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{-gnateS} (@command{gcc})
4162 Generate SCO (Source Coverage Obligation) information in the ALI
4163 file. This information is used by advanced coverage tools. See
4164 unit @file{SCOs} in the compiler sources for details in files
4165 @file{scos.ads} and @file{scos.adb}.
4168 @cindex @option{-gnatE} (@command{gcc})
4169 Full dynamic elaboration checks.
4172 @cindex @option{-gnatf} (@command{gcc})
4173 Full errors. Multiple errors per line, all undefined references, do not
4174 attempt to suppress cascaded errors.
4177 @cindex @option{-gnatF} (@command{gcc})
4178 Externals names are folded to all uppercase.
4180 @item ^-gnatg^/GNAT_INTERNAL^
4181 @cindex @option{^-gnatg^/GNAT_INTERNAL^} (@command{gcc})
4182 Internal GNAT implementation mode. This should not be used for
4183 applications programs, it is intended only for use by the compiler
4184 and its run-time library. For documentation, see the GNAT sources.
4185 Note that @option{^-gnatg^/GNAT_INTERNAL^} implies
4186 @option{^-gnatwae^/WARNINGS=ALL,ERRORS^} and
4187 @option{^-gnatyg^/STYLE_CHECKS=GNAT^}
4188 so that all standard warnings and all standard style options are turned on.
4189 All warnings and style error messages are treated as errors.
4193 @cindex @option{-gnatG[nn]} (@command{gcc})
4196 @item /EXPAND_SOURCE, /LEXPAND_SOURCE=nnn
4198 List generated expanded code in source form.
4200 @item ^-gnath^/HELP^
4201 @cindex @option{^-gnath^/HELP^} (@command{gcc})
4202 Output usage information. The output is written to @file{stdout}.
4204 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
4205 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
4206 Identifier character set
4208 (@var{c}=1/2/3/4/8/9/p/f/n/w).
4210 For details of the possible selections for @var{c},
4211 see @ref{Character Set Control}.
4213 @item ^-gnatI^/IGNORE_REP_CLAUSES^
4214 @cindex @option{^-gnatI^IGNORE_REP_CLAUSES^} (@command{gcc})
4215 Ignore representation clauses. When this switch is used,
4216 representation clauses are treated as comments. This is useful
4217 when initially porting code where you want to ignore rep clause
4218 problems, and also for compiling foreign code (particularly
4219 for use with ASIS). The representation clauses that are ignored
4220 are: enumeration_representation_clause, record_representation_clause,
4221 and attribute_definition_clause for the following attributes:
4222 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
4223 Object_Size, Size, Small, Stream_Size, and Value_Size.
4224 Note that this option should be used only for compiling -- the
4225 code is likely to malfunction at run time.
4228 @cindex @option{-gnatjnn} (@command{gcc})
4229 Reformat error messages to fit on nn character lines
4231 @item -gnatk=@var{n}
4232 @cindex @option{-gnatk} (@command{gcc})
4233 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
4236 @cindex @option{-gnatl} (@command{gcc})
4237 Output full source listing with embedded error messages.
4240 @cindex @option{-gnatL} (@command{gcc})
4241 Used in conjunction with -gnatG or -gnatD to intersperse original
4242 source lines (as comment lines with line numbers) in the expanded
4245 @item -gnatm=@var{n}
4246 @cindex @option{-gnatm} (@command{gcc})
4247 Limit number of detected error or warning messages to @var{n}
4248 where @var{n} is in the range 1..999999. The default setting if
4249 no switch is given is 9999. If the number of warnings reaches this
4250 limit, then a message is output and further warnings are suppressed,
4251 but the compilation is continued. If the number of error messages
4252 reaches this limit, then a message is output and the compilation
4253 is abandoned. The equal sign here is optional. A value of zero
4254 means that no limit applies.
4257 @cindex @option{-gnatn} (@command{gcc})
4258 Activate inlining for subprograms for which
4259 pragma @code{inline} is specified. This inlining is performed
4260 by the GCC back-end.
4263 @cindex @option{-gnatN} (@command{gcc})
4264 Activate front end inlining for subprograms for which
4265 pragma @code{Inline} is specified. This inlining is performed
4266 by the front end and will be visible in the
4267 @option{-gnatG} output.
4269 When using a gcc-based back end (in practice this means using any version
4270 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
4271 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
4272 Historically front end inlining was more extensive than the gcc back end
4273 inlining, but that is no longer the case.
4276 @cindex @option{-gnato} (@command{gcc})
4277 Enable numeric overflow checking (which is not normally enabled by
4278 default). Note that division by zero is a separate check that is not
4279 controlled by this switch (division by zero checking is on by default).
4282 @cindex @option{-gnatp} (@command{gcc})
4283 Suppress all checks. See @ref{Run-Time Checks} for details.
4286 @cindex @option{-gnatP} (@command{gcc})
4287 Enable polling. This is required on some systems (notably Windows NT) to
4288 obtain asynchronous abort and asynchronous transfer of control capability.
4289 @xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full
4293 @cindex @option{-gnatq} (@command{gcc})
4294 Don't quit. Try semantics, even if parse errors.
4297 @cindex @option{-gnatQ} (@command{gcc})
4298 Don't quit. Generate @file{ALI} and tree files even if illegalities.
4301 @cindex @option{-gnatr} (@command{gcc})
4302 Treat pragma Restrictions as Restriction_Warnings.
4304 @item ^-gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]}^/REPRESENTATION_INFO^
4305 @cindex @option{-gnatR} (@command{gcc})
4306 Output representation information for declared types and objects.
4309 @cindex @option{-gnats} (@command{gcc})
4313 @cindex @option{-gnatS} (@command{gcc})
4314 Print package Standard.
4317 @cindex @option{-gnatt} (@command{gcc})
4318 Generate tree output file.
4320 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
4321 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@command{gcc})
4322 All compiler tables start at @var{nnn} times usual starting size.
4325 @cindex @option{-gnatu} (@command{gcc})
4326 List units for this compilation.
4329 @cindex @option{-gnatU} (@command{gcc})
4330 Tag all error messages with the unique string ``error:''
4333 @cindex @option{-gnatv} (@command{gcc})
4334 Verbose mode. Full error output with source lines to @file{stdout}.
4337 @cindex @option{-gnatV} (@command{gcc})
4338 Control level of validity checking (@pxref{Validity Checking}).
4340 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}@r{[},@dots{}@r{]})^
4341 @cindex @option{^-gnatw^/WARNINGS^} (@command{gcc})
4343 ^@var{xxx} is a string of option letters that^the list of options^ denotes
4344 the exact warnings that
4345 are enabled or disabled (@pxref{Warning Message Control}).
4347 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
4348 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
4349 Wide character encoding method
4351 (@var{e}=n/h/u/s/e/8).
4354 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
4358 @cindex @option{-gnatx} (@command{gcc})
4359 Suppress generation of cross-reference information.
4361 @item ^-gnaty^/STYLE_CHECKS=(option,option@dots{})^
4362 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@command{gcc})
4363 Enable built-in style checks (@pxref{Style Checking}).
4365 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
4366 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@command{gcc})
4367 Distribution stub generation and compilation
4369 (@var{m}=r/c for receiver/caller stubs).
4372 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
4373 to be generated and compiled).
4376 @item ^-I^/SEARCH=^@var{dir}
4377 @cindex @option{^-I^/SEARCH^} (@command{gcc})
4379 Direct GNAT to search the @var{dir} directory for source files needed by
4380 the current compilation
4381 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4383 @item ^-I-^/NOCURRENT_DIRECTORY^
4384 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gcc})
4386 Except for the source file named in the command line, do not look for source
4387 files in the directory containing the source file named in the command line
4388 (@pxref{Search Paths and the Run-Time Library (RTL)}).
4392 @cindex @option{-mbig-switch} (@command{gcc})
4393 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
4394 This standard gcc switch causes the compiler to use larger offsets in its
4395 jump table representation for @code{case} statements.
4396 This may result in less efficient code, but is sometimes necessary
4397 (for example on HP-UX targets)
4398 @cindex HP-UX and @option{-mbig-switch} option
4399 in order to compile large and/or nested @code{case} statements.
4402 @cindex @option{-o} (@command{gcc})
4403 This switch is used in @command{gcc} to redirect the generated object file
4404 and its associated ALI file. Beware of this switch with GNAT, because it may
4405 cause the object file and ALI file to have different names which in turn
4406 may confuse the binder and the linker.
4410 @cindex @option{-nostdinc} (@command{gcc})
4411 Inhibit the search of the default location for the GNAT Run Time
4412 Library (RTL) source files.
4415 @cindex @option{-nostdlib} (@command{gcc})
4416 Inhibit the search of the default location for the GNAT Run Time
4417 Library (RTL) ALI files.
4421 @cindex @option{-O} (@command{gcc})
4422 @var{n} controls the optimization level.
4426 No optimization, the default setting if no @option{-O} appears
4429 Normal optimization, the default if you specify @option{-O} without
4430 an operand. A good compromise between code quality and compilation
4434 Extensive optimization, may improve execution time, possibly at the cost of
4435 substantially increased compilation time.
4438 Same as @option{-O2}, and also includes inline expansion for small subprograms
4442 Optimize space usage
4446 See also @ref{Optimization Levels}.
4451 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4452 Equivalent to @option{/OPTIMIZE=NONE}.
4453 This is the default behavior in the absence of an @option{/OPTIMIZE}
4456 @item /OPTIMIZE@r{[}=(keyword@r{[},@dots{}@r{]})@r{]}
4457 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4458 Selects the level of optimization for your program. The supported
4459 keywords are as follows:
4462 Perform most optimizations, including those that
4464 This is the default if the @option{/OPTIMIZE} qualifier is supplied
4465 without keyword options.
4468 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4471 Perform some optimizations, but omit ones that are costly.
4474 Same as @code{SOME}.
4477 Full optimization as in @option{/OPTIMIZE=ALL}, and also attempts
4478 automatic inlining of small subprograms within a unit
4481 Try to unroll loops. This keyword may be specified together with
4482 any keyword above other than @code{NONE}. Loop unrolling
4483 usually, but not always, improves the performance of programs.
4486 Optimize space usage
4490 See also @ref{Optimization Levels}.
4494 @item -pass-exit-codes
4495 @cindex @option{-pass-exit-codes} (@command{gcc})
4496 Catch exit codes from the compiler and use the most meaningful as
4500 @item --RTS=@var{rts-path}
4501 @cindex @option{--RTS} (@command{gcc})
4502 Specifies the default location of the runtime library. Same meaning as the
4503 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
4506 @cindex @option{^-S^/ASM^} (@command{gcc})
4507 ^Used in place of @option{-c} to^Used to^
4508 cause the assembler source file to be
4509 generated, using @file{^.s^.S^} as the extension,
4510 instead of the object file.
4511 This may be useful if you need to examine the generated assembly code.
4513 @item ^-fverbose-asm^/VERBOSE_ASM^
4514 @cindex @option{^-fverbose-asm^/VERBOSE_ASM^} (@command{gcc})
4515 ^Used in conjunction with @option{-S}^Used in place of @option{/ASM}^
4516 to cause the generated assembly code file to be annotated with variable
4517 names, making it significantly easier to follow.
4520 @cindex @option{^-v^/VERBOSE^} (@command{gcc})
4521 Show commands generated by the @command{gcc} driver. Normally used only for
4522 debugging purposes or if you need to be sure what version of the
4523 compiler you are executing.
4527 @cindex @option{-V} (@command{gcc})
4528 Execute @var{ver} version of the compiler. This is the @command{gcc}
4529 version, not the GNAT version.
4532 @item ^-w^/NO_BACK_END_WARNINGS^
4533 @cindex @option{-w} (@command{gcc})
4534 Turn off warnings generated by the back end of the compiler. Use of
4535 this switch also causes the default for front end warnings to be set
4536 to suppress (as though @option{-gnatws} had appeared at the start of
4542 @c Combining qualifiers does not work on VMS
4543 You may combine a sequence of GNAT switches into a single switch. For
4544 example, the combined switch
4546 @cindex Combining GNAT switches
4552 is equivalent to specifying the following sequence of switches:
4555 -gnato -gnatf -gnati3
4560 The following restrictions apply to the combination of switches
4565 The switch @option{-gnatc} if combined with other switches must come
4566 first in the string.
4569 The switch @option{-gnats} if combined with other switches must come
4570 first in the string.
4574 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4575 may not be combined with any other switches.
4579 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4580 switch), then all further characters in the switch are interpreted
4581 as style modifiers (see description of @option{-gnaty}).
4584 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4585 switch), then all further characters in the switch are interpreted
4586 as debug flags (see description of @option{-gnatd}).
4589 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4590 switch), then all further characters in the switch are interpreted
4591 as warning mode modifiers (see description of @option{-gnatw}).
4594 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4595 switch), then all further characters in the switch are interpreted
4596 as validity checking options (@pxref{Validity Checking}).
4600 @node Output and Error Message Control
4601 @subsection Output and Error Message Control
4605 The standard default format for error messages is called ``brief format''.
4606 Brief format messages are written to @file{stderr} (the standard error
4607 file) and have the following form:
4610 e.adb:3:04: Incorrect spelling of keyword "function"
4611 e.adb:4:20: ";" should be "is"
4615 The first integer after the file name is the line number in the file,
4616 and the second integer is the column number within the line.
4618 @code{GPS} can parse the error messages
4619 and point to the referenced character.
4621 The following switches provide control over the error message
4627 @cindex @option{-gnatv} (@command{gcc})
4630 The v stands for verbose.
4632 The effect of this setting is to write long-format error
4633 messages to @file{stdout} (the standard output file.
4634 The same program compiled with the
4635 @option{-gnatv} switch would generate:
4639 3. funcion X (Q : Integer)
4641 >>> Incorrect spelling of keyword "function"
4644 >>> ";" should be "is"
4649 The vertical bar indicates the location of the error, and the @samp{>>>}
4650 prefix can be used to search for error messages. When this switch is
4651 used the only source lines output are those with errors.
4654 @cindex @option{-gnatl} (@command{gcc})
4656 The @code{l} stands for list.
4658 This switch causes a full listing of
4659 the file to be generated. In the case where a body is
4660 compiled, the corresponding spec is also listed, along
4661 with any subunits. Typical output from compiling a package
4662 body @file{p.adb} might look like:
4664 @smallexample @c ada
4668 1. package body p is
4670 3. procedure a is separate;
4681 2. pragma Elaborate_Body
4705 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4706 standard output is redirected, a brief summary is written to
4707 @file{stderr} (standard error) giving the number of error messages and
4708 warning messages generated.
4710 @item -^gnatl^OUTPUT_FILE^=file
4711 @cindex @option{^-gnatl^OUTPUT_FILE^=fname} (@command{gcc})
4712 This has the same effect as @option{-gnatl} except that the output is
4713 written to a file instead of to standard output. If the given name
4714 @file{fname} does not start with a period, then it is the full name
4715 of the file to be written. If @file{fname} is an extension, it is
4716 appended to the name of the file being compiled. For example, if
4717 file @file{xyz.adb} is compiled with @option{^-gnatl^OUTPUT_FILE^=.lst},
4718 then the output is written to file ^xyz.adb.lst^xyz.adb_lst^.
4721 @cindex @option{-gnatU} (@command{gcc})
4722 This switch forces all error messages to be preceded by the unique
4723 string ``error:''. This means that error messages take a few more
4724 characters in space, but allows easy searching for and identification
4728 @cindex @option{-gnatb} (@command{gcc})
4730 The @code{b} stands for brief.
4732 This switch causes GNAT to generate the
4733 brief format error messages to @file{stderr} (the standard error
4734 file) as well as the verbose
4735 format message or full listing (which as usual is written to
4736 @file{stdout} (the standard output file).
4738 @item -gnatm=@var{n}
4739 @cindex @option{-gnatm} (@command{gcc})
4741 The @code{m} stands for maximum.
4743 @var{n} is a decimal integer in the
4744 range of 1 to 999999 and limits the number of error or warning
4745 messages to be generated. For example, using
4746 @option{-gnatm2} might yield
4749 e.adb:3:04: Incorrect spelling of keyword "function"
4750 e.adb:5:35: missing ".."
4751 fatal error: maximum number of errors detected
4752 compilation abandoned
4756 The default setting if
4757 no switch is given is 9999. If the number of warnings reaches this
4758 limit, then a message is output and further warnings are suppressed,
4759 but the compilation is continued. If the number of error messages
4760 reaches this limit, then a message is output and the compilation
4761 is abandoned. A value of zero means that no limit applies.
4764 Note that the equal sign is optional, so the switches
4765 @option{-gnatm2} and @option{-gnatm=2} are equivalent.
4768 @cindex @option{-gnatf} (@command{gcc})
4769 @cindex Error messages, suppressing
4771 The @code{f} stands for full.
4773 Normally, the compiler suppresses error messages that are likely to be
4774 redundant. This switch causes all error
4775 messages to be generated. In particular, in the case of
4776 references to undefined variables. If a given variable is referenced
4777 several times, the normal format of messages is
4779 e.adb:7:07: "V" is undefined (more references follow)
4783 where the parenthetical comment warns that there are additional
4784 references to the variable @code{V}. Compiling the same program with the
4785 @option{-gnatf} switch yields
4788 e.adb:7:07: "V" is undefined
4789 e.adb:8:07: "V" is undefined
4790 e.adb:8:12: "V" is undefined
4791 e.adb:8:16: "V" is undefined
4792 e.adb:9:07: "V" is undefined
4793 e.adb:9:12: "V" is undefined
4797 The @option{-gnatf} switch also generates additional information for
4798 some error messages. Some examples are:
4802 Details on possibly non-portable unchecked conversion
4804 List possible interpretations for ambiguous calls
4806 Additional details on incorrect parameters
4810 @cindex @option{-gnatjnn} (@command{gcc})
4811 In normal operation mode (or if @option{-gnatj0} is used, then error messages
4812 with continuation lines are treated as though the continuation lines were
4813 separate messages (and so a warning with two continuation lines counts as
4814 three warnings, and is listed as three separate messages).
4816 If the @option{-gnatjnn} switch is used with a positive value for nn, then
4817 messages are output in a different manner. A message and all its continuation
4818 lines are treated as a unit, and count as only one warning or message in the
4819 statistics totals. Furthermore, the message is reformatted so that no line
4820 is longer than nn characters.
4823 @cindex @option{-gnatq} (@command{gcc})
4825 The @code{q} stands for quit (really ``don't quit'').
4827 In normal operation mode, the compiler first parses the program and
4828 determines if there are any syntax errors. If there are, appropriate
4829 error messages are generated and compilation is immediately terminated.
4831 GNAT to continue with semantic analysis even if syntax errors have been
4832 found. This may enable the detection of more errors in a single run. On
4833 the other hand, the semantic analyzer is more likely to encounter some
4834 internal fatal error when given a syntactically invalid tree.
4837 @cindex @option{-gnatQ} (@command{gcc})
4838 In normal operation mode, the @file{ALI} file is not generated if any
4839 illegalities are detected in the program. The use of @option{-gnatQ} forces
4840 generation of the @file{ALI} file. This file is marked as being in
4841 error, so it cannot be used for binding purposes, but it does contain
4842 reasonably complete cross-reference information, and thus may be useful
4843 for use by tools (e.g., semantic browsing tools or integrated development
4844 environments) that are driven from the @file{ALI} file. This switch
4845 implies @option{-gnatq}, since the semantic phase must be run to get a
4846 meaningful ALI file.
4848 In addition, if @option{-gnatt} is also specified, then the tree file is
4849 generated even if there are illegalities. It may be useful in this case
4850 to also specify @option{-gnatq} to ensure that full semantic processing
4851 occurs. The resulting tree file can be processed by ASIS, for the purpose
4852 of providing partial information about illegal units, but if the error
4853 causes the tree to be badly malformed, then ASIS may crash during the
4856 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4857 being in error, @command{gnatmake} will attempt to recompile the source when it
4858 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4860 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4861 since ALI files are never generated if @option{-gnats} is set.
4865 @node Warning Message Control
4866 @subsection Warning Message Control
4867 @cindex Warning messages
4869 In addition to error messages, which correspond to illegalities as defined
4870 in the Ada Reference Manual, the compiler detects two kinds of warning
4873 First, the compiler considers some constructs suspicious and generates a
4874 warning message to alert you to a possible error. Second, if the
4875 compiler detects a situation that is sure to raise an exception at
4876 run time, it generates a warning message. The following shows an example
4877 of warning messages:
4879 e.adb:4:24: warning: creation of object may raise Storage_Error
4880 e.adb:10:17: warning: static value out of range
4881 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4885 GNAT considers a large number of situations as appropriate
4886 for the generation of warning messages. As always, warnings are not
4887 definite indications of errors. For example, if you do an out-of-range
4888 assignment with the deliberate intention of raising a
4889 @code{Constraint_Error} exception, then the warning that may be
4890 issued does not indicate an error. Some of the situations for which GNAT
4891 issues warnings (at least some of the time) are given in the following
4892 list. This list is not complete, and new warnings are often added to
4893 subsequent versions of GNAT. The list is intended to give a general idea
4894 of the kinds of warnings that are generated.
4898 Possible infinitely recursive calls
4901 Out-of-range values being assigned
4904 Possible order of elaboration problems
4907 Assertions (pragma Assert) that are sure to fail
4913 Address clauses with possibly unaligned values, or where an attempt is
4914 made to overlay a smaller variable with a larger one.
4917 Fixed-point type declarations with a null range
4920 Direct_IO or Sequential_IO instantiated with a type that has access values
4923 Variables that are never assigned a value
4926 Variables that are referenced before being initialized
4929 Task entries with no corresponding @code{accept} statement
4932 Duplicate accepts for the same task entry in a @code{select}
4935 Objects that take too much storage
4938 Unchecked conversion between types of differing sizes
4941 Missing @code{return} statement along some execution path in a function
4944 Incorrect (unrecognized) pragmas
4947 Incorrect external names
4950 Allocation from empty storage pool
4953 Potentially blocking operation in protected type
4956 Suspicious parenthesization of expressions
4959 Mismatching bounds in an aggregate
4962 Attempt to return local value by reference
4965 Premature instantiation of a generic body
4968 Attempt to pack aliased components
4971 Out of bounds array subscripts
4974 Wrong length on string assignment
4977 Violations of style rules if style checking is enabled
4980 Unused @code{with} clauses
4983 @code{Bit_Order} usage that does not have any effect
4986 @code{Standard.Duration} used to resolve universal fixed expression
4989 Dereference of possibly null value
4992 Declaration that is likely to cause storage error
4995 Internal GNAT unit @code{with}'ed by application unit
4998 Values known to be out of range at compile time
5001 Unreferenced labels and variables
5004 Address overlays that could clobber memory
5007 Unexpected initialization when address clause present
5010 Bad alignment for address clause
5013 Useless type conversions
5016 Redundant assignment statements and other redundant constructs
5019 Useless exception handlers
5022 Accidental hiding of name by child unit
5025 Access before elaboration detected at compile time
5028 A range in a @code{for} loop that is known to be null or might be null
5033 The following section lists compiler switches that are available
5034 to control the handling of warning messages. It is also possible
5035 to exercise much finer control over what warnings are issued and
5036 suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,,
5037 gnat_rm, GNAT Reference manual}.
5042 @emph{Activate all optional errors.}
5043 @cindex @option{-gnatwa} (@command{gcc})
5044 This switch activates most optional warning messages, see remaining list
5045 in this section for details on optional warning messages that can be
5046 individually controlled. The warnings that are not turned on by this
5048 @option{-gnatwd} (implicit dereferencing),
5049 @option{-gnatwh} (hiding),
5050 @option{-gnatwl} (elaboration warnings),
5051 @option{-gnatw.o} (warn on values set by out parameters ignored)
5052 and @option{-gnatwt} (tracking of deleted conditional code).
5053 All other optional warnings are turned on.
5056 @emph{Suppress all optional errors.}
5057 @cindex @option{-gnatwA} (@command{gcc})
5058 This switch suppresses all optional warning messages, see remaining list
5059 in this section for details on optional warning messages that can be
5060 individually controlled.
5063 @emph{Activate warnings on failing assertions.}
5064 @cindex @option{-gnatw.a} (@command{gcc})
5065 @cindex Assert failures
5066 This switch activates warnings for assertions where the compiler can tell at
5067 compile time that the assertion will fail. Note that this warning is given
5068 even if assertions are disabled. The default is that such warnings are
5072 @emph{Suppress warnings on failing assertions.}
5073 @cindex @option{-gnatw.A} (@command{gcc})
5074 @cindex Assert failures
5075 This switch suppresses warnings for assertions where the compiler can tell at
5076 compile time that the assertion will fail.
5079 @emph{Activate warnings on bad fixed values.}
5080 @cindex @option{-gnatwb} (@command{gcc})
5081 @cindex Bad fixed values
5082 @cindex Fixed-point Small value
5084 This switch activates warnings for static fixed-point expressions whose
5085 value is not an exact multiple of Small. Such values are implementation
5086 dependent, since an implementation is free to choose either of the multiples
5087 that surround the value. GNAT always chooses the closer one, but this is not
5088 required behavior, and it is better to specify a value that is an exact
5089 multiple, ensuring predictable execution. The default is that such warnings
5093 @emph{Suppress warnings on bad fixed values.}
5094 @cindex @option{-gnatwB} (@command{gcc})
5095 This switch suppresses warnings for static fixed-point expressions whose
5096 value is not an exact multiple of Small.
5099 @emph{Activate warnings on biased representation.}
5100 @cindex @option{-gnatw.b} (@command{gcc})
5101 @cindex Biased representation
5102 This switch activates warnings when a size clause, value size clause, component
5103 clause, or component size clause forces the use of biased representation for an
5104 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
5105 to represent 10/11). The default is that such warnings are generated.
5108 @emph{Suppress warnings on biased representation.}
5109 @cindex @option{-gnatwB} (@command{gcc})
5110 This switch suppresses warnings for representation clauses that force the use
5111 of biased representation.
5114 @emph{Activate warnings on conditionals.}
5115 @cindex @option{-gnatwc} (@command{gcc})
5116 @cindex Conditionals, constant
5117 This switch activates warnings for conditional expressions used in
5118 tests that are known to be True or False at compile time. The default
5119 is that such warnings are not generated.
5120 Note that this warning does
5121 not get issued for the use of boolean variables or constants whose
5122 values are known at compile time, since this is a standard technique
5123 for conditional compilation in Ada, and this would generate too many
5124 false positive warnings.
5126 This warning option also activates a special test for comparisons using
5127 the operators ``>='' and`` <=''.
5128 If the compiler can tell that only the equality condition is possible,
5129 then it will warn that the ``>'' or ``<'' part of the test
5130 is useless and that the operator could be replaced by ``=''.
5131 An example would be comparing a @code{Natural} variable <= 0.
5133 This warning option also generates warnings if
5134 one or both tests is optimized away in a membership test for integer
5135 values if the result can be determined at compile time. Range tests on
5136 enumeration types are not included, since it is common for such tests
5137 to include an end point.
5139 This warning can also be turned on using @option{-gnatwa}.
5142 @emph{Suppress warnings on conditionals.}
5143 @cindex @option{-gnatwC} (@command{gcc})
5144 This switch suppresses warnings for conditional expressions used in
5145 tests that are known to be True or False at compile time.
5148 @emph{Activate warnings on missing component clauses.}
5149 @cindex @option{-gnatw.c} (@command{gcc})
5150 @cindex Component clause, missing
5151 This switch activates warnings for record components where a record
5152 representation clause is present and has component clauses for the
5153 majority, but not all, of the components. A warning is given for each
5154 component for which no component clause is present.
5156 This warning can also be turned on using @option{-gnatwa}.
5159 @emph{Suppress warnings on missing component clauses.}
5160 @cindex @option{-gnatwC} (@command{gcc})
5161 This switch suppresses warnings for record components that are
5162 missing a component clause in the situation described above.
5165 @emph{Activate warnings on implicit dereferencing.}
5166 @cindex @option{-gnatwd} (@command{gcc})
5167 If this switch is set, then the use of a prefix of an access type
5168 in an indexed component, slice, or selected component without an
5169 explicit @code{.all} will generate a warning. With this warning
5170 enabled, access checks occur only at points where an explicit
5171 @code{.all} appears in the source code (assuming no warnings are
5172 generated as a result of this switch). The default is that such
5173 warnings are not generated.
5174 Note that @option{-gnatwa} does not affect the setting of
5175 this warning option.
5178 @emph{Suppress warnings on implicit dereferencing.}
5179 @cindex @option{-gnatwD} (@command{gcc})
5180 @cindex Implicit dereferencing
5181 @cindex Dereferencing, implicit
5182 This switch suppresses warnings for implicit dereferences in
5183 indexed components, slices, and selected components.
5186 @emph{Treat warnings as errors.}
5187 @cindex @option{-gnatwe} (@command{gcc})
5188 @cindex Warnings, treat as error
5189 This switch causes warning messages to be treated as errors.
5190 The warning string still appears, but the warning messages are counted
5191 as errors, and prevent the generation of an object file.
5194 @emph{Activate every optional warning}
5195 @cindex @option{-gnatw.e} (@command{gcc})
5196 @cindex Warnings, activate every optional warning
5197 This switch activates all optional warnings, including those which
5198 are not activated by @code{-gnatwa}.
5201 @emph{Activate warnings on unreferenced formals.}
5202 @cindex @option{-gnatwf} (@command{gcc})
5203 @cindex Formals, unreferenced
5204 This switch causes a warning to be generated if a formal parameter
5205 is not referenced in the body of the subprogram. This warning can
5206 also be turned on using @option{-gnatwa} or @option{-gnatwu}. The
5207 default is that these warnings are not generated.
5210 @emph{Suppress warnings on unreferenced formals.}
5211 @cindex @option{-gnatwF} (@command{gcc})
5212 This switch suppresses warnings for unreferenced formal
5213 parameters. Note that the
5214 combination @option{-gnatwu} followed by @option{-gnatwF} has the
5215 effect of warning on unreferenced entities other than subprogram
5219 @emph{Activate warnings on unrecognized pragmas.}
5220 @cindex @option{-gnatwg} (@command{gcc})
5221 @cindex Pragmas, unrecognized
5222 This switch causes a warning to be generated if an unrecognized
5223 pragma is encountered. Apart from issuing this warning, the
5224 pragma is ignored and has no effect. This warning can
5225 also be turned on using @option{-gnatwa}. The default
5226 is that such warnings are issued (satisfying the Ada Reference
5227 Manual requirement that such warnings appear).
5230 @emph{Suppress warnings on unrecognized pragmas.}
5231 @cindex @option{-gnatwG} (@command{gcc})
5232 This switch suppresses warnings for unrecognized pragmas.
5235 @emph{Activate warnings on hiding.}
5236 @cindex @option{-gnatwh} (@command{gcc})
5237 @cindex Hiding of Declarations
5238 This switch activates warnings on hiding declarations.
5239 A declaration is considered hiding
5240 if it is for a non-overloadable entity, and it declares an entity with the
5241 same name as some other entity that is directly or use-visible. The default
5242 is that such warnings are not generated.
5243 Note that @option{-gnatwa} does not affect the setting of this warning option.
5246 @emph{Suppress warnings on hiding.}
5247 @cindex @option{-gnatwH} (@command{gcc})
5248 This switch suppresses warnings on hiding declarations.
5251 @emph{Activate warnings on implementation units.}
5252 @cindex @option{-gnatwi} (@command{gcc})
5253 This switch activates warnings for a @code{with} of an internal GNAT
5254 implementation unit, defined as any unit from the @code{Ada},
5255 @code{Interfaces}, @code{GNAT},
5256 ^^@code{DEC},^ or @code{System}
5257 hierarchies that is not
5258 documented in either the Ada Reference Manual or the GNAT
5259 Programmer's Reference Manual. Such units are intended only
5260 for internal implementation purposes and should not be @code{with}'ed
5261 by user programs. The default is that such warnings are generated
5262 This warning can also be turned on using @option{-gnatwa}.
5265 @emph{Disable warnings on implementation units.}
5266 @cindex @option{-gnatwI} (@command{gcc})
5267 This switch disables warnings for a @code{with} of an internal GNAT
5268 implementation unit.
5271 @emph{Activate warnings on obsolescent features (Annex J).}
5272 @cindex @option{-gnatwj} (@command{gcc})
5273 @cindex Features, obsolescent
5274 @cindex Obsolescent features
5275 If this warning option is activated, then warnings are generated for
5276 calls to subprograms marked with @code{pragma Obsolescent} and
5277 for use of features in Annex J of the Ada Reference Manual. In the
5278 case of Annex J, not all features are flagged. In particular use
5279 of the renamed packages (like @code{Text_IO}) and use of package
5280 @code{ASCII} are not flagged, since these are very common and
5281 would generate many annoying positive warnings. The default is that
5282 such warnings are not generated. This warning is also turned on by
5283 the use of @option{-gnatwa}.
5285 In addition to the above cases, warnings are also generated for
5286 GNAT features that have been provided in past versions but which
5287 have been superseded (typically by features in the new Ada standard).
5288 For example, @code{pragma Ravenscar} will be flagged since its
5289 function is replaced by @code{pragma Profile(Ravenscar)}.
5291 Note that this warning option functions differently from the
5292 restriction @code{No_Obsolescent_Features} in two respects.
5293 First, the restriction applies only to annex J features.
5294 Second, the restriction does flag uses of package @code{ASCII}.
5297 @emph{Suppress warnings on obsolescent features (Annex J).}
5298 @cindex @option{-gnatwJ} (@command{gcc})
5299 This switch disables warnings on use of obsolescent features.
5302 @emph{Activate warnings on variables that could be constants.}
5303 @cindex @option{-gnatwk} (@command{gcc})
5304 This switch activates warnings for variables that are initialized but
5305 never modified, and then could be declared constants. The default is that
5306 such warnings are not given.
5307 This warning can also be turned on using @option{-gnatwa}.
5310 @emph{Suppress warnings on variables that could be constants.}
5311 @cindex @option{-gnatwK} (@command{gcc})
5312 This switch disables warnings on variables that could be declared constants.
5315 @emph{Activate warnings for elaboration pragmas.}
5316 @cindex @option{-gnatwl} (@command{gcc})
5317 @cindex Elaboration, warnings
5318 This switch activates warnings on missing
5319 @code{Elaborate_All} and @code{Elaborate} pragmas.
5320 See the section in this guide on elaboration checking for details on
5321 when such pragmas should be used. In dynamic elaboration mode, this switch
5322 generations warnings about the need to add elaboration pragmas. Note however,
5323 that if you blindly follow these warnings, and add @code{Elaborate_All}
5324 warnings wherever they are recommended, you basically end up with the
5325 equivalent of the static elaboration model, which may not be what you want for
5326 legacy code for which the static model does not work.
5328 For the static model, the messages generated are labeled "info:" (for
5329 information messages). They are not warnings to add elaboration pragmas,
5330 merely informational messages showing what implicit elaboration pragmas
5331 have been added, for use in analyzing elaboration circularity problems.
5333 Warnings are also generated if you
5334 are using the static mode of elaboration, and a @code{pragma Elaborate}
5335 is encountered. The default is that such warnings
5337 This warning is not automatically turned on by the use of @option{-gnatwa}.
5340 @emph{Suppress warnings for elaboration pragmas.}
5341 @cindex @option{-gnatwL} (@command{gcc})
5342 This switch suppresses warnings on missing Elaborate and Elaborate_All pragmas.
5343 See the section in this guide on elaboration checking for details on
5344 when such pragmas should be used.
5347 @emph{Activate warnings on modified but unreferenced variables.}
5348 @cindex @option{-gnatwm} (@command{gcc})
5349 This switch activates warnings for variables that are assigned (using
5350 an initialization value or with one or more assignment statements) but
5351 whose value is never read. The warning is suppressed for volatile
5352 variables and also for variables that are renamings of other variables
5353 or for which an address clause is given.
5354 This warning can also be turned on using @option{-gnatwa}.
5355 The default is that these warnings are not given.
5358 @emph{Disable warnings on modified but unreferenced variables.}
5359 @cindex @option{-gnatwM} (@command{gcc})
5360 This switch disables warnings for variables that are assigned or
5361 initialized, but never read.
5364 @emph{Activate warnings on suspicious modulus values.}
5365 @cindex @option{-gnatw.m} (@command{gcc})
5366 This switch activates warnings for modulus values that seem suspicious.
5367 The cases caught are where the size is the same as the modulus (e.g.
5368 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
5369 with no size clause. The guess in both cases is that 2**x was intended
5370 rather than x. The default is that these warnings are given.
5373 @emph{Disable warnings on suspicious modulus values.}
5374 @cindex @option{-gnatw.M} (@command{gcc})
5375 This switch disables warnings for suspicious modulus values.
5378 @emph{Set normal warnings mode.}
5379 @cindex @option{-gnatwn} (@command{gcc})
5380 This switch sets normal warning mode, in which enabled warnings are
5381 issued and treated as warnings rather than errors. This is the default
5382 mode. the switch @option{-gnatwn} can be used to cancel the effect of
5383 an explicit @option{-gnatws} or
5384 @option{-gnatwe}. It also cancels the effect of the
5385 implicit @option{-gnatwe} that is activated by the
5386 use of @option{-gnatg}.
5389 @emph{Activate warnings on address clause overlays.}
5390 @cindex @option{-gnatwo} (@command{gcc})
5391 @cindex Address Clauses, warnings
5392 This switch activates warnings for possibly unintended initialization
5393 effects of defining address clauses that cause one variable to overlap
5394 another. The default is that such warnings are generated.
5395 This warning can also be turned on using @option{-gnatwa}.
5398 @emph{Suppress warnings on address clause overlays.}
5399 @cindex @option{-gnatwO} (@command{gcc})
5400 This switch suppresses warnings on possibly unintended initialization
5401 effects of defining address clauses that cause one variable to overlap
5405 @emph{Activate warnings on modified but unreferenced out parameters.}
5406 @cindex @option{-gnatw.o} (@command{gcc})
5407 This switch activates warnings for variables that are modified by using
5408 them as actuals for a call to a procedure with an out mode formal, where
5409 the resulting assigned value is never read. It is applicable in the case
5410 where there is more than one out mode formal. If there is only one out
5411 mode formal, the warning is issued by default (controlled by -gnatwu).
5412 The warning is suppressed for volatile
5413 variables and also for variables that are renamings of other variables
5414 or for which an address clause is given.
5415 The default is that these warnings are not given. Note that this warning
5416 is not included in -gnatwa, it must be activated explicitly.
5419 @emph{Disable warnings on modified but unreferenced out parameters.}
5420 @cindex @option{-gnatw.O} (@command{gcc})
5421 This switch suppresses warnings for variables that are modified by using
5422 them as actuals for a call to a procedure with an out mode formal, where
5423 the resulting assigned value is never read.
5426 @emph{Activate warnings on ineffective pragma Inlines.}
5427 @cindex @option{-gnatwp} (@command{gcc})
5428 @cindex Inlining, warnings
5429 This switch activates warnings for failure of front end inlining
5430 (activated by @option{-gnatN}) to inline a particular call. There are
5431 many reasons for not being able to inline a call, including most
5432 commonly that the call is too complex to inline. The default is
5433 that such warnings are not given.
5434 This warning can also be turned on using @option{-gnatwa}.
5435 Warnings on ineffective inlining by the gcc back-end can be activated
5436 separately, using the gcc switch -Winline.
5439 @emph{Suppress warnings on ineffective pragma Inlines.}
5440 @cindex @option{-gnatwP} (@command{gcc})
5441 This switch suppresses warnings on ineffective pragma Inlines. If the
5442 inlining mechanism cannot inline a call, it will simply ignore the
5446 @emph{Activate warnings on parameter ordering.}
5447 @cindex @option{-gnatw.p} (@command{gcc})
5448 @cindex Parameter order, warnings
5449 This switch activates warnings for cases of suspicious parameter
5450 ordering when the list of arguments are all simple identifiers that
5451 match the names of the formals, but are in a different order. The
5452 warning is suppressed if any use of named parameter notation is used,
5453 so this is the appropriate way to suppress a false positive (and
5454 serves to emphasize that the "misordering" is deliberate). The
5456 that such warnings are not given.
5457 This warning can also be turned on using @option{-gnatwa}.
5460 @emph{Suppress warnings on parameter ordering.}
5461 @cindex @option{-gnatw.P} (@command{gcc})
5462 This switch suppresses warnings on cases of suspicious parameter
5466 @emph{Activate warnings on questionable missing parentheses.}
5467 @cindex @option{-gnatwq} (@command{gcc})
5468 @cindex Parentheses, warnings
5469 This switch activates warnings for cases where parentheses are not used and
5470 the result is potential ambiguity from a readers point of view. For example
5471 (not a > b) when a and b are modular means ((not a) > b) and very likely the
5472 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
5473 quite likely ((-x) mod 5) was intended. In such situations it seems best to
5474 follow the rule of always parenthesizing to make the association clear, and
5475 this warning switch warns if such parentheses are not present. The default
5476 is that these warnings are given.
5477 This warning can also be turned on using @option{-gnatwa}.
5480 @emph{Suppress warnings on questionable missing parentheses.}
5481 @cindex @option{-gnatwQ} (@command{gcc})
5482 This switch suppresses warnings for cases where the association is not
5483 clear and the use of parentheses is preferred.
5486 @emph{Activate warnings on redundant constructs.}
5487 @cindex @option{-gnatwr} (@command{gcc})
5488 This switch activates warnings for redundant constructs. The following
5489 is the current list of constructs regarded as redundant:
5493 Assignment of an item to itself.
5495 Type conversion that converts an expression to its own type.
5497 Use of the attribute @code{Base} where @code{typ'Base} is the same
5500 Use of pragma @code{Pack} when all components are placed by a record
5501 representation clause.
5503 Exception handler containing only a reraise statement (raise with no
5504 operand) which has no effect.
5506 Use of the operator abs on an operand that is known at compile time
5509 Comparison of boolean expressions to an explicit True value.
5512 This warning can also be turned on using @option{-gnatwa}.
5513 The default is that warnings for redundant constructs are not given.
5516 @emph{Suppress warnings on redundant constructs.}
5517 @cindex @option{-gnatwR} (@command{gcc})
5518 This switch suppresses warnings for redundant constructs.
5521 @emph{Activate warnings for object renaming function.}
5522 @cindex @option{-gnatw.r} (@command{gcc})
5523 This switch activates warnings for an object renaming that renames a
5524 function call, which is equivalent to a constant declaration (as
5525 opposed to renaming the function itself). The default is that these
5526 warnings are given. This warning can also be turned on using
5530 @emph{Suppress warnings for object renaming function.}
5531 @cindex @option{-gnatwT} (@command{gcc})
5532 This switch suppresses warnings for object renaming function.
5535 @emph{Suppress all warnings.}
5536 @cindex @option{-gnatws} (@command{gcc})
5537 This switch completely suppresses the
5538 output of all warning messages from the GNAT front end.
5539 Note that it does not suppress warnings from the @command{gcc} back end.
5540 To suppress these back end warnings as well, use the switch @option{-w}
5541 in addition to @option{-gnatws}.
5544 @emph{Activate warnings for tracking of deleted conditional code.}
5545 @cindex @option{-gnatwt} (@command{gcc})
5546 @cindex Deactivated code, warnings
5547 @cindex Deleted code, warnings
5548 This switch activates warnings for tracking of code in conditionals (IF and
5549 CASE statements) that is detected to be dead code which cannot be executed, and
5550 which is removed by the front end. This warning is off by default, and is not
5551 turned on by @option{-gnatwa}, it has to be turned on explicitly. This may be
5552 useful for detecting deactivated code in certified applications.
5555 @emph{Suppress warnings for tracking of deleted conditional code.}
5556 @cindex @option{-gnatwT} (@command{gcc})
5557 This switch suppresses warnings for tracking of deleted conditional code.
5560 @emph{Activate warnings on unused entities.}
5561 @cindex @option{-gnatwu} (@command{gcc})
5562 This switch activates warnings to be generated for entities that
5563 are declared but not referenced, and for units that are @code{with}'ed
5565 referenced. In the case of packages, a warning is also generated if
5566 no entities in the package are referenced. This means that if the package
5567 is referenced but the only references are in @code{use}
5568 clauses or @code{renames}
5569 declarations, a warning is still generated. A warning is also generated
5570 for a generic package that is @code{with}'ed but never instantiated.
5571 In the case where a package or subprogram body is compiled, and there
5572 is a @code{with} on the corresponding spec
5573 that is only referenced in the body,
5574 a warning is also generated, noting that the
5575 @code{with} can be moved to the body. The default is that
5576 such warnings are not generated.
5577 This switch also activates warnings on unreferenced formals
5578 (it includes the effect of @option{-gnatwf}).
5579 This warning can also be turned on using @option{-gnatwa}.
5582 @emph{Suppress warnings on unused entities.}
5583 @cindex @option{-gnatwU} (@command{gcc})
5584 This switch suppresses warnings for unused entities and packages.
5585 It also turns off warnings on unreferenced formals (and thus includes
5586 the effect of @option{-gnatwF}).
5589 @emph{Activate warnings on unassigned variables.}
5590 @cindex @option{-gnatwv} (@command{gcc})
5591 @cindex Unassigned variable warnings
5592 This switch activates warnings for access to variables which
5593 may not be properly initialized. The default is that
5594 such warnings are generated.
5595 This warning can also be turned on using @option{-gnatwa}.
5598 @emph{Suppress warnings on unassigned variables.}
5599 @cindex @option{-gnatwV} (@command{gcc})
5600 This switch suppresses warnings for access to variables which
5601 may not be properly initialized.
5602 For variables of a composite type, the warning can also be suppressed in
5603 Ada 2005 by using a default initialization with a box. For example, if
5604 Table is an array of records whose components are only partially uninitialized,
5605 then the following code:
5607 @smallexample @c ada
5608 Tab : Table := (others => <>);
5611 will suppress warnings on subsequent statements that access components
5615 @emph{Activate warnings on wrong low bound assumption.}
5616 @cindex @option{-gnatww} (@command{gcc})
5617 @cindex String indexing warnings
5618 This switch activates warnings for indexing an unconstrained string parameter
5619 with a literal or S'Length. This is a case where the code is assuming that the
5620 low bound is one, which is in general not true (for example when a slice is
5621 passed). The default is that such warnings are generated.
5622 This warning can also be turned on using @option{-gnatwa}.
5625 @emph{Suppress warnings on wrong low bound assumption.}
5626 @cindex @option{-gnatwW} (@command{gcc})
5627 This switch suppresses warnings for indexing an unconstrained string parameter
5628 with a literal or S'Length. Note that this warning can also be suppressed
5629 in a particular case by adding an
5630 assertion that the lower bound is 1,
5631 as shown in the following example.
5633 @smallexample @c ada
5634 procedure K (S : String) is
5635 pragma Assert (S'First = 1);
5640 @emph{Activate warnings on unnecessary Warnings Off pragmas}
5641 @cindex @option{-gnatw.w} (@command{gcc})
5642 @cindex Warnings Off control
5643 This switch activates warnings for use of @code{pragma Warnings (Off, entity}
5644 where either the pragma is entirely useless (because it suppresses no
5645 warnings), or it could be replaced by @code{pragma Unreferenced} or
5646 @code{pragma Unmodified}.The default is that these warnings are not given.
5647 Note that this warning is not included in -gnatwa, it must be
5648 activated explicitly.
5651 @emph{Suppress warnings on unnecessary Warnings Off pragmas}
5652 @cindex @option{-gnatw.W} (@command{gcc})
5653 This switch suppresses warnings for use of @code{pragma Warnings (Off, entity}.
5656 @emph{Activate warnings on Export/Import pragmas.}
5657 @cindex @option{-gnatwx} (@command{gcc})
5658 @cindex Export/Import pragma warnings
5659 This switch activates warnings on Export/Import pragmas when
5660 the compiler detects a possible conflict between the Ada and
5661 foreign language calling sequences. For example, the use of
5662 default parameters in a convention C procedure is dubious
5663 because the C compiler cannot supply the proper default, so
5664 a warning is issued. The default is that such warnings are
5666 This warning can also be turned on using @option{-gnatwa}.
5669 @emph{Suppress warnings on Export/Import pragmas.}
5670 @cindex @option{-gnatwX} (@command{gcc})
5671 This switch suppresses warnings on Export/Import pragmas.
5672 The sense of this is that you are telling the compiler that
5673 you know what you are doing in writing the pragma, and it
5674 should not complain at you.
5677 @emph{Activate warnings for No_Exception_Propagation mode.}
5678 @cindex @option{-gnatwm} (@command{gcc})
5679 This switch activates warnings for exception usage when pragma Restrictions
5680 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
5681 explicit exception raises which are not covered by a local handler, and for
5682 exception handlers which do not cover a local raise. The default is that these
5683 warnings are not given.
5686 @emph{Disable warnings for No_Exception_Propagation mode.}
5687 This switch disables warnings for exception usage when pragma Restrictions
5688 (No_Exception_Propagation) is in effect.
5691 @emph{Activate warnings for Ada 2005 compatibility issues.}
5692 @cindex @option{-gnatwy} (@command{gcc})
5693 @cindex Ada 2005 compatibility issues warnings
5694 For the most part Ada 2005 is upwards compatible with Ada 95,
5695 but there are some exceptions (for example the fact that
5696 @code{interface} is now a reserved word in Ada 2005). This
5697 switch activates several warnings to help in identifying
5698 and correcting such incompatibilities. The default is that
5699 these warnings are generated. Note that at one point Ada 2005
5700 was called Ada 0Y, hence the choice of character.
5701 This warning can also be turned on using @option{-gnatwa}.
5704 @emph{Disable warnings for Ada 2005 compatibility issues.}
5705 @cindex @option{-gnatwY} (@command{gcc})
5706 @cindex Ada 2005 compatibility issues warnings
5707 This switch suppresses several warnings intended to help in identifying
5708 incompatibilities between Ada 95 and Ada 2005.
5711 @emph{Activate warnings on unchecked conversions.}
5712 @cindex @option{-gnatwz} (@command{gcc})
5713 @cindex Unchecked_Conversion warnings
5714 This switch activates warnings for unchecked conversions
5715 where the types are known at compile time to have different
5717 is that such warnings are generated. Warnings are also
5718 generated for subprogram pointers with different conventions,
5719 and, on VMS only, for data pointers with different conventions.
5720 This warning can also be turned on using @option{-gnatwa}.
5723 @emph{Suppress warnings on unchecked conversions.}
5724 @cindex @option{-gnatwZ} (@command{gcc})
5725 This switch suppresses warnings for unchecked conversions
5726 where the types are known at compile time to have different
5727 sizes or conventions.
5729 @item ^-Wunused^WARNINGS=UNUSED^
5730 @cindex @option{-Wunused}
5731 The warnings controlled by the @option{-gnatw} switch are generated by
5732 the front end of the compiler. The @option{GCC} back end can provide
5733 additional warnings and they are controlled by the @option{-W} switch.
5734 For example, @option{^-Wunused^WARNINGS=UNUSED^} activates back end
5735 warnings for entities that are declared but not referenced.
5737 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
5738 @cindex @option{-Wuninitialized}
5739 Similarly, @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^} activates
5740 the back end warning for uninitialized variables. This switch must be
5741 used in conjunction with an optimization level greater than zero.
5743 @item ^-Wall^/ALL_BACK_END_WARNINGS^
5744 @cindex @option{-Wall}
5745 This switch enables all the above warnings from the @option{GCC} back end.
5746 The code generator detects a number of warning situations that are missed
5747 by the @option{GNAT} front end, and this switch can be used to activate them.
5748 The use of this switch also sets the default front end warning mode to
5749 @option{-gnatwa}, that is, most front end warnings activated as well.
5751 @item ^-w^/NO_BACK_END_WARNINGS^
5753 Conversely, this switch suppresses warnings from the @option{GCC} back end.
5754 The use of this switch also sets the default front end warning mode to
5755 @option{-gnatws}, that is, front end warnings suppressed as well.
5761 A string of warning parameters can be used in the same parameter. For example:
5768 will turn on all optional warnings except for elaboration pragma warnings,
5769 and also specify that warnings should be treated as errors.
5771 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
5796 @node Debugging and Assertion Control
5797 @subsection Debugging and Assertion Control
5801 @cindex @option{-gnata} (@command{gcc})
5807 The pragmas @code{Assert} and @code{Debug} normally have no effect and
5808 are ignored. This switch, where @samp{a} stands for assert, causes
5809 @code{Assert} and @code{Debug} pragmas to be activated.
5811 The pragmas have the form:
5815 @b{pragma} Assert (@var{Boolean-expression} @r{[},
5816 @var{static-string-expression}@r{]})
5817 @b{pragma} Debug (@var{procedure call})
5822 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
5823 If the result is @code{True}, the pragma has no effect (other than
5824 possible side effects from evaluating the expression). If the result is
5825 @code{False}, the exception @code{Assert_Failure} declared in the package
5826 @code{System.Assertions} is
5827 raised (passing @var{static-string-expression}, if present, as the
5828 message associated with the exception). If no string expression is
5829 given the default is a string giving the file name and line number
5832 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5833 @code{pragma Debug} may appear within a declaration sequence, allowing
5834 debugging procedures to be called between declarations.
5837 @item /DEBUG@r{[}=debug-level@r{]}
5839 Specifies how much debugging information is to be included in
5840 the resulting object file where 'debug-level' is one of the following:
5843 Include both debugger symbol records and traceback
5845 This is the default setting.
5847 Include both debugger symbol records and traceback in
5850 Excludes both debugger symbol records and traceback
5851 the object file. Same as /NODEBUG.
5853 Includes only debugger symbol records in the object
5854 file. Note that this doesn't include traceback information.
5859 @node Validity Checking
5860 @subsection Validity Checking
5861 @findex Validity Checking
5864 The Ada Reference Manual defines the concept of invalid values (see
5865 RM 13.9.1). The primary source of invalid values is uninitialized
5866 variables. A scalar variable that is left uninitialized may contain
5867 an invalid value; the concept of invalid does not apply to access or
5870 It is an error to read an invalid value, but the RM does not require
5871 run-time checks to detect such errors, except for some minimal
5872 checking to prevent erroneous execution (i.e. unpredictable
5873 behavior). This corresponds to the @option{-gnatVd} switch below,
5874 which is the default. For example, by default, if the expression of a
5875 case statement is invalid, it will raise Constraint_Error rather than
5876 causing a wild jump, and if an array index on the left-hand side of an
5877 assignment is invalid, it will raise Constraint_Error rather than
5878 overwriting an arbitrary memory location.
5880 The @option{-gnatVa} may be used to enable additional validity checks,
5881 which are not required by the RM. These checks are often very
5882 expensive (which is why the RM does not require them). These checks
5883 are useful in tracking down uninitialized variables, but they are
5884 not usually recommended for production builds.
5886 The other @option{-gnatV^@var{x}^^} switches below allow finer-grained
5887 control; you can enable whichever validity checks you desire. However,
5888 for most debugging purposes, @option{-gnatVa} is sufficient, and the
5889 default @option{-gnatVd} (i.e. standard Ada behavior) is usually
5890 sufficient for non-debugging use.
5892 The @option{-gnatB} switch tells the compiler to assume that all
5893 values are valid (that is, within their declared subtype range)
5894 except in the context of a use of the Valid attribute. This means
5895 the compiler can generate more efficient code, since the range
5896 of values is better known at compile time. However, an uninitialized
5897 variable can cause wild jumps and memory corruption in this mode.
5899 The @option{-gnatV^@var{x}^^} switch allows control over the validity
5900 checking mode as described below.
5902 The @code{x} argument is a string of letters that
5903 indicate validity checks that are performed or not performed in addition
5904 to the default checks required by Ada as described above.
5907 The options allowed for this qualifier
5908 indicate validity checks that are performed or not performed in addition
5909 to the default checks required by Ada as described above.
5915 @emph{All validity checks.}
5916 @cindex @option{-gnatVa} (@command{gcc})
5917 All validity checks are turned on.
5919 That is, @option{-gnatVa} is
5920 equivalent to @option{gnatVcdfimorst}.
5924 @emph{Validity checks for copies.}
5925 @cindex @option{-gnatVc} (@command{gcc})
5926 The right hand side of assignments, and the initializing values of
5927 object declarations are validity checked.
5930 @emph{Default (RM) validity checks.}
5931 @cindex @option{-gnatVd} (@command{gcc})
5932 Some validity checks are done by default following normal Ada semantics
5934 A check is done in case statements that the expression is within the range
5935 of the subtype. If it is not, Constraint_Error is raised.
5936 For assignments to array components, a check is done that the expression used
5937 as index is within the range. If it is not, Constraint_Error is raised.
5938 Both these validity checks may be turned off using switch @option{-gnatVD}.
5939 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5940 switch @option{-gnatVd} will leave the checks turned on.
5941 Switch @option{-gnatVD} should be used only if you are sure that all such
5942 expressions have valid values. If you use this switch and invalid values
5943 are present, then the program is erroneous, and wild jumps or memory
5944 overwriting may occur.
5947 @emph{Validity checks for elementary components.}
5948 @cindex @option{-gnatVe} (@command{gcc})
5949 In the absence of this switch, assignments to record or array components are
5950 not validity checked, even if validity checks for assignments generally
5951 (@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not
5952 require valid data, but assignment of individual components does. So for
5953 example, there is a difference between copying the elements of an array with a
5954 slice assignment, compared to assigning element by element in a loop. This
5955 switch allows you to turn off validity checking for components, even when they
5956 are assigned component by component.
5959 @emph{Validity checks for floating-point values.}
5960 @cindex @option{-gnatVf} (@command{gcc})
5961 In the absence of this switch, validity checking occurs only for discrete
5962 values. If @option{-gnatVf} is specified, then validity checking also applies
5963 for floating-point values, and NaNs and infinities are considered invalid,
5964 as well as out of range values for constrained types. Note that this means
5965 that standard IEEE infinity mode is not allowed. The exact contexts
5966 in which floating-point values are checked depends on the setting of other
5967 options. For example,
5968 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5969 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5970 (the order does not matter) specifies that floating-point parameters of mode
5971 @code{in} should be validity checked.
5974 @emph{Validity checks for @code{in} mode parameters}
5975 @cindex @option{-gnatVi} (@command{gcc})
5976 Arguments for parameters of mode @code{in} are validity checked in function
5977 and procedure calls at the point of call.
5980 @emph{Validity checks for @code{in out} mode parameters.}
5981 @cindex @option{-gnatVm} (@command{gcc})
5982 Arguments for parameters of mode @code{in out} are validity checked in
5983 procedure calls at the point of call. The @code{'m'} here stands for
5984 modify, since this concerns parameters that can be modified by the call.
5985 Note that there is no specific option to test @code{out} parameters,
5986 but any reference within the subprogram will be tested in the usual
5987 manner, and if an invalid value is copied back, any reference to it
5988 will be subject to validity checking.
5991 @emph{No validity checks.}
5992 @cindex @option{-gnatVn} (@command{gcc})
5993 This switch turns off all validity checking, including the default checking
5994 for case statements and left hand side subscripts. Note that the use of
5995 the switch @option{-gnatp} suppresses all run-time checks, including
5996 validity checks, and thus implies @option{-gnatVn}. When this switch
5997 is used, it cancels any other @option{-gnatV} previously issued.
6000 @emph{Validity checks for operator and attribute operands.}
6001 @cindex @option{-gnatVo} (@command{gcc})
6002 Arguments for predefined operators and attributes are validity checked.
6003 This includes all operators in package @code{Standard},
6004 the shift operators defined as intrinsic in package @code{Interfaces}
6005 and operands for attributes such as @code{Pos}. Checks are also made
6006 on individual component values for composite comparisons, and on the
6007 expressions in type conversions and qualified expressions. Checks are
6008 also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc).
6011 @emph{Validity checks for parameters.}
6012 @cindex @option{-gnatVp} (@command{gcc})
6013 This controls the treatment of parameters within a subprogram (as opposed
6014 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
6015 of parameters on a call. If either of these call options is used, then
6016 normally an assumption is made within a subprogram that the input arguments
6017 have been validity checking at the point of call, and do not need checking
6018 again within a subprogram). If @option{-gnatVp} is set, then this assumption
6019 is not made, and parameters are not assumed to be valid, so their validity
6020 will be checked (or rechecked) within the subprogram.
6023 @emph{Validity checks for function returns.}
6024 @cindex @option{-gnatVr} (@command{gcc})
6025 The expression in @code{return} statements in functions is validity
6029 @emph{Validity checks for subscripts.}
6030 @cindex @option{-gnatVs} (@command{gcc})
6031 All subscripts expressions are checked for validity, whether they appear
6032 on the right side or left side (in default mode only left side subscripts
6033 are validity checked).
6036 @emph{Validity checks for tests.}
6037 @cindex @option{-gnatVt} (@command{gcc})
6038 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
6039 statements are checked, as well as guard expressions in entry calls.
6044 The @option{-gnatV} switch may be followed by
6045 ^a string of letters^a list of options^
6046 to turn on a series of validity checking options.
6048 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
6049 specifies that in addition to the default validity checking, copies and
6050 function return expressions are to be validity checked.
6051 In order to make it easier
6052 to specify the desired combination of effects,
6054 the upper case letters @code{CDFIMORST} may
6055 be used to turn off the corresponding lower case option.
6058 the prefix @code{NO} on an option turns off the corresponding validity
6061 @item @code{NOCOPIES}
6062 @item @code{NODEFAULT}
6063 @item @code{NOFLOATS}
6064 @item @code{NOIN_PARAMS}
6065 @item @code{NOMOD_PARAMS}
6066 @item @code{NOOPERANDS}
6067 @item @code{NORETURNS}
6068 @item @code{NOSUBSCRIPTS}
6069 @item @code{NOTESTS}
6073 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
6074 turns on all validity checking options except for
6075 checking of @code{@b{in out}} procedure arguments.
6077 The specification of additional validity checking generates extra code (and
6078 in the case of @option{-gnatVa} the code expansion can be substantial).
6079 However, these additional checks can be very useful in detecting
6080 uninitialized variables, incorrect use of unchecked conversion, and other
6081 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
6082 is useful in conjunction with the extra validity checking, since this
6083 ensures that wherever possible uninitialized variables have invalid values.
6085 See also the pragma @code{Validity_Checks} which allows modification of
6086 the validity checking mode at the program source level, and also allows for
6087 temporary disabling of validity checks.
6089 @node Style Checking
6090 @subsection Style Checking
6091 @findex Style checking
6094 The @option{-gnaty^x^(option,option,@dots{})^} switch
6095 @cindex @option{-gnaty} (@command{gcc})
6096 causes the compiler to
6097 enforce specified style rules. A limited set of style rules has been used
6098 in writing the GNAT sources themselves. This switch allows user programs
6099 to activate all or some of these checks. If the source program fails a
6100 specified style check, an appropriate warning message is given, preceded by
6101 the character sequence ``(style)''.
6103 @code{(option,option,@dots{})} is a sequence of keywords
6106 The string @var{x} is a sequence of letters or digits
6108 indicating the particular style
6109 checks to be performed. The following checks are defined:
6114 @emph{Specify indentation level.}
6115 If a digit from 1-9 appears
6116 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
6117 then proper indentation is checked, with the digit indicating the
6118 indentation level required. A value of zero turns off this style check.
6119 The general style of required indentation is as specified by
6120 the examples in the Ada Reference Manual. Full line comments must be
6121 aligned with the @code{--} starting on a column that is a multiple of
6122 the alignment level, or they may be aligned the same way as the following
6123 non-blank line (this is useful when full line comments appear in the middle
6127 @emph{Check attribute casing.}
6128 Attribute names, including the case of keywords such as @code{digits}
6129 used as attributes names, must be written in mixed case, that is, the
6130 initial letter and any letter following an underscore must be uppercase.
6131 All other letters must be lowercase.
6133 @item ^A^ARRAY_INDEXES^
6134 @emph{Use of array index numbers in array attributes.}
6135 When using the array attributes First, Last, Range,
6136 or Length, the index number must be omitted for one-dimensional arrays
6137 and is required for multi-dimensional arrays.
6140 @emph{Blanks not allowed at statement end.}
6141 Trailing blanks are not allowed at the end of statements. The purpose of this
6142 rule, together with h (no horizontal tabs), is to enforce a canonical format
6143 for the use of blanks to separate source tokens.
6145 @item ^B^BOOLEAN_OPERATORS^
6146 @emph{Check Boolean operators.}
6147 The use of AND/OR operators is not permitted except in the cases of modular
6148 operands, array operands, and simple stand-alone boolean variables or
6149 boolean constants. In all other cases AND THEN/OR ELSE are required.
6152 @emph{Check comments.}
6153 Comments must meet the following set of rules:
6158 The ``@code{--}'' that starts the column must either start in column one,
6159 or else at least one blank must precede this sequence.
6162 Comments that follow other tokens on a line must have at least one blank
6163 following the ``@code{--}'' at the start of the comment.
6166 Full line comments must have two blanks following the ``@code{--}'' that
6167 starts the comment, with the following exceptions.
6170 A line consisting only of the ``@code{--}'' characters, possibly preceded
6171 by blanks is permitted.
6174 A comment starting with ``@code{--x}'' where @code{x} is a special character
6176 This allows proper processing of the output generated by specialized tools
6177 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
6179 language (where ``@code{--#}'' is used). For the purposes of this rule, a
6180 special character is defined as being in one of the ASCII ranges
6181 @code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}.
6182 Note that this usage is not permitted
6183 in GNAT implementation units (i.e., when @option{-gnatg} is used).
6186 A line consisting entirely of minus signs, possibly preceded by blanks, is
6187 permitted. This allows the construction of box comments where lines of minus
6188 signs are used to form the top and bottom of the box.
6191 A comment that starts and ends with ``@code{--}'' is permitted as long as at
6192 least one blank follows the initial ``@code{--}''. Together with the preceding
6193 rule, this allows the construction of box comments, as shown in the following
6196 ---------------------------
6197 -- This is a box comment --
6198 -- with two text lines. --
6199 ---------------------------
6203 @item ^d^DOS_LINE_ENDINGS^
6204 @emph{Check no DOS line terminators present.}
6205 All lines must be terminated by a single ASCII.LF
6206 character (in particular the DOS line terminator sequence CR/LF is not
6210 @emph{Check end/exit labels.}
6211 Optional labels on @code{end} statements ending subprograms and on
6212 @code{exit} statements exiting named loops, are required to be present.
6215 @emph{No form feeds or vertical tabs.}
6216 Neither form feeds nor vertical tab characters are permitted
6220 @emph{GNAT style mode}
6221 The set of style check switches is set to match that used by the GNAT sources.
6222 This may be useful when developing code that is eventually intended to be
6223 incorporated into GNAT. For further details, see GNAT sources.
6226 @emph{No horizontal tabs.}
6227 Horizontal tab characters are not permitted in the source text.
6228 Together with the b (no blanks at end of line) check, this
6229 enforces a canonical form for the use of blanks to separate
6233 @emph{Check if-then layout.}
6234 The keyword @code{then} must appear either on the same
6235 line as corresponding @code{if}, or on a line on its own, lined
6236 up under the @code{if} with at least one non-blank line in between
6237 containing all or part of the condition to be tested.
6240 @emph{check mode IN keywords}
6241 Mode @code{in} (the default mode) is not
6242 allowed to be given explicitly. @code{in out} is fine,
6243 but not @code{in} on its own.
6246 @emph{Check keyword casing.}
6247 All keywords must be in lower case (with the exception of keywords
6248 such as @code{digits} used as attribute names to which this check
6252 @emph{Check layout.}
6253 Layout of statement and declaration constructs must follow the
6254 recommendations in the Ada Reference Manual, as indicated by the
6255 form of the syntax rules. For example an @code{else} keyword must
6256 be lined up with the corresponding @code{if} keyword.
6258 There are two respects in which the style rule enforced by this check
6259 option are more liberal than those in the Ada Reference Manual. First
6260 in the case of record declarations, it is permissible to put the
6261 @code{record} keyword on the same line as the @code{type} keyword, and
6262 then the @code{end} in @code{end record} must line up under @code{type}.
6263 This is also permitted when the type declaration is split on two lines.
6264 For example, any of the following three layouts is acceptable:
6266 @smallexample @c ada
6289 Second, in the case of a block statement, a permitted alternative
6290 is to put the block label on the same line as the @code{declare} or
6291 @code{begin} keyword, and then line the @code{end} keyword up under
6292 the block label. For example both the following are permitted:
6294 @smallexample @c ada
6312 The same alternative format is allowed for loops. For example, both of
6313 the following are permitted:
6315 @smallexample @c ada
6317 Clear : while J < 10 loop
6328 @item ^Lnnn^MAX_NESTING=nnn^
6329 @emph{Set maximum nesting level}
6330 The maximum level of nesting of constructs (including subprograms, loops,
6331 blocks, packages, and conditionals) may not exceed the given value
6332 @option{nnn}. A value of zero disconnects this style check.
6334 @item ^m^LINE_LENGTH^
6335 @emph{Check maximum line length.}
6336 The length of source lines must not exceed 79 characters, including
6337 any trailing blanks. The value of 79 allows convenient display on an
6338 80 character wide device or window, allowing for possible special
6339 treatment of 80 character lines. Note that this count is of
6340 characters in the source text. This means that a tab character counts
6341 as one character in this count but a wide character sequence counts as
6342 a single character (however many bytes are needed in the encoding).
6344 @item ^Mnnn^MAX_LENGTH=nnn^
6345 @emph{Set maximum line length.}
6346 The length of lines must not exceed the
6347 given value @option{nnn}. The maximum value that can be specified is 32767.
6349 @item ^n^STANDARD_CASING^
6350 @emph{Check casing of entities in Standard.}
6351 Any identifier from Standard must be cased
6352 to match the presentation in the Ada Reference Manual (for example,
6353 @code{Integer} and @code{ASCII.NUL}).
6356 @emph{Turn off all style checks}
6357 All style check options are turned off.
6359 @item ^o^ORDERED_SUBPROGRAMS^
6360 @emph{Check order of subprogram bodies.}
6361 All subprogram bodies in a given scope
6362 (e.g.@: a package body) must be in alphabetical order. The ordering
6363 rule uses normal Ada rules for comparing strings, ignoring casing
6364 of letters, except that if there is a trailing numeric suffix, then
6365 the value of this suffix is used in the ordering (e.g.@: Junk2 comes
6368 @item ^O^OVERRIDING_INDICATORS^
6369 @emph{Check that overriding subprograms are explicitly marked as such.}
6370 The declaration of a primitive operation of a type extension that overrides
6371 an inherited operation must carry an overriding indicator.
6374 @emph{Check pragma casing.}
6375 Pragma names must be written in mixed case, that is, the
6376 initial letter and any letter following an underscore must be uppercase.
6377 All other letters must be lowercase.
6379 @item ^r^REFERENCES^
6380 @emph{Check references.}
6381 All identifier references must be cased in the same way as the
6382 corresponding declaration. No specific casing style is imposed on
6383 identifiers. The only requirement is for consistency of references
6386 @item ^S^STATEMENTS_AFTER_THEN_ELSE^
6387 @emph{Check no statements after THEN/ELSE.}
6388 No statements are allowed
6389 on the same line as a THEN or ELSE keyword following the
6390 keyword in an IF statement. OR ELSE and AND THEN are not affected,
6391 and a special exception allows a pragma to appear after ELSE.
6394 @emph{Check separate specs.}
6395 Separate declarations (``specs'') are required for subprograms (a
6396 body is not allowed to serve as its own declaration). The only
6397 exception is that parameterless library level procedures are
6398 not required to have a separate declaration. This exception covers
6399 the most frequent form of main program procedures.
6402 @emph{Check token spacing.}
6403 The following token spacing rules are enforced:
6408 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
6411 The token @code{=>} must be surrounded by spaces.
6414 The token @code{<>} must be preceded by a space or a left parenthesis.
6417 Binary operators other than @code{**} must be surrounded by spaces.
6418 There is no restriction on the layout of the @code{**} binary operator.
6421 Colon must be surrounded by spaces.
6424 Colon-equal (assignment, initialization) must be surrounded by spaces.
6427 Comma must be the first non-blank character on the line, or be
6428 immediately preceded by a non-blank character, and must be followed
6432 If the token preceding a left parenthesis ends with a letter or digit, then
6433 a space must separate the two tokens.
6436 A right parenthesis must either be the first non-blank character on
6437 a line, or it must be preceded by a non-blank character.
6440 A semicolon must not be preceded by a space, and must not be followed by
6441 a non-blank character.
6444 A unary plus or minus may not be followed by a space.
6447 A vertical bar must be surrounded by spaces.
6450 @item ^u^UNNECESSARY_BLANK_LINES^
6451 @emph{Check unnecessary blank lines.}
6452 Unnecessary blank lines are not allowed. A blank line is considered
6453 unnecessary if it appears at the end of the file, or if more than
6454 one blank line occurs in sequence.
6456 @item ^x^XTRA_PARENS^
6457 @emph{Check extra parentheses.}
6458 Unnecessary extra level of parentheses (C-style) are not allowed
6459 around conditions in @code{if} statements, @code{while} statements and
6460 @code{exit} statements.
6462 @item ^y^ALL_BUILTIN^
6463 @emph{Set all standard style check options}
6464 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
6465 options enabled with the exception of @option{-gnatyo}, @option{-gnatyI},
6466 @option{-gnatyS}, @option{-gnatyLnnn},
6467 @option{-gnatyd}, @option{-gnatyu}, and @option{-gnatyx}.
6471 @emph{Remove style check options}
6472 This causes any subsequent options in the string to act as canceling the
6473 corresponding style check option. To cancel maximum nesting level control,
6474 use @option{L} parameter witout any integer value after that, because any
6475 digit following @option{-} in the parameter string of the @option{-gnaty}
6476 option will be threated as canceling indentation check. The same is true
6477 for @option{M} parameter. @option{y} and @option{N} parameters are not
6478 allowed after @option{-}.
6481 This causes any subsequent options in the string to enable the corresponding
6482 style check option. That is, it cancels the effect of a previous ^-^REMOVE^,
6488 @emph{Removing style check options}
6489 If the name of a style check is preceded by @option{NO} then the corresponding
6490 style check is turned off. For example @option{NOCOMMENTS} turns off style
6491 checking for comments.
6496 In the above rules, appearing in column one is always permitted, that is,
6497 counts as meeting either a requirement for a required preceding space,
6498 or as meeting a requirement for no preceding space.
6500 Appearing at the end of a line is also always permitted, that is, counts
6501 as meeting either a requirement for a following space, or as meeting
6502 a requirement for no following space.
6505 If any of these style rules is violated, a message is generated giving
6506 details on the violation. The initial characters of such messages are
6507 always ``@code{(style)}''. Note that these messages are treated as warning
6508 messages, so they normally do not prevent the generation of an object
6509 file. The @option{-gnatwe} switch can be used to treat warning messages,
6510 including style messages, as fatal errors.
6514 @option{-gnaty} on its own (that is not
6515 followed by any letters or digits), then the effect is equivalent
6516 to the use of @option{-gnatyy}, as described above, that is all
6517 built-in standard style check options are enabled.
6521 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
6522 the exception of ORDERED_SUBPROGRAMS, UNNECESSARY_BLANK_LINES,
6523 XTRA_PARENS, and DOS_LINE_ENDINGS. In addition
6535 clears any previously set style checks.
6537 @node Run-Time Checks
6538 @subsection Run-Time Checks
6539 @cindex Division by zero
6540 @cindex Access before elaboration
6541 @cindex Checks, division by zero
6542 @cindex Checks, access before elaboration
6543 @cindex Checks, stack overflow checking
6546 By default, the following checks are suppressed: integer overflow
6547 checks, stack overflow checks, and checks for access before
6548 elaboration on subprogram calls. All other checks, including range
6549 checks and array bounds checks, are turned on by default. The
6550 following @command{gcc} switches refine this default behavior.
6555 @cindex @option{-gnatp} (@command{gcc})
6556 @cindex Suppressing checks
6557 @cindex Checks, suppressing
6559 This switch causes the unit to be compiled
6560 as though @code{pragma Suppress (All_checks)}
6561 had been present in the source. Validity checks are also eliminated (in
6562 other words @option{-gnatp} also implies @option{-gnatVn}.
6563 Use this switch to improve the performance
6564 of the code at the expense of safety in the presence of invalid data or
6567 Note that when checks are suppressed, the compiler is allowed, but not
6568 required, to omit the checking code. If the run-time cost of the
6569 checking code is zero or near-zero, the compiler will generate it even
6570 if checks are suppressed. In particular, if the compiler can prove
6571 that a certain check will necessarily fail, it will generate code to
6572 do an unconditional ``raise'', even if checks are suppressed. The
6573 compiler warns in this case. Another case in which checks may not be
6574 eliminated is when they are embedded in certain run time routines such
6575 as math library routines.
6577 Of course, run-time checks are omitted whenever the compiler can prove
6578 that they will not fail, whether or not checks are suppressed.
6580 Note that if you suppress a check that would have failed, program
6581 execution is erroneous, which means the behavior is totally
6582 unpredictable. The program might crash, or print wrong answers, or
6583 do anything else. It might even do exactly what you wanted it to do
6584 (and then it might start failing mysteriously next week or next
6585 year). The compiler will generate code based on the assumption that
6586 the condition being checked is true, which can result in disaster if
6587 that assumption is wrong.
6590 @cindex @option{-gnato} (@command{gcc})
6591 @cindex Overflow checks
6592 @cindex Check, overflow
6593 Enables overflow checking for integer operations.
6594 This causes GNAT to generate slower and larger executable
6595 programs by adding code to check for overflow (resulting in raising
6596 @code{Constraint_Error} as required by standard Ada
6597 semantics). These overflow checks correspond to situations in which
6598 the true value of the result of an operation may be outside the base
6599 range of the result type. The following example shows the distinction:
6601 @smallexample @c ada
6602 X1 : Integer := "Integer'Last";
6603 X2 : Integer range 1 .. 5 := "5";
6604 X3 : Integer := "Integer'Last";
6605 X4 : Integer range 1 .. 5 := "5";
6606 F : Float := "2.0E+20";
6615 Note that if explicit values are assigned at compile time, the
6616 compiler may be able to detect overflow at compile time, in which case
6617 no actual run-time checking code is required, and Constraint_Error
6618 will be raised unconditionally, with or without
6619 @option{-gnato}. That's why the assigned values in the above fragment
6620 are in quotes, the meaning is "assign a value not known to the
6621 compiler that happens to be equal to ...". The remaining discussion
6622 assumes that the compiler cannot detect the values at compile time.
6624 Here the first addition results in a value that is outside the base range
6625 of Integer, and hence requires an overflow check for detection of the
6626 constraint error. Thus the first assignment to @code{X1} raises a
6627 @code{Constraint_Error} exception only if @option{-gnato} is set.
6629 The second increment operation results in a violation of the explicit
6630 range constraint; such range checks are performed by default, and are
6631 unaffected by @option{-gnato}.
6633 The two conversions of @code{F} both result in values that are outside
6634 the base range of type @code{Integer} and thus will raise
6635 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
6636 The fact that the result of the second conversion is assigned to
6637 variable @code{X4} with a restricted range is irrelevant, since the problem
6638 is in the conversion, not the assignment.
6640 Basically the rule is that in the default mode (@option{-gnato} not
6641 used), the generated code assures that all integer variables stay
6642 within their declared ranges, or within the base range if there is
6643 no declared range. This prevents any serious problems like indexes
6644 out of range for array operations.
6646 What is not checked in default mode is an overflow that results in
6647 an in-range, but incorrect value. In the above example, the assignments
6648 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
6649 range of the target variable, but the result is wrong in the sense that
6650 it is too large to be represented correctly. Typically the assignment
6651 to @code{X1} will result in wrap around to the largest negative number.
6652 The conversions of @code{F} will result in some @code{Integer} value
6653 and if that integer value is out of the @code{X4} range then the
6654 subsequent assignment would generate an exception.
6656 @findex Machine_Overflows
6657 Note that the @option{-gnato} switch does not affect the code generated
6658 for any floating-point operations; it applies only to integer
6660 For floating-point, GNAT has the @code{Machine_Overflows}
6661 attribute set to @code{False} and the normal mode of operation is to
6662 generate IEEE NaN and infinite values on overflow or invalid operations
6663 (such as dividing 0.0 by 0.0).
6665 The reason that we distinguish overflow checking from other kinds of
6666 range constraint checking is that a failure of an overflow check, unlike
6667 for example the failure of a range check, can result in an incorrect
6668 value, but cannot cause random memory destruction (like an out of range
6669 subscript), or a wild jump (from an out of range case value). Overflow
6670 checking is also quite expensive in time and space, since in general it
6671 requires the use of double length arithmetic.
6673 Note again that @option{-gnato} is off by default, so overflow checking is
6674 not performed in default mode. This means that out of the box, with the
6675 default settings, GNAT does not do all the checks expected from the
6676 language description in the Ada Reference Manual. If you want all constraint
6677 checks to be performed, as described in this Manual, then you must
6678 explicitly use the -gnato switch either on the @command{gnatmake} or
6679 @command{gcc} command.
6682 @cindex @option{-gnatE} (@command{gcc})
6683 @cindex Elaboration checks
6684 @cindex Check, elaboration
6685 Enables dynamic checks for access-before-elaboration
6686 on subprogram calls and generic instantiations.
6687 Note that @option{-gnatE} is not necessary for safety, because in the
6688 default mode, GNAT ensures statically that the checks would not fail.
6689 For full details of the effect and use of this switch,
6690 @xref{Compiling Using gcc}.
6693 @cindex @option{-fstack-check} (@command{gcc})
6694 @cindex Stack Overflow Checking
6695 @cindex Checks, stack overflow checking
6696 Activates stack overflow checking. For full details of the effect and use of
6697 this switch see @ref{Stack Overflow Checking}.
6702 The setting of these switches only controls the default setting of the
6703 checks. You may modify them using either @code{Suppress} (to remove
6704 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
6707 @node Using gcc for Syntax Checking
6708 @subsection Using @command{gcc} for Syntax Checking
6711 @cindex @option{-gnats} (@command{gcc})
6715 The @code{s} stands for ``syntax''.
6718 Run GNAT in syntax checking only mode. For
6719 example, the command
6722 $ gcc -c -gnats x.adb
6726 compiles file @file{x.adb} in syntax-check-only mode. You can check a
6727 series of files in a single command
6729 , and can use wild cards to specify such a group of files.
6730 Note that you must specify the @option{-c} (compile
6731 only) flag in addition to the @option{-gnats} flag.
6734 You may use other switches in conjunction with @option{-gnats}. In
6735 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
6736 format of any generated error messages.
6738 When the source file is empty or contains only empty lines and/or comments,
6739 the output is a warning:
6742 $ gcc -c -gnats -x ada toto.txt
6743 toto.txt:1:01: warning: empty file, contains no compilation units
6747 Otherwise, the output is simply the error messages, if any. No object file or
6748 ALI file is generated by a syntax-only compilation. Also, no units other
6749 than the one specified are accessed. For example, if a unit @code{X}
6750 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
6751 check only mode does not access the source file containing unit
6754 @cindex Multiple units, syntax checking
6755 Normally, GNAT allows only a single unit in a source file. However, this
6756 restriction does not apply in syntax-check-only mode, and it is possible
6757 to check a file containing multiple compilation units concatenated
6758 together. This is primarily used by the @code{gnatchop} utility
6759 (@pxref{Renaming Files Using gnatchop}).
6762 @node Using gcc for Semantic Checking
6763 @subsection Using @command{gcc} for Semantic Checking
6766 @cindex @option{-gnatc} (@command{gcc})
6770 The @code{c} stands for ``check''.
6772 Causes the compiler to operate in semantic check mode,
6773 with full checking for all illegalities specified in the
6774 Ada Reference Manual, but without generation of any object code
6775 (no object file is generated).
6777 Because dependent files must be accessed, you must follow the GNAT
6778 semantic restrictions on file structuring to operate in this mode:
6782 The needed source files must be accessible
6783 (@pxref{Search Paths and the Run-Time Library (RTL)}).
6786 Each file must contain only one compilation unit.
6789 The file name and unit name must match (@pxref{File Naming Rules}).
6792 The output consists of error messages as appropriate. No object file is
6793 generated. An @file{ALI} file is generated for use in the context of
6794 cross-reference tools, but this file is marked as not being suitable
6795 for binding (since no object file is generated).
6796 The checking corresponds exactly to the notion of
6797 legality in the Ada Reference Manual.
6799 Any unit can be compiled in semantics-checking-only mode, including
6800 units that would not normally be compiled (subunits,
6801 and specifications where a separate body is present).
6804 @node Compiling Different Versions of Ada
6805 @subsection Compiling Different Versions of Ada
6808 The switches described in this section allow you to explicitly specify
6809 the version of the Ada language that your programs are written in.
6810 By default @value{EDITION} assumes @value{DEFAULTLANGUAGEVERSION},
6811 but you can also specify @value{NONDEFAULTLANGUAGEVERSION} or
6812 indicate Ada 83 compatibility mode.
6815 @cindex Compatibility with Ada 83
6817 @item -gnat83 (Ada 83 Compatibility Mode)
6818 @cindex @option{-gnat83} (@command{gcc})
6819 @cindex ACVC, Ada 83 tests
6823 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
6824 specifies that the program is to be compiled in Ada 83 mode. With
6825 @option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
6826 semantics where this can be done easily.
6827 It is not possible to guarantee this switch does a perfect
6828 job; some subtle tests, such as are
6829 found in earlier ACVC tests (and that have been removed from the ACATS suite
6830 for Ada 95), might not compile correctly.
6831 Nevertheless, this switch may be useful in some circumstances, for example
6832 where, due to contractual reasons, existing code needs to be maintained
6833 using only Ada 83 features.
6835 With few exceptions (most notably the need to use @code{<>} on
6836 @cindex Generic formal parameters
6837 unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005
6838 reserved words, and the use of packages
6839 with optional bodies), it is not necessary to specify the
6840 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
6841 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
6842 a correct Ada 83 program is usually also a correct program
6843 in these later versions of the language standard.
6844 For further information, please refer to @ref{Compatibility and Porting Guide}.
6846 @item -gnat95 (Ada 95 mode)
6847 @cindex @option{-gnat95} (@command{gcc})
6851 This switch directs the compiler to implement the Ada 95 version of the
6853 Since Ada 95 is almost completely upwards
6854 compatible with Ada 83, Ada 83 programs may generally be compiled using
6855 this switch (see the description of the @option{-gnat83} switch for further
6856 information about Ada 83 mode).
6857 If an Ada 2005 program is compiled in Ada 95 mode,
6858 uses of the new Ada 2005 features will cause error
6859 messages or warnings.
6861 This switch also can be used to cancel the effect of a previous
6862 @option{-gnat83} or @option{-gnat05} switch earlier in the command line.
6864 @item -gnat05 (Ada 2005 mode)
6865 @cindex @option{-gnat05} (@command{gcc})
6866 @cindex Ada 2005 mode
6869 This switch directs the compiler to implement the Ada 2005 version of the
6871 Since Ada 2005 is almost completely upwards
6872 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
6873 may generally be compiled using this switch (see the description of the
6874 @option{-gnat83} and @option{-gnat95} switches for further
6877 For information about the approved ``Ada Issues'' that have been incorporated
6878 into Ada 2005, see @url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/AIs}.
6879 Included with GNAT releases is a file @file{features-ada0y} that describes
6880 the set of implemented Ada 2005 features.
6884 @node Character Set Control
6885 @subsection Character Set Control
6887 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
6888 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@command{gcc})
6891 Normally GNAT recognizes the Latin-1 character set in source program
6892 identifiers, as described in the Ada Reference Manual.
6894 GNAT to recognize alternate character sets in identifiers. @var{c} is a
6895 single character ^^or word^ indicating the character set, as follows:
6899 ISO 8859-1 (Latin-1) identifiers
6902 ISO 8859-2 (Latin-2) letters allowed in identifiers
6905 ISO 8859-3 (Latin-3) letters allowed in identifiers
6908 ISO 8859-4 (Latin-4) letters allowed in identifiers
6911 ISO 8859-5 (Cyrillic) letters allowed in identifiers
6914 ISO 8859-15 (Latin-9) letters allowed in identifiers
6917 IBM PC letters (code page 437) allowed in identifiers
6920 IBM PC letters (code page 850) allowed in identifiers
6922 @item ^f^FULL_UPPER^
6923 Full upper-half codes allowed in identifiers
6926 No upper-half codes allowed in identifiers
6929 Wide-character codes (that is, codes greater than 255)
6930 allowed in identifiers
6933 @xref{Foreign Language Representation}, for full details on the
6934 implementation of these character sets.
6936 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
6937 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@command{gcc})
6938 Specify the method of encoding for wide characters.
6939 @var{e} is one of the following:
6944 Hex encoding (brackets coding also recognized)
6947 Upper half encoding (brackets encoding also recognized)
6950 Shift/JIS encoding (brackets encoding also recognized)
6953 EUC encoding (brackets encoding also recognized)
6956 UTF-8 encoding (brackets encoding also recognized)
6959 Brackets encoding only (default value)
6961 For full details on these encoding
6962 methods see @ref{Wide Character Encodings}.
6963 Note that brackets coding is always accepted, even if one of the other
6964 options is specified, so for example @option{-gnatW8} specifies that both
6965 brackets and UTF-8 encodings will be recognized. The units that are
6966 with'ed directly or indirectly will be scanned using the specified
6967 representation scheme, and so if one of the non-brackets scheme is
6968 used, it must be used consistently throughout the program. However,
6969 since brackets encoding is always recognized, it may be conveniently
6970 used in standard libraries, allowing these libraries to be used with
6971 any of the available coding schemes.
6974 If no @option{-gnatW?} parameter is present, then the default
6975 representation is normally Brackets encoding only. However, if the
6976 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
6977 byte order mark or BOM for UTF-8), then these three characters are
6978 skipped and the default representation for the file is set to UTF-8.
6980 Note that the wide character representation that is specified (explicitly
6981 or by default) for the main program also acts as the default encoding used
6982 for Wide_Text_IO files if not specifically overridden by a WCEM form
6986 @node File Naming Control
6987 @subsection File Naming Control
6990 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6991 @cindex @option{-gnatk} (@command{gcc})
6992 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6993 1-999, indicates the maximum allowable length of a file name (not
6994 including the @file{.ads} or @file{.adb} extension). The default is not
6995 to enable file name krunching.
6997 For the source file naming rules, @xref{File Naming Rules}.
7000 @node Subprogram Inlining Control
7001 @subsection Subprogram Inlining Control
7006 @cindex @option{-gnatn} (@command{gcc})
7008 The @code{n} here is intended to suggest the first syllable of the
7011 GNAT recognizes and processes @code{Inline} pragmas. However, for the
7012 inlining to actually occur, optimization must be enabled. To enable
7013 inlining of subprograms specified by pragma @code{Inline},
7014 you must also specify this switch.
7015 In the absence of this switch, GNAT does not attempt
7016 inlining and does not need to access the bodies of
7017 subprograms for which @code{pragma Inline} is specified if they are not
7018 in the current unit.
7020 If you specify this switch the compiler will access these bodies,
7021 creating an extra source dependency for the resulting object file, and
7022 where possible, the call will be inlined.
7023 For further details on when inlining is possible
7024 see @ref{Inlining of Subprograms}.
7027 @cindex @option{-gnatN} (@command{gcc})
7028 This switch activates front-end inlining which also
7029 generates additional dependencies.
7031 When using a gcc-based back end (in practice this means using any version
7032 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
7033 @option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred.
7034 Historically front end inlining was more extensive than the gcc back end
7035 inlining, but that is no longer the case.
7038 @node Auxiliary Output Control
7039 @subsection Auxiliary Output Control
7043 @cindex @option{-gnatt} (@command{gcc})
7044 @cindex Writing internal trees
7045 @cindex Internal trees, writing to file
7046 Causes GNAT to write the internal tree for a unit to a file (with the
7047 extension @file{.adt}.
7048 This not normally required, but is used by separate analysis tools.
7050 these tools do the necessary compilations automatically, so you should
7051 not have to specify this switch in normal operation.
7052 Note that the combination of switches @option{-gnatct}
7053 generates a tree in the form required by ASIS applications.
7056 @cindex @option{-gnatu} (@command{gcc})
7057 Print a list of units required by this compilation on @file{stdout}.
7058 The listing includes all units on which the unit being compiled depends
7059 either directly or indirectly.
7062 @item -pass-exit-codes
7063 @cindex @option{-pass-exit-codes} (@command{gcc})
7064 If this switch is not used, the exit code returned by @command{gcc} when
7065 compiling multiple files indicates whether all source files have
7066 been successfully used to generate object files or not.
7068 When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended
7069 exit status and allows an integrated development environment to better
7070 react to a compilation failure. Those exit status are:
7074 There was an error in at least one source file.
7076 At least one source file did not generate an object file.
7078 The compiler died unexpectedly (internal error for example).
7080 An object file has been generated for every source file.
7085 @node Debugging Control
7086 @subsection Debugging Control
7090 @cindex Debugging options
7093 @cindex @option{-gnatd} (@command{gcc})
7094 Activate internal debugging switches. @var{x} is a letter or digit, or
7095 string of letters or digits, which specifies the type of debugging
7096 outputs desired. Normally these are used only for internal development
7097 or system debugging purposes. You can find full documentation for these
7098 switches in the body of the @code{Debug} unit in the compiler source
7099 file @file{debug.adb}.
7103 @cindex @option{-gnatG} (@command{gcc})
7104 This switch causes the compiler to generate auxiliary output containing
7105 a pseudo-source listing of the generated expanded code. Like most Ada
7106 compilers, GNAT works by first transforming the high level Ada code into
7107 lower level constructs. For example, tasking operations are transformed
7108 into calls to the tasking run-time routines. A unique capability of GNAT
7109 is to list this expanded code in a form very close to normal Ada source.
7110 This is very useful in understanding the implications of various Ada
7111 usage on the efficiency of the generated code. There are many cases in
7112 Ada (e.g.@: the use of controlled types), where simple Ada statements can
7113 generate a lot of run-time code. By using @option{-gnatG} you can identify
7114 these cases, and consider whether it may be desirable to modify the coding
7115 approach to improve efficiency.
7117 The optional parameter @code{nn} if present after -gnatG specifies an
7118 alternative maximum line length that overrides the normal default of 72.
7119 This value is in the range 40-999999, values less than 40 being silently
7120 reset to 40. The equal sign is optional.
7122 The format of the output is very similar to standard Ada source, and is
7123 easily understood by an Ada programmer. The following special syntactic
7124 additions correspond to low level features used in the generated code that
7125 do not have any exact analogies in pure Ada source form. The following
7126 is a partial list of these special constructions. See the spec
7127 of package @code{Sprint} in file @file{sprint.ads} for a full list.
7129 If the switch @option{-gnatL} is used in conjunction with
7130 @cindex @option{-gnatL} (@command{gcc})
7131 @option{-gnatG}, then the original source lines are interspersed
7132 in the expanded source (as comment lines with the original line number).
7135 @item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]}
7136 Shows the storage pool being used for an allocator.
7138 @item at end @var{procedure-name};
7139 Shows the finalization (cleanup) procedure for a scope.
7141 @item (if @var{expr} then @var{expr} else @var{expr})
7142 Conditional expression equivalent to the @code{x?y:z} construction in C.
7144 @item @var{target}^^^(@var{source})
7145 A conversion with floating-point truncation instead of rounding.
7147 @item @var{target}?(@var{source})
7148 A conversion that bypasses normal Ada semantic checking. In particular
7149 enumeration types and fixed-point types are treated simply as integers.
7151 @item @var{target}?^^^(@var{source})
7152 Combines the above two cases.
7154 @item @var{x} #/ @var{y}
7155 @itemx @var{x} #mod @var{y}
7156 @itemx @var{x} #* @var{y}
7157 @itemx @var{x} #rem @var{y}
7158 A division or multiplication of fixed-point values which are treated as
7159 integers without any kind of scaling.
7161 @item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]}
7162 Shows the storage pool associated with a @code{free} statement.
7164 @item [subtype or type declaration]
7165 Used to list an equivalent declaration for an internally generated
7166 type that is referenced elsewhere in the listing.
7168 @item freeze @var{type-name} @ovar{actions}
7169 Shows the point at which @var{type-name} is frozen, with possible
7170 associated actions to be performed at the freeze point.
7172 @item reference @var{itype}
7173 Reference (and hence definition) to internal type @var{itype}.
7175 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
7176 Intrinsic function call.
7178 @item @var{label-name} : label
7179 Declaration of label @var{labelname}.
7181 @item #$ @var{subprogram-name}
7182 An implicit call to a run-time support routine
7183 (to meet the requirement of H.3.1(9) in a
7186 @item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr}
7187 A multiple concatenation (same effect as @var{expr} & @var{expr} &
7188 @var{expr}, but handled more efficiently).
7190 @item [constraint_error]
7191 Raise the @code{Constraint_Error} exception.
7193 @item @var{expression}'reference
7194 A pointer to the result of evaluating @var{expression}.
7196 @item @var{target-type}!(@var{source-expression})
7197 An unchecked conversion of @var{source-expression} to @var{target-type}.
7199 @item [@var{numerator}/@var{denominator}]
7200 Used to represent internal real literals (that) have no exact
7201 representation in base 2-16 (for example, the result of compile time
7202 evaluation of the expression 1.0/27.0).
7206 @cindex @option{-gnatD} (@command{gcc})
7207 When used in conjunction with @option{-gnatG}, this switch causes
7208 the expanded source, as described above for
7209 @option{-gnatG} to be written to files with names
7210 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
7211 instead of to the standard output file. For
7212 example, if the source file name is @file{hello.adb}, then a file
7213 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
7214 information generated by the @command{gcc} @option{^-g^/DEBUG^} switch
7215 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
7216 you to do source level debugging using the generated code which is
7217 sometimes useful for complex code, for example to find out exactly
7218 which part of a complex construction raised an exception. This switch
7219 also suppress generation of cross-reference information (see
7220 @option{-gnatx}) since otherwise the cross-reference information
7221 would refer to the @file{^.dg^.DG^} file, which would cause
7222 confusion since this is not the original source file.
7224 Note that @option{-gnatD} actually implies @option{-gnatG}
7225 automatically, so it is not necessary to give both options.
7226 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
7228 If the switch @option{-gnatL} is used in conjunction with
7229 @cindex @option{-gnatL} (@command{gcc})
7230 @option{-gnatDG}, then the original source lines are interspersed
7231 in the expanded source (as comment lines with the original line number).
7233 The optional parameter @code{nn} if present after -gnatD specifies an
7234 alternative maximum line length that overrides the normal default of 72.
7235 This value is in the range 40-999999, values less than 40 being silently
7236 reset to 40. The equal sign is optional.
7239 @cindex @option{-gnatr} (@command{gcc})
7240 @cindex pragma Restrictions
7241 This switch causes pragma Restrictions to be treated as Restriction_Warnings
7242 so that violation of restrictions causes warnings rather than illegalities.
7243 This is useful during the development process when new restrictions are added
7244 or investigated. The switch also causes pragma Profile to be treated as
7245 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
7246 restriction warnings rather than restrictions.
7249 @item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]}
7250 @cindex @option{-gnatR} (@command{gcc})
7251 This switch controls output from the compiler of a listing showing
7252 representation information for declared types and objects. For
7253 @option{-gnatR0}, no information is output (equivalent to omitting
7254 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
7255 so @option{-gnatR} with no parameter has the same effect), size and alignment
7256 information is listed for declared array and record types. For
7257 @option{-gnatR2}, size and alignment information is listed for all
7258 declared types and objects. Finally @option{-gnatR3} includes symbolic
7259 expressions for values that are computed at run time for
7260 variant records. These symbolic expressions have a mostly obvious
7261 format with #n being used to represent the value of the n'th
7262 discriminant. See source files @file{repinfo.ads/adb} in the
7263 @code{GNAT} sources for full details on the format of @option{-gnatR3}
7264 output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then
7265 the output is to a file with the name @file{^file.rep^file_REP^} where
7266 file is the name of the corresponding source file.
7269 @item /REPRESENTATION_INFO
7270 @cindex @option{/REPRESENTATION_INFO} (@command{gcc})
7271 This qualifier controls output from the compiler of a listing showing
7272 representation information for declared types and objects. For
7273 @option{/REPRESENTATION_INFO=NONE}, no information is output
7274 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
7275 @option{/REPRESENTATION_INFO} without option is equivalent to
7276 @option{/REPRESENTATION_INFO=ARRAYS}.
7277 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
7278 information is listed for declared array and record types. For
7279 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
7280 is listed for all expression information for values that are computed
7281 at run time for variant records. These symbolic expressions have a mostly
7282 obvious format with #n being used to represent the value of the n'th
7283 discriminant. See source files @file{REPINFO.ADS/ADB} in the
7284 @code{GNAT} sources for full details on the format of
7285 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
7286 If _FILE is added at the end of an option
7287 (e.g.@: @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
7288 then the output is to a file with the name @file{file_REP} where
7289 file is the name of the corresponding source file.
7291 Note that it is possible for record components to have zero size. In
7292 this case, the component clause uses an obvious extension of permitted
7293 Ada syntax, for example @code{at 0 range 0 .. -1}.
7295 Representation information requires that code be generated (since it is the
7296 code generator that lays out complex data structures). If an attempt is made
7297 to output representation information when no code is generated, for example
7298 when a subunit is compiled on its own, then no information can be generated
7299 and the compiler outputs a message to this effect.
7302 @cindex @option{-gnatS} (@command{gcc})
7303 The use of the switch @option{-gnatS} for an
7304 Ada compilation will cause the compiler to output a
7305 representation of package Standard in a form very
7306 close to standard Ada. It is not quite possible to
7307 do this entirely in standard Ada (since new
7308 numeric base types cannot be created in standard
7309 Ada), but the output is easily
7310 readable to any Ada programmer, and is useful to
7311 determine the characteristics of target dependent
7312 types in package Standard.
7315 @cindex @option{-gnatx} (@command{gcc})
7316 Normally the compiler generates full cross-referencing information in
7317 the @file{ALI} file. This information is used by a number of tools,
7318 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
7319 suppresses this information. This saves some space and may slightly
7320 speed up compilation, but means that these tools cannot be used.
7323 @node Exception Handling Control
7324 @subsection Exception Handling Control
7327 GNAT uses two methods for handling exceptions at run-time. The
7328 @code{setjmp/longjmp} method saves the context when entering
7329 a frame with an exception handler. Then when an exception is
7330 raised, the context can be restored immediately, without the
7331 need for tracing stack frames. This method provides very fast
7332 exception propagation, but introduces significant overhead for
7333 the use of exception handlers, even if no exception is raised.
7335 The other approach is called ``zero cost'' exception handling.
7336 With this method, the compiler builds static tables to describe
7337 the exception ranges. No dynamic code is required when entering
7338 a frame containing an exception handler. When an exception is
7339 raised, the tables are used to control a back trace of the
7340 subprogram invocation stack to locate the required exception
7341 handler. This method has considerably poorer performance for
7342 the propagation of exceptions, but there is no overhead for
7343 exception handlers if no exception is raised. Note that in this
7344 mode and in the context of mixed Ada and C/C++ programming,
7345 to propagate an exception through a C/C++ code, the C/C++ code
7346 must be compiled with the @option{-funwind-tables} GCC's
7349 The following switches may be used to control which of the
7350 two exception handling methods is used.
7356 @cindex @option{--RTS=sjlj} (@command{gnatmake})
7357 This switch causes the setjmp/longjmp run-time (when available) to be used
7358 for exception handling. If the default
7359 mechanism for the target is zero cost exceptions, then
7360 this switch can be used to modify this default, and must be
7361 used for all units in the partition.
7362 This option is rarely used. One case in which it may be
7363 advantageous is if you have an application where exception
7364 raising is common and the overall performance of the
7365 application is improved by favoring exception propagation.
7368 @cindex @option{--RTS=zcx} (@command{gnatmake})
7369 @cindex Zero Cost Exceptions
7370 This switch causes the zero cost approach to be used
7371 for exception handling. If this is the default mechanism for the
7372 target (see below), then this switch is unneeded. If the default
7373 mechanism for the target is setjmp/longjmp exceptions, then
7374 this switch can be used to modify this default, and must be
7375 used for all units in the partition.
7376 This option can only be used if the zero cost approach
7377 is available for the target in use, otherwise it will generate an error.
7381 The same option @option{--RTS} must be used both for @command{gcc}
7382 and @command{gnatbind}. Passing this option to @command{gnatmake}
7383 (@pxref{Switches for gnatmake}) will ensure the required consistency
7384 through the compilation and binding steps.
7386 @node Units to Sources Mapping Files
7387 @subsection Units to Sources Mapping Files
7391 @item -gnatem^^=^@var{path}
7392 @cindex @option{-gnatem} (@command{gcc})
7393 A mapping file is a way to communicate to the compiler two mappings:
7394 from unit names to file names (without any directory information) and from
7395 file names to path names (with full directory information). These mappings
7396 are used by the compiler to short-circuit the path search.
7398 The use of mapping files is not required for correct operation of the
7399 compiler, but mapping files can improve efficiency, particularly when
7400 sources are read over a slow network connection. In normal operation,
7401 you need not be concerned with the format or use of mapping files,
7402 and the @option{-gnatem} switch is not a switch that you would use
7403 explicitly. it is intended only for use by automatic tools such as
7404 @command{gnatmake} running under the project file facility. The
7405 description here of the format of mapping files is provided
7406 for completeness and for possible use by other tools.
7408 A mapping file is a sequence of sets of three lines. In each set,
7409 the first line is the unit name, in lower case, with ``@code{%s}''
7411 specs and ``@code{%b}'' appended for bodies; the second line is the
7412 file name; and the third line is the path name.
7418 /gnat/project1/sources/main.2.ada
7421 When the switch @option{-gnatem} is specified, the compiler will create
7422 in memory the two mappings from the specified file. If there is any problem
7423 (nonexistent file, truncated file or duplicate entries), no mapping will
7426 Several @option{-gnatem} switches may be specified; however, only the last
7427 one on the command line will be taken into account.
7429 When using a project file, @command{gnatmake} create a temporary mapping file
7430 and communicates it to the compiler using this switch.
7434 @node Integrated Preprocessing
7435 @subsection Integrated Preprocessing
7438 GNAT sources may be preprocessed immediately before compilation.
7439 In this case, the actual
7440 text of the source is not the text of the source file, but is derived from it
7441 through a process called preprocessing. Integrated preprocessing is specified
7442 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
7443 indicates, through a text file, the preprocessing data to be used.
7444 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
7447 Note that when integrated preprocessing is used, the output from the
7448 preprocessor is not written to any external file. Instead it is passed
7449 internally to the compiler. If you need to preserve the result of
7450 preprocessing in a file, then you should use @command{gnatprep}
7451 to perform the desired preprocessing in stand-alone mode.
7454 It is recommended that @command{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
7455 used when Integrated Preprocessing is used. The reason is that preprocessing
7456 with another Preprocessing Data file without changing the sources will
7457 not trigger recompilation without this switch.
7460 Note that @command{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
7461 always trigger recompilation for sources that are preprocessed,
7462 because @command{gnatmake} cannot compute the checksum of the source after
7466 The actual preprocessing function is described in details in section
7467 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
7468 preprocessing is triggered and parameterized.
7472 @item -gnatep=@var{file}
7473 @cindex @option{-gnatep} (@command{gcc})
7474 This switch indicates to the compiler the file name (without directory
7475 information) of the preprocessor data file to use. The preprocessor data file
7476 should be found in the source directories.
7479 A preprocessing data file is a text file with significant lines indicating
7480 how should be preprocessed either a specific source or all sources not
7481 mentioned in other lines. A significant line is a nonempty, non-comment line.
7482 Comments are similar to Ada comments.
7485 Each significant line starts with either a literal string or the character '*'.
7486 A literal string is the file name (without directory information) of the source
7487 to preprocess. A character '*' indicates the preprocessing for all the sources
7488 that are not specified explicitly on other lines (order of the lines is not
7489 significant). It is an error to have two lines with the same file name or two
7490 lines starting with the character '*'.
