1 \input texinfo @c -*-texinfo-*-
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6 @c GNAT DOCUMENTATION o
10 @c Copyright (C) 1992-2004 Ada Core Technologies, Inc. o
12 @c GNAT is free software; you can redistribute it and/or modify it under o
13 @c terms of the GNU General Public License as published by the Free Soft- o
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15 @c sion. GNAT is distributed in the hope that it will be useful, but WITH- o
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17 @c or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License o
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21 @c MA 02111-1307, USA. o
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27 @c GNAT_UGN Style Guide
29 @c 1. Always put a @noindent on the line before the first paragraph
30 @c after any of these commands:
42 @c 2. DO NOT use @example. Use @smallexample instead.
43 @c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample
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45 @c source file. Instead, use one of the following annotated
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50 @c @smallexample @c projectfile
51 @c b) The "@c ada" markup will result in boldface for reserved words
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55 @c d) The "@c projectfile" markup is like "@c ada" except that the set
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58 @c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
59 @c command must be preceded by two empty lines
61 @c 4. The @item command should be on a line of its own if it is in an
62 @c @itemize or @enumerate command.
64 @c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
67 @c 6. DO NOT put trailing spaces at the end of a line. Such spaces will
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70 @c 7. DO NOT use @cartouche for examples that are longer than around 10 lines.
71 @c This command inhibits page breaks, so long examples in a @cartouche can
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74 @c NOTE: This file should be submitted to xgnatugn with either the vms flag
75 @c or the unw flag set. The unw flag covers topics for both Unix and
78 @c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
81 @setfilename gnat_ugn_vms.info
85 @setfilename gnat_ugn_unw.info
89 @settitle GNAT User's Guide for Native Platforms / OpenVMS Alpha
90 @dircategory GNU Ada tools
92 * GNAT User's Guide (gnat_ugn_vms) for Native Platforms / OpenVMS Alpha
97 @settitle GNAT User's Guide for Native Platforms / Unix and Windows
99 * GNAT User's Guide (gnat_ugn_unw) for Native Platforms / Unix and Windows
103 @include gcc-common.texi
105 @setchapternewpage odd
110 Copyright @copyright{} 1995-2004, Free Software Foundation
112 Permission is granted to copy, distribute and/or modify this document
113 under the terms of the GNU Free Documentation License, Version 1.2
114 or any later version published by the Free Software Foundation;
115 with the Invariant Sections being ``GNU Free Documentation License'', with the
116 Front-Cover Texts being
118 ``GNAT User's Guide for Native Platforms / OpenVMS Alpha'',
121 ``GNAT User's Guide for Native Platforms / Unix and Windows'',
123 and with no Back-Cover Texts.
124 A copy of the license is included in the section entitled
125 ``GNU Free Documentation License''.
130 @title GNAT User's Guide
131 @center @titlefont{for Native Platforms}
136 @titlefont{@i{Unix and Windows}}
139 @titlefont{@i{OpenVMS Alpha}}
144 @subtitle GNAT, The GNU Ada 95 Compiler
145 @subtitle GCC version @value{version-GCC}
147 @author Ada Core Technologies, Inc.
150 @vskip 0pt plus 1filll
158 @node Top, About This Guide, (dir), (dir)
159 @top GNAT User's Guide
163 GNAT User's Guide for Native Platforms / OpenVMS Alpha
168 GNAT User's Guide for Native Platforms / Unix and Windows
172 GNAT, The GNU Ada 95 Compiler@*
173 GCC version @value{version-GCC}@*
176 Ada Core Technologies, Inc.@*
180 * Getting Started with GNAT::
181 * The GNAT Compilation Model::
182 * Compiling Using gcc::
183 * Binding Using gnatbind::
184 * Linking Using gnatlink::
185 * The GNAT Make Program gnatmake::
186 * Improving Performance::
187 * Renaming Files Using gnatchop::
188 * Configuration Pragmas::
189 * Handling Arbitrary File Naming Conventions Using gnatname::
190 * GNAT Project Manager::
191 * The Cross-Referencing Tools gnatxref and gnatfind::
192 * The GNAT Pretty-Printer gnatpp::
193 * File Name Krunching Using gnatkr::
194 * Preprocessing Using gnatprep::
196 * The GNAT Run-Time Library Builder gnatlbr::
198 * The GNAT Library Browser gnatls::
199 * Cleaning Up Using gnatclean::
201 * GNAT and Libraries::
202 * Using the GNU make Utility::
204 * Finding Memory Problems::
205 * Creating Sample Bodies Using gnatstub::
206 * Other Utility Programs::
207 * Running and Debugging Ada Programs::
209 * Compatibility with DEC Ada::
211 * Platform-Specific Information for the Run-Time Libraries::
212 * Example of Binder Output File::
213 * Elaboration Order Handling in GNAT::
215 * Compatibility and Porting Guide::
217 * Microsoft Windows Topics::
219 * GNU Free Documentation License::
222 --- The Detailed Node Listing ---
226 * What This Guide Contains::
227 * What You Should Know before Reading This Guide::
228 * Related Information::
231 Getting Started with GNAT
234 * Running a Simple Ada Program::
235 * Running a Program with Multiple Units::
236 * Using the gnatmake Utility::
238 * Editing with Emacs::
241 * Introduction to GPS::
242 * Introduction to Glide and GVD::
245 The GNAT Compilation Model
247 * Source Representation::
248 * Foreign Language Representation::
249 * File Naming Rules::
250 * Using Other File Names::
251 * Alternative File Naming Schemes::
252 * Generating Object Files::
253 * Source Dependencies::
254 * The Ada Library Information Files::
255 * Binding an Ada Program::
256 * Mixed Language Programming::
257 * Building Mixed Ada & C++ Programs::
258 * Comparison between GNAT and C/C++ Compilation Models::
259 * Comparison between GNAT and Conventional Ada Library Models::
261 * Placement of temporary files::
264 Foreign Language Representation
267 * Other 8-Bit Codes::
268 * Wide Character Encodings::
270 Compiling Ada Programs With gcc
272 * Compiling Programs::
274 * Search Paths and the Run-Time Library (RTL)::
275 * Order of Compilation Issues::
280 * Output and Error Message Control::
281 * Warning Message Control::
282 * Debugging and Assertion Control::
283 * Validity Checking::
286 * Stack Overflow Checking::
287 * Using gcc for Syntax Checking::
288 * Using gcc for Semantic Checking::
289 * Compiling Ada 83 Programs::
290 * Character Set Control::
291 * File Naming Control::
292 * Subprogram Inlining Control::
293 * Auxiliary Output Control::
294 * Debugging Control::
295 * Exception Handling Control::
296 * Units to Sources Mapping Files::
297 * Integrated Preprocessing::
302 Binding Ada Programs With gnatbind
305 * Switches for gnatbind::
306 * Command-Line Access::
307 * Search Paths for gnatbind::
308 * Examples of gnatbind Usage::
310 Switches for gnatbind
312 * Consistency-Checking Modes::
313 * Binder Error Message Control::
314 * Elaboration Control::
316 * Binding with Non-Ada Main Programs::
317 * Binding Programs with No Main Subprogram::
319 Linking Using gnatlink
322 * Switches for gnatlink::
323 * Setting Stack Size from gnatlink::
324 * Setting Heap Size from gnatlink::
326 The GNAT Make Program gnatmake
329 * Switches for gnatmake::
330 * Mode Switches for gnatmake::
331 * Notes on the Command Line::
332 * How gnatmake Works::
333 * Examples of gnatmake Usage::
336 Improving Performance
337 * Performance Considerations::
338 * Reducing the Size of Ada Executables with gnatelim::
340 Performance Considerations
341 * Controlling Run-Time Checks::
342 * Use of Restrictions::
343 * Optimization Levels::
344 * Debugging Optimized Code::
345 * Inlining of Subprograms::
346 * Optimization and Strict Aliasing::
348 * Coverage Analysis::
351 Reducing the Size of Ada Executables with gnatelim
354 * Correcting the List of Eliminate Pragmas::
355 * Making Your Executables Smaller::
356 * Summary of the gnatelim Usage Cycle::
358 Renaming Files Using gnatchop
360 * Handling Files with Multiple Units::
361 * Operating gnatchop in Compilation Mode::
362 * Command Line for gnatchop::
363 * Switches for gnatchop::
364 * Examples of gnatchop Usage::
366 Configuration Pragmas
368 * Handling of Configuration Pragmas::
369 * The Configuration Pragmas Files::
371 Handling Arbitrary File Naming Conventions Using gnatname
373 * Arbitrary File Naming Conventions::
375 * Switches for gnatname::
376 * Examples of gnatname Usage::
381 * Examples of Project Files::
382 * Project File Syntax::
383 * Objects and Sources in Project Files::
384 * Importing Projects::
385 * Project Extension::
386 * External References in Project Files::
387 * Packages in Project Files::
388 * Variables from Imported Projects::
391 * Using Third-Party Libraries through Projects::
392 * Stand-alone Library Projects::
393 * Switches Related to Project Files::
394 * Tools Supporting Project Files::
395 * An Extended Example::
396 * Project File Complete Syntax::
399 The Cross-Referencing Tools gnatxref and gnatfind
401 * gnatxref Switches::
402 * gnatfind Switches::
403 * Project Files for gnatxref and gnatfind::
404 * Regular Expressions in gnatfind and gnatxref::
405 * Examples of gnatxref Usage::
406 * Examples of gnatfind Usage::
409 The GNAT Pretty-Printer gnatpp
411 * Switches for gnatpp::
415 File Name Krunching Using gnatkr
420 * Examples of gnatkr Usage::
422 Preprocessing Using gnatprep
425 * Switches for gnatprep::
426 * Form of Definitions File::
427 * Form of Input Text for gnatprep::
430 The GNAT Run-Time Library Builder gnatlbr
433 * Switches for gnatlbr::
434 * Examples of gnatlbr Usage::
437 The GNAT Library Browser gnatls
440 * Switches for gnatls::
441 * Examples of gnatls Usage::
443 Cleaning Up Using gnatclean
445 * Running gnatclean::
446 * Switches for gnatclean::
447 * Examples of gnatclean Usage::
453 * Introduction to Libraries in GNAT::
454 * General Ada Libraries::
455 * Stand-alone Ada Libraries::
456 * Rebuilding the GNAT Run-Time Library::
458 Using the GNU make Utility
460 * Using gnatmake in a Makefile::
461 * Automatically Creating a List of Directories::
462 * Generating the Command Line Switches::
463 * Overcoming Command Line Length Limits::
466 Finding Memory Problems
471 * The GNAT Debug Pool Facility::
477 * Switches for gnatmem::
478 * Example of gnatmem Usage::
481 The GNAT Debug Pool Facility
483 Creating Sample Bodies Using gnatstub
486 * Switches for gnatstub::
488 Other Utility Programs
490 * Using Other Utility Programs with GNAT::
491 * The External Symbol Naming Scheme of GNAT::
493 * Ada Mode for Glide::
495 * Converting Ada Files to html with gnathtml::
497 Running and Debugging Ada Programs
499 * The GNAT Debugger GDB::
501 * Introduction to GDB Commands::
502 * Using Ada Expressions::
503 * Calling User-Defined Subprograms::
504 * Using the Next Command in a Function::
507 * Debugging Generic Units::
508 * GNAT Abnormal Termination or Failure to Terminate::
509 * Naming Conventions for GNAT Source Files::
510 * Getting Internal Debugging Information::
518 Compatibility with DEC Ada
520 * Ada 95 Compatibility::
521 * Differences in the Definition of Package System::
522 * Language-Related Features::
523 * The Package STANDARD::
524 * The Package SYSTEM::
525 * Tasking and Task-Related Features::
526 * Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems::
527 * Pragmas and Pragma-Related Features::
528 * Library of Predefined Units::
530 * Main Program Definition::
531 * Implementation-Defined Attributes::
532 * Compiler and Run-Time Interfacing::
533 * Program Compilation and Library Management::
535 * Implementation Limits::
538 Language-Related Features
540 * Integer Types and Representations::
541 * Floating-Point Types and Representations::
542 * Pragmas Float_Representation and Long_Float::
543 * Fixed-Point Types and Representations::
544 * Record and Array Component Alignment::
546 * Other Representation Clauses::
548 Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
550 * Assigning Task IDs::
551 * Task IDs and Delays::
552 * Task-Related Pragmas::
553 * Scheduling and Task Priority::
555 * External Interrupts::
557 Pragmas and Pragma-Related Features
559 * Restrictions on the Pragma INLINE::
560 * Restrictions on the Pragma INTERFACE::
561 * Restrictions on the Pragma SYSTEM_NAME::
563 Library of Predefined Units
565 * Changes to DECLIB::
569 * Shared Libraries and Options Files::
573 Platform-Specific Information for the Run-Time Libraries
575 * Summary of Run-Time Configurations::
576 * Specifying a Run-Time Library::
577 * Choosing between Native and FSU Threads Libraries::
578 * Choosing the Scheduling Policy::
579 * Solaris-Specific Considerations::
580 * IRIX-Specific Considerations::
581 * Linux-Specific Considerations::
582 * AIX-Specific Considerations::
584 Example of Binder Output File
586 Elaboration Order Handling in GNAT
588 * Elaboration Code in Ada 95::
589 * Checking the Elaboration Order in Ada 95::
590 * Controlling the Elaboration Order in Ada 95::
591 * Controlling Elaboration in GNAT - Internal Calls::
592 * Controlling Elaboration in GNAT - External Calls::
593 * Default Behavior in GNAT - Ensuring Safety::
594 * Treatment of Pragma Elaborate::
595 * Elaboration Issues for Library Tasks::
596 * Mixing Elaboration Models::
597 * What to Do If the Default Elaboration Behavior Fails::
598 * Elaboration for Access-to-Subprogram Values::
599 * Summary of Procedures for Elaboration Control::
600 * Other Elaboration Order Considerations::
604 * Basic Assembler Syntax::
605 * A Simple Example of Inline Assembler::
606 * Output Variables in Inline Assembler::
607 * Input Variables in Inline Assembler::
608 * Inlining Inline Assembler Code::
609 * Other Asm Functionality::
610 * A Complete Example::
612 Compatibility and Porting Guide
614 * Compatibility with Ada 83::
615 * Implementation-dependent characteristics::
616 * Compatibility with DEC Ada 83::
617 * Compatibility with Other Ada 95 Systems::
618 * Representation Clauses::
621 Microsoft Windows Topics
623 * Using GNAT on Windows::
624 * CONSOLE and WINDOWS subsystems::
626 * Mixed-Language Programming on Windows::
627 * Windows Calling Conventions::
628 * Introduction to Dynamic Link Libraries (DLLs)::
629 * Using DLLs with GNAT::
630 * Building DLLs with GNAT::
631 * GNAT and Windows Resources::
633 * GNAT and COM/DCOM Objects::
641 @node About This Guide
642 @unnumbered About This Guide
646 This guide describes the use of of GNAT, a full language compiler for the Ada
647 95 programming language, implemented on HP OpenVMS Alpha platforms.
650 This guide describes the use of GNAT, a compiler and software development
651 toolset for the full Ada 95 programming language.
653 It describes the features of the compiler and tools, and details
654 how to use them to build Ada 95 applications.
657 * What This Guide Contains::
658 * What You Should Know before Reading This Guide::
659 * Related Information::
663 @node What This Guide Contains
664 @unnumberedsec What This Guide Contains
667 This guide contains the following chapters:
671 @ref{Getting Started with GNAT}, describes how to get started compiling
672 and running Ada programs with the GNAT Ada programming environment.
674 @ref{The GNAT Compilation Model}, describes the compilation model used
678 @ref{Compiling Using gcc}, describes how to compile
679 Ada programs with @code{gcc}, the Ada compiler.
682 @ref{Binding Using gnatbind}, describes how to
683 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
687 @ref{Linking Using gnatlink},
688 describes @code{gnatlink}, a
689 program that provides for linking using the GNAT run-time library to
690 construct a program. @code{gnatlink} can also incorporate foreign language
691 object units into the executable.
694 @ref{The GNAT Make Program gnatmake}, describes @code{gnatmake}, a
695 utility that automatically determines the set of sources
696 needed by an Ada compilation unit, and executes the necessary compilations
700 @ref{Improving Performance}, shows various techniques for making your
701 Ada program run faster or take less space.
702 It discusses the effect of the compiler's optimization switch and
703 also describes the @command{gnatelim} tool.
706 @ref{Renaming Files Using gnatchop}, describes
707 @code{gnatchop}, a utility that allows you to preprocess a file that
708 contains Ada source code, and split it into one or more new files, one
709 for each compilation unit.
712 @ref{Configuration Pragmas}, describes the configuration pragmas
716 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
717 shows how to override the default GNAT file naming conventions,
718 either for an individual unit or globally.
721 @ref{GNAT Project Manager}, describes how to use project files
722 to organize large projects.
725 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
726 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
727 way to navigate through sources.
730 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
731 version of an Ada source file with control over casing, indentation,
732 comment placement, and other elements of program presentation style.
736 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
737 file name krunching utility, used to handle shortened
738 file names on operating systems with a limit on the length of names.
741 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
742 preprocessor utility that allows a single source file to be used to
743 generate multiple or parameterized source files, by means of macro
748 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
749 a tool for rebuilding the GNAT run time with user-supplied
750 configuration pragmas.
754 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
755 utility that displays information about compiled units, including dependences
756 on the corresponding sources files, and consistency of compilations.
759 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
760 to delete files that are produced by the compiler, binder and linker.
764 @ref{GNAT and Libraries}, describes the process of creating and using
765 Libraries with GNAT. It also describes how to recompile the GNAT run-time
769 @ref{Using the GNU make Utility}, describes some techniques for using
770 the GNAT toolset in Makefiles.
774 @ref{Finding Memory Problems}, describes
776 @command{gnatmem}, a utility that monitors dynamic allocation and deallocation
777 and helps detect ``memory leaks'', and
779 the GNAT Debug Pool facility, which helps detect incorrect memory references.
782 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
783 a utility that generates empty but compilable bodies for library units.
786 @ref{Other Utility Programs}, discusses several other GNAT utilities,
787 including @code{gnathtml}.
790 @ref{Running and Debugging Ada Programs}, describes how to run and debug
795 @ref{Compatibility with DEC Ada}, details the compatibility of GNAT with
796 DEC Ada 83 @footnote{``DEC Ada'' refers to the legacy product originally
797 developed by Digital Equipment Corporation and currently supported by HP.}
802 @ref{Platform-Specific Information for the Run-Time Libraries},
803 describes the various run-time
804 libraries supported by GNAT on various platforms and explains how to
805 choose a particular library.
808 @ref{Example of Binder Output File}, shows the source code for the binder
809 output file for a sample program.
812 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
813 you deal with elaboration order issues.
816 @ref{Inline Assembler}, shows how to use the inline assembly facility
820 @ref{Compatibility and Porting Guide}, includes sections on compatibility
821 of GNAT with other Ada 83 and Ada 95 compilation systems, to assist
822 in porting code from other environments.
826 @ref{Microsoft Windows Topics}, presents information relevant to the
827 Microsoft Windows platform.
832 @c *************************************************
833 @node What You Should Know before Reading This Guide
834 @c *************************************************
835 @unnumberedsec What You Should Know before Reading This Guide
837 @cindex Ada 95 Language Reference Manual
839 This user's guide assumes that you are familiar with Ada 95 language, as
840 described in the International Standard ANSI/ISO/IEC-8652:1995, January
843 @node Related Information
844 @unnumberedsec Related Information
847 For further information about related tools, refer to the following
852 @cite{GNAT Reference Manual}, which contains all reference
853 material for the GNAT implementation of Ada 95.
857 @cite{Using the GNAT Programming System}, which describes the GPS
858 integrated development environment.
861 @cite{GNAT Programming System Tutorial}, which introduces the
862 main GPS features through examples.
866 @cite{Ada 95 Language Reference Manual}, which contains all reference
867 material for the Ada 95 programming language.
870 @cite{Debugging with GDB}
872 , located in the GNU:[DOCS] directory,
874 contains all details on the use of the GNU source-level debugger.
877 @cite{GNU Emacs Manual}
879 , located in the GNU:[DOCS] directory if the EMACS kit is installed,
881 contains full information on the extensible editor and programming
888 @unnumberedsec Conventions
890 @cindex Typographical conventions
893 Following are examples of the typographical and graphic conventions used
898 @code{Functions}, @code{utility program names}, @code{standard names},
905 @file{File Names}, @file{button names}, and @file{field names}.
914 [optional information or parameters]
917 Examples are described by text
919 and then shown this way.
924 Commands that are entered by the user are preceded in this manual by the
925 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
926 uses this sequence as a prompt, then the commands will appear exactly as
927 you see them in the manual. If your system uses some other prompt, then
928 the command will appear with the @code{$} replaced by whatever prompt
929 character you are using.
932 Full file names are shown with the ``@code{/}'' character
933 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
934 If you are using GNAT on a Windows platform, please note that
935 the ``@code{\}'' character should be used instead.
940 @c ****************************
941 @node Getting Started with GNAT
942 @chapter Getting Started with GNAT
945 This chapter describes some simple ways of using GNAT to build
946 executable Ada programs.
948 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
949 show how to use the command line environment.
950 @ref{Introduction to Glide and GVD}, provides a brief
951 introduction to the visually-oriented IDE for GNAT.
952 Supplementing Glide on some platforms is GPS, the
953 GNAT Programming System, which offers a richer graphical
954 ``look and feel'', enhanced configurability, support for
955 development in other programming language, comprehensive
956 browsing features, and many other capabilities.
957 For information on GPS please refer to
958 @cite{Using the GNAT Programming System}.
963 * Running a Simple Ada Program::
964 * Running a Program with Multiple Units::
965 * Using the gnatmake Utility::
967 * Editing with Emacs::
970 * Introduction to GPS::
971 * Introduction to Glide and GVD::
976 @section Running GNAT
979 Three steps are needed to create an executable file from an Ada source
984 The source file(s) must be compiled.
986 The file(s) must be bound using the GNAT binder.
988 All appropriate object files must be linked to produce an executable.
992 All three steps are most commonly handled by using the @code{gnatmake}
993 utility program that, given the name of the main program, automatically
994 performs the necessary compilation, binding and linking steps.
997 @node Running a Simple Ada Program
998 @section Running a Simple Ada Program
1001 Any text editor may be used to prepare an Ada program.
1004 used, the optional Ada mode may be helpful in laying out the program.
1007 program text is a normal text file. We will suppose in our initial
1008 example that you have used your editor to prepare the following
1009 standard format text file:
1011 @smallexample @c ada
1013 with Ada.Text_IO; use Ada.Text_IO;
1016 Put_Line ("Hello WORLD!");
1022 This file should be named @file{hello.adb}.
1023 With the normal default file naming conventions, GNAT requires
1025 contain a single compilation unit whose file name is the
1027 with periods replaced by hyphens; the
1028 extension is @file{ads} for a
1029 spec and @file{adb} for a body.
1030 You can override this default file naming convention by use of the
1031 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1032 Alternatively, if you want to rename your files according to this default
1033 convention, which is probably more convenient if you will be using GNAT
1034 for all your compilations, then the @code{gnatchop} utility
1035 can be used to generate correctly-named source files
1036 (@pxref{Renaming Files Using gnatchop}).
1038 You can compile the program using the following command (@code{$} is used
1039 as the command prompt in the examples in this document):
1046 @code{gcc} is the command used to run the compiler. This compiler is
1047 capable of compiling programs in several languages, including Ada 95 and
1048 C. It assumes that you have given it an Ada program if the file extension is
1049 either @file{.ads} or @file{.adb}, and it will then call
1050 the GNAT compiler to compile the specified file.
1053 The @option{-c} switch is required. It tells @command{gcc} to only do a
1054 compilation. (For C programs, @command{gcc} can also do linking, but this
1055 capability is not used directly for Ada programs, so the @option{-c}
1056 switch must always be present.)
1059 This compile command generates a file
1060 @file{hello.o}, which is the object
1061 file corresponding to your Ada program. It also generates
1062 an ``Ada Library Information'' file @file{hello.ali},
1063 which contains additional information used to check
1064 that an Ada program is consistent.
1065 To build an executable file,
1066 use @code{gnatbind} to bind the program
1067 and @code{gnatlink} to link it. The
1068 argument to both @code{gnatbind} and @code{gnatlink} is the name of the
1069 @file{ALI} file, but the default extension of @file{.ali} can
1070 be omitted. This means that in the most common case, the argument
1071 is simply the name of the main program:
1079 A simpler method of carrying out these steps is to use
1081 a master program that invokes all the required
1082 compilation, binding and linking tools in the correct order. In particular,
1083 @command{gnatmake} automatically recompiles any sources that have been
1084 modified since they were last compiled, or sources that depend
1085 on such modified sources, so that ``version skew'' is avoided.
1086 @cindex Version skew (avoided by @command{gnatmake})
1089 $ gnatmake hello.adb
1093 The result is an executable program called @file{hello}, which can be
1096 @c The following should be removed (BMB 2001-01-23)
1098 @c $ ^./hello^$ RUN HELLO^
1099 @c @end smallexample
1106 assuming that the current directory is on the search path
1107 for executable programs.
1110 and, if all has gone well, you will see
1117 appear in response to this command.
1120 @c ****************************************
1121 @node Running a Program with Multiple Units
1122 @section Running a Program with Multiple Units
1125 Consider a slightly more complicated example that has three files: a
1126 main program, and the spec and body of a package:
1128 @smallexample @c ada
1131 package Greetings is
1136 with Ada.Text_IO; use Ada.Text_IO;
1137 package body Greetings is
1140 Put_Line ("Hello WORLD!");
1143 procedure Goodbye is
1145 Put_Line ("Goodbye WORLD!");
1162 Following the one-unit-per-file rule, place this program in the
1163 following three separate files:
1167 spec of package @code{Greetings}
1170 body of package @code{Greetings}
1173 body of main program
1177 To build an executable version of
1178 this program, we could use four separate steps to compile, bind, and link
1179 the program, as follows:
1183 $ gcc -c greetings.adb
1189 Note that there is no required order of compilation when using GNAT.
1190 In particular it is perfectly fine to compile the main program first.
1191 Also, it is not necessary to compile package specs in the case where
1192 there is an accompanying body; you only need to compile the body. If you want
1193 to submit these files to the compiler for semantic checking and not code
1194 generation, then use the
1195 @option{-gnatc} switch:
1198 $ gcc -c greetings.ads -gnatc
1202 Although the compilation can be done in separate steps as in the
1203 above example, in practice it is almost always more convenient
1204 to use the @code{gnatmake} tool. All you need to know in this case
1205 is the name of the main program's source file. The effect of the above four
1206 commands can be achieved with a single one:
1209 $ gnatmake gmain.adb
1213 In the next section we discuss the advantages of using @code{gnatmake} in
1216 @c *****************************
1217 @node Using the gnatmake Utility
1218 @section Using the @command{gnatmake} Utility
1221 If you work on a program by compiling single components at a time using
1222 @code{gcc}, you typically keep track of the units you modify. In order to
1223 build a consistent system, you compile not only these units, but also any
1224 units that depend on the units you have modified.
1225 For example, in the preceding case,
1226 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1227 you edit @file{greetings.ads}, you must recompile both
1228 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1229 units that depend on @file{greetings.ads}.
1231 @code{gnatbind} will warn you if you forget one of these compilation
1232 steps, so that it is impossible to generate an inconsistent program as a
1233 result of forgetting to do a compilation. Nevertheless it is tedious and
1234 error-prone to keep track of dependencies among units.
1235 One approach to handle the dependency-bookkeeping is to use a
1236 makefile. However, makefiles present maintenance problems of their own:
1237 if the dependencies change as you change the program, you must make
1238 sure that the makefile is kept up-to-date manually, which is also an
1239 error-prone process.
