desired manner, then @command{gnatmake} will automatically
9293 maintain and update this organization. If no ALI files are found on the
9294 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9295 the new object and ALI files are created in the
9296 directory containing the source being compiled. If another organization
9297 is desired, where objects and sources are kept in different directories,
9298 a useful technique is to create dummy ALI files in the desired directories.
9299 When detecting such a dummy file, @command{gnatmake} will be forced to
9300 recompile the corresponding source file, and it will be put the resulting
9301 object and ALI files in the directory where it found the dummy file.
9303 @item ^-j^/PROCESSES=^@var{n}
9304 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9305 @cindex Parallel make
9306 Use @var{n} processes to carry out the (re)compilations. On a
9307 multiprocessor machine compilations will occur in parallel. In the
9308 event of compilation errors, messages from various compilations might
9309 get interspersed (but @command{gnatmake} will give you the full ordered
9310 list of failing compiles at the end). If this is problematic, rerun
9311 the make process with n set to 1 to get a clean list of messages.
9313 @item ^-k^/CONTINUE_ON_ERROR^
9314 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9315 Keep going. Continue as much as possible after a compilation error. To
9316 ease the programmer's task in case of compilation errors, the list of
9317 sources for which the compile fails is given when @command{gnatmake}
9320 If @command{gnatmake} is invoked with several @file{file_names} and with this
9321 switch, if there are compilation errors when building an executable,
9322 @command{gnatmake} will not attempt to build the following executables.
9324 @item ^-l^/ACTIONS=LINK^
9325 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9326 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9327 and linking. Linking will not be performed if combined with
9328 @option{^-c^/ACTIONS=COMPILE^}
9329 but not with @option{^-b^/ACTIONS=BIND^}.
9330 When not combined with @option{^-b^/ACTIONS=BIND^}
9331 all the units in the closure of the main program must have been previously
9332 compiled and must be up to date, and the main program needs to have been bound.
9333 The root unit specified by @var{file_name}
9334 may be given without extension, with the source extension or, if no GNAT
9335 Project File is specified, with the ALI file extension.
9337 @item ^-m^/MINIMAL_RECOMPILATION^
9338 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9339 Specify that the minimum necessary amount of recompilations
9340 be performed. In this mode @command{gnatmake} ignores time
9341 stamp differences when the only
9342 modifications to a source file consist in adding/removing comments,
9343 empty lines, spaces or tabs. This means that if you have changed the
9344 comments in a source file or have simply reformatted it, using this
9345 switch will tell @command{gnatmake} not to recompile files that depend on it
9346 (provided other sources on which these files depend have undergone no
9347 semantic modifications). Note that the debugging information may be
9348 out of date with respect to the sources if the @option{-m} switch causes
9349 a compilation to be switched, so the use of this switch represents a
9350 trade-off between compilation time and accurate debugging information.
9352 @item ^-M^/DEPENDENCIES_LIST^
9353 @cindex Dependencies, producing list
9354 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9355 Check if all objects are up to date. If they are, output the object
9356 dependences to @file{stdout} in a form that can be directly exploited in
9357 a @file{Makefile}. By default, each source file is prefixed with its
9358 (relative or absolute) directory name. This name is whatever you
9359 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9360 and @option{^-I^/SEARCH^} switches. If you use
9361 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9362 @option{^-q^/QUIET^}
9363 (see below), only the source file names,
9364 without relative paths, are output. If you just specify the
9365 @option{^-M^/DEPENDENCIES_LIST^}
9366 switch, dependencies of the GNAT internal system files are omitted. This
9367 is typically what you want. If you also specify
9368 the @option{^-a^/ALL_FILES^} switch,
9369 dependencies of the GNAT internal files are also listed. Note that
9370 dependencies of the objects in external Ada libraries (see switch
9371 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9374 @item ^-n^/DO_OBJECT_CHECK^
9375 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9376 Don't compile, bind, or link. Checks if all objects are up to date.
9377 If they are not, the full name of the first file that needs to be
9378 recompiled is printed.
9379 Repeated use of this option, followed by compiling the indicated source
9380 file, will eventually result in recompiling all required units.
9382 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9383 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9384 Output executable name. The name of the final executable program will be
9385 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9386 name for the executable will be the name of the input file in appropriate form
9387 for an executable file on the host system.
9389 This switch cannot be used when invoking @command{gnatmake} with several
9392 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9393 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9394 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9395 automatically missing object directories, library directories and exec
9398 @item ^-P^/PROJECT_FILE=^@var{project}
9399 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9400 Use project file @var{project}. Only one such switch can be used.
9401 @xref{gnatmake and Project Files}.
9404 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9405 Quiet. When this flag is not set, the commands carried out by
9406 @command{gnatmake} are displayed.
9408 @item ^-s^/SWITCH_CHECK/^
9409 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9410 Recompile if compiler switches have changed since last compilation.
9411 All compiler switches but -I and -o are taken into account in the
9413 orders between different ``first letter'' switches are ignored, but
9414 orders between same switches are taken into account. For example,
9415 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9416 is equivalent to @option{-O -g}.
9418 This switch is recommended when Integrated Preprocessing is used.
9421 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9422 Unique. Recompile at most the main files. It implies -c. Combined with
9423 -f, it is equivalent to calling the compiler directly. Note that using
9424 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9425 (@pxref{Project Files and Main Subprograms}).
9427 @item ^-U^/ALL_PROJECTS^
9428 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9429 When used without a project file or with one or several mains on the command
9430 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9431 on the command line, all sources of all project files are checked and compiled
9432 if not up to date, and libraries are rebuilt, if necessary.
9435 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9436 Verbose. Display the reason for all recompilations @command{gnatmake}
9437 decides are necessary, with the highest verbosity level.
9439 @item ^-vl^/LOW_VERBOSITY^
9440 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9441 Verbosity level Low. Display fewer lines than in verbosity Medium.
9443 @item ^-vm^/MEDIUM_VERBOSITY^
9444 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9445 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9447 @item ^-vh^/HIGH_VERBOSITY^
9448 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9449 Verbosity level High. Equivalent to ^-v^/REASONS^.
9451 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9452 Indicate the verbosity of the parsing of GNAT project files.
9453 @xref{Switches Related to Project Files}.
9455 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9456 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9457 Indicate that sources that are not part of any Project File may be compiled.
9458 Normally, when using Project Files, only sources that are part of a Project
9459 File may be compile. When this switch is used, a source outside of all Project
9460 Files may be compiled. The ALI file and the object file will be put in the
9461 object directory of the main Project. The compilation switches used will only
9462 be those specified on the command line. Even when
9463 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9464 command line need to be sources of a project file.
9466 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9467 Indicate that external variable @var{name} has the value @var{value}.
9468 The Project Manager will use this value for occurrences of
9469 @code{external(name)} when parsing the project file.
9470 @xref{Switches Related to Project Files}.
9473 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9474 No main subprogram. Bind and link the program even if the unit name
9475 given on the command line is a package name. The resulting executable
9476 will execute the elaboration routines of the package and its closure,
9477 then the finalization routines.
9482 @item @command{gcc} @asis{switches}
9484 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9485 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9488 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9489 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9490 automatically treated as a compiler switch, and passed on to all
9491 compilations that are carried out.
9496 Source and library search path switches:
9500 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9501 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9502 When looking for source files also look in directory @var{dir}.
9503 The order in which source files search is undertaken is
9504 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9506 @item ^-aL^/SKIP_MISSING=^@var{dir}
9507 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9508 Consider @var{dir} as being an externally provided Ada library.
9509 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9510 files have been located in directory @var{dir}. This allows you to have
9511 missing bodies for the units in @var{dir} and to ignore out of date bodies
9512 for the same units. You still need to specify
9513 the location of the specs for these units by using the switches
9514 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9515 or @option{^-I^/SEARCH=^@var{dir}}.
9516 Note: this switch is provided for compatibility with previous versions
9517 of @command{gnatmake}. The easier method of causing standard libraries
9518 to be excluded from consideration is to write-protect the corresponding
9521 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9522 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9523 When searching for library and object files, look in directory
9524 @var{dir}. The order in which library files are searched is described in
9525 @ref{Search Paths for gnatbind}.
9527 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9528 @cindex Search paths, for @command{gnatmake}
9529 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9530 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9531 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9533 @item ^-I^/SEARCH=^@var{dir}
9534 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9535 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9536 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9538 @item ^-I-^/NOCURRENT_DIRECTORY^
9539 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9540 @cindex Source files, suppressing search
9541 Do not look for source files in the directory containing the source
9542 file named in the command line.
9543 Do not look for ALI or object files in the directory
9544 where @command{gnatmake} was invoked.
9546 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9547 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9548 @cindex Linker libraries
9549 Add directory @var{dir} to the list of directories in which the linker
9550 will search for libraries. This is equivalent to
9551 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9553 Furthermore, under Windows, the sources pointed to by the libraries path
9554 set in the registry are not searched for.
9558 @cindex @option{-nostdinc} (@command{gnatmake})
9559 Do not look for source files in the system default directory.
9562 @cindex @option{-nostdlib} (@command{gnatmake})
9563 Do not look for library files in the system default directory.
9565 @item --RTS=@var{rts-path}
9566 @cindex @option{--RTS} (@command{gnatmake})
9567 Specifies the default location of the runtime library. GNAT looks for the
9569 in the following directories, and stops as soon as a valid runtime is found
9570 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9571 @file{ada_object_path} present):
9574 @item <current directory>/$rts_path
9576 @item <default-search-dir>/$rts_path
9578 @item <default-search-dir>/rts-$rts_path
9582 The selected path is handled like a normal RTS path.
9586 @node Mode Switches for gnatmake
9587 @section Mode Switches for @command{gnatmake}
9590 The mode switches (referred to as @code{mode_switches}) allow the
9591 inclusion of switches that are to be passed to the compiler itself, the
9592 binder or the linker. The effect of a mode switch is to cause all
9593 subsequent switches up to the end of the switch list, or up to the next
9594 mode switch, to be interpreted as switches to be passed on to the
9595 designated component of GNAT.
9599 @item -cargs @var{switches}
9600 @cindex @option{-cargs} (@command{gnatmake})
9601 Compiler switches. Here @var{switches} is a list of switches
9602 that are valid switches for @command{gcc}. They will be passed on to
9603 all compile steps performed by @command{gnatmake}.
9605 @item -bargs @var{switches}
9606 @cindex @option{-bargs} (@command{gnatmake})
9607 Binder switches. Here @var{switches} is a list of switches
9608 that are valid switches for @code{gnatbind}. They will be passed on to
9609 all bind steps performed by @command{gnatmake}.
9611 @item -largs @var{switches}
9612 @cindex @option{-largs} (@command{gnatmake})
9613 Linker switches. Here @var{switches} is a list of switches
9614 that are valid switches for @command{gnatlink}. They will be passed on to
9615 all link steps performed by @command{gnatmake}.
9617 @item -margs @var{switches}
9618 @cindex @option{-margs} (@command{gnatmake})
9619 Make switches. The switches are directly interpreted by @command{gnatmake},
9620 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9624 @node Notes on the Command Line
9625 @section Notes on the Command Line
9628 This section contains some additional useful notes on the operation
9629 of the @command{gnatmake} command.
9633 @cindex Recompilation, by @command{gnatmake}
9634 If @command{gnatmake} finds no ALI files, it recompiles the main program
9635 and all other units required by the main program.
9636 This means that @command{gnatmake}
9637 can be used for the initial compile, as well as during subsequent steps of
9638 the development cycle.
9641 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9642 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9643 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9647 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9648 is used to specify both source and
9649 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9650 instead if you just want to specify
9651 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9652 if you want to specify library paths
9656 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9657 This may conveniently be used to exclude standard libraries from
9658 consideration and in particular it means that the use of the
9659 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9660 unless @option{^-a^/ALL_FILES^} is also specified.
9663 @command{gnatmake} has been designed to make the use of Ada libraries
9664 particularly convenient. Assume you have an Ada library organized
9665 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9666 of your Ada compilation units,
9667 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9668 specs of these units, but no bodies. Then to compile a unit
9669 stored in @code{main.adb}, which uses this Ada library you would just type
9673 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9676 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9677 /SKIP_MISSING=@i{[OBJ_DIR]} main
9682 Using @command{gnatmake} along with the
9683 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9684 switch provides a mechanism for avoiding unnecessary recompilations. Using
9686 you can update the comments/format of your
9687 source files without having to recompile everything. Note, however, that
9688 adding or deleting lines in a source files may render its debugging
9689 info obsolete. If the file in question is a spec, the impact is rather
9690 limited, as that debugging info will only be useful during the
9691 elaboration phase of your program. For bodies the impact can be more
9692 significant. In all events, your debugger will warn you if a source file
9693 is more recent than the corresponding object, and alert you to the fact
9694 that the debugging information may be out of date.
9697 @node How gnatmake Works
9698 @section How @command{gnatmake} Works
9701 Generally @command{gnatmake} automatically performs all necessary
9702 recompilations and you don't need to worry about how it works. However,
9703 it may be useful to have some basic understanding of the @command{gnatmake}
9704 approach and in particular to understand how it uses the results of
9705 previous compilations without incorrectly depending on them.
9707 First a definition: an object file is considered @dfn{up to date} if the
9708 corresponding ALI file exists and if all the source files listed in the
9709 dependency section of this ALI file have time stamps matching those in
9710 the ALI file. This means that neither the source file itself nor any
9711 files that it depends on have been modified, and hence there is no need
9712 to recompile this file.
9714 @command{gnatmake} works by first checking if the specified main unit is up
9715 to date. If so, no compilations are required for the main unit. If not,
9716 @command{gnatmake} compiles the main program to build a new ALI file that
9717 reflects the latest sources. Then the ALI file of the main unit is
9718 examined to find all the source files on which the main program depends,
9719 and @command{gnatmake} recursively applies the above procedure on all these
9722 This process ensures that @command{gnatmake} only trusts the dependencies
9723 in an existing ALI file if they are known to be correct. Otherwise it
9724 always recompiles to determine a new, guaranteed accurate set of
9725 dependencies. As a result the program is compiled ``upside down'' from what may
9726 be more familiar as the required order of compilation in some other Ada
9727 systems. In particular, clients are compiled before the units on which
9728 they depend. The ability of GNAT to compile in any order is critical in
9729 allowing an order of compilation to be chosen that guarantees that
9730 @command{gnatmake} will recompute a correct set of new dependencies if
9733 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9734 imported by several of the executables, it will be recompiled at most once.
9736 Note: when using non-standard naming conventions
9737 (@pxref{Using Other File Names}), changing through a configuration pragmas
9738 file the version of a source and invoking @command{gnatmake} to recompile may
9739 have no effect, if the previous version of the source is still accessible
9740 by @command{gnatmake}. It may be necessary to use the switch
9741 ^-f^/FORCE_COMPILE^.
9743 @node Examples of gnatmake Usage
9744 @section Examples of @command{gnatmake} Usage
9747 @item gnatmake hello.adb
9748 Compile all files necessary to bind and link the main program
9749 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9750 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9752 @item gnatmake main1 main2 main3
9753 Compile all files necessary to bind and link the main programs
9754 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9755 (containing unit @code{Main2}) and @file{main3.adb}
9756 (containing unit @code{Main3}) and bind and link the resulting object files
9757 to generate three executable files @file{^main1^MAIN1.EXE^},
9758 @file{^main2^MAIN2.EXE^}
9759 and @file{^main3^MAIN3.EXE^}.
9762 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9766 @item gnatmake Main_Unit /QUIET
9767 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9768 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9770 Compile all files necessary to bind and link the main program unit
9771 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9772 be done with optimization level 2 and the order of elaboration will be
9773 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9774 displaying commands it is executing.
9777 @c *************************
9778 @node Improving Performance
9779 @chapter Improving Performance
9780 @cindex Improving performance
9783 This chapter presents several topics related to program performance.
9784 It first describes some of the tradeoffs that need to be considered
9785 and some of the techniques for making your program run faster.
9786 It then documents the @command{gnatelim} tool and unused subprogram/data
9787 elimination feature, which can reduce the size of program executables.
9789 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9790 driver (see @ref{The GNAT Driver and Project Files}).
9794 * Performance Considerations::
9795 * Text_IO Suggestions::
9796 * Reducing Size of Ada Executables with gnatelim::
9797 * Reducing Size of Executables with unused subprogram/data elimination::
9801 @c *****************************
9802 @node Performance Considerations
9803 @section Performance Considerations
9806 The GNAT system provides a number of options that allow a trade-off
9811 performance of the generated code
9814 speed of compilation
9817 minimization of dependences and recompilation
9820 the degree of run-time checking.
9824 The defaults (if no options are selected) aim at improving the speed
9825 of compilation and minimizing dependences, at the expense of performance
9826 of the generated code:
9833 no inlining of subprogram calls
9836 all run-time checks enabled except overflow and elaboration checks
9840 These options are suitable for most program development purposes. This
9841 chapter describes how you can modify these choices, and also provides
9842 some guidelines on debugging optimized code.
9845 * Controlling Run-Time Checks::
9846 * Use of Restrictions::
9847 * Optimization Levels::
9848 * Debugging Optimized Code::
9849 * Inlining of Subprograms::
9850 * Other Optimization Switches::
9851 * Optimization and Strict Aliasing::
9854 * Coverage Analysis::
9858 @node Controlling Run-Time Checks
9859 @subsection Controlling Run-Time Checks
9862 By default, GNAT generates all run-time checks, except integer overflow
9863 checks, stack overflow checks, and checks for access before elaboration on
9864 subprogram calls. The latter are not required in default mode, because all
9865 necessary checking is done at compile time.
9866 @cindex @option{-gnatp} (@command{gcc})
9867 @cindex @option{-gnato} (@command{gcc})
9868 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9869 be modified. @xref{Run-Time Checks}.
9871 Our experience is that the default is suitable for most development
9874 We treat integer overflow specially because these
9875 are quite expensive and in our experience are not as important as other
9876 run-time checks in the development process. Note that division by zero
9877 is not considered an overflow check, and divide by zero checks are
9878 generated where required by default.
9880 Elaboration checks are off by default, and also not needed by default, since
9881 GNAT uses a static elaboration analysis approach that avoids the need for
9882 run-time checking. This manual contains a full chapter discussing the issue
9883 of elaboration checks, and if the default is not satisfactory for your use,
9884 you should read this chapter.
9886 For validity checks, the minimal checks required by the Ada Reference
9887 Manual (for case statements and assignments to array elements) are on
9888 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9889 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9890 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9891 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9892 are also suppressed entirely if @option{-gnatp} is used.
9894 @cindex Overflow checks
9895 @cindex Checks, overflow
9898 @cindex pragma Suppress
9899 @cindex pragma Unsuppress
9900 Note that the setting of the switches controls the default setting of
9901 the checks. They may be modified using either @code{pragma Suppress} (to
9902 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9903 checks) in the program source.
9905 @node Use of Restrictions
9906 @subsection Use of Restrictions
9909 The use of pragma Restrictions allows you to control which features are
9910 permitted in your program. Apart from the obvious point that if you avoid
9911 relatively expensive features like finalization (enforceable by the use
9912 of pragma Restrictions (No_Finalization), the use of this pragma does not
9913 affect the generated code in most cases.
9915 One notable exception to this rule is that the possibility of task abort
9916 results in some distributed overhead, particularly if finalization or
9917 exception handlers are used. The reason is that certain sections of code
9918 have to be marked as non-abortable.
9920 If you use neither the @code{abort} statement, nor asynchronous transfer
9921 of control (@code{select @dots{} then abort}), then this distributed overhead
9922 is removed, which may have a general positive effect in improving
9923 overall performance. Especially code involving frequent use of tasking
9924 constructs and controlled types will show much improved performance.
9925 The relevant restrictions pragmas are
9927 @smallexample @c ada
9928 pragma Restrictions (No_Abort_Statements);
9929 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9933 It is recommended that these restriction pragmas be used if possible. Note
9934 that this also means that you can write code without worrying about the
9935 possibility of an immediate abort at any point.
9937 @node Optimization Levels
9938 @subsection Optimization Levels
9939 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9942 Without any optimization ^option,^qualifier,^
9943 the compiler's goal is to reduce the cost of
9944 compilation and to make debugging produce the expected results.
9945 Statements are independent: if you stop the program with a breakpoint between
9946 statements, you can then assign a new value to any variable or change
9947 the program counter to any other statement in the subprogram and get exactly
9948 the results you would expect from the source code.
9950 Turning on optimization makes the compiler attempt to improve the
9951 performance and/or code size at the expense of compilation time and
9952 possibly the ability to debug the program.
9955 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
9956 the last such option is the one that is effective.
9959 The default is optimization off. This results in the fastest compile
9960 times, but GNAT makes absolutely no attempt to optimize, and the
9961 generated programs are considerably larger and slower than when
9962 optimization is enabled. You can use the
9964 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
9965 @option{-O2}, @option{-O3}, and @option{-Os})
9968 @code{OPTIMIZE} qualifier
9970 to @command{gcc} to control the optimization level:
9973 @item ^-O0^/OPTIMIZE=NONE^
9974 No optimization (the default);
9975 generates unoptimized code but has
9976 the fastest compilation time.
9978 Note that many other compilers do fairly extensive optimization
9979 even if ``no optimization'' is specified. With gcc, it is
9980 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
9981 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
9982 really does mean no optimization at all. This difference between
9983 gcc and other compilers should be kept in mind when doing
9984 performance comparisons.
9986 @item ^-O1^/OPTIMIZE=SOME^
9987 Moderate optimization;
9988 optimizes reasonably well but does not
9989 degrade compilation time significantly.
9991 @item ^-O2^/OPTIMIZE=ALL^
9993 @itemx /OPTIMIZE=DEVELOPMENT
9996 generates highly optimized code and has
9997 the slowest compilation time.
9999 @item ^-O3^/OPTIMIZE=INLINING^
10000 Full optimization as in @option{-O2},
10001 and also attempts automatic inlining of small
10002 subprograms within a unit (@pxref{Inlining of Subprograms}).
10004 @item ^-Os^/OPTIMIZE=SPACE^
10005 Optimize space usage of resulting program.
10009 Higher optimization levels perform more global transformations on the
10010 program and apply more expensive analysis algorithms in order to generate
10011 faster and more compact code. The price in compilation time, and the
10012 resulting improvement in execution time,
10013 both depend on the particular application and the hardware environment.
10014 You should experiment to find the best level for your application.
10016 Since the precise set of optimizations done at each level will vary from
10017 release to release (and sometime from target to target), it is best to think
10018 of the optimization settings in general terms.
10019 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
10020 the GNU Compiler Collection (GCC)}, for details about
10021 ^the @option{-O} settings and a number of @option{-f} options that^how to^
10022 individually enable or disable specific optimizations.
10024 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
10025 been tested extensively at all optimization levels. There are some bugs
10026 which appear only with optimization turned on, but there have also been
10027 bugs which show up only in @emph{unoptimized} code. Selecting a lower
10028 level of optimization does not improve the reliability of the code
10029 generator, which in practice is highly reliable at all optimization
10032 Note regarding the use of @option{-O3}: The use of this optimization level
10033 is generally discouraged with GNAT, since it often results in larger
10034 executables which run more slowly. See further discussion of this point
10035 in @ref{Inlining of Subprograms}.
10037 @node Debugging Optimized Code
10038 @subsection Debugging Optimized Code
10039 @cindex Debugging optimized code
10040 @cindex Optimization and debugging
10043 Although it is possible to do a reasonable amount of debugging at
10045 nonzero optimization levels,
10046 the higher the level the more likely that
10049 @option{/OPTIMIZE} settings other than @code{NONE},
10050 such settings will make it more likely that
10052 source-level constructs will have been eliminated by optimization.
10053 For example, if a loop is strength-reduced, the loop
10054 control variable may be completely eliminated and thus cannot be
10055 displayed in the debugger.
10056 This can only happen at @option{-O2} or @option{-O3}.
10057 Explicit temporary variables that you code might be eliminated at
10058 ^level^setting^ @option{-O1} or higher.
10060 The use of the @option{^-g^/DEBUG^} switch,
10061 @cindex @option{^-g^/DEBUG^} (@command{gcc})
10062 which is needed for source-level debugging,
10063 affects the size of the program executable on disk,
10064 and indeed the debugging information can be quite large.
10065 However, it has no effect on the generated code (and thus does not
10066 degrade performance)
10068 Since the compiler generates debugging tables for a compilation unit before
10069 it performs optimizations, the optimizing transformations may invalidate some
10070 of the debugging data. You therefore need to anticipate certain
10071 anomalous situations that may arise while debugging optimized code.
10072 These are the most common cases:
10076 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
10078 the PC bouncing back and forth in the code. This may result from any of
10079 the following optimizations:
10083 @i{Common subexpression elimination:} using a single instance of code for a
10084 quantity that the source computes several times. As a result you
10085 may not be able to stop on what looks like a statement.
10088 @i{Invariant code motion:} moving an expression that does not change within a
10089 loop, to the beginning of the loop.
10092 @i{Instruction scheduling:} moving instructions so as to
10093 overlap loads and stores (typically) with other code, or in
10094 general to move computations of values closer to their uses. Often
10095 this causes you to pass an assignment statement without the assignment
10096 happening and then later bounce back to the statement when the
10097 value is actually needed. Placing a breakpoint on a line of code
10098 and then stepping over it may, therefore, not always cause all the
10099 expected side-effects.
10103 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
10104 two identical pieces of code are merged and the program counter suddenly
10105 jumps to a statement that is not supposed to be executed, simply because
10106 it (and the code following) translates to the same thing as the code
10107 that @emph{was} supposed to be executed. This effect is typically seen in
10108 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
10109 a @code{break} in a C @code{^switch^switch^} statement.
10112 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
10113 There are various reasons for this effect:
10117 In a subprogram prologue, a parameter may not yet have been moved to its
10121 A variable may be dead, and its register re-used. This is
10122 probably the most common cause.
10125 As mentioned above, the assignment of a value to a variable may
10129 A variable may be eliminated entirely by value propagation or
10130 other means. In this case, GCC may incorrectly generate debugging
10131 information for the variable
10135 In general, when an unexpected value appears for a local variable or parameter
10136 you should first ascertain if that value was actually computed by
10137 your program, as opposed to being incorrectly reported by the debugger.
10139 array elements in an object designated by an access value
10140 are generally less of a problem, once you have ascertained that the access
10142 Typically, this means checking variables in the preceding code and in the
10143 calling subprogram to verify that the value observed is explainable from other
10144 values (one must apply the procedure recursively to those
10145 other values); or re-running the code and stopping a little earlier
10146 (perhaps before the call) and stepping to better see how the variable obtained
10147 the value in question; or continuing to step @emph{from} the point of the
10148 strange value to see if code motion had simply moved the variable's
10153 In light of such anomalies, a recommended technique is to use @option{-O0}
10154 early in the software development cycle, when extensive debugging capabilities
10155 are most needed, and then move to @option{-O1} and later @option{-O2} as
10156 the debugger becomes less critical.
10157 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
10158 a release management issue.
10160 Note that if you use @option{-g} you can then use the @command{strip} program
10161 on the resulting executable,
10162 which removes both debugging information and global symbols.
10165 @node Inlining of Subprograms
10166 @subsection Inlining of Subprograms
10169 A call to a subprogram in the current unit is inlined if all the
10170 following conditions are met:
10174 The optimization level is at least @option{-O1}.
10177 The called subprogram is suitable for inlining: It must be small enough
10178 and not contain something that @command{gcc} cannot support in inlined
10182 @cindex pragma Inline
10184 Either @code{pragma Inline} applies to the subprogram, or it is local
10185 to the unit and called once from within it, or it is small and automatic
10186 inlining (optimization level @option{-O3}) is specified.
10190 Calls to subprograms in @code{with}'ed units are normally not inlined.
10191 To achieve actual inlining (that is, replacement of the call by the code
10192 in the body of the subprogram), the following conditions must all be true.
10196 The optimization level is at least @option{-O1}.
10199 The called subprogram is suitable for inlining: It must be small enough
10200 and not contain something that @command{gcc} cannot support in inlined
10204 The call appears in a body (not in a package spec).
10207 There is a @code{pragma Inline} for the subprogram.
10210 @cindex @option{-gnatn} (@command{gcc})
10211 The @option{^-gnatn^/INLINE^} switch
10212 is used in the @command{gcc} command line
10215 Even if all these conditions are met, it may not be possible for
10216 the compiler to inline the call, due to the length of the body,
10217 or features in the body that make it impossible for the compiler
10218 to do the inlining.
10220 Note that specifying the @option{-gnatn} switch causes additional
10221 compilation dependencies. Consider the following:
10223 @smallexample @c ada
10243 With the default behavior (no @option{-gnatn} switch specified), the
10244 compilation of the @code{Main} procedure depends only on its own source,
10245 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10246 means that editing the body of @code{R} does not require recompiling
10249 On the other hand, the call @code{R.Q} is not inlined under these
10250 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10251 is compiled, the call will be inlined if the body of @code{Q} is small
10252 enough, but now @code{Main} depends on the body of @code{R} in
10253 @file{r.adb} as well as on the spec. This means that if this body is edited,
10254 the main program must be recompiled. Note that this extra dependency
10255 occurs whether or not the call is in fact inlined by @command{gcc}.
10257 The use of front end inlining with @option{-gnatN} generates similar
10258 additional dependencies.
10260 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10261 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10262 can be used to prevent
10263 all inlining. This switch overrides all other conditions and ensures
10264 that no inlining occurs. The extra dependences resulting from
10265 @option{-gnatn} will still be active, even if
10266 this switch is used to suppress the resulting inlining actions.
10268 @cindex @option{-fno-inline-functions} (@command{gcc})
10269 Note: The @option{-fno-inline-functions} switch can be used to prevent
10270 automatic inlining of small subprograms if @option{-O3} is used.
10272 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10273 Note: The @option{-fno-inline-functions-called-once} switch
10274 can be used to prevent inlining of subprograms local to the unit
10275 and called once from within it if @option{-O1} is used.
10277 Note regarding the use of @option{-O3}: There is no difference in inlining
10278 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10279 pragma @code{Inline} assuming the use of @option{-gnatn}
10280 or @option{-gnatN} (the switches that activate inlining). If you have used
10281 pragma @code{Inline} in appropriate cases, then it is usually much better
10282 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10283 in this case only has the effect of inlining subprograms you did not
10284 think should be inlined. We often find that the use of @option{-O3} slows
10285 down code by performing excessive inlining, leading to increased instruction
10286 cache pressure from the increased code size. So the bottom line here is
10287 that you should not automatically assume that @option{-O3} is better than
10288 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10289 it actually improves performance.
10291 @node Other Optimization Switches
10292 @subsection Other Optimization Switches
10293 @cindex Optimization Switches
10295 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10296 @command{gcc} optimization switches are potentially usable. These switches
10297 have not been extensively tested with GNAT but can generally be expected
10298 to work. Examples of switches in this category are
10299 @option{-funroll-loops} and
10300 the various target-specific @option{-m} options (in particular, it has been
10301 observed that @option{-march=pentium4} can significantly improve performance
10302 on appropriate machines). For full details of these switches, see
10303 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10304 the GNU Compiler Collection (GCC)}.
10306 @node Optimization and Strict Aliasing
10307 @subsection Optimization and Strict Aliasing
10309 @cindex Strict Aliasing
10310 @cindex No_Strict_Aliasing
10313 The strong typing capabilities of Ada allow an optimizer to generate
10314 efficient code in situations where other languages would be forced to
10315 make worst case assumptions preventing such optimizations. Consider
10316 the following example:
10318 @smallexample @c ada
10321 type Int1 is new Integer;
10322 type Int2 is new Integer;
10323 type Int1A is access Int1;
10324 type Int2A is access Int2;
10331 for J in Data'Range loop
10332 if Data (J) = Int1V.all then
10333 Int2V.all := Int2V.all + 1;
10342 In this example, since the variable @code{Int1V} can only access objects
10343 of type @code{Int1}, and @code{Int2V} can only access objects of type
10344 @code{Int2}, there is no possibility that the assignment to
10345 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10346 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10347 for all iterations of the loop and avoid the extra memory reference
10348 required to dereference it each time through the loop.
10350 This kind of optimization, called strict aliasing analysis, is
10351 triggered by specifying an optimization level of @option{-O2} or
10352 higher or @option{-Os} and allows @code{GNAT} to generate more efficient code
10353 when access values are involved.
10355 However, although this optimization is always correct in terms of
10356 the formal semantics of the Ada Reference Manual, difficulties can
10357 arise if features like @code{Unchecked_Conversion} are used to break
10358 the typing system. Consider the following complete program example:
10360 @smallexample @c ada
10363 type int1 is new integer;
10364 type int2 is new integer;
10365 type a1 is access int1;
10366 type a2 is access int2;
10371 function to_a2 (Input : a1) return a2;
10374 with Unchecked_Conversion;
10376 function to_a2 (Input : a1) return a2 is
10378 new Unchecked_Conversion (a1, a2);
10380 return to_a2u (Input);
10386 with Text_IO; use Text_IO;
10388 v1 : a1 := new int1;
10389 v2 : a2 := to_a2 (v1);
10393 put_line (int1'image (v1.all));
10399 This program prints out 0 in @option{-O0} or @option{-O1}
10400 mode, but it prints out 1 in @option{-O2} mode. That's
10401 because in strict aliasing mode, the compiler can and
10402 does assume that the assignment to @code{v2.all} could not
10403 affect the value of @code{v1.all}, since different types
10406 This behavior is not a case of non-conformance with the standard, since
10407 the Ada RM specifies that an unchecked conversion where the resulting
10408 bit pattern is not a correct value of the target type can result in an
10409 abnormal value and attempting to reference an abnormal value makes the
10410 execution of a program erroneous. That's the case here since the result
10411 does not point to an object of type @code{int2}. This means that the
10412 effect is entirely unpredictable.
10414 However, although that explanation may satisfy a language
10415 lawyer, in practice an applications programmer expects an
10416 unchecked conversion involving pointers to create true
10417 aliases and the behavior of printing 1 seems plain wrong.
10418 In this case, the strict aliasing optimization is unwelcome.
10420 Indeed the compiler recognizes this possibility, and the
10421 unchecked conversion generates a warning:
10424 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10425 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10426 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10430 Unfortunately the problem is recognized when compiling the body of
10431 package @code{p2}, but the actual "bad" code is generated while
10432 compiling the body of @code{m} and this latter compilation does not see
10433 the suspicious @code{Unchecked_Conversion}.
10435 As implied by the warning message, there are approaches you can use to
10436 avoid the unwanted strict aliasing optimization in a case like this.
10438 One possibility is to simply avoid the use of @option{-O2}, but
10439 that is a bit drastic, since it throws away a number of useful
10440 optimizations that do not involve strict aliasing assumptions.
10442 A less drastic approach is to compile the program using the
10443 option @option{-fno-strict-aliasing}. Actually it is only the
10444 unit containing the dereferencing of the suspicious pointer
10445 that needs to be compiled. So in this case, if we compile
10446 unit @code{m} with this switch, then we get the expected
10447 value of zero printed. Analyzing which units might need
10448 the switch can be painful, so a more reasonable approach
10449 is to compile the entire program with options @option{-O2}
10450 and @option{-fno-strict-aliasing}. If the performance is
10451 satisfactory with this combination of options, then the
10452 advantage is that the entire issue of possible "wrong"
10453 optimization due to strict aliasing is avoided.
10455 To avoid the use of compiler switches, the configuration
10456 pragma @code{No_Strict_Aliasing} with no parameters may be
10457 used to specify that for all access types, the strict
10458 aliasing optimization should be suppressed.
10460 However, these approaches are still overkill, in that they causes
10461 all manipulations of all access values to be deoptimized. A more
10462 refined approach is to concentrate attention on the specific
10463 access type identified as problematic.
10465 First, if a careful analysis of uses of the pointer shows
10466 that there are no possible problematic references, then
10467 the warning can be suppressed by bracketing the
10468 instantiation of @code{Unchecked_Conversion} to turn
10471 @smallexample @c ada
10472 pragma Warnings (Off);
10474 new Unchecked_Conversion (a1, a2);
10475 pragma Warnings (On);
10479 Of course that approach is not appropriate for this particular
10480 example, since indeed there is a problematic reference. In this
10481 case we can take one of two other approaches.
10483 The first possibility is to move the instantiation of unchecked
10484 conversion to the unit in which the type is declared. In
10485 this example, we would move the instantiation of
10486 @code{Unchecked_Conversion} from the body of package
10487 @code{p2} to the spec of package @code{p1}. Now the
10488 warning disappears. That's because any use of the
10489 access type knows there is a suspicious unchecked
10490 conversion, and the strict aliasing optimization
10491 is automatically suppressed for the type.
10493 If it is not practical to move the unchecked conversion to the same unit
10494 in which the destination access type is declared (perhaps because the
10495 source type is not visible in that unit), you may use pragma
10496 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10497 same declarative sequence as the declaration of the access type:
10499 @smallexample @c ada
10500 type a2 is access int2;
10501 pragma No_Strict_Aliasing (a2);
10505 Here again, the compiler now knows that the strict aliasing optimization
10506 should be suppressed for any reference to type @code{a2} and the
10507 expected behavior is obtained.
10509 Finally, note that although the compiler can generate warnings for
10510 simple cases of unchecked conversions, there are tricker and more
10511 indirect ways of creating type incorrect aliases which the compiler
10512 cannot detect. Examples are the use of address overlays and unchecked
10513 conversions involving composite types containing access types as
10514 components. In such cases, no warnings are generated, but there can
10515 still be aliasing problems. One safe coding practice is to forbid the
10516 use of address clauses for type overlaying, and to allow unchecked
10517 conversion only for primitive types. This is not really a significant
10518 restriction since any possible desired effect can be achieved by
10519 unchecked conversion of access values.
10521 The aliasing analysis done in strict aliasing mode can certainly
10522 have significant benefits. We have seen cases of large scale
10523 application code where the time is increased by up to 5% by turning
10524 this optimization off. If you have code that includes significant
10525 usage of unchecked conversion, you might want to just stick with
10526 @option{-O1} and avoid the entire issue. If you get adequate
10527 performance at this level of optimization level, that's probably
10528 the safest approach. If tests show that you really need higher
10529 levels of optimization, then you can experiment with @option{-O2}
10530 and @option{-O2 -fno-strict-aliasing} to see how much effect this
10531 has on size and speed of the code. If you really need to use
10532 @option{-O2} with strict aliasing in effect, then you should
10533 review any uses of unchecked conversion of access types,
10534 particularly if you are getting the warnings described above.
10537 @node Coverage Analysis
10538 @subsection Coverage Analysis
10541 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10542 the user to determine the distribution of execution time across a program,
10543 @pxref{Profiling} for details of usage.
10547 @node Text_IO Suggestions
10548 @section @code{Text_IO} Suggestions
10549 @cindex @code{Text_IO} and performance
10552 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10553 the requirement of maintaining page and line counts. If performance
10554 is critical, a recommendation is to use @code{Stream_IO} instead of
10555 @code{Text_IO} for volume output, since this package has less overhead.
10557 If @code{Text_IO} must be used, note that by default output to the standard
10558 output and standard error files is unbuffered (this provides better
10559 behavior when output statements are used for debugging, or if the
10560 progress of a program is observed by tracking the output, e.g. by
10561 using the Unix @command{tail -f} command to watch redirected output.
10563 If you are generating large volumes of output with @code{Text_IO} and
10564 performance is an important factor, use a designated file instead
10565 of the standard output file, or change the standard output file to
10566 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10570 @node Reducing Size of Ada Executables with gnatelim
10571 @section Reducing Size of Ada Executables with @code{gnatelim}
10575 This section describes @command{gnatelim}, a tool which detects unused
10576 subprograms and helps the compiler to create a smaller executable for your
10581 * Running gnatelim::
10582 * Correcting the List of Eliminate Pragmas::
10583 * Making Your Executables Smaller::
10584 * Summary of the gnatelim Usage Cycle::
10587 @node About gnatelim
10588 @subsection About @code{gnatelim}
10591 When a program shares a set of Ada
10592 packages with other programs, it may happen that this program uses
10593 only a fraction of the subprograms defined in these packages. The code
10594 created for these unused subprograms increases the size of the executable.
10596 @code{gnatelim} tracks unused subprograms in an Ada program and
10597 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10598 subprograms that are declared but never called. By placing the list of
10599 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10600 recompiling your program, you may decrease the size of its executable,
10601 because the compiler will not generate the code for 'eliminated' subprograms.
10602 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10603 information about this pragma.
10605 @code{gnatelim} needs as its input data the name of the main subprogram
10606 and a bind file for a main subprogram.
10608 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10609 the main subprogram. @code{gnatelim} can work with both Ada and C
10610 bind files; when both are present, it uses the Ada bind file.
10611 The following commands will build the program and create the bind file:
10614 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10615 $ gnatbind main_prog
10618 Note that @code{gnatelim} needs neither object nor ALI files.
10620 @node Running gnatelim
10621 @subsection Running @code{gnatelim}
10624 @code{gnatelim} has the following command-line interface:
10627 $ gnatelim @ovar{options} name
10631 @code{name} should be a name of a source file that contains the main subprogram
10632 of a program (partition).
10634 @code{gnatelim} has the following switches:
10639 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10640 Quiet mode: by default @code{gnatelim} outputs to the standard error
10641 stream the number of program units left to be processed. This option turns
10644 @item ^-v^/VERBOSE^
10645 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10646 Verbose mode: @code{gnatelim} version information is printed as Ada
10647 comments to the standard output stream. Also, in addition to the number of
10648 program units left @code{gnatelim} will output the name of the current unit
10652 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10653 Also look for subprograms from the GNAT run time that can be eliminated. Note
10654 that when @file{gnat.adc} is produced using this switch, the entire program
10655 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10657 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10658 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10659 When looking for source files also look in directory @var{dir}. Specifying
10660 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10661 sources in the current directory.
10663 @item ^-b^/BIND_FILE=^@var{bind_file}
10664 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10665 Specifies @var{bind_file} as the bind file to process. If not set, the name
10666 of the bind file is computed from the full expanded Ada name
10667 of a main subprogram.
10669 @item ^-C^/CONFIG_FILE=^@var{config_file}
10670 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10671 Specifies a file @var{config_file} that contains configuration pragmas. The
10672 file must be specified with full path.
10674 @item ^--GCC^/COMPILER^=@var{compiler_name}
10675 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10676 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10677 available on the path.
10679 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10680 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10681 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10682 available on the path.
10686 @code{gnatelim} sends its output to the standard output stream, and all the
10687 tracing and debug information is sent to the standard error stream.
10688 In order to produce a proper GNAT configuration file
10689 @file{gnat.adc}, redirection must be used:
10693 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10696 $ gnatelim main_prog.adb > gnat.adc
10705 $ gnatelim main_prog.adb >> gnat.adc
10709 in order to append the @code{gnatelim} output to the existing contents of
10713 @node Correcting the List of Eliminate Pragmas
10714 @subsection Correcting the List of Eliminate Pragmas
10717 In some rare cases @code{gnatelim} may try to eliminate
10718 subprograms that are actually called in the program. In this case, the
10719 compiler will generate an error message of the form:
10722 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10726 You will need to manually remove the wrong @code{Eliminate} pragmas from
10727 the @file{gnat.adc} file. You should recompile your program
10728 from scratch after that, because you need a consistent @file{gnat.adc} file
10729 during the entire compilation.
10731 @node Making Your Executables Smaller
10732 @subsection Making Your Executables Smaller
10735 In order to get a smaller executable for your program you now have to
10736 recompile the program completely with the new @file{gnat.adc} file
10737 created by @code{gnatelim} in your current directory:
10740 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10744 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10745 recompile everything
10746 with the set of pragmas @code{Eliminate} that you have obtained with
10747 @command{gnatelim}).
10749 Be aware that the set of @code{Eliminate} pragmas is specific to each
10750 program. It is not recommended to merge sets of @code{Eliminate}
10751 pragmas created for different programs in one @file{gnat.adc} file.
10753 @node Summary of the gnatelim Usage Cycle
10754 @subsection Summary of the gnatelim Usage Cycle
10757 Here is a quick summary of the steps to be taken in order to reduce
10758 the size of your executables with @code{gnatelim}. You may use
10759 other GNAT options to control the optimization level,
10760 to produce the debugging information, to set search path, etc.
10764 Produce a bind file
10767 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10768 $ gnatbind main_prog
10772 Generate a list of @code{Eliminate} pragmas
10775 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10778 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10783 Recompile the application
10786 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10791 @node Reducing Size of Executables with unused subprogram/data elimination
10792 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10793 @findex unused subprogram/data elimination
10796 This section describes how you can eliminate unused subprograms and data from
10797 your executable just by setting options at compilation time.
10800 * About unused subprogram/data elimination::
10801 * Compilation options::
10802 * Example of unused subprogram/data elimination::
10805 @node About unused subprogram/data elimination
10806 @subsection About unused subprogram/data elimination
10809 By default, an executable contains all code and data of its composing objects
10810 (directly linked or coming from statically linked libraries), even data or code
10811 never used by this executable.
10813 This feature will allow you to eliminate such unused code from your
10814 executable, making it smaller (in disk and in memory).
10816 This functionality is available on all Linux platforms except for the IA-64
10817 architecture and on all cross platforms using the ELF binary file format.
10818 In both cases GNU binutils version 2.16 or later are required to enable it.
10820 @node Compilation options
10821 @subsection Compilation options
10824 The operation of eliminating the unused code and data from the final executable
10825 is directly performed by the linker.
10827 In order to do this, it has to work with objects compiled with the
10829 @option{-ffunction-sections} @option{-fdata-sections}.
10830 @cindex @option{-ffunction-sections} (@command{gcc})
10831 @cindex @option{-fdata-sections} (@command{gcc})
10832 These options are usable with C and Ada files.
10833 They will place respectively each
10834 function or data in a separate section in the resulting object file.
10836 Once the objects and static libraries are created with these options, the
10837 linker can perform the dead code elimination. You can do this by setting
10838 the @option{-Wl,--gc-sections} option to gcc command or in the
10839 @option{-largs} section of @command{gnatmake}. This will perform a
10840 garbage collection of code and data never referenced.
10842 If the linker performs a partial link (@option{-r} ld linker option), then you
10843 will need to provide one or several entry point using the
10844 @option{-e} / @option{--entry} ld option.
10846 Note that objects compiled without the @option{-ffunction-sections} and
10847 @option{-fdata-sections} options can still be linked with the executable.
10848 However, no dead code elimination will be performed on those objects (they will
10851 The GNAT static library is now compiled with -ffunction-sections and
10852 -fdata-sections on some platforms. This allows you to eliminate the unused code
10853 and data of the GNAT library from your executable.
10855 @node Example of unused subprogram/data elimination
10856 @subsection Example of unused subprogram/data elimination
10859 Here is a simple example:
10861 @smallexample @c ada
10870 Used_Data : Integer;
10871 Unused_Data : Integer;
10873 procedure Used (Data : Integer);
10874 procedure Unused (Data : Integer);
10877 package body Aux is
10878 procedure Used (Data : Integer) is
10883 procedure Unused (Data : Integer) is
10885 Unused_Data := Data;
10891 @code{Unused} and @code{Unused_Data} are never referenced in this code
10892 excerpt, and hence they may be safely removed from the final executable.
10897 $ nm test | grep used
10898 020015f0 T aux__unused
10899 02005d88 B aux__unused_data
10900 020015cc T aux__used
10901 02005d84 B aux__used_data
10903 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10904 -largs -Wl,--gc-sections
10906 $ nm test | grep used
10907 02005350 T aux__used
10908 0201ffe0 B aux__used_data
10912 It can be observed that the procedure @code{Unused} and the object
10913 @code{Unused_Data} are removed by the linker when using the
10914 appropriate options.
10916 @c ********************************
10917 @node Renaming Files Using gnatchop
10918 @chapter Renaming Files Using @code{gnatchop}
10922 This chapter discusses how to handle files with multiple units by using
10923 the @code{gnatchop} utility. This utility is also useful in renaming
10924 files to meet the standard GNAT default file naming conventions.
10927 * Handling Files with Multiple Units::
10928 * Operating gnatchop in Compilation Mode::
10929 * Command Line for gnatchop::
10930 * Switches for gnatchop::
10931 * Examples of gnatchop Usage::
10934 @node Handling Files with Multiple Units
10935 @section Handling Files with Multiple Units
10938 The basic compilation model of GNAT requires that a file submitted to the
10939 compiler have only one unit and there be a strict correspondence
10940 between the file name and the unit name.
10942 The @code{gnatchop} utility allows both of these rules to be relaxed,
10943 allowing GNAT to process files which contain multiple compilation units
10944 and files with arbitrary file names. @code{gnatchop}
10945 reads the specified file and generates one or more output files,
10946 containing one unit per file. The unit and the file name correspond,
10947 as required by GNAT.
10949 If you want to permanently restructure a set of ``foreign'' files so that
10950 they match the GNAT rules, and do the remaining development using the
10951 GNAT structure, you can simply use @command{gnatchop} once, generate the
10952 new set of files and work with them from that point on.
10954 Alternatively, if you want to keep your files in the ``foreign'' format,
10955 perhaps to maintain compatibility with some other Ada compilation
10956 system, you can set up a procedure where you use @command{gnatchop} each
10957 time you compile, regarding the source files that it writes as temporary
10958 files that you throw away.
10960 Note that if your file containing multiple units starts with a byte order
10961 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
10962 will each start with a copy of this BOM, meaning that they can be compiled
10963 automatically in UTF-8 mode without needing to specify an explicit encoding.
10965 @node Operating gnatchop in Compilation Mode
10966 @section Operating gnatchop in Compilation Mode
10969 The basic function of @code{gnatchop} is to take a file with multiple units
10970 and split it into separate files. The boundary between files is reasonably
10971 clear, except for the issue of comments and pragmas. In default mode, the
10972 rule is that any pragmas between units belong to the previous unit, except
10973 that configuration pragmas always belong to the following unit. Any comments
10974 belong to the following unit. These rules
10975 almost always result in the right choice of
10976 the split point without needing to mark it explicitly and most users will
10977 find this default to be what they want. In this default mode it is incorrect to
10978 submit a file containing only configuration pragmas, or one that ends in
10979 configuration pragmas, to @code{gnatchop}.
10981 However, using a special option to activate ``compilation mode'',
10983 can perform another function, which is to provide exactly the semantics
10984 required by the RM for handling of configuration pragmas in a compilation.
10985 In the absence of configuration pragmas (at the main file level), this
10986 option has no effect, but it causes such configuration pragmas to be handled
10987 in a quite different manner.
10989 First, in compilation mode, if @code{gnatchop} is given a file that consists of
10990 only configuration pragmas, then this file is appended to the
10991 @file{gnat.adc} file in the current directory. This behavior provides
10992 the required behavior described in the RM for the actions to be taken
10993 on submitting such a file to the compiler, namely that these pragmas
10994 should apply to all subsequent compilations in the same compilation
10995 environment. Using GNAT, the current directory, possibly containing a
10996 @file{gnat.adc} file is the representation
10997 of a compilation environment. For more information on the
10998 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
11000 Second, in compilation mode, if @code{gnatchop}
11001 is given a file that starts with
11002 configuration pragmas, and contains one or more units, then these
11003 configuration pragmas are prepended to each of the chopped files. This
11004 behavior provides the required behavior described in the RM for the
11005 actions to be taken on compiling such a file, namely that the pragmas
11006 apply to all units in the compilation, but not to subsequently compiled
11009 Finally, if configuration pragmas appear between units, they are appended
11010 to the previous unit. This results in the previous unit being illegal,
11011 since the compiler does not accept configuration pragmas that follow
11012 a unit. This provides the required RM behavior that forbids configuration
11013 pragmas other than those preceding the first compilation unit of a
11016 For most purposes, @code{gnatchop} will be used in default mode. The
11017 compilation mode described above is used only if you need exactly
11018 accurate behavior with respect to compilations, and you have files
11019 that contain multiple units and configuration pragmas. In this
11020 circumstance the use of @code{gnatchop} with the compilation mode
11021 switch provides the required behavior, and is for example the mode
11022 in which GNAT processes the ACVC tests.
11024 @node Command Line for gnatchop
11025 @section Command Line for @code{gnatchop}
11028 The @code{gnatchop} command has the form:
11031 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11036 The only required argument is the file name of the file to be chopped.
11037 There are no restrictions on the form of this file name. The file itself
11038 contains one or more Ada units, in normal GNAT format, concatenated
11039 together. As shown, more than one file may be presented to be chopped.
11041 When run in default mode, @code{gnatchop} generates one output file in
11042 the current directory for each unit in each of the files.
11044 @var{directory}, if specified, gives the name of the directory to which
11045 the output files will be written. If it is not specified, all files are
11046 written to the current directory.
11048 For example, given a
11049 file called @file{hellofiles} containing
11051 @smallexample @c ada
11056 with Text_IO; use Text_IO;
11059 Put_Line ("Hello");
11069 $ gnatchop ^hellofiles^HELLOFILES.^
11073 generates two files in the current directory, one called
11074 @file{hello.ads} containing the single line that is the procedure spec,
11075 and the other called @file{hello.adb} containing the remaining text. The
11076 original file is not affected. The generated files can be compiled in
11080 When gnatchop is invoked on a file that is empty or that contains only empty
11081 lines and/or comments, gnatchop will not fail, but will not produce any
11084 For example, given a
11085 file called @file{toto.txt} containing
11087 @smallexample @c ada
11099 $ gnatchop ^toto.txt^TOT.TXT^
11103 will not produce any new file and will result in the following warnings:
11106 toto.txt:1:01: warning: empty file, contains no compilation units
11107 no compilation units found
11108 no source files written
11111 @node Switches for gnatchop
11112 @section Switches for @code{gnatchop}
11115 @command{gnatchop} recognizes the following switches:
11121 @cindex @option{--version} @command{gnatchop}
11122 Display Copyright and version, then exit disregarding all other options.
11125 @cindex @option{--help} @command{gnatchop}
11126 If @option{--version} was not used, display usage, then exit disregarding
11129 @item ^-c^/COMPILATION^
11130 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
11131 Causes @code{gnatchop} to operate in compilation mode, in which
11132 configuration pragmas are handled according to strict RM rules. See
11133 previous section for a full description of this mode.
11136 @item -gnat@var{xxx}
11137 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
11138 used to parse the given file. Not all @var{xxx} options make sense,
11139 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
11140 process a source file that uses Latin-2 coding for identifiers.
11144 Causes @code{gnatchop} to generate a brief help summary to the standard
11145 output file showing usage information.
11147 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
11148 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
11149 Limit generated file names to the specified number @code{mm}
11151 This is useful if the
11152 resulting set of files is required to be interoperable with systems
11153 which limit the length of file names.
11155 If no value is given, or
11156 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
11157 a default of 39, suitable for OpenVMS Alpha
11158 Systems, is assumed
11161 No space is allowed between the @option{-k} and the numeric value. The numeric
11162 value may be omitted in which case a default of @option{-k8},
11164 with DOS-like file systems, is used. If no @option{-k} switch
11166 there is no limit on the length of file names.
11169 @item ^-p^/PRESERVE^
11170 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
11171 Causes the file ^modification^creation^ time stamp of the input file to be
11172 preserved and used for the time stamp of the output file(s). This may be
11173 useful for preserving coherency of time stamps in an environment where
11174 @code{gnatchop} is used as part of a standard build process.
11177 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
11178 Causes output of informational messages indicating the set of generated
11179 files to be suppressed. Warnings and error messages are unaffected.
11181 @item ^-r^/REFERENCE^
11182 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
11183 @findex Source_Reference
11184 Generate @code{Source_Reference} pragmas. Use this switch if the output
11185 files are regarded as temporary and development is to be done in terms
11186 of the original unchopped file. This switch causes
11187 @code{Source_Reference} pragmas to be inserted into each of the
11188 generated files to refers back to the original file name and line number.
11189 The result is that all error messages refer back to the original
11191 In addition, the debugging information placed into the object file (when
11192 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
11194 also refers back to this original file so that tools like profilers and
11195 debuggers will give information in terms of the original unchopped file.
11197 If the original file to be chopped itself contains
11198 a @code{Source_Reference}
11199 pragma referencing a third file, then gnatchop respects
11200 this pragma, and the generated @code{Source_Reference} pragmas
11201 in the chopped file refer to the original file, with appropriate
11202 line numbers. This is particularly useful when @code{gnatchop}
11203 is used in conjunction with @code{gnatprep} to compile files that
11204 contain preprocessing statements and multiple units.
11206 @item ^-v^/VERBOSE^
11207 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
11208 Causes @code{gnatchop} to operate in verbose mode. The version
11209 number and copyright notice are output, as well as exact copies of
11210 the gnat1 commands spawned to obtain the chop control information.
11212 @item ^-w^/OVERWRITE^
11213 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
11214 Overwrite existing file names. Normally @code{gnatchop} regards it as a
11215 fatal error if there is already a file with the same name as a
11216 file it would otherwise output, in other words if the files to be
11217 chopped contain duplicated units. This switch bypasses this
11218 check, and causes all but the last instance of such duplicated
11219 units to be skipped.
11222 @item --GCC=@var{xxxx}
11223 @cindex @option{--GCC=} (@code{gnatchop})
11224 Specify the path of the GNAT parser to be used. When this switch is used,
11225 no attempt is made to add the prefix to the GNAT parser executable.
11229 @node Examples of gnatchop Usage
11230 @section Examples of @code{gnatchop} Usage
11234 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
11237 @item gnatchop -w hello_s.ada prerelease/files
11240 Chops the source file @file{hello_s.ada}. The output files will be
11241 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
11243 files with matching names in that directory (no files in the current
11244 directory are modified).
11246 @item gnatchop ^archive^ARCHIVE.^
11247 Chops the source file @file{^archive^ARCHIVE.^}
11248 into the current directory. One
11249 useful application of @code{gnatchop} is in sending sets of sources
11250 around, for example in email messages. The required sources are simply
11251 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11253 @command{gnatchop} is used at the other end to reconstitute the original
11256 @item gnatchop file1 file2 file3 direc
11257 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11258 the resulting files in the directory @file{direc}. Note that if any units
11259 occur more than once anywhere within this set of files, an error message
11260 is generated, and no files are written. To override this check, use the
11261 @option{^-w^/OVERWRITE^} switch,
11262 in which case the last occurrence in the last file will
11263 be the one that is output, and earlier duplicate occurrences for a given
11264 unit will be skipped.
11267 @node Configuration Pragmas
11268 @chapter Configuration Pragmas
11269 @cindex Configuration pragmas
11270 @cindex Pragmas, configuration
11273 Configuration pragmas include those pragmas described as
11274 such in the Ada Reference Manual, as well as
11275 implementation-dependent pragmas that are configuration pragmas.
11276 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11277 for details on these additional GNAT-specific configuration pragmas.
11278 Most notably, the pragma @code{Source_File_Name}, which allows
11279 specifying non-default names for source files, is a configuration
11280 pragma. The following is a complete list of configuration pragmas
11281 recognized by GNAT:
11293 Compile_Time_Warning
11295 Component_Alignment
11302 External_Name_Casing
11305 Float_Representation
11318 Priority_Specific_Dispatching
11321 Propagate_Exceptions
11324 Restricted_Run_Time
11326 Restrictions_Warnings
11329 Source_File_Name_Project
11332 Suppress_Exception_Locations
11333 Task_Dispatching_Policy
11339 Wide_Character_Encoding
11344 * Handling of Configuration Pragmas::
11345 * The Configuration Pragmas Files::
11348 @node Handling of Configuration Pragmas
11349 @section Handling of Configuration Pragmas
11351 Configuration pragmas may either appear at the start of a compilation
11352 unit, in which case they apply only to that unit, or they may apply to
11353 all compilations performed in a given compilation environment.
11355 GNAT also provides the @code{gnatchop} utility to provide an automatic
11356 way to handle configuration pragmas following the semantics for
11357 compilations (that is, files with multiple units), described in the RM.
11358 See @ref{Operating gnatchop in Compilation Mode} for details.
11359 However, for most purposes, it will be more convenient to edit the
11360 @file{gnat.adc} file that contains configuration pragmas directly,
11361 as described in the following section.
11363 @node The Configuration Pragmas Files
11364 @section The Configuration Pragmas Files
11365 @cindex @file{gnat.adc}
11368 In GNAT a compilation environment is defined by the current
11369 directory at the time that a compile command is given. This current
11370 directory is searched for a file whose name is @file{gnat.adc}. If
11371 this file is present, it is expected to contain one or more
11372 configuration pragmas that will be applied to the current compilation.
11373 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11376 Configuration pragmas may be entered into the @file{gnat.adc} file
11377 either by running @code{gnatchop} on a source file that consists only of
11378 configuration pragmas, or more conveniently by
11379 direct editing of the @file{gnat.adc} file, which is a standard format
11382 In addition to @file{gnat.adc}, additional files containing configuration
11383 pragmas may be applied to the current compilation using the switch
11384 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11385 contains only configuration pragmas. These configuration pragmas are
11386 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11387 is present and switch @option{-gnatA} is not used).
11389 It is allowed to specify several switches @option{-gnatec}, all of which
11390 will be taken into account.
11392 If you are using project file, a separate mechanism is provided using
11393 project attributes, see @ref{Specifying Configuration Pragmas} for more
11397 Of special interest to GNAT OpenVMS Alpha is the following
11398 configuration pragma:
11400 @smallexample @c ada
11402 pragma Extend_System (Aux_DEC);
11407 In the presence of this pragma, GNAT adds to the definition of the
11408 predefined package SYSTEM all the additional types and subprograms that are
11409 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11412 @node Handling Arbitrary File Naming Conventions Using gnatname
11413 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11414 @cindex Arbitrary File Naming Conventions
11417 * Arbitrary File Naming Conventions::
11418 * Running gnatname::
11419 * Switches for gnatname::
11420 * Examples of gnatname Usage::
11423 @node Arbitrary File Naming Conventions
11424 @section Arbitrary File Naming Conventions
11427 The GNAT compiler must be able to know the source file name of a compilation
11428 unit. When using the standard GNAT default file naming conventions
11429 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11430 does not need additional information.
11433 When the source file names do not follow the standard GNAT default file naming
11434 conventions, the GNAT compiler must be given additional information through
11435 a configuration pragmas file (@pxref{Configuration Pragmas})
11437 When the non-standard file naming conventions are well-defined,
11438 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11439 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11440 if the file naming conventions are irregular or arbitrary, a number
11441 of pragma @code{Source_File_Name} for individual compilation units
11443 To help maintain the correspondence between compilation unit names and
11444 source file names within the compiler,
11445 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11448 @node Running gnatname
11449 @section Running @code{gnatname}
11452 The usual form of the @code{gnatname} command is
11455 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11456 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11460 All of the arguments are optional. If invoked without any argument,
11461 @code{gnatname} will display its usage.
11464 When used with at least one naming pattern, @code{gnatname} will attempt to
11465 find all the compilation units in files that follow at least one of the
11466 naming patterns. To find these compilation units,
11467 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11471 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11472 Each Naming Pattern is enclosed between double quotes.
11473 A Naming Pattern is a regular expression similar to the wildcard patterns
11474 used in file names by the Unix shells or the DOS prompt.
11477 @code{gnatname} may be called with several sections of directories/patterns.
11478 Sections are separated by switch @code{--and}. In each section, there must be
11479 at least one pattern. If no directory is specified in a section, the current
11480 directory (or the project directory is @code{-P} is used) is implied.
11481 The options other that the directory switches and the patterns apply globally
11482 even if they are in different sections.
11485 Examples of Naming Patterns are
11494 For a more complete description of the syntax of Naming Patterns,
11495 see the second kind of regular expressions described in @file{g-regexp.ads}
11496 (the ``Glob'' regular expressions).
11499 When invoked with no switch @code{-P}, @code{gnatname} will create a
11500 configuration pragmas file @file{gnat.adc} in the current working directory,
11501 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11504 @node Switches for gnatname
11505 @section Switches for @code{gnatname}
11508 Switches for @code{gnatname} must precede any specified Naming Pattern.
11511 You may specify any of the following switches to @code{gnatname}:
11517 @cindex @option{--version} @command{gnatname}
11518 Display Copyright and version, then exit disregarding all other options.
11521 @cindex @option{--help} @command{gnatname}
11522 If @option{--version} was not used, display usage, then exit disregarding
11526 Start another section of directories/patterns.
11528 @item ^-c^/CONFIG_FILE=^@file{file}
11529 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11530 Create a configuration pragmas file @file{file} (instead of the default
11533 There may be zero, one or more space between @option{-c} and
11536 @file{file} may include directory information. @file{file} must be
11537 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11538 When a switch @option{^-c^/CONFIG_FILE^} is
11539 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11541 @item ^-d^/SOURCE_DIRS=^@file{dir}
11542 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11543 Look for source files in directory @file{dir}. There may be zero, one or more
11544 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11545 When a switch @option{^-d^/SOURCE_DIRS^}
11546 is specified, the current working directory will not be searched for source
11547 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11548 or @option{^-D^/DIR_FILES^} switch.
11549 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11550 If @file{dir} is a relative path, it is relative to the directory of
11551 the configuration pragmas file specified with switch
11552 @option{^-c^/CONFIG_FILE^},
11553 or to the directory of the project file specified with switch
11554 @option{^-P^/PROJECT_FILE^} or,
11555 if neither switch @option{^-c^/CONFIG_FILE^}
11556 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11557 current working directory. The directory
11558 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11560 @item ^-D^/DIRS_FILE=^@file{file}
11561 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11562 Look for source files in all directories listed in text file @file{file}.
11563 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11565 @file{file} must be an existing, readable text file.
11566 Each nonempty line in @file{file} must be a directory.
11567 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11568 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11571 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11572 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11573 Foreign patterns. Using this switch, it is possible to add sources of languages
11574 other than Ada to the list of sources of a project file.
11575 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11578 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11581 will look for Ada units in all files with the @file{.ada} extension,
11582 and will add to the list of file for project @file{prj.gpr} the C files
11583 with extension @file{.^c^C^}.
11586 @cindex @option{^-h^/HELP^} (@code{gnatname})
11587 Output usage (help) information. The output is written to @file{stdout}.
11589 @item ^-P^/PROJECT_FILE=^@file{proj}
11590 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11591 Create or update project file @file{proj}. There may be zero, one or more space
11592 between @option{-P} and @file{proj}. @file{proj} may include directory
11593 information. @file{proj} must be writable.
11594 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11595 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11596 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11598 @item ^-v^/VERBOSE^
11599 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11600 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11601 This includes name of the file written, the name of the directories to search
11602 and, for each file in those directories whose name matches at least one of
11603 the Naming Patterns, an indication of whether the file contains a unit,
11604 and if so the name of the unit.
11606 @item ^-v -v^/VERBOSE /VERBOSE^
11607 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11608 Very Verbose mode. In addition to the output produced in verbose mode,
11609 for each file in the searched directories whose name matches none of
11610 the Naming Patterns, an indication is given that there is no match.
11612 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11613 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11614 Excluded patterns. Using this switch, it is possible to exclude some files
11615 that would match the name patterns. For example,
11617 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11620 will look for Ada units in all files with the @file{.ada} extension,
11621 except those whose names end with @file{_nt.ada}.
11625 @node Examples of gnatname Usage
11626 @section Examples of @code{gnatname} Usage
11630 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11636 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11641 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11642 and be writable. In addition, the directory
11643 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11644 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11647 Note the optional spaces after @option{-c} and @option{-d}.
11652 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11653 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11656 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11657 /EXCLUDED_PATTERN=*_nt_body.ada
11658 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11659 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11663 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11664 even in conjunction with one or several switches
11665 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11666 are used in this example.
11668 @c *****************************************
11669 @c * G N A T P r o j e c t M a n a g e r *
11670 @c *****************************************
11671 @node GNAT Project Manager
11672 @chapter GNAT Project Manager
11676 * Examples of Project Files::
11677 * Project File Syntax::
11678 * Objects and Sources in Project Files::
11679 * Importing Projects::
11680 * Project Extension::
11681 * Project Hierarchy Extension::
11682 * External References in Project Files::
11683 * Packages in Project Files::
11684 * Variables from Imported Projects::
11686 * Library Projects::
11687 * Stand-alone Library Projects::
11688 * Switches Related to Project Files::
11689 * Tools Supporting Project Files::
11690 * An Extended Example::
11691 * Project File Complete Syntax::
11694 @c ****************
11695 @c * Introduction *
11696 @c ****************
11699 @section Introduction
11702 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11703 you to manage complex builds involving a number of source files, directories,
11704 and compilation options for different system configurations. In particular,
11705 project files allow you to specify:
11708 The directory or set of directories containing the source files, and/or the
11709 names of the specific source files themselves
11711 The directory in which the compiler's output
11712 (@file{ALI} files, object files, tree files) is to be placed
11714 The directory in which the executable programs is to be placed
11716 ^Switch^Switch^ settings for any of the project-enabled tools
11717 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11718 @code{gnatfind}); you can apply these settings either globally or to individual
11721 The source files containing the main subprogram(s) to be built
11723 The source programming language(s) (currently Ada and/or C)
11725 Source file naming conventions; you can specify these either globally or for
11726 individual compilation units
11733 @node Project Files
11734 @subsection Project Files
11737 Project files are written in a syntax close to that of Ada, using familiar
11738 notions such as packages, context clauses, declarations, default values,
11739 assignments, and inheritance. Finally, project files can be built
11740 hierarchically from other project files, simplifying complex system
11741 integration and project reuse.
11743 A @dfn{project} is a specific set of values for various compilation properties.
11744 The settings for a given project are described by means of
11745 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11746 Property values in project files are either strings or lists of strings.
11747 Properties that are not explicitly set receive default values. A project
11748 file may interrogate the values of @dfn{external variables} (user-defined
11749 command-line switches or environment variables), and it may specify property
11750 settings conditionally, based on the value of such variables.
11752 In simple cases, a project's source files depend only on other source files
11753 in the same project, or on the predefined libraries. (@emph{Dependence} is
11755 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11756 the Project Manager also allows more sophisticated arrangements,
11757 where the source files in one project depend on source files in other
11761 One project can @emph{import} other projects containing needed source files.
11763 You can organize GNAT projects in a hierarchy: a @emph{child} project
11764 can extend a @emph{parent} project, inheriting the parent's source files and
11765 optionally overriding any of them with alternative versions
11769 More generally, the Project Manager lets you structure large development
11770 efforts into hierarchical subsystems, where build decisions are delegated
11771 to the subsystem level, and thus different compilation environments
11772 (^switch^switch^ settings) used for different subsystems.
11774 The Project Manager is invoked through the
11775 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11776 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11778 There may be zero, one or more spaces between @option{-P} and
11779 @option{@emph{projectfile}}.
11781 If you want to define (on the command line) an external variable that is
11782 queried by the project file, you must use the
11783 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11784 The Project Manager parses and interprets the project file, and drives the
11785 invoked tool based on the project settings.
11787 The Project Manager supports a wide range of development strategies,
11788 for systems of all sizes. Here are some typical practices that are
11792 Using a common set of source files, but generating object files in different
11793 directories via different ^switch^switch^ settings
11795 Using a mostly-shared set of source files, but with different versions of
11800 The destination of an executable can be controlled inside a project file
11801 using the @option{^-o^-o^}
11803 In the absence of such a ^switch^switch^ either inside
11804 the project file or on the command line, any executable files generated by
11805 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11806 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11807 in the object directory of the project.
11809 You can use project files to achieve some of the effects of a source
11810 versioning system (for example, defining separate projects for
11811 the different sets of sources that comprise different releases) but the
11812 Project Manager is independent of any source configuration management tools
11813 that might be used by the developers.
11815 The next section introduces the main features of GNAT's project facility
11816 through a sequence of examples; subsequent sections will present the syntax
11817 and semantics in more detail. A more formal description of the project
11818 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11821 @c *****************************
11822 @c * Examples of Project Files *
11823 @c *****************************
11825 @node Examples of Project Files
11826 @section Examples of Project Files
11828 This section illustrates some of the typical uses of project files and
11829 explains their basic structure and behavior.
11832 * Common Sources with Different ^Switches^Switches^ and Directories::
11833 * Using External Variables::
11834 * Importing Other Projects::
11835 * Extending a Project::
11838 @node Common Sources with Different ^Switches^Switches^ and Directories
11839 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11843 * Specifying the Object Directory::
11844 * Specifying the Exec Directory::
11845 * Project File Packages::
11846 * Specifying ^Switch^Switch^ Settings::
11847 * Main Subprograms::
11848 * Executable File Names::
11849 * Source File Naming Conventions::
11850 * Source Language(s)::
11854 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11855 @file{proc.adb} are in the @file{/common} directory. The file
11856 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11857 package @code{Pack}. We want to compile these source files under two sets
11858 of ^switches^switches^:
11861 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11862 and the @option{^-gnata^-gnata^},
11863 @option{^-gnato^-gnato^},
11864 and @option{^-gnatE^-gnatE^} switches to the
11865 compiler; the compiler's output is to appear in @file{/common/debug}
11867 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11868 to the compiler; the compiler's output is to appear in @file{/common/release}
11872 The GNAT project files shown below, respectively @file{debug.gpr} and
11873 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11886 ^/common/debug^[COMMON.DEBUG]^
11891 ^/common/release^[COMMON.RELEASE]^
11896 Here are the corresponding project files:
11898 @smallexample @c projectfile
11901 for Object_Dir use "debug";
11902 for Main use ("proc");
11905 for ^Default_Switches^Default_Switches^ ("Ada")
11907 for Executable ("proc.adb") use "proc1";
11912 package Compiler is
11913 for ^Default_Switches^Default_Switches^ ("Ada")
11914 use ("-fstack-check",
11917 "^-gnatE^-gnatE^");
11923 @smallexample @c projectfile
11926 for Object_Dir use "release";
11927 for Exec_Dir use ".";
11928 for Main use ("proc");
11930 package Compiler is
11931 for ^Default_Switches^Default_Switches^ ("Ada")
11939 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11940 insensitive), and analogously the project defined by @file{release.gpr} is
11941 @code{"Release"}. For consistency the file should have the same name as the
11942 project, and the project file's extension should be @code{"gpr"}. These
11943 conventions are not required, but a warning is issued if they are not followed.
11945 If the current directory is @file{^/temp^[TEMP]^}, then the command
11947 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
11951 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
11952 as well as the @code{^proc1^PROC1.EXE^} executable,
11953 using the ^switch^switch^ settings defined in the project file.
11955 Likewise, the command
11957 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
11961 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
11962 and the @code{^proc^PROC.EXE^}
11963 executable in @file{^/common^[COMMON]^},
11964 using the ^switch^switch^ settings from the project file.
11967 @unnumberedsubsubsec Source Files
11970 If a project file does not explicitly specify a set of source directories or
11971 a set of source files, then by default the project's source files are the
11972 Ada source files in the project file directory. Thus @file{pack.ads},
11973 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
11975 @node Specifying the Object Directory
11976 @unnumberedsubsubsec Specifying the Object Directory
11979 Several project properties are modeled by Ada-style @emph{attributes};
11980 a property is defined by supplying the equivalent of an Ada attribute
11981 definition clause in the project file.
11982 A project's object directory is another such a property; the corresponding
11983 attribute is @code{Object_Dir}, and its value is also a string expression,
11984 specified either as absolute or relative. In the later case,
11985 it is relative to the project file directory. Thus the compiler's
11986 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
11987 (for the @code{Debug} project)
11988 and to @file{^/common/release^[COMMON.RELEASE]^}
11989 (for the @code{Release} project).
11990 If @code{Object_Dir} is not specified, then the default is the project file
11993 @node Specifying the Exec Directory
11994 @unnumberedsubsubsec Specifying the Exec Directory
11997 A project's exec directory is another property; the corresponding
11998 attribute is @code{Exec_Dir}, and its value is also a string expression,
11999 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
12000 then the default is the object directory (which may also be the project file
12001 directory if attribute @code{Object_Dir} is not specified). Thus the executable
12002 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
12003 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
12004 and in @file{^/common^[COMMON]^} for the @code{Release} project.
12006 @node Project File Packages
12007 @unnumberedsubsubsec Project File Packages
12010 A GNAT tool that is integrated with the Project Manager is modeled by a
12011 corresponding package in the project file. In the example above,
12012 The @code{Debug} project defines the packages @code{Builder}
12013 (for @command{gnatmake}) and @code{Compiler};
12014 the @code{Release} project defines only the @code{Compiler} package.
12016 The Ada-like package syntax is not to be taken literally. Although packages in
12017 project files bear a surface resemblance to packages in Ada source code, the
12018 notation is simply a way to convey a grouping of properties for a named
12019 entity. Indeed, the package names permitted in project files are restricted
12020 to a predefined set, corresponding to the project-aware tools, and the contents
12021 of packages are limited to a small set of constructs.
12022 The packages in the example above contain attribute definitions.
12024 @node Specifying ^Switch^Switch^ Settings
12025 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
12028 ^Switch^Switch^ settings for a project-aware tool can be specified through
12029 attributes in the package that corresponds to the tool.
12030 The example above illustrates one of the relevant attributes,
12031 @code{^Default_Switches^Default_Switches^}, which is defined in packages
12032 in both project files.
12033 Unlike simple attributes like @code{Source_Dirs},
12034 @code{^Default_Switches^Default_Switches^} is
12035 known as an @emph{associative array}. When you define this attribute, you must
12036 supply an ``index'' (a literal string), and the effect of the attribute
12037 definition is to set the value of the array at the specified index.
12038 For the @code{^Default_Switches^Default_Switches^} attribute,
12039 the index is a programming language (in our case, Ada),
12040 and the value specified (after @code{use}) must be a list
12041 of string expressions.
12043 The attributes permitted in project files are restricted to a predefined set.
12044 Some may appear at project level, others in packages.
12045 For any attribute that is an associative array, the index must always be a
12046 literal string, but the restrictions on this string (e.g., a file name or a
12047 language name) depend on the individual attribute.
12048 Also depending on the attribute, its specified value will need to be either a
12049 string or a string list.
12051 In the @code{Debug} project, we set the switches for two tools,
12052 @command{gnatmake} and the compiler, and thus we include the two corresponding
12053 packages; each package defines the @code{^Default_Switches^Default_Switches^}
12054 attribute with index @code{"Ada"}.
12055 Note that the package corresponding to
12056 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
12057 similar, but only includes the @code{Compiler} package.
12059 In project @code{Debug} above, the ^switches^switches^ starting with
12060 @option{-gnat} that are specified in package @code{Compiler}
12061 could have been placed in package @code{Builder}, since @command{gnatmake}
12062 transmits all such ^switches^switches^ to the compiler.
12064 @node Main Subprograms
12065 @unnumberedsubsubsec Main Subprograms
12068 One of the specifiable properties of a project is a list of files that contain
12069 main subprograms. This property is captured in the @code{Main} attribute,
12070 whose value is a list of strings. If a project defines the @code{Main}
12071 attribute, it is not necessary to identify the main subprogram(s) when
12072 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
12074 @node Executable File Names
12075 @unnumberedsubsubsec Executable File Names
12078 By default, the executable file name corresponding to a main source is
12079 deduced from the main source file name. Through the attributes
12080 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
12081 it is possible to change this default.
12082 In project @code{Debug} above, the executable file name
12083 for main source @file{^proc.adb^PROC.ADB^} is
12084 @file{^proc1^PROC1.EXE^}.
12085 Attribute @code{Executable_Suffix}, when specified, may change the suffix
12086 of the executable files, when no attribute @code{Executable} applies:
12087 its value replace the platform-specific executable suffix.
12088 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
12089 specify a non-default executable file name when several mains are built at once
12090 in a single @command{gnatmake} command.
12092 @node Source File Naming Conventions
12093 @unnumberedsubsubsec Source File Naming Conventions
12096 Since the project files above do not specify any source file naming
12097 conventions, the GNAT defaults are used. The mechanism for defining source
12098 file naming conventions -- a package named @code{Naming} --
12099 is described below (@pxref{Naming Schemes}).
12101 @node Source Language(s)
12102 @unnumberedsubsubsec Source Language(s)
12105 Since the project files do not specify a @code{Languages} attribute, by
12106 default the GNAT tools assume that the language of the project file is Ada.
12107 More generally, a project can comprise source files
12108 in Ada, C, and/or other languages.
12110 @node Using External Variables
12111 @subsection Using External Variables
12114 Instead of supplying different project files for debug and release, we can
12115 define a single project file that queries an external variable (set either
12116 on the command line or via an ^environment variable^logical name^) in order to
12117 conditionally define the appropriate settings. Again, assume that the
12118 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
12119 located in directory @file{^/common^[COMMON]^}. The following project file,
12120 @file{build.gpr}, queries the external variable named @code{STYLE} and
12121 defines an object directory and ^switch^switch^ settings based on whether
12122 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
12123 the default is @code{"deb"}.
12125 @smallexample @c projectfile
12128 for Main use ("proc");
12130 type Style_Type is ("deb", "rel");
12131 Style : Style_Type := external ("STYLE", "deb");
12135 for Object_Dir use "debug";
12138 for Object_Dir use "release";
12139 for Exec_Dir use ".";
12148 for ^Default_Switches^Default_Switches^ ("Ada")
12150 for Executable ("proc") use "proc1";
12159 package Compiler is
12163 for ^Default_Switches^Default_Switches^ ("Ada")
12164 use ("^-gnata^-gnata^",
12166 "^-gnatE^-gnatE^");
12169 for ^Default_Switches^Default_Switches^ ("Ada")
12180 @code{Style_Type} is an example of a @emph{string type}, which is the project
12181 file analog of an Ada enumeration type but whose components are string literals
12182 rather than identifiers. @code{Style} is declared as a variable of this type.
12184 The form @code{external("STYLE", "deb")} is known as an
12185 @emph{external reference}; its first argument is the name of an
12186 @emph{external variable}, and the second argument is a default value to be
12187 used if the external variable doesn't exist. You can define an external
12188 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
12189 or you can use ^an environment variable^a logical name^
12190 as an external variable.
12192 Each @code{case} construct is expanded by the Project Manager based on the
12193 value of @code{Style}. Thus the command
12196 gnatmake -P/common/build.gpr -XSTYLE=deb
12202 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
12207 is equivalent to the @command{gnatmake} invocation using the project file
12208 @file{debug.gpr} in the earlier example. So is the command
12210 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
12214 since @code{"deb"} is the default for @code{STYLE}.
12220 gnatmake -P/common/build.gpr -XSTYLE=rel
12226 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
12231 is equivalent to the @command{gnatmake} invocation using the project file
12232 @file{release.gpr} in the earlier example.
12234 @node Importing Other Projects
12235 @subsection Importing Other Projects
12236 @cindex @code{ADA_PROJECT_PATH}
12239 A compilation unit in a source file in one project may depend on compilation
12240 units in source files in other projects. To compile this unit under
12241 control of a project file, the
12242 dependent project must @emph{import} the projects containing the needed source
12244 This effect is obtained using syntax similar to an Ada @code{with} clause,
12245 but where @code{with}ed entities are strings that denote project files.
12247 As an example, suppose that the two projects @code{GUI_Proj} and
12248 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
12249 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
12250 and @file{^/comm^[COMM]^}, respectively.
12251 Suppose that the source files for @code{GUI_Proj} are
12252 @file{gui.ads} and @file{gui.adb}, and that the source files for
12253 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
12254 files is located in its respective project file directory. Schematically:
12273 We want to develop an application in directory @file{^/app^[APP]^} that
12274 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
12275 the corresponding project files (e.g.@: the ^switch^switch^ settings
12276 and object directory).
12277 Skeletal code for a main procedure might be something like the following:
12279 @smallexample @c ada
12282 procedure App_Main is
12291 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12294 @smallexample @c projectfile
12296 with "/gui/gui_proj", "/comm/comm_proj";
12297 project App_Proj is
12298 for Main use ("app_main");
12304 Building an executable is achieved through the command:
12306 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12309 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12310 in the directory where @file{app_proj.gpr} resides.
12312 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12313 (as illustrated above) the @code{with} clause can omit the extension.
12315 Our example specified an absolute path for each imported project file.
12316 Alternatively, the directory name of an imported object can be omitted
12320 The imported project file is in the same directory as the importing project
12323 You have defined ^an environment variable^a logical name^
12324 that includes the directory containing
12325 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
12326 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12327 directory names separated by colons (semicolons on Windows).
12331 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
12332 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12335 @smallexample @c projectfile
12337 with "gui_proj", "comm_proj";
12338 project App_Proj is
12339 for Main use ("app_main");
12345 Importing other projects can create ambiguities.
12346 For example, the same unit might be present in different imported projects, or
12347 it might be present in both the importing project and in an imported project.
12348 Both of these conditions are errors. Note that in the current version of
12349 the Project Manager, it is illegal to have an ambiguous unit even if the
12350 unit is never referenced by the importing project. This restriction may be
12351 relaxed in a future release.
12353 @node Extending a Project
12354 @subsection Extending a Project
12357 In large software systems it is common to have multiple
12358 implementations of a common interface; in Ada terms, multiple versions of a
12359 package body for the same spec. For example, one implementation
12360 might be safe for use in tasking programs, while another might only be used
12361 in sequential applications. This can be modeled in GNAT using the concept
12362 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12363 another project (the ``parent'') then by default all source files of the
12364 parent project are inherited by the child, but the child project can
12365 override any of the parent's source files with new versions, and can also
12366 add new files. This facility is the project analog of a type extension in
12367 Object-Oriented Programming. Project hierarchies are permitted (a child
12368 project may be the parent of yet another project), and a project that
12369 inherits one project can also import other projects.
12371 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12372 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12373 @file{pack.adb}, and @file{proc.adb}:
12386 Note that the project file can simply be empty (that is, no attribute or
12387 package is defined):
12389 @smallexample @c projectfile
12391 project Seq_Proj is
12397 implying that its source files are all the Ada source files in the project
12400 Suppose we want to supply an alternate version of @file{pack.adb}, in
12401 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12402 @file{pack.ads} and @file{proc.adb}. We can define a project
12403 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12407 ^/tasking^[TASKING]^
12413 project Tasking_Proj extends "/seq/seq_proj" is
12419 The version of @file{pack.adb} used in a build depends on which project file
12422 Note that we could have obtained the desired behavior using project import
12423 rather than project inheritance; a @code{base} project would contain the
12424 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12425 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12426 would import @code{base} and add a different version of @file{pack.adb}. The
12427 choice depends on whether other sources in the original project need to be
12428 overridden. If they do, then project extension is necessary, otherwise,
12429 importing is sufficient.
12432 In a project file that extends another project file, it is possible to
12433 indicate that an inherited source is not part of the sources of the extending
12434 project. This is necessary sometimes when a package spec has been overloaded
12435 and no longer requires a body: in this case, it is necessary to indicate that
12436 the inherited body is not part of the sources of the project, otherwise there
12437 will be a compilation error when compiling the spec.
12439 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12440 Its value is a string list: a list of file names. It is also possible to use
12441 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12442 the file name of a text file containing a list of file names, one per line.
12444 @smallexample @c @projectfile
12445 project B extends "a" is
12446 for Source_Files use ("pkg.ads");
12447 -- New spec of Pkg does not need a completion
12448 for Excluded_Source_Files use ("pkg.adb");
12452 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12453 is still needed: if it is possible to build using @command{gnatmake} when such
12454 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12455 it is possible to remove the source completely from a system that includes
12458 @c ***********************
12459 @c * Project File Syntax *
12460 @c ***********************
12462 @node Project File Syntax
12463 @section Project File Syntax
12467 * Qualified Projects::
12473 * Associative Array Attributes::
12474 * case Constructions::
12478 This section describes the structure of project files.
12480 A project may be an @emph{independent project}, entirely defined by a single
12481 project file. Any Ada source file in an independent project depends only
12482 on the predefined library and other Ada source files in the same project.
12485 A project may also @dfn{depend on} other projects, in either or both of
12486 the following ways:
12488 @item It may import any number of projects
12489 @item It may extend at most one other project
12493 The dependence relation is a directed acyclic graph (the subgraph reflecting
12494 the ``extends'' relation is a tree).
12496 A project's @dfn{immediate sources} are the source files directly defined by
12497 that project, either implicitly by residing in the project file's directory,
12498 or explicitly through any of the source-related attributes described below.
12499 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12500 of @var{proj} together with the immediate sources (unless overridden) of any
12501 project on which @var{proj} depends (either directly or indirectly).
12504 @subsection Basic Syntax
12507 As seen in the earlier examples, project files have an Ada-like syntax.
12508 The minimal project file is:
12509 @smallexample @c projectfile
12518 The identifier @code{Empty} is the name of the project.
12519 This project name must be present after the reserved
12520 word @code{end} at the end of the project file, followed by a semi-colon.
12522 Any name in a project file, such as the project name or a variable name,
12523 has the same syntax as an Ada identifier.
12525 The reserved words of project files are the Ada 95 reserved words plus
12526 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12527 reserved words currently used in project file syntax are:
12563 Comments in project files have the same syntax as in Ada, two consecutive
12564 hyphens through the end of the line.
12566 @node Qualified Projects
12567 @subsection Qualified Projects
12570 Before the reserved @code{project}, there may be one or two "qualifiers", that
12571 is identifiers or other reserved words, to qualify the project.
12573 The current list of qualifiers is:
12577 @code{abstract}: qualify a project with no sources. A qualified abstract
12578 project must either have no declaration of attributes @code{Source_Dirs},
12579 @code{Source_Files}, @code{Languages} or @code{Source_List_File}, or one of
12580 @code{Source_Dirs}, @code{Source_Files}, or @code{Languages} must be declared
12581 as empty. If it extends another project, the project it extends must also be a
12582 qualified abstract project.
12585 @code{standard}: a standard project is a non library project with sources.
12588 @code{aggregate}: for future extension
12591 @code{aggregate library}: for future extension
12594 @code{library}: a library project must declare both attributes
12595 @code{Library_Name} and @code{Library_Dir}.
12598 @code{configuration}: a configuration project cannot be in a project tree.
12602 @subsection Packages
12605 A project file may contain @emph{packages}. The name of a package must be one
12606 of the identifiers from the following list. A package
12607 with a given name may only appear once in a project file. Package names are
12608 case insensitive. The following package names are legal:
12624 @code{Cross_Reference}
12628 @code{Pretty_Printer}
12638 @code{Language_Processing}
12642 In its simplest form, a package may be empty:
12644 @smallexample @c projectfile
12654 A package may contain @emph{attribute declarations},
12655 @emph{variable declarations} and @emph{case constructions}, as will be
12658 When there is ambiguity between a project name and a package name,
12659 the name always designates the project. To avoid possible confusion, it is
12660 always a good idea to avoid naming a project with one of the
12661 names allowed for packages or any name that starts with @code{gnat}.
12664 @subsection Expressions
12667 An @emph{expression} is either a @emph{string expression} or a
12668 @emph{string list expression}.
12670 A @emph{string expression} is either a @emph{simple string expression} or a
12671 @emph{compound string expression}.
12673 A @emph{simple string expression} is one of the following:
12675 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12676 @item A string-valued variable reference (@pxref{Variables})
12677 @item A string-valued attribute reference (@pxref{Attributes})
12678 @item An external reference (@pxref{External References in Project Files})
12682 A @emph{compound string expression} is a concatenation of string expressions,
12683 using the operator @code{"&"}
12685 Path & "/" & File_Name & ".ads"
12689 A @emph{string list expression} is either a
12690 @emph{simple string list expression} or a
12691 @emph{compound string list expression}.
12693 A @emph{simple string list expression} is one of the following:
12695 @item A parenthesized list of zero or more string expressions,
12696 separated by commas
12698 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12701 @item A string list-valued variable reference
12702 @item A string list-valued attribute reference
12706 A @emph{compound string list expression} is the concatenation (using
12707 @code{"&"}) of a simple string list expression and an expression. Note that
12708 each term in a compound string list expression, except the first, may be
12709 either a string expression or a string list expression.
12711 @smallexample @c projectfile
12713 File_Name_List := () & File_Name; -- One string in this list
12714 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12716 Big_List := File_Name_List & Extended_File_Name_List;
12717 -- Concatenation of two string lists: three strings
12718 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12719 -- Illegal: must start with a string list
12724 @subsection String Types
12727 A @emph{string type declaration} introduces a discrete set of string literals.
12728 If a string variable is declared to have this type, its value
12729 is restricted to the given set of literals.
12731 Here is an example of a string type declaration:
12733 @smallexample @c projectfile
12734 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12738 Variables of a string type are called @emph{typed variables}; all other
12739 variables are called @emph{untyped variables}. Typed variables are
12740 particularly useful in @code{case} constructions, to support conditional
12741 attribute declarations.
12742 (@pxref{case Constructions}).
12744 The string literals in the list are case sensitive and must all be different.
12745 They may include any graphic characters allowed in Ada, including spaces.
12747 A string type may only be declared at the project level, not inside a package.
12749 A string type may be referenced by its name if it has been declared in the same
12750 project file, or by an expanded name whose prefix is the name of the project
12751 in which it is declared.
12754 @subsection Variables
12757 A variable may be declared at the project file level, or within a package.
12758 Here are some examples of variable declarations:
12760 @smallexample @c projectfile
12762 This_OS : OS := external ("OS"); -- a typed variable declaration
12763 That_OS := "GNU/Linux"; -- an untyped variable declaration
12768 The syntax of a @emph{typed variable declaration} is identical to the Ada
12769 syntax for an object declaration. By contrast, the syntax of an untyped
12770 variable declaration is identical to an Ada assignment statement. In fact,
12771 variable declarations in project files have some of the characteristics of
12772 an assignment, in that successive declarations for the same variable are
12773 allowed. Untyped variable declarations do establish the expected kind of the
12774 variable (string or string list), and successive declarations for it must
12775 respect the initial kind.
12778 A string variable declaration (typed or untyped) declares a variable
12779 whose value is a string. This variable may be used as a string expression.
12780 @smallexample @c projectfile
12781 File_Name := "readme.txt";
12782 Saved_File_Name := File_Name & ".saved";
12786 A string list variable declaration declares a variable whose value is a list
12787 of strings. The list may contain any number (zero or more) of strings.
12789 @smallexample @c projectfile
12791 List_With_One_Element := ("^-gnaty^-gnaty^");
12792 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12793 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12794 "pack2.ada", "util_.ada", "util.ada");
12798 The same typed variable may not be declared more than once at project level,
12799 and it may not be declared more than once in any package; it is in effect
12802 The same untyped variable may be declared several times. Declarations are
12803 elaborated in the order in which they appear, so the new value replaces
12804 the old one, and any subsequent reference to the variable uses the new value.
12805 However, as noted above, if a variable has been declared as a string, all
12807 declarations must give it a string value. Similarly, if a variable has
12808 been declared as a string list, all subsequent declarations
12809 must give it a string list value.
12811 A @emph{variable reference} may take several forms:
12814 @item The simple variable name, for a variable in the current package (if any)
12815 or in the current project
12816 @item An expanded name, whose prefix is a context name.
12820 A @emph{context} may be one of the following:
12823 @item The name of an existing package in the current project
12824 @item The name of an imported project of the current project
12825 @item The name of an ancestor project (i.e., a project extended by the current
12826 project, either directly or indirectly)
12827 @item An expanded name whose prefix is an imported/parent project name, and
12828 whose selector is a package name in that project.
12832 A variable reference may be used in an expression.
12835 @subsection Attributes
12838 A project (and its packages) may have @emph{attributes} that define
12839 the project's properties. Some attributes have values that are strings;
12840 others have values that are string lists.
12842 There are two categories of attributes: @emph{simple attributes}
12843 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12845 Legal project attribute names, and attribute names for each legal package are
12846 listed below. Attributes names are case-insensitive.
12848 The following attributes are defined on projects (all are simple attributes):
12850 @multitable @columnfractions .4 .3
12851 @item @emph{Attribute Name}
12853 @item @code{Source_Files}
12855 @item @code{Source_Dirs}
12857 @item @code{Source_List_File}
12859 @item @code{Object_Dir}
12861 @item @code{Exec_Dir}
12863 @item @code{Excluded_Source_Dirs}
12865 @item @code{Excluded_Source_Files}
12867 @item @code{Excluded_Source_List_File}
12869 @item @code{Languages}
12873 @item @code{Library_Dir}
12875 @item @code{Library_Name}
12877 @item @code{Library_Kind}
12879 @item @code{Library_Version}
12881 @item @code{Library_Interface}
12883 @item @code{Library_Auto_Init}
12885 @item @code{Library_Options}
12887 @item @code{Library_Src_Dir}
12889 @item @code{Library_ALI_Dir}
12891 @item @code{Library_GCC}
12893 @item @code{Library_Symbol_File}
12895 @item @code{Library_Symbol_Policy}
12897 @item @code{Library_Reference_Symbol_File}
12899 @item @code{Externally_Built}
12904 The following attributes are defined for package @code{Naming}
12905 (@pxref{Naming Schemes}):
12907 @multitable @columnfractions .4 .2 .2 .2
12908 @item Attribute Name @tab Category @tab Index @tab Value
12909 @item @code{Spec_Suffix}
12910 @tab associative array
12913 @item @code{Body_Suffix}
12914 @tab associative array
12917 @item @code{Separate_Suffix}
12918 @tab simple attribute
12921 @item @code{Casing}
12922 @tab simple attribute
12925 @item @code{Dot_Replacement}
12926 @tab simple attribute
12930 @tab associative array
12934 @tab associative array
12937 @item @code{Specification_Exceptions}
12938 @tab associative array
12941 @item @code{Implementation_Exceptions}
12942 @tab associative array
12948 The following attributes are defined for packages @code{Builder},
12949 @code{Compiler}, @code{Binder},
12950 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
12951 (@pxref{^Switches^Switches^ and Project Files}).
12953 @multitable @columnfractions .4 .2 .2 .2
12954 @item Attribute Name @tab Category @tab Index @tab Value
12955 @item @code{^Default_Switches^Default_Switches^}
12956 @tab associative array
12959 @item @code{^Switches^Switches^}
12960 @tab associative array
12966 In addition, package @code{Compiler} has a single string attribute
12967 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
12968 string attribute @code{Global_Configuration_Pragmas}.
12971 Each simple attribute has a default value: the empty string (for string-valued
12972 attributes) and the empty list (for string list-valued attributes).
12974 An attribute declaration defines a new value for an attribute.
12976 Examples of simple attribute declarations:
12978 @smallexample @c projectfile
12979 for Object_Dir use "objects";
12980 for Source_Dirs use ("units", "test/drivers");
12984 The syntax of a @dfn{simple attribute declaration} is similar to that of an
12985 attribute definition clause in Ada.
12987 Attributes references may be appear in expressions.
12988 The general form for such a reference is @code{<entity>'<attribute>}:
12989 Associative array attributes are functions. Associative
12990 array attribute references must have an argument that is a string literal.
12994 @smallexample @c projectfile
12996 Naming'Dot_Replacement
12997 Imported_Project'Source_Dirs
12998 Imported_Project.Naming'Casing
12999 Builder'^Default_Switches^Default_Switches^("Ada")
13003 The prefix of an attribute may be:
13005 @item @code{project} for an attribute of the current project
13006 @item The name of an existing package of the current project
13007 @item The name of an imported project
13008 @item The name of a parent project that is extended by the current project
13009 @item An expanded name whose prefix is imported/parent project name,
13010 and whose selector is a package name
13015 @smallexample @c projectfile
13018 for Source_Dirs use project'Source_Dirs & "units";
13019 for Source_Dirs use project'Source_Dirs & "test/drivers"
13025 In the first attribute declaration, initially the attribute @code{Source_Dirs}
13026 has the default value: an empty string list. After this declaration,
13027 @code{Source_Dirs} is a string list of one element: @code{"units"}.
13028 After the second attribute declaration @code{Source_Dirs} is a string list of
13029 two elements: @code{"units"} and @code{"test/drivers"}.
13031 Note: this example is for illustration only. In practice,
13032 the project file would contain only one attribute declaration:
13034 @smallexample @c projectfile
13035 for Source_Dirs use ("units", "test/drivers");
13038 @node Associative Array Attributes
13039 @subsection Associative Array Attributes
13042 Some attributes are defined as @emph{associative arrays}. An associative
13043 array may be regarded as a function that takes a string as a parameter
13044 and delivers a string or string list value as its result.
13046 Here are some examples of single associative array attribute associations:
13048 @smallexample @c projectfile
13049 for Body ("main") use "Main.ada";
13050 for ^Switches^Switches^ ("main.ada")
13052 "^-gnatv^-gnatv^");
13053 for ^Switches^Switches^ ("main.ada")
13054 use Builder'^Switches^Switches^ ("main.ada")
13059 Like untyped variables and simple attributes, associative array attributes
13060 may be declared several times. Each declaration supplies a new value for the
13061 attribute, and replaces the previous setting.
13064 An associative array attribute may be declared as a full associative array
13065 declaration, with the value of the same attribute in an imported or extended
13068 @smallexample @c projectfile
13070 for Default_Switches use Default.Builder'Default_Switches;
13075 In this example, @code{Default} must be either a project imported by the
13076 current project, or the project that the current project extends. If the
13077 attribute is in a package (in this case, in package @code{Builder}), the same
13078 package needs to be specified.
13081 A full associative array declaration replaces any other declaration for the
13082 attribute, including other full associative array declaration. Single
13083 associative array associations may be declare after a full associative
13084 declaration, modifying the value for a single association of the attribute.
13086 @node case Constructions
13087 @subsection @code{case} Constructions
13090 A @code{case} construction is used in a project file to effect conditional
13092 Here is a typical example:
13094 @smallexample @c projectfile
13097 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
13099 OS : OS_Type := external ("OS", "GNU/Linux");
13103 package Compiler is
13105 when "GNU/Linux" | "Unix" =>
13106 for ^Default_Switches^Default_Switches^ ("Ada")
13107 use ("^-gnath^-gnath^");
13109 for ^Default_Switches^Default_Switches^ ("Ada")
13110 use ("^-gnatP^-gnatP^");
13119 The syntax of a @code{case} construction is based on the Ada case statement
13120 (although there is no @code{null} construction for empty alternatives).
13122 The case expression must be a typed string variable.
13123 Each alternative comprises the reserved word @code{when}, either a list of
13124 literal strings separated by the @code{"|"} character or the reserved word
13125 @code{others}, and the @code{"=>"} token.
13126 Each literal string must belong to the string type that is the type of the
13128 An @code{others} alternative, if present, must occur last.
13130 After each @code{=>}, there are zero or more constructions. The only
13131 constructions allowed in a case construction are other case constructions,
13132 attribute declarations and variable declarations. String type declarations and
13133 package declarations are not allowed. Variable declarations are restricted to
13134 variables that have already been declared before the case construction.
13136 The value of the case variable is often given by an external reference
13137 (@pxref{External References in Project Files}).
13139 @c ****************************************
13140 @c * Objects and Sources in Project Files *
13141 @c ****************************************
13143 @node Objects and Sources in Project Files
13144 @section Objects and Sources in Project Files
13147 * Object Directory::
13149 * Source Directories::
13150 * Source File Names::
13154 Each project has exactly one object directory and one or more source
13155 directories. The source directories must contain at least one source file,
13156 unless the project file explicitly specifies that no source files are present
13157 (@pxref{Source File Names}).
13159 @node Object Directory
13160 @subsection Object Directory
13163 The object directory for a project is the directory containing the compiler's
13164 output (such as @file{ALI} files and object files) for the project's immediate
13167 The object directory is given by the value of the attribute @code{Object_Dir}
13168 in the project file.
13170 @smallexample @c projectfile
13171 for Object_Dir use "objects";
13175 The attribute @code{Object_Dir} has a string value, the path name of the object
13176 directory. The path name may be absolute or relative to the directory of the
13177 project file. This directory must already exist, and be readable and writable.
13179 By default, when the attribute @code{Object_Dir} is not given an explicit value
13180 or when its value is the empty string, the object directory is the same as the
13181 directory containing the project file.
13183 @node Exec Directory
13184 @subsection Exec Directory
13187 The exec directory for a project is the directory containing the executables
13188 for the project's main subprograms.
13190 The exec directory is given by the value of the attribute @code{Exec_Dir}
13191 in the project file.
13193 @smallexample @c projectfile
13194 for Exec_Dir use "executables";
13198 The attribute @code{Exec_Dir} has a string value, the path name of the exec
13199 directory. The path name may be absolute or relative to the directory of the
13200 project file. This directory must already exist, and be writable.
13202 By default, when the attribute @code{Exec_Dir} is not given an explicit value
13203 or when its value is the empty string, the exec directory is the same as the
13204 object directory of the project file.
13206 @node Source Directories
13207 @subsection Source Directories
13210 The source directories of a project are specified by the project file
13211 attribute @code{Source_Dirs}.
13213 This attribute's value is a string list. If the attribute is not given an
13214 explicit value, then there is only one source directory, the one where the
13215 project file resides.
13217 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
13220 @smallexample @c projectfile
13221 for Source_Dirs use ();
13225 indicates that the project contains no source files.
13227 Otherwise, each string in the string list designates one or more
13228 source directories.
13230 @smallexample @c projectfile
13231 for Source_Dirs use ("sources", "test/drivers");
13235 If a string in the list ends with @code{"/**"}, then the directory whose path
13236 name precedes the two asterisks, as well as all its subdirectories
13237 (recursively), are source directories.
13239 @smallexample @c projectfile
13240 for Source_Dirs use ("/system/sources/**");
13244 Here the directory @code{/system/sources} and all of its subdirectories
13245 (recursively) are source directories.
13247 To specify that the source directories are the directory of the project file
13248 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
13249 @smallexample @c projectfile
13250 for Source_Dirs use ("./**");
13254 Each of the source directories must exist and be readable.
13256 @node Source File Names
13257 @subsection Source File Names
13260 In a project that contains source files, their names may be specified by the
13261 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
13262 (a string). Source file names never include any directory information.
13264 If the attribute @code{Source_Files} is given an explicit value, then each
13265 element of the list is a source file name.
13267 @smallexample @c projectfile
13268 for Source_Files use ("main.adb");
13269 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
13273 If the attribute @code{Source_Files} is not given an explicit value,
13274 but the attribute @code{Source_List_File} is given a string value,
13275 then the source file names are contained in the text file whose path name
13276 (absolute or relative to the directory of the project file) is the
13277 value of the attribute @code{Source_List_File}.
13279 Each line in the file that is not empty or is not a comment
13280 contains a source file name.
13282 @smallexample @c projectfile
13283 for Source_List_File use "source_list.txt";
13287 By default, if neither the attribute @code{Source_Files} nor the attribute
13288 @code{Source_List_File} is given an explicit value, then each file in the
13289 source directories that conforms to the project's naming scheme
13290 (@pxref{Naming Schemes}) is an immediate source of the project.
13292 A warning is issued if both attributes @code{Source_Files} and
13293 @code{Source_List_File} are given explicit values. In this case, the attribute
13294 @code{Source_Files} prevails.
13296 Each source file name must be the name of one existing source file
13297 in one of the source directories.
13299 A @code{Source_Files} attribute whose value is an empty list
13300 indicates that there are no source files in the project.
13302 If the order of the source directories is known statically, that is if
13303 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13304 be several files with the same source file name. In this case, only the file
13305 in the first directory is considered as an immediate source of the project
13306 file. If the order of the source directories is not known statically, it is
13307 an error to have several files with the same source file name.
13309 Projects can be specified to have no Ada source
13310 files: the value of (@code{Source_Dirs} or @code{Source_Files} may be an empty
13311 list, or the @code{"Ada"} may be absent from @code{Languages}:
13313 @smallexample @c projectfile
13314 for Source_Dirs use ();
13315 for Source_Files use ();
13316 for Languages use ("C", "C++");
13320 Otherwise, a project must contain at least one immediate source.
13322 Projects with no source files are useful as template packages
13323 (@pxref{Packages in Project Files}) for other projects; in particular to
13324 define a package @code{Naming} (@pxref{Naming Schemes}).
13326 @c ****************************
13327 @c * Importing Projects *
13328 @c ****************************
13330 @node Importing Projects
13331 @section Importing Projects
13332 @cindex @code{ADA_PROJECT_PATH}
13335 An immediate source of a project P may depend on source files that
13336 are neither immediate sources of P nor in the predefined library.
13337 To get this effect, P must @emph{import} the projects that contain the needed
13340 @smallexample @c projectfile
13342 with "project1", "utilities.gpr";
13343 with "/namings/apex.gpr";
13350 As can be seen in this example, the syntax for importing projects is similar
13351 to the syntax for importing compilation units in Ada. However, project files
13352 use literal strings instead of names, and the @code{with} clause identifies
13353 project files rather than packages.
13355 Each literal string is the file name or path name (absolute or relative) of a
13356 project file. If a string corresponds to a file name, with no path or a
13357 relative path, then its location is determined by the @emph{project path}. The
13358 latter can be queried using @code{gnatls -v}. It contains:
13362 In first position, the directory containing the current project file.
13364 In last position, the default project directory. This default project directory
13365 is part of the GNAT installation and is the standard place to install project
13366 files giving access to standard support libraries.
13368 @ref{Installing a library}
13372 In between, all the directories referenced in the
13373 ^environment variable^logical name^ @env{ADA_PROJECT_PATH} if it exists.
13377 If a relative pathname is used, as in
13379 @smallexample @c projectfile
13384 then the full path for the project is constructed by concatenating this
13385 relative path to those in the project path, in order, until a matching file is
13386 found. Any symbolic link will be fully resolved in the directory of the
13387 importing project file before the imported project file is examined.
13389 If the @code{with}'ed project file name does not have an extension,
13390 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13391 then the file name as specified in the @code{with} clause (no extension) will
13392 be used. In the above example, if a file @code{project1.gpr} is found, then it
13393 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13394 then it will be used; if neither file exists, this is an error.
13396 A warning is issued if the name of the project file does not match the
13397 name of the project; this check is case insensitive.
13399 Any source file that is an immediate source of the imported project can be
13400 used by the immediate sources of the importing project, transitively. Thus
13401 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13402 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13403 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13404 because if and when @code{B} ceases to import @code{C}, some sources in
13405 @code{A} will no longer compile.
13407 A side effect of this capability is that normally cyclic dependencies are not
13408 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13409 is not allowed to import @code{A}. However, there are cases when cyclic
13410 dependencies would be beneficial. For these cases, another form of import
13411 between projects exists, the @code{limited with}: a project @code{A} that
13412 imports a project @code{B} with a straight @code{with} may also be imported,
13413 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13414 to @code{A} include at least one @code{limited with}.
13416 @smallexample @c 0projectfile
13422 limited with "../a/a.gpr";
13430 limited with "../a/a.gpr";
13436 In the above legal example, there are two project cycles:
13439 @item A -> C -> D -> A
13443 In each of these cycle there is one @code{limited with}: import of @code{A}
13444 from @code{B} and import of @code{A} from @code{D}.
13446 The difference between straight @code{with} and @code{limited with} is that
13447 the name of a project imported with a @code{limited with} cannot be used in the
13448 project that imports it. In particular, its packages cannot be renamed and
13449 its variables cannot be referred to.
13451 An exception to the above rules for @code{limited with} is that for the main
13452 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13453 @code{limited with} is equivalent to a straight @code{with}. For example,
13454 in the example above, projects @code{B} and @code{D} could not be main
13455 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13456 each have a @code{limited with} that is the only one in a cycle of importing
13459 @c *********************
13460 @c * Project Extension *
13461 @c *********************
13463 @node Project Extension
13464 @section Project Extension
13467 During development of a large system, it is sometimes necessary to use
13468 modified versions of some of the source files, without changing the original
13469 sources. This can be achieved through the @emph{project extension} facility.
13471 @smallexample @c projectfile
13472 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13476 A project extension declaration introduces an extending project
13477 (the @emph{child}) and a project being extended (the @emph{parent}).
13479 By default, a child project inherits all the sources of its parent.
13480 However, inherited sources can be overridden: a unit in a parent is hidden
13481 by a unit of the same name in the child.
13483 Inherited sources are considered to be sources (but not immediate sources)
13484 of the child project; see @ref{Project File Syntax}.
13486 An inherited source file retains any switches specified in the parent project.
13488 For example if the project @code{Utilities} contains the spec and the
13489 body of an Ada package @code{Util_IO}, then the project
13490 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13491 The original body of @code{Util_IO} will not be considered in program builds.
13492 However, the package spec will still be found in the project
13495 A child project can have only one parent, except when it is qualified as
13496 abstract. But it may import any number of other projects.
13498 A project is not allowed to import directly or indirectly at the same time a
13499 child project and any of its ancestors.
13501 @c *******************************
13502 @c * Project Hierarchy Extension *
13503 @c *******************************
13505 @node Project Hierarchy Extension
13506 @section Project Hierarchy Extension
13509 When extending a large system spanning multiple projects, it is often
13510 inconvenient to extend every project in the hierarchy that is impacted by a
13511 small change introduced. In such cases, it is possible to create a virtual
13512 extension of entire hierarchy using @code{extends all} relationship.
13514 When the project is extended using @code{extends all} inheritance, all projects
13515 that are imported by it, both directly and indirectly, are considered virtually
13516 extended. That is, the Project Manager creates "virtual projects"
13517 that extend every project in the hierarchy; all these virtual projects have
13518 no sources of their own and have as object directory the object directory of
13519 the root of "extending all" project.
13521 It is possible to explicitly extend one or more projects in the hierarchy
13522 in order to modify the sources. These extending projects must be imported by
13523 the "extending all" project, which will replace the corresponding virtual
13524 projects with the explicit ones.
13526 When building such a project hierarchy extension, the Project Manager will
13527 ensure that both modified sources and sources in virtual extending projects
13528 that depend on them, are recompiled.
13530 By means of example, consider the following hierarchy of projects.
13534 project A, containing package P1
13536 project B importing A and containing package P2 which depends on P1
13538 project C importing B and containing package P3 which depends on P2
13542 We want to modify packages P1 and P3.
13544 This project hierarchy will need to be extended as follows:
13548 Create project A1 that extends A, placing modified P1 there:
13550 @smallexample @c 0projectfile
13551 project A1 extends "(@dots{})/A" is
13556 Create project C1 that "extends all" C and imports A1, placing modified
13559 @smallexample @c 0projectfile
13560 with "(@dots{})/A1";
13561 project C1 extends all "(@dots{})/C" is
13566 When you build project C1, your entire modified project space will be
13567 recompiled, including the virtual project B1 that has been impacted by the
13568 "extending all" inheritance of project C.
13570 Note that if a Library Project in the hierarchy is virtually extended,
13571 the virtual project that extends the Library Project is not a Library Project.
13573 @c ****************************************
13574 @c * External References in Project Files *
13575 @c ****************************************
13577 @node External References in Project Files
13578 @section External References in Project Files
13581 A project file may contain references to external variables; such references
13582 are called @emph{external references}.
13584 An external variable is either defined as part of the environment (an
13585 environment variable in Unix, for example) or else specified on the command
13586 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13587 If both, then the command line value is used.
13589 The value of an external reference is obtained by means of the built-in
13590 function @code{external}, which returns a string value.
13591 This function has two forms:
13593 @item @code{external (external_variable_name)}
13594 @item @code{external (external_variable_name, default_value)}
13598 Each parameter must be a string literal. For example:
13600 @smallexample @c projectfile
13602 external ("OS", "GNU/Linux")
13606 In the form with one parameter, the function returns the value of
13607 the external variable given as parameter. If this name is not present in the
13608 environment, the function returns an empty string.
13610 In the form with two string parameters, the second argument is
13611 the value returned when the variable given as the first argument is not
13612 present in the environment. In the example above, if @code{"OS"} is not
13613 the name of ^an environment variable^a logical name^ and is not passed on
13614 the command line, then the returned value is @code{"GNU/Linux"}.
13616 An external reference may be part of a string expression or of a string
13617 list expression, and can therefore appear in a variable declaration or
13618 an attribute declaration.
13620 @smallexample @c projectfile
13622 type Mode_Type is ("Debug", "Release");
13623 Mode : Mode_Type := external ("MODE");
13630 @c *****************************
13631 @c * Packages in Project Files *
13632 @c *****************************
13634 @node Packages in Project Files
13635 @section Packages in Project Files
13638 A @emph{package} defines the settings for project-aware tools within a
13640 For each such tool one can declare a package; the names for these
13641 packages are preset (@pxref{Packages}).
13642 A package may contain variable declarations, attribute declarations, and case
13645 @smallexample @c projectfile
13648 package Builder is -- used by gnatmake
13649 for ^Default_Switches^Default_Switches^ ("Ada")
13658 The syntax of package declarations mimics that of package in Ada.
13660 Most of the packages have an attribute
13661 @code{^Default_Switches^Default_Switches^}.
13662 This attribute is an associative array, and its value is a string list.
13663 The index of the associative array is the name of a programming language (case
13664 insensitive). This attribute indicates the ^switch^switch^
13665 or ^switches^switches^ to be used
13666 with the corresponding tool.
13668 Some packages also have another attribute, @code{^Switches^Switches^},
13669 an associative array whose value is a string list.
13670 The index is the name of a source file.
13671 This attribute indicates the ^switch^switch^
13672 or ^switches^switches^ to be used by the corresponding
13673 tool when dealing with this specific file.
13675 Further information on these ^switch^switch^-related attributes is found in
13676 @ref{^Switches^Switches^ and Project Files}.
13678 A package may be declared as a @emph{renaming} of another package; e.g., from
13679 the project file for an imported project.
13681 @smallexample @c projectfile
13683 with "/global/apex.gpr";
13685 package Naming renames Apex.Naming;
13692 Packages that are renamed in other project files often come from project files
13693 that have no sources: they are just used as templates. Any modification in the
13694 template will be reflected automatically in all the project files that rename
13695 a package from the template.
13697 In addition to the tool-oriented packages, you can also declare a package
13698 named @code{Naming} to establish specialized source file naming conventions
13699 (@pxref{Naming Schemes}).
13701 @c ************************************
13702 @c * Variables from Imported Projects *
13703 @c ************************************
13705 @node Variables from Imported Projects
13706 @section Variables from Imported Projects
13709 An attribute or variable defined in an imported or parent project can
13710 be used in expressions in the importing / extending project.
13711 Such an attribute or variable is denoted by an expanded name whose prefix
13712 is either the name of the project or the expanded name of a package within
13715 @smallexample @c projectfile
13718 project Main extends "base" is
13719 Var1 := Imported.Var;
13720 Var2 := Base.Var & ".new";
13725 for ^Default_Switches^Default_Switches^ ("Ada")
13726 use Imported.Builder'Ada_^Switches^Switches^ &
13727 "^-gnatg^-gnatg^" &
13733 package Compiler is
13734 for ^Default_Switches^Default_Switches^ ("Ada")
13735 use Base.Compiler'Ada_^Switches^Switches^;
13746 The value of @code{Var1} is a copy of the variable @code{Var} defined
13747 in the project file @file{"imported.gpr"}
13749 the value of @code{Var2} is a copy of the value of variable @code{Var}
13750 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13752 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13753 @code{Builder} is a string list that includes in its value a copy of the value
13754 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13755 in project file @file{imported.gpr} plus two new elements:
13756 @option{"^-gnatg^-gnatg^"}
13757 and @option{"^-v^-v^"};
13759 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13760 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13761 defined in the @code{Compiler} package in project file @file{base.gpr},
13762 the project being extended.
13765 @c ******************
13766 @c * Naming Schemes *
13767 @c ******************
13769 @node Naming Schemes
13770 @section Naming Schemes
13773 Sometimes an Ada software system is ported from a foreign compilation
13774 environment to GNAT, and the file names do not use the default GNAT
13775 conventions. Instead of changing all the file names (which for a variety
13776 of reasons might not be possible), you can define the relevant file
13777 naming scheme in the @code{Naming} package in your project file.
13780 Note that the use of pragmas described in
13781 @ref{Alternative File Naming Schemes} by mean of a configuration
13782 pragmas file is not supported when using project files. You must use
13783 the features described in this paragraph. You can however use specify
13784 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13787 For example, the following
13788 package models the Apex file naming rules:
13790 @smallexample @c projectfile
13793 for Casing use "lowercase";
13794 for Dot_Replacement use ".";
13795 for Spec_Suffix ("Ada") use ".1.ada";
13796 for Body_Suffix ("Ada") use ".2.ada";
13803 For example, the following package models the HP Ada file naming rules:
13805 @smallexample @c projectfile
13808 for Casing use "lowercase";
13809 for Dot_Replacement use "__";
13810 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13811 for Body_Suffix ("Ada") use ".^ada^ada^";
13817 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13818 names in lower case)
13822 You can define the following attributes in package @code{Naming}:
13826 @item @code{Casing}
13827 This must be a string with one of the three values @code{"lowercase"},
13828 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13831 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13833 @item @code{Dot_Replacement}
13834 This must be a string whose value satisfies the following conditions:
13837 @item It must not be empty
13838 @item It cannot start or end with an alphanumeric character
13839 @item It cannot be a single underscore
13840 @item It cannot start with an underscore followed by an alphanumeric
13841 @item It cannot contain a dot @code{'.'} except if the entire string
13846 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13848 @item @code{Spec_Suffix}
13849 This is an associative array (indexed by the programming language name, case
13850 insensitive) whose value is a string that must satisfy the following
13854 @item It must not be empty
13855 @item It must include at least one dot
13858 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13859 @code{"^.ads^.ADS^"}.
13861 @item @code{Body_Suffix}
13862 This is an associative array (indexed by the programming language name, case
13863 insensitive) whose value is a string that must satisfy the following
13867 @item It must not be empty
13868 @item It must include at least one dot
13869 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13872 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13873 same string, then a file name that ends with the longest of these two suffixes
13874 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13875 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13877 If the suffix does not start with a '.', a file with a name exactly equal
13878 to the suffix will also be part of the project (for instance if you define
13879 the suffix as @code{Makefile}, a file called @file{Makefile} will be part
13880 of the project. This is not interesting in general when using projects to
13881 compile. However, it might become useful when a project is also used to
13882 find the list of source files in an editor, like the GNAT Programming System
13885 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13886 @code{"^.adb^.ADB^"}.
13888 @item @code{Separate_Suffix}
13889 This must be a string whose value satisfies the same conditions as
13890 @code{Body_Suffix}. The same "longest suffix" rules apply.
13893 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13894 value as @code{Body_Suffix ("Ada")}.
13898 You can use the associative array attribute @code{Spec} to define
13899 the source file name for an individual Ada compilation unit's spec. The array
13900 index must be a string literal that identifies the Ada unit (case insensitive).
13901 The value of this attribute must be a string that identifies the file that
13902 contains this unit's spec (case sensitive or insensitive depending on the
13905 @smallexample @c projectfile
13906 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13909 When the source file contains several units, you can indicate at what
13910 position the unit occurs in the file, with the following. The first unit
13911 in the file has index 1
13913 @smallexample @c projectfile
13914 for Body ("top") use "foo.a" at 1;
13915 for Body ("foo") use "foo.a" at 2;
13920 You can use the associative array attribute @code{Body} to
13921 define the source file name for an individual Ada compilation unit's body
13922 (possibly a subunit). The array index must be a string literal that identifies
13923 the Ada unit (case insensitive). The value of this attribute must be a string
13924 that identifies the file that contains this unit's body or subunit (case
13925 sensitive or insensitive depending on the operating system).
13927 @smallexample @c projectfile
13928 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13932 @c ********************
13933 @c * Library Projects *
13934 @c ********************
13936 @node Library Projects
13937 @section Library Projects
13940 @emph{Library projects} are projects whose object code is placed in a library.
13941 (Note that this facility is not yet supported on all platforms).
13943 @code{gnatmake} or @code{gprbuild} will collect all object files into a
13944 single archive, which might either be a shared or a static library. This
13945 library can later on be linked with multiple executables, potentially
13946 reducing their sizes.
13948 If your project file specifies languages other than Ada, but you are still
13949 using @code{gnatmake} to compile and link, the latter will not try to
13950 compile your sources other than Ada (you should use @code{gprbuild} if that
13951 is your intent). However, @code{gnatmake} will automatically link all object
13952 files found in the object directory, whether or not they were compiled from
13953 an Ada source file. This specific behavior only applies when multiple
13954 languages are specified.
13956 To create a library project, you need to define in its project file
13957 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
13958 Additionally, you may define other library-related attributes such as
13959 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
13960 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
13962 The @code{Library_Name} attribute has a string value. There is no restriction
13963 on the name of a library. It is the responsibility of the developer to
13964 choose a name that will be accepted by the platform. It is recommended to
13965 choose names that could be Ada identifiers; such names are almost guaranteed
13966 to be acceptable on all platforms.
13968 The @code{Library_Dir} attribute has a string value that designates the path
13969 (absolute or relative) of the directory where the library will reside.
13970 It must designate an existing directory, and this directory must be writable,
13971 different from the project's object directory and from any source directory
13972 in the project tree.
13974 If both @code{Library_Name} and @code{Library_Dir} are specified and
13975 are legal, then the project file defines a library project. The optional
13976 library-related attributes are checked only for such project files.
13978 The @code{Library_Kind} attribute has a string value that must be one of the
13979 following (case insensitive): @code{"static"}, @code{"dynamic"} or
13980 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
13981 attribute is not specified, the library is a static library, that is
13982 an archive of object files that can be potentially linked into a
13983 static executable. Otherwise, the library may be dynamic or
13984 relocatable, that is a library that is loaded only at the start of execution.
13986 If you need to build both a static and a dynamic library, you should use two
13987 different object directories, since in some cases some extra code needs to
13988 be generated for the latter. For such cases, it is recommended to either use
13989 two different project files, or a single one which uses external variables
13990 to indicate what kind of library should be build.
13992 The @code{Library_ALI_Dir} attribute may be specified to indicate the
13993 directory where the ALI files of the library will be copied. When it is
13994 not specified, the ALI files are copied to the directory specified in
13995 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
13996 must be writable and different from the project's object directory and from
13997 any source directory in the project tree.
13999 The @code{Library_Version} attribute has a string value whose interpretation
14000 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
14001 used only for dynamic/relocatable libraries as the internal name of the
14002 library (the @code{"soname"}). If the library file name (built from the
14003 @code{Library_Name}) is different from the @code{Library_Version}, then the
14004 library file will be a symbolic link to the actual file whose name will be
14005 @code{Library_Version}.
14009 @smallexample @c projectfile
14015 for Library_Dir use "lib_dir";
14016 for Library_Name use "dummy";
14017 for Library_Kind use "relocatable";
14018 for Library_Version use "libdummy.so." & Version;
14025 Directory @file{lib_dir} will contain the internal library file whose name
14026 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
14027 @file{libdummy.so.1}.
14029 When @command{gnatmake} detects that a project file
14030 is a library project file, it will check all immediate sources of the project
14031 and rebuild the library if any of the sources have been recompiled.
14033 Standard project files can import library project files. In such cases,
14034 the libraries will only be rebuilt if some of its sources are recompiled
14035 because they are in the closure of some other source in an importing project.
14036 Sources of the library project files that are not in such a closure will
14037 not be checked, unless the full library is checked, because one of its sources
14038 needs to be recompiled.
14040 For instance, assume the project file @code{A} imports the library project file
14041 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
14042 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
14043 @file{l2.ads}, @file{l2.adb}.
14045 If @file{l1.adb} has been modified, then the library associated with @code{L}
14046 will be rebuilt when compiling all the immediate sources of @code{A} only
14047 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
14050 To be sure that all the sources in the library associated with @code{L} are
14051 up to date, and that all the sources of project @code{A} are also up to date,
14052 the following two commands needs to be used:
14059 When a library is built or rebuilt, an attempt is made first to delete all
14060 files in the library directory.
14061 All @file{ALI} files will also be copied from the object directory to the
14062 library directory. To build executables, @command{gnatmake} will use the
14063 library rather than the individual object files.
14066 It is also possible to create library project files for third-party libraries
14067 that are precompiled and cannot be compiled locally thanks to the
14068 @code{externally_built} attribute. (See @ref{Installing a library}).
14071 @c *******************************
14072 @c * Stand-alone Library Projects *
14073 @c *******************************
14075 @node Stand-alone Library Projects
14076 @section Stand-alone Library Projects
14079 A Stand-alone Library is a library that contains the necessary code to
14080 elaborate the Ada units that are included in the library. A Stand-alone
14081 Library is suitable to be used in an executable when the main is not
14082 in Ada. However, Stand-alone Libraries may also be used with an Ada main
14085 A Stand-alone Library Project is a Library Project where the library is
14086 a Stand-alone Library.
14088 To be a Stand-alone Library Project, in addition to the two attributes
14089 that make a project a Library Project (@code{Library_Name} and
14090 @code{Library_Dir}, see @ref{Library Projects}), the attribute
14091 @code{Library_Interface} must be defined.
14093 @smallexample @c projectfile
14095 for Library_Dir use "lib_dir";
14096 for Library_Name use "dummy";
14097 for Library_Interface use ("int1", "int1.child");
14101 Attribute @code{Library_Interface} has a nonempty string list value,
14102 each string in the list designating a unit contained in an immediate source
14103 of the project file.
14105 When a Stand-alone Library is built, first the binder is invoked to build
14106 a package whose name depends on the library name
14107 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
14108 This binder-generated package includes initialization and
14109 finalization procedures whose
14110 names depend on the library name (dummyinit and dummyfinal in the example
14111 above). The object corresponding to this package is included in the library.
14113 A dynamic or relocatable Stand-alone Library is automatically initialized
14114 if automatic initialization of Stand-alone Libraries is supported on the
14115 platform and if attribute @code{Library_Auto_Init} is not specified or
14116 is specified with the value "true". A static Stand-alone Library is never
14117 automatically initialized.
14119 Single string attribute @code{Library_Auto_Init} may be specified with only
14120 two possible values: "false" or "true" (case-insensitive). Specifying
14121 "false" for attribute @code{Library_Auto_Init} will prevent automatic
14122 initialization of dynamic or relocatable libraries.
14124 When a non-automatically initialized Stand-alone Library is used
14125 in an executable, its initialization procedure must be called before
14126 any service of the library is used.
14127 When the main subprogram is in Ada, it may mean that the initialization
14128 procedure has to be called during elaboration of another package.
14130 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
14131 (those that are listed in attribute @code{Library_Interface}) are copied to
14132 the Library Directory. As a consequence, only the Interface Units may be
14133 imported from Ada units outside of the library. If other units are imported,
14134 the binding phase will fail.
14136 When a Stand-Alone Library is bound, the switches that are specified in
14137 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
14138 used in the call to @command{gnatbind}.
14140 The string list attribute @code{Library_Options} may be used to specified
14141 additional switches to the call to @command{gcc} to link the library.
14143 The attribute @code{Library_Src_Dir}, may be specified for a
14144 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
14145 single string value. Its value must be the path (absolute or relative to the
14146 project directory) of an existing directory. This directory cannot be the
14147 object directory or one of the source directories, but it can be the same as
14148 the library directory. The sources of the Interface
14149 Units of the library, necessary to an Ada client of the library, will be
14150 copied to the designated directory, called Interface Copy directory.
14151 These sources includes the specs of the Interface Units, but they may also
14152 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
14153 are used, or when there is a generic units in the spec. Before the sources
14154 are copied to the Interface Copy directory, an attempt is made to delete all
14155 files in the Interface Copy directory.
14157 @c *************************************
14158 @c * Switches Related to Project Files *
14159 @c *************************************
14160 @node Switches Related to Project Files
14161 @section Switches Related to Project Files
14164 The following switches are used by GNAT tools that support project files:
14168 @item ^-P^/PROJECT_FILE=^@var{project}
14169 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
14170 Indicates the name of a project file. This project file will be parsed with
14171 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
14172 if any, and using the external references indicated
14173 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
14175 There may zero, one or more spaces between @option{-P} and @var{project}.
14179 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
14182 Since the Project Manager parses the project file only after all the switches
14183 on the command line are checked, the order of the switches
14184 @option{^-P^/PROJECT_FILE^},
14185 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
14186 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
14188 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
14189 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
14190 Indicates that external variable @var{name} has the value @var{value}.
14191 The Project Manager will use this value for occurrences of
14192 @code{external(name)} when parsing the project file.
14196 If @var{name} or @var{value} includes a space, then @var{name=value} should be
14197 put between quotes.
14205 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
14206 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
14207 @var{name}, only the last one is used.
14210 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
14211 takes precedence over the value of the same name in the environment.
14213 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
14214 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
14215 Indicates the verbosity of the parsing of GNAT project files.
14218 @option{-vP0} means Default;
14219 @option{-vP1} means Medium;
14220 @option{-vP2} means High.
14224 There are three possible options for this qualifier: DEFAULT, MEDIUM and
14229 The default is ^Default^DEFAULT^: no output for syntactically correct
14232 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
14233 only the last one is used.
14235 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
14236 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
14237 Add directory <dir> at the beginning of the project search path, in order,
14238 after the current working directory.
14242 @cindex @option{-eL} (any project-aware tool)
14243 Follow all symbolic links when processing project files.
14246 @item ^--subdirs^/SUBDIRS^=<subdir>
14247 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
14248 This switch is recognized by gnatmake and gnatclean. It indicate that the real
14249 directories (except the source directories) are the subdirectories <subdir>
14250 of the directories specified in the project files. This applies in particular
14251 to object directories, library directories and exec directories. If the
14252 subdirectories do not exist, they are created automatically.
14256 @c **********************************
14257 @c * Tools Supporting Project Files *
14258 @c **********************************
14260 @node Tools Supporting Project Files
14261 @section Tools Supporting Project Files
14264 * gnatmake and Project Files::
14265 * The GNAT Driver and Project Files::
14268 @node gnatmake and Project Files
14269 @subsection gnatmake and Project Files
14272 This section covers several topics related to @command{gnatmake} and
14273 project files: defining ^switches^switches^ for @command{gnatmake}
14274 and for the tools that it invokes; specifying configuration pragmas;
14275 the use of the @code{Main} attribute; building and rebuilding library project
14279 * ^Switches^Switches^ and Project Files::
14280 * Specifying Configuration Pragmas::
14281 * Project Files and Main Subprograms::
14282 * Library Project Files::
14285 @node ^Switches^Switches^ and Project Files
14286 @subsubsection ^Switches^Switches^ and Project Files
14289 It is not currently possible to specify VMS style qualifiers in the project
14290 files; only Unix style ^switches^switches^ may be specified.
14294 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
14295 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
14296 attribute, a @code{^Switches^Switches^} attribute, or both;
14297 as their names imply, these ^switch^switch^-related
14298 attributes affect the ^switches^switches^ that are used for each of these GNAT
14300 @command{gnatmake} is invoked. As will be explained below, these
14301 component-specific ^switches^switches^ precede
14302 the ^switches^switches^ provided on the @command{gnatmake} command line.
14304 The @code{^Default_Switches^Default_Switches^} attribute is an associative
14305 array indexed by language name (case insensitive) whose value is a string list.
14308 @smallexample @c projectfile
14310 package Compiler is
14311 for ^Default_Switches^Default_Switches^ ("Ada")
14312 use ("^-gnaty^-gnaty^",
14319 The @code{^Switches^Switches^} attribute is also an associative array,
14320 indexed by a file name (which may or may not be case sensitive, depending
14321 on the operating system) whose value is a string list. For example:
14323 @smallexample @c projectfile
14326 for ^Switches^Switches^ ("main1.adb")
14328 for ^Switches^Switches^ ("main2.adb")
14335 For the @code{Builder} package, the file names must designate source files
14336 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14337 file names must designate @file{ALI} or source files for main subprograms.
14338 In each case just the file name without an explicit extension is acceptable.
14340 For each tool used in a program build (@command{gnatmake}, the compiler, the
14341 binder, and the linker), the corresponding package @dfn{contributes} a set of
14342 ^switches^switches^ for each file on which the tool is invoked, based on the
14343 ^switch^switch^-related attributes defined in the package.
14344 In particular, the ^switches^switches^
14345 that each of these packages contributes for a given file @var{f} comprise:
14349 the value of attribute @code{^Switches^Switches^ (@var{f})},
14350 if it is specified in the package for the given file,
14352 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14353 if it is specified in the package.
14357 If neither of these attributes is defined in the package, then the package does
14358 not contribute any ^switches^switches^ for the given file.
14360 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14361 two sets, in the following order: those contributed for the file
14362 by the @code{Builder} package;
14363 and the switches passed on the command line.
14365 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14366 the ^switches^switches^ passed to the tool comprise three sets,
14367 in the following order:
14371 the applicable ^switches^switches^ contributed for the file
14372 by the @code{Builder} package in the project file supplied on the command line;
14375 those contributed for the file by the package (in the relevant project file --
14376 see below) corresponding to the tool; and
14379 the applicable switches passed on the command line.
14383 The term @emph{applicable ^switches^switches^} reflects the fact that
14384 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14385 tools, depending on the individual ^switch^switch^.
14387 @command{gnatmake} may invoke the compiler on source files from different
14388 projects. The Project Manager will use the appropriate project file to
14389 determine the @code{Compiler} package for each source file being compiled.
14390 Likewise for the @code{Binder} and @code{Linker} packages.
14392 As an example, consider the following package in a project file:
14394 @smallexample @c projectfile
14397 package Compiler is
14398 for ^Default_Switches^Default_Switches^ ("Ada")
14400 for ^Switches^Switches^ ("a.adb")
14402 for ^Switches^Switches^ ("b.adb")
14404 "^-gnaty^-gnaty^");
14411 If @command{gnatmake} is invoked with this project file, and it needs to
14412 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14413 @file{a.adb} will be compiled with the ^switch^switch^
14414 @option{^-O1^-O1^},
14415 @file{b.adb} with ^switches^switches^
14417 and @option{^-gnaty^-gnaty^},
14418 and @file{c.adb} with @option{^-g^-g^}.
14420 The following example illustrates the ordering of the ^switches^switches^
14421 contributed by different packages:
14423 @smallexample @c projectfile
14427 for ^Switches^Switches^ ("main.adb")
14435 package Compiler is
14436 for ^Switches^Switches^ ("main.adb")
14444 If you issue the command:
14447 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14451 then the compiler will be invoked on @file{main.adb} with the following
14452 sequence of ^switches^switches^
14455 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14458 with the last @option{^-O^-O^}
14459 ^switch^switch^ having precedence over the earlier ones;
14460 several other ^switches^switches^
14461 (such as @option{^-c^-c^}) are added implicitly.
14463 The ^switches^switches^
14465 and @option{^-O1^-O1^} are contributed by package
14466 @code{Builder}, @option{^-O2^-O2^} is contributed
14467 by the package @code{Compiler}
14468 and @option{^-O0^-O0^} comes from the command line.
14470 The @option{^-g^-g^}
14471 ^switch^switch^ will also be passed in the invocation of
14472 @command{Gnatlink.}
14474 A final example illustrates switch contributions from packages in different
14477 @smallexample @c projectfile
14480 for Source_Files use ("pack.ads", "pack.adb");
14481 package Compiler is
14482 for ^Default_Switches^Default_Switches^ ("Ada")
14483 use ("^-gnata^-gnata^");
14491 for Source_Files use ("foo_main.adb", "bar_main.adb");
14493 for ^Switches^Switches^ ("foo_main.adb")
14501 -- Ada source file:
14503 procedure Foo_Main is
14511 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14515 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14516 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14517 @option{^-gnato^-gnato^} (passed on the command line).
14518 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14519 are @option{^-g^-g^} from @code{Proj4.Builder},
14520 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14521 and @option{^-gnato^-gnato^} from the command line.
14524 When using @command{gnatmake} with project files, some ^switches^switches^ or
14525 arguments may be expressed as relative paths. As the working directory where
14526 compilation occurs may change, these relative paths are converted to absolute
14527 paths. For the ^switches^switches^ found in a project file, the relative paths
14528 are relative to the project file directory, for the switches on the command
14529 line, they are relative to the directory where @command{gnatmake} is invoked.
14530 The ^switches^switches^ for which this occurs are:
14536 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14538 ^-o^-o^, object files specified in package @code{Linker} or after
14539 -largs on the command line). The exception to this rule is the ^switch^switch^
14540 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14542 @node Specifying Configuration Pragmas
14543 @subsubsection Specifying Configuration Pragmas
14545 When using @command{gnatmake} with project files, if there exists a file
14546 @file{gnat.adc} that contains configuration pragmas, this file will be
14549 Configuration pragmas can be defined by means of the following attributes in
14550 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14551 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14553 Both these attributes are single string attributes. Their values is the path
14554 name of a file containing configuration pragmas. If a path name is relative,
14555 then it is relative to the project directory of the project file where the
14556 attribute is defined.
14558 When compiling a source, the configuration pragmas used are, in order,
14559 those listed in the file designated by attribute
14560 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14561 project file, if it is specified, and those listed in the file designated by
14562 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14563 the project file of the source, if it exists.
14565 @node Project Files and Main Subprograms
14566 @subsubsection Project Files and Main Subprograms
14569 When using a project file, you can invoke @command{gnatmake}
14570 with one or several main subprograms, by specifying their source files on the
14574 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14578 Each of these needs to be a source file of the same project, except
14579 when the switch ^-u^/UNIQUE^ is used.
14582 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14583 same project, one of the project in the tree rooted at the project specified
14584 on the command line. The package @code{Builder} of this common project, the
14585 "main project" is the one that is considered by @command{gnatmake}.
14588 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14589 imported directly or indirectly by the project specified on the command line.
14590 Note that if such a source file is not part of the project specified on the
14591 command line, the ^switches^switches^ found in package @code{Builder} of the
14592 project specified on the command line, if any, that are transmitted
14593 to the compiler will still be used, not those found in the project file of
14597 When using a project file, you can also invoke @command{gnatmake} without
14598 explicitly specifying any main, and the effect depends on whether you have
14599 defined the @code{Main} attribute. This attribute has a string list value,
14600 where each element in the list is the name of a source file (the file
14601 extension is optional) that contains a unit that can be a main subprogram.
14603 If the @code{Main} attribute is defined in a project file as a non-empty
14604 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14605 line, then invoking @command{gnatmake} with this project file but without any
14606 main on the command line is equivalent to invoking @command{gnatmake} with all
14607 the file names in the @code{Main} attribute on the command line.
14610 @smallexample @c projectfile
14613 for Main use ("main1", "main2", "main3");
14619 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14621 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14623 When the project attribute @code{Main} is not specified, or is specified
14624 as an empty string list, or when the switch @option{-u} is used on the command
14625 line, then invoking @command{gnatmake} with no main on the command line will
14626 result in all immediate sources of the project file being checked, and
14627 potentially recompiled. Depending on the presence of the switch @option{-u},
14628 sources from other project files on which the immediate sources of the main
14629 project file depend are also checked and potentially recompiled. In other
14630 words, the @option{-u} switch is applied to all of the immediate sources of the
14633 When no main is specified on the command line and attribute @code{Main} exists
14634 and includes several mains, or when several mains are specified on the
14635 command line, the default ^switches^switches^ in package @code{Builder} will
14636 be used for all mains, even if there are specific ^switches^switches^
14637 specified for one or several mains.
14639 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14640 the specific ^switches^switches^ for each main, if they are specified.
14642 @node Library Project Files
14643 @subsubsection Library Project Files
14646 When @command{gnatmake} is invoked with a main project file that is a library
14647 project file, it is not allowed to specify one or more mains on the command
14651 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14652 ^-l^/ACTION=LINK^ have special meanings.
14655 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14656 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14659 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14660 to @command{gnatmake} that the binder generated file should be compiled
14661 (in the case of a stand-alone library) and that the library should be built.
14665 @node The GNAT Driver and Project Files
14666 @subsection The GNAT Driver and Project Files
14669 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14670 can benefit from project files:
14671 @command{^gnatbind^gnatbind^},
14672 @command{^gnatcheck^gnatcheck^}),
14673 @command{^gnatclean^gnatclean^}),
14674 @command{^gnatelim^gnatelim^},
14675 @command{^gnatfind^gnatfind^},
14676 @command{^gnatlink^gnatlink^},
14677 @command{^gnatls^gnatls^},
14678 @command{^gnatmetric^gnatmetric^},
14679 @command{^gnatpp^gnatpp^},
14680 @command{^gnatstub^gnatstub^},
14681 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14682 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14683 They must be invoked through the @command{gnat} driver.
14685 The @command{gnat} driver is a wrapper that accepts a number of commands and
14686 calls the corresponding tool. It was designed initially for VMS platforms (to
14687 convert VMS qualifiers to Unix-style switches), but it is now available on all
14690 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14691 (case insensitive):
14695 BIND to invoke @command{^gnatbind^gnatbind^}
14697 CHOP to invoke @command{^gnatchop^gnatchop^}
14699 CLEAN to invoke @command{^gnatclean^gnatclean^}
14701 COMP or COMPILE to invoke the compiler
14703 ELIM to invoke @command{^gnatelim^gnatelim^}
14705 FIND to invoke @command{^gnatfind^gnatfind^}
14707 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14709 LINK to invoke @command{^gnatlink^gnatlink^}
14711 LS or LIST to invoke @command{^gnatls^gnatls^}
14713 MAKE to invoke @command{^gnatmake^gnatmake^}
14715 NAME to invoke @command{^gnatname^gnatname^}
14717 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14719 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14721 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14723 STUB to invoke @command{^gnatstub^gnatstub^}
14725 XREF to invoke @command{^gnatxref^gnatxref^}
14729 (note that the compiler is invoked using the command
14730 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14733 On non-VMS platforms, between @command{gnat} and the command, two
14734 special switches may be used:
14738 @command{-v} to display the invocation of the tool.
14740 @command{-dn} to prevent the @command{gnat} driver from removing
14741 the temporary files it has created. These temporary files are
14742 configuration files and temporary file list files.
14746 The command may be followed by switches and arguments for the invoked
14750 gnat bind -C main.ali
14756 Switches may also be put in text files, one switch per line, and the text
14757 files may be specified with their path name preceded by '@@'.
14760 gnat bind @@args.txt main.ali
14764 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14765 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14766 (@option{^-P^/PROJECT_FILE^},
14767 @option{^-X^/EXTERNAL_REFERENCE^} and
14768 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14769 the switches of the invoking tool.
14772 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14773 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14774 the immediate sources of the specified project file.
14777 When GNAT METRIC is used with a project file, but with no source
14778 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14779 with all the immediate sources of the specified project file and with
14780 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14784 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14785 a project file, no source is specified on the command line and
14786 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14787 the underlying tool (^gnatpp^gnatpp^ or
14788 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14789 not only for the immediate sources of the main project.
14791 (-U stands for Universal or Union of the project files of the project tree)
14795 For each of the following commands, there is optionally a corresponding
14796 package in the main project.
14800 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14803 package @code{Check} for command CHECK (invoking
14804 @code{^gnatcheck^gnatcheck^})
14807 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14810 package @code{Cross_Reference} for command XREF (invoking
14811 @code{^gnatxref^gnatxref^})
14814 package @code{Eliminate} for command ELIM (invoking
14815 @code{^gnatelim^gnatelim^})
14818 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14821 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14824 package @code{Gnatstub} for command STUB
14825 (invoking @code{^gnatstub^gnatstub^})
14828 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14831 package @code{Metrics} for command METRIC
14832 (invoking @code{^gnatmetric^gnatmetric^})
14835 package @code{Pretty_Printer} for command PP or PRETTY
14836 (invoking @code{^gnatpp^gnatpp^})
14841 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14842 a simple variable with a string list value. It contains ^switches^switches^
14843 for the invocation of @code{^gnatls^gnatls^}.
14845 @smallexample @c projectfile
14849 for ^Switches^Switches^
14858 All other packages have two attribute @code{^Switches^Switches^} and
14859 @code{^Default_Switches^Default_Switches^}.
14862 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14863 source file name, that has a string list value: the ^switches^switches^ to be
14864 used when the tool corresponding to the package is invoked for the specific
14868 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14869 indexed by the programming language that has a string list value.
14870 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14871 ^switches^switches^ for the invocation of the tool corresponding
14872 to the package, except if a specific @code{^Switches^Switches^} attribute
14873 is specified for the source file.
14875 @smallexample @c projectfile
14879 for Source_Dirs use ("./**");
14882 for ^Switches^Switches^ use
14889 package Compiler is
14890 for ^Default_Switches^Default_Switches^ ("Ada")
14891 use ("^-gnatv^-gnatv^",
14892 "^-gnatwa^-gnatwa^");
14898 for ^Default_Switches^Default_Switches^ ("Ada")
14906 for ^Default_Switches^Default_Switches^ ("Ada")
14908 for ^Switches^Switches^ ("main.adb")
14917 for ^Default_Switches^Default_Switches^ ("Ada")
14924 package Cross_Reference is
14925 for ^Default_Switches^Default_Switches^ ("Ada")
14930 end Cross_Reference;
14936 With the above project file, commands such as
14939 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
14940 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
14941 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
14942 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
14943 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
14947 will set up the environment properly and invoke the tool with the switches
14948 found in the package corresponding to the tool:
14949 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
14950 except @code{^Switches^Switches^ ("main.adb")}
14951 for @code{^gnatlink^gnatlink^}.
14952 It is also possible to invoke some of the tools,
14953 @code{^gnatcheck^gnatcheck^}),
14954 @code{^gnatmetric^gnatmetric^}),
14955 and @code{^gnatpp^gnatpp^})
14956 on a set of project units thanks to the combination of the switches
14957 @option{-P}, @option{-U} and possibly the main unit when one is interested
14958 in its closure. For instance,
14962 will compute the metrics for all the immediate units of project
14965 gnat metric -Pproj -U
14967 will compute the metrics for all the units of the closure of projects
14968 rooted at @code{proj}.
14970 gnat metric -Pproj -U main_unit
14972 will compute the metrics for the closure of units rooted at
14973 @code{main_unit}. This last possibility relies implicitly
14974 on @command{gnatbind}'s option @option{-R}.
14976 @c **********************
14977 @node An Extended Example
14978 @section An Extended Example
14981 Suppose that we have two programs, @var{prog1} and @var{prog2},
14982 whose sources are in corresponding directories. We would like
14983 to build them with a single @command{gnatmake} command, and we want to place
14984 their object files into @file{build} subdirectories of the source directories.
14985 Furthermore, we want to have to have two separate subdirectories
14986 in @file{build} -- @file{release} and @file{debug} -- which will contain
14987 the object files compiled with different set of compilation flags.
14989 In other words, we have the following structure:
15006 Here are the project files that we must place in a directory @file{main}
15007 to maintain this structure:
15011 @item We create a @code{Common} project with a package @code{Compiler} that
15012 specifies the compilation ^switches^switches^:
15017 @b{project} Common @b{is}
15019 @b{for} Source_Dirs @b{use} (); -- No source files
15023 @b{type} Build_Type @b{is} ("release", "debug");
15024 Build : Build_Type := External ("BUILD", "debug");
15027 @b{package} Compiler @b{is}
15028 @b{case} Build @b{is}
15029 @b{when} "release" =>
15030 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15031 @b{use} ("^-O2^-O2^");
15032 @b{when} "debug" =>
15033 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15034 @b{use} ("^-g^-g^");
15042 @item We create separate projects for the two programs:
15049 @b{project} Prog1 @b{is}
15051 @b{for} Source_Dirs @b{use} ("prog1");
15052 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
15054 @b{package} Compiler @b{renames} Common.Compiler;
15065 @b{project} Prog2 @b{is}
15067 @b{for} Source_Dirs @b{use} ("prog2");
15068 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
15070 @b{package} Compiler @b{renames} Common.Compiler;
15076 @item We create a wrapping project @code{Main}:
15085 @b{project} Main @b{is}
15087 @b{package} Compiler @b{renames} Common.Compiler;
15093 @item Finally we need to create a dummy procedure that @code{with}s (either
15094 explicitly or implicitly) all the sources of our two programs.
15099 Now we can build the programs using the command
15102 gnatmake ^-P^/PROJECT_FILE=^main dummy
15106 for the Debug mode, or
15110 gnatmake -Pmain -XBUILD=release
15116 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
15121 for the Release mode.
15123 @c ********************************
15124 @c * Project File Complete Syntax *
15125 @c ********************************
15127 @node Project File Complete Syntax
15128 @section Project File Complete Syntax
15132 context_clause project_declaration
15138 @b{with} path_name @{ , path_name @} ;
15143 project_declaration ::=
15144 simple_project_declaration | project_extension
15146 simple_project_declaration ::=
15147 @b{project} <project_>simple_name @b{is}
15148 @{declarative_item@}
15149 @b{end} <project_>simple_name;
15151 project_extension ::=
15152 @b{project} <project_>simple_name @b{extends} path_name @b{is}
15153 @{declarative_item@}
15154 @b{end} <project_>simple_name;
15156 declarative_item ::=
15157 package_declaration |
15158 typed_string_declaration |
15159 other_declarative_item
15161 package_declaration ::=
15162 package_spec | package_renaming
15165 @b{package} package_identifier @b{is}
15166 @{simple_declarative_item@}
15167 @b{end} package_identifier ;
15169 package_identifier ::=
15170 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
15171 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
15172 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
15174 package_renaming ::==
15175 @b{package} package_identifier @b{renames}
15176 <project_>simple_name.package_identifier ;
15178 typed_string_declaration ::=
15179 @b{type} <typed_string_>_simple_name @b{is}
15180 ( string_literal @{, string_literal@} );
15182 other_declarative_item ::=
15183 attribute_declaration |
15184 typed_variable_declaration |
15185 variable_declaration |
15188 attribute_declaration ::=
15189 full_associative_array_declaration |
15190 @b{for} attribute_designator @b{use} expression ;
15192 full_associative_array_declaration ::=
15193 @b{for} <associative_array_attribute_>simple_name @b{use}
15194 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
15196 attribute_designator ::=
15197 <simple_attribute_>simple_name |
15198 <associative_array_attribute_>simple_name ( string_literal )
15200 typed_variable_declaration ::=
15201 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
15203 variable_declaration ::=
15204 <variable_>simple_name := expression;
15214 attribute_reference
15220 ( <string_>expression @{ , <string_>expression @} )
15223 @b{external} ( string_literal [, string_literal] )
15225 attribute_reference ::=
15226 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
15228 attribute_prefix ::=
15230 <project_>simple_name | package_identifier |
15231 <project_>simple_name . package_identifier
15233 case_construction ::=
15234 @b{case} <typed_variable_>name @b{is}
15239 @b{when} discrete_choice_list =>
15240 @{case_construction | attribute_declaration@}
15242 discrete_choice_list ::=
15243 string_literal @{| string_literal@} |
15247 simple_name @{. simple_name@}
15250 identifier (same as Ada)
15254 @node The Cross-Referencing Tools gnatxref and gnatfind
15255 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
15260 The compiler generates cross-referencing information (unless
15261 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
15262 This information indicates where in the source each entity is declared and
15263 referenced. Note that entities in package Standard are not included, but
15264 entities in all other predefined units are included in the output.
15266 Before using any of these two tools, you need to compile successfully your
15267 application, so that GNAT gets a chance to generate the cross-referencing
15270 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
15271 information to provide the user with the capability to easily locate the
15272 declaration and references to an entity. These tools are quite similar,
15273 the difference being that @code{gnatfind} is intended for locating
15274 definitions and/or references to a specified entity or entities, whereas
15275 @code{gnatxref} is oriented to generating a full report of all
15278 To use these tools, you must not compile your application using the
15279 @option{-gnatx} switch on the @command{gnatmake} command line
15280 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
15281 information will not be generated.
15283 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
15284 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
15287 * gnatxref Switches::
15288 * gnatfind Switches::
15289 * Project Files for gnatxref and gnatfind::
15290 * Regular Expressions in gnatfind and gnatxref::
15291 * Examples of gnatxref Usage::
15292 * Examples of gnatfind Usage::
15295 @node gnatxref Switches
15296 @section @code{gnatxref} Switches
15299 The command invocation for @code{gnatxref} is:
15301 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
15310 identifies the source files for which a report is to be generated. The
15311 ``with''ed units will be processed too. You must provide at least one file.
15313 These file names are considered to be regular expressions, so for instance
15314 specifying @file{source*.adb} is the same as giving every file in the current
15315 directory whose name starts with @file{source} and whose extension is
15318 You shouldn't specify any directory name, just base names. @command{gnatxref}
15319 and @command{gnatfind} will be able to locate these files by themselves using
15320 the source path. If you specify directories, no result is produced.
15325 The switches can be:
15329 @cindex @option{--version} @command{gnatxref}
15330 Display Copyright and version, then exit disregarding all other options.
15333 @cindex @option{--help} @command{gnatxref}
15334 If @option{--version} was not used, display usage, then exit disregarding
15337 @item ^-a^/ALL_FILES^
15338 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15339 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15340 the read-only files found in the library search path. Otherwise, these files
15341 will be ignored. This option can be used to protect Gnat sources or your own
15342 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15343 much faster, and their output much smaller. Read-only here refers to access
15344 or permissions status in the file system for the current user.
15347 @cindex @option{-aIDIR} (@command{gnatxref})
15348 When looking for source files also look in directory DIR. The order in which
15349 source file search is undertaken is the same as for @command{gnatmake}.
15352 @cindex @option{-aODIR} (@command{gnatxref})
15353 When searching for library and object files, look in directory
15354 DIR. The order in which library files are searched is the same as for
15355 @command{gnatmake}.
15358 @cindex @option{-nostdinc} (@command{gnatxref})
15359 Do not look for sources in the system default directory.
15362 @cindex @option{-nostdlib} (@command{gnatxref})
15363 Do not look for library files in the system default directory.
15365 @item --RTS=@var{rts-path}
15366 @cindex @option{--RTS} (@command{gnatxref})
15367 Specifies the default location of the runtime library. Same meaning as the
15368 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15370 @item ^-d^/DERIVED_TYPES^
15371 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15372 If this switch is set @code{gnatxref} will output the parent type
15373 reference for each matching derived types.
15375 @item ^-f^/FULL_PATHNAME^
15376 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15377 If this switch is set, the output file names will be preceded by their
15378 directory (if the file was found in the search path). If this switch is
15379 not set, the directory will not be printed.
15381 @item ^-g^/IGNORE_LOCALS^
15382 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15383 If this switch is set, information is output only for library-level
15384 entities, ignoring local entities. The use of this switch may accelerate
15385 @code{gnatfind} and @code{gnatxref}.
15388 @cindex @option{-IDIR} (@command{gnatxref})
15389 Equivalent to @samp{-aODIR -aIDIR}.
15392 @cindex @option{-pFILE} (@command{gnatxref})
15393 Specify a project file to use @xref{Project Files}.
15394 If you need to use the @file{.gpr}
15395 project files, you should use gnatxref through the GNAT driver
15396 (@command{gnat xref -Pproject}).
15398 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15399 project file in the current directory.
15401 If a project file is either specified or found by the tools, then the content
15402 of the source directory and object directory lines are added as if they
15403 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15404 and @samp{^-aO^OBJECT_SEARCH^}.
15406 Output only unused symbols. This may be really useful if you give your
15407 main compilation unit on the command line, as @code{gnatxref} will then
15408 display every unused entity and 'with'ed package.
15412 Instead of producing the default output, @code{gnatxref} will generate a
15413 @file{tags} file that can be used by vi. For examples how to use this
15414 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15415 to the standard output, thus you will have to redirect it to a file.
15421 All these switches may be in any order on the command line, and may even
15422 appear after the file names. They need not be separated by spaces, thus
15423 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15424 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15426 @node gnatfind Switches
15427 @section @code{gnatfind} Switches
15430 The command line for @code{gnatfind} is:
15433 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15434 @r{[}@var{file1} @var{file2} @dots{}]
15442 An entity will be output only if it matches the regular expression found
15443 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15445 Omitting the pattern is equivalent to specifying @samp{*}, which
15446 will match any entity. Note that if you do not provide a pattern, you
15447 have to provide both a sourcefile and a line.
15449 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15450 for matching purposes. At the current time there is no support for
15451 8-bit codes other than Latin-1, or for wide characters in identifiers.
15454 @code{gnatfind} will look for references, bodies or declarations
15455 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15456 and column @var{column}. See @ref{Examples of gnatfind Usage}
15457 for syntax examples.
15460 is a decimal integer identifying the line number containing
15461 the reference to the entity (or entities) to be located.
15464 is a decimal integer identifying the exact location on the
15465 line of the first character of the identifier for the
15466 entity reference. Columns are numbered from 1.
15468 @item file1 file2 @dots{}
15469 The search will be restricted to these source files. If none are given, then
15470 the search will be done for every library file in the search path.
15471 These file must appear only after the pattern or sourcefile.
15473 These file names are considered to be regular expressions, so for instance
15474 specifying @file{source*.adb} is the same as giving every file in the current
15475 directory whose name starts with @file{source} and whose extension is
15478 The location of the spec of the entity will always be displayed, even if it
15479 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15480 occurrences of the entity in the separate units of the ones given on the
15481 command line will also be displayed.
15483 Note that if you specify at least one file in this part, @code{gnatfind} may
15484 sometimes not be able to find the body of the subprograms.
15489 At least one of 'sourcefile' or 'pattern' has to be present on
15492 The following switches are available:
15496 @cindex @option{--version} @command{gnatfind}
15497 Display Copyright and version, then exit disregarding all other options.
15500 @cindex @option{--help} @command{gnatfind}
15501 If @option{--version} was not used, display usage, then exit disregarding
15504 @item ^-a^/ALL_FILES^
15505 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15506 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15507 the read-only files found in the library search path. Otherwise, these files
15508 will be ignored. This option can be used to protect Gnat sources or your own
15509 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15510 much faster, and their output much smaller. Read-only here refers to access
15511 or permission status in the file system for the current user.
15514 @cindex @option{-aIDIR} (@command{gnatfind})
15515 When looking for source files also look in directory DIR. The order in which
15516 source file search is undertaken is the same as for @command{gnatmake}.
15519 @cindex @option{-aODIR} (@command{gnatfind})
15520 When searching for library and object files, look in directory
15521 DIR. The order in which library files are searched is the same as for
15522 @command{gnatmake}.
15525 @cindex @option{-nostdinc} (@command{gnatfind})
15526 Do not look for sources in the system default directory.
15529 @cindex @option{-nostdlib} (@command{gnatfind})
15530 Do not look for library files in the system default directory.
15532 @item --RTS=@var{rts-path}
15533 @cindex @option{--RTS} (@command{gnatfind})
15534 Specifies the default location of the runtime library. Same meaning as the
15535 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15537 @item ^-d^/DERIVED_TYPE_INFORMATION^
15538 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15539 If this switch is set, then @code{gnatfind} will output the parent type
15540 reference for each matching derived types.
15542 @item ^-e^/EXPRESSIONS^
15543 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15544 By default, @code{gnatfind} accept the simple regular expression set for
15545 @samp{pattern}. If this switch is set, then the pattern will be
15546 considered as full Unix-style regular expression.
15548 @item ^-f^/FULL_PATHNAME^
15549 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15550 If this switch is set, the output file names will be preceded by their
15551 directory (if the file was found in the search path). If this switch is
15552 not set, the directory will not be printed.
15554 @item ^-g^/IGNORE_LOCALS^
15555 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15556 If this switch is set, information is output only for library-level
15557 entities, ignoring local entities. The use of this switch may accelerate
15558 @code{gnatfind} and @code{gnatxref}.
15561 @cindex @option{-IDIR} (@command{gnatfind})
15562 Equivalent to @samp{-aODIR -aIDIR}.
15565 @cindex @option{-pFILE} (@command{gnatfind})
15566 Specify a project file (@pxref{Project Files}) to use.
15567 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15568 project file in the current directory.
15570 If a project file is either specified or found by the tools, then the content
15571 of the source directory and object directory lines are added as if they
15572 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15573 @samp{^-aO^/OBJECT_SEARCH^}.
15575 @item ^-r^/REFERENCES^
15576 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15577 By default, @code{gnatfind} will output only the information about the
15578 declaration, body or type completion of the entities. If this switch is
15579 set, the @code{gnatfind} will locate every reference to the entities in
15580 the files specified on the command line (or in every file in the search
15581 path if no file is given on the command line).
15583 @item ^-s^/PRINT_LINES^
15584 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15585 If this switch is set, then @code{gnatfind} will output the content
15586 of the Ada source file lines were the entity was found.
15588 @item ^-t^/TYPE_HIERARCHY^
15589 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15590 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15591 the specified type. It act like -d option but recursively from parent
15592 type to parent type. When this switch is set it is not possible to
15593 specify more than one file.
15598 All these switches may be in any order on the command line, and may even
15599 appear after the file names. They need not be separated by spaces, thus
15600 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15601 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15603 As stated previously, gnatfind will search in every directory in the
15604 search path. You can force it to look only in the current directory if
15605 you specify @code{*} at the end of the command line.
15607 @node Project Files for gnatxref and gnatfind
15608 @section Project Files for @command{gnatxref} and @command{gnatfind}
15611 Project files allow a programmer to specify how to compile its
15612 application, where to find sources, etc. These files are used
15614 primarily by GPS, but they can also be used
15617 @code{gnatxref} and @code{gnatfind}.
15619 A project file name must end with @file{.gpr}. If a single one is
15620 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15621 extract the information from it. If multiple project files are found, none of
15622 them is read, and you have to use the @samp{-p} switch to specify the one
15625 The following lines can be included, even though most of them have default
15626 values which can be used in most cases.
15627 The lines can be entered in any order in the file.
15628 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15629 each line. If you have multiple instances, only the last one is taken into
15634 [default: @code{"^./^[]^"}]
15635 specifies a directory where to look for source files. Multiple @code{src_dir}
15636 lines can be specified and they will be searched in the order they
15640 [default: @code{"^./^[]^"}]
15641 specifies a directory where to look for object and library files. Multiple
15642 @code{obj_dir} lines can be specified, and they will be searched in the order
15645 @item comp_opt=SWITCHES
15646 [default: @code{""}]
15647 creates a variable which can be referred to subsequently by using
15648 the @code{$@{comp_opt@}} notation. This is intended to store the default
15649 switches given to @command{gnatmake} and @command{gcc}.
15651 @item bind_opt=SWITCHES
15652 [default: @code{""}]
15653 creates a variable which can be referred to subsequently by using
15654 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15655 switches given to @command{gnatbind}.
15657 @item link_opt=SWITCHES
15658 [default: @code{""}]
15659 creates a variable which can be referred to subsequently by using
15660 the @samp{$@{link_opt@}} notation. This is intended to store the default
15661 switches given to @command{gnatlink}.
15663 @item main=EXECUTABLE
15664 [default: @code{""}]
15665 specifies the name of the executable for the application. This variable can
15666 be referred to in the following lines by using the @samp{$@{main@}} notation.
15669 @item comp_cmd=COMMAND
15670 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15673 @item comp_cmd=COMMAND
15674 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15676 specifies the command used to compile a single file in the application.
15679 @item make_cmd=COMMAND
15680 [default: @code{"GNAT MAKE $@{main@}
15681 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15682 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15683 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15686 @item make_cmd=COMMAND
15687 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15688 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15689 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15691 specifies the command used to recompile the whole application.
15693 @item run_cmd=COMMAND
15694 [default: @code{"$@{main@}"}]
15695 specifies the command used to run the application.
15697 @item debug_cmd=COMMAND
15698 [default: @code{"gdb $@{main@}"}]
15699 specifies the command used to debug the application
15704 @command{gnatxref} and @command{gnatfind} only take into account the
15705 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15707 @node Regular Expressions in gnatfind and gnatxref
15708 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15711 As specified in the section about @command{gnatfind}, the pattern can be a
15712 regular expression. Actually, there are to set of regular expressions
15713 which are recognized by the program:
15716 @item globbing patterns
15717 These are the most usual regular expression. They are the same that you
15718 generally used in a Unix shell command line, or in a DOS session.
15720 Here is a more formal grammar:
15727 term ::= elmt -- matches elmt
15728 term ::= elmt elmt -- concatenation (elmt then elmt)
15729 term ::= * -- any string of 0 or more characters
15730 term ::= ? -- matches any character
15731 term ::= [char @{char@}] -- matches any character listed
15732 term ::= [char - char] -- matches any character in range
15736 @item full regular expression
15737 The second set of regular expressions is much more powerful. This is the
15738 type of regular expressions recognized by utilities such a @file{grep}.
15740 The following is the form of a regular expression, expressed in Ada
15741 reference manual style BNF is as follows
15748 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15750 term ::= item @{item@} -- concatenation (item then item)
15752 item ::= elmt -- match elmt
15753 item ::= elmt * -- zero or more elmt's
15754 item ::= elmt + -- one or more elmt's
15755 item ::= elmt ? -- matches elmt or nothing
15758 elmt ::= nschar -- matches given character
15759 elmt ::= [nschar @{nschar@}] -- matches any character listed
15760 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15761 elmt ::= [char - char] -- matches chars in given range
15762 elmt ::= \ char -- matches given character
15763 elmt ::= . -- matches any single character
15764 elmt ::= ( regexp ) -- parens used for grouping
15766 char ::= any character, including special characters
15767 nschar ::= any character except ()[].*+?^^^
15771 Following are a few examples:
15775 will match any of the two strings @samp{abcde} and @samp{fghi},
15778 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15779 @samp{abcccd}, and so on,
15782 will match any string which has only lowercase characters in it (and at
15783 least one character.
15788 @node Examples of gnatxref Usage
15789 @section Examples of @code{gnatxref} Usage
15791 @subsection General Usage
15794 For the following examples, we will consider the following units:
15796 @smallexample @c ada
15802 3: procedure Foo (B : in Integer);
15809 1: package body Main is
15810 2: procedure Foo (B : in Integer) is
15821 2: procedure Print (B : Integer);
15830 The first thing to do is to recompile your application (for instance, in
15831 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15832 the cross-referencing information.
15833 You can then issue any of the following commands:
15835 @item gnatxref main.adb
15836 @code{gnatxref} generates cross-reference information for main.adb
15837 and every unit 'with'ed by main.adb.
15839 The output would be:
15847 Decl: main.ads 3:20
15848 Body: main.adb 2:20
15849 Ref: main.adb 4:13 5:13 6:19
15852 Ref: main.adb 6:8 7:8
15862 Decl: main.ads 3:15
15863 Body: main.adb 2:15
15866 Body: main.adb 1:14
15869 Ref: main.adb 6:12 7:12
15873 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15874 its body is in main.adb, line 1, column 14 and is not referenced any where.
15876 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15877 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15879 @item gnatxref package1.adb package2.ads
15880 @code{gnatxref} will generates cross-reference information for
15881 package1.adb, package2.ads and any other package 'with'ed by any
15887 @subsection Using gnatxref with vi
15889 @code{gnatxref} can generate a tags file output, which can be used
15890 directly from @command{vi}. Note that the standard version of @command{vi}
15891 will not work properly with overloaded symbols. Consider using another
15892 free implementation of @command{vi}, such as @command{vim}.
15895 $ gnatxref -v gnatfind.adb > tags
15899 will generate the tags file for @code{gnatfind} itself (if the sources
15900 are in the search path!).
15902 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15903 (replacing @var{entity} by whatever you are looking for), and vi will
15904 display a new file with the corresponding declaration of entity.
15907 @node Examples of gnatfind Usage
15908 @section Examples of @code{gnatfind} Usage
15912 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15913 Find declarations for all entities xyz referenced at least once in
15914 main.adb. The references are search in every library file in the search
15917 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15920 The output will look like:
15922 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15923 ^directory/^[directory]^main.adb:24:10: xyz <= body
15924 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15928 that is to say, one of the entities xyz found in main.adb is declared at
15929 line 12 of main.ads (and its body is in main.adb), and another one is
15930 declared at line 45 of foo.ads
15932 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
15933 This is the same command as the previous one, instead @code{gnatfind} will
15934 display the content of the Ada source file lines.
15936 The output will look like:
15939 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15941 ^directory/^[directory]^main.adb:24:10: xyz <= body
15943 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15948 This can make it easier to find exactly the location your are looking
15951 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
15952 Find references to all entities containing an x that are
15953 referenced on line 123 of main.ads.
15954 The references will be searched only in main.ads and foo.adb.
15956 @item gnatfind main.ads:123
15957 Find declarations and bodies for all entities that are referenced on
15958 line 123 of main.ads.
15960 This is the same as @code{gnatfind "*":main.adb:123}.
15962 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
15963 Find the declaration for the entity referenced at column 45 in
15964 line 123 of file main.adb in directory mydir. Note that it
15965 is usual to omit the identifier name when the column is given,
15966 since the column position identifies a unique reference.
15968 The column has to be the beginning of the identifier, and should not
15969 point to any character in the middle of the identifier.
15973 @c *********************************
15974 @node The GNAT Pretty-Printer gnatpp
15975 @chapter The GNAT Pretty-Printer @command{gnatpp}
15977 @cindex Pretty-Printer
15980 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
15981 for source reformatting / pretty-printing.
15982 It takes an Ada source file as input and generates a reformatted
15984 You can specify various style directives via switches; e.g.,
15985 identifier case conventions, rules of indentation, and comment layout.
15987 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
15988 tree for the input source and thus requires the input to be syntactically and
15989 semantically legal.
15990 If this condition is not met, @command{gnatpp} will terminate with an
15991 error message; no output file will be generated.
15993 If the source files presented to @command{gnatpp} contain
15994 preprocessing directives, then the output file will
15995 correspond to the generated source after all
15996 preprocessing is carried out. There is no way
15997 using @command{gnatpp} to obtain pretty printed files that
15998 include the preprocessing directives.
16000 If the compilation unit
16001 contained in the input source depends semantically upon units located
16002 outside the current directory, you have to provide the source search path
16003 when invoking @command{gnatpp}, if these units are contained in files with
16004 names that do not follow the GNAT file naming rules, you have to provide
16005 the configuration file describing the corresponding naming scheme;
16006 see the description of the @command{gnatpp}
16007 switches below. Another possibility is to use a project file and to
16008 call @command{gnatpp} through the @command{gnat} driver
16010 The @command{gnatpp} command has the form
16013 $ gnatpp @ovar{switches} @var{filename}
16020 @var{switches} is an optional sequence of switches defining such properties as
16021 the formatting rules, the source search path, and the destination for the
16025 @var{filename} is the name (including the extension) of the source file to
16026 reformat; ``wildcards'' or several file names on the same gnatpp command are
16027 allowed. The file name may contain path information; it does not have to
16028 follow the GNAT file naming rules
16032 * Switches for gnatpp::
16033 * Formatting Rules::
16036 @node Switches for gnatpp
16037 @section Switches for @command{gnatpp}
16040 The following subsections describe the various switches accepted by
16041 @command{gnatpp}, organized by category.
16044 You specify a switch by supplying a name and generally also a value.
16045 In many cases the values for a switch with a given name are incompatible with
16047 (for example the switch that controls the casing of a reserved word may have
16048 exactly one value: upper case, lower case, or
16049 mixed case) and thus exactly one such switch can be in effect for an
16050 invocation of @command{gnatpp}.
16051 If more than one is supplied, the last one is used.
16052 However, some values for the same switch are mutually compatible.
16053 You may supply several such switches to @command{gnatpp}, but then
16054 each must be specified in full, with both the name and the value.
16055 Abbreviated forms (the name appearing once, followed by each value) are
16057 For example, to set
16058 the alignment of the assignment delimiter both in declarations and in
16059 assignment statements, you must write @option{-A2A3}
16060 (or @option{-A2 -A3}), but not @option{-A23}.
16064 In many cases the set of options for a given qualifier are incompatible with
16065 each other (for example the qualifier that controls the casing of a reserved
16066 word may have exactly one option, which specifies either upper case, lower
16067 case, or mixed case), and thus exactly one such option can be in effect for
16068 an invocation of @command{gnatpp}.
16069 If more than one is supplied, the last one is used.
16070 However, some qualifiers have options that are mutually compatible,
16071 and then you may then supply several such options when invoking
16075 In most cases, it is obvious whether or not the
16076 ^values for a switch with a given name^options for a given qualifier^
16077 are compatible with each other.
16078 When the semantics might not be evident, the summaries below explicitly
16079 indicate the effect.
16082 * Alignment Control::
16084 * Construct Layout Control::
16085 * General Text Layout Control::
16086 * Other Formatting Options::
16087 * Setting the Source Search Path::
16088 * Output File Control::
16089 * Other gnatpp Switches::
16092 @node Alignment Control
16093 @subsection Alignment Control
16094 @cindex Alignment control in @command{gnatpp}
16097 Programs can be easier to read if certain constructs are vertically aligned.
16098 By default all alignments are set ON.
16099 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
16100 OFF, and then use one or more of the other
16101 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
16102 to activate alignment for specific constructs.
16105 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
16109 Set all alignments to ON
16112 @item ^-A0^/ALIGN=OFF^
16113 Set all alignments to OFF
16115 @item ^-A1^/ALIGN=COLONS^
16116 Align @code{:} in declarations
16118 @item ^-A2^/ALIGN=DECLARATIONS^
16119 Align @code{:=} in initializations in declarations
16121 @item ^-A3^/ALIGN=STATEMENTS^
16122 Align @code{:=} in assignment statements
16124 @item ^-A4^/ALIGN=ARROWS^
16125 Align @code{=>} in associations
16127 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
16128 Align @code{at} keywords in the component clauses in record
16129 representation clauses
16133 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
16136 @node Casing Control
16137 @subsection Casing Control
16138 @cindex Casing control in @command{gnatpp}
16141 @command{gnatpp} allows you to specify the casing for reserved words,
16142 pragma names, attribute designators and identifiers.
16143 For identifiers you may define a
16144 general rule for name casing but also override this rule
16145 via a set of dictionary files.
16147 Three types of casing are supported: lower case, upper case, and mixed case.
16148 Lower and upper case are self-explanatory (but since some letters in
16149 Latin1 and other GNAT-supported character sets
16150 exist only in lower-case form, an upper case conversion will have no
16152 ``Mixed case'' means that the first letter, and also each letter immediately
16153 following an underscore, are converted to their uppercase forms;
16154 all the other letters are converted to their lowercase forms.
16157 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
16158 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
16159 Attribute designators are lower case
16161 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
16162 Attribute designators are upper case
16164 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
16165 Attribute designators are mixed case (this is the default)
16167 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
16168 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
16169 Keywords (technically, these are known in Ada as @emph{reserved words}) are
16170 lower case (this is the default)
16172 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
16173 Keywords are upper case
16175 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
16176 @item ^-nD^/NAME_CASING=AS_DECLARED^
16177 Name casing for defining occurrences are as they appear in the source file
16178 (this is the default)
16180 @item ^-nU^/NAME_CASING=UPPER_CASE^
16181 Names are in upper case
16183 @item ^-nL^/NAME_CASING=LOWER_CASE^
16184 Names are in lower case
16186 @item ^-nM^/NAME_CASING=MIXED_CASE^
16187 Names are in mixed case
16189 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
16190 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
16191 Pragma names are lower case
16193 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
16194 Pragma names are upper case
16196 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
16197 Pragma names are mixed case (this is the default)
16199 @item ^-D@var{file}^/DICTIONARY=@var{file}^
16200 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
16201 Use @var{file} as a @emph{dictionary file} that defines
16202 the casing for a set of specified names,
16203 thereby overriding the effect on these names by
16204 any explicit or implicit
16205 ^-n^/NAME_CASING^ switch.
16206 To supply more than one dictionary file,
16207 use ^several @option{-D} switches^a list of files as options^.
16210 @option{gnatpp} implicitly uses a @emph{default dictionary file}
16211 to define the casing for the Ada predefined names and
16212 the names declared in the GNAT libraries.
16214 @item ^-D-^/SPECIFIC_CASING^
16215 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
16216 Do not use the default dictionary file;
16217 instead, use the casing
16218 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
16223 The structure of a dictionary file, and details on the conventions
16224 used in the default dictionary file, are defined in @ref{Name Casing}.
16226 The @option{^-D-^/SPECIFIC_CASING^} and
16227 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
16230 @node Construct Layout Control
16231 @subsection Construct Layout Control
16232 @cindex Layout control in @command{gnatpp}
16235 This group of @command{gnatpp} switches controls the layout of comments and
16236 complex syntactic constructs. See @ref{Formatting Comments} for details
16240 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
16241 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
16242 All the comments remain unchanged
16244 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
16245 GNAT-style comment line indentation (this is the default).
16247 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
16248 Reference-manual comment line indentation.
16250 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
16251 GNAT-style comment beginning
16253 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
16254 Reformat comment blocks
16256 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
16257 Keep unchanged special form comments
16259 Reformat comment blocks
16261 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
16262 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
16263 GNAT-style layout (this is the default)
16265 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
16268 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
16271 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
16273 All the VT characters are removed from the comment text. All the HT characters
16274 are expanded with the sequences of space characters to get to the next tab
16277 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
16278 @item ^--no-separate-is^/NO_SEPARATE_IS^
16279 Do not place the keyword @code{is} on a separate line in a subprogram body in
16280 case if the spec occupies more then one line.
16282 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
16283 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
16284 Place the keyword @code{loop} in FOR and WHILE loop statements and the
16285 keyword @code{then} in IF statements on a separate line.
16287 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
16288 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
16289 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
16290 keyword @code{then} in IF statements on a separate line. This option is
16291 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
16293 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
16294 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
16295 Start each USE clause in a context clause from a separate line.
16297 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
16298 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
16299 Use a separate line for a loop or block statement name, but do not use an extra
16300 indentation level for the statement itself.
16306 The @option{-c1} and @option{-c2} switches are incompatible.
16307 The @option{-c3} and @option{-c4} switches are compatible with each other and
16308 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
16309 the other comment formatting switches.
16311 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
16316 For the @option{/COMMENTS_LAYOUT} qualifier:
16319 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16321 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16322 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16326 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16327 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16330 @node General Text Layout Control
16331 @subsection General Text Layout Control
16334 These switches allow control over line length and indentation.
16337 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16338 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16339 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16341 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16342 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16343 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16345 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16346 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16347 Indentation level for continuation lines (relative to the line being
16348 continued), @var{nnn} from 1@dots{}9.
16350 value is one less then the (normal) indentation level, unless the
16351 indentation is set to 1 (in which case the default value for continuation
16352 line indentation is also 1)
16355 @node Other Formatting Options
16356 @subsection Other Formatting Options
16359 These switches control the inclusion of missing end/exit labels, and
16360 the indentation level in @b{case} statements.
16363 @item ^-e^/NO_MISSED_LABELS^
16364 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16365 Do not insert missing end/exit labels. An end label is the name of
16366 a construct that may optionally be repeated at the end of the
16367 construct's declaration;
16368 e.g., the names of packages, subprograms, and tasks.
16369 An exit label is the name of a loop that may appear as target
16370 of an exit statement within the loop.
16371 By default, @command{gnatpp} inserts these end/exit labels when
16372 they are absent from the original source. This option suppresses such
16373 insertion, so that the formatted source reflects the original.
16375 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16376 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16377 Insert a Form Feed character after a pragma Page.
16379 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16380 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16381 Do not use an additional indentation level for @b{case} alternatives
16382 and variants if there are @var{nnn} or more (the default
16384 If @var{nnn} is 0, an additional indentation level is
16385 used for @b{case} alternatives and variants regardless of their number.
16388 @node Setting the Source Search Path
16389 @subsection Setting the Source Search Path
16392 To define the search path for the input source file, @command{gnatpp}
16393 uses the same switches as the GNAT compiler, with the same effects.
16396 @item ^-I^/SEARCH=^@var{dir}
16397 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16398 The same as the corresponding gcc switch
16400 @item ^-I-^/NOCURRENT_DIRECTORY^
16401 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16402 The same as the corresponding gcc switch
16404 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16405 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16406 The same as the corresponding gcc switch
16408 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16409 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16410 The same as the corresponding gcc switch
16414 @node Output File Control
16415 @subsection Output File Control
16418 By default the output is sent to the file whose name is obtained by appending
16419 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16420 (if the file with this name already exists, it is unconditionally overwritten).
16421 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16422 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16424 The output may be redirected by the following switches:
16427 @item ^-pipe^/STANDARD_OUTPUT^
16428 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16429 Send the output to @code{Standard_Output}
16431 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16432 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16433 Write the output into @var{output_file}.
16434 If @var{output_file} already exists, @command{gnatpp} terminates without
16435 reading or processing the input file.
16437 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16438 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16439 Write the output into @var{output_file}, overwriting the existing file
16440 (if one is present).
16442 @item ^-r^/REPLACE^
16443 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16444 Replace the input source file with the reformatted output, and copy the
16445 original input source into the file whose name is obtained by appending the
16446 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16447 If a file with this name already exists, @command{gnatpp} terminates without
16448 reading or processing the input file.
16450 @item ^-rf^/OVERRIDING_REPLACE^
16451 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16452 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16453 already exists, it is overwritten.
16455 @item ^-rnb^/REPLACE_NO_BACKUP^
16456 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16457 Replace the input source file with the reformatted output without
16458 creating any backup copy of the input source.
16460 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16461 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16462 Specifies the format of the reformatted output file. The @var{xxx}
16463 ^string specified with the switch^option^ may be either
16465 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16466 @item ``@option{^crlf^CRLF^}''
16467 the same as @option{^crlf^CRLF^}
16468 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16469 @item ``@option{^lf^LF^}''
16470 the same as @option{^unix^UNIX^}
16473 @item ^-W^/RESULT_ENCODING=^@var{e}
16474 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16475 Specify the wide character encoding method used to write the code in the
16477 @var{e} is one of the following:
16485 Upper half encoding
16487 @item ^s^SHIFT_JIS^
16497 Brackets encoding (default value)
16503 Options @option{^-pipe^/STANDARD_OUTPUT^},
16504 @option{^-o^/OUTPUT^} and
16505 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16506 contains only one file to reformat.
16508 @option{^--eol^/END_OF_LINE^}
16510 @option{^-W^/RESULT_ENCODING^}
16511 cannot be used together
16512 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16514 @node Other gnatpp Switches
16515 @subsection Other @code{gnatpp} Switches
16518 The additional @command{gnatpp} switches are defined in this subsection.
16521 @item ^-files @var{filename}^/FILES=@var{output_file}^
16522 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16523 Take the argument source files from the specified file. This file should be an
16524 ordinary textual file containing file names separated by spaces or
16525 line breaks. You can use this switch more then once in the same call to
16526 @command{gnatpp}. You also can combine this switch with explicit list of
16529 @item ^-v^/VERBOSE^
16530 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16532 @command{gnatpp} generates version information and then
16533 a trace of the actions it takes to produce or obtain the ASIS tree.
16535 @item ^-w^/WARNINGS^
16536 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16538 @command{gnatpp} generates a warning whenever it cannot provide
16539 a required layout in the result source.
16542 @node Formatting Rules
16543 @section Formatting Rules
16546 The following subsections show how @command{gnatpp} treats ``white space'',
16547 comments, program layout, and name casing.
16548 They provide the detailed descriptions of the switches shown above.
16551 * White Space and Empty Lines::
16552 * Formatting Comments::
16553 * Construct Layout::
16557 @node White Space and Empty Lines
16558 @subsection White Space and Empty Lines
16561 @command{gnatpp} does not have an option to control space characters.
16562 It will add or remove spaces according to the style illustrated by the
16563 examples in the @cite{Ada Reference Manual}.
16565 The only format effectors
16566 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16567 that will appear in the output file are platform-specific line breaks,
16568 and also format effectors within (but not at the end of) comments.
16569 In particular, each horizontal tab character that is not inside
16570 a comment will be treated as a space and thus will appear in the
16571 output file as zero or more spaces depending on
16572 the reformatting of the line in which it appears.
16573 The only exception is a Form Feed character, which is inserted after a
16574 pragma @code{Page} when @option{-ff} is set.
16576 The output file will contain no lines with trailing ``white space'' (spaces,
16579 Empty lines in the original source are preserved
16580 only if they separate declarations or statements.
16581 In such contexts, a
16582 sequence of two or more empty lines is replaced by exactly one empty line.
16583 Note that a blank line will be removed if it separates two ``comment blocks''
16584 (a comment block is a sequence of whole-line comments).
16585 In order to preserve a visual separation between comment blocks, use an
16586 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16587 Likewise, if for some reason you wish to have a sequence of empty lines,
16588 use a sequence of empty comments instead.
16590 @node Formatting Comments
16591 @subsection Formatting Comments
16594 Comments in Ada code are of two kinds:
16597 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16598 ``white space'') on a line
16601 an @emph{end-of-line comment}, which follows some other Ada lexical element
16606 The indentation of a whole-line comment is that of either
16607 the preceding or following line in
16608 the formatted source, depending on switch settings as will be described below.
16610 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16611 between the end of the preceding Ada lexical element and the beginning
16612 of the comment as appear in the original source,
16613 unless either the comment has to be split to
16614 satisfy the line length limitation, or else the next line contains a
16615 whole line comment that is considered a continuation of this end-of-line
16616 comment (because it starts at the same position).
16618 cases, the start of the end-of-line comment is moved right to the nearest
16619 multiple of the indentation level.
16620 This may result in a ``line overflow'' (the right-shifted comment extending
16621 beyond the maximum line length), in which case the comment is split as
16624 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16625 (GNAT-style comment line indentation)
16626 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16627 (reference-manual comment line indentation).
16628 With reference-manual style, a whole-line comment is indented as if it
16629 were a declaration or statement at the same place
16630 (i.e., according to the indentation of the preceding line(s)).
16631 With GNAT style, a whole-line comment that is immediately followed by an
16632 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16633 word @b{begin}, is indented based on the construct that follows it.
16636 @smallexample @c ada
16648 Reference-manual indentation produces:
16650 @smallexample @c ada
16662 while GNAT-style indentation produces:
16664 @smallexample @c ada
16676 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16677 (GNAT style comment beginning) has the following
16682 For each whole-line comment that does not end with two hyphens,
16683 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16684 to ensure that there are at least two spaces between these hyphens and the
16685 first non-blank character of the comment.
16689 For an end-of-line comment, if in the original source the next line is a
16690 whole-line comment that starts at the same position
16691 as the end-of-line comment,
16692 then the whole-line comment (and all whole-line comments
16693 that follow it and that start at the same position)
16694 will start at this position in the output file.
16697 That is, if in the original source we have:
16699 @smallexample @c ada
16702 A := B + C; -- B must be in the range Low1..High1
16703 -- C must be in the range Low2..High2
16704 --B+C will be in the range Low1+Low2..High1+High2
16710 Then in the formatted source we get
16712 @smallexample @c ada
16715 A := B + C; -- B must be in the range Low1..High1
16716 -- C must be in the range Low2..High2
16717 -- B+C will be in the range Low1+Low2..High1+High2
16723 A comment that exceeds the line length limit will be split.
16725 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16726 the line belongs to a reformattable block, splitting the line generates a
16727 @command{gnatpp} warning.
16728 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16729 comments may be reformatted in typical
16730 word processor style (that is, moving words between lines and putting as
16731 many words in a line as possible).
16734 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16735 that has a special format (that is, a character that is neither a letter nor digit
16736 not white space nor line break immediately following the leading @code{--} of
16737 the comment) should be without any change moved from the argument source
16738 into reformatted source. This switch allows to preserve comments that are used
16739 as a special marks in the code (e.g.@: SPARK annotation).
16741 @node Construct Layout
16742 @subsection Construct Layout
16745 In several cases the suggested layout in the Ada Reference Manual includes
16746 an extra level of indentation that many programmers prefer to avoid. The
16747 affected cases include:
16751 @item Record type declaration (RM 3.8)
16753 @item Record representation clause (RM 13.5.1)
16755 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16757 @item Block statement in case if a block has a statement identifier (RM 5.6)
16761 In compact mode (when GNAT style layout or compact layout is set),
16762 the pretty printer uses one level of indentation instead
16763 of two. This is achieved in the record definition and record representation
16764 clause cases by putting the @code{record} keyword on the same line as the
16765 start of the declaration or representation clause, and in the block and loop
16766 case by putting the block or loop header on the same line as the statement
16770 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16771 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16772 layout on the one hand, and uncompact layout
16773 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16774 can be illustrated by the following examples:
16778 @multitable @columnfractions .5 .5
16779 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16782 @smallexample @c ada
16789 @smallexample @c ada
16798 @smallexample @c ada
16800 a at 0 range 0 .. 31;
16801 b at 4 range 0 .. 31;
16805 @smallexample @c ada
16808 a at 0 range 0 .. 31;
16809 b at 4 range 0 .. 31;
16814 @smallexample @c ada
16822 @smallexample @c ada
16832 @smallexample @c ada
16833 Clear : for J in 1 .. 10 loop
16838 @smallexample @c ada
16840 for J in 1 .. 10 loop
16851 GNAT style, compact layout Uncompact layout
16853 type q is record type q is
16854 a : integer; record
16855 b : integer; a : integer;
16856 end record; b : integer;
16859 for q use record for q use
16860 a at 0 range 0 .. 31; record
16861 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16862 end record; b at 4 range 0 .. 31;
16865 Block : declare Block :
16866 A : Integer := 3; declare
16867 begin A : Integer := 3;
16869 end Block; Proc (A, A);
16872 Clear : for J in 1 .. 10 loop Clear :
16873 A (J) := 0; for J in 1 .. 10 loop
16874 end loop Clear; A (J) := 0;
16881 A further difference between GNAT style layout and compact layout is that
16882 GNAT style layout inserts empty lines as separation for
16883 compound statements, return statements and bodies.
16885 Note that the layout specified by
16886 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16887 for named block and loop statements overrides the layout defined by these
16888 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16889 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16890 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16893 @subsection Name Casing
16896 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16897 the same casing as the corresponding defining identifier.
16899 You control the casing for defining occurrences via the
16900 @option{^-n^/NAME_CASING^} switch.
16902 With @option{-nD} (``as declared'', which is the default),
16905 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16907 defining occurrences appear exactly as in the source file
16908 where they are declared.
16909 The other ^values for this switch^options for this qualifier^ ---
16910 @option{^-nU^UPPER_CASE^},
16911 @option{^-nL^LOWER_CASE^},
16912 @option{^-nM^MIXED_CASE^} ---
16914 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16915 If @command{gnatpp} changes the casing of a defining
16916 occurrence, it analogously changes the casing of all the
16917 usage occurrences of this name.
16919 If the defining occurrence of a name is not in the source compilation unit
16920 currently being processed by @command{gnatpp}, the casing of each reference to
16921 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16922 switch (subject to the dictionary file mechanism described below).
16923 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16925 casing for the defining occurrence of the name.
16927 Some names may need to be spelled with casing conventions that are not
16928 covered by the upper-, lower-, and mixed-case transformations.
16929 You can arrange correct casing by placing such names in a
16930 @emph{dictionary file},
16931 and then supplying a @option{^-D^/DICTIONARY^} switch.
16932 The casing of names from dictionary files overrides
16933 any @option{^-n^/NAME_CASING^} switch.
16935 To handle the casing of Ada predefined names and the names from GNAT libraries,
16936 @command{gnatpp} assumes a default dictionary file.
16937 The name of each predefined entity is spelled with the same casing as is used
16938 for the entity in the @cite{Ada Reference Manual}.
16939 The name of each entity in the GNAT libraries is spelled with the same casing
16940 as is used in the declaration of that entity.
16942 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
16943 default dictionary file.
16944 Instead, the casing for predefined and GNAT-defined names will be established
16945 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
16946 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
16947 will appear as just shown,
16948 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
16949 To ensure that even such names are rendered in uppercase,
16950 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
16951 (or else, less conveniently, place these names in upper case in a dictionary
16954 A dictionary file is
16955 a plain text file; each line in this file can be either a blank line
16956 (containing only space characters and ASCII.HT characters), an Ada comment
16957 line, or the specification of exactly one @emph{casing schema}.
16959 A casing schema is a string that has the following syntax:
16963 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
16965 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
16970 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
16971 @var{identifier} lexical element and the @var{letter_or_digit} category.)
16973 The casing schema string can be followed by white space and/or an Ada-style
16974 comment; any amount of white space is allowed before the string.
16976 If a dictionary file is passed as
16978 the value of a @option{-D@var{file}} switch
16981 an option to the @option{/DICTIONARY} qualifier
16984 simple name and every identifier, @command{gnatpp} checks if the dictionary
16985 defines the casing for the name or for some of its parts (the term ``subword''
16986 is used below to denote the part of a name which is delimited by ``_'' or by
16987 the beginning or end of the word and which does not contain any ``_'' inside):
16991 if the whole name is in the dictionary, @command{gnatpp} uses for this name
16992 the casing defined by the dictionary; no subwords are checked for this word
16995 for every subword @command{gnatpp} checks if the dictionary contains the
16996 corresponding string of the form @code{*@var{simple_identifier}*},
16997 and if it does, the casing of this @var{simple_identifier} is used
17001 if the whole name does not contain any ``_'' inside, and if for this name
17002 the dictionary contains two entries - one of the form @var{identifier},
17003 and another - of the form *@var{simple_identifier}*, then the first one
17004 is applied to define the casing of this name
17007 if more than one dictionary file is passed as @command{gnatpp} switches, each
17008 dictionary adds new casing exceptions and overrides all the existing casing
17009 exceptions set by the previous dictionaries
17012 when @command{gnatpp} checks if the word or subword is in the dictionary,
17013 this check is not case sensitive
17017 For example, suppose we have the following source to reformat:
17019 @smallexample @c ada
17022 name1 : integer := 1;
17023 name4_name3_name2 : integer := 2;
17024 name2_name3_name4 : Boolean;
17027 name2_name3_name4 := name4_name3_name2 > name1;
17033 And suppose we have two dictionaries:
17050 If @command{gnatpp} is called with the following switches:
17054 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
17057 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
17062 then we will get the following name casing in the @command{gnatpp} output:
17064 @smallexample @c ada
17067 NAME1 : Integer := 1;
17068 Name4_NAME3_Name2 : Integer := 2;
17069 Name2_NAME3_Name4 : Boolean;
17072 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
17077 @c *********************************
17078 @node The GNAT Metric Tool gnatmetric
17079 @chapter The GNAT Metric Tool @command{gnatmetric}
17081 @cindex Metric tool
17084 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
17085 for computing various program metrics.
17086 It takes an Ada source file as input and generates a file containing the
17087 metrics data as output. Various switches control which
17088 metrics are computed and output.
17090 @command{gnatmetric} generates and uses the ASIS
17091 tree for the input source and thus requires the input to be syntactically and
17092 semantically legal.
17093 If this condition is not met, @command{gnatmetric} will generate
17094 an error message; no metric information for this file will be
17095 computed and reported.
17097 If the compilation unit contained in the input source depends semantically
17098 upon units in files located outside the current directory, you have to provide
17099 the source search path when invoking @command{gnatmetric}.
17100 If it depends semantically upon units that are contained
17101 in files with names that do not follow the GNAT file naming rules, you have to
17102 provide the configuration file describing the corresponding naming scheme (see
17103 the description of the @command{gnatmetric} switches below.)
17104 Alternatively, you may use a project file and invoke @command{gnatmetric}
17105 through the @command{gnat} driver.
17107 The @command{gnatmetric} command has the form
17110 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
17117 @var{switches} specify the metrics to compute and define the destination for
17121 Each @var{filename} is the name (including the extension) of a source
17122 file to process. ``Wildcards'' are allowed, and
17123 the file name may contain path information.
17124 If no @var{filename} is supplied, then the @var{switches} list must contain
17126 @option{-files} switch (@pxref{Other gnatmetric Switches}).
17127 Including both a @option{-files} switch and one or more
17128 @var{filename} arguments is permitted.
17131 @samp{-cargs @var{gcc_switches}} is a list of switches for
17132 @command{gcc}. They will be passed on to all compiler invocations made by
17133 @command{gnatmetric} to generate the ASIS trees. Here you can provide
17134 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17135 and use the @option{-gnatec} switch to set the configuration file.
17139 * Switches for gnatmetric::
17142 @node Switches for gnatmetric
17143 @section Switches for @command{gnatmetric}
17146 The following subsections describe the various switches accepted by
17147 @command{gnatmetric}, organized by category.
17150 * Output Files Control::
17151 * Disable Metrics For Local Units::
17152 * Specifying a set of metrics to compute::
17153 * Other gnatmetric Switches::
17154 * Generate project-wide metrics::
17157 @node Output Files Control
17158 @subsection Output File Control
17159 @cindex Output file control in @command{gnatmetric}
17162 @command{gnatmetric} has two output formats. It can generate a
17163 textual (human-readable) form, and also XML. By default only textual
17164 output is generated.
17166 When generating the output in textual form, @command{gnatmetric} creates
17167 for each Ada source file a corresponding text file
17168 containing the computed metrics, except for the case when the set of metrics
17169 specified by gnatmetric parameters consists only of metrics that are computed
17170 for the whole set of analyzed sources, but not for each Ada source.
17171 By default, this file is placed in the same directory as where the source
17172 file is located, and its name is obtained
17173 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
17176 All the output information generated in XML format is placed in a single
17177 file. By default this file is placed in the current directory and has the
17178 name ^@file{metrix.xml}^@file{METRIX$XML}^.
17180 Some of the computed metrics are summed over the units passed to
17181 @command{gnatmetric}; for example, the total number of lines of code.
17182 By default this information is sent to @file{stdout}, but a file
17183 can be specified with the @option{-og} switch.
17185 The following switches control the @command{gnatmetric} output:
17188 @cindex @option{^-x^/XML^} (@command{gnatmetric})
17190 Generate the XML output
17192 @cindex @option{^-xs^/XSD^} (@command{gnatmetric})
17194 Generate the XML output and the XML schema file that describes the structure
17195 of the XML metric report, this schema is assigned to the XML file. The schema
17196 file has the same name as the XML output file with @file{.xml} suffix replaced
17199 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
17200 @item ^-nt^/NO_TEXT^
17201 Do not generate the output in text form (implies @option{^-x^/XML^})
17203 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
17204 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
17205 Put textual files with detailed metrics into @var{output_dir}
17207 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
17208 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
17209 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
17210 in the name of the output file.
17212 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
17213 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
17214 Put global metrics into @var{file_name}
17216 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
17217 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
17218 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
17220 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
17221 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
17222 Use ``short'' source file names in the output. (The @command{gnatmetric}
17223 output includes the name(s) of the Ada source file(s) from which the metrics
17224 are computed. By default each name includes the absolute path. The
17225 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
17226 to exclude all directory information from the file names that are output.)
17230 @node Disable Metrics For Local Units
17231 @subsection Disable Metrics For Local Units
17232 @cindex Disable Metrics For Local Units in @command{gnatmetric}
17235 @command{gnatmetric} relies on the GNAT compilation model @minus{}
17237 unit per one source file. It computes line metrics for the whole source
17238 file, and it also computes syntax
17239 and complexity metrics for the file's outermost unit.
17241 By default, @command{gnatmetric} will also compute all metrics for certain
17242 kinds of locally declared program units:
17246 subprogram (and generic subprogram) bodies;
17249 package (and generic package) specs and bodies;
17252 task object and type specifications and bodies;
17255 protected object and type specifications and bodies.
17259 These kinds of entities will be referred to as
17260 @emph{eligible local program units}, or simply @emph{eligible local units},
17261 @cindex Eligible local unit (for @command{gnatmetric})
17262 in the discussion below.
17264 Note that a subprogram declaration, generic instantiation,
17265 or renaming declaration only receives metrics
17266 computation when it appear as the outermost entity
17269 Suppression of metrics computation for eligible local units can be
17270 obtained via the following switch:
17273 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
17274 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
17275 Do not compute detailed metrics for eligible local program units
17279 @node Specifying a set of metrics to compute
17280 @subsection Specifying a set of metrics to compute
17283 By default all the metrics are computed and reported. The switches
17284 described in this subsection allow you to control, on an individual
17285 basis, whether metrics are computed and
17286 reported. If at least one positive metric
17287 switch is specified (that is, a switch that defines that a given
17288 metric or set of metrics is to be computed), then only
17289 explicitly specified metrics are reported.
17292 * Line Metrics Control::
17293 * Syntax Metrics Control::
17294 * Complexity Metrics Control::
17295 * Object-Oriented Metrics Control::
17298 @node Line Metrics Control
17299 @subsubsection Line Metrics Control
17300 @cindex Line metrics control in @command{gnatmetric}
17303 For any (legal) source file, and for each of its
17304 eligible local program units, @command{gnatmetric} computes the following
17309 the total number of lines;
17312 the total number of code lines (i.e., non-blank lines that are not comments)
17315 the number of comment lines
17318 the number of code lines containing end-of-line comments;
17321 the comment percentage: the ratio between the number of lines that contain
17322 comments and the number of all non-blank lines, expressed as a percentage;
17325 the number of empty lines and lines containing only space characters and/or
17326 format effectors (blank lines)
17329 the average number of code lines in subprogram bodies, task bodies, entry
17330 bodies and statement sequences in package bodies (this metric is only computed
17331 across the whole set of the analyzed units)
17336 @command{gnatmetric} sums the values of the line metrics for all the
17337 files being processed and then generates the cumulative results. The tool
17338 also computes for all the files being processed the average number of code
17341 You can use the following switches to select the specific line metrics
17342 to be computed and reported.
17345 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17348 @cindex @option{--no-lines@var{x}}
17351 @item ^--lines-all^/LINE_COUNT_METRICS=ALL^
17352 Report all the line metrics
17354 @item ^--no-lines-all^/LINE_COUNT_METRICS=NONE^
17355 Do not report any of line metrics
17357 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES^
17358 Report the number of all lines
17360 @item ^--no-lines^/LINE_COUNT_METRICS=NOALL_LINES^
17361 Do not report the number of all lines
17363 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES^
17364 Report the number of code lines
17366 @item ^--no-lines-code^/LINE_COUNT_METRICS=NOCODE_LINES^
17367 Do not report the number of code lines
17369 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES^
17370 Report the number of comment lines
17372 @item ^--no-lines-comment^/LINE_COUNT_METRICS=NOCOMMENT_LINES^
17373 Do not report the number of comment lines
17375 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES^
17376 Report the number of code lines containing
17377 end-of-line comments
17379 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=NOCODE_COMMENT_LINES^
17380 Do not report the number of code lines containing
17381 end-of-line comments
17383 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE^
17384 Report the comment percentage in the program text
17386 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=NOCOMMENT_PERCENTAGE^
17387 Do not report the comment percentage in the program text
17389 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES^
17390 Report the number of blank lines
17392 @item ^--no-lines-blank^/LINE_COUNT_METRICS=NOBLANK_LINES^
17393 Do not report the number of blank lines
17395 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES^
17396 Report the average number of code lines in subprogram bodies, task bodies,
17397 entry bodies and statement sequences in package bodies. The metric is computed
17398 and reported for the whole set of processed Ada sources only.
17400 @item ^--no-lines-average^/LINE_COUNT_METRICS=NOAVERAGE_BODY_LINES^
17401 Do not report the average number of code lines in subprogram bodies,
17402 task bodies, entry bodies and statement sequences in package bodies.
17406 @node Syntax Metrics Control
17407 @subsubsection Syntax Metrics Control
17408 @cindex Syntax metrics control in @command{gnatmetric}
17411 @command{gnatmetric} computes various syntactic metrics for the
17412 outermost unit and for each eligible local unit:
17415 @item LSLOC (``Logical Source Lines Of Code'')
17416 The total number of declarations and the total number of statements
17418 @item Maximal static nesting level of inner program units
17420 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17421 package, a task unit, a protected unit, a
17422 protected entry, a generic unit, or an explicitly declared subprogram other
17423 than an enumeration literal.''
17425 @item Maximal nesting level of composite syntactic constructs
17426 This corresponds to the notion of the
17427 maximum nesting level in the GNAT built-in style checks
17428 (@pxref{Style Checking})
17432 For the outermost unit in the file, @command{gnatmetric} additionally computes
17433 the following metrics:
17436 @item Public subprograms
17437 This metric is computed for package specs. It is the
17438 number of subprograms and generic subprograms declared in the visible
17439 part (including the visible part of nested packages, protected objects, and
17442 @item All subprograms
17443 This metric is computed for bodies and subunits. The
17444 metric is equal to a total number of subprogram bodies in the compilation
17446 Neither generic instantiations nor renamings-as-a-body nor body stubs
17447 are counted. Any subprogram body is counted, independently of its nesting
17448 level and enclosing constructs. Generic bodies and bodies of protected
17449 subprograms are counted in the same way as ``usual'' subprogram bodies.
17452 This metric is computed for package specs and
17453 generic package declarations. It is the total number of types
17454 that can be referenced from outside this compilation unit, plus the
17455 number of types from all the visible parts of all the visible generic
17456 packages. Generic formal types are not counted. Only types, not subtypes,
17460 Along with the total number of public types, the following
17461 types are counted and reported separately:
17468 Root tagged types (abstract, non-abstract, private, non-private). Type
17469 extensions are @emph{not} counted
17472 Private types (including private extensions)
17483 This metric is computed for any compilation unit. It is equal to the total
17484 number of the declarations of different types given in the compilation unit.
17485 The private and the corresponding full type declaration are counted as one
17486 type declaration. Incomplete type declarations and generic formal types
17488 No distinction is made among different kinds of types (abstract,
17489 private etc.); the total number of types is computed and reported.
17494 By default, all the syntax metrics are computed and reported. You can use the
17495 following switches to select specific syntax metrics.
17499 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17502 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17505 @item ^--syntax-all^/SYNTAX_METRICS=ALL^
17506 Report all the syntax metrics
17508 @item ^--no-syntax-all^/SYNTAX_METRICS=NONE^
17509 Do not report any of syntax metrics
17511 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS^
17512 Report the total number of declarations
17514 @item ^--no-declarations^/SYNTAX_METRICS=NODECLARATIONS^
17515 Do not report the total number of declarations
17517 @item ^--statements^/SYNTAX_METRICS=STATEMENTS^
17518 Report the total number of statements
17520 @item ^--no-statements^/SYNTAX_METRICS=NOSTATEMENTS^
17521 Do not report the total number of statements
17523 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS^
17524 Report the number of public subprograms in a compilation unit
17526 @item ^--no-public-subprograms^/SYNTAX_METRICS=NOPUBLIC_SUBPROGRAMS^
17527 Do not report the number of public subprograms in a compilation unit
17529 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS^
17530 Report the number of all the subprograms in a compilation unit
17532 @item ^--no-all-subprograms^/SYNTAX_METRICS=NOALL_SUBPROGRAMS^
17533 Do not report the number of all the subprograms in a compilation unit
17535 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES^
17536 Report the number of public types in a compilation unit
17538 @item ^--no-public-types^/SYNTAX_METRICS=NOPUBLIC_TYPES^
17539 Do not report the number of public types in a compilation unit
17541 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES^
17542 Report the number of all the types in a compilation unit
17544 @item ^--no-all-types^/SYNTAX_METRICS=NOALL_TYPES^
17545 Do not report the number of all the types in a compilation unit
17547 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING^
17548 Report the maximal program unit nesting level
17550 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17551 Do not report the maximal program unit nesting level
17553 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING^
17554 Report the maximal construct nesting level
17556 @item ^--no-construct-nesting^/SYNTAX_METRICS=NOCONSTRUCT_NESTING^
17557 Do not report the maximal construct nesting level
17561 @node Complexity Metrics Control
17562 @subsubsection Complexity Metrics Control
17563 @cindex Complexity metrics control in @command{gnatmetric}
17566 For a program unit that is an executable body (a subprogram body (including
17567 generic bodies), task body, entry body or a package body containing
17568 its own statement sequence) @command{gnatmetric} computes the following
17569 complexity metrics:
17573 McCabe cyclomatic complexity;
17576 McCabe essential complexity;
17579 maximal loop nesting level
17584 The McCabe complexity metrics are defined
17585 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17587 According to McCabe, both control statements and short-circuit control forms
17588 should be taken into account when computing cyclomatic complexity. For each
17589 body, we compute three metric values:
17593 the complexity introduced by control
17594 statements only, without taking into account short-circuit forms,
17597 the complexity introduced by short-circuit control forms only, and
17601 cyclomatic complexity, which is the sum of these two values.
17605 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17606 the code in the exception handlers and in all the nested program units.
17608 By default, all the complexity metrics are computed and reported.
17609 For more fine-grained control you can use
17610 the following switches:
17613 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17616 @cindex @option{--no-complexity@var{x}}
17619 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL^
17620 Report all the complexity metrics
17622 @item ^--no-complexity-all^/COMPLEXITY_METRICS=NONE^
17623 Do not report any of complexity metrics
17625 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC^
17626 Report the McCabe Cyclomatic Complexity
17628 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=NOCYCLOMATIC^
17629 Do not report the McCabe Cyclomatic Complexity
17631 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL^
17632 Report the Essential Complexity
17634 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=NOESSENTIAL^
17635 Do not report the Essential Complexity
17637 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17638 Report maximal loop nesting level
17640 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=NOLOOP_NESTING^
17641 Do not report maximal loop nesting level
17643 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY^
17644 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17645 task bodies, entry bodies and statement sequences in package bodies.
17646 The metric is computed and reported for whole set of processed Ada sources
17649 @item ^--no-complexity-average^/COMPLEXITY_METRICS=NOAVERAGE_COMPLEXITY^
17650 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17651 bodies, task bodies, entry bodies and statement sequences in package bodies
17653 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17654 @item ^-ne^/NO_EXITS_AS_GOTOS^
17655 Do not consider @code{exit} statements as @code{goto}s when
17656 computing Essential Complexity
17658 @item ^--extra-exit-points^/EXTRA_EXIT_POINTS^
17659 Report the extra exit points for subprogram bodies. As an exit point, this
17660 metric counts @code{return} statements and raise statements in case when the
17661 raised exception is not handled in the same body. In case of a function this
17662 metric subtracts 1 from the number of exit points, because a function body
17663 must contain at least one @code{return} statement.
17665 @item ^--no-extra-exit-points^/NOEXTRA_EXIT_POINTS^
17666 Do not report the extra exit points for subprogram bodies
17670 @node Object-Oriented Metrics Control
17671 @subsubsection Object-Oriented Metrics Control
17672 @cindex Object-Oriented metrics control in @command{gnatmetric}
17675 @cindex Coupling metrics (in in @command{gnatmetric})
17676 Coupling metrics are object-oriented metrics that measure the
17677 dependencies between a given class (or a group of classes) and the
17678 ``external world'' (that is, the other classes in the program). In this
17679 subsection the term ``class'' is used in its
17680 traditional object-oriented programming sense
17681 (an instantiable module that contains data and/or method members).
17682 A @emph{category} (of classes)
17683 is a group of closely related classes that are reused and/or
17686 A class @code{K}'s @emph{efferent coupling} is the number of classes
17687 that @code{K} depends upon.
17688 A category's efferent coupling is the number of classes outside the
17689 category that the classes inside the category depend upon.
17691 A class @code{K}'s @emph{afferent coupling} is the number of classes
17692 that depend upon @code{K}.
17693 A category's afferent coupling is the number of classes outside the
17694 category that depend on classes belonging to the category.
17696 Ada's implementation of the object-oriented paradigm does not use the
17697 traditional class notion, so the definition of the coupling
17698 metrics for Ada maps the class and class category notions
17699 onto Ada constructs.
17701 For the coupling metrics, several kinds of modules -- a library package,
17702 a library generic package, and a library generic package instantiation --
17703 that define a tagged type or an interface type are
17704 considered to be a class. A category consists of a library package (or
17705 a library generic package) that defines a tagged or an interface type,
17706 together with all its descendant (generic) packages that define tagged
17707 or interface types. For any package counted as a class,
17708 its body and subunits (if any) are considered
17709 together with its spec when counting the dependencies, and coupling
17710 metrics are reported for spec units only. For dependencies
17711 between classes, the Ada semantic dependencies are considered.
17712 For coupling metrics, only dependencies on units that are considered as
17713 classes, are considered.
17715 When computing coupling metrics, @command{gnatmetric} counts only
17716 dependencies between units that are arguments of the gnatmetric call.
17717 Coupling metrics are program-wide (or project-wide) metrics, so to
17718 get a valid result, you should call @command{gnatmetric} for
17719 the whole set of sources that make up your program. It can be done
17720 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17721 option (see See @ref{The GNAT Driver and Project Files} for details.
17723 By default, all the coupling metrics are disabled. You can use the following
17724 switches to specify the coupling metrics to be computed and reported:
17729 @cindex @option{--package@var{x}} (@command{gnatmetric})
17730 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17731 @cindex @option{--category@var{x}} (@command{gnatmetric})
17732 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17736 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17739 @item ^--coupling-all^/COUPLING_METRICS=ALL^
17740 Report all the coupling metrics
17742 @item ^--no-coupling-all^/COUPLING_METRICS=NONE^
17743 Do not report any of metrics
17745 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT^
17746 Report package efferent coupling
17748 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=NOPACKAGE_EFFERENT^
17749 Do not report package efferent coupling
17751 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT^
17752 Report package afferent coupling
17754 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=NOPACKAGE_AFFERENT^
17755 Do not report package afferent coupling
17757 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT^
17758 Report category efferent coupling
17760 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=NOCATEGORY_EFFERENT^
17761 Do not report category efferent coupling
17763 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT^
17764 Report category afferent coupling
17766 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=NOCATEGORY_AFFERENT^
17767 Do not report category afferent coupling
17771 @node Other gnatmetric Switches
17772 @subsection Other @code{gnatmetric} Switches
17775 Additional @command{gnatmetric} switches are as follows:
17778 @item ^-files @var{filename}^/FILES=@var{filename}^
17779 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17780 Take the argument source files from the specified file. This file should be an
17781 ordinary text file containing file names separated by spaces or
17782 line breaks. You can use this switch more then once in the same call to
17783 @command{gnatmetric}. You also can combine this switch with
17784 an explicit list of files.
17786 @item ^-v^/VERBOSE^
17787 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17789 @command{gnatmetric} generates version information and then
17790 a trace of sources being processed.
17792 @item ^-dv^/DEBUG_OUTPUT^
17793 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17795 @command{gnatmetric} generates various messages useful to understand what
17796 happens during the metrics computation
17799 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17803 @node Generate project-wide metrics
17804 @subsection Generate project-wide metrics
17806 In order to compute metrics on all units of a given project, you can use
17807 the @command{gnat} driver along with the @option{-P} option:
17813 If the project @code{proj} depends upon other projects, you can compute
17814 the metrics on the project closure using the @option{-U} option:
17816 gnat metric -Pproj -U
17820 Finally, if not all the units are relevant to a particular main
17821 program in the project closure, you can generate metrics for the set
17822 of units needed to create a given main program (unit closure) using
17823 the @option{-U} option followed by the name of the main unit:
17825 gnat metric -Pproj -U main
17829 @c ***********************************
17830 @node File Name Krunching Using gnatkr
17831 @chapter File Name Krunching Using @code{gnatkr}
17835 This chapter discusses the method used by the compiler to shorten
17836 the default file names chosen for Ada units so that they do not
17837 exceed the maximum length permitted. It also describes the
17838 @code{gnatkr} utility that can be used to determine the result of
17839 applying this shortening.
17843 * Krunching Method::
17844 * Examples of gnatkr Usage::
17848 @section About @code{gnatkr}
17851 The default file naming rule in GNAT
17852 is that the file name must be derived from
17853 the unit name. The exact default rule is as follows:
17856 Take the unit name and replace all dots by hyphens.
17858 If such a replacement occurs in the
17859 second character position of a name, and the first character is
17860 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17861 then replace the dot by the character
17862 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17863 instead of a minus.
17865 The reason for this exception is to avoid clashes
17866 with the standard names for children of System, Ada, Interfaces,
17867 and GNAT, which use the prefixes
17868 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17871 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17872 switch of the compiler activates a ``krunching''
17873 circuit that limits file names to nn characters (where nn is a decimal
17874 integer). For example, using OpenVMS,
17875 where the maximum file name length is
17876 39, the value of nn is usually set to 39, but if you want to generate
17877 a set of files that would be usable if ported to a system with some
17878 different maximum file length, then a different value can be specified.
17879 The default value of 39 for OpenVMS need not be specified.
17881 The @code{gnatkr} utility can be used to determine the krunched name for
17882 a given file, when krunched to a specified maximum length.
17885 @section Using @code{gnatkr}
17888 The @code{gnatkr} command has the form
17892 $ gnatkr @var{name} @ovar{length}
17898 $ gnatkr @var{name} /COUNT=nn
17903 @var{name} is the uncrunched file name, derived from the name of the unit
17904 in the standard manner described in the previous section (i.e., in particular
17905 all dots are replaced by hyphens). The file name may or may not have an
17906 extension (defined as a suffix of the form period followed by arbitrary
17907 characters other than period). If an extension is present then it will
17908 be preserved in the output. For example, when krunching @file{hellofile.ads}
17909 to eight characters, the result will be hellofil.ads.
17911 Note: for compatibility with previous versions of @code{gnatkr} dots may
17912 appear in the name instead of hyphens, but the last dot will always be
17913 taken as the start of an extension. So if @code{gnatkr} is given an argument
17914 such as @file{Hello.World.adb} it will be treated exactly as if the first
17915 period had been a hyphen, and for example krunching to eight characters
17916 gives the result @file{hellworl.adb}.
17918 Note that the result is always all lower case (except on OpenVMS where it is
17919 all upper case). Characters of the other case are folded as required.
17921 @var{length} represents the length of the krunched name. The default
17922 when no argument is given is ^8^39^ characters. A length of zero stands for
17923 unlimited, in other words do not chop except for system files where the
17924 implied crunching length is always eight characters.
17927 The output is the krunched name. The output has an extension only if the
17928 original argument was a file name with an extension.
17930 @node Krunching Method
17931 @section Krunching Method
17934 The initial file name is determined by the name of the unit that the file
17935 contains. The name is formed by taking the full expanded name of the
17936 unit and replacing the separating dots with hyphens and
17937 using ^lowercase^uppercase^
17938 for all letters, except that a hyphen in the second character position is
17939 replaced by a ^tilde^dollar sign^ if the first character is
17940 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
17941 The extension is @code{.ads} for a
17942 spec and @code{.adb} for a body.
17943 Krunching does not affect the extension, but the file name is shortened to
17944 the specified length by following these rules:
17948 The name is divided into segments separated by hyphens, tildes or
17949 underscores and all hyphens, tildes, and underscores are
17950 eliminated. If this leaves the name short enough, we are done.
17953 If the name is too long, the longest segment is located (left-most
17954 if there are two of equal length), and shortened by dropping
17955 its last character. This is repeated until the name is short enough.
17957 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
17958 to fit the name into 8 characters as required by some operating systems.
17961 our-strings-wide_fixed 22
17962 our strings wide fixed 19
17963 our string wide fixed 18
17964 our strin wide fixed 17
17965 our stri wide fixed 16
17966 our stri wide fixe 15
17967 our str wide fixe 14
17968 our str wid fixe 13
17974 Final file name: oustwifi.adb
17978 The file names for all predefined units are always krunched to eight
17979 characters. The krunching of these predefined units uses the following
17980 special prefix replacements:
17984 replaced by @file{^a^A^-}
17987 replaced by @file{^g^G^-}
17990 replaced by @file{^i^I^-}
17993 replaced by @file{^s^S^-}
17996 These system files have a hyphen in the second character position. That
17997 is why normal user files replace such a character with a
17998 ^tilde^dollar sign^, to
17999 avoid confusion with system file names.
18001 As an example of this special rule, consider
18002 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
18005 ada-strings-wide_fixed 22
18006 a- strings wide fixed 18
18007 a- string wide fixed 17
18008 a- strin wide fixed 16
18009 a- stri wide fixed 15
18010 a- stri wide fixe 14
18011 a- str wide fixe 13
18017 Final file name: a-stwifi.adb
18021 Of course no file shortening algorithm can guarantee uniqueness over all
18022 possible unit names, and if file name krunching is used then it is your
18023 responsibility to ensure that no name clashes occur. The utility
18024 program @code{gnatkr} is supplied for conveniently determining the
18025 krunched name of a file.
18027 @node Examples of gnatkr Usage
18028 @section Examples of @code{gnatkr} Usage
18035 $ gnatkr very_long_unit_name.ads --> velounna.ads
18036 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
18037 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
18038 $ gnatkr grandparent-parent-child --> grparchi
18040 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
18041 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
18044 @node Preprocessing Using gnatprep
18045 @chapter Preprocessing Using @code{gnatprep}
18049 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
18051 Although designed for use with GNAT, @code{gnatprep} does not depend on any
18052 special GNAT features.
18053 For further discussion of conditional compilation in general, see
18054 @ref{Conditional Compilation}.
18057 * Preprocessing Symbols::
18059 * Switches for gnatprep::
18060 * Form of Definitions File::
18061 * Form of Input Text for gnatprep::
18064 @node Preprocessing Symbols
18065 @section Preprocessing Symbols
18068 Preprocessing symbols are defined in definition files and referred to in
18069 sources to be preprocessed. A Preprocessing symbol is an identifier, following
18070 normal Ada (case-insensitive) rules for its syntax, with the restriction that
18071 all characters need to be in the ASCII set (no accented letters).
18073 @node Using gnatprep
18074 @section Using @code{gnatprep}
18077 To call @code{gnatprep} use
18080 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
18087 is an optional sequence of switches as described in the next section.
18090 is the full name of the input file, which is an Ada source
18091 file containing preprocessor directives.
18094 is the full name of the output file, which is an Ada source
18095 in standard Ada form. When used with GNAT, this file name will
18096 normally have an ads or adb suffix.
18099 is the full name of a text file containing definitions of
18100 preprocessing symbols to be referenced by the preprocessor. This argument is
18101 optional, and can be replaced by the use of the @option{-D} switch.
18105 @node Switches for gnatprep
18106 @section Switches for @code{gnatprep}
18111 @item ^-b^/BLANK_LINES^
18112 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
18113 Causes both preprocessor lines and the lines deleted by
18114 preprocessing to be replaced by blank lines in the output source file,
18115 preserving line numbers in the output file.
18117 @item ^-c^/COMMENTS^
18118 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
18119 Causes both preprocessor lines and the lines deleted
18120 by preprocessing to be retained in the output source as comments marked
18121 with the special string @code{"--! "}. This option will result in line numbers
18122 being preserved in the output file.
18124 @item ^-C^/REPLACE_IN_COMMENTS^
18125 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
18126 Causes comments to be scanned. Normally comments are ignored by gnatprep.
18127 If this option is specified, then comments are scanned and any $symbol
18128 substitutions performed as in program text. This is particularly useful
18129 when structured comments are used (e.g., when writing programs in the
18130 SPARK dialect of Ada). Note that this switch is not available when
18131 doing integrated preprocessing (it would be useless in this context
18132 since comments are ignored by the compiler in any case).
18134 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
18135 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
18136 Defines a new preprocessing symbol, associated with value. If no value is given
18137 on the command line, then symbol is considered to be @code{True}. This switch
18138 can be used in place of a definition file.
18142 @cindex @option{/REMOVE} (@command{gnatprep})
18143 This is the default setting which causes lines deleted by preprocessing
18144 to be entirely removed from the output file.
18147 @item ^-r^/REFERENCE^
18148 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
18149 Causes a @code{Source_Reference} pragma to be generated that
18150 references the original input file, so that error messages will use
18151 the file name of this original file. The use of this switch implies
18152 that preprocessor lines are not to be removed from the file, so its
18153 use will force @option{^-b^/BLANK_LINES^} mode if
18154 @option{^-c^/COMMENTS^}
18155 has not been specified explicitly.
18157 Note that if the file to be preprocessed contains multiple units, then
18158 it will be necessary to @code{gnatchop} the output file from
18159 @code{gnatprep}. If a @code{Source_Reference} pragma is present
18160 in the preprocessed file, it will be respected by
18161 @code{gnatchop ^-r^/REFERENCE^}
18162 so that the final chopped files will correctly refer to the original
18163 input source file for @code{gnatprep}.
18165 @item ^-s^/SYMBOLS^
18166 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
18167 Causes a sorted list of symbol names and values to be
18168 listed on the standard output file.
18170 @item ^-u^/UNDEFINED^
18171 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
18172 Causes undefined symbols to be treated as having the value FALSE in the context
18173 of a preprocessor test. In the absence of this option, an undefined symbol in
18174 a @code{#if} or @code{#elsif} test will be treated as an error.
18180 Note: if neither @option{-b} nor @option{-c} is present,
18181 then preprocessor lines and
18182 deleted lines are completely removed from the output, unless -r is
18183 specified, in which case -b is assumed.
18186 @node Form of Definitions File
18187 @section Form of Definitions File
18190 The definitions file contains lines of the form
18197 where symbol is a preprocessing symbol, and value is one of the following:
18201 Empty, corresponding to a null substitution
18203 A string literal using normal Ada syntax
18205 Any sequence of characters from the set
18206 (letters, digits, period, underline).
18210 Comment lines may also appear in the definitions file, starting with
18211 the usual @code{--},
18212 and comments may be added to the definitions lines.
18214 @node Form of Input Text for gnatprep
18215 @section Form of Input Text for @code{gnatprep}
18218 The input text may contain preprocessor conditional inclusion lines,
18219 as well as general symbol substitution sequences.
18221 The preprocessor conditional inclusion commands have the form
18226 #if @i{expression} @r{[}then@r{]}
18228 #elsif @i{expression} @r{[}then@r{]}
18230 #elsif @i{expression} @r{[}then@r{]}
18241 In this example, @i{expression} is defined by the following grammar:
18243 @i{expression} ::= <symbol>
18244 @i{expression} ::= <symbol> = "<value>"
18245 @i{expression} ::= <symbol> = <symbol>
18246 @i{expression} ::= <symbol> 'Defined
18247 @i{expression} ::= not @i{expression}
18248 @i{expression} ::= @i{expression} and @i{expression}
18249 @i{expression} ::= @i{expression} or @i{expression}
18250 @i{expression} ::= @i{expression} and then @i{expression}
18251 @i{expression} ::= @i{expression} or else @i{expression}
18252 @i{expression} ::= ( @i{expression} )
18255 The following restriction exists: it is not allowed to have "and" or "or"
18256 following "not" in the same expression without parentheses. For example, this
18263 This should be one of the following:
18271 For the first test (@i{expression} ::= <symbol>) the symbol must have
18272 either the value true or false, that is to say the right-hand of the
18273 symbol definition must be one of the (case-insensitive) literals
18274 @code{True} or @code{False}. If the value is true, then the
18275 corresponding lines are included, and if the value is false, they are
18278 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
18279 the symbol has been defined in the definition file or by a @option{-D}
18280 switch on the command line. Otherwise, the test is false.
18282 The equality tests are case insensitive, as are all the preprocessor lines.
18284 If the symbol referenced is not defined in the symbol definitions file,
18285 then the effect depends on whether or not switch @option{-u}
18286 is specified. If so, then the symbol is treated as if it had the value
18287 false and the test fails. If this switch is not specified, then
18288 it is an error to reference an undefined symbol. It is also an error to
18289 reference a symbol that is defined with a value other than @code{True}
18292 The use of the @code{not} operator inverts the sense of this logical test.
18293 The @code{not} operator cannot be combined with the @code{or} or @code{and}
18294 operators, without parentheses. For example, "if not X or Y then" is not
18295 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
18297 The @code{then} keyword is optional as shown
18299 The @code{#} must be the first non-blank character on a line, but
18300 otherwise the format is free form. Spaces or tabs may appear between
18301 the @code{#} and the keyword. The keywords and the symbols are case
18302 insensitive as in normal Ada code. Comments may be used on a
18303 preprocessor line, but other than that, no other tokens may appear on a
18304 preprocessor line. Any number of @code{elsif} clauses can be present,
18305 including none at all. The @code{else} is optional, as in Ada.
18307 The @code{#} marking the start of a preprocessor line must be the first
18308 non-blank character on the line, i.e., it must be preceded only by
18309 spaces or horizontal tabs.
18311 Symbol substitution outside of preprocessor lines is obtained by using
18319 anywhere within a source line, except in a comment or within a
18320 string literal. The identifier
18321 following the @code{$} must match one of the symbols defined in the symbol
18322 definition file, and the result is to substitute the value of the
18323 symbol in place of @code{$symbol} in the output file.
18325 Note that although the substitution of strings within a string literal
18326 is not possible, it is possible to have a symbol whose defined value is
18327 a string literal. So instead of setting XYZ to @code{hello} and writing:
18330 Header : String := "$XYZ";
18334 you should set XYZ to @code{"hello"} and write:
18337 Header : String := $XYZ;
18341 and then the substitution will occur as desired.
18344 @node The GNAT Run-Time Library Builder gnatlbr
18345 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18347 @cindex Library builder
18350 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18351 supplied configuration pragmas.
18354 * Running gnatlbr::
18355 * Switches for gnatlbr::
18356 * Examples of gnatlbr Usage::
18359 @node Running gnatlbr
18360 @section Running @code{gnatlbr}
18363 The @code{gnatlbr} command has the form
18366 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18369 @node Switches for gnatlbr
18370 @section Switches for @code{gnatlbr}
18373 @code{gnatlbr} recognizes the following switches:
18377 @item /CREATE=directory
18378 @cindex @code{/CREATE} (@code{gnatlbr})
18379 Create the new run-time library in the specified directory.
18381 @item /SET=directory
18382 @cindex @code{/SET} (@code{gnatlbr})
18383 Make the library in the specified directory the current run-time library.
18385 @item /DELETE=directory
18386 @cindex @code{/DELETE} (@code{gnatlbr})
18387 Delete the run-time library in the specified directory.
18390 @cindex @code{/CONFIG} (@code{gnatlbr})
18391 With /CREATE: Use the configuration pragmas in the specified file when
18392 building the library.
18394 With /SET: Use the configuration pragmas in the specified file when
18399 @node Examples of gnatlbr Usage
18400 @section Example of @code{gnatlbr} Usage
18403 Contents of VAXFLOAT.ADC:
18404 pragma Float_Representation (VAX_Float);
18406 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18408 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18413 @node The GNAT Library Browser gnatls
18414 @chapter The GNAT Library Browser @code{gnatls}
18416 @cindex Library browser
18419 @code{gnatls} is a tool that outputs information about compiled
18420 units. It gives the relationship between objects, unit names and source
18421 files. It can also be used to check the source dependencies of a unit
18422 as well as various characteristics.
18424 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18425 driver (see @ref{The GNAT Driver and Project Files}).
18429 * Switches for gnatls::
18430 * Examples of gnatls Usage::
18433 @node Running gnatls
18434 @section Running @code{gnatls}
18437 The @code{gnatls} command has the form
18440 $ gnatls switches @var{object_or_ali_file}
18444 The main argument is the list of object or @file{ali} files
18445 (@pxref{The Ada Library Information Files})
18446 for which information is requested.
18448 In normal mode, without additional option, @code{gnatls} produces a
18449 four-column listing. Each line represents information for a specific
18450 object. The first column gives the full path of the object, the second
18451 column gives the name of the principal unit in this object, the third
18452 column gives the status of the source and the fourth column gives the
18453 full path of the source representing this unit.
18454 Here is a simple example of use:
18458 ^./^[]^demo1.o demo1 DIF demo1.adb
18459 ^./^[]^demo2.o demo2 OK demo2.adb
18460 ^./^[]^hello.o h1 OK hello.adb
18461 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18462 ^./^[]^instr.o instr OK instr.adb
18463 ^./^[]^tef.o tef DIF tef.adb
18464 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18465 ^./^[]^tgef.o tgef DIF tgef.adb
18469 The first line can be interpreted as follows: the main unit which is
18471 object file @file{demo1.o} is demo1, whose main source is in
18472 @file{demo1.adb}. Furthermore, the version of the source used for the
18473 compilation of demo1 has been modified (DIF). Each source file has a status
18474 qualifier which can be:
18477 @item OK (unchanged)
18478 The version of the source file used for the compilation of the
18479 specified unit corresponds exactly to the actual source file.
18481 @item MOK (slightly modified)
18482 The version of the source file used for the compilation of the
18483 specified unit differs from the actual source file but not enough to
18484 require recompilation. If you use gnatmake with the qualifier
18485 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18486 MOK will not be recompiled.
18488 @item DIF (modified)
18489 No version of the source found on the path corresponds to the source
18490 used to build this object.
18492 @item ??? (file not found)
18493 No source file was found for this unit.
18495 @item HID (hidden, unchanged version not first on PATH)
18496 The version of the source that corresponds exactly to the source used
18497 for compilation has been found on the path but it is hidden by another
18498 version of the same source that has been modified.
18502 @node Switches for gnatls
18503 @section Switches for @code{gnatls}
18506 @code{gnatls} recognizes the following switches:
18510 @cindex @option{--version} @command{gnatls}
18511 Display Copyright and version, then exit disregarding all other options.
18514 @cindex @option{--help} @command{gnatls}
18515 If @option{--version} was not used, display usage, then exit disregarding
18518 @item ^-a^/ALL_UNITS^
18519 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18520 Consider all units, including those of the predefined Ada library.
18521 Especially useful with @option{^-d^/DEPENDENCIES^}.
18523 @item ^-d^/DEPENDENCIES^
18524 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18525 List sources from which specified units depend on.
18527 @item ^-h^/OUTPUT=OPTIONS^
18528 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18529 Output the list of options.
18531 @item ^-o^/OUTPUT=OBJECTS^
18532 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18533 Only output information about object files.
18535 @item ^-s^/OUTPUT=SOURCES^
18536 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18537 Only output information about source files.
18539 @item ^-u^/OUTPUT=UNITS^
18540 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18541 Only output information about compilation units.
18543 @item ^-files^/FILES^=@var{file}
18544 @cindex @option{^-files^/FILES^} (@code{gnatls})
18545 Take as arguments the files listed in text file @var{file}.
18546 Text file @var{file} may contain empty lines that are ignored.
18547 Each nonempty line should contain the name of an existing file.
18548 Several such switches may be specified simultaneously.
18550 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18551 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18552 @itemx ^-I^/SEARCH=^@var{dir}
18553 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18555 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18556 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18557 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18558 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18559 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18560 flags (@pxref{Switches for gnatmake}).
18562 @item --RTS=@var{rts-path}
18563 @cindex @option{--RTS} (@code{gnatls})
18564 Specifies the default location of the runtime library. Same meaning as the
18565 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18567 @item ^-v^/OUTPUT=VERBOSE^
18568 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18569 Verbose mode. Output the complete source, object and project paths. Do not use
18570 the default column layout but instead use long format giving as much as
18571 information possible on each requested units, including special
18572 characteristics such as:
18575 @item Preelaborable
18576 The unit is preelaborable in the Ada sense.
18579 No elaboration code has been produced by the compiler for this unit.
18582 The unit is pure in the Ada sense.
18584 @item Elaborate_Body
18585 The unit contains a pragma Elaborate_Body.
18588 The unit contains a pragma Remote_Types.
18590 @item Shared_Passive
18591 The unit contains a pragma Shared_Passive.
18594 This unit is part of the predefined environment and cannot be modified
18597 @item Remote_Call_Interface
18598 The unit contains a pragma Remote_Call_Interface.
18604 @node Examples of gnatls Usage
18605 @section Example of @code{gnatls} Usage
18609 Example of using the verbose switch. Note how the source and
18610 object paths are affected by the -I switch.
18613 $ gnatls -v -I.. demo1.o
18615 GNATLS 5.03w (20041123-34)
18616 Copyright 1997-2004 Free Software Foundation, Inc.
18618 Source Search Path:
18619 <Current_Directory>
18621 /home/comar/local/adainclude/
18623 Object Search Path:
18624 <Current_Directory>
18626 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18628 Project Search Path:
18629 <Current_Directory>
18630 /home/comar/local/lib/gnat/
18635 Kind => subprogram body
18636 Flags => No_Elab_Code
18637 Source => demo1.adb modified
18641 The following is an example of use of the dependency list.
18642 Note the use of the -s switch
18643 which gives a straight list of source files. This can be useful for
18644 building specialized scripts.
18647 $ gnatls -d demo2.o
18648 ./demo2.o demo2 OK demo2.adb
18654 $ gnatls -d -s -a demo1.o
18656 /home/comar/local/adainclude/ada.ads
18657 /home/comar/local/adainclude/a-finali.ads
18658 /home/comar/local/adainclude/a-filico.ads
18659 /home/comar/local/adainclude/a-stream.ads
18660 /home/comar/local/adainclude/a-tags.ads
18663 /home/comar/local/adainclude/gnat.ads
18664 /home/comar/local/adainclude/g-io.ads
18666 /home/comar/local/adainclude/system.ads
18667 /home/comar/local/adainclude/s-exctab.ads
18668 /home/comar/local/adainclude/s-finimp.ads
18669 /home/comar/local/adainclude/s-finroo.ads
18670 /home/comar/local/adainclude/s-secsta.ads
18671 /home/comar/local/adainclude/s-stalib.ads
18672 /home/comar/local/adainclude/s-stoele.ads
18673 /home/comar/local/adainclude/s-stratt.ads
18674 /home/comar/local/adainclude/s-tasoli.ads
18675 /home/comar/local/adainclude/s-unstyp.ads
18676 /home/comar/local/adainclude/unchconv.ads
18682 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18684 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18685 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18686 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18687 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18688 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18692 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18693 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18695 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18696 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18697 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18698 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
18699 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
18700 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
18701 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
18702 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
18703 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
18704 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
18705 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
18709 @node Cleaning Up Using gnatclean
18710 @chapter Cleaning Up Using @code{gnatclean}
18712 @cindex Cleaning tool
18715 @code{gnatclean} is a tool that allows the deletion of files produced by the
18716 compiler, binder and linker, including ALI files, object files, tree files,
18717 expanded source files, library files, interface copy source files, binder
18718 generated files and executable files.
18721 * Running gnatclean::
18722 * Switches for gnatclean::
18723 @c * Examples of gnatclean Usage::
18726 @node Running gnatclean
18727 @section Running @code{gnatclean}
18730 The @code{gnatclean} command has the form:
18733 $ gnatclean switches @var{names}
18737 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18738 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18739 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18742 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18743 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18744 the linker. In informative-only mode, specified by switch
18745 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18746 normal mode is listed, but no file is actually deleted.
18748 @node Switches for gnatclean
18749 @section Switches for @code{gnatclean}
18752 @code{gnatclean} recognizes the following switches:
18756 @cindex @option{--version} @command{gnatclean}
18757 Display Copyright and version, then exit disregarding all other options.
18760 @cindex @option{--help} @command{gnatclean}
18761 If @option{--version} was not used, display usage, then exit disregarding
18764 @item ^-c^/COMPILER_FILES_ONLY^
18765 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18766 Only attempt to delete the files produced by the compiler, not those produced
18767 by the binder or the linker. The files that are not to be deleted are library
18768 files, interface copy files, binder generated files and executable files.
18770 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18771 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18772 Indicate that ALI and object files should normally be found in directory
18775 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18776 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18777 When using project files, if some errors or warnings are detected during
18778 parsing and verbose mode is not in effect (no use of switch
18779 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18780 file, rather than its simple file name.
18783 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18784 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18786 @item ^-n^/NODELETE^
18787 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18788 Informative-only mode. Do not delete any files. Output the list of the files
18789 that would have been deleted if this switch was not specified.
18791 @item ^-P^/PROJECT_FILE=^@var{project}
18792 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18793 Use project file @var{project}. Only one such switch can be used.
18794 When cleaning a project file, the files produced by the compilation of the
18795 immediate sources or inherited sources of the project files are to be
18796 deleted. This is not depending on the presence or not of executable names
18797 on the command line.
18800 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18801 Quiet output. If there are no errors, do not output anything, except in
18802 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18803 (switch ^-n^/NODELETE^).
18805 @item ^-r^/RECURSIVE^
18806 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18807 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18808 clean all imported and extended project files, recursively. If this switch
18809 is not specified, only the files related to the main project file are to be
18810 deleted. This switch has no effect if no project file is specified.
18812 @item ^-v^/VERBOSE^
18813 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18816 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18817 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18818 Indicates the verbosity of the parsing of GNAT project files.
18819 @xref{Switches Related to Project Files}.
18821 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18822 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18823 Indicates that external variable @var{name} has the value @var{value}.
18824 The Project Manager will use this value for occurrences of
18825 @code{external(name)} when parsing the project file.
18826 @xref{Switches Related to Project Files}.
18828 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18829 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18830 When searching for ALI and object files, look in directory
18833 @item ^-I^/SEARCH=^@var{dir}
18834 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18835 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18837 @item ^-I-^/NOCURRENT_DIRECTORY^
18838 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18839 @cindex Source files, suppressing search
18840 Do not look for ALI or object files in the directory
18841 where @code{gnatclean} was invoked.
18845 @c @node Examples of gnatclean Usage
18846 @c @section Examples of @code{gnatclean} Usage
18849 @node GNAT and Libraries
18850 @chapter GNAT and Libraries
18851 @cindex Library, building, installing, using
18854 This chapter describes how to build and use libraries with GNAT, and also shows
18855 how to recompile the GNAT run-time library. You should be familiar with the
18856 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18860 * Introduction to Libraries in GNAT::
18861 * General Ada Libraries::
18862 * Stand-alone Ada Libraries::
18863 * Rebuilding the GNAT Run-Time Library::
18866 @node Introduction to Libraries in GNAT
18867 @section Introduction to Libraries in GNAT
18870 A library is, conceptually, a collection of objects which does not have its
18871 own main thread of execution, but rather provides certain services to the
18872 applications that use it. A library can be either statically linked with the
18873 application, in which case its code is directly included in the application,
18874 or, on platforms that support it, be dynamically linked, in which case
18875 its code is shared by all applications making use of this library.
18877 GNAT supports both types of libraries.
18878 In the static case, the compiled code can be provided in different ways. The
18879 simplest approach is to provide directly the set of objects resulting from
18880 compilation of the library source files. Alternatively, you can group the
18881 objects into an archive using whatever commands are provided by the operating
18882 system. For the latter case, the objects are grouped into a shared library.
18884 In the GNAT environment, a library has three types of components:
18890 @xref{The Ada Library Information Files}.
18892 Object files, an archive or a shared library.
18896 A GNAT library may expose all its source files, which is useful for
18897 documentation purposes. Alternatively, it may expose only the units needed by
18898 an external user to make use of the library. That is to say, the specs
18899 reflecting the library services along with all the units needed to compile
18900 those specs, which can include generic bodies or any body implementing an
18901 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18902 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18904 All compilation units comprising an application, including those in a library,
18905 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18906 computes the elaboration order from the @file{ALI} files and this is why they
18907 constitute a mandatory part of GNAT libraries.
18908 @emph{Stand-alone libraries} are the exception to this rule because a specific
18909 library elaboration routine is produced independently of the application(s)
18912 @node General Ada Libraries
18913 @section General Ada Libraries
18916 * Building a library::
18917 * Installing a library::
18918 * Using a library::
18921 @node Building a library
18922 @subsection Building a library
18925 The easiest way to build a library is to use the Project Manager,
18926 which supports a special type of project called a @emph{Library Project}
18927 (@pxref{Library Projects}).
18929 A project is considered a library project, when two project-level attributes
18930 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
18931 control different aspects of library configuration, additional optional
18932 project-level attributes can be specified:
18935 This attribute controls whether the library is to be static or dynamic
18937 @item Library_Version
18938 This attribute specifies the library version; this value is used
18939 during dynamic linking of shared libraries to determine if the currently
18940 installed versions of the binaries are compatible.
18942 @item Library_Options
18944 These attributes specify additional low-level options to be used during
18945 library generation, and redefine the actual application used to generate
18950 The GNAT Project Manager takes full care of the library maintenance task,
18951 including recompilation of the source files for which objects do not exist
18952 or are not up to date, assembly of the library archive, and installation of
18953 the library (i.e., copying associated source, object and @file{ALI} files
18954 to the specified location).
18956 Here is a simple library project file:
18957 @smallexample @c ada
18959 for Source_Dirs use ("src1", "src2");
18960 for Object_Dir use "obj";
18961 for Library_Name use "mylib";
18962 for Library_Dir use "lib";
18963 for Library_Kind use "dynamic";
18968 and the compilation command to build and install the library:
18970 @smallexample @c ada
18971 $ gnatmake -Pmy_lib
18975 It is not entirely trivial to perform manually all the steps required to
18976 produce a library. We recommend that you use the GNAT Project Manager
18977 for this task. In special cases where this is not desired, the necessary
18978 steps are discussed below.
18980 There are various possibilities for compiling the units that make up the
18981 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
18982 with a conventional script. For simple libraries, it is also possible to create
18983 a dummy main program which depends upon all the packages that comprise the
18984 interface of the library. This dummy main program can then be given to
18985 @command{gnatmake}, which will ensure that all necessary objects are built.
18987 After this task is accomplished, you should follow the standard procedure
18988 of the underlying operating system to produce the static or shared library.
18990 Here is an example of such a dummy program:
18991 @smallexample @c ada
18993 with My_Lib.Service1;
18994 with My_Lib.Service2;
18995 with My_Lib.Service3;
18996 procedure My_Lib_Dummy is
19004 Here are the generic commands that will build an archive or a shared library.
19007 # compiling the library
19008 $ gnatmake -c my_lib_dummy.adb
19010 # we don't need the dummy object itself
19011 $ rm my_lib_dummy.o my_lib_dummy.ali
19013 # create an archive with the remaining objects
19014 $ ar rc libmy_lib.a *.o
19015 # some systems may require "ranlib" to be run as well
19017 # or create a shared library
19018 $ gcc -shared -o libmy_lib.so *.o
19019 # some systems may require the code to have been compiled with -fPIC
19021 # remove the object files that are now in the library
19024 # Make the ALI files read-only so that gnatmake will not try to
19025 # regenerate the objects that are in the library
19030 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
19031 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
19032 be accessed by the directive @option{-l@var{xxx}} at link time.
19034 @node Installing a library
19035 @subsection Installing a library
19036 @cindex @code{ADA_PROJECT_PATH}
19039 If you use project files, library installation is part of the library build
19040 process. Thus no further action is needed in order to make use of the
19041 libraries that are built as part of the general application build. A usable
19042 version of the library is installed in the directory specified by the
19043 @code{Library_Dir} attribute of the library project file.
19045 You may want to install a library in a context different from where the library
19046 is built. This situation arises with third party suppliers, who may want
19047 to distribute a library in binary form where the user is not expected to be
19048 able to recompile the library. The simplest option in this case is to provide
19049 a project file slightly different from the one used to build the library, by
19050 using the @code{externally_built} attribute. For instance, the project
19051 file used to build the library in the previous section can be changed into the
19052 following one when the library is installed:
19054 @smallexample @c projectfile
19056 for Source_Dirs use ("src1", "src2");
19057 for Library_Name use "mylib";
19058 for Library_Dir use "lib";
19059 for Library_Kind use "dynamic";
19060 for Externally_Built use "true";
19065 This project file assumes that the directories @file{src1},
19066 @file{src2}, and @file{lib} exist in
19067 the directory containing the project file. The @code{externally_built}
19068 attribute makes it clear to the GNAT builder that it should not attempt to
19069 recompile any of the units from this library. It allows the library provider to
19070 restrict the source set to the minimum necessary for clients to make use of the
19071 library as described in the first section of this chapter. It is the
19072 responsibility of the library provider to install the necessary sources, ALI
19073 files and libraries in the directories mentioned in the project file. For
19074 convenience, the user's library project file should be installed in a location
19075 that will be searched automatically by the GNAT
19076 builder. These are the directories referenced in the @env{ADA_PROJECT_PATH}
19077 environment variable (@pxref{Importing Projects}), and also the default GNAT
19078 library location that can be queried with @command{gnatls -v} and is usually of
19079 the form $gnat_install_root/lib/gnat.
19081 When project files are not an option, it is also possible, but not recommended,
19082 to install the library so that the sources needed to use the library are on the
19083 Ada source path and the ALI files & libraries be on the Ada Object path (see
19084 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
19085 administrator can place general-purpose libraries in the default compiler
19086 paths, by specifying the libraries' location in the configuration files
19087 @file{ada_source_path} and @file{ada_object_path}. These configuration files
19088 must be located in the GNAT installation tree at the same place as the gcc spec
19089 file. The location of the gcc spec file can be determined as follows:
19095 The configuration files mentioned above have a simple format: each line
19096 must contain one unique directory name.
19097 Those names are added to the corresponding path
19098 in their order of appearance in the file. The names can be either absolute
19099 or relative; in the latter case, they are relative to where theses files
19102 The files @file{ada_source_path} and @file{ada_object_path} might not be
19104 GNAT installation, in which case, GNAT will look for its run-time library in
19105 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
19106 objects and @file{ALI} files). When the files exist, the compiler does not
19107 look in @file{adainclude} and @file{adalib}, and thus the
19108 @file{ada_source_path} file
19109 must contain the location for the GNAT run-time sources (which can simply
19110 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
19111 contain the location for the GNAT run-time objects (which can simply
19114 You can also specify a new default path to the run-time library at compilation
19115 time with the switch @option{--RTS=rts-path}. You can thus choose / change
19116 the run-time library you want your program to be compiled with. This switch is
19117 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
19118 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
19120 It is possible to install a library before or after the standard GNAT
19121 library, by reordering the lines in the configuration files. In general, a
19122 library must be installed before the GNAT library if it redefines
19125 @node Using a library
19126 @subsection Using a library
19128 @noindent Once again, the project facility greatly simplifies the use of
19129 libraries. In this context, using a library is just a matter of adding a
19130 @code{with} clause in the user project. For instance, to make use of the
19131 library @code{My_Lib} shown in examples in earlier sections, you can
19134 @smallexample @c projectfile
19141 Even if you have a third-party, non-Ada library, you can still use GNAT's
19142 Project Manager facility to provide a wrapper for it. For example, the
19143 following project, when @code{with}ed by your main project, will link with the
19144 third-party library @file{liba.a}:
19146 @smallexample @c projectfile
19149 for Externally_Built use "true";
19150 for Source_Files use ();
19151 for Library_Dir use "lib";
19152 for Library_Name use "a";
19153 for Library_Kind use "static";
19157 This is an alternative to the use of @code{pragma Linker_Options}. It is
19158 especially interesting in the context of systems with several interdependent
19159 static libraries where finding a proper linker order is not easy and best be
19160 left to the tools having visibility over project dependence information.
19163 In order to use an Ada library manually, you need to make sure that this
19164 library is on both your source and object path
19165 (see @ref{Search Paths and the Run-Time Library (RTL)}
19166 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
19167 in an archive or a shared library, you need to specify the desired
19168 library at link time.
19170 For example, you can use the library @file{mylib} installed in
19171 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
19174 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
19179 This can be expressed more simply:
19184 when the following conditions are met:
19187 @file{/dir/my_lib_src} has been added by the user to the environment
19188 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
19189 @file{ada_source_path}
19191 @file{/dir/my_lib_obj} has been added by the user to the environment
19192 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
19193 @file{ada_object_path}
19195 a pragma @code{Linker_Options} has been added to one of the sources.
19198 @smallexample @c ada
19199 pragma Linker_Options ("-lmy_lib");
19203 @node Stand-alone Ada Libraries
19204 @section Stand-alone Ada Libraries
19205 @cindex Stand-alone library, building, using
19208 * Introduction to Stand-alone Libraries::
19209 * Building a Stand-alone Library::
19210 * Creating a Stand-alone Library to be used in a non-Ada context::
19211 * Restrictions in Stand-alone Libraries::
19214 @node Introduction to Stand-alone Libraries
19215 @subsection Introduction to Stand-alone Libraries
19218 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
19220 elaborate the Ada units that are included in the library. In contrast with
19221 an ordinary library, which consists of all sources, objects and @file{ALI}
19223 library, a SAL may specify a restricted subset of compilation units
19224 to serve as a library interface. In this case, the fully
19225 self-sufficient set of files will normally consist of an objects
19226 archive, the sources of interface units' specs, and the @file{ALI}
19227 files of interface units.
19228 If an interface spec contains a generic unit or an inlined subprogram,
19230 source must also be provided; if the units that must be provided in the source
19231 form depend on other units, the source and @file{ALI} files of those must
19234 The main purpose of a SAL is to minimize the recompilation overhead of client
19235 applications when a new version of the library is installed. Specifically,
19236 if the interface sources have not changed, client applications do not need to
19237 be recompiled. If, furthermore, a SAL is provided in the shared form and its
19238 version, controlled by @code{Library_Version} attribute, is not changed,
19239 then the clients do not need to be relinked.
19241 SALs also allow the library providers to minimize the amount of library source
19242 text exposed to the clients. Such ``information hiding'' might be useful or
19243 necessary for various reasons.
19245 Stand-alone libraries are also well suited to be used in an executable whose
19246 main routine is not written in Ada.
19248 @node Building a Stand-alone Library
19249 @subsection Building a Stand-alone Library
19252 GNAT's Project facility provides a simple way of building and installing
19253 stand-alone libraries; see @ref{Stand-alone Library Projects}.
19254 To be a Stand-alone Library Project, in addition to the two attributes
19255 that make a project a Library Project (@code{Library_Name} and
19256 @code{Library_Dir}; see @ref{Library Projects}), the attribute
19257 @code{Library_Interface} must be defined. For example:
19259 @smallexample @c projectfile
19261 for Library_Dir use "lib_dir";
19262 for Library_Name use "dummy";
19263 for Library_Interface use ("int1", "int1.child");
19268 Attribute @code{Library_Interface} has a non-empty string list value,
19269 each string in the list designating a unit contained in an immediate source
19270 of the project file.
19272 When a Stand-alone Library is built, first the binder is invoked to build
19273 a package whose name depends on the library name
19274 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
19275 This binder-generated package includes initialization and
19276 finalization procedures whose
19277 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
19279 above). The object corresponding to this package is included in the library.
19281 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
19282 calling of these procedures if a static SAL is built, or if a shared SAL
19284 with the project-level attribute @code{Library_Auto_Init} set to
19287 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
19288 (those that are listed in attribute @code{Library_Interface}) are copied to
19289 the Library Directory. As a consequence, only the Interface Units may be
19290 imported from Ada units outside of the library. If other units are imported,
19291 the binding phase will fail.
19293 The attribute @code{Library_Src_Dir} may be specified for a
19294 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
19295 single string value. Its value must be the path (absolute or relative to the
19296 project directory) of an existing directory. This directory cannot be the
19297 object directory or one of the source directories, but it can be the same as
19298 the library directory. The sources of the Interface
19299 Units of the library that are needed by an Ada client of the library will be
19300 copied to the designated directory, called the Interface Copy directory.
19301 These sources include the specs of the Interface Units, but they may also
19302 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
19303 are used, or when there is a generic unit in the spec. Before the sources
19304 are copied to the Interface Copy directory, an attempt is made to delete all
19305 files in the Interface Copy directory.
19307 Building stand-alone libraries by hand is somewhat tedious, but for those
19308 occasions when it is necessary here are the steps that you need to perform:
19311 Compile all library sources.
19314 Invoke the binder with the switch @option{-n} (No Ada main program),
19315 with all the @file{ALI} files of the interfaces, and
19316 with the switch @option{-L} to give specific names to the @code{init}
19317 and @code{final} procedures. For example:
19319 gnatbind -n int1.ali int2.ali -Lsal1
19323 Compile the binder generated file:
19329 Link the dynamic library with all the necessary object files,
19330 indicating to the linker the names of the @code{init} (and possibly
19331 @code{final}) procedures for automatic initialization (and finalization).
19332 The built library should be placed in a directory different from
19333 the object directory.
19336 Copy the @code{ALI} files of the interface to the library directory,
19337 add in this copy an indication that it is an interface to a SAL
19338 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19339 with letter ``P'') and make the modified copy of the @file{ALI} file
19344 Using SALs is not different from using other libraries
19345 (see @ref{Using a library}).
19347 @node Creating a Stand-alone Library to be used in a non-Ada context
19348 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19351 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19354 The only extra step required is to ensure that library interface subprograms
19355 are compatible with the main program, by means of @code{pragma Export}
19356 or @code{pragma Convention}.
19358 Here is an example of simple library interface for use with C main program:
19360 @smallexample @c ada
19361 package Interface is
19363 procedure Do_Something;
19364 pragma Export (C, Do_Something, "do_something");
19366 procedure Do_Something_Else;
19367 pragma Export (C, Do_Something_Else, "do_something_else");
19373 On the foreign language side, you must provide a ``foreign'' view of the
19374 library interface; remember that it should contain elaboration routines in
19375 addition to interface subprograms.
19377 The example below shows the content of @code{mylib_interface.h} (note
19378 that there is no rule for the naming of this file, any name can be used)
19380 /* the library elaboration procedure */
19381 extern void mylibinit (void);
19383 /* the library finalization procedure */
19384 extern void mylibfinal (void);
19386 /* the interface exported by the library */
19387 extern void do_something (void);
19388 extern void do_something_else (void);
19392 Libraries built as explained above can be used from any program, provided
19393 that the elaboration procedures (named @code{mylibinit} in the previous
19394 example) are called before the library services are used. Any number of
19395 libraries can be used simultaneously, as long as the elaboration
19396 procedure of each library is called.
19398 Below is an example of a C program that uses the @code{mylib} library.
19401 #include "mylib_interface.h"
19406 /* First, elaborate the library before using it */
19409 /* Main program, using the library exported entities */
19411 do_something_else ();
19413 /* Library finalization at the end of the program */
19420 Note that invoking any library finalization procedure generated by
19421 @code{gnatbind} shuts down the Ada run-time environment.
19423 finalization of all Ada libraries must be performed at the end of the program.
19424 No call to these libraries or to the Ada run-time library should be made
19425 after the finalization phase.
19427 @node Restrictions in Stand-alone Libraries
19428 @subsection Restrictions in Stand-alone Libraries
19431 The pragmas listed below should be used with caution inside libraries,
19432 as they can create incompatibilities with other Ada libraries:
19434 @item pragma @code{Locking_Policy}
19435 @item pragma @code{Queuing_Policy}
19436 @item pragma @code{Task_Dispatching_Policy}
19437 @item pragma @code{Unreserve_All_Interrupts}
19441 When using a library that contains such pragmas, the user must make sure
19442 that all libraries use the same pragmas with the same values. Otherwise,
19443 @code{Program_Error} will
19444 be raised during the elaboration of the conflicting
19445 libraries. The usage of these pragmas and its consequences for the user
19446 should therefore be well documented.
19448 Similarly, the traceback in the exception occurrence mechanism should be
19449 enabled or disabled in a consistent manner across all libraries.
19450 Otherwise, Program_Error will be raised during the elaboration of the
19451 conflicting libraries.
19453 If the @code{Version} or @code{Body_Version}
19454 attributes are used inside a library, then you need to
19455 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19456 libraries, so that version identifiers can be properly computed.
19457 In practice these attributes are rarely used, so this is unlikely
19458 to be a consideration.
19460 @node Rebuilding the GNAT Run-Time Library
19461 @section Rebuilding the GNAT Run-Time Library
19462 @cindex GNAT Run-Time Library, rebuilding
19463 @cindex Building the GNAT Run-Time Library
19464 @cindex Rebuilding the GNAT Run-Time Library
19465 @cindex Run-Time Library, rebuilding
19468 It may be useful to recompile the GNAT library in various contexts, the
19469 most important one being the use of partition-wide configuration pragmas
19470 such as @code{Normalize_Scalars}. A special Makefile called
19471 @code{Makefile.adalib} is provided to that effect and can be found in
19472 the directory containing the GNAT library. The location of this
19473 directory depends on the way the GNAT environment has been installed and can
19474 be determined by means of the command:
19481 The last entry in the object search path usually contains the
19482 gnat library. This Makefile contains its own documentation and in
19483 particular the set of instructions needed to rebuild a new library and
19486 @node Using the GNU make Utility
19487 @chapter Using the GNU @code{make} Utility
19491 This chapter offers some examples of makefiles that solve specific
19492 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19493 make, make, GNU @code{make}}), nor does it try to replace the
19494 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19496 All the examples in this section are specific to the GNU version of
19497 make. Although @command{make} is a standard utility, and the basic language
19498 is the same, these examples use some advanced features found only in
19502 * Using gnatmake in a Makefile::
19503 * Automatically Creating a List of Directories::
19504 * Generating the Command Line Switches::
19505 * Overcoming Command Line Length Limits::
19508 @node Using gnatmake in a Makefile
19509 @section Using gnatmake in a Makefile
19514 Complex project organizations can be handled in a very powerful way by
19515 using GNU make combined with gnatmake. For instance, here is a Makefile
19516 which allows you to build each subsystem of a big project into a separate
19517 shared library. Such a makefile allows you to significantly reduce the link
19518 time of very big applications while maintaining full coherence at
19519 each step of the build process.
19521 The list of dependencies are handled automatically by
19522 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19523 the appropriate directories.
19525 Note that you should also read the example on how to automatically
19526 create the list of directories
19527 (@pxref{Automatically Creating a List of Directories})
19528 which might help you in case your project has a lot of subdirectories.
19533 @font@heightrm=cmr8
19536 ## This Makefile is intended to be used with the following directory
19538 ## - The sources are split into a series of csc (computer software components)
19539 ## Each of these csc is put in its own directory.
19540 ## Their name are referenced by the directory names.
19541 ## They will be compiled into shared library (although this would also work
19542 ## with static libraries
19543 ## - The main program (and possibly other packages that do not belong to any
19544 ## csc is put in the top level directory (where the Makefile is).
19545 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19546 ## \_ second_csc (sources) __ lib (will contain the library)
19548 ## Although this Makefile is build for shared library, it is easy to modify
19549 ## to build partial link objects instead (modify the lines with -shared and
19552 ## With this makefile, you can change any file in the system or add any new
19553 ## file, and everything will be recompiled correctly (only the relevant shared
19554 ## objects will be recompiled, and the main program will be re-linked).
19556 # The list of computer software component for your project. This might be
19557 # generated automatically.
19560 # Name of the main program (no extension)
19563 # If we need to build objects with -fPIC, uncomment the following line
19566 # The following variable should give the directory containing libgnat.so
19567 # You can get this directory through 'gnatls -v'. This is usually the last
19568 # directory in the Object_Path.
19571 # The directories for the libraries
19572 # (This macro expands the list of CSC to the list of shared libraries, you
19573 # could simply use the expanded form:
19574 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19575 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19577 $@{MAIN@}: objects $@{LIB_DIR@}
19578 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19579 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19582 # recompile the sources
19583 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19585 # Note: In a future version of GNAT, the following commands will be simplified
19586 # by a new tool, gnatmlib
19588 mkdir -p $@{dir $@@ @}
19589 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19590 cd $@{dir $@@ @} && cp -f ../*.ali .
19592 # The dependencies for the modules
19593 # Note that we have to force the expansion of *.o, since in some cases
19594 # make won't be able to do it itself.
19595 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19596 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19597 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19599 # Make sure all of the shared libraries are in the path before starting the
19602 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19605 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19606 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19607 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19608 $@{RM@} *.o *.ali $@{MAIN@}
19611 @node Automatically Creating a List of Directories
19612 @section Automatically Creating a List of Directories
19615 In most makefiles, you will have to specify a list of directories, and
19616 store it in a variable. For small projects, it is often easier to
19617 specify each of them by hand, since you then have full control over what
19618 is the proper order for these directories, which ones should be
19621 However, in larger projects, which might involve hundreds of
19622 subdirectories, it might be more convenient to generate this list
19625 The example below presents two methods. The first one, although less
19626 general, gives you more control over the list. It involves wildcard
19627 characters, that are automatically expanded by @command{make}. Its
19628 shortcoming is that you need to explicitly specify some of the
19629 organization of your project, such as for instance the directory tree
19630 depth, whether some directories are found in a separate tree, @enddots{}
19632 The second method is the most general one. It requires an external
19633 program, called @command{find}, which is standard on all Unix systems. All
19634 the directories found under a given root directory will be added to the
19640 @font@heightrm=cmr8
19643 # The examples below are based on the following directory hierarchy:
19644 # All the directories can contain any number of files
19645 # ROOT_DIRECTORY -> a -> aa -> aaa
19648 # -> b -> ba -> baa
19651 # This Makefile creates a variable called DIRS, that can be reused any time
19652 # you need this list (see the other examples in this section)
19654 # The root of your project's directory hierarchy
19658 # First method: specify explicitly the list of directories
19659 # This allows you to specify any subset of all the directories you need.
19662 DIRS := a/aa/ a/ab/ b/ba/
19665 # Second method: use wildcards
19666 # Note that the argument(s) to wildcard below should end with a '/'.
19667 # Since wildcards also return file names, we have to filter them out
19668 # to avoid duplicate directory names.
19669 # We thus use make's @code{dir} and @code{sort} functions.
19670 # It sets DIRs to the following value (note that the directories aaa and baa
19671 # are not given, unless you change the arguments to wildcard).
19672 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19675 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19676 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19679 # Third method: use an external program
19680 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19681 # This is the most complete command: it sets DIRs to the following value:
19682 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19685 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19689 @node Generating the Command Line Switches
19690 @section Generating the Command Line Switches
19693 Once you have created the list of directories as explained in the
19694 previous section (@pxref{Automatically Creating a List of Directories}),
19695 you can easily generate the command line arguments to pass to gnatmake.
19697 For the sake of completeness, this example assumes that the source path
19698 is not the same as the object path, and that you have two separate lists
19702 # see "Automatically creating a list of directories" to create
19707 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19708 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19711 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19714 @node Overcoming Command Line Length Limits
19715 @section Overcoming Command Line Length Limits
19718 One problem that might be encountered on big projects is that many
19719 operating systems limit the length of the command line. It is thus hard to give
19720 gnatmake the list of source and object directories.
19722 This example shows how you can set up environment variables, which will
19723 make @command{gnatmake} behave exactly as if the directories had been
19724 specified on the command line, but have a much higher length limit (or
19725 even none on most systems).
19727 It assumes that you have created a list of directories in your Makefile,
19728 using one of the methods presented in
19729 @ref{Automatically Creating a List of Directories}.
19730 For the sake of completeness, we assume that the object
19731 path (where the ALI files are found) is different from the sources patch.
19733 Note a small trick in the Makefile below: for efficiency reasons, we
19734 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19735 expanded immediately by @code{make}. This way we overcome the standard
19736 make behavior which is to expand the variables only when they are
19739 On Windows, if you are using the standard Windows command shell, you must
19740 replace colons with semicolons in the assignments to these variables.
19745 @font@heightrm=cmr8
19748 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19749 # This is the same thing as putting the -I arguments on the command line.
19750 # (the equivalent of using -aI on the command line would be to define
19751 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19752 # You can of course have different values for these variables.
19754 # Note also that we need to keep the previous values of these variables, since
19755 # they might have been set before running 'make' to specify where the GNAT
19756 # library is installed.
19758 # see "Automatically creating a list of directories" to create these
19764 space:=$@{empty@} $@{empty@}
19765 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19766 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19767 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19768 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19769 export ADA_INCLUDE_PATH
19770 export ADA_OBJECT_PATH
19777 @node Memory Management Issues
19778 @chapter Memory Management Issues
19781 This chapter describes some useful memory pools provided in the GNAT library
19782 and in particular the GNAT Debug Pool facility, which can be used to detect
19783 incorrect uses of access values (including ``dangling references'').
19785 It also describes the @command{gnatmem} tool, which can be used to track down
19790 * Some Useful Memory Pools::
19791 * The GNAT Debug Pool Facility::
19793 * The gnatmem Tool::
19797 @node Some Useful Memory Pools
19798 @section Some Useful Memory Pools
19799 @findex Memory Pool
19800 @cindex storage, pool
19803 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19804 storage pool. Allocations use the standard system call @code{malloc} while
19805 deallocations use the standard system call @code{free}. No reclamation is
19806 performed when the pool goes out of scope. For performance reasons, the
19807 standard default Ada allocators/deallocators do not use any explicit storage
19808 pools but if they did, they could use this storage pool without any change in
19809 behavior. That is why this storage pool is used when the user
19810 manages to make the default implicit allocator explicit as in this example:
19811 @smallexample @c ada
19812 type T1 is access Something;
19813 -- no Storage pool is defined for T2
19814 type T2 is access Something_Else;
19815 for T2'Storage_Pool use T1'Storage_Pool;
19816 -- the above is equivalent to
19817 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19821 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19822 pool. The allocation strategy is similar to @code{Pool_Local}'s
19823 except that the all
19824 storage allocated with this pool is reclaimed when the pool object goes out of
19825 scope. This pool provides a explicit mechanism similar to the implicit one
19826 provided by several Ada 83 compilers for allocations performed through a local
19827 access type and whose purpose was to reclaim memory when exiting the
19828 scope of a given local access. As an example, the following program does not
19829 leak memory even though it does not perform explicit deallocation:
19831 @smallexample @c ada
19832 with System.Pool_Local;
19833 procedure Pooloc1 is
19834 procedure Internal is
19835 type A is access Integer;
19836 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19837 for A'Storage_Pool use X;
19840 for I in 1 .. 50 loop
19845 for I in 1 .. 100 loop
19852 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19853 @code{Storage_Size} is specified for an access type.
19854 The whole storage for the pool is
19855 allocated at once, usually on the stack at the point where the access type is
19856 elaborated. It is automatically reclaimed when exiting the scope where the
19857 access type is defined. This package is not intended to be used directly by the
19858 user and it is implicitly used for each such declaration:
19860 @smallexample @c ada
19861 type T1 is access Something;
19862 for T1'Storage_Size use 10_000;
19865 @node The GNAT Debug Pool Facility
19866 @section The GNAT Debug Pool Facility
19868 @cindex storage, pool, memory corruption
19871 The use of unchecked deallocation and unchecked conversion can easily
19872 lead to incorrect memory references. The problems generated by such
19873 references are usually difficult to tackle because the symptoms can be
19874 very remote from the origin of the problem. In such cases, it is
19875 very helpful to detect the problem as early as possible. This is the
19876 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19878 In order to use the GNAT specific debugging pool, the user must
19879 associate a debug pool object with each of the access types that may be
19880 related to suspected memory problems. See Ada Reference Manual 13.11.
19881 @smallexample @c ada
19882 type Ptr is access Some_Type;
19883 Pool : GNAT.Debug_Pools.Debug_Pool;
19884 for Ptr'Storage_Pool use Pool;
19888 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19889 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19890 allow the user to redefine allocation and deallocation strategies. They
19891 also provide a checkpoint for each dereference, through the use of
19892 the primitive operation @code{Dereference} which is implicitly called at
19893 each dereference of an access value.
19895 Once an access type has been associated with a debug pool, operations on
19896 values of the type may raise four distinct exceptions,
19897 which correspond to four potential kinds of memory corruption:
19900 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19902 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19904 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19906 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19910 For types associated with a Debug_Pool, dynamic allocation is performed using
19911 the standard GNAT allocation routine. References to all allocated chunks of
19912 memory are kept in an internal dictionary. Several deallocation strategies are
19913 provided, whereupon the user can choose to release the memory to the system,
19914 keep it allocated for further invalid access checks, or fill it with an easily
19915 recognizable pattern for debug sessions. The memory pattern is the old IBM
19916 hexadecimal convention: @code{16#DEADBEEF#}.
19918 See the documentation in the file g-debpoo.ads for more information on the
19919 various strategies.
19921 Upon each dereference, a check is made that the access value denotes a
19922 properly allocated memory location. Here is a complete example of use of
19923 @code{Debug_Pools}, that includes typical instances of memory corruption:
19924 @smallexample @c ada
19928 with Gnat.Io; use Gnat.Io;
19929 with Unchecked_Deallocation;
19930 with Unchecked_Conversion;
19931 with GNAT.Debug_Pools;
19932 with System.Storage_Elements;
19933 with Ada.Exceptions; use Ada.Exceptions;
19934 procedure Debug_Pool_Test is
19936 type T is access Integer;
19937 type U is access all T;
19939 P : GNAT.Debug_Pools.Debug_Pool;
19940 for T'Storage_Pool use P;
19942 procedure Free is new Unchecked_Deallocation (Integer, T);
19943 function UC is new Unchecked_Conversion (U, T);
19946 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
19956 Put_Line (Integer'Image(B.all));
19958 when E : others => Put_Line ("raised: " & Exception_Name (E));
19963 when E : others => Put_Line ("raised: " & Exception_Name (E));
19967 Put_Line (Integer'Image(B.all));
19969 when E : others => Put_Line ("raised: " & Exception_Name (E));
19974 when E : others => Put_Line ("raised: " & Exception_Name (E));
19977 end Debug_Pool_Test;
19981 The debug pool mechanism provides the following precise diagnostics on the
19982 execution of this erroneous program:
19985 Total allocated bytes : 0
19986 Total deallocated bytes : 0
19987 Current Water Mark: 0
19991 Total allocated bytes : 8
19992 Total deallocated bytes : 0
19993 Current Water Mark: 8
19996 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
19997 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
19998 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
19999 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
20001 Total allocated bytes : 8
20002 Total deallocated bytes : 4
20003 Current Water Mark: 4
20008 @node The gnatmem Tool
20009 @section The @command{gnatmem} Tool
20013 The @code{gnatmem} utility monitors dynamic allocation and
20014 deallocation activity in a program, and displays information about
20015 incorrect deallocations and possible sources of memory leaks.
20016 It is designed to work in association with a static runtime library
20017 only and in this context provides three types of information:
20020 General information concerning memory management, such as the total
20021 number of allocations and deallocations, the amount of allocated
20022 memory and the high water mark, i.e.@: the largest amount of allocated
20023 memory in the course of program execution.
20026 Backtraces for all incorrect deallocations, that is to say deallocations
20027 which do not correspond to a valid allocation.
20030 Information on each allocation that is potentially the origin of a memory
20035 * Running gnatmem::
20036 * Switches for gnatmem::
20037 * Example of gnatmem Usage::
20040 @node Running gnatmem
20041 @subsection Running @code{gnatmem}
20044 @code{gnatmem} makes use of the output created by the special version of
20045 allocation and deallocation routines that record call information. This
20046 allows to obtain accurate dynamic memory usage history at a minimal cost to
20047 the execution speed. Note however, that @code{gnatmem} is not supported on
20048 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
20049 Solaris and Windows NT/2000/XP (x86).
20052 The @code{gnatmem} command has the form
20055 $ gnatmem @ovar{switches} user_program
20059 The program must have been linked with the instrumented version of the
20060 allocation and deallocation routines. This is done by linking with the
20061 @file{libgmem.a} library. For correct symbolic backtrace information,
20062 the user program should be compiled with debugging options
20063 (see @ref{Switches for gcc}). For example to build @file{my_program}:
20066 $ gnatmake -g my_program -largs -lgmem
20070 As library @file{libgmem.a} contains an alternate body for package
20071 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
20072 when an executable is linked with library @file{libgmem.a}. It is then not
20073 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
20076 When @file{my_program} is executed, the file @file{gmem.out} is produced.
20077 This file contains information about all allocations and deallocations
20078 performed by the program. It is produced by the instrumented allocations and
20079 deallocations routines and will be used by @code{gnatmem}.
20081 In order to produce symbolic backtrace information for allocations and
20082 deallocations performed by the GNAT run-time library, you need to use a
20083 version of that library that has been compiled with the @option{-g} switch
20084 (see @ref{Rebuilding the GNAT Run-Time Library}).
20086 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
20087 examine. If the location of @file{gmem.out} file was not explicitly supplied by
20088 @option{-i} switch, gnatmem will assume that this file can be found in the
20089 current directory. For example, after you have executed @file{my_program},
20090 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
20093 $ gnatmem my_program
20097 This will produce the output with the following format:
20099 *************** debut cc
20101 $ gnatmem my_program
20105 Total number of allocations : 45
20106 Total number of deallocations : 6
20107 Final Water Mark (non freed mem) : 11.29 Kilobytes
20108 High Water Mark : 11.40 Kilobytes
20113 Allocation Root # 2
20114 -------------------
20115 Number of non freed allocations : 11
20116 Final Water Mark (non freed mem) : 1.16 Kilobytes
20117 High Water Mark : 1.27 Kilobytes
20119 my_program.adb:23 my_program.alloc
20125 The first block of output gives general information. In this case, the
20126 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
20127 Unchecked_Deallocation routine occurred.
20130 Subsequent paragraphs display information on all allocation roots.
20131 An allocation root is a specific point in the execution of the program
20132 that generates some dynamic allocation, such as a ``@code{@b{new}}''
20133 construct. This root is represented by an execution backtrace (or subprogram
20134 call stack). By default the backtrace depth for allocations roots is 1, so
20135 that a root corresponds exactly to a source location. The backtrace can
20136 be made deeper, to make the root more specific.
20138 @node Switches for gnatmem
20139 @subsection Switches for @code{gnatmem}
20142 @code{gnatmem} recognizes the following switches:
20147 @cindex @option{-q} (@code{gnatmem})
20148 Quiet. Gives the minimum output needed to identify the origin of the
20149 memory leaks. Omits statistical information.
20152 @cindex @var{N} (@code{gnatmem})
20153 N is an integer literal (usually between 1 and 10) which controls the
20154 depth of the backtraces defining allocation root. The default value for
20155 N is 1. The deeper the backtrace, the more precise the localization of
20156 the root. Note that the total number of roots can depend on this
20157 parameter. This parameter must be specified @emph{before} the name of the
20158 executable to be analyzed, to avoid ambiguity.
20161 @cindex @option{-b} (@code{gnatmem})
20162 This switch has the same effect as just depth parameter.
20164 @item -i @var{file}
20165 @cindex @option{-i} (@code{gnatmem})
20166 Do the @code{gnatmem} processing starting from @file{file}, rather than
20167 @file{gmem.out} in the current directory.
20170 @cindex @option{-m} (@code{gnatmem})
20171 This switch causes @code{gnatmem} to mask the allocation roots that have less
20172 than n leaks. The default value is 1. Specifying the value of 0 will allow to
20173 examine even the roots that didn't result in leaks.
20176 @cindex @option{-s} (@code{gnatmem})
20177 This switch causes @code{gnatmem} to sort the allocation roots according to the
20178 specified order of sort criteria, each identified by a single letter. The
20179 currently supported criteria are @code{n, h, w} standing respectively for
20180 number of unfreed allocations, high watermark, and final watermark
20181 corresponding to a specific root. The default order is @code{nwh}.
20185 @node Example of gnatmem Usage
20186 @subsection Example of @code{gnatmem} Usage
20189 The following example shows the use of @code{gnatmem}
20190 on a simple memory-leaking program.
20191 Suppose that we have the following Ada program:
20193 @smallexample @c ada
20196 with Unchecked_Deallocation;
20197 procedure Test_Gm is
20199 type T is array (1..1000) of Integer;
20200 type Ptr is access T;
20201 procedure Free is new Unchecked_Deallocation (T, Ptr);
20204 procedure My_Alloc is
20209 procedure My_DeAlloc is
20217 for I in 1 .. 5 loop
20218 for J in I .. 5 loop
20229 The program needs to be compiled with debugging option and linked with
20230 @code{gmem} library:
20233 $ gnatmake -g test_gm -largs -lgmem
20237 Then we execute the program as usual:
20244 Then @code{gnatmem} is invoked simply with
20250 which produces the following output (result may vary on different platforms):
20255 Total number of allocations : 18
20256 Total number of deallocations : 5
20257 Final Water Mark (non freed mem) : 53.00 Kilobytes
20258 High Water Mark : 56.90 Kilobytes
20260 Allocation Root # 1
20261 -------------------
20262 Number of non freed allocations : 11
20263 Final Water Mark (non freed mem) : 42.97 Kilobytes
20264 High Water Mark : 46.88 Kilobytes
20266 test_gm.adb:11 test_gm.my_alloc
20268 Allocation Root # 2
20269 -------------------
20270 Number of non freed allocations : 1
20271 Final Water Mark (non freed mem) : 10.02 Kilobytes
20272 High Water Mark : 10.02 Kilobytes
20274 s-secsta.adb:81 system.secondary_stack.ss_init
20276 Allocation Root # 3
20277 -------------------
20278 Number of non freed allocations : 1
20279 Final Water Mark (non freed mem) : 12 Bytes
20280 High Water Mark : 12 Bytes
20282 s-secsta.adb:181 system.secondary_stack.ss_init
20286 Note that the GNAT run time contains itself a certain number of
20287 allocations that have no corresponding deallocation,
20288 as shown here for root #2 and root
20289 #3. This is a normal behavior when the number of non-freed allocations
20290 is one, it allocates dynamic data structures that the run time needs for
20291 the complete lifetime of the program. Note also that there is only one
20292 allocation root in the user program with a single line back trace:
20293 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
20294 program shows that 'My_Alloc' is called at 2 different points in the
20295 source (line 21 and line 24). If those two allocation roots need to be
20296 distinguished, the backtrace depth parameter can be used:
20299 $ gnatmem 3 test_gm
20303 which will give the following output:
20308 Total number of allocations : 18
20309 Total number of deallocations : 5
20310 Final Water Mark (non freed mem) : 53.00 Kilobytes
20311 High Water Mark : 56.90 Kilobytes
20313 Allocation Root # 1
20314 -------------------
20315 Number of non freed allocations : 10
20316 Final Water Mark (non freed mem) : 39.06 Kilobytes
20317 High Water Mark : 42.97 Kilobytes
20319 test_gm.adb:11 test_gm.my_alloc
20320 test_gm.adb:24 test_gm
20321 b_test_gm.c:52 main
20323 Allocation Root # 2
20324 -------------------
20325 Number of non freed allocations : 1
20326 Final Water Mark (non freed mem) : 10.02 Kilobytes
20327 High Water Mark : 10.02 Kilobytes
20329 s-secsta.adb:81 system.secondary_stack.ss_init
20330 s-secsta.adb:283 <system__secondary_stack___elabb>
20331 b_test_gm.c:33 adainit
20333 Allocation Root # 3
20334 -------------------
20335 Number of non freed allocations : 1
20336 Final Water Mark (non freed mem) : 3.91 Kilobytes
20337 High Water Mark : 3.91 Kilobytes
20339 test_gm.adb:11 test_gm.my_alloc
20340 test_gm.adb:21 test_gm
20341 b_test_gm.c:52 main
20343 Allocation Root # 4
20344 -------------------
20345 Number of non freed allocations : 1
20346 Final Water Mark (non freed mem) : 12 Bytes
20347 High Water Mark : 12 Bytes
20349 s-secsta.adb:181 system.secondary_stack.ss_init
20350 s-secsta.adb:283 <system__secondary_stack___elabb>
20351 b_test_gm.c:33 adainit
20355 The allocation root #1 of the first example has been split in 2 roots #1
20356 and #3 thanks to the more precise associated backtrace.
20360 @node Stack Related Facilities
20361 @chapter Stack Related Facilities
20364 This chapter describes some useful tools associated with stack
20365 checking and analysis. In
20366 particular, it deals with dynamic and static stack usage measurements.
20369 * Stack Overflow Checking::
20370 * Static Stack Usage Analysis::
20371 * Dynamic Stack Usage Analysis::
20374 @node Stack Overflow Checking
20375 @section Stack Overflow Checking
20376 @cindex Stack Overflow Checking
20377 @cindex -fstack-check
20380 For most operating systems, @command{gcc} does not perform stack overflow
20381 checking by default. This means that if the main environment task or
20382 some other task exceeds the available stack space, then unpredictable
20383 behavior will occur. Most native systems offer some level of protection by
20384 adding a guard page at the end of each task stack. This mechanism is usually
20385 not enough for dealing properly with stack overflow situations because
20386 a large local variable could ``jump'' above the guard page.
20387 Furthermore, when the
20388 guard page is hit, there may not be any space left on the stack for executing
20389 the exception propagation code. Enabling stack checking avoids
20392 To activate stack checking, compile all units with the gcc option
20393 @option{-fstack-check}. For example:
20396 gcc -c -fstack-check package1.adb
20400 Units compiled with this option will generate extra instructions to check
20401 that any use of the stack (for procedure calls or for declaring local
20402 variables in declare blocks) does not exceed the available stack space.
20403 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20405 For declared tasks, the stack size is controlled by the size
20406 given in an applicable @code{Storage_Size} pragma or by the value specified
20407 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20408 the default size as defined in the GNAT runtime otherwise.
20410 For the environment task, the stack size depends on
20411 system defaults and is unknown to the compiler. Stack checking
20412 may still work correctly if a fixed
20413 size stack is allocated, but this cannot be guaranteed.
20415 To ensure that a clean exception is signalled for stack
20416 overflow, set the environment variable
20417 @env{GNAT_STACK_LIMIT} to indicate the maximum
20418 stack area that can be used, as in:
20419 @cindex GNAT_STACK_LIMIT
20422 SET GNAT_STACK_LIMIT 1600
20426 The limit is given in kilobytes, so the above declaration would
20427 set the stack limit of the environment task to 1.6 megabytes.
20428 Note that the only purpose of this usage is to limit the amount
20429 of stack used by the environment task. If it is necessary to
20430 increase the amount of stack for the environment task, then this
20431 is an operating systems issue, and must be addressed with the
20432 appropriate operating systems commands.
20435 To have a fixed size stack in the environment task, the stack must be put
20436 in the P0 address space and its size specified. Use these switches to
20440 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20444 The quotes are required to keep case. The number after @samp{STACK=} is the
20445 size of the environmental task stack in pagelets (512 bytes). In this example
20446 the stack size is about 2 megabytes.
20449 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20450 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20451 more details about the @option{/p0image} qualifier and the @option{stack}
20455 @node Static Stack Usage Analysis
20456 @section Static Stack Usage Analysis
20457 @cindex Static Stack Usage Analysis
20458 @cindex -fstack-usage
20461 A unit compiled with @option{-fstack-usage} will generate an extra file
20463 the maximum amount of stack used, on a per-function basis.
20464 The file has the same
20465 basename as the target object file with a @file{.su} extension.
20466 Each line of this file is made up of three fields:
20470 The name of the function.
20474 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20477 The second field corresponds to the size of the known part of the function
20480 The qualifier @code{static} means that the function frame size
20482 It usually means that all local variables have a static size.
20483 In this case, the second field is a reliable measure of the function stack
20486 The qualifier @code{dynamic} means that the function frame size is not static.
20487 It happens mainly when some local variables have a dynamic size. When this
20488 qualifier appears alone, the second field is not a reliable measure
20489 of the function stack analysis. When it is qualified with @code{bounded}, it
20490 means that the second field is a reliable maximum of the function stack
20493 @node Dynamic Stack Usage Analysis
20494 @section Dynamic Stack Usage Analysis
20497 It is possible to measure the maximum amount of stack used by a task, by
20498 adding a switch to @command{gnatbind}, as:
20501 $ gnatbind -u0 file
20505 With this option, at each task termination, its stack usage is output on
20507 It is not always convenient to output the stack usage when the program
20508 is still running. Hence, it is possible to delay this output until program
20509 termination. for a given number of tasks specified as the argument of the
20510 @option{-u} option. For instance:
20513 $ gnatbind -u100 file
20517 will buffer the stack usage information of the first 100 tasks to terminate and
20518 output this info at program termination. Results are displayed in four
20522 Index | Task Name | Stack Size | Stack Usage [Value +/- Variation]
20529 is a number associated with each task.
20532 is the name of the task analyzed.
20535 is the maximum size for the stack.
20538 is the measure done by the stack analyzer. In order to prevent overflow, the stack
20539 is not entirely analyzed, and it's not possible to know exactly how
20540 much has actually been used. The report thus contains the theoretical stack usage
20541 (Value) and the possible variation (Variation) around this value.
20546 The environment task stack, e.g., the stack that contains the main unit, is
20547 only processed when the environment variable GNAT_STACK_LIMIT is set.
20550 @c *********************************
20552 @c *********************************
20553 @node Verifying Properties Using gnatcheck
20554 @chapter Verifying Properties Using @command{gnatcheck}
20556 @cindex @command{gnatcheck}
20559 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20560 of Ada source files according to a given set of semantic rules.
20563 In order to check compliance with a given rule, @command{gnatcheck} has to
20564 semantically analyze the Ada sources.
20565 Therefore, checks can only be performed on
20566 legal Ada units. Moreover, when a unit depends semantically upon units located
20567 outside the current directory, the source search path has to be provided when
20568 calling @command{gnatcheck}, either through a specified project file or
20569 through @command{gnatcheck} switches as described below.
20571 A number of rules are predefined in @command{gnatcheck} and are described
20572 later in this chapter.
20573 You can also add new rules, by modifying the @command{gnatcheck} code and
20574 rebuilding the tool. In order to add a simple rule making some local checks,
20575 a small amount of straightforward ASIS-based programming is usually needed.
20577 Project support for @command{gnatcheck} is provided by the GNAT
20578 driver (see @ref{The GNAT Driver and Project Files}).
20580 Invoking @command{gnatcheck} on the command line has the form:
20583 $ gnatcheck @ovar{switches} @{@var{filename}@}
20584 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20585 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20592 @var{switches} specify the general tool options
20595 Each @var{filename} is the name (including the extension) of a source
20596 file to process. ``Wildcards'' are allowed, and
20597 the file name may contain path information.
20600 Each @var{arg_list_filename} is the name (including the extension) of a text
20601 file containing the names of the source files to process, separated by spaces
20605 @var{gcc_switches} is a list of switches for
20606 @command{gcc}. They will be passed on to all compiler invocations made by
20607 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20608 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20609 and use the @option{-gnatec} switch to set the configuration file.
20612 @var{rule_options} is a list of options for controlling a set of
20613 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20617 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20620 * Format of the Report File::
20621 * General gnatcheck Switches::
20622 * gnatcheck Rule Options::
20623 * Adding the Results of Compiler Checks to gnatcheck Output::
20624 * Project-Wide Checks::
20625 * Predefined Rules::
20628 @node Format of the Report File
20629 @section Format of the Report File
20630 @cindex Report file (for @code{gnatcheck})
20633 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20635 It also creates a text file that
20636 contains the complete report of the last gnatcheck run. By default this file is
20637 named named @file{^gnatcheck.out^GNATCHECK.OUT^} and it is located in the current
20638 directory, @option{^-o^/OUTPUT^} option can be used to change the name and/or
20639 location of the report file. This report contains:
20641 @item a list of the Ada source files being checked,
20642 @item a list of enabled and disabled rules,
20643 @item a list of the diagnostic messages, ordered in three different ways
20644 and collected in three separate
20645 sections. Section 1 contains the raw list of diagnostic messages. It
20646 corresponds to the output going to @file{stdout}. Section 2 contains
20647 messages ordered by rules.
20648 Section 3 contains messages ordered by source files.
20651 @node General gnatcheck Switches
20652 @section General @command{gnatcheck} Switches
20655 The following switches control the general @command{gnatcheck} behavior
20659 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20661 Process all units including those with read-only ALI files such as
20662 those from GNAT Run-Time library.
20666 @cindex @option{-d} (@command{gnatcheck})
20671 @cindex @option{-dd} (@command{gnatcheck})
20673 Progress indicator mode (for use in GPS)
20676 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20678 List the predefined and user-defined rules. For more details see
20679 @ref{Predefined Rules}.
20681 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20683 Use full source locations references in the report file. For a construct from
20684 a generic instantiation a full source location is a chain from the location
20685 of this construct in the generic unit to the place where this unit is
20688 @cindex @option{^-log^/LOG^} (@command{gnatcheck})
20690 Duplicate all the output sent to Stderr into a log file. The log file is
20691 named @var{gnatcheck.log} and is located in the current directory.
20693 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
20694 @item ^-m@i{nnn}^/DIAGNOSTIC_LIMIT=@i{nnn}^
20695 Maximum number of diagnoses to be sent to Stdout, @i{nnn} from o@dots{}1000,
20696 the default value is 500. Zero means that there is no limitation on
20697 the number of diagnostic messages to be printed into Stdout.
20699 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20701 Quiet mode. All the diagnoses about rule violations are placed in the
20702 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20704 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20706 Short format of the report file (no version information, no list of applied
20707 rules, no list of checked sources is included)
20709 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20710 @item ^-s1^/COMPILER_STYLE^
20711 Include the compiler-style section in the report file
20713 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20714 @item ^-s2^/BY_RULES^
20715 Include the section containing diagnoses ordered by rules in the report file
20717 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20718 @item ^-s3^/BY_FILES_BY_RULES^
20719 Include the section containing diagnoses ordered by files and then by rules
20722 @cindex @option{^-t^/TIME^} (@command{gnatcheck})
20724 Print out execution time.
20726 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20727 @item ^-v^/VERBOSE^
20728 Verbose mode; @command{gnatcheck} generates version information and then
20729 a trace of sources being processed.
20731 @cindex @option{^-o ^/OUTPUT^} (@command{gnatcheck})
20732 @item ^-o ^/OUTPUT=^@var{report_file}
20733 Set name of report file file to @var{report_file} .
20738 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20739 @option{^-s2^/BY_RULES^} or
20740 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20741 then the @command{gnatcheck} report file will only contain sections
20742 explicitly denoted by these options.
20744 @node gnatcheck Rule Options
20745 @section @command{gnatcheck} Rule Options
20748 The following options control the processing performed by
20749 @command{gnatcheck}.
20752 @cindex @option{+ALL} (@command{gnatcheck})
20754 Turn all the rule checks ON.
20756 @cindex @option{-ALL} (@command{gnatcheck})
20758 Turn all the rule checks OFF.
20760 @cindex @option{+R} (@command{gnatcheck})
20761 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20762 Turn on the check for a specified rule with the specified parameter, if any.
20763 @var{rule_id} must be the identifier of one of the currently implemented rules
20764 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20765 are not case-sensitive. The @var{param} item must
20766 be a string representing a valid parameter(s) for the specified rule.
20767 If it contains any space characters then this string must be enclosed in
20770 @cindex @option{-R} (@command{gnatcheck})
20771 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20772 Turn off the check for a specified rule with the specified parameter, if any.
20774 @cindex @option{-from} (@command{gnatcheck})
20775 @item -from=@var{rule_option_filename}
20776 Read the rule options from the text file @var{rule_option_filename}, referred as
20777 ``rule file'' below.
20782 The default behavior is that all the rule checks are disabled.
20784 A rule file is a text file containing a set of rule options.
20785 @cindex Rule file (for @code{gnatcheck})
20786 The file may contain empty lines and Ada-style comments (comment
20787 lines and end-of-line comments). The rule file has free format; that is,
20788 you do not have to start a new rule option on a new line.
20790 A rule file may contain other @option{-from=@var{rule_option_filename}}
20791 options, each such option being replaced with the content of the
20792 corresponding rule file during the rule files processing. In case a
20793 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20794 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20795 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20796 the processing of rule files is interrupted and a part of their content
20800 @node Adding the Results of Compiler Checks to gnatcheck Output
20801 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20804 The @command{gnatcheck} tool can include in the generated diagnostic messages
20806 the report file the results of the checks performed by the compiler. Though
20807 disabled by default, this effect may be obtained by using @option{+R} with
20808 the following rule identifiers and parameters:
20812 To record restrictions violations (that are performed by the compiler if the
20813 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20815 @code{Restrictions} with the same parameters as pragma
20816 @code{Restrictions} or @code{Restriction_Warnings}.
20819 To record compiler style checks(@pxref{Style Checking}), use the rule named
20820 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20821 which enables all the standard style checks that corresponds to @option{-gnatyy}
20822 GNAT style check option, or a string that has exactly the same
20823 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20824 @code{Style_Checks} (for further information about this pragma,
20825 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}). For example,
20826 @code{+RStyle_Checks:O} rule option activates and adds to @command{gnatcheck}
20827 output the compiler style check that corresponds to @code{-gnatyO} style
20831 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20832 named @code{Warnings} with a parameter that is a valid
20833 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20834 (for further information about this pragma, @pxref{Pragma Warnings,,,
20835 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20836 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20837 all the specific warnings, but not suppresses the warning mode,
20838 and 'e' parameter, corresponding to @option{-gnatwe} that means
20839 "treat warnings as errors", does not have any effect.
20843 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20844 option with the corresponding restriction name as a parameter. @code{-R} is
20845 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20846 warnings and style checks, use the corresponding warning and style options.
20848 @node Project-Wide Checks
20849 @section Project-Wide Checks
20850 @cindex Project-wide checks (for @command{gnatcheck})
20853 In order to perform checks on all units of a given project, you can use
20854 the GNAT driver along with the @option{-P} option:
20856 gnat check -Pproj -rules -from=my_rules
20860 If the project @code{proj} depends upon other projects, you can perform
20861 checks on the project closure using the @option{-U} option:
20863 gnat check -Pproj -U -rules -from=my_rules
20867 Finally, if not all the units are relevant to a particular main
20868 program in the project closure, you can perform checks for the set
20869 of units needed to create a given main program (unit closure) using
20870 the @option{-U} option followed by the name of the main unit:
20872 gnat check -Pproj -U main -rules -from=my_rules
20876 @node Predefined Rules
20877 @section Predefined Rules
20878 @cindex Predefined rules (for @command{gnatcheck})
20881 @c (Jan 2007) Since the global rules are still under development and are not
20882 @c documented, there is no point in explaining the difference between
20883 @c global and local rules
20885 A rule in @command{gnatcheck} is either local or global.
20886 A @emph{local rule} is a rule that applies to a well-defined section
20887 of a program and that can be checked by analyzing only this section.
20888 A @emph{global rule} requires analysis of some global properties of the
20889 whole program (mostly related to the program call graph).
20890 As of @value{NOW}, the implementation of global rules should be
20891 considered to be at a preliminary stage. You can use the
20892 @option{+GLOBAL} option to enable all the global rules, and the
20893 @option{-GLOBAL} rule option to disable all the global rules.
20895 All the global rules in the list below are
20896 so indicated by marking them ``GLOBAL''.
20897 This +GLOBAL and -GLOBAL options are not
20898 included in the list of gnatcheck options above, because at the moment they
20899 are considered as a temporary debug options.
20901 @command{gnatcheck} performs rule checks for generic
20902 instances only for global rules. This limitation may be relaxed in a later
20907 The following subsections document the rules implemented in
20908 @command{gnatcheck}.
20909 The subsection title is the same as the rule identifier, which may be
20910 used as a parameter of the @option{+R} or @option{-R} options.
20914 * Abstract_Type_Declarations::
20915 * Anonymous_Arrays::
20916 * Anonymous_Subtypes::
20918 * Boolean_Relational_Operators::
20920 * Ceiling_Violations::
20922 * Controlled_Type_Declarations::
20923 * Declarations_In_Blocks::
20924 * Default_Parameters::
20925 * Discriminated_Records::
20926 * Enumeration_Ranges_In_CASE_Statements::
20927 * Exceptions_As_Control_Flow::
20928 * Exits_From_Conditional_Loops::
20929 * EXIT_Statements_With_No_Loop_Name::
20930 * Expanded_Loop_Exit_Names::
20931 * Explicit_Full_Discrete_Ranges::
20932 * Float_Equality_Checks::
20933 * Forbidden_Pragmas::
20934 * Function_Style_Procedures::
20935 * Generics_In_Subprograms::
20936 * GOTO_Statements::
20937 * Implicit_IN_Mode_Parameters::
20938 * Implicit_SMALL_For_Fixed_Point_Types::
20939 * Improperly_Located_Instantiations::
20940 * Improper_Returns::
20941 * Library_Level_Subprograms::
20944 * Improperly_Called_Protected_Entries::
20947 * Misnamed_Identifiers::
20948 * Multiple_Entries_In_Protected_Definitions::
20950 * Non_Qualified_Aggregates::
20951 * Non_Short_Circuit_Operators::
20952 * Non_SPARK_Attributes::
20953 * Non_Tagged_Derived_Types::
20954 * Non_Visible_Exceptions::
20955 * Numeric_Literals::
20956 * OTHERS_In_Aggregates::
20957 * OTHERS_In_CASE_Statements::
20958 * OTHERS_In_Exception_Handlers::
20959 * Outer_Loop_Exits::
20960 * Overloaded_Operators::
20961 * Overly_Nested_Control_Structures::
20962 * Parameters_Out_Of_Order::
20963 * Positional_Actuals_For_Defaulted_Generic_Parameters::
20964 * Positional_Actuals_For_Defaulted_Parameters::
20965 * Positional_Components::
20966 * Positional_Generic_Parameters::
20967 * Positional_Parameters::
20968 * Predefined_Numeric_Types::
20969 * Raising_External_Exceptions::
20970 * Raising_Predefined_Exceptions::
20971 * Separate_Numeric_Error_Handlers::
20974 * Side_Effect_Functions::
20977 * Unassigned_OUT_Parameters::
20978 * Uncommented_BEGIN_In_Package_Bodies::
20979 * Unconditional_Exits::
20980 * Unconstrained_Array_Returns::
20981 * Universal_Ranges::
20982 * Unnamed_Blocks_And_Loops::
20984 * Unused_Subprograms::
20986 * USE_PACKAGE_Clauses::
20987 * Volatile_Objects_Without_Address_Clauses::
20991 @node Abstract_Type_Declarations
20992 @subsection @code{Abstract_Type_Declarations}
20993 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
20996 Flag all declarations of abstract types. For an abstract private
20997 type, both the private and full type declarations are flagged.
20999 This rule has no parameters.
21002 @node Anonymous_Arrays
21003 @subsection @code{Anonymous_Arrays}
21004 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
21007 Flag all anonymous array type definitions (by Ada semantics these can only
21008 occur in object declarations).
21010 This rule has no parameters.
21012 @node Anonymous_Subtypes
21013 @subsection @code{Anonymous_Subtypes}
21014 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
21017 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
21018 any instance of a subtype indication with a constraint, other than one
21019 that occurs immediately within a subtype declaration. Any use of a range
21020 other than as a constraint used immediately within a subtype declaration
21021 is considered as an anonymous subtype.
21023 An effect of this rule is that @code{for} loops such as the following are
21024 flagged (since @code{1..N} is formally a ``range''):
21026 @smallexample @c ada
21027 for I in 1 .. N loop
21033 Declaring an explicit subtype solves the problem:
21035 @smallexample @c ada
21036 subtype S is Integer range 1..N;
21044 This rule has no parameters.
21047 @subsection @code{Blocks}
21048 @cindex @code{Blocks} rule (for @command{gnatcheck})
21051 Flag each block statement.
21053 This rule has no parameters.
21055 @node Boolean_Relational_Operators
21056 @subsection @code{Boolean_Relational_Operators}
21057 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
21060 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
21061 ``>='', ``='' and ``/='') for the predefined Boolean type.
21062 (This rule is useful in enforcing the SPARK language restrictions.)
21064 Calls to predefined relational operators of any type derived from
21065 @code{Standard.Boolean} are not detected. Calls to user-defined functions
21066 with these designators, and uses of operators that are renamings
21067 of the predefined relational operators for @code{Standard.Boolean},
21068 are likewise not detected.
21070 This rule has no parameters.
21073 @node Ceiling_Violations
21074 @subsection @code{Ceiling_Violations} (under construction, GLOBAL)
21075 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
21078 Flag invocations of a protected operation by a task whose priority exceeds
21079 the protected object's ceiling.
21081 As of @value{NOW}, this rule has the following limitations:
21086 We consider only pragmas Priority and Interrupt_Priority as means to define
21087 a task/protected operation priority. We do not consider the effect of using
21088 Ada.Dynamic_Priorities.Set_Priority procedure;
21091 We consider only base task priorities, and no priority inheritance. That is,
21092 we do not make a difference between calls issued during task activation and
21093 execution of the sequence of statements from task body;
21096 Any situation when the priority of protected operation caller is set by a
21097 dynamic expression (that is, the corresponding Priority or
21098 Interrupt_Priority pragma has a non-static expression as an argument) we
21099 treat as a priority inconsistency (and, therefore, detect this situation).
21103 At the moment the notion of the main subprogram is not implemented in
21104 gnatcheck, so any pragma Priority in a library level subprogram body (in case
21105 if this subprogram can be a main subprogram of a partition) changes the
21106 priority of an environment task. So if we have more then one such pragma in
21107 the set of processed sources, the pragma that is processed last, defines the
21108 priority of an environment task.
21110 This rule has no parameters.
21113 @node Controlled_Type_Declarations
21114 @subsection @code{Controlled_Type_Declarations}
21115 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
21118 Flag all declarations of controlled types. A declaration of a private type
21119 is flagged if its full declaration declares a controlled type. A declaration
21120 of a derived type is flagged if its ancestor type is controlled. Subtype
21121 declarations are not checked. A declaration of a type that itself is not a
21122 descendant of a type declared in @code{Ada.Finalization} but has a controlled
21123 component is not checked.
21125 This rule has no parameters.
21129 @node Declarations_In_Blocks
21130 @subsection @code{Declarations_In_Blocks}
21131 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
21134 Flag all block statements containing local declarations. A @code{declare}
21135 block with an empty @i{declarative_part} or with a @i{declarative part}
21136 containing only pragmas and/or @code{use} clauses is not flagged.
21138 This rule has no parameters.
21141 @node Default_Parameters
21142 @subsection @code{Default_Parameters}
21143 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
21146 Flag all default expressions for subprogram parameters. Parameter
21147 declarations of formal and generic subprograms are also checked.
21149 This rule has no parameters.
21152 @node Discriminated_Records
21153 @subsection @code{Discriminated_Records}
21154 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
21157 Flag all declarations of record types with discriminants. Only the
21158 declarations of record and record extension types are checked. Incomplete,
21159 formal, private, derived and private extension type declarations are not
21160 checked. Task and protected type declarations also are not checked.
21162 This rule has no parameters.
21165 @node Enumeration_Ranges_In_CASE_Statements
21166 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
21167 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
21170 Flag each use of a range of enumeration literals as a choice in a
21171 @code{case} statement.
21172 All forms for specifying a range (explicit ranges
21173 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
21174 An enumeration range is
21175 flagged even if contains exactly one enumeration value or no values at all. A
21176 type derived from an enumeration type is considered as an enumeration type.
21178 This rule helps prevent maintenance problems arising from adding an
21179 enumeration value to a type and having it implicitly handled by an existing
21180 @code{case} statement with an enumeration range that includes the new literal.
21182 This rule has no parameters.
21185 @node Exceptions_As_Control_Flow
21186 @subsection @code{Exceptions_As_Control_Flow}
21187 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
21190 Flag each place where an exception is explicitly raised and handled in the
21191 same subprogram body. A @code{raise} statement in an exception handler,
21192 package body, task body or entry body is not flagged.
21194 The rule has no parameters.
21196 @node Exits_From_Conditional_Loops
21197 @subsection @code{Exits_From_Conditional_Loops}
21198 @cindex @code{Exits_From_Conditional_Loops} (for @command{gnatcheck})
21201 Flag any exit statement if it transfers the control out of a @code{for} loop
21202 or a @code{while} loop. This includes cases when the @code{exit} statement
21203 applies to a @code{FOR} or @code{while} loop, and cases when it is enclosed
21204 in some @code{for} or @code{while} loop, but transfers the control from some
21205 outer (inconditional) @code{loop} statement.
21207 The rule has no parameters.
21210 @node EXIT_Statements_With_No_Loop_Name
21211 @subsection @code{EXIT_Statements_With_No_Loop_Name}
21212 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
21215 Flag each @code{exit} statement that does not specify the name of the loop
21218 The rule has no parameters.
21221 @node Expanded_Loop_Exit_Names
21222 @subsection @code{Expanded_Loop_Exit_Names}
21223 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
21226 Flag all expanded loop names in @code{exit} statements.
21228 This rule has no parameters.
21230 @node Explicit_Full_Discrete_Ranges
21231 @subsection @code{Explicit_Full_Discrete_Ranges}
21232 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
21235 Flag each discrete range that has the form @code{A'First .. A'Last}.
21237 This rule has no parameters.
21239 @node Float_Equality_Checks
21240 @subsection @code{Float_Equality_Checks}
21241 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
21244 Flag all calls to the predefined equality operations for floating-point types.
21245 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
21246 User-defined equality operations are not flagged, nor are ``@code{=}''
21247 and ``@code{/=}'' operations for fixed-point types.
21249 This rule has no parameters.
21252 @node Forbidden_Pragmas
21253 @subsection @code{Forbidden_Pragmas}
21254 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
21257 Flag each use of the specified pragmas. The pragmas to be detected
21258 are named in the rule's parameters.
21260 This rule has the following parameters:
21263 @item For the @option{+R} option
21266 @item @emph{Pragma_Name}
21267 Adds the specified pragma to the set of pragmas to be
21268 checked and sets the checks for all the specified pragmas
21269 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
21270 does not correspond to any pragma name defined in the Ada
21271 standard or to the name of a GNAT-specific pragma defined
21272 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
21273 Manual}, it is treated as the name of unknown pragma.
21276 All the GNAT-specific pragmas are detected; this sets
21277 the checks for all the specified pragmas ON.
21280 All pragmas are detected; this sets the rule ON.
21283 @item For the @option{-R} option
21285 @item @emph{Pragma_Name}
21286 Removes the specified pragma from the set of pragmas to be
21287 checked without affecting checks for
21288 other pragmas. @emph{Pragma_Name} is treated as a name
21289 of a pragma. If it does not correspond to any pragma
21290 defined in the Ada standard or to any name defined in
21291 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
21292 this option is treated as turning OFF detection of all unknown pragmas.
21295 Turn OFF detection of all GNAT-specific pragmas
21298 Clear the list of the pragmas to be detected and
21304 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
21305 the syntax of an Ada identifier and therefore can not be considered
21306 as a pragma name, a diagnostic message is generated and the corresponding
21307 parameter is ignored.
21309 When more then one parameter is given in the same rule option, the parameters
21310 must be separated by a comma.
21312 If more then one option for this rule is specified for the @command{gnatcheck}
21313 call, a new option overrides the previous one(s).
21315 The @option{+R} option with no parameters turns the rule ON with the set of
21316 pragmas to be detected defined by the previous rule options.
21317 (By default this set is empty, so if the only option specified for the rule is
21318 @option{+RForbidden_Pragmas} (with
21319 no parameter), then the rule is enabled, but it does not detect anything).
21320 The @option{-R} option with no parameter turns the rule OFF, but it does not
21321 affect the set of pragmas to be detected.
21326 @node Function_Style_Procedures
21327 @subsection @code{Function_Style_Procedures}
21328 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
21331 Flag each procedure that can be rewritten as a function. A procedure can be
21332 converted into a function if it has exactly one parameter of mode @code{out}
21333 and no parameters of mode @code{in out}. Procedure declarations,
21334 formal procedure declarations, and generic procedure declarations are always
21336 bodies and body stubs are flagged only if they do not have corresponding
21337 separate declarations. Procedure renamings and procedure instantiations are
21340 If a procedure can be rewritten as a function, but its @code{out} parameter is
21341 of a limited type, it is not flagged.
21343 Protected procedures are not flagged. Null procedures also are not flagged.
21345 This rule has no parameters.
21348 @node Generics_In_Subprograms
21349 @subsection @code{Generics_In_Subprograms}
21350 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
21353 Flag each declaration of a generic unit in a subprogram. Generic
21354 declarations in the bodies of generic subprograms are also flagged.
21355 A generic unit nested in another generic unit is not flagged.
21356 If a generic unit is
21357 declared in a local package that is declared in a subprogram body, the
21358 generic unit is flagged.
21360 This rule has no parameters.
21363 @node GOTO_Statements
21364 @subsection @code{GOTO_Statements}
21365 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
21368 Flag each occurrence of a @code{goto} statement.
21370 This rule has no parameters.
21373 @node Implicit_IN_Mode_Parameters
21374 @subsection @code{Implicit_IN_Mode_Parameters}
21375 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21378 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21379 Note that @code{access} parameters, although they technically behave
21380 like @code{in} parameters, are not flagged.
21382 This rule has no parameters.
21385 @node Implicit_SMALL_For_Fixed_Point_Types
21386 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21387 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21390 Flag each fixed point type declaration that lacks an explicit
21391 representation clause to define its @code{'Small} value.
21392 Since @code{'Small} can be defined only for ordinary fixed point types,
21393 decimal fixed point type declarations are not checked.
21395 This rule has no parameters.
21398 @node Improperly_Located_Instantiations
21399 @subsection @code{Improperly_Located_Instantiations}
21400 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21403 Flag all generic instantiations in library-level package specs
21404 (including library generic packages) and in all subprogram bodies.
21406 Instantiations in task and entry bodies are not flagged. Instantiations in the
21407 bodies of protected subprograms are flagged.
21409 This rule has no parameters.
21413 @node Improper_Returns
21414 @subsection @code{Improper_Returns}
21415 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21418 Flag each explicit @code{return} statement in procedures, and
21419 multiple @code{return} statements in functions.
21420 Diagnostic messages are generated for all @code{return} statements
21421 in a procedure (thus each procedure must be written so that it
21422 returns implicitly at the end of its statement part),
21423 and for all @code{return} statements in a function after the first one.
21424 This rule supports the stylistic convention that each subprogram
21425 should have no more than one point of normal return.
21427 This rule has no parameters.
21430 @node Library_Level_Subprograms
21431 @subsection @code{Library_Level_Subprograms}
21432 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21435 Flag all library-level subprograms (including generic subprogram instantiations).
21437 This rule has no parameters.
21440 @node Local_Packages
21441 @subsection @code{Local_Packages}
21442 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21445 Flag all local packages declared in package and generic package
21447 Local packages in bodies are not flagged.
21449 This rule has no parameters.
21452 @node Improperly_Called_Protected_Entries
21453 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21454 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21457 Flag each protected entry that can be called from more than one task.
21459 This rule has no parameters.
21463 @subsection @code{Metrics}
21464 @cindex @code{Metrics} rule (for @command{gnatcheck})
21467 There is a set of checks based on computing a metric value and comparing the
21468 result with the specified upper (or lower, depending on a specific metric)
21469 value specified for a given metric. A construct is flagged if a given metric
21470 is applicable (can be computed) for it and the computed value is greater
21471 then (lover then) the specified upper (lower) bound.
21473 The name of any metric-based rule consists of the prefix @code{Metrics_}
21474 followed by the name of the corresponding metric (see the table below).
21475 For @option{+R} option, each metric-based rule has a numeric parameter
21476 specifying the bound (integer or real, depending on a metric), @option{-R}
21477 option for metric rules does not have a parameter.
21479 The following table shows the metric names for that the corresponding
21480 metrics-based checks are supported by gnatcheck, including the
21481 constraint that must be satisfied by the bound that is specified for the check
21482 and what bound - upper (U) or lower (L) - should be specified.
21484 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21486 @headitem Check Name @tab Description @tab Bounds Value
21489 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21491 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21492 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21493 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21494 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21498 The meaning and the computed values for all these metrics are exactly
21499 the same as for the corresponding metrics in @command{gnatmetric}.
21501 @emph{Example:} the rule
21503 +RMetrics_Cyclomatic_Complexity : 7
21506 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21508 To turn OFF the check for cyclomatic complexity metric, use the following option:
21510 -RMetrics_Cyclomatic_Complexity
21513 @node Misnamed_Identifiers
21514 @subsection @code{Misnamed_Identifiers}
21515 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21518 Flag the declaration of each identifier that does not have a suffix
21519 corresponding to the kind of entity being declared.
21520 The following declarations are checked:
21527 subtype declarations
21530 constant declarations (but not number declarations)
21533 package renaming declarations (but not generic package renaming
21538 This rule may have parameters. When used without parameters, the rule enforces
21539 the following checks:
21543 type-defining names end with @code{_T}, unless the type is an access type,
21544 in which case the suffix must be @code{_A}
21546 constant names end with @code{_C}
21548 names defining package renamings end with @code{_R}
21552 For a private or incomplete type declaration the following checks are
21553 made for the defining name suffix:
21557 For an incomplete type declaration: if the corresponding full type
21558 declaration is available, the defining identifier from the full type
21559 declaration is checked, but the defining identifier from the incomplete type
21560 declaration is not; otherwise the defining identifier from the incomplete
21561 type declaration is checked against the suffix specified for type
21565 For a private type declaration (including private extensions), the defining
21566 identifier from the private type declaration is checked against the type
21567 suffix (even if the corresponding full declaration is an access type
21568 declaration), and the defining identifier from the corresponding full type
21569 declaration is not checked.
21573 For a deferred constant, the defining name in the corresponding full constant
21574 declaration is not checked.
21576 Defining names of formal types are not checked.
21578 The rule may have the following parameters:
21582 For the @option{+R} option:
21585 Sets the default listed above for all the names to be checked.
21587 @item Type_Suffix=@emph{string}
21588 Specifies the suffix for a type name.
21590 @item Access_Suffix=@emph{string}
21591 Specifies the suffix for an access type name. If
21592 this parameter is set, it overrides for access
21593 types the suffix set by the @code{Type_Suffix} parameter.
21594 For access types, @emph{string} may have the following format:
21595 @emph{suffix1(suffix2)}. That means that an access type name
21596 should have the @emph{suffix1} suffix except for the case when
21597 the designated type is also an access type, in this case the
21598 type name should have the @emph{suffix1 & suffix2} suffix.
21600 @item Class_Access_Suffix=@emph{string}
21601 Specifies the suffix for the name of an access type that points to some class-wide
21602 type. If this parameter is set, it overrides for such access
21603 types the suffix set by the @code{Type_Suffix} or @code{Access_Suffix}
21606 @item Class_Subtype_Suffix=@emph{string}
21607 Specifies the suffix for the name of a subtype that denotes a class-wide type.
21609 @item Constant_Suffix=@emph{string}
21610 Specifies the suffix for a constant name.
21612 @item Renaming_Suffix=@emph{string}
21613 Specifies the suffix for a package renaming name.
21617 For the @option{-R} option:
21620 Remove all the suffixes specified for the
21621 identifier suffix checks, whether by default or
21622 as specified by other rule parameters. All the
21623 checks for this rule are disabled as a result.
21626 Removes the suffix specified for types. This
21627 disables checks for types but does not disable
21628 any other checks for this rule (including the
21629 check for access type names if @code{Access_Suffix} is
21632 @item Access_Suffix
21633 Removes the suffix specified for access types.
21634 This disables checks for access type names but
21635 does not disable any other checks for this rule.
21636 If @code{Type_Suffix} is set, access type names are
21637 checked as ordinary type names.
21639 @item Class_Access_Suffix
21640 Removes the suffix specified for access types pointing to class-wide
21641 type. This disables specific checks for names of access types pointing to
21642 class-wide types but does not disable any other checks for this rule.
21643 If @code{Type_Suffix} is set, access type names are
21644 checked as ordinary type names. If @code{Access_Suffix} is set, these
21645 access types are checked as any other access type name.
21647 @item Class_Subtype_Suffix=@emph{string}
21648 Removes the suffix specified for subtype names.
21649 This disables checks for subtype names but
21650 does not disable any other checks for this rule.
21652 @item Constant_Suffix
21653 Removes the suffix specified for constants. This
21654 disables checks for constant names but does not
21655 disable any other checks for this rule.
21657 @item Renaming_Suffix
21658 Removes the suffix specified for package
21659 renamings. This disables checks for package
21660 renamings but does not disable any other checks
21666 If more than one parameter is used, parameters must be separated by commas.
21668 If more than one option is specified for the @command{gnatcheck} invocation,
21669 a new option overrides the previous one(s).
21671 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21673 name suffixes specified by previous options used for this rule.
21675 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21676 all the checks but keeps
21677 all the suffixes specified by previous options used for this rule.
21679 The @emph{string} value must be a valid suffix for an Ada identifier (after
21680 trimming all the leading and trailing space characters, if any).
21681 Parameters are not case sensitive, except the @emph{string} part.
21683 If any error is detected in a rule parameter, the parameter is ignored.
21684 In such a case the options that are set for the rule are not
21689 @node Multiple_Entries_In_Protected_Definitions
21690 @subsection @code{Multiple_Entries_In_Protected_Definitions}
21691 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
21694 Flag each protected definition (i.e., each protected object/type declaration)
21695 that defines more than one entry.
21696 Diagnostic messages are generated for all the entry declarations
21697 except the first one. An entry family is counted as one entry. Entries from
21698 the private part of the protected definition are also checked.
21700 This rule has no parameters.
21703 @subsection @code{Name_Clashes}
21704 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
21707 Check that certain names are not used as defining identifiers. To activate
21708 this rule, you need to supply a reference to the dictionary file(s) as a rule
21709 parameter(s) (more then one dictionary file can be specified). If no
21710 dictionary file is set, this rule will not cause anything to be flagged.
21711 Only defining occurrences, not references, are checked.
21712 The check is not case-sensitive.
21714 This rule is enabled by default, but without setting any corresponding
21715 dictionary file(s); thus the default effect is to do no checks.
21717 A dictionary file is a plain text file. The maximum line length for this file
21718 is 1024 characters. If the line is longer then this limit, extra characters
21721 Each line can be either an empty line, a comment line, or a line containing
21722 a list of identifiers separated by space or HT characters.
21723 A comment is an Ada-style comment (from @code{--} to end-of-line).
21724 Identifiers must follow the Ada syntax for identifiers.
21725 A line containing one or more identifiers may end with a comment.
21727 @node Non_Qualified_Aggregates
21728 @subsection @code{Non_Qualified_Aggregates}
21729 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
21732 Flag each non-qualified aggregate.
21733 A non-qualified aggregate is an
21734 aggregate that is not the expression of a qualified expression. A
21735 string literal is not considered an aggregate, but an array
21736 aggregate of a string type is considered as a normal aggregate.
21737 Aggregates of anonymous array types are not flagged.
21739 This rule has no parameters.
21742 @node Non_Short_Circuit_Operators
21743 @subsection @code{Non_Short_Circuit_Operators}
21744 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
21747 Flag all calls to predefined @code{and} and @code{or} operators for
21748 any boolean type. Calls to
21749 user-defined @code{and} and @code{or} and to operators defined by renaming
21750 declarations are not flagged. Calls to predefined @code{and} and @code{or}
21751 operators for modular types or boolean array types are not flagged.
21753 This rule has no parameters.
21757 @node Non_SPARK_Attributes
21758 @subsection @code{Non_SPARK_Attributes}
21759 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
21762 The SPARK language defines the following subset of Ada 95 attribute
21763 designators as those that can be used in SPARK programs. The use of
21764 any other attribute is flagged.
21767 @item @code{'Adjacent}
21770 @item @code{'Ceiling}
21771 @item @code{'Component_Size}
21772 @item @code{'Compose}
21773 @item @code{'Copy_Sign}
21774 @item @code{'Delta}
21775 @item @code{'Denorm}
21776 @item @code{'Digits}
21777 @item @code{'Exponent}
21778 @item @code{'First}
21779 @item @code{'Floor}
21781 @item @code{'Fraction}
21783 @item @code{'Leading_Part}
21784 @item @code{'Length}
21785 @item @code{'Machine}
21786 @item @code{'Machine_Emax}
21787 @item @code{'Machine_Emin}
21788 @item @code{'Machine_Mantissa}
21789 @item @code{'Machine_Overflows}
21790 @item @code{'Machine_Radix}
21791 @item @code{'Machine_Rounds}
21794 @item @code{'Model}
21795 @item @code{'Model_Emin}
21796 @item @code{'Model_Epsilon}
21797 @item @code{'Model_Mantissa}
21798 @item @code{'Model_Small}
21799 @item @code{'Modulus}
21802 @item @code{'Range}
21803 @item @code{'Remainder}
21804 @item @code{'Rounding}
21805 @item @code{'Safe_First}
21806 @item @code{'Safe_Last}
21807 @item @code{'Scaling}
21808 @item @code{'Signed_Zeros}
21810 @item @code{'Small}
21812 @item @code{'Truncation}
21813 @item @code{'Unbiased_Rounding}
21815 @item @code{'Valid}
21819 This rule has no parameters.
21822 @node Non_Tagged_Derived_Types
21823 @subsection @code{Non_Tagged_Derived_Types}
21824 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
21827 Flag all derived type declarations that do not have a record extension part.
21829 This rule has no parameters.
21833 @node Non_Visible_Exceptions
21834 @subsection @code{Non_Visible_Exceptions}
21835 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
21838 Flag constructs leading to the possibility of propagating an exception
21839 out of the scope in which the exception is declared.
21840 Two cases are detected:
21844 An exception declaration in a subprogram body, task body or block
21845 statement is flagged if the body or statement does not contain a handler for
21846 that exception or a handler with an @code{others} choice.
21849 A @code{raise} statement in an exception handler of a subprogram body,
21850 task body or block statement is flagged if it (re)raises a locally
21851 declared exception. This may occur under the following circumstances:
21854 it explicitly raises a locally declared exception, or
21856 it does not specify an exception name (i.e., it is simply @code{raise;})
21857 and the enclosing handler contains a locally declared exception in its
21863 Renamings of local exceptions are not flagged.
21865 This rule has no parameters.
21868 @node Numeric_Literals
21869 @subsection @code{Numeric_Literals}
21870 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
21873 Flag each use of a numeric literal in an index expression, and in any
21874 circumstance except for the following:
21878 a literal occurring in the initialization expression for a constant
21879 declaration or a named number declaration, or
21882 an integer literal that is less than or equal to a value
21883 specified by the @option{N} rule parameter.
21887 This rule may have the following parameters for the @option{+R} option:
21891 @emph{N} is an integer literal used as the maximal value that is not flagged
21892 (i.e., integer literals not exceeding this value are allowed)
21895 All integer literals are flagged
21899 If no parameters are set, the maximum unflagged value is 1.
21901 The last specified check limit (or the fact that there is no limit at
21902 all) is used when multiple @option{+R} options appear.
21904 The @option{-R} option for this rule has no parameters.
21905 It disables the rule but retains the last specified maximum unflagged value.
21906 If the @option{+R} option subsequently appears, this value is used as the
21907 threshold for the check.
21910 @node OTHERS_In_Aggregates
21911 @subsection @code{OTHERS_In_Aggregates}
21912 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
21915 Flag each use of an @code{others} choice in extension aggregates.
21916 In record and array aggregates, an @code{others} choice is flagged unless
21917 it is used to refer to all components, or to all but one component.
21919 If, in case of a named array aggregate, there are two associations, one
21920 with an @code{others} choice and another with a discrete range, the
21921 @code{others} choice is flagged even if the discrete range specifies
21922 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
21924 This rule has no parameters.
21926 @node OTHERS_In_CASE_Statements
21927 @subsection @code{OTHERS_In_CASE_Statements}
21928 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
21931 Flag any use of an @code{others} choice in a @code{case} statement.
21933 This rule has no parameters.
21935 @node OTHERS_In_Exception_Handlers
21936 @subsection @code{OTHERS_In_Exception_Handlers}
21937 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
21940 Flag any use of an @code{others} choice in an exception handler.
21942 This rule has no parameters.
21945 @node Outer_Loop_Exits
21946 @subsection @code{Outer_Loop_Exits}
21947 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
21950 Flag each @code{exit} statement containing a loop name that is not the name
21951 of the immediately enclosing @code{loop} statement.
21953 This rule has no parameters.
21956 @node Overloaded_Operators
21957 @subsection @code{Overloaded_Operators}
21958 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
21961 Flag each function declaration that overloads an operator symbol.
21962 A function body is checked only if the body does not have a
21963 separate spec. Formal functions are also checked. For a
21964 renaming declaration, only renaming-as-declaration is checked
21966 This rule has no parameters.
21969 @node Overly_Nested_Control_Structures
21970 @subsection @code{Overly_Nested_Control_Structures}
21971 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
21974 Flag each control structure whose nesting level exceeds the value provided
21975 in the rule parameter.
21977 The control structures checked are the following:
21980 @item @code{if} statement
21981 @item @code{case} statement
21982 @item @code{loop} statement
21983 @item Selective accept statement
21984 @item Timed entry call statement
21985 @item Conditional entry call
21986 @item Asynchronous select statement
21990 The rule has the following parameter for the @option{+R} option:
21994 Positive integer specifying the maximal control structure nesting
21995 level that is not flagged
21999 If the parameter for the @option{+R} option is not specified or
22000 if it is not a positive integer, @option{+R} option is ignored.
22002 If more then one option is specified for the gnatcheck call, the later option and
22003 new parameter override the previous one(s).
22006 @node Parameters_Out_Of_Order
22007 @subsection @code{Parameters_Out_Of_Order}
22008 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
22011 Flag each subprogram and entry declaration whose formal parameters are not
22012 ordered according to the following scheme:
22016 @item @code{in} and @code{access} parameters first,
22017 then @code{in out} parameters,
22018 and then @code{out} parameters;
22020 @item for @code{in} mode, parameters with default initialization expressions
22025 Only the first violation of the described order is flagged.
22027 The following constructs are checked:
22030 @item subprogram declarations (including null procedures);
22031 @item generic subprogram declarations;
22032 @item formal subprogram declarations;
22033 @item entry declarations;
22034 @item subprogram bodies and subprogram body stubs that do not
22035 have separate specifications
22039 Subprogram renamings are not checked.
22041 This rule has no parameters.
22044 @node Positional_Actuals_For_Defaulted_Generic_Parameters
22045 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
22046 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
22049 Flag each generic actual parameter corresponding to a generic formal
22050 parameter with a default initialization, if positional notation is used.
22052 This rule has no parameters.
22054 @node Positional_Actuals_For_Defaulted_Parameters
22055 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
22056 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
22059 Flag each actual parameter to a subprogram or entry call where the
22060 corresponding formal parameter has a default expression, if positional
22063 This rule has no parameters.
22065 @node Positional_Components
22066 @subsection @code{Positional_Components}
22067 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
22070 Flag each array, record and extension aggregate that includes positional
22073 This rule has no parameters.
22076 @node Positional_Generic_Parameters
22077 @subsection @code{Positional_Generic_Parameters}
22078 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
22081 Flag each instantiation using positional parameter notation.
22083 This rule has no parameters.
22086 @node Positional_Parameters
22087 @subsection @code{Positional_Parameters}
22088 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
22091 Flag each subprogram or entry call using positional parameter notation,
22092 except for the following:
22096 Invocations of prefix or infix operators are not flagged
22098 If the called subprogram or entry has only one formal parameter,
22099 the call is not flagged;
22101 If a subprogram call uses the @emph{Object.Operation} notation, then
22104 the first parameter (that is, @emph{Object}) is not flagged;
22106 if the called subprogram has only two parameters, the second parameter
22107 of the call is not flagged;
22112 This rule has no parameters.
22117 @node Predefined_Numeric_Types
22118 @subsection @code{Predefined_Numeric_Types}
22119 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
22122 Flag each explicit use of the name of any numeric type or subtype defined
22123 in package @code{Standard}.
22125 The rationale for this rule is to detect when the
22126 program may depend on platform-specific characteristics of the implementation
22127 of the predefined numeric types. Note that this rule is over-pessimistic;
22128 for example, a program that uses @code{String} indexing
22129 likely needs a variable of type @code{Integer}.
22130 Another example is the flagging of predefined numeric types with explicit
22133 @smallexample @c ada
22134 subtype My_Integer is Integer range Left .. Right;
22135 Vy_Var : My_Integer;
22139 This rule detects only numeric types and subtypes defined in
22140 @code{Standard}. The use of numeric types and subtypes defined in other
22141 predefined packages (such as @code{System.Any_Priority} or
22142 @code{Ada.Text_IO.Count}) is not flagged
22144 This rule has no parameters.
22148 @node Raising_External_Exceptions
22149 @subsection @code{Raising_External_Exceptions}
22150 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
22153 Flag any @code{raise} statement, in a program unit declared in a library
22154 package or in a generic library package, for an exception that is
22155 neither a predefined exception nor an exception that is also declared (or
22156 renamed) in the visible part of the package.
22158 This rule has no parameters.
22162 @node Raising_Predefined_Exceptions
22163 @subsection @code{Raising_Predefined_Exceptions}
22164 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
22167 Flag each @code{raise} statement that raises a predefined exception
22168 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
22169 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
22171 This rule has no parameters.
22173 @node Separate_Numeric_Error_Handlers
22174 @subsection @code{Separate_Numeric_Error_Handlers}
22175 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
22178 Flags each exception handler that contains a choice for
22179 the predefined @code{Constraint_Error} exception, but does not contain
22180 the choice for the predefined @code{Numeric_Error} exception, or
22181 that contains the choice for @code{Numeric_Error}, but does not contain the
22182 choice for @code{Constraint_Error}.
22184 This rule has no parameters.
22188 @subsection @code{Recursion} (under construction, GLOBAL)
22189 @cindex @code{Recursion} rule (for @command{gnatcheck})
22192 Flag recursive subprograms (cycles in the call graph). Declarations, and not
22193 calls, of recursive subprograms are detected.
22195 This rule has no parameters.
22199 @node Side_Effect_Functions
22200 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
22201 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
22204 Flag functions with side effects.
22206 We define a side effect as changing any data object that is not local for the
22207 body of this function.
22209 At the moment, we do NOT consider a side effect any input-output operations
22210 (changing a state or a content of any file).
22212 We do not consider protected functions for this rule (???)
22214 There are the following sources of side effect:
22217 @item Explicit (or direct) side-effect:
22221 direct assignment to a non-local variable;
22224 direct call to an entity that is known to change some data object that is
22225 not local for the body of this function (Note, that if F1 calls F2 and F2
22226 does have a side effect, this does not automatically mean that F1 also
22227 have a side effect, because it may be the case that F2 is declared in
22228 F1's body and it changes some data object that is global for F2, but
22232 @item Indirect side-effect:
22235 Subprogram calls implicitly issued by:
22238 computing initialization expressions from type declarations as a part
22239 of object elaboration or allocator evaluation;
22241 computing implicit parameters of subprogram or entry calls or generic
22246 activation of a task that change some non-local data object (directly or
22250 elaboration code of a package that is a result of a package instantiation;
22253 controlled objects;
22256 @item Situations when we can suspect a side-effect, but the full static check
22257 is either impossible or too hard:
22260 assignment to access variables or to the objects pointed by access
22264 call to a subprogram pointed by access-to-subprogram value
22272 This rule has no parameters.
22276 @subsection @code{Slices}
22277 @cindex @code{Slices} rule (for @command{gnatcheck})
22280 Flag all uses of array slicing
22282 This rule has no parameters.
22285 @node Unassigned_OUT_Parameters
22286 @subsection @code{Unassigned_OUT_Parameters}
22287 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
22290 Flags procedures' @code{out} parameters that are not assigned, and
22291 identifies the contexts in which the assignments are missing.
22293 An @code{out} parameter is flagged in the statements in the procedure
22294 body's handled sequence of statements (before the procedure body's
22295 @code{exception} part, if any) if this sequence of statements contains
22296 no assignments to the parameter.
22298 An @code{out} parameter is flagged in an exception handler in the exception
22299 part of the procedure body's handled sequence of statements if the handler
22300 contains no assignment to the parameter.
22302 Bodies of generic procedures are also considered.
22304 The following are treated as assignments to an @code{out} parameter:
22308 an assignment statement, with the parameter or some component as the target;
22311 passing the parameter (or one of its components) as an @code{out} or
22312 @code{in out} parameter.
22316 This rule does not have any parameters.
22320 @node Uncommented_BEGIN_In_Package_Bodies
22321 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
22322 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
22325 Flags each package body with declarations and a statement part that does not
22326 include a trailing comment on the line containing the @code{begin} keyword;
22327 this trailing comment needs to specify the package name and nothing else.
22328 The @code{begin} is not flagged if the package body does not
22329 contain any declarations.
22331 If the @code{begin} keyword is placed on the
22332 same line as the last declaration or the first statement, it is flagged
22333 independently of whether the line contains a trailing comment. The
22334 diagnostic message is attached to the line containing the first statement.
22336 This rule has no parameters.
22338 @node Unconditional_Exits
22339 @subsection @code{Unconditional_Exits}
22340 @cindex @code{Unconditional_Exits} rule (for @command{gnatcheck})
22343 Flag unconditional @code{exit} statements.
22345 This rule has no parameters.
22347 @node Unconstrained_Array_Returns
22348 @subsection @code{Unconstrained_Array_Returns}
22349 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
22352 Flag each function returning an unconstrained array. Function declarations,
22353 function bodies (and body stubs) having no separate specifications,
22354 and generic function instantiations are checked.
22355 Generic function declarations, function calls and function renamings are
22358 This rule has no parameters.
22360 @node Universal_Ranges
22361 @subsection @code{Universal_Ranges}
22362 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
22365 Flag discrete ranges that are a part of an index constraint, constrained
22366 array definition, or @code{for}-loop parameter specification, and whose bounds
22367 are both of type @i{universal_integer}. Ranges that have at least one
22368 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
22369 or an expression of non-universal type) are not flagged.
22371 This rule has no parameters.
22374 @node Unnamed_Blocks_And_Loops
22375 @subsection @code{Unnamed_Blocks_And_Loops}
22376 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
22379 Flag each unnamed block statement and loop statement.
22381 The rule has no parameters.
22386 @node Unused_Subprograms
22387 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
22388 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
22391 Flag all unused subprograms.
22393 This rule has no parameters.
22399 @node USE_PACKAGE_Clauses
22400 @subsection @code{USE_PACKAGE_Clauses}
22401 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
22404 Flag all @code{use} clauses for packages; @code{use type} clauses are
22407 This rule has no parameters.
22411 @node Volatile_Objects_Without_Address_Clauses
22412 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22413 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22416 Flag each volatile object that does not have an address clause.
22418 The following check is made: if the pragma @code{Volatile} is applied to a
22419 data object or to its type, then an address clause must
22420 be supplied for this object.
22422 This rule does not check the components of data objects,
22423 array components that are volatile as a result of the pragma
22424 @code{Volatile_Components}, or objects that are volatile because
22425 they are atomic as a result of pragmas @code{Atomic} or
22426 @code{Atomic_Components}.
22428 Only variable declarations, and not constant declarations, are checked.
22430 This rule has no parameters.
22433 @c *********************************
22434 @node Creating Sample Bodies Using gnatstub
22435 @chapter Creating Sample Bodies Using @command{gnatstub}
22439 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22440 for library unit declarations.
22442 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22443 driver (see @ref{The GNAT Driver and Project Files}).
22445 To create a body stub, @command{gnatstub} has to compile the library
22446 unit declaration. Therefore, bodies can be created only for legal
22447 library units. Moreover, if a library unit depends semantically upon
22448 units located outside the current directory, you have to provide
22449 the source search path when calling @command{gnatstub}, see the description
22450 of @command{gnatstub} switches below.
22452 By default, all the program unit body stubs generated by @code{gnatstub}
22453 raise the predefined @code{Program_Error} exception, which will catch
22454 accidental calls of generated stubs. This behavior can be changed with
22455 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
22458 * Running gnatstub::
22459 * Switches for gnatstub::
22462 @node Running gnatstub
22463 @section Running @command{gnatstub}
22466 @command{gnatstub} has the command-line interface of the form
22469 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22476 is the name of the source file that contains a library unit declaration
22477 for which a body must be created. The file name may contain the path
22479 The file name does not have to follow the GNAT file name conventions. If the
22481 does not follow GNAT file naming conventions, the name of the body file must
22483 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22484 If the file name follows the GNAT file naming
22485 conventions and the name of the body file is not provided,
22488 of the body file from the argument file name by replacing the @file{.ads}
22490 with the @file{.adb} suffix.
22493 indicates the directory in which the body stub is to be placed (the default
22498 is an optional sequence of switches as described in the next section
22501 @node Switches for gnatstub
22502 @section Switches for @command{gnatstub}
22508 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22509 If the destination directory already contains a file with the name of the
22511 for the argument spec file, replace it with the generated body stub.
22513 @item ^-hs^/HEADER=SPEC^
22514 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22515 Put the comment header (i.e., all the comments preceding the
22516 compilation unit) from the source of the library unit declaration
22517 into the body stub.
22519 @item ^-hg^/HEADER=GENERAL^
22520 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22521 Put a sample comment header into the body stub.
22523 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22524 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22525 Use the content of the file as the comment header for a generated body stub.
22529 @cindex @option{-IDIR} (@command{gnatstub})
22531 @cindex @option{-I-} (@command{gnatstub})
22534 @item /NOCURRENT_DIRECTORY
22535 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22537 ^These switches have ^This switch has^ the same meaning as in calls to
22539 ^They define ^It defines ^ the source search path in the call to
22540 @command{gcc} issued
22541 by @command{gnatstub} to compile an argument source file.
22543 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22544 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22545 This switch has the same meaning as in calls to @command{gcc}.
22546 It defines the additional configuration file to be passed to the call to
22547 @command{gcc} issued
22548 by @command{gnatstub} to compile an argument source file.
22550 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22551 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22552 (@var{n} is a non-negative integer). Set the maximum line length in the
22553 body stub to @var{n}; the default is 79. The maximum value that can be
22554 specified is 32767. Note that in the special case of configuration
22555 pragma files, the maximum is always 32767 regardless of whether or
22556 not this switch appears.
22558 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22559 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22560 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22561 the generated body sample to @var{n}.
22562 The default indentation is 3.
22564 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22565 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22566 Order local bodies alphabetically. (By default local bodies are ordered
22567 in the same way as the corresponding local specs in the argument spec file.)
22569 @item ^-i^/INDENTATION=^@var{n}
22570 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22571 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22573 @item ^-k^/TREE_FILE=SAVE^
22574 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22575 Do not remove the tree file (i.e., the snapshot of the compiler internal
22576 structures used by @command{gnatstub}) after creating the body stub.
22578 @item ^-l^/LINE_LENGTH=^@var{n}
22579 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22580 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22582 @item ^--no-exception^/NO_EXCEPTION^
22583 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
22584 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
22585 This is not always possible for function stubs.
22587 @item ^-o ^/BODY=^@var{body-name}
22588 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22589 Body file name. This should be set if the argument file name does not
22591 the GNAT file naming
22592 conventions. If this switch is omitted the default name for the body will be
22594 from the argument file name according to the GNAT file naming conventions.
22597 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22598 Quiet mode: do not generate a confirmation when a body is
22599 successfully created, and do not generate a message when a body is not
22603 @item ^-r^/TREE_FILE=REUSE^
22604 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22605 Reuse the tree file (if it exists) instead of creating it. Instead of
22606 creating the tree file for the library unit declaration, @command{gnatstub}
22607 tries to find it in the current directory and use it for creating
22608 a body. If the tree file is not found, no body is created. This option
22609 also implies @option{^-k^/SAVE^}, whether or not
22610 the latter is set explicitly.
22612 @item ^-t^/TREE_FILE=OVERWRITE^
22613 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22614 Overwrite the existing tree file. If the current directory already
22615 contains the file which, according to the GNAT file naming rules should
22616 be considered as a tree file for the argument source file,
22618 will refuse to create the tree file needed to create a sample body
22619 unless this option is set.
22621 @item ^-v^/VERBOSE^
22622 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22623 Verbose mode: generate version information.
22627 @c *********************************
22628 @node Generating Ada Bindings for C and C++ headers
22629 @chapter Generating Ada Bindings for C and C++ headers
22633 GNAT now comes with a new experimental binding generator for C and C++
22634 headers which is intended to do 95% of the tedious work of generating
22635 Ada specs from C or C++ header files. Note that this still is a work in
22636 progress, not designed to generate 100% correct Ada specs.
22638 The code generated is using the Ada 2005 syntax, which makes it
22639 easier to interface with other languages than previous versions of Ada.
22642 * Running the binding generator::
22643 * Generating bindings for C++ headers::
22647 @node Running the binding generator
22648 @section Running the binding generator
22651 The binding generator is part of the @command{gcc} compiler and can be
22652 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
22653 spec files for the header files specified on the command line, and all
22654 header files needed by these files transitivitely. For example:
22657 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
22658 $ gcc -c -gnat05 *.ads
22661 will generate, under GNU/Linux, the following files: @file{time_h.ads},
22662 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
22663 correspond to the files @file{/usr/include/time.h},
22664 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
22665 mode these Ada specs.
22667 The @code{-C} switch tells @command{gcc} to extract comments from headers,
22668 and will attempt to generate corresponding Ada comments.
22670 If you want to generate a single Ada file and not the transitive closure, you
22671 can use instead the @option{-fdump-ada-spec-slim} switch.
22673 Note that we recommend when possible to use the @command{g++} driver to
22674 generate bindings, even for most C headers, since this will in general
22675 generate better Ada specs. For generating bindings for C++ headers, it is
22676 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
22677 is equivalent in this case. If @command{g++} cannot work on your C headers
22678 because of incompatibilities between C and C++, then you can fallback to
22679 @command{gcc} instead.
22681 For an example of better bindings generated from the C++ front-end,
22682 the name of the parameters (when available) are actually ignored by the C
22683 front-end. Consider the following C header:
22686 extern void foo (int variable);
22689 with the C front-end, @code{variable} is ignored, and the above is handled as:
22692 extern void foo (int);
22695 generating a generic:
22698 procedure foo (param1 : int);
22701 with the C++ front-end, the name is available, and we generate:
22704 procedure foo (variable : int);
22707 In some cases, the generated bindings will be more complete or more meaningful
22708 when defining some macros, which you can do via the @option{-D} switch. This
22709 is for example the case with @file{Xlib.h} under GNU/Linux:
22712 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
22715 The above will generate more complete bindings than a straight call without
22716 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
22718 In other cases, it is not possible to parse a header file in a stand alone
22719 manner, because other include files need to be included first. In this
22720 case, the solution is to create a small header file including the needed
22721 @code{#include} and possible @code{#define} directives. For example, to
22722 generate Ada bindings for @file{readline/readline.h}, you need to first
22723 include @file{stdio.h}, so you can create a file with the following two
22724 lines in e.g. @file{readline1.h}:
22728 #include <readline/readline.h>
22731 and then generate Ada bindings from this file:
22734 $ g++ -c -fdump-ada-spec readline1.h
22737 @node Generating bindings for C++ headers
22738 @section Generating bindings for C++ headers
22741 Generating bindings for C++ headers is done using the same options, always
22742 with the @command{g++} compiler.
22744 In this mode, C++ classes will be mapped to Ada tagged types, constructors
22745 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
22746 multiple inheritance of abstract classes will be mapped to Ada interfaces
22747 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
22748 information on interfacing to C++).
22750 For example, given the following C++ header file:
22757 virtual int Number_Of_Teeth () = 0;
22762 virtual void Set_Owner (char* Name) = 0;
22768 virtual void Set_Age (int New_Age);
22771 class Dog : Animal, Carnivore, Domestic @{
22776 virtual int Number_Of_Teeth ();
22777 virtual void Set_Owner (char* Name);
22785 The corresponding Ada code is generated:
22787 @smallexample @c ada
22790 package Class_Carnivore is
22791 type Carnivore is limited interface;
22792 pragma Import (CPP, Carnivore);
22794 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
22796 use Class_Carnivore;
22798 package Class_Domestic is
22799 type Domestic is limited interface;
22800 pragma Import (CPP, Domestic);
22802 procedure Set_Owner
22803 (this : access Domestic;
22804 Name : Interfaces.C.Strings.chars_ptr) is abstract;
22806 use Class_Domestic;
22808 package Class_Animal is
22809 type Animal is tagged limited record
22810 Age_Count : aliased int;
22812 pragma Import (CPP, Animal);
22814 procedure Set_Age (this : access Animal; New_Age : int);
22815 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
22819 package Class_Dog is
22820 type Dog is new Animal and Carnivore and Domestic with record
22821 Tooth_Count : aliased int;
22822 Owner : Interfaces.C.Strings.chars_ptr;
22824 pragma Import (CPP, Dog);
22826 function Number_Of_Teeth (this : access Dog) return int;
22827 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
22829 procedure Set_Owner
22830 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
22831 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
22833 function New_Dog return Dog'Class;
22834 pragma CPP_Constructor (New_Dog);
22835 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
22846 @item -fdump-ada-spec
22847 @cindex @option{-fdump-ada-spec} (@command{gcc})
22848 Generate Ada spec files for the given header files transitively (including
22849 all header files that these headers depend upon).
22851 @item -fdump-ada-spec-slim
22852 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
22853 Generate Ada spec files for the header files specified on the command line
22857 @cindex @option{-C} (@command{gcc})
22858 Extract comments from headers and generate Ada comments in the Ada spec files.
22861 @node Other Utility Programs
22862 @chapter Other Utility Programs
22865 This chapter discusses some other utility programs available in the Ada
22869 * Using Other Utility Programs with GNAT::
22870 * The External Symbol Naming Scheme of GNAT::
22871 * Converting Ada Files to html with gnathtml::
22872 * Installing gnathtml::
22879 @node Using Other Utility Programs with GNAT
22880 @section Using Other Utility Programs with GNAT
22883 The object files generated by GNAT are in standard system format and in
22884 particular the debugging information uses this format. This means
22885 programs generated by GNAT can be used with existing utilities that
22886 depend on these formats.
22889 In general, any utility program that works with C will also often work with
22890 Ada programs generated by GNAT. This includes software utilities such as
22891 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
22895 @node The External Symbol Naming Scheme of GNAT
22896 @section The External Symbol Naming Scheme of GNAT
22899 In order to interpret the output from GNAT, when using tools that are
22900 originally intended for use with other languages, it is useful to
22901 understand the conventions used to generate link names from the Ada
22904 All link names are in all lowercase letters. With the exception of library
22905 procedure names, the mechanism used is simply to use the full expanded
22906 Ada name with dots replaced by double underscores. For example, suppose
22907 we have the following package spec:
22909 @smallexample @c ada
22920 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
22921 the corresponding link name is @code{qrs__mn}.
22923 Of course if a @code{pragma Export} is used this may be overridden:
22925 @smallexample @c ada
22930 pragma Export (Var1, C, External_Name => "var1_name");
22932 pragma Export (Var2, C, Link_Name => "var2_link_name");
22939 In this case, the link name for @var{Var1} is whatever link name the
22940 C compiler would assign for the C function @var{var1_name}. This typically
22941 would be either @var{var1_name} or @var{_var1_name}, depending on operating
22942 system conventions, but other possibilities exist. The link name for
22943 @var{Var2} is @var{var2_link_name}, and this is not operating system
22947 One exception occurs for library level procedures. A potential ambiguity
22948 arises between the required name @code{_main} for the C main program,
22949 and the name we would otherwise assign to an Ada library level procedure
22950 called @code{Main} (which might well not be the main program).
22952 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
22953 names. So if we have a library level procedure such as
22955 @smallexample @c ada
22958 procedure Hello (S : String);
22964 the external name of this procedure will be @var{_ada_hello}.
22967 @node Converting Ada Files to html with gnathtml
22968 @section Converting Ada Files to HTML with @code{gnathtml}
22971 This @code{Perl} script allows Ada source files to be browsed using
22972 standard Web browsers. For installation procedure, see the section
22973 @xref{Installing gnathtml}.
22975 Ada reserved keywords are highlighted in a bold font and Ada comments in
22976 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
22977 switch to suppress the generation of cross-referencing information, user
22978 defined variables and types will appear in a different color; you will
22979 be able to click on any identifier and go to its declaration.
22981 The command line is as follow:
22983 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
22987 You can pass it as many Ada files as you want. @code{gnathtml} will generate
22988 an html file for every ada file, and a global file called @file{index.htm}.
22989 This file is an index of every identifier defined in the files.
22991 The available ^switches^options^ are the following ones:
22995 @cindex @option{-83} (@code{gnathtml})
22996 Only the Ada 83 subset of keywords will be highlighted.
22998 @item -cc @var{color}
22999 @cindex @option{-cc} (@code{gnathtml})
23000 This option allows you to change the color used for comments. The default
23001 value is green. The color argument can be any name accepted by html.
23004 @cindex @option{-d} (@code{gnathtml})
23005 If the Ada files depend on some other files (for instance through
23006 @code{with} clauses, the latter files will also be converted to html.
23007 Only the files in the user project will be converted to html, not the files
23008 in the run-time library itself.
23011 @cindex @option{-D} (@code{gnathtml})
23012 This command is the same as @option{-d} above, but @command{gnathtml} will
23013 also look for files in the run-time library, and generate html files for them.
23015 @item -ext @var{extension}
23016 @cindex @option{-ext} (@code{gnathtml})
23017 This option allows you to change the extension of the generated HTML files.
23018 If you do not specify an extension, it will default to @file{htm}.
23021 @cindex @option{-f} (@code{gnathtml})
23022 By default, gnathtml will generate html links only for global entities
23023 ('with'ed units, global variables and types,@dots{}). If you specify
23024 @option{-f} on the command line, then links will be generated for local
23027 @item -l @var{number}
23028 @cindex @option{-l} (@code{gnathtml})
23029 If this ^switch^option^ is provided and @var{number} is not 0, then
23030 @code{gnathtml} will number the html files every @var{number} line.
23033 @cindex @option{-I} (@code{gnathtml})
23034 Specify a directory to search for library files (@file{.ALI} files) and
23035 source files. You can provide several -I switches on the command line,
23036 and the directories will be parsed in the order of the command line.
23039 @cindex @option{-o} (@code{gnathtml})
23040 Specify the output directory for html files. By default, gnathtml will
23041 saved the generated html files in a subdirectory named @file{html/}.
23043 @item -p @var{file}
23044 @cindex @option{-p} (@code{gnathtml})
23045 If you are using Emacs and the most recent Emacs Ada mode, which provides
23046 a full Integrated Development Environment for compiling, checking,
23047 running and debugging applications, you may use @file{.gpr} files
23048 to give the directories where Emacs can find sources and object files.
23050 Using this ^switch^option^, you can tell gnathtml to use these files.
23051 This allows you to get an html version of your application, even if it
23052 is spread over multiple directories.
23054 @item -sc @var{color}
23055 @cindex @option{-sc} (@code{gnathtml})
23056 This ^switch^option^ allows you to change the color used for symbol
23058 The default value is red. The color argument can be any name accepted by html.
23060 @item -t @var{file}
23061 @cindex @option{-t} (@code{gnathtml})
23062 This ^switch^option^ provides the name of a file. This file contains a list of
23063 file names to be converted, and the effect is exactly as though they had
23064 appeared explicitly on the command line. This
23065 is the recommended way to work around the command line length limit on some
23070 @node Installing gnathtml
23071 @section Installing @code{gnathtml}
23074 @code{Perl} needs to be installed on your machine to run this script.
23075 @code{Perl} is freely available for almost every architecture and
23076 Operating System via the Internet.
23078 On Unix systems, you may want to modify the first line of the script
23079 @code{gnathtml}, to explicitly tell the Operating system where Perl
23080 is. The syntax of this line is:
23082 #!full_path_name_to_perl
23086 Alternatively, you may run the script using the following command line:
23089 $ perl gnathtml.pl @ovar{switches} @var{files}
23098 The GNAT distribution provides an Ada 95 template for the HP Language
23099 Sensitive Editor (LSE), a component of DECset. In order to
23100 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
23107 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
23108 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
23109 the collection phase with the /DEBUG qualifier.
23112 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
23113 $ DEFINE LIB$DEBUG PCA$COLLECTOR
23114 $ RUN/DEBUG <PROGRAM_NAME>
23120 @c ******************************
23121 @node Code Coverage and Profiling
23122 @chapter Code Coverage and Profiling
23123 @cindex Code Coverage
23127 This chapter describes how to use @code{gcov} - coverage testing tool - and
23128 @code{gprof} - profiler tool - on your Ada programs.
23131 * Code Coverage of Ada Programs using gcov::
23132 * Profiling an Ada Program using gprof::
23135 @node Code Coverage of Ada Programs using gcov
23136 @section Code Coverage of Ada Programs using gcov
23138 @cindex -fprofile-arcs
23139 @cindex -ftest-coverage
23141 @cindex Code Coverage
23144 @code{gcov} is a test coverage program: it analyzes the execution of a given
23145 program on selected tests, to help you determine the portions of the program
23146 that are still untested.
23148 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
23149 User's Guide. You can refer to this documentation for a more complete
23152 This chapter provides a quick startup guide, and
23153 details some Gnat-specific features.
23156 * Quick startup guide::
23160 @node Quick startup guide
23161 @subsection Quick startup guide
23163 In order to perform coverage analysis of a program using @code{gcov}, 3
23168 Code instrumentation during the compilation process
23170 Execution of the instrumented program
23172 Execution of the @code{gcov} tool to generate the result.
23175 The code instrumentation needed by gcov is created at the object level:
23176 The source code is not modified in any way, because the instrumentation code is
23177 inserted by gcc during the compilation process. To compile your code with code
23178 coverage activated, you need to recompile your whole project using the
23180 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
23181 @code{-fprofile-arcs}.
23184 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
23185 -largs -fprofile-arcs
23188 This compilation process will create @file{.gcno} files together with
23189 the usual object files.
23191 Once the program is compiled with coverage instrumentation, you can
23192 run it as many times as needed - on portions of a test suite for
23193 example. The first execution will produce @file{.gcda} files at the
23194 same location as the @file{.gcno} files. The following executions
23195 will update those files, so that a cumulative result of the covered
23196 portions of the program is generated.
23198 Finally, you need to call the @code{gcov} tool. The different options of
23199 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
23201 This will create annotated source files with a @file{.gcov} extension:
23202 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
23204 @node Gnat specifics
23205 @subsection Gnat specifics
23207 Because Ada semantics, portions of the source code may be shared among
23208 several object files. This is the case for example when generics are
23209 involved, when inlining is active or when declarations generate initialisation
23210 calls. In order to take
23211 into account this shared code, you need to call @code{gcov} on all
23212 source files of the tested program at once.
23214 The list of source files might exceed the system's maximum command line
23215 length. In order to bypass this limitation, a new mechanism has been
23216 implemented in @code{gcov}: you can now list all your project's files into a
23217 text file, and provide this file to gcov as a parameter, preceded by a @@
23218 (e.g. @samp{gcov @@mysrclist.txt}).
23220 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
23221 not supported as there can be unresolved symbols during the final link.
23223 @node Profiling an Ada Program using gprof
23224 @section Profiling an Ada Program using gprof
23230 This section is not meant to be an exhaustive documentation of @code{gprof}.
23231 Full documentation for it can be found in the GNU Profiler User's Guide
23232 documentation that is part of this GNAT distribution.
23234 Profiling a program helps determine the parts of a program that are executed
23235 most often, and are therefore the most time-consuming.
23237 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
23238 better handle Ada programs and multitasking.
23239 It is currently supported on the following platforms
23244 solaris sparc/sparc64/x86
23250 In order to profile a program using @code{gprof}, 3 steps are needed:
23254 Code instrumentation, requiring a full recompilation of the project with the
23257 Execution of the program under the analysis conditions, i.e. with the desired
23260 Analysis of the results using the @code{gprof} tool.
23264 The following sections detail the different steps, and indicate how
23265 to interpret the results:
23267 * Compilation for profiling::
23268 * Program execution::
23270 * Interpretation of profiling results::
23273 @node Compilation for profiling
23274 @subsection Compilation for profiling
23278 In order to profile a program the first step is to tell the compiler
23279 to generate the necessary profiling information. The compiler switch to be used
23280 is @code{-pg}, which must be added to other compilation switches. This
23281 switch needs to be specified both during compilation and link stages, and can
23282 be specified once when using gnatmake:
23285 gnatmake -f -pg -P my_project
23289 Note that only the objects that were compiled with the @samp{-pg} switch will be
23290 profiled; if you need to profile your whole project, use the
23291 @samp{-f} gnatmake switch to force full recompilation.
23293 @node Program execution
23294 @subsection Program execution
23297 Once the program has been compiled for profiling, you can run it as usual.
23299 The only constraint imposed by profiling is that the program must terminate
23300 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
23303 Once the program completes execution, a data file called @file{gmon.out} is
23304 generated in the directory where the program was launched from. If this file
23305 already exists, it will be overwritten.
23307 @node Running gprof
23308 @subsection Running gprof
23311 The @code{gprof} tool is called as follow:
23314 gprof my_prog gmon.out
23325 The complete form of the gprof command line is the following:
23328 gprof [^switches^options^] [executable [data-file]]
23332 @code{gprof} supports numerous ^switch^options^. The order of these
23333 ^switch^options^ does not matter. The full list of options can be found in
23334 the GNU Profiler User's Guide documentation that comes with this documentation.
23336 The following is the subset of those switches that is most relevant:
23340 @item --demangle[=@var{style}]
23341 @itemx --no-demangle
23342 @cindex @option{--demangle} (@code{gprof})
23343 These options control whether symbol names should be demangled when
23344 printing output. The default is to demangle C++ symbols. The
23345 @code{--no-demangle} option may be used to turn off demangling. Different
23346 compilers have different mangling styles. The optional demangling style
23347 argument can be used to choose an appropriate demangling style for your
23348 compiler, in particular Ada symbols generated by GNAT can be demangled using
23349 @code{--demangle=gnat}.
23351 @item -e @var{function_name}
23352 @cindex @option{-e} (@code{gprof})
23353 The @samp{-e @var{function}} option tells @code{gprof} not to print
23354 information about the function @var{function_name} (and its
23355 children@dots{}) in the call graph. The function will still be listed
23356 as a child of any functions that call it, but its index number will be
23357 shown as @samp{[not printed]}. More than one @samp{-e} option may be
23358 given; only one @var{function_name} may be indicated with each @samp{-e}
23361 @item -E @var{function_name}
23362 @cindex @option{-E} (@code{gprof})
23363 The @code{-E @var{function}} option works like the @code{-e} option, but
23364 execution time spent in the function (and children who were not called from
23365 anywhere else), will not be used to compute the percentages-of-time for
23366 the call graph. More than one @samp{-E} option may be given; only one
23367 @var{function_name} may be indicated with each @samp{-E} option.
23369 @item -f @var{function_name}
23370 @cindex @option{-f} (@code{gprof})
23371 The @samp{-f @var{function}} option causes @code{gprof} to limit the
23372 call graph to the function @var{function_name} and its children (and
23373 their children@dots{}). More than one @samp{-f} option may be given;
23374 only one @var{function_name} may be indicated with each @samp{-f}
23377 @item -F @var{function_name}
23378 @cindex @option{-F} (@code{gprof})
23379 The @samp{-F @var{function}} option works like the @code{-f} option, but
23380 only time spent in the function and its children (and their
23381 children@dots{}) will be used to determine total-time and
23382 percentages-of-time for the call graph. More than one @samp{-F} option
23383 may be given; only one @var{function_name} may be indicated with each
23384 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
23388 @node Interpretation of profiling results
23389 @subsection Interpretation of profiling results
23393 The results of the profiling analysis are represented by two arrays: the
23394 'flat profile' and the 'call graph'. Full documentation of those outputs
23395 can be found in the GNU Profiler User's Guide.
23397 The flat profile shows the time spent in each function of the program, and how
23398 many time it has been called. This allows you to locate easily the most
23399 time-consuming functions.
23401 The call graph shows, for each subprogram, the subprograms that call it,
23402 and the subprograms that it calls. It also provides an estimate of the time
23403 spent in each of those callers/called subprograms.
23406 @c ******************************
23407 @node Running and Debugging Ada Programs
23408 @chapter Running and Debugging Ada Programs
23412 This chapter discusses how to debug Ada programs.
23414 It applies to GNAT on the Alpha OpenVMS platform;
23415 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
23416 since HP has implemented Ada support in the OpenVMS debugger on I64.
23419 An incorrect Ada program may be handled in three ways by the GNAT compiler:
23423 The illegality may be a violation of the static semantics of Ada. In
23424 that case GNAT diagnoses the constructs in the program that are illegal.
23425 It is then a straightforward matter for the user to modify those parts of
23429 The illegality may be a violation of the dynamic semantics of Ada. In
23430 that case the program compiles and executes, but may generate incorrect
23431 results, or may terminate abnormally with some exception.
23434 When presented with a program that contains convoluted errors, GNAT
23435 itself may terminate abnormally without providing full diagnostics on
23436 the incorrect user program.
23440 * The GNAT Debugger GDB::
23442 * Introduction to GDB Commands::
23443 * Using Ada Expressions::
23444 * Calling User-Defined Subprograms::
23445 * Using the Next Command in a Function::
23448 * Debugging Generic Units::
23449 * GNAT Abnormal Termination or Failure to Terminate::
23450 * Naming Conventions for GNAT Source Files::
23451 * Getting Internal Debugging Information::
23452 * Stack Traceback::
23458 @node The GNAT Debugger GDB
23459 @section The GNAT Debugger GDB
23462 @code{GDB} is a general purpose, platform-independent debugger that
23463 can be used to debug mixed-language programs compiled with @command{gcc},
23464 and in particular is capable of debugging Ada programs compiled with
23465 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
23466 complex Ada data structures.
23468 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
23470 located in the GNU:[DOCS] directory,
23472 for full details on the usage of @code{GDB}, including a section on
23473 its usage on programs. This manual should be consulted for full
23474 details. The section that follows is a brief introduction to the
23475 philosophy and use of @code{GDB}.
23477 When GNAT programs are compiled, the compiler optionally writes debugging
23478 information into the generated object file, including information on
23479 line numbers, and on declared types and variables. This information is
23480 separate from the generated code. It makes the object files considerably
23481 larger, but it does not add to the size of the actual executable that
23482 will be loaded into memory, and has no impact on run-time performance. The
23483 generation of debug information is triggered by the use of the
23484 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
23485 used to carry out the compilations. It is important to emphasize that
23486 the use of these options does not change the generated code.
23488 The debugging information is written in standard system formats that
23489 are used by many tools, including debuggers and profilers. The format
23490 of the information is typically designed to describe C types and
23491 semantics, but GNAT implements a translation scheme which allows full
23492 details about Ada types and variables to be encoded into these
23493 standard C formats. Details of this encoding scheme may be found in
23494 the file exp_dbug.ads in the GNAT source distribution. However, the
23495 details of this encoding are, in general, of no interest to a user,
23496 since @code{GDB} automatically performs the necessary decoding.
23498 When a program is bound and linked, the debugging information is
23499 collected from the object files, and stored in the executable image of
23500 the program. Again, this process significantly increases the size of
23501 the generated executable file, but it does not increase the size of
23502 the executable program itself. Furthermore, if this program is run in
23503 the normal manner, it runs exactly as if the debug information were
23504 not present, and takes no more actual memory.
23506 However, if the program is run under control of @code{GDB}, the
23507 debugger is activated. The image of the program is loaded, at which
23508 point it is ready to run. If a run command is given, then the program
23509 will run exactly as it would have if @code{GDB} were not present. This
23510 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
23511 entirely non-intrusive until a breakpoint is encountered. If no
23512 breakpoint is ever hit, the program will run exactly as it would if no
23513 debugger were present. When a breakpoint is hit, @code{GDB} accesses
23514 the debugging information and can respond to user commands to inspect
23515 variables, and more generally to report on the state of execution.
23519 @section Running GDB
23522 This section describes how to initiate the debugger.
23523 @c The above sentence is really just filler, but it was otherwise
23524 @c clumsy to get the first paragraph nonindented given the conditional
23525 @c nature of the description
23528 The debugger can be launched from a @code{GPS} menu or
23529 directly from the command line. The description below covers the latter use.
23530 All the commands shown can be used in the @code{GPS} debug console window,
23531 but there are usually more GUI-based ways to achieve the same effect.
23534 The command to run @code{GDB} is
23537 $ ^gdb program^GDB PROGRAM^
23541 where @code{^program^PROGRAM^} is the name of the executable file. This
23542 activates the debugger and results in a prompt for debugger commands.
23543 The simplest command is simply @code{run}, which causes the program to run
23544 exactly as if the debugger were not present. The following section
23545 describes some of the additional commands that can be given to @code{GDB}.
23547 @c *******************************
23548 @node Introduction to GDB Commands
23549 @section Introduction to GDB Commands
23552 @code{GDB} contains a large repertoire of commands. @xref{Top,,
23553 Debugging with GDB, gdb, Debugging with GDB},
23555 located in the GNU:[DOCS] directory,
23557 for extensive documentation on the use
23558 of these commands, together with examples of their use. Furthermore,
23559 the command @command{help} invoked from within GDB activates a simple help
23560 facility which summarizes the available commands and their options.
23561 In this section we summarize a few of the most commonly
23562 used commands to give an idea of what @code{GDB} is about. You should create
23563 a simple program with debugging information and experiment with the use of
23564 these @code{GDB} commands on the program as you read through the
23568 @item set args @var{arguments}
23569 The @var{arguments} list above is a list of arguments to be passed to
23570 the program on a subsequent run command, just as though the arguments
23571 had been entered on a normal invocation of the program. The @code{set args}
23572 command is not needed if the program does not require arguments.
23575 The @code{run} command causes execution of the program to start from
23576 the beginning. If the program is already running, that is to say if
23577 you are currently positioned at a breakpoint, then a prompt will ask
23578 for confirmation that you want to abandon the current execution and
23581 @item breakpoint @var{location}
23582 The breakpoint command sets a breakpoint, that is to say a point at which
23583 execution will halt and @code{GDB} will await further
23584 commands. @var{location} is
23585 either a line number within a file, given in the format @code{file:linenumber},
23586 or it is the name of a subprogram. If you request that a breakpoint be set on
23587 a subprogram that is overloaded, a prompt will ask you to specify on which of
23588 those subprograms you want to breakpoint. You can also
23589 specify that all of them should be breakpointed. If the program is run
23590 and execution encounters the breakpoint, then the program
23591 stops and @code{GDB} signals that the breakpoint was encountered by
23592 printing the line of code before which the program is halted.
23594 @item breakpoint exception @var{name}
23595 A special form of the breakpoint command which breakpoints whenever
23596 exception @var{name} is raised.
23597 If @var{name} is omitted,
23598 then a breakpoint will occur when any exception is raised.
23600 @item print @var{expression}
23601 This will print the value of the given expression. Most simple
23602 Ada expression formats are properly handled by @code{GDB}, so the expression
23603 can contain function calls, variables, operators, and attribute references.
23606 Continues execution following a breakpoint, until the next breakpoint or the
23607 termination of the program.
23610 Executes a single line after a breakpoint. If the next statement
23611 is a subprogram call, execution continues into (the first statement of)
23612 the called subprogram.
23615 Executes a single line. If this line is a subprogram call, executes and
23616 returns from the call.
23619 Lists a few lines around the current source location. In practice, it
23620 is usually more convenient to have a separate edit window open with the
23621 relevant source file displayed. Successive applications of this command
23622 print subsequent lines. The command can be given an argument which is a
23623 line number, in which case it displays a few lines around the specified one.
23626 Displays a backtrace of the call chain. This command is typically
23627 used after a breakpoint has occurred, to examine the sequence of calls that
23628 leads to the current breakpoint. The display includes one line for each
23629 activation record (frame) corresponding to an active subprogram.
23632 At a breakpoint, @code{GDB} can display the values of variables local
23633 to the current frame. The command @code{up} can be used to
23634 examine the contents of other active frames, by moving the focus up
23635 the stack, that is to say from callee to caller, one frame at a time.
23638 Moves the focus of @code{GDB} down from the frame currently being
23639 examined to the frame of its callee (the reverse of the previous command),
23641 @item frame @var{n}
23642 Inspect the frame with the given number. The value 0 denotes the frame
23643 of the current breakpoint, that is to say the top of the call stack.
23648 The above list is a very short introduction to the commands that
23649 @code{GDB} provides. Important additional capabilities, including conditional
23650 breakpoints, the ability to execute command sequences on a breakpoint,
23651 the ability to debug at the machine instruction level and many other
23652 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
23653 Debugging with GDB}. Note that most commands can be abbreviated
23654 (for example, c for continue, bt for backtrace).
23656 @node Using Ada Expressions
23657 @section Using Ada Expressions
23658 @cindex Ada expressions
23661 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
23662 extensions. The philosophy behind the design of this subset is
23666 That @code{GDB} should provide basic literals and access to operations for
23667 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
23668 leaving more sophisticated computations to subprograms written into the
23669 program (which therefore may be called from @code{GDB}).
23672 That type safety and strict adherence to Ada language restrictions
23673 are not particularly important to the @code{GDB} user.
23676 That brevity is important to the @code{GDB} user.
23680 Thus, for brevity, the debugger acts as if there were
23681 implicit @code{with} and @code{use} clauses in effect for all user-written
23682 packages, thus making it unnecessary to fully qualify most names with
23683 their packages, regardless of context. Where this causes ambiguity,
23684 @code{GDB} asks the user's intent.
23686 For details on the supported Ada syntax, see @ref{Top,, Debugging with
23687 GDB, gdb, Debugging with GDB}.
23689 @node Calling User-Defined Subprograms
23690 @section Calling User-Defined Subprograms
23693 An important capability of @code{GDB} is the ability to call user-defined
23694 subprograms while debugging. This is achieved simply by entering
23695 a subprogram call statement in the form:
23698 call subprogram-name (parameters)
23702 The keyword @code{call} can be omitted in the normal case where the
23703 @code{subprogram-name} does not coincide with any of the predefined
23704 @code{GDB} commands.
23706 The effect is to invoke the given subprogram, passing it the
23707 list of parameters that is supplied. The parameters can be expressions and
23708 can include variables from the program being debugged. The
23709 subprogram must be defined
23710 at the library level within your program, and @code{GDB} will call the
23711 subprogram within the environment of your program execution (which
23712 means that the subprogram is free to access or even modify variables
23713 within your program).
23715 The most important use of this facility is in allowing the inclusion of
23716 debugging routines that are tailored to particular data structures
23717 in your program. Such debugging routines can be written to provide a suitably
23718 high-level description of an abstract type, rather than a low-level dump
23719 of its physical layout. After all, the standard
23720 @code{GDB print} command only knows the physical layout of your
23721 types, not their abstract meaning. Debugging routines can provide information
23722 at the desired semantic level and are thus enormously useful.
23724 For example, when debugging GNAT itself, it is crucial to have access to
23725 the contents of the tree nodes used to represent the program internally.
23726 But tree nodes are represented simply by an integer value (which in turn
23727 is an index into a table of nodes).
23728 Using the @code{print} command on a tree node would simply print this integer
23729 value, which is not very useful. But the PN routine (defined in file
23730 treepr.adb in the GNAT sources) takes a tree node as input, and displays
23731 a useful high level representation of the tree node, which includes the
23732 syntactic category of the node, its position in the source, the integers
23733 that denote descendant nodes and parent node, as well as varied
23734 semantic information. To study this example in more detail, you might want to
23735 look at the body of the PN procedure in the stated file.
23737 @node Using the Next Command in a Function
23738 @section Using the Next Command in a Function
23741 When you use the @code{next} command in a function, the current source
23742 location will advance to the next statement as usual. A special case
23743 arises in the case of a @code{return} statement.
23745 Part of the code for a return statement is the ``epilog'' of the function.
23746 This is the code that returns to the caller. There is only one copy of
23747 this epilog code, and it is typically associated with the last return
23748 statement in the function if there is more than one return. In some
23749 implementations, this epilog is associated with the first statement
23752 The result is that if you use the @code{next} command from a return
23753 statement that is not the last return statement of the function you
23754 may see a strange apparent jump to the last return statement or to
23755 the start of the function. You should simply ignore this odd jump.
23756 The value returned is always that from the first return statement
23757 that was stepped through.
23759 @node Ada Exceptions
23760 @section Breaking on Ada Exceptions
23764 You can set breakpoints that trip when your program raises
23765 selected exceptions.
23768 @item break exception
23769 Set a breakpoint that trips whenever (any task in the) program raises
23772 @item break exception @var{name}
23773 Set a breakpoint that trips whenever (any task in the) program raises
23774 the exception @var{name}.
23776 @item break exception unhandled
23777 Set a breakpoint that trips whenever (any task in the) program raises an
23778 exception for which there is no handler.
23780 @item info exceptions
23781 @itemx info exceptions @var{regexp}
23782 The @code{info exceptions} command permits the user to examine all defined
23783 exceptions within Ada programs. With a regular expression, @var{regexp}, as
23784 argument, prints out only those exceptions whose name matches @var{regexp}.
23792 @code{GDB} allows the following task-related commands:
23796 This command shows a list of current Ada tasks, as in the following example:
23803 ID TID P-ID Thread Pri State Name
23804 1 8088000 0 807e000 15 Child Activation Wait main_task
23805 2 80a4000 1 80ae000 15 Accept/Select Wait b
23806 3 809a800 1 80a4800 15 Child Activation Wait a
23807 * 4 80ae800 3 80b8000 15 Running c
23811 In this listing, the asterisk before the first task indicates it to be the
23812 currently running task. The first column lists the task ID that is used
23813 to refer to tasks in the following commands.
23815 @item break @var{linespec} task @var{taskid}
23816 @itemx break @var{linespec} task @var{taskid} if @dots{}
23817 @cindex Breakpoints and tasks
23818 These commands are like the @code{break @dots{} thread @dots{}}.
23819 @var{linespec} specifies source lines.
23821 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
23822 to specify that you only want @code{GDB} to stop the program when a
23823 particular Ada task reaches this breakpoint. @var{taskid} is one of the
23824 numeric task identifiers assigned by @code{GDB}, shown in the first
23825 column of the @samp{info tasks} display.
23827 If you do not specify @samp{task @var{taskid}} when you set a
23828 breakpoint, the breakpoint applies to @emph{all} tasks of your
23831 You can use the @code{task} qualifier on conditional breakpoints as
23832 well; in this case, place @samp{task @var{taskid}} before the
23833 breakpoint condition (before the @code{if}).
23835 @item task @var{taskno}
23836 @cindex Task switching
23838 This command allows to switch to the task referred by @var{taskno}. In
23839 particular, This allows to browse the backtrace of the specified
23840 task. It is advised to switch back to the original task before
23841 continuing execution otherwise the scheduling of the program may be
23846 For more detailed information on the tasking support,
23847 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
23849 @node Debugging Generic Units
23850 @section Debugging Generic Units
23851 @cindex Debugging Generic Units
23855 GNAT always uses code expansion for generic instantiation. This means that
23856 each time an instantiation occurs, a complete copy of the original code is
23857 made, with appropriate substitutions of formals by actuals.
23859 It is not possible to refer to the original generic entities in
23860 @code{GDB}, but it is always possible to debug a particular instance of
23861 a generic, by using the appropriate expanded names. For example, if we have
23863 @smallexample @c ada
23868 generic package k is
23869 procedure kp (v1 : in out integer);
23873 procedure kp (v1 : in out integer) is
23879 package k1 is new k;
23880 package k2 is new k;
23882 var : integer := 1;
23895 Then to break on a call to procedure kp in the k2 instance, simply
23899 (gdb) break g.k2.kp
23903 When the breakpoint occurs, you can step through the code of the
23904 instance in the normal manner and examine the values of local variables, as for
23907 @node GNAT Abnormal Termination or Failure to Terminate
23908 @section GNAT Abnormal Termination or Failure to Terminate
23909 @cindex GNAT Abnormal Termination or Failure to Terminate
23912 When presented with programs that contain serious errors in syntax
23914 GNAT may on rare occasions experience problems in operation, such
23916 segmentation fault or illegal memory access, raising an internal
23917 exception, terminating abnormally, or failing to terminate at all.
23918 In such cases, you can activate
23919 various features of GNAT that can help you pinpoint the construct in your
23920 program that is the likely source of the problem.
23922 The following strategies are presented in increasing order of
23923 difficulty, corresponding to your experience in using GNAT and your
23924 familiarity with compiler internals.
23928 Run @command{gcc} with the @option{-gnatf}. This first
23929 switch causes all errors on a given line to be reported. In its absence,
23930 only the first error on a line is displayed.
23932 The @option{-gnatdO} switch causes errors to be displayed as soon as they
23933 are encountered, rather than after compilation is terminated. If GNAT
23934 terminates prematurely or goes into an infinite loop, the last error
23935 message displayed may help to pinpoint the culprit.
23938 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
23939 mode, @command{gcc} produces ongoing information about the progress of the
23940 compilation and provides the name of each procedure as code is
23941 generated. This switch allows you to find which Ada procedure was being
23942 compiled when it encountered a code generation problem.
23945 @cindex @option{-gnatdc} switch
23946 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
23947 switch that does for the front-end what @option{^-v^VERBOSE^} does
23948 for the back end. The system prints the name of each unit,
23949 either a compilation unit or nested unit, as it is being analyzed.
23951 Finally, you can start
23952 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
23953 front-end of GNAT, and can be run independently (normally it is just
23954 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
23955 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
23956 @code{where} command is the first line of attack; the variable
23957 @code{lineno} (seen by @code{print lineno}), used by the second phase of
23958 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
23959 which the execution stopped, and @code{input_file name} indicates the name of
23963 @node Naming Conventions for GNAT Source Files
23964 @section Naming Conventions for GNAT Source Files
23967 In order to examine the workings of the GNAT system, the following
23968 brief description of its organization may be helpful:
23972 Files with prefix @file{^sc^SC^} contain the lexical scanner.
23975 All files prefixed with @file{^par^PAR^} are components of the parser. The
23976 numbers correspond to chapters of the Ada Reference Manual. For example,
23977 parsing of select statements can be found in @file{par-ch9.adb}.
23980 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
23981 numbers correspond to chapters of the Ada standard. For example, all
23982 issues involving context clauses can be found in @file{sem_ch10.adb}. In
23983 addition, some features of the language require sufficient special processing
23984 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
23985 dynamic dispatching, etc.
23988 All files prefixed with @file{^exp^EXP^} perform normalization and
23989 expansion of the intermediate representation (abstract syntax tree, or AST).
23990 these files use the same numbering scheme as the parser and semantics files.
23991 For example, the construction of record initialization procedures is done in
23992 @file{exp_ch3.adb}.
23995 The files prefixed with @file{^bind^BIND^} implement the binder, which
23996 verifies the consistency of the compilation, determines an order of
23997 elaboration, and generates the bind file.
24000 The files @file{atree.ads} and @file{atree.adb} detail the low-level
24001 data structures used by the front-end.
24004 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
24005 the abstract syntax tree as produced by the parser.
24008 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
24009 all entities, computed during semantic analysis.
24012 Library management issues are dealt with in files with prefix
24018 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
24019 defined in Annex A.
24024 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
24025 defined in Annex B.
24029 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
24030 both language-defined children and GNAT run-time routines.
24034 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
24035 general-purpose packages, fully documented in their specs. All
24036 the other @file{.c} files are modifications of common @command{gcc} files.
24039 @node Getting Internal Debugging Information
24040 @section Getting Internal Debugging Information
24043 Most compilers have internal debugging switches and modes. GNAT
24044 does also, except GNAT internal debugging switches and modes are not
24045 secret. A summary and full description of all the compiler and binder
24046 debug flags are in the file @file{debug.adb}. You must obtain the
24047 sources of the compiler to see the full detailed effects of these flags.
24049 The switches that print the source of the program (reconstructed from
24050 the internal tree) are of general interest for user programs, as are the
24052 the full internal tree, and the entity table (the symbol table
24053 information). The reconstructed source provides a readable version of the
24054 program after the front-end has completed analysis and expansion,
24055 and is useful when studying the performance of specific constructs.
24056 For example, constraint checks are indicated, complex aggregates
24057 are replaced with loops and assignments, and tasking primitives
24058 are replaced with run-time calls.
24060 @node Stack Traceback
24061 @section Stack Traceback
24063 @cindex stack traceback
24064 @cindex stack unwinding
24067 Traceback is a mechanism to display the sequence of subprogram calls that
24068 leads to a specified execution point in a program. Often (but not always)
24069 the execution point is an instruction at which an exception has been raised.
24070 This mechanism is also known as @i{stack unwinding} because it obtains
24071 its information by scanning the run-time stack and recovering the activation
24072 records of all active subprograms. Stack unwinding is one of the most
24073 important tools for program debugging.
24075 The first entry stored in traceback corresponds to the deepest calling level,
24076 that is to say the subprogram currently executing the instruction
24077 from which we want to obtain the traceback.
24079 Note that there is no runtime performance penalty when stack traceback
24080 is enabled, and no exception is raised during program execution.
24083 * Non-Symbolic Traceback::
24084 * Symbolic Traceback::
24087 @node Non-Symbolic Traceback
24088 @subsection Non-Symbolic Traceback
24089 @cindex traceback, non-symbolic
24092 Note: this feature is not supported on all platforms. See
24093 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
24097 * Tracebacks From an Unhandled Exception::
24098 * Tracebacks From Exception Occurrences (non-symbolic)::
24099 * Tracebacks From Anywhere in a Program (non-symbolic)::
24102 @node Tracebacks From an Unhandled Exception
24103 @subsubsection Tracebacks From an Unhandled Exception
24106 A runtime non-symbolic traceback is a list of addresses of call instructions.
24107 To enable this feature you must use the @option{-E}
24108 @code{gnatbind}'s option. With this option a stack traceback is stored as part
24109 of exception information. You can retrieve this information using the
24110 @code{addr2line} tool.
24112 Here is a simple example:
24114 @smallexample @c ada
24120 raise Constraint_Error;
24135 $ gnatmake stb -bargs -E
24138 Execution terminated by unhandled exception
24139 Exception name: CONSTRAINT_ERROR
24141 Call stack traceback locations:
24142 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24146 As we see the traceback lists a sequence of addresses for the unhandled
24147 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
24148 guess that this exception come from procedure P1. To translate these
24149 addresses into the source lines where the calls appear, the
24150 @code{addr2line} tool, described below, is invaluable. The use of this tool
24151 requires the program to be compiled with debug information.
24154 $ gnatmake -g stb -bargs -E
24157 Execution terminated by unhandled exception
24158 Exception name: CONSTRAINT_ERROR
24160 Call stack traceback locations:
24161 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24163 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
24164 0x4011f1 0x77e892a4
24166 00401373 at d:/stb/stb.adb:5
24167 0040138B at d:/stb/stb.adb:10
24168 0040139C at d:/stb/stb.adb:14
24169 00401335 at d:/stb/b~stb.adb:104
24170 004011C4 at /build/@dots{}/crt1.c:200
24171 004011F1 at /build/@dots{}/crt1.c:222
24172 77E892A4 in ?? at ??:0
24176 The @code{addr2line} tool has several other useful options:
24180 to get the function name corresponding to any location
24182 @item --demangle=gnat
24183 to use the gnat decoding mode for the function names. Note that
24184 for binutils version 2.9.x the option is simply @option{--demangle}.
24188 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
24189 0x40139c 0x401335 0x4011c4 0x4011f1
24191 00401373 in stb.p1 at d:/stb/stb.adb:5
24192 0040138B in stb.p2 at d:/stb/stb.adb:10
24193 0040139C in stb at d:/stb/stb.adb:14
24194 00401335 in main at d:/stb/b~stb.adb:104
24195 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
24196 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
24200 From this traceback we can see that the exception was raised in
24201 @file{stb.adb} at line 5, which was reached from a procedure call in
24202 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
24203 which contains the call to the main program.
24204 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
24205 and the output will vary from platform to platform.
24207 It is also possible to use @code{GDB} with these traceback addresses to debug
24208 the program. For example, we can break at a given code location, as reported
24209 in the stack traceback:
24215 Furthermore, this feature is not implemented inside Windows DLL. Only
24216 the non-symbolic traceback is reported in this case.
24219 (gdb) break *0x401373
24220 Breakpoint 1 at 0x401373: file stb.adb, line 5.
24224 It is important to note that the stack traceback addresses
24225 do not change when debug information is included. This is particularly useful
24226 because it makes it possible to release software without debug information (to
24227 minimize object size), get a field report that includes a stack traceback
24228 whenever an internal bug occurs, and then be able to retrieve the sequence
24229 of calls with the same program compiled with debug information.
24231 @node Tracebacks From Exception Occurrences (non-symbolic)
24232 @subsubsection Tracebacks From Exception Occurrences
24235 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
24236 The stack traceback is attached to the exception information string, and can
24237 be retrieved in an exception handler within the Ada program, by means of the
24238 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
24240 @smallexample @c ada
24242 with Ada.Exceptions;
24247 use Ada.Exceptions;
24255 Text_IO.Put_Line (Exception_Information (E));
24269 This program will output:
24274 Exception name: CONSTRAINT_ERROR
24275 Message: stb.adb:12
24276 Call stack traceback locations:
24277 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
24280 @node Tracebacks From Anywhere in a Program (non-symbolic)
24281 @subsubsection Tracebacks From Anywhere in a Program
24284 It is also possible to retrieve a stack traceback from anywhere in a
24285 program. For this you need to
24286 use the @code{GNAT.Traceback} API. This package includes a procedure called
24287 @code{Call_Chain} that computes a complete stack traceback, as well as useful
24288 display procedures described below. It is not necessary to use the
24289 @option{-E gnatbind} option in this case, because the stack traceback mechanism
24290 is invoked explicitly.
24293 In the following example we compute a traceback at a specific location in
24294 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
24295 convert addresses to strings:
24297 @smallexample @c ada
24299 with GNAT.Traceback;
24300 with GNAT.Debug_Utilities;
24306 use GNAT.Traceback;
24309 TB : Tracebacks_Array (1 .. 10);
24310 -- We are asking for a maximum of 10 stack frames.
24312 -- Len will receive the actual number of stack frames returned.
24314 Call_Chain (TB, Len);
24316 Text_IO.Put ("In STB.P1 : ");
24318 for K in 1 .. Len loop
24319 Text_IO.Put (Debug_Utilities.Image (TB (K)));
24340 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
24341 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
24345 You can then get further information by invoking the @code{addr2line}
24346 tool as described earlier (note that the hexadecimal addresses
24347 need to be specified in C format, with a leading ``0x'').
24349 @node Symbolic Traceback
24350 @subsection Symbolic Traceback
24351 @cindex traceback, symbolic
24354 A symbolic traceback is a stack traceback in which procedure names are
24355 associated with each code location.
24358 Note that this feature is not supported on all platforms. See
24359 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
24360 list of currently supported platforms.
24363 Note that the symbolic traceback requires that the program be compiled
24364 with debug information. If it is not compiled with debug information
24365 only the non-symbolic information will be valid.
24368 * Tracebacks From Exception Occurrences (symbolic)::
24369 * Tracebacks From Anywhere in a Program (symbolic)::
24372 @node Tracebacks From Exception Occurrences (symbolic)
24373 @subsubsection Tracebacks From Exception Occurrences
24375 @smallexample @c ada
24377 with GNAT.Traceback.Symbolic;
24383 raise Constraint_Error;
24400 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
24405 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
24408 0040149F in stb.p1 at stb.adb:8
24409 004014B7 in stb.p2 at stb.adb:13
24410 004014CF in stb.p3 at stb.adb:18
24411 004015DD in ada.stb at stb.adb:22
24412 00401461 in main at b~stb.adb:168
24413 004011C4 in __mingw_CRTStartup at crt1.c:200
24414 004011F1 in mainCRTStartup at crt1.c:222
24415 77E892A4 in ?? at ??:0
24419 In the above example the ``.\'' syntax in the @command{gnatmake} command
24420 is currently required by @command{addr2line} for files that are in
24421 the current working directory.
24422 Moreover, the exact sequence of linker options may vary from platform
24424 The above @option{-largs} section is for Windows platforms. By contrast,
24425 under Unix there is no need for the @option{-largs} section.
24426 Differences across platforms are due to details of linker implementation.
24428 @node Tracebacks From Anywhere in a Program (symbolic)
24429 @subsubsection Tracebacks From Anywhere in a Program
24432 It is possible to get a symbolic stack traceback
24433 from anywhere in a program, just as for non-symbolic tracebacks.
24434 The first step is to obtain a non-symbolic
24435 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
24436 information. Here is an example:
24438 @smallexample @c ada
24440 with GNAT.Traceback;
24441 with GNAT.Traceback.Symbolic;
24446 use GNAT.Traceback;
24447 use GNAT.Traceback.Symbolic;
24450 TB : Tracebacks_Array (1 .. 10);
24451 -- We are asking for a maximum of 10 stack frames.
24453 -- Len will receive the actual number of stack frames returned.
24455 Call_Chain (TB, Len);
24456 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
24469 @c ******************************
24471 @node Compatibility with HP Ada
24472 @chapter Compatibility with HP Ada
24473 @cindex Compatibility
24478 @cindex Compatibility between GNAT and HP Ada
24479 This chapter compares HP Ada (formerly known as ``DEC Ada'')
24480 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
24481 GNAT is highly compatible
24482 with HP Ada, and it should generally be straightforward to port code
24483 from the HP Ada environment to GNAT. However, there are a few language
24484 and implementation differences of which the user must be aware. These
24485 differences are discussed in this chapter. In
24486 addition, the operating environment and command structure for the
24487 compiler are different, and these differences are also discussed.
24489 For further details on these and other compatibility issues,
24490 see Appendix E of the HP publication
24491 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
24493 Except where otherwise indicated, the description of GNAT for OpenVMS
24494 applies to both the Alpha and I64 platforms.
24496 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
24497 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24499 The discussion in this chapter addresses specifically the implementation
24500 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
24501 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
24502 GNAT always follows the Alpha implementation.
24504 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
24505 attributes are recognized, although only a subset of them can sensibly
24506 be implemented. The description of pragmas in
24507 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
24508 indicates whether or not they are applicable to non-VMS systems.
24511 * Ada Language Compatibility::
24512 * Differences in the Definition of Package System::
24513 * Language-Related Features::
24514 * The Package STANDARD::
24515 * The Package SYSTEM::
24516 * Tasking and Task-Related Features::
24517 * Pragmas and Pragma-Related Features::
24518 * Library of Predefined Units::
24520 * Main Program Definition::
24521 * Implementation-Defined Attributes::
24522 * Compiler and Run-Time Interfacing::
24523 * Program Compilation and Library Management::
24525 * Implementation Limits::
24526 * Tools and Utilities::
24529 @node Ada Language Compatibility
24530 @section Ada Language Compatibility
24533 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
24534 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
24535 with Ada 83, and therefore Ada 83 programs will compile
24536 and run under GNAT with
24537 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
24538 provides details on specific incompatibilities.
24540 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
24541 as well as the pragma @code{ADA_83}, to force the compiler to
24542 operate in Ada 83 mode. This mode does not guarantee complete
24543 conformance to Ada 83, but in practice is sufficient to
24544 eliminate most sources of incompatibilities.
24545 In particular, it eliminates the recognition of the
24546 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
24547 in Ada 83 programs is legal, and handles the cases of packages
24548 with optional bodies, and generics that instantiate unconstrained
24549 types without the use of @code{(<>)}.
24551 @node Differences in the Definition of Package System
24552 @section Differences in the Definition of Package @code{System}
24555 An Ada compiler is allowed to add
24556 implementation-dependent declarations to package @code{System}.
24558 GNAT does not take advantage of this permission, and the version of
24559 @code{System} provided by GNAT exactly matches that defined in the Ada
24562 However, HP Ada adds an extensive set of declarations to package
24564 as fully documented in the HP Ada manuals. To minimize changes required
24565 for programs that make use of these extensions, GNAT provides the pragma
24566 @code{Extend_System} for extending the definition of package System. By using:
24567 @cindex pragma @code{Extend_System}
24568 @cindex @code{Extend_System} pragma
24570 @smallexample @c ada
24573 pragma Extend_System (Aux_DEC);
24579 the set of definitions in @code{System} is extended to include those in
24580 package @code{System.Aux_DEC}.
24581 @cindex @code{System.Aux_DEC} package
24582 @cindex @code{Aux_DEC} package (child of @code{System})
24583 These definitions are incorporated directly into package @code{System},
24584 as though they had been declared there. For a
24585 list of the declarations added, see the spec of this package,
24586 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
24587 @cindex @file{s-auxdec.ads} file
24588 The pragma @code{Extend_System} is a configuration pragma, which means that
24589 it can be placed in the file @file{gnat.adc}, so that it will automatically
24590 apply to all subsequent compilations. See @ref{Configuration Pragmas},
24591 for further details.
24593 An alternative approach that avoids the use of the non-standard
24594 @code{Extend_System} pragma is to add a context clause to the unit that
24595 references these facilities:
24597 @smallexample @c ada
24599 with System.Aux_DEC;
24600 use System.Aux_DEC;
24605 The effect is not quite semantically identical to incorporating
24606 the declarations directly into package @code{System},
24607 but most programs will not notice a difference
24608 unless they use prefix notation (e.g.@: @code{System.Integer_8})
24609 to reference the entities directly in package @code{System}.
24610 For units containing such references,
24611 the prefixes must either be removed, or the pragma @code{Extend_System}
24614 @node Language-Related Features
24615 @section Language-Related Features
24618 The following sections highlight differences in types,
24619 representations of types, operations, alignment, and
24623 * Integer Types and Representations::
24624 * Floating-Point Types and Representations::
24625 * Pragmas Float_Representation and Long_Float::
24626 * Fixed-Point Types and Representations::
24627 * Record and Array Component Alignment::
24628 * Address Clauses::
24629 * Other Representation Clauses::
24632 @node Integer Types and Representations
24633 @subsection Integer Types and Representations
24636 The set of predefined integer types is identical in HP Ada and GNAT.
24637 Furthermore the representation of these integer types is also identical,
24638 including the capability of size clauses forcing biased representation.
24641 HP Ada for OpenVMS Alpha systems has defined the
24642 following additional integer types in package @code{System}:
24659 @code{LARGEST_INTEGER}
24663 In GNAT, the first four of these types may be obtained from the
24664 standard Ada package @code{Interfaces}.
24665 Alternatively, by use of the pragma @code{Extend_System}, identical
24666 declarations can be referenced directly in package @code{System}.
24667 On both GNAT and HP Ada, the maximum integer size is 64 bits.
24669 @node Floating-Point Types and Representations
24670 @subsection Floating-Point Types and Representations
24671 @cindex Floating-Point types
24674 The set of predefined floating-point types is identical in HP Ada and GNAT.
24675 Furthermore the representation of these floating-point
24676 types is also identical. One important difference is that the default
24677 representation for HP Ada is @code{VAX_Float}, but the default representation
24680 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
24681 pragma @code{Float_Representation} as described in the HP Ada
24683 For example, the declarations:
24685 @smallexample @c ada
24687 type F_Float is digits 6;
24688 pragma Float_Representation (VAX_Float, F_Float);
24693 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
24695 This set of declarations actually appears in @code{System.Aux_DEC},
24697 the full set of additional floating-point declarations provided in
24698 the HP Ada version of package @code{System}.
24699 This and similar declarations may be accessed in a user program
24700 by using pragma @code{Extend_System}. The use of this
24701 pragma, and the related pragma @code{Long_Float} is described in further
24702 detail in the following section.
24704 @node Pragmas Float_Representation and Long_Float
24705 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
24708 HP Ada provides the pragma @code{Float_Representation}, which
24709 acts as a program library switch to allow control over
24710 the internal representation chosen for the predefined
24711 floating-point types declared in the package @code{Standard}.
24712 The format of this pragma is as follows:
24714 @smallexample @c ada
24716 pragma Float_Representation(VAX_Float | IEEE_Float);
24721 This pragma controls the representation of floating-point
24726 @code{VAX_Float} specifies that floating-point
24727 types are represented by default with the VAX system hardware types
24728 @code{F-floating}, @code{D-floating}, @code{G-floating}.
24729 Note that the @code{H-floating}
24730 type was available only on VAX systems, and is not available
24731 in either HP Ada or GNAT.
24734 @code{IEEE_Float} specifies that floating-point
24735 types are represented by default with the IEEE single and
24736 double floating-point types.
24740 GNAT provides an identical implementation of the pragma
24741 @code{Float_Representation}, except that it functions as a
24742 configuration pragma. Note that the
24743 notion of configuration pragma corresponds closely to the
24744 HP Ada notion of a program library switch.
24746 When no pragma is used in GNAT, the default is @code{IEEE_Float},
24748 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
24749 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
24750 advisable to change the format of numbers passed to standard library
24751 routines, and if necessary explicit type conversions may be needed.
24753 The use of @code{IEEE_Float} is recommended in GNAT since it is more
24754 efficient, and (given that it conforms to an international standard)
24755 potentially more portable.
24756 The situation in which @code{VAX_Float} may be useful is in interfacing
24757 to existing code and data that expect the use of @code{VAX_Float}.
24758 In such a situation use the predefined @code{VAX_Float}
24759 types in package @code{System}, as extended by
24760 @code{Extend_System}. For example, use @code{System.F_Float}
24761 to specify the 32-bit @code{F-Float} format.
24764 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
24765 to allow control over the internal representation chosen
24766 for the predefined type @code{Long_Float} and for floating-point
24767 type declarations with digits specified in the range 7 .. 15.
24768 The format of this pragma is as follows:
24770 @smallexample @c ada
24772 pragma Long_Float (D_FLOAT | G_FLOAT);
24776 @node Fixed-Point Types and Representations
24777 @subsection Fixed-Point Types and Representations
24780 On HP Ada for OpenVMS Alpha systems, rounding is
24781 away from zero for both positive and negative numbers.
24782 Therefore, @code{+0.5} rounds to @code{1},
24783 and @code{-0.5} rounds to @code{-1}.
24785 On GNAT the results of operations
24786 on fixed-point types are in accordance with the Ada
24787 rules. In particular, results of operations on decimal
24788 fixed-point types are truncated.
24790 @node Record and Array Component Alignment
24791 @subsection Record and Array Component Alignment
24794 On HP Ada for OpenVMS Alpha, all non-composite components
24795 are aligned on natural boundaries. For example, 1-byte
24796 components are aligned on byte boundaries, 2-byte
24797 components on 2-byte boundaries, 4-byte components on 4-byte
24798 byte boundaries, and so on. The OpenVMS Alpha hardware
24799 runs more efficiently with naturally aligned data.
24801 On GNAT, alignment rules are compatible
24802 with HP Ada for OpenVMS Alpha.
24804 @node Address Clauses
24805 @subsection Address Clauses
24808 In HP Ada and GNAT, address clauses are supported for
24809 objects and imported subprograms.
24810 The predefined type @code{System.Address} is a private type
24811 in both compilers on Alpha OpenVMS, with the same representation
24812 (it is simply a machine pointer). Addition, subtraction, and comparison
24813 operations are available in the standard Ada package
24814 @code{System.Storage_Elements}, or in package @code{System}
24815 if it is extended to include @code{System.Aux_DEC} using a
24816 pragma @code{Extend_System} as previously described.
24818 Note that code that @code{with}'s both this extended package @code{System}
24819 and the package @code{System.Storage_Elements} should not @code{use}
24820 both packages, or ambiguities will result. In general it is better
24821 not to mix these two sets of facilities. The Ada package was
24822 designed specifically to provide the kind of features that HP Ada
24823 adds directly to package @code{System}.
24825 The type @code{System.Address} is a 64-bit integer type in GNAT for
24826 I64 OpenVMS. For more information,
24827 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24829 GNAT is compatible with HP Ada in its handling of address
24830 clauses, except for some limitations in
24831 the form of address clauses for composite objects with
24832 initialization. Such address clauses are easily replaced
24833 by the use of an explicitly-defined constant as described
24834 in the Ada Reference Manual (13.1(22)). For example, the sequence
24837 @smallexample @c ada
24839 X, Y : Integer := Init_Func;
24840 Q : String (X .. Y) := "abc";
24842 for Q'Address use Compute_Address;
24847 will be rejected by GNAT, since the address cannot be computed at the time
24848 that @code{Q} is declared. To achieve the intended effect, write instead:
24850 @smallexample @c ada
24853 X, Y : Integer := Init_Func;
24854 Q_Address : constant Address := Compute_Address;
24855 Q : String (X .. Y) := "abc";
24857 for Q'Address use Q_Address;
24863 which will be accepted by GNAT (and other Ada compilers), and is also
24864 compatible with Ada 83. A fuller description of the restrictions
24865 on address specifications is found in @ref{Top, GNAT Reference Manual,
24866 About This Guide, gnat_rm, GNAT Reference Manual}.
24868 @node Other Representation Clauses
24869 @subsection Other Representation Clauses
24872 GNAT implements in a compatible manner all the representation
24873 clauses supported by HP Ada. In addition, GNAT
24874 implements the representation clause forms that were introduced in Ada 95,
24875 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
24877 @node The Package STANDARD
24878 @section The Package @code{STANDARD}
24881 The package @code{STANDARD}, as implemented by HP Ada, is fully
24882 described in the @cite{Ada Reference Manual} and in the
24883 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
24884 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
24886 In addition, HP Ada supports the Latin-1 character set in
24887 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
24888 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
24889 the type @code{WIDE_CHARACTER}.
24891 The floating-point types supported by GNAT are those
24892 supported by HP Ada, but the defaults are different, and are controlled by
24893 pragmas. See @ref{Floating-Point Types and Representations}, for details.
24895 @node The Package SYSTEM
24896 @section The Package @code{SYSTEM}
24899 HP Ada provides a specific version of the package
24900 @code{SYSTEM} for each platform on which the language is implemented.
24901 For the complete spec of the package @code{SYSTEM}, see
24902 Appendix F of the @cite{HP Ada Language Reference Manual}.
24904 On HP Ada, the package @code{SYSTEM} includes the following conversion
24907 @item @code{TO_ADDRESS(INTEGER)}
24909 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
24911 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
24913 @item @code{TO_INTEGER(ADDRESS)}
24915 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
24917 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
24918 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
24922 By default, GNAT supplies a version of @code{SYSTEM} that matches
24923 the definition given in the @cite{Ada Reference Manual}.
24925 is a subset of the HP system definitions, which is as
24926 close as possible to the original definitions. The only difference
24927 is that the definition of @code{SYSTEM_NAME} is different:
24929 @smallexample @c ada
24931 type Name is (SYSTEM_NAME_GNAT);
24932 System_Name : constant Name := SYSTEM_NAME_GNAT;
24937 Also, GNAT adds the Ada declarations for
24938 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
24940 However, the use of the following pragma causes GNAT
24941 to extend the definition of package @code{SYSTEM} so that it
24942 encompasses the full set of HP-specific extensions,
24943 including the functions listed above:
24945 @smallexample @c ada
24947 pragma Extend_System (Aux_DEC);
24952 The pragma @code{Extend_System} is a configuration pragma that
24953 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
24954 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
24956 HP Ada does not allow the recompilation of the package
24957 @code{SYSTEM}. Instead HP Ada provides several pragmas
24958 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
24959 to modify values in the package @code{SYSTEM}.
24960 On OpenVMS Alpha systems, the pragma
24961 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
24962 its single argument.
24964 GNAT does permit the recompilation of package @code{SYSTEM} using
24965 the special switch @option{-gnatg}, and this switch can be used if
24966 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
24967 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
24968 or @code{MEMORY_SIZE} by any other means.
24970 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
24971 enumeration literal @code{SYSTEM_NAME_GNAT}.
24973 The definitions provided by the use of
24975 @smallexample @c ada
24976 pragma Extend_System (AUX_Dec);
24980 are virtually identical to those provided by the HP Ada 83 package
24981 @code{SYSTEM}. One important difference is that the name of the
24983 function for type @code{UNSIGNED_LONGWORD} is changed to
24984 @code{TO_ADDRESS_LONG}.
24985 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
24986 discussion of why this change was necessary.
24989 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
24991 an extension to Ada 83 not strictly compatible with the reference manual.
24992 GNAT, in order to be exactly compatible with the standard,
24993 does not provide this capability. In HP Ada 83, the
24994 point of this definition is to deal with a call like:
24996 @smallexample @c ada
24997 TO_ADDRESS (16#12777#);
25001 Normally, according to Ada 83 semantics, one would expect this to be
25002 ambiguous, since it matches both the @code{INTEGER} and
25003 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
25004 However, in HP Ada 83, there is no ambiguity, since the
25005 definition using @i{universal_integer} takes precedence.
25007 In GNAT, since the version with @i{universal_integer} cannot be supplied,
25009 not possible to be 100% compatible. Since there are many programs using
25010 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
25012 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
25013 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
25015 @smallexample @c ada
25016 function To_Address (X : Integer) return Address;
25017 pragma Pure_Function (To_Address);
25019 function To_Address_Long (X : Unsigned_Longword) return Address;
25020 pragma Pure_Function (To_Address_Long);
25024 This means that programs using @code{TO_ADDRESS} for
25025 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
25027 @node Tasking and Task-Related Features
25028 @section Tasking and Task-Related Features
25031 This section compares the treatment of tasking in GNAT
25032 and in HP Ada for OpenVMS Alpha.
25033 The GNAT description applies to both Alpha and I64 OpenVMS.
25034 For detailed information on tasking in
25035 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
25036 relevant run-time reference manual.
25039 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
25040 * Assigning Task IDs::
25041 * Task IDs and Delays::
25042 * Task-Related Pragmas::
25043 * Scheduling and Task Priority::
25045 * External Interrupts::
25048 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25049 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25052 On OpenVMS Alpha systems, each Ada task (except a passive
25053 task) is implemented as a single stream of execution
25054 that is created and managed by the kernel. On these
25055 systems, HP Ada tasking support is based on DECthreads,
25056 an implementation of the POSIX standard for threads.
25058 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
25059 code that calls DECthreads routines can be used together.
25060 The interaction between Ada tasks and DECthreads routines
25061 can have some benefits. For example when on OpenVMS Alpha,
25062 HP Ada can call C code that is already threaded.
25064 GNAT uses the facilities of DECthreads,
25065 and Ada tasks are mapped to threads.
25067 @node Assigning Task IDs
25068 @subsection Assigning Task IDs
25071 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
25072 the environment task that executes the main program. On
25073 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
25074 that have been created but are not yet activated.
25076 On OpenVMS Alpha systems, task IDs are assigned at
25077 activation. On GNAT systems, task IDs are also assigned at
25078 task creation but do not have the same form or values as
25079 task ID values in HP Ada. There is no null task, and the
25080 environment task does not have a specific task ID value.
25082 @node Task IDs and Delays
25083 @subsection Task IDs and Delays
25086 On OpenVMS Alpha systems, tasking delays are implemented
25087 using Timer System Services. The Task ID is used for the
25088 identification of the timer request (the @code{REQIDT} parameter).
25089 If Timers are used in the application take care not to use
25090 @code{0} for the identification, because cancelling such a timer
25091 will cancel all timers and may lead to unpredictable results.
25093 @node Task-Related Pragmas
25094 @subsection Task-Related Pragmas
25097 Ada supplies the pragma @code{TASK_STORAGE}, which allows
25098 specification of the size of the guard area for a task
25099 stack. (The guard area forms an area of memory that has no
25100 read or write access and thus helps in the detection of
25101 stack overflow.) On OpenVMS Alpha systems, if the pragma
25102 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
25103 area is created. In the absence of a pragma @code{TASK_STORAGE},
25104 a default guard area is created.
25106 GNAT supplies the following task-related pragmas:
25109 @item @code{TASK_INFO}
25111 This pragma appears within a task definition and
25112 applies to the task in which it appears. The argument
25113 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
25115 @item @code{TASK_STORAGE}
25117 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
25118 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
25119 @code{SUPPRESS}, and @code{VOLATILE}.
25121 @node Scheduling and Task Priority
25122 @subsection Scheduling and Task Priority
25125 HP Ada implements the Ada language requirement that
25126 when two tasks are eligible for execution and they have
25127 different priorities, the lower priority task does not
25128 execute while the higher priority task is waiting. The HP
25129 Ada Run-Time Library keeps a task running until either the
25130 task is suspended or a higher priority task becomes ready.
25132 On OpenVMS Alpha systems, the default strategy is round-
25133 robin with preemption. Tasks of equal priority take turns
25134 at the processor. A task is run for a certain period of
25135 time and then placed at the tail of the ready queue for
25136 its priority level.
25138 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
25139 which can be used to enable or disable round-robin
25140 scheduling of tasks with the same priority.
25141 See the relevant HP Ada run-time reference manual for
25142 information on using the pragmas to control HP Ada task
25145 GNAT follows the scheduling rules of Annex D (Real-Time
25146 Annex) of the @cite{Ada Reference Manual}. In general, this
25147 scheduling strategy is fully compatible with HP Ada
25148 although it provides some additional constraints (as
25149 fully documented in Annex D).
25150 GNAT implements time slicing control in a manner compatible with
25151 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
25152 are identical to the HP Ada 83 pragma of the same name.
25153 Note that it is not possible to mix GNAT tasking and
25154 HP Ada 83 tasking in the same program, since the two run-time
25155 libraries are not compatible.
25157 @node The Task Stack
25158 @subsection The Task Stack
25161 In HP Ada, a task stack is allocated each time a
25162 non-passive task is activated. As soon as the task is
25163 terminated, the storage for the task stack is deallocated.
25164 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
25165 a default stack size is used. Also, regardless of the size
25166 specified, some additional space is allocated for task
25167 management purposes. On OpenVMS Alpha systems, at least
25168 one page is allocated.
25170 GNAT handles task stacks in a similar manner. In accordance with
25171 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
25172 an alternative method for controlling the task stack size.
25173 The specification of the attribute @code{T'STORAGE_SIZE} is also
25174 supported in a manner compatible with HP Ada.
25176 @node External Interrupts
25177 @subsection External Interrupts
25180 On HP Ada, external interrupts can be associated with task entries.
25181 GNAT is compatible with HP Ada in its handling of external interrupts.
25183 @node Pragmas and Pragma-Related Features
25184 @section Pragmas and Pragma-Related Features
25187 Both HP Ada and GNAT supply all language-defined pragmas
25188 as specified by the Ada 83 standard. GNAT also supplies all
25189 language-defined pragmas introduced by Ada 95 and Ada 2005.
25190 In addition, GNAT implements the implementation-defined pragmas
25194 @item @code{AST_ENTRY}
25196 @item @code{COMMON_OBJECT}
25198 @item @code{COMPONENT_ALIGNMENT}
25200 @item @code{EXPORT_EXCEPTION}
25202 @item @code{EXPORT_FUNCTION}
25204 @item @code{EXPORT_OBJECT}
25206 @item @code{EXPORT_PROCEDURE}
25208 @item @code{EXPORT_VALUED_PROCEDURE}
25210 @item @code{FLOAT_REPRESENTATION}
25214 @item @code{IMPORT_EXCEPTION}
25216 @item @code{IMPORT_FUNCTION}
25218 @item @code{IMPORT_OBJECT}
25220 @item @code{IMPORT_PROCEDURE}
25222 @item @code{IMPORT_VALUED_PROCEDURE}
25224 @item @code{INLINE_GENERIC}
25226 @item @code{INTERFACE_NAME}
25228 @item @code{LONG_FLOAT}
25230 @item @code{MAIN_STORAGE}
25232 @item @code{PASSIVE}
25234 @item @code{PSECT_OBJECT}
25236 @item @code{SHARE_GENERIC}
25238 @item @code{SUPPRESS_ALL}
25240 @item @code{TASK_STORAGE}
25242 @item @code{TIME_SLICE}
25248 These pragmas are all fully implemented, with the exception of @code{TITLE},
25249 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
25250 recognized, but which have no
25251 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
25252 use of Ada protected objects. In GNAT, all generics are inlined.
25254 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
25255 a separate subprogram specification which must appear before the
25258 GNAT also supplies a number of implementation-defined pragmas as follows:
25260 @item @code{ABORT_DEFER}
25262 @item @code{ADA_83}
25264 @item @code{ADA_95}
25266 @item @code{ADA_05}
25268 @item @code{ANNOTATE}
25270 @item @code{ASSERT}
25272 @item @code{C_PASS_BY_COPY}
25274 @item @code{CPP_CLASS}
25276 @item @code{CPP_CONSTRUCTOR}
25278 @item @code{CPP_DESTRUCTOR}
25282 @item @code{EXTEND_SYSTEM}
25284 @item @code{LINKER_ALIAS}
25286 @item @code{LINKER_SECTION}
25288 @item @code{MACHINE_ATTRIBUTE}
25290 @item @code{NO_RETURN}
25292 @item @code{PURE_FUNCTION}
25294 @item @code{SOURCE_FILE_NAME}
25296 @item @code{SOURCE_REFERENCE}
25298 @item @code{TASK_INFO}
25300 @item @code{UNCHECKED_UNION}
25302 @item @code{UNIMPLEMENTED_UNIT}
25304 @item @code{UNIVERSAL_DATA}
25306 @item @code{UNSUPPRESS}
25308 @item @code{WARNINGS}
25310 @item @code{WEAK_EXTERNAL}
25314 For full details on these GNAT implementation-defined pragmas,
25315 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
25319 * Restrictions on the Pragma INLINE::
25320 * Restrictions on the Pragma INTERFACE::
25321 * Restrictions on the Pragma SYSTEM_NAME::
25324 @node Restrictions on the Pragma INLINE
25325 @subsection Restrictions on Pragma @code{INLINE}
25328 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
25330 @item Parameters cannot have a task type.
25332 @item Function results cannot be task types, unconstrained
25333 array types, or unconstrained types with discriminants.
25335 @item Bodies cannot declare the following:
25337 @item Subprogram body or stub (imported subprogram is allowed)
25341 @item Generic declarations
25343 @item Instantiations
25347 @item Access types (types derived from access types allowed)
25349 @item Array or record types
25351 @item Dependent tasks
25353 @item Direct recursive calls of subprogram or containing
25354 subprogram, directly or via a renaming
25360 In GNAT, the only restriction on pragma @code{INLINE} is that the
25361 body must occur before the call if both are in the same
25362 unit, and the size must be appropriately small. There are
25363 no other specific restrictions which cause subprograms to
25364 be incapable of being inlined.
25366 @node Restrictions on the Pragma INTERFACE
25367 @subsection Restrictions on Pragma @code{INTERFACE}
25370 The following restrictions on pragma @code{INTERFACE}
25371 are enforced by both HP Ada and GNAT:
25373 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
25374 Default is the default on OpenVMS Alpha systems.
25376 @item Parameter passing: Language specifies default
25377 mechanisms but can be overridden with an @code{EXPORT} pragma.
25380 @item Ada: Use internal Ada rules.
25382 @item Bliss, C: Parameters must be mode @code{in}; cannot be
25383 record or task type. Result cannot be a string, an
25384 array, or a record.
25386 @item Fortran: Parameters cannot have a task type. Result cannot
25387 be a string, an array, or a record.
25392 GNAT is entirely upwards compatible with HP Ada, and in addition allows
25393 record parameters for all languages.
25395 @node Restrictions on the Pragma SYSTEM_NAME
25396 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
25399 For HP Ada for OpenVMS Alpha, the enumeration literal
25400 for the type @code{NAME} is @code{OPENVMS_AXP}.
25401 In GNAT, the enumeration
25402 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
25404 @node Library of Predefined Units
25405 @section Library of Predefined Units
25408 A library of predefined units is provided as part of the
25409 HP Ada and GNAT implementations. HP Ada does not provide
25410 the package @code{MACHINE_CODE} but instead recommends importing
25413 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
25414 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
25416 The HP Ada Predefined Library units are modified to remove post-Ada 83
25417 incompatibilities and to make them interoperable with GNAT
25418 (@pxref{Changes to DECLIB}, for details).
25419 The units are located in the @file{DECLIB} directory.
25421 The GNAT RTL is contained in
25422 the @file{ADALIB} directory, and
25423 the default search path is set up to find @code{DECLIB} units in preference
25424 to @code{ADALIB} units with the same name (@code{TEXT_IO},
25425 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
25428 * Changes to DECLIB::
25431 @node Changes to DECLIB
25432 @subsection Changes to @code{DECLIB}
25435 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
25436 compatibility are minor and include the following:
25439 @item Adjusting the location of pragmas and record representation
25440 clauses to obey Ada 95 (and thus Ada 2005) rules
25442 @item Adding the proper notation to generic formal parameters
25443 that take unconstrained types in instantiation
25445 @item Adding pragma @code{ELABORATE_BODY} to package specs
25446 that have package bodies not otherwise allowed
25448 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
25449 ``@code{PROTECTD}''.
25450 Currently these are found only in the @code{STARLET} package spec.
25452 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
25453 where the address size is constrained to 32 bits.
25457 None of the above changes is visible to users.
25463 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
25466 @item Command Language Interpreter (CLI interface)
25468 @item DECtalk Run-Time Library (DTK interface)
25470 @item Librarian utility routines (LBR interface)
25472 @item General Purpose Run-Time Library (LIB interface)
25474 @item Math Run-Time Library (MTH interface)
25476 @item National Character Set Run-Time Library (NCS interface)
25478 @item Compiled Code Support Run-Time Library (OTS interface)
25480 @item Parallel Processing Run-Time Library (PPL interface)
25482 @item Screen Management Run-Time Library (SMG interface)
25484 @item Sort Run-Time Library (SOR interface)
25486 @item String Run-Time Library (STR interface)
25488 @item STARLET System Library
25491 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
25493 @item X Windows Toolkit (XT interface)
25495 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
25499 GNAT provides implementations of these HP bindings in the @code{DECLIB}
25500 directory, on both the Alpha and I64 OpenVMS platforms.
25502 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
25504 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
25505 A pragma @code{Linker_Options} has been added to packages @code{Xm},
25506 @code{Xt}, and @code{X_Lib}
25507 causing the default X/Motif sharable image libraries to be linked in. This
25508 is done via options files named @file{xm.opt}, @file{xt.opt}, and
25509 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
25511 It may be necessary to edit these options files to update or correct the
25512 library names if, for example, the newer X/Motif bindings from
25513 @file{ADA$EXAMPLES}
25514 had been (previous to installing GNAT) copied and renamed to supersede the
25515 default @file{ADA$PREDEFINED} versions.
25518 * Shared Libraries and Options Files::
25519 * Interfaces to C::
25522 @node Shared Libraries and Options Files
25523 @subsection Shared Libraries and Options Files
25526 When using the HP Ada
25527 predefined X and Motif bindings, the linking with their sharable images is
25528 done automatically by @command{GNAT LINK}.
25529 When using other X and Motif bindings, you need
25530 to add the corresponding sharable images to the command line for
25531 @code{GNAT LINK}. When linking with shared libraries, or with
25532 @file{.OPT} files, you must
25533 also add them to the command line for @command{GNAT LINK}.
25535 A shared library to be used with GNAT is built in the same way as other
25536 libraries under VMS. The VMS Link command can be used in standard fashion.
25538 @node Interfaces to C
25539 @subsection Interfaces to C
25543 provides the following Ada types and operations:
25546 @item C types package (@code{C_TYPES})
25548 @item C strings (@code{C_TYPES.NULL_TERMINATED})
25550 @item Other_types (@code{SHORT_INT})
25554 Interfacing to C with GNAT, you can use the above approach
25555 described for HP Ada or the facilities of Annex B of
25556 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
25557 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
25558 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
25560 The @option{-gnatF} qualifier forces default and explicit
25561 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
25562 to be uppercased for compatibility with the default behavior
25563 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
25565 @node Main Program Definition
25566 @section Main Program Definition
25569 The following section discusses differences in the
25570 definition of main programs on HP Ada and GNAT.
25571 On HP Ada, main programs are defined to meet the
25572 following conditions:
25574 @item Procedure with no formal parameters (returns @code{0} upon
25577 @item Procedure with no formal parameters (returns @code{42} when
25578 an unhandled exception is raised)
25580 @item Function with no formal parameters whose returned value
25581 is of a discrete type
25583 @item Procedure with one @code{out} formal of a discrete type for
25584 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
25589 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
25590 a main function or main procedure returns a discrete
25591 value whose size is less than 64 bits (32 on VAX systems),
25592 the value is zero- or sign-extended as appropriate.
25593 On GNAT, main programs are defined as follows:
25595 @item Must be a non-generic, parameterless subprogram that
25596 is either a procedure or function returning an Ada
25597 @code{STANDARD.INTEGER} (the predefined type)
25599 @item Cannot be a generic subprogram or an instantiation of a
25603 @node Implementation-Defined Attributes
25604 @section Implementation-Defined Attributes
25607 GNAT provides all HP Ada implementation-defined
25610 @node Compiler and Run-Time Interfacing
25611 @section Compiler and Run-Time Interfacing
25614 HP Ada provides the following qualifiers to pass options to the linker
25617 @item @option{/WAIT} and @option{/SUBMIT}
25619 @item @option{/COMMAND}
25621 @item @option{/@r{[}NO@r{]}MAP}
25623 @item @option{/OUTPUT=@var{file-spec}}
25625 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25629 To pass options to the linker, GNAT provides the following
25633 @item @option{/EXECUTABLE=@var{exec-name}}
25635 @item @option{/VERBOSE}
25637 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25641 For more information on these switches, see
25642 @ref{Switches for gnatlink}.
25643 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
25644 to control optimization. HP Ada also supplies the
25647 @item @code{OPTIMIZE}
25649 @item @code{INLINE}
25651 @item @code{INLINE_GENERIC}
25653 @item @code{SUPPRESS_ALL}
25655 @item @code{PASSIVE}
25659 In GNAT, optimization is controlled strictly by command
25660 line parameters, as described in the corresponding section of this guide.
25661 The HP pragmas for control of optimization are
25662 recognized but ignored.
25664 Note that in GNAT, the default is optimization off, whereas in HP Ada
25665 the default is that optimization is turned on.
25667 @node Program Compilation and Library Management
25668 @section Program Compilation and Library Management
25671 HP Ada and GNAT provide a comparable set of commands to
25672 build programs. HP Ada also provides a program library,
25673 which is a concept that does not exist on GNAT. Instead,
25674 GNAT provides directories of sources that are compiled as
25677 The following table summarizes
25678 the HP Ada commands and provides
25679 equivalent GNAT commands. In this table, some GNAT
25680 equivalents reflect the fact that GNAT does not use the
25681 concept of a program library. Instead, it uses a model
25682 in which collections of source and object files are used
25683 in a manner consistent with other languages like C and
25684 Fortran. Therefore, standard system file commands are used
25685 to manipulate these elements. Those GNAT commands are marked with
25687 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
25690 @multitable @columnfractions .35 .65
25692 @item @emph{HP Ada Command}
25693 @tab @emph{GNAT Equivalent / Description}
25695 @item @command{ADA}
25696 @tab @command{GNAT COMPILE}@*
25697 Invokes the compiler to compile one or more Ada source files.
25699 @item @command{ACS ATTACH}@*
25700 @tab [No equivalent]@*
25701 Switches control of terminal from current process running the program
25704 @item @command{ACS CHECK}
25705 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
25706 Forms the execution closure of one
25707 or more compiled units and checks completeness and currency.
25709 @item @command{ACS COMPILE}
25710 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25711 Forms the execution closure of one or
25712 more specified units, checks completeness and currency,
25713 identifies units that have revised source files, compiles same,
25714 and recompiles units that are or will become obsolete.
25715 Also completes incomplete generic instantiations.
25717 @item @command{ACS COPY FOREIGN}
25719 Copies a foreign object file into the program library as a
25722 @item @command{ACS COPY UNIT}
25724 Copies a compiled unit from one program library to another.
25726 @item @command{ACS CREATE LIBRARY}
25727 @tab Create /directory (*)@*
25728 Creates a program library.
25730 @item @command{ACS CREATE SUBLIBRARY}
25731 @tab Create /directory (*)@*
25732 Creates a program sublibrary.
25734 @item @command{ACS DELETE LIBRARY}
25736 Deletes a program library and its contents.
25738 @item @command{ACS DELETE SUBLIBRARY}
25740 Deletes a program sublibrary and its contents.
25742 @item @command{ACS DELETE UNIT}
25743 @tab Delete file (*)@*
25744 On OpenVMS systems, deletes one or more compiled units from
25745 the current program library.
25747 @item @command{ACS DIRECTORY}
25748 @tab Directory (*)@*
25749 On OpenVMS systems, lists units contained in the current
25752 @item @command{ACS ENTER FOREIGN}
25754 Allows the import of a foreign body as an Ada library
25755 spec and enters a reference to a pointer.
25757 @item @command{ACS ENTER UNIT}
25759 Enters a reference (pointer) from the current program library to
25760 a unit compiled into another program library.
25762 @item @command{ACS EXIT}
25763 @tab [No equivalent]@*
25764 Exits from the program library manager.
25766 @item @command{ACS EXPORT}
25768 Creates an object file that contains system-specific object code
25769 for one or more units. With GNAT, object files can simply be copied
25770 into the desired directory.
25772 @item @command{ACS EXTRACT SOURCE}
25774 Allows access to the copied source file for each Ada compilation unit
25776 @item @command{ACS HELP}
25777 @tab @command{HELP GNAT}@*
25778 Provides online help.
25780 @item @command{ACS LINK}
25781 @tab @command{GNAT LINK}@*
25782 Links an object file containing Ada units into an executable file.
25784 @item @command{ACS LOAD}
25786 Loads (partially compiles) Ada units into the program library.
25787 Allows loading a program from a collection of files into a library
25788 without knowing the relationship among units.
25790 @item @command{ACS MERGE}
25792 Merges into the current program library, one or more units from
25793 another library where they were modified.
25795 @item @command{ACS RECOMPILE}
25796 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25797 Recompiles from external or copied source files any obsolete
25798 unit in the closure. Also, completes any incomplete generic
25801 @item @command{ACS REENTER}
25802 @tab @command{GNAT MAKE}@*
25803 Reenters current references to units compiled after last entered
25804 with the @command{ACS ENTER UNIT} command.
25806 @item @command{ACS SET LIBRARY}
25807 @tab Set default (*)@*
25808 Defines a program library to be the compilation context as well
25809 as the target library for compiler output and commands in general.
25811 @item @command{ACS SET PRAGMA}
25812 @tab Edit @file{gnat.adc} (*)@*
25813 Redefines specified values of the library characteristics
25814 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
25815 and @code{Float_Representation}.
25817 @item @command{ACS SET SOURCE}
25818 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
25819 Defines the source file search list for the @command{ACS COMPILE} command.
25821 @item @command{ACS SHOW LIBRARY}
25822 @tab Directory (*)@*
25823 Lists information about one or more program libraries.
25825 @item @command{ACS SHOW PROGRAM}
25826 @tab [No equivalent]@*
25827 Lists information about the execution closure of one or
25828 more units in the program library.
25830 @item @command{ACS SHOW SOURCE}
25831 @tab Show logical @code{ADA_INCLUDE_PATH}@*
25832 Shows the source file search used when compiling units.
25834 @item @command{ACS SHOW VERSION}
25835 @tab Compile with @option{VERBOSE} option
25836 Displays the version number of the compiler and program library
25839 @item @command{ACS SPAWN}
25840 @tab [No equivalent]@*
25841 Creates a subprocess of the current process (same as @command{DCL SPAWN}
25844 @item @command{ACS VERIFY}
25845 @tab [No equivalent]@*
25846 Performs a series of consistency checks on a program library to
25847 determine whether the library structure and library files are in
25854 @section Input-Output
25857 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
25858 Management Services (RMS) to perform operations on
25862 HP Ada and GNAT predefine an identical set of input-
25863 output packages. To make the use of the
25864 generic @code{TEXT_IO} operations more convenient, HP Ada
25865 provides predefined library packages that instantiate the
25866 integer and floating-point operations for the predefined
25867 integer and floating-point types as shown in the following table.
25869 @multitable @columnfractions .45 .55
25870 @item @emph{Package Name} @tab Instantiation
25872 @item @code{INTEGER_TEXT_IO}
25873 @tab @code{INTEGER_IO(INTEGER)}
25875 @item @code{SHORT_INTEGER_TEXT_IO}
25876 @tab @code{INTEGER_IO(SHORT_INTEGER)}
25878 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
25879 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
25881 @item @code{FLOAT_TEXT_IO}
25882 @tab @code{FLOAT_IO(FLOAT)}
25884 @item @code{LONG_FLOAT_TEXT_IO}
25885 @tab @code{FLOAT_IO(LONG_FLOAT)}
25889 The HP Ada predefined packages and their operations
25890 are implemented using OpenVMS Alpha files and input-output
25891 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
25892 Familiarity with the following is recommended:
25894 @item RMS file organizations and access methods
25896 @item OpenVMS file specifications and directories
25898 @item OpenVMS File Definition Language (FDL)
25902 GNAT provides I/O facilities that are completely
25903 compatible with HP Ada. The distribution includes the
25904 standard HP Ada versions of all I/O packages, operating
25905 in a manner compatible with HP Ada. In particular, the
25906 following packages are by default the HP Ada (Ada 83)
25907 versions of these packages rather than the renamings
25908 suggested in Annex J of the Ada Reference Manual:
25910 @item @code{TEXT_IO}
25912 @item @code{SEQUENTIAL_IO}
25914 @item @code{DIRECT_IO}
25918 The use of the standard child package syntax (for
25919 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
25921 GNAT provides HP-compatible predefined instantiations
25922 of the @code{TEXT_IO} packages, and also
25923 provides the standard predefined instantiations required
25924 by the @cite{Ada Reference Manual}.
25926 For further information on how GNAT interfaces to the file
25927 system or how I/O is implemented in programs written in
25928 mixed languages, see @ref{Implementation of the Standard I/O,,,
25929 gnat_rm, GNAT Reference Manual}.
25930 This chapter covers the following:
25932 @item Standard I/O packages
25934 @item @code{FORM} strings
25936 @item @code{ADA.DIRECT_IO}
25938 @item @code{ADA.SEQUENTIAL_IO}
25940 @item @code{ADA.TEXT_IO}
25942 @item Stream pointer positioning
25944 @item Reading and writing non-regular files
25946 @item @code{GET_IMMEDIATE}
25948 @item Treating @code{TEXT_IO} files as streams
25955 @node Implementation Limits
25956 @section Implementation Limits
25959 The following table lists implementation limits for HP Ada
25961 @multitable @columnfractions .60 .20 .20
25963 @item @emph{Compilation Parameter}
25968 @item In a subprogram or entry declaration, maximum number of
25969 formal parameters that are of an unconstrained record type
25974 @item Maximum identifier length (number of characters)
25979 @item Maximum number of characters in a source line
25984 @item Maximum collection size (number of bytes)
25989 @item Maximum number of discriminants for a record type
25994 @item Maximum number of formal parameters in an entry or
25995 subprogram declaration
26000 @item Maximum number of dimensions in an array type
26005 @item Maximum number of library units and subunits in a compilation.
26010 @item Maximum number of library units and subunits in an execution.
26015 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
26016 or @code{PSECT_OBJECT}
26021 @item Maximum number of enumeration literals in an enumeration type
26027 @item Maximum number of lines in a source file
26032 @item Maximum number of bits in any object
26037 @item Maximum size of the static portion of a stack frame (approximate)
26042 @node Tools and Utilities
26043 @section Tools and Utilities
26046 The following table lists some of the OpenVMS development tools
26047 available for HP Ada, and the corresponding tools for
26048 use with @value{EDITION} on Alpha and I64 platforms.
26049 Aside from the debugger, all the OpenVMS tools identified are part
26050 of the DECset package.
26053 @c Specify table in TeX since Texinfo does a poor job
26057 \settabs\+Language-Sensitive Editor\quad
26058 &Product with HP Ada\quad
26061 &\it Product with HP Ada
26062 & \it Product with GNAT Pro\cr
26064 \+Code Management System
26068 \+Language-Sensitive Editor
26070 & emacs or HP LSE (Alpha)\cr
26080 & OpenVMS Debug (I64)\cr
26082 \+Source Code Analyzer /
26099 \+Coverage Analyzer
26103 \+Module Management
26105 & Not applicable\cr
26115 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
26116 @c the TeX version above for the printed version
26118 @c @multitable @columnfractions .3 .4 .4
26119 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
26121 @tab @i{Tool with HP Ada}
26122 @tab @i{Tool with @value{EDITION}}
26123 @item Code Management@*System
26126 @item Language-Sensitive@*Editor
26128 @tab emacs or HP LSE (Alpha)
26137 @tab OpenVMS Debug (I64)
26138 @item Source Code Analyzer /@*Cross Referencer
26142 @tab HP Digital Test@*Manager (DTM)
26144 @item Performance and@*Coverage Analyzer
26147 @item Module Management@*System
26149 @tab Not applicable
26156 @c **************************************
26157 @node Platform-Specific Information for the Run-Time Libraries
26158 @appendix Platform-Specific Information for the Run-Time Libraries
26159 @cindex Tasking and threads libraries
26160 @cindex Threads libraries and tasking
26161 @cindex Run-time libraries (platform-specific information)
26164 The GNAT run-time implementation may vary with respect to both the
26165 underlying threads library and the exception handling scheme.
26166 For threads support, one or more of the following are supplied:
26168 @item @b{native threads library}, a binding to the thread package from
26169 the underlying operating system
26171 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
26172 POSIX thread package
26176 For exception handling, either or both of two models are supplied:
26178 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
26179 Most programs should experience a substantial speed improvement by
26180 being compiled with a ZCX run-time.
26181 This is especially true for
26182 tasking applications or applications with many exception handlers.}
26183 @cindex Zero-Cost Exceptions
26184 @cindex ZCX (Zero-Cost Exceptions)
26185 which uses binder-generated tables that
26186 are interrogated at run time to locate a handler
26188 @item @b{setjmp / longjmp} (``SJLJ''),
26189 @cindex setjmp/longjmp Exception Model
26190 @cindex SJLJ (setjmp/longjmp Exception Model)
26191 which uses dynamically-set data to establish
26192 the set of handlers
26196 This appendix summarizes which combinations of threads and exception support
26197 are supplied on various GNAT platforms.
26198 It then shows how to select a particular library either
26199 permanently or temporarily,
26200 explains the properties of (and tradeoffs among) the various threads
26201 libraries, and provides some additional
26202 information about several specific platforms.
26205 * Summary of Run-Time Configurations::
26206 * Specifying a Run-Time Library::
26207 * Choosing the Scheduling Policy::
26208 * Solaris-Specific Considerations::
26209 * Linux-Specific Considerations::
26210 * AIX-Specific Considerations::
26211 * Irix-Specific Considerations::
26212 * RTX-Specific Considerations::
26215 @node Summary of Run-Time Configurations
26216 @section Summary of Run-Time Configurations
26218 @multitable @columnfractions .30 .70
26219 @item @b{alpha-openvms}
26220 @item @code{@ @ }@i{rts-native (default)}
26221 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26222 @item @code{@ @ @ @ }Exceptions @tab ZCX
26224 @item @b{alpha-tru64}
26225 @item @code{@ @ }@i{rts-native (default)}
26226 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26227 @item @code{@ @ @ @ }Exceptions @tab ZCX
26229 @item @code{@ @ }@i{rts-sjlj}
26230 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26231 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26233 @item @b{ia64-hp_linux}
26234 @item @code{@ @ }@i{rts-native (default)}
26235 @item @code{@ @ @ @ }Tasking @tab pthread library
26236 @item @code{@ @ @ @ }Exceptions @tab ZCX
26238 @item @b{ia64-hpux}
26239 @item @code{@ @ }@i{rts-native (default)}
26240 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26241 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26243 @item @b{ia64-openvms}
26244 @item @code{@ @ }@i{rts-native (default)}
26245 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26246 @item @code{@ @ @ @ }Exceptions @tab ZCX
26248 @item @b{ia64-sgi_linux}
26249 @item @code{@ @ }@i{rts-native (default)}
26250 @item @code{@ @ @ @ }Tasking @tab pthread library
26251 @item @code{@ @ @ @ }Exceptions @tab ZCX
26253 @item @b{mips-irix}
26254 @item @code{@ @ }@i{rts-native (default)}
26255 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
26256 @item @code{@ @ @ @ }Exceptions @tab ZCX
26259 @item @code{@ @ }@i{rts-native (default)}
26260 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26261 @item @code{@ @ @ @ }Exceptions @tab ZCX
26263 @item @code{@ @ }@i{rts-sjlj}
26264 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26265 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26268 @item @code{@ @ }@i{rts-native (default)}
26269 @item @code{@ @ @ @ }Tasking @tab native AIX threads
26270 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26272 @item @b{ppc-darwin}
26273 @item @code{@ @ }@i{rts-native (default)}
26274 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
26275 @item @code{@ @ @ @ }Exceptions @tab ZCX
26277 @item @b{sparc-solaris} @tab
26278 @item @code{@ @ }@i{rts-native (default)}
26279 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26280 @item @code{@ @ @ @ }Exceptions @tab ZCX
26282 @item @code{@ @ }@i{rts-pthread}
26283 @item @code{@ @ @ @ }Tasking @tab pthread library
26284 @item @code{@ @ @ @ }Exceptions @tab ZCX
26286 @item @code{@ @ }@i{rts-sjlj}
26287 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26288 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26290 @item @b{sparc64-solaris} @tab
26291 @item @code{@ @ }@i{rts-native (default)}
26292 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26293 @item @code{@ @ @ @ }Exceptions @tab ZCX
26295 @item @b{x86-linux}
26296 @item @code{@ @ }@i{rts-native (default)}
26297 @item @code{@ @ @ @ }Tasking @tab pthread library
26298 @item @code{@ @ @ @ }Exceptions @tab ZCX
26300 @item @code{@ @ }@i{rts-sjlj}
26301 @item @code{@ @ @ @ }Tasking @tab pthread library
26302 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26305 @item @code{@ @ }@i{rts-native (default)}
26306 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
26307 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26309 @item @b{x86-solaris}
26310 @item @code{@ @ }@i{rts-native (default)}
26311 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
26312 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26314 @item @b{x86-windows}
26315 @item @code{@ @ }@i{rts-native (default)}
26316 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26317 @item @code{@ @ @ @ }Exceptions @tab ZCX
26319 @item @code{@ @ }@i{rts-sjlj (default)}
26320 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26321 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26323 @item @b{x86-windows-rtx}
26324 @item @code{@ @ }@i{rts-rtx-rtss (default)}
26325 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
26326 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26328 @item @code{@ @ }@i{rts-rtx-w32}
26329 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
26330 @item @code{@ @ @ @ }Exceptions @tab ZCX
26332 @item @b{x86_64-linux}
26333 @item @code{@ @ }@i{rts-native (default)}
26334 @item @code{@ @ @ @ }Tasking @tab pthread library
26335 @item @code{@ @ @ @ }Exceptions @tab ZCX
26337 @item @code{@ @ }@i{rts-sjlj}
26338 @item @code{@ @ @ @ }Tasking @tab pthread library
26339 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26343 @node Specifying a Run-Time Library
26344 @section Specifying a Run-Time Library
26347 The @file{adainclude} subdirectory containing the sources of the GNAT
26348 run-time library, and the @file{adalib} subdirectory containing the
26349 @file{ALI} files and the static and/or shared GNAT library, are located
26350 in the gcc target-dependent area:
26353 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
26357 As indicated above, on some platforms several run-time libraries are supplied.
26358 These libraries are installed in the target dependent area and
26359 contain a complete source and binary subdirectory. The detailed description
26360 below explains the differences between the different libraries in terms of
26361 their thread support.
26363 The default run-time library (when GNAT is installed) is @emph{rts-native}.
26364 This default run time is selected by the means of soft links.
26365 For example on x86-linux:
26371 +--- adainclude----------+
26373 +--- adalib-----------+ |
26375 +--- rts-native | |
26377 | +--- adainclude <---+
26379 | +--- adalib <----+
26390 If the @i{rts-sjlj} library is to be selected on a permanent basis,
26391 these soft links can be modified with the following commands:
26395 $ rm -f adainclude adalib
26396 $ ln -s rts-sjlj/adainclude adainclude
26397 $ ln -s rts-sjlj/adalib adalib
26401 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
26402 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
26403 @file{$target/ada_object_path}.
26405 Selecting another run-time library temporarily can be
26406 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
26407 @cindex @option{--RTS} option
26409 @node Choosing the Scheduling Policy
26410 @section Choosing the Scheduling Policy
26413 When using a POSIX threads implementation, you have a choice of several
26414 scheduling policies: @code{SCHED_FIFO},
26415 @cindex @code{SCHED_FIFO} scheduling policy
26417 @cindex @code{SCHED_RR} scheduling policy
26418 and @code{SCHED_OTHER}.
26419 @cindex @code{SCHED_OTHER} scheduling policy
26420 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
26421 or @code{SCHED_RR} requires special (e.g., root) privileges.
26423 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
26425 @cindex @code{SCHED_FIFO} scheduling policy
26426 you can use one of the following:
26430 @code{pragma Time_Slice (0.0)}
26431 @cindex pragma Time_Slice
26433 the corresponding binder option @option{-T0}
26434 @cindex @option{-T0} option
26436 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
26437 @cindex pragma Task_Dispatching_Policy
26441 To specify @code{SCHED_RR},
26442 @cindex @code{SCHED_RR} scheduling policy
26443 you should use @code{pragma Time_Slice} with a
26444 value greater than @code{0.0}, or else use the corresponding @option{-T}
26447 @node Solaris-Specific Considerations
26448 @section Solaris-Specific Considerations
26449 @cindex Solaris Sparc threads libraries
26452 This section addresses some topics related to the various threads libraries
26456 * Solaris Threads Issues::
26459 @node Solaris Threads Issues
26460 @subsection Solaris Threads Issues
26463 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
26464 library based on POSIX threads --- @emph{rts-pthread}.
26465 @cindex rts-pthread threads library
26466 This run-time library has the advantage of being mostly shared across all
26467 POSIX-compliant thread implementations, and it also provides under
26468 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
26469 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
26470 and @code{PTHREAD_PRIO_PROTECT}
26471 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
26472 semantics that can be selected using the predefined pragma
26473 @code{Locking_Policy}
26474 @cindex pragma Locking_Policy (under rts-pthread)
26476 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
26477 @cindex @code{Inheritance_Locking} (under rts-pthread)
26478 @cindex @code{Ceiling_Locking} (under rts-pthread)
26480 As explained above, the native run-time library is based on the Solaris thread
26481 library (@code{libthread}) and is the default library.
26483 When the Solaris threads library is used (this is the default), programs
26484 compiled with GNAT can automatically take advantage of
26485 and can thus execute on multiple processors.
26486 The user can alternatively specify a processor on which the program should run
26487 to emulate a single-processor system. The multiprocessor / uniprocessor choice
26489 setting the environment variable @env{GNAT_PROCESSOR}
26490 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
26491 to one of the following:
26495 Use the default configuration (run the program on all
26496 available processors) - this is the same as having @code{GNAT_PROCESSOR}
26500 Let the run-time implementation choose one processor and run the program on
26503 @item 0 .. Last_Proc
26504 Run the program on the specified processor.
26505 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
26506 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
26509 @node Linux-Specific Considerations
26510 @section Linux-Specific Considerations
26511 @cindex Linux threads libraries
26514 On GNU/Linux without NPTL support (usually system with GNU C Library
26515 older than 2.3), the signal model is not POSIX compliant, which means
26516 that to send a signal to the process, you need to send the signal to all
26517 threads, e.g.@: by using @code{killpg()}.
26519 @node AIX-Specific Considerations
26520 @section AIX-Specific Considerations
26521 @cindex AIX resolver library
26524 On AIX, the resolver library initializes some internal structure on
26525 the first call to @code{get*by*} functions, which are used to implement
26526 @code{GNAT.Sockets.Get_Host_By_Name} and
26527 @code{GNAT.Sockets.Get_Host_By_Address}.
26528 If such initialization occurs within an Ada task, and the stack size for
26529 the task is the default size, a stack overflow may occur.
26531 To avoid this overflow, the user should either ensure that the first call
26532 to @code{GNAT.Sockets.Get_Host_By_Name} or
26533 @code{GNAT.Sockets.Get_Host_By_Addrss}
26534 occurs in the environment task, or use @code{pragma Storage_Size} to
26535 specify a sufficiently large size for the stack of the task that contains
26538 @node Irix-Specific Considerations
26539 @section Irix-Specific Considerations
26540 @cindex Irix libraries
26543 The GCC support libraries coming with the Irix compiler have moved to
26544 their canonical place with respect to the general Irix ABI related
26545 conventions. Running applications built with the default shared GNAT
26546 run-time now requires the LD_LIBRARY_PATH environment variable to
26547 include this location. A possible way to achieve this is to issue the
26548 following command line on a bash prompt:
26552 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
26556 @node RTX-Specific Considerations
26557 @section RTX-Specific Considerations
26558 @cindex RTX libraries
26561 The Real-time Extension (RTX) to Windows is based on the Windows Win32
26562 API. Applications can be built to work in two different modes:
26566 Windows executables that run in Ring 3 to utilize memory protection
26567 (@emph{rts-rtx-w32}).
26570 Real-time subsystem (RTSS) executables that run in Ring 0, where
26571 performance can be optimized with RTSS applications taking precedent
26572 over all Windows applications (@emph{rts-rtx-rtss}).
26576 @c *******************************
26577 @node Example of Binder Output File
26578 @appendix Example of Binder Output File
26581 This Appendix displays the source code for @command{gnatbind}'s output
26582 file generated for a simple ``Hello World'' program.
26583 Comments have been added for clarification purposes.
26585 @smallexample @c adanocomment
26589 -- The package is called Ada_Main unless this name is actually used
26590 -- as a unit name in the partition, in which case some other unique
26594 package ada_main is
26596 Elab_Final_Code : Integer;
26597 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
26599 -- The main program saves the parameters (argument count,
26600 -- argument values, environment pointer) in global variables
26601 -- for later access by other units including
26602 -- Ada.Command_Line.
26604 gnat_argc : Integer;
26605 gnat_argv : System.Address;
26606 gnat_envp : System.Address;
26608 -- The actual variables are stored in a library routine. This
26609 -- is useful for some shared library situations, where there
26610 -- are problems if variables are not in the library.
26612 pragma Import (C, gnat_argc);
26613 pragma Import (C, gnat_argv);
26614 pragma Import (C, gnat_envp);
26616 -- The exit status is similarly an external location
26618 gnat_exit_status : Integer;
26619 pragma Import (C, gnat_exit_status);
26621 GNAT_Version : constant String :=
26622 "GNAT Version: 6.0.0w (20061115)";
26623 pragma Export (C, GNAT_Version, "__gnat_version");
26625 -- This is the generated adafinal routine that performs
26626 -- finalization at the end of execution. In the case where
26627 -- Ada is the main program, this main program makes a call
26628 -- to adafinal at program termination.
26630 procedure adafinal;
26631 pragma Export (C, adafinal, "adafinal");
26633 -- This is the generated adainit routine that performs
26634 -- initialization at the start of execution. In the case
26635 -- where Ada is the main program, this main program makes
26636 -- a call to adainit at program startup.
26639 pragma Export (C, adainit, "adainit");
26641 -- This routine is called at the start of execution. It is
26642 -- a dummy routine that is used by the debugger to breakpoint
26643 -- at the start of execution.
26645 procedure Break_Start;
26646 pragma Import (C, Break_Start, "__gnat_break_start");
26648 -- This is the actual generated main program (it would be
26649 -- suppressed if the no main program switch were used). As
26650 -- required by standard system conventions, this program has
26651 -- the external name main.
26655 argv : System.Address;
26656 envp : System.Address)
26658 pragma Export (C, main, "main");
26660 -- The following set of constants give the version
26661 -- identification values for every unit in the bound
26662 -- partition. This identification is computed from all
26663 -- dependent semantic units, and corresponds to the
26664 -- string that would be returned by use of the
26665 -- Body_Version or Version attributes.
26667 type Version_32 is mod 2 ** 32;
26668 u00001 : constant Version_32 := 16#7880BEB3#;
26669 u00002 : constant Version_32 := 16#0D24CBD0#;
26670 u00003 : constant Version_32 := 16#3283DBEB#;
26671 u00004 : constant Version_32 := 16#2359F9ED#;
26672 u00005 : constant Version_32 := 16#664FB847#;
26673 u00006 : constant Version_32 := 16#68E803DF#;
26674 u00007 : constant Version_32 := 16#5572E604#;
26675 u00008 : constant Version_32 := 16#46B173D8#;
26676 u00009 : constant Version_32 := 16#156A40CF#;
26677 u00010 : constant Version_32 := 16#033DABE0#;
26678 u00011 : constant Version_32 := 16#6AB38FEA#;
26679 u00012 : constant Version_32 := 16#22B6217D#;
26680 u00013 : constant Version_32 := 16#68A22947#;
26681 u00014 : constant Version_32 := 16#18CC4A56#;
26682 u00015 : constant Version_32 := 16#08258E1B#;
26683 u00016 : constant Version_32 := 16#367D5222#;
26684 u00017 : constant Version_32 := 16#20C9ECA4#;
26685 u00018 : constant Version_32 := 16#50D32CB6#;
26686 u00019 : constant Version_32 := 16#39A8BB77#;
26687 u00020 : constant Version_32 := 16#5CF8FA2B#;
26688 u00021 : constant Version_32 := 16#2F1EB794#;
26689 u00022 : constant Version_32 := 16#31AB6444#;
26690 u00023 : constant Version_32 := 16#1574B6E9#;
26691 u00024 : constant Version_32 := 16#5109C189#;
26692 u00025 : constant Version_32 := 16#56D770CD#;
26693 u00026 : constant Version_32 := 16#02F9DE3D#;
26694 u00027 : constant Version_32 := 16#08AB6B2C#;
26695 u00028 : constant Version_32 := 16#3FA37670#;
26696 u00029 : constant Version_32 := 16#476457A0#;
26697 u00030 : constant Version_32 := 16#731E1B6E#;
26698 u00031 : constant Version_32 := 16#23C2E789#;
26699 u00032 : constant Version_32 := 16#0F1BD6A1#;
26700 u00033 : constant Version_32 := 16#7C25DE96#;
26701 u00034 : constant Version_32 := 16#39ADFFA2#;
26702 u00035 : constant Version_32 := 16#571DE3E7#;
26703 u00036 : constant Version_32 := 16#5EB646AB#;
26704 u00037 : constant Version_32 := 16#4249379B#;
26705 u00038 : constant Version_32 := 16#0357E00A#;
26706 u00039 : constant Version_32 := 16#3784FB72#;
26707 u00040 : constant Version_32 := 16#2E723019#;
26708 u00041 : constant Version_32 := 16#623358EA#;
26709 u00042 : constant Version_32 := 16#107F9465#;
26710 u00043 : constant Version_32 := 16#6843F68A#;
26711 u00044 : constant Version_32 := 16#63305874#;
26712 u00045 : constant Version_32 := 16#31E56CE1#;
26713 u00046 : constant Version_32 := 16#02917970#;
26714 u00047 : constant Version_32 := 16#6CCBA70E#;
26715 u00048 : constant Version_32 := 16#41CD4204#;
26716 u00049 : constant Version_32 := 16#572E3F58#;
26717 u00050 : constant Version_32 := 16#20729FF5#;
26718 u00051 : constant Version_32 := 16#1D4F93E8#;
26719 u00052 : constant Version_32 := 16#30B2EC3D#;
26720 u00053 : constant Version_32 := 16#34054F96#;
26721 u00054 : constant Version_32 := 16#5A199860#;
26722 u00055 : constant Version_32 := 16#0E7F912B#;
26723 u00056 : constant Version_32 := 16#5760634A#;
26724 u00057 : constant Version_32 := 16#5D851835#;
26726 -- The following Export pragmas export the version numbers
26727 -- with symbolic names ending in B (for body) or S
26728 -- (for spec) so that they can be located in a link. The
26729 -- information provided here is sufficient to track down
26730 -- the exact versions of units used in a given build.
26732 pragma Export (C, u00001, "helloB");
26733 pragma Export (C, u00002, "system__standard_libraryB");
26734 pragma Export (C, u00003, "system__standard_libraryS");
26735 pragma Export (C, u00004, "adaS");
26736 pragma Export (C, u00005, "ada__text_ioB");
26737 pragma Export (C, u00006, "ada__text_ioS");
26738 pragma Export (C, u00007, "ada__exceptionsB");
26739 pragma Export (C, u00008, "ada__exceptionsS");
26740 pragma Export (C, u00009, "gnatS");
26741 pragma Export (C, u00010, "gnat__heap_sort_aB");
26742 pragma Export (C, u00011, "gnat__heap_sort_aS");
26743 pragma Export (C, u00012, "systemS");
26744 pragma Export (C, u00013, "system__exception_tableB");
26745 pragma Export (C, u00014, "system__exception_tableS");
26746 pragma Export (C, u00015, "gnat__htableB");
26747 pragma Export (C, u00016, "gnat__htableS");
26748 pragma Export (C, u00017, "system__exceptionsS");
26749 pragma Export (C, u00018, "system__machine_state_operationsB");
26750 pragma Export (C, u00019, "system__machine_state_operationsS");
26751 pragma Export (C, u00020, "system__machine_codeS");
26752 pragma Export (C, u00021, "system__storage_elementsB");
26753 pragma Export (C, u00022, "system__storage_elementsS");
26754 pragma Export (C, u00023, "system__secondary_stackB");
26755 pragma Export (C, u00024, "system__secondary_stackS");
26756 pragma Export (C, u00025, "system__parametersB");
26757 pragma Export (C, u00026, "system__parametersS");
26758 pragma Export (C, u00027, "system__soft_linksB");
26759 pragma Export (C, u00028, "system__soft_linksS");
26760 pragma Export (C, u00029, "system__stack_checkingB");
26761 pragma Export (C, u00030, "system__stack_checkingS");
26762 pragma Export (C, u00031, "system__tracebackB");
26763 pragma Export (C, u00032, "system__tracebackS");
26764 pragma Export (C, u00033, "ada__streamsS");
26765 pragma Export (C, u00034, "ada__tagsB");
26766 pragma Export (C, u00035, "ada__tagsS");
26767 pragma Export (C, u00036, "system__string_opsB");
26768 pragma Export (C, u00037, "system__string_opsS");
26769 pragma Export (C, u00038, "interfacesS");
26770 pragma Export (C, u00039, "interfaces__c_streamsB");
26771 pragma Export (C, u00040, "interfaces__c_streamsS");
26772 pragma Export (C, u00041, "system__file_ioB");
26773 pragma Export (C, u00042, "system__file_ioS");
26774 pragma Export (C, u00043, "ada__finalizationB");
26775 pragma Export (C, u00044, "ada__finalizationS");
26776 pragma Export (C, u00045, "system__finalization_rootB");
26777 pragma Export (C, u00046, "system__finalization_rootS");
26778 pragma Export (C, u00047, "system__finalization_implementationB");
26779 pragma Export (C, u00048, "system__finalization_implementationS");
26780 pragma Export (C, u00049, "system__string_ops_concat_3B");
26781 pragma Export (C, u00050, "system__string_ops_concat_3S");
26782 pragma Export (C, u00051, "system__stream_attributesB");
26783 pragma Export (C, u00052, "system__stream_attributesS");
26784 pragma Export (C, u00053, "ada__io_exceptionsS");
26785 pragma Export (C, u00054, "system__unsigned_typesS");
26786 pragma Export (C, u00055, "system__file_control_blockS");
26787 pragma Export (C, u00056, "ada__finalization__list_controllerB");
26788 pragma Export (C, u00057, "ada__finalization__list_controllerS");
26790 -- BEGIN ELABORATION ORDER
26793 -- gnat.heap_sort_a (spec)
26794 -- gnat.heap_sort_a (body)
26795 -- gnat.htable (spec)
26796 -- gnat.htable (body)
26797 -- interfaces (spec)
26799 -- system.machine_code (spec)
26800 -- system.parameters (spec)
26801 -- system.parameters (body)
26802 -- interfaces.c_streams (spec)
26803 -- interfaces.c_streams (body)
26804 -- system.standard_library (spec)
26805 -- ada.exceptions (spec)
26806 -- system.exception_table (spec)
26807 -- system.exception_table (body)
26808 -- ada.io_exceptions (spec)
26809 -- system.exceptions (spec)
26810 -- system.storage_elements (spec)
26811 -- system.storage_elements (body)
26812 -- system.machine_state_operations (spec)
26813 -- system.machine_state_operations (body)
26814 -- system.secondary_stack (spec)
26815 -- system.stack_checking (spec)
26816 -- system.soft_links (spec)
26817 -- system.soft_links (body)
26818 -- system.stack_checking (body)
26819 -- system.secondary_stack (body)
26820 -- system.standard_library (body)
26821 -- system.string_ops (spec)
26822 -- system.string_ops (body)
26825 -- ada.streams (spec)
26826 -- system.finalization_root (spec)
26827 -- system.finalization_root (body)
26828 -- system.string_ops_concat_3 (spec)
26829 -- system.string_ops_concat_3 (body)
26830 -- system.traceback (spec)
26831 -- system.traceback (body)
26832 -- ada.exceptions (body)
26833 -- system.unsigned_types (spec)
26834 -- system.stream_attributes (spec)
26835 -- system.stream_attributes (body)
26836 -- system.finalization_implementation (spec)
26837 -- system.finalization_implementation (body)
26838 -- ada.finalization (spec)
26839 -- ada.finalization (body)
26840 -- ada.finalization.list_controller (spec)
26841 -- ada.finalization.list_controller (body)
26842 -- system.file_control_block (spec)
26843 -- system.file_io (spec)
26844 -- system.file_io (body)
26845 -- ada.text_io (spec)
26846 -- ada.text_io (body)
26848 -- END ELABORATION ORDER
26852 -- The following source file name pragmas allow the generated file
26853 -- names to be unique for different main programs. They are needed
26854 -- since the package name will always be Ada_Main.
26856 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26857 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26859 -- Generated package body for Ada_Main starts here
26861 package body ada_main is
26863 -- The actual finalization is performed by calling the
26864 -- library routine in System.Standard_Library.Adafinal
26866 procedure Do_Finalize;
26867 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
26874 procedure adainit is
26876 -- These booleans are set to True once the associated unit has
26877 -- been elaborated. It is also used to avoid elaborating the
26878 -- same unit twice.
26881 pragma Import (Ada, E040, "interfaces__c_streams_E");
26884 pragma Import (Ada, E008, "ada__exceptions_E");
26887 pragma Import (Ada, E014, "system__exception_table_E");
26890 pragma Import (Ada, E053, "ada__io_exceptions_E");
26893 pragma Import (Ada, E017, "system__exceptions_E");
26896 pragma Import (Ada, E024, "system__secondary_stack_E");
26899 pragma Import (Ada, E030, "system__stack_checking_E");
26902 pragma Import (Ada, E028, "system__soft_links_E");
26905 pragma Import (Ada, E035, "ada__tags_E");
26908 pragma Import (Ada, E033, "ada__streams_E");
26911 pragma Import (Ada, E046, "system__finalization_root_E");
26914 pragma Import (Ada, E048, "system__finalization_implementation_E");
26917 pragma Import (Ada, E044, "ada__finalization_E");
26920 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
26923 pragma Import (Ada, E055, "system__file_control_block_E");
26926 pragma Import (Ada, E042, "system__file_io_E");
26929 pragma Import (Ada, E006, "ada__text_io_E");
26931 -- Set_Globals is a library routine that stores away the
26932 -- value of the indicated set of global values in global
26933 -- variables within the library.
26935 procedure Set_Globals
26936 (Main_Priority : Integer;
26937 Time_Slice_Value : Integer;
26938 WC_Encoding : Character;
26939 Locking_Policy : Character;
26940 Queuing_Policy : Character;
26941 Task_Dispatching_Policy : Character;
26942 Adafinal : System.Address;
26943 Unreserve_All_Interrupts : Integer;
26944 Exception_Tracebacks : Integer);
26945 @findex __gnat_set_globals
26946 pragma Import (C, Set_Globals, "__gnat_set_globals");
26948 -- SDP_Table_Build is a library routine used to build the
26949 -- exception tables. See unit Ada.Exceptions in files
26950 -- a-except.ads/adb for full details of how zero cost
26951 -- exception handling works. This procedure, the call to
26952 -- it, and the two following tables are all omitted if the
26953 -- build is in longjmp/setjmp exception mode.
26955 @findex SDP_Table_Build
26956 @findex Zero Cost Exceptions
26957 procedure SDP_Table_Build
26958 (SDP_Addresses : System.Address;
26959 SDP_Count : Natural;
26960 Elab_Addresses : System.Address;
26961 Elab_Addr_Count : Natural);
26962 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
26964 -- Table of Unit_Exception_Table addresses. Used for zero
26965 -- cost exception handling to build the top level table.
26967 ST : aliased constant array (1 .. 23) of System.Address := (
26969 Ada.Text_Io'UET_Address,
26970 Ada.Exceptions'UET_Address,
26971 Gnat.Heap_Sort_A'UET_Address,
26972 System.Exception_Table'UET_Address,
26973 System.Machine_State_Operations'UET_Address,
26974 System.Secondary_Stack'UET_Address,
26975 System.Parameters'UET_Address,
26976 System.Soft_Links'UET_Address,
26977 System.Stack_Checking'UET_Address,
26978 System.Traceback'UET_Address,
26979 Ada.Streams'UET_Address,
26980 Ada.Tags'UET_Address,
26981 System.String_Ops'UET_Address,
26982 Interfaces.C_Streams'UET_Address,
26983 System.File_Io'UET_Address,
26984 Ada.Finalization'UET_Address,
26985 System.Finalization_Root'UET_Address,
26986 System.Finalization_Implementation'UET_Address,
26987 System.String_Ops_Concat_3'UET_Address,
26988 System.Stream_Attributes'UET_Address,
26989 System.File_Control_Block'UET_Address,
26990 Ada.Finalization.List_Controller'UET_Address);
26992 -- Table of addresses of elaboration routines. Used for
26993 -- zero cost exception handling to make sure these
26994 -- addresses are included in the top level procedure
26997 EA : aliased constant array (1 .. 23) of System.Address := (
26998 adainit'Code_Address,
26999 Do_Finalize'Code_Address,
27000 Ada.Exceptions'Elab_Spec'Address,
27001 System.Exceptions'Elab_Spec'Address,
27002 Interfaces.C_Streams'Elab_Spec'Address,
27003 System.Exception_Table'Elab_Body'Address,
27004 Ada.Io_Exceptions'Elab_Spec'Address,
27005 System.Stack_Checking'Elab_Spec'Address,
27006 System.Soft_Links'Elab_Body'Address,
27007 System.Secondary_Stack'Elab_Body'Address,
27008 Ada.Tags'Elab_Spec'Address,
27009 Ada.Tags'Elab_Body'Address,
27010 Ada.Streams'Elab_Spec'Address,
27011 System.Finalization_Root'Elab_Spec'Address,
27012 Ada.Exceptions'Elab_Body'Address,
27013 System.Finalization_Implementation'Elab_Spec'Address,
27014 System.Finalization_Implementation'Elab_Body'Address,
27015 Ada.Finalization'Elab_Spec'Address,
27016 Ada.Finalization.List_Controller'Elab_Spec'Address,
27017 System.File_Control_Block'Elab_Spec'Address,
27018 System.File_Io'Elab_Body'Address,
27019 Ada.Text_Io'Elab_Spec'Address,
27020 Ada.Text_Io'Elab_Body'Address);
27022 -- Start of processing for adainit
27026 -- Call SDP_Table_Build to build the top level procedure
27027 -- table for zero cost exception handling (omitted in
27028 -- longjmp/setjmp mode).
27030 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
27032 -- Call Set_Globals to record various information for
27033 -- this partition. The values are derived by the binder
27034 -- from information stored in the ali files by the compiler.
27036 @findex __gnat_set_globals
27038 (Main_Priority => -1,
27039 -- Priority of main program, -1 if no pragma Priority used
27041 Time_Slice_Value => -1,
27042 -- Time slice from Time_Slice pragma, -1 if none used
27044 WC_Encoding => 'b',
27045 -- Wide_Character encoding used, default is brackets
27047 Locking_Policy => ' ',
27048 -- Locking_Policy used, default of space means not
27049 -- specified, otherwise it is the first character of
27050 -- the policy name.
27052 Queuing_Policy => ' ',
27053 -- Queuing_Policy used, default of space means not
27054 -- specified, otherwise it is the first character of
27055 -- the policy name.
27057 Task_Dispatching_Policy => ' ',
27058 -- Task_Dispatching_Policy used, default of space means
27059 -- not specified, otherwise first character of the
27062 Adafinal => System.Null_Address,
27063 -- Address of Adafinal routine, not used anymore
27065 Unreserve_All_Interrupts => 0,
27066 -- Set true if pragma Unreserve_All_Interrupts was used
27068 Exception_Tracebacks => 0);
27069 -- Indicates if exception tracebacks are enabled
27071 Elab_Final_Code := 1;
27073 -- Now we have the elaboration calls for all units in the partition.
27074 -- The Elab_Spec and Elab_Body attributes generate references to the
27075 -- implicit elaboration procedures generated by the compiler for
27076 -- each unit that requires elaboration.
27079 Interfaces.C_Streams'Elab_Spec;
27083 Ada.Exceptions'Elab_Spec;
27086 System.Exception_Table'Elab_Body;
27090 Ada.Io_Exceptions'Elab_Spec;
27094 System.Exceptions'Elab_Spec;
27098 System.Stack_Checking'Elab_Spec;
27101 System.Soft_Links'Elab_Body;
27106 System.Secondary_Stack'Elab_Body;
27110 Ada.Tags'Elab_Spec;
27113 Ada.Tags'Elab_Body;
27117 Ada.Streams'Elab_Spec;
27121 System.Finalization_Root'Elab_Spec;
27125 Ada.Exceptions'Elab_Body;
27129 System.Finalization_Implementation'Elab_Spec;
27132 System.Finalization_Implementation'Elab_Body;
27136 Ada.Finalization'Elab_Spec;
27140 Ada.Finalization.List_Controller'Elab_Spec;
27144 System.File_Control_Block'Elab_Spec;
27148 System.File_Io'Elab_Body;
27152 Ada.Text_Io'Elab_Spec;
27155 Ada.Text_Io'Elab_Body;
27159 Elab_Final_Code := 0;
27167 procedure adafinal is
27176 -- main is actually a function, as in the ANSI C standard,
27177 -- defined to return the exit status. The three parameters
27178 -- are the argument count, argument values and environment
27181 @findex Main Program
27184 argv : System.Address;
27185 envp : System.Address)
27188 -- The initialize routine performs low level system
27189 -- initialization using a standard library routine which
27190 -- sets up signal handling and performs any other
27191 -- required setup. The routine can be found in file
27194 @findex __gnat_initialize
27195 procedure initialize;
27196 pragma Import (C, initialize, "__gnat_initialize");
27198 -- The finalize routine performs low level system
27199 -- finalization using a standard library routine. The
27200 -- routine is found in file a-final.c and in the standard
27201 -- distribution is a dummy routine that does nothing, so
27202 -- really this is a hook for special user finalization.
27204 @findex __gnat_finalize
27205 procedure finalize;
27206 pragma Import (C, finalize, "__gnat_finalize");
27208 -- We get to the main program of the partition by using
27209 -- pragma Import because if we try to with the unit and
27210 -- call it Ada style, then not only do we waste time
27211 -- recompiling it, but also, we don't really know the right
27212 -- switches (e.g.@: identifier character set) to be used
27215 procedure Ada_Main_Program;
27216 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27218 -- Start of processing for main
27221 -- Save global variables
27227 -- Call low level system initialization
27231 -- Call our generated Ada initialization routine
27235 -- This is the point at which we want the debugger to get
27240 -- Now we call the main program of the partition
27244 -- Perform Ada finalization
27248 -- Perform low level system finalization
27252 -- Return the proper exit status
27253 return (gnat_exit_status);
27256 -- This section is entirely comments, so it has no effect on the
27257 -- compilation of the Ada_Main package. It provides the list of
27258 -- object files and linker options, as well as some standard
27259 -- libraries needed for the link. The gnatlink utility parses
27260 -- this b~hello.adb file to read these comment lines to generate
27261 -- the appropriate command line arguments for the call to the
27262 -- system linker. The BEGIN/END lines are used for sentinels for
27263 -- this parsing operation.
27265 -- The exact file names will of course depend on the environment,
27266 -- host/target and location of files on the host system.
27268 @findex Object file list
27269 -- BEGIN Object file/option list
27272 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27273 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27274 -- END Object file/option list
27280 The Ada code in the above example is exactly what is generated by the
27281 binder. We have added comments to more clearly indicate the function
27282 of each part of the generated @code{Ada_Main} package.
27284 The code is standard Ada in all respects, and can be processed by any
27285 tools that handle Ada. In particular, it is possible to use the debugger
27286 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27287 suppose that for reasons that you do not understand, your program is crashing
27288 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27289 you can place a breakpoint on the call:
27291 @smallexample @c ada
27292 Ada.Text_Io'Elab_Body;
27296 and trace the elaboration routine for this package to find out where
27297 the problem might be (more usually of course you would be debugging
27298 elaboration code in your own application).
27300 @node Elaboration Order Handling in GNAT
27301 @appendix Elaboration Order Handling in GNAT
27302 @cindex Order of elaboration
27303 @cindex Elaboration control
27306 * Elaboration Code::
27307 * Checking the Elaboration Order::
27308 * Controlling the Elaboration Order::
27309 * Controlling Elaboration in GNAT - Internal Calls::
27310 * Controlling Elaboration in GNAT - External Calls::
27311 * Default Behavior in GNAT - Ensuring Safety::
27312 * Treatment of Pragma Elaborate::
27313 * Elaboration Issues for Library Tasks::
27314 * Mixing Elaboration Models::
27315 * What to Do If the Default Elaboration Behavior Fails::
27316 * Elaboration for Access-to-Subprogram Values::
27317 * Summary of Procedures for Elaboration Control::
27318 * Other Elaboration Order Considerations::
27322 This chapter describes the handling of elaboration code in Ada and
27323 in GNAT, and discusses how the order of elaboration of program units can
27324 be controlled in GNAT, either automatically or with explicit programming
27327 @node Elaboration Code
27328 @section Elaboration Code
27331 Ada provides rather general mechanisms for executing code at elaboration
27332 time, that is to say before the main program starts executing. Such code arises
27336 @item Initializers for variables.
27337 Variables declared at the library level, in package specs or bodies, can
27338 require initialization that is performed at elaboration time, as in:
27339 @smallexample @c ada
27341 Sqrt_Half : Float := Sqrt (0.5);
27345 @item Package initialization code
27346 Code in a @code{BEGIN-END} section at the outer level of a package body is
27347 executed as part of the package body elaboration code.
27349 @item Library level task allocators
27350 Tasks that are declared using task allocators at the library level
27351 start executing immediately and hence can execute at elaboration time.
27355 Subprogram calls are possible in any of these contexts, which means that
27356 any arbitrary part of the program may be executed as part of the elaboration
27357 code. It is even possible to write a program which does all its work at
27358 elaboration time, with a null main program, although stylistically this
27359 would usually be considered an inappropriate way to structure
27362 An important concern arises in the context of elaboration code:
27363 we have to be sure that it is executed in an appropriate order. What we
27364 have is a series of elaboration code sections, potentially one section
27365 for each unit in the program. It is important that these execute
27366 in the correct order. Correctness here means that, taking the above
27367 example of the declaration of @code{Sqrt_Half},
27368 if some other piece of
27369 elaboration code references @code{Sqrt_Half},
27370 then it must run after the
27371 section of elaboration code that contains the declaration of
27374 There would never be any order of elaboration problem if we made a rule
27375 that whenever you @code{with} a unit, you must elaborate both the spec and body
27376 of that unit before elaborating the unit doing the @code{with}'ing:
27378 @smallexample @c ada
27382 package Unit_2 is @dots{}
27388 would require that both the body and spec of @code{Unit_1} be elaborated
27389 before the spec of @code{Unit_2}. However, a rule like that would be far too
27390 restrictive. In particular, it would make it impossible to have routines
27391 in separate packages that were mutually recursive.
27393 You might think that a clever enough compiler could look at the actual
27394 elaboration code and determine an appropriate correct order of elaboration,
27395 but in the general case, this is not possible. Consider the following
27398 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
27400 the variable @code{Sqrt_1}, which is declared in the elaboration code
27401 of the body of @code{Unit_1}:
27403 @smallexample @c ada
27405 Sqrt_1 : Float := Sqrt (0.1);
27410 The elaboration code of the body of @code{Unit_1} also contains:
27412 @smallexample @c ada
27415 if expression_1 = 1 then
27416 Q := Unit_2.Func_2;
27423 @code{Unit_2} is exactly parallel,
27424 it has a procedure @code{Func_2} that references
27425 the variable @code{Sqrt_2}, which is declared in the elaboration code of
27426 the body @code{Unit_2}:
27428 @smallexample @c ada
27430 Sqrt_2 : Float := Sqrt (0.1);
27435 The elaboration code of the body of @code{Unit_2} also contains:
27437 @smallexample @c ada
27440 if expression_2 = 2 then
27441 Q := Unit_1.Func_1;
27448 Now the question is, which of the following orders of elaboration is
27473 If you carefully analyze the flow here, you will see that you cannot tell
27474 at compile time the answer to this question.
27475 If @code{expression_1} is not equal to 1,
27476 and @code{expression_2} is not equal to 2,
27477 then either order is acceptable, because neither of the function calls is
27478 executed. If both tests evaluate to true, then neither order is acceptable
27479 and in fact there is no correct order.
27481 If one of the two expressions is true, and the other is false, then one
27482 of the above orders is correct, and the other is incorrect. For example,
27483 if @code{expression_1} /= 1 and @code{expression_2} = 2,
27484 then the call to @code{Func_1}
27485 will occur, but not the call to @code{Func_2.}
27486 This means that it is essential
27487 to elaborate the body of @code{Unit_1} before
27488 the body of @code{Unit_2}, so the first
27489 order of elaboration is correct and the second is wrong.
27491 By making @code{expression_1} and @code{expression_2}
27492 depend on input data, or perhaps
27493 the time of day, we can make it impossible for the compiler or binder
27494 to figure out which of these expressions will be true, and hence it
27495 is impossible to guarantee a safe order of elaboration at run time.
27497 @node Checking the Elaboration Order
27498 @section Checking the Elaboration Order
27501 In some languages that involve the same kind of elaboration problems,
27502 e.g.@: Java and C++, the programmer is expected to worry about these
27503 ordering problems himself, and it is common to
27504 write a program in which an incorrect elaboration order gives
27505 surprising results, because it references variables before they
27507 Ada is designed to be a safe language, and a programmer-beware approach is
27508 clearly not sufficient. Consequently, the language provides three lines
27512 @item Standard rules
27513 Some standard rules restrict the possible choice of elaboration
27514 order. In particular, if you @code{with} a unit, then its spec is always
27515 elaborated before the unit doing the @code{with}. Similarly, a parent
27516 spec is always elaborated before the child spec, and finally
27517 a spec is always elaborated before its corresponding body.
27519 @item Dynamic elaboration checks
27520 @cindex Elaboration checks
27521 @cindex Checks, elaboration
27522 Dynamic checks are made at run time, so that if some entity is accessed
27523 before it is elaborated (typically by means of a subprogram call)
27524 then the exception (@code{Program_Error}) is raised.
27526 @item Elaboration control
27527 Facilities are provided for the programmer to specify the desired order
27531 Let's look at these facilities in more detail. First, the rules for
27532 dynamic checking. One possible rule would be simply to say that the
27533 exception is raised if you access a variable which has not yet been
27534 elaborated. The trouble with this approach is that it could require
27535 expensive checks on every variable reference. Instead Ada has two
27536 rules which are a little more restrictive, but easier to check, and
27540 @item Restrictions on calls
27541 A subprogram can only be called at elaboration time if its body
27542 has been elaborated. The rules for elaboration given above guarantee
27543 that the spec of the subprogram has been elaborated before the
27544 call, but not the body. If this rule is violated, then the
27545 exception @code{Program_Error} is raised.
27547 @item Restrictions on instantiations
27548 A generic unit can only be instantiated if the body of the generic
27549 unit has been elaborated. Again, the rules for elaboration given above
27550 guarantee that the spec of the generic unit has been elaborated
27551 before the instantiation, but not the body. If this rule is
27552 violated, then the exception @code{Program_Error} is raised.
27556 The idea is that if the body has been elaborated, then any variables
27557 it references must have been elaborated; by checking for the body being
27558 elaborated we guarantee that none of its references causes any
27559 trouble. As we noted above, this is a little too restrictive, because a
27560 subprogram that has no non-local references in its body may in fact be safe
27561 to call. However, it really would be unsafe to rely on this, because
27562 it would mean that the caller was aware of details of the implementation
27563 in the body. This goes against the basic tenets of Ada.
27565 A plausible implementation can be described as follows.
27566 A Boolean variable is associated with each subprogram
27567 and each generic unit. This variable is initialized to False, and is set to
27568 True at the point body is elaborated. Every call or instantiation checks the
27569 variable, and raises @code{Program_Error} if the variable is False.
27571 Note that one might think that it would be good enough to have one Boolean
27572 variable for each package, but that would not deal with cases of trying
27573 to call a body in the same package as the call
27574 that has not been elaborated yet.
27575 Of course a compiler may be able to do enough analysis to optimize away
27576 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
27577 does such optimizations, but still the easiest conceptual model is to
27578 think of there being one variable per subprogram.
27580 @node Controlling the Elaboration Order
27581 @section Controlling the Elaboration Order
27584 In the previous section we discussed the rules in Ada which ensure
27585 that @code{Program_Error} is raised if an incorrect elaboration order is
27586 chosen. This prevents erroneous executions, but we need mechanisms to
27587 specify a correct execution and avoid the exception altogether.
27588 To achieve this, Ada provides a number of features for controlling
27589 the order of elaboration. We discuss these features in this section.
27591 First, there are several ways of indicating to the compiler that a given
27592 unit has no elaboration problems:
27595 @item packages that do not require a body
27596 A library package that does not require a body does not permit
27597 a body (this rule was introduced in Ada 95).
27598 Thus if we have a such a package, as in:
27600 @smallexample @c ada
27603 package Definitions is
27605 type m is new integer;
27607 type a is array (1 .. 10) of m;
27608 type b is array (1 .. 20) of m;
27616 A package that @code{with}'s @code{Definitions} may safely instantiate
27617 @code{Definitions.Subp} because the compiler can determine that there
27618 definitely is no package body to worry about in this case
27621 @cindex pragma Pure
27623 Places sufficient restrictions on a unit to guarantee that
27624 no call to any subprogram in the unit can result in an
27625 elaboration problem. This means that the compiler does not need
27626 to worry about the point of elaboration of such units, and in
27627 particular, does not need to check any calls to any subprograms
27630 @item pragma Preelaborate
27631 @findex Preelaborate
27632 @cindex pragma Preelaborate
27633 This pragma places slightly less stringent restrictions on a unit than
27635 but these restrictions are still sufficient to ensure that there
27636 are no elaboration problems with any calls to the unit.
27638 @item pragma Elaborate_Body
27639 @findex Elaborate_Body
27640 @cindex pragma Elaborate_Body
27641 This pragma requires that the body of a unit be elaborated immediately
27642 after its spec. Suppose a unit @code{A} has such a pragma,
27643 and unit @code{B} does
27644 a @code{with} of unit @code{A}. Recall that the standard rules require
27645 the spec of unit @code{A}
27646 to be elaborated before the @code{with}'ing unit; given the pragma in
27647 @code{A}, we also know that the body of @code{A}
27648 will be elaborated before @code{B}, so
27649 that calls to @code{A} are safe and do not need a check.
27654 unlike pragma @code{Pure} and pragma @code{Preelaborate},
27656 @code{Elaborate_Body} does not guarantee that the program is
27657 free of elaboration problems, because it may not be possible
27658 to satisfy the requested elaboration order.
27659 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
27661 marks @code{Unit_1} as @code{Elaborate_Body},
27662 and not @code{Unit_2,} then the order of
27663 elaboration will be:
27675 Now that means that the call to @code{Func_1} in @code{Unit_2}
27676 need not be checked,
27677 it must be safe. But the call to @code{Func_2} in
27678 @code{Unit_1} may still fail if
27679 @code{Expression_1} is equal to 1,
27680 and the programmer must still take
27681 responsibility for this not being the case.
27683 If all units carry a pragma @code{Elaborate_Body}, then all problems are
27684 eliminated, except for calls entirely within a body, which are
27685 in any case fully under programmer control. However, using the pragma
27686 everywhere is not always possible.
27687 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
27688 we marked both of them as having pragma @code{Elaborate_Body}, then
27689 clearly there would be no possible elaboration order.
27691 The above pragmas allow a server to guarantee safe use by clients, and
27692 clearly this is the preferable approach. Consequently a good rule
27693 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
27694 and if this is not possible,
27695 mark them as @code{Elaborate_Body} if possible.
27696 As we have seen, there are situations where neither of these
27697 three pragmas can be used.
27698 So we also provide methods for clients to control the
27699 order of elaboration of the servers on which they depend:
27702 @item pragma Elaborate (unit)
27704 @cindex pragma Elaborate
27705 This pragma is placed in the context clause, after a @code{with} clause,
27706 and it requires that the body of the named unit be elaborated before
27707 the unit in which the pragma occurs. The idea is to use this pragma
27708 if the current unit calls at elaboration time, directly or indirectly,
27709 some subprogram in the named unit.
27711 @item pragma Elaborate_All (unit)
27712 @findex Elaborate_All
27713 @cindex pragma Elaborate_All
27714 This is a stronger version of the Elaborate pragma. Consider the
27718 Unit A @code{with}'s unit B and calls B.Func in elab code
27719 Unit B @code{with}'s unit C, and B.Func calls C.Func
27723 Now if we put a pragma @code{Elaborate (B)}
27724 in unit @code{A}, this ensures that the
27725 body of @code{B} is elaborated before the call, but not the
27726 body of @code{C}, so
27727 the call to @code{C.Func} could still cause @code{Program_Error} to
27730 The effect of a pragma @code{Elaborate_All} is stronger, it requires
27731 not only that the body of the named unit be elaborated before the
27732 unit doing the @code{with}, but also the bodies of all units that the
27733 named unit uses, following @code{with} links transitively. For example,
27734 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
27736 not only that the body of @code{B} be elaborated before @code{A},
27738 body of @code{C}, because @code{B} @code{with}'s @code{C}.
27742 We are now in a position to give a usage rule in Ada for avoiding
27743 elaboration problems, at least if dynamic dispatching and access to
27744 subprogram values are not used. We will handle these cases separately
27747 The rule is simple. If a unit has elaboration code that can directly or
27748 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
27749 a generic package in a @code{with}'ed unit,
27750 then if the @code{with}'ed unit does not have
27751 pragma @code{Pure} or @code{Preelaborate}, then the client should have
27752 a pragma @code{Elaborate_All}
27753 for the @code{with}'ed unit. By following this rule a client is
27754 assured that calls can be made without risk of an exception.
27756 For generic subprogram instantiations, the rule can be relaxed to
27757 require only a pragma @code{Elaborate} since elaborating the body
27758 of a subprogram cannot cause any transitive elaboration (we are
27759 not calling the subprogram in this case, just elaborating its
27762 If this rule is not followed, then a program may be in one of four
27766 @item No order exists
27767 No order of elaboration exists which follows the rules, taking into
27768 account any @code{Elaborate}, @code{Elaborate_All},
27769 or @code{Elaborate_Body} pragmas. In
27770 this case, an Ada compiler must diagnose the situation at bind
27771 time, and refuse to build an executable program.
27773 @item One or more orders exist, all incorrect
27774 One or more acceptable elaboration orders exist, and all of them
27775 generate an elaboration order problem. In this case, the binder
27776 can build an executable program, but @code{Program_Error} will be raised
27777 when the program is run.
27779 @item Several orders exist, some right, some incorrect
27780 One or more acceptable elaboration orders exists, and some of them
27781 work, and some do not. The programmer has not controlled
27782 the order of elaboration, so the binder may or may not pick one of
27783 the correct orders, and the program may or may not raise an
27784 exception when it is run. This is the worst case, because it means
27785 that the program may fail when moved to another compiler, or even
27786 another version of the same compiler.
27788 @item One or more orders exists, all correct
27789 One ore more acceptable elaboration orders exist, and all of them
27790 work. In this case the program runs successfully. This state of
27791 affairs can be guaranteed by following the rule we gave above, but
27792 may be true even if the rule is not followed.
27796 Note that one additional advantage of following our rules on the use
27797 of @code{Elaborate} and @code{Elaborate_All}
27798 is that the program continues to stay in the ideal (all orders OK) state
27799 even if maintenance
27800 changes some bodies of some units. Conversely, if a program that does
27801 not follow this rule happens to be safe at some point, this state of affairs
27802 may deteriorate silently as a result of maintenance changes.
27804 You may have noticed that the above discussion did not mention
27805 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
27806 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
27807 code in the body makes calls to some other unit, so it is still necessary
27808 to use @code{Elaborate_All} on such units.
27810 @node Controlling Elaboration in GNAT - Internal Calls
27811 @section Controlling Elaboration in GNAT - Internal Calls
27814 In the case of internal calls, i.e., calls within a single package, the
27815 programmer has full control over the order of elaboration, and it is up
27816 to the programmer to elaborate declarations in an appropriate order. For
27819 @smallexample @c ada
27822 function One return Float;
27826 function One return Float is
27835 will obviously raise @code{Program_Error} at run time, because function
27836 One will be called before its body is elaborated. In this case GNAT will
27837 generate a warning that the call will raise @code{Program_Error}:
27843 2. function One return Float;
27845 4. Q : Float := One;
27847 >>> warning: cannot call "One" before body is elaborated
27848 >>> warning: Program_Error will be raised at run time
27851 6. function One return Float is
27864 Note that in this particular case, it is likely that the call is safe, because
27865 the function @code{One} does not access any global variables.
27866 Nevertheless in Ada, we do not want the validity of the check to depend on
27867 the contents of the body (think about the separate compilation case), so this
27868 is still wrong, as we discussed in the previous sections.
27870 The error is easily corrected by rearranging the declarations so that the
27871 body of @code{One} appears before the declaration containing the call
27872 (note that in Ada 95 and Ada 2005,
27873 declarations can appear in any order, so there is no restriction that
27874 would prevent this reordering, and if we write:
27876 @smallexample @c ada
27879 function One return Float;
27881 function One return Float is
27892 then all is well, no warning is generated, and no
27893 @code{Program_Error} exception
27895 Things are more complicated when a chain of subprograms is executed:
27897 @smallexample @c ada
27900 function A return Integer;
27901 function B return Integer;
27902 function C return Integer;
27904 function B return Integer is begin return A; end;
27905 function C return Integer is begin return B; end;
27909 function A return Integer is begin return 1; end;
27915 Now the call to @code{C}
27916 at elaboration time in the declaration of @code{X} is correct, because
27917 the body of @code{C} is already elaborated,
27918 and the call to @code{B} within the body of
27919 @code{C} is correct, but the call
27920 to @code{A} within the body of @code{B} is incorrect, because the body
27921 of @code{A} has not been elaborated, so @code{Program_Error}
27922 will be raised on the call to @code{A}.
27923 In this case GNAT will generate a
27924 warning that @code{Program_Error} may be
27925 raised at the point of the call. Let's look at the warning:
27931 2. function A return Integer;
27932 3. function B return Integer;
27933 4. function C return Integer;
27935 6. function B return Integer is begin return A; end;
27937 >>> warning: call to "A" before body is elaborated may
27938 raise Program_Error
27939 >>> warning: "B" called at line 7
27940 >>> warning: "C" called at line 9
27942 7. function C return Integer is begin return B; end;
27944 9. X : Integer := C;
27946 11. function A return Integer is begin return 1; end;
27956 Note that the message here says ``may raise'', instead of the direct case,
27957 where the message says ``will be raised''. That's because whether
27959 actually called depends in general on run-time flow of control.
27960 For example, if the body of @code{B} said
27962 @smallexample @c ada
27965 function B return Integer is
27967 if some-condition-depending-on-input-data then
27978 then we could not know until run time whether the incorrect call to A would
27979 actually occur, so @code{Program_Error} might
27980 or might not be raised. It is possible for a compiler to
27981 do a better job of analyzing bodies, to
27982 determine whether or not @code{Program_Error}
27983 might be raised, but it certainly
27984 couldn't do a perfect job (that would require solving the halting problem
27985 and is provably impossible), and because this is a warning anyway, it does
27986 not seem worth the effort to do the analysis. Cases in which it
27987 would be relevant are rare.
27989 In practice, warnings of either of the forms given
27990 above will usually correspond to
27991 real errors, and should be examined carefully and eliminated.
27992 In the rare case where a warning is bogus, it can be suppressed by any of
27993 the following methods:
27997 Compile with the @option{-gnatws} switch set
28000 Suppress @code{Elaboration_Check} for the called subprogram
28003 Use pragma @code{Warnings_Off} to turn warnings off for the call
28007 For the internal elaboration check case,
28008 GNAT by default generates the
28009 necessary run-time checks to ensure
28010 that @code{Program_Error} is raised if any
28011 call fails an elaboration check. Of course this can only happen if a
28012 warning has been issued as described above. The use of pragma
28013 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
28014 some of these checks, meaning that it may be possible (but is not
28015 guaranteed) for a program to be able to call a subprogram whose body
28016 is not yet elaborated, without raising a @code{Program_Error} exception.
28018 @node Controlling Elaboration in GNAT - External Calls
28019 @section Controlling Elaboration in GNAT - External Calls
28022 The previous section discussed the case in which the execution of a
28023 particular thread of elaboration code occurred entirely within a
28024 single unit. This is the easy case to handle, because a programmer
28025 has direct and total control over the order of elaboration, and
28026 furthermore, checks need only be generated in cases which are rare
28027 and which the compiler can easily detect.
28028 The situation is more complex when separate compilation is taken into account.
28029 Consider the following:
28031 @smallexample @c ada
28035 function Sqrt (Arg : Float) return Float;
28038 package body Math is
28039 function Sqrt (Arg : Float) return Float is
28048 X : Float := Math.Sqrt (0.5);
28061 where @code{Main} is the main program. When this program is executed, the
28062 elaboration code must first be executed, and one of the jobs of the
28063 binder is to determine the order in which the units of a program are
28064 to be elaborated. In this case we have four units: the spec and body
28066 the spec of @code{Stuff} and the body of @code{Main}).
28067 In what order should the four separate sections of elaboration code
28070 There are some restrictions in the order of elaboration that the binder
28071 can choose. In particular, if unit U has a @code{with}
28072 for a package @code{X}, then you
28073 are assured that the spec of @code{X}
28074 is elaborated before U , but you are
28075 not assured that the body of @code{X}
28076 is elaborated before U.
28077 This means that in the above case, the binder is allowed to choose the
28088 but that's not good, because now the call to @code{Math.Sqrt}
28089 that happens during
28090 the elaboration of the @code{Stuff}
28091 spec happens before the body of @code{Math.Sqrt} is
28092 elaborated, and hence causes @code{Program_Error} exception to be raised.
28093 At first glance, one might say that the binder is misbehaving, because
28094 obviously you want to elaborate the body of something you @code{with}
28096 that is not a general rule that can be followed in all cases. Consider
28098 @smallexample @c ada
28101 package X is @dots{}
28103 package Y is @dots{}
28106 package body Y is @dots{}
28109 package body X is @dots{}
28115 This is a common arrangement, and, apart from the order of elaboration
28116 problems that might arise in connection with elaboration code, this works fine.
28117 A rule that says that you must first elaborate the body of anything you
28118 @code{with} cannot work in this case:
28119 the body of @code{X} @code{with}'s @code{Y},
28120 which means you would have to
28121 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
28123 you have to elaborate the body of @code{X} first, but @dots{} and we have a
28124 loop that cannot be broken.
28126 It is true that the binder can in many cases guess an order of elaboration
28127 that is unlikely to cause a @code{Program_Error}
28128 exception to be raised, and it tries to do so (in the
28129 above example of @code{Math/Stuff/Spec}, the GNAT binder will
28131 elaborate the body of @code{Math} right after its spec, so all will be well).
28133 However, a program that blindly relies on the binder to be helpful can
28134 get into trouble, as we discussed in the previous sections, so
28136 provides a number of facilities for assisting the programmer in
28137 developing programs that are robust with respect to elaboration order.
28139 @node Default Behavior in GNAT - Ensuring Safety
28140 @section Default Behavior in GNAT - Ensuring Safety
28143 The default behavior in GNAT ensures elaboration safety. In its
28144 default mode GNAT implements the
28145 rule we previously described as the right approach. Let's restate it:
28149 @emph{If a unit has elaboration code that can directly or indirectly make a
28150 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
28151 package in a @code{with}'ed unit, then if the @code{with}'ed unit
28152 does not have pragma @code{Pure} or
28153 @code{Preelaborate}, then the client should have an
28154 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
28156 @emph{In the case of instantiating a generic subprogram, it is always
28157 sufficient to have only an @code{Elaborate} pragma for the
28158 @code{with}'ed unit.}
28162 By following this rule a client is assured that calls and instantiations
28163 can be made without risk of an exception.
28165 In this mode GNAT traces all calls that are potentially made from
28166 elaboration code, and puts in any missing implicit @code{Elaborate}
28167 and @code{Elaborate_All} pragmas.
28168 The advantage of this approach is that no elaboration problems
28169 are possible if the binder can find an elaboration order that is
28170 consistent with these implicit @code{Elaborate} and
28171 @code{Elaborate_All} pragmas. The
28172 disadvantage of this approach is that no such order may exist.
28174 If the binder does not generate any diagnostics, then it means that it has
28175 found an elaboration order that is guaranteed to be safe. However, the binder
28176 may still be relying on implicitly generated @code{Elaborate} and
28177 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
28180 If it is important to guarantee portability, then the compilations should
28183 (warn on elaboration problems) switch. This will cause warning messages
28184 to be generated indicating the missing @code{Elaborate} and
28185 @code{Elaborate_All} pragmas.
28186 Consider the following source program:
28188 @smallexample @c ada
28193 m : integer := k.r;
28200 where it is clear that there
28201 should be a pragma @code{Elaborate_All}
28202 for unit @code{k}. An implicit pragma will be generated, and it is
28203 likely that the binder will be able to honor it. However, if you want
28204 to port this program to some other Ada compiler than GNAT.
28205 it is safer to include the pragma explicitly in the source. If this
28206 unit is compiled with the
28208 switch, then the compiler outputs a warning:
28215 3. m : integer := k.r;
28217 >>> warning: call to "r" may raise Program_Error
28218 >>> warning: missing pragma Elaborate_All for "k"
28226 and these warnings can be used as a guide for supplying manually
28227 the missing pragmas. It is usually a bad idea to use this warning
28228 option during development. That's because it will warn you when
28229 you need to put in a pragma, but cannot warn you when it is time
28230 to take it out. So the use of pragma @code{Elaborate_All} may lead to
28231 unnecessary dependencies and even false circularities.
28233 This default mode is more restrictive than the Ada Reference
28234 Manual, and it is possible to construct programs which will compile
28235 using the dynamic model described there, but will run into a
28236 circularity using the safer static model we have described.
28238 Of course any Ada compiler must be able to operate in a mode
28239 consistent with the requirements of the Ada Reference Manual,
28240 and in particular must have the capability of implementing the
28241 standard dynamic model of elaboration with run-time checks.
28243 In GNAT, this standard mode can be achieved either by the use of
28244 the @option{-gnatE} switch on the compiler (@command{gcc} or
28245 @command{gnatmake}) command, or by the use of the configuration pragma:
28247 @smallexample @c ada
28248 pragma Elaboration_Checks (RM);
28252 Either approach will cause the unit affected to be compiled using the
28253 standard dynamic run-time elaboration checks described in the Ada
28254 Reference Manual. The static model is generally preferable, since it
28255 is clearly safer to rely on compile and link time checks rather than
28256 run-time checks. However, in the case of legacy code, it may be
28257 difficult to meet the requirements of the static model. This
28258 issue is further discussed in
28259 @ref{What to Do If the Default Elaboration Behavior Fails}.
28261 Note that the static model provides a strict subset of the allowed
28262 behavior and programs of the Ada Reference Manual, so if you do
28263 adhere to the static model and no circularities exist,
28264 then you are assured that your program will
28265 work using the dynamic model, providing that you remove any
28266 pragma Elaborate statements from the source.
28268 @node Treatment of Pragma Elaborate
28269 @section Treatment of Pragma Elaborate
28270 @cindex Pragma Elaborate
28273 The use of @code{pragma Elaborate}
28274 should generally be avoided in Ada 95 and Ada 2005 programs,
28275 since there is no guarantee that transitive calls
28276 will be properly handled. Indeed at one point, this pragma was placed
28277 in Annex J (Obsolescent Features), on the grounds that it is never useful.
28279 Now that's a bit restrictive. In practice, the case in which
28280 @code{pragma Elaborate} is useful is when the caller knows that there
28281 are no transitive calls, or that the called unit contains all necessary
28282 transitive @code{pragma Elaborate} statements, and legacy code often
28283 contains such uses.
28285 Strictly speaking the static mode in GNAT should ignore such pragmas,
28286 since there is no assurance at compile time that the necessary safety
28287 conditions are met. In practice, this would cause GNAT to be incompatible
28288 with correctly written Ada 83 code that had all necessary
28289 @code{pragma Elaborate} statements in place. Consequently, we made the
28290 decision that GNAT in its default mode will believe that if it encounters
28291 a @code{pragma Elaborate} then the programmer knows what they are doing,
28292 and it will trust that no elaboration errors can occur.
28294 The result of this decision is two-fold. First to be safe using the
28295 static mode, you should remove all @code{pragma Elaborate} statements.
28296 Second, when fixing circularities in existing code, you can selectively
28297 use @code{pragma Elaborate} statements to convince the static mode of
28298 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
28301 When using the static mode with @option{-gnatwl}, any use of
28302 @code{pragma Elaborate} will generate a warning about possible
28305 @node Elaboration Issues for Library Tasks
28306 @section Elaboration Issues for Library Tasks
28307 @cindex Library tasks, elaboration issues
28308 @cindex Elaboration of library tasks
28311 In this section we examine special elaboration issues that arise for
28312 programs that declare library level tasks.
28314 Generally the model of execution of an Ada program is that all units are
28315 elaborated, and then execution of the program starts. However, the
28316 declaration of library tasks definitely does not fit this model. The
28317 reason for this is that library tasks start as soon as they are declared
28318 (more precisely, as soon as the statement part of the enclosing package
28319 body is reached), that is to say before elaboration
28320 of the program is complete. This means that if such a task calls a
28321 subprogram, or an entry in another task, the callee may or may not be
28322 elaborated yet, and in the standard
28323 Reference Manual model of dynamic elaboration checks, you can even
28324 get timing dependent Program_Error exceptions, since there can be
28325 a race between the elaboration code and the task code.
28327 The static model of elaboration in GNAT seeks to avoid all such
28328 dynamic behavior, by being conservative, and the conservative
28329 approach in this particular case is to assume that all the code
28330 in a task body is potentially executed at elaboration time if
28331 a task is declared at the library level.
28333 This can definitely result in unexpected circularities. Consider
28334 the following example
28336 @smallexample @c ada
28342 type My_Int is new Integer;
28344 function Ident (M : My_Int) return My_Int;
28348 package body Decls is
28349 task body Lib_Task is
28355 function Ident (M : My_Int) return My_Int is
28363 procedure Put_Val (Arg : Decls.My_Int);
28367 package body Utils is
28368 procedure Put_Val (Arg : Decls.My_Int) is
28370 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28377 Decls.Lib_Task.Start;
28382 If the above example is compiled in the default static elaboration
28383 mode, then a circularity occurs. The circularity comes from the call
28384 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
28385 this call occurs in elaboration code, we need an implicit pragma
28386 @code{Elaborate_All} for @code{Utils}. This means that not only must
28387 the spec and body of @code{Utils} be elaborated before the body
28388 of @code{Decls}, but also the spec and body of any unit that is
28389 @code{with'ed} by the body of @code{Utils} must also be elaborated before
28390 the body of @code{Decls}. This is the transitive implication of
28391 pragma @code{Elaborate_All} and it makes sense, because in general
28392 the body of @code{Put_Val} might have a call to something in a
28393 @code{with'ed} unit.
28395 In this case, the body of Utils (actually its spec) @code{with's}
28396 @code{Decls}. Unfortunately this means that the body of @code{Decls}
28397 must be elaborated before itself, in case there is a call from the
28398 body of @code{Utils}.
28400 Here is the exact chain of events we are worrying about:
28404 In the body of @code{Decls} a call is made from within the body of a library
28405 task to a subprogram in the package @code{Utils}. Since this call may
28406 occur at elaboration time (given that the task is activated at elaboration
28407 time), we have to assume the worst, i.e., that the
28408 call does happen at elaboration time.
28411 This means that the body and spec of @code{Util} must be elaborated before
28412 the body of @code{Decls} so that this call does not cause an access before
28416 Within the body of @code{Util}, specifically within the body of
28417 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
28421 One such @code{with}'ed package is package @code{Decls}, so there
28422 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
28423 In fact there is such a call in this example, but we would have to
28424 assume that there was such a call even if it were not there, since
28425 we are not supposed to write the body of @code{Decls} knowing what
28426 is in the body of @code{Utils}; certainly in the case of the
28427 static elaboration model, the compiler does not know what is in
28428 other bodies and must assume the worst.
28431 This means that the spec and body of @code{Decls} must also be
28432 elaborated before we elaborate the unit containing the call, but
28433 that unit is @code{Decls}! This means that the body of @code{Decls}
28434 must be elaborated before itself, and that's a circularity.
28438 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
28439 the body of @code{Decls} you will get a true Ada Reference Manual
28440 circularity that makes the program illegal.
28442 In practice, we have found that problems with the static model of
28443 elaboration in existing code often arise from library tasks, so
28444 we must address this particular situation.
28446 Note that if we compile and run the program above, using the dynamic model of
28447 elaboration (that is to say use the @option{-gnatE} switch),
28448 then it compiles, binds,
28449 links, and runs, printing the expected result of 2. Therefore in some sense
28450 the circularity here is only apparent, and we need to capture
28451 the properties of this program that distinguish it from other library-level
28452 tasks that have real elaboration problems.
28454 We have four possible answers to this question:
28459 Use the dynamic model of elaboration.
28461 If we use the @option{-gnatE} switch, then as noted above, the program works.
28462 Why is this? If we examine the task body, it is apparent that the task cannot
28464 @code{accept} statement until after elaboration has been completed, because
28465 the corresponding entry call comes from the main program, not earlier.
28466 This is why the dynamic model works here. But that's really giving
28467 up on a precise analysis, and we prefer to take this approach only if we cannot
28469 problem in any other manner. So let us examine two ways to reorganize
28470 the program to avoid the potential elaboration problem.
28473 Split library tasks into separate packages.
28475 Write separate packages, so that library tasks are isolated from
28476 other declarations as much as possible. Let us look at a variation on
28479 @smallexample @c ada
28487 package body Decls1 is
28488 task body Lib_Task is
28496 type My_Int is new Integer;
28497 function Ident (M : My_Int) return My_Int;
28501 package body Decls2 is
28502 function Ident (M : My_Int) return My_Int is
28510 procedure Put_Val (Arg : Decls2.My_Int);
28514 package body Utils is
28515 procedure Put_Val (Arg : Decls2.My_Int) is
28517 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
28524 Decls1.Lib_Task.Start;
28529 All we have done is to split @code{Decls} into two packages, one
28530 containing the library task, and one containing everything else. Now
28531 there is no cycle, and the program compiles, binds, links and executes
28532 using the default static model of elaboration.
28535 Declare separate task types.
28537 A significant part of the problem arises because of the use of the
28538 single task declaration form. This means that the elaboration of
28539 the task type, and the elaboration of the task itself (i.e.@: the
28540 creation of the task) happen at the same time. A good rule
28541 of style in Ada is to always create explicit task types. By
28542 following the additional step of placing task objects in separate
28543 packages from the task type declaration, many elaboration problems
28544 are avoided. Here is another modified example of the example program:
28546 @smallexample @c ada
28548 task type Lib_Task_Type is
28552 type My_Int is new Integer;
28554 function Ident (M : My_Int) return My_Int;
28558 package body Decls is
28559 task body Lib_Task_Type is
28565 function Ident (M : My_Int) return My_Int is
28573 procedure Put_Val (Arg : Decls.My_Int);
28577 package body Utils is
28578 procedure Put_Val (Arg : Decls.My_Int) is
28580 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28586 Lib_Task : Decls.Lib_Task_Type;
28592 Declst.Lib_Task.Start;
28597 What we have done here is to replace the @code{task} declaration in
28598 package @code{Decls} with a @code{task type} declaration. Then we
28599 introduce a separate package @code{Declst} to contain the actual
28600 task object. This separates the elaboration issues for
28601 the @code{task type}
28602 declaration, which causes no trouble, from the elaboration issues
28603 of the task object, which is also unproblematic, since it is now independent
28604 of the elaboration of @code{Utils}.
28605 This separation of concerns also corresponds to
28606 a generally sound engineering principle of separating declarations
28607 from instances. This version of the program also compiles, binds, links,
28608 and executes, generating the expected output.
28611 Use No_Entry_Calls_In_Elaboration_Code restriction.
28612 @cindex No_Entry_Calls_In_Elaboration_Code
28614 The previous two approaches described how a program can be restructured
28615 to avoid the special problems caused by library task bodies. in practice,
28616 however, such restructuring may be difficult to apply to existing legacy code,
28617 so we must consider solutions that do not require massive rewriting.
28619 Let us consider more carefully why our original sample program works
28620 under the dynamic model of elaboration. The reason is that the code
28621 in the task body blocks immediately on the @code{accept}
28622 statement. Now of course there is nothing to prohibit elaboration
28623 code from making entry calls (for example from another library level task),
28624 so we cannot tell in isolation that
28625 the task will not execute the accept statement during elaboration.
28627 However, in practice it is very unusual to see elaboration code
28628 make any entry calls, and the pattern of tasks starting
28629 at elaboration time and then immediately blocking on @code{accept} or
28630 @code{select} statements is very common. What this means is that
28631 the compiler is being too pessimistic when it analyzes the
28632 whole package body as though it might be executed at elaboration
28635 If we know that the elaboration code contains no entry calls, (a very safe
28636 assumption most of the time, that could almost be made the default
28637 behavior), then we can compile all units of the program under control
28638 of the following configuration pragma:
28641 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
28645 This pragma can be placed in the @file{gnat.adc} file in the usual
28646 manner. If we take our original unmodified program and compile it
28647 in the presence of a @file{gnat.adc} containing the above pragma,
28648 then once again, we can compile, bind, link, and execute, obtaining
28649 the expected result. In the presence of this pragma, the compiler does
28650 not trace calls in a task body, that appear after the first @code{accept}
28651 or @code{select} statement, and therefore does not report a potential
28652 circularity in the original program.
28654 The compiler will check to the extent it can that the above
28655 restriction is not violated, but it is not always possible to do a
28656 complete check at compile time, so it is important to use this
28657 pragma only if the stated restriction is in fact met, that is to say
28658 no task receives an entry call before elaboration of all units is completed.
28662 @node Mixing Elaboration Models
28663 @section Mixing Elaboration Models
28665 So far, we have assumed that the entire program is either compiled
28666 using the dynamic model or static model, ensuring consistency. It
28667 is possible to mix the two models, but rules have to be followed
28668 if this mixing is done to ensure that elaboration checks are not
28671 The basic rule is that @emph{a unit compiled with the static model cannot
28672 be @code{with'ed} by a unit compiled with the dynamic model}. The
28673 reason for this is that in the static model, a unit assumes that
28674 its clients guarantee to use (the equivalent of) pragma
28675 @code{Elaborate_All} so that no elaboration checks are required
28676 in inner subprograms, and this assumption is violated if the
28677 client is compiled with dynamic checks.
28679 The precise rule is as follows. A unit that is compiled with dynamic
28680 checks can only @code{with} a unit that meets at least one of the
28681 following criteria:
28686 The @code{with'ed} unit is itself compiled with dynamic elaboration
28687 checks (that is with the @option{-gnatE} switch.
28690 The @code{with'ed} unit is an internal GNAT implementation unit from
28691 the System, Interfaces, Ada, or GNAT hierarchies.
28694 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
28697 The @code{with'ing} unit (that is the client) has an explicit pragma
28698 @code{Elaborate_All} for the @code{with'ed} unit.
28703 If this rule is violated, that is if a unit with dynamic elaboration
28704 checks @code{with's} a unit that does not meet one of the above four
28705 criteria, then the binder (@code{gnatbind}) will issue a warning
28706 similar to that in the following example:
28709 warning: "x.ads" has dynamic elaboration checks and with's
28710 warning: "y.ads" which has static elaboration checks
28714 These warnings indicate that the rule has been violated, and that as a result
28715 elaboration checks may be missed in the resulting executable file.
28716 This warning may be suppressed using the @option{-ws} binder switch
28717 in the usual manner.
28719 One useful application of this mixing rule is in the case of a subsystem
28720 which does not itself @code{with} units from the remainder of the
28721 application. In this case, the entire subsystem can be compiled with
28722 dynamic checks to resolve a circularity in the subsystem, while
28723 allowing the main application that uses this subsystem to be compiled
28724 using the more reliable default static model.
28726 @node What to Do If the Default Elaboration Behavior Fails
28727 @section What to Do If the Default Elaboration Behavior Fails
28730 If the binder cannot find an acceptable order, it outputs detailed
28731 diagnostics. For example:
28737 error: elaboration circularity detected
28738 info: "proc (body)" must be elaborated before "pack (body)"
28739 info: reason: Elaborate_All probably needed in unit "pack (body)"
28740 info: recompile "pack (body)" with -gnatwl
28741 info: for full details
28742 info: "proc (body)"
28743 info: is needed by its spec:
28744 info: "proc (spec)"
28745 info: which is withed by:
28746 info: "pack (body)"
28747 info: "pack (body)" must be elaborated before "proc (body)"
28748 info: reason: pragma Elaborate in unit "proc (body)"
28754 In this case we have a cycle that the binder cannot break. On the one
28755 hand, there is an explicit pragma Elaborate in @code{proc} for
28756 @code{pack}. This means that the body of @code{pack} must be elaborated
28757 before the body of @code{proc}. On the other hand, there is elaboration
28758 code in @code{pack} that calls a subprogram in @code{proc}. This means
28759 that for maximum safety, there should really be a pragma
28760 Elaborate_All in @code{pack} for @code{proc} which would require that
28761 the body of @code{proc} be elaborated before the body of
28762 @code{pack}. Clearly both requirements cannot be satisfied.
28763 Faced with a circularity of this kind, you have three different options.
28766 @item Fix the program
28767 The most desirable option from the point of view of long-term maintenance
28768 is to rearrange the program so that the elaboration problems are avoided.
28769 One useful technique is to place the elaboration code into separate
28770 child packages. Another is to move some of the initialization code to
28771 explicitly called subprograms, where the program controls the order
28772 of initialization explicitly. Although this is the most desirable option,
28773 it may be impractical and involve too much modification, especially in
28774 the case of complex legacy code.
28776 @item Perform dynamic checks
28777 If the compilations are done using the
28779 (dynamic elaboration check) switch, then GNAT behaves in a quite different
28780 manner. Dynamic checks are generated for all calls that could possibly result
28781 in raising an exception. With this switch, the compiler does not generate
28782 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
28783 exactly as specified in the @cite{Ada Reference Manual}.
28784 The binder will generate
28785 an executable program that may or may not raise @code{Program_Error}, and then
28786 it is the programmer's job to ensure that it does not raise an exception. Note
28787 that it is important to compile all units with the switch, it cannot be used
28790 @item Suppress checks
28791 The drawback of dynamic checks is that they generate a
28792 significant overhead at run time, both in space and time. If you
28793 are absolutely sure that your program cannot raise any elaboration
28794 exceptions, and you still want to use the dynamic elaboration model,
28795 then you can use the configuration pragma
28796 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
28797 example this pragma could be placed in the @file{gnat.adc} file.
28799 @item Suppress checks selectively
28800 When you know that certain calls or instantiations in elaboration code cannot
28801 possibly lead to an elaboration error, and the binder nevertheless complains
28802 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
28803 elaboration circularities, it is possible to remove those warnings locally and
28804 obtain a program that will bind. Clearly this can be unsafe, and it is the
28805 responsibility of the programmer to make sure that the resulting program has no
28806 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
28807 used with different granularity to suppress warnings and break elaboration
28812 Place the pragma that names the called subprogram in the declarative part
28813 that contains the call.
28816 Place the pragma in the declarative part, without naming an entity. This
28817 disables warnings on all calls in the corresponding declarative region.
28820 Place the pragma in the package spec that declares the called subprogram,
28821 and name the subprogram. This disables warnings on all elaboration calls to
28825 Place the pragma in the package spec that declares the called subprogram,
28826 without naming any entity. This disables warnings on all elaboration calls to
28827 all subprograms declared in this spec.
28829 @item Use Pragma Elaborate
28830 As previously described in section @xref{Treatment of Pragma Elaborate},
28831 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
28832 that no elaboration checks are required on calls to the designated unit.
28833 There may be cases in which the caller knows that no transitive calls
28834 can occur, so that a @code{pragma Elaborate} will be sufficient in a
28835 case where @code{pragma Elaborate_All} would cause a circularity.
28839 These five cases are listed in order of decreasing safety, and therefore
28840 require increasing programmer care in their application. Consider the
28843 @smallexample @c adanocomment
28845 function F1 return Integer;
28850 function F2 return Integer;
28851 function Pure (x : integer) return integer;
28852 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
28853 -- pragma Suppress (Elaboration_Check); -- (4)
28857 package body Pack1 is
28858 function F1 return Integer is
28862 Val : integer := Pack2.Pure (11); -- Elab. call (1)
28865 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
28866 -- pragma Suppress(Elaboration_Check); -- (2)
28868 X1 := Pack2.F2 + 1; -- Elab. call (2)
28873 package body Pack2 is
28874 function F2 return Integer is
28878 function Pure (x : integer) return integer is
28880 return x ** 3 - 3 * x;
28884 with Pack1, Ada.Text_IO;
28887 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
28890 In the absence of any pragmas, an attempt to bind this program produces
28891 the following diagnostics:
28897 error: elaboration circularity detected
28898 info: "pack1 (body)" must be elaborated before "pack1 (body)"
28899 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
28900 info: recompile "pack1 (body)" with -gnatwl for full details
28901 info: "pack1 (body)"
28902 info: must be elaborated along with its spec:
28903 info: "pack1 (spec)"
28904 info: which is withed by:
28905 info: "pack2 (body)"
28906 info: which must be elaborated along with its spec:
28907 info: "pack2 (spec)"
28908 info: which is withed by:
28909 info: "pack1 (body)"
28912 The sources of the circularity are the two calls to @code{Pack2.Pure} and
28913 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
28914 F2 is safe, even though F2 calls F1, because the call appears after the
28915 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
28916 remove the warning on the call. It is also possible to use pragma (2)
28917 because there are no other potentially unsafe calls in the block.
28920 The call to @code{Pure} is safe because this function does not depend on the
28921 state of @code{Pack2}. Therefore any call to this function is safe, and it
28922 is correct to place pragma (3) in the corresponding package spec.
28925 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
28926 warnings on all calls to functions declared therein. Note that this is not
28927 necessarily safe, and requires more detailed examination of the subprogram
28928 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
28929 be already elaborated.
28933 It is hard to generalize on which of these four approaches should be
28934 taken. Obviously if it is possible to fix the program so that the default
28935 treatment works, this is preferable, but this may not always be practical.
28936 It is certainly simple enough to use
28938 but the danger in this case is that, even if the GNAT binder
28939 finds a correct elaboration order, it may not always do so,
28940 and certainly a binder from another Ada compiler might not. A
28941 combination of testing and analysis (for which the warnings generated
28944 switch can be useful) must be used to ensure that the program is free
28945 of errors. One switch that is useful in this testing is the
28946 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
28949 Normally the binder tries to find an order that has the best chance
28950 of avoiding elaboration problems. However, if this switch is used, the binder
28951 plays a devil's advocate role, and tries to choose the order that
28952 has the best chance of failing. If your program works even with this
28953 switch, then it has a better chance of being error free, but this is still
28956 For an example of this approach in action, consider the C-tests (executable
28957 tests) from the ACVC suite. If these are compiled and run with the default
28958 treatment, then all but one of them succeed without generating any error
28959 diagnostics from the binder. However, there is one test that fails, and
28960 this is not surprising, because the whole point of this test is to ensure
28961 that the compiler can handle cases where it is impossible to determine
28962 a correct order statically, and it checks that an exception is indeed
28963 raised at run time.
28965 This one test must be compiled and run using the
28967 switch, and then it passes. Alternatively, the entire suite can
28968 be run using this switch. It is never wrong to run with the dynamic
28969 elaboration switch if your code is correct, and we assume that the
28970 C-tests are indeed correct (it is less efficient, but efficiency is
28971 not a factor in running the ACVC tests.)
28973 @node Elaboration for Access-to-Subprogram Values
28974 @section Elaboration for Access-to-Subprogram Values
28975 @cindex Access-to-subprogram
28978 Access-to-subprogram types (introduced in Ada 95) complicate
28979 the handling of elaboration. The trouble is that it becomes
28980 impossible to tell at compile time which procedure
28981 is being called. This means that it is not possible for the binder
28982 to analyze the elaboration requirements in this case.
28984 If at the point at which the access value is created
28985 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
28986 the body of the subprogram is
28987 known to have been elaborated, then the access value is safe, and its use
28988 does not require a check. This may be achieved by appropriate arrangement
28989 of the order of declarations if the subprogram is in the current unit,
28990 or, if the subprogram is in another unit, by using pragma
28991 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
28992 on the referenced unit.
28994 If the referenced body is not known to have been elaborated at the point
28995 the access value is created, then any use of the access value must do a
28996 dynamic check, and this dynamic check will fail and raise a
28997 @code{Program_Error} exception if the body has not been elaborated yet.
28998 GNAT will generate the necessary checks, and in addition, if the
29000 switch is set, will generate warnings that such checks are required.
29002 The use of dynamic dispatching for tagged types similarly generates
29003 a requirement for dynamic checks, and premature calls to any primitive
29004 operation of a tagged type before the body of the operation has been
29005 elaborated, will result in the raising of @code{Program_Error}.
29007 @node Summary of Procedures for Elaboration Control
29008 @section Summary of Procedures for Elaboration Control
29009 @cindex Elaboration control
29012 First, compile your program with the default options, using none of
29013 the special elaboration control switches. If the binder successfully
29014 binds your program, then you can be confident that, apart from issues
29015 raised by the use of access-to-subprogram types and dynamic dispatching,
29016 the program is free of elaboration errors. If it is important that the
29017 program be portable, then use the
29019 switch to generate warnings about missing @code{Elaborate} or
29020 @code{Elaborate_All} pragmas, and supply the missing pragmas.
29022 If the program fails to bind using the default static elaboration
29023 handling, then you can fix the program to eliminate the binder
29024 message, or recompile the entire program with the
29025 @option{-gnatE} switch to generate dynamic elaboration checks,
29026 and, if you are sure there really are no elaboration problems,
29027 use a global pragma @code{Suppress (Elaboration_Check)}.
29029 @node Other Elaboration Order Considerations
29030 @section Other Elaboration Order Considerations
29032 This section has been entirely concerned with the issue of finding a valid
29033 elaboration order, as defined by the Ada Reference Manual. In a case
29034 where several elaboration orders are valid, the task is to find one
29035 of the possible valid elaboration orders (and the static model in GNAT
29036 will ensure that this is achieved).
29038 The purpose of the elaboration rules in the Ada Reference Manual is to
29039 make sure that no entity is accessed before it has been elaborated. For
29040 a subprogram, this means that the spec and body must have been elaborated
29041 before the subprogram is called. For an object, this means that the object
29042 must have been elaborated before its value is read or written. A violation
29043 of either of these two requirements is an access before elaboration order,
29044 and this section has been all about avoiding such errors.
29046 In the case where more than one order of elaboration is possible, in the
29047 sense that access before elaboration errors are avoided, then any one of
29048 the orders is ``correct'' in the sense that it meets the requirements of
29049 the Ada Reference Manual, and no such error occurs.
29051 However, it may be the case for a given program, that there are
29052 constraints on the order of elaboration that come not from consideration
29053 of avoiding elaboration errors, but rather from extra-lingual logic
29054 requirements. Consider this example:
29056 @smallexample @c ada
29057 with Init_Constants;
29058 package Constants is
29063 package Init_Constants is
29064 procedure P; -- require a body
29065 end Init_Constants;
29068 package body Init_Constants is
29069 procedure P is begin null; end;
29073 end Init_Constants;
29077 Z : Integer := Constants.X + Constants.Y;
29081 with Text_IO; use Text_IO;
29084 Put_Line (Calc.Z'Img);
29089 In this example, there is more than one valid order of elaboration. For
29090 example both the following are correct orders:
29093 Init_Constants spec
29096 Init_Constants body
29101 Init_Constants spec
29102 Init_Constants body
29109 There is no language rule to prefer one or the other, both are correct
29110 from an order of elaboration point of view. But the programmatic effects
29111 of the two orders are very different. In the first, the elaboration routine
29112 of @code{Calc} initializes @code{Z} to zero, and then the main program
29113 runs with this value of zero. But in the second order, the elaboration
29114 routine of @code{Calc} runs after the body of Init_Constants has set
29115 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
29118 One could perhaps by applying pretty clever non-artificial intelligence
29119 to the situation guess that it is more likely that the second order of
29120 elaboration is the one desired, but there is no formal linguistic reason
29121 to prefer one over the other. In fact in this particular case, GNAT will
29122 prefer the second order, because of the rule that bodies are elaborated
29123 as soon as possible, but it's just luck that this is what was wanted
29124 (if indeed the second order was preferred).
29126 If the program cares about the order of elaboration routines in a case like
29127 this, it is important to specify the order required. In this particular
29128 case, that could have been achieved by adding to the spec of Calc:
29130 @smallexample @c ada
29131 pragma Elaborate_All (Constants);
29135 which requires that the body (if any) and spec of @code{Constants},
29136 as well as the body and spec of any unit @code{with}'ed by
29137 @code{Constants} be elaborated before @code{Calc} is elaborated.
29139 Clearly no automatic method can always guess which alternative you require,
29140 and if you are working with legacy code that had constraints of this kind
29141 which were not properly specified by adding @code{Elaborate} or
29142 @code{Elaborate_All} pragmas, then indeed it is possible that two different
29143 compilers can choose different orders.
29145 However, GNAT does attempt to diagnose the common situation where there
29146 are uninitialized variables in the visible part of a package spec, and the
29147 corresponding package body has an elaboration block that directly or
29148 indirectly initialized one or more of these variables. This is the situation
29149 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
29150 a warning that suggests this addition if it detects this situation.
29152 The @code{gnatbind}
29153 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
29154 out problems. This switch causes bodies to be elaborated as late as possible
29155 instead of as early as possible. In the example above, it would have forced
29156 the choice of the first elaboration order. If you get different results
29157 when using this switch, and particularly if one set of results is right,
29158 and one is wrong as far as you are concerned, it shows that you have some
29159 missing @code{Elaborate} pragmas. For the example above, we have the
29163 gnatmake -f -q main
29166 gnatmake -f -q main -bargs -p
29172 It is of course quite unlikely that both these results are correct, so
29173 it is up to you in a case like this to investigate the source of the
29174 difference, by looking at the two elaboration orders that are chosen,
29175 and figuring out which is correct, and then adding the necessary
29176 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
29180 @c *******************************
29181 @node Conditional Compilation
29182 @appendix Conditional Compilation
29183 @c *******************************
29184 @cindex Conditional compilation
29187 It is often necessary to arrange for a single source program
29188 to serve multiple purposes, where it is compiled in different
29189 ways to achieve these different goals. Some examples of the
29190 need for this feature are
29193 @item Adapting a program to a different hardware environment
29194 @item Adapting a program to a different target architecture
29195 @item Turning debugging features on and off
29196 @item Arranging for a program to compile with different compilers
29200 In C, or C++, the typical approach would be to use the preprocessor
29201 that is defined as part of the language. The Ada language does not
29202 contain such a feature. This is not an oversight, but rather a very
29203 deliberate design decision, based on the experience that overuse of
29204 the preprocessing features in C and C++ can result in programs that
29205 are extremely difficult to maintain. For example, if we have ten
29206 switches that can be on or off, this means that there are a thousand
29207 separate programs, any one of which might not even be syntactically
29208 correct, and even if syntactically correct, the resulting program
29209 might not work correctly. Testing all combinations can quickly become
29212 Nevertheless, the need to tailor programs certainly exists, and in
29213 this Appendix we will discuss how this can
29214 be achieved using Ada in general, and GNAT in particular.
29217 * Use of Boolean Constants::
29218 * Debugging - A Special Case::
29219 * Conditionalizing Declarations::
29220 * Use of Alternative Implementations::
29224 @node Use of Boolean Constants
29225 @section Use of Boolean Constants
29228 In the case where the difference is simply which code
29229 sequence is executed, the cleanest solution is to use Boolean
29230 constants to control which code is executed.
29232 @smallexample @c ada
29234 FP_Initialize_Required : constant Boolean := True;
29236 if FP_Initialize_Required then
29243 Not only will the code inside the @code{if} statement not be executed if
29244 the constant Boolean is @code{False}, but it will also be completely
29245 deleted from the program.
29246 However, the code is only deleted after the @code{if} statement
29247 has been checked for syntactic and semantic correctness.
29248 (In contrast, with preprocessors the code is deleted before the
29249 compiler ever gets to see it, so it is not checked until the switch
29251 @cindex Preprocessors (contrasted with conditional compilation)
29253 Typically the Boolean constants will be in a separate package,
29256 @smallexample @c ada
29259 FP_Initialize_Required : constant Boolean := True;
29260 Reset_Available : constant Boolean := False;
29267 The @code{Config} package exists in multiple forms for the various targets,
29268 with an appropriate script selecting the version of @code{Config} needed.
29269 Then any other unit requiring conditional compilation can do a @code{with}
29270 of @code{Config} to make the constants visible.
29273 @node Debugging - A Special Case
29274 @section Debugging - A Special Case
29277 A common use of conditional code is to execute statements (for example
29278 dynamic checks, or output of intermediate results) under control of a
29279 debug switch, so that the debugging behavior can be turned on and off.
29280 This can be done using a Boolean constant to control whether the code
29283 @smallexample @c ada
29286 Put_Line ("got to the first stage!");
29294 @smallexample @c ada
29296 if Debugging and then Temperature > 999.0 then
29297 raise Temperature_Crazy;
29303 Since this is a common case, there are special features to deal with
29304 this in a convenient manner. For the case of tests, Ada 2005 has added
29305 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
29306 @cindex pragma @code{Assert}
29307 on the @code{Assert} pragma that has always been available in GNAT, so this
29308 feature may be used with GNAT even if you are not using Ada 2005 features.
29309 The use of pragma @code{Assert} is described in
29310 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
29311 example, the last test could be written:
29313 @smallexample @c ada
29314 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
29320 @smallexample @c ada
29321 pragma Assert (Temperature <= 999.0);
29325 In both cases, if assertions are active and the temperature is excessive,
29326 the exception @code{Assert_Failure} will be raised, with the given string in
29327 the first case or a string indicating the location of the pragma in the second
29328 case used as the exception message.
29330 You can turn assertions on and off by using the @code{Assertion_Policy}
29332 @cindex pragma @code{Assertion_Policy}
29333 This is an Ada 2005 pragma which is implemented in all modes by
29334 GNAT, but only in the latest versions of GNAT which include Ada 2005
29335 capability. Alternatively, you can use the @option{-gnata} switch
29336 @cindex @option{-gnata} switch
29337 to enable assertions from the command line (this is recognized by all versions
29340 For the example above with the @code{Put_Line}, the GNAT-specific pragma
29341 @code{Debug} can be used:
29342 @cindex pragma @code{Debug}
29344 @smallexample @c ada
29345 pragma Debug (Put_Line ("got to the first stage!"));
29349 If debug pragmas are enabled, the argument, which must be of the form of
29350 a procedure call, is executed (in this case, @code{Put_Line} will be called).
29351 Only one call can be present, but of course a special debugging procedure
29352 containing any code you like can be included in the program and then
29353 called in a pragma @code{Debug} argument as needed.
29355 One advantage of pragma @code{Debug} over the @code{if Debugging then}
29356 construct is that pragma @code{Debug} can appear in declarative contexts,
29357 such as at the very beginning of a procedure, before local declarations have
29360 Debug pragmas are enabled using either the @option{-gnata} switch that also
29361 controls assertions, or with a separate Debug_Policy pragma.
29362 @cindex pragma @code{Debug_Policy}
29363 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
29364 in Ada 95 and Ada 83 programs as well), and is analogous to
29365 pragma @code{Assertion_Policy} to control assertions.
29367 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
29368 and thus they can appear in @file{gnat.adc} if you are not using a
29369 project file, or in the file designated to contain configuration pragmas
29371 They then apply to all subsequent compilations. In practice the use of
29372 the @option{-gnata} switch is often the most convenient method of controlling
29373 the status of these pragmas.
29375 Note that a pragma is not a statement, so in contexts where a statement
29376 sequence is required, you can't just write a pragma on its own. You have
29377 to add a @code{null} statement.
29379 @smallexample @c ada
29382 @dots{} -- some statements
29384 pragma Assert (Num_Cases < 10);
29391 @node Conditionalizing Declarations
29392 @section Conditionalizing Declarations
29395 In some cases, it may be necessary to conditionalize declarations to meet
29396 different requirements. For example we might want a bit string whose length
29397 is set to meet some hardware message requirement.
29399 In some cases, it may be possible to do this using declare blocks controlled
29400 by conditional constants:
29402 @smallexample @c ada
29404 if Small_Machine then
29406 X : Bit_String (1 .. 10);
29412 X : Large_Bit_String (1 .. 1000);
29421 Note that in this approach, both declarations are analyzed by the
29422 compiler so this can only be used where both declarations are legal,
29423 even though one of them will not be used.
29425 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
29426 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
29427 that are parameterized by these constants. For example
29429 @smallexample @c ada
29432 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
29438 If @code{Bits_Per_Word} is set to 32, this generates either
29440 @smallexample @c ada
29443 Field1 at 0 range 0 .. 32;
29449 for the big endian case, or
29451 @smallexample @c ada
29454 Field1 at 0 range 10 .. 32;
29460 for the little endian case. Since a powerful subset of Ada expression
29461 notation is usable for creating static constants, clever use of this
29462 feature can often solve quite difficult problems in conditionalizing
29463 compilation (note incidentally that in Ada 95, the little endian
29464 constant was introduced as @code{System.Default_Bit_Order}, so you do not
29465 need to define this one yourself).
29468 @node Use of Alternative Implementations
29469 @section Use of Alternative Implementations
29472 In some cases, none of the approaches described above are adequate. This
29473 can occur for example if the set of declarations required is radically
29474 different for two different configurations.
29476 In this situation, the official Ada way of dealing with conditionalizing
29477 such code is to write separate units for the different cases. As long as
29478 this does not result in excessive duplication of code, this can be done
29479 without creating maintenance problems. The approach is to share common
29480 code as far as possible, and then isolate the code and declarations
29481 that are different. Subunits are often a convenient method for breaking
29482 out a piece of a unit that is to be conditionalized, with separate files
29483 for different versions of the subunit for different targets, where the
29484 build script selects the right one to give to the compiler.
29485 @cindex Subunits (and conditional compilation)
29487 As an example, consider a situation where a new feature in Ada 2005
29488 allows something to be done in a really nice way. But your code must be able
29489 to compile with an Ada 95 compiler. Conceptually you want to say:
29491 @smallexample @c ada
29494 @dots{} neat Ada 2005 code
29496 @dots{} not quite as neat Ada 95 code
29502 where @code{Ada_2005} is a Boolean constant.
29504 But this won't work when @code{Ada_2005} is set to @code{False},
29505 since the @code{then} clause will be illegal for an Ada 95 compiler.
29506 (Recall that although such unreachable code would eventually be deleted
29507 by the compiler, it still needs to be legal. If it uses features
29508 introduced in Ada 2005, it will be illegal in Ada 95.)
29510 So instead we write
29512 @smallexample @c ada
29513 procedure Insert is separate;
29517 Then we have two files for the subunit @code{Insert}, with the two sets of
29519 If the package containing this is called @code{File_Queries}, then we might
29523 @item @file{file_queries-insert-2005.adb}
29524 @item @file{file_queries-insert-95.adb}
29528 and the build script renames the appropriate file to
29531 file_queries-insert.adb
29535 and then carries out the compilation.
29537 This can also be done with project files' naming schemes. For example:
29539 @smallexample @c project
29540 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
29544 Note also that with project files it is desirable to use a different extension
29545 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
29546 conflict may arise through another commonly used feature: to declare as part
29547 of the project a set of directories containing all the sources obeying the
29548 default naming scheme.
29550 The use of alternative units is certainly feasible in all situations,
29551 and for example the Ada part of the GNAT run-time is conditionalized
29552 based on the target architecture using this approach. As a specific example,
29553 consider the implementation of the AST feature in VMS. There is one
29561 which is the same for all architectures, and three bodies:
29565 used for all non-VMS operating systems
29566 @item s-asthan-vms-alpha.adb
29567 used for VMS on the Alpha
29568 @item s-asthan-vms-ia64.adb
29569 used for VMS on the ia64
29573 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
29574 this operating system feature is not available, and the two remaining
29575 versions interface with the corresponding versions of VMS to provide
29576 VMS-compatible AST handling. The GNAT build script knows the architecture
29577 and operating system, and automatically selects the right version,
29578 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
29580 Another style for arranging alternative implementations is through Ada's
29581 access-to-subprogram facility.
29582 In case some functionality is to be conditionally included,
29583 you can declare an access-to-procedure variable @code{Ref} that is initialized
29584 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
29586 In some library package, set @code{Ref} to @code{Proc'Access} for some
29587 procedure @code{Proc} that performs the relevant processing.
29588 The initialization only occurs if the library package is included in the
29590 The same idea can also be implemented using tagged types and dispatching
29594 @node Preprocessing
29595 @section Preprocessing
29596 @cindex Preprocessing
29599 Although it is quite possible to conditionalize code without the use of
29600 C-style preprocessing, as described earlier in this section, it is
29601 nevertheless convenient in some cases to use the C approach. Moreover,
29602 older Ada compilers have often provided some preprocessing capability,
29603 so legacy code may depend on this approach, even though it is not
29606 To accommodate such use, GNAT provides a preprocessor (modeled to a large
29607 extent on the various preprocessors that have been used
29608 with legacy code on other compilers, to enable easier transition).
29610 The preprocessor may be used in two separate modes. It can be used quite
29611 separately from the compiler, to generate a separate output source file
29612 that is then fed to the compiler as a separate step. This is the
29613 @code{gnatprep} utility, whose use is fully described in
29614 @ref{Preprocessing Using gnatprep}.
29615 @cindex @code{gnatprep}
29617 The preprocessing language allows such constructs as
29621 #if DEBUG or PRIORITY > 4 then
29622 bunch of declarations
29624 completely different bunch of declarations
29630 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
29631 defined either on the command line or in a separate file.
29633 The other way of running the preprocessor is even closer to the C style and
29634 often more convenient. In this approach the preprocessing is integrated into
29635 the compilation process. The compiler is fed the preprocessor input which
29636 includes @code{#if} lines etc, and then the compiler carries out the
29637 preprocessing internally and processes the resulting output.
29638 For more details on this approach, see @ref{Integrated Preprocessing}.
29641 @c *******************************
29642 @node Inline Assembler
29643 @appendix Inline Assembler
29644 @c *******************************
29647 If you need to write low-level software that interacts directly
29648 with the hardware, Ada provides two ways to incorporate assembly
29649 language code into your program. First, you can import and invoke
29650 external routines written in assembly language, an Ada feature fully
29651 supported by GNAT@. However, for small sections of code it may be simpler
29652 or more efficient to include assembly language statements directly
29653 in your Ada source program, using the facilities of the implementation-defined
29654 package @code{System.Machine_Code}, which incorporates the gcc
29655 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29656 including the following:
29659 @item No need to use non-Ada tools
29660 @item Consistent interface over different targets
29661 @item Automatic usage of the proper calling conventions
29662 @item Access to Ada constants and variables
29663 @item Definition of intrinsic routines
29664 @item Possibility of inlining a subprogram comprising assembler code
29665 @item Code optimizer can take Inline Assembler code into account
29668 This chapter presents a series of examples to show you how to use
29669 the Inline Assembler. Although it focuses on the Intel x86,
29670 the general approach applies also to other processors.
29671 It is assumed that you are familiar with Ada
29672 and with assembly language programming.
29675 * Basic Assembler Syntax::
29676 * A Simple Example of Inline Assembler::
29677 * Output Variables in Inline Assembler::
29678 * Input Variables in Inline Assembler::
29679 * Inlining Inline Assembler Code::
29680 * Other Asm Functionality::
29683 @c ---------------------------------------------------------------------------
29684 @node Basic Assembler Syntax
29685 @section Basic Assembler Syntax
29688 The assembler used by GNAT and gcc is based not on the Intel assembly
29689 language, but rather on a language that descends from the AT&T Unix
29690 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
29691 The following table summarizes the main features of @emph{as} syntax
29692 and points out the differences from the Intel conventions.
29693 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
29694 pre-processor) documentation for further information.
29697 @item Register names
29698 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
29700 Intel: No extra punctuation; for example @code{eax}
29702 @item Immediate operand
29703 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
29705 Intel: No extra punctuation; for example @code{4}
29708 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
29710 Intel: No extra punctuation; for example @code{loc}
29712 @item Memory contents
29713 gcc / @emph{as}: No extra punctuation; for example @code{loc}
29715 Intel: Square brackets; for example @code{[loc]}
29717 @item Register contents
29718 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
29720 Intel: Square brackets; for example @code{[eax]}
29722 @item Hexadecimal numbers
29723 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
29725 Intel: Trailing ``h''; for example @code{A0h}
29728 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
29731 Intel: Implicit, deduced by assembler; for example @code{mov}
29733 @item Instruction repetition
29734 gcc / @emph{as}: Split into two lines; for example
29740 Intel: Keep on one line; for example @code{rep stosl}
29742 @item Order of operands
29743 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
29745 Intel: Destination first; for example @code{mov eax, 4}
29748 @c ---------------------------------------------------------------------------
29749 @node A Simple Example of Inline Assembler
29750 @section A Simple Example of Inline Assembler
29753 The following example will generate a single assembly language statement,
29754 @code{nop}, which does nothing. Despite its lack of run-time effect,
29755 the example will be useful in illustrating the basics of
29756 the Inline Assembler facility.
29758 @smallexample @c ada
29760 with System.Machine_Code; use System.Machine_Code;
29761 procedure Nothing is
29768 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29769 here it takes one parameter, a @emph{template string} that must be a static
29770 expression and that will form the generated instruction.
29771 @code{Asm} may be regarded as a compile-time procedure that parses
29772 the template string and additional parameters (none here),
29773 from which it generates a sequence of assembly language instructions.
29775 The examples in this chapter will illustrate several of the forms
29776 for invoking @code{Asm}; a complete specification of the syntax
29777 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
29780 Under the standard GNAT conventions, the @code{Nothing} procedure
29781 should be in a file named @file{nothing.adb}.
29782 You can build the executable in the usual way:
29786 However, the interesting aspect of this example is not its run-time behavior
29787 but rather the generated assembly code.
29788 To see this output, invoke the compiler as follows:
29790 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
29792 where the options are:
29796 compile only (no bind or link)
29798 generate assembler listing
29799 @item -fomit-frame-pointer
29800 do not set up separate stack frames
29802 do not add runtime checks
29805 This gives a human-readable assembler version of the code. The resulting
29806 file will have the same name as the Ada source file, but with a @code{.s}
29807 extension. In our example, the file @file{nothing.s} has the following
29812 .file "nothing.adb"
29814 ___gnu_compiled_ada:
29817 .globl __ada_nothing
29829 The assembly code you included is clearly indicated by
29830 the compiler, between the @code{#APP} and @code{#NO_APP}
29831 delimiters. The character before the 'APP' and 'NOAPP'
29832 can differ on different targets. For example, GNU/Linux uses '#APP' while
29833 on NT you will see '/APP'.
29835 If you make a mistake in your assembler code (such as using the
29836 wrong size modifier, or using a wrong operand for the instruction) GNAT
29837 will report this error in a temporary file, which will be deleted when
29838 the compilation is finished. Generating an assembler file will help
29839 in such cases, since you can assemble this file separately using the
29840 @emph{as} assembler that comes with gcc.
29842 Assembling the file using the command
29845 as @file{nothing.s}
29848 will give you error messages whose lines correspond to the assembler
29849 input file, so you can easily find and correct any mistakes you made.
29850 If there are no errors, @emph{as} will generate an object file
29851 @file{nothing.out}.
29853 @c ---------------------------------------------------------------------------
29854 @node Output Variables in Inline Assembler
29855 @section Output Variables in Inline Assembler
29858 The examples in this section, showing how to access the processor flags,
29859 illustrate how to specify the destination operands for assembly language
29862 @smallexample @c ada
29864 with Interfaces; use Interfaces;
29865 with Ada.Text_IO; use Ada.Text_IO;
29866 with System.Machine_Code; use System.Machine_Code;
29867 procedure Get_Flags is
29868 Flags : Unsigned_32;
29871 Asm ("pushfl" & LF & HT & -- push flags on stack
29872 "popl %%eax" & LF & HT & -- load eax with flags
29873 "movl %%eax, %0", -- store flags in variable
29874 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29875 Put_Line ("Flags register:" & Flags'Img);
29880 In order to have a nicely aligned assembly listing, we have separated
29881 multiple assembler statements in the Asm template string with linefeed
29882 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29883 The resulting section of the assembly output file is:
29890 movl %eax, -40(%ebp)
29895 It would have been legal to write the Asm invocation as:
29898 Asm ("pushfl popl %%eax movl %%eax, %0")
29901 but in the generated assembler file, this would come out as:
29905 pushfl popl %eax movl %eax, -40(%ebp)
29909 which is not so convenient for the human reader.
29911 We use Ada comments
29912 at the end of each line to explain what the assembler instructions
29913 actually do. This is a useful convention.
29915 When writing Inline Assembler instructions, you need to precede each register
29916 and variable name with a percent sign. Since the assembler already requires
29917 a percent sign at the beginning of a register name, you need two consecutive
29918 percent signs for such names in the Asm template string, thus @code{%%eax}.
29919 In the generated assembly code, one of the percent signs will be stripped off.
29921 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29922 variables: operands you later define using @code{Input} or @code{Output}
29923 parameters to @code{Asm}.
29924 An output variable is illustrated in
29925 the third statement in the Asm template string:
29929 The intent is to store the contents of the eax register in a variable that can
29930 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29931 necessarily work, since the compiler might optimize by using a register
29932 to hold Flags, and the expansion of the @code{movl} instruction would not be
29933 aware of this optimization. The solution is not to store the result directly
29934 but rather to advise the compiler to choose the correct operand form;
29935 that is the purpose of the @code{%0} output variable.
29937 Information about the output variable is supplied in the @code{Outputs}
29938 parameter to @code{Asm}:
29940 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29943 The output is defined by the @code{Asm_Output} attribute of the target type;
29944 the general format is
29946 Type'Asm_Output (constraint_string, variable_name)
29949 The constraint string directs the compiler how
29950 to store/access the associated variable. In the example
29952 Unsigned_32'Asm_Output ("=m", Flags);
29954 the @code{"m"} (memory) constraint tells the compiler that the variable
29955 @code{Flags} should be stored in a memory variable, thus preventing
29956 the optimizer from keeping it in a register. In contrast,
29958 Unsigned_32'Asm_Output ("=r", Flags);
29960 uses the @code{"r"} (register) constraint, telling the compiler to
29961 store the variable in a register.
29963 If the constraint is preceded by the equal character (@strong{=}), it tells
29964 the compiler that the variable will be used to store data into it.
29966 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29967 allowing the optimizer to choose whatever it deems best.
29969 There are a fairly large number of constraints, but the ones that are
29970 most useful (for the Intel x86 processor) are the following:
29976 global (i.e.@: can be stored anywhere)
29994 use one of eax, ebx, ecx or edx
29996 use one of eax, ebx, ecx, edx, esi or edi
29999 The full set of constraints is described in the gcc and @emph{as}
30000 documentation; note that it is possible to combine certain constraints
30001 in one constraint string.
30003 You specify the association of an output variable with an assembler operand
30004 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
30006 @smallexample @c ada
30008 Asm ("pushfl" & LF & HT & -- push flags on stack
30009 "popl %%eax" & LF & HT & -- load eax with flags
30010 "movl %%eax, %0", -- store flags in variable
30011 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30015 @code{%0} will be replaced in the expanded code by the appropriate operand,
30017 the compiler decided for the @code{Flags} variable.
30019 In general, you may have any number of output variables:
30022 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
30024 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
30025 of @code{Asm_Output} attributes
30029 @smallexample @c ada
30031 Asm ("movl %%eax, %0" & LF & HT &
30032 "movl %%ebx, %1" & LF & HT &
30034 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
30035 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
30036 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
30040 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
30041 in the Ada program.
30043 As a variation on the @code{Get_Flags} example, we can use the constraints
30044 string to direct the compiler to store the eax register into the @code{Flags}
30045 variable, instead of including the store instruction explicitly in the
30046 @code{Asm} template string:
30048 @smallexample @c ada
30050 with Interfaces; use Interfaces;
30051 with Ada.Text_IO; use Ada.Text_IO;
30052 with System.Machine_Code; use System.Machine_Code;
30053 procedure Get_Flags_2 is
30054 Flags : Unsigned_32;
30057 Asm ("pushfl" & LF & HT & -- push flags on stack
30058 "popl %%eax", -- save flags in eax
30059 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
30060 Put_Line ("Flags register:" & Flags'Img);
30066 The @code{"a"} constraint tells the compiler that the @code{Flags}
30067 variable will come from the eax register. Here is the resulting code:
30075 movl %eax,-40(%ebp)
30080 The compiler generated the store of eax into Flags after
30081 expanding the assembler code.
30083 Actually, there was no need to pop the flags into the eax register;
30084 more simply, we could just pop the flags directly into the program variable:
30086 @smallexample @c ada
30088 with Interfaces; use Interfaces;
30089 with Ada.Text_IO; use Ada.Text_IO;
30090 with System.Machine_Code; use System.Machine_Code;
30091 procedure Get_Flags_3 is
30092 Flags : Unsigned_32;
30095 Asm ("pushfl" & LF & HT & -- push flags on stack
30096 "pop %0", -- save flags in Flags
30097 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30098 Put_Line ("Flags register:" & Flags'Img);
30103 @c ---------------------------------------------------------------------------
30104 @node Input Variables in Inline Assembler
30105 @section Input Variables in Inline Assembler
30108 The example in this section illustrates how to specify the source operands
30109 for assembly language statements.
30110 The program simply increments its input value by 1:
30112 @smallexample @c ada
30114 with Interfaces; use Interfaces;
30115 with Ada.Text_IO; use Ada.Text_IO;
30116 with System.Machine_Code; use System.Machine_Code;
30117 procedure Increment is
30119 function Incr (Value : Unsigned_32) return Unsigned_32 is
30120 Result : Unsigned_32;
30123 Inputs => Unsigned_32'Asm_Input ("a", Value),
30124 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30128 Value : Unsigned_32;
30132 Put_Line ("Value before is" & Value'Img);
30133 Value := Incr (Value);
30134 Put_Line ("Value after is" & Value'Img);
30139 The @code{Outputs} parameter to @code{Asm} specifies
30140 that the result will be in the eax register and that it is to be stored
30141 in the @code{Result} variable.
30143 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
30144 but with an @code{Asm_Input} attribute.
30145 The @code{"="} constraint, indicating an output value, is not present.
30147 You can have multiple input variables, in the same way that you can have more
30148 than one output variable.
30150 The parameter count (%0, %1) etc, now starts at the first input
30151 statement, and continues with the output statements.
30152 When both parameters use the same variable, the
30153 compiler will treat them as the same %n operand, which is the case here.
30155 Just as the @code{Outputs} parameter causes the register to be stored into the
30156 target variable after execution of the assembler statements, so does the
30157 @code{Inputs} parameter cause its variable to be loaded into the register
30158 before execution of the assembler statements.
30160 Thus the effect of the @code{Asm} invocation is:
30162 @item load the 32-bit value of @code{Value} into eax
30163 @item execute the @code{incl %eax} instruction
30164 @item store the contents of eax into the @code{Result} variable
30167 The resulting assembler file (with @option{-O2} optimization) contains:
30170 _increment__incr.1:
30183 @c ---------------------------------------------------------------------------
30184 @node Inlining Inline Assembler Code
30185 @section Inlining Inline Assembler Code
30188 For a short subprogram such as the @code{Incr} function in the previous
30189 section, the overhead of the call and return (creating / deleting the stack
30190 frame) can be significant, compared to the amount of code in the subprogram
30191 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
30192 which directs the compiler to expand invocations of the subprogram at the
30193 point(s) of call, instead of setting up a stack frame for out-of-line calls.
30194 Here is the resulting program:
30196 @smallexample @c ada
30198 with Interfaces; use Interfaces;
30199 with Ada.Text_IO; use Ada.Text_IO;
30200 with System.Machine_Code; use System.Machine_Code;
30201 procedure Increment_2 is
30203 function Incr (Value : Unsigned_32) return Unsigned_32 is
30204 Result : Unsigned_32;
30207 Inputs => Unsigned_32'Asm_Input ("a", Value),
30208 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30211 pragma Inline (Increment);
30213 Value : Unsigned_32;
30217 Put_Line ("Value before is" & Value'Img);
30218 Value := Increment (Value);
30219 Put_Line ("Value after is" & Value'Img);
30224 Compile the program with both optimization (@option{-O2}) and inlining
30225 (@option{-gnatn}) enabled.
30227 The @code{Incr} function is still compiled as usual, but at the
30228 point in @code{Increment} where our function used to be called:
30233 call _increment__incr.1
30238 the code for the function body directly appears:
30251 thus saving the overhead of stack frame setup and an out-of-line call.
30253 @c ---------------------------------------------------------------------------
30254 @node Other Asm Functionality
30255 @section Other @code{Asm} Functionality
30258 This section describes two important parameters to the @code{Asm}
30259 procedure: @code{Clobber}, which identifies register usage;
30260 and @code{Volatile}, which inhibits unwanted optimizations.
30263 * The Clobber Parameter::
30264 * The Volatile Parameter::
30267 @c ---------------------------------------------------------------------------
30268 @node The Clobber Parameter
30269 @subsection The @code{Clobber} Parameter
30272 One of the dangers of intermixing assembly language and a compiled language
30273 such as Ada is that the compiler needs to be aware of which registers are
30274 being used by the assembly code. In some cases, such as the earlier examples,
30275 the constraint string is sufficient to indicate register usage (e.g.,
30277 the eax register). But more generally, the compiler needs an explicit
30278 identification of the registers that are used by the Inline Assembly
30281 Using a register that the compiler doesn't know about
30282 could be a side effect of an instruction (like @code{mull}
30283 storing its result in both eax and edx).
30284 It can also arise from explicit register usage in your
30285 assembly code; for example:
30288 Asm ("movl %0, %%ebx" & LF & HT &
30290 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30291 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
30295 where the compiler (since it does not analyze the @code{Asm} template string)
30296 does not know you are using the ebx register.
30298 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
30299 to identify the registers that will be used by your assembly code:
30303 Asm ("movl %0, %%ebx" & LF & HT &
30305 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30306 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30311 The Clobber parameter is a static string expression specifying the
30312 register(s) you are using. Note that register names are @emph{not} prefixed
30313 by a percent sign. Also, if more than one register is used then their names
30314 are separated by commas; e.g., @code{"eax, ebx"}
30316 The @code{Clobber} parameter has several additional uses:
30318 @item Use ``register'' name @code{cc} to indicate that flags might have changed
30319 @item Use ``register'' name @code{memory} if you changed a memory location
30322 @c ---------------------------------------------------------------------------
30323 @node The Volatile Parameter
30324 @subsection The @code{Volatile} Parameter
30325 @cindex Volatile parameter
30328 Compiler optimizations in the presence of Inline Assembler may sometimes have
30329 unwanted effects. For example, when an @code{Asm} invocation with an input
30330 variable is inside a loop, the compiler might move the loading of the input
30331 variable outside the loop, regarding it as a one-time initialization.
30333 If this effect is not desired, you can disable such optimizations by setting
30334 the @code{Volatile} parameter to @code{True}; for example:
30336 @smallexample @c ada
30338 Asm ("movl %0, %%ebx" & LF & HT &
30340 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30341 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30347 By default, @code{Volatile} is set to @code{False} unless there is no
30348 @code{Outputs} parameter.
30350 Although setting @code{Volatile} to @code{True} prevents unwanted
30351 optimizations, it will also disable other optimizations that might be
30352 important for efficiency. In general, you should set @code{Volatile}
30353 to @code{True} only if the compiler's optimizations have created
30355 @c END OF INLINE ASSEMBLER CHAPTER
30356 @c ===============================
30358 @c ***********************************
30359 @c * Compatibility and Porting Guide *
30360 @c ***********************************
30361 @node Compatibility and Porting Guide
30362 @appendix Compatibility and Porting Guide
30365 This chapter describes the compatibility issues that may arise between
30366 GNAT and other Ada compilation systems (including those for Ada 83),
30367 and shows how GNAT can expedite porting
30368 applications developed in other Ada environments.
30371 * Compatibility with Ada 83::
30372 * Compatibility between Ada 95 and Ada 2005::
30373 * Implementation-dependent characteristics::
30374 * Compatibility with Other Ada Systems::
30375 * Representation Clauses::
30377 @c Brief section is only in non-VMS version
30378 @c Full chapter is in VMS version
30379 * Compatibility with HP Ada 83::
30382 * Transitioning to 64-Bit GNAT for OpenVMS::
30386 @node Compatibility with Ada 83
30387 @section Compatibility with Ada 83
30388 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
30391 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
30392 particular, the design intention was that the difficulties associated
30393 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
30394 that occur when moving from one Ada 83 system to another.
30396 However, there are a number of points at which there are minor
30397 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
30398 full details of these issues,
30399 and should be consulted for a complete treatment.
30401 following subsections treat the most likely issues to be encountered.
30404 * Legal Ada 83 programs that are illegal in Ada 95::
30405 * More deterministic semantics::
30406 * Changed semantics::
30407 * Other language compatibility issues::
30410 @node Legal Ada 83 programs that are illegal in Ada 95
30411 @subsection Legal Ada 83 programs that are illegal in Ada 95
30413 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
30414 Ada 95 and thus also in Ada 2005:
30417 @item Character literals
30418 Some uses of character literals are ambiguous. Since Ada 95 has introduced
30419 @code{Wide_Character} as a new predefined character type, some uses of
30420 character literals that were legal in Ada 83 are illegal in Ada 95.
30422 @smallexample @c ada
30423 for Char in 'A' .. 'Z' loop @dots{} end loop;
30427 The problem is that @code{'A'} and @code{'Z'} could be from either
30428 @code{Character} or @code{Wide_Character}. The simplest correction
30429 is to make the type explicit; e.g.:
30430 @smallexample @c ada
30431 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
30434 @item New reserved words
30435 The identifiers @code{abstract}, @code{aliased}, @code{protected},
30436 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
30437 Existing Ada 83 code using any of these identifiers must be edited to
30438 use some alternative name.
30440 @item Freezing rules
30441 The rules in Ada 95 are slightly different with regard to the point at
30442 which entities are frozen, and representation pragmas and clauses are
30443 not permitted past the freeze point. This shows up most typically in
30444 the form of an error message complaining that a representation item
30445 appears too late, and the appropriate corrective action is to move
30446 the item nearer to the declaration of the entity to which it refers.
30448 A particular case is that representation pragmas
30451 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
30453 cannot be applied to a subprogram body. If necessary, a separate subprogram
30454 declaration must be introduced to which the pragma can be applied.
30456 @item Optional bodies for library packages
30457 In Ada 83, a package that did not require a package body was nevertheless
30458 allowed to have one. This lead to certain surprises in compiling large
30459 systems (situations in which the body could be unexpectedly ignored by the
30460 binder). In Ada 95, if a package does not require a body then it is not
30461 permitted to have a body. To fix this problem, simply remove a redundant
30462 body if it is empty, or, if it is non-empty, introduce a dummy declaration
30463 into the spec that makes the body required. One approach is to add a private
30464 part to the package declaration (if necessary), and define a parameterless
30465 procedure called @code{Requires_Body}, which must then be given a dummy
30466 procedure body in the package body, which then becomes required.
30467 Another approach (assuming that this does not introduce elaboration
30468 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
30469 since one effect of this pragma is to require the presence of a package body.
30471 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
30472 In Ada 95, the exception @code{Numeric_Error} is a renaming of
30473 @code{Constraint_Error}.
30474 This means that it is illegal to have separate exception handlers for
30475 the two exceptions. The fix is simply to remove the handler for the
30476 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
30477 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
30479 @item Indefinite subtypes in generics
30480 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
30481 as the actual for a generic formal private type, but then the instantiation
30482 would be illegal if there were any instances of declarations of variables
30483 of this type in the generic body. In Ada 95, to avoid this clear violation
30484 of the methodological principle known as the ``contract model'',
30485 the generic declaration explicitly indicates whether
30486 or not such instantiations are permitted. If a generic formal parameter
30487 has explicit unknown discriminants, indicated by using @code{(<>)} after the
30488 type name, then it can be instantiated with indefinite types, but no
30489 stand-alone variables can be declared of this type. Any attempt to declare
30490 such a variable will result in an illegality at the time the generic is
30491 declared. If the @code{(<>)} notation is not used, then it is illegal
30492 to instantiate the generic with an indefinite type.
30493 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
30494 It will show up as a compile time error, and
30495 the fix is usually simply to add the @code{(<>)} to the generic declaration.
30498 @node More deterministic semantics
30499 @subsection More deterministic semantics
30503 Conversions from real types to integer types round away from 0. In Ada 83
30504 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
30505 implementation freedom was intended to support unbiased rounding in
30506 statistical applications, but in practice it interfered with portability.
30507 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
30508 is required. Numeric code may be affected by this change in semantics.
30509 Note, though, that this issue is no worse than already existed in Ada 83
30510 when porting code from one vendor to another.
30513 The Real-Time Annex introduces a set of policies that define the behavior of
30514 features that were implementation dependent in Ada 83, such as the order in
30515 which open select branches are executed.
30518 @node Changed semantics
30519 @subsection Changed semantics
30522 The worst kind of incompatibility is one where a program that is legal in
30523 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
30524 possible in Ada 83. Fortunately this is extremely rare, but the one
30525 situation that you should be alert to is the change in the predefined type
30526 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
30529 @item Range of type @code{Character}
30530 The range of @code{Standard.Character} is now the full 256 characters
30531 of Latin-1, whereas in most Ada 83 implementations it was restricted
30532 to 128 characters. Although some of the effects of
30533 this change will be manifest in compile-time rejection of legal
30534 Ada 83 programs it is possible for a working Ada 83 program to have
30535 a different effect in Ada 95, one that was not permitted in Ada 83.
30536 As an example, the expression
30537 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
30538 delivers @code{255} as its value.
30539 In general, you should look at the logic of any
30540 character-processing Ada 83 program and see whether it needs to be adapted
30541 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
30542 character handling package that may be relevant if code needs to be adapted
30543 to account for the additional Latin-1 elements.
30544 The desirable fix is to
30545 modify the program to accommodate the full character set, but in some cases
30546 it may be convenient to define a subtype or derived type of Character that
30547 covers only the restricted range.
30551 @node Other language compatibility issues
30552 @subsection Other language compatibility issues
30555 @item @option{-gnat83} switch
30556 All implementations of GNAT provide a switch that causes GNAT to operate
30557 in Ada 83 mode. In this mode, some but not all compatibility problems
30558 of the type described above are handled automatically. For example, the
30559 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
30560 as identifiers as in Ada 83.
30562 in practice, it is usually advisable to make the necessary modifications
30563 to the program to remove the need for using this switch.
30564 See @ref{Compiling Different Versions of Ada}.
30566 @item Support for removed Ada 83 pragmas and attributes
30567 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
30568 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
30569 compilers are allowed, but not required, to implement these missing
30570 elements. In contrast with some other compilers, GNAT implements all
30571 such pragmas and attributes, eliminating this compatibility concern. These
30572 include @code{pragma Interface} and the floating point type attributes
30573 (@code{Emax}, @code{Mantissa}, etc.), among other items.
30577 @node Compatibility between Ada 95 and Ada 2005
30578 @section Compatibility between Ada 95 and Ada 2005
30579 @cindex Compatibility between Ada 95 and Ada 2005
30582 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
30583 a number of incompatibilities. Several are enumerated below;
30584 for a complete description please see the
30585 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
30586 @cite{Rationale for Ada 2005}.
30589 @item New reserved words.
30590 The words @code{interface}, @code{overriding} and @code{synchronized} are
30591 reserved in Ada 2005.
30592 A pre-Ada 2005 program that uses any of these as an identifier will be
30595 @item New declarations in predefined packages.
30596 A number of packages in the predefined environment contain new declarations:
30597 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
30598 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
30599 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
30600 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
30601 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
30602 If an Ada 95 program does a @code{with} and @code{use} of any of these
30603 packages, the new declarations may cause name clashes.
30605 @item Access parameters.
30606 A nondispatching subprogram with an access parameter cannot be renamed
30607 as a dispatching operation. This was permitted in Ada 95.
30609 @item Access types, discriminants, and constraints.
30610 Rule changes in this area have led to some incompatibilities; for example,
30611 constrained subtypes of some access types are not permitted in Ada 2005.
30613 @item Aggregates for limited types.
30614 The allowance of aggregates for limited types in Ada 2005 raises the
30615 possibility of ambiguities in legal Ada 95 programs, since additional types
30616 now need to be considered in expression resolution.
30618 @item Fixed-point multiplication and division.
30619 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
30620 were legal in Ada 95 and invoked the predefined versions of these operations,
30622 The ambiguity may be resolved either by applying a type conversion to the
30623 expression, or by explicitly invoking the operation from package
30626 @item Return-by-reference types.
30627 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
30628 can declare a function returning a value from an anonymous access type.
30632 @node Implementation-dependent characteristics
30633 @section Implementation-dependent characteristics
30635 Although the Ada language defines the semantics of each construct as
30636 precisely as practical, in some situations (for example for reasons of
30637 efficiency, or where the effect is heavily dependent on the host or target
30638 platform) the implementation is allowed some freedom. In porting Ada 83
30639 code to GNAT, you need to be aware of whether / how the existing code
30640 exercised such implementation dependencies. Such characteristics fall into
30641 several categories, and GNAT offers specific support in assisting the
30642 transition from certain Ada 83 compilers.
30645 * Implementation-defined pragmas::
30646 * Implementation-defined attributes::
30648 * Elaboration order::
30649 * Target-specific aspects::
30652 @node Implementation-defined pragmas
30653 @subsection Implementation-defined pragmas
30656 Ada compilers are allowed to supplement the language-defined pragmas, and
30657 these are a potential source of non-portability. All GNAT-defined pragmas
30658 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
30659 Reference Manual}, and these include several that are specifically
30660 intended to correspond to other vendors' Ada 83 pragmas.
30661 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
30662 For compatibility with HP Ada 83, GNAT supplies the pragmas
30663 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
30664 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
30665 and @code{Volatile}.
30666 Other relevant pragmas include @code{External} and @code{Link_With}.
30667 Some vendor-specific
30668 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
30670 avoiding compiler rejection of units that contain such pragmas; they are not
30671 relevant in a GNAT context and hence are not otherwise implemented.
30673 @node Implementation-defined attributes
30674 @subsection Implementation-defined attributes
30676 Analogous to pragmas, the set of attributes may be extended by an
30677 implementation. All GNAT-defined attributes are described in
30678 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
30679 Manual}, and these include several that are specifically intended
30680 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
30681 the attribute @code{VADS_Size} may be useful. For compatibility with HP
30682 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
30686 @subsection Libraries
30688 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
30689 code uses vendor-specific libraries then there are several ways to manage
30690 this in Ada 95 or Ada 2005:
30693 If the source code for the libraries (specs and bodies) are
30694 available, then the libraries can be migrated in the same way as the
30697 If the source code for the specs but not the bodies are
30698 available, then you can reimplement the bodies.
30700 Some features introduced by Ada 95 obviate the need for library support. For
30701 example most Ada 83 vendors supplied a package for unsigned integers. The
30702 Ada 95 modular type feature is the preferred way to handle this need, so
30703 instead of migrating or reimplementing the unsigned integer package it may
30704 be preferable to retrofit the application using modular types.
30707 @node Elaboration order
30708 @subsection Elaboration order
30710 The implementation can choose any elaboration order consistent with the unit
30711 dependency relationship. This freedom means that some orders can result in
30712 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
30713 to invoke a subprogram its body has been elaborated, or to instantiate a
30714 generic before the generic body has been elaborated. By default GNAT
30715 attempts to choose a safe order (one that will not encounter access before
30716 elaboration problems) by implicitly inserting @code{Elaborate} or
30717 @code{Elaborate_All} pragmas where
30718 needed. However, this can lead to the creation of elaboration circularities
30719 and a resulting rejection of the program by gnatbind. This issue is
30720 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
30721 In brief, there are several
30722 ways to deal with this situation:
30726 Modify the program to eliminate the circularities, e.g.@: by moving
30727 elaboration-time code into explicitly-invoked procedures
30729 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
30730 @code{Elaborate} pragmas, and then inhibit the generation of implicit
30731 @code{Elaborate_All}
30732 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
30733 (by selectively suppressing elaboration checks via pragma
30734 @code{Suppress(Elaboration_Check)} when it is safe to do so).
30737 @node Target-specific aspects
30738 @subsection Target-specific aspects
30740 Low-level applications need to deal with machine addresses, data
30741 representations, interfacing with assembler code, and similar issues. If
30742 such an Ada 83 application is being ported to different target hardware (for
30743 example where the byte endianness has changed) then you will need to
30744 carefully examine the program logic; the porting effort will heavily depend
30745 on the robustness of the original design. Moreover, Ada 95 (and thus
30746 Ada 2005) are sometimes
30747 incompatible with typical Ada 83 compiler practices regarding implicit
30748 packing, the meaning of the Size attribute, and the size of access values.
30749 GNAT's approach to these issues is described in @ref{Representation Clauses}.
30751 @node Compatibility with Other Ada Systems
30752 @section Compatibility with Other Ada Systems
30755 If programs avoid the use of implementation dependent and
30756 implementation defined features, as documented in the @cite{Ada
30757 Reference Manual}, there should be a high degree of portability between
30758 GNAT and other Ada systems. The following are specific items which
30759 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
30760 compilers, but do not affect porting code to GNAT@.
30761 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
30762 the following issues may or may not arise for Ada 2005 programs
30763 when other compilers appear.)
30766 @item Ada 83 Pragmas and Attributes
30767 Ada 95 compilers are allowed, but not required, to implement the missing
30768 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
30769 GNAT implements all such pragmas and attributes, eliminating this as
30770 a compatibility concern, but some other Ada 95 compilers reject these
30771 pragmas and attributes.
30773 @item Specialized Needs Annexes
30774 GNAT implements the full set of special needs annexes. At the
30775 current time, it is the only Ada 95 compiler to do so. This means that
30776 programs making use of these features may not be portable to other Ada
30777 95 compilation systems.
30779 @item Representation Clauses
30780 Some other Ada 95 compilers implement only the minimal set of
30781 representation clauses required by the Ada 95 reference manual. GNAT goes
30782 far beyond this minimal set, as described in the next section.
30785 @node Representation Clauses
30786 @section Representation Clauses
30789 The Ada 83 reference manual was quite vague in describing both the minimal
30790 required implementation of representation clauses, and also their precise
30791 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
30792 minimal set of capabilities required is still quite limited.
30794 GNAT implements the full required set of capabilities in
30795 Ada 95 and Ada 2005, but also goes much further, and in particular
30796 an effort has been made to be compatible with existing Ada 83 usage to the
30797 greatest extent possible.
30799 A few cases exist in which Ada 83 compiler behavior is incompatible with
30800 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
30801 intentional or accidental dependence on specific implementation dependent
30802 characteristics of these Ada 83 compilers. The following is a list of
30803 the cases most likely to arise in existing Ada 83 code.
30806 @item Implicit Packing
30807 Some Ada 83 compilers allowed a Size specification to cause implicit
30808 packing of an array or record. This could cause expensive implicit
30809 conversions for change of representation in the presence of derived
30810 types, and the Ada design intends to avoid this possibility.
30811 Subsequent AI's were issued to make it clear that such implicit
30812 change of representation in response to a Size clause is inadvisable,
30813 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
30814 Reference Manuals as implementation advice that is followed by GNAT@.
30815 The problem will show up as an error
30816 message rejecting the size clause. The fix is simply to provide
30817 the explicit pragma @code{Pack}, or for more fine tuned control, provide
30818 a Component_Size clause.
30820 @item Meaning of Size Attribute
30821 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
30822 the minimal number of bits required to hold values of the type. For example,
30823 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
30824 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
30825 some 32 in this situation. This problem will usually show up as a compile
30826 time error, but not always. It is a good idea to check all uses of the
30827 'Size attribute when porting Ada 83 code. The GNAT specific attribute
30828 Object_Size can provide a useful way of duplicating the behavior of
30829 some Ada 83 compiler systems.
30831 @item Size of Access Types
30832 A common assumption in Ada 83 code is that an access type is in fact a pointer,
30833 and that therefore it will be the same size as a System.Address value. This
30834 assumption is true for GNAT in most cases with one exception. For the case of
30835 a pointer to an unconstrained array type (where the bounds may vary from one
30836 value of the access type to another), the default is to use a ``fat pointer'',
30837 which is represented as two separate pointers, one to the bounds, and one to
30838 the array. This representation has a number of advantages, including improved
30839 efficiency. However, it may cause some difficulties in porting existing Ada 83
30840 code which makes the assumption that, for example, pointers fit in 32 bits on
30841 a machine with 32-bit addressing.
30843 To get around this problem, GNAT also permits the use of ``thin pointers'' for
30844 access types in this case (where the designated type is an unconstrained array
30845 type). These thin pointers are indeed the same size as a System.Address value.
30846 To specify a thin pointer, use a size clause for the type, for example:
30848 @smallexample @c ada
30849 type X is access all String;
30850 for X'Size use Standard'Address_Size;
30854 which will cause the type X to be represented using a single pointer.
30855 When using this representation, the bounds are right behind the array.
30856 This representation is slightly less efficient, and does not allow quite
30857 such flexibility in the use of foreign pointers or in using the
30858 Unrestricted_Access attribute to create pointers to non-aliased objects.
30859 But for any standard portable use of the access type it will work in
30860 a functionally correct manner and allow porting of existing code.
30861 Note that another way of forcing a thin pointer representation
30862 is to use a component size clause for the element size in an array,
30863 or a record representation clause for an access field in a record.
30867 @c This brief section is only in the non-VMS version
30868 @c The complete chapter on HP Ada is in the VMS version
30869 @node Compatibility with HP Ada 83
30870 @section Compatibility with HP Ada 83
30873 The VMS version of GNAT fully implements all the pragmas and attributes
30874 provided by HP Ada 83, as well as providing the standard HP Ada 83
30875 libraries, including Starlet. In addition, data layouts and parameter
30876 passing conventions are highly compatible. This means that porting
30877 existing HP Ada 83 code to GNAT in VMS systems should be easier than
30878 most other porting efforts. The following are some of the most
30879 significant differences between GNAT and HP Ada 83.
30882 @item Default floating-point representation
30883 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
30884 it is VMS format. GNAT does implement the necessary pragmas
30885 (Long_Float, Float_Representation) for changing this default.
30888 The package System in GNAT exactly corresponds to the definition in the
30889 Ada 95 reference manual, which means that it excludes many of the
30890 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
30891 that contains the additional definitions, and a special pragma,
30892 Extend_System allows this package to be treated transparently as an
30893 extension of package System.
30896 The definitions provided by Aux_DEC are exactly compatible with those
30897 in the HP Ada 83 version of System, with one exception.
30898 HP Ada provides the following declarations:
30900 @smallexample @c ada
30901 TO_ADDRESS (INTEGER)
30902 TO_ADDRESS (UNSIGNED_LONGWORD)
30903 TO_ADDRESS (@i{universal_integer})
30907 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
30908 an extension to Ada 83 not strictly compatible with the reference manual.
30909 In GNAT, we are constrained to be exactly compatible with the standard,
30910 and this means we cannot provide this capability. In HP Ada 83, the
30911 point of this definition is to deal with a call like:
30913 @smallexample @c ada
30914 TO_ADDRESS (16#12777#);
30918 Normally, according to the Ada 83 standard, one would expect this to be
30919 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
30920 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
30921 definition using @i{universal_integer} takes precedence.
30923 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
30924 is not possible to be 100% compatible. Since there are many programs using
30925 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
30926 to change the name of the function in the UNSIGNED_LONGWORD case, so the
30927 declarations provided in the GNAT version of AUX_Dec are:
30929 @smallexample @c ada
30930 function To_Address (X : Integer) return Address;
30931 pragma Pure_Function (To_Address);
30933 function To_Address_Long (X : Unsigned_Longword)
30935 pragma Pure_Function (To_Address_Long);
30939 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
30940 change the name to TO_ADDRESS_LONG@.
30942 @item Task_Id values
30943 The Task_Id values assigned will be different in the two systems, and GNAT
30944 does not provide a specified value for the Task_Id of the environment task,
30945 which in GNAT is treated like any other declared task.
30949 For full details on these and other less significant compatibility issues,
30950 see appendix E of the HP publication entitled @cite{HP Ada, Technical
30951 Overview and Comparison on HP Platforms}.
30953 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
30954 attributes are recognized, although only a subset of them can sensibly
30955 be implemented. The description of pragmas in @ref{Implementation
30956 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
30957 indicates whether or not they are applicable to non-VMS systems.
30961 @node Transitioning to 64-Bit GNAT for OpenVMS
30962 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
30965 This section is meant to assist users of pre-2006 @value{EDITION}
30966 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
30967 the version of the GNAT technology supplied in 2006 and later for
30968 OpenVMS on both Alpha and I64.
30971 * Introduction to transitioning::
30972 * Migration of 32 bit code::
30973 * Taking advantage of 64 bit addressing::
30974 * Technical details::
30977 @node Introduction to transitioning
30978 @subsection Introduction
30981 64-bit @value{EDITION} for Open VMS has been designed to meet
30986 Providing a full conforming implementation of Ada 95 and Ada 2005
30989 Allowing maximum backward compatibility, thus easing migration of existing
30993 Supplying a path for exploiting the full 64-bit address range
30997 Ada's strong typing semantics has made it
30998 impractical to have different 32-bit and 64-bit modes. As soon as
30999 one object could possibly be outside the 32-bit address space, this
31000 would make it necessary for the @code{System.Address} type to be 64 bits.
31001 In particular, this would cause inconsistencies if 32-bit code is
31002 called from 64-bit code that raises an exception.
31004 This issue has been resolved by always using 64-bit addressing
31005 at the system level, but allowing for automatic conversions between
31006 32-bit and 64-bit addresses where required. Thus users who
31007 do not currently require 64-bit addressing capabilities, can
31008 recompile their code with only minimal changes (and indeed
31009 if the code is written in portable Ada, with no assumptions about
31010 the size of the @code{Address} type, then no changes at all are necessary).
31012 this approach provides a simple, gradual upgrade path to future
31013 use of larger memories than available for 32-bit systems.
31014 Also, newly written applications or libraries will by default
31015 be fully compatible with future systems exploiting 64-bit
31016 addressing capabilities.
31018 @ref{Migration of 32 bit code}, will focus on porting applications
31019 that do not require more than 2 GB of
31020 addressable memory. This code will be referred to as
31021 @emph{32-bit code}.
31022 For applications intending to exploit the full 64-bit address space,
31023 @ref{Taking advantage of 64 bit addressing},
31024 will consider further changes that may be required.
31025 Such code will be referred to below as @emph{64-bit code}.
31027 @node Migration of 32 bit code
31028 @subsection Migration of 32-bit code
31033 * Unchecked conversions::
31034 * Predefined constants::
31035 * Interfacing with C::
31036 * Experience with source compatibility::
31039 @node Address types
31040 @subsubsection Address types
31043 To solve the problem of mixing 64-bit and 32-bit addressing,
31044 while maintaining maximum backward compatibility, the following
31045 approach has been taken:
31049 @code{System.Address} always has a size of 64 bits
31052 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
31056 Since @code{System.Short_Address} is a subtype of @code{System.Address},
31057 a @code{Short_Address}
31058 may be used where an @code{Address} is required, and vice versa, without
31059 needing explicit type conversions.
31060 By virtue of the Open VMS parameter passing conventions,
31062 and exported subprograms that have 32-bit address parameters are
31063 compatible with those that have 64-bit address parameters.
31064 (See @ref{Making code 64 bit clean} for details.)
31066 The areas that may need attention are those where record types have
31067 been defined that contain components of the type @code{System.Address}, and
31068 where objects of this type are passed to code expecting a record layout with
31071 Different compilers on different platforms cannot be
31072 expected to represent the same type in the same way,
31073 since alignment constraints
31074 and other system-dependent properties affect the compiler's decision.
31075 For that reason, Ada code
31076 generally uses representation clauses to specify the expected
31077 layout where required.
31079 If such a representation clause uses 32 bits for a component having
31080 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
31081 will detect that error and produce a specific diagnostic message.
31082 The developer should then determine whether the representation
31083 should be 64 bits or not and make either of two changes:
31084 change the size to 64 bits and leave the type as @code{System.Address}, or
31085 leave the size as 32 bits and change the type to @code{System.Short_Address}.
31086 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
31087 required in any code setting or accessing the field; the compiler will
31088 automatically perform any needed conversions between address
31092 @subsubsection Access types
31095 By default, objects designated by access values are always
31096 allocated in the 32-bit
31097 address space. Thus legacy code will never contain
31098 any objects that are not addressable with 32-bit addresses, and
31099 the compiler will never raise exceptions as result of mixing
31100 32-bit and 64-bit addresses.
31102 However, the access values themselves are represented in 64 bits, for optimum
31103 performance and future compatibility with 64-bit code. As was
31104 the case with @code{System.Address}, the compiler will give an error message
31105 if an object or record component has a representation clause that
31106 requires the access value to fit in 32 bits. In such a situation,
31107 an explicit size clause for the access type, specifying 32 bits,
31108 will have the desired effect.
31110 General access types (declared with @code{access all}) can never be
31111 32 bits, as values of such types must be able to refer to any object
31112 of the designated type,
31113 including objects residing outside the 32-bit address range.
31114 Existing Ada 83 code will not contain such type definitions,
31115 however, since general access types were introduced in Ada 95.
31117 @node Unchecked conversions
31118 @subsubsection Unchecked conversions
31121 In the case of an @code{Unchecked_Conversion} where the source type is a
31122 64-bit access type or the type @code{System.Address}, and the target
31123 type is a 32-bit type, the compiler will generate a warning.
31124 Even though the generated code will still perform the required
31125 conversions, it is highly recommended in these cases to use
31126 respectively a 32-bit access type or @code{System.Short_Address}
31127 as the source type.
31129 @node Predefined constants
31130 @subsubsection Predefined constants
31133 The following table shows the correspondence between pre-2006 versions of
31134 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
31137 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
31138 @item @b{Constant} @tab @b{Old} @tab @b{New}
31139 @item @code{System.Word_Size} @tab 32 @tab 64
31140 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
31141 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
31142 @item @code{System.Address_Size} @tab 32 @tab 64
31146 If you need to refer to the specific
31147 memory size of a 32-bit implementation, instead of the
31148 actual memory size, use @code{System.Short_Memory_Size}
31149 rather than @code{System.Memory_Size}.
31150 Similarly, references to @code{System.Address_Size} may need
31151 to be replaced by @code{System.Short_Address'Size}.
31152 The program @command{gnatfind} may be useful for locating
31153 references to the above constants, so that you can verify that they
31156 @node Interfacing with C
31157 @subsubsection Interfacing with C
31160 In order to minimize the impact of the transition to 64-bit addresses on
31161 legacy programs, some fundamental types in the @code{Interfaces.C}
31162 package hierarchy continue to be represented in 32 bits.
31163 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
31164 This eases integration with the default HP C layout choices, for example
31165 as found in the system routines in @code{DECC$SHR.EXE}.
31166 Because of this implementation choice, the type fully compatible with
31167 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
31168 Depending on the context the compiler will issue a
31169 warning or an error when type @code{Address} is used, alerting the user to a
31170 potential problem. Otherwise 32-bit programs that use
31171 @code{Interfaces.C} should normally not require code modifications
31173 The other issue arising with C interfacing concerns pragma @code{Convention}.
31174 For VMS 64-bit systems, there is an issue of the appropriate default size
31175 of C convention pointers in the absence of an explicit size clause. The HP
31176 C compiler can choose either 32 or 64 bits depending on compiler options.
31177 GNAT chooses 32-bits rather than 64-bits in the default case where no size
31178 clause is given. This proves a better choice for porting 32-bit legacy
31179 applications. In order to have a 64-bit representation, it is necessary to
31180 specify a size representation clause. For example:
31182 @smallexample @c ada
31183 type int_star is access Interfaces.C.int;
31184 pragma Convention(C, int_star);
31185 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
31188 @node Experience with source compatibility
31189 @subsubsection Experience with source compatibility
31192 The Security Server and STARLET on I64 provide an interesting ``test case''
31193 for source compatibility issues, since it is in such system code
31194 where assumptions about @code{Address} size might be expected to occur.
31195 Indeed, there were a small number of occasions in the Security Server
31196 file @file{jibdef.ads}
31197 where a representation clause for a record type specified
31198 32 bits for a component of type @code{Address}.
31199 All of these errors were detected by the compiler.
31200 The repair was obvious and immediate; to simply replace @code{Address} by
31201 @code{Short_Address}.
31203 In the case of STARLET, there were several record types that should
31204 have had representation clauses but did not. In these record types
31205 there was an implicit assumption that an @code{Address} value occupied
31207 These compiled without error, but their usage resulted in run-time error
31208 returns from STARLET system calls.
31209 Future GNAT technology enhancements may include a tool that detects and flags
31210 these sorts of potential source code porting problems.
31212 @c ****************************************
31213 @node Taking advantage of 64 bit addressing
31214 @subsection Taking advantage of 64-bit addressing
31217 * Making code 64 bit clean::
31218 * Allocating memory from the 64 bit storage pool::
31219 * Restrictions on use of 64 bit objects::
31220 * Using 64 bit storage pools by default::
31221 * General access types::
31222 * STARLET and other predefined libraries::
31225 @node Making code 64 bit clean
31226 @subsubsection Making code 64-bit clean
31229 In order to prevent problems that may occur when (parts of) a
31230 system start using memory outside the 32-bit address range,
31231 we recommend some additional guidelines:
31235 For imported subprograms that take parameters of the
31236 type @code{System.Address}, ensure that these subprograms can
31237 indeed handle 64-bit addresses. If not, or when in doubt,
31238 change the subprogram declaration to specify
31239 @code{System.Short_Address} instead.
31242 Resolve all warnings related to size mismatches in
31243 unchecked conversions. Failing to do so causes
31244 erroneous execution if the source object is outside
31245 the 32-bit address space.
31248 (optional) Explicitly use the 32-bit storage pool
31249 for access types used in a 32-bit context, or use
31250 generic access types where possible
31251 (@pxref{Restrictions on use of 64 bit objects}).
31255 If these rules are followed, the compiler will automatically insert
31256 any necessary checks to ensure that no addresses or access values
31257 passed to 32-bit code ever refer to objects outside the 32-bit
31259 Any attempt to do this will raise @code{Constraint_Error}.
31261 @node Allocating memory from the 64 bit storage pool
31262 @subsubsection Allocating memory from the 64-bit storage pool
31265 For any access type @code{T} that potentially requires memory allocations
31266 beyond the 32-bit address space,
31267 use the following representation clause:
31269 @smallexample @c ada
31270 for T'Storage_Pool use System.Pool_64;
31273 @node Restrictions on use of 64 bit objects
31274 @subsubsection Restrictions on use of 64-bit objects
31277 Taking the address of an object allocated from a 64-bit storage pool,
31278 and then passing this address to a subprogram expecting
31279 @code{System.Short_Address},
31280 or assigning it to a variable of type @code{Short_Address}, will cause
31281 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
31282 (@pxref{Making code 64 bit clean}), or checks are suppressed,
31283 no exception is raised and execution
31284 will become erroneous.
31286 @node Using 64 bit storage pools by default
31287 @subsubsection Using 64-bit storage pools by default
31290 In some cases it may be desirable to have the compiler allocate
31291 from 64-bit storage pools by default. This may be the case for
31292 libraries that are 64-bit clean, but may be used in both 32-bit
31293 and 64-bit contexts. For these cases the following configuration
31294 pragma may be specified:
31296 @smallexample @c ada
31297 pragma Pool_64_Default;
31301 Any code compiled in the context of this pragma will by default
31302 use the @code{System.Pool_64} storage pool. This default may be overridden
31303 for a specific access type @code{T} by the representation clause:
31305 @smallexample @c ada
31306 for T'Storage_Pool use System.Pool_32;
31310 Any object whose address may be passed to a subprogram with a
31311 @code{Short_Address} argument, or assigned to a variable of type
31312 @code{Short_Address}, needs to be allocated from this pool.
31314 @node General access types
31315 @subsubsection General access types
31318 Objects designated by access values from a
31319 general access type (declared with @code{access all}) are never allocated
31320 from a 64-bit storage pool. Code that uses general access types will
31321 accept objects allocated in either 32-bit or 64-bit address spaces,
31322 but never allocate objects outside the 32-bit address space.
31323 Using general access types ensures maximum compatibility with both
31324 32-bit and 64-bit code.
31326 @node STARLET and other predefined libraries
31327 @subsubsection STARLET and other predefined libraries
31330 All code that comes as part of GNAT is 64-bit clean, but the
31331 restrictions given in @ref{Restrictions on use of 64 bit objects},
31332 still apply. Look at the package
31333 specs to see in which contexts objects allocated
31334 in 64-bit address space are acceptable.
31336 @node Technical details
31337 @subsection Technical details
31340 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
31341 Ada standard with respect to the type of @code{System.Address}. Previous
31342 versions of GNAT Pro have defined this type as private and implemented it as a
31345 In order to allow defining @code{System.Short_Address} as a proper subtype,
31346 and to match the implicit sign extension in parameter passing,
31347 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
31348 visible (i.e., non-private) integer type.
31349 Standard operations on the type, such as the binary operators ``+'', ``-'',
31350 etc., that take @code{Address} operands and return an @code{Address} result,
31351 have been hidden by declaring these
31352 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
31353 ambiguities that would otherwise result from overloading.
31354 (Note that, although @code{Address} is a visible integer type,
31355 good programming practice dictates against exploiting the type's
31356 integer properties such as literals, since this will compromise
31359 Defining @code{Address} as a visible integer type helps achieve
31360 maximum compatibility for existing Ada code,
31361 without sacrificing the capabilities of the 64-bit architecture.
31364 @c ************************************************
31366 @node Microsoft Windows Topics
31367 @appendix Microsoft Windows Topics
31373 This chapter describes topics that are specific to the Microsoft Windows
31374 platforms (NT, 2000, and XP Professional).
31377 * Using GNAT on Windows::
31378 * Using a network installation of GNAT::
31379 * CONSOLE and WINDOWS subsystems::
31380 * Temporary Files::
31381 * Mixed-Language Programming on Windows::
31382 * Windows Calling Conventions::
31383 * Introduction to Dynamic Link Libraries (DLLs)::
31384 * Using DLLs with GNAT::
31385 * Building DLLs with GNAT::
31386 * Building DLLs with GNAT Project files::
31387 * Building DLLs with gnatdll::
31388 * GNAT and Windows Resources::
31389 * Debugging a DLL::
31390 * Setting Stack Size from gnatlink::
31391 * Setting Heap Size from gnatlink::
31394 @node Using GNAT on Windows
31395 @section Using GNAT on Windows
31398 One of the strengths of the GNAT technology is that its tool set
31399 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
31400 @code{gdb} debugger, etc.) is used in the same way regardless of the
31403 On Windows this tool set is complemented by a number of Microsoft-specific
31404 tools that have been provided to facilitate interoperability with Windows
31405 when this is required. With these tools:
31410 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
31414 You can use any Dynamically Linked Library (DLL) in your Ada code (both
31415 relocatable and non-relocatable DLLs are supported).
31418 You can build Ada DLLs for use in other applications. These applications
31419 can be written in a language other than Ada (e.g., C, C++, etc). Again both
31420 relocatable and non-relocatable Ada DLLs are supported.
31423 You can include Windows resources in your Ada application.
31426 You can use or create COM/DCOM objects.
31430 Immediately below are listed all known general GNAT-for-Windows restrictions.
31431 Other restrictions about specific features like Windows Resources and DLLs
31432 are listed in separate sections below.
31437 It is not possible to use @code{GetLastError} and @code{SetLastError}
31438 when tasking, protected records, or exceptions are used. In these
31439 cases, in order to implement Ada semantics, the GNAT run-time system
31440 calls certain Win32 routines that set the last error variable to 0 upon
31441 success. It should be possible to use @code{GetLastError} and
31442 @code{SetLastError} when tasking, protected record, and exception
31443 features are not used, but it is not guaranteed to work.
31446 It is not possible to link against Microsoft libraries except for
31447 import libraries. The library must be built to be compatible with
31448 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
31449 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
31450 not be compatible with the GNAT runtime. Even if the library is
31451 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
31454 When the compilation environment is located on FAT32 drives, users may
31455 experience recompilations of the source files that have not changed if
31456 Daylight Saving Time (DST) state has changed since the last time files
31457 were compiled. NTFS drives do not have this problem.
31460 No components of the GNAT toolset use any entries in the Windows
31461 registry. The only entries that can be created are file associations and
31462 PATH settings, provided the user has chosen to create them at installation
31463 time, as well as some minimal book-keeping information needed to correctly
31464 uninstall or integrate different GNAT products.
31467 @node Using a network installation of GNAT
31468 @section Using a network installation of GNAT
31471 Make sure the system on which GNAT is installed is accessible from the
31472 current machine, i.e., the install location is shared over the network.
31473 Shared resources are accessed on Windows by means of UNC paths, which
31474 have the format @code{\\server\sharename\path}
31476 In order to use such a network installation, simply add the UNC path of the
31477 @file{bin} directory of your GNAT installation in front of your PATH. For
31478 example, if GNAT is installed in @file{\GNAT} directory of a share location
31479 called @file{c-drive} on a machine @file{LOKI}, the following command will
31482 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
31484 Be aware that every compilation using the network installation results in the
31485 transfer of large amounts of data across the network and will likely cause
31486 serious performance penalty.
31488 @node CONSOLE and WINDOWS subsystems
31489 @section CONSOLE and WINDOWS subsystems
31490 @cindex CONSOLE Subsystem
31491 @cindex WINDOWS Subsystem
31495 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
31496 (which is the default subsystem) will always create a console when
31497 launching the application. This is not something desirable when the
31498 application has a Windows GUI. To get rid of this console the
31499 application must be using the @code{WINDOWS} subsystem. To do so
31500 the @option{-mwindows} linker option must be specified.
31503 $ gnatmake winprog -largs -mwindows
31506 @node Temporary Files
31507 @section Temporary Files
31508 @cindex Temporary files
31511 It is possible to control where temporary files gets created by setting
31512 the @env{TMP} environment variable. The file will be created:
31515 @item Under the directory pointed to by the @env{TMP} environment variable if
31516 this directory exists.
31518 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
31519 set (or not pointing to a directory) and if this directory exists.
31521 @item Under the current working directory otherwise.
31525 This allows you to determine exactly where the temporary
31526 file will be created. This is particularly useful in networked
31527 environments where you may not have write access to some
31530 @node Mixed-Language Programming on Windows
31531 @section Mixed-Language Programming on Windows
31534 Developing pure Ada applications on Windows is no different than on
31535 other GNAT-supported platforms. However, when developing or porting an
31536 application that contains a mix of Ada and C/C++, the choice of your
31537 Windows C/C++ development environment conditions your overall
31538 interoperability strategy.
31540 If you use @command{gcc} to compile the non-Ada part of your application,
31541 there are no Windows-specific restrictions that affect the overall
31542 interoperability with your Ada code. If you plan to use
31543 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
31544 the following limitations:
31548 You cannot link your Ada code with an object or library generated with
31549 Microsoft tools if these use the @code{.tls} section (Thread Local
31550 Storage section) since the GNAT linker does not yet support this section.
31553 You cannot link your Ada code with an object or library generated with
31554 Microsoft tools if these use I/O routines other than those provided in
31555 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
31556 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
31557 libraries can cause a conflict with @code{msvcrt.dll} services. For
31558 instance Visual C++ I/O stream routines conflict with those in
31563 If you do want to use the Microsoft tools for your non-Ada code and hit one
31564 of the above limitations, you have two choices:
31568 Encapsulate your non-Ada code in a DLL to be linked with your Ada
31569 application. In this case, use the Microsoft or whatever environment to
31570 build the DLL and use GNAT to build your executable
31571 (@pxref{Using DLLs with GNAT}).
31574 Or you can encapsulate your Ada code in a DLL to be linked with the
31575 other part of your application. In this case, use GNAT to build the DLL
31576 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
31577 environment to build your executable.
31580 @node Windows Calling Conventions
31581 @section Windows Calling Conventions
31586 * C Calling Convention::
31587 * Stdcall Calling Convention::
31588 * Win32 Calling Convention::
31589 * DLL Calling Convention::
31593 When a subprogram @code{F} (caller) calls a subprogram @code{G}
31594 (callee), there are several ways to push @code{G}'s parameters on the
31595 stack and there are several possible scenarios to clean up the stack
31596 upon @code{G}'s return. A calling convention is an agreed upon software
31597 protocol whereby the responsibilities between the caller (@code{F}) and
31598 the callee (@code{G}) are clearly defined. Several calling conventions
31599 are available for Windows:
31603 @code{C} (Microsoft defined)
31606 @code{Stdcall} (Microsoft defined)
31609 @code{Win32} (GNAT specific)
31612 @code{DLL} (GNAT specific)
31615 @node C Calling Convention
31616 @subsection @code{C} Calling Convention
31619 This is the default calling convention used when interfacing to C/C++
31620 routines compiled with either @command{gcc} or Microsoft Visual C++.
31622 In the @code{C} calling convention subprogram parameters are pushed on the
31623 stack by the caller from right to left. The caller itself is in charge of
31624 cleaning up the stack after the call. In addition, the name of a routine
31625 with @code{C} calling convention is mangled by adding a leading underscore.
31627 The name to use on the Ada side when importing (or exporting) a routine
31628 with @code{C} calling convention is the name of the routine. For
31629 instance the C function:
31632 int get_val (long);
31636 should be imported from Ada as follows:
31638 @smallexample @c ada
31640 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31641 pragma Import (C, Get_Val, External_Name => "get_val");
31646 Note that in this particular case the @code{External_Name} parameter could
31647 have been omitted since, when missing, this parameter is taken to be the
31648 name of the Ada entity in lower case. When the @code{Link_Name} parameter
31649 is missing, as in the above example, this parameter is set to be the
31650 @code{External_Name} with a leading underscore.
31652 When importing a variable defined in C, you should always use the @code{C}
31653 calling convention unless the object containing the variable is part of a
31654 DLL (in which case you should use the @code{Stdcall} calling
31655 convention, @pxref{Stdcall Calling Convention}).
31657 @node Stdcall Calling Convention
31658 @subsection @code{Stdcall} Calling Convention
31661 This convention, which was the calling convention used for Pascal
31662 programs, is used by Microsoft for all the routines in the Win32 API for
31663 efficiency reasons. It must be used to import any routine for which this
31664 convention was specified.
31666 In the @code{Stdcall} calling convention subprogram parameters are pushed
31667 on the stack by the caller from right to left. The callee (and not the
31668 caller) is in charge of cleaning the stack on routine exit. In addition,
31669 the name of a routine with @code{Stdcall} calling convention is mangled by
31670 adding a leading underscore (as for the @code{C} calling convention) and a
31671 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
31672 bytes) of the parameters passed to the routine.
31674 The name to use on the Ada side when importing a C routine with a
31675 @code{Stdcall} calling convention is the name of the C routine. The leading
31676 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
31677 the compiler. For instance the Win32 function:
31680 @b{APIENTRY} int get_val (long);
31684 should be imported from Ada as follows:
31686 @smallexample @c ada
31688 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31689 pragma Import (Stdcall, Get_Val);
31690 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
31695 As for the @code{C} calling convention, when the @code{External_Name}
31696 parameter is missing, it is taken to be the name of the Ada entity in lower
31697 case. If instead of writing the above import pragma you write:
31699 @smallexample @c ada
31701 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31702 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
31707 then the imported routine is @code{_retrieve_val@@4}. However, if instead
31708 of specifying the @code{External_Name} parameter you specify the
31709 @code{Link_Name} as in the following example:
31711 @smallexample @c ada
31713 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31714 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
31719 then the imported routine is @code{retrieve_val}, that is, there is no
31720 decoration at all. No leading underscore and no Stdcall suffix
31721 @code{@@}@code{@var{nn}}.
31724 This is especially important as in some special cases a DLL's entry
31725 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
31726 name generated for a call has it.
31729 It is also possible to import variables defined in a DLL by using an
31730 import pragma for a variable. As an example, if a DLL contains a
31731 variable defined as:
31738 then, to access this variable from Ada you should write:
31740 @smallexample @c ada
31742 My_Var : Interfaces.C.int;
31743 pragma Import (Stdcall, My_Var);
31748 Note that to ease building cross-platform bindings this convention
31749 will be handled as a @code{C} calling convention on non-Windows platforms.
31751 @node Win32 Calling Convention
31752 @subsection @code{Win32} Calling Convention
31755 This convention, which is GNAT-specific is fully equivalent to the
31756 @code{Stdcall} calling convention described above.
31758 @node DLL Calling Convention
31759 @subsection @code{DLL} Calling Convention
31762 This convention, which is GNAT-specific is fully equivalent to the
31763 @code{Stdcall} calling convention described above.
31765 @node Introduction to Dynamic Link Libraries (DLLs)
31766 @section Introduction to Dynamic Link Libraries (DLLs)
31770 A Dynamically Linked Library (DLL) is a library that can be shared by
31771 several applications running under Windows. A DLL can contain any number of
31772 routines and variables.
31774 One advantage of DLLs is that you can change and enhance them without
31775 forcing all the applications that depend on them to be relinked or
31776 recompiled. However, you should be aware than all calls to DLL routines are
31777 slower since, as you will understand below, such calls are indirect.
31779 To illustrate the remainder of this section, suppose that an application
31780 wants to use the services of a DLL @file{API.dll}. To use the services
31781 provided by @file{API.dll} you must statically link against the DLL or
31782 an import library which contains a jump table with an entry for each
31783 routine and variable exported by the DLL. In the Microsoft world this
31784 import library is called @file{API.lib}. When using GNAT this import
31785 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
31786 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
31788 After you have linked your application with the DLL or the import library
31789 and you run your application, here is what happens:
31793 Your application is loaded into memory.
31796 The DLL @file{API.dll} is mapped into the address space of your
31797 application. This means that:
31801 The DLL will use the stack of the calling thread.
31804 The DLL will use the virtual address space of the calling process.
31807 The DLL will allocate memory from the virtual address space of the calling
31811 Handles (pointers) can be safely exchanged between routines in the DLL
31812 routines and routines in the application using the DLL.
31816 The entries in the jump table (from the import library @file{libAPI.dll.a}
31817 or @file{API.lib} or automatically created when linking against a DLL)
31818 which is part of your application are initialized with the addresses
31819 of the routines and variables in @file{API.dll}.
31822 If present in @file{API.dll}, routines @code{DllMain} or
31823 @code{DllMainCRTStartup} are invoked. These routines typically contain
31824 the initialization code needed for the well-being of the routines and
31825 variables exported by the DLL.
31829 There is an additional point which is worth mentioning. In the Windows
31830 world there are two kind of DLLs: relocatable and non-relocatable
31831 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
31832 in the target application address space. If the addresses of two
31833 non-relocatable DLLs overlap and these happen to be used by the same
31834 application, a conflict will occur and the application will run
31835 incorrectly. Hence, when possible, it is always preferable to use and
31836 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
31837 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
31838 User's Guide) removes the debugging symbols from the DLL but the DLL can
31839 still be relocated.
31841 As a side note, an interesting difference between Microsoft DLLs and
31842 Unix shared libraries, is the fact that on most Unix systems all public
31843 routines are exported by default in a Unix shared library, while under
31844 Windows it is possible (but not required) to list exported routines in
31845 a definition file (@pxref{The Definition File}).
31847 @node Using DLLs with GNAT
31848 @section Using DLLs with GNAT
31851 * Creating an Ada Spec for the DLL Services::
31852 * Creating an Import Library::
31856 To use the services of a DLL, say @file{API.dll}, in your Ada application
31861 The Ada spec for the routines and/or variables you want to access in
31862 @file{API.dll}. If not available this Ada spec must be built from the C/C++
31863 header files provided with the DLL.
31866 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
31867 mentioned an import library is a statically linked library containing the
31868 import table which will be filled at load time to point to the actual
31869 @file{API.dll} routines. Sometimes you don't have an import library for the
31870 DLL you want to use. The following sections will explain how to build
31871 one. Note that this is optional.
31874 The actual DLL, @file{API.dll}.
31878 Once you have all the above, to compile an Ada application that uses the
31879 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
31880 you simply issue the command
31883 $ gnatmake my_ada_app -largs -lAPI
31887 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
31888 tells the GNAT linker to look first for a library named @file{API.lib}
31889 (Microsoft-style name) and if not found for a libraries named
31890 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
31891 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
31892 contains the following pragma
31894 @smallexample @c ada
31895 pragma Linker_Options ("-lAPI");
31899 you do not have to add @option{-largs -lAPI} at the end of the
31900 @command{gnatmake} command.
31902 If any one of the items above is missing you will have to create it
31903 yourself. The following sections explain how to do so using as an
31904 example a fictitious DLL called @file{API.dll}.
31906 @node Creating an Ada Spec for the DLL Services
31907 @subsection Creating an Ada Spec for the DLL Services
31910 A DLL typically comes with a C/C++ header file which provides the
31911 definitions of the routines and variables exported by the DLL. The Ada
31912 equivalent of this header file is a package spec that contains definitions
31913 for the imported entities. If the DLL you intend to use does not come with
31914 an Ada spec you have to generate one such spec yourself. For example if
31915 the header file of @file{API.dll} is a file @file{api.h} containing the
31916 following two definitions:
31928 then the equivalent Ada spec could be:
31930 @smallexample @c ada
31933 with Interfaces.C.Strings;
31938 function Get (Str : C.Strings.Chars_Ptr) return C.int;
31941 pragma Import (C, Get);
31942 pragma Import (DLL, Some_Var);
31949 Note that a variable is
31950 @strong{always imported with a Stdcall convention}. A function
31951 can have @code{C} or @code{Stdcall} convention.
31952 (@pxref{Windows Calling Conventions}).
31954 @node Creating an Import Library
31955 @subsection Creating an Import Library
31956 @cindex Import library
31959 * The Definition File::
31960 * GNAT-Style Import Library::
31961 * Microsoft-Style Import Library::
31965 If a Microsoft-style import library @file{API.lib} or a GNAT-style
31966 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
31967 with @file{API.dll} you can skip this section. You can also skip this
31968 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
31969 as in this case it is possible to link directly against the
31970 DLL. Otherwise read on.
31972 @node The Definition File
31973 @subsubsection The Definition File
31974 @cindex Definition file
31978 As previously mentioned, and unlike Unix systems, the list of symbols
31979 that are exported from a DLL must be provided explicitly in Windows.
31980 The main goal of a definition file is precisely that: list the symbols
31981 exported by a DLL. A definition file (usually a file with a @code{.def}
31982 suffix) has the following structure:
31987 @r{[}LIBRARY @var{name}@r{]}
31988 @r{[}DESCRIPTION @var{string}@r{]}
31998 @item LIBRARY @var{name}
31999 This section, which is optional, gives the name of the DLL.
32001 @item DESCRIPTION @var{string}
32002 This section, which is optional, gives a description string that will be
32003 embedded in the import library.
32006 This section gives the list of exported symbols (procedures, functions or
32007 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
32008 section of @file{API.def} looks like:
32022 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
32023 (@pxref{Windows Calling Conventions}) for a Stdcall
32024 calling convention function in the exported symbols list.
32027 There can actually be other sections in a definition file, but these
32028 sections are not relevant to the discussion at hand.
32030 @node GNAT-Style Import Library
32031 @subsubsection GNAT-Style Import Library
32034 To create a static import library from @file{API.dll} with the GNAT tools
32035 you should proceed as follows:
32039 Create the definition file @file{API.def} (@pxref{The Definition File}).
32040 For that use the @code{dll2def} tool as follows:
32043 $ dll2def API.dll > API.def
32047 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
32048 to standard output the list of entry points in the DLL. Note that if
32049 some routines in the DLL have the @code{Stdcall} convention
32050 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
32051 suffix then you'll have to edit @file{api.def} to add it, and specify
32052 @option{-k} to @command{gnatdll} when creating the import library.
32055 Here are some hints to find the right @code{@@}@var{nn} suffix.
32059 If you have the Microsoft import library (.lib), it is possible to get
32060 the right symbols by using Microsoft @code{dumpbin} tool (see the
32061 corresponding Microsoft documentation for further details).
32064 $ dumpbin /exports api.lib
32068 If you have a message about a missing symbol at link time the compiler
32069 tells you what symbol is expected. You just have to go back to the
32070 definition file and add the right suffix.
32074 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
32075 (@pxref{Using gnatdll}) as follows:
32078 $ gnatdll -e API.def -d API.dll
32082 @code{gnatdll} takes as input a definition file @file{API.def} and the
32083 name of the DLL containing the services listed in the definition file
32084 @file{API.dll}. The name of the static import library generated is
32085 computed from the name of the definition file as follows: if the
32086 definition file name is @var{xyz}@code{.def}, the import library name will
32087 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
32088 @option{-e} could have been removed because the name of the definition
32089 file (before the ``@code{.def}'' suffix) is the same as the name of the
32090 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
32093 @node Microsoft-Style Import Library
32094 @subsubsection Microsoft-Style Import Library
32097 With GNAT you can either use a GNAT-style or Microsoft-style import
32098 library. A Microsoft import library is needed only if you plan to make an
32099 Ada DLL available to applications developed with Microsoft
32100 tools (@pxref{Mixed-Language Programming on Windows}).
32102 To create a Microsoft-style import library for @file{API.dll} you
32103 should proceed as follows:
32107 Create the definition file @file{API.def} from the DLL. For this use either
32108 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
32109 tool (see the corresponding Microsoft documentation for further details).
32112 Build the actual import library using Microsoft's @code{lib} utility:
32115 $ lib -machine:IX86 -def:API.def -out:API.lib
32119 If you use the above command the definition file @file{API.def} must
32120 contain a line giving the name of the DLL:
32127 See the Microsoft documentation for further details about the usage of
32131 @node Building DLLs with GNAT
32132 @section Building DLLs with GNAT
32133 @cindex DLLs, building
32136 This section explain how to build DLLs using the GNAT built-in DLL
32137 support. With the following procedure it is straight forward to build
32138 and use DLLs with GNAT.
32142 @item building object files
32144 The first step is to build all objects files that are to be included
32145 into the DLL. This is done by using the standard @command{gnatmake} tool.
32147 @item building the DLL
32149 To build the DLL you must use @command{gcc}'s @option{-shared}
32150 option. It is quite simple to use this method:
32153 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
32156 It is important to note that in this case all symbols found in the
32157 object files are automatically exported. It is possible to restrict
32158 the set of symbols to export by passing to @command{gcc} a definition
32159 file, @pxref{The Definition File}. For example:
32162 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
32165 If you use a definition file you must export the elaboration procedures
32166 for every package that required one. Elaboration procedures are named
32167 using the package name followed by "_E".
32169 @item preparing DLL to be used
32171 For the DLL to be used by client programs the bodies must be hidden
32172 from it and the .ali set with read-only attribute. This is very important
32173 otherwise GNAT will recompile all packages and will not actually use
32174 the code in the DLL. For example:
32178 $ copy *.ads *.ali api.dll apilib
32179 $ attrib +R apilib\*.ali
32184 At this point it is possible to use the DLL by directly linking
32185 against it. Note that you must use the GNAT shared runtime when using
32186 GNAT shared libraries. This is achieved by using @option{-shared} binder's
32190 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
32193 @node Building DLLs with GNAT Project files
32194 @section Building DLLs with GNAT Project files
32195 @cindex DLLs, building
32198 There is nothing specific to Windows in the build process.
32199 @pxref{Library Projects}.
32202 Due to a system limitation, it is not possible under Windows to create threads
32203 when inside the @code{DllMain} routine which is used for auto-initialization
32204 of shared libraries, so it is not possible to have library level tasks in SALs.
32206 @node Building DLLs with gnatdll
32207 @section Building DLLs with gnatdll
32208 @cindex DLLs, building
32211 * Limitations When Using Ada DLLs from Ada::
32212 * Exporting Ada Entities::
32213 * Ada DLLs and Elaboration::
32214 * Ada DLLs and Finalization::
32215 * Creating a Spec for Ada DLLs::
32216 * Creating the Definition File::
32221 Note that it is preferred to use the built-in GNAT DLL support
32222 (@pxref{Building DLLs with GNAT}) or GNAT Project files
32223 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
32225 This section explains how to build DLLs containing Ada code using
32226 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
32227 remainder of this section.
32229 The steps required to build an Ada DLL that is to be used by Ada as well as
32230 non-Ada applications are as follows:
32234 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
32235 @code{Stdcall} calling convention to avoid any Ada name mangling for the
32236 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
32237 skip this step if you plan to use the Ada DLL only from Ada applications.
32240 Your Ada code must export an initialization routine which calls the routine
32241 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
32242 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
32243 routine exported by the Ada DLL must be invoked by the clients of the DLL
32244 to initialize the DLL.
32247 When useful, the DLL should also export a finalization routine which calls
32248 routine @code{adafinal} generated by @command{gnatbind} to perform the
32249 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
32250 The finalization routine exported by the Ada DLL must be invoked by the
32251 clients of the DLL when the DLL services are no further needed.
32254 You must provide a spec for the services exported by the Ada DLL in each
32255 of the programming languages to which you plan to make the DLL available.
32258 You must provide a definition file listing the exported entities
32259 (@pxref{The Definition File}).
32262 Finally you must use @code{gnatdll} to produce the DLL and the import
32263 library (@pxref{Using gnatdll}).
32267 Note that a relocatable DLL stripped using the @code{strip}
32268 binutils tool will not be relocatable anymore. To build a DLL without
32269 debug information pass @code{-largs -s} to @code{gnatdll}. This
32270 restriction does not apply to a DLL built using a Library Project.
32271 @pxref{Library Projects}.
32273 @node Limitations When Using Ada DLLs from Ada
32274 @subsection Limitations When Using Ada DLLs from Ada
32277 When using Ada DLLs from Ada applications there is a limitation users
32278 should be aware of. Because on Windows the GNAT run time is not in a DLL of
32279 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
32280 each Ada DLL includes the services of the GNAT run time that are necessary
32281 to the Ada code inside the DLL. As a result, when an Ada program uses an
32282 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
32283 one in the main program.
32285 It is therefore not possible to exchange GNAT run-time objects between the
32286 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
32287 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
32290 It is completely safe to exchange plain elementary, array or record types,
32291 Windows object handles, etc.
32293 @node Exporting Ada Entities
32294 @subsection Exporting Ada Entities
32295 @cindex Export table
32298 Building a DLL is a way to encapsulate a set of services usable from any
32299 application. As a result, the Ada entities exported by a DLL should be
32300 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
32301 any Ada name mangling. As an example here is an Ada package
32302 @code{API}, spec and body, exporting two procedures, a function, and a
32305 @smallexample @c ada
32308 with Interfaces.C; use Interfaces;
32310 Count : C.int := 0;
32311 function Factorial (Val : C.int) return C.int;
32313 procedure Initialize_API;
32314 procedure Finalize_API;
32315 -- Initialization & Finalization routines. More in the next section.
32317 pragma Export (C, Initialize_API);
32318 pragma Export (C, Finalize_API);
32319 pragma Export (C, Count);
32320 pragma Export (C, Factorial);
32326 @smallexample @c ada
32329 package body API is
32330 function Factorial (Val : C.int) return C.int is
32333 Count := Count + 1;
32334 for K in 1 .. Val loop
32340 procedure Initialize_API is
32342 pragma Import (C, Adainit);
32345 end Initialize_API;
32347 procedure Finalize_API is
32348 procedure Adafinal;
32349 pragma Import (C, Adafinal);
32359 If the Ada DLL you are building will only be used by Ada applications
32360 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
32361 convention. As an example, the previous package could be written as
32364 @smallexample @c ada
32368 Count : Integer := 0;
32369 function Factorial (Val : Integer) return Integer;
32371 procedure Initialize_API;
32372 procedure Finalize_API;
32373 -- Initialization and Finalization routines.
32379 @smallexample @c ada
32382 package body API is
32383 function Factorial (Val : Integer) return Integer is
32384 Fact : Integer := 1;
32386 Count := Count + 1;
32387 for K in 1 .. Val loop
32394 -- The remainder of this package body is unchanged.
32401 Note that if you do not export the Ada entities with a @code{C} or
32402 @code{Stdcall} convention you will have to provide the mangled Ada names
32403 in the definition file of the Ada DLL
32404 (@pxref{Creating the Definition File}).
32406 @node Ada DLLs and Elaboration
32407 @subsection Ada DLLs and Elaboration
32408 @cindex DLLs and elaboration
32411 The DLL that you are building contains your Ada code as well as all the
32412 routines in the Ada library that are needed by it. The first thing a
32413 user of your DLL must do is elaborate the Ada code
32414 (@pxref{Elaboration Order Handling in GNAT}).
32416 To achieve this you must export an initialization routine
32417 (@code{Initialize_API} in the previous example), which must be invoked
32418 before using any of the DLL services. This elaboration routine must call
32419 the Ada elaboration routine @code{adainit} generated by the GNAT binder
32420 (@pxref{Binding with Non-Ada Main Programs}). See the body of
32421 @code{Initialize_Api} for an example. Note that the GNAT binder is
32422 automatically invoked during the DLL build process by the @code{gnatdll}
32423 tool (@pxref{Using gnatdll}).
32425 When a DLL is loaded, Windows systematically invokes a routine called
32426 @code{DllMain}. It would therefore be possible to call @code{adainit}
32427 directly from @code{DllMain} without having to provide an explicit
32428 initialization routine. Unfortunately, it is not possible to call
32429 @code{adainit} from the @code{DllMain} if your program has library level
32430 tasks because access to the @code{DllMain} entry point is serialized by
32431 the system (that is, only a single thread can execute ``through'' it at a
32432 time), which means that the GNAT run time will deadlock waiting for the
32433 newly created task to complete its initialization.
32435 @node Ada DLLs and Finalization
32436 @subsection Ada DLLs and Finalization
32437 @cindex DLLs and finalization
32440 When the services of an Ada DLL are no longer needed, the client code should
32441 invoke the DLL finalization routine, if available. The DLL finalization
32442 routine is in charge of releasing all resources acquired by the DLL. In the
32443 case of the Ada code contained in the DLL, this is achieved by calling
32444 routine @code{adafinal} generated by the GNAT binder
32445 (@pxref{Binding with Non-Ada Main Programs}).
32446 See the body of @code{Finalize_Api} for an
32447 example. As already pointed out the GNAT binder is automatically invoked
32448 during the DLL build process by the @code{gnatdll} tool
32449 (@pxref{Using gnatdll}).
32451 @node Creating a Spec for Ada DLLs
32452 @subsection Creating a Spec for Ada DLLs
32455 To use the services exported by the Ada DLL from another programming
32456 language (e.g.@: C), you have to translate the specs of the exported Ada
32457 entities in that language. For instance in the case of @code{API.dll},
32458 the corresponding C header file could look like:
32463 extern int *_imp__count;
32464 #define count (*_imp__count)
32465 int factorial (int);
32471 It is important to understand that when building an Ada DLL to be used by
32472 other Ada applications, you need two different specs for the packages
32473 contained in the DLL: one for building the DLL and the other for using
32474 the DLL. This is because the @code{DLL} calling convention is needed to
32475 use a variable defined in a DLL, but when building the DLL, the variable
32476 must have either the @code{Ada} or @code{C} calling convention. As an
32477 example consider a DLL comprising the following package @code{API}:
32479 @smallexample @c ada
32483 Count : Integer := 0;
32485 -- Remainder of the package omitted.
32492 After producing a DLL containing package @code{API}, the spec that
32493 must be used to import @code{API.Count} from Ada code outside of the
32496 @smallexample @c ada
32501 pragma Import (DLL, Count);
32507 @node Creating the Definition File
32508 @subsection Creating the Definition File
32511 The definition file is the last file needed to build the DLL. It lists
32512 the exported symbols. As an example, the definition file for a DLL
32513 containing only package @code{API} (where all the entities are exported
32514 with a @code{C} calling convention) is:
32529 If the @code{C} calling convention is missing from package @code{API},
32530 then the definition file contains the mangled Ada names of the above
32531 entities, which in this case are:
32540 api__initialize_api
32545 @node Using gnatdll
32546 @subsection Using @code{gnatdll}
32550 * gnatdll Example::
32551 * gnatdll behind the Scenes::
32556 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
32557 and non-Ada sources that make up your DLL have been compiled.
32558 @code{gnatdll} is actually in charge of two distinct tasks: build the
32559 static import library for the DLL and the actual DLL. The form of the
32560 @code{gnatdll} command is
32564 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
32569 where @var{list-of-files} is a list of ALI and object files. The object
32570 file list must be the exact list of objects corresponding to the non-Ada
32571 sources whose services are to be included in the DLL. The ALI file list
32572 must be the exact list of ALI files for the corresponding Ada sources
32573 whose services are to be included in the DLL. If @var{list-of-files} is
32574 missing, only the static import library is generated.
32577 You may specify any of the following switches to @code{gnatdll}:
32580 @item -a@ovar{address}
32581 @cindex @option{-a} (@code{gnatdll})
32582 Build a non-relocatable DLL at @var{address}. If @var{address} is not
32583 specified the default address @var{0x11000000} will be used. By default,
32584 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
32585 advise the reader to build relocatable DLL.
32587 @item -b @var{address}
32588 @cindex @option{-b} (@code{gnatdll})
32589 Set the relocatable DLL base address. By default the address is
32592 @item -bargs @var{opts}
32593 @cindex @option{-bargs} (@code{gnatdll})
32594 Binder options. Pass @var{opts} to the binder.
32596 @item -d @var{dllfile}
32597 @cindex @option{-d} (@code{gnatdll})
32598 @var{dllfile} is the name of the DLL. This switch must be present for
32599 @code{gnatdll} to do anything. The name of the generated import library is
32600 obtained algorithmically from @var{dllfile} as shown in the following
32601 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
32602 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
32603 by option @option{-e}) is obtained algorithmically from @var{dllfile}
32604 as shown in the following example:
32605 if @var{dllfile} is @code{xyz.dll}, the definition
32606 file used is @code{xyz.def}.
32608 @item -e @var{deffile}
32609 @cindex @option{-e} (@code{gnatdll})
32610 @var{deffile} is the name of the definition file.
32613 @cindex @option{-g} (@code{gnatdll})
32614 Generate debugging information. This information is stored in the object
32615 file and copied from there to the final DLL file by the linker,
32616 where it can be read by the debugger. You must use the
32617 @option{-g} switch if you plan on using the debugger or the symbolic
32621 @cindex @option{-h} (@code{gnatdll})
32622 Help mode. Displays @code{gnatdll} switch usage information.
32625 @cindex @option{-I} (@code{gnatdll})
32626 Direct @code{gnatdll} to search the @var{dir} directory for source and
32627 object files needed to build the DLL.
32628 (@pxref{Search Paths and the Run-Time Library (RTL)}).
32631 @cindex @option{-k} (@code{gnatdll})
32632 Removes the @code{@@}@var{nn} suffix from the import library's exported
32633 names, but keeps them for the link names. You must specify this
32634 option if you want to use a @code{Stdcall} function in a DLL for which
32635 the @code{@@}@var{nn} suffix has been removed. This is the case for most
32636 of the Windows NT DLL for example. This option has no effect when
32637 @option{-n} option is specified.
32639 @item -l @var{file}
32640 @cindex @option{-l} (@code{gnatdll})
32641 The list of ALI and object files used to build the DLL are listed in
32642 @var{file}, instead of being given in the command line. Each line in
32643 @var{file} contains the name of an ALI or object file.
32646 @cindex @option{-n} (@code{gnatdll})
32647 No Import. Do not create the import library.
32650 @cindex @option{-q} (@code{gnatdll})
32651 Quiet mode. Do not display unnecessary messages.
32654 @cindex @option{-v} (@code{gnatdll})
32655 Verbose mode. Display extra information.
32657 @item -largs @var{opts}
32658 @cindex @option{-largs} (@code{gnatdll})
32659 Linker options. Pass @var{opts} to the linker.
32662 @node gnatdll Example
32663 @subsubsection @code{gnatdll} Example
32666 As an example the command to build a relocatable DLL from @file{api.adb}
32667 once @file{api.adb} has been compiled and @file{api.def} created is
32670 $ gnatdll -d api.dll api.ali
32674 The above command creates two files: @file{libapi.dll.a} (the import
32675 library) and @file{api.dll} (the actual DLL). If you want to create
32676 only the DLL, just type:
32679 $ gnatdll -d api.dll -n api.ali
32683 Alternatively if you want to create just the import library, type:
32686 $ gnatdll -d api.dll
32689 @node gnatdll behind the Scenes
32690 @subsubsection @code{gnatdll} behind the Scenes
32693 This section details the steps involved in creating a DLL. @code{gnatdll}
32694 does these steps for you. Unless you are interested in understanding what
32695 goes on behind the scenes, you should skip this section.
32697 We use the previous example of a DLL containing the Ada package @code{API},
32698 to illustrate the steps necessary to build a DLL. The starting point is a
32699 set of objects that will make up the DLL and the corresponding ALI
32700 files. In the case of this example this means that @file{api.o} and
32701 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
32706 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
32707 the information necessary to generate relocation information for the
32713 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
32718 In addition to the base file, the @command{gnatlink} command generates an
32719 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
32720 asks @command{gnatlink} to generate the routines @code{DllMain} and
32721 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
32722 is loaded into memory.
32725 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
32726 export table (@file{api.exp}). The export table contains the relocation
32727 information in a form which can be used during the final link to ensure
32728 that the Windows loader is able to place the DLL anywhere in memory.
32732 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32733 --output-exp api.exp
32738 @code{gnatdll} builds the base file using the new export table. Note that
32739 @command{gnatbind} must be called once again since the binder generated file
32740 has been deleted during the previous call to @command{gnatlink}.
32745 $ gnatlink api -o api.jnk api.exp -mdll
32746 -Wl,--base-file,api.base
32751 @code{gnatdll} builds the new export table using the new base file and
32752 generates the DLL import library @file{libAPI.dll.a}.
32756 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32757 --output-exp api.exp --output-lib libAPI.a
32762 Finally @code{gnatdll} builds the relocatable DLL using the final export
32768 $ gnatlink api api.exp -o api.dll -mdll
32773 @node Using dlltool
32774 @subsubsection Using @code{dlltool}
32777 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
32778 DLLs and static import libraries. This section summarizes the most
32779 common @code{dlltool} switches. The form of the @code{dlltool} command
32783 $ dlltool @ovar{switches}
32787 @code{dlltool} switches include:
32790 @item --base-file @var{basefile}
32791 @cindex @option{--base-file} (@command{dlltool})
32792 Read the base file @var{basefile} generated by the linker. This switch
32793 is used to create a relocatable DLL.
32795 @item --def @var{deffile}
32796 @cindex @option{--def} (@command{dlltool})
32797 Read the definition file.
32799 @item --dllname @var{name}
32800 @cindex @option{--dllname} (@command{dlltool})
32801 Gives the name of the DLL. This switch is used to embed the name of the
32802 DLL in the static import library generated by @code{dlltool} with switch
32803 @option{--output-lib}.
32806 @cindex @option{-k} (@command{dlltool})
32807 Kill @code{@@}@var{nn} from exported names
32808 (@pxref{Windows Calling Conventions}
32809 for a discussion about @code{Stdcall}-style symbols.
32812 @cindex @option{--help} (@command{dlltool})
32813 Prints the @code{dlltool} switches with a concise description.
32815 @item --output-exp @var{exportfile}
32816 @cindex @option{--output-exp} (@command{dlltool})
32817 Generate an export file @var{exportfile}. The export file contains the
32818 export table (list of symbols in the DLL) and is used to create the DLL.
32820 @item --output-lib @var{libfile}
32821 @cindex @option{--output-lib} (@command{dlltool})
32822 Generate a static import library @var{libfile}.
32825 @cindex @option{-v} (@command{dlltool})
32828 @item --as @var{assembler-name}
32829 @cindex @option{--as} (@command{dlltool})
32830 Use @var{assembler-name} as the assembler. The default is @code{as}.
32833 @node GNAT and Windows Resources
32834 @section GNAT and Windows Resources
32835 @cindex Resources, windows
32838 * Building Resources::
32839 * Compiling Resources::
32840 * Using Resources::
32844 Resources are an easy way to add Windows specific objects to your
32845 application. The objects that can be added as resources include:
32874 This section explains how to build, compile and use resources.
32876 @node Building Resources
32877 @subsection Building Resources
32878 @cindex Resources, building
32881 A resource file is an ASCII file. By convention resource files have an
32882 @file{.rc} extension.
32883 The easiest way to build a resource file is to use Microsoft tools
32884 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
32885 @code{dlgedit.exe} to build dialogs.
32886 It is always possible to build an @file{.rc} file yourself by writing a
32889 It is not our objective to explain how to write a resource file. A
32890 complete description of the resource script language can be found in the
32891 Microsoft documentation.
32893 @node Compiling Resources
32894 @subsection Compiling Resources
32897 @cindex Resources, compiling
32900 This section describes how to build a GNAT-compatible (COFF) object file
32901 containing the resources. This is done using the Resource Compiler
32902 @code{windres} as follows:
32905 $ windres -i myres.rc -o myres.o
32909 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
32910 file. You can specify an alternate preprocessor (usually named
32911 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
32912 parameter. A list of all possible options may be obtained by entering
32913 the command @code{windres} @option{--help}.
32915 It is also possible to use the Microsoft resource compiler @code{rc.exe}
32916 to produce a @file{.res} file (binary resource file). See the
32917 corresponding Microsoft documentation for further details. In this case
32918 you need to use @code{windres} to translate the @file{.res} file to a
32919 GNAT-compatible object file as follows:
32922 $ windres -i myres.res -o myres.o
32925 @node Using Resources
32926 @subsection Using Resources
32927 @cindex Resources, using
32930 To include the resource file in your program just add the
32931 GNAT-compatible object file for the resource(s) to the linker
32932 arguments. With @command{gnatmake} this is done by using the @option{-largs}
32936 $ gnatmake myprog -largs myres.o
32939 @node Debugging a DLL
32940 @section Debugging a DLL
32941 @cindex DLL debugging
32944 * Program and DLL Both Built with GCC/GNAT::
32945 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
32949 Debugging a DLL is similar to debugging a standard program. But
32950 we have to deal with two different executable parts: the DLL and the
32951 program that uses it. We have the following four possibilities:
32955 The program and the DLL are built with @code{GCC/GNAT}.
32957 The program is built with foreign tools and the DLL is built with
32960 The program is built with @code{GCC/GNAT} and the DLL is built with
32966 In this section we address only cases one and two above.
32967 There is no point in trying to debug
32968 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
32969 information in it. To do so you must use a debugger compatible with the
32970 tools suite used to build the DLL.
32972 @node Program and DLL Both Built with GCC/GNAT
32973 @subsection Program and DLL Both Built with GCC/GNAT
32976 This is the simplest case. Both the DLL and the program have @code{GDB}
32977 compatible debugging information. It is then possible to break anywhere in
32978 the process. Let's suppose here that the main procedure is named
32979 @code{ada_main} and that in the DLL there is an entry point named
32983 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
32984 program must have been built with the debugging information (see GNAT -g
32985 switch). Here are the step-by-step instructions for debugging it:
32988 @item Launch @code{GDB} on the main program.
32994 @item Start the program and stop at the beginning of the main procedure
33001 This step is required to be able to set a breakpoint inside the DLL. As long
33002 as the program is not run, the DLL is not loaded. This has the
33003 consequence that the DLL debugging information is also not loaded, so it is not
33004 possible to set a breakpoint in the DLL.
33006 @item Set a breakpoint inside the DLL
33009 (gdb) break ada_dll
33016 At this stage a breakpoint is set inside the DLL. From there on
33017 you can use the standard approach to debug the whole program
33018 (@pxref{Running and Debugging Ada Programs}).
33021 @c This used to work, probably because the DLLs were non-relocatable
33022 @c keep this section around until the problem is sorted out.
33024 To break on the @code{DllMain} routine it is not possible to follow
33025 the procedure above. At the time the program stop on @code{ada_main}
33026 the @code{DllMain} routine as already been called. Either you can use
33027 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
33030 @item Launch @code{GDB} on the main program.
33036 @item Load DLL symbols
33039 (gdb) add-sym api.dll
33042 @item Set a breakpoint inside the DLL
33045 (gdb) break ada_dll.adb:45
33048 Note that at this point it is not possible to break using the routine symbol
33049 directly as the program is not yet running. The solution is to break
33050 on the proper line (break in @file{ada_dll.adb} line 45).
33052 @item Start the program
33061 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
33062 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
33065 * Debugging the DLL Directly::
33066 * Attaching to a Running Process::
33070 In this case things are slightly more complex because it is not possible to
33071 start the main program and then break at the beginning to load the DLL and the
33072 associated DLL debugging information. It is not possible to break at the
33073 beginning of the program because there is no @code{GDB} debugging information,
33074 and therefore there is no direct way of getting initial control. This
33075 section addresses this issue by describing some methods that can be used
33076 to break somewhere in the DLL to debug it.
33079 First suppose that the main procedure is named @code{main} (this is for
33080 example some C code built with Microsoft Visual C) and that there is a
33081 DLL named @code{test.dll} containing an Ada entry point named
33085 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
33086 been built with debugging information (see GNAT -g option).
33088 @node Debugging the DLL Directly
33089 @subsubsection Debugging the DLL Directly
33093 Find out the executable starting address
33096 $ objdump --file-header main.exe
33099 The starting address is reported on the last line. For example:
33102 main.exe: file format pei-i386
33103 architecture: i386, flags 0x0000010a:
33104 EXEC_P, HAS_DEBUG, D_PAGED
33105 start address 0x00401010
33109 Launch the debugger on the executable.
33116 Set a breakpoint at the starting address, and launch the program.
33119 $ (gdb) break *0x00401010
33123 The program will stop at the given address.
33126 Set a breakpoint on a DLL subroutine.
33129 (gdb) break ada_dll.adb:45
33132 Or if you want to break using a symbol on the DLL, you need first to
33133 select the Ada language (language used by the DLL).
33136 (gdb) set language ada
33137 (gdb) break ada_dll
33141 Continue the program.
33148 This will run the program until it reaches the breakpoint that has been
33149 set. From that point you can use the standard way to debug a program
33150 as described in (@pxref{Running and Debugging Ada Programs}).
33155 It is also possible to debug the DLL by attaching to a running process.
33157 @node Attaching to a Running Process
33158 @subsubsection Attaching to a Running Process
33159 @cindex DLL debugging, attach to process
33162 With @code{GDB} it is always possible to debug a running process by
33163 attaching to it. It is possible to debug a DLL this way. The limitation
33164 of this approach is that the DLL must run long enough to perform the
33165 attach operation. It may be useful for instance to insert a time wasting
33166 loop in the code of the DLL to meet this criterion.
33170 @item Launch the main program @file{main.exe}.
33176 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
33177 that the process PID for @file{main.exe} is 208.
33185 @item Attach to the running process to be debugged.
33191 @item Load the process debugging information.
33194 (gdb) symbol-file main.exe
33197 @item Break somewhere in the DLL.
33200 (gdb) break ada_dll
33203 @item Continue process execution.
33212 This last step will resume the process execution, and stop at
33213 the breakpoint we have set. From there you can use the standard
33214 approach to debug a program as described in
33215 (@pxref{Running and Debugging Ada Programs}).
33217 @node Setting Stack Size from gnatlink
33218 @section Setting Stack Size from @command{gnatlink}
33221 It is possible to specify the program stack size at link time. On modern
33222 versions of Windows, starting with XP, this is mostly useful to set the size of
33223 the main stack (environment task). The other task stacks are set with pragma
33224 Storage_Size or with the @command{gnatbind -d} command.
33226 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
33227 reserve size of individual tasks, the link-time stack size applies to all
33228 tasks, and pragma Storage_Size has no effect.
33229 In particular, Stack Overflow checks are made against this
33230 link-time specified size.
33232 This setting can be done with
33233 @command{gnatlink} using either:
33237 @item using @option{-Xlinker} linker option
33240 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
33243 This sets the stack reserve size to 0x10000 bytes and the stack commit
33244 size to 0x1000 bytes.
33246 @item using @option{-Wl} linker option
33249 $ gnatlink hello -Wl,--stack=0x1000000
33252 This sets the stack reserve size to 0x1000000 bytes. Note that with
33253 @option{-Wl} option it is not possible to set the stack commit size
33254 because the coma is a separator for this option.
33258 @node Setting Heap Size from gnatlink
33259 @section Setting Heap Size from @command{gnatlink}
33262 Under Windows systems, it is possible to specify the program heap size from
33263 @command{gnatlink} using either:
33267 @item using @option{-Xlinker} linker option
33270 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
33273 This sets the heap reserve size to 0x10000 bytes and the heap commit
33274 size to 0x1000 bytes.
33276 @item using @option{-Wl} linker option
33279 $ gnatlink hello -Wl,--heap=0x1000000
33282 This sets the heap reserve size to 0x1000000 bytes. Note that with
33283 @option{-Wl} option it is not possible to set the heap commit size
33284 because the coma is a separator for this option.
33290 @c **********************************
33291 @c * GNU Free Documentation License *
33292 @c **********************************
33294 @c GNU Free Documentation License
33296 @node Index,,GNU Free Documentation License, Top
33302 @c Put table of contents at end, otherwise it precedes the "title page" in
33303 @c the .txt version
33304 @c Edit the pdf file to move the contents to the beginning, after the title