7493 After the file name or the character '*', another optional literal string
7494 indicating the file name of the definition file to be used for preprocessing
7495 (@pxref{Form of Definitions File}). The definition files are found by the
7496 compiler in one of the source directories. In some cases, when compiling
7497 a source in a directory other than the current directory, if the definition
7498 file is in the current directory, it may be necessary to add the current
7499 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
7500 the compiler would not find the definition file.
7503 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
7504 be found. Those ^switches^switches^ are:
7509 Causes both preprocessor lines and the lines deleted by
7510 preprocessing to be replaced by blank lines, preserving the line number.
7511 This ^switch^switch^ is always implied; however, if specified after @option{-c}
7512 it cancels the effect of @option{-c}.
7515 Causes both preprocessor lines and the lines deleted
7516 by preprocessing to be retained as comments marked
7517 with the special string ``@code{--! }''.
7519 @item -Dsymbol=value
7520 Define or redefine a symbol, associated with value. A symbol is an Ada
7521 identifier, or an Ada reserved word, with the exception of @code{if},
7522 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7523 @code{value} is either a literal string, an Ada identifier or any Ada reserved
7524 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
7525 same name defined in a definition file.
7528 Causes a sorted list of symbol names and values to be
7529 listed on the standard output file.
7532 Causes undefined symbols to be treated as having the value @code{FALSE}
7534 of a preprocessor test. In the absence of this option, an undefined symbol in
7535 a @code{#if} or @code{#elsif} test will be treated as an error.
7540 Examples of valid lines in a preprocessor data file:
7543 "toto.adb" "prep.def" -u
7544 -- preprocess "toto.adb", using definition file "prep.def",
7545 -- undefined symbol are False.
7548 -- preprocess all other sources without a definition file;
7549 -- suppressed lined are commented; symbol VERSION has the value V101.
7551 "titi.adb" "prep2.def" -s
7552 -- preprocess "titi.adb", using definition file "prep2.def";
7553 -- list all symbols with their values.
7556 @item ^-gnateD^/DATA_PREPROCESSING=^symbol@r{[}=value@r{]}
7557 @cindex @option{-gnateD} (@command{gcc})
7558 Define or redefine a preprocessing symbol, associated with value. If no value
7559 is given on the command line, then the value of the symbol is @code{True}.
7560 A symbol is an identifier, following normal Ada (case-insensitive)
7561 rules for its syntax, and value is any sequence (including an empty sequence)
7562 of characters from the set (letters, digits, period, underline).
7563 Ada reserved words may be used as symbols, with the exceptions of @code{if},
7564 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
7567 A symbol declared with this ^switch^switch^ on the command line replaces a
7568 symbol with the same name either in a definition file or specified with a
7569 ^switch^switch^ -D in the preprocessor data file.
7572 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
7575 When integrated preprocessing is performed and the preprocessor modifies
7576 the source text, write the result of this preprocessing into a file
7577 <source>^.prep^_prep^.
7581 @node Code Generation Control
7582 @subsection Code Generation Control
7586 The GCC technology provides a wide range of target dependent
7587 @option{-m} switches for controlling
7588 details of code generation with respect to different versions of
7589 architectures. This includes variations in instruction sets (e.g.@:
7590 different members of the power pc family), and different requirements
7591 for optimal arrangement of instructions (e.g.@: different members of
7592 the x86 family). The list of available @option{-m} switches may be
7593 found in the GCC documentation.
7595 Use of these @option{-m} switches may in some cases result in improved
7598 The GNAT Pro technology is tested and qualified without any
7599 @option{-m} switches,
7600 so generally the most reliable approach is to avoid the use of these
7601 switches. However, we generally expect most of these switches to work
7602 successfully with GNAT Pro, and many customers have reported successful
7603 use of these options.
7605 Our general advice is to avoid the use of @option{-m} switches unless
7606 special needs lead to requirements in this area. In particular,
7607 there is no point in using @option{-m} switches to improve performance
7608 unless you actually see a performance improvement.
7612 @subsection Return Codes
7613 @cindex Return Codes
7614 @cindex @option{/RETURN_CODES=VMS}
7617 On VMS, GNAT compiled programs return POSIX-style codes by default,
7618 e.g.@: @option{/RETURN_CODES=POSIX}.
7620 To enable VMS style return codes, use GNAT BIND and LINK with the option
7621 @option{/RETURN_CODES=VMS}. For example:
7624 GNAT BIND MYMAIN.ALI /RETURN_CODES=VMS
7625 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
7629 Programs built with /RETURN_CODES=VMS are suitable to be called in
7630 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
7631 are suitable for spawning with appropriate GNAT RTL routines.
7635 @node Search Paths and the Run-Time Library (RTL)
7636 @section Search Paths and the Run-Time Library (RTL)
7639 With the GNAT source-based library system, the compiler must be able to
7640 find source files for units that are needed by the unit being compiled.
7641 Search paths are used to guide this process.
7643 The compiler compiles one source file whose name must be given
7644 explicitly on the command line. In other words, no searching is done
7645 for this file. To find all other source files that are needed (the most
7646 common being the specs of units), the compiler examines the following
7647 directories, in the following order:
7651 The directory containing the source file of the main unit being compiled
7652 (the file name on the command line).
7655 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
7656 @command{gcc} command line, in the order given.
7659 @findex ADA_PRJ_INCLUDE_FILE
7660 Each of the directories listed in the text file whose name is given
7661 by the @env{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
7664 @env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7665 driver when project files are used. It should not normally be set
7669 @findex ADA_INCLUDE_PATH
7670 Each of the directories listed in the value of the
7671 @env{ADA_INCLUDE_PATH} ^environment variable^logical name^.
7673 Construct this value
7674 exactly as the @env{PATH} environment variable: a list of directory
7675 names separated by colons (semicolons when working with the NT version).
7678 Normally, define this value as a logical name containing a comma separated
7679 list of directory names.
7681 This variable can also be defined by means of an environment string
7682 (an argument to the HP C exec* set of functions).
7686 DEFINE ANOTHER_PATH FOO:[BAG]
7687 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7690 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7691 first, followed by the standard Ada
7692 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
7693 If this is not redefined, the user will obtain the HP Ada 83 IO packages
7694 (Text_IO, Sequential_IO, etc)
7695 instead of the standard Ada packages. Thus, in order to get the standard Ada
7696 packages by default, ADA_INCLUDE_PATH must be redefined.
7700 The content of the @file{ada_source_path} file which is part of the GNAT
7701 installation tree and is used to store standard libraries such as the
7702 GNAT Run Time Library (RTL) source files.
7704 @ref{Installing a library}
7709 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
7710 inhibits the use of the directory
7711 containing the source file named in the command line. You can still
7712 have this directory on your search path, but in this case it must be
7713 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
7715 Specifying the switch @option{-nostdinc}
7716 inhibits the search of the default location for the GNAT Run Time
7717 Library (RTL) source files.
7719 The compiler outputs its object files and ALI files in the current
7722 Caution: The object file can be redirected with the @option{-o} switch;
7723 however, @command{gcc} and @code{gnat1} have not been coordinated on this
7724 so the @file{ALI} file will not go to the right place. Therefore, you should
7725 avoid using the @option{-o} switch.
7729 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7730 children make up the GNAT RTL, together with the simple @code{System.IO}
7731 package used in the @code{"Hello World"} example. The sources for these units
7732 are needed by the compiler and are kept together in one directory. Not
7733 all of the bodies are needed, but all of the sources are kept together
7734 anyway. In a normal installation, you need not specify these directory
7735 names when compiling or binding. Either the environment variables or
7736 the built-in defaults cause these files to be found.
7738 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
7739 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
7740 consisting of child units of @code{GNAT}. This is a collection of generally
7741 useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About
7742 This Guid, gnat_rm, GNAT Reference Manual}, for further details.
7744 Besides simplifying access to the RTL, a major use of search paths is
7745 in compiling sources from multiple directories. This can make
7746 development environments much more flexible.
7748 @node Order of Compilation Issues
7749 @section Order of Compilation Issues
7752 If, in our earlier example, there was a spec for the @code{hello}
7753 procedure, it would be contained in the file @file{hello.ads}; yet this
7754 file would not have to be explicitly compiled. This is the result of the
7755 model we chose to implement library management. Some of the consequences
7756 of this model are as follows:
7760 There is no point in compiling specs (except for package
7761 specs with no bodies) because these are compiled as needed by clients. If
7762 you attempt a useless compilation, you will receive an error message.
7763 It is also useless to compile subunits because they are compiled as needed
7767 There are no order of compilation requirements: performing a
7768 compilation never obsoletes anything. The only way you can obsolete
7769 something and require recompilations is to modify one of the
7770 source files on which it depends.
7773 There is no library as such, apart from the ALI files
7774 (@pxref{The Ada Library Information Files}, for information on the format
7775 of these files). For now we find it convenient to create separate ALI files,
7776 but eventually the information therein may be incorporated into the object
7780 When you compile a unit, the source files for the specs of all units
7781 that it @code{with}'s, all its subunits, and the bodies of any generics it
7782 instantiates must be available (reachable by the search-paths mechanism
7783 described above), or you will receive a fatal error message.
7790 The following are some typical Ada compilation command line examples:
7793 @item $ gcc -c xyz.adb
7794 Compile body in file @file{xyz.adb} with all default options.
7797 @item $ gcc -c -O2 -gnata xyz-def.adb
7800 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
7803 Compile the child unit package in file @file{xyz-def.adb} with extensive
7804 optimizations, and pragma @code{Assert}/@code{Debug} statements
7807 @item $ gcc -c -gnatc abc-def.adb
7808 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
7812 @node Binding Using gnatbind
7813 @chapter Binding Using @code{gnatbind}
7817 * Running gnatbind::
7818 * Switches for gnatbind::
7819 * Command-Line Access::
7820 * Search Paths for gnatbind::
7821 * Examples of gnatbind Usage::
7825 This chapter describes the GNAT binder, @code{gnatbind}, which is used
7826 to bind compiled GNAT objects.
7828 Note: to invoke @code{gnatbind} with a project file, use the @code{gnat}
7829 driver (see @ref{The GNAT Driver and Project Files}).
7831 The @code{gnatbind} program performs four separate functions:
7835 Checks that a program is consistent, in accordance with the rules in
7836 Chapter 10 of the Ada Reference Manual. In particular, error
7837 messages are generated if a program uses inconsistent versions of a
7841 Checks that an acceptable order of elaboration exists for the program
7842 and issues an error message if it cannot find an order of elaboration
7843 that satisfies the rules in Chapter 10 of the Ada Language Manual.
7846 Generates a main program incorporating the given elaboration order.
7847 This program is a small Ada package (body and spec) that
7848 must be subsequently compiled
7849 using the GNAT compiler. The necessary compilation step is usually
7850 performed automatically by @command{gnatlink}. The two most important
7851 functions of this program
7852 are to call the elaboration routines of units in an appropriate order
7853 and to call the main program.
7856 Determines the set of object files required by the given main program.
7857 This information is output in the forms of comments in the generated program,
7858 to be read by the @command{gnatlink} utility used to link the Ada application.
7861 @node Running gnatbind
7862 @section Running @code{gnatbind}
7865 The form of the @code{gnatbind} command is
7868 $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches}
7872 where @file{@var{mainprog}.adb} is the Ada file containing the main program
7873 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
7874 package in two files whose names are
7875 @file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}.
7876 For example, if given the
7877 parameter @file{hello.ali}, for a main program contained in file
7878 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
7879 and @file{b~hello.adb}.
7881 When doing consistency checking, the binder takes into consideration
7882 any source files it can locate. For example, if the binder determines
7883 that the given main program requires the package @code{Pack}, whose
7885 file is @file{pack.ali} and whose corresponding source spec file is
7886 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
7887 (using the same search path conventions as previously described for the
7888 @command{gcc} command). If it can locate this source file, it checks that
7890 or source checksums of the source and its references to in @file{ALI} files
7891 match. In other words, any @file{ALI} files that mentions this spec must have
7892 resulted from compiling this version of the source file (or in the case
7893 where the source checksums match, a version close enough that the
7894 difference does not matter).
7896 @cindex Source files, use by binder
7897 The effect of this consistency checking, which includes source files, is
7898 that the binder ensures that the program is consistent with the latest
7899 version of the source files that can be located at bind time. Editing a
7900 source file without compiling files that depend on the source file cause
7901 error messages to be generated by the binder.
7903 For example, suppose you have a main program @file{hello.adb} and a
7904 package @code{P}, from file @file{p.ads} and you perform the following
7909 Enter @code{gcc -c hello.adb} to compile the main program.
7912 Enter @code{gcc -c p.ads} to compile package @code{P}.
7915 Edit file @file{p.ads}.
7918 Enter @code{gnatbind hello}.
7922 At this point, the file @file{p.ali} contains an out-of-date time stamp
7923 because the file @file{p.ads} has been edited. The attempt at binding
7924 fails, and the binder generates the following error messages:
7927 error: "hello.adb" must be recompiled ("p.ads" has been modified)
7928 error: "p.ads" has been modified and must be recompiled
7932 Now both files must be recompiled as indicated, and then the bind can
7933 succeed, generating a main program. You need not normally be concerned
7934 with the contents of this file, but for reference purposes a sample
7935 binder output file is given in @ref{Example of Binder Output File}.
7937 In most normal usage, the default mode of @command{gnatbind} which is to
7938 generate the main package in Ada, as described in the previous section.
7939 In particular, this means that any Ada programmer can read and understand
7940 the generated main program. It can also be debugged just like any other
7941 Ada code provided the @option{^-g^/DEBUG^} switch is used for
7942 @command{gnatbind} and @command{gnatlink}.
7944 However for some purposes it may be convenient to generate the main
7945 program in C rather than Ada. This may for example be helpful when you
7946 are generating a mixed language program with the main program in C. The
7947 GNAT compiler itself is an example.
7948 The use of the @option{^-C^/BIND_FILE=C^} switch
7949 for both @code{gnatbind} and @command{gnatlink} will cause the program to
7950 be generated in C (and compiled using the gnu C compiler).
7952 @node Switches for gnatbind
7953 @section Switches for @command{gnatbind}
7956 The following switches are available with @code{gnatbind}; details will
7957 be presented in subsequent sections.
7960 * Consistency-Checking Modes::
7961 * Binder Error Message Control::
7962 * Elaboration Control::
7964 * Binding with Non-Ada Main Programs::
7965 * Binding Programs with No Main Subprogram::
7972 @cindex @option{--version} @command{gnatbind}
7973 Display Copyright and version, then exit disregarding all other options.
7976 @cindex @option{--help} @command{gnatbind}
7977 If @option{--version} was not used, display usage, then exit disregarding
7981 @cindex @option{-a} @command{gnatbind}
7982 Indicates that, if supported by the platform, the adainit procedure should
7983 be treated as an initialisation routine by the linker (a constructor). This
7984 is intended to be used by the Project Manager to automatically initialize
7985 shared Stand-Alone Libraries.
7987 @item ^-aO^/OBJECT_SEARCH^
7988 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
7989 Specify directory to be searched for ALI files.
7991 @item ^-aI^/SOURCE_SEARCH^
7992 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7993 Specify directory to be searched for source file.
7995 @item ^-A^/BIND_FILE=ADA^
7996 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
7997 Generate binder program in Ada (default)
7999 @item ^-b^/REPORT_ERRORS=BRIEF^
8000 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
8001 Generate brief messages to @file{stderr} even if verbose mode set.
8003 @item ^-c^/NOOUTPUT^
8004 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
8005 Check only, no generation of binder output file.
8007 @item ^-C^/BIND_FILE=C^
8008 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
8009 Generate binder program in C
8011 @item ^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8012 @cindex @option{^-d^/DEFAULT_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind})
8013 This switch can be used to change the default task stack size value
8014 to a specified size @var{nn}, which is expressed in bytes by default, or
8015 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8017 In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent,
8018 in effect, to completing all task specs with
8019 @smallexample @c ada
8020 pragma Storage_Size (nn);
8022 When they do not already have such a pragma.
8024 @item ^-D^/DEFAULT_SECONDARY_STACK_SIZE=^@var{nn}@r{[}k@r{|}m@r{]}
8025 @cindex @option{^-D^/DEFAULT_SECONDARY_STACK_SIZE=nnnnn^} (@command{gnatbind})
8026 This switch can be used to change the default secondary stack size value
8027 to a specified size @var{nn}, which is expressed in bytes by default, or
8028 in kilobytes when suffixed with @var{k} or in megabytes when suffixed
8031 The secondary stack is used to deal with functions that return a variable
8032 sized result, for example a function returning an unconstrained
8033 String. There are two ways in which this secondary stack is allocated.
8035 For most targets, the secondary stack is growing on demand and is allocated
8036 as a chain of blocks in the heap. The -D option is not very
8037 relevant. It only give some control over the size of the allocated
8038 blocks (whose size is the minimum of the default secondary stack size value,
8039 and the actual size needed for the current allocation request).
8041 For certain targets, notably VxWorks 653,
8042 the secondary stack is allocated by carving off a fixed ratio chunk of the
8043 primary task stack. The -D option is used to define the
8044 size of the environment task's secondary stack.
8046 @item ^-e^/ELABORATION_DEPENDENCIES^
8047 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
8048 Output complete list of elaboration-order dependencies.
8050 @item ^-E^/STORE_TRACEBACKS^
8051 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
8052 Store tracebacks in exception occurrences when the target supports it.
8053 This is the default with the zero cost exception mechanism.
8055 @c The following may get moved to an appendix
8056 This option is currently supported on the following targets:
8057 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
8059 See also the packages @code{GNAT.Traceback} and
8060 @code{GNAT.Traceback.Symbolic} for more information.
8062 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
8063 @command{gcc} option.
8066 @item ^-F^/FORCE_ELABS_FLAGS^
8067 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
8068 Force the checks of elaboration flags. @command{gnatbind} does not normally
8069 generate checks of elaboration flags for the main executable, except when
8070 a Stand-Alone Library is used. However, there are cases when this cannot be
8071 detected by gnatbind. An example is importing an interface of a Stand-Alone
8072 Library through a pragma Import and only specifying through a linker switch
8073 this Stand-Alone Library. This switch is used to guarantee that elaboration
8074 flag checks are generated.
8077 @cindex @option{^-h^/HELP^} (@command{gnatbind})
8078 Output usage (help) information
8081 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8082 Specify directory to be searched for source and ALI files.
8084 @item ^-I-^/NOCURRENT_DIRECTORY^
8085 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
8086 Do not look for sources in the current directory where @code{gnatbind} was
8087 invoked, and do not look for ALI files in the directory containing the
8088 ALI file named in the @code{gnatbind} command line.
8090 @item ^-l^/ORDER_OF_ELABORATION^
8091 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
8092 Output chosen elaboration order.
8094 @item ^-L@var{xxx}^/BUILD_LIBRARY=@var{xxx}^
8095 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
8096 Bind the units for library building. In this case the adainit and
8097 adafinal procedures (@pxref{Binding with Non-Ada Main Programs})
8098 are renamed to ^@var{xxx}init^@var{XXX}INIT^ and
8099 ^@var{xxx}final^@var{XXX}FINAL^.
8100 Implies ^-n^/NOCOMPILE^.
8102 (@xref{GNAT and Libraries}, for more details.)
8105 On OpenVMS, these init and final procedures are exported in uppercase
8106 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
8107 the init procedure will be "TOTOINIT" and the exported name of the final
8108 procedure will be "TOTOFINAL".
8111 @item ^-Mxyz^/RENAME_MAIN=xyz^
8112 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
8113 Rename generated main program from main to xyz. This option is
8114 supported on cross environments only.
8116 @item ^-m^/ERROR_LIMIT=^@var{n}
8117 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
8118 Limit number of detected errors or warnings to @var{n}, where @var{n} is
8119 in the range 1..999999. The default value if no switch is
8120 given is 9999. If the number of warnings reaches this limit, then a
8121 message is output and further warnings are suppressed, the bind
8122 continues in this case. If the number of errors reaches this
8123 limit, then a message is output and the bind is abandoned.
8124 A value of zero means that no limit is enforced. The equal
8128 Furthermore, under Windows, the sources pointed to by the libraries path
8129 set in the registry are not searched for.
8133 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8137 @cindex @option{-nostdinc} (@command{gnatbind})
8138 Do not look for sources in the system default directory.
8141 @cindex @option{-nostdlib} (@command{gnatbind})
8142 Do not look for library files in the system default directory.
8144 @item --RTS=@var{rts-path}
8145 @cindex @option{--RTS} (@code{gnatbind})
8146 Specifies the default location of the runtime library. Same meaning as the
8147 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
8149 @item ^-o ^/OUTPUT=^@var{file}
8150 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
8151 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
8152 Note that if this option is used, then linking must be done manually,
8153 gnatlink cannot be used.
8155 @item ^-O^/OBJECT_LIST^
8156 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
8159 @item ^-p^/PESSIMISTIC_ELABORATION^
8160 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
8161 Pessimistic (worst-case) elaboration order
8164 @cindex @option{^-R^-R^} (@command{gnatbind})
8165 Output closure source list.
8167 @item ^-s^/READ_SOURCES=ALL^
8168 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
8169 Require all source files to be present.
8171 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
8172 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
8173 Specifies the value to be used when detecting uninitialized scalar
8174 objects with pragma Initialize_Scalars.
8175 The @var{xxx} ^string specified with the switch^option^ may be either
8177 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
8178 @item ``@option{^lo^LOW^}'' for the lowest possible value
8179 @item ``@option{^hi^HIGH^}'' for the highest possible value
8180 @item ``@option{@var{xx}}'' for a value consisting of repeated bytes with the
8181 value @code{16#@var{xx}#} (i.e., @var{xx} is a string of two hexadecimal digits).
8184 In addition, you can specify @option{-Sev} to indicate that the value is
8185 to be set at run time. In this case, the program will look for an environment
8186 @cindex GNAT_INIT_SCALARS
8187 variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one
8188 of @option{in/lo/hi/@var{xx}} with the same meanings as above.
8189 If no environment variable is found, or if it does not have a valid value,
8190 then the default is @option{in} (invalid values).
8194 @cindex @option{-static} (@code{gnatbind})
8195 Link against a static GNAT run time.
8198 @cindex @option{-shared} (@code{gnatbind})
8199 Link against a shared GNAT run time when available.
8202 @item ^-t^/NOTIME_STAMP_CHECK^
8203 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8204 Tolerate time stamp and other consistency errors
8206 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
8207 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
8208 Set the time slice value to @var{n} milliseconds. If the system supports
8209 the specification of a specific time slice value, then the indicated value
8210 is used. If the system does not support specific time slice values, but
8211 does support some general notion of round-robin scheduling, then any
8212 nonzero value will activate round-robin scheduling.
8214 A value of zero is treated specially. It turns off time
8215 slicing, and in addition, indicates to the tasking run time that the
8216 semantics should match as closely as possible the Annex D
8217 requirements of the Ada RM, and in particular sets the default
8218 scheduling policy to @code{FIFO_Within_Priorities}.
8220 @item ^-u@var{n}^/DYNAMIC_STACK_USAGE=@var{n}^
8221 @cindex @option{^-u^/DYNAMIC_STACK_USAGE^} (@code{gnatbind})
8222 Enable dynamic stack usage, with @var{n} results stored and displayed
8223 at program termination. A result is generated when a task
8224 terminates. Results that can't be stored are displayed on the fly, at
8225 task termination. This option is currently not supported on Itanium
8226 platforms. (See @ref{Dynamic Stack Usage Analysis} for details.)
8228 @item ^-v^/REPORT_ERRORS=VERBOSE^
8229 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8230 Verbose mode. Write error messages, header, summary output to
8235 @cindex @option{-w} (@code{gnatbind})
8236 Warning mode (@var{x}=s/e for suppress/treat as error)
8240 @item /WARNINGS=NORMAL
8241 @cindex @option{/WARNINGS} (@code{gnatbind})
8242 Normal warnings mode. Warnings are issued but ignored
8244 @item /WARNINGS=SUPPRESS
8245 @cindex @option{/WARNINGS} (@code{gnatbind})
8246 All warning messages are suppressed
8248 @item /WARNINGS=ERROR
8249 @cindex @option{/WARNINGS} (@code{gnatbind})
8250 Warning messages are treated as fatal errors
8253 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8254 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8255 Override default wide character encoding for standard Text_IO files.
8257 @item ^-x^/READ_SOURCES=NONE^
8258 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
8259 Exclude source files (check object consistency only).
8262 @item /READ_SOURCES=AVAILABLE
8263 @cindex @option{/READ_SOURCES} (@code{gnatbind})
8264 Default mode, in which sources are checked for consistency only if
8268 @item ^-y^/ENABLE_LEAP_SECONDS^
8269 @cindex @option{^-y^/ENABLE_LEAP_SECONDS^} (@code{gnatbind})
8270 Enable leap seconds support in @code{Ada.Calendar} and its children.
8272 @item ^-z^/ZERO_MAIN^
8273 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8279 You may obtain this listing of switches by running @code{gnatbind} with
8283 @node Consistency-Checking Modes
8284 @subsection Consistency-Checking Modes
8287 As described earlier, by default @code{gnatbind} checks
8288 that object files are consistent with one another and are consistent
8289 with any source files it can locate. The following switches control binder
8294 @item ^-s^/READ_SOURCES=ALL^
8295 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
8296 Require source files to be present. In this mode, the binder must be
8297 able to locate all source files that are referenced, in order to check
8298 their consistency. In normal mode, if a source file cannot be located it
8299 is simply ignored. If you specify this switch, a missing source
8302 @item ^-Wx^/WIDE_CHARACTER_ENCODING=^@var{e}
8303 @cindex @option{^-Wx^/WIDE_CHARACTER_ENCODING^} (@code{gnatbind})
8304 Override default wide character encoding for standard Text_IO files.
8305 Normally the default wide character encoding method used for standard
8306 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
8307 the main source input (see description of switch
8308 @option{^-gnatWx^/WIDE_CHARACTER_ENCODING^} for the compiler). The
8309 use of this switch for the binder (which has the same set of
8310 possible arguments) overrides this default as specified.
8312 @item ^-x^/READ_SOURCES=NONE^
8313 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
8314 Exclude source files. In this mode, the binder only checks that ALI
8315 files are consistent with one another. Source files are not accessed.
8316 The binder runs faster in this mode, and there is still a guarantee that
8317 the resulting program is self-consistent.
8318 If a source file has been edited since it was last compiled, and you
8319 specify this switch, the binder will not detect that the object
8320 file is out of date with respect to the source file. Note that this is the
8321 mode that is automatically used by @command{gnatmake} because in this
8322 case the checking against sources has already been performed by
8323 @command{gnatmake} in the course of compilation (i.e.@: before binding).
8326 @item /READ_SOURCES=AVAILABLE
8327 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
8328 This is the default mode in which source files are checked if they are
8329 available, and ignored if they are not available.
8333 @node Binder Error Message Control
8334 @subsection Binder Error Message Control
8337 The following switches provide control over the generation of error
8338 messages from the binder:
8342 @item ^-v^/REPORT_ERRORS=VERBOSE^
8343 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
8344 Verbose mode. In the normal mode, brief error messages are generated to
8345 @file{stderr}. If this switch is present, a header is written
8346 to @file{stdout} and any error messages are directed to @file{stdout}.
8347 All that is written to @file{stderr} is a brief summary message.
8349 @item ^-b^/REPORT_ERRORS=BRIEF^
8350 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
8351 Generate brief error messages to @file{stderr} even if verbose mode is
8352 specified. This is relevant only when used with the
8353 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
8357 @cindex @option{-m} (@code{gnatbind})
8358 Limits the number of error messages to @var{n}, a decimal integer in the
8359 range 1-999. The binder terminates immediately if this limit is reached.
8362 @cindex @option{-M} (@code{gnatbind})
8363 Renames the generated main program from @code{main} to @code{xxx}.
8364 This is useful in the case of some cross-building environments, where
8365 the actual main program is separate from the one generated
8369 @item ^-ws^/WARNINGS=SUPPRESS^
8370 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
8372 Suppress all warning messages.
8374 @item ^-we^/WARNINGS=ERROR^
8375 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
8376 Treat any warning messages as fatal errors.
8379 @item /WARNINGS=NORMAL
8380 Standard mode with warnings generated, but warnings do not get treated
8384 @item ^-t^/NOTIME_STAMP_CHECK^
8385 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
8386 @cindex Time stamp checks, in binder
8387 @cindex Binder consistency checks
8388 @cindex Consistency checks, in binder
8389 The binder performs a number of consistency checks including:
8393 Check that time stamps of a given source unit are consistent
8395 Check that checksums of a given source unit are consistent
8397 Check that consistent versions of @code{GNAT} were used for compilation
8399 Check consistency of configuration pragmas as required
8403 Normally failure of such checks, in accordance with the consistency
8404 requirements of the Ada Reference Manual, causes error messages to be
8405 generated which abort the binder and prevent the output of a binder
8406 file and subsequent link to obtain an executable.
8408 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
8409 into warnings, so that
8410 binding and linking can continue to completion even in the presence of such
8411 errors. The result may be a failed link (due to missing symbols), or a
8412 non-functional executable which has undefined semantics.
8413 @emph{This means that
8414 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
8418 @node Elaboration Control
8419 @subsection Elaboration Control
8422 The following switches provide additional control over the elaboration
8423 order. For full details see @ref{Elaboration Order Handling in GNAT}.
8426 @item ^-p^/PESSIMISTIC_ELABORATION^
8427 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
8428 Normally the binder attempts to choose an elaboration order that is
8429 likely to minimize the likelihood of an elaboration order error resulting
8430 in raising a @code{Program_Error} exception. This switch reverses the
8431 action of the binder, and requests that it deliberately choose an order
8432 that is likely to maximize the likelihood of an elaboration error.
8433 This is useful in ensuring portability and avoiding dependence on
8434 accidental fortuitous elaboration ordering.
8436 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
8438 elaboration checking is used (@option{-gnatE} switch used for compilation).
8439 This is because in the default static elaboration mode, all necessary
8440 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
8441 These implicit pragmas are still respected by the binder in
8442 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
8443 safe elaboration order is assured.
8446 @node Output Control
8447 @subsection Output Control
8450 The following switches allow additional control over the output
8451 generated by the binder.
8456 @item ^-A^/BIND_FILE=ADA^
8457 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
8458 Generate binder program in Ada (default). The binder program is named
8459 @file{b~@var{mainprog}.adb} by default. This can be changed with
8460 @option{^-o^/OUTPUT^} @code{gnatbind} option.
8462 @item ^-c^/NOOUTPUT^
8463 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
8464 Check only. Do not generate the binder output file. In this mode the
8465 binder performs all error checks but does not generate an output file.
8467 @item ^-C^/BIND_FILE=C^
8468 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
8469 Generate binder program in C. The binder program is named
8470 @file{b_@var{mainprog}.c}.
8471 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
8474 @item ^-e^/ELABORATION_DEPENDENCIES^
8475 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
8476 Output complete list of elaboration-order dependencies, showing the
8477 reason for each dependency. This output can be rather extensive but may
8478 be useful in diagnosing problems with elaboration order. The output is
8479 written to @file{stdout}.
8482 @cindex @option{^-h^/HELP^} (@code{gnatbind})
8483 Output usage information. The output is written to @file{stdout}.
8485 @item ^-K^/LINKER_OPTION_LIST^
8486 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
8487 Output linker options to @file{stdout}. Includes library search paths,
8488 contents of pragmas Ident and Linker_Options, and libraries added
8491 @item ^-l^/ORDER_OF_ELABORATION^
8492 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
8493 Output chosen elaboration order. The output is written to @file{stdout}.
8495 @item ^-O^/OBJECT_LIST^
8496 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
8497 Output full names of all the object files that must be linked to provide
8498 the Ada component of the program. The output is written to @file{stdout}.
8499 This list includes the files explicitly supplied and referenced by the user
8500 as well as implicitly referenced run-time unit files. The latter are
8501 omitted if the corresponding units reside in shared libraries. The
8502 directory names for the run-time units depend on the system configuration.
8504 @item ^-o ^/OUTPUT=^@var{file}
8505 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
8506 Set name of output file to @var{file} instead of the normal
8507 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
8508 binder generated body filename. In C mode you would normally give
8509 @var{file} an extension of @file{.c} because it will be a C source program.
8510 Note that if this option is used, then linking must be done manually.
8511 It is not possible to use gnatlink in this case, since it cannot locate
8514 @item ^-r^/RESTRICTION_LIST^
8515 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
8516 Generate list of @code{pragma Restrictions} that could be applied to
8517 the current unit. This is useful for code audit purposes, and also may
8518 be used to improve code generation in some cases.
8522 @node Binding with Non-Ada Main Programs
8523 @subsection Binding with Non-Ada Main Programs
8526 In our description so far we have assumed that the main
8527 program is in Ada, and that the task of the binder is to generate a
8528 corresponding function @code{main} that invokes this Ada main
8529 program. GNAT also supports the building of executable programs where
8530 the main program is not in Ada, but some of the called routines are
8531 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
8532 The following switch is used in this situation:
8536 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
8537 No main program. The main program is not in Ada.
8541 In this case, most of the functions of the binder are still required,
8542 but instead of generating a main program, the binder generates a file
8543 containing the following callable routines:
8548 You must call this routine to initialize the Ada part of the program by
8549 calling the necessary elaboration routines. A call to @code{adainit} is
8550 required before the first call to an Ada subprogram.
8552 Note that it is assumed that the basic execution environment must be setup
8553 to be appropriate for Ada execution at the point where the first Ada
8554 subprogram is called. In particular, if the Ada code will do any
8555 floating-point operations, then the FPU must be setup in an appropriate
8556 manner. For the case of the x86, for example, full precision mode is
8557 required. The procedure GNAT.Float_Control.Reset may be used to ensure
8558 that the FPU is in the right state.
8562 You must call this routine to perform any library-level finalization
8563 required by the Ada subprograms. A call to @code{adafinal} is required
8564 after the last call to an Ada subprogram, and before the program
8569 If the @option{^-n^/NOMAIN^} switch
8570 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
8571 @cindex Binder, multiple input files
8572 is given, more than one ALI file may appear on
8573 the command line for @code{gnatbind}. The normal @dfn{closure}
8574 calculation is performed for each of the specified units. Calculating
8575 the closure means finding out the set of units involved by tracing
8576 @code{with} references. The reason it is necessary to be able to
8577 specify more than one ALI file is that a given program may invoke two or
8578 more quite separate groups of Ada units.
8580 The binder takes the name of its output file from the last specified ALI
8581 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
8582 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
8583 The output is an Ada unit in source form that can
8584 be compiled with GNAT unless the -C switch is used in which case the
8585 output is a C source file, which must be compiled using the C compiler.
8586 This compilation occurs automatically as part of the @command{gnatlink}
8589 Currently the GNAT run time requires a FPU using 80 bits mode
8590 precision. Under targets where this is not the default it is required to
8591 call GNAT.Float_Control.Reset before using floating point numbers (this
8592 include float computation, float input and output) in the Ada code. A
8593 side effect is that this could be the wrong mode for the foreign code
8594 where floating point computation could be broken after this call.
8596 @node Binding Programs with No Main Subprogram
8597 @subsection Binding Programs with No Main Subprogram
8600 It is possible to have an Ada program which does not have a main
8601 subprogram. This program will call the elaboration routines of all the
8602 packages, then the finalization routines.
8604 The following switch is used to bind programs organized in this manner:
8607 @item ^-z^/ZERO_MAIN^
8608 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
8609 Normally the binder checks that the unit name given on the command line
8610 corresponds to a suitable main subprogram. When this switch is used,
8611 a list of ALI files can be given, and the execution of the program
8612 consists of elaboration of these units in an appropriate order. Note
8613 that the default wide character encoding method for standard Text_IO
8614 files is always set to Brackets if this switch is set (you can use
8616 @option{^-Wx^WIDE_CHARACTER_ENCODING^} to override this default).
8619 @node Command-Line Access
8620 @section Command-Line Access
8623 The package @code{Ada.Command_Line} provides access to the command-line
8624 arguments and program name. In order for this interface to operate
8625 correctly, the two variables
8637 are declared in one of the GNAT library routines. These variables must
8638 be set from the actual @code{argc} and @code{argv} values passed to the
8639 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
8640 generates the C main program to automatically set these variables.
8641 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
8642 set these variables. If they are not set, the procedures in
8643 @code{Ada.Command_Line} will not be available, and any attempt to use
8644 them will raise @code{Constraint_Error}. If command line access is
8645 required, your main program must set @code{gnat_argc} and
8646 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
8649 @node Search Paths for gnatbind
8650 @section Search Paths for @code{gnatbind}
8653 The binder takes the name of an ALI file as its argument and needs to
8654 locate source files as well as other ALI files to verify object consistency.
8656 For source files, it follows exactly the same search rules as @command{gcc}
8657 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
8658 directories searched are:
8662 The directory containing the ALI file named in the command line, unless
8663 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
8666 All directories specified by @option{^-I^/SEARCH^}
8667 switches on the @code{gnatbind}
8668 command line, in the order given.
8671 @findex ADA_PRJ_OBJECTS_FILE
8672 Each of the directories listed in the text file whose name is given
8673 by the @env{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
8676 @env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
8677 driver when project files are used. It should not normally be set
8681 @findex ADA_OBJECTS_PATH
8682 Each of the directories listed in the value of the
8683 @env{ADA_OBJECTS_PATH} ^environment variable^logical name^.
8685 Construct this value
8686 exactly as the @env{PATH} environment variable: a list of directory
8687 names separated by colons (semicolons when working with the NT version
8691 Normally, define this value as a logical name containing a comma separated
8692 list of directory names.
8694 This variable can also be defined by means of an environment string
8695 (an argument to the HP C exec* set of functions).
8699 DEFINE ANOTHER_PATH FOO:[BAG]
8700 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
8703 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
8704 first, followed by the standard Ada
8705 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
8706 If this is not redefined, the user will obtain the HP Ada 83 IO packages
8707 (Text_IO, Sequential_IO, etc)
8708 instead of the standard Ada packages. Thus, in order to get the standard Ada
8709 packages by default, ADA_OBJECTS_PATH must be redefined.
8713 The content of the @file{ada_object_path} file which is part of the GNAT
8714 installation tree and is used to store standard libraries such as the
8715 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
8718 @ref{Installing a library}
8723 In the binder the switch @option{^-I^/SEARCH^}
8724 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
8725 is used to specify both source and
8726 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8727 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
8728 instead if you want to specify
8729 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
8730 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
8731 if you want to specify library paths
8732 only. This means that for the binder
8733 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
8734 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
8735 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
8736 The binder generates the bind file (a C language source file) in the
8737 current working directory.
8743 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8744 children make up the GNAT Run-Time Library, together with the package
8745 GNAT and its children, which contain a set of useful additional
8746 library functions provided by GNAT. The sources for these units are
8747 needed by the compiler and are kept together in one directory. The ALI
8748 files and object files generated by compiling the RTL are needed by the
8749 binder and the linker and are kept together in one directory, typically
8750 different from the directory containing the sources. In a normal
8751 installation, you need not specify these directory names when compiling
8752 or binding. Either the environment variables or the built-in defaults
8753 cause these files to be found.
8755 Besides simplifying access to the RTL, a major use of search paths is
8756 in compiling sources from multiple directories. This can make
8757 development environments much more flexible.
8759 @node Examples of gnatbind Usage
8760 @section Examples of @code{gnatbind} Usage
8763 This section contains a number of examples of using the GNAT binding
8764 utility @code{gnatbind}.
8767 @item gnatbind hello
8768 The main program @code{Hello} (source program in @file{hello.adb}) is
8769 bound using the standard switch settings. The generated main program is
8770 @file{b~hello.adb}. This is the normal, default use of the binder.
8773 @item gnatbind hello -o mainprog.adb
8776 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
8778 The main program @code{Hello} (source program in @file{hello.adb}) is
8779 bound using the standard switch settings. The generated main program is
8780 @file{mainprog.adb} with the associated spec in
8781 @file{mainprog.ads}. Note that you must specify the body here not the
8782 spec, in the case where the output is in Ada. Note that if this option
8783 is used, then linking must be done manually, since gnatlink will not
8784 be able to find the generated file.
8787 @item gnatbind main -C -o mainprog.c -x
8790 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
8792 The main program @code{Main} (source program in
8793 @file{main.adb}) is bound, excluding source files from the
8794 consistency checking, generating
8795 the file @file{mainprog.c}.
8798 @item gnatbind -x main_program -C -o mainprog.c
8799 This command is exactly the same as the previous example. Switches may
8800 appear anywhere in the command line, and single letter switches may be
8801 combined into a single switch.
8805 @item gnatbind -n math dbase -C -o ada-control.c
8808 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
8810 The main program is in a language other than Ada, but calls to
8811 subprograms in packages @code{Math} and @code{Dbase} appear. This call
8812 to @code{gnatbind} generates the file @file{ada-control.c} containing
8813 the @code{adainit} and @code{adafinal} routines to be called before and
8814 after accessing the Ada units.
8817 @c ------------------------------------
8818 @node Linking Using gnatlink
8819 @chapter Linking Using @command{gnatlink}
8820 @c ------------------------------------
8824 This chapter discusses @command{gnatlink}, a tool that links
8825 an Ada program and builds an executable file. This utility
8826 invokes the system linker ^(via the @command{gcc} command)^^
8827 with a correct list of object files and library references.
8828 @command{gnatlink} automatically determines the list of files and
8829 references for the Ada part of a program. It uses the binder file
8830 generated by the @command{gnatbind} to determine this list.
8832 Note: to invoke @code{gnatlink} with a project file, use the @code{gnat}
8833 driver (see @ref{The GNAT Driver and Project Files}).
8836 * Running gnatlink::
8837 * Switches for gnatlink::
8840 @node Running gnatlink
8841 @section Running @command{gnatlink}
8844 The form of the @command{gnatlink} command is
8847 $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]}
8848 @ovar{non-Ada objects} @ovar{linker options}
8852 The arguments of @command{gnatlink} (switches, main @file{ALI} file,
8854 or linker options) may be in any order, provided that no non-Ada object may
8855 be mistaken for a main @file{ALI} file.
8856 Any file name @file{F} without the @file{.ali}
8857 extension will be taken as the main @file{ALI} file if a file exists
8858 whose name is the concatenation of @file{F} and @file{.ali}.
8861 @file{@var{mainprog}.ali} references the ALI file of the main program.
8862 The @file{.ali} extension of this file can be omitted. From this
8863 reference, @command{gnatlink} locates the corresponding binder file
8864 @file{b~@var{mainprog}.adb} and, using the information in this file along
8865 with the list of non-Ada objects and linker options, constructs a
8866 linker command file to create the executable.
8868 The arguments other than the @command{gnatlink} switches and the main
8869 @file{ALI} file are passed to the linker uninterpreted.
8870 They typically include the names of
8871 object files for units written in other languages than Ada and any library
8872 references required to resolve references in any of these foreign language
8873 units, or in @code{Import} pragmas in any Ada units.
8875 @var{linker options} is an optional list of linker specific
8877 The default linker called by gnatlink is @command{gcc} which in
8878 turn calls the appropriate system linker.
8879 Standard options for the linker such as @option{-lmy_lib} or
8880 @option{-Ldir} can be added as is.
8881 For options that are not recognized by
8882 @command{gcc} as linker options, use the @command{gcc} switches
8883 @option{-Xlinker} or @option{-Wl,}.
8884 Refer to the GCC documentation for
8885 details. Here is an example showing how to generate a linker map:
8888 $ ^gnatlink my_prog -Wl,-Map,MAPFILE^GNAT LINK my_prog.ali /MAP^
8891 Using @var{linker options} it is possible to set the program stack and
8894 See @ref{Setting Stack Size from gnatlink} and
8895 @ref{Setting Heap Size from gnatlink}.
8898 @command{gnatlink} determines the list of objects required by the Ada
8899 program and prepends them to the list of objects passed to the linker.
8900 @command{gnatlink} also gathers any arguments set by the use of
8901 @code{pragma Linker_Options} and adds them to the list of arguments
8902 presented to the linker.
8905 @command{gnatlink} accepts the following types of extra files on the command
8906 line: objects (@file{.OBJ}), libraries (@file{.OLB}), sharable images
8907 (@file{.EXE}), and options files (@file{.OPT}). These are recognized and
8908 handled according to their extension.
8911 @node Switches for gnatlink
8912 @section Switches for @command{gnatlink}
8915 The following switches are available with the @command{gnatlink} utility:
8921 @cindex @option{--version} @command{gnatlink}
8922 Display Copyright and version, then exit disregarding all other options.
8925 @cindex @option{--help} @command{gnatlink}
8926 If @option{--version} was not used, display usage, then exit disregarding
8929 @item ^-A^/BIND_FILE=ADA^
8930 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatlink})
8931 The binder has generated code in Ada. This is the default.
8933 @item ^-C^/BIND_FILE=C^
8934 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatlink})
8935 If instead of generating a file in Ada, the binder has generated one in
8936 C, then the linker needs to know about it. Use this switch to signal
8937 to @command{gnatlink} that the binder has generated C code rather than
8940 @item ^-f^/FORCE_OBJECT_FILE_LIST^
8941 @cindex Command line length
8942 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@command{gnatlink})
8943 On some targets, the command line length is limited, and @command{gnatlink}
8944 will generate a separate file for the linker if the list of object files
8946 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
8947 to be generated even if
8948 the limit is not exceeded. This is useful in some cases to deal with
8949 special situations where the command line length is exceeded.
8952 @cindex Debugging information, including
8953 @cindex @option{^-g^/DEBUG^} (@command{gnatlink})
8954 The option to include debugging information causes the Ada bind file (in
8955 other words, @file{b~@var{mainprog}.adb}) to be compiled with
8956 @option{^-g^/DEBUG^}.
8957 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
8958 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
8959 Without @option{^-g^/DEBUG^}, the binder removes these files by
8960 default. The same procedure apply if a C bind file was generated using
8961 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
8962 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
8964 @item ^-n^/NOCOMPILE^
8965 @cindex @option{^-n^/NOCOMPILE^} (@command{gnatlink})
8966 Do not compile the file generated by the binder. This may be used when
8967 a link is rerun with different options, but there is no need to recompile
8971 @cindex @option{^-v^/VERBOSE^} (@command{gnatlink})
8972 Causes additional information to be output, including a full list of the
8973 included object files. This switch option is most useful when you want
8974 to see what set of object files are being used in the link step.
8976 @item ^-v -v^/VERBOSE/VERBOSE^
8977 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@command{gnatlink})
8978 Very verbose mode. Requests that the compiler operate in verbose mode when
8979 it compiles the binder file, and that the system linker run in verbose mode.
8981 @item ^-o ^/EXECUTABLE=^@var{exec-name}
8982 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatlink})
8983 @var{exec-name} specifies an alternate name for the generated
8984 executable program. If this switch is omitted, the executable has the same
8985 name as the main unit. For example, @code{gnatlink try.ali} creates
8986 an executable called @file{^try^TRY.EXE^}.
8989 @item -b @var{target}
8990 @cindex @option{-b} (@command{gnatlink})
8991 Compile your program to run on @var{target}, which is the name of a
8992 system configuration. You must have a GNAT cross-compiler built if
8993 @var{target} is not the same as your host system.
8996 @cindex @option{-B} (@command{gnatlink})
8997 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8998 from @var{dir} instead of the default location. Only use this switch
8999 when multiple versions of the GNAT compiler are available.
9000 @xref{Directory Options,,, gcc, The GNU Compiler Collection},
9001 for further details. You would normally use the @option{-b} or
9002 @option{-V} switch instead.
9004 @item --GCC=@var{compiler_name}
9005 @cindex @option{--GCC=compiler_name} (@command{gnatlink})
9006 Program used for compiling the binder file. The default is
9007 @command{gcc}. You need to use quotes around @var{compiler_name} if
9008 @code{compiler_name} contains spaces or other separator characters.
9009 As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to
9010 use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
9011 inserted after your command name. Thus in the above example the compiler
9012 command that will be used by @command{gnatlink} will be @code{foo -c -x -y}.
9013 A limitation of this syntax is that the name and path name of the executable
9014 itself must not include any embedded spaces. If the compiler executable is
9015 different from the default one (gcc or <prefix>-gcc), then the back-end
9016 switches in the ALI file are not used to compile the binder generated source.
9017 For example, this is the case with @option{--GCC="foo -x -y"}. But the back end
9018 switches will be used for @option{--GCC="gcc -gnatv"}. If several
9019 @option{--GCC=compiler_name} are used, only the last @var{compiler_name}
9020 is taken into account. However, all the additional switches are also taken
9022 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9023 @option{--GCC="bar -x -y -z -t"}.
9025 @item --LINK=@var{name}
9026 @cindex @option{--LINK=} (@command{gnatlink})
9027 @var{name} is the name of the linker to be invoked. This is especially
9028 useful in mixed language programs since languages such as C++ require
9029 their own linker to be used. When this switch is omitted, the default
9030 name for the linker is @command{gcc}. When this switch is used, the
9031 specified linker is called instead of @command{gcc} with exactly the same
9032 parameters that would have been passed to @command{gcc} so if the desired
9033 linker requires different parameters it is necessary to use a wrapper
9034 script that massages the parameters before invoking the real linker. It
9035 may be useful to control the exact invocation by using the verbose
9041 @item /DEBUG=TRACEBACK
9042 @cindex @code{/DEBUG=TRACEBACK} (@command{gnatlink})
9043 This qualifier causes sufficient information to be included in the
9044 executable file to allow a traceback, but does not include the full
9045 symbol information needed by the debugger.
9047 @item /IDENTIFICATION="<string>"
9048 @code{"<string>"} specifies the string to be stored in the image file
9049 identification field in the image header.
9050 It overrides any pragma @code{Ident} specified string.
9052 @item /NOINHIBIT-EXEC
9053 Generate the executable file even if there are linker warnings.
9055 @item /NOSTART_FILES
9056 Don't link in the object file containing the ``main'' transfer address.
9057 Used when linking with a foreign language main program compiled with an
9061 Prefer linking with object libraries over sharable images, even without
9067 @node The GNAT Make Program gnatmake
9068 @chapter The GNAT Make Program @command{gnatmake}
9072 * Running gnatmake::
9073 * Switches for gnatmake::
9074 * Mode Switches for gnatmake::
9075 * Notes on the Command Line::
9076 * How gnatmake Works::
9077 * Examples of gnatmake Usage::
9080 A typical development cycle when working on an Ada program consists of
9081 the following steps:
9085 Edit some sources to fix bugs.
9091 Compile all sources affected.
9101 The third step can be tricky, because not only do the modified files
9102 @cindex Dependency rules
9103 have to be compiled, but any files depending on these files must also be
9104 recompiled. The dependency rules in Ada can be quite complex, especially
9105 in the presence of overloading, @code{use} clauses, generics and inlined
9108 @command{gnatmake} automatically takes care of the third and fourth steps
9109 of this process. It determines which sources need to be compiled,
9110 compiles them, and binds and links the resulting object files.
9112 Unlike some other Ada make programs, the dependencies are always
9113 accurately recomputed from the new sources. The source based approach of
9114 the GNAT compilation model makes this possible. This means that if
9115 changes to the source program cause corresponding changes in
9116 dependencies, they will always be tracked exactly correctly by
9119 @node Running gnatmake
9120 @section Running @command{gnatmake}
9123 The usual form of the @command{gnatmake} command is
9126 $ gnatmake @ovar{switches} @var{file_name}
9127 @ovar{file_names} @ovar{mode_switches}
9131 The only required argument is one @var{file_name}, which specifies
9132 a compilation unit that is a main program. Several @var{file_names} can be
9133 specified: this will result in several executables being built.
9134 If @code{switches} are present, they can be placed before the first
9135 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
9136 If @var{mode_switches} are present, they must always be placed after
9137 the last @var{file_name} and all @code{switches}.
9139 If you are using standard file extensions (@file{.adb} and @file{.ads}), then the
9140 extension may be omitted from the @var{file_name} arguments. However, if
9141 you are using non-standard extensions, then it is required that the
9142 extension be given. A relative or absolute directory path can be
9143 specified in a @var{file_name}, in which case, the input source file will
9144 be searched for in the specified directory only. Otherwise, the input
9145 source file will first be searched in the directory where
9146 @command{gnatmake} was invoked and if it is not found, it will be search on
9147 the source path of the compiler as described in
9148 @ref{Search Paths and the Run-Time Library (RTL)}.
9150 All @command{gnatmake} output (except when you specify
9151 @option{^-M^/DEPENDENCIES_LIST^}) is to
9152 @file{stderr}. The output produced by the
9153 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
9156 @node Switches for gnatmake
9157 @section Switches for @command{gnatmake}
9160 You may specify any of the following switches to @command{gnatmake}:
9166 @cindex @option{--version} @command{gnatmake}
9167 Display Copyright and version, then exit disregarding all other options.
9170 @cindex @option{--help} @command{gnatmake}
9171 If @option{--version} was not used, display usage, then exit disregarding
9175 @item --GCC=@var{compiler_name}
9176 @cindex @option{--GCC=compiler_name} (@command{gnatmake})
9177 Program used for compiling. The default is `@command{gcc}'. You need to use
9178 quotes around @var{compiler_name} if @code{compiler_name} contains
9179 spaces or other separator characters. As an example @option{--GCC="foo -x
9180 -y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your
9181 compiler. A limitation of this syntax is that the name and path name of
9182 the executable itself must not include any embedded spaces. Note that
9183 switch @option{-c} is always inserted after your command name. Thus in the
9184 above example the compiler command that will be used by @command{gnatmake}
9185 will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are
9186 used, only the last @var{compiler_name} is taken into account. However,
9187 all the additional switches are also taken into account. Thus,
9188 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
9189 @option{--GCC="bar -x -y -z -t"}.
9191 @item --GNATBIND=@var{binder_name}
9192 @cindex @option{--GNATBIND=binder_name} (@command{gnatmake})
9193 Program used for binding. The default is `@code{gnatbind}'. You need to
9194 use quotes around @var{binder_name} if @var{binder_name} contains spaces
9195 or other separator characters. As an example @option{--GNATBIND="bar -x
9196 -y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your
9197 binder. Binder switches that are normally appended by @command{gnatmake}
9198 to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
9199 A limitation of this syntax is that the name and path name of the executable
9200 itself must not include any embedded spaces.
9202 @item --GNATLINK=@var{linker_name}
9203 @cindex @option{--GNATLINK=linker_name} (@command{gnatmake})
9204 Program used for linking. The default is `@command{gnatlink}'. You need to
9205 use quotes around @var{linker_name} if @var{linker_name} contains spaces
9206 or other separator characters. As an example @option{--GNATLINK="lan -x
9207 -y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your
9208 linker. Linker switches that are normally appended by @command{gnatmake} to
9209 `@command{gnatlink}' are now appended to the end of @code{lan -x -y}.
9210 A limitation of this syntax is that the name and path name of the executable
9211 itself must not include any embedded spaces.
9215 @item ^-a^/ALL_FILES^
9216 @cindex @option{^-a^/ALL_FILES^} (@command{gnatmake})
9217 Consider all files in the make process, even the GNAT internal system
9218 files (for example, the predefined Ada library files), as well as any
9219 locked files. Locked files are files whose ALI file is write-protected.
9221 @command{gnatmake} does not check these files,
9222 because the assumption is that the GNAT internal files are properly up
9223 to date, and also that any write protected ALI files have been properly
9224 installed. Note that if there is an installation problem, such that one
9225 of these files is not up to date, it will be properly caught by the
9227 You may have to specify this switch if you are working on GNAT
9228 itself. The switch @option{^-a^/ALL_FILES^} is also useful
9229 in conjunction with @option{^-f^/FORCE_COMPILE^}
9230 if you need to recompile an entire application,
9231 including run-time files, using special configuration pragmas,
9232 such as a @code{Normalize_Scalars} pragma.
9235 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
9238 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
9241 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
9244 @item ^-b^/ACTIONS=BIND^
9245 @cindex @option{^-b^/ACTIONS=BIND^} (@command{gnatmake})
9246 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
9247 compilation and binding, but no link.
9248 Can be combined with @option{^-l^/ACTIONS=LINK^}
9249 to do binding and linking. When not combined with
9250 @option{^-c^/ACTIONS=COMPILE^}
9251 all the units in the closure of the main program must have been previously
9252 compiled and must be up to date. The root unit specified by @var{file_name}
9253 may be given without extension, with the source extension or, if no GNAT
9254 Project File is specified, with the ALI file extension.
9256 @item ^-c^/ACTIONS=COMPILE^
9257 @cindex @option{^-c^/ACTIONS=COMPILE^} (@command{gnatmake})
9258 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
9259 is also specified. Do not perform linking, except if both
9260 @option{^-b^/ACTIONS=BIND^} and
9261 @option{^-l^/ACTIONS=LINK^} are also specified.
9262 If the root unit specified by @var{file_name} is not a main unit, this is the
9263 default. Otherwise @command{gnatmake} will attempt binding and linking
9264 unless all objects are up to date and the executable is more recent than
9268 @cindex @option{^-C^/MAPPING^} (@command{gnatmake})
9269 Use a temporary mapping file. A mapping file is a way to communicate to the
9270 compiler two mappings: from unit names to file names (without any directory
9271 information) and from file names to path names (with full directory
9272 information). These mappings are used by the compiler to short-circuit the path
9273 search. When @command{gnatmake} is invoked with this switch, it will create
9274 a temporary mapping file, initially populated by the project manager,
9275 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
9276 Each invocation of the compiler will add the newly accessed sources to the
9277 mapping file. This will improve the source search during the next invocation
9280 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
9281 @cindex @option{^-C=^/USE_MAPPING^} (@command{gnatmake})
9282 Use a specific mapping file. The file, specified as a path name (absolute or
9283 relative) by this switch, should already exist, otherwise the switch is
9284 ineffective. The specified mapping file will be communicated to the compiler.
9285 This switch is not compatible with a project file
9286 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
9287 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
9289 @item ^-d^/DISPLAY_PROGRESS^
9290 @cindex @option{^-d^/DISPLAY_PROGRESS^} (@command{gnatmake})
9291 Display progress for each source, up to date or not, as a single line
9294 completed x out of y (zz%)
9297 If the file needs to be compiled this is displayed after the invocation of
9298 the compiler. These lines are displayed even in quiet output mode.
9300 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
9301 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@command{gnatmake})
9302 Put all object files and ALI file in directory @var{dir}.
9303 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
9304 and ALI files go in the current working directory.
9306 This switch cannot be used when using a project file.
9310 @cindex @option{-eL} (@command{gnatmake})
9311 Follow all symbolic links when processing project files.
9314 @item ^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^
9315 @cindex @option{^-eS^/STANDARD_OUTPUT_FOR_COMMANDS^} (@command{gnatmake})
9316 Output the commands for the compiler, the binder and the linker
9317 on ^standard output^SYS$OUTPUT^,
9318 instead of ^standard error^SYS$ERROR^.
9320 @item ^-f^/FORCE_COMPILE^
9321 @cindex @option{^-f^/FORCE_COMPILE^} (@command{gnatmake})
9322 Force recompilations. Recompile all sources, even though some object
9323 files may be up to date, but don't recompile predefined or GNAT internal
9324 files or locked files (files with a write-protected ALI file),
9325 unless the @option{^-a^/ALL_FILES^} switch is also specified.
9327 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
9328 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@command{gnatmake})
9329 When using project files, if some errors or warnings are detected during
9330 parsing and verbose mode is not in effect (no use of switch
9331 ^-v^/VERBOSE^), then error lines start with the full path name of the project
9332 file, rather than its simple file name.
9335 @cindex @option{^-g^/DEBUG^} (@command{gnatmake})
9336 Enable debugging. This switch is simply passed to the compiler and to the
9339 @item ^-i^/IN_PLACE^
9340 @cindex @option{^-i^/IN_PLACE^} (@command{gnatmake})
9341 In normal mode, @command{gnatmake} compiles all object files and ALI files
9342 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
9343 then instead object files and ALI files that already exist are overwritten
9344 in place. This means that once a large project is organized into separate
9345 directories in the desired manner, then @command{gnatmake} will automatically
9346 maintain and update this organization. If no ALI files are found on the
9347 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
9348 the new object and ALI files are created in the
9349 directory containing the source being compiled. If another organization
9350 is desired, where objects and sources are kept in different directories,
9351 a useful technique is to create dummy ALI files in the desired directories.
9352 When detecting such a dummy file, @command{gnatmake} will be forced to
9353 recompile the corresponding source file, and it will be put the resulting
9354 object and ALI files in the directory where it found the dummy file.
9356 @item ^-j^/PROCESSES=^@var{n}
9357 @cindex @option{^-j^/PROCESSES^} (@command{gnatmake})
9358 @cindex Parallel make
9359 Use @var{n} processes to carry out the (re)compilations. On a
9360 multiprocessor machine compilations will occur in parallel. In the
9361 event of compilation errors, messages from various compilations might
9362 get interspersed (but @command{gnatmake} will give you the full ordered
9363 list of failing compiles at the end). If this is problematic, rerun
9364 the make process with n set to 1 to get a clean list of messages.
9366 @item ^-k^/CONTINUE_ON_ERROR^
9367 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@command{gnatmake})
9368 Keep going. Continue as much as possible after a compilation error. To
9369 ease the programmer's task in case of compilation errors, the list of
9370 sources for which the compile fails is given when @command{gnatmake}
9373 If @command{gnatmake} is invoked with several @file{file_names} and with this
9374 switch, if there are compilation errors when building an executable,
9375 @command{gnatmake} will not attempt to build the following executables.
9377 @item ^-l^/ACTIONS=LINK^
9378 @cindex @option{^-l^/ACTIONS=LINK^} (@command{gnatmake})
9379 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
9380 and linking. Linking will not be performed if combined with
9381 @option{^-c^/ACTIONS=COMPILE^}
9382 but not with @option{^-b^/ACTIONS=BIND^}.
9383 When not combined with @option{^-b^/ACTIONS=BIND^}
9384 all the units in the closure of the main program must have been previously
9385 compiled and must be up to date, and the main program needs to have been bound.
9386 The root unit specified by @var{file_name}
9387 may be given without extension, with the source extension or, if no GNAT
9388 Project File is specified, with the ALI file extension.
9390 @item ^-m^/MINIMAL_RECOMPILATION^
9391 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@command{gnatmake})
9392 Specify that the minimum necessary amount of recompilations
9393 be performed. In this mode @command{gnatmake} ignores time
9394 stamp differences when the only
9395 modifications to a source file consist in adding/removing comments,
9396 empty lines, spaces or tabs. This means that if you have changed the
9397 comments in a source file or have simply reformatted it, using this
9398 switch will tell @command{gnatmake} not to recompile files that depend on it
9399 (provided other sources on which these files depend have undergone no
9400 semantic modifications). Note that the debugging information may be
9401 out of date with respect to the sources if the @option{-m} switch causes
9402 a compilation to be switched, so the use of this switch represents a
9403 trade-off between compilation time and accurate debugging information.
9405 @item ^-M^/DEPENDENCIES_LIST^
9406 @cindex Dependencies, producing list
9407 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@command{gnatmake})
9408 Check if all objects are up to date. If they are, output the object
9409 dependences to @file{stdout} in a form that can be directly exploited in
9410 a @file{Makefile}. By default, each source file is prefixed with its
9411 (relative or absolute) directory name. This name is whatever you
9412 specified in the various @option{^-aI^/SOURCE_SEARCH^}
9413 and @option{^-I^/SEARCH^} switches. If you use
9414 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
9415 @option{^-q^/QUIET^}
9416 (see below), only the source file names,
9417 without relative paths, are output. If you just specify the
9418 @option{^-M^/DEPENDENCIES_LIST^}
9419 switch, dependencies of the GNAT internal system files are omitted. This
9420 is typically what you want. If you also specify
9421 the @option{^-a^/ALL_FILES^} switch,
9422 dependencies of the GNAT internal files are also listed. Note that
9423 dependencies of the objects in external Ada libraries (see switch
9424 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
9427 @item ^-n^/DO_OBJECT_CHECK^
9428 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@command{gnatmake})
9429 Don't compile, bind, or link. Checks if all objects are up to date.
9430 If they are not, the full name of the first file that needs to be
9431 recompiled is printed.
9432 Repeated use of this option, followed by compiling the indicated source
9433 file, will eventually result in recompiling all required units.
9435 @item ^-o ^/EXECUTABLE=^@var{exec_name}
9436 @cindex @option{^-o^/EXECUTABLE^} (@command{gnatmake})
9437 Output executable name. The name of the final executable program will be
9438 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
9439 name for the executable will be the name of the input file in appropriate form
9440 for an executable file on the host system.
9442 This switch cannot be used when invoking @command{gnatmake} with several
9445 @item ^-p or --create-missing-dirs^/CREATE_MISSING_DIRS^
9446 @cindex @option{^-p^/CREATE_MISSING_DIRS^} (@command{gnatmake})
9447 When using project files (^-P^/PROJECT_FILE=^@var{project}), create
9448 automatically missing object directories, library directories and exec
9451 @item ^-P^/PROJECT_FILE=^@var{project}
9452 @cindex @option{^-P^/PROJECT_FILE^} (@command{gnatmake})
9453 Use project file @var{project}. Only one such switch can be used.
9454 @xref{gnatmake and Project Files}.
9457 @cindex @option{^-q^/QUIET^} (@command{gnatmake})
9458 Quiet. When this flag is not set, the commands carried out by
9459 @command{gnatmake} are displayed.
9461 @item ^-s^/SWITCH_CHECK/^
9462 @cindex @option{^-s^/SWITCH_CHECK^} (@command{gnatmake})
9463 Recompile if compiler switches have changed since last compilation.
9464 All compiler switches but -I and -o are taken into account in the
9466 orders between different ``first letter'' switches are ignored, but
9467 orders between same switches are taken into account. For example,
9468 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
9469 is equivalent to @option{-O -g}.
9471 This switch is recommended when Integrated Preprocessing is used.
9474 @cindex @option{^-u^/UNIQUE^} (@command{gnatmake})
9475 Unique. Recompile at most the main files. It implies -c. Combined with
9476 -f, it is equivalent to calling the compiler directly. Note that using
9477 ^-u^/UNIQUE^ with a project file and no main has a special meaning
9478 (@pxref{Project Files and Main Subprograms}).
9480 @item ^-U^/ALL_PROJECTS^
9481 @cindex @option{^-U^/ALL_PROJECTS^} (@command{gnatmake})
9482 When used without a project file or with one or several mains on the command
9483 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
9484 on the command line, all sources of all project files are checked and compiled
9485 if not up to date, and libraries are rebuilt, if necessary.
9488 @cindex @option{^-v^/REASONS^} (@command{gnatmake})
9489 Verbose. Display the reason for all recompilations @command{gnatmake}
9490 decides are necessary, with the highest verbosity level.
9492 @item ^-vl^/LOW_VERBOSITY^
9493 @cindex @option{^-vl^/LOW_VERBOSITY^} (@command{gnatmake})
9494 Verbosity level Low. Display fewer lines than in verbosity Medium.
9496 @item ^-vm^/MEDIUM_VERBOSITY^
9497 @cindex @option{^-vm^/MEDIUM_VERBOSITY^} (@command{gnatmake})
9498 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
9500 @item ^-vh^/HIGH_VERBOSITY^
9501 @cindex @option{^-vm^/HIGH_VERBOSITY^} (@command{gnatmake})
9502 Verbosity level High. Equivalent to ^-v^/REASONS^.
9504 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
9505 Indicate the verbosity of the parsing of GNAT project files.
9506 @xref{Switches Related to Project Files}.
9508 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
9509 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@command{gnatmake})
9510 Indicate that sources that are not part of any Project File may be compiled.
9511 Normally, when using Project Files, only sources that are part of a Project
9512 File may be compile. When this switch is used, a source outside of all Project
9513 Files may be compiled. The ALI file and the object file will be put in the
9514 object directory of the main Project. The compilation switches used will only
9515 be those specified on the command line. Even when
9516 @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} is used, mains specified on the
9517 command line need to be sources of a project file.
9519 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
9520 Indicate that external variable @var{name} has the value @var{value}.
9521 The Project Manager will use this value for occurrences of
9522 @code{external(name)} when parsing the project file.
9523 @xref{Switches Related to Project Files}.
9526 @cindex @option{^-z^/NOMAIN^} (@command{gnatmake})
9527 No main subprogram. Bind and link the program even if the unit name
9528 given on the command line is a package name. The resulting executable
9529 will execute the elaboration routines of the package and its closure,
9530 then the finalization routines.
9535 @item @command{gcc} @asis{switches}
9537 Any uppercase or multi-character switch that is not a @command{gnatmake} switch
9538 is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.)
9541 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
9542 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
9543 automatically treated as a compiler switch, and passed on to all
9544 compilations that are carried out.
9549 Source and library search path switches:
9553 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
9554 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatmake})
9555 When looking for source files also look in directory @var{dir}.
9556 The order in which source files search is undertaken is
9557 described in @ref{Search Paths and the Run-Time Library (RTL)}.
9559 @item ^-aL^/SKIP_MISSING=^@var{dir}
9560 @cindex @option{^-aL^/SKIP_MISSING^} (@command{gnatmake})
9561 Consider @var{dir} as being an externally provided Ada library.
9562 Instructs @command{gnatmake} to skip compilation units whose @file{.ALI}
9563 files have been located in directory @var{dir}. This allows you to have
9564 missing bodies for the units in @var{dir} and to ignore out of date bodies
9565 for the same units. You still need to specify
9566 the location of the specs for these units by using the switches
9567 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
9568 or @option{^-I^/SEARCH=^@var{dir}}.
9569 Note: this switch is provided for compatibility with previous versions
9570 of @command{gnatmake}. The easier method of causing standard libraries
9571 to be excluded from consideration is to write-protect the corresponding
9574 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
9575 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatmake})
9576 When searching for library and object files, look in directory
9577 @var{dir}. The order in which library files are searched is described in
9578 @ref{Search Paths for gnatbind}.
9580 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
9581 @cindex Search paths, for @command{gnatmake}
9582 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@command{gnatmake})
9583 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
9584 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9586 @item ^-I^/SEARCH=^@var{dir}
9587 @cindex @option{^-I^/SEARCH^} (@command{gnatmake})
9588 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
9589 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
9591 @item ^-I-^/NOCURRENT_DIRECTORY^
9592 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatmake})
9593 @cindex Source files, suppressing search
9594 Do not look for source files in the directory containing the source
9595 file named in the command line.
9596 Do not look for ALI or object files in the directory
9597 where @command{gnatmake} was invoked.
9599 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
9600 @cindex @option{^-L^/LIBRARY_SEARCH^} (@command{gnatmake})
9601 @cindex Linker libraries
9602 Add directory @var{dir} to the list of directories in which the linker
9603 will search for libraries. This is equivalent to
9604 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
9606 Furthermore, under Windows, the sources pointed to by the libraries path
9607 set in the registry are not searched for.
9611 @cindex @option{-nostdinc} (@command{gnatmake})
9612 Do not look for source files in the system default directory.
9615 @cindex @option{-nostdlib} (@command{gnatmake})
9616 Do not look for library files in the system default directory.
9618 @item --RTS=@var{rts-path}
9619 @cindex @option{--RTS} (@command{gnatmake})
9620 Specifies the default location of the runtime library. GNAT looks for the
9622 in the following directories, and stops as soon as a valid runtime is found
9623 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
9624 @file{ada_object_path} present):
9627 @item <current directory>/$rts_path
9629 @item <default-search-dir>/$rts_path
9631 @item <default-search-dir>/rts-$rts_path
9635 The selected path is handled like a normal RTS path.
9639 @node Mode Switches for gnatmake
9640 @section Mode Switches for @command{gnatmake}
9643 The mode switches (referred to as @code{mode_switches}) allow the
9644 inclusion of switches that are to be passed to the compiler itself, the
9645 binder or the linker. The effect of a mode switch is to cause all
9646 subsequent switches up to the end of the switch list, or up to the next
9647 mode switch, to be interpreted as switches to be passed on to the
9648 designated component of GNAT.
9652 @item -cargs @var{switches}
9653 @cindex @option{-cargs} (@command{gnatmake})
9654 Compiler switches. Here @var{switches} is a list of switches
9655 that are valid switches for @command{gcc}. They will be passed on to
9656 all compile steps performed by @command{gnatmake}.
9658 @item -bargs @var{switches}
9659 @cindex @option{-bargs} (@command{gnatmake})
9660 Binder switches. Here @var{switches} is a list of switches
9661 that are valid switches for @code{gnatbind}. They will be passed on to
9662 all bind steps performed by @command{gnatmake}.
9664 @item -largs @var{switches}
9665 @cindex @option{-largs} (@command{gnatmake})
9666 Linker switches. Here @var{switches} is a list of switches
9667 that are valid switches for @command{gnatlink}. They will be passed on to
9668 all link steps performed by @command{gnatmake}.
9670 @item -margs @var{switches}
9671 @cindex @option{-margs} (@command{gnatmake})
9672 Make switches. The switches are directly interpreted by @command{gnatmake},
9673 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
9677 @node Notes on the Command Line
9678 @section Notes on the Command Line
9681 This section contains some additional useful notes on the operation
9682 of the @command{gnatmake} command.
9686 @cindex Recompilation, by @command{gnatmake}
9687 If @command{gnatmake} finds no ALI files, it recompiles the main program
9688 and all other units required by the main program.
9689 This means that @command{gnatmake}
9690 can be used for the initial compile, as well as during subsequent steps of
9691 the development cycle.
9694 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
9695 is a subunit or body of a generic unit, @command{gnatmake} recompiles
9696 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
9700 In @command{gnatmake} the switch @option{^-I^/SEARCH^}
9701 is used to specify both source and
9702 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
9703 instead if you just want to specify
9704 source paths only and @option{^-aO^/OBJECT_SEARCH^}
9705 if you want to specify library paths
9709 @command{gnatmake} will ignore any files whose ALI file is write-protected.
9710 This may conveniently be used to exclude standard libraries from
9711 consideration and in particular it means that the use of the
9712 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
9713 unless @option{^-a^/ALL_FILES^} is also specified.
9716 @command{gnatmake} has been designed to make the use of Ada libraries
9717 particularly convenient. Assume you have an Ada library organized
9718 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
9719 of your Ada compilation units,
9720 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
9721 specs of these units, but no bodies. Then to compile a unit
9722 stored in @code{main.adb}, which uses this Ada library you would just type
9726 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
9729 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
9730 /SKIP_MISSING=@i{[OBJ_DIR]} main
9735 Using @command{gnatmake} along with the
9736 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
9737 switch provides a mechanism for avoiding unnecessary recompilations. Using
9739 you can update the comments/format of your
9740 source files without having to recompile everything. Note, however, that
9741 adding or deleting lines in a source files may render its debugging
9742 info obsolete. If the file in question is a spec, the impact is rather
9743 limited, as that debugging info will only be useful during the
9744 elaboration phase of your program. For bodies the impact can be more
9745 significant. In all events, your debugger will warn you if a source file
9746 is more recent than the corresponding object, and alert you to the fact
9747 that the debugging information may be out of date.
9750 @node How gnatmake Works
9751 @section How @command{gnatmake} Works
9754 Generally @command{gnatmake} automatically performs all necessary
9755 recompilations and you don't need to worry about how it works. However,
9756 it may be useful to have some basic understanding of the @command{gnatmake}
9757 approach and in particular to understand how it uses the results of
9758 previous compilations without incorrectly depending on them.
9760 First a definition: an object file is considered @dfn{up to date} if the
9761 corresponding ALI file exists and if all the source files listed in the
9762 dependency section of this ALI file have time stamps matching those in
9763 the ALI file. This means that neither the source file itself nor any
9764 files that it depends on have been modified, and hence there is no need
9765 to recompile this file.
9767 @command{gnatmake} works by first checking if the specified main unit is up
9768 to date. If so, no compilations are required for the main unit. If not,
9769 @command{gnatmake} compiles the main program to build a new ALI file that
9770 reflects the latest sources. Then the ALI file of the main unit is
9771 examined to find all the source files on which the main program depends,
9772 and @command{gnatmake} recursively applies the above procedure on all these
9775 This process ensures that @command{gnatmake} only trusts the dependencies
9776 in an existing ALI file if they are known to be correct. Otherwise it
9777 always recompiles to determine a new, guaranteed accurate set of
9778 dependencies. As a result the program is compiled ``upside down'' from what may
9779 be more familiar as the required order of compilation in some other Ada
9780 systems. In particular, clients are compiled before the units on which
9781 they depend. The ability of GNAT to compile in any order is critical in
9782 allowing an order of compilation to be chosen that guarantees that
9783 @command{gnatmake} will recompute a correct set of new dependencies if
9786 When invoking @command{gnatmake} with several @var{file_names}, if a unit is
9787 imported by several of the executables, it will be recompiled at most once.
9789 Note: when using non-standard naming conventions
9790 (@pxref{Using Other File Names}), changing through a configuration pragmas
9791 file the version of a source and invoking @command{gnatmake} to recompile may
9792 have no effect, if the previous version of the source is still accessible
9793 by @command{gnatmake}. It may be necessary to use the switch
9794 ^-f^/FORCE_COMPILE^.
9796 @node Examples of gnatmake Usage
9797 @section Examples of @command{gnatmake} Usage
9800 @item gnatmake hello.adb
9801 Compile all files necessary to bind and link the main program
9802 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
9803 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
9805 @item gnatmake main1 main2 main3
9806 Compile all files necessary to bind and link the main programs
9807 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
9808 (containing unit @code{Main2}) and @file{main3.adb}
9809 (containing unit @code{Main3}) and bind and link the resulting object files
9810 to generate three executable files @file{^main1^MAIN1.EXE^},
9811 @file{^main2^MAIN2.EXE^}
9812 and @file{^main3^MAIN3.EXE^}.
9815 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
9819 @item gnatmake Main_Unit /QUIET
9820 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
9821 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
9823 Compile all files necessary to bind and link the main program unit
9824 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
9825 be done with optimization level 2 and the order of elaboration will be
9826 listed by the binder. @command{gnatmake} will operate in quiet mode, not
9827 displaying commands it is executing.
9830 @c *************************
9831 @node Improving Performance
9832 @chapter Improving Performance
9833 @cindex Improving performance
9836 This chapter presents several topics related to program performance.
9837 It first describes some of the tradeoffs that need to be considered
9838 and some of the techniques for making your program run faster.
9839 It then documents the @command{gnatelim} tool and unused subprogram/data
9840 elimination feature, which can reduce the size of program executables.
9842 Note: to invoke @command{gnatelim} with a project file, use the @code{gnat}
9843 driver (see @ref{The GNAT Driver and Project Files}).
9847 * Performance Considerations::
9848 * Text_IO Suggestions::
9849 * Reducing Size of Ada Executables with gnatelim::
9850 * Reducing Size of Executables with unused subprogram/data elimination::
9854 @c *****************************
9855 @node Performance Considerations
9856 @section Performance Considerations
9859 The GNAT system provides a number of options that allow a trade-off
9864 performance of the generated code
9867 speed of compilation
9870 minimization of dependences and recompilation
9873 the degree of run-time checking.
9877 The defaults (if no options are selected) aim at improving the speed
9878 of compilation and minimizing dependences, at the expense of performance
9879 of the generated code:
9886 no inlining of subprogram calls
9889 all run-time checks enabled except overflow and elaboration checks
9893 These options are suitable for most program development purposes. This
9894 chapter describes how you can modify these choices, and also provides
9895 some guidelines on debugging optimized code.
9898 * Controlling Run-Time Checks::
9899 * Use of Restrictions::
9900 * Optimization Levels::
9901 * Debugging Optimized Code::
9902 * Inlining of Subprograms::
9903 * Other Optimization Switches::
9904 * Optimization and Strict Aliasing::
9907 * Coverage Analysis::
9911 @node Controlling Run-Time Checks
9912 @subsection Controlling Run-Time Checks
9915 By default, GNAT generates all run-time checks, except integer overflow
9916 checks, stack overflow checks, and checks for access before elaboration on
9917 subprogram calls. The latter are not required in default mode, because all
9918 necessary checking is done at compile time.
9919 @cindex @option{-gnatp} (@command{gcc})
9920 @cindex @option{-gnato} (@command{gcc})
9921 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
9922 be modified. @xref{Run-Time Checks}.
9924 Our experience is that the default is suitable for most development
9927 We treat integer overflow specially because these
9928 are quite expensive and in our experience are not as important as other
9929 run-time checks in the development process. Note that division by zero
9930 is not considered an overflow check, and divide by zero checks are
9931 generated where required by default.
9933 Elaboration checks are off by default, and also not needed by default, since
9934 GNAT uses a static elaboration analysis approach that avoids the need for
9935 run-time checking. This manual contains a full chapter discussing the issue
9936 of elaboration checks, and if the default is not satisfactory for your use,
9937 you should read this chapter.
9939 For validity checks, the minimal checks required by the Ada Reference
9940 Manual (for case statements and assignments to array elements) are on
9941 by default. These can be suppressed by use of the @option{-gnatVn} switch.
9942 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
9943 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
9944 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
9945 are also suppressed entirely if @option{-gnatp} is used.
9947 @cindex Overflow checks
9948 @cindex Checks, overflow
9951 @cindex pragma Suppress
9952 @cindex pragma Unsuppress
9953 Note that the setting of the switches controls the default setting of
9954 the checks. They may be modified using either @code{pragma Suppress} (to
9955 remove checks) or @code{pragma Unsuppress} (to add back suppressed
9956 checks) in the program source.
9958 @node Use of Restrictions
9959 @subsection Use of Restrictions
9962 The use of pragma Restrictions allows you to control which features are
9963 permitted in your program. Apart from the obvious point that if you avoid
9964 relatively expensive features like finalization (enforceable by the use
9965 of pragma Restrictions (No_Finalization), the use of this pragma does not
9966 affect the generated code in most cases.
9968 One notable exception to this rule is that the possibility of task abort
9969 results in some distributed overhead, particularly if finalization or
9970 exception handlers are used. The reason is that certain sections of code
9971 have to be marked as non-abortable.
9973 If you use neither the @code{abort} statement, nor asynchronous transfer
9974 of control (@code{select @dots{} then abort}), then this distributed overhead
9975 is removed, which may have a general positive effect in improving
9976 overall performance. Especially code involving frequent use of tasking
9977 constructs and controlled types will show much improved performance.
9978 The relevant restrictions pragmas are
9980 @smallexample @c ada
9981 pragma Restrictions (No_Abort_Statements);
9982 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
9986 It is recommended that these restriction pragmas be used if possible. Note
9987 that this also means that you can write code without worrying about the
9988 possibility of an immediate abort at any point.
9990 @node Optimization Levels
9991 @subsection Optimization Levels
9992 @cindex @option{^-O^/OPTIMIZE^} (@command{gcc})
9995 Without any optimization ^option,^qualifier,^
9996 the compiler's goal is to reduce the cost of
9997 compilation and to make debugging produce the expected results.
9998 Statements are independent: if you stop the program with a breakpoint between
9999 statements, you can then assign a new value to any variable or change
10000 the program counter to any other statement in the subprogram and get exactly
10001 the results you would expect from the source code.
10003 Turning on optimization makes the compiler attempt to improve the
10004 performance and/or code size at the expense of compilation time and
10005 possibly the ability to debug the program.
10007 If you use multiple
10008 ^-O options, with or without level numbers,^/OPTIMIZE qualifiers,^
10009 the last such option is the one that is effective.
10012 The default is optimization off. This results in the fastest compile
10013 times, but GNAT makes absolutely no attempt to optimize, and the
10014 generated programs are considerably larger and slower than when
10015 optimization is enabled. You can use the
10017 @option{-O} switch (the permitted forms are @option{-O0}, @option{-O1}
10018 @option{-O2}, @option{-O3}, and @option{-Os})
10021 @code{OPTIMIZE} qualifier
10023 to @command{gcc} to control the optimization level:
10026 @item ^-O0^/OPTIMIZE=NONE^
10027 No optimization (the default);
10028 generates unoptimized code but has
10029 the fastest compilation time.
10031 Note that many other compilers do fairly extensive optimization
10032 even if ``no optimization'' is specified. With gcc, it is
10033 very unusual to use ^-O0^/OPTIMIZE=NONE^ for production if
10034 execution time is of any concern, since ^-O0^/OPTIMIZE=NONE^
10035 really does mean no optimization at all. This difference between
10036 gcc and other compilers should be kept in mind when doing
10037 performance comparisons.
10039 @item ^-O1^/OPTIMIZE=SOME^
10040 Moderate optimization;
10041 optimizes reasonably well but does not
10042 degrade compilation time significantly.
10044 @item ^-O2^/OPTIMIZE=ALL^
10046 @itemx /OPTIMIZE=DEVELOPMENT
10049 generates highly optimized code and has
10050 the slowest compilation time.
10052 @item ^-O3^/OPTIMIZE=INLINING^
10053 Full optimization as in @option{-O2},
10054 and also attempts automatic inlining of small
10055 subprograms within a unit (@pxref{Inlining of Subprograms}).
10057 @item ^-Os^/OPTIMIZE=SPACE^
10058 Optimize space usage of resulting program.
10062 Higher optimization levels perform more global transformations on the
10063 program and apply more expensive analysis algorithms in order to generate
10064 faster and more compact code. The price in compilation time, and the
10065 resulting improvement in execution time,
10066 both depend on the particular application and the hardware environment.
10067 You should experiment to find the best level for your application.
10069 Since the precise set of optimizations done at each level will vary from
10070 release to release (and sometime from target to target), it is best to think
10071 of the optimization settings in general terms.
10072 @xref{Optimize Options,, Options That Control Optimization, gcc, Using
10073 the GNU Compiler Collection (GCC)}, for details about
10074 ^the @option{-O} settings and a number of @option{-f} options that^how to^
10075 individually enable or disable specific optimizations.
10077 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
10078 been tested extensively at all optimization levels. There are some bugs
10079 which appear only with optimization turned on, but there have also been
10080 bugs which show up only in @emph{unoptimized} code. Selecting a lower
10081 level of optimization does not improve the reliability of the code
10082 generator, which in practice is highly reliable at all optimization
10085 Note regarding the use of @option{-O3}: The use of this optimization level
10086 is generally discouraged with GNAT, since it often results in larger
10087 executables which run more slowly. See further discussion of this point
10088 in @ref{Inlining of Subprograms}.
10090 @node Debugging Optimized Code
10091 @subsection Debugging Optimized Code
10092 @cindex Debugging optimized code
10093 @cindex Optimization and debugging
10096 Although it is possible to do a reasonable amount of debugging at
10098 nonzero optimization levels,
10099 the higher the level the more likely that
10102 @option{/OPTIMIZE} settings other than @code{NONE},
10103 such settings will make it more likely that
10105 source-level constructs will have been eliminated by optimization.
10106 For example, if a loop is strength-reduced, the loop
10107 control variable may be completely eliminated and thus cannot be
10108 displayed in the debugger.
10109 This can only happen at @option{-O2} or @option{-O3}.
10110 Explicit temporary variables that you code might be eliminated at
10111 ^level^setting^ @option{-O1} or higher.
10113 The use of the @option{^-g^/DEBUG^} switch,
10114 @cindex @option{^-g^/DEBUG^} (@command{gcc})
10115 which is needed for source-level debugging,
10116 affects the size of the program executable on disk,
10117 and indeed the debugging information can be quite large.
10118 However, it has no effect on the generated code (and thus does not
10119 degrade performance)
10121 Since the compiler generates debugging tables for a compilation unit before
10122 it performs optimizations, the optimizing transformations may invalidate some
10123 of the debugging data. You therefore need to anticipate certain
10124 anomalous situations that may arise while debugging optimized code.
10125 These are the most common cases:
10129 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
10131 the PC bouncing back and forth in the code. This may result from any of
10132 the following optimizations:
10136 @i{Common subexpression elimination:} using a single instance of code for a
10137 quantity that the source computes several times. As a result you
10138 may not be able to stop on what looks like a statement.
10141 @i{Invariant code motion:} moving an expression that does not change within a
10142 loop, to the beginning of the loop.
10145 @i{Instruction scheduling:} moving instructions so as to
10146 overlap loads and stores (typically) with other code, or in
10147 general to move computations of values closer to their uses. Often
10148 this causes you to pass an assignment statement without the assignment
10149 happening and then later bounce back to the statement when the
10150 value is actually needed. Placing a breakpoint on a line of code
10151 and then stepping over it may, therefore, not always cause all the
10152 expected side-effects.
10156 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
10157 two identical pieces of code are merged and the program counter suddenly
10158 jumps to a statement that is not supposed to be executed, simply because
10159 it (and the code following) translates to the same thing as the code
10160 that @emph{was} supposed to be executed. This effect is typically seen in
10161 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
10162 a @code{break} in a C @code{^switch^switch^} statement.
10165 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
10166 There are various reasons for this effect:
10170 In a subprogram prologue, a parameter may not yet have been moved to its
10174 A variable may be dead, and its register re-used. This is
10175 probably the most common cause.
10178 As mentioned above, the assignment of a value to a variable may
10182 A variable may be eliminated entirely by value propagation or
10183 other means. In this case, GCC may incorrectly generate debugging
10184 information for the variable
10188 In general, when an unexpected value appears for a local variable or parameter
10189 you should first ascertain if that value was actually computed by
10190 your program, as opposed to being incorrectly reported by the debugger.
10192 array elements in an object designated by an access value
10193 are generally less of a problem, once you have ascertained that the access
10195 Typically, this means checking variables in the preceding code and in the
10196 calling subprogram to verify that the value observed is explainable from other
10197 values (one must apply the procedure recursively to those
10198 other values); or re-running the code and stopping a little earlier
10199 (perhaps before the call) and stepping to better see how the variable obtained
10200 the value in question; or continuing to step @emph{from} the point of the
10201 strange value to see if code motion had simply moved the variable's
10206 In light of such anomalies, a recommended technique is to use @option{-O0}
10207 early in the software development cycle, when extensive debugging capabilities
10208 are most needed, and then move to @option{-O1} and later @option{-O2} as
10209 the debugger becomes less critical.
10210 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
10211 a release management issue.
10213 Note that if you use @option{-g} you can then use the @command{strip} program
10214 on the resulting executable,
10215 which removes both debugging information and global symbols.
10218 @node Inlining of Subprograms
10219 @subsection Inlining of Subprograms
10222 A call to a subprogram in the current unit is inlined if all the
10223 following conditions are met:
10227 The optimization level is at least @option{-O1}.
10230 The called subprogram is suitable for inlining: It must be small enough
10231 and not contain something that @command{gcc} cannot support in inlined
10235 @cindex pragma Inline
10237 Either @code{pragma Inline} applies to the subprogram, or it is local
10238 to the unit and called once from within it, or it is small and automatic
10239 inlining (optimization level @option{-O3}) is specified.
10243 Calls to subprograms in @code{with}'ed units are normally not inlined.
10244 To achieve actual inlining (that is, replacement of the call by the code
10245 in the body of the subprogram), the following conditions must all be true.
10249 The optimization level is at least @option{-O1}.
10252 The called subprogram is suitable for inlining: It must be small enough
10253 and not contain something that @command{gcc} cannot support in inlined
10257 The call appears in a body (not in a package spec).
10260 There is a @code{pragma Inline} for the subprogram.
10263 @cindex @option{-gnatn} (@command{gcc})
10264 The @option{^-gnatn^/INLINE^} switch
10265 is used in the @command{gcc} command line
10268 Even if all these conditions are met, it may not be possible for
10269 the compiler to inline the call, due to the length of the body,
10270 or features in the body that make it impossible for the compiler
10271 to do the inlining.
10273 Note that specifying the @option{-gnatn} switch causes additional
10274 compilation dependencies. Consider the following:
10276 @smallexample @c ada
10296 With the default behavior (no @option{-gnatn} switch specified), the
10297 compilation of the @code{Main} procedure depends only on its own source,
10298 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
10299 means that editing the body of @code{R} does not require recompiling
10302 On the other hand, the call @code{R.Q} is not inlined under these
10303 circumstances. If the @option{-gnatn} switch is present when @code{Main}
10304 is compiled, the call will be inlined if the body of @code{Q} is small
10305 enough, but now @code{Main} depends on the body of @code{R} in
10306 @file{r.adb} as well as on the spec. This means that if this body is edited,
10307 the main program must be recompiled. Note that this extra dependency
10308 occurs whether or not the call is in fact inlined by @command{gcc}.
10310 The use of front end inlining with @option{-gnatN} generates similar
10311 additional dependencies.
10313 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@command{gcc})
10314 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
10315 can be used to prevent
10316 all inlining. This switch overrides all other conditions and ensures
10317 that no inlining occurs. The extra dependences resulting from
10318 @option{-gnatn} will still be active, even if
10319 this switch is used to suppress the resulting inlining actions.
10321 @cindex @option{-fno-inline-functions} (@command{gcc})
10322 Note: The @option{-fno-inline-functions} switch can be used to prevent
10323 automatic inlining of small subprograms if @option{-O3} is used.
10325 @cindex @option{-fno-inline-functions-called-once} (@command{gcc})
10326 Note: The @option{-fno-inline-functions-called-once} switch
10327 can be used to prevent inlining of subprograms local to the unit
10328 and called once from within it if @option{-O1} is used.
10330 Note regarding the use of @option{-O3}: There is no difference in inlining
10331 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
10332 pragma @code{Inline} assuming the use of @option{-gnatn}
10333 or @option{-gnatN} (the switches that activate inlining). If you have used
10334 pragma @code{Inline} in appropriate cases, then it is usually much better
10335 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
10336 in this case only has the effect of inlining subprograms you did not
10337 think should be inlined. We often find that the use of @option{-O3} slows
10338 down code by performing excessive inlining, leading to increased instruction
10339 cache pressure from the increased code size. So the bottom line here is
10340 that you should not automatically assume that @option{-O3} is better than
10341 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
10342 it actually improves performance.
10344 @node Other Optimization Switches
10345 @subsection Other Optimization Switches
10346 @cindex Optimization Switches
10348 Since @code{GNAT} uses the @command{gcc} back end, all the specialized
10349 @command{gcc} optimization switches are potentially usable. These switches
10350 have not been extensively tested with GNAT but can generally be expected
10351 to work. Examples of switches in this category are
10352 @option{-funroll-loops} and
10353 the various target-specific @option{-m} options (in particular, it has been
10354 observed that @option{-march=pentium4} can significantly improve performance
10355 on appropriate machines). For full details of these switches, see
10356 @ref{Submodel Options,, Hardware Models and Configurations, gcc, Using
10357 the GNU Compiler Collection (GCC)}.
10359 @node Optimization and Strict Aliasing
10360 @subsection Optimization and Strict Aliasing
10362 @cindex Strict Aliasing
10363 @cindex No_Strict_Aliasing
10366 The strong typing capabilities of Ada allow an optimizer to generate
10367 efficient code in situations where other languages would be forced to
10368 make worst case assumptions preventing such optimizations. Consider
10369 the following example:
10371 @smallexample @c ada
10374 type Int1 is new Integer;
10375 type Int2 is new Integer;
10376 type Int1A is access Int1;
10377 type Int2A is access Int2;
10384 for J in Data'Range loop
10385 if Data (J) = Int1V.all then
10386 Int2V.all := Int2V.all + 1;
10395 In this example, since the variable @code{Int1V} can only access objects
10396 of type @code{Int1}, and @code{Int2V} can only access objects of type
10397 @code{Int2}, there is no possibility that the assignment to
10398 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
10399 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
10400 for all iterations of the loop and avoid the extra memory reference
10401 required to dereference it each time through the loop.
10403 This kind of optimization, called strict aliasing analysis, is
10404 triggered by specifying an optimization level of @option{-O2} or
10405 higher or @option{-Os} and allows @code{GNAT} to generate more efficient code
10406 when access values are involved.
10408 However, although this optimization is always correct in terms of
10409 the formal semantics of the Ada Reference Manual, difficulties can
10410 arise if features like @code{Unchecked_Conversion} are used to break
10411 the typing system. Consider the following complete program example:
10413 @smallexample @c ada
10416 type int1 is new integer;
10417 type int2 is new integer;
10418 type a1 is access int1;
10419 type a2 is access int2;
10424 function to_a2 (Input : a1) return a2;
10427 with Unchecked_Conversion;
10429 function to_a2 (Input : a1) return a2 is
10431 new Unchecked_Conversion (a1, a2);
10433 return to_a2u (Input);
10439 with Text_IO; use Text_IO;
10441 v1 : a1 := new int1;
10442 v2 : a2 := to_a2 (v1);
10446 put_line (int1'image (v1.all));
10452 This program prints out 0 in @option{-O0} or @option{-O1}
10453 mode, but it prints out 1 in @option{-O2} mode. That's
10454 because in strict aliasing mode, the compiler can and
10455 does assume that the assignment to @code{v2.all} could not
10456 affect the value of @code{v1.all}, since different types
10459 This behavior is not a case of non-conformance with the standard, since
10460 the Ada RM specifies that an unchecked conversion where the resulting
10461 bit pattern is not a correct value of the target type can result in an
10462 abnormal value and attempting to reference an abnormal value makes the
10463 execution of a program erroneous. That's the case here since the result
10464 does not point to an object of type @code{int2}. This means that the
10465 effect is entirely unpredictable.
10467 However, although that explanation may satisfy a language
10468 lawyer, in practice an applications programmer expects an
10469 unchecked conversion involving pointers to create true
10470 aliases and the behavior of printing 1 seems plain wrong.
10471 In this case, the strict aliasing optimization is unwelcome.
10473 Indeed the compiler recognizes this possibility, and the
10474 unchecked conversion generates a warning:
10477 p2.adb:5:07: warning: possible aliasing problem with type "a2"
10478 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
10479 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
10483 Unfortunately the problem is recognized when compiling the body of
10484 package @code{p2}, but the actual "bad" code is generated while
10485 compiling the body of @code{m} and this latter compilation does not see
10486 the suspicious @code{Unchecked_Conversion}.
10488 As implied by the warning message, there are approaches you can use to
10489 avoid the unwanted strict aliasing optimization in a case like this.
10491 One possibility is to simply avoid the use of @option{-O2}, but
10492 that is a bit drastic, since it throws away a number of useful
10493 optimizations that do not involve strict aliasing assumptions.
10495 A less drastic approach is to compile the program using the
10496 option @option{-fno-strict-aliasing}. Actually it is only the
10497 unit containing the dereferencing of the suspicious pointer
10498 that needs to be compiled. So in this case, if we compile
10499 unit @code{m} with this switch, then we get the expected
10500 value of zero printed. Analyzing which units might need
10501 the switch can be painful, so a more reasonable approach
10502 is to compile the entire program with options @option{-O2}
10503 and @option{-fno-strict-aliasing}. If the performance is
10504 satisfactory with this combination of options, then the
10505 advantage is that the entire issue of possible "wrong"
10506 optimization due to strict aliasing is avoided.
10508 To avoid the use of compiler switches, the configuration
10509 pragma @code{No_Strict_Aliasing} with no parameters may be
10510 used to specify that for all access types, the strict
10511 aliasing optimization should be suppressed.
10513 However, these approaches are still overkill, in that they causes
10514 all manipulations of all access values to be deoptimized. A more
10515 refined approach is to concentrate attention on the specific
10516 access type identified as problematic.
10518 First, if a careful analysis of uses of the pointer shows
10519 that there are no possible problematic references, then
10520 the warning can be suppressed by bracketing the
10521 instantiation of @code{Unchecked_Conversion} to turn
10524 @smallexample @c ada
10525 pragma Warnings (Off);
10527 new Unchecked_Conversion (a1, a2);
10528 pragma Warnings (On);
10532 Of course that approach is not appropriate for this particular
10533 example, since indeed there is a problematic reference. In this
10534 case we can take one of two other approaches.
10536 The first possibility is to move the instantiation of unchecked
10537 conversion to the unit in which the type is declared. In
10538 this example, we would move the instantiation of
10539 @code{Unchecked_Conversion} from the body of package
10540 @code{p2} to the spec of package @code{p1}. Now the
10541 warning disappears. That's because any use of the
10542 access type knows there is a suspicious unchecked
10543 conversion, and the strict aliasing optimization
10544 is automatically suppressed for the type.
10546 If it is not practical to move the unchecked conversion to the same unit
10547 in which the destination access type is declared (perhaps because the
10548 source type is not visible in that unit), you may use pragma
10549 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
10550 same declarative sequence as the declaration of the access type:
10552 @smallexample @c ada
10553 type a2 is access int2;
10554 pragma No_Strict_Aliasing (a2);
10558 Here again, the compiler now knows that the strict aliasing optimization
10559 should be suppressed for any reference to type @code{a2} and the
10560 expected behavior is obtained.
10562 Finally, note that although the compiler can generate warnings for
10563 simple cases of unchecked conversions, there are tricker and more
10564 indirect ways of creating type incorrect aliases which the compiler
10565 cannot detect. Examples are the use of address overlays and unchecked
10566 conversions involving composite types containing access types as
10567 components. In such cases, no warnings are generated, but there can
10568 still be aliasing problems. One safe coding practice is to forbid the
10569 use of address clauses for type overlaying, and to allow unchecked
10570 conversion only for primitive types. This is not really a significant
10571 restriction since any possible desired effect can be achieved by
10572 unchecked conversion of access values.
10574 The aliasing analysis done in strict aliasing mode can certainly
10575 have significant benefits. We have seen cases of large scale
10576 application code where the time is increased by up to 5% by turning
10577 this optimization off. If you have code that includes significant
10578 usage of unchecked conversion, you might want to just stick with
10579 @option{-O1} and avoid the entire issue. If you get adequate
10580 performance at this level of optimization level, that's probably
10581 the safest approach. If tests show that you really need higher
10582 levels of optimization, then you can experiment with @option{-O2}
10583 and @option{-O2 -fno-strict-aliasing} to see how much effect this
10584 has on size and speed of the code. If you really need to use
10585 @option{-O2} with strict aliasing in effect, then you should
10586 review any uses of unchecked conversion of access types,
10587 particularly if you are getting the warnings described above.
10590 @node Coverage Analysis
10591 @subsection Coverage Analysis
10594 GNAT supports the HP Performance Coverage Analyzer (PCA), which allows
10595 the user to determine the distribution of execution time across a program,
10596 @pxref{Profiling} for details of usage.
10600 @node Text_IO Suggestions
10601 @section @code{Text_IO} Suggestions
10602 @cindex @code{Text_IO} and performance
10605 The @code{Ada.Text_IO} package has fairly high overheads due in part to
10606 the requirement of maintaining page and line counts. If performance
10607 is critical, a recommendation is to use @code{Stream_IO} instead of
10608 @code{Text_IO} for volume output, since this package has less overhead.
10610 If @code{Text_IO} must be used, note that by default output to the standard
10611 output and standard error files is unbuffered (this provides better
10612 behavior when output statements are used for debugging, or if the
10613 progress of a program is observed by tracking the output, e.g. by
10614 using the Unix @command{tail -f} command to watch redirected output.
10616 If you are generating large volumes of output with @code{Text_IO} and
10617 performance is an important factor, use a designated file instead
10618 of the standard output file, or change the standard output file to
10619 be buffered using @code{Interfaces.C_Streams.setvbuf}.
10623 @node Reducing Size of Ada Executables with gnatelim
10624 @section Reducing Size of Ada Executables with @code{gnatelim}
10628 This section describes @command{gnatelim}, a tool which detects unused
10629 subprograms and helps the compiler to create a smaller executable for your
10634 * Running gnatelim::
10635 * Correcting the List of Eliminate Pragmas::
10636 * Making Your Executables Smaller::
10637 * Summary of the gnatelim Usage Cycle::
10640 @node About gnatelim
10641 @subsection About @code{gnatelim}
10644 When a program shares a set of Ada
10645 packages with other programs, it may happen that this program uses
10646 only a fraction of the subprograms defined in these packages. The code
10647 created for these unused subprograms increases the size of the executable.
10649 @code{gnatelim} tracks unused subprograms in an Ada program and
10650 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
10651 subprograms that are declared but never called. By placing the list of
10652 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
10653 recompiling your program, you may decrease the size of its executable,
10654 because the compiler will not generate the code for 'eliminated' subprograms.
10655 @xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more
10656 information about this pragma.
10658 @code{gnatelim} needs as its input data the name of the main subprogram
10659 and a bind file for a main subprogram.
10661 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
10662 the main subprogram. @code{gnatelim} can work with both Ada and C
10663 bind files; when both are present, it uses the Ada bind file.
10664 The following commands will build the program and create the bind file:
10667 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
10668 $ gnatbind main_prog
10671 Note that @code{gnatelim} needs neither object nor ALI files.
10673 @node Running gnatelim
10674 @subsection Running @code{gnatelim}
10677 @code{gnatelim} has the following command-line interface:
10680 $ gnatelim @ovar{options} name
10684 @code{name} should be a name of a source file that contains the main subprogram
10685 of a program (partition).
10687 @code{gnatelim} has the following switches:
10692 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
10693 Quiet mode: by default @code{gnatelim} outputs to the standard error
10694 stream the number of program units left to be processed. This option turns
10697 @item ^-v^/VERBOSE^
10698 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
10699 Verbose mode: @code{gnatelim} version information is printed as Ada
10700 comments to the standard output stream. Also, in addition to the number of
10701 program units left @code{gnatelim} will output the name of the current unit
10705 @cindex @option{^-a^/ALL^} (@command{gnatelim})
10706 Also look for subprograms from the GNAT run time that can be eliminated. Note
10707 that when @file{gnat.adc} is produced using this switch, the entire program
10708 must be recompiled with switch @option{^-a^/ALL_FILES^} to @command{gnatmake}.
10710 @item ^-I^/INCLUDE_DIRS=^@var{dir}
10711 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
10712 When looking for source files also look in directory @var{dir}. Specifying
10713 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
10714 sources in the current directory.
10716 @item ^-b^/BIND_FILE=^@var{bind_file}
10717 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
10718 Specifies @var{bind_file} as the bind file to process. If not set, the name
10719 of the bind file is computed from the full expanded Ada name
10720 of a main subprogram.
10722 @item ^-C^/CONFIG_FILE=^@var{config_file}
10723 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
10724 Specifies a file @var{config_file} that contains configuration pragmas. The
10725 file must be specified with full path.
10727 @item ^--GCC^/COMPILER^=@var{compiler_name}
10728 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
10729 Instructs @code{gnatelim} to use specific @command{gcc} compiler instead of one
10730 available on the path.
10732 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
10733 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
10734 Instructs @code{gnatelim} to use specific @command{gnatmake} instead of one
10735 available on the path.
10739 @code{gnatelim} sends its output to the standard output stream, and all the
10740 tracing and debug information is sent to the standard error stream.
10741 In order to produce a proper GNAT configuration file
10742 @file{gnat.adc}, redirection must be used:
10746 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
10749 $ gnatelim main_prog.adb > gnat.adc
10758 $ gnatelim main_prog.adb >> gnat.adc
10762 in order to append the @code{gnatelim} output to the existing contents of
10766 @node Correcting the List of Eliminate Pragmas
10767 @subsection Correcting the List of Eliminate Pragmas
10770 In some rare cases @code{gnatelim} may try to eliminate
10771 subprograms that are actually called in the program. In this case, the
10772 compiler will generate an error message of the form:
10775 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
10779 You will need to manually remove the wrong @code{Eliminate} pragmas from
10780 the @file{gnat.adc} file. You should recompile your program
10781 from scratch after that, because you need a consistent @file{gnat.adc} file
10782 during the entire compilation.
10784 @node Making Your Executables Smaller
10785 @subsection Making Your Executables Smaller
10788 In order to get a smaller executable for your program you now have to
10789 recompile the program completely with the new @file{gnat.adc} file
10790 created by @code{gnatelim} in your current directory:
10793 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10797 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
10798 recompile everything
10799 with the set of pragmas @code{Eliminate} that you have obtained with
10800 @command{gnatelim}).
10802 Be aware that the set of @code{Eliminate} pragmas is specific to each
10803 program. It is not recommended to merge sets of @code{Eliminate}
10804 pragmas created for different programs in one @file{gnat.adc} file.