1241 The @code{gnatmake} utility takes care of these details automatically.
1242 Invoke it using either one of the following forms:
1245 $ gnatmake gmain.adb
1246 $ gnatmake ^gmain^GMAIN^
1250 The argument is the name of the file containing the main program;
1251 you may omit the extension. @code{gnatmake}
1252 examines the environment, automatically recompiles any files that need
1253 recompiling, and binds and links the resulting set of object files,
1254 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1255 In a large program, it
1256 can be extremely helpful to use @code{gnatmake}, because working out by hand
1257 what needs to be recompiled can be difficult.
1259 Note that @code{gnatmake}
1260 takes into account all the Ada 95 rules that
1261 establish dependencies among units. These include dependencies that result
1262 from inlining subprogram bodies, and from
1263 generic instantiation. Unlike some other
1264 Ada make tools, @code{gnatmake} does not rely on the dependencies that were
1265 found by the compiler on a previous compilation, which may possibly
1266 be wrong when sources change. @code{gnatmake} determines the exact set of
1267 dependencies from scratch each time it is run.
1270 @node Editing with Emacs
1271 @section Editing with Emacs
1275 Emacs is an extensible self-documenting text editor that is available in a
1276 separate VMSINSTAL kit.
1278 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1279 click on the Emacs Help menu and run the Emacs Tutorial.
1280 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1281 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1283 Documentation on Emacs and other tools is available in Emacs under the
1284 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1285 use the middle mouse button to select a topic (e.g. Emacs).
1287 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1288 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1289 get to the Emacs manual.
1290 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1293 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1294 which is sufficiently extensible to provide for a complete programming
1295 environment and shell for the sophisticated user.
1299 @node Introduction to GPS
1300 @section Introduction to GPS
1301 @cindex GPS (GNAT Programming System)
1302 @cindex GNAT Programming System (GPS)
1304 Although the command line interface (@command{gnatmake}, etc.) alone
1305 is sufficient, a graphical Interactive Development
1306 Environment can make it easier for you to compose, navigate, and debug
1307 programs. This section describes the main features of GPS
1308 (``GNAT Programming System''), the GNAT graphical IDE.
1309 You will see how to use GPS to build and debug an executable, and
1310 you will also learn some of the basics of the GNAT ``project'' facility.
1312 GPS enables you to do much more than is presented here;
1313 e.g., you can produce a call graph, interface to a third-party
1314 Version Control System, and inspect the generated assembly language
1316 Indeed, GPS also supports languages other than Ada.
1317 Such additional information, and an explanation of all of the GPS menu
1318 items. may be found in the on-line help, which includes
1319 a user's guide and a tutorial (these are also accessible from the GNAT
1323 * Building a New Program with GPS::
1324 * Simple Debugging with GPS::
1328 @node Building a New Program with GPS
1329 @subsection Building a New Program with GPS
1331 GPS invokes the GNAT compilation tools using information
1332 contained in a @emph{project} (also known as a @emph{project file}):
1333 a collection of properties such
1334 as source directories, identities of main subprograms, tool switches, etc.,
1335 and their associated values.
1336 (See @ref{GNAT Project Manager}, for details.)
1337 In order to run GPS, you will need to either create a new project
1338 or else open an existing one.
1340 This section will explain how you can use GPS to create a project,
1341 to associate Ada source files with a project, and to build and run
1345 @item @emph{Creating a project}
1347 Invoke GPS, either from the command line or the platform's IDE.
1348 After it starts, GPS will display a ``Welcome'' screen with three
1353 @code{Start with default project in directory}
1356 @code{Create new project with wizard}
1359 @code{Open existing project}
1363 Select @code{Create new project with wizard} and press @code{OK}.
1364 A new window will appear. In the text box labeled with
1365 @code{Enter the name of the project to create}, type @file{sample}
1366 as the project name.
1367 In the next box, browse to choose the directory in which you
1368 would like to create the project file.
1369 After selecting an appropriate directory, press @code{Forward}.
1371 A window will appear with the title
1372 @code{Version Control System Configuration}.
1373 Simply press @code{Forward}.
1375 A window will appear with the title
1376 @code{Please select the source directories for this project}.
1377 The directory that you specified for the project file will be selected
1378 by default as the one to use for sources; simply press @code{Forward}.
1380 A window will appear with the title
1381 @code{Please select the build directory for this project}.
1382 The directory that you specified for the project file will be selected
1383 by default for object files and executables;
1384 simply press @code{Forward}.
1386 A window will appear with the title
1387 @code{Please select the main units for this project}.
1388 You will supply this information later, after creating the source file.
1389 Simply press @code{Forward} for now.
1391 A window will appear with the title
1392 @code{Please select the switches to build the project}.
1393 Press @code{Apply}. This will create a project file named
1394 @file{sample.prj} in the directory that you had specified.
1396 @item @emph{Creating and saving the source file}
1398 After you create the new project, a GPS window will appear, which is
1399 partitioned into two main sections:
1403 A @emph{Workspace area}, initially greyed out, which you will use for
1404 creating and editing source files
1407 Directly below, a @emph{Messages area}, which initially displays a
1408 ``Welcome'' message.
1409 (If the Messages area is not visible, drag its border upward to expand it.)
1413 Select @code{File} on the menu bar, and then the @code{New} command.
1414 The Workspace area will become white, and you can now
1415 enter the source program explicitly.
1416 Type the following text
1418 @smallexample @c ada
1420 with Ada.Text_IO; use Ada.Text_IO;
1423 Put_Line("Hello from GPS!");
1429 Select @code{File}, then @code{Save As}, and enter the source file name
1431 The file will be saved in the same directory you specified as the
1432 location of the default project file.
1435 @item @emph{Updating the project file}
1437 You need to add the new source file to the project.
1439 the @code{Project} menu and then @code{Edit project properties}.
1440 Click the @code{Main files} tab on the left, and then the
1442 Choose @file{hello.adb} from the list, and press @code{Open}.
1443 The project settings window will reflect this action.
1446 @item @emph{Building and running the program}
1448 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1449 and select @file{hello.adb}.
1450 The Messages window will display the resulting invocations of @command{gcc},
1451 @command{gnatbind}, and @command{gnatlink}
1452 (reflecting the default switch settings from the
1453 project file that you created) and then a ``successful compilation/build''
1456 To run the program, choose the @code{Build} menu, then @code{Run}, and
1457 select @command{hello}.
1458 An @emph{Arguments Selection} window will appear.
1459 There are no command line arguments, so just click @code{OK}.
1461 The Messages window will now display the program's output (the string
1462 @code{Hello from GPS}), and at the bottom of the GPS window a status
1463 update is displayed (@code{Run: hello}).
1464 Close the GPS window (or select @code{File}, then @code{Exit}) to
1465 terminate this GPS session.
1470 @node Simple Debugging with GPS
1471 @subsection Simple Debugging with GPS
1473 This section illustrates basic debugging techniques (setting breakpoints,
1474 examining/modifying variables, single stepping).
1477 @item @emph{Opening a project}
1479 Start GPS and select @code{Open existing project}; browse to
1480 specify the project file @file{sample.prj} that you had created in the
1483 @item @emph{Creating a source file}
1485 Select @code{File}, then @code{New}, and type in the following program:
1487 @smallexample @c ada
1489 with Ada.Text_IO; use Ada.Text_IO;
1490 procedure Example is
1491 Line : String (1..80);
1494 Put_Line("Type a line of text at each prompt; an empty line to exit");
1498 Put_Line (Line (1..N) );
1506 Select @code{File}, then @code{Save as}, and enter the file name
1509 @item @emph{Updating the project file}
1511 Add @code{Example} as a new main unit for the project:
1514 Select @code{Project}, then @code{Edit Project Properties}.
1517 Select the @code{Main files} tab, click @code{Add}, then
1518 select the file @file{example.adb} from the list, and
1520 You will see the file name appear in the list of main units
1526 @item @emph{Building/running the executable}
1528 To build the executable
1529 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1531 Run the program to see its effect (in the Messages area).
1532 Each line that you enter is displayed; an empty line will
1533 cause the loop to exit and the program to terminate.
1535 @item @emph{Debugging the program}
1537 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1538 which are required for debugging, are on by default when you create
1540 Thus unless you intentionally remove these settings, you will be able
1541 to debug any program that you develop using GPS.
1544 @item @emph{Initializing}
1546 Select @code{Debug}, then @code{Initialize}, then @file{example}
1548 @item @emph{Setting a breakpoint}
1550 After performing the initialization step, you will observe a small
1551 icon to the right of each line number.
1552 This serves as a toggle for breakpoints; clicking the icon will
1553 set a breakpoint at the corresponding line (the icon will change to
1554 a red circle with an ``x''), and clicking it again
1555 will remove the breakpoint / reset the icon.
1557 For purposes of this example, set a breakpoint at line 10 (the
1558 statement @code{Put_Line@ (Line@ (1..N));}
1560 @item @emph{Starting program execution}
1562 Select @code{Debug}, then @code{Run}. When the
1563 @code{Program Arguments} window appears, click @code{OK}.
1564 A console window will appear; enter some line of text,
1565 e.g. @code{abcde}, at the prompt.
1566 The program will pause execution when it gets to the
1567 breakpoint, and the corresponding line is highlighted.
1569 @item @emph{Examining a variable}
1571 Move the mouse over one of the occurrences of the variable @code{N}.
1572 You will see the value (5) displayed, in ``tool tip'' fashion.
1573 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1574 You will see information about @code{N} appear in the @code{Debugger Data}
1575 pane, showing the value as 5.
1578 @item @emph{Assigning a new value to a variable}
1580 Right click on the @code{N} in the @code{Debugger Data} pane, and
1581 select @code{Set value of N}.
1582 When the input window appears, enter the value @code{4} and click
1584 This value does not automatically appear in the @code{Debugger Data}
1585 pane; to see it, right click again on the @code{N} in the
1586 @code{Debugger Data} pane and select @code{Update value}.
1587 The new value, 4, will appear in red.
1589 @item @emph{Single stepping}
1591 Select @code{Debug}, then @code{Next}.
1592 This will cause the next statement to be executed, in this case the
1593 call of @code{Put_Line} with the string slice.
1594 Notice in the console window that the displayed string is simply
1595 @code{abcd} and not @code{abcde} which you had entered.
1596 This is because the upper bound of the slice is now 4 rather than 5.
1598 @item @emph{Removing a breakpoint}
1600 Toggle the breakpoint icon at line 10.
1602 @item @emph{Resuming execution from a breakpoint}
1604 Select @code{Debug}, then @code{Continue}.
1605 The program will reach the next iteration of the loop, and
1606 wait for input after displaying the prompt.
1607 This time, just hit the @kbd{Enter} key.
1608 The value of @code{N} will be 0, and the program will terminate.
1609 The console window will disappear.
1614 @node Introduction to Glide and GVD
1615 @section Introduction to Glide and GVD
1619 This section describes the main features of Glide,
1620 a GNAT graphical IDE, and also shows how to use the basic commands in GVD,
1621 the GNU Visual Debugger.
1622 These tools may be present in addition to, or in place of, GPS on some
1624 Additional information on Glide and GVD may be found
1625 in the on-line help for these tools.
1628 * Building a New Program with Glide::
1629 * Simple Debugging with GVD::
1630 * Other Glide Features::
1633 @node Building a New Program with Glide
1634 @subsection Building a New Program with Glide
1636 The simplest way to invoke Glide is to enter @command{glide}
1637 at the command prompt. It will generally be useful to issue this
1638 as a background command, thus allowing you to continue using
1639 your command window for other purposes while Glide is running:
1646 Glide will start up with an initial screen displaying the top-level menu items
1647 as well as some other information. The menu selections are as follows
1649 @item @code{Buffers}
1660 For this introductory example, you will need to create a new Ada source file.
1661 First, select the @code{Files} menu. This will pop open a menu with around
1662 a dozen or so items. To create a file, select the @code{Open file...} choice.
1663 Depending on the platform, you may see a pop-up window where you can browse
1664 to an appropriate directory and then enter the file name, or else simply
1665 see a line at the bottom of the Glide window where you can likewise enter
1666 the file name. Note that in Glide, when you attempt to open a non-existent
1667 file, the effect is to create a file with that name. For this example enter
1668 @file{hello.adb} as the name of the file.
1670 A new buffer will now appear, occupying the entire Glide window,
1671 with the file name at the top. The menu selections are slightly different
1672 from the ones you saw on the opening screen; there is an @code{Entities} item,
1673 and in place of @code{Glide} there is now an @code{Ada} item. Glide uses
1674 the file extension to identify the source language, so @file{adb} indicates
1677 You will enter some of the source program lines explicitly,
1678 and use the syntax-oriented template mechanism to enter other lines.
1679 First, type the following text:
1681 with Ada.Text_IO; use Ada.Text_IO;
1687 Observe that Glide uses different colors to distinguish reserved words from
1688 identifiers. Also, after the @code{procedure Hello is} line, the cursor is
1689 automatically indented in anticipation of declarations. When you enter
1690 @code{begin}, Glide recognizes that there are no declarations and thus places
1691 @code{begin} flush left. But after the @code{begin} line the cursor is again
1692 indented, where the statement(s) will be placed.
1694 The main part of the program will be a @code{for} loop. Instead of entering
1695 the text explicitly, however, use a statement template. Select the @code{Ada}
1696 item on the top menu bar, move the mouse to the @code{Statements} item,
1697 and you will see a large selection of alternatives. Choose @code{for loop}.
1698 You will be prompted (at the bottom of the buffer) for a loop name;
1699 simply press the @key{Enter} key since a loop name is not needed.
1700 You should see the beginning of a @code{for} loop appear in the source
1701 program window. You will now be prompted for the name of the loop variable;
1702 enter a line with the identifier @code{ind} (lower case). Note that,
1703 by default, Glide capitalizes the name (you can override such behavior
1704 if you wish, although this is outside the scope of this introduction).
1705 Next, Glide prompts you for the loop range; enter a line containing
1706 @code{1..5} and you will see this also appear in the source program,
1707 together with the remaining elements of the @code{for} loop syntax.
1709 Next enter the statement (with an intentional error, a missing semicolon)
1710 that will form the body of the loop:
1712 Put_Line("Hello, World" & Integer'Image(I))
1716 Finally, type @code{end Hello;} as the last line in the program.
1717 Now save the file: choose the @code{File} menu item, and then the
1718 @code{Save buffer} selection. You will see a message at the bottom
1719 of the buffer confirming that the file has been saved.
1721 You are now ready to attempt to build the program. Select the @code{Ada}
1722 item from the top menu bar. Although we could choose simply to compile
1723 the file, we will instead attempt to do a build (which invokes
1724 @command{gnatmake}) since, if the compile is successful, we want to build
1725 an executable. Thus select @code{Ada build}. This will fail because of the
1726 compilation error, and you will notice that the Glide window has been split:
1727 the top window contains the source file, and the bottom window contains the
1728 output from the GNAT tools. Glide allows you to navigate from a compilation
1729 error to the source file position corresponding to the error: click the
1730 middle mouse button (or simultaneously press the left and right buttons,
1731 on a two-button mouse) on the diagnostic line in the tool window. The
1732 focus will shift to the source window, and the cursor will be positioned
1733 on the character at which the error was detected.
1735 Correct the error: type in a semicolon to terminate the statement.
1736 Although you can again save the file explicitly, you can also simply invoke
1737 @code{Ada} @result{} @code{Build} and you will be prompted to save the file.
1738 This time the build will succeed; the tool output window shows you the
1739 options that are supplied by default. The GNAT tools' output (e.g.
1740 object and ALI files, executable) will go in the directory from which
1743 To execute the program, choose @code{Ada} and then @code{Run}.
1744 You should see the program's output displayed in the bottom window:
1754 @node Simple Debugging with GVD
1755 @subsection Simple Debugging with GVD
1758 This section describes how to set breakpoints, examine/modify variables,
1759 and step through execution.
1761 In order to enable debugging, you need to pass the @option{-g} switch
1762 to both the compiler and to @command{gnatlink}. If you are using
1763 the command line, passing @option{-g} to @command{gnatmake} will have
1764 this effect. You can then launch GVD, e.g. on the @code{hello} program,
1765 by issuing the command:
1772 If you are using Glide, then @option{-g} is passed to the relevant tools
1773 by default when you do a build. Start the debugger by selecting the
1774 @code{Ada} menu item, and then @code{Debug}.
1776 GVD comes up in a multi-part window. One pane shows the names of files
1777 comprising your executable; another pane shows the source code of the current
1778 unit (initially your main subprogram), another pane shows the debugger output
1779 and user interactions, and the fourth pane (the data canvas at the top
1780 of the window) displays data objects that you have selected.
1782 To the left of the source file pane, you will notice green dots adjacent
1783 to some lines. These are lines for which object code exists and where
1784 breakpoints can thus be set. You set/reset a breakpoint by clicking
1785 the green dot. When a breakpoint is set, the dot is replaced by an @code{X}
1786 in a red circle. Clicking the circle toggles the breakpoint off,
1787 and the red circle is replaced by the green dot.
1789 For this example, set a breakpoint at the statement where @code{Put_Line}
1792 Start program execution by selecting the @code{Run} button on the top menu bar.
1793 (The @code{Start} button will also start your program, but it will
1794 cause program execution to break at the entry to your main subprogram.)
1795 Evidence of reaching the breakpoint will appear: the source file line will be
1796 highlighted, and the debugger interactions pane will display
1799 You can examine the values of variables in several ways. Move the mouse
1800 over an occurrence of @code{Ind} in the @code{for} loop, and you will see
1801 the value (now @code{1}) displayed. Alternatively, right-click on @code{Ind}
1802 and select @code{Display Ind}; a box showing the variable's name and value
1803 will appear in the data canvas.
1805 Although a loop index is a constant with respect to Ada semantics,
1806 you can change its value in the debugger. Right-click in the box
1807 for @code{Ind}, and select the @code{Set Value of Ind} item.
1808 Enter @code{2} as the new value, and press @command{OK}.
1809 The box for @code{Ind} shows the update.
1811 Press the @code{Step} button on the top menu bar; this will step through
1812 one line of program text (the invocation of @code{Put_Line}), and you can
1813 observe the effect of having modified @code{Ind} since the value displayed
1816 Remove the breakpoint, and resume execution by selecting the @code{Cont}
1817 button. You will see the remaining output lines displayed in the debugger
1818 interaction window, along with a message confirming normal program
1821 @node Other Glide Features
1822 @subsection Other Glide Features
1825 You may have observed that some of the menu selections contain abbreviations;
1826 e.g., @code{(C-x C-f)} for @code{Open file...} in the @code{Files} menu.
1827 These are @emph{shortcut keys} that you can use instead of selecting
1828 menu items. The @key{C} stands for @key{Ctrl}; thus @code{(C-x C-f)} means
1829 @key{Ctrl-x} followed by @key{Ctrl-f}, and this sequence can be used instead
1830 of selecting @code{Files} and then @code{Open file...}.
1832 To abort a Glide command, type @key{Ctrl-g}.
1834 If you want Glide to start with an existing source file, you can either
1835 launch Glide as above and then open the file via @code{Files} @result{}
1836 @code{Open file...}, or else simply pass the name of the source file
1837 on the command line:
1844 While you are using Glide, a number of @emph{buffers} exist.
1845 You create some explicitly; e.g., when you open/create a file.
1846 Others arise as an effect of the commands that you issue; e.g., the buffer
1847 containing the output of the tools invoked during a build. If a buffer
1848 is hidden, you can bring it into a visible window by first opening
1849 the @code{Buffers} menu and then selecting the desired entry.
1851 If a buffer occupies only part of the Glide screen and you want to expand it
1852 to fill the entire screen, then click in the buffer and then select
1853 @code{Files} @result{} @code{One Window}.
1855 If a window is occupied by one buffer and you want to split the window
1856 to bring up a second buffer, perform the following steps:
1858 @item Select @code{Files} @result{} @code{Split Window};
1859 this will produce two windows each of which holds the original buffer
1860 (these are not copies, but rather different views of the same buffer contents)
1862 @item With the focus in one of the windows,
1863 select the desired buffer from the @code{Buffers} menu
1867 To exit from Glide, choose @code{Files} @result{} @code{Exit}.
1870 @node The GNAT Compilation Model
1871 @chapter The GNAT Compilation Model
1872 @cindex GNAT compilation model
1873 @cindex Compilation model
1876 * Source Representation::
1877 * Foreign Language Representation::
1878 * File Naming Rules::
1879 * Using Other File Names::
1880 * Alternative File Naming Schemes::
1881 * Generating Object Files::
1882 * Source Dependencies::
1883 * The Ada Library Information Files::
1884 * Binding an Ada Program::
1885 * Mixed Language Programming::
1886 * Building Mixed Ada & C++ Programs::
1887 * Comparison between GNAT and C/C++ Compilation Models::
1888 * Comparison between GNAT and Conventional Ada Library Models::
1890 * Placement of temporary files::
1895 This chapter describes the compilation model used by GNAT. Although
1896 similar to that used by other languages, such as C and C++, this model
1897 is substantially different from the traditional Ada compilation models,
1898 which are based on a library. The model is initially described without
1899 reference to the library-based model. If you have not previously used an
1900 Ada compiler, you need only read the first part of this chapter. The
1901 last section describes and discusses the differences between the GNAT
1902 model and the traditional Ada compiler models. If you have used other
1903 Ada compilers, this section will help you to understand those
1904 differences, and the advantages of the GNAT model.
1906 @node Source Representation
1907 @section Source Representation
1911 Ada source programs are represented in standard text files, using
1912 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1913 7-bit ASCII set, plus additional characters used for
1914 representing foreign languages (@pxref{Foreign Language Representation}
1915 for support of non-USA character sets). The format effector characters
1916 are represented using their standard ASCII encodings, as follows:
1921 Vertical tab, @code{16#0B#}
1925 Horizontal tab, @code{16#09#}
1929 Carriage return, @code{16#0D#}
1933 Line feed, @code{16#0A#}
1937 Form feed, @code{16#0C#}
1941 Source files are in standard text file format. In addition, GNAT will
1942 recognize a wide variety of stream formats, in which the end of physical
1943 physical lines is marked by any of the following sequences:
1944 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1945 in accommodating files that are imported from other operating systems.
1947 @cindex End of source file
1948 @cindex Source file, end
1950 The end of a source file is normally represented by the physical end of
1951 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1952 recognized as signalling the end of the source file. Again, this is
1953 provided for compatibility with other operating systems where this
1954 code is used to represent the end of file.
1956 Each file contains a single Ada compilation unit, including any pragmas
1957 associated with the unit. For example, this means you must place a
1958 package declaration (a package @dfn{spec}) and the corresponding body in
1959 separate files. An Ada @dfn{compilation} (which is a sequence of
1960 compilation units) is represented using a sequence of files. Similarly,
1961 you will place each subunit or child unit in a separate file.
1963 @node Foreign Language Representation
1964 @section Foreign Language Representation
1967 GNAT supports the standard character sets defined in Ada 95 as well as
1968 several other non-standard character sets for use in localized versions
1969 of the compiler (@pxref{Character Set Control}).
1972 * Other 8-Bit Codes::
1973 * Wide Character Encodings::
1981 The basic character set is Latin-1. This character set is defined by ISO
1982 standard 8859, part 1. The lower half (character codes @code{16#00#}
1983 ... @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1984 is used to represent additional characters. These include extended letters
1985 used by European languages, such as French accents, the vowels with umlauts
1986 used in German, and the extra letter A-ring used in Swedish.
1988 @findex Ada.Characters.Latin_1
1989 For a complete list of Latin-1 codes and their encodings, see the source
1990 file of library unit @code{Ada.Characters.Latin_1} in file
1991 @file{a-chlat1.ads}.
1992 You may use any of these extended characters freely in character or
1993 string literals. In addition, the extended characters that represent
1994 letters can be used in identifiers.
1996 @node Other 8-Bit Codes
1997 @subsection Other 8-Bit Codes
2000 GNAT also supports several other 8-bit coding schemes:
2003 @item ISO 8859-2 (Latin-2)
2006 Latin-2 letters allowed in identifiers, with uppercase and lowercase
2009 @item ISO 8859-3 (Latin-3)
2012 Latin-3 letters allowed in identifiers, with uppercase and lowercase
2015 @item ISO 8859-4 (Latin-4)
2018 Latin-4 letters allowed in identifiers, with uppercase and lowercase
2021 @item ISO 8859-5 (Cyrillic)
2024 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
2025 lowercase equivalence.
2027 @item ISO 8859-15 (Latin-9)
2030 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
2031 lowercase equivalence
2033 @item IBM PC (code page 437)
2034 @cindex code page 437
2035 This code page is the normal default for PCs in the U.S. It corresponds
2036 to the original IBM PC character set. This set has some, but not all, of
2037 the extended Latin-1 letters, but these letters do not have the same
2038 encoding as Latin-1. In this mode, these letters are allowed in
2039 identifiers with uppercase and lowercase equivalence.
2041 @item IBM PC (code page 850)
2042 @cindex code page 850
2043 This code page is a modification of 437 extended to include all the
2044 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
2045 mode, all these letters are allowed in identifiers with uppercase and
2046 lowercase equivalence.
2048 @item Full Upper 8-bit
2049 Any character in the range 80-FF allowed in identifiers, and all are
2050 considered distinct. In other words, there are no uppercase and lowercase
2051 equivalences in this range. This is useful in conjunction with
2052 certain encoding schemes used for some foreign character sets (e.g.
2053 the typical method of representing Chinese characters on the PC).
2056 No upper-half characters in the range 80-FF are allowed in identifiers.
2057 This gives Ada 83 compatibility for identifier names.
2061 For precise data on the encodings permitted, and the uppercase and lowercase
2062 equivalences that are recognized, see the file @file{csets.adb} in
2063 the GNAT compiler sources. You will need to obtain a full source release
2064 of GNAT to obtain this file.
2066 @node Wide Character Encodings
2067 @subsection Wide Character Encodings
2070 GNAT allows wide character codes to appear in character and string
2071 literals, and also optionally in identifiers, by means of the following
2072 possible encoding schemes:
2077 In this encoding, a wide character is represented by the following five
2085 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
2086 characters (using uppercase letters) of the wide character code. For
2087 example, ESC A345 is used to represent the wide character with code
2089 This scheme is compatible with use of the full Wide_Character set.
2091 @item Upper-Half Coding
2092 @cindex Upper-Half Coding
2093 The wide character with encoding @code{16#abcd#} where the upper bit is on
2094 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
2095 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
2096 character, but is not required to be in the upper half. This method can
2097 be also used for shift-JIS or EUC, where the internal coding matches the
2100 @item Shift JIS Coding
2101 @cindex Shift JIS Coding
2102 A wide character is represented by a two-character sequence,
2104 @code{16#cd#}, with the restrictions described for upper-half encoding as
2105 described above. The internal character code is the corresponding JIS
2106 character according to the standard algorithm for Shift-JIS
2107 conversion. Only characters defined in the JIS code set table can be
2108 used with this encoding method.
2112 A wide character is represented by a two-character sequence
2114 @code{16#cd#}, with both characters being in the upper half. The internal
2115 character code is the corresponding JIS character according to the EUC
2116 encoding algorithm. Only characters defined in the JIS code set table
2117 can be used with this encoding method.
2120 A wide character is represented using
2121 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
2122 10646-1/Am.2. Depending on the character value, the representation
2123 is a one, two, or three byte sequence:
2128 16#0000#-16#007f#: 2#0xxxxxxx#
2129 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
2130 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
2135 where the xxx bits correspond to the left-padded bits of the
2136 16-bit character value. Note that all lower half ASCII characters
2137 are represented as ASCII bytes and all upper half characters and
2138 other wide characters are represented as sequences of upper-half
2139 (The full UTF-8 scheme allows for encoding 31-bit characters as
2140 6-byte sequences, but in this implementation, all UTF-8 sequences
2141 of four or more bytes length will be treated as illegal).
2142 @item Brackets Coding
2143 In this encoding, a wide character is represented by the following eight
2151 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
2152 characters (using uppercase letters) of the wide character code. For
2153 example, [``A345''] is used to represent the wide character with code
2154 @code{16#A345#}. It is also possible (though not required) to use the
2155 Brackets coding for upper half characters. For example, the code
2156 @code{16#A3#} can be represented as @code{[``A3'']}.
2158 This scheme is compatible with use of the full Wide_Character set,
2159 and is also the method used for wide character encoding in the standard
2160 ACVC (Ada Compiler Validation Capability) test suite distributions.
2165 Note: Some of these coding schemes do not permit the full use of the
2166 Ada 95 character set. For example, neither Shift JIS, nor EUC allow the
2167 use of the upper half of the Latin-1 set.
2169 @node File Naming Rules
2170 @section File Naming Rules
2173 The default file name is determined by the name of the unit that the
2174 file contains. The name is formed by taking the full expanded name of
2175 the unit and replacing the separating dots with hyphens and using
2176 ^lowercase^uppercase^ for all letters.
2178 An exception arises if the file name generated by the above rules starts
2179 with one of the characters
2186 and the second character is a
2187 minus. In this case, the character ^tilde^dollar sign^ is used in place
2188 of the minus. The reason for this special rule is to avoid clashes with
2189 the standard names for child units of the packages System, Ada,
2190 Interfaces, and GNAT, which use the prefixes
2199 The file extension is @file{.ads} for a spec and
2200 @file{.adb} for a body. The following list shows some
2201 examples of these rules.
2208 @item arith_functions.ads
2209 Arith_Functions (package spec)
2210 @item arith_functions.adb
2211 Arith_Functions (package body)
2213 Func.Spec (child package spec)
2215 Func.Spec (child package body)
2217 Sub (subunit of Main)
2218 @item ^a~bad.adb^A$BAD.ADB^
2219 A.Bad (child package body)
2223 Following these rules can result in excessively long
2224 file names if corresponding
2225 unit names are long (for example, if child units or subunits are
2226 heavily nested). An option is available to shorten such long file names
2227 (called file name ``krunching''). This may be particularly useful when
2228 programs being developed with GNAT are to be used on operating systems
2229 with limited file name lengths. @xref{Using gnatkr}.
2231 Of course, no file shortening algorithm can guarantee uniqueness over
2232 all possible unit names; if file name krunching is used, it is your
2233 responsibility to ensure no name clashes occur. Alternatively you
2234 can specify the exact file names that you want used, as described
2235 in the next section. Finally, if your Ada programs are migrating from a
2236 compiler with a different naming convention, you can use the gnatchop
2237 utility to produce source files that follow the GNAT naming conventions.
2238 (For details @pxref{Renaming Files Using gnatchop}.)
2240 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2241 systems, case is not significant. So for example on @code{Windows XP}
2242 if the canonical name is @code{main-sub.adb}, you can use the file name
2243 @code{Main-Sub.adb} instead. However, case is significant for other
2244 operating systems, so for example, if you want to use other than
2245 canonically cased file names on a Unix system, you need to follow
2246 the procedures described in the next section.
2248 @node Using Other File Names
2249 @section Using Other File Names
2253 In the previous section, we have described the default rules used by
2254 GNAT to determine the file name in which a given unit resides. It is
2255 often convenient to follow these default rules, and if you follow them,
2256 the compiler knows without being explicitly told where to find all
2259 However, in some cases, particularly when a program is imported from
2260 another Ada compiler environment, it may be more convenient for the
2261 programmer to specify which file names contain which units. GNAT allows
2262 arbitrary file names to be used by means of the Source_File_Name pragma.
2263 The form of this pragma is as shown in the following examples:
2264 @cindex Source_File_Name pragma
2266 @smallexample @c ada
2268 pragma Source_File_Name (My_Utilities.Stacks,
2269 Spec_File_Name => "myutilst_a.ada");
2270 pragma Source_File_name (My_Utilities.Stacks,
2271 Body_File_Name => "myutilst.ada");
2276 As shown in this example, the first argument for the pragma is the unit
2277 name (in this example a child unit). The second argument has the form
2278 of a named association. The identifier
2279 indicates whether the file name is for a spec or a body;
2280 the file name itself is given by a string literal.
2282 The source file name pragma is a configuration pragma, which means that
2283 normally it will be placed in the @file{gnat.adc}
2284 file used to hold configuration
2285 pragmas that apply to a complete compilation environment.
2286 For more details on how the @file{gnat.adc} file is created and used
2287 @pxref{Handling of Configuration Pragmas}
2288 @cindex @file{gnat.adc}
2291 GNAT allows completely arbitrary file names to be specified using the
2292 source file name pragma. However, if the file name specified has an
2293 extension other than @file{.ads} or @file{.adb} it is necessary to use
2294 a special syntax when compiling the file. The name in this case must be
2295 preceded by the special sequence @code{-x} followed by a space and the name
2296 of the language, here @code{ada}, as in:
2299 $ gcc -c -x ada peculiar_file_name.sim
2304 @code{gnatmake} handles non-standard file names in the usual manner (the
2305 non-standard file name for the main program is simply used as the
2306 argument to gnatmake). Note that if the extension is also non-standard,
2307 then it must be included in the gnatmake command, it may not be omitted.
2309 @node Alternative File Naming Schemes
2310 @section Alternative File Naming Schemes
2311 @cindex File naming schemes, alternative
2314 In the previous section, we described the use of the @code{Source_File_Name}
2315 pragma to allow arbitrary names to be assigned to individual source files.
2316 However, this approach requires one pragma for each file, and especially in
2317 large systems can result in very long @file{gnat.adc} files, and also create
2318 a maintenance problem.
2320 GNAT also provides a facility for specifying systematic file naming schemes
2321 other than the standard default naming scheme previously described. An
2322 alternative scheme for naming is specified by the use of
2323 @code{Source_File_Name} pragmas having the following format:
2324 @cindex Source_File_Name pragma
2326 @smallexample @c ada
2327 pragma Source_File_Name (
2328 Spec_File_Name => FILE_NAME_PATTERN
2329 [,Casing => CASING_SPEC]
2330 [,Dot_Replacement => STRING_LITERAL]);
2332 pragma Source_File_Name (
2333 Body_File_Name => FILE_NAME_PATTERN
2334 [,Casing => CASING_SPEC]
2335 [,Dot_Replacement => STRING_LITERAL]);
2337 pragma Source_File_Name (
2338 Subunit_File_Name => FILE_NAME_PATTERN
2339 [,Casing => CASING_SPEC]
2340 [,Dot_Replacement => STRING_LITERAL]);
2342 FILE_NAME_PATTERN ::= STRING_LITERAL
2343 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2347 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2348 It contains a single asterisk character, and the unit name is substituted
2349 systematically for this asterisk. The optional parameter
2350 @code{Casing} indicates
2351 whether the unit name is to be all upper-case letters, all lower-case letters,
2352 or mixed-case. If no
2353 @code{Casing} parameter is used, then the default is all
2354 ^lower-case^upper-case^.
2356 The optional @code{Dot_Replacement} string is used to replace any periods
2357 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2358 argument is used then separating dots appear unchanged in the resulting
2360 Although the above syntax indicates that the
2361 @code{Casing} argument must appear
2362 before the @code{Dot_Replacement} argument, but it
2363 is also permissible to write these arguments in the opposite order.
2365 As indicated, it is possible to specify different naming schemes for
2366 bodies, specs, and subunits. Quite often the rule for subunits is the
2367 same as the rule for bodies, in which case, there is no need to give
2368 a separate @code{Subunit_File_Name} rule, and in this case the
2369 @code{Body_File_name} rule is used for subunits as well.
2371 The separate rule for subunits can also be used to implement the rather
2372 unusual case of a compilation environment (e.g. a single directory) which
2373 contains a subunit and a child unit with the same unit name. Although
2374 both units cannot appear in the same partition, the Ada Reference Manual
2375 allows (but does not require) the possibility of the two units coexisting
2376 in the same environment.
2378 The file name translation works in the following steps:
2383 If there is a specific @code{Source_File_Name} pragma for the given unit,
2384 then this is always used, and any general pattern rules are ignored.
2387 If there is a pattern type @code{Source_File_Name} pragma that applies to
2388 the unit, then the resulting file name will be used if the file exists. If
2389 more than one pattern matches, the latest one will be tried first, and the
2390 first attempt resulting in a reference to a file that exists will be used.
2393 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2394 for which the corresponding file exists, then the standard GNAT default
2395 naming rules are used.
2400 As an example of the use of this mechanism, consider a commonly used scheme
2401 in which file names are all lower case, with separating periods copied
2402 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2403 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2406 @smallexample @c ada
2407 pragma Source_File_Name
2408 (Spec_File_Name => "*.1.ada");
2409 pragma Source_File_Name
2410 (Body_File_Name => "*.2.ada");
2414 The default GNAT scheme is actually implemented by providing the following
2415 default pragmas internally:
2417 @smallexample @c ada
2418 pragma Source_File_Name
2419 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2420 pragma Source_File_Name
2421 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2425 Our final example implements a scheme typically used with one of the
2426 Ada 83 compilers, where the separator character for subunits was ``__''
2427 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2428 by adding @file{.ADA}, and subunits by
2429 adding @file{.SEP}. All file names were
2430 upper case. Child units were not present of course since this was an
2431 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2432 the same double underscore separator for child units.
2434 @smallexample @c ada
2435 pragma Source_File_Name
2436 (Spec_File_Name => "*_.ADA",
2437 Dot_Replacement => "__",
2438 Casing = Uppercase);
2439 pragma Source_File_Name
2440 (Body_File_Name => "*.ADA",
2441 Dot_Replacement => "__",
2442 Casing = Uppercase);
2443 pragma Source_File_Name
2444 (Subunit_File_Name => "*.SEP",
2445 Dot_Replacement => "__",
2446 Casing = Uppercase);
2449 @node Generating Object Files
2450 @section Generating Object Files
2453 An Ada program consists of a set of source files, and the first step in
2454 compiling the program is to generate the corresponding object files.
2455 These are generated by compiling a subset of these source files.
2456 The files you need to compile are the following:
2460 If a package spec has no body, compile the package spec to produce the
2461 object file for the package.
2464 If a package has both a spec and a body, compile the body to produce the
2465 object file for the package. The source file for the package spec need
2466 not be compiled in this case because there is only one object file, which
2467 contains the code for both the spec and body of the package.
2470 For a subprogram, compile the subprogram body to produce the object file
2471 for the subprogram. The spec, if one is present, is as usual in a
2472 separate file, and need not be compiled.
2476 In the case of subunits, only compile the parent unit. A single object
2477 file is generated for the entire subunit tree, which includes all the
2481 Compile child units independently of their parent units
2482 (though, of course, the spec of all the ancestor unit must be present in order
2483 to compile a child unit).
2487 Compile generic units in the same manner as any other units. The object
2488 files in this case are small dummy files that contain at most the
2489 flag used for elaboration checking. This is because GNAT always handles generic
2490 instantiation by means of macro expansion. However, it is still necessary to
2491 compile generic units, for dependency checking and elaboration purposes.
2495 The preceding rules describe the set of files that must be compiled to
2496 generate the object files for a program. Each object file has the same
2497 name as the corresponding source file, except that the extension is
2500 You may wish to compile other files for the purpose of checking their
2501 syntactic and semantic correctness. For example, in the case where a
2502 package has a separate spec and body, you would not normally compile the
2503 spec. However, it is convenient in practice to compile the spec to make
2504 sure it is error-free before compiling clients of this spec, because such
2505 compilations will fail if there is an error in the spec.
2507 GNAT provides an option for compiling such files purely for the
2508 purposes of checking correctness; such compilations are not required as
2509 part of the process of building a program. To compile a file in this
2510 checking mode, use the @option{-gnatc} switch.
2512 @node Source Dependencies
2513 @section Source Dependencies
2516 A given object file clearly depends on the source file which is compiled
2517 to produce it. Here we are using @dfn{depends} in the sense of a typical
2518 @code{make} utility; in other words, an object file depends on a source
2519 file if changes to the source file require the object file to be
2521 In addition to this basic dependency, a given object may depend on
2522 additional source files as follows:
2526 If a file being compiled @code{with}'s a unit @var{X}, the object file
2527 depends on the file containing the spec of unit @var{X}. This includes
2528 files that are @code{with}'ed implicitly either because they are parents
2529 of @code{with}'ed child units or they are run-time units required by the
2530 language constructs used in a particular unit.
2533 If a file being compiled instantiates a library level generic unit, the
2534 object file depends on both the spec and body files for this generic
2538 If a file being compiled instantiates a generic unit defined within a
2539 package, the object file depends on the body file for the package as
2540 well as the spec file.
2544 @cindex @option{-gnatn} switch
2545 If a file being compiled contains a call to a subprogram for which
2546 pragma @code{Inline} applies and inlining is activated with the
2547 @option{-gnatn} switch, the object file depends on the file containing the
2548 body of this subprogram as well as on the file containing the spec. Note
2549 that for inlining to actually occur as a result of the use of this switch,
2550 it is necessary to compile in optimizing mode.
2552 @cindex @option{-gnatN} switch
2553 The use of @option{-gnatN} activates a more extensive inlining optimization
2554 that is performed by the front end of the compiler. This inlining does
2555 not require that the code generation be optimized. Like @option{-gnatn},
2556 the use of this switch generates additional dependencies.
2558 @option{-gnatN} automatically implies @option{-gnatn} so it is not necessary
2559 to specify both options.
2562 If an object file O depends on the proper body of a subunit through inlining
2563 or instantiation, it depends on the parent unit of the subunit. This means that
2564 any modification of the parent unit or one of its subunits affects the
2568 The object file for a parent unit depends on all its subunit body files.
2571 The previous two rules meant that for purposes of computing dependencies and
2572 recompilation, a body and all its subunits are treated as an indivisible whole.
2575 These rules are applied transitively: if unit @code{A} @code{with}'s
2576 unit @code{B}, whose elaboration calls an inlined procedure in package
2577 @code{C}, the object file for unit @code{A} will depend on the body of
2578 @code{C}, in file @file{c.adb}.
2580 The set of dependent files described by these rules includes all the
2581 files on which the unit is semantically dependent, as described in the
2582 Ada 95 Language Reference Manual. However, it is a superset of what the
2583 ARM describes, because it includes generic, inline, and subunit dependencies.
2585 An object file must be recreated by recompiling the corresponding source
2586 file if any of the source files on which it depends are modified. For
2587 example, if the @code{make} utility is used to control compilation,
2588 the rule for an Ada object file must mention all the source files on
2589 which the object file depends, according to the above definition.
2590 The determination of the necessary
2591 recompilations is done automatically when one uses @code{gnatmake}.
2594 @node The Ada Library Information Files
2595 @section The Ada Library Information Files
2596 @cindex Ada Library Information files
2597 @cindex @file{ALI} files
2600 Each compilation actually generates two output files. The first of these
2601 is the normal object file that has a @file{.o} extension. The second is a
2602 text file containing full dependency information. It has the same
2603 name as the source file, but an @file{.ali} extension.
2604 This file is known as the Ada Library Information (@file{ALI}) file.
2605 The following information is contained in the @file{ALI} file.
2609 Version information (indicates which version of GNAT was used to compile
2610 the unit(s) in question)
2613 Main program information (including priority and time slice settings,
2614 as well as the wide character encoding used during compilation).
2617 List of arguments used in the @code{gcc} command for the compilation
2620 Attributes of the unit, including configuration pragmas used, an indication
2621 of whether the compilation was successful, exception model used etc.
2624 A list of relevant restrictions applying to the unit (used for consistency)
2628 Categorization information (e.g. use of pragma @code{Pure}).
2631 Information on all @code{with}'ed units, including presence of
2632 @code{Elaborate} or @code{Elaborate_All} pragmas.
2635 Information from any @code{Linker_Options} pragmas used in the unit
2638 Information on the use of @code{Body_Version} or @code{Version}
2639 attributes in the unit.
2642 Dependency information. This is a list of files, together with
2643 time stamp and checksum information. These are files on which
2644 the unit depends in the sense that recompilation is required
2645 if any of these units are modified.
2648 Cross-reference data. Contains information on all entities referenced
2649 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2650 provide cross-reference information.
2655 For a full detailed description of the format of the @file{ALI} file,
2656 see the source of the body of unit @code{Lib.Writ}, contained in file
2657 @file{lib-writ.adb} in the GNAT compiler sources.
2659 @node Binding an Ada Program
2660 @section Binding an Ada Program
2663 When using languages such as C and C++, once the source files have been
2664 compiled the only remaining step in building an executable program
2665 is linking the object modules together. This means that it is possible to
2666 link an inconsistent version of a program, in which two units have
2667 included different versions of the same header.
2669 The rules of Ada do not permit such an inconsistent program to be built.
2670 For example, if two clients have different versions of the same package,
2671 it is illegal to build a program containing these two clients.
2672 These rules are enforced by the GNAT binder, which also determines an
2673 elaboration order consistent with the Ada rules.
2675 The GNAT binder is run after all the object files for a program have
2676 been created. It is given the name of the main program unit, and from
2677 this it determines the set of units required by the program, by reading the
2678 corresponding ALI files. It generates error messages if the program is
2679 inconsistent or if no valid order of elaboration exists.
2681 If no errors are detected, the binder produces a main program, in Ada by
2682 default, that contains calls to the elaboration procedures of those
2683 compilation unit that require them, followed by
2684 a call to the main program. This Ada program is compiled to generate the
2685 object file for the main program. The name of
2686 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2687 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2690 Finally, the linker is used to build the resulting executable program,
2691 using the object from the main program from the bind step as well as the
2692 object files for the Ada units of the program.
2694 @node Mixed Language Programming
2695 @section Mixed Language Programming
2696 @cindex Mixed Language Programming
2699 This section describes how to develop a mixed-language program,
2700 specifically one that comprises units in both Ada and C.
2703 * Interfacing to C::
2704 * Calling Conventions::
2707 @node Interfacing to C
2708 @subsection Interfacing to C
2710 Interfacing Ada with a foreign language such as C involves using
2711 compiler directives to import and/or export entity definitions in each
2712 language---using @code{extern} statements in C, for instance, and the
2713 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada. For
2714 a full treatment of these topics, read Appendix B, section 1 of the Ada
2715 95 Language Reference Manual.
2717 There are two ways to build a program using GNAT that contains some Ada
2718 sources and some foreign language sources, depending on whether or not
2719 the main subprogram is written in Ada. Here is a source example with
2720 the main subprogram in Ada:
2726 void print_num (int num)
2728 printf ("num is %d.\n", num);
2734 /* num_from_Ada is declared in my_main.adb */
2735 extern int num_from_Ada;
2739 return num_from_Ada;
2743 @smallexample @c ada
2745 procedure My_Main is
2747 -- Declare then export an Integer entity called num_from_Ada
2748 My_Num : Integer := 10;
2749 pragma Export (C, My_Num, "num_from_Ada");
2751 -- Declare an Ada function spec for Get_Num, then use
2752 -- C function get_num for the implementation.
2753 function Get_Num return Integer;
2754 pragma Import (C, Get_Num, "get_num");
2756 -- Declare an Ada procedure spec for Print_Num, then use
2757 -- C function print_num for the implementation.
2758 procedure Print_Num (Num : Integer);
2759 pragma Import (C, Print_Num, "print_num");
2762 Print_Num (Get_Num);
2768 To build this example, first compile the foreign language files to
2769 generate object files:
2776 Then, compile the Ada units to produce a set of object files and ALI
2779 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2783 Run the Ada binder on the Ada main program:
2785 gnatbind my_main.ali
2789 Link the Ada main program, the Ada objects and the other language
2792 gnatlink my_main.ali file1.o file2.o
2796 The last three steps can be grouped in a single command:
2798 gnatmake my_main.adb -largs file1.o file2.o
2801 @cindex Binder output file
2803 If the main program is in a language other than Ada, then you may have
2804 more than one entry point into the Ada subsystem. You must use a special
2805 binder option to generate callable routines that initialize and
2806 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2807 Calls to the initialization and finalization routines must be inserted
2808 in the main program, or some other appropriate point in the code. The
2809 call to initialize the Ada units must occur before the first Ada
2810 subprogram is called, and the call to finalize the Ada units must occur
2811 after the last Ada subprogram returns. The binder will place the
2812 initialization and finalization subprograms into the
2813 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2814 sources. To illustrate, we have the following example:
2818 extern void adainit (void);
2819 extern void adafinal (void);
2820 extern int add (int, int);
2821 extern int sub (int, int);
2823 int main (int argc, char *argv[])
2829 /* Should print "21 + 7 = 28" */
2830 printf ("%d + %d = %d\n", a, b, add (a, b));
2831 /* Should print "21 - 7 = 14" */
2832 printf ("%d - %d = %d\n", a, b, sub (a, b));
2838 @smallexample @c ada
2841 function Add (A, B : Integer) return Integer;
2842 pragma Export (C, Add, "add");
2846 package body Unit1 is
2847 function Add (A, B : Integer) return Integer is
2855 function Sub (A, B : Integer) return Integer;
2856 pragma Export (C, Sub, "sub");
2860 package body Unit2 is
2861 function Sub (A, B : Integer) return Integer is
2870 The build procedure for this application is similar to the last
2871 example's. First, compile the foreign language files to generate object
2878 Next, compile the Ada units to produce a set of object files and ALI
2881 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2882 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2886 Run the Ada binder on every generated ALI file. Make sure to use the
2887 @option{-n} option to specify a foreign main program:
2889 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2893 Link the Ada main program, the Ada objects and the foreign language
2894 objects. You need only list the last ALI file here:
2896 gnatlink unit2.ali main.o -o exec_file
2899 This procedure yields a binary executable called @file{exec_file}.
2902 @node Calling Conventions
2903 @subsection Calling Conventions
2904 @cindex Foreign Languages
2905 @cindex Calling Conventions
2906 GNAT follows standard calling sequence conventions and will thus interface
2907 to any other language that also follows these conventions. The following
2908 Convention identifiers are recognized by GNAT:
2911 @cindex Interfacing to Ada
2912 @cindex Other Ada compilers
2913 @cindex Convention Ada
2915 This indicates that the standard Ada calling sequence will be
2916 used and all Ada data items may be passed without any limitations in the
2917 case where GNAT is used to generate both the caller and callee. It is also
2918 possible to mix GNAT generated code and code generated by another Ada
2919 compiler. In this case, the data types should be restricted to simple
2920 cases, including primitive types. Whether complex data types can be passed
2921 depends on the situation. Probably it is safe to pass simple arrays, such
2922 as arrays of integers or floats. Records may or may not work, depending
2923 on whether both compilers lay them out identically. Complex structures
2924 involving variant records, access parameters, tasks, or protected types,
2925 are unlikely to be able to be passed.
2927 Note that in the case of GNAT running
2928 on a platform that supports DEC Ada 83, a higher degree of compatibility
2929 can be guaranteed, and in particular records are layed out in an identical
2930 manner in the two compilers. Note also that if output from two different
2931 compilers is mixed, the program is responsible for dealing with elaboration
2932 issues. Probably the safest approach is to write the main program in the
2933 version of Ada other than GNAT, so that it takes care of its own elaboration
2934 requirements, and then call the GNAT-generated adainit procedure to ensure
2935 elaboration of the GNAT components. Consult the documentation of the other
2936 Ada compiler for further details on elaboration.
2938 However, it is not possible to mix the tasking run time of GNAT and
2939 DEC Ada 83, All the tasking operations must either be entirely within
2940 GNAT compiled sections of the program, or entirely within DEC Ada 83
2941 compiled sections of the program.
2943 @cindex Interfacing to Assembly
2944 @cindex Convention Assembler
2946 Specifies assembler as the convention. In practice this has the
2947 same effect as convention Ada (but is not equivalent in the sense of being
2948 considered the same convention).
2950 @cindex Convention Asm
2953 Equivalent to Assembler.
2955 @cindex Interfacing to COBOL
2956 @cindex Convention COBOL
2959 Data will be passed according to the conventions described
2960 in section B.4 of the Ada 95 Reference Manual.
2963 @cindex Interfacing to C
2964 @cindex Convention C
2966 Data will be passed according to the conventions described
2967 in section B.3 of the Ada 95 Reference Manual.
2969 @findex C varargs function
2970 @cindex Intefacing to C varargs function
2971 @cindex varargs function intefacs
2972 @item C varargs function
2973 In C, @code{varargs} allows a function to take a variable number of
2974 arguments. There is no direct equivalent in this to Ada. One
2975 approach that can be used is to create a C wrapper for each
2976 different profile and then interface to this C wrapper. For
2977 example, to print an @code{int} value using @code{printf},
2978 create a C function @code{printfi} that takes two arguments, a
2979 pointer to a string and an int, and calls @code{printf}.
2980 Then in the Ada program, use pragma @code{Import} to
2981 interface to printfi.
2983 It may work on some platforms to directly interface to
2984 a @code{varargs} function by providing a specific Ada profile
2985 for a a particular call. However, this does not work on
2986 all platforms, since there is no guarantee that the
2987 calling sequence for a two argument normal C function
2988 is the same as for calling a @code{varargs} C function with
2989 the same two arguments.
2991 @cindex Convention Default
2996 @cindex Convention External
3002 @cindex Interfacing to C++
3003 @cindex Convention C++
3005 This stands for C++. For most purposes this is identical to C.
3006 See the separate description of the specialized GNAT pragmas relating to
3007 C++ interfacing for further details.
3010 @cindex Interfacing to Fortran
3011 @cindex Convention Fortran
3013 Data will be passed according to the conventions described
3014 in section B.5 of the Ada 95 Reference Manual.
3017 This applies to an intrinsic operation, as defined in the Ada 95
3018 Reference Manual. If a a pragma Import (Intrinsic) applies to a subprogram,
3019 this means that the body of the subprogram is provided by the compiler itself,
3020 usually by means of an efficient code sequence, and that the user does not
3021 supply an explicit body for it. In an application program, the pragma can
3022 only be applied to the following two sets of names, which the GNAT compiler
3027 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_-
3028 Arithmetic. The corresponding subprogram declaration must have
3029 two formal parameters. The
3030 first one must be a signed integer type or a modular type with a binary
3031 modulus, and the second parameter must be of type Natural.
3032 The return type must be the same as the type of the first argument. The size
3033 of this type can only be 8, 16, 32, or 64.
3034 @item binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
3035 The corresponding operator declaration must have parameters and result type
3036 that have the same root numeric type (for example, all three are long_float
3037 types). This simplifies the definition of operations that use type checking
3038 to perform dimensional checks:
3040 @smallexample @c ada
3041 type Distance is new Long_Float;
3042 type Time is new Long_Float;
3043 type Velocity is new Long_Float;
3044 function "/" (D : Distance; T : Time)
3046 pragma Import (Intrinsic, "/");
3050 This common idiom is often programmed with a generic definition and an
3051 explicit body. The pragma makes it simpler to introduce such declarations.
3052 It incurs no overhead in compilation time or code size, because it is
3053 implemented as a single machine instruction.
3059 @cindex Convention Stdcall
3061 This is relevant only to NT/Win95 implementations of GNAT,
3062 and specifies that the Stdcall calling sequence will be used, as defined
3066 @cindex Convention DLL
3068 This is equivalent to Stdcall.
3071 @cindex Convention Win32
3073 This is equivalent to Stdcall.
3077 @cindex Convention Stubbed
3079 This is a special convention that indicates that the compiler
3080 should provide a stub body that raises @code{Program_Error}.
3084 GNAT additionally provides a useful pragma @code{Convention_Identifier}
3085 that can be used to parametrize conventions and allow additional synonyms
3086 to be specified. For example if you have legacy code in which the convention
3087 identifier Fortran77 was used for Fortran, you can use the configuration
3090 @smallexample @c ada
3091 pragma Convention_Identifier (Fortran77, Fortran);
3095 And from now on the identifier Fortran77 may be used as a convention
3096 identifier (for example in an @code{Import} pragma) with the same
3099 @node Building Mixed Ada & C++ Programs
3100 @section Building Mixed Ada & C++ Programs
3103 A programmer inexperienced with mixed-language development may find that
3104 building an application containing both Ada and C++ code can be a
3105 challenge. As a matter of fact, interfacing with C++ has not been
3106 standardized in the Ada 95 Reference Manual due to the immaturity of --
3107 and lack of standards for -- C++ at the time. This section gives a few
3108 hints that should make this task easier. The first section addresses
3109 the differences regarding interfacing with C. The second section
3110 looks into the delicate problem of linking the complete application from
3111 its Ada and C++ parts. The last section gives some hints on how the GNAT
3112 run time can be adapted in order to allow inter-language dispatching
3113 with a new C++ compiler.
3116 * Interfacing to C++::
3117 * Linking a Mixed C++ & Ada Program::
3118 * A Simple Example::
3119 * Adapting the Run Time to a New C++ Compiler::
3122 @node Interfacing to C++
3123 @subsection Interfacing to C++
3126 GNAT supports interfacing with C++ compilers generating code that is
3127 compatible with the standard Application Binary Interface of the given
3131 Interfacing can be done at 3 levels: simple data, subprograms, and
3132 classes. In the first two cases, GNAT offers a specific @var{Convention
3133 CPP} that behaves exactly like @var{Convention C}. Usually, C++ mangles
3134 the names of subprograms, and currently, GNAT does not provide any help
3135 to solve the demangling problem. This problem can be addressed in two
3139 by modifying the C++ code in order to force a C convention using
3140 the @code{extern "C"} syntax.
3143 by figuring out the mangled name and use it as the Link_Name argument of
3148 Interfacing at the class level can be achieved by using the GNAT specific
3149 pragmas such as @code{CPP_Class} and @code{CPP_Virtual}. See the GNAT
3150 Reference Manual for additional information.
3152 @node Linking a Mixed C++ & Ada Program
3153 @subsection Linking a Mixed C++ & Ada Program
3156 Usually the linker of the C++ development system must be used to link
3157 mixed applications because most C++ systems will resolve elaboration
3158 issues (such as calling constructors on global class instances)
3159 transparently during the link phase. GNAT has been adapted to ease the
3160 use of a foreign linker for the last phase. Three cases can be
3165 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3166 The C++ linker can simply be called by using the C++ specific driver
3167 called @code{c++}. Note that this setup is not very common because it
3168 may involve recompiling the whole GCC tree from sources, which makes it
3169 harder to upgrade the compilation system for one language without
3170 destabilizing the other.
3175 $ gnatmake ada_unit -largs file1.o file2.o --LINK=c++
3179 Using GNAT and G++ from two different GCC installations: If both
3180 compilers are on the PATH, the previous method may be used. It is
3181 important to note that environment variables such as C_INCLUDE_PATH,
3182 GCC_EXEC_PREFIX, BINUTILS_ROOT, and GCC_ROOT will affect both compilers
3183 at the same time and may make one of the two compilers operate
3184 improperly if set during invocation of the wrong compiler. It is also
3185 very important that the linker uses the proper @file{libgcc.a} GCC
3186 library -- that is, the one from the C++ compiler installation. The
3187 implicit link command as suggested in the gnatmake command from the
3188 former example can be replaced by an explicit link command with the
3189 full-verbosity option in order to verify which library is used:
3192 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3194 If there is a problem due to interfering environment variables, it can
3195 be worked around by using an intermediate script. The following example
3196 shows the proper script to use when GNAT has not been installed at its
3197 default location and g++ has been installed at its default location:
3205 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3209 Using a non-GNU C++ compiler: The commands previously described can be
3210 used to insure that the C++ linker is used. Nonetheless, you need to add
3211 the path to libgcc explicitly, since some libraries needed by GNAT are
3212 located in this directory:
3217 CC $* `gcc -print-libgcc-file-name`
3218 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3221 Where CC is the name of the non-GNU C++ compiler.
3225 @node A Simple Example
3226 @subsection A Simple Example
3228 The following example, provided as part of the GNAT examples, shows how
3229 to achieve procedural interfacing between Ada and C++ in both
3230 directions. The C++ class A has two methods. The first method is exported
3231 to Ada by the means of an extern C wrapper function. The second method
3232 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3233 a limited record with a layout comparable to the C++ class. The Ada
3234 subprogram, in turn, calls the C++ method. So, starting from the C++
3235 main program, the process passes back and forth between the two
3239 Here are the compilation commands:
3241 $ gnatmake -c simple_cpp_interface
3244 $ gnatbind -n simple_cpp_interface
3245 $ gnatlink simple_cpp_interface -o cpp_main --LINK=$(CPLUSPLUS)
3246 -lstdc++ ex7.o cpp_main.o
3250 Here are the corresponding sources:
3258 void adainit (void);
3259 void adafinal (void);
3260 void method1 (A *t);
3282 class A : public Origin @{
3284 void method1 (void);
3285 virtual void method2 (int v);
3295 extern "C" @{ void ada_method2 (A *t, int v);@}
3297 void A::method1 (void)
3300 printf ("in A::method1, a_value = %d \n",a_value);
3304 void A::method2 (int v)
3306 ada_method2 (this, v);
3307 printf ("in A::method2, a_value = %d \n",a_value);
3314 printf ("in A::A, a_value = %d \n",a_value);
3318 @b{package} @b{body} Simple_Cpp_Interface @b{is}
3320 @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer) @b{is}
3324 @b{end} Ada_Method2;
3326 @b{end} Simple_Cpp_Interface;
3328 @b{package} Simple_Cpp_Interface @b{is}
3329 @b{type} A @b{is} @b{limited}
3334 @b{pragma} Convention (C, A);
3336 @b{procedure} Method1 (This : @b{in} @b{out} A);
3337 @b{pragma} Import (C, Method1);
3339 @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer);
3340 @b{pragma} Export (C, Ada_Method2);
3342 @b{end} Simple_Cpp_Interface;
3345 @node Adapting the Run Time to a New C++ Compiler
3346 @subsection Adapting the Run Time to a New C++ Compiler
3348 GNAT offers the capability to derive Ada 95 tagged types directly from
3349 preexisting C++ classes and . See ``Interfacing with C++'' in the
3350 @cite{GNAT Reference Manual}. The mechanism used by GNAT for achieving
3352 has been made user configurable through a GNAT library unit
3353 @code{Interfaces.CPP}. The default version of this file is adapted to
3354 the GNU C++ compiler. Internal knowledge of the virtual
3355 table layout used by the new C++ compiler is needed to configure
3356 properly this unit. The Interface of this unit is known by the compiler
3357 and cannot be changed except for the value of the constants defining the
3358 characteristics of the virtual table: CPP_DT_Prologue_Size, CPP_DT_Entry_Size,
3359 CPP_TSD_Prologue_Size, CPP_TSD_Entry_Size. Read comments in the source
3360 of this unit for more details.
3362 @node Comparison between GNAT and C/C++ Compilation Models
3363 @section Comparison between GNAT and C/C++ Compilation Models
3366 The GNAT model of compilation is close to the C and C++ models. You can
3367 think of Ada specs as corresponding to header files in C. As in C, you
3368 don't need to compile specs; they are compiled when they are used. The
3369 Ada @code{with} is similar in effect to the @code{#include} of a C
3372 One notable difference is that, in Ada, you may compile specs separately
3373 to check them for semantic and syntactic accuracy. This is not always
3374 possible with C headers because they are fragments of programs that have
3375 less specific syntactic or semantic rules.
3377 The other major difference is the requirement for running the binder,
3378 which performs two important functions. First, it checks for
3379 consistency. In C or C++, the only defense against assembling
3380 inconsistent programs lies outside the compiler, in a makefile, for
3381 example. The binder satisfies the Ada requirement that it be impossible
3382 to construct an inconsistent program when the compiler is used in normal
3385 @cindex Elaboration order control
3386 The other important function of the binder is to deal with elaboration
3387 issues. There are also elaboration issues in C++ that are handled
3388 automatically. This automatic handling has the advantage of being
3389 simpler to use, but the C++ programmer has no control over elaboration.
3390 Where @code{gnatbind} might complain there was no valid order of
3391 elaboration, a C++ compiler would simply construct a program that
3392 malfunctioned at run time.
3394 @node Comparison between GNAT and Conventional Ada Library Models
3395 @section Comparison between GNAT and Conventional Ada Library Models
3398 This section is intended to be useful to Ada programmers who have
3399 previously used an Ada compiler implementing the traditional Ada library
3400 model, as described in the Ada 95 Language Reference Manual. If you
3401 have not used such a system, please go on to the next section.
3403 @cindex GNAT library
3404 In GNAT, there is no @dfn{library} in the normal sense. Instead, the set of
3405 source files themselves acts as the library. Compiling Ada programs does
3406 not generate any centralized information, but rather an object file and
3407 a ALI file, which are of interest only to the binder and linker.
3408 In a traditional system, the compiler reads information not only from
3409 the source file being compiled, but also from the centralized library.
3410 This means that the effect of a compilation depends on what has been
3411 previously compiled. In particular:
3415 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3416 to the version of the unit most recently compiled into the library.
3419 Inlining is effective only if the necessary body has already been
3420 compiled into the library.
3423 Compiling a unit may obsolete other units in the library.
3427 In GNAT, compiling one unit never affects the compilation of any other
3428 units because the compiler reads only source files. Only changes to source
3429 files can affect the results of a compilation. In particular:
3433 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3434 to the source version of the unit that is currently accessible to the
3439 Inlining requires the appropriate source files for the package or
3440 subprogram bodies to be available to the compiler. Inlining is always
3441 effective, independent of the order in which units are complied.
3444 Compiling a unit never affects any other compilations. The editing of
3445 sources may cause previous compilations to be out of date if they
3446 depended on the source file being modified.
3450 The most important result of these differences is that order of compilation
3451 is never significant in GNAT. There is no situation in which one is
3452 required to do one compilation before another. What shows up as order of
3453 compilation requirements in the traditional Ada library becomes, in
3454 GNAT, simple source dependencies; in other words, there is only a set
3455 of rules saying what source files must be present when a file is
3459 @node Placement of temporary files
3460 @section Placement of temporary files
3461 @cindex Temporary files (user control over placement)
3464 GNAT creates temporary files in the directory designated by the environment
3465 variable @env{TMPDIR}.
3466 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3467 for detailed information on how environment variables are resolved.
3468 For most users the easiest way to make use of this feature is to simply
3469 define @env{TMPDIR} as a job level logical name).
3470 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3471 for compiler temporary files, then you can include something like the
3472 following command in your @file{LOGIN.COM} file:
3475 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3479 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3480 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3481 designated by @env{TEMP}.
3482 If none of these environment variables are defined then GNAT uses the
3483 directory designated by the logical name @code{SYS$SCRATCH:}
3484 (by default the user's home directory). If all else fails
3485 GNAT uses the current directory for temporary files.
3489 @c *************************
3490 @node Compiling Using gcc
3491 @chapter Compiling Using @code{gcc}
3494 This chapter discusses how to compile Ada programs using the @code{gcc}
3495 command. It also describes the set of switches
3496 that can be used to control the behavior of the compiler.
3498 * Compiling Programs::
3499 * Switches for gcc::
3500 * Search Paths and the Run-Time Library (RTL)::
3501 * Order of Compilation Issues::
3505 @node Compiling Programs
3506 @section Compiling Programs
3509 The first step in creating an executable program is to compile the units
3510 of the program using the @code{gcc} command. You must compile the
3515 the body file (@file{.adb}) for a library level subprogram or generic
3519 the spec file (@file{.ads}) for a library level package or generic
3520 package that has no body
3523 the body file (@file{.adb}) for a library level package
3524 or generic package that has a body
3529 You need @emph{not} compile the following files
3534 the spec of a library unit which has a body
3541 because they are compiled as part of compiling related units. GNAT
3543 when the corresponding body is compiled, and subunits when the parent is
3546 @cindex cannot generate code
3547 If you attempt to compile any of these files, you will get one of the
3548 following error messages (where fff is the name of the file you compiled):
3551 cannot generate code for file @var{fff} (package spec)
3552 to check package spec, use -gnatc
3554 cannot generate code for file @var{fff} (missing subunits)
3555 to check parent unit, use -gnatc
3557 cannot generate code for file @var{fff} (subprogram spec)
3558 to check subprogram spec, use -gnatc
3560 cannot generate code for file @var{fff} (subunit)
3561 to check subunit, use -gnatc
3565 As indicated by the above error messages, if you want to submit
3566 one of these files to the compiler to check for correct semantics
3567 without generating code, then use the @option{-gnatc} switch.
3569 The basic command for compiling a file containing an Ada unit is
3572 $ gcc -c [@var{switches}] @file{file name}
3576 where @var{file name} is the name of the Ada file (usually
3578 @file{.ads} for a spec or @file{.adb} for a body).
3581 @option{-c} switch to tell @code{gcc} to compile, but not link, the file.
3583 The result of a successful compilation is an object file, which has the
3584 same name as the source file but an extension of @file{.o} and an Ada
3585 Library Information (ALI) file, which also has the same name as the
3586 source file, but with @file{.ali} as the extension. GNAT creates these
3587 two output files in the current directory, but you may specify a source
3588 file in any directory using an absolute or relative path specification
3589 containing the directory information.
3592 @code{gcc} is actually a driver program that looks at the extensions of
3593 the file arguments and loads the appropriate compiler. For example, the
3594 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3595 These programs are in directories known to the driver program (in some
3596 configurations via environment variables you set), but need not be in
3597 your path. The @code{gcc} driver also calls the assembler and any other
3598 utilities needed to complete the generation of the required object
3601 It is possible to supply several file names on the same @code{gcc}
3602 command. This causes @code{gcc} to call the appropriate compiler for
3603 each file. For example, the following command lists three separate
3604 files to be compiled:
3607 $ gcc -c x.adb y.adb z.c
3611 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3612 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3613 The compiler generates three object files @file{x.o}, @file{y.o} and
3614 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3615 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3618 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3621 @node Switches for gcc
3622 @section Switches for @code{gcc}
3625 The @code{gcc} command accepts switches that control the
3626 compilation process. These switches are fully described in this section.
3627 First we briefly list all the switches, in alphabetical order, then we
3628 describe the switches in more detail in functionally grouped sections.
3631 * Output and Error Message Control::
3632 * Warning Message Control::
3633 * Debugging and Assertion Control::
3634 * Validity Checking::
3637 * Stack Overflow Checking::
3638 * Using gcc for Syntax Checking::
3639 * Using gcc for Semantic Checking::
3640 * Compiling Ada 83 Programs::
3641 * Character Set Control::
3642 * File Naming Control::
3643 * Subprogram Inlining Control::
3644 * Auxiliary Output Control::
3645 * Debugging Control::
3646 * Exception Handling Control::
3647 * Units to Sources Mapping Files::
3648 * Integrated Preprocessing::
3649 * Code Generation Control::
3658 @cindex @option{-b} (@code{gcc})
3659 @item -b @var{target}
3660 Compile your program to run on @var{target}, which is the name of a
3661 system configuration. You must have a GNAT cross-compiler built if
3662 @var{target} is not the same as your host system.
3665 @cindex @option{-B} (@code{gcc})
3666 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3667 from @var{dir} instead of the default location. Only use this switch
3668 when multiple versions of the GNAT compiler are available. See the
3669 @code{gcc} manual page for further details. You would normally use the
3670 @option{-b} or @option{-V} switch instead.
3673 @cindex @option{-c} (@code{gcc})
3674 Compile. Always use this switch when compiling Ada programs.
3676 Note: for some other languages when using @code{gcc}, notably in
3677 the case of C and C++, it is possible to use
3678 use @code{gcc} without a @option{-c} switch to
3679 compile and link in one step. In the case of GNAT, you
3680 cannot use this approach, because the binder must be run
3681 and @code{gcc} cannot be used to run the GNAT binder.
3685 @cindex @option{-fno-inline} (@code{gcc})
3686 Suppresses all back-end inlining, even if other optimization or inlining
3688 This includes suppression of inlining that results
3689 from the use of the pragma @code{Inline_Always}.
3690 See also @option{-gnatn} and @option{-gnatN}.
3692 @item -fno-strict-aliasing
3693 @cindex @option{-fno-strict-aliasing} (@code{gcc})
3694 Causes the compiler to avoid assumptions regarding non-aliasing
3695 of objects of different types. See section
3696 @pxref{Optimization and Strict Aliasing} for details.
3699 @cindex @option{-fstack-check} (@code{gcc})
3700 Activates stack checking.
3701 See @ref{Stack Overflow Checking} for details of the use of this option.
3704 @cindex @option{^-g^/DEBUG^} (@code{gcc})
3705 Generate debugging information. This information is stored in the object
3706 file and copied from there to the final executable file by the linker,
3707 where it can be read by the debugger. You must use the
3708 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
3711 @cindex @option{-gnat83} (@code{gcc})
3712 Enforce Ada 83 restrictions.
3715 @cindex @option{-gnata} (@code{gcc})
3716 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
3720 @cindex @option{-gnatA} (@code{gcc})
3721 Avoid processing @file{gnat.adc}. If a gnat.adc file is present,
3725 @cindex @option{-gnatb} (@code{gcc})
3726 Generate brief messages to @file{stderr} even if verbose mode set.
3729 @cindex @option{-gnatc} (@code{gcc})
3730 Check syntax and semantics only (no code generation attempted).
3733 @cindex @option{-gnatd} (@code{gcc})
3734 Specify debug options for the compiler. The string of characters after
3735 the @option{-gnatd} specify the specific debug options. The possible
3736 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
3737 compiler source file @file{debug.adb} for details of the implemented
3738 debug options. Certain debug options are relevant to applications
3739 programmers, and these are documented at appropriate points in this
3743 @cindex @option{-gnatD} (@code{gcc})
3744 Create expanded source files for source level debugging. This switch
3745 also suppress generation of cross-reference information
3746 (see @option{-gnatx}).
3748 @item -gnatec=@var{path}
3749 @cindex @option{-gnatec} (@code{gcc})
3750 Specify a configuration pragma file
3752 (the equal sign is optional)
3754 (see @ref{The Configuration Pragmas Files}).
3756 @item ^-gnateD^/DATA_PREPROCESSING=^symbol[=value]
3757 @cindex @option{-gnateD} (@code{gcc})
3758 Defines a symbol, associated with value, for preprocessing.
3759 (see @ref{Integrated Preprocessing})
3762 @cindex @option{-gnatef} (@code{gcc})
3763 Display full source path name in brief error messages.
3765 @item -gnatem=@var{path}
3766 @cindex @option{-gnatem} (@code{gcc})
3767 Specify a mapping file
3769 (the equal sign is optional)
3771 (see @ref{Units to Sources Mapping Files}).
3773 @item -gnatep=@var{file}
3774 @cindex @option{-gnatep} (@code{gcc})
3775 Specify a preprocessing data file
3777 (the equal sign is optional)
3779 (see @ref{Integrated Preprocessing}).
3782 @cindex @option{-gnatE} (@code{gcc})
3783 Full dynamic elaboration checks.
3786 @cindex @option{-gnatf} (@code{gcc})
3787 Full errors. Multiple errors per line, all undefined references, do not
3788 attempt to suppress cascaded errors.
3791 @cindex @option{-gnatF} (@code{gcc})
3792 Externals names are folded to all uppercase.
3795 @cindex @option{-gnatg} (@code{gcc})
3796 Internal GNAT implementation mode. This should not be used for
3797 applications programs, it is intended only for use by the compiler
3798 and its run-time library. For documentation, see the GNAT sources.
3799 Note that @option{-gnatg} implies @option{-gnatwu} so that warnings
3800 are generated on unreferenced entities, and all warnings are treated
3804 @cindex @option{-gnatG} (@code{gcc})
3805 List generated expanded code in source form.
3807 @item ^-gnath^/HELP^
3808 @cindex @option{^-gnath^/HELP^} (@code{gcc})
3809 Output usage information. The output is written to @file{stdout}.
3811 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
3812 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@code{gcc})
3813 Identifier character set
3815 (@var{c}=1/2/3/4/8/9/p/f/n/w).
3818 For details of the possible selections for @var{c},
3819 see @xref{Character Set Control}.
3822 @item -gnatk=@var{n}
3823 @cindex @option{-gnatk} (@code{gcc})
3824 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
3827 @cindex @option{-gnatl} (@code{gcc})
3828 Output full source listing with embedded error messages.
3831 @cindex @option{-gnatL} (@code{gcc})
3832 Use the longjmp/setjmp method for exception handling
3834 @item -gnatm=@var{n}
3835 @cindex @option{-gnatm} (@code{gcc})
3836 Limit number of detected error or warning messages to @var{n}
3837 where @var{n} is in the range 1..999_999. The default setting if
3838 no switch is given is 9999. Compilation is terminated if this
3842 @cindex @option{-gnatn} (@code{gcc})
3843 Activate inlining for subprograms for which
3844 pragma @code{inline} is specified. This inlining is performed
3845 by the GCC back-end.
3848 @cindex @option{-gnatN} (@code{gcc})
3849 Activate front end inlining for subprograms for which
3850 pragma @code{Inline} is specified. This inlining is performed
3851 by the front end and will be visible in the
3852 @option{-gnatG} output.
3853 In some cases, this has proved more effective than the back end
3854 inlining resulting from the use of
3857 @option{-gnatN} automatically implies
3858 @option{-gnatn} so it is not necessary
3859 to specify both options. There are a few cases that the back-end inlining
3860 catches that cannot be dealt with in the front-end.
3863 @cindex @option{-gnato} (@code{gcc})
3864 Enable numeric overflow checking (which is not normally enabled by
3865 default). Not that division by zero is a separate check that is not
3866 controlled by this switch (division by zero checking is on by default).
3869 @cindex @option{-gnatp} (@code{gcc})
3870 Suppress all checks.
3873 @cindex @option{-gnatP} (@code{gcc})
3874 Enable polling. This is required on some systems (notably Windows NT) to
3875 obtain asynchronous abort and asynchronous transfer of control capability.
3876 See the description of pragma Polling in the GNAT Reference Manual for
3880 @cindex @option{-gnatq} (@code{gcc})
3881 Don't quit; try semantics, even if parse errors.
3884 @cindex @option{-gnatQ} (@code{gcc})
3885 Don't quit; generate @file{ALI} and tree files even if illegalities.
3887 @item ^-gnatR[0/1/2/3[s]]^/REPRESENTATION_INFO^
3888 @cindex @option{-gnatR} (@code{gcc})
3889 Output representation information for declared types and objects.
3892 @cindex @option{-gnats} (@code{gcc})
3896 @cindex @option{-gnatS} (@code{gcc})
3897 Print package Standard.
3900 @cindex @option{-gnatt} (@code{gcc})
3901 Generate tree output file.
3903 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
3904 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@code{gcc})
3905 All compiler tables start at @var{nnn} times usual starting size.
3908 @cindex @option{-gnatu} (@code{gcc})
3909 List units for this compilation.
3912 @cindex @option{-gnatU} (@code{gcc})
3913 Tag all error messages with the unique string ``error:''
3916 @cindex @option{-gnatv} (@code{gcc})
3917 Verbose mode. Full error output with source lines to @file{stdout}.
3920 @cindex @option{-gnatV} (@code{gcc})
3921 Control level of validity checking. See separate section describing
3924 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}[,...])^
3925 @cindex @option{^-gnatw^/WARNINGS^} (@code{gcc})
3927 ^@var{xxx} is a string of option letters that^the list of options^ denotes
3928 the exact warnings that
3929 are enabled or disabled. (see @ref{Warning Message Control})
3931 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
3932 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@code{gcc})
3933 Wide character encoding method
3935 (@var{e}=n/h/u/s/e/8).
3938 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
3942 @cindex @option{-gnatx} (@code{gcc})
3943 Suppress generation of cross-reference information.
3945 @item ^-gnaty^/STYLE_CHECKS=(option,option..)^
3946 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@code{gcc})
3947 Enable built-in style checks. (see @ref{Style Checking})
3949 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
3950 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@code{gcc})
3951 Distribution stub generation and compilation
3953 (@var{m}=r/c for receiver/caller stubs).
3956 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
3957 to be generated and compiled).
3961 Use the zero cost method for exception handling
3963 @item ^-I^/SEARCH=^@var{dir}
3964 @cindex @option{^-I^/SEARCH^} (@code{gcc})
3966 Direct GNAT to search the @var{dir} directory for source files needed by
3967 the current compilation
3968 (@pxref{Search Paths and the Run-Time Library (RTL)}).
3970 @item ^-I-^/NOCURRENT_DIRECTORY^
3971 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gcc})
3973 Except for the source file named in the command line, do not look for source
3974 files in the directory containing the source file named in the command line
3975 (@pxref{Search Paths and the Run-Time Library (RTL)}).
3979 @cindex @option{-mbig-switch} (@command{gcc})
3980 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
3981 This standard gcc switch causes the compiler to use larger offsets in its
3982 jump table representation for @code{case} statements.
3983 This may result in less efficient code, but is sometimes necessary
3984 (for example on HP-UX targets)
3985 @cindex HP-UX and @option{-mbig-switch} option
3986 in order to compile large and/or nested @code{case} statements.
3989 @cindex @option{-o} (@code{gcc})
3990 This switch is used in @code{gcc} to redirect the generated object file
3991 and its associated ALI file. Beware of this switch with GNAT, because it may
3992 cause the object file and ALI file to have different names which in turn
3993 may confuse the binder and the linker.
3997 @cindex @option{-nostdinc} (@command{gcc})
3998 Inhibit the search of the default location for the GNAT Run Time
3999 Library (RTL) source files.
4002 @cindex @option{-nostdlib} (@command{gcc})
4003 Inhibit the search of the default location for the GNAT Run Time
4004 Library (RTL) ALI files.
4008 @cindex @option{-O} (@code{gcc})
4009 @var{n} controls the optimization level.
4013 No optimization, the default setting if no @option{-O} appears
4016 Normal optimization, the default if you specify @option{-O} without
4020 Extensive optimization
4023 Extensive optimization with automatic inlining of subprograms not
4024 specified by pragma @code{Inline}. This applies only to
4025 inlining within a unit. For details on control of inlining
4026 see @xref{Subprogram Inlining Control}.
4032 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4033 Equivalent to @option{/OPTIMIZE=NONE}.
4034 This is the default behavior in the absence of an @option{/OPTMIZE}
4037 @item /OPTIMIZE[=(keyword[,...])]
4038 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4039 Selects the level of optimization for your program. The supported
4040 keywords are as follows:
4043 Perform most optimizations, including those that
4045 This is the default if the @option{/OPTMIZE} qualifier is supplied
4046 without keyword options.
4049 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4052 Perform some optimizations, but omit ones that are costly.
4055 Same as @code{SOME}.
4058 Full optimization, and also attempt automatic inlining of small
4059 subprograms within a unit even when pragma @code{Inline}
4060 is not specified (@pxref{Inlining of Subprograms}).
4063 Try to unroll loops. This keyword may be specified together with
4064 any keyword above other than @code{NONE}. Loop unrolling
4065 usually, but not always, improves the performance of programs.
4070 @item -pass-exit-codes
4071 @cindex @option{-pass-exit-codes} (@code{gcc})
4072 Catch exit codes from the compiler and use the most meaningful as
4076 @item --RTS=@var{rts-path}
4077 @cindex @option{--RTS} (@code{gcc})
4078 Specifies the default location of the runtime library. Same meaning as the
4079 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
4082 @cindex @option{^-S^/ASM^} (@code{gcc})
4083 ^Used in place of @option{-c} to^Used to^
4084 cause the assembler source file to be
4085 generated, using @file{^.s^.S^} as the extension,
4086 instead of the object file.
4087 This may be useful if you need to examine the generated assembly code.
4090 @cindex @option{^-v^/VERBOSE^} (@code{gcc})
4091 Show commands generated by the @code{gcc} driver. Normally used only for
4092 debugging purposes or if you need to be sure what version of the
4093 compiler you are executing.
4097 @cindex @option{-V} (@code{gcc})
4098 Execute @var{ver} version of the compiler. This is the @code{gcc}
4099 version, not the GNAT version.
4105 You may combine a sequence of GNAT switches into a single switch. For
4106 example, the combined switch
4108 @cindex Combining GNAT switches
4114 is equivalent to specifying the following sequence of switches:
4117 -gnato -gnatf -gnati3
4122 @c NEED TO CHECK THIS FOR VMS
4125 The following restrictions apply to the combination of switches
4130 The switch @option{-gnatc} if combined with other switches must come
4131 first in the string.
4134 The switch @option{-gnats} if combined with other switches must come
4135 first in the string.
4139 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4140 may not be combined with any other switches.
4144 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4145 switch), then all further characters in the switch are interpreted
4146 as style modifiers (see description of @option{-gnaty}).
4149 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4150 switch), then all further characters in the switch are interpreted
4151 as debug flags (see description of @option{-gnatd}).
4154 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4155 switch), then all further characters in the switch are interpreted
4156 as warning mode modifiers (see description of @option{-gnatw}).
4159 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4160 switch), then all further characters in the switch are interpreted
4161 as validity checking options (see description of @option{-gnatV}).
4166 @node Output and Error Message Control
4167 @subsection Output and Error Message Control
4171 The standard default format for error messages is called ``brief format''.
4172 Brief format messages are written to @file{stderr} (the standard error
4173 file) and have the following form:
4176 e.adb:3:04: Incorrect spelling of keyword "function"
4177 e.adb:4:20: ";" should be "is"
4181 The first integer after the file name is the line number in the file,
4182 and the second integer is the column number within the line.
4183 @code{glide} can parse the error messages
4184 and point to the referenced character.
4185 The following switches provide control over the error message
4191 @cindex @option{-gnatv} (@code{gcc})
4194 The v stands for verbose.
4196 The effect of this setting is to write long-format error
4197 messages to @file{stdout} (the standard output file.
4198 The same program compiled with the
4199 @option{-gnatv} switch would generate:
4203 3. funcion X (Q : Integer)
4205 >>> Incorrect spelling of keyword "function"
4208 >>> ";" should be "is"
4213 The vertical bar indicates the location of the error, and the @samp{>>>}
4214 prefix can be used to search for error messages. When this switch is
4215 used the only source lines output are those with errors.
4218 @cindex @option{-gnatl} (@code{gcc})
4220 The @code{l} stands for list.
4222 This switch causes a full listing of
4223 the file to be generated. The output might look as follows:
4229 3. funcion X (Q : Integer)
4231 >>> Incorrect spelling of keyword "function"
4234 >>> ";" should be "is"
4246 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4247 standard output is redirected, a brief summary is written to
4248 @file{stderr} (standard error) giving the number of error messages and
4249 warning messages generated.
4252 @cindex @option{-gnatU} (@code{gcc})
4253 This switch forces all error messages to be preceded by the unique
4254 string ``error:''. This means that error messages take a few more
4255 characters in space, but allows easy searching for and identification
4259 @cindex @option{-gnatb} (@code{gcc})
4261 The @code{b} stands for brief.
4263 This switch causes GNAT to generate the
4264 brief format error messages to @file{stderr} (the standard error
4265 file) as well as the verbose
4266 format message or full listing (which as usual is written to
4267 @file{stdout} (the standard output file).
4269 @item -gnatm^^=^@var{n}
4270 @cindex @option{-gnatm} (@code{gcc})
4272 The @code{m} stands for maximum.
4274 @var{n} is a decimal integer in the
4275 range of 1 to 999 and limits the number of error messages to be
4276 generated. For example, using @option{-gnatm2} might yield
4279 e.adb:3:04: Incorrect spelling of keyword "function"
4280 e.adb:5:35: missing ".."
4281 fatal error: maximum errors reached
4282 compilation abandoned
4286 @cindex @option{-gnatf} (@code{gcc})
4287 @cindex Error messages, suppressing
4289 The @code{f} stands for full.
4291 Normally, the compiler suppresses error messages that are likely to be
4292 redundant. This switch causes all error
4293 messages to be generated. In particular, in the case of
4294 references to undefined variables. If a given variable is referenced
4295 several times, the normal format of messages is
4297 e.adb:7:07: "V" is undefined (more references follow)
4301 where the parenthetical comment warns that there are additional
4302 references to the variable @code{V}. Compiling the same program with the
4303 @option{-gnatf} switch yields
4306 e.adb:7:07: "V" is undefined
4307 e.adb:8:07: "V" is undefined
4308 e.adb:8:12: "V" is undefined
4309 e.adb:8:16: "V" is undefined
4310 e.adb:9:07: "V" is undefined
4311 e.adb:9:12: "V" is undefined
4315 The @option{-gnatf} switch also generates additional information for
4316 some error messages. Some examples are:
4320 Full details on entities not available in high integrity mode
4322 Details on possibly non-portable unchecked conversion
4324 List possible interpretations for ambiguous calls
4326 Additional details on incorrect parameters
4331 @cindex @option{-gnatq} (@code{gcc})
4333 The @code{q} stands for quit (really ``don't quit'').
4335 In normal operation mode, the compiler first parses the program and
4336 determines if there are any syntax errors. If there are, appropriate
4337 error messages are generated and compilation is immediately terminated.
4339 GNAT to continue with semantic analysis even if syntax errors have been
4340 found. This may enable the detection of more errors in a single run. On
4341 the other hand, the semantic analyzer is more likely to encounter some
4342 internal fatal error when given a syntactically invalid tree.
4345 @cindex @option{-gnatQ} (@code{gcc})
4346 In normal operation mode, the @file{ALI} file is not generated if any
4347 illegalities are detected in the program. The use of @option{-gnatQ} forces
4348 generation of the @file{ALI} file. This file is marked as being in
4349 error, so it cannot be used for binding purposes, but it does contain
4350 reasonably complete cross-reference information, and thus may be useful
4351 for use by tools (e.g. semantic browsing tools or integrated development
4352 environments) that are driven from the @file{ALI} file. This switch
4353 implies @option{-gnatq}, since the semantic phase must be run to get a
4354 meaningful ALI file.
4356 In addition, if @option{-gnatt} is also specified, then the tree file is
4357 generated even if there are illegalities. It may be useful in this case
4358 to also specify @option{-gnatq} to ensure that full semantic processing
4359 occurs. The resulting tree file can be processed by ASIS, for the purpose
4360 of providing partial information about illegal units, but if the error
4361 causes the tree to be badly malformed, then ASIS may crash during the
4364 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4365 being in error, @code{gnatmake} will attempt to recompile the source when it
4366 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4368 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4369 since ALI files are never generated if @option{-gnats} is set.
4374 @node Warning Message Control
4375 @subsection Warning Message Control
4376 @cindex Warning messages
4378 In addition to error messages, which correspond to illegalities as defined
4379 in the Ada 95 Reference Manual, the compiler detects two kinds of warning
4382 First, the compiler considers some constructs suspicious and generates a
4383 warning message to alert you to a possible error. Second, if the
4384 compiler detects a situation that is sure to raise an exception at
4385 run time, it generates a warning message. The following shows an example
4386 of warning messages:
4388 e.adb:4:24: warning: creation of object may raise Storage_Error
4389 e.adb:10:17: warning: static value out of range
4390 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4394 GNAT considers a large number of situations as appropriate
4395 for the generation of warning messages. As always, warnings are not
4396 definite indications of errors. For example, if you do an out-of-range
4397 assignment with the deliberate intention of raising a
4398 @code{Constraint_Error} exception, then the warning that may be
4399 issued does not indicate an error. Some of the situations for which GNAT
4400 issues warnings (at least some of the time) are given in the following
4401 list. This list is not complete, and new warnings are often added to
4402 subsequent versions of GNAT. The list is intended to give a general idea
4403 of the kinds of warnings that are generated.
4407 Possible infinitely recursive calls
4410 Out-of-range values being assigned
4413 Possible order of elaboration problems
4419 Fixed-point type declarations with a null range
4422 Variables that are never assigned a value
4425 Variables that are referenced before being initialized
4428 Task entries with no corresponding @code{accept} statement
4431 Duplicate accepts for the same task entry in a @code{select}
4434 Objects that take too much storage
4437 Unchecked conversion between types of differing sizes
4440 Missing @code{return} statement along some execution path in a function
4443 Incorrect (unrecognized) pragmas
4446 Incorrect external names
4449 Allocation from empty storage pool
4452 Potentially blocking operation in protected type
4455 Suspicious parenthesization of expressions
4458 Mismatching bounds in an aggregate
4461 Attempt to return local value by reference
4465 Premature instantiation of a generic body
4468 Attempt to pack aliased components
4471 Out of bounds array subscripts
4474 Wrong length on string assignment
4477 Violations of style rules if style checking is enabled
4480 Unused @code{with} clauses
4483 @code{Bit_Order} usage that does not have any effect
4486 @code{Standard.Duration} used to resolve universal fixed expression
4489 Dereference of possibly null value
4492 Declaration that is likely to cause storage error
4495 Internal GNAT unit @code{with}'ed by application unit
4498 Values known to be out of range at compile time
4501 Unreferenced labels and variables
4504 Address overlays that could clobber memory
4507 Unexpected initialization when address clause present
4510 Bad alignment for address clause
4513 Useless type conversions
4516 Redundant assignment statements and other redundant constructs
4519 Useless exception handlers
4522 Accidental hiding of name by child unit
4526 Access before elaboration detected at compile time
4529 A range in a @code{for} loop that is known to be null or might be null
4534 The following switches are available to control the handling of
4540 @emph{Activate all optional errors.}
4541 @cindex @option{-gnatwa} (@code{gcc})
4542 This switch activates most optional warning messages, see remaining list
4543 in this section for details on optional warning messages that can be
4544 individually controlled. The warnings that are not turned on by this
4546 @option{-gnatwd} (implicit dereferencing),
4547 @option{-gnatwh} (hiding),
4548 and @option{-gnatwl} (elaboration warnings).
4549 All other optional warnings are turned on.
4552 @emph{Suppress all optional errors.}
4553 @cindex @option{-gnatwA} (@code{gcc})
4554 This switch suppresses all optional warning messages, see remaining list
4555 in this section for details on optional warning messages that can be
4556 individually controlled.
4559 @emph{Activate warnings on conditionals.}
4560 @cindex @option{-gnatwc} (@code{gcc})
4561 @cindex Conditionals, constant
4562 This switch activates warnings for conditional expressions used in
4563 tests that are known to be True or False at compile time. The default
4564 is that such warnings are not generated.
4565 Note that this warning does
4566 not get issued for the use of boolean variables or constants whose
4567 values are known at compile time, since this is a standard technique
4568 for conditional compilation in Ada, and this would generate too many
4569 ``false positive'' warnings.
4570 This warning can also be turned on using @option{-gnatwa}.
4573 @emph{Suppress warnings on conditionals.}
4574 @cindex @option{-gnatwC} (@code{gcc})
4575 This switch suppresses warnings for conditional expressions used in
4576 tests that are known to be True or False at compile time.
4579 @emph{Activate warnings on implicit dereferencing.}
4580 @cindex @option{-gnatwd} (@code{gcc})
4581 If this switch is set, then the use of a prefix of an access type
4582 in an indexed component, slice, or selected component without an
4583 explicit @code{.all} will generate a warning. With this warning
4584 enabled, access checks occur only at points where an explicit
4585 @code{.all} appears in the source code (assuming no warnings are
4586 generated as a result of this switch). The default is that such
4587 warnings are not generated.
4588 Note that @option{-gnatwa} does not affect the setting of
4589 this warning option.
4592 @emph{Suppress warnings on implicit dereferencing.}
4593 @cindex @option{-gnatwD} (@code{gcc})
4594 @cindex Implicit dereferencing
4595 @cindex Dereferencing, implicit
4596 This switch suppresses warnings for implicit dereferences in
4597 indexed components, slices, and selected components.
4600 @emph{Treat warnings as errors.}
4601 @cindex @option{-gnatwe} (@code{gcc})
4602 @cindex Warnings, treat as error
4603 This switch causes warning messages to be treated as errors.
4604 The warning string still appears, but the warning messages are counted
4605 as errors, and prevent the generation of an object file.
4608 @emph{Activate warnings on unreferenced formals.}
4609 @cindex @option{-gnatwf} (@code{gcc})
4610 @cindex Formals, unreferenced
4611 This switch causes a warning to be generated if a formal parameter
4612 is not referenced in the body of the subprogram. This warning can
4613 also be turned on using @option{-gnatwa} or @option{-gnatwu}.
4616 @emph{Suppress warnings on unreferenced formals.}
4617 @cindex @option{-gnatwF} (@code{gcc})
4618 This switch suppresses warnings for unreferenced formal
4619 parameters. Note that the
4620 combination @option{-gnatwu} followed by @option{-gnatwF} has the
4621 effect of warning on unreferenced entities other than subprogram
4625 @emph{Activate warnings on unrecognized pragmas.}
4626 @cindex @option{-gnatwg} (@code{gcc})
4627 @cindex Pragmas, unrecognized
4628 This switch causes a warning to be generated if an unrecognized
4629 pragma is encountered. Apart from issuing this warning, the
4630 pragma is ignored and has no effect. This warning can
4631 also be turned on using @option{-gnatwa}. The default
4632 is that such warnings are issued (satisfying the Ada Reference
4633 Manual requirement that such warnings appear).
4636 @emph{Suppress warnings on unrecognized pragmas.}
4637 @cindex @option{-gnatwG} (@code{gcc})
4638 This switch suppresses warnings for unrecognized pragmas.
4641 @emph{Activate warnings on hiding.}
4642 @cindex @option{-gnatwh} (@code{gcc})
4643 @cindex Hiding of Declarations
4644 This switch activates warnings on hiding declarations.
4645 A declaration is considered hiding
4646 if it is for a non-overloadable entity, and it declares an entity with the
4647 same name as some other entity that is directly or use-visible. The default
4648 is that such warnings are not generated.
4649 Note that @option{-gnatwa} does not affect the setting of this warning option.
4652 @emph{Suppress warnings on hiding.}
4653 @cindex @option{-gnatwH} (@code{gcc})
4654 This switch suppresses warnings on hiding declarations.
4657 @emph{Activate warnings on implementation units.}
4658 @cindex @option{-gnatwi} (@code{gcc})
4659 This switch activates warnings for a @code{with} of an internal GNAT
4660 implementation unit, defined as any unit from the @code{Ada},
4661 @code{Interfaces}, @code{GNAT},
4662 ^^@code{DEC},^ or @code{System}
4663 hierarchies that is not
4664 documented in either the Ada Reference Manual or the GNAT
4665 Programmer's Reference Manual. Such units are intended only
4666 for internal implementation purposes and should not be @code{with}'ed
4667 by user programs. The default is that such warnings are generated
4668 This warning can also be turned on using @option{-gnatwa}.
4671 @emph{Disable warnings on implementation units.}
4672 @cindex @option{-gnatwI} (@code{gcc})
4673 This switch disables warnings for a @code{with} of an internal GNAT
4674 implementation unit.
4677 @emph{Activate warnings on obsolescent features (Annex J).}
4678 @cindex @option{-gnatwj} (@code{gcc})
4679 @cindex Features, obsolescent
4680 @cindex Obsolescent features
4681 If this warning option is activated, then warnings are generated for
4682 calls to subprograms marked with @code{pragma Obsolescent} and
4683 for use of features in Annex J of the Ada Reference Manual. In the
4684 case of Annex J, not all features are flagged. In particular use
4685 of the renamed packages (like @code{Text_IO}) and use of package
4686 @code{ASCII} are not flagged, since these are very common and
4687 would generate many annoying positive warnings. The default is that
4688 such warnings are not generated.
4691 @emph{Suppress warnings on obsolescent features (Annex J).}
4692 @cindex @option{-gnatwJ} (@code{gcc})
4693 This switch disables warnings on use of obsolescent features.
4696 @emph{Activate warnings on variables that could be constants.}
4697 @cindex @option{-gnatwk} (@code{gcc})
4698 This switch activates warnings for variables that are initialized but
4699 never modified, and then could be declared constants.
4702 @emph{Suppress warnings on variables that could be constants.}
4703 @cindex @option{-gnatwK} (@code{gcc})
4704 This switch disables warnings on variables that could be declared constants.
4707 @emph{Activate warnings for missing elaboration pragmas.}
4708 @cindex @option{-gnatwl} (@code{gcc})
4709 @cindex Elaboration, warnings
4710 This switch activates warnings on missing
4711 @code{pragma Elaborate_All} statements.
4712 See the section in this guide on elaboration checking for details on
4713 when such pragma should be used. Warnings are also generated if you
4714 are using the static mode of elaboration, and a @code{pragma Elaborate}
4715 is encountered. The default is that such warnings
4717 This warning is not automatically turned on by the use of @option{-gnatwa}.
4720 @emph{Suppress warnings for missing elaboration pragmas.}
4721 @cindex @option{-gnatwL} (@code{gcc})
4722 This switch suppresses warnings on missing pragma Elaborate_All statements.
4723 See the section in this guide on elaboration checking for details on
4724 when such pragma should be used.
4727 @emph{Activate warnings on modified but unreferenced variables.}
4728 @cindex @option{-gnatwm} (@code{gcc})
4729 This switch activates warnings for variables that are assigned (using
4730 an initialization value or with one or more assignment statements) but
4731 whose value is never read. The warning is suppressed for volatile
4732 variables and also for variables that are renamings of other variables
4733 or for which an address clause is given.
4734 This warning can also be turned on using @option{-gnatwa}.
4737 @emph{Disable warnings on modified but unreferenced variables.}
4738 @cindex @option{-gnatwM} (@code{gcc})
4739 This switch disables warnings for variables that are assigned or
4740 initialized, but never read.
4743 @emph{Set normal warnings mode.}
4744 @cindex @option{-gnatwn} (@code{gcc})
4745 This switch sets normal warning mode, in which enabled warnings are
4746 issued and treated as warnings rather than errors. This is the default
4747 mode. the switch @option{-gnatwn} can be used to cancel the effect of
4748 an explicit @option{-gnatws} or
4749 @option{-gnatwe}. It also cancels the effect of the
4750 implicit @option{-gnatwe} that is activated by the
4751 use of @option{-gnatg}.
4754 @emph{Activate warnings on address clause overlays.}
4755 @cindex @option{-gnatwo} (@code{gcc})
4756 @cindex Address Clauses, warnings
4757 This switch activates warnings for possibly unintended initialization
4758 effects of defining address clauses that cause one variable to overlap
4759 another. The default is that such warnings are generated.
4760 This warning can also be turned on using @option{-gnatwa}.
4763 @emph{Suppress warnings on address clause overlays.}
4764 @cindex @option{-gnatwO} (@code{gcc})
4765 This switch suppresses warnings on possibly unintended initialization
4766 effects of defining address clauses that cause one variable to overlap
4770 @emph{Activate warnings on ineffective pragma Inlines.}
4771 @cindex @option{-gnatwp} (@code{gcc})
4772 @cindex Inlining, warnings
4773 This switch activates warnings for failure of front end inlining
4774 (activated by @option{-gnatN}) to inline a particular call. There are
4775 many reasons for not being able to inline a call, including most
4776 commonly that the call is too complex to inline.
4777 This warning can also be turned on using @option{-gnatwa}.
4780 @emph{Suppress warnings on ineffective pragma Inlines.}
4781 @cindex @option{-gnatwP} (@code{gcc})
4782 This switch suppresses warnings on ineffective pragma Inlines. If the
4783 inlining mechanism cannot inline a call, it will simply ignore the
4787 @emph{Activate warnings on redundant constructs.}
4788 @cindex @option{-gnatwr} (@code{gcc})
4789 This switch activates warnings for redundant constructs. The following
4790 is the current list of constructs regarded as redundant:
4791 This warning can also be turned on using @option{-gnatwa}.
4795 Assignment of an item to itself.
4797 Type conversion that converts an expression to its own type.
4799 Use of the attribute @code{Base} where @code{typ'Base} is the same
4802 Use of pragma @code{Pack} when all components are placed by a record
4803 representation clause.
4805 Exception handler containing only a reraise statement (raise with no
4806 operand) which has no effect.
4808 Use of the operator abs on an operand that is known at compile time
4811 Use of an unnecessary extra level of parentheses (C-style) around conditions
4812 in @code{if} statements, @code{while} statements and @code{exit} statements.
4814 Comparison of boolean expressions to an explicit True value.
4818 @emph{Suppress warnings on redundant constructs.}
4819 @cindex @option{-gnatwR} (@code{gcc})
4820 This switch suppresses warnings for redundant constructs.
4823 @emph{Suppress all warnings.}
4824 @cindex @option{-gnatws} (@code{gcc})
4825 This switch completely suppresses the
4826 output of all warning messages from the GNAT front end.
4827 Note that it does not suppress warnings from the @code{gcc} back end.
4828 To suppress these back end warnings as well, use the switch @option{-w}
4829 in addition to @option{-gnatws}.
4832 @emph{Activate warnings on unused entities.}
4833 @cindex @option{-gnatwu} (@code{gcc})
4834 This switch activates warnings to be generated for entities that
4835 are declared but not referenced, and for units that are @code{with}'ed
4837 referenced. In the case of packages, a warning is also generated if
4838 no entities in the package are referenced. This means that if the package
4839 is referenced but the only references are in @code{use}
4840 clauses or @code{renames}
4841 declarations, a warning is still generated. A warning is also generated
4842 for a generic package that is @code{with}'ed but never instantiated.
4843 In the case where a package or subprogram body is compiled, and there
4844 is a @code{with} on the corresponding spec
4845 that is only referenced in the body,
4846 a warning is also generated, noting that the
4847 @code{with} can be moved to the body. The default is that
4848 such warnings are not generated.
4849 This switch also activates warnings on unreferenced formals
4850 (it is includes the effect of @option{-gnatwf}).
4851 This warning can also be turned on using @option{-gnatwa}.
4854 @emph{Suppress warnings on unused entities.}
4855 @cindex @option{-gnatwU} (@code{gcc})
4856 This switch suppresses warnings for unused entities and packages.
4857 It also turns off warnings on unreferenced formals (and thus includes
4858 the effect of @option{-gnatwF}).
4861 @emph{Activate warnings on unassigned variables.}
4862 @cindex @option{-gnatwv} (@code{gcc})
4863 @cindex Unassigned variable warnings
4864 This switch activates warnings for access to variables which
4865 may not be properly initialized. The default is that
4866 such warnings are generated.
4869 @emph{Suppress warnings on unassigned variables.}
4870 @cindex @option{-gnatwV} (@code{gcc})
4871 This switch suppresses warnings for access to variables which
4872 may not be properly initialized.
4875 @emph{Activate warnings on Export/Import pragmas.}
4876 @cindex @option{-gnatwx} (@code{gcc})
4877 @cindex Export/Import pragma warnings
4878 This switch activates warnings on Export/Import pragmas when
4879 the compiler detects a possible conflict between the Ada and
4880 foreign language calling sequences. For example, the use of
4881 default parameters in a convention C procedure is dubious
4882 because the C compiler cannot supply the proper default, so
4883 a warning is issued. The default is that such warnings are
4887 @emph{Suppress warnings on Export/Import pragmas.}
4888 @cindex @option{-gnatwX} (@code{gcc})
4889 This switch suppresses warnings on Export/Import pragmas.
4890 The sense of this is that you are telling the compiler that
4891 you know what you are doing in writing the pragma, and it
4892 should not complain at you.
4895 @emph{Activate warnings on unchecked conversions.}
4896 @cindex @option{-gnatwz} (@code{gcc})
4897 @cindex Unchecked_Conversion warnings
4898 This switch activates warnings for unchecked conversions
4899 where the types are known at compile time to have different
4901 is that such warnings are generated.
4904 @emph{Suppress warnings on unchecked conversions.}
4905 @cindex @option{-gnatwZ} (@code{gcc})
4906 This switch suppresses warnings for unchecked conversions
4907 where the types are known at compile time to have different
4910 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
4911 @cindex @option{-Wuninitialized}
4912 The warnings controlled by the @option{-gnatw} switch are generated by the
4913 front end of the compiler. In some cases, the @option{^gcc^GCC^} back end
4914 can provide additional warnings. One such useful warning is provided by
4915 @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^}. This must be used in
4916 conjunction with tunrning on optimization mode. This causes the flow
4917 analysis circuits of the back end optimizer to output additional
4918 warnings about uninitialized variables.
4920 @item ^-w^/NO_BACK_END_WARNINGS^
4922 This switch suppresses warnings from the @option{^gcc^GCC^} back end. It may
4923 be used in conjunction with @option{-gnatws} to ensure that all warnings
4924 are suppressed during the entire compilation process.
4930 A string of warning parameters can be used in the same parameter. For example:
4937 will turn on all optional warnings except for elaboration pragma warnings,
4938 and also specify that warnings should be treated as errors.
4940 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
4966 @node Debugging and Assertion Control
4967 @subsection Debugging and Assertion Control
4971 @cindex @option{-gnata} (@code{gcc})
4977 The pragmas @code{Assert} and @code{Debug} normally have no effect and
4978 are ignored. This switch, where @samp{a} stands for assert, causes
4979 @code{Assert} and @code{Debug} pragmas to be activated.
4981 The pragmas have the form:
4985 @b{pragma} Assert (@var{Boolean-expression} [,
4986 @var{static-string-expression}])
4987 @b{pragma} Debug (@var{procedure call})
4992 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
4993 If the result is @code{True}, the pragma has no effect (other than
4994 possible side effects from evaluating the expression). If the result is
4995 @code{False}, the exception @code{Assert_Failure} declared in the package
4996 @code{System.Assertions} is
4997 raised (passing @var{static-string-expression}, if present, as the
4998 message associated with the exception). If no string expression is
4999 given the default is a string giving the file name and line number
5002 The @code{Debug} pragma causes @var{procedure} to be called. Note that
5003 @code{pragma Debug} may appear within a declaration sequence, allowing
5004 debugging procedures to be called between declarations.
5007 @item /DEBUG[=debug-level]
5009 Specifies how much debugging information is to be included in
5010 the resulting object file where 'debug-level' is one of the following:
5013 Include both debugger symbol records and traceback
5015 This is the default setting.
5017 Include both debugger symbol records and traceback in
5020 Excludes both debugger symbol records and traceback
5021 the object file. Same as /NODEBUG.
5023 Includes only debugger symbol records in the object
5024 file. Note that this doesn't include traceback information.
5029 @node Validity Checking
5030 @subsection Validity Checking
5031 @findex Validity Checking
5034 The Ada 95 Reference Manual has specific requirements for checking
5035 for invalid values. In particular, RM 13.9.1 requires that the
5036 evaluation of invalid values (for example from unchecked conversions),
5037 not result in erroneous execution. In GNAT, the result of such an
5038 evaluation in normal default mode is to either use the value
5039 unmodified, or to raise Constraint_Error in those cases where use
5040 of the unmodified value would cause erroneous execution. The cases
5041 where unmodified values might lead to erroneous execution are case
5042 statements (where a wild jump might result from an invalid value),
5043 and subscripts on the left hand side (where memory corruption could
5044 occur as a result of an invalid value).
5046 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5049 The @code{x} argument is a string of letters that
5050 indicate validity checks that are performed or not performed in addition
5051 to the default checks described above.
5054 The options allowed for this qualifier
5055 indicate validity checks that are performed or not performed in addition
5056 to the default checks described above.
5063 @emph{All validity checks.}
5064 @cindex @option{-gnatVa} (@code{gcc})
5065 All validity checks are turned on.
5067 That is, @option{-gnatVa} is
5068 equivalent to @option{gnatVcdfimorst}.
5072 @emph{Validity checks for copies.}
5073 @cindex @option{-gnatVc} (@code{gcc})
5074 The right hand side of assignments, and the initializing values of
5075 object declarations are validity checked.
5078 @emph{Default (RM) validity checks.}
5079 @cindex @option{-gnatVd} (@code{gcc})
5080 Some validity checks are done by default following normal Ada semantics
5082 A check is done in case statements that the expression is within the range
5083 of the subtype. If it is not, Constraint_Error is raised.
5084 For assignments to array components, a check is done that the expression used
5085 as index is within the range. If it is not, Constraint_Error is raised.
5086 Both these validity checks may be turned off using switch @option{-gnatVD}.
5087 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5088 switch @option{-gnatVd} will leave the checks turned on.
5089 Switch @option{-gnatVD} should be used only if you are sure that all such
5090 expressions have valid values. If you use this switch and invalid values
5091 are present, then the program is erroneous, and wild jumps or memory
5092 overwriting may occur.
5095 @emph{Validity checks for floating-point values.}
5096 @cindex @option{-gnatVf} (@code{gcc})
5097 In the absence of this switch, validity checking occurs only for discrete
5098 values. If @option{-gnatVf} is specified, then validity checking also applies
5099 for floating-point values, and NaN's and infinities are considered invalid,
5100 as well as out of range values for constrained types. Note that this means
5101 that standard @code{IEEE} infinity mode is not allowed. The exact contexts
5102 in which floating-point values are checked depends on the setting of other
5103 options. For example,
5104 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5105 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5106 (the order does not matter) specifies that floating-point parameters of mode
5107 @code{in} should be validity checked.
5110 @emph{Validity checks for @code{in} mode parameters}
5111 @cindex @option{-gnatVi} (@code{gcc})
5112 Arguments for parameters of mode @code{in} are validity checked in function
5113 and procedure calls at the point of call.
5116 @emph{Validity checks for @code{in out} mode parameters.}
5117 @cindex @option{-gnatVm} (@code{gcc})
5118 Arguments for parameters of mode @code{in out} are validity checked in
5119 procedure calls at the point of call. The @code{'m'} here stands for
5120 modify, since this concerns parameters that can be modified by the call.
5121 Note that there is no specific option to test @code{out} parameters,
5122 but any reference within the subprogram will be tested in the usual
5123 manner, and if an invalid value is copied back, any reference to it
5124 will be subject to validity checking.
5127 @emph{No validity checks.}
5128 @cindex @option{-gnatVn} (@code{gcc})
5129 This switch turns off all validity checking, including the default checking
5130 for case statements and left hand side subscripts. Note that the use of
5131 the switch @option{-gnatp} suppresses all run-time checks, including
5132 validity checks, and thus implies @option{-gnatVn}. When this switch
5133 is used, it cancels any other @option{-gnatV} previously issued.
5136 @emph{Validity checks for operator and attribute operands.}
5137 @cindex @option{-gnatVo} (@code{gcc})
5138 Arguments for predefined operators and attributes are validity checked.
5139 This includes all operators in package @code{Standard},
5140 the shift operators defined as intrinsic in package @code{Interfaces}
5141 and operands for attributes such as @code{Pos}. Checks are also made
5142 on individual component values for composite comparisons.
5145 @emph{Validity checks for parameters.}
5146 @cindex @option{-gnatVp} (@code{gcc})
5147 This controls the treatment of parameters within a subprogram (as opposed
5148 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5149 of parameters on a call. If either of these call options is used, then
5150 normally an assumption is made within a subprogram that the input arguments
5151 have been validity checking at the point of call, and do not need checking
5152 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5153 is not made, and parameters are not assumed to be valid, so their validity
5154 will be checked (or rechecked) within the subprogram.
5157 @emph{Validity checks for function returns.}
5158 @cindex @option{-gnatVr} (@code{gcc})
5159 The expression in @code{return} statements in functions is validity
5163 @emph{Validity checks for subscripts.}
5164 @cindex @option{-gnatVs} (@code{gcc})
5165 All subscripts expressions are checked for validity, whether they appear
5166 on the right side or left side (in default mode only left side subscripts
5167 are validity checked).
5170 @emph{Validity checks for tests.}
5171 @cindex @option{-gnatVt} (@code{gcc})
5172 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
5173 statements are checked, as well as guard expressions in entry calls.
5178 The @option{-gnatV} switch may be followed by
5179 ^a string of letters^a list of options^
5180 to turn on a series of validity checking options.
5182 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
5183 specifies that in addition to the default validity checking, copies and
5184 function return expressions are to be validity checked.
5185 In order to make it easier
5186 to specify the desired combination of effects,
5188 the upper case letters @code{CDFIMORST} may
5189 be used to turn off the corresponding lower case option.
5192 the prefix @code{NO} on an option turns off the corresponding validity
5195 @item @code{NOCOPIES}
5196 @item @code{NODEFAULT}
5197 @item @code{NOFLOATS}
5198 @item @code{NOIN_PARAMS}
5199 @item @code{NOMOD_PARAMS}
5200 @item @code{NOOPERANDS}
5201 @item @code{NORETURNS}
5202 @item @code{NOSUBSCRIPTS}
5203 @item @code{NOTESTS}
5207 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
5208 turns on all validity checking options except for
5209 checking of @code{@b{in out}} procedure arguments.
5211 The specification of additional validity checking generates extra code (and
5212 in the case of @option{-gnatVa} the code expansion can be substantial.
5213 However, these additional checks can be very useful in detecting
5214 uninitialized variables, incorrect use of unchecked conversion, and other
5215 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
5216 is useful in conjunction with the extra validity checking, since this
5217 ensures that wherever possible uninitialized variables have invalid values.
5219 See also the pragma @code{Validity_Checks} which allows modification of
5220 the validity checking mode at the program source level, and also allows for
5221 temporary disabling of validity checks.
5224 @node Style Checking
5225 @subsection Style Checking
5226 @findex Style checking
5229 The @option{-gnaty^x^(option,option,...)^} switch
5230 @cindex @option{-gnaty} (@code{gcc})
5231 causes the compiler to
5232 enforce specified style rules. A limited set of style rules has been used
5233 in writing the GNAT sources themselves. This switch allows user programs
5234 to activate all or some of these checks. If the source program fails a
5235 specified style check, an appropriate warning message is given, preceded by
5236 the character sequence ``(style)''.
5238 @code{(option,option,...)} is a sequence of keywords
5241 The string @var{x} is a sequence of letters or digits
5243 indicating the particular style
5244 checks to be performed. The following checks are defined:
5249 @emph{Specify indentation level.}
5250 If a digit from 1-9 appears
5251 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
5252 then proper indentation is checked, with the digit indicating the
5253 indentation level required.
5254 The general style of required indentation is as specified by
5255 the examples in the Ada Reference Manual. Full line comments must be
5256 aligned with the @code{--} starting on a column that is a multiple of
5257 the alignment level.
5260 @emph{Check attribute casing.}
5261 If the ^letter a^word ATTRIBUTE^ appears in the string after @option{-gnaty}
5262 then attribute names, including the case of keywords such as @code{digits}
5263 used as attributes names, must be written in mixed case, that is, the
5264 initial letter and any letter following an underscore must be uppercase.
5265 All other letters must be lowercase.
5268 @emph{Blanks not allowed at statement end.}
5269 If the ^letter b^word BLANKS^ appears in the string after @option{-gnaty} then
5270 trailing blanks are not allowed at the end of statements. The purpose of this
5271 rule, together with h (no horizontal tabs), is to enforce a canonical format
5272 for the use of blanks to separate source tokens.
5275 @emph{Check comments.}
5276 If the ^letter c^word COMMENTS^ appears in the string after @option{-gnaty}
5277 then comments must meet the following set of rules:
5282 The ``@code{--}'' that starts the column must either start in column one,
5283 or else at least one blank must precede this sequence.
5286 Comments that follow other tokens on a line must have at least one blank
5287 following the ``@code{--}'' at the start of the comment.
5290 Full line comments must have two blanks following the ``@code{--}'' that
5291 starts the comment, with the following exceptions.
5294 A line consisting only of the ``@code{--}'' characters, possibly preceded
5295 by blanks is permitted.
5298 A comment starting with ``@code{--x}'' where @code{x} is a special character
5300 This allows proper processing of the output generated by specialized tools
5301 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
5303 language (where ``@code{--#}'' is used). For the purposes of this rule, a
5304 special character is defined as being in one of the ASCII ranges
5305 @code{16#21#..16#2F#} or @code{16#3A#..16#3F#}.
5306 Note that this usage is not permitted
5307 in GNAT implementation units (i.e. when @option{-gnatg} is used).
5310 A line consisting entirely of minus signs, possibly preceded by blanks, is
5311 permitted. This allows the construction of box comments where lines of minus
5312 signs are used to form the top and bottom of the box.
5315 If a comment starts and ends with ``@code{--}'' is permitted as long as at
5316 least one blank follows the initial ``@code{--}''. Together with the preceding
5317 rule, this allows the construction of box comments, as shown in the following
5320 ---------------------------
5321 -- This is a box comment --
5322 -- with two text lines. --
5323 ---------------------------
5328 @emph{Check end/exit labels.}
5329 If the ^letter e^word END^ appears in the string after @option{-gnaty} then
5330 optional labels on @code{end} statements ending subprograms and on
5331 @code{exit} statements exiting named loops, are required to be present.
5334 @emph{No form feeds or vertical tabs.}
5335 If the ^letter f^word VTABS^ appears in the string after @option{-gnaty} then
5336 neither form feeds nor vertical tab characters are not permitted
5340 @emph{No horizontal tabs.}
5341 If the ^letter h^word HTABS^ appears in the string after @option{-gnaty} then
5342 horizontal tab characters are not permitted in the source text.
5343 Together with the b (no blanks at end of line) check, this
5344 enforces a canonical form for the use of blanks to separate
5348 @emph{Check if-then layout.}
5349 If the ^letter i^word IF_THEN^ appears in the string after @option{-gnaty},
5350 then the keyword @code{then} must appear either on the same
5351 line as corresponding @code{if}, or on a line on its own, lined
5352 up under the @code{if} with at least one non-blank line in between
5353 containing all or part of the condition to be tested.
5356 @emph{Check keyword casing.}
5357 If the ^letter k^word KEYWORD^ appears in the string after @option{-gnaty} then
5358 all keywords must be in lower case (with the exception of keywords
5359 such as @code{digits} used as attribute names to which this check
5363 @emph{Check layout.}
5364 If the ^letter l^word LAYOUT^ appears in the string after @option{-gnaty} then
5365 layout of statement and declaration constructs must follow the
5366 recommendations in the Ada Reference Manual, as indicated by the
5367 form of the syntax rules. For example an @code{else} keyword must
5368 be lined up with the corresponding @code{if} keyword.
5370 There are two respects in which the style rule enforced by this check
5371 option are more liberal than those in the Ada Reference Manual. First
5372 in the case of record declarations, it is permissible to put the
5373 @code{record} keyword on the same line as the @code{type} keyword, and
5374 then the @code{end} in @code{end record} must line up under @code{type}.
5375 For example, either of the following two layouts is acceptable:
5377 @smallexample @c ada
5393 Second, in the case of a block statement, a permitted alternative
5394 is to put the block label on the same line as the @code{declare} or
5395 @code{begin} keyword, and then line the @code{end} keyword up under
5396 the block label. For example both the following are permitted:
5398 @smallexample @c ada
5416 The same alternative format is allowed for loops. For example, both of
5417 the following are permitted:
5419 @smallexample @c ada
5421 Clear : while J < 10 loop
5432 @item ^Lnnn^MAX_NESTING=nnn^
5433 @emph{Set maximum nesting level}
5434 If the sequence ^Lnnn^MAX_NESTING=nnn^, where nnn is a decimal number in
5435 the range 0-999, appears in the string after @option{-gnaty} then the
5436 maximum level of nesting of constructs (including subprograms, loops,
5437 blocks, packages, and conditionals) may not exceed the given value. A
5438 value of zero disconnects this style check.
5440 @item ^m^LINE_LENGTH^
5441 @emph{Check maximum line length.}
5442 If the ^letter m^word LINE_LENGTH^ appears in the string after @option{-gnaty}
5443 then the length of source lines must not exceed 79 characters, including
5444 any trailing blanks. The value of 79 allows convenient display on an
5445 80 character wide device or window, allowing for possible special
5446 treatment of 80 character lines. Note that this count is of raw
5447 characters in the source text. This means that a tab character counts
5448 as one character in this count and a wide character sequence counts as
5449 several characters (however many are needed in the encoding).
5451 @item ^Mnnn^MAX_LENGTH=nnn^
5452 @emph{Set maximum line length.}
5453 If the sequence ^M^MAX_LENGTH=^nnn, where nnn is a decimal number, appears in
5454 the string after @option{-gnaty} then the length of lines must not exceed the
5457 @item ^n^STANDARD_CASING^
5458 @emph{Check casing of entities in Standard.}
5459 If the ^letter n^word STANDARD_CASING^ appears in the string
5460 after @option{-gnaty} then any identifier from Standard must be cased
5461 to match the presentation in the Ada Reference Manual (for example,
5462 @code{Integer} and @code{ASCII.NUL}).
5464 @item ^o^ORDERED_SUBPROGRAMS^
5465 @emph{Check order of subprogram bodies.}
5466 If the ^letter o^word ORDERED_SUBPROGRAMS^ appears in the string
5467 after @option{-gnaty} then all subprogram bodies in a given scope
5468 (e.g. a package body) must be in alphabetical order. The ordering
5469 rule uses normal Ada rules for comparing strings, ignoring casing
5470 of letters, except that if there is a trailing numeric suffix, then
5471 the value of this suffix is used in the ordering (e.g. Junk2 comes
5475 @emph{Check pragma casing.}
5476 If the ^letter p^word PRAGMA^ appears in the string after @option{-gnaty} then
5477 pragma names must be written in mixed case, that is, the
5478 initial letter and any letter following an underscore must be uppercase.
5479 All other letters must be lowercase.
5481 @item ^r^REFERENCES^
5482 @emph{Check references.}
5483 If the ^letter r^word REFERENCES^ appears in the string after @option{-gnaty}
5484 then all identifier references must be cased in the same way as the
5485 corresponding declaration. No specific casing style is imposed on
5486 identifiers. The only requirement is for consistency of references
5490 @emph{Check separate specs.}
5491 If the ^letter s^word SPECS^ appears in the string after @option{-gnaty} then
5492 separate declarations (``specs'') are required for subprograms (a
5493 body is not allowed to serve as its own declaration). The only
5494 exception is that parameterless library level procedures are
5495 not required to have a separate declaration. This exception covers
5496 the most frequent form of main program procedures.
5499 @emph{Check token spacing.}
5500 If the ^letter t^word TOKEN^ appears in the string after @option{-gnaty} then
5501 the following token spacing rules are enforced:
5506 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
5509 The token @code{=>} must be surrounded by spaces.
5512 The token @code{<>} must be preceded by a space or a left parenthesis.
5515 Binary operators other than @code{**} must be surrounded by spaces.
5516 There is no restriction on the layout of the @code{**} binary operator.
5519 Colon must be surrounded by spaces.
5522 Colon-equal (assignment, initialization) must be surrounded by spaces.
5525 Comma must be the first non-blank character on the line, or be
5526 immediately preceded by a non-blank character, and must be followed
5530 If the token preceding a left parenthesis ends with a letter or digit, then
5531 a space must separate the two tokens.
5534 A right parenthesis must either be the first non-blank character on
5535 a line, or it must be preceded by a non-blank character.
5538 A semicolon must not be preceded by a space, and must not be followed by
5539 a non-blank character.
5542 A unary plus or minus may not be followed by a space.
5545 A vertical bar must be surrounded by spaces.
5549 In the above rules, appearing in column one is always permitted, that is,
5550 counts as meeting either a requirement for a required preceding space,
5551 or as meeting a requirement for no preceding space.
5553 Appearing at the end of a line is also always permitted, that is, counts
5554 as meeting either a requirement for a following space, or as meeting
5555 a requirement for no following space.
5560 If any of these style rules is violated, a message is generated giving
5561 details on the violation. The initial characters of such messages are
5562 always ``@code{(style)}''. Note that these messages are treated as warning
5563 messages, so they normally do not prevent the generation of an object
5564 file. The @option{-gnatwe} switch can be used to treat warning messages,
5565 including style messages, as fatal errors.
5569 @option{-gnaty} on its own (that is not
5570 followed by any letters or digits),
5571 is equivalent to @code{gnaty3abcefhiklmprst}, that is all checking
5572 options enabled with the exception of -gnatyo,
5575 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
5576 the exception of ORDERED_SUBPROGRAMS,
5578 with an indentation level of 3. This is the standard
5579 checking option that is used for the GNAT sources.
5588 clears any previously set style checks.
5590 @node Run-Time Checks
5591 @subsection Run-Time Checks
5592 @cindex Division by zero
5593 @cindex Access before elaboration
5594 @cindex Checks, division by zero
5595 @cindex Checks, access before elaboration
5598 If you compile with the default options, GNAT will insert many run-time
5599 checks into the compiled code, including code that performs range
5600 checking against constraints, but not arithmetic overflow checking for
5601 integer operations (including division by zero) or checks for access
5602 before elaboration on subprogram calls. All other run-time checks, as
5603 required by the Ada 95 Reference Manual, are generated by default.
5604 The following @code{gcc} switches refine this default behavior:
5609 @cindex @option{-gnatp} (@code{gcc})
5610 @cindex Suppressing checks
5611 @cindex Checks, suppressing
5613 Suppress all run-time checks as though @code{pragma Suppress (all_checks})
5614 had been present in the source. Validity checks are also suppressed (in
5615 other words @option{-gnatp} also implies @option{-gnatVn}.
5616 Use this switch to improve the performance
5617 of the code at the expense of safety in the presence of invalid data or
5621 @cindex @option{-gnato} (@code{gcc})
5622 @cindex Overflow checks
5623 @cindex Check, overflow
5624 Enables overflow checking for integer operations.
5625 This causes GNAT to generate slower and larger executable
5626 programs by adding code to check for overflow (resulting in raising
5627 @code{Constraint_Error} as required by standard Ada
5628 semantics). These overflow checks correspond to situations in which
5629 the true value of the result of an operation may be outside the base
5630 range of the result type. The following example shows the distinction:
5632 @smallexample @c ada
5633 X1 : Integer := Integer'Last;
5634 X2 : Integer range 1 .. 5 := 5;
5635 X3 : Integer := Integer'Last;
5636 X4 : Integer range 1 .. 5 := 5;
5637 F : Float := 2.0E+20;
5646 Here the first addition results in a value that is outside the base range
5647 of Integer, and hence requires an overflow check for detection of the
5648 constraint error. Thus the first assignment to @code{X1} raises a
5649 @code{Constraint_Error} exception only if @option{-gnato} is set.
5651 The second increment operation results in a violation
5652 of the explicit range constraint, and such range checks are always
5653 performed (unless specifically suppressed with a pragma @code{suppress}
5654 or the use of @option{-gnatp}).
5656 The two conversions of @code{F} both result in values that are outside
5657 the base range of type @code{Integer} and thus will raise
5658 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
5659 The fact that the result of the second conversion is assigned to
5660 variable @code{X4} with a restricted range is irrelevant, since the problem
5661 is in the conversion, not the assignment.
5663 Basically the rule is that in the default mode (@option{-gnato} not
5664 used), the generated code assures that all integer variables stay
5665 within their declared ranges, or within the base range if there is
5666 no declared range. This prevents any serious problems like indexes
5667 out of range for array operations.
5669 What is not checked in default mode is an overflow that results in
5670 an in-range, but incorrect value. In the above example, the assignments
5671 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
5672 range of the target variable, but the result is wrong in the sense that
5673 it is too large to be represented correctly. Typically the assignment
5674 to @code{X1} will result in wrap around to the largest negative number.
5675 The conversions of @code{F} will result in some @code{Integer} value
5676 and if that integer value is out of the @code{X4} range then the
5677 subsequent assignment would generate an exception.
5679 @findex Machine_Overflows
5680 Note that the @option{-gnato} switch does not affect the code generated
5681 for any floating-point operations; it applies only to integer
5683 For floating-point, GNAT has the @code{Machine_Overflows}
5684 attribute set to @code{False} and the normal mode of operation is to
5685 generate IEEE NaN and infinite values on overflow or invalid operations
5686 (such as dividing 0.0 by 0.0).
5688 The reason that we distinguish overflow checking from other kinds of
5689 range constraint checking is that a failure of an overflow check can
5690 generate an incorrect value, but cannot cause erroneous behavior. This
5691 is unlike the situation with a constraint check on an array subscript,
5692 where failure to perform the check can result in random memory description,
5693 or the range check on a case statement, where failure to perform the check
5694 can cause a wild jump.
5696 Note again that @option{-gnato} is off by default, so overflow checking is
5697 not performed in default mode. This means that out of the box, with the
5698 default settings, GNAT does not do all the checks expected from the
5699 language description in the Ada Reference Manual. If you want all constraint
5700 checks to be performed, as described in this Manual, then you must
5701 explicitly use the -gnato switch either on the @code{gnatmake} or
5705 @cindex @option{-gnatE} (@code{gcc})
5706 @cindex Elaboration checks
5707 @cindex Check, elaboration
5708 Enables dynamic checks for access-before-elaboration
5709 on subprogram calls and generic instantiations.
5710 For full details of the effect and use of this switch,
5711 @xref{Compiling Using gcc}.
5716 The setting of these switches only controls the default setting of the
5717 checks. You may modify them using either @code{Suppress} (to remove
5718 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
5721 @node Stack Overflow Checking
5722 @subsection Stack Overflow Checking
5723 @cindex Stack Overflow Checking
5724 @cindex -fstack-check
5727 For most operating systems, @code{gcc} does not perform stack overflow
5728 checking by default. This means that if the main environment task or
5729 some other task exceeds the available stack space, then unpredictable
5730 behavior will occur.
5732 To activate stack checking, compile all units with the gcc option
5733 @option{-fstack-check}. For example:
5736 gcc -c -fstack-check package1.adb
5740 Units compiled with this option will generate extra instructions to check
5741 that any use of the stack (for procedure calls or for declaring local
5742 variables in declare blocks) do not exceed the available stack space.
5743 If the space is exceeded, then a @code{Storage_Error} exception is raised.
5745 For declared tasks, the stack size is always controlled by the size
5746 given in an applicable @code{Storage_Size} pragma (or is set to
5747 the default size if no pragma is used.
5749 For the environment task, the stack size depends on
5750 system defaults and is unknown to the compiler. The stack
5751 may even dynamically grow on some systems, precluding the
5752 normal Ada semantics for stack overflow. In the worst case,
5753 unbounded stack usage, causes unbounded stack expansion
5754 resulting in the system running out of virtual memory.
5756 The stack checking may still work correctly if a fixed
5757 size stack is allocated, but this cannot be guaranteed.
5758 To ensure that a clean exception is signalled for stack
5759 overflow, set the environment variable
5760 @code{GNAT_STACK_LIMIT} to indicate the maximum
5761 stack area that can be used, as in:
5762 @cindex GNAT_STACK_LIMIT
5765 SET GNAT_STACK_LIMIT 1600
5769 The limit is given in kilobytes, so the above declaration would
5770 set the stack limit of the environment task to 1.6 megabytes.
5771 Note that the only purpose of this usage is to limit the amount
5772 of stack used by the environment task. If it is necessary to
5773 increase the amount of stack for the environment task, then this
5774 is an operating systems issue, and must be addressed with the
5775 appropriate operating systems commands.
5778 @node Using gcc for Syntax Checking
5779 @subsection Using @code{gcc} for Syntax Checking
5782 @cindex @option{-gnats} (@code{gcc})
5786 The @code{s} stands for ``syntax''.
5789 Run GNAT in syntax checking only mode. For
5790 example, the command
5793 $ gcc -c -gnats x.adb
5797 compiles file @file{x.adb} in syntax-check-only mode. You can check a
5798 series of files in a single command
5800 , and can use wild cards to specify such a group of files.
5801 Note that you must specify the @option{-c} (compile
5802 only) flag in addition to the @option{-gnats} flag.
5805 You may use other switches in conjunction with @option{-gnats}. In
5806 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
5807 format of any generated error messages.
5809 When the source file is empty or contains only empty lines and/or comments,
5810 the output is a warning:
5813 $ gcc -c -gnats -x ada toto.txt
5814 toto.txt:1:01: warning: empty file, contains no compilation units
5818 Otherwise, the output is simply the error messages, if any. No object file or
5819 ALI file is generated by a syntax-only compilation. Also, no units other
5820 than the one specified are accessed. For example, if a unit @code{X}
5821 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
5822 check only mode does not access the source file containing unit
5825 @cindex Multiple units, syntax checking
5826 Normally, GNAT allows only a single unit in a source file. However, this
5827 restriction does not apply in syntax-check-only mode, and it is possible
5828 to check a file containing multiple compilation units concatenated
5829 together. This is primarily used by the @code{gnatchop} utility
5830 (@pxref{Renaming Files Using gnatchop}).
5834 @node Using gcc for Semantic Checking
5835 @subsection Using @code{gcc} for Semantic Checking
5838 @cindex @option{-gnatc} (@code{gcc})
5842 The @code{c} stands for ``check''.
5844 Causes the compiler to operate in semantic check mode,
5845 with full checking for all illegalities specified in the
5846 Ada 95 Reference Manual, but without generation of any object code
5847 (no object file is generated).
5849 Because dependent files must be accessed, you must follow the GNAT
5850 semantic restrictions on file structuring to operate in this mode:
5854 The needed source files must be accessible
5855 (@pxref{Search Paths and the Run-Time Library (RTL)}).
5858 Each file must contain only one compilation unit.
5861 The file name and unit name must match (@pxref{File Naming Rules}).
5864 The output consists of error messages as appropriate. No object file is
5865 generated. An @file{ALI} file is generated for use in the context of
5866 cross-reference tools, but this file is marked as not being suitable
5867 for binding (since no object file is generated).
5868 The checking corresponds exactly to the notion of
5869 legality in the Ada 95 Reference Manual.
5871 Any unit can be compiled in semantics-checking-only mode, including
5872 units that would not normally be compiled (subunits,
5873 and specifications where a separate body is present).
5876 @node Compiling Ada 83 Programs
5877 @subsection Compiling Ada 83 Programs
5879 @cindex Ada 83 compatibility
5881 @cindex @option{-gnat83} (@code{gcc})
5882 @cindex ACVC, Ada 83 tests
5885 Although GNAT is primarily an Ada 95 compiler, it accepts this switch to
5886 specify that an Ada 83 program is to be compiled in Ada 83 mode. If you specify
5887 this switch, GNAT rejects most Ada 95 extensions and applies Ada 83 semantics
5888 where this can be done easily.
5889 It is not possible to guarantee this switch does a perfect
5890 job; for example, some subtle tests, such as are
5891 found in earlier ACVC tests (and that have been removed from the ACATS suite
5892 for Ada 95), might not compile correctly.
5893 Nevertheless, this switch may be useful in some circumstances, for example
5894 where, due to contractual reasons, legacy code needs to be maintained
5895 using only Ada 83 features.
5897 With few exceptions (most notably the need to use @code{<>} on
5898 @cindex Generic formal parameters
5899 unconstrained generic formal parameters, the use of the new Ada 95
5900 reserved words, and the use of packages
5901 with optional bodies), it is not necessary to use the
5902 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
5903 exceptions, Ada 95 is upwardly compatible with Ada 83. This
5904 means that a correct Ada 83 program is usually also a correct Ada 95
5906 For further information, please refer to @ref{Compatibility and Porting Guide}.
5910 @node Character Set Control
5911 @subsection Character Set Control
5913 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
5914 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@code{gcc})
5917 Normally GNAT recognizes the Latin-1 character set in source program
5918 identifiers, as described in the Ada 95 Reference Manual.
5920 GNAT to recognize alternate character sets in identifiers. @var{c} is a
5921 single character ^^or word^ indicating the character set, as follows:
5925 ISO 8859-1 (Latin-1) identifiers
5928 ISO 8859-2 (Latin-2) letters allowed in identifiers
5931 ISO 8859-3 (Latin-3) letters allowed in identifiers
5934 ISO 8859-4 (Latin-4) letters allowed in identifiers
5937 ISO 8859-5 (Cyrillic) letters allowed in identifiers
5940 ISO 8859-15 (Latin-9) letters allowed in identifiers
5943 IBM PC letters (code page 437) allowed in identifiers
5946 IBM PC letters (code page 850) allowed in identifiers
5948 @item ^f^FULL_UPPER^
5949 Full upper-half codes allowed in identifiers
5952 No upper-half codes allowed in identifiers
5955 Wide-character codes (that is, codes greater than 255)
5956 allowed in identifiers
5959 @xref{Foreign Language Representation}, for full details on the
5960 implementation of these character sets.
5962 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
5963 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@code{gcc})
5964 Specify the method of encoding for wide characters.
5965 @var{e} is one of the following:
5970 Hex encoding (brackets coding also recognized)
5973 Upper half encoding (brackets encoding also recognized)
5976 Shift/JIS encoding (brackets encoding also recognized)
5979 EUC encoding (brackets encoding also recognized)
5982 UTF-8 encoding (brackets encoding also recognized)
5985 Brackets encoding only (default value)
5987 For full details on the these encoding
5988 methods see @xref{Wide Character Encodings}.
5989 Note that brackets coding is always accepted, even if one of the other
5990 options is specified, so for example @option{-gnatW8} specifies that both
5991 brackets and @code{UTF-8} encodings will be recognized. The units that are
5992 with'ed directly or indirectly will be scanned using the specified
5993 representation scheme, and so if one of the non-brackets scheme is
5994 used, it must be used consistently throughout the program. However,
5995 since brackets encoding is always recognized, it may be conveniently
5996 used in standard libraries, allowing these libraries to be used with
5997 any of the available coding schemes.
5998 scheme. If no @option{-gnatW?} parameter is present, then the default
5999 representation is Brackets encoding only.
6001 Note that the wide character representation that is specified (explicitly
6002 or by default) for the main program also acts as the default encoding used
6003 for Wide_Text_IO files if not specifically overridden by a WCEM form
6007 @node File Naming Control
6008 @subsection File Naming Control
6011 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
6012 @cindex @option{-gnatk} (@code{gcc})
6013 Activates file name ``krunching''. @var{n}, a decimal integer in the range
6014 1-999, indicates the maximum allowable length of a file name (not
6015 including the @file{.ads} or @file{.adb} extension). The default is not
6016 to enable file name krunching.
6018 For the source file naming rules, @xref{File Naming Rules}.
6022 @node Subprogram Inlining Control
6023 @subsection Subprogram Inlining Control
6028 @cindex @option{-gnatn} (@code{gcc})
6030 The @code{n} here is intended to suggest the first syllable of the
6033 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6034 inlining to actually occur, optimization must be enabled. To enable
6035 inlining of subprograms specified by pragma @code{Inline},
6036 you must also specify this switch.
6037 In the absence of this switch, GNAT does not attempt
6038 inlining and does not need to access the bodies of
6039 subprograms for which @code{pragma Inline} is specified if they are not
6040 in the current unit.
6042 If you specify this switch the compiler will access these bodies,
6043 creating an extra source dependency for the resulting object file, and
6044 where possible, the call will be inlined.
6045 For further details on when inlining is possible
6046 see @xref{Inlining of Subprograms}.
6049 @cindex @option{-gnatN} (@code{gcc})
6050 The front end inlining activated by this switch is generally more extensive,
6051 and quite often more effective than the standard @option{-gnatn} inlining mode.
6052 It will also generate additional dependencies.
6054 @option{-gnatN} automatically implies @option{-gnatn} so it is not necessary
6055 to specify both options.
6058 @node Auxiliary Output Control
6059 @subsection Auxiliary Output Control
6063 @cindex @option{-gnatt} (@code{gcc})
6064 @cindex Writing internal trees
6065 @cindex Internal trees, writing to file
6066 Causes GNAT to write the internal tree for a unit to a file (with the
6067 extension @file{.adt}.
6068 This not normally required, but is used by separate analysis tools.
6070 these tools do the necessary compilations automatically, so you should
6071 not have to specify this switch in normal operation.
6074 @cindex @option{-gnatu} (@code{gcc})
6075 Print a list of units required by this compilation on @file{stdout}.
6076 The listing includes all units on which the unit being compiled depends
6077 either directly or indirectly.
6080 @item -pass-exit-codes
6081 @cindex @option{-pass-exit-codes} (@code{gcc})
6082 If this switch is not used, the exit code returned by @code{gcc} when
6083 compiling multiple files indicates whether all source files have
6084 been successfully used to generate object files or not.
6086 When @option{-pass-exit-codes} is used, @code{gcc} exits with an extended
6087 exit status and allows an integrated development environment to better
6088 react to a compilation failure. Those exit status are:
6092 There was an error in at least one source file.
6094 At least one source file did not generate an object file.
6096 The compiler died unexpectedly (internal error for example).
6098 An object file has been generated for every source file.
6103 @node Debugging Control
6104 @subsection Debugging Control
6108 @cindex Debugging options
6111 @cindex @option{-gnatd} (@code{gcc})
6112 Activate internal debugging switches. @var{x} is a letter or digit, or
6113 string of letters or digits, which specifies the type of debugging
6114 outputs desired. Normally these are used only for internal development
6115 or system debugging purposes. You can find full documentation for these
6116 switches in the body of the @code{Debug} unit in the compiler source
6117 file @file{debug.adb}.
6121 @cindex @option{-gnatG} (@code{gcc})
6122 This switch causes the compiler to generate auxiliary output containing
6123 a pseudo-source listing of the generated expanded code. Like most Ada
6124 compilers, GNAT works by first transforming the high level Ada code into
6125 lower level constructs. For example, tasking operations are transformed
6126 into calls to the tasking run-time routines. A unique capability of GNAT
6127 is to list this expanded code in a form very close to normal Ada source.
6128 This is very useful in understanding the implications of various Ada
6129 usage on the efficiency of the generated code. There are many cases in
6130 Ada (e.g. the use of controlled types), where simple Ada statements can
6131 generate a lot of run-time code. By using @option{-gnatG} you can identify
6132 these cases, and consider whether it may be desirable to modify the coding
6133 approach to improve efficiency.
6135 The format of the output is very similar to standard Ada source, and is
6136 easily understood by an Ada programmer. The following special syntactic
6137 additions correspond to low level features used in the generated code that
6138 do not have any exact analogies in pure Ada source form. The following
6139 is a partial list of these special constructions. See the specification
6140 of package @code{Sprint} in file @file{sprint.ads} for a full list.
6143 @item new @var{xxx} [storage_pool = @var{yyy}]
6144 Shows the storage pool being used for an allocator.
6146 @item at end @var{procedure-name};
6147 Shows the finalization (cleanup) procedure for a scope.
6149 @item (if @var{expr} then @var{expr} else @var{expr})
6150 Conditional expression equivalent to the @code{x?y:z} construction in C.
6152 @item @var{target}^^^(@var{source})
6153 A conversion with floating-point truncation instead of rounding.
6155 @item @var{target}?(@var{source})
6156 A conversion that bypasses normal Ada semantic checking. In particular
6157 enumeration types and fixed-point types are treated simply as integers.
6159 @item @var{target}?^^^(@var{source})
6160 Combines the above two cases.
6162 @item @var{x} #/ @var{y}
6163 @itemx @var{x} #mod @var{y}
6164 @itemx @var{x} #* @var{y}
6165 @itemx @var{x} #rem @var{y}
6166 A division or multiplication of fixed-point values which are treated as
6167 integers without any kind of scaling.
6169 @item free @var{expr} [storage_pool = @var{xxx}]
6170 Shows the storage pool associated with a @code{free} statement.
6172 @item freeze @var{typename} [@var{actions}]
6173 Shows the point at which @var{typename} is frozen, with possible
6174 associated actions to be performed at the freeze point.
6176 @item reference @var{itype}
6177 Reference (and hence definition) to internal type @var{itype}.
6179 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
6180 Intrinsic function call.
6182 @item @var{labelname} : label
6183 Declaration of label @var{labelname}.
6185 @item @var{expr} && @var{expr} && @var{expr} ... && @var{expr}
6186 A multiple concatenation (same effect as @var{expr} & @var{expr} &
6187 @var{expr}, but handled more efficiently).
6189 @item [constraint_error]
6190 Raise the @code{Constraint_Error} exception.
6192 @item @var{expression}'reference
6193 A pointer to the result of evaluating @var{expression}.
6195 @item @var{target-type}!(@var{source-expression})
6196 An unchecked conversion of @var{source-expression} to @var{target-type}.
6198 @item [@var{numerator}/@var{denominator}]
6199 Used to represent internal real literals (that) have no exact
6200 representation in base 2-16 (for example, the result of compile time
6201 evaluation of the expression 1.0/27.0).
6205 @cindex @option{-gnatD} (@code{gcc})
6206 When used in conjunction with @option{-gnatG}, this switch causes
6207 the expanded source, as described above for
6208 @option{-gnatG} to be written to files with names
6209 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
6210 instead of to the standard ooutput file. For
6211 example, if the source file name is @file{hello.adb}, then a file
6212 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
6213 information generated by the @code{gcc} @option{^-g^/DEBUG^} switch
6214 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
6215 you to do source level debugging using the generated code which is
6216 sometimes useful for complex code, for example to find out exactly
6217 which part of a complex construction raised an exception. This switch
6218 also suppress generation of cross-reference information (see
6219 @option{-gnatx}) since otherwise the cross-reference information
6220 would refer to the @file{^.dg^.DG^} file, which would cause
6221 confusion since this is not the original source file.
6223 Note that @option{-gnatD} actually implies @option{-gnatG}
6224 automatically, so it is not necessary to give both options.
6225 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
6228 @item -gnatR[0|1|2|3[s]]
6229 @cindex @option{-gnatR} (@code{gcc})
6230 This switch controls output from the compiler of a listing showing
6231 representation information for declared types and objects. For
6232 @option{-gnatR0}, no information is output (equivalent to omitting
6233 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
6234 so @option{-gnatR} with no parameter has the same effect), size and alignment
6235 information is listed for declared array and record types. For
6236 @option{-gnatR2}, size and alignment information is listed for all
6237 expression information for values that are computed at run time for
6238 variant records. These symbolic expressions have a mostly obvious
6239 format with #n being used to represent the value of the n'th
6240 discriminant. See source files @file{repinfo.ads/adb} in the
6241 @code{GNAT} sources for full details on the format of @option{-gnatR3}
6242 output. If the switch is followed by an s (e.g. @option{-gnatR2s}), then
6243 the output is to a file with the name @file{^file.rep^file_REP^} where
6244 file is the name of the corresponding source file.
6247 @item /REPRESENTATION_INFO
6248 @cindex @option{/REPRESENTATION_INFO} (@code{gcc})
6249 This qualifier controls output from the compiler of a listing showing
6250 representation information for declared types and objects. For
6251 @option{/REPRESENTATION_INFO=NONE}, no information is output
6252 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
6253 @option{/REPRESENTATION_INFO} without option is equivalent to
6254 @option{/REPRESENTATION_INFO=ARRAYS}.
6255 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
6256 information is listed for declared array and record types. For
6257 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
6258 is listed for all expression information for values that are computed
6259 at run time for variant records. These symbolic expressions have a mostly
6260 obvious format with #n being used to represent the value of the n'th
6261 discriminant. See source files @file{REPINFO.ADS/ADB} in the
6262 @code{GNAT} sources for full details on the format of
6263 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
6264 If _FILE is added at the end of an option
6265 (e.g. @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
6266 then the output is to a file with the name @file{file_REP} where
6267 file is the name of the corresponding source file.
6271 @cindex @option{-gnatS} (@code{gcc})
6272 The use of the switch @option{-gnatS} for an
6273 Ada compilation will cause the compiler to output a
6274 representation of package Standard in a form very
6275 close to standard Ada. It is not quite possible to
6276 do this entirely in standard Ada (since new
6277 numeric base types cannot be created in standard
6278 Ada), but the output is easily
6279 readable to any Ada programmer, and is useful to
6280 determine the characteristics of target dependent
6281 types in package Standard.
6284 @cindex @option{-gnatx} (@code{gcc})
6285 Normally the compiler generates full cross-referencing information in
6286 the @file{ALI} file. This information is used by a number of tools,
6287 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
6288 suppresses this information. This saves some space and may slightly
6289 speed up compilation, but means that these tools cannot be used.
6292 @node Exception Handling Control
6293 @subsection Exception Handling Control
6296 GNAT uses two methods for handling exceptions at run-time. The
6297 @code{longjmp/setjmp} method saves the context when entering
6298 a frame with an exception handler. Then when an exception is
6299 raised, the context can be restored immediately, without the
6300 need for tracing stack frames. This method provides very fast
6301 exception propagation, but introduces significant overhead for
6302 the use of exception handlers, even if no exception is raised.
6304 The other approach is called ``zero cost'' exception handling.
6305 With this method, the compiler builds static tables to describe
6306 the exception ranges. No dynamic code is required when entering
6307 a frame containing an exception handler. When an exception is
6308 raised, the tables are used to control a back trace of the
6309 subprogram invocation stack to locate the required exception
6310 handler. This method has considerably poorer performance for
6311 the propagation of exceptions, but there is no overhead for
6312 exception handlers if no exception is raised.
6314 The following switches can be used to control which of the
6315 two exception handling methods is used.
6321 @cindex @option{-gnatL} (@code{gcc})
6322 This switch causes the longjmp/setjmp approach to be used
6323 for exception handling. If this is the default mechanism for the
6324 target (see below), then this has no effect. If the default
6325 mechanism for the target is zero cost exceptions, then
6326 this switch can be used to modify this default, but it must be
6327 used for all units in the partition, including all run-time
6328 library units. One way to achieve this is to use the
6329 @option{-a} and @option{-f} switches for @code{gnatmake}.
6330 This option is rarely used. One case in which it may be
6331 advantageous is if you have an application where exception
6332 raising is common and the overall performance of the
6333 application is improved by favoring exception propagation.
6336 @cindex @option{-gnatZ} (@code{gcc})
6337 @cindex Zero Cost Exceptions
6338 This switch causes the zero cost approach to be sed
6339 for exception handling. If this is the default mechanism for the
6340 target (see below), then this has no effect. If the default
6341 mechanism for the target is longjmp/setjmp exceptions, then
6342 this switch can be used to modify this default, but it must be
6343 used for all units in the partition, including all run-time
6344 library units. One way to achieve this is to use the
6345 @option{-a} and @option{-f} switches for @code{gnatmake}.
6346 This option can only be used if the zero cost approach
6347 is available for the target in use (see below).
6351 The @code{longjmp/setjmp} approach is available on all targets, but
6352 the @code{zero cost} approach is only available on selected targets.
6353 To determine whether zero cost exceptions can be used for a
6354 particular target, look at the private part of the file system.ads.
6355 Either @code{GCC_ZCX_Support} or @code{Front_End_ZCX_Support} must
6356 be True to use the zero cost approach. If both of these switches
6357 are set to False, this means that zero cost exception handling
6358 is not yet available for that target. The switch
6359 @code{ZCX_By_Default} indicates the default approach. If this
6360 switch is set to True, then the @code{zero cost} approach is
6363 @node Units to Sources Mapping Files
6364 @subsection Units to Sources Mapping Files
6368 @item -gnatem^^=^@var{path}
6369 @cindex @option{-gnatem} (@code{gcc})
6370 A mapping file is a way to communicate to the compiler two mappings:
6371 from unit names to file names (without any directory information) and from
6372 file names to path names (with full directory information). These mappings
6373 are used by the compiler to short-circuit the path search.
6375 The use of mapping files is not required for correct operation of the
6376 compiler, but mapping files can improve efficiency, particularly when
6377 sources are read over a slow network connection. In normal operation,
6378 you need not be concerned with the format or use of mapping files,
6379 and the @option{-gnatem} switch is not a switch that you would use
6380 explicitly. it is intended only for use by automatic tools such as
6381 @code{gnatmake} running under the project file facility. The
6382 description here of the format of mapping files is provided
6383 for completeness and for possible use by other tools.
6385 A mapping file is a sequence of sets of three lines. In each set,
6386 the first line is the unit name, in lower case, with ``@code{%s}''
6388 specifications and ``@code{%b}'' appended for bodies; the second line is the
6389 file name; and the third line is the path name.
6395 /gnat/project1/sources/main.2.ada
6398 When the switch @option{-gnatem} is specified, the compiler will create
6399 in memory the two mappings from the specified file. If there is any problem
6400 (non existent file, truncated file or duplicate entries), no mapping
6403 Several @option{-gnatem} switches may be specified; however, only the last
6404 one on the command line will be taken into account.
6406 When using a project file, @code{gnatmake} create a temporary mapping file
6407 and communicates it to the compiler using this switch.
6412 @node Integrated Preprocessing
6413 @subsection Integrated Preprocessing
6416 GNAT sources may be preprocessed immediately before compilation; the actual
6417 text of the source is not the text of the source file, but is derived from it
6418 through a process called preprocessing. Integrated preprocessing is specified
6419 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
6420 indicates, through a text file, the preprocessing data to be used.
6421 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
6424 It is recommended that @code{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
6425 used when Integrated Preprocessing is used. The reason is that preprocessing
6426 with another Preprocessing Data file without changing the sources will
6427 not trigger recompilation without this switch.
6430 Note that @code{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
6431 always trigger recompilation for sources that are preprocessed,
6432 because @code{gnatmake} cannot compute the checksum of the source after
6436 The actual preprocessing function is described in details in section
6437 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
6438 preprocessing is triggered and parameterized.
6442 @item -gnatep=@var{file}
6443 @cindex @option{-gnatep} (@code{gcc})
6444 This switch indicates to the compiler the file name (without directory
6445 information) of the preprocessor data file to use. The preprocessor data file
6446 should be found in the source directories.
6449 A preprocessing data file is a text file with significant lines indicating
6450 how should be preprocessed either a specific source or all sources not
6451 mentioned in other lines. A significant line is a non empty, non comment line.
6452 Comments are similar to Ada comments.
6455 Each significant line starts with either a literal string or the character '*'.
6456 A literal string is the file name (without directory information) of the source
6457 to preprocess. A character '*' indicates the preprocessing for all the sources
6458 that are not specified explicitly on other lines (order of the lines is not
6459 significant). It is an error to have two lines with the same file name or two
6460 lines starting with the character '*'.
6463 After the file name or the character '*', another optional literal string
6464 indicating the file name of the definition file to be used for preprocessing.
6465 (see @ref{Form of Definitions File}. The definition files are found by the
6466 compiler in one of the source directories. In some cases, when compiling
6467 a source in a directory other than the current directory, if the definition
6468 file is in the current directory, it may be necessary to add the current
6469 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
6470 the compiler would not find the definition file.
6473 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
6474 be found. Those ^switches^switches^ are:
6479 Causes both preprocessor lines and the lines deleted by
6480 preprocessing to be replaced by blank lines, preserving the line number.
6481 This ^switch^switch^ is always implied; however, if specified after @option{-c}
6482 it cancels the effect of @option{-c}.
6485 Causes both preprocessor lines and the lines deleted
6486 by preprocessing to be retained as comments marked
6487 with the special string ``@code{--! }''.
6489 @item -Dsymbol=value
6490 Define or redefine a symbol, associated with value. A symbol is an Ada
6491 identifier, or an Ada reserved word, with the exception of @code{if},
6492 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
6493 @code{value} is either a literal string, an Ada identifier or any Ada reserved
6494 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
6495 same name defined in a definition file.
6498 Causes a sorted list of symbol names and values to be
6499 listed on the standard output file.
6502 Causes undefined symbols to be treated as having the value @code{FALSE}
6504 of a preprocessor test. In the absence of this option, an undefined symbol in
6505 a @code{#if} or @code{#elsif} test will be treated as an error.
6510 Examples of valid lines in a preprocessor data file:
6513 "toto.adb" "prep.def" -u
6514 -- preprocess "toto.adb", using definition file "prep.def",
6515 -- undefined symbol are False.
6518 -- preprocess all other sources without a definition file;
6519 -- suppressed lined are commented; symbol VERSION has the value V101.
6521 "titi.adb" "prep2.def" -s
6522 -- preprocess "titi.adb", using definition file "prep2.def";
6523 -- list all symbols with their values.
6526 @item ^-gnateD^/DATA_PREPROCESSING=^symbol[=value]
6527 @cindex @option{-gnateD} (@code{gcc})
6528 Define or redefine a preprocessing symbol, associated with value. If no value
6529 is given on the command line, then the value of the symbol is @code{True}.
6530 A symbol is an identifier, following normal Ada (case-insensitive)
6531 rules for its syntax, and value is any sequence (including an empty sequence)
6532 of characters from the set (letters, digits, period, underline).
6533 Ada reserved words may be used as symbols, with the exceptions of @code{if},
6534 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
6537 A symbol declared with this ^switch^switch^ on the command line replaces a
6538 symbol with the same name either in a definition file or specified with a
6539 ^switch^switch^ -D in the preprocessor data file.
6542 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
6546 @node Code Generation Control
6547 @subsection Code Generation Control
6551 The GCC technology provides a wide range of target dependent
6552 @option{-m} switches for controlling
6553 details of code generation with respect to different versions of
6554 architectures. This includes variations in instruction sets (e.g.
6555 different members of the power pc family), and different requirements
6556 for optimal arrangement of instructions (e.g. different members of
6557 the x86 family). The list of available @option{-m} switches may be
6558 found in the GCC documentation.
6560 Use of the these @option{-m} switches may in some cases result in improved
6563 The GNAT Pro technology is tested and qualified without any
6564 @option{-m} switches,
6565 so generally the most reliable approach is to avoid the use of these
6566 switches. However, we generally expect most of these switches to work
6567 successfully with GNAT Pro, and many customers have reported successful
6568 use of these options.
6570 Our general advice is to avoid the use of @option{-m} switches unless
6571 special needs lead to requirements in this area. In particular,
6572 there is no point in using @option{-m} switches to improve performance
6573 unless you actually see a performance improvement.
6577 @subsection Return Codes
6578 @cindex Return Codes
6579 @cindex @option{/RETURN_CODES=VMS}
6582 On VMS, GNAT compiled programs return POSIX-style codes by default,
6583 e.g. @option{/RETURN_CODES=POSIX}.
6585 To enable VMS style return codes, GNAT LINK with the option
6586 @option{/RETURN_CODES=VMS}. For example:
6589 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
6593 Programs built with /RETURN_CODES=VMS are suitable to be called in
6594 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
6595 are suitable for spawning with appropriate GNAT RTL routines.
6600 @node Search Paths and the Run-Time Library (RTL)
6601 @section Search Paths and the Run-Time Library (RTL)
6604 With the GNAT source-based library system, the compiler must be able to
6605 find source files for units that are needed by the unit being compiled.
6606 Search paths are used to guide this process.
6608 The compiler compiles one source file whose name must be given
6609 explicitly on the command line. In other words, no searching is done
6610 for this file. To find all other source files that are needed (the most
6611 common being the specs of units), the compiler examines the following
6612 directories, in the following order:
6616 The directory containing the source file of the main unit being compiled
6617 (the file name on the command line).
6620 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
6621 @code{gcc} command line, in the order given.
6624 @findex ADA_INCLUDE_PATH
6625 Each of the directories listed in the value of the
6626 @code{ADA_INCLUDE_PATH} ^environment variable^logical name^.
6628 Construct this value
6629 exactly as the @code{PATH} environment variable: a list of directory
6630 names separated by colons (semicolons when working with the NT version).
6633 Normally, define this value as a logical name containing a comma separated
6634 list of directory names.
6636 This variable can also be defined by means of an environment string
6637 (an argument to the DEC C exec* set of functions).
6641 DEFINE ANOTHER_PATH FOO:[BAG]
6642 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
6645 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
6646 first, followed by the standard Ada 95
6647 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
6648 If this is not redefined, the user will obtain the DEC Ada 83 IO packages
6649 (Text_IO, Sequential_IO, etc)
6650 instead of the Ada95 packages. Thus, in order to get the Ada 95
6651 packages by default, ADA_INCLUDE_PATH must be redefined.
6655 @findex ADA_PRJ_INCLUDE_FILE
6656 Each of the directories listed in the text file whose name is given
6657 by the @code{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
6660 @code{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
6661 driver when project files are used. It should not normally be set
6665 The content of the @file{ada_source_path} file which is part of the GNAT
6666 installation tree and is used to store standard libraries such as the
6667 GNAT Run Time Library (RTL) source files.
6669 @ref{Installing the library}
6674 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
6675 inhibits the use of the directory
6676 containing the source file named in the command line. You can still
6677 have this directory on your search path, but in this case it must be
6678 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
6680 Specifying the switch @option{-nostdinc}
6681 inhibits the search of the default location for the GNAT Run Time
6682 Library (RTL) source files.
6684 The compiler outputs its object files and ALI files in the current
6687 Caution: The object file can be redirected with the @option{-o} switch;
6688 however, @code{gcc} and @code{gnat1} have not been coordinated on this
6689 so the @file{ALI} file will not go to the right place. Therefore, you should
6690 avoid using the @option{-o} switch.
6694 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
6695 children make up the GNAT RTL, together with the simple @code{System.IO}
6696 package used in the @code{"Hello World"} example. The sources for these units
6697 are needed by the compiler and are kept together in one directory. Not
6698 all of the bodies are needed, but all of the sources are kept together
6699 anyway. In a normal installation, you need not specify these directory
6700 names when compiling or binding. Either the environment variables or
6701 the built-in defaults cause these files to be found.
6703 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
6704 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
6705 consisting of child units of @code{GNAT}. This is a collection of generally
6706 useful types, subprograms, etc. See the @cite{GNAT Reference Manual} for
6709 Besides simplifying access to the RTL, a major use of search paths is
6710 in compiling sources from multiple directories. This can make
6711 development environments much more flexible.
6714 @node Order of Compilation Issues
6715 @section Order of Compilation Issues
6718 If, in our earlier example, there was a spec for the @code{hello}
6719 procedure, it would be contained in the file @file{hello.ads}; yet this
6720 file would not have to be explicitly compiled. This is the result of the
6721 model we chose to implement library management. Some of the consequences
6722 of this model are as follows:
6726 There is no point in compiling specs (except for package
6727 specs with no bodies) because these are compiled as needed by clients. If
6728 you attempt a useless compilation, you will receive an error message.
6729 It is also useless to compile subunits because they are compiled as needed
6733 There are no order of compilation requirements: performing a
6734 compilation never obsoletes anything. The only way you can obsolete
6735 something and require recompilations is to modify one of the
6736 source files on which it depends.
6739 There is no library as such, apart from the ALI files
6740 (@pxref{The Ada Library Information Files}, for information on the format
6741 of these files). For now we find it convenient to create separate ALI files,
6742 but eventually the information therein may be incorporated into the object
6746 When you compile a unit, the source files for the specs of all units
6747 that it @code{with}'s, all its subunits, and the bodies of any generics it
6748 instantiates must be available (reachable by the search-paths mechanism
6749 described above), or you will receive a fatal error message.
6756 The following are some typical Ada compilation command line examples:
6759 @item $ gcc -c xyz.adb
6760 Compile body in file @file{xyz.adb} with all default options.
6763 @item $ gcc -c -O2 -gnata xyz-def.adb
6766 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
6769 Compile the child unit package in file @file{xyz-def.adb} with extensive
6770 optimizations, and pragma @code{Assert}/@code{Debug} statements
6773 @item $ gcc -c -gnatc abc-def.adb
6774 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
6778 @node Binding Using gnatbind
6779 @chapter Binding Using @code{gnatbind}
6783 * Running gnatbind::
6784 * Switches for gnatbind::
6785 * Command-Line Access::
6786 * Search Paths for gnatbind::
6787 * Examples of gnatbind Usage::
6791 This chapter describes the GNAT binder, @code{gnatbind}, which is used
6792 to bind compiled GNAT objects. The @code{gnatbind} program performs
6793 four separate functions:
6797 Checks that a program is consistent, in accordance with the rules in
6798 Chapter 10 of the Ada 95 Reference Manual. In particular, error
6799 messages are generated if a program uses inconsistent versions of a
6803 Checks that an acceptable order of elaboration exists for the program
6804 and issues an error message if it cannot find an order of elaboration
6805 that satisfies the rules in Chapter 10 of the Ada 95 Language Manual.
6808 Generates a main program incorporating the given elaboration order.
6809 This program is a small Ada package (body and spec) that
6810 must be subsequently compiled
6811 using the GNAT compiler. The necessary compilation step is usually
6812 performed automatically by @code{gnatlink}. The two most important
6813 functions of this program
6814 are to call the elaboration routines of units in an appropriate order
6815 and to call the main program.
6818 Determines the set of object files required by the given main program.
6819 This information is output in the forms of comments in the generated program,
6820 to be read by the @code{gnatlink} utility used to link the Ada application.
6824 @node Running gnatbind
6825 @section Running @code{gnatbind}
6828 The form of the @code{gnatbind} command is
6831 $ gnatbind [@i{switches}] @i{mainprog}[.ali] [@i{switches}]
6835 where @file{@i{mainprog}.adb} is the Ada file containing the main program
6836 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
6837 package in two files whose names are
6838 @file{b~@i{mainprog}.ads}, and @file{b~@i{mainprog}.adb}.
6839 For example, if given the
6840 parameter @file{hello.ali}, for a main program contained in file
6841 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
6842 and @file{b~hello.adb}.
6844 When doing consistency checking, the binder takes into consideration
6845 any source files it can locate. For example, if the binder determines
6846 that the given main program requires the package @code{Pack}, whose
6848 file is @file{pack.ali} and whose corresponding source spec file is
6849 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
6850 (using the same search path conventions as previously described for the
6851 @code{gcc} command). If it can locate this source file, it checks that
6853 or source checksums of the source and its references to in @file{ALI} files
6854 match. In other words, any @file{ALI} files that mentions this spec must have
6855 resulted from compiling this version of the source file (or in the case
6856 where the source checksums match, a version close enough that the
6857 difference does not matter).
6859 @cindex Source files, use by binder
6860 The effect of this consistency checking, which includes source files, is
6861 that the binder ensures that the program is consistent with the latest
6862 version of the source files that can be located at bind time. Editing a
6863 source file without compiling files that depend on the source file cause
6864 error messages to be generated by the binder.
6866 For example, suppose you have a main program @file{hello.adb} and a
6867 package @code{P}, from file @file{p.ads} and you perform the following
6872 Enter @code{gcc -c hello.adb} to compile the main program.
6875 Enter @code{gcc -c p.ads} to compile package @code{P}.
6878 Edit file @file{p.ads}.
6881 Enter @code{gnatbind hello}.
6885 At this point, the file @file{p.ali} contains an out-of-date time stamp
6886 because the file @file{p.ads} has been edited. The attempt at binding
6887 fails, and the binder generates the following error messages:
6890 error: "hello.adb" must be recompiled ("p.ads" has been modified)
6891 error: "p.ads" has been modified and must be recompiled
6895 Now both files must be recompiled as indicated, and then the bind can
6896 succeed, generating a main program. You need not normally be concerned
6897 with the contents of this file, but for reference purposes a sample
6898 binder output file is given in @ref{Example of Binder Output File}.
6900 In most normal usage, the default mode of @command{gnatbind} which is to
6901 generate the main package in Ada, as described in the previous section.
6902 In particular, this means that any Ada programmer can read and understand
6903 the generated main program. It can also be debugged just like any other
6904 Ada code provided the @option{^-g^/DEBUG^} switch is used for
6905 @command{gnatbind} and @command{gnatlink}.
6907 However for some purposes it may be convenient to generate the main
6908 program in C rather than Ada. This may for example be helpful when you
6909 are generating a mixed language program with the main program in C. The
6910 GNAT compiler itself is an example.
6911 The use of the @option{^-C^/BIND_FILE=C^} switch
6912 for both @code{gnatbind} and @code{gnatlink} will cause the program to
6913 be generated in C (and compiled using the gnu C compiler).
6916 @node Switches for gnatbind
6917 @section Switches for @command{gnatbind}
6920 The following switches are available with @code{gnatbind}; details will
6921 be presented in subsequent sections.
6924 * Consistency-Checking Modes::
6925 * Binder Error Message Control::
6926 * Elaboration Control::
6928 * Binding with Non-Ada Main Programs::
6929 * Binding Programs with No Main Subprogram::
6934 @item ^-aO^/OBJECT_SEARCH^
6935 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
6936 Specify directory to be searched for ALI files.
6938 @item ^-aI^/SOURCE_SEARCH^
6939 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
6940 Specify directory to be searched for source file.
6942 @item ^-A^/BIND_FILE=ADA^
6943 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
6944 Generate binder program in Ada (default)
6946 @item ^-b^/REPORT_ERRORS=BRIEF^
6947 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
6948 Generate brief messages to @file{stderr} even if verbose mode set.
6950 @item ^-c^/NOOUTPUT^
6951 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
6952 Check only, no generation of binder output file.
6954 @item ^-C^/BIND_FILE=C^
6955 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
6956 Generate binder program in C
6958 @item ^-e^/ELABORATION_DEPENDENCIES^
6959 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
6960 Output complete list of elaboration-order dependencies.
6962 @item ^-E^/STORE_TRACEBACKS^
6963 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
6964 Store tracebacks in exception occurrences when the target supports it.
6965 This is the default with the zero cost exception mechanism.
6967 @c The following may get moved to an appendix
6968 This option is currently supported on the following targets:
6969 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
6971 See also the packages @code{GNAT.Traceback} and
6972 @code{GNAT.Traceback.Symbolic} for more information.
6974 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
6978 @item ^-F^/FORCE_ELABS_FLAGS^
6979 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
6980 Force the checks of elaboration flags. @command{gnatbind} does not normally
6981 generate checks of elaboration flags for the main executable, except when
6982 a Stand-Alone Library is used. However, there are cases when this cannot be
6983 detected by gnatbind. An example is importing an interface of a Stand-Alone
6984 Library through a pragma Import and only specifying through a linker switch
6985 this Stand-Alone Library. This switch is used to guarantee that elaboration
6986 flag checks are generated.
6989 @cindex @option{^-h^/HELP^} (@command{gnatbind})
6990 Output usage (help) information
6993 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
6994 Specify directory to be searched for source and ALI files.
6996 @item ^-I-^/NOCURRENT_DIRECTORY^
6997 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
6998 Do not look for sources in the current directory where @code{gnatbind} was
6999 invoked, and do not look for ALI files in the directory containing the
7000 ALI file named in the @code{gnatbind} command line.
7002 @item ^-l^/ORDER_OF_ELABORATION^
7003 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
7004 Output chosen elaboration order.
7006 @item ^-Lxxx^/BUILD_LIBRARY=xxx^
7007 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
7008 Binds the units for library building. In this case the adainit and
7009 adafinal procedures (See @pxref{Binding with Non-Ada Main Programs})
7010 are renamed to ^xxxinit^XXXINIT^ and
7011 ^xxxfinal^XXXFINAL^.
7012 Implies ^-n^/NOCOMPILE^.
7014 (@pxref{GNAT and Libraries}, for more details.)
7017 On OpenVMS, these init and final procedures are exported in uppercase
7018 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
7019 the init procedure will be "TOTOINIT" and the exported name of the final
7020 procedure will be "TOTOFINAL".
7023 @item ^-Mxyz^/RENAME_MAIN=xyz^
7024 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
7025 Rename generated main program from main to xyz
7027 @item ^-m^/ERROR_LIMIT=^@var{n}
7028 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
7029 Limit number of detected errors to @var{n}, where @var{n} is
7030 in the range 1..999_999. The default value if no switch is
7031 given is 9999. Binding is terminated if the limit is exceeded.
7033 Furthermore, under Windows, the sources pointed to by the libraries path
7034 set in the registry are not searched for.
7038 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7042 @cindex @option{-nostdinc} (@command{gnatbind})
7043 Do not look for sources in the system default directory.
7046 @cindex @option{-nostdlib} (@command{gnatbind})
7047 Do not look for library files in the system default directory.
7049 @item --RTS=@var{rts-path}
7050 @cindex @option{--RTS} (@code{gnatbind})
7051 Specifies the default location of the runtime library. Same meaning as the
7052 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
7054 @item ^-o ^/OUTPUT=^@var{file}
7055 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
7056 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
7057 Note that if this option is used, then linking must be done manually,
7058 gnatlink cannot be used.
7060 @item ^-O^/OBJECT_LIST^
7061 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
7064 @item ^-p^/PESSIMISTIC_ELABORATION^
7065 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
7066 Pessimistic (worst-case) elaboration order
7068 @item ^-s^/READ_SOURCES=ALL^
7069 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
7070 Require all source files to be present.
7072 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
7073 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
7074 Specifies the value to be used when detecting uninitialized scalar
7075 objects with pragma Initialize_Scalars.
7076 The @var{xxx} ^string specified with the switch^option^ may be either
7078 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
7079 @item ``@option{^lo^LOW^}'' for the lowest possible value
7080 possible, and the low
7081 @item ``@option{^hi^HIGH^}'' for the highest possible value
7082 @item ``@option{xx}'' for a value consisting of repeated bytes with the
7083 value 16#xx# (i.e. xx is a string of two hexadecimal digits).
7086 In addition, you can specify @option{-Sev} to indicate that the value is
7087 to be set at run time. In this case, the program will look for an environment
7088 @cindex GNAT_INIT_SCALARS
7089 variable of the form @code{GNAT_INIT_SCALARS=xx}, where xx is one
7090 of @option{in/lo/hi/xx} with the same meanings as above.
7091 If no environment variable is found, or if it does not have a valid value,
7092 then the default is @option{in} (invalid values).
7096 @cindex @option{-static} (@code{gnatbind})
7097 Link against a static GNAT run time.
7100 @cindex @option{-shared} (@code{gnatbind})
7101 Link against a shared GNAT run time when available.
7104 @item ^-t^/NOTIME_STAMP_CHECK^
7105 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7106 Tolerate time stamp and other consistency errors
7108 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
7109 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
7110 Set the time slice value to @var{n} milliseconds. If the system supports
7111 the specification of a specific time slice value, then the indicated value
7112 is used. If the system does not support specific time slice values, but
7113 does support some general notion of round-robin scheduling, then any
7114 non-zero value will activate round-robin scheduling.
7116 A value of zero is treated specially. It turns off time
7117 slicing, and in addition, indicates to the tasking run time that the
7118 semantics should match as closely as possible the Annex D
7119 requirements of the Ada RM, and in particular sets the default
7120 scheduling policy to @code{FIFO_Within_Priorities}.
7122 @item ^-v^/REPORT_ERRORS=VERBOSE^
7123 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7124 Verbose mode. Write error messages, header, summary output to
7129 @cindex @option{-w} (@code{gnatbind})
7130 Warning mode (@var{x}=s/e for suppress/treat as error)
7134 @item /WARNINGS=NORMAL
7135 @cindex @option{/WARNINGS} (@code{gnatbind})
7136 Normal warnings mode. Warnings are issued but ignored
7138 @item /WARNINGS=SUPPRESS
7139 @cindex @option{/WARNINGS} (@code{gnatbind})
7140 All warning messages are suppressed
7142 @item /WARNINGS=ERROR
7143 @cindex @option{/WARNINGS} (@code{gnatbind})
7144 Warning messages are treated as fatal errors
7147 @item ^-x^/READ_SOURCES=NONE^
7148 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
7149 Exclude source files (check object consistency only).
7152 @item /READ_SOURCES=AVAILABLE
7153 @cindex @option{/READ_SOURCES} (@code{gnatbind})
7154 Default mode, in which sources are checked for consistency only if
7158 @item ^-z^/ZERO_MAIN^
7159 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7165 You may obtain this listing of switches by running @code{gnatbind} with
7170 @node Consistency-Checking Modes
7171 @subsection Consistency-Checking Modes
7174 As described earlier, by default @code{gnatbind} checks
7175 that object files are consistent with one another and are consistent
7176 with any source files it can locate. The following switches control binder
7181 @item ^-s^/READ_SOURCES=ALL^
7182 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
7183 Require source files to be present. In this mode, the binder must be
7184 able to locate all source files that are referenced, in order to check
7185 their consistency. In normal mode, if a source file cannot be located it
7186 is simply ignored. If you specify this switch, a missing source
7189 @item ^-x^/READ_SOURCES=NONE^
7190 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
7191 Exclude source files. In this mode, the binder only checks that ALI
7192 files are consistent with one another. Source files are not accessed.
7193 The binder runs faster in this mode, and there is still a guarantee that
7194 the resulting program is self-consistent.
7195 If a source file has been edited since it was last compiled, and you
7196 specify this switch, the binder will not detect that the object
7197 file is out of date with respect to the source file. Note that this is the
7198 mode that is automatically used by @code{gnatmake} because in this
7199 case the checking against sources has already been performed by
7200 @code{gnatmake} in the course of compilation (i.e. before binding).
7203 @item /READ_SOURCES=AVAILABLE
7204 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
7205 This is the default mode in which source files are checked if they are
7206 available, and ignored if they are not available.
7210 @node Binder Error Message Control
7211 @subsection Binder Error Message Control
7214 The following switches provide control over the generation of error
7215 messages from the binder:
7219 @item ^-v^/REPORT_ERRORS=VERBOSE^
7220 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7221 Verbose mode. In the normal mode, brief error messages are generated to
7222 @file{stderr}. If this switch is present, a header is written
7223 to @file{stdout} and any error messages are directed to @file{stdout}.
7224 All that is written to @file{stderr} is a brief summary message.
7226 @item ^-b^/REPORT_ERRORS=BRIEF^
7227 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
7228 Generate brief error messages to @file{stderr} even if verbose mode is
7229 specified. This is relevant only when used with the
7230 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
7234 @cindex @option{-m} (@code{gnatbind})
7235 Limits the number of error messages to @var{n}, a decimal integer in the
7236 range 1-999. The binder terminates immediately if this limit is reached.
7239 @cindex @option{-M} (@code{gnatbind})
7240 Renames the generated main program from @code{main} to @code{xxx}.
7241 This is useful in the case of some cross-building environments, where
7242 the actual main program is separate from the one generated
7246 @item ^-ws^/WARNINGS=SUPPRESS^
7247 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
7249 Suppress all warning messages.
7251 @item ^-we^/WARNINGS=ERROR^
7252 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
7253 Treat any warning messages as fatal errors.
7256 @item /WARNINGS=NORMAL
7257 Standard mode with warnings generated, but warnings do not get treated
7261 @item ^-t^/NOTIME_STAMP_CHECK^
7262 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7263 @cindex Time stamp checks, in binder
7264 @cindex Binder consistency checks
7265 @cindex Consistency checks, in binder
7266 The binder performs a number of consistency checks including:
7270 Check that time stamps of a given source unit are consistent
7272 Check that checksums of a given source unit are consistent
7274 Check that consistent versions of @code{GNAT} were used for compilation
7276 Check consistency of configuration pragmas as required
7280 Normally failure of such checks, in accordance with the consistency
7281 requirements of the Ada Reference Manual, causes error messages to be
7282 generated which abort the binder and prevent the output of a binder
7283 file and subsequent link to obtain an executable.
7285 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
7286 into warnings, so that
7287 binding and linking can continue to completion even in the presence of such
7288 errors. The result may be a failed link (due to missing symbols), or a
7289 non-functional executable which has undefined semantics.
7290 @emph{This means that
7291 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
7295 @node Elaboration Control
7296 @subsection Elaboration Control
7299 The following switches provide additional control over the elaboration
7300 order. For full details see @xref{Elaboration Order Handling in GNAT}.
7303 @item ^-p^/PESSIMISTIC_ELABORATION^
7304 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
7305 Normally the binder attempts to choose an elaboration order that is
7306 likely to minimize the likelihood of an elaboration order error resulting
7307 in raising a @code{Program_Error} exception. This switch reverses the
7308 action of the binder, and requests that it deliberately choose an order
7309 that is likely to maximize the likelihood of an elaboration error.
7310 This is useful in ensuring portability and avoiding dependence on
7311 accidental fortuitous elaboration ordering.
7313 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
7315 elaboration checking is used (@option{-gnatE} switch used for compilation).
7316 This is because in the default static elaboration mode, all necessary
7317 @code{Elaborate_All} pragmas are implicitly inserted.
7318 These implicit pragmas are still respected by the binder in
7319 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
7320 safe elaboration order is assured.
7323 @node Output Control
7324 @subsection Output Control
7327 The following switches allow additional control over the output
7328 generated by the binder.
7333 @item ^-A^/BIND_FILE=ADA^
7334 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
7335 Generate binder program in Ada (default). The binder program is named
7336 @file{b~@var{mainprog}.adb} by default. This can be changed with
7337 @option{^-o^/OUTPUT^} @code{gnatbind} option.
7339 @item ^-c^/NOOUTPUT^
7340 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
7341 Check only. Do not generate the binder output file. In this mode the
7342 binder performs all error checks but does not generate an output file.
7344 @item ^-C^/BIND_FILE=C^
7345 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
7346 Generate binder program in C. The binder program is named
7347 @file{b_@var{mainprog}.c}.
7348 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
7351 @item ^-e^/ELABORATION_DEPENDENCIES^
7352 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
7353 Output complete list of elaboration-order dependencies, showing the
7354 reason for each dependency. This output can be rather extensive but may
7355 be useful in diagnosing problems with elaboration order. The output is
7356 written to @file{stdout}.
7359 @cindex @option{^-h^/HELP^} (@code{gnatbind})
7360 Output usage information. The output is written to @file{stdout}.
7362 @item ^-K^/LINKER_OPTION_LIST^
7363 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
7364 Output linker options to @file{stdout}. Includes library search paths,
7365 contents of pragmas Ident and Linker_Options, and libraries added
7368 @item ^-l^/ORDER_OF_ELABORATION^
7369 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
7370 Output chosen elaboration order. The output is written to @file{stdout}.
7372 @item ^-O^/OBJECT_LIST^
7373 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
7374 Output full names of all the object files that must be linked to provide
7375 the Ada component of the program. The output is written to @file{stdout}.
7376 This list includes the files explicitly supplied and referenced by the user
7377 as well as implicitly referenced run-time unit files. The latter are
7378 omitted if the corresponding units reside in shared libraries. The
7379 directory names for the run-time units depend on the system configuration.
7381 @item ^-o ^/OUTPUT=^@var{file}
7382 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
7383 Set name of output file to @var{file} instead of the normal
7384 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
7385 binder generated body filename. In C mode you would normally give
7386 @var{file} an extension of @file{.c} because it will be a C source program.
7387 Note that if this option is used, then linking must be done manually.
7388 It is not possible to use gnatlink in this case, since it cannot locate
7391 @item ^-r^/RESTRICTION_LIST^
7392 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
7393 Generate list of @code{pragma Restrictions} that could be applied to
7394 the current unit. This is useful for code audit purposes, and also may
7395 be used to improve code generation in some cases.
7399 @node Binding with Non-Ada Main Programs
7400 @subsection Binding with Non-Ada Main Programs
7403 In our description so far we have assumed that the main
7404 program is in Ada, and that the task of the binder is to generate a
7405 corresponding function @code{main} that invokes this Ada main
7406 program. GNAT also supports the building of executable programs where
7407 the main program is not in Ada, but some of the called routines are
7408 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
7409 The following switch is used in this situation:
7413 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
7414 No main program. The main program is not in Ada.
7418 In this case, most of the functions of the binder are still required,
7419 but instead of generating a main program, the binder generates a file
7420 containing the following callable routines:
7425 You must call this routine to initialize the Ada part of the program by
7426 calling the necessary elaboration routines. A call to @code{adainit} is
7427 required before the first call to an Ada subprogram.
7429 Note that it is assumed that the basic execution environment must be setup
7430 to be appropriate for Ada execution at the point where the first Ada
7431 subprogram is called. In particular, if the Ada code will do any
7432 floating-point operations, then the FPU must be setup in an appropriate
7433 manner. For the case of the x86, for example, full precision mode is
7434 required. The procedure GNAT.Float_Control.Reset may be used to ensure
7435 that the FPU is in the right state.
7439 You must call this routine to perform any library-level finalization
7440 required by the Ada subprograms. A call to @code{adafinal} is required
7441 after the last call to an Ada subprogram, and before the program
7446 If the @option{^-n^/NOMAIN^} switch
7447 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7448 @cindex Binder, multiple input files
7449 is given, more than one ALI file may appear on
7450 the command line for @code{gnatbind}. The normal @dfn{closure}
7451 calculation is performed for each of the specified units. Calculating
7452 the closure means finding out the set of units involved by tracing
7453 @code{with} references. The reason it is necessary to be able to
7454 specify more than one ALI file is that a given program may invoke two or
7455 more quite separate groups of Ada units.
7457 The binder takes the name of its output file from the last specified ALI
7458 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
7459 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
7460 The output is an Ada unit in source form that can
7461 be compiled with GNAT unless the -C switch is used in which case the
7462 output is a C source file, which must be compiled using the C compiler.
7463 This compilation occurs automatically as part of the @code{gnatlink}
7466 Currently the GNAT run time requires a FPU using 80 bits mode
7467 precision. Under targets where this is not the default it is required to
7468 call GNAT.Float_Control.Reset before using floating point numbers (this
7469 include float computation, float input and output) in the Ada code. A
7470 side effect is that this could be the wrong mode for the foreign code
7471 where floating point computation could be broken after this call.
7473 @node Binding Programs with No Main Subprogram
7474 @subsection Binding Programs with No Main Subprogram
7477 It is possible to have an Ada program which does not have a main
7478 subprogram. This program will call the elaboration routines of all the
7479 packages, then the finalization routines.
7481 The following switch is used to bind programs organized in this manner:
7484 @item ^-z^/ZERO_MAIN^
7485 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7486 Normally the binder checks that the unit name given on the command line
7487 corresponds to a suitable main subprogram. When this switch is used,
7488 a list of ALI files can be given, and the execution of the program
7489 consists of elaboration of these units in an appropriate order.
7493 @node Command-Line Access
7494 @section Command-Line Access
7497 The package @code{Ada.Command_Line} provides access to the command-line
7498 arguments and program name. In order for this interface to operate
7499 correctly, the two variables
7511 are declared in one of the GNAT library routines. These variables must
7512 be set from the actual @code{argc} and @code{argv} values passed to the
7513 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
7514 generates the C main program to automatically set these variables.
7515 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
7516 set these variables. If they are not set, the procedures in
7517 @code{Ada.Command_Line} will not be available, and any attempt to use
7518 them will raise @code{Constraint_Error}. If command line access is
7519 required, your main program must set @code{gnat_argc} and
7520 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
7524 @node Search Paths for gnatbind
7525 @section Search Paths for @code{gnatbind}
7528 The binder takes the name of an ALI file as its argument and needs to
7529 locate source files as well as other ALI files to verify object consistency.
7531 For source files, it follows exactly the same search rules as @code{gcc}
7532 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
7533 directories searched are:
7537 The directory containing the ALI file named in the command line, unless
7538 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
7541 All directories specified by @option{^-I^/SEARCH^}
7542 switches on the @code{gnatbind}
7543 command line, in the order given.
7546 @findex ADA_OBJECTS_PATH
7547 Each of the directories listed in the value of the
7548 @code{ADA_OBJECTS_PATH} ^environment variable^logical name^.
7550 Construct this value
7551 exactly as the @code{PATH} environment variable: a list of directory
7552 names separated by colons (semicolons when working with the NT version
7556 Normally, define this value as a logical name containing a comma separated
7557 list of directory names.
7559 This variable can also be defined by means of an environment string
7560 (an argument to the DEC C exec* set of functions).
7564 DEFINE ANOTHER_PATH FOO:[BAG]
7565 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7568 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7569 first, followed by the standard Ada 95
7570 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
7571 If this is not redefined, the user will obtain the DEC Ada 83 IO packages
7572 (Text_IO, Sequential_IO, etc)
7573 instead of the Ada95 packages. Thus, in order to get the Ada 95
7574 packages by default, ADA_OBJECTS_PATH must be redefined.
7578 @findex ADA_PRJ_OBJECTS_FILE
7579 Each of the directories listed in the text file whose name is given
7580 by the @code{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
7583 @code{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7584 driver when project files are used. It should not normally be set
7588 The content of the @file{ada_object_path} file which is part of the GNAT
7589 installation tree and is used to store standard libraries such as the
7590 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
7593 @ref{Installing the library}
7598 In the binder the switch @option{^-I^/SEARCH^}
7599 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
7600 is used to specify both source and
7601 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
7602 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7603 instead if you want to specify
7604 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
7605 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
7606 if you want to specify library paths
7607 only. This means that for the binder
7608 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
7609 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
7610 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
7611 The binder generates the bind file (a C language source file) in the
7612 current working directory.
7618 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7619 children make up the GNAT Run-Time Library, together with the package
7620 GNAT and its children, which contain a set of useful additional
7621 library functions provided by GNAT. The sources for these units are
7622 needed by the compiler and are kept together in one directory. The ALI
7623 files and object files generated by compiling the RTL are needed by the
7624 binder and the linker and are kept together in one directory, typically
7625 different from the directory containing the sources. In a normal
7626 installation, you need not specify these directory names when compiling
7627 or binding. Either the environment variables or the built-in defaults
7628 cause these files to be found.
7630 Besides simplifying access to the RTL, a major use of search paths is
7631 in compiling sources from multiple directories. This can make
7632 development environments much more flexible.
7634 @node Examples of gnatbind Usage
7635 @section Examples of @code{gnatbind} Usage
7638 This section contains a number of examples of using the GNAT binding
7639 utility @code{gnatbind}.
7642 @item gnatbind hello
7643 The main program @code{Hello} (source program in @file{hello.adb}) is
7644 bound using the standard switch settings. The generated main program is
7645 @file{b~hello.adb}. This is the normal, default use of the binder.
7648 @item gnatbind hello -o mainprog.adb
7651 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
7653 The main program @code{Hello} (source program in @file{hello.adb}) is
7654 bound using the standard switch settings. The generated main program is
7655 @file{mainprog.adb} with the associated spec in
7656 @file{mainprog.ads}. Note that you must specify the body here not the
7657 spec, in the case where the output is in Ada. Note that if this option
7658 is used, then linking must be done manually, since gnatlink will not
7659 be able to find the generated file.
7662 @item gnatbind main -C -o mainprog.c -x
7665 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
7667 The main program @code{Main} (source program in
7668 @file{main.adb}) is bound, excluding source files from the
7669 consistency checking, generating
7670 the file @file{mainprog.c}.
7673 @item gnatbind -x main_program -C -o mainprog.c
7674 This command is exactly the same as the previous example. Switches may
7675 appear anywhere in the command line, and single letter switches may be
7676 combined into a single switch.
7680 @item gnatbind -n math dbase -C -o ada-control.c
7683 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
7685 The main program is in a language other than Ada, but calls to
7686 subprograms in packages @code{Math} and @code{Dbase