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;
3282 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
3284 function Constructor (v : Integer) return Root;
3285 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
3287 function Constructor (v, w : Integer) return Root;
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;
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
4088 (@pxref{Validity Checking}).
4091 @cindex @option{-gnatc} (@command{gcc})
4092 Check syntax and semantics only (no code generation attempted).
4095 @cindex @option{-gnatC} (@command{gcc})
4096 Generate CodePeer information (no code generation attempted).
4097 This switch will generate an intermediate representation suitable for
4098 use by CodePeer (@file{.scil} files). This switch is not compatible with
4099 code generation (it will, among other things, disable some switches such
4100 as -gnatn, and enable others such as -gnata).
4103 @cindex @option{-gnatd} (@command{gcc})
4104 Specify debug options for the compiler. The string of characters after
4105 the @option{-gnatd} specify the specific debug options. The possible
4106 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
4107 compiler source file @file{debug.adb} for details of the implemented
4108 debug options. Certain debug options are relevant to applications
4109 programmers, and these are documented at appropriate points in this
4114 @cindex @option{-gnatD[nn]} (@command{gcc})
4117 @item /XDEBUG /LXDEBUG=nnn
4119 Create expanded source files for source level debugging. This switch
4120 also suppress generation of cross-reference information
4121 (see @option{-gnatx}).
4123 @item -gnatec=@var{path}
4124 @cindex @option{-gnatec} (@command{gcc})
4125 Specify a configuration pragma file
4127 (the equal sign is optional)
4129 (@pxref{The Configuration Pragmas Files}).
4131 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=@var{value}@r{]}
4132 @cindex @option{-gnateD} (@command{gcc})
4133 Defines a symbol, associated with @var{value}, for preprocessing.
4134 (@pxref{Integrated Preprocessing}).
4137 @cindex @option{-gnatef} (@command{gcc})
4138 Display full source path name in brief error messages.
4141 @cindex @option{-gnateG} (@command{gcc})
4142 Save result of preprocessing in a text file.
4144 @item -gnatem=@var{path}
4145 @cindex @option{-gnatem} (@command{gcc})
4146 Specify a mapping file
4148 (the equal sign is optional)
4150 (@pxref{Units to Sources Mapping Files}).
4152 @item -gnatep=@var{file}
4153 @cindex @option{-gnatep} (@command{gcc})
4154 Specify a preprocessing data file
4156 (the equal sign is optional)
4158 (@pxref{Integrated Preprocessing}).
4161 @cindex @option{-gnatE} (@command{gcc})
4162 Full dynamic elaboration checks.
4165 @cindex @option{-gnatf} (@command{gcc})
4166 Full errors. Multiple errors per line, all undefined references, do not
4167 attempt to suppress cascaded errors.
4170 @cindex @option{-gnatF} (@command{gcc})
4171 Externals names are folded to all uppercase.
4173 @item ^-gnatg^/GNAT_INTERNAL^
4174 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
4175 Internal GNAT implementation mode. This should not be used for
4176 applications programs, it is intended only for use by the compiler
4177 and its run-time library. For documentation, see the GNAT sources.
4178 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
4179 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
4180 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
4181 so that all standard warnings and all standard style options are turned on.
4182 All warnings and style error messages are treated as errors.
4186 @cindex @option{-gnatG[nn]} (@command{gcc})
4189 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
4191 List generated expanded code in source form.
4193 @item ^-gnath^/HELP^
4194 @cindex @option{^-gnath^/HELP^} (@command{gcc})
4195 Output usage information. The output is written to @file{stdout}.
4197 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
4198 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
4199 Identifier character set
4201 (@var{c}=1/2/3/4/8/9/p/f/n/w).
4203 For details of the possible selections for @var{c},
4204 see @ref{Character Set Control}.
4206 @item ^-gnatI^/IGNORE_REP_CLAUSES^
4207 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
4208 Ignore representation clauses. When this switch is used,
4209 representation clauses are treated as comments. This is useful
4210 when initially porting code where you want to ignore rep clause
4211 problems, and also for compiling foreign code (particularly
4212 for use with ASIS). The representation clauses that are ignored
4213 are: enumeration_representation_clause, record_representation_clause,
4214 and attribute_definition_clause for the following attributes:
4215 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
4216 Object_Size, Size, Small, Stream_Size, and Value_Size.
4217 Note that this option should be used only for compiling -- the
4218 code is likely to malfunction at run time.
4221 @cindex @option{-gnatjnn} (@command{gcc})
4222 Reformat error messages to fit on nn character lines
4224 @item -gnatk=@var{n}
4225 @cindex @option{-gnatk} (@command{gcc})
4226 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4229 @cindex @option{-gnatl} (@command{gcc})
4230 Output full source listing with embedded error messages.
4233 @cindex @option{-gnatL} (@command{gcc})
4234 Used in conjunction with -gnatG or -gnatD to intersperse original
4235 source lines (as comment lines with line numbers) in the expanded
4238 @item -gnatm=@var{n}
4239 @cindex @option{-gnatm} (@command{gcc})
4240 Limit number of detected error or warning messages to @var{n}
4241 where @var{n} is in the range 1..999999. The default setting if
4242 no switch is given is 9999. If the number of warnings reaches this
4243 limit, then a message is output and further warnings are suppressed,
4244 but the compilation is continued. If the number of error messages
4245 reaches this limit, then a message is output and the compilation
4246 is abandoned. The equal sign here is optional. A value of zero
4247 means that no limit applies.
4250 @cindex @option{-gnatn} (@command{gcc})
4251 Activate inlining for subprograms for which
4252 pragma @code{inline} is specified. This inlining is performed
4253 by the GCC back-end.
4256 @cindex @option{-gnatN} (@command{gcc})
4257 Activate front end inlining for subprograms for which
4258 pragma @code{Inline} is specified. This inlining is performed
4259 by the front end and will be visible in the
4260 @option{-gnatG} output.
4262 When using a gcc-based back end (in practice this means using any version
4263 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4264 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4265 Historically front end inlining was more extensive than the gcc back end
4266 inlining, but that is no longer the case.
4269 @cindex @option{-gnato} (@command{gcc})
4270 Enable numeric overflow checking (which is not normally enabled by
4271 default). Note that division by zero is a separate check that is not
4272 controlled by this switch (division by zero checking is on by default).
4275 @cindex @option{-gnatp} (@command{gcc})
4276 Suppress all checks. See @ref{Run-Time Checks} for details.
4279 @cindex @option{-gnatP} (@command{gcc})
4280 Enable polling. This is required on some systems (notably Windows NT) to
4281 obtain asynchronous abort and asynchronous transfer of control capability.
4282 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4286 @cindex @option{-gnatq} (@command{gcc})
4287 Don't quit. Try semantics, even if parse errors.
4290 @cindex @option{-gnatQ} (@command{gcc})
4291 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4294 @cindex @option{-gnatr} (@command{gcc})
4295 Treat pragma Restrictions as Restriction_Warnings.
4297 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4298 @cindex @option{-gnatR} (@command{gcc})
4299 Output representation information for declared types and objects.
4302 @cindex @option{-gnats} (@command{gcc})
4306 @cindex @option{-gnatS} (@command{gcc})
4307 Print package Standard.
4310 @cindex @option{-gnatt} (@command{gcc})
4311 Generate tree output file.
4313 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4314 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4315 All compiler tables start at @var{nnn} times usual starting size.
4318 @cindex @option{-gnatu} (@command{gcc})
4319 List units for this compilation.
4322 @cindex @option{-gnatU} (@command{gcc})
4323 Tag all error messages with the unique string ``error:''
4326 @cindex @option{-gnatv} (@command{gcc})
4327 Verbose mode. Full error output with source lines to @file{stdout}.
4330 @cindex @option{-gnatV} (@command{gcc})
4331 Control level of validity checking (@pxref{Validity Checking}).
4333 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4334 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4336 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4337 the exact warnings that
4338 are enabled or disabled (@pxref{Warning Message Control}).
4340 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4341 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4342 Wide character encoding method
4344 (@var{e}=n/h/u/s/e/8).
4347 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4351 @cindex @option{-gnatx} (@command{gcc})
4352 Suppress generation of cross-reference information.
4354 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4355 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4356 Enable built-in style checks (@pxref{Style Checking}).
4358 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4359 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4360 Distribution stub generation and compilation
4362 (@var{m}=r/c for receiver/caller stubs).
4365 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4366 to be generated and compiled).
4369 @item ^-I^/SEARCH=^@var{dir}
4370 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4372 Direct GNAT to search the @var{dir} directory for source files needed by
4373 the current compilation
4374 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4376 @item ^-I-^/NOCURRENT_DIRECTORY^
4377 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4379 Except for the source file named in the command line, do not look for source
4380 files in the directory containing the source file named in the command line
4381 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4385 @cindex @option{-mbig-switch} (@command{gcc})
4386 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4387 This standard gcc switch causes the compiler to use larger offsets in its
4388 jump table representation for @code{case} statements.
4389 This may result in less efficient code, but is sometimes necessary
4390 (for example on HP-UX targets)
4391 @cindex HP-UX and @option{-mbig-switch} option
4392 in order to compile large and/or nested @code{case} statements.
4395 @cindex @option{-o} (@command{gcc})
4396 This switch is used in @command{gcc} to redirect the generated object file
4397 and its associated ALI file. Beware of this switch with GNAT, because it may
4398 cause the object file and ALI file to have different names which in turn
4399 may confuse the binder and the linker.
4403 @cindex @option{-nostdinc} (@command{gcc})
4404 Inhibit the search of the default location for the GNAT Run Time
4405 Library (RTL) source files.
4408 @cindex @option{-nostdlib} (@command{gcc})
4409 Inhibit the search of the default location for the GNAT Run Time
4410 Library (RTL) ALI files.
4414 @cindex @option{-O} (@command{gcc})
4415 @var{n} controls the optimization level.
4419 No optimization, the default setting if no @option{-O} appears
4422 Normal optimization, the default if you specify @option{-O} without
4423 an operand. A good compromise between code quality and compilation
4427 Extensive optimization, may improve execution time, possibly at the cost of
4428 substantially increased compilation time.
4431 Same as @option{-O2}, and also includes inline expansion for small subprograms
4435 Optimize space usage
4439 See also @ref{Optimization Levels}.
4444 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4445 Equivalent to @option{/OPTIMIZE=NONE}.
4446 This is the default behavior in the absence of an @option{/OPTIMIZE}
4449 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4450 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4451 Selects the level of optimization for your program. The supported
4452 keywords are as follows:
4455 Perform most optimizations, including those that
4457 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4458 without keyword options.
4461 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4464 Perform some optimizations, but omit ones that are costly.
4467 Same as @code{SOME}.
4470 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4471 automatic inlining of small subprograms within a unit
4474 Try to unroll loops. This keyword may be specified together with
4475 any keyword above other than @code{NONE}. Loop unrolling
4476 usually, but not always, improves the performance of programs.
4479 Optimize space usage
4483 See also @ref{Optimization Levels}.
4487 @item -pass-exit-codes
4488 @cindex @option{-pass-exit-codes} (@command{gcc})
4489 Catch exit codes from the compiler and use the most meaningful as
4493 @item --RTS=@var{rts-path}
4494 @cindex @option{--RTS} (@command{gcc})
4495 Specifies the default location of the runtime library. Same meaning as the
4496 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4499 @cindex @option{^-S^/ASM^} (@command{gcc})
4500 ^Used in place of @option{-c} to^Used to^
4501 cause the assembler source file to be
4502 generated, using @file{^.s^.S^} as the extension,
4503 instead of the object file.
4504 This may be useful if you need to examine the generated assembly code.
4506 @item ^-fverbose-asm^/VERBOSE_ASM^
4507 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4508 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4509 to cause the generated assembly code file to be annotated with variable
4510 names, making it significantly easier to follow.
4513 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4514 Show commands generated by the @command{gcc} driver. Normally used only for
4515 debugging purposes or if you need to be sure what version of the
4516 compiler you are executing.
4520 @cindex @option{-V} (@command{gcc})
4521 Execute @var{ver} version of the compiler. This is the @command{gcc}
4522 version, not the GNAT version.
4525 @item ^-w^/NO_BACK_END_WARNINGS^
4526 @cindex @option{-w} (@command{gcc})
4527 Turn off warnings generated by the back end of the compiler. Use of
4528 this switch also causes the default for front end warnings to be set
4529 to suppress (as though @option{-gnatws} had appeared at the start of
4535 @c Combining qualifiers does not work on VMS
4536 You may combine a sequence of GNAT switches into a single switch. For
4537 example, the combined switch
4539 @cindex Combining GNAT switches
4545 is equivalent to specifying the following sequence of switches:
4548 -gnato -gnatf -gnati3
4553 The following restrictions apply to the combination of switches
4558 The switch @option{-gnatc} if combined with other switches must come
4559 first in the string.
4562 The switch @option{-gnats} if combined with other switches must come
4563 first in the string.
4567 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4568 may not be combined with any other switches.
4572 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4573 switch), then all further characters in the switch are interpreted
4574 as style modifiers (see description of @option{-gnaty}).
4577 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4578 switch), then all further characters in the switch are interpreted
4579 as debug flags (see description of @option{-gnatd}).
4582 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4583 switch), then all further characters in the switch are interpreted
4584 as warning mode modifiers (see description of @option{-gnatw}).
4587 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4588 switch), then all further characters in the switch are interpreted
4589 as validity checking options (@pxref{Validity Checking}).
4593 @node Output and Error Message Control
4594 @subsection Output and Error Message Control
4598 The standard default format for error messages is called ``brief format''.
4599 Brief format messages are written to @file{stderr} (the standard error
4600 file) and have the following form:
4603 e.adb:3:04: Incorrect spelling of keyword "function"
4604 e.adb:4:20: ";" should be "is"
4608 The first integer after the file name is the line number in the file,
4609 and the second integer is the column number within the line.
4611 @code{GPS} can parse the error messages
4612 and point to the referenced character.
4614 The following switches provide control over the error message
4620 @cindex @option{-gnatv} (@command{gcc})
4623 The v stands for verbose.
4625 The effect of this setting is to write long-format error
4626 messages to @file{stdout} (the standard output file.
4627 The same program compiled with the
4628 @option{-gnatv} switch would generate:
4632 3. funcion X (Q : Integer)
4634 >>> Incorrect spelling of keyword "function"
4637 >>> ";" should be "is"
4642 The vertical bar indicates the location of the error, and the @samp{>>>}
4643 prefix can be used to search for error messages. When this switch is
4644 used the only source lines output are those with errors.
4647 @cindex @option{-gnatl} (@command{gcc})
4649 The @code{l} stands for list.
4651 This switch causes a full listing of
4652 the file to be generated. In the case where a body is
4653 compiled, the corresponding spec is also listed, along
4654 with any subunits. Typical output from compiling a package
4655 body @file{p.adb} might look like:
4657 @smallexample @c ada
4661 1. package body p is
4663 3. procedure a is separate;
4674 2. pragma Elaborate_Body
4698 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4699 standard output is redirected, a brief summary is written to
4700 @file{stderr} (standard error) giving the number of error messages and
4701 warning messages generated.
4703 @item -^gnatl^OUTPUT_FILE^=file
4704 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4705 This has the same effect as @option{-gnatl} except that the output is
4706 written to a file instead of to standard output. If the given name
4707 @file{fname} does not start with a period, then it is the full name
4708 of the file to be written. If @file{fname} is an extension, it is
4709 appended to the name of the file being compiled. For example, if
4710 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4711 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4714 @cindex @option{-gnatU} (@command{gcc})
4715 This switch forces all error messages to be preceded by the unique
4716 string ``error:''. This means that error messages take a few more
4717 characters in space, but allows easy searching for and identification
4721 @cindex @option{-gnatb} (@command{gcc})
4723 The @code{b} stands for brief.
4725 This switch causes GNAT to generate the
4726 brief format error messages to @file{stderr} (the standard error
4727 file) as well as the verbose
4728 format message or full listing (which as usual is written to
4729 @file{stdout} (the standard output file).
4731 @item -gnatm=@var{n}
4732 @cindex @option{-gnatm} (@command{gcc})
4734 The @code{m} stands for maximum.
4736 @var{n} is a decimal integer in the
4737 range of 1 to 999999 and limits the number of error or warning
4738 messages to be generated. For example, using
4739 @option{-gnatm2} might yield
4742 e.adb:3:04: Incorrect spelling of keyword "function"
4743 e.adb:5:35: missing ".."
4744 fatal error: maximum number of errors detected
4745 compilation abandoned
4749 The default setting if
4750 no switch is given is 9999. If the number of warnings reaches this
4751 limit, then a message is output and further warnings are suppressed,
4752 but the compilation is continued. If the number of error messages
4753 reaches this limit, then a message is output and the compilation
4754 is abandoned. A value of zero means that no limit applies.
4757 Note that the equal sign is optional, so the switches
4758 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4761 @cindex @option{-gnatf} (@command{gcc})
4762 @cindex Error messages, suppressing
4764 The @code{f} stands for full.
4766 Normally, the compiler suppresses error messages that are likely to be
4767 redundant. This switch causes all error
4768 messages to be generated. In particular, in the case of
4769 references to undefined variables. If a given variable is referenced
4770 several times, the normal format of messages is
4772 e.adb:7:07: "V" is undefined (more references follow)
4776 where the parenthetical comment warns that there are additional
4777 references to the variable @code{V}. Compiling the same program with the
4778 @option{-gnatf} switch yields
4781 e.adb:7:07: "V" is undefined
4782 e.adb:8:07: "V" is undefined
4783 e.adb:8:12: "V" is undefined
4784 e.adb:8:16: "V" is undefined
4785 e.adb:9:07: "V" is undefined
4786 e.adb:9:12: "V" is undefined
4790 The @option{-gnatf} switch also generates additional information for
4791 some error messages. Some examples are:
4795 Details on possibly non-portable unchecked conversion
4797 List possible interpretations for ambiguous calls
4799 Additional details on incorrect parameters
4803 @cindex @option{-gnatjnn} (@command{gcc})
4804 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4805 with continuation lines are treated as though the continuation lines were
4806 separate messages (and so a warning with two continuation lines counts as
4807 three warnings, and is listed as three separate messages).
4809 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4810 messages are output in a different manner. A message and all its continuation
4811 lines are treated as a unit, and count as only one warning or message in the
4812 statistics totals. Furthermore, the message is reformatted so that no line
4813 is longer than nn characters.
4816 @cindex @option{-gnatq} (@command{gcc})
4818 The @code{q} stands for quit (really ``don't quit'').
4820 In normal operation mode, the compiler first parses the program and
4821 determines if there are any syntax errors. If there are, appropriate
4822 error messages are generated and compilation is immediately terminated.
4824 GNAT to continue with semantic analysis even if syntax errors have been
4825 found. This may enable the detection of more errors in a single run. On
4826 the other hand, the semantic analyzer is more likely to encounter some
4827 internal fatal error when given a syntactically invalid tree.
4830 @cindex @option{-gnatQ} (@command{gcc})
4831 In normal operation mode, the @file{ALI} file is not generated if any
4832 illegalities are detected in the program. The use of @option{-gnatQ} forces
4833 generation of the @file{ALI} file. This file is marked as being in
4834 error, so it cannot be used for binding purposes, but it does contain
4835 reasonably complete cross-reference information, and thus may be useful
4836 for use by tools (e.g., semantic browsing tools or integrated development
4837 environments) that are driven from the @file{ALI} file. This switch
4838 implies @option{-gnatq}, since the semantic phase must be run to get a
4839 meaningful ALI file.
4841 In addition, if @option{-gnatt} is also specified, then the tree file is
4842 generated even if there are illegalities. It may be useful in this case
4843 to also specify @option{-gnatq} to ensure that full semantic processing
4844 occurs. The resulting tree file can be processed by ASIS, for the purpose
4845 of providing partial information about illegal units, but if the error
4846 causes the tree to be badly malformed, then ASIS may crash during the
4849 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4850 being in error, @command{gnatmake} will attempt to recompile the source when it
4851 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4853 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4854 since ALI files are never generated if @option{-gnats} is set.
4858 @node Warning Message Control
4859 @subsection Warning Message Control
4860 @cindex Warning messages
4862 In addition to error messages, which correspond to illegalities as defined
4863 in the Ada Reference Manual, the compiler detects two kinds of warning
4866 First, the compiler considers some constructs suspicious and generates a
4867 warning message to alert you to a possible error. Second, if the
4868 compiler detects a situation that is sure to raise an exception at
4869 run time, it generates a warning message. The following shows an example
4870 of warning messages:
4872 e.adb:4:24: warning: creation of object may raise Storage_Error
4873 e.adb:10:17: warning: static value out of range
4874 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4878 GNAT considers a large number of situations as appropriate
4879 for the generation of warning messages. As always, warnings are not
4880 definite indications of errors. For example, if you do an out-of-range
4881 assignment with the deliberate intention of raising a
4882 @code{Constraint_Error} exception, then the warning that may be
4883 issued does not indicate an error. Some of the situations for which GNAT
4884 issues warnings (at least some of the time) are given in the following
4885 list. This list is not complete, and new warnings are often added to
4886 subsequent versions of GNAT. The list is intended to give a general idea
4887 of the kinds of warnings that are generated.
4891 Possible infinitely recursive calls
4894 Out-of-range values being assigned
4897 Possible order of elaboration problems
4900 Assertions (pragma Assert) that are sure to fail
4906 Address clauses with possibly unaligned values, or where an attempt is
4907 made to overlay a smaller variable with a larger one.
4910 Fixed-point type declarations with a null range
4913 Direct_IO or Sequential_IO instantiated with a type that has access values
4916 Variables that are never assigned a value
4919 Variables that are referenced before being initialized
4922 Task entries with no corresponding @code{accept} statement
4925 Duplicate accepts for the same task entry in a @code{select}
4928 Objects that take too much storage
4931 Unchecked conversion between types of differing sizes
4934 Missing @code{return} statement along some execution path in a function
4937 Incorrect (unrecognized) pragmas
4940 Incorrect external names
4943 Allocation from empty storage pool
4946 Potentially blocking operation in protected type
4949 Suspicious parenthesization of expressions
4952 Mismatching bounds in an aggregate
4955 Attempt to return local value by reference
4958 Premature instantiation of a generic body
4961 Attempt to pack aliased components
4964 Out of bounds array subscripts
4967 Wrong length on string assignment
4970 Violations of style rules if style checking is enabled
4973 Unused @code{with} clauses
4976 @code{Bit_Order} usage that does not have any effect
4979 @code{Standard.Duration} used to resolve universal fixed expression
4982 Dereference of possibly null value
4985 Declaration that is likely to cause storage error
4988 Internal GNAT unit @code{with}'ed by application unit
4991 Values known to be out of range at compile time
4994 Unreferenced labels and variables
4997 Address overlays that could clobber memory
5000 Unexpected initialization when address clause present
5003 Bad alignment for address clause
5006 Useless type conversions
5009 Redundant assignment statements and other redundant constructs
5012 Useless exception handlers
5015 Accidental hiding of name by child unit
5018 Access before elaboration detected at compile time
5021 A range in a @code{for} loop that is known to be null or might be null
5026 The following section lists compiler switches that are available
5027 to control the handling of warning messages. It is also possible
5028 to exercise much finer control over what warnings are issued and
5029 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
5030 gnat_rm, GNAT Reference manual}.
5035 @emph{Activate all optional errors.}
5036 @cindex @option{-gnatwa} (@command{gcc})
5037 This switch activates most optional warning messages, see remaining list
5038 in this section for details on optional warning messages that can be
5039 individually controlled. The warnings that are not turned on by this
5041 @option{-gnatwd} (implicit dereferencing),
5042 @option{-gnatwh} (hiding),
5043 @option{-gnatwl} (elaboration warnings),
5044 @option{-gnatw.o} (warn on values set by out parameters ignored)
5045 and @option{-gnatwt} (tracking of deleted conditional code).
5046 All other optional warnings are turned on.
5049 @emph{Suppress all optional errors.}
5050 @cindex @option{-gnatwA} (@command{gcc})
5051 This switch suppresses all optional warning messages, see remaining list
5052 in this section for details on optional warning messages that can be
5053 individually controlled.
5056 @emph{Activate warnings on failing assertions.}
5057 @cindex @option{-gnatw.a} (@command{gcc})
5058 @cindex Assert failures
5059 This switch activates warnings for assertions where the compiler can tell at
5060 compile time that the assertion will fail. Note that this warning is given
5061 even if assertions are disabled. The default is that such warnings are
5065 @emph{Suppress warnings on failing assertions.}
5066 @cindex @option{-gnatw.A} (@command{gcc})
5067 @cindex Assert failures
5068 This switch suppresses warnings for assertions where the compiler can tell at
5069 compile time that the assertion will fail.
5072 @emph{Activate warnings on bad fixed values.}
5073 @cindex @option{-gnatwb} (@command{gcc})
5074 @cindex Bad fixed values
5075 @cindex Fixed-point Small value
5077 This switch activates warnings for static fixed-point expressions whose
5078 value is not an exact multiple of Small. Such values are implementation
5079 dependent, since an implementation is free to choose either of the multiples
5080 that surround the value. GNAT always chooses the closer one, but this is not
5081 required behavior, and it is better to specify a value that is an exact
5082 multiple, ensuring predictable execution. The default is that such warnings
5086 @emph{Suppress warnings on bad fixed values.}
5087 @cindex @option{-gnatwB} (@command{gcc})
5088 This switch suppresses warnings for static fixed-point expressions whose
5089 value is not an exact multiple of Small.
5092 @emph{Activate warnings on biased representation.}
5093 @cindex @option{-gnatw.b} (@command{gcc})
5094 @cindex Biased representation
5095 This switch activates warnings when a size clause, value size clause, component
5096 clause, or component size clause forces the use of biased representation for an
5097 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
5098 to represent 10/11). The default is that such warnings are generated.
5101 @emph{Suppress warnings on biased representation.}
5102 @cindex @option{-gnatwB} (@command{gcc})
5103 This switch suppresses warnings for representation clauses that force the use
5104 of biased representation.
5107 @emph{Activate warnings on conditionals.}
5108 @cindex @option{-gnatwc} (@command{gcc})
5109 @cindex Conditionals, constant
5110 This switch activates warnings for conditional expressions used in
5111 tests that are known to be True or False at compile time. The default
5112 is that such warnings are not generated.
5113 Note that this warning does
5114 not get issued for the use of boolean variables or constants whose
5115 values are known at compile time, since this is a standard technique
5116 for conditional compilation in Ada, and this would generate too many
5117 false positive warnings.
5119 This warning option also activates a special test for comparisons using
5120 the operators ``>='' and`` <=''.
5121 If the compiler can tell that only the equality condition is possible,
5122 then it will warn that the ``>'' or ``<'' part of the test
5123 is useless and that the operator could be replaced by ``=''.
5124 An example would be comparing a @code{Natural} variable <= 0.
5126 This warning option also generates warnings if
5127 one or both tests is optimized away in a membership test for integer
5128 values if the result can be determined at compile time. Range tests on
5129 enumeration types are not included, since it is common for such tests
5130 to include an end point.
5132 This warning can also be turned on using @option{-gnatwa}.
5135 @emph{Suppress warnings on conditionals.}
5136 @cindex @option{-gnatwC} (@command{gcc})
5137 This switch suppresses warnings for conditional expressions used in
5138 tests that are known to be True or False at compile time.
5141 @emph{Activate warnings on missing component clauses.}
5142 @cindex @option{-gnatw.c} (@command{gcc})
5143 @cindex Component clause, missing
5144 This switch activates warnings for record components where a record
5145 representation clause is present and has component clauses for the
5146 majority, but not all, of the components. A warning is given for each
5147 component for which no component clause is present.
5149 This warning can also be turned on using @option{-gnatwa}.
5152 @emph{Suppress warnings on missing component clauses.}
5153 @cindex @option{-gnatwC} (@command{gcc})
5154 This switch suppresses warnings for record components that are
5155 missing a component clause in the situation described above.
5158 @emph{Activate warnings on implicit dereferencing.}
5159 @cindex @option{-gnatwd} (@command{gcc})
5160 If this switch is set, then the use of a prefix of an access type
5161 in an indexed component, slice, or selected component without an
5162 explicit @code{.all} will generate a warning. With this warning
5163 enabled, access checks occur only at points where an explicit
5164 @code{.all} appears in the source code (assuming no warnings are
5165 generated as a result of this switch). The default is that such
5166 warnings are not generated.
5167 Note that @option{-gnatwa} does not affect the setting of
5168 this warning option.
5171 @emph{Suppress warnings on implicit dereferencing.}
5172 @cindex @option{-gnatwD} (@command{gcc})
5173 @cindex Implicit dereferencing
5174 @cindex Dereferencing, implicit
5175 This switch suppresses warnings for implicit dereferences in
5176 indexed components, slices, and selected components.
5179 @emph{Treat warnings as errors.}
5180 @cindex @option{-gnatwe} (@command{gcc})
5181 @cindex Warnings, treat as error
5182 This switch causes warning messages to be treated as errors.
5183 The warning string still appears, but the warning messages are counted
5184 as errors, and prevent the generation of an object file.
5187 @emph{Activate every optional warning}
5188 @cindex @option{-gnatw.e} (@command{gcc})
5189 @cindex Warnings, activate every optional warning
5190 This switch activates all optional warnings, including those which
5191 are not activated by @code{-gnatwa}.
5194 @emph{Activate warnings on unreferenced formals.}
5195 @cindex @option{-gnatwf} (@command{gcc})
5196 @cindex Formals, unreferenced
5197 This switch causes a warning to be generated if a formal parameter
5198 is not referenced in the body of the subprogram. This warning can
5199 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
5200 default is that these warnings are not generated.
5203 @emph{Suppress warnings on unreferenced formals.}
5204 @cindex @option{-gnatwF} (@command{gcc})
5205 This switch suppresses warnings for unreferenced formal
5206 parameters. Note that the
5207 combination @option{-gnatwu} followed by @option{-gnatwF} has the
5208 effect of warning on unreferenced entities other than subprogram
5212 @emph{Activate warnings on unrecognized pragmas.}
5213 @cindex @option{-gnatwg} (@command{gcc})
5214 @cindex Pragmas, unrecognized
5215 This switch causes a warning to be generated if an unrecognized
5216 pragma is encountered. Apart from issuing this warning, the
5217 pragma is ignored and has no effect. This warning can
5218 also be turned on using @option{-gnatwa}. The default
5219 is that such warnings are issued (satisfying the Ada Reference
5220 Manual requirement that such warnings appear).
5223 @emph{Suppress warnings on unrecognized pragmas.}
5224 @cindex @option{-gnatwG} (@command{gcc})
5225 This switch suppresses warnings for unrecognized pragmas.
5228 @emph{Activate warnings on hiding.}
5229 @cindex @option{-gnatwh} (@command{gcc})
5230 @cindex Hiding of Declarations
5231 This switch activates warnings on hiding declarations.
5232 A declaration is considered hiding
5233 if it is for a non-overloadable entity, and it declares an entity with the
5234 same name as some other entity that is directly or use-visible. The default
5235 is that such warnings are not generated.
5236 Note that @option{-gnatwa} does not affect the setting of this warning option.
5239 @emph{Suppress warnings on hiding.}
5240 @cindex @option{-gnatwH} (@command{gcc})
5241 This switch suppresses warnings on hiding declarations.
5244 @emph{Activate warnings on implementation units.}
5245 @cindex @option{-gnatwi} (@command{gcc})
5246 This switch activates warnings for a @code{with} of an internal GNAT
5247 implementation unit, defined as any unit from the @code{Ada},
5248 @code{Interfaces}, @code{GNAT},
5249 ^^@code{DEC},^ or @code{System}
5250 hierarchies that is not
5251 documented in either the Ada Reference Manual or the GNAT
5252 Programmer's Reference Manual. Such units are intended only
5253 for internal implementation purposes and should not be @code{with}'ed
5254 by user programs. The default is that such warnings are generated
5255 This warning can also be turned on using @option{-gnatwa}.
5258 @emph{Disable warnings on implementation units.}
5259 @cindex @option{-gnatwI} (@command{gcc})
5260 This switch disables warnings for a @code{with} of an internal GNAT
5261 implementation unit.
5264 @emph{Activate warnings on obsolescent features (Annex J).}
5265 @cindex @option{-gnatwj} (@command{gcc})
5266 @cindex Features, obsolescent
5267 @cindex Obsolescent features
5268 If this warning option is activated, then warnings are generated for
5269 calls to subprograms marked with @code{pragma Obsolescent} and
5270 for use of features in Annex J of the Ada Reference Manual. In the
5271 case of Annex J, not all features are flagged. In particular use
5272 of the renamed packages (like @code{Text_IO}) and use of package
5273 @code{ASCII} are not flagged, since these are very common and
5274 would generate many annoying positive warnings. The default is that
5275 such warnings are not generated. This warning is also turned on by
5276 the use of @option{-gnatwa}.
5278 In addition to the above cases, warnings are also generated for
5279 GNAT features that have been provided in past versions but which
5280 have been superseded (typically by features in the new Ada standard).
5281 For example, @code{pragma Ravenscar} will be flagged since its
5282 function is replaced by @code{pragma Profile(Ravenscar)}.
5284 Note that this warning option functions differently from the
5285 restriction @code{No_Obsolescent_Features} in two respects.
5286 First, the restriction applies only to annex J features.
5287 Second, the restriction does flag uses of package @code{ASCII}.
5290 @emph{Suppress warnings on obsolescent features (Annex J).}
5291 @cindex @option{-gnatwJ} (@command{gcc})
5292 This switch disables warnings on use of obsolescent features.
5295 @emph{Activate warnings on variables that could be constants.}
5296 @cindex @option{-gnatwk} (@command{gcc})
5297 This switch activates warnings for variables that are initialized but
5298 never modified, and then could be declared constants. The default is that
5299 such warnings are not given.
5300 This warning can also be turned on using @option{-gnatwa}.
5303 @emph{Suppress warnings on variables that could be constants.}
5304 @cindex @option{-gnatwK} (@command{gcc})
5305 This switch disables warnings on variables that could be declared constants.
5308 @emph{Activate warnings for elaboration pragmas.}
5309 @cindex @option{-gnatwl} (@command{gcc})
5310 @cindex Elaboration, warnings
5311 This switch activates warnings on missing
5312 @code{Elaborate_All} and @code{Elaborate} pragmas.
5313 See the section in this guide on elaboration checking for details on
5314 when such pragmas should be used. In dynamic elaboration mode, this switch
5315 generations warnings about the need to add elaboration pragmas. Note however,
5316 that if you blindly follow these warnings, and add @code{Elaborate_All}
5317 warnings wherever they are recommended, you basically end up with the
5318 equivalent of the static elaboration model, which may not be what you want for
5319 legacy code for which the static model does not work.
5321 For the static model, the messages generated are labeled "info:" (for
5322 information messages). They are not warnings to add elaboration pragmas,
5323 merely informational messages showing what implicit elaboration pragmas
5324 have been added, for use in analyzing elaboration circularity problems.
5326 Warnings are also generated if you
5327 are using the static mode of elaboration, and a @code{pragma Elaborate}
5328 is encountered. The default is that such warnings
5330 This warning is not automatically turned on by the use of @option{-gnatwa}.
5333 @emph{Suppress warnings for elaboration pragmas.}
5334 @cindex @option{-gnatwL} (@command{gcc})
5335 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5336 See the section in this guide on elaboration checking for details on
5337 when such pragmas should be used.
5340 @emph{Activate warnings on modified but unreferenced variables.}
5341 @cindex @option{-gnatwm} (@command{gcc})
5342 This switch activates warnings for variables that are assigned (using
5343 an initialization value or with one or more assignment statements) but
5344 whose value is never read. The warning is suppressed for volatile
5345 variables and also for variables that are renamings of other variables
5346 or for which an address clause is given.
5347 This warning can also be turned on using @option{-gnatwa}.
5348 The default is that these warnings are not given.
5351 @emph{Disable warnings on modified but unreferenced variables.}
5352 @cindex @option{-gnatwM} (@command{gcc})
5353 This switch disables warnings for variables that are assigned or
5354 initialized, but never read.
5357 @emph{Activate warnings on suspicious modulus values.}
5358 @cindex @option{-gnatw.m} (@command{gcc})
5359 This switch activates warnings for modulus values that seem suspicious.
5360 The cases caught are where the size is the same as the modulus (e.g.
5361 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
5362 with no size clause. The guess in both cases is that 2**x was intended
5363 rather than x. The default is that these warnings are given.
5366 @emph{Disable warnings on suspicious modulus values.}
5367 @cindex @option{-gnatw.M} (@command{gcc})
5368 This switch disables warnings for suspicious modulus values.
5371 @emph{Set normal warnings mode.}
5372 @cindex @option{-gnatwn} (@command{gcc})
5373 This switch sets normal warning mode, in which enabled warnings are
5374 issued and treated as warnings rather than errors. This is the default
5375 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5376 an explicit @option{-gnatws} or
5377 @option{-gnatwe}. It also cancels the effect of the
5378 implicit @option{-gnatwe} that is activated by the
5379 use of @option{-gnatg}.
5382 @emph{Activate warnings on address clause overlays.}
5383 @cindex @option{-gnatwo} (@command{gcc})
5384 @cindex Address Clauses, warnings
5385 This switch activates warnings for possibly unintended initialization
5386 effects of defining address clauses that cause one variable to overlap
5387 another. The default is that such warnings are generated.
5388 This warning can also be turned on using @option{-gnatwa}.
5391 @emph{Suppress warnings on address clause overlays.}
5392 @cindex @option{-gnatwO} (@command{gcc})
5393 This switch suppresses warnings on possibly unintended initialization
5394 effects of defining address clauses that cause one variable to overlap
5398 @emph{Activate warnings on modified but unreferenced out parameters.}
5399 @cindex @option{-gnatw.o} (@command{gcc})
5400 This switch activates warnings for variables that are modified by using
5401 them as actuals for a call to a procedure with an out mode formal, where
5402 the resulting assigned value is never read. It is applicable in the case
5403 where there is more than one out mode formal. If there is only one out
5404 mode formal, the warning is issued by default (controlled by -gnatwu).
5405 The warning is suppressed for volatile
5406 variables and also for variables that are renamings of other variables
5407 or for which an address clause is given.
5408 The default is that these warnings are not given. Note that this warning
5409 is not included in -gnatwa, it must be activated explicitly.
5412 @emph{Disable warnings on modified but unreferenced out parameters.}
5413 @cindex @option{-gnatw.O} (@command{gcc})
5414 This switch suppresses warnings for variables that are modified by using
5415 them as actuals for a call to a procedure with an out mode formal, where
5416 the resulting assigned value is never read.
5419 @emph{Activate warnings on ineffective pragma Inlines.}
5420 @cindex @option{-gnatwp} (@command{gcc})
5421 @cindex Inlining, warnings
5422 This switch activates warnings for failure of front end inlining
5423 (activated by @option{-gnatN}) to inline a particular call. There are
5424 many reasons for not being able to inline a call, including most
5425 commonly that the call is too complex to inline. The default is
5426 that such warnings are not given.
5427 This warning can also be turned on using @option{-gnatwa}.
5428 Warnings on ineffective inlining by the gcc back-end can be activated
5429 separately, using the gcc switch -Winline.
5432 @emph{Suppress warnings on ineffective pragma Inlines.}
5433 @cindex @option{-gnatwP} (@command{gcc})
5434 This switch suppresses warnings on ineffective pragma Inlines. If the
5435 inlining mechanism cannot inline a call, it will simply ignore the
5439 @emph{Activate warnings on parameter ordering.}
5440 @cindex @option{-gnatw.p} (@command{gcc})
5441 @cindex Parameter order, warnings
5442 This switch activates warnings for cases of suspicious parameter
5443 ordering when the list of arguments are all simple identifiers that
5444 match the names of the formals, but are in a different order. The
5445 warning is suppressed if any use of named parameter notation is used,
5446 so this is the appropriate way to suppress a false positive (and
5447 serves to emphasize that the "misordering" is deliberate). The
5449 that such warnings are not given.
5450 This warning can also be turned on using @option{-gnatwa}.
5453 @emph{Suppress warnings on parameter ordering.}
5454 @cindex @option{-gnatw.P} (@command{gcc})
5455 This switch suppresses warnings on cases of suspicious parameter
5459 @emph{Activate warnings on questionable missing parentheses.}
5460 @cindex @option{-gnatwq} (@command{gcc})
5461 @cindex Parentheses, warnings
5462 This switch activates warnings for cases where parentheses are not used and
5463 the result is potential ambiguity from a readers point of view. For example
5464 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5465 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5466 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5467 follow the rule of always parenthesizing to make the association clear, and
5468 this warning switch warns if such parentheses are not present. The default
5469 is that these warnings are given.
5470 This warning can also be turned on using @option{-gnatwa}.
5473 @emph{Suppress warnings on questionable missing parentheses.}
5474 @cindex @option{-gnatwQ} (@command{gcc})
5475 This switch suppresses warnings for cases where the association is not
5476 clear and the use of parentheses is preferred.
5479 @emph{Activate warnings on redundant constructs.}
5480 @cindex @option{-gnatwr} (@command{gcc})
5481 This switch activates warnings for redundant constructs. The following
5482 is the current list of constructs regarded as redundant:
5486 Assignment of an item to itself.
5488 Type conversion that converts an expression to its own type.
5490 Use of the attribute @code{Base} where @code{typ'Base} is the same
5493 Use of pragma @code{Pack} when all components are placed by a record
5494 representation clause.
5496 Exception handler containing only a reraise statement (raise with no
5497 operand) which has no effect.
5499 Use of the operator abs on an operand that is known at compile time
5502 Comparison of boolean expressions to an explicit True value.
5505 This warning can also be turned on using @option{-gnatwa}.
5506 The default is that warnings for redundant constructs are not given.
5509 @emph{Suppress warnings on redundant constructs.}
5510 @cindex @option{-gnatwR} (@command{gcc})
5511 This switch suppresses warnings for redundant constructs.
5514 @emph{Activate warnings for object renaming function.}
5515 @cindex @option{-gnatw.r} (@command{gcc})
5516 This switch activates warnings for an object renaming that renames a
5517 function call, which is equivalent to a constant declaration (as
5518 opposed to renaming the function itself). The default is that these
5519 warnings are given. This warning can also be turned on using
5523 @emph{Suppress warnings for object renaming function.}
5524 @cindex @option{-gnatwT} (@command{gcc})
5525 This switch suppresses warnings for object renaming function.
5528 @emph{Suppress all warnings.}
5529 @cindex @option{-gnatws} (@command{gcc})
5530 This switch completely suppresses the
5531 output of all warning messages from the GNAT front end.
5532 Note that it does not suppress warnings from the @command{gcc} back end.
5533 To suppress these back end warnings as well, use the switch @option{-w}
5534 in addition to @option{-gnatws}.
5537 @emph{Activate warnings for tracking of deleted conditional code.}
5538 @cindex @option{-gnatwt} (@command{gcc})
5539 @cindex Deactivated code, warnings
5540 @cindex Deleted code, warnings
5541 This switch activates warnings for tracking of code in conditionals (IF and
5542 CASE statements) that is detected to be dead code which cannot be executed, and
5543 which is removed by the front end. This warning is off by default, and is not
5544 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5545 useful for detecting deactivated code in certified applications.
5548 @emph{Suppress warnings for tracking of deleted conditional code.}
5549 @cindex @option{-gnatwT} (@command{gcc})
5550 This switch suppresses warnings for tracking of deleted conditional code.
5553 @emph{Activate warnings on unused entities.}
5554 @cindex @option{-gnatwu} (@command{gcc})
5555 This switch activates warnings to be generated for entities that
5556 are declared but not referenced, and for units that are @code{with}'ed
5558 referenced. In the case of packages, a warning is also generated if
5559 no entities in the package are referenced. This means that if the package
5560 is referenced but the only references are in @code{use}
5561 clauses or @code{renames}
5562 declarations, a warning is still generated. A warning is also generated
5563 for a generic package that is @code{with}'ed but never instantiated.
5564 In the case where a package or subprogram body is compiled, and there
5565 is a @code{with} on the corresponding spec
5566 that is only referenced in the body,
5567 a warning is also generated, noting that the
5568 @code{with} can be moved to the body. The default is that
5569 such warnings are not generated.
5570 This switch also activates warnings on unreferenced formals
5571 (it includes the effect of @option{-gnatwf}).
5572 This warning can also be turned on using @option{-gnatwa}.
5575 @emph{Suppress warnings on unused entities.}
5576 @cindex @option{-gnatwU} (@command{gcc})
5577 This switch suppresses warnings for unused entities and packages.
5578 It also turns off warnings on unreferenced formals (and thus includes
5579 the effect of @option{-gnatwF}).
5582 @emph{Activate warnings on unassigned variables.}
5583 @cindex @option{-gnatwv} (@command{gcc})
5584 @cindex Unassigned variable warnings
5585 This switch activates warnings for access to variables which
5586 may not be properly initialized. The default is that
5587 such warnings are generated.
5588 This warning can also be turned on using @option{-gnatwa}.
5591 @emph{Suppress warnings on unassigned variables.}
5592 @cindex @option{-gnatwV} (@command{gcc})
5593 This switch suppresses warnings for access to variables which
5594 may not be properly initialized.
5595 For variables of a composite type, the warning can also be suppressed in
5596 Ada 2005 by using a default initialization with a box. For example, if
5597 Table is an array of records whose components are only partially uninitialized,
5598 then the following code:
5600 @smallexample @c ada
5601 Tab : Table := (others => <>);
5604 will suppress warnings on subsequent statements that access components
5608 @emph{Activate warnings on wrong low bound assumption.}
5609 @cindex @option{-gnatww} (@command{gcc})
5610 @cindex String indexing warnings
5611 This switch activates warnings for indexing an unconstrained string parameter
5612 with a literal or S'Length. This is a case where the code is assuming that the
5613 low bound is one, which is in general not true (for example when a slice is
5614 passed). The default is that such warnings are generated.
5615 This warning can also be turned on using @option{-gnatwa}.
5618 @emph{Suppress warnings on wrong low bound assumption.}
5619 @cindex @option{-gnatwW} (@command{gcc})
5620 This switch suppresses warnings for indexing an unconstrained string parameter
5621 with a literal or S'Length. Note that this warning can also be suppressed
5622 in a particular case by adding an
5623 assertion that the lower bound is 1,
5624 as shown in the following example.
5626 @smallexample @c ada
5627 procedure K (S : String) is
5628 pragma Assert (S'First = 1);
5633 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5634 @cindex @option{-gnatw.w} (@command{gcc})
5635 @cindex Warnings Off control
5636 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5637 where either the pragma is entirely useless (because it suppresses no
5638 warnings), or it could be replaced by @code{pragma Unreferenced} or
5639 @code{pragma Unmodified}.The default is that these warnings are not given.
5640 Note that this warning is not included in -gnatwa, it must be
5641 activated explicitly.
5644 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5645 @cindex @option{-gnatw.W} (@command{gcc})
5646 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5649 @emph{Activate warnings on Export/Import pragmas.}
5650 @cindex @option{-gnatwx} (@command{gcc})
5651 @cindex Export/Import pragma warnings
5652 This switch activates warnings on Export/Import pragmas when
5653 the compiler detects a possible conflict between the Ada and
5654 foreign language calling sequences. For example, the use of
5655 default parameters in a convention C procedure is dubious
5656 because the C compiler cannot supply the proper default, so
5657 a warning is issued. The default is that such warnings are
5659 This warning can also be turned on using @option{-gnatwa}.
5662 @emph{Suppress warnings on Export/Import pragmas.}
5663 @cindex @option{-gnatwX} (@command{gcc})
5664 This switch suppresses warnings on Export/Import pragmas.
5665 The sense of this is that you are telling the compiler that
5666 you know what you are doing in writing the pragma, and it
5667 should not complain at you.
5670 @emph{Activate warnings for No_Exception_Propagation mode.}
5671 @cindex @option{-gnatwm} (@command{gcc})
5672 This switch activates warnings for exception usage when pragma Restrictions
5673 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5674 explicit exception raises which are not covered by a local handler, and for
5675 exception handlers which do not cover a local raise. The default is that these
5676 warnings are not given.
5679 @emph{Disable warnings for No_Exception_Propagation mode.}
5680 This switch disables warnings for exception usage when pragma Restrictions
5681 (No_Exception_Propagation) is in effect.
5684 @emph{Activate warnings for Ada 2005 compatibility issues.}
5685 @cindex @option{-gnatwy} (@command{gcc})
5686 @cindex Ada 2005 compatibility issues warnings
5687 For the most part Ada 2005 is upwards compatible with Ada 95,
5688 but there are some exceptions (for example the fact that
5689 @code{interface} is now a reserved word in Ada 2005). This
5690 switch activates several warnings to help in identifying
5691 and correcting such incompatibilities. The default is that
5692 these warnings are generated. Note that at one point Ada 2005
5693 was called Ada 0Y, hence the choice of character.
5694 This warning can also be turned on using @option{-gnatwa}.
5697 @emph{Disable warnings for Ada 2005 compatibility issues.}
5698 @cindex @option{-gnatwY} (@command{gcc})
5699 @cindex Ada 2005 compatibility issues warnings
5700 This switch suppresses several warnings intended to help in identifying
5701 incompatibilities between Ada 95 and Ada 2005.
5704 @emph{Activate warnings on unchecked conversions.}
5705 @cindex @option{-gnatwz} (@command{gcc})
5706 @cindex Unchecked_Conversion warnings
5707 This switch activates warnings for unchecked conversions
5708 where the types are known at compile time to have different
5710 is that such warnings are generated. Warnings are also
5711 generated for subprogram pointers with different conventions,
5712 and, on VMS only, for data pointers with different conventions.
5713 This warning can also be turned on using @option{-gnatwa}.
5716 @emph{Suppress warnings on unchecked conversions.}
5717 @cindex @option{-gnatwZ} (@command{gcc})
5718 This switch suppresses warnings for unchecked conversions
5719 where the types are known at compile time to have different
5720 sizes or conventions.
5722 @item ^-Wunused^WARNINGS=UNUSED^
5723 @cindex @option{-Wunused}
5724 The warnings controlled by the @option{-gnatw} switch are generated by
5725 the front end of the compiler. The @option{GCC} back end can provide
5726 additional warnings and they are controlled by the @option{-W} switch.
5727 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5728 warnings for entities that are declared but not referenced.
5730 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5731 @cindex @option{-Wuninitialized}
5732 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5733 the back end warning for uninitialized variables. This switch must be
5734 used in conjunction with an optimization level greater than zero.
5736 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5737 @cindex @option{-Wall}
5738 This switch enables all the above warnings from the @option{GCC} back end.
5739 The code generator detects a number of warning situations that are missed
5740 by the @option{GNAT} front end, and this switch can be used to activate them.
5741 The use of this switch also sets the default front end warning mode to
5742 @option{-gnatwa}, that is, most front end warnings activated as well.
5744 @item ^-w^/NO_BACK_END_WARNINGS^
5746 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5747 The use of this switch also sets the default front end warning mode to
5748 @option{-gnatws}, that is, front end warnings suppressed as well.
5754 A string of warning parameters can be used in the same parameter. For example:
5761 will turn on all optional warnings except for elaboration pragma warnings,
5762 and also specify that warnings should be treated as errors.
5764 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5789 @node Debugging and Assertion Control
5790 @subsection Debugging and Assertion Control
5794 @cindex @option{-gnata} (@command{gcc})
5800 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5801 are ignored. This switch, where @samp{a} stands for assert, causes
5802 @code{Assert} and @code{Debug} pragmas to be activated.
5804 The pragmas have the form:
5808 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5809 @var{static-string-expression}@r{]})
5810 @b{pragma} Debug (@var{procedure call})
5815 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5816 If the result is @code{True}, the pragma has no effect (other than
5817 possible side effects from evaluating the expression). If the result is
5818 @code{False}, the exception @code{Assert_Failure} declared in the package
5819 @code{System.Assertions} is
5820 raised (passing @var{static-string-expression}, if present, as the
5821 message associated with the exception). If no string expression is
5822 given the default is a string giving the file name and line number
5825 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5826 @code{pragma Debug} may appear within a declaration sequence, allowing
5827 debugging procedures to be called between declarations.
5830 @item /DEBUG@r{[}=debug-level@r{]}
5832 Specifies how much debugging information is to be included in
5833 the resulting object file where 'debug-level' is one of the following:
5836 Include both debugger symbol records and traceback
5838 This is the default setting.
5840 Include both debugger symbol records and traceback in
5843 Excludes both debugger symbol records and traceback
5844 the object file. Same as /NODEBUG.
5846 Includes only debugger symbol records in the object
5847 file. Note that this doesn't include traceback information.
5852 @node Validity Checking
5853 @subsection Validity Checking
5854 @findex Validity Checking
5857 The Ada Reference Manual defines the concept of invalid values (see
5858 RM 13.9.1). The primary source of invalid values is uninitialized
5859 variables. A scalar variable that is left uninitialized may contain
5860 an invalid value; the concept of invalid does not apply to access or
5863 It is an error to read an invalid value, but the RM does not require
5864 run-time checks to detect such errors, except for some minimal
5865 checking to prevent erroneous execution (i.e. unpredictable
5866 behavior). This corresponds to the @option{-gnatVd} switch below,
5867 which is the default. For example, by default, if the expression of a
5868 case statement is invalid, it will raise Constraint_Error rather than
5869 causing a wild jump, and if an array index on the left-hand side of an
5870 assignment is invalid, it will raise Constraint_Error rather than
5871 overwriting an arbitrary memory location.
5873 The @option{-gnatVa} may be used to enable additional validity checks,
5874 which are not required by the RM. These checks are often very
5875 expensive (which is why the RM does not require them). These checks
5876 are useful in tracking down uninitialized variables, but they are
5877 not usually recommended for production builds.
5879 The other @option{-gnatV^@var{x}^^} switches below allow finer-grained
5880 control; you can enable whichever validity checks you desire. However,
5881 for most debugging purposes, @option{-gnatVa} is sufficient, and the
5882 default @option{-gnatVd} (i.e. standard Ada behavior) is usually
5883 sufficient for non-debugging use.
5885 The @option{-gnatB} switch tells the compiler to assume that all
5886 values are valid (that is, within their declared subtype range)
5887 except in the context of a use of the Valid attribute. This means
5888 the compiler can generate more efficient code, since the range
5889 of values is better known at compile time. However, an uninitialized
5890 variable can cause wild jumps and memory corruption in this mode.
5892 The @option{-gnatV^@var{x}^^} switch allows control over the validity
5893 checking mode as described below.
5895 The @code{x} argument is a string of letters that
5896 indicate validity checks that are performed or not performed in addition
5897 to the default checks required by Ada as described above.
5900 The options allowed for this qualifier
5901 indicate validity checks that are performed or not performed in addition
5902 to the default checks required by Ada as described above.
5908 @emph{All validity checks.}
5909 @cindex @option{-gnatVa} (@command{gcc})
5910 All validity checks are turned on.
5912 That is, @option{-gnatVa} is
5913 equivalent to @option{gnatVcdfimorst}.
5917 @emph{Validity checks for copies.}
5918 @cindex @option{-gnatVc} (@command{gcc})
5919 The right hand side of assignments, and the initializing values of
5920 object declarations are validity checked.
5923 @emph{Default (RM) validity checks.}
5924 @cindex @option{-gnatVd} (@command{gcc})
5925 Some validity checks are done by default following normal Ada semantics
5927 A check is done in case statements that the expression is within the range
5928 of the subtype. If it is not, Constraint_Error is raised.
5929 For assignments to array components, a check is done that the expression used
5930 as index is within the range. If it is not, Constraint_Error is raised.
5931 Both these validity checks may be turned off using switch @option{-gnatVD}.
5932 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5933 switch @option{-gnatVd} will leave the checks turned on.
5934 Switch @option{-gnatVD} should be used only if you are sure that all such
5935 expressions have valid values. If you use this switch and invalid values
5936 are present, then the program is erroneous, and wild jumps or memory
5937 overwriting may occur.
5940 @emph{Validity checks for elementary components.}
5941 @cindex @option{-gnatVe} (@command{gcc})
5942 In the absence of this switch, assignments to record or array components are
5943 not validity checked, even if validity checks for assignments generally
5944 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5945 require valid data, but assignment of individual components does. So for
5946 example, there is a difference between copying the elements of an array with a
5947 slice assignment, compared to assigning element by element in a loop. This
5948 switch allows you to turn off validity checking for components, even when they
5949 are assigned component by component.
5952 @emph{Validity checks for floating-point values.}
5953 @cindex @option{-gnatVf} (@command{gcc})
5954 In the absence of this switch, validity checking occurs only for discrete
5955 values. If @option{-gnatVf} is specified, then validity checking also applies
5956 for floating-point values, and NaNs and infinities are considered invalid,
5957 as well as out of range values for constrained types. Note that this means
5958 that standard IEEE infinity mode is not allowed. The exact contexts
5959 in which floating-point values are checked depends on the setting of other
5960 options. For example,
5961 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5962 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5963 (the order does not matter) specifies that floating-point parameters of mode
5964 @code{in} should be validity checked.
5967 @emph{Validity checks for @code{in} mode parameters}
5968 @cindex @option{-gnatVi} (@command{gcc})
5969 Arguments for parameters of mode @code{in} are validity checked in function
5970 and procedure calls at the point of call.
5973 @emph{Validity checks for @code{in out} mode parameters.}
5974 @cindex @option{-gnatVm} (@command{gcc})
5975 Arguments for parameters of mode @code{in out} are validity checked in
5976 procedure calls at the point of call. The @code{'m'} here stands for
5977 modify, since this concerns parameters that can be modified by the call.
5978 Note that there is no specific option to test @code{out} parameters,
5979 but any reference within the subprogram will be tested in the usual
5980 manner, and if an invalid value is copied back, any reference to it
5981 will be subject to validity checking.
5984 @emph{No validity checks.}
5985 @cindex @option{-gnatVn} (@command{gcc})
5986 This switch turns off all validity checking, including the default checking
5987 for case statements and left hand side subscripts. Note that the use of
5988 the switch @option{-gnatp} suppresses all run-time checks, including
5989 validity checks, and thus implies @option{-gnatVn}. When this switch
5990 is used, it cancels any other @option{-gnatV} previously issued.
5993 @emph{Validity checks for operator and attribute operands.}
5994 @cindex @option{-gnatVo} (@command{gcc})
5995 Arguments for predefined operators and attributes are validity checked.
5996 This includes all operators in package @code{Standard},
5997 the shift operators defined as intrinsic in package @code{Interfaces}
5998 and operands for attributes such as @code{Pos}. Checks are also made
5999 on individual component values for composite comparisons, and on the
6000 expressions in type conversions and qualified expressions. Checks are
6001 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
6004 @emph{Validity checks for parameters.}
6005 @cindex @option{-gnatVp} (@command{gcc})
6006 This controls the treatment of parameters within a subprogram (as opposed
6007 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
6008 of parameters on a call. If either of these call options is used, then
6009 normally an assumption is made within a subprogram that the input arguments
6010 have been validity checking at the point of call, and do not need checking
6011 again within a subprogram). If @option{-gnatVp} is set, then this assumption
6012 is not made, and parameters are not assumed to be valid, so their validity
6013 will be checked (or rechecked) within the subprogram.
6016 @emph{Validity checks for function returns.}
6017 @cindex @option{-gnatVr} (@command{gcc})
6018 The expression in @code{return} statements in functions is validity
6022 @emph{Validity checks for subscripts.}
6023 @cindex @option{-gnatVs} (@command{gcc})
6024 All subscripts expressions are checked for validity, whether they appear
6025 on the right side or left side (in default mode only left side subscripts
6026 are validity checked).
6029 @emph{Validity checks for tests.}
6030 @cindex @option{-gnatVt} (@command{gcc})
6031 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
6032 statements are checked, as well as guard expressions in entry calls.
6037 The @option{-gnatV} switch may be followed by
6038 ^a string of letters^a list of options^
6039 to turn on a series of validity checking options.
6041 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
6042 specifies that in addition to the default validity checking, copies and
6043 function return expressions are to be validity checked.
6044 In order to make it easier
6045 to specify the desired combination of effects,
6047 the upper case letters @code{CDFIMORST} may
6048 be used to turn off the corresponding lower case option.
6051 the prefix @code{NO} on an option turns off the corresponding validity
6054 @item @code{NOCOPIES}
6055 @item @code{NODEFAULT}
6056 @item @code{NOFLOATS}
6057 @item @code{NOIN_PARAMS}
6058 @item @code{NOMOD_PARAMS}
6059 @item @code{NOOPERANDS}
6060 @item @code{NORETURNS}
6061 @item @code{NOSUBSCRIPTS}
6062 @item @code{NOTESTS}
6066 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
6067 turns on all validity checking options except for
6068 checking of @code{@b{in out}} procedure arguments.
6070 The specification of additional validity checking generates extra code (and
6071 in the case of @option{-gnatVa} the code expansion can be substantial).
6072 However, these additional checks can be very useful in detecting
6073 uninitialized variables, incorrect use of unchecked conversion, and other
6074 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
6075 is useful in conjunction with the extra validity checking, since this
6076 ensures that wherever possible uninitialized variables have invalid values.
6078 See also the pragma @code{Validity_Checks} which allows modification of
6079 the validity checking mode at the program source level, and also allows for
6080 temporary disabling of validity checks.
6082 @node Style Checking
6083 @subsection Style Checking
6084 @findex Style checking
6087 The @option{-gnaty^x^(option,option,@dots{})^} switch
6088 @cindex @option{-gnaty} (@command{gcc})
6089 causes the compiler to
6090 enforce specified style rules. A limited set of style rules has been used
6091 in writing the GNAT sources themselves. This switch allows user programs
6092 to activate all or some of these checks. If the source program fails a
6093 specified style check, an appropriate warning message is given, preceded by
6094 the character sequence ``(style)''.
6096 @code{(option,option,@dots{})} is a sequence of keywords
6099 The string @var{x} is a sequence of letters or digits
6101 indicating the particular style
6102 checks to be performed. The following checks are defined:
6107 @emph{Specify indentation level.}
6108 If a digit from 1-9 appears
6109 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
6110 then proper indentation is checked, with the digit indicating the
6111 indentation level required. A value of zero turns off this style check.
6112 The general style of required indentation is as specified by
6113 the examples in the Ada Reference Manual. Full line comments must be
6114 aligned with the @code{--} starting on a column that is a multiple of
6115 the alignment level, or they may be aligned the same way as the following
6116 non-blank line (this is useful when full line comments appear in the middle
6120 @emph{Check attribute casing.}
6121 Attribute names, including the case of keywords such as @code{digits}
6122 used as attributes names, must be written in mixed case, that is, the
6123 initial letter and any letter following an underscore must be uppercase.
6124 All other letters must be lowercase.
6126 @item ^A^ARRAY_INDEXES^
6127 @emph{Use of array index numbers in array attributes.}
6128 When using the array attributes First, Last, Range,
6129 or Length, the index number must be omitted for one-dimensional arrays
6130 and is required for multi-dimensional arrays.
6133 @emph{Blanks not allowed at statement end.}
6134 Trailing blanks are not allowed at the end of statements. The purpose of this
6135 rule, together with h (no horizontal tabs), is to enforce a canonical format
6136 for the use of blanks to separate source tokens.
6138 @item ^B^BOOLEAN_OPERATORS^
6139 @emph{Check Boolean operators.}
6140 The use of AND/OR operators is not permitted except in the cases of modular
6141 operands, array operands, and simple stand-alone boolean variables or
6142 boolean constants. In all other cases AND THEN/OR ELSE are required.
6145 @emph{Check comments.}
6146 Comments must meet the following set of rules:
6151 The ``@code{--}'' that starts the column must either start in column one,
6152 or else at least one blank must precede this sequence.
6155 Comments that follow other tokens on a line must have at least one blank
6156 following the ``@code{--}'' at the start of the comment.
6159 Full line comments must have two blanks following the ``@code{--}'' that
6160 starts the comment, with the following exceptions.
6163 A line consisting only of the ``@code{--}'' characters, possibly preceded
6164 by blanks is permitted.
6167 A comment starting with ``@code{--x}'' where @code{x} is a special character
6169 This allows proper processing of the output generated by specialized tools
6170 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
6172 language (where ``@code{--#}'' is used). For the purposes of this rule, a
6173 special character is defined as being in one of the ASCII ranges
6174 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
6175 Note that this usage is not permitted
6176 in GNAT implementation units (i.e., when @option{-gnatg} is used).
6179 A line consisting entirely of minus signs, possibly preceded by blanks, is
6180 permitted. This allows the construction of box comments where lines of minus
6181 signs are used to form the top and bottom of the box.
6184 A comment that starts and ends with ``@code{--}'' is permitted as long as at
6185 least one blank follows the initial ``@code{--}''. Together with the preceding
6186 rule, this allows the construction of box comments, as shown in the following
6189 ---------------------------
6190 -- This is a box comment --
6191 -- with two text lines. --
6192 ---------------------------
6196 @item ^d^DOS_LINE_ENDINGS^
6197 @emph{Check no DOS line terminators present.}
6198 All lines must be terminated by a single ASCII.LF
6199 character (in particular the DOS line terminator sequence CR/LF is not
6203 @emph{Check end/exit labels.}
6204 Optional labels on @code{end} statements ending subprograms and on
6205 @code{exit} statements exiting named loops, are required to be present.
6208 @emph{No form feeds or vertical tabs.}
6209 Neither form feeds nor vertical tab characters are permitted
6213 @emph{GNAT style mode}
6214 The set of style check switches is set to match that used by the GNAT sources.
6215 This may be useful when developing code that is eventually intended to be
6216 incorporated into GNAT. For further details, see GNAT sources.
6219 @emph{No horizontal tabs.}
6220 Horizontal tab characters are not permitted in the source text.
6221 Together with the b (no blanks at end of line) check, this
6222 enforces a canonical form for the use of blanks to separate
6226 @emph{Check if-then layout.}
6227 The keyword @code{then} must appear either on the same
6228 line as corresponding @code{if}, or on a line on its own, lined
6229 up under the @code{if} with at least one non-blank line in between
6230 containing all or part of the condition to be tested.
6233 @emph{check mode IN keywords}
6234 Mode @code{in} (the default mode) is not
6235 allowed to be given explicitly. @code{in out} is fine,
6236 but not @code{in} on its own.
6239 @emph{Check keyword casing.}
6240 All keywords must be in lower case (with the exception of keywords
6241 such as @code{digits} used as attribute names to which this check
6245 @emph{Check layout.}
6246 Layout of statement and declaration constructs must follow the
6247 recommendations in the Ada Reference Manual, as indicated by the
6248 form of the syntax rules. For example an @code{else} keyword must
6249 be lined up with the corresponding @code{if} keyword.
6251 There are two respects in which the style rule enforced by this check
6252 option are more liberal than those in the Ada Reference Manual. First
6253 in the case of record declarations, it is permissible to put the
6254 @code{record} keyword on the same line as the @code{type} keyword, and
6255 then the @code{end} in @code{end record} must line up under @code{type}.
6256 This is also permitted when the type declaration is split on two lines.
6257 For example, any of the following three layouts is acceptable:
6259 @smallexample @c ada
6282 Second, in the case of a block statement, a permitted alternative
6283 is to put the block label on the same line as the @code{declare} or
6284 @code{begin} keyword, and then line the @code{end} keyword up under
6285 the block label. For example both the following are permitted:
6287 @smallexample @c ada
6305 The same alternative format is allowed for loops. For example, both of
6306 the following are permitted:
6308 @smallexample @c ada
6310 Clear : while J < 10 loop
6321 @item ^Lnnn^MAX_NESTING=nnn^
6322 @emph{Set maximum nesting level}
6323 The maximum level of nesting of constructs (including subprograms, loops,
6324 blocks, packages, and conditionals) may not exceed the given value
6325 @option{nnn}. A value of zero disconnects this style check.
6327 @item ^m^LINE_LENGTH^
6328 @emph{Check maximum line length.}
6329 The length of source lines must not exceed 79 characters, including
6330 any trailing blanks. The value of 79 allows convenient display on an
6331 80 character wide device or window, allowing for possible special
6332 treatment of 80 character lines. Note that this count is of
6333 characters in the source text. This means that a tab character counts
6334 as one character in this count but a wide character sequence counts as
6335 a single character (however many bytes are needed in the encoding).
6337 @item ^Mnnn^MAX_LENGTH=nnn^
6338 @emph{Set maximum line length.}
6339 The length of lines must not exceed the
6340 given value @option{nnn}. The maximum value that can be specified is 32767.
6342 @item ^n^STANDARD_CASING^
6343 @emph{Check casing of entities in Standard.}
6344 Any identifier from Standard must be cased
6345 to match the presentation in the Ada Reference Manual (for example,
6346 @code{Integer} and @code{ASCII.NUL}).
6349 @emph{Turn off all style checks}
6350 All style check options are turned off.
6352 @item ^o^ORDERED_SUBPROGRAMS^
6353 @emph{Check order of subprogram bodies.}
6354 All subprogram bodies in a given scope
6355 (e.g.@: a package body) must be in alphabetical order. The ordering
6356 rule uses normal Ada rules for comparing strings, ignoring casing
6357 of letters, except that if there is a trailing numeric suffix, then
6358 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6361 @item ^O^OVERRIDING_INDICATORS^
6362 @emph{Check that overriding subprograms are explicitly marked as such.}
6363 The declaration of a primitive operation of a type extension that overrides
6364 an inherited operation must carry an overriding indicator.
6367 @emph{Check pragma casing.}
6368 Pragma names must be written in mixed case, that is, the
6369 initial letter and any letter following an underscore must be uppercase.
6370 All other letters must be lowercase.
6372 @item ^r^REFERENCES^
6373 @emph{Check references.}
6374 All identifier references must be cased in the same way as the
6375 corresponding declaration. No specific casing style is imposed on
6376 identifiers. The only requirement is for consistency of references
6379 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6380 @emph{Check no statements after THEN/ELSE.}
6381 No statements are allowed
6382 on the same line as a THEN or ELSE keyword following the
6383 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6384 and a special exception allows a pragma to appear after ELSE.
6387 @emph{Check separate specs.}
6388 Separate declarations (``specs'') are required for subprograms (a
6389 body is not allowed to serve as its own declaration). The only
6390 exception is that parameterless library level procedures are
6391 not required to have a separate declaration. This exception covers
6392 the most frequent form of main program procedures.
6395 @emph{Check token spacing.}
6396 The following token spacing rules are enforced:
6401 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6404 The token @code{=>} must be surrounded by spaces.
6407 The token @code{<>} must be preceded by a space or a left parenthesis.
6410 Binary operators other than @code{**} must be surrounded by spaces.
6411 There is no restriction on the layout of the @code{**} binary operator.
6414 Colon must be surrounded by spaces.
6417 Colon-equal (assignment, initialization) must be surrounded by spaces.
6420 Comma must be the first non-blank character on the line, or be
6421 immediately preceded by a non-blank character, and must be followed
6425 If the token preceding a left parenthesis ends with a letter or digit, then
6426 a space must separate the two tokens.
6429 A right parenthesis must either be the first non-blank character on
6430 a line, or it must be preceded by a non-blank character.
6433 A semicolon must not be preceded by a space, and must not be followed by
6434 a non-blank character.
6437 A unary plus or minus may not be followed by a space.
6440 A vertical bar must be surrounded by spaces.
6443 @item ^u^UNNECESSARY_BLANK_LINES^
6444 @emph{Check unnecessary blank lines.}
6445 Unnecessary blank lines are not allowed. A blank line is considered
6446 unnecessary if it appears at the end of the file, or if more than
6447 one blank line occurs in sequence.
6449 @item ^x^XTRA_PARENS^
6450 @emph{Check extra parentheses.}
6451 Unnecessary extra level of parentheses (C-style) are not allowed
6452 around conditions in @code{if} statements, @code{while} statements and
6453 @code{exit} statements.
6455 @item ^y^ALL_BUILTIN^
6456 @emph{Set all standard style check options}
6457 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6458 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6459 @option{-gnatyS}, @option{-gnatyLnnn},
6460 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6464 @emph{Remove style check options}
6465 This causes any subsequent options in the string to act as canceling the
6466 corresponding style check option. To cancel maximum nesting level control,
6467 use @option{L} parameter witout any integer value after that, because any
6468 digit following @option{-} in the parameter string of the @option{-gnaty}
6469 option will be threated as canceling indentation check. The same is true
6470 for @option{M} parameter. @option{y} and @option{N} parameters are not
6471 allowed after @option{-}.
6474 This causes any subsequent options in the string to enable the corresponding
6475 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6481 @emph{Removing style check options}
6482 If the name of a style check is preceded by @option{NO} then the corresponding
6483 style check is turned off. For example @option{NOCOMMENTS} turns off style
6484 checking for comments.
6489 In the above rules, appearing in column one is always permitted, that is,
6490 counts as meeting either a requirement for a required preceding space,
6491 or as meeting a requirement for no preceding space.
6493 Appearing at the end of a line is also always permitted, that is, counts
6494 as meeting either a requirement for a following space, or as meeting
6495 a requirement for no following space.
6498 If any of these style rules is violated, a message is generated giving
6499 details on the violation. The initial characters of such messages are
6500 always ``@code{(style)}''. Note that these messages are treated as warning
6501 messages, so they normally do not prevent the generation of an object
6502 file. The @option{-gnatwe} switch can be used to treat warning messages,
6503 including style messages, as fatal errors.
6507 @option{-gnaty} on its own (that is not
6508 followed by any letters or digits), then the effect is equivalent
6509 to the use of @option{-gnatyy}, as described above, that is all
6510 built-in standard style check options are enabled.
6514 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6515 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6516 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6528 clears any previously set style checks.
6530 @node Run-Time Checks
6531 @subsection Run-Time Checks
6532 @cindex Division by zero
6533 @cindex Access before elaboration
6534 @cindex Checks, division by zero
6535 @cindex Checks, access before elaboration
6536 @cindex Checks, stack overflow checking
6539 By default, the following checks are suppressed: integer overflow
6540 checks, stack overflow checks, and checks for access before
6541 elaboration on subprogram calls. All other checks, including range
6542 checks and array bounds checks, are turned on by default. The
6543 following @command{gcc} switches refine this default behavior.
6548 @cindex @option{-gnatp} (@command{gcc})
6549 @cindex Suppressing checks
6550 @cindex Checks, suppressing
6552 This switch causes the unit to be compiled
6553 as though @code{pragma Suppress (All_checks)}
6554 had been present in the source. Validity checks are also eliminated (in
6555 other words @option{-gnatp} also implies @option{-gnatVn}.
6556 Use this switch to improve the performance
6557 of the code at the expense of safety in the presence of invalid data or
6560 Note that when checks are suppressed, the compiler is allowed, but not
6561 required, to omit the checking code. If the run-time cost of the
6562 checking code is zero or near-zero, the compiler will generate it even
6563 if checks are suppressed. In particular, if the compiler can prove
6564 that a certain check will necessarily fail, it will generate code to
6565 do an unconditional ``raise'', even if checks are suppressed. The
6566 compiler warns in this case. Another case in which checks may not be
6567 eliminated is when they are embedded in certain run time routines such
6568 as math library routines.
6570 Of course, run-time checks are omitted whenever the compiler can prove
6571 that they will not fail, whether or not checks are suppressed.
6573 Note that if you suppress a check that would have failed, program
6574 execution is erroneous, which means the behavior is totally
6575 unpredictable. The program might crash, or print wrong answers, or
6576 do anything else. It might even do exactly what you wanted it to do
6577 (and then it might start failing mysteriously next week or next
6578 year). The compiler will generate code based on the assumption that
6579 the condition being checked is true, which can result in disaster if
6580 that assumption is wrong.
6583 @cindex @option{-gnato} (@command{gcc})
6584 @cindex Overflow checks
6585 @cindex Check, overflow
6586 Enables overflow checking for integer operations.
6587 This causes GNAT to generate slower and larger executable
6588 programs by adding code to check for overflow (resulting in raising
6589 @code{Constraint_Error} as required by standard Ada
6590 semantics). These overflow checks correspond to situations in which
6591 the true value of the result of an operation may be outside the base
6592 range of the result type. The following example shows the distinction:
6594 @smallexample @c ada
6595 X1 : Integer := "Integer'Last";
6596 X2 : Integer range 1 .. 5 := "5";
6597 X3 : Integer := "Integer'Last";
6598 X4 : Integer range 1 .. 5 := "5";
6599 F : Float := "2.0E+20";
6608 Note that if explicit values are assigned at compile time, the
6609 compiler may be able to detect overflow at compile time, in which case
6610 no actual run-time checking code is required, and Constraint_Error
6611 will be raised unconditionally, with or without
6612 @option{-gnato}. That's why the assigned values in the above fragment
6613 are in quotes, the meaning is "assign a value not known to the
6614 compiler that happens to be equal to ...". The remaining discussion
6615 assumes that the compiler cannot detect the values at compile time.
6617 Here the first addition results in a value that is outside the base range
6618 of Integer, and hence requires an overflow check for detection of the
6619 constraint error. Thus the first assignment to @code{X1} raises a
6620 @code{Constraint_Error} exception only if @option{-gnato} is set.
6622 The second increment operation results in a violation of the explicit
6623 range constraint; such range checks are performed by default, and are
6624 unaffected by @option{-gnato}.
6626 The two conversions of @code{F} both result in values that are outside
6627 the base range of type @code{Integer} and thus will raise
6628 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6629 The fact that the result of the second conversion is assigned to
6630 variable @code{X4} with a restricted range is irrelevant, since the problem
6631 is in the conversion, not the assignment.
6633 Basically the rule is that in the default mode (@option{-gnato} not
6634 used), the generated code assures that all integer variables stay
6635 within their declared ranges, or within the base range if there is
6636 no declared range. This prevents any serious problems like indexes
6637 out of range for array operations.
6639 What is not checked in default mode is an overflow that results in
6640 an in-range, but incorrect value. In the above example, the assignments
6641 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6642 range of the target variable, but the result is wrong in the sense that
6643 it is too large to be represented correctly. Typically the assignment
6644 to @code{X1} will result in wrap around to the largest negative number.
6645 The conversions of @code{F} will result in some @code{Integer} value
6646 and if that integer value is out of the @code{X4} range then the
6647 subsequent assignment would generate an exception.
6649 @findex Machine_Overflows
6650 Note that the @option{-gnato} switch does not affect the code generated
6651 for any floating-point operations; it applies only to integer
6653 For floating-point, GNAT has the @code{Machine_Overflows}
6654 attribute set to @code{False} and the normal mode of operation is to
6655 generate IEEE NaN and infinite values on overflow or invalid operations
6656 (such as dividing 0.0 by 0.0).
6658 The reason that we distinguish overflow checking from other kinds of
6659 range constraint checking is that a failure of an overflow check, unlike
6660 for example the failure of a range check, can result in an incorrect
6661 value, but cannot cause random memory destruction (like an out of range
6662 subscript), or a wild jump (from an out of range case value). Overflow
6663 checking is also quite expensive in time and space, since in general it
6664 requires the use of double length arithmetic.
6666 Note again that @option{-gnato} is off by default, so overflow checking is
6667 not performed in default mode. This means that out of the box, with the
6668 default settings, GNAT does not do all the checks expected from the
6669 language description in the Ada Reference Manual. If you want all constraint
6670 checks to be performed, as described in this Manual, then you must
6671 explicitly use the -gnato switch either on the @command{gnatmake} or
6672 @command{gcc} command.
6675 @cindex @option{-gnatE} (@command{gcc})
6676 @cindex Elaboration checks
6677 @cindex Check, elaboration
6678 Enables dynamic checks for access-before-elaboration
6679 on subprogram calls and generic instantiations.
6680 Note that @option{-gnatE} is not necessary for safety, because in the
6681 default mode, GNAT ensures statically that the checks would not fail.
6682 For full details of the effect and use of this switch,
6683 @xref{Compiling Using gcc}.
6686 @cindex @option{-fstack-check} (@command{gcc})
6687 @cindex Stack Overflow Checking
6688 @cindex Checks, stack overflow checking
6689 Activates stack overflow checking. For full details of the effect and use of
6690 this switch see @ref{Stack Overflow Checking}.
6695 The setting of these switches only controls the default setting of the
6696 checks. You may modify them using either @code{Suppress} (to remove
6697 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6700 @node Using gcc for Syntax Checking
6701 @subsection Using @command{gcc} for Syntax Checking
6704 @cindex @option{-gnats} (@command{gcc})
6708 The @code{s} stands for ``syntax''.
6711 Run GNAT in syntax checking only mode. For
6712 example, the command
6715 $ gcc -c -gnats x.adb
6719 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6720 series of files in a single command
6722 , and can use wild cards to specify such a group of files.
6723 Note that you must specify the @option{-c} (compile
6724 only) flag in addition to the @option{-gnats} flag.
6727 You may use other switches in conjunction with @option{-gnats}. In
6728 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6729 format of any generated error messages.
6731 When the source file is empty or contains only empty lines and/or comments,
6732 the output is a warning:
6735 $ gcc -c -gnats -x ada toto.txt
6736 toto.txt:1:01: warning: empty file, contains no compilation units
6740 Otherwise, the output is simply the error messages, if any. No object file or
6741 ALI file is generated by a syntax-only compilation. Also, no units other
6742 than the one specified are accessed. For example, if a unit @code{X}
6743 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6744 check only mode does not access the source file containing unit
6747 @cindex Multiple units, syntax checking
6748 Normally, GNAT allows only a single unit in a source file. However, this
6749 restriction does not apply in syntax-check-only mode, and it is possible
6750 to check a file containing multiple compilation units concatenated
6751 together. This is primarily used by the @code{gnatchop} utility
6752 (@pxref{Renaming Files Using gnatchop}).
6755 @node Using gcc for Semantic Checking
6756 @subsection Using @command{gcc} for Semantic Checking
6759 @cindex @option{-gnatc} (@command{gcc})
6763 The @code{c} stands for ``check''.
6765 Causes the compiler to operate in semantic check mode,
6766 with full checking for all illegalities specified in the
6767 Ada Reference Manual, but without generation of any object code
6768 (no object file is generated).
6770 Because dependent files must be accessed, you must follow the GNAT
6771 semantic restrictions on file structuring to operate in this mode:
6775 The needed source files must be accessible
6776 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6779 Each file must contain only one compilation unit.
6782 The file name and unit name must match (@pxref{File Naming Rules}).
6785 The output consists of error messages as appropriate. No object file is
6786 generated. An @file{ALI} file is generated for use in the context of
6787 cross-reference tools, but this file is marked as not being suitable
6788 for binding (since no object file is generated).
6789 The checking corresponds exactly to the notion of
6790 legality in the Ada Reference Manual.
6792 Any unit can be compiled in semantics-checking-only mode, including
6793 units that would not normally be compiled (subunits,
6794 and specifications where a separate body is present).
6797 @node Compiling Different Versions of Ada
6798 @subsection Compiling Different Versions of Ada
6801 The switches described in this section allow you to explicitly specify
6802 the version of the Ada language that your programs are written in.
6803 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6804 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6805 indicate Ada 83 compatibility mode.
6808 @cindex Compatibility with Ada 83
6810 @item -gnat83 (Ada 83 Compatibility Mode)
6811 @cindex @option{-gnat83} (@command{gcc})
6812 @cindex ACVC, Ada 83 tests
6816 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6817 specifies that the program is to be compiled in Ada 83 mode. With
6818 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6819 semantics where this can be done easily.
6820 It is not possible to guarantee this switch does a perfect
6821 job; some subtle tests, such as are
6822 found in earlier ACVC tests (and that have been removed from the ACATS suite
6823 for Ada 95), might not compile correctly.
6824 Nevertheless, this switch may be useful in some circumstances, for example
6825 where, due to contractual reasons, existing code needs to be maintained
6826 using only Ada 83 features.
6828 With few exceptions (most notably the need to use @code{<>} on
6829 @cindex Generic formal parameters
6830 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6831 reserved words, and the use of packages
6832 with optional bodies), it is not necessary to specify the
6833 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6834 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6835 a correct Ada 83 program is usually also a correct program
6836 in these later versions of the language standard.
6837 For further information, please refer to @ref{Compatibility and Porting Guide}.
6839 @item -gnat95 (Ada 95 mode)
6840 @cindex @option{-gnat95} (@command{gcc})
6844 This switch directs the compiler to implement the Ada 95 version of the
6846 Since Ada 95 is almost completely upwards
6847 compatible with Ada 83, Ada 83 programs may generally be compiled using
6848 this switch (see the description of the @option{-gnat83} switch for further
6849 information about Ada 83 mode).
6850 If an Ada 2005 program is compiled in Ada 95 mode,
6851 uses of the new Ada 2005 features will cause error
6852 messages or warnings.
6854 This switch also can be used to cancel the effect of a previous
6855 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6857 @item -gnat05 (Ada 2005 mode)
6858 @cindex @option{-gnat05} (@command{gcc})
6859 @cindex Ada 2005 mode
6862 This switch directs the compiler to implement the Ada 2005 version of the
6864 Since Ada 2005 is almost completely upwards
6865 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6866 may generally be compiled using this switch (see the description of the
6867 @option{-gnat83} and @option{-gnat95} switches for further
6870 For information about the approved ``Ada Issues'' that have been incorporated
6871 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6872 Included with GNAT releases is a file @file{features-ada0y} that describes
6873 the set of implemented Ada 2005 features.
6877 @node Character Set Control
6878 @subsection Character Set Control
6880 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6881 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6884 Normally GNAT recognizes the Latin-1 character set in source program
6885 identifiers, as described in the Ada Reference Manual.
6887 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6888 single character ^^or word^ indicating the character set, as follows:
6892 ISO 8859-1 (Latin-1) identifiers
6895 ISO 8859-2 (Latin-2) letters allowed in identifiers
6898 ISO 8859-3 (Latin-3) letters allowed in identifiers
6901 ISO 8859-4 (Latin-4) letters allowed in identifiers
6904 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6907 ISO 8859-15 (Latin-9) letters allowed in identifiers
6910 IBM PC letters (code page 437) allowed in identifiers
6913 IBM PC letters (code page 850) allowed in identifiers
6915 @item ^f^FULL_UPPER^
6916 Full upper-half codes allowed in identifiers
6919 No upper-half codes allowed in identifiers
6922 Wide-character codes (that is, codes greater than 255)
6923 allowed in identifiers
6926 @xref{Foreign Language Representation}, for full details on the
6927 implementation of these character sets.
6929 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6930 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6931 Specify the method of encoding for wide characters.
6932 @var{e} is one of the following:
6937 Hex encoding (brackets coding also recognized)
6940 Upper half encoding (brackets encoding also recognized)
6943 Shift/JIS encoding (brackets encoding also recognized)
6946 EUC encoding (brackets encoding also recognized)
6949 UTF-8 encoding (brackets encoding also recognized)
6952 Brackets encoding only (default value)
6954 For full details on these encoding
6955 methods see @ref{Wide Character Encodings}.
6956 Note that brackets coding is always accepted, even if one of the other
6957 options is specified, so for example @option{-gnatW8} specifies that both
6958 brackets and UTF-8 encodings will be recognized. The units that are
6959 with'ed directly or indirectly will be scanned using the specified
6960 representation scheme, and so if one of the non-brackets scheme is
6961 used, it must be used consistently throughout the program. However,
6962 since brackets encoding is always recognized, it may be conveniently
6963 used in standard libraries, allowing these libraries to be used with
6964 any of the available coding schemes.
6967 If no @option{-gnatW?} parameter is present, then the default
6968 representation is normally Brackets encoding only. However, if the
6969 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6970 byte order mark or BOM for UTF-8), then these three characters are
6971 skipped and the default representation for the file is set to UTF-8.
6973 Note that the wide character representation that is specified (explicitly
6974 or by default) for the main program also acts as the default encoding used
6975 for Wide_Text_IO files if not specifically overridden by a WCEM form
6979 @node File Naming Control
6980 @subsection File Naming Control
6983 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6984 @cindex @option{-gnatk} (@command{gcc})
6985 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6986 1-999, indicates the maximum allowable length of a file name (not
6987 including the @file{.ads} or @file{.adb} extension). The default is not
6988 to enable file name krunching.
6990 For the source file naming rules, @xref{File Naming Rules}.
6993 @node Subprogram Inlining Control
6994 @subsection Subprogram Inlining Control
6999 @cindex @option{-gnatn} (@command{gcc})
7001 The @code{n} here is intended to suggest the first syllable of the
7004 GNAT recognizes and processes @code{Inline} pragmas. However, for the
7005 inlining to actually occur, optimization must be enabled. To enable
7006 inlining of subprograms specified by pragma @code{Inline},
7007 you must also specify this switch.
7008 In the absence of this switch, GNAT does not attempt
7009 inlining and does not need to access the bodies of
7010 subprograms for which @code{pragma Inline} is specified if they are not
7011 in the current unit.
7013 If you specify this switch the compiler will access these bodies,
7014 creating an extra source dependency for the resulting object file, and
7015 where possible, the call will be inlined.
7016 For further details on when inlining is possible
7017 see @ref{Inlining of Subprograms}.
7020 @cindex @option{-gnatN} (@command{gcc})
7021 This switch activates front-end inlining which also
7022 generates additional dependencies.
7024 When using a gcc-based back end (in practice this means using any version
7025 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
7026 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
7027 Historically front end inlining was more extensive than the gcc back end
7028 inlining, but that is no longer the case.
7031 @node Auxiliary Output Control
7032 @subsection Auxiliary Output Control
7036 @cindex @option{-gnatt} (@command{gcc})
7037 @cindex Writing internal trees
7038 @cindex Internal trees, writing to file
7039 Causes GNAT to write the internal tree for a unit to a file (with the
7040 extension @file{.adt}.
7041 This not normally required, but is used by separate analysis tools.
7043 these tools do the necessary compilations automatically, so you should
7044 not have to specify this switch in normal operation.
7045 Note that the combination of switches @option{-gnatct}
7046 generates a tree in the form required by ASIS applications.
7049 @cindex @option{-gnatu} (@command{gcc})
7050 Print a list of units required by this compilation on @file{stdout}.
7051 The listing includes all units on which the unit being compiled depends
7052 either directly or indirectly.
7055 @item -pass-exit-codes
7056 @cindex @option{-pass-exit-codes} (@command{gcc})
7057 If this switch is not used, the exit code returned by @command{gcc} when
7058 compiling multiple files indicates whether all source files have
7059 been successfully used to generate object files or not.
7061 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
7062 exit status and allows an integrated development environment to better
7063 react to a compilation failure. Those exit status are:
7067 There was an error in at least one source file.
7069 At least one source file did not generate an object file.
7071 The compiler died unexpectedly (internal error for example).
7073 An object file has been generated for every source file.
7078 @node Debugging Control
7079 @subsection Debugging Control
7083 @cindex Debugging options
7086 @cindex @option{-gnatd} (@command{gcc})
7087 Activate internal debugging switches. @var{x} is a letter or digit, or
7088 string of letters or digits, which specifies the type of debugging
7089 outputs desired. Normally these are used only for internal development
7090 or system debugging purposes. You can find full documentation for these
7091 switches in the body of the @code{Debug} unit in the compiler source
7092 file @file{debug.adb}.
7096 @cindex @option{-gnatG} (@command{gcc})
7097 This switch causes the compiler to generate auxiliary output containing
7098 a pseudo-source listing of the generated expanded code. Like most Ada
7099 compilers, GNAT works by first transforming the high level Ada code into
7100 lower level constructs. For example, tasking operations are transformed
7101 into calls to the tasking run-time routines. A unique capability of GNAT
7102 is to list this expanded code in a form very close to normal Ada source.
7103 This is very useful in understanding the implications of various Ada
7104 usage on the efficiency of the generated code. There are many cases in
7105 Ada (e.g.@: the use of controlled types), where simple Ada statements can
7106 generate a lot of run-time code. By using @option{-gnatG} you can identify
7107 these cases, and consider whether it may be desirable to modify the coding
7108 approach to improve efficiency.
7110 The optional parameter @code{nn} if present after -gnatG specifies an
7111 alternative maximum line length that overrides the normal default of 72.
7112 This value is in the range 40-999999, values less than 40 being silently
7113 reset to 40. The equal sign is optional.
7115 The format of the output is very similar to standard Ada source, and is
7116 easily understood by an Ada programmer. The following special syntactic
7117 additions correspond to low level features used in the generated code that
7118 do not have any exact analogies in pure Ada source form. The following
7119 is a partial list of these special constructions. See the spec
7120 of package @code{Sprint} in file @file{sprint.ads} for a full list.
7122 If the switch @option{-gnatL} is used in conjunction with
7123 @cindex @option{-gnatL} (@command{gcc})
7124 @option{-gnatG}, then the original source lines are interspersed
7125 in the expanded source (as comment lines with the original line number).
7128 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
7129 Shows the storage pool being used for an allocator.
7131 @item at end @var{procedure-name};
7132 Shows the finalization (cleanup) procedure for a scope.
7134 @item (if @var{expr} then @var{expr} else @var{expr})
7135 Conditional expression equivalent to the @code{x?y:z} construction in C.
7137 @item @var{target}^^^(@var{source})
7138 A conversion with floating-point truncation instead of rounding.
7140 @item @var{target}?(@var{source})
7141 A conversion that bypasses normal Ada semantic checking. In particular
7142 enumeration types and fixed-point types are treated simply as integers.
7144 @item @var{target}?^^^(@var{source})
7145 Combines the above two cases.
7147 @item @var{x} #/ @var{y}
7148 @itemx @var{x} #mod @var{y}
7149 @itemx @var{x} #* @var{y}
7150 @itemx @var{x} #rem @var{y}
7151 A division or multiplication of fixed-point values which are treated as
7152 integers without any kind of scaling.
7154 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
7155 Shows the storage pool associated with a @code{free} statement.
7157 @item [subtype or type declaration]
7158 Used to list an equivalent declaration for an internally generated
7159 type that is referenced elsewhere in the listing.
7161 @item freeze @var{type-name} @ovar{actions}
7162 Shows the point at which @var{type-name} is frozen, with possible
7163 associated actions to be performed at the freeze point.
7165 @item reference @var{itype}
7166 Reference (and hence definition) to internal type @var{itype}.
7168 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
7169 Intrinsic function call.
7171 @item @var{label-name} : label
7172 Declaration of label @var{labelname}.
7174 @item #$ @var{subprogram-name}
7175 An implicit call to a run-time support routine
7176 (to meet the requirement of H.3.1(9) in a
7179 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
7180 A multiple concatenation (same effect as @var{expr} & @var{expr} &
7181 @var{expr}, but handled more efficiently).
7183 @item [constraint_error]
7184 Raise the @code{Constraint_Error} exception.
7186 @item @var{expression}'reference
7187 A pointer to the result of evaluating @var{expression}.
7189 @item @var{target-type}!(@var{source-expression})
7190 An unchecked conversion of @var{source-expression} to @var{target-type}.
7192 @item [@var{numerator}/@var{denominator}]
7193 Used to represent internal real literals (that) have no exact
7194 representation in base 2-16 (for example, the result of compile time
7195 evaluation of the expression 1.0/27.0).
7199 @cindex @option{-gnatD} (@command{gcc})
7200 When used in conjunction with @option{-gnatG}, this switch causes
7201 the expanded source, as described above for
7202 @option{-gnatG} to be written to files with names
7203 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
7204 instead of to the standard output file. For
7205 example, if the source file name is @file{hello.adb}, then a file
7206 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
7207 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
7208 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
7209 you to do source level debugging using the generated code which is
7210 sometimes useful for complex code, for example to find out exactly
7211 which part of a complex construction raised an exception. This switch
7212 also suppress generation of cross-reference information (see
7213 @option{-gnatx}) since otherwise the cross-reference information
7214 would refer to the @file{^.dg^.DG^} file, which would cause
7215 confusion since this is not the original source file.
7217 Note that @option{-gnatD} actually implies @option{-gnatG}
7218 automatically, so it is not necessary to give both options.
7219 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
7221 If the switch @option{-gnatL} is used in conjunction with
7222 @cindex @option{-gnatL} (@command{gcc})
7223 @option{-gnatDG}, then the original source lines are interspersed
7224 in the expanded source (as comment lines with the original line number).
7226 The optional parameter @code{nn} if present after -gnatD specifies an
7227 alternative maximum line length that overrides the normal default of 72.
7228 This value is in the range 40-999999, values less than 40 being silently
7229 reset to 40. The equal sign is optional.
7232 @cindex @option{-gnatr} (@command{gcc})
7233 @cindex pragma Restrictions
7234 This switch causes pragma Restrictions to be treated as Restriction_Warnings
7235 so that violation of restrictions causes warnings rather than illegalities.
7236 This is useful during the development process when new restrictions are added
7237 or investigated. The switch also causes pragma Profile to be treated as
7238 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
7239 restriction warnings rather than restrictions.
7242 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
7243 @cindex @option{-gnatR} (@command{gcc})
7244 This switch controls output from the compiler of a listing showing
7245 representation information for declared types and objects. For
7246 @option{-gnatR0}, no information is output (equivalent to omitting
7247 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
7248 so @option{-gnatR} with no parameter has the same effect), size and alignment
7249 information is listed for declared array and record types. For
7250 @option{-gnatR2}, size and alignment information is listed for all
7251 declared types and objects. Finally @option{-gnatR3} includes symbolic
7252 expressions for values that are computed at run time for
7253 variant records. These symbolic expressions have a mostly obvious
7254 format with #n being used to represent the value of the n'th
7255 discriminant. See source files @file{repinfo.ads/adb} in the
7256 @code{GNAT} sources for full details on the format of @option{-gnatR3}
7257 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
7258 the output is to a file with the name @file{^file.rep^file_REP^} where
7259 file is the name of the corresponding source file.
7262 @item /REPRESENTATION_INFO
7263 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
7264 This qualifier controls output from the compiler of a listing showing
7265 representation information for declared types and objects. For
7266 @option{/REPRESENTATION_INFO=NONE}, no information is output
7267 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
7268 @option{/REPRESENTATION_INFO} without option is equivalent to
7269 @option{/REPRESENTATION_INFO=ARRAYS}.
7270 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
7271 information is listed for declared array and record types. For
7272 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
7273 is listed for all expression information for values that are computed
7274 at run time for variant records. These symbolic expressions have a mostly
7275 obvious format with #n being used to represent the value of the n'th
7276 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7277 @code{GNAT} sources for full details on the format of
7278 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7279 If _FILE is added at the end of an option
7280 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7281 then the output is to a file with the name @file{file_REP} where
7282 file is the name of the corresponding source file.
7284 Note that it is possible for record components to have zero size. In
7285 this case, the component clause uses an obvious extension of permitted
7286 Ada syntax, for example @code{at 0 range 0 .. -1}.
7288 Representation information requires that code be generated (since it is the
7289 code generator that lays out complex data structures). If an attempt is made
7290 to output representation information when no code is generated, for example
7291 when a subunit is compiled on its own, then no information can be generated
7292 and the compiler outputs a message to this effect.
7295 @cindex @option{-gnatS} (@command{gcc})
7296 The use of the switch @option{-gnatS} for an
7297 Ada compilation will cause the compiler to output a
7298 representation of package Standard in a form very
7299 close to standard Ada. It is not quite possible to
7300 do this entirely in standard Ada (since new
7301 numeric base types cannot be created in standard
7302 Ada), but the output is easily
7303 readable to any Ada programmer, and is useful to
7304 determine the characteristics of target dependent
7305 types in package Standard.
7308 @cindex @option{-gnatx} (@command{gcc})
7309 Normally the compiler generates full cross-referencing information in
7310 the @file{ALI} file. This information is used by a number of tools,
7311 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7312 suppresses this information. This saves some space and may slightly
7313 speed up compilation, but means that these tools cannot be used.
7316 @node Exception Handling Control
7317 @subsection Exception Handling Control
7320 GNAT uses two methods for handling exceptions at run-time. The
7321 @code{setjmp/longjmp} method saves the context when entering
7322 a frame with an exception handler. Then when an exception is
7323 raised, the context can be restored immediately, without the
7324 need for tracing stack frames. This method provides very fast
7325 exception propagation, but introduces significant overhead for
7326 the use of exception handlers, even if no exception is raised.