10806 @node Summary of the gnatelim Usage Cycle
10807 @subsection Summary of the gnatelim Usage Cycle
10810 Here is a quick summary of the steps to be taken in order to reduce
10811 the size of your executables with @code{gnatelim}. You may use
10812 other GNAT options to control the optimization level,
10813 to produce the debugging information, to set search path, etc.
10817 Produce a bind file
10820 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
10821 $ gnatbind main_prog
10825 Generate a list of @code{Eliminate} pragmas
10828 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
10831 $ gnatelim main_prog >@r{[}>@r{]} gnat.adc
10836 Recompile the application
10839 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
10844 @node Reducing Size of Executables with unused subprogram/data elimination
10845 @section Reducing Size of Executables with Unused Subprogram/Data Elimination
10846 @findex unused subprogram/data elimination
10849 This section describes how you can eliminate unused subprograms and data from
10850 your executable just by setting options at compilation time.
10853 * About unused subprogram/data elimination::
10854 * Compilation options::
10855 * Example of unused subprogram/data elimination::
10858 @node About unused subprogram/data elimination
10859 @subsection About unused subprogram/data elimination
10862 By default, an executable contains all code and data of its composing objects
10863 (directly linked or coming from statically linked libraries), even data or code
10864 never used by this executable.
10866 This feature will allow you to eliminate such unused code from your
10867 executable, making it smaller (in disk and in memory).
10869 This functionality is available on all Linux platforms except for the IA-64
10870 architecture and on all cross platforms using the ELF binary file format.
10871 In both cases GNU binutils version 2.16 or later are required to enable it.
10873 @node Compilation options
10874 @subsection Compilation options
10877 The operation of eliminating the unused code and data from the final executable
10878 is directly performed by the linker.
10880 In order to do this, it has to work with objects compiled with the
10882 @option{-ffunction-sections} @option{-fdata-sections}.
10883 @cindex @option{-ffunction-sections} (@command{gcc})
10884 @cindex @option{-fdata-sections} (@command{gcc})
10885 These options are usable with C and Ada files.
10886 They will place respectively each
10887 function or data in a separate section in the resulting object file.
10889 Once the objects and static libraries are created with these options, the
10890 linker can perform the dead code elimination. You can do this by setting
10891 the @option{-Wl,--gc-sections} option to gcc command or in the
10892 @option{-largs} section of @command{gnatmake}. This will perform a
10893 garbage collection of code and data never referenced.
10895 If the linker performs a partial link (@option{-r} ld linker option), then you
10896 will need to provide one or several entry point using the
10897 @option{-e} / @option{--entry} ld option.
10899 Note that objects compiled without the @option{-ffunction-sections} and
10900 @option{-fdata-sections} options can still be linked with the executable.
10901 However, no dead code elimination will be performed on those objects (they will
10904 The GNAT static library is now compiled with -ffunction-sections and
10905 -fdata-sections on some platforms. This allows you to eliminate the unused code
10906 and data of the GNAT library from your executable.
10908 @node Example of unused subprogram/data elimination
10909 @subsection Example of unused subprogram/data elimination
10912 Here is a simple example:
10914 @smallexample @c ada
10923 Used_Data : Integer;
10924 Unused_Data : Integer;
10926 procedure Used (Data : Integer);
10927 procedure Unused (Data : Integer);
10930 package body Aux is
10931 procedure Used (Data : Integer) is
10936 procedure Unused (Data : Integer) is
10938 Unused_Data := Data;
10944 @code{Unused} and @code{Unused_Data} are never referenced in this code
10945 excerpt, and hence they may be safely removed from the final executable.
10950 $ nm test | grep used
10951 020015f0 T aux__unused
10952 02005d88 B aux__unused_data
10953 020015cc T aux__used
10954 02005d84 B aux__used_data
10956 $ gnatmake test -cargs -fdata-sections -ffunction-sections \
10957 -largs -Wl,--gc-sections
10959 $ nm test | grep used
10960 02005350 T aux__used
10961 0201ffe0 B aux__used_data
10965 It can be observed that the procedure @code{Unused} and the object
10966 @code{Unused_Data} are removed by the linker when using the
10967 appropriate options.
10969 @c ********************************
10970 @node Renaming Files Using gnatchop
10971 @chapter Renaming Files Using @code{gnatchop}
10975 This chapter discusses how to handle files with multiple units by using
10976 the @code{gnatchop} utility. This utility is also useful in renaming
10977 files to meet the standard GNAT default file naming conventions.
10980 * Handling Files with Multiple Units::
10981 * Operating gnatchop in Compilation Mode::
10982 * Command Line for gnatchop::
10983 * Switches for gnatchop::
10984 * Examples of gnatchop Usage::
10987 @node Handling Files with Multiple Units
10988 @section Handling Files with Multiple Units
10991 The basic compilation model of GNAT requires that a file submitted to the
10992 compiler have only one unit and there be a strict correspondence
10993 between the file name and the unit name.
10995 The @code{gnatchop} utility allows both of these rules to be relaxed,
10996 allowing GNAT to process files which contain multiple compilation units
10997 and files with arbitrary file names. @code{gnatchop}
10998 reads the specified file and generates one or more output files,
10999 containing one unit per file. The unit and the file name correspond,
11000 as required by GNAT.
11002 If you want to permanently restructure a set of ``foreign'' files so that
11003 they match the GNAT rules, and do the remaining development using the
11004 GNAT structure, you can simply use @command{gnatchop} once, generate the
11005 new set of files and work with them from that point on.
11007 Alternatively, if you want to keep your files in the ``foreign'' format,
11008 perhaps to maintain compatibility with some other Ada compilation
11009 system, you can set up a procedure where you use @command{gnatchop} each
11010 time you compile, regarding the source files that it writes as temporary
11011 files that you throw away.
11013 Note that if your file containing multiple units starts with a byte order
11014 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
11015 will each start with a copy of this BOM, meaning that they can be compiled
11016 automatically in UTF-8 mode without needing to specify an explicit encoding.
11018 @node Operating gnatchop in Compilation Mode
11019 @section Operating gnatchop in Compilation Mode
11022 The basic function of @code{gnatchop} is to take a file with multiple units
11023 and split it into separate files. The boundary between files is reasonably
11024 clear, except for the issue of comments and pragmas. In default mode, the
11025 rule is that any pragmas between units belong to the previous unit, except
11026 that configuration pragmas always belong to the following unit. Any comments
11027 belong to the following unit. These rules
11028 almost always result in the right choice of
11029 the split point without needing to mark it explicitly and most users will
11030 find this default to be what they want. In this default mode it is incorrect to
11031 submit a file containing only configuration pragmas, or one that ends in
11032 configuration pragmas, to @code{gnatchop}.
11034 However, using a special option to activate ``compilation mode'',
11036 can perform another function, which is to provide exactly the semantics
11037 required by the RM for handling of configuration pragmas in a compilation.
11038 In the absence of configuration pragmas (at the main file level), this
11039 option has no effect, but it causes such configuration pragmas to be handled
11040 in a quite different manner.
11042 First, in compilation mode, if @code{gnatchop} is given a file that consists of
11043 only configuration pragmas, then this file is appended to the
11044 @file{gnat.adc} file in the current directory. This behavior provides
11045 the required behavior described in the RM for the actions to be taken
11046 on submitting such a file to the compiler, namely that these pragmas
11047 should apply to all subsequent compilations in the same compilation
11048 environment. Using GNAT, the current directory, possibly containing a
11049 @file{gnat.adc} file is the representation
11050 of a compilation environment. For more information on the
11051 @file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}.
11053 Second, in compilation mode, if @code{gnatchop}
11054 is given a file that starts with
11055 configuration pragmas, and contains one or more units, then these
11056 configuration pragmas are prepended to each of the chopped files. This
11057 behavior provides the required behavior described in the RM for the
11058 actions to be taken on compiling such a file, namely that the pragmas
11059 apply to all units in the compilation, but not to subsequently compiled
11062 Finally, if configuration pragmas appear between units, they are appended
11063 to the previous unit. This results in the previous unit being illegal,
11064 since the compiler does not accept configuration pragmas that follow
11065 a unit. This provides the required RM behavior that forbids configuration
11066 pragmas other than those preceding the first compilation unit of a
11069 For most purposes, @code{gnatchop} will be used in default mode. The
11070 compilation mode described above is used only if you need exactly
11071 accurate behavior with respect to compilations, and you have files
11072 that contain multiple units and configuration pragmas. In this
11073 circumstance the use of @code{gnatchop} with the compilation mode
11074 switch provides the required behavior, and is for example the mode
11075 in which GNAT processes the ACVC tests.
11077 @node Command Line for gnatchop
11078 @section Command Line for @code{gnatchop}
11081 The @code{gnatchop} command has the form:
11084 $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]}
11089 The only required argument is the file name of the file to be chopped.
11090 There are no restrictions on the form of this file name. The file itself
11091 contains one or more Ada units, in normal GNAT format, concatenated
11092 together. As shown, more than one file may be presented to be chopped.
11094 When run in default mode, @code{gnatchop} generates one output file in
11095 the current directory for each unit in each of the files.
11097 @var{directory}, if specified, gives the name of the directory to which
11098 the output files will be written. If it is not specified, all files are
11099 written to the current directory.
11101 For example, given a
11102 file called @file{hellofiles} containing
11104 @smallexample @c ada
11109 with Text_IO; use Text_IO;
11112 Put_Line ("Hello");
11122 $ gnatchop ^hellofiles^HELLOFILES.^
11126 generates two files in the current directory, one called
11127 @file{hello.ads} containing the single line that is the procedure spec,
11128 and the other called @file{hello.adb} containing the remaining text. The
11129 original file is not affected. The generated files can be compiled in
11133 When gnatchop is invoked on a file that is empty or that contains only empty
11134 lines and/or comments, gnatchop will not fail, but will not produce any
11137 For example, given a
11138 file called @file{toto.txt} containing
11140 @smallexample @c ada
11152 $ gnatchop ^toto.txt^TOT.TXT^
11156 will not produce any new file and will result in the following warnings:
11159 toto.txt:1:01: warning: empty file, contains no compilation units
11160 no compilation units found
11161 no source files written
11164 @node Switches for gnatchop
11165 @section Switches for @code{gnatchop}
11168 @command{gnatchop} recognizes the following switches:
11174 @cindex @option{--version} @command{gnatchop}
11175 Display Copyright and version, then exit disregarding all other options.
11178 @cindex @option{--help} @command{gnatchop}
11179 If @option{--version} was not used, display usage, then exit disregarding
11182 @item ^-c^/COMPILATION^
11183 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
11184 Causes @code{gnatchop} to operate in compilation mode, in which
11185 configuration pragmas are handled according to strict RM rules. See
11186 previous section for a full description of this mode.
11189 @item -gnat@var{xxx}
11190 This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is
11191 used to parse the given file. Not all @var{xxx} options make sense,
11192 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
11193 process a source file that uses Latin-2 coding for identifiers.
11197 Causes @code{gnatchop} to generate a brief help summary to the standard
11198 output file showing usage information.
11200 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
11201 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
11202 Limit generated file names to the specified number @code{mm}
11204 This is useful if the
11205 resulting set of files is required to be interoperable with systems
11206 which limit the length of file names.
11208 If no value is given, or
11209 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
11210 a default of 39, suitable for OpenVMS Alpha
11211 Systems, is assumed
11214 No space is allowed between the @option{-k} and the numeric value. The numeric
11215 value may be omitted in which case a default of @option{-k8},
11217 with DOS-like file systems, is used. If no @option{-k} switch
11219 there is no limit on the length of file names.
11222 @item ^-p^/PRESERVE^
11223 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
11224 Causes the file ^modification^creation^ time stamp of the input file to be
11225 preserved and used for the time stamp of the output file(s). This may be
11226 useful for preserving coherency of time stamps in an environment where
11227 @code{gnatchop} is used as part of a standard build process.
11230 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
11231 Causes output of informational messages indicating the set of generated
11232 files to be suppressed. Warnings and error messages are unaffected.
11234 @item ^-r^/REFERENCE^
11235 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
11236 @findex Source_Reference
11237 Generate @code{Source_Reference} pragmas. Use this switch if the output
11238 files are regarded as temporary and development is to be done in terms
11239 of the original unchopped file. This switch causes
11240 @code{Source_Reference} pragmas to be inserted into each of the
11241 generated files to refers back to the original file name and line number.
11242 The result is that all error messages refer back to the original
11244 In addition, the debugging information placed into the object file (when
11245 the @option{^-g^/DEBUG^} switch of @command{gcc} or @command{gnatmake} is
11247 also refers back to this original file so that tools like profilers and
11248 debuggers will give information in terms of the original unchopped file.
11250 If the original file to be chopped itself contains
11251 a @code{Source_Reference}
11252 pragma referencing a third file, then gnatchop respects
11253 this pragma, and the generated @code{Source_Reference} pragmas
11254 in the chopped file refer to the original file, with appropriate
11255 line numbers. This is particularly useful when @code{gnatchop}
11256 is used in conjunction with @code{gnatprep} to compile files that
11257 contain preprocessing statements and multiple units.
11259 @item ^-v^/VERBOSE^
11260 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
11261 Causes @code{gnatchop} to operate in verbose mode. The version
11262 number and copyright notice are output, as well as exact copies of
11263 the gnat1 commands spawned to obtain the chop control information.
11265 @item ^-w^/OVERWRITE^
11266 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
11267 Overwrite existing file names. Normally @code{gnatchop} regards it as a
11268 fatal error if there is already a file with the same name as a
11269 file it would otherwise output, in other words if the files to be
11270 chopped contain duplicated units. This switch bypasses this
11271 check, and causes all but the last instance of such duplicated
11272 units to be skipped.
11275 @item --GCC=@var{xxxx}
11276 @cindex @option{--GCC=} (@code{gnatchop})
11277 Specify the path of the GNAT parser to be used. When this switch is used,
11278 no attempt is made to add the prefix to the GNAT parser executable.
11282 @node Examples of gnatchop Usage
11283 @section Examples of @code{gnatchop} Usage
11287 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
11290 @item gnatchop -w hello_s.ada prerelease/files
11293 Chops the source file @file{hello_s.ada}. The output files will be
11294 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
11296 files with matching names in that directory (no files in the current
11297 directory are modified).
11299 @item gnatchop ^archive^ARCHIVE.^
11300 Chops the source file @file{^archive^ARCHIVE.^}
11301 into the current directory. One
11302 useful application of @code{gnatchop} is in sending sets of sources
11303 around, for example in email messages. The required sources are simply
11304 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
11306 @command{gnatchop} is used at the other end to reconstitute the original
11309 @item gnatchop file1 file2 file3 direc
11310 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
11311 the resulting files in the directory @file{direc}. Note that if any units
11312 occur more than once anywhere within this set of files, an error message
11313 is generated, and no files are written. To override this check, use the
11314 @option{^-w^/OVERWRITE^} switch,
11315 in which case the last occurrence in the last file will
11316 be the one that is output, and earlier duplicate occurrences for a given
11317 unit will be skipped.
11320 @node Configuration Pragmas
11321 @chapter Configuration Pragmas
11322 @cindex Configuration pragmas
11323 @cindex Pragmas, configuration
11326 Configuration pragmas include those pragmas described as
11327 such in the Ada Reference Manual, as well as
11328 implementation-dependent pragmas that are configuration pragmas.
11329 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
11330 for details on these additional GNAT-specific configuration pragmas.
11331 Most notably, the pragma @code{Source_File_Name}, which allows
11332 specifying non-default names for source files, is a configuration
11333 pragma. The following is a complete list of configuration pragmas
11334 recognized by GNAT:
11342 Assume_No_Invalid_Values
11347 Compile_Time_Warning
11349 Component_Alignment
11350 Convention_Identifier
11358 External_Name_Casing
11361 Float_Representation
11374 Priority_Specific_Dispatching
11377 Propagate_Exceptions
11380 Restricted_Run_Time
11382 Restrictions_Warnings
11385 Source_File_Name_Project
11388 Suppress_Exception_Locations
11389 Task_Dispatching_Policy
11395 Wide_Character_Encoding
11400 * Handling of Configuration Pragmas::
11401 * The Configuration Pragmas Files::
11404 @node Handling of Configuration Pragmas
11405 @section Handling of Configuration Pragmas
11407 Configuration pragmas may either appear at the start of a compilation
11408 unit, in which case they apply only to that unit, or they may apply to
11409 all compilations performed in a given compilation environment.
11411 GNAT also provides the @code{gnatchop} utility to provide an automatic
11412 way to handle configuration pragmas following the semantics for
11413 compilations (that is, files with multiple units), described in the RM.
11414 See @ref{Operating gnatchop in Compilation Mode} for details.
11415 However, for most purposes, it will be more convenient to edit the
11416 @file{gnat.adc} file that contains configuration pragmas directly,
11417 as described in the following section.
11419 @node The Configuration Pragmas Files
11420 @section The Configuration Pragmas Files
11421 @cindex @file{gnat.adc}
11424 In GNAT a compilation environment is defined by the current
11425 directory at the time that a compile command is given. This current
11426 directory is searched for a file whose name is @file{gnat.adc}. If
11427 this file is present, it is expected to contain one or more
11428 configuration pragmas that will be applied to the current compilation.
11429 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
11432 Configuration pragmas may be entered into the @file{gnat.adc} file
11433 either by running @code{gnatchop} on a source file that consists only of
11434 configuration pragmas, or more conveniently by
11435 direct editing of the @file{gnat.adc} file, which is a standard format
11438 In addition to @file{gnat.adc}, additional files containing configuration
11439 pragmas may be applied to the current compilation using the switch
11440 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
11441 contains only configuration pragmas. These configuration pragmas are
11442 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
11443 is present and switch @option{-gnatA} is not used).
11445 It is allowed to specify several switches @option{-gnatec}, all of which
11446 will be taken into account.
11448 If you are using project file, a separate mechanism is provided using
11449 project attributes, see @ref{Specifying Configuration Pragmas} for more
11453 Of special interest to GNAT OpenVMS Alpha is the following
11454 configuration pragma:
11456 @smallexample @c ada
11458 pragma Extend_System (Aux_DEC);
11463 In the presence of this pragma, GNAT adds to the definition of the
11464 predefined package SYSTEM all the additional types and subprograms that are
11465 defined in HP Ada. See @ref{Compatibility with HP Ada} for details.
11468 @node Handling Arbitrary File Naming Conventions Using gnatname
11469 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
11470 @cindex Arbitrary File Naming Conventions
11473 * Arbitrary File Naming Conventions::
11474 * Running gnatname::
11475 * Switches for gnatname::
11476 * Examples of gnatname Usage::
11479 @node Arbitrary File Naming Conventions
11480 @section Arbitrary File Naming Conventions
11483 The GNAT compiler must be able to know the source file name of a compilation
11484 unit. When using the standard GNAT default file naming conventions
11485 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
11486 does not need additional information.
11489 When the source file names do not follow the standard GNAT default file naming
11490 conventions, the GNAT compiler must be given additional information through
11491 a configuration pragmas file (@pxref{Configuration Pragmas})
11493 When the non-standard file naming conventions are well-defined,
11494 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
11495 (@pxref{Alternative File Naming Schemes}) may be sufficient. However,
11496 if the file naming conventions are irregular or arbitrary, a number
11497 of pragma @code{Source_File_Name} for individual compilation units
11499 To help maintain the correspondence between compilation unit names and
11500 source file names within the compiler,
11501 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
11504 @node Running gnatname
11505 @section Running @code{gnatname}
11508 The usual form of the @code{gnatname} command is
11511 $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}
11512 @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]}
11516 All of the arguments are optional. If invoked without any argument,
11517 @code{gnatname} will display its usage.
11520 When used with at least one naming pattern, @code{gnatname} will attempt to
11521 find all the compilation units in files that follow at least one of the
11522 naming patterns. To find these compilation units,
11523 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
11527 One or several Naming Patterns may be given as arguments to @code{gnatname}.
11528 Each Naming Pattern is enclosed between double quotes.
11529 A Naming Pattern is a regular expression similar to the wildcard patterns
11530 used in file names by the Unix shells or the DOS prompt.
11533 @code{gnatname} may be called with several sections of directories/patterns.
11534 Sections are separated by switch @code{--and}. In each section, there must be
11535 at least one pattern. If no directory is specified in a section, the current
11536 directory (or the project directory is @code{-P} is used) is implied.
11537 The options other that the directory switches and the patterns apply globally
11538 even if they are in different sections.
11541 Examples of Naming Patterns are
11550 For a more complete description of the syntax of Naming Patterns,
11551 see the second kind of regular expressions described in @file{g-regexp.ads}
11552 (the ``Glob'' regular expressions).
11555 When invoked with no switch @code{-P}, @code{gnatname} will create a
11556 configuration pragmas file @file{gnat.adc} in the current working directory,
11557 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
11560 @node Switches for gnatname
11561 @section Switches for @code{gnatname}
11564 Switches for @code{gnatname} must precede any specified Naming Pattern.
11567 You may specify any of the following switches to @code{gnatname}:
11573 @cindex @option{--version} @command{gnatname}
11574 Display Copyright and version, then exit disregarding all other options.
11577 @cindex @option{--help} @command{gnatname}
11578 If @option{--version} was not used, display usage, then exit disregarding
11582 Start another section of directories/patterns.
11584 @item ^-c^/CONFIG_FILE=^@file{file}
11585 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
11586 Create a configuration pragmas file @file{file} (instead of the default
11589 There may be zero, one or more space between @option{-c} and
11592 @file{file} may include directory information. @file{file} must be
11593 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
11594 When a switch @option{^-c^/CONFIG_FILE^} is
11595 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
11597 @item ^-d^/SOURCE_DIRS=^@file{dir}
11598 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
11599 Look for source files in directory @file{dir}. There may be zero, one or more
11600 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
11601 When a switch @option{^-d^/SOURCE_DIRS^}
11602 is specified, the current working directory will not be searched for source
11603 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
11604 or @option{^-D^/DIR_FILES^} switch.
11605 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
11606 If @file{dir} is a relative path, it is relative to the directory of
11607 the configuration pragmas file specified with switch
11608 @option{^-c^/CONFIG_FILE^},
11609 or to the directory of the project file specified with switch
11610 @option{^-P^/PROJECT_FILE^} or,
11611 if neither switch @option{^-c^/CONFIG_FILE^}
11612 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
11613 current working directory. The directory
11614 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
11616 @item ^-D^/DIRS_FILE=^@file{file}
11617 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
11618 Look for source files in all directories listed in text file @file{file}.
11619 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
11621 @file{file} must be an existing, readable text file.
11622 Each nonempty line in @file{file} must be a directory.
11623 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
11624 switches @option{^-d^/SOURCE_DIRS^} as there are nonempty lines in
11627 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
11628 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
11629 Foreign patterns. Using this switch, it is possible to add sources of languages
11630 other than Ada to the list of sources of a project file.
11631 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
11634 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
11637 will look for Ada units in all files with the @file{.ada} extension,
11638 and will add to the list of file for project @file{prj.gpr} the C files
11639 with extension @file{.^c^C^}.
11642 @cindex @option{^-h^/HELP^} (@code{gnatname})
11643 Output usage (help) information. The output is written to @file{stdout}.
11645 @item ^-P^/PROJECT_FILE=^@file{proj}
11646 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
11647 Create or update project file @file{proj}. There may be zero, one or more space
11648 between @option{-P} and @file{proj}. @file{proj} may include directory
11649 information. @file{proj} must be writable.
11650 There may be only one switch @option{^-P^/PROJECT_FILE^}.
11651 When a switch @option{^-P^/PROJECT_FILE^} is specified,
11652 no switch @option{^-c^/CONFIG_FILE^} may be specified.
11654 @item ^-v^/VERBOSE^
11655 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
11656 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
11657 This includes name of the file written, the name of the directories to search
11658 and, for each file in those directories whose name matches at least one of
11659 the Naming Patterns, an indication of whether the file contains a unit,
11660 and if so the name of the unit.
11662 @item ^-v -v^/VERBOSE /VERBOSE^
11663 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
11664 Very Verbose mode. In addition to the output produced in verbose mode,
11665 for each file in the searched directories whose name matches none of
11666 the Naming Patterns, an indication is given that there is no match.
11668 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
11669 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
11670 Excluded patterns. Using this switch, it is possible to exclude some files
11671 that would match the name patterns. For example,
11673 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
11676 will look for Ada units in all files with the @file{.ada} extension,
11677 except those whose names end with @file{_nt.ada}.
11681 @node Examples of gnatname Usage
11682 @section Examples of @code{gnatname} Usage
11686 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
11692 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
11697 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
11698 and be writable. In addition, the directory
11699 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
11700 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
11703 Note the optional spaces after @option{-c} and @option{-d}.
11708 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
11709 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
11712 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
11713 /EXCLUDED_PATTERN=*_nt_body.ada
11714 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
11715 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
11719 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
11720 even in conjunction with one or several switches
11721 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
11722 are used in this example.
11724 @c *****************************************
11725 @c * G N A T P r o j e c t M a n a g e r *
11726 @c *****************************************
11727 @node GNAT Project Manager
11728 @chapter GNAT Project Manager
11732 * Examples of Project Files::
11733 * Project File Syntax::
11734 * Objects and Sources in Project Files::
11735 * Importing Projects::
11736 * Project Extension::
11737 * Project Hierarchy Extension::
11738 * External References in Project Files::
11739 * Packages in Project Files::
11740 * Variables from Imported Projects::
11742 * Library Projects::
11743 * Stand-alone Library Projects::
11744 * Switches Related to Project Files::
11745 * Tools Supporting Project Files::
11746 * An Extended Example::
11747 * Project File Complete Syntax::
11750 @c ****************
11751 @c * Introduction *
11752 @c ****************
11755 @section Introduction
11758 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
11759 you to manage complex builds involving a number of source files, directories,
11760 and compilation options for different system configurations. In particular,
11761 project files allow you to specify:
11764 The directory or set of directories containing the source files, and/or the
11765 names of the specific source files themselves
11767 The directory in which the compiler's output
11768 (@file{ALI} files, object files, tree files) is to be placed
11770 The directory in which the executable programs is to be placed
11772 ^Switch^Switch^ settings for any of the project-enabled tools
11773 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
11774 @code{gnatfind}); you can apply these settings either globally or to individual
11777 The source files containing the main subprogram(s) to be built
11779 The source programming language(s) (currently Ada and/or C)
11781 Source file naming conventions; you can specify these either globally or for
11782 individual compilation units
11789 @node Project Files
11790 @subsection Project Files
11793 Project files are written in a syntax close to that of Ada, using familiar
11794 notions such as packages, context clauses, declarations, default values,
11795 assignments, and inheritance. Finally, project files can be built
11796 hierarchically from other project files, simplifying complex system
11797 integration and project reuse.
11799 A @dfn{project} is a specific set of values for various compilation properties.
11800 The settings for a given project are described by means of
11801 a @dfn{project file}, which is a text file written in an Ada-like syntax.
11802 Property values in project files are either strings or lists of strings.
11803 Properties that are not explicitly set receive default values. A project
11804 file may interrogate the values of @dfn{external variables} (user-defined
11805 command-line switches or environment variables), and it may specify property
11806 settings conditionally, based on the value of such variables.
11808 In simple cases, a project's source files depend only on other source files
11809 in the same project, or on the predefined libraries. (@emph{Dependence} is
11811 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
11812 the Project Manager also allows more sophisticated arrangements,
11813 where the source files in one project depend on source files in other
11817 One project can @emph{import} other projects containing needed source files.
11819 You can organize GNAT projects in a hierarchy: a @emph{child} project
11820 can extend a @emph{parent} project, inheriting the parent's source files and
11821 optionally overriding any of them with alternative versions
11825 More generally, the Project Manager lets you structure large development
11826 efforts into hierarchical subsystems, where build decisions are delegated
11827 to the subsystem level, and thus different compilation environments
11828 (^switch^switch^ settings) used for different subsystems.
11830 The Project Manager is invoked through the
11831 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
11832 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
11834 There may be zero, one or more spaces between @option{-P} and
11835 @option{@emph{projectfile}}.
11837 If you want to define (on the command line) an external variable that is
11838 queried by the project file, you must use the
11839 @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
11840 The Project Manager parses and interprets the project file, and drives the
11841 invoked tool based on the project settings.
11843 The Project Manager supports a wide range of development strategies,
11844 for systems of all sizes. Here are some typical practices that are
11848 Using a common set of source files, but generating object files in different
11849 directories via different ^switch^switch^ settings
11851 Using a mostly-shared set of source files, but with different versions of
11856 The destination of an executable can be controlled inside a project file
11857 using the @option{^-o^-o^}
11859 In the absence of such a ^switch^switch^ either inside
11860 the project file or on the command line, any executable files generated by
11861 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
11862 in the project file. If no @code{Exec_Dir} is specified, they will be placed
11863 in the object directory of the project.
11865 You can use project files to achieve some of the effects of a source
11866 versioning system (for example, defining separate projects for
11867 the different sets of sources that comprise different releases) but the
11868 Project Manager is independent of any source configuration management tools
11869 that might be used by the developers.
11871 The next section introduces the main features of GNAT's project facility
11872 through a sequence of examples; subsequent sections will present the syntax
11873 and semantics in more detail. A more formal description of the project
11874 facility appears in @ref{Project File Reference,,, gnat_rm, GNAT
11877 @c *****************************
11878 @c * Examples of Project Files *
11879 @c *****************************
11881 @node Examples of Project Files
11882 @section Examples of Project Files
11884 This section illustrates some of the typical uses of project files and
11885 explains their basic structure and behavior.
11888 * Common Sources with Different ^Switches^Switches^ and Directories::
11889 * Using External Variables::
11890 * Importing Other Projects::
11891 * Extending a Project::
11894 @node Common Sources with Different ^Switches^Switches^ and Directories
11895 @subsection Common Sources with Different ^Switches^Switches^ and Directories
11899 * Specifying the Object Directory::
11900 * Specifying the Exec Directory::
11901 * Project File Packages::
11902 * Specifying ^Switch^Switch^ Settings::
11903 * Main Subprograms::
11904 * Executable File Names::
11905 * Source File Naming Conventions::
11906 * Source Language(s)::
11910 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
11911 @file{proc.adb} are in the @file{/common} directory. The file
11912 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
11913 package @code{Pack}. We want to compile these source files under two sets
11914 of ^switches^switches^:
11917 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
11918 and the @option{^-gnata^-gnata^},
11919 @option{^-gnato^-gnato^},
11920 and @option{^-gnatE^-gnatE^} switches to the
11921 compiler; the compiler's output is to appear in @file{/common/debug}
11923 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
11924 to the compiler; the compiler's output is to appear in @file{/common/release}
11928 The GNAT project files shown below, respectively @file{debug.gpr} and
11929 @file{release.gpr} in the @file{/common} directory, achieve these effects.
11942 ^/common/debug^[COMMON.DEBUG]^
11947 ^/common/release^[COMMON.RELEASE]^
11952 Here are the corresponding project files:
11954 @smallexample @c projectfile
11957 for Object_Dir use "debug";
11958 for Main use ("proc");
11961 for ^Default_Switches^Default_Switches^ ("Ada")
11963 for Executable ("proc.adb") use "proc1";
11968 package Compiler is
11969 for ^Default_Switches^Default_Switches^ ("Ada")
11970 use ("-fstack-check",
11973 "^-gnatE^-gnatE^");
11979 @smallexample @c projectfile
11982 for Object_Dir use "release";
11983 for Exec_Dir use ".";
11984 for Main use ("proc");
11986 package Compiler is
11987 for ^Default_Switches^Default_Switches^ ("Ada")
11995 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
11996 insensitive), and analogously the project defined by @file{release.gpr} is
11997 @code{"Release"}. For consistency the file should have the same name as the
11998 project, and the project file's extension should be @code{"gpr"}. These
11999 conventions are not required, but a warning is issued if they are not followed.
12001 If the current directory is @file{^/temp^[TEMP]^}, then the command
12003 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
12007 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
12008 as well as the @code{^proc1^PROC1.EXE^} executable,
12009 using the ^switch^switch^ settings defined in the project file.
12011 Likewise, the command
12013 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
12017 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
12018 and the @code{^proc^PROC.EXE^}
12019 executable in @file{^/common^[COMMON]^},
12020 using the ^switch^switch^ settings from the project file.
12023 @unnumberedsubsubsec Source Files
12026 If a project file does not explicitly specify a set of source directories or
12027 a set of source files, then by default the project's source files are the
12028 Ada source files in the project file directory. Thus @file{pack.ads},
12029 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
12031 @node Specifying the Object Directory
12032 @unnumberedsubsubsec Specifying the Object Directory
12035 Several project properties are modeled by Ada-style @emph{attributes};
12036 a property is defined by supplying the equivalent of an Ada attribute
12037 definition clause in the project file.
12038 A project's object directory is another such a property; the corresponding
12039 attribute is @code{Object_Dir}, and its value is also a string expression,
12040 specified either as absolute or relative. In the later case,
12041 it is relative to the project file directory. Thus the compiler's
12042 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
12043 (for the @code{Debug} project)
12044 and to @file{^/common/release^[COMMON.RELEASE]^}
12045 (for the @code{Release} project).
12046 If @code{Object_Dir} is not specified, then the default is the project file
12049 @node Specifying the Exec Directory
12050 @unnumberedsubsubsec Specifying the Exec Directory
12053 A project's exec directory is another property; the corresponding
12054 attribute is @code{Exec_Dir}, and its value is also a string expression,
12055 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
12056 then the default is the object directory (which may also be the project file
12057 directory if attribute @code{Object_Dir} is not specified). Thus the executable
12058 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
12059 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
12060 and in @file{^/common^[COMMON]^} for the @code{Release} project.
12062 @node Project File Packages
12063 @unnumberedsubsubsec Project File Packages
12066 A GNAT tool that is integrated with the Project Manager is modeled by a
12067 corresponding package in the project file. In the example above,
12068 The @code{Debug} project defines the packages @code{Builder}
12069 (for @command{gnatmake}) and @code{Compiler};
12070 the @code{Release} project defines only the @code{Compiler} package.
12072 The Ada-like package syntax is not to be taken literally. Although packages in
12073 project files bear a surface resemblance to packages in Ada source code, the
12074 notation is simply a way to convey a grouping of properties for a named
12075 entity. Indeed, the package names permitted in project files are restricted
12076 to a predefined set, corresponding to the project-aware tools, and the contents
12077 of packages are limited to a small set of constructs.
12078 The packages in the example above contain attribute definitions.
12080 @node Specifying ^Switch^Switch^ Settings
12081 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
12084 ^Switch^Switch^ settings for a project-aware tool can be specified through
12085 attributes in the package that corresponds to the tool.
12086 The example above illustrates one of the relevant attributes,
12087 @code{^Default_Switches^Default_Switches^}, which is defined in packages
12088 in both project files.
12089 Unlike simple attributes like @code{Source_Dirs},
12090 @code{^Default_Switches^Default_Switches^} is
12091 known as an @emph{associative array}. When you define this attribute, you must
12092 supply an ``index'' (a literal string), and the effect of the attribute
12093 definition is to set the value of the array at the specified index.
12094 For the @code{^Default_Switches^Default_Switches^} attribute,
12095 the index is a programming language (in our case, Ada),
12096 and the value specified (after @code{use}) must be a list
12097 of string expressions.
12099 The attributes permitted in project files are restricted to a predefined set.
12100 Some may appear at project level, others in packages.
12101 For any attribute that is an associative array, the index must always be a
12102 literal string, but the restrictions on this string (e.g., a file name or a
12103 language name) depend on the individual attribute.
12104 Also depending on the attribute, its specified value will need to be either a
12105 string or a string list.
12107 In the @code{Debug} project, we set the switches for two tools,
12108 @command{gnatmake} and the compiler, and thus we include the two corresponding
12109 packages; each package defines the @code{^Default_Switches^Default_Switches^}
12110 attribute with index @code{"Ada"}.
12111 Note that the package corresponding to
12112 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
12113 similar, but only includes the @code{Compiler} package.
12115 In project @code{Debug} above, the ^switches^switches^ starting with
12116 @option{-gnat} that are specified in package @code{Compiler}
12117 could have been placed in package @code{Builder}, since @command{gnatmake}
12118 transmits all such ^switches^switches^ to the compiler.
12120 @node Main Subprograms
12121 @unnumberedsubsubsec Main Subprograms
12124 One of the specifiable properties of a project is a list of files that contain
12125 main subprograms. This property is captured in the @code{Main} attribute,
12126 whose value is a list of strings. If a project defines the @code{Main}
12127 attribute, it is not necessary to identify the main subprogram(s) when
12128 invoking @command{gnatmake} (@pxref{gnatmake and Project Files}).
12130 @node Executable File Names
12131 @unnumberedsubsubsec Executable File Names
12134 By default, the executable file name corresponding to a main source is
12135 deduced from the main source file name. Through the attributes
12136 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
12137 it is possible to change this default.
12138 In project @code{Debug} above, the executable file name
12139 for main source @file{^proc.adb^PROC.ADB^} is
12140 @file{^proc1^PROC1.EXE^}.
12141 Attribute @code{Executable_Suffix}, when specified, may change the suffix
12142 of the executable files, when no attribute @code{Executable} applies:
12143 its value replace the platform-specific executable suffix.
12144 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
12145 specify a non-default executable file name when several mains are built at once
12146 in a single @command{gnatmake} command.
12148 @node Source File Naming Conventions
12149 @unnumberedsubsubsec Source File Naming Conventions
12152 Since the project files above do not specify any source file naming
12153 conventions, the GNAT defaults are used. The mechanism for defining source
12154 file naming conventions -- a package named @code{Naming} --
12155 is described below (@pxref{Naming Schemes}).
12157 @node Source Language(s)
12158 @unnumberedsubsubsec Source Language(s)
12161 Since the project files do not specify a @code{Languages} attribute, by
12162 default the GNAT tools assume that the language of the project file is Ada.
12163 More generally, a project can comprise source files
12164 in Ada, C, and/or other languages.
12166 @node Using External Variables
12167 @subsection Using External Variables
12170 Instead of supplying different project files for debug and release, we can
12171 define a single project file that queries an external variable (set either
12172 on the command line or via an ^environment variable^logical name^) in order to
12173 conditionally define the appropriate settings. Again, assume that the
12174 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
12175 located in directory @file{^/common^[COMMON]^}. The following project file,
12176 @file{build.gpr}, queries the external variable named @code{STYLE} and
12177 defines an object directory and ^switch^switch^ settings based on whether
12178 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
12179 the default is @code{"deb"}.
12181 @smallexample @c projectfile
12184 for Main use ("proc");
12186 type Style_Type is ("deb", "rel");
12187 Style : Style_Type := external ("STYLE", "deb");
12191 for Object_Dir use "debug";
12194 for Object_Dir use "release";
12195 for Exec_Dir use ".";
12204 for ^Default_Switches^Default_Switches^ ("Ada")
12206 for Executable ("proc") use "proc1";
12215 package Compiler is
12219 for ^Default_Switches^Default_Switches^ ("Ada")
12220 use ("^-gnata^-gnata^",
12222 "^-gnatE^-gnatE^");
12225 for ^Default_Switches^Default_Switches^ ("Ada")
12236 @code{Style_Type} is an example of a @emph{string type}, which is the project
12237 file analog of an Ada enumeration type but whose components are string literals
12238 rather than identifiers. @code{Style} is declared as a variable of this type.
12240 The form @code{external("STYLE", "deb")} is known as an
12241 @emph{external reference}; its first argument is the name of an
12242 @emph{external variable}, and the second argument is a default value to be
12243 used if the external variable doesn't exist. You can define an external
12244 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
12245 or you can use ^an environment variable^a logical name^
12246 as an external variable.
12248 Each @code{case} construct is expanded by the Project Manager based on the
12249 value of @code{Style}. Thus the command
12252 gnatmake -P/common/build.gpr -XSTYLE=deb
12258 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
12263 is equivalent to the @command{gnatmake} invocation using the project file
12264 @file{debug.gpr} in the earlier example. So is the command
12266 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
12270 since @code{"deb"} is the default for @code{STYLE}.
12276 gnatmake -P/common/build.gpr -XSTYLE=rel
12282 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
12287 is equivalent to the @command{gnatmake} invocation using the project file
12288 @file{release.gpr} in the earlier example.
12290 @node Importing Other Projects
12291 @subsection Importing Other Projects
12292 @cindex @code{ADA_PROJECT_PATH}
12293 @cindex @code{GPR_PROJECT_PATH}
12296 A compilation unit in a source file in one project may depend on compilation
12297 units in source files in other projects. To compile this unit under
12298 control of a project file, the
12299 dependent project must @emph{import} the projects containing the needed source
12301 This effect is obtained using syntax similar to an Ada @code{with} clause,
12302 but where @code{with}ed entities are strings that denote project files.
12304 As an example, suppose that the two projects @code{GUI_Proj} and
12305 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
12306 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
12307 and @file{^/comm^[COMM]^}, respectively.
12308 Suppose that the source files for @code{GUI_Proj} are
12309 @file{gui.ads} and @file{gui.adb}, and that the source files for
12310 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
12311 files is located in its respective project file directory. Schematically:
12330 We want to develop an application in directory @file{^/app^[APP]^} that
12331 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
12332 the corresponding project files (e.g.@: the ^switch^switch^ settings
12333 and object directory).
12334 Skeletal code for a main procedure might be something like the following:
12336 @smallexample @c ada
12339 procedure App_Main is
12348 Here is a project file, @file{app_proj.gpr}, that achieves the desired
12351 @smallexample @c projectfile
12353 with "/gui/gui_proj", "/comm/comm_proj";
12354 project App_Proj is
12355 for Main use ("app_main");
12361 Building an executable is achieved through the command:
12363 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
12366 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
12367 in the directory where @file{app_proj.gpr} resides.
12369 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
12370 (as illustrated above) the @code{with} clause can omit the extension.
12372 Our example specified an absolute path for each imported project file.
12373 Alternatively, the directory name of an imported object can be omitted
12377 The imported project file is in the same directory as the importing project
12380 You have defined one or two ^environment variables^logical names^
12381 that includes the directory containing
12382 the needed project file. The syntax of @code{GPR_PROJECT_PATH} and
12383 @code{ADA_PROJECT_PATH} is the same as
12384 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
12385 directory names separated by colons (semicolons on Windows).
12389 Thus, if we define @code{ADA_PROJECT_PATH} or @code{GPR_PROJECT_PATH}
12390 to include @file{^/gui^[GUI]^} and
12391 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
12394 @smallexample @c projectfile
12396 with "gui_proj", "comm_proj";
12397 project App_Proj is
12398 for Main use ("app_main");
12404 Importing other projects can create ambiguities.
12405 For example, the same unit might be present in different imported projects, or
12406 it might be present in both the importing project and in an imported project.
12407 Both of these conditions are errors. Note that in the current version of
12408 the Project Manager, it is illegal to have an ambiguous unit even if the
12409 unit is never referenced by the importing project. This restriction may be
12410 relaxed in a future release.
12412 @node Extending a Project
12413 @subsection Extending a Project
12416 In large software systems it is common to have multiple
12417 implementations of a common interface; in Ada terms, multiple versions of a
12418 package body for the same spec. For example, one implementation
12419 might be safe for use in tasking programs, while another might only be used
12420 in sequential applications. This can be modeled in GNAT using the concept
12421 of @emph{project extension}. If one project (the ``child'') @emph{extends}
12422 another project (the ``parent'') then by default all source files of the
12423 parent project are inherited by the child, but the child project can
12424 override any of the parent's source files with new versions, and can also
12425 add new files. This facility is the project analog of a type extension in
12426 Object-Oriented Programming. Project hierarchies are permitted (a child
12427 project may be the parent of yet another project), and a project that
12428 inherits one project can also import other projects.
12430 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
12431 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
12432 @file{pack.adb}, and @file{proc.adb}:
12445 Note that the project file can simply be empty (that is, no attribute or
12446 package is defined):
12448 @smallexample @c projectfile
12450 project Seq_Proj is
12456 implying that its source files are all the Ada source files in the project
12459 Suppose we want to supply an alternate version of @file{pack.adb}, in
12460 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
12461 @file{pack.ads} and @file{proc.adb}. We can define a project
12462 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
12466 ^/tasking^[TASKING]^
12472 project Tasking_Proj extends "/seq/seq_proj" is
12478 The version of @file{pack.adb} used in a build depends on which project file
12481 Note that we could have obtained the desired behavior using project import
12482 rather than project inheritance; a @code{base} project would contain the
12483 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
12484 import @code{base} and add @file{pack.adb}, and likewise a tasking project
12485 would import @code{base} and add a different version of @file{pack.adb}. The
12486 choice depends on whether other sources in the original project need to be
12487 overridden. If they do, then project extension is necessary, otherwise,
12488 importing is sufficient.
12491 In a project file that extends another project file, it is possible to
12492 indicate that an inherited source is not part of the sources of the extending
12493 project. This is necessary sometimes when a package spec has been overloaded
12494 and no longer requires a body: in this case, it is necessary to indicate that
12495 the inherited body is not part of the sources of the project, otherwise there
12496 will be a compilation error when compiling the spec.
12498 For that purpose, the attribute @code{Excluded_Source_Files} is used.
12499 Its value is a string list: a list of file names. It is also possible to use
12500 attribute @code{Excluded_Source_List_File}. Its value is a single string:
12501 the file name of a text file containing a list of file names, one per line.
12503 @smallexample @c @projectfile
12504 project B extends "a" is
12505 for Source_Files use ("pkg.ads");
12506 -- New spec of Pkg does not need a completion
12507 for Excluded_Source_Files use ("pkg.adb");
12511 Attribute @code{Excluded_Source_Files} may also be used to check if a source
12512 is still needed: if it is possible to build using @command{gnatmake} when such
12513 a source is put in attribute @code{Excluded_Source_Files} of a project P, then
12514 it is possible to remove the source completely from a system that includes
12517 @c ***********************
12518 @c * Project File Syntax *
12519 @c ***********************
12521 @node Project File Syntax
12522 @section Project File Syntax
12526 * Qualified Projects::
12532 * Associative Array Attributes::
12533 * case Constructions::
12537 This section describes the structure of project files.
12539 A project may be an @emph{independent project}, entirely defined by a single
12540 project file. Any Ada source file in an independent project depends only
12541 on the predefined library and other Ada source files in the same project.
12544 A project may also @dfn{depend on} other projects, in either or both of
12545 the following ways:
12547 @item It may import any number of projects
12548 @item It may extend at most one other project
12552 The dependence relation is a directed acyclic graph (the subgraph reflecting
12553 the ``extends'' relation is a tree).
12555 A project's @dfn{immediate sources} are the source files directly defined by
12556 that project, either implicitly by residing in the project file's directory,
12557 or explicitly through any of the source-related attributes described below.
12558 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
12559 of @var{proj} together with the immediate sources (unless overridden) of any
12560 project on which @var{proj} depends (either directly or indirectly).
12563 @subsection Basic Syntax
12566 As seen in the earlier examples, project files have an Ada-like syntax.
12567 The minimal project file is:
12568 @smallexample @c projectfile
12577 The identifier @code{Empty} is the name of the project.
12578 This project name must be present after the reserved
12579 word @code{end} at the end of the project file, followed by a semi-colon.
12581 Any name in a project file, such as the project name or a variable name,
12582 has the same syntax as an Ada identifier.
12584 The reserved words of project files are the Ada 95 reserved words plus
12585 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
12586 reserved words currently used in project file syntax are:
12622 Comments in project files have the same syntax as in Ada, two consecutive
12623 hyphens through the end of the line.
12625 @node Qualified Projects
12626 @subsection Qualified Projects
12629 Before the reserved @code{project}, there may be one or two "qualifiers", that
12630 is identifiers or other reserved words, to qualify the project.
12632 The current list of qualifiers is:
12636 @code{abstract}: qualify a project with no sources. A qualified abstract
12637 project must either have no declaration of attributes @code{Source_Dirs},
12638 @code{Source_Files}, @code{Languages} or @code{Source_List_File}, or one of
12639 @code{Source_Dirs}, @code{Source_Files}, or @code{Languages} must be declared
12640 as empty. If it extends another project, the project it extends must also be a
12641 qualified abstract project.
12644 @code{standard}: a standard project is a non library project with sources.
12647 @code{aggregate}: for future extension
12650 @code{aggregate library}: for future extension
12653 @code{library}: a library project must declare both attributes
12654 @code{Library_Name} and @code{Library_Dir}.
12657 @code{configuration}: a configuration project cannot be in a project tree.
12661 @subsection Packages
12664 A project file may contain @emph{packages}. The name of a package must be one
12665 of the identifiers from the following list. A package
12666 with a given name may only appear once in a project file. Package names are
12667 case insensitive. The following package names are legal:
12683 @code{Cross_Reference}
12687 @code{Pretty_Printer}
12697 @code{Language_Processing}
12701 In its simplest form, a package may be empty:
12703 @smallexample @c projectfile
12713 A package may contain @emph{attribute declarations},
12714 @emph{variable declarations} and @emph{case constructions}, as will be
12717 When there is ambiguity between a project name and a package name,
12718 the name always designates the project. To avoid possible confusion, it is
12719 always a good idea to avoid naming a project with one of the
12720 names allowed for packages or any name that starts with @code{gnat}.
12723 @subsection Expressions
12726 An @emph{expression} is either a @emph{string expression} or a
12727 @emph{string list expression}.
12729 A @emph{string expression} is either a @emph{simple string expression} or a
12730 @emph{compound string expression}.
12732 A @emph{simple string expression} is one of the following:
12734 @item A literal string; e.g.@: @code{"comm/my_proj.gpr"}
12735 @item A string-valued variable reference (@pxref{Variables})
12736 @item A string-valued attribute reference (@pxref{Attributes})
12737 @item An external reference (@pxref{External References in Project Files})
12741 A @emph{compound string expression} is a concatenation of string expressions,
12742 using the operator @code{"&"}
12744 Path & "/" & File_Name & ".ads"
12748 A @emph{string list expression} is either a
12749 @emph{simple string list expression} or a
12750 @emph{compound string list expression}.
12752 A @emph{simple string list expression} is one of the following:
12754 @item A parenthesized list of zero or more string expressions,
12755 separated by commas
12757 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
12760 @item A string list-valued variable reference
12761 @item A string list-valued attribute reference
12765 A @emph{compound string list expression} is the concatenation (using
12766 @code{"&"}) of a simple string list expression and an expression. Note that
12767 each term in a compound string list expression, except the first, may be
12768 either a string expression or a string list expression.
12770 @smallexample @c projectfile
12772 File_Name_List := () & File_Name; -- One string in this list
12773 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
12775 Big_List := File_Name_List & Extended_File_Name_List;
12776 -- Concatenation of two string lists: three strings
12777 Illegal_List := "gnat.adc" & Extended_File_Name_List;
12778 -- Illegal: must start with a string list
12783 @subsection String Types
12786 A @emph{string type declaration} introduces a discrete set of string literals.
12787 If a string variable is declared to have this type, its value
12788 is restricted to the given set of literals.
12790 Here is an example of a string type declaration:
12792 @smallexample @c projectfile
12793 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
12797 Variables of a string type are called @emph{typed variables}; all other
12798 variables are called @emph{untyped variables}. Typed variables are
12799 particularly useful in @code{case} constructions, to support conditional
12800 attribute declarations.
12801 (@pxref{case Constructions}).
12803 The string literals in the list are case sensitive and must all be different.
12804 They may include any graphic characters allowed in Ada, including spaces.
12806 A string type may only be declared at the project level, not inside a package.
12808 A string type may be referenced by its name if it has been declared in the same
12809 project file, or by an expanded name whose prefix is the name of the project
12810 in which it is declared.
12813 @subsection Variables
12816 A variable may be declared at the project file level, or within a package.
12817 Here are some examples of variable declarations:
12819 @smallexample @c projectfile
12821 This_OS : OS := external ("OS"); -- a typed variable declaration
12822 That_OS := "GNU/Linux"; -- an untyped variable declaration
12827 The syntax of a @emph{typed variable declaration} is identical to the Ada
12828 syntax for an object declaration. By contrast, the syntax of an untyped
12829 variable declaration is identical to an Ada assignment statement. In fact,
12830 variable declarations in project files have some of the characteristics of
12831 an assignment, in that successive declarations for the same variable are
12832 allowed. Untyped variable declarations do establish the expected kind of the
12833 variable (string or string list), and successive declarations for it must
12834 respect the initial kind.
12837 A string variable declaration (typed or untyped) declares a variable
12838 whose value is a string. This variable may be used as a string expression.
12839 @smallexample @c projectfile
12840 File_Name := "readme.txt";
12841 Saved_File_Name := File_Name & ".saved";
12845 A string list variable declaration declares a variable whose value is a list
12846 of strings. The list may contain any number (zero or more) of strings.
12848 @smallexample @c projectfile
12850 List_With_One_Element := ("^-gnaty^-gnaty^");
12851 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
12852 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
12853 "pack2.ada", "util_.ada", "util.ada");
12857 The same typed variable may not be declared more than once at project level,
12858 and it may not be declared more than once in any package; it is in effect
12861 The same untyped variable may be declared several times. Declarations are
12862 elaborated in the order in which they appear, so the new value replaces
12863 the old one, and any subsequent reference to the variable uses the new value.
12864 However, as noted above, if a variable has been declared as a string, all
12866 declarations must give it a string value. Similarly, if a variable has
12867 been declared as a string list, all subsequent declarations
12868 must give it a string list value.
12870 A @emph{variable reference} may take several forms:
12873 @item The simple variable name, for a variable in the current package (if any)
12874 or in the current project
12875 @item An expanded name, whose prefix is a context name.
12879 A @emph{context} may be one of the following:
12882 @item The name of an existing package in the current project
12883 @item The name of an imported project of the current project
12884 @item The name of an ancestor project (i.e., a project extended by the current
12885 project, either directly or indirectly)
12886 @item An expanded name whose prefix is an imported/parent project name, and
12887 whose selector is a package name in that project.
12891 A variable reference may be used in an expression.
12894 @subsection Attributes
12897 A project (and its packages) may have @emph{attributes} that define
12898 the project's properties. Some attributes have values that are strings;
12899 others have values that are string lists.
12901 There are two categories of attributes: @emph{simple attributes}
12902 and @emph{associative arrays} (@pxref{Associative Array Attributes}).
12904 Legal project attribute names, and attribute names for each legal package are
12905 listed below. Attributes names are case-insensitive.
12907 The following attributes are defined on projects (all are simple attributes):
12909 @multitable @columnfractions .4 .3
12910 @item @emph{Attribute Name}
12912 @item @code{Source_Files}
12914 @item @code{Source_Dirs}
12916 @item @code{Source_List_File}
12918 @item @code{Object_Dir}
12920 @item @code{Exec_Dir}
12922 @item @code{Excluded_Source_Dirs}
12924 @item @code{Excluded_Source_Files}
12926 @item @code{Excluded_Source_List_File}
12928 @item @code{Languages}
12932 @item @code{Library_Dir}
12934 @item @code{Library_Name}
12936 @item @code{Library_Kind}
12938 @item @code{Library_Version}
12940 @item @code{Library_Interface}
12942 @item @code{Library_Auto_Init}
12944 @item @code{Library_Options}
12946 @item @code{Library_Src_Dir}
12948 @item @code{Library_ALI_Dir}
12950 @item @code{Library_GCC}
12952 @item @code{Library_Symbol_File}
12954 @item @code{Library_Symbol_Policy}
12956 @item @code{Library_Reference_Symbol_File}
12958 @item @code{Externally_Built}
12963 The following attributes are defined for package @code{Naming}
12964 (@pxref{Naming Schemes}):
12966 @multitable @columnfractions .4 .2 .2 .2
12967 @item Attribute Name @tab Category @tab Index @tab Value
12968 @item @code{Spec_Suffix}
12969 @tab associative array
12972 @item @code{Body_Suffix}
12973 @tab associative array
12976 @item @code{Separate_Suffix}
12977 @tab simple attribute
12980 @item @code{Casing}
12981 @tab simple attribute
12984 @item @code{Dot_Replacement}
12985 @tab simple attribute
12989 @tab associative array
12993 @tab associative array
12996 @item @code{Specification_Exceptions}
12997 @tab associative array
13000 @item @code{Implementation_Exceptions}
13001 @tab associative array
13007 The following attributes are defined for packages @code{Builder},
13008 @code{Compiler}, @code{Binder},
13009 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
13010 (@pxref{^Switches^Switches^ and Project Files}).
13012 @multitable @columnfractions .4 .2 .2 .2
13013 @item Attribute Name @tab Category @tab Index @tab Value
13014 @item @code{^Default_Switches^Default_Switches^}
13015 @tab associative array
13018 @item @code{^Switches^Switches^}
13019 @tab associative array
13025 In addition, package @code{Compiler} has a single string attribute
13026 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
13027 string attribute @code{Global_Configuration_Pragmas}.
13030 Each simple attribute has a default value: the empty string (for string-valued
13031 attributes) and the empty list (for string list-valued attributes).
13033 An attribute declaration defines a new value for an attribute.
13035 Examples of simple attribute declarations:
13037 @smallexample @c projectfile
13038 for Object_Dir use "objects";
13039 for Source_Dirs use ("units", "test/drivers");
13043 The syntax of a @dfn{simple attribute declaration} is similar to that of an
13044 attribute definition clause in Ada.
13046 Attributes references may be appear in expressions.
13047 The general form for such a reference is @code{<entity>'<attribute>}:
13048 Associative array attributes are functions. Associative
13049 array attribute references must have an argument that is a string literal.
13053 @smallexample @c projectfile
13055 Naming'Dot_Replacement
13056 Imported_Project'Source_Dirs
13057 Imported_Project.Naming'Casing
13058 Builder'^Default_Switches^Default_Switches^("Ada")
13062 The prefix of an attribute may be:
13064 @item @code{project} for an attribute of the current project
13065 @item The name of an existing package of the current project
13066 @item The name of an imported project
13067 @item The name of a parent project that is extended by the current project
13068 @item An expanded name whose prefix is imported/parent project name,
13069 and whose selector is a package name
13074 @smallexample @c projectfile
13077 for Source_Dirs use project'Source_Dirs & "units";
13078 for Source_Dirs use project'Source_Dirs & "test/drivers"
13084 In the first attribute declaration, initially the attribute @code{Source_Dirs}
13085 has the default value: an empty string list. After this declaration,
13086 @code{Source_Dirs} is a string list of one element: @code{"units"}.
13087 After the second attribute declaration @code{Source_Dirs} is a string list of
13088 two elements: @code{"units"} and @code{"test/drivers"}.
13090 Note: this example is for illustration only. In practice,
13091 the project file would contain only one attribute declaration:
13093 @smallexample @c projectfile
13094 for Source_Dirs use ("units", "test/drivers");
13097 @node Associative Array Attributes
13098 @subsection Associative Array Attributes
13101 Some attributes are defined as @emph{associative arrays}. An associative
13102 array may be regarded as a function that takes a string as a parameter
13103 and delivers a string or string list value as its result.
13105 Here are some examples of single associative array attribute associations:
13107 @smallexample @c projectfile
13108 for Body ("main") use "Main.ada";
13109 for ^Switches^Switches^ ("main.ada")
13111 "^-gnatv^-gnatv^");
13112 for ^Switches^Switches^ ("main.ada")
13113 use Builder'^Switches^Switches^ ("main.ada")
13118 Like untyped variables and simple attributes, associative array attributes
13119 may be declared several times. Each declaration supplies a new value for the
13120 attribute, and replaces the previous setting.
13123 An associative array attribute may be declared as a full associative array
13124 declaration, with the value of the same attribute in an imported or extended
13127 @smallexample @c projectfile
13129 for Default_Switches use Default.Builder'Default_Switches;
13134 In this example, @code{Default} must be either a project imported by the
13135 current project, or the project that the current project extends. If the
13136 attribute is in a package (in this case, in package @code{Builder}), the same
13137 package needs to be specified.
13140 A full associative array declaration replaces any other declaration for the
13141 attribute, including other full associative array declaration. Single
13142 associative array associations may be declare after a full associative
13143 declaration, modifying the value for a single association of the attribute.
13145 @node case Constructions
13146 @subsection @code{case} Constructions
13149 A @code{case} construction is used in a project file to effect conditional
13151 Here is a typical example:
13153 @smallexample @c projectfile
13156 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
13158 OS : OS_Type := external ("OS", "GNU/Linux");
13162 package Compiler is
13164 when "GNU/Linux" | "Unix" =>
13165 for ^Default_Switches^Default_Switches^ ("Ada")
13166 use ("^-gnath^-gnath^");
13168 for ^Default_Switches^Default_Switches^ ("Ada")
13169 use ("^-gnatP^-gnatP^");
13178 The syntax of a @code{case} construction is based on the Ada case statement
13179 (although there is no @code{null} construction for empty alternatives).
13181 The case expression must be a typed string variable.
13182 Each alternative comprises the reserved word @code{when}, either a list of
13183 literal strings separated by the @code{"|"} character or the reserved word
13184 @code{others}, and the @code{"=>"} token.
13185 Each literal string must belong to the string type that is the type of the
13187 An @code{others} alternative, if present, must occur last.
13189 After each @code{=>}, there are zero or more constructions. The only
13190 constructions allowed in a case construction are other case constructions,
13191 attribute declarations and variable declarations. String type declarations and
13192 package declarations are not allowed. Variable declarations are restricted to
13193 variables that have already been declared before the case construction.
13195 The value of the case variable is often given by an external reference
13196 (@pxref{External References in Project Files}).
13198 @c ****************************************
13199 @c * Objects and Sources in Project Files *
13200 @c ****************************************
13202 @node Objects and Sources in Project Files
13203 @section Objects and Sources in Project Files
13206 * Object Directory::
13208 * Source Directories::
13209 * Source File Names::
13213 Each project has exactly one object directory and one or more source
13214 directories. The source directories must contain at least one source file,
13215 unless the project file explicitly specifies that no source files are present
13216 (@pxref{Source File Names}).
13218 @node Object Directory
13219 @subsection Object Directory
13222 The object directory for a project is the directory containing the compiler's
13223 output (such as @file{ALI} files and object files) for the project's immediate
13226 The object directory is given by the value of the attribute @code{Object_Dir}
13227 in the project file.
13229 @smallexample @c projectfile
13230 for Object_Dir use "objects";
13234 The attribute @code{Object_Dir} has a string value, the path name of the object
13235 directory. The path name may be absolute or relative to the directory of the
13236 project file. This directory must already exist, and be readable and writable.
13238 By default, when the attribute @code{Object_Dir} is not given an explicit value
13239 or when its value is the empty string, the object directory is the same as the
13240 directory containing the project file.
13242 @node Exec Directory
13243 @subsection Exec Directory
13246 The exec directory for a project is the directory containing the executables
13247 for the project's main subprograms.
13249 The exec directory is given by the value of the attribute @code{Exec_Dir}
13250 in the project file.
13252 @smallexample @c projectfile
13253 for Exec_Dir use "executables";
13257 The attribute @code{Exec_Dir} has a string value, the path name of the exec
13258 directory. The path name may be absolute or relative to the directory of the
13259 project file. This directory must already exist, and be writable.
13261 By default, when the attribute @code{Exec_Dir} is not given an explicit value
13262 or when its value is the empty string, the exec directory is the same as the
13263 object directory of the project file.
13265 @node Source Directories
13266 @subsection Source Directories
13269 The source directories of a project are specified by the project file
13270 attribute @code{Source_Dirs}.
13272 This attribute's value is a string list. If the attribute is not given an
13273 explicit value, then there is only one source directory, the one where the
13274 project file resides.
13276 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
13279 @smallexample @c projectfile
13280 for Source_Dirs use ();
13284 indicates that the project contains no source files.
13286 Otherwise, each string in the string list designates one or more
13287 source directories.
13289 @smallexample @c projectfile
13290 for Source_Dirs use ("sources", "test/drivers");
13294 If a string in the list ends with @code{"/**"}, then the directory whose path
13295 name precedes the two asterisks, as well as all its subdirectories
13296 (recursively), are source directories.
13298 @smallexample @c projectfile
13299 for Source_Dirs use ("/system/sources/**");
13303 Here the directory @code{/system/sources} and all of its subdirectories
13304 (recursively) are source directories.
13306 To specify that the source directories are the directory of the project file
13307 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
13308 @smallexample @c projectfile
13309 for Source_Dirs use ("./**");
13313 Each of the source directories must exist and be readable.
13315 @node Source File Names
13316 @subsection Source File Names
13319 In a project that contains source files, their names may be specified by the
13320 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
13321 (a string). Source file names never include any directory information.
13323 If the attribute @code{Source_Files} is given an explicit value, then each
13324 element of the list is a source file name.
13326 @smallexample @c projectfile
13327 for Source_Files use ("main.adb");
13328 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
13332 If the attribute @code{Source_Files} is not given an explicit value,
13333 but the attribute @code{Source_List_File} is given a string value,
13334 then the source file names are contained in the text file whose path name
13335 (absolute or relative to the directory of the project file) is the
13336 value of the attribute @code{Source_List_File}.
13338 Each line in the file that is not empty or is not a comment
13339 contains a source file name.
13341 @smallexample @c projectfile
13342 for Source_List_File use "source_list.txt";
13346 By default, if neither the attribute @code{Source_Files} nor the attribute
13347 @code{Source_List_File} is given an explicit value, then each file in the
13348 source directories that conforms to the project's naming scheme
13349 (@pxref{Naming Schemes}) is an immediate source of the project.
13351 A warning is issued if both attributes @code{Source_Files} and
13352 @code{Source_List_File} are given explicit values. In this case, the attribute
13353 @code{Source_Files} prevails.
13355 Each source file name must be the name of one existing source file
13356 in one of the source directories.
13358 A @code{Source_Files} attribute whose value is an empty list
13359 indicates that there are no source files in the project.
13361 If the order of the source directories is known statically, that is if
13362 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
13363 be several files with the same source file name. In this case, only the file
13364 in the first directory is considered as an immediate source of the project
13365 file. If the order of the source directories is not known statically, it is
13366 an error to have several files with the same source file name.
13368 Projects can be specified to have no Ada source
13369 files: the value of @code{Source_Dirs} or @code{Source_Files} may be an empty
13370 list, or the @code{"Ada"} may be absent from @code{Languages}:
13372 @smallexample @c projectfile
13373 for Source_Dirs use ();
13374 for Source_Files use ();
13375 for Languages use ("C", "C++");
13379 Otherwise, a project must contain at least one immediate source.
13381 Projects with no source files are useful as template packages
13382 (@pxref{Packages in Project Files}) for other projects; in particular to
13383 define a package @code{Naming} (@pxref{Naming Schemes}).
13385 @c ****************************
13386 @c * Importing Projects *
13387 @c ****************************
13389 @node Importing Projects
13390 @section Importing Projects
13391 @cindex @code{ADA_PROJECT_PATH}
13392 @cindex @code{GPR_PROJECT_PATH}
13395 An immediate source of a project P may depend on source files that
13396 are neither immediate sources of P nor in the predefined library.
13397 To get this effect, P must @emph{import} the projects that contain the needed
13400 @smallexample @c projectfile
13402 with "project1", "utilities.gpr";
13403 with "/namings/apex.gpr";
13410 As can be seen in this example, the syntax for importing projects is similar
13411 to the syntax for importing compilation units in Ada. However, project files
13412 use literal strings instead of names, and the @code{with} clause identifies
13413 project files rather than packages.
13415 Each literal string is the file name or path name (absolute or relative) of a
13416 project file. If a string corresponds to a file name, with no path or a
13417 relative path, then its location is determined by the @emph{project path}. The
13418 latter can be queried using @code{gnatls -v}. It contains:
13422 In first position, the directory containing the current project file.
13424 In last position, the default project directory. This default project directory
13425 is part of the GNAT installation and is the standard place to install project
13426 files giving access to standard support libraries.
13428 @ref{Installing a library}
13432 In between, all the directories referenced in the
13433 ^environment variables^logical names^ @env{GPR_PROJECT_PATH}
13434 and @env{ADA_PROJECT_PATH} if they exist, and in that order.
13438 If a relative pathname is used, as in
13440 @smallexample @c projectfile
13445 then the full path for the project is constructed by concatenating this
13446 relative path to those in the project path, in order, until a matching file is
13447 found. Any symbolic link will be fully resolved in the directory of the
13448 importing project file before the imported project file is examined.
13450 If the @code{with}'ed project file name does not have an extension,
13451 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
13452 then the file name as specified in the @code{with} clause (no extension) will
13453 be used. In the above example, if a file @code{project1.gpr} is found, then it
13454 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
13455 then it will be used; if neither file exists, this is an error.
13457 A warning is issued if the name of the project file does not match the
13458 name of the project; this check is case insensitive.
13460 Any source file that is an immediate source of the imported project can be
13461 used by the immediate sources of the importing project, transitively. Thus
13462 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
13463 sources of @code{A} may depend on the immediate sources of @code{C}, even if
13464 @code{A} does not import @code{C} explicitly. However, this is not recommended,
13465 because if and when @code{B} ceases to import @code{C}, some sources in
13466 @code{A} will no longer compile.
13468 A side effect of this capability is that normally cyclic dependencies are not
13469 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
13470 is not allowed to import @code{A}. However, there are cases when cyclic
13471 dependencies would be beneficial. For these cases, another form of import
13472 between projects exists, the @code{limited with}: a project @code{A} that
13473 imports a project @code{B} with a straight @code{with} may also be imported,
13474 directly or indirectly, by @code{B} on the condition that imports from @code{B}
13475 to @code{A} include at least one @code{limited with}.
13477 @smallexample @c 0projectfile
13483 limited with "../a/a.gpr";
13491 limited with "../a/a.gpr";
13497 In the above legal example, there are two project cycles:
13500 @item A -> C -> D -> A
13504 In each of these cycle there is one @code{limited with}: import of @code{A}
13505 from @code{B} and import of @code{A} from @code{D}.
13507 The difference between straight @code{with} and @code{limited with} is that
13508 the name of a project imported with a @code{limited with} cannot be used in the
13509 project that imports it. In particular, its packages cannot be renamed and
13510 its variables cannot be referred to.
13512 An exception to the above rules for @code{limited with} is that for the main
13513 project specified to @command{gnatmake} or to the @command{GNAT} driver a
13514 @code{limited with} is equivalent to a straight @code{with}. For example,
13515 in the example above, projects @code{B} and @code{D} could not be main
13516 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
13517 each have a @code{limited with} that is the only one in a cycle of importing
13520 @c *********************
13521 @c * Project Extension *
13522 @c *********************
13524 @node Project Extension
13525 @section Project Extension
13528 During development of a large system, it is sometimes necessary to use
13529 modified versions of some of the source files, without changing the original
13530 sources. This can be achieved through the @emph{project extension} facility.
13532 @smallexample @c projectfile
13533 project Modified_Utilities extends "/baseline/utilities.gpr" is @dots{}
13537 A project extension declaration introduces an extending project
13538 (the @emph{child}) and a project being extended (the @emph{parent}).
13540 By default, a child project inherits all the sources of its parent.
13541 However, inherited sources can be overridden: a unit in a parent is hidden
13542 by a unit of the same name in the child.
13544 Inherited sources are considered to be sources (but not immediate sources)
13545 of the child project; see @ref{Project File Syntax}.
13547 An inherited source file retains any switches specified in the parent project.
13549 For example if the project @code{Utilities} contains the spec and the
13550 body of an Ada package @code{Util_IO}, then the project
13551 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
13552 The original body of @code{Util_IO} will not be considered in program builds.
13553 However, the package spec will still be found in the project
13556 A child project can have only one parent, except when it is qualified as
13557 abstract. But it may import any number of other projects.
13559 A project is not allowed to import directly or indirectly at the same time a
13560 child project and any of its ancestors.
13562 @c *******************************
13563 @c * Project Hierarchy Extension *
13564 @c *******************************
13566 @node Project Hierarchy Extension
13567 @section Project Hierarchy Extension
13570 When extending a large system spanning multiple projects, it is often
13571 inconvenient to extend every project in the hierarchy that is impacted by a
13572 small change introduced. In such cases, it is possible to create a virtual
13573 extension of entire hierarchy using @code{extends all} relationship.
13575 When the project is extended using @code{extends all} inheritance, all projects
13576 that are imported by it, both directly and indirectly, are considered virtually
13577 extended. That is, the Project Manager creates "virtual projects"
13578 that extend every project in the hierarchy; all these virtual projects have
13579 no sources of their own and have as object directory the object directory of
13580 the root of "extending all" project.
13582 It is possible to explicitly extend one or more projects in the hierarchy
13583 in order to modify the sources. These extending projects must be imported by
13584 the "extending all" project, which will replace the corresponding virtual
13585 projects with the explicit ones.
13587 When building such a project hierarchy extension, the Project Manager will
13588 ensure that both modified sources and sources in virtual extending projects
13589 that depend on them, are recompiled.
13591 By means of example, consider the following hierarchy of projects.
13595 project A, containing package P1
13597 project B importing A and containing package P2 which depends on P1
13599 project C importing B and containing package P3 which depends on P2
13603 We want to modify packages P1 and P3.
13605 This project hierarchy will need to be extended as follows:
13609 Create project A1 that extends A, placing modified P1 there:
13611 @smallexample @c 0projectfile
13612 project A1 extends "(@dots{})/A" is
13617 Create project C1 that "extends all" C and imports A1, placing modified
13620 @smallexample @c 0projectfile
13621 with "(@dots{})/A1";
13622 project C1 extends all "(@dots{})/C" is
13627 When you build project C1, your entire modified project space will be
13628 recompiled, including the virtual project B1 that has been impacted by the
13629 "extending all" inheritance of project C.
13631 Note that if a Library Project in the hierarchy is virtually extended,
13632 the virtual project that extends the Library Project is not a Library Project.
13634 @c ****************************************
13635 @c * External References in Project Files *
13636 @c ****************************************
13638 @node External References in Project Files
13639 @section External References in Project Files
13642 A project file may contain references to external variables; such references
13643 are called @emph{external references}.
13645 An external variable is either defined as part of the environment (an
13646 environment variable in Unix, for example) or else specified on the command
13647 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
13648 If both, then the command line value is used.
13650 The value of an external reference is obtained by means of the built-in
13651 function @code{external}, which returns a string value.
13652 This function has two forms:
13654 @item @code{external (external_variable_name)}
13655 @item @code{external (external_variable_name, default_value)}
13659 Each parameter must be a string literal. For example:
13661 @smallexample @c projectfile
13663 external ("OS", "GNU/Linux")
13667 In the form with one parameter, the function returns the value of
13668 the external variable given as parameter. If this name is not present in the
13669 environment, the function returns an empty string.
13671 In the form with two string parameters, the second argument is
13672 the value returned when the variable given as the first argument is not
13673 present in the environment. In the example above, if @code{"OS"} is not
13674 the name of ^an environment variable^a logical name^ and is not passed on
13675 the command line, then the returned value is @code{"GNU/Linux"}.
13677 An external reference may be part of a string expression or of a string
13678 list expression, and can therefore appear in a variable declaration or
13679 an attribute declaration.
13681 @smallexample @c projectfile
13683 type Mode_Type is ("Debug", "Release");
13684 Mode : Mode_Type := external ("MODE");
13691 @c *****************************
13692 @c * Packages in Project Files *
13693 @c *****************************
13695 @node Packages in Project Files
13696 @section Packages in Project Files
13699 A @emph{package} defines the settings for project-aware tools within a
13701 For each such tool one can declare a package; the names for these
13702 packages are preset (@pxref{Packages}).
13703 A package may contain variable declarations, attribute declarations, and case
13706 @smallexample @c projectfile
13709 package Builder is -- used by gnatmake
13710 for ^Default_Switches^Default_Switches^ ("Ada")
13719 The syntax of package declarations mimics that of package in Ada.
13721 Most of the packages have an attribute
13722 @code{^Default_Switches^Default_Switches^}.
13723 This attribute is an associative array, and its value is a string list.
13724 The index of the associative array is the name of a programming language (case
13725 insensitive). This attribute indicates the ^switch^switch^
13726 or ^switches^switches^ to be used
13727 with the corresponding tool.
13729 Some packages also have another attribute, @code{^Switches^Switches^},
13730 an associative array whose value is a string list.
13731 The index is the name of a source file.
13732 This attribute indicates the ^switch^switch^
13733 or ^switches^switches^ to be used by the corresponding
13734 tool when dealing with this specific file.
13736 Further information on these ^switch^switch^-related attributes is found in
13737 @ref{^Switches^Switches^ and Project Files}.
13739 A package may be declared as a @emph{renaming} of another package; e.g., from
13740 the project file for an imported project.
13742 @smallexample @c projectfile
13744 with "/global/apex.gpr";
13746 package Naming renames Apex.Naming;
13753 Packages that are renamed in other project files often come from project files
13754 that have no sources: they are just used as templates. Any modification in the
13755 template will be reflected automatically in all the project files that rename
13756 a package from the template.
13758 In addition to the tool-oriented packages, you can also declare a package
13759 named @code{Naming} to establish specialized source file naming conventions
13760 (@pxref{Naming Schemes}).
13762 @c ************************************
13763 @c * Variables from Imported Projects *
13764 @c ************************************
13766 @node Variables from Imported Projects
13767 @section Variables from Imported Projects
13770 An attribute or variable defined in an imported or parent project can
13771 be used in expressions in the importing / extending project.
13772 Such an attribute or variable is denoted by an expanded name whose prefix
13773 is either the name of the project or the expanded name of a package within
13776 @smallexample @c projectfile
13779 project Main extends "base" is
13780 Var1 := Imported.Var;
13781 Var2 := Base.Var & ".new";
13786 for ^Default_Switches^Default_Switches^ ("Ada")
13787 use Imported.Builder'Ada_^Switches^Switches^ &
13788 "^-gnatg^-gnatg^" &
13794 package Compiler is
13795 for ^Default_Switches^Default_Switches^ ("Ada")
13796 use Base.Compiler'Ada_^Switches^Switches^;
13807 The value of @code{Var1} is a copy of the variable @code{Var} defined
13808 in the project file @file{"imported.gpr"}
13810 the value of @code{Var2} is a copy of the value of variable @code{Var}
13811 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
13813 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13814 @code{Builder} is a string list that includes in its value a copy of the value
13815 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
13816 in project file @file{imported.gpr} plus two new elements:
13817 @option{"^-gnatg^-gnatg^"}
13818 and @option{"^-v^-v^"};
13820 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
13821 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
13822 defined in the @code{Compiler} package in project file @file{base.gpr},
13823 the project being extended.
13826 @c ******************
13827 @c * Naming Schemes *
13828 @c ******************
13830 @node Naming Schemes
13831 @section Naming Schemes
13834 Sometimes an Ada software system is ported from a foreign compilation
13835 environment to GNAT, and the file names do not use the default GNAT
13836 conventions. Instead of changing all the file names (which for a variety
13837 of reasons might not be possible), you can define the relevant file
13838 naming scheme in the @code{Naming} package in your project file.
13841 Note that the use of pragmas described in
13842 @ref{Alternative File Naming Schemes} by mean of a configuration
13843 pragmas file is not supported when using project files. You must use
13844 the features described in this paragraph. You can however use specify
13845 other configuration pragmas (@pxref{Specifying Configuration Pragmas}).
13848 For example, the following
13849 package models the Apex file naming rules:
13851 @smallexample @c projectfile
13854 for Casing use "lowercase";
13855 for Dot_Replacement use ".";
13856 for Spec_Suffix ("Ada") use ".1.ada";
13857 for Body_Suffix ("Ada") use ".2.ada";
13864 For example, the following package models the HP Ada file naming rules:
13866 @smallexample @c projectfile
13869 for Casing use "lowercase";
13870 for Dot_Replacement use "__";
13871 for Spec_Suffix ("Ada") use "_.^ada^ada^";
13872 for Body_Suffix ("Ada") use ".^ada^ada^";
13878 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
13879 names in lower case)
13883 You can define the following attributes in package @code{Naming}:
13887 @item @code{Casing}
13888 This must be a string with one of the three values @code{"lowercase"},
13889 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
13892 If @code{Casing} is not specified, then the default is @code{"lowercase"}.
13894 @item @code{Dot_Replacement}
13895 This must be a string whose value satisfies the following conditions:
13898 @item It must not be empty
13899 @item It cannot start or end with an alphanumeric character
13900 @item It cannot be a single underscore
13901 @item It cannot start with an underscore followed by an alphanumeric
13902 @item It cannot contain a dot @code{'.'} except if the entire string
13907 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
13909 @item @code{Spec_Suffix}
13910 This is an associative array (indexed by the programming language name, case
13911 insensitive) whose value is a string that must satisfy the following
13915 @item It must not be empty
13916 @item It must include at least one dot
13919 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
13920 @code{"^.ads^.ADS^"}.
13922 @item @code{Body_Suffix}
13923 This is an associative array (indexed by the programming language name, case
13924 insensitive) whose value is a string that must satisfy the following
13928 @item It must not be empty
13929 @item It must include at least one dot
13930 @item It cannot be the same as @code{Spec_Suffix ("Ada")}
13933 If @code{Body_Suffix ("Ada")} and @code{Spec_Suffix ("Ada")} end with the
13934 same string, then a file name that ends with the longest of these two suffixes
13935 will be a body if the longest suffix is @code{Body_Suffix ("Ada")} or a spec
13936 if the longest suffix is @code{Spec_Suffix ("Ada")}.
13938 If the suffix does not start with a '.', a file with a name exactly equal
13939 to the suffix will also be part of the project (for instance if you define
13940 the suffix as @code{Makefile}, a file called @file{Makefile} will be part
13941 of the project. This is not interesting in general when using projects to
13942 compile. However, it might become useful when a project is also used to
13943 find the list of source files in an editor, like the GNAT Programming System
13946 If @code{Body_Suffix ("Ada")} is not specified, then the default is
13947 @code{"^.adb^.ADB^"}.
13949 @item @code{Separate_Suffix}
13950 This must be a string whose value satisfies the same conditions as
13951 @code{Body_Suffix}. The same "longest suffix" rules apply.
13954 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
13955 value as @code{Body_Suffix ("Ada")}.
13959 You can use the associative array attribute @code{Spec} to define
13960 the source file name for an individual Ada compilation unit's spec. The array
13961 index must be a string literal that identifies the Ada unit (case insensitive).
13962 The value of this attribute must be a string that identifies the file that
13963 contains this unit's spec (case sensitive or insensitive depending on the
13966 @smallexample @c projectfile
13967 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
13970 When the source file contains several units, you can indicate at what
13971 position the unit occurs in the file, with the following. The first unit
13972 in the file has index 1
13974 @smallexample @c projectfile
13975 for Body ("top") use "foo.a" at 1;
13976 for Body ("foo") use "foo.a" at 2;
13981 You can use the associative array attribute @code{Body} to
13982 define the source file name for an individual Ada compilation unit's body
13983 (possibly a subunit). The array index must be a string literal that identifies
13984 the Ada unit (case insensitive). The value of this attribute must be a string
13985 that identifies the file that contains this unit's body or subunit (case
13986 sensitive or insensitive depending on the operating system).
13988 @smallexample @c projectfile
13989 for Body ("MyPack.MyChild") use "mypack.mychild.body";
13993 @c ********************
13994 @c * Library Projects *
13995 @c ********************
13997 @node Library Projects
13998 @section Library Projects
14001 @emph{Library projects} are projects whose object code is placed in a library.
14002 (Note that this facility is not yet supported on all platforms).
14004 @code{gnatmake} or @code{gprbuild} will collect all object files into a
14005 single archive, which might either be a shared or a static library. This
14006 library can later on be linked with multiple executables, potentially
14007 reducing their sizes.
14009 If your project file specifies languages other than Ada, but you are still
14010 using @code{gnatmake} to compile and link, the latter will not try to
14011 compile your sources other than Ada (you should use @code{gprbuild} if that
14012 is your intent). However, @code{gnatmake} will automatically link all object
14013 files found in the object directory, whether or not they were compiled from
14014 an Ada source file. This specific behavior only applies when multiple
14015 languages are specified.
14017 To create a library project, you need to define in its project file
14018 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
14019 Additionally, you may define other library-related attributes such as
14020 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
14021 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
14023 The @code{Library_Name} attribute has a string value. There is no restriction
14024 on the name of a library. It is the responsibility of the developer to
14025 choose a name that will be accepted by the platform. It is recommended to
14026 choose names that could be Ada identifiers; such names are almost guaranteed
14027 to be acceptable on all platforms.
14029 The @code{Library_Dir} attribute has a string value that designates the path
14030 (absolute or relative) of the directory where the library will reside.
14031 It must designate an existing directory, and this directory must be writable,
14032 different from the project's object directory and from any source directory
14033 in the project tree.
14035 If both @code{Library_Name} and @code{Library_Dir} are specified and
14036 are legal, then the project file defines a library project. The optional
14037 library-related attributes are checked only for such project files.
14039 The @code{Library_Kind} attribute has a string value that must be one of the
14040 following (case insensitive): @code{"static"}, @code{"dynamic"} or
14041 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
14042 attribute is not specified, the library is a static library, that is
14043 an archive of object files that can be potentially linked into a
14044 static executable. Otherwise, the library may be dynamic or
14045 relocatable, that is a library that is loaded only at the start of execution.
14047 If you need to build both a static and a dynamic library, you should use two
14048 different object directories, since in some cases some extra code needs to
14049 be generated for the latter. For such cases, it is recommended to either use
14050 two different project files, or a single one which uses external variables
14051 to indicate what kind of library should be build.
14053 The @code{Library_ALI_Dir} attribute may be specified to indicate the
14054 directory where the ALI files of the library will be copied. When it is
14055 not specified, the ALI files are copied to the directory specified in
14056 attribute @code{Library_Dir}. The directory specified by @code{Library_ALI_Dir}
14057 must be writable and different from the project's object directory and from
14058 any source directory in the project tree.
14060 The @code{Library_Version} attribute has a string value whose interpretation
14061 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
14062 used only for dynamic/relocatable libraries as the internal name of the
14063 library (the @code{"soname"}). If the library file name (built from the
14064 @code{Library_Name}) is different from the @code{Library_Version}, then the
14065 library file will be a symbolic link to the actual file whose name will be
14066 @code{Library_Version}.
14070 @smallexample @c projectfile
14076 for Library_Dir use "lib_dir";
14077 for Library_Name use "dummy";
14078 for Library_Kind use "relocatable";
14079 for Library_Version use "libdummy.so." & Version;
14086 Directory @file{lib_dir} will contain the internal library file whose name
14087 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
14088 @file{libdummy.so.1}.
14090 When @command{gnatmake} detects that a project file
14091 is a library project file, it will check all immediate sources of the project
14092 and rebuild the library if any of the sources have been recompiled.
14094 Standard project files can import library project files. In such cases,
14095 the libraries will only be rebuilt if some of its sources are recompiled
14096 because they are in the closure of some other source in an importing project.
14097 Sources of the library project files that are not in such a closure will
14098 not be checked, unless the full library is checked, because one of its sources
14099 needs to be recompiled.
14101 For instance, assume the project file @code{A} imports the library project file
14102 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
14103 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
14104 @file{l2.ads}, @file{l2.adb}.
14106 If @file{l1.adb} has been modified, then the library associated with @code{L}
14107 will be rebuilt when compiling all the immediate sources of @code{A} only
14108 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
14111 To be sure that all the sources in the library associated with @code{L} are
14112 up to date, and that all the sources of project @code{A} are also up to date,
14113 the following two commands needs to be used:
14120 When a library is built or rebuilt, an attempt is made first to delete all
14121 files in the library directory.
14122 All @file{ALI} files will also be copied from the object directory to the
14123 library directory. To build executables, @command{gnatmake} will use the
14124 library rather than the individual object files.
14127 It is also possible to create library project files for third-party libraries
14128 that are precompiled and cannot be compiled locally thanks to the
14129 @code{externally_built} attribute. (See @ref{Installing a library}).
14132 @c *******************************
14133 @c * Stand-alone Library Projects *
14134 @c *******************************
14136 @node Stand-alone Library Projects
14137 @section Stand-alone Library Projects
14140 A Stand-alone Library is a library that contains the necessary code to
14141 elaborate the Ada units that are included in the library. A Stand-alone
14142 Library is suitable to be used in an executable when the main is not
14143 in Ada. However, Stand-alone Libraries may also be used with an Ada main
14146 A Stand-alone Library Project is a Library Project where the library is
14147 a Stand-alone Library.
14149 To be a Stand-alone Library Project, in addition to the two attributes
14150 that make a project a Library Project (@code{Library_Name} and
14151 @code{Library_Dir}, see @ref{Library Projects}), the attribute
14152 @code{Library_Interface} must be defined.
14154 @smallexample @c projectfile
14156 for Library_Dir use "lib_dir";
14157 for Library_Name use "dummy";
14158 for Library_Interface use ("int1", "int1.child");
14162 Attribute @code{Library_Interface} has a nonempty string list value,
14163 each string in the list designating a unit contained in an immediate source
14164 of the project file.
14166 When a Stand-alone Library is built, first the binder is invoked to build
14167 a package whose name depends on the library name
14168 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
14169 This binder-generated package includes initialization and
14170 finalization procedures whose
14171 names depend on the library name (dummyinit and dummyfinal in the example
14172 above). The object corresponding to this package is included in the library.
14174 A dynamic or relocatable Stand-alone Library is automatically initialized
14175 if automatic initialization of Stand-alone Libraries is supported on the
14176 platform and if attribute @code{Library_Auto_Init} is not specified or
14177 is specified with the value "true". A static Stand-alone Library is never
14178 automatically initialized.
14180 Single string attribute @code{Library_Auto_Init} may be specified with only
14181 two possible values: "false" or "true" (case-insensitive). Specifying
14182 "false" for attribute @code{Library_Auto_Init} will prevent automatic
14183 initialization of dynamic or relocatable libraries.
14185 When a non-automatically initialized Stand-alone Library is used
14186 in an executable, its initialization procedure must be called before
14187 any service of the library is used.
14188 When the main subprogram is in Ada, it may mean that the initialization
14189 procedure has to be called during elaboration of another package.
14191 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
14192 (those that are listed in attribute @code{Library_Interface}) are copied to
14193 the Library Directory. As a consequence, only the Interface Units may be
14194 imported from Ada units outside of the library. If other units are imported,
14195 the binding phase will fail.
14197 When a Stand-Alone Library is bound, the switches that are specified in
14198 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
14199 used in the call to @command{gnatbind}.
14201 The string list attribute @code{Library_Options} may be used to specified
14202 additional switches to the call to @command{gcc} to link the library.
14204 The attribute @code{Library_Src_Dir}, may be specified for a
14205 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
14206 single string value. Its value must be the path (absolute or relative to the
14207 project directory) of an existing directory. This directory cannot be the
14208 object directory or one of the source directories, but it can be the same as
14209 the library directory. The sources of the Interface
14210 Units of the library, necessary to an Ada client of the library, will be
14211 copied to the designated directory, called Interface Copy directory.
14212 These sources includes the specs of the Interface Units, but they may also
14213 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
14214 are used, or when there is a generic units in the spec. Before the sources
14215 are copied to the Interface Copy directory, an attempt is made to delete all
14216 files in the Interface Copy directory.
14218 @c *************************************
14219 @c * Switches Related to Project Files *
14220 @c *************************************
14221 @node Switches Related to Project Files
14222 @section Switches Related to Project Files
14225 The following switches are used by GNAT tools that support project files:
14229 @item ^-P^/PROJECT_FILE=^@var{project}
14230 @cindex @option{^-P^/PROJECT_FILE^} (any project-aware tool)
14231 Indicates the name of a project file. This project file will be parsed with
14232 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
14233 if any, and using the external references indicated
14234 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
14236 There may zero, one or more spaces between @option{-P} and @var{project}.
14240 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
14243 Since the Project Manager parses the project file only after all the switches
14244 on the command line are checked, the order of the switches
14245 @option{^-P^/PROJECT_FILE^},
14246 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
14247 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
14249 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
14250 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any project-aware tool)
14251 Indicates that external variable @var{name} has the value @var{value}.
14252 The Project Manager will use this value for occurrences of
14253 @code{external(name)} when parsing the project file.
14257 If @var{name} or @var{value} includes a space, then @var{name=value} should be
14258 put between quotes.
14266 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
14267 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
14268 @var{name}, only the last one is used.
14271 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
14272 takes precedence over the value of the same name in the environment.
14274 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
14275 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (any project-aware tool)
14276 Indicates the verbosity of the parsing of GNAT project files.
14279 @option{-vP0} means Default;
14280 @option{-vP1} means Medium;
14281 @option{-vP2} means High.
14285 There are three possible options for this qualifier: DEFAULT, MEDIUM and
14290 The default is ^Default^DEFAULT^: no output for syntactically correct
14293 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
14294 only the last one is used.
14296 @item ^-aP^/ADD_PROJECT_SEARCH_DIR=^<dir>
14297 @cindex @option{^-aP^/ADD_PROJECT_SEARCH_DIR=^} (any project-aware tool)
14298 Add directory <dir> at the beginning of the project search path, in order,
14299 after the current working directory.
14303 @cindex @option{-eL} (any project-aware tool)
14304 Follow all symbolic links when processing project files.
14307 @item ^--subdirs^/SUBDIRS^=<subdir>
14308 @cindex @option{^--subdirs^/SUBDIRS^=} (gnatmake and gnatclean)
14309 This switch is recognized by gnatmake and gnatclean. It indicate that the real
14310 directories (except the source directories) are the subdirectories <subdir>
14311 of the directories specified in the project files. This applies in particular
14312 to object directories, library directories and exec directories. If the
14313 subdirectories do not exist, they are created automatically.
14317 @c **********************************
14318 @c * Tools Supporting Project Files *
14319 @c **********************************
14321 @node Tools Supporting Project Files
14322 @section Tools Supporting Project Files
14325 * gnatmake and Project Files::
14326 * The GNAT Driver and Project Files::
14329 @node gnatmake and Project Files
14330 @subsection gnatmake and Project Files
14333 This section covers several topics related to @command{gnatmake} and
14334 project files: defining ^switches^switches^ for @command{gnatmake}
14335 and for the tools that it invokes; specifying configuration pragmas;
14336 the use of the @code{Main} attribute; building and rebuilding library project
14340 * ^Switches^Switches^ and Project Files::
14341 * Specifying Configuration Pragmas::
14342 * Project Files and Main Subprograms::
14343 * Library Project Files::
14346 @node ^Switches^Switches^ and Project Files
14347 @subsubsection ^Switches^Switches^ and Project Files
14350 It is not currently possible to specify VMS style qualifiers in the project
14351 files; only Unix style ^switches^switches^ may be specified.
14355 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
14356 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
14357 attribute, a @code{^Switches^Switches^} attribute, or both;
14358 as their names imply, these ^switch^switch^-related
14359 attributes affect the ^switches^switches^ that are used for each of these GNAT
14361 @command{gnatmake} is invoked. As will be explained below, these
14362 component-specific ^switches^switches^ precede
14363 the ^switches^switches^ provided on the @command{gnatmake} command line.
14365 The @code{^Default_Switches^Default_Switches^} attribute is an associative
14366 array indexed by language name (case insensitive) whose value is a string list.
14369 @smallexample @c projectfile
14371 package Compiler is
14372 for ^Default_Switches^Default_Switches^ ("Ada")
14373 use ("^-gnaty^-gnaty^",
14380 The @code{^Switches^Switches^} attribute is also an associative array,
14381 indexed by a file name (which may or may not be case sensitive, depending
14382 on the operating system) whose value is a string list. For example:
14384 @smallexample @c projectfile
14387 for ^Switches^Switches^ ("main1.adb")
14389 for ^Switches^Switches^ ("main2.adb")
14396 For the @code{Builder} package, the file names must designate source files
14397 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
14398 file names must designate @file{ALI} or source files for main subprograms.
14399 In each case just the file name without an explicit extension is acceptable.
14401 For each tool used in a program build (@command{gnatmake}, the compiler, the
14402 binder, and the linker), the corresponding package @dfn{contributes} a set of
14403 ^switches^switches^ for each file on which the tool is invoked, based on the
14404 ^switch^switch^-related attributes defined in the package.
14405 In particular, the ^switches^switches^
14406 that each of these packages contributes for a given file @var{f} comprise:
14410 the value of attribute @code{^Switches^Switches^ (@var{f})},
14411 if it is specified in the package for the given file,
14413 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
14414 if it is specified in the package.
14418 If neither of these attributes is defined in the package, then the package does
14419 not contribute any ^switches^switches^ for the given file.
14421 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
14422 two sets, in the following order: those contributed for the file
14423 by the @code{Builder} package;
14424 and the switches passed on the command line.
14426 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
14427 the ^switches^switches^ passed to the tool comprise three sets,
14428 in the following order:
14432 the applicable ^switches^switches^ contributed for the file
14433 by the @code{Builder} package in the project file supplied on the command line;
14436 those contributed for the file by the package (in the relevant project file --
14437 see below) corresponding to the tool; and
14440 the applicable switches passed on the command line.
14444 The term @emph{applicable ^switches^switches^} reflects the fact that
14445 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
14446 tools, depending on the individual ^switch^switch^.
14448 @command{gnatmake} may invoke the compiler on source files from different
14449 projects. The Project Manager will use the appropriate project file to
14450 determine the @code{Compiler} package for each source file being compiled.
14451 Likewise for the @code{Binder} and @code{Linker} packages.
14453 As an example, consider the following package in a project file:
14455 @smallexample @c projectfile
14458 package Compiler is
14459 for ^Default_Switches^Default_Switches^ ("Ada")
14461 for ^Switches^Switches^ ("a.adb")
14463 for ^Switches^Switches^ ("b.adb")
14465 "^-gnaty^-gnaty^");
14472 If @command{gnatmake} is invoked with this project file, and it needs to
14473 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
14474 @file{a.adb} will be compiled with the ^switch^switch^
14475 @option{^-O1^-O1^},
14476 @file{b.adb} with ^switches^switches^
14478 and @option{^-gnaty^-gnaty^},
14479 and @file{c.adb} with @option{^-g^-g^}.
14481 The following example illustrates the ordering of the ^switches^switches^
14482 contributed by different packages:
14484 @smallexample @c projectfile
14488 for ^Switches^Switches^ ("main.adb")
14496 package Compiler is
14497 for ^Switches^Switches^ ("main.adb")
14505 If you issue the command:
14508 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
14512 then the compiler will be invoked on @file{main.adb} with the following
14513 sequence of ^switches^switches^
14516 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
14519 with the last @option{^-O^-O^}
14520 ^switch^switch^ having precedence over the earlier ones;
14521 several other ^switches^switches^
14522 (such as @option{^-c^-c^}) are added implicitly.
14524 The ^switches^switches^
14526 and @option{^-O1^-O1^} are contributed by package
14527 @code{Builder}, @option{^-O2^-O2^} is contributed
14528 by the package @code{Compiler}
14529 and @option{^-O0^-O0^} comes from the command line.
14531 The @option{^-g^-g^}
14532 ^switch^switch^ will also be passed in the invocation of
14533 @command{Gnatlink.}
14535 A final example illustrates switch contributions from packages in different
14538 @smallexample @c projectfile
14541 for Source_Files use ("pack.ads", "pack.adb");
14542 package Compiler is
14543 for ^Default_Switches^Default_Switches^ ("Ada")
14544 use ("^-gnata^-gnata^");
14552 for Source_Files use ("foo_main.adb", "bar_main.adb");
14554 for ^Switches^Switches^ ("foo_main.adb")
14562 -- Ada source file:
14564 procedure Foo_Main is
14572 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
14576 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
14577 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
14578 @option{^-gnato^-gnato^} (passed on the command line).
14579 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
14580 are @option{^-g^-g^} from @code{Proj4.Builder},
14581 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
14582 and @option{^-gnato^-gnato^} from the command line.
14585 When using @command{gnatmake} with project files, some ^switches^switches^ or
14586 arguments may be expressed as relative paths. As the working directory where
14587 compilation occurs may change, these relative paths are converted to absolute
14588 paths. For the ^switches^switches^ found in a project file, the relative paths
14589 are relative to the project file directory, for the switches on the command
14590 line, they are relative to the directory where @command{gnatmake} is invoked.
14591 The ^switches^switches^ for which this occurs are:
14597 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
14599 ^-o^-o^, object files specified in package @code{Linker} or after
14600 -largs on the command line). The exception to this rule is the ^switch^switch^
14601 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
14603 @node Specifying Configuration Pragmas
14604 @subsubsection Specifying Configuration Pragmas
14606 When using @command{gnatmake} with project files, if there exists a file
14607 @file{gnat.adc} that contains configuration pragmas, this file will be
14610 Configuration pragmas can be defined by means of the following attributes in
14611 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
14612 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
14614 Both these attributes are single string attributes. Their values is the path
14615 name of a file containing configuration pragmas. If a path name is relative,
14616 then it is relative to the project directory of the project file where the
14617 attribute is defined.
14619 When compiling a source, the configuration pragmas used are, in order,
14620 those listed in the file designated by attribute
14621 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
14622 project file, if it is specified, and those listed in the file designated by
14623 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
14624 the project file of the source, if it exists.
14626 @node Project Files and Main Subprograms
14627 @subsubsection Project Files and Main Subprograms
14630 When using a project file, you can invoke @command{gnatmake}
14631 with one or several main subprograms, by specifying their source files on the
14635 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
14639 Each of these needs to be a source file of the same project, except
14640 when the switch ^-u^/UNIQUE^ is used.
14643 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
14644 same project, one of the project in the tree rooted at the project specified
14645 on the command line. The package @code{Builder} of this common project, the
14646 "main project" is the one that is considered by @command{gnatmake}.
14649 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
14650 imported directly or indirectly by the project specified on the command line.
14651 Note that if such a source file is not part of the project specified on the
14652 command line, the ^switches^switches^ found in package @code{Builder} of the
14653 project specified on the command line, if any, that are transmitted
14654 to the compiler will still be used, not those found in the project file of
14658 When using a project file, you can also invoke @command{gnatmake} without
14659 explicitly specifying any main, and the effect depends on whether you have
14660 defined the @code{Main} attribute. This attribute has a string list value,
14661 where each element in the list is the name of a source file (the file
14662 extension is optional) that contains a unit that can be a main subprogram.
14664 If the @code{Main} attribute is defined in a project file as a non-empty
14665 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
14666 line, then invoking @command{gnatmake} with this project file but without any
14667 main on the command line is equivalent to invoking @command{gnatmake} with all
14668 the file names in the @code{Main} attribute on the command line.
14671 @smallexample @c projectfile
14674 for Main use ("main1", "main2", "main3");
14680 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
14682 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
14684 When the project attribute @code{Main} is not specified, or is specified
14685 as an empty string list, or when the switch @option{-u} is used on the command
14686 line, then invoking @command{gnatmake} with no main on the command line will
14687 result in all immediate sources of the project file being checked, and
14688 potentially recompiled. Depending on the presence of the switch @option{-u},
14689 sources from other project files on which the immediate sources of the main
14690 project file depend are also checked and potentially recompiled. In other
14691 words, the @option{-u} switch is applied to all of the immediate sources of the
14694 When no main is specified on the command line and attribute @code{Main} exists
14695 and includes several mains, or when several mains are specified on the
14696 command line, the default ^switches^switches^ in package @code{Builder} will
14697 be used for all mains, even if there are specific ^switches^switches^
14698 specified for one or several mains.
14700 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
14701 the specific ^switches^switches^ for each main, if they are specified.
14703 @node Library Project Files
14704 @subsubsection Library Project Files
14707 When @command{gnatmake} is invoked with a main project file that is a library
14708 project file, it is not allowed to specify one or more mains on the command
14712 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
14713 ^-l^/ACTION=LINK^ have special meanings.
14716 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
14717 to @command{gnatmake} that @command{gnatbind} should be invoked for the
14720 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
14721 to @command{gnatmake} that the binder generated file should be compiled
14722 (in the case of a stand-alone library) and that the library should be built.
14726 @node The GNAT Driver and Project Files
14727 @subsection The GNAT Driver and Project Files
14730 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
14731 can benefit from project files:
14732 @command{^gnatbind^gnatbind^},
14733 @command{^gnatcheck^gnatcheck^}),
14734 @command{^gnatclean^gnatclean^}),
14735 @command{^gnatelim^gnatelim^},
14736 @command{^gnatfind^gnatfind^},
14737 @command{^gnatlink^gnatlink^},
14738 @command{^gnatls^gnatls^},
14739 @command{^gnatmetric^gnatmetric^},
14740 @command{^gnatpp^gnatpp^},
14741 @command{^gnatstub^gnatstub^},
14742 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
14743 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
14744 They must be invoked through the @command{gnat} driver.
14746 The @command{gnat} driver is a wrapper that accepts a number of commands and
14747 calls the corresponding tool. It was designed initially for VMS platforms (to
14748 convert VMS qualifiers to Unix-style switches), but it is now available on all
14751 On non-VMS platforms, the @command{gnat} driver accepts the following commands
14752 (case insensitive):
14756 BIND to invoke @command{^gnatbind^gnatbind^}
14758 CHOP to invoke @command{^gnatchop^gnatchop^}
14760 CLEAN to invoke @command{^gnatclean^gnatclean^}
14762 COMP or COMPILE to invoke the compiler
14764 ELIM to invoke @command{^gnatelim^gnatelim^}
14766 FIND to invoke @command{^gnatfind^gnatfind^}
14768 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
14770 LINK to invoke @command{^gnatlink^gnatlink^}
14772 LS or LIST to invoke @command{^gnatls^gnatls^}
14774 MAKE to invoke @command{^gnatmake^gnatmake^}
14776 NAME to invoke @command{^gnatname^gnatname^}
14778 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
14780 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
14782 METRIC to invoke @command{^gnatmetric^gnatmetric^}
14784 STUB to invoke @command{^gnatstub^gnatstub^}
14786 XREF to invoke @command{^gnatxref^gnatxref^}
14790 (note that the compiler is invoked using the command
14791 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}).
14794 On non-VMS platforms, between @command{gnat} and the command, two
14795 special switches may be used:
14799 @command{-v} to display the invocation of the tool.
14801 @command{-dn} to prevent the @command{gnat} driver from removing
14802 the temporary files it has created. These temporary files are
14803 configuration files and temporary file list files.
14807 The command may be followed by switches and arguments for the invoked
14811 gnat bind -C main.ali
14817 Switches may also be put in text files, one switch per line, and the text
14818 files may be specified with their path name preceded by '@@'.
14821 gnat bind @@args.txt main.ali
14825 In addition, for commands BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
14826 METRIC, PP or PRETTY, STUB and XREF, the project file related switches
14827 (@option{^-P^/PROJECT_FILE^},
14828 @option{^-X^/EXTERNAL_REFERENCE^} and
14829 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
14830 the switches of the invoking tool.
14833 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
14834 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
14835 the immediate sources of the specified project file.
14838 When GNAT METRIC is used with a project file, but with no source
14839 specified on the command line, it invokes @command{^gnatmetric^gnatmetric^}
14840 with all the immediate sources of the specified project file and with
14841 @option{^-d^/DIRECTORY^} with the parameter pointing to the object directory
14845 In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with
14846 a project file, no source is specified on the command line and
14847 switch ^-U^/ALL_PROJECTS^ is specified on the command line, then
14848 the underlying tool (^gnatpp^gnatpp^ or
14849 ^gnatmetric^gnatmetric^) is invoked for all sources of all projects,
14850 not only for the immediate sources of the main project.
14852 (-U stands for Universal or Union of the project files of the project tree)
14856 For each of the following commands, there is optionally a corresponding
14857 package in the main project.
14861 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
14864 package @code{Check} for command CHECK (invoking
14865 @code{^gnatcheck^gnatcheck^})
14868 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
14871 package @code{Cross_Reference} for command XREF (invoking
14872 @code{^gnatxref^gnatxref^})
14875 package @code{Eliminate} for command ELIM (invoking
14876 @code{^gnatelim^gnatelim^})
14879 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
14882 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
14885 package @code{Gnatstub} for command STUB
14886 (invoking @code{^gnatstub^gnatstub^})
14889 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
14892 package @code{Metrics} for command METRIC
14893 (invoking @code{^gnatmetric^gnatmetric^})
14896 package @code{Pretty_Printer} for command PP or PRETTY
14897 (invoking @code{^gnatpp^gnatpp^})
14902 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
14903 a simple variable with a string list value. It contains ^switches^switches^
14904 for the invocation of @code{^gnatls^gnatls^}.
14906 @smallexample @c projectfile
14910 for ^Switches^Switches^
14919 All other packages have two attribute @code{^Switches^Switches^} and
14920 @code{^Default_Switches^Default_Switches^}.
14923 @code{^Switches^Switches^} is an associative array attribute, indexed by the
14924 source file name, that has a string list value: the ^switches^switches^ to be
14925 used when the tool corresponding to the package is invoked for the specific
14929 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
14930 indexed by the programming language that has a string list value.
14931 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
14932 ^switches^switches^ for the invocation of the tool corresponding
14933 to the package, except if a specific @code{^Switches^Switches^} attribute
14934 is specified for the source file.
14936 @smallexample @c projectfile
14940 for Source_Dirs use ("./**");
14943 for ^Switches^Switches^ use
14950 package Compiler is
14951 for ^Default_Switches^Default_Switches^ ("Ada")
14952 use ("^-gnatv^-gnatv^",
14953 "^-gnatwa^-gnatwa^");
14959 for ^Default_Switches^Default_Switches^ ("Ada")
14967 for ^Default_Switches^Default_Switches^ ("Ada")
14969 for ^Switches^Switches^ ("main.adb")
14978 for ^Default_Switches^Default_Switches^ ("Ada")
14985 package Cross_Reference is
14986 for ^Default_Switches^Default_Switches^ ("Ada")
14991 end Cross_Reference;
14997 With the above project file, commands such as
15000 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
15001 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
15002 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
15003 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
15004 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
15008 will set up the environment properly and invoke the tool with the switches
15009 found in the package corresponding to the tool:
15010 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
15011 except @code{^Switches^Switches^ ("main.adb")}
15012 for @code{^gnatlink^gnatlink^}.
15013 It is also possible to invoke some of the tools,
15014 @code{^gnatcheck^gnatcheck^}),
15015 @code{^gnatmetric^gnatmetric^}),
15016 and @code{^gnatpp^gnatpp^})
15017 on a set of project units thanks to the combination of the switches
15018 @option{-P}, @option{-U} and possibly the main unit when one is interested
15019 in its closure. For instance,
15023 will compute the metrics for all the immediate units of project
15026 gnat metric -Pproj -U
15028 will compute the metrics for all the units of the closure of projects
15029 rooted at @code{proj}.
15031 gnat metric -Pproj -U main_unit
15033 will compute the metrics for the closure of units rooted at
15034 @code{main_unit}. This last possibility relies implicitly
15035 on @command{gnatbind}'s option @option{-R}.
15037 @c **********************
15038 @node An Extended Example
15039 @section An Extended Example
15042 Suppose that we have two programs, @var{prog1} and @var{prog2},
15043 whose sources are in corresponding directories. We would like
15044 to build them with a single @command{gnatmake} command, and we want to place
15045 their object files into @file{build} subdirectories of the source directories.
15046 Furthermore, we want to have to have two separate subdirectories
15047 in @file{build} -- @file{release} and @file{debug} -- which will contain
15048 the object files compiled with different set of compilation flags.
15050 In other words, we have the following structure:
15067 Here are the project files that we must place in a directory @file{main}
15068 to maintain this structure:
15072 @item We create a @code{Common} project with a package @code{Compiler} that
15073 specifies the compilation ^switches^switches^:
15078 @b{project} Common @b{is}
15080 @b{for} Source_Dirs @b{use} (); -- No source files
15084 @b{type} Build_Type @b{is} ("release", "debug");
15085 Build : Build_Type := External ("BUILD", "debug");
15088 @b{package} Compiler @b{is}
15089 @b{case} Build @b{is}
15090 @b{when} "release" =>
15091 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15092 @b{use} ("^-O2^-O2^");
15093 @b{when} "debug" =>
15094 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
15095 @b{use} ("^-g^-g^");
15103 @item We create separate projects for the two programs:
15110 @b{project} Prog1 @b{is}
15112 @b{for} Source_Dirs @b{use} ("prog1");
15113 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
15115 @b{package} Compiler @b{renames} Common.Compiler;
15126 @b{project} Prog2 @b{is}
15128 @b{for} Source_Dirs @b{use} ("prog2");
15129 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
15131 @b{package} Compiler @b{renames} Common.Compiler;
15137 @item We create a wrapping project @code{Main}:
15146 @b{project} Main @b{is}
15148 @b{package} Compiler @b{renames} Common.Compiler;
15154 @item Finally we need to create a dummy procedure that @code{with}s (either
15155 explicitly or implicitly) all the sources of our two programs.
15160 Now we can build the programs using the command
15163 gnatmake ^-P^/PROJECT_FILE=^main dummy
15167 for the Debug mode, or
15171 gnatmake -Pmain -XBUILD=release
15177 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
15182 for the Release mode.
15184 @c ********************************
15185 @c * Project File Complete Syntax *
15186 @c ********************************
15188 @node Project File Complete Syntax
15189 @section Project File Complete Syntax
15193 context_clause project_declaration
15199 @b{with} path_name @{ , path_name @} ;
15204 project_declaration ::=
15205 simple_project_declaration | project_extension
15207 simple_project_declaration ::=
15208 @b{project} <project_>simple_name @b{is}
15209 @{declarative_item@}
15210 @b{end} <project_>simple_name;
15212 project_extension ::=
15213 @b{project} <project_>simple_name @b{extends} path_name @b{is}
15214 @{declarative_item@}
15215 @b{end} <project_>simple_name;
15217 declarative_item ::=
15218 package_declaration |
15219 typed_string_declaration |
15220 other_declarative_item
15222 package_declaration ::=
15223 package_spec | package_renaming
15226 @b{package} package_identifier @b{is}
15227 @{simple_declarative_item@}
15228 @b{end} package_identifier ;
15230 package_identifier ::=
15231 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
15232 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
15233 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
15235 package_renaming ::==
15236 @b{package} package_identifier @b{renames}
15237 <project_>simple_name.package_identifier ;
15239 typed_string_declaration ::=
15240 @b{type} <typed_string_>_simple_name @b{is}
15241 ( string_literal @{, string_literal@} );
15243 other_declarative_item ::=
15244 attribute_declaration |
15245 typed_variable_declaration |
15246 variable_declaration |
15249 attribute_declaration ::=
15250 full_associative_array_declaration |
15251 @b{for} attribute_designator @b{use} expression ;
15253 full_associative_array_declaration ::=
15254 @b{for} <associative_array_attribute_>simple_name @b{use}
15255 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
15257 attribute_designator ::=
15258 <simple_attribute_>simple_name |
15259 <associative_array_attribute_>simple_name ( string_literal )
15261 typed_variable_declaration ::=
15262 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
15264 variable_declaration ::=
15265 <variable_>simple_name := expression;
15275 attribute_reference
15281 ( <string_>expression @{ , <string_>expression @} )
15284 @b{external} ( string_literal [, string_literal] )
15286 attribute_reference ::=
15287 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
15289 attribute_prefix ::=
15291 <project_>simple_name | package_identifier |
15292 <project_>simple_name . package_identifier
15294 case_construction ::=
15295 @b{case} <typed_variable_>name @b{is}
15300 @b{when} discrete_choice_list =>
15301 @{case_construction | attribute_declaration@}
15303 discrete_choice_list ::=
15304 string_literal @{| string_literal@} |
15308 simple_name @{. simple_name@}
15311 identifier (same as Ada)
15315 @node The Cross-Referencing Tools gnatxref and gnatfind
15316 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
15321 The compiler generates cross-referencing information (unless
15322 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
15323 This information indicates where in the source each entity is declared and
15324 referenced. Note that entities in package Standard are not included, but
15325 entities in all other predefined units are included in the output.
15327 Before using any of these two tools, you need to compile successfully your
15328 application, so that GNAT gets a chance to generate the cross-referencing
15331 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
15332 information to provide the user with the capability to easily locate the
15333 declaration and references to an entity. These tools are quite similar,
15334 the difference being that @code{gnatfind} is intended for locating
15335 definitions and/or references to a specified entity or entities, whereas
15336 @code{gnatxref} is oriented to generating a full report of all
15339 To use these tools, you must not compile your application using the
15340 @option{-gnatx} switch on the @command{gnatmake} command line
15341 (@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
15342 information will not be generated.
15344 Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file,
15345 use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}).
15348 * gnatxref Switches::
15349 * gnatfind Switches::
15350 * Project Files for gnatxref and gnatfind::
15351 * Regular Expressions in gnatfind and gnatxref::
15352 * Examples of gnatxref Usage::
15353 * Examples of gnatfind Usage::
15356 @node gnatxref Switches
15357 @section @code{gnatxref} Switches
15360 The command invocation for @code{gnatxref} is:
15362 $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]}
15371 identifies the source files for which a report is to be generated. The
15372 ``with''ed units will be processed too. You must provide at least one file.
15374 These file names are considered to be regular expressions, so for instance
15375 specifying @file{source*.adb} is the same as giving every file in the current
15376 directory whose name starts with @file{source} and whose extension is
15379 You shouldn't specify any directory name, just base names. @command{gnatxref}
15380 and @command{gnatfind} will be able to locate these files by themselves using
15381 the source path. If you specify directories, no result is produced.
15386 The switches can be:
15390 @cindex @option{--version} @command{gnatxref}
15391 Display Copyright and version, then exit disregarding all other options.
15394 @cindex @option{--help} @command{gnatxref}
15395 If @option{--version} was not used, display usage, then exit disregarding
15398 @item ^-a^/ALL_FILES^
15399 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
15400 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15401 the read-only files found in the library search path. Otherwise, these files
15402 will be ignored. This option can be used to protect Gnat sources or your own
15403 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15404 much faster, and their output much smaller. Read-only here refers to access
15405 or permissions status in the file system for the current user.
15408 @cindex @option{-aIDIR} (@command{gnatxref})
15409 When looking for source files also look in directory DIR. The order in which
15410 source file search is undertaken is the same as for @command{gnatmake}.
15413 @cindex @option{-aODIR} (@command{gnatxref})
15414 When searching for library and object files, look in directory
15415 DIR. The order in which library files are searched is the same as for
15416 @command{gnatmake}.
15419 @cindex @option{-nostdinc} (@command{gnatxref})
15420 Do not look for sources in the system default directory.
15423 @cindex @option{-nostdlib} (@command{gnatxref})
15424 Do not look for library files in the system default directory.
15426 @item --RTS=@var{rts-path}
15427 @cindex @option{--RTS} (@command{gnatxref})
15428 Specifies the default location of the runtime library. Same meaning as the
15429 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15431 @item ^-d^/DERIVED_TYPES^
15432 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
15433 If this switch is set @code{gnatxref} will output the parent type
15434 reference for each matching derived types.
15436 @item ^-f^/FULL_PATHNAME^
15437 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
15438 If this switch is set, the output file names will be preceded by their
15439 directory (if the file was found in the search path). If this switch is
15440 not set, the directory will not be printed.
15442 @item ^-g^/IGNORE_LOCALS^
15443 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
15444 If this switch is set, information is output only for library-level
15445 entities, ignoring local entities. The use of this switch may accelerate
15446 @code{gnatfind} and @code{gnatxref}.
15449 @cindex @option{-IDIR} (@command{gnatxref})
15450 Equivalent to @samp{-aODIR -aIDIR}.
15453 @cindex @option{-pFILE} (@command{gnatxref})
15454 Specify a project file to use @xref{Project Files}.
15455 If you need to use the @file{.gpr}
15456 project files, you should use gnatxref through the GNAT driver
15457 (@command{gnat xref -Pproject}).
15459 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15460 project file in the current directory.
15462 If a project file is either specified or found by the tools, then the content
15463 of the source directory and object directory lines are added as if they
15464 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
15465 and @samp{^-aO^OBJECT_SEARCH^}.
15467 Output only unused symbols. This may be really useful if you give your
15468 main compilation unit on the command line, as @code{gnatxref} will then
15469 display every unused entity and 'with'ed package.
15473 Instead of producing the default output, @code{gnatxref} will generate a
15474 @file{tags} file that can be used by vi. For examples how to use this
15475 feature, see @ref{Examples of gnatxref Usage}. The tags file is output
15476 to the standard output, thus you will have to redirect it to a file.
15482 All these switches may be in any order on the command line, and may even
15483 appear after the file names. They need not be separated by spaces, thus
15484 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15485 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15487 @node gnatfind Switches
15488 @section @code{gnatfind} Switches
15491 The command line for @code{gnatfind} is:
15494 $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]}
15495 @r{[}@var{file1} @var{file2} @dots{}]
15503 An entity will be output only if it matches the regular expression found
15504 in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}.
15506 Omitting the pattern is equivalent to specifying @samp{*}, which
15507 will match any entity. Note that if you do not provide a pattern, you
15508 have to provide both a sourcefile and a line.
15510 Entity names are given in Latin-1, with uppercase/lowercase equivalence
15511 for matching purposes. At the current time there is no support for
15512 8-bit codes other than Latin-1, or for wide characters in identifiers.
15515 @code{gnatfind} will look for references, bodies or declarations
15516 of symbols referenced in @file{@var{sourcefile}}, at line @var{line}
15517 and column @var{column}. See @ref{Examples of gnatfind Usage}
15518 for syntax examples.
15521 is a decimal integer identifying the line number containing
15522 the reference to the entity (or entities) to be located.
15525 is a decimal integer identifying the exact location on the
15526 line of the first character of the identifier for the
15527 entity reference. Columns are numbered from 1.
15529 @item file1 file2 @dots{}
15530 The search will be restricted to these source files. If none are given, then
15531 the search will be done for every library file in the search path.
15532 These file must appear only after the pattern or sourcefile.
15534 These file names are considered to be regular expressions, so for instance
15535 specifying @file{source*.adb} is the same as giving every file in the current
15536 directory whose name starts with @file{source} and whose extension is
15539 The location of the spec of the entity will always be displayed, even if it
15540 isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The
15541 occurrences of the entity in the separate units of the ones given on the
15542 command line will also be displayed.
15544 Note that if you specify at least one file in this part, @code{gnatfind} may
15545 sometimes not be able to find the body of the subprograms.
15550 At least one of 'sourcefile' or 'pattern' has to be present on
15553 The following switches are available:
15557 @cindex @option{--version} @command{gnatfind}
15558 Display Copyright and version, then exit disregarding all other options.
15561 @cindex @option{--help} @command{gnatfind}
15562 If @option{--version} was not used, display usage, then exit disregarding
15565 @item ^-a^/ALL_FILES^
15566 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
15567 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
15568 the read-only files found in the library search path. Otherwise, these files
15569 will be ignored. This option can be used to protect Gnat sources or your own
15570 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
15571 much faster, and their output much smaller. Read-only here refers to access
15572 or permission status in the file system for the current user.
15575 @cindex @option{-aIDIR} (@command{gnatfind})
15576 When looking for source files also look in directory DIR. The order in which
15577 source file search is undertaken is the same as for @command{gnatmake}.
15580 @cindex @option{-aODIR} (@command{gnatfind})
15581 When searching for library and object files, look in directory
15582 DIR. The order in which library files are searched is the same as for
15583 @command{gnatmake}.
15586 @cindex @option{-nostdinc} (@command{gnatfind})
15587 Do not look for sources in the system default directory.
15590 @cindex @option{-nostdlib} (@command{gnatfind})
15591 Do not look for library files in the system default directory.
15593 @item --RTS=@var{rts-path}
15594 @cindex @option{--RTS} (@command{gnatfind})
15595 Specifies the default location of the runtime library. Same meaning as the
15596 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
15598 @item ^-d^/DERIVED_TYPE_INFORMATION^
15599 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
15600 If this switch is set, then @code{gnatfind} will output the parent type
15601 reference for each matching derived types.
15603 @item ^-e^/EXPRESSIONS^
15604 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
15605 By default, @code{gnatfind} accept the simple regular expression set for
15606 @samp{pattern}. If this switch is set, then the pattern will be
15607 considered as full Unix-style regular expression.
15609 @item ^-f^/FULL_PATHNAME^
15610 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
15611 If this switch is set, the output file names will be preceded by their
15612 directory (if the file was found in the search path). If this switch is
15613 not set, the directory will not be printed.
15615 @item ^-g^/IGNORE_LOCALS^
15616 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
15617 If this switch is set, information is output only for library-level
15618 entities, ignoring local entities. The use of this switch may accelerate
15619 @code{gnatfind} and @code{gnatxref}.
15622 @cindex @option{-IDIR} (@command{gnatfind})
15623 Equivalent to @samp{-aODIR -aIDIR}.
15626 @cindex @option{-pFILE} (@command{gnatfind})
15627 Specify a project file (@pxref{Project Files}) to use.
15628 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
15629 project file in the current directory.
15631 If a project file is either specified or found by the tools, then the content
15632 of the source directory and object directory lines are added as if they
15633 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
15634 @samp{^-aO^/OBJECT_SEARCH^}.
15636 @item ^-r^/REFERENCES^
15637 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
15638 By default, @code{gnatfind} will output only the information about the
15639 declaration, body or type completion of the entities. If this switch is
15640 set, the @code{gnatfind} will locate every reference to the entities in
15641 the files specified on the command line (or in every file in the search
15642 path if no file is given on the command line).
15644 @item ^-s^/PRINT_LINES^
15645 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
15646 If this switch is set, then @code{gnatfind} will output the content
15647 of the Ada source file lines were the entity was found.
15649 @item ^-t^/TYPE_HIERARCHY^
15650 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
15651 If this switch is set, then @code{gnatfind} will output the type hierarchy for
15652 the specified type. It act like -d option but recursively from parent
15653 type to parent type. When this switch is set it is not possible to
15654 specify more than one file.
15659 All these switches may be in any order on the command line, and may even
15660 appear after the file names. They need not be separated by spaces, thus
15661 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
15662 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
15664 As stated previously, gnatfind will search in every directory in the
15665 search path. You can force it to look only in the current directory if
15666 you specify @code{*} at the end of the command line.
15668 @node Project Files for gnatxref and gnatfind
15669 @section Project Files for @command{gnatxref} and @command{gnatfind}
15672 Project files allow a programmer to specify how to compile its
15673 application, where to find sources, etc. These files are used
15675 primarily by GPS, but they can also be used
15678 @code{gnatxref} and @code{gnatfind}.
15680 A project file name must end with @file{.gpr}. If a single one is
15681 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
15682 extract the information from it. If multiple project files are found, none of
15683 them is read, and you have to use the @samp{-p} switch to specify the one
15686 The following lines can be included, even though most of them have default
15687 values which can be used in most cases.
15688 The lines can be entered in any order in the file.
15689 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
15690 each line. If you have multiple instances, only the last one is taken into
15695 [default: @code{"^./^[]^"}]
15696 specifies a directory where to look for source files. Multiple @code{src_dir}
15697 lines can be specified and they will be searched in the order they
15701 [default: @code{"^./^[]^"}]
15702 specifies a directory where to look for object and library files. Multiple
15703 @code{obj_dir} lines can be specified, and they will be searched in the order
15706 @item comp_opt=SWITCHES
15707 [default: @code{""}]
15708 creates a variable which can be referred to subsequently by using
15709 the @code{$@{comp_opt@}} notation. This is intended to store the default
15710 switches given to @command{gnatmake} and @command{gcc}.
15712 @item bind_opt=SWITCHES
15713 [default: @code{""}]
15714 creates a variable which can be referred to subsequently by using
15715 the @samp{$@{bind_opt@}} notation. This is intended to store the default
15716 switches given to @command{gnatbind}.
15718 @item link_opt=SWITCHES
15719 [default: @code{""}]
15720 creates a variable which can be referred to subsequently by using
15721 the @samp{$@{link_opt@}} notation. This is intended to store the default
15722 switches given to @command{gnatlink}.
15724 @item main=EXECUTABLE
15725 [default: @code{""}]
15726 specifies the name of the executable for the application. This variable can
15727 be referred to in the following lines by using the @samp{$@{main@}} notation.
15730 @item comp_cmd=COMMAND
15731 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
15734 @item comp_cmd=COMMAND
15735 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
15737 specifies the command used to compile a single file in the application.
15740 @item make_cmd=COMMAND
15741 [default: @code{"GNAT MAKE $@{main@}
15742 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
15743 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
15744 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
15747 @item make_cmd=COMMAND
15748 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
15749 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
15750 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
15752 specifies the command used to recompile the whole application.
15754 @item run_cmd=COMMAND
15755 [default: @code{"$@{main@}"}]
15756 specifies the command used to run the application.
15758 @item debug_cmd=COMMAND
15759 [default: @code{"gdb $@{main@}"}]
15760 specifies the command used to debug the application
15765 @command{gnatxref} and @command{gnatfind} only take into account the
15766 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
15768 @node Regular Expressions in gnatfind and gnatxref
15769 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
15772 As specified in the section about @command{gnatfind}, the pattern can be a
15773 regular expression. Actually, there are to set of regular expressions
15774 which are recognized by the program:
15777 @item globbing patterns
15778 These are the most usual regular expression. They are the same that you
15779 generally used in a Unix shell command line, or in a DOS session.
15781 Here is a more formal grammar:
15788 term ::= elmt -- matches elmt
15789 term ::= elmt elmt -- concatenation (elmt then elmt)
15790 term ::= * -- any string of 0 or more characters
15791 term ::= ? -- matches any character
15792 term ::= [char @{char@}] -- matches any character listed
15793 term ::= [char - char] -- matches any character in range
15797 @item full regular expression
15798 The second set of regular expressions is much more powerful. This is the
15799 type of regular expressions recognized by utilities such a @file{grep}.
15801 The following is the form of a regular expression, expressed in Ada
15802 reference manual style BNF is as follows
15809 regexp ::= term @{| term@} -- alternation (term or term @dots{})
15811 term ::= item @{item@} -- concatenation (item then item)
15813 item ::= elmt -- match elmt
15814 item ::= elmt * -- zero or more elmt's
15815 item ::= elmt + -- one or more elmt's
15816 item ::= elmt ? -- matches elmt or nothing
15819 elmt ::= nschar -- matches given character
15820 elmt ::= [nschar @{nschar@}] -- matches any character listed
15821 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
15822 elmt ::= [char - char] -- matches chars in given range
15823 elmt ::= \ char -- matches given character
15824 elmt ::= . -- matches any single character
15825 elmt ::= ( regexp ) -- parens used for grouping
15827 char ::= any character, including special characters
15828 nschar ::= any character except ()[].*+?^^^
15832 Following are a few examples:
15836 will match any of the two strings @samp{abcde} and @samp{fghi},
15839 will match any string like @samp{abd}, @samp{abcd}, @samp{abccd},
15840 @samp{abcccd}, and so on,
15843 will match any string which has only lowercase characters in it (and at
15844 least one character.
15849 @node Examples of gnatxref Usage
15850 @section Examples of @code{gnatxref} Usage
15852 @subsection General Usage
15855 For the following examples, we will consider the following units:
15857 @smallexample @c ada
15863 3: procedure Foo (B : in Integer);
15870 1: package body Main is
15871 2: procedure Foo (B : in Integer) is
15882 2: procedure Print (B : Integer);
15891 The first thing to do is to recompile your application (for instance, in
15892 that case just by doing a @samp{gnatmake main}, so that GNAT generates
15893 the cross-referencing information.
15894 You can then issue any of the following commands:
15896 @item gnatxref main.adb
15897 @code{gnatxref} generates cross-reference information for main.adb
15898 and every unit 'with'ed by main.adb.
15900 The output would be:
15908 Decl: main.ads 3:20
15909 Body: main.adb 2:20
15910 Ref: main.adb 4:13 5:13 6:19
15913 Ref: main.adb 6:8 7:8
15923 Decl: main.ads 3:15
15924 Body: main.adb 2:15
15927 Body: main.adb 1:14
15930 Ref: main.adb 6:12 7:12
15934 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
15935 its body is in main.adb, line 1, column 14 and is not referenced any where.
15937 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
15938 it referenced in main.adb, line 6 column 12 and line 7 column 12.
15940 @item gnatxref package1.adb package2.ads
15941 @code{gnatxref} will generates cross-reference information for
15942 package1.adb, package2.ads and any other package 'with'ed by any
15948 @subsection Using gnatxref with vi
15950 @code{gnatxref} can generate a tags file output, which can be used
15951 directly from @command{vi}. Note that the standard version of @command{vi}
15952 will not work properly with overloaded symbols. Consider using another
15953 free implementation of @command{vi}, such as @command{vim}.
15956 $ gnatxref -v gnatfind.adb > tags
15960 will generate the tags file for @code{gnatfind} itself (if the sources
15961 are in the search path!).
15963 From @command{vi}, you can then use the command @samp{:tag @var{entity}}
15964 (replacing @var{entity} by whatever you are looking for), and vi will
15965 display a new file with the corresponding declaration of entity.
15968 @node Examples of gnatfind Usage
15969 @section Examples of @code{gnatfind} Usage
15973 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
15974 Find declarations for all entities xyz referenced at least once in
15975 main.adb. The references are search in every library file in the search
15978 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
15981 The output will look like:
15983 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
15984 ^directory/^[directory]^main.adb:24:10: xyz <= body
15985 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
15989 that is to say, one of the entities xyz found in main.adb is declared at
15990 line 12 of main.ads (and its body is in main.adb), and another one is
15991 declared at line 45 of foo.ads
15993 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
15994 This is the same command as the previous one, instead @code{gnatfind} will
15995 display the content of the Ada source file lines.
15997 The output will look like:
16000 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
16002 ^directory/^[directory]^main.adb:24:10: xyz <= body
16004 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
16009 This can make it easier to find exactly the location your are looking
16012 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
16013 Find references to all entities containing an x that are
16014 referenced on line 123 of main.ads.
16015 The references will be searched only in main.ads and foo.adb.
16017 @item gnatfind main.ads:123
16018 Find declarations and bodies for all entities that are referenced on
16019 line 123 of main.ads.
16021 This is the same as @code{gnatfind "*":main.adb:123}.
16023 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
16024 Find the declaration for the entity referenced at column 45 in
16025 line 123 of file main.adb in directory mydir. Note that it
16026 is usual to omit the identifier name when the column is given,
16027 since the column position identifies a unique reference.
16029 The column has to be the beginning of the identifier, and should not
16030 point to any character in the middle of the identifier.
16034 @c *********************************
16035 @node The GNAT Pretty-Printer gnatpp
16036 @chapter The GNAT Pretty-Printer @command{gnatpp}
16038 @cindex Pretty-Printer
16041 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
16042 for source reformatting / pretty-printing.
16043 It takes an Ada source file as input and generates a reformatted
16045 You can specify various style directives via switches; e.g.,
16046 identifier case conventions, rules of indentation, and comment layout.
16048 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
16049 tree for the input source and thus requires the input to be syntactically and
16050 semantically legal.
16051 If this condition is not met, @command{gnatpp} will terminate with an
16052 error message; no output file will be generated.
16054 If the source files presented to @command{gnatpp} contain
16055 preprocessing directives, then the output file will
16056 correspond to the generated source after all
16057 preprocessing is carried out. There is no way
16058 using @command{gnatpp} to obtain pretty printed files that
16059 include the preprocessing directives.
16061 If the compilation unit
16062 contained in the input source depends semantically upon units located
16063 outside the current directory, you have to provide the source search path
16064 when invoking @command{gnatpp}, if these units are contained in files with
16065 names that do not follow the GNAT file naming rules, you have to provide
16066 the configuration file describing the corresponding naming scheme;
16067 see the description of the @command{gnatpp}
16068 switches below. Another possibility is to use a project file and to
16069 call @command{gnatpp} through the @command{gnat} driver
16071 The @command{gnatpp} command has the form
16074 $ gnatpp @ovar{switches} @var{filename}
16081 @var{switches} is an optional sequence of switches defining such properties as
16082 the formatting rules, the source search path, and the destination for the
16086 @var{filename} is the name (including the extension) of the source file to
16087 reformat; ``wildcards'' or several file names on the same gnatpp command are
16088 allowed. The file name may contain path information; it does not have to
16089 follow the GNAT file naming rules
16093 * Switches for gnatpp::
16094 * Formatting Rules::
16097 @node Switches for gnatpp
16098 @section Switches for @command{gnatpp}
16101 The following subsections describe the various switches accepted by
16102 @command{gnatpp}, organized by category.
16105 You specify a switch by supplying a name and generally also a value.
16106 In many cases the values for a switch with a given name are incompatible with
16108 (for example the switch that controls the casing of a reserved word may have
16109 exactly one value: upper case, lower case, or
16110 mixed case) and thus exactly one such switch can be in effect for an
16111 invocation of @command{gnatpp}.
16112 If more than one is supplied, the last one is used.
16113 However, some values for the same switch are mutually compatible.
16114 You may supply several such switches to @command{gnatpp}, but then
16115 each must be specified in full, with both the name and the value.
16116 Abbreviated forms (the name appearing once, followed by each value) are
16118 For example, to set
16119 the alignment of the assignment delimiter both in declarations and in
16120 assignment statements, you must write @option{-A2A3}
16121 (or @option{-A2 -A3}), but not @option{-A23}.
16125 In many cases the set of options for a given qualifier are incompatible with
16126 each other (for example the qualifier that controls the casing of a reserved
16127 word may have exactly one option, which specifies either upper case, lower
16128 case, or mixed case), and thus exactly one such option can be in effect for
16129 an invocation of @command{gnatpp}.
16130 If more than one is supplied, the last one is used.
16131 However, some qualifiers have options that are mutually compatible,
16132 and then you may then supply several such options when invoking
16136 In most cases, it is obvious whether or not the
16137 ^values for a switch with a given name^options for a given qualifier^
16138 are compatible with each other.
16139 When the semantics might not be evident, the summaries below explicitly
16140 indicate the effect.
16143 * Alignment Control::
16145 * Construct Layout Control::
16146 * General Text Layout Control::
16147 * Other Formatting Options::
16148 * Setting the Source Search Path::
16149 * Output File Control::
16150 * Other gnatpp Switches::
16153 @node Alignment Control
16154 @subsection Alignment Control
16155 @cindex Alignment control in @command{gnatpp}
16158 Programs can be easier to read if certain constructs are vertically aligned.
16159 By default all alignments are set ON.
16160 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
16161 OFF, and then use one or more of the other
16162 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
16163 to activate alignment for specific constructs.
16166 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
16170 Set all alignments to ON
16173 @item ^-A0^/ALIGN=OFF^
16174 Set all alignments to OFF
16176 @item ^-A1^/ALIGN=COLONS^
16177 Align @code{:} in declarations
16179 @item ^-A2^/ALIGN=DECLARATIONS^
16180 Align @code{:=} in initializations in declarations
16182 @item ^-A3^/ALIGN=STATEMENTS^
16183 Align @code{:=} in assignment statements
16185 @item ^-A4^/ALIGN=ARROWS^
16186 Align @code{=>} in associations
16188 @item ^-A5^/ALIGN=COMPONENT_CLAUSES^
16189 Align @code{at} keywords in the component clauses in record
16190 representation clauses
16194 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
16197 @node Casing Control
16198 @subsection Casing Control
16199 @cindex Casing control in @command{gnatpp}
16202 @command{gnatpp} allows you to specify the casing for reserved words,
16203 pragma names, attribute designators and identifiers.
16204 For identifiers you may define a
16205 general rule for name casing but also override this rule
16206 via a set of dictionary files.
16208 Three types of casing are supported: lower case, upper case, and mixed case.
16209 Lower and upper case are self-explanatory (but since some letters in
16210 Latin1 and other GNAT-supported character sets
16211 exist only in lower-case form, an upper case conversion will have no
16213 ``Mixed case'' means that the first letter, and also each letter immediately
16214 following an underscore, are converted to their uppercase forms;
16215 all the other letters are converted to their lowercase forms.
16218 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
16219 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
16220 Attribute designators are lower case
16222 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
16223 Attribute designators are upper case
16225 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
16226 Attribute designators are mixed case (this is the default)
16228 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
16229 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
16230 Keywords (technically, these are known in Ada as @emph{reserved words}) are
16231 lower case (this is the default)
16233 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
16234 Keywords are upper case
16236 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
16237 @item ^-nD^/NAME_CASING=AS_DECLARED^
16238 Name casing for defining occurrences are as they appear in the source file
16239 (this is the default)
16241 @item ^-nU^/NAME_CASING=UPPER_CASE^
16242 Names are in upper case
16244 @item ^-nL^/NAME_CASING=LOWER_CASE^
16245 Names are in lower case
16247 @item ^-nM^/NAME_CASING=MIXED_CASE^
16248 Names are in mixed case
16250 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
16251 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
16252 Pragma names are lower case
16254 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
16255 Pragma names are upper case
16257 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
16258 Pragma names are mixed case (this is the default)
16260 @item ^-D@var{file}^/DICTIONARY=@var{file}^
16261 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
16262 Use @var{file} as a @emph{dictionary file} that defines
16263 the casing for a set of specified names,
16264 thereby overriding the effect on these names by
16265 any explicit or implicit
16266 ^-n^/NAME_CASING^ switch.
16267 To supply more than one dictionary file,
16268 use ^several @option{-D} switches^a list of files as options^.
16271 @option{gnatpp} implicitly uses a @emph{default dictionary file}
16272 to define the casing for the Ada predefined names and
16273 the names declared in the GNAT libraries.
16275 @item ^-D-^/SPECIFIC_CASING^
16276 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
16277 Do not use the default dictionary file;
16278 instead, use the casing
16279 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
16284 The structure of a dictionary file, and details on the conventions
16285 used in the default dictionary file, are defined in @ref{Name Casing}.
16287 The @option{^-D-^/SPECIFIC_CASING^} and
16288 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
16291 @node Construct Layout Control
16292 @subsection Construct Layout Control
16293 @cindex Layout control in @command{gnatpp}
16296 This group of @command{gnatpp} switches controls the layout of comments and
16297 complex syntactic constructs. See @ref{Formatting Comments} for details
16301 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
16302 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
16303 All the comments remain unchanged
16305 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
16306 GNAT-style comment line indentation (this is the default).
16308 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
16309 Reference-manual comment line indentation.
16311 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
16312 GNAT-style comment beginning
16314 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
16315 Reformat comment blocks
16317 @item ^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^
16318 Keep unchanged special form comments
16320 Reformat comment blocks
16322 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
16323 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
16324 GNAT-style layout (this is the default)
16326 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
16329 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
16332 @cindex @option{^-N^/NOTABS^} (@command{gnatpp})
16334 All the VT characters are removed from the comment text. All the HT characters
16335 are expanded with the sequences of space characters to get to the next tab
16338 @cindex @option{^--no-separate-is^/NO_SEPARATE_IS^} (@command{gnatpp})
16339 @item ^--no-separate-is^/NO_SEPARATE_IS^
16340 Do not place the keyword @code{is} on a separate line in a subprogram body in
16341 case if the spec occupies more then one line.
16343 @cindex @option{^--separate-label^/SEPARATE_LABEL^} (@command{gnatpp})
16344 @item ^--separate-label^/SEPARATE_LABEL^
16345 Place statement label(s) on a separate line, with the following statement
16348 @cindex @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} (@command{gnatpp})
16349 @item ^--separate-loop-then^/SEPARATE_LOOP_THEN^
16350 Place the keyword @code{loop} in FOR and WHILE loop statements and the
16351 keyword @code{then} in IF statements on a separate line.
16353 @cindex @option{^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^} (@command{gnatpp})
16354 @item ^--no-separate-loop-then^/NO_SEPARATE_LOOP_THEN^
16355 Do not place the keyword @code{loop} in FOR and WHILE loop statements and the
16356 keyword @code{then} in IF statements on a separate line. This option is
16357 incompatible with @option{^--separate-loop-then^/SEPARATE_LOOP_THEN^} option.
16359 @cindex @option{^--use-on-new-line^/USE_ON_NEW_LINE^} (@command{gnatpp})
16360 @item ^--use-on-new-line^/USE_ON_NEW_LINE^
16361 Start each USE clause in a context clause from a separate line.
16363 @cindex @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^} (@command{gnatpp})
16364 @item ^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^
16365 Use a separate line for a loop or block statement name, but do not use an extra
16366 indentation level for the statement itself.
16372 The @option{-c1} and @option{-c2} switches are incompatible.
16373 The @option{-c3} and @option{-c4} switches are compatible with each other and
16374 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
16375 the other comment formatting switches.
16377 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
16382 For the @option{/COMMENTS_LAYOUT} qualifier:
16385 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
16387 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
16388 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
16392 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
16393 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
16396 @node General Text Layout Control
16397 @subsection General Text Layout Control
16400 These switches allow control over line length and indentation.
16403 @item ^-M@var{nnn}^/LINE_LENGTH_MAX=@var{nnn}^
16404 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
16405 Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79
16407 @item ^-i@var{nnn}^/INDENTATION_LEVEL=@var{nnn}^
16408 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
16409 Indentation level, @var{nnn} from 1@dots{}9, the default value is 3
16411 @item ^-cl@var{nnn}^/CONTINUATION_INDENT=@var{nnn}^
16412 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
16413 Indentation level for continuation lines (relative to the line being
16414 continued), @var{nnn} from 1@dots{}9.
16416 value is one less then the (normal) indentation level, unless the
16417 indentation is set to 1 (in which case the default value for continuation
16418 line indentation is also 1)
16421 @node Other Formatting Options
16422 @subsection Other Formatting Options
16425 These switches control the inclusion of missing end/exit labels, and
16426 the indentation level in @b{case} statements.
16429 @item ^-e^/NO_MISSED_LABELS^
16430 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
16431 Do not insert missing end/exit labels. An end label is the name of
16432 a construct that may optionally be repeated at the end of the
16433 construct's declaration;
16434 e.g., the names of packages, subprograms, and tasks.
16435 An exit label is the name of a loop that may appear as target
16436 of an exit statement within the loop.
16437 By default, @command{gnatpp} inserts these end/exit labels when
16438 they are absent from the original source. This option suppresses such
16439 insertion, so that the formatted source reflects the original.
16441 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
16442 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
16443 Insert a Form Feed character after a pragma Page.
16445 @item ^-T@var{nnn}^/MAX_INDENT=@var{nnn}^
16446 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
16447 Do not use an additional indentation level for @b{case} alternatives
16448 and variants if there are @var{nnn} or more (the default
16450 If @var{nnn} is 0, an additional indentation level is
16451 used for @b{case} alternatives and variants regardless of their number.
16454 @node Setting the Source Search Path
16455 @subsection Setting the Source Search Path
16458 To define the search path for the input source file, @command{gnatpp}
16459 uses the same switches as the GNAT compiler, with the same effects.
16462 @item ^-I^/SEARCH=^@var{dir}
16463 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
16464 The same as the corresponding gcc switch
16466 @item ^-I-^/NOCURRENT_DIRECTORY^
16467 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
16468 The same as the corresponding gcc switch
16470 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
16471 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
16472 The same as the corresponding gcc switch
16474 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
16475 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
16476 The same as the corresponding gcc switch
16480 @node Output File Control
16481 @subsection Output File Control
16484 By default the output is sent to the file whose name is obtained by appending
16485 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
16486 (if the file with this name already exists, it is unconditionally overwritten).
16487 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
16488 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
16490 The output may be redirected by the following switches:
16493 @item ^-pipe^/STANDARD_OUTPUT^
16494 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
16495 Send the output to @code{Standard_Output}
16497 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
16498 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
16499 Write the output into @var{output_file}.
16500 If @var{output_file} already exists, @command{gnatpp} terminates without
16501 reading or processing the input file.
16503 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
16504 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
16505 Write the output into @var{output_file}, overwriting the existing file
16506 (if one is present).
16508 @item ^-r^/REPLACE^
16509 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
16510 Replace the input source file with the reformatted output, and copy the
16511 original input source into the file whose name is obtained by appending the
16512 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
16513 If a file with this name already exists, @command{gnatpp} terminates without
16514 reading or processing the input file.
16516 @item ^-rf^/OVERRIDING_REPLACE^
16517 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
16518 Like @option{^-r^/REPLACE^} except that if the file with the specified name
16519 already exists, it is overwritten.
16521 @item ^-rnb^/REPLACE_NO_BACKUP^
16522 @cindex @option{^-rnb^/REPLACE_NO_BACKUP^} (@code{gnatpp})
16523 Replace the input source file with the reformatted output without
16524 creating any backup copy of the input source.
16526 @item ^--eol=@var{xxx}^/END_OF_LINE=@var{xxx}^
16527 @cindex @option{^--eol^/END_OF_LINE^} (@code{gnatpp})
16528 Specifies the format of the reformatted output file. The @var{xxx}
16529 ^string specified with the switch^option^ may be either
16531 @item ``@option{^dos^DOS^}'' MS DOS style, lines end with CR LF characters
16532 @item ``@option{^crlf^CRLF^}''
16533 the same as @option{^crlf^CRLF^}
16534 @item ``@option{^unix^UNIX^}'' UNIX style, lines end with LF character
16535 @item ``@option{^lf^LF^}''
16536 the same as @option{^unix^UNIX^}
16539 @item ^-W^/RESULT_ENCODING=^@var{e}
16540 @cindex @option{^-W^/RESULT_ENCODING=^} (@command{gnatpp})
16541 Specify the wide character encoding method used to write the code in the
16543 @var{e} is one of the following:
16551 Upper half encoding
16553 @item ^s^SHIFT_JIS^
16563 Brackets encoding (default value)
16569 Options @option{^-pipe^/STANDARD_OUTPUT^},
16570 @option{^-o^/OUTPUT^} and
16571 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
16572 contains only one file to reformat.
16574 @option{^--eol^/END_OF_LINE^}
16576 @option{^-W^/RESULT_ENCODING^}
16577 cannot be used together
16578 with @option{^-pipe^/STANDARD_OUTPUT^} option.
16580 @node Other gnatpp Switches
16581 @subsection Other @code{gnatpp} Switches
16584 The additional @command{gnatpp} switches are defined in this subsection.
16587 @item ^-files @var{filename}^/FILES=@var{output_file}^
16588 @cindex @option{^-files^/FILES^} (@code{gnatpp})
16589 Take the argument source files from the specified file. This file should be an
16590 ordinary textual file containing file names separated by spaces or
16591 line breaks. You can use this switch more then once in the same call to
16592 @command{gnatpp}. You also can combine this switch with explicit list of
16595 @item ^-v^/VERBOSE^
16596 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
16598 @command{gnatpp} generates version information and then
16599 a trace of the actions it takes to produce or obtain the ASIS tree.
16601 @item ^-w^/WARNINGS^
16602 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
16604 @command{gnatpp} generates a warning whenever it cannot provide
16605 a required layout in the result source.
16608 @node Formatting Rules
16609 @section Formatting Rules
16612 The following subsections show how @command{gnatpp} treats ``white space'',
16613 comments, program layout, and name casing.
16614 They provide the detailed descriptions of the switches shown above.
16617 * White Space and Empty Lines::
16618 * Formatting Comments::
16619 * Construct Layout::
16623 @node White Space and Empty Lines
16624 @subsection White Space and Empty Lines
16627 @command{gnatpp} does not have an option to control space characters.
16628 It will add or remove spaces according to the style illustrated by the
16629 examples in the @cite{Ada Reference Manual}.
16631 The only format effectors
16632 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
16633 that will appear in the output file are platform-specific line breaks,
16634 and also format effectors within (but not at the end of) comments.
16635 In particular, each horizontal tab character that is not inside
16636 a comment will be treated as a space and thus will appear in the
16637 output file as zero or more spaces depending on
16638 the reformatting of the line in which it appears.
16639 The only exception is a Form Feed character, which is inserted after a
16640 pragma @code{Page} when @option{-ff} is set.
16642 The output file will contain no lines with trailing ``white space'' (spaces,
16645 Empty lines in the original source are preserved
16646 only if they separate declarations or statements.
16647 In such contexts, a
16648 sequence of two or more empty lines is replaced by exactly one empty line.
16649 Note that a blank line will be removed if it separates two ``comment blocks''
16650 (a comment block is a sequence of whole-line comments).
16651 In order to preserve a visual separation between comment blocks, use an
16652 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
16653 Likewise, if for some reason you wish to have a sequence of empty lines,
16654 use a sequence of empty comments instead.
16656 @node Formatting Comments
16657 @subsection Formatting Comments
16660 Comments in Ada code are of two kinds:
16663 a @emph{whole-line comment}, which appears by itself (possibly preceded by
16664 ``white space'') on a line
16667 an @emph{end-of-line comment}, which follows some other Ada lexical element
16672 The indentation of a whole-line comment is that of either
16673 the preceding or following line in
16674 the formatted source, depending on switch settings as will be described below.
16676 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
16677 between the end of the preceding Ada lexical element and the beginning
16678 of the comment as appear in the original source,
16679 unless either the comment has to be split to
16680 satisfy the line length limitation, or else the next line contains a
16681 whole line comment that is considered a continuation of this end-of-line
16682 comment (because it starts at the same position).
16684 cases, the start of the end-of-line comment is moved right to the nearest
16685 multiple of the indentation level.
16686 This may result in a ``line overflow'' (the right-shifted comment extending
16687 beyond the maximum line length), in which case the comment is split as
16690 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
16691 (GNAT-style comment line indentation)
16692 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
16693 (reference-manual comment line indentation).
16694 With reference-manual style, a whole-line comment is indented as if it
16695 were a declaration or statement at the same place
16696 (i.e., according to the indentation of the preceding line(s)).
16697 With GNAT style, a whole-line comment that is immediately followed by an
16698 @b{if} or @b{case} statement alternative, a record variant, or the reserved
16699 word @b{begin}, is indented based on the construct that follows it.
16702 @smallexample @c ada
16714 Reference-manual indentation produces:
16716 @smallexample @c ada
16728 while GNAT-style indentation produces:
16730 @smallexample @c ada
16742 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
16743 (GNAT style comment beginning) has the following
16748 For each whole-line comment that does not end with two hyphens,
16749 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
16750 to ensure that there are at least two spaces between these hyphens and the
16751 first non-blank character of the comment.
16755 For an end-of-line comment, if in the original source the next line is a
16756 whole-line comment that starts at the same position
16757 as the end-of-line comment,
16758 then the whole-line comment (and all whole-line comments
16759 that follow it and that start at the same position)
16760 will start at this position in the output file.
16763 That is, if in the original source we have:
16765 @smallexample @c ada
16768 A := B + C; -- B must be in the range Low1..High1
16769 -- C must be in the range Low2..High2
16770 --B+C will be in the range Low1+Low2..High1+High2
16776 Then in the formatted source we get
16778 @smallexample @c ada
16781 A := B + C; -- B must be in the range Low1..High1
16782 -- C must be in the range Low2..High2
16783 -- B+C will be in the range Low1+Low2..High1+High2
16789 A comment that exceeds the line length limit will be split.
16791 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
16792 the line belongs to a reformattable block, splitting the line generates a
16793 @command{gnatpp} warning.
16794 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
16795 comments may be reformatted in typical
16796 word processor style (that is, moving words between lines and putting as
16797 many words in a line as possible).
16800 The @option{^-c5^/COMMENTS_LAYOUT=KEEP_SPECIAL^} switch specifies, that comments
16801 that has a special format (that is, a character that is neither a letter nor digit
16802 not white space nor line break immediately following the leading @code{--} of
16803 the comment) should be without any change moved from the argument source
16804 into reformatted source. This switch allows to preserve comments that are used
16805 as a special marks in the code (e.g.@: SPARK annotation).
16807 @node Construct Layout
16808 @subsection Construct Layout
16811 In several cases the suggested layout in the Ada Reference Manual includes
16812 an extra level of indentation that many programmers prefer to avoid. The
16813 affected cases include:
16817 @item Record type declaration (RM 3.8)
16819 @item Record representation clause (RM 13.5.1)
16821 @item Loop statement in case if a loop has a statement identifier (RM 5.6)
16823 @item Block statement in case if a block has a statement identifier (RM 5.6)
16827 In compact mode (when GNAT style layout or compact layout is set),
16828 the pretty printer uses one level of indentation instead
16829 of two. This is achieved in the record definition and record representation
16830 clause cases by putting the @code{record} keyword on the same line as the
16831 start of the declaration or representation clause, and in the block and loop
16832 case by putting the block or loop header on the same line as the statement
16836 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
16837 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
16838 layout on the one hand, and uncompact layout
16839 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
16840 can be illustrated by the following examples:
16844 @multitable @columnfractions .5 .5
16845 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
16848 @smallexample @c ada
16855 @smallexample @c ada
16864 @smallexample @c ada
16866 a at 0 range 0 .. 31;
16867 b at 4 range 0 .. 31;
16871 @smallexample @c ada
16874 a at 0 range 0 .. 31;
16875 b at 4 range 0 .. 31;
16880 @smallexample @c ada
16888 @smallexample @c ada
16898 @smallexample @c ada
16899 Clear : for J in 1 .. 10 loop
16904 @smallexample @c ada
16906 for J in 1 .. 10 loop
16917 GNAT style, compact layout Uncompact layout
16919 type q is record type q is
16920 a : integer; record
16921 b : integer; a : integer;
16922 end record; b : integer;
16925 for q use record for q use
16926 a at 0 range 0 .. 31; record
16927 b at 4 range 0 .. 31; a at 0 range 0 .. 31;
16928 end record; b at 4 range 0 .. 31;
16931 Block : declare Block :
16932 A : Integer := 3; declare
16933 begin A : Integer := 3;
16935 end Block; Proc (A, A);
16938 Clear : for J in 1 .. 10 loop Clear :
16939 A (J) := 0; for J in 1 .. 10 loop
16940 end loop Clear; A (J) := 0;
16947 A further difference between GNAT style layout and compact layout is that
16948 GNAT style layout inserts empty lines as separation for
16949 compound statements, return statements and bodies.
16951 Note that the layout specified by
16952 @option{^--separate-stmt-name^/STMT_NAME_ON_NEW_LINE^}
16953 for named block and loop statements overrides the layout defined by these
16954 constructs by @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^},
16955 @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^} or
16956 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} option.
16959 @subsection Name Casing
16962 @command{gnatpp} always converts the usage occurrence of a (simple) name to
16963 the same casing as the corresponding defining identifier.
16965 You control the casing for defining occurrences via the
16966 @option{^-n^/NAME_CASING^} switch.
16968 With @option{-nD} (``as declared'', which is the default),
16971 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
16973 defining occurrences appear exactly as in the source file
16974 where they are declared.
16975 The other ^values for this switch^options for this qualifier^ ---
16976 @option{^-nU^UPPER_CASE^},
16977 @option{^-nL^LOWER_CASE^},
16978 @option{^-nM^MIXED_CASE^} ---
16980 ^upper, lower, or mixed case, respectively^the corresponding casing^.
16981 If @command{gnatpp} changes the casing of a defining
16982 occurrence, it analogously changes the casing of all the
16983 usage occurrences of this name.
16985 If the defining occurrence of a name is not in the source compilation unit
16986 currently being processed by @command{gnatpp}, the casing of each reference to
16987 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
16988 switch (subject to the dictionary file mechanism described below).
16989 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
16991 casing for the defining occurrence of the name.
16993 Some names may need to be spelled with casing conventions that are not
16994 covered by the upper-, lower-, and mixed-case transformations.
16995 You can arrange correct casing by placing such names in a
16996 @emph{dictionary file},
16997 and then supplying a @option{^-D^/DICTIONARY^} switch.
16998 The casing of names from dictionary files overrides
16999 any @option{^-n^/NAME_CASING^} switch.
17001 To handle the casing of Ada predefined names and the names from GNAT libraries,
17002 @command{gnatpp} assumes a default dictionary file.
17003 The name of each predefined entity is spelled with the same casing as is used
17004 for the entity in the @cite{Ada Reference Manual}.
17005 The name of each entity in the GNAT libraries is spelled with the same casing
17006 as is used in the declaration of that entity.
17008 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
17009 default dictionary file.
17010 Instead, the casing for predefined and GNAT-defined names will be established
17011 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
17012 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
17013 will appear as just shown,
17014 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
17015 To ensure that even such names are rendered in uppercase,
17016 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
17017 (or else, less conveniently, place these names in upper case in a dictionary
17020 A dictionary file is
17021 a plain text file; each line in this file can be either a blank line
17022 (containing only space characters and ASCII.HT characters), an Ada comment
17023 line, or the specification of exactly one @emph{casing schema}.
17025 A casing schema is a string that has the following syntax:
17029 @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}*
17031 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
17036 (See @cite{Ada Reference Manual}, Section 2.3) for the definition of the
17037 @var{identifier} lexical element and the @var{letter_or_digit} category.)
17039 The casing schema string can be followed by white space and/or an Ada-style
17040 comment; any amount of white space is allowed before the string.
17042 If a dictionary file is passed as
17044 the value of a @option{-D@var{file}} switch
17047 an option to the @option{/DICTIONARY} qualifier
17050 simple name and every identifier, @command{gnatpp} checks if the dictionary
17051 defines the casing for the name or for some of its parts (the term ``subword''
17052 is used below to denote the part of a name which is delimited by ``_'' or by
17053 the beginning or end of the word and which does not contain any ``_'' inside):
17057 if the whole name is in the dictionary, @command{gnatpp} uses for this name
17058 the casing defined by the dictionary; no subwords are checked for this word
17061 for every subword @command{gnatpp} checks if the dictionary contains the
17062 corresponding string of the form @code{*@var{simple_identifier}*},
17063 and if it does, the casing of this @var{simple_identifier} is used
17067 if the whole name does not contain any ``_'' inside, and if for this name
17068 the dictionary contains two entries - one of the form @var{identifier},
17069 and another - of the form *@var{simple_identifier}*, then the first one
17070 is applied to define the casing of this name
17073 if more than one dictionary file is passed as @command{gnatpp} switches, each
17074 dictionary adds new casing exceptions and overrides all the existing casing
17075 exceptions set by the previous dictionaries
17078 when @command{gnatpp} checks if the word or subword is in the dictionary,
17079 this check is not case sensitive
17083 For example, suppose we have the following source to reformat:
17085 @smallexample @c ada
17088 name1 : integer := 1;
17089 name4_name3_name2 : integer := 2;
17090 name2_name3_name4 : Boolean;
17093 name2_name3_name4 := name4_name3_name2 > name1;
17099 And suppose we have two dictionaries:
17116 If @command{gnatpp} is called with the following switches:
17120 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
17123 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
17128 then we will get the following name casing in the @command{gnatpp} output:
17130 @smallexample @c ada
17133 NAME1 : Integer := 1;
17134 Name4_NAME3_Name2 : Integer := 2;
17135 Name2_NAME3_Name4 : Boolean;
17138 Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1;
17143 @c *********************************
17144 @node The GNAT Metric Tool gnatmetric
17145 @chapter The GNAT Metric Tool @command{gnatmetric}
17147 @cindex Metric tool
17150 ^The @command{gnatmetric} tool^@command{GNAT METRIC}^ is an ASIS-based utility
17151 for computing various program metrics.
17152 It takes an Ada source file as input and generates a file containing the
17153 metrics data as output. Various switches control which
17154 metrics are computed and output.
17156 @command{gnatmetric} generates and uses the ASIS
17157 tree for the input source and thus requires the input to be syntactically and
17158 semantically legal.
17159 If this condition is not met, @command{gnatmetric} will generate
17160 an error message; no metric information for this file will be
17161 computed and reported.
17163 If the compilation unit contained in the input source depends semantically
17164 upon units in files located outside the current directory, you have to provide
17165 the source search path when invoking @command{gnatmetric}.
17166 If it depends semantically upon units that are contained
17167 in files with names that do not follow the GNAT file naming rules, you have to
17168 provide the configuration file describing the corresponding naming scheme (see
17169 the description of the @command{gnatmetric} switches below.)
17170 Alternatively, you may use a project file and invoke @command{gnatmetric}
17171 through the @command{gnat} driver.
17173 The @command{gnatmetric} command has the form
17176 $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]}
17183 @var{switches} specify the metrics to compute and define the destination for
17187 Each @var{filename} is the name (including the extension) of a source
17188 file to process. ``Wildcards'' are allowed, and
17189 the file name may contain path information.
17190 If no @var{filename} is supplied, then the @var{switches} list must contain
17192 @option{-files} switch (@pxref{Other gnatmetric Switches}).
17193 Including both a @option{-files} switch and one or more
17194 @var{filename} arguments is permitted.
17197 @samp{-cargs @var{gcc_switches}} is a list of switches for
17198 @command{gcc}. They will be passed on to all compiler invocations made by
17199 @command{gnatmetric} to generate the ASIS trees. Here you can provide
17200 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
17201 and use the @option{-gnatec} switch to set the configuration file.
17205 * Switches for gnatmetric::
17208 @node Switches for gnatmetric
17209 @section Switches for @command{gnatmetric}
17212 The following subsections describe the various switches accepted by
17213 @command{gnatmetric}, organized by category.
17216 * Output Files Control::
17217 * Disable Metrics For Local Units::
17218 * Specifying a set of metrics to compute::
17219 * Other gnatmetric Switches::
17220 * Generate project-wide metrics::
17223 @node Output Files Control
17224 @subsection Output File Control
17225 @cindex Output file control in @command{gnatmetric}
17228 @command{gnatmetric} has two output formats. It can generate a
17229 textual (human-readable) form, and also XML. By default only textual
17230 output is generated.
17232 When generating the output in textual form, @command{gnatmetric} creates
17233 for each Ada source file a corresponding text file
17234 containing the computed metrics, except for the case when the set of metrics
17235 specified by gnatmetric parameters consists only of metrics that are computed
17236 for the whole set of analyzed sources, but not for each Ada source.
17237 By default, this file is placed in the same directory as where the source
17238 file is located, and its name is obtained
17239 by appending the ^@file{.metrix}^@file{$METRIX}^ suffix to the name of the
17242 All the output information generated in XML format is placed in a single
17243 file. By default this file is placed in the current directory and has the
17244 name ^@file{metrix.xml}^@file{METRIX$XML}^.
17246 Some of the computed metrics are summed over the units passed to
17247 @command{gnatmetric}; for example, the total number of lines of code.
17248 By default this information is sent to @file{stdout}, but a file
17249 can be specified with the @option{-og} switch.
17251 The following switches control the @command{gnatmetric} output:
17254 @cindex @option{^-x^/XML^} (@command{gnatmetric})
17256 Generate the XML output
17258 @cindex @option{^-xs^/XSD^} (@command{gnatmetric})
17260 Generate the XML output and the XML schema file that describes the structure
17261 of the XML metric report, this schema is assigned to the XML file. The schema
17262 file has the same name as the XML output file with @file{.xml} suffix replaced
17265 @cindex @option{^-nt^/NO_TEXT^} (@command{gnatmetric})
17266 @item ^-nt^/NO_TEXT^
17267 Do not generate the output in text form (implies @option{^-x^/XML^})
17269 @cindex @option{^-d^/DIRECTORY^} (@command{gnatmetric})
17270 @item ^-d @var{output_dir}^/DIRECTORY=@var{output_dir}^
17271 Put textual files with detailed metrics into @var{output_dir}
17273 @cindex @option{^-o^/SUFFIX_DETAILS^} (@command{gnatmetric})
17274 @item ^-o @var{file_suffix}^/SUFFIX_DETAILS=@var{file_suffix}^
17275 Use @var{file_suffix}, instead of ^@file{.metrix}^@file{$METRIX}^
17276 in the name of the output file.
17278 @cindex @option{^-og^/GLOBAL_OUTPUT^} (@command{gnatmetric})
17279 @item ^-og @var{file_name}^/GLOBAL_OUTPUT=@var{file_name}^
17280 Put global metrics into @var{file_name}
17282 @cindex @option{^-ox^/XML_OUTPUT^} (@command{gnatmetric})
17283 @item ^-ox @var{file_name}^/XML_OUTPUT=@var{file_name}^
17284 Put the XML output into @var{file_name} (also implies @option{^-x^/XML^})
17286 @cindex @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} (@command{gnatmetric})
17287 @item ^-sfn^/SHORT_SOURCE_FILE_NAME^
17288 Use ``short'' source file names in the output. (The @command{gnatmetric}
17289 output includes the name(s) of the Ada source file(s) from which the metrics
17290 are computed. By default each name includes the absolute path. The
17291 @option{^-sfn^/SHORT_SOURCE_FILE_NAME^} switch causes @command{gnatmetric}
17292 to exclude all directory information from the file names that are output.)
17296 @node Disable Metrics For Local Units
17297 @subsection Disable Metrics For Local Units
17298 @cindex Disable Metrics For Local Units in @command{gnatmetric}
17301 @command{gnatmetric} relies on the GNAT compilation model @minus{}
17303 unit per one source file. It computes line metrics for the whole source
17304 file, and it also computes syntax
17305 and complexity metrics for the file's outermost unit.
17307 By default, @command{gnatmetric} will also compute all metrics for certain
17308 kinds of locally declared program units:
17312 subprogram (and generic subprogram) bodies;
17315 package (and generic package) specs and bodies;
17318 task object and type specifications and bodies;
17321 protected object and type specifications and bodies.
17325 These kinds of entities will be referred to as
17326 @emph{eligible local program units}, or simply @emph{eligible local units},
17327 @cindex Eligible local unit (for @command{gnatmetric})
17328 in the discussion below.
17330 Note that a subprogram declaration, generic instantiation,
17331 or renaming declaration only receives metrics
17332 computation when it appear as the outermost entity
17335 Suppression of metrics computation for eligible local units can be
17336 obtained via the following switch:
17339 @cindex @option{^-n@var{x}^/SUPPRESS^} (@command{gnatmetric})
17340 @item ^-nolocal^/SUPPRESS=LOCAL_DETAILS^
17341 Do not compute detailed metrics for eligible local program units
17345 @node Specifying a set of metrics to compute
17346 @subsection Specifying a set of metrics to compute
17349 By default all the metrics are computed and reported. The switches
17350 described in this subsection allow you to control, on an individual
17351 basis, whether metrics are computed and
17352 reported. If at least one positive metric
17353 switch is specified (that is, a switch that defines that a given
17354 metric or set of metrics is to be computed), then only
17355 explicitly specified metrics are reported.
17358 * Line Metrics Control::
17359 * Syntax Metrics Control::
17360 * Complexity Metrics Control::
17361 * Object-Oriented Metrics Control::
17364 @node Line Metrics Control
17365 @subsubsection Line Metrics Control
17366 @cindex Line metrics control in @command{gnatmetric}
17369 For any (legal) source file, and for each of its
17370 eligible local program units, @command{gnatmetric} computes the following
17375 the total number of lines;
17378 the total number of code lines (i.e., non-blank lines that are not comments)
17381 the number of comment lines
17384 the number of code lines containing end-of-line comments;
17387 the comment percentage: the ratio between the number of lines that contain
17388 comments and the number of all non-blank lines, expressed as a percentage;
17391 the number of empty lines and lines containing only space characters and/or
17392 format effectors (blank lines)
17395 the average number of code lines in subprogram bodies, task bodies, entry
17396 bodies and statement sequences in package bodies (this metric is only computed
17397 across the whole set of the analyzed units)
17402 @command{gnatmetric} sums the values of the line metrics for all the
17403 files being processed and then generates the cumulative results. The tool
17404 also computes for all the files being processed the average number of code
17407 You can use the following switches to select the specific line metrics
17408 to be computed and reported.
17411 @cindex @option{^--lines@var{x}^/LINE_COUNT_METRICS^} (@command{gnatmetric})
17414 @cindex @option{--no-lines@var{x}}
17417 @item ^--lines-all^/LINE_COUNT_METRICS=ALL^
17418 Report all the line metrics
17420 @item ^--no-lines-all^/LINE_COUNT_METRICS=NONE^
17421 Do not report any of line metrics
17423 @item ^--lines^/LINE_COUNT_METRICS=ALL_LINES^
17424 Report the number of all lines
17426 @item ^--no-lines^/LINE_COUNT_METRICS=NOALL_LINES^
17427 Do not report the number of all lines
17429 @item ^--lines-code^/LINE_COUNT_METRICS=CODE_LINES^
17430 Report the number of code lines
17432 @item ^--no-lines-code^/LINE_COUNT_METRICS=NOCODE_LINES^
17433 Do not report the number of code lines
17435 @item ^--lines-comment^/LINE_COUNT_METRICS=COMMENT_LINES^
17436 Report the number of comment lines
17438 @item ^--no-lines-comment^/LINE_COUNT_METRICS=NOCOMMENT_LINES^
17439 Do not report the number of comment lines
17441 @item ^--lines-eol-comment^/LINE_COUNT_METRICS=CODE_COMMENT_LINES^
17442 Report the number of code lines containing
17443 end-of-line comments
17445 @item ^--no-lines-eol-comment^/LINE_COUNT_METRICS=NOCODE_COMMENT_LINES^
17446 Do not report the number of code lines containing
17447 end-of-line comments
17449 @item ^--lines-ratio^/LINE_COUNT_METRICS=COMMENT_PERCENTAGE^
17450 Report the comment percentage in the program text
17452 @item ^--no-lines-ratio^/LINE_COUNT_METRICS=NOCOMMENT_PERCENTAGE^
17453 Do not report the comment percentage in the program text
17455 @item ^--lines-blank^/LINE_COUNT_METRICS=BLANK_LINES^
17456 Report the number of blank lines
17458 @item ^--no-lines-blank^/LINE_COUNT_METRICS=NOBLANK_LINES^
17459 Do not report the number of blank lines
17461 @item ^--lines-average^/LINE_COUNT_METRICS=AVERAGE_BODY_LINES^
17462 Report the average number of code lines in subprogram bodies, task bodies,
17463 entry bodies and statement sequences in package bodies. The metric is computed
17464 and reported for the whole set of processed Ada sources only.
17466 @item ^--no-lines-average^/LINE_COUNT_METRICS=NOAVERAGE_BODY_LINES^
17467 Do not report the average number of code lines in subprogram bodies,
17468 task bodies, entry bodies and statement sequences in package bodies.
17472 @node Syntax Metrics Control
17473 @subsubsection Syntax Metrics Control
17474 @cindex Syntax metrics control in @command{gnatmetric}
17477 @command{gnatmetric} computes various syntactic metrics for the
17478 outermost unit and for each eligible local unit:
17481 @item LSLOC (``Logical Source Lines Of Code'')
17482 The total number of declarations and the total number of statements
17484 @item Maximal static nesting level of inner program units
17486 @cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a
17487 package, a task unit, a protected unit, a
17488 protected entry, a generic unit, or an explicitly declared subprogram other
17489 than an enumeration literal.''
17491 @item Maximal nesting level of composite syntactic constructs
17492 This corresponds to the notion of the
17493 maximum nesting level in the GNAT built-in style checks
17494 (@pxref{Style Checking})
17498 For the outermost unit in the file, @command{gnatmetric} additionally computes
17499 the following metrics:
17502 @item Public subprograms
17503 This metric is computed for package specs. It is the
17504 number of subprograms and generic subprograms declared in the visible
17505 part (including the visible part of nested packages, protected objects, and
17508 @item All subprograms
17509 This metric is computed for bodies and subunits. The
17510 metric is equal to a total number of subprogram bodies in the compilation
17512 Neither generic instantiations nor renamings-as-a-body nor body stubs
17513 are counted. Any subprogram body is counted, independently of its nesting
17514 level and enclosing constructs. Generic bodies and bodies of protected
17515 subprograms are counted in the same way as ``usual'' subprogram bodies.
17518 This metric is computed for package specs and
17519 generic package declarations. It is the total number of types
17520 that can be referenced from outside this compilation unit, plus the
17521 number of types from all the visible parts of all the visible generic
17522 packages. Generic formal types are not counted. Only types, not subtypes,
17526 Along with the total number of public types, the following
17527 types are counted and reported separately:
17534 Root tagged types (abstract, non-abstract, private, non-private). Type
17535 extensions are @emph{not} counted
17538 Private types (including private extensions)
17549 This metric is computed for any compilation unit. It is equal to the total
17550 number of the declarations of different types given in the compilation unit.
17551 The private and the corresponding full type declaration are counted as one
17552 type declaration. Incomplete type declarations and generic formal types
17554 No distinction is made among different kinds of types (abstract,
17555 private etc.); the total number of types is computed and reported.
17560 By default, all the syntax metrics are computed and reported. You can use the
17561 following switches to select specific syntax metrics.
17565 @cindex @option{^--syntax@var{x}^/SYNTAX_METRICS^} (@command{gnatmetric})
17568 @cindex @option{--no-syntax@var{x}} (@command{gnatmetric})
17571 @item ^--syntax-all^/SYNTAX_METRICS=ALL^
17572 Report all the syntax metrics
17574 @item ^--no-syntax-all^/SYNTAX_METRICS=NONE^
17575 Do not report any of syntax metrics
17577 @item ^--declarations^/SYNTAX_METRICS=DECLARATIONS^
17578 Report the total number of declarations
17580 @item ^--no-declarations^/SYNTAX_METRICS=NODECLARATIONS^
17581 Do not report the total number of declarations
17583 @item ^--statements^/SYNTAX_METRICS=STATEMENTS^
17584 Report the total number of statements
17586 @item ^--no-statements^/SYNTAX_METRICS=NOSTATEMENTS^
17587 Do not report the total number of statements
17589 @item ^--public-subprograms^/SYNTAX_METRICS=PUBLIC_SUBPROGRAMS^
17590 Report the number of public subprograms in a compilation unit
17592 @item ^--no-public-subprograms^/SYNTAX_METRICS=NOPUBLIC_SUBPROGRAMS^
17593 Do not report the number of public subprograms in a compilation unit
17595 @item ^--all-subprograms^/SYNTAX_METRICS=ALL_SUBPROGRAMS^
17596 Report the number of all the subprograms in a compilation unit
17598 @item ^--no-all-subprograms^/SYNTAX_METRICS=NOALL_SUBPROGRAMS^
17599 Do not report the number of all the subprograms in a compilation unit
17601 @item ^--public-types^/SYNTAX_METRICS=PUBLIC_TYPES^
17602 Report the number of public types in a compilation unit
17604 @item ^--no-public-types^/SYNTAX_METRICS=NOPUBLIC_TYPES^
17605 Do not report the number of public types in a compilation unit
17607 @item ^--all-types^/SYNTAX_METRICS=ALL_TYPES^
17608 Report the number of all the types in a compilation unit
17610 @item ^--no-all-types^/SYNTAX_METRICS=NOALL_TYPES^
17611 Do not report the number of all the types in a compilation unit
17613 @item ^--unit-nesting^/SYNTAX_METRICS=UNIT_NESTING^
17614 Report the maximal program unit nesting level
17616 @item ^--no-unit-nesting^/SYNTAX_METRICS=UNIT_NESTING_OFF^
17617 Do not report the maximal program unit nesting level
17619 @item ^--construct-nesting^/SYNTAX_METRICS=CONSTRUCT_NESTING^
17620 Report the maximal construct nesting level
17622 @item ^--no-construct-nesting^/SYNTAX_METRICS=NOCONSTRUCT_NESTING^
17623 Do not report the maximal construct nesting level
17627 @node Complexity Metrics Control
17628 @subsubsection Complexity Metrics Control
17629 @cindex Complexity metrics control in @command{gnatmetric}
17632 For a program unit that is an executable body (a subprogram body (including
17633 generic bodies), task body, entry body or a package body containing
17634 its own statement sequence) @command{gnatmetric} computes the following
17635 complexity metrics:
17639 McCabe cyclomatic complexity;
17642 McCabe essential complexity;
17645 maximal loop nesting level
17650 The McCabe complexity metrics are defined
17651 in @url{http://www.mccabe.com/pdf/nist235r.pdf}
17653 According to McCabe, both control statements and short-circuit control forms
17654 should be taken into account when computing cyclomatic complexity. For each
17655 body, we compute three metric values:
17659 the complexity introduced by control
17660 statements only, without taking into account short-circuit forms,
17663 the complexity introduced by short-circuit control forms only, and
17667 cyclomatic complexity, which is the sum of these two values.
17671 When computing cyclomatic and essential complexity, @command{gnatmetric} skips
17672 the code in the exception handlers and in all the nested program units.
17674 By default, all the complexity metrics are computed and reported.
17675 For more fine-grained control you can use
17676 the following switches:
17679 @cindex @option{^-complexity@var{x}^/COMPLEXITY_METRICS^} (@command{gnatmetric})
17682 @cindex @option{--no-complexity@var{x}}
17685 @item ^--complexity-all^/COMPLEXITY_METRICS=ALL^
17686 Report all the complexity metrics
17688 @item ^--no-complexity-all^/COMPLEXITY_METRICS=NONE^
17689 Do not report any of complexity metrics
17691 @item ^--complexity-cyclomatic^/COMPLEXITY_METRICS=CYCLOMATIC^
17692 Report the McCabe Cyclomatic Complexity
17694 @item ^--no-complexity-cyclomatic^/COMPLEXITY_METRICS=NOCYCLOMATIC^
17695 Do not report the McCabe Cyclomatic Complexity
17697 @item ^--complexity-essential^/COMPLEXITY_METRICS=ESSENTIAL^
17698 Report the Essential Complexity
17700 @item ^--no-complexity-essential^/COMPLEXITY_METRICS=NOESSENTIAL^
17701 Do not report the Essential Complexity
17703 @item ^--loop-nesting^/COMPLEXITY_METRICS=LOOP_NESTING_ON^
17704 Report maximal loop nesting level
17706 @item ^--no-loop-nesting^/COMPLEXITY_METRICS=NOLOOP_NESTING^
17707 Do not report maximal loop nesting level
17709 @item ^--complexity-average^/COMPLEXITY_METRICS=AVERAGE_COMPLEXITY^
17710 Report the average McCabe Cyclomatic Complexity for all the subprogram bodies,
17711 task bodies, entry bodies and statement sequences in package bodies.
17712 The metric is computed and reported for whole set of processed Ada sources
17715 @item ^--no-complexity-average^/COMPLEXITY_METRICS=NOAVERAGE_COMPLEXITY^
17716 Do not report the average McCabe Cyclomatic Complexity for all the subprogram
17717 bodies, task bodies, entry bodies and statement sequences in package bodies
17719 @cindex @option{^-ne^/NO_EXITS_AS_GOTOS^} (@command{gnatmetric})
17720 @item ^-ne^/NO_EXITS_AS_GOTOS^
17721 Do not consider @code{exit} statements as @code{goto}s when
17722 computing Essential Complexity
17724 @item ^--extra-exit-points^/EXTRA_EXIT_POINTS^
17725 Report the extra exit points for subprogram bodies. As an exit point, this
17726 metric counts @code{return} statements and raise statements in case when the
17727 raised exception is not handled in the same body. In case of a function this
17728 metric subtracts 1 from the number of exit points, because a function body
17729 must contain at least one @code{return} statement.
17731 @item ^--no-extra-exit-points^/NOEXTRA_EXIT_POINTS^
17732 Do not report the extra exit points for subprogram bodies
17736 @node Object-Oriented Metrics Control
17737 @subsubsection Object-Oriented Metrics Control
17738 @cindex Object-Oriented metrics control in @command{gnatmetric}
17741 @cindex Coupling metrics (in in @command{gnatmetric})
17742 Coupling metrics are object-oriented metrics that measure the
17743 dependencies between a given class (or a group of classes) and the
17744 ``external world'' (that is, the other classes in the program). In this
17745 subsection the term ``class'' is used in its
17746 traditional object-oriented programming sense
17747 (an instantiable module that contains data and/or method members).
17748 A @emph{category} (of classes)
17749 is a group of closely related classes that are reused and/or
17752 A class @code{K}'s @emph{efferent coupling} is the number of classes
17753 that @code{K} depends upon.
17754 A category's efferent coupling is the number of classes outside the
17755 category that the classes inside the category depend upon.
17757 A class @code{K}'s @emph{afferent coupling} is the number of classes
17758 that depend upon @code{K}.
17759 A category's afferent coupling is the number of classes outside the
17760 category that depend on classes belonging to the category.
17762 Ada's implementation of the object-oriented paradigm does not use the
17763 traditional class notion, so the definition of the coupling
17764 metrics for Ada maps the class and class category notions
17765 onto Ada constructs.
17767 For the coupling metrics, several kinds of modules -- a library package,
17768 a library generic package, and a library generic package instantiation --
17769 that define a tagged type or an interface type are
17770 considered to be a class. A category consists of a library package (or
17771 a library generic package) that defines a tagged or an interface type,
17772 together with all its descendant (generic) packages that define tagged
17773 or interface types. For any package counted as a class,
17774 its body and subunits (if any) are considered
17775 together with its spec when counting the dependencies, and coupling
17776 metrics are reported for spec units only. For dependencies
17777 between classes, the Ada semantic dependencies are considered.
17778 For coupling metrics, only dependencies on units that are considered as
17779 classes, are considered.
17781 When computing coupling metrics, @command{gnatmetric} counts only
17782 dependencies between units that are arguments of the gnatmetric call.
17783 Coupling metrics are program-wide (or project-wide) metrics, so to
17784 get a valid result, you should call @command{gnatmetric} for
17785 the whole set of sources that make up your program. It can be done
17786 by calling @command{gnatmetric} from the GNAT driver with @option{-U}
17787 option (see See @ref{The GNAT Driver and Project Files} for details.
17789 By default, all the coupling metrics are disabled. You can use the following
17790 switches to specify the coupling metrics to be computed and reported:
17795 @cindex @option{--package@var{x}} (@command{gnatmetric})
17796 @cindex @option{--no-package@var{x}} (@command{gnatmetric})
17797 @cindex @option{--category@var{x}} (@command{gnatmetric})
17798 @cindex @option{--no-category@var{x}} (@command{gnatmetric})
17802 @cindex @option{/COUPLING_METRICS} (@command{gnatmetric})
17805 @item ^--coupling-all^/COUPLING_METRICS=ALL^
17806 Report all the coupling metrics
17808 @item ^--no-coupling-all^/COUPLING_METRICS=NONE^
17809 Do not report any of metrics
17811 @item ^--package-efferent-coupling^/COUPLING_METRICS=PACKAGE_EFFERENT^
17812 Report package efferent coupling
17814 @item ^--no-package-efferent-coupling^/COUPLING_METRICS=NOPACKAGE_EFFERENT^
17815 Do not report package efferent coupling
17817 @item ^--package-afferent-coupling^/COUPLING_METRICS=PACKAGE_AFFERENT^
17818 Report package afferent coupling
17820 @item ^--no-package-afferent-coupling^/COUPLING_METRICS=NOPACKAGE_AFFERENT^
17821 Do not report package afferent coupling
17823 @item ^--category-efferent-coupling^/COUPLING_METRICS=CATEGORY_EFFERENT^
17824 Report category efferent coupling
17826 @item ^--no-category-efferent-coupling^/COUPLING_METRICS=NOCATEGORY_EFFERENT^
17827 Do not report category efferent coupling
17829 @item ^--category-afferent-coupling^/COUPLING_METRICS=CATEGORY_AFFERENT^
17830 Report category afferent coupling
17832 @item ^--no-category-afferent-coupling^/COUPLING_METRICS=NOCATEGORY_AFFERENT^
17833 Do not report category afferent coupling
17837 @node Other gnatmetric Switches
17838 @subsection Other @code{gnatmetric} Switches
17841 Additional @command{gnatmetric} switches are as follows:
17844 @item ^-files @var{filename}^/FILES=@var{filename}^
17845 @cindex @option{^-files^/FILES^} (@code{gnatmetric})
17846 Take the argument source files from the specified file. This file should be an
17847 ordinary text file containing file names separated by spaces or
17848 line breaks. You can use this switch more then once in the same call to
17849 @command{gnatmetric}. You also can combine this switch with
17850 an explicit list of files.
17852 @item ^-v^/VERBOSE^
17853 @cindex @option{^-v^/VERBOSE^} (@code{gnatmetric})
17855 @command{gnatmetric} generates version information and then
17856 a trace of sources being processed.
17858 @item ^-dv^/DEBUG_OUTPUT^
17859 @cindex @option{^-dv^/DEBUG_OUTPUT^} (@code{gnatmetric})
17861 @command{gnatmetric} generates various messages useful to understand what
17862 happens during the metrics computation
17865 @cindex @option{^-q^/QUIET^} (@code{gnatmetric})
17869 @node Generate project-wide metrics
17870 @subsection Generate project-wide metrics
17872 In order to compute metrics on all units of a given project, you can use
17873 the @command{gnat} driver along with the @option{-P} option:
17879 If the project @code{proj} depends upon other projects, you can compute
17880 the metrics on the project closure using the @option{-U} option:
17882 gnat metric -Pproj -U
17886 Finally, if not all the units are relevant to a particular main
17887 program in the project closure, you can generate metrics for the set
17888 of units needed to create a given main program (unit closure) using
17889 the @option{-U} option followed by the name of the main unit:
17891 gnat metric -Pproj -U main
17895 @c ***********************************
17896 @node File Name Krunching Using gnatkr
17897 @chapter File Name Krunching Using @code{gnatkr}
17901 This chapter discusses the method used by the compiler to shorten
17902 the default file names chosen for Ada units so that they do not
17903 exceed the maximum length permitted. It also describes the
17904 @code{gnatkr} utility that can be used to determine the result of
17905 applying this shortening.
17909 * Krunching Method::
17910 * Examples of gnatkr Usage::
17914 @section About @code{gnatkr}
17917 The default file naming rule in GNAT
17918 is that the file name must be derived from
17919 the unit name. The exact default rule is as follows:
17922 Take the unit name and replace all dots by hyphens.
17924 If such a replacement occurs in the
17925 second character position of a name, and the first character is
17926 ^@samp{a}, @samp{g}, @samp{s}, or @samp{i}, ^@samp{A}, @samp{G}, @samp{S}, or @samp{I},^
17927 then replace the dot by the character
17928 ^@samp{~} (tilde)^@samp{$} (dollar sign)^
17929 instead of a minus.
17931 The reason for this exception is to avoid clashes
17932 with the standard names for children of System, Ada, Interfaces,
17933 and GNAT, which use the prefixes
17934 ^@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-},^@samp{S-}, @samp{A-}, @samp{I-}, and @samp{G-},^
17937 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
17938 switch of the compiler activates a ``krunching''
17939 circuit that limits file names to nn characters (where nn is a decimal
17940 integer). For example, using OpenVMS,
17941 where the maximum file name length is
17942 39, the value of nn is usually set to 39, but if you want to generate
17943 a set of files that would be usable if ported to a system with some
17944 different maximum file length, then a different value can be specified.
17945 The default value of 39 for OpenVMS need not be specified.
17947 The @code{gnatkr} utility can be used to determine the krunched name for
17948 a given file, when krunched to a specified maximum length.
17951 @section Using @code{gnatkr}
17954 The @code{gnatkr} command has the form
17958 $ gnatkr @var{name} @ovar{length}
17964 $ gnatkr @var{name} /COUNT=nn
17969 @var{name} is the uncrunched file name, derived from the name of the unit
17970 in the standard manner described in the previous section (i.e., in particular
17971 all dots are replaced by hyphens). The file name may or may not have an
17972 extension (defined as a suffix of the form period followed by arbitrary
17973 characters other than period). If an extension is present then it will
17974 be preserved in the output. For example, when krunching @file{hellofile.ads}
17975 to eight characters, the result will be hellofil.ads.
17977 Note: for compatibility with previous versions of @code{gnatkr} dots may
17978 appear in the name instead of hyphens, but the last dot will always be
17979 taken as the start of an extension. So if @code{gnatkr} is given an argument
17980 such as @file{Hello.World.adb} it will be treated exactly as if the first
17981 period had been a hyphen, and for example krunching to eight characters
17982 gives the result @file{hellworl.adb}.
17984 Note that the result is always all lower case (except on OpenVMS where it is
17985 all upper case). Characters of the other case are folded as required.
17987 @var{length} represents the length of the krunched name. The default
17988 when no argument is given is ^8^39^ characters. A length of zero stands for
17989 unlimited, in other words do not chop except for system files where the
17990 implied crunching length is always eight characters.
17993 The output is the krunched name. The output has an extension only if the
17994 original argument was a file name with an extension.
17996 @node Krunching Method
17997 @section Krunching Method
18000 The initial file name is determined by the name of the unit that the file
18001 contains. The name is formed by taking the full expanded name of the
18002 unit and replacing the separating dots with hyphens and
18003 using ^lowercase^uppercase^
18004 for all letters, except that a hyphen in the second character position is
18005 replaced by a ^tilde^dollar sign^ if the first character is
18006 ^@samp{a}, @samp{i}, @samp{g}, or @samp{s}^@samp{A}, @samp{I}, @samp{G}, or @samp{S}^.
18007 The extension is @code{.ads} for a
18008 spec and @code{.adb} for a body.
18009 Krunching does not affect the extension, but the file name is shortened to
18010 the specified length by following these rules:
18014 The name is divided into segments separated by hyphens, tildes or
18015 underscores and all hyphens, tildes, and underscores are
18016 eliminated. If this leaves the name short enough, we are done.
18019 If the name is too long, the longest segment is located (left-most
18020 if there are two of equal length), and shortened by dropping
18021 its last character. This is repeated until the name is short enough.
18023 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
18024 to fit the name into 8 characters as required by some operating systems.
18027 our-strings-wide_fixed 22
18028 our strings wide fixed 19
18029 our string wide fixed 18
18030 our strin wide fixed 17
18031 our stri wide fixed 16
18032 our stri wide fixe 15
18033 our str wide fixe 14
18034 our str wid fixe 13
18040 Final file name: oustwifi.adb
18044 The file names for all predefined units are always krunched to eight
18045 characters. The krunching of these predefined units uses the following
18046 special prefix replacements:
18050 replaced by @file{^a^A^-}
18053 replaced by @file{^g^G^-}
18056 replaced by @file{^i^I^-}
18059 replaced by @file{^s^S^-}
18062 These system files have a hyphen in the second character position. That
18063 is why normal user files replace such a character with a
18064 ^tilde^dollar sign^, to
18065 avoid confusion with system file names.
18067 As an example of this special rule, consider
18068 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
18071 ada-strings-wide_fixed 22
18072 a- strings wide fixed 18
18073 a- string wide fixed 17
18074 a- strin wide fixed 16
18075 a- stri wide fixed 15
18076 a- stri wide fixe 14
18077 a- str wide fixe 13
18083 Final file name: a-stwifi.adb
18087 Of course no file shortening algorithm can guarantee uniqueness over all
18088 possible unit names, and if file name krunching is used then it is your
18089 responsibility to ensure that no name clashes occur. The utility
18090 program @code{gnatkr} is supplied for conveniently determining the
18091 krunched name of a file.
18093 @node Examples of gnatkr Usage
18094 @section Examples of @code{gnatkr} Usage
18101 $ gnatkr very_long_unit_name.ads --> velounna.ads
18102 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
18103 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
18104 $ gnatkr grandparent-parent-child --> grparchi
18106 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
18107 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
18110 @node Preprocessing Using gnatprep
18111 @chapter Preprocessing Using @code{gnatprep}
18115 This chapter discusses how to use GNAT's @code{gnatprep} utility for simple
18117 Although designed for use with GNAT, @code{gnatprep} does not depend on any
18118 special GNAT features.
18119 For further discussion of conditional compilation in general, see
18120 @ref{Conditional Compilation}.
18123 * Preprocessing Symbols::
18125 * Switches for gnatprep::
18126 * Form of Definitions File::
18127 * Form of Input Text for gnatprep::
18130 @node Preprocessing Symbols
18131 @section Preprocessing Symbols
18134 Preprocessing symbols are defined in definition files and referred to in
18135 sources to be preprocessed. A Preprocessing symbol is an identifier, following
18136 normal Ada (case-insensitive) rules for its syntax, with the restriction that
18137 all characters need to be in the ASCII set (no accented letters).
18139 @node Using gnatprep
18140 @section Using @code{gnatprep}
18143 To call @code{gnatprep} use
18146 $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile}
18153 is an optional sequence of switches as described in the next section.
18156 is the full name of the input file, which is an Ada source
18157 file containing preprocessor directives.
18160 is the full name of the output file, which is an Ada source
18161 in standard Ada form. When used with GNAT, this file name will
18162 normally have an ads or adb suffix.
18165 is the full name of a text file containing definitions of
18166 preprocessing symbols to be referenced by the preprocessor. This argument is
18167 optional, and can be replaced by the use of the @option{-D} switch.
18171 @node Switches for gnatprep
18172 @section Switches for @code{gnatprep}
18177 @item ^-b^/BLANK_LINES^
18178 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
18179 Causes both preprocessor lines and the lines deleted by
18180 preprocessing to be replaced by blank lines in the output source file,
18181 preserving line numbers in the output file.
18183 @item ^-c^/COMMENTS^
18184 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
18185 Causes both preprocessor lines and the lines deleted
18186 by preprocessing to be retained in the output source as comments marked
18187 with the special string @code{"--! "}. This option will result in line numbers
18188 being preserved in the output file.
18190 @item ^-C^/REPLACE_IN_COMMENTS^
18191 @cindex @option{^-C^/REPLACE_IN_COMMENTS^} (@command{gnatprep})
18192 Causes comments to be scanned. Normally comments are ignored by gnatprep.
18193 If this option is specified, then comments are scanned and any $symbol
18194 substitutions performed as in program text. This is particularly useful
18195 when structured comments are used (e.g., when writing programs in the
18196 SPARK dialect of Ada). Note that this switch is not available when
18197 doing integrated preprocessing (it would be useless in this context
18198 since comments are ignored by the compiler in any case).
18200 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
18201 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
18202 Defines a new preprocessing symbol, associated with value. If no value is given
18203 on the command line, then symbol is considered to be @code{True}. This switch
18204 can be used in place of a definition file.
18208 @cindex @option{/REMOVE} (@command{gnatprep})
18209 This is the default setting which causes lines deleted by preprocessing
18210 to be entirely removed from the output file.
18213 @item ^-r^/REFERENCE^
18214 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
18215 Causes a @code{Source_Reference} pragma to be generated that
18216 references the original input file, so that error messages will use
18217 the file name of this original file. The use of this switch implies
18218 that preprocessor lines are not to be removed from the file, so its
18219 use will force @option{^-b^/BLANK_LINES^} mode if
18220 @option{^-c^/COMMENTS^}
18221 has not been specified explicitly.
18223 Note that if the file to be preprocessed contains multiple units, then
18224 it will be necessary to @code{gnatchop} the output file from
18225 @code{gnatprep}. If a @code{Source_Reference} pragma is present
18226 in the preprocessed file, it will be respected by
18227 @code{gnatchop ^-r^/REFERENCE^}
18228 so that the final chopped files will correctly refer to the original
18229 input source file for @code{gnatprep}.
18231 @item ^-s^/SYMBOLS^
18232 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
18233 Causes a sorted list of symbol names and values to be
18234 listed on the standard output file.
18236 @item ^-u^/UNDEFINED^
18237 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
18238 Causes undefined symbols to be treated as having the value FALSE in the context
18239 of a preprocessor test. In the absence of this option, an undefined symbol in
18240 a @code{#if} or @code{#elsif} test will be treated as an error.
18246 Note: if neither @option{-b} nor @option{-c} is present,
18247 then preprocessor lines and
18248 deleted lines are completely removed from the output, unless -r is
18249 specified, in which case -b is assumed.
18252 @node Form of Definitions File
18253 @section Form of Definitions File
18256 The definitions file contains lines of the form
18263 where symbol is a preprocessing symbol, and value is one of the following:
18267 Empty, corresponding to a null substitution
18269 A string literal using normal Ada syntax
18271 Any sequence of characters from the set
18272 (letters, digits, period, underline).
18276 Comment lines may also appear in the definitions file, starting with
18277 the usual @code{--},
18278 and comments may be added to the definitions lines.
18280 @node Form of Input Text for gnatprep
18281 @section Form of Input Text for @code{gnatprep}
18284 The input text may contain preprocessor conditional inclusion lines,
18285 as well as general symbol substitution sequences.
18287 The preprocessor conditional inclusion commands have the form
18292 #if @i{expression} @r{[}then@r{]}
18294 #elsif @i{expression} @r{[}then@r{]}
18296 #elsif @i{expression} @r{[}then@r{]}
18307 In this example, @i{expression} is defined by the following grammar:
18309 @i{expression} ::= <symbol>
18310 @i{expression} ::= <symbol> = "<value>"
18311 @i{expression} ::= <symbol> = <symbol>
18312 @i{expression} ::= <symbol> 'Defined
18313 @i{expression} ::= not @i{expression}
18314 @i{expression} ::= @i{expression} and @i{expression}
18315 @i{expression} ::= @i{expression} or @i{expression}
18316 @i{expression} ::= @i{expression} and then @i{expression}
18317 @i{expression} ::= @i{expression} or else @i{expression}
18318 @i{expression} ::= ( @i{expression} )
18321 The following restriction exists: it is not allowed to have "and" or "or"
18322 following "not" in the same expression without parentheses. For example, this
18329 This should be one of the following:
18337 For the first test (@i{expression} ::= <symbol>) the symbol must have
18338 either the value true or false, that is to say the right-hand of the
18339 symbol definition must be one of the (case-insensitive) literals
18340 @code{True} or @code{False}. If the value is true, then the
18341 corresponding lines are included, and if the value is false, they are
18344 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
18345 the symbol has been defined in the definition file or by a @option{-D}
18346 switch on the command line. Otherwise, the test is false.
18348 The equality tests are case insensitive, as are all the preprocessor lines.
18350 If the symbol referenced is not defined in the symbol definitions file,
18351 then the effect depends on whether or not switch @option{-u}
18352 is specified. If so, then the symbol is treated as if it had the value
18353 false and the test fails. If this switch is not specified, then
18354 it is an error to reference an undefined symbol. It is also an error to
18355 reference a symbol that is defined with a value other than @code{True}
18358 The use of the @code{not} operator inverts the sense of this logical test.
18359 The @code{not} operator cannot be combined with the @code{or} or @code{and}
18360 operators, without parentheses. For example, "if not X or Y then" is not
18361 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
18363 The @code{then} keyword is optional as shown
18365 The @code{#} must be the first non-blank character on a line, but
18366 otherwise the format is free form. Spaces or tabs may appear between
18367 the @code{#} and the keyword. The keywords and the symbols are case
18368 insensitive as in normal Ada code. Comments may be used on a
18369 preprocessor line, but other than that, no other tokens may appear on a
18370 preprocessor line. Any number of @code{elsif} clauses can be present,
18371 including none at all. The @code{else} is optional, as in Ada.
18373 The @code{#} marking the start of a preprocessor line must be the first
18374 non-blank character on the line, i.e., it must be preceded only by
18375 spaces or horizontal tabs.
18377 Symbol substitution outside of preprocessor lines is obtained by using
18385 anywhere within a source line, except in a comment or within a
18386 string literal. The identifier
18387 following the @code{$} must match one of the symbols defined in the symbol
18388 definition file, and the result is to substitute the value of the
18389 symbol in place of @code{$symbol} in the output file.
18391 Note that although the substitution of strings within a string literal
18392 is not possible, it is possible to have a symbol whose defined value is
18393 a string literal. So instead of setting XYZ to @code{hello} and writing:
18396 Header : String := "$XYZ";
18400 you should set XYZ to @code{"hello"} and write:
18403 Header : String := $XYZ;
18407 and then the substitution will occur as desired.
18410 @node The GNAT Run-Time Library Builder gnatlbr
18411 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
18413 @cindex Library builder
18416 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
18417 supplied configuration pragmas.
18420 * Running gnatlbr::
18421 * Switches for gnatlbr::
18422 * Examples of gnatlbr Usage::
18425 @node Running gnatlbr
18426 @section Running @code{gnatlbr}
18429 The @code{gnatlbr} command has the form
18432 $ GNAT LIBRARY /@r{[}CREATE@r{|}SET@r{|}DELETE@r{]}=directory @r{[}/CONFIG=file@r{]}
18435 @node Switches for gnatlbr
18436 @section Switches for @code{gnatlbr}
18439 @code{gnatlbr} recognizes the following switches:
18443 @item /CREATE=directory
18444 @cindex @code{/CREATE} (@code{gnatlbr})
18445 Create the new run-time library in the specified directory.
18447 @item /SET=directory
18448 @cindex @code{/SET} (@code{gnatlbr})
18449 Make the library in the specified directory the current run-time library.
18451 @item /DELETE=directory
18452 @cindex @code{/DELETE} (@code{gnatlbr})
18453 Delete the run-time library in the specified directory.
18456 @cindex @code{/CONFIG} (@code{gnatlbr})
18457 With /CREATE: Use the configuration pragmas in the specified file when
18458 building the library.
18460 With /SET: Use the configuration pragmas in the specified file when
18465 @node Examples of gnatlbr Usage
18466 @section Example of @code{gnatlbr} Usage
18469 Contents of VAXFLOAT.ADC:
18470 pragma Float_Representation (VAX_Float);
18472 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
18474 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
18479 @node The GNAT Library Browser gnatls
18480 @chapter The GNAT Library Browser @code{gnatls}
18482 @cindex Library browser
18485 @code{gnatls} is a tool that outputs information about compiled
18486 units. It gives the relationship between objects, unit names and source
18487 files. It can also be used to check the source dependencies of a unit
18488 as well as various characteristics.
18490 Note: to invoke @code{gnatls} with a project file, use the @code{gnat}
18491 driver (see @ref{The GNAT Driver and Project Files}).
18495 * Switches for gnatls::
18496 * Examples of gnatls Usage::
18499 @node Running gnatls
18500 @section Running @code{gnatls}
18503 The @code{gnatls} command has the form
18506 $ gnatls switches @var{object_or_ali_file}
18510 The main argument is the list of object or @file{ali} files
18511 (@pxref{The Ada Library Information Files})
18512 for which information is requested.
18514 In normal mode, without additional option, @code{gnatls} produces a
18515 four-column listing. Each line represents information for a specific
18516 object. The first column gives the full path of the object, the second
18517 column gives the name of the principal unit in this object, the third
18518 column gives the status of the source and the fourth column gives the
18519 full path of the source representing this unit.
18520 Here is a simple example of use:
18524 ^./^[]^demo1.o demo1 DIF demo1.adb
18525 ^./^[]^demo2.o demo2 OK demo2.adb
18526 ^./^[]^hello.o h1 OK hello.adb
18527 ^./^[]^instr-child.o instr.child MOK instr-child.adb
18528 ^./^[]^instr.o instr OK instr.adb
18529 ^./^[]^tef.o tef DIF tef.adb
18530 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
18531 ^./^[]^tgef.o tgef DIF tgef.adb
18535 The first line can be interpreted as follows: the main unit which is
18537 object file @file{demo1.o} is demo1, whose main source is in
18538 @file{demo1.adb}. Furthermore, the version of the source used for the
18539 compilation of demo1 has been modified (DIF). Each source file has a status
18540 qualifier which can be:
18543 @item OK (unchanged)
18544 The version of the source file used for the compilation of the
18545 specified unit corresponds exactly to the actual source file.
18547 @item MOK (slightly modified)
18548 The version of the source file used for the compilation of the
18549 specified unit differs from the actual source file but not enough to
18550 require recompilation. If you use gnatmake with the qualifier
18551 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
18552 MOK will not be recompiled.
18554 @item DIF (modified)
18555 No version of the source found on the path corresponds to the source
18556 used to build this object.
18558 @item ??? (file not found)
18559 No source file was found for this unit.
18561 @item HID (hidden, unchanged version not first on PATH)
18562 The version of the source that corresponds exactly to the source used
18563 for compilation has been found on the path but it is hidden by another
18564 version of the same source that has been modified.
18568 @node Switches for gnatls
18569 @section Switches for @code{gnatls}
18572 @code{gnatls} recognizes the following switches:
18576 @cindex @option{--version} @command{gnatls}
18577 Display Copyright and version, then exit disregarding all other options.
18580 @cindex @option{--help} @command{gnatls}
18581 If @option{--version} was not used, display usage, then exit disregarding
18584 @item ^-a^/ALL_UNITS^
18585 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
18586 Consider all units, including those of the predefined Ada library.
18587 Especially useful with @option{^-d^/DEPENDENCIES^}.
18589 @item ^-d^/DEPENDENCIES^
18590 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
18591 List sources from which specified units depend on.
18593 @item ^-h^/OUTPUT=OPTIONS^
18594 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
18595 Output the list of options.
18597 @item ^-o^/OUTPUT=OBJECTS^
18598 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
18599 Only output information about object files.
18601 @item ^-s^/OUTPUT=SOURCES^
18602 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
18603 Only output information about source files.
18605 @item ^-u^/OUTPUT=UNITS^
18606 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
18607 Only output information about compilation units.
18609 @item ^-files^/FILES^=@var{file}
18610 @cindex @option{^-files^/FILES^} (@code{gnatls})
18611 Take as arguments the files listed in text file @var{file}.
18612 Text file @var{file} may contain empty lines that are ignored.
18613 Each nonempty line should contain the name of an existing file.
18614 Several such switches may be specified simultaneously.
18616 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18617 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
18618 @itemx ^-I^/SEARCH=^@var{dir}
18619 @itemx ^-I-^/NOCURRENT_DIRECTORY^
18621 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
18622 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
18623 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
18624 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
18625 Source path manipulation. Same meaning as the equivalent @command{gnatmake}
18626 flags (@pxref{Switches for gnatmake}).
18628 @item --RTS=@var{rts-path}
18629 @cindex @option{--RTS} (@code{gnatls})
18630 Specifies the default location of the runtime library. Same meaning as the
18631 equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}).
18633 @item ^-v^/OUTPUT=VERBOSE^
18634 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
18635 Verbose mode. Output the complete source, object and project paths. Do not use
18636 the default column layout but instead use long format giving as much as
18637 information possible on each requested units, including special
18638 characteristics such as:
18641 @item Preelaborable
18642 The unit is preelaborable in the Ada sense.
18645 No elaboration code has been produced by the compiler for this unit.
18648 The unit is pure in the Ada sense.
18650 @item Elaborate_Body
18651 The unit contains a pragma Elaborate_Body.
18654 The unit contains a pragma Remote_Types.
18656 @item Shared_Passive
18657 The unit contains a pragma Shared_Passive.
18660 This unit is part of the predefined environment and cannot be modified
18663 @item Remote_Call_Interface
18664 The unit contains a pragma Remote_Call_Interface.
18670 @node Examples of gnatls Usage
18671 @section Example of @code{gnatls} Usage
18675 Example of using the verbose switch. Note how the source and
18676 object paths are affected by the -I switch.
18679 $ gnatls -v -I.. demo1.o
18681 GNATLS 5.03w (20041123-34)
18682 Copyright 1997-2004 Free Software Foundation, Inc.
18684 Source Search Path:
18685 <Current_Directory>
18687 /home/comar/local/adainclude/
18689 Object Search Path:
18690 <Current_Directory>
18692 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
18694 Project Search Path:
18695 <Current_Directory>
18696 /home/comar/local/lib/gnat/
18701 Kind => subprogram body
18702 Flags => No_Elab_Code
18703 Source => demo1.adb modified
18707 The following is an example of use of the dependency list.
18708 Note the use of the -s switch
18709 which gives a straight list of source files. This can be useful for
18710 building specialized scripts.
18713 $ gnatls -d demo2.o
18714 ./demo2.o demo2 OK demo2.adb
18720 $ gnatls -d -s -a demo1.o
18722 /home/comar/local/adainclude/ada.ads
18723 /home/comar/local/adainclude/a-finali.ads
18724 /home/comar/local/adainclude/a-filico.ads
18725 /home/comar/local/adainclude/a-stream.ads
18726 /home/comar/local/adainclude/a-tags.ads
18729 /home/comar/local/adainclude/gnat.ads
18730 /home/comar/local/adainclude/g-io.ads
18732 /home/comar/local/adainclude/system.ads
18733 /home/comar/local/adainclude/s-exctab.ads
18734 /home/comar/local/adainclude/s-finimp.ads
18735 /home/comar/local/adainclude/s-finroo.ads
18736 /home/comar/local/adainclude/s-secsta.ads
18737 /home/comar/local/adainclude/s-stalib.ads
18738 /home/comar/local/adainclude/s-stoele.ads
18739 /home/comar/local/adainclude/s-stratt.ads
18740 /home/comar/local/adainclude/s-tasoli.ads
18741 /home/comar/local/adainclude/s-unstyp.ads
18742 /home/comar/local/adainclude/unchconv.ads
18748 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
18750 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
18751 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
18752 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
18753 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
18754 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
18758 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
18759 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
18761 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
18762 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
18763 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
18764 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
18765 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
18766 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
18767 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
18768 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
18769 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
18770 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
18771 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
18775 @node Cleaning Up Using gnatclean
18776 @chapter Cleaning Up Using @code{gnatclean}
18778 @cindex Cleaning tool
18781 @code{gnatclean} is a tool that allows the deletion of files produced by the
18782 compiler, binder and linker, including ALI files, object files, tree files,
18783 expanded source files, library files, interface copy source files, binder
18784 generated files and executable files.
18787 * Running gnatclean::
18788 * Switches for gnatclean::
18789 @c * Examples of gnatclean Usage::
18792 @node Running gnatclean
18793 @section Running @code{gnatclean}
18796 The @code{gnatclean} command has the form:
18799 $ gnatclean switches @var{names}
18803 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
18804 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
18805 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
18808 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
18809 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
18810 the linker. In informative-only mode, specified by switch
18811 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
18812 normal mode is listed, but no file is actually deleted.
18814 @node Switches for gnatclean
18815 @section Switches for @code{gnatclean}
18818 @code{gnatclean} recognizes the following switches:
18822 @cindex @option{--version} @command{gnatclean}
18823 Display Copyright and version, then exit disregarding all other options.
18826 @cindex @option{--help} @command{gnatclean}
18827 If @option{--version} was not used, display usage, then exit disregarding
18830 @item ^-c^/COMPILER_FILES_ONLY^
18831 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
18832 Only attempt to delete the files produced by the compiler, not those produced
18833 by the binder or the linker. The files that are not to be deleted are library
18834 files, interface copy files, binder generated files and executable files.
18836 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
18837 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
18838 Indicate that ALI and object files should normally be found in directory
18841 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
18842 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
18843 When using project files, if some errors or warnings are detected during
18844 parsing and verbose mode is not in effect (no use of switch
18845 ^-v^/VERBOSE^), then error lines start with the full path name of the project
18846 file, rather than its simple file name.
18849 @cindex @option{^-h^/HELP^} (@code{gnatclean})
18850 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
18852 @item ^-n^/NODELETE^
18853 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
18854 Informative-only mode. Do not delete any files. Output the list of the files
18855 that would have been deleted if this switch was not specified.
18857 @item ^-P^/PROJECT_FILE=^@var{project}
18858 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
18859 Use project file @var{project}. Only one such switch can be used.
18860 When cleaning a project file, the files produced by the compilation of the
18861 immediate sources or inherited sources of the project files are to be
18862 deleted. This is not depending on the presence or not of executable names
18863 on the command line.
18866 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
18867 Quiet output. If there are no errors, do not output anything, except in
18868 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
18869 (switch ^-n^/NODELETE^).
18871 @item ^-r^/RECURSIVE^
18872 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
18873 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
18874 clean all imported and extended project files, recursively. If this switch
18875 is not specified, only the files related to the main project file are to be
18876 deleted. This switch has no effect if no project file is specified.
18878 @item ^-v^/VERBOSE^
18879 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
18882 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
18883 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
18884 Indicates the verbosity of the parsing of GNAT project files.
18885 @xref{Switches Related to Project Files}.
18887 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
18888 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
18889 Indicates that external variable @var{name} has the value @var{value}.
18890 The Project Manager will use this value for occurrences of
18891 @code{external(name)} when parsing the project file.
18892 @xref{Switches Related to Project Files}.
18894 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
18895 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
18896 When searching for ALI and object files, look in directory
18899 @item ^-I^/SEARCH=^@var{dir}
18900 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
18901 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
18903 @item ^-I-^/NOCURRENT_DIRECTORY^
18904 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
18905 @cindex Source files, suppressing search
18906 Do not look for ALI or object files in the directory
18907 where @code{gnatclean} was invoked.
18911 @c @node Examples of gnatclean Usage
18912 @c @section Examples of @code{gnatclean} Usage
18915 @node GNAT and Libraries
18916 @chapter GNAT and Libraries
18917 @cindex Library, building, installing, using
18920 This chapter describes how to build and use libraries with GNAT, and also shows
18921 how to recompile the GNAT run-time library. You should be familiar with the
18922 Project Manager facility (@pxref{GNAT Project Manager}) before reading this
18926 * Introduction to Libraries in GNAT::
18927 * General Ada Libraries::
18928 * Stand-alone Ada Libraries::
18929 * Rebuilding the GNAT Run-Time Library::
18932 @node Introduction to Libraries in GNAT
18933 @section Introduction to Libraries in GNAT
18936 A library is, conceptually, a collection of objects which does not have its
18937 own main thread of execution, but rather provides certain services to the
18938 applications that use it. A library can be either statically linked with the
18939 application, in which case its code is directly included in the application,
18940 or, on platforms that support it, be dynamically linked, in which case
18941 its code is shared by all applications making use of this library.
18943 GNAT supports both types of libraries.
18944 In the static case, the compiled code can be provided in different ways. The
18945 simplest approach is to provide directly the set of objects resulting from
18946 compilation of the library source files. Alternatively, you can group the
18947 objects into an archive using whatever commands are provided by the operating
18948 system. For the latter case, the objects are grouped into a shared library.
18950 In the GNAT environment, a library has three types of components:
18956 @xref{The Ada Library Information Files}.
18958 Object files, an archive or a shared library.
18962 A GNAT library may expose all its source files, which is useful for
18963 documentation purposes. Alternatively, it may expose only the units needed by
18964 an external user to make use of the library. That is to say, the specs
18965 reflecting the library services along with all the units needed to compile
18966 those specs, which can include generic bodies or any body implementing an
18967 inlined routine. In the case of @emph{stand-alone libraries} those exposed
18968 units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}).
18970 All compilation units comprising an application, including those in a library,
18971 need to be elaborated in an order partially defined by Ada's semantics. GNAT
18972 computes the elaboration order from the @file{ALI} files and this is why they
18973 constitute a mandatory part of GNAT libraries.
18974 @emph{Stand-alone libraries} are the exception to this rule because a specific
18975 library elaboration routine is produced independently of the application(s)
18978 @node General Ada Libraries
18979 @section General Ada Libraries
18982 * Building a library::
18983 * Installing a library::
18984 * Using a library::
18987 @node Building a library
18988 @subsection Building a library
18991 The easiest way to build a library is to use the Project Manager,
18992 which supports a special type of project called a @emph{Library Project}
18993 (@pxref{Library Projects}).
18995 A project is considered a library project, when two project-level attributes
18996 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
18997 control different aspects of library configuration, additional optional
18998 project-level attributes can be specified:
19001 This attribute controls whether the library is to be static or dynamic
19003 @item Library_Version
19004 This attribute specifies the library version; this value is used
19005 during dynamic linking of shared libraries to determine if the currently
19006 installed versions of the binaries are compatible.
19008 @item Library_Options
19010 These attributes specify additional low-level options to be used during
19011 library generation, and redefine the actual application used to generate
19016 The GNAT Project Manager takes full care of the library maintenance task,
19017 including recompilation of the source files for which objects do not exist
19018 or are not up to date, assembly of the library archive, and installation of
19019 the library (i.e., copying associated source, object and @file{ALI} files
19020 to the specified location).
19022 Here is a simple library project file:
19023 @smallexample @c ada
19025 for Source_Dirs use ("src1", "src2");
19026 for Object_Dir use "obj";
19027 for Library_Name use "mylib";
19028 for Library_Dir use "lib";
19029 for Library_Kind use "dynamic";
19034 and the compilation command to build and install the library:
19036 @smallexample @c ada
19037 $ gnatmake -Pmy_lib
19041 It is not entirely trivial to perform manually all the steps required to
19042 produce a library. We recommend that you use the GNAT Project Manager
19043 for this task. In special cases where this is not desired, the necessary
19044 steps are discussed below.
19046 There are various possibilities for compiling the units that make up the
19047 library: for example with a Makefile (@pxref{Using the GNU make Utility}) or
19048 with a conventional script. For simple libraries, it is also possible to create
19049 a dummy main program which depends upon all the packages that comprise the
19050 interface of the library. This dummy main program can then be given to
19051 @command{gnatmake}, which will ensure that all necessary objects are built.
19053 After this task is accomplished, you should follow the standard procedure
19054 of the underlying operating system to produce the static or shared library.
19056 Here is an example of such a dummy program:
19057 @smallexample @c ada
19059 with My_Lib.Service1;
19060 with My_Lib.Service2;
19061 with My_Lib.Service3;
19062 procedure My_Lib_Dummy is
19070 Here are the generic commands that will build an archive or a shared library.
19073 # compiling the library
19074 $ gnatmake -c my_lib_dummy.adb
19076 # we don't need the dummy object itself
19077 $ rm my_lib_dummy.o my_lib_dummy.ali
19079 # create an archive with the remaining objects
19080 $ ar rc libmy_lib.a *.o
19081 # some systems may require "ranlib" to be run as well
19083 # or create a shared library
19084 $ gcc -shared -o libmy_lib.so *.o
19085 # some systems may require the code to have been compiled with -fPIC
19087 # remove the object files that are now in the library
19090 # Make the ALI files read-only so that gnatmake will not try to
19091 # regenerate the objects that are in the library
19096 Please note that the library must have a name of the form @file{lib@var{xxx}.a}
19097 or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to
19098 be accessed by the directive @option{-l@var{xxx}} at link time.
19100 @node Installing a library
19101 @subsection Installing a library
19102 @cindex @code{ADA_PROJECT_PATH}
19103 @cindex @code{GPR_PROJECT_PATH}
19106 If you use project files, library installation is part of the library build
19107 process. Thus no further action is needed in order to make use of the
19108 libraries that are built as part of the general application build. A usable
19109 version of the library is installed in the directory specified by the
19110 @code{Library_Dir} attribute of the library project file.
19112 You may want to install a library in a context different from where the library
19113 is built. This situation arises with third party suppliers, who may want
19114 to distribute a library in binary form where the user is not expected to be
19115 able to recompile the library. The simplest option in this case is to provide
19116 a project file slightly different from the one used to build the library, by
19117 using the @code{externally_built} attribute. For instance, the project
19118 file used to build the library in the previous section can be changed into the
19119 following one when the library is installed:
19121 @smallexample @c projectfile
19123 for Source_Dirs use ("src1", "src2");
19124 for Library_Name use "mylib";
19125 for Library_Dir use "lib";
19126 for Library_Kind use "dynamic";
19127 for Externally_Built use "true";
19132 This project file assumes that the directories @file{src1},
19133 @file{src2}, and @file{lib} exist in
19134 the directory containing the project file. The @code{externally_built}
19135 attribute makes it clear to the GNAT builder that it should not attempt to
19136 recompile any of the units from this library. It allows the library provider to
19137 restrict the source set to the minimum necessary for clients to make use of the
19138 library as described in the first section of this chapter. It is the
19139 responsibility of the library provider to install the necessary sources, ALI
19140 files and libraries in the directories mentioned in the project file. For
19141 convenience, the user's library project file should be installed in a location
19142 that will be searched automatically by the GNAT
19143 builder. These are the directories referenced in the @env{GPR_PROJECT_PATH}
19144 environment variable (@pxref{Importing Projects}), and also the default GNAT
19145 library location that can be queried with @command{gnatls -v} and is usually of
19146 the form $gnat_install_root/lib/gnat.
19148 When project files are not an option, it is also possible, but not recommended,
19149 to install the library so that the sources needed to use the library are on the
19150 Ada source path and the ALI files & libraries be on the Ada Object path (see
19151 @ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
19152 administrator can place general-purpose libraries in the default compiler
19153 paths, by specifying the libraries' location in the configuration files
19154 @file{ada_source_path} and @file{ada_object_path}. These configuration files
19155 must be located in the GNAT installation tree at the same place as the gcc spec
19156 file. The location of the gcc spec file can be determined as follows:
19162 The configuration files mentioned above have a simple format: each line
19163 must contain one unique directory name.
19164 Those names are added to the corresponding path
19165 in their order of appearance in the file. The names can be either absolute
19166 or relative; in the latter case, they are relative to where theses files
19169 The files @file{ada_source_path} and @file{ada_object_path} might not be
19171 GNAT installation, in which case, GNAT will look for its run-time library in
19172 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
19173 objects and @file{ALI} files). When the files exist, the compiler does not
19174 look in @file{adainclude} and @file{adalib}, and thus the
19175 @file{ada_source_path} file
19176 must contain the location for the GNAT run-time sources (which can simply
19177 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
19178 contain the location for the GNAT run-time objects (which can simply
19181 You can also specify a new default path to the run-time library at compilation
19182 time with the switch @option{--RTS=rts-path}. You can thus choose / change
19183 the run-time library you want your program to be compiled with. This switch is
19184 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
19185 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
19187 It is possible to install a library before or after the standard GNAT
19188 library, by reordering the lines in the configuration files. In general, a
19189 library must be installed before the GNAT library if it redefines
19192 @node Using a library
19193 @subsection Using a library
19195 @noindent Once again, the project facility greatly simplifies the use of
19196 libraries. In this context, using a library is just a matter of adding a
19197 @code{with} clause in the user project. For instance, to make use of the
19198 library @code{My_Lib} shown in examples in earlier sections, you can
19201 @smallexample @c projectfile
19208 Even if you have a third-party, non-Ada library, you can still use GNAT's
19209 Project Manager facility to provide a wrapper for it. For example, the
19210 following project, when @code{with}ed by your main project, will link with the
19211 third-party library @file{liba.a}:
19213 @smallexample @c projectfile
19216 for Externally_Built use "true";
19217 for Source_Files use ();
19218 for Library_Dir use "lib";
19219 for Library_Name use "a";
19220 for Library_Kind use "static";
19224 This is an alternative to the use of @code{pragma Linker_Options}. It is
19225 especially interesting in the context of systems with several interdependent
19226 static libraries where finding a proper linker order is not easy and best be
19227 left to the tools having visibility over project dependence information.
19230 In order to use an Ada library manually, you need to make sure that this
19231 library is on both your source and object path
19232 (see @ref{Search Paths and the Run-Time Library (RTL)}
19233 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
19234 in an archive or a shared library, you need to specify the desired
19235 library at link time.
19237 For example, you can use the library @file{mylib} installed in
19238 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
19241 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
19246 This can be expressed more simply:
19251 when the following conditions are met:
19254 @file{/dir/my_lib_src} has been added by the user to the environment
19255 variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file
19256 @file{ada_source_path}
19258 @file{/dir/my_lib_obj} has been added by the user to the environment
19259 variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file
19260 @file{ada_object_path}
19262 a pragma @code{Linker_Options} has been added to one of the sources.
19265 @smallexample @c ada
19266 pragma Linker_Options ("-lmy_lib");
19270 @node Stand-alone Ada Libraries
19271 @section Stand-alone Ada Libraries
19272 @cindex Stand-alone library, building, using
19275 * Introduction to Stand-alone Libraries::
19276 * Building a Stand-alone Library::
19277 * Creating a Stand-alone Library to be used in a non-Ada context::
19278 * Restrictions in Stand-alone Libraries::
19281 @node Introduction to Stand-alone Libraries
19282 @subsection Introduction to Stand-alone Libraries
19285 A Stand-alone Library (abbreviated ``SAL'') is a library that contains the
19287 elaborate the Ada units that are included in the library. In contrast with
19288 an ordinary library, which consists of all sources, objects and @file{ALI}
19290 library, a SAL may specify a restricted subset of compilation units
19291 to serve as a library interface. In this case, the fully
19292 self-sufficient set of files will normally consist of an objects
19293 archive, the sources of interface units' specs, and the @file{ALI}
19294 files of interface units.
19295 If an interface spec contains a generic unit or an inlined subprogram,
19297 source must also be provided; if the units that must be provided in the source
19298 form depend on other units, the source and @file{ALI} files of those must
19301 The main purpose of a SAL is to minimize the recompilation overhead of client
19302 applications when a new version of the library is installed. Specifically,
19303 if the interface sources have not changed, client applications do not need to
19304 be recompiled. If, furthermore, a SAL is provided in the shared form and its
19305 version, controlled by @code{Library_Version} attribute, is not changed,
19306 then the clients do not need to be relinked.
19308 SALs also allow the library providers to minimize the amount of library source
19309 text exposed to the clients. Such ``information hiding'' might be useful or
19310 necessary for various reasons.
19312 Stand-alone libraries are also well suited to be used in an executable whose
19313 main routine is not written in Ada.
19315 @node Building a Stand-alone Library
19316 @subsection Building a Stand-alone Library
19319 GNAT's Project facility provides a simple way of building and installing
19320 stand-alone libraries; see @ref{Stand-alone Library Projects}.
19321 To be a Stand-alone Library Project, in addition to the two attributes
19322 that make a project a Library Project (@code{Library_Name} and
19323 @code{Library_Dir}; see @ref{Library Projects}), the attribute
19324 @code{Library_Interface} must be defined. For example:
19326 @smallexample @c projectfile
19328 for Library_Dir use "lib_dir";
19329 for Library_Name use "dummy";
19330 for Library_Interface use ("int1", "int1.child");
19335 Attribute @code{Library_Interface} has a non-empty string list value,
19336 each string in the list designating a unit contained in an immediate source
19337 of the project file.
19339 When a Stand-alone Library is built, first the binder is invoked to build
19340 a package whose name depends on the library name
19341 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
19342 This binder-generated package includes initialization and
19343 finalization procedures whose
19344 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
19346 above). The object corresponding to this package is included in the library.
19348 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
19349 calling of these procedures if a static SAL is built, or if a shared SAL
19351 with the project-level attribute @code{Library_Auto_Init} set to
19354 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
19355 (those that are listed in attribute @code{Library_Interface}) are copied to
19356 the Library Directory. As a consequence, only the Interface Units may be
19357 imported from Ada units outside of the library. If other units are imported,
19358 the binding phase will fail.
19360 The attribute @code{Library_Src_Dir} may be specified for a
19361 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
19362 single string value. Its value must be the path (absolute or relative to the
19363 project directory) of an existing directory. This directory cannot be the
19364 object directory or one of the source directories, but it can be the same as
19365 the library directory. The sources of the Interface
19366 Units of the library that are needed by an Ada client of the library will be
19367 copied to the designated directory, called the Interface Copy directory.
19368 These sources include the specs of the Interface Units, but they may also
19369 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
19370 are used, or when there is a generic unit in the spec. Before the sources
19371 are copied to the Interface Copy directory, an attempt is made to delete all
19372 files in the Interface Copy directory.
19374 Building stand-alone libraries by hand is somewhat tedious, but for those
19375 occasions when it is necessary here are the steps that you need to perform:
19378 Compile all library sources.
19381 Invoke the binder with the switch @option{-n} (No Ada main program),
19382 with all the @file{ALI} files of the interfaces, and
19383 with the switch @option{-L} to give specific names to the @code{init}
19384 and @code{final} procedures. For example:
19386 gnatbind -n int1.ali int2.ali -Lsal1
19390 Compile the binder generated file:
19396 Link the dynamic library with all the necessary object files,
19397 indicating to the linker the names of the @code{init} (and possibly
19398 @code{final}) procedures for automatic initialization (and finalization).
19399 The built library should be placed in a directory different from
19400 the object directory.
19403 Copy the @code{ALI} files of the interface to the library directory,
19404 add in this copy an indication that it is an interface to a SAL
19405 (i.e., add a word @option{SL} on the line in the @file{ALI} file that starts
19406 with letter ``P'') and make the modified copy of the @file{ALI} file
19411 Using SALs is not different from using other libraries
19412 (see @ref{Using a library}).
19414 @node Creating a Stand-alone Library to be used in a non-Ada context
19415 @subsection Creating a Stand-alone Library to be used in a non-Ada context
19418 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
19421 The only extra step required is to ensure that library interface subprograms
19422 are compatible with the main program, by means of @code{pragma Export}
19423 or @code{pragma Convention}.
19425 Here is an example of simple library interface for use with C main program:
19427 @smallexample @c ada
19428 package Interface is
19430 procedure Do_Something;
19431 pragma Export (C, Do_Something, "do_something");
19433 procedure Do_Something_Else;
19434 pragma Export (C, Do_Something_Else, "do_something_else");
19440 On the foreign language side, you must provide a ``foreign'' view of the
19441 library interface; remember that it should contain elaboration routines in
19442 addition to interface subprograms.
19444 The example below shows the content of @code{mylib_interface.h} (note
19445 that there is no rule for the naming of this file, any name can be used)
19447 /* the library elaboration procedure */
19448 extern void mylibinit (void);
19450 /* the library finalization procedure */
19451 extern void mylibfinal (void);
19453 /* the interface exported by the library */
19454 extern void do_something (void);
19455 extern void do_something_else (void);
19459 Libraries built as explained above can be used from any program, provided
19460 that the elaboration procedures (named @code{mylibinit} in the previous
19461 example) are called before the library services are used. Any number of
19462 libraries can be used simultaneously, as long as the elaboration
19463 procedure of each library is called.
19465 Below is an example of a C program that uses the @code{mylib} library.
19468 #include "mylib_interface.h"
19473 /* First, elaborate the library before using it */
19476 /* Main program, using the library exported entities */
19478 do_something_else ();
19480 /* Library finalization at the end of the program */
19487 Note that invoking any library finalization procedure generated by
19488 @code{gnatbind} shuts down the Ada run-time environment.
19490 finalization of all Ada libraries must be performed at the end of the program.
19491 No call to these libraries or to the Ada run-time library should be made
19492 after the finalization phase.
19494 @node Restrictions in Stand-alone Libraries
19495 @subsection Restrictions in Stand-alone Libraries
19498 The pragmas listed below should be used with caution inside libraries,
19499 as they can create incompatibilities with other Ada libraries:
19501 @item pragma @code{Locking_Policy}
19502 @item pragma @code{Queuing_Policy}
19503 @item pragma @code{Task_Dispatching_Policy}
19504 @item pragma @code{Unreserve_All_Interrupts}
19508 When using a library that contains such pragmas, the user must make sure
19509 that all libraries use the same pragmas with the same values. Otherwise,
19510 @code{Program_Error} will
19511 be raised during the elaboration of the conflicting
19512 libraries. The usage of these pragmas and its consequences for the user
19513 should therefore be well documented.
19515 Similarly, the traceback in the exception occurrence mechanism should be
19516 enabled or disabled in a consistent manner across all libraries.
19517 Otherwise, Program_Error will be raised during the elaboration of the
19518 conflicting libraries.
19520 If the @code{Version} or @code{Body_Version}
19521 attributes are used inside a library, then you need to
19522 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
19523 libraries, so that version identifiers can be properly computed.
19524 In practice these attributes are rarely used, so this is unlikely
19525 to be a consideration.
19527 @node Rebuilding the GNAT Run-Time Library
19528 @section Rebuilding the GNAT Run-Time Library
19529 @cindex GNAT Run-Time Library, rebuilding
19530 @cindex Building the GNAT Run-Time Library
19531 @cindex Rebuilding the GNAT Run-Time Library
19532 @cindex Run-Time Library, rebuilding
19535 It may be useful to recompile the GNAT library in various contexts, the
19536 most important one being the use of partition-wide configuration pragmas
19537 such as @code{Normalize_Scalars}. A special Makefile called
19538 @code{Makefile.adalib} is provided to that effect and can be found in
19539 the directory containing the GNAT library. The location of this
19540 directory depends on the way the GNAT environment has been installed and can
19541 be determined by means of the command:
19548 The last entry in the object search path usually contains the
19549 gnat library. This Makefile contains its own documentation and in
19550 particular the set of instructions needed to rebuild a new library and
19553 @node Using the GNU make Utility
19554 @chapter Using the GNU @code{make} Utility
19558 This chapter offers some examples of makefiles that solve specific
19559 problems. It does not explain how to write a makefile (@pxref{Top,, GNU
19560 make, make, GNU @code{make}}), nor does it try to replace the
19561 @command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}).
19563 All the examples in this section are specific to the GNU version of
19564 make. Although @command{make} is a standard utility, and the basic language
19565 is the same, these examples use some advanced features found only in
19569 * Using gnatmake in a Makefile::
19570 * Automatically Creating a List of Directories::
19571 * Generating the Command Line Switches::
19572 * Overcoming Command Line Length Limits::
19575 @node Using gnatmake in a Makefile
19576 @section Using gnatmake in a Makefile
19581 Complex project organizations can be handled in a very powerful way by
19582 using GNU make combined with gnatmake. For instance, here is a Makefile
19583 which allows you to build each subsystem of a big project into a separate
19584 shared library. Such a makefile allows you to significantly reduce the link
19585 time of very big applications while maintaining full coherence at
19586 each step of the build process.
19588 The list of dependencies are handled automatically by
19589 @command{gnatmake}. The Makefile is simply used to call gnatmake in each of
19590 the appropriate directories.
19592 Note that you should also read the example on how to automatically
19593 create the list of directories
19594 (@pxref{Automatically Creating a List of Directories})
19595 which might help you in case your project has a lot of subdirectories.
19600 @font@heightrm=cmr8
19603 ## This Makefile is intended to be used with the following directory
19605 ## - The sources are split into a series of csc (computer software components)
19606 ## Each of these csc is put in its own directory.
19607 ## Their name are referenced by the directory names.
19608 ## They will be compiled into shared library (although this would also work
19609 ## with static libraries
19610 ## - The main program (and possibly other packages that do not belong to any
19611 ## csc is put in the top level directory (where the Makefile is).
19612 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
19613 ## \_ second_csc (sources) __ lib (will contain the library)
19615 ## Although this Makefile is build for shared library, it is easy to modify
19616 ## to build partial link objects instead (modify the lines with -shared and
19619 ## With this makefile, you can change any file in the system or add any new
19620 ## file, and everything will be recompiled correctly (only the relevant shared
19621 ## objects will be recompiled, and the main program will be re-linked).
19623 # The list of computer software component for your project. This might be
19624 # generated automatically.
19627 # Name of the main program (no extension)
19630 # If we need to build objects with -fPIC, uncomment the following line
19633 # The following variable should give the directory containing libgnat.so
19634 # You can get this directory through 'gnatls -v'. This is usually the last
19635 # directory in the Object_Path.
19638 # The directories for the libraries
19639 # (This macro expands the list of CSC to the list of shared libraries, you
19640 # could simply use the expanded form:
19641 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
19642 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
19644 $@{MAIN@}: objects $@{LIB_DIR@}
19645 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
19646 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
19649 # recompile the sources
19650 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
19652 # Note: In a future version of GNAT, the following commands will be simplified
19653 # by a new tool, gnatmlib
19655 mkdir -p $@{dir $@@ @}
19656 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
19657 cd $@{dir $@@ @} && cp -f ../*.ali .
19659 # The dependencies for the modules
19660 # Note that we have to force the expansion of *.o, since in some cases
19661 # make won't be able to do it itself.
19662 aa/lib/libaa.so: $@{wildcard aa/*.o@}
19663 bb/lib/libbb.so: $@{wildcard bb/*.o@}
19664 cc/lib/libcc.so: $@{wildcard cc/*.o@}
19666 # Make sure all of the shared libraries are in the path before starting the
19669 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
19672 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
19673 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
19674 $@{RM@} $@{CSC_LIST:%=%/*.o@}
19675 $@{RM@} *.o *.ali $@{MAIN@}
19678 @node Automatically Creating a List of Directories
19679 @section Automatically Creating a List of Directories
19682 In most makefiles, you will have to specify a list of directories, and
19683 store it in a variable. For small projects, it is often easier to
19684 specify each of them by hand, since you then have full control over what
19685 is the proper order for these directories, which ones should be
19688 However, in larger projects, which might involve hundreds of
19689 subdirectories, it might be more convenient to generate this list
19692 The example below presents two methods. The first one, although less
19693 general, gives you more control over the list. It involves wildcard
19694 characters, that are automatically expanded by @command{make}. Its
19695 shortcoming is that you need to explicitly specify some of the
19696 organization of your project, such as for instance the directory tree
19697 depth, whether some directories are found in a separate tree, @enddots{}
19699 The second method is the most general one. It requires an external
19700 program, called @command{find}, which is standard on all Unix systems. All
19701 the directories found under a given root directory will be added to the
19707 @font@heightrm=cmr8
19710 # The examples below are based on the following directory hierarchy:
19711 # All the directories can contain any number of files
19712 # ROOT_DIRECTORY -> a -> aa -> aaa
19715 # -> b -> ba -> baa
19718 # This Makefile creates a variable called DIRS, that can be reused any time
19719 # you need this list (see the other examples in this section)
19721 # The root of your project's directory hierarchy
19725 # First method: specify explicitly the list of directories
19726 # This allows you to specify any subset of all the directories you need.
19729 DIRS := a/aa/ a/ab/ b/ba/
19732 # Second method: use wildcards
19733 # Note that the argument(s) to wildcard below should end with a '/'.
19734 # Since wildcards also return file names, we have to filter them out
19735 # to avoid duplicate directory names.
19736 # We thus use make's @code{dir} and @code{sort} functions.
19737 # It sets DIRs to the following value (note that the directories aaa and baa
19738 # are not given, unless you change the arguments to wildcard).
19739 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
19742 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
19743 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
19746 # Third method: use an external program
19747 # This command is much faster if run on local disks, avoiding NFS slowdowns.
19748 # This is the most complete command: it sets DIRs to the following value:
19749 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
19752 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
19756 @node Generating the Command Line Switches
19757 @section Generating the Command Line Switches
19760 Once you have created the list of directories as explained in the
19761 previous section (@pxref{Automatically Creating a List of Directories}),
19762 you can easily generate the command line arguments to pass to gnatmake.
19764 For the sake of completeness, this example assumes that the source path
19765 is not the same as the object path, and that you have two separate lists
19769 # see "Automatically creating a list of directories" to create
19774 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
19775 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
19778 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
19781 @node Overcoming Command Line Length Limits
19782 @section Overcoming Command Line Length Limits
19785 One problem that might be encountered on big projects is that many
19786 operating systems limit the length of the command line. It is thus hard to give
19787 gnatmake the list of source and object directories.
19789 This example shows how you can set up environment variables, which will
19790 make @command{gnatmake} behave exactly as if the directories had been
19791 specified on the command line, but have a much higher length limit (or
19792 even none on most systems).
19794 It assumes that you have created a list of directories in your Makefile,
19795 using one of the methods presented in
19796 @ref{Automatically Creating a List of Directories}.
19797 For the sake of completeness, we assume that the object
19798 path (where the ALI files are found) is different from the sources patch.
19800 Note a small trick in the Makefile below: for efficiency reasons, we
19801 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
19802 expanded immediately by @code{make}. This way we overcome the standard
19803 make behavior which is to expand the variables only when they are
19806 On Windows, if you are using the standard Windows command shell, you must
19807 replace colons with semicolons in the assignments to these variables.
19812 @font@heightrm=cmr8
19815 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
19816 # This is the same thing as putting the -I arguments on the command line.
19817 # (the equivalent of using -aI on the command line would be to define
19818 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
19819 # You can of course have different values for these variables.
19821 # Note also that we need to keep the previous values of these variables, since
19822 # they might have been set before running 'make' to specify where the GNAT
19823 # library is installed.
19825 # see "Automatically creating a list of directories" to create these
19831 space:=$@{empty@} $@{empty@}
19832 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
19833 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
19834 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
19835 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
19836 export ADA_INCLUDE_PATH
19837 export ADA_OBJECT_PATH
19844 @node Memory Management Issues
19845 @chapter Memory Management Issues
19848 This chapter describes some useful memory pools provided in the GNAT library
19849 and in particular the GNAT Debug Pool facility, which can be used to detect
19850 incorrect uses of access values (including ``dangling references'').
19852 It also describes the @command{gnatmem} tool, which can be used to track down
19857 * Some Useful Memory Pools::
19858 * The GNAT Debug Pool Facility::
19860 * The gnatmem Tool::
19864 @node Some Useful Memory Pools
19865 @section Some Useful Memory Pools
19866 @findex Memory Pool
19867 @cindex storage, pool
19870 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
19871 storage pool. Allocations use the standard system call @code{malloc} while
19872 deallocations use the standard system call @code{free}. No reclamation is
19873 performed when the pool goes out of scope. For performance reasons, the
19874 standard default Ada allocators/deallocators do not use any explicit storage
19875 pools but if they did, they could use this storage pool without any change in
19876 behavior. That is why this storage pool is used when the user
19877 manages to make the default implicit allocator explicit as in this example:
19878 @smallexample @c ada
19879 type T1 is access Something;
19880 -- no Storage pool is defined for T2
19881 type T2 is access Something_Else;
19882 for T2'Storage_Pool use T1'Storage_Pool;
19883 -- the above is equivalent to
19884 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
19888 The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage
19889 pool. The allocation strategy is similar to @code{Pool_Local}'s
19890 except that the all
19891 storage allocated with this pool is reclaimed when the pool object goes out of
19892 scope. This pool provides a explicit mechanism similar to the implicit one
19893 provided by several Ada 83 compilers for allocations performed through a local
19894 access type and whose purpose was to reclaim memory when exiting the
19895 scope of a given local access. As an example, the following program does not
19896 leak memory even though it does not perform explicit deallocation:
19898 @smallexample @c ada
19899 with System.Pool_Local;
19900 procedure Pooloc1 is
19901 procedure Internal is
19902 type A is access Integer;
19903 X : System.Pool_Local.Unbounded_Reclaim_Pool;
19904 for A'Storage_Pool use X;
19907 for I in 1 .. 50 loop
19912 for I in 1 .. 100 loop
19919 The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when
19920 @code{Storage_Size} is specified for an access type.
19921 The whole storage for the pool is
19922 allocated at once, usually on the stack at the point where the access type is
19923 elaborated. It is automatically reclaimed when exiting the scope where the
19924 access type is defined. This package is not intended to be used directly by the
19925 user and it is implicitly used for each such declaration:
19927 @smallexample @c ada
19928 type T1 is access Something;
19929 for T1'Storage_Size use 10_000;
19932 @node The GNAT Debug Pool Facility
19933 @section The GNAT Debug Pool Facility
19935 @cindex storage, pool, memory corruption
19938 The use of unchecked deallocation and unchecked conversion can easily
19939 lead to incorrect memory references. The problems generated by such
19940 references are usually difficult to tackle because the symptoms can be
19941 very remote from the origin of the problem. In such cases, it is
19942 very helpful to detect the problem as early as possible. This is the
19943 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
19945 In order to use the GNAT specific debugging pool, the user must
19946 associate a debug pool object with each of the access types that may be
19947 related to suspected memory problems. See Ada Reference Manual 13.11.
19948 @smallexample @c ada
19949 type Ptr is access Some_Type;
19950 Pool : GNAT.Debug_Pools.Debug_Pool;
19951 for Ptr'Storage_Pool use Pool;
19955 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
19956 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
19957 allow the user to redefine allocation and deallocation strategies. They
19958 also provide a checkpoint for each dereference, through the use of
19959 the primitive operation @code{Dereference} which is implicitly called at
19960 each dereference of an access value.
19962 Once an access type has been associated with a debug pool, operations on
19963 values of the type may raise four distinct exceptions,
19964 which correspond to four potential kinds of memory corruption:
19967 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
19969 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
19971 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
19973 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
19977 For types associated with a Debug_Pool, dynamic allocation is performed using
19978 the standard GNAT allocation routine. References to all allocated chunks of
19979 memory are kept in an internal dictionary. Several deallocation strategies are
19980 provided, whereupon the user can choose to release the memory to the system,
19981 keep it allocated for further invalid access checks, or fill it with an easily
19982 recognizable pattern for debug sessions. The memory pattern is the old IBM
19983 hexadecimal convention: @code{16#DEADBEEF#}.
19985 See the documentation in the file g-debpoo.ads for more information on the
19986 various strategies.
19988 Upon each dereference, a check is made that the access value denotes a
19989 properly allocated memory location. Here is a complete example of use of
19990 @code{Debug_Pools}, that includes typical instances of memory corruption:
19991 @smallexample @c ada
19995 with Gnat.Io; use Gnat.Io;
19996 with Unchecked_Deallocation;
19997 with Unchecked_Conversion;
19998 with GNAT.Debug_Pools;
19999 with System.Storage_Elements;
20000 with Ada.Exceptions; use Ada.Exceptions;
20001 procedure Debug_Pool_Test is
20003 type T is access Integer;
20004 type U is access all T;
20006 P : GNAT.Debug_Pools.Debug_Pool;
20007 for T'Storage_Pool use P;
20009 procedure Free is new Unchecked_Deallocation (Integer, T);
20010 function UC is new Unchecked_Conversion (U, T);
20013 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
20023 Put_Line (Integer'Image(B.all));
20025 when E : others => Put_Line ("raised: " & Exception_Name (E));
20030 when E : others => Put_Line ("raised: " & Exception_Name (E));
20034 Put_Line (Integer'Image(B.all));
20036 when E : others => Put_Line ("raised: " & Exception_Name (E));
20041 when E : others => Put_Line ("raised: " & Exception_Name (E));
20044 end Debug_Pool_Test;
20048 The debug pool mechanism provides the following precise diagnostics on the
20049 execution of this erroneous program:
20052 Total allocated bytes : 0
20053 Total deallocated bytes : 0
20054 Current Water Mark: 0
20058 Total allocated bytes : 8
20059 Total deallocated bytes : 0
20060 Current Water Mark: 8
20063 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
20064 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
20065 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
20066 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
20068 Total allocated bytes : 8
20069 Total deallocated bytes : 4
20070 Current Water Mark: 4
20075 @node The gnatmem Tool
20076 @section The @command{gnatmem} Tool
20080 The @code{gnatmem} utility monitors dynamic allocation and
20081 deallocation activity in a program, and displays information about
20082 incorrect deallocations and possible sources of memory leaks.
20083 It is designed to work in association with a static runtime library
20084 only and in this context provides three types of information:
20087 General information concerning memory management, such as the total
20088 number of allocations and deallocations, the amount of allocated
20089 memory and the high water mark, i.e.@: the largest amount of allocated
20090 memory in the course of program execution.
20093 Backtraces for all incorrect deallocations, that is to say deallocations
20094 which do not correspond to a valid allocation.
20097 Information on each allocation that is potentially the origin of a memory
20102 * Running gnatmem::
20103 * Switches for gnatmem::
20104 * Example of gnatmem Usage::
20107 @node Running gnatmem
20108 @subsection Running @code{gnatmem}
20111 @code{gnatmem} makes use of the output created by the special version of
20112 allocation and deallocation routines that record call information. This
20113 allows to obtain accurate dynamic memory usage history at a minimal cost to
20114 the execution speed. Note however, that @code{gnatmem} is not supported on
20115 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux,
20116 Solaris and Windows NT/2000/XP (x86).
20119 The @code{gnatmem} command has the form
20122 $ gnatmem @ovar{switches} user_program
20126 The program must have been linked with the instrumented version of the
20127 allocation and deallocation routines. This is done by linking with the
20128 @file{libgmem.a} library. For correct symbolic backtrace information,
20129 the user program should be compiled with debugging options
20130 (see @ref{Switches for gcc}). For example to build @file{my_program}:
20133 $ gnatmake -g my_program -largs -lgmem
20137 As library @file{libgmem.a} contains an alternate body for package
20138 @code{System.Memory}, @file{s-memory.adb} should not be compiled and linked
20139 when an executable is linked with library @file{libgmem.a}. It is then not
20140 recommended to use @command{gnatmake} with switch @option{^-a^/ALL_FILES^}.
20143 When @file{my_program} is executed, the file @file{gmem.out} is produced.
20144 This file contains information about all allocations and deallocations
20145 performed by the program. It is produced by the instrumented allocations and
20146 deallocations routines and will be used by @code{gnatmem}.
20148 In order to produce symbolic backtrace information for allocations and
20149 deallocations performed by the GNAT run-time library, you need to use a
20150 version of that library that has been compiled with the @option{-g} switch
20151 (see @ref{Rebuilding the GNAT Run-Time Library}).
20153 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
20154 examine. If the location of @file{gmem.out} file was not explicitly supplied by
20155 @option{-i} switch, gnatmem will assume that this file can be found in the
20156 current directory. For example, after you have executed @file{my_program},
20157 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
20160 $ gnatmem my_program
20164 This will produce the output with the following format:
20166 *************** debut cc
20168 $ gnatmem my_program
20172 Total number of allocations : 45
20173 Total number of deallocations : 6
20174 Final Water Mark (non freed mem) : 11.29 Kilobytes
20175 High Water Mark : 11.40 Kilobytes
20180 Allocation Root # 2
20181 -------------------
20182 Number of non freed allocations : 11
20183 Final Water Mark (non freed mem) : 1.16 Kilobytes
20184 High Water Mark : 1.27 Kilobytes
20186 my_program.adb:23 my_program.alloc
20192 The first block of output gives general information. In this case, the
20193 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
20194 Unchecked_Deallocation routine occurred.
20197 Subsequent paragraphs display information on all allocation roots.
20198 An allocation root is a specific point in the execution of the program
20199 that generates some dynamic allocation, such as a ``@code{@b{new}}''
20200 construct. This root is represented by an execution backtrace (or subprogram
20201 call stack). By default the backtrace depth for allocations roots is 1, so
20202 that a root corresponds exactly to a source location. The backtrace can
20203 be made deeper, to make the root more specific.
20205 @node Switches for gnatmem
20206 @subsection Switches for @code{gnatmem}
20209 @code{gnatmem} recognizes the following switches:
20214 @cindex @option{-q} (@code{gnatmem})
20215 Quiet. Gives the minimum output needed to identify the origin of the
20216 memory leaks. Omits statistical information.
20219 @cindex @var{N} (@code{gnatmem})
20220 N is an integer literal (usually between 1 and 10) which controls the
20221 depth of the backtraces defining allocation root. The default value for
20222 N is 1. The deeper the backtrace, the more precise the localization of
20223 the root. Note that the total number of roots can depend on this
20224 parameter. This parameter must be specified @emph{before} the name of the
20225 executable to be analyzed, to avoid ambiguity.
20228 @cindex @option{-b} (@code{gnatmem})
20229 This switch has the same effect as just depth parameter.
20231 @item -i @var{file}
20232 @cindex @option{-i} (@code{gnatmem})
20233 Do the @code{gnatmem} processing starting from @file{file}, rather than
20234 @file{gmem.out} in the current directory.
20237 @cindex @option{-m} (@code{gnatmem})
20238 This switch causes @code{gnatmem} to mask the allocation roots that have less
20239 than n leaks. The default value is 1. Specifying the value of 0 will allow to
20240 examine even the roots that didn't result in leaks.
20243 @cindex @option{-s} (@code{gnatmem})
20244 This switch causes @code{gnatmem} to sort the allocation roots according to the
20245 specified order of sort criteria, each identified by a single letter. The
20246 currently supported criteria are @code{n, h, w} standing respectively for
20247 number of unfreed allocations, high watermark, and final watermark
20248 corresponding to a specific root. The default order is @code{nwh}.
20252 @node Example of gnatmem Usage
20253 @subsection Example of @code{gnatmem} Usage
20256 The following example shows the use of @code{gnatmem}
20257 on a simple memory-leaking program.
20258 Suppose that we have the following Ada program:
20260 @smallexample @c ada
20263 with Unchecked_Deallocation;
20264 procedure Test_Gm is
20266 type T is array (1..1000) of Integer;
20267 type Ptr is access T;
20268 procedure Free is new Unchecked_Deallocation (T, Ptr);
20271 procedure My_Alloc is
20276 procedure My_DeAlloc is
20284 for I in 1 .. 5 loop
20285 for J in I .. 5 loop
20296 The program needs to be compiled with debugging option and linked with
20297 @code{gmem} library:
20300 $ gnatmake -g test_gm -largs -lgmem
20304 Then we execute the program as usual:
20311 Then @code{gnatmem} is invoked simply with
20317 which produces the following output (result may vary on different platforms):
20322 Total number of allocations : 18
20323 Total number of deallocations : 5
20324 Final Water Mark (non freed mem) : 53.00 Kilobytes
20325 High Water Mark : 56.90 Kilobytes
20327 Allocation Root # 1
20328 -------------------
20329 Number of non freed allocations : 11
20330 Final Water Mark (non freed mem) : 42.97 Kilobytes
20331 High Water Mark : 46.88 Kilobytes
20333 test_gm.adb:11 test_gm.my_alloc
20335 Allocation Root # 2
20336 -------------------
20337 Number of non freed allocations : 1
20338 Final Water Mark (non freed mem) : 10.02 Kilobytes
20339 High Water Mark : 10.02 Kilobytes
20341 s-secsta.adb:81 system.secondary_stack.ss_init
20343 Allocation Root # 3
20344 -------------------
20345 Number of non freed allocations : 1
20346 Final Water Mark (non freed mem) : 12 Bytes
20347 High Water Mark : 12 Bytes
20349 s-secsta.adb:181 system.secondary_stack.ss_init
20353 Note that the GNAT run time contains itself a certain number of
20354 allocations that have no corresponding deallocation,
20355 as shown here for root #2 and root
20356 #3. This is a normal behavior when the number of non-freed allocations
20357 is one, it allocates dynamic data structures that the run time needs for
20358 the complete lifetime of the program. Note also that there is only one
20359 allocation root in the user program with a single line back trace:
20360 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
20361 program shows that 'My_Alloc' is called at 2 different points in the
20362 source (line 21 and line 24). If those two allocation roots need to be
20363 distinguished, the backtrace depth parameter can be used:
20366 $ gnatmem 3 test_gm
20370 which will give the following output:
20375 Total number of allocations : 18
20376 Total number of deallocations : 5
20377 Final Water Mark (non freed mem) : 53.00 Kilobytes
20378 High Water Mark : 56.90 Kilobytes
20380 Allocation Root # 1
20381 -------------------
20382 Number of non freed allocations : 10
20383 Final Water Mark (non freed mem) : 39.06 Kilobytes
20384 High Water Mark : 42.97 Kilobytes
20386 test_gm.adb:11 test_gm.my_alloc
20387 test_gm.adb:24 test_gm
20388 b_test_gm.c:52 main
20390 Allocation Root # 2
20391 -------------------
20392 Number of non freed allocations : 1
20393 Final Water Mark (non freed mem) : 10.02 Kilobytes
20394 High Water Mark : 10.02 Kilobytes
20396 s-secsta.adb:81 system.secondary_stack.ss_init
20397 s-secsta.adb:283 <system__secondary_stack___elabb>
20398 b_test_gm.c:33 adainit
20400 Allocation Root # 3
20401 -------------------
20402 Number of non freed allocations : 1
20403 Final Water Mark (non freed mem) : 3.91 Kilobytes
20404 High Water Mark : 3.91 Kilobytes
20406 test_gm.adb:11 test_gm.my_alloc
20407 test_gm.adb:21 test_gm
20408 b_test_gm.c:52 main
20410 Allocation Root # 4
20411 -------------------
20412 Number of non freed allocations : 1
20413 Final Water Mark (non freed mem) : 12 Bytes
20414 High Water Mark : 12 Bytes
20416 s-secsta.adb:181 system.secondary_stack.ss_init
20417 s-secsta.adb:283 <system__secondary_stack___elabb>
20418 b_test_gm.c:33 adainit
20422 The allocation root #1 of the first example has been split in 2 roots #1
20423 and #3 thanks to the more precise associated backtrace.
20427 @node Stack Related Facilities
20428 @chapter Stack Related Facilities
20431 This chapter describes some useful tools associated with stack
20432 checking and analysis. In
20433 particular, it deals with dynamic and static stack usage measurements.
20436 * Stack Overflow Checking::
20437 * Static Stack Usage Analysis::
20438 * Dynamic Stack Usage Analysis::
20441 @node Stack Overflow Checking
20442 @section Stack Overflow Checking
20443 @cindex Stack Overflow Checking
20444 @cindex -fstack-check
20447 For most operating systems, @command{gcc} does not perform stack overflow
20448 checking by default. This means that if the main environment task or
20449 some other task exceeds the available stack space, then unpredictable
20450 behavior will occur. Most native systems offer some level of protection by
20451 adding a guard page at the end of each task stack. This mechanism is usually
20452 not enough for dealing properly with stack overflow situations because
20453 a large local variable could ``jump'' above the guard page.
20454 Furthermore, when the
20455 guard page is hit, there may not be any space left on the stack for executing
20456 the exception propagation code. Enabling stack checking avoids
20459 To activate stack checking, compile all units with the gcc option
20460 @option{-fstack-check}. For example:
20463 gcc -c -fstack-check package1.adb
20467 Units compiled with this option will generate extra instructions to check
20468 that any use of the stack (for procedure calls or for declaring local
20469 variables in declare blocks) does not exceed the available stack space.
20470 If the space is exceeded, then a @code{Storage_Error} exception is raised.
20472 For declared tasks, the stack size is controlled by the size
20473 given in an applicable @code{Storage_Size} pragma or by the value specified
20474 at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to
20475 the default size as defined in the GNAT runtime otherwise.
20477 For the environment task, the stack size depends on
20478 system defaults and is unknown to the compiler. Stack checking
20479 may still work correctly if a fixed
20480 size stack is allocated, but this cannot be guaranteed.
20482 To ensure that a clean exception is signalled for stack
20483 overflow, set the environment variable
20484 @env{GNAT_STACK_LIMIT} to indicate the maximum
20485 stack area that can be used, as in:
20486 @cindex GNAT_STACK_LIMIT
20489 SET GNAT_STACK_LIMIT 1600
20493 The limit is given in kilobytes, so the above declaration would
20494 set the stack limit of the environment task to 1.6 megabytes.
20495 Note that the only purpose of this usage is to limit the amount
20496 of stack used by the environment task. If it is necessary to
20497 increase the amount of stack for the environment task, then this
20498 is an operating systems issue, and must be addressed with the
20499 appropriate operating systems commands.
20502 To have a fixed size stack in the environment task, the stack must be put
20503 in the P0 address space and its size specified. Use these switches to
20507 gnatmake my_progs -largs "-Wl,--opt=STACK=4000,/p0image"
20511 The quotes are required to keep case. The number after @samp{STACK=} is the
20512 size of the environmental task stack in pagelets (512 bytes). In this example
20513 the stack size is about 2 megabytes.
20516 A consequence of the @option{/p0image} qualifier is also to makes RMS buffers
20517 be placed in P0 space. Refer to @cite{HP OpenVMS Linker Utility Manual} for
20518 more details about the @option{/p0image} qualifier and the @option{stack}
20522 @node Static Stack Usage Analysis
20523 @section Static Stack Usage Analysis
20524 @cindex Static Stack Usage Analysis
20525 @cindex -fstack-usage
20528 A unit compiled with @option{-fstack-usage} will generate an extra file
20530 the maximum amount of stack used, on a per-function basis.
20531 The file has the same
20532 basename as the target object file with a @file{.su} extension.
20533 Each line of this file is made up of three fields:
20537 The name of the function.
20541 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
20544 The second field corresponds to the size of the known part of the function
20547 The qualifier @code{static} means that the function frame size
20549 It usually means that all local variables have a static size.
20550 In this case, the second field is a reliable measure of the function stack
20553 The qualifier @code{dynamic} means that the function frame size is not static.
20554 It happens mainly when some local variables have a dynamic size. When this
20555 qualifier appears alone, the second field is not a reliable measure
20556 of the function stack analysis. When it is qualified with @code{bounded}, it
20557 means that the second field is a reliable maximum of the function stack
20560 @node Dynamic Stack Usage Analysis
20561 @section Dynamic Stack Usage Analysis
20564 It is possible to measure the maximum amount of stack used by a task, by
20565 adding a switch to @command{gnatbind}, as:
20568 $ gnatbind -u0 file
20572 With this option, at each task termination, its stack usage is output on
20574 It is not always convenient to output the stack usage when the program
20575 is still running. Hence, it is possible to delay this output until program
20576 termination. for a given number of tasks specified as the argument of the
20577 @option{-u} option. For instance:
20580 $ gnatbind -u100 file
20584 will buffer the stack usage information of the first 100 tasks to terminate and
20585 output this info at program termination. Results are displayed in four
20589 Index | Task Name | Stack Size | Stack Usage [Value +/- Variation]
20596 is a number associated with each task.
20599 is the name of the task analyzed.
20602 is the maximum size for the stack.
20605 is the measure done by the stack analyzer. In order to prevent overflow, the stack
20606 is not entirely analyzed, and it's not possible to know exactly how
20607 much has actually been used. The report thus contains the theoretical stack usage
20608 (Value) and the possible variation (Variation) around this value.
20613 The environment task stack, e.g., the stack that contains the main unit, is
20614 only processed when the environment variable GNAT_STACK_LIMIT is set.
20617 @c *********************************
20619 @c *********************************
20620 @node Verifying Properties Using gnatcheck
20621 @chapter Verifying Properties Using @command{gnatcheck}
20623 @cindex @command{gnatcheck}
20626 The @command{gnatcheck} tool is an ASIS-based utility that checks properties
20627 of Ada source files according to a given set of semantic rules.
20630 In order to check compliance with a given rule, @command{gnatcheck} has to
20631 semantically analyze the Ada sources.
20632 Therefore, checks can only be performed on
20633 legal Ada units. Moreover, when a unit depends semantically upon units located
20634 outside the current directory, the source search path has to be provided when
20635 calling @command{gnatcheck}, either through a specified project file or
20636 through @command{gnatcheck} switches as described below.
20638 A number of rules are predefined in @command{gnatcheck} and are described
20639 later in this chapter.
20640 You can also add new rules, by modifying the @command{gnatcheck} code and
20641 rebuilding the tool. In order to add a simple rule making some local checks,
20642 a small amount of straightforward ASIS-based programming is usually needed.
20644 Project support for @command{gnatcheck} is provided by the GNAT
20645 driver (see @ref{The GNAT Driver and Project Files}).
20647 Invoking @command{gnatcheck} on the command line has the form:
20650 $ gnatcheck @ovar{switches} @{@var{filename}@}
20651 @r{[}^-files^/FILES^=@{@var{arg_list_filename}@}@r{]}
20652 @r{[}-cargs @var{gcc_switches}@r{]} @r{[}-rules @var{rule_options}@r{]}
20659 @var{switches} specify the general tool options
20662 Each @var{filename} is the name (including the extension) of a source
20663 file to process. ``Wildcards'' are allowed, and
20664 the file name may contain path information.
20667 Each @var{arg_list_filename} is the name (including the extension) of a text
20668 file containing the names of the source files to process, separated by spaces
20672 @var{gcc_switches} is a list of switches for
20673 @command{gcc}. They will be passed on to all compiler invocations made by
20674 @command{gnatcheck} to generate the ASIS trees. Here you can provide
20675 @option{^-I^/INCLUDE_DIRS=^} switches to form the source search path,
20676 and use the @option{-gnatec} switch to set the configuration file.
20679 @var{rule_options} is a list of options for controlling a set of
20680 rules to be checked by @command{gnatcheck} (@pxref{gnatcheck Rule Options}).
20684 Either a @file{@var{filename}} or an @file{@var{arg_list_filename}} must be supplied.
20687 * Format of the Report File::
20688 * General gnatcheck Switches::
20689 * gnatcheck Rule Options::
20690 * Adding the Results of Compiler Checks to gnatcheck Output::
20691 * Project-Wide Checks::
20692 * Predefined Rules::
20695 @node Format of the Report File
20696 @section Format of the Report File
20697 @cindex Report file (for @code{gnatcheck})
20700 The @command{gnatcheck} tool outputs on @file{stdout} all messages concerning
20702 It also creates a text file that
20703 contains the complete report of the last gnatcheck run. By default this file is
20704 named named @file{^gnatcheck.out^GNATCHECK.OUT^} and it is located in the current
20705 directory, @option{^-o^/OUTPUT^} option can be used to change the name and/or
20706 location of the report file. This report contains:
20708 @item a list of the Ada source files being checked,
20709 @item a list of enabled and disabled rules,
20710 @item a list of the diagnostic messages, ordered in three different ways
20711 and collected in three separate
20712 sections. Section 1 contains the raw list of diagnostic messages. It
20713 corresponds to the output going to @file{stdout}. Section 2 contains
20714 messages ordered by rules.
20715 Section 3 contains messages ordered by source files.
20718 @node General gnatcheck Switches
20719 @section General @command{gnatcheck} Switches
20722 The following switches control the general @command{gnatcheck} behavior
20726 @cindex @option{^-a^/ALL^} (@command{gnatcheck})
20728 Process all units including those with read-only ALI files such as
20729 those from GNAT Run-Time library.
20733 @cindex @option{-d} (@command{gnatcheck})
20738 @cindex @option{-dd} (@command{gnatcheck})
20740 Progress indicator mode (for use in GPS)
20743 @cindex @option{^-h^/HELP^} (@command{gnatcheck})
20745 List the predefined and user-defined rules. For more details see
20746 @ref{Predefined Rules}.
20748 @cindex @option{^-l^/LOCS^} (@command{gnatcheck})
20750 Use full source locations references in the report file. For a construct from
20751 a generic instantiation a full source location is a chain from the location
20752 of this construct in the generic unit to the place where this unit is
20755 @cindex @option{^-log^/LOG^} (@command{gnatcheck})
20757 Duplicate all the output sent to Stderr into a log file. The log file is
20758 named @var{gnatcheck.log} and is located in the current directory.
20760 @cindex @option{^-m^/DIAGNOSTIC_LIMIT^} (@command{gnatcheck})
20761 @item ^-m@i{nnn}^/DIAGNOSTIC_LIMIT=@i{nnn}^
20762 Maximum number of diagnoses to be sent to Stdout, @i{nnn} from o@dots{}1000,
20763 the default value is 500. Zero means that there is no limitation on
20764 the number of diagnostic messages to be printed into Stdout.
20766 @cindex @option{^-q^/QUIET^} (@command{gnatcheck})
20768 Quiet mode. All the diagnoses about rule violations are placed in the
20769 @command{gnatcheck} report file only, without duplicating in @file{stdout}.
20771 @cindex @option{^-s^/SHORT^} (@command{gnatcheck})
20773 Short format of the report file (no version information, no list of applied
20774 rules, no list of checked sources is included)
20776 @cindex @option{^-s1^/COMPILER_STYLE^} (@command{gnatcheck})
20777 @item ^-s1^/COMPILER_STYLE^
20778 Include the compiler-style section in the report file
20780 @cindex @option{^-s2^/BY_RULES^} (@command{gnatcheck})
20781 @item ^-s2^/BY_RULES^
20782 Include the section containing diagnoses ordered by rules in the report file
20784 @cindex @option{^-s3^/BY_FILES_BY_RULES^} (@command{gnatcheck})
20785 @item ^-s3^/BY_FILES_BY_RULES^
20786 Include the section containing diagnoses ordered by files and then by rules
20789 @cindex @option{^-t^/TIME^} (@command{gnatcheck})
20791 Print out execution time.
20793 @cindex @option{^-v^/VERBOSE^} (@command{gnatcheck})
20794 @item ^-v^/VERBOSE^
20795 Verbose mode; @command{gnatcheck} generates version information and then
20796 a trace of sources being processed.
20798 @cindex @option{^-o ^/OUTPUT^} (@command{gnatcheck})
20799 @item ^-o ^/OUTPUT=^@var{report_file}
20800 Set name of report file file to @var{report_file} .
20805 Note that if any of the options @option{^-s1^/COMPILER_STYLE^},
20806 @option{^-s2^/BY_RULES^} or
20807 @option{^-s3^/BY_FILES_BY_RULES^} is specified,
20808 then the @command{gnatcheck} report file will only contain sections
20809 explicitly denoted by these options.
20811 @node gnatcheck Rule Options
20812 @section @command{gnatcheck} Rule Options
20815 The following options control the processing performed by
20816 @command{gnatcheck}.
20819 @cindex @option{+ALL} (@command{gnatcheck})
20821 Turn all the rule checks ON.
20823 @cindex @option{-ALL} (@command{gnatcheck})
20825 Turn all the rule checks OFF.
20827 @cindex @option{+R} (@command{gnatcheck})
20828 @item +R@var{rule_id}@r{[}:@var{param}@r{]}
20829 Turn on the check for a specified rule with the specified parameter, if any.
20830 @var{rule_id} must be the identifier of one of the currently implemented rules
20831 (use @option{^-h^/HELP^} for the list of implemented rules). Rule identifiers
20832 are not case-sensitive. The @var{param} item must
20833 be a string representing a valid parameter(s) for the specified rule.
20834 If it contains any space characters then this string must be enclosed in
20837 @cindex @option{-R} (@command{gnatcheck})
20838 @item -R@var{rule_id}@r{[}:@var{param}@r{]}
20839 Turn off the check for a specified rule with the specified parameter, if any.
20841 @cindex @option{-from} (@command{gnatcheck})
20842 @item -from=@var{rule_option_filename}
20843 Read the rule options from the text file @var{rule_option_filename}, referred as
20844 ``rule file'' below.
20849 The default behavior is that all the rule checks are disabled.
20851 A rule file is a text file containing a set of rule options.
20852 @cindex Rule file (for @code{gnatcheck})
20853 The file may contain empty lines and Ada-style comments (comment
20854 lines and end-of-line comments). The rule file has free format; that is,
20855 you do not have to start a new rule option on a new line.
20857 A rule file may contain other @option{-from=@var{rule_option_filename}}
20858 options, each such option being replaced with the content of the
20859 corresponding rule file during the rule files processing. In case a
20860 cycle is detected (that is, @file{@var{rule_file_1}} reads rule options
20861 from @file{@var{rule_file_2}}, and @file{@var{rule_file_2}} reads
20862 (directly or indirectly) rule options from @file{@var{rule_file_1}}),
20863 the processing of rule files is interrupted and a part of their content
20867 @node Adding the Results of Compiler Checks to gnatcheck Output
20868 @section Adding the Results of Compiler Checks to @command{gnatcheck} Output
20871 The @command{gnatcheck} tool can include in the generated diagnostic messages
20873 the report file the results of the checks performed by the compiler. Though
20874 disabled by default, this effect may be obtained by using @option{+R} with
20875 the following rule identifiers and parameters:
20879 To record restrictions violations (that are performed by the compiler if the
20880 pragma @code{Restrictions} or @code{Restriction_Warnings} are given),
20882 @code{Restrictions} with the same parameters as pragma
20883 @code{Restrictions} or @code{Restriction_Warnings}.
20886 To record compiler style checks(@pxref{Style Checking}), use the rule named
20887 @code{Style_Checks}. A parameter of this rule can be either @code{All_Checks},
20888 which enables all the standard style checks that corresponds to @option{-gnatyy}
20889 GNAT style check option, or a string that has exactly the same
20890 structure and semantics as the @code{string_LITERAL} parameter of GNAT pragma
20891 @code{Style_Checks} (for further information about this pragma,
20892 @pxref{Pragma Style_Checks,,, gnat_rm, GNAT Reference Manual}). For example,
20893 @code{+RStyle_Checks:O} rule option activates and adds to @command{gnatcheck}
20894 output the compiler style check that corresponds to
20895 @code{-gnatyO} style check option.
20898 To record compiler warnings (@pxref{Warning Message Control}), use the rule
20899 named @code{Warnings} with a parameter that is a valid
20900 @i{static_string_expression} argument of GNAT pragma @code{Warnings}
20901 (for further information about this pragma, @pxref{Pragma Warnings,,,
20902 gnat_rm, GNAT Reference Manual}). Note, that in case of gnatcheck
20903 's' parameter, that corresponds to the GNAT @option{-gnatws} option, disables
20904 all the specific warnings, but not suppresses the warning mode,
20905 and 'e' parameter, corresponding to @option{-gnatwe} that means
20906 "treat warnings as errors", does not have any effect.
20910 To disable a specific restriction check, use @code{-RStyle_Checks} gnatcheck
20911 option with the corresponding restriction name as a parameter. @code{-R} is
20912 not available for @code{Style_Checks} and @code{Warnings} options, to disable
20913 warnings and style checks, use the corresponding warning and style options.
20915 @node Project-Wide Checks
20916 @section Project-Wide Checks
20917 @cindex Project-wide checks (for @command{gnatcheck})
20920 In order to perform checks on all units of a given project, you can use
20921 the GNAT driver along with the @option{-P} option:
20923 gnat check -Pproj -rules -from=my_rules
20927 If the project @code{proj} depends upon other projects, you can perform
20928 checks on the project closure using the @option{-U} option:
20930 gnat check -Pproj -U -rules -from=my_rules
20934 Finally, if not all the units are relevant to a particular main
20935 program in the project closure, you can perform checks for the set
20936 of units needed to create a given main program (unit closure) using
20937 the @option{-U} option followed by the name of the main unit:
20939 gnat check -Pproj -U main -rules -from=my_rules
20943 @node Predefined Rules
20944 @section Predefined Rules
20945 @cindex Predefined rules (for @command{gnatcheck})
20948 @c (Jan 2007) Since the global rules are still under development and are not
20949 @c documented, there is no point in explaining the difference between
20950 @c global and local rules
20952 A rule in @command{gnatcheck} is either local or global.
20953 A @emph{local rule} is a rule that applies to a well-defined section
20954 of a program and that can be checked by analyzing only this section.
20955 A @emph{global rule} requires analysis of some global properties of the
20956 whole program (mostly related to the program call graph).
20957 As of @value{NOW}, the implementation of global rules should be
20958 considered to be at a preliminary stage. You can use the
20959 @option{+GLOBAL} option to enable all the global rules, and the
20960 @option{-GLOBAL} rule option to disable all the global rules.
20962 All the global rules in the list below are
20963 so indicated by marking them ``GLOBAL''.
20964 This +GLOBAL and -GLOBAL options are not
20965 included in the list of gnatcheck options above, because at the moment they
20966 are considered as a temporary debug options.
20968 @command{gnatcheck} performs rule checks for generic
20969 instances only for global rules. This limitation may be relaxed in a later
20974 The following subsections document the rules implemented in
20975 @command{gnatcheck}.
20976 The subsection title is the same as the rule identifier, which may be
20977 used as a parameter of the @option{+R} or @option{-R} options.
20981 * Abstract_Type_Declarations::
20982 * Anonymous_Arrays::
20983 * Anonymous_Subtypes::
20985 * Boolean_Relational_Operators::
20987 * Ceiling_Violations::
20989 * Complex_Inlined_Subprograms::
20990 * Controlled_Type_Declarations::
20991 * Declarations_In_Blocks::
20992 * Deep_Inheritance_Hierarchies::
20993 * Deeply_Nested_Generics::
20994 * Deeply_Nested_Inlining::
20996 * Deeply_Nested_Local_Inlining::
20998 * Default_Parameters::
20999 * Direct_Calls_To_Primitives::
21000 * Discriminated_Records::
21001 * Enumeration_Ranges_In_CASE_Statements::
21002 * Exceptions_As_Control_Flow::
21003 * Exits_From_Conditional_Loops::
21004 * EXIT_Statements_With_No_Loop_Name::
21005 * Expanded_Loop_Exit_Names::
21006 * Explicit_Full_Discrete_Ranges::
21007 * Float_Equality_Checks::
21008 * Forbidden_Attributes::
21009 * Forbidden_Pragmas::
21010 * Function_Style_Procedures::
21011 * Generics_In_Subprograms::
21012 * GOTO_Statements::
21013 * Implicit_IN_Mode_Parameters::
21014 * Implicit_SMALL_For_Fixed_Point_Types::
21015 * Improperly_Located_Instantiations::
21016 * Improper_Returns::
21017 * Library_Level_Subprograms::
21020 * Improperly_Called_Protected_Entries::
21023 * Misnamed_Controlling_Parameters::
21024 * Misnamed_Identifiers::
21025 * Multiple_Entries_In_Protected_Definitions::
21027 * Non_Qualified_Aggregates::
21028 * Non_Short_Circuit_Operators::
21029 * Non_SPARK_Attributes::
21030 * Non_Tagged_Derived_Types::
21031 * Non_Visible_Exceptions::
21032 * Numeric_Literals::
21033 * OTHERS_In_Aggregates::
21034 * OTHERS_In_CASE_Statements::
21035 * OTHERS_In_Exception_Handlers::
21036 * Outer_Loop_Exits::
21037 * Overloaded_Operators::
21038 * Overly_Nested_Control_Structures::
21039 * Parameters_Out_Of_Order::
21040 * Positional_Actuals_For_Defaulted_Generic_Parameters::
21041 * Positional_Actuals_For_Defaulted_Parameters::
21042 * Positional_Components::
21043 * Positional_Generic_Parameters::
21044 * Positional_Parameters::
21045 * Predefined_Numeric_Types::
21046 * Raising_External_Exceptions::
21047 * Raising_Predefined_Exceptions::
21048 * Separate_Numeric_Error_Handlers::
21051 * Side_Effect_Functions::
21054 * Too_Many_Parents::
21055 * Unassigned_OUT_Parameters::
21056 * Uncommented_BEGIN_In_Package_Bodies::
21057 * Unconditional_Exits::
21058 * Unconstrained_Array_Returns::
21059 * Universal_Ranges::
21060 * Unnamed_Blocks_And_Loops::
21062 * Unused_Subprograms::
21064 * USE_PACKAGE_Clauses::
21065 * Visible_Components::
21066 * Volatile_Objects_Without_Address_Clauses::
21070 @node Abstract_Type_Declarations
21071 @subsection @code{Abstract_Type_Declarations}
21072 @cindex @code{Abstract_Type_Declarations} rule (for @command{gnatcheck})
21075 Flag all declarations of abstract types. For an abstract private
21076 type, both the private and full type declarations are flagged.
21078 This rule has no parameters.
21081 @node Anonymous_Arrays
21082 @subsection @code{Anonymous_Arrays}
21083 @cindex @code{Anonymous_Arrays} rule (for @command{gnatcheck})
21086 Flag all anonymous array type definitions (by Ada semantics these can only
21087 occur in object declarations).
21089 This rule has no parameters.
21091 @node Anonymous_Subtypes
21092 @subsection @code{Anonymous_Subtypes}
21093 @cindex @code{Anonymous_Subtypes} rule (for @command{gnatcheck})
21096 Flag all uses of anonymous subtypes. A use of an anonymous subtype is
21097 any instance of a subtype indication with a constraint, other than one
21098 that occurs immediately within a subtype declaration. Any use of a range
21099 other than as a constraint used immediately within a subtype declaration
21100 is considered as an anonymous subtype.
21102 An effect of this rule is that @code{for} loops such as the following are
21103 flagged (since @code{1..N} is formally a ``range''):
21105 @smallexample @c ada
21106 for I in 1 .. N loop
21112 Declaring an explicit subtype solves the problem:
21114 @smallexample @c ada
21115 subtype S is Integer range 1..N;
21123 This rule has no parameters.
21126 @subsection @code{Blocks}
21127 @cindex @code{Blocks} rule (for @command{gnatcheck})
21130 Flag each block statement.
21132 This rule has no parameters.
21134 @node Boolean_Relational_Operators
21135 @subsection @code{Boolean_Relational_Operators}
21136 @cindex @code{Boolean_Relational_Operators} rule (for @command{gnatcheck})
21139 Flag each call to a predefined relational operator (``<'', ``>'', ``<='',
21140 ``>='', ``='' and ``/='') for the predefined Boolean type.
21141 (This rule is useful in enforcing the SPARK language restrictions.)
21143 Calls to predefined relational operators of any type derived from
21144 @code{Standard.Boolean} are not detected. Calls to user-defined functions
21145 with these designators, and uses of operators that are renamings
21146 of the predefined relational operators for @code{Standard.Boolean},
21147 are likewise not detected.
21149 This rule has no parameters.
21152 @node Ceiling_Violations
21153 @subsection @code{Ceiling5_Violations} (under construction, GLOBAL)
21154 @cindex @code{Ceiling_Violations} rule (for @command{gnatcheck})
21157 Flag invocations of a protected operation by a task whose priority exceeds
21158 the protected object's ceiling.
21160 As of @value{NOW}, this rule has the following limitations:
21165 We consider only pragmas Priority and Interrupt_Priority as means to define
21166 a task/protected operation priority. We do not consider the effect of using
21167 Ada.Dynamic_Priorities.Set_Priority procedure;
21170 We consider only base task priorities, and no priority inheritance. That is,
21171 we do not make a difference between calls issued during task activation and
21172 execution of the sequence of statements from task body;
21175 Any situation when the priority of protected operation caller is set by a
21176 dynamic expression (that is, the corresponding Priority or
21177 Interrupt_Priority pragma has a non-static expression as an argument) we
21178 treat as a priority inconsistency (and, therefore, detect this situation).
21182 At the moment the notion of the main subprogram is not implemented in
21183 gnatcheck, so any pragma Priority in a library level subprogram body (in case
21184 if this subprogram can be a main subprogram of a partition) changes the
21185 priority of an environment task. So if we have more then one such pragma in
21186 the set of processed sources, the pragma that is processed last, defines the
21187 priority of an environment task.
21189 This rule has no parameters.
21192 @node Controlled_Type_Declarations
21193 @subsection @code{Controlled_Type_Declarations}
21194 @cindex @code{Controlled_Type_Declarations} rule (for @command{gnatcheck})
21197 Flag all declarations of controlled types. A declaration of a private type
21198 is flagged if its full declaration declares a controlled type. A declaration
21199 of a derived type is flagged if its ancestor type is controlled. Subtype
21200 declarations are not checked. A declaration of a type that itself is not a
21201 descendant of a type declared in @code{Ada.Finalization} but has a controlled
21202 component is not checked.
21204 This rule has no parameters.
21207 @node Complex_Inlined_Subprograms
21208 @subsection @code{Complex_Inlined_Subprograms}
21209 @cindex @code{Complex_Inlined_Subprograms} rule (for @command{gnatcheck})
21212 Flags the body of a subprogram (or generic subprogram) if
21213 pragma Inline has been applied to the subprogram but the body
21214 is too complex to be expanded inline.
21216 A subprogram (or generic subprogram) is considered too complex for inline
21217 expansion if its body meets at least one of the following conditions:
21221 The number of local declarations and statements exceeds
21222 a value specified by the @option{N} rule parameter;
21225 The body contains a @code{loop}, @code{if} or @code{case} statement;
21229 This rule has the following (mandatory) parameter for the @option{+R} option:
21233 Positive integer specifying the maximum allowed total number of local
21234 declarations and statements in the subprogram body.
21238 @node Declarations_In_Blocks
21239 @subsection @code{Declarations_In_Blocks}
21240 @cindex @code{Declarations_In_Blocks} rule (for @command{gnatcheck})
21243 Flag all block statements containing local declarations. A @code{declare}
21244 block with an empty @i{declarative_part} or with a @i{declarative part}
21245 containing only pragmas and/or @code{use} clauses is not flagged.
21247 This rule has no parameters.
21250 @node Deep_Inheritance_Hierarchies
21251 @subsection @code{Deep_Inheritance_Hierarchies}
21252 @cindex @code{Deep_Inheritance_Hierarchies} rule (for @command{gnatcheck})
21255 Flags a tagged derived type declaration if its depth (in its inheritance
21256 hierarchy) exceeds the value specified by the @option{N} rule parameter.
21258 The depth of a root tagged type (ie, a tagged type that is not a derived type)
21260 If tagged type T2 derives directly from tagged type T1, then the depth of T2
21261 is one more than the depth of T1.
21263 This rule does not flag interface types or private extension
21264 declarations. In the case of a private extension, the correspondong full
21265 declaration is checked.
21267 This rule has the following (mandatory) parameter for the @option{+R} option:
21271 Positive integer specifying the maximal allowed depth of any inheritance
21276 @node Deeply_Nested_Generics
21277 @subsection @code{Deeply_Nested_Generics}
21278 @cindex @code{Deeply_Nested_Generics} rule (for @command{gnatcheck})
21281 Flags a generic declaration nested in another generic declaration if
21282 the nesting level of the inner generic exceeds
21283 a value specified by the @option{N} rule parameter.
21284 The nesting level is the number of generic declaratons that enclose the given
21285 (generic) declaration. Formal packages are not flagged by this rule.
21287 This rule has the following (mandatory) parameters for the @option{+R} option:
21291 Positive integer specifying the maximal allowed nesting level
21292 for a generic declaration.
21295 @node Deeply_Nested_Inlining
21296 @subsection @code{Deeply_Nested_Inlining}
21297 @cindex @code{Deeply_Nested_Inlining} rule (for @command{gnatcheck})
21300 Flags the body of a subprogram (or generic subprogram) if
21301 pragma Inline has been applied to the subprogram but the body
21302 contains a call to another inlined subprogram that results in nested inlining
21303 with nesting depth exceeding the value specified by the
21304 @option{N} rule parameter.
21306 This rule assumes that pragma Inline applies equally to calls on
21307 subprograms regardless of whether the subprogram declaration appears in the
21308 same compilation unit as the call, or in a separately compiled
21309 (e.g., @i{with}ed) unit.
21311 This rule may be useful when either the @option{-gnatn} or @option{-gnatN}
21314 If a subprogram should be flagged according to this rule, the body declaration
21315 is flagged only if it is not a completion of a subprogram declaration.
21317 This rule requires the global analysis of all the compilation units that
21318 are @command{gnatcheck} arguments; such analysis may affect the tool's
21321 This rule has the following (mandatory) parameter for the @option{+R} option:
21325 Positive integer specifying the maximal allowed level of nested inlining.
21330 @node Deeply_Nested_Local_Inlining
21331 @subsection @code{Deeply_Nested_Local_Inlining}
21332 @cindex @code{Deeply_Nested_Local_Inlining} rule (for @command{gnatcheck})
21335 Flags a subprogram body if a pragma @code{Inline} is applied to the
21336 corresponding subprogram (or generic subprogram) and the body contains a call
21337 to another inlined subprogram that results in nested inlining with nesting
21338 depth more then a value specified by the @option{N} rule parameter.
21339 This rule is similar to @code{Deeply_Nested_Inlining} rule, but it
21340 assumes that calls to subprograms in
21341 with'ed units are not inlided, so all the analysis of the depth of inlining is
21342 limited by the compilation unit where the subprogram body is located and the
21343 units it depends semantically upon. Such analysis may be usefull for the case
21344 when neiter @option{-gnatn} nor @option{-gnatN} option is used when building
21347 This rule has the following (mandatory) parameters for the @option{+R} option:
21351 Positive integer specifying the maximal allowed level of nested inlining.
21356 @node Default_Parameters
21357 @subsection @code{Default_Parameters}
21358 @cindex @code{Default_Parameters} rule (for @command{gnatcheck})
21361 Flag all default expressions for subprogram parameters. Parameter
21362 declarations of formal and generic subprograms are also checked.
21364 This rule has no parameters.
21367 @node Direct_Calls_To_Primitives
21368 @subsection @code{Direct_Calls_To_Primitives}
21369 @cindex @code{Direct_Calls_To_Primitives} rule (for @command{gnatcheck})
21372 Flags any non-dispatching call to a dispatching primitive operation, except
21373 for the common idiom where a primitive subprogram for a tagged type
21374 directly calls the same primitive subprogram of the type's immediate ancestor.
21376 This rule has no parameters.
21379 @node Discriminated_Records
21380 @subsection @code{Discriminated_Records}
21381 @cindex @code{Discriminated_Records} rule (for @command{gnatcheck})
21384 Flag all declarations of record types with discriminants. Only the
21385 declarations of record and record extension types are checked. Incomplete,
21386 formal, private, derived and private extension type declarations are not
21387 checked. Task and protected type declarations also are not checked.
21389 This rule has no parameters.
21392 @node Enumeration_Ranges_In_CASE_Statements
21393 @subsection @code{Enumeration_Ranges_In_CASE_Statements}
21394 @cindex @code{Enumeration_Ranges_In_CASE_Statements} (for @command{gnatcheck})
21397 Flag each use of a range of enumeration literals as a choice in a
21398 @code{case} statement.
21399 All forms for specifying a range (explicit ranges
21400 such as @code{A .. B}, subtype marks and @code{'Range} attributes) are flagged.
21401 An enumeration range is
21402 flagged even if contains exactly one enumeration value or no values at all. A
21403 type derived from an enumeration type is considered as an enumeration type.
21405 This rule helps prevent maintenance problems arising from adding an
21406 enumeration value to a type and having it implicitly handled by an existing
21407 @code{case} statement with an enumeration range that includes the new literal.
21409 This rule has no parameters.
21412 @node Exceptions_As_Control_Flow
21413 @subsection @code{Exceptions_As_Control_Flow}
21414 @cindex @code{Exceptions_As_Control_Flow} (for @command{gnatcheck})
21417 Flag each place where an exception is explicitly raised and handled in the
21418 same subprogram body. A @code{raise} statement in an exception handler,
21419 package body, task body or entry body is not flagged.
21421 The rule has no parameters.
21423 @node Exits_From_Conditional_Loops
21424 @subsection @code{Exits_From_Conditional_Loops}
21425 @cindex @code{Exits_From_Conditional_Loops} (for @command{gnatcheck})
21428 Flag any exit statement if it transfers the control out of a @code{for} loop
21429 or a @code{while} loop. This includes cases when the @code{exit} statement
21430 applies to a @code{FOR} or @code{while} loop, and cases when it is enclosed
21431 in some @code{for} or @code{while} loop, but transfers the control from some
21432 outer (inconditional) @code{loop} statement.
21434 The rule has no parameters.
21437 @node EXIT_Statements_With_No_Loop_Name
21438 @subsection @code{EXIT_Statements_With_No_Loop_Name}
21439 @cindex @code{EXIT_Statements_With_No_Loop_Name} (for @command{gnatcheck})
21442 Flag each @code{exit} statement that does not specify the name of the loop
21445 The rule has no parameters.
21448 @node Expanded_Loop_Exit_Names
21449 @subsection @code{Expanded_Loop_Exit_Names}
21450 @cindex @code{Expanded_Loop_Exit_Names} rule (for @command{gnatcheck})
21453 Flag all expanded loop names in @code{exit} statements.
21455 This rule has no parameters.
21457 @node Explicit_Full_Discrete_Ranges
21458 @subsection @code{Explicit_Full_Discrete_Ranges}
21459 @cindex @code{Explicit_Full_Discrete_Ranges} rule (for @command{gnatcheck})
21462 Flag each discrete range that has the form @code{A'First .. A'Last}.
21464 This rule has no parameters.
21466 @node Float_Equality_Checks
21467 @subsection @code{Float_Equality_Checks}
21468 @cindex @code{Float_Equality_Checks} rule (for @command{gnatcheck})
21471 Flag all calls to the predefined equality operations for floating-point types.
21472 Both ``@code{=}'' and ``@code{/=}'' operations are checked.
21473 User-defined equality operations are not flagged, nor are ``@code{=}''
21474 and ``@code{/=}'' operations for fixed-point types.
21476 This rule has no parameters.
21479 @node Forbidden_Attributes
21480 @subsection @code{Forbidden_Attributes}
21481 @cindex @code{Forbidden_Attributes} rule (for @command{gnatcheck})
21484 Flag each use of the specified attributes. The attributes to be detected are
21485 named in the rule's parameters.
21487 This rule has the following parameters:
21490 @item For the @option{+R} option
21493 @item @emph{Attribute_Designator}
21494 Adds the specified attribute to the set of attributes to be detected and sets
21495 the detection checks for all the specified attributes ON.
21496 If @emph{Attribute_Designator}
21497 does not denote any attribute defined in the Ada standard
21499 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
21500 Manual}, it is treated as the name of unknown attribute.
21503 All the GNAT-specific attributes are detected; this sets
21504 the detection checks for all the specified attributes ON.
21507 All attributes are detected; this sets the rule ON.
21510 @item For the @option{-R} option
21512 @item @emph{Attribute_Designator}
21513 Removes the specified attribute from the set of attributes to be
21514 detected without affecting detection checks for
21515 other attributes. If @emph{Attribute_Designator} does not correspond to any
21516 attribute defined in the Ada standard or in
21517 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference Manual},
21518 this option is treated as turning OFF detection of all unknown attributes.
21521 Turn OFF detection of all GNAT-specific attributes
21524 Clear the list of the attributes to be detected and
21530 Parameters are not case sensitive. If @emph{Attribute_Designator} does not
21531 have the syntax of an Ada identifier and therefore can not be considered as a
21532 (part of an) attribute designator, a diagnostic message is generated and the
21533 corresponding parameter is ignored. (If an attribute allows a static
21534 expression to be a part of the attribute designator, this expression is
21535 ignored by this rule.)
21537 When more then one parameter is given in the same rule option, the parameters
21538 must be separated by commas.
21540 If more then one option for this rule is specified for the gnatcheck call, a
21541 new option overrides the previous one(s).
21543 The @option{+R} option with no parameters turns the rule ON, with the set of
21544 attributes to be detected defined by the previous rule options.
21545 (By default this set is empty, so if the only option specified for the rule is
21546 @option{+RForbidden_Attributes} (with
21547 no parameter), then the rule is enabled, but it does not detect anything).
21548 The @option{-R} option with no parameter turns the rule OFF, but it does not
21549 affect the set of attributes to be detected.
21552 @node Forbidden_Pragmas
21553 @subsection @code{Forbidden_Pragmas}
21554 @cindex @code{Forbidden_Pragmas} rule (for @command{gnatcheck})
21557 Flag each use of the specified pragmas. The pragmas to be detected
21558 are named in the rule's parameters.
21560 This rule has the following parameters:
21563 @item For the @option{+R} option
21566 @item @emph{Pragma_Name}
21567 Adds the specified pragma to the set of pragmas to be
21568 checked and sets the checks for all the specified pragmas
21569 ON. @emph{Pragma_Name} is treated as a name of a pragma. If it
21570 does not correspond to any pragma name defined in the Ada
21571 standard or to the name of a GNAT-specific pragma defined
21572 in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
21573 Manual}, it is treated as the name of unknown pragma.
21576 All the GNAT-specific pragmas are detected; this sets
21577 the checks for all the specified pragmas ON.
21580 All pragmas are detected; this sets the rule ON.
21583 @item For the @option{-R} option
21585 @item @emph{Pragma_Name}
21586 Removes the specified pragma from the set of pragmas to be
21587 checked without affecting checks for
21588 other pragmas. @emph{Pragma_Name} is treated as a name
21589 of a pragma. If it does not correspond to any pragma
21590 defined in the Ada standard or to any name defined in
21591 @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual},
21592 this option is treated as turning OFF detection of all unknown pragmas.
21595 Turn OFF detection of all GNAT-specific pragmas
21598 Clear the list of the pragmas to be detected and
21604 Parameters are not case sensitive. If @emph{Pragma_Name} does not have
21605 the syntax of an Ada identifier and therefore can not be considered
21606 as a pragma name, a diagnostic message is generated and the corresponding
21607 parameter is ignored.
21609 When more then one parameter is given in the same rule option, the parameters
21610 must be separated by a comma.
21612 If more then one option for this rule is specified for the @command{gnatcheck}
21613 call, a new option overrides the previous one(s).
21615 The @option{+R} option with no parameters turns the rule ON with the set of
21616 pragmas to be detected defined by the previous rule options.
21617 (By default this set is empty, so if the only option specified for the rule is
21618 @option{+RForbidden_Pragmas} (with
21619 no parameter), then the rule is enabled, but it does not detect anything).
21620 The @option{-R} option with no parameter turns the rule OFF, but it does not
21621 affect the set of pragmas to be detected.
21626 @node Function_Style_Procedures
21627 @subsection @code{Function_Style_Procedures}
21628 @cindex @code{Function_Style_Procedures} rule (for @command{gnatcheck})
21631 Flag each procedure that can be rewritten as a function. A procedure can be
21632 converted into a function if it has exactly one parameter of mode @code{out}
21633 and no parameters of mode @code{in out}. Procedure declarations,
21634 formal procedure declarations, and generic procedure declarations are always
21636 bodies and body stubs are flagged only if they do not have corresponding
21637 separate declarations. Procedure renamings and procedure instantiations are
21640 If a procedure can be rewritten as a function, but its @code{out} parameter is
21641 of a limited type, it is not flagged.
21643 Protected procedures are not flagged. Null procedures also are not flagged.
21645 This rule has no parameters.
21648 @node Generics_In_Subprograms
21649 @subsection @code{Generics_In_Subprograms}
21650 @cindex @code{Generics_In_Subprograms} rule (for @command{gnatcheck})
21653 Flag each declaration of a generic unit in a subprogram. Generic
21654 declarations in the bodies of generic subprograms are also flagged.
21655 A generic unit nested in another generic unit is not flagged.
21656 If a generic unit is
21657 declared in a local package that is declared in a subprogram body, the
21658 generic unit is flagged.
21660 This rule has no parameters.
21663 @node GOTO_Statements
21664 @subsection @code{GOTO_Statements}
21665 @cindex @code{GOTO_Statements} rule (for @command{gnatcheck})
21668 Flag each occurrence of a @code{goto} statement.
21670 This rule has no parameters.
21673 @node Implicit_IN_Mode_Parameters
21674 @subsection @code{Implicit_IN_Mode_Parameters}
21675 @cindex @code{Implicit_IN_Mode_Parameters} rule (for @command{gnatcheck})
21678 Flag each occurrence of a formal parameter with an implicit @code{in} mode.
21679 Note that @code{access} parameters, although they technically behave
21680 like @code{in} parameters, are not flagged.
21682 This rule has no parameters.
21685 @node Implicit_SMALL_For_Fixed_Point_Types
21686 @subsection @code{Implicit_SMALL_For_Fixed_Point_Types}
21687 @cindex @code{Implicit_SMALL_For_Fixed_Point_Types} rule (for @command{gnatcheck})
21690 Flag each fixed point type declaration that lacks an explicit
21691 representation clause to define its @code{'Small} value.
21692 Since @code{'Small} can be defined only for ordinary fixed point types,
21693 decimal fixed point type declarations are not checked.
21695 This rule has no parameters.
21698 @node Improperly_Located_Instantiations
21699 @subsection @code{Improperly_Located_Instantiations}
21700 @cindex @code{Improperly_Located_Instantiations} rule (for @command{gnatcheck})
21703 Flag all generic instantiations in library-level package specs
21704 (including library generic packages) and in all subprogram bodies.
21706 Instantiations in task and entry bodies are not flagged. Instantiations in the
21707 bodies of protected subprograms are flagged.
21709 This rule has no parameters.
21713 @node Improper_Returns
21714 @subsection @code{Improper_Returns}
21715 @cindex @code{Improper_Returns} rule (for @command{gnatcheck})
21718 Flag each explicit @code{return} statement in procedures, and
21719 multiple @code{return} statements in functions.
21720 Diagnostic messages are generated for all @code{return} statements
21721 in a procedure (thus each procedure must be written so that it
21722 returns implicitly at the end of its statement part),
21723 and for all @code{return} statements in a function after the first one.
21724 This rule supports the stylistic convention that each subprogram
21725 should have no more than one point of normal return.
21727 This rule has no parameters.
21730 @node Library_Level_Subprograms
21731 @subsection @code{Library_Level_Subprograms}
21732 @cindex @code{Library_Level_Subprograms} rule (for @command{gnatcheck})
21735 Flag all library-level subprograms (including generic subprogram instantiations).
21737 This rule has no parameters.
21740 @node Local_Packages
21741 @subsection @code{Local_Packages}
21742 @cindex @code{Local_Packages} rule (for @command{gnatcheck})
21745 Flag all local packages declared in package and generic package
21747 Local packages in bodies are not flagged.
21749 This rule has no parameters.
21752 @node Improperly_Called_Protected_Entries
21753 @subsection @code{Improperly_Called_Protected_Entries} (under construction, GLOBAL)
21754 @cindex @code{Improperly_Called_Protected_Entries} rule (for @command{gnatcheck})
21757 Flag each protected entry that can be called from more than one task.
21759 This rule has no parameters.
21763 @subsection @code{Metrics}
21764 @cindex @code{Metrics} rule (for @command{gnatcheck})
21767 There is a set of checks based on computing a metric value and comparing the
21768 result with the specified upper (or lower, depending on a specific metric)
21769 value specified for a given metric. A construct is flagged if a given metric
21770 is applicable (can be computed) for it and the computed value is greater
21771 then (lover then) the specified upper (lower) bound.
21773 The name of any metric-based rule consists of the prefix @code{Metrics_}
21774 followed by the name of the corresponding metric (see the table below).
21775 For @option{+R} option, each metric-based rule has a numeric parameter
21776 specifying the bound (integer or real, depending on a metric), @option{-R}
21777 option for metric rules does not have a parameter.
21779 The following table shows the metric names for that the corresponding
21780 metrics-based checks are supported by gnatcheck, including the
21781 constraint that must be satisfied by the bound that is specified for the check
21782 and what bound - upper (U) or lower (L) - should be specified.
21784 @multitable {@code{Cyclomatic_Complexity}}{Cyclomatic complexity}{Positive integer}
21786 @headitem Check Name @tab Description @tab Bounds Value
21789 @item @b{Check Name} @tab @b{Description} @tab @b{Bounds Value}
21791 @c Above conditional code is workaround to bug in texi2html (Feb 2008)
21792 @item @code{Essential_Complexity} @tab Essential complexity @tab Positive integer (U)
21793 @item @code{Cyclomatic_Complexity} @tab Cyclomatic complexity @tab Positive integer (U)
21794 @item @code{LSLOC} @tab Logical Source Lines of Code @tab Positive integer (U)
21798 The meaning and the computed values for all these metrics are exactly
21799 the same as for the corresponding metrics in @command{gnatmetric}.
21801 @emph{Example:} the rule
21803 +RMetrics_Cyclomatic_Complexity : 7
21806 means that all bodies with cyclomatic complexity exceeding 7 will be flagged.
21808 To turn OFF the check for cyclomatic complexity metric, use the following option:
21810 -RMetrics_Cyclomatic_Complexity
21814 @node Misnamed_Controlling_Parameters
21815 @subsection @code{Misnamed_Controlling_Parameters}
21816 @cindex @code{Misnamed_Controlling_Parameters} rule (for @command{gnatcheck})
21819 Flags a declaration of a dispatching operation, if the first parameter is
21820 not a controlling one and its name is not @code{This} (the check for
21821 parameter name is not case-sensitive). Declarations of dispatching functions
21822 with controlling result and no controlling parameter are never flagged.
21824 A subprogram body declaration, subprogram renaming declaration of subprogram
21825 body stub is flagged only if it is not a completion of a prior subprogram
21828 This rule has no parameters.
21832 @node Misnamed_Identifiers
21833 @subsection @code{Misnamed_Identifiers}
21834 @cindex @code{Misnamed_Identifiers} rule (for @command{gnatcheck})
21837 Flag the declaration of each identifier that does not have a suffix
21838 corresponding to the kind of entity being declared.
21839 The following declarations are checked:
21846 subtype declarations
21849 constant declarations (but not number declarations)
21852 package renaming declarations (but not generic package renaming
21857 This rule may have parameters. When used without parameters, the rule enforces
21858 the following checks:
21862 type-defining names end with @code{_T}, unless the type is an access type,
21863 in which case the suffix must be @code{_A}
21865 constant names end with @code{_C}
21867 names defining package renamings end with @code{_R}
21871 For a private or incomplete type declaration the following checks are
21872 made for the defining name suffix:
21876 For an incomplete type declaration: if the corresponding full type
21877 declaration is available, the defining identifier from the full type
21878 declaration is checked, but the defining identifier from the incomplete type
21879 declaration is not; otherwise the defining identifier from the incomplete
21880 type declaration is checked against the suffix specified for type
21884 For a private type declaration (including private extensions), the defining
21885 identifier from the private type declaration is checked against the type
21886 suffix (even if the corresponding full declaration is an access type
21887 declaration), and the defining identifier from the corresponding full type
21888 declaration is not checked.
21892 For a deferred constant, the defining name in the corresponding full constant
21893 declaration is not checked.
21895 Defining names of formal types are not checked.
21897 The rule may have the following parameters:
21901 For the @option{+R} option:
21904 Sets the default listed above for all the names to be checked.
21906 @item Type_Suffix=@emph{string}
21907 Specifies the suffix for a type name.
21909 @item Access_Suffix=@emph{string}
21910 Specifies the suffix for an access type name. If
21911 this parameter is set, it overrides for access
21912 types the suffix set by the @code{Type_Suffix} parameter.
21913 For access types, @emph{string} may have the following format:
21914 @emph{suffix1(suffix2)}. That means that an access type name
21915 should have the @emph{suffix1} suffix except for the case when
21916 the designated type is also an access type, in this case the
21917 type name should have the @emph{suffix1 & suffix2} suffix.
21919 @item Class_Access_Suffix=@emph{string}
21920 Specifies the suffix for the name of an access type that points to some class-wide
21921 type. If this parameter is set, it overrides for such access
21922 types the suffix set by the @code{Type_Suffix} or @code{Access_Suffix}
21925 @item Class_Subtype_Suffix=@emph{string}
21926 Specifies the suffix for the name of a subtype that denotes a class-wide type.
21928 @item Constant_Suffix=@emph{string}
21929 Specifies the suffix for a constant name.
21931 @item Renaming_Suffix=@emph{string}
21932 Specifies the suffix for a package renaming name.
21936 For the @option{-R} option:
21939 Remove all the suffixes specified for the
21940 identifier suffix checks, whether by default or
21941 as specified by other rule parameters. All the
21942 checks for this rule are disabled as a result.
21945 Removes the suffix specified for types. This
21946 disables checks for types but does not disable
21947 any other checks for this rule (including the
21948 check for access type names if @code{Access_Suffix} is
21951 @item Access_Suffix
21952 Removes the suffix specified for access types.
21953 This disables checks for access type names but
21954 does not disable any other checks for this rule.
21955 If @code{Type_Suffix} is set, access type names are
21956 checked as ordinary type names.
21958 @item Class_Access_Suffix
21959 Removes the suffix specified for access types pointing to class-wide
21960 type. This disables specific checks for names of access types pointing to
21961 class-wide types but does not disable any other checks for this rule.
21962 If @code{Type_Suffix} is set, access type names are
21963 checked as ordinary type names. If @code{Access_Suffix} is set, these
21964 access types are checked as any other access type name.
21966 @item Class_Subtype_Suffix=@emph{string}
21967 Removes the suffix specified for subtype names.
21968 This disables checks for subtype names but
21969 does not disable any other checks for this rule.
21971 @item Constant_Suffix
21972 Removes the suffix specified for constants. This
21973 disables checks for constant names but does not
21974 disable any other checks for this rule.
21976 @item Renaming_Suffix
21977 Removes the suffix specified for package
21978 renamings. This disables checks for package
21979 renamings but does not disable any other checks
21985 If more than one parameter is used, parameters must be separated by commas.
21987 If more than one option is specified for the @command{gnatcheck} invocation,
21988 a new option overrides the previous one(s).
21990 The @option{+RMisnamed_Identifiers} option (with no parameter) enables
21992 name suffixes specified by previous options used for this rule.
21994 The @option{-RMisnamed_Identifiers} option (with no parameter) disables
21995 all the checks but keeps
21996 all the suffixes specified by previous options used for this rule.
21998 The @emph{string} value must be a valid suffix for an Ada identifier (after
21999 trimming all the leading and trailing space characters, if any).
22000 Parameters are not case sensitive, except the @emph{string} part.
22002 If any error is detected in a rule parameter, the parameter is ignored.
22003 In such a case the options that are set for the rule are not
22008 @node Multiple_Entries_In_Protected_Definitions
22009 @subsection @code{Multiple_Entries_In_Protected_Definitions}
22010 @cindex @code{Multiple_Entries_In_Protected_Definitions} rule (for @command{gnatcheck})
22013 Flag each protected definition (i.e., each protected object/type declaration)
22014 that defines more than one entry.
22015 Diagnostic messages are generated for all the entry declarations
22016 except the first one. An entry family is counted as one entry. Entries from
22017 the private part of the protected definition are also checked.
22019 This rule has no parameters.
22022 @subsection @code{Name_Clashes}
22023 @cindex @code{Name_Clashes} rule (for @command{gnatcheck})
22026 Check that certain names are not used as defining identifiers. To activate
22027 this rule, you need to supply a reference to the dictionary file(s) as a rule
22028 parameter(s) (more then one dictionary file can be specified). If no
22029 dictionary file is set, this rule will not cause anything to be flagged.
22030 Only defining occurrences, not references, are checked.
22031 The check is not case-sensitive.
22033 This rule is enabled by default, but without setting any corresponding
22034 dictionary file(s); thus the default effect is to do no checks.
22036 A dictionary file is a plain text file. The maximum line length for this file
22037 is 1024 characters. If the line is longer then this limit, extra characters
22040 Each line can be either an empty line, a comment line, or a line containing
22041 a list of identifiers separated by space or HT characters.
22042 A comment is an Ada-style comment (from @code{--} to end-of-line).
22043 Identifiers must follow the Ada syntax for identifiers.
22044 A line containing one or more identifiers may end with a comment.
22046 @node Non_Qualified_Aggregates
22047 @subsection @code{Non_Qualified_Aggregates}
22048 @cindex @code{Non_Qualified_Aggregates} rule (for @command{gnatcheck})
22051 Flag each non-qualified aggregate.
22052 A non-qualified aggregate is an
22053 aggregate that is not the expression of a qualified expression. A
22054 string literal is not considered an aggregate, but an array
22055 aggregate of a string type is considered as a normal aggregate.
22056 Aggregates of anonymous array types are not flagged.
22058 This rule has no parameters.
22061 @node Non_Short_Circuit_Operators
22062 @subsection @code{Non_Short_Circuit_Operators}
22063 @cindex @code{Non_Short_Circuit_Operators} rule (for @command{gnatcheck})
22066 Flag all calls to predefined @code{and} and @code{or} operators for
22067 any boolean type. Calls to
22068 user-defined @code{and} and @code{or} and to operators defined by renaming
22069 declarations are not flagged. Calls to predefined @code{and} and @code{or}
22070 operators for modular types or boolean array types are not flagged.
22072 This rule has no parameters.
22076 @node Non_SPARK_Attributes
22077 @subsection @code{Non_SPARK_Attributes}
22078 @cindex @code{Non_SPARK_Attributes} rule (for @command{gnatcheck})
22081 The SPARK language defines the following subset of Ada 95 attribute
22082 designators as those that can be used in SPARK programs. The use of
22083 any other attribute is flagged.
22086 @item @code{'Adjacent}
22089 @item @code{'Ceiling}
22090 @item @code{'Component_Size}
22091 @item @code{'Compose}
22092 @item @code{'Copy_Sign}
22093 @item @code{'Delta}
22094 @item @code{'Denorm}
22095 @item @code{'Digits}
22096 @item @code{'Exponent}
22097 @item @code{'First}
22098 @item @code{'Floor}
22100 @item @code{'Fraction}
22102 @item @code{'Leading_Part}
22103 @item @code{'Length}
22104 @item @code{'Machine}
22105 @item @code{'Machine_Emax}
22106 @item @code{'Machine_Emin}
22107 @item @code{'Machine_Mantissa}
22108 @item @code{'Machine_Overflows}
22109 @item @code{'Machine_Radix}
22110 @item @code{'Machine_Rounds}
22113 @item @code{'Model}
22114 @item @code{'Model_Emin}
22115 @item @code{'Model_Epsilon}
22116 @item @code{'Model_Mantissa}
22117 @item @code{'Model_Small}
22118 @item @code{'Modulus}
22121 @item @code{'Range}
22122 @item @code{'Remainder}
22123 @item @code{'Rounding}
22124 @item @code{'Safe_First}
22125 @item @code{'Safe_Last}
22126 @item @code{'Scaling}
22127 @item @code{'Signed_Zeros}
22129 @item @code{'Small}
22131 @item @code{'Truncation}
22132 @item @code{'Unbiased_Rounding}
22134 @item @code{'Valid}
22138 This rule has no parameters.
22141 @node Non_Tagged_Derived_Types
22142 @subsection @code{Non_Tagged_Derived_Types}
22143 @cindex @code{Non_Tagged_Derived_Types} rule (for @command{gnatcheck})
22146 Flag all derived type declarations that do not have a record extension part.
22148 This rule has no parameters.
22152 @node Non_Visible_Exceptions
22153 @subsection @code{Non_Visible_Exceptions}
22154 @cindex @code{Non_Visible_Exceptions} rule (for @command{gnatcheck})
22157 Flag constructs leading to the possibility of propagating an exception
22158 out of the scope in which the exception is declared.
22159 Two cases are detected:
22163 An exception declaration in a subprogram body, task body or block
22164 statement is flagged if the body or statement does not contain a handler for
22165 that exception or a handler with an @code{others} choice.
22168 A @code{raise} statement in an exception handler of a subprogram body,
22169 task body or block statement is flagged if it (re)raises a locally
22170 declared exception. This may occur under the following circumstances:
22173 it explicitly raises a locally declared exception, or
22175 it does not specify an exception name (i.e., it is simply @code{raise;})
22176 and the enclosing handler contains a locally declared exception in its
22182 Renamings of local exceptions are not flagged.
22184 This rule has no parameters.
22187 @node Numeric_Literals
22188 @subsection @code{Numeric_Literals}
22189 @cindex @code{Numeric_Literals} rule (for @command{gnatcheck})
22192 Flag each use of a numeric literal in an index expression, and in any
22193 circumstance except for the following:
22197 a literal occurring in the initialization expression for a constant
22198 declaration or a named number declaration, or
22201 an integer literal that is less than or equal to a value
22202 specified by the @option{N} rule parameter.
22206 This rule may have the following parameters for the @option{+R} option:
22210 @emph{N} is an integer literal used as the maximal value that is not flagged
22211 (i.e., integer literals not exceeding this value are allowed)
22214 All integer literals are flagged
22218 If no parameters are set, the maximum unflagged value is 1.
22220 The last specified check limit (or the fact that there is no limit at
22221 all) is used when multiple @option{+R} options appear.
22223 The @option{-R} option for this rule has no parameters.
22224 It disables the rule but retains the last specified maximum unflagged value.
22225 If the @option{+R} option subsequently appears, this value is used as the
22226 threshold for the check.
22229 @node OTHERS_In_Aggregates
22230 @subsection @code{OTHERS_In_Aggregates}
22231 @cindex @code{OTHERS_In_Aggregates} rule (for @command{gnatcheck})
22234 Flag each use of an @code{others} choice in extension aggregates.
22235 In record and array aggregates, an @code{others} choice is flagged unless
22236 it is used to refer to all components, or to all but one component.
22238 If, in case of a named array aggregate, there are two associations, one
22239 with an @code{others} choice and another with a discrete range, the
22240 @code{others} choice is flagged even if the discrete range specifies
22241 exactly one component; for example, @code{(1..1 => 0, others => 1)}.
22243 This rule has no parameters.
22245 @node OTHERS_In_CASE_Statements
22246 @subsection @code{OTHERS_In_CASE_Statements}
22247 @cindex @code{OTHERS_In_CASE_Statements} rule (for @command{gnatcheck})
22250 Flag any use of an @code{others} choice in a @code{case} statement.
22252 This rule has no parameters.
22254 @node OTHERS_In_Exception_Handlers
22255 @subsection @code{OTHERS_In_Exception_Handlers}
22256 @cindex @code{OTHERS_In_Exception_Handlers} rule (for @command{gnatcheck})
22259 Flag any use of an @code{others} choice in an exception handler.
22261 This rule has no parameters.
22264 @node Outer_Loop_Exits
22265 @subsection @code{Outer_Loop_Exits}
22266 @cindex @code{Outer_Loop_Exits} rule (for @command{gnatcheck})
22269 Flag each @code{exit} statement containing a loop name that is not the name
22270 of the immediately enclosing @code{loop} statement.
22272 This rule has no parameters.
22275 @node Overloaded_Operators
22276 @subsection @code{Overloaded_Operators}
22277 @cindex @code{Overloaded_Operators} rule (for @command{gnatcheck})
22280 Flag each function declaration that overloads an operator symbol.
22281 A function body is checked only if the body does not have a
22282 separate spec. Formal functions are also checked. For a
22283 renaming declaration, only renaming-as-declaration is checked
22285 This rule has no parameters.
22288 @node Overly_Nested_Control_Structures
22289 @subsection @code{Overly_Nested_Control_Structures}
22290 @cindex @code{Overly_Nested_Control_Structures} rule (for @command{gnatcheck})
22293 Flag each control structure whose nesting level exceeds the value provided
22294 in the rule parameter.
22296 The control structures checked are the following:
22299 @item @code{if} statement
22300 @item @code{case} statement
22301 @item @code{loop} statement
22302 @item Selective accept statement
22303 @item Timed entry call statement
22304 @item Conditional entry call
22305 @item Asynchronous select statement
22309 The rule has the following parameter for the @option{+R} option:
22313 Positive integer specifying the maximal control structure nesting
22314 level that is not flagged
22318 If the parameter for the @option{+R} option is not specified or
22319 if it is not a positive integer, @option{+R} option is ignored.
22321 If more then one option is specified for the gnatcheck call, the later option and
22322 new parameter override the previous one(s).
22325 @node Parameters_Out_Of_Order
22326 @subsection @code{Parameters_Out_Of_Order}
22327 @cindex @code{Parameters_Out_Of_Order} rule (for @command{gnatcheck})
22330 Flag each subprogram and entry declaration whose formal parameters are not
22331 ordered according to the following scheme:
22335 @item @code{in} and @code{access} parameters first,
22336 then @code{in out} parameters,
22337 and then @code{out} parameters;
22339 @item for @code{in} mode, parameters with default initialization expressions
22344 Only the first violation of the described order is flagged.
22346 The following constructs are checked:
22349 @item subprogram declarations (including null procedures);
22350 @item generic subprogram declarations;
22351 @item formal subprogram declarations;
22352 @item entry declarations;
22353 @item subprogram bodies and subprogram body stubs that do not
22354 have separate specifications
22358 Subprogram renamings are not checked.
22360 This rule has no parameters.
22363 @node Positional_Actuals_For_Defaulted_Generic_Parameters
22364 @subsection @code{Positional_Actuals_For_Defaulted_Generic_Parameters}
22365 @cindex @code{Positional_Actuals_For_Defaulted_Generic_Parameters} rule (for @command{gnatcheck})
22368 Flag each generic actual parameter corresponding to a generic formal
22369 parameter with a default initialization, if positional notation is used.
22371 This rule has no parameters.
22373 @node Positional_Actuals_For_Defaulted_Parameters
22374 @subsection @code{Positional_Actuals_For_Defaulted_Parameters}
22375 @cindex @code{Positional_Actuals_For_Defaulted_Parameters} rule (for @command{gnatcheck})
22378 Flag each actual parameter to a subprogram or entry call where the
22379 corresponding formal parameter has a default expression, if positional
22382 This rule has no parameters.
22384 @node Positional_Components
22385 @subsection @code{Positional_Components}
22386 @cindex @code{Positional_Components} rule (for @command{gnatcheck})
22389 Flag each array, record and extension aggregate that includes positional
22392 This rule has no parameters.
22395 @node Positional_Generic_Parameters
22396 @subsection @code{Positional_Generic_Parameters}
22397 @cindex @code{Positional_Generic_Parameters} rule (for @command{gnatcheck})
22400 Flag each instantiation using positional parameter notation.
22402 This rule has no parameters.
22405 @node Positional_Parameters
22406 @subsection @code{Positional_Parameters}
22407 @cindex @code{Positional_Parameters} rule (for @command{gnatcheck})
22410 Flag each subprogram or entry call using positional parameter notation,
22411 except for the following:
22415 Invocations of prefix or infix operators are not flagged
22417 If the called subprogram or entry has only one formal parameter,
22418 the call is not flagged;
22420 If a subprogram call uses the @emph{Object.Operation} notation, then
22423 the first parameter (that is, @emph{Object}) is not flagged;
22425 if the called subprogram has only two parameters, the second parameter
22426 of the call is not flagged;
22431 This rule has no parameters.
22436 @node Predefined_Numeric_Types
22437 @subsection @code{Predefined_Numeric_Types}
22438 @cindex @code{Predefined_Numeric_Types} rule (for @command{gnatcheck})
22441 Flag each explicit use of the name of any numeric type or subtype defined
22442 in package @code{Standard}.
22444 The rationale for this rule is to detect when the
22445 program may depend on platform-specific characteristics of the implementation
22446 of the predefined numeric types. Note that this rule is over-pessimistic;
22447 for example, a program that uses @code{String} indexing
22448 likely needs a variable of type @code{Integer}.
22449 Another example is the flagging of predefined numeric types with explicit
22452 @smallexample @c ada
22453 subtype My_Integer is Integer range Left .. Right;
22454 Vy_Var : My_Integer;
22458 This rule detects only numeric types and subtypes defined in
22459 @code{Standard}. The use of numeric types and subtypes defined in other
22460 predefined packages (such as @code{System.Any_Priority} or
22461 @code{Ada.Text_IO.Count}) is not flagged
22463 This rule has no parameters.
22467 @node Raising_External_Exceptions
22468 @subsection @code{Raising_External_Exceptions}
22469 @cindex @code{Raising_External_Exceptions} rule (for @command{gnatcheck})
22472 Flag any @code{raise} statement, in a program unit declared in a library
22473 package or in a generic library package, for an exception that is
22474 neither a predefined exception nor an exception that is also declared (or
22475 renamed) in the visible part of the package.
22477 This rule has no parameters.
22481 @node Raising_Predefined_Exceptions
22482 @subsection @code{Raising_Predefined_Exceptions}
22483 @cindex @code{Raising_Predefined_Exceptions} rule (for @command{gnatcheck})
22486 Flag each @code{raise} statement that raises a predefined exception
22487 (i.e., one of the exceptions @code{Constraint_Error}, @code{Numeric_Error},
22488 @code{Program_Error}, @code{Storage_Error}, or @code{Tasking_Error}).
22490 This rule has no parameters.
22492 @node Separate_Numeric_Error_Handlers
22493 @subsection @code{Separate_Numeric_Error_Handlers}
22494 @cindex @code{Separate_Numeric_Error_Handlers} rule (for @command{gnatcheck})
22497 Flags each exception handler that contains a choice for
22498 the predefined @code{Constraint_Error} exception, but does not contain
22499 the choice for the predefined @code{Numeric_Error} exception, or
22500 that contains the choice for @code{Numeric_Error}, but does not contain the
22501 choice for @code{Constraint_Error}.
22503 This rule has no parameters.
22507 @subsection @code{Recursion} (under construction, GLOBAL)
22508 @cindex @code{Recursion} rule (for @command{gnatcheck})
22511 Flag recursive subprograms (cycles in the call graph). Declarations, and not
22512 calls, of recursive subprograms are detected.
22514 This rule has no parameters.
22518 @node Side_Effect_Functions
22519 @subsection @code{Side_Effect_Functions} (under construction, GLOBAL)
22520 @cindex @code{Side_Effect_Functions} rule (for @command{gnatcheck})
22523 Flag functions with side effects.
22525 We define a side effect as changing any data object that is not local for the
22526 body of this function.
22528 At the moment, we do NOT consider a side effect any input-output operations
22529 (changing a state or a content of any file).
22531 We do not consider protected functions for this rule (???)
22533 There are the following sources of side effect:
22536 @item Explicit (or direct) side-effect:
22540 direct assignment to a non-local variable;
22543 direct call to an entity that is known to change some data object that is
22544 not local for the body of this function (Note, that if F1 calls F2 and F2
22545 does have a side effect, this does not automatically mean that F1 also
22546 have a side effect, because it may be the case that F2 is declared in
22547 F1's body and it changes some data object that is global for F2, but
22551 @item Indirect side-effect:
22554 Subprogram calls implicitly issued by:
22557 computing initialization expressions from type declarations as a part
22558 of object elaboration or allocator evaluation;
22560 computing implicit parameters of subprogram or entry calls or generic
22565 activation of a task that change some non-local data object (directly or
22569 elaboration code of a package that is a result of a package instantiation;
22572 controlled objects;
22575 @item Situations when we can suspect a side-effect, but the full static check
22576 is either impossible or too hard:
22579 assignment to access variables or to the objects pointed by access
22583 call to a subprogram pointed by access-to-subprogram value
22591 This rule has no parameters.
22595 @subsection @code{Slices}
22596 @cindex @code{Slices} rule (for @command{gnatcheck})
22599 Flag all uses of array slicing
22601 This rule has no parameters.
22604 @node Too_Many_Parents
22605 @subsection @code{Too_Many_Parents}
22606 @cindex @code{Too_Many_Parents} rule (for @command{gnatcheck})
22609 Flags any type declaration, single task declaration or single protected
22610 declaration that has more then @option{N} parents, @option{N} is a parameter
22612 A parent here is either a (sub)type denoted by the subtype mark from the
22613 parent_subtype_indication (in case of a derived type declaration), or
22614 any of the progenitors from the interface list, if any.
22616 This rule has the following (mandatory) parameters for the @option{+R} option:
22620 Positive integer specifying the maximal allowed number of parents.
22624 @node Unassigned_OUT_Parameters
22625 @subsection @code{Unassigned_OUT_Parameters}
22626 @cindex @code{Unassigned_OUT_Parameters} rule (for @command{gnatcheck})
22629 Flags procedures' @code{out} parameters that are not assigned, and
22630 identifies the contexts in which the assignments are missing.
22632 An @code{out} parameter is flagged in the statements in the procedure
22633 body's handled sequence of statements (before the procedure body's
22634 @code{exception} part, if any) if this sequence of statements contains
22635 no assignments to the parameter.
22637 An @code{out} parameter is flagged in an exception handler in the exception
22638 part of the procedure body's handled sequence of statements if the handler
22639 contains no assignment to the parameter.
22641 Bodies of generic procedures are also considered.
22643 The following are treated as assignments to an @code{out} parameter:
22647 an assignment statement, with the parameter or some component as the target;
22650 passing the parameter (or one of its components) as an @code{out} or
22651 @code{in out} parameter.
22655 This rule does not have any parameters.
22659 @node Uncommented_BEGIN_In_Package_Bodies
22660 @subsection @code{Uncommented_BEGIN_In_Package_Bodies}
22661 @cindex @code{Uncommented_BEGIN_In_Package_Bodies} rule (for @command{gnatcheck})
22664 Flags each package body with declarations and a statement part that does not
22665 include a trailing comment on the line containing the @code{begin} keyword;
22666 this trailing comment needs to specify the package name and nothing else.
22667 The @code{begin} is not flagged if the package body does not
22668 contain any declarations.
22670 If the @code{begin} keyword is placed on the
22671 same line as the last declaration or the first statement, it is flagged
22672 independently of whether the line contains a trailing comment. The
22673 diagnostic message is attached to the line containing the first statement.
22675 This rule has no parameters.
22677 @node Unconditional_Exits
22678 @subsection @code{Unconditional_Exits}
22679 @cindex @code{Unconditional_Exits} rule (for @command{gnatcheck})
22682 Flag unconditional @code{exit} statements.
22684 This rule has no parameters.
22686 @node Unconstrained_Array_Returns
22687 @subsection @code{Unconstrained_Array_Returns}
22688 @cindex @code{Unconstrained_Array_Returns} rule (for @command{gnatcheck})
22691 Flag each function returning an unconstrained array. Function declarations,
22692 function bodies (and body stubs) having no separate specifications,
22693 and generic function instantiations are checked.
22694 Generic function declarations, function calls and function renamings are
22697 This rule has no parameters.
22699 @node Universal_Ranges
22700 @subsection @code{Universal_Ranges}
22701 @cindex @code{Universal_Ranges} rule (for @command{gnatcheck})
22704 Flag discrete ranges that are a part of an index constraint, constrained
22705 array definition, or @code{for}-loop parameter specification, and whose bounds
22706 are both of type @i{universal_integer}. Ranges that have at least one
22707 bound of a specific type (such as @code{1 .. N}, where @code{N} is a variable
22708 or an expression of non-universal type) are not flagged.
22710 This rule has no parameters.
22713 @node Unnamed_Blocks_And_Loops
22714 @subsection @code{Unnamed_Blocks_And_Loops}
22715 @cindex @code{Unnamed_Blocks_And_Loops} rule (for @command{gnatcheck})
22718 Flag each unnamed block statement and loop statement.
22720 The rule has no parameters.
22725 @node Unused_Subprograms
22726 @subsection @code{Unused_Subprograms} (under construction, GLOBAL)
22727 @cindex @code{Unused_Subprograms} rule (for @command{gnatcheck})
22730 Flag all unused subprograms.
22732 This rule has no parameters.
22738 @node USE_PACKAGE_Clauses
22739 @subsection @code{USE_PACKAGE_Clauses}
22740 @cindex @code{USE_PACKAGE_Clauses} rule (for @command{gnatcheck})
22743 Flag all @code{use} clauses for packages; @code{use type} clauses are
22746 This rule has no parameters.
22749 @node Visible_Components
22750 @subsection @code{Visible_Components}
22751 @cindex @code{Visible_Components} rule (for @command{gnatcheck})
22754 Flags all the type declarations located in the visible part of a library
22755 package or a library generic package that can declare a visible component. A
22756 type is considered as declaring a visible component if it contains a record
22757 definition by its own or as a part of a record extension. Type declaration is
22758 flagged even if it contains a record definition that defines no components.
22760 Declarations located in private parts of local (generic) packages are not
22761 flagged. Declarations in private packages are not flagged.
22763 This rule has no parameters.
22766 @node Volatile_Objects_Without_Address_Clauses
22767 @subsection @code{Volatile_Objects_Without_Address_Clauses}
22768 @cindex @code{Volatile_Objects_Without_Address_Clauses} rule (for @command{gnatcheck})
22771 Flag each volatile object that does not have an address clause.
22773 The following check is made: if the pragma @code{Volatile} is applied to a
22774 data object or to its type, then an address clause must
22775 be supplied for this object.
22777 This rule does not check the components of data objects,
22778 array components that are volatile as a result of the pragma
22779 @code{Volatile_Components}, or objects that are volatile because
22780 they are atomic as a result of pragmas @code{Atomic} or
22781 @code{Atomic_Components}.
22783 Only variable declarations, and not constant declarations, are checked.
22785 This rule has no parameters.
22788 @c *********************************
22789 @node Creating Sample Bodies Using gnatstub
22790 @chapter Creating Sample Bodies Using @command{gnatstub}
22794 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
22795 for library unit declarations.
22797 Note: to invoke @code{gnatstub} with a project file, use the @code{gnat}
22798 driver (see @ref{The GNAT Driver and Project Files}).
22800 To create a body stub, @command{gnatstub} has to compile the library
22801 unit declaration. Therefore, bodies can be created only for legal
22802 library units. Moreover, if a library unit depends semantically upon
22803 units located outside the current directory, you have to provide
22804 the source search path when calling @command{gnatstub}, see the description
22805 of @command{gnatstub} switches below.
22807 By default, all the program unit body stubs generated by @code{gnatstub}
22808 raise the predefined @code{Program_Error} exception, which will catch
22809 accidental calls of generated stubs. This behavior can be changed with
22810 option @option{^--no-exception^/NO_EXCEPTION^} (see below).
22813 * Running gnatstub::
22814 * Switches for gnatstub::
22817 @node Running gnatstub
22818 @section Running @command{gnatstub}
22821 @command{gnatstub} has the command-line interface of the form
22824 $ gnatstub @ovar{switches} @var{filename} @ovar{directory}
22831 is the name of the source file that contains a library unit declaration
22832 for which a body must be created. The file name may contain the path
22834 The file name does not have to follow the GNAT file name conventions. If the
22836 does not follow GNAT file naming conventions, the name of the body file must
22838 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
22839 If the file name follows the GNAT file naming
22840 conventions and the name of the body file is not provided,
22843 of the body file from the argument file name by replacing the @file{.ads}
22845 with the @file{.adb} suffix.
22848 indicates the directory in which the body stub is to be placed (the default
22853 is an optional sequence of switches as described in the next section
22856 @node Switches for gnatstub
22857 @section Switches for @command{gnatstub}
22863 @cindex @option{^-f^/FULL^} (@command{gnatstub})
22864 If the destination directory already contains a file with the name of the
22866 for the argument spec file, replace it with the generated body stub.
22868 @item ^-hs^/HEADER=SPEC^
22869 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
22870 Put the comment header (i.e., all the comments preceding the
22871 compilation unit) from the source of the library unit declaration
22872 into the body stub.
22874 @item ^-hg^/HEADER=GENERAL^
22875 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
22876 Put a sample comment header into the body stub.
22878 @item ^--header-file=@var{filename}^/FROM_HEADER_FILE=@var{filename}^
22879 @cindex @option{^--header-file^/FROM_HEADER_FILE=^} (@command{gnatstub})
22880 Use the content of the file as the comment header for a generated body stub.
22884 @cindex @option{-IDIR} (@command{gnatstub})
22886 @cindex @option{-I-} (@command{gnatstub})
22889 @item /NOCURRENT_DIRECTORY
22890 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
22892 ^These switches have ^This switch has^ the same meaning as in calls to
22894 ^They define ^It defines ^ the source search path in the call to
22895 @command{gcc} issued
22896 by @command{gnatstub} to compile an argument source file.
22898 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
22899 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
22900 This switch has the same meaning as in calls to @command{gcc}.
22901 It defines the additional configuration file to be passed to the call to
22902 @command{gcc} issued
22903 by @command{gnatstub} to compile an argument source file.
22905 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
22906 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
22907 (@var{n} is a non-negative integer). Set the maximum line length in the
22908 body stub to @var{n}; the default is 79. The maximum value that can be
22909 specified is 32767. Note that in the special case of configuration
22910 pragma files, the maximum is always 32767 regardless of whether or
22911 not this switch appears.
22913 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
22914 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
22915 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
22916 the generated body sample to @var{n}.
22917 The default indentation is 3.
22919 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
22920 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
22921 Order local bodies alphabetically. (By default local bodies are ordered
22922 in the same way as the corresponding local specs in the argument spec file.)
22924 @item ^-i^/INDENTATION=^@var{n}
22925 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
22926 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
22928 @item ^-k^/TREE_FILE=SAVE^
22929 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
22930 Do not remove the tree file (i.e., the snapshot of the compiler internal
22931 structures used by @command{gnatstub}) after creating the body stub.
22933 @item ^-l^/LINE_LENGTH=^@var{n}
22934 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
22935 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
22937 @item ^--no-exception^/NO_EXCEPTION^
22938 @cindex @option{^--no-exception^/NO_EXCEPTION^} (@command{gnatstub})
22939 Avoind raising PROGRAM_ERROR in the generated bodies of program unit stubs.
22940 This is not always possible for function stubs.
22942 @item ^--no-local-header^/NO_LOCAL_HEADER^
22943 @cindex @option{^--no-local-header^/NO_LOCAL_HEADER^} (@command{gnatstub})
22944 Do not place local comment header with unit name before body stub for a
22947 @item ^-o ^/BODY=^@var{body-name}
22948 @cindex @option{^-o^/BODY^} (@command{gnatstub})
22949 Body file name. This should be set if the argument file name does not
22951 the GNAT file naming
22952 conventions. If this switch is omitted the default name for the body will be
22954 from the argument file name according to the GNAT file naming conventions.
22957 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
22958 Quiet mode: do not generate a confirmation when a body is
22959 successfully created, and do not generate a message when a body is not
22963 @item ^-r^/TREE_FILE=REUSE^
22964 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
22965 Reuse the tree file (if it exists) instead of creating it. Instead of
22966 creating the tree file for the library unit declaration, @command{gnatstub}
22967 tries to find it in the current directory and use it for creating
22968 a body. If the tree file is not found, no body is created. This option
22969 also implies @option{^-k^/SAVE^}, whether or not
22970 the latter is set explicitly.
22972 @item ^-t^/TREE_FILE=OVERWRITE^
22973 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
22974 Overwrite the existing tree file. If the current directory already
22975 contains the file which, according to the GNAT file naming rules should
22976 be considered as a tree file for the argument source file,
22978 will refuse to create the tree file needed to create a sample body
22979 unless this option is set.
22981 @item ^-v^/VERBOSE^
22982 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
22983 Verbose mode: generate version information.
22987 @c *********************************
22988 @node Generating Ada Bindings for C and C++ headers
22989 @chapter Generating Ada Bindings for C and C++ headers
22993 GNAT now comes with a new experimental binding generator for C and C++
22994 headers which is intended to do 95% of the tedious work of generating
22995 Ada specs from C or C++ header files. Note that this still is a work in
22996 progress, not designed to generate 100% correct Ada specs.
22998 The code generated is using the Ada 2005 syntax, which makes it
22999 easier to interface with other languages than previous versions of Ada.
23002 * Running the binding generator::
23003 * Generating bindings for C++ headers::
23007 @node Running the binding generator
23008 @section Running the binding generator
23011 The binding generator is part of the @command{gcc} compiler and can be
23012 invoked via the @option{-fdump-ada-spec} switch, which will generate Ada
23013 spec files for the header files specified on the command line, and all
23014 header files needed by these files transitivitely. For example:
23017 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
23018 $ gcc -c -gnat05 *.ads
23021 will generate, under GNU/Linux, the following files: @file{time_h.ads},
23022 @file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which
23023 correspond to the files @file{/usr/include/time.h},
23024 @file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005
23025 mode these Ada specs.
23027 The @code{-C} switch tells @command{gcc} to extract comments from headers,
23028 and will attempt to generate corresponding Ada comments.
23030 If you want to generate a single Ada file and not the transitive closure, you
23031 can use instead the @option{-fdump-ada-spec-slim} switch.
23033 Note that we recommend when possible to use the @command{g++} driver to
23034 generate bindings, even for most C headers, since this will in general
23035 generate better Ada specs. For generating bindings for C++ headers, it is
23036 mandatory to use the @command{g++} command, or @command{gcc -x c++} which
23037 is equivalent in this case. If @command{g++} cannot work on your C headers
23038 because of incompatibilities between C and C++, then you can fallback to
23039 @command{gcc} instead.
23041 For an example of better bindings generated from the C++ front-end,
23042 the name of the parameters (when available) are actually ignored by the C
23043 front-end. Consider the following C header:
23046 extern void foo (int variable);
23049 with the C front-end, @code{variable} is ignored, and the above is handled as:
23052 extern void foo (int);
23055 generating a generic:
23058 procedure foo (param1 : int);
23061 with the C++ front-end, the name is available, and we generate:
23064 procedure foo (variable : int);
23067 In some cases, the generated bindings will be more complete or more meaningful
23068 when defining some macros, which you can do via the @option{-D} switch. This
23069 is for example the case with @file{Xlib.h} under GNU/Linux:
23072 g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
23075 The above will generate more complete bindings than a straight call without
23076 the @option{-DXLIB_ILLEGAL_ACCESS} switch.
23078 In other cases, it is not possible to parse a header file in a stand alone
23079 manner, because other include files need to be included first. In this
23080 case, the solution is to create a small header file including the needed
23081 @code{#include} and possible @code{#define} directives. For example, to
23082 generate Ada bindings for @file{readline/readline.h}, you need to first
23083 include @file{stdio.h}, so you can create a file with the following two
23084 lines in e.g. @file{readline1.h}:
23088 #include <readline/readline.h>
23091 and then generate Ada bindings from this file:
23094 $ g++ -c -fdump-ada-spec readline1.h
23097 @node Generating bindings for C++ headers
23098 @section Generating bindings for C++ headers
23101 Generating bindings for C++ headers is done using the same options, always
23102 with the @command{g++} compiler.
23104 In this mode, C++ classes will be mapped to Ada tagged types, constructors
23105 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
23106 multiple inheritance of abstract classes will be mapped to Ada interfaces
23107 (@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional
23108 information on interfacing to C++).
23110 For example, given the following C++ header file:
23117 virtual int Number_Of_Teeth () = 0;
23122 virtual void Set_Owner (char* Name) = 0;
23128 virtual void Set_Age (int New_Age);
23131 class Dog : Animal, Carnivore, Domestic @{
23136 virtual int Number_Of_Teeth ();
23137 virtual void Set_Owner (char* Name);
23145 The corresponding Ada code is generated:
23147 @smallexample @c ada
23150 package Class_Carnivore is
23151 type Carnivore is limited interface;
23152 pragma Import (CPP, Carnivore);
23154 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
23156 use Class_Carnivore;
23158 package Class_Domestic is
23159 type Domestic is limited interface;
23160 pragma Import (CPP, Domestic);
23162 procedure Set_Owner
23163 (this : access Domestic;
23164 Name : Interfaces.C.Strings.chars_ptr) is abstract;
23166 use Class_Domestic;
23168 package Class_Animal is
23169 type Animal is tagged limited record
23170 Age_Count : aliased int;
23172 pragma Import (CPP, Animal);
23174 procedure Set_Age (this : access Animal; New_Age : int);
23175 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
23179 package Class_Dog is
23180 type Dog is new Animal and Carnivore and Domestic with record
23181 Tooth_Count : aliased int;
23182 Owner : Interfaces.C.Strings.chars_ptr;
23184 pragma Import (CPP, Dog);
23186 function Number_Of_Teeth (this : access Dog) return int;
23187 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
23189 procedure Set_Owner
23190 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
23191 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
23193 function New_Dog return Dog;
23194 pragma CPP_Constructor (New_Dog);
23195 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
23206 @item -fdump-ada-spec
23207 @cindex @option{-fdump-ada-spec} (@command{gcc})
23208 Generate Ada spec files for the given header files transitively (including
23209 all header files that these headers depend upon).
23211 @item -fdump-ada-spec-slim
23212 @cindex @option{-fdump-ada-spec-slim} (@command{gcc})
23213 Generate Ada spec files for the header files specified on the command line
23217 @cindex @option{-C} (@command{gcc})
23218 Extract comments from headers and generate Ada comments in the Ada spec files.
23221 @node Other Utility Programs
23222 @chapter Other Utility Programs
23225 This chapter discusses some other utility programs available in the Ada
23229 * Using Other Utility Programs with GNAT::
23230 * The External Symbol Naming Scheme of GNAT::
23231 * Converting Ada Files to html with gnathtml::
23232 * Installing gnathtml::
23239 @node Using Other Utility Programs with GNAT
23240 @section Using Other Utility Programs with GNAT
23243 The object files generated by GNAT are in standard system format and in
23244 particular the debugging information uses this format. This means
23245 programs generated by GNAT can be used with existing utilities that
23246 depend on these formats.
23249 In general, any utility program that works with C will also often work with
23250 Ada programs generated by GNAT. This includes software utilities such as
23251 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
23255 @node The External Symbol Naming Scheme of GNAT
23256 @section The External Symbol Naming Scheme of GNAT
23259 In order to interpret the output from GNAT, when using tools that are
23260 originally intended for use with other languages, it is useful to
23261 understand the conventions used to generate link names from the Ada
23264 All link names are in all lowercase letters. With the exception of library
23265 procedure names, the mechanism used is simply to use the full expanded
23266 Ada name with dots replaced by double underscores. For example, suppose
23267 we have the following package spec:
23269 @smallexample @c ada
23280 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
23281 the corresponding link name is @code{qrs__mn}.
23283 Of course if a @code{pragma Export} is used this may be overridden:
23285 @smallexample @c ada
23290 pragma Export (Var1, C, External_Name => "var1_name");
23292 pragma Export (Var2, C, Link_Name => "var2_link_name");
23299 In this case, the link name for @var{Var1} is whatever link name the
23300 C compiler would assign for the C function @var{var1_name}. This typically
23301 would be either @var{var1_name} or @var{_var1_name}, depending on operating
23302 system conventions, but other possibilities exist. The link name for
23303 @var{Var2} is @var{var2_link_name}, and this is not operating system
23307 One exception occurs for library level procedures. A potential ambiguity
23308 arises between the required name @code{_main} for the C main program,
23309 and the name we would otherwise assign to an Ada library level procedure
23310 called @code{Main} (which might well not be the main program).
23312 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
23313 names. So if we have a library level procedure such as
23315 @smallexample @c ada
23318 procedure Hello (S : String);
23324 the external name of this procedure will be @var{_ada_hello}.
23327 @node Converting Ada Files to html with gnathtml
23328 @section Converting Ada Files to HTML with @code{gnathtml}
23331 This @code{Perl} script allows Ada source files to be browsed using
23332 standard Web browsers. For installation procedure, see the section
23333 @xref{Installing gnathtml}.
23335 Ada reserved keywords are highlighted in a bold font and Ada comments in
23336 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
23337 switch to suppress the generation of cross-referencing information, user
23338 defined variables and types will appear in a different color; you will
23339 be able to click on any identifier and go to its declaration.
23341 The command line is as follow:
23343 $ perl gnathtml.pl @ovar{^switches^options^} @var{ada-files}
23347 You can pass it as many Ada files as you want. @code{gnathtml} will generate
23348 an html file for every ada file, and a global file called @file{index.htm}.
23349 This file is an index of every identifier defined in the files.
23351 The available ^switches^options^ are the following ones:
23355 @cindex @option{-83} (@code{gnathtml})
23356 Only the Ada 83 subset of keywords will be highlighted.
23358 @item -cc @var{color}
23359 @cindex @option{-cc} (@code{gnathtml})
23360 This option allows you to change the color used for comments. The default
23361 value is green. The color argument can be any name accepted by html.
23364 @cindex @option{-d} (@code{gnathtml})
23365 If the Ada files depend on some other files (for instance through
23366 @code{with} clauses, the latter files will also be converted to html.
23367 Only the files in the user project will be converted to html, not the files
23368 in the run-time library itself.
23371 @cindex @option{-D} (@code{gnathtml})
23372 This command is the same as @option{-d} above, but @command{gnathtml} will
23373 also look for files in the run-time library, and generate html files for them.
23375 @item -ext @var{extension}
23376 @cindex @option{-ext} (@code{gnathtml})
23377 This option allows you to change the extension of the generated HTML files.
23378 If you do not specify an extension, it will default to @file{htm}.
23381 @cindex @option{-f} (@code{gnathtml})
23382 By default, gnathtml will generate html links only for global entities
23383 ('with'ed units, global variables and types,@dots{}). If you specify
23384 @option{-f} on the command line, then links will be generated for local
23387 @item -l @var{number}
23388 @cindex @option{-l} (@code{gnathtml})
23389 If this ^switch^option^ is provided and @var{number} is not 0, then
23390 @code{gnathtml} will number the html files every @var{number} line.
23393 @cindex @option{-I} (@code{gnathtml})
23394 Specify a directory to search for library files (@file{.ALI} files) and
23395 source files. You can provide several -I switches on the command line,
23396 and the directories will be parsed in the order of the command line.
23399 @cindex @option{-o} (@code{gnathtml})
23400 Specify the output directory for html files. By default, gnathtml will
23401 saved the generated html files in a subdirectory named @file{html/}.
23403 @item -p @var{file}
23404 @cindex @option{-p} (@code{gnathtml})
23405 If you are using Emacs and the most recent Emacs Ada mode, which provides
23406 a full Integrated Development Environment for compiling, checking,
23407 running and debugging applications, you may use @file{.gpr} files
23408 to give the directories where Emacs can find sources and object files.
23410 Using this ^switch^option^, you can tell gnathtml to use these files.
23411 This allows you to get an html version of your application, even if it
23412 is spread over multiple directories.
23414 @item -sc @var{color}
23415 @cindex @option{-sc} (@code{gnathtml})
23416 This ^switch^option^ allows you to change the color used for symbol
23418 The default value is red. The color argument can be any name accepted by html.
23420 @item -t @var{file}
23421 @cindex @option{-t} (@code{gnathtml})
23422 This ^switch^option^ provides the name of a file. This file contains a list of
23423 file names to be converted, and the effect is exactly as though they had
23424 appeared explicitly on the command line. This
23425 is the recommended way to work around the command line length limit on some
23430 @node Installing gnathtml
23431 @section Installing @code{gnathtml}
23434 @code{Perl} needs to be installed on your machine to run this script.
23435 @code{Perl} is freely available for almost every architecture and
23436 Operating System via the Internet.
23438 On Unix systems, you may want to modify the first line of the script
23439 @code{gnathtml}, to explicitly tell the Operating system where Perl
23440 is. The syntax of this line is:
23442 #!full_path_name_to_perl
23446 Alternatively, you may run the script using the following command line:
23449 $ perl gnathtml.pl @ovar{switches} @var{files}
23458 The GNAT distribution provides an Ada 95 template for the HP Language
23459 Sensitive Editor (LSE), a component of DECset. In order to
23460 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
23467 GNAT supports The HP Performance Coverage Analyzer (PCA), a component
23468 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
23469 the collection phase with the /DEBUG qualifier.
23472 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
23473 $ DEFINE LIB$DEBUG PCA$COLLECTOR
23474 $ RUN/DEBUG <PROGRAM_NAME>
23480 @c ******************************
23481 @node Code Coverage and Profiling
23482 @chapter Code Coverage and Profiling
23483 @cindex Code Coverage
23487 This chapter describes how to use @code{gcov} - coverage testing tool - and
23488 @code{gprof} - profiler tool - on your Ada programs.
23491 * Code Coverage of Ada Programs using gcov::
23492 * Profiling an Ada Program using gprof::
23495 @node Code Coverage of Ada Programs using gcov
23496 @section Code Coverage of Ada Programs using gcov
23498 @cindex -fprofile-arcs
23499 @cindex -ftest-coverage
23501 @cindex Code Coverage
23504 @code{gcov} is a test coverage program: it analyzes the execution of a given
23505 program on selected tests, to help you determine the portions of the program
23506 that are still untested.
23508 @code{gcov} is part of the GCC suite, and is described in detail in the GCC
23509 User's Guide. You can refer to this documentation for a more complete
23512 This chapter provides a quick startup guide, and
23513 details some Gnat-specific features.
23516 * Quick startup guide::
23520 @node Quick startup guide
23521 @subsection Quick startup guide
23523 In order to perform coverage analysis of a program using @code{gcov}, 3
23528 Code instrumentation during the compilation process
23530 Execution of the instrumented program
23532 Execution of the @code{gcov} tool to generate the result.
23535 The code instrumentation needed by gcov is created at the object level:
23536 The source code is not modified in any way, because the instrumentation code is
23537 inserted by gcc during the compilation process. To compile your code with code
23538 coverage activated, you need to recompile your whole project using the
23540 @code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using
23541 @code{-fprofile-arcs}.
23544 $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \
23545 -largs -fprofile-arcs
23548 This compilation process will create @file{.gcno} files together with
23549 the usual object files.
23551 Once the program is compiled with coverage instrumentation, you can
23552 run it as many times as needed - on portions of a test suite for
23553 example. The first execution will produce @file{.gcda} files at the
23554 same location as the @file{.gcno} files. The following executions
23555 will update those files, so that a cumulative result of the covered
23556 portions of the program is generated.
23558 Finally, you need to call the @code{gcov} tool. The different options of
23559 @code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'.
23561 This will create annotated source files with a @file{.gcov} extension:
23562 @file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}.
23564 @node Gnat specifics
23565 @subsection Gnat specifics
23567 Because Ada semantics, portions of the source code may be shared among
23568 several object files. This is the case for example when generics are
23569 involved, when inlining is active or when declarations generate initialisation
23570 calls. In order to take
23571 into account this shared code, you need to call @code{gcov} on all
23572 source files of the tested program at once.
23574 The list of source files might exceed the system's maximum command line
23575 length. In order to bypass this limitation, a new mechanism has been
23576 implemented in @code{gcov}: you can now list all your project's files into a
23577 text file, and provide this file to gcov as a parameter, preceded by a @@
23578 (e.g. @samp{gcov @@mysrclist.txt}).
23580 Note that on AIX compiling a static library with @code{-fprofile-arcs} is
23581 not supported as there can be unresolved symbols during the final link.
23583 @node Profiling an Ada Program using gprof
23584 @section Profiling an Ada Program using gprof
23590 This section is not meant to be an exhaustive documentation of @code{gprof}.
23591 Full documentation for it can be found in the GNU Profiler User's Guide
23592 documentation that is part of this GNAT distribution.
23594 Profiling a program helps determine the parts of a program that are executed
23595 most often, and are therefore the most time-consuming.
23597 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
23598 better handle Ada programs and multitasking.
23599 It is currently supported on the following platforms
23604 solaris sparc/sparc64/x86
23610 In order to profile a program using @code{gprof}, 3 steps are needed:
23614 Code instrumentation, requiring a full recompilation of the project with the
23617 Execution of the program under the analysis conditions, i.e. with the desired
23620 Analysis of the results using the @code{gprof} tool.
23624 The following sections detail the different steps, and indicate how
23625 to interpret the results:
23627 * Compilation for profiling::
23628 * Program execution::
23630 * Interpretation of profiling results::
23633 @node Compilation for profiling
23634 @subsection Compilation for profiling
23638 In order to profile a program the first step is to tell the compiler
23639 to generate the necessary profiling information. The compiler switch to be used
23640 is @code{-pg}, which must be added to other compilation switches. This
23641 switch needs to be specified both during compilation and link stages, and can
23642 be specified once when using gnatmake:
23645 gnatmake -f -pg -P my_project
23649 Note that only the objects that were compiled with the @samp{-pg} switch will be
23650 profiled; if you need to profile your whole project, use the
23651 @samp{-f} gnatmake switch to force full recompilation.
23653 @node Program execution
23654 @subsection Program execution
23657 Once the program has been compiled for profiling, you can run it as usual.
23659 The only constraint imposed by profiling is that the program must terminate
23660 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
23663 Once the program completes execution, a data file called @file{gmon.out} is
23664 generated in the directory where the program was launched from. If this file
23665 already exists, it will be overwritten.
23667 @node Running gprof
23668 @subsection Running gprof
23671 The @code{gprof} tool is called as follow:
23674 gprof my_prog gmon.out
23685 The complete form of the gprof command line is the following:
23688 gprof [^switches^options^] [executable [data-file]]
23692 @code{gprof} supports numerous ^switch^options^. The order of these
23693 ^switch^options^ does not matter. The full list of options can be found in
23694 the GNU Profiler User's Guide documentation that comes with this documentation.
23696 The following is the subset of those switches that is most relevant:
23700 @item --demangle[=@var{style}]
23701 @itemx --no-demangle
23702 @cindex @option{--demangle} (@code{gprof})
23703 These options control whether symbol names should be demangled when
23704 printing output. The default is to demangle C++ symbols. The
23705 @code{--no-demangle} option may be used to turn off demangling. Different
23706 compilers have different mangling styles. The optional demangling style
23707 argument can be used to choose an appropriate demangling style for your
23708 compiler, in particular Ada symbols generated by GNAT can be demangled using
23709 @code{--demangle=gnat}.
23711 @item -e @var{function_name}
23712 @cindex @option{-e} (@code{gprof})
23713 The @samp{-e @var{function}} option tells @code{gprof} not to print
23714 information about the function @var{function_name} (and its
23715 children@dots{}) in the call graph. The function will still be listed
23716 as a child of any functions that call it, but its index number will be
23717 shown as @samp{[not printed]}. More than one @samp{-e} option may be
23718 given; only one @var{function_name} may be indicated with each @samp{-e}
23721 @item -E @var{function_name}
23722 @cindex @option{-E} (@code{gprof})
23723 The @code{-E @var{function}} option works like the @code{-e} option, but
23724 execution time spent in the function (and children who were not called from
23725 anywhere else), will not be used to compute the percentages-of-time for
23726 the call graph. More than one @samp{-E} option may be given; only one
23727 @var{function_name} may be indicated with each @samp{-E} option.
23729 @item -f @var{function_name}
23730 @cindex @option{-f} (@code{gprof})
23731 The @samp{-f @var{function}} option causes @code{gprof} to limit the
23732 call graph to the function @var{function_name} and its children (and
23733 their children@dots{}). More than one @samp{-f} option may be given;
23734 only one @var{function_name} may be indicated with each @samp{-f}
23737 @item -F @var{function_name}
23738 @cindex @option{-F} (@code{gprof})
23739 The @samp{-F @var{function}} option works like the @code{-f} option, but
23740 only time spent in the function and its children (and their
23741 children@dots{}) will be used to determine total-time and
23742 percentages-of-time for the call graph. More than one @samp{-F} option
23743 may be given; only one @var{function_name} may be indicated with each
23744 @samp{-F} option. The @samp{-F} option overrides the @samp{-E} option.
23748 @node Interpretation of profiling results
23749 @subsection Interpretation of profiling results
23753 The results of the profiling analysis are represented by two arrays: the
23754 'flat profile' and the 'call graph'. Full documentation of those outputs
23755 can be found in the GNU Profiler User's Guide.
23757 The flat profile shows the time spent in each function of the program, and how
23758 many time it has been called. This allows you to locate easily the most
23759 time-consuming functions.
23761 The call graph shows, for each subprogram, the subprograms that call it,
23762 and the subprograms that it calls. It also provides an estimate of the time
23763 spent in each of those callers/called subprograms.
23766 @c ******************************
23767 @node Running and Debugging Ada Programs
23768 @chapter Running and Debugging Ada Programs
23772 This chapter discusses how to debug Ada programs.
23774 It applies to GNAT on the Alpha OpenVMS platform;
23775 for I64 OpenVMS please refer to the @cite{OpenVMS Debugger Manual},
23776 since HP has implemented Ada support in the OpenVMS debugger on I64.
23779 An incorrect Ada program may be handled in three ways by the GNAT compiler:
23783 The illegality may be a violation of the static semantics of Ada. In
23784 that case GNAT diagnoses the constructs in the program that are illegal.
23785 It is then a straightforward matter for the user to modify those parts of
23789 The illegality may be a violation of the dynamic semantics of Ada. In
23790 that case the program compiles and executes, but may generate incorrect
23791 results, or may terminate abnormally with some exception.
23794 When presented with a program that contains convoluted errors, GNAT
23795 itself may terminate abnormally without providing full diagnostics on
23796 the incorrect user program.
23800 * The GNAT Debugger GDB::
23802 * Introduction to GDB Commands::
23803 * Using Ada Expressions::
23804 * Calling User-Defined Subprograms::
23805 * Using the Next Command in a Function::
23808 * Debugging Generic Units::
23809 * GNAT Abnormal Termination or Failure to Terminate::
23810 * Naming Conventions for GNAT Source Files::
23811 * Getting Internal Debugging Information::
23812 * Stack Traceback::
23818 @node The GNAT Debugger GDB
23819 @section The GNAT Debugger GDB
23822 @code{GDB} is a general purpose, platform-independent debugger that
23823 can be used to debug mixed-language programs compiled with @command{gcc},
23824 and in particular is capable of debugging Ada programs compiled with
23825 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
23826 complex Ada data structures.
23828 @xref{Top,, Debugging with GDB, gdb, Debugging with GDB},
23830 located in the GNU:[DOCS] directory,
23832 for full details on the usage of @code{GDB}, including a section on
23833 its usage on programs. This manual should be consulted for full
23834 details. The section that follows is a brief introduction to the
23835 philosophy and use of @code{GDB}.
23837 When GNAT programs are compiled, the compiler optionally writes debugging
23838 information into the generated object file, including information on
23839 line numbers, and on declared types and variables. This information is
23840 separate from the generated code. It makes the object files considerably
23841 larger, but it does not add to the size of the actual executable that
23842 will be loaded into memory, and has no impact on run-time performance. The
23843 generation of debug information is triggered by the use of the
23844 ^-g^/DEBUG^ switch in the @command{gcc} or @command{gnatmake} command
23845 used to carry out the compilations. It is important to emphasize that
23846 the use of these options does not change the generated code.
23848 The debugging information is written in standard system formats that
23849 are used by many tools, including debuggers and profilers. The format
23850 of the information is typically designed to describe C types and
23851 semantics, but GNAT implements a translation scheme which allows full
23852 details about Ada types and variables to be encoded into these
23853 standard C formats. Details of this encoding scheme may be found in
23854 the file exp_dbug.ads in the GNAT source distribution. However, the
23855 details of this encoding are, in general, of no interest to a user,
23856 since @code{GDB} automatically performs the necessary decoding.
23858 When a program is bound and linked, the debugging information is
23859 collected from the object files, and stored in the executable image of
23860 the program. Again, this process significantly increases the size of
23861 the generated executable file, but it does not increase the size of
23862 the executable program itself. Furthermore, if this program is run in
23863 the normal manner, it runs exactly as if the debug information were
23864 not present, and takes no more actual memory.
23866 However, if the program is run under control of @code{GDB}, the
23867 debugger is activated. The image of the program is loaded, at which
23868 point it is ready to run. If a run command is given, then the program
23869 will run exactly as it would have if @code{GDB} were not present. This
23870 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
23871 entirely non-intrusive until a breakpoint is encountered. If no
23872 breakpoint is ever hit, the program will run exactly as it would if no
23873 debugger were present. When a breakpoint is hit, @code{GDB} accesses
23874 the debugging information and can respond to user commands to inspect
23875 variables, and more generally to report on the state of execution.
23879 @section Running GDB
23882 This section describes how to initiate the debugger.
23883 @c The above sentence is really just filler, but it was otherwise
23884 @c clumsy to get the first paragraph nonindented given the conditional
23885 @c nature of the description
23888 The debugger can be launched from a @code{GPS} menu or
23889 directly from the command line. The description below covers the latter use.
23890 All the commands shown can be used in the @code{GPS} debug console window,
23891 but there are usually more GUI-based ways to achieve the same effect.
23894 The command to run @code{GDB} is
23897 $ ^gdb program^GDB PROGRAM^
23901 where @code{^program^PROGRAM^} is the name of the executable file. This
23902 activates the debugger and results in a prompt for debugger commands.
23903 The simplest command is simply @code{run}, which causes the program to run
23904 exactly as if the debugger were not present. The following section
23905 describes some of the additional commands that can be given to @code{GDB}.
23907 @c *******************************
23908 @node Introduction to GDB Commands
23909 @section Introduction to GDB Commands
23912 @code{GDB} contains a large repertoire of commands. @xref{Top,,
23913 Debugging with GDB, gdb, Debugging with GDB},
23915 located in the GNU:[DOCS] directory,
23917 for extensive documentation on the use
23918 of these commands, together with examples of their use. Furthermore,
23919 the command @command{help} invoked from within GDB activates a simple help
23920 facility which summarizes the available commands and their options.
23921 In this section we summarize a few of the most commonly
23922 used commands to give an idea of what @code{GDB} is about. You should create
23923 a simple program with debugging information and experiment with the use of
23924 these @code{GDB} commands on the program as you read through the
23928 @item set args @var{arguments}
23929 The @var{arguments} list above is a list of arguments to be passed to
23930 the program on a subsequent run command, just as though the arguments
23931 had been entered on a normal invocation of the program. The @code{set args}
23932 command is not needed if the program does not require arguments.
23935 The @code{run} command causes execution of the program to start from
23936 the beginning. If the program is already running, that is to say if
23937 you are currently positioned at a breakpoint, then a prompt will ask
23938 for confirmation that you want to abandon the current execution and
23941 @item breakpoint @var{location}
23942 The breakpoint command sets a breakpoint, that is to say a point at which
23943 execution will halt and @code{GDB} will await further
23944 commands. @var{location} is
23945 either a line number within a file, given in the format @code{file:linenumber},
23946 or it is the name of a subprogram. If you request that a breakpoint be set on
23947 a subprogram that is overloaded, a prompt will ask you to specify on which of
23948 those subprograms you want to breakpoint. You can also
23949 specify that all of them should be breakpointed. If the program is run
23950 and execution encounters the breakpoint, then the program
23951 stops and @code{GDB} signals that the breakpoint was encountered by
23952 printing the line of code before which the program is halted.
23954 @item breakpoint exception @var{name}
23955 A special form of the breakpoint command which breakpoints whenever
23956 exception @var{name} is raised.
23957 If @var{name} is omitted,
23958 then a breakpoint will occur when any exception is raised.
23960 @item print @var{expression}
23961 This will print the value of the given expression. Most simple
23962 Ada expression formats are properly handled by @code{GDB}, so the expression
23963 can contain function calls, variables, operators, and attribute references.
23966 Continues execution following a breakpoint, until the next breakpoint or the
23967 termination of the program.
23970 Executes a single line after a breakpoint. If the next statement
23971 is a subprogram call, execution continues into (the first statement of)
23972 the called subprogram.
23975 Executes a single line. If this line is a subprogram call, executes and
23976 returns from the call.
23979 Lists a few lines around the current source location. In practice, it
23980 is usually more convenient to have a separate edit window open with the
23981 relevant source file displayed. Successive applications of this command
23982 print subsequent lines. The command can be given an argument which is a
23983 line number, in which case it displays a few lines around the specified one.
23986 Displays a backtrace of the call chain. This command is typically
23987 used after a breakpoint has occurred, to examine the sequence of calls that
23988 leads to the current breakpoint. The display includes one line for each
23989 activation record (frame) corresponding to an active subprogram.
23992 At a breakpoint, @code{GDB} can display the values of variables local
23993 to the current frame. The command @code{up} can be used to
23994 examine the contents of other active frames, by moving the focus up
23995 the stack, that is to say from callee to caller, one frame at a time.
23998 Moves the focus of @code{GDB} down from the frame currently being
23999 examined to the frame of its callee (the reverse of the previous command),
24001 @item frame @var{n}
24002 Inspect the frame with the given number. The value 0 denotes the frame
24003 of the current breakpoint, that is to say the top of the call stack.
24008 The above list is a very short introduction to the commands that
24009 @code{GDB} provides. Important additional capabilities, including conditional
24010 breakpoints, the ability to execute command sequences on a breakpoint,
24011 the ability to debug at the machine instruction level and many other
24012 features are described in detail in @ref{Top,, Debugging with GDB, gdb,
24013 Debugging with GDB}. Note that most commands can be abbreviated
24014 (for example, c for continue, bt for backtrace).
24016 @node Using Ada Expressions
24017 @section Using Ada Expressions
24018 @cindex Ada expressions
24021 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
24022 extensions. The philosophy behind the design of this subset is
24026 That @code{GDB} should provide basic literals and access to operations for
24027 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
24028 leaving more sophisticated computations to subprograms written into the
24029 program (which therefore may be called from @code{GDB}).
24032 That type safety and strict adherence to Ada language restrictions
24033 are not particularly important to the @code{GDB} user.
24036 That brevity is important to the @code{GDB} user.
24040 Thus, for brevity, the debugger acts as if there were
24041 implicit @code{with} and @code{use} clauses in effect for all user-written
24042 packages, thus making it unnecessary to fully qualify most names with
24043 their packages, regardless of context. Where this causes ambiguity,
24044 @code{GDB} asks the user's intent.
24046 For details on the supported Ada syntax, see @ref{Top,, Debugging with
24047 GDB, gdb, Debugging with GDB}.
24049 @node Calling User-Defined Subprograms
24050 @section Calling User-Defined Subprograms
24053 An important capability of @code{GDB} is the ability to call user-defined
24054 subprograms while debugging. This is achieved simply by entering
24055 a subprogram call statement in the form:
24058 call subprogram-name (parameters)
24062 The keyword @code{call} can be omitted in the normal case where the
24063 @code{subprogram-name} does not coincide with any of the predefined
24064 @code{GDB} commands.
24066 The effect is to invoke the given subprogram, passing it the
24067 list of parameters that is supplied. The parameters can be expressions and
24068 can include variables from the program being debugged. The
24069 subprogram must be defined
24070 at the library level within your program, and @code{GDB} will call the
24071 subprogram within the environment of your program execution (which
24072 means that the subprogram is free to access or even modify variables
24073 within your program).
24075 The most important use of this facility is in allowing the inclusion of
24076 debugging routines that are tailored to particular data structures
24077 in your program. Such debugging routines can be written to provide a suitably
24078 high-level description of an abstract type, rather than a low-level dump
24079 of its physical layout. After all, the standard
24080 @code{GDB print} command only knows the physical layout of your
24081 types, not their abstract meaning. Debugging routines can provide information
24082 at the desired semantic level and are thus enormously useful.
24084 For example, when debugging GNAT itself, it is crucial to have access to
24085 the contents of the tree nodes used to represent the program internally.
24086 But tree nodes are represented simply by an integer value (which in turn
24087 is an index into a table of nodes).
24088 Using the @code{print} command on a tree node would simply print this integer
24089 value, which is not very useful. But the PN routine (defined in file
24090 treepr.adb in the GNAT sources) takes a tree node as input, and displays
24091 a useful high level representation of the tree node, which includes the
24092 syntactic category of the node, its position in the source, the integers
24093 that denote descendant nodes and parent node, as well as varied
24094 semantic information. To study this example in more detail, you might want to
24095 look at the body of the PN procedure in the stated file.
24097 @node Using the Next Command in a Function
24098 @section Using the Next Command in a Function
24101 When you use the @code{next} command in a function, the current source
24102 location will advance to the next statement as usual. A special case
24103 arises in the case of a @code{return} statement.
24105 Part of the code for a return statement is the ``epilog'' of the function.
24106 This is the code that returns to the caller. There is only one copy of
24107 this epilog code, and it is typically associated with the last return
24108 statement in the function if there is more than one return. In some
24109 implementations, this epilog is associated with the first statement
24112 The result is that if you use the @code{next} command from a return
24113 statement that is not the last return statement of the function you
24114 may see a strange apparent jump to the last return statement or to
24115 the start of the function. You should simply ignore this odd jump.
24116 The value returned is always that from the first return statement
24117 that was stepped through.
24119 @node Ada Exceptions
24120 @section Breaking on Ada Exceptions
24124 You can set breakpoints that trip when your program raises
24125 selected exceptions.
24128 @item break exception
24129 Set a breakpoint that trips whenever (any task in the) program raises
24132 @item break exception @var{name}
24133 Set a breakpoint that trips whenever (any task in the) program raises
24134 the exception @var{name}.
24136 @item break exception unhandled
24137 Set a breakpoint that trips whenever (any task in the) program raises an
24138 exception for which there is no handler.
24140 @item info exceptions
24141 @itemx info exceptions @var{regexp}
24142 The @code{info exceptions} command permits the user to examine all defined
24143 exceptions within Ada programs. With a regular expression, @var{regexp}, as
24144 argument, prints out only those exceptions whose name matches @var{regexp}.
24152 @code{GDB} allows the following task-related commands:
24156 This command shows a list of current Ada tasks, as in the following example:
24163 ID TID P-ID Thread Pri State Name
24164 1 8088000 0 807e000 15 Child Activation Wait main_task
24165 2 80a4000 1 80ae000 15 Accept/Select Wait b
24166 3 809a800 1 80a4800 15 Child Activation Wait a
24167 * 4 80ae800 3 80b8000 15 Running c
24171 In this listing, the asterisk before the first task indicates it to be the
24172 currently running task. The first column lists the task ID that is used
24173 to refer to tasks in the following commands.
24175 @item break @var{linespec} task @var{taskid}
24176 @itemx break @var{linespec} task @var{taskid} if @dots{}
24177 @cindex Breakpoints and tasks
24178 These commands are like the @code{break @dots{} thread @dots{}}.
24179 @var{linespec} specifies source lines.
24181 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
24182 to specify that you only want @code{GDB} to stop the program when a
24183 particular Ada task reaches this breakpoint. @var{taskid} is one of the
24184 numeric task identifiers assigned by @code{GDB}, shown in the first
24185 column of the @samp{info tasks} display.
24187 If you do not specify @samp{task @var{taskid}} when you set a
24188 breakpoint, the breakpoint applies to @emph{all} tasks of your
24191 You can use the @code{task} qualifier on conditional breakpoints as
24192 well; in this case, place @samp{task @var{taskid}} before the
24193 breakpoint condition (before the @code{if}).
24195 @item task @var{taskno}
24196 @cindex Task switching
24198 This command allows to switch to the task referred by @var{taskno}. In
24199 particular, This allows to browse the backtrace of the specified
24200 task. It is advised to switch back to the original task before
24201 continuing execution otherwise the scheduling of the program may be
24206 For more detailed information on the tasking support,
24207 see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}.
24209 @node Debugging Generic Units
24210 @section Debugging Generic Units
24211 @cindex Debugging Generic Units
24215 GNAT always uses code expansion for generic instantiation. This means that
24216 each time an instantiation occurs, a complete copy of the original code is
24217 made, with appropriate substitutions of formals by actuals.
24219 It is not possible to refer to the original generic entities in
24220 @code{GDB}, but it is always possible to debug a particular instance of
24221 a generic, by using the appropriate expanded names. For example, if we have
24223 @smallexample @c ada
24228 generic package k is
24229 procedure kp (v1 : in out integer);
24233 procedure kp (v1 : in out integer) is
24239 package k1 is new k;
24240 package k2 is new k;
24242 var : integer := 1;
24255 Then to break on a call to procedure kp in the k2 instance, simply
24259 (gdb) break g.k2.kp
24263 When the breakpoint occurs, you can step through the code of the
24264 instance in the normal manner and examine the values of local variables, as for
24267 @node GNAT Abnormal Termination or Failure to Terminate
24268 @section GNAT Abnormal Termination or Failure to Terminate
24269 @cindex GNAT Abnormal Termination or Failure to Terminate
24272 When presented with programs that contain serious errors in syntax
24274 GNAT may on rare occasions experience problems in operation, such
24276 segmentation fault or illegal memory access, raising an internal
24277 exception, terminating abnormally, or failing to terminate at all.
24278 In such cases, you can activate
24279 various features of GNAT that can help you pinpoint the construct in your
24280 program that is the likely source of the problem.
24282 The following strategies are presented in increasing order of
24283 difficulty, corresponding to your experience in using GNAT and your
24284 familiarity with compiler internals.
24288 Run @command{gcc} with the @option{-gnatf}. This first
24289 switch causes all errors on a given line to be reported. In its absence,
24290 only the first error on a line is displayed.
24292 The @option{-gnatdO} switch causes errors to be displayed as soon as they
24293 are encountered, rather than after compilation is terminated. If GNAT
24294 terminates prematurely or goes into an infinite loop, the last error
24295 message displayed may help to pinpoint the culprit.
24298 Run @command{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this
24299 mode, @command{gcc} produces ongoing information about the progress of the
24300 compilation and provides the name of each procedure as code is
24301 generated. This switch allows you to find which Ada procedure was being
24302 compiled when it encountered a code generation problem.
24305 @cindex @option{-gnatdc} switch
24306 Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
24307 switch that does for the front-end what @option{^-v^VERBOSE^} does
24308 for the back end. The system prints the name of each unit,
24309 either a compilation unit or nested unit, as it is being analyzed.
24311 Finally, you can start
24312 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
24313 front-end of GNAT, and can be run independently (normally it is just
24314 called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you
24315 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
24316 @code{where} command is the first line of attack; the variable
24317 @code{lineno} (seen by @code{print lineno}), used by the second phase of
24318 @code{gnat1} and by the @command{gcc} backend, indicates the source line at
24319 which the execution stopped, and @code{input_file name} indicates the name of
24323 @node Naming Conventions for GNAT Source Files
24324 @section Naming Conventions for GNAT Source Files
24327 In order to examine the workings of the GNAT system, the following
24328 brief description of its organization may be helpful:
24332 Files with prefix @file{^sc^SC^} contain the lexical scanner.
24335 All files prefixed with @file{^par^PAR^} are components of the parser. The
24336 numbers correspond to chapters of the Ada Reference Manual. For example,
24337 parsing of select statements can be found in @file{par-ch9.adb}.
24340 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
24341 numbers correspond to chapters of the Ada standard. For example, all
24342 issues involving context clauses can be found in @file{sem_ch10.adb}. In
24343 addition, some features of the language require sufficient special processing
24344 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
24345 dynamic dispatching, etc.
24348 All files prefixed with @file{^exp^EXP^} perform normalization and
24349 expansion of the intermediate representation (abstract syntax tree, or AST).
24350 these files use the same numbering scheme as the parser and semantics files.
24351 For example, the construction of record initialization procedures is done in
24352 @file{exp_ch3.adb}.
24355 The files prefixed with @file{^bind^BIND^} implement the binder, which
24356 verifies the consistency of the compilation, determines an order of
24357 elaboration, and generates the bind file.
24360 The files @file{atree.ads} and @file{atree.adb} detail the low-level
24361 data structures used by the front-end.
24364 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
24365 the abstract syntax tree as produced by the parser.
24368 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
24369 all entities, computed during semantic analysis.
24372 Library management issues are dealt with in files with prefix
24378 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
24379 defined in Annex A.
24384 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
24385 defined in Annex B.
24389 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
24390 both language-defined children and GNAT run-time routines.
24394 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
24395 general-purpose packages, fully documented in their specs. All
24396 the other @file{.c} files are modifications of common @command{gcc} files.
24399 @node Getting Internal Debugging Information
24400 @section Getting Internal Debugging Information
24403 Most compilers have internal debugging switches and modes. GNAT
24404 does also, except GNAT internal debugging switches and modes are not
24405 secret. A summary and full description of all the compiler and binder
24406 debug flags are in the file @file{debug.adb}. You must obtain the
24407 sources of the compiler to see the full detailed effects of these flags.
24409 The switches that print the source of the program (reconstructed from
24410 the internal tree) are of general interest for user programs, as are the
24412 the full internal tree, and the entity table (the symbol table
24413 information). The reconstructed source provides a readable version of the
24414 program after the front-end has completed analysis and expansion,
24415 and is useful when studying the performance of specific constructs.
24416 For example, constraint checks are indicated, complex aggregates
24417 are replaced with loops and assignments, and tasking primitives
24418 are replaced with run-time calls.
24420 @node Stack Traceback
24421 @section Stack Traceback
24423 @cindex stack traceback
24424 @cindex stack unwinding
24427 Traceback is a mechanism to display the sequence of subprogram calls that
24428 leads to a specified execution point in a program. Often (but not always)
24429 the execution point is an instruction at which an exception has been raised.
24430 This mechanism is also known as @i{stack unwinding} because it obtains
24431 its information by scanning the run-time stack and recovering the activation
24432 records of all active subprograms. Stack unwinding is one of the most
24433 important tools for program debugging.
24435 The first entry stored in traceback corresponds to the deepest calling level,
24436 that is to say the subprogram currently executing the instruction
24437 from which we want to obtain the traceback.
24439 Note that there is no runtime performance penalty when stack traceback
24440 is enabled, and no exception is raised during program execution.
24443 * Non-Symbolic Traceback::
24444 * Symbolic Traceback::
24447 @node Non-Symbolic Traceback
24448 @subsection Non-Symbolic Traceback
24449 @cindex traceback, non-symbolic
24452 Note: this feature is not supported on all platforms. See
24453 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
24457 * Tracebacks From an Unhandled Exception::
24458 * Tracebacks From Exception Occurrences (non-symbolic)::
24459 * Tracebacks From Anywhere in a Program (non-symbolic)::
24462 @node Tracebacks From an Unhandled Exception
24463 @subsubsection Tracebacks From an Unhandled Exception
24466 A runtime non-symbolic traceback is a list of addresses of call instructions.
24467 To enable this feature you must use the @option{-E}
24468 @code{gnatbind}'s option. With this option a stack traceback is stored as part
24469 of exception information. You can retrieve this information using the
24470 @code{addr2line} tool.
24472 Here is a simple example:
24474 @smallexample @c ada
24480 raise Constraint_Error;
24495 $ gnatmake stb -bargs -E
24498 Execution terminated by unhandled exception
24499 Exception name: CONSTRAINT_ERROR
24501 Call stack traceback locations:
24502 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24506 As we see the traceback lists a sequence of addresses for the unhandled
24507 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
24508 guess that this exception come from procedure P1. To translate these
24509 addresses into the source lines where the calls appear, the
24510 @code{addr2line} tool, described below, is invaluable. The use of this tool
24511 requires the program to be compiled with debug information.
24514 $ gnatmake -g stb -bargs -E
24517 Execution terminated by unhandled exception
24518 Exception name: CONSTRAINT_ERROR
24520 Call stack traceback locations:
24521 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
24523 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
24524 0x4011f1 0x77e892a4
24526 00401373 at d:/stb/stb.adb:5
24527 0040138B at d:/stb/stb.adb:10
24528 0040139C at d:/stb/stb.adb:14
24529 00401335 at d:/stb/b~stb.adb:104
24530 004011C4 at /build/@dots{}/crt1.c:200
24531 004011F1 at /build/@dots{}/crt1.c:222
24532 77E892A4 in ?? at ??:0
24536 The @code{addr2line} tool has several other useful options:
24540 to get the function name corresponding to any location
24542 @item --demangle=gnat
24543 to use the gnat decoding mode for the function names. Note that
24544 for binutils version 2.9.x the option is simply @option{--demangle}.
24548 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
24549 0x40139c 0x401335 0x4011c4 0x4011f1
24551 00401373 in stb.p1 at d:/stb/stb.adb:5
24552 0040138B in stb.p2 at d:/stb/stb.adb:10
24553 0040139C in stb at d:/stb/stb.adb:14
24554 00401335 in main at d:/stb/b~stb.adb:104
24555 004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200
24556 004011F1 in <mainCRTStartup> at /build/@dots{}/crt1.c:222
24560 From this traceback we can see that the exception was raised in
24561 @file{stb.adb} at line 5, which was reached from a procedure call in
24562 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
24563 which contains the call to the main program.
24564 @xref{Running gnatbind}. The remaining entries are assorted runtime routines,
24565 and the output will vary from platform to platform.
24567 It is also possible to use @code{GDB} with these traceback addresses to debug
24568 the program. For example, we can break at a given code location, as reported
24569 in the stack traceback:
24575 Furthermore, this feature is not implemented inside Windows DLL. Only
24576 the non-symbolic traceback is reported in this case.
24579 (gdb) break *0x401373
24580 Breakpoint 1 at 0x401373: file stb.adb, line 5.
24584 It is important to note that the stack traceback addresses
24585 do not change when debug information is included. This is particularly useful
24586 because it makes it possible to release software without debug information (to
24587 minimize object size), get a field report that includes a stack traceback
24588 whenever an internal bug occurs, and then be able to retrieve the sequence
24589 of calls with the same program compiled with debug information.
24591 @node Tracebacks From Exception Occurrences (non-symbolic)
24592 @subsubsection Tracebacks From Exception Occurrences
24595 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
24596 The stack traceback is attached to the exception information string, and can
24597 be retrieved in an exception handler within the Ada program, by means of the
24598 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
24600 @smallexample @c ada
24602 with Ada.Exceptions;
24607 use Ada.Exceptions;
24615 Text_IO.Put_Line (Exception_Information (E));
24629 This program will output:
24634 Exception name: CONSTRAINT_ERROR
24635 Message: stb.adb:12
24636 Call stack traceback locations:
24637 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
24640 @node Tracebacks From Anywhere in a Program (non-symbolic)
24641 @subsubsection Tracebacks From Anywhere in a Program
24644 It is also possible to retrieve a stack traceback from anywhere in a
24645 program. For this you need to
24646 use the @code{GNAT.Traceback} API. This package includes a procedure called
24647 @code{Call_Chain} that computes a complete stack traceback, as well as useful
24648 display procedures described below. It is not necessary to use the
24649 @option{-E gnatbind} option in this case, because the stack traceback mechanism
24650 is invoked explicitly.
24653 In the following example we compute a traceback at a specific location in
24654 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
24655 convert addresses to strings:
24657 @smallexample @c ada
24659 with GNAT.Traceback;
24660 with GNAT.Debug_Utilities;
24666 use GNAT.Traceback;
24669 TB : Tracebacks_Array (1 .. 10);
24670 -- We are asking for a maximum of 10 stack frames.
24672 -- Len will receive the actual number of stack frames returned.
24674 Call_Chain (TB, Len);
24676 Text_IO.Put ("In STB.P1 : ");
24678 for K in 1 .. Len loop
24679 Text_IO.Put (Debug_Utilities.Image (TB (K)));
24700 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
24701 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
24705 You can then get further information by invoking the @code{addr2line}
24706 tool as described earlier (note that the hexadecimal addresses
24707 need to be specified in C format, with a leading ``0x'').
24709 @node Symbolic Traceback
24710 @subsection Symbolic Traceback
24711 @cindex traceback, symbolic
24714 A symbolic traceback is a stack traceback in which procedure names are
24715 associated with each code location.
24718 Note that this feature is not supported on all platforms. See
24719 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
24720 list of currently supported platforms.
24723 Note that the symbolic traceback requires that the program be compiled
24724 with debug information. If it is not compiled with debug information
24725 only the non-symbolic information will be valid.
24728 * Tracebacks From Exception Occurrences (symbolic)::
24729 * Tracebacks From Anywhere in a Program (symbolic)::
24732 @node Tracebacks From Exception Occurrences (symbolic)
24733 @subsubsection Tracebacks From Exception Occurrences
24735 @smallexample @c ada
24737 with GNAT.Traceback.Symbolic;
24743 raise Constraint_Error;
24760 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
24765 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
24768 0040149F in stb.p1 at stb.adb:8
24769 004014B7 in stb.p2 at stb.adb:13
24770 004014CF in stb.p3 at stb.adb:18
24771 004015DD in ada.stb at stb.adb:22
24772 00401461 in main at b~stb.adb:168
24773 004011C4 in __mingw_CRTStartup at crt1.c:200
24774 004011F1 in mainCRTStartup at crt1.c:222
24775 77E892A4 in ?? at ??:0
24779 In the above example the ``.\'' syntax in the @command{gnatmake} command
24780 is currently required by @command{addr2line} for files that are in
24781 the current working directory.
24782 Moreover, the exact sequence of linker options may vary from platform
24784 The above @option{-largs} section is for Windows platforms. By contrast,
24785 under Unix there is no need for the @option{-largs} section.
24786 Differences across platforms are due to details of linker implementation.
24788 @node Tracebacks From Anywhere in a Program (symbolic)
24789 @subsubsection Tracebacks From Anywhere in a Program
24792 It is possible to get a symbolic stack traceback
24793 from anywhere in a program, just as for non-symbolic tracebacks.
24794 The first step is to obtain a non-symbolic
24795 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
24796 information. Here is an example:
24798 @smallexample @c ada
24800 with GNAT.Traceback;
24801 with GNAT.Traceback.Symbolic;
24806 use GNAT.Traceback;
24807 use GNAT.Traceback.Symbolic;
24810 TB : Tracebacks_Array (1 .. 10);
24811 -- We are asking for a maximum of 10 stack frames.
24813 -- Len will receive the actual number of stack frames returned.
24815 Call_Chain (TB, Len);
24816 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
24829 @c ******************************
24831 @node Compatibility with HP Ada
24832 @chapter Compatibility with HP Ada
24833 @cindex Compatibility
24838 @cindex Compatibility between GNAT and HP Ada
24839 This chapter compares HP Ada (formerly known as ``DEC Ada'')
24840 for OpenVMS Alpha and GNAT for OpenVMS for Alpha and for I64.
24841 GNAT is highly compatible
24842 with HP Ada, and it should generally be straightforward to port code
24843 from the HP Ada environment to GNAT. However, there are a few language
24844 and implementation differences of which the user must be aware. These
24845 differences are discussed in this chapter. In
24846 addition, the operating environment and command structure for the
24847 compiler are different, and these differences are also discussed.
24849 For further details on these and other compatibility issues,
24850 see Appendix E of the HP publication
24851 @cite{HP Ada, Technical Overview and Comparison on HP Platforms}.
24853 Except where otherwise indicated, the description of GNAT for OpenVMS
24854 applies to both the Alpha and I64 platforms.
24856 For information on porting Ada code from GNAT on Alpha OpenVMS to GNAT on
24857 I64 OpenVMS, see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
24859 The discussion in this chapter addresses specifically the implementation
24860 of Ada 83 for HP OpenVMS Alpha Systems. In cases where the implementation
24861 of HP Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
24862 GNAT always follows the Alpha implementation.
24864 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
24865 attributes are recognized, although only a subset of them can sensibly
24866 be implemented. The description of pragmas in
24867 @xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
24868 indicates whether or not they are applicable to non-VMS systems.
24871 * Ada Language Compatibility::
24872 * Differences in the Definition of Package System::
24873 * Language-Related Features::
24874 * The Package STANDARD::
24875 * The Package SYSTEM::
24876 * Tasking and Task-Related Features::
24877 * Pragmas and Pragma-Related Features::
24878 * Library of Predefined Units::
24880 * Main Program Definition::
24881 * Implementation-Defined Attributes::
24882 * Compiler and Run-Time Interfacing::
24883 * Program Compilation and Library Management::
24885 * Implementation Limits::
24886 * Tools and Utilities::
24889 @node Ada Language Compatibility
24890 @section Ada Language Compatibility
24893 GNAT handles Ada 95 and Ada 2005 as well as Ada 83, whereas HP Ada is only
24894 for Ada 83. Ada 95 and Ada 2005 are almost completely upwards compatible
24895 with Ada 83, and therefore Ada 83 programs will compile
24896 and run under GNAT with
24897 no changes or only minor changes. The @cite{Annotated Ada Reference Manual}
24898 provides details on specific incompatibilities.
24900 GNAT provides the switch @option{/83} on the @command{GNAT COMPILE} command,
24901 as well as the pragma @code{ADA_83}, to force the compiler to
24902 operate in Ada 83 mode. This mode does not guarantee complete
24903 conformance to Ada 83, but in practice is sufficient to
24904 eliminate most sources of incompatibilities.
24905 In particular, it eliminates the recognition of the
24906 additional Ada 95 and Ada 2005 keywords, so that their use as identifiers
24907 in Ada 83 programs is legal, and handles the cases of packages
24908 with optional bodies, and generics that instantiate unconstrained
24909 types without the use of @code{(<>)}.
24911 @node Differences in the Definition of Package System
24912 @section Differences in the Definition of Package @code{System}
24915 An Ada compiler is allowed to add
24916 implementation-dependent declarations to package @code{System}.
24918 GNAT does not take advantage of this permission, and the version of
24919 @code{System} provided by GNAT exactly matches that defined in the Ada
24922 However, HP Ada adds an extensive set of declarations to package
24924 as fully documented in the HP Ada manuals. To minimize changes required
24925 for programs that make use of these extensions, GNAT provides the pragma
24926 @code{Extend_System} for extending the definition of package System. By using:
24927 @cindex pragma @code{Extend_System}
24928 @cindex @code{Extend_System} pragma
24930 @smallexample @c ada
24933 pragma Extend_System (Aux_DEC);
24939 the set of definitions in @code{System} is extended to include those in
24940 package @code{System.Aux_DEC}.
24941 @cindex @code{System.Aux_DEC} package
24942 @cindex @code{Aux_DEC} package (child of @code{System})
24943 These definitions are incorporated directly into package @code{System},
24944 as though they had been declared there. For a
24945 list of the declarations added, see the spec of this package,
24946 which can be found in the file @file{s-auxdec.ads} in the GNAT library.
24947 @cindex @file{s-auxdec.ads} file
24948 The pragma @code{Extend_System} is a configuration pragma, which means that
24949 it can be placed in the file @file{gnat.adc}, so that it will automatically
24950 apply to all subsequent compilations. See @ref{Configuration Pragmas},
24951 for further details.
24953 An alternative approach that avoids the use of the non-standard
24954 @code{Extend_System} pragma is to add a context clause to the unit that
24955 references these facilities:
24957 @smallexample @c ada
24959 with System.Aux_DEC;
24960 use System.Aux_DEC;
24965 The effect is not quite semantically identical to incorporating
24966 the declarations directly into package @code{System},
24967 but most programs will not notice a difference
24968 unless they use prefix notation (e.g.@: @code{System.Integer_8})
24969 to reference the entities directly in package @code{System}.
24970 For units containing such references,
24971 the prefixes must either be removed, or the pragma @code{Extend_System}
24974 @node Language-Related Features
24975 @section Language-Related Features
24978 The following sections highlight differences in types,
24979 representations of types, operations, alignment, and
24983 * Integer Types and Representations::
24984 * Floating-Point Types and Representations::
24985 * Pragmas Float_Representation and Long_Float::
24986 * Fixed-Point Types and Representations::
24987 * Record and Array Component Alignment::
24988 * Address Clauses::
24989 * Other Representation Clauses::
24992 @node Integer Types and Representations
24993 @subsection Integer Types and Representations
24996 The set of predefined integer types is identical in HP Ada and GNAT.
24997 Furthermore the representation of these integer types is also identical,
24998 including the capability of size clauses forcing biased representation.
25001 HP Ada for OpenVMS Alpha systems has defined the
25002 following additional integer types in package @code{System}:
25019 @code{LARGEST_INTEGER}
25023 In GNAT, the first four of these types may be obtained from the
25024 standard Ada package @code{Interfaces}.
25025 Alternatively, by use of the pragma @code{Extend_System}, identical
25026 declarations can be referenced directly in package @code{System}.
25027 On both GNAT and HP Ada, the maximum integer size is 64 bits.
25029 @node Floating-Point Types and Representations
25030 @subsection Floating-Point Types and Representations
25031 @cindex Floating-Point types
25034 The set of predefined floating-point types is identical in HP Ada and GNAT.
25035 Furthermore the representation of these floating-point
25036 types is also identical. One important difference is that the default
25037 representation for HP Ada is @code{VAX_Float}, but the default representation
25040 Specific types may be declared to be @code{VAX_Float} or IEEE, using the
25041 pragma @code{Float_Representation} as described in the HP Ada
25043 For example, the declarations:
25045 @smallexample @c ada
25047 type F_Float is digits 6;
25048 pragma Float_Representation (VAX_Float, F_Float);
25053 declares a type @code{F_Float} that will be represented in @code{VAX_Float}
25055 This set of declarations actually appears in @code{System.Aux_DEC},
25057 the full set of additional floating-point declarations provided in
25058 the HP Ada version of package @code{System}.
25059 This and similar declarations may be accessed in a user program
25060 by using pragma @code{Extend_System}. The use of this
25061 pragma, and the related pragma @code{Long_Float} is described in further
25062 detail in the following section.
25064 @node Pragmas Float_Representation and Long_Float
25065 @subsection Pragmas @code{Float_Representation} and @code{Long_Float}
25068 HP Ada provides the pragma @code{Float_Representation}, which
25069 acts as a program library switch to allow control over
25070 the internal representation chosen for the predefined
25071 floating-point types declared in the package @code{Standard}.
25072 The format of this pragma is as follows:
25074 @smallexample @c ada
25076 pragma Float_Representation(VAX_Float | IEEE_Float);
25081 This pragma controls the representation of floating-point
25086 @code{VAX_Float} specifies that floating-point
25087 types are represented by default with the VAX system hardware types
25088 @code{F-floating}, @code{D-floating}, @code{G-floating}.
25089 Note that the @code{H-floating}
25090 type was available only on VAX systems, and is not available
25091 in either HP Ada or GNAT.
25094 @code{IEEE_Float} specifies that floating-point
25095 types are represented by default with the IEEE single and
25096 double floating-point types.
25100 GNAT provides an identical implementation of the pragma
25101 @code{Float_Representation}, except that it functions as a
25102 configuration pragma. Note that the
25103 notion of configuration pragma corresponds closely to the
25104 HP Ada notion of a program library switch.
25106 When no pragma is used in GNAT, the default is @code{IEEE_Float},
25108 from HP Ada 83, where the default is @code{VAX_Float}. In addition, the
25109 predefined libraries in GNAT are built using @code{IEEE_Float}, so it is not
25110 advisable to change the format of numbers passed to standard library
25111 routines, and if necessary explicit type conversions may be needed.
25113 The use of @code{IEEE_Float} is recommended in GNAT since it is more
25114 efficient, and (given that it conforms to an international standard)
25115 potentially more portable.
25116 The situation in which @code{VAX_Float} may be useful is in interfacing
25117 to existing code and data that expect the use of @code{VAX_Float}.
25118 In such a situation use the predefined @code{VAX_Float}
25119 types in package @code{System}, as extended by
25120 @code{Extend_System}. For example, use @code{System.F_Float}
25121 to specify the 32-bit @code{F-Float} format.
25124 On OpenVMS systems, HP Ada provides the pragma @code{Long_Float}
25125 to allow control over the internal representation chosen
25126 for the predefined type @code{Long_Float} and for floating-point
25127 type declarations with digits specified in the range 7 .. 15.
25128 The format of this pragma is as follows:
25130 @smallexample @c ada
25132 pragma Long_Float (D_FLOAT | G_FLOAT);
25136 @node Fixed-Point Types and Representations
25137 @subsection Fixed-Point Types and Representations
25140 On HP Ada for OpenVMS Alpha systems, rounding is
25141 away from zero for both positive and negative numbers.
25142 Therefore, @code{+0.5} rounds to @code{1},
25143 and @code{-0.5} rounds to @code{-1}.
25145 On GNAT the results of operations
25146 on fixed-point types are in accordance with the Ada
25147 rules. In particular, results of operations on decimal
25148 fixed-point types are truncated.
25150 @node Record and Array Component Alignment
25151 @subsection Record and Array Component Alignment
25154 On HP Ada for OpenVMS Alpha, all non-composite components
25155 are aligned on natural boundaries. For example, 1-byte
25156 components are aligned on byte boundaries, 2-byte
25157 components on 2-byte boundaries, 4-byte components on 4-byte
25158 byte boundaries, and so on. The OpenVMS Alpha hardware
25159 runs more efficiently with naturally aligned data.
25161 On GNAT, alignment rules are compatible
25162 with HP Ada for OpenVMS Alpha.
25164 @node Address Clauses
25165 @subsection Address Clauses
25168 In HP Ada and GNAT, address clauses are supported for
25169 objects and imported subprograms.
25170 The predefined type @code{System.Address} is a private type
25171 in both compilers on Alpha OpenVMS, with the same representation
25172 (it is simply a machine pointer). Addition, subtraction, and comparison
25173 operations are available in the standard Ada package
25174 @code{System.Storage_Elements}, or in package @code{System}
25175 if it is extended to include @code{System.Aux_DEC} using a
25176 pragma @code{Extend_System} as previously described.
25178 Note that code that @code{with}'s both this extended package @code{System}
25179 and the package @code{System.Storage_Elements} should not @code{use}
25180 both packages, or ambiguities will result. In general it is better
25181 not to mix these two sets of facilities. The Ada package was
25182 designed specifically to provide the kind of features that HP Ada
25183 adds directly to package @code{System}.
25185 The type @code{System.Address} is a 64-bit integer type in GNAT for
25186 I64 OpenVMS. For more information,
25187 see @ref{Transitioning to 64-Bit GNAT for OpenVMS}.
25189 GNAT is compatible with HP Ada in its handling of address
25190 clauses, except for some limitations in
25191 the form of address clauses for composite objects with
25192 initialization. Such address clauses are easily replaced
25193 by the use of an explicitly-defined constant as described
25194 in the Ada Reference Manual (13.1(22)). For example, the sequence
25197 @smallexample @c ada
25199 X, Y : Integer := Init_Func;
25200 Q : String (X .. Y) := "abc";
25202 for Q'Address use Compute_Address;
25207 will be rejected by GNAT, since the address cannot be computed at the time
25208 that @code{Q} is declared. To achieve the intended effect, write instead:
25210 @smallexample @c ada
25213 X, Y : Integer := Init_Func;
25214 Q_Address : constant Address := Compute_Address;
25215 Q : String (X .. Y) := "abc";
25217 for Q'Address use Q_Address;
25223 which will be accepted by GNAT (and other Ada compilers), and is also
25224 compatible with Ada 83. A fuller description of the restrictions
25225 on address specifications is found in @ref{Top, GNAT Reference Manual,
25226 About This Guide, gnat_rm, GNAT Reference Manual}.
25228 @node Other Representation Clauses
25229 @subsection Other Representation Clauses
25232 GNAT implements in a compatible manner all the representation
25233 clauses supported by HP Ada. In addition, GNAT
25234 implements the representation clause forms that were introduced in Ada 95,
25235 including @code{COMPONENT_SIZE} and @code{SIZE} clauses for objects.
25237 @node The Package STANDARD
25238 @section The Package @code{STANDARD}
25241 The package @code{STANDARD}, as implemented by HP Ada, is fully
25242 described in the @cite{Ada Reference Manual} and in the
25243 @cite{HP Ada Language Reference Manual}. As implemented by GNAT, the
25244 package @code{STANDARD} is described in the @cite{Ada Reference Manual}.
25246 In addition, HP Ada supports the Latin-1 character set in
25247 the type @code{CHARACTER}. GNAT supports the Latin-1 character set
25248 in the type @code{CHARACTER} and also Unicode (ISO 10646 BMP) in
25249 the type @code{WIDE_CHARACTER}.
25251 The floating-point types supported by GNAT are those
25252 supported by HP Ada, but the defaults are different, and are controlled by
25253 pragmas. See @ref{Floating-Point Types and Representations}, for details.
25255 @node The Package SYSTEM
25256 @section The Package @code{SYSTEM}
25259 HP Ada provides a specific version of the package
25260 @code{SYSTEM} for each platform on which the language is implemented.
25261 For the complete spec of the package @code{SYSTEM}, see
25262 Appendix F of the @cite{HP Ada Language Reference Manual}.
25264 On HP Ada, the package @code{SYSTEM} includes the following conversion
25267 @item @code{TO_ADDRESS(INTEGER)}
25269 @item @code{TO_ADDRESS(UNSIGNED_LONGWORD)}
25271 @item @code{TO_ADDRESS(}@i{universal_integer}@code{)}
25273 @item @code{TO_INTEGER(ADDRESS)}
25275 @item @code{TO_UNSIGNED_LONGWORD(ADDRESS)}
25277 @item Function @code{IMPORT_VALUE return UNSIGNED_LONGWORD} and the
25278 functions @code{IMPORT_ADDRESS} and @code{IMPORT_LARGEST_VALUE}
25282 By default, GNAT supplies a version of @code{SYSTEM} that matches
25283 the definition given in the @cite{Ada Reference Manual}.
25285 is a subset of the HP system definitions, which is as
25286 close as possible to the original definitions. The only difference
25287 is that the definition of @code{SYSTEM_NAME} is different:
25289 @smallexample @c ada
25291 type Name is (SYSTEM_NAME_GNAT);
25292 System_Name : constant Name := SYSTEM_NAME_GNAT;
25297 Also, GNAT adds the Ada declarations for
25298 @code{BIT_ORDER} and @code{DEFAULT_BIT_ORDER}.
25300 However, the use of the following pragma causes GNAT
25301 to extend the definition of package @code{SYSTEM} so that it
25302 encompasses the full set of HP-specific extensions,
25303 including the functions listed above:
25305 @smallexample @c ada
25307 pragma Extend_System (Aux_DEC);
25312 The pragma @code{Extend_System} is a configuration pragma that
25313 is most conveniently placed in the @file{gnat.adc} file. @xref{Pragma
25314 Extend_System,,, gnat_rm, GNAT Reference Manual} for further details.
25316 HP Ada does not allow the recompilation of the package
25317 @code{SYSTEM}. Instead HP Ada provides several pragmas
25318 (@code{SYSTEM_NAME}, @code{STORAGE_UNIT}, and @code{MEMORY_SIZE})
25319 to modify values in the package @code{SYSTEM}.
25320 On OpenVMS Alpha systems, the pragma
25321 @code{SYSTEM_NAME} takes the enumeration literal @code{OPENVMS_AXP} as
25322 its single argument.
25324 GNAT does permit the recompilation of package @code{SYSTEM} using
25325 the special switch @option{-gnatg}, and this switch can be used if
25326 it is necessary to modify the definitions in @code{SYSTEM}. GNAT does
25327 not permit the specification of @code{SYSTEM_NAME}, @code{STORAGE_UNIT}
25328 or @code{MEMORY_SIZE} by any other means.
25330 On GNAT systems, the pragma @code{SYSTEM_NAME} takes the
25331 enumeration literal @code{SYSTEM_NAME_GNAT}.
25333 The definitions provided by the use of
25335 @smallexample @c ada
25336 pragma Extend_System (AUX_Dec);
25340 are virtually identical to those provided by the HP Ada 83 package
25341 @code{SYSTEM}. One important difference is that the name of the
25343 function for type @code{UNSIGNED_LONGWORD} is changed to
25344 @code{TO_ADDRESS_LONG}.
25345 @xref{Address Clauses,,, gnat_rm, GNAT Reference Manual} for a
25346 discussion of why this change was necessary.
25349 The version of @code{TO_ADDRESS} taking a @i{universal_integer} argument
25351 an extension to Ada 83 not strictly compatible with the reference manual.
25352 GNAT, in order to be exactly compatible with the standard,
25353 does not provide this capability. In HP Ada 83, the
25354 point of this definition is to deal with a call like:
25356 @smallexample @c ada
25357 TO_ADDRESS (16#12777#);
25361 Normally, according to Ada 83 semantics, one would expect this to be
25362 ambiguous, since it matches both the @code{INTEGER} and
25363 @code{UNSIGNED_LONGWORD} forms of @code{TO_ADDRESS}.
25364 However, in HP Ada 83, there is no ambiguity, since the
25365 definition using @i{universal_integer} takes precedence.
25367 In GNAT, since the version with @i{universal_integer} cannot be supplied,
25369 not possible to be 100% compatible. Since there are many programs using
25370 numeric constants for the argument to @code{TO_ADDRESS}, the decision in
25372 to change the name of the function in the @code{UNSIGNED_LONGWORD} case,
25373 so the declarations provided in the GNAT version of @code{AUX_Dec} are:
25375 @smallexample @c ada
25376 function To_Address (X : Integer) return Address;
25377 pragma Pure_Function (To_Address);
25379 function To_Address_Long (X : Unsigned_Longword) return Address;
25380 pragma Pure_Function (To_Address_Long);
25384 This means that programs using @code{TO_ADDRESS} for
25385 @code{UNSIGNED_LONGWORD} must change the name to @code{TO_ADDRESS_LONG}.
25387 @node Tasking and Task-Related Features
25388 @section Tasking and Task-Related Features
25391 This section compares the treatment of tasking in GNAT
25392 and in HP Ada for OpenVMS Alpha.
25393 The GNAT description applies to both Alpha and I64 OpenVMS.
25394 For detailed information on tasking in
25395 HP Ada, see the @cite{HP Ada Language Reference Manual} and the
25396 relevant run-time reference manual.
25399 * Implementation of Tasks in HP Ada for OpenVMS Alpha Systems::
25400 * Assigning Task IDs::
25401 * Task IDs and Delays::
25402 * Task-Related Pragmas::
25403 * Scheduling and Task Priority::
25405 * External Interrupts::
25408 @node Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25409 @subsection Implementation of Tasks in HP Ada for OpenVMS Alpha Systems
25412 On OpenVMS Alpha systems, each Ada task (except a passive
25413 task) is implemented as a single stream of execution
25414 that is created and managed by the kernel. On these
25415 systems, HP Ada tasking support is based on DECthreads,
25416 an implementation of the POSIX standard for threads.
25418 Also, on OpenVMS Alpha systems, HP Ada tasks and foreign
25419 code that calls DECthreads routines can be used together.
25420 The interaction between Ada tasks and DECthreads routines
25421 can have some benefits. For example when on OpenVMS Alpha,
25422 HP Ada can call C code that is already threaded.
25424 GNAT uses the facilities of DECthreads,
25425 and Ada tasks are mapped to threads.
25427 @node Assigning Task IDs
25428 @subsection Assigning Task IDs
25431 The HP Ada Run-Time Library always assigns @code{%TASK 1} to
25432 the environment task that executes the main program. On
25433 OpenVMS Alpha systems, @code{%TASK 0} is often used for tasks
25434 that have been created but are not yet activated.
25436 On OpenVMS Alpha systems, task IDs are assigned at
25437 activation. On GNAT systems, task IDs are also assigned at
25438 task creation but do not have the same form or values as
25439 task ID values in HP Ada. There is no null task, and the
25440 environment task does not have a specific task ID value.
25442 @node Task IDs and Delays
25443 @subsection Task IDs and Delays
25446 On OpenVMS Alpha systems, tasking delays are implemented
25447 using Timer System Services. The Task ID is used for the
25448 identification of the timer request (the @code{REQIDT} parameter).
25449 If Timers are used in the application take care not to use
25450 @code{0} for the identification, because cancelling such a timer
25451 will cancel all timers and may lead to unpredictable results.
25453 @node Task-Related Pragmas
25454 @subsection Task-Related Pragmas
25457 Ada supplies the pragma @code{TASK_STORAGE}, which allows
25458 specification of the size of the guard area for a task
25459 stack. (The guard area forms an area of memory that has no
25460 read or write access and thus helps in the detection of
25461 stack overflow.) On OpenVMS Alpha systems, if the pragma
25462 @code{TASK_STORAGE} specifies a value of zero, a minimal guard
25463 area is created. In the absence of a pragma @code{TASK_STORAGE},
25464 a default guard area is created.
25466 GNAT supplies the following task-related pragmas:
25469 @item @code{TASK_INFO}
25471 This pragma appears within a task definition and
25472 applies to the task in which it appears. The argument
25473 must be of type @code{SYSTEM.TASK_INFO.TASK_INFO_TYPE}.
25475 @item @code{TASK_STORAGE}
25477 GNAT implements pragma @code{TASK_STORAGE} in the same way as HP Ada.
25478 Both HP Ada and GNAT supply the pragmas @code{PASSIVE},
25479 @code{SUPPRESS}, and @code{VOLATILE}.
25481 @node Scheduling and Task Priority
25482 @subsection Scheduling and Task Priority
25485 HP Ada implements the Ada language requirement that
25486 when two tasks are eligible for execution and they have
25487 different priorities, the lower priority task does not
25488 execute while the higher priority task is waiting. The HP
25489 Ada Run-Time Library keeps a task running until either the
25490 task is suspended or a higher priority task becomes ready.
25492 On OpenVMS Alpha systems, the default strategy is round-
25493 robin with preemption. Tasks of equal priority take turns
25494 at the processor. A task is run for a certain period of
25495 time and then placed at the tail of the ready queue for
25496 its priority level.
25498 HP Ada provides the implementation-defined pragma @code{TIME_SLICE},
25499 which can be used to enable or disable round-robin
25500 scheduling of tasks with the same priority.
25501 See the relevant HP Ada run-time reference manual for
25502 information on using the pragmas to control HP Ada task
25505 GNAT follows the scheduling rules of Annex D (Real-Time
25506 Annex) of the @cite{Ada Reference Manual}. In general, this
25507 scheduling strategy is fully compatible with HP Ada
25508 although it provides some additional constraints (as
25509 fully documented in Annex D).
25510 GNAT implements time slicing control in a manner compatible with
25511 HP Ada 83, by means of the pragma @code{Time_Slice}, whose semantics
25512 are identical to the HP Ada 83 pragma of the same name.
25513 Note that it is not possible to mix GNAT tasking and
25514 HP Ada 83 tasking in the same program, since the two run-time
25515 libraries are not compatible.
25517 @node The Task Stack
25518 @subsection The Task Stack
25521 In HP Ada, a task stack is allocated each time a
25522 non-passive task is activated. As soon as the task is
25523 terminated, the storage for the task stack is deallocated.
25524 If you specify a size of zero (bytes) with @code{T'STORAGE_SIZE},
25525 a default stack size is used. Also, regardless of the size
25526 specified, some additional space is allocated for task
25527 management purposes. On OpenVMS Alpha systems, at least
25528 one page is allocated.
25530 GNAT handles task stacks in a similar manner. In accordance with
25531 the Ada rules, it provides the pragma @code{STORAGE_SIZE} as
25532 an alternative method for controlling the task stack size.
25533 The specification of the attribute @code{T'STORAGE_SIZE} is also
25534 supported in a manner compatible with HP Ada.
25536 @node External Interrupts
25537 @subsection External Interrupts
25540 On HP Ada, external interrupts can be associated with task entries.
25541 GNAT is compatible with HP Ada in its handling of external interrupts.
25543 @node Pragmas and Pragma-Related Features
25544 @section Pragmas and Pragma-Related Features
25547 Both HP Ada and GNAT supply all language-defined pragmas
25548 as specified by the Ada 83 standard. GNAT also supplies all
25549 language-defined pragmas introduced by Ada 95 and Ada 2005.
25550 In addition, GNAT implements the implementation-defined pragmas
25554 @item @code{AST_ENTRY}
25556 @item @code{COMMON_OBJECT}
25558 @item @code{COMPONENT_ALIGNMENT}
25560 @item @code{EXPORT_EXCEPTION}
25562 @item @code{EXPORT_FUNCTION}
25564 @item @code{EXPORT_OBJECT}
25566 @item @code{EXPORT_PROCEDURE}
25568 @item @code{EXPORT_VALUED_PROCEDURE}
25570 @item @code{FLOAT_REPRESENTATION}
25574 @item @code{IMPORT_EXCEPTION}
25576 @item @code{IMPORT_FUNCTION}
25578 @item @code{IMPORT_OBJECT}
25580 @item @code{IMPORT_PROCEDURE}
25582 @item @code{IMPORT_VALUED_PROCEDURE}
25584 @item @code{INLINE_GENERIC}
25586 @item @code{INTERFACE_NAME}
25588 @item @code{LONG_FLOAT}
25590 @item @code{MAIN_STORAGE}
25592 @item @code{PASSIVE}
25594 @item @code{PSECT_OBJECT}
25596 @item @code{SHARE_GENERIC}
25598 @item @code{SUPPRESS_ALL}
25600 @item @code{TASK_STORAGE}
25602 @item @code{TIME_SLICE}
25608 These pragmas are all fully implemented, with the exception of @code{TITLE},
25609 @code{PASSIVE}, and @code{SHARE_GENERIC}, which are
25610 recognized, but which have no
25611 effect in GNAT. The effect of @code{PASSIVE} may be obtained by the
25612 use of Ada protected objects. In GNAT, all generics are inlined.
25614 Unlike HP Ada, the GNAT ``@code{EXPORT_}@i{subprogram}'' pragmas require
25615 a separate subprogram specification which must appear before the
25618 GNAT also supplies a number of implementation-defined pragmas as follows:
25620 @item @code{ABORT_DEFER}
25622 @item @code{ADA_83}
25624 @item @code{ADA_95}
25626 @item @code{ADA_05}
25628 @item @code{ANNOTATE}
25630 @item @code{ASSERT}
25632 @item @code{C_PASS_BY_COPY}
25634 @item @code{CPP_CLASS}
25636 @item @code{CPP_CONSTRUCTOR}
25638 @item @code{CPP_DESTRUCTOR}
25642 @item @code{EXTEND_SYSTEM}
25644 @item @code{LINKER_ALIAS}
25646 @item @code{LINKER_SECTION}
25648 @item @code{MACHINE_ATTRIBUTE}
25650 @item @code{NO_RETURN}
25652 @item @code{PURE_FUNCTION}
25654 @item @code{SOURCE_FILE_NAME}
25656 @item @code{SOURCE_REFERENCE}
25658 @item @code{TASK_INFO}
25660 @item @code{UNCHECKED_UNION}
25662 @item @code{UNIMPLEMENTED_UNIT}
25664 @item @code{UNIVERSAL_DATA}
25666 @item @code{UNSUPPRESS}
25668 @item @code{WARNINGS}
25670 @item @code{WEAK_EXTERNAL}
25674 For full details on these GNAT implementation-defined pragmas,
25675 see @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference
25679 * Restrictions on the Pragma INLINE::
25680 * Restrictions on the Pragma INTERFACE::
25681 * Restrictions on the Pragma SYSTEM_NAME::
25684 @node Restrictions on the Pragma INLINE
25685 @subsection Restrictions on Pragma @code{INLINE}
25688 HP Ada enforces the following restrictions on the pragma @code{INLINE}:
25690 @item Parameters cannot have a task type.
25692 @item Function results cannot be task types, unconstrained
25693 array types, or unconstrained types with discriminants.
25695 @item Bodies cannot declare the following:
25697 @item Subprogram body or stub (imported subprogram is allowed)
25701 @item Generic declarations
25703 @item Instantiations
25707 @item Access types (types derived from access types allowed)
25709 @item Array or record types
25711 @item Dependent tasks
25713 @item Direct recursive calls of subprogram or containing
25714 subprogram, directly or via a renaming
25720 In GNAT, the only restriction on pragma @code{INLINE} is that the
25721 body must occur before the call if both are in the same
25722 unit, and the size must be appropriately small. There are
25723 no other specific restrictions which cause subprograms to
25724 be incapable of being inlined.
25726 @node Restrictions on the Pragma INTERFACE
25727 @subsection Restrictions on Pragma @code{INTERFACE}
25730 The following restrictions on pragma @code{INTERFACE}
25731 are enforced by both HP Ada and GNAT:
25733 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
25734 Default is the default on OpenVMS Alpha systems.
25736 @item Parameter passing: Language specifies default
25737 mechanisms but can be overridden with an @code{EXPORT} pragma.
25740 @item Ada: Use internal Ada rules.
25742 @item Bliss, C: Parameters must be mode @code{in}; cannot be
25743 record or task type. Result cannot be a string, an
25744 array, or a record.
25746 @item Fortran: Parameters cannot have a task type. Result cannot
25747 be a string, an array, or a record.
25752 GNAT is entirely upwards compatible with HP Ada, and in addition allows
25753 record parameters for all languages.
25755 @node Restrictions on the Pragma SYSTEM_NAME
25756 @subsection Restrictions on Pragma @code{SYSTEM_NAME}
25759 For HP Ada for OpenVMS Alpha, the enumeration literal
25760 for the type @code{NAME} is @code{OPENVMS_AXP}.
25761 In GNAT, the enumeration
25762 literal for the type @code{NAME} is @code{SYSTEM_NAME_GNAT}.
25764 @node Library of Predefined Units
25765 @section Library of Predefined Units
25768 A library of predefined units is provided as part of the
25769 HP Ada and GNAT implementations. HP Ada does not provide
25770 the package @code{MACHINE_CODE} but instead recommends importing
25773 The GNAT versions of the HP Ada Run-Time Library (@code{ADA$PREDEFINED:})
25774 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
25776 The HP Ada Predefined Library units are modified to remove post-Ada 83
25777 incompatibilities and to make them interoperable with GNAT
25778 (@pxref{Changes to DECLIB}, for details).
25779 The units are located in the @file{DECLIB} directory.
25781 The GNAT RTL is contained in
25782 the @file{ADALIB} directory, and
25783 the default search path is set up to find @code{DECLIB} units in preference
25784 to @code{ADALIB} units with the same name (@code{TEXT_IO},
25785 @code{SEQUENTIAL_IO}, and @code{DIRECT_IO}, for example).
25788 * Changes to DECLIB::
25791 @node Changes to DECLIB
25792 @subsection Changes to @code{DECLIB}
25795 The changes made to the HP Ada predefined library for GNAT and post-Ada 83
25796 compatibility are minor and include the following:
25799 @item Adjusting the location of pragmas and record representation
25800 clauses to obey Ada 95 (and thus Ada 2005) rules
25802 @item Adding the proper notation to generic formal parameters
25803 that take unconstrained types in instantiation
25805 @item Adding pragma @code{ELABORATE_BODY} to package specs
25806 that have package bodies not otherwise allowed
25808 @item Replacing occurrences of the identifier ``@code{PROTECTED}'' by
25809 ``@code{PROTECTD}''.
25810 Currently these are found only in the @code{STARLET} package spec.
25812 @item Changing @code{SYSTEM.ADDRESS} to @code{SYSTEM.SHORT_ADDRESS}
25813 where the address size is constrained to 32 bits.
25817 None of the above changes is visible to users.
25823 On OpenVMS Alpha, HP Ada provides the following strongly-typed bindings:
25826 @item Command Language Interpreter (CLI interface)
25828 @item DECtalk Run-Time Library (DTK interface)
25830 @item Librarian utility routines (LBR interface)
25832 @item General Purpose Run-Time Library (LIB interface)
25834 @item Math Run-Time Library (MTH interface)
25836 @item National Character Set Run-Time Library (NCS interface)
25838 @item Compiled Code Support Run-Time Library (OTS interface)
25840 @item Parallel Processing Run-Time Library (PPL interface)
25842 @item Screen Management Run-Time Library (SMG interface)
25844 @item Sort Run-Time Library (SOR interface)
25846 @item String Run-Time Library (STR interface)
25848 @item STARLET System Library
25851 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
25853 @item X Windows Toolkit (XT interface)
25855 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
25859 GNAT provides implementations of these HP bindings in the @code{DECLIB}
25860 directory, on both the Alpha and I64 OpenVMS platforms.
25862 The X/Motif bindings used to build @code{DECLIB} are whatever versions are
25864 HP Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
25865 A pragma @code{Linker_Options} has been added to packages @code{Xm},
25866 @code{Xt}, and @code{X_Lib}
25867 causing the default X/Motif sharable image libraries to be linked in. This
25868 is done via options files named @file{xm.opt}, @file{xt.opt}, and
25869 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
25871 It may be necessary to edit these options files to update or correct the
25872 library names if, for example, the newer X/Motif bindings from
25873 @file{ADA$EXAMPLES}
25874 had been (previous to installing GNAT) copied and renamed to supersede the
25875 default @file{ADA$PREDEFINED} versions.
25878 * Shared Libraries and Options Files::
25879 * Interfaces to C::
25882 @node Shared Libraries and Options Files
25883 @subsection Shared Libraries and Options Files
25886 When using the HP Ada
25887 predefined X and Motif bindings, the linking with their sharable images is
25888 done automatically by @command{GNAT LINK}.
25889 When using other X and Motif bindings, you need
25890 to add the corresponding sharable images to the command line for
25891 @code{GNAT LINK}. When linking with shared libraries, or with
25892 @file{.OPT} files, you must
25893 also add them to the command line for @command{GNAT LINK}.
25895 A shared library to be used with GNAT is built in the same way as other
25896 libraries under VMS. The VMS Link command can be used in standard fashion.
25898 @node Interfaces to C
25899 @subsection Interfaces to C
25903 provides the following Ada types and operations:
25906 @item C types package (@code{C_TYPES})
25908 @item C strings (@code{C_TYPES.NULL_TERMINATED})
25910 @item Other_types (@code{SHORT_INT})
25914 Interfacing to C with GNAT, you can use the above approach
25915 described for HP Ada or the facilities of Annex B of
25916 the @cite{Ada Reference Manual} (packages @code{INTERFACES.C},
25917 @code{INTERFACES.C.STRINGS} and @code{INTERFACES.C.POINTERS}). For more
25918 information, see @ref{Interfacing to C,,, gnat_rm, GNAT Reference Manual}.
25920 The @option{-gnatF} qualifier forces default and explicit
25921 @code{External_Name} parameters in pragmas @code{Import} and @code{Export}
25922 to be uppercased for compatibility with the default behavior
25923 of HP C. The qualifier has no effect on @code{Link_Name} parameters.
25925 @node Main Program Definition
25926 @section Main Program Definition
25929 The following section discusses differences in the
25930 definition of main programs on HP Ada and GNAT.
25931 On HP Ada, main programs are defined to meet the
25932 following conditions:
25934 @item Procedure with no formal parameters (returns @code{0} upon
25937 @item Procedure with no formal parameters (returns @code{42} when
25938 an unhandled exception is raised)
25940 @item Function with no formal parameters whose returned value
25941 is of a discrete type
25943 @item Procedure with one @code{out} formal of a discrete type for
25944 which a specification of pragma @code{EXPORT_VALUED_PROCEDURE} is given.
25949 When declared with the pragma @code{EXPORT_VALUED_PROCEDURE},
25950 a main function or main procedure returns a discrete
25951 value whose size is less than 64 bits (32 on VAX systems),
25952 the value is zero- or sign-extended as appropriate.
25953 On GNAT, main programs are defined as follows:
25955 @item Must be a non-generic, parameterless subprogram that
25956 is either a procedure or function returning an Ada
25957 @code{STANDARD.INTEGER} (the predefined type)
25959 @item Cannot be a generic subprogram or an instantiation of a
25963 @node Implementation-Defined Attributes
25964 @section Implementation-Defined Attributes
25967 GNAT provides all HP Ada implementation-defined
25970 @node Compiler and Run-Time Interfacing
25971 @section Compiler and Run-Time Interfacing
25974 HP Ada provides the following qualifiers to pass options to the linker
25977 @item @option{/WAIT} and @option{/SUBMIT}
25979 @item @option{/COMMAND}
25981 @item @option{/@r{[}NO@r{]}MAP}
25983 @item @option{/OUTPUT=@var{file-spec}}
25985 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
25989 To pass options to the linker, GNAT provides the following
25993 @item @option{/EXECUTABLE=@var{exec-name}}
25995 @item @option{/VERBOSE}
25997 @item @option{/@r{[}NO@r{]}DEBUG} and @option{/@r{[}NO@r{]}TRACEBACK}
26001 For more information on these switches, see
26002 @ref{Switches for gnatlink}.
26003 In HP Ada, the command-line switch @option{/OPTIMIZE} is available
26004 to control optimization. HP Ada also supplies the
26007 @item @code{OPTIMIZE}
26009 @item @code{INLINE}
26011 @item @code{INLINE_GENERIC}
26013 @item @code{SUPPRESS_ALL}
26015 @item @code{PASSIVE}
26019 In GNAT, optimization is controlled strictly by command
26020 line parameters, as described in the corresponding section of this guide.
26021 The HP pragmas for control of optimization are
26022 recognized but ignored.
26024 Note that in GNAT, the default is optimization off, whereas in HP Ada
26025 the default is that optimization is turned on.
26027 @node Program Compilation and Library Management
26028 @section Program Compilation and Library Management
26031 HP Ada and GNAT provide a comparable set of commands to
26032 build programs. HP Ada also provides a program library,
26033 which is a concept that does not exist on GNAT. Instead,
26034 GNAT provides directories of sources that are compiled as
26037 The following table summarizes
26038 the HP Ada commands and provides
26039 equivalent GNAT commands. In this table, some GNAT
26040 equivalents reflect the fact that GNAT does not use the
26041 concept of a program library. Instead, it uses a model
26042 in which collections of source and object files are used
26043 in a manner consistent with other languages like C and
26044 Fortran. Therefore, standard system file commands are used
26045 to manipulate these elements. Those GNAT commands are marked with
26047 Note that, unlike HP Ada, none of the GNAT commands accepts wild cards.
26050 @multitable @columnfractions .35 .65
26052 @item @emph{HP Ada Command}
26053 @tab @emph{GNAT Equivalent / Description}
26055 @item @command{ADA}
26056 @tab @command{GNAT COMPILE}@*
26057 Invokes the compiler to compile one or more Ada source files.
26059 @item @command{ACS ATTACH}@*
26060 @tab [No equivalent]@*
26061 Switches control of terminal from current process running the program
26064 @item @command{ACS CHECK}
26065 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
26066 Forms the execution closure of one
26067 or more compiled units and checks completeness and currency.
26069 @item @command{ACS COMPILE}
26070 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
26071 Forms the execution closure of one or
26072 more specified units, checks completeness and currency,
26073 identifies units that have revised source files, compiles same,
26074 and recompiles units that are or will become obsolete.
26075 Also completes incomplete generic instantiations.
26077 @item @command{ACS COPY FOREIGN}
26079 Copies a foreign object file into the program library as a
26082 @item @command{ACS COPY UNIT}
26084 Copies a compiled unit from one program library to another.
26086 @item @command{ACS CREATE LIBRARY}
26087 @tab Create /directory (*)@*
26088 Creates a program library.
26090 @item @command{ACS CREATE SUBLIBRARY}
26091 @tab Create /directory (*)@*
26092 Creates a program sublibrary.
26094 @item @command{ACS DELETE LIBRARY}
26096 Deletes a program library and its contents.
26098 @item @command{ACS DELETE SUBLIBRARY}
26100 Deletes a program sublibrary and its contents.
26102 @item @command{ACS DELETE UNIT}
26103 @tab Delete file (*)@*
26104 On OpenVMS systems, deletes one or more compiled units from
26105 the current program library.
26107 @item @command{ACS DIRECTORY}
26108 @tab Directory (*)@*
26109 On OpenVMS systems, lists units contained in the current
26112 @item @command{ACS ENTER FOREIGN}
26114 Allows the import of a foreign body as an Ada library
26115 spec and enters a reference to a pointer.
26117 @item @command{ACS ENTER UNIT}
26119 Enters a reference (pointer) from the current program library to
26120 a unit compiled into another program library.
26122 @item @command{ACS EXIT}
26123 @tab [No equivalent]@*
26124 Exits from the program library manager.
26126 @item @command{ACS EXPORT}
26128 Creates an object file that contains system-specific object code
26129 for one or more units. With GNAT, object files can simply be copied
26130 into the desired directory.
26132 @item @command{ACS EXTRACT SOURCE}
26134 Allows access to the copied source file for each Ada compilation unit
26136 @item @command{ACS HELP}
26137 @tab @command{HELP GNAT}@*
26138 Provides online help.
26140 @item @command{ACS LINK}
26141 @tab @command{GNAT LINK}@*
26142 Links an object file containing Ada units into an executable file.
26144 @item @command{ACS LOAD}
26146 Loads (partially compiles) Ada units into the program library.
26147 Allows loading a program from a collection of files into a library
26148 without knowing the relationship among units.
26150 @item @command{ACS MERGE}
26152 Merges into the current program library, one or more units from
26153 another library where they were modified.
26155 @item @command{ACS RECOMPILE}
26156 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
26157 Recompiles from external or copied source files any obsolete
26158 unit in the closure. Also, completes any incomplete generic
26161 @item @command{ACS REENTER}
26162 @tab @command{GNAT MAKE}@*
26163 Reenters current references to units compiled after last entered
26164 with the @command{ACS ENTER UNIT} command.
26166 @item @command{ACS SET LIBRARY}
26167 @tab Set default (*)@*
26168 Defines a program library to be the compilation context as well
26169 as the target library for compiler output and commands in general.
26171 @item @command{ACS SET PRAGMA}
26172 @tab Edit @file{gnat.adc} (*)@*
26173 Redefines specified values of the library characteristics
26174 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
26175 and @code{Float_Representation}.
26177 @item @command{ACS SET SOURCE}
26178 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
26179 Defines the source file search list for the @command{ACS COMPILE} command.
26181 @item @command{ACS SHOW LIBRARY}
26182 @tab Directory (*)@*
26183 Lists information about one or more program libraries.
26185 @item @command{ACS SHOW PROGRAM}
26186 @tab [No equivalent]@*
26187 Lists information about the execution closure of one or
26188 more units in the program library.
26190 @item @command{ACS SHOW SOURCE}
26191 @tab Show logical @code{ADA_INCLUDE_PATH}@*
26192 Shows the source file search used when compiling units.
26194 @item @command{ACS SHOW VERSION}
26195 @tab Compile with @option{VERBOSE} option
26196 Displays the version number of the compiler and program library
26199 @item @command{ACS SPAWN}
26200 @tab [No equivalent]@*
26201 Creates a subprocess of the current process (same as @command{DCL SPAWN}
26204 @item @command{ACS VERIFY}
26205 @tab [No equivalent]@*
26206 Performs a series of consistency checks on a program library to
26207 determine whether the library structure and library files are in
26214 @section Input-Output
26217 On OpenVMS Alpha systems, HP Ada uses OpenVMS Record
26218 Management Services (RMS) to perform operations on
26222 HP Ada and GNAT predefine an identical set of input-
26223 output packages. To make the use of the
26224 generic @code{TEXT_IO} operations more convenient, HP Ada
26225 provides predefined library packages that instantiate the
26226 integer and floating-point operations for the predefined
26227 integer and floating-point types as shown in the following table.
26229 @multitable @columnfractions .45 .55
26230 @item @emph{Package Name} @tab Instantiation
26232 @item @code{INTEGER_TEXT_IO}
26233 @tab @code{INTEGER_IO(INTEGER)}
26235 @item @code{SHORT_INTEGER_TEXT_IO}
26236 @tab @code{INTEGER_IO(SHORT_INTEGER)}
26238 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
26239 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
26241 @item @code{FLOAT_TEXT_IO}
26242 @tab @code{FLOAT_IO(FLOAT)}
26244 @item @code{LONG_FLOAT_TEXT_IO}
26245 @tab @code{FLOAT_IO(LONG_FLOAT)}
26249 The HP Ada predefined packages and their operations
26250 are implemented using OpenVMS Alpha files and input-output
26251 facilities. HP Ada supports asynchronous input-output on OpenVMS Alpha.
26252 Familiarity with the following is recommended:
26254 @item RMS file organizations and access methods
26256 @item OpenVMS file specifications and directories
26258 @item OpenVMS File Definition Language (FDL)
26262 GNAT provides I/O facilities that are completely
26263 compatible with HP Ada. The distribution includes the
26264 standard HP Ada versions of all I/O packages, operating
26265 in a manner compatible with HP Ada. In particular, the
26266 following packages are by default the HP Ada (Ada 83)
26267 versions of these packages rather than the renamings
26268 suggested in Annex J of the Ada Reference Manual:
26270 @item @code{TEXT_IO}
26272 @item @code{SEQUENTIAL_IO}
26274 @item @code{DIRECT_IO}
26278 The use of the standard child package syntax (for
26279 example, @code{ADA.TEXT_IO}) retrieves the post-Ada 83 versions of these
26281 GNAT provides HP-compatible predefined instantiations
26282 of the @code{TEXT_IO} packages, and also
26283 provides the standard predefined instantiations required
26284 by the @cite{Ada Reference Manual}.
26286 For further information on how GNAT interfaces to the file
26287 system or how I/O is implemented in programs written in
26288 mixed languages, see @ref{Implementation of the Standard I/O,,,
26289 gnat_rm, GNAT Reference Manual}.
26290 This chapter covers the following:
26292 @item Standard I/O packages
26294 @item @code{FORM} strings
26296 @item @code{ADA.DIRECT_IO}
26298 @item @code{ADA.SEQUENTIAL_IO}
26300 @item @code{ADA.TEXT_IO}
26302 @item Stream pointer positioning
26304 @item Reading and writing non-regular files
26306 @item @code{GET_IMMEDIATE}
26308 @item Treating @code{TEXT_IO} files as streams
26315 @node Implementation Limits
26316 @section Implementation Limits
26319 The following table lists implementation limits for HP Ada
26321 @multitable @columnfractions .60 .20 .20
26323 @item @emph{Compilation Parameter}
26328 @item In a subprogram or entry declaration, maximum number of
26329 formal parameters that are of an unconstrained record type
26334 @item Maximum identifier length (number of characters)
26339 @item Maximum number of characters in a source line
26344 @item Maximum collection size (number of bytes)
26349 @item Maximum number of discriminants for a record type
26354 @item Maximum number of formal parameters in an entry or
26355 subprogram declaration
26360 @item Maximum number of dimensions in an array type
26365 @item Maximum number of library units and subunits in a compilation.
26370 @item Maximum number of library units and subunits in an execution.
26375 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
26376 or @code{PSECT_OBJECT}
26381 @item Maximum number of enumeration literals in an enumeration type
26387 @item Maximum number of lines in a source file
26392 @item Maximum number of bits in any object
26397 @item Maximum size of the static portion of a stack frame (approximate)
26402 @node Tools and Utilities
26403 @section Tools and Utilities
26406 The following table lists some of the OpenVMS development tools
26407 available for HP Ada, and the corresponding tools for
26408 use with @value{EDITION} on Alpha and I64 platforms.
26409 Aside from the debugger, all the OpenVMS tools identified are part
26410 of the DECset package.
26413 @c Specify table in TeX since Texinfo does a poor job
26417 \settabs\+Language-Sensitive Editor\quad
26418 &Product with HP Ada\quad
26421 &\it Product with HP Ada
26422 & \it Product with GNAT Pro\cr
26424 \+Code Management System
26428 \+Language-Sensitive Editor
26430 & emacs or HP LSE (Alpha)\cr
26440 & OpenVMS Debug (I64)\cr
26442 \+Source Code Analyzer /
26459 \+Coverage Analyzer
26463 \+Module Management
26465 & Not applicable\cr
26475 @c This is the Texinfo version of the table. It renders poorly in pdf, hence
26476 @c the TeX version above for the printed version
26478 @c @multitable @columnfractions .3 .4 .4
26479 @multitable {Source Code Analyzer /}{Tool with HP Ada}{Tool with GNAT Pro}
26481 @tab @i{Tool with HP Ada}
26482 @tab @i{Tool with @value{EDITION}}
26483 @item Code Management@*System
26486 @item Language-Sensitive@*Editor
26488 @tab emacs or HP LSE (Alpha)
26497 @tab OpenVMS Debug (I64)
26498 @item Source Code Analyzer /@*Cross Referencer
26502 @tab HP Digital Test@*Manager (DTM)
26504 @item Performance and@*Coverage Analyzer
26507 @item Module Management@*System
26509 @tab Not applicable
26516 @c **************************************
26517 @node Platform-Specific Information for the Run-Time Libraries
26518 @appendix Platform-Specific Information for the Run-Time Libraries
26519 @cindex Tasking and threads libraries
26520 @cindex Threads libraries and tasking
26521 @cindex Run-time libraries (platform-specific information)
26524 The GNAT run-time implementation may vary with respect to both the
26525 underlying threads library and the exception handling scheme.
26526 For threads support, one or more of the following are supplied:
26528 @item @b{native threads library}, a binding to the thread package from
26529 the underlying operating system
26531 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
26532 POSIX thread package
26536 For exception handling, either or both of two models are supplied:
26538 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
26539 Most programs should experience a substantial speed improvement by
26540 being compiled with a ZCX run-time.
26541 This is especially true for
26542 tasking applications or applications with many exception handlers.}
26543 @cindex Zero-Cost Exceptions
26544 @cindex ZCX (Zero-Cost Exceptions)
26545 which uses binder-generated tables that
26546 are interrogated at run time to locate a handler
26548 @item @b{setjmp / longjmp} (``SJLJ''),
26549 @cindex setjmp/longjmp Exception Model
26550 @cindex SJLJ (setjmp/longjmp Exception Model)
26551 which uses dynamically-set data to establish
26552 the set of handlers
26556 This appendix summarizes which combinations of threads and exception support
26557 are supplied on various GNAT platforms.
26558 It then shows how to select a particular library either
26559 permanently or temporarily,
26560 explains the properties of (and tradeoffs among) the various threads
26561 libraries, and provides some additional
26562 information about several specific platforms.
26565 * Summary of Run-Time Configurations::
26566 * Specifying a Run-Time Library::
26567 * Choosing the Scheduling Policy::
26568 * Solaris-Specific Considerations::
26569 * Linux-Specific Considerations::
26570 * AIX-Specific Considerations::
26571 * Irix-Specific Considerations::
26572 * RTX-Specific Considerations::
26575 @node Summary of Run-Time Configurations
26576 @section Summary of Run-Time Configurations
26578 @multitable @columnfractions .30 .70
26579 @item @b{alpha-openvms}
26580 @item @code{@ @ }@i{rts-native (default)}
26581 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26582 @item @code{@ @ @ @ }Exceptions @tab ZCX
26584 @item @b{alpha-tru64}
26585 @item @code{@ @ }@i{rts-native (default)}
26586 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26587 @item @code{@ @ @ @ }Exceptions @tab ZCX
26589 @item @code{@ @ }@i{rts-sjlj}
26590 @item @code{@ @ @ @ }Tasking @tab native TRU64 threads
26591 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26593 @item @b{ia64-hp_linux}
26594 @item @code{@ @ }@i{rts-native (default)}
26595 @item @code{@ @ @ @ }Tasking @tab pthread library
26596 @item @code{@ @ @ @ }Exceptions @tab ZCX
26598 @item @b{ia64-hpux}
26599 @item @code{@ @ }@i{rts-native (default)}
26600 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26601 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26603 @item @b{ia64-openvms}
26604 @item @code{@ @ }@i{rts-native (default)}
26605 @item @code{@ @ @ @ }Tasking @tab native VMS threads
26606 @item @code{@ @ @ @ }Exceptions @tab ZCX
26608 @item @b{ia64-sgi_linux}
26609 @item @code{@ @ }@i{rts-native (default)}
26610 @item @code{@ @ @ @ }Tasking @tab pthread library
26611 @item @code{@ @ @ @ }Exceptions @tab ZCX
26613 @item @b{mips-irix}
26614 @item @code{@ @ }@i{rts-native (default)}
26615 @item @code{@ @ @ @ }Tasking @tab native IRIX threads
26616 @item @code{@ @ @ @ }Exceptions @tab ZCX
26619 @item @code{@ @ }@i{rts-native (default)}
26620 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26621 @item @code{@ @ @ @ }Exceptions @tab ZCX
26623 @item @code{@ @ }@i{rts-sjlj}
26624 @item @code{@ @ @ @ }Tasking @tab native HP-UX threads
26625 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26628 @item @code{@ @ }@i{rts-native (default)}
26629 @item @code{@ @ @ @ }Tasking @tab native AIX threads
26630 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26632 @item @b{ppc-darwin}
26633 @item @code{@ @ }@i{rts-native (default)}
26634 @item @code{@ @ @ @ }Tasking @tab native MacOS threads
26635 @item @code{@ @ @ @ }Exceptions @tab ZCX
26637 @item @b{sparc-solaris} @tab
26638 @item @code{@ @ }@i{rts-native (default)}
26639 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26640 @item @code{@ @ @ @ }Exceptions @tab ZCX
26642 @item @code{@ @ }@i{rts-pthread}
26643 @item @code{@ @ @ @ }Tasking @tab pthread library
26644 @item @code{@ @ @ @ }Exceptions @tab ZCX
26646 @item @code{@ @ }@i{rts-sjlj}
26647 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26648 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26650 @item @b{sparc64-solaris} @tab
26651 @item @code{@ @ }@i{rts-native (default)}
26652 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
26653 @item @code{@ @ @ @ }Exceptions @tab ZCX
26655 @item @b{x86-linux}
26656 @item @code{@ @ }@i{rts-native (default)}
26657 @item @code{@ @ @ @ }Tasking @tab pthread library
26658 @item @code{@ @ @ @ }Exceptions @tab ZCX
26660 @item @code{@ @ }@i{rts-sjlj}
26661 @item @code{@ @ @ @ }Tasking @tab pthread library
26662 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26665 @item @code{@ @ }@i{rts-native (default)}
26666 @item @code{@ @ @ @ }Tasking @tab native LynxOS threads
26667 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26669 @item @b{x86-solaris}
26670 @item @code{@ @ }@i{rts-native (default)}
26671 @item @code{@ @ @ @ }Tasking @tab native Solaris threads
26672 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26674 @item @b{x86-windows}
26675 @item @code{@ @ }@i{rts-native (default)}
26676 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26677 @item @code{@ @ @ @ }Exceptions @tab ZCX
26679 @item @code{@ @ }@i{rts-sjlj (default)}
26680 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
26681 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26683 @item @b{x86-windows-rtx}
26684 @item @code{@ @ }@i{rts-rtx-rtss (default)}
26685 @item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode)
26686 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26688 @item @code{@ @ }@i{rts-rtx-w32}
26689 @item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode)
26690 @item @code{@ @ @ @ }Exceptions @tab ZCX
26692 @item @b{x86_64-linux}
26693 @item @code{@ @ }@i{rts-native (default)}
26694 @item @code{@ @ @ @ }Tasking @tab pthread library
26695 @item @code{@ @ @ @ }Exceptions @tab ZCX
26697 @item @code{@ @ }@i{rts-sjlj}
26698 @item @code{@ @ @ @ }Tasking @tab pthread library
26699 @item @code{@ @ @ @ }Exceptions @tab SJLJ
26703 @node Specifying a Run-Time Library
26704 @section Specifying a Run-Time Library
26707 The @file{adainclude} subdirectory containing the sources of the GNAT
26708 run-time library, and the @file{adalib} subdirectory containing the
26709 @file{ALI} files and the static and/or shared GNAT library, are located
26710 in the gcc target-dependent area:
26713 target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
26717 As indicated above, on some platforms several run-time libraries are supplied.
26718 These libraries are installed in the target dependent area and
26719 contain a complete source and binary subdirectory. The detailed description
26720 below explains the differences between the different libraries in terms of
26721 their thread support.
26723 The default run-time library (when GNAT is installed) is @emph{rts-native}.
26724 This default run time is selected by the means of soft links.
26725 For example on x86-linux:
26731 +--- adainclude----------+
26733 +--- adalib-----------+ |
26735 +--- rts-native | |
26737 | +--- adainclude <---+
26739 | +--- adalib <----+
26750 If the @i{rts-sjlj} library is to be selected on a permanent basis,
26751 these soft links can be modified with the following commands:
26755 $ rm -f adainclude adalib
26756 $ ln -s rts-sjlj/adainclude adainclude
26757 $ ln -s rts-sjlj/adalib adalib
26761 Alternatively, you can specify @file{rts-sjlj/adainclude} in the file
26762 @file{$target/ada_source_path} and @file{rts-sjlj/adalib} in
26763 @file{$target/ada_object_path}.
26765 Selecting another run-time library temporarily can be
26766 achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj}
26767 @cindex @option{--RTS} option
26769 @node Choosing the Scheduling Policy
26770 @section Choosing the Scheduling Policy
26773 When using a POSIX threads implementation, you have a choice of several
26774 scheduling policies: @code{SCHED_FIFO},
26775 @cindex @code{SCHED_FIFO} scheduling policy
26777 @cindex @code{SCHED_RR} scheduling policy
26778 and @code{SCHED_OTHER}.
26779 @cindex @code{SCHED_OTHER} scheduling policy
26780 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
26781 or @code{SCHED_RR} requires special (e.g., root) privileges.
26783 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
26785 @cindex @code{SCHED_FIFO} scheduling policy
26786 you can use one of the following:
26790 @code{pragma Time_Slice (0.0)}
26791 @cindex pragma Time_Slice
26793 the corresponding binder option @option{-T0}
26794 @cindex @option{-T0} option
26796 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
26797 @cindex pragma Task_Dispatching_Policy
26801 To specify @code{SCHED_RR},
26802 @cindex @code{SCHED_RR} scheduling policy
26803 you should use @code{pragma Time_Slice} with a
26804 value greater than @code{0.0}, or else use the corresponding @option{-T}
26807 @node Solaris-Specific Considerations
26808 @section Solaris-Specific Considerations
26809 @cindex Solaris Sparc threads libraries
26812 This section addresses some topics related to the various threads libraries
26816 * Solaris Threads Issues::
26819 @node Solaris Threads Issues
26820 @subsection Solaris Threads Issues
26823 GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time
26824 library based on POSIX threads --- @emph{rts-pthread}.
26825 @cindex rts-pthread threads library
26826 This run-time library has the advantage of being mostly shared across all
26827 POSIX-compliant thread implementations, and it also provides under
26828 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
26829 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
26830 and @code{PTHREAD_PRIO_PROTECT}
26831 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
26832 semantics that can be selected using the predefined pragma
26833 @code{Locking_Policy}
26834 @cindex pragma Locking_Policy (under rts-pthread)
26836 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
26837 @cindex @code{Inheritance_Locking} (under rts-pthread)
26838 @cindex @code{Ceiling_Locking} (under rts-pthread)
26840 As explained above, the native run-time library is based on the Solaris thread
26841 library (@code{libthread}) and is the default library.
26843 When the Solaris threads library is used (this is the default), programs
26844 compiled with GNAT can automatically take advantage of
26845 and can thus execute on multiple processors.
26846 The user can alternatively specify a processor on which the program should run
26847 to emulate a single-processor system. The multiprocessor / uniprocessor choice
26849 setting the environment variable @env{GNAT_PROCESSOR}
26850 @cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
26851 to one of the following:
26855 Use the default configuration (run the program on all
26856 available processors) - this is the same as having @code{GNAT_PROCESSOR}
26860 Let the run-time implementation choose one processor and run the program on
26863 @item 0 .. Last_Proc
26864 Run the program on the specified processor.
26865 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
26866 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
26869 @node Linux-Specific Considerations
26870 @section Linux-Specific Considerations
26871 @cindex Linux threads libraries
26874 On GNU/Linux without NPTL support (usually system with GNU C Library
26875 older than 2.3), the signal model is not POSIX compliant, which means
26876 that to send a signal to the process, you need to send the signal to all
26877 threads, e.g.@: by using @code{killpg()}.
26879 @node AIX-Specific Considerations
26880 @section AIX-Specific Considerations
26881 @cindex AIX resolver library
26884 On AIX, the resolver library initializes some internal structure on
26885 the first call to @code{get*by*} functions, which are used to implement
26886 @code{GNAT.Sockets.Get_Host_By_Name} and
26887 @code{GNAT.Sockets.Get_Host_By_Address}.
26888 If such initialization occurs within an Ada task, and the stack size for
26889 the task is the default size, a stack overflow may occur.
26891 To avoid this overflow, the user should either ensure that the first call
26892 to @code{GNAT.Sockets.Get_Host_By_Name} or
26893 @code{GNAT.Sockets.Get_Host_By_Addrss}
26894 occurs in the environment task, or use @code{pragma Storage_Size} to
26895 specify a sufficiently large size for the stack of the task that contains
26898 @node Irix-Specific Considerations
26899 @section Irix-Specific Considerations
26900 @cindex Irix libraries
26903 The GCC support libraries coming with the Irix compiler have moved to
26904 their canonical place with respect to the general Irix ABI related
26905 conventions. Running applications built with the default shared GNAT
26906 run-time now requires the LD_LIBRARY_PATH environment variable to
26907 include this location. A possible way to achieve this is to issue the
26908 following command line on a bash prompt:
26912 $ LD_LIBRARY_PATH=$LD_LIBRARY_PATH:`dirname \`gcc --print-file-name=libgcc_s.so\``
26916 @node RTX-Specific Considerations
26917 @section RTX-Specific Considerations
26918 @cindex RTX libraries
26921 The Real-time Extension (RTX) to Windows is based on the Windows Win32
26922 API. Applications can be built to work in two different modes:
26926 Windows executables that run in Ring 3 to utilize memory protection
26927 (@emph{rts-rtx-w32}).
26930 Real-time subsystem (RTSS) executables that run in Ring 0, where
26931 performance can be optimized with RTSS applications taking precedent
26932 over all Windows applications (@emph{rts-rtx-rtss}).
26936 @c *******************************
26937 @node Example of Binder Output File
26938 @appendix Example of Binder Output File
26941 This Appendix displays the source code for @command{gnatbind}'s output
26942 file generated for a simple ``Hello World'' program.
26943 Comments have been added for clarification purposes.
26945 @smallexample @c adanocomment
26949 -- The package is called Ada_Main unless this name is actually used
26950 -- as a unit name in the partition, in which case some other unique
26954 package ada_main is
26956 Elab_Final_Code : Integer;
26957 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
26959 -- The main program saves the parameters (argument count,
26960 -- argument values, environment pointer) in global variables
26961 -- for later access by other units including
26962 -- Ada.Command_Line.
26964 gnat_argc : Integer;
26965 gnat_argv : System.Address;
26966 gnat_envp : System.Address;
26968 -- The actual variables are stored in a library routine. This
26969 -- is useful for some shared library situations, where there
26970 -- are problems if variables are not in the library.
26972 pragma Import (C, gnat_argc);
26973 pragma Import (C, gnat_argv);
26974 pragma Import (C, gnat_envp);
26976 -- The exit status is similarly an external location
26978 gnat_exit_status : Integer;
26979 pragma Import (C, gnat_exit_status);
26981 GNAT_Version : constant String :=
26982 "GNAT Version: 6.0.0w (20061115)";
26983 pragma Export (C, GNAT_Version, "__gnat_version");
26985 -- This is the generated adafinal routine that performs
26986 -- finalization at the end of execution. In the case where
26987 -- Ada is the main program, this main program makes a call
26988 -- to adafinal at program termination.
26990 procedure adafinal;
26991 pragma Export (C, adafinal, "adafinal");
26993 -- This is the generated adainit routine that performs
26994 -- initialization at the start of execution. In the case
26995 -- where Ada is the main program, this main program makes
26996 -- a call to adainit at program startup.
26999 pragma Export (C, adainit, "adainit");
27001 -- This routine is called at the start of execution. It is
27002 -- a dummy routine that is used by the debugger to breakpoint
27003 -- at the start of execution.
27005 procedure Break_Start;
27006 pragma Import (C, Break_Start, "__gnat_break_start");
27008 -- This is the actual generated main program (it would be
27009 -- suppressed if the no main program switch were used). As
27010 -- required by standard system conventions, this program has
27011 -- the external name main.
27015 argv : System.Address;
27016 envp : System.Address)
27018 pragma Export (C, main, "main");
27020 -- The following set of constants give the version
27021 -- identification values for every unit in the bound
27022 -- partition. This identification is computed from all
27023 -- dependent semantic units, and corresponds to the
27024 -- string that would be returned by use of the
27025 -- Body_Version or Version attributes.
27027 type Version_32 is mod 2 ** 32;
27028 u00001 : constant Version_32 := 16#7880BEB3#;
27029 u00002 : constant Version_32 := 16#0D24CBD0#;
27030 u00003 : constant Version_32 := 16#3283DBEB#;
27031 u00004 : constant Version_32 := 16#2359F9ED#;
27032 u00005 : constant Version_32 := 16#664FB847#;
27033 u00006 : constant Version_32 := 16#68E803DF#;
27034 u00007 : constant Version_32 := 16#5572E604#;
27035 u00008 : constant Version_32 := 16#46B173D8#;
27036 u00009 : constant Version_32 := 16#156A40CF#;
27037 u00010 : constant Version_32 := 16#033DABE0#;
27038 u00011 : constant Version_32 := 16#6AB38FEA#;
27039 u00012 : constant Version_32 := 16#22B6217D#;
27040 u00013 : constant Version_32 := 16#68A22947#;
27041 u00014 : constant Version_32 := 16#18CC4A56#;
27042 u00015 : constant Version_32 := 16#08258E1B#;
27043 u00016 : constant Version_32 := 16#367D5222#;
27044 u00017 : constant Version_32 := 16#20C9ECA4#;
27045 u00018 : constant Version_32 := 16#50D32CB6#;
27046 u00019 : constant Version_32 := 16#39A8BB77#;
27047 u00020 : constant Version_32 := 16#5CF8FA2B#;
27048 u00021 : constant Version_32 := 16#2F1EB794#;
27049 u00022 : constant Version_32 := 16#31AB6444#;
27050 u00023 : constant Version_32 := 16#1574B6E9#;
27051 u00024 : constant Version_32 := 16#5109C189#;
27052 u00025 : constant Version_32 := 16#56D770CD#;
27053 u00026 : constant Version_32 := 16#02F9DE3D#;
27054 u00027 : constant Version_32 := 16#08AB6B2C#;
27055 u00028 : constant Version_32 := 16#3FA37670#;
27056 u00029 : constant Version_32 := 16#476457A0#;
27057 u00030 : constant Version_32 := 16#731E1B6E#;
27058 u00031 : constant Version_32 := 16#23C2E789#;
27059 u00032 : constant Version_32 := 16#0F1BD6A1#;
27060 u00033 : constant Version_32 := 16#7C25DE96#;
27061 u00034 : constant Version_32 := 16#39ADFFA2#;
27062 u00035 : constant Version_32 := 16#571DE3E7#;
27063 u00036 : constant Version_32 := 16#5EB646AB#;
27064 u00037 : constant Version_32 := 16#4249379B#;
27065 u00038 : constant Version_32 := 16#0357E00A#;
27066 u00039 : constant Version_32 := 16#3784FB72#;
27067 u00040 : constant Version_32 := 16#2E723019#;
27068 u00041 : constant Version_32 := 16#623358EA#;
27069 u00042 : constant Version_32 := 16#107F9465#;
27070 u00043 : constant Version_32 := 16#6843F68A#;
27071 u00044 : constant Version_32 := 16#63305874#;
27072 u00045 : constant Version_32 := 16#31E56CE1#;
27073 u00046 : constant Version_32 := 16#02917970#;
27074 u00047 : constant Version_32 := 16#6CCBA70E#;
27075 u00048 : constant Version_32 := 16#41CD4204#;
27076 u00049 : constant Version_32 := 16#572E3F58#;
27077 u00050 : constant Version_32 := 16#20729FF5#;
27078 u00051 : constant Version_32 := 16#1D4F93E8#;
27079 u00052 : constant Version_32 := 16#30B2EC3D#;
27080 u00053 : constant Version_32 := 16#34054F96#;
27081 u00054 : constant Version_32 := 16#5A199860#;
27082 u00055 : constant Version_32 := 16#0E7F912B#;
27083 u00056 : constant Version_32 := 16#5760634A#;
27084 u00057 : constant Version_32 := 16#5D851835#;
27086 -- The following Export pragmas export the version numbers
27087 -- with symbolic names ending in B (for body) or S
27088 -- (for spec) so that they can be located in a link. The
27089 -- information provided here is sufficient to track down
27090 -- the exact versions of units used in a given build.
27092 pragma Export (C, u00001, "helloB");
27093 pragma Export (C, u00002, "system__standard_libraryB");
27094 pragma Export (C, u00003, "system__standard_libraryS");
27095 pragma Export (C, u00004, "adaS");
27096 pragma Export (C, u00005, "ada__text_ioB");
27097 pragma Export (C, u00006, "ada__text_ioS");
27098 pragma Export (C, u00007, "ada__exceptionsB");
27099 pragma Export (C, u00008, "ada__exceptionsS");
27100 pragma Export (C, u00009, "gnatS");
27101 pragma Export (C, u00010, "gnat__heap_sort_aB");
27102 pragma Export (C, u00011, "gnat__heap_sort_aS");
27103 pragma Export (C, u00012, "systemS");
27104 pragma Export (C, u00013, "system__exception_tableB");
27105 pragma Export (C, u00014, "system__exception_tableS");
27106 pragma Export (C, u00015, "gnat__htableB");
27107 pragma Export (C, u00016, "gnat__htableS");
27108 pragma Export (C, u00017, "system__exceptionsS");
27109 pragma Export (C, u00018, "system__machine_state_operationsB");
27110 pragma Export (C, u00019, "system__machine_state_operationsS");
27111 pragma Export (C, u00020, "system__machine_codeS");
27112 pragma Export (C, u00021, "system__storage_elementsB");
27113 pragma Export (C, u00022, "system__storage_elementsS");
27114 pragma Export (C, u00023, "system__secondary_stackB");
27115 pragma Export (C, u00024, "system__secondary_stackS");
27116 pragma Export (C, u00025, "system__parametersB");
27117 pragma Export (C, u00026, "system__parametersS");
27118 pragma Export (C, u00027, "system__soft_linksB");
27119 pragma Export (C, u00028, "system__soft_linksS");
27120 pragma Export (C, u00029, "system__stack_checkingB");
27121 pragma Export (C, u00030, "system__stack_checkingS");
27122 pragma Export (C, u00031, "system__tracebackB");
27123 pragma Export (C, u00032, "system__tracebackS");
27124 pragma Export (C, u00033, "ada__streamsS");
27125 pragma Export (C, u00034, "ada__tagsB");
27126 pragma Export (C, u00035, "ada__tagsS");
27127 pragma Export (C, u00036, "system__string_opsB");
27128 pragma Export (C, u00037, "system__string_opsS");
27129 pragma Export (C, u00038, "interfacesS");
27130 pragma Export (C, u00039, "interfaces__c_streamsB");
27131 pragma Export (C, u00040, "interfaces__c_streamsS");
27132 pragma Export (C, u00041, "system__file_ioB");
27133 pragma Export (C, u00042, "system__file_ioS");
27134 pragma Export (C, u00043, "ada__finalizationB");
27135 pragma Export (C, u00044, "ada__finalizationS");
27136 pragma Export (C, u00045, "system__finalization_rootB");
27137 pragma Export (C, u00046, "system__finalization_rootS");
27138 pragma Export (C, u00047, "system__finalization_implementationB");
27139 pragma Export (C, u00048, "system__finalization_implementationS");
27140 pragma Export (C, u00049, "system__string_ops_concat_3B");
27141 pragma Export (C, u00050, "system__string_ops_concat_3S");
27142 pragma Export (C, u00051, "system__stream_attributesB");
27143 pragma Export (C, u00052, "system__stream_attributesS");
27144 pragma Export (C, u00053, "ada__io_exceptionsS");
27145 pragma Export (C, u00054, "system__unsigned_typesS");
27146 pragma Export (C, u00055, "system__file_control_blockS");
27147 pragma Export (C, u00056, "ada__finalization__list_controllerB");
27148 pragma Export (C, u00057, "ada__finalization__list_controllerS");
27150 -- BEGIN ELABORATION ORDER
27153 -- gnat.heap_sort_a (spec)
27154 -- gnat.heap_sort_a (body)
27155 -- gnat.htable (spec)
27156 -- gnat.htable (body)
27157 -- interfaces (spec)
27159 -- system.machine_code (spec)
27160 -- system.parameters (spec)
27161 -- system.parameters (body)
27162 -- interfaces.c_streams (spec)
27163 -- interfaces.c_streams (body)
27164 -- system.standard_library (spec)
27165 -- ada.exceptions (spec)
27166 -- system.exception_table (spec)
27167 -- system.exception_table (body)
27168 -- ada.io_exceptions (spec)
27169 -- system.exceptions (spec)
27170 -- system.storage_elements (spec)
27171 -- system.storage_elements (body)
27172 -- system.machine_state_operations (spec)
27173 -- system.machine_state_operations (body)
27174 -- system.secondary_stack (spec)
27175 -- system.stack_checking (spec)
27176 -- system.soft_links (spec)
27177 -- system.soft_links (body)
27178 -- system.stack_checking (body)
27179 -- system.secondary_stack (body)
27180 -- system.standard_library (body)
27181 -- system.string_ops (spec)
27182 -- system.string_ops (body)
27185 -- ada.streams (spec)
27186 -- system.finalization_root (spec)
27187 -- system.finalization_root (body)
27188 -- system.string_ops_concat_3 (spec)
27189 -- system.string_ops_concat_3 (body)
27190 -- system.traceback (spec)
27191 -- system.traceback (body)
27192 -- ada.exceptions (body)
27193 -- system.unsigned_types (spec)
27194 -- system.stream_attributes (spec)
27195 -- system.stream_attributes (body)
27196 -- system.finalization_implementation (spec)
27197 -- system.finalization_implementation (body)
27198 -- ada.finalization (spec)
27199 -- ada.finalization (body)
27200 -- ada.finalization.list_controller (spec)
27201 -- ada.finalization.list_controller (body)
27202 -- system.file_control_block (spec)
27203 -- system.file_io (spec)
27204 -- system.file_io (body)
27205 -- ada.text_io (spec)
27206 -- ada.text_io (body)
27208 -- END ELABORATION ORDER
27212 -- The following source file name pragmas allow the generated file
27213 -- names to be unique for different main programs. They are needed
27214 -- since the package name will always be Ada_Main.
27216 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
27217 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
27219 -- Generated package body for Ada_Main starts here
27221 package body ada_main is
27223 -- The actual finalization is performed by calling the
27224 -- library routine in System.Standard_Library.Adafinal
27226 procedure Do_Finalize;
27227 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
27234 procedure adainit is
27236 -- These booleans are set to True once the associated unit has
27237 -- been elaborated. It is also used to avoid elaborating the
27238 -- same unit twice.
27241 pragma Import (Ada, E040, "interfaces__c_streams_E");
27244 pragma Import (Ada, E008, "ada__exceptions_E");
27247 pragma Import (Ada, E014, "system__exception_table_E");
27250 pragma Import (Ada, E053, "ada__io_exceptions_E");
27253 pragma Import (Ada, E017, "system__exceptions_E");
27256 pragma Import (Ada, E024, "system__secondary_stack_E");
27259 pragma Import (Ada, E030, "system__stack_checking_E");
27262 pragma Import (Ada, E028, "system__soft_links_E");
27265 pragma Import (Ada, E035, "ada__tags_E");
27268 pragma Import (Ada, E033, "ada__streams_E");
27271 pragma Import (Ada, E046, "system__finalization_root_E");
27274 pragma Import (Ada, E048, "system__finalization_implementation_E");
27277 pragma Import (Ada, E044, "ada__finalization_E");
27280 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
27283 pragma Import (Ada, E055, "system__file_control_block_E");
27286 pragma Import (Ada, E042, "system__file_io_E");
27289 pragma Import (Ada, E006, "ada__text_io_E");
27291 -- Set_Globals is a library routine that stores away the
27292 -- value of the indicated set of global values in global
27293 -- variables within the library.
27295 procedure Set_Globals
27296 (Main_Priority : Integer;
27297 Time_Slice_Value : Integer;
27298 WC_Encoding : Character;
27299 Locking_Policy : Character;
27300 Queuing_Policy : Character;
27301 Task_Dispatching_Policy : Character;
27302 Adafinal : System.Address;
27303 Unreserve_All_Interrupts : Integer;
27304 Exception_Tracebacks : Integer);
27305 @findex __gnat_set_globals
27306 pragma Import (C, Set_Globals, "__gnat_set_globals");
27308 -- SDP_Table_Build is a library routine used to build the
27309 -- exception tables. See unit Ada.Exceptions in files
27310 -- a-except.ads/adb for full details of how zero cost
27311 -- exception handling works. This procedure, the call to
27312 -- it, and the two following tables are all omitted if the
27313 -- build is in longjmp/setjmp exception mode.
27315 @findex SDP_Table_Build
27316 @findex Zero Cost Exceptions
27317 procedure SDP_Table_Build
27318 (SDP_Addresses : System.Address;
27319 SDP_Count : Natural;
27320 Elab_Addresses : System.Address;
27321 Elab_Addr_Count : Natural);
27322 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
27324 -- Table of Unit_Exception_Table addresses. Used for zero
27325 -- cost exception handling to build the top level table.
27327 ST : aliased constant array (1 .. 23) of System.Address := (
27329 Ada.Text_Io'UET_Address,
27330 Ada.Exceptions'UET_Address,
27331 Gnat.Heap_Sort_A'UET_Address,
27332 System.Exception_Table'UET_Address,
27333 System.Machine_State_Operations'UET_Address,
27334 System.Secondary_Stack'UET_Address,
27335 System.Parameters'UET_Address,
27336 System.Soft_Links'UET_Address,
27337 System.Stack_Checking'UET_Address,
27338 System.Traceback'UET_Address,
27339 Ada.Streams'UET_Address,
27340 Ada.Tags'UET_Address,
27341 System.String_Ops'UET_Address,
27342 Interfaces.C_Streams'UET_Address,
27343 System.File_Io'UET_Address,
27344 Ada.Finalization'UET_Address,
27345 System.Finalization_Root'UET_Address,
27346 System.Finalization_Implementation'UET_Address,
27347 System.String_Ops_Concat_3'UET_Address,
27348 System.Stream_Attributes'UET_Address,
27349 System.File_Control_Block'UET_Address,
27350 Ada.Finalization.List_Controller'UET_Address);
27352 -- Table of addresses of elaboration routines. Used for
27353 -- zero cost exception handling to make sure these
27354 -- addresses are included in the top level procedure
27357 EA : aliased constant array (1 .. 23) of System.Address := (
27358 adainit'Code_Address,
27359 Do_Finalize'Code_Address,
27360 Ada.Exceptions'Elab_Spec'Address,
27361 System.Exceptions'Elab_Spec'Address,
27362 Interfaces.C_Streams'Elab_Spec'Address,
27363 System.Exception_Table'Elab_Body'Address,
27364 Ada.Io_Exceptions'Elab_Spec'Address,
27365 System.Stack_Checking'Elab_Spec'Address,
27366 System.Soft_Links'Elab_Body'Address,
27367 System.Secondary_Stack'Elab_Body'Address,
27368 Ada.Tags'Elab_Spec'Address,
27369 Ada.Tags'Elab_Body'Address,
27370 Ada.Streams'Elab_Spec'Address,
27371 System.Finalization_Root'Elab_Spec'Address,
27372 Ada.Exceptions'Elab_Body'Address,
27373 System.Finalization_Implementation'Elab_Spec'Address,
27374 System.Finalization_Implementation'Elab_Body'Address,
27375 Ada.Finalization'Elab_Spec'Address,
27376 Ada.Finalization.List_Controller'Elab_Spec'Address,
27377 System.File_Control_Block'Elab_Spec'Address,
27378 System.File_Io'Elab_Body'Address,
27379 Ada.Text_Io'Elab_Spec'Address,
27380 Ada.Text_Io'Elab_Body'Address);
27382 -- Start of processing for adainit
27386 -- Call SDP_Table_Build to build the top level procedure
27387 -- table for zero cost exception handling (omitted in
27388 -- longjmp/setjmp mode).
27390 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
27392 -- Call Set_Globals to record various information for
27393 -- this partition. The values are derived by the binder
27394 -- from information stored in the ali files by the compiler.
27396 @findex __gnat_set_globals
27398 (Main_Priority => -1,
27399 -- Priority of main program, -1 if no pragma Priority used
27401 Time_Slice_Value => -1,
27402 -- Time slice from Time_Slice pragma, -1 if none used
27404 WC_Encoding => 'b',
27405 -- Wide_Character encoding used, default is brackets
27407 Locking_Policy => ' ',
27408 -- Locking_Policy used, default of space means not
27409 -- specified, otherwise it is the first character of
27410 -- the policy name.
27412 Queuing_Policy => ' ',
27413 -- Queuing_Policy used, default of space means not
27414 -- specified, otherwise it is the first character of
27415 -- the policy name.
27417 Task_Dispatching_Policy => ' ',
27418 -- Task_Dispatching_Policy used, default of space means
27419 -- not specified, otherwise first character of the
27422 Adafinal => System.Null_Address,
27423 -- Address of Adafinal routine, not used anymore
27425 Unreserve_All_Interrupts => 0,
27426 -- Set true if pragma Unreserve_All_Interrupts was used
27428 Exception_Tracebacks => 0);
27429 -- Indicates if exception tracebacks are enabled
27431 Elab_Final_Code := 1;
27433 -- Now we have the elaboration calls for all units in the partition.
27434 -- The Elab_Spec and Elab_Body attributes generate references to the
27435 -- implicit elaboration procedures generated by the compiler for
27436 -- each unit that requires elaboration.
27439 Interfaces.C_Streams'Elab_Spec;
27443 Ada.Exceptions'Elab_Spec;
27446 System.Exception_Table'Elab_Body;
27450 Ada.Io_Exceptions'Elab_Spec;
27454 System.Exceptions'Elab_Spec;
27458 System.Stack_Checking'Elab_Spec;
27461 System.Soft_Links'Elab_Body;
27466 System.Secondary_Stack'Elab_Body;
27470 Ada.Tags'Elab_Spec;
27473 Ada.Tags'Elab_Body;
27477 Ada.Streams'Elab_Spec;
27481 System.Finalization_Root'Elab_Spec;
27485 Ada.Exceptions'Elab_Body;
27489 System.Finalization_Implementation'Elab_Spec;
27492 System.Finalization_Implementation'Elab_Body;
27496 Ada.Finalization'Elab_Spec;
27500 Ada.Finalization.List_Controller'Elab_Spec;
27504 System.File_Control_Block'Elab_Spec;
27508 System.File_Io'Elab_Body;
27512 Ada.Text_Io'Elab_Spec;
27515 Ada.Text_Io'Elab_Body;
27519 Elab_Final_Code := 0;
27527 procedure adafinal is
27536 -- main is actually a function, as in the ANSI C standard,
27537 -- defined to return the exit status. The three parameters
27538 -- are the argument count, argument values and environment
27541 @findex Main Program
27544 argv : System.Address;
27545 envp : System.Address)
27548 -- The initialize routine performs low level system
27549 -- initialization using a standard library routine which
27550 -- sets up signal handling and performs any other
27551 -- required setup. The routine can be found in file
27554 @findex __gnat_initialize
27555 procedure initialize;
27556 pragma Import (C, initialize, "__gnat_initialize");
27558 -- The finalize routine performs low level system
27559 -- finalization using a standard library routine. The
27560 -- routine is found in file a-final.c and in the standard
27561 -- distribution is a dummy routine that does nothing, so
27562 -- really this is a hook for special user finalization.
27564 @findex __gnat_finalize
27565 procedure finalize;
27566 pragma Import (C, finalize, "__gnat_finalize");
27568 -- We get to the main program of the partition by using
27569 -- pragma Import because if we try to with the unit and
27570 -- call it Ada style, then not only do we waste time
27571 -- recompiling it, but also, we don't really know the right
27572 -- switches (e.g.@: identifier character set) to be used
27575 procedure Ada_Main_Program;
27576 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27578 -- Start of processing for main
27581 -- Save global variables
27587 -- Call low level system initialization
27591 -- Call our generated Ada initialization routine
27595 -- This is the point at which we want the debugger to get
27600 -- Now we call the main program of the partition
27604 -- Perform Ada finalization
27608 -- Perform low level system finalization
27612 -- Return the proper exit status
27613 return (gnat_exit_status);
27616 -- This section is entirely comments, so it has no effect on the
27617 -- compilation of the Ada_Main package. It provides the list of
27618 -- object files and linker options, as well as some standard
27619 -- libraries needed for the link. The gnatlink utility parses
27620 -- this b~hello.adb file to read these comment lines to generate
27621 -- the appropriate command line arguments for the call to the
27622 -- system linker. The BEGIN/END lines are used for sentinels for
27623 -- this parsing operation.
27625 -- The exact file names will of course depend on the environment,
27626 -- host/target and location of files on the host system.
27628 @findex Object file list
27629 -- BEGIN Object file/option list
27632 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27633 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27634 -- END Object file/option list
27640 The Ada code in the above example is exactly what is generated by the
27641 binder. We have added comments to more clearly indicate the function
27642 of each part of the generated @code{Ada_Main} package.
27644 The code is standard Ada in all respects, and can be processed by any
27645 tools that handle Ada. In particular, it is possible to use the debugger
27646 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27647 suppose that for reasons that you do not understand, your program is crashing
27648 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27649 you can place a breakpoint on the call:
27651 @smallexample @c ada
27652 Ada.Text_Io'Elab_Body;
27656 and trace the elaboration routine for this package to find out where
27657 the problem might be (more usually of course you would be debugging
27658 elaboration code in your own application).
27660 @node Elaboration Order Handling in GNAT
27661 @appendix Elaboration Order Handling in GNAT
27662 @cindex Order of elaboration
27663 @cindex Elaboration control
27666 * Elaboration Code::
27667 * Checking the Elaboration Order::
27668 * Controlling the Elaboration Order::
27669 * Controlling Elaboration in GNAT - Internal Calls::
27670 * Controlling Elaboration in GNAT - External Calls::
27671 * Default Behavior in GNAT - Ensuring Safety::
27672 * Treatment of Pragma Elaborate::
27673 * Elaboration Issues for Library Tasks::
27674 * Mixing Elaboration Models::
27675 * What to Do If the Default Elaboration Behavior Fails::
27676 * Elaboration for Access-to-Subprogram Values::
27677 * Summary of Procedures for Elaboration Control::
27678 * Other Elaboration Order Considerations::
27682 This chapter describes the handling of elaboration code in Ada and
27683 in GNAT, and discusses how the order of elaboration of program units can
27684 be controlled in GNAT, either automatically or with explicit programming
27687 @node Elaboration Code
27688 @section Elaboration Code
27691 Ada provides rather general mechanisms for executing code at elaboration
27692 time, that is to say before the main program starts executing. Such code arises
27696 @item Initializers for variables.
27697 Variables declared at the library level, in package specs or bodies, can
27698 require initialization that is performed at elaboration time, as in:
27699 @smallexample @c ada
27701 Sqrt_Half : Float := Sqrt (0.5);
27705 @item Package initialization code
27706 Code in a @code{BEGIN-END} section at the outer level of a package body is
27707 executed as part of the package body elaboration code.
27709 @item Library level task allocators
27710 Tasks that are declared using task allocators at the library level
27711 start executing immediately and hence can execute at elaboration time.
27715 Subprogram calls are possible in any of these contexts, which means that
27716 any arbitrary part of the program may be executed as part of the elaboration
27717 code. It is even possible to write a program which does all its work at
27718 elaboration time, with a null main program, although stylistically this
27719 would usually be considered an inappropriate way to structure
27722 An important concern arises in the context of elaboration code:
27723 we have to be sure that it is executed in an appropriate order. What we
27724 have is a series of elaboration code sections, potentially one section
27725 for each unit in the program. It is important that these execute
27726 in the correct order. Correctness here means that, taking the above
27727 example of the declaration of @code{Sqrt_Half},
27728 if some other piece of
27729 elaboration code references @code{Sqrt_Half},
27730 then it must run after the
27731 section of elaboration code that contains the declaration of
27734 There would never be any order of elaboration problem if we made a rule
27735 that whenever you @code{with} a unit, you must elaborate both the spec and body
27736 of that unit before elaborating the unit doing the @code{with}'ing:
27738 @smallexample @c ada
27742 package Unit_2 is @dots{}
27748 would require that both the body and spec of @code{Unit_1} be elaborated
27749 before the spec of @code{Unit_2}. However, a rule like that would be far too
27750 restrictive. In particular, it would make it impossible to have routines
27751 in separate packages that were mutually recursive.
27753 You might think that a clever enough compiler could look at the actual
27754 elaboration code and determine an appropriate correct order of elaboration,
27755 but in the general case, this is not possible. Consider the following
27758 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
27760 the variable @code{Sqrt_1}, which is declared in the elaboration code
27761 of the body of @code{Unit_1}:
27763 @smallexample @c ada
27765 Sqrt_1 : Float := Sqrt (0.1);
27770 The elaboration code of the body of @code{Unit_1} also contains:
27772 @smallexample @c ada
27775 if expression_1 = 1 then
27776 Q := Unit_2.Func_2;
27783 @code{Unit_2} is exactly parallel,
27784 it has a procedure @code{Func_2} that references
27785 the variable @code{Sqrt_2}, which is declared in the elaboration code of
27786 the body @code{Unit_2}:
27788 @smallexample @c ada
27790 Sqrt_2 : Float := Sqrt (0.1);
27795 The elaboration code of the body of @code{Unit_2} also contains:
27797 @smallexample @c ada
27800 if expression_2 = 2 then
27801 Q := Unit_1.Func_1;
27808 Now the question is, which of the following orders of elaboration is
27833 If you carefully analyze the flow here, you will see that you cannot tell
27834 at compile time the answer to this question.
27835 If @code{expression_1} is not equal to 1,
27836 and @code{expression_2} is not equal to 2,
27837 then either order is acceptable, because neither of the function calls is
27838 executed. If both tests evaluate to true, then neither order is acceptable
27839 and in fact there is no correct order.
27841 If one of the two expressions is true, and the other is false, then one
27842 of the above orders is correct, and the other is incorrect. For example,
27843 if @code{expression_1} /= 1 and @code{expression_2} = 2,
27844 then the call to @code{Func_1}
27845 will occur, but not the call to @code{Func_2.}
27846 This means that it is essential
27847 to elaborate the body of @code{Unit_1} before
27848 the body of @code{Unit_2}, so the first
27849 order of elaboration is correct and the second is wrong.
27851 By making @code{expression_1} and @code{expression_2}
27852 depend on input data, or perhaps
27853 the time of day, we can make it impossible for the compiler or binder
27854 to figure out which of these expressions will be true, and hence it
27855 is impossible to guarantee a safe order of elaboration at run time.
27857 @node Checking the Elaboration Order
27858 @section Checking the Elaboration Order
27861 In some languages that involve the same kind of elaboration problems,
27862 e.g.@: Java and C++, the programmer is expected to worry about these
27863 ordering problems himself, and it is common to
27864 write a program in which an incorrect elaboration order gives
27865 surprising results, because it references variables before they
27867 Ada is designed to be a safe language, and a programmer-beware approach is
27868 clearly not sufficient. Consequently, the language provides three lines
27872 @item Standard rules
27873 Some standard rules restrict the possible choice of elaboration
27874 order. In particular, if you @code{with} a unit, then its spec is always
27875 elaborated before the unit doing the @code{with}. Similarly, a parent
27876 spec is always elaborated before the child spec, and finally
27877 a spec is always elaborated before its corresponding body.
27879 @item Dynamic elaboration checks
27880 @cindex Elaboration checks
27881 @cindex Checks, elaboration
27882 Dynamic checks are made at run time, so that if some entity is accessed
27883 before it is elaborated (typically by means of a subprogram call)
27884 then the exception (@code{Program_Error}) is raised.
27886 @item Elaboration control
27887 Facilities are provided for the programmer to specify the desired order
27891 Let's look at these facilities in more detail. First, the rules for
27892 dynamic checking. One possible rule would be simply to say that the
27893 exception is raised if you access a variable which has not yet been
27894 elaborated. The trouble with this approach is that it could require
27895 expensive checks on every variable reference. Instead Ada has two
27896 rules which are a little more restrictive, but easier to check, and
27900 @item Restrictions on calls
27901 A subprogram can only be called at elaboration time if its body
27902 has been elaborated. The rules for elaboration given above guarantee
27903 that the spec of the subprogram has been elaborated before the
27904 call, but not the body. If this rule is violated, then the
27905 exception @code{Program_Error} is raised.
27907 @item Restrictions on instantiations
27908 A generic unit can only be instantiated if the body of the generic
27909 unit has been elaborated. Again, the rules for elaboration given above
27910 guarantee that the spec of the generic unit has been elaborated
27911 before the instantiation, but not the body. If this rule is
27912 violated, then the exception @code{Program_Error} is raised.
27916 The idea is that if the body has been elaborated, then any variables
27917 it references must have been elaborated; by checking for the body being
27918 elaborated we guarantee that none of its references causes any
27919 trouble. As we noted above, this is a little too restrictive, because a
27920 subprogram that has no non-local references in its body may in fact be safe
27921 to call. However, it really would be unsafe to rely on this, because
27922 it would mean that the caller was aware of details of the implementation
27923 in the body. This goes against the basic tenets of Ada.
27925 A plausible implementation can be described as follows.
27926 A Boolean variable is associated with each subprogram
27927 and each generic unit. This variable is initialized to False, and is set to
27928 True at the point body is elaborated. Every call or instantiation checks the
27929 variable, and raises @code{Program_Error} if the variable is False.
27931 Note that one might think that it would be good enough to have one Boolean
27932 variable for each package, but that would not deal with cases of trying
27933 to call a body in the same package as the call
27934 that has not been elaborated yet.
27935 Of course a compiler may be able to do enough analysis to optimize away
27936 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
27937 does such optimizations, but still the easiest conceptual model is to
27938 think of there being one variable per subprogram.
27940 @node Controlling the Elaboration Order
27941 @section Controlling the Elaboration Order
27944 In the previous section we discussed the rules in Ada which ensure
27945 that @code{Program_Error} is raised if an incorrect elaboration order is
27946 chosen. This prevents erroneous executions, but we need mechanisms to
27947 specify a correct execution and avoid the exception altogether.
27948 To achieve this, Ada provides a number of features for controlling
27949 the order of elaboration. We discuss these features in this section.
27951 First, there are several ways of indicating to the compiler that a given
27952 unit has no elaboration problems:
27955 @item packages that do not require a body
27956 A library package that does not require a body does not permit
27957 a body (this rule was introduced in Ada 95).
27958 Thus if we have a such a package, as in:
27960 @smallexample @c ada
27963 package Definitions is
27965 type m is new integer;
27967 type a is array (1 .. 10) of m;
27968 type b is array (1 .. 20) of m;
27976 A package that @code{with}'s @code{Definitions} may safely instantiate
27977 @code{Definitions.Subp} because the compiler can determine that there
27978 definitely is no package body to worry about in this case
27981 @cindex pragma Pure
27983 Places sufficient restrictions on a unit to guarantee that
27984 no call to any subprogram in the unit can result in an
27985 elaboration problem. This means that the compiler does not need
27986 to worry about the point of elaboration of such units, and in
27987 particular, does not need to check any calls to any subprograms
27990 @item pragma Preelaborate
27991 @findex Preelaborate
27992 @cindex pragma Preelaborate
27993 This pragma places slightly less stringent restrictions on a unit than
27995 but these restrictions are still sufficient to ensure that there
27996 are no elaboration problems with any calls to the unit.
27998 @item pragma Elaborate_Body
27999 @findex Elaborate_Body
28000 @cindex pragma Elaborate_Body
28001 This pragma requires that the body of a unit be elaborated immediately
28002 after its spec. Suppose a unit @code{A} has such a pragma,
28003 and unit @code{B} does
28004 a @code{with} of unit @code{A}. Recall that the standard rules require
28005 the spec of unit @code{A}
28006 to be elaborated before the @code{with}'ing unit; given the pragma in
28007 @code{A}, we also know that the body of @code{A}
28008 will be elaborated before @code{B}, so
28009 that calls to @code{A} are safe and do not need a check.
28014 unlike pragma @code{Pure} and pragma @code{Preelaborate},
28016 @code{Elaborate_Body} does not guarantee that the program is
28017 free of elaboration problems, because it may not be possible
28018 to satisfy the requested elaboration order.
28019 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
28021 marks @code{Unit_1} as @code{Elaborate_Body},
28022 and not @code{Unit_2,} then the order of
28023 elaboration will be:
28035 Now that means that the call to @code{Func_1} in @code{Unit_2}
28036 need not be checked,
28037 it must be safe. But the call to @code{Func_2} in
28038 @code{Unit_1} may still fail if
28039 @code{Expression_1} is equal to 1,
28040 and the programmer must still take
28041 responsibility for this not being the case.
28043 If all units carry a pragma @code{Elaborate_Body}, then all problems are
28044 eliminated, except for calls entirely within a body, which are
28045 in any case fully under programmer control. However, using the pragma
28046 everywhere is not always possible.
28047 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
28048 we marked both of them as having pragma @code{Elaborate_Body}, then
28049 clearly there would be no possible elaboration order.
28051 The above pragmas allow a server to guarantee safe use by clients, and
28052 clearly this is the preferable approach. Consequently a good rule
28053 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
28054 and if this is not possible,
28055 mark them as @code{Elaborate_Body} if possible.
28056 As we have seen, there are situations where neither of these
28057 three pragmas can be used.
28058 So we also provide methods for clients to control the
28059 order of elaboration of the servers on which they depend:
28062 @item pragma Elaborate (unit)
28064 @cindex pragma Elaborate
28065 This pragma is placed in the context clause, after a @code{with} clause,
28066 and it requires that the body of the named unit be elaborated before
28067 the unit in which the pragma occurs. The idea is to use this pragma
28068 if the current unit calls at elaboration time, directly or indirectly,
28069 some subprogram in the named unit.
28071 @item pragma Elaborate_All (unit)
28072 @findex Elaborate_All
28073 @cindex pragma Elaborate_All
28074 This is a stronger version of the Elaborate pragma. Consider the
28078 Unit A @code{with}'s unit B and calls B.Func in elab code
28079 Unit B @code{with}'s unit C, and B.Func calls C.Func
28083 Now if we put a pragma @code{Elaborate (B)}
28084 in unit @code{A}, this ensures that the
28085 body of @code{B} is elaborated before the call, but not the
28086 body of @code{C}, so
28087 the call to @code{C.Func} could still cause @code{Program_Error} to
28090 The effect of a pragma @code{Elaborate_All} is stronger, it requires
28091 not only that the body of the named unit be elaborated before the
28092 unit doing the @code{with}, but also the bodies of all units that the
28093 named unit uses, following @code{with} links transitively. For example,
28094 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
28096 not only that the body of @code{B} be elaborated before @code{A},
28098 body of @code{C}, because @code{B} @code{with}'s @code{C}.
28102 We are now in a position to give a usage rule in Ada for avoiding
28103 elaboration problems, at least if dynamic dispatching and access to
28104 subprogram values are not used. We will handle these cases separately
28107 The rule is simple. If a unit has elaboration code that can directly or
28108 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
28109 a generic package in a @code{with}'ed unit,
28110 then if the @code{with}'ed unit does not have
28111 pragma @code{Pure} or @code{Preelaborate}, then the client should have
28112 a pragma @code{Elaborate_All}
28113 for the @code{with}'ed unit. By following this rule a client is
28114 assured that calls can be made without risk of an exception.
28116 For generic subprogram instantiations, the rule can be relaxed to
28117 require only a pragma @code{Elaborate} since elaborating the body
28118 of a subprogram cannot cause any transitive elaboration (we are
28119 not calling the subprogram in this case, just elaborating its
28122 If this rule is not followed, then a program may be in one of four
28126 @item No order exists
28127 No order of elaboration exists which follows the rules, taking into
28128 account any @code{Elaborate}, @code{Elaborate_All},
28129 or @code{Elaborate_Body} pragmas. In
28130 this case, an Ada compiler must diagnose the situation at bind
28131 time, and refuse to build an executable program.
28133 @item One or more orders exist, all incorrect
28134 One or more acceptable elaboration orders exist, and all of them
28135 generate an elaboration order problem. In this case, the binder
28136 can build an executable program, but @code{Program_Error} will be raised
28137 when the program is run.
28139 @item Several orders exist, some right, some incorrect
28140 One or more acceptable elaboration orders exists, and some of them
28141 work, and some do not. The programmer has not controlled
28142 the order of elaboration, so the binder may or may not pick one of
28143 the correct orders, and the program may or may not raise an
28144 exception when it is run. This is the worst case, because it means
28145 that the program may fail when moved to another compiler, or even
28146 another version of the same compiler.
28148 @item One or more orders exists, all correct
28149 One ore more acceptable elaboration orders exist, and all of them
28150 work. In this case the program runs successfully. This state of
28151 affairs can be guaranteed by following the rule we gave above, but
28152 may be true even if the rule is not followed.
28156 Note that one additional advantage of following our rules on the use
28157 of @code{Elaborate} and @code{Elaborate_All}
28158 is that the program continues to stay in the ideal (all orders OK) state
28159 even if maintenance
28160 changes some bodies of some units. Conversely, if a program that does
28161 not follow this rule happens to be safe at some point, this state of affairs
28162 may deteriorate silently as a result of maintenance changes.
28164 You may have noticed that the above discussion did not mention
28165 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
28166 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
28167 code in the body makes calls to some other unit, so it is still necessary
28168 to use @code{Elaborate_All} on such units.
28170 @node Controlling Elaboration in GNAT - Internal Calls
28171 @section Controlling Elaboration in GNAT - Internal Calls
28174 In the case of internal calls, i.e., calls within a single package, the
28175 programmer has full control over the order of elaboration, and it is up
28176 to the programmer to elaborate declarations in an appropriate order. For
28179 @smallexample @c ada
28182 function One return Float;
28186 function One return Float is
28195 will obviously raise @code{Program_Error} at run time, because function
28196 One will be called before its body is elaborated. In this case GNAT will
28197 generate a warning that the call will raise @code{Program_Error}:
28203 2. function One return Float;
28205 4. Q : Float := One;
28207 >>> warning: cannot call "One" before body is elaborated
28208 >>> warning: Program_Error will be raised at run time
28211 6. function One return Float is
28224 Note that in this particular case, it is likely that the call is safe, because
28225 the function @code{One} does not access any global variables.
28226 Nevertheless in Ada, we do not want the validity of the check to depend on
28227 the contents of the body (think about the separate compilation case), so this
28228 is still wrong, as we discussed in the previous sections.
28230 The error is easily corrected by rearranging the declarations so that the
28231 body of @code{One} appears before the declaration containing the call
28232 (note that in Ada 95 and Ada 2005,
28233 declarations can appear in any order, so there is no restriction that
28234 would prevent this reordering, and if we write:
28236 @smallexample @c ada
28239 function One return Float;
28241 function One return Float is
28252 then all is well, no warning is generated, and no
28253 @code{Program_Error} exception
28255 Things are more complicated when a chain of subprograms is executed:
28257 @smallexample @c ada
28260 function A return Integer;
28261 function B return Integer;
28262 function C return Integer;
28264 function B return Integer is begin return A; end;
28265 function C return Integer is begin return B; end;
28269 function A return Integer is begin return 1; end;
28275 Now the call to @code{C}
28276 at elaboration time in the declaration of @code{X} is correct, because
28277 the body of @code{C} is already elaborated,
28278 and the call to @code{B} within the body of
28279 @code{C} is correct, but the call
28280 to @code{A} within the body of @code{B} is incorrect, because the body
28281 of @code{A} has not been elaborated, so @code{Program_Error}
28282 will be raised on the call to @code{A}.
28283 In this case GNAT will generate a
28284 warning that @code{Program_Error} may be
28285 raised at the point of the call. Let's look at the warning:
28291 2. function A return Integer;
28292 3. function B return Integer;
28293 4. function C return Integer;
28295 6. function B return Integer is begin return A; end;
28297 >>> warning: call to "A" before body is elaborated may
28298 raise Program_Error
28299 >>> warning: "B" called at line 7
28300 >>> warning: "C" called at line 9
28302 7. function C return Integer is begin return B; end;
28304 9. X : Integer := C;
28306 11. function A return Integer is begin return 1; end;
28316 Note that the message here says ``may raise'', instead of the direct case,
28317 where the message says ``will be raised''. That's because whether
28319 actually called depends in general on run-time flow of control.
28320 For example, if the body of @code{B} said
28322 @smallexample @c ada
28325 function B return Integer is
28327 if some-condition-depending-on-input-data then
28338 then we could not know until run time whether the incorrect call to A would
28339 actually occur, so @code{Program_Error} might
28340 or might not be raised. It is possible for a compiler to
28341 do a better job of analyzing bodies, to
28342 determine whether or not @code{Program_Error}
28343 might be raised, but it certainly
28344 couldn't do a perfect job (that would require solving the halting problem
28345 and is provably impossible), and because this is a warning anyway, it does
28346 not seem worth the effort to do the analysis. Cases in which it
28347 would be relevant are rare.
28349 In practice, warnings of either of the forms given
28350 above will usually correspond to
28351 real errors, and should be examined carefully and eliminated.
28352 In the rare case where a warning is bogus, it can be suppressed by any of
28353 the following methods:
28357 Compile with the @option{-gnatws} switch set
28360 Suppress @code{Elaboration_Check} for the called subprogram
28363 Use pragma @code{Warnings_Off} to turn warnings off for the call
28367 For the internal elaboration check case,
28368 GNAT by default generates the
28369 necessary run-time checks to ensure
28370 that @code{Program_Error} is raised if any
28371 call fails an elaboration check. Of course this can only happen if a
28372 warning has been issued as described above. The use of pragma
28373 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
28374 some of these checks, meaning that it may be possible (but is not
28375 guaranteed) for a program to be able to call a subprogram whose body
28376 is not yet elaborated, without raising a @code{Program_Error} exception.
28378 @node Controlling Elaboration in GNAT - External Calls
28379 @section Controlling Elaboration in GNAT - External Calls
28382 The previous section discussed the case in which the execution of a
28383 particular thread of elaboration code occurred entirely within a
28384 single unit. This is the easy case to handle, because a programmer
28385 has direct and total control over the order of elaboration, and
28386 furthermore, checks need only be generated in cases which are rare
28387 and which the compiler can easily detect.
28388 The situation is more complex when separate compilation is taken into account.
28389 Consider the following:
28391 @smallexample @c ada
28395 function Sqrt (Arg : Float) return Float;
28398 package body Math is
28399 function Sqrt (Arg : Float) return Float is
28408 X : Float := Math.Sqrt (0.5);
28421 where @code{Main} is the main program. When this program is executed, the
28422 elaboration code must first be executed, and one of the jobs of the
28423 binder is to determine the order in which the units of a program are
28424 to be elaborated. In this case we have four units: the spec and body
28426 the spec of @code{Stuff} and the body of @code{Main}).
28427 In what order should the four separate sections of elaboration code
28430 There are some restrictions in the order of elaboration that the binder
28431 can choose. In particular, if unit U has a @code{with}
28432 for a package @code{X}, then you
28433 are assured that the spec of @code{X}
28434 is elaborated before U , but you are
28435 not assured that the body of @code{X}
28436 is elaborated before U.
28437 This means that in the above case, the binder is allowed to choose the
28448 but that's not good, because now the call to @code{Math.Sqrt}
28449 that happens during
28450 the elaboration of the @code{Stuff}
28451 spec happens before the body of @code{Math.Sqrt} is
28452 elaborated, and hence causes @code{Program_Error} exception to be raised.
28453 At first glance, one might say that the binder is misbehaving, because
28454 obviously you want to elaborate the body of something you @code{with}
28456 that is not a general rule that can be followed in all cases. Consider
28458 @smallexample @c ada
28461 package X is @dots{}
28463 package Y is @dots{}
28466 package body Y is @dots{}
28469 package body X is @dots{}
28475 This is a common arrangement, and, apart from the order of elaboration
28476 problems that might arise in connection with elaboration code, this works fine.
28477 A rule that says that you must first elaborate the body of anything you
28478 @code{with} cannot work in this case:
28479 the body of @code{X} @code{with}'s @code{Y},
28480 which means you would have to
28481 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
28483 you have to elaborate the body of @code{X} first, but @dots{} and we have a
28484 loop that cannot be broken.
28486 It is true that the binder can in many cases guess an order of elaboration
28487 that is unlikely to cause a @code{Program_Error}
28488 exception to be raised, and it tries to do so (in the
28489 above example of @code{Math/Stuff/Spec}, the GNAT binder will
28491 elaborate the body of @code{Math} right after its spec, so all will be well).
28493 However, a program that blindly relies on the binder to be helpful can
28494 get into trouble, as we discussed in the previous sections, so
28496 provides a number of facilities for assisting the programmer in
28497 developing programs that are robust with respect to elaboration order.
28499 @node Default Behavior in GNAT - Ensuring Safety
28500 @section Default Behavior in GNAT - Ensuring Safety
28503 The default behavior in GNAT ensures elaboration safety. In its
28504 default mode GNAT implements the
28505 rule we previously described as the right approach. Let's restate it:
28509 @emph{If a unit has elaboration code that can directly or indirectly make a
28510 call to a subprogram in a @code{with}'ed unit, or instantiate a generic
28511 package in a @code{with}'ed unit, then if the @code{with}'ed unit
28512 does not have pragma @code{Pure} or
28513 @code{Preelaborate}, then the client should have an
28514 @code{Elaborate_All} pragma for the @code{with}'ed unit.}
28516 @emph{In the case of instantiating a generic subprogram, it is always
28517 sufficient to have only an @code{Elaborate} pragma for the
28518 @code{with}'ed unit.}
28522 By following this rule a client is assured that calls and instantiations
28523 can be made without risk of an exception.
28525 In this mode GNAT traces all calls that are potentially made from
28526 elaboration code, and puts in any missing implicit @code{Elaborate}
28527 and @code{Elaborate_All} pragmas.
28528 The advantage of this approach is that no elaboration problems
28529 are possible if the binder can find an elaboration order that is
28530 consistent with these implicit @code{Elaborate} and
28531 @code{Elaborate_All} pragmas. The
28532 disadvantage of this approach is that no such order may exist.
28534 If the binder does not generate any diagnostics, then it means that it has
28535 found an elaboration order that is guaranteed to be safe. However, the binder
28536 may still be relying on implicitly generated @code{Elaborate} and
28537 @code{Elaborate_All} pragmas so portability to other compilers than GNAT is not
28540 If it is important to guarantee portability, then the compilations should
28543 (warn on elaboration problems) switch. This will cause warning messages
28544 to be generated indicating the missing @code{Elaborate} and
28545 @code{Elaborate_All} pragmas.
28546 Consider the following source program:
28548 @smallexample @c ada
28553 m : integer := k.r;
28560 where it is clear that there
28561 should be a pragma @code{Elaborate_All}
28562 for unit @code{k}. An implicit pragma will be generated, and it is
28563 likely that the binder will be able to honor it. However, if you want
28564 to port this program to some other Ada compiler than GNAT.
28565 it is safer to include the pragma explicitly in the source. If this
28566 unit is compiled with the
28568 switch, then the compiler outputs a warning:
28575 3. m : integer := k.r;
28577 >>> warning: call to "r" may raise Program_Error
28578 >>> warning: missing pragma Elaborate_All for "k"
28586 and these warnings can be used as a guide for supplying manually
28587 the missing pragmas. It is usually a bad idea to use this warning
28588 option during development. That's because it will warn you when
28589 you need to put in a pragma, but cannot warn you when it is time
28590 to take it out. So the use of pragma @code{Elaborate_All} may lead to
28591 unnecessary dependencies and even false circularities.
28593 This default mode is more restrictive than the Ada Reference
28594 Manual, and it is possible to construct programs which will compile
28595 using the dynamic model described there, but will run into a
28596 circularity using the safer static model we have described.
28598 Of course any Ada compiler must be able to operate in a mode
28599 consistent with the requirements of the Ada Reference Manual,
28600 and in particular must have the capability of implementing the
28601 standard dynamic model of elaboration with run-time checks.
28603 In GNAT, this standard mode can be achieved either by the use of
28604 the @option{-gnatE} switch on the compiler (@command{gcc} or
28605 @command{gnatmake}) command, or by the use of the configuration pragma:
28607 @smallexample @c ada
28608 pragma Elaboration_Checks (DYNAMIC);
28612 Either approach will cause the unit affected to be compiled using the
28613 standard dynamic run-time elaboration checks described in the Ada
28614 Reference Manual. The static model is generally preferable, since it
28615 is clearly safer to rely on compile and link time checks rather than
28616 run-time checks. However, in the case of legacy code, it may be
28617 difficult to meet the requirements of the static model. This
28618 issue is further discussed in
28619 @ref{What to Do If the Default Elaboration Behavior Fails}.
28621 Note that the static model provides a strict subset of the allowed
28622 behavior and programs of the Ada Reference Manual, so if you do
28623 adhere to the static model and no circularities exist,
28624 then you are assured that your program will
28625 work using the dynamic model, providing that you remove any
28626 pragma Elaborate statements from the source.
28628 @node Treatment of Pragma Elaborate
28629 @section Treatment of Pragma Elaborate
28630 @cindex Pragma Elaborate
28633 The use of @code{pragma Elaborate}
28634 should generally be avoided in Ada 95 and Ada 2005 programs,
28635 since there is no guarantee that transitive calls
28636 will be properly handled. Indeed at one point, this pragma was placed
28637 in Annex J (Obsolescent Features), on the grounds that it is never useful.
28639 Now that's a bit restrictive. In practice, the case in which
28640 @code{pragma Elaborate} is useful is when the caller knows that there
28641 are no transitive calls, or that the called unit contains all necessary
28642 transitive @code{pragma Elaborate} statements, and legacy code often
28643 contains such uses.
28645 Strictly speaking the static mode in GNAT should ignore such pragmas,
28646 since there is no assurance at compile time that the necessary safety
28647 conditions are met. In practice, this would cause GNAT to be incompatible
28648 with correctly written Ada 83 code that had all necessary
28649 @code{pragma Elaborate} statements in place. Consequently, we made the
28650 decision that GNAT in its default mode will believe that if it encounters
28651 a @code{pragma Elaborate} then the programmer knows what they are doing,
28652 and it will trust that no elaboration errors can occur.
28654 The result of this decision is two-fold. First to be safe using the
28655 static mode, you should remove all @code{pragma Elaborate} statements.
28656 Second, when fixing circularities in existing code, you can selectively
28657 use @code{pragma Elaborate} statements to convince the static mode of
28658 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
28661 When using the static mode with @option{-gnatwl}, any use of
28662 @code{pragma Elaborate} will generate a warning about possible
28665 @node Elaboration Issues for Library Tasks
28666 @section Elaboration Issues for Library Tasks
28667 @cindex Library tasks, elaboration issues
28668 @cindex Elaboration of library tasks
28671 In this section we examine special elaboration issues that arise for
28672 programs that declare library level tasks.
28674 Generally the model of execution of an Ada program is that all units are
28675 elaborated, and then execution of the program starts. However, the
28676 declaration of library tasks definitely does not fit this model. The
28677 reason for this is that library tasks start as soon as they are declared
28678 (more precisely, as soon as the statement part of the enclosing package
28679 body is reached), that is to say before elaboration
28680 of the program is complete. This means that if such a task calls a
28681 subprogram, or an entry in another task, the callee may or may not be
28682 elaborated yet, and in the standard
28683 Reference Manual model of dynamic elaboration checks, you can even
28684 get timing dependent Program_Error exceptions, since there can be
28685 a race between the elaboration code and the task code.
28687 The static model of elaboration in GNAT seeks to avoid all such
28688 dynamic behavior, by being conservative, and the conservative
28689 approach in this particular case is to assume that all the code
28690 in a task body is potentially executed at elaboration time if
28691 a task is declared at the library level.
28693 This can definitely result in unexpected circularities. Consider
28694 the following example
28696 @smallexample @c ada
28702 type My_Int is new Integer;
28704 function Ident (M : My_Int) return My_Int;
28708 package body Decls is
28709 task body Lib_Task is
28715 function Ident (M : My_Int) return My_Int is
28723 procedure Put_Val (Arg : Decls.My_Int);
28727 package body Utils is
28728 procedure Put_Val (Arg : Decls.My_Int) is
28730 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28737 Decls.Lib_Task.Start;
28742 If the above example is compiled in the default static elaboration
28743 mode, then a circularity occurs. The circularity comes from the call
28744 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
28745 this call occurs in elaboration code, we need an implicit pragma
28746 @code{Elaborate_All} for @code{Utils}. This means that not only must
28747 the spec and body of @code{Utils} be elaborated before the body
28748 of @code{Decls}, but also the spec and body of any unit that is
28749 @code{with'ed} by the body of @code{Utils} must also be elaborated before
28750 the body of @code{Decls}. This is the transitive implication of
28751 pragma @code{Elaborate_All} and it makes sense, because in general
28752 the body of @code{Put_Val} might have a call to something in a
28753 @code{with'ed} unit.
28755 In this case, the body of Utils (actually its spec) @code{with's}
28756 @code{Decls}. Unfortunately this means that the body of @code{Decls}
28757 must be elaborated before itself, in case there is a call from the
28758 body of @code{Utils}.
28760 Here is the exact chain of events we are worrying about:
28764 In the body of @code{Decls} a call is made from within the body of a library
28765 task to a subprogram in the package @code{Utils}. Since this call may
28766 occur at elaboration time (given that the task is activated at elaboration
28767 time), we have to assume the worst, i.e., that the
28768 call does happen at elaboration time.
28771 This means that the body and spec of @code{Util} must be elaborated before
28772 the body of @code{Decls} so that this call does not cause an access before
28776 Within the body of @code{Util}, specifically within the body of
28777 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
28781 One such @code{with}'ed package is package @code{Decls}, so there
28782 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
28783 In fact there is such a call in this example, but we would have to
28784 assume that there was such a call even if it were not there, since
28785 we are not supposed to write the body of @code{Decls} knowing what
28786 is in the body of @code{Utils}; certainly in the case of the
28787 static elaboration model, the compiler does not know what is in
28788 other bodies and must assume the worst.
28791 This means that the spec and body of @code{Decls} must also be
28792 elaborated before we elaborate the unit containing the call, but
28793 that unit is @code{Decls}! This means that the body of @code{Decls}
28794 must be elaborated before itself, and that's a circularity.
28798 Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in
28799 the body of @code{Decls} you will get a true Ada Reference Manual
28800 circularity that makes the program illegal.
28802 In practice, we have found that problems with the static model of
28803 elaboration in existing code often arise from library tasks, so
28804 we must address this particular situation.
28806 Note that if we compile and run the program above, using the dynamic model of
28807 elaboration (that is to say use the @option{-gnatE} switch),
28808 then it compiles, binds,
28809 links, and runs, printing the expected result of 2. Therefore in some sense
28810 the circularity here is only apparent, and we need to capture
28811 the properties of this program that distinguish it from other library-level
28812 tasks that have real elaboration problems.
28814 We have four possible answers to this question:
28819 Use the dynamic model of elaboration.
28821 If we use the @option{-gnatE} switch, then as noted above, the program works.
28822 Why is this? If we examine the task body, it is apparent that the task cannot
28824 @code{accept} statement until after elaboration has been completed, because
28825 the corresponding entry call comes from the main program, not earlier.
28826 This is why the dynamic model works here. But that's really giving
28827 up on a precise analysis, and we prefer to take this approach only if we cannot
28829 problem in any other manner. So let us examine two ways to reorganize
28830 the program to avoid the potential elaboration problem.
28833 Split library tasks into separate packages.
28835 Write separate packages, so that library tasks are isolated from
28836 other declarations as much as possible. Let us look at a variation on
28839 @smallexample @c ada
28847 package body Decls1 is
28848 task body Lib_Task is
28856 type My_Int is new Integer;
28857 function Ident (M : My_Int) return My_Int;
28861 package body Decls2 is
28862 function Ident (M : My_Int) return My_Int is
28870 procedure Put_Val (Arg : Decls2.My_Int);
28874 package body Utils is
28875 procedure Put_Val (Arg : Decls2.My_Int) is
28877 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
28884 Decls1.Lib_Task.Start;
28889 All we have done is to split @code{Decls} into two packages, one
28890 containing the library task, and one containing everything else. Now
28891 there is no cycle, and the program compiles, binds, links and executes
28892 using the default static model of elaboration.
28895 Declare separate task types.
28897 A significant part of the problem arises because of the use of the
28898 single task declaration form. This means that the elaboration of
28899 the task type, and the elaboration of the task itself (i.e.@: the
28900 creation of the task) happen at the same time. A good rule
28901 of style in Ada is to always create explicit task types. By
28902 following the additional step of placing task objects in separate
28903 packages from the task type declaration, many elaboration problems
28904 are avoided. Here is another modified example of the example program:
28906 @smallexample @c ada
28908 task type Lib_Task_Type is
28912 type My_Int is new Integer;
28914 function Ident (M : My_Int) return My_Int;
28918 package body Decls is
28919 task body Lib_Task_Type is
28925 function Ident (M : My_Int) return My_Int is
28933 procedure Put_Val (Arg : Decls.My_Int);
28937 package body Utils is
28938 procedure Put_Val (Arg : Decls.My_Int) is
28940 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
28946 Lib_Task : Decls.Lib_Task_Type;
28952 Declst.Lib_Task.Start;
28957 What we have done here is to replace the @code{task} declaration in
28958 package @code{Decls} with a @code{task type} declaration. Then we
28959 introduce a separate package @code{Declst} to contain the actual
28960 task object. This separates the elaboration issues for
28961 the @code{task type}
28962 declaration, which causes no trouble, from the elaboration issues
28963 of the task object, which is also unproblematic, since it is now independent
28964 of the elaboration of @code{Utils}.
28965 This separation of concerns also corresponds to
28966 a generally sound engineering principle of separating declarations
28967 from instances. This version of the program also compiles, binds, links,
28968 and executes, generating the expected output.
28971 Use No_Entry_Calls_In_Elaboration_Code restriction.
28972 @cindex No_Entry_Calls_In_Elaboration_Code
28974 The previous two approaches described how a program can be restructured
28975 to avoid the special problems caused by library task bodies. in practice,
28976 however, such restructuring may be difficult to apply to existing legacy code,
28977 so we must consider solutions that do not require massive rewriting.
28979 Let us consider more carefully why our original sample program works
28980 under the dynamic model of elaboration. The reason is that the code
28981 in the task body blocks immediately on the @code{accept}
28982 statement. Now of course there is nothing to prohibit elaboration
28983 code from making entry calls (for example from another library level task),
28984 so we cannot tell in isolation that
28985 the task will not execute the accept statement during elaboration.
28987 However, in practice it is very unusual to see elaboration code
28988 make any entry calls, and the pattern of tasks starting
28989 at elaboration time and then immediately blocking on @code{accept} or
28990 @code{select} statements is very common. What this means is that
28991 the compiler is being too pessimistic when it analyzes the
28992 whole package body as though it might be executed at elaboration
28995 If we know that the elaboration code contains no entry calls, (a very safe
28996 assumption most of the time, that could almost be made the default
28997 behavior), then we can compile all units of the program under control
28998 of the following configuration pragma:
29001 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
29005 This pragma can be placed in the @file{gnat.adc} file in the usual
29006 manner. If we take our original unmodified program and compile it
29007 in the presence of a @file{gnat.adc} containing the above pragma,
29008 then once again, we can compile, bind, link, and execute, obtaining
29009 the expected result. In the presence of this pragma, the compiler does
29010 not trace calls in a task body, that appear after the first @code{accept}
29011 or @code{select} statement, and therefore does not report a potential
29012 circularity in the original program.
29014 The compiler will check to the extent it can that the above
29015 restriction is not violated, but it is not always possible to do a
29016 complete check at compile time, so it is important to use this
29017 pragma only if the stated restriction is in fact met, that is to say
29018 no task receives an entry call before elaboration of all units is completed.
29022 @node Mixing Elaboration Models
29023 @section Mixing Elaboration Models
29025 So far, we have assumed that the entire program is either compiled
29026 using the dynamic model or static model, ensuring consistency. It
29027 is possible to mix the two models, but rules have to be followed
29028 if this mixing is done to ensure that elaboration checks are not
29031 The basic rule is that @emph{a unit compiled with the static model cannot
29032 be @code{with'ed} by a unit compiled with the dynamic model}. The
29033 reason for this is that in the static model, a unit assumes that
29034 its clients guarantee to use (the equivalent of) pragma
29035 @code{Elaborate_All} so that no elaboration checks are required
29036 in inner subprograms, and this assumption is violated if the
29037 client is compiled with dynamic checks.
29039 The precise rule is as follows. A unit that is compiled with dynamic
29040 checks can only @code{with} a unit that meets at least one of the
29041 following criteria:
29046 The @code{with'ed} unit is itself compiled with dynamic elaboration
29047 checks (that is with the @option{-gnatE} switch.
29050 The @code{with'ed} unit is an internal GNAT implementation unit from
29051 the System, Interfaces, Ada, or GNAT hierarchies.
29054 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
29057 The @code{with'ing} unit (that is the client) has an explicit pragma
29058 @code{Elaborate_All} for the @code{with'ed} unit.
29063 If this rule is violated, that is if a unit with dynamic elaboration
29064 checks @code{with's} a unit that does not meet one of the above four
29065 criteria, then the binder (@code{gnatbind}) will issue a warning
29066 similar to that in the following example:
29069 warning: "x.ads" has dynamic elaboration checks and with's
29070 warning: "y.ads" which has static elaboration checks
29074 These warnings indicate that the rule has been violated, and that as a result
29075 elaboration checks may be missed in the resulting executable file.
29076 This warning may be suppressed using the @option{-ws} binder switch
29077 in the usual manner.
29079 One useful application of this mixing rule is in the case of a subsystem
29080 which does not itself @code{with} units from the remainder of the
29081 application. In this case, the entire subsystem can be compiled with
29082 dynamic checks to resolve a circularity in the subsystem, while
29083 allowing the main application that uses this subsystem to be compiled
29084 using the more reliable default static model.
29086 @node What to Do If the Default Elaboration Behavior Fails
29087 @section What to Do If the Default Elaboration Behavior Fails
29090 If the binder cannot find an acceptable order, it outputs detailed
29091 diagnostics. For example:
29097 error: elaboration circularity detected
29098 info: "proc (body)" must be elaborated before "pack (body)"
29099 info: reason: Elaborate_All probably needed in unit "pack (body)"
29100 info: recompile "pack (body)" with -gnatwl
29101 info: for full details
29102 info: "proc (body)"
29103 info: is needed by its spec:
29104 info: "proc (spec)"
29105 info: which is withed by:
29106 info: "pack (body)"
29107 info: "pack (body)" must be elaborated before "proc (body)"
29108 info: reason: pragma Elaborate in unit "proc (body)"
29114 In this case we have a cycle that the binder cannot break. On the one
29115 hand, there is an explicit pragma Elaborate in @code{proc} for
29116 @code{pack}. This means that the body of @code{pack} must be elaborated
29117 before the body of @code{proc}. On the other hand, there is elaboration
29118 code in @code{pack} that calls a subprogram in @code{proc}. This means
29119 that for maximum safety, there should really be a pragma
29120 Elaborate_All in @code{pack} for @code{proc} which would require that
29121 the body of @code{proc} be elaborated before the body of
29122 @code{pack}. Clearly both requirements cannot be satisfied.
29123 Faced with a circularity of this kind, you have three different options.
29126 @item Fix the program
29127 The most desirable option from the point of view of long-term maintenance
29128 is to rearrange the program so that the elaboration problems are avoided.
29129 One useful technique is to place the elaboration code into separate
29130 child packages. Another is to move some of the initialization code to
29131 explicitly called subprograms, where the program controls the order
29132 of initialization explicitly. Although this is the most desirable option,
29133 it may be impractical and involve too much modification, especially in
29134 the case of complex legacy code.
29136 @item Perform dynamic checks
29137 If the compilations are done using the
29139 (dynamic elaboration check) switch, then GNAT behaves in a quite different
29140 manner. Dynamic checks are generated for all calls that could possibly result
29141 in raising an exception. With this switch, the compiler does not generate
29142 implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is
29143 exactly as specified in the @cite{Ada Reference Manual}.
29144 The binder will generate
29145 an executable program that may or may not raise @code{Program_Error}, and then
29146 it is the programmer's job to ensure that it does not raise an exception. Note
29147 that it is important to compile all units with the switch, it cannot be used
29150 @item Suppress checks
29151 The drawback of dynamic checks is that they generate a
29152 significant overhead at run time, both in space and time. If you
29153 are absolutely sure that your program cannot raise any elaboration
29154 exceptions, and you still want to use the dynamic elaboration model,
29155 then you can use the configuration pragma
29156 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
29157 example this pragma could be placed in the @file{gnat.adc} file.
29159 @item Suppress checks selectively
29160 When you know that certain calls or instantiations in elaboration code cannot
29161 possibly lead to an elaboration error, and the binder nevertheless complains
29162 about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to
29163 elaboration circularities, it is possible to remove those warnings locally and
29164 obtain a program that will bind. Clearly this can be unsafe, and it is the
29165 responsibility of the programmer to make sure that the resulting program has no
29166 elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be
29167 used with different granularity to suppress warnings and break elaboration
29172 Place the pragma that names the called subprogram in the declarative part
29173 that contains the call.
29176 Place the pragma in the declarative part, without naming an entity. This
29177 disables warnings on all calls in the corresponding declarative region.
29180 Place the pragma in the package spec that declares the called subprogram,
29181 and name the subprogram. This disables warnings on all elaboration calls to
29185 Place the pragma in the package spec that declares the called subprogram,
29186 without naming any entity. This disables warnings on all elaboration calls to
29187 all subprograms declared in this spec.
29189 @item Use Pragma Elaborate
29190 As previously described in section @xref{Treatment of Pragma Elaborate},
29191 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
29192 that no elaboration checks are required on calls to the designated unit.
29193 There may be cases in which the caller knows that no transitive calls
29194 can occur, so that a @code{pragma Elaborate} will be sufficient in a
29195 case where @code{pragma Elaborate_All} would cause a circularity.
29199 These five cases are listed in order of decreasing safety, and therefore
29200 require increasing programmer care in their application. Consider the
29203 @smallexample @c adanocomment
29205 function F1 return Integer;
29210 function F2 return Integer;
29211 function Pure (x : integer) return integer;
29212 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
29213 -- pragma Suppress (Elaboration_Check); -- (4)
29217 package body Pack1 is
29218 function F1 return Integer is
29222 Val : integer := Pack2.Pure (11); -- Elab. call (1)
29225 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
29226 -- pragma Suppress(Elaboration_Check); -- (2)
29228 X1 := Pack2.F2 + 1; -- Elab. call (2)
29233 package body Pack2 is
29234 function F2 return Integer is
29238 function Pure (x : integer) return integer is
29240 return x ** 3 - 3 * x;
29244 with Pack1, Ada.Text_IO;
29247 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
29250 In the absence of any pragmas, an attempt to bind this program produces
29251 the following diagnostics:
29257 error: elaboration circularity detected
29258 info: "pack1 (body)" must be elaborated before "pack1 (body)"
29259 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
29260 info: recompile "pack1 (body)" with -gnatwl for full details
29261 info: "pack1 (body)"
29262 info: must be elaborated along with its spec:
29263 info: "pack1 (spec)"
29264 info: which is withed by:
29265 info: "pack2 (body)"
29266 info: which must be elaborated along with its spec:
29267 info: "pack2 (spec)"
29268 info: which is withed by:
29269 info: "pack1 (body)"
29272 The sources of the circularity are the two calls to @code{Pack2.Pure} and
29273 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
29274 F2 is safe, even though F2 calls F1, because the call appears after the
29275 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
29276 remove the warning on the call. It is also possible to use pragma (2)
29277 because there are no other potentially unsafe calls in the block.
29280 The call to @code{Pure} is safe because this function does not depend on the
29281 state of @code{Pack2}. Therefore any call to this function is safe, and it
29282 is correct to place pragma (3) in the corresponding package spec.
29285 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
29286 warnings on all calls to functions declared therein. Note that this is not
29287 necessarily safe, and requires more detailed examination of the subprogram
29288 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
29289 be already elaborated.
29293 It is hard to generalize on which of these four approaches should be
29294 taken. Obviously if it is possible to fix the program so that the default
29295 treatment works, this is preferable, but this may not always be practical.
29296 It is certainly simple enough to use
29298 but the danger in this case is that, even if the GNAT binder
29299 finds a correct elaboration order, it may not always do so,
29300 and certainly a binder from another Ada compiler might not. A
29301 combination of testing and analysis (for which the warnings generated
29304 switch can be useful) must be used to ensure that the program is free
29305 of errors. One switch that is useful in this testing is the
29306 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
29309 Normally the binder tries to find an order that has the best chance
29310 of avoiding elaboration problems. However, if this switch is used, the binder
29311 plays a devil's advocate role, and tries to choose the order that
29312 has the best chance of failing. If your program works even with this
29313 switch, then it has a better chance of being error free, but this is still
29316 For an example of this approach in action, consider the C-tests (executable
29317 tests) from the ACVC suite. If these are compiled and run with the default
29318 treatment, then all but one of them succeed without generating any error
29319 diagnostics from the binder. However, there is one test that fails, and
29320 this is not surprising, because the whole point of this test is to ensure
29321 that the compiler can handle cases where it is impossible to determine
29322 a correct order statically, and it checks that an exception is indeed
29323 raised at run time.
29325 This one test must be compiled and run using the
29327 switch, and then it passes. Alternatively, the entire suite can
29328 be run using this switch. It is never wrong to run with the dynamic
29329 elaboration switch if your code is correct, and we assume that the
29330 C-tests are indeed correct (it is less efficient, but efficiency is
29331 not a factor in running the ACVC tests.)
29333 @node Elaboration for Access-to-Subprogram Values
29334 @section Elaboration for Access-to-Subprogram Values
29335 @cindex Access-to-subprogram
29338 Access-to-subprogram types (introduced in Ada 95) complicate
29339 the handling of elaboration. The trouble is that it becomes
29340 impossible to tell at compile time which procedure
29341 is being called. This means that it is not possible for the binder
29342 to analyze the elaboration requirements in this case.
29344 If at the point at which the access value is created
29345 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
29346 the body of the subprogram is
29347 known to have been elaborated, then the access value is safe, and its use
29348 does not require a check. This may be achieved by appropriate arrangement
29349 of the order of declarations if the subprogram is in the current unit,
29350 or, if the subprogram is in another unit, by using pragma
29351 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
29352 on the referenced unit.
29354 If the referenced body is not known to have been elaborated at the point
29355 the access value is created, then any use of the access value must do a
29356 dynamic check, and this dynamic check will fail and raise a
29357 @code{Program_Error} exception if the body has not been elaborated yet.
29358 GNAT will generate the necessary checks, and in addition, if the
29360 switch is set, will generate warnings that such checks are required.
29362 The use of dynamic dispatching for tagged types similarly generates
29363 a requirement for dynamic checks, and premature calls to any primitive
29364 operation of a tagged type before the body of the operation has been
29365 elaborated, will result in the raising of @code{Program_Error}.
29367 @node Summary of Procedures for Elaboration Control
29368 @section Summary of Procedures for Elaboration Control
29369 @cindex Elaboration control
29372 First, compile your program with the default options, using none of
29373 the special elaboration control switches. If the binder successfully
29374 binds your program, then you can be confident that, apart from issues
29375 raised by the use of access-to-subprogram types and dynamic dispatching,
29376 the program is free of elaboration errors. If it is important that the
29377 program be portable, then use the
29379 switch to generate warnings about missing @code{Elaborate} or
29380 @code{Elaborate_All} pragmas, and supply the missing pragmas.
29382 If the program fails to bind using the default static elaboration
29383 handling, then you can fix the program to eliminate the binder
29384 message, or recompile the entire program with the
29385 @option{-gnatE} switch to generate dynamic elaboration checks,
29386 and, if you are sure there really are no elaboration problems,
29387 use a global pragma @code{Suppress (Elaboration_Check)}.
29389 @node Other Elaboration Order Considerations
29390 @section Other Elaboration Order Considerations
29392 This section has been entirely concerned with the issue of finding a valid
29393 elaboration order, as defined by the Ada Reference Manual. In a case
29394 where several elaboration orders are valid, the task is to find one
29395 of the possible valid elaboration orders (and the static model in GNAT
29396 will ensure that this is achieved).
29398 The purpose of the elaboration rules in the Ada Reference Manual is to
29399 make sure that no entity is accessed before it has been elaborated. For
29400 a subprogram, this means that the spec and body must have been elaborated
29401 before the subprogram is called. For an object, this means that the object
29402 must have been elaborated before its value is read or written. A violation
29403 of either of these two requirements is an access before elaboration order,
29404 and this section has been all about avoiding such errors.
29406 In the case where more than one order of elaboration is possible, in the
29407 sense that access before elaboration errors are avoided, then any one of
29408 the orders is ``correct'' in the sense that it meets the requirements of
29409 the Ada Reference Manual, and no such error occurs.
29411 However, it may be the case for a given program, that there are
29412 constraints on the order of elaboration that come not from consideration
29413 of avoiding elaboration errors, but rather from extra-lingual logic
29414 requirements. Consider this example:
29416 @smallexample @c ada
29417 with Init_Constants;
29418 package Constants is
29423 package Init_Constants is
29424 procedure P; -- require a body
29425 end Init_Constants;
29428 package body Init_Constants is
29429 procedure P is begin null; end;
29433 end Init_Constants;
29437 Z : Integer := Constants.X + Constants.Y;
29441 with Text_IO; use Text_IO;
29444 Put_Line (Calc.Z'Img);
29449 In this example, there is more than one valid order of elaboration. For
29450 example both the following are correct orders:
29453 Init_Constants spec
29456 Init_Constants body
29461 Init_Constants spec
29462 Init_Constants body
29469 There is no language rule to prefer one or the other, both are correct
29470 from an order of elaboration point of view. But the programmatic effects
29471 of the two orders are very different. In the first, the elaboration routine
29472 of @code{Calc} initializes @code{Z} to zero, and then the main program
29473 runs with this value of zero. But in the second order, the elaboration
29474 routine of @code{Calc} runs after the body of Init_Constants has set
29475 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
29478 One could perhaps by applying pretty clever non-artificial intelligence
29479 to the situation guess that it is more likely that the second order of
29480 elaboration is the one desired, but there is no formal linguistic reason
29481 to prefer one over the other. In fact in this particular case, GNAT will
29482 prefer the second order, because of the rule that bodies are elaborated
29483 as soon as possible, but it's just luck that this is what was wanted
29484 (if indeed the second order was preferred).
29486 If the program cares about the order of elaboration routines in a case like
29487 this, it is important to specify the order required. In this particular
29488 case, that could have been achieved by adding to the spec of Calc:
29490 @smallexample @c ada
29491 pragma Elaborate_All (Constants);
29495 which requires that the body (if any) and spec of @code{Constants},
29496 as well as the body and spec of any unit @code{with}'ed by
29497 @code{Constants} be elaborated before @code{Calc} is elaborated.
29499 Clearly no automatic method can always guess which alternative you require,
29500 and if you are working with legacy code that had constraints of this kind
29501 which were not properly specified by adding @code{Elaborate} or
29502 @code{Elaborate_All} pragmas, then indeed it is possible that two different
29503 compilers can choose different orders.
29505 However, GNAT does attempt to diagnose the common situation where there
29506 are uninitialized variables in the visible part of a package spec, and the
29507 corresponding package body has an elaboration block that directly or
29508 indirectly initialized one or more of these variables. This is the situation
29509 in which a pragma Elaborate_Body is usually desirable, and GNAT will generate
29510 a warning that suggests this addition if it detects this situation.
29512 The @code{gnatbind}
29513 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
29514 out problems. This switch causes bodies to be elaborated as late as possible
29515 instead of as early as possible. In the example above, it would have forced
29516 the choice of the first elaboration order. If you get different results
29517 when using this switch, and particularly if one set of results is right,
29518 and one is wrong as far as you are concerned, it shows that you have some
29519 missing @code{Elaborate} pragmas. For the example above, we have the
29523 gnatmake -f -q main
29526 gnatmake -f -q main -bargs -p
29532 It is of course quite unlikely that both these results are correct, so
29533 it is up to you in a case like this to investigate the source of the
29534 difference, by looking at the two elaboration orders that are chosen,
29535 and figuring out which is correct, and then adding the necessary
29536 @code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order.
29540 @c *******************************
29541 @node Conditional Compilation
29542 @appendix Conditional Compilation
29543 @c *******************************
29544 @cindex Conditional compilation
29547 It is often necessary to arrange for a single source program
29548 to serve multiple purposes, where it is compiled in different
29549 ways to achieve these different goals. Some examples of the
29550 need for this feature are
29553 @item Adapting a program to a different hardware environment
29554 @item Adapting a program to a different target architecture
29555 @item Turning debugging features on and off
29556 @item Arranging for a program to compile with different compilers
29560 In C, or C++, the typical approach would be to use the preprocessor
29561 that is defined as part of the language. The Ada language does not
29562 contain such a feature. This is not an oversight, but rather a very
29563 deliberate design decision, based on the experience that overuse of
29564 the preprocessing features in C and C++ can result in programs that
29565 are extremely difficult to maintain. For example, if we have ten
29566 switches that can be on or off, this means that there are a thousand
29567 separate programs, any one of which might not even be syntactically
29568 correct, and even if syntactically correct, the resulting program
29569 might not work correctly. Testing all combinations can quickly become
29572 Nevertheless, the need to tailor programs certainly exists, and in
29573 this Appendix we will discuss how this can
29574 be achieved using Ada in general, and GNAT in particular.
29577 * Use of Boolean Constants::
29578 * Debugging - A Special Case::
29579 * Conditionalizing Declarations::
29580 * Use of Alternative Implementations::
29584 @node Use of Boolean Constants
29585 @section Use of Boolean Constants
29588 In the case where the difference is simply which code
29589 sequence is executed, the cleanest solution is to use Boolean
29590 constants to control which code is executed.
29592 @smallexample @c ada
29594 FP_Initialize_Required : constant Boolean := True;
29596 if FP_Initialize_Required then
29603 Not only will the code inside the @code{if} statement not be executed if
29604 the constant Boolean is @code{False}, but it will also be completely
29605 deleted from the program.
29606 However, the code is only deleted after the @code{if} statement
29607 has been checked for syntactic and semantic correctness.
29608 (In contrast, with preprocessors the code is deleted before the
29609 compiler ever gets to see it, so it is not checked until the switch
29611 @cindex Preprocessors (contrasted with conditional compilation)
29613 Typically the Boolean constants will be in a separate package,
29616 @smallexample @c ada
29619 FP_Initialize_Required : constant Boolean := True;
29620 Reset_Available : constant Boolean := False;
29627 The @code{Config} package exists in multiple forms for the various targets,
29628 with an appropriate script selecting the version of @code{Config} needed.
29629 Then any other unit requiring conditional compilation can do a @code{with}
29630 of @code{Config} to make the constants visible.
29633 @node Debugging - A Special Case
29634 @section Debugging - A Special Case
29637 A common use of conditional code is to execute statements (for example
29638 dynamic checks, or output of intermediate results) under control of a
29639 debug switch, so that the debugging behavior can be turned on and off.
29640 This can be done using a Boolean constant to control whether the code
29643 @smallexample @c ada
29646 Put_Line ("got to the first stage!");
29654 @smallexample @c ada
29656 if Debugging and then Temperature > 999.0 then
29657 raise Temperature_Crazy;
29663 Since this is a common case, there are special features to deal with
29664 this in a convenient manner. For the case of tests, Ada 2005 has added
29665 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
29666 @cindex pragma @code{Assert}
29667 on the @code{Assert} pragma that has always been available in GNAT, so this
29668 feature may be used with GNAT even if you are not using Ada 2005 features.
29669 The use of pragma @code{Assert} is described in
29670 @ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an
29671 example, the last test could be written:
29673 @smallexample @c ada
29674 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
29680 @smallexample @c ada
29681 pragma Assert (Temperature <= 999.0);
29685 In both cases, if assertions are active and the temperature is excessive,
29686 the exception @code{Assert_Failure} will be raised, with the given string in
29687 the first case or a string indicating the location of the pragma in the second
29688 case used as the exception message.
29690 You can turn assertions on and off by using the @code{Assertion_Policy}
29692 @cindex pragma @code{Assertion_Policy}
29693 This is an Ada 2005 pragma which is implemented in all modes by
29694 GNAT, but only in the latest versions of GNAT which include Ada 2005
29695 capability. Alternatively, you can use the @option{-gnata} switch
29696 @cindex @option{-gnata} switch
29697 to enable assertions from the command line (this is recognized by all versions
29700 For the example above with the @code{Put_Line}, the GNAT-specific pragma
29701 @code{Debug} can be used:
29702 @cindex pragma @code{Debug}
29704 @smallexample @c ada
29705 pragma Debug (Put_Line ("got to the first stage!"));
29709 If debug pragmas are enabled, the argument, which must be of the form of
29710 a procedure call, is executed (in this case, @code{Put_Line} will be called).
29711 Only one call can be present, but of course a special debugging procedure
29712 containing any code you like can be included in the program and then
29713 called in a pragma @code{Debug} argument as needed.
29715 One advantage of pragma @code{Debug} over the @code{if Debugging then}
29716 construct is that pragma @code{Debug} can appear in declarative contexts,
29717 such as at the very beginning of a procedure, before local declarations have
29720 Debug pragmas are enabled using either the @option{-gnata} switch that also
29721 controls assertions, or with a separate Debug_Policy pragma.
29722 @cindex pragma @code{Debug_Policy}
29723 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
29724 in Ada 95 and Ada 83 programs as well), and is analogous to
29725 pragma @code{Assertion_Policy} to control assertions.
29727 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
29728 and thus they can appear in @file{gnat.adc} if you are not using a
29729 project file, or in the file designated to contain configuration pragmas
29731 They then apply to all subsequent compilations. In practice the use of
29732 the @option{-gnata} switch is often the most convenient method of controlling
29733 the status of these pragmas.
29735 Note that a pragma is not a statement, so in contexts where a statement
29736 sequence is required, you can't just write a pragma on its own. You have
29737 to add a @code{null} statement.
29739 @smallexample @c ada
29742 @dots{} -- some statements
29744 pragma Assert (Num_Cases < 10);
29751 @node Conditionalizing Declarations
29752 @section Conditionalizing Declarations
29755 In some cases, it may be necessary to conditionalize declarations to meet
29756 different requirements. For example we might want a bit string whose length
29757 is set to meet some hardware message requirement.
29759 In some cases, it may be possible to do this using declare blocks controlled
29760 by conditional constants:
29762 @smallexample @c ada
29764 if Small_Machine then
29766 X : Bit_String (1 .. 10);
29772 X : Large_Bit_String (1 .. 1000);
29781 Note that in this approach, both declarations are analyzed by the
29782 compiler so this can only be used where both declarations are legal,
29783 even though one of them will not be used.
29785 Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, or
29786 Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations
29787 that are parameterized by these constants. For example
29789 @smallexample @c ada
29792 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
29798 If @code{Bits_Per_Word} is set to 32, this generates either
29800 @smallexample @c ada
29803 Field1 at 0 range 0 .. 32;
29809 for the big endian case, or
29811 @smallexample @c ada
29814 Field1 at 0 range 10 .. 32;
29820 for the little endian case. Since a powerful subset of Ada expression
29821 notation is usable for creating static constants, clever use of this
29822 feature can often solve quite difficult problems in conditionalizing
29823 compilation (note incidentally that in Ada 95, the little endian
29824 constant was introduced as @code{System.Default_Bit_Order}, so you do not
29825 need to define this one yourself).
29828 @node Use of Alternative Implementations
29829 @section Use of Alternative Implementations
29832 In some cases, none of the approaches described above are adequate. This
29833 can occur for example if the set of declarations required is radically
29834 different for two different configurations.
29836 In this situation, the official Ada way of dealing with conditionalizing
29837 such code is to write separate units for the different cases. As long as
29838 this does not result in excessive duplication of code, this can be done
29839 without creating maintenance problems. The approach is to share common
29840 code as far as possible, and then isolate the code and declarations
29841 that are different. Subunits are often a convenient method for breaking
29842 out a piece of a unit that is to be conditionalized, with separate files
29843 for different versions of the subunit for different targets, where the
29844 build script selects the right one to give to the compiler.
29845 @cindex Subunits (and conditional compilation)
29847 As an example, consider a situation where a new feature in Ada 2005
29848 allows something to be done in a really nice way. But your code must be able
29849 to compile with an Ada 95 compiler. Conceptually you want to say:
29851 @smallexample @c ada
29854 @dots{} neat Ada 2005 code
29856 @dots{} not quite as neat Ada 95 code
29862 where @code{Ada_2005} is a Boolean constant.
29864 But this won't work when @code{Ada_2005} is set to @code{False},
29865 since the @code{then} clause will be illegal for an Ada 95 compiler.
29866 (Recall that although such unreachable code would eventually be deleted
29867 by the compiler, it still needs to be legal. If it uses features
29868 introduced in Ada 2005, it will be illegal in Ada 95.)
29870 So instead we write
29872 @smallexample @c ada
29873 procedure Insert is separate;
29877 Then we have two files for the subunit @code{Insert}, with the two sets of
29879 If the package containing this is called @code{File_Queries}, then we might
29883 @item @file{file_queries-insert-2005.adb}
29884 @item @file{file_queries-insert-95.adb}
29888 and the build script renames the appropriate file to
29891 file_queries-insert.adb
29895 and then carries out the compilation.
29897 This can also be done with project files' naming schemes. For example:
29899 @smallexample @c project
29900 For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
29904 Note also that with project files it is desirable to use a different extension
29905 than @file{ads} / @file{adb} for alternative versions. Otherwise a naming
29906 conflict may arise through another commonly used feature: to declare as part
29907 of the project a set of directories containing all the sources obeying the
29908 default naming scheme.
29910 The use of alternative units is certainly feasible in all situations,
29911 and for example the Ada part of the GNAT run-time is conditionalized
29912 based on the target architecture using this approach. As a specific example,
29913 consider the implementation of the AST feature in VMS. There is one
29921 which is the same for all architectures, and three bodies:
29925 used for all non-VMS operating systems
29926 @item s-asthan-vms-alpha.adb
29927 used for VMS on the Alpha
29928 @item s-asthan-vms-ia64.adb
29929 used for VMS on the ia64
29933 The dummy version @file{s-asthan.adb} simply raises exceptions noting that
29934 this operating system feature is not available, and the two remaining
29935 versions interface with the corresponding versions of VMS to provide
29936 VMS-compatible AST handling. The GNAT build script knows the architecture
29937 and operating system, and automatically selects the right version,
29938 renaming it if necessary to @file{s-asthan.adb} before the run-time build.
29940 Another style for arranging alternative implementations is through Ada's
29941 access-to-subprogram facility.
29942 In case some functionality is to be conditionally included,
29943 you can declare an access-to-procedure variable @code{Ref} that is initialized
29944 to designate a ``do nothing'' procedure, and then invoke @code{Ref.all}
29946 In some library package, set @code{Ref} to @code{Proc'Access} for some
29947 procedure @code{Proc} that performs the relevant processing.
29948 The initialization only occurs if the library package is included in the
29950 The same idea can also be implemented using tagged types and dispatching
29954 @node Preprocessing
29955 @section Preprocessing
29956 @cindex Preprocessing
29959 Although it is quite possible to conditionalize code without the use of
29960 C-style preprocessing, as described earlier in this section, it is
29961 nevertheless convenient in some cases to use the C approach. Moreover,
29962 older Ada compilers have often provided some preprocessing capability,
29963 so legacy code may depend on this approach, even though it is not
29966 To accommodate such use, GNAT provides a preprocessor (modeled to a large
29967 extent on the various preprocessors that have been used
29968 with legacy code on other compilers, to enable easier transition).
29970 The preprocessor may be used in two separate modes. It can be used quite
29971 separately from the compiler, to generate a separate output source file
29972 that is then fed to the compiler as a separate step. This is the
29973 @code{gnatprep} utility, whose use is fully described in
29974 @ref{Preprocessing Using gnatprep}.
29975 @cindex @code{gnatprep}
29977 The preprocessing language allows such constructs as
29981 #if DEBUG or PRIORITY > 4 then
29982 bunch of declarations
29984 completely different bunch of declarations
29990 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
29991 defined either on the command line or in a separate file.
29993 The other way of running the preprocessor is even closer to the C style and
29994 often more convenient. In this approach the preprocessing is integrated into
29995 the compilation process. The compiler is fed the preprocessor input which
29996 includes @code{#if} lines etc, and then the compiler carries out the
29997 preprocessing internally and processes the resulting output.
29998 For more details on this approach, see @ref{Integrated Preprocessing}.
30001 @c *******************************
30002 @node Inline Assembler
30003 @appendix Inline Assembler
30004 @c *******************************
30007 If you need to write low-level software that interacts directly
30008 with the hardware, Ada provides two ways to incorporate assembly
30009 language code into your program. First, you can import and invoke
30010 external routines written in assembly language, an Ada feature fully
30011 supported by GNAT@. However, for small sections of code it may be simpler
30012 or more efficient to include assembly language statements directly
30013 in your Ada source program, using the facilities of the implementation-defined
30014 package @code{System.Machine_Code}, which incorporates the gcc
30015 Inline Assembler. The Inline Assembler approach offers a number of advantages,
30016 including the following:
30019 @item No need to use non-Ada tools
30020 @item Consistent interface over different targets
30021 @item Automatic usage of the proper calling conventions
30022 @item Access to Ada constants and variables
30023 @item Definition of intrinsic routines
30024 @item Possibility of inlining a subprogram comprising assembler code
30025 @item Code optimizer can take Inline Assembler code into account
30028 This chapter presents a series of examples to show you how to use
30029 the Inline Assembler. Although it focuses on the Intel x86,
30030 the general approach applies also to other processors.
30031 It is assumed that you are familiar with Ada
30032 and with assembly language programming.
30035 * Basic Assembler Syntax::
30036 * A Simple Example of Inline Assembler::
30037 * Output Variables in Inline Assembler::
30038 * Input Variables in Inline Assembler::
30039 * Inlining Inline Assembler Code::
30040 * Other Asm Functionality::
30043 @c ---------------------------------------------------------------------------
30044 @node Basic Assembler Syntax
30045 @section Basic Assembler Syntax
30048 The assembler used by GNAT and gcc is based not on the Intel assembly
30049 language, but rather on a language that descends from the AT&T Unix
30050 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
30051 The following table summarizes the main features of @emph{as} syntax
30052 and points out the differences from the Intel conventions.
30053 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
30054 pre-processor) documentation for further information.
30057 @item Register names
30058 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
30060 Intel: No extra punctuation; for example @code{eax}
30062 @item Immediate operand
30063 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
30065 Intel: No extra punctuation; for example @code{4}
30068 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
30070 Intel: No extra punctuation; for example @code{loc}
30072 @item Memory contents
30073 gcc / @emph{as}: No extra punctuation; for example @code{loc}
30075 Intel: Square brackets; for example @code{[loc]}
30077 @item Register contents
30078 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
30080 Intel: Square brackets; for example @code{[eax]}
30082 @item Hexadecimal numbers
30083 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
30085 Intel: Trailing ``h''; for example @code{A0h}
30088 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
30091 Intel: Implicit, deduced by assembler; for example @code{mov}
30093 @item Instruction repetition
30094 gcc / @emph{as}: Split into two lines; for example
30100 Intel: Keep on one line; for example @code{rep stosl}
30102 @item Order of operands
30103 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
30105 Intel: Destination first; for example @code{mov eax, 4}
30108 @c ---------------------------------------------------------------------------
30109 @node A Simple Example of Inline Assembler
30110 @section A Simple Example of Inline Assembler
30113 The following example will generate a single assembly language statement,
30114 @code{nop}, which does nothing. Despite its lack of run-time effect,
30115 the example will be useful in illustrating the basics of
30116 the Inline Assembler facility.
30118 @smallexample @c ada
30120 with System.Machine_Code; use System.Machine_Code;
30121 procedure Nothing is
30128 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
30129 here it takes one parameter, a @emph{template string} that must be a static
30130 expression and that will form the generated instruction.
30131 @code{Asm} may be regarded as a compile-time procedure that parses
30132 the template string and additional parameters (none here),
30133 from which it generates a sequence of assembly language instructions.
30135 The examples in this chapter will illustrate several of the forms
30136 for invoking @code{Asm}; a complete specification of the syntax
30137 is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference
30140 Under the standard GNAT conventions, the @code{Nothing} procedure
30141 should be in a file named @file{nothing.adb}.
30142 You can build the executable in the usual way:
30146 However, the interesting aspect of this example is not its run-time behavior
30147 but rather the generated assembly code.
30148 To see this output, invoke the compiler as follows:
30150 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
30152 where the options are:
30156 compile only (no bind or link)
30158 generate assembler listing
30159 @item -fomit-frame-pointer
30160 do not set up separate stack frames
30162 do not add runtime checks
30165 This gives a human-readable assembler version of the code. The resulting
30166 file will have the same name as the Ada source file, but with a @code{.s}
30167 extension. In our example, the file @file{nothing.s} has the following
30172 .file "nothing.adb"
30174 ___gnu_compiled_ada:
30177 .globl __ada_nothing
30189 The assembly code you included is clearly indicated by
30190 the compiler, between the @code{#APP} and @code{#NO_APP}
30191 delimiters. The character before the 'APP' and 'NOAPP'
30192 can differ on different targets. For example, GNU/Linux uses '#APP' while
30193 on NT you will see '/APP'.
30195 If you make a mistake in your assembler code (such as using the
30196 wrong size modifier, or using a wrong operand for the instruction) GNAT
30197 will report this error in a temporary file, which will be deleted when
30198 the compilation is finished. Generating an assembler file will help
30199 in such cases, since you can assemble this file separately using the
30200 @emph{as} assembler that comes with gcc.
30202 Assembling the file using the command
30205 as @file{nothing.s}
30208 will give you error messages whose lines correspond to the assembler
30209 input file, so you can easily find and correct any mistakes you made.
30210 If there are no errors, @emph{as} will generate an object file
30211 @file{nothing.out}.
30213 @c ---------------------------------------------------------------------------
30214 @node Output Variables in Inline Assembler
30215 @section Output Variables in Inline Assembler
30218 The examples in this section, showing how to access the processor flags,
30219 illustrate how to specify the destination operands for assembly language
30222 @smallexample @c ada
30224 with Interfaces; use Interfaces;
30225 with Ada.Text_IO; use Ada.Text_IO;
30226 with System.Machine_Code; use System.Machine_Code;
30227 procedure Get_Flags is
30228 Flags : Unsigned_32;
30231 Asm ("pushfl" & LF & HT & -- push flags on stack
30232 "popl %%eax" & LF & HT & -- load eax with flags
30233 "movl %%eax, %0", -- store flags in variable
30234 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30235 Put_Line ("Flags register:" & Flags'Img);
30240 In order to have a nicely aligned assembly listing, we have separated
30241 multiple assembler statements in the Asm template string with linefeed
30242 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
30243 The resulting section of the assembly output file is:
30250 movl %eax, -40(%ebp)
30255 It would have been legal to write the Asm invocation as:
30258 Asm ("pushfl popl %%eax movl %%eax, %0")
30261 but in the generated assembler file, this would come out as:
30265 pushfl popl %eax movl %eax, -40(%ebp)
30269 which is not so convenient for the human reader.
30271 We use Ada comments
30272 at the end of each line to explain what the assembler instructions
30273 actually do. This is a useful convention.
30275 When writing Inline Assembler instructions, you need to precede each register
30276 and variable name with a percent sign. Since the assembler already requires
30277 a percent sign at the beginning of a register name, you need two consecutive
30278 percent signs for such names in the Asm template string, thus @code{%%eax}.
30279 In the generated assembly code, one of the percent signs will be stripped off.
30281 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
30282 variables: operands you later define using @code{Input} or @code{Output}
30283 parameters to @code{Asm}.
30284 An output variable is illustrated in
30285 the third statement in the Asm template string:
30289 The intent is to store the contents of the eax register in a variable that can
30290 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
30291 necessarily work, since the compiler might optimize by using a register
30292 to hold Flags, and the expansion of the @code{movl} instruction would not be
30293 aware of this optimization. The solution is not to store the result directly
30294 but rather to advise the compiler to choose the correct operand form;
30295 that is the purpose of the @code{%0} output variable.
30297 Information about the output variable is supplied in the @code{Outputs}
30298 parameter to @code{Asm}:
30300 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30303 The output is defined by the @code{Asm_Output} attribute of the target type;
30304 the general format is
30306 Type'Asm_Output (constraint_string, variable_name)
30309 The constraint string directs the compiler how
30310 to store/access the associated variable. In the example
30312 Unsigned_32'Asm_Output ("=m", Flags);
30314 the @code{"m"} (memory) constraint tells the compiler that the variable
30315 @code{Flags} should be stored in a memory variable, thus preventing
30316 the optimizer from keeping it in a register. In contrast,
30318 Unsigned_32'Asm_Output ("=r", Flags);
30320 uses the @code{"r"} (register) constraint, telling the compiler to
30321 store the variable in a register.
30323 If the constraint is preceded by the equal character (@strong{=}), it tells
30324 the compiler that the variable will be used to store data into it.
30326 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
30327 allowing the optimizer to choose whatever it deems best.
30329 There are a fairly large number of constraints, but the ones that are
30330 most useful (for the Intel x86 processor) are the following:
30336 global (i.e.@: can be stored anywhere)
30354 use one of eax, ebx, ecx or edx
30356 use one of eax, ebx, ecx, edx, esi or edi
30359 The full set of constraints is described in the gcc and @emph{as}
30360 documentation; note that it is possible to combine certain constraints
30361 in one constraint string.
30363 You specify the association of an output variable with an assembler operand
30364 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
30366 @smallexample @c ada
30368 Asm ("pushfl" & LF & HT & -- push flags on stack
30369 "popl %%eax" & LF & HT & -- load eax with flags
30370 "movl %%eax, %0", -- store flags in variable
30371 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30375 @code{%0} will be replaced in the expanded code by the appropriate operand,
30377 the compiler decided for the @code{Flags} variable.
30379 In general, you may have any number of output variables:
30382 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
30384 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
30385 of @code{Asm_Output} attributes
30389 @smallexample @c ada
30391 Asm ("movl %%eax, %0" & LF & HT &
30392 "movl %%ebx, %1" & LF & HT &
30394 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
30395 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
30396 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
30400 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
30401 in the Ada program.
30403 As a variation on the @code{Get_Flags} example, we can use the constraints
30404 string to direct the compiler to store the eax register into the @code{Flags}
30405 variable, instead of including the store instruction explicitly in the
30406 @code{Asm} template string:
30408 @smallexample @c ada
30410 with Interfaces; use Interfaces;
30411 with Ada.Text_IO; use Ada.Text_IO;
30412 with System.Machine_Code; use System.Machine_Code;
30413 procedure Get_Flags_2 is
30414 Flags : Unsigned_32;
30417 Asm ("pushfl" & LF & HT & -- push flags on stack
30418 "popl %%eax", -- save flags in eax
30419 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
30420 Put_Line ("Flags register:" & Flags'Img);
30426 The @code{"a"} constraint tells the compiler that the @code{Flags}
30427 variable will come from the eax register. Here is the resulting code:
30435 movl %eax,-40(%ebp)
30440 The compiler generated the store of eax into Flags after
30441 expanding the assembler code.
30443 Actually, there was no need to pop the flags into the eax register;
30444 more simply, we could just pop the flags directly into the program variable:
30446 @smallexample @c ada
30448 with Interfaces; use Interfaces;
30449 with Ada.Text_IO; use Ada.Text_IO;
30450 with System.Machine_Code; use System.Machine_Code;
30451 procedure Get_Flags_3 is
30452 Flags : Unsigned_32;
30455 Asm ("pushfl" & LF & HT & -- push flags on stack
30456 "pop %0", -- save flags in Flags
30457 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
30458 Put_Line ("Flags register:" & Flags'Img);
30463 @c ---------------------------------------------------------------------------
30464 @node Input Variables in Inline Assembler
30465 @section Input Variables in Inline Assembler
30468 The example in this section illustrates how to specify the source operands
30469 for assembly language statements.
30470 The program simply increments its input value by 1:
30472 @smallexample @c ada
30474 with Interfaces; use Interfaces;
30475 with Ada.Text_IO; use Ada.Text_IO;
30476 with System.Machine_Code; use System.Machine_Code;
30477 procedure Increment is
30479 function Incr (Value : Unsigned_32) return Unsigned_32 is
30480 Result : Unsigned_32;
30483 Inputs => Unsigned_32'Asm_Input ("a", Value),
30484 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30488 Value : Unsigned_32;
30492 Put_Line ("Value before is" & Value'Img);
30493 Value := Incr (Value);
30494 Put_Line ("Value after is" & Value'Img);
30499 The @code{Outputs} parameter to @code{Asm} specifies
30500 that the result will be in the eax register and that it is to be stored
30501 in the @code{Result} variable.
30503 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
30504 but with an @code{Asm_Input} attribute.
30505 The @code{"="} constraint, indicating an output value, is not present.
30507 You can have multiple input variables, in the same way that you can have more
30508 than one output variable.
30510 The parameter count (%0, %1) etc, now starts at the first input
30511 statement, and continues with the output statements.
30512 When both parameters use the same variable, the
30513 compiler will treat them as the same %n operand, which is the case here.
30515 Just as the @code{Outputs} parameter causes the register to be stored into the
30516 target variable after execution of the assembler statements, so does the
30517 @code{Inputs} parameter cause its variable to be loaded into the register
30518 before execution of the assembler statements.
30520 Thus the effect of the @code{Asm} invocation is:
30522 @item load the 32-bit value of @code{Value} into eax
30523 @item execute the @code{incl %eax} instruction
30524 @item store the contents of eax into the @code{Result} variable
30527 The resulting assembler file (with @option{-O2} optimization) contains:
30530 _increment__incr.1:
30543 @c ---------------------------------------------------------------------------
30544 @node Inlining Inline Assembler Code
30545 @section Inlining Inline Assembler Code
30548 For a short subprogram such as the @code{Incr} function in the previous
30549 section, the overhead of the call and return (creating / deleting the stack
30550 frame) can be significant, compared to the amount of code in the subprogram
30551 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
30552 which directs the compiler to expand invocations of the subprogram at the
30553 point(s) of call, instead of setting up a stack frame for out-of-line calls.
30554 Here is the resulting program:
30556 @smallexample @c ada
30558 with Interfaces; use Interfaces;
30559 with Ada.Text_IO; use Ada.Text_IO;
30560 with System.Machine_Code; use System.Machine_Code;
30561 procedure Increment_2 is
30563 function Incr (Value : Unsigned_32) return Unsigned_32 is
30564 Result : Unsigned_32;
30567 Inputs => Unsigned_32'Asm_Input ("a", Value),
30568 Outputs => Unsigned_32'Asm_Output ("=a", Result));
30571 pragma Inline (Increment);
30573 Value : Unsigned_32;
30577 Put_Line ("Value before is" & Value'Img);
30578 Value := Increment (Value);
30579 Put_Line ("Value after is" & Value'Img);
30584 Compile the program with both optimization (@option{-O2}) and inlining
30585 (@option{-gnatn}) enabled.
30587 The @code{Incr} function is still compiled as usual, but at the
30588 point in @code{Increment} where our function used to be called:
30593 call _increment__incr.1
30598 the code for the function body directly appears:
30611 thus saving the overhead of stack frame setup and an out-of-line call.
30613 @c ---------------------------------------------------------------------------
30614 @node Other Asm Functionality
30615 @section Other @code{Asm} Functionality
30618 This section describes two important parameters to the @code{Asm}
30619 procedure: @code{Clobber}, which identifies register usage;
30620 and @code{Volatile}, which inhibits unwanted optimizations.
30623 * The Clobber Parameter::
30624 * The Volatile Parameter::
30627 @c ---------------------------------------------------------------------------
30628 @node The Clobber Parameter
30629 @subsection The @code{Clobber} Parameter
30632 One of the dangers of intermixing assembly language and a compiled language
30633 such as Ada is that the compiler needs to be aware of which registers are
30634 being used by the assembly code. In some cases, such as the earlier examples,
30635 the constraint string is sufficient to indicate register usage (e.g.,
30637 the eax register). But more generally, the compiler needs an explicit
30638 identification of the registers that are used by the Inline Assembly
30641 Using a register that the compiler doesn't know about
30642 could be a side effect of an instruction (like @code{mull}
30643 storing its result in both eax and edx).
30644 It can also arise from explicit register usage in your
30645 assembly code; for example:
30648 Asm ("movl %0, %%ebx" & LF & HT &
30650 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30651 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
30655 where the compiler (since it does not analyze the @code{Asm} template string)
30656 does not know you are using the ebx register.
30658 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
30659 to identify the registers that will be used by your assembly code:
30663 Asm ("movl %0, %%ebx" & LF & HT &
30665 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30666 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30671 The Clobber parameter is a static string expression specifying the
30672 register(s) you are using. Note that register names are @emph{not} prefixed
30673 by a percent sign. Also, if more than one register is used then their names
30674 are separated by commas; e.g., @code{"eax, ebx"}
30676 The @code{Clobber} parameter has several additional uses:
30678 @item Use ``register'' name @code{cc} to indicate that flags might have changed
30679 @item Use ``register'' name @code{memory} if you changed a memory location
30682 @c ---------------------------------------------------------------------------
30683 @node The Volatile Parameter
30684 @subsection The @code{Volatile} Parameter
30685 @cindex Volatile parameter
30688 Compiler optimizations in the presence of Inline Assembler may sometimes have
30689 unwanted effects. For example, when an @code{Asm} invocation with an input
30690 variable is inside a loop, the compiler might move the loading of the input
30691 variable outside the loop, regarding it as a one-time initialization.
30693 If this effect is not desired, you can disable such optimizations by setting
30694 the @code{Volatile} parameter to @code{True}; for example:
30696 @smallexample @c ada
30698 Asm ("movl %0, %%ebx" & LF & HT &
30700 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30701 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30707 By default, @code{Volatile} is set to @code{False} unless there is no
30708 @code{Outputs} parameter.
30710 Although setting @code{Volatile} to @code{True} prevents unwanted
30711 optimizations, it will also disable other optimizations that might be
30712 important for efficiency. In general, you should set @code{Volatile}
30713 to @code{True} only if the compiler's optimizations have created
30715 @c END OF INLINE ASSEMBLER CHAPTER
30716 @c ===============================
30718 @c ***********************************
30719 @c * Compatibility and Porting Guide *
30720 @c ***********************************
30721 @node Compatibility and Porting Guide
30722 @appendix Compatibility and Porting Guide
30725 This chapter describes the compatibility issues that may arise between
30726 GNAT and other Ada compilation systems (including those for Ada 83),
30727 and shows how GNAT can expedite porting
30728 applications developed in other Ada environments.
30731 * Compatibility with Ada 83::
30732 * Compatibility between Ada 95 and Ada 2005::
30733 * Implementation-dependent characteristics::
30734 * Compatibility with Other Ada Systems::
30735 * Representation Clauses::
30737 @c Brief section is only in non-VMS version
30738 @c Full chapter is in VMS version
30739 * Compatibility with HP Ada 83::
30742 * Transitioning to 64-Bit GNAT for OpenVMS::
30746 @node Compatibility with Ada 83
30747 @section Compatibility with Ada 83
30748 @cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005)
30751 Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In
30752 particular, the design intention was that the difficulties associated
30753 with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those
30754 that occur when moving from one Ada 83 system to another.
30756 However, there are a number of points at which there are minor
30757 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
30758 full details of these issues,
30759 and should be consulted for a complete treatment.
30761 following subsections treat the most likely issues to be encountered.
30764 * Legal Ada 83 programs that are illegal in Ada 95::
30765 * More deterministic semantics::
30766 * Changed semantics::
30767 * Other language compatibility issues::
30770 @node Legal Ada 83 programs that are illegal in Ada 95
30771 @subsection Legal Ada 83 programs that are illegal in Ada 95
30773 Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in
30774 Ada 95 and thus also in Ada 2005:
30777 @item Character literals
30778 Some uses of character literals are ambiguous. Since Ada 95 has introduced
30779 @code{Wide_Character} as a new predefined character type, some uses of
30780 character literals that were legal in Ada 83 are illegal in Ada 95.
30782 @smallexample @c ada
30783 for Char in 'A' .. 'Z' loop @dots{} end loop;
30787 The problem is that @code{'A'} and @code{'Z'} could be from either
30788 @code{Character} or @code{Wide_Character}. The simplest correction
30789 is to make the type explicit; e.g.:
30790 @smallexample @c ada
30791 for Char in Character range 'A' .. 'Z' loop @dots{} end loop;
30794 @item New reserved words
30795 The identifiers @code{abstract}, @code{aliased}, @code{protected},
30796 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
30797 Existing Ada 83 code using any of these identifiers must be edited to
30798 use some alternative name.
30800 @item Freezing rules
30801 The rules in Ada 95 are slightly different with regard to the point at
30802 which entities are frozen, and representation pragmas and clauses are
30803 not permitted past the freeze point. This shows up most typically in
30804 the form of an error message complaining that a representation item
30805 appears too late, and the appropriate corrective action is to move
30806 the item nearer to the declaration of the entity to which it refers.
30808 A particular case is that representation pragmas
30811 extended HP Ada 83 compatibility pragmas such as @code{Export_Procedure})
30813 cannot be applied to a subprogram body. If necessary, a separate subprogram
30814 declaration must be introduced to which the pragma can be applied.
30816 @item Optional bodies for library packages
30817 In Ada 83, a package that did not require a package body was nevertheless
30818 allowed to have one. This lead to certain surprises in compiling large
30819 systems (situations in which the body could be unexpectedly ignored by the
30820 binder). In Ada 95, if a package does not require a body then it is not
30821 permitted to have a body. To fix this problem, simply remove a redundant
30822 body if it is empty, or, if it is non-empty, introduce a dummy declaration
30823 into the spec that makes the body required. One approach is to add a private
30824 part to the package declaration (if necessary), and define a parameterless
30825 procedure called @code{Requires_Body}, which must then be given a dummy
30826 procedure body in the package body, which then becomes required.
30827 Another approach (assuming that this does not introduce elaboration
30828 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
30829 since one effect of this pragma is to require the presence of a package body.
30831 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
30832 In Ada 95, the exception @code{Numeric_Error} is a renaming of
30833 @code{Constraint_Error}.
30834 This means that it is illegal to have separate exception handlers for
30835 the two exceptions. The fix is simply to remove the handler for the
30836 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
30837 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
30839 @item Indefinite subtypes in generics
30840 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
30841 as the actual for a generic formal private type, but then the instantiation
30842 would be illegal if there were any instances of declarations of variables
30843 of this type in the generic body. In Ada 95, to avoid this clear violation
30844 of the methodological principle known as the ``contract model'',
30845 the generic declaration explicitly indicates whether
30846 or not such instantiations are permitted. If a generic formal parameter
30847 has explicit unknown discriminants, indicated by using @code{(<>)} after the
30848 type name, then it can be instantiated with indefinite types, but no
30849 stand-alone variables can be declared of this type. Any attempt to declare
30850 such a variable will result in an illegality at the time the generic is
30851 declared. If the @code{(<>)} notation is not used, then it is illegal
30852 to instantiate the generic with an indefinite type.
30853 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
30854 It will show up as a compile time error, and
30855 the fix is usually simply to add the @code{(<>)} to the generic declaration.
30858 @node More deterministic semantics
30859 @subsection More deterministic semantics
30863 Conversions from real types to integer types round away from 0. In Ada 83
30864 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
30865 implementation freedom was intended to support unbiased rounding in
30866 statistical applications, but in practice it interfered with portability.
30867 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
30868 is required. Numeric code may be affected by this change in semantics.
30869 Note, though, that this issue is no worse than already existed in Ada 83
30870 when porting code from one vendor to another.
30873 The Real-Time Annex introduces a set of policies that define the behavior of
30874 features that were implementation dependent in Ada 83, such as the order in
30875 which open select branches are executed.
30878 @node Changed semantics
30879 @subsection Changed semantics
30882 The worst kind of incompatibility is one where a program that is legal in
30883 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
30884 possible in Ada 83. Fortunately this is extremely rare, but the one
30885 situation that you should be alert to is the change in the predefined type
30886 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
30889 @item Range of type @code{Character}
30890 The range of @code{Standard.Character} is now the full 256 characters
30891 of Latin-1, whereas in most Ada 83 implementations it was restricted
30892 to 128 characters. Although some of the effects of
30893 this change will be manifest in compile-time rejection of legal
30894 Ada 83 programs it is possible for a working Ada 83 program to have
30895 a different effect in Ada 95, one that was not permitted in Ada 83.
30896 As an example, the expression
30897 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
30898 delivers @code{255} as its value.
30899 In general, you should look at the logic of any
30900 character-processing Ada 83 program and see whether it needs to be adapted
30901 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
30902 character handling package that may be relevant if code needs to be adapted
30903 to account for the additional Latin-1 elements.
30904 The desirable fix is to
30905 modify the program to accommodate the full character set, but in some cases
30906 it may be convenient to define a subtype or derived type of Character that
30907 covers only the restricted range.
30911 @node Other language compatibility issues
30912 @subsection Other language compatibility issues
30915 @item @option{-gnat83} switch
30916 All implementations of GNAT provide a switch that causes GNAT to operate
30917 in Ada 83 mode. In this mode, some but not all compatibility problems
30918 of the type described above are handled automatically. For example, the
30919 new reserved words introduced in Ada 95 and Ada 2005 are treated simply
30920 as identifiers as in Ada 83.
30922 in practice, it is usually advisable to make the necessary modifications
30923 to the program to remove the need for using this switch.
30924 See @ref{Compiling Different Versions of Ada}.
30926 @item Support for removed Ada 83 pragmas and attributes
30927 A number of pragmas and attributes from Ada 83 were removed from Ada 95,
30928 generally because they were replaced by other mechanisms. Ada 95 and Ada 2005
30929 compilers are allowed, but not required, to implement these missing
30930 elements. In contrast with some other compilers, GNAT implements all
30931 such pragmas and attributes, eliminating this compatibility concern. These
30932 include @code{pragma Interface} and the floating point type attributes
30933 (@code{Emax}, @code{Mantissa}, etc.), among other items.
30937 @node Compatibility between Ada 95 and Ada 2005
30938 @section Compatibility between Ada 95 and Ada 2005
30939 @cindex Compatibility between Ada 95 and Ada 2005
30942 Although Ada 2005 was designed to be upwards compatible with Ada 95, there are
30943 a number of incompatibilities. Several are enumerated below;
30944 for a complete description please see the
30945 Annotated Ada 2005 Reference Manual, or section 9.1.1 in
30946 @cite{Rationale for Ada 2005}.
30949 @item New reserved words.
30950 The words @code{interface}, @code{overriding} and @code{synchronized} are
30951 reserved in Ada 2005.
30952 A pre-Ada 2005 program that uses any of these as an identifier will be
30955 @item New declarations in predefined packages.
30956 A number of packages in the predefined environment contain new declarations:
30957 @code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings},
30958 @code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded},
30959 @code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed},
30960 @code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded},
30961 @code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}.
30962 If an Ada 95 program does a @code{with} and @code{use} of any of these
30963 packages, the new declarations may cause name clashes.
30965 @item Access parameters.
30966 A nondispatching subprogram with an access parameter cannot be renamed
30967 as a dispatching operation. This was permitted in Ada 95.
30969 @item Access types, discriminants, and constraints.
30970 Rule changes in this area have led to some incompatibilities; for example,
30971 constrained subtypes of some access types are not permitted in Ada 2005.
30973 @item Aggregates for limited types.
30974 The allowance of aggregates for limited types in Ada 2005 raises the
30975 possibility of ambiguities in legal Ada 95 programs, since additional types
30976 now need to be considered in expression resolution.
30978 @item Fixed-point multiplication and division.
30979 Certain expressions involving ``*'' or ``/'' for a fixed-point type, which
30980 were legal in Ada 95 and invoked the predefined versions of these operations,
30982 The ambiguity may be resolved either by applying a type conversion to the
30983 expression, or by explicitly invoking the operation from package
30986 @item Return-by-reference types.
30987 The Ada 95 return-by-reference mechanism has been removed. Instead, the user
30988 can declare a function returning a value from an anonymous access type.
30992 @node Implementation-dependent characteristics
30993 @section Implementation-dependent characteristics
30995 Although the Ada language defines the semantics of each construct as
30996 precisely as practical, in some situations (for example for reasons of
30997 efficiency, or where the effect is heavily dependent on the host or target
30998 platform) the implementation is allowed some freedom. In porting Ada 83
30999 code to GNAT, you need to be aware of whether / how the existing code
31000 exercised such implementation dependencies. Such characteristics fall into
31001 several categories, and GNAT offers specific support in assisting the
31002 transition from certain Ada 83 compilers.
31005 * Implementation-defined pragmas::
31006 * Implementation-defined attributes::
31008 * Elaboration order::
31009 * Target-specific aspects::
31012 @node Implementation-defined pragmas
31013 @subsection Implementation-defined pragmas
31016 Ada compilers are allowed to supplement the language-defined pragmas, and
31017 these are a potential source of non-portability. All GNAT-defined pragmas
31018 are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT
31019 Reference Manual}, and these include several that are specifically
31020 intended to correspond to other vendors' Ada 83 pragmas.
31021 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
31022 For compatibility with HP Ada 83, GNAT supplies the pragmas
31023 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
31024 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
31025 and @code{Volatile}.
31026 Other relevant pragmas include @code{External} and @code{Link_With}.
31027 Some vendor-specific
31028 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
31030 avoiding compiler rejection of units that contain such pragmas; they are not
31031 relevant in a GNAT context and hence are not otherwise implemented.
31033 @node Implementation-defined attributes
31034 @subsection Implementation-defined attributes
31036 Analogous to pragmas, the set of attributes may be extended by an
31037 implementation. All GNAT-defined attributes are described in
31038 @ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference
31039 Manual}, and these include several that are specifically intended
31040 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
31041 the attribute @code{VADS_Size} may be useful. For compatibility with HP
31042 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
31046 @subsection Libraries
31048 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
31049 code uses vendor-specific libraries then there are several ways to manage
31050 this in Ada 95 or Ada 2005:
31053 If the source code for the libraries (specs and bodies) are
31054 available, then the libraries can be migrated in the same way as the
31057 If the source code for the specs but not the bodies are
31058 available, then you can reimplement the bodies.
31060 Some features introduced by Ada 95 obviate the need for library support. For
31061 example most Ada 83 vendors supplied a package for unsigned integers. The
31062 Ada 95 modular type feature is the preferred way to handle this need, so
31063 instead of migrating or reimplementing the unsigned integer package it may
31064 be preferable to retrofit the application using modular types.
31067 @node Elaboration order
31068 @subsection Elaboration order
31070 The implementation can choose any elaboration order consistent with the unit
31071 dependency relationship. This freedom means that some orders can result in
31072 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
31073 to invoke a subprogram its body has been elaborated, or to instantiate a
31074 generic before the generic body has been elaborated. By default GNAT
31075 attempts to choose a safe order (one that will not encounter access before
31076 elaboration problems) by implicitly inserting @code{Elaborate} or
31077 @code{Elaborate_All} pragmas where
31078 needed. However, this can lead to the creation of elaboration circularities
31079 and a resulting rejection of the program by gnatbind. This issue is
31080 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
31081 In brief, there are several
31082 ways to deal with this situation:
31086 Modify the program to eliminate the circularities, e.g.@: by moving
31087 elaboration-time code into explicitly-invoked procedures
31089 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
31090 @code{Elaborate} pragmas, and then inhibit the generation of implicit
31091 @code{Elaborate_All}
31092 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
31093 (by selectively suppressing elaboration checks via pragma
31094 @code{Suppress(Elaboration_Check)} when it is safe to do so).
31097 @node Target-specific aspects
31098 @subsection Target-specific aspects
31100 Low-level applications need to deal with machine addresses, data
31101 representations, interfacing with assembler code, and similar issues. If
31102 such an Ada 83 application is being ported to different target hardware (for
31103 example where the byte endianness has changed) then you will need to
31104 carefully examine the program logic; the porting effort will heavily depend
31105 on the robustness of the original design. Moreover, Ada 95 (and thus
31106 Ada 2005) are sometimes
31107 incompatible with typical Ada 83 compiler practices regarding implicit
31108 packing, the meaning of the Size attribute, and the size of access values.
31109 GNAT's approach to these issues is described in @ref{Representation Clauses}.
31111 @node Compatibility with Other Ada Systems
31112 @section Compatibility with Other Ada Systems
31115 If programs avoid the use of implementation dependent and
31116 implementation defined features, as documented in the @cite{Ada
31117 Reference Manual}, there should be a high degree of portability between
31118 GNAT and other Ada systems. The following are specific items which
31119 have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95
31120 compilers, but do not affect porting code to GNAT@.
31121 (As of @value{NOW}, GNAT is the only compiler available for Ada 2005;
31122 the following issues may or may not arise for Ada 2005 programs
31123 when other compilers appear.)
31126 @item Ada 83 Pragmas and Attributes
31127 Ada 95 compilers are allowed, but not required, to implement the missing
31128 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
31129 GNAT implements all such pragmas and attributes, eliminating this as
31130 a compatibility concern, but some other Ada 95 compilers reject these
31131 pragmas and attributes.
31133 @item Specialized Needs Annexes
31134 GNAT implements the full set of special needs annexes. At the
31135 current time, it is the only Ada 95 compiler to do so. This means that
31136 programs making use of these features may not be portable to other Ada
31137 95 compilation systems.
31139 @item Representation Clauses
31140 Some other Ada 95 compilers implement only the minimal set of
31141 representation clauses required by the Ada 95 reference manual. GNAT goes
31142 far beyond this minimal set, as described in the next section.
31145 @node Representation Clauses
31146 @section Representation Clauses
31149 The Ada 83 reference manual was quite vague in describing both the minimal
31150 required implementation of representation clauses, and also their precise
31151 effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the
31152 minimal set of capabilities required is still quite limited.
31154 GNAT implements the full required set of capabilities in
31155 Ada 95 and Ada 2005, but also goes much further, and in particular
31156 an effort has been made to be compatible with existing Ada 83 usage to the
31157 greatest extent possible.
31159 A few cases exist in which Ada 83 compiler behavior is incompatible with
31160 the requirements in Ada 95 (and thus also Ada 2005). These are instances of
31161 intentional or accidental dependence on specific implementation dependent
31162 characteristics of these Ada 83 compilers. The following is a list of
31163 the cases most likely to arise in existing Ada 83 code.
31166 @item Implicit Packing
31167 Some Ada 83 compilers allowed a Size specification to cause implicit
31168 packing of an array or record. This could cause expensive implicit
31169 conversions for change of representation in the presence of derived
31170 types, and the Ada design intends to avoid this possibility.
31171 Subsequent AI's were issued to make it clear that such implicit
31172 change of representation in response to a Size clause is inadvisable,
31173 and this recommendation is represented explicitly in the Ada 95 (and Ada 2005)
31174 Reference Manuals as implementation advice that is followed by GNAT@.
31175 The problem will show up as an error
31176 message rejecting the size clause. The fix is simply to provide
31177 the explicit pragma @code{Pack}, or for more fine tuned control, provide
31178 a Component_Size clause.
31180 @item Meaning of Size Attribute
31181 The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as
31182 the minimal number of bits required to hold values of the type. For example,
31183 on a 32-bit machine, the size of @code{Natural} will typically be 31 and not
31184 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
31185 some 32 in this situation. This problem will usually show up as a compile
31186 time error, but not always. It is a good idea to check all uses of the
31187 'Size attribute when porting Ada 83 code. The GNAT specific attribute
31188 Object_Size can provide a useful way of duplicating the behavior of
31189 some Ada 83 compiler systems.
31191 @item Size of Access Types
31192 A common assumption in Ada 83 code is that an access type is in fact a pointer,
31193 and that therefore it will be the same size as a System.Address value. This
31194 assumption is true for GNAT in most cases with one exception. For the case of
31195 a pointer to an unconstrained array type (where the bounds may vary from one
31196 value of the access type to another), the default is to use a ``fat pointer'',
31197 which is represented as two separate pointers, one to the bounds, and one to
31198 the array. This representation has a number of advantages, including improved
31199 efficiency. However, it may cause some difficulties in porting existing Ada 83
31200 code which makes the assumption that, for example, pointers fit in 32 bits on
31201 a machine with 32-bit addressing.
31203 To get around this problem, GNAT also permits the use of ``thin pointers'' for
31204 access types in this case (where the designated type is an unconstrained array
31205 type). These thin pointers are indeed the same size as a System.Address value.
31206 To specify a thin pointer, use a size clause for the type, for example:
31208 @smallexample @c ada
31209 type X is access all String;
31210 for X'Size use Standard'Address_Size;
31214 which will cause the type X to be represented using a single pointer.
31215 When using this representation, the bounds are right behind the array.
31216 This representation is slightly less efficient, and does not allow quite
31217 such flexibility in the use of foreign pointers or in using the
31218 Unrestricted_Access attribute to create pointers to non-aliased objects.
31219 But for any standard portable use of the access type it will work in
31220 a functionally correct manner and allow porting of existing code.
31221 Note that another way of forcing a thin pointer representation
31222 is to use a component size clause for the element size in an array,
31223 or a record representation clause for an access field in a record.
31227 @c This brief section is only in the non-VMS version
31228 @c The complete chapter on HP Ada is in the VMS version
31229 @node Compatibility with HP Ada 83
31230 @section Compatibility with HP Ada 83
31233 The VMS version of GNAT fully implements all the pragmas and attributes
31234 provided by HP Ada 83, as well as providing the standard HP Ada 83
31235 libraries, including Starlet. In addition, data layouts and parameter
31236 passing conventions are highly compatible. This means that porting
31237 existing HP Ada 83 code to GNAT in VMS systems should be easier than
31238 most other porting efforts. The following are some of the most
31239 significant differences between GNAT and HP Ada 83.
31242 @item Default floating-point representation
31243 In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83,
31244 it is VMS format. GNAT does implement the necessary pragmas
31245 (Long_Float, Float_Representation) for changing this default.
31248 The package System in GNAT exactly corresponds to the definition in the
31249 Ada 95 reference manual, which means that it excludes many of the
31250 HP Ada 83 extensions. However, a separate package Aux_DEC is provided
31251 that contains the additional definitions, and a special pragma,
31252 Extend_System allows this package to be treated transparently as an
31253 extension of package System.
31256 The definitions provided by Aux_DEC are exactly compatible with those
31257 in the HP Ada 83 version of System, with one exception.
31258 HP Ada provides the following declarations:
31260 @smallexample @c ada
31261 TO_ADDRESS (INTEGER)
31262 TO_ADDRESS (UNSIGNED_LONGWORD)
31263 TO_ADDRESS (@i{universal_integer})
31267 The version of TO_ADDRESS taking a @i{universal integer} argument is in fact
31268 an extension to Ada 83 not strictly compatible with the reference manual.
31269 In GNAT, we are constrained to be exactly compatible with the standard,
31270 and this means we cannot provide this capability. In HP Ada 83, the
31271 point of this definition is to deal with a call like:
31273 @smallexample @c ada
31274 TO_ADDRESS (16#12777#);
31278 Normally, according to the Ada 83 standard, one would expect this to be
31279 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
31280 of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the
31281 definition using @i{universal_integer} takes precedence.
31283 In GNAT, since the version with @i{universal_integer} cannot be supplied, it
31284 is not possible to be 100% compatible. Since there are many programs using
31285 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
31286 to change the name of the function in the UNSIGNED_LONGWORD case, so the
31287 declarations provided in the GNAT version of AUX_Dec are:
31289 @smallexample @c ada
31290 function To_Address (X : Integer) return Address;
31291 pragma Pure_Function (To_Address);
31293 function To_Address_Long (X : Unsigned_Longword)
31295 pragma Pure_Function (To_Address_Long);
31299 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
31300 change the name to TO_ADDRESS_LONG@.
31302 @item Task_Id values
31303 The Task_Id values assigned will be different in the two systems, and GNAT
31304 does not provide a specified value for the Task_Id of the environment task,
31305 which in GNAT is treated like any other declared task.
31309 For full details on these and other less significant compatibility issues,
31310 see appendix E of the HP publication entitled @cite{HP Ada, Technical
31311 Overview and Comparison on HP Platforms}.
31313 For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and
31314 attributes are recognized, although only a subset of them can sensibly
31315 be implemented. The description of pragmas in @ref{Implementation
31316 Defined Pragmas,,, gnat_rm, GNAT Reference Manual}
31317 indicates whether or not they are applicable to non-VMS systems.
31321 @node Transitioning to 64-Bit GNAT for OpenVMS
31322 @section Transitioning to 64-Bit @value{EDITION} for OpenVMS
31325 This section is meant to assist users of pre-2006 @value{EDITION}
31326 for Alpha OpenVMS who are transitioning to 64-bit @value{EDITION},
31327 the version of the GNAT technology supplied in 2006 and later for
31328 OpenVMS on both Alpha and I64.
31331 * Introduction to transitioning::
31332 * Migration of 32 bit code::
31333 * Taking advantage of 64 bit addressing::
31334 * Technical details::
31337 @node Introduction to transitioning
31338 @subsection Introduction
31341 64-bit @value{EDITION} for Open VMS has been designed to meet
31346 Providing a full conforming implementation of Ada 95 and Ada 2005
31349 Allowing maximum backward compatibility, thus easing migration of existing
31353 Supplying a path for exploiting the full 64-bit address range
31357 Ada's strong typing semantics has made it
31358 impractical to have different 32-bit and 64-bit modes. As soon as
31359 one object could possibly be outside the 32-bit address space, this
31360 would make it necessary for the @code{System.Address} type to be 64 bits.
31361 In particular, this would cause inconsistencies if 32-bit code is
31362 called from 64-bit code that raises an exception.
31364 This issue has been resolved by always using 64-bit addressing
31365 at the system level, but allowing for automatic conversions between
31366 32-bit and 64-bit addresses where required. Thus users who
31367 do not currently require 64-bit addressing capabilities, can
31368 recompile their code with only minimal changes (and indeed
31369 if the code is written in portable Ada, with no assumptions about
31370 the size of the @code{Address} type, then no changes at all are necessary).
31372 this approach provides a simple, gradual upgrade path to future
31373 use of larger memories than available for 32-bit systems.
31374 Also, newly written applications or libraries will by default
31375 be fully compatible with future systems exploiting 64-bit
31376 addressing capabilities.
31378 @ref{Migration of 32 bit code}, will focus on porting applications
31379 that do not require more than 2 GB of
31380 addressable memory. This code will be referred to as
31381 @emph{32-bit code}.
31382 For applications intending to exploit the full 64-bit address space,
31383 @ref{Taking advantage of 64 bit addressing},
31384 will consider further changes that may be required.
31385 Such code will be referred to below as @emph{64-bit code}.
31387 @node Migration of 32 bit code
31388 @subsection Migration of 32-bit code
31393 * Unchecked conversions::
31394 * Predefined constants::
31395 * Interfacing with C::
31396 * Experience with source compatibility::
31399 @node Address types
31400 @subsubsection Address types
31403 To solve the problem of mixing 64-bit and 32-bit addressing,
31404 while maintaining maximum backward compatibility, the following
31405 approach has been taken:
31409 @code{System.Address} always has a size of 64 bits
31412 @code{System.Short_Address} is a 32-bit subtype of @code{System.Address}
31416 Since @code{System.Short_Address} is a subtype of @code{System.Address},
31417 a @code{Short_Address}
31418 may be used where an @code{Address} is required, and vice versa, without
31419 needing explicit type conversions.
31420 By virtue of the Open VMS parameter passing conventions,
31422 and exported subprograms that have 32-bit address parameters are
31423 compatible with those that have 64-bit address parameters.
31424 (See @ref{Making code 64 bit clean} for details.)
31426 The areas that may need attention are those where record types have
31427 been defined that contain components of the type @code{System.Address}, and
31428 where objects of this type are passed to code expecting a record layout with
31431 Different compilers on different platforms cannot be
31432 expected to represent the same type in the same way,
31433 since alignment constraints
31434 and other system-dependent properties affect the compiler's decision.
31435 For that reason, Ada code
31436 generally uses representation clauses to specify the expected
31437 layout where required.
31439 If such a representation clause uses 32 bits for a component having
31440 the type @code{System.Address}, 64-bit @value{EDITION} for OpenVMS
31441 will detect that error and produce a specific diagnostic message.
31442 The developer should then determine whether the representation
31443 should be 64 bits or not and make either of two changes:
31444 change the size to 64 bits and leave the type as @code{System.Address}, or
31445 leave the size as 32 bits and change the type to @code{System.Short_Address}.
31446 Since @code{Short_Address} is a subtype of @code{Address}, no changes are
31447 required in any code setting or accessing the field; the compiler will
31448 automatically perform any needed conversions between address
31452 @subsubsection Access types
31455 By default, objects designated by access values are always
31456 allocated in the 32-bit
31457 address space. Thus legacy code will never contain
31458 any objects that are not addressable with 32-bit addresses, and
31459 the compiler will never raise exceptions as result of mixing
31460 32-bit and 64-bit addresses.
31462 However, the access values themselves are represented in 64 bits, for optimum
31463 performance and future compatibility with 64-bit code. As was
31464 the case with @code{System.Address}, the compiler will give an error message
31465 if an object or record component has a representation clause that
31466 requires the access value to fit in 32 bits. In such a situation,
31467 an explicit size clause for the access type, specifying 32 bits,
31468 will have the desired effect.
31470 General access types (declared with @code{access all}) can never be
31471 32 bits, as values of such types must be able to refer to any object
31472 of the designated type,
31473 including objects residing outside the 32-bit address range.
31474 Existing Ada 83 code will not contain such type definitions,
31475 however, since general access types were introduced in Ada 95.
31477 @node Unchecked conversions
31478 @subsubsection Unchecked conversions
31481 In the case of an @code{Unchecked_Conversion} where the source type is a
31482 64-bit access type or the type @code{System.Address}, and the target
31483 type is a 32-bit type, the compiler will generate a warning.
31484 Even though the generated code will still perform the required
31485 conversions, it is highly recommended in these cases to use
31486 respectively a 32-bit access type or @code{System.Short_Address}
31487 as the source type.
31489 @node Predefined constants
31490 @subsubsection Predefined constants
31493 The following table shows the correspondence between pre-2006 versions of
31494 @value{EDITION} on Alpha OpenVMS (``Old'') and 64-bit @value{EDITION}
31497 @multitable {@code{System.Short_Memory_Size}} {2**32} {2**64}
31498 @item @b{Constant} @tab @b{Old} @tab @b{New}
31499 @item @code{System.Word_Size} @tab 32 @tab 64
31500 @item @code{System.Memory_Size} @tab 2**32 @tab 2**64
31501 @item @code{System.Short_Memory_Size} @tab 2**32 @tab 2**32
31502 @item @code{System.Address_Size} @tab 32 @tab 64
31506 If you need to refer to the specific
31507 memory size of a 32-bit implementation, instead of the
31508 actual memory size, use @code{System.Short_Memory_Size}
31509 rather than @code{System.Memory_Size}.
31510 Similarly, references to @code{System.Address_Size} may need
31511 to be replaced by @code{System.Short_Address'Size}.
31512 The program @command{gnatfind} may be useful for locating
31513 references to the above constants, so that you can verify that they
31516 @node Interfacing with C
31517 @subsubsection Interfacing with C
31520 In order to minimize the impact of the transition to 64-bit addresses on
31521 legacy programs, some fundamental types in the @code{Interfaces.C}
31522 package hierarchy continue to be represented in 32 bits.
31523 These types are: @code{ptrdiff_t}, @code{size_t}, and @code{chars_ptr}.
31524 This eases integration with the default HP C layout choices, for example
31525 as found in the system routines in @code{DECC$SHR.EXE}.
31526 Because of this implementation choice, the type fully compatible with
31527 @code{chars_ptr} is now @code{Short_Address} and not @code{Address}.
31528 Depending on the context the compiler will issue a
31529 warning or an error when type @code{Address} is used, alerting the user to a
31530 potential problem. Otherwise 32-bit programs that use
31531 @code{Interfaces.C} should normally not require code modifications
31533 The other issue arising with C interfacing concerns pragma @code{Convention}.
31534 For VMS 64-bit systems, there is an issue of the appropriate default size
31535 of C convention pointers in the absence of an explicit size clause. The HP
31536 C compiler can choose either 32 or 64 bits depending on compiler options.
31537 GNAT chooses 32-bits rather than 64-bits in the default case where no size
31538 clause is given. This proves a better choice for porting 32-bit legacy
31539 applications. In order to have a 64-bit representation, it is necessary to
31540 specify a size representation clause. For example:
31542 @smallexample @c ada
31543 type int_star is access Interfaces.C.int;
31544 pragma Convention(C, int_star);
31545 for int_star'Size use 64; -- Necessary to get 64 and not 32 bits
31548 @node Experience with source compatibility
31549 @subsubsection Experience with source compatibility
31552 The Security Server and STARLET on I64 provide an interesting ``test case''
31553 for source compatibility issues, since it is in such system code
31554 where assumptions about @code{Address} size might be expected to occur.
31555 Indeed, there were a small number of occasions in the Security Server
31556 file @file{jibdef.ads}
31557 where a representation clause for a record type specified
31558 32 bits for a component of type @code{Address}.
31559 All of these errors were detected by the compiler.
31560 The repair was obvious and immediate; to simply replace @code{Address} by
31561 @code{Short_Address}.
31563 In the case of STARLET, there were several record types that should
31564 have had representation clauses but did not. In these record types
31565 there was an implicit assumption that an @code{Address} value occupied
31567 These compiled without error, but their usage resulted in run-time error
31568 returns from STARLET system calls.
31569 Future GNAT technology enhancements may include a tool that detects and flags
31570 these sorts of potential source code porting problems.
31572 @c ****************************************
31573 @node Taking advantage of 64 bit addressing
31574 @subsection Taking advantage of 64-bit addressing
31577 * Making code 64 bit clean::
31578 * Allocating memory from the 64 bit storage pool::
31579 * Restrictions on use of 64 bit objects::
31580 * Using 64 bit storage pools by default::
31581 * General access types::
31582 * STARLET and other predefined libraries::
31585 @node Making code 64 bit clean
31586 @subsubsection Making code 64-bit clean
31589 In order to prevent problems that may occur when (parts of) a
31590 system start using memory outside the 32-bit address range,
31591 we recommend some additional guidelines:
31595 For imported subprograms that take parameters of the
31596 type @code{System.Address}, ensure that these subprograms can
31597 indeed handle 64-bit addresses. If not, or when in doubt,
31598 change the subprogram declaration to specify
31599 @code{System.Short_Address} instead.
31602 Resolve all warnings related to size mismatches in
31603 unchecked conversions. Failing to do so causes
31604 erroneous execution if the source object is outside
31605 the 32-bit address space.
31608 (optional) Explicitly use the 32-bit storage pool
31609 for access types used in a 32-bit context, or use
31610 generic access types where possible
31611 (@pxref{Restrictions on use of 64 bit objects}).
31615 If these rules are followed, the compiler will automatically insert
31616 any necessary checks to ensure that no addresses or access values
31617 passed to 32-bit code ever refer to objects outside the 32-bit
31619 Any attempt to do this will raise @code{Constraint_Error}.
31621 @node Allocating memory from the 64 bit storage pool
31622 @subsubsection Allocating memory from the 64-bit storage pool
31625 For any access type @code{T} that potentially requires memory allocations
31626 beyond the 32-bit address space,
31627 use the following representation clause:
31629 @smallexample @c ada
31630 for T'Storage_Pool use System.Pool_64;
31633 @node Restrictions on use of 64 bit objects
31634 @subsubsection Restrictions on use of 64-bit objects
31637 Taking the address of an object allocated from a 64-bit storage pool,
31638 and then passing this address to a subprogram expecting
31639 @code{System.Short_Address},
31640 or assigning it to a variable of type @code{Short_Address}, will cause
31641 @code{Constraint_Error} to be raised. In case the code is not 64-bit clean
31642 (@pxref{Making code 64 bit clean}), or checks are suppressed,
31643 no exception is raised and execution
31644 will become erroneous.
31646 @node Using 64 bit storage pools by default
31647 @subsubsection Using 64-bit storage pools by default
31650 In some cases it may be desirable to have the compiler allocate
31651 from 64-bit storage pools by default. This may be the case for
31652 libraries that are 64-bit clean, but may be used in both 32-bit
31653 and 64-bit contexts. For these cases the following configuration
31654 pragma may be specified:
31656 @smallexample @c ada
31657 pragma Pool_64_Default;
31661 Any code compiled in the context of this pragma will by default
31662 use the @code{System.Pool_64} storage pool. This default may be overridden
31663 for a specific access type @code{T} by the representation clause:
31665 @smallexample @c ada
31666 for T'Storage_Pool use System.Pool_32;
31670 Any object whose address may be passed to a subprogram with a
31671 @code{Short_Address} argument, or assigned to a variable of type
31672 @code{Short_Address}, needs to be allocated from this pool.
31674 @node General access types
31675 @subsubsection General access types
31678 Objects designated by access values from a
31679 general access type (declared with @code{access all}) are never allocated
31680 from a 64-bit storage pool. Code that uses general access types will
31681 accept objects allocated in either 32-bit or 64-bit address spaces,
31682 but never allocate objects outside the 32-bit address space.
31683 Using general access types ensures maximum compatibility with both
31684 32-bit and 64-bit code.
31686 @node STARLET and other predefined libraries
31687 @subsubsection STARLET and other predefined libraries
31690 All code that comes as part of GNAT is 64-bit clean, but the
31691 restrictions given in @ref{Restrictions on use of 64 bit objects},
31692 still apply. Look at the package
31693 specs to see in which contexts objects allocated
31694 in 64-bit address space are acceptable.
31696 @node Technical details
31697 @subsection Technical details
31700 64-bit @value{EDITION} for Open VMS takes advantage of the freedom given in the
31701 Ada standard with respect to the type of @code{System.Address}. Previous
31702 versions of GNAT Pro have defined this type as private and implemented it as a
31705 In order to allow defining @code{System.Short_Address} as a proper subtype,
31706 and to match the implicit sign extension in parameter passing,
31707 in 64-bit @value{EDITION} for Open VMS, @code{System.Address} is defined as a
31708 visible (i.e., non-private) integer type.
31709 Standard operations on the type, such as the binary operators ``+'', ``-'',
31710 etc., that take @code{Address} operands and return an @code{Address} result,
31711 have been hidden by declaring these
31712 @code{abstract}, a feature introduced in Ada 95 that helps avoid the potential
31713 ambiguities that would otherwise result from overloading.
31714 (Note that, although @code{Address} is a visible integer type,
31715 good programming practice dictates against exploiting the type's
31716 integer properties such as literals, since this will compromise
31719 Defining @code{Address} as a visible integer type helps achieve
31720 maximum compatibility for existing Ada code,
31721 without sacrificing the capabilities of the 64-bit architecture.
31724 @c ************************************************
31726 @node Microsoft Windows Topics
31727 @appendix Microsoft Windows Topics
31733 This chapter describes topics that are specific to the Microsoft Windows
31734 platforms (NT, 2000, and XP Professional).
31737 * Using GNAT on Windows::
31738 * Using a network installation of GNAT::
31739 * CONSOLE and WINDOWS subsystems::
31740 * Temporary Files::
31741 * Mixed-Language Programming on Windows::
31742 * Windows Calling Conventions::
31743 * Introduction to Dynamic Link Libraries (DLLs)::
31744 * Using DLLs with GNAT::
31745 * Building DLLs with GNAT::
31746 * Building DLLs with GNAT Project files::
31747 * Building DLLs with gnatdll::
31748 * GNAT and Windows Resources::
31749 * Debugging a DLL::
31750 * Setting Stack Size from gnatlink::
31751 * Setting Heap Size from gnatlink::
31754 @node Using GNAT on Windows
31755 @section Using GNAT on Windows
31758 One of the strengths of the GNAT technology is that its tool set
31759 (@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the
31760 @code{gdb} debugger, etc.) is used in the same way regardless of the
31763 On Windows this tool set is complemented by a number of Microsoft-specific
31764 tools that have been provided to facilitate interoperability with Windows
31765 when this is required. With these tools:
31770 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
31774 You can use any Dynamically Linked Library (DLL) in your Ada code (both
31775 relocatable and non-relocatable DLLs are supported).
31778 You can build Ada DLLs for use in other applications. These applications
31779 can be written in a language other than Ada (e.g., C, C++, etc). Again both
31780 relocatable and non-relocatable Ada DLLs are supported.
31783 You can include Windows resources in your Ada application.
31786 You can use or create COM/DCOM objects.
31790 Immediately below are listed all known general GNAT-for-Windows restrictions.
31791 Other restrictions about specific features like Windows Resources and DLLs
31792 are listed in separate sections below.
31797 It is not possible to use @code{GetLastError} and @code{SetLastError}
31798 when tasking, protected records, or exceptions are used. In these
31799 cases, in order to implement Ada semantics, the GNAT run-time system
31800 calls certain Win32 routines that set the last error variable to 0 upon
31801 success. It should be possible to use @code{GetLastError} and
31802 @code{SetLastError} when tasking, protected record, and exception
31803 features are not used, but it is not guaranteed to work.
31806 It is not possible to link against Microsoft libraries except for
31807 import libraries. The library must be built to be compatible with
31808 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
31809 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
31810 not be compatible with the GNAT runtime. Even if the library is
31811 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
31814 When the compilation environment is located on FAT32 drives, users may
31815 experience recompilations of the source files that have not changed if
31816 Daylight Saving Time (DST) state has changed since the last time files
31817 were compiled. NTFS drives do not have this problem.
31820 No components of the GNAT toolset use any entries in the Windows
31821 registry. The only entries that can be created are file associations and
31822 PATH settings, provided the user has chosen to create them at installation
31823 time, as well as some minimal book-keeping information needed to correctly
31824 uninstall or integrate different GNAT products.
31827 @node Using a network installation of GNAT
31828 @section Using a network installation of GNAT
31831 Make sure the system on which GNAT is installed is accessible from the
31832 current machine, i.e., the install location is shared over the network.
31833 Shared resources are accessed on Windows by means of UNC paths, which
31834 have the format @code{\\server\sharename\path}
31836 In order to use such a network installation, simply add the UNC path of the
31837 @file{bin} directory of your GNAT installation in front of your PATH. For
31838 example, if GNAT is installed in @file{\GNAT} directory of a share location
31839 called @file{c-drive} on a machine @file{LOKI}, the following command will
31842 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
31844 Be aware that every compilation using the network installation results in the
31845 transfer of large amounts of data across the network and will likely cause
31846 serious performance penalty.
31848 @node CONSOLE and WINDOWS subsystems
31849 @section CONSOLE and WINDOWS subsystems
31850 @cindex CONSOLE Subsystem
31851 @cindex WINDOWS Subsystem
31855 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
31856 (which is the default subsystem) will always create a console when
31857 launching the application. This is not something desirable when the
31858 application has a Windows GUI. To get rid of this console the
31859 application must be using the @code{WINDOWS} subsystem. To do so
31860 the @option{-mwindows} linker option must be specified.
31863 $ gnatmake winprog -largs -mwindows
31866 @node Temporary Files
31867 @section Temporary Files
31868 @cindex Temporary files
31871 It is possible to control where temporary files gets created by setting
31872 the @env{TMP} environment variable. The file will be created:
31875 @item Under the directory pointed to by the @env{TMP} environment variable if
31876 this directory exists.
31878 @item Under @file{c:\temp}, if the @env{TMP} environment variable is not
31879 set (or not pointing to a directory) and if this directory exists.
31881 @item Under the current working directory otherwise.
31885 This allows you to determine exactly where the temporary
31886 file will be created. This is particularly useful in networked
31887 environments where you may not have write access to some
31890 @node Mixed-Language Programming on Windows
31891 @section Mixed-Language Programming on Windows
31894 Developing pure Ada applications on Windows is no different than on
31895 other GNAT-supported platforms. However, when developing or porting an
31896 application that contains a mix of Ada and C/C++, the choice of your
31897 Windows C/C++ development environment conditions your overall
31898 interoperability strategy.
31900 If you use @command{gcc} to compile the non-Ada part of your application,
31901 there are no Windows-specific restrictions that affect the overall
31902 interoperability with your Ada code. If you plan to use
31903 Microsoft tools (e.g.@: Microsoft Visual C/C++), you should be aware of
31904 the following limitations:
31908 You cannot link your Ada code with an object or library generated with
31909 Microsoft tools if these use the @code{.tls} section (Thread Local
31910 Storage section) since the GNAT linker does not yet support this section.
31913 You cannot link your Ada code with an object or library generated with
31914 Microsoft tools if these use I/O routines other than those provided in
31915 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
31916 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
31917 libraries can cause a conflict with @code{msvcrt.dll} services. For
31918 instance Visual C++ I/O stream routines conflict with those in
31923 If you do want to use the Microsoft tools for your non-Ada code and hit one
31924 of the above limitations, you have two choices:
31928 Encapsulate your non-Ada code in a DLL to be linked with your Ada
31929 application. In this case, use the Microsoft or whatever environment to
31930 build the DLL and use GNAT to build your executable
31931 (@pxref{Using DLLs with GNAT}).
31934 Or you can encapsulate your Ada code in a DLL to be linked with the
31935 other part of your application. In this case, use GNAT to build the DLL
31936 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
31937 environment to build your executable.
31940 @node Windows Calling Conventions
31941 @section Windows Calling Conventions
31946 * C Calling Convention::
31947 * Stdcall Calling Convention::
31948 * Win32 Calling Convention::
31949 * DLL Calling Convention::
31953 When a subprogram @code{F} (caller) calls a subprogram @code{G}
31954 (callee), there are several ways to push @code{G}'s parameters on the
31955 stack and there are several possible scenarios to clean up the stack
31956 upon @code{G}'s return. A calling convention is an agreed upon software
31957 protocol whereby the responsibilities between the caller (@code{F}) and
31958 the callee (@code{G}) are clearly defined. Several calling conventions
31959 are available for Windows:
31963 @code{C} (Microsoft defined)
31966 @code{Stdcall} (Microsoft defined)
31969 @code{Win32} (GNAT specific)
31972 @code{DLL} (GNAT specific)
31975 @node C Calling Convention
31976 @subsection @code{C} Calling Convention
31979 This is the default calling convention used when interfacing to C/C++
31980 routines compiled with either @command{gcc} or Microsoft Visual C++.
31982 In the @code{C} calling convention subprogram parameters are pushed on the
31983 stack by the caller from right to left. The caller itself is in charge of
31984 cleaning up the stack after the call. In addition, the name of a routine
31985 with @code{C} calling convention is mangled by adding a leading underscore.
31987 The name to use on the Ada side when importing (or exporting) a routine
31988 with @code{C} calling convention is the name of the routine. For
31989 instance the C function:
31992 int get_val (long);
31996 should be imported from Ada as follows:
31998 @smallexample @c ada
32000 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32001 pragma Import (C, Get_Val, External_Name => "get_val");
32006 Note that in this particular case the @code{External_Name} parameter could
32007 have been omitted since, when missing, this parameter is taken to be the
32008 name of the Ada entity in lower case. When the @code{Link_Name} parameter
32009 is missing, as in the above example, this parameter is set to be the
32010 @code{External_Name} with a leading underscore.
32012 When importing a variable defined in C, you should always use the @code{C}
32013 calling convention unless the object containing the variable is part of a
32014 DLL (in which case you should use the @code{Stdcall} calling
32015 convention, @pxref{Stdcall Calling Convention}).
32017 @node Stdcall Calling Convention
32018 @subsection @code{Stdcall} Calling Convention
32021 This convention, which was the calling convention used for Pascal
32022 programs, is used by Microsoft for all the routines in the Win32 API for
32023 efficiency reasons. It must be used to import any routine for which this
32024 convention was specified.
32026 In the @code{Stdcall} calling convention subprogram parameters are pushed
32027 on the stack by the caller from right to left. The callee (and not the
32028 caller) is in charge of cleaning the stack on routine exit. In addition,
32029 the name of a routine with @code{Stdcall} calling convention is mangled by
32030 adding a leading underscore (as for the @code{C} calling convention) and a
32031 trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in
32032 bytes) of the parameters passed to the routine.
32034 The name to use on the Ada side when importing a C routine with a
32035 @code{Stdcall} calling convention is the name of the C routine. The leading
32036 underscore and trailing @code{@@}@code{@var{nn}} are added automatically by
32037 the compiler. For instance the Win32 function:
32040 @b{APIENTRY} int get_val (long);
32044 should be imported from Ada as follows:
32046 @smallexample @c ada
32048 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32049 pragma Import (Stdcall, Get_Val);
32050 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
32055 As for the @code{C} calling convention, when the @code{External_Name}
32056 parameter is missing, it is taken to be the name of the Ada entity in lower
32057 case. If instead of writing the above import pragma you write:
32059 @smallexample @c ada
32061 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32062 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
32067 then the imported routine is @code{_retrieve_val@@4}. However, if instead
32068 of specifying the @code{External_Name} parameter you specify the
32069 @code{Link_Name} as in the following example:
32071 @smallexample @c ada
32073 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
32074 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
32079 then the imported routine is @code{retrieve_val}, that is, there is no
32080 decoration at all. No leading underscore and no Stdcall suffix
32081 @code{@@}@code{@var{nn}}.
32084 This is especially important as in some special cases a DLL's entry
32085 point name lacks a trailing @code{@@}@code{@var{nn}} while the exported
32086 name generated for a call has it.
32089 It is also possible to import variables defined in a DLL by using an
32090 import pragma for a variable. As an example, if a DLL contains a
32091 variable defined as:
32098 then, to access this variable from Ada you should write:
32100 @smallexample @c ada
32102 My_Var : Interfaces.C.int;
32103 pragma Import (Stdcall, My_Var);
32108 Note that to ease building cross-platform bindings this convention
32109 will be handled as a @code{C} calling convention on non-Windows platforms.
32111 @node Win32 Calling Convention
32112 @subsection @code{Win32} Calling Convention
32115 This convention, which is GNAT-specific is fully equivalent to the
32116 @code{Stdcall} calling convention described above.
32118 @node DLL Calling Convention
32119 @subsection @code{DLL} Calling Convention
32122 This convention, which is GNAT-specific is fully equivalent to the
32123 @code{Stdcall} calling convention described above.
32125 @node Introduction to Dynamic Link Libraries (DLLs)
32126 @section Introduction to Dynamic Link Libraries (DLLs)
32130 A Dynamically Linked Library (DLL) is a library that can be shared by
32131 several applications running under Windows. A DLL can contain any number of
32132 routines and variables.
32134 One advantage of DLLs is that you can change and enhance them without
32135 forcing all the applications that depend on them to be relinked or
32136 recompiled. However, you should be aware than all calls to DLL routines are
32137 slower since, as you will understand below, such calls are indirect.
32139 To illustrate the remainder of this section, suppose that an application
32140 wants to use the services of a DLL @file{API.dll}. To use the services
32141 provided by @file{API.dll} you must statically link against the DLL or
32142 an import library which contains a jump table with an entry for each
32143 routine and variable exported by the DLL. In the Microsoft world this
32144 import library is called @file{API.lib}. When using GNAT this import
32145 library is called either @file{libAPI.dll.a}, @file{libapi.dll.a},
32146 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
32148 After you have linked your application with the DLL or the import library
32149 and you run your application, here is what happens:
32153 Your application is loaded into memory.
32156 The DLL @file{API.dll} is mapped into the address space of your
32157 application. This means that:
32161 The DLL will use the stack of the calling thread.
32164 The DLL will use the virtual address space of the calling process.
32167 The DLL will allocate memory from the virtual address space of the calling
32171 Handles (pointers) can be safely exchanged between routines in the DLL
32172 routines and routines in the application using the DLL.
32176 The entries in the jump table (from the import library @file{libAPI.dll.a}
32177 or @file{API.lib} or automatically created when linking against a DLL)
32178 which is part of your application are initialized with the addresses
32179 of the routines and variables in @file{API.dll}.
32182 If present in @file{API.dll}, routines @code{DllMain} or
32183 @code{DllMainCRTStartup} are invoked. These routines typically contain
32184 the initialization code needed for the well-being of the routines and
32185 variables exported by the DLL.
32189 There is an additional point which is worth mentioning. In the Windows
32190 world there are two kind of DLLs: relocatable and non-relocatable
32191 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
32192 in the target application address space. If the addresses of two
32193 non-relocatable DLLs overlap and these happen to be used by the same
32194 application, a conflict will occur and the application will run
32195 incorrectly. Hence, when possible, it is always preferable to use and
32196 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
32197 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
32198 User's Guide) removes the debugging symbols from the DLL but the DLL can
32199 still be relocated.
32201 As a side note, an interesting difference between Microsoft DLLs and
32202 Unix shared libraries, is the fact that on most Unix systems all public
32203 routines are exported by default in a Unix shared library, while under
32204 Windows it is possible (but not required) to list exported routines in
32205 a definition file (@pxref{The Definition File}).
32207 @node Using DLLs with GNAT
32208 @section Using DLLs with GNAT
32211 * Creating an Ada Spec for the DLL Services::
32212 * Creating an Import Library::
32216 To use the services of a DLL, say @file{API.dll}, in your Ada application
32221 The Ada spec for the routines and/or variables you want to access in
32222 @file{API.dll}. If not available this Ada spec must be built from the C/C++
32223 header files provided with the DLL.
32226 The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously
32227 mentioned an import library is a statically linked library containing the
32228 import table which will be filled at load time to point to the actual
32229 @file{API.dll} routines. Sometimes you don't have an import library for the
32230 DLL you want to use. The following sections will explain how to build
32231 one. Note that this is optional.
32234 The actual DLL, @file{API.dll}.
32238 Once you have all the above, to compile an Ada application that uses the
32239 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
32240 you simply issue the command
32243 $ gnatmake my_ada_app -largs -lAPI
32247 The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command
32248 tells the GNAT linker to look first for a library named @file{API.lib}
32249 (Microsoft-style name) and if not found for a libraries named
32250 @file{libAPI.dll.a}, @file{API.dll.a} or @file{libAPI.a}.
32251 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
32252 contains the following pragma
32254 @smallexample @c ada
32255 pragma Linker_Options ("-lAPI");
32259 you do not have to add @option{-largs -lAPI} at the end of the
32260 @command{gnatmake} command.
32262 If any one of the items above is missing you will have to create it
32263 yourself. The following sections explain how to do so using as an
32264 example a fictitious DLL called @file{API.dll}.
32266 @node Creating an Ada Spec for the DLL Services
32267 @subsection Creating an Ada Spec for the DLL Services
32270 A DLL typically comes with a C/C++ header file which provides the
32271 definitions of the routines and variables exported by the DLL. The Ada
32272 equivalent of this header file is a package spec that contains definitions
32273 for the imported entities. If the DLL you intend to use does not come with
32274 an Ada spec you have to generate one such spec yourself. For example if
32275 the header file of @file{API.dll} is a file @file{api.h} containing the
32276 following two definitions:
32288 then the equivalent Ada spec could be:
32290 @smallexample @c ada
32293 with Interfaces.C.Strings;
32298 function Get (Str : C.Strings.Chars_Ptr) return C.int;
32301 pragma Import (C, Get);
32302 pragma Import (DLL, Some_Var);
32309 Note that a variable is
32310 @strong{always imported with a Stdcall convention}. A function
32311 can have @code{C} or @code{Stdcall} convention.
32312 (@pxref{Windows Calling Conventions}).
32314 @node Creating an Import Library
32315 @subsection Creating an Import Library
32316 @cindex Import library
32319 * The Definition File::
32320 * GNAT-Style Import Library::
32321 * Microsoft-Style Import Library::
32325 If a Microsoft-style import library @file{API.lib} or a GNAT-style
32326 import library @file{libAPI.dll.a} or @file{libAPI.a} is available
32327 with @file{API.dll} you can skip this section. You can also skip this
32328 section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools
32329 as in this case it is possible to link directly against the
32330 DLL. Otherwise read on.
32332 @node The Definition File
32333 @subsubsection The Definition File
32334 @cindex Definition file
32338 As previously mentioned, and unlike Unix systems, the list of symbols
32339 that are exported from a DLL must be provided explicitly in Windows.
32340 The main goal of a definition file is precisely that: list the symbols
32341 exported by a DLL. A definition file (usually a file with a @code{.def}
32342 suffix) has the following structure:
32347 @r{[}LIBRARY @var{name}@r{]}
32348 @r{[}DESCRIPTION @var{string}@r{]}
32358 @item LIBRARY @var{name}
32359 This section, which is optional, gives the name of the DLL.
32361 @item DESCRIPTION @var{string}
32362 This section, which is optional, gives a description string that will be
32363 embedded in the import library.
32366 This section gives the list of exported symbols (procedures, functions or
32367 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
32368 section of @file{API.def} looks like:
32382 Note that you must specify the correct suffix (@code{@@}@code{@var{nn}})
32383 (@pxref{Windows Calling Conventions}) for a Stdcall
32384 calling convention function in the exported symbols list.
32387 There can actually be other sections in a definition file, but these
32388 sections are not relevant to the discussion at hand.
32390 @node GNAT-Style Import Library
32391 @subsubsection GNAT-Style Import Library
32394 To create a static import library from @file{API.dll} with the GNAT tools
32395 you should proceed as follows:
32399 Create the definition file @file{API.def} (@pxref{The Definition File}).
32400 For that use the @code{dll2def} tool as follows:
32403 $ dll2def API.dll > API.def
32407 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
32408 to standard output the list of entry points in the DLL. Note that if
32409 some routines in the DLL have the @code{Stdcall} convention
32410 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn}
32411 suffix then you'll have to edit @file{api.def} to add it, and specify
32412 @option{-k} to @command{gnatdll} when creating the import library.
32415 Here are some hints to find the right @code{@@}@var{nn} suffix.
32419 If you have the Microsoft import library (.lib), it is possible to get
32420 the right symbols by using Microsoft @code{dumpbin} tool (see the
32421 corresponding Microsoft documentation for further details).
32424 $ dumpbin /exports api.lib
32428 If you have a message about a missing symbol at link time the compiler
32429 tells you what symbol is expected. You just have to go back to the
32430 definition file and add the right suffix.
32434 Build the import library @code{libAPI.dll.a}, using @code{gnatdll}
32435 (@pxref{Using gnatdll}) as follows:
32438 $ gnatdll -e API.def -d API.dll
32442 @code{gnatdll} takes as input a definition file @file{API.def} and the
32443 name of the DLL containing the services listed in the definition file
32444 @file{API.dll}. The name of the static import library generated is
32445 computed from the name of the definition file as follows: if the
32446 definition file name is @var{xyz}@code{.def}, the import library name will
32447 be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option
32448 @option{-e} could have been removed because the name of the definition
32449 file (before the ``@code{.def}'' suffix) is the same as the name of the
32450 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
32453 @node Microsoft-Style Import Library
32454 @subsubsection Microsoft-Style Import Library
32457 With GNAT you can either use a GNAT-style or Microsoft-style import
32458 library. A Microsoft import library is needed only if you plan to make an
32459 Ada DLL available to applications developed with Microsoft
32460 tools (@pxref{Mixed-Language Programming on Windows}).
32462 To create a Microsoft-style import library for @file{API.dll} you
32463 should proceed as follows:
32467 Create the definition file @file{API.def} from the DLL. For this use either
32468 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
32469 tool (see the corresponding Microsoft documentation for further details).
32472 Build the actual import library using Microsoft's @code{lib} utility:
32475 $ lib -machine:IX86 -def:API.def -out:API.lib
32479 If you use the above command the definition file @file{API.def} must
32480 contain a line giving the name of the DLL:
32487 See the Microsoft documentation for further details about the usage of
32491 @node Building DLLs with GNAT
32492 @section Building DLLs with GNAT
32493 @cindex DLLs, building
32496 This section explain how to build DLLs using the GNAT built-in DLL
32497 support. With the following procedure it is straight forward to build
32498 and use DLLs with GNAT.
32502 @item building object files
32504 The first step is to build all objects files that are to be included
32505 into the DLL. This is done by using the standard @command{gnatmake} tool.
32507 @item building the DLL
32509 To build the DLL you must use @command{gcc}'s @option{-shared}
32510 option. It is quite simple to use this method:
32513 $ gcc -shared -o api.dll obj1.o obj2.o @dots{}
32516 It is important to note that in this case all symbols found in the
32517 object files are automatically exported. It is possible to restrict
32518 the set of symbols to export by passing to @command{gcc} a definition
32519 file, @pxref{The Definition File}. For example:
32522 $ gcc -shared -o api.dll api.def obj1.o obj2.o @dots{}
32525 If you use a definition file you must export the elaboration procedures
32526 for every package that required one. Elaboration procedures are named
32527 using the package name followed by "_E".
32529 @item preparing DLL to be used
32531 For the DLL to be used by client programs the bodies must be hidden
32532 from it and the .ali set with read-only attribute. This is very important
32533 otherwise GNAT will recompile all packages and will not actually use
32534 the code in the DLL. For example:
32538 $ copy *.ads *.ali api.dll apilib
32539 $ attrib +R apilib\*.ali
32544 At this point it is possible to use the DLL by directly linking
32545 against it. Note that you must use the GNAT shared runtime when using
32546 GNAT shared libraries. This is achieved by using @option{-shared} binder's
32550 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
32553 @node Building DLLs with GNAT Project files
32554 @section Building DLLs with GNAT Project files
32555 @cindex DLLs, building
32558 There is nothing specific to Windows in the build process.
32559 @pxref{Library Projects}.
32562 Due to a system limitation, it is not possible under Windows to create threads
32563 when inside the @code{DllMain} routine which is used for auto-initialization
32564 of shared libraries, so it is not possible to have library level tasks in SALs.
32566 @node Building DLLs with gnatdll
32567 @section Building DLLs with gnatdll
32568 @cindex DLLs, building
32571 * Limitations When Using Ada DLLs from Ada::
32572 * Exporting Ada Entities::
32573 * Ada DLLs and Elaboration::
32574 * Ada DLLs and Finalization::
32575 * Creating a Spec for Ada DLLs::
32576 * Creating the Definition File::
32581 Note that it is preferred to use the built-in GNAT DLL support
32582 (@pxref{Building DLLs with GNAT}) or GNAT Project files
32583 (@pxref{Building DLLs with GNAT Project files}) to build DLLs.
32585 This section explains how to build DLLs containing Ada code using
32586 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
32587 remainder of this section.
32589 The steps required to build an Ada DLL that is to be used by Ada as well as
32590 non-Ada applications are as follows:
32594 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
32595 @code{Stdcall} calling convention to avoid any Ada name mangling for the
32596 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
32597 skip this step if you plan to use the Ada DLL only from Ada applications.
32600 Your Ada code must export an initialization routine which calls the routine
32601 @code{adainit} generated by @command{gnatbind} to perform the elaboration of
32602 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
32603 routine exported by the Ada DLL must be invoked by the clients of the DLL
32604 to initialize the DLL.
32607 When useful, the DLL should also export a finalization routine which calls
32608 routine @code{adafinal} generated by @command{gnatbind} to perform the
32609 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
32610 The finalization routine exported by the Ada DLL must be invoked by the
32611 clients of the DLL when the DLL services are no further needed.
32614 You must provide a spec for the services exported by the Ada DLL in each
32615 of the programming languages to which you plan to make the DLL available.
32618 You must provide a definition file listing the exported entities
32619 (@pxref{The Definition File}).
32622 Finally you must use @code{gnatdll} to produce the DLL and the import
32623 library (@pxref{Using gnatdll}).
32627 Note that a relocatable DLL stripped using the @code{strip}
32628 binutils tool will not be relocatable anymore. To build a DLL without
32629 debug information pass @code{-largs -s} to @code{gnatdll}. This
32630 restriction does not apply to a DLL built using a Library Project.
32631 @pxref{Library Projects}.
32633 @node Limitations When Using Ada DLLs from Ada
32634 @subsection Limitations When Using Ada DLLs from Ada
32637 When using Ada DLLs from Ada applications there is a limitation users
32638 should be aware of. Because on Windows the GNAT run time is not in a DLL of
32639 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
32640 each Ada DLL includes the services of the GNAT run time that are necessary
32641 to the Ada code inside the DLL. As a result, when an Ada program uses an
32642 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
32643 one in the main program.
32645 It is therefore not possible to exchange GNAT run-time objects between the
32646 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
32647 handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects
32650 It is completely safe to exchange plain elementary, array or record types,
32651 Windows object handles, etc.
32653 @node Exporting Ada Entities
32654 @subsection Exporting Ada Entities
32655 @cindex Export table
32658 Building a DLL is a way to encapsulate a set of services usable from any
32659 application. As a result, the Ada entities exported by a DLL should be
32660 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
32661 any Ada name mangling. As an example here is an Ada package
32662 @code{API}, spec and body, exporting two procedures, a function, and a
32665 @smallexample @c ada
32668 with Interfaces.C; use Interfaces;
32670 Count : C.int := 0;
32671 function Factorial (Val : C.int) return C.int;
32673 procedure Initialize_API;
32674 procedure Finalize_API;
32675 -- Initialization & Finalization routines. More in the next section.
32677 pragma Export (C, Initialize_API);
32678 pragma Export (C, Finalize_API);
32679 pragma Export (C, Count);
32680 pragma Export (C, Factorial);
32686 @smallexample @c ada
32689 package body API is
32690 function Factorial (Val : C.int) return C.int is
32693 Count := Count + 1;
32694 for K in 1 .. Val loop
32700 procedure Initialize_API is
32702 pragma Import (C, Adainit);
32705 end Initialize_API;
32707 procedure Finalize_API is
32708 procedure Adafinal;
32709 pragma Import (C, Adafinal);
32719 If the Ada DLL you are building will only be used by Ada applications
32720 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
32721 convention. As an example, the previous package could be written as
32724 @smallexample @c ada
32728 Count : Integer := 0;
32729 function Factorial (Val : Integer) return Integer;
32731 procedure Initialize_API;
32732 procedure Finalize_API;
32733 -- Initialization and Finalization routines.
32739 @smallexample @c ada
32742 package body API is
32743 function Factorial (Val : Integer) return Integer is
32744 Fact : Integer := 1;
32746 Count := Count + 1;
32747 for K in 1 .. Val loop
32754 -- The remainder of this package body is unchanged.
32761 Note that if you do not export the Ada entities with a @code{C} or
32762 @code{Stdcall} convention you will have to provide the mangled Ada names
32763 in the definition file of the Ada DLL
32764 (@pxref{Creating the Definition File}).
32766 @node Ada DLLs and Elaboration
32767 @subsection Ada DLLs and Elaboration
32768 @cindex DLLs and elaboration
32771 The DLL that you are building contains your Ada code as well as all the
32772 routines in the Ada library that are needed by it. The first thing a
32773 user of your DLL must do is elaborate the Ada code
32774 (@pxref{Elaboration Order Handling in GNAT}).
32776 To achieve this you must export an initialization routine
32777 (@code{Initialize_API} in the previous example), which must be invoked
32778 before using any of the DLL services. This elaboration routine must call
32779 the Ada elaboration routine @code{adainit} generated by the GNAT binder
32780 (@pxref{Binding with Non-Ada Main Programs}). See the body of
32781 @code{Initialize_Api} for an example. Note that the GNAT binder is
32782 automatically invoked during the DLL build process by the @code{gnatdll}
32783 tool (@pxref{Using gnatdll}).
32785 When a DLL is loaded, Windows systematically invokes a routine called
32786 @code{DllMain}. It would therefore be possible to call @code{adainit}
32787 directly from @code{DllMain} without having to provide an explicit
32788 initialization routine. Unfortunately, it is not possible to call
32789 @code{adainit} from the @code{DllMain} if your program has library level
32790 tasks because access to the @code{DllMain} entry point is serialized by
32791 the system (that is, only a single thread can execute ``through'' it at a
32792 time), which means that the GNAT run time will deadlock waiting for the
32793 newly created task to complete its initialization.
32795 @node Ada DLLs and Finalization
32796 @subsection Ada DLLs and Finalization
32797 @cindex DLLs and finalization
32800 When the services of an Ada DLL are no longer needed, the client code should
32801 invoke the DLL finalization routine, if available. The DLL finalization
32802 routine is in charge of releasing all resources acquired by the DLL. In the
32803 case of the Ada code contained in the DLL, this is achieved by calling
32804 routine @code{adafinal} generated by the GNAT binder
32805 (@pxref{Binding with Non-Ada Main Programs}).
32806 See the body of @code{Finalize_Api} for an
32807 example. As already pointed out the GNAT binder is automatically invoked
32808 during the DLL build process by the @code{gnatdll} tool
32809 (@pxref{Using gnatdll}).
32811 @node Creating a Spec for Ada DLLs
32812 @subsection Creating a Spec for Ada DLLs
32815 To use the services exported by the Ada DLL from another programming
32816 language (e.g.@: C), you have to translate the specs of the exported Ada
32817 entities in that language. For instance in the case of @code{API.dll},
32818 the corresponding C header file could look like:
32823 extern int *_imp__count;
32824 #define count (*_imp__count)
32825 int factorial (int);
32831 It is important to understand that when building an Ada DLL to be used by
32832 other Ada applications, you need two different specs for the packages
32833 contained in the DLL: one for building the DLL and the other for using
32834 the DLL. This is because the @code{DLL} calling convention is needed to
32835 use a variable defined in a DLL, but when building the DLL, the variable
32836 must have either the @code{Ada} or @code{C} calling convention. As an
32837 example consider a DLL comprising the following package @code{API}:
32839 @smallexample @c ada
32843 Count : Integer := 0;
32845 -- Remainder of the package omitted.
32852 After producing a DLL containing package @code{API}, the spec that
32853 must be used to import @code{API.Count} from Ada code outside of the
32856 @smallexample @c ada
32861 pragma Import (DLL, Count);
32867 @node Creating the Definition File
32868 @subsection Creating the Definition File
32871 The definition file is the last file needed to build the DLL. It lists
32872 the exported symbols. As an example, the definition file for a DLL
32873 containing only package @code{API} (where all the entities are exported
32874 with a @code{C} calling convention) is:
32889 If the @code{C} calling convention is missing from package @code{API},
32890 then the definition file contains the mangled Ada names of the above
32891 entities, which in this case are:
32900 api__initialize_api
32905 @node Using gnatdll
32906 @subsection Using @code{gnatdll}
32910 * gnatdll Example::
32911 * gnatdll behind the Scenes::
32916 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
32917 and non-Ada sources that make up your DLL have been compiled.
32918 @code{gnatdll} is actually in charge of two distinct tasks: build the
32919 static import library for the DLL and the actual DLL. The form of the
32920 @code{gnatdll} command is
32924 $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]}
32929 where @var{list-of-files} is a list of ALI and object files. The object
32930 file list must be the exact list of objects corresponding to the non-Ada
32931 sources whose services are to be included in the DLL. The ALI file list
32932 must be the exact list of ALI files for the corresponding Ada sources
32933 whose services are to be included in the DLL. If @var{list-of-files} is
32934 missing, only the static import library is generated.
32937 You may specify any of the following switches to @code{gnatdll}:
32940 @item -a@ovar{address}
32941 @cindex @option{-a} (@code{gnatdll})
32942 Build a non-relocatable DLL at @var{address}. If @var{address} is not
32943 specified the default address @var{0x11000000} will be used. By default,
32944 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
32945 advise the reader to build relocatable DLL.
32947 @item -b @var{address}
32948 @cindex @option{-b} (@code{gnatdll})
32949 Set the relocatable DLL base address. By default the address is
32952 @item -bargs @var{opts}
32953 @cindex @option{-bargs} (@code{gnatdll})
32954 Binder options. Pass @var{opts} to the binder.
32956 @item -d @var{dllfile}
32957 @cindex @option{-d} (@code{gnatdll})
32958 @var{dllfile} is the name of the DLL. This switch must be present for
32959 @code{gnatdll} to do anything. The name of the generated import library is
32960 obtained algorithmically from @var{dllfile} as shown in the following
32961 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
32962 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
32963 by option @option{-e}) is obtained algorithmically from @var{dllfile}
32964 as shown in the following example:
32965 if @var{dllfile} is @code{xyz.dll}, the definition
32966 file used is @code{xyz.def}.
32968 @item -e @var{deffile}
32969 @cindex @option{-e} (@code{gnatdll})
32970 @var{deffile} is the name of the definition file.
32973 @cindex @option{-g} (@code{gnatdll})
32974 Generate debugging information. This information is stored in the object
32975 file and copied from there to the final DLL file by the linker,
32976 where it can be read by the debugger. You must use the
32977 @option{-g} switch if you plan on using the debugger or the symbolic
32981 @cindex @option{-h} (@code{gnatdll})
32982 Help mode. Displays @code{gnatdll} switch usage information.
32985 @cindex @option{-I} (@code{gnatdll})
32986 Direct @code{gnatdll} to search the @var{dir} directory for source and
32987 object files needed to build the DLL.
32988 (@pxref{Search Paths and the Run-Time Library (RTL)}).
32991 @cindex @option{-k} (@code{gnatdll})
32992 Removes the @code{@@}@var{nn} suffix from the import library's exported
32993 names, but keeps them for the link names. You must specify this
32994 option if you want to use a @code{Stdcall} function in a DLL for which
32995 the @code{@@}@var{nn} suffix has been removed. This is the case for most
32996 of the Windows NT DLL for example. This option has no effect when
32997 @option{-n} option is specified.
32999 @item -l @var{file}
33000 @cindex @option{-l} (@code{gnatdll})
33001 The list of ALI and object files used to build the DLL are listed in
33002 @var{file}, instead of being given in the command line. Each line in
33003 @var{file} contains the name of an ALI or object file.
33006 @cindex @option{-n} (@code{gnatdll})
33007 No Import. Do not create the import library.
33010 @cindex @option{-q} (@code{gnatdll})
33011 Quiet mode. Do not display unnecessary messages.
33014 @cindex @option{-v} (@code{gnatdll})
33015 Verbose mode. Display extra information.
33017 @item -largs @var{opts}
33018 @cindex @option{-largs} (@code{gnatdll})
33019 Linker options. Pass @var{opts} to the linker.
33022 @node gnatdll Example
33023 @subsubsection @code{gnatdll} Example
33026 As an example the command to build a relocatable DLL from @file{api.adb}
33027 once @file{api.adb} has been compiled and @file{api.def} created is
33030 $ gnatdll -d api.dll api.ali
33034 The above command creates two files: @file{libapi.dll.a} (the import
33035 library) and @file{api.dll} (the actual DLL). If you want to create
33036 only the DLL, just type:
33039 $ gnatdll -d api.dll -n api.ali
33043 Alternatively if you want to create just the import library, type:
33046 $ gnatdll -d api.dll
33049 @node gnatdll behind the Scenes
33050 @subsubsection @code{gnatdll} behind the Scenes
33053 This section details the steps involved in creating a DLL. @code{gnatdll}
33054 does these steps for you. Unless you are interested in understanding what
33055 goes on behind the scenes, you should skip this section.
33057 We use the previous example of a DLL containing the Ada package @code{API},
33058 to illustrate the steps necessary to build a DLL. The starting point is a
33059 set of objects that will make up the DLL and the corresponding ALI
33060 files. In the case of this example this means that @file{api.o} and
33061 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
33066 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
33067 the information necessary to generate relocation information for the
33073 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
33078 In addition to the base file, the @command{gnatlink} command generates an
33079 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
33080 asks @command{gnatlink} to generate the routines @code{DllMain} and
33081 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
33082 is loaded into memory.
33085 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
33086 export table (@file{api.exp}). The export table contains the relocation
33087 information in a form which can be used during the final link to ensure
33088 that the Windows loader is able to place the DLL anywhere in memory.
33092 $ dlltool --dllname api.dll --def api.def --base-file api.base \
33093 --output-exp api.exp
33098 @code{gnatdll} builds the base file using the new export table. Note that
33099 @command{gnatbind} must be called once again since the binder generated file
33100 has been deleted during the previous call to @command{gnatlink}.
33105 $ gnatlink api -o api.jnk api.exp -mdll
33106 -Wl,--base-file,api.base
33111 @code{gnatdll} builds the new export table using the new base file and
33112 generates the DLL import library @file{libAPI.dll.a}.
33116 $ dlltool --dllname api.dll --def api.def --base-file api.base \
33117 --output-exp api.exp --output-lib libAPI.a
33122 Finally @code{gnatdll} builds the relocatable DLL using the final export
33128 $ gnatlink api api.exp -o api.dll -mdll
33133 @node Using dlltool
33134 @subsubsection Using @code{dlltool}
33137 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
33138 DLLs and static import libraries. This section summarizes the most
33139 common @code{dlltool} switches. The form of the @code{dlltool} command
33143 $ dlltool @ovar{switches}
33147 @code{dlltool} switches include:
33150 @item --base-file @var{basefile}
33151 @cindex @option{--base-file} (@command{dlltool})
33152 Read the base file @var{basefile} generated by the linker. This switch
33153 is used to create a relocatable DLL.
33155 @item --def @var{deffile}
33156 @cindex @option{--def} (@command{dlltool})
33157 Read the definition file.
33159 @item --dllname @var{name}
33160 @cindex @option{--dllname} (@command{dlltool})
33161 Gives the name of the DLL. This switch is used to embed the name of the
33162 DLL in the static import library generated by @code{dlltool} with switch
33163 @option{--output-lib}.
33166 @cindex @option{-k} (@command{dlltool})
33167 Kill @code{@@}@var{nn} from exported names
33168 (@pxref{Windows Calling Conventions}
33169 for a discussion about @code{Stdcall}-style symbols.
33172 @cindex @option{--help} (@command{dlltool})
33173 Prints the @code{dlltool} switches with a concise description.
33175 @item --output-exp @var{exportfile}
33176 @cindex @option{--output-exp} (@command{dlltool})
33177 Generate an export file @var{exportfile}. The export file contains the
33178 export table (list of symbols in the DLL) and is used to create the DLL.
33180 @item --output-lib @var{libfile}
33181 @cindex @option{--output-lib} (@command{dlltool})
33182 Generate a static import library @var{libfile}.
33185 @cindex @option{-v} (@command{dlltool})
33188 @item --as @var{assembler-name}
33189 @cindex @option{--as} (@command{dlltool})
33190 Use @var{assembler-name} as the assembler. The default is @code{as}.
33193 @node GNAT and Windows Resources
33194 @section GNAT and Windows Resources
33195 @cindex Resources, windows
33198 * Building Resources::
33199 * Compiling Resources::
33200 * Using Resources::
33204 Resources are an easy way to add Windows specific objects to your
33205 application. The objects that can be added as resources include:
33234 This section explains how to build, compile and use resources.
33236 @node Building Resources
33237 @subsection Building Resources
33238 @cindex Resources, building
33241 A resource file is an ASCII file. By convention resource files have an
33242 @file{.rc} extension.
33243 The easiest way to build a resource file is to use Microsoft tools
33244 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
33245 @code{dlgedit.exe} to build dialogs.
33246 It is always possible to build an @file{.rc} file yourself by writing a
33249 It is not our objective to explain how to write a resource file. A
33250 complete description of the resource script language can be found in the
33251 Microsoft documentation.
33253 @node Compiling Resources
33254 @subsection Compiling Resources
33257 @cindex Resources, compiling
33260 This section describes how to build a GNAT-compatible (COFF) object file
33261 containing the resources. This is done using the Resource Compiler
33262 @code{windres} as follows:
33265 $ windres -i myres.rc -o myres.o
33269 By default @code{windres} will run @command{gcc} to preprocess the @file{.rc}
33270 file. You can specify an alternate preprocessor (usually named
33271 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
33272 parameter. A list of all possible options may be obtained by entering
33273 the command @code{windres} @option{--help}.
33275 It is also possible to use the Microsoft resource compiler @code{rc.exe}
33276 to produce a @file{.res} file (binary resource file). See the
33277 corresponding Microsoft documentation for further details. In this case
33278 you need to use @code{windres} to translate the @file{.res} file to a
33279 GNAT-compatible object file as follows:
33282 $ windres -i myres.res -o myres.o
33285 @node Using Resources
33286 @subsection Using Resources
33287 @cindex Resources, using
33290 To include the resource file in your program just add the
33291 GNAT-compatible object file for the resource(s) to the linker
33292 arguments. With @command{gnatmake} this is done by using the @option{-largs}
33296 $ gnatmake myprog -largs myres.o
33299 @node Debugging a DLL
33300 @section Debugging a DLL
33301 @cindex DLL debugging
33304 * Program and DLL Both Built with GCC/GNAT::
33305 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
33309 Debugging a DLL is similar to debugging a standard program. But
33310 we have to deal with two different executable parts: the DLL and the
33311 program that uses it. We have the following four possibilities:
33315 The program and the DLL are built with @code{GCC/GNAT}.
33317 The program is built with foreign tools and the DLL is built with
33320 The program is built with @code{GCC/GNAT} and the DLL is built with
33326 In this section we address only cases one and two above.
33327 There is no point in trying to debug
33328 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
33329 information in it. To do so you must use a debugger compatible with the
33330 tools suite used to build the DLL.
33332 @node Program and DLL Both Built with GCC/GNAT
33333 @subsection Program and DLL Both Built with GCC/GNAT
33336 This is the simplest case. Both the DLL and the program have @code{GDB}
33337 compatible debugging information. It is then possible to break anywhere in
33338 the process. Let's suppose here that the main procedure is named
33339 @code{ada_main} and that in the DLL there is an entry point named
33343 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
33344 program must have been built with the debugging information (see GNAT -g
33345 switch). Here are the step-by-step instructions for debugging it:
33348 @item Launch @code{GDB} on the main program.
33354 @item Start the program and stop at the beginning of the main procedure
33361 This step is required to be able to set a breakpoint inside the DLL. As long
33362 as the program is not run, the DLL is not loaded. This has the
33363 consequence that the DLL debugging information is also not loaded, so it is not
33364 possible to set a breakpoint in the DLL.
33366 @item Set a breakpoint inside the DLL
33369 (gdb) break ada_dll
33376 At this stage a breakpoint is set inside the DLL. From there on
33377 you can use the standard approach to debug the whole program
33378 (@pxref{Running and Debugging Ada Programs}).
33381 @c This used to work, probably because the DLLs were non-relocatable
33382 @c keep this section around until the problem is sorted out.
33384 To break on the @code{DllMain} routine it is not possible to follow
33385 the procedure above. At the time the program stop on @code{ada_main}
33386 the @code{DllMain} routine as already been called. Either you can use
33387 the procedure below @pxref{Debugging the DLL Directly} or this procedure:
33390 @item Launch @code{GDB} on the main program.
33396 @item Load DLL symbols
33399 (gdb) add-sym api.dll
33402 @item Set a breakpoint inside the DLL
33405 (gdb) break ada_dll.adb:45
33408 Note that at this point it is not possible to break using the routine symbol
33409 directly as the program is not yet running. The solution is to break
33410 on the proper line (break in @file{ada_dll.adb} line 45).
33412 @item Start the program
33421 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
33422 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
33425 * Debugging the DLL Directly::
33426 * Attaching to a Running Process::
33430 In this case things are slightly more complex because it is not possible to
33431 start the main program and then break at the beginning to load the DLL and the
33432 associated DLL debugging information. It is not possible to break at the
33433 beginning of the program because there is no @code{GDB} debugging information,
33434 and therefore there is no direct way of getting initial control. This
33435 section addresses this issue by describing some methods that can be used
33436 to break somewhere in the DLL to debug it.
33439 First suppose that the main procedure is named @code{main} (this is for
33440 example some C code built with Microsoft Visual C) and that there is a
33441 DLL named @code{test.dll} containing an Ada entry point named
33445 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
33446 been built with debugging information (see GNAT -g option).
33448 @node Debugging the DLL Directly
33449 @subsubsection Debugging the DLL Directly
33453 Find out the executable starting address
33456 $ objdump --file-header main.exe
33459 The starting address is reported on the last line. For example:
33462 main.exe: file format pei-i386
33463 architecture: i386, flags 0x0000010a:
33464 EXEC_P, HAS_DEBUG, D_PAGED
33465 start address 0x00401010
33469 Launch the debugger on the executable.
33476 Set a breakpoint at the starting address, and launch the program.
33479 $ (gdb) break *0x00401010
33483 The program will stop at the given address.
33486 Set a breakpoint on a DLL subroutine.
33489 (gdb) break ada_dll.adb:45
33492 Or if you want to break using a symbol on the DLL, you need first to
33493 select the Ada language (language used by the DLL).
33496 (gdb) set language ada
33497 (gdb) break ada_dll
33501 Continue the program.
33508 This will run the program until it reaches the breakpoint that has been
33509 set. From that point you can use the standard way to debug a program
33510 as described in (@pxref{Running and Debugging Ada Programs}).
33515 It is also possible to debug the DLL by attaching to a running process.
33517 @node Attaching to a Running Process
33518 @subsubsection Attaching to a Running Process
33519 @cindex DLL debugging, attach to process
33522 With @code{GDB} it is always possible to debug a running process by
33523 attaching to it. It is possible to debug a DLL this way. The limitation
33524 of this approach is that the DLL must run long enough to perform the
33525 attach operation. It may be useful for instance to insert a time wasting
33526 loop in the code of the DLL to meet this criterion.
33530 @item Launch the main program @file{main.exe}.
33536 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
33537 that the process PID for @file{main.exe} is 208.
33545 @item Attach to the running process to be debugged.
33551 @item Load the process debugging information.
33554 (gdb) symbol-file main.exe
33557 @item Break somewhere in the DLL.
33560 (gdb) break ada_dll
33563 @item Continue process execution.
33572 This last step will resume the process execution, and stop at
33573 the breakpoint we have set. From there you can use the standard
33574 approach to debug a program as described in
33575 (@pxref{Running and Debugging Ada Programs}).
33577 @node Setting Stack Size from gnatlink
33578 @section Setting Stack Size from @command{gnatlink}
33581 It is possible to specify the program stack size at link time. On modern
33582 versions of Windows, starting with XP, this is mostly useful to set the size of
33583 the main stack (environment task). The other task stacks are set with pragma
33584 Storage_Size or with the @command{gnatbind -d} command.
33586 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
33587 reserve size of individual tasks, the link-time stack size applies to all
33588 tasks, and pragma Storage_Size has no effect.
33589 In particular, Stack Overflow checks are made against this
33590 link-time specified size.
33592 This setting can be done with
33593 @command{gnatlink} using either:
33597 @item using @option{-Xlinker} linker option
33600 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
33603 This sets the stack reserve size to 0x10000 bytes and the stack commit
33604 size to 0x1000 bytes.
33606 @item using @option{-Wl} linker option
33609 $ gnatlink hello -Wl,--stack=0x1000000
33612 This sets the stack reserve size to 0x1000000 bytes. Note that with
33613 @option{-Wl} option it is not possible to set the stack commit size
33614 because the coma is a separator for this option.
33618 @node Setting Heap Size from gnatlink
33619 @section Setting Heap Size from @command{gnatlink}
33622 Under Windows systems, it is possible to specify the program heap size from
33623 @command{gnatlink} using either:
33627 @item using @option{-Xlinker} linker option
33630 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
33633 This sets the heap reserve size to 0x10000 bytes and the heap commit
33634 size to 0x1000 bytes.
33636 @item using @option{-Wl} linker option
33639 $ gnatlink hello -Wl,--heap=0x1000000
33642 This sets the heap reserve size to 0x1000000 bytes. Note that with
33643 @option{-Wl} option it is not possible to set the heap commit size
33644 because the coma is a separator for this option.
33650 @c **********************************
33651 @c * GNU Free Documentation License *
33652 @c **********************************
33654 @c GNU Free Documentation License
33656 @node Index,,GNU Free Documentation License, Top
33662 @c Put table of contents at end, otherwise it precedes the "title page" in
33663 @c the .txt version
33664 @c Edit the pdf file to move the contents to the beginning, after the title