7328 The other approach is called ``zero cost'' exception handling.
7329 With this method, the compiler builds static tables to describe
7330 the exception ranges. No dynamic code is required when entering
7331 a frame containing an exception handler. When an exception is
7332 raised, the tables are used to control a back trace of the
7333 subprogram invocation stack to locate the required exception
7334 handler. This method has considerably poorer performance for
7335 the propagation of exceptions, but there is no overhead for
7336 exception handlers if no exception is raised. Note that in this
7337 mode and in the context of mixed Ada and C/C++ programming,
7338 to propagate an exception through a C/C++ code, the C/C++ code
7339 must be compiled with the @option{-funwind-tables} GCC's
7342 The following switches may be used to control which of the
7343 two exception handling methods is used.
7349 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7350 This switch causes the setjmp/longjmp run-time (when available) to be used
7351 for exception handling. If the default
7352 mechanism for the target is zero cost exceptions, then
7353 this switch can be used to modify this default, and must be
7354 used for all units in the partition.
7355 This option is rarely used. One case in which it may be
7356 advantageous is if you have an application where exception
7357 raising is common and the overall performance of the
7358 application is improved by favoring exception propagation.
7361 @cindex @option{--RTS=zcx} (@command{gnatmake})
7362 @cindex Zero Cost Exceptions
7363 This switch causes the zero cost approach to be used
7364 for exception handling. If this is the default mechanism for the
7365 target (see below), then this switch is unneeded. If the default
7366 mechanism for the target is setjmp/longjmp exceptions, then
7367 this switch can be used to modify this default, and must be
7368 used for all units in the partition.
7369 This option can only be used if the zero cost approach
7370 is available for the target in use, otherwise it will generate an error.
7374 The same option @option{--RTS} must be used both for @command{gcc}
7375 and @command{gnatbind}. Passing this option to @command{gnatmake}
7376 (@pxref{Switches for gnatmake}) will ensure the required consistency
7377 through the compilation and binding steps.
7379 @node Units to Sources Mapping Files
7380 @subsection Units to Sources Mapping Files
7384 @item -gnatem^^=^@var{path}
7385 @cindex @option{-gnatem} (@command{gcc})
7386 A mapping file is a way to communicate to the compiler two mappings:
7387 from unit names to file names (without any directory information) and from
7388 file names to path names (with full directory information). These mappings
7389 are used by the compiler to short-circuit the path search.
7391 The use of mapping files is not required for correct operation of the
7392 compiler, but mapping files can improve efficiency, particularly when
7393 sources are read over a slow network connection. In normal operation,
7394 you need not be concerned with the format or use of mapping files,
7395 and the @option{-gnatem} switch is not a switch that you would use
7396 explicitly. it is intended only for use by automatic tools such as
7397 @command{gnatmake} running under the project file facility. The
7398 description here of the format of mapping files is provided
7399 for completeness and for possible use by other tools.
7401 A mapping file is a sequence of sets of three lines. In each set,
7402 the first line is the unit name, in lower case, with ``@code{%s}''
7404 specs and ``@code{%b}'' appended for bodies; the second line is the
7405 file name; and the third line is the path name.
7411 /gnat/project1/sources/main.2.ada
7414 When the switch @option{-gnatem} is specified, the compiler will create
7415 in memory the two mappings from the specified file. If there is any problem
7416 (nonexistent file, truncated file or duplicate entries), no mapping will
7419 Several @option{-gnatem} switches may be specified; however, only the last
7420 one on the command line will be taken into account.
7422 When using a project file, @command{gnatmake} create a temporary mapping file
7423 and communicates it to the compiler using this switch.
7427 @node Integrated Preprocessing
7428 @subsection Integrated Preprocessing
7431 GNAT sources may be preprocessed immediately before compilation.
7432 In this case, the actual
7433 text of the source is not the text of the source file, but is derived from it
7434 through a process called preprocessing. Integrated preprocessing is specified
7435 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7436 indicates, through a text file, the preprocessing data to be used.
7437 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7440 Note that when integrated preprocessing is used, the output from the
7441 preprocessor is not written to any external file. Instead it is passed
7442 internally to the compiler. If you need to preserve the result of
7443 preprocessing in a file, then you should use @command{gnatprep}
7444 to perform the desired preprocessing in stand-alone mode.
7447 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7448 used when Integrated Preprocessing is used. The reason is that preprocessing
7449 with another Preprocessing Data file without changing the sources will
7450 not trigger recompilation without this switch.
7453 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7454 always trigger recompilation for sources that are preprocessed,
7455 because @command{gnatmake} cannot compute the checksum of the source after
7459 The actual preprocessing function is described in details in section
7460 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7461 preprocessing is triggered and parameterized.
7465 @item -gnatep=@var{file}
7466 @cindex @option{-gnatep} (@command{gcc})
7467 This switch indicates to the compiler the file name (without directory
7468 information) of the preprocessor data file to use. The preprocessor data file
7469 should be found in the source directories.
7472 A preprocessing data file is a text file with significant lines indicating
7473 how should be preprocessed either a specific source or all sources not
7474 mentioned in other lines. A significant line is a nonempty, non-comment line.
7475 Comments are similar to Ada comments.
7478 Each significant line starts with either a literal string or the character '*'.
7479 A literal string is the file name (without directory information) of the source
7480 to preprocess. A character '*' indicates the preprocessing for all the sources
7481 that are not specified explicitly on other lines (order of the lines is not
7482 significant). It is an error to have two lines with the same file name or two
7483 lines starting with the character '*'.
7486 After the file name or the character '*', another optional literal string
7487 indicating the file name of the definition file to be used for preprocessing
7488 (@pxref{Form of Definitions File}). The definition files are found by the
7489 compiler in one of the source directories. In some cases, when compiling
7490 a source in a directory other than the current directory, if the definition
7491 file is in the current directory, it may be necessary to add the current
7492 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7493 the compiler would not find the definition file.
7496 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7497 be found. Those ^switches^switches^ are:
7502 Causes both preprocessor lines and the lines deleted by
7503 preprocessing to be replaced by blank lines, preserving the line number.
7504 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7505 it cancels the effect of @option{-c}.
7508 Causes both preprocessor lines and the lines deleted
7509 by preprocessing to be retained as comments marked
7510 with the special string ``@code{--! }''.
7512 @item -Dsymbol=value
7513 Define or redefine a symbol, associated with value. A symbol is an Ada
7514 identifier, or an Ada reserved word, with the exception of @code{if},
7515 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7516 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7517 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7518 same name defined in a definition file.
7521 Causes a sorted list of symbol names and values to be
7522 listed on the standard output file.
7525 Causes undefined symbols to be treated as having the value @code{FALSE}
7527 of a preprocessor test. In the absence of this option, an undefined symbol in
7528 a @code{#if} or @code{#elsif} test will be treated as an error.
7533 Examples of valid lines in a preprocessor data file:
7536 "toto.adb" "prep.def" -u
7537 -- preprocess "toto.adb", using definition file "prep.def",
7538 -- undefined symbol are False.
7541 -- preprocess all other sources without a definition file;
7542 -- suppressed lined are commented; symbol VERSION has the value V101.
7544 "titi.adb" "prep2.def" -s
7545 -- preprocess "titi.adb", using definition file "prep2.def";
7546 -- list all symbols with their values.
7549 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7550 @cindex @option{-gnateD} (@command{gcc})
7551 Define or redefine a preprocessing symbol, associated with value. If no value
7552 is given on the command line, then the value of the symbol is @code{True}.
7553 A symbol is an identifier, following normal Ada (case-insensitive)
7554 rules for its syntax, and value is any sequence (including an empty sequence)
7555 of characters from the set (letters, digits, period, underline).
7556 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7557 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7560 A symbol declared with this ^switch^switch^ on the command line replaces a
7561 symbol with the same name either in a definition file or specified with a
7562 ^switch^switch^ -D in the preprocessor data file.
7565 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7568 When integrated preprocessing is performed and the preprocessor modifies
7569 the source text, write the result of this preprocessing into a file
7570 <source>^.prep^_prep^.
7574 @node Code Generation Control
7575 @subsection Code Generation Control
7579 The GCC technology provides a wide range of target dependent
7580 @option{-m} switches for controlling
7581 details of code generation with respect to different versions of
7582 architectures. This includes variations in instruction sets (e.g.@:
7583 different members of the power pc family), and different requirements
7584 for optimal arrangement of instructions (e.g.@: different members of
7585 the x86 family). The list of available @option{-m} switches may be
7586 found in the GCC documentation.
7588 Use of these @option{-m} switches may in some cases result in improved
7591 The GNAT Pro technology is tested and qualified without any
7592 @option{-m} switches,
7593 so generally the most reliable approach is to avoid the use of these
7594 switches. However, we generally expect most of these switches to work
7595 successfully with GNAT Pro, and many customers have reported successful
7596 use of these options.
7598 Our general advice is to avoid the use of @option{-m} switches unless
7599 special needs lead to requirements in this area. In particular,
7600 there is no point in using @option{-m} switches to improve performance
7601 unless you actually see a performance improvement.
7605 @subsection Return Codes
7606 @cindex Return Codes
7607 @cindex @option{/RETURN_CODES=VMS}
7610 On VMS, GNAT compiled programs return POSIX-style codes by default,
7611 e.g.@: @option{/RETURN_CODES=POSIX}.
7613 To enable VMS style return codes, use GNAT BIND and LINK with the option
7614 @option{/RETURN_CODES=VMS}. For example:
7617 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7618 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7622 Programs built with /RETURN_CODES=VMS are suitable to be called in
7623 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7624 are suitable for spawning with appropriate GNAT RTL routines.
7628 @node Search Paths and the Run-Time Library (RTL)
7629 @section Search Paths and the Run-Time Library (RTL)
7632 With the GNAT source-based library system, the compiler must be able to
7633 find source files for units that are needed by the unit being compiled.
7634 Search paths are used to guide this process.
7636 The compiler compiles one source file whose name must be given
7637 explicitly on the command line. In other words, no searching is done
7638 for this file. To find all other source files that are needed (the most
7639 common being the specs of units), the compiler examines the following
7640 directories, in the following order:
7644 The directory containing the source file of the main unit being compiled
7645 (the file name on the command line).
7648 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7649 @command{gcc} command line, in the order given.
7652 @findex ADA_PRJ_INCLUDE_FILE
7653 Each of the directories listed in the text file whose name is given
7654 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7657 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7658 driver when project files are used. It should not normally be set
7662 @findex ADA_INCLUDE_PATH
7663 Each of the directories listed in the value of the
7664 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7666 Construct this value
7667 exactly as the @env{PATH} environment variable: a list of directory
7668 names separated by colons (semicolons when working with the NT version).
7671 Normally, define this value as a logical name containing a comma separated
7672 list of directory names.
7674 This variable can also be defined by means of an environment string
7675 (an argument to the HP C exec* set of functions).
7679 DEFINE ANOTHER_PATH FOO:[BAG]
7680 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7683 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7684 first, followed by the standard Ada
7685 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7686 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7687 (Text_IO, Sequential_IO, etc)
7688 instead of the standard Ada packages. Thus, in order to get the standard Ada
7689 packages by default, ADA_INCLUDE_PATH must be redefined.
7693 The content of the @file{ada_source_path} file which is part of the GNAT
7694 installation tree and is used to store standard libraries such as the
7695 GNAT Run Time Library (RTL) source files.
7697 @ref{Installing a library}
7702 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7703 inhibits the use of the directory
7704 containing the source file named in the command line. You can still
7705 have this directory on your search path, but in this case it must be
7706 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7708 Specifying the switch @option{-nostdinc}
7709 inhibits the search of the default location for the GNAT Run Time
7710 Library (RTL) source files.
7712 The compiler outputs its object files and ALI files in the current
7715 Caution: The object file can be redirected with the @option{-o} switch;
7716 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7717 so the @file{ALI} file will not go to the right place. Therefore, you should
7718 avoid using the @option{-o} switch.
7722 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7723 children make up the GNAT RTL, together with the simple @code{System.IO}
7724 package used in the @code{"Hello World"} example. The sources for these units
7725 are needed by the compiler and are kept together in one directory. Not
7726 all of the bodies are needed, but all of the sources are kept together
7727 anyway. In a normal installation, you need not specify these directory
7728 names when compiling or binding. Either the environment variables or
7729 the built-in defaults cause these files to be found.
7731 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7732 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7733 consisting of child units of @code{GNAT}. This is a collection of generally
7734 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7735 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7737 Besides simplifying access to the RTL, a major use of search paths is
7738 in compiling sources from multiple directories. This can make
7739 development environments much more flexible.
7741 @node Order of Compilation Issues
7742 @section Order of Compilation Issues
7745 If, in our earlier example, there was a spec for the @code{hello}
7746 procedure, it would be contained in the file @file{hello.ads}; yet this
7747 file would not have to be explicitly compiled. This is the result of the
7748 model we chose to implement library management. Some of the consequences
7749 of this model are as follows:
7753 There is no point in compiling specs (except for package
7754 specs with no bodies) because these are compiled as needed by clients. If
7755 you attempt a useless compilation, you will receive an error message.
7756 It is also useless to compile subunits because they are compiled as needed
7760 There are no order of compilation requirements: performing a
7761 compilation never obsoletes anything. The only way you can obsolete
7762 something and require recompilations is to modify one of the
7763 source files on which it depends.
7766 There is no library as such, apart from the ALI files
7767 (@pxref{The Ada Library Information Files}, for information on the format
7768 of these files). For now we find it convenient to create separate ALI files,
7769 but eventually the information therein may be incorporated into the object
7773 When you compile a unit, the source files for the specs of all units
7774 that it @code{with}'s, all its subunits, and the bodies of any generics it
7775 instantiates must be available (reachable by the search-paths mechanism
7776 described above), or you will receive a fatal error message.
7783 The following are some typical Ada compilation command line examples:
7786 @item $ gcc -c xyz.adb
7787 Compile body in file @file{xyz.adb} with all default options.
7790 @item $ gcc -c -O2 -gnata xyz-def.adb
7793 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7796 Compile the child unit package in file @file{xyz-def.adb} with extensive
7797 optimizations, and pragma @code{Assert}/@code{Debug} statements
7800 @item $ gcc -c -gnatc abc-def.adb
7801 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7805 @node Binding Using gnatbind
7806 @chapter Binding Using @code{gnatbind}
7810 * Running gnatbind::
7811 * Switches for gnatbind::
7812 * Command-Line Access::
7813 * Search Paths for gnatbind::
7814 * Examples of gnatbind Usage::
7818 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7819 to bind compiled GNAT objects.
7821 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7822 driver (see @ref{The GNAT Driver and Project Files}).
7824 The @code{gnatbind} program performs four separate functions:
7828 Checks that a program is consistent, in accordance with the rules in
7829 Chapter 10 of the Ada Reference Manual. In particular, error
7830 messages are generated if a program uses inconsistent versions of a
7834 Checks that an acceptable order of elaboration exists for the program
7835 and issues an error message if it cannot find an order of elaboration
7836 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7839 Generates a main program incorporating the given elaboration order.
7840 This program is a small Ada package (body and spec) that
7841 must be subsequently compiled
7842 using the GNAT compiler. The necessary compilation step is usually
7843 performed automatically by @command{gnatlink}. The two most important
7844 functions of this program
7845 are to call the elaboration routines of units in an appropriate order
7846 and to call the main program.
7849 Determines the set of object files required by the given main program.
7850 This information is output in the forms of comments in the generated program,
7851 to be read by the @command{gnatlink} utility used to link the Ada application.
7854 @node Running gnatbind
7855 @section Running @code{gnatbind}
7858 The form of the @code{gnatbind} command is
7861 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7865 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7866 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7867 package in two files whose names are
7868 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7869 For example, if given the
7870 parameter @file{hello.ali}, for a main program contained in file
7871 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7872 and @file{b~hello.adb}.
7874 When doing consistency checking, the binder takes into consideration
7875 any source files it can locate. For example, if the binder determines
7876 that the given main program requires the package @code{Pack}, whose
7878 file is @file{pack.ali} and whose corresponding source spec file is
7879 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7880 (using the same search path conventions as previously described for the
7881 @command{gcc} command). If it can locate this source file, it checks that
7883 or source checksums of the source and its references to in @file{ALI} files
7884 match. In other words, any @file{ALI} files that mentions this spec must have
7885 resulted from compiling this version of the source file (or in the case
7886 where the source checksums match, a version close enough that the
7887 difference does not matter).
7889 @cindex Source files, use by binder
7890 The effect of this consistency checking, which includes source files, is
7891 that the binder ensures that the program is consistent with the latest
7892 version of the source files that can be located at bind time. Editing a
7893 source file without compiling files that depend on the source file cause
7894 error messages to be generated by the binder.
7896 For example, suppose you have a main program @file{hello.adb} and a
7897 package @code{P}, from file @file{p.ads} and you perform the following
7902 Enter @code{gcc -c hello.adb} to compile the main program.
7905 Enter @code{gcc -c p.ads} to compile package @code{P}.
7908 Edit file @file{p.ads}.
7911 Enter @code{gnatbind hello}.
7915 At this point, the file @file{p.ali} contains an out-of-date time stamp
7916 because the file @file{p.ads} has been edited. The attempt at binding
7917 fails, and the binder generates the following error messages:
7920 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7921 error: "p.ads" has been modified and must be recompiled
7925 Now both files must be recompiled as indicated, and then the bind can
7926 succeed, generating a main program. You need not normally be concerned
7927 with the contents of this file, but for reference purposes a sample
7928 binder output file is given in @ref{Example of Binder Output File}.
7930 In most normal usage, the default mode of @command{gnatbind} which is to
7931 generate the main package in Ada, as described in the previous section.
7932 In particular, this means that any Ada programmer can read and understand
7933 the generated main program. It can also be debugged just like any other
7934 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7935 @command{gnatbind} and @command{gnatlink}.
7937 However for some purposes it may be convenient to generate the main
7938 program in C rather than Ada. This may for example be helpful when you
7939 are generating a mixed language program with the main program in C. The
7940 GNAT compiler itself is an example.
7941 The use of the @option{^-C^/BIND_FILE=C^} switch
7942 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7943 be generated in C (and compiled using the gnu C compiler).
7945 @node Switches for gnatbind
7946 @section Switches for @command{gnatbind}
7949 The following switches are available with @code{gnatbind}; details will
7950 be presented in subsequent sections.
7953 * Consistency-Checking Modes::
7954 * Binder Error Message Control::
7955 * Elaboration Control::
7957 * Binding with Non-Ada Main Programs::
7958 * Binding Programs with No Main Subprogram::
7965 @cindex @option{--version} @command{gnatbind}
7966 Display Copyright and version, then exit disregarding all other options.
7969 @cindex @option{--help} @command{gnatbind}
7970 If @option{--version} was not used, display usage, then exit disregarding
7974 @cindex @option{-a} @command{gnatbind}
7975 Indicates that, if supported by the platform, the adainit procedure should
7976 be treated as an initialisation routine by the linker (a constructor). This
7977 is intended to be used by the Project Manager to automatically initialize
7978 shared Stand-Alone Libraries.
7980 @item ^-aO^/OBJECT_SEARCH^
7981 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7982 Specify directory to be searched for ALI files.
7984 @item ^-aI^/SOURCE_SEARCH^
7985 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7986 Specify directory to be searched for source file.
7988 @item ^-A^/BIND_FILE=ADA^
7989 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7990 Generate binder program in Ada (default)
7992 @item ^-b^/REPORT_ERRORS=BRIEF^
7993 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
7994 Generate brief messages to @file{stderr} even if verbose mode set.
7996 @item ^-c^/NOOUTPUT^
7997 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
7998 Check only, no generation of binder output file.
8000 @item ^-C^/BIND_FILE=C^
8001 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
8002 Generate binder program in C
8004 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8005 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
8006 This switch can be used to change the default task stack size value
8007 to a specified size @var{nn}, which is expressed in bytes by default, or
8008 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8010 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
8011 in effect, to completing all task specs with
8012 @smallexample @c ada
8013 pragma Storage_Size (nn);
8015 When they do not already have such a pragma.
8017 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8018 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
8019 This switch can be used to change the default secondary stack size value
8020 to a specified size @var{nn}, which is expressed in bytes by default, or
8021 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8024 The secondary stack is used to deal with functions that return a variable
8025 sized result, for example a function returning an unconstrained
8026 String. There are two ways in which this secondary stack is allocated.
8028 For most targets, the secondary stack is growing on demand and is allocated
8029 as a chain of blocks in the heap. The -D option is not very
8030 relevant. It only give some control over the size of the allocated
8031 blocks (whose size is the minimum of the default secondary stack size value,
8032 and the actual size needed for the current allocation request).
8034 For certain targets, notably VxWorks 653,
8035 the secondary stack is allocated by carving off a fixed ratio chunk of the
8036 primary task stack. The -D option is used to define the
8037 size of the environment task's secondary stack.
8039 @item ^-e^/ELABORATION_DEPENDENCIES^
8040 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
8041 Output complete list of elaboration-order dependencies.
8043 @item ^-E^/STORE_TRACEBACKS^
8044 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
8045 Store tracebacks in exception occurrences when the target supports it.
8046 This is the default with the zero cost exception mechanism.
8048 @c The following may get moved to an appendix
8049 This option is currently supported on the following targets:
8050 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
8052 See also the packages @code{GNAT.Traceback} and
8053 @code{GNAT.Traceback.Symbolic} for more information.
8055 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
8056 @command{gcc} option.
8059 @item ^-F^/FORCE_ELABS_FLAGS^
8060 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
8061 Force the checks of elaboration flags. @command{gnatbind} does not normally
8062 generate checks of elaboration flags for the main executable, except when
8063 a Stand-Alone Library is used. However, there are cases when this cannot be
8064 detected by gnatbind. An example is importing an interface of a Stand-Alone
8065 Library through a pragma Import and only specifying through a linker switch
8066 this Stand-Alone Library. This switch is used to guarantee that elaboration
8067 flag checks are generated.
8070 @cindex @option{^-h^/HELP^} (@command{gnatbind})
8071 Output usage (help) information
8074 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8075 Specify directory to be searched for source and ALI files.
8077 @item ^-I-^/NOCURRENT_DIRECTORY^
8078 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
8079 Do not look for sources in the current directory where @code{gnatbind} was
8080 invoked, and do not look for ALI files in the directory containing the
8081 ALI file named in the @code{gnatbind} command line.
8083 @item ^-l^/ORDER_OF_ELABORATION^
8084 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
8085 Output chosen elaboration order.
8087 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
8088 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
8089 Bind the units for library building. In this case the adainit and
8090 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
8091 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
8092 ^@var{xxx}final^@var{XXX}FINAL^.
8093 Implies ^-n^/NOCOMPILE^.
8095 (@xref{GNAT and Libraries}, for more details.)
8098 On OpenVMS, these init and final procedures are exported in uppercase
8099 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
8100 the init procedure will be "TOTOINIT" and the exported name of the final
8101 procedure will be "TOTOFINAL".
8104 @item ^-Mxyz^/RENAME_MAIN=xyz^
8105 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
8106 Rename generated main program from main to xyz. This option is
8107 supported on cross environments only.
8109 @item ^-m^/ERROR_LIMIT=^@var{n}
8110 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
8111 Limit number of detected errors or warnings to @var{n}, where @var{n} is
8112 in the range 1..999999. The default value if no switch is
8113 given is 9999. If the number of warnings reaches this limit, then a
8114 message is output and further warnings are suppressed, the bind
8115 continues in this case. If the number of errors reaches this
8116 limit, then a message is output and the bind is abandoned.
8117 A value of zero means that no limit is enforced. The equal
8121 Furthermore, under Windows, the sources pointed to by the libraries path
8122 set in the registry are not searched for.
8126 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8130 @cindex @option{-nostdinc} (@command{gnatbind})
8131 Do not look for sources in the system default directory.
8134 @cindex @option{-nostdlib} (@command{gnatbind})
8135 Do not look for library files in the system default directory.
8137 @item --RTS=@var{rts-path}
8138 @cindex @option{--RTS} (@code{gnatbind})
8139 Specifies the default location of the runtime library. Same meaning as the
8140 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
8142 @item ^-o ^/OUTPUT=^@var{file}
8143 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
8144 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
8145 Note that if this option is used, then linking must be done manually,
8146 gnatlink cannot be used.
8148 @item ^-O^/OBJECT_LIST^
8149 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
8152 @item ^-p^/PESSIMISTIC_ELABORATION^
8153 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
8154 Pessimistic (worst-case) elaboration order
8157 @cindex @option{^-R^-R^} (@command{gnatbind})
8158 Output closure source list.
8160 @item ^-s^/READ_SOURCES=ALL^
8161 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
8162 Require all source files to be present.
8164 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
8165 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
8166 Specifies the value to be used when detecting uninitialized scalar
8167 objects with pragma Initialize_Scalars.
8168 The @var{xxx} ^string specified with the switch^option^ may be either
8170 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
8171 @item ``@option{^lo^LOW^}'' for the lowest possible value
8172 @item ``@option{^hi^HIGH^}'' for the highest possible value
8173 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
8174 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
8177 In addition, you can specify @option{-Sev} to indicate that the value is
8178 to be set at run time. In this case, the program will look for an environment
8179 @cindex GNAT_INIT_SCALARS
8180 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
8181 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
8182 If no environment variable is found, or if it does not have a valid value,
8183 then the default is @option{in} (invalid values).
8187 @cindex @option{-static} (@code{gnatbind})
8188 Link against a static GNAT run time.
8191 @cindex @option{-shared} (@code{gnatbind})
8192 Link against a shared GNAT run time when available.
8195 @item ^-t^/NOTIME_STAMP_CHECK^
8196 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8197 Tolerate time stamp and other consistency errors
8199 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
8200 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
8201 Set the time slice value to @var{n} milliseconds. If the system supports
8202 the specification of a specific time slice value, then the indicated value
8203 is used. If the system does not support specific time slice values, but
8204 does support some general notion of round-robin scheduling, then any
8205 nonzero value will activate round-robin scheduling.
8207 A value of zero is treated specially. It turns off time
8208 slicing, and in addition, indicates to the tasking run time that the
8209 semantics should match as closely as possible the Annex D
8210 requirements of the Ada RM, and in particular sets the default
8211 scheduling policy to @code{FIFO_Within_Priorities}.
8213 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
8214 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
8215 Enable dynamic stack usage, with @var{n} results stored and displayed
8216 at program termination. A result is generated when a task
8217 terminates. Results that can't be stored are displayed on the fly, at
8218 task termination. This option is currently not supported on Itanium
8219 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
8221 @item ^-v^/REPORT_ERRORS=VERBOSE^
8222 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8223 Verbose mode. Write error messages, header, summary output to
8228 @cindex @option{-w} (@code{gnatbind})
8229 Warning mode (@var{x}=s/e for suppress/treat as error)
8233 @item /WARNINGS=NORMAL
8234 @cindex @option{/WARNINGS} (@code{gnatbind})
8235 Normal warnings mode. Warnings are issued but ignored
8237 @item /WARNINGS=SUPPRESS
8238 @cindex @option{/WARNINGS} (@code{gnatbind})
8239 All warning messages are suppressed
8241 @item /WARNINGS=ERROR
8242 @cindex @option{/WARNINGS} (@code{gnatbind})
8243 Warning messages are treated as fatal errors
8246 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8247 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8248 Override default wide character encoding for standard Text_IO files.
8250 @item ^-x^/READ_SOURCES=NONE^
8251 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
8252 Exclude source files (check object consistency only).
8255 @item /READ_SOURCES=AVAILABLE
8256 @cindex @option{/READ_SOURCES} (@code{gnatbind})
8257 Default mode, in which sources are checked for consistency only if
8261 @item ^-y^/ENABLE_LEAP_SECONDS^
8262 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
8263 Enable leap seconds support in @code{Ada.Calendar} and its children.
8265 @item ^-z^/ZERO_MAIN^
8266 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8272 You may obtain this listing of switches by running @code{gnatbind} with
8276 @node Consistency-Checking Modes
8277 @subsection Consistency-Checking Modes
8280 As described earlier, by default @code{gnatbind} checks
8281 that object files are consistent with one another and are consistent
8282 with any source files it can locate. The following switches control binder
8287 @item ^-s^/READ_SOURCES=ALL^
8288 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8289 Require source files to be present. In this mode, the binder must be
8290 able to locate all source files that are referenced, in order to check
8291 their consistency. In normal mode, if a source file cannot be located it
8292 is simply ignored. If you specify this switch, a missing source
8295 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8296 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8297 Override default wide character encoding for standard Text_IO files.
8298 Normally the default wide character encoding method used for standard
8299 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8300 the main source input (see description of switch
8301 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8302 use of this switch for the binder (which has the same set of
8303 possible arguments) overrides this default as specified.
8305 @item ^-x^/READ_SOURCES=NONE^
8306 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8307 Exclude source files. In this mode, the binder only checks that ALI
8308 files are consistent with one another. Source files are not accessed.
8309 The binder runs faster in this mode, and there is still a guarantee that
8310 the resulting program is self-consistent.
8311 If a source file has been edited since it was last compiled, and you
8312 specify this switch, the binder will not detect that the object
8313 file is out of date with respect to the source file. Note that this is the
8314 mode that is automatically used by @command{gnatmake} because in this
8315 case the checking against sources has already been performed by
8316 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8319 @item /READ_SOURCES=AVAILABLE
8320 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8321 This is the default mode in which source files are checked if they are
8322 available, and ignored if they are not available.
8326 @node Binder Error Message Control
8327 @subsection Binder Error Message Control
8330 The following switches provide control over the generation of error
8331 messages from the binder:
8335 @item ^-v^/REPORT_ERRORS=VERBOSE^
8336 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8337 Verbose mode. In the normal mode, brief error messages are generated to
8338 @file{stderr}. If this switch is present, a header is written
8339 to @file{stdout} and any error messages are directed to @file{stdout}.
8340 All that is written to @file{stderr} is a brief summary message.
8342 @item ^-b^/REPORT_ERRORS=BRIEF^
8343 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8344 Generate brief error messages to @file{stderr} even if verbose mode is
8345 specified. This is relevant only when used with the
8346 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8350 @cindex @option{-m} (@code{gnatbind})
8351 Limits the number of error messages to @var{n}, a decimal integer in the
8352 range 1-999. The binder terminates immediately if this limit is reached.
8355 @cindex @option{-M} (@code{gnatbind})
8356 Renames the generated main program from @code{main} to @code{xxx}.
8357 This is useful in the case of some cross-building environments, where
8358 the actual main program is separate from the one generated
8362 @item ^-ws^/WARNINGS=SUPPRESS^
8363 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8365 Suppress all warning messages.
8367 @item ^-we^/WARNINGS=ERROR^
8368 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8369 Treat any warning messages as fatal errors.
8372 @item /WARNINGS=NORMAL
8373 Standard mode with warnings generated, but warnings do not get treated
8377 @item ^-t^/NOTIME_STAMP_CHECK^
8378 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8379 @cindex Time stamp checks, in binder
8380 @cindex Binder consistency checks
8381 @cindex Consistency checks, in binder
8382 The binder performs a number of consistency checks including:
8386 Check that time stamps of a given source unit are consistent
8388 Check that checksums of a given source unit are consistent
8390 Check that consistent versions of @code{GNAT} were used for compilation
8392 Check consistency of configuration pragmas as required
8396 Normally failure of such checks, in accordance with the consistency
8397 requirements of the Ada Reference Manual, causes error messages to be
8398 generated which abort the binder and prevent the output of a binder
8399 file and subsequent link to obtain an executable.
8401 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8402 into warnings, so that
8403 binding and linking can continue to completion even in the presence of such
8404 errors. The result may be a failed link (due to missing symbols), or a
8405 non-functional executable which has undefined semantics.
8406 @emph{This means that
8407 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8411 @node Elaboration Control
8412 @subsection Elaboration Control
8415 The following switches provide additional control over the elaboration
8416 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8419 @item ^-p^/PESSIMISTIC_ELABORATION^
8420 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8421 Normally the binder attempts to choose an elaboration order that is
8422 likely to minimize the likelihood of an elaboration order error resulting
8423 in raising a @code{Program_Error} exception. This switch reverses the
8424 action of the binder, and requests that it deliberately choose an order
8425 that is likely to maximize the likelihood of an elaboration error.
8426 This is useful in ensuring portability and avoiding dependence on
8427 accidental fortuitous elaboration ordering.
8429 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8431 elaboration checking is used (@option{-gnatE} switch used for compilation).
8432 This is because in the default static elaboration mode, all necessary
8433 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8434 These implicit pragmas are still respected by the binder in
8435 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8436 safe elaboration order is assured.
8439 @node Output Control
8440 @subsection Output Control
8443 The following switches allow additional control over the output
8444 generated by the binder.
8449 @item ^-A^/BIND_FILE=ADA^
8450 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8451 Generate binder program in Ada (default). The binder program is named
8452 @file{b~@var{mainprog}.adb} by default. This can be changed with
8453 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8455 @item ^-c^/NOOUTPUT^
8456 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8457 Check only. Do not generate the binder output file. In this mode the
8458 binder performs all error checks but does not generate an output file.
8460 @item ^-C^/BIND_FILE=C^
8461 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8462 Generate binder program in C. The binder program is named
8463 @file{b_@var{mainprog}.c}.
8464 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8467 @item ^-e^/ELABORATION_DEPENDENCIES^
8468 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8469 Output complete list of elaboration-order dependencies, showing the
8470 reason for each dependency. This output can be rather extensive but may
8471 be useful in diagnosing problems with elaboration order. The output is
8472 written to @file{stdout}.
8475 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8476 Output usage information. The output is written to @file{stdout}.
8478 @item ^-K^/LINKER_OPTION_LIST^
8479 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8480 Output linker options to @file{stdout}. Includes library search paths,
8481 contents of pragmas Ident and Linker_Options, and libraries added
8484 @item ^-l^/ORDER_OF_ELABORATION^
8485 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8486 Output chosen elaboration order. The output is written to @file{stdout}.
8488 @item ^-O^/OBJECT_LIST^
8489 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8490 Output full names of all the object files that must be linked to provide
8491 the Ada component of the program. The output is written to @file{stdout}.
8492 This list includes the files explicitly supplied and referenced by the user
8493 as well as implicitly referenced run-time unit files. The latter are
8494 omitted if the corresponding units reside in shared libraries. The
8495 directory names for the run-time units depend on the system configuration.
8497 @item ^-o ^/OUTPUT=^@var{file}
8498 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8499 Set name of output file to @var{file} instead of the normal
8500 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8501 binder generated body filename. In C mode you would normally give
8502 @var{file} an extension of @file{.c} because it will be a C source program.
8503 Note that if this option is used, then linking must be done manually.
8504 It is not possible to use gnatlink in this case, since it cannot locate
8507 @item ^-r^/RESTRICTION_LIST^
8508 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8509 Generate list of @code{pragma Restrictions} that could be applied to
8510 the current unit. This is useful for code audit purposes, and also may
8511 be used to improve code generation in some cases.
8515 @node Binding with Non-Ada Main Programs
8516 @subsection Binding with Non-Ada Main Programs
8519 In our description so far we have assumed that the main
8520 program is in Ada, and that the task of the binder is to generate a
8521 corresponding function @code{main} that invokes this Ada main
8522 program. GNAT also supports the building of executable programs where
8523 the main program is not in Ada, but some of the called routines are
8524 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8525 The following switch is used in this situation:
8529 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8530 No main program. The main program is not in Ada.
8534 In this case, most of the functions of the binder are still required,
8535 but instead of generating a main program, the binder generates a file
8536 containing the following callable routines:
8541 You must call this routine to initialize the Ada part of the program by
8542 calling the necessary elaboration routines. A call to @code{adainit} is
8543 required before the first call to an Ada subprogram.
8545 Note that it is assumed that the basic execution environment must be setup
8546 to be appropriate for Ada execution at the point where the first Ada
8547 subprogram is called. In particular, if the Ada code will do any
8548 floating-point operations, then the FPU must be setup in an appropriate
8549 manner. For the case of the x86, for example, full precision mode is
8550 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8551 that the FPU is in the right state.
8555 You must call this routine to perform any library-level finalization
8556 required by the Ada subprograms. A call to @code{adafinal} is required
8557 after the last call to an Ada subprogram, and before the program
8562 If the @option{^-n^/NOMAIN^} switch
8563 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8564 @cindex Binder, multiple input files
8565 is given, more than one ALI file may appear on
8566 the command line for @code{gnatbind}. The normal @dfn{closure}
8567 calculation is performed for each of the specified units. Calculating
8568 the closure means finding out the set of units involved by tracing
8569 @code{with} references. The reason it is necessary to be able to
8570 specify more than one ALI file is that a given program may invoke two or
8571 more quite separate groups of Ada units.
8573 The binder takes the name of its output file from the last specified ALI
8574 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8575 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8576 The output is an Ada unit in source form that can
8577 be compiled with GNAT unless the -C switch is used in which case the
8578 output is a C source file, which must be compiled using the C compiler.
8579 This compilation occurs automatically as part of the @command{gnatlink}
8582 Currently the GNAT run time requires a FPU using 80 bits mode
8583 precision. Under targets where this is not the default it is required to
8584 call GNAT.Float_Control.Reset before using floating point numbers (this
8585 include float computation, float input and output) in the Ada code. A
8586 side effect is that this could be the wrong mode for the foreign code
8587 where floating point computation could be broken after this call.
8589 @node Binding Programs with No Main Subprogram
8590 @subsection Binding Programs with No Main Subprogram
8593 It is possible to have an Ada program which does not have a main
8594 subprogram. This program will call the elaboration routines of all the
8595 packages, then the finalization routines.
8597 The following switch is used to bind programs organized in this manner:
8600 @item ^-z^/ZERO_MAIN^
8601 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8602 Normally the binder checks that the unit name given on the command line
8603 corresponds to a suitable main subprogram. When this switch is used,
8604 a list of ALI files can be given, and the execution of the program
8605 consists of elaboration of these units in an appropriate order. Note
8606 that the default wide character encoding method for standard Text_IO
8607 files is always set to Brackets if this switch is set (you can use
8609 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8612 @node Command-Line Access
8613 @section Command-Line Access
8616 The package @code{Ada.Command_Line} provides access to the command-line
8617 arguments and program name. In order for this interface to operate
8618 correctly, the two variables
8630 are declared in one of the GNAT library routines. These variables must
8631 be set from the actual @code{argc} and @code{argv} values passed to the
8632 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8633 generates the C main program to automatically set these variables.
8634 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8635 set these variables. If they are not set, the procedures in
8636 @code{Ada.Command_Line} will not be available, and any attempt to use
8637 them will raise @code{Constraint_Error}. If command line access is
8638 required, your main program must set @code{gnat_argc} and
8639 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8642 @node Search Paths for gnatbind
8643 @section Search Paths for @code{gnatbind}
8646 The binder takes the name of an ALI file as its argument and needs to
8647 locate source files as well as other ALI files to verify object consistency.
8649 For source files, it follows exactly the same search rules as @command{gcc}
8650 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8651 directories searched are:
8655 The directory containing the ALI file named in the command line, unless
8656 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8659 All directories specified by @option{^-I^/SEARCH^}
8660 switches on the @code{gnatbind}
8661 command line, in the order given.
8664 @findex ADA_PRJ_OBJECTS_FILE
8665 Each of the directories listed in the text file whose name is given
8666 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8669 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8670 driver when project files are used. It should not normally be set
8674 @findex ADA_OBJECTS_PATH
8675 Each of the directories listed in the value of the
8676 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8678 Construct this value
8679 exactly as the @env{PATH} environment variable: a list of directory
8680 names separated by colons (semicolons when working with the NT version
8684 Normally, define this value as a logical name containing a comma separated
8685 list of directory names.
8687 This variable can also be defined by means of an environment string
8688 (an argument to the HP C exec* set of functions).
8692 DEFINE ANOTHER_PATH FOO:[BAG]
8693 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8696 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8697 first, followed by the standard Ada
8698 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8699 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8700 (Text_IO, Sequential_IO, etc)
8701 instead of the standard Ada packages. Thus, in order to get the standard Ada
8702 packages by default, ADA_OBJECTS_PATH must be redefined.
8706 The content of the @file{ada_object_path} file which is part of the GNAT
8707 installation tree and is used to store standard libraries such as the
8708 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8711 @ref{Installing a library}
8716 In the binder the switch @option{^-I^/SEARCH^}
8717 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8718 is used to specify both source and
8719 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8720 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8721 instead if you want to specify
8722 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8723 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8724 if you want to specify library paths
8725 only. This means that for the binder
8726 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8727 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8728 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8729 The binder generates the bind file (a C language source file) in the
8730 current working directory.
8736 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8737 children make up the GNAT Run-Time Library, together with the package
8738 GNAT and its children, which contain a set of useful additional
8739 library functions provided by GNAT. The sources for these units are
8740 needed by the compiler and are kept together in one directory. The ALI
8741 files and object files generated by compiling the RTL are needed by the
8742 binder and the linker and are kept together in one directory, typically
8743 different from the directory containing the sources. In a normal
8744 installation, you need not specify these directory names when compiling
8745 or binding. Either the environment variables or the built-in defaults
8746 cause these files to be found.
8748 Besides simplifying access to the RTL, a major use of search paths is
8749 in compiling sources from multiple directories. This can make
8750 development environments much more flexible.
8752 @node Examples of gnatbind Usage
8753 @section Examples of @code{gnatbind} Usage
8756 This section contains a number of examples of using the GNAT binding
8757 utility @code{gnatbind}.
8760 @item gnatbind hello
8761 The main program @code{Hello} (source program in @file{hello.adb}) is
8762 bound using the standard switch settings. The generated main program is
8763 @file{b~hello.adb}. This is the normal, default use of the binder.
8766 @item gnatbind hello -o mainprog.adb
8769 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8771 The main program @code{Hello} (source program in @file{hello.adb}) is
8772 bound using the standard switch settings. The generated main program is
8773 @file{mainprog.adb} with the associated spec in
8774 @file{mainprog.ads}. Note that you must specify the body here not the
8775 spec, in the case where the output is in Ada. Note that if this option
8776 is used, then linking must be done manually, since gnatlink will not
8777 be able to find the generated file.
8780 @item gnatbind main -C -o mainprog.c -x
8783 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8785 The main program @code{Main} (source program in
8786 @file{main.adb}) is bound, excluding source files from the
8787 consistency checking, generating
8788 the file @file{mainprog.c}.
8791 @item gnatbind -x main_program -C -o mainprog.c
8792 This command is exactly the same as the previous example. Switches may
8793 appear anywhere in the command line, and single letter switches may be
8794 combined into a single switch.
8798 @item gnatbind -n math dbase -C -o ada-control.c
8801 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8803 The main program is in a language other than Ada, but calls to
8804 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8805 to @code{gnatbind} generates the file @file{ada-control.c} containing
8806 the @code{adainit} and @code{adafinal} routines to be called before and
8807 after accessing the Ada units.
8810 @c ------------------------------------
8811 @node Linking Using gnatlink
8812 @chapter Linking Using @command{gnatlink}
8813 @c ------------------------------------
8817 This chapter discusses @command{gnatlink}, a tool that links
8818 an Ada program and builds an executable file. This utility
8819 invokes the system linker ^(via the @command{gcc} command)^^
8820 with a correct list of object files and library references.
8821 @command{gnatlink} automatically determines the list of files and
8822 references for the Ada part of a program. It uses the binder file
8823 generated by the @command{gnatbind} to determine this list.
8825 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8826 driver (see @ref{The GNAT Driver and Project Files}).
8829 * Running gnatlink::
8830 * Switches for gnatlink::
8833 @node Running gnatlink
8834 @section Running @command{gnatlink}
8837 The form of the @command{gnatlink} command is
8840 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8841 @ovar{non-Ada objects} @ovar{linker options}
8845 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8847 or linker options) may be in any order, provided that no non-Ada object may
8848 be mistaken for a main @file{ALI} file.
8849 Any file name @file{F} without the @file{.ali}
8850 extension will be taken as the main @file{ALI} file if a file exists
8851 whose name is the concatenation of @file{F} and @file{.ali}.
8854 @file{@var{mainprog}.ali} references the ALI file of the main program.
8855 The @file{.ali} extension of this file can be omitted. From this
8856 reference, @command{gnatlink} locates the corresponding binder file
8857 @file{b~@var{mainprog}.adb} and, using the information in this file along
8858 with the list of non-Ada objects and linker options, constructs a
8859 linker command file to create the executable.
8861 The arguments other than the @command{gnatlink} switches and the main
8862 @file{ALI} file are passed to the linker uninterpreted.
8863 They typically include the names of
8864 object files for units written in other languages than Ada and any library
8865 references required to resolve references in any of these foreign language
8866 units, or in @code{Import} pragmas in any Ada units.
8868 @var{linker options} is an optional list of linker specific
8870 The default linker called by gnatlink is @command{gcc} which in
8871 turn calls the appropriate system linker.
8872 Standard options for the linker such as @option{-lmy_lib} or
8873 @option{-Ldir} can be added as is.
8874 For options that are not recognized by
8875 @command{gcc} as linker options, use the @command{gcc} switches
8876 @option{-Xlinker} or @option{-Wl,}.
8877 Refer to the GCC documentation for
8878 details. Here is an example showing how to generate a linker map:
8881 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8884 Using @var{linker options} it is possible to set the program stack and
8887 See @ref{Setting Stack Size from gnatlink} and
8888 @ref{Setting Heap Size from gnatlink}.
8891 @command{gnatlink} determines the list of objects required by the Ada
8892 program and prepends them to the list of objects passed to the linker.
8893 @command{gnatlink} also gathers any arguments set by the use of
8894 @code{pragma Linker_Options} and adds them to the list of arguments
8895 presented to the linker.
8898 @command{gnatlink} accepts the following types of extra files on the command
8899 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8900 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8901 handled according to their extension.
8904 @node Switches for gnatlink
8905 @section Switches for @command{gnatlink}
8908 The following switches are available with the @command{gnatlink} utility:
8914 @cindex @option{--version} @command{gnatlink}
8915 Display Copyright and version, then exit disregarding all other options.
8918 @cindex @option{--help} @command{gnatlink}
8919 If @option{--version} was not used, display usage, then exit disregarding
8922 @item ^-A^/BIND_FILE=ADA^
8923 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8924 The binder has generated code in Ada. This is the default.
8926 @item ^-C^/BIND_FILE=C^
8927 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8928 If instead of generating a file in Ada, the binder has generated one in
8929 C, then the linker needs to know about it. Use this switch to signal
8930 to @command{gnatlink} that the binder has generated C code rather than
8933 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8934 @cindex Command line length
8935 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8936 On some targets, the command line length is limited, and @command{gnatlink}
8937 will generate a separate file for the linker if the list of object files
8939 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8940 to be generated even if
8941 the limit is not exceeded. This is useful in some cases to deal with
8942 special situations where the command line length is exceeded.
8945 @cindex Debugging information, including
8946 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8947 The option to include debugging information causes the Ada bind file (in
8948 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8949 @option{^-g^/DEBUG^}.
8950 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8951 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8952 Without @option{^-g^/DEBUG^}, the binder removes these files by
8953 default. The same procedure apply if a C bind file was generated using
8954 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8955 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8957 @item ^-n^/NOCOMPILE^
8958 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8959 Do not compile the file generated by the binder. This may be used when
8960 a link is rerun with different options, but there is no need to recompile
8964 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8965 Causes additional information to be output, including a full list of the
8966 included object files. This switch option is most useful when you want
8967 to see what set of object files are being used in the link step.
8969 @item ^-v -v^/VERBOSE/VERBOSE^
8970 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8971 Very verbose mode. Requests that the compiler operate in verbose mode when
8972 it compiles the binder file, and that the system linker run in verbose mode.
8974 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8975 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8976 @var{exec-name} specifies an alternate name for the generated
8977 executable program. If this switch is omitted, the executable has the same
8978 name as the main unit. For example, @code{gnatlink try.ali} creates
8979 an executable called @file{^try^TRY.EXE^}.
8982 @item -b @var{target}
8983 @cindex @option{-b} (@command{gnatlink})
8984 Compile your program to run on @var{target}, which is the name of a
8985 system configuration. You must have a GNAT cross-compiler built if
8986 @var{target} is not the same as your host system.
8989 @cindex @option{-B} (@command{gnatlink})
8990 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8991 from @var{dir} instead of the default location. Only use this switch
8992 when multiple versions of the GNAT compiler are available.
8993 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
8994 for further details. You would normally use the @option{-b} or
8995 @option{-V} switch instead.
8997 @item --GCC=@var{compiler_name}
8998 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
8999 Program used for compiling the binder file. The default is
9000 @command{gcc}. You need to use quotes around @var{compiler_name} if
9001 @code{compiler_name} contains spaces or other separator characters.
9002 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
9003 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
9004 inserted after your command name. Thus in the above example the compiler
9005 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
9006 A limitation of this syntax is that the name and path name of the executable
9007 itself must not include any embedded spaces. If the compiler executable is
9008 different from the default one (gcc or <prefix>-gcc), then the back-end
9009 switches in the ALI file are not used to compile the binder generated source.
9010 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
9011 switches will be used for @option{--GCC="gcc -gnatv"}. If several
9012 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
9013 is taken into account. However, all the additional switches are also taken
9015 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9016 @option{--GCC="bar -x -y -z -t"}.
9018 @item --LINK=@var{name}
9019 @cindex @option{--LINK=} (@command{gnatlink})
9020 @var{name} is the name of the linker to be invoked. This is especially
9021 useful in mixed language programs since languages such as C++ require
9022 their own linker to be used. When this switch is omitted, the default
9023 name for the linker is @command{gcc}. When this switch is used, the
9024 specified linker is called instead of @command{gcc} with exactly the same
9025 parameters that would have been passed to @command{gcc} so if the desired
9026 linker requires different parameters it is necessary to use a wrapper
9027 script that massages the parameters before invoking the real linker. It
9028 may be useful to control the exact invocation by using the verbose
9034 @item /DEBUG=TRACEBACK
9035 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
9036 This qualifier causes sufficient information to be included in the
9037 executable file to allow a traceback, but does not include the full
9038 symbol information needed by the debugger.
9040 @item /IDENTIFICATION="<string>"
9041 @code{"<string>"} specifies the string to be stored in the image file
9042 identification field in the image header.
9043 It overrides any pragma @code{Ident} specified string.
9045 @item /NOINHIBIT-EXEC
9046 Generate the executable file even if there are linker warnings.
9048 @item /NOSTART_FILES
9049 Don't link in the object file containing the ``main'' transfer address.
9050 Used when linking with a foreign language main program compiled with an
9054 Prefer linking with object libraries over sharable images, even without
9060 @node The GNAT Make Program gnatmake
9061 @chapter The GNAT Make Program @command{gnatmake}
9065 * Running gnatmake::
9066 * Switches for gnatmake::
9067 * Mode Switches for gnatmake::
9068 * Notes on the Command Line::
9069 * How gnatmake Works::
9070 * Examples of gnatmake Usage::
9073 A typical development cycle when working on an Ada program consists of
9074 the following steps:
9078 Edit some sources to fix bugs.
9084 Compile all sources affected.
9094 The third step can be tricky, because not only do the modified files
9095 @cindex Dependency rules
9096 have to be compiled, but any files depending on these files must also be
9097 recompiled. The dependency rules in Ada can be quite complex, especially
9098 in the presence of overloading, @code{use} clauses, generics and inlined
9101 @command{gnatmake} automatically takes care of the third and fourth steps
9102 of this process. It determines which sources need to be compiled,
9103 compiles them, and binds and links the resulting object files.
9105 Unlike some other Ada make programs, the dependencies are always
9106 accurately recomputed from the new sources. The source based approach of
9107 the GNAT compilation model makes this possible. This means that if
9108 changes to the source program cause corresponding changes in
9109 dependencies, they will always be tracked exactly correctly by
9112 @node Running gnatmake
9113 @section Running @command{gnatmake}
9116 The usual form of the @command{gnatmake} command is
9119 $ gnatmake @ovar{switches} @var{file_name}
9120 @ovar{file_names} @ovar{mode_switches}
9124 The only required argument is one @var{file_name}, which specifies
9125 a compilation unit that is a main program. Several @var{file_names} can be
9126 specified: this will result in several executables being built.
9127 If @code{switches} are present, they can be placed before the first
9128 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
9129 If @var{mode_switches} are present, they must always be placed after
9130 the last @var{file_name} and all @code{switches}.
9132 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
9133 extension may be omitted from the @var{file_name} arguments. However, if
9134 you are using non-standard extensions, then it is required that the
9135 extension be given. A relative or absolute directory path can be
9136 specified in a @var{file_name}, in which case, the input source file will
9137 be searched for in the specified directory only. Otherwise, the input
9138 source file will first be searched in the directory where
9139 @command{gnatmake} was invoked and if it is not found, it will be search on
9140 the source path of the compiler as described in
9141 @ref{Search Paths and the Run-Time Library (RTL)}.
9143 All @command{gnatmake} output (except when you specify
9144 @option{^-M^/DEPENDENCIES_LIST^}) is to
9145 @file{stderr}. The output produced by the
9146 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
9149 @node Switches for gnatmake
9150 @section Switches for @command{gnatmake}
9153 You may specify any of the following switches to @command{gnatmake}:
9159 @cindex @option{--version} @command{gnatmake}
9160 Display Copyright and version, then exit disregarding all other options.
9163 @cindex @option{--help} @command{gnatmake}
9164 If @option{--version} was not used, display usage, then exit disregarding
9168 @item --GCC=@var{compiler_name}
9169 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
9170 Program used for compiling. The default is `@command{gcc}'. You need to use
9171 quotes around @var{compiler_name} if @code{compiler_name} contains
9172 spaces or other separator characters. As an example @option{--GCC="foo -x
9173 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
9174 compiler. A limitation of this syntax is that the name and path name of
9175 the executable itself must not include any embedded spaces. Note that
9176 switch @option{-c} is always inserted after your command name. Thus in the
9177 above example the compiler command that will be used by @command{gnatmake}
9178 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
9179 used, only the last @var{compiler_name} is taken into account. However,
9180 all the additional switches are also taken into account. Thus,
9181 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9182 @option{--GCC="bar -x -y -z -t"}.
9184 @item --GNATBIND=@var{binder_name}
9185 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
9186 Program used for binding. The default is `@code{gnatbind}'. You need to
9187 use quotes around @var{binder_name} if @var{binder_name} contains spaces
9188 or other separator characters. As an example @option{--GNATBIND="bar -x
9189 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
9190 binder. Binder switches that are normally appended by @command{gnatmake}
9191 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
9192 A limitation of this syntax is that the name and path name of the executable
9193 itself must not include any embedded spaces.
9195 @item --GNATLINK=@var{linker_name}
9196 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
9197 Program used for linking. The default is `@command{gnatlink}'. You need to
9198 use quotes around @var{linker_name} if @var{linker_name} contains spaces
9199 or other separator characters. As an example @option{--GNATLINK="lan -x
9200 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
9201 linker. Linker switches that are normally appended by @command{gnatmake} to
9202 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
9203 A limitation of this syntax is that the name and path name of the executable
9204 itself must not include any embedded spaces.
9208 @item ^-a^/ALL_FILES^
9209 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
9210 Consider all files in the make process, even the GNAT internal system
9211 files (for example, the predefined Ada library files), as well as any
9212 locked files. Locked files are files whose ALI file is write-protected.
9214 @command{gnatmake} does not check these files,
9215 because the assumption is that the GNAT internal files are properly up
9216 to date, and also that any write protected ALI files have been properly
9217 installed. Note that if there is an installation problem, such that one
9218 of these files is not up to date, it will be properly caught by the
9220 You may have to specify this switch if you are working on GNAT
9221 itself. The switch @option{^-a^/ALL_FILES^} is also useful
9222 in conjunction with @option{^-f^/FORCE_COMPILE^}
9223 if you need to recompile an entire application,
9224 including run-time files, using special configuration pragmas,
9225 such as a @code{Normalize_Scalars} pragma.
9228 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
9231 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
9234 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
9237 @item ^-b^/ACTIONS=BIND^
9238 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
9239 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
9240 compilation and binding, but no link.
9241 Can be combined with @option{^-l^/ACTIONS=LINK^}
9242 to do binding and linking. When not combined with
9243 @option{^-c^/ACTIONS=COMPILE^}
9244 all the units in the closure of the main program must have been previously
9245 compiled and must be up to date. The root unit specified by @var{file_name}
9246 may be given without extension, with the source extension or, if no GNAT
9247 Project File is specified, with the ALI file extension.
9249 @item ^-c^/ACTIONS=COMPILE^
9250 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
9251 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
9252 is also specified. Do not perform linking, except if both
9253 @option{^-b^/ACTIONS=BIND^} and
9254 @option{^-l^/ACTIONS=LINK^} are also specified.
9255 If the root unit specified by @var{file_name} is not a main unit, this is the
9256 default. Otherwise @command{gnatmake} will attempt binding and linking
9257 unless all objects are up to date and the executable is more recent than
9261 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
9262 Use a temporary mapping file. A mapping file is a way to communicate to the
9263 compiler two mappings: from unit names to file names (without any directory
9264 information) and from file names to path names (with full directory
9265 information). These mappings are used by the compiler to short-circuit the path
9266 search. When @command{gnatmake} is invoked with this switch, it will create
9267 a temporary mapping file, initially populated by the project manager,
9268 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
9269 Each invocation of the compiler will add the newly accessed sources to the
9270 mapping file. This will improve the source search during the next invocation
9273 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
9274 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
9275 Use a specific mapping file. The file, specified as a path name (absolute or
9276 relative) by this switch, should already exist, otherwise the switch is
9277 ineffective. The specified mapping file will be communicated to the compiler.
9278 This switch is not compatible with a project file
9279 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9280 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9282 @item ^-d^/DISPLAY_PROGRESS^
9283 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9284 Display progress for each source, up to date or not, as a single line
9287 completed x out of y (zz%)
9290 If the file needs to be compiled this is displayed after the invocation of
9291 the compiler. These lines are displayed even in quiet output mode.
9293 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9294 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9295 Put all object files and ALI file in directory @var{dir}.
9296 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9297 and ALI files go in the current working directory.
9299 This switch cannot be used when using a project file.
9303 @cindex @option{-eL} (@command{gnatmake})
9304 Follow all symbolic links when processing project files.
9307 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9308 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9309 Output the commands for the compiler, the binder and the linker
9310 on ^standard output^SYS$OUTPUT^,
9311 instead of ^standard error^SYS$ERROR^.
9313 @item ^-f^/FORCE_COMPILE^
9314 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9315 Force recompilations. Recompile all sources, even though some object
9316 files may be up to date, but don't recompile predefined or GNAT internal
9317 files or locked files (files with a write-protected ALI file),
9318 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9320 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9321 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9322 When using project files, if some errors or warnings are detected during
9323 parsing and verbose mode is not in effect (no use of switch
9324 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9325 file, rather than its simple file name.
9328 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9329 Enable debugging. This switch is simply passed to the compiler and to the
9332 @item ^-i^/IN_PLACE^
9333 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9334 In normal mode, @command{gnatmake} compiles all object files and ALI files
9335 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9336 then instead object files and ALI files that already exist are overwritten
9337 in place. This means that once a large project is organized into separate
9338 directories in the desired manner, then @command{gnatmake} will automatically
9339 maintain and update this organization. If no ALI files are found on the
9340 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9341 the new object and ALI files are created in the
9342 directory containing the source being compiled. If another organization
9343 is desired, where objects and sources are kept in different directories,
9344 a useful technique is to create dummy ALI files in the desired directories.
9345 When detecting such a dummy file, @command{gnatmake} will be forced to
9346 recompile the corresponding source file, and it will be put the resulting
9347 object and ALI files in the directory where it found the dummy file.
9349 @item ^-j^/PROCESSES=^@var{n}
9350 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9351 @cindex Parallel make
9352 Use @var{n} processes to carry out the (re)compilations. On a
9353 multiprocessor machine compilations will occur in parallel. In the
9354 event of compilation errors, messages from various compilations might
9355 get interspersed (but @command{gnatmake} will give you the full ordered
9356 list of failing compiles at the end). If this is problematic, rerun
9357 the make process with n set to 1 to get a clean list of messages.
9359 @item ^-k^/CONTINUE_ON_ERROR^
9360 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9361 Keep going. Continue as much as possible after a compilation error. To
9362 ease the programmer's task in case of compilation errors, the list of
9363 sources for which the compile fails is given when @command{gnatmake}
9366 If @command{gnatmake} is invoked with several @file{file_names} and with this
9367 switch, if there are compilation errors when building an executable,
9368 @command{gnatmake} will not attempt to build the following executables.
9370 @item ^-l^/ACTIONS=LINK^
9371 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9372 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9373 and linking. Linking will not be performed if combined with
9374 @option{^-c^/ACTIONS=COMPILE^}
9375 but not with @option{^-b^/ACTIONS=BIND^}.
9376 When not combined with @option{^-b^/ACTIONS=BIND^}
9377 all the units in the closure of the main program must have been previously
9378 compiled and must be up to date, and the main program needs to have been bound.
9379 The root unit specified by @var{file_name}
9380 may be given without extension, with the source extension or, if no GNAT
9381 Project File is specified, with the ALI file extension.
9383 @item ^-m^/MINIMAL_RECOMPILATION^
9384 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9385 Specify that the minimum necessary amount of recompilations
9386 be performed. In this mode @command{gnatmake} ignores time
9387 stamp differences when the only
9388 modifications to a source file consist in adding/removing comments,
9389 empty lines, spaces or tabs. This means that if you have changed the
9390 comments in a source file or have simply reformatted it, using this
9391 switch will tell @command{gnatmake} not to recompile files that depend on it
9392 (provided other sources on which these files depend have undergone no
9393 semantic modifications). Note that the debugging information may be
9394 out of date with respect to the sources if the @option{-m} switch causes
9395 a compilation to be switched, so the use of this switch represents a
9396 trade-off between compilation time and accurate debugging information.
9398 @item ^-M^/DEPENDENCIES_LIST^
9399 @cindex Dependencies, producing list
9400 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9401 Check if all objects are up to date. If they are, output the object
9402 dependences to @file{stdout} in a form that can be directly exploited in
9403 a @file{Makefile}. By default, each source file is prefixed with its
9404 (relative or absolute) directory name. This name is whatever you
9405 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9406 and @option{^-I^/SEARCH^} switches. If you use
9407 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9408 @option{^-q^/QUIET^}
9409 (see below), only the source file names,
9410 without relative paths, are output. If you just specify the
9411 @option{^-M^/DEPENDENCIES_LIST^}
9412 switch, dependencies of the GNAT internal system files are omitted. This
9413 is typically what you want. If you also specify
9414 the @option{^-a^/ALL_FILES^} switch,
9415 dependencies of the GNAT internal files are also listed. Note that
9416 dependencies of the objects in external Ada libraries (see switch
9417 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9420 @item ^-n^/DO_OBJECT_CHECK^
9421 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9422 Don't compile, bind, or link. Checks if all objects are up to date.
9423 If they are not, the full name of the first file that needs to be
9424 recompiled is printed.
9425 Repeated use of this option, followed by compiling the indicated source
9426 file, will eventually result in recompiling all required units.
9428 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9429 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9430 Output executable name. The name of the final executable program will be
9431 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9432 name for the executable will be the name of the input file in appropriate form
9433 for an executable file on the host system.
9435 This switch cannot be used when invoking @command{gnatmake} with several
9438 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9439 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9440 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9441 automatically missing object directories, library directories and exec
9444 @item ^-P^/PROJECT_FILE=^@var{project}
9445 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9446 Use project file @var{project}. Only one such switch can be used.
9447 @xref{gnatmake and Project Files}.
9450 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9451 Quiet. When this flag is not set, the commands carried out by
9452 @command{gnatmake} are displayed.
9454 @item ^-s^/SWITCH_CHECK/^
9455 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9456 Recompile if compiler switches have changed since last compilation.
9457 All compiler switches but -I and -o are taken into account in the
9459 orders between different ``first letter'' switches are ignored, but
9460 orders between same switches are taken into account. For example,
9461 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9462 is equivalent to @option{-O -g}.
9464 This switch is recommended when Integrated Preprocessing is used.
9467 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9468 Unique. Recompile at most the main files. It implies -c. Combined with
9469 -f, it is equivalent to calling the compiler directly. Note that using
9470 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9471 (@pxref{Project Files and Main Subprograms}).
9473 @item ^-U^/ALL_PROJECTS^
9474 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9475 When used without a project file or with one or several mains on the command
9476 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9477 on the command line, all sources of all project files are checked and compiled
9478 if not up to date, and libraries are rebuilt, if necessary.
9481 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9482 Verbose. Display the reason for all recompilations @command{gnatmake}
9483 decides are necessary, with the highest verbosity level.
9485 @item ^-vl^/LOW_VERBOSITY^
9486 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9487 Verbosity level Low. Display fewer lines than in verbosity Medium.
9489 @item ^-vm^/MEDIUM_VERBOSITY^
9490 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9491 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9493 @item ^-vh^/HIGH_VERBOSITY^
9494 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9495 Verbosity level High. Equivalent to ^-v^/REASONS^.
9497 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9498 Indicate the verbosity of the parsing of GNAT project files.
9499 @xref{Switches Related to Project Files}.
9501 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9502 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9503 Indicate that sources that are not part of any Project File may be compiled.
9504 Normally, when using Project Files, only sources that are part of a Project
9505 File may be compile. When this switch is used, a source outside of all Project
9506 Files may be compiled. The ALI file and the object file will be put in the
9507 object directory of the main Project. The compilation switches used will only
9508 be those specified on the command line. Even when
9509 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9510 command line need to be sources of a project file.
9512 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9513 Indicate that external variable @var{name} has the value @var{value}.
9514 The Project Manager will use this value for occurrences of
9515 @code{external(name)} when parsing the project file.
9516 @xref{Switches Related to Project Files}.
9519 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9520 No main subprogram. Bind and link the program even if the unit name
9521 given on the command line is a package name. The resulting executable
9522 will execute the elaboration routines of the package and its closure,
9523 then the finalization routines.
9528 @item @command{gcc} @asis{switches}
9530 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9531 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9534 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9535 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9536 automatically treated as a compiler switch, and passed on to all
9537 compilations that are carried out.
9542 Source and library search path switches:
9546 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9547 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9548 When looking for source files also look in directory @var{dir}.
9549 The order in which source files search is undertaken is
9550 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9552 @item ^-aL^/SKIP_MISSING=^@var{dir}
9553 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9554 Consider @var{dir} as being an externally provided Ada library.
9555 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9556 files have been located in directory @var{dir}. This allows you to have
9557 missing bodies for the units in @var{dir} and to ignore out of date bodies
9558 for the same units. You still need to specify
9559 the location of the specs for these units by using the switches
9560 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9561 or @option{^-I^/SEARCH=^@var{dir}}.
9562 Note: this switch is provided for compatibility with previous versions
9563 of @command{gnatmake}. The easier method of causing standard libraries
9564 to be excluded from consideration is to write-protect the corresponding
9567 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9568 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9569 When searching for library and object files, look in directory
9570 @var{dir}. The order in which library files are searched is described in
9571 @ref{Search Paths for gnatbind}.
9573 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9574 @cindex Search paths, for @command{gnatmake}
9575 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9576 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9577 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9579 @item ^-I^/SEARCH=^@var{dir}
9580 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9581 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9582 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9584 @item ^-I-^/NOCURRENT_DIRECTORY^
9585 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9586 @cindex Source files, suppressing search
9587 Do not look for source files in the directory containing the source
9588 file named in the command line.
9589 Do not look for ALI or object files in the directory
9590 where @command{gnatmake} was invoked.
9592 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9593 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9594 @cindex Linker libraries
9595 Add directory @var{dir} to the list of directories in which the linker
9596 will search for libraries. This is equivalent to
9597 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9599 Furthermore, under Windows, the sources pointed to by the libraries path
9600 set in the registry are not searched for.
9604 @cindex @option{-nostdinc} (@command{gnatmake})
9605 Do not look for source files in the system default directory.
9608 @cindex @option{-nostdlib} (@command{gnatmake})
9609 Do not look for library files in the system default directory.
9611 @item --RTS=@var{rts-path}
9612 @cindex @option{--RTS} (@command{gnatmake})
9613 Specifies the default location of the runtime library. GNAT looks for the
9615 in the following directories, and stops as soon as a valid runtime is found
9616 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9617 @file{ada_object_path} present):
9620 @item <current directory>/$rts_path
9622 @item <default-search-dir>/$rts_path
9624 @item <default-search-dir>/rts-$rts_path
9628 The selected path is handled like a normal RTS path.
9632 @node Mode Switches for gnatmake
9633 @section Mode Switches for @command{gnatmake}
9636 The mode switches (referred to as @code{mode_switches}) allow the
9637 inclusion of switches that are to be passed to the compiler itself, the
9638 binder or the linker. The effect of a mode switch is to cause all
9639 subsequent switches up to the end of the switch list, or up to the next
9640 mode switch, to be interpreted as switches to be passed on to the
9641 designated component of GNAT.
9645 @item -cargs @var{switches}
9646 @cindex @option{-cargs} (@command{gnatmake})
9647 Compiler switches. Here @var{switches} is a list of switches
9648 that are valid switches for @command{gcc}. They will be passed on to
9649 all compile steps performed by @command{gnatmake}.
9651 @item -bargs @var{switches}
9652 @cindex @option{-bargs} (@command{gnatmake})
9653 Binder switches. Here @var{switches} is a list of switches
9654 that are valid switches for @code{gnatbind}. They will be passed on to
9655 all bind steps performed by @command{gnatmake}.
9657 @item -largs @var{switches}
9658 @cindex @option{-largs} (@command{gnatmake})
9659 Linker switches. Here @var{switches} is a list of switches
9660 that are valid switches for @command{gnatlink}. They will be passed on to
9661 all link steps performed by @command{gnatmake}.
9663 @item -margs @var{switches}
9664 @cindex @option{-margs} (@command{gnatmake})
9665 Make switches. The switches are directly interpreted by @command{gnatmake},
9666 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9670 @node Notes on the Command Line
9671 @section Notes on the Command Line
9674 This section contains some additional useful notes on the operation
9675 of the @command{gnatmake} command.
9679 @cindex Recompilation, by @command{gnatmake}
9680 If @command{gnatmake} finds no ALI files, it recompiles the main program
9681 and all other units required by the main program.
9682 This means that @command{gnatmake}
9683 can be used for the initial compile, as well as during subsequent steps of
9684 the development cycle.
9687 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9688 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9689 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9693 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9694 is used to specify both source and
9695 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9696 instead if you just want to specify
9697 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9698 if you want to specify library paths
9702 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9703 This may conveniently be used to exclude standard libraries from
9704 consideration and in particular it means that the use of the
9705 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9706 unless @option{^-a^/ALL_FILES^} is also specified.
9709 @command{gnatmake} has been designed to make the use of Ada libraries
9710 particularly convenient. Assume you have an Ada library organized
9711 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9712 of your Ada compilation units,
9713 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9714 specs of these units, but no bodies. Then to compile a unit
9715 stored in @code{main.adb}, which uses this Ada library you would just type
9719 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9722 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9723 /SKIP_MISSING=@i{[OBJ_DIR]} main
9728 Using @command{gnatmake} along with the
9729 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9730 switch provides a mechanism for avoiding unnecessary recompilations. Using
9732 you can update the comments/format of your
9733 source files without having to recompile everything. Note, however, that
9734 adding or deleting lines in a source files may render its debugging
9735 info obsolete. If the file in question is a spec, the impact is rather
9736 limited, as that debugging info will only be useful during the
9737 elaboration phase of your program. For bodies the impact can be more
9738 significant. In all events, your debugger will warn you if a source file
9739 is more recent than the corresponding object, and alert you to the fact
9740 that the debugging information may be out of date.
9743 @node How gnatmake Works
9744 @section How @command{gnatmake} Works
9747 Generally @command{gnatmake} automatically performs all necessary
9748 recompilations and you don't need to worry about how it works. However,
9749 it may be useful to have some basic understanding of the @command{gnatmake}
9750 approach and in particular to understand how it uses the results of
9751 previous compilations without incorrectly depending on them.
9753 First a definition: an object file is considered @dfn{up to date} if the
9754 corresponding ALI file exists and if all the source files listed in the
9755 dependency section of this ALI file have time stamps matching those in
9756 the ALI file. This means that neither the source file itself nor any
9757 files that it depends on have been modified, and hence there is no need
9758 to recompile this file.
9760 @command{gnatmake} works by first checking if the specified main unit is up
9761 to date. If so, no compilations are required for the main unit. If not,
9762 @command{gnatmake} compiles the main program to build a new ALI file that
9763 reflects the latest sources. Then the ALI file of the main unit is
9764 examined to find all the source files on which the main program depends,
9765 and @command{gnatmake} recursively applies the above procedure on all these
9768 This process ensures that @command{gnatmake} only trusts the dependencies
9769 in an existing ALI file if they are known to be correct. Otherwise it
9770 always recompiles to determine a new, guaranteed accurate set of
9771 dependencies. As a result the program is compiled ``upside down'' from what may
9772 be more familiar as the required order of compilation in some other Ada
9773 systems. In particular, clients are compiled before the units on which
9774 they depend. The ability of GNAT to compile in any order is critical in
9775 allowing an order of compilation to be chosen that guarantees that
9776 @command{gnatmake} will recompute a correct set of new dependencies if
9779 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9780 imported by several of the executables, it will be recompiled at most once.
9782 Note: when using non-standard naming conventions
9783 (@pxref{Using Other File Names}), changing through a configuration pragmas
9784 file the version of a source and invoking @command{gnatmake} to recompile may
9785 have no effect, if the previous version of the source is still accessible
9786 by @command{gnatmake}. It may be necessary to use the switch
9787 ^-f^/FORCE_COMPILE^.
9789 @node Examples of gnatmake Usage
9790 @section Examples of @command{gnatmake} Usage
9793 @item gnatmake hello.adb
9794 Compile all files necessary to bind and link the main program
9795 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9796 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9798 @item gnatmake main1 main2 main3
9799 Compile all files necessary to bind and link the main programs
9800 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9801 (containing unit @code{Main2}) and @file{main3.adb}
9802 (containing unit @code{Main3}) and bind and link the resulting object files
9803 to generate three executable files @file{^main1^MAIN1.EXE^},
9804 @file{^main2^MAIN2.EXE^}
9805 and @file{^main3^MAIN3.EXE^}.
9808 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9812 @item gnatmake Main_Unit /QUIET
9813 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9814 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9816 Compile all files necessary to bind and link the main program unit
9817 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9818 be done with optimization level 2 and the order of elaboration will be
9819 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9820 displaying commands it is executing.
9823 @c *************************
9824 @node Improving Performance
9825 @chapter Improving Performance
9826 @cindex Improving performance
9829 This chapter presents several topics related to program performance.
9830 It first describes some of the tradeoffs that need to be considered
9831 and some of the techniques for making your program run faster.
9832 It then documents the @command{gnatelim} tool and unused subprogram/data
9833 elimination feature, which can reduce the size of program executables.
9835 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9836 driver (see @ref{The GNAT Driver and Project Files}).
9840 * Performance Considerations::
9841 * Text_IO Suggestions::
9842 * Reducing Size of Ada Executables with gnatelim::
9843 * Reducing Size of Executables with unused subprogram/data elimination::
9847 @c *****************************
9848 @node Performance Considerations
9849 @section Performance Considerations
9852 The GNAT system provides a number of options that allow a trade-off
9857 performance of the generated code
9860 speed of compilation
9863 minimization of dependences and recompilation
9866 the degree of run-time checking.
9870 The defaults (if no options are selected) aim at improving the speed
9871 of compilation and minimizing dependences, at the expense of performance
9872 of the generated code:
9879 no inlining of subprogram calls
9882 all run-time checks enabled except overflow and elaboration checks
9886 These options are suitable for most program development purposes. This
9887 chapter describes how you can modify these choices, and also provides
9888 some guidelines on debugging optimized code.
9891 * Controlling Run-Time Checks::
9892 * Use of Restrictions::
9893 * Optimization Levels::
9894 * Debugging Optimized Code::
9895 * Inlining of Subprograms::
9896 * Other Optimization Switches::
9897 * Optimization and Strict Aliasing::
9900 * Coverage Analysis::
9904 @node Controlling Run-Time Checks
9905 @subsection Controlling Run-Time Checks
9908 By default, GNAT generates all run-time checks, except integer overflow
9909 checks, stack overflow checks, and checks for access before elaboration on
9910 subprogram calls. The latter are not required in default mode, because all
9911 necessary checking is done at compile time.
9912 @cindex @option{-gnatp} (@command{gcc})
9913 @cindex @option{-gnato} (@command{gcc})
9914 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9915 be modified. @xref{Run-Time Checks}.
9917 Our experience is that the default is suitable for most development
9920 We treat integer overflow specially because these
9921 are quite expensive and in our experience are not as important as other
9922 run-time checks in the development process. Note that division by zero
9923 is not considered an overflow check, and divide by zero checks are
9924 generated where required by default.
9926 Elaboration checks are off by default, and also not needed by default, since
9927 GNAT uses a static elaboration analysis approach that avoids the need for
9928 run-time checking. This manual contains a full chapter discussing the issue
9929 of elaboration checks, and if the default is not satisfactory for your use,
9930 you should read this chapter.
9932 For validity checks, the minimal checks required by the Ada Reference
9933 Manual (for case statements and assignments to array elements) are on
9934 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9935 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9936 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9937 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9938 are also suppressed entirely if @option{-gnatp} is used.
9940 @cindex Overflow checks
9941 @cindex Checks, overflow
9944 @cindex pragma Suppress
9945 @cindex pragma Unsuppress
9946 Note that the setting of the switches controls the default setting of
9947 the checks. They may be modified using either @code{pragma Suppress} (to
9948 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9949 checks) in the program source.
9951 @node Use of Restrictions
9952 @subsection Use of Restrictions
9955 The use of pragma Restrictions allows you to control which features are
9956 permitted in your program. Apart from the obvious point that if you avoid
9957 relatively expensive features like finalization (enforceable by the use
9958 of pragma Restrictions (No_Finalization), the use of this pragma does not
9959 affect the generated code in most cases.
9961 One notable exception to this rule is that the possibility of task abort
9962 results in some distributed overhead, particularly if finalization or
9963 exception handlers are used. The reason is that certain sections of code
9964 have to be marked as non-abortable.
9966 If you use neither the @code{abort} statement, nor asynchronous transfer
9967 of control (@code{select @dots{} then abort}), then this distributed overhead
9968 is removed, which may have a general positive effect in improving
9969 overall performance. Especially code involving frequent use of tasking
9970 constructs and controlled types will show much improved performance.
9971 The relevant restrictions pragmas are
9973 @smallexample @c ada
9974 pragma Restrictions (No_Abort_Statements);
9975 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9979 It is recommended that these restriction pragmas be used if possible. Note
9980 that this also means that you can write code without worrying about the
9981 possibility of an immediate abort at any point.
9983 @node Optimization Levels
9984 @subsection Optimization Levels
9985 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9988 Without any optimization ^option,^qualifier,^
9989 the compiler's goal is to reduce the cost of
9990 compilation and to make debugging produce the expected results.
9991 Statements are independent: if you stop the program with a breakpoint between
9992 statements, you can then assign a new value to any variable or change
9993 the program counter to any other statement in the subprogram and get exactly
9994 the results you would expect from the source code.
9996 Turning on optimization makes the compiler attempt to improve the
9997 performance and/or code size at the expense of compilation time and
9998 possibly the ability to debug the program.
10000 If you use multiple
10001 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
10002 the last such option is the one that is effective.
10005 The default is optimization off. This results in the fastest compile
10006 times, but GNAT makes absolutely no attempt to optimize, and the
10007 generated programs are considerably larger and slower than when
10008 optimization is enabled. You can use the
10010 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
10011 @option{-O2}, @option{-O3}, and @option{-Os})
10014 @code{OPTIMIZE} qualifier
10016 to @command{gcc} to control the optimization level:
10019 @item ^-O0^/OPTIMIZE=NONE^
10020 No optimization (the default);
10021 generates unoptimized code but has
10022 the fastest compilation time.
10024 Note that many other compilers do fairly extensive optimization
10025 even if ``no optimization'' is specified. With gcc, it is
10026 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
10027 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
10028 really does mean no optimization at all. This difference between
10029 gcc and other compilers should be kept in mind when doing
10030 performance comparisons.
10032 @item ^-O1^/OPTIMIZE=SOME^
10033 Moderate optimization;
10034 optimizes reasonably well but does not
10035 degrade compilation time significantly.
10037 @item ^-O2^/OPTIMIZE=ALL^
10039 @itemx /OPTIMIZE=DEVELOPMENT
10042 generates highly optimized code and has
10043 the slowest compilation time.
10045 @item ^-O3^/OPTIMIZE=INLINING^
10046 Full optimization as in @option{-O2},
10047 and also attempts automatic inlining of small
10048 subprograms within a unit (@pxref{Inlining of Subprograms}).
10050 @item ^-Os^/OPTIMIZE=SPACE^
10051 Optimize space usage of resulting program.
10055 Higher optimization levels perform more global transformations on the
10056 program and apply more expensive analysis algorithms in order to generate
10057 faster and more compact code. The price in compilation time, and the
10058 resulting improvement in execution time,
10059 both depend on the particular application and the hardware environment.
10060 You should experiment to find the best level for your application.
10062 Since the precise set of optimizations done at each level will vary from
10063 release to release (and sometime from target to target), it is best to think
10064 of the optimization settings in general terms.
10065 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
10066 the GNU Compiler Collection (GCC)}, for details about
10067 ^the @option{-O} settings and a number of @option{-f} options that^how to^
10068 individually enable or disable specific optimizations.
10070 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
10071 been tested extensively at all optimization levels. There are some bugs
10072 which appear only with optimization turned on, but there have also been
10073 bugs which show up only in @emph{unoptimized} code. Selecting a lower
10074 level of optimization does not improve the reliability of the code
10075 generator, which in practice is highly reliable at all optimization
10078 Note regarding the use of @option{-O3}: The use of this optimization level
10079 is generally discouraged with GNAT, since it often results in larger
10080 executables which run more slowly. See further discussion of this point
10081 in @ref{Inlining of Subprograms}.
10083 @node Debugging Optimized Code
10084 @subsection Debugging Optimized Code
10085 @cindex Debugging optimized code
10086 @cindex Optimization and debugging
10089 Although it is possible to do a reasonable amount of debugging at
10091 nonzero optimization levels,
10092 the higher the level the more likely that
10095 @option{/OPTIMIZE} settings other than @code{NONE},
10096 such settings will make it more likely that
10098 source-level constructs will have been eliminated by optimization.
10099 For example, if a loop is strength-reduced, the loop
10100 control variable may be completely eliminated and thus cannot be
10101 displayed in the debugger.
10102 This can only happen at @option{-O2} or @option{-O3}.
10103 Explicit temporary variables that you code might be eliminated at
10104 ^level^setting^ @option{-O1} or higher.
10106 The use of the @option{^-g^/DEBUG^} switch,
10107 @cindex @option{^-g^/DEBUG^} (@command{gcc})
10108 which is needed for source-level debugging,
10109 affects the size of the program executable on disk,
10110 and indeed the debugging information can be quite large.
10111 However, it has no effect on the generated code (and thus does not
10112 degrade performance)
10114 Since the compiler generates debugging tables for a compilation unit before
10115 it performs optimizations, the optimizing transformations may invalidate some
10116 of the debugging data. You therefore need to anticipate certain
10117 anomalous situations that may arise while debugging optimized code.
10118 These are the most common cases:
10122 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
10124 the PC bouncing back and forth in the code. This may result from any of
10125 the following optimizations:
10129 @i{Common subexpression elimination:} using a single instance of code for a
10130 quantity that the source computes several times. As a result you
10131 may not be able to stop on what looks like a statement.
10134 @i{Invariant code motion:} moving an expression that does not change within a
10135 loop, to the beginning of the loop.
10138 @i{Instruction scheduling:} moving instructions so as to
10139 overlap loads and stores (typically) with other code, or in
10140 general to move computations of values closer to their uses. Often
10141 this causes you to pass an assignment statement without the assignment
10142 happening and then later bounce back to the statement when the
10143 value is actually needed. Placing a breakpoint on a line of code
10144 and then stepping over it may, therefore, not always cause all the
10145 expected side-effects.
10149 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
10150 two identical pieces of code are merged and the program counter suddenly
10151 jumps to a statement that is not supposed to be executed, simply because
10152 it (and the code following) translates to the same thing as the code
10153 that @emph{was} supposed to be executed. This effect is typically seen in
10154 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
10155 a @code{break} in a C @code{^switch^switch^} statement.
10158 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
10159 There are various reasons for this effect:
10163 In a subprogram prologue, a parameter may not yet have been moved to its
10167 A variable may be dead, and its register re-used. This is
10168 probably the most common cause.
10171 As mentioned above, the assignment of a value to a variable may
10175 A variable may be eliminated entirely by value propagation or
10176 other means. In this case, GCC may incorrectly generate debugging
10177 information for the variable
10181 In general, when an unexpected value appears for a local variable or parameter
10182 you should first ascertain if that value was actually computed by
10183 your program, as opposed to being incorrectly reported by the debugger.
10185 array elements in an object designated by an access value
10186 are generally less of a problem, once you have ascertained that the access
10188 Typically, this means checking variables in the preceding code and in the
10189 calling subprogram to verify that the value observed is explainable from other
10190 values (one must apply the procedure recursively to those
10191 other values); or re-running the code and stopping a little earlier
10192 (perhaps before the call) and stepping to better see how the variable obtained
10193 the value in question; or continuing to step @emph{from} the point of the
10194 strange value to see if code motion had simply moved the variable's
10199 In light of such anomalies, a recommended technique is to use @option{-O0}
10200 early in the software development cycle, when extensive debugging capabilities
10201 are most needed, and then move to @option{-O1} and later @option{-O2} as
10202 the debugger becomes less critical.
10203 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
10204 a release management issue.
10206 Note that if you use @option{-g} you can then use the @command{strip} program
10207 on the resulting executable,
10208 which removes both debugging information and global symbols.
10211 @node Inlining of Subprograms
10212 @subsection Inlining of Subprograms
10215 A call to a subprogram in the current unit is inlined if all the
10216 following conditions are met:
10220 The optimization level is at least @option{-O1}.
10223 The called subprogram is suitable for inlining: It must be small enough
10224 and not contain something that @command{gcc} cannot support in inlined
10228 @cindex pragma Inline
10230 Either @code{pragma Inline} applies to the subprogram, or it is local
10231 to the unit and called once from within it, or it is small and automatic
10232 inlining (optimization level @option{-O3}) is specified.
10236 Calls to subprograms in @code{with}'ed units are normally not inlined.
10237 To achieve actual inlining (that is, replacement of the call by the code
10238 in the body of the subprogram), the following conditions must all be true.
10242 The optimization level is at least @option{-O1}.
10245 The called subprogram is suitable for inlining: It must be small enough
10246 and not contain something that @command{gcc} cannot support in inlined
10250 The call appears in a body (not in a package spec).
10253 There is a @code{pragma Inline} for the subprogram.
10256 @cindex @option{-gnatn} (@command{gcc})
10257 The @option{^-gnatn^/INLINE^} switch
10258 is used in the @command{gcc} command line
10261 Even if all these conditions are met, it may not be possible for
10262 the compiler to inline the call, due to the length of the body,
10263 or features in the body that make it impossible for the compiler
10264 to do the inlining.
10266 Note that specifying the @option{-gnatn} switch causes additional
10267 compilation dependencies. Consider the following:
10269 @smallexample @c ada
10289 With the default behavior (no @option{-gnatn} switch specified), the
10290 compilation of the @code{Main} procedure depends only on its own source,
10291 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10292 means that editing the body of @code{R} does not require recompiling
10295 On the other hand, the call @code{R.Q} is not inlined under these
10296 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10297 is compiled, the call will be inlined if the body of @code{Q} is small
10298 enough, but now @code{Main} depends on the body of @code{R} in
10299 @file{r.adb} as well as on the spec. This means that if this body is edited,
10300 the main program must be recompiled. Note that this extra dependency
10301 occurs whether or not the call is in fact inlined by @command{gcc}.
10303 The use of front end inlining with @option{-gnatN} generates similar
10304 additional dependencies.
10306 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10307 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10308 can be used to prevent
10309 all inlining. This switch overrides all other conditions and ensures
10310 that no inlining occurs. The extra dependences resulting from
10311 @option{-gnatn} will still be active, even if
10312 this switch is used to suppress the resulting inlining actions.
10314 @cindex @option{-fno-inline-functions} (@command{gcc})
10315 Note: The @option{-fno-inline-functions} switch can be used to prevent
10316 automatic inlining of small subprograms if @option{-O3} is used.
10318 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10319 Note: The @option{-fno-inline-functions-called-once} switch
10320 can be used to prevent inlining of subprograms local to the unit
10321 and called once from within it if @option{-O1} is used.
10323 Note regarding the use of @option{-O3}: There is no difference in inlining
10324 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10325 pragma @code{Inline} assuming the use of @option{-gnatn}
10326 or @option{-gnatN} (the switches that activate inlining). If you have used
10327 pragma @code{Inline} in appropriate cases, then it is usually much better
10328 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10329 in this case only has the effect of inlining subprograms you did not
10330 think should be inlined. We often find that the use of @option{-O3} slows
10331 down code by performing excessive inlining, leading to increased instruction
10332 cache pressure from the increased code size. So the bottom line here is
10333 that you should not automatically assume that @option{-O3} is better than
10334 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10335 it actually improves performance.
10337 @node Other Optimization Switches
10338 @subsection Other Optimization Switches
10339 @cindex Optimization Switches
10341 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10342 @command{gcc} optimization switches are potentially usable. These switches
10343 have not been extensively tested with GNAT but can generally be expected
10344 to work. Examples of switches in this category are
10345 @option{-funroll-loops} and
10346 the various target-specific @option{-m} options (in particular, it has been
10347 observed that @option{-march=pentium4} can significantly improve performance
10348 on appropriate machines). For full details of these switches, see
10349 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10350 the GNU Compiler Collection (GCC)}.
10352 @node Optimization and Strict Aliasing
10353 @subsection Optimization and Strict Aliasing
10355 @cindex Strict Aliasing
10356 @cindex No_Strict_Aliasing
10359 The strong typing capabilities of Ada allow an optimizer to generate
10360 efficient code in situations where other languages would be forced to
10361 make worst case assumptions preventing such optimizations. Consider
10362 the following example:
10364 @smallexample @c ada
10367 type Int1 is new Integer;
10368 type Int2 is new Integer;
10369 type Int1A is access Int1;
10370 type Int2A is access Int2;
10377 for J in Data'Range loop
10378 if Data (J) = Int1V.all then
10379 Int2V.all := Int2V.all + 1;
10388 In this example, since the variable @code{Int1V} can only access objects
10389 of type @code{Int1}, and @code{Int2V} can only access objects of type
10390 @code{Int2}, there is no possibility that the assignment to
10391 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10392 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10393 for all iterations of the loop and avoid the extra memory reference
10394 required to dereference it each time through the loop.
10396 This kind of optimization, called strict aliasing analysis, is
10397 triggered by specifying an optimization level of @option{-O2} or
10398 higher or @option{-Os} and allows @code{GNAT} to generate more efficient code
10399 when access values are involved.
10401 However, although this optimization is always correct in terms of
10402 the formal semantics of the Ada Reference Manual, difficulties can
10403 arise if features like @code{Unchecked_Conversion} are used to break
10404 the typing system. Consider the following complete program example:
10406 @smallexample @c ada
10409 type int1 is new integer;
10410 type int2 is new integer;
10411 type a1 is access int1;
10412 type a2 is access int2;
10417 function to_a2 (Input : a1) return a2;
10420 with Unchecked_Conversion;
10422 function to_a2 (Input : a1) return a2 is
10424 new Unchecked_Conversion (a1, a2);
10426 return to_a2u (Input);
10432 with Text_IO; use Text_IO;
10434 v1 : a1 := new int1;
10435 v2 : a2 := to_a2 (v1);
10439 put_line (int1'image (v1.all));
10445 This program prints out 0 in @option{-O0} or @option{-O1}
10446 mode, but it prints out 1 in @option{-O2} mode. That's
10447 because in strict aliasing mode, the compiler can and
10448 does assume that the assignment to @code{v2.all} could not
10449 affect the value of @code{v1.all}, since different types
10452 This behavior is not a case of non-conformance with the standard, since
10453 the Ada RM specifies that an unchecked conversion where the resulting
10454 bit pattern is not a correct value of the target type can result in an
10455 abnormal value and attempting to reference an abnormal value makes the
10456 execution of a program erroneous. That's the case here since the result
10457 does not point to an object of type @code{int2}. This means that the
10458 effect is entirely unpredictable.
10460 However, although that explanation may satisfy a language
10461 lawyer, in practice an applications programmer expects an
10462 unchecked conversion involving pointers to create true
10463 aliases and the behavior of printing 1 seems plain wrong.
10464 In this case, the strict aliasing optimization is unwelcome.
10466 Indeed the compiler recognizes this possibility, and the
10467 unchecked conversion generates a warning:
10470 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10471 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10472 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10476 Unfortunately the problem is recognized when compiling the body of
10477 package @code{p2}, but the actual "bad" code is generated while
10478 compiling the body of @code{m} and this latter compilation does not see
10479 the suspicious @code{Unchecked_Conversion}.
10481 As implied by the warning message, there are approaches you can use to
10482 avoid the unwanted strict aliasing optimization in a case like this.
10484 One possibility is to simply avoid the use of @option{-O2}, but
10485 that is a bit drastic, since it throws away a number of useful
10486 optimizations that do not involve strict aliasing assumptions.
10488 A less drastic approach is to compile the program using the
10489 option @option{-fno-strict-aliasing}. Actually it is only the
10490 unit containing the dereferencing of the suspicious pointer
10491 that needs to be compiled. So in this case, if we compile
10492 unit @code{m} with this switch, then we get the expected
10493 value of zero printed. Analyzing which units might need
10494 the switch can be painful, so a more reasonable approach
10495 is to compile the entire program with options @option{-O2}
10496 and @option{-fno-strict-aliasing}. If the performance is
10497 satisfactory with this combination of options, then the
10498 advantage is that the entire issue of possible "wrong"
10499 optimization due to strict aliasing is avoided.
10501 To avoid the use of compiler switches, the configuration
10502 pragma @code{No_Strict_Aliasing} with no parameters may be
10503 used to specify that for all access types, the strict
10504 aliasing optimization should be suppressed.
10506 However, these approaches are still overkill, in that they causes
10507 all manipulations of all access values to be deoptimized. A more
10508 refined approach is to concentrate attention on the specific
10509 access type identified as problematic.
10511 First, if a careful analysis of uses of the pointer shows
10512 that there are no possible problematic references, then
10513 the warning can be suppressed by bracketing the
10514 instantiation of @code{Unchecked_Conversion} to turn
10517 @smallexample @c ada
10518 pragma Warnings (Off);
10520 new Unchecked_Conversion (a1, a2);
10521 pragma Warnings (On);
10525 Of course that approach is not appropriate for this particular
10526 example, since indeed there is a problematic reference. In this
10527 case we can take one of two other approaches.
10529 The first possibility is to move the instantiation of unchecked
10530 conversion to the unit in which the type is declared. In
10531 this example, we would move the instantiation of
10532 @code{Unchecked_Conversion} from the body of package
10533 @code{p2} to the spec of package @code{p1}. Now the
10534 warning disappears. That's because any use of the
10535 access type knows there is a suspicious unchecked
10536 conversion, and the strict aliasing optimization
10537 is automatically suppressed for the type.
10539 If it is not practical to move the unchecked conversion to the same unit
10540 in which the destination access type is declared (perhaps because the
10541 source type is not visible in that unit), you may use pragma
10542 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10543 same declarative sequence as the declaration of the access type:
10545 @smallexample @c ada
10546 type a2 is access int2;
10547 pragma No_Strict_Aliasing (a2);
10551 Here again, the compiler now knows that the strict aliasing optimization
10552 should be suppressed for any reference to type @code{a2} and the
10553 expected behavior is obtained.
10555 Finally, note that although the compiler can generate warnings for
10556 simple cases of unchecked conversions, there are tricker and more
10557 indirect ways of creating type incorrect aliases which the compiler
10558 cannot detect. Examples are the use of address overlays and unchecked
10559 conversions involving composite types containing access types as
10560 components. In such cases, no warnings are generated, but there can
10561 still be aliasing problems. One safe coding practice is to forbid the
10562 use of address clauses for type overlaying, and to allow unchecked
10563 conversion only for primitive types. This is not really a significant
10564 restriction since any possible desired effect can be achieved by
10565 unchecked conversion of access values.
10567 The aliasing analysis done in strict aliasing mode can certainly
10568 have significant benefits. We have seen cases of large scale
10569 application code where the time is increased by up to 5% by turning
10570 this optimization off. If you have code that includes significant
10571 usage of unchecked conversion, you might want to just stick with
10572 @option{-O1} and avoid the entire issue. If you get adequate
10573 performance at this level of optimization level, that's probably
10574 the safest approach. If tests show that you really need higher
10575 levels of optimization, then you can experiment with @option{-O2}
10576 and @option{-O2 -fno-strict-aliasing} to see how much effect this
10577 has on size and speed of the code. If you really need to use
10578 @option{-O2} with strict aliasing in effect, then you should
10579 review any uses of unchecked conversion of access types,
10580 particularly if you are getting the warnings described above.
10583 @node Coverage Analysis
10584 @subsection Coverage Analysis
10587 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10588 the user to determine the distribution of execution time across a program,
10589 @pxref{Profiling} for details of usage.
10593 @node Text_IO Suggestions
10594 @section @code{Text_IO} Suggestions
10595 @cindex @code{Text_IO} and performance
10598 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10599 the requirement of maintaining page and line counts. If performance
10600 is critical, a recommendation is to use @code{Stream_IO} instead of
10601 @code{Text_IO} for volume output, since this package has less overhead.
10603 If @code{Text_IO} must be used, note that by default output to the standard
10604 output and standard error files is unbuffered (this provides better
10605 behavior when output statements are used for debugging, or if the
10606 progress of a program is observed by tracking the output, e.g. by
10607 using the Unix @command{tail -f} command to watch redirected output.
10609 If you are generating large volumes of output with @code{Text_IO} and
10610 performance is an important factor, use a designated file instead
10611 of the standard output file, or change the standard output file to
10612 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10616 @node Reducing Size of Ada Executables with gnatelim
10617 @section Reducing Size of Ada Executables with @code{gnatelim}
10621 This section describes @command{gnatelim}, a tool which detects unused
10622 subprograms and helps the compiler to create a smaller executable for your
10627 * Running gnatelim::
10628 * Correcting the List of Eliminate Pragmas::
10629 * Making Your Executables Smaller::
10630 * Summary of the gnatelim Usage Cycle::
10633 @node About gnatelim
10634 @subsection About @code{gnatelim}
10637 When a program shares a set of Ada
10638 packages with other programs, it may happen that this program uses
10639 only a fraction of the subprograms defined in these packages. The code
10640 created for these unused subprograms increases the size of the executable.
10642 @code{gnatelim} tracks unused subprograms in an Ada program and
10643 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10644 subprograms that are declared but never called. By placing the list of
10645 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10646 recompiling your program, you may decrease the size of its executable,
10647 because the compiler will not generate the code for 'eliminated' subprograms.
10648 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10649 information about this pragma.
10651 @code{gnatelim} needs as its input data the name of the main subprogram
10652 and a bind file for a main subprogram.
10654 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10655 the main subprogram. @code{gnatelim} can work with both Ada and C
10656 bind files; when both are present, it uses the Ada bind file.
10657 The following commands will build the program and create the bind file:
10660 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10661 $ gnatbind main_prog
10664 Note that @code{gnatelim} needs neither object nor ALI files.
10666 @node Running gnatelim
10667 @subsection Running @code{gnatelim}
10670 @code{gnatelim} has the following command-line interface:
10673 $ gnatelim @ovar{options} name
10677 @code{name} should be a name of a source file that contains the main subprogram
10678 of a program (partition).
10680 @code{gnatelim} has the following switches:
10685 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10686 Quiet mode: by default @code{gnatelim} outputs to the standard error
10687 stream the number of program units left to be processed. This option turns
10690 @item ^-v^/VERBOSE^
10691 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10692 Verbose mode: @code{gnatelim} version information is printed as Ada
10693 comments to the standard output stream. Also, in addition to the number of
10694 program units left @code{gnatelim} will output the name of the current unit
10698 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10699 Also look for subprograms from the GNAT run time that can be eliminated. Note
10700 that when @file{gnat.adc} is produced using this switch, the entire program
10701 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10703 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10704 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10705 When looking for source files also look in directory @var{dir}. Specifying
10706 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10707 sources in the current directory.
10709 @item ^-b^/BIND_FILE=^@var{bind_file}
10710 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10711 Specifies @var{bind_file} as the bind file to process. If not set, the name
10712 of the bind file is computed from the full expanded Ada name
10713 of a main subprogram.
10715 @item ^-C^/CONFIG_FILE=^@var{config_file}
10716 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10717 Specifies a file @var{config_file} that contains configuration pragmas. The
10718 file must be specified with full path.
10720 @item ^--GCC^/COMPILER^=@var{compiler_name}
10721 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10722 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10723 available on the path.
10725 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10726 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10727 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10728 available on the path.
10732 @code{gnatelim} sends its output to the standard output stream, and all the
10733 tracing and debug information is sent to the standard error stream.
10734 In order to produce a proper GNAT configuration file
10735 @file{gnat.adc}, redirection must be used:
10739 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10742 $ gnatelim main_prog.adb > gnat.adc
10751 $ gnatelim main_prog.adb >> gnat.adc
10755 in order to append the @code{gnatelim} output to the existing contents of
10759 @node Correcting the List of Eliminate Pragmas
10760 @subsection Correcting the List of Eliminate Pragmas
10763 In some rare cases @code{gnatelim} may try to eliminate
10764 subprograms that are actually called in the program. In this case, the
10765 compiler will generate an error message of the form:
10768 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10772 You will need to manually remove the wrong @code{Eliminate} pragmas from
10773 the @file{gnat.adc} file. You should recompile your program
10774 from scratch after that, because you need a consistent @file{gnat.adc} file
10775 during the entire compilation.
10777 @node Making Your Executables Smaller
10778 @subsection Making Your Executables Smaller
10781 In order to get a smaller executable for your program you now have to
10782 recompile the program completely with the new @file{gnat.adc} file
10783 created by @code{gnatelim} in your current directory:
10786 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10790 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10791 recompile everything
10792 with the set of pragmas @code{Eliminate} that you have obtained with
10793 @command{gnatelim}).
10795 Be aware that the set of @code{Eliminate} pragmas is specific to each
10796 program. It is not recommended to merge sets of @code{Eliminate}
10797 pragmas created for different programs in one @file{gnat.adc} file.
10799 @node Summary of the gnatelim Usage Cycle
10800 @subsection Summary of the gnatelim Usage Cycle
10803 Here is a quick summary of the steps to be taken in order to reduce
10804 the size of your executables with @code{gnatelim}. You may use
10805 other GNAT options to control the optimization level,
10806 to produce the debugging information, to set search path, etc.
10810 Produce a bind file
10813 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10814 $ gnatbind main_prog
10818 Generate a list of @code{Eliminate} pragmas
10821 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10824 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10829 Recompile the application
10832 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10837 @node Reducing Size of Executables with unused subprogram/data elimination
10838 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10839 @findex unused subprogram/data elimination
10842 This section describes how you can eliminate unused subprograms and data from
10843 your executable just by setting options at compilation time.
10846 * About unused subprogram/data elimination::
10847 * Compilation options::
10848 * Example of unused subprogram/data elimination::
10851 @node About unused subprogram/data elimination
10852 @subsection About unused subprogram/data elimination
10855 By default, an executable contains all code and data of its composing objects
10856 (directly linked or coming from statically linked libraries), even data or code
10857 never used by this executable.
10859 This feature will allow you to eliminate such unused code from your
10860 executable, making it smaller (in disk and in memory).
10862 This functionality is available on all Linux platforms except for the IA-64
10863 architecture and on all cross platforms using the ELF binary file format.
10864 In both cases GNU binutils version 2.16 or later are required to enable it.
10866 @node Compilation options
10867 @subsection Compilation options
10870 The operation of eliminating the unused code and data from the final executable
10871 is directly performed by the linker.
10873 In order to do this, it has to work with objects compiled with the
10875 @option{-ffunction-sections} @option{-fdata-sections}.
10876 @cindex @option{-ffunction-sections} (@command{gcc})
10877 @cindex @option{-fdata-sections} (@command{gcc})
10878 These options are usable with C and Ada files.
10879 They will place respectively each
10880 function or data in a separate section in the resulting object file.
10882 Once the objects and static libraries are created with these options, the
10883 linker can perform the dead code elimination. You can do this by setting
10884 the @option{-Wl,--gc-sections} option to gcc command or in the
10885 @option{-largs} section of @command{gnatmake}. This will perform a
10886 garbage collection of code and data never referenced.
10888 If the linker performs a partial link (@option{-r} ld linker option), then you
10889 will need to provide one or several entry point using the
10890 @option{-e} / @option{--entry} ld option.
10892 Note that objects compiled without the @option{-ffunction-sections} and
10893 @option{-fdata-sections} options can still be linked with the executable.
10894 However, no dead code elimination will be performed on those objects (they will
10897 The GNAT static library is now compiled with -ffunction-sections and
10898 -fdata-sections on some platforms. This allows you to eliminate the unused code
10899 and data of the GNAT library from your executable.
10901 @node Example of unused subprogram/data elimination
10902 @subsection Example of unused subprogram/data elimination
10905 Here is a simple example:
10907 @smallexample @c ada
10916 Used_Data : Integer;
10917 Unused_Data : Integer;
10919 procedure Used (Data : Integer);
10920 procedure Unused (Data : Integer);
10923 package body Aux is
10924 procedure Used (Data : Integer) is
10929 procedure Unused (Data : Integer) is
10931 Unused_Data := Data;
10937 @code{Unused} and @code{Unused_Data} are never referenced in this code
10938 excerpt, and hence they may be safely removed from the final executable.
10943 $ nm test | grep used
10944 020015f0 T aux__unused
10945 02005d88 B aux__unused_data
10946 020015cc T aux__used
10947 02005d84 B aux__used_data
10949 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10950 -largs -Wl,--gc-sections
10952 $ nm test | grep used
10953 02005350 T aux__used
10954 0201ffe0 B aux__used_data
10958 It can be observed that the procedure @code{Unused} and the object
10959 @code{Unused_Data} are removed by the linker when using the
10960 appropriate options.
10962 @c ********************************
10963 @node Renaming Files Using gnatchop
10964 @chapter Renaming Files Using @code{gnatchop}
10968 This chapter discusses how to handle files with multiple units by using
10969 the @code{gnatchop} utility. This utility is also useful in renaming
10970 files to meet the standard GNAT default file naming conventions.
10973 * Handling Files with Multiple Units::
10974 * Operating gnatchop in Compilation Mode::
10975 * Command Line for gnatchop::
10976 * Switches for gnatchop::
10977 * Examples of gnatchop Usage::
10980 @node Handling Files with Multiple Units
10981 @section Handling Files with Multiple Units
10984 The basic compilation model of GNAT requires that a file submitted to the
10985 compiler have only one unit and there be a strict correspondence
10986 between the file name and the unit name.
10988 The @code{gnatchop} utility allows both of these rules to be relaxed,
10989 allowing GNAT to process files which contain multiple compilation units
10990 and files with arbitrary file names. @code{gnatchop}
10991 reads the specified file and generates one or more output files,
10992 containing one unit per file. The unit and the file name correspond,
10993 as required by GNAT.
10995 If you want to permanently restructure a set of ``foreign'' files so that
10996 they match the GNAT rules, and do the remaining development using the
10997 GNAT structure, you can simply use @command{gnatchop} once, generate the
10998 new set of files and work with them from that point on.
11000 Alternatively, if you want to keep your files in the ``foreign'' format,
11001 perhaps to maintain compatibility with some other Ada compilation
11002 system, you can set up a procedure where you use @command{gnatchop} each
11003 time you compile, regarding the source files that it writes as temporary
11004 files that you throw away.
11006 Note that if your file containing multiple units starts with a byte order
11007 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
11008 will each start with a copy of this BOM, meaning that they can be compiled
11009 automatically in UTF-8 mode without needing to specify an explicit encoding.
11011 @node Operating gnatchop in Compilation Mode
11012 @section Operating gnatchop in Compilation Mode
11015 The basic function of @code{gnatchop} is to take a file with multiple units
11016 and split it into separate files. The boundary between files is reasonably
11017 clear, except for the issue of comments and pragmas. In default mode, the
11018 rule is that any pragmas between units belong to the previous unit, except
11019 that configuration pragmas always belong to the following unit. Any comments
11020 belong to the following unit. These rules
11021 almost always result in the right choice of
11022 the split point without needing to mark it explicitly and most users will
11023 find this default to be what they want. In this default mode it is incorrect to
11024 submit a file containing only configuration pragmas, or one that ends in
11025 configuration pragmas, to @code{gnatchop}.
11027 However, using a special option to activate ``compilation mode'',
11029 can perform another function, which is to provide exactly the semantics
11030 required by the RM for handling of configuration pragmas in a compilation.
11031 In the absence of configuration pragmas (at the main file level), this
11032 option has no effect, but it causes such configuration pragmas to be handled
11033 in a quite different manner.
11035 First, in compilation mode, if @code{gnatchop} is given a file that consists of
11036 only configuration pragmas, then this file is appended to the
11037 @file{gnat.adc} file in the current directory. This behavior provides
11038 the required behavior described in the RM for the actions to be taken
11039 on submitting such a file to the compiler, namely that these pragmas
11040 should apply to all subsequent compilations in the same compilation
11041 environment. Using GNAT, the current directory, possibly containing a
11042 @file{gnat.adc} file is the representation
11043 of a compilation environment. For more information on the
11044 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
11046 Second, in compilation mode, if @code{gnatchop}
11047 is given a file that starts with
11048 configuration pragmas, and contains one or more units, then these
11049 configuration pragmas are prepended to each of the chopped files. This
11050 behavior provides the required behavior described in the RM for the
11051 actions to be taken on compiling such a file, namely that the pragmas
11052 apply to all units in the compilation, but not to subsequently compiled
11055 Finally, if configuration pragmas appear between units, they are appended
11056 to the previous unit. This results in the previous unit being illegal,
11057 since the compiler does not accept configuration pragmas that follow
11058 a unit. This provides the required RM behavior that forbids configuration
11059 pragmas other than those preceding the first compilation unit of a
11062 For most purposes, @code{gnatchop} will be used in default mode. The
11063 compilation mode described above is used only if you need exactly
11064 accurate behavior with respect to compilations, and you have files
11065 that contain multiple units and configuration pragmas. In this
11066 circumstance the use of @code{gnatchop} with the compilation mode
11067 switch provides the required behavior, and is for example the mode
11068 in which GNAT processes the ACVC tests.
11070 @node Command Line for gnatchop
11071 @section Command Line for @code{gnatchop}
11074 The @code{gnatchop} command has the form:
11077 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11082 The only required argument is the file name of the file to be chopped.
11083 There are no restrictions on the form of this file name. The file itself
11084 contains one or more Ada units, in normal GNAT format, concatenated
11085 together. As shown, more than one file may be presented to be chopped.
11087 When run in default mode, @code{gnatchop} generates one output file in
11088 the current directory for each unit in each of the files.
11090 @var{directory}, if specified, gives the name of the directory to which
11091 the output files will be written. If it is not specified, all files are
11092 written to the current directory.
11094 For example, given a
11095 file called @file{hellofiles} containing
11097 @smallexample @c ada
11102 with Text_IO; use Text_IO;
11105 Put_Line ("Hello");
11115 $ gnatchop ^hellofiles^HELLOFILES.^
11119 generates two files in the current directory, one called
11120 @file{hello.ads} containing the single line that is the procedure spec,
11121 and the other called @file{hello.adb} containing the remaining text. The
11122 original file is not affected. The generated files can be compiled in
11126 When gnatchop is invoked on a file that is empty or that contains only empty
11127 lines and/or comments, gnatchop will not fail, but will not produce any
11130 For example, given a
11131 file called @file{toto.txt} containing
11133 @smallexample @c ada
11145 $ gnatchop ^toto.txt^TOT.TXT^
11149 will not produce any new file and will result in the following warnings:
11152 toto.txt:1:01: warning: empty file, contains no compilation units
11153 no compilation units found
11154 no source files written
11157 @node Switches for gnatchop
11158 @section Switches for @code{gnatchop}
11161 @command{gnatchop} recognizes the following switches:
11167 @cindex @option{--version} @command{gnatchop}
11168 Display Copyright and version, then exit disregarding all other options.
11171 @cindex @option{--help} @command{gnatchop}
11172 If @option{--version} was not used, display usage, then exit disregarding
11175 @item ^-c^/COMPILATION^
11176 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
11177 Causes @code{gnatchop} to operate in compilation mode, in which
11178 configuration pragmas are handled according to strict RM rules. See
11179 previous section for a full description of this mode.
11182 @item -gnat@var{xxx}
11183 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
11184 used to parse the given file. Not all @var{xxx} options make sense,
11185 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
11186 process a source file that uses Latin-2 coding for identifiers.
11190 Causes @code{gnatchop} to generate a brief help summary to the standard
11191 output file showing usage information.
11193 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
11194 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
11195 Limit generated file names to the specified number @code{mm}
11197 This is useful if the
11198 resulting set of files is required to be interoperable with systems
11199 which limit the length of file names.
11201 If no value is given, or
11202 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
11203 a default of 39, suitable for OpenVMS Alpha
11204 Systems, is assumed
11207 No space is allowed between the @option{-k} and the numeric value. The numeric
11208 value may be omitted in which case a default of @option{-k8},
11210 with DOS-like file systems, is used. If no @option{-k} switch
11212 there is no limit on the length of file names.
11215 @item ^-p^/PRESERVE^
11216 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
11217 Causes the file ^modification^creation^ time stamp of the input file to be
11218 preserved and used for the time stamp of the output file(s). This may be
11219 useful for preserving coherency of time stamps in an environment where
11220 @code{gnatchop} is used as part of a standard build process.
11223 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
11224 Causes output of informational messages indicating the set of generated
11225 files to be suppressed. Warnings and error messages are unaffected.
11227 @item ^-r^/REFERENCE^
11228 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
11229 @findex Source_Reference
11230 Generate @code{Source_Reference} pragmas. Use this switch if the output
11231 files are regarded as temporary and development is to be done in terms
11232 of the original unchopped file. This switch causes
11233 @code{Source_Reference} pragmas to be inserted into each of the
11234 generated files to refers back to the original file name and line number.
11235 The result is that all error messages refer back to the original
11237 In addition, the debugging information placed into the object file (when
11238 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
11240 also refers back to this original file so that tools like profilers and
11241 debuggers will give information in terms of the original unchopped file.
11243 If the original file to be chopped itself contains
11244 a @code{Source_Reference}
11245 pragma referencing a third file, then gnatchop respects
11246 this pragma, and the generated @code{Source_Reference} pragmas
11247 in the chopped file refer to the original file, with appropriate
11248 line numbers. This is particularly useful when @code{gnatchop}
11249 is used in conjunction with @code{gnatprep} to compile files that
11250 contain preprocessing statements and multiple units.
11252 @item ^-v^/VERBOSE^
11253 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
11254 Causes @code{gnatchop} to operate in verbose mode. The version
11255 number and copyright notice are output, as well as exact copies of
11256 the gnat1 commands spawned to obtain the chop control information.
11258 @item ^-w^/OVERWRITE^
11259 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
11260 Overwrite existing file names. Normally @code{gnatchop} regards it as a
11261 fatal error if there is already a file with the same name as a
11262 file it would otherwise output, in other words if the files to be
11263 chopped contain duplicated units. This switch bypasses this
11264 check, and causes all but the last instance of such duplicated
11265 units to be skipped.
11268 @item --GCC=@var{xxxx}
11269 @cindex @option{--GCC=} (@code{gnatchop})
11270 Specify the path of the GNAT parser to be used. When this switch is used,
11271 no attempt is made to add the prefix to the GNAT parser executable.
11275 @node Examples of gnatchop Usage
11276 @section Examples of @code{gnatchop} Usage
11280 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
11283 @item gnatchop -w hello_s.ada prerelease/files
11286 Chops the source file @file{hello_s.ada}. The output files will be
11287 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
11289 files with matching names in that directory (no files in the current
11290 directory are modified).
11292 @item gnatchop ^archive^ARCHIVE.^
11293 Chops the source file @file{^archive^ARCHIVE.^}
11294 into the current directory. One
11295 useful application of @code{gnatchop} is in sending sets of sources
11296 around, for example in email messages. The required sources are simply
11297 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11299 @command{gnatchop} is used at the other end to reconstitute the original
11302 @item gnatchop file1 file2 file3 direc
11303 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11304 the resulting files in the directory @file{direc}. Note that if any units
11305 occur more than once anywhere within this set of files, an error message
11306 is generated, and no files are written. To override this check, use the
11307 @option{^-w^/OVERWRITE^} switch,
11308 in which case the last occurrence in the last file will
11309 be the one that is output, and earlier duplicate occurrences for a given
11310 unit will be skipped.
11313 @node Configuration Pragmas
11314 @chapter Configuration Pragmas
11315 @cindex Configuration pragmas
11316 @cindex Pragmas, configuration
11319 Configuration pragmas include those pragmas described as
11320 such in the Ada Reference Manual, as well as
11321 implementation-dependent pragmas that are configuration pragmas.
11322 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11323 for details on these additional GNAT-specific configuration pragmas.
11324 Most notably, the pragma @code{Source_File_Name}, which allows
11325 specifying non-default names for source files, is a configuration
11326 pragma. The following is a complete list of configuration pragmas
11327 recognized by GNAT:
11335 Assume_No_Invalid_Values
11340 Compile_Time_Warning
11342 Component_Alignment
11343 Convention_Identifier
11351 External_Name_Casing
11354 Float_Representation
11367 Priority_Specific_Dispatching
11370 Propagate_Exceptions
11373 Restricted_Run_Time
11375 Restrictions_Warnings
11378 Source_File_Name_Project
11381 Suppress_Exception_Locations
11382 Task_Dispatching_Policy
11388 Wide_Character_Encoding
11393 * Handling of Configuration Pragmas::
11394 * The Configuration Pragmas Files::
11397 @node Handling of Configuration Pragmas
11398 @section Handling of Configuration Pragmas
11400 Configuration pragmas may either appear at the start of a compilation
11401 unit, in which case they apply only to that unit, or they may apply to
11402 all compilations performed in a given compilation environment.
11404 GNAT also provides the @code{gnatchop} utility to provide an automatic
11405 way to handle configuration pragmas following the semantics for
11406 compilations (that is, files with multiple units), described in the RM.
11407 See @ref{Operating gnatchop in Compilation Mode} for details.
11408 However, for most purposes, it will be more convenient to edit the
11409 @file{gnat.adc} file that contains configuration pragmas directly,
11410 as described in the following section.
11412 @node The Configuration Pragmas Files
11413 @section The Configuration Pragmas Files
11414 @cindex @file{gnat.adc}
11417 In GNAT a compilation environment is defined by the current
11418 directory at the time that a compile command is given. This current
11419 directory is searched for a file whose name is @file{gnat.adc}. If
11420 this file is present, it is expected to contain one or more
11421 configuration pragmas that will be applied to the current compilation.
11422 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11425 Configuration pragmas may be entered into the @file{gnat.adc} file
11426 either by running @code{gnatchop} on a source file that consists only of
11427 configuration pragmas, or more conveniently by
11428 direct editing of the @file{gnat.adc} file, which is a standard format
11431 In addition to @file{gnat.adc}, additional files containing configuration
11432 pragmas may be applied to the current compilation using the switch
11433 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11434 contains only configuration pragmas. These configuration pragmas are
11435 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11436 is present and switch @option{-gnatA} is not used).
11438 It is allowed to specify several switches @option{-gnatec}, all of which
11439 will be taken into account.
11441 If you are using project file, a separate mechanism is provided using
11442 project attributes, see @ref{Specifying Configuration Pragmas} for more
11446 Of special interest to GNAT OpenVMS Alpha is the following
11447 configuration pragma:
11449 @smallexample @c ada
11451 pragma Extend_System (Aux_DEC);
11456 In the presence of this pragma, GNAT adds to the definition of the
11457 predefined package SYSTEM all the additional types and subprograms that are
11458 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11461 @node Handling Arbitrary File Naming Conventions Using gnatname
11462 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11463 @cindex Arbitrary File Naming Conventions
11466 * Arbitrary File Naming Conventions::
11467 * Running gnatname::
11468 * Switches for gnatname::
11469 * Examples of gnatname Usage::
11472 @node Arbitrary File Naming Conventions
11473 @section Arbitrary File Naming Conventions
11476 The GNAT compiler must be able to know the source file name of a compilation
11477 unit. When using the standard GNAT default file naming conventions
11478 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11479 does not need additional information.
11482 When the source file names do not follow the standard GNAT default file naming
11483 conventions, the GNAT compiler must be given additional information through
11484 a configuration pragmas file (@pxref{Configuration Pragmas})
11486 When the non-standard file naming conventions are well-defined,
11487 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11488 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11489 if the file naming conventions are irregular or arbitrary, a number
11490 of pragma @code{Source_File_Name} for individual compilation units
11492 To help maintain the correspondence between compilation unit names and
11493 source file names within the compiler,
11494 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11497 @node Running gnatname
11498 @section Running @code{gnatname}
11501 The usual form of the @code{gnatname} command is
11504 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11505 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11509 All of the arguments are optional. If invoked without any argument,
11510 @code{gnatname} will display its usage.
11513 When used with at least one naming pattern, @code{gnatname} will attempt to
11514 find all the compilation units in files that follow at least one of the
11515 naming patterns. To find these compilation units,
11516 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11520 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11521 Each Naming Pattern is enclosed between double quotes.
11522 A Naming Pattern is a regular expression similar to the wildcard patterns
11523 used in file names by the Unix shells or the DOS prompt.
11526 @code{gnatname} may be called with several sections of directories/patterns.
11527 Sections are separated by switch @code{--and}. In each section, there must be
11528 at least one pattern. If no directory is specified in a section, the current
11529 directory (or the project directory is @code{-P} is used) is implied.
11530 The options other that the directory switches and the patterns apply globally
11531 even if they are in different sections.
11534 Examples of Naming Patterns are
11543 For a more complete description of the syntax of Naming Patterns,
11544 see the second kind of regular expressions described in @file{g-regexp.ads}
11545 (the ``Glob'' regular expressions).
11548 When invoked with no switch @code{-P}, @code{gnatname} will create a
11549 configuration pragmas file @file{gnat.adc} in the current working directory,
11550 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11553 @node Switches for gnatname
11554 @section Switches for @code{gnatname}
11557 Switches for @code{gnatname} must precede any specified Naming Pattern.
11560 You may specify any of the following switches to @code{gnatname}:
11566 @cindex @option{--version} @command{gnatname}
11567 Display Copyright and version, then exit disregarding all other options.
11570 @cindex @option{--help} @command{gnatname}
11571 If @option{--version} was not used, display usage, then exit disregarding
11575 Start another section of directories/patterns.
11577 @item ^-c^/CONFIG_FILE=^@file{file}
11578 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11579 Create a configuration pragmas file @file{file} (instead of the default
11582 There may be zero, one or more space between @option{-c} and
11585 @file{file} may include directory information. @file{file} must be
11586 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11587 When a switch @option{^-c^/CONFIG_FILE^} is
11588 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11590 @item ^-d^/SOURCE_DIRS=^@file{dir}
11591 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11592 Look for source files in directory @file{dir}. There may be zero, one or more
11593 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11594 When a switch @option{^-d^/SOURCE_DIRS^}
11595 is specified, the current working directory will not be searched for source
11596 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11597 or @option{^-D^/DIR_FILES^} switch.
11598 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11599 If @file{dir} is a relative path, it is relative to the directory of
11600 the configuration pragmas file specified with switch
11601 @option{^-c^/CONFIG_FILE^},
11602 or to the directory of the project file specified with switch
11603 @option{^-P^/PROJECT_FILE^} or,
11604 if neither switch @option{^-c^/CONFIG_FILE^}
11605 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11606 current working directory. The directory
11607 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11609 @item ^-D^/DIRS_FILE=^@file{file}
11610 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11611 Look for source files in all directories listed in text file @file{file}.
11612 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11614 @file{file} must be an existing, readable text file.
11615 Each nonempty line in @file{file} must be a directory.
11616 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11617 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11620 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11621 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11622 Foreign patterns. Using this switch, it is possible to add sources of languages
11623 other than Ada to the list of sources of a project file.
11624 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11627 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11630 will look for Ada units in all files with the @file{.ada} extension,
11631 and will add to the list of file for project @file{prj.gpr} the C files
11632 with extension @file{.^c^C^}.
11635 @cindex @option{^-h^/HELP^} (@code{gnatname})
11636 Output usage (help) information. The output is written to @file{stdout}.
11638 @item ^-P^/PROJECT_FILE=^@file{proj}
11639 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11640 Create or update project file @file{proj}. There may be zero, one or more space
11641 between @option{-P} and @file{proj}. @file{proj} may include directory
11642 information. @file{proj} must be writable.
11643 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11644 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11645 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11647 @item ^-v^/VERBOSE^
11648 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11649 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11650 This includes name of the file written, the name of the directories to search
11651 and, for each file in those directories whose name matches at least one of
11652 the Naming Patterns, an indication of whether the file contains a unit,
11653 and if so the name of the unit.
11655 @item ^-v -v^/VERBOSE /VERBOSE^
11656 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11657 Very Verbose mode. In addition to the output produced in verbose mode,
11658 for each file in the searched directories whose name matches none of
11659 the Naming Patterns, an indication is given that there is no match.
11661 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11662 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11663 Excluded patterns. Using this switch, it is possible to exclude some files
11664 that would match the name patterns. For example,
11666 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11669 will look for Ada units in all files with the @file{.ada} extension,
11670 except those whose names end with @file{_nt.ada}.
11674 @node Examples of gnatname Usage
11675 @section Examples of @code{gnatname} Usage
11679 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11685 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11690 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11691 and be writable. In addition, the directory
11692 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11693 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11696 Note the optional spaces after @option{-c} and @option{-d}.
11701 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11702 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11705 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11706 /EXCLUDED_PATTERN=*_nt_body.ada
11707 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11708 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11712 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11713 even in conjunction with one or several switches
11714 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11715 are used in this example.
11717 @c *****************************************
11718 @c * G N A T P r o j e c t M a n a g e r *
11719 @c *****************************************
11720 @node GNAT Project Manager
11721 @chapter GNAT Project Manager
11725 * Examples of Project Files::
11726 * Project File Syntax::
11727 * Objects and Sources in Project Files::
11728 * Importing Projects::
11729 * Project Extension::
11730 * Project Hierarchy Extension::
11731 * External References in Project Files::
11732 * Packages in Project Files::
11733 * Variables from Imported Projects::
11735 * Library Projects::
11736 * Stand-alone Library Projects::
11737 * Switches Related to Project Files::
11738 * Tools Supporting Project Files::
11739 * An Extended Example::
11740 * Project File Complete Syntax::
11743 @c ****************
11744 @c * Introduction *
11745 @c ****************
11748 @section Introduction
11751 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11752 you to manage complex builds involving a number of source files, directories,
11753 and compilation options for different system configurations. In particular,
11754 project files allow you to specify:
11757 The directory or set of directories containing the source files, and/or the
11758 names of the specific source files themselves
11760 The directory in which the compiler's output
11761 (@file{ALI} files, object files, tree files) is to be placed
11763 The directory in which the executable programs is to be placed
11765 ^Switch^Switch^ settings for any of the project-enabled tools
11766 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11767 @code{gnatfind}); you can apply these settings either globally or to individual
11770 The source files containing the main subprogram(s) to be built
11772 The source programming language(s) (currently Ada and/or C)
11774 Source file naming conventions; you can specify these either globally or for
11775 individual compilation units
11782 @node Project Files
11783 @subsection Project Files
11786 Project files are written in a syntax close to that of Ada, using familiar
11787 notions such as packages, context clauses, declarations, default values,
11788 assignments, and inheritance. Finally, project files can be built
11789 hierarchically from other project files, simplifying complex system
11790 integration and project reuse.
11792 A @dfn{project} is a specific set of values for various compilation properties.
11793 The settings for a given project are described by means of
11794 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11795 Property values in project files are either strings or lists of strings.
11796 Properties that are not explicitly set receive default values. A project
11797 file may interrogate the values of @dfn{external variables} (user-defined
11798 command-line switches or environment variables), and it may specify property
11799 settings conditionally, based on the value of such variables.
11801 In simple cases, a project's source files depend only on other source files
11802 in the same project, or on the predefined libraries. (@emph{Dependence} is
11804 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11805 the Project Manager also allows more sophisticated arrangements,
11806 where the source files in one project depend on source files in other
11810 One project can @emph{import} other projects containing needed source files.
11812 You can organize GNAT projects in a hierarchy: a @emph{child} project
11813 can extend a @emph{parent} project, inheriting the parent's source files and
11814 optionally overriding any of them with alternative versions
11818 More generally, the Project Manager lets you structure large development
11819 efforts into hierarchical subsystems, where build decisions are delegated
11820 to the subsystem level, and thus different compilation environments
11821 (^switch^switch^ settings) used for different subsystems.
11823 The Project Manager is invoked through the
11824 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11825 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11827 There may be zero, one or more spaces between @option{-P} and
11828 @option{@emph{projectfile}}.
11830 If you want to define (on the command line) an external variable that is
11831 queried by the project file, you must use the
11832 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11833 The Project Manager parses and interprets the project file, and drives the
11834 invoked tool based on the project settings.
11836 The Project Manager supports a wide range of development strategies,
11837 for systems of all sizes. Here are some typical practices that are
11841 Using a common set of source files, but generating object files in different
11842 directories via different ^switch^switch^ settings
11844 Using a mostly-shared set of source files, but with different versions of
11849 The destination of an executable can be controlled inside a project file
11850 using the @option{^-o^-o^}
11852 In the absence of such a ^switch^switch^ either inside
11853 the project file or on the command line, any executable files generated by
11854 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11855 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11856 in the object directory of the project.
11858 You can use project files to achieve some of the effects of a source
11859 versioning system (for example, defining separate projects for
11860 the different sets of sources that comprise different releases) but the
11861 Project Manager is independent of any source configuration management tools
11862 that might be used by the developers.
11864 The next section introduces the main features of GNAT's project facility
11865 through a sequence of examples; subsequent sections will present the syntax
11866 and semantics in more detail. A more formal description of the project
11867 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11870 @c *****************************
11871 @c * Examples of Project Files *
11872 @c *****************************
11874 @node Examples of Project Files
11875 @section Examples of Project Files
11877 This section illustrates some of the typical uses of project files and
11878 explains their basic structure and behavior.
11881 * Common Sources with Different ^Switches^Switches^ and Directories::
11882 * Using External Variables::
11883 * Importing Other Projects::
11884 * Extending a Project::
11887 @node Common Sources with Different ^Switches^Switches^ and Directories
11888 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11892 * Specifying the Object Directory::
11893 * Specifying the Exec Directory::
11894 * Project File Packages::
11895 * Specifying ^Switch^Switch^ Settings::
11896 * Main Subprograms::
11897 * Executable File Names::
11898 * Source File Naming Conventions::
11899 * Source Language(s)::
11903 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11904 @file{proc.adb} are in the @file{/common} directory. The file
11905 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11906 package @code{Pack}. We want to compile these source files under two sets
11907 of ^switches^switches^:
11910 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11911 and the @option{^-gnata^-gnata^},
11912 @option{^-gnato^-gnato^},
11913 and @option{^-gnatE^-gnatE^} switches to the
11914 compiler; the compiler's output is to appear in @file{/common/debug}
11916 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11917 to the compiler; the compiler's output is to appear in @file{/common/release}
11921 The GNAT project files shown below, respectively @file{debug.gpr} and
11922 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11935 ^/common/debug^[COMMON.DEBUG]^
11940 ^/common/release^[COMMON.RELEASE]^
11945 Here are the corresponding project files:
11947 @smallexample @c projectfile
11950 for Object_Dir use "debug";
11951 for Main use ("proc");
11954 for ^Default_Switches^Default_Switches^ ("Ada")
11956 for Executable ("proc.adb") use "proc1";
11961 package Compiler is
11962 for ^Default_Switches^Default_Switches^ ("Ada")
11963 use ("-fstack-check",
11966 "^-gnatE^-gnatE^");
11972 @smallexample @c projectfile
11975 for Object_Dir use "release";
11976 for Exec_Dir use ".";
11977 for Main use ("proc");
11979 package Compiler is
11980 for ^Default_Switches^Default_Switches^ ("Ada")
11988 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11989 insensitive), and analogously the project defined by @file{release.gpr} is
11990 @code{"Release"}. For consistency the file should have the same name as the
11991 project, and the project file's extension should be @code{"gpr"}. These
11992 conventions are not required, but a warning is issued if they are not followed.
11994 If the current directory is @file{^/temp^[TEMP]^}, then the command
11996 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
12000 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
12001 as well as the @code{^proc1^PROC1.EXE^} executable,
12002 using the ^switch^switch^ settings defined in the project file.
12004 Likewise, the command
12006 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
12010 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
12011 and the @code{^proc^PROC.EXE^}
12012 executable in @file{^/common^[COMMON]^},
12013 using the ^switch^switch^ settings from the project file.
12016 @unnumberedsubsubsec Source Files
12019 If a project file does not explicitly specify a set of source directories or
12020 a set of source files, then by default the project's source files are the
12021 Ada source files in the project file directory. Thus @file{pack.ads},
12022 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
12024 @node Specifying the Object Directory
12025 @unnumberedsubsubsec Specifying the Object Directory
12028 Several project properties are modeled by Ada-style @emph{attributes};
12029 a property is defined by supplying the equivalent of an Ada attribute
12030 definition clause in the project file.
12031 A project's object directory is another such a property; the corresponding
12032 attribute is @code{Object_Dir}, and its value is also a string expression,
12033 specified either as absolute or relative. In the later case,
12034 it is relative to the project file directory. Thus the compiler's
12035 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
12036 (for the @code{Debug} project)
12037 and to @file{^/common/release^[COMMON.RELEASE]^}
12038 (for the @code{Release} project).
12039 If @code{Object_Dir} is not specified, then the default is the project file
12042 @node Specifying the Exec Directory
12043 @unnumberedsubsubsec Specifying the Exec Directory
12046 A project's exec directory is another property; the corresponding
12047 attribute is @code{Exec_Dir}, and its value is also a string expression,
12048 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
12049 then the default is the object directory (which may also be the project file
12050 directory if attribute @code{Object_Dir} is not specified). Thus the executable
12051 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
12052 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
12053 and in @file{^/common^[COMMON]^} for the @code{Release} project.
12055 @node Project File Packages
12056 @unnumberedsubsubsec Project File Packages
12059 A GNAT tool that is integrated with the Project Manager is modeled by a
12060 corresponding package in the project file. In the example above,
12061 The @code{Debug} project defines the packages @code{Builder}
12062 (for @command{gnatmake}) and @code{Compiler};
12063 the @code{Release} project defines only the @code{Compiler} package.
12065 The Ada-like package syntax is not to be taken literally. Although packages in
12066 project files bear a surface resemblance to packages in Ada source code, the
12067 notation is simply a way to convey a grouping of properties for a named
12068 entity. Indeed, the package names permitted in project files are restricted
12069 to a predefined set, corresponding to the project-aware tools, and the contents
12070 of packages are limited to a small set of constructs.
12071 The packages in the example above contain attribute definitions.
12073 @node Specifying ^Switch^Switch^ Settings
12074 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
12077 ^Switch^Switch^ settings for a project-aware tool can be specified through
12078 attributes in the package that corresponds to the tool.
12079 The example above illustrates one of the relevant attributes,
12080 @code{^Default_Switches^Default_Switches^}, which is defined in packages
12081 in both project files.
12082 Unlike simple attributes like @code{Source_Dirs},
12083 @code{^Default_Switches^Default_Switches^} is
12084 known as an @emph{associative array}. When you define this attribute, you must
12085 supply an ``index'' (a literal string), and the effect of the attribute
12086 definition is to set the value of the array at the specified index.
12087 For the @code{^Default_Switches^Default_Switches^} attribute,
12088 the index is a programming language (in our case, Ada),
12089 and the value specified (after @code{use}) must be a list
12090 of string expressions.
12092 The attributes permitted in project files are restricted to a predefined set.
12093 Some may appear at project level, others in packages.
12094 For any attribute that is an associative array, the index must always be a
12095 literal string, but the restrictions on this string (e.g., a file name or a
12096 language name) depend on the individual attribute.
12097 Also depending on the attribute, its specified value will need to be either a
12098 string or a string list.
12100 In the @code{Debug} project, we set the switches for two tools,
12101 @command{gnatmake} and the compiler, and thus we include the two corresponding
12102 packages; each package defines the @code{^Default_Switches^Default_Switches^}
12103 attribute with index @code{"Ada"}.
12104 Note that the package corresponding to
12105 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
12106 similar, but only includes the @code{Compiler} package.
12108 In project @code{Debug} above, the ^switches^switches^ starting with
12109 @option{-gnat} that are specified in package @code{Compiler}
12110 could have been placed in package @code{Builder}, since @command{gnatmake}
12111 transmits all such ^switches^switches^ to the compiler.
12113 @node Main Subprograms
12114 @unnumberedsubsubsec Main Subprograms
12117 One of the specifiable properties of a project is a list of files that contain
12118 main subprograms. This property is captured in the @code{Main} attribute,
12119 whose value is a list of strings. If a project defines the @code{Main}
12120 attribute, it is not necessary to identify the main subprogram(s) when
12121 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
12123 @node Executable File Names
12124 @unnumberedsubsubsec Executable File Names
12127 By default, the executable file name corresponding to a main source is
12128 deduced from the main source file name. Through the attributes
12129 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
12130 it is possible to change this default.
12131 In project @code{Debug} above, the executable file name
12132 for main source @file{^proc.adb^PROC.ADB^} is
12133 @file{^proc1^PROC1.EXE^}.
12134 Attribute @code{Executable_Suffix}, when specified, may change the suffix
12135 of the executable files, when no attribute @code{Executable} applies:
12136 its value replace the platform-specific executable suffix.
12137 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
12138 specify a non-default executable file name when several mains are built at once
12139 in a single @command{gnatmake} command.
12141 @node Source File Naming Conventions
12142 @unnumberedsubsubsec Source File Naming Conventions
12145 Since the project files above do not specify any source file naming
12146 conventions, the GNAT defaults are used. The mechanism for defining source
12147 file naming conventions -- a package named @code{Naming} --
12148 is described below (@pxref{Naming Schemes}).
12150 @node Source Language(s)
12151 @unnumberedsubsubsec Source Language(s)
12154 Since the project files do not specify a @code{Languages} attribute, by
12155 default the GNAT tools assume that the language of the project file is Ada.
12156 More generally, a project can comprise source files
12157 in Ada, C, and/or other languages.
12159 @node Using External Variables
12160 @subsection Using External Variables
12163 Instead of supplying different project files for debug and release, we can
12164 define a single project file that queries an external variable (set either
12165 on the command line or via an ^environment variable^logical name^) in order to
12166 conditionally define the appropriate settings. Again, assume that the
12167 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
12168 located in directory @file{^/common^[COMMON]^}. The following project file,
12169 @file{build.gpr}, queries the external variable named @code{STYLE} and
12170 defines an object directory and ^switch^switch^ settings based on whether
12171 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
12172 the default is @code{"deb"}.
12174 @smallexample @c projectfile
12177 for Main use ("proc");
12179 type Style_Type is ("deb", "rel");
12180 Style : Style_Type := external ("STYLE", "deb");
12184 for Object_Dir use "debug";
12187 for Object_Dir use "release";
12188 for Exec_Dir use ".";
12197 for ^Default_Switches^Default_Switches^ ("Ada")
12199 for Executable ("proc") use "proc1";
12208 package Compiler is
12212 for ^Default_Switches^Default_Switches^ ("Ada")
12213 use ("^-gnata^-gnata^",
12215 "^-gnatE^-gnatE^");
12218 for ^Default_Switches^Default_Switches^ ("Ada")
12229 @code{Style_Type} is an example of a @emph{string type}, which is the project
12230 file analog of an Ada enumeration type but whose components are string literals
12231 rather than identifiers. @code{Style} is declared as a variable of this type.
12233 The form @code{external("STYLE", "deb")} is known as an
12234 @emph{external reference}; its first argument is the name of an
12235 @emph{external variable}, and the second argument is a default value to be
12236 used if the external variable doesn't exist. You can define an external
12237 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
12238 or you can use ^an environment variable^a logical name^
12239 as an external variable.
12241 Each @code{case} construct is expanded by the Project Manager based on the
12242 value of @code{Style}. Thus the command
12245 gnatmake -P/common/build.gpr -XSTYLE=deb
12251 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
12256 is equivalent to the @command{gnatmake} invocation using the project file
12257 @file{debug.gpr} in the earlier example. So is the command
12259 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
12263 since @code{"deb"} is the default for @code{STYLE}.
12269 gnatmake -P/common/build.gpr -XSTYLE=rel
12275 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
12280 is equivalent to the @command{gnatmake} invocation using the project file
12281 @file{release.gpr} in the earlier example.
12283 @node Importing Other Projects
12284 @subsection Importing Other Projects
12285 @cindex @code{ADA_PROJECT_PATH}
12286 @cindex @code{GPR_PROJECT_PATH}
12289 A compilation unit in a source file in one project may depend on compilation
12290 units in source files in other projects. To compile this unit under
12291 control of a project file, the
12292 dependent project must @emph{import} the projects containing the needed source
12294 This effect is obtained using syntax similar to an Ada @code{with} clause,
12295 but where @code{with}ed entities are strings that denote project files.
12297 As an example, suppose that the two projects @code{GUI_Proj} and
12298 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
12299 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
12300 and @file{^/comm^[COMM]^}, respectively.
12301 Suppose that the source files for @code{GUI_Proj} are
12302 @file{gui.ads} and @file{gui.adb}, and that the source files for
12303 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
12304 files is located in its respective project file directory. Schematically:
12323 We want to develop an application in directory @file{^/app^[APP]^} that
12324 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
12325 the corresponding project files (e.g.@: the ^switch^switch^ settings
12326 and object directory).
12327 Skeletal code for a main procedure might be something like the following:
12329 @smallexample @c ada
12332 procedure App_Main is
12341 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12344 @smallexample @c projectfile
12346 with "/gui/gui_proj", "/comm/comm_proj";
12347 project App_Proj is
12348 for Main use ("app_main");
12354 Building an executable is achieved through the command:
12356 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12359 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12360 in the directory where @file{app_proj.gpr} resides.
12362 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12363 (as illustrated above) the @code{with} clause can omit the extension.
12365 Our example specified an absolute path for each imported project file.
12366 Alternatively, the directory name of an imported object can be omitted
12370 The imported project file is in the same directory as the importing project
12373 You have defined one or two ^environment variables^logical names^
12374 that includes the directory containing
12375 the needed project file. The syntax of @code{GPR_PROJECT_PATH} and
12376 @code{ADA_PROJECT_PATH} is the same as
12377 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12378 directory names separated by colons (semicolons on Windows).
12382 Thus, if we define @code{ADA_PROJECT_PATH} or @code{GPR_PROJECT_PATH}
12383 to include @file{^/gui^[GUI]^} and
12384 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12387 @smallexample @c projectfile
12389 with "gui_proj", "comm_proj";
12390 project App_Proj is
12391 for Main use ("app_main");
12397 Importing other projects can create ambiguities.
12398 For example, the same unit might be present in different imported projects, or
12399 it might be present in both the importing project and in an imported project.
12400 Both of these conditions are errors. Note that in the current version of
12401 the Project Manager, it is illegal to have an ambiguous unit even if the
12402 unit is never referenced by the importing project. This restriction may be
12403 relaxed in a future release.
12405 @node Extending a Project
12406 @subsection Extending a Project
12409 In large software systems it is common to have multiple
12410 implementations of a common interface; in Ada terms, multiple versions of a
12411 package body for the same spec. For example, one implementation
12412 might be safe for use in tasking programs, while another might only be used
12413 in sequential applications. This can be modeled in GNAT using the concept
12414 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12415 another project (the ``parent'') then by default all source files of the
12416 parent project are inherited by the child, but the child project can
12417 override any of the parent's source files with new versions, and can also
12418 add new files. This facility is the project analog of a type extension in
12419 Object-Oriented Programming. Project hierarchies are permitted (a child
12420 project may be the parent of yet another project), and a project that
12421 inherits one project can also import other projects.
12423 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12424 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12425 @file{pack.adb}, and @file{proc.adb}:
12438 Note that the project file can simply be empty (that is, no attribute or
12439 package is defined):
12441 @smallexample @c projectfile
12443 project Seq_Proj is
12449 implying that its source files are all the Ada source files in the project
12452 Suppose we want to supply an alternate version of @file{pack.adb}, in
12453 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12454 @file{pack.ads} and @file{proc.adb}. We can define a project
12455 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12459 ^/tasking^[TASKING]^
12465 project Tasking_Proj extends "/seq/seq_proj" is
12471 The version of @file{pack.adb} used in a build depends on which project file
12474 Note that we could have obtained the desired behavior using project import
12475 rather than project inheritance; a @code{base} project would contain the
12476 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12477 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12478 would import @code{base} and add a different version of @file{pack.adb}. The
12479 choice depends on whether other sources in the original project need to be
12480 overridden. If they do, then project extension is necessary, otherwise,
12481 importing is sufficient.
12484 In a project file that extends another project file, it is possible to
12485 indicate that an inherited source is not part of the sources of the extending
12486 project. This is necessary sometimes when a package spec has been overloaded
12487 and no longer requires a body: in this case, it is necessary to indicate that
12488 the inherited body is not part of the sources of the project, otherwise there
12489 will be a compilation error when compiling the spec.
12491 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12492 Its value is a string list: a list of file names. It is also possible to use
12493 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12494 the file name of a text file containing a list of file names, one per line.
12496 @smallexample @c @projectfile
12497 project B extends "a" is
12498 for Source_Files use ("pkg.ads");
12499 -- New spec of Pkg does not need a completion
12500 for Excluded_Source_Files use ("pkg.adb");
12504 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12505 is still needed: if it is possible to build using @command{gnatmake} when such
12506 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12507 it is possible to remove the source completely from a system that includes
12510 @c ***********************
12511 @c * Project File Syntax *
12512 @c ***********************
12514 @node Project File Syntax
12515 @section Project File Syntax
12519 * Qualified Projects::
12525 * Associative Array Attributes::
12526 * case Constructions::
12530 This section describes the structure of project files.
12532 A project may be an @emph{independent project}, entirely defined by a single
12533 project file. Any Ada source file in an independent project depends only
12534 on the predefined library and other Ada source files in the same project.
12537 A project may also @dfn{depend on} other projects, in either or both of
12538 the following ways:
12540 @item It may import any number of projects
12541 @item It may extend at most one other project
12545 The dependence relation is a directed acyclic graph (the subgraph reflecting
12546 the ``extends'' relation is a tree).
12548 A project's @dfn{immediate sources} are the source files directly defined by
12549 that project, either implicitly by residing in the project file's directory,
12550 or explicitly through any of the source-related attributes described below.
12551 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12552 of @var{proj} together with the immediate sources (unless overridden) of any
12553 project on which @var{proj} depends (either directly or indirectly).
12556 @subsection Basic Syntax
12559 As seen in the earlier examples, project files have an Ada-like syntax.
12560 The minimal project file is:
12561 @smallexample @c projectfile
12570 The identifier @code{Empty} is the name of the project.
12571 This project name must be present after the reserved
12572 word @code{end} at the end of the project file, followed by a semi-colon.
12574 Any name in a project file, such as the project name or a variable name,
12575 has the same syntax as an Ada identifier.
12577 The reserved words of project files are the Ada 95 reserved words plus
12578 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12579 reserved words currently used in project file syntax are:
12615 Comments in project files have the same syntax as in Ada, two consecutive
12616 hyphens through the end of the line.
12618 @node Qualified Projects
12619 @subsection Qualified Projects
12622 Before the reserved @code{project}, there may be one or two "qualifiers", that
12623 is identifiers or other reserved words, to qualify the project.
12625 The current list of qualifiers is:
12629 @code{abstract}: qualify a project with no sources. A qualified abstract
12630 project must either have no declaration of attributes @code{Source_Dirs},
12631 @code{Source_Files}, @code{Languages} or @code{Source_List_File}, or one of
12632 @code{Source_Dirs}, @code{Source_Files}, or @code{Languages} must be declared
12633 as empty. If it extends another project, the project it extends must also be a
12634 qualified abstract project.
12637 @code{standard}: a standard project is a non library project with sources.
12640 @code{aggregate}: for future extension
12643 @code{aggregate library}: for future extension
12646 @code{library}: a library project must declare both attributes
12647 @code{Library_Name} and @code{Library_Dir}.
12650 @code{configuration}: a configuration project cannot be in a project tree.
12654 @subsection Packages
12657 A project file may contain @emph{packages}. The name of a package must be one
12658 of the identifiers from the following list. A package
12659 with a given name may only appear once in a project file. Package names are
12660 case insensitive. The following package names are legal:
12676 @code{Cross_Reference}
12680 @code{Pretty_Printer}
12690 @code{Language_Processing}
12694 In its simplest form, a package may be empty:
12696 @smallexample @c projectfile
12706 A package may contain @emph{attribute declarations},
12707 @emph{variable declarations} and @emph{case constructions}, as will be
12710 When there is ambiguity between a project name and a package name,
12711 the name always designates the project. To avoid possible confusion, it is
12712 always a good idea to avoid naming a project with one of the
12713 names allowed for packages or any name that starts with @code{gnat}.
12716 @subsection Expressions
12719 An @emph{expression} is either a @emph{string expression} or a
12720 @emph{string list expression}.
12722 A @emph{string expression} is either a @emph{simple string expression} or a
12723 @emph{compound string expression}.
12725 A @emph{simple string expression} is one of the following:
12727 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12728 @item A string-valued variable reference (@pxref{Variables})
12729 @item A string-valued attribute reference (@pxref{Attributes})
12730 @item An external reference (@pxref{External References in Project Files})
12734 A @emph{compound string expression} is a concatenation of string expressions,
12735 using the operator @code{"&"}
12737 Path & "/" & File_Name & ".ads"
12741 A @emph{string list expression} is either a
12742 @emph{simple string list expression} or a
12743 @emph{compound string list expression}.
12745 A @emph{simple string list expression} is one of the following:
12747 @item A parenthesized list of zero or more string expressions,
12748 separated by commas
12750 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12753 @item A string list-valued variable reference
12754 @item A string list-valued attribute reference
12758 A @emph{compound string list expression} is the concatenation (using
12759 @code{"&"}) of a simple string list expression and an expression. Note that
12760 each term in a compound string list expression, except the first, may be
12761 either a string expression or a string list expression.
12763 @smallexample @c projectfile
12765 File_Name_List := () & File_Name; -- One string in this list
12766 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12768 Big_List := File_Name_List & Extended_File_Name_List;
12769 -- Concatenation of two string lists: three strings
12770 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12771 -- Illegal: must start with a string list
12776 @subsection String Types
12779 A @emph{string type declaration} introduces a discrete set of string literals.
12780 If a string variable is declared to have this type, its value
12781 is restricted to the given set of literals.
12783 Here is an example of a string type declaration:
12785 @smallexample @c projectfile
12786 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12790 Variables of a string type are called @emph{typed variables}; all other
12791 variables are called @emph{untyped variables}. Typed variables are
12792 particularly useful in @code{case} constructions, to support conditional
12793 attribute declarations.
12794 (@pxref{case Constructions}).
12796 The string literals in the list are case sensitive and must all be different.
12797 They may include any graphic characters allowed in Ada, including spaces.
12799 A string type may only be declared at the project level, not inside a package.
12801 A string type may be referenced by its name if it has been declared in the same
12802 project file, or by an expanded name whose prefix is the name of the project
12803 in which it is declared.
12806 @subsection Variables
12809 A variable may be declared at the project file level, or within a package.
12810 Here are some examples of variable declarations:
12812 @smallexample @c projectfile
12814 This_OS : OS := external ("OS"); -- a typed variable declaration
12815 That_OS := "GNU/Linux"; -- an untyped variable declaration
12820 The syntax of a @emph{typed variable declaration} is identical to the Ada
12821 syntax for an object declaration. By contrast, the syntax of an untyped
12822 variable declaration is identical to an Ada assignment statement. In fact,
12823 variable declarations in project files have some of the characteristics of
12824 an assignment, in that successive declarations for the same variable are
12825 allowed. Untyped variable declarations do establish the expected kind of the
12826 variable (string or string list), and successive declarations for it must
12827 respect the initial kind.
12830 A string variable declaration (typed or untyped) declares a variable
12831 whose value is a string. This variable may be used as a string expression.
12832 @smallexample @c projectfile
12833 File_Name := "readme.txt";
12834 Saved_File_Name := File_Name & ".saved";
12838 A string list variable declaration declares a variable whose value is a list
12839 of strings. The list may contain any number (zero or more) of strings.
12841 @smallexample @c projectfile
12843 List_With_One_Element := ("^-gnaty^-gnaty^");
12844 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12845 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12846 "pack2.ada", "util_.ada", "util.ada");
12850 The same typed variable may not be declared more than once at project level,
12851 and it may not be declared more than once in any package; it is in effect
12854 The same untyped variable may be declared several times. Declarations are
12855 elaborated in the order in which they appear, so the new value replaces
12856 the old one, and any subsequent reference to the variable uses the new value.
12857 However, as noted above, if a variable has been declared as a string, all
12859 declarations must give it a string value. Similarly, if a variable has
12860 been declared as a string list, all subsequent declarations
12861 must give it a string list value.
12863 A @emph{variable reference} may take several forms:
12866 @item The simple variable name, for a variable in the current package (if any)
12867 or in the current project
12868 @item An expanded name, whose prefix is a context name.
12872 A @emph{context} may be one of the following:
12875 @item The name of an existing package in the current project
12876 @item The name of an imported project of the current project
12877 @item The name of an ancestor project (i.e., a project extended by the current
12878 project, either directly or indirectly)
12879 @item An expanded name whose prefix is an imported/parent project name, and
12880 whose selector is a package name in that project.
12884 A variable reference may be used in an expression.
12887 @subsection Attributes
12890 A project (and its packages) may have @emph{attributes} that define
12891 the project's properties. Some attributes have values that are strings;
12892 others have values that are string lists.
12894 There are two categories of attributes: @emph{simple attributes}
12895 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12897 Legal project attribute names, and attribute names for each legal package are
12898 listed below. Attributes names are case-insensitive.
12900 The following attributes are defined on projects (all are simple attributes):
12902 @multitable @columnfractions .4 .3
12903 @item @emph{Attribute Name}
12905 @item @code{Source_Files}
12907 @item @code{Source_Dirs}
12909 @item @code{Source_List_File}
12911 @item @code{Object_Dir}
12913 @item @code{Exec_Dir}
12915 @item @code{Excluded_Source_Dirs}
12917 @item @code{Excluded_Source_Files}
12919 @item @code{Excluded_Source_List_File}
12921 @item @code{Languages}
12925 @item @code{Library_Dir}
12927 @item @code{Library_Name}
12929 @item @code{Library_Kind}
12931 @item @code{Library_Version}
12933 @item @code{Library_Interface}
12935 @item @code{Library_Auto_Init}
12937 @item @code{Library_Options}
12939 @item @code{Library_Src_Dir}
12941 @item @code{Library_ALI_Dir}
12943 @item @code{Library_GCC}
12945 @item @code{Library_Symbol_File}
12947 @item @code{Library_Symbol_Policy}
12949 @item @code{Library_Reference_Symbol_File}
12951 @item @code{Externally_Built}
12956 The following attributes are defined for package @code{Naming}
12957 (@pxref{Naming Schemes}):
12959 @multitable @columnfractions .4 .2 .2 .2
12960 @item Attribute Name @tab Category @tab Index @tab Value
12961 @item @code{Spec_Suffix}
12962 @tab associative array
12965 @item @code{Body_Suffix}
12966 @tab associative array
12969 @item @code{Separate_Suffix}
12970 @tab simple attribute
12973 @item @code{Casing}
12974 @tab simple attribute
12977 @item @code{Dot_Replacement}
12978 @tab simple attribute
12982 @tab associative array
12986 @tab associative array
12989 @item @code{Specification_Exceptions}
12990 @tab associative array
12993 @item @code{Implementation_Exceptions}
12994 @tab associative array
13000 The following attributes are defined for packages @code{Builder},
13001 @code{Compiler}, @code{Binder},
13002 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
13003 (@pxref{^Switches^Switches^ and Project Files}).
13005 @multitable @columnfractions .4 .2 .2 .2
13006 @item Attribute Name @tab Category @tab Index @tab Value
13007 @item @code{^Default_Switches^Default_Switches^}
13008 @tab associative array
13011 @item @code{^Switches^Switches^}
13012 @tab associative array
13018 In addition, package @code{Compiler} has a single string attribute
13019 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
13020 string attribute @code{Global_Configuration_Pragmas}.
13023 Each simple attribute has a default value: the empty string (for string-valued
13024 attributes) and the empty list (for string list-valued attributes).
13026 An attribute declaration defines a new value for an attribute.
13028 Examples of simple attribute declarations:
13030 @smallexample @c projectfile
13031 for Object_Dir use "objects";
13032 for Source_Dirs use ("units", "test/drivers");
13036 The syntax of a @dfn{simple attribute declaration} is similar to that of an
13037 attribute definition clause in Ada.
13039 Attributes references may be appear in expressions.
13040 The general form for such a reference is @code{<entity>'<attribute>}:
13041 Associative array attributes are functions. Associative
13042 array attribute references must have an argument that is a string literal.
13046 @smallexample @c projectfile
13048 Naming'Dot_Replacement
13049 Imported_Project'Source_Dirs
13050 Imported_Project.Naming'Casing
13051 Builder'^Default_Switches^Default_Switches^("Ada")
13055 The prefix of an attribute may be:
13057 @item @code{project} for an attribute of the current project
13058 @item The name of an existing package of the current project
13059 @item The name of an imported project
13060 @item The name of a parent project that is extended by the current project
13061 @item An expanded name whose prefix is imported/parent project name,
13062 and whose selector is a package name
13067 @smallexample @c projectfile
13070 for Source_Dirs use project'Source_Dirs & "units";
13071 for Source_Dirs use project'Source_Dirs & "test/drivers"
13077 In the first attribute declaration, initially the attribute @code{Source_Dirs}
13078 has the default value: an empty string list. After this declaration,
13079 @code{Source_Dirs} is a string list of one element: @code{"units"}.
13080 After the second attribute declaration @code{Source_Dirs} is a string list of
13081 two elements: @code{"units"} and @code{"test/drivers"}.
13083 Note: this example is for illustration only. In practice,
13084 the project file would contain only one attribute declaration:
13086 @smallexample @c projectfile
13087 for Source_Dirs use ("units", "test/drivers");
13090 @node Associative Array Attributes
13091 @subsection Associative Array Attributes
13094 Some attributes are defined as @emph{associative arrays}. An associative
13095 array may be regarded as a function that takes a string as a parameter
13096 and delivers a string or string list value as its result.
13098 Here are some examples of single associative array attribute associations:
13100 @smallexample @c projectfile
13101 for Body ("main") use "Main.ada";
13102 for ^Switches^Switches^ ("main.ada")
13104 "^-gnatv^-gnatv^");
13105 for ^Switches^Switches^ ("main.ada")
13106 use Builder'^Switches^Switches^ ("main.ada")
13111 Like untyped variables and simple attributes, associative array attributes
13112 may be declared several times. Each declaration supplies a new value for the
13113 attribute, and replaces the previous setting.
13116 An associative array attribute may be declared as a full associative array
13117 declaration, with the value of the same attribute in an imported or extended
13120 @smallexample @c projectfile
13122 for Default_Switches use Default.Builder'Default_Switches;
13127 In this example, @code{Default} must be either a project imported by the
13128 current project, or the project that the current project extends. If the
13129 attribute is in a package (in this case, in package @code{Builder}), the same
13130 package needs to be specified.
13133 A full associative array declaration replaces any other declaration for the
13134 attribute, including other full associative array declaration. Single
13135 associative array associations may be declare after a full associative
13136 declaration, modifying the value for a single association of the attribute.
13138 @node case Constructions
13139 @subsection @code{case} Constructions
13142 A @code{case} construction is used in a project file to effect conditional
13144 Here is a typical example:
13146 @smallexample @c projectfile
13149 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
13151 OS : OS_Type := external ("OS", "GNU/Linux");
13155 package Compiler is
13157 when "GNU/Linux" | "Unix" =>
13158 for ^Default_Switches^Default_Switches^ ("Ada")
13159 use ("^-gnath^-gnath^");
13161 for ^Default_Switches^Default_Switches^ ("Ada")
13162 use ("^-gnatP^-gnatP^");
13171 The syntax of a @code{case} construction is based on the Ada case statement
13172 (although there is no @code{null} construction for empty alternatives).
13174 The case expression must be a typed string variable.
13175 Each alternative comprises the reserved word @code{when}, either a list of
13176 literal strings separated by the @code{"|"} character or the reserved word
13177 @code{others}, and the @code{"=>"} token.
13178 Each literal string must belong to the string type that is the type of the
13180 An @code{others} alternative, if present, must occur last.
13182 After each @code{=>}, there are zero or more constructions. The only
13183 constructions allowed in a case construction are other case constructions,
13184 attribute declarations and variable declarations. String type declarations and
13185 package declarations are not allowed. Variable declarations are restricted to
13186 variables that have already been declared before the case construction.
13188 The value of the case variable is often given by an external reference
13189 (@pxref{External References in Project Files}).
13191 @c ****************************************
13192 @c * Objects and Sources in Project Files *
13193 @c ****************************************
13195 @node Objects and Sources in Project Files
13196 @section Objects and Sources in Project Files
13199 * Object Directory::
13201 * Source Directories::
13202 * Source File Names::
13206 Each project has exactly one object directory and one or more source
13207 directories. The source directories must contain at least one source file,
13208 unless the project file explicitly specifies that no source files are present
13209 (@pxref{Source File Names}).
13211 @node Object Directory
13212 @subsection Object Directory
13215 The object directory for a project is the directory containing the compiler's
13216 output (such as @file{ALI} files and object files) for the project's immediate
13219 The object directory is given by the value of the attribute @code{Object_Dir}
13220 in the project file.
13222 @smallexample @c projectfile
13223 for Object_Dir use "objects";
13227 The attribute @code{Object_Dir} has a string value, the path name of the object
13228 directory. The path name may be absolute or relative to the directory of the
13229 project file. This directory must already exist, and be readable and writable.
13231 By default, when the attribute @code{Object_Dir} is not given an explicit value
13232 or when its value is the empty string, the object directory is the same as the
13233 directory containing the project file.
13235 @node Exec Directory
13236 @subsection Exec Directory
13239 The exec directory for a project is the directory containing the executables
13240 for the project's main subprograms.
13242 The exec directory is given by the value of the attribute @code{Exec_Dir}
13243 in the project file.
13245 @smallexample @c projectfile
13246 for Exec_Dir use "executables";
13250 The attribute @code{Exec_Dir} has a string value, the path name of the exec
13251 directory. The path name may be absolute or relative to the directory of the
13252 project file. This directory must already exist, and be writable.
13254 By default, when the attribute @code{Exec_Dir} is not given an explicit value
13255 or when its value is the empty string, the exec directory is the same as the
13256 object directory of the project file.
13258 @node Source Directories
13259 @subsection Source Directories
13262 The source directories of a project are specified by the project file
13263 attribute @code{Source_Dirs}.
13265 This attribute's value is a string list. If the attribute is not given an
13266 explicit value, then there is only one source directory, the one where the
13267 project file resides.
13269 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
13272 @smallexample @c projectfile
13273 for Source_Dirs use ();
13277 indicates that the project contains no source files.
13279 Otherwise, each string in the string list designates one or more
13280 source directories.
13282 @smallexample @c projectfile
13283 for Source_Dirs use ("sources", "test/drivers");
13287 If a string in the list ends with @code{"/**"}, then the directory whose path
13288 name precedes the two asterisks, as well as all its subdirectories
13289 (recursively), are source directories.
13291 @smallexample @c projectfile
13292 for Source_Dirs use ("/system/sources/**");
13296 Here the directory @code{/system/sources} and all of its subdirectories
13297 (recursively) are source directories.
13299 To specify that the source directories are the directory of the project file
13300 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
13301 @smallexample @c projectfile
13302 for Source_Dirs use ("./**");
13306 Each of the source directories must exist and be readable.
13308 @node Source File Names
13309 @subsection Source File Names
13312 In a project that contains source files, their names may be specified by the
13313 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
13314 (a string). Source file names never include any directory information.
13316 If the attribute @code{Source_Files} is given an explicit value, then each
13317 element of the list is a source file name.
13319 @smallexample @c projectfile
13320 for Source_Files use ("main.adb");
13321 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
13325 If the attribute @code{Source_Files} is not given an explicit value,
13326 but the attribute @code{Source_List_File} is given a string value,
13327 then the source file names are contained in the text file whose path name
13328 (absolute or relative to the directory of the project file) is the
13329 value of the attribute @code{Source_List_File}.
13331 Each line in the file that is not empty or is not a comment
13332 contains a source file name.
13334 @smallexample @c projectfile
13335 for Source_List_File use "source_list.txt";
13339 By default, if neither the attribute @code{Source_Files} nor the attribute
13340 @code{Source_List_File} is given an explicit value, then each file in the
13341 source directories that conforms to the project's naming scheme
13342 (@pxref{Naming Schemes}) is an immediate source of the project.
13344 A warning is issued if both attributes @code{Source_Files} and
13345 @code{Source_List_File} are given explicit values. In this case, the attribute
13346 @code{Source_Files} prevails.
13348 Each source file name must be the name of one existing source file
13349 in one of the source directories.
13351 A @code{Source_Files} attribute whose value is an empty list
13352 indicates that there are no source files in the project.
13354 If the order of the source directories is known statically, that is if
13355 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13356 be several files with the same source file name. In this case, only the file
13357 in the first directory is considered as an immediate source of the project
13358 file. If the order of the source directories is not known statically, it is
13359 an error to have several files with the same source file name.
13361 Projects can be specified to have no Ada source
13362 files: the value of @code{Source_Dirs} or @code{Source_Files} may be an empty
13363 list, or the @code{"Ada"} may be absent from @code{Languages}:
13365 @smallexample @c projectfile
13366 for Source_Dirs use ();
13367 for Source_Files use ();
13368 for Languages use ("C", "C++");
13372 Otherwise, a project must contain at least one immediate source.
13374 Projects with no source files are useful as template packages
13375 (@pxref{Packages in Project Files}) for other projects; in particular to
13376 define a package @code{Naming} (@pxref{Naming Schemes}).
13378 @c ****************************
13379 @c * Importing Projects *
13380 @c ****************************
13382 @node Importing Projects
13383 @section Importing Projects
13384 @cindex @code{ADA_PROJECT_PATH}
13385 @cindex @code{GPR_PROJECT_PATH}
13388 An immediate source of a project P may depend on source files that
13389 are neither immediate sources of P nor in the predefined library.
13390 To get this effect, P must @emph{import} the projects that contain the needed
13393 @smallexample @c projectfile
13395 with "project1", "utilities.gpr";
13396 with "/namings/apex.gpr";
13403 As can be seen in this example, the syntax for importing projects is similar
13404 to the syntax for importing compilation units in Ada. However, project files
13405 use literal strings instead of names, and the @code{with} clause identifies
13406 project files rather than packages.
13408 Each literal string is the file name or path name (absolute or relative) of a
13409 project file. If a string corresponds to a file name, with no path or a
13410 relative path, then its location is determined by the @emph{project path}. The
13411 latter can be queried using @code{gnatls -v}. It contains:
13415 In first position, the directory containing the current project file.
13417 In last position, the default project directory. This default project directory
13418 is part of the GNAT installation and is the standard place to install project
13419 files giving access to standard support libraries.
13421 @ref{Installing a library}
13425 In between, all the directories referenced in the
13426 ^environment variables^logical names^ @env{GPR_PROJECT_PATH}
13427 and @env{ADA_PROJECT_PATH} if they exist, and in that order.
13431 If a relative pathname is used, as in
13433 @smallexample @c projectfile
13438 then the full path for the project is constructed by concatenating this
13439 relative path to those in the project path, in order, until a matching file is
13440 found. Any symbolic link will be fully resolved in the directory of the
13441 importing project file before the imported project file is examined.
13443 If the @code{with}'ed project file name does not have an extension,
13444 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13445 then the file name as specified in the @code{with} clause (no extension) will
13446 be used. In the above example, if a file @code{project1.gpr} is found, then it
13447 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13448 then it will be used; if neither file exists, this is an error.
13450 A warning is issued if the name of the project file does not match the
13451 name of the project; this check is case insensitive.
13453 Any source file that is an immediate source of the imported project can be
13454 used by the immediate sources of the importing project, transitively. Thus
13455 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13456 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13457 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13458 because if and when @code{B} ceases to import @code{C}, some sources in
13459 @code{A} will no longer compile.
13461 A side effect of this capability is that normally cyclic dependencies are not
13462 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13463 is not allowed to import @code{A}. However, there are cases when cyclic
13464 dependencies would be beneficial. For these cases, another form of import
13465 between projects exists, the @code{limited with}: a project @code{A} that
13466 imports a project @code{B} with a straight @code{with} may also be imported,
13467 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13468 to @code{A} include at least one @code{limited with}.
13470 @smallexample @c 0projectfile
13476 limited with "../a/a.gpr";
13484 limited with "../a/a.gpr";
13490 In the above legal example, there are two project cycles:
13493 @item A -> C -> D -> A
13497 In each of these cycle there is one @code{limited with}: import of @code{A}
13498 from @code{B} and import of @code{A} from @code{D}.
13500 The difference between straight @code{with} and @code{limited with} is that
13501 the name of a project imported with a @code{limited with} cannot be used in the
13502 project that imports it. In particular, its packages cannot be renamed and
13503 its variables cannot be referred to.
13505 An exception to the above rules for @code{limited with} is that for the main
13506 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13507 @code{limited with} is equivalent to a straight @code{with}. For example,
13508 in the example above, projects @code{B} and @code{D} could not be main
13509 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13510 each have a @code{limited with} that is the only one in a cycle of importing
13513 @c *********************
13514 @c * Project Extension *
13515 @c *********************
13517 @node Project Extension
13518 @section Project Extension
13521 During development of a large system, it is sometimes necessary to use
13522 modified versions of some of the source files, without changing the original
13523 sources. This can be achieved through the @emph{project extension} facility.
13525 @smallexample @c projectfile
13526 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13530 A project extension declaration introduces an extending project
13531 (the @emph{child}) and a project being extended (the @emph{parent}).
13533 By default, a child project inherits all the sources of its parent.
13534 However, inherited sources can be overridden: a unit in a parent is hidden
13535 by a unit of the same name in the child.
13537 Inherited sources are considered to be sources (but not immediate sources)
13538 of the child project; see @ref{Project File Syntax}.
13540 An inherited source file retains any switches specified in the parent project.
13542 For example if the project @code{Utilities} contains the spec and the
13543 body of an Ada package @code{Util_IO}, then the project
13544 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13545 The original body of @code{Util_IO} will not be considered in program builds.
13546 However, the package spec will still be found in the project
13549 A child project can have only one parent, except when it is qualified as
13550 abstract. But it may import any number of other projects.
13552 A project is not allowed to import directly or indirectly at the same time a
13553 child project and any of its ancestors.
13555 @c *******************************
13556 @c * Project Hierarchy Extension *
13557 @c *******************************
13559 @node Project Hierarchy Extension
13560 @section Project Hierarchy Extension
13563 When extending a large system spanning multiple projects, it is often
13564 inconvenient to extend every project in the hierarchy that is impacted by a
13565 small change introduced. In such cases, it is possible to create a virtual
13566 extension of entire hierarchy using @code{extends all} relationship.
13568 When the project is extended using @code{extends all} inheritance, all projects
13569 that are imported by it, both directly and indirectly, are considered virtually
13570 extended. That is, the Project Manager creates "virtual projects"
13571 that extend every project in the hierarchy; all these virtual projects have
13572 no sources of their own and have as object directory the object directory of
13573 the root of "extending all" project.
13575 It is possible to explicitly extend one or more projects in the hierarchy
13576 in order to modify the sources. These extending projects must be imported by
13577 the "extending all" project, which will replace the corresponding virtual
13578 projects with the explicit ones.
13580 When building such a project hierarchy extension, the Project Manager will
13581 ensure that both modified sources and sources in virtual extending projects
13582 that depend on them, are recompiled.
13584 By means of example, consider the following hierarchy of projects.
13588 project A, containing package P1
13590 project B importing A and containing package P2 which depends on P1
13592 project C importing B and containing package P3 which depends on P2
13596 We want to modify packages P1 and P3.
13598 This project hierarchy will need to be extended as follows:
13602 Create project A1 that extends A, placing modified P1 there:
13604 @smallexample @c 0projectfile
13605 project A1 extends "(@dots{})/A" is
13610 Create project C1 that "extends all" C and imports A1, placing modified
13613 @smallexample @c 0projectfile
13614 with "(@dots{})/A1";
13615 project C1 extends all "(@dots{})/C" is
13620 When you build project C1, your entire modified project space will be
13621 recompiled, including the virtual project B1 that has been impacted by the
13622 "extending all" inheritance of project C.
13624 Note that if a Library Project in the hierarchy is virtually extended,
13625 the virtual project that extends the Library Project is not a Library Project.
13627 @c ****************************************
13628 @c * External References in Project Files *
13629 @c ****************************************
13631 @node External References in Project Files
13632 @section External References in Project Files
13635 A project file may contain references to external variables; such references
13636 are called @emph{external references}.
13638 An external variable is either defined as part of the environment (an
13639 environment variable in Unix, for example) or else specified on the command
13640 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13641 If both, then the command line value is used.
13643 The value of an external reference is obtained by means of the built-in
13644 function @code{external}, which returns a string value.
13645 This function has two forms:
13647 @item @code{external (external_variable_name)}
13648 @item @code{external (external_variable_name, default_value)}
13652 Each parameter must be a string literal. For example:
13654 @smallexample @c projectfile
13656 external ("OS", "GNU/Linux")
13660 In the form with one parameter, the function returns the value of
13661 the external variable given as parameter. If this name is not present in the
13662 environment, the function returns an empty string.
13664 In the form with two string parameters, the second argument is
13665 the value returned when the variable given as the first argument is not
13666 present in the environment. In the example above, if @code{"OS"} is not
13667 the name of ^an environment variable^a logical name^ and is not passed on
13668 the command line, then the returned value is @code{"GNU/Linux"}.
13670 An external reference may be part of a string expression or of a string
13671 list expression, and can therefore appear in a variable declaration or
13672 an attribute declaration.
13674 @smallexample @c projectfile
13676 type Mode_Type is ("Debug", "Release");
13677 Mode : Mode_Type := external ("MODE");
13684 @c *****************************
13685 @c * Packages in Project Files *
13686 @c *****************************
13688 @node Packages in Project Files
13689 @section Packages in Project Files
13692 A @emph{package} defines the settings for project-aware tools within a
13694 For each such tool one can declare a package; the names for these
13695 packages are preset (@pxref{Packages}).
13696 A package may contain variable declarations, attribute declarations, and case
13699 @smallexample @c projectfile
13702 package Builder is -- used by gnatmake
13703 for ^Default_Switches^Default_Switches^ ("Ada")
13712 The syntax of package declarations mimics that of package in Ada.
13714 Most of the packages have an attribute
13715 @code{^Default_Switches^Default_Switches^}.
13716 This attribute is an associative array, and its value is a string list.
13717 The index of the associative array is the name of a programming language (case
13718 insensitive). This attribute indicates the ^switch^switch^
13719 or ^switches^switches^ to be used
13720 with the corresponding tool.
13722 Some packages also have another attribute, @code{^Switches^Switches^},
13723 an associative array whose value is a string list.
13724 The index is the name of a source file.
13725 This attribute indicates the ^switch^switch^
13726 or ^switches^switches^ to be used by the corresponding
13727 tool when dealing with this specific file.
13729 Further information on these ^switch^switch^-related attributes is found in
13730 @ref{^Switches^Switches^ and Project Files}.
13732 A package may be declared as a @emph{renaming} of another package; e.g., from
13733 the project file for an imported project.
13735 @smallexample @c projectfile
13737 with "/global/apex.gpr";
13739 package Naming renames Apex.Naming;
13746 Packages that are renamed in other project files often come from project files
13747 that have no sources: they are just used as templates. Any modification in the
13748 template will be reflected automatically in all the project files that rename
13749 a package from the template.
13751 In addition to the tool-oriented packages, you can also declare a package
13752 named @code{Naming} to establish specialized source file naming conventions
13753 (@pxref{Naming Schemes}).
13755 @c ************************************
13756 @c * Variables from Imported Projects *
13757 @c ************************************
13759 @node Variables from Imported Projects
13760 @section Variables from Imported Projects
13763 An attribute or variable defined in an imported or parent project can
13764 be used in expressions in the importing / extending project.
13765 Such an attribute or variable is denoted by an expanded name whose prefix
13766 is either the name of the project or the expanded name of a package within
13769 @smallexample @c projectfile
13772 project Main extends "base" is
13773 Var1 := Imported.Var;
13774 Var2 := Base.Var & ".new";
13779 for ^Default_Switches^Default_Switches^ ("Ada")
13780 use Imported.Builder'Ada_^Switches^Switches^ &
13781 "^-gnatg^-gnatg^" &
13787 package Compiler is
13788 for ^Default_Switches^Default_Switches^ ("Ada")
13789 use Base.Compiler'Ada_^Switches^Switches^;
13800 The value of @code{Var1} is a copy of the variable @code{Var} defined
13801 in the project file @file{"imported.gpr"}
13803 the value of @code{Var2} is a copy of the value of variable @code{Var}
13804 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13806 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13807 @code{Builder} is a string list that includes in its value a copy of the value
13808 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13809 in project file @file{imported.gpr} plus two new elements:
13810 @option{"^-gnatg^-gnatg^"}
13811 and @option{"^-v^-v^"};
13813 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13814 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13815 defined in the @code{Compiler} package in project file @file{base.gpr},
13816 the project being extended.
13819 @c ******************
13820 @c * Naming Schemes *
13821 @c ******************
13823 @node Naming Schemes
13824 @section Naming Schemes
13827 Sometimes an Ada software system is ported from a foreign compilation
13828 environment to GNAT, and the file names do not use the default GNAT
13829 conventions. Instead of changing all the file names (which for a variety
13830 of reasons might not be possible), you can define the relevant file
13831 naming scheme in the @code{Naming} package in your project file.
13834 Note that the use of pragmas described in
13835 @ref{Alternative File Naming Schemes} by mean of a configuration
13836 pragmas file is not supported when using project files. You must use
13837 the features described in this paragraph. You can however use specify
13838 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13841 For example, the following
13842 package models the Apex file naming rules:
13844 @smallexample @c projectfile
13847 for Casing use "lowercase";
13848 for Dot_Replacement use ".";
13849 for Spec_Suffix ("Ada") use ".1.ada";
13850 for Body_Suffix ("Ada") use ".2.ada";
13857 For example, the following package models the HP Ada file naming rules:
13859 @smallexample @c projectfile
13862 for Casing use "lowercase";
13863 for Dot_Replacement use "__";
13864 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13865 for Body_Suffix ("Ada") use ".^ada^ada^";
13871 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13872 names in lower case)
13876 You can define the following attributes in package @code{Naming}:
13880 @item @code{Casing}
13881 This must be a string with one of the three values @code{"lowercase"},
13882 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13885 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13887 @item @code{Dot_Replacement}
13888 This must be a string whose value satisfies the following conditions:
13891 @item It must not be empty
13892 @item It cannot start or end with an alphanumeric character
13893 @item It cannot be a single underscore
13894 @item It cannot start with an underscore followed by an alphanumeric
13895 @item It cannot contain a dot @code{'.'} except if the entire string
13900 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13902 @item @code{Spec_Suffix}
13903 This is an associative array (indexed by the programming language name, case
13904 insensitive) whose value is a string that must satisfy the following
13908 @item It must not be empty
13909 @item It must include at least one dot
13912 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13913 @code{"^.ads^.ADS^"}.
13915 @item @code{Body_Suffix}
13916 This is an associative array (indexed by the programming language name, case
13917 insensitive) whose value is a string that must satisfy the following
13921 @item It must not be empty
13922 @item It must include at least one dot
13923 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13926 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13927 same string, then a file name that ends with the longest of these two suffixes
13928 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13929 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13931 If the suffix does not start with a '.', a file with a name exactly equal
13932 to the suffix will also be part of the project (for instance if you define
13933 the suffix as @code{Makefile}, a file called @file{Makefile} will be part
13934 of the project. This is not interesting in general when using projects to
13935 compile. However, it might become useful when a project is also used to
13936 find the list of source files in an editor, like the GNAT Programming System
13939 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13940 @code{"^.adb^.ADB^"}.
13942 @item @code{Separate_Suffix}
13943 This must be a string whose value satisfies the same conditions as
13944 @code{Body_Suffix}. The same "longest suffix" rules apply.
13947 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13948 value as @code{Body_Suffix ("Ada")}.
13952 You can use the associative array attribute @code{Spec} to define
13953 the source file name for an individual Ada compilation unit's spec. The array
13954 index must be a string literal that identifies the Ada unit (case insensitive).
13955 The value of this attribute must be a string that identifies the file that
13956 contains this unit's spec (case sensitive or insensitive depending on the
13959 @smallexample @c projectfile
13960 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13963 When the source file contains several units, you can indicate at what
13964 position the unit occurs in the file, with the following. The first unit
13965 in the file has index 1
13967 @smallexample @c projectfile
13968 for Body ("top") use "foo.a" at 1;
13969 for Body ("foo") use "foo.a" at 2;
13974 You can use the associative array attribute @code{Body} to
13975 define the source file name for an individual Ada compilation unit's body
13976 (possibly a subunit). The array index must be a string literal that identifies
13977 the Ada unit (case insensitive). The value of this attribute must be a string
13978 that identifies the file that contains this unit's body or subunit (case
13979 sensitive or insensitive depending on the operating system).
13981 @smallexample @c projectfile
13982 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13986 @c ********************
13987 @c * Library Projects *
13988 @c ********************
13990 @node Library Projects
13991 @section Library Projects
13994 @emph{Library projects} are projects whose object code is placed in a library.
13995 (Note that this facility is not yet supported on all platforms).
13997 @code{gnatmake} or @code{gprbuild} will collect all object files into a
13998 single archive, which might either be a shared or a static library. This
13999 library can later on be linked with multiple executables, potentially
14000 reducing their sizes.
14002 If your project file specifies languages other than Ada, but you are still
14003 using @code{gnatmake} to compile and link, the latter will not try to
14004 compile your sources other than Ada (you should use @code{gprbuild} if that
14005 is your intent). However, @code{gnatmake} will automatically link all object
14006 files found in the object directory, whether or not they were compiled from
14007 an Ada source file. This specific behavior only applies when multiple
14008 languages are specified.
14010 To create a library project, you need to define in its project file
14011 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
14012 Additionally, you may define other library-related attributes such as
14013 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
14014 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
14016 The @code{Library_Name} attribute has a string value. There is no restriction
14017 on the name of a library. It is the responsibility of the developer to
14018 choose a name that will be accepted by the platform. It is recommended to
14019 choose names that could be Ada identifiers; such names are almost guaranteed
14020 to be acceptable on all platforms.
14022 The @code{Library_Dir} attribute has a string value that designates the path
14023 (absolute or relative) of the directory where the library will reside.
14024 It must designate an existing directory, and this directory must be writable,
14025 different from the project's object directory and from any source directory
14026 in the project tree.
14028 If both @code{Library_Name} and @code{Library_Dir} are specified and
14029 are legal, then the project file defines a library project. The optional
14030 library-related attributes are checked only for such project files.
14032 The @code{Library_Kind} attribute has a string value that must be one of the
14033 following (case insensitive): @code{"static"}, @code{"dynamic"} or
14034 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
14035 attribute is not specified, the library is a static library, that is
14036 an archive of object files that can be potentially linked into a
14037 static executable. Otherwise, the library may be dynamic or
14038 relocatable, that is a library that is loaded only at the start of execution.
14040 If you need to build both a static and a dynamic library, you should use two
14041 different object directories, since in some cases some extra code needs to
14042 be generated for the latter. For such cases, it is recommended to either use
14043 two different project files, or a single one which uses external variables
14044 to indicate what kind of library should be build.
14046 The @code{Library_ALI_Dir} attribute may be specified to indicate the
14047 directory where the ALI files of the library will be copied. When it is
14048 not specified, the ALI files are copied to the directory specified in
14049 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
14050 must be writable and different from the project's object directory and from
14051 any source directory in the project tree.
14053 The @code{Library_Version} attribute has a string value whose interpretation
14054 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
14055 used only for dynamic/relocatable libraries as the internal name of the
14056 library (the @code{"soname"}). If the library file name (built from the
14057 @code{Library_Name}) is different from the @code{Library_Version}, then the
14058 library file will be a symbolic link to the actual file whose name will be
14059 @code{Library_Version}.
14063 @smallexample @c projectfile
14069 for Library_Dir use "lib_dir";
14070 for Library_Name use "dummy";
14071 for Library_Kind use "relocatable";
14072 for Library_Version use "libdummy.so." & Version;
14079 Directory @file{lib_dir} will contain the internal library file whose name
14080 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
14081 @file{libdummy.so.1}.
14083 When @command{gnatmake} detects that a project file
14084 is a library project file, it will check all immediate sources of the project
14085 and rebuild the library if any of the sources have been recompiled.
14087 Standard project files can import library project files. In such cases,
14088 the libraries will only be rebuilt if some of its sources are recompiled
14089 because they are in the closure of some other source in an importing project.
14090 Sources of the library project files that are not in such a closure will
14091 not be checked, unless the full library is checked, because one of its sources
14092 needs to be recompiled.
14094 For instance, assume the project file @code{A} imports the library project file
14095 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
14096 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
14097 @file{l2.ads}, @file{l2.adb}.
14099 If @file{l1.adb} has been modified, then the library associated with @code{L}
14100 will be rebuilt when compiling all the immediate sources of @code{A} only
14101 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
14104 To be sure that all the sources in the library associated with @code{L} are
14105 up to date, and that all the sources of project @code{A} are also up to date,
14106 the following two commands needs to be used:
14113 When a library is built or rebuilt, an attempt is made first to delete all
14114 files in the library directory.
14115 All @file{ALI} files will also be copied from the object directory to the
14116 library directory. To build executables, @command{gnatmake} will use the
14117 library rather than the individual object files.
14120 It is also possible to create library project files for third-party libraries
14121 that are precompiled and cannot be compiled locally thanks to the
14122 @code{externally_built} attribute. (See @ref{Installing a library}).
14125 @c *******************************
14126 @c * Stand-alone Library Projects *
14127 @c *******************************
14129 @node Stand-alone Library Projects
14130 @section Stand-alone Library Projects
14133 A Stand-alone Library is a library that contains the necessary code to
14134 elaborate the Ada units that are included in the library. A Stand-alone
14135 Library is suitable to be used in an executable when the main is not
14136 in Ada. However, Stand-alone Libraries may also be used with an Ada main
14139 A Stand-alone Library Project is a Library Project where the library is
14140 a Stand-alone Library.
14142 To be a Stand-alone Library Project, in addition to the two attributes
14143 that make a project a Library Project (@code{Library_Name} and
14144 @code{Library_Dir}, see @ref{Library Projects}), the attribute
14145 @code{Library_Interface} must be defined.
14147 @smallexample @c projectfile
14149 for Library_Dir use "lib_dir";
14150 for Library_Name use "dummy";
14151 for Library_Interface use ("int1", "int1.child");
14155 Attribute @code{Library_Interface} has a nonempty string list value,
14156 each string in the list designating a unit contained in an immediate source
14157 of the project file.
14159 When a Stand-alone Library is built, first the binder is invoked to build
14160 a package whose name depends on the library name
14161 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
14162 This binder-generated package includes initialization and
14163 finalization procedures whose
14164 names depend on the library name (dummyinit and dummyfinal in the example
14165 above). The object corresponding to this package is included in the library.
14167 A dynamic or relocatable Stand-alone Library is automatically initialized
14168 if automatic initialization of Stand-alone Libraries is supported on the
14169 platform and if attribute @code{Library_Auto_Init} is not specified or
14170 is specified with the value "true". A static Stand-alone Library is never
14171 automatically initialized.
14173 Single string attribute @code{Library_Auto_Init} may be specified with only
14174 two possible values: "false" or "true" (case-insensitive). Specifying
14175 "false" for attribute @code{Library_Auto_Init} will prevent automatic
14176 initialization of dynamic or relocatable libraries.
14178 When a non-automatically initialized Stand-alone Library is used
14179 in an executable, its initialization procedure must be called before
14180 any service of the library is used.
14181 When the main subprogram is in Ada, it may mean that the initialization
14182 procedure has to be called during elaboration of another package.
14184 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
14185 (those that are listed in attribute @code{Library_Interface}) are copied to
14186 the Library Directory. As a consequence, only the Interface Units may be
14187 imported from Ada units outside of the library. If other units are imported,
14188 the binding phase will fail.
14190 When a Stand-Alone Library is bound, the switches that are specified in
14191 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
14192 used in the call to @command{gnatbind}.
14194 The string list attribute @code{Library_Options} may be used to specified
14195 additional switches to the call to @command{gcc} to link the library.
14197 The attribute @code{Library_Src_Dir}, may be specified for a
14198 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
14199 single string value. Its value must be the path (absolute or relative to the
14200 project directory) of an existing directory. This directory cannot be the
14201 object directory or one of the source directories, but it can be the same as
14202 the library directory. The sources of the Interface
14203 Units of the library, necessary to an Ada client of the library, will be
14204 copied to the designated directory, called Interface Copy directory.
14205 These sources includes the specs of the Interface Units, but they may also
14206 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
14207 are used, or when there is a generic units in the spec. Before the sources
14208 are copied to the Interface Copy directory, an attempt is made to delete all
14209 files in the Interface Copy directory.
14211 @c *************************************
14212 @c * Switches Related to Project Files *
14213 @c *************************************
14214 @node Switches Related to Project Files
14215 @section Switches Related to Project Files
14218 The following switches are used by GNAT tools that support project files:
14222 @item ^-P^/PROJECT_FILE=^@var{project}
14223 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
14224 Indicates the name of a project file. This project file will be parsed with
14225 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
14226 if any, and using the external references indicated
14227 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
14229 There may zero, one or more spaces between @option{-P} and @var{project}.
14233 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
14236 Since the Project Manager parses the project file only after all the switches
14237 on the command line are checked, the order of the switches
14238 @option{^-P^/PROJECT_FILE^},
14239 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
14240 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
14242 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
14243 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
14244 Indicates that external variable @var{name} has the value @var{value}.
14245 The Project Manager will use this value for occurrences of
14246 @code{external(name)} when parsing the project file.
14250 If @var{name} or @var{value} includes a space, then @var{name=value} should be
14251 put between quotes.
14259 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
14260 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
14261 @var{name}, only the last one is used.
14264 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
14265 takes precedence over the value of the same name in the environment.
14267 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
14268 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
14269 Indicates the verbosity of the parsing of GNAT project files.
14272 @option{-vP0} means Default;
14273 @option{-vP1} means Medium;
14274 @option{-vP2} means High.
14278 There are three possible options for this qualifier: DEFAULT, MEDIUM and
14283 The default is ^Default^DEFAULT^: no output for syntactically correct
14286 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
14287 only the last one is used.
14289 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
14290 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
14291 Add directory <dir> at the beginning of the project search path, in order,
14292 after the current working directory.
14296 @cindex @option{-eL} (any project-aware tool)
14297 Follow all symbolic links when processing project files.
14300 @item ^--subdirs^/SUBDIRS^=<subdir>
14301 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
14302 This switch is recognized by gnatmake and gnatclean. It indicate that the real
14303 directories (except the source directories) are the subdirectories <subdir>
14304 of the directories specified in the project files. This applies in particular
14305 to object directories, library directories and exec directories. If the
14306 subdirectories do not exist, they are created automatically.
14310 @c **********************************
14311 @c * Tools Supporting Project Files *
14312 @c **********************************
14314 @node Tools Supporting Project Files
14315 @section Tools Supporting Project Files
14318 * gnatmake and Project Files::
14319 * The GNAT Driver and Project Files::
14322 @node gnatmake and Project Files
14323 @subsection gnatmake and Project Files
14326 This section covers several topics related to @command{gnatmake} and
14327 project files: defining ^switches^switches^ for @command{gnatmake}
14328 and for the tools that it invokes; specifying configuration pragmas;
14329 the use of the @code{Main} attribute; building and rebuilding library project
14333 * ^Switches^Switches^ and Project Files::
14334 * Specifying Configuration Pragmas::
14335 * Project Files and Main Subprograms::
14336 * Library Project Files::
14339 @node ^Switches^Switches^ and Project Files
14340 @subsubsection ^Switches^Switches^ and Project Files
14343 It is not currently possible to specify VMS style qualifiers in the project
14344 files; only Unix style ^switches^switches^ may be specified.
14348 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
14349 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
14350 attribute, a @code{^Switches^Switches^} attribute, or both;
14351 as their names imply, these ^switch^switch^-related
14352 attributes affect the ^switches^switches^ that are used for each of these GNAT
14354 @command{gnatmake} is invoked. As will be explained below, these
14355 component-specific ^switches^switches^ precede
14356 the ^switches^switches^ provided on the @command{gnatmake} command line.
14358 The @code{^Default_Switches^Default_Switches^} attribute is an associative
14359 array indexed by language name (case insensitive) whose value is a string list.
14362 @smallexample @c projectfile
14364 package Compiler is
14365 for ^Default_Switches^Default_Switches^ ("Ada")
14366 use ("^-gnaty^-gnaty^",
14373 The @code{^Switches^Switches^} attribute is also an associative array,
14374 indexed by a file name (which may or may not be case sensitive, depending
14375 on the operating system) whose value is a string list. For example:
14377 @smallexample @c projectfile
14380 for ^Switches^Switches^ ("main1.adb")
14382 for ^Switches^Switches^ ("main2.adb")
14389 For the @code{Builder} package, the file names must designate source files
14390 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14391 file names must designate @file{ALI} or source files for main subprograms.
14392 In each case just the file name without an explicit extension is acceptable.
14394 For each tool used in a program build (@command{gnatmake}, the compiler, the
14395 binder, and the linker), the corresponding package @dfn{contributes} a set of
14396 ^switches^switches^ for each file on which the tool is invoked, based on the
14397 ^switch^switch^-related attributes defined in the package.
14398 In particular, the ^switches^switches^
14399 that each of these packages contributes for a given file @var{f} comprise:
14403 the value of attribute @code{^Switches^Switches^ (@var{f})},
14404 if it is specified in the package for the given file,
14406 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14407 if it is specified in the package.
14411 If neither of these attributes is defined in the package, then the package does
14412 not contribute any ^switches^switches^ for the given file.
14414 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14415 two sets, in the following order: those contributed for the file
14416 by the @code{Builder} package;
14417 and the switches passed on the command line.
14419 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14420 the ^switches^switches^ passed to the tool comprise three sets,
14421 in the following order:
14425 the applicable ^switches^switches^ contributed for the file
14426 by the @code{Builder} package in the project file supplied on the command line;
14429 those contributed for the file by the package (in the relevant project file --
14430 see below) corresponding to the tool; and
14433 the applicable switches passed on the command line.
14437 The term @emph{applicable ^switches^switches^} reflects the fact that
14438 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14439 tools, depending on the individual ^switch^switch^.
14441 @command{gnatmake} may invoke the compiler on source files from different
14442 projects. The Project Manager will use the appropriate project file to
14443 determine the @code{Compiler} package for each source file being compiled.
14444 Likewise for the @code{Binder} and @code{Linker} packages.
14446 As an example, consider the following package in a project file:
14448 @smallexample @c projectfile
14451 package Compiler is
14452 for ^Default_Switches^Default_Switches^ ("Ada")
14454 for ^Switches^Switches^ ("a.adb")
14456 for ^Switches^Switches^ ("b.adb")
14458 "^-gnaty^-gnaty^");
14465 If @command{gnatmake} is invoked with this project file, and it needs to
14466 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14467 @file{a.adb} will be compiled with the ^switch^switch^
14468 @option{^-O1^-O1^},
14469 @file{b.adb} with ^switches^switches^
14471 and @option{^-gnaty^-gnaty^},
14472 and @file{c.adb} with @option{^-g^-g^}.
14474 The following example illustrates the ordering of the ^switches^switches^
14475 contributed by different packages:
14477 @smallexample @c projectfile
14481 for ^Switches^Switches^ ("main.adb")
14489 package Compiler is
14490 for ^Switches^Switches^ ("main.adb")
14498 If you issue the command:
14501 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14505 then the compiler will be invoked on @file{main.adb} with the following
14506 sequence of ^switches^switches^
14509 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14512 with the last @option{^-O^-O^}
14513 ^switch^switch^ having precedence over the earlier ones;
14514 several other ^switches^switches^
14515 (such as @option{^-c^-c^}) are added implicitly.
14517 The ^switches^switches^
14519 and @option{^-O1^-O1^} are contributed by package
14520 @code{Builder}, @option{^-O2^-O2^} is contributed
14521 by the package @code{Compiler}
14522 and @option{^-O0^-O0^} comes from the command line.
14524 The @option{^-g^-g^}
14525 ^switch^switch^ will also be passed in the invocation of
14526 @command{Gnatlink.}
14528 A final example illustrates switch contributions from packages in different
14531 @smallexample @c projectfile
14534 for Source_Files use ("pack.ads", "pack.adb");
14535 package Compiler is
14536 for ^Default_Switches^Default_Switches^ ("Ada")
14537 use ("^-gnata^-gnata^");
14545 for Source_Files use ("foo_main.adb", "bar_main.adb");
14547 for ^Switches^Switches^ ("foo_main.adb")
14555 -- Ada source file:
14557 procedure Foo_Main is
14565 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14569 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14570 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14571 @option{^-gnato^-gnato^} (passed on the command line).
14572 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14573 are @option{^-g^-g^} from @code{Proj4.Builder},
14574 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14575 and @option{^-gnato^-gnato^} from the command line.
14578 When using @command{gnatmake} with project files, some ^switches^switches^ or
14579 arguments may be expressed as relative paths. As the working directory where
14580 compilation occurs may change, these relative paths are converted to absolute
14581 paths. For the ^switches^switches^ found in a project file, the relative paths
14582 are relative to the project file directory, for the switches on the command
14583 line, they are relative to the directory where @command{gnatmake} is invoked.
14584 The ^switches^switches^ for which this occurs are:
14590 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14592 ^-o^-o^, object files specified in package @code{Linker} or after
14593 -largs on the command line). The exception to this rule is the ^switch^switch^
14594 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14596 @node Specifying Configuration Pragmas
14597 @subsubsection Specifying Configuration Pragmas
14599 When using @command{gnatmake} with project files, if there exists a file
14600 @file{gnat.adc} that contains configuration pragmas, this file will be
14603 Configuration pragmas can be defined by means of the following attributes in
14604 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14605 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14607 Both these attributes are single string attributes. Their values is the path
14608 name of a file containing configuration pragmas. If a path name is relative,
14609 then it is relative to the project directory of the project file where the
14610 attribute is defined.
14612 When compiling a source, the configuration pragmas used are, in order,
14613 those listed in the file designated by attribute
14614 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14615 project file, if it is specified, and those listed in the file designated by
14616 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14617 the project file of the source, if it exists.
14619 @node Project Files and Main Subprograms
14620 @subsubsection Project Files and Main Subprograms
14623 When using a project file, you can invoke @command{gnatmake}
14624 with one or several main subprograms, by specifying their source files on the
14628 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14632 Each of these needs to be a source file of the same project, except
14633 when the switch ^-u^/UNIQUE^ is used.
14636 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14637 same project, one of the project in the tree rooted at the project specified
14638 on the command line. The package @code{Builder} of this common project, the
14639 "main project" is the one that is considered by @command{gnatmake}.
14642 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14643 imported directly or indirectly by the project specified on the command line.
14644 Note that if such a source file is not part of the project specified on the
14645 command line, the ^switches^switches^ found in package @code{Builder} of the
14646 project specified on the command line, if any, that are transmitted
14647 to the compiler will still be used, not those found in the project file of
14651 When using a project file, you can also invoke @command{gnatmake} without
14652 explicitly specifying any main, and the effect depends on whether you have
14653 defined the @code{Main} attribute. This attribute has a string list value,
14654 where each element in the list is the name of a source file (the file
14655 extension is optional) that contains a unit that can be a main subprogram.
14657 If the @code{Main} attribute is defined in a project file as a non-empty
14658 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14659 line, then invoking @command{gnatmake} with this project file but without any
14660 main on the command line is equivalent to invoking @command{gnatmake} with all
14661 the file names in the @code{Main} attribute on the command line.
14664 @smallexample @c projectfile
14667 for Main use ("main1", "main2", "main3");
14673 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14675 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14677 When the project attribute @code{Main} is not specified, or is specified
14678 as an empty string list, or when the switch @option{-u} is used on the command
14679 line, then invoking @command{gnatmake} with no main on the command line will
14680 result in all immediate sources of the project file being checked, and
14681 potentially recompiled. Depending on the presence of the switch @option{-u},
14682 sources from other project files on which the immediate sources of the main
14683 project file depend are also checked and potentially recompiled. In other
14684 words, the @option{-u} switch is applied to all of the immediate sources of the
14687 When no main is specified on the command line and attribute @code{Main} exists
14688 and includes several mains, or when several mains are specified on the
14689 command line, the default ^switches^switches^ in package @code{Builder} will
14690 be used for all mains, even if there are specific ^switches^switches^
14691 specified for one or several mains.
14693 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14694 the specific ^switches^switches^ for each main, if they are specified.
14696 @node Library Project Files
14697 @subsubsection Library Project Files
14700 When @command{gnatmake} is invoked with a main project file that is a library
14701 project file, it is not allowed to specify one or more mains on the command
14705 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14706 ^-l^/ACTION=LINK^ have special meanings.
14709 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14710 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14713 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14714 to @command{gnatmake} that the binder generated file should be compiled
14715 (in the case of a stand-alone library) and that the library should be built.
14719 @node The GNAT Driver and Project Files
14720 @subsection The GNAT Driver and Project Files
14723 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14724 can benefit from project files:
14725 @command{^gnatbind^gnatbind^},
14726 @command{^gnatcheck^gnatcheck^}),
14727 @command{^gnatclean^gnatclean^}),
14728 @command{^gnatelim^gnatelim^},
14729 @command{^gnatfind^gnatfind^},
14730 @command{^gnatlink^gnatlink^},
14731 @command{^gnatls^gnatls^},
14732 @command{^gnatmetric^gnatmetric^},
14733 @command{^gnatpp^gnatpp^},
14734 @command{^gnatstub^gnatstub^},
14735 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14736 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14737 They must be invoked through the @command{gnat} driver.
14739 The @command{gnat} driver is a wrapper that accepts a number of commands and
14740 calls the corresponding tool. It was designed initially for VMS platforms (to
14741 convert VMS qualifiers to Unix-style switches), but it is now available on all
14744 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14745 (case insensitive):
14749 BIND to invoke @command{^gnatbind^gnatbind^}
14751 CHOP to invoke @command{^gnatchop^gnatchop^}
14753 CLEAN to invoke @command{^gnatclean^gnatclean^}
14755 COMP or COMPILE to invoke the compiler
14757 ELIM to invoke @command{^gnatelim^gnatelim^}
14759 FIND to invoke @command{^gnatfind^gnatfind^}
14761 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14763 LINK to invoke @command{^gnatlink^gnatlink^}
14765 LS or LIST to invoke @command{^gnatls^gnatls^}
14767 MAKE to invoke @command{^gnatmake^gnatmake^}
14769 NAME to invoke @command{^gnatname^gnatname^}
14771 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14773 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14775 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14777 STUB to invoke @command{^gnatstub^gnatstub^}
14779 XREF to invoke @command{^gnatxref^gnatxref^}
14783 (note that the compiler is invoked using the command
14784 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14787 On non-VMS platforms, between @command{gnat} and the command, two
14788 special switches may be used:
14792 @command{-v} to display the invocation of the tool.
14794 @command{-dn} to prevent the @command{gnat} driver from removing
14795 the temporary files it has created. These temporary files are
14796 configuration files and temporary file list files.
14800 The command may be followed by switches and arguments for the invoked
14804 gnat bind -C main.ali
14810 Switches may also be put in text files, one switch per line, and the text
14811 files may be specified with their path name preceded by '@@'.
14814 gnat bind @@args.txt main.ali
14818 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14819 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14820 (@option{^-P^/PROJECT_FILE^},
14821 @option{^-X^/EXTERNAL_REFERENCE^} and
14822 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14823 the switches of the invoking tool.
14826 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14827 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14828 the immediate sources of the specified project file.
14831 When GNAT METRIC is used with a project file, but with no source
14832 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14833 with all the immediate sources of the specified project file and with
14834 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14838 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14839 a project file, no source is specified on the command line and
14840 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14841 the underlying tool (^gnatpp^gnatpp^ or
14842 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14843 not only for the immediate sources of the main project.
14845 (-U stands for Universal or Union of the project files of the project tree)
14849 For each of the following commands, there is optionally a corresponding
14850 package in the main project.
14854 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14857 package @code{Check} for command CHECK (invoking
14858 @code{^gnatcheck^gnatcheck^})
14861 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14864 package @code{Cross_Reference} for command XREF (invoking
14865 @code{^gnatxref^gnatxref^})
14868 package @code{Eliminate} for command ELIM (invoking
14869 @code{^gnatelim^gnatelim^})
14872 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14875 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14878 package @code{Gnatstub} for command STUB
14879 (invoking @code{^gnatstub^gnatstub^})
14882 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14885 package @code{Metrics} for command METRIC
14886 (invoking @code{^gnatmetric^gnatmetric^})
14889 package @code{Pretty_Printer} for command PP or PRETTY
14890 (invoking @code{^gnatpp^gnatpp^})
14895 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14896 a simple variable with a string list value. It contains ^switches^switches^
14897 for the invocation of @code{^gnatls^gnatls^}.
14899 @smallexample @c projectfile
14903 for ^Switches^Switches^
14912 All other packages have two attribute @code{^Switches^Switches^} and
14913 @code{^Default_Switches^Default_Switches^}.
14916 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14917 source file name, that has a string list value: the ^switches^switches^ to be
14918 used when the tool corresponding to the package is invoked for the specific
14922 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14923 indexed by the programming language that has a string list value.
14924 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14925 ^switches^switches^ for the invocation of the tool corresponding
14926 to the package, except if a specific @code{^Switches^Switches^} attribute
14927 is specified for the source file.
14929 @smallexample @c projectfile
14933 for Source_Dirs use ("./**");
14936 for ^Switches^Switches^ use
14943 package Compiler is
14944 for ^Default_Switches^Default_Switches^ ("Ada")
14945 use ("^-gnatv^-gnatv^",
14946 "^-gnatwa^-gnatwa^");
14952 for ^Default_Switches^Default_Switches^ ("Ada")
14960 for ^Default_Switches^Default_Switches^ ("Ada")
14962 for ^Switches^Switches^ ("main.adb")
14971 for ^Default_Switches^Default_Switches^ ("Ada")
14978 package Cross_Reference is
14979 for ^Default_Switches^Default_Switches^ ("Ada")
14984 end Cross_Reference;
14990 With the above project file, commands such as
14993 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
14994 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
14995 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
14996 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
14997 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
15001 will set up the environment properly and invoke the tool with the switches
15002 found in the package corresponding to the tool:
15003 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
15004 except @code{^Switches^Switches^ ("main.adb")}
15005 for @code{^gnatlink^gnatlink^}.
15006 It is also possible to invoke some of the tools,
15007 @code{^gnatcheck^gnatcheck^}),
15008 @code{^gnatmetric^gnatmetric^}),
15009 and @code{^gnatpp^gnatpp^})
15010 on a set of project units thanks to the combination of the switches
15011 @option{-P}, @option{-U} and possibly the main unit when one is interested
15012 in its closure. For instance,
15016 will compute the metrics for all the immediate units of project
15019 gnat metric -Pproj -U
15021 will compute the metrics for all the units of the closure of projects
15022 rooted at @code{proj}.
15024 gnat metric -Pproj -U main_unit
15026 will compute the metrics for the closure of units rooted at
15027 @code{main_unit}. This last possibility relies implicitly
15028 on @command{gnatbind}'s option @option{-R}.
15030 @c **********************
15031 @node An Extended Example
15032 @section An Extended Example
15035 Suppose that we have two programs, @var{prog1} and @var{prog2},
15036 whose sources are in corresponding directories. We would like
15037 to build them with a single @command{gnatmake} command, and we want to place
15038 their object files into @file{build} subdirectories of the source directories.
15039 Furthermore, we want to have to have two separate subdirectories
15040 in @file{build} -- @file{release} and @file{debug} -- which will contain
15041 the object files compiled with different set of compilation flags.
15043 In other words, we have the following structure:
15060 Here are the project files that we must place in a directory @file{main}
15061 to maintain this structure:
15065 @item We create a @code{Common} project with a package @code{Compiler} that
15066 specifies the compilation ^switches^switches^:
15071 @b{project} Common @b{is}
15073 @b{for} Source_Dirs @b{use} (); -- No source files
15077 @b{type} Build_Type @b{is} ("release", "debug");
15078 Build : Build_Type := External ("BUILD", "debug");
15081 @b{package} Compiler @b{is}
15082 @b{case} Build @b{is}
15083 @b{when} "release" =>
15084 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15085 @b{use} ("^-O2^-O2^");
15086 @b{when} "debug" =>
15087 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15088 @b{use} ("^-g^-g^");
15096 @item We create separate projects for the two programs:
15103 @b{project} Prog1 @b{is}
15105 @b{for} Source_Dirs @b{use} ("prog1");
15106 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
15108 @b{package} Compiler @b{renames} Common.Compiler;
15119 @b{project} Prog2 @b{is}
15121 @b{for} Source_Dirs @b{use} ("prog2");
15122 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
15124 @b{package} Compiler @b{renames} Common.Compiler;
15130 @item We create a wrapping project @code{Main}:
15139 @b{project} Main @b{is}
15141 @b{package} Compiler @b{renames} Common.Compiler;
15147 @item Finally we need to create a dummy procedure that @code{with}s (either
15148 explicitly or implicitly) all the sources of our two programs.
15153 Now we can build the programs using the command
15156 gnatmake ^-P^/PROJECT_FILE=^main dummy
15160 for the Debug mode, or
15164 gnatmake -Pmain -XBUILD=release
15170 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
15175 for the Release mode.
15177 @c ********************************
15178 @c * Project File Complete Syntax *
15179 @c ********************************
15181 @node Project File Complete Syntax
15182 @section Project File Complete Syntax
15186 context_clause project_declaration
15192 @b{with} path_name @{ , path_name @} ;
15197 project_declaration ::=
15198 simple_project_declaration | project_extension
15200 simple_project_declaration ::=
15201 @b{project} <project_>simple_name @b{is}
15202 @{declarative_item@}
15203 @b{end} <project_>simple_name;
15205 project_extension ::=
15206 @b{project} <project_>simple_name @b{extends} path_name @b{is}
15207 @{declarative_item@}
15208 @b{end} <project_>simple_name;
15210 declarative_item ::=
15211 package_declaration |
15212 typed_string_declaration |
15213 other_declarative_item
15215 package_declaration ::=
15216 package_spec | package_renaming
15219 @b{package} package_identifier @b{is}
15220 @{simple_declarative_item@}
15221 @b{end} package_identifier ;
15223 package_identifier ::=
15224 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
15225 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
15226 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
15228 package_renaming ::==
15229 @b{package} package_identifier @b{renames}
15230 <project_>simple_name.package_identifier ;
15232 typed_string_declaration ::=
15233 @b{type} <typed_string_>_simple_name @b{is}
15234 ( string_literal @{, string_literal@} );
15236 other_declarative_item ::=
15237 attribute_declaration |
15238 typed_variable_declaration |
15239 variable_declaration |
15242 attribute_declaration ::=
15243 full_associative_array_declaration |
15244 @b{for} attribute_designator @b{use} expression ;
15246 full_associative_array_declaration ::=
15247 @b{for} <associative_array_attribute_>simple_name @b{use}
15248 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
15250 attribute_designator ::=
15251 <simple_attribute_>simple_name |
15252 <associative_array_attribute_>simple_name ( string_literal )
15254 typed_variable_declaration ::=
15255 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
15257 variable_declaration ::=
15258 <variable_>simple_name := expression;
15268 attribute_reference
15274 ( <string_>expression @{ , <string_>expression @} )
15277 @b{external} ( string_literal [, string_literal] )
15279 attribute_reference ::=
15280 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
15282 attribute_prefix ::=
15284 <project_>simple_name | package_identifier |
15285 <project_>simple_name . package_identifier
15287 case_construction ::=
15288 @b{case} <typed_variable_>name @b{is}
15293 @b{when} discrete_choice_list =>
15294 @{case_construction | attribute_declaration@}
15296 discrete_choice_list ::=
15297 string_literal @{| string_literal@} |
15301 simple_name @{. simple_name@}
15304 identifier (same as Ada)
15308 @node The Cross-Referencing Tools gnatxref and gnatfind
15309 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
15314 The compiler generates cross-referencing information (unless
15315 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
15316 This information indicates where in the source each entity is declared and
15317 referenced. Note that entities in package Standard are not included, but
15318 entities in all other predefined units are included in the output.
15320 Before using any of these two tools, you need to compile successfully your
15321 application, so that GNAT gets a chance to generate the cross-referencing
15324 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
15325 information to provide the user with the capability to easily locate the
15326 declaration and references to an entity. These tools are quite similar,
15327 the difference being that @code{gnatfind} is intended for locating
15328 definitions and/or references to a specified entity or entities, whereas
15329 @code{gnatxref} is oriented to generating a full report of all
15332 To use these tools, you must not compile your application using the
15333 @option{-gnatx} switch on the @command{gnatmake} command line
15334 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
15335 information will not be generated.
15337 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
15338 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
15341 * gnatxref Switches::
15342 * gnatfind Switches::
15343 * Project Files for gnatxref and gnatfind::
15344 * Regular Expressions in gnatfind and gnatxref::
15345 * Examples of gnatxref Usage::
15346 * Examples of gnatfind Usage::
15349 @node gnatxref Switches
15350 @section @code{gnatxref} Switches
15353 The command invocation for @code{gnatxref} is:
15355 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
15364 identifies the source files for which a report is to be generated. The
15365 ``with''ed units will be processed too. You must provide at least one file.
15367 These file names are considered to be regular expressions, so for instance
15368 specifying @file{source*.adb} is the same as giving every file in the current
15369 directory whose name starts with @file{source} and whose extension is
15372 You shouldn't specify any directory name, just base names. @command{gnatxref}
15373 and @command{gnatfind} will be able to locate these files by themselves using
15374 the source path. If you specify directories, no result is produced.
15379 The switches can be:
15383 @cindex @option{--version} @command{gnatxref}
15384 Display Copyright and version, then exit disregarding all other options.
15387 @cindex @option{--help} @command{gnatxref}
15388 If @option{--version} was not used, display usage, then exit disregarding
15391 @item ^-a^/ALL_FILES^
15392 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15393 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15394 the read-only files found in the library search path. Otherwise, these files
15395 will be ignored. This option can be used to protect Gnat sources or your own
15396 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15397 much faster, and their output much smaller. Read-only here refers to access
15398 or permissions status in the file system for the current user.
15401 @cindex @option{-aIDIR} (@command{gnatxref})
15402 When looking for source files also look in directory DIR. The order in which
15403 source file search is undertaken is the same as for @command{gnatmake}.
15406 @cindex @option{-aODIR} (@command{gnatxref})
15407 When searching for library and object files, look in directory
15408 DIR. The order in which library files are searched is the same as for
15409 @command{gnatmake}.
15412 @cindex @option{-nostdinc} (@command{gnatxref})
15413 Do not look for sources in the system default directory.
15416 @cindex @option{-nostdlib} (@command{gnatxref})
15417 Do not look for library files in the system default directory.
15419 @item --RTS=@var{rts-path}
15420 @cindex @option{--RTS} (@command{gnatxref})
15421 Specifies the default location of the runtime library. Same meaning as the
15422 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15424 @item ^-d^/DERIVED_TYPES^
15425 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15426 If this switch is set @code{gnatxref} will output the parent type
15427 reference for each matching derived types.
15429 @item ^-f^/FULL_PATHNAME^
15430 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15431 If this switch is set, the output file names will be preceded by their
15432 directory (if the file was found in the search path). If this switch is
15433 not set, the directory will not be printed.
15435 @item ^-g^/IGNORE_LOCALS^
15436 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15437 If this switch is set, information is output only for library-level
15438 entities, ignoring local entities. The use of this switch may accelerate
15439 @code{gnatfind} and @code{gnatxref}.
15442 @cindex @option{-IDIR} (@command{gnatxref})
15443 Equivalent to @samp{-aODIR -aIDIR}.
15446 @cindex @option{-pFILE} (@command{gnatxref})
15447 Specify a project file to use @xref{Project Files}.
15448 If you need to use the @file{.gpr}
15449 project files, you should use gnatxref through the GNAT driver
15450 (@command{gnat xref -Pproject}).
15452 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15453 project file in the current directory.
15455 If a project file is either specified or found by the tools, then the content
15456 of the source directory and object directory lines are added as if they
15457 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15458 and @samp{^-aO^OBJECT_SEARCH^}.
15460 Output only unused symbols. This may be really useful if you give your
15461 main compilation unit on the command line, as @code{gnatxref} will then
15462 display every unused entity and 'with'ed package.
15466 Instead of producing the default output, @code{gnatxref} will generate a
15467 @file{tags} file that can be used by vi. For examples how to use this
15468 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15469 to the standard output, thus you will have to redirect it to a file.
15475 All these switches may be in any order on the command line, and may even
15476 appear after the file names. They need not be separated by spaces, thus
15477 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15478 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15480 @node gnatfind Switches
15481 @section @code{gnatfind} Switches
15484 The command line for @code{gnatfind} is:
15487 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15488 @r{[}@var{file1} @var{file2} @dots{}]
15496 An entity will be output only if it matches the regular expression found
15497 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15499 Omitting the pattern is equivalent to specifying @samp{*}, which
15500 will match any entity. Note that if you do not provide a pattern, you
15501 have to provide both a sourcefile and a line.
15503 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15504 for matching purposes. At the current time there is no support for
15505 8-bit codes other than Latin-1, or for wide characters in identifiers.
15508 @code{gnatfind} will look for references, bodies or declarations
15509 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15510 and column @var{column}. See @ref{Examples of gnatfind Usage}
15511 for syntax examples.
15514 is a decimal integer identifying the line number containing
15515 the reference to the entity (or entities) to be located.
15518 is a decimal integer identifying the exact location on the
15519 line of the first character of the identifier for the
15520 entity reference. Columns are numbered from 1.
15522 @item file1 file2 @dots{}
15523 The search will be restricted to these source files. If none are given, then
15524 the search will be done for every library file in the search path.
15525 These file must appear only after the pattern or sourcefile.
15527 These file names are considered to be regular expressions, so for instance
15528 specifying @file{source*.adb} is the same as giving every file in the current
15529 directory whose name starts with @file{source} and whose extension is
15532 The location of the spec of the entity will always be displayed, even if it
15533 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15534 occurrences of the entity in the separate units of the ones given on the
15535 command line will also be displayed.
15537 Note that if you specify at least one file in this part, @code{gnatfind} may
15538 sometimes not be able to find the body of the subprograms.
15543 At least one of 'sourcefile' or 'pattern' has to be present on
15546 The following switches are available:
15550 @cindex @option{--version} @command{gnatfind}
15551 Display Copyright and version, then exit disregarding all other options.
15554 @cindex @option{--help} @command{gnatfind}
15555 If @option{--version} was not used, display usage, then exit disregarding
15558 @item ^-a^/ALL_FILES^
15559 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15560 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15561 the read-only files found in the library search path. Otherwise, these files
15562 will be ignored. This option can be used to protect Gnat sources or your own
15563 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15564 much faster, and their output much smaller. Read-only here refers to access
15565 or permission status in the file system for the current user.
15568 @cindex @option{-aIDIR} (@command{gnatfind})
15569 When looking for source files also look in directory DIR. The order in which
15570 source file search is undertaken is the same as for @command{gnatmake}.
15573 @cindex @option{-aODIR} (@command{gnatfind})
15574 When searching for library and object files, look in directory
15575 DIR. The order in which library files are searched is the same as for
15576 @command{gnatmake}.
15579 @cindex @option{-nostdinc} (@command{gnatfind})
15580 Do not look for sources in the system default directory.
15583 @cindex @option{-nostdlib} (@command{gnatfind})
15584 Do not look for library files in the system default directory.
15586 @item --RTS=@var{rts-path}
15587 @cindex @option{--RTS} (@command{gnatfind})
15588 Specifies the default location of the runtime library. Same meaning as the
15589 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15591 @item ^-d^/DERIVED_TYPE_INFORMATION^
15592 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15593 If this switch is set, then @code{gnatfind} will output the parent type
15594 reference for each matching derived types.
15596 @item ^-e^/EXPRESSIONS^
15597 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15598 By default, @code{gnatfind} accept the simple regular expression set for
15599 @samp{pattern}. If this switch is set, then the pattern will be
15600 considered as full Unix-style regular expression.
15602 @item ^-f^/FULL_PATHNAME^
15603 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15604 If this switch is set, the output file names will be preceded by their
15605 directory (if the file was found in the search path). If this switch is
15606 not set, the directory will not be printed.
15608 @item ^-g^/IGNORE_LOCALS^
15609 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15610 If this switch is set, information is output only for library-level
15611 entities, ignoring local entities. The use of this switch may accelerate
15612 @code{gnatfind} and @code{gnatxref}.
15615 @cindex @option{-IDIR} (@command{gnatfind})
15616 Equivalent to @samp{-aODIR -aIDIR}.
15619 @cindex @option{-pFILE} (@command{gnatfind})
15620 Specify a project file (@pxref{Project Files}) to use.
15621 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15622 project file in the current directory.
15624 If a project file is either specified or found by the tools, then the content
15625 of the source directory and object directory lines are added as if they
15626 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15627 @samp{^-aO^/OBJECT_SEARCH^}.
15629 @item ^-r^/REFERENCES^
15630 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15631 By default, @code{gnatfind} will output only the information about the
15632 declaration, body or type completion of the entities. If this switch is
15633 set, the @code{gnatfind} will locate every reference to the entities in
15634 the files specified on the command line (or in every file in the search
15635 path if no file is given on the command line).
15637 @item ^-s^/PRINT_LINES^
15638 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15639 If this switch is set, then @code{gnatfind} will output the content
15640 of the Ada source file lines were the entity was found.
15642 @item ^-t^/TYPE_HIERARCHY^
15643 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15644 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15645 the specified type. It act like -d option but recursively from parent
15646 type to parent type. When this switch is set it is not possible to
15647 specify more than one file.
15652 All these switches may be in any order on the command line, and may even
15653 appear after the file names. They need not be separated by spaces, thus
15654 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15655 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15657 As stated previously, gnatfind will search in every directory in the
15658 search path. You can force it to look only in the current directory if
15659 you specify @code{*} at the end of the command line.
15661 @node Project Files for gnatxref and gnatfind
15662 @section Project Files for @command{gnatxref} and @command{gnatfind}
15665 Project files allow a programmer to specify how to compile its
15666 application, where to find sources, etc. These files are used
15668 primarily by GPS, but they can also be used
15671 @code{gnatxref} and @code{gnatfind}.
15673 A project file name must end with @file{.gpr}. If a single one is
15674 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15675 extract the information from it. If multiple project files are found, none of
15676 them is read, and you have to use the @samp{-p} switch to specify the one
15679 The following lines can be included, even though most of them have default
15680 values which can be used in most cases.
15681 The lines can be entered in any order in the file.
15682 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15683 each line. If you have multiple instances, only the last one is taken into
15688 [default: @code{"^./^[]^"}]
15689 specifies a directory where to look for source files. Multiple @code{src_dir}
15690 lines can be specified and they will be searched in the order they
15694 [default: @code{"^./^[]^"}]
15695 specifies a directory where to look for object and library files. Multiple
15696 @code{obj_dir} lines can be specified, and they will be searched in the order
15699 @item comp_opt=SWITCHES
15700 [default: @code{""}]
15701 creates a variable which can be referred to subsequently by using
15702 the @code{$@{comp_opt@}} notation. This is intended to store the default
15703 switches given to @command{gnatmake} and @command{gcc}.
15705 @item bind_opt=SWITCHES
15706 [default: @code{""}]
15707 creates a variable which can be referred to subsequently by using
15708 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15709 switches given to @command{gnatbind}.
15711 @item link_opt=SWITCHES
15712 [default: @code{""}]
15713 creates a variable which can be referred to subsequently by using
15714 the @samp{$@{link_opt@}} notation. This is intended to store the default
15715 switches given to @command{gnatlink}.
15717 @item main=EXECUTABLE
15718 [default: @code{""}]
15719 specifies the name of the executable for the application. This variable can
15720 be referred to in the following lines by using the @samp{$@{main@}} notation.
15723 @item comp_cmd=COMMAND
15724 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15727 @item comp_cmd=COMMAND
15728 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15730 specifies the command used to compile a single file in the application.
15733 @item make_cmd=COMMAND
15734 [default: @code{"GNAT MAKE $@{main@}
15735 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15736 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15737 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15740 @item make_cmd=COMMAND
15741 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15742 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15743 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15745 specifies the command used to recompile the whole application.
15747 @item run_cmd=COMMAND
15748 [default: @code{"$@{main@}"}]
15749 specifies the command used to run the application.
15751 @item debug_cmd=COMMAND
15752 [default: @code{"gdb $@{main@}"}]
15753 specifies the command used to debug the application
15758 @command{gnatxref} and @command{gnatfind} only take into account the
15759 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15761 @node Regular Expressions in gnatfind and gnatxref
15762 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15765 As specified in the section about @command{gnatfind}, the pattern can be a
15766 regular expression. Actually, there are to set of regular expressions
15767 which are recognized by the program:
15770 @item globbing patterns
15771 These are the most usual regular expression. They are the same that you
15772 generally used in a Unix shell command line, or in a DOS session.
15774 Here is a more formal grammar:
15781 term ::= elmt -- matches elmt
15782 term ::= elmt elmt -- concatenation (elmt then elmt)
15783 term ::= * -- any string of 0 or more characters
15784 term ::= ? -- matches any character
15785 term ::= [char @{char@}] -- matches any character listed
15786 term ::= [char - char] -- matches any character in range
15790 @item full regular expression
15791 The second set of regular expressions is much more powerful. This is the
15792 type of regular expressions recognized by utilities such a @file{grep}.
15794 The following is the form of a regular expression, expressed in Ada
15795 reference manual style BNF is as follows
15802 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15804 term ::= item @{item@} -- concatenation (item then item)
15806 item ::= elmt -- match elmt
15807 item ::= elmt * -- zero or more elmt's
15808 item ::= elmt + -- one or more elmt's
15809 item ::= elmt ? -- matches elmt or nothing
15812 elmt ::= nschar -- matches given character
15813 elmt ::= [nschar @{nschar@}] -- matches any character listed
15814 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15815 elmt ::= [char - char] -- matches chars in given range
15816 elmt ::= \ char -- matches given character
15817 elmt ::= . -- matches any single character
15818 elmt ::= ( regexp ) -- parens used for grouping
15820 char ::= any character, including special characters
15821 nschar ::= any character except ()[].*+?^^^
15825 Following are a few examples:
15829 will match any of the two strings @samp{abcde} and @samp{fghi},
15832 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15833 @samp{abcccd}, and so on,
15836 will match any string which has only lowercase characters in it (and at
15837 least one character.
15842 @node Examples of gnatxref Usage
15843 @section Examples of @code{gnatxref} Usage
15845 @subsection General Usage
15848 For the following examples, we will consider the following units:
15850 @smallexample @c ada
15856 3: procedure Foo (B : in Integer);
15863 1: package body Main is
15864 2: procedure Foo (B : in Integer) is
15875 2: procedure Print (B : Integer);
15884 The first thing to do is to recompile your application (for instance, in
15885 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15886 the cross-referencing information.
15887 You can then issue any of the following commands:
15889 @item gnatxref main.adb
15890 @code{gnatxref} generates cross-reference information for main.adb
15891 and every unit 'with'ed by main.adb.
15893 The output would be:
15901 Decl: main.ads 3:20
15902 Body: main.adb 2:20
15903 Ref: main.adb 4:13 5:13 6:19
15906 Ref: main.adb 6:8 7:8
15916 Decl: main.ads 3:15
15917 Body: main.adb 2:15
15920 Body: main.adb 1:14
15923 Ref: main.adb 6:12 7:12
15927 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15928 its body is in main.adb, line 1, column 14 and is not referenced any where.
15930 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15931 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15933 @item gnatxref package1.adb package2.ads
15934 @code{gnatxref} will generates cross-reference information for
15935 package1.adb, package2.ads and any other package 'with'ed by any
15941 @subsection Using gnatxref with vi
15943 @code{gnatxref} can generate a tags file output, which can be used
15944 directly from @command{vi}. Note that the standard version of @command{vi}
15945 will not work properly with overloaded symbols. Consider using another
15946 free implementation of @command{vi}, such as @command{vim}.
15949 $ gnatxref -v gnatfind.adb > tags
15953 will generate the tags file for @code{gnatfind} itself (if the sources
15954 are in the search path!).
15956 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15957 (replacing @var{entity} by whatever you are looking for), and vi will
15958 display a new file with the corresponding declaration of entity.
15961 @node Examples of gnatfind Usage
15962 @section Examples of @code{gnatfind} Usage
15966 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15967 Find declarations for all entities xyz referenced at least once in
15968 main.adb. The references are search in every library file in the search
15971 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15974 The output will look like:
15976 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15977 ^directory/^[directory]^main.adb:24:10: xyz <= body
15978 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15982 that is to say, one of the entities xyz found in main.adb is declared at
15983 line 12 of main.ads (and its body is in main.adb), and another one is
15984 declared at line 45 of foo.ads
15986 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
15987 This is the same command as the previous one, instead @code{gnatfind} will
15988 display the content of the Ada source file lines.
15990 The output will look like:
15993 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15995 ^directory/^[directory]^main.adb:24:10: xyz <= body
15997 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
16002 This can make it easier to find exactly the location your are looking
16005 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
16006 Find references to all entities containing an x that are
16007 referenced on line 123 of main.ads.
16008 The references will be searched only in main.ads and foo.adb.
16010 @item gnatfind main.ads:123
16011 Find declarations and bodies for all entities that are referenced on
16012 line 123 of main.ads.
16014 This is the same as @code{gnatfind "*":main.adb:123}.
16016 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
16017 Find the declaration for the entity referenced at column 45 in
16018 line 123 of file main.adb in directory mydir. Note that it
16019 is usual to omit the identifier name when the column is given,
16020 since the column position identifies a unique reference.
16022 The column has to be the beginning of the identifier, and should not
16023 point to any character in the middle of the identifier.
16027 @c *********************************
16028 @node The GNAT Pretty-Printer gnatpp
16029 @chapter The GNAT Pretty-Printer @command{gnatpp}
16031 @cindex Pretty-Printer
16034 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
16035 for source reformatting / pretty-printing.
16036 It takes an Ada source file as input and generates a reformatted
16038 You can specify various style directives via switches; e.g.,
16039 identifier case conventions, rules of indentation, and comment layout.
16041 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
16042 tree for the input source and thus requires the input to be syntactically and
16043 semantically legal.
16044 If this condition is not met, @command{gnatpp} will terminate with an
16045 error message; no output file will be generated.
16047 If the source files presented to @command{gnatpp} contain
16048 preprocessing directives, then the output file will
16049 correspond to the generated source after all
16050 preprocessing is carried out. There is no way
16051 using @command{gnatpp} to obtain pretty printed files that
16052 include the preprocessing directives.
16054 If the compilation unit
16055 contained in the input source depends semantically upon units located
16056 outside the current directory, you have to provide the source search path
16057 when invoking @command{gnatpp}, if these units are contained in files with
16058 names that do not follow the GNAT file naming rules, you have to provide
16059 the configuration file describing the corresponding naming scheme;
16060 see the description of the @command{gnatpp}
16061 switches below. Another possibility is to use a project file and to
16062 call @command{gnatpp} through the @command{gnat} driver
16064 The @command{gnatpp} command has the form
16067 $ gnatpp @ovar{switches} @var{filename}
16074 @var{switches} is an optional sequence of switches defining such properties as
16075 the formatting rules, the source search path, and the destination for the
16079 @var{filename} is the name (including the extension) of the source file to
16080 reformat; ``wildcards'' or several file names on the same gnatpp command are
16081 allowed. The file name may contain path information; it does not have to
16082 follow the GNAT file naming rules
16086 * Switches for gnatpp::
16087 * Formatting Rules::
16090 @node Switches for gnatpp
16091 @section Switches for @command{gnatpp}
16094 The following subsections describe the various switches accepted by
16095 @command{gnatpp}, organized by category.
16098 You specify a switch by supplying a name and generally also a value.
16099 In many cases the values for a switch with a given name are incompatible with
16101 (for example the switch that controls the casing of a reserved word may have
16102 exactly one value: upper case, lower case, or
16103 mixed case) and thus exactly one such switch can be in effect for an
16104 invocation of @command{gnatpp}.
16105 If more than one is supplied, the last one is used.
16106 However, some values for the same switch are mutually compatible.
16107 You may supply several such switches to @command{gnatpp}, but then
16108 each must be specified in full, with both the name and the value.
16109 Abbreviated forms (the name appearing once, followed by each value) are
16111 For example, to set
16112 the alignment of the assignment delimiter both in declarations and in
16113 assignment statements, you must write @option{-A2A3}
16114 (or @option{-A2 -A3}), but not @option{-A23}.
16118 In many cases the set of options for a given qualifier are incompatible with
16119 each other (for example the qualifier that controls the casing of a reserved
16120 word may have exactly one option, which specifies either upper case, lower
16121 case, or mixed case), and thus exactly one such option can be in effect for
16122 an invocation of @command{gnatpp}.
16123 If more than one is supplied, the last one is used.
16124 However, some qualifiers have options that are mutually compatible,
16125 and then you may then supply several such options when invoking
16129 In most cases, it is obvious whether or not the
16130 ^values for a switch with a given name^options for a given qualifier^
16131 are compatible with each other.
16132 When the semantics might not be evident, the summaries below explicitly
16133 indicate the effect.
16136 * Alignment Control::
16138 * Construct Layout Control::
16139 * General Text Layout Control::
16140 * Other Formatting Options::
16141 * Setting the Source Search Path::
16142 * Output File Control::
16143 * Other gnatpp Switches::
16146 @node Alignment Control
16147 @subsection Alignment Control
16148 @cindex Alignment control in @command{gnatpp}
16151 Programs can be easier to read if certain constructs are vertically aligned.
16152 By default all alignments are set ON.
16153 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
16154 OFF, and then use one or more of the other
16155 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
16156 to activate alignment for specific constructs.
16159 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
16163 Set all alignments to ON
16166 @item ^-A0^/ALIGN=OFF^
16167 Set all alignments to OFF
16169 @item ^-A1^/ALIGN=COLONS^
16170 Align @code{:} in declarations
16172 @item ^-A2^/ALIGN=DECLARATIONS^
16173 Align @code{:=} in initializations in declarations
16175 @item ^-A3^/ALIGN=STATEMENTS^
16176 Align @code{:=} in assignment statements
16178 @item ^-A4^/ALIGN=ARROWS^
16179 Align @code{=>} in associations
16181 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
16182 Align @code{at} keywords in the component clauses in record
16183 representation clauses
16187 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
16190 @node Casing Control
16191 @subsection Casing Control
16192 @cindex Casing control in @command{gnatpp}
16195 @command{gnatpp} allows you to specify the casing for reserved words,
16196 pragma names, attribute designators and identifiers.
16197 For identifiers you may define a
16198 general rule for name casing but also override this rule
16199 via a set of dictionary files.
16201 Three types of casing are supported: lower case, upper case, and mixed case.
16202 Lower and upper case are self-explanatory (but since some letters in
16203 Latin1 and other GNAT-supported character sets
16204 exist only in lower-case form, an upper case conversion will have no
16206 ``Mixed case'' means that the first letter, and also each letter immediately
16207 following an underscore, are converted to their uppercase forms;
16208 all the other letters are converted to their lowercase forms.
16211 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
16212 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
16213 Attribute designators are lower case
16215 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
16216 Attribute designators are upper case
16218 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
16219 Attribute designators are mixed case (this is the default)
16221 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
16222 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
16223 Keywords (technically, these are known in Ada as @emph{reserved words}) are
16224 lower case (this is the default)
16226 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
16227 Keywords are upper case
16229 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
16230 @item ^-nD^/NAME_CASING=AS_DECLARED^
16231 Name casing for defining occurrences are as they appear in the source file
16232 (this is the default)
16234 @item ^-nU^/NAME_CASING=UPPER_CASE^
16235 Names are in upper case
16237 @item ^-nL^/NAME_CASING=LOWER_CASE^
16238 Names are in lower case
16240 @item ^-nM^/NAME_CASING=MIXED_CASE^
16241 Names are in mixed case
16243 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
16244 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
16245 Pragma names are lower case
16247 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
16248 Pragma names are upper case
16250 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
16251 Pragma names are mixed case (this is the default)
16253 @item ^-D@var{file}^/DICTIONARY=@var{file}^
16254 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
16255 Use @var{file} as a @emph{dictionary file} that defines
16256 the casing for a set of specified names,
16257 thereby overriding the effect on these names by
16258 any explicit or implicit
16259 ^-n^/NAME_CASING^ switch.
16260 To supply more than one dictionary file,
16261 use ^several @option{-D} switches^a list of files as options^.
16264 @option{gnatpp} implicitly uses a @emph{default dictionary file}
16265 to define the casing for the Ada predefined names and
16266 the names declared in the GNAT libraries.
16268 @item ^-D-^/SPECIFIC_CASING^
16269 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
16270 Do not use the default dictionary file;
16271 instead, use the casing
16272 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
16277 The structure of a dictionary file, and details on the conventions
16278 used in the default dictionary file, are defined in @ref{Name Casing}.
16280 The @option{^-D-^/SPECIFIC_CASING^} and
16281 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
16284 @node Construct Layout Control
16285 @subsection Construct Layout Control
16286 @cindex Layout control in @command{gnatpp}
16289 This group of @command{gnatpp} switches controls the layout of comments and
16290 complex syntactic constructs. See @ref{Formatting Comments} for details
16294 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
16295 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
16296 All the comments remain unchanged
16298 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
16299 GNAT-style comment line indentation (this is the default).
16301 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
16302 Reference-manual comment line indentation.
16304 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
16305 GNAT-style comment beginning
16307 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
16308 Reformat comment blocks
16310 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
16311 Keep unchanged special form comments
16313 Reformat comment blocks
16315 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
16316 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
16317 GNAT-style layout (this is the default)
16319 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
16322 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
16325 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
16327 All the VT characters are removed from the comment text. All the HT characters
16328 are expanded with the sequences of space characters to get to the next tab
16331 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
16332 @item ^--no-separate-is^/NO_SEPARATE_IS^
16333 Do not place the keyword @code{is} on a separate line in a subprogram body in
16334 case if the spec occupies more then one line.
16336 @cindex @option{^--separate-label^/SEPARATE_LABEL^} (@command{gnatpp})
16337 @item ^--separate-label^/SEPARATE_LABEL^
16338 Place statement label(s) on a separate line, with the following statement
16341 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
16342 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
16343 Place the keyword @code{loop} in FOR and WHILE loop statements and the
16344 keyword @code{then} in IF statements on a separate line.
16346 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
16347 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
16348 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
16349 keyword @code{then} in IF statements on a separate line. This option is
16350 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
16352 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
16353 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
16354 Start each USE clause in a context clause from a separate line.
16356 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
16357 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
16358 Use a separate line for a loop or block statement name, but do not use an extra
16359 indentation level for the statement itself.
16365 The @option{-c1} and @option{-c2} switches are incompatible.
16366 The @option{-c3} and @option{-c4} switches are compatible with each other and
16367 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
16368 the other comment formatting switches.
16370 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
16375 For the @option{/COMMENTS_LAYOUT} qualifier:
16378 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16380 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16381 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16385 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16386 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16389 @node General Text Layout Control
16390 @subsection General Text Layout Control
16393 These switches allow control over line length and indentation.
16396 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16397 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16398 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16400 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16401 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16402 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16404 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16405 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16406 Indentation level for continuation lines (relative to the line being
16407 continued), @var{nnn} from 1@dots{}9.
16409 value is one less then the (normal) indentation level, unless the
16410 indentation is set to 1 (in which case the default value for continuation
16411 line indentation is also 1)
16414 @node Other Formatting Options
16415 @subsection Other Formatting Options
16418 These switches control the inclusion of missing end/exit labels, and
16419 the indentation level in @b{case} statements.
16422 @item ^-e^/NO_MISSED_LABELS^
16423 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16424 Do not insert missing end/exit labels. An end label is the name of
16425 a construct that may optionally be repeated at the end of the
16426 construct's declaration;
16427 e.g., the names of packages, subprograms, and tasks.
16428 An exit label is the name of a loop that may appear as target
16429 of an exit statement within the loop.
16430 By default, @command{gnatpp} inserts these end/exit labels when
16431 they are absent from the original source. This option suppresses such
16432 insertion, so that the formatted source reflects the original.
16434 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16435 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16436 Insert a Form Feed character after a pragma Page.
16438 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16439 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16440 Do not use an additional indentation level for @b{case} alternatives
16441 and variants if there are @var{nnn} or more (the default
16443 If @var{nnn} is 0, an additional indentation level is
16444 used for @b{case} alternatives and variants regardless of their number.
16447 @node Setting the Source Search Path
16448 @subsection Setting the Source Search Path
16451 To define the search path for the input source file, @command{gnatpp}
16452 uses the same switches as the GNAT compiler, with the same effects.
16455 @item ^-I^/SEARCH=^@var{dir}
16456 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16457 The same as the corresponding gcc switch
16459 @item ^-I-^/NOCURRENT_DIRECTORY^
16460 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16461 The same as the corresponding gcc switch
16463 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16464 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16465 The same as the corresponding gcc switch
16467 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16468 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16469 The same as the corresponding gcc switch
16473 @node Output File Control
16474 @subsection Output File Control
16477 By default the output is sent to the file whose name is obtained by appending
16478 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16479 (if the file with this name already exists, it is unconditionally overwritten).
16480 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16481 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16483 The output may be redirected by the following switches:
16486 @item ^-pipe^/STANDARD_OUTPUT^
16487 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16488 Send the output to @code{Standard_Output}
16490 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16491 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16492 Write the output into @var{output_file}.
16493 If @var{output_file} already exists, @command{gnatpp} terminates without
16494 reading or processing the input file.
16496 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16497 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16498 Write the output into @var{output_file}, overwriting the existing file
16499 (if one is present).
16501 @item ^-r^/REPLACE^
16502 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16503 Replace the input source file with the reformatted output, and copy the
16504 original input source into the file whose name is obtained by appending the
16505 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16506 If a file with this name already exists, @command{gnatpp} terminates without
16507 reading or processing the input file.
16509 @item ^-rf^/OVERRIDING_REPLACE^
16510 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16511 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16512 already exists, it is overwritten.
16514 @item ^-rnb^/REPLACE_NO_BACKUP^
16515 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16516 Replace the input source file with the reformatted output without
16517 creating any backup copy of the input source.
16519 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16520 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16521 Specifies the format of the reformatted output file. The @var{xxx}
16522 ^string specified with the switch^option^ may be either
16524 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16525 @item ``@option{^crlf^CRLF^}''
16526 the same as @option{^crlf^CRLF^}
16527 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16528 @item ``@option{^lf^LF^}''
16529 the same as @option{^unix^UNIX^}
16532 @item ^-W^/RESULT_ENCODING=^@var{e}
16533 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16534 Specify the wide character encoding method used to write the code in the
16536 @var{e} is one of the following:
16544 Upper half encoding
16546 @item ^s^SHIFT_JIS^
16556 Brackets encoding (default value)
16562 Options @option{^-pipe^/STANDARD_OUTPUT^},
16563 @option{^-o^/OUTPUT^} and
16564 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16565 contains only one file to reformat.
16567 @option{^--eol^/END_OF_LINE^}
16569 @option{^-W^/RESULT_ENCODING^}
16570 cannot be used together
16571 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16573 @node Other gnatpp Switches
16574 @subsection Other @code{gnatpp} Switches
16577 The additional @command{gnatpp} switches are defined in this subsection.
16580 @item ^-files @var{filename}^/FILES=@var{output_file}^
16581 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16582 Take the argument source files from the specified file. This file should be an
16583 ordinary textual file containing file names separated by spaces or
16584 line breaks. You can use this switch more then once in the same call to
16585 @command{gnatpp}. You also can combine this switch with explicit list of
16588 @item ^-v^/VERBOSE^
16589 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16591 @command{gnatpp} generates version information and then
16592 a trace of the actions it takes to produce or obtain the ASIS tree.
16594 @item ^-w^/WARNINGS^
16595 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16597 @command{gnatpp} generates a warning whenever it cannot provide
16598 a required layout in the result source.
16601 @node Formatting Rules
16602 @section Formatting Rules
16605 The following subsections show how @command{gnatpp} treats ``white space'',
16606 comments, program layout, and name casing.
16607 They provide the detailed descriptions of the switches shown above.
16610 * White Space and Empty Lines::
16611 * Formatting Comments::
16612 * Construct Layout::
16616 @node White Space and Empty Lines
16617 @subsection White Space and Empty Lines
16620 @command{gnatpp} does not have an option to control space characters.
16621 It will add or remove spaces according to the style illustrated by the
16622 examples in the @cite{Ada Reference Manual}.
16624 The only format effectors
16625 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16626 that will appear in the output file are platform-specific line breaks,
16627 and also format effectors within (but not at the end of) comments.
16628 In particular, each horizontal tab character that is not inside
16629 a comment will be treated as a space and thus will appear in the
16630 output file as zero or more spaces depending on
16631 the reformatting of the line in which it appears.
16632 The only exception is a Form Feed character, which is inserted after a
16633 pragma @code{Page} when @option{-ff} is set.
16635 The output file will contain no lines with trailing ``white space'' (spaces,
16638 Empty lines in the original source are preserved
16639 only if they separate declarations or statements.
16640 In such contexts, a
16641 sequence of two or more empty lines is replaced by exactly one empty line.
16642 Note that a blank line will be removed if it separates two ``comment blocks''
16643 (a comment block is a sequence of whole-line comments).
16644 In order to preserve a visual separation between comment blocks, use an
16645 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16646 Likewise, if for some reason you wish to have a sequence of empty lines,
16647 use a sequence of empty comments instead.
16649 @node Formatting Comments
16650 @subsection Formatting Comments
16653 Comments in Ada code are of two kinds:
16656 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16657 ``white space'') on a line
16660 an @emph{end-of-line comment}, which follows some other Ada lexical element
16665 The indentation of a whole-line comment is that of either
16666 the preceding or following line in
16667 the formatted source, depending on switch settings as will be described below.
16669 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16670 between the end of the preceding Ada lexical element and the beginning
16671 of the comment as appear in the original source,
16672 unless either the comment has to be split to
16673 satisfy the line length limitation, or else the next line contains a
16674 whole line comment that is considered a continuation of this end-of-line
16675 comment (because it starts at the same position).
16677 cases, the start of the end-of-line comment is moved right to the nearest
16678 multiple of the indentation level.
16679 This may result in a ``line overflow'' (the right-shifted comment extending
16680 beyond the maximum line length), in which case the comment is split as
16683 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16684 (GNAT-style comment line indentation)
16685 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16686 (reference-manual comment line indentation).
16687 With reference-manual style, a whole-line comment is indented as if it
16688 were a declaration or statement at the same place
16689 (i.e., according to the indentation of the preceding line(s)).
16690 With GNAT style, a whole-line comment that is immediately followed by an
16691 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16692 word @b{begin}, is indented based on the construct that follows it.
16695 @smallexample @c ada
16707 Reference-manual indentation produces:
16709 @smallexample @c ada
16721 while GNAT-style indentation produces:
16723 @smallexample @c ada
16735 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16736 (GNAT style comment beginning) has the following
16741 For each whole-line comment that does not end with two hyphens,
16742 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16743 to ensure that there are at least two spaces between these hyphens and the
16744 first non-blank character of the comment.
16748 For an end-of-line comment, if in the original source the next line is a
16749 whole-line comment that starts at the same position
16750 as the end-of-line comment,
16751 then the whole-line comment (and all whole-line comments
16752 that follow it and that start at the same position)
16753 will start at this position in the output file.
16756 That is, if in the original source we have:
16758 @smallexample @c ada
16761 A := B + C; -- B must be in the range Low1..High1
16762 -- C must be in the range Low2..High2
16763 --B+C will be in the range Low1+Low2..High1+High2
16769 Then in the formatted source we get
16771 @smallexample @c ada
16774 A := B + C; -- B must be in the range Low1..High1
16775 -- C must be in the range Low2..High2
16776 -- B+C will be in the range Low1+Low2..High1+High2
16782 A comment that exceeds the line length limit will be split.
16784 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16785 the line belongs to a reformattable block, splitting the line generates a
16786 @command{gnatpp} warning.
16787 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16788 comments may be reformatted in typical
16789 word processor style (that is, moving words between lines and putting as
16790 many words in a line as possible).
16793 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16794 that has a special format (that is, a character that is neither a letter nor digit
16795 not white space nor line break immediately following the leading @code{--} of
16796 the comment) should be without any change moved from the argument source
16797 into reformatted source. This switch allows to preserve comments that are used
16798 as a special marks in the code (e.g.@: SPARK annotation).
16800 @node Construct Layout
16801 @subsection Construct Layout
16804 In several cases the suggested layout in the Ada Reference Manual includes
16805 an extra level of indentation that many programmers prefer to avoid. The
16806 affected cases include:
16810 @item Record type declaration (RM 3.8)
16812 @item Record representation clause (RM 13.5.1)
16814 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16816 @item Block statement in case if a block has a statement identifier (RM 5.6)
16820 In compact mode (when GNAT style layout or compact layout is set),
16821 the pretty printer uses one level of indentation instead
16822 of two. This is achieved in the record definition and record representation
16823 clause cases by putting the @code{record} keyword on the same line as the
16824 start of the declaration or representation clause, and in the block and loop
16825 case by putting the block or loop header on the same line as the statement
16829 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16830 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16831 layout on the one hand, and uncompact layout
16832 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16833 can be illustrated by the following examples:
16837 @multitable @columnfractions .5 .5
16838 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16841 @smallexample @c ada
16848 @smallexample @c ada
16857 @smallexample @c ada
16859 a at 0 range 0 .. 31;
16860 b at 4 range 0 .. 31;
16864 @smallexample @c ada
16867 a at 0 range 0 .. 31;
16868 b at 4 range 0 .. 31;
16873 @smallexample @c ada
16881 @smallexample @c ada
16891 @smallexample @c ada
16892 Clear : for J in 1 .. 10 loop
16897 @smallexample @c ada
16899 for J in 1 .. 10 loop
16910 GNAT style, compact layout Uncompact layout
16912 type q is record type q is
16913 a : integer; record
16914 b : integer; a : integer;
16915 end record; b : integer;
16918 for q use record for q use
16919 a at 0 range 0 .. 31; record
16920 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16921 end record; b at 4 range 0 .. 31;
16924 Block : declare Block :
16925 A : Integer := 3; declare
16926 begin A : Integer := 3;
16928 end Block; Proc (A, A);
16931 Clear : for J in 1 .. 10 loop Clear :
16932 A (J) := 0; for J in 1 .. 10 loop
16933 end loop Clear; A (J) := 0;
16940 A further difference between GNAT style layout and compact layout is that
16941 GNAT style layout inserts empty lines as separation for
16942 compound statements, return statements and bodies.
16944 Note that the layout specified by
16945 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16946 for named block and loop statements overrides the layout defined by these
16947 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16948 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16949 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16952 @subsection Name Casing
16955 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16956 the same casing as the corresponding defining identifier.
16958 You control the casing for defining occurrences via the
16959 @option{^-n^/NAME_CASING^} switch.
16961 With @option{-nD} (``as declared'', which is the default),
16964 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16966 defining occurrences appear exactly as in the source file
16967 where they are declared.
16968 The other ^values for this switch^options for this qualifier^ ---
16969 @option{^-nU^UPPER_CASE^},
16970 @option{^-nL^LOWER_CASE^},
16971 @option{^-nM^MIXED_CASE^} ---
16973 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16974 If @command{gnatpp} changes the casing of a defining
16975 occurrence, it analogously changes the casing of all the
16976 usage occurrences of this name.
16978 If the defining occurrence of a name is not in the source compilation unit
16979 currently being processed by @command{gnatpp}, the casing of each reference to
16980 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16981 switch (subject to the dictionary file mechanism described below).
16982 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16984 casing for the defining occurrence of the name.
16986 Some names may need to be spelled with casing conventions that are not
16987 covered by the upper-, lower-, and mixed-case transformations.
16988 You can arrange correct casing by placing such names in a
16989 @emph{dictionary file},
16990 and then supplying a @option{^-D^/DICTIONARY^} switch.
16991 The casing of names from dictionary files overrides
16992 any @option{^-n^/NAME_CASING^} switch.
16994 To handle the casing of Ada predefined names and the names from GNAT libraries,
16995 @command{gnatpp} assumes a default dictionary file.
16996 The name of each predefined entity is spelled with the same casing as is used
16997 for the entity in the @cite{Ada Reference Manual}.
16998 The name of each entity in the GNAT libraries is spelled with the same casing
16999 as is used in the declaration of that entity.
17001 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
17002 default dictionary file.
17003 Instead, the casing for predefined and GNAT-defined names will be established
17004 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
17005 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
17006 will appear as just shown,
17007 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
17008 To ensure that even such names are rendered in uppercase,
17009 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
17010 (or else, less conveniently, place these names in upper case in a dictionary
17013 A dictionary file is
17014 a plain text file; each line in this file can be either a blank line
17015 (containing only space characters and ASCII.HT characters), an Ada comment
17016 line, or the specification of exactly one @emph{casing schema}.
17018 A casing schema is a string that has the following syntax:
17022 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
17024 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
17029 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
17030 @var{identifier} lexical element and the @var{letter_or_digit} category.)
17032 The casing schema string can be followed by white space and/or an Ada-style
17033 comment; any amount of white space is allowed before the string.
17035 If a dictionary file is passed as
17037 the value of a @option{-D@var{file}} switch
17040 an option to the @option{/DICTIONARY} qualifier
17043 simple name and every identifier, @command{gnatpp} checks if the dictionary
17044 defines the casing for the name or for some of its parts (the term ``subword''
17045 is used below to denote the part of a name which is delimited by ``_'' or by
17046 the beginning or end of the word and which does not contain any ``_'' inside):
17050 if the whole name is in the dictionary, @command{gnatpp} uses for this name
17051 the casing defined by the dictionary; no subwords are checked for this word
17054 for every subword @command{gnatpp} checks if the dictionary contains the
17055 corresponding string of the form @code{*@var{simple_identifier}*},
17056 and if it does, the casing of this @var{simple_identifier} is used
17060 if the whole name does not contain any ``_'' inside, and if for this name
17061 the dictionary contains two entries - one of the form @var{identifier},
17062 and another - of the form *@var{simple_identifier}*, then the first one
17063 is applied to define the casing of this name
17066 if more than one dictionary file is passed as @command{gnatpp} switches, each
17067 dictionary adds new casing exceptions and overrides all the existing casing
17068 exceptions set by the previous dictionaries
17071 when @command{gnatpp} checks if the word or subword is in the dictionary,
17072 this check is not case sensitive
17076 For example, suppose we have the following source to reformat:
17078 @smallexample @c ada
17081 name1 : integer := 1;
17082 name4_name3_name2 : integer := 2;
17083 name2_name3_name4 : Boolean;
17086 name2_name3_name4 := name4_name3_name2 > name1;
17092 And suppose we have two dictionaries:
17109 If @command{gnatpp} is called with the following switches:
17113 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
17116 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
17121 then we will get the following name casing in the @command{gnatpp} output:
17123 @smallexample @c ada
17126 NAME1 : Integer := 1;
17127 Name4_NAME3_Name2 : Integer := 2;
17128 Name2_NAME3_Name4 : Boolean;
17131 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
17136 @c *********************************
17137 @node The GNAT Metric Tool gnatmetric
17138 @chapter The GNAT Metric Tool @command{gnatmetric}
17140 @cindex Metric tool
17143 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
17144 for computing various program metrics.
17145 It takes an Ada source file as input and generates a file containing the
17146 metrics data as output. Various switches control which
17147 metrics are computed and output.
17149 @command{gnatmetric} generates and uses the ASIS
17150 tree for the input source and thus requires the input to be syntactically and
17151 semantically legal.
17152 If this condition is not met, @command{gnatmetric} will generate
17153 an error message; no metric information for this file will be
17154 computed and reported.
17156 If the compilation unit contained in the input source depends semantically
17157 upon units in files located outside the current directory, you have to provide
17158 the source search path when invoking @command{gnatmetric}.
17159 If it depends semantically upon units that are contained
17160 in files with names that do not follow the GNAT file naming rules, you have to
17161 provide the configuration file describing the corresponding naming scheme (see
17162 the description of the @command{gnatmetric} switches below.)
17163 Alternatively, you may use a project file and invoke @command{gnatmetric}
17164 through the @command{gnat} driver.
17166 The @command{gnatmetric} command has the form
17169 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
17176 @var{switches} specify the metrics to compute and define the destination for
17180 Each @var{filename} is the name (including the extension) of a source
17181 file to process. ``Wildcards'' are allowed, and
17182 the file name may contain path information.
17183 If no @var{filename} is supplied, then the @var{switches} list must contain
17185 @option{-files} switch (@pxref{Other gnatmetric Switches}).
17186 Including both a @option{-files} switch and one or more
17187 @var{filename} arguments is permitted.
17190 @samp{-cargs @var{gcc_switches}} is a list of switches for
17191 @command{gcc}. They will be passed on to all compiler invocations made by
17192 @command{gnatmetric} to generate the ASIS trees. Here you can provide
17193 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17194 and use the @option{-gnatec} switch to set the configuration file.
17198 * Switches for gnatmetric::
17201 @node Switches for gnatmetric
17202 @section Switches for @command{gnatmetric}
17205 The following subsections describe the various switches accepted by
17206 @command{gnatmetric}, organized by category.
17209 * Output Files Control::
17210 * Disable Metrics For Local Units::
17211 * Specifying a set of metrics to compute::
17212 * Other gnatmetric Switches::
17213 * Generate project-wide metrics::
17216 @node Output Files Control
17217 @subsection Output File Control
17218 @cindex Output file control in @command{gnatmetric}
17221 @command{gnatmetric} has two output formats. It can generate a
17222 textual (human-readable) form, and also XML. By default only textual
17223 output is generated.
17225 When generating the output in textual form, @command{gnatmetric} creates
17226 for each Ada source file a corresponding text file
17227 containing the computed metrics, except for the case when the set of metrics
17228 specified by gnatmetric parameters consists only of metrics that are computed
17229 for the whole set of analyzed sources, but not for each Ada source.
17230 By default, this file is placed in the same directory as where the source
17231 file is located, and its name is obtained
17232 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
17235 All the output information generated in XML format is placed in a single
17236 file. By default this file is placed in the current directory and has the
17237 name ^@file{metrix.xml}^@file{METRIX$XML}^.
17239 Some of the computed metrics are summed over the units passed to
17240 @command{gnatmetric}; for example, the total number of lines of code.
17241 By default this information is sent to @file{stdout}, but a file
17242 can be specified with the @option{-og} switch.
17244 The following switches control the @command{gnatmetric} output:
17247 @cindex @option{^-x^/XML^} (@command{gnatmetric})
17249 Generate the XML output
17251 @cindex @option{^-xs^/XSD^} (@command{gnatmetric})
17253 Generate the XML output and the XML schema file that describes the structure
17254 of the XML metric report, this schema is assigned to the XML file. The schema
17255 file has the same name as the XML output file with @file{.xml} suffix replaced
17258 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
17259 @item ^-nt^/NO_TEXT^
17260 Do not generate the output in text form (implies @option{^-x^/XML^})
17262 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
17263 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
17264 Put textual files with detailed metrics into @var{output_dir}
17266 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
17267 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
17268 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
17269 in the name of the output file.
17271 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
17272 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
17273 Put global metrics into @var{file_name}
17275 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
17276 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
17277 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
17279 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
17280 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
17281 Use ``short'' source file names in the output. (The @command{gnatmetric}
17282 output includes the name(s) of the Ada source file(s) from which the metrics
17283 are computed. By default each name includes the absolute path. The
17284 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
17285 to exclude all directory information from the file names that are output.)
17289 @node Disable Metrics For Local Units
17290 @subsection Disable Metrics For Local Units
17291 @cindex Disable Metrics For Local Units in @command{gnatmetric}
17294 @command{gnatmetric} relies on the GNAT compilation model @minus{}
17296 unit per one source file. It computes line metrics for the whole source
17297 file, and it also computes syntax
17298 and complexity metrics for the file's outermost unit.
17300 By default, @command{gnatmetric} will also compute all metrics for certain
17301 kinds of locally declared program units:
17305 subprogram (and generic subprogram) bodies;
17308 package (and generic package) specs and bodies;
17311 task object and type specifications and bodies;
17314 protected object and type specifications and bodies.
17318 These kinds of entities will be referred to as
17319 @emph{eligible local program units}, or simply @emph{eligible local units},
17320 @cindex Eligible local unit (for @command{gnatmetric})
17321 in the discussion below.
17323 Note that a subprogram declaration, generic instantiation,
17324 or renaming declaration only receives metrics
17325 computation when it appear as the outermost entity
17328 Suppression of metrics computation for eligible local units can be
17329 obtained via the following switch:
17332 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
17333 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
17334 Do not compute detailed metrics for eligible local program units
17338 @node Specifying a set of metrics to compute
17339 @subsection Specifying a set of metrics to compute
17342 By default all the metrics are computed and reported. The switches
17343 described in this subsection allow you to control, on an individual
17344 basis, whether metrics are computed and
17345 reported. If at least one positive metric
17346 switch is specified (that is, a switch that defines that a given
17347 metric or set of metrics is to be computed), then only
17348 explicitly specified metrics are reported.
17351 * Line Metrics Control::
17352 * Syntax Metrics Control::
17353 * Complexity Metrics Control::
17354 * Object-Oriented Metrics Control::
17357 @node Line Metrics Control
17358 @subsubsection Line Metrics Control
17359 @cindex Line metrics control in @command{gnatmetric}
17362 For any (legal) source file, and for each of its
17363 eligible local program units, @command{gnatmetric} computes the following
17368 the total number of lines;
17371 the total number of code lines (i.e., non-blank lines that are not comments)
17374 the number of comment lines
17377 the number of code lines containing end-of-line comments;
17380 the comment percentage: the ratio between the number of lines that contain
17381 comments and the number of all non-blank lines, expressed as a percentage;
17384 the number of empty lines and lines containing only space characters and/or
17385 format effectors (blank lines)
17388 the average number of code lines in subprogram bodies, task bodies, entry
17389 bodies and statement sequences in package bodies (this metric is only computed
17390 across the whole set of the analyzed units)
17395 @command{gnatmetric} sums the values of the line metrics for all the
17396 files being processed and then generates the cumulative results. The tool
17397 also computes for all the files being processed the average number of code
17400 You can use the following switches to select the specific line metrics
17401 to be computed and reported.
17404 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17407 @cindex @option{--no-lines@var{x}}
17410 @item ^--lines-all^/LINE_COUNT_METRICS=ALL^
17411 Report all the line metrics
17413 @item ^--no-lines-all^/LINE_COUNT_METRICS=NONE^
17414 Do not report any of line metrics
17416 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES^
17417 Report the number of all lines
17419 @item ^--no-lines^/LINE_COUNT_METRICS=NOALL_LINES^
17420 Do not report the number of all lines
17422 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES^
17423 Report the number of code lines
17425 @item ^--no-lines-code^/LINE_COUNT_METRICS=NOCODE_LINES^
17426 Do not report the number of code lines
17428 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES^
17429 Report the number of comment lines
17431 @item ^--no-lines-comment^/LINE_COUNT_METRICS=NOCOMMENT_LINES^
17432 Do not report the number of comment lines
17434 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES^
17435 Report the number of code lines containing
17436 end-of-line comments
17438 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=NOCODE_COMMENT_LINES^
17439 Do not report the number of code lines containing
17440 end-of-line comments
17442 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE^
17443 Report the comment percentage in the program text
17445 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=NOCOMMENT_PERCENTAGE^
17446 Do not report the comment percentage in the program text
17448 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES^
17449 Report the number of blank lines
17451 @item ^--no-lines-blank^/LINE_COUNT_METRICS=NOBLANK_LINES^
17452 Do not report the number of blank lines
17454 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES^
17455 Report the average number of code lines in subprogram bodies, task bodies,
17456 entry bodies and statement sequences in package bodies. The metric is computed
17457 and reported for the whole set of processed Ada sources only.
17459 @item ^--no-lines-average^/LINE_COUNT_METRICS=NOAVERAGE_BODY_LINES^
17460 Do not report the average number of code lines in subprogram bodies,
17461 task bodies, entry bodies and statement sequences in package bodies.
17465 @node Syntax Metrics Control
17466 @subsubsection Syntax Metrics Control
17467 @cindex Syntax metrics control in @command{gnatmetric}
17470 @command{gnatmetric} computes various syntactic metrics for the
17471 outermost unit and for each eligible local unit:
17474 @item LSLOC (``Logical Source Lines Of Code'')
17475 The total number of declarations and the total number of statements
17477 @item Maximal static nesting level of inner program units
17479 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17480 package, a task unit, a protected unit, a
17481 protected entry, a generic unit, or an explicitly declared subprogram other
17482 than an enumeration literal.''
17484 @item Maximal nesting level of composite syntactic constructs
17485 This corresponds to the notion of the
17486 maximum nesting level in the GNAT built-in style checks
17487 (@pxref{Style Checking})
17491 For the outermost unit in the file, @command{gnatmetric} additionally computes
17492 the following metrics:
17495 @item Public subprograms
17496 This metric is computed for package specs. It is the
17497 number of subprograms and generic subprograms declared in the visible
17498 part (including the visible part of nested packages, protected objects, and
17501 @item All subprograms
17502 This metric is computed for bodies and subunits. The
17503 metric is equal to a total number of subprogram bodies in the compilation
17505 Neither generic instantiations nor renamings-as-a-body nor body stubs
17506 are counted. Any subprogram body is counted, independently of its nesting
17507 level and enclosing constructs. Generic bodies and bodies of protected
17508 subprograms are counted in the same way as ``usual'' subprogram bodies.
17511 This metric is computed for package specs and
17512 generic package declarations. It is the total number of types
17513 that can be referenced from outside this compilation unit, plus the
17514 number of types from all the visible parts of all the visible generic
17515 packages. Generic formal types are not counted. Only types, not subtypes,
17519 Along with the total number of public types, the following
17520 types are counted and reported separately:
17527 Root tagged types (abstract, non-abstract, private, non-private). Type
17528 extensions are @emph{not} counted
17531 Private types (including private extensions)
17542 This metric is computed for any compilation unit. It is equal to the total
17543 number of the declarations of different types given in the compilation unit.
17544 The private and the corresponding full type declaration are counted as one
17545 type declaration. Incomplete type declarations and generic formal types
17547 No distinction is made among different kinds of types (abstract,
17548 private etc.); the total number of types is computed and reported.
17553 By default, all the syntax metrics are computed and reported. You can use the
17554 following switches to select specific syntax metrics.
17558 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17561 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17564 @item ^--syntax-all^/SYNTAX_METRICS=ALL^
17565 Report all the syntax metrics
17567 @item ^--no-syntax-all^/SYNTAX_METRICS=NONE^
17568 Do not report any of syntax metrics
17570 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS^
17571 Report the total number of declarations
17573 @item ^--no-declarations^/SYNTAX_METRICS=NODECLARATIONS^
17574 Do not report the total number of declarations
17576 @item ^--statements^/SYNTAX_METRICS=STATEMENTS^
17577 Report the total number of statements
17579 @item ^--no-statements^/SYNTAX_METRICS=NOSTATEMENTS^
17580 Do not report the total number of statements
17582 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS^
17583 Report the number of public subprograms in a compilation unit
17585 @item ^--no-public-subprograms^/SYNTAX_METRICS=NOPUBLIC_SUBPROGRAMS^
17586 Do not report the number of public subprograms in a compilation unit
17588 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS^
17589 Report the number of all the subprograms in a compilation unit
17591 @item ^--no-all-subprograms^/SYNTAX_METRICS=NOALL_SUBPROGRAMS^
17592 Do not report the number of all the subprograms in a compilation unit
17594 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES^
17595 Report the number of public types in a compilation unit
17597 @item ^--no-public-types^/SYNTAX_METRICS=NOPUBLIC_TYPES^
17598 Do not report the number of public types in a compilation unit
17600 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES^
17601 Report the number of all the types in a compilation unit
17603 @item ^--no-all-types^/SYNTAX_METRICS=NOALL_TYPES^
17604 Do not report the number of all the types in a compilation unit
17606 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING^
17607 Report the maximal program unit nesting level
17609 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17610 Do not report the maximal program unit nesting level
17612 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING^
17613 Report the maximal construct nesting level
17615 @item ^--no-construct-nesting^/SYNTAX_METRICS=NOCONSTRUCT_NESTING^
17616 Do not report the maximal construct nesting level
17620 @node Complexity Metrics Control
17621 @subsubsection Complexity Metrics Control
17622 @cindex Complexity metrics control in @command{gnatmetric}
17625 For a program unit that is an executable body (a subprogram body (including
17626 generic bodies), task body, entry body or a package body containing
17627 its own statement sequence) @command{gnatmetric} computes the following
17628 complexity metrics:
17632 McCabe cyclomatic complexity;
17635 McCabe essential complexity;
17638 maximal loop nesting level
17643 The McCabe complexity metrics are defined
17644 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17646 According to McCabe, both control statements and short-circuit control forms
17647 should be taken into account when computing cyclomatic complexity. For each
17648 body, we compute three metric values:
17652 the complexity introduced by control
17653 statements only, without taking into account short-circuit forms,
17656 the complexity introduced by short-circuit control forms only, and
17660 cyclomatic complexity, which is the sum of these two values.
17664 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17665 the code in the exception handlers and in all the nested program units.
17667 By default, all the complexity metrics are computed and reported.
17668 For more fine-grained control you can use
17669 the following switches:
17672 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17675 @cindex @option{--no-complexity@var{x}}
17678 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL^
17679 Report all the complexity metrics
17681 @item ^--no-complexity-all^/COMPLEXITY_METRICS=NONE^
17682 Do not report any of complexity metrics
17684 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC^
17685 Report the McCabe Cyclomatic Complexity
17687 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=NOCYCLOMATIC^
17688 Do not report the McCabe Cyclomatic Complexity
17690 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL^
17691 Report the Essential Complexity
17693 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=NOESSENTIAL^
17694 Do not report the Essential Complexity
17696 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17697 Report maximal loop nesting level
17699 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=NOLOOP_NESTING^
17700 Do not report maximal loop nesting level
17702 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY^
17703 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17704 task bodies, entry bodies and statement sequences in package bodies.
17705 The metric is computed and reported for whole set of processed Ada sources
17708 @item ^--no-complexity-average^/COMPLEXITY_METRICS=NOAVERAGE_COMPLEXITY^
17709 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17710 bodies, task bodies, entry bodies and statement sequences in package bodies
17712 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17713 @item ^-ne^/NO_EXITS_AS_GOTOS^
17714 Do not consider @code{exit} statements as @code{goto}s when
17715 computing Essential Complexity
17717 @item ^--extra-exit-points^/EXTRA_EXIT_POINTS^
17718 Report the extra exit points for subprogram bodies. As an exit point, this
17719 metric counts @code{return} statements and raise statements in case when the
17720 raised exception is not handled in the same body. In case of a function this
17721 metric subtracts 1 from the number of exit points, because a function body
17722 must contain at least one @code{return} statement.
17724 @item ^--no-extra-exit-points^/NOEXTRA_EXIT_POINTS^
17725 Do not report the extra exit points for subprogram bodies
17729 @node Object-Oriented Metrics Control
17730 @subsubsection Object-Oriented Metrics Control
17731 @cindex Object-Oriented metrics control in @command{gnatmetric}
17734 @cindex Coupling metrics (in in @command{gnatmetric})
17735 Coupling metrics are object-oriented metrics that measure the
17736 dependencies between a given class (or a group of classes) and the
17737 ``external world'' (that is, the other classes in the program). In this
17738 subsection the term ``class'' is used in its
17739 traditional object-oriented programming sense
17740 (an instantiable module that contains data and/or method members).
17741 A @emph{category} (of classes)
17742 is a group of closely related classes that are reused and/or
17745 A class @code{K}'s @emph{efferent coupling} is the number of classes
17746 that @code{K} depends upon.
17747 A category's efferent coupling is the number of classes outside the
17748 category that the classes inside the category depend upon.
17750 A class @code{K}'s @emph{afferent coupling} is the number of classes
17751 that depend upon @code{K}.
17752 A category's afferent coupling is the number of classes outside the
17753 category that depend on classes belonging to the category.
17755 Ada's implementation of the object-oriented paradigm does not use the
17756 traditional class notion, so the definition of the coupling
17757 metrics for Ada maps the class and class category notions
17758 onto Ada constructs.
17760 For the coupling metrics, several kinds of modules -- a library package,
17761 a library generic package, and a library generic package instantiation --
17762 that define a tagged type or an interface type are
17763 considered to be a class. A category consists of a library package (or
17764 a library generic package) that defines a tagged or an interface type,
17765 together with all its descendant (generic) packages that define tagged
17766 or interface types. For any package counted as a class,
17767 its body and subunits (if any) are considered
17768 together with its spec when counting the dependencies, and coupling
17769 metrics are reported for spec units only. For dependencies
17770 between classes, the Ada semantic dependencies are considered.
17771 For coupling metrics, only dependencies on units that are considered as
17772 classes, are considered.
17774 When computing coupling metrics, @command{gnatmetric} counts only
17775 dependencies between units that are arguments of the gnatmetric call.
17776 Coupling metrics are program-wide (or project-wide) metrics, so to
17777 get a valid result, you should call @command{gnatmetric} for
17778 the whole set of sources that make up your program. It can be done
17779 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17780 option (see See @ref{The GNAT Driver and Project Files} for details.
17782 By default, all the coupling metrics are disabled. You can use the following
17783 switches to specify the coupling metrics to be computed and reported:
17788 @cindex @option{--package@var{x}} (@command{gnatmetric})
17789 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17790 @cindex @option{--category@var{x}} (@command{gnatmetric})
17791 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17795 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17798 @item ^--coupling-all^/COUPLING_METRICS=ALL^
17799 Report all the coupling metrics
17801 @item ^--no-coupling-all^/COUPLING_METRICS=NONE^
17802 Do not report any of metrics
17804 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT^
17805 Report package efferent coupling
17807 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=NOPACKAGE_EFFERENT^
17808 Do not report package efferent coupling
17810 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT^
17811 Report package afferent coupling
17813 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=NOPACKAGE_AFFERENT^
17814 Do not report package afferent coupling
17816 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT^
17817 Report category efferent coupling
17819 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=NOCATEGORY_EFFERENT^
17820 Do not report category efferent coupling
17822 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT^
17823 Report category afferent coupling
17825 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=NOCATEGORY_AFFERENT^
17826 Do not report category afferent coupling
17830 @node Other gnatmetric Switches
17831 @subsection Other @code{gnatmetric} Switches
17834 Additional @command{gnatmetric} switches are as follows:
17837 @item ^-files @var{filename}^/FILES=@var{filename}^
17838 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17839 Take the argument source files from the specified file. This file should be an
17840 ordinary text file containing file names separated by spaces or
17841 line breaks. You can use this switch more then once in the same call to
17842 @command{gnatmetric}. You also can combine this switch with
17843 an explicit list of files.
17845 @item ^-v^/VERBOSE^
17846 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17848 @command{gnatmetric} generates version information and then
17849 a trace of sources being processed.
17851 @item ^-dv^/DEBUG_OUTPUT^
17852 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17854 @command{gnatmetric} generates various messages useful to understand what
17855 happens during the metrics computation
17858 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17862 @node Generate project-wide metrics
17863 @subsection Generate project-wide metrics
17865 In order to compute metrics on all units of a given project, you can use
17866 the @command{gnat} driver along with the @option{-P} option:
17872 If the project @code{proj} depends upon other projects, you can compute
17873 the metrics on the project closure using the @option{-U} option:
17875 gnat metric -Pproj -U
17879 Finally, if not all the units are relevant to a particular main
17880 program in the project closure, you can generate metrics for the set
17881 of units needed to create a given main program (unit closure) using
17882 the @option{-U} option followed by the name of the main unit:
17884 gnat metric -Pproj -U main
17888 @c ***********************************
17889 @node File Name Krunching Using gnatkr
17890 @chapter File Name Krunching Using @code{gnatkr}
17894 This chapter discusses the method used by the compiler to shorten
17895 the default file names chosen for Ada units so that they do not
17896 exceed the maximum length permitted. It also describes the
17897 @code{gnatkr} utility that can be used to determine the result of
17898 applying this shortening.
17902 * Krunching Method::
17903 * Examples of gnatkr Usage::
17907 @section About @code{gnatkr}
17910 The default file naming rule in GNAT
17911 is that the file name must be derived from
17912 the unit name. The exact default rule is as follows:
17915 Take the unit name and replace all dots by hyphens.
17917 If such a replacement occurs in the
17918 second character position of a name, and the first character is
17919 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17920 then replace the dot by the character
17921 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17922 instead of a minus.
17924 The reason for this exception is to avoid clashes
17925 with the standard names for children of System, Ada, Interfaces,
17926 and GNAT, which use the prefixes
17927 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17930 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17931 switch of the compiler activates a ``krunching''
17932 circuit that limits file names to nn characters (where nn is a decimal
17933 integer). For example, using OpenVMS,
17934 where the maximum file name length is
17935 39, the value of nn is usually set to 39, but if you want to generate
17936 a set of files that would be usable if ported to a system with some
17937 different maximum file length, then a different value can be specified.
17938 The default value of 39 for OpenVMS need not be specified.
17940 The @code{gnatkr} utility can be used to determine the krunched name for
17941 a given file, when krunched to a specified maximum length.
17944 @section Using @code{gnatkr}
17947 The @code{gnatkr} command has the form
17951 $ gnatkr @var{name} @ovar{length}
17957 $ gnatkr @var{name} /COUNT=nn
17962 @var{name} is the uncrunched file name, derived from the name of the unit
17963 in the standard manner described in the previous section (i.e., in particular
17964 all dots are replaced by hyphens). The file name may or may not have an
17965 extension (defined as a suffix of the form period followed by arbitrary
17966 characters other than period). If an extension is present then it will
17967 be preserved in the output. For example, when krunching @file{hellofile.ads}
17968 to eight characters, the result will be hellofil.ads.
17970 Note: for compatibility with previous versions of @code{gnatkr} dots may
17971 appear in the name instead of hyphens, but the last dot will always be
17972 taken as the start of an extension. So if @code{gnatkr} is given an argument
17973 such as @file{Hello.World.adb} it will be treated exactly as if the first
17974 period had been a hyphen, and for example krunching to eight characters
17975 gives the result @file{hellworl.adb}.
17977 Note that the result is always all lower case (except on OpenVMS where it is
17978 all upper case). Characters of the other case are folded as required.
17980 @var{length} represents the length of the krunched name. The default
17981 when no argument is given is ^8^39^ characters. A length of zero stands for
17982 unlimited, in other words do not chop except for system files where the
17983 implied crunching length is always eight characters.
17986 The output is the krunched name. The output has an extension only if the
17987 original argument was a file name with an extension.
17989 @node Krunching Method
17990 @section Krunching Method
17993 The initial file name is determined by the name of the unit that the file
17994 contains. The name is formed by taking the full expanded name of the
17995 unit and replacing the separating dots with hyphens and
17996 using ^lowercase^uppercase^
17997 for all letters, except that a hyphen in the second character position is
17998 replaced by a ^tilde^dollar sign^ if the first character is
17999 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
18000 The extension is @code{.ads} for a
18001 spec and @code{.adb} for a body.
18002 Krunching does not affect the extension, but the file name is shortened to
18003 the specified length by following these rules:
18007 The name is divided into segments separated by hyphens, tildes or
18008 underscores and all hyphens, tildes, and underscores are
18009 eliminated. If this leaves the name short enough, we are done.
18012 If the name is too long, the longest segment is located (left-most
18013 if there are two of equal length), and shortened by dropping
18014 its last character. This is repeated until the name is short enough.
18016 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
18017 to fit the name into 8 characters as required by some operating systems.
18020 our-strings-wide_fixed 22
18021 our strings wide fixed 19
18022 our string wide fixed 18
18023 our strin wide fixed 17
18024 our stri wide fixed 16
18025 our stri wide fixe 15
18026 our str wide fixe 14
18027 our str wid fixe 13
18033 Final file name: oustwifi.adb
18037 The file names for all predefined units are always krunched to eight
18038 characters. The krunching of these predefined units uses the following
18039 special prefix replacements:
18043 replaced by @file{^a^A^-}
18046 replaced by @file{^g^G^-}
18049 replaced by @file{^i^I^-}
18052 replaced by @file{^s^S^-}
18055 These system files have a hyphen in the second character position. That
18056 is why normal user files replace such a character with a
18057 ^tilde^dollar sign^, to
18058 avoid confusion with system file names.
18060 As an example of this special rule, consider
18061 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
18064 ada-strings-wide_fixed 22
18065 a- strings wide fixed 18
18066 a- string wide fixed 17
18067 a- strin wide fixed 16
18068 a- stri wide fixed 15
18069 a- stri wide fixe 14
18070 a- str wide fixe 13
18076 Final file name: a-stwifi.adb
18080 Of course no file shortening algorithm can guarantee uniqueness over all
18081 possible unit names, and if file name krunching is used then it is your
18082 responsibility to ensure that no name clashes occur. The utility
18083 program @code{gnatkr} is supplied for conveniently determining the
18084 krunched name of a file.
18086 @node Examples of gnatkr Usage
18087 @section Examples of @code{gnatkr} Usage
18094 $ gnatkr very_long_unit_name.ads --> velounna.ads
18095 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
18096 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
18097 $ gnatkr grandparent-parent-child --> grparchi
18099 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
18100 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
18103 @node Preprocessing Using gnatprep
18104 @chapter Preprocessing Using @code{gnatprep}
18108 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
18110 Although designed for use with GNAT, @code{gnatprep} does not depend on any
18111 special GNAT features.
18112 For further discussion of conditional compilation in general, see
18113 @ref{Conditional Compilation}.
18116 * Preprocessing Symbols::
18118 * Switches for gnatprep::
18119 * Form of Definitions File::
18120 * Form of Input Text for gnatprep::
18123 @node Preprocessing Symbols
18124 @section Preprocessing Symbols
18127 Preprocessing symbols are defined in definition files and referred to in
18128 sources to be preprocessed. A Preprocessing symbol is an identifier, following
18129 normal Ada (case-insensitive) rules for its syntax, with the restriction that
18130 all characters need to be in the ASCII set (no accented letters).
18132 @node Using gnatprep
18133 @section Using @code{gnatprep}
18136 To call @code{gnatprep} use
18139 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
18146 is an optional sequence of switches as described in the next section.
18149 is the full name of the input file, which is an Ada source
18150 file containing preprocessor directives.
18153 is the full name of the output file, which is an Ada source
18154 in standard Ada form. When used with GNAT, this file name will
18155 normally have an ads or adb suffix.
18158 is the full name of a text file containing definitions of
18159 preprocessing symbols to be referenced by the preprocessor. This argument is
18160 optional, and can be replaced by the use of the @option{-D} switch.
18164 @node Switches for gnatprep
18165 @section Switches for @code{gnatprep}
18170 @item ^-b^/BLANK_LINES^
18171 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
18172 Causes both preprocessor lines and the lines deleted by
18173 preprocessing to be replaced by blank lines in the output source file,
18174 preserving line numbers in the output file.
18176 @item ^-c^/COMMENTS^
18177 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
18178 Causes both preprocessor lines and the lines deleted
18179 by preprocessing to be retained in the output source as comments marked
18180 with the special string @code{"--! "}. This option will result in line numbers
18181 being preserved in the output file.
18183 @item ^-C^/REPLACE_IN_COMMENTS^
18184 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
18185 Causes comments to be scanned. Normally comments are ignored by gnatprep.
18186 If this option is specified, then comments are scanned and any $symbol
18187 substitutions performed as in program text. This is particularly useful
18188 when structured comments are used (e.g., when writing programs in the
18189 SPARK dialect of Ada). Note that this switch is not available when
18190 doing integrated preprocessing (it would be useless in this context
18191 since comments are ignored by the compiler in any case).
18193 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
18194 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
18195 Defines a new preprocessing symbol, associated with value. If no value is given
18196 on the command line, then symbol is considered to be @code{True}. This switch
18197 can be used in place of a definition file.
18201 @cindex @option{/REMOVE} (@command{gnatprep})
18202 This is the default setting which causes lines deleted by preprocessing
18203 to be entirely removed from the output file.
18206 @item ^-r^/REFERENCE^
18207 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
18208 Causes a @code{Source_Reference} pragma to be generated that
18209 references the original input file, so that error messages will use
18210 the file name of this original file. The use of this switch implies
18211 that preprocessor lines are not to be removed from the file, so its
18212 use will force @option{^-b^/BLANK_LINES^} mode if
18213 @option{^-c^/COMMENTS^}
18214 has not been specified explicitly.
18216 Note that if the file to be preprocessed contains multiple units, then
18217 it will be necessary to @code{gnatchop} the output file from
18218 @code{gnatprep}. If a @code{Source_Reference} pragma is present
18219 in the preprocessed file, it will be respected by
18220 @code{gnatchop ^-r^/REFERENCE^}
18221 so that the final chopped files will correctly refer to the original
18222 input source file for @code{gnatprep}.
18224 @item ^-s^/SYMBOLS^
18225 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
18226 Causes a sorted list of symbol names and values to be
18227 listed on the standard output file.
18229 @item ^-u^/UNDEFINED^
18230 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
18231 Causes undefined symbols to be treated as having the value FALSE in the context
18232 of a preprocessor test. In the absence of this option, an undefined symbol in
18233 a @code{#if} or @code{#elsif} test will be treated as an error.
18239 Note: if neither @option{-b} nor @option{-c} is present,
18240 then preprocessor lines and
18241 deleted lines are completely removed from the output, unless -r is
18242 specified, in which case -b is assumed.
18245 @node Form of Definitions File
18246 @section Form of Definitions File
18249 The definitions file contains lines of the form
18256 where symbol is a preprocessing symbol, and value is one of the following:
18260 Empty, corresponding to a null substitution
18262 A string literal using normal Ada syntax
18264 Any sequence of characters from the set
18265 (letters, digits, period, underline).
18269 Comment lines may also appear in the definitions file, starting with
18270 the usual @code{--},
18271 and comments may be added to the definitions lines.
18273 @node Form of Input Text for gnatprep
18274 @section Form of Input Text for @code{gnatprep}
18277 The input text may contain preprocessor conditional inclusion lines,
18278 as well as general symbol substitution sequences.
18280 The preprocessor conditional inclusion commands have the form
18285 #if @i{expression} @r{[}then@r{]}
18287 #elsif @i{expression} @r{[}then@r{]}
18289 #elsif @i{expression} @r{[}then@r{]}
18300 In this example, @i{expression} is defined by the following grammar:
18302 @i{expression} ::= <symbol>
18303 @i{expression} ::= <symbol> = "<value>"
18304 @i{expression} ::= <symbol> = <symbol>
18305 @i{expression} ::= <symbol> 'Defined
18306 @i{expression} ::= not @i{expression}
18307 @i{expression} ::= @i{expression} and @i{expression}
18308 @i{expression} ::= @i{expression} or @i{expression}
18309 @i{expression} ::= @i{expression} and then @i{expression}
18310 @i{expression} ::= @i{expression} or else @i{expression}
18311 @i{expression} ::= ( @i{expression} )
18314 The following restriction exists: it is not allowed to have "and" or "or"
18315 following "not" in the same expression without parentheses. For example, this
18322 This should be one of the following:
18330 For the first test (@i{expression} ::= <symbol>) the symbol must have
18331 either the value true or false, that is to say the right-hand of the
18332 symbol definition must be one of the (case-insensitive) literals
18333 @code{True} or @code{False}. If the value is true, then the
18334 corresponding lines are included, and if the value is false, they are
18337 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
18338 the symbol has been defined in the definition file or by a @option{-D}
18339 switch on the command line. Otherwise, the test is false.
18341 The equality tests are case insensitive, as are all the preprocessor lines.
18343 If the symbol referenced is not defined in the symbol definitions file,
18344 then the effect depends on whether or not switch @option{-u}
18345 is specified. If so, then the symbol is treated as if it had the value
18346 false and the test fails. If this switch is not specified, then
18347 it is an error to reference an undefined symbol. It is also an error to
18348 reference a symbol that is defined with a value other than @code{True}
18351 The use of the @code{not} operator inverts the sense of this logical test.
18352 The @code{not} operator cannot be combined with the @code{or} or @code{and}
18353 operators, without parentheses. For example, "if not X or Y then" is not
18354 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
18356 The @code{then} keyword is optional as shown
18358 The @code{#} must be the first non-blank character on a line, but
18359 otherwise the format is free form. Spaces or tabs may appear between
18360 the @code{#} and the keyword. The keywords and the symbols are case
18361 insensitive as in normal Ada code. Comments may be used on a
18362 preprocessor line, but other than that, no other tokens may appear on a
18363 preprocessor line. Any number of @code{elsif} clauses can be present,
18364 including none at all. The @code{else} is optional, as in Ada.
18366 The @code{#} marking the start of a preprocessor line must be the first
18367 non-blank character on the line, i.e., it must be preceded only by
18368 spaces or horizontal tabs.
18370 Symbol substitution outside of preprocessor lines is obtained by using
18378 anywhere within a source line, except in a comment or within a
18379 string literal. The identifier
18380 following the @code{$} must match one of the symbols defined in the symbol
18381 definition file, and the result is to substitute the value of the
18382 symbol in place of @code{$symbol} in the output file.
18384 Note that although the substitution of strings within a string literal
18385 is not possible, it is possible to have a symbol whose defined value is
18386 a string literal. So instead of setting XYZ to @code{hello} and writing:
18389 Header : String := "$XYZ";
18393 you should set XYZ to @code{"hello"} and write:
18396 Header : String := $XYZ;
18400 and then the substitution will occur as desired.
18403 @node The GNAT Run-Time Library Builder gnatlbr
18404 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18406 @cindex Library builder
18409 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18410 supplied configuration pragmas.
18413 * Running gnatlbr::
18414 * Switches for gnatlbr::
18415 * Examples of gnatlbr Usage::
18418 @node Running gnatlbr
18419 @section Running @code{gnatlbr}
18422 The @code{gnatlbr} command has the form
18425 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18428 @node Switches for gnatlbr
18429 @section Switches for @code{gnatlbr}
18432 @code{gnatlbr} recognizes the following switches:
18436 @item /CREATE=directory
18437 @cindex @code{/CREATE} (@code{gnatlbr})
18438 Create the new run-time library in the specified directory.
18440 @item /SET=directory
18441 @cindex @code{/SET} (@code{gnatlbr})
18442 Make the library in the specified directory the current run-time library.
18444 @item /DELETE=directory
18445 @cindex @code{/DELETE} (@code{gnatlbr})
18446 Delete the run-time library in the specified directory.
18449 @cindex @code{/CONFIG} (@code{gnatlbr})
18450 With /CREATE: Use the configuration pragmas in the specified file when
18451 building the library.
18453 With /SET: Use the configuration pragmas in the specified file when
18458 @node Examples of gnatlbr Usage
18459 @section Example of @code{gnatlbr} Usage
18462 Contents of VAXFLOAT.ADC:
18463 pragma Float_Representation (VAX_Float);
18465 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18467 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18472 @node The GNAT Library Browser gnatls
18473 @chapter The GNAT Library Browser @code{gnatls}
18475 @cindex Library browser
18478 @code{gnatls} is a tool that outputs information about compiled
18479 units. It gives the relationship between objects, unit names and source
18480 files. It can also be used to check the source dependencies of a unit
18481 as well as various characteristics.
18483 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18484 driver (see @ref{The GNAT Driver and Project Files}).
18488 * Switches for gnatls::
18489 * Examples of gnatls Usage::
18492 @node Running gnatls
18493 @section Running @code{gnatls}
18496 The @code{gnatls} command has the form
18499 $ gnatls switches @var{object_or_ali_file}
18503 The main argument is the list of object or @file{ali} files
18504 (@pxref{The Ada Library Information Files})
18505 for which information is requested.
18507 In normal mode, without additional option, @code{gnatls} produces a
18508 four-column listing. Each line represents information for a specific
18509 object. The first column gives the full path of the object, the second
18510 column gives the name of the principal unit in this object, the third
18511 column gives the status of the source and the fourth column gives the
18512 full path of the source representing this unit.
18513 Here is a simple example of use:
18517 ^./^[]^demo1.o demo1 DIF demo1.adb
18518 ^./^[]^demo2.o demo2 OK demo2.adb
18519 ^./^[]^hello.o h1 OK hello.adb
18520 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18521 ^./^[]^instr.o instr OK instr.adb
18522 ^./^[]^tef.o tef DIF tef.adb
18523 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18524 ^./^[]^tgef.o tgef DIF tgef.adb
18528 The first line can be interpreted as follows: the main unit which is
18530 object file @file{demo1.o} is demo1, whose main source is in
18531 @file{demo1.adb}. Furthermore, the version of the source used for the
18532 compilation of demo1 has been modified (DIF). Each source file has a status
18533 qualifier which can be:
18536 @item OK (unchanged)
18537 The version of the source file used for the compilation of the
18538 specified unit corresponds exactly to the actual source file.
18540 @item MOK (slightly modified)
18541 The version of the source file used for the compilation of the
18542 specified unit differs from the actual source file but not enough to
18543 require recompilation. If you use gnatmake with the qualifier
18544 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18545 MOK will not be recompiled.
18547 @item DIF (modified)
18548 No version of the source found on the path corresponds to the source
18549 used to build this object.
18551 @item ??? (file not found)
18552 No source file was found for this unit.
18554 @item HID (hidden, unchanged version not first on PATH)
18555 The version of the source that corresponds exactly to the source used
18556 for compilation has been found on the path but it is hidden by another
18557 version of the same source that has been modified.
18561 @node Switches for gnatls
18562 @section Switches for @code{gnatls}
18565 @code{gnatls} recognizes the following switches:
18569 @cindex @option{--version} @command{gnatls}
18570 Display Copyright and version, then exit disregarding all other options.
18573 @cindex @option{--help} @command{gnatls}
18574 If @option{--version} was not used, display usage, then exit disregarding
18577 @item ^-a^/ALL_UNITS^
18578 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18579 Consider all units, including those of the predefined Ada library.
18580 Especially useful with @option{^-d^/DEPENDENCIES^}.
18582 @item ^-d^/DEPENDENCIES^
18583 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18584 List sources from which specified units depend on.
18586 @item ^-h^/OUTPUT=OPTIONS^
18587 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18588 Output the list of options.
18590 @item ^-o^/OUTPUT=OBJECTS^
18591 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18592 Only output information about object files.
18594 @item ^-s^/OUTPUT=SOURCES^
18595 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18596 Only output information about source files.
18598 @item ^-u^/OUTPUT=UNITS^
18599 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18600 Only output information about compilation units.
18602 @item ^-files^/FILES^=@var{file}
18603 @cindex @option{^-files^/FILES^} (@code{gnatls})
18604 Take as arguments the files listed in text file @var{file}.
18605 Text file @var{file} may contain empty lines that are ignored.
18606 Each nonempty line should contain the name of an existing file.
18607 Several such switches may be specified simultaneously.
18609 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18610 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18611 @itemx ^-I^/SEARCH=^@var{dir}
18612 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18614 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18615 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18616 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18617 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18618 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18619 flags (@pxref{Switches for gnatmake}).
18621 @item --RTS=@var{rts-path}
18622 @cindex @option{--RTS} (@code{gnatls})
18623 Specifies the default location of the runtime library. Same meaning as the
18624 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18626 @item ^-v^/OUTPUT=VERBOSE^
18627 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18628 Verbose mode. Output the complete source, object and project paths. Do not use
18629 the default column layout but instead use long format giving as much as
18630 information possible on each requested units, including special
18631 characteristics such as:
18634 @item Preelaborable
18635 The unit is preelaborable in the Ada sense.
18638 No elaboration code has been produced by the compiler for this unit.
18641 The unit is pure in the Ada sense.
18643 @item Elaborate_Body
18644 The unit contains a pragma Elaborate_Body.
18647 The unit contains a pragma Remote_Types.
18649 @item Shared_Passive
18650 The unit contains a pragma Shared_Passive.
18653 This unit is part of the predefined environment and cannot be modified
18656 @item Remote_Call_Interface
18657 The unit contains a pragma Remote_Call_Interface.
18663 @node Examples of gnatls Usage
18664 @section Example of @code{gnatls} Usage
18668 Example of using the verbose switch. Note how the source and
18669 object paths are affected by the -I switch.
18672 $ gnatls -v -I.. demo1.o
18674 GNATLS 5.03w (20041123-34)
18675 Copyright 1997-2004 Free Software Foundation, Inc.
18677 Source Search Path:
18678 <Current_Directory>
18680 /home/comar/local/adainclude/
18682 Object Search Path:
18683 <Current_Directory>
18685 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18687 Project Search Path:
18688 <Current_Directory>
18689 /home/comar/local/lib/gnat/
18694 Kind => subprogram body
18695 Flags => No_Elab_Code
18696 Source => demo1.adb modified
18700 The following is an example of use of the dependency list.
18701 Note the use of the -s switch
18702 which gives a straight list of source files. This can be useful for
18703 building specialized scripts.
18706 $ gnatls -d demo2.o
18707 ./demo2.o demo2 OK demo2.adb
18713 $ gnatls -d -s -a demo1.o
18715 /home/comar/local/adainclude/ada.ads
18716 /home/comar/local/adainclude/a-finali.ads
18717 /home/comar/local/adainclude/a-filico.ads
18718 /home/comar/local/adainclude/a-stream.ads
18719 /home/comar/local/adainclude/a-tags.ads
18722 /home/comar/local/adainclude/gnat.ads
18723 /home/comar/local/adainclude/g-io.ads
18725 /home/comar/local/adainclude/system.ads
18726 /home/comar/local/adainclude/s-exctab.ads
18727 /home/comar/local/adainclude/s-finimp.ads
18728 /home/comar/local/adainclude/s-finroo.ads
18729 /home/comar/local/adainclude/s-secsta.ads
18730 /home/comar/local/adainclude/s-stalib.ads
18731 /home/comar/local/adainclude/s-stoele.ads
18732 /home/comar/local/adainclude/s-stratt.ads
18733 /home/comar/local/adainclude/s-tasoli.ads
18734 /home/comar/local/adainclude/s-unstyp.ads
18735 /home/comar/local/adainclude/unchconv.ads
18741 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18743 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18744 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18745 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18746 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18747 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18751 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18752 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18754 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18755 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18756 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18757 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
18758 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
18759 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
18760 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
18761 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
18762 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
18763 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
18764 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
18768 @node Cleaning Up Using gnatclean
18769 @chapter Cleaning Up Using @code{gnatclean}
18771 @cindex Cleaning tool
18774 @code{gnatclean} is a tool that allows the deletion of files produced by the
18775 compiler, binder and linker, including ALI files, object files, tree files,
18776 expanded source files, library files, interface copy source files, binder
18777 generated files and executable files.
18780 * Running gnatclean::
18781 * Switches for gnatclean::
18782 @c * Examples of gnatclean Usage::
18785 @node Running gnatclean
18786 @section Running @code{gnatclean}
18789 The @code{gnatclean} command has the form:
18792 $ gnatclean switches @var{names}
18796 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18797 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18798 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18801 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18802 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18803 the linker. In informative-only mode, specified by switch
18804 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18805 normal mode is listed, but no file is actually deleted.
18807 @node Switches for gnatclean
18808 @section Switches for @code{gnatclean}
18811 @code{gnatclean} recognizes the following switches:
18815 @cindex @option{--version} @command{gnatclean}
18816 Display Copyright and version, then exit disregarding all other options.
18819 @cindex @option{--help} @command{gnatclean}
18820 If @option{--version} was not used, display usage, then exit disregarding
18823 @item ^-c^/COMPILER_FILES_ONLY^
18824 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18825 Only attempt to delete the files produced by the compiler, not those produced
18826 by the binder or the linker. The files that are not to be deleted are library
18827 files, interface copy files, binder generated files and executable files.
18829 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18830 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18831 Indicate that ALI and object files should normally be found in directory
18834 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18835 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18836 When using project files, if some errors or warnings are detected during
18837 parsing and verbose mode is not in effect (no use of switch
18838 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18839 file, rather than its simple file name.
18842 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18843 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18845 @item ^-n^/NODELETE^
18846 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18847 Informative-only mode. Do not delete any files. Output the list of the files
18848 that would have been deleted if this switch was not specified.
18850 @item ^-P^/PROJECT_FILE=^@var{project}
18851 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18852 Use project file @var{project}. Only one such switch can be used.
18853 When cleaning a project file, the files produced by the compilation of the
18854 immediate sources or inherited sources of the project files are to be
18855 deleted. This is not depending on the presence or not of executable names
18856 on the command line.
18859 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18860 Quiet output. If there are no errors, do not output anything, except in
18861 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18862 (switch ^-n^/NODELETE^).
18864 @item ^-r^/RECURSIVE^
18865 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18866 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18867 clean all imported and extended project files, recursively. If this switch
18868 is not specified, only the files related to the main project file are to be
18869 deleted. This switch has no effect if no project file is specified.
18871 @item ^-v^/VERBOSE^
18872 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18875 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18876 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18877 Indicates the verbosity of the parsing of GNAT project files.
18878 @xref{Switches Related to Project Files}.
18880 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18881 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18882 Indicates that external variable @var{name} has the value @var{value}.
18883 The Project Manager will use this value for occurrences of
18884 @code{external(name)} when parsing the project file.
18885 @xref{Switches Related to Project Files}.
18887 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18888 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18889 When searching for ALI and object files, look in directory
18892 @item ^-I^/SEARCH=^@var{dir}
18893 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18894 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18896 @item ^-I-^/NOCURRENT_DIRECTORY^
18897 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18898 @cindex Source files, suppressing search
18899 Do not look for ALI or object files in the directory
18900 where @code{gnatclean} was invoked.
18904 @c @node Examples of gnatclean Usage
18905 @c @section Examples of @code{gnatclean} Usage
18908 @node GNAT and Libraries
18909 @chapter GNAT and Libraries
18910 @cindex Library, building, installing, using
18913 This chapter describes how to build and use libraries with GNAT, and also shows
18914 how to recompile the GNAT run-time library. You should be familiar with the
18915 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18919 * Introduction to Libraries in GNAT::
18920 * General Ada Libraries::
18921 * Stand-alone Ada Libraries::
18922 * Rebuilding the GNAT Run-Time Library::
18925 @node Introduction to Libraries in GNAT
18926 @section Introduction to Libraries in GNAT
18929 A library is, conceptually, a collection of objects which does not have its
18930 own main thread of execution, but rather provides certain services to the
18931 applications that use it. A library can be either statically linked with the
18932 application, in which case its code is directly included in the application,
18933 or, on platforms that support it, be dynamically linked, in which case
18934 its code is shared by all applications making use of this library.
18936 GNAT supports both types of libraries.
18937 In the static case, the compiled code can be provided in different ways. The
18938 simplest approach is to provide directly the set of objects resulting from
18939 compilation of the library source files. Alternatively, you can group the
18940 objects into an archive using whatever commands are provided by the operating
18941 system. For the latter case, the objects are grouped into a shared library.
18943 In the GNAT environment, a library has three types of components:
18949 @xref{The Ada Library Information Files}.
18951 Object files, an archive or a shared library.
18955 A GNAT library may expose all its source files, which is useful for
18956 documentation purposes. Alternatively, it may expose only the units needed by
18957 an external user to make use of the library. That is to say, the specs
18958 reflecting the library services along with all the units needed to compile
18959 those specs, which can include generic bodies or any body implementing an
18960 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18961 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18963 All compilation units comprising an application, including those in a library,
18964 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18965 computes the elaboration order from the @file{ALI} files and this is why they
18966 constitute a mandatory part of GNAT libraries.
18967 @emph{Stand-alone libraries} are the exception to this rule because a specific
18968 library elaboration routine is produced independently of the application(s)
18971 @node General Ada Libraries
18972 @section General Ada Libraries
18975 * Building a library::
18976 * Installing a library::
18977 * Using a library::
18980 @node Building a library
18981 @subsection Building a library
18984 The easiest way to build a library is to use the Project Manager,
18985 which supports a special type of project called a @emph{Library Project}
18986 (@pxref{Library Projects}).
18988 A project is considered a library project, when two project-level attributes
18989 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
18990 control different aspects of library configuration, additional optional
18991 project-level attributes can be specified:
18994 This attribute controls whether the library is to be static or dynamic
18996 @item Library_Version
18997 This attribute specifies the library version; this value is used
18998 during dynamic linking of shared libraries to determine if the currently
18999 installed versions of the binaries are compatible.
19001 @item Library_Options
19003 These attributes specify additional low-level options to be used during
19004 library generation, and redefine the actual application used to generate
19009 The GNAT Project Manager takes full care of the library maintenance task,
19010 including recompilation of the source files for which objects do not exist
19011 or are not up to date, assembly of the library archive, and installation of
19012 the library (i.e., copying associated source, object and @file{ALI} files
19013 to the specified location).
19015 Here is a simple library project file:
19016 @smallexample @c ada
19018 for Source_Dirs use ("src1", "src2");
19019 for Object_Dir use "obj";
19020 for Library_Name use "mylib";
19021 for Library_Dir use "lib";
19022 for Library_Kind use "dynamic";
19027 and the compilation command to build and install the library:
19029 @smallexample @c ada
19030 $ gnatmake -Pmy_lib
19034 It is not entirely trivial to perform manually all the steps required to
19035 produce a library. We recommend that you use the GNAT Project Manager
19036 for this task. In special cases where this is not desired, the necessary
19037 steps are discussed below.
19039 There are various possibilities for compiling the units that make up the
19040 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
19041 with a conventional script. For simple libraries, it is also possible to create
19042 a dummy main program which depends upon all the packages that comprise the
19043 interface of the library. This dummy main program can then be given to
19044 @command{gnatmake}, which will ensure that all necessary objects are built.
19046 After this task is accomplished, you should follow the standard procedure
19047 of the underlying operating system to produce the static or shared library.
19049 Here is an example of such a dummy program:
19050 @smallexample @c ada
19052 with My_Lib.Service1;
19053 with My_Lib.Service2;
19054 with My_Lib.Service3;
19055 procedure My_Lib_Dummy is
19063 Here are the generic commands that will build an archive or a shared library.
19066 # compiling the library
19067 $ gnatmake -c my_lib_dummy.adb
19069 # we don't need the dummy object itself
19070 $ rm my_lib_dummy.o my_lib_dummy.ali
19072 # create an archive with the remaining objects
19073 $ ar rc libmy_lib.a *.o
19074 # some systems may require "ranlib" to be run as well
19076 # or create a shared library
19077 $ gcc -shared -o libmy_lib.so *.o
19078 # some systems may require the code to have been compiled with -fPIC
19080 # remove the object files that are now in the library
19083 # Make the ALI files read-only so that gnatmake will not try to
19084 # regenerate the objects that are in the library
19089 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
19090 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
19091 be accessed by the directive @option{-l@var{xxx}} at link time.
19093 @node Installing a library
19094 @subsection Installing a library
19095 @cindex @code{ADA_PROJECT_PATH}
19096 @cindex @code{GPR_PROJECT_PATH}
19099 If you use project files, library installation is part of the library build
19100 process. Thus no further action is needed in order to make use of the
19101 libraries that are built as part of the general application build. A usable
19102 version of the library is installed in the directory specified by the
19103 @code{Library_Dir} attribute of the library project file.
19105 You may want to install a library in a context different from where the library
19106 is built. This situation arises with third party suppliers, who may want
19107 to distribute a library in binary form where the user is not expected to be
19108 able to recompile the library. The simplest option in this case is to provide
19109 a project file slightly different from the one used to build the library, by
19110 using the @code{externally_built} attribute. For instance, the project
19111 file used to build the library in the previous section can be changed into the
19112 following one when the library is installed:
19114 @smallexample @c projectfile
19116 for Source_Dirs use ("src1", "src2");
19117 for Library_Name use "mylib";
19118 for Library_Dir use "lib";
19119 for Library_Kind use "dynamic";
19120 for Externally_Built use "true";
19125 This project file assumes that the directories @file{src1},
19126 @file{src2}, and @file{lib} exist in
19127 the directory containing the project file. The @code{externally_built}
19128 attribute makes it clear to the GNAT builder that it should not attempt to
19129 recompile any of the units from this library. It allows the library provider to
19130 restrict the source set to the minimum necessary for clients to make use of the
19131 library as described in the first section of this chapter. It is the
19132 responsibility of the library provider to install the necessary sources, ALI
19133 files and libraries in the directories mentioned in the project file. For
19134 convenience, the user's library project file should be installed in a location
19135 that will be searched automatically by the GNAT
19136 builder. These are the directories referenced in the @env{GPR_PROJECT_PATH}
19137 environment variable (@pxref{Importing Projects}), and also the default GNAT
19138 library location that can be queried with @command{gnatls -v} and is usually of
19139 the form $gnat_install_root/lib/gnat.
19141 When project files are not an option, it is also possible, but not recommended,
19142 to install the library so that the sources needed to use the library are on the
19143 Ada source path and the ALI files & libraries be on the Ada Object path (see
19144 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
19145 administrator can place general-purpose libraries in the default compiler
19146 paths, by specifying the libraries' location in the configuration files
19147 @file{ada_source_path} and @file{ada_object_path}. These configuration files
19148 must be located in the GNAT installation tree at the same place as the gcc spec
19149 file. The location of the gcc spec file can be determined as follows:
19155 The configuration files mentioned above have a simple format: each line
19156 must contain one unique directory name.
19157 Those names are added to the corresponding path
19158 in their order of appearance in the file. The names can be either absolute
19159 or relative; in the latter case, they are relative to where theses files
19162 The files @file{ada_source_path} and @file{ada_object_path} might not be
19164 GNAT installation, in which case, GNAT will look for its run-time library in
19165 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
19166 objects and @file{ALI} files). When the files exist, the compiler does not
19167 look in @file{adainclude} and @file{adalib}, and thus the
19168 @file{ada_source_path} file
19169 must contain the location for the GNAT run-time sources (which can simply
19170 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
19171 contain the location for the GNAT run-time objects (which can simply
19174 You can also specify a new default path to the run-time library at compilation
19175 time with the switch @option{--RTS=rts-path}. You can thus choose / change
19176 the run-time library you want your program to be compiled with. This switch is
19177 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
19178 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
19180 It is possible to install a library before or after the standard GNAT
19181 library, by reordering the lines in the configuration files. In general, a
19182 library must be installed before the GNAT library if it redefines
19185 @node Using a library
19186 @subsection Using a library
19188 @noindent Once again, the project facility greatly simplifies the use of
19189 libraries. In this context, using a library is just a matter of adding a
19190 @code{with} clause in the user project. For instance, to make use of the
19191 library @code{My_Lib} shown in examples in earlier sections, you can
19194 @smallexample @c projectfile
19201 Even if you have a third-party, non-Ada library, you can still use GNAT's
19202 Project Manager facility to provide a wrapper for it. For example, the
19203 following project, when @code{with}ed by your main project, will link with the
19204 third-party library @file{liba.a}:
19206 @smallexample @c projectfile
19209 for Externally_Built use "true";
19210 for Source_Files use ();
19211 for Library_Dir use "lib";
19212 for Library_Name use "a";
19213 for Library_Kind use "static";
19217 This is an alternative to the use of @code{pragma Linker_Options}. It is
19218 especially interesting in the context of systems with several interdependent
19219 static libraries where finding a proper linker order is not easy and best be
19220 left to the tools having visibility over project dependence information.
19223 In order to use an Ada library manually, you need to make sure that this
19224 library is on both your source and object path
19225 (see @ref{Search Paths and the Run-Time Library (RTL)}
19226 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
19227 in an archive or a shared library, you need to specify the desired
19228 library at link time.
19230 For example, you can use the library @file{mylib} installed in
19231 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
19234 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
19239 This can be expressed more simply:
19244 when the following conditions are met:
19247 @file{/dir/my_lib_src} has been added by the user to the environment
19248 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
19249 @file{ada_source_path}
19251 @file{/dir/my_lib_obj} has been added by the user to the environment
19252 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
19253 @file{ada_object_path}
19255 a pragma @code{Linker_Options} has been added to one of the sources.
19258 @smallexample @c ada
19259 pragma Linker_Options ("-lmy_lib");
19263 @node Stand-alone Ada Libraries
19264 @section Stand-alone Ada Libraries
19265 @cindex Stand-alone library, building, using
19268 * Introduction to Stand-alone Libraries::
19269 * Building a Stand-alone Library::
19270 * Creating a Stand-alone Library to be used in a non-Ada context::
19271 * Restrictions in Stand-alone Libraries::
19274 @node Introduction to Stand-alone Libraries
19275 @subsection Introduction to Stand-alone Libraries
19278 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
19280 elaborate the Ada units that are included in the library. In contrast with
19281 an ordinary library, which consists of all sources, objects and @file{ALI}
19283 library, a SAL may specify a restricted subset of compilation units
19284 to serve as a library interface. In this case, the fully
19285 self-sufficient set of files will normally consist of an objects
19286 archive, the sources of interface units' specs, and the @file{ALI}
19287 files of interface units.
19288 If an interface spec contains a generic unit or an inlined subprogram,
19290 source must also be provided; if the units that must be provided in the source
19291 form depend on other units, the source and @file{ALI} files of those must
19294 The main purpose of a SAL is to minimize the recompilation overhead of client
19295 applications when a new version of the library is installed. Specifically,
19296 if the interface sources have not changed, client applications do not need to
19297 be recompiled. If, furthermore, a SAL is provided in the shared form and its
19298 version, controlled by @code{Library_Version} attribute, is not changed,
19299 then the clients do not need to be relinked.
19301 SALs also allow the library providers to minimize the amount of library source
19302 text exposed to the clients. Such ``information hiding'' might be useful or
19303 necessary for various reasons.
19305 Stand-alone libraries are also well suited to be used in an executable whose
19306 main routine is not written in Ada.
19308 @node Building a Stand-alone Library
19309 @subsection Building a Stand-alone Library
19312 GNAT's Project facility provides a simple way of building and installing
19313 stand-alone libraries; see @ref{Stand-alone Library Projects}.
19314 To be a Stand-alone Library Project, in addition to the two attributes
19315 that make a project a Library Project (@code{Library_Name} and
19316 @code{Library_Dir}; see @ref{Library Projects}), the attribute
19317 @code{Library_Interface} must be defined. For example:
19319 @smallexample @c projectfile
19321 for Library_Dir use "lib_dir";
19322 for Library_Name use "dummy";
19323 for Library_Interface use ("int1", "int1.child");
19328 Attribute @code{Library_Interface} has a non-empty string list value,
19329 each string in the list designating a unit contained in an immediate source
19330 of the project file.
19332 When a Stand-alone Library is built, first the binder is invoked to build
19333 a package whose name depends on the library name
19334 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
19335 This binder-generated package includes initialization and
19336 finalization procedures whose
19337 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
19339 above). The object corresponding to this package is included in the library.
19341 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
19342 calling of these procedures if a static SAL is built, or if a shared SAL
19344 with the project-level attribute @code{Library_Auto_Init} set to
19347 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
19348 (those that are listed in attribute @code{Library_Interface}) are copied to
19349 the Library Directory. As a consequence, only the Interface Units may be
19350 imported from Ada units outside of the library. If other units are imported,
19351 the binding phase will fail.
19353 The attribute @code{Library_Src_Dir} may be specified for a
19354 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
19355 single string value. Its value must be the path (absolute or relative to the
19356 project directory) of an existing directory. This directory cannot be the
19357 object directory or one of the source directories, but it can be the same as
19358 the library directory. The sources of the Interface
19359 Units of the library that are needed by an Ada client of the library will be
19360 copied to the designated directory, called the Interface Copy directory.
19361 These sources include the specs of the Interface Units, but they may also
19362 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
19363 are used, or when there is a generic unit in the spec. Before the sources
19364 are copied to the Interface Copy directory, an attempt is made to delete all
19365 files in the Interface Copy directory.
19367 Building stand-alone libraries by hand is somewhat tedious, but for those
19368 occasions when it is necessary here are the steps that you need to perform:
19371 Compile all library sources.
19374 Invoke the binder with the switch @option{-n} (No Ada main program),
19375 with all the @file{ALI} files of the interfaces, and
19376 with the switch @option{-L} to give specific names to the @code{init}
19377 and @code{final} procedures. For example:
19379 gnatbind -n int1.ali int2.ali -Lsal1
19383 Compile the binder generated file:
19389 Link the dynamic library with all the necessary object files,
19390 indicating to the linker the names of the @code{init} (and possibly
19391 @code{final}) procedures for automatic initialization (and finalization).
19392 The built library should be placed in a directory different from
19393 the object directory.
19396 Copy the @code{ALI} files of the interface to the library directory,
19397 add in this copy an indication that it is an interface to a SAL
19398 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19399 with letter ``P'') and make the modified copy of the @file{ALI} file
19404 Using SALs is not different from using other libraries
19405 (see @ref{Using a library}).
19407 @node Creating a Stand-alone Library to be used in a non-Ada context
19408 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19411 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19414 The only extra step required is to ensure that library interface subprograms
19415 are compatible with the main program, by means of @code{pragma Export}
19416 or @code{pragma Convention}.
19418 Here is an example of simple library interface for use with C main program:
19420 @smallexample @c ada
19421 package Interface is
19423 procedure Do_Something;
19424 pragma Export (C, Do_Something, "do_something");
19426 procedure Do_Something_Else;
19427 pragma Export (C, Do_Something_Else, "do_something_else");
19433 On the foreign language side, you must provide a ``foreign'' view of the
19434 library interface; remember that it should contain elaboration routines in
19435 addition to interface subprograms.
19437 The example below shows the content of @code{mylib_interface.h} (note
19438 that there is no rule for the naming of this file, any name can be used)
19440 /* the library elaboration procedure */
19441 extern void mylibinit (void);
19443 /* the library finalization procedure */
19444 extern void mylibfinal (void);
19446 /* the interface exported by the library */
19447 extern void do_something (void);
19448 extern void do_something_else (void);
19452 Libraries built as explained above can be used from any program, provided
19453 that the elaboration procedures (named @code{mylibinit} in the previous
19454 example) are called before the library services are used. Any number of
19455 libraries can be used simultaneously, as long as the elaboration
19456 procedure of each library is called.
19458 Below is an example of a C program that uses the @code{mylib} library.
19461 #include "mylib_interface.h"
19466 /* First, elaborate the library before using it */
19469 /* Main program, using the library exported entities */
19471 do_something_else ();
19473 /* Library finalization at the end of the program */
19480 Note that invoking any library finalization procedure generated by
19481 @code{gnatbind} shuts down the Ada run-time environment.
19483 finalization of all Ada libraries must be performed at the end of the program.
19484 No call to these libraries or to the Ada run-time library should be made
19485 after the finalization phase.
19487 @node Restrictions in Stand-alone Libraries
19488 @subsection Restrictions in Stand-alone Libraries
19491 The pragmas listed below should be used with caution inside libraries,
19492 as they can create incompatibilities with other Ada libraries:
19494 @item pragma @code{Locking_Policy}
19495 @item pragma @code{Queuing_Policy}
19496 @item pragma @code{Task_Dispatching_Policy}
19497 @item pragma @code{Unreserve_All_Interrupts}
19501 When using a library that contains such pragmas, the user must make sure
19502 that all libraries use the same pragmas with the same values. Otherwise,
19503 @code{Program_Error} will
19504 be raised during the elaboration of the conflicting
19505 libraries. The usage of these pragmas and its consequences for the user
19506 should therefore be well documented.
19508 Similarly, the traceback in the exception occurrence mechanism should be
19509 enabled or disabled in a consistent manner across all libraries.
19510 Otherwise, Program_Error will be raised during the elaboration of the
19511 conflicting libraries.
19513 If the @code{Version} or @code{Body_Version}
19514 attributes are used inside a library, then you need to
19515 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19516 libraries, so that version identifiers can be properly computed.
19517 In practice these attributes are rarely used, so this is unlikely
19518 to be a consideration.
19520 @node Rebuilding the GNAT Run-Time Library
19521 @section Rebuilding the GNAT Run-Time Library
19522 @cindex GNAT Run-Time Library, rebuilding
19523 @cindex Building the GNAT Run-Time Library
19524 @cindex Rebuilding the GNAT Run-Time Library
19525 @cindex Run-Time Library, rebuilding
19528 It may be useful to recompile the GNAT library in various contexts, the
19529 most important one being the use of partition-wide configuration pragmas
19530 such as @code{Normalize_Scalars}. A special Makefile called
19531 @code{Makefile.adalib} is provided to that effect and can be found in
19532 the directory containing the GNAT library. The location of this
19533 directory depends on the way the GNAT environment has been installed and can
19534 be determined by means of the command:
19541 The last entry in the object search path usually contains the
19542 gnat library. This Makefile contains its own documentation and in
19543 particular the set of instructions needed to rebuild a new library and
19546 @node Using the GNU make Utility
19547 @chapter Using the GNU @code{make} Utility
19551 This chapter offers some examples of makefiles that solve specific
19552 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19553 make, make, GNU @code{make}}), nor does it try to replace the
19554 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19556 All the examples in this section are specific to the GNU version of
19557 make. Although @command{make} is a standard utility, and the basic language
19558 is the same, these examples use some advanced features found only in
19562 * Using gnatmake in a Makefile::
19563 * Automatically Creating a List of Directories::
19564 * Generating the Command Line Switches::
19565 * Overcoming Command Line Length Limits::
19568 @node Using gnatmake in a Makefile
19569 @section Using gnatmake in a Makefile
19574 Complex project organizations can be handled in a very powerful way by
19575 using GNU make combined with gnatmake. For instance, here is a Makefile
19576 which allows you to build each subsystem of a big project into a separate
19577 shared library. Such a makefile allows you to significantly reduce the link
19578 time of very big applications while maintaining full coherence at
19579 each step of the build process.
19581 The list of dependencies are handled automatically by
19582 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19583 the appropriate directories.
19585 Note that you should also read the example on how to automatically
19586 create the list of directories
19587 (@pxref{Automatically Creating a List of Directories})
19588 which might help you in case your project has a lot of subdirectories.
19593 @font@heightrm=cmr8
19596 ## This Makefile is intended to be used with the following directory
19598 ## - The sources are split into a series of csc (computer software components)
19599 ## Each of these csc is put in its own directory.
19600 ## Their name are referenced by the directory names.
19601 ## They will be compiled into shared library (although this would also work
19602 ## with static libraries
19603 ## - The main program (and possibly other packages that do not belong to any
19604 ## csc is put in the top level directory (where the Makefile is).
19605 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19606 ## \_ second_csc (sources) __ lib (will contain the library)
19608 ## Although this Makefile is build for shared library, it is easy to modify
19609 ## to build partial link objects instead (modify the lines with -shared and
19612 ## With this makefile, you can change any file in the system or add any new
19613 ## file, and everything will be recompiled correctly (only the relevant shared
19614 ## objects will be recompiled, and the main program will be re-linked).
19616 # The list of computer software component for your project. This might be
19617 # generated automatically.
19620 # Name of the main program (no extension)
19623 # If we need to build objects with -fPIC, uncomment the following line
19626 # The following variable should give the directory containing libgnat.so
19627 # You can get this directory through 'gnatls -v'. This is usually the last
19628 # directory in the Object_Path.
19631 # The directories for the libraries
19632 # (This macro expands the list of CSC to the list of shared libraries, you
19633 # could simply use the expanded form:
19634 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19635 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19637 $@{MAIN@}: objects $@{LIB_DIR@}
19638 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19639 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19642 # recompile the sources
19643 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19645 # Note: In a future version of GNAT, the following commands will be simplified
19646 # by a new tool, gnatmlib
19648 mkdir -p $@{dir $@@ @}
19649 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19650 cd $@{dir $@@ @} && cp -f ../*.ali .
19652 # The dependencies for the modules
19653 # Note that we have to force the expansion of *.o, since in some cases
19654 # make won't be able to do it itself.
19655 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19656 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19657 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19659 # Make sure all of the shared libraries are in the path before starting the
19662 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19665 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19666 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19667 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19668 $@{RM@} *.o *.ali $@{MAIN@}
19671 @node Automatically Creating a List of Directories
19672 @section Automatically Creating a List of Directories
19675 In most makefiles, you will have to specify a list of directories, and
19676 store it in a variable. For small projects, it is often easier to
19677 specify each of them by hand, since you then have full control over what
19678 is the proper order for these directories, which ones should be
19681 However, in larger projects, which might involve hundreds of
19682 subdirectories, it might be more convenient to generate this list
19685 The example below presents two methods. The first one, although less
19686 general, gives you more control over the list. It involves wildcard
19687 characters, that are automatically expanded by @command{make}. Its
19688 shortcoming is that you need to explicitly specify some of the
19689 organization of your project, such as for instance the directory tree
19690 depth, whether some directories are found in a separate tree, @enddots{}
19692 The second method is the most general one. It requires an external
19693 program, called @command{find}, which is standard on all Unix systems. All
19694 the directories found under a given root directory will be added to the
19700 @font@heightrm=cmr8
19703 # The examples below are based on the following directory hierarchy:
19704 # All the directories can contain any number of files
19705 # ROOT_DIRECTORY -> a -> aa -> aaa
19708 # -> b -> ba -> baa
19711 # This Makefile creates a variable called DIRS, that can be reused any time
19712 # you need this list (see the other examples in this section)
19714 # The root of your project's directory hierarchy
19718 # First method: specify explicitly the list of directories
19719 # This allows you to specify any subset of all the directories you need.
19722 DIRS := a/aa/ a/ab/ b/ba/
19725 # Second method: use wildcards
19726 # Note that the argument(s) to wildcard below should end with a '/'.
19727 # Since wildcards also return file names, we have to filter them out
19728 # to avoid duplicate directory names.
19729 # We thus use make's @code{dir} and @code{sort} functions.
19730 # It sets DIRs to the following value (note that the directories aaa and baa
19731 # are not given, unless you change the arguments to wildcard).
19732 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19735 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19736 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19739 # Third method: use an external program
19740 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19741 # This is the most complete command: it sets DIRs to the following value:
19742 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19745 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19749 @node Generating the Command Line Switches
19750 @section Generating the Command Line Switches
19753 Once you have created the list of directories as explained in the
19754 previous section (@pxref{Automatically Creating a List of Directories}),
19755 you can easily generate the command line arguments to pass to gnatmake.
19757 For the sake of completeness, this example assumes that the source path
19758 is not the same as the object path, and that you have two separate lists
19762 # see "Automatically creating a list of directories" to create
19767 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19768 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19771 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19774 @node Overcoming Command Line Length Limits
19775 @section Overcoming Command Line Length Limits
19778 One problem that might be encountered on big projects is that many
19779 operating systems limit the length of the command line. It is thus hard to give
19780 gnatmake the list of source and object directories.
19782 This example shows how you can set up environment variables, which will
19783 make @command{gnatmake} behave exactly as if the directories had been
19784 specified on the command line, but have a much higher length limit (or
19785 even none on most systems).
19787 It assumes that you have created a list of directories in your Makefile,
19788 using one of the methods presented in
19789 @ref{Automatically Creating a List of Directories}.
19790 For the sake of completeness, we assume that the object
19791 path (where the ALI files are found) is different from the sources patch.
19793 Note a small trick in the Makefile below: for efficiency reasons, we
19794 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19795 expanded immediately by @code{make}. This way we overcome the standard
19796 make behavior which is to expand the variables only when they are
19799 On Windows, if you are using the standard Windows command shell, you must
19800 replace colons with semicolons in the assignments to these variables.
19805 @font@heightrm=cmr8
19808 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19809 # This is the same thing as putting the -I arguments on the command line.
19810 # (the equivalent of using -aI on the command line would be to define
19811 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19812 # You can of course have different values for these variables.
19814 # Note also that we need to keep the previous values of these variables, since
19815 # they might have been set before running 'make' to specify where the GNAT
19816 # library is installed.
19818 # see "Automatically creating a list of directories" to create these
19824 space:=$@{empty@} $@{empty@}
19825 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19826 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19827 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19828 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19829 export ADA_INCLUDE_PATH
19830 export ADA_OBJECT_PATH
19837 @node Memory Management Issues
19838 @chapter Memory Management Issues
19841 This chapter describes some useful memory pools provided in the GNAT library
19842 and in particular the GNAT Debug Pool facility, which can be used to detect
19843 incorrect uses of access values (including ``dangling references'').
19845 It also describes the @command{gnatmem} tool, which can be used to track down
19850 * Some Useful Memory Pools::
19851 * The GNAT Debug Pool Facility::
19853 * The gnatmem Tool::
19857 @node Some Useful Memory Pools
19858 @section Some Useful Memory Pools
19859 @findex Memory Pool
19860 @cindex storage, pool
19863 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19864 storage pool. Allocations use the standard system call @code{malloc} while
19865 deallocations use the standard system call @code{free}. No reclamation is
19866 performed when the pool goes out of scope. For performance reasons, the
19867 standard default Ada allocators/deallocators do not use any explicit storage
19868 pools but if they did, they could use this storage pool without any change in
19869 behavior. That is why this storage pool is used when the user
19870 manages to make the default implicit allocator explicit as in this example:
19871 @smallexample @c ada
19872 type T1 is access Something;
19873 -- no Storage pool is defined for T2
19874 type T2 is access Something_Else;
19875 for T2'Storage_Pool use T1'Storage_Pool;
19876 -- the above is equivalent to
19877 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19881 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19882 pool. The allocation strategy is similar to @code{Pool_Local}'s
19883 except that the all
19884 storage allocated with this pool is reclaimed when the pool object goes out of
19885 scope. This pool provides a explicit mechanism similar to the implicit one
19886 provided by several Ada 83 compilers for allocations performed through a local
19887 access type and whose purpose was to reclaim memory when exiting the
19888 scope of a given local access. As an example, the following program does not
19889 leak memory even though it does not perform explicit deallocation:
19891 @smallexample @c ada
19892 with System.Pool_Local;
19893 procedure Pooloc1 is
19894 procedure Internal is
19895 type A is access Integer;
19896 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19897 for A'Storage_Pool use X;
19900 for I in 1 .. 50 loop
19905 for I in 1 .. 100 loop
19912 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19913 @code{Storage_Size} is specified for an access type.
19914 The whole storage for the pool is
19915 allocated at once, usually on the stack at the point where the access type is
19916 elaborated. It is automatically reclaimed when exiting the scope where the
19917 access type is defined. This package is not intended to be used directly by the
19918 user and it is implicitly used for each such declaration:
19920 @smallexample @c ada
19921 type T1 is access Something;
19922 for T1'Storage_Size use 10_000;
19925 @node The GNAT Debug Pool Facility
19926 @section The GNAT Debug Pool Facility
19928 @cindex storage, pool, memory corruption
19931 The use of unchecked deallocation and unchecked conversion can easily
19932 lead to incorrect memory references. The problems generated by such
19933 references are usually difficult to tackle because the symptoms can be
19934 very remote from the origin of the problem. In such cases, it is
19935 very helpful to detect the problem as early as possible. This is the
19936 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19938 In order to use the GNAT specific debugging pool, the user must
19939 associate a debug pool object with each of the access types that may be
19940 related to suspected memory problems. See Ada Reference Manual 13.11.
19941 @smallexample @c ada
19942 type Ptr is access Some_Type;
19943 Pool : GNAT.Debug_Pools.Debug_Pool;
19944 for Ptr'Storage_Pool use Pool;
19948 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19949 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19950 allow the user to redefine allocation and deallocation strategies. They
19951 also provide a checkpoint for each dereference, through the use of
19952 the primitive operation @code{Dereference} which is implicitly called at
19953 each dereference of an access value.
19955 Once an access type has been associated with a debug pool, operations on
19956 values of the type may raise four distinct exceptions,
19957 which correspond to four potential kinds of memory corruption:
19960 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19962 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19964 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19966 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19970 For types associated with a Debug_Pool, dynamic allocation is performed using
19971 the standard GNAT allocation routine. References to all allocated chunks of
19972 memory are kept in an internal dictionary. Several deallocation strategies are
19973 provided, whereupon the user can choose to release the memory to the system,
19974 keep it allocated for further invalid access checks, or fill it with an easily
19975 recognizable pattern for debug sessions. The memory pattern is the old IBM
19976 hexadecimal convention: @code{16#DEADBEEF#}.
19978 See the documentation in the file g-debpoo.ads for more information on the
19979 various strategies.
19981 Upon each dereference, a check is made that the access value denotes a
19982 properly allocated memory location. Here is a complete example of use of
19983 @code{Debug_Pools}, that includes typical instances of memory corruption:
19984 @smallexample @c ada
19988 with Gnat.Io; use Gnat.Io;
19989 with Unchecked_Deallocation;
19990 with Unchecked_Conversion;
19991 with GNAT.Debug_Pools;
19992 with System.Storage_Elements;
19993 with Ada.Exceptions; use Ada.Exceptions;
19994 procedure Debug_Pool_Test is
19996 type T is access Integer;
19997 type U is access all T;
19999 P : GNAT.Debug_Pools.Debug_Pool;
20000 for T'Storage_Pool use P;
20002 procedure Free is new Unchecked_Deallocation (Integer, T);
20003 function UC is new Unchecked_Conversion (U, T);
20006 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
20016 Put_Line (Integer'Image(B.all));
20018 when E : others => Put_Line ("raised: " & Exception_Name (E));
20023 when E : others => Put_Line ("raised: " & Exception_Name (E));
20027 Put_Line (Integer'Image(B.all));
20029 when E : others => Put_Line ("raised: " & Exception_Name (E));
20034 when E : others => Put_Line ("raised: " & Exception_Name (E));
20037 end Debug_Pool_Test;
20041 The debug pool mechanism provides the following precise diagnostics on the
20042 execution of this erroneous program:
20045 Total allocated bytes : 0
20046 Total deallocated bytes : 0
20047 Current Water Mark: 0
20051 Total allocated bytes : 8
20052 Total deallocated bytes : 0
20053 Current Water Mark: 8
20056 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
20057 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
20058 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
20059 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
20061 Total allocated bytes : 8
20062 Total deallocated bytes : 4
20063 Current Water Mark: 4
20068 @node The gnatmem Tool
20069 @section The @command{gnatmem} Tool
20073 The @code{gnatmem} utility monitors dynamic allocation and
20074 deallocation activity in a program, and displays information about
20075 incorrect deallocations and possible sources of memory leaks.
20076 It is designed to work in association with a static runtime library
20077 only and in this context provides three types of information:
20080 General information concerning memory management, such as the total
20081 number of allocations and deallocations, the amount of allocated
20082 memory and the high water mark, i.e.@: the largest amount of allocated
20083 memory in the course of program execution.
20086 Backtraces for all incorrect deallocations, that is to say deallocations
20087 which do not correspond to a valid allocation.
20090 Information on each allocation that is potentially the origin of a memory
20095 * Running gnatmem::
20096 * Switches for gnatmem::
20097 * Example of gnatmem Usage::
20100 @node Running gnatmem
20101 @subsection Running @code{gnatmem}
20104 @code{gnatmem} makes use of the output created by the special version of
20105 allocation and deallocation routines that record call information. This
20106 allows to obtain accurate dynamic memory usage history at a minimal cost to
20107 the execution speed. Note however, that @code{gnatmem} is not supported on
20108 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
20109 Solaris and Windows NT/2000/XP (x86).
20112 The @code{gnatmem} command has the form
20115 $ gnatmem @ovar{switches} user_program
20119 The program must have been linked with the instrumented version of the
20120 allocation and deallocation routines. This is done by linking with the
20121 @file{libgmem.a} library. For correct symbolic backtrace information,
20122 the user program should be compiled with debugging options
20123 (see @ref{Switches for gcc}). For example to build @file{my_program}:
20126 $ gnatmake -g my_program -largs -lgmem
20130 As library @file{libgmem.a} contains an alternate body for package
20131 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
20132 when an executable is linked with library @file{libgmem.a}. It is then not
20133 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
20136 When @file{my_program} is executed, the file @file{gmem.out} is produced.
20137 This file contains information about all allocations and deallocations
20138 performed by the program. It is produced by the instrumented allocations and
20139 deallocations routines and will be used by @code{gnatmem}.
20141 In order to produce symbolic backtrace information for allocations and
20142 deallocations performed by the GNAT run-time library, you need to use a
20143 version of that library that has been compiled with the @option{-g} switch
20144 (see @ref{Rebuilding the GNAT Run-Time Library}).
20146 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
20147 examine. If the location of @file{gmem.out} file was not explicitly supplied by
20148 @option{-i} switch, gnatmem will assume that this file can be found in the
20149 current directory. For example, after you have executed @file{my_program},
20150 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
20153 $ gnatmem my_program
20157 This will produce the output with the following format:
20159 *************** debut cc
20161 $ gnatmem my_program
20165 Total number of allocations : 45
20166 Total number of deallocations : 6
20167 Final Water Mark (non freed mem) : 11.29 Kilobytes
20168 High Water Mark : 11.40 Kilobytes
20173 Allocation Root # 2
20174 -------------------
20175 Number of non freed allocations : 11
20176 Final Water Mark (non freed mem) : 1.16 Kilobytes
20177 High Water Mark : 1.27 Kilobytes
20179 my_program.adb:23 my_program.alloc
20185 The first block of output gives general information. In this case, the
20186 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
20187 Unchecked_Deallocation routine occurred.
20190 Subsequent paragraphs display information on all allocation roots.
20191 An allocation root is a specific point in the execution of the program
20192 that generates some dynamic allocation, such as a ``@code{@b{new}}''
20193 construct. This root is represented by an execution backtrace (or subprogram
20194 call stack). By default the backtrace depth for allocations roots is 1, so
20195 that a root corresponds exactly to a source location. The backtrace can
20196 be made deeper, to make the root more specific.
20198 @node Switches for gnatmem
20199 @subsection Switches for @code{gnatmem}
20202 @code{gnatmem} recognizes the following switches:
20207 @cindex @option{-q} (@code{gnatmem})
20208 Quiet. Gives the minimum output needed to identify the origin of the
20209 memory leaks. Omits statistical information.
20212 @cindex @var{N} (@code{gnatmem})
20213 N is an integer literal (usually between 1 and 10) which controls the
20214 depth of the backtraces defining allocation root. The default value for
20215 N is 1. The deeper the backtrace, the more precise the localization of
20216 the root. Note that the total number of roots can depend on this
20217 parameter. This parameter must be specified @emph{before} the name of the
20218 executable to be analyzed, to avoid ambiguity.
20221 @cindex @option{-b} (@code{gnatmem})
20222 This switch has the same effect as just depth parameter.
20224 @item -i @var{file}
20225 @cindex @option{-i} (@code{gnatmem})
20226 Do the @code{gnatmem} processing starting from @file{file}, rather than
20227 @file{gmem.out} in the current directory.
20230 @cindex @option{-m} (@code{gnatmem})
20231 This switch causes @code{gnatmem} to mask the allocation roots that have less
20232 than n leaks. The default value is 1. Specifying the value of 0 will allow to
20233 examine even the roots that didn't result in leaks.
20236 @cindex @option{-s} (@code{gnatmem})
20237 This switch causes @code{gnatmem} to sort the allocation roots according to the
20238 specified order of sort criteria, each identified by a single letter. The
20239 currently supported criteria are @code{n, h, w} standing respectively for
20240 number of unfreed allocations, high watermark, and final watermark
20241 corresponding to a specific root. The default order is @code{nwh}.
20245 @node Example of gnatmem Usage
20246 @subsection Example of @code{gnatmem} Usage
20249 The following example shows the use of @code{gnatmem}
20250 on a simple memory-leaking program.
20251 Suppose that we have the following Ada program:
20253 @smallexample @c ada
20256 with Unchecked_Deallocation;
20257 procedure Test_Gm is
20259 type T is array (1..1000) of Integer;
20260 type Ptr is access T;
20261 procedure Free is new Unchecked_Deallocation (T, Ptr);
20264 procedure My_Alloc is
20269 procedure My_DeAlloc is
20277 for I in 1 .. 5 loop
20278 for J in I .. 5 loop
20289 The program needs to be compiled with debugging option and linked with
20290 @code{gmem} library:
20293 $ gnatmake -g test_gm -largs -lgmem
20297 Then we execute the program as usual:
20304 Then @code{gnatmem} is invoked simply with
20310 which produces the following output (result may vary on different platforms):
20315 Total number of allocations : 18
20316 Total number of deallocations : 5
20317 Final Water Mark (non freed mem) : 53.00 Kilobytes
20318 High Water Mark : 56.90 Kilobytes
20320 Allocation Root # 1
20321 -------------------
20322 Number of non freed allocations : 11
20323 Final Water Mark (non freed mem) : 42.97 Kilobytes
20324 High Water Mark : 46.88 Kilobytes
20326 test_gm.adb:11 test_gm.my_alloc
20328 Allocation Root # 2
20329 -------------------
20330 Number of non freed allocations : 1
20331 Final Water Mark (non freed mem) : 10.02 Kilobytes
20332 High Water Mark : 10.02 Kilobytes
20334 s-secsta.adb:81 system.secondary_stack.ss_init
20336 Allocation Root # 3
20337 -------------------
20338 Number of non freed allocations : 1
20339 Final Water Mark (non freed mem) : 12 Bytes
20340 High Water Mark : 12 Bytes
20342 s-secsta.adb:181 system.secondary_stack.ss_init
20346 Note that the GNAT run time contains itself a certain number of
20347 allocations that have no corresponding deallocation,
20348 as shown here for root #2 and root
20349 #3. This is a normal behavior when the number of non-freed allocations
20350 is one, it allocates dynamic data structures that the run time needs for
20351 the complete lifetime of the program. Note also that there is only one
20352 allocation root in the user program with a single line back trace:
20353 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
20354 program shows that 'My_Alloc' is called at 2 different points in the
20355 source (line 21 and line 24). If those two allocation roots need to be
20356 distinguished, the backtrace depth parameter can be used:
20359 $ gnatmem 3 test_gm
20363 which will give the following output:
20368 Total number of allocations : 18
20369 Total number of deallocations : 5
20370 Final Water Mark (non freed mem) : 53.00 Kilobytes
20371 High Water Mark : 56.90 Kilobytes
20373 Allocation Root # 1
20374 -------------------
20375 Number of non freed allocations : 10
20376 Final Water Mark (non freed mem) : 39.06 Kilobytes
20377 High Water Mark : 42.97 Kilobytes
20379 test_gm.adb:11 test_gm.my_alloc
20380 test_gm.adb:24 test_gm
20381 b_test_gm.c:52 main
20383 Allocation Root # 2
20384 -------------------
20385 Number of non freed allocations : 1
20386 Final Water Mark (non freed mem) : 10.02 Kilobytes
20387 High Water Mark : 10.02 Kilobytes
20389 s-secsta.adb:81 system.secondary_stack.ss_init
20390 s-secsta.adb:283 <system__secondary_stack___elabb>
20391 b_test_gm.c:33 adainit
20393 Allocation Root # 3
20394 -------------------
20395 Number of non freed allocations : 1
20396 Final Water Mark (non freed mem) : 3.91 Kilobytes
20397 High Water Mark : 3.91 Kilobytes
20399 test_gm.adb:11 test_gm.my_alloc
20400 test_gm.adb:21 test_gm
20401 b_test_gm.c:52 main
20403 Allocation Root # 4
20404 -------------------
20405 Number of non freed allocations : 1
20406 Final Water Mark (non freed mem) : 12 Bytes
20407 High Water Mark : 12 Bytes
20409 s-secsta.adb:181 system.secondary_stack.ss_init
20410 s-secsta.adb:283 <system__secondary_stack___elabb>
20411 b_test_gm.c:33 adainit
20415 The allocation root #1 of the first example has been split in 2 roots #1
20416 and #3 thanks to the more precise associated backtrace.
20420 @node Stack Related Facilities
20421 @chapter Stack Related Facilities
20424 This chapter describes some useful tools associated with stack
20425 checking and analysis. In
20426 particular, it deals with dynamic and static stack usage measurements.
20429 * Stack Overflow Checking::
20430 * Static Stack Usage Analysis::
20431 * Dynamic Stack Usage Analysis::
20434 @node Stack Overflow Checking
20435 @section Stack Overflow Checking
20436 @cindex Stack Overflow Checking
20437 @cindex -fstack-check
20440 For most operating systems, @command{gcc} does not perform stack overflow
20441 checking by default. This means that if the main environment task or
20442 some other task exceeds the available stack space, then unpredictable
20443 behavior will occur. Most native systems offer some level of protection by
20444 adding a guard page at the end of each task stack. This mechanism is usually
20445 not enough for dealing properly with stack overflow situations because
20446 a large local variable could ``jump'' above the guard page.
20447 Furthermore, when the
20448 guard page is hit, there may not be any space left on the stack for executing
20449 the exception propagation code. Enabling stack checking avoids
20452 To activate stack checking, compile all units with the gcc option
20453 @option{-fstack-check}. For example:
20456 gcc -c -fstack-check package1.adb
20460 Units compiled with this option will generate extra instructions to check
20461 that any use of the stack (for procedure calls or for declaring local
20462 variables in declare blocks) does not exceed the available stack space.
20463 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20465 For declared tasks, the stack size is controlled by the size
20466 given in an applicable @code{Storage_Size} pragma or by the value specified
20467 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20468 the default size as defined in the GNAT runtime otherwise.
20470 For the environment task, the stack size depends on
20471 system defaults and is unknown to the compiler. Stack checking
20472 may still work correctly if a fixed
20473 size stack is allocated, but this cannot be guaranteed.
20475 To ensure that a clean exception is signalled for stack
20476 overflow, set the environment variable
20477 @env{GNAT_STACK_LIMIT} to indicate the maximum
20478 stack area that can be used, as in:
20479 @cindex GNAT_STACK_LIMIT
20482 SET GNAT_STACK_LIMIT 1600
20486 The limit is given in kilobytes, so the above declaration would
20487 set the stack limit of the environment task to 1.6 megabytes.
20488 Note that the only purpose of this usage is to limit the amount
20489 of stack used by the environment task. If it is necessary to
20490 increase the amount of stack for the environment task, then this
20491 is an operating systems issue, and must be addressed with the
20492 appropriate operating systems commands.
20495 To have a fixed size stack in the environment task, the stack must be put
20496 in the P0 address space and its size specified. Use these switches to
20500 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20504 The quotes are required to keep case. The number after @samp{STACK=} is the
20505 size of the environmental task stack in pagelets (512 bytes). In this example
20506 the stack size is about 2 megabytes.
20509 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20510 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20511 more details about the @option{/p0image} qualifier and the @option{stack}
20515 @node Static Stack Usage Analysis
20516 @section Static Stack Usage Analysis
20517 @cindex Static Stack Usage Analysis
20518 @cindex -fstack-usage
20521 A unit compiled with @option{-fstack-usage} will generate an extra file
20523 the maximum amount of stack used, on a per-function basis.
20524 The file has the same
20525 basename as the target object file with a @file{.su} extension.
20526 Each line of this file is made up of three fields:
20530 The name of the function.
20534 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20537 The second field corresponds to the size of the known part of the function
20540 The qualifier @code{static} means that the function frame size
20542 It usually means that all local variables have a static size.
20543 In this case, the second field is a reliable measure of the function stack
20546 The qualifier @code{dynamic} means that the function frame size is not static.
20547 It happens mainly when some local variables have a dynamic size. When this
20548 qualifier appears alone, the second field is not a reliable measure
20549 of the function stack analysis. When it is qualified with @code{bounded}, it
20550 means that the second field is a reliable maximum of the function stack
20553 @node Dynamic Stack Usage Analysis
20554 @section Dynamic Stack Usage Analysis
20557 It is possible to measure the maximum amount of stack used by a task, by
20558 adding a switch to @command{gnatbind}, as:
20561 $ gnatbind -u0 file
20565 With this option, at each task termination, its stack usage is output on
20567 It is not always convenient to output the stack usage when the program
20568 is still running. Hence, it is possible to delay this output until program
20569 termination. for a given number of tasks specified as the argument of the
20570 @option{-u} option. For instance:
20573 $ gnatbind -u100 file
20577 will buffer the stack usage information of the first 100 tasks to terminate and
20578 output this info at program termination. Results are displayed in four
20582 Index | Task Name | Stack Size | Stack Usage [Value +/- Variation]
20589 is a number associated with each task.
20592 is the name of the task analyzed.
20595 is the maximum size for the stack.
20598 is the measure done by the stack analyzer. In order to prevent overflow, the stack
20599 is not entirely analyzed, and it's not possible to know exactly how
20600 much has actually been used. The report thus contains the theoretical stack usage
20601 (Value) and the possible variation (Variation) around this value.
20606 The environment task stack, e.g., the stack that contains the main unit, is
20607 only processed when the environment variable GNAT_STACK_LIMIT is set.
20610 @c *********************************
20612 @c *********************************
20613 @node Verifying Properties Using gnatcheck
20614 @chapter Verifying Properties Using @command{gnatcheck}
20616 @cindex @command{gnatcheck}
20619 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20620 of Ada source files according to a given set of semantic rules.
20623 In order to check compliance with a given rule, @command{gnatcheck} has to
20624 semantically analyze the Ada sources.
20625 Therefore, checks can only be performed on
20626 legal Ada units. Moreover, when a unit depends semantically upon units located
20627 outside the current directory, the source search path has to be provided when
20628 calling @command{gnatcheck}, either through a specified project file or
20629 through @command{gnatcheck} switches as described below.
20631 A number of rules are predefined in @command{gnatcheck} and are described
20632 later in this chapter.
20633 You can also add new rules, by modifying the @command{gnatcheck} code and
20634 rebuilding the tool. In order to add a simple rule making some local checks,
20635 a small amount of straightforward ASIS-based programming is usually needed.
20637 Project support for @command{gnatcheck} is provided by the GNAT
20638 driver (see @ref{The GNAT Driver and Project Files}).
20640 Invoking @command{gnatcheck} on the command line has the form:
20643 $ gnatcheck @ovar{switches} @{@var{filename}@}
20644 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20645 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20652 @var{switches} specify the general tool options
20655 Each @var{filename} is the name (including the extension) of a source
20656 file to process. ``Wildcards'' are allowed, and
20657 the file name may contain path information.
20660 Each @var{arg_list_filename} is the name (including the extension) of a text
20661 file containing the names of the source files to process, separated by spaces
20665 @var{gcc_switches} is a list of switches for
20666 @command{gcc}. They will be passed on to all compiler invocations made by
20667 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20668 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20669 and use the @option{-gnatec} switch to set the configuration file.
20672 @var{rule_options} is a list of options for controlling a set of
20673 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20677 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20680 * Format of the Report File::
20681 * General gnatcheck Switches::
20682 * gnatcheck Rule Options::
20683 * Adding the Results of Compiler Checks to gnatcheck Output::
20684 * Project-Wide Checks::
20685 * Predefined Rules::
20688 @node Format of the Report File
20689 @section Format of the Report File
20690 @cindex Report file (for @code{gnatcheck})
20693 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20695 It also creates a text file that
20696 contains the complete report of the last gnatcheck run. By default this file is
20697 named named @file{^gnatcheck.out^GNATCHECK.OUT^} and it is located in the current
20698 directory, @option{^-o^/OUTPUT^} option can be used to change the name and/or
20699 location of the report file. This report contains:
20701 @item a list of the Ada source files being checked,
20702 @item a list of enabled and disabled rules,
20703 @item a list of the diagnostic messages, ordered in three different ways
20704 and collected in three separate
20705 sections. Section 1 contains the raw list of diagnostic messages. It
20706 corresponds to the output going to @file{stdout}. Section 2 contains
20707 messages ordered by rules.
20708 Section 3 contains messages ordered by source files.
20711 @node General gnatcheck Switches
20712 @section General @command{gnatcheck} Switches
20715 The following switches control the general @command{gnatcheck} behavior
20719 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20721 Process all units including those with read-only ALI files such as
20722 those from GNAT Run-Time library.
20726 @cindex @option{-d} (@command{gnatcheck})
20731 @cindex @option{-dd} (@command{gnatcheck})
20733 Progress indicator mode (for use in GPS)
20736 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20738 List the predefined and user-defined rules. For more details see
20739 @ref{Predefined Rules}.
20741 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20743 Use full source locations references in the report file. For a construct from
20744 a generic instantiation a full source location is a chain from the location
20745 of this construct in the generic unit to the place where this unit is
20748 @cindex @option{^-log^/LOG^} (@command{gnatcheck})
20750 Duplicate all the output sent to Stderr into a log file. The log file is
20751 named @var{gnatcheck.log} and is located in the current directory.
20753 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
20754 @item ^-m@i{nnn}^/DIAGNOSTIC_LIMIT=@i{nnn}^
20755 Maximum number of diagnoses to be sent to Stdout, @i{nnn} from o@dots{}1000,
20756 the default value is 500. Zero means that there is no limitation on
20757 the number of diagnostic messages to be printed into Stdout.
20759 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20761 Quiet mode. All the diagnoses about rule violations are placed in the
20762 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20764 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20766 Short format of the report file (no version information, no list of applied
20767 rules, no list of checked sources is included)
20769 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20770 @item ^-s1^/COMPILER_STYLE^
20771 Include the compiler-style section in the report file
20773 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20774 @item ^-s2^/BY_RULES^
20775 Include the section containing diagnoses ordered by rules in the report file
20777 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20778 @item ^-s3^/BY_FILES_BY_RULES^
20779 Include the section containing diagnoses ordered by files and then by rules
20782 @cindex @option{^-t^/TIME^} (@command{gnatcheck})
20784 Print out execution time.
20786 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20787 @item ^-v^/VERBOSE^
20788 Verbose mode; @command{gnatcheck} generates version information and then
20789 a trace of sources being processed.
20791 @cindex @option{^-o ^/OUTPUT^} (@command{gnatcheck})
20792 @item ^-o ^/OUTPUT=^@var{report_file}
20793 Set name of report file file to @var{report_file} .
20798 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20799 @option{^-s2^/BY_RULES^} or
20800 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20801 then the @command{gnatcheck} report file will only contain sections
20802 explicitly denoted by these options.
20804 @node gnatcheck Rule Options
20805 @section @command{gnatcheck} Rule Options
20808 The following options control the processing performed by
20809 @command{gnatcheck}.
20812 @cindex @option{+ALL} (@command{gnatcheck})
20814 Turn all the rule checks ON.
20816 @cindex @option{-ALL} (@command{gnatcheck})
20818 Turn all the rule checks OFF.
20820 @cindex @option{+R} (@command{gnatcheck})
20821 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20822 Turn on the check for a specified rule with the specified parameter, if any.
20823 @var{rule_id} must be the identifier of one of the currently implemented rules
20824 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20825 are not case-sensitive. The @var{param} item must
20826 be a string representing a valid parameter(s) for the specified rule.
20827 If it contains any space characters then this string must be enclosed in
20830 @cindex @option{-R} (@command{gnatcheck})
20831 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20832 Turn off the check for a specified rule with the specified parameter, if any.
20834 @cindex @option{-from} (@command{gnatcheck})
20835 @item -from=@var{rule_option_filename}
20836 Read the rule options from the text file @var{rule_option_filename}, referred as
20837 ``rule file'' below.
20842 The default behavior is that all the rule checks are disabled.
20844 A rule file is a text file containing a set of rule options.
20845 @cindex Rule file (for @code{gnatcheck})
20846 The file may contain empty lines and Ada-style comments (comment
20847 lines and end-of-line comments). The rule file has free format; that is,
20848 you do not have to start a new rule option on a new line.
20850 A rule file may contain other @option{-from=@var{rule_option_filename}}
20851 options, each such option being replaced with the content of the
20852 corresponding rule file during the rule files processing. In case a
20853 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20854 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20855 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20856 the processing of rule files is interrupted and a part of their content
20860 @node Adding the Results of Compiler Checks to gnatcheck Output
20861 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20864 The @command{gnatcheck} tool can include in the generated diagnostic messages
20866 the report file the results of the checks performed by the compiler. Though
20867 disabled by default, this effect may be obtained by using @option{+R} with
20868 the following rule identifiers and parameters:
20872 To record restrictions violations (that are performed by the compiler if the
20873 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20875 @code{Restrictions} with the same parameters as pragma
20876 @code{Restrictions} or @code{Restriction_Warnings}.
20879 To record compiler style checks(@pxref{Style Checking}), use the rule named
20880 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20881 which enables all the standard style checks that corresponds to @option{-gnatyy}
20882 GNAT style check option, or a string that has exactly the same
20883 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20884 @code{Style_Checks} (for further information about this pragma,
20885 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}). For example,
20886 @code{+RStyle_Checks:O} rule option activates and adds to @command{gnatcheck}
20887 output the compiler style check that corresponds to
20888 @code{-gnatyO} style check option.
20891 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20892 named @code{Warnings} with a parameter that is a valid
20893 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20894 (for further information about this pragma, @pxref{Pragma Warnings,,,
20895 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20896 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20897 all the specific warnings, but not suppresses the warning mode,
20898 and 'e' parameter, corresponding to @option{-gnatwe} that means
20899 "treat warnings as errors", does not have any effect.
20903 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20904 option with the corresponding restriction name as a parameter. @code{-R} is
20905 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20906 warnings and style checks, use the corresponding warning and style options.
20908 @node Project-Wide Checks
20909 @section Project-Wide Checks
20910 @cindex Project-wide checks (for @command{gnatcheck})
20913 In order to perform checks on all units of a given project, you can use
20914 the GNAT driver along with the @option{-P} option:
20916 gnat check -Pproj -rules -from=my_rules
20920 If the project @code{proj} depends upon other projects, you can perform
20921 checks on the project closure using the @option{-U} option:
20923 gnat check -Pproj -U -rules -from=my_rules
20927 Finally, if not all the units are relevant to a particular main
20928 program in the project closure, you can perform checks for the set
20929 of units needed to create a given main program (unit closure) using
20930 the @option{-U} option followed by the name of the main unit:
20932 gnat check -Pproj -U main -rules -from=my_rules
20936 @node Predefined Rules
20937 @section Predefined Rules
20938 @cindex Predefined rules (for @command{gnatcheck})
20941 @c (Jan 2007) Since the global rules are still under development and are not
20942 @c documented, there is no point in explaining the difference between
20943 @c global and local rules
20945 A rule in @command{gnatcheck} is either local or global.
20946 A @emph{local rule} is a rule that applies to a well-defined section
20947 of a program and that can be checked by analyzing only this section.
20948 A @emph{global rule} requires analysis of some global properties of the
20949 whole program (mostly related to the program call graph).
20950 As of @value{NOW}, the implementation of global rules should be
20951 considered to be at a preliminary stage. You can use the
20952 @option{+GLOBAL} option to enable all the global rules, and the
20953 @option{-GLOBAL} rule option to disable all the global rules.
20955 All the global rules in the list below are
20956 so indicated by marking them ``GLOBAL''.
20957 This +GLOBAL and -GLOBAL options are not
20958 included in the list of gnatcheck options above, because at the moment they
20959 are considered as a temporary debug options.
20961 @command{gnatcheck} performs rule checks for generic
20962 instances only for global rules. This limitation may be relaxed in a later
20967 The following subsections document the rules implemented in
20968 @command{gnatcheck}.
20969 The subsection title is the same as the rule identifier, which may be
20970 used as a parameter of the @option{+R} or @option{-R} options.
20974 * Abstract_Type_Declarations::
20975 * Anonymous_Arrays::
20976 * Anonymous_Subtypes::
20978 * Boolean_Relational_Operators::
20980 * Ceiling_Violations::
20982 * Controlled_Type_Declarations::
20983 * Declarations_In_Blocks::
20984 * Default_Parameters::
20985 * Discriminated_Records::
20986 * Enumeration_Ranges_In_CASE_Statements::
20987 * Exceptions_As_Control_Flow::
20988 * Exits_From_Conditional_Loops::
20989 * EXIT_Statements_With_No_Loop_Name::
20990 * Expanded_Loop_Exit_Names::
20991 * Explicit_Full_Discrete_Ranges::
20992 * Float_Equality_Checks::
20993 * Forbidden_Pragmas::
20994 * Function_Style_Procedures::
20995 * Generics_In_Subprograms::
20996 * GOTO_Statements::
20997 * Implicit_IN_Mode_Parameters::
20998 * Implicit_SMALL_For_Fixed_Point_Types::
20999 * Improperly_Located_Instantiations::
21000 * Improper_Returns::
21001 * Library_Level_Subprograms::
21004 * Improperly_Called_Protected_Entries::
21007 * Misnamed_Identifiers::
21008 * Multiple_Entries_In_Protected_Definitions::
21010 * Non_Qualified_Aggregates::
21011 * Non_Short_Circuit_Operators::
21012 * Non_SPARK_Attributes::
21013 * Non_Tagged_Derived_Types::
21014 * Non_Visible_Exceptions::
21015 * Numeric_Literals::
21016 * OTHERS_In_Aggregates::
21017 * OTHERS_In_CASE_Statements::
21018 * OTHERS_In_Exception_Handlers::
21019 * Outer_Loop_Exits::
21020 * Overloaded_Operators::
21021 * Overly_Nested_Control_Structures::
21022 * Parameters_Out_Of_Order::
21023 * Positional_Actuals_For_Defaulted_Generic_Parameters::
21024 * Positional_Actuals_For_Defaulted_Parameters::
21025 * Positional_Components::
21026 * Positional_Generic_Parameters::
21027 * Positional_Parameters::
21028 * Predefined_Numeric_Types::
21029 * Raising_External_Exceptions::
21030 * Raising_Predefined_Exceptions::
21031 * Separate_Numeric_Error_Handlers::
21034 * Side_Effect_Functions::
21037 * Unassigned_OUT_Parameters::
21038 * Uncommented_BEGIN_In_Package_Bodies::
21039 * Unconditional_Exits::
21040 * Unconstrained_Array_Returns::
21041 * Universal_Ranges::
21042 * Unnamed_Blocks_And_Loops::
21044 * Unused_Subprograms::
21046 * USE_PACKAGE_Clauses::
21047 * Volatile_Objects_Without_Address_Clauses::
21051 @node Abstract_Type_Declarations
21052 @subsection @code{Abstract_Type_Declarations}
21053 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
21056 Flag all declarations of abstract types. For an abstract private
21057 type, both the private and full type declarations are flagged.
21059 This rule has no parameters.
21062 @node Anonymous_Arrays
21063 @subsection @code{Anonymous_Arrays}
21064 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
21067 Flag all anonymous array type definitions (by Ada semantics these can only
21068 occur in object declarations).
21070 This rule has no parameters.
21072 @node Anonymous_Subtypes
21073 @subsection @code{Anonymous_Subtypes}
21074 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
21077 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
21078 any instance of a subtype indication with a constraint, other than one
21079 that occurs immediately within a subtype declaration. Any use of a range
21080 other than as a constraint used immediately within a subtype declaration
21081 is considered as an anonymous subtype.
21083 An effect of this rule is that @code{for} loops such as the following are
21084 flagged (since @code{1..N} is formally a ``range''):
21086 @smallexample @c ada
21087 for I in 1 .. N loop
21093 Declaring an explicit subtype solves the problem:
21095 @smallexample @c ada
21096 subtype S is Integer range 1..N;
21104 This rule has no parameters.
21107 @subsection @code{Blocks}
21108 @cindex @code{Blocks} rule (for @command{gnatcheck})
21111 Flag each block statement.
21113 This rule has no parameters.
21115 @node Boolean_Relational_Operators
21116 @subsection @code{Boolean_Relational_Operators}
21117 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
21120 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
21121 ``>='', ``='' and ``/='') for the predefined Boolean type.
21122 (This rule is useful in enforcing the SPARK language restrictions.)
21124 Calls to predefined relational operators of any type derived from
21125 @code{Standard.Boolean} are not detected. Calls to user-defined functions
21126 with these designators, and uses of operators that are renamings
21127 of the predefined relational operators for @code{Standard.Boolean},
21128 are likewise not detected.
21130 This rule has no parameters.
21133 @node Ceiling_Violations
21134 @subsection @code{Ceiling_Violations} (under construction, GLOBAL)
21135 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
21138 Flag invocations of a protected operation by a task whose priority exceeds
21139 the protected object's ceiling.
21141 As of @value{NOW}, this rule has the following limitations:
21146 We consider only pragmas Priority and Interrupt_Priority as means to define
21147 a task/protected operation priority. We do not consider the effect of using
21148 Ada.Dynamic_Priorities.Set_Priority procedure;
21151 We consider only base task priorities, and no priority inheritance. That is,
21152 we do not make a difference between calls issued during task activation and
21153 execution of the sequence of statements from task body;
21156 Any situation when the priority of protected operation caller is set by a
21157 dynamic expression (that is, the corresponding Priority or
21158 Interrupt_Priority pragma has a non-static expression as an argument) we
21159 treat as a priority inconsistency (and, therefore, detect this situation).
21163 At the moment the notion of the main subprogram is not implemented in
21164 gnatcheck, so any pragma Priority in a library level subprogram body (in case
21165 if this subprogram can be a main subprogram of a partition) changes the
21166 priority of an environment task. So if we have more then one such pragma in
21167 the set of processed sources, the pragma that is processed last, defines the
21168 priority of an environment task.
21170 This rule has no parameters.
21173 @node Controlled_Type_Declarations
21174 @subsection @code{Controlled_Type_Declarations}
21175 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
21178 Flag all declarations of controlled types. A declaration of a private type
21179 is flagged if its full declaration declares a controlled type. A declaration
21180 of a derived type is flagged if its ancestor type is controlled. Subtype
21181 declarations are not checked. A declaration of a type that itself is not a
21182 descendant of a type declared in @code{Ada.Finalization} but has a controlled
21183 component is not checked.
21185 This rule has no parameters.
21189 @node Declarations_In_Blocks
21190 @subsection @code{Declarations_In_Blocks}
21191 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
21194 Flag all block statements containing local declarations. A @code{declare}
21195 block with an empty @i{declarative_part} or with a @i{declarative part}
21196 containing only pragmas and/or @code{use} clauses is not flagged.
21198 This rule has no parameters.
21201 @node Default_Parameters
21202 @subsection @code{Default_Parameters}
21203 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
21206 Flag all default expressions for subprogram parameters. Parameter
21207 declarations of formal and generic subprograms are also checked.
21209 This rule has no parameters.
21212 @node Discriminated_Records
21213 @subsection @code{Discriminated_Records}
21214 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
21217 Flag all declarations of record types with discriminants. Only the
21218 declarations of record and record extension types are checked. Incomplete,
21219 formal, private, derived and private extension type declarations are not
21220 checked. Task and protected type declarations also are not checked.
21222 This rule has no parameters.
21225 @node Enumeration_Ranges_In_CASE_Statements
21226 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
21227 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
21230 Flag each use of a range of enumeration literals as a choice in a
21231 @code{case} statement.
21232 All forms for specifying a range (explicit ranges
21233 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
21234 An enumeration range is
21235 flagged even if contains exactly one enumeration value or no values at all. A
21236 type derived from an enumeration type is considered as an enumeration type.
21238 This rule helps prevent maintenance problems arising from adding an
21239 enumeration value to a type and having it implicitly handled by an existing
21240 @code{case} statement with an enumeration range that includes the new literal.
21242 This rule has no parameters.
21245 @node Exceptions_As_Control_Flow
21246 @subsection @code{Exceptions_As_Control_Flow}
21247 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
21250 Flag each place where an exception is explicitly raised and handled in the
21251 same subprogram body. A @code{raise} statement in an exception handler,
21252 package body, task body or entry body is not flagged.
21254 The rule has no parameters.
21256 @node Exits_From_Conditional_Loops
21257 @subsection @code{Exits_From_Conditional_Loops}
21258 @cindex @code{Exits_From_Conditional_Loops} (for @command{gnatcheck})
21261 Flag any exit statement if it transfers the control out of a @code{for} loop
21262 or a @code{while} loop. This includes cases when the @code{exit} statement
21263 applies to a @code{FOR} or @code{while} loop, and cases when it is enclosed
21264 in some @code{for} or @code{while} loop, but transfers the control from some
21265 outer (inconditional) @code{loop} statement.
21267 The rule has no parameters.
21270 @node EXIT_Statements_With_No_Loop_Name
21271 @subsection @code{EXIT_Statements_With_No_Loop_Name}
21272 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
21275 Flag each @code{exit} statement that does not specify the name of the loop
21278 The rule has no parameters.
21281 @node Expanded_Loop_Exit_Names
21282 @subsection @code{Expanded_Loop_Exit_Names}
21283 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
21286 Flag all expanded loop names in @code{exit} statements.
21288 This rule has no parameters.
21290 @node Explicit_Full_Discrete_Ranges
21291 @subsection @code{Explicit_Full_Discrete_Ranges}
21292 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
21295 Flag each discrete range that has the form @code{A'First .. A'Last}.
21297 This rule has no parameters.
21299 @node Float_Equality_Checks
21300 @subsection @code{Float_Equality_Checks}
21301 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
21304 Flag all calls to the predefined equality operations for floating-point types.
21305 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
21306 User-defined equality operations are not flagged, nor are ``@code{=}''
21307 and ``@code{/=}'' operations for fixed-point types.
21309 This rule has no parameters.
21312 @node Forbidden_Pragmas
21313 @subsection @code{Forbidden_Pragmas}
21314 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
21317 Flag each use of the specified pragmas. The pragmas to be detected
21318 are named in the rule's parameters.
21320 This rule has the following parameters:
21323 @item For the @option{+R} option
21326 @item @emph{Pragma_Name}
21327 Adds the specified pragma to the set of pragmas to be
21328 checked and sets the checks for all the specified pragmas
21329 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
21330 does not correspond to any pragma name defined in the Ada
21331 standard or to the name of a GNAT-specific pragma defined
21332 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
21333 Manual}, it is treated as the name of unknown pragma.
21336 All the GNAT-specific pragmas are detected; this sets
21337 the checks for all the specified pragmas ON.
21340 All pragmas are detected; this sets the rule ON.
21343 @item For the @option{-R} option
21345 @item @emph{Pragma_Name}
21346 Removes the specified pragma from the set of pragmas to be
21347 checked without affecting checks for
21348 other pragmas. @emph{Pragma_Name} is treated as a name
21349 of a pragma. If it does not correspond to any pragma
21350 defined in the Ada standard or to any name defined in
21351 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
21352 this option is treated as turning OFF detection of all unknown pragmas.
21355 Turn OFF detection of all GNAT-specific pragmas
21358 Clear the list of the pragmas to be detected and
21364 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
21365 the syntax of an Ada identifier and therefore can not be considered
21366 as a pragma name, a diagnostic message is generated and the corresponding
21367 parameter is ignored.
21369 When more then one parameter is given in the same rule option, the parameters
21370 must be separated by a comma.
21372 If more then one option for this rule is specified for the @command{gnatcheck}
21373 call, a new option overrides the previous one(s).
21375 The @option{+R} option with no parameters turns the rule ON with the set of
21376 pragmas to be detected defined by the previous rule options.
21377 (By default this set is empty, so if the only option specified for the rule is
21378 @option{+RForbidden_Pragmas} (with
21379 no parameter), then the rule is enabled, but it does not detect anything).
21380 The @option{-R} option with no parameter turns the rule OFF, but it does not
21381 affect the set of pragmas to be detected.
21386 @node Function_Style_Procedures
21387 @subsection @code{Function_Style_Procedures}
21388 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
21391 Flag each procedure that can be rewritten as a function. A procedure can be
21392 converted into a function if it has exactly one parameter of mode @code{out}
21393 and no parameters of mode @code{in out}. Procedure declarations,
21394 formal procedure declarations, and generic procedure declarations are always
21396 bodies and body stubs are flagged only if they do not have corresponding
21397 separate declarations. Procedure renamings and procedure instantiations are
21400 If a procedure can be rewritten as a function, but its @code{out} parameter is
21401 of a limited type, it is not flagged.
21403 Protected procedures are not flagged. Null procedures also are not flagged.
21405 This rule has no parameters.
21408 @node Generics_In_Subprograms
21409 @subsection @code{Generics_In_Subprograms}
21410 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
21413 Flag each declaration of a generic unit in a subprogram. Generic
21414 declarations in the bodies of generic subprograms are also flagged.
21415 A generic unit nested in another generic unit is not flagged.
21416 If a generic unit is
21417 declared in a local package that is declared in a subprogram body, the
21418 generic unit is flagged.
21420 This rule has no parameters.
21423 @node GOTO_Statements
21424 @subsection @code{GOTO_Statements}
21425 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
21428 Flag each occurrence of a @code{goto} statement.
21430 This rule has no parameters.
21433 @node Implicit_IN_Mode_Parameters
21434 @subsection @code{Implicit_IN_Mode_Parameters}
21435 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21438 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21439 Note that @code{access} parameters, although they technically behave
21440 like @code{in} parameters, are not flagged.
21442 This rule has no parameters.
21445 @node Implicit_SMALL_For_Fixed_Point_Types
21446 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21447 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21450 Flag each fixed point type declaration that lacks an explicit
21451 representation clause to define its @code{'Small} value.
21452 Since @code{'Small} can be defined only for ordinary fixed point types,
21453 decimal fixed point type declarations are not checked.
21455 This rule has no parameters.
21458 @node Improperly_Located_Instantiations
21459 @subsection @code{Improperly_Located_Instantiations}
21460 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21463 Flag all generic instantiations in library-level package specs
21464 (including library generic packages) and in all subprogram bodies.
21466 Instantiations in task and entry bodies are not flagged. Instantiations in the
21467 bodies of protected subprograms are flagged.
21469 This rule has no parameters.
21473 @node Improper_Returns
21474 @subsection @code{Improper_Returns}
21475 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21478 Flag each explicit @code{return} statement in procedures, and
21479 multiple @code{return} statements in functions.
21480 Diagnostic messages are generated for all @code{return} statements
21481 in a procedure (thus each procedure must be written so that it
21482 returns implicitly at the end of its statement part),
21483 and for all @code{return} statements in a function after the first one.
21484 This rule supports the stylistic convention that each subprogram
21485 should have no more than one point of normal return.
21487 This rule has no parameters.
21490 @node Library_Level_Subprograms
21491 @subsection @code{Library_Level_Subprograms}
21492 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21495 Flag all library-level subprograms (including generic subprogram instantiations).
21497 This rule has no parameters.
21500 @node Local_Packages
21501 @subsection @code{Local_Packages}
21502 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21505 Flag all local packages declared in package and generic package
21507 Local packages in bodies are not flagged.
21509 This rule has no parameters.
21512 @node Improperly_Called_Protected_Entries
21513 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21514 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21517 Flag each protected entry that can be called from more than one task.
21519 This rule has no parameters.
21523 @subsection @code{Metrics}
21524 @cindex @code{Metrics} rule (for @command{gnatcheck})
21527 There is a set of checks based on computing a metric value and comparing the
21528 result with the specified upper (or lower, depending on a specific metric)
21529 value specified for a given metric. A construct is flagged if a given metric
21530 is applicable (can be computed) for it and the computed value is greater
21531 then (lover then) the specified upper (lower) bound.
21533 The name of any metric-based rule consists of the prefix @code{Metrics_}
21534 followed by the name of the corresponding metric (see the table below).
21535 For @option{+R} option, each metric-based rule has a numeric parameter
21536 specifying the bound (integer or real, depending on a metric), @option{-R}
21537 option for metric rules does not have a parameter.
21539 The following table shows the metric names for that the corresponding
21540 metrics-based checks are supported by gnatcheck, including the
21541 constraint that must be satisfied by the bound that is specified for the check
21542 and what bound - upper (U) or lower (L) - should be specified.
21544 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21546 @headitem Check Name @tab Description @tab Bounds Value
21549 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21551 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21552 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21553 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21554 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21558 The meaning and the computed values for all these metrics are exactly
21559 the same as for the corresponding metrics in @command{gnatmetric}.
21561 @emph{Example:} the rule
21563 +RMetrics_Cyclomatic_Complexity : 7
21566 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21568 To turn OFF the check for cyclomatic complexity metric, use the following option:
21570 -RMetrics_Cyclomatic_Complexity
21573 @node Misnamed_Identifiers
21574 @subsection @code{Misnamed_Identifiers}
21575 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21578 Flag the declaration of each identifier that does not have a suffix
21579 corresponding to the kind of entity being declared.
21580 The following declarations are checked:
21587 subtype declarations
21590 constant declarations (but not number declarations)
21593 package renaming declarations (but not generic package renaming
21598 This rule may have parameters. When used without parameters, the rule enforces
21599 the following checks:
21603 type-defining names end with @code{_T}, unless the type is an access type,
21604 in which case the suffix must be @code{_A}
21606 constant names end with @code{_C}
21608 names defining package renamings end with @code{_R}
21612 For a private or incomplete type declaration the following checks are
21613 made for the defining name suffix:
21617 For an incomplete type declaration: if the corresponding full type
21618 declaration is available, the defining identifier from the full type
21619 declaration is checked, but the defining identifier from the incomplete type
21620 declaration is not; otherwise the defining identifier from the incomplete
21621 type declaration is checked against the suffix specified for type
21625 For a private type declaration (including private extensions), the defining
21626 identifier from the private type declaration is checked against the type
21627 suffix (even if the corresponding full declaration is an access type
21628 declaration), and the defining identifier from the corresponding full type
21629 declaration is not checked.
21633 For a deferred constant, the defining name in the corresponding full constant
21634 declaration is not checked.
21636 Defining names of formal types are not checked.
21638 The rule may have the following parameters:
21642 For the @option{+R} option:
21645 Sets the default listed above for all the names to be checked.
21647 @item Type_Suffix=@emph{string}
21648 Specifies the suffix for a type name.
21650 @item Access_Suffix=@emph{string}
21651 Specifies the suffix for an access type name. If
21652 this parameter is set, it overrides for access
21653 types the suffix set by the @code{Type_Suffix} parameter.
21654 For access types, @emph{string} may have the following format:
21655 @emph{suffix1(suffix2)}. That means that an access type name
21656 should have the @emph{suffix1} suffix except for the case when
21657 the designated type is also an access type, in this case the
21658 type name should have the @emph{suffix1 & suffix2} suffix.
21660 @item Class_Access_Suffix=@emph{string}
21661 Specifies the suffix for the name of an access type that points to some class-wide
21662 type. If this parameter is set, it overrides for such access
21663 types the suffix set by the @code{Type_Suffix} or @code{Access_Suffix}
21666 @item Class_Subtype_Suffix=@emph{string}
21667 Specifies the suffix for the name of a subtype that denotes a class-wide type.
21669 @item Constant_Suffix=@emph{string}
21670 Specifies the suffix for a constant name.
21672 @item Renaming_Suffix=@emph{string}
21673 Specifies the suffix for a package renaming name.
21677 For the @option{-R} option:
21680 Remove all the suffixes specified for the
21681 identifier suffix checks, whether by default or
21682 as specified by other rule parameters. All the
21683 checks for this rule are disabled as a result.
21686 Removes the suffix specified for types. This
21687 disables checks for types but does not disable
21688 any other checks for this rule (including the
21689 check for access type names if @code{Access_Suffix} is
21692 @item Access_Suffix
21693 Removes the suffix specified for access types.
21694 This disables checks for access type names but
21695 does not disable any other checks for this rule.
21696 If @code{Type_Suffix} is set, access type names are
21697 checked as ordinary type names.
21699 @item Class_Access_Suffix
21700 Removes the suffix specified for access types pointing to class-wide
21701 type. This disables specific checks for names of access types pointing to
21702 class-wide types but does not disable any other checks for this rule.
21703 If @code{Type_Suffix} is set, access type names are
21704 checked as ordinary type names. If @code{Access_Suffix} is set, these
21705 access types are checked as any other access type name.
21707 @item Class_Subtype_Suffix=@emph{string}
21708 Removes the suffix specified for subtype names.
21709 This disables checks for subtype names but
21710 does not disable any other checks for this rule.
21712 @item Constant_Suffix
21713 Removes the suffix specified for constants. This
21714 disables checks for constant names but does not
21715 disable any other checks for this rule.
21717 @item Renaming_Suffix
21718 Removes the suffix specified for package
21719 renamings. This disables checks for package
21720 renamings but does not disable any other checks
21726 If more than one parameter is used, parameters must be separated by commas.
21728 If more than one option is specified for the @command{gnatcheck} invocation,
21729 a new option overrides the previous one(s).
21731 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21733 name suffixes specified by previous options used for this rule.
21735 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21736 all the checks but keeps
21737 all the suffixes specified by previous options used for this rule.
21739 The @emph{string} value must be a valid suffix for an Ada identifier (after
21740 trimming all the leading and trailing space characters, if any).
21741 Parameters are not case sensitive, except the @emph{string} part.
21743 If any error is detected in a rule parameter, the parameter is ignored.
21744 In such a case the options that are set for the rule are not
21749 @node Multiple_Entries_In_Protected_Definitions
21750 @subsection @code{Multiple_Entries_In_Protected_Definitions}
21751 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
21754 Flag each protected definition (i.e., each protected object/type declaration)
21755 that defines more than one entry.
21756 Diagnostic messages are generated for all the entry declarations
21757 except the first one. An entry family is counted as one entry. Entries from
21758 the private part of the protected definition are also checked.
21760 This rule has no parameters.
21763 @subsection @code{Name_Clashes}
21764 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
21767 Check that certain names are not used as defining identifiers. To activate
21768 this rule, you need to supply a reference to the dictionary file(s) as a rule
21769 parameter(s) (more then one dictionary file can be specified). If no
21770 dictionary file is set, this rule will not cause anything to be flagged.
21771 Only defining occurrences, not references, are checked.
21772 The check is not case-sensitive.
21774 This rule is enabled by default, but without setting any corresponding
21775 dictionary file(s); thus the default effect is to do no checks.
21777 A dictionary file is a plain text file. The maximum line length for this file
21778 is 1024 characters. If the line is longer then this limit, extra characters
21781 Each line can be either an empty line, a comment line, or a line containing
21782 a list of identifiers separated by space or HT characters.
21783 A comment is an Ada-style comment (from @code{--} to end-of-line).
21784 Identifiers must follow the Ada syntax for identifiers.
21785 A line containing one or more identifiers may end with a comment.
21787 @node Non_Qualified_Aggregates
21788 @subsection @code{Non_Qualified_Aggregates}
21789 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
21792 Flag each non-qualified aggregate.
21793 A non-qualified aggregate is an
21794 aggregate that is not the expression of a qualified expression. A
21795 string literal is not considered an aggregate, but an array
21796 aggregate of a string type is considered as a normal aggregate.
21797 Aggregates of anonymous array types are not flagged.
21799 This rule has no parameters.
21802 @node Non_Short_Circuit_Operators
21803 @subsection @code{Non_Short_Circuit_Operators}
21804 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
21807 Flag all calls to predefined @code{and} and @code{or} operators for
21808 any boolean type. Calls to
21809 user-defined @code{and} and @code{or} and to operators defined by renaming
21810 declarations are not flagged. Calls to predefined @code{and} and @code{or}
21811 operators for modular types or boolean array types are not flagged.
21813 This rule has no parameters.
21817 @node Non_SPARK_Attributes
21818 @subsection @code{Non_SPARK_Attributes}
21819 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
21822 The SPARK language defines the following subset of Ada 95 attribute
21823 designators as those that can be used in SPARK programs. The use of
21824 any other attribute is flagged.
21827 @item @code{'Adjacent}
21830 @item @code{'Ceiling}
21831 @item @code{'Component_Size}
21832 @item @code{'Compose}
21833 @item @code{'Copy_Sign}
21834 @item @code{'Delta}
21835 @item @code{'Denorm}
21836 @item @code{'Digits}
21837 @item @code{'Exponent}
21838 @item @code{'First}
21839 @item @code{'Floor}
21841 @item @code{'Fraction}
21843 @item @code{'Leading_Part}
21844 @item @code{'Length}
21845 @item @code{'Machine}
21846 @item @code{'Machine_Emax}
21847 @item @code{'Machine_Emin}
21848 @item @code{'Machine_Mantissa}
21849 @item @code{'Machine_Overflows}
21850 @item @code{'Machine_Radix}
21851 @item @code{'Machine_Rounds}
21854 @item @code{'Model}
21855 @item @code{'Model_Emin}
21856 @item @code{'Model_Epsilon}
21857 @item @code{'Model_Mantissa}
21858 @item @code{'Model_Small}
21859 @item @code{'Modulus}
21862 @item @code{'Range}
21863 @item @code{'Remainder}
21864 @item @code{'Rounding}
21865 @item @code{'Safe_First}
21866 @item @code{'Safe_Last}
21867 @item @code{'Scaling}
21868 @item @code{'Signed_Zeros}
21870 @item @code{'Small}
21872 @item @code{'Truncation}
21873 @item @code{'Unbiased_Rounding}
21875 @item @code{'Valid}
21879 This rule has no parameters.
21882 @node Non_Tagged_Derived_Types
21883 @subsection @code{Non_Tagged_Derived_Types}
21884 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
21887 Flag all derived type declarations that do not have a record extension part.
21889 This rule has no parameters.
21893 @node Non_Visible_Exceptions
21894 @subsection @code{Non_Visible_Exceptions}
21895 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
21898 Flag constructs leading to the possibility of propagating an exception
21899 out of the scope in which the exception is declared.
21900 Two cases are detected:
21904 An exception declaration in a subprogram body, task body or block
21905 statement is flagged if the body or statement does not contain a handler for
21906 that exception or a handler with an @code{others} choice.
21909 A @code{raise} statement in an exception handler of a subprogram body,
21910 task body or block statement is flagged if it (re)raises a locally
21911 declared exception. This may occur under the following circumstances:
21914 it explicitly raises a locally declared exception, or
21916 it does not specify an exception name (i.e., it is simply @code{raise;})
21917 and the enclosing handler contains a locally declared exception in its
21923 Renamings of local exceptions are not flagged.
21925 This rule has no parameters.
21928 @node Numeric_Literals
21929 @subsection @code{Numeric_Literals}
21930 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
21933 Flag each use of a numeric literal in an index expression, and in any
21934 circumstance except for the following:
21938 a literal occurring in the initialization expression for a constant
21939 declaration or a named number declaration, or
21942 an integer literal that is less than or equal to a value
21943 specified by the @option{N} rule parameter.
21947 This rule may have the following parameters for the @option{+R} option:
21951 @emph{N} is an integer literal used as the maximal value that is not flagged
21952 (i.e., integer literals not exceeding this value are allowed)
21955 All integer literals are flagged
21959 If no parameters are set, the maximum unflagged value is 1.
21961 The last specified check limit (or the fact that there is no limit at
21962 all) is used when multiple @option{+R} options appear.
21964 The @option{-R} option for this rule has no parameters.
21965 It disables the rule but retains the last specified maximum unflagged value.
21966 If the @option{+R} option subsequently appears, this value is used as the
21967 threshold for the check.
21970 @node OTHERS_In_Aggregates
21971 @subsection @code{OTHERS_In_Aggregates}
21972 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
21975 Flag each use of an @code{others} choice in extension aggregates.
21976 In record and array aggregates, an @code{others} choice is flagged unless
21977 it is used to refer to all components, or to all but one component.
21979 If, in case of a named array aggregate, there are two associations, one
21980 with an @code{others} choice and another with a discrete range, the
21981 @code{others} choice is flagged even if the discrete range specifies
21982 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
21984 This rule has no parameters.
21986 @node OTHERS_In_CASE_Statements
21987 @subsection @code{OTHERS_In_CASE_Statements}
21988 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
21991 Flag any use of an @code{others} choice in a @code{case} statement.
21993 This rule has no parameters.
21995 @node OTHERS_In_Exception_Handlers
21996 @subsection @code{OTHERS_In_Exception_Handlers}
21997 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
22000 Flag any use of an @code{others} choice in an exception handler.
22002 This rule has no parameters.
22005 @node Outer_Loop_Exits
22006 @subsection @code{Outer_Loop_Exits}
22007 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
22010 Flag each @code{exit} statement containing a loop name that is not the name
22011 of the immediately enclosing @code{loop} statement.
22013 This rule has no parameters.
22016 @node Overloaded_Operators
22017 @subsection @code{Overloaded_Operators}
22018 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
22021 Flag each function declaration that overloads an operator symbol.
22022 A function body is checked only if the body does not have a
22023 separate spec. Formal functions are also checked. For a
22024 renaming declaration, only renaming-as-declaration is checked
22026 This rule has no parameters.
22029 @node Overly_Nested_Control_Structures
22030 @subsection @code{Overly_Nested_Control_Structures}
22031 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
22034 Flag each control structure whose nesting level exceeds the value provided
22035 in the rule parameter.
22037 The control structures checked are the following:
22040 @item @code{if} statement
22041 @item @code{case} statement
22042 @item @code{loop} statement
22043 @item Selective accept statement
22044 @item Timed entry call statement
22045 @item Conditional entry call
22046 @item Asynchronous select statement
22050 The rule has the following parameter for the @option{+R} option:
22054 Positive integer specifying the maximal control structure nesting
22055 level that is not flagged
22059 If the parameter for the @option{+R} option is not specified or
22060 if it is not a positive integer, @option{+R} option is ignored.
22062 If more then one option is specified for the gnatcheck call, the later option and
22063 new parameter override the previous one(s).
22066 @node Parameters_Out_Of_Order
22067 @subsection @code{Parameters_Out_Of_Order}
22068 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
22071 Flag each subprogram and entry declaration whose formal parameters are not
22072 ordered according to the following scheme:
22076 @item @code{in} and @code{access} parameters first,
22077 then @code{in out} parameters,
22078 and then @code{out} parameters;
22080 @item for @code{in} mode, parameters with default initialization expressions
22085 Only the first violation of the described order is flagged.
22087 The following constructs are checked:
22090 @item subprogram declarations (including null procedures);
22091 @item generic subprogram declarations;
22092 @item formal subprogram declarations;
22093 @item entry declarations;
22094 @item subprogram bodies and subprogram body stubs that do not
22095 have separate specifications
22099 Subprogram renamings are not checked.
22101 This rule has no parameters.
22104 @node Positional_Actuals_For_Defaulted_Generic_Parameters
22105 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
22106 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
22109 Flag each generic actual parameter corresponding to a generic formal
22110 parameter with a default initialization, if positional notation is used.
22112 This rule has no parameters.
22114 @node Positional_Actuals_For_Defaulted_Parameters
22115 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
22116 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
22119 Flag each actual parameter to a subprogram or entry call where the
22120 corresponding formal parameter has a default expression, if positional
22123 This rule has no parameters.
22125 @node Positional_Components
22126 @subsection @code{Positional_Components}
22127 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
22130 Flag each array, record and extension aggregate that includes positional
22133 This rule has no parameters.
22136 @node Positional_Generic_Parameters
22137 @subsection @code{Positional_Generic_Parameters}
22138 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
22141 Flag each instantiation using positional parameter notation.
22143 This rule has no parameters.
22146 @node Positional_Parameters
22147 @subsection @code{Positional_Parameters}
22148 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
22151 Flag each subprogram or entry call using positional parameter notation,
22152 except for the following:
22156 Invocations of prefix or infix operators are not flagged
22158 If the called subprogram or entry has only one formal parameter,
22159 the call is not flagged;
22161 If a subprogram call uses the @emph{Object.Operation} notation, then
22164 the first parameter (that is, @emph{Object}) is not flagged;
22166 if the called subprogram has only two parameters, the second parameter
22167 of the call is not flagged;
22172 This rule has no parameters.
22177 @node Predefined_Numeric_Types
22178 @subsection @code{Predefined_Numeric_Types}
22179 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
22182 Flag each explicit use of the name of any numeric type or subtype defined
22183 in package @code{Standard}.
22185 The rationale for this rule is to detect when the
22186 program may depend on platform-specific characteristics of the implementation
22187 of the predefined numeric types. Note that this rule is over-pessimistic;
22188 for example, a program that uses @code{String} indexing
22189 likely needs a variable of type @code{Integer}.
22190 Another example is the flagging of predefined numeric types with explicit
22193 @smallexample @c ada
22194 subtype My_Integer is Integer range Left .. Right;
22195 Vy_Var : My_Integer;
22199 This rule detects only numeric types and subtypes defined in
22200 @code{Standard}. The use of numeric types and subtypes defined in other
22201 predefined packages (such as @code{System.Any_Priority} or
22202 @code{Ada.Text_IO.Count}) is not flagged
22204 This rule has no parameters.
22208 @node Raising_External_Exceptions
22209 @subsection @code{Raising_External_Exceptions}
22210 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
22213 Flag any @code{raise} statement, in a program unit declared in a library
22214 package or in a generic library package, for an exception that is
22215 neither a predefined exception nor an exception that is also declared (or
22216 renamed) in the visible part of the package.
22218 This rule has no parameters.
22222 @node Raising_Predefined_Exceptions
22223 @subsection @code{Raising_Predefined_Exceptions}
22224 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
22227 Flag each @code{raise} statement that raises a predefined exception
22228 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
22229 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
22231 This rule has no parameters.
22233 @node Separate_Numeric_Error_Handlers
22234 @subsection @code{Separate_Numeric_Error_Handlers}
22235 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
22238 Flags each exception handler that contains a choice for
22239 the predefined @code{Constraint_Error} exception, but does not contain
22240 the choice for the predefined @code{Numeric_Error} exception, or
22241 that contains the choice for @code{Numeric_Error}, but does not contain the
22242 choice for @code{Constraint_Error}.
22244 This rule has no parameters.
22248 @subsection @code{Recursion} (under construction, GLOBAL)
22249 @cindex @code{Recursion} rule (for @command{gnatcheck})
22252 Flag recursive subprograms (cycles in the call graph). Declarations, and not
22253 calls, of recursive subprograms are detected.
22255 This rule has no parameters.
22259 @node Side_Effect_Functions
22260 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
22261 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
22264 Flag functions with side effects.
22266 We define a side effect as changing any data object that is not local for the
22267 body of this function.
22269 At the moment, we do NOT consider a side effect any input-output operations
22270 (changing a state or a content of any file).
22272 We do not consider protected functions for this rule (???)
22274 There are the following sources of side effect:
22277 @item Explicit (or direct) side-effect:
22281 direct assignment to a non-local variable;
22284 direct call to an entity that is known to change some data object that is
22285 not local for the body of this function (Note, that if F1 calls F2 and F2
22286 does have a side effect, this does not automatically mean that F1 also
22287 have a side effect, because it may be the case that F2 is declared in
22288 F1's body and it changes some data object that is global for F2, but
22292 @item Indirect side-effect:
22295 Subprogram calls implicitly issued by:
22298 computing initialization expressions from type declarations as a part
22299 of object elaboration or allocator evaluation;
22301 computing implicit parameters of subprogram or entry calls or generic
22306 activation of a task that change some non-local data object (directly or
22310 elaboration code of a package that is a result of a package instantiation;
22313 controlled objects;
22316 @item Situations when we can suspect a side-effect, but the full static check
22317 is either impossible or too hard:
22320 assignment to access variables or to the objects pointed by access
22324 call to a subprogram pointed by access-to-subprogram value
22332 This rule has no parameters.
22336 @subsection @code{Slices}
22337 @cindex @code{Slices} rule (for @command{gnatcheck})
22340 Flag all uses of array slicing
22342 This rule has no parameters.
22345 @node Unassigned_OUT_Parameters
22346 @subsection @code{Unassigned_OUT_Parameters}
22347 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
22350 Flags procedures' @code{out} parameters that are not assigned, and
22351 identifies the contexts in which the assignments are missing.
22353 An @code{out} parameter is flagged in the statements in the procedure
22354 body's handled sequence of statements (before the procedure body's
22355 @code{exception} part, if any) if this sequence of statements contains
22356 no assignments to the parameter.
22358 An @code{out} parameter is flagged in an exception handler in the exception
22359 part of the procedure body's handled sequence of statements if the handler
22360 contains no assignment to the parameter.
22362 Bodies of generic procedures are also considered.
22364 The following are treated as assignments to an @code{out} parameter:
22368 an assignment statement, with the parameter or some component as the target;
22371 passing the parameter (or one of its components) as an @code{out} or
22372 @code{in out} parameter.
22376 This rule does not have any parameters.
22380 @node Uncommented_BEGIN_In_Package_Bodies
22381 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
22382 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
22385 Flags each package body with declarations and a statement part that does not
22386 include a trailing comment on the line containing the @code{begin} keyword;
22387 this trailing comment needs to specify the package name and nothing else.
22388 The @code{begin} is not flagged if the package body does not
22389 contain any declarations.
22391 If the @code{begin} keyword is placed on the
22392 same line as the last declaration or the first statement, it is flagged
22393 independently of whether the line contains a trailing comment. The
22394 diagnostic message is attached to the line containing the first statement.
22396 This rule has no parameters.
22398 @node Unconditional_Exits
22399 @subsection @code{Unconditional_Exits}
22400 @cindex @code{Unconditional_Exits} rule (for @command{gnatcheck})
22403 Flag unconditional @code{exit} statements.
22405 This rule has no parameters.
22407 @node Unconstrained_Array_Returns
22408 @subsection @code{Unconstrained_Array_Returns}
22409 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
22412 Flag each function returning an unconstrained array. Function declarations,
22413 function bodies (and body stubs) having no separate specifications,
22414 and generic function instantiations are checked.
22415 Generic function declarations, function calls and function renamings are
22418 This rule has no parameters.
22420 @node Universal_Ranges
22421 @subsection @code{Universal_Ranges}
22422 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
22425 Flag discrete ranges that are a part of an index constraint, constrained
22426 array definition, or @code{for}-loop parameter specification, and whose bounds
22427 are both of type @i{universal_integer}. Ranges that have at least one
22428 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
22429 or an expression of non-universal type) are not flagged.
22431 This rule has no parameters.
22434 @node Unnamed_Blocks_And_Loops
22435 @subsection @code{Unnamed_Blocks_And_Loops}
22436 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
22439 Flag each unnamed block statement and loop statement.
22441 The rule has no parameters.
22446 @node Unused_Subprograms
22447 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
22448 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
22451 Flag all unused subprograms.
22453 This rule has no parameters.
22459 @node USE_PACKAGE_Clauses
22460 @subsection @code{USE_PACKAGE_Clauses}
22461 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
22464 Flag all @code{use} clauses for packages; @code{use type} clauses are
22467 This rule has no parameters.
22471 @node Volatile_Objects_Without_Address_Clauses
22472 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22473 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22476 Flag each volatile object that does not have an address clause.
22478 The following check is made: if the pragma @code{Volatile} is applied to a
22479 data object or to its type, then an address clause must
22480 be supplied for this object.
22482 This rule does not check the components of data objects,
22483 array components that are volatile as a result of the pragma
22484 @code{Volatile_Components}, or objects that are volatile because
22485 they are atomic as a result of pragmas @code{Atomic} or
22486 @code{Atomic_Components}.
22488 Only variable declarations, and not constant declarations, are checked.
22490 This rule has no parameters.
22493 @c *********************************
22494 @node Creating Sample Bodies Using gnatstub
22495 @chapter Creating Sample Bodies Using @command{gnatstub}
22499 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22500 for library unit declarations.
22502 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22503 driver (see @ref{The GNAT Driver and Project Files}).
22505 To create a body stub, @command{gnatstub} has to compile the library
22506 unit declaration. Therefore, bodies can be created only for legal
22507 library units. Moreover, if a library unit depends semantically upon
22508 units located outside the current directory, you have to provide
22509 the source search path when calling @command{gnatstub}, see the description
22510 of @command{gnatstub} switches below.
22512 By default, all the program unit body stubs generated by @code{gnatstub}
22513 raise the predefined @code{Program_Error} exception, which will catch
22514 accidental calls of generated stubs. This behavior can be changed with
22515 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
22518 * Running gnatstub::
22519 * Switches for gnatstub::
22522 @node Running gnatstub
22523 @section Running @command{gnatstub}
22526 @command{gnatstub} has the command-line interface of the form
22529 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22536 is the name of the source file that contains a library unit declaration
22537 for which a body must be created. The file name may contain the path
22539 The file name does not have to follow the GNAT file name conventions. If the
22541 does not follow GNAT file naming conventions, the name of the body file must
22543 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22544 If the file name follows the GNAT file naming
22545 conventions and the name of the body file is not provided,
22548 of the body file from the argument file name by replacing the @file{.ads}
22550 with the @file{.adb} suffix.
22553 indicates the directory in which the body stub is to be placed (the default
22558 is an optional sequence of switches as described in the next section
22561 @node Switches for gnatstub
22562 @section Switches for @command{gnatstub}
22568 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22569 If the destination directory already contains a file with the name of the
22571 for the argument spec file, replace it with the generated body stub.
22573 @item ^-hs^/HEADER=SPEC^
22574 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22575 Put the comment header (i.e., all the comments preceding the
22576 compilation unit) from the source of the library unit declaration
22577 into the body stub.
22579 @item ^-hg^/HEADER=GENERAL^
22580 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22581 Put a sample comment header into the body stub.
22583 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22584 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22585 Use the content of the file as the comment header for a generated body stub.
22589 @cindex @option{-IDIR} (@command{gnatstub})
22591 @cindex @option{-I-} (@command{gnatstub})
22594 @item /NOCURRENT_DIRECTORY
22595 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22597 ^These switches have ^This switch has^ the same meaning as in calls to
22599 ^They define ^It defines ^ the source search path in the call to
22600 @command{gcc} issued
22601 by @command{gnatstub} to compile an argument source file.
22603 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22604 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22605 This switch has the same meaning as in calls to @command{gcc}.
22606 It defines the additional configuration file to be passed to the call to
22607 @command{gcc} issued
22608 by @command{gnatstub} to compile an argument source file.
22610 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22611 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22612 (@var{n} is a non-negative integer). Set the maximum line length in the
22613 body stub to @var{n}; the default is 79. The maximum value that can be
22614 specified is 32767. Note that in the special case of configuration
22615 pragma files, the maximum is always 32767 regardless of whether or
22616 not this switch appears.
22618 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22619 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22620 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22621 the generated body sample to @var{n}.
22622 The default indentation is 3.
22624 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22625 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22626 Order local bodies alphabetically. (By default local bodies are ordered
22627 in the same way as the corresponding local specs in the argument spec file.)
22629 @item ^-i^/INDENTATION=^@var{n}
22630 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22631 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22633 @item ^-k^/TREE_FILE=SAVE^
22634 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22635 Do not remove the tree file (i.e., the snapshot of the compiler internal
22636 structures used by @command{gnatstub}) after creating the body stub.
22638 @item ^-l^/LINE_LENGTH=^@var{n}
22639 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22640 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22642 @item ^--no-exception^/NO_EXCEPTION^
22643 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
22644 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
22645 This is not always possible for function stubs.
22647 @item ^--no-local-header^/NO_LOCAL_HEADER^
22648 @cindex @option{^--no-local-header^/NO_LOCAL_HEADER^} (@command{gnatstub})
22649 Do not place local comment header with unit name before body stub for a
22652 @item ^-o ^/BODY=^@var{body-name}
22653 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22654 Body file name. This should be set if the argument file name does not
22656 the GNAT file naming
22657 conventions. If this switch is omitted the default name for the body will be
22659 from the argument file name according to the GNAT file naming conventions.
22662 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22663 Quiet mode: do not generate a confirmation when a body is
22664 successfully created, and do not generate a message when a body is not
22668 @item ^-r^/TREE_FILE=REUSE^
22669 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22670 Reuse the tree file (if it exists) instead of creating it. Instead of
22671 creating the tree file for the library unit declaration, @command{gnatstub}
22672 tries to find it in the current directory and use it for creating
22673 a body. If the tree file is not found, no body is created. This option
22674 also implies @option{^-k^/SAVE^}, whether or not
22675 the latter is set explicitly.
22677 @item ^-t^/TREE_FILE=OVERWRITE^
22678 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22679 Overwrite the existing tree file. If the current directory already
22680 contains the file which, according to the GNAT file naming rules should
22681 be considered as a tree file for the argument source file,
22683 will refuse to create the tree file needed to create a sample body
22684 unless this option is set.
22686 @item ^-v^/VERBOSE^
22687 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22688 Verbose mode: generate version information.
22692 @c *********************************
22693 @node Generating Ada Bindings for C and C++ headers
22694 @chapter Generating Ada Bindings for C and C++ headers
22698 GNAT now comes with a new experimental binding generator for C and C++
22699 headers which is intended to do 95% of the tedious work of generating
22700 Ada specs from C or C++ header files. Note that this still is a work in
22701 progress, not designed to generate 100% correct Ada specs.
22703 The code generated is using the Ada 2005 syntax, which makes it
22704 easier to interface with other languages than previous versions of Ada.
22707 * Running the binding generator::
22708 * Generating bindings for C++ headers::
22712 @node Running the binding generator
22713 @section Running the binding generator
22716 The binding generator is part of the @command{gcc} compiler and can be
22717 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
22718 spec files for the header files specified on the command line, and all
22719 header files needed by these files transitivitely. For example:
22722 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
22723 $ gcc -c -gnat05 *.ads
22726 will generate, under GNU/Linux, the following files: @file{time_h.ads},
22727 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
22728 correspond to the files @file{/usr/include/time.h},
22729 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
22730 mode these Ada specs.
22732 The @code{-C} switch tells @command{gcc} to extract comments from headers,
22733 and will attempt to generate corresponding Ada comments.
22735 If you want to generate a single Ada file and not the transitive closure, you
22736 can use instead the @option{-fdump-ada-spec-slim} switch.
22738 Note that we recommend when possible to use the @command{g++} driver to
22739 generate bindings, even for most C headers, since this will in general
22740 generate better Ada specs. For generating bindings for C++ headers, it is
22741 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
22742 is equivalent in this case. If @command{g++} cannot work on your C headers
22743 because of incompatibilities between C and C++, then you can fallback to
22744 @command{gcc} instead.
22746 For an example of better bindings generated from the C++ front-end,
22747 the name of the parameters (when available) are actually ignored by the C
22748 front-end. Consider the following C header:
22751 extern void foo (int variable);
22754 with the C front-end, @code{variable} is ignored, and the above is handled as:
22757 extern void foo (int);
22760 generating a generic:
22763 procedure foo (param1 : int);
22766 with the C++ front-end, the name is available, and we generate:
22769 procedure foo (variable : int);
22772 In some cases, the generated bindings will be more complete or more meaningful
22773 when defining some macros, which you can do via the @option{-D} switch. This
22774 is for example the case with @file{Xlib.h} under GNU/Linux:
22777 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
22780 The above will generate more complete bindings than a straight call without
22781 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
22783 In other cases, it is not possible to parse a header file in a stand alone
22784 manner, because other include files need to be included first. In this
22785 case, the solution is to create a small header file including the needed
22786 @code{#include} and possible @code{#define} directives. For example, to
22787 generate Ada bindings for @file{readline/readline.h}, you need to first
22788 include @file{stdio.h}, so you can create a file with the following two
22789 lines in e.g. @file{readline1.h}:
22793 #include <readline/readline.h>
22796 and then generate Ada bindings from this file:
22799 $ g++ -c -fdump-ada-spec readline1.h
22802 @node Generating bindings for C++ headers
22803 @section Generating bindings for C++ headers
22806 Generating bindings for C++ headers is done using the same options, always
22807 with the @command{g++} compiler.
22809 In this mode, C++ classes will be mapped to Ada tagged types, constructors
22810 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
22811 multiple inheritance of abstract classes will be mapped to Ada interfaces
22812 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
22813 information on interfacing to C++).
22815 For example, given the following C++ header file:
22822 virtual int Number_Of_Teeth () = 0;
22827 virtual void Set_Owner (char* Name) = 0;
22833 virtual void Set_Age (int New_Age);
22836 class Dog : Animal, Carnivore, Domestic @{
22841 virtual int Number_Of_Teeth ();
22842 virtual void Set_Owner (char* Name);
22850 The corresponding Ada code is generated:
22852 @smallexample @c ada
22855 package Class_Carnivore is
22856 type Carnivore is limited interface;
22857 pragma Import (CPP, Carnivore);
22859 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
22861 use Class_Carnivore;
22863 package Class_Domestic is
22864 type Domestic is limited interface;
22865 pragma Import (CPP, Domestic);
22867 procedure Set_Owner
22868 (this : access Domestic;
22869 Name : Interfaces.C.Strings.chars_ptr) is abstract;
22871 use Class_Domestic;
22873 package Class_Animal is
22874 type Animal is tagged limited record
22875 Age_Count : aliased int;
22877 pragma Import (CPP, Animal);
22879 procedure Set_Age (this : access Animal; New_Age : int);
22880 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
22884 package Class_Dog is
22885 type Dog is new Animal and Carnivore and Domestic with record
22886 Tooth_Count : aliased int;
22887 Owner : Interfaces.C.Strings.chars_ptr;
22889 pragma Import (CPP, Dog);
22891 function Number_Of_Teeth (this : access Dog) return int;
22892 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
22894 procedure Set_Owner
22895 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
22896 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
22898 function New_Dog return Dog;
22899 pragma CPP_Constructor (New_Dog);
22900 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
22911 @item -fdump-ada-spec
22912 @cindex @option{-fdump-ada-spec} (@command{gcc})
22913 Generate Ada spec files for the given header files transitively (including
22914 all header files that these headers depend upon).
22916 @item -fdump-ada-spec-slim
22917 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
22918 Generate Ada spec files for the header files specified on the command line
22922 @cindex @option{-C} (@command{gcc})
22923 Extract comments from headers and generate Ada comments in the Ada spec files.
22926 @node Other Utility Programs
22927 @chapter Other Utility Programs
22930 This chapter discusses some other utility programs available in the Ada
22934 * Using Other Utility Programs with GNAT::
22935 * The External Symbol Naming Scheme of GNAT::
22936 * Converting Ada Files to html with gnathtml::
22937 * Installing gnathtml::
22944 @node Using Other Utility Programs with GNAT
22945 @section Using Other Utility Programs with GNAT
22948 The object files generated by GNAT are in standard system format and in
22949 particular the debugging information uses this format. This means
22950 programs generated by GNAT can be used with existing utilities that
22951 depend on these formats.
22954 In general, any utility program that works with C will also often work with
22955 Ada programs generated by GNAT. This includes software utilities such as
22956 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
22960 @node The External Symbol Naming Scheme of GNAT
22961 @section The External Symbol Naming Scheme of GNAT
22964 In order to interpret the output from GNAT, when using tools that are
22965 originally intended for use with other languages, it is useful to
22966 understand the conventions used to generate link names from the Ada
22969 All link names are in all lowercase letters. With the exception of library
22970 procedure names, the mechanism used is simply to use the full expanded
22971 Ada name with dots replaced by double underscores. For example, suppose
22972 we have the following package spec:
22974 @smallexample @c ada
22985 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
22986 the corresponding link name is @code{qrs__mn}.
22988 Of course if a @code{pragma Export} is used this may be overridden:
22990 @smallexample @c ada
22995 pragma Export (Var1, C, External_Name => "var1_name");
22997 pragma Export (Var2, C, Link_Name => "var2_link_name");
23004 In this case, the link name for @var{Var1} is whatever link name the
23005 C compiler would assign for the C function @var{var1_name}. This typically
23006 would be either @var{var1_name} or @var{_var1_name}, depending on operating
23007 system conventions, but other possibilities exist. The link name for
23008 @var{Var2} is @var{var2_link_name}, and this is not operating system
23012 One exception occurs for library level procedures. A potential ambiguity
23013 arises between the required name @code{_main} for the C main program,
23014 and the name we would otherwise assign to an Ada library level procedure
23015 called @code{Main} (which might well not be the main program).
23017 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
23018 names. So if we have a library level procedure such as
23020 @smallexample @c ada
23023 procedure Hello (S : String);
23029 the external name of this procedure will be @var{_ada_hello}.
23032 @node Converting Ada Files to html with gnathtml
23033 @section Converting Ada Files to HTML with @code{gnathtml}
23036 This @code{Perl} script allows Ada source files to be browsed using
23037 standard Web browsers. For installation procedure, see the section
23038 @xref{Installing gnathtml}.
23040 Ada reserved keywords are highlighted in a bold font and Ada comments in
23041 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
23042 switch to suppress the generation of cross-referencing information, user
23043 defined variables and types will appear in a different color; you will
23044 be able to click on any identifier and go to its declaration.
23046 The command line is as follow:
23048 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
23052 You can pass it as many Ada files as you want. @code{gnathtml} will generate
23053 an html file for every ada file, and a global file called @file{index.htm}.
23054 This file is an index of every identifier defined in the files.
23056 The available ^switches^options^ are the following ones:
23060 @cindex @option{-83} (@code{gnathtml})
23061 Only the Ada 83 subset of keywords will be highlighted.
23063 @item -cc @var{color}
23064 @cindex @option{-cc} (@code{gnathtml})
23065 This option allows you to change the color used for comments. The default
23066 value is green. The color argument can be any name accepted by html.
23069 @cindex @option{-d} (@code{gnathtml})
23070 If the Ada files depend on some other files (for instance through
23071 @code{with} clauses, the latter files will also be converted to html.
23072 Only the files in the user project will be converted to html, not the files
23073 in the run-time library itself.
23076 @cindex @option{-D} (@code{gnathtml})
23077 This command is the same as @option{-d} above, but @command{gnathtml} will
23078 also look for files in the run-time library, and generate html files for them.
23080 @item -ext @var{extension}
23081 @cindex @option{-ext} (@code{gnathtml})
23082 This option allows you to change the extension of the generated HTML files.
23083 If you do not specify an extension, it will default to @file{htm}.
23086 @cindex @option{-f} (@code{gnathtml})
23087 By default, gnathtml will generate html links only for global entities
23088 ('with'ed units, global variables and types,@dots{}). If you specify
23089 @option{-f} on the command line, then links will be generated for local
23092 @item -l @var{number}
23093 @cindex @option{-l} (@code{gnathtml})
23094 If this ^switch^option^ is provided and @var{number} is not 0, then
23095 @code{gnathtml} will number the html files every @var{number} line.
23098 @cindex @option{-I} (@code{gnathtml})
23099 Specify a directory to search for library files (@file{.ALI} files) and
23100 source files. You can provide several -I switches on the command line,
23101 and the directories will be parsed in the order of the command line.
23104 @cindex @option{-o} (@code{gnathtml})
23105 Specify the output directory for html files. By default, gnathtml will
23106 saved the generated html files in a subdirectory named @file{html/}.
23108 @item -p @var{file}
23109 @cindex @option{-p} (@code{gnathtml})
23110 If you are using Emacs and the most recent Emacs Ada mode, which provides
23111 a full Integrated Development Environment for compiling, checking,
23112 running and debugging applications, you may use @file{.gpr} files
23113 to give the directories where Emacs can find sources and object files.
23115 Using this ^switch^option^, you can tell gnathtml to use these files.
23116 This allows you to get an html version of your application, even if it
23117 is spread over multiple directories.
23119 @item -sc @var{color}
23120 @cindex @option{-sc} (@code{gnathtml})
23121 This ^switch^option^ allows you to change the color used for symbol
23123 The default value is red. The color argument can be any name accepted by html.
23125 @item -t @var{file}
23126 @cindex @option{-t} (@code{gnathtml})
23127 This ^switch^option^ provides the name of a file. This file contains a list of
23128 file names to be converted, and the effect is exactly as though they had
23129 appeared explicitly on the command line. This
23130 is the recommended way to work around the command line length limit on some
23135 @node Installing gnathtml
23136 @section Installing @code{gnathtml}
23139 @code{Perl} needs to be installed on your machine to run this script.
23140 @code{Perl} is freely available for almost every architecture and
23141 Operating System via the Internet.
23143 On Unix systems, you may want to modify the first line of the script
23144 @code{gnathtml}, to explicitly tell the Operating system where Perl
23145 is. The syntax of this line is:
23147 #!full_path_name_to_perl
23151 Alternatively, you may run the script using the following command line:
23154 $ perl gnathtml.pl @ovar{switches} @var{files}
23163 The GNAT distribution provides an Ada 95 template for the HP Language
23164 Sensitive Editor (LSE), a component of DECset. In order to
23165 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
23172 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
23173 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
23174 the collection phase with the /DEBUG qualifier.
23177 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
23178 $ DEFINE LIB$DEBUG PCA$COLLECTOR
23179 $ RUN/DEBUG <PROGRAM_NAME>
23185 @c ******************************
23186 @node Code Coverage and Profiling
23187 @chapter Code Coverage and Profiling
23188 @cindex Code Coverage
23192 This chapter describes how to use @code{gcov} - coverage testing tool - and
23193 @code{gprof} - profiler tool - on your Ada programs.
23196 * Code Coverage of Ada Programs using gcov::
23197 * Profiling an Ada Program using gprof::
23200 @node Code Coverage of Ada Programs using gcov
23201 @section Code Coverage of Ada Programs using gcov
23203 @cindex -fprofile-arcs
23204 @cindex -ftest-coverage
23206 @cindex Code Coverage
23209 @code{gcov} is a test coverage program: it analyzes the execution of a given
23210 program on selected tests, to help you determine the portions of the program
23211 that are still untested.
23213 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
23214 User's Guide. You can refer to this documentation for a more complete
23217 This chapter provides a quick startup guide, and
23218 details some Gnat-specific features.
23221 * Quick startup guide::
23225 @node Quick startup guide
23226 @subsection Quick startup guide
23228 In order to perform coverage analysis of a program using @code{gcov}, 3
23233 Code instrumentation during the compilation process
23235 Execution of the instrumented program
23237 Execution of the @code{gcov} tool to generate the result.
23240 The code instrumentation needed by gcov is created at the object level:
23241 The source code is not modified in any way, because the instrumentation code is
23242 inserted by gcc during the compilation process. To compile your code with code
23243 coverage activated, you need to recompile your whole project using the
23245 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
23246 @code{-fprofile-arcs}.
23249 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
23250 -largs -fprofile-arcs
23253 This compilation process will create @file{.gcno} files together with
23254 the usual object files.
23256 Once the program is compiled with coverage instrumentation, you can
23257 run it as many times as needed - on portions of a test suite for
23258 example. The first execution will produce @file{.gcda} files at the
23259 same location as the @file{.gcno} files. The following executions
23260 will update those files, so that a cumulative result of the covered
23261 portions of the program is generated.
23263 Finally, you need to call the @code{gcov} tool. The different options of
23264 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
23266 This will create annotated source files with a @file{.gcov} extension:
23267 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
23269 @node Gnat specifics
23270 @subsection Gnat specifics
23272 Because Ada semantics, portions of the source code may be shared among
23273 several object files. This is the case for example when generics are
23274 involved, when inlining is active or when declarations generate initialisation
23275 calls. In order to take
23276 into account this shared code, you need to call @code{gcov} on all
23277 source files of the tested program at once.
23279 The list of source files might exceed the system's maximum command line
23280 length. In order to bypass this limitation, a new mechanism has been
23281 implemented in @code{gcov}: you can now list all your project's files into a
23282 text file, and provide this file to gcov as a parameter, preceded by a @@
23283 (e.g. @samp{gcov @@mysrclist.txt}).
23285 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
23286 not supported as there can be unresolved symbols during the final link.
23288 @node Profiling an Ada Program using gprof
23289 @section Profiling an Ada Program using gprof
23295 This section is not meant to be an exhaustive documentation of @code{gprof}.
23296 Full documentation for it can be found in the GNU Profiler User's Guide
23297 documentation that is part of this GNAT distribution.
23299 Profiling a program helps determine the parts of a program that are executed
23300 most often, and are therefore the most time-consuming.
23302 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
23303 better handle Ada programs and multitasking.
23304 It is currently supported on the following platforms
23309 solaris sparc/sparc64/x86
23315 In order to profile a program using @code{gprof}, 3 steps are needed:
23319 Code instrumentation, requiring a full recompilation of the project with the
23322 Execution of the program under the analysis conditions, i.e. with the desired
23325 Analysis of the results using the @code{gprof} tool.
23329 The following sections detail the different steps, and indicate how
23330 to interpret the results:
23332 * Compilation for profiling::
23333 * Program execution::
23335 * Interpretation of profiling results::
23338 @node Compilation for profiling
23339 @subsection Compilation for profiling
23343 In order to profile a program the first step is to tell the compiler
23344 to generate the necessary profiling information. The compiler switch to be used
23345 is @code{-pg}, which must be added to other compilation switches. This
23346 switch needs to be specified both during compilation and link stages, and can
23347 be specified once when using gnatmake:
23350 gnatmake -f -pg -P my_project
23354 Note that only the objects that were compiled with the @samp{-pg} switch will be
23355 profiled; if you need to profile your whole project, use the
23356 @samp{-f} gnatmake switch to force full recompilation.
23358 @node Program execution
23359 @subsection Program execution
23362 Once the program has been compiled for profiling, you can run it as usual.
23364 The only constraint imposed by profiling is that the program must terminate
23365 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
23368 Once the program completes execution, a data file called @file{gmon.out} is
23369 generated in the directory where the program was launched from. If this file
23370 already exists, it will be overwritten.
23372 @node Running gprof
23373 @subsection Running gprof
23376 The @code{gprof} tool is called as follow:
23379 gprof my_prog gmon.out
23390 The complete form of the gprof command line is the following:
23393 gprof [^switches^options^] [executable [data-file]]
23397 @code{gprof} supports numerous ^switch^options^. The order of these
23398 ^switch^options^ does not matter. The full list of options can be found in
23399 the GNU Profiler User's Guide documentation that comes with this documentation.
23401 The following is the subset of those switches that is most relevant:
23405 @item --demangle[=@var{style}]
23406 @itemx --no-demangle
23407 @cindex @option{--demangle} (@code{gprof})
23408 These options control whether symbol names should be demangled when
23409 printing output. The default is to demangle C++ symbols. The
23410 @code{--no-demangle} option may be used to turn off demangling. Different
23411 compilers have different mangling styles. The optional demangling style
23412 argument can be used to choose an appropriate demangling style for your
23413 compiler, in particular Ada symbols generated by GNAT can be demangled using
23414 @code{--demangle=gnat}.
23416 @item -e @var{function_name}
23417 @cindex @option{-e} (@code{gprof})
23418 The @samp{-e @var{function}} option tells @code{gprof} not to print
23419 information about the function @var{function_name} (and its
23420 children@dots{}) in the call graph. The function will still be listed
23421 as a child of any functions that call it, but its index number will be
23422 shown as @samp{[not printed]}. More than one @samp{-e} option may be
23423 given; only one @var{function_name} may be indicated with each @samp{-e}
23426 @item -E @var{function_name}
23427 @cindex @option{-E} (@code{gprof})
23428 The @code{-E @var{function}} option works like the @code{-e} option, but
23429 execution time spent in the function (and children who were not called from
23430 anywhere else), will not be used to compute the percentages-of-time for
23431 the call graph. More than one @samp{-E} option may be given; only one
23432 @var{function_name} may be indicated with each @samp{-E} option.
23434 @item -f @var{function_name}
23435 @cindex @option{-f} (@code{gprof})
23436 The @samp{-f @var{function}} option causes @code{gprof} to limit the
23437 call graph to the function @var{function_name} and its children (and
23438 their children@dots{}). More than one @samp{-f} option may be given;
23439 only one @var{function_name} may be indicated with each @samp{-f}
23442 @item -F @var{function_name}
23443 @cindex @option{-F} (@code{gprof})
23444 The @samp{-F @var{function}} option works like the @code{-f} option, but
23445 only time spent in the function and its children (and their
23446 children@dots{}) will be used to determine total-time and
23447 percentages-of-time for the call graph. More than one @samp{-F} option
23448 may be given; only one @var{function_name} may be indicated with each
23449 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
23453 @node Interpretation of profiling results
23454 @subsection Interpretation of profiling results
23458 The results of the profiling analysis are represented by two arrays: the
23459 'flat profile' and the 'call graph'. Full documentation of those outputs
23460 can be found in the GNU Profiler User's Guide.
23462 The flat profile shows the time spent in each function of the program, and how
23463 many time it has been called. This allows you to locate easily the most
23464 time-consuming functions.
23466 The call graph shows, for each subprogram, the subprograms that call it,
23467 and the subprograms that it calls. It also provides an estimate of the time
23468 spent in each of those callers/called subprograms.
23471 @c ******************************
23472 @node Running and Debugging Ada Programs
23473 @chapter Running and Debugging Ada Programs
23477 This chapter discusses how to debug Ada programs.
23479 It applies to GNAT on the Alpha OpenVMS platform;
23480 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
23481 since HP has implemented Ada support in the OpenVMS debugger on I64.
23484 An incorrect Ada program may be handled in three ways by the GNAT compiler:
23488 The illegality may be a violation of the static semantics of Ada. In
23489 that case GNAT diagnoses the constructs in the program that are illegal.
23490 It is then a straightforward matter for the user to modify those parts of
23494 The illegality may be a violation of the dynamic semantics of Ada. In
23495 that case the program compiles and executes, but may generate incorrect
23496 results, or may terminate abnormally with some exception.
23499 When presented with a program that contains convoluted errors, GNAT
23500 itself may terminate abnormally without providing full diagnostics on
23501 the incorrect user program.
23505 * The GNAT Debugger GDB::
23507 * Introduction to GDB Commands::
23508 * Using Ada Expressions::
23509 * Calling User-Defined Subprograms::
23510 * Using the Next Command in a Function::
23513 * Debugging Generic Units::
23514 * GNAT Abnormal Termination or Failure to Terminate::
23515 * Naming Conventions for GNAT Source Files::
23516 * Getting Internal Debugging Information::
23517 * Stack Traceback::
23523 @node The GNAT Debugger GDB
23524 @section The GNAT Debugger GDB
23527 @code{GDB} is a general purpose, platform-independent debugger that
23528 can be used to debug mixed-language programs compiled with @command{gcc},
23529 and in particular is capable of debugging Ada programs compiled with
23530 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
23531 complex Ada data structures.
23533 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
23535 located in the GNU:[DOCS] directory,
23537 for full details on the usage of @code{GDB}, including a section on
23538 its usage on programs. This manual should be consulted for full
23539 details. The section that follows is a brief introduction to the
23540 philosophy and use of @code{GDB}.
23542 When GNAT programs are compiled, the compiler optionally writes debugging
23543 information into the generated object file, including information on
23544 line numbers, and on declared types and variables. This information is
23545 separate from the generated code. It makes the object files considerably
23546 larger, but it does not add to the size of the actual executable that
23547 will be loaded into memory, and has no impact on run-time performance. The
23548 generation of debug information is triggered by the use of the
23549 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
23550 used to carry out the compilations. It is important to emphasize that
23551 the use of these options does not change the generated code.
23553 The debugging information is written in standard system formats that
23554 are used by many tools, including debuggers and profilers. The format
23555 of the information is typically designed to describe C types and
23556 semantics, but GNAT implements a translation scheme which allows full
23557 details about Ada types and variables to be encoded into these
23558 standard C formats. Details of this encoding scheme may be found in
23559 the file exp_dbug.ads in the GNAT source distribution. However, the
23560 details of this encoding are, in general, of no interest to a user,
23561 since @code{GDB} automatically performs the necessary decoding.
23563 When a program is bound and linked, the debugging information is
23564 collected from the object files, and stored in the executable image of
23565 the program. Again, this process significantly increases the size of
23566 the generated executable file, but it does not increase the size of
23567 the executable program itself. Furthermore, if this program is run in
23568 the normal manner, it runs exactly as if the debug information were
23569 not present, and takes no more actual memory.
23571 However, if the program is run under control of @code{GDB}, the
23572 debugger is activated. The image of the program is loaded, at which
23573 point it is ready to run. If a run command is given, then the program
23574 will run exactly as it would have if @code{GDB} were not present. This
23575 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
23576 entirely non-intrusive until a breakpoint is encountered. If no
23577 breakpoint is ever hit, the program will run exactly as it would if no
23578 debugger were present. When a breakpoint is hit, @code{GDB} accesses
23579 the debugging information and can respond to user commands to inspect
23580 variables, and more generally to report on the state of execution.
23584 @section Running GDB
23587 This section describes how to initiate the debugger.
23588 @c The above sentence is really just filler, but it was otherwise
23589 @c clumsy to get the first paragraph nonindented given the conditional
23590 @c nature of the description
23593 The debugger can be launched from a @code{GPS} menu or
23594 directly from the command line. The description below covers the latter use.
23595 All the commands shown can be used in the @code{GPS} debug console window,
23596 but there are usually more GUI-based ways to achieve the same effect.
23599 The command to run @code{GDB} is
23602 $ ^gdb program^GDB PROGRAM^
23606 where @code{^program^PROGRAM^} is the name of the executable file. This
23607 activates the debugger and results in a prompt for debugger commands.
23608 The simplest command is simply @code{run}, which causes the program to run
23609 exactly as if the debugger were not present. The following section
23610 describes some of the additional commands that can be given to @code{GDB}.
23612 @c *******************************
23613 @node Introduction to GDB Commands
23614 @section Introduction to GDB Commands
23617 @code{GDB} contains a large repertoire of commands. @xref{Top,,
23618 Debugging with GDB, gdb, Debugging with GDB},
23620 located in the GNU:[DOCS] directory,
23622 for extensive documentation on the use
23623 of these commands, together with examples of their use. Furthermore,
23624 the command @command{help} invoked from within GDB activates a simple help
23625 facility which summarizes the available commands and their options.
23626 In this section we summarize a few of the most commonly
23627 used commands to give an idea of what @code{GDB} is about. You should create
23628 a simple program with debugging information and experiment with the use of
23629 these @code{GDB} commands on the program as you read through the
23633 @item set args @var{arguments}
23634 The @var{arguments} list above is a list of arguments to be passed to
23635 the program on a subsequent run command, just as though the arguments
23636 had been entered on a normal invocation of the program. The @code{set args}
23637 command is not needed if the program does not require arguments.
23640 The @code{run} command causes execution of the program to start from
23641 the beginning. If the program is already running, that is to say if
23642 you are currently positioned at a breakpoint, then a prompt will ask
23643 for confirmation that you want to abandon the current execution and
23646 @item breakpoint @var{location}
23647 The breakpoint command sets a breakpoint, that is to say a point at which
23648 execution will halt and @code{GDB} will await further
23649 commands. @var{location} is
23650 either a line number within a file, given in the format @code{file:linenumber},
23651 or it is the name of a subprogram. If you request that a breakpoint be set on
23652 a subprogram that is overloaded, a prompt will ask you to specify on which of
23653 those subprograms you want to breakpoint. You can also
23654 specify that all of them should be breakpointed. If the program is run
23655 and execution encounters the breakpoint, then the program
23656 stops and @code{GDB} signals that the breakpoint was encountered by
23657 printing the line of code before which the program is halted.
23659 @item breakpoint exception @var{name}
23660 A special form of the breakpoint command which breakpoints whenever
23661 exception @var{name} is raised.
23662 If @var{name} is omitted,
23663 then a breakpoint will occur when any exception is raised.
23665 @item print @var{expression}
23666 This will print the value of the given expression. Most simple
23667 Ada expression formats are properly handled by @code{GDB}, so the expression
23668 can contain function calls, variables, operators, and attribute references.
23671 Continues execution following a breakpoint, until the next breakpoint or the
23672 termination of the program.
23675 Executes a single line after a breakpoint. If the next statement
23676 is a subprogram call, execution continues into (the first statement of)
23677 the called subprogram.
23680 Executes a single line. If this line is a subprogram call, executes and
23681 returns from the call.
23684 Lists a few lines around the current source location. In practice, it
23685 is usually more convenient to have a separate edit window open with the
23686 relevant source file displayed. Successive applications of this command
23687 print subsequent lines. The command can be given an argument which is a
23688 line number, in which case it displays a few lines around the specified one.
23691 Displays a backtrace of the call chain. This command is typically
23692 used after a breakpoint has occurred, to examine the sequence of calls that
23693 leads to the current breakpoint. The display includes one line for each
23694 activation record (frame) corresponding to an active subprogram.
23697 At a breakpoint, @code{GDB} can display the values of variables local
23698 to the current frame. The command @code{up} can be used to
23699 examine the contents of other active frames, by moving the focus up
23700 the stack, that is to say from callee to caller, one frame at a time.
23703 Moves the focus of @code{GDB} down from the frame currently being
23704 examined to the frame of its callee (the reverse of the previous command),
23706 @item frame @var{n}
23707 Inspect the frame with the given number. The value 0 denotes the frame
23708 of the current breakpoint, that is to say the top of the call stack.
23713 The above list is a very short introduction to the commands that
23714 @code{GDB} provides. Important additional capabilities, including conditional
23715 breakpoints, the ability to execute command sequences on a breakpoint,
23716 the ability to debug at the machine instruction level and many other
23717 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
23718 Debugging with GDB}. Note that most commands can be abbreviated
23719 (for example, c for continue, bt for backtrace).
23721 @node Using Ada Expressions
23722 @section Using Ada Expressions
23723 @cindex Ada expressions
23726 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
23727 extensions. The philosophy behind the design of this subset is
23731 That @code{GDB} should provide basic literals and access to operations for
23732 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
23733 leaving more sophisticated computations to subprograms written into the
23734 program (which therefore may be called from @code{GDB}).
23737 That type safety and strict adherence to Ada language restrictions
23738 are not particularly important to the @code{GDB} user.
23741 That brevity is important to the @code{GDB} user.
23745 Thus, for brevity, the debugger acts as if there were
23746 implicit @code{with} and @code{use} clauses in effect for all user-written
23747 packages, thus making it unnecessary to fully qualify most names with
23748 their packages, regardless of context. Where this causes ambiguity,
23749 @code{GDB} asks the user's intent.
23751 For details on the supported Ada syntax, see @ref{Top,, Debugging with
23752 GDB, gdb, Debugging with GDB}.
23754 @node Calling User-Defined Subprograms
23755 @section Calling User-Defined Subprograms
23758 An important capability of @code{GDB} is the ability to call user-defined
23759 subprograms while debugging. This is achieved simply by entering
23760 a subprogram call statement in the form:
23763 call subprogram-name (parameters)
23767 The keyword @code{call} can be omitted in the normal case where the
23768 @code{subprogram-name} does not coincide with any of the predefined
23769 @code{GDB} commands.
23771 The effect is to invoke the given subprogram, passing it the
23772 list of parameters that is supplied. The parameters can be expressions and
23773 can include variables from the program being debugged. The
23774 subprogram must be defined
23775 at the library level within your program, and @code{GDB} will call the
23776 subprogram within the environment of your program execution (which
23777 means that the subprogram is free to access or even modify variables
23778 within your program).
23780 The most important use of this facility is in allowing the inclusion of
23781 debugging routines that are tailored to particular data structures
23782 in your program. Such debugging routines can be written to provide a suitably
23783 high-level description of an abstract type, rather than a low-level dump
23784 of its physical layout. After all, the standard
23785 @code{GDB print} command only knows the physical layout of your
23786 types, not their abstract meaning. Debugging routines can provide information
23787 at the desired semantic level and are thus enormously useful.
23789 For example, when debugging GNAT itself, it is crucial to have access to
23790 the contents of the tree nodes used to represent the program internally.
23791 But tree nodes are represented simply by an integer value (which in turn
23792 is an index into a table of nodes).
23793 Using the @code{print} command on a tree node would simply print this integer
23794 value, which is not very useful. But the PN routine (defined in file
23795 treepr.adb in the GNAT sources) takes a tree node as input, and displays
23796 a useful high level representation of the tree node, which includes the
23797 syntactic category of the node, its position in the source, the integers
23798 that denote descendant nodes and parent node, as well as varied
23799 semantic information. To study this example in more detail, you might want to
23800 look at the body of the PN procedure in the stated file.
23802 @node Using the Next Command in a Function
23803 @section Using the Next Command in a Function
23806 When you use the @code{next} command in a function, the current source
23807 location will advance to the next statement as usual. A special case
23808 arises in the case of a @code{return} statement.
23810 Part of the code for a return statement is the ``epilog'' of the function.
23811 This is the code that returns to the caller. There is only one copy of
23812 this epilog code, and it is typically associated with the last return
23813 statement in the function if there is more than one return. In some
23814 implementations, this epilog is associated with the first statement
23817 The result is that if you use the @code{next} command from a return
23818 statement that is not the last return statement of the function you
23819 may see a strange apparent jump to the last return statement or to
23820 the start of the function. You should simply ignore this odd jump.
23821 The value returned is always that from the first return statement
23822 that was stepped through.
23824 @node Ada Exceptions
23825 @section Breaking on Ada Exceptions
23829 You can set breakpoints that trip when your program raises
23830 selected exceptions.
23833 @item break exception
23834 Set a breakpoint that trips whenever (any task in the) program raises
23837 @item break exception @var{name}
23838 Set a breakpoint that trips whenever (any task in the) program raises
23839 the exception @var{name}.
23841 @item break exception unhandled
23842 Set a breakpoint that trips whenever (any task in the) program raises an
23843 exception for which there is no handler.
23845 @item info exceptions
23846 @itemx info exceptions @var{regexp}
23847 The @code{info exceptions} command permits the user to examine all defined
23848 exceptions within Ada programs. With a regular expression, @var{regexp}, as
23849 argument, prints out only those exceptions whose name matches @var{regexp}.
23857 @code{GDB} allows the following task-related commands:
23861 This command shows a list of current Ada tasks, as in the following example:
23868 ID TID P-ID Thread Pri State Name
23869 1 8088000 0 807e000 15 Child Activation Wait main_task
23870 2 80a4000 1 80ae000 15 Accept/Select Wait b
23871 3 809a800 1 80a4800 15 Child Activation Wait a
23872 * 4 80ae800 3 80b8000 15 Running c
23876 In this listing, the asterisk before the first task indicates it to be the
23877 currently running task. The first column lists the task ID that is used
23878 to refer to tasks in the following commands.
23880 @item break @var{linespec} task @var{taskid}
23881 @itemx break @var{linespec} task @var{taskid} if @dots{}
23882 @cindex Breakpoints and tasks
23883 These commands are like the @code{break @dots{} thread @dots{}}.
23884 @var{linespec} specifies source lines.
23886 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
23887 to specify that you only want @code{GDB} to stop the program when a
23888 particular Ada task reaches this breakpoint. @var{taskid} is one of the
23889 numeric task identifiers assigned by @code{GDB}, shown in the first
23890 column of the @samp{info tasks} display.
23892 If you do not specify @samp{task @var{taskid}} when you set a
23893 breakpoint, the breakpoint applies to @emph{all} tasks of your
23896 You can use the @code{task} qualifier on conditional breakpoints as
23897 well; in this case, place @samp{task @var{taskid}} before the
23898 breakpoint condition (before the @code{if}).
23900 @item task @var{taskno}
23901 @cindex Task switching
23903 This command allows to switch to the task referred by @var{taskno}. In
23904 particular, This allows to browse the backtrace of the specified
23905 task. It is advised to switch back to the original task before
23906 continuing execution otherwise the scheduling of the program may be
23911 For more detailed information on the tasking support,
23912 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
23914 @node Debugging Generic Units
23915 @section Debugging Generic Units
23916 @cindex Debugging Generic Units
23920 GNAT always uses code expansion for generic instantiation. This means that
23921 each time an instantiation occurs, a complete copy of the original code is
23922 made, with appropriate substitutions of formals by actuals.
23924 It is not possible to refer to the original generic entities in
23925 @code{GDB}, but it is always possible to debug a particular instance of
23926 a generic, by using the appropriate expanded names. For example, if we have
23928 @smallexample @c ada
23933 generic package k is
23934 procedure kp (v1 : in out integer);
23938 procedure kp (v1 : in out integer) is
23944 package k1 is new k;
23945 package k2 is new k;
23947 var : integer := 1;
23960 Then to break on a call to procedure kp in the k2 instance, simply
23964 (gdb) break g.k2.kp
23968 When the breakpoint occurs, you can step through the code of the
23969 instance in the normal manner and examine the values of local variables, as for
23972 @node GNAT Abnormal Termination or Failure to Terminate
23973 @section GNAT Abnormal Termination or Failure to Terminate
23974 @cindex GNAT Abnormal Termination or Failure to Terminate
23977 When presented with programs that contain serious errors in syntax
23979 GNAT may on rare occasions experience problems in operation, such
23981 segmentation fault or illegal memory access, raising an internal
23982 exception, terminating abnormally, or failing to terminate at all.
23983 In such cases, you can activate
23984 various features of GNAT that can help you pinpoint the construct in your
23985 program that is the likely source of the problem.
23987 The following strategies are presented in increasing order of
23988 difficulty, corresponding to your experience in using GNAT and your
23989 familiarity with compiler internals.
23993 Run @command{gcc} with the @option{-gnatf}. This first
23994 switch causes all errors on a given line to be reported. In its absence,
23995 only the first error on a line is displayed.
23997 The @option{-gnatdO} switch causes errors to be displayed as soon as they
23998 are encountered, rather than after compilation is terminated. If GNAT
23999 terminates prematurely or goes into an infinite loop, the last error
24000 message displayed may help to pinpoint the culprit.
24003 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
24004 mode, @command{gcc} produces ongoing information about the progress of the
24005 compilation and provides the name of each procedure as code is
24006 generated. This switch allows you to find which Ada procedure was being
24007 compiled when it encountered a code generation problem.
24010 @cindex @option{-gnatdc} switch
24011 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
24012 switch that does for the front-end what @option{^-v^VERBOSE^} does
24013 for the back end. The system prints the name of each unit,
24014 either a compilation unit or nested unit, as it is being analyzed.
24016 Finally, you can start
24017 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
24018 front-end of GNAT, and can be run independently (normally it is just
24019 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
24020 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
24021 @code{where} command is the first line of attack; the variable
24022 @code{lineno} (seen by @code{print lineno}), used by the second phase of
24023 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
24024 which the execution stopped, and @code{input_file name} indicates the name of
24028 @node Naming Conventions for GNAT Source Files
24029 @section Naming Conventions for GNAT Source Files
24032 In order to examine the workings of the GNAT system, the following
24033 brief description of its organization may be helpful:
24037 Files with prefix @file{^sc^SC^} contain the lexical scanner.
24040 All files prefixed with @file{^par^PAR^} are components of the parser. The
24041 numbers correspond to chapters of the Ada Reference Manual. For example,
24042 parsing of select statements can be found in @file{par-ch9.adb}.
24045 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
24046 numbers correspond to chapters of the Ada standard. For example, all
24047 issues involving context clauses can be found in @file{sem_ch10.adb}. In
24048 addition, some features of the language require sufficient special processing
24049 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
24050 dynamic dispatching, etc.
24053 All files prefixed with @file{^exp^EXP^} perform normalization and
24054 expansion of the intermediate representation (abstract syntax tree, or AST).
24055 these files use the same numbering scheme as the parser and semantics files.
24056 For example, the construction of record initialization procedures is done in
24057 @file{exp_ch3.adb}.
24060 The files prefixed with @file{^bind^BIND^} implement the binder, which
24061 verifies the consistency of the compilation, determines an order of
24062 elaboration, and generates the bind file.
24065 The files @file{atree.ads} and @file{atree.adb} detail the low-level
24066 data structures used by the front-end.
24069 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
24070 the abstract syntax tree as produced by the parser.
24073 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
24074 all entities, computed during semantic analysis.
24077 Library management issues are dealt with in files with prefix
24083 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
24084 defined in Annex A.
24089 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
24090 defined in Annex B.
24094 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
24095 both language-defined children and GNAT run-time routines.
24099 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
24100 general-purpose packages, fully documented in their specs. All
24101 the other @file{.c} files are modifications of common @command{gcc} files.
24104 @node Getting Internal Debugging Information
24105 @section Getting Internal Debugging Information
24108 Most compilers have internal debugging switches and modes. GNAT
24109 does also, except GNAT internal debugging switches and modes are not
24110 secret. A summary and full description of all the compiler and binder
24111 debug flags are in the file @file{debug.adb}. You must obtain the
24112 sources of the compiler to see the full detailed effects of these flags.
24114 The switches that print the source of the program (reconstructed from
24115 the internal tree) are of general interest for user programs, as are the
24117 the full internal tree, and the entity table (the symbol table
24118 information). The reconstructed source provides a readable version of the
24119 program after the front-end has completed analysis and expansion,
24120 and is useful when studying the performance of specific constructs.
24121 For example, constraint checks are indicated, complex aggregates
24122 are replaced with loops and assignments, and tasking primitives
24123 are replaced with run-time calls.
24125 @node Stack Traceback
24126 @section Stack Traceback
24128 @cindex stack traceback
24129 @cindex stack unwinding
24132 Traceback is a mechanism to display the sequence of subprogram calls that
24133 leads to a specified execution point in a program. Often (but not always)
24134 the execution point is an instruction at which an exception has been raised.
24135 This mechanism is also known as @i{stack unwinding} because it obtains
24136 its information by scanning the run-time stack and recovering the activation
24137 records of all active subprograms. Stack unwinding is one of the most
24138 important tools for program debugging.
24140 The first entry stored in traceback corresponds to the deepest calling level,
24141 that is to say the subprogram currently executing the instruction
24142 from which we want to obtain the traceback.
24144 Note that there is no runtime performance penalty when stack traceback
24145 is enabled, and no exception is raised during program execution.
24148 * Non-Symbolic Traceback::
24149 * Symbolic Traceback::
24152 @node Non-Symbolic Traceback
24153 @subsection Non-Symbolic Traceback
24154 @cindex traceback, non-symbolic
24157 Note: this feature is not supported on all platforms. See
24158 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
24162 * Tracebacks From an Unhandled Exception::
24163 * Tracebacks From Exception Occurrences (non-symbolic)::
24164 * Tracebacks From Anywhere in a Program (non-symbolic)::
24167 @node Tracebacks From an Unhandled Exception
24168 @subsubsection Tracebacks From an Unhandled Exception
24171 A runtime non-symbolic traceback is a list of addresses of call instructions.
24172 To enable this feature you must use the @option{-E}
24173 @code{gnatbind}'s option. With this option a stack traceback is stored as part
24174 of exception information. You can retrieve this information using the
24175 @code{addr2line} tool.
24177 Here is a simple example:
24179 @smallexample @c ada
24185 raise Constraint_Error;
24200 $ gnatmake stb -bargs -E
24203 Execution terminated by unhandled exception
24204 Exception name: CONSTRAINT_ERROR
24206 Call stack traceback locations:
24207 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24211 As we see the traceback lists a sequence of addresses for the unhandled
24212 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
24213 guess that this exception come from procedure P1. To translate these
24214 addresses into the source lines where the calls appear, the
24215 @code{addr2line} tool, described below, is invaluable. The use of this tool
24216 requires the program to be compiled with debug information.
24219 $ gnatmake -g stb -bargs -E
24222 Execution terminated by unhandled exception
24223 Exception name: CONSTRAINT_ERROR
24225 Call stack traceback locations:
24226 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24228 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
24229 0x4011f1 0x77e892a4
24231 00401373 at d:/stb/stb.adb:5
24232 0040138B at d:/stb/stb.adb:10
24233 0040139C at d:/stb/stb.adb:14
24234 00401335 at d:/stb/b~stb.adb:104
24235 004011C4 at /build/@dots{}/crt1.c:200
24236 004011F1 at /build/@dots{}/crt1.c:222
24237 77E892A4 in ?? at ??:0
24241 The @code{addr2line} tool has several other useful options:
24245 to get the function name corresponding to any location
24247 @item --demangle=gnat
24248 to use the gnat decoding mode for the function names. Note that
24249 for binutils version 2.9.x the option is simply @option{--demangle}.
24253 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
24254 0x40139c 0x401335 0x4011c4 0x4011f1
24256 00401373 in stb.p1 at d:/stb/stb.adb:5
24257 0040138B in stb.p2 at d:/stb/stb.adb:10
24258 0040139C in stb at d:/stb/stb.adb:14
24259 00401335 in main at d:/stb/b~stb.adb:104
24260 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
24261 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
24265 From this traceback we can see that the exception was raised in
24266 @file{stb.adb} at line 5, which was reached from a procedure call in
24267 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
24268 which contains the call to the main program.
24269 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
24270 and the output will vary from platform to platform.
24272 It is also possible to use @code{GDB} with these traceback addresses to debug
24273 the program. For example, we can break at a given code location, as reported
24274 in the stack traceback:
24280 Furthermore, this feature is not implemented inside Windows DLL. Only
24281 the non-symbolic traceback is reported in this case.
24284 (gdb) break *0x401373
24285 Breakpoint 1 at 0x401373: file stb.adb, line 5.
24289 It is important to note that the stack traceback addresses
24290 do not change when debug information is included. This is particularly useful
24291 because it makes it possible to release software without debug information (to
24292 minimize object size), get a field report that includes a stack traceback
24293 whenever an internal bug occurs, and then be able to retrieve the sequence
24294 of calls with the same program compiled with debug information.
24296 @node Tracebacks From Exception Occurrences (non-symbolic)
24297 @subsubsection Tracebacks From Exception Occurrences
24300 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
24301 The stack traceback is attached to the exception information string, and can
24302 be retrieved in an exception handler within the Ada program, by means of the
24303 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
24305 @smallexample @c ada
24307 with Ada.Exceptions;
24312 use Ada.Exceptions;
24320 Text_IO.Put_Line (Exception_Information (E));
24334 This program will output:
24339 Exception name: CONSTRAINT_ERROR
24340 Message: stb.adb:12
24341 Call stack traceback locations:
24342 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
24345 @node Tracebacks From Anywhere in a Program (non-symbolic)
24346 @subsubsection Tracebacks From Anywhere in a Program
24349 It is also possible to retrieve a stack traceback from anywhere in a
24350 program. For this you need to
24351 use the @code{GNAT.Traceback} API. This package includes a procedure called
24352 @code{Call_Chain} that computes a complete stack traceback, as well as useful
24353 display procedures described below. It is not necessary to use the
24354 @option{-E gnatbind} option in this case, because the stack traceback mechanism
24355 is invoked explicitly.
24358 In the following example we compute a traceback at a specific location in
24359 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
24360 convert addresses to strings:
24362 @smallexample @c ada
24364 with GNAT.Traceback;
24365 with GNAT.Debug_Utilities;
24371 use GNAT.Traceback;
24374 TB : Tracebacks_Array (1 .. 10);
24375 -- We are asking for a maximum of 10 stack frames.
24377 -- Len will receive the actual number of stack frames returned.
24379 Call_Chain (TB, Len);
24381 Text_IO.Put ("In STB.P1 : ");
24383 for K in 1 .. Len loop
24384 Text_IO.Put (Debug_Utilities.Image (TB (K)));
24405 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
24406 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
24410 You can then get further information by invoking the @code{addr2line}
24411 tool as described earlier (note that the hexadecimal addresses
24412 need to be specified in C format, with a leading ``0x'').
24414 @node Symbolic Traceback
24415 @subsection Symbolic Traceback
24416 @cindex traceback, symbolic
24419 A symbolic traceback is a stack traceback in which procedure names are
24420 associated with each code location.
24423 Note that this feature is not supported on all platforms. See
24424 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
24425 list of currently supported platforms.
24428 Note that the symbolic traceback requires that the program be compiled
24429 with debug information. If it is not compiled with debug information
24430 only the non-symbolic information will be valid.
24433 * Tracebacks From Exception Occurrences (symbolic)::
24434 * Tracebacks From Anywhere in a Program (symbolic)::
24437 @node Tracebacks From Exception Occurrences (symbolic)
24438 @subsubsection Tracebacks From Exception Occurrences
24440 @smallexample @c ada
24442 with GNAT.Traceback.Symbolic;
24448 raise Constraint_Error;
24465 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
24470 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
24473 0040149F in stb.p1 at stb.adb:8
24474 004014B7 in stb.p2 at stb.adb:13
24475 004014CF in stb.p3 at stb.adb:18
24476 004015DD in ada.stb at stb.adb:22
24477 00401461 in main at b~stb.adb:168
24478 004011C4 in __mingw_CRTStartup at crt1.c:200
24479 004011F1 in mainCRTStartup at crt1.c:222
24480 77E892A4 in ?? at ??:0
24484 In the above example the ``.\'' syntax in the @command{gnatmake} command
24485 is currently required by @command{addr2line} for files that are in
24486 the current working directory.
24487 Moreover, the exact sequence of linker options may vary from platform
24489 The above @option{-largs} section is for Windows platforms. By contrast,
24490 under Unix there is no need for the @option{-largs} section.
24491 Differences across platforms are due to details of linker implementation.
24493 @node Tracebacks From Anywhere in a Program (symbolic)
24494 @subsubsection Tracebacks From Anywhere in a Program
24497 It is possible to get a symbolic stack traceback
24498 from anywhere in a program, just as for non-symbolic tracebacks.
24499 The first step is to obtain a non-symbolic
24500 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
24501 information. Here is an example:
24503 @smallexample @c ada
24505 with GNAT.Traceback;
24506 with GNAT.Traceback.Symbolic;
24511 use GNAT.Traceback;
24512 use GNAT.Traceback.Symbolic;
24515 TB : Tracebacks_Array (1 .. 10);
24516 -- We are asking for a maximum of 10 stack frames.
24518 -- Len will receive the actual number of stack frames returned.
24520 Call_Chain (TB, Len);
24521 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
24534 @c ******************************
24536 @node Compatibility with HP Ada
24537 @chapter Compatibility with HP Ada
24538 @cindex Compatibility
24543 @cindex Compatibility between GNAT and HP Ada
24544 This chapter compares HP Ada (formerly known as ``DEC Ada'')
24545 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
24546 GNAT is highly compatible
24547 with HP Ada, and it should generally be straightforward to port code
24548 from the HP Ada environment to GNAT. However, there are a few language
24549 and implementation differences of which the user must be aware. These
24550 differences are discussed in this chapter. In
24551 addition, the operating environment and command structure for the
24552 compiler are different, and these differences are also discussed.
24554 For further details on these and other compatibility issues,
24555 see Appendix E of the HP publication
24556 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
24558 Except where otherwise indicated, the description of GNAT for OpenVMS
24559 applies to both the Alpha and I64 platforms.
24561 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
24562 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24564 The discussion in this chapter addresses specifically the implementation
24565 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
24566 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
24567 GNAT always follows the Alpha implementation.
24569 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
24570 attributes are recognized, although only a subset of them can sensibly
24571 be implemented. The description of pragmas in
24572 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
24573 indicates whether or not they are applicable to non-VMS systems.
24576 * Ada Language Compatibility::
24577 * Differences in the Definition of Package System::
24578 * Language-Related Features::
24579 * The Package STANDARD::
24580 * The Package SYSTEM::
24581 * Tasking and Task-Related Features::
24582 * Pragmas and Pragma-Related Features::
24583 * Library of Predefined Units::
24585 * Main Program Definition::
24586 * Implementation-Defined Attributes::
24587 * Compiler and Run-Time Interfacing::
24588 * Program Compilation and Library Management::
24590 * Implementation Limits::
24591 * Tools and Utilities::
24594 @node Ada Language Compatibility
24595 @section Ada Language Compatibility
24598 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
24599 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
24600 with Ada 83, and therefore Ada 83 programs will compile
24601 and run under GNAT with
24602 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
24603 provides details on specific incompatibilities.
24605 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
24606 as well as the pragma @code{ADA_83}, to force the compiler to
24607 operate in Ada 83 mode. This mode does not guarantee complete
24608 conformance to Ada 83, but in practice is sufficient to
24609 eliminate most sources of incompatibilities.
24610 In particular, it eliminates the recognition of the
24611 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
24612 in Ada 83 programs is legal, and handles the cases of packages
24613 with optional bodies, and generics that instantiate unconstrained
24614 types without the use of @code{(<>)}.
24616 @node Differences in the Definition of Package System
24617 @section Differences in the Definition of Package @code{System}
24620 An Ada compiler is allowed to add
24621 implementation-dependent declarations to package @code{System}.
24623 GNAT does not take advantage of this permission, and the version of
24624 @code{System} provided by GNAT exactly matches that defined in the Ada
24627 However, HP Ada adds an extensive set of declarations to package
24629 as fully documented in the HP Ada manuals. To minimize changes required
24630 for programs that make use of these extensions, GNAT provides the pragma
24631 @code{Extend_System} for extending the definition of package System. By using:
24632 @cindex pragma @code{Extend_System}
24633 @cindex @code{Extend_System} pragma
24635 @smallexample @c ada
24638 pragma Extend_System (Aux_DEC);
24644 the set of definitions in @code{System} is extended to include those in
24645 package @code{System.Aux_DEC}.
24646 @cindex @code{System.Aux_DEC} package
24647 @cindex @code{Aux_DEC} package (child of @code{System})
24648 These definitions are incorporated directly into package @code{System},
24649 as though they had been declared there. For a
24650 list of the declarations added, see the spec of this package,
24651 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
24652 @cindex @file{s-auxdec.ads} file
24653 The pragma @code{Extend_System} is a configuration pragma, which means that
24654 it can be placed in the file @file{gnat.adc}, so that it will automatically
24655 apply to all subsequent compilations. See @ref{Configuration Pragmas},
24656 for further details.
24658 An alternative approach that avoids the use of the non-standard
24659 @code{Extend_System} pragma is to add a context clause to the unit that
24660 references these facilities:
24662 @smallexample @c ada
24664 with System.Aux_DEC;
24665 use System.Aux_DEC;
24670 The effect is not quite semantically identical to incorporating
24671 the declarations directly into package @code{System},
24672 but most programs will not notice a difference
24673 unless they use prefix notation (e.g.@: @code{System.Integer_8})
24674 to reference the entities directly in package @code{System}.
24675 For units containing such references,
24676 the prefixes must either be removed, or the pragma @code{Extend_System}
24679 @node Language-Related Features
24680 @section Language-Related Features
24683 The following sections highlight differences in types,
24684 representations of types, operations, alignment, and
24688 * Integer Types and Representations::
24689 * Floating-Point Types and Representations::
24690 * Pragmas Float_Representation and Long_Float::
24691 * Fixed-Point Types and Representations::
24692 * Record and Array Component Alignment::
24693 * Address Clauses::
24694 * Other Representation Clauses::
24697 @node Integer Types and Representations
24698 @subsection Integer Types and Representations
24701 The set of predefined integer types is identical in HP Ada and GNAT.
24702 Furthermore the representation of these integer types is also identical,
24703 including the capability of size clauses forcing biased representation.
24706 HP Ada for OpenVMS Alpha systems has defined the
24707 following additional integer types in package @code{System}:
24724 @code{LARGEST_INTEGER}
24728 In GNAT, the first four of these types may be obtained from the
24729 standard Ada package @code{Interfaces}.
24730 Alternatively, by use of the pragma @code{Extend_System}, identical
24731 declarations can be referenced directly in package @code{System}.
24732 On both GNAT and HP Ada, the maximum integer size is 64 bits.
24734 @node Floating-Point Types and Representations
24735 @subsection Floating-Point Types and Representations
24736 @cindex Floating-Point types
24739 The set of predefined floating-point types is identical in HP Ada and GNAT.
24740 Furthermore the representation of these floating-point
24741 types is also identical. One important difference is that the default
24742 representation for HP Ada is @code{VAX_Float}, but the default representation
24745 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
24746 pragma @code{Float_Representation} as described in the HP Ada
24748 For example, the declarations:
24750 @smallexample @c ada
24752 type F_Float is digits 6;
24753 pragma Float_Representation (VAX_Float, F_Float);
24758 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
24760 This set of declarations actually appears in @code{System.Aux_DEC},
24762 the full set of additional floating-point declarations provided in
24763 the HP Ada version of package @code{System}.
24764 This and similar declarations may be accessed in a user program
24765 by using pragma @code{Extend_System}. The use of this
24766 pragma, and the related pragma @code{Long_Float} is described in further
24767 detail in the following section.
24769 @node Pragmas Float_Representation and Long_Float
24770 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
24773 HP Ada provides the pragma @code{Float_Representation}, which
24774 acts as a program library switch to allow control over
24775 the internal representation chosen for the predefined
24776 floating-point types declared in the package @code{Standard}.
24777 The format of this pragma is as follows:
24779 @smallexample @c ada
24781 pragma Float_Representation(VAX_Float | IEEE_Float);
24786 This pragma controls the representation of floating-point
24791 @code{VAX_Float} specifies that floating-point
24792 types are represented by default with the VAX system hardware types
24793 @code{F-floating}, @code{D-floating}, @code{G-floating}.
24794 Note that the @code{H-floating}
24795 type was available only on VAX systems, and is not available
24796 in either HP Ada or GNAT.
24799 @code{IEEE_Float} specifies that floating-point
24800 types are represented by default with the IEEE single and
24801 double floating-point types.
24805 GNAT provides an identical implementation of the pragma
24806 @code{Float_Representation}, except that it functions as a
24807 configuration pragma. Note that the
24808 notion of configuration pragma corresponds closely to the
24809 HP Ada notion of a program library switch.
24811 When no pragma is used in GNAT, the default is @code{IEEE_Float},
24813 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
24814 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
24815 advisable to change the format of numbers passed to standard library
24816 routines, and if necessary explicit type conversions may be needed.
24818 The use of @code{IEEE_Float} is recommended in GNAT since it is more
24819 efficient, and (given that it conforms to an international standard)
24820 potentially more portable.
24821 The situation in which @code{VAX_Float} may be useful is in interfacing
24822 to existing code and data that expect the use of @code{VAX_Float}.
24823 In such a situation use the predefined @code{VAX_Float}
24824 types in package @code{System}, as extended by
24825 @code{Extend_System}. For example, use @code{System.F_Float}
24826 to specify the 32-bit @code{F-Float} format.
24829 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
24830 to allow control over the internal representation chosen
24831 for the predefined type @code{Long_Float} and for floating-point
24832 type declarations with digits specified in the range 7 .. 15.
24833 The format of this pragma is as follows:
24835 @smallexample @c ada
24837 pragma Long_Float (D_FLOAT | G_FLOAT);
24841 @node Fixed-Point Types and Representations
24842 @subsection Fixed-Point Types and Representations
24845 On HP Ada for OpenVMS Alpha systems, rounding is
24846 away from zero for both positive and negative numbers.
24847 Therefore, @code{+0.5} rounds to @code{1},
24848 and @code{-0.5} rounds to @code{-1}.
24850 On GNAT the results of operations
24851 on fixed-point types are in accordance with the Ada
24852 rules. In particular, results of operations on decimal
24853 fixed-point types are truncated.
24855 @node Record and Array Component Alignment
24856 @subsection Record and Array Component Alignment
24859 On HP Ada for OpenVMS Alpha, all non-composite components
24860 are aligned on natural boundaries. For example, 1-byte
24861 components are aligned on byte boundaries, 2-byte
24862 components on 2-byte boundaries, 4-byte components on 4-byte
24863 byte boundaries, and so on. The OpenVMS Alpha hardware
24864 runs more efficiently with naturally aligned data.
24866 On GNAT, alignment rules are compatible
24867 with HP Ada for OpenVMS Alpha.
24869 @node Address Clauses
24870 @subsection Address Clauses
24873 In HP Ada and GNAT, address clauses are supported for
24874 objects and imported subprograms.
24875 The predefined type @code{System.Address} is a private type
24876 in both compilers on Alpha OpenVMS, with the same representation
24877 (it is simply a machine pointer). Addition, subtraction, and comparison
24878 operations are available in the standard Ada package
24879 @code{System.Storage_Elements}, or in package @code{System}
24880 if it is extended to include @code{System.Aux_DEC} using a
24881 pragma @code{Extend_System} as previously described.
24883 Note that code that @code{with}'s both this extended package @code{System}
24884 and the package @code{System.Storage_Elements} should not @code{use}
24885 both packages, or ambiguities will result. In general it is better
24886 not to mix these two sets of facilities. The Ada package was
24887 designed specifically to provide the kind of features that HP Ada
24888 adds directly to package @code{System}.
24890 The type @code{System.Address} is a 64-bit integer type in GNAT for
24891 I64 OpenVMS. For more information,
24892 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24894 GNAT is compatible with HP Ada in its handling of address
24895 clauses, except for some limitations in
24896 the form of address clauses for composite objects with
24897 initialization. Such address clauses are easily replaced
24898 by the use of an explicitly-defined constant as described
24899 in the Ada Reference Manual (13.1(22)). For example, the sequence
24902 @smallexample @c ada
24904 X, Y : Integer := Init_Func;
24905 Q : String (X .. Y) := "abc";
24907 for Q'Address use Compute_Address;
24912 will be rejected by GNAT, since the address cannot be computed at the time
24913 that @code{Q} is declared. To achieve the intended effect, write instead:
24915 @smallexample @c ada
24918 X, Y : Integer := Init_Func;
24919 Q_Address : constant Address := Compute_Address;
24920 Q : String (X .. Y) := "abc";
24922 for Q'Address use Q_Address;
24928 which will be accepted by GNAT (and other Ada compilers), and is also
24929 compatible with Ada 83. A fuller description of the restrictions
24930 on address specifications is found in @ref{Top, GNAT Reference Manual,
24931 About This Guide, gnat_rm, GNAT Reference Manual}.
24933 @node Other Representation Clauses
24934 @subsection Other Representation Clauses
24937 GNAT implements in a compatible manner all the representation
24938 clauses supported by HP Ada. In addition, GNAT
24939 implements the representation clause forms that were introduced in Ada 95,
24940 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
24942 @node The Package STANDARD
24943 @section The Package @code{STANDARD}
24946 The package @code{STANDARD}, as implemented by HP Ada, is fully
24947 described in the @cite{Ada Reference Manual} and in the
24948 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
24949 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
24951 In addition, HP Ada supports the Latin-1 character set in
24952 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
24953 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
24954 the type @code{WIDE_CHARACTER}.
24956 The floating-point types supported by GNAT are those
24957 supported by HP Ada, but the defaults are different, and are controlled by
24958 pragmas. See @ref{Floating-Point Types and Representations}, for details.
24960 @node The Package SYSTEM
24961 @section The Package @code{SYSTEM}
24964 HP Ada provides a specific version of the package
24965 @code{SYSTEM} for each platform on which the language is implemented.
24966 For the complete spec of the package @code{SYSTEM}, see
24967 Appendix F of the @cite{HP Ada Language Reference Manual}.
24969 On HP Ada, the package @code{SYSTEM} includes the following conversion
24972 @item @code{TO_ADDRESS(INTEGER)}
24974 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
24976 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
24978 @item @code{TO_INTEGER(ADDRESS)}
24980 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
24982 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
24983 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
24987 By default, GNAT supplies a version of @code{SYSTEM} that matches
24988 the definition given in the @cite{Ada Reference Manual}.
24990 is a subset of the HP system definitions, which is as
24991 close as possible to the original definitions. The only difference
24992 is that the definition of @code{SYSTEM_NAME} is different:
24994 @smallexample @c ada
24996 type Name is (SYSTEM_NAME_GNAT);
24997 System_Name : constant Name := SYSTEM_NAME_GNAT;
25002 Also, GNAT adds the Ada declarations for
25003 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
25005 However, the use of the following pragma causes GNAT
25006 to extend the definition of package @code{SYSTEM} so that it
25007 encompasses the full set of HP-specific extensions,
25008 including the functions listed above:
25010 @smallexample @c ada
25012 pragma Extend_System (Aux_DEC);
25017 The pragma @code{Extend_System} is a configuration pragma that
25018 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
25019 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
25021 HP Ada does not allow the recompilation of the package
25022 @code{SYSTEM}. Instead HP Ada provides several pragmas
25023 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
25024 to modify values in the package @code{SYSTEM}.
25025 On OpenVMS Alpha systems, the pragma
25026 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
25027 its single argument.
25029 GNAT does permit the recompilation of package @code{SYSTEM} using
25030 the special switch @option{-gnatg}, and this switch can be used if
25031 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
25032 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
25033 or @code{MEMORY_SIZE} by any other means.
25035 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
25036 enumeration literal @code{SYSTEM_NAME_GNAT}.
25038 The definitions provided by the use of
25040 @smallexample @c ada
25041 pragma Extend_System (AUX_Dec);
25045 are virtually identical to those provided by the HP Ada 83 package
25046 @code{SYSTEM}. One important difference is that the name of the
25048 function for type @code{UNSIGNED_LONGWORD} is changed to
25049 @code{TO_ADDRESS_LONG}.
25050 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
25051 discussion of why this change was necessary.
25054 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
25056 an extension to Ada 83 not strictly compatible with the reference manual.
25057 GNAT, in order to be exactly compatible with the standard,
25058 does not provide this capability. In HP Ada 83, the
25059 point of this definition is to deal with a call like:
25061 @smallexample @c ada
25062 TO_ADDRESS (16#12777#);
25066 Normally, according to Ada 83 semantics, one would expect this to be
25067 ambiguous, since it matches both the @code{INTEGER} and
25068 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
25069 However, in HP Ada 83, there is no ambiguity, since the
25070 definition using @i{universal_integer} takes precedence.
25072 In GNAT, since the version with @i{universal_integer} cannot be supplied,
25074 not possible to be 100% compatible. Since there are many programs using
25075 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
25077 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
25078 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
25080 @smallexample @c ada
25081 function To_Address (X : Integer) return Address;
25082 pragma Pure_Function (To_Address);
25084 function To_Address_Long (X : Unsigned_Longword) return Address;
25085 pragma Pure_Function (To_Address_Long);
25089 This means that programs using @code{TO_ADDRESS} for
25090 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
25092 @node Tasking and Task-Related Features
25093 @section Tasking and Task-Related Features
25096 This section compares the treatment of tasking in GNAT
25097 and in HP Ada for OpenVMS Alpha.
25098 The GNAT description applies to both Alpha and I64 OpenVMS.
25099 For detailed information on tasking in
25100 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
25101 relevant run-time reference manual.
25104 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
25105 * Assigning Task IDs::
25106 * Task IDs and Delays::
25107 * Task-Related Pragmas::
25108 * Scheduling and Task Priority::
25110 * External Interrupts::
25113 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25114 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25117 On OpenVMS Alpha systems, each Ada task (except a passive
25118 task) is implemented as a single stream of execution
25119 that is created and managed by the kernel. On these
25120 systems, HP Ada tasking support is based on DECthreads,
25121 an implementation of the POSIX standard for threads.
25123 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
25124 code that calls DECthreads routines can be used together.
25125 The interaction between Ada tasks and DECthreads routines
25126 can have some benefits. For example when on OpenVMS Alpha,
25127 HP Ada can call C code that is already threaded.
25129 GNAT uses the facilities of DECthreads,
25130 and Ada tasks are mapped to threads.
25132 @node Assigning Task IDs
25133 @subsection Assigning Task IDs
25136 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
25137 the environment task that executes the main program. On
25138 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
25139 that have been created but are not yet activated.
25141 On OpenVMS Alpha systems, task IDs are assigned at
25142 activation. On GNAT systems, task IDs are also assigned at
25143 task creation but do not have the same form or values as
25144 task ID values in HP Ada. There is no null task, and the
25145 environment task does not have a specific task ID value.
25147 @node Task IDs and Delays
25148 @subsection Task IDs and Delays
25151 On OpenVMS Alpha systems, tasking delays are implemented
25152 using Timer System Services. The Task ID is used for the
25153 identification of the timer request (the @code{REQIDT} parameter).
25154 If Timers are used in the application take care not to use
25155 @code{0} for the identification, because cancelling such a timer
25156 will cancel all timers and may lead to unpredictable results.
25158 @node Task-Related Pragmas
25159 @subsection Task-Related Pragmas
25162 Ada supplies the pragma @code{TASK_STORAGE}, which allows
25163 specification of the size of the guard area for a task
25164 stack. (The guard area forms an area of memory that has no
25165 read or write access and thus helps in the detection of
25166 stack overflow.) On OpenVMS Alpha systems, if the pragma
25167 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
25168 area is created. In the absence of a pragma @code{TASK_STORAGE},
25169 a default guard area is created.
25171 GNAT supplies the following task-related pragmas:
25174 @item @code{TASK_INFO}
25176 This pragma appears within a task definition and
25177 applies to the task in which it appears. The argument
25178 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
25180 @item @code{TASK_STORAGE}
25182 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
25183 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
25184 @code{SUPPRESS}, and @code{VOLATILE}.
25186 @node Scheduling and Task Priority
25187 @subsection Scheduling and Task Priority
25190 HP Ada implements the Ada language requirement that
25191 when two tasks are eligible for execution and they have
25192 different priorities, the lower priority task does not
25193 execute while the higher priority task is waiting. The HP
25194 Ada Run-Time Library keeps a task running until either the
25195 task is suspended or a higher priority task becomes ready.
25197 On OpenVMS Alpha systems, the default strategy is round-
25198 robin with preemption. Tasks of equal priority take turns
25199 at the processor. A task is run for a certain period of
25200 time and then placed at the tail of the ready queue for
25201 its priority level.
25203 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
25204 which can be used to enable or disable round-robin
25205 scheduling of tasks with the same priority.
25206 See the relevant HP Ada run-time reference manual for
25207 information on using the pragmas to control HP Ada task
25210 GNAT follows the scheduling rules of Annex D (Real-Time
25211 Annex) of the @cite{Ada Reference Manual}. In general, this
25212 scheduling strategy is fully compatible with HP Ada
25213 although it provides some additional constraints (as
25214 fully documented in Annex D).
25215 GNAT implements time slicing control in a manner compatible with
25216 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
25217 are identical to the HP Ada 83 pragma of the same name.
25218 Note that it is not possible to mix GNAT tasking and
25219 HP Ada 83 tasking in the same program, since the two run-time
25220 libraries are not compatible.
25222 @node The Task Stack
25223 @subsection The Task Stack
25226 In HP Ada, a task stack is allocated each time a
25227 non-passive task is activated. As soon as the task is
25228 terminated, the storage for the task stack is deallocated.
25229 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
25230 a default stack size is used. Also, regardless of the size
25231 specified, some additional space is allocated for task
25232 management purposes. On OpenVMS Alpha systems, at least
25233 one page is allocated.
25235 GNAT handles task stacks in a similar manner. In accordance with
25236 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
25237 an alternative method for controlling the task stack size.
25238 The specification of the attribute @code{T'STORAGE_SIZE} is also
25239 supported in a manner compatible with HP Ada.
25241 @node External Interrupts
25242 @subsection External Interrupts
25245 On HP Ada, external interrupts can be associated with task entries.
25246 GNAT is compatible with HP Ada in its handling of external interrupts.
25248 @node Pragmas and Pragma-Related Features
25249 @section Pragmas and Pragma-Related Features
25252 Both HP Ada and GNAT supply all language-defined pragmas
25253 as specified by the Ada 83 standard. GNAT also supplies all
25254 language-defined pragmas introduced by Ada 95 and Ada 2005.
25255 In addition, GNAT implements the implementation-defined pragmas
25259 @item @code{AST_ENTRY}
25261 @item @code{COMMON_OBJECT}
25263 @item @code{COMPONENT_ALIGNMENT}
25265 @item @code{EXPORT_EXCEPTION}
25267 @item @code{EXPORT_FUNCTION}
25269 @item @code{EXPORT_OBJECT}
25271 @item @code{EXPORT_PROCEDURE}
25273 @item @code{EXPORT_VALUED_PROCEDURE}
25275 @item @code{FLOAT_REPRESENTATION}
25279 @item @code{IMPORT_EXCEPTION}
25281 @item @code{IMPORT_FUNCTION}
25283 @item @code{IMPORT_OBJECT}
25285 @item @code{IMPORT_PROCEDURE}
25287 @item @code{IMPORT_VALUED_PROCEDURE}
25289 @item @code{INLINE_GENERIC}
25291 @item @code{INTERFACE_NAME}
25293 @item @code{LONG_FLOAT}
25295 @item @code{MAIN_STORAGE}
25297 @item @code{PASSIVE}
25299 @item @code{PSECT_OBJECT}
25301 @item @code{SHARE_GENERIC}
25303 @item @code{SUPPRESS_ALL}
25305 @item @code{TASK_STORAGE}
25307 @item @code{TIME_SLICE}
25313 These pragmas are all fully implemented, with the exception of @code{TITLE},
25314 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
25315 recognized, but which have no
25316 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
25317 use of Ada protected objects. In GNAT, all generics are inlined.
25319 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
25320 a separate subprogram specification which must appear before the
25323 GNAT also supplies a number of implementation-defined pragmas as follows:
25325 @item @code{ABORT_DEFER}
25327 @item @code{ADA_83}
25329 @item @code{ADA_95}
25331 @item @code{ADA_05}
25333 @item @code{ANNOTATE}
25335 @item @code{ASSERT}
25337 @item @code{C_PASS_BY_COPY}
25339 @item @code{CPP_CLASS}
25341 @item @code{CPP_CONSTRUCTOR}
25343 @item @code{CPP_DESTRUCTOR}
25347 @item @code{EXTEND_SYSTEM}
25349 @item @code{LINKER_ALIAS}
25351 @item @code{LINKER_SECTION}
25353 @item @code{MACHINE_ATTRIBUTE}
25355 @item @code{NO_RETURN}
25357 @item @code{PURE_FUNCTION}
25359 @item @code{SOURCE_FILE_NAME}
25361 @item @code{SOURCE_REFERENCE}
25363 @item @code{TASK_INFO}
25365 @item @code{UNCHECKED_UNION}
25367 @item @code{UNIMPLEMENTED_UNIT}
25369 @item @code{UNIVERSAL_DATA}
25371 @item @code{UNSUPPRESS}
25373 @item @code{WARNINGS}
25375 @item @code{WEAK_EXTERNAL}
25379 For full details on these GNAT implementation-defined pragmas,
25380 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
25384 * Restrictions on the Pragma INLINE::
25385 * Restrictions on the Pragma INTERFACE::
25386 * Restrictions on the Pragma SYSTEM_NAME::
25389 @node Restrictions on the Pragma INLINE
25390 @subsection Restrictions on Pragma @code{INLINE}
25393 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
25395 @item Parameters cannot have a task type.
25397 @item Function results cannot be task types, unconstrained
25398 array types, or unconstrained types with discriminants.
25400 @item Bodies cannot declare the following:
25402 @item Subprogram body or stub (imported subprogram is allowed)
25406 @item Generic declarations
25408 @item Instantiations
25412 @item Access types (types derived from access types allowed)
25414 @item Array or record types
25416 @item Dependent tasks
25418 @item Direct recursive calls of subprogram or containing
25419 subprogram, directly or via a renaming
25425 In GNAT, the only restriction on pragma @code{INLINE} is that the
25426 body must occur before the call if both are in the same
25427 unit, and the size must be appropriately small. There are
25428 no other specific restrictions which cause subprograms to
25429 be incapable of being inlined.
25431 @node Restrictions on the Pragma INTERFACE
25432 @subsection Restrictions on Pragma @code{INTERFACE}
25435 The following restrictions on pragma @code{INTERFACE}
25436 are enforced by both HP Ada and GNAT:
25438 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
25439 Default is the default on OpenVMS Alpha systems.
25441 @item Parameter passing: Language specifies default
25442 mechanisms but can be overridden with an @code{EXPORT} pragma.
25445 @item Ada: Use internal Ada rules.
25447 @item Bliss, C: Parameters must be mode @code{in}; cannot be
25448 record or task type. Result cannot be a string, an
25449 array, or a record.
25451 @item Fortran: Parameters cannot have a task type. Result cannot
25452 be a string, an array, or a record.
25457 GNAT is entirely upwards compatible with HP Ada, and in addition allows
25458 record parameters for all languages.
25460 @node Restrictions on the Pragma SYSTEM_NAME
25461 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
25464 For HP Ada for OpenVMS Alpha, the enumeration literal
25465 for the type @code{NAME} is @code{OPENVMS_AXP}.
25466 In GNAT, the enumeration
25467 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
25469 @node Library of Predefined Units
25470 @section Library of Predefined Units
25473 A library of predefined units is provided as part of the
25474 HP Ada and GNAT implementations. HP Ada does not provide
25475 the package @code{MACHINE_CODE} but instead recommends importing
25478 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
25479 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
25481 The HP Ada Predefined Library units are modified to remove post-Ada 83
25482 incompatibilities and to make them interoperable with GNAT
25483 (@pxref{Changes to DECLIB}, for details).
25484 The units are located in the @file{DECLIB} directory.
25486 The GNAT RTL is contained in
25487 the @file{ADALIB} directory, and
25488 the default search path is set up to find @code{DECLIB} units in preference
25489 to @code{ADALIB} units with the same name (@code{TEXT_IO},
25490 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
25493 * Changes to DECLIB::
25496 @node Changes to DECLIB
25497 @subsection Changes to @code{DECLIB}
25500 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
25501 compatibility are minor and include the following:
25504 @item Adjusting the location of pragmas and record representation
25505 clauses to obey Ada 95 (and thus Ada 2005) rules
25507 @item Adding the proper notation to generic formal parameters
25508 that take unconstrained types in instantiation
25510 @item Adding pragma @code{ELABORATE_BODY} to package specs
25511 that have package bodies not otherwise allowed
25513 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
25514 ``@code{PROTECTD}''.
25515 Currently these are found only in the @code{STARLET} package spec.
25517 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
25518 where the address size is constrained to 32 bits.
25522 None of the above changes is visible to users.
25528 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
25531 @item Command Language Interpreter (CLI interface)
25533 @item DECtalk Run-Time Library (DTK interface)
25535 @item Librarian utility routines (LBR interface)
25537 @item General Purpose Run-Time Library (LIB interface)
25539 @item Math Run-Time Library (MTH interface)
25541 @item National Character Set Run-Time Library (NCS interface)
25543 @item Compiled Code Support Run-Time Library (OTS interface)
25545 @item Parallel Processing Run-Time Library (PPL interface)
25547 @item Screen Management Run-Time Library (SMG interface)
25549 @item Sort Run-Time Library (SOR interface)
25551 @item String Run-Time Library (STR interface)
25553 @item STARLET System Library
25556 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
25558 @item X Windows Toolkit (XT interface)
25560 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
25564 GNAT provides implementations of these HP bindings in the @code{DECLIB}
25565 directory, on both the Alpha and I64 OpenVMS platforms.
25567 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
25569 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
25570 A pragma @code{Linker_Options} has been added to packages @code{Xm},
25571 @code{Xt}, and @code{X_Lib}
25572 causing the default X/Motif sharable image libraries to be linked in. This
25573 is done via options files named @file{xm.opt}, @file{xt.opt}, and
25574 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
25576 It may be necessary to edit these options files to update or correct the
25577 library names if, for example, the newer X/Motif bindings from
25578 @file{ADA$EXAMPLES}
25579 had been (previous to installing GNAT) copied and renamed to supersede the
25580 default @file{ADA$PREDEFINED} versions.
25583 * Shared Libraries and Options Files::
25584 * Interfaces to C::
25587 @node Shared Libraries and Options Files
25588 @subsection Shared Libraries and Options Files
25591 When using the HP Ada
25592 predefined X and Motif bindings, the linking with their sharable images is
25593 done automatically by @command{GNAT LINK}.
25594 When using other X and Motif bindings, you need
25595 to add the corresponding sharable images to the command line for
25596 @code{GNAT LINK}. When linking with shared libraries, or with
25597 @file{.OPT} files, you must
25598 also add them to the command line for @command{GNAT LINK}.
25600 A shared library to be used with GNAT is built in the same way as other
25601 libraries under VMS. The VMS Link command can be used in standard fashion.
25603 @node Interfaces to C
25604 @subsection Interfaces to C
25608 provides the following Ada types and operations:
25611 @item C types package (@code{C_TYPES})
25613 @item C strings (@code{C_TYPES.NULL_TERMINATED})
25615 @item Other_types (@code{SHORT_INT})
25619 Interfacing to C with GNAT, you can use the above approach
25620 described for HP Ada or the facilities of Annex B of
25621 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
25622 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
25623 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
25625 The @option{-gnatF} qualifier forces default and explicit
25626 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
25627 to be uppercased for compatibility with the default behavior
25628 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
25630 @node Main Program Definition
25631 @section Main Program Definition
25634 The following section discusses differences in the
25635 definition of main programs on HP Ada and GNAT.
25636 On HP Ada, main programs are defined to meet the
25637 following conditions:
25639 @item Procedure with no formal parameters (returns @code{0} upon
25642 @item Procedure with no formal parameters (returns @code{42} when
25643 an unhandled exception is raised)
25645 @item Function with no formal parameters whose returned value
25646 is of a discrete type
25648 @item Procedure with one @code{out} formal of a discrete type for
25649 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
25654 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
25655 a main function or main procedure returns a discrete
25656 value whose size is less than 64 bits (32 on VAX systems),
25657 the value is zero- or sign-extended as appropriate.
25658 On GNAT, main programs are defined as follows:
25660 @item Must be a non-generic, parameterless subprogram that
25661 is either a procedure or function returning an Ada
25662 @code{STANDARD.INTEGER} (the predefined type)
25664 @item Cannot be a generic subprogram or an instantiation of a
25668 @node Implementation-Defined Attributes
25669 @section Implementation-Defined Attributes
25672 GNAT provides all HP Ada implementation-defined
25675 @node Compiler and Run-Time Interfacing
25676 @section Compiler and Run-Time Interfacing
25679 HP Ada provides the following qualifiers to pass options to the linker
25682 @item @option{/WAIT} and @option{/SUBMIT}
25684 @item @option{/COMMAND}
25686 @item @option{/@r{[}NO@r{]}MAP}
25688 @item @option{/OUTPUT=@var{file-spec}}
25690 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25694 To pass options to the linker, GNAT provides the following
25698 @item @option{/EXECUTABLE=@var{exec-name}}
25700 @item @option{/VERBOSE}
25702 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25706 For more information on these switches, see
25707 @ref{Switches for gnatlink}.
25708 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
25709 to control optimization. HP Ada also supplies the
25712 @item @code{OPTIMIZE}
25714 @item @code{INLINE}
25716 @item @code{INLINE_GENERIC}
25718 @item @code{SUPPRESS_ALL}
25720 @item @code{PASSIVE}
25724 In GNAT, optimization is controlled strictly by command
25725 line parameters, as described in the corresponding section of this guide.
25726 The HP pragmas for control of optimization are
25727 recognized but ignored.
25729 Note that in GNAT, the default is optimization off, whereas in HP Ada
25730 the default is that optimization is turned on.
25732 @node Program Compilation and Library Management
25733 @section Program Compilation and Library Management
25736 HP Ada and GNAT provide a comparable set of commands to
25737 build programs. HP Ada also provides a program library,
25738 which is a concept that does not exist on GNAT. Instead,
25739 GNAT provides directories of sources that are compiled as
25742 The following table summarizes
25743 the HP Ada commands and provides
25744 equivalent GNAT commands. In this table, some GNAT
25745 equivalents reflect the fact that GNAT does not use the
25746 concept of a program library. Instead, it uses a model
25747 in which collections of source and object files are used
25748 in a manner consistent with other languages like C and
25749 Fortran. Therefore, standard system file commands are used
25750 to manipulate these elements. Those GNAT commands are marked with
25752 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
25755 @multitable @columnfractions .35 .65
25757 @item @emph{HP Ada Command}
25758 @tab @emph{GNAT Equivalent / Description}
25760 @item @command{ADA}
25761 @tab @command{GNAT COMPILE}@*
25762 Invokes the compiler to compile one or more Ada source files.
25764 @item @command{ACS ATTACH}@*
25765 @tab [No equivalent]@*
25766 Switches control of terminal from current process running the program
25769 @item @command{ACS CHECK}
25770 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
25771 Forms the execution closure of one
25772 or more compiled units and checks completeness and currency.
25774 @item @command{ACS COMPILE}
25775 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25776 Forms the execution closure of one or
25777 more specified units, checks completeness and currency,
25778 identifies units that have revised source files, compiles same,
25779 and recompiles units that are or will become obsolete.
25780 Also completes incomplete generic instantiations.
25782 @item @command{ACS COPY FOREIGN}
25784 Copies a foreign object file into the program library as a
25787 @item @command{ACS COPY UNIT}
25789 Copies a compiled unit from one program library to another.
25791 @item @command{ACS CREATE LIBRARY}
25792 @tab Create /directory (*)@*
25793 Creates a program library.
25795 @item @command{ACS CREATE SUBLIBRARY}
25796 @tab Create /directory (*)@*
25797 Creates a program sublibrary.
25799 @item @command{ACS DELETE LIBRARY}
25801 Deletes a program library and its contents.
25803 @item @command{ACS DELETE SUBLIBRARY}
25805 Deletes a program sublibrary and its contents.
25807 @item @command{ACS DELETE UNIT}
25808 @tab Delete file (*)@*
25809 On OpenVMS systems, deletes one or more compiled units from
25810 the current program library.
25812 @item @command{ACS DIRECTORY}
25813 @tab Directory (*)@*
25814 On OpenVMS systems, lists units contained in the current
25817 @item @command{ACS ENTER FOREIGN}
25819 Allows the import of a foreign body as an Ada library
25820 spec and enters a reference to a pointer.
25822 @item @command{ACS ENTER UNIT}
25824 Enters a reference (pointer) from the current program library to
25825 a unit compiled into another program library.
25827 @item @command{ACS EXIT}
25828 @tab [No equivalent]@*
25829 Exits from the program library manager.
25831 @item @command{ACS EXPORT}
25833 Creates an object file that contains system-specific object code
25834 for one or more units. With GNAT, object files can simply be copied
25835 into the desired directory.
25837 @item @command{ACS EXTRACT SOURCE}
25839 Allows access to the copied source file for each Ada compilation unit
25841 @item @command{ACS HELP}
25842 @tab @command{HELP GNAT}@*
25843 Provides online help.
25845 @item @command{ACS LINK}
25846 @tab @command{GNAT LINK}@*
25847 Links an object file containing Ada units into an executable file.
25849 @item @command{ACS LOAD}
25851 Loads (partially compiles) Ada units into the program library.
25852 Allows loading a program from a collection of files into a library
25853 without knowing the relationship among units.
25855 @item @command{ACS MERGE}
25857 Merges into the current program library, one or more units from
25858 another library where they were modified.
25860 @item @command{ACS RECOMPILE}
25861 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
25862 Recompiles from external or copied source files any obsolete
25863 unit in the closure. Also, completes any incomplete generic
25866 @item @command{ACS REENTER}
25867 @tab @command{GNAT MAKE}@*
25868 Reenters current references to units compiled after last entered
25869 with the @command{ACS ENTER UNIT} command.
25871 @item @command{ACS SET LIBRARY}
25872 @tab Set default (*)@*
25873 Defines a program library to be the compilation context as well
25874 as the target library for compiler output and commands in general.
25876 @item @command{ACS SET PRAGMA}
25877 @tab Edit @file{gnat.adc} (*)@*
25878 Redefines specified values of the library characteristics
25879 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
25880 and @code{Float_Representation}.
25882 @item @command{ACS SET SOURCE}
25883 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
25884 Defines the source file search list for the @command{ACS COMPILE} command.
25886 @item @command{ACS SHOW LIBRARY}
25887 @tab Directory (*)@*
25888 Lists information about one or more program libraries.
25890 @item @command{ACS SHOW PROGRAM}
25891 @tab [No equivalent]@*
25892 Lists information about the execution closure of one or
25893 more units in the program library.
25895 @item @command{ACS SHOW SOURCE}
25896 @tab Show logical @code{ADA_INCLUDE_PATH}@*
25897 Shows the source file search used when compiling units.
25899 @item @command{ACS SHOW VERSION}
25900 @tab Compile with @option{VERBOSE} option
25901 Displays the version number of the compiler and program library
25904 @item @command{ACS SPAWN}
25905 @tab [No equivalent]@*
25906 Creates a subprocess of the current process (same as @command{DCL SPAWN}
25909 @item @command{ACS VERIFY}
25910 @tab [No equivalent]@*
25911 Performs a series of consistency checks on a program library to
25912 determine whether the library structure and library files are in
25919 @section Input-Output
25922 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
25923 Management Services (RMS) to perform operations on
25927 HP Ada and GNAT predefine an identical set of input-
25928 output packages. To make the use of the
25929 generic @code{TEXT_IO} operations more convenient, HP Ada
25930 provides predefined library packages that instantiate the
25931 integer and floating-point operations for the predefined
25932 integer and floating-point types as shown in the following table.
25934 @multitable @columnfractions .45 .55
25935 @item @emph{Package Name} @tab Instantiation
25937 @item @code{INTEGER_TEXT_IO}
25938 @tab @code{INTEGER_IO(INTEGER)}
25940 @item @code{SHORT_INTEGER_TEXT_IO}
25941 @tab @code{INTEGER_IO(SHORT_INTEGER)}
25943 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
25944 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
25946 @item @code{FLOAT_TEXT_IO}
25947 @tab @code{FLOAT_IO(FLOAT)}
25949 @item @code{LONG_FLOAT_TEXT_IO}
25950 @tab @code{FLOAT_IO(LONG_FLOAT)}
25954 The HP Ada predefined packages and their operations
25955 are implemented using OpenVMS Alpha files and input-output
25956 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
25957 Familiarity with the following is recommended:
25959 @item RMS file organizations and access methods
25961 @item OpenVMS file specifications and directories
25963 @item OpenVMS File Definition Language (FDL)
25967 GNAT provides I/O facilities that are completely
25968 compatible with HP Ada. The distribution includes the
25969 standard HP Ada versions of all I/O packages, operating
25970 in a manner compatible with HP Ada. In particular, the
25971 following packages are by default the HP Ada (Ada 83)
25972 versions of these packages rather than the renamings
25973 suggested in Annex J of the Ada Reference Manual:
25975 @item @code{TEXT_IO}
25977 @item @code{SEQUENTIAL_IO}
25979 @item @code{DIRECT_IO}
25983 The use of the standard child package syntax (for
25984 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
25986 GNAT provides HP-compatible predefined instantiations
25987 of the @code{TEXT_IO} packages, and also
25988 provides the standard predefined instantiations required
25989 by the @cite{Ada Reference Manual}.
25991 For further information on how GNAT interfaces to the file
25992 system or how I/O is implemented in programs written in
25993 mixed languages, see @ref{Implementation of the Standard I/O,,,
25994 gnat_rm, GNAT Reference Manual}.
25995 This chapter covers the following:
25997 @item Standard I/O packages
25999 @item @code{FORM} strings
26001 @item @code{ADA.DIRECT_IO}
26003 @item @code{ADA.SEQUENTIAL_IO}
26005 @item @code{ADA.TEXT_IO}
26007 @item Stream pointer positioning
26009 @item Reading and writing non-regular files
26011 @item @code{GET_IMMEDIATE}
26013 @item Treating @code{TEXT_IO} files as streams
26020 @node Implementation Limits
26021 @section Implementation Limits
26024 The following table lists implementation limits for HP Ada
26026 @multitable @columnfractions .60 .20 .20
26028 @item @emph{Compilation Parameter}
26033 @item In a subprogram or entry declaration, maximum number of
26034 formal parameters that are of an unconstrained record type
26039 @item Maximum identifier length (number of characters)
26044 @item Maximum number of characters in a source line
26049 @item Maximum collection size (number of bytes)
26054 @item Maximum number of discriminants for a record type
26059 @item Maximum number of formal parameters in an entry or
26060 subprogram declaration
26065 @item Maximum number of dimensions in an array type
26070 @item Maximum number of library units and subunits in a compilation.
26075 @item Maximum number of library units and subunits in an execution.
26080 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
26081 or @code{PSECT_OBJECT}
26086 @item Maximum number of enumeration literals in an enumeration type
26092 @item Maximum number of lines in a source file
26097 @item Maximum number of bits in any object
26102 @item Maximum size of the static portion of a stack frame (approximate)
26107 @node Tools and Utilities
26108 @section Tools and Utilities
26111 The following table lists some of the OpenVMS development tools
26112 available for HP Ada, and the corresponding tools for
26113 use with @value{EDITION} on Alpha and I64 platforms.
26114 Aside from the debugger, all the OpenVMS tools identified are part
26115 of the DECset package.
26118 @c Specify table in TeX since Texinfo does a poor job
26122 \settabs\+Language-Sensitive Editor\quad
26123 &Product with HP Ada\quad
26126 &\it Product with HP Ada
26127 & \it Product with GNAT Pro\cr
26129 \+Code Management System
26133 \+Language-Sensitive Editor
26135 & emacs or HP LSE (Alpha)\cr
26145 & OpenVMS Debug (I64)\cr
26147 \+Source Code Analyzer /
26164 \+Coverage Analyzer
26168 \+Module Management
26170 & Not applicable\cr
26180 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
26181 @c the TeX version above for the printed version
26183 @c @multitable @columnfractions .3 .4 .4
26184 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
26186 @tab @i{Tool with HP Ada}
26187 @tab @i{Tool with @value{EDITION}}
26188 @item Code Management@*System
26191 @item Language-Sensitive@*Editor
26193 @tab emacs or HP LSE (Alpha)
26202 @tab OpenVMS Debug (I64)
26203 @item Source Code Analyzer /@*Cross Referencer
26207 @tab HP Digital Test@*Manager (DTM)
26209 @item Performance and@*Coverage Analyzer
26212 @item Module Management@*System
26214 @tab Not applicable
26221 @c **************************************
26222 @node Platform-Specific Information for the Run-Time Libraries
26223 @appendix Platform-Specific Information for the Run-Time Libraries
26224 @cindex Tasking and threads libraries
26225 @cindex Threads libraries and tasking
26226 @cindex Run-time libraries (platform-specific information)
26229 The GNAT run-time implementation may vary with respect to both the
26230 underlying threads library and the exception handling scheme.
26231 For threads support, one or more of the following are supplied:
26233 @item @b{native threads library}, a binding to the thread package from
26234 the underlying operating system
26236 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
26237 POSIX thread package
26241 For exception handling, either or both of two models are supplied:
26243 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
26244 Most programs should experience a substantial speed improvement by
26245 being compiled with a ZCX run-time.
26246 This is especially true for
26247 tasking applications or applications with many exception handlers.}
26248 @cindex Zero-Cost Exceptions
26249 @cindex ZCX (Zero-Cost Exceptions)
26250 which uses binder-generated tables that
26251 are interrogated at run time to locate a handler
26253 @item @b{setjmp / longjmp} (``SJLJ''),
26254 @cindex setjmp/longjmp Exception Model
26255 @cindex SJLJ (setjmp/longjmp Exception Model)
26256 which uses dynamically-set data to establish
26257 the set of handlers
26261 This appendix summarizes which combinations of threads and exception support
26262 are supplied on various GNAT platforms.
26263 It then shows how to select a particular library either
26264 permanently or temporarily,
26265 explains the properties of (and tradeoffs among) the various threads
26266 libraries, and provides some additional
26267 information about several specific platforms.
26270 * Summary of Run-Time Configurations::
26271 * Specifying a Run-Time Library::
26272 * Choosing the Scheduling Policy::
26273 * Solaris-Specific Considerations::
26274 * Linux-Specific Considerations::
26275 * AIX-Specific Considerations::
26276 * Irix-Specific Considerations::
26277 * RTX-Specific Considerations::
26280 @node Summary of Run-Time Configurations
26281 @section Summary of Run-Time Configurations
26283 @multitable @columnfractions .30 .70
26284 @item @b{alpha-openvms}
26285 @item @code{@ @ }@i{rts-native (default)}
26286 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26287 @item @code{@ @ @ @ }Exceptions @tab ZCX
26289 @item @b{alpha-tru64}
26290 @item @code{@ @ }@i{rts-native (default)}
26291 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26292 @item @code{@ @ @ @ }Exceptions @tab ZCX
26294 @item @code{@ @ }@i{rts-sjlj}
26295 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26296 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26298 @item @b{ia64-hp_linux}
26299 @item @code{@ @ }@i{rts-native (default)}
26300 @item @code{@ @ @ @ }Tasking @tab pthread library
26301 @item @code{@ @ @ @ }Exceptions @tab ZCX
26303 @item @b{ia64-hpux}
26304 @item @code{@ @ }@i{rts-native (default)}
26305 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26306 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26308 @item @b{ia64-openvms}
26309 @item @code{@ @ }@i{rts-native (default)}
26310 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26311 @item @code{@ @ @ @ }Exceptions @tab ZCX
26313 @item @b{ia64-sgi_linux}
26314 @item @code{@ @ }@i{rts-native (default)}
26315 @item @code{@ @ @ @ }Tasking @tab pthread library
26316 @item @code{@ @ @ @ }Exceptions @tab ZCX
26318 @item @b{mips-irix}
26319 @item @code{@ @ }@i{rts-native (default)}
26320 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
26321 @item @code{@ @ @ @ }Exceptions @tab ZCX
26324 @item @code{@ @ }@i{rts-native (default)}
26325 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26326 @item @code{@ @ @ @ }Exceptions @tab ZCX
26328 @item @code{@ @ }@i{rts-sjlj}
26329 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26330 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26333 @item @code{@ @ }@i{rts-native (default)}
26334 @item @code{@ @ @ @ }Tasking @tab native AIX threads
26335 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26337 @item @b{ppc-darwin}
26338 @item @code{@ @ }@i{rts-native (default)}
26339 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
26340 @item @code{@ @ @ @ }Exceptions @tab ZCX
26342 @item @b{sparc-solaris} @tab
26343 @item @code{@ @ }@i{rts-native (default)}
26344 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26345 @item @code{@ @ @ @ }Exceptions @tab ZCX
26347 @item @code{@ @ }@i{rts-pthread}
26348 @item @code{@ @ @ @ }Tasking @tab pthread library
26349 @item @code{@ @ @ @ }Exceptions @tab ZCX
26351 @item @code{@ @ }@i{rts-sjlj}
26352 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26353 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26355 @item @b{sparc64-solaris} @tab
26356 @item @code{@ @ }@i{rts-native (default)}
26357 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26358 @item @code{@ @ @ @ }Exceptions @tab ZCX
26360 @item @b{x86-linux}
26361 @item @code{@ @ }@i{rts-native (default)}
26362 @item @code{@ @ @ @ }Tasking @tab pthread library
26363 @item @code{@ @ @ @ }Exceptions @tab ZCX
26365 @item @code{@ @ }@i{rts-sjlj}
26366 @item @code{@ @ @ @ }Tasking @tab pthread library
26367 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26370 @item @code{@ @ }@i{rts-native (default)}
26371 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
26372 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26374 @item @b{x86-solaris}
26375 @item @code{@ @ }@i{rts-native (default)}
26376 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
26377 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26379 @item @b{x86-windows}
26380 @item @code{@ @ }@i{rts-native (default)}
26381 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26382 @item @code{@ @ @ @ }Exceptions @tab ZCX
26384 @item @code{@ @ }@i{rts-sjlj (default)}
26385 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26386 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26388 @item @b{x86-windows-rtx}
26389 @item @code{@ @ }@i{rts-rtx-rtss (default)}
26390 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
26391 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26393 @item @code{@ @ }@i{rts-rtx-w32}
26394 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
26395 @item @code{@ @ @ @ }Exceptions @tab ZCX
26397 @item @b{x86_64-linux}
26398 @item @code{@ @ }@i{rts-native (default)}
26399 @item @code{@ @ @ @ }Tasking @tab pthread library
26400 @item @code{@ @ @ @ }Exceptions @tab ZCX
26402 @item @code{@ @ }@i{rts-sjlj}
26403 @item @code{@ @ @ @ }Tasking @tab pthread library
26404 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26408 @node Specifying a Run-Time Library
26409 @section Specifying a Run-Time Library
26412 The @file{adainclude} subdirectory containing the sources of the GNAT
26413 run-time library, and the @file{adalib} subdirectory containing the
26414 @file{ALI} files and the static and/or shared GNAT library, are located
26415 in the gcc target-dependent area:
26418 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
26422 As indicated above, on some platforms several run-time libraries are supplied.
26423 These libraries are installed in the target dependent area and
26424 contain a complete source and binary subdirectory. The detailed description
26425 below explains the differences between the different libraries in terms of
26426 their thread support.
26428 The default run-time library (when GNAT is installed) is @emph{rts-native}.
26429 This default run time is selected by the means of soft links.
26430 For example on x86-linux:
26436 +--- adainclude----------+
26438 +--- adalib-----------+ |
26440 +--- rts-native | |
26442 | +--- adainclude <---+
26444 | +--- adalib <----+
26455 If the @i{rts-sjlj} library is to be selected on a permanent basis,
26456 these soft links can be modified with the following commands:
26460 $ rm -f adainclude adalib
26461 $ ln -s rts-sjlj/adainclude adainclude
26462 $ ln -s rts-sjlj/adalib adalib
26466 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
26467 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
26468 @file{$target/ada_object_path}.
26470 Selecting another run-time library temporarily can be
26471 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
26472 @cindex @option{--RTS} option
26474 @node Choosing the Scheduling Policy
26475 @section Choosing the Scheduling Policy
26478 When using a POSIX threads implementation, you have a choice of several
26479 scheduling policies: @code{SCHED_FIFO},
26480 @cindex @code{SCHED_FIFO} scheduling policy
26482 @cindex @code{SCHED_RR} scheduling policy
26483 and @code{SCHED_OTHER}.
26484 @cindex @code{SCHED_OTHER} scheduling policy
26485 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
26486 or @code{SCHED_RR} requires special (e.g., root) privileges.
26488 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
26490 @cindex @code{SCHED_FIFO} scheduling policy
26491 you can use one of the following:
26495 @code{pragma Time_Slice (0.0)}
26496 @cindex pragma Time_Slice
26498 the corresponding binder option @option{-T0}
26499 @cindex @option{-T0} option
26501 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
26502 @cindex pragma Task_Dispatching_Policy
26506 To specify @code{SCHED_RR},
26507 @cindex @code{SCHED_RR} scheduling policy
26508 you should use @code{pragma Time_Slice} with a
26509 value greater than @code{0.0}, or else use the corresponding @option{-T}
26512 @node Solaris-Specific Considerations
26513 @section Solaris-Specific Considerations
26514 @cindex Solaris Sparc threads libraries
26517 This section addresses some topics related to the various threads libraries
26521 * Solaris Threads Issues::
26524 @node Solaris Threads Issues
26525 @subsection Solaris Threads Issues
26528 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
26529 library based on POSIX threads --- @emph{rts-pthread}.
26530 @cindex rts-pthread threads library
26531 This run-time library has the advantage of being mostly shared across all
26532 POSIX-compliant thread implementations, and it also provides under
26533 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
26534 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
26535 and @code{PTHREAD_PRIO_PROTECT}
26536 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
26537 semantics that can be selected using the predefined pragma
26538 @code{Locking_Policy}
26539 @cindex pragma Locking_Policy (under rts-pthread)
26541 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
26542 @cindex @code{Inheritance_Locking} (under rts-pthread)
26543 @cindex @code{Ceiling_Locking} (under rts-pthread)
26545 As explained above, the native run-time library is based on the Solaris thread
26546 library (@code{libthread}) and is the default library.
26548 When the Solaris threads library is used (this is the default), programs
26549 compiled with GNAT can automatically take advantage of
26550 and can thus execute on multiple processors.
26551 The user can alternatively specify a processor on which the program should run
26552 to emulate a single-processor system. The multiprocessor / uniprocessor choice
26554 setting the environment variable @env{GNAT_PROCESSOR}
26555 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
26556 to one of the following:
26560 Use the default configuration (run the program on all
26561 available processors) - this is the same as having @code{GNAT_PROCESSOR}
26565 Let the run-time implementation choose one processor and run the program on
26568 @item 0 .. Last_Proc
26569 Run the program on the specified processor.
26570 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
26571 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
26574 @node Linux-Specific Considerations
26575 @section Linux-Specific Considerations
26576 @cindex Linux threads libraries
26579 On GNU/Linux without NPTL support (usually system with GNU C Library
26580 older than 2.3), the signal model is not POSIX compliant, which means
26581 that to send a signal to the process, you need to send the signal to all
26582 threads, e.g.@: by using @code{killpg()}.
26584 @node AIX-Specific Considerations
26585 @section AIX-Specific Considerations
26586 @cindex AIX resolver library
26589 On AIX, the resolver library initializes some internal structure on
26590 the first call to @code{get*by*} functions, which are used to implement
26591 @code{GNAT.Sockets.Get_Host_By_Name} and
26592 @code{GNAT.Sockets.Get_Host_By_Address}.
26593 If such initialization occurs within an Ada task, and the stack size for
26594 the task is the default size, a stack overflow may occur.
26596 To avoid this overflow, the user should either ensure that the first call
26597 to @code{GNAT.Sockets.Get_Host_By_Name} or
26598 @code{GNAT.Sockets.Get_Host_By_Addrss}
26599 occurs in the environment task, or use @code{pragma Storage_Size} to
26600 specify a sufficiently large size for the stack of the task that contains
26603 @node Irix-Specific Considerations
26604 @section Irix-Specific Considerations
26605 @cindex Irix libraries
26608 The GCC support libraries coming with the Irix compiler have moved to
26609 their canonical place with respect to the general Irix ABI related
26610 conventions. Running applications built with the default shared GNAT
26611 run-time now requires the LD_LIBRARY_PATH environment variable to
26612 include this location. A possible way to achieve this is to issue the
26613 following command line on a bash prompt:
26617 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
26621 @node RTX-Specific Considerations
26622 @section RTX-Specific Considerations
26623 @cindex RTX libraries
26626 The Real-time Extension (RTX) to Windows is based on the Windows Win32
26627 API. Applications can be built to work in two different modes:
26631 Windows executables that run in Ring 3 to utilize memory protection
26632 (@emph{rts-rtx-w32}).
26635 Real-time subsystem (RTSS) executables that run in Ring 0, where
26636 performance can be optimized with RTSS applications taking precedent
26637 over all Windows applications (@emph{rts-rtx-rtss}).
26641 @c *******************************
26642 @node Example of Binder Output File
26643 @appendix Example of Binder Output File
26646 This Appendix displays the source code for @command{gnatbind}'s output
26647 file generated for a simple ``Hello World'' program.
26648 Comments have been added for clarification purposes.
26650 @smallexample @c adanocomment
26654 -- The package is called Ada_Main unless this name is actually used
26655 -- as a unit name in the partition, in which case some other unique
26659 package ada_main is
26661 Elab_Final_Code : Integer;
26662 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
26664 -- The main program saves the parameters (argument count,
26665 -- argument values, environment pointer) in global variables
26666 -- for later access by other units including
26667 -- Ada.Command_Line.
26669 gnat_argc : Integer;
26670 gnat_argv : System.Address;
26671 gnat_envp : System.Address;
26673 -- The actual variables are stored in a library routine. This
26674 -- is useful for some shared library situations, where there
26675 -- are problems if variables are not in the library.
26677 pragma Import (C, gnat_argc);
26678 pragma Import (C, gnat_argv);
26679 pragma Import (C, gnat_envp);
26681 -- The exit status is similarly an external location
26683 gnat_exit_status : Integer;
26684 pragma Import (C, gnat_exit_status);
26686 GNAT_Version : constant String :=
26687 "GNAT Version: 6.0.0w (20061115)";
26688 pragma Export (C, GNAT_Version, "__gnat_version");
26690 -- This is the generated adafinal routine that performs
26691 -- finalization at the end of execution. In the case where
26692 -- Ada is the main program, this main program makes a call
26693 -- to adafinal at program termination.
26695 procedure adafinal;
26696 pragma Export (C, adafinal, "adafinal");
26698 -- This is the generated adainit routine that performs
26699 -- initialization at the start of execution. In the case
26700 -- where Ada is the main program, this main program makes
26701 -- a call to adainit at program startup.
26704 pragma Export (C, adainit, "adainit");
26706 -- This routine is called at the start of execution. It is
26707 -- a dummy routine that is used by the debugger to breakpoint
26708 -- at the start of execution.
26710 procedure Break_Start;
26711 pragma Import (C, Break_Start, "__gnat_break_start");
26713 -- This is the actual generated main program (it would be
26714 -- suppressed if the no main program switch were used). As
26715 -- required by standard system conventions, this program has
26716 -- the external name main.
26720 argv : System.Address;
26721 envp : System.Address)
26723 pragma Export (C, main, "main");
26725 -- The following set of constants give the version
26726 -- identification values for every unit in the bound
26727 -- partition. This identification is computed from all
26728 -- dependent semantic units, and corresponds to the
26729 -- string that would be returned by use of the
26730 -- Body_Version or Version attributes.
26732 type Version_32 is mod 2 ** 32;
26733 u00001 : constant Version_32 := 16#7880BEB3#;
26734 u00002 : constant Version_32 := 16#0D24CBD0#;
26735 u00003 : constant Version_32 := 16#3283DBEB#;
26736 u00004 : constant Version_32 := 16#2359F9ED#;
26737 u00005 : constant Version_32 := 16#664FB847#;
26738 u00006 : constant Version_32 := 16#68E803DF#;
26739 u00007 : constant Version_32 := 16#5572E604#;
26740 u00008 : constant Version_32 := 16#46B173D8#;
26741 u00009 : constant Version_32 := 16#156A40CF#;
26742 u00010 : constant Version_32 := 16#033DABE0#;
26743 u00011 : constant Version_32 := 16#6AB38FEA#;
26744 u00012 : constant Version_32 := 16#22B6217D#;
26745 u00013 : constant Version_32 := 16#68A22947#;
26746 u00014 : constant Version_32 := 16#18CC4A56#;
26747 u00015 : constant Version_32 := 16#08258E1B#;
26748 u00016 : constant Version_32 := 16#367D5222#;
26749 u00017 : constant Version_32 := 16#20C9ECA4#;
26750 u00018 : constant Version_32 := 16#50D32CB6#;
26751 u00019 : constant Version_32 := 16#39A8BB77#;
26752 u00020 : constant Version_32 := 16#5CF8FA2B#;
26753 u00021 : constant Version_32 := 16#2F1EB794#;
26754 u00022 : constant Version_32 := 16#31AB6444#;
26755 u00023 : constant Version_32 := 16#1574B6E9#;
26756 u00024 : constant Version_32 := 16#5109C189#;
26757 u00025 : constant Version_32 := 16#56D770CD#;
26758 u00026 : constant Version_32 := 16#02F9DE3D#;
26759 u00027 : constant Version_32 := 16#08AB6B2C#;
26760 u00028 : constant Version_32 := 16#3FA37670#;
26761 u00029 : constant Version_32 := 16#476457A0#;
26762 u00030 : constant Version_32 := 16#731E1B6E#;
26763 u00031 : constant Version_32 := 16#23C2E789#;
26764 u00032 : constant Version_32 := 16#0F1BD6A1#;
26765 u00033 : constant Version_32 := 16#7C25DE96#;
26766 u00034 : constant Version_32 := 16#39ADFFA2#;
26767 u00035 : constant Version_32 := 16#571DE3E7#;
26768 u00036 : constant Version_32 := 16#5EB646AB#;
26769 u00037 : constant Version_32 := 16#4249379B#;
26770 u00038 : constant Version_32 := 16#0357E00A#;
26771 u00039 : constant Version_32 := 16#3784FB72#;
26772 u00040 : constant Version_32 := 16#2E723019#;
26773 u00041 : constant Version_32 := 16#623358EA#;
26774 u00042 : constant Version_32 := 16#107F9465#;
26775 u00043 : constant Version_32 := 16#6843F68A#;
26776 u00044 : constant Version_32 := 16#63305874#;
26777 u00045 : constant Version_32 := 16#31E56CE1#;
26778 u00046 : constant Version_32 := 16#02917970#;
26779 u00047 : constant Version_32 := 16#6CCBA70E#;
26780 u00048 : constant Version_32 := 16#41CD4204#;
26781 u00049 : constant Version_32 := 16#572E3F58#;
26782 u00050 : constant Version_32 := 16#20729FF5#;
26783 u00051 : constant Version_32 := 16#1D4F93E8#;
26784 u00052 : constant Version_32 := 16#30B2EC3D#;
26785 u00053 : constant Version_32 := 16#34054F96#;
26786 u00054 : constant Version_32 := 16#5A199860#;
26787 u00055 : constant Version_32 := 16#0E7F912B#;
26788 u00056 : constant Version_32 := 16#5760634A#;
26789 u00057 : constant Version_32 := 16#5D851835#;
26791 -- The following Export pragmas export the version numbers
26792 -- with symbolic names ending in B (for body) or S
26793 -- (for spec) so that they can be located in a link. The
26794 -- information provided here is sufficient to track down
26795 -- the exact versions of units used in a given build.
26797 pragma Export (C, u00001, "helloB");
26798 pragma Export (C, u00002, "system__standard_libraryB");
26799 pragma Export (C, u00003, "system__standard_libraryS");
26800 pragma Export (C, u00004, "adaS");
26801 pragma Export (C, u00005, "ada__text_ioB");
26802 pragma Export (C, u00006, "ada__text_ioS");
26803 pragma Export (C, u00007, "ada__exceptionsB");
26804 pragma Export (C, u00008, "ada__exceptionsS");
26805 pragma Export (C, u00009, "gnatS");
26806 pragma Export (C, u00010, "gnat__heap_sort_aB");
26807 pragma Export (C, u00011, "gnat__heap_sort_aS");
26808 pragma Export (C, u00012, "systemS");
26809 pragma Export (C, u00013, "system__exception_tableB");
26810 pragma Export (C, u00014, "system__exception_tableS");
26811 pragma Export (C, u00015, "gnat__htableB");
26812 pragma Export (C, u00016, "gnat__htableS");
26813 pragma Export (C, u00017, "system__exceptionsS");
26814 pragma Export (C, u00018, "system__machine_state_operationsB");
26815 pragma Export (C, u00019, "system__machine_state_operationsS");
26816 pragma Export (C, u00020, "system__machine_codeS");
26817 pragma Export (C, u00021, "system__storage_elementsB");
26818 pragma Export (C, u00022, "system__storage_elementsS");
26819 pragma Export (C, u00023, "system__secondary_stackB");
26820 pragma Export (C, u00024, "system__secondary_stackS");
26821 pragma Export (C, u00025, "system__parametersB");
26822 pragma Export (C, u00026, "system__parametersS");
26823 pragma Export (C, u00027, "system__soft_linksB");
26824 pragma Export (C, u00028, "system__soft_linksS");
26825 pragma Export (C, u00029, "system__stack_checkingB");
26826 pragma Export (C, u00030, "system__stack_checkingS");
26827 pragma Export (C, u00031, "system__tracebackB");
26828 pragma Export (C, u00032, "system__tracebackS");
26829 pragma Export (C, u00033, "ada__streamsS");
26830 pragma Export (C, u00034, "ada__tagsB");
26831 pragma Export (C, u00035, "ada__tagsS");
26832 pragma Export (C, u00036, "system__string_opsB");
26833 pragma Export (C, u00037, "system__string_opsS");
26834 pragma Export (C, u00038, "interfacesS");
26835 pragma Export (C, u00039, "interfaces__c_streamsB");
26836 pragma Export (C, u00040, "interfaces__c_streamsS");
26837 pragma Export (C, u00041, "system__file_ioB");
26838 pragma Export (C, u00042, "system__file_ioS");
26839 pragma Export (C, u00043, "ada__finalizationB");
26840 pragma Export (C, u00044, "ada__finalizationS");
26841 pragma Export (C, u00045, "system__finalization_rootB");
26842 pragma Export (C, u00046, "system__finalization_rootS");
26843 pragma Export (C, u00047, "system__finalization_implementationB");
26844 pragma Export (C, u00048, "system__finalization_implementationS");
26845 pragma Export (C, u00049, "system__string_ops_concat_3B");
26846 pragma Export (C, u00050, "system__string_ops_concat_3S");
26847 pragma Export (C, u00051, "system__stream_attributesB");
26848 pragma Export (C, u00052, "system__stream_attributesS");
26849 pragma Export (C, u00053, "ada__io_exceptionsS");
26850 pragma Export (C, u00054, "system__unsigned_typesS");
26851 pragma Export (C, u00055, "system__file_control_blockS");
26852 pragma Export (C, u00056, "ada__finalization__list_controllerB");
26853 pragma Export (C, u00057, "ada__finalization__list_controllerS");
26855 -- BEGIN ELABORATION ORDER
26858 -- gnat.heap_sort_a (spec)
26859 -- gnat.heap_sort_a (body)
26860 -- gnat.htable (spec)
26861 -- gnat.htable (body)
26862 -- interfaces (spec)
26864 -- system.machine_code (spec)
26865 -- system.parameters (spec)
26866 -- system.parameters (body)
26867 -- interfaces.c_streams (spec)
26868 -- interfaces.c_streams (body)
26869 -- system.standard_library (spec)
26870 -- ada.exceptions (spec)
26871 -- system.exception_table (spec)
26872 -- system.exception_table (body)
26873 -- ada.io_exceptions (spec)
26874 -- system.exceptions (spec)
26875 -- system.storage_elements (spec)
26876 -- system.storage_elements (body)
26877 -- system.machine_state_operations (spec)
26878 -- system.machine_state_operations (body)
26879 -- system.secondary_stack (spec)
26880 -- system.stack_checking (spec)
26881 -- system.soft_links (spec)
26882 -- system.soft_links (body)
26883 -- system.stack_checking (body)
26884 -- system.secondary_stack (body)
26885 -- system.standard_library (body)
26886 -- system.string_ops (spec)
26887 -- system.string_ops (body)
26890 -- ada.streams (spec)
26891 -- system.finalization_root (spec)
26892 -- system.finalization_root (body)
26893 -- system.string_ops_concat_3 (spec)
26894 -- system.string_ops_concat_3 (body)
26895 -- system.traceback (spec)
26896 -- system.traceback (body)
26897 -- ada.exceptions (body)
26898 -- system.unsigned_types (spec)
26899 -- system.stream_attributes (spec)
26900 -- system.stream_attributes (body)
26901 -- system.finalization_implementation (spec)
26902 -- system.finalization_implementation (body)
26903 -- ada.finalization (spec)
26904 -- ada.finalization (body)
26905 -- ada.finalization.list_controller (spec)
26906 -- ada.finalization.list_controller (body)
26907 -- system.file_control_block (spec)
26908 -- system.file_io (spec)
26909 -- system.file_io (body)
26910 -- ada.text_io (spec)
26911 -- ada.text_io (body)
26913 -- END ELABORATION ORDER
26917 -- The following source file name pragmas allow the generated file
26918 -- names to be unique for different main programs. They are needed
26919 -- since the package name will always be Ada_Main.
26921 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26922 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26924 -- Generated package body for Ada_Main starts here
26926 package body ada_main is
26928 -- The actual finalization is performed by calling the
26929 -- library routine in System.Standard_Library.Adafinal
26931 procedure Do_Finalize;
26932 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
26939 procedure adainit is
26941 -- These booleans are set to True once the associated unit has
26942 -- been elaborated. It is also used to avoid elaborating the
26943 -- same unit twice.
26946 pragma Import (Ada, E040, "interfaces__c_streams_E");
26949 pragma Import (Ada, E008, "ada__exceptions_E");
26952 pragma Import (Ada, E014, "system__exception_table_E");
26955 pragma Import (Ada, E053, "ada__io_exceptions_E");
26958 pragma Import (Ada, E017, "system__exceptions_E");
26961 pragma Import (Ada, E024, "system__secondary_stack_E");
26964 pragma Import (Ada, E030, "system__stack_checking_E");
26967 pragma Import (Ada, E028, "system__soft_links_E");
26970 pragma Import (Ada, E035, "ada__tags_E");
26973 pragma Import (Ada, E033, "ada__streams_E");
26976 pragma Import (Ada, E046, "system__finalization_root_E");
26979 pragma Import (Ada, E048, "system__finalization_implementation_E");
26982 pragma Import (Ada, E044, "ada__finalization_E");
26985 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
26988 pragma Import (Ada, E055, "system__file_control_block_E");
26991 pragma Import (Ada, E042, "system__file_io_E");
26994 pragma Import (Ada, E006, "ada__text_io_E");
26996 -- Set_Globals is a library routine that stores away the
26997 -- value of the indicated set of global values in global
26998 -- variables within the library.
27000 procedure Set_Globals
27001 (Main_Priority : Integer;
27002 Time_Slice_Value : Integer;
27003 WC_Encoding : Character;
27004 Locking_Policy : Character;
27005 Queuing_Policy : Character;
27006 Task_Dispatching_Policy : Character;
27007 Adafinal : System.Address;
27008 Unreserve_All_Interrupts : Integer;
27009 Exception_Tracebacks : Integer);
27010 @findex __gnat_set_globals
27011 pragma Import (C, Set_Globals, "__gnat_set_globals");
27013 -- SDP_Table_Build is a library routine used to build the
27014 -- exception tables. See unit Ada.Exceptions in files
27015 -- a-except.ads/adb for full details of how zero cost
27016 -- exception handling works. This procedure, the call to
27017 -- it, and the two following tables are all omitted if the
27018 -- build is in longjmp/setjmp exception mode.
27020 @findex SDP_Table_Build
27021 @findex Zero Cost Exceptions
27022 procedure SDP_Table_Build
27023 (SDP_Addresses : System.Address;
27024 SDP_Count : Natural;
27025 Elab_Addresses : System.Address;
27026 Elab_Addr_Count : Natural);
27027 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
27029 -- Table of Unit_Exception_Table addresses. Used for zero
27030 -- cost exception handling to build the top level table.
27032 ST : aliased constant array (1 .. 23) of System.Address := (
27034 Ada.Text_Io'UET_Address,
27035 Ada.Exceptions'UET_Address,
27036 Gnat.Heap_Sort_A'UET_Address,
27037 System.Exception_Table'UET_Address,
27038 System.Machine_State_Operations'UET_Address,
27039 System.Secondary_Stack'UET_Address,
27040 System.Parameters'UET_Address,
27041 System.Soft_Links'UET_Address,
27042 System.Stack_Checking'UET_Address,
27043 System.Traceback'UET_Address,
27044 Ada.Streams'UET_Address,
27045 Ada.Tags'UET_Address,
27046 System.String_Ops'UET_Address,
27047 Interfaces.C_Streams'UET_Address,
27048 System.File_Io'UET_Address,
27049 Ada.Finalization'UET_Address,
27050 System.Finalization_Root'UET_Address,
27051 System.Finalization_Implementation'UET_Address,
27052 System.String_Ops_Concat_3'UET_Address,
27053 System.Stream_Attributes'UET_Address,
27054 System.File_Control_Block'UET_Address,
27055 Ada.Finalization.List_Controller'UET_Address);
27057 -- Table of addresses of elaboration routines. Used for
27058 -- zero cost exception handling to make sure these
27059 -- addresses are included in the top level procedure
27062 EA : aliased constant array (1 .. 23) of System.Address := (
27063 adainit'Code_Address,
27064 Do_Finalize'Code_Address,
27065 Ada.Exceptions'Elab_Spec'Address,
27066 System.Exceptions'Elab_Spec'Address,
27067 Interfaces.C_Streams'Elab_Spec'Address,
27068 System.Exception_Table'Elab_Body'Address,
27069 Ada.Io_Exceptions'Elab_Spec'Address,
27070 System.Stack_Checking'Elab_Spec'Address,
27071 System.Soft_Links'Elab_Body'Address,
27072 System.Secondary_Stack'Elab_Body'Address,
27073 Ada.Tags'Elab_Spec'Address,
27074 Ada.Tags'Elab_Body'Address,
27075 Ada.Streams'Elab_Spec'Address,
27076 System.Finalization_Root'Elab_Spec'Address,
27077 Ada.Exceptions'Elab_Body'Address,
27078 System.Finalization_Implementation'Elab_Spec'Address,
27079 System.Finalization_Implementation'Elab_Body'Address,
27080 Ada.Finalization'Elab_Spec'Address,
27081 Ada.Finalization.List_Controller'Elab_Spec'Address,
27082 System.File_Control_Block'Elab_Spec'Address,
27083 System.File_Io'Elab_Body'Address,
27084 Ada.Text_Io'Elab_Spec'Address,
27085 Ada.Text_Io'Elab_Body'Address);
27087 -- Start of processing for adainit
27091 -- Call SDP_Table_Build to build the top level procedure
27092 -- table for zero cost exception handling (omitted in
27093 -- longjmp/setjmp mode).
27095 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
27097 -- Call Set_Globals to record various information for
27098 -- this partition. The values are derived by the binder
27099 -- from information stored in the ali files by the compiler.
27101 @findex __gnat_set_globals
27103 (Main_Priority => -1,
27104 -- Priority of main program, -1 if no pragma Priority used
27106 Time_Slice_Value => -1,
27107 -- Time slice from Time_Slice pragma, -1 if none used
27109 WC_Encoding => 'b',
27110 -- Wide_Character encoding used, default is brackets
27112 Locking_Policy => ' ',
27113 -- Locking_Policy used, default of space means not
27114 -- specified, otherwise it is the first character of
27115 -- the policy name.
27117 Queuing_Policy => ' ',
27118 -- Queuing_Policy used, default of space means not
27119 -- specified, otherwise it is the first character of
27120 -- the policy name.
27122 Task_Dispatching_Policy => ' ',
27123 -- Task_Dispatching_Policy used, default of space means
27124 -- not specified, otherwise first character of the
27127 Adafinal => System.Null_Address,
27128 -- Address of Adafinal routine, not used anymore
27130 Unreserve_All_Interrupts => 0,
27131 -- Set true if pragma Unreserve_All_Interrupts was used
27133 Exception_Tracebacks => 0);
27134 -- Indicates if exception tracebacks are enabled
27136 Elab_Final_Code := 1;
27138 -- Now we have the elaboration calls for all units in the partition.
27139 -- The Elab_Spec and Elab_Body attributes generate references to the
27140 -- implicit elaboration procedures generated by the compiler for
27141 -- each unit that requires elaboration.
27144 Interfaces.C_Streams'Elab_Spec;
27148 Ada.Exceptions'Elab_Spec;
27151 System.Exception_Table'Elab_Body;
27155 Ada.Io_Exceptions'Elab_Spec;
27159 System.Exceptions'Elab_Spec;
27163 System.Stack_Checking'Elab_Spec;
27166 System.Soft_Links'Elab_Body;
27171 System.Secondary_Stack'Elab_Body;
27175 Ada.Tags'Elab_Spec;
27178 Ada.Tags'Elab_Body;
27182 Ada.Streams'Elab_Spec;
27186 System.Finalization_Root'Elab_Spec;
27190 Ada.Exceptions'Elab_Body;
27194 System.Finalization_Implementation'Elab_Spec;
27197 System.Finalization_Implementation'Elab_Body;
27201 Ada.Finalization'Elab_Spec;
27205 Ada.Finalization.List_Controller'Elab_Spec;
27209 System.File_Control_Block'Elab_Spec;
27213 System.File_Io'Elab_Body;
27217 Ada.Text_Io'Elab_Spec;
27220 Ada.Text_Io'Elab_Body;
27224 Elab_Final_Code := 0;
27232 procedure adafinal is
27241 -- main is actually a function, as in the ANSI C standard,
27242 -- defined to return the exit status. The three parameters
27243 -- are the argument count, argument values and environment
27246 @findex Main Program
27249 argv : System.Address;
27250 envp : System.Address)
27253 -- The initialize routine performs low level system
27254 -- initialization using a standard library routine which
27255 -- sets up signal handling and performs any other
27256 -- required setup. The routine can be found in file
27259 @findex __gnat_initialize
27260 procedure initialize;
27261 pragma Import (C, initialize, "__gnat_initialize");
27263 -- The finalize routine performs low level system
27264 -- finalization using a standard library routine. The
27265 -- routine is found in file a-final.c and in the standard
27266 -- distribution is a dummy routine that does nothing, so
27267 -- really this is a hook for special user finalization.
27269 @findex __gnat_finalize
27270 procedure finalize;
27271 pragma Import (C, finalize, "__gnat_finalize");
27273 -- We get to the main program of the partition by using
27274 -- pragma Import because if we try to with the unit and
27275 -- call it Ada style, then not only do we waste time
27276 -- recompiling it, but also, we don't really know the right
27277 -- switches (e.g.@: identifier character set) to be used
27280 procedure Ada_Main_Program;
27281 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27283 -- Start of processing for main
27286 -- Save global variables
27292 -- Call low level system initialization
27296 -- Call our generated Ada initialization routine
27300 -- This is the point at which we want the debugger to get
27305 -- Now we call the main program of the partition
27309 -- Perform Ada finalization
27313 -- Perform low level system finalization
27317 -- Return the proper exit status
27318 return (gnat_exit_status);
27321 -- This section is entirely comments, so it has no effect on the
27322 -- compilation of the Ada_Main package. It provides the list of
27323 -- object files and linker options, as well as some standard
27324 -- libraries needed for the link. The gnatlink utility parses
27325 -- this b~hello.adb file to read these comment lines to generate
27326 -- the appropriate command line arguments for the call to the
27327 -- system linker. The BEGIN/END lines are used for sentinels for
27328 -- this parsing operation.
27330 -- The exact file names will of course depend on the environment,
27331 -- host/target and location of files on the host system.
27333 @findex Object file list
27334 -- BEGIN Object file/option list
27337 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27338 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27339 -- END Object file/option list
27345 The Ada code in the above example is exactly what is generated by the
27346 binder. We have added comments to more clearly indicate the function
27347 of each part of the generated @code{Ada_Main} package.
27349 The code is standard Ada in all respects, and can be processed by any
27350 tools that handle Ada. In particular, it is possible to use the debugger
27351 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27352 suppose that for reasons that you do not understand, your program is crashing
27353 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27354 you can place a breakpoint on the call:
27356 @smallexample @c ada
27357 Ada.Text_Io'Elab_Body;
27361 and trace the elaboration routine for this package to find out where
27362 the problem might be (more usually of course you would be debugging
27363 elaboration code in your own application).
27365 @node Elaboration Order Handling in GNAT
27366 @appendix Elaboration Order Handling in GNAT
27367 @cindex Order of elaboration
27368 @cindex Elaboration control
27371 * Elaboration Code::
27372 * Checking the Elaboration Order::
27373 * Controlling the Elaboration Order::
27374 * Controlling Elaboration in GNAT - Internal Calls::
27375 * Controlling Elaboration in GNAT - External Calls::
27376 * Default Behavior in GNAT - Ensuring Safety::
27377 * Treatment of Pragma Elaborate::
27378 * Elaboration Issues for Library Tasks::
27379 * Mixing Elaboration Models::
27380 * What to Do If the Default Elaboration Behavior Fails::
27381 * Elaboration for Access-to-Subprogram Values::
27382 * Summary of Procedures for Elaboration Control::
27383 * Other Elaboration Order Considerations::
27387 This chapter describes the handling of elaboration code in Ada and
27388 in GNAT, and discusses how the order of elaboration of program units can
27389 be controlled in GNAT, either automatically or with explicit programming
27392 @node Elaboration Code
27393 @section Elaboration Code
27396 Ada provides rather general mechanisms for executing code at elaboration
27397 time, that is to say before the main program starts executing. Such code arises
27401 @item Initializers for variables.
27402 Variables declared at the library level, in package specs or bodies, can
27403 require initialization that is performed at elaboration time, as in:
27404 @smallexample @c ada
27406 Sqrt_Half : Float := Sqrt (0.5);
27410 @item Package initialization code
27411 Code in a @code{BEGIN-END} section at the outer level of a package body is
27412 executed as part of the package body elaboration code.
27414 @item Library level task allocators
27415 Tasks that are declared using task allocators at the library level
27416 start executing immediately and hence can execute at elaboration time.
27420 Subprogram calls are possible in any of these contexts, which means that
27421 any arbitrary part of the program may be executed as part of the elaboration
27422 code. It is even possible to write a program which does all its work at
27423 elaboration time, with a null main program, although stylistically this
27424 would usually be considered an inappropriate way to structure
27427 An important concern arises in the context of elaboration code:
27428 we have to be sure that it is executed in an appropriate order. What we
27429 have is a series of elaboration code sections, potentially one section
27430 for each unit in the program. It is important that these execute
27431 in the correct order. Correctness here means that, taking the above
27432 example of the declaration of @code{Sqrt_Half},
27433 if some other piece of
27434 elaboration code references @code{Sqrt_Half},
27435 then it must run after the
27436 section of elaboration code that contains the declaration of
27439 There would never be any order of elaboration problem if we made a rule
27440 that whenever you @code{with} a unit, you must elaborate both the spec and body
27441 of that unit before elaborating the unit doing the @code{with}'ing:
27443 @smallexample @c ada
27447 package Unit_2 is @dots{}
27453 would require that both the body and spec of @code{Unit_1} be elaborated
27454 before the spec of @code{Unit_2}. However, a rule like that would be far too
27455 restrictive. In particular, it would make it impossible to have routines
27456 in separate packages that were mutually recursive.
27458 You might think that a clever enough compiler could look at the actual
27459 elaboration code and determine an appropriate correct order of elaboration,
27460 but in the general case, this is not possible. Consider the following
27463 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
27465 the variable @code{Sqrt_1}, which is declared in the elaboration code
27466 of the body of @code{Unit_1}:
27468 @smallexample @c ada
27470 Sqrt_1 : Float := Sqrt (0.1);
27475 The elaboration code of the body of @code{Unit_1} also contains:
27477 @smallexample @c ada
27480 if expression_1 = 1 then
27481 Q := Unit_2.Func_2;
27488 @code{Unit_2} is exactly parallel,
27489 it has a procedure @code{Func_2} that references
27490 the variable @code{Sqrt_2}, which is declared in the elaboration code of
27491 the body @code{Unit_2}:
27493 @smallexample @c ada
27495 Sqrt_2 : Float := Sqrt (0.1);
27500 The elaboration code of the body of @code{Unit_2} also contains:
27502 @smallexample @c ada
27505 if expression_2 = 2 then
27506 Q := Unit_1.Func_1;
27513 Now the question is, which of the following orders of elaboration is
27538 If you carefully analyze the flow here, you will see that you cannot tell
27539 at compile time the answer to this question.
27540 If @code{expression_1} is not equal to 1,
27541 and @code{expression_2} is not equal to 2,
27542 then either order is acceptable, because neither of the function calls is
27543 executed. If both tests evaluate to true, then neither order is acceptable
27544 and in fact there is no correct order.
27546 If one of the two expressions is true, and the other is false, then one
27547 of the above orders is correct, and the other is incorrect. For example,
27548 if @code{expression_1} /= 1 and @code{expression_2} = 2,
27549 then the call to @code{Func_1}
27550 will occur, but not the call to @code{Func_2.}
27551 This means that it is essential
27552 to elaborate the body of @code{Unit_1} before
27553 the body of @code{Unit_2}, so the first
27554 order of elaboration is correct and the second is wrong.
27556 By making @code{expression_1} and @code{expression_2}
27557 depend on input data, or perhaps
27558 the time of day, we can make it impossible for the compiler or binder
27559 to figure out which of these expressions will be true, and hence it
27560 is impossible to guarantee a safe order of elaboration at run time.
27562 @node Checking the Elaboration Order
27563 @section Checking the Elaboration Order
27566 In some languages that involve the same kind of elaboration problems,
27567 e.g.@: Java and C++, the programmer is expected to worry about these
27568 ordering problems himself, and it is common to
27569 write a program in which an incorrect elaboration order gives
27570 surprising results, because it references variables before they
27572 Ada is designed to be a safe language, and a programmer-beware approach is
27573 clearly not sufficient. Consequently, the language provides three lines
27577 @item Standard rules
27578 Some standard rules restrict the possible choice of elaboration
27579 order. In particular, if you @code{with} a unit, then its spec is always
27580 elaborated before the unit doing the @code{with}. Similarly, a parent
27581 spec is always elaborated before the child spec, and finally
27582 a spec is always elaborated before its corresponding body.
27584 @item Dynamic elaboration checks
27585 @cindex Elaboration checks
27586 @cindex Checks, elaboration
27587 Dynamic checks are made at run time, so that if some entity is accessed
27588 before it is elaborated (typically by means of a subprogram call)
27589 then the exception (@code{Program_Error}) is raised.
27591 @item Elaboration control
27592 Facilities are provided for the programmer to specify the desired order
27596 Let's look at these facilities in more detail. First, the rules for
27597 dynamic checking. One possible rule would be simply to say that the
27598 exception is raised if you access a variable which has not yet been
27599 elaborated. The trouble with this approach is that it could require
27600 expensive checks on every variable reference. Instead Ada has two
27601 rules which are a little more restrictive, but easier to check, and
27605 @item Restrictions on calls
27606 A subprogram can only be called at elaboration time if its body
27607 has been elaborated. The rules for elaboration given above guarantee
27608 that the spec of the subprogram has been elaborated before the
27609 call, but not the body. If this rule is violated, then the
27610 exception @code{Program_Error} is raised.
27612 @item Restrictions on instantiations
27613 A generic unit can only be instantiated if the body of the generic
27614 unit has been elaborated. Again, the rules for elaboration given above
27615 guarantee that the spec of the generic unit has been elaborated
27616 before the instantiation, but not the body. If this rule is
27617 violated, then the exception @code{Program_Error} is raised.
27621 The idea is that if the body has been elaborated, then any variables
27622 it references must have been elaborated; by checking for the body being
27623 elaborated we guarantee that none of its references causes any
27624 trouble. As we noted above, this is a little too restrictive, because a
27625 subprogram that has no non-local references in its body may in fact be safe
27626 to call. However, it really would be unsafe to rely on this, because
27627 it would mean that the caller was aware of details of the implementation
27628 in the body. This goes against the basic tenets of Ada.
27630 A plausible implementation can be described as follows.
27631 A Boolean variable is associated with each subprogram
27632 and each generic unit. This variable is initialized to False, and is set to
27633 True at the point body is elaborated. Every call or instantiation checks the
27634 variable, and raises @code{Program_Error} if the variable is False.
27636 Note that one might think that it would be good enough to have one Boolean
27637 variable for each package, but that would not deal with cases of trying
27638 to call a body in the same package as the call
27639 that has not been elaborated yet.
27640 Of course a compiler may be able to do enough analysis to optimize away
27641 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
27642 does such optimizations, but still the easiest conceptual model is to
27643 think of there being one variable per subprogram.
27645 @node Controlling the Elaboration Order
27646 @section Controlling the Elaboration Order
27649 In the previous section we discussed the rules in Ada which ensure
27650 that @code{Program_Error} is raised if an incorrect elaboration order is
27651 chosen. This prevents erroneous executions, but we need mechanisms to
27652 specify a correct execution and avoid the exception altogether.
27653 To achieve this, Ada provides a number of features for controlling
27654 the order of elaboration. We discuss these features in this section.
27656 First, there are several ways of indicating to the compiler that a given
27657 unit has no elaboration problems:
27660 @item packages that do not require a body
27661 A library package that does not require a body does not permit
27662 a body (this rule was introduced in Ada 95).
27663 Thus if we have a such a package, as in:
27665 @smallexample @c ada
27668 package Definitions is
27670 type m is new integer;
27672 type a is array (1 .. 10) of m;
27673 type b is array (1 .. 20) of m;
27681 A package that @code{with}'s @code{Definitions} may safely instantiate
27682 @code{Definitions.Subp} because the compiler can determine that there
27683 definitely is no package body to worry about in this case
27686 @cindex pragma Pure
27688 Places sufficient restrictions on a unit to guarantee that
27689 no call to any subprogram in the unit can result in an
27690 elaboration problem. This means that the compiler does not need
27691 to worry about the point of elaboration of such units, and in
27692 particular, does not need to check any calls to any subprograms
27695 @item pragma Preelaborate
27696 @findex Preelaborate
27697 @cindex pragma Preelaborate
27698 This pragma places slightly less stringent restrictions on a unit than
27700 but these restrictions are still sufficient to ensure that there
27701 are no elaboration problems with any calls to the unit.
27703 @item pragma Elaborate_Body
27704 @findex Elaborate_Body
27705 @cindex pragma Elaborate_Body
27706 This pragma requires that the body of a unit be elaborated immediately
27707 after its spec. Suppose a unit @code{A} has such a pragma,
27708 and unit @code{B} does
27709 a @code{with} of unit @code{A}. Recall that the standard rules require
27710 the spec of unit @code{A}
27711 to be elaborated before the @code{with}'ing unit; given the pragma in
27712 @code{A}, we also know that the body of @code{A}
27713 will be elaborated before @code{B}, so
27714 that calls to @code{A} are safe and do not need a check.
27719 unlike pragma @code{Pure} and pragma @code{Preelaborate},
27721 @code{Elaborate_Body} does not guarantee that the program is
27722 free of elaboration problems, because it may not be possible
27723 to satisfy the requested elaboration order.
27724 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
27726 marks @code{Unit_1} as @code{Elaborate_Body},
27727 and not @code{Unit_2,} then the order of
27728 elaboration will be:
27740 Now that means that the call to @code{Func_1} in @code{Unit_2}
27741 need not be checked,
27742 it must be safe. But the call to @code{Func_2} in
27743 @code{Unit_1} may still fail if
27744 @code{Expression_1} is equal to 1,
27745 and the programmer must still take
27746 responsibility for this not being the case.
27748 If all units carry a pragma @code{Elaborate_Body}, then all problems are
27749 eliminated, except for calls entirely within a body, which are
27750 in any case fully under programmer control. However, using the pragma
27751 everywhere is not always possible.
27752 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
27753 we marked both of them as having pragma @code{Elaborate_Body}, then
27754 clearly there would be no possible elaboration order.
27756 The above pragmas allow a server to guarantee safe use by clients, and
27757 clearly this is the preferable approach. Consequently a good rule
27758 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
27759 and if this is not possible,
27760 mark them as @code{Elaborate_Body} if possible.
27761 As we have seen, there are situations where neither of these
27762 three pragmas can be used.
27763 So we also provide methods for clients to control the
27764 order of elaboration of the servers on which they depend:
27767 @item pragma Elaborate (unit)
27769 @cindex pragma Elaborate
27770 This pragma is placed in the context clause, after a @code{with} clause,
27771 and it requires that the body of the named unit be elaborated before
27772 the unit in which the pragma occurs. The idea is to use this pragma
27773 if the current unit calls at elaboration time, directly or indirectly,
27774 some subprogram in the named unit.
27776 @item pragma Elaborate_All (unit)
27777 @findex Elaborate_All
27778 @cindex pragma Elaborate_All
27779 This is a stronger version of the Elaborate pragma. Consider the
27783 Unit A @code{with}'s unit B and calls B.Func in elab code
27784 Unit B @code{with}'s unit C, and B.Func calls C.Func
27788 Now if we put a pragma @code{Elaborate (B)}
27789 in unit @code{A}, this ensures that the
27790 body of @code{B} is elaborated before the call, but not the
27791 body of @code{C}, so
27792 the call to @code{C.Func} could still cause @code{Program_Error} to
27795 The effect of a pragma @code{Elaborate_All} is stronger, it requires
27796 not only that the body of the named unit be elaborated before the
27797 unit doing the @code{with}, but also the bodies of all units that the
27798 named unit uses, following @code{with} links transitively. For example,
27799 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
27801 not only that the body of @code{B} be elaborated before @code{A},
27803 body of @code{C}, because @code{B} @code{with}'s @code{C}.
27807 We are now in a position to give a usage rule in Ada for avoiding
27808 elaboration problems, at least if dynamic dispatching and access to
27809 subprogram values are not used. We will handle these cases separately
27812 The rule is simple. If a unit has elaboration code that can directly or
27813 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
27814 a generic package in a @code{with}'ed unit,
27815 then if the @code{with}'ed unit does not have
27816 pragma @code{Pure} or @code{Preelaborate}, then the client should have
27817 a pragma @code{Elaborate_All}
27818 for the @code{with}'ed unit. By following this rule a client is
27819 assured that calls can be made without risk of an exception.
27821 For generic subprogram instantiations, the rule can be relaxed to
27822 require only a pragma @code{Elaborate} since elaborating the body
27823 of a subprogram cannot cause any transitive elaboration (we are
27824 not calling the subprogram in this case, just elaborating its
27827 If this rule is not followed, then a program may be in one of four
27831 @item No order exists
27832 No order of elaboration exists which follows the rules, taking into
27833 account any @code{Elaborate}, @code{Elaborate_All},
27834 or @code{Elaborate_Body} pragmas. In
27835 this case, an Ada compiler must diagnose the situation at bind
27836 time, and refuse to build an executable program.
27838 @item One or more orders exist, all incorrect
27839 One or more acceptable elaboration orders exist, and all of them
27840 generate an elaboration order problem. In this case, the binder
27841 can build an executable program, but @code{Program_Error} will be raised
27842 when the program is run.
27844 @item Several orders exist, some right, some incorrect
27845 One or more acceptable elaboration orders exists, and some of them
27846 work, and some do not. The programmer has not controlled
27847 the order of elaboration, so the binder may or may not pick one of
27848 the correct orders, and the program may or may not raise an
27849 exception when it is run. This is the worst case, because it means
27850 that the program may fail when moved to another compiler, or even
27851 another version of the same compiler.
27853 @item One or more orders exists, all correct
27854 One ore more acceptable elaboration orders exist, and all of them
27855 work. In this case the program runs successfully. This state of
27856 affairs can be guaranteed by following the rule we gave above, but
27857 may be true even if the rule is not followed.
27861 Note that one additional advantage of following our rules on the use
27862 of @code{Elaborate} and @code{Elaborate_All}
27863 is that the program continues to stay in the ideal (all orders OK) state
27864 even if maintenance
27865 changes some bodies of some units. Conversely, if a program that does
27866 not follow this rule happens to be safe at some point, this state of affairs
27867 may deteriorate silently as a result of maintenance changes.
27869 You may have noticed that the above discussion did not mention
27870 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
27871 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
27872 code in the body makes calls to some other unit, so it is still necessary
27873 to use @code{Elaborate_All} on such units.
27875 @node Controlling Elaboration in GNAT - Internal Calls
27876 @section Controlling Elaboration in GNAT - Internal Calls
27879 In the case of internal calls, i.e., calls within a single package, the
27880 programmer has full control over the order of elaboration, and it is up
27881 to the programmer to elaborate declarations in an appropriate order. For
27884 @smallexample @c ada
27887 function One return Float;
27891 function One return Float is
27900 will obviously raise @code{Program_Error} at run time, because function
27901 One will be called before its body is elaborated. In this case GNAT will
27902 generate a warning that the call will raise @code{Program_Error}:
27908 2. function One return Float;
27910 4. Q : Float := One;
27912 >>> warning: cannot call "One" before body is elaborated
27913 >>> warning: Program_Error will be raised at run time
27916 6. function One return Float is
27929 Note that in this particular case, it is likely that the call is safe, because
27930 the function @code{One} does not access any global variables.
27931 Nevertheless in Ada, we do not want the validity of the check to depend on
27932 the contents of the body (think about the separate compilation case), so this
27933 is still wrong, as we discussed in the previous sections.
27935 The error is easily corrected by rearranging the declarations so that the
27936 body of @code{One} appears before the declaration containing the call
27937 (note that in Ada 95 and Ada 2005,
27938 declarations can appear in any order, so there is no restriction that
27939 would prevent this reordering, and if we write:
27941 @smallexample @c ada
27944 function One return Float;
27946 function One return Float is
27957 then all is well, no warning is generated, and no
27958 @code{Program_Error} exception
27960 Things are more complicated when a chain of subprograms is executed:
27962 @smallexample @c ada
27965 function A return Integer;
27966 function B return Integer;
27967 function C return Integer;
27969 function B return Integer is begin return A; end;
27970 function C return Integer is begin return B; end;
27974 function A return Integer is begin return 1; end;
27980 Now the call to @code{C}
27981 at elaboration time in the declaration of @code{X} is correct, because
27982 the body of @code{C} is already elaborated,
27983 and the call to @code{B} within the body of
27984 @code{C} is correct, but the call
27985 to @code{A} within the body of @code{B} is incorrect, because the body
27986 of @code{A} has not been elaborated, so @code{Program_Error}
27987 will be raised on the call to @code{A}.
27988 In this case GNAT will generate a
27989 warning that @code{Program_Error} may be
27990 raised at the point of the call. Let's look at the warning:
27996 2. function A return Integer;
27997 3. function B return Integer;
27998 4. function C return Integer;
28000 6. function B return Integer is begin return A; end;
28002 >>> warning: call to "A" before body is elaborated may
28003 raise Program_Error
28004 >>> warning: "B" called at line 7
28005 >>> warning: "C" called at line 9
28007 7. function C return Integer is begin return B; end;
28009 9. X : Integer := C;
28011 11. function A return Integer is begin return 1; end;
28021 Note that the message here says ``may raise'', instead of the direct case,
28022 where the message says ``will be raised''. That's because whether
28024 actually called depends in general on run-time flow of control.
28025 For example, if the body of @code{B} said
28027 @smallexample @c ada
28030 function B return Integer is
28032 if some-condition-depending-on-input-data then
28043 then we could not know until run time whether the incorrect call to A would
28044 actually occur, so @code{Program_Error} might
28045 or might not be raised. It is possible for a compiler to
28046 do a better job of analyzing bodies, to
28047 determine whether or not @code{Program_Error}
28048 might be raised, but it certainly
28049 couldn't do a perfect job (that would require solving the halting problem
28050 and is provably impossible), and because this is a warning anyway, it does
28051 not seem worth the effort to do the analysis. Cases in which it
28052 would be relevant are rare.
28054 In practice, warnings of either of the forms given
28055 above will usually correspond to
28056 real errors, and should be examined carefully and eliminated.
28057 In the rare case where a warning is bogus, it can be suppressed by any of
28058 the following methods:
28062 Compile with the @option{-gnatws} switch set
28065 Suppress @code{Elaboration_Check} for the called subprogram
28068 Use pragma @code{Warnings_Off} to turn warnings off for the call
28072 For the internal elaboration check case,
28073 GNAT by default generates the
28074 necessary run-time checks to ensure
28075 that @code{Program_Error} is raised if any
28076 call fails an elaboration check. Of course this can only happen if a
28077 warning has been issued as described above. The use of pragma
28078 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
28079 some of these checks, meaning that it may be possible (but is not
28080 guaranteed) for a program to be able to call a subprogram whose body
28081 is not yet elaborated, without raising a @code{Program_Error} exception.
28083 @node Controlling Elaboration in GNAT - External Calls
28084 @section Controlling Elaboration in GNAT - External Calls
28087 The previous section discussed the case in which the execution of a
28088 particular thread of elaboration code occurred entirely within a
28089 single unit. This is the easy case to handle, because a programmer
28090 has direct and total control over the order of elaboration, and
28091 furthermore, checks need only be generated in cases which are rare
28092 and which the compiler can easily detect.
28093 The situation is more complex when separate compilation is taken into account.
28094 Consider the following:
28096 @smallexample @c ada
28100 function Sqrt (Arg : Float) return Float;
28103 package body Math is
28104 function Sqrt (Arg : Float) return Float is
28113 X : Float := Math.Sqrt (0.5);
28126 where @code{Main} is the main program. When this program is executed, the
28127 elaboration code must first be executed, and one of the jobs of the
28128 binder is to determine the order in which the units of a program are
28129 to be elaborated. In this case we have four units: the spec and body
28131 the spec of @code{Stuff} and the body of @code{Main}).
28132 In what order should the four separate sections of elaboration code
28135 There are some restrictions in the order of elaboration that the binder
28136 can choose. In particular, if unit U has a @code{with}
28137 for a package @code{X}, then you
28138 are assured that the spec of @code{X}
28139 is elaborated before U , but you are
28140 not assured that the body of @code{X}
28141 is elaborated before U.
28142 This means that in the above case, the binder is allowed to choose the
28153 but that's not good, because now the call to @code{Math.Sqrt}
28154 that happens during
28155 the elaboration of the @code{Stuff}
28156 spec happens before the body of @code{Math.Sqrt} is
28157 elaborated, and hence causes @code{Program_Error} exception to be raised.
28158 At first glance, one might say that the binder is misbehaving, because
28159 obviously you want to elaborate the body of something you @code{with}
28161 that is not a general rule that can be followed in all cases. Consider
28163 @smallexample @c ada
28166 package X is @dots{}
28168 package Y is @dots{}
28171 package body Y is @dots{}
28174 package body X is @dots{}
28180 This is a common arrangement, and, apart from the order of elaboration
28181 problems that might arise in connection with elaboration code, this works fine.
28182 A rule that says that you must first elaborate the body of anything you
28183 @code{with} cannot work in this case:
28184 the body of @code{X} @code{with}'s @code{Y},
28185 which means you would have to
28186 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
28188 you have to elaborate the body of @code{X} first, but @dots{} and we have a
28189 loop that cannot be broken.
28191 It is true that the binder can in many cases guess an order of elaboration
28192 that is unlikely to cause a @code{Program_Error}
28193 exception to be raised, and it tries to do so (in the
28194 above example of @code{Math/Stuff/Spec}, the GNAT binder will
28196 elaborate the body of @code{Math} right after its spec, so all will be well).
28198 However, a program that blindly relies on the binder to be helpful can
28199 get into trouble, as we discussed in the previous sections, so
28201 provides a number of facilities for assisting the programmer in
28202 developing programs that are robust with respect to elaboration order.
28204 @node Default Behavior in GNAT - Ensuring Safety
28205 @section Default Behavior in GNAT - Ensuring Safety
28208 The default behavior in GNAT ensures elaboration safety. In its
28209 default mode GNAT implements the
28210 rule we previously described as the right approach. Let's restate it:
28214 @emph{If a unit has elaboration code that can directly or indirectly make a
28215 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
28216 package in a @code{with}'ed unit, then if the @code{with}'ed unit
28217 does not have pragma @code{Pure} or
28218 @code{Preelaborate}, then the client should have an
28219 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
28221 @emph{In the case of instantiating a generic subprogram, it is always
28222 sufficient to have only an @code{Elaborate} pragma for the
28223 @code{with}'ed unit.}
28227 By following this rule a client is assured that calls and instantiations
28228 can be made without risk of an exception.
28230 In this mode GNAT traces all calls that are potentially made from
28231 elaboration code, and puts in any missing implicit @code{Elaborate}
28232 and @code{Elaborate_All} pragmas.
28233 The advantage of this approach is that no elaboration problems
28234 are possible if the binder can find an elaboration order that is
28235 consistent with these implicit @code{Elaborate} and
28236 @code{Elaborate_All} pragmas. The
28237 disadvantage of this approach is that no such order may exist.
28239 If the binder does not generate any diagnostics, then it means that it has
28240 found an elaboration order that is guaranteed to be safe. However, the binder
28241 may still be relying on implicitly generated @code{Elaborate} and
28242 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
28245 If it is important to guarantee portability, then the compilations should
28248 (warn on elaboration problems) switch. This will cause warning messages
28249 to be generated indicating the missing @code{Elaborate} and
28250 @code{Elaborate_All} pragmas.
28251 Consider the following source program:
28253 @smallexample @c ada
28258 m : integer := k.r;
28265 where it is clear that there
28266 should be a pragma @code{Elaborate_All}
28267 for unit @code{k}. An implicit pragma will be generated, and it is
28268 likely that the binder will be able to honor it. However, if you want
28269 to port this program to some other Ada compiler than GNAT.
28270 it is safer to include the pragma explicitly in the source. If this
28271 unit is compiled with the
28273 switch, then the compiler outputs a warning:
28280 3. m : integer := k.r;
28282 >>> warning: call to "r" may raise Program_Error
28283 >>> warning: missing pragma Elaborate_All for "k"
28291 and these warnings can be used as a guide for supplying manually
28292 the missing pragmas. It is usually a bad idea to use this warning
28293 option during development. That's because it will warn you when
28294 you need to put in a pragma, but cannot warn you when it is time
28295 to take it out. So the use of pragma @code{Elaborate_All} may lead to
28296 unnecessary dependencies and even false circularities.
28298 This default mode is more restrictive than the Ada Reference
28299 Manual, and it is possible to construct programs which will compile
28300 using the dynamic model described there, but will run into a
28301 circularity using the safer static model we have described.
28303 Of course any Ada compiler must be able to operate in a mode
28304 consistent with the requirements of the Ada Reference Manual,
28305 and in particular must have the capability of implementing the
28306 standard dynamic model of elaboration with run-time checks.
28308 In GNAT, this standard mode can be achieved either by the use of
28309 the @option{-gnatE} switch on the compiler (@command{gcc} or
28310 @command{gnatmake}) command, or by the use of the configuration pragma:
28312 @smallexample @c ada
28313 pragma Elaboration_Checks (DYNAMIC);
28317 Either approach will cause the unit affected to be compiled using the
28318 standard dynamic run-time elaboration checks described in the Ada
28319 Reference Manual. The static model is generally preferable, since it
28320 is clearly safer to rely on compile and link time checks rather than
28321 run-time checks. However, in the case of legacy code, it may be
28322 difficult to meet the requirements of the static model. This
28323 issue is further discussed in
28324 @ref{What to Do If the Default Elaboration Behavior Fails}.
28326 Note that the static model provides a strict subset of the allowed
28327 behavior and programs of the Ada Reference Manual, so if you do
28328 adhere to the static model and no circularities exist,
28329 then you are assured that your program will
28330 work using the dynamic model, providing that you remove any
28331 pragma Elaborate statements from the source.
28333 @node Treatment of Pragma Elaborate
28334 @section Treatment of Pragma Elaborate
28335 @cindex Pragma Elaborate
28338 The use of @code{pragma Elaborate}
28339 should generally be avoided in Ada 95 and Ada 2005 programs,
28340 since there is no guarantee that transitive calls
28341 will be properly handled. Indeed at one point, this pragma was placed
28342 in Annex J (Obsolescent Features), on the grounds that it is never useful.
28344 Now that's a bit restrictive. In practice, the case in which
28345 @code{pragma Elaborate} is useful is when the caller knows that there
28346 are no transitive calls, or that the called unit contains all necessary
28347 transitive @code{pragma Elaborate} statements, and legacy code often
28348 contains such uses.
28350 Strictly speaking the static mode in GNAT should ignore such pragmas,
28351 since there is no assurance at compile time that the necessary safety
28352 conditions are met. In practice, this would cause GNAT to be incompatible
28353 with correctly written Ada 83 code that had all necessary
28354 @code{pragma Elaborate} statements in place. Consequently, we made the
28355 decision that GNAT in its default mode will believe that if it encounters
28356 a @code{pragma Elaborate} then the programmer knows what they are doing,
28357 and it will trust that no elaboration errors can occur.
28359 The result of this decision is two-fold. First to be safe using the
28360 static mode, you should remove all @code{pragma Elaborate} statements.
28361 Second, when fixing circularities in existing code, you can selectively
28362 use @code{pragma Elaborate} statements to convince the static mode of
28363 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
28366 When using the static mode with @option{-gnatwl}, any use of
28367 @code{pragma Elaborate} will generate a warning about possible
28370 @node Elaboration Issues for Library Tasks
28371 @section Elaboration Issues for Library Tasks
28372 @cindex Library tasks, elaboration issues
28373 @cindex Elaboration of library tasks
28376 In this section we examine special elaboration issues that arise for
28377 programs that declare library level tasks.
28379 Generally the model of execution of an Ada program is that all units are
28380 elaborated, and then execution of the program starts. However, the
28381 declaration of library tasks definitely does not fit this model. The
28382 reason for this is that library tasks start as soon as they are declared
28383 (more precisely, as soon as the statement part of the enclosing package
28384 body is reached), that is to say before elaboration
28385 of the program is complete. This means that if such a task calls a
28386 subprogram, or an entry in another task, the callee may or may not be
28387 elaborated yet, and in the standard
28388 Reference Manual model of dynamic elaboration checks, you can even
28389 get timing dependent Program_Error exceptions, since there can be
28390 a race between the elaboration code and the task code.
28392 The static model of elaboration in GNAT seeks to avoid all such
28393 dynamic behavior, by being conservative, and the conservative
28394 approach in this particular case is to assume that all the code
28395 in a task body is potentially executed at elaboration time if
28396 a task is declared at the library level.
28398 This can definitely result in unexpected circularities. Consider
28399 the following example
28401 @smallexample @c ada
28407 type My_Int is new Integer;
28409 function Ident (M : My_Int) return My_Int;
28413 package body Decls is
28414 task body Lib_Task is
28420 function Ident (M : My_Int) return My_Int is
28428 procedure Put_Val (Arg : Decls.My_Int);
28432 package body Utils is
28433 procedure Put_Val (Arg : Decls.My_Int) is
28435 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28442 Decls.Lib_Task.Start;
28447 If the above example is compiled in the default static elaboration
28448 mode, then a circularity occurs. The circularity comes from the call
28449 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
28450 this call occurs in elaboration code, we need an implicit pragma
28451 @code{Elaborate_All} for @code{Utils}. This means that not only must
28452 the spec and body of @code{Utils} be elaborated before the body
28453 of @code{Decls}, but also the spec and body of any unit that is
28454 @code{with'ed} by the body of @code{Utils} must also be elaborated before
28455 the body of @code{Decls}. This is the transitive implication of
28456 pragma @code{Elaborate_All} and it makes sense, because in general
28457 the body of @code{Put_Val} might have a call to something in a
28458 @code{with'ed} unit.
28460 In this case, the body of Utils (actually its spec) @code{with's}
28461 @code{Decls}. Unfortunately this means that the body of @code{Decls}
28462 must be elaborated before itself, in case there is a call from the
28463 body of @code{Utils}.
28465 Here is the exact chain of events we are worrying about:
28469 In the body of @code{Decls} a call is made from within the body of a library
28470 task to a subprogram in the package @code{Utils}. Since this call may
28471 occur at elaboration time (given that the task is activated at elaboration
28472 time), we have to assume the worst, i.e., that the
28473 call does happen at elaboration time.
28476 This means that the body and spec of @code{Util} must be elaborated before
28477 the body of @code{Decls} so that this call does not cause an access before
28481 Within the body of @code{Util}, specifically within the body of
28482 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
28486 One such @code{with}'ed package is package @code{Decls}, so there
28487 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
28488 In fact there is such a call in this example, but we would have to
28489 assume that there was such a call even if it were not there, since
28490 we are not supposed to write the body of @code{Decls} knowing what
28491 is in the body of @code{Utils}; certainly in the case of the
28492 static elaboration model, the compiler does not know what is in
28493 other bodies and must assume the worst.
28496 This means that the spec and body of @code{Decls} must also be
28497 elaborated before we elaborate the unit containing the call, but
28498 that unit is @code{Decls}! This means that the body of @code{Decls}
28499 must be elaborated before itself, and that's a circularity.
28503 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
28504 the body of @code{Decls} you will get a true Ada Reference Manual
28505 circularity that makes the program illegal.
28507 In practice, we have found that problems with the static model of
28508 elaboration in existing code often arise from library tasks, so
28509 we must address this particular situation.
28511 Note that if we compile and run the program above, using the dynamic model of
28512 elaboration (that is to say use the @option{-gnatE} switch),
28513 then it compiles, binds,
28514 links, and runs, printing the expected result of 2. Therefore in some sense
28515 the circularity here is only apparent, and we need to capture
28516 the properties of this program that distinguish it from other library-level
28517 tasks that have real elaboration problems.
28519 We have four possible answers to this question:
28524 Use the dynamic model of elaboration.
28526 If we use the @option{-gnatE} switch, then as noted above, the program works.
28527 Why is this? If we examine the task body, it is apparent that the task cannot
28529 @code{accept} statement until after elaboration has been completed, because
28530 the corresponding entry call comes from the main program, not earlier.
28531 This is why the dynamic model works here. But that's really giving
28532 up on a precise analysis, and we prefer to take this approach only if we cannot
28534 problem in any other manner. So let us examine two ways to reorganize
28535 the program to avoid the potential elaboration problem.
28538 Split library tasks into separate packages.
28540 Write separate packages, so that library tasks are isolated from
28541 other declarations as much as possible. Let us look at a variation on
28544 @smallexample @c ada
28552 package body Decls1 is
28553 task body Lib_Task is
28561 type My_Int is new Integer;
28562 function Ident (M : My_Int) return My_Int;
28566 package body Decls2 is
28567 function Ident (M : My_Int) return My_Int is
28575 procedure Put_Val (Arg : Decls2.My_Int);
28579 package body Utils is
28580 procedure Put_Val (Arg : Decls2.My_Int) is
28582 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
28589 Decls1.Lib_Task.Start;
28594 All we have done is to split @code{Decls} into two packages, one
28595 containing the library task, and one containing everything else. Now
28596 there is no cycle, and the program compiles, binds, links and executes
28597 using the default static model of elaboration.
28600 Declare separate task types.
28602 A significant part of the problem arises because of the use of the
28603 single task declaration form. This means that the elaboration of
28604 the task type, and the elaboration of the task itself (i.e.@: the
28605 creation of the task) happen at the same time. A good rule
28606 of style in Ada is to always create explicit task types. By
28607 following the additional step of placing task objects in separate
28608 packages from the task type declaration, many elaboration problems
28609 are avoided. Here is another modified example of the example program:
28611 @smallexample @c ada
28613 task type Lib_Task_Type is
28617 type My_Int is new Integer;
28619 function Ident (M : My_Int) return My_Int;
28623 package body Decls is
28624 task body Lib_Task_Type is
28630 function Ident (M : My_Int) return My_Int is
28638 procedure Put_Val (Arg : Decls.My_Int);
28642 package body Utils is
28643 procedure Put_Val (Arg : Decls.My_Int) is
28645 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28651 Lib_Task : Decls.Lib_Task_Type;
28657 Declst.Lib_Task.Start;
28662 What we have done here is to replace the @code{task} declaration in
28663 package @code{Decls} with a @code{task type} declaration. Then we
28664 introduce a separate package @code{Declst} to contain the actual
28665 task object. This separates the elaboration issues for
28666 the @code{task type}
28667 declaration, which causes no trouble, from the elaboration issues
28668 of the task object, which is also unproblematic, since it is now independent
28669 of the elaboration of @code{Utils}.
28670 This separation of concerns also corresponds to
28671 a generally sound engineering principle of separating declarations
28672 from instances. This version of the program also compiles, binds, links,
28673 and executes, generating the expected output.
28676 Use No_Entry_Calls_In_Elaboration_Code restriction.
28677 @cindex No_Entry_Calls_In_Elaboration_Code
28679 The previous two approaches described how a program can be restructured
28680 to avoid the special problems caused by library task bodies. in practice,
28681 however, such restructuring may be difficult to apply to existing legacy code,
28682 so we must consider solutions that do not require massive rewriting.
28684 Let us consider more carefully why our original sample program works
28685 under the dynamic model of elaboration. The reason is that the code
28686 in the task body blocks immediately on the @code{accept}
28687 statement. Now of course there is nothing to prohibit elaboration
28688 code from making entry calls (for example from another library level task),
28689 so we cannot tell in isolation that
28690 the task will not execute the accept statement during elaboration.
28692 However, in practice it is very unusual to see elaboration code
28693 make any entry calls, and the pattern of tasks starting
28694 at elaboration time and then immediately blocking on @code{accept} or
28695 @code{select} statements is very common. What this means is that
28696 the compiler is being too pessimistic when it analyzes the
28697 whole package body as though it might be executed at elaboration
28700 If we know that the elaboration code contains no entry calls, (a very safe
28701 assumption most of the time, that could almost be made the default
28702 behavior), then we can compile all units of the program under control
28703 of the following configuration pragma:
28706 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
28710 This pragma can be placed in the @file{gnat.adc} file in the usual
28711 manner. If we take our original unmodified program and compile it
28712 in the presence of a @file{gnat.adc} containing the above pragma,
28713 then once again, we can compile, bind, link, and execute, obtaining
28714 the expected result. In the presence of this pragma, the compiler does
28715 not trace calls in a task body, that appear after the first @code{accept}
28716 or @code{select} statement, and therefore does not report a potential
28717 circularity in the original program.
28719 The compiler will check to the extent it can that the above
28720 restriction is not violated, but it is not always possible to do a
28721 complete check at compile time, so it is important to use this
28722 pragma only if the stated restriction is in fact met, that is to say
28723 no task receives an entry call before elaboration of all units is completed.
28727 @node Mixing Elaboration Models
28728 @section Mixing Elaboration Models
28730 So far, we have assumed that the entire program is either compiled
28731 using the dynamic model or static model, ensuring consistency. It
28732 is possible to mix the two models, but rules have to be followed
28733 if this mixing is done to ensure that elaboration checks are not
28736 The basic rule is that @emph{a unit compiled with the static model cannot
28737 be @code{with'ed} by a unit compiled with the dynamic model}. The
28738 reason for this is that in the static model, a unit assumes that
28739 its clients guarantee to use (the equivalent of) pragma
28740 @code{Elaborate_All} so that no elaboration checks are required
28741 in inner subprograms, and this assumption is violated if the
28742 client is compiled with dynamic checks.
28744 The precise rule is as follows. A unit that is compiled with dynamic
28745 checks can only @code{with} a unit that meets at least one of the
28746 following criteria:
28751 The @code{with'ed} unit is itself compiled with dynamic elaboration
28752 checks (that is with the @option{-gnatE} switch.
28755 The @code{with'ed} unit is an internal GNAT implementation unit from
28756 the System, Interfaces, Ada, or GNAT hierarchies.
28759 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
28762 The @code{with'ing} unit (that is the client) has an explicit pragma
28763 @code{Elaborate_All} for the @code{with'ed} unit.
28768 If this rule is violated, that is if a unit with dynamic elaboration
28769 checks @code{with's} a unit that does not meet one of the above four
28770 criteria, then the binder (@code{gnatbind}) will issue a warning
28771 similar to that in the following example:
28774 warning: "x.ads" has dynamic elaboration checks and with's
28775 warning: "y.ads" which has static elaboration checks
28779 These warnings indicate that the rule has been violated, and that as a result
28780 elaboration checks may be missed in the resulting executable file.
28781 This warning may be suppressed using the @option{-ws} binder switch
28782 in the usual manner.
28784 One useful application of this mixing rule is in the case of a subsystem
28785 which does not itself @code{with} units from the remainder of the
28786 application. In this case, the entire subsystem can be compiled with
28787 dynamic checks to resolve a circularity in the subsystem, while
28788 allowing the main application that uses this subsystem to be compiled
28789 using the more reliable default static model.
28791 @node What to Do If the Default Elaboration Behavior Fails
28792 @section What to Do If the Default Elaboration Behavior Fails
28795 If the binder cannot find an acceptable order, it outputs detailed
28796 diagnostics. For example:
28802 error: elaboration circularity detected
28803 info: "proc (body)" must be elaborated before "pack (body)"
28804 info: reason: Elaborate_All probably needed in unit "pack (body)"
28805 info: recompile "pack (body)" with -gnatwl
28806 info: for full details
28807 info: "proc (body)"
28808 info: is needed by its spec:
28809 info: "proc (spec)"
28810 info: which is withed by:
28811 info: "pack (body)"
28812 info: "pack (body)" must be elaborated before "proc (body)"
28813 info: reason: pragma Elaborate in unit "proc (body)"
28819 In this case we have a cycle that the binder cannot break. On the one
28820 hand, there is an explicit pragma Elaborate in @code{proc} for
28821 @code{pack}. This means that the body of @code{pack} must be elaborated
28822 before the body of @code{proc}. On the other hand, there is elaboration
28823 code in @code{pack} that calls a subprogram in @code{proc}. This means
28824 that for maximum safety, there should really be a pragma
28825 Elaborate_All in @code{pack} for @code{proc} which would require that
28826 the body of @code{proc} be elaborated before the body of
28827 @code{pack}. Clearly both requirements cannot be satisfied.
28828 Faced with a circularity of this kind, you have three different options.
28831 @item Fix the program
28832 The most desirable option from the point of view of long-term maintenance
28833 is to rearrange the program so that the elaboration problems are avoided.
28834 One useful technique is to place the elaboration code into separate
28835 child packages. Another is to move some of the initialization code to
28836 explicitly called subprograms, where the program controls the order
28837 of initialization explicitly. Although this is the most desirable option,
28838 it may be impractical and involve too much modification, especially in
28839 the case of complex legacy code.
28841 @item Perform dynamic checks
28842 If the compilations are done using the
28844 (dynamic elaboration check) switch, then GNAT behaves in a quite different
28845 manner. Dynamic checks are generated for all calls that could possibly result
28846 in raising an exception. With this switch, the compiler does not generate
28847 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
28848 exactly as specified in the @cite{Ada Reference Manual}.
28849 The binder will generate
28850 an executable program that may or may not raise @code{Program_Error}, and then
28851 it is the programmer's job to ensure that it does not raise an exception. Note
28852 that it is important to compile all units with the switch, it cannot be used
28855 @item Suppress checks
28856 The drawback of dynamic checks is that they generate a
28857 significant overhead at run time, both in space and time. If you
28858 are absolutely sure that your program cannot raise any elaboration
28859 exceptions, and you still want to use the dynamic elaboration model,
28860 then you can use the configuration pragma
28861 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
28862 example this pragma could be placed in the @file{gnat.adc} file.
28864 @item Suppress checks selectively
28865 When you know that certain calls or instantiations in elaboration code cannot
28866 possibly lead to an elaboration error, and the binder nevertheless complains
28867 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
28868 elaboration circularities, it is possible to remove those warnings locally and
28869 obtain a program that will bind. Clearly this can be unsafe, and it is the
28870 responsibility of the programmer to make sure that the resulting program has no
28871 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
28872 used with different granularity to suppress warnings and break elaboration
28877 Place the pragma that names the called subprogram in the declarative part
28878 that contains the call.
28881 Place the pragma in the declarative part, without naming an entity. This
28882 disables warnings on all calls in the corresponding declarative region.
28885 Place the pragma in the package spec that declares the called subprogram,
28886 and name the subprogram. This disables warnings on all elaboration calls to
28890 Place the pragma in the package spec that declares the called subprogram,
28891 without naming any entity. This disables warnings on all elaboration calls to
28892 all subprograms declared in this spec.
28894 @item Use Pragma Elaborate
28895 As previously described in section @xref{Treatment of Pragma Elaborate},
28896 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
28897 that no elaboration checks are required on calls to the designated unit.
28898 There may be cases in which the caller knows that no transitive calls
28899 can occur, so that a @code{pragma Elaborate} will be sufficient in a
28900 case where @code{pragma Elaborate_All} would cause a circularity.
28904 These five cases are listed in order of decreasing safety, and therefore
28905 require increasing programmer care in their application. Consider the
28908 @smallexample @c adanocomment
28910 function F1 return Integer;
28915 function F2 return Integer;
28916 function Pure (x : integer) return integer;
28917 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
28918 -- pragma Suppress (Elaboration_Check); -- (4)
28922 package body Pack1 is
28923 function F1 return Integer is
28927 Val : integer := Pack2.Pure (11); -- Elab. call (1)
28930 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
28931 -- pragma Suppress(Elaboration_Check); -- (2)
28933 X1 := Pack2.F2 + 1; -- Elab. call (2)
28938 package body Pack2 is
28939 function F2 return Integer is
28943 function Pure (x : integer) return integer is
28945 return x ** 3 - 3 * x;
28949 with Pack1, Ada.Text_IO;
28952 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
28955 In the absence of any pragmas, an attempt to bind this program produces
28956 the following diagnostics:
28962 error: elaboration circularity detected
28963 info: "pack1 (body)" must be elaborated before "pack1 (body)"
28964 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
28965 info: recompile "pack1 (body)" with -gnatwl for full details
28966 info: "pack1 (body)"
28967 info: must be elaborated along with its spec:
28968 info: "pack1 (spec)"
28969 info: which is withed by:
28970 info: "pack2 (body)"
28971 info: which must be elaborated along with its spec:
28972 info: "pack2 (spec)"
28973 info: which is withed by:
28974 info: "pack1 (body)"
28977 The sources of the circularity are the two calls to @code{Pack2.Pure} and
28978 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
28979 F2 is safe, even though F2 calls F1, because the call appears after the
28980 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
28981 remove the warning on the call. It is also possible to use pragma (2)
28982 because there are no other potentially unsafe calls in the block.
28985 The call to @code{Pure} is safe because this function does not depend on the
28986 state of @code{Pack2}. Therefore any call to this function is safe, and it
28987 is correct to place pragma (3) in the corresponding package spec.
28990 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
28991 warnings on all calls to functions declared therein. Note that this is not
28992 necessarily safe, and requires more detailed examination of the subprogram
28993 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
28994 be already elaborated.
28998 It is hard to generalize on which of these four approaches should be
28999 taken. Obviously if it is possible to fix the program so that the default
29000 treatment works, this is preferable, but this may not always be practical.
29001 It is certainly simple enough to use
29003 but the danger in this case is that, even if the GNAT binder
29004 finds a correct elaboration order, it may not always do so,
29005 and certainly a binder from another Ada compiler might not. A
29006 combination of testing and analysis (for which the warnings generated
29009 switch can be useful) must be used to ensure that the program is free
29010 of errors. One switch that is useful in this testing is the
29011 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
29014 Normally the binder tries to find an order that has the best chance
29015 of avoiding elaboration problems. However, if this switch is used, the binder
29016 plays a devil's advocate role, and tries to choose the order that
29017 has the best chance of failing. If your program works even with this
29018 switch, then it has a better chance of being error free, but this is still
29021 For an example of this approach in action, consider the C-tests (executable
29022 tests) from the ACVC suite. If these are compiled and run with the default
29023 treatment, then all but one of them succeed without generating any error
29024 diagnostics from the binder. However, there is one test that fails, and
29025 this is not surprising, because the whole point of this test is to ensure
29026 that the compiler can handle cases where it is impossible to determine
29027 a correct order statically, and it checks that an exception is indeed
29028 raised at run time.
29030 This one test must be compiled and run using the
29032 switch, and then it passes. Alternatively, the entire suite can
29033 be run using this switch. It is never wrong to run with the dynamic
29034 elaboration switch if your code is correct, and we assume that the
29035 C-tests are indeed correct (it is less efficient, but efficiency is
29036 not a factor in running the ACVC tests.)
29038 @node Elaboration for Access-to-Subprogram Values
29039 @section Elaboration for Access-to-Subprogram Values
29040 @cindex Access-to-subprogram
29043 Access-to-subprogram types (introduced in Ada 95) complicate
29044 the handling of elaboration. The trouble is that it becomes
29045 impossible to tell at compile time which procedure
29046 is being called. This means that it is not possible for the binder
29047 to analyze the elaboration requirements in this case.
29049 If at the point at which the access value is created
29050 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
29051 the body of the subprogram is
29052 known to have been elaborated, then the access value is safe, and its use
29053 does not require a check. This may be achieved by appropriate arrangement
29054 of the order of declarations if the subprogram is in the current unit,
29055 or, if the subprogram is in another unit, by using pragma
29056 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
29057 on the referenced unit.
29059 If the referenced body is not known to have been elaborated at the point
29060 the access value is created, then any use of the access value must do a
29061 dynamic check, and this dynamic check will fail and raise a
29062 @code{Program_Error} exception if the body has not been elaborated yet.
29063 GNAT will generate the necessary checks, and in addition, if the
29065 switch is set, will generate warnings that such checks are required.
29067 The use of dynamic dispatching for tagged types similarly generates
29068 a requirement for dynamic checks, and premature calls to any primitive
29069 operation of a tagged type before the body of the operation has been
29070 elaborated, will result in the raising of @code{Program_Error}.
29072 @node Summary of Procedures for Elaboration Control
29073 @section Summary of Procedures for Elaboration Control
29074 @cindex Elaboration control
29077 First, compile your program with the default options, using none of
29078 the special elaboration control switches. If the binder successfully
29079 binds your program, then you can be confident that, apart from issues
29080 raised by the use of access-to-subprogram types and dynamic dispatching,
29081 the program is free of elaboration errors. If it is important that the
29082 program be portable, then use the
29084 switch to generate warnings about missing @code{Elaborate} or
29085 @code{Elaborate_All} pragmas, and supply the missing pragmas.
29087 If the program fails to bind using the default static elaboration
29088 handling, then you can fix the program to eliminate the binder
29089 message, or recompile the entire program with the
29090 @option{-gnatE} switch to generate dynamic elaboration checks,
29091 and, if you are sure there really are no elaboration problems,
29092 use a global pragma @code{Suppress (Elaboration_Check)}.
29094 @node Other Elaboration Order Considerations
29095 @section Other Elaboration Order Considerations
29097 This section has been entirely concerned with the issue of finding a valid
29098 elaboration order, as defined by the Ada Reference Manual. In a case
29099 where several elaboration orders are valid, the task is to find one
29100 of the possible valid elaboration orders (and the static model in GNAT
29101 will ensure that this is achieved).
29103 The purpose of the elaboration rules in the Ada Reference Manual is to
29104 make sure that no entity is accessed before it has been elaborated. For
29105 a subprogram, this means that the spec and body must have been elaborated
29106 before the subprogram is called. For an object, this means that the object
29107 must have been elaborated before its value is read or written. A violation
29108 of either of these two requirements is an access before elaboration order,
29109 and this section has been all about avoiding such errors.
29111 In the case where more than one order of elaboration is possible, in the
29112 sense that access before elaboration errors are avoided, then any one of
29113 the orders is ``correct'' in the sense that it meets the requirements of
29114 the Ada Reference Manual, and no such error occurs.
29116 However, it may be the case for a given program, that there are
29117 constraints on the order of elaboration that come not from consideration
29118 of avoiding elaboration errors, but rather from extra-lingual logic
29119 requirements. Consider this example:
29121 @smallexample @c ada
29122 with Init_Constants;
29123 package Constants is
29128 package Init_Constants is
29129 procedure P; -- require a body
29130 end Init_Constants;
29133 package body Init_Constants is
29134 procedure P is begin null; end;
29138 end Init_Constants;
29142 Z : Integer := Constants.X + Constants.Y;
29146 with Text_IO; use Text_IO;
29149 Put_Line (Calc.Z'Img);
29154 In this example, there is more than one valid order of elaboration. For
29155 example both the following are correct orders:
29158 Init_Constants spec
29161 Init_Constants body
29166 Init_Constants spec
29167 Init_Constants body
29174 There is no language rule to prefer one or the other, both are correct
29175 from an order of elaboration point of view. But the programmatic effects
29176 of the two orders are very different. In the first, the elaboration routine
29177 of @code{Calc} initializes @code{Z} to zero, and then the main program
29178 runs with this value of zero. But in the second order, the elaboration
29179 routine of @code{Calc} runs after the body of Init_Constants has set
29180 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
29183 One could perhaps by applying pretty clever non-artificial intelligence
29184 to the situation guess that it is more likely that the second order of
29185 elaboration is the one desired, but there is no formal linguistic reason
29186 to prefer one over the other. In fact in this particular case, GNAT will
29187 prefer the second order, because of the rule that bodies are elaborated
29188 as soon as possible, but it's just luck that this is what was wanted
29189 (if indeed the second order was preferred).
29191 If the program cares about the order of elaboration routines in a case like
29192 this, it is important to specify the order required. In this particular
29193 case, that could have been achieved by adding to the spec of Calc:
29195 @smallexample @c ada
29196 pragma Elaborate_All (Constants);
29200 which requires that the body (if any) and spec of @code{Constants},
29201 as well as the body and spec of any unit @code{with}'ed by
29202 @code{Constants} be elaborated before @code{Calc} is elaborated.
29204 Clearly no automatic method can always guess which alternative you require,
29205 and if you are working with legacy code that had constraints of this kind
29206 which were not properly specified by adding @code{Elaborate} or
29207 @code{Elaborate_All} pragmas, then indeed it is possible that two different
29208 compilers can choose different orders.
29210 However, GNAT does attempt to diagnose the common situation where there
29211 are uninitialized variables in the visible part of a package spec, and the
29212 corresponding package body has an elaboration block that directly or
29213 indirectly initialized one or more of these variables. This is the situation
29214 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
29215 a warning that suggests this addition if it detects this situation.
29217 The @code{gnatbind}
29218 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
29219 out problems. This switch causes bodies to be elaborated as late as possible
29220 instead of as early as possible. In the example above, it would have forced
29221 the choice of the first elaboration order. If you get different results
29222 when using this switch, and particularly if one set of results is right,
29223 and one is wrong as far as you are concerned, it shows that you have some
29224 missing @code{Elaborate} pragmas. For the example above, we have the
29228 gnatmake -f -q main
29231 gnatmake -f -q main -bargs -p
29237 It is of course quite unlikely that both these results are correct, so
29238 it is up to you in a case like this to investigate the source of the
29239 difference, by looking at the two elaboration orders that are chosen,
29240 and figuring out which is correct, and then adding the necessary
29241 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
29245 @c *******************************
29246 @node Conditional Compilation
29247 @appendix Conditional Compilation
29248 @c *******************************
29249 @cindex Conditional compilation
29252 It is often necessary to arrange for a single source program
29253 to serve multiple purposes, where it is compiled in different
29254 ways to achieve these different goals. Some examples of the
29255 need for this feature are
29258 @item Adapting a program to a different hardware environment
29259 @item Adapting a program to a different target architecture
29260 @item Turning debugging features on and off
29261 @item Arranging for a program to compile with different compilers
29265 In C, or C++, the typical approach would be to use the preprocessor
29266 that is defined as part of the language. The Ada language does not
29267 contain such a feature. This is not an oversight, but rather a very
29268 deliberate design decision, based on the experience that overuse of
29269 the preprocessing features in C and C++ can result in programs that
29270 are extremely difficult to maintain. For example, if we have ten
29271 switches that can be on or off, this means that there are a thousand
29272 separate programs, any one of which might not even be syntactically
29273 correct, and even if syntactically correct, the resulting program
29274 might not work correctly. Testing all combinations can quickly become
29277 Nevertheless, the need to tailor programs certainly exists, and in
29278 this Appendix we will discuss how this can
29279 be achieved using Ada in general, and GNAT in particular.
29282 * Use of Boolean Constants::
29283 * Debugging - A Special Case::
29284 * Conditionalizing Declarations::
29285 * Use of Alternative Implementations::
29289 @node Use of Boolean Constants
29290 @section Use of Boolean Constants
29293 In the case where the difference is simply which code
29294 sequence is executed, the cleanest solution is to use Boolean
29295 constants to control which code is executed.
29297 @smallexample @c ada
29299 FP_Initialize_Required : constant Boolean := True;
29301 if FP_Initialize_Required then
29308 Not only will the code inside the @code{if} statement not be executed if
29309 the constant Boolean is @code{False}, but it will also be completely
29310 deleted from the program.
29311 However, the code is only deleted after the @code{if} statement
29312 has been checked for syntactic and semantic correctness.
29313 (In contrast, with preprocessors the code is deleted before the
29314 compiler ever gets to see it, so it is not checked until the switch
29316 @cindex Preprocessors (contrasted with conditional compilation)
29318 Typically the Boolean constants will be in a separate package,
29321 @smallexample @c ada
29324 FP_Initialize_Required : constant Boolean := True;
29325 Reset_Available : constant Boolean := False;
29332 The @code{Config} package exists in multiple forms for the various targets,
29333 with an appropriate script selecting the version of @code{Config} needed.
29334 Then any other unit requiring conditional compilation can do a @code{with}
29335 of @code{Config} to make the constants visible.
29338 @node Debugging - A Special Case
29339 @section Debugging - A Special Case
29342 A common use of conditional code is to execute statements (for example
29343 dynamic checks, or output of intermediate results) under control of a
29344 debug switch, so that the debugging behavior can be turned on and off.
29345 This can be done using a Boolean constant to control whether the code
29348 @smallexample @c ada
29351 Put_Line ("got to the first stage!");
29359 @smallexample @c ada
29361 if Debugging and then Temperature > 999.0 then
29362 raise Temperature_Crazy;
29368 Since this is a common case, there are special features to deal with
29369 this in a convenient manner. For the case of tests, Ada 2005 has added
29370 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
29371 @cindex pragma @code{Assert}
29372 on the @code{Assert} pragma that has always been available in GNAT, so this
29373 feature may be used with GNAT even if you are not using Ada 2005 features.
29374 The use of pragma @code{Assert} is described in
29375 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
29376 example, the last test could be written:
29378 @smallexample @c ada
29379 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
29385 @smallexample @c ada
29386 pragma Assert (Temperature <= 999.0);
29390 In both cases, if assertions are active and the temperature is excessive,
29391 the exception @code{Assert_Failure} will be raised, with the given string in
29392 the first case or a string indicating the location of the pragma in the second
29393 case used as the exception message.
29395 You can turn assertions on and off by using the @code{Assertion_Policy}
29397 @cindex pragma @code{Assertion_Policy}
29398 This is an Ada 2005 pragma which is implemented in all modes by
29399 GNAT, but only in the latest versions of GNAT which include Ada 2005
29400 capability. Alternatively, you can use the @option{-gnata} switch
29401 @cindex @option{-gnata} switch
29402 to enable assertions from the command line (this is recognized by all versions
29405 For the example above with the @code{Put_Line}, the GNAT-specific pragma
29406 @code{Debug} can be used:
29407 @cindex pragma @code{Debug}
29409 @smallexample @c ada
29410 pragma Debug (Put_Line ("got to the first stage!"));
29414 If debug pragmas are enabled, the argument, which must be of the form of
29415 a procedure call, is executed (in this case, @code{Put_Line} will be called).
29416 Only one call can be present, but of course a special debugging procedure
29417 containing any code you like can be included in the program and then
29418 called in a pragma @code{Debug} argument as needed.
29420 One advantage of pragma @code{Debug} over the @code{if Debugging then}
29421 construct is that pragma @code{Debug} can appear in declarative contexts,
29422 such as at the very beginning of a procedure, before local declarations have
29425 Debug pragmas are enabled using either the @option{-gnata} switch that also
29426 controls assertions, or with a separate Debug_Policy pragma.
29427 @cindex pragma @code{Debug_Policy}
29428 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
29429 in Ada 95 and Ada 83 programs as well), and is analogous to
29430 pragma @code{Assertion_Policy} to control assertions.
29432 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
29433 and thus they can appear in @file{gnat.adc} if you are not using a
29434 project file, or in the file designated to contain configuration pragmas
29436 They then apply to all subsequent compilations. In practice the use of
29437 the @option{-gnata} switch is often the most convenient method of controlling
29438 the status of these pragmas.
29440 Note that a pragma is not a statement, so in contexts where a statement
29441 sequence is required, you can't just write a pragma on its own. You have
29442 to add a @code{null} statement.
29444 @smallexample @c ada
29447 @dots{} -- some statements
29449 pragma Assert (Num_Cases < 10);
29456 @node Conditionalizing Declarations
29457 @section Conditionalizing Declarations
29460 In some cases, it may be necessary to conditionalize declarations to meet
29461 different requirements. For example we might want a bit string whose length
29462 is set to meet some hardware message requirement.
29464 In some cases, it may be possible to do this using declare blocks controlled
29465 by conditional constants:
29467 @smallexample @c ada
29469 if Small_Machine then
29471 X : Bit_String (1 .. 10);
29477 X : Large_Bit_String (1 .. 1000);
29486 Note that in this approach, both declarations are analyzed by the
29487 compiler so this can only be used where both declarations are legal,
29488 even though one of them will not be used.
29490 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
29491 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
29492 that are parameterized by these constants. For example
29494 @smallexample @c ada
29497 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
29503 If @code{Bits_Per_Word} is set to 32, this generates either
29505 @smallexample @c ada
29508 Field1 at 0 range 0 .. 32;
29514 for the big endian case, or
29516 @smallexample @c ada
29519 Field1 at 0 range 10 .. 32;
29525 for the little endian case. Since a powerful subset of Ada expression
29526 notation is usable for creating static constants, clever use of this
29527 feature can often solve quite difficult problems in conditionalizing
29528 compilation (note incidentally that in Ada 95, the little endian
29529 constant was introduced as @code{System.Default_Bit_Order}, so you do not
29530 need to define this one yourself).
29533 @node Use of Alternative Implementations
29534 @section Use of Alternative Implementations
29537 In some cases, none of the approaches described above are adequate. This
29538 can occur for example if the set of declarations required is radically
29539 different for two different configurations.
29541 In this situation, the official Ada way of dealing with conditionalizing
29542 such code is to write separate units for the different cases. As long as
29543 this does not result in excessive duplication of code, this can be done
29544 without creating maintenance problems. The approach is to share common
29545 code as far as possible, and then isolate the code and declarations
29546 that are different. Subunits are often a convenient method for breaking
29547 out a piece of a unit that is to be conditionalized, with separate files
29548 for different versions of the subunit for different targets, where the
29549 build script selects the right one to give to the compiler.
29550 @cindex Subunits (and conditional compilation)
29552 As an example, consider a situation where a new feature in Ada 2005
29553 allows something to be done in a really nice way. But your code must be able
29554 to compile with an Ada 95 compiler. Conceptually you want to say:
29556 @smallexample @c ada
29559 @dots{} neat Ada 2005 code
29561 @dots{} not quite as neat Ada 95 code
29567 where @code{Ada_2005} is a Boolean constant.
29569 But this won't work when @code{Ada_2005} is set to @code{False},
29570 since the @code{then} clause will be illegal for an Ada 95 compiler.
29571 (Recall that although such unreachable code would eventually be deleted
29572 by the compiler, it still needs to be legal. If it uses features
29573 introduced in Ada 2005, it will be illegal in Ada 95.)
29575 So instead we write
29577 @smallexample @c ada
29578 procedure Insert is separate;
29582 Then we have two files for the subunit @code{Insert}, with the two sets of
29584 If the package containing this is called @code{File_Queries}, then we might
29588 @item @file{file_queries-insert-2005.adb}
29589 @item @file{file_queries-insert-95.adb}
29593 and the build script renames the appropriate file to
29596 file_queries-insert.adb
29600 and then carries out the compilation.
29602 This can also be done with project files' naming schemes. For example:
29604 @smallexample @c project
29605 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
29609 Note also that with project files it is desirable to use a different extension
29610 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
29611 conflict may arise through another commonly used feature: to declare as part
29612 of the project a set of directories containing all the sources obeying the
29613 default naming scheme.
29615 The use of alternative units is certainly feasible in all situations,
29616 and for example the Ada part of the GNAT run-time is conditionalized
29617 based on the target architecture using this approach. As a specific example,
29618 consider the implementation of the AST feature in VMS. There is one
29626 which is the same for all architectures, and three bodies:
29630 used for all non-VMS operating systems
29631 @item s-asthan-vms-alpha.adb
29632 used for VMS on the Alpha
29633 @item s-asthan-vms-ia64.adb
29634 used for VMS on the ia64
29638 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
29639 this operating system feature is not available, and the two remaining
29640 versions interface with the corresponding versions of VMS to provide
29641 VMS-compatible AST handling. The GNAT build script knows the architecture
29642 and operating system, and automatically selects the right version,
29643 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
29645 Another style for arranging alternative implementations is through Ada's
29646 access-to-subprogram facility.
29647 In case some functionality is to be conditionally included,
29648 you can declare an access-to-procedure variable @code{Ref} that is initialized
29649 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
29651 In some library package, set @code{Ref} to @code{Proc'Access} for some
29652 procedure @code{Proc} that performs the relevant processing.
29653 The initialization only occurs if the library package is included in the
29655 The same idea can also be implemented using tagged types and dispatching
29659 @node Preprocessing
29660 @section Preprocessing
29661 @cindex Preprocessing
29664 Although it is quite possible to conditionalize code without the use of
29665 C-style preprocessing, as described earlier in this section, it is
29666 nevertheless convenient in some cases to use the C approach. Moreover,
29667 older Ada compilers have often provided some preprocessing capability,
29668 so legacy code may depend on this approach, even though it is not
29671 To accommodate such use, GNAT provides a preprocessor (modeled to a large
29672 extent on the various preprocessors that have been used
29673 with legacy code on other compilers, to enable easier transition).
29675 The preprocessor may be used in two separate modes. It can be used quite
29676 separately from the compiler, to generate a separate output source file
29677 that is then fed to the compiler as a separate step. This is the
29678 @code{gnatprep} utility, whose use is fully described in
29679 @ref{Preprocessing Using gnatprep}.
29680 @cindex @code{gnatprep}
29682 The preprocessing language allows such constructs as
29686 #if DEBUG or PRIORITY > 4 then
29687 bunch of declarations
29689 completely different bunch of declarations
29695 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
29696 defined either on the command line or in a separate file.
29698 The other way of running the preprocessor is even closer to the C style and
29699 often more convenient. In this approach the preprocessing is integrated into
29700 the compilation process. The compiler is fed the preprocessor input which
29701 includes @code{#if} lines etc, and then the compiler carries out the
29702 preprocessing internally and processes the resulting output.
29703 For more details on this approach, see @ref{Integrated Preprocessing}.
29706 @c *******************************
29707 @node Inline Assembler
29708 @appendix Inline Assembler
29709 @c *******************************
29712 If you need to write low-level software that interacts directly
29713 with the hardware, Ada provides two ways to incorporate assembly
29714 language code into your program. First, you can import and invoke
29715 external routines written in assembly language, an Ada feature fully
29716 supported by GNAT@. However, for small sections of code it may be simpler
29717 or more efficient to include assembly language statements directly
29718 in your Ada source program, using the facilities of the implementation-defined
29719 package @code{System.Machine_Code}, which incorporates the gcc
29720 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29721 including the following:
29724 @item No need to use non-Ada tools
29725 @item Consistent interface over different targets
29726 @item Automatic usage of the proper calling conventions
29727 @item Access to Ada constants and variables
29728 @item Definition of intrinsic routines
29729 @item Possibility of inlining a subprogram comprising assembler code
29730 @item Code optimizer can take Inline Assembler code into account
29733 This chapter presents a series of examples to show you how to use
29734 the Inline Assembler. Although it focuses on the Intel x86,
29735 the general approach applies also to other processors.
29736 It is assumed that you are familiar with Ada
29737 and with assembly language programming.
29740 * Basic Assembler Syntax::
29741 * A Simple Example of Inline Assembler::
29742 * Output Variables in Inline Assembler::
29743 * Input Variables in Inline Assembler::
29744 * Inlining Inline Assembler Code::
29745 * Other Asm Functionality::
29748 @c ---------------------------------------------------------------------------
29749 @node Basic Assembler Syntax
29750 @section Basic Assembler Syntax
29753 The assembler used by GNAT and gcc is based not on the Intel assembly
29754 language, but rather on a language that descends from the AT&T Unix
29755 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
29756 The following table summarizes the main features of @emph{as} syntax
29757 and points out the differences from the Intel conventions.
29758 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
29759 pre-processor) documentation for further information.
29762 @item Register names
29763 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
29765 Intel: No extra punctuation; for example @code{eax}
29767 @item Immediate operand
29768 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
29770 Intel: No extra punctuation; for example @code{4}
29773 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
29775 Intel: No extra punctuation; for example @code{loc}
29777 @item Memory contents
29778 gcc / @emph{as}: No extra punctuation; for example @code{loc}
29780 Intel: Square brackets; for example @code{[loc]}
29782 @item Register contents
29783 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
29785 Intel: Square brackets; for example @code{[eax]}
29787 @item Hexadecimal numbers
29788 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
29790 Intel: Trailing ``h''; for example @code{A0h}
29793 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
29796 Intel: Implicit, deduced by assembler; for example @code{mov}
29798 @item Instruction repetition
29799 gcc / @emph{as}: Split into two lines; for example
29805 Intel: Keep on one line; for example @code{rep stosl}
29807 @item Order of operands
29808 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
29810 Intel: Destination first; for example @code{mov eax, 4}
29813 @c ---------------------------------------------------------------------------
29814 @node A Simple Example of Inline Assembler
29815 @section A Simple Example of Inline Assembler
29818 The following example will generate a single assembly language statement,
29819 @code{nop}, which does nothing. Despite its lack of run-time effect,
29820 the example will be useful in illustrating the basics of
29821 the Inline Assembler facility.
29823 @smallexample @c ada
29825 with System.Machine_Code; use System.Machine_Code;
29826 procedure Nothing is
29833 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29834 here it takes one parameter, a @emph{template string} that must be a static
29835 expression and that will form the generated instruction.
29836 @code{Asm} may be regarded as a compile-time procedure that parses
29837 the template string and additional parameters (none here),
29838 from which it generates a sequence of assembly language instructions.
29840 The examples in this chapter will illustrate several of the forms
29841 for invoking @code{Asm}; a complete specification of the syntax
29842 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
29845 Under the standard GNAT conventions, the @code{Nothing} procedure
29846 should be in a file named @file{nothing.adb}.
29847 You can build the executable in the usual way:
29851 However, the interesting aspect of this example is not its run-time behavior
29852 but rather the generated assembly code.
29853 To see this output, invoke the compiler as follows:
29855 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
29857 where the options are:
29861 compile only (no bind or link)
29863 generate assembler listing
29864 @item -fomit-frame-pointer
29865 do not set up separate stack frames
29867 do not add runtime checks
29870 This gives a human-readable assembler version of the code. The resulting
29871 file will have the same name as the Ada source file, but with a @code{.s}
29872 extension. In our example, the file @file{nothing.s} has the following
29877 .file "nothing.adb"
29879 ___gnu_compiled_ada:
29882 .globl __ada_nothing
29894 The assembly code you included is clearly indicated by
29895 the compiler, between the @code{#APP} and @code{#NO_APP}
29896 delimiters. The character before the 'APP' and 'NOAPP'
29897 can differ on different targets. For example, GNU/Linux uses '#APP' while
29898 on NT you will see '/APP'.
29900 If you make a mistake in your assembler code (such as using the
29901 wrong size modifier, or using a wrong operand for the instruction) GNAT
29902 will report this error in a temporary file, which will be deleted when
29903 the compilation is finished. Generating an assembler file will help
29904 in such cases, since you can assemble this file separately using the
29905 @emph{as} assembler that comes with gcc.
29907 Assembling the file using the command
29910 as @file{nothing.s}
29913 will give you error messages whose lines correspond to the assembler
29914 input file, so you can easily find and correct any mistakes you made.
29915 If there are no errors, @emph{as} will generate an object file
29916 @file{nothing.out}.
29918 @c ---------------------------------------------------------------------------
29919 @node Output Variables in Inline Assembler
29920 @section Output Variables in Inline Assembler
29923 The examples in this section, showing how to access the processor flags,
29924 illustrate how to specify the destination operands for assembly language
29927 @smallexample @c ada
29929 with Interfaces; use Interfaces;
29930 with Ada.Text_IO; use Ada.Text_IO;
29931 with System.Machine_Code; use System.Machine_Code;
29932 procedure Get_Flags is
29933 Flags : Unsigned_32;
29936 Asm ("pushfl" & LF & HT & -- push flags on stack
29937 "popl %%eax" & LF & HT & -- load eax with flags
29938 "movl %%eax, %0", -- store flags in variable
29939 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29940 Put_Line ("Flags register:" & Flags'Img);
29945 In order to have a nicely aligned assembly listing, we have separated
29946 multiple assembler statements in the Asm template string with linefeed
29947 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29948 The resulting section of the assembly output file is:
29955 movl %eax, -40(%ebp)
29960 It would have been legal to write the Asm invocation as:
29963 Asm ("pushfl popl %%eax movl %%eax, %0")
29966 but in the generated assembler file, this would come out as:
29970 pushfl popl %eax movl %eax, -40(%ebp)
29974 which is not so convenient for the human reader.
29976 We use Ada comments
29977 at the end of each line to explain what the assembler instructions
29978 actually do. This is a useful convention.
29980 When writing Inline Assembler instructions, you need to precede each register
29981 and variable name with a percent sign. Since the assembler already requires
29982 a percent sign at the beginning of a register name, you need two consecutive
29983 percent signs for such names in the Asm template string, thus @code{%%eax}.
29984 In the generated assembly code, one of the percent signs will be stripped off.
29986 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29987 variables: operands you later define using @code{Input} or @code{Output}
29988 parameters to @code{Asm}.
29989 An output variable is illustrated in
29990 the third statement in the Asm template string:
29994 The intent is to store the contents of the eax register in a variable that can
29995 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29996 necessarily work, since the compiler might optimize by using a register
29997 to hold Flags, and the expansion of the @code{movl} instruction would not be
29998 aware of this optimization. The solution is not to store the result directly
29999 but rather to advise the compiler to choose the correct operand form;
30000 that is the purpose of the @code{%0} output variable.
30002 Information about the output variable is supplied in the @code{Outputs}
30003 parameter to @code{Asm}:
30005 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30008 The output is defined by the @code{Asm_Output} attribute of the target type;
30009 the general format is
30011 Type'Asm_Output (constraint_string, variable_name)
30014 The constraint string directs the compiler how
30015 to store/access the associated variable. In the example
30017 Unsigned_32'Asm_Output ("=m", Flags);
30019 the @code{"m"} (memory) constraint tells the compiler that the variable
30020 @code{Flags} should be stored in a memory variable, thus preventing
30021 the optimizer from keeping it in a register. In contrast,
30023 Unsigned_32'Asm_Output ("=r", Flags);
30025 uses the @code{"r"} (register) constraint, telling the compiler to
30026 store the variable in a register.
30028 If the constraint is preceded by the equal character (@strong{=}), it tells
30029 the compiler that the variable will be used to store data into it.
30031 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
30032 allowing the optimizer to choose whatever it deems best.
30034 There are a fairly large number of constraints, but the ones that are
30035 most useful (for the Intel x86 processor) are the following:
30041 global (i.e.@: can be stored anywhere)
30059 use one of eax, ebx, ecx or edx
30061 use one of eax, ebx, ecx, edx, esi or edi
30064 The full set of constraints is described in the gcc and @emph{as}
30065 documentation; note that it is possible to combine certain constraints
30066 in one constraint string.
30068 You specify the association of an output variable with an assembler operand
30069 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
30071 @smallexample @c ada
30073 Asm ("pushfl" & LF & HT & -- push flags on stack
30074 "popl %%eax" & LF & HT & -- load eax with flags
30075 "movl %%eax, %0", -- store flags in variable
30076 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30080 @code{%0} will be replaced in the expanded code by the appropriate operand,
30082 the compiler decided for the @code{Flags} variable.
30084 In general, you may have any number of output variables:
30087 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
30089 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
30090 of @code{Asm_Output} attributes
30094 @smallexample @c ada
30096 Asm ("movl %%eax, %0" & LF & HT &
30097 "movl %%ebx, %1" & LF & HT &
30099 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
30100 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
30101 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
30105 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
30106 in the Ada program.
30108 As a variation on the @code{Get_Flags} example, we can use the constraints
30109 string to direct the compiler to store the eax register into the @code{Flags}
30110 variable, instead of including the store instruction explicitly in the
30111 @code{Asm} template string:
30113 @smallexample @c ada
30115 with Interfaces; use Interfaces;
30116 with Ada.Text_IO; use Ada.Text_IO;
30117 with System.Machine_Code; use System.Machine_Code;
30118 procedure Get_Flags_2 is
30119 Flags : Unsigned_32;
30122 Asm ("pushfl" & LF & HT & -- push flags on stack
30123 "popl %%eax", -- save flags in eax
30124 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
30125 Put_Line ("Flags register:" & Flags'Img);
30131 The @code{"a"} constraint tells the compiler that the @code{Flags}
30132 variable will come from the eax register. Here is the resulting code:
30140 movl %eax,-40(%ebp)
30145 The compiler generated the store of eax into Flags after
30146 expanding the assembler code.
30148 Actually, there was no need to pop the flags into the eax register;
30149 more simply, we could just pop the flags directly into the program variable:
30151 @smallexample @c ada
30153 with Interfaces; use Interfaces;
30154 with Ada.Text_IO; use Ada.Text_IO;
30155 with System.Machine_Code; use System.Machine_Code;
30156 procedure Get_Flags_3 is
30157 Flags : Unsigned_32;
30160 Asm ("pushfl" & LF & HT & -- push flags on stack
30161 "pop %0", -- save flags in Flags
30162 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30163 Put_Line ("Flags register:" & Flags'Img);
30168 @c ---------------------------------------------------------------------------
30169 @node Input Variables in Inline Assembler
30170 @section Input Variables in Inline Assembler
30173 The example in this section illustrates how to specify the source operands
30174 for assembly language statements.
30175 The program simply increments its input value by 1:
30177 @smallexample @c ada
30179 with Interfaces; use Interfaces;
30180 with Ada.Text_IO; use Ada.Text_IO;
30181 with System.Machine_Code; use System.Machine_Code;
30182 procedure Increment is
30184 function Incr (Value : Unsigned_32) return Unsigned_32 is
30185 Result : Unsigned_32;
30188 Inputs => Unsigned_32'Asm_Input ("a", Value),
30189 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30193 Value : Unsigned_32;
30197 Put_Line ("Value before is" & Value'Img);
30198 Value := Incr (Value);
30199 Put_Line ("Value after is" & Value'Img);
30204 The @code{Outputs} parameter to @code{Asm} specifies
30205 that the result will be in the eax register and that it is to be stored
30206 in the @code{Result} variable.
30208 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
30209 but with an @code{Asm_Input} attribute.
30210 The @code{"="} constraint, indicating an output value, is not present.
30212 You can have multiple input variables, in the same way that you can have more
30213 than one output variable.
30215 The parameter count (%0, %1) etc, now starts at the first input
30216 statement, and continues with the output statements.
30217 When both parameters use the same variable, the
30218 compiler will treat them as the same %n operand, which is the case here.
30220 Just as the @code{Outputs} parameter causes the register to be stored into the
30221 target variable after execution of the assembler statements, so does the
30222 @code{Inputs} parameter cause its variable to be loaded into the register
30223 before execution of the assembler statements.
30225 Thus the effect of the @code{Asm} invocation is:
30227 @item load the 32-bit value of @code{Value} into eax
30228 @item execute the @code{incl %eax} instruction
30229 @item store the contents of eax into the @code{Result} variable
30232 The resulting assembler file (with @option{-O2} optimization) contains:
30235 _increment__incr.1:
30248 @c ---------------------------------------------------------------------------
30249 @node Inlining Inline Assembler Code
30250 @section Inlining Inline Assembler Code
30253 For a short subprogram such as the @code{Incr} function in the previous
30254 section, the overhead of the call and return (creating / deleting the stack
30255 frame) can be significant, compared to the amount of code in the subprogram
30256 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
30257 which directs the compiler to expand invocations of the subprogram at the
30258 point(s) of call, instead of setting up a stack frame for out-of-line calls.
30259 Here is the resulting program:
30261 @smallexample @c ada
30263 with Interfaces; use Interfaces;
30264 with Ada.Text_IO; use Ada.Text_IO;
30265 with System.Machine_Code; use System.Machine_Code;
30266 procedure Increment_2 is
30268 function Incr (Value : Unsigned_32) return Unsigned_32 is
30269 Result : Unsigned_32;
30272 Inputs => Unsigned_32'Asm_Input ("a", Value),
30273 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30276 pragma Inline (Increment);
30278 Value : Unsigned_32;
30282 Put_Line ("Value before is" & Value'Img);
30283 Value := Increment (Value);
30284 Put_Line ("Value after is" & Value'Img);
30289 Compile the program with both optimization (@option{-O2}) and inlining
30290 (@option{-gnatn}) enabled.
30292 The @code{Incr} function is still compiled as usual, but at the
30293 point in @code{Increment} where our function used to be called:
30298 call _increment__incr.1
30303 the code for the function body directly appears:
30316 thus saving the overhead of stack frame setup and an out-of-line call.
30318 @c ---------------------------------------------------------------------------
30319 @node Other Asm Functionality
30320 @section Other @code{Asm} Functionality
30323 This section describes two important parameters to the @code{Asm}
30324 procedure: @code{Clobber}, which identifies register usage;
30325 and @code{Volatile}, which inhibits unwanted optimizations.
30328 * The Clobber Parameter::
30329 * The Volatile Parameter::
30332 @c ---------------------------------------------------------------------------
30333 @node The Clobber Parameter
30334 @subsection The @code{Clobber} Parameter
30337 One of the dangers of intermixing assembly language and a compiled language
30338 such as Ada is that the compiler needs to be aware of which registers are
30339 being used by the assembly code. In some cases, such as the earlier examples,
30340 the constraint string is sufficient to indicate register usage (e.g.,
30342 the eax register). But more generally, the compiler needs an explicit
30343 identification of the registers that are used by the Inline Assembly
30346 Using a register that the compiler doesn't know about
30347 could be a side effect of an instruction (like @code{mull}
30348 storing its result in both eax and edx).
30349 It can also arise from explicit register usage in your
30350 assembly code; for example:
30353 Asm ("movl %0, %%ebx" & LF & HT &
30355 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30356 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
30360 where the compiler (since it does not analyze the @code{Asm} template string)
30361 does not know you are using the ebx register.
30363 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
30364 to identify the registers that will be used by your assembly code:
30368 Asm ("movl %0, %%ebx" & LF & HT &
30370 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30371 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30376 The Clobber parameter is a static string expression specifying the
30377 register(s) you are using. Note that register names are @emph{not} prefixed
30378 by a percent sign. Also, if more than one register is used then their names
30379 are separated by commas; e.g., @code{"eax, ebx"}
30381 The @code{Clobber} parameter has several additional uses:
30383 @item Use ``register'' name @code{cc} to indicate that flags might have changed
30384 @item Use ``register'' name @code{memory} if you changed a memory location
30387 @c ---------------------------------------------------------------------------
30388 @node The Volatile Parameter
30389 @subsection The @code{Volatile} Parameter
30390 @cindex Volatile parameter
30393 Compiler optimizations in the presence of Inline Assembler may sometimes have
30394 unwanted effects. For example, when an @code{Asm} invocation with an input
30395 variable is inside a loop, the compiler might move the loading of the input
30396 variable outside the loop, regarding it as a one-time initialization.
30398 If this effect is not desired, you can disable such optimizations by setting
30399 the @code{Volatile} parameter to @code{True}; for example:
30401 @smallexample @c ada
30403 Asm ("movl %0, %%ebx" & LF & HT &
30405 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30406 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30412 By default, @code{Volatile} is set to @code{False} unless there is no
30413 @code{Outputs} parameter.
30415 Although setting @code{Volatile} to @code{True} prevents unwanted
30416 optimizations, it will also disable other optimizations that might be
30417 important for efficiency. In general, you should set @code{Volatile}
30418 to @code{True} only if the compiler's optimizations have created
30420 @c END OF INLINE ASSEMBLER CHAPTER
30421 @c ===============================
30423 @c ***********************************
30424 @c * Compatibility and Porting Guide *
30425 @c ***********************************
30426 @node Compatibility and Porting Guide
30427 @appendix Compatibility and Porting Guide
30430 This chapter describes the compatibility issues that may arise between
30431 GNAT and other Ada compilation systems (including those for Ada 83),
30432 and shows how GNAT can expedite porting
30433 applications developed in other Ada environments.
30436 * Compatibility with Ada 83::
30437 * Compatibility between Ada 95 and Ada 2005::
30438 * Implementation-dependent characteristics::
30439 * Compatibility with Other Ada Systems::
30440 * Representation Clauses::
30442 @c Brief section is only in non-VMS version
30443 @c Full chapter is in VMS version
30444 * Compatibility with HP Ada 83::
30447 * Transitioning to 64-Bit GNAT for OpenVMS::
30451 @node Compatibility with Ada 83
30452 @section Compatibility with Ada 83
30453 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
30456 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
30457 particular, the design intention was that the difficulties associated
30458 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
30459 that occur when moving from one Ada 83 system to another.
30461 However, there are a number of points at which there are minor
30462 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
30463 full details of these issues,
30464 and should be consulted for a complete treatment.
30466 following subsections treat the most likely issues to be encountered.
30469 * Legal Ada 83 programs that are illegal in Ada 95::
30470 * More deterministic semantics::
30471 * Changed semantics::
30472 * Other language compatibility issues::
30475 @node Legal Ada 83 programs that are illegal in Ada 95
30476 @subsection Legal Ada 83 programs that are illegal in Ada 95
30478 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
30479 Ada 95 and thus also in Ada 2005:
30482 @item Character literals
30483 Some uses of character literals are ambiguous. Since Ada 95 has introduced
30484 @code{Wide_Character} as a new predefined character type, some uses of
30485 character literals that were legal in Ada 83 are illegal in Ada 95.
30487 @smallexample @c ada
30488 for Char in 'A' .. 'Z' loop @dots{} end loop;
30492 The problem is that @code{'A'} and @code{'Z'} could be from either
30493 @code{Character} or @code{Wide_Character}. The simplest correction
30494 is to make the type explicit; e.g.:
30495 @smallexample @c ada
30496 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
30499 @item New reserved words
30500 The identifiers @code{abstract}, @code{aliased}, @code{protected},
30501 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
30502 Existing Ada 83 code using any of these identifiers must be edited to
30503 use some alternative name.
30505 @item Freezing rules
30506 The rules in Ada 95 are slightly different with regard to the point at
30507 which entities are frozen, and representation pragmas and clauses are
30508 not permitted past the freeze point. This shows up most typically in
30509 the form of an error message complaining that a representation item
30510 appears too late, and the appropriate corrective action is to move
30511 the item nearer to the declaration of the entity to which it refers.
30513 A particular case is that representation pragmas
30516 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
30518 cannot be applied to a subprogram body. If necessary, a separate subprogram
30519 declaration must be introduced to which the pragma can be applied.
30521 @item Optional bodies for library packages
30522 In Ada 83, a package that did not require a package body was nevertheless
30523 allowed to have one. This lead to certain surprises in compiling large
30524 systems (situations in which the body could be unexpectedly ignored by the
30525 binder). In Ada 95, if a package does not require a body then it is not
30526 permitted to have a body. To fix this problem, simply remove a redundant
30527 body if it is empty, or, if it is non-empty, introduce a dummy declaration
30528 into the spec that makes the body required. One approach is to add a private
30529 part to the package declaration (if necessary), and define a parameterless
30530 procedure called @code{Requires_Body}, which must then be given a dummy
30531 procedure body in the package body, which then becomes required.
30532 Another approach (assuming that this does not introduce elaboration
30533 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
30534 since one effect of this pragma is to require the presence of a package body.
30536 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
30537 In Ada 95, the exception @code{Numeric_Error} is a renaming of
30538 @code{Constraint_Error}.
30539 This means that it is illegal to have separate exception handlers for
30540 the two exceptions. The fix is simply to remove the handler for the
30541 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
30542 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
30544 @item Indefinite subtypes in generics
30545 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
30546 as the actual for a generic formal private type, but then the instantiation
30547 would be illegal if there were any instances of declarations of variables
30548 of this type in the generic body. In Ada 95, to avoid this clear violation
30549 of the methodological principle known as the ``contract model'',
30550 the generic declaration explicitly indicates whether
30551 or not such instantiations are permitted. If a generic formal parameter
30552 has explicit unknown discriminants, indicated by using @code{(<>)} after the
30553 type name, then it can be instantiated with indefinite types, but no
30554 stand-alone variables can be declared of this type. Any attempt to declare
30555 such a variable will result in an illegality at the time the generic is
30556 declared. If the @code{(<>)} notation is not used, then it is illegal
30557 to instantiate the generic with an indefinite type.
30558 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
30559 It will show up as a compile time error, and
30560 the fix is usually simply to add the @code{(<>)} to the generic declaration.
30563 @node More deterministic semantics
30564 @subsection More deterministic semantics
30568 Conversions from real types to integer types round away from 0. In Ada 83
30569 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
30570 implementation freedom was intended to support unbiased rounding in
30571 statistical applications, but in practice it interfered with portability.
30572 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
30573 is required. Numeric code may be affected by this change in semantics.
30574 Note, though, that this issue is no worse than already existed in Ada 83
30575 when porting code from one vendor to another.
30578 The Real-Time Annex introduces a set of policies that define the behavior of
30579 features that were implementation dependent in Ada 83, such as the order in
30580 which open select branches are executed.
30583 @node Changed semantics
30584 @subsection Changed semantics
30587 The worst kind of incompatibility is one where a program that is legal in
30588 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
30589 possible in Ada 83. Fortunately this is extremely rare, but the one
30590 situation that you should be alert to is the change in the predefined type
30591 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
30594 @item Range of type @code{Character}
30595 The range of @code{Standard.Character} is now the full 256 characters
30596 of Latin-1, whereas in most Ada 83 implementations it was restricted
30597 to 128 characters. Although some of the effects of
30598 this change will be manifest in compile-time rejection of legal
30599 Ada 83 programs it is possible for a working Ada 83 program to have
30600 a different effect in Ada 95, one that was not permitted in Ada 83.
30601 As an example, the expression
30602 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
30603 delivers @code{255} as its value.
30604 In general, you should look at the logic of any
30605 character-processing Ada 83 program and see whether it needs to be adapted
30606 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
30607 character handling package that may be relevant if code needs to be adapted
30608 to account for the additional Latin-1 elements.
30609 The desirable fix is to
30610 modify the program to accommodate the full character set, but in some cases
30611 it may be convenient to define a subtype or derived type of Character that
30612 covers only the restricted range.
30616 @node Other language compatibility issues
30617 @subsection Other language compatibility issues
30620 @item @option{-gnat83} switch
30621 All implementations of GNAT provide a switch that causes GNAT to operate
30622 in Ada 83 mode. In this mode, some but not all compatibility problems
30623 of the type described above are handled automatically. For example, the
30624 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
30625 as identifiers as in Ada 83.
30627 in practice, it is usually advisable to make the necessary modifications
30628 to the program to remove the need for using this switch.
30629 See @ref{Compiling Different Versions of Ada}.
30631 @item Support for removed Ada 83 pragmas and attributes
30632 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
30633 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
30634 compilers are allowed, but not required, to implement these missing
30635 elements. In contrast with some other compilers, GNAT implements all
30636 such pragmas and attributes, eliminating this compatibility concern. These
30637 include @code{pragma Interface} and the floating point type attributes
30638 (@code{Emax}, @code{Mantissa}, etc.), among other items.
30642 @node Compatibility between Ada 95 and Ada 2005
30643 @section Compatibility between Ada 95 and Ada 2005
30644 @cindex Compatibility between Ada 95 and Ada 2005
30647 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
30648 a number of incompatibilities. Several are enumerated below;
30649 for a complete description please see the
30650 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
30651 @cite{Rationale for Ada 2005}.
30654 @item New reserved words.
30655 The words @code{interface}, @code{overriding} and @code{synchronized} are
30656 reserved in Ada 2005.
30657 A pre-Ada 2005 program that uses any of these as an identifier will be
30660 @item New declarations in predefined packages.
30661 A number of packages in the predefined environment contain new declarations:
30662 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
30663 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
30664 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
30665 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
30666 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
30667 If an Ada 95 program does a @code{with} and @code{use} of any of these
30668 packages, the new declarations may cause name clashes.
30670 @item Access parameters.
30671 A nondispatching subprogram with an access parameter cannot be renamed
30672 as a dispatching operation. This was permitted in Ada 95.
30674 @item Access types, discriminants, and constraints.
30675 Rule changes in this area have led to some incompatibilities; for example,
30676 constrained subtypes of some access types are not permitted in Ada 2005.
30678 @item Aggregates for limited types.
30679 The allowance of aggregates for limited types in Ada 2005 raises the
30680 possibility of ambiguities in legal Ada 95 programs, since additional types
30681 now need to be considered in expression resolution.
30683 @item Fixed-point multiplication and division.
30684 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
30685 were legal in Ada 95 and invoked the predefined versions of these operations,
30687 The ambiguity may be resolved either by applying a type conversion to the
30688 expression, or by explicitly invoking the operation from package
30691 @item Return-by-reference types.
30692 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
30693 can declare a function returning a value from an anonymous access type.
30697 @node Implementation-dependent characteristics
30698 @section Implementation-dependent characteristics
30700 Although the Ada language defines the semantics of each construct as
30701 precisely as practical, in some situations (for example for reasons of
30702 efficiency, or where the effect is heavily dependent on the host or target
30703 platform) the implementation is allowed some freedom. In porting Ada 83
30704 code to GNAT, you need to be aware of whether / how the existing code
30705 exercised such implementation dependencies. Such characteristics fall into
30706 several categories, and GNAT offers specific support in assisting the
30707 transition from certain Ada 83 compilers.
30710 * Implementation-defined pragmas::
30711 * Implementation-defined attributes::
30713 * Elaboration order::
30714 * Target-specific aspects::
30717 @node Implementation-defined pragmas
30718 @subsection Implementation-defined pragmas
30721 Ada compilers are allowed to supplement the language-defined pragmas, and
30722 these are a potential source of non-portability. All GNAT-defined pragmas
30723 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
30724 Reference Manual}, and these include several that are specifically
30725 intended to correspond to other vendors' Ada 83 pragmas.
30726 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
30727 For compatibility with HP Ada 83, GNAT supplies the pragmas
30728 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
30729 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
30730 and @code{Volatile}.
30731 Other relevant pragmas include @code{External} and @code{Link_With}.
30732 Some vendor-specific
30733 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
30735 avoiding compiler rejection of units that contain such pragmas; they are not
30736 relevant in a GNAT context and hence are not otherwise implemented.
30738 @node Implementation-defined attributes
30739 @subsection Implementation-defined attributes
30741 Analogous to pragmas, the set of attributes may be extended by an
30742 implementation. All GNAT-defined attributes are described in
30743 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
30744 Manual}, and these include several that are specifically intended
30745 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
30746 the attribute @code{VADS_Size} may be useful. For compatibility with HP
30747 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
30751 @subsection Libraries
30753 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
30754 code uses vendor-specific libraries then there are several ways to manage
30755 this in Ada 95 or Ada 2005:
30758 If the source code for the libraries (specs and bodies) are
30759 available, then the libraries can be migrated in the same way as the
30762 If the source code for the specs but not the bodies are
30763 available, then you can reimplement the bodies.
30765 Some features introduced by Ada 95 obviate the need for library support. For
30766 example most Ada 83 vendors supplied a package for unsigned integers. The
30767 Ada 95 modular type feature is the preferred way to handle this need, so
30768 instead of migrating or reimplementing the unsigned integer package it may
30769 be preferable to retrofit the application using modular types.
30772 @node Elaboration order
30773 @subsection Elaboration order
30775 The implementation can choose any elaboration order consistent with the unit
30776 dependency relationship. This freedom means that some orders can result in
30777 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
30778 to invoke a subprogram its body has been elaborated, or to instantiate a
30779 generic before the generic body has been elaborated. By default GNAT
30780 attempts to choose a safe order (one that will not encounter access before
30781 elaboration problems) by implicitly inserting @code{Elaborate} or
30782 @code{Elaborate_All} pragmas where
30783 needed. However, this can lead to the creation of elaboration circularities
30784 and a resulting rejection of the program by gnatbind. This issue is
30785 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
30786 In brief, there are several
30787 ways to deal with this situation:
30791 Modify the program to eliminate the circularities, e.g.@: by moving
30792 elaboration-time code into explicitly-invoked procedures
30794 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
30795 @code{Elaborate} pragmas, and then inhibit the generation of implicit
30796 @code{Elaborate_All}
30797 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
30798 (by selectively suppressing elaboration checks via pragma
30799 @code{Suppress(Elaboration_Check)} when it is safe to do so).
30802 @node Target-specific aspects
30803 @subsection Target-specific aspects
30805 Low-level applications need to deal with machine addresses, data
30806 representations, interfacing with assembler code, and similar issues. If
30807 such an Ada 83 application is being ported to different target hardware (for
30808 example where the byte endianness has changed) then you will need to
30809 carefully examine the program logic; the porting effort will heavily depend
30810 on the robustness of the original design. Moreover, Ada 95 (and thus
30811 Ada 2005) are sometimes
30812 incompatible with typical Ada 83 compiler practices regarding implicit
30813 packing, the meaning of the Size attribute, and the size of access values.
30814 GNAT's approach to these issues is described in @ref{Representation Clauses}.
30816 @node Compatibility with Other Ada Systems
30817 @section Compatibility with Other Ada Systems
30820 If programs avoid the use of implementation dependent and
30821 implementation defined features, as documented in the @cite{Ada
30822 Reference Manual}, there should be a high degree of portability between
30823 GNAT and other Ada systems. The following are specific items which
30824 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
30825 compilers, but do not affect porting code to GNAT@.
30826 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
30827 the following issues may or may not arise for Ada 2005 programs
30828 when other compilers appear.)
30831 @item Ada 83 Pragmas and Attributes
30832 Ada 95 compilers are allowed, but not required, to implement the missing
30833 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
30834 GNAT implements all such pragmas and attributes, eliminating this as
30835 a compatibility concern, but some other Ada 95 compilers reject these
30836 pragmas and attributes.
30838 @item Specialized Needs Annexes
30839 GNAT implements the full set of special needs annexes. At the
30840 current time, it is the only Ada 95 compiler to do so. This means that
30841 programs making use of these features may not be portable to other Ada
30842 95 compilation systems.
30844 @item Representation Clauses
30845 Some other Ada 95 compilers implement only the minimal set of
30846 representation clauses required by the Ada 95 reference manual. GNAT goes
30847 far beyond this minimal set, as described in the next section.
30850 @node Representation Clauses
30851 @section Representation Clauses
30854 The Ada 83 reference manual was quite vague in describing both the minimal
30855 required implementation of representation clauses, and also their precise
30856 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
30857 minimal set of capabilities required is still quite limited.
30859 GNAT implements the full required set of capabilities in
30860 Ada 95 and Ada 2005, but also goes much further, and in particular
30861 an effort has been made to be compatible with existing Ada 83 usage to the
30862 greatest extent possible.
30864 A few cases exist in which Ada 83 compiler behavior is incompatible with
30865 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
30866 intentional or accidental dependence on specific implementation dependent
30867 characteristics of these Ada 83 compilers. The following is a list of
30868 the cases most likely to arise in existing Ada 83 code.
30871 @item Implicit Packing
30872 Some Ada 83 compilers allowed a Size specification to cause implicit
30873 packing of an array or record. This could cause expensive implicit
30874 conversions for change of representation in the presence of derived
30875 types, and the Ada design intends to avoid this possibility.
30876 Subsequent AI's were issued to make it clear that such implicit
30877 change of representation in response to a Size clause is inadvisable,
30878 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
30879 Reference Manuals as implementation advice that is followed by GNAT@.
30880 The problem will show up as an error
30881 message rejecting the size clause. The fix is simply to provide
30882 the explicit pragma @code{Pack}, or for more fine tuned control, provide
30883 a Component_Size clause.
30885 @item Meaning of Size Attribute
30886 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
30887 the minimal number of bits required to hold values of the type. For example,
30888 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
30889 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
30890 some 32 in this situation. This problem will usually show up as a compile
30891 time error, but not always. It is a good idea to check all uses of the
30892 'Size attribute when porting Ada 83 code. The GNAT specific attribute
30893 Object_Size can provide a useful way of duplicating the behavior of
30894 some Ada 83 compiler systems.
30896 @item Size of Access Types
30897 A common assumption in Ada 83 code is that an access type is in fact a pointer,
30898 and that therefore it will be the same size as a System.Address value. This
30899 assumption is true for GNAT in most cases with one exception. For the case of
30900 a pointer to an unconstrained array type (where the bounds may vary from one
30901 value of the access type to another), the default is to use a ``fat pointer'',
30902 which is represented as two separate pointers, one to the bounds, and one to
30903 the array. This representation has a number of advantages, including improved
30904 efficiency. However, it may cause some difficulties in porting existing Ada 83
30905 code which makes the assumption that, for example, pointers fit in 32 bits on
30906 a machine with 32-bit addressing.
30908 To get around this problem, GNAT also permits the use of ``thin pointers'' for
30909 access types in this case (where the designated type is an unconstrained array
30910 type). These thin pointers are indeed the same size as a System.Address value.
30911 To specify a thin pointer, use a size clause for the type, for example:
30913 @smallexample @c ada
30914 type X is access all String;
30915 for X'Size use Standard'Address_Size;
30919 which will cause the type X to be represented using a single pointer.
30920 When using this representation, the bounds are right behind the array.
30921 This representation is slightly less efficient, and does not allow quite
30922 such flexibility in the use of foreign pointers or in using the
30923 Unrestricted_Access attribute to create pointers to non-aliased objects.
30924 But for any standard portable use of the access type it will work in
30925 a functionally correct manner and allow porting of existing code.
30926 Note that another way of forcing a thin pointer representation
30927 is to use a component size clause for the element size in an array,
30928 or a record representation clause for an access field in a record.
30932 @c This brief section is only in the non-VMS version
30933 @c The complete chapter on HP Ada is in the VMS version
30934 @node Compatibility with HP Ada 83
30935 @section Compatibility with HP Ada 83
30938 The VMS version of GNAT fully implements all the pragmas and attributes
30939 provided by HP Ada 83, as well as providing the standard HP Ada 83
30940 libraries, including Starlet. In addition, data layouts and parameter
30941 passing conventions are highly compatible. This means that porting
30942 existing HP Ada 83 code to GNAT in VMS systems should be easier than
30943 most other porting efforts. The following are some of the most
30944 significant differences between GNAT and HP Ada 83.
30947 @item Default floating-point representation
30948 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
30949 it is VMS format. GNAT does implement the necessary pragmas
30950 (Long_Float, Float_Representation) for changing this default.
30953 The package System in GNAT exactly corresponds to the definition in the
30954 Ada 95 reference manual, which means that it excludes many of the
30955 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
30956 that contains the additional definitions, and a special pragma,
30957 Extend_System allows this package to be treated transparently as an
30958 extension of package System.
30961 The definitions provided by Aux_DEC are exactly compatible with those
30962 in the HP Ada 83 version of System, with one exception.
30963 HP Ada provides the following declarations:
30965 @smallexample @c ada
30966 TO_ADDRESS (INTEGER)
30967 TO_ADDRESS (UNSIGNED_LONGWORD)
30968 TO_ADDRESS (@i{universal_integer})
30972 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
30973 an extension to Ada 83 not strictly compatible with the reference manual.
30974 In GNAT, we are constrained to be exactly compatible with the standard,
30975 and this means we cannot provide this capability. In HP Ada 83, the
30976 point of this definition is to deal with a call like:
30978 @smallexample @c ada
30979 TO_ADDRESS (16#12777#);
30983 Normally, according to the Ada 83 standard, one would expect this to be
30984 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
30985 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
30986 definition using @i{universal_integer} takes precedence.
30988 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
30989 is not possible to be 100% compatible. Since there are many programs using
30990 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
30991 to change the name of the function in the UNSIGNED_LONGWORD case, so the
30992 declarations provided in the GNAT version of AUX_Dec are:
30994 @smallexample @c ada
30995 function To_Address (X : Integer) return Address;
30996 pragma Pure_Function (To_Address);
30998 function To_Address_Long (X : Unsigned_Longword)
31000 pragma Pure_Function (To_Address_Long);
31004 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
31005 change the name to TO_ADDRESS_LONG@.
31007 @item Task_Id values
31008 The Task_Id values assigned will be different in the two systems, and GNAT
31009 does not provide a specified value for the Task_Id of the environment task,
31010 which in GNAT is treated like any other declared task.
31014 For full details on these and other less significant compatibility issues,
31015 see appendix E of the HP publication entitled @cite{HP Ada, Technical
31016 Overview and Comparison on HP Platforms}.
31018 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
31019 attributes are recognized, although only a subset of them can sensibly
31020 be implemented. The description of pragmas in @ref{Implementation
31021 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
31022 indicates whether or not they are applicable to non-VMS systems.
31026 @node Transitioning to 64-Bit GNAT for OpenVMS
31027 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
31030 This section is meant to assist users of pre-2006 @value{EDITION}
31031 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
31032 the version of the GNAT technology supplied in 2006 and later for
31033 OpenVMS on both Alpha and I64.
31036 * Introduction to transitioning::
31037 * Migration of 32 bit code::
31038 * Taking advantage of 64 bit addressing::
31039 * Technical details::
31042 @node Introduction to transitioning
31043 @subsection Introduction
31046 64-bit @value{EDITION} for Open VMS has been designed to meet
31051 Providing a full conforming implementation of Ada 95 and Ada 2005
31054 Allowing maximum backward compatibility, thus easing migration of existing
31058 Supplying a path for exploiting the full 64-bit address range
31062 Ada's strong typing semantics has made it
31063 impractical to have different 32-bit and 64-bit modes. As soon as
31064 one object could possibly be outside the 32-bit address space, this
31065 would make it necessary for the @code{System.Address} type to be 64 bits.
31066 In particular, this would cause inconsistencies if 32-bit code is
31067 called from 64-bit code that raises an exception.
31069 This issue has been resolved by always using 64-bit addressing
31070 at the system level, but allowing for automatic conversions between
31071 32-bit and 64-bit addresses where required. Thus users who
31072 do not currently require 64-bit addressing capabilities, can
31073 recompile their code with only minimal changes (and indeed
31074 if the code is written in portable Ada, with no assumptions about
31075 the size of the @code{Address} type, then no changes at all are necessary).
31077 this approach provides a simple, gradual upgrade path to future
31078 use of larger memories than available for 32-bit systems.
31079 Also, newly written applications or libraries will by default
31080 be fully compatible with future systems exploiting 64-bit
31081 addressing capabilities.
31083 @ref{Migration of 32 bit code}, will focus on porting applications
31084 that do not require more than 2 GB of
31085 addressable memory. This code will be referred to as
31086 @emph{32-bit code}.
31087 For applications intending to exploit the full 64-bit address space,
31088 @ref{Taking advantage of 64 bit addressing},
31089 will consider further changes that may be required.
31090 Such code will be referred to below as @emph{64-bit code}.
31092 @node Migration of 32 bit code
31093 @subsection Migration of 32-bit code
31098 * Unchecked conversions::
31099 * Predefined constants::
31100 * Interfacing with C::
31101 * Experience with source compatibility::
31104 @node Address types
31105 @subsubsection Address types
31108 To solve the problem of mixing 64-bit and 32-bit addressing,
31109 while maintaining maximum backward compatibility, the following
31110 approach has been taken:
31114 @code{System.Address} always has a size of 64 bits
31117 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
31121 Since @code{System.Short_Address} is a subtype of @code{System.Address},
31122 a @code{Short_Address}
31123 may be used where an @code{Address} is required, and vice versa, without
31124 needing explicit type conversions.
31125 By virtue of the Open VMS parameter passing conventions,
31127 and exported subprograms that have 32-bit address parameters are
31128 compatible with those that have 64-bit address parameters.
31129 (See @ref{Making code 64 bit clean} for details.)
31131 The areas that may need attention are those where record types have
31132 been defined that contain components of the type @code{System.Address}, and
31133 where objects of this type are passed to code expecting a record layout with
31136 Different compilers on different platforms cannot be
31137 expected to represent the same type in the same way,
31138 since alignment constraints
31139 and other system-dependent properties affect the compiler's decision.
31140 For that reason, Ada code
31141 generally uses representation clauses to specify the expected
31142 layout where required.
31144 If such a representation clause uses 32 bits for a component having
31145 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
31146 will detect that error and produce a specific diagnostic message.
31147 The developer should then determine whether the representation
31148 should be 64 bits or not and make either of two changes:
31149 change the size to 64 bits and leave the type as @code{System.Address}, or
31150 leave the size as 32 bits and change the type to @code{System.Short_Address}.
31151 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
31152 required in any code setting or accessing the field; the compiler will
31153 automatically perform any needed conversions between address
31157 @subsubsection Access types
31160 By default, objects designated by access values are always
31161 allocated in the 32-bit
31162 address space. Thus legacy code will never contain
31163 any objects that are not addressable with 32-bit addresses, and
31164 the compiler will never raise exceptions as result of mixing
31165 32-bit and 64-bit addresses.
31167 However, the access values themselves are represented in 64 bits, for optimum
31168 performance and future compatibility with 64-bit code. As was
31169 the case with @code{System.Address}, the compiler will give an error message
31170 if an object or record component has a representation clause that
31171 requires the access value to fit in 32 bits. In such a situation,
31172 an explicit size clause for the access type, specifying 32 bits,
31173 will have the desired effect.
31175 General access types (declared with @code{access all}) can never be
31176 32 bits, as values of such types must be able to refer to any object
31177 of the designated type,
31178 including objects residing outside the 32-bit address range.
31179 Existing Ada 83 code will not contain such type definitions,
31180 however, since general access types were introduced in Ada 95.
31182 @node Unchecked conversions
31183 @subsubsection Unchecked conversions
31186 In the case of an @code{Unchecked_Conversion} where the source type is a
31187 64-bit access type or the type @code{System.Address}, and the target
31188 type is a 32-bit type, the compiler will generate a warning.
31189 Even though the generated code will still perform the required
31190 conversions, it is highly recommended in these cases to use
31191 respectively a 32-bit access type or @code{System.Short_Address}
31192 as the source type.
31194 @node Predefined constants
31195 @subsubsection Predefined constants
31198 The following table shows the correspondence between pre-2006 versions of
31199 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
31202 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
31203 @item @b{Constant} @tab @b{Old} @tab @b{New}
31204 @item @code{System.Word_Size} @tab 32 @tab 64
31205 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
31206 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
31207 @item @code{System.Address_Size} @tab 32 @tab 64
31211 If you need to refer to the specific
31212 memory size of a 32-bit implementation, instead of the
31213 actual memory size, use @code{System.Short_Memory_Size}
31214 rather than @code{System.Memory_Size}.
31215 Similarly, references to @code{System.Address_Size} may need
31216 to be replaced by @code{System.Short_Address'Size}.
31217 The program @command{gnatfind} may be useful for locating
31218 references to the above constants, so that you can verify that they
31221 @node Interfacing with C
31222 @subsubsection Interfacing with C
31225 In order to minimize the impact of the transition to 64-bit addresses on
31226 legacy programs, some fundamental types in the @code{Interfaces.C}
31227 package hierarchy continue to be represented in 32 bits.
31228 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
31229 This eases integration with the default HP C layout choices, for example
31230 as found in the system routines in @code{DECC$SHR.EXE}.
31231 Because of this implementation choice, the type fully compatible with
31232 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
31233 Depending on the context the compiler will issue a
31234 warning or an error when type @code{Address} is used, alerting the user to a
31235 potential problem. Otherwise 32-bit programs that use
31236 @code{Interfaces.C} should normally not require code modifications
31238 The other issue arising with C interfacing concerns pragma @code{Convention}.
31239 For VMS 64-bit systems, there is an issue of the appropriate default size
31240 of C convention pointers in the absence of an explicit size clause. The HP
31241 C compiler can choose either 32 or 64 bits depending on compiler options.
31242 GNAT chooses 32-bits rather than 64-bits in the default case where no size
31243 clause is given. This proves a better choice for porting 32-bit legacy
31244 applications. In order to have a 64-bit representation, it is necessary to
31245 specify a size representation clause. For example:
31247 @smallexample @c ada
31248 type int_star is access Interfaces.C.int;
31249 pragma Convention(C, int_star);
31250 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
31253 @node Experience with source compatibility
31254 @subsubsection Experience with source compatibility
31257 The Security Server and STARLET on I64 provide an interesting ``test case''
31258 for source compatibility issues, since it is in such system code
31259 where assumptions about @code{Address} size might be expected to occur.
31260 Indeed, there were a small number of occasions in the Security Server
31261 file @file{jibdef.ads}
31262 where a representation clause for a record type specified
31263 32 bits for a component of type @code{Address}.
31264 All of these errors were detected by the compiler.
31265 The repair was obvious and immediate; to simply replace @code{Address} by
31266 @code{Short_Address}.
31268 In the case of STARLET, there were several record types that should
31269 have had representation clauses but did not. In these record types
31270 there was an implicit assumption that an @code{Address} value occupied
31272 These compiled without error, but their usage resulted in run-time error
31273 returns from STARLET system calls.
31274 Future GNAT technology enhancements may include a tool that detects and flags
31275 these sorts of potential source code porting problems.
31277 @c ****************************************
31278 @node Taking advantage of 64 bit addressing
31279 @subsection Taking advantage of 64-bit addressing
31282 * Making code 64 bit clean::
31283 * Allocating memory from the 64 bit storage pool::
31284 * Restrictions on use of 64 bit objects::
31285 * Using 64 bit storage pools by default::
31286 * General access types::
31287 * STARLET and other predefined libraries::
31290 @node Making code 64 bit clean
31291 @subsubsection Making code 64-bit clean
31294 In order to prevent problems that may occur when (parts of) a
31295 system start using memory outside the 32-bit address range,
31296 we recommend some additional guidelines:
31300 For imported subprograms that take parameters of the
31301 type @code{System.Address}, ensure that these subprograms can
31302 indeed handle 64-bit addresses. If not, or when in doubt,
31303 change the subprogram declaration to specify
31304 @code{System.Short_Address} instead.
31307 Resolve all warnings related to size mismatches in
31308 unchecked conversions. Failing to do so causes
31309 erroneous execution if the source object is outside
31310 the 32-bit address space.
31313 (optional) Explicitly use the 32-bit storage pool
31314 for access types used in a 32-bit context, or use
31315 generic access types where possible
31316 (@pxref{Restrictions on use of 64 bit objects}).
31320 If these rules are followed, the compiler will automatically insert
31321 any necessary checks to ensure that no addresses or access values
31322 passed to 32-bit code ever refer to objects outside the 32-bit
31324 Any attempt to do this will raise @code{Constraint_Error}.
31326 @node Allocating memory from the 64 bit storage pool
31327 @subsubsection Allocating memory from the 64-bit storage pool
31330 For any access type @code{T} that potentially requires memory allocations
31331 beyond the 32-bit address space,
31332 use the following representation clause:
31334 @smallexample @c ada
31335 for T'Storage_Pool use System.Pool_64;
31338 @node Restrictions on use of 64 bit objects
31339 @subsubsection Restrictions on use of 64-bit objects
31342 Taking the address of an object allocated from a 64-bit storage pool,
31343 and then passing this address to a subprogram expecting
31344 @code{System.Short_Address},
31345 or assigning it to a variable of type @code{Short_Address}, will cause
31346 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
31347 (@pxref{Making code 64 bit clean}), or checks are suppressed,
31348 no exception is raised and execution
31349 will become erroneous.
31351 @node Using 64 bit storage pools by default
31352 @subsubsection Using 64-bit storage pools by default
31355 In some cases it may be desirable to have the compiler allocate
31356 from 64-bit storage pools by default. This may be the case for
31357 libraries that are 64-bit clean, but may be used in both 32-bit
31358 and 64-bit contexts. For these cases the following configuration
31359 pragma may be specified:
31361 @smallexample @c ada
31362 pragma Pool_64_Default;
31366 Any code compiled in the context of this pragma will by default
31367 use the @code{System.Pool_64} storage pool. This default may be overridden
31368 for a specific access type @code{T} by the representation clause:
31370 @smallexample @c ada
31371 for T'Storage_Pool use System.Pool_32;
31375 Any object whose address may be passed to a subprogram with a
31376 @code{Short_Address} argument, or assigned to a variable of type
31377 @code{Short_Address}, needs to be allocated from this pool.
31379 @node General access types
31380 @subsubsection General access types
31383 Objects designated by access values from a
31384 general access type (declared with @code{access all}) are never allocated
31385 from a 64-bit storage pool. Code that uses general access types will
31386 accept objects allocated in either 32-bit or 64-bit address spaces,
31387 but never allocate objects outside the 32-bit address space.
31388 Using general access types ensures maximum compatibility with both
31389 32-bit and 64-bit code.
31391 @node STARLET and other predefined libraries
31392 @subsubsection STARLET and other predefined libraries
31395 All code that comes as part of GNAT is 64-bit clean, but the
31396 restrictions given in @ref{Restrictions on use of 64 bit objects},
31397 still apply. Look at the package
31398 specs to see in which contexts objects allocated
31399 in 64-bit address space are acceptable.
31401 @node Technical details
31402 @subsection Technical details
31405 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
31406 Ada standard with respect to the type of @code{System.Address}. Previous
31407 versions of GNAT Pro have defined this type as private and implemented it as a
31410 In order to allow defining @code{System.Short_Address} as a proper subtype,
31411 and to match the implicit sign extension in parameter passing,
31412 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
31413 visible (i.e., non-private) integer type.
31414 Standard operations on the type, such as the binary operators ``+'', ``-'',
31415 etc., that take @code{Address} operands and return an @code{Address} result,
31416 have been hidden by declaring these
31417 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
31418 ambiguities that would otherwise result from overloading.
31419 (Note that, although @code{Address} is a visible integer type,
31420 good programming practice dictates against exploiting the type's
31421 integer properties such as literals, since this will compromise
31424 Defining @code{Address} as a visible integer type helps achieve
31425 maximum compatibility for existing Ada code,
31426 without sacrificing the capabilities of the 64-bit architecture.
31429 @c ************************************************
31431 @node Microsoft Windows Topics
31432 @appendix Microsoft Windows Topics
31438 This chapter describes topics that are specific to the Microsoft Windows
31439 platforms (NT, 2000, and XP Professional).
31442 * Using GNAT on Windows::
31443 * Using a network installation of GNAT::
31444 * CONSOLE and WINDOWS subsystems::
31445 * Temporary Files::
31446 * Mixed-Language Programming on Windows::
31447 * Windows Calling Conventions::
31448 * Introduction to Dynamic Link Libraries (DLLs)::
31449 * Using DLLs with GNAT::
31450 * Building DLLs with GNAT::
31451 * Building DLLs with GNAT Project files::
31452 * Building DLLs with gnatdll::
31453 * GNAT and Windows Resources::
31454 * Debugging a DLL::
31455 * Setting Stack Size from gnatlink::
31456 * Setting Heap Size from gnatlink::
31459 @node Using GNAT on Windows
31460 @section Using GNAT on Windows
31463 One of the strengths of the GNAT technology is that its tool set
31464 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
31465 @code{gdb} debugger, etc.) is used in the same way regardless of the
31468 On Windows this tool set is complemented by a number of Microsoft-specific
31469 tools that have been provided to facilitate interoperability with Windows
31470 when this is required. With these tools:
31475 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
31479 You can use any Dynamically Linked Library (DLL) in your Ada code (both
31480 relocatable and non-relocatable DLLs are supported).
31483 You can build Ada DLLs for use in other applications. These applications
31484 can be written in a language other than Ada (e.g., C, C++, etc). Again both
31485 relocatable and non-relocatable Ada DLLs are supported.
31488 You can include Windows resources in your Ada application.
31491 You can use or create COM/DCOM objects.
31495 Immediately below are listed all known general GNAT-for-Windows restrictions.
31496 Other restrictions about specific features like Windows Resources and DLLs
31497 are listed in separate sections below.
31502 It is not possible to use @code{GetLastError} and @code{SetLastError}
31503 when tasking, protected records, or exceptions are used. In these
31504 cases, in order to implement Ada semantics, the GNAT run-time system
31505 calls certain Win32 routines that set the last error variable to 0 upon
31506 success. It should be possible to use @code{GetLastError} and
31507 @code{SetLastError} when tasking, protected record, and exception
31508 features are not used, but it is not guaranteed to work.
31511 It is not possible to link against Microsoft libraries except for
31512 import libraries. The library must be built to be compatible with
31513 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
31514 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
31515 not be compatible with the GNAT runtime. Even if the library is
31516 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
31519 When the compilation environment is located on FAT32 drives, users may
31520 experience recompilations of the source files that have not changed if
31521 Daylight Saving Time (DST) state has changed since the last time files
31522 were compiled. NTFS drives do not have this problem.
31525 No components of the GNAT toolset use any entries in the Windows
31526 registry. The only entries that can be created are file associations and
31527 PATH settings, provided the user has chosen to create them at installation
31528 time, as well as some minimal book-keeping information needed to correctly
31529 uninstall or integrate different GNAT products.
31532 @node Using a network installation of GNAT
31533 @section Using a network installation of GNAT
31536 Make sure the system on which GNAT is installed is accessible from the
31537 current machine, i.e., the install location is shared over the network.
31538 Shared resources are accessed on Windows by means of UNC paths, which
31539 have the format @code{\\server\sharename\path}
31541 In order to use such a network installation, simply add the UNC path of the
31542 @file{bin} directory of your GNAT installation in front of your PATH. For
31543 example, if GNAT is installed in @file{\GNAT} directory of a share location
31544 called @file{c-drive} on a machine @file{LOKI}, the following command will
31547 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
31549 Be aware that every compilation using the network installation results in the
31550 transfer of large amounts of data across the network and will likely cause
31551 serious performance penalty.
31553 @node CONSOLE and WINDOWS subsystems
31554 @section CONSOLE and WINDOWS subsystems
31555 @cindex CONSOLE Subsystem
31556 @cindex WINDOWS Subsystem
31560 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
31561 (which is the default subsystem) will always create a console when
31562 launching the application. This is not something desirable when the
31563 application has a Windows GUI. To get rid of this console the
31564 application must be using the @code{WINDOWS} subsystem. To do so
31565 the @option{-mwindows} linker option must be specified.
31568 $ gnatmake winprog -largs -mwindows
31571 @node Temporary Files
31572 @section Temporary Files
31573 @cindex Temporary files
31576 It is possible to control where temporary files gets created by setting
31577 the @env{TMP} environment variable. The file will be created:
31580 @item Under the directory pointed to by the @env{TMP} environment variable if
31581 this directory exists.
31583 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
31584 set (or not pointing to a directory) and if this directory exists.
31586 @item Under the current working directory otherwise.
31590 This allows you to determine exactly where the temporary
31591 file will be created. This is particularly useful in networked
31592 environments where you may not have write access to some
31595 @node Mixed-Language Programming on Windows
31596 @section Mixed-Language Programming on Windows
31599 Developing pure Ada applications on Windows is no different than on
31600 other GNAT-supported platforms. However, when developing or porting an
31601 application that contains a mix of Ada and C/C++, the choice of your
31602 Windows C/C++ development environment conditions your overall
31603 interoperability strategy.
31605 If you use @command{gcc} to compile the non-Ada part of your application,
31606 there are no Windows-specific restrictions that affect the overall
31607 interoperability with your Ada code. If you plan to use
31608 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
31609 the following limitations:
31613 You cannot link your Ada code with an object or library generated with
31614 Microsoft tools if these use the @code{.tls} section (Thread Local
31615 Storage section) since the GNAT linker does not yet support this section.
31618 You cannot link your Ada code with an object or library generated with
31619 Microsoft tools if these use I/O routines other than those provided in
31620 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
31621 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
31622 libraries can cause a conflict with @code{msvcrt.dll} services. For
31623 instance Visual C++ I/O stream routines conflict with those in
31628 If you do want to use the Microsoft tools for your non-Ada code and hit one
31629 of the above limitations, you have two choices:
31633 Encapsulate your non-Ada code in a DLL to be linked with your Ada
31634 application. In this case, use the Microsoft or whatever environment to
31635 build the DLL and use GNAT to build your executable
31636 (@pxref{Using DLLs with GNAT}).
31639 Or you can encapsulate your Ada code in a DLL to be linked with the
31640 other part of your application. In this case, use GNAT to build the DLL
31641 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
31642 environment to build your executable.
31645 @node Windows Calling Conventions
31646 @section Windows Calling Conventions
31651 * C Calling Convention::
31652 * Stdcall Calling Convention::
31653 * Win32 Calling Convention::
31654 * DLL Calling Convention::
31658 When a subprogram @code{F} (caller) calls a subprogram @code{G}
31659 (callee), there are several ways to push @code{G}'s parameters on the
31660 stack and there are several possible scenarios to clean up the stack
31661 upon @code{G}'s return. A calling convention is an agreed upon software
31662 protocol whereby the responsibilities between the caller (@code{F}) and
31663 the callee (@code{G}) are clearly defined. Several calling conventions
31664 are available for Windows:
31668 @code{C} (Microsoft defined)
31671 @code{Stdcall} (Microsoft defined)
31674 @code{Win32} (GNAT specific)
31677 @code{DLL} (GNAT specific)
31680 @node C Calling Convention
31681 @subsection @code{C} Calling Convention
31684 This is the default calling convention used when interfacing to C/C++
31685 routines compiled with either @command{gcc} or Microsoft Visual C++.
31687 In the @code{C} calling convention subprogram parameters are pushed on the
31688 stack by the caller from right to left. The caller itself is in charge of
31689 cleaning up the stack after the call. In addition, the name of a routine
31690 with @code{C} calling convention is mangled by adding a leading underscore.
31692 The name to use on the Ada side when importing (or exporting) a routine
31693 with @code{C} calling convention is the name of the routine. For
31694 instance the C function:
31697 int get_val (long);
31701 should be imported from Ada as follows:
31703 @smallexample @c ada
31705 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31706 pragma Import (C, Get_Val, External_Name => "get_val");
31711 Note that in this particular case the @code{External_Name} parameter could
31712 have been omitted since, when missing, this parameter is taken to be the
31713 name of the Ada entity in lower case. When the @code{Link_Name} parameter
31714 is missing, as in the above example, this parameter is set to be the
31715 @code{External_Name} with a leading underscore.
31717 When importing a variable defined in C, you should always use the @code{C}
31718 calling convention unless the object containing the variable is part of a
31719 DLL (in which case you should use the @code{Stdcall} calling
31720 convention, @pxref{Stdcall Calling Convention}).
31722 @node Stdcall Calling Convention
31723 @subsection @code{Stdcall} Calling Convention
31726 This convention, which was the calling convention used for Pascal
31727 programs, is used by Microsoft for all the routines in the Win32 API for
31728 efficiency reasons. It must be used to import any routine for which this
31729 convention was specified.
31731 In the @code{Stdcall} calling convention subprogram parameters are pushed
31732 on the stack by the caller from right to left. The callee (and not the
31733 caller) is in charge of cleaning the stack on routine exit. In addition,
31734 the name of a routine with @code{Stdcall} calling convention is mangled by
31735 adding a leading underscore (as for the @code{C} calling convention) and a
31736 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
31737 bytes) of the parameters passed to the routine.
31739 The name to use on the Ada side when importing a C routine with a
31740 @code{Stdcall} calling convention is the name of the C routine. The leading
31741 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
31742 the compiler. For instance the Win32 function:
31745 @b{APIENTRY} int get_val (long);
31749 should be imported from Ada as follows:
31751 @smallexample @c ada
31753 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31754 pragma Import (Stdcall, Get_Val);
31755 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
31760 As for the @code{C} calling convention, when the @code{External_Name}
31761 parameter is missing, it is taken to be the name of the Ada entity in lower
31762 case. If instead of writing the above import pragma you write:
31764 @smallexample @c ada
31766 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31767 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
31772 then the imported routine is @code{_retrieve_val@@4}. However, if instead
31773 of specifying the @code{External_Name} parameter you specify the
31774 @code{Link_Name} as in the following example:
31776 @smallexample @c ada
31778 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
31779 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
31784 then the imported routine is @code{retrieve_val}, that is, there is no
31785 decoration at all. No leading underscore and no Stdcall suffix
31786 @code{@@}@code{@var{nn}}.
31789 This is especially important as in some special cases a DLL's entry
31790 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
31791 name generated for a call has it.
31794 It is also possible to import variables defined in a DLL by using an
31795 import pragma for a variable. As an example, if a DLL contains a
31796 variable defined as:
31803 then, to access this variable from Ada you should write:
31805 @smallexample @c ada
31807 My_Var : Interfaces.C.int;
31808 pragma Import (Stdcall, My_Var);
31813 Note that to ease building cross-platform bindings this convention
31814 will be handled as a @code{C} calling convention on non-Windows platforms.
31816 @node Win32 Calling Convention
31817 @subsection @code{Win32} Calling Convention
31820 This convention, which is GNAT-specific is fully equivalent to the
31821 @code{Stdcall} calling convention described above.
31823 @node DLL Calling Convention
31824 @subsection @code{DLL} Calling Convention
31827 This convention, which is GNAT-specific is fully equivalent to the
31828 @code{Stdcall} calling convention described above.
31830 @node Introduction to Dynamic Link Libraries (DLLs)
31831 @section Introduction to Dynamic Link Libraries (DLLs)
31835 A Dynamically Linked Library (DLL) is a library that can be shared by
31836 several applications running under Windows. A DLL can contain any number of
31837 routines and variables.
31839 One advantage of DLLs is that you can change and enhance them without
31840 forcing all the applications that depend on them to be relinked or
31841 recompiled. However, you should be aware than all calls to DLL routines are
31842 slower since, as you will understand below, such calls are indirect.
31844 To illustrate the remainder of this section, suppose that an application
31845 wants to use the services of a DLL @file{API.dll}. To use the services
31846 provided by @file{API.dll} you must statically link against the DLL or
31847 an import library which contains a jump table with an entry for each
31848 routine and variable exported by the DLL. In the Microsoft world this
31849 import library is called @file{API.lib}. When using GNAT this import
31850 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
31851 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
31853 After you have linked your application with the DLL or the import library
31854 and you run your application, here is what happens:
31858 Your application is loaded into memory.
31861 The DLL @file{API.dll} is mapped into the address space of your
31862 application. This means that:
31866 The DLL will use the stack of the calling thread.
31869 The DLL will use the virtual address space of the calling process.
31872 The DLL will allocate memory from the virtual address space of the calling
31876 Handles (pointers) can be safely exchanged between routines in the DLL
31877 routines and routines in the application using the DLL.
31881 The entries in the jump table (from the import library @file{libAPI.dll.a}
31882 or @file{API.lib} or automatically created when linking against a DLL)
31883 which is part of your application are initialized with the addresses
31884 of the routines and variables in @file{API.dll}.
31887 If present in @file{API.dll}, routines @code{DllMain} or
31888 @code{DllMainCRTStartup} are invoked. These routines typically contain
31889 the initialization code needed for the well-being of the routines and
31890 variables exported by the DLL.
31894 There is an additional point which is worth mentioning. In the Windows
31895 world there are two kind of DLLs: relocatable and non-relocatable
31896 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
31897 in the target application address space. If the addresses of two
31898 non-relocatable DLLs overlap and these happen to be used by the same
31899 application, a conflict will occur and the application will run
31900 incorrectly. Hence, when possible, it is always preferable to use and
31901 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
31902 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
31903 User's Guide) removes the debugging symbols from the DLL but the DLL can
31904 still be relocated.
31906 As a side note, an interesting difference between Microsoft DLLs and
31907 Unix shared libraries, is the fact that on most Unix systems all public
31908 routines are exported by default in a Unix shared library, while under
31909 Windows it is possible (but not required) to list exported routines in
31910 a definition file (@pxref{The Definition File}).
31912 @node Using DLLs with GNAT
31913 @section Using DLLs with GNAT
31916 * Creating an Ada Spec for the DLL Services::
31917 * Creating an Import Library::
31921 To use the services of a DLL, say @file{API.dll}, in your Ada application
31926 The Ada spec for the routines and/or variables you want to access in
31927 @file{API.dll}. If not available this Ada spec must be built from the C/C++
31928 header files provided with the DLL.
31931 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
31932 mentioned an import library is a statically linked library containing the
31933 import table which will be filled at load time to point to the actual
31934 @file{API.dll} routines. Sometimes you don't have an import library for the
31935 DLL you want to use. The following sections will explain how to build
31936 one. Note that this is optional.
31939 The actual DLL, @file{API.dll}.
31943 Once you have all the above, to compile an Ada application that uses the
31944 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
31945 you simply issue the command
31948 $ gnatmake my_ada_app -largs -lAPI
31952 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
31953 tells the GNAT linker to look first for a library named @file{API.lib}
31954 (Microsoft-style name) and if not found for a libraries named
31955 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
31956 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
31957 contains the following pragma
31959 @smallexample @c ada
31960 pragma Linker_Options ("-lAPI");
31964 you do not have to add @option{-largs -lAPI} at the end of the
31965 @command{gnatmake} command.
31967 If any one of the items above is missing you will have to create it
31968 yourself. The following sections explain how to do so using as an
31969 example a fictitious DLL called @file{API.dll}.
31971 @node Creating an Ada Spec for the DLL Services
31972 @subsection Creating an Ada Spec for the DLL Services
31975 A DLL typically comes with a C/C++ header file which provides the
31976 definitions of the routines and variables exported by the DLL. The Ada
31977 equivalent of this header file is a package spec that contains definitions
31978 for the imported entities. If the DLL you intend to use does not come with
31979 an Ada spec you have to generate one such spec yourself. For example if
31980 the header file of @file{API.dll} is a file @file{api.h} containing the
31981 following two definitions:
31993 then the equivalent Ada spec could be:
31995 @smallexample @c ada
31998 with Interfaces.C.Strings;
32003 function Get (Str : C.Strings.Chars_Ptr) return C.int;
32006 pragma Import (C, Get);
32007 pragma Import (DLL, Some_Var);
32014 Note that a variable is
32015 @strong{always imported with a Stdcall convention}. A function
32016 can have @code{C} or @code{Stdcall} convention.
32017 (@pxref{Windows Calling Conventions}).
32019 @node Creating an Import Library
32020 @subsection Creating an Import Library
32021 @cindex Import library
32024 * The Definition File::
32025 * GNAT-Style Import Library::
32026 * Microsoft-Style Import Library::
32030 If a Microsoft-style import library @file{API.lib} or a GNAT-style
32031 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
32032 with @file{API.dll} you can skip this section. You can also skip this
32033 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
32034 as in this case it is possible to link directly against the
32035 DLL. Otherwise read on.
32037 @node The Definition File
32038 @subsubsection The Definition File
32039 @cindex Definition file
32043 As previously mentioned, and unlike Unix systems, the list of symbols
32044 that are exported from a DLL must be provided explicitly in Windows.
32045 The main goal of a definition file is precisely that: list the symbols
32046 exported by a DLL. A definition file (usually a file with a @code{.def}
32047 suffix) has the following structure:
32052 @r{[}LIBRARY @var{name}@r{]}
32053 @r{[}DESCRIPTION @var{string}@r{]}
32063 @item LIBRARY @var{name}
32064 This section, which is optional, gives the name of the DLL.
32066 @item DESCRIPTION @var{string}
32067 This section, which is optional, gives a description string that will be
32068 embedded in the import library.
32071 This section gives the list of exported symbols (procedures, functions or
32072 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
32073 section of @file{API.def} looks like:
32087 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
32088 (@pxref{Windows Calling Conventions}) for a Stdcall
32089 calling convention function in the exported symbols list.
32092 There can actually be other sections in a definition file, but these
32093 sections are not relevant to the discussion at hand.
32095 @node GNAT-Style Import Library
32096 @subsubsection GNAT-Style Import Library
32099 To create a static import library from @file{API.dll} with the GNAT tools
32100 you should proceed as follows:
32104 Create the definition file @file{API.def} (@pxref{The Definition File}).
32105 For that use the @code{dll2def} tool as follows:
32108 $ dll2def API.dll > API.def
32112 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
32113 to standard output the list of entry points in the DLL. Note that if
32114 some routines in the DLL have the @code{Stdcall} convention
32115 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
32116 suffix then you'll have to edit @file{api.def} to add it, and specify
32117 @option{-k} to @command{gnatdll} when creating the import library.
32120 Here are some hints to find the right @code{@@}@var{nn} suffix.
32124 If you have the Microsoft import library (.lib), it is possible to get
32125 the right symbols by using Microsoft @code{dumpbin} tool (see the
32126 corresponding Microsoft documentation for further details).
32129 $ dumpbin /exports api.lib
32133 If you have a message about a missing symbol at link time the compiler
32134 tells you what symbol is expected. You just have to go back to the
32135 definition file and add the right suffix.
32139 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
32140 (@pxref{Using gnatdll}) as follows:
32143 $ gnatdll -e API.def -d API.dll
32147 @code{gnatdll} takes as input a definition file @file{API.def} and the
32148 name of the DLL containing the services listed in the definition file
32149 @file{API.dll}. The name of the static import library generated is
32150 computed from the name of the definition file as follows: if the
32151 definition file name is @var{xyz}@code{.def}, the import library name will
32152 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
32153 @option{-e} could have been removed because the name of the definition
32154 file (before the ``@code{.def}'' suffix) is the same as the name of the
32155 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
32158 @node Microsoft-Style Import Library
32159 @subsubsection Microsoft-Style Import Library
32162 With GNAT you can either use a GNAT-style or Microsoft-style import
32163 library. A Microsoft import library is needed only if you plan to make an
32164 Ada DLL available to applications developed with Microsoft
32165 tools (@pxref{Mixed-Language Programming on Windows}).
32167 To create a Microsoft-style import library for @file{API.dll} you
32168 should proceed as follows:
32172 Create the definition file @file{API.def} from the DLL. For this use either
32173 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
32174 tool (see the corresponding Microsoft documentation for further details).
32177 Build the actual import library using Microsoft's @code{lib} utility:
32180 $ lib -machine:IX86 -def:API.def -out:API.lib
32184 If you use the above command the definition file @file{API.def} must
32185 contain a line giving the name of the DLL:
32192 See the Microsoft documentation for further details about the usage of
32196 @node Building DLLs with GNAT
32197 @section Building DLLs with GNAT
32198 @cindex DLLs, building
32201 This section explain how to build DLLs using the GNAT built-in DLL
32202 support. With the following procedure it is straight forward to build
32203 and use DLLs with GNAT.
32207 @item building object files
32209 The first step is to build all objects files that are to be included
32210 into the DLL. This is done by using the standard @command{gnatmake} tool.
32212 @item building the DLL
32214 To build the DLL you must use @command{gcc}'s @option{-shared}
32215 option. It is quite simple to use this method:
32218 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
32221 It is important to note that in this case all symbols found in the
32222 object files are automatically exported. It is possible to restrict
32223 the set of symbols to export by passing to @command{gcc} a definition
32224 file, @pxref{The Definition File}. For example:
32227 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
32230 If you use a definition file you must export the elaboration procedures
32231 for every package that required one. Elaboration procedures are named
32232 using the package name followed by "_E".
32234 @item preparing DLL to be used
32236 For the DLL to be used by client programs the bodies must be hidden
32237 from it and the .ali set with read-only attribute. This is very important
32238 otherwise GNAT will recompile all packages and will not actually use
32239 the code in the DLL. For example:
32243 $ copy *.ads *.ali api.dll apilib
32244 $ attrib +R apilib\*.ali
32249 At this point it is possible to use the DLL by directly linking
32250 against it. Note that you must use the GNAT shared runtime when using
32251 GNAT shared libraries. This is achieved by using @option{-shared} binder's
32255 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
32258 @node Building DLLs with GNAT Project files
32259 @section Building DLLs with GNAT Project files
32260 @cindex DLLs, building
32263 There is nothing specific to Windows in the build process.
32264 @pxref{Library Projects}.
32267 Due to a system limitation, it is not possible under Windows to create threads
32268 when inside the @code{DllMain} routine which is used for auto-initialization
32269 of shared libraries, so it is not possible to have library level tasks in SALs.
32271 @node Building DLLs with gnatdll
32272 @section Building DLLs with gnatdll
32273 @cindex DLLs, building
32276 * Limitations When Using Ada DLLs from Ada::
32277 * Exporting Ada Entities::
32278 * Ada DLLs and Elaboration::
32279 * Ada DLLs and Finalization::
32280 * Creating a Spec for Ada DLLs::
32281 * Creating the Definition File::
32286 Note that it is preferred to use the built-in GNAT DLL support
32287 (@pxref{Building DLLs with GNAT}) or GNAT Project files
32288 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
32290 This section explains how to build DLLs containing Ada code using
32291 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
32292 remainder of this section.
32294 The steps required to build an Ada DLL that is to be used by Ada as well as
32295 non-Ada applications are as follows:
32299 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
32300 @code{Stdcall} calling convention to avoid any Ada name mangling for the
32301 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
32302 skip this step if you plan to use the Ada DLL only from Ada applications.
32305 Your Ada code must export an initialization routine which calls the routine
32306 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
32307 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
32308 routine exported by the Ada DLL must be invoked by the clients of the DLL
32309 to initialize the DLL.
32312 When useful, the DLL should also export a finalization routine which calls
32313 routine @code{adafinal} generated by @command{gnatbind} to perform the
32314 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
32315 The finalization routine exported by the Ada DLL must be invoked by the
32316 clients of the DLL when the DLL services are no further needed.
32319 You must provide a spec for the services exported by the Ada DLL in each
32320 of the programming languages to which you plan to make the DLL available.
32323 You must provide a definition file listing the exported entities
32324 (@pxref{The Definition File}).
32327 Finally you must use @code{gnatdll} to produce the DLL and the import
32328 library (@pxref{Using gnatdll}).
32332 Note that a relocatable DLL stripped using the @code{strip}
32333 binutils tool will not be relocatable anymore. To build a DLL without
32334 debug information pass @code{-largs -s} to @code{gnatdll}. This
32335 restriction does not apply to a DLL built using a Library Project.
32336 @pxref{Library Projects}.
32338 @node Limitations When Using Ada DLLs from Ada
32339 @subsection Limitations When Using Ada DLLs from Ada
32342 When using Ada DLLs from Ada applications there is a limitation users
32343 should be aware of. Because on Windows the GNAT run time is not in a DLL of
32344 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
32345 each Ada DLL includes the services of the GNAT run time that are necessary
32346 to the Ada code inside the DLL. As a result, when an Ada program uses an
32347 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
32348 one in the main program.
32350 It is therefore not possible to exchange GNAT run-time objects between the
32351 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
32352 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
32355 It is completely safe to exchange plain elementary, array or record types,
32356 Windows object handles, etc.
32358 @node Exporting Ada Entities
32359 @subsection Exporting Ada Entities
32360 @cindex Export table
32363 Building a DLL is a way to encapsulate a set of services usable from any
32364 application. As a result, the Ada entities exported by a DLL should be
32365 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
32366 any Ada name mangling. As an example here is an Ada package
32367 @code{API}, spec and body, exporting two procedures, a function, and a
32370 @smallexample @c ada
32373 with Interfaces.C; use Interfaces;
32375 Count : C.int := 0;
32376 function Factorial (Val : C.int) return C.int;
32378 procedure Initialize_API;
32379 procedure Finalize_API;
32380 -- Initialization & Finalization routines. More in the next section.
32382 pragma Export (C, Initialize_API);
32383 pragma Export (C, Finalize_API);
32384 pragma Export (C, Count);
32385 pragma Export (C, Factorial);
32391 @smallexample @c ada
32394 package body API is
32395 function Factorial (Val : C.int) return C.int is
32398 Count := Count + 1;
32399 for K in 1 .. Val loop
32405 procedure Initialize_API is
32407 pragma Import (C, Adainit);
32410 end Initialize_API;
32412 procedure Finalize_API is
32413 procedure Adafinal;
32414 pragma Import (C, Adafinal);
32424 If the Ada DLL you are building will only be used by Ada applications
32425 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
32426 convention. As an example, the previous package could be written as
32429 @smallexample @c ada
32433 Count : Integer := 0;
32434 function Factorial (Val : Integer) return Integer;
32436 procedure Initialize_API;
32437 procedure Finalize_API;
32438 -- Initialization and Finalization routines.
32444 @smallexample @c ada
32447 package body API is
32448 function Factorial (Val : Integer) return Integer is
32449 Fact : Integer := 1;
32451 Count := Count + 1;
32452 for K in 1 .. Val loop
32459 -- The remainder of this package body is unchanged.
32466 Note that if you do not export the Ada entities with a @code{C} or
32467 @code{Stdcall} convention you will have to provide the mangled Ada names
32468 in the definition file of the Ada DLL
32469 (@pxref{Creating the Definition File}).
32471 @node Ada DLLs and Elaboration
32472 @subsection Ada DLLs and Elaboration
32473 @cindex DLLs and elaboration
32476 The DLL that you are building contains your Ada code as well as all the
32477 routines in the Ada library that are needed by it. The first thing a
32478 user of your DLL must do is elaborate the Ada code
32479 (@pxref{Elaboration Order Handling in GNAT}).
32481 To achieve this you must export an initialization routine
32482 (@code{Initialize_API} in the previous example), which must be invoked
32483 before using any of the DLL services. This elaboration routine must call
32484 the Ada elaboration routine @code{adainit} generated by the GNAT binder
32485 (@pxref{Binding with Non-Ada Main Programs}). See the body of
32486 @code{Initialize_Api} for an example. Note that the GNAT binder is
32487 automatically invoked during the DLL build process by the @code{gnatdll}
32488 tool (@pxref{Using gnatdll}).
32490 When a DLL is loaded, Windows systematically invokes a routine called
32491 @code{DllMain}. It would therefore be possible to call @code{adainit}
32492 directly from @code{DllMain} without having to provide an explicit
32493 initialization routine. Unfortunately, it is not possible to call
32494 @code{adainit} from the @code{DllMain} if your program has library level
32495 tasks because access to the @code{DllMain} entry point is serialized by
32496 the system (that is, only a single thread can execute ``through'' it at a
32497 time), which means that the GNAT run time will deadlock waiting for the
32498 newly created task to complete its initialization.
32500 @node Ada DLLs and Finalization
32501 @subsection Ada DLLs and Finalization
32502 @cindex DLLs and finalization
32505 When the services of an Ada DLL are no longer needed, the client code should
32506 invoke the DLL finalization routine, if available. The DLL finalization
32507 routine is in charge of releasing all resources acquired by the DLL. In the
32508 case of the Ada code contained in the DLL, this is achieved by calling
32509 routine @code{adafinal} generated by the GNAT binder
32510 (@pxref{Binding with Non-Ada Main Programs}).
32511 See the body of @code{Finalize_Api} for an
32512 example. As already pointed out the GNAT binder is automatically invoked
32513 during the DLL build process by the @code{gnatdll} tool
32514 (@pxref{Using gnatdll}).
32516 @node Creating a Spec for Ada DLLs
32517 @subsection Creating a Spec for Ada DLLs
32520 To use the services exported by the Ada DLL from another programming
32521 language (e.g.@: C), you have to translate the specs of the exported Ada
32522 entities in that language. For instance in the case of @code{API.dll},
32523 the corresponding C header file could look like:
32528 extern int *_imp__count;
32529 #define count (*_imp__count)
32530 int factorial (int);
32536 It is important to understand that when building an Ada DLL to be used by
32537 other Ada applications, you need two different specs for the packages
32538 contained in the DLL: one for building the DLL and the other for using
32539 the DLL. This is because the @code{DLL} calling convention is needed to
32540 use a variable defined in a DLL, but when building the DLL, the variable
32541 must have either the @code{Ada} or @code{C} calling convention. As an
32542 example consider a DLL comprising the following package @code{API}:
32544 @smallexample @c ada
32548 Count : Integer := 0;
32550 -- Remainder of the package omitted.
32557 After producing a DLL containing package @code{API}, the spec that
32558 must be used to import @code{API.Count} from Ada code outside of the
32561 @smallexample @c ada
32566 pragma Import (DLL, Count);
32572 @node Creating the Definition File
32573 @subsection Creating the Definition File
32576 The definition file is the last file needed to build the DLL. It lists
32577 the exported symbols. As an example, the definition file for a DLL
32578 containing only package @code{API} (where all the entities are exported
32579 with a @code{C} calling convention) is:
32594 If the @code{C} calling convention is missing from package @code{API},
32595 then the definition file contains the mangled Ada names of the above
32596 entities, which in this case are:
32605 api__initialize_api
32610 @node Using gnatdll
32611 @subsection Using @code{gnatdll}
32615 * gnatdll Example::
32616 * gnatdll behind the Scenes::
32621 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
32622 and non-Ada sources that make up your DLL have been compiled.
32623 @code{gnatdll} is actually in charge of two distinct tasks: build the
32624 static import library for the DLL and the actual DLL. The form of the
32625 @code{gnatdll} command is
32629 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
32634 where @var{list-of-files} is a list of ALI and object files. The object
32635 file list must be the exact list of objects corresponding to the non-Ada
32636 sources whose services are to be included in the DLL. The ALI file list
32637 must be the exact list of ALI files for the corresponding Ada sources
32638 whose services are to be included in the DLL. If @var{list-of-files} is
32639 missing, only the static import library is generated.
32642 You may specify any of the following switches to @code{gnatdll}:
32645 @item -a@ovar{address}
32646 @cindex @option{-a} (@code{gnatdll})
32647 Build a non-relocatable DLL at @var{address}. If @var{address} is not
32648 specified the default address @var{0x11000000} will be used. By default,
32649 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
32650 advise the reader to build relocatable DLL.
32652 @item -b @var{address}
32653 @cindex @option{-b} (@code{gnatdll})
32654 Set the relocatable DLL base address. By default the address is
32657 @item -bargs @var{opts}
32658 @cindex @option{-bargs} (@code{gnatdll})
32659 Binder options. Pass @var{opts} to the binder.
32661 @item -d @var{dllfile}
32662 @cindex @option{-d} (@code{gnatdll})
32663 @var{dllfile} is the name of the DLL. This switch must be present for
32664 @code{gnatdll} to do anything. The name of the generated import library is
32665 obtained algorithmically from @var{dllfile} as shown in the following
32666 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
32667 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
32668 by option @option{-e}) is obtained algorithmically from @var{dllfile}
32669 as shown in the following example:
32670 if @var{dllfile} is @code{xyz.dll}, the definition
32671 file used is @code{xyz.def}.
32673 @item -e @var{deffile}
32674 @cindex @option{-e} (@code{gnatdll})
32675 @var{deffile} is the name of the definition file.
32678 @cindex @option{-g} (@code{gnatdll})
32679 Generate debugging information. This information is stored in the object
32680 file and copied from there to the final DLL file by the linker,
32681 where it can be read by the debugger. You must use the
32682 @option{-g} switch if you plan on using the debugger or the symbolic
32686 @cindex @option{-h} (@code{gnatdll})
32687 Help mode. Displays @code{gnatdll} switch usage information.
32690 @cindex @option{-I} (@code{gnatdll})
32691 Direct @code{gnatdll} to search the @var{dir} directory for source and
32692 object files needed to build the DLL.
32693 (@pxref{Search Paths and the Run-Time Library (RTL)}).
32696 @cindex @option{-k} (@code{gnatdll})
32697 Removes the @code{@@}@var{nn} suffix from the import library's exported
32698 names, but keeps them for the link names. You must specify this
32699 option if you want to use a @code{Stdcall} function in a DLL for which
32700 the @code{@@}@var{nn} suffix has been removed. This is the case for most
32701 of the Windows NT DLL for example. This option has no effect when
32702 @option{-n} option is specified.
32704 @item -l @var{file}
32705 @cindex @option{-l} (@code{gnatdll})
32706 The list of ALI and object files used to build the DLL are listed in
32707 @var{file}, instead of being given in the command line. Each line in
32708 @var{file} contains the name of an ALI or object file.
32711 @cindex @option{-n} (@code{gnatdll})
32712 No Import. Do not create the import library.
32715 @cindex @option{-q} (@code{gnatdll})
32716 Quiet mode. Do not display unnecessary messages.
32719 @cindex @option{-v} (@code{gnatdll})
32720 Verbose mode. Display extra information.
32722 @item -largs @var{opts}
32723 @cindex @option{-largs} (@code{gnatdll})
32724 Linker options. Pass @var{opts} to the linker.
32727 @node gnatdll Example
32728 @subsubsection @code{gnatdll} Example
32731 As an example the command to build a relocatable DLL from @file{api.adb}
32732 once @file{api.adb} has been compiled and @file{api.def} created is
32735 $ gnatdll -d api.dll api.ali
32739 The above command creates two files: @file{libapi.dll.a} (the import
32740 library) and @file{api.dll} (the actual DLL). If you want to create
32741 only the DLL, just type:
32744 $ gnatdll -d api.dll -n api.ali
32748 Alternatively if you want to create just the import library, type:
32751 $ gnatdll -d api.dll
32754 @node gnatdll behind the Scenes
32755 @subsubsection @code{gnatdll} behind the Scenes
32758 This section details the steps involved in creating a DLL. @code{gnatdll}
32759 does these steps for you. Unless you are interested in understanding what
32760 goes on behind the scenes, you should skip this section.
32762 We use the previous example of a DLL containing the Ada package @code{API},
32763 to illustrate the steps necessary to build a DLL. The starting point is a
32764 set of objects that will make up the DLL and the corresponding ALI
32765 files. In the case of this example this means that @file{api.o} and
32766 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
32771 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
32772 the information necessary to generate relocation information for the
32778 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
32783 In addition to the base file, the @command{gnatlink} command generates an
32784 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
32785 asks @command{gnatlink} to generate the routines @code{DllMain} and
32786 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
32787 is loaded into memory.
32790 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
32791 export table (@file{api.exp}). The export table contains the relocation
32792 information in a form which can be used during the final link to ensure
32793 that the Windows loader is able to place the DLL anywhere in memory.
32797 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32798 --output-exp api.exp
32803 @code{gnatdll} builds the base file using the new export table. Note that
32804 @command{gnatbind} must be called once again since the binder generated file
32805 has been deleted during the previous call to @command{gnatlink}.
32810 $ gnatlink api -o api.jnk api.exp -mdll
32811 -Wl,--base-file,api.base
32816 @code{gnatdll} builds the new export table using the new base file and
32817 generates the DLL import library @file{libAPI.dll.a}.
32821 $ dlltool --dllname api.dll --def api.def --base-file api.base \
32822 --output-exp api.exp --output-lib libAPI.a
32827 Finally @code{gnatdll} builds the relocatable DLL using the final export
32833 $ gnatlink api api.exp -o api.dll -mdll
32838 @node Using dlltool
32839 @subsubsection Using @code{dlltool}
32842 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
32843 DLLs and static import libraries. This section summarizes the most
32844 common @code{dlltool} switches. The form of the @code{dlltool} command
32848 $ dlltool @ovar{switches}
32852 @code{dlltool} switches include:
32855 @item --base-file @var{basefile}
32856 @cindex @option{--base-file} (@command{dlltool})
32857 Read the base file @var{basefile} generated by the linker. This switch
32858 is used to create a relocatable DLL.
32860 @item --def @var{deffile}
32861 @cindex @option{--def} (@command{dlltool})
32862 Read the definition file.
32864 @item --dllname @var{name}
32865 @cindex @option{--dllname} (@command{dlltool})
32866 Gives the name of the DLL. This switch is used to embed the name of the
32867 DLL in the static import library generated by @code{dlltool} with switch
32868 @option{--output-lib}.
32871 @cindex @option{-k} (@command{dlltool})
32872 Kill @code{@@}@var{nn} from exported names
32873 (@pxref{Windows Calling Conventions}
32874 for a discussion about @code{Stdcall}-style symbols.
32877 @cindex @option{--help} (@command{dlltool})
32878 Prints the @code{dlltool} switches with a concise description.
32880 @item --output-exp @var{exportfile}
32881 @cindex @option{--output-exp} (@command{dlltool})
32882 Generate an export file @var{exportfile}. The export file contains the
32883 export table (list of symbols in the DLL) and is used to create the DLL.
32885 @item --output-lib @var{libfile}
32886 @cindex @option{--output-lib} (@command{dlltool})
32887 Generate a static import library @var{libfile}.
32890 @cindex @option{-v} (@command{dlltool})
32893 @item --as @var{assembler-name}
32894 @cindex @option{--as} (@command{dlltool})
32895 Use @var{assembler-name} as the assembler. The default is @code{as}.
32898 @node GNAT and Windows Resources
32899 @section GNAT and Windows Resources
32900 @cindex Resources, windows
32903 * Building Resources::
32904 * Compiling Resources::
32905 * Using Resources::
32909 Resources are an easy way to add Windows specific objects to your
32910 application. The objects that can be added as resources include:
32939 This section explains how to build, compile and use resources.
32941 @node Building Resources
32942 @subsection Building Resources
32943 @cindex Resources, building
32946 A resource file is an ASCII file. By convention resource files have an
32947 @file{.rc} extension.
32948 The easiest way to build a resource file is to use Microsoft tools
32949 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
32950 @code{dlgedit.exe} to build dialogs.
32951 It is always possible to build an @file{.rc} file yourself by writing a
32954 It is not our objective to explain how to write a resource file. A
32955 complete description of the resource script language can be found in the
32956 Microsoft documentation.
32958 @node Compiling Resources
32959 @subsection Compiling Resources
32962 @cindex Resources, compiling
32965 This section describes how to build a GNAT-compatible (COFF) object file
32966 containing the resources. This is done using the Resource Compiler
32967 @code{windres} as follows:
32970 $ windres -i myres.rc -o myres.o
32974 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
32975 file. You can specify an alternate preprocessor (usually named
32976 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
32977 parameter. A list of all possible options may be obtained by entering
32978 the command @code{windres} @option{--help}.
32980 It is also possible to use the Microsoft resource compiler @code{rc.exe}
32981 to produce a @file{.res} file (binary resource file). See the
32982 corresponding Microsoft documentation for further details. In this case
32983 you need to use @code{windres} to translate the @file{.res} file to a
32984 GNAT-compatible object file as follows:
32987 $ windres -i myres.res -o myres.o
32990 @node Using Resources
32991 @subsection Using Resources
32992 @cindex Resources, using
32995 To include the resource file in your program just add the
32996 GNAT-compatible object file for the resource(s) to the linker
32997 arguments. With @command{gnatmake} this is done by using the @option{-largs}
33001 $ gnatmake myprog -largs myres.o
33004 @node Debugging a DLL
33005 @section Debugging a DLL
33006 @cindex DLL debugging
33009 * Program and DLL Both Built with GCC/GNAT::
33010 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
33014 Debugging a DLL is similar to debugging a standard program. But
33015 we have to deal with two different executable parts: the DLL and the
33016 program that uses it. We have the following four possibilities:
33020 The program and the DLL are built with @code{GCC/GNAT}.
33022 The program is built with foreign tools and the DLL is built with
33025 The program is built with @code{GCC/GNAT} and the DLL is built with
33031 In this section we address only cases one and two above.
33032 There is no point in trying to debug
33033 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
33034 information in it. To do so you must use a debugger compatible with the
33035 tools suite used to build the DLL.
33037 @node Program and DLL Both Built with GCC/GNAT
33038 @subsection Program and DLL Both Built with GCC/GNAT
33041 This is the simplest case. Both the DLL and the program have @code{GDB}
33042 compatible debugging information. It is then possible to break anywhere in
33043 the process. Let's suppose here that the main procedure is named
33044 @code{ada_main} and that in the DLL there is an entry point named
33048 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
33049 program must have been built with the debugging information (see GNAT -g
33050 switch). Here are the step-by-step instructions for debugging it:
33053 @item Launch @code{GDB} on the main program.
33059 @item Start the program and stop at the beginning of the main procedure
33066 This step is required to be able to set a breakpoint inside the DLL. As long
33067 as the program is not run, the DLL is not loaded. This has the
33068 consequence that the DLL debugging information is also not loaded, so it is not
33069 possible to set a breakpoint in the DLL.
33071 @item Set a breakpoint inside the DLL
33074 (gdb) break ada_dll
33081 At this stage a breakpoint is set inside the DLL. From there on
33082 you can use the standard approach to debug the whole program
33083 (@pxref{Running and Debugging Ada Programs}).
33086 @c This used to work, probably because the DLLs were non-relocatable
33087 @c keep this section around until the problem is sorted out.
33089 To break on the @code{DllMain} routine it is not possible to follow
33090 the procedure above. At the time the program stop on @code{ada_main}
33091 the @code{DllMain} routine as already been called. Either you can use
33092 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
33095 @item Launch @code{GDB} on the main program.
33101 @item Load DLL symbols
33104 (gdb) add-sym api.dll
33107 @item Set a breakpoint inside the DLL
33110 (gdb) break ada_dll.adb:45
33113 Note that at this point it is not possible to break using the routine symbol
33114 directly as the program is not yet running. The solution is to break
33115 on the proper line (break in @file{ada_dll.adb} line 45).
33117 @item Start the program
33126 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
33127 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
33130 * Debugging the DLL Directly::
33131 * Attaching to a Running Process::
33135 In this case things are slightly more complex because it is not possible to
33136 start the main program and then break at the beginning to load the DLL and the
33137 associated DLL debugging information. It is not possible to break at the
33138 beginning of the program because there is no @code{GDB} debugging information,
33139 and therefore there is no direct way of getting initial control. This
33140 section addresses this issue by describing some methods that can be used
33141 to break somewhere in the DLL to debug it.
33144 First suppose that the main procedure is named @code{main} (this is for
33145 example some C code built with Microsoft Visual C) and that there is a
33146 DLL named @code{test.dll} containing an Ada entry point named
33150 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
33151 been built with debugging information (see GNAT -g option).
33153 @node Debugging the DLL Directly
33154 @subsubsection Debugging the DLL Directly
33158 Find out the executable starting address
33161 $ objdump --file-header main.exe
33164 The starting address is reported on the last line. For example:
33167 main.exe: file format pei-i386
33168 architecture: i386, flags 0x0000010a:
33169 EXEC_P, HAS_DEBUG, D_PAGED
33170 start address 0x00401010
33174 Launch the debugger on the executable.
33181 Set a breakpoint at the starting address, and launch the program.
33184 $ (gdb) break *0x00401010
33188 The program will stop at the given address.
33191 Set a breakpoint on a DLL subroutine.
33194 (gdb) break ada_dll.adb:45
33197 Or if you want to break using a symbol on the DLL, you need first to
33198 select the Ada language (language used by the DLL).
33201 (gdb) set language ada
33202 (gdb) break ada_dll
33206 Continue the program.
33213 This will run the program until it reaches the breakpoint that has been
33214 set. From that point you can use the standard way to debug a program
33215 as described in (@pxref{Running and Debugging Ada Programs}).
33220 It is also possible to debug the DLL by attaching to a running process.
33222 @node Attaching to a Running Process
33223 @subsubsection Attaching to a Running Process
33224 @cindex DLL debugging, attach to process
33227 With @code{GDB} it is always possible to debug a running process by
33228 attaching to it. It is possible to debug a DLL this way. The limitation
33229 of this approach is that the DLL must run long enough to perform the
33230 attach operation. It may be useful for instance to insert a time wasting
33231 loop in the code of the DLL to meet this criterion.
33235 @item Launch the main program @file{main.exe}.
33241 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
33242 that the process PID for @file{main.exe} is 208.
33250 @item Attach to the running process to be debugged.
33256 @item Load the process debugging information.
33259 (gdb) symbol-file main.exe
33262 @item Break somewhere in the DLL.
33265 (gdb) break ada_dll
33268 @item Continue process execution.
33277 This last step will resume the process execution, and stop at
33278 the breakpoint we have set. From there you can use the standard
33279 approach to debug a program as described in
33280 (@pxref{Running and Debugging Ada Programs}).
33282 @node Setting Stack Size from gnatlink
33283 @section Setting Stack Size from @command{gnatlink}
33286 It is possible to specify the program stack size at link time. On modern
33287 versions of Windows, starting with XP, this is mostly useful to set the size of
33288 the main stack (environment task). The other task stacks are set with pragma
33289 Storage_Size or with the @command{gnatbind -d} command.
33291 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
33292 reserve size of individual tasks, the link-time stack size applies to all
33293 tasks, and pragma Storage_Size has no effect.
33294 In particular, Stack Overflow checks are made against this
33295 link-time specified size.
33297 This setting can be done with
33298 @command{gnatlink} using either:
33302 @item using @option{-Xlinker} linker option
33305 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
33308 This sets the stack reserve size to 0x10000 bytes and the stack commit
33309 size to 0x1000 bytes.
33311 @item using @option{-Wl} linker option
33314 $ gnatlink hello -Wl,--stack=0x1000000
33317 This sets the stack reserve size to 0x1000000 bytes. Note that with
33318 @option{-Wl} option it is not possible to set the stack commit size
33319 because the coma is a separator for this option.
33323 @node Setting Heap Size from gnatlink
33324 @section Setting Heap Size from @command{gnatlink}
33327 Under Windows systems, it is possible to specify the program heap size from
33328 @command{gnatlink} using either:
33332 @item using @option{-Xlinker} linker option
33335 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
33338 This sets the heap reserve size to 0x10000 bytes and the heap commit
33339 size to 0x1000 bytes.
33341 @item using @option{-Wl} linker option
33344 $ gnatlink hello -Wl,--heap=0x1000000
33347 This sets the heap reserve size to 0x1000000 bytes. Note that with
33348 @option{-Wl} option it is not possible to set the heap commit size
33349 because the coma is a separator for this option.
33355 @c **********************************
33356 @c * GNU Free Documentation License *
33357 @c **********************************
33359 @c GNU Free Documentation License
33361 @node Index,,GNU Free Documentation License, Top
33367 @c Put table of contents at end, otherwise it precedes the "title page" in
33368 @c the .txt version
33369 @c Edit the pdf file to move the contents to the beginning, after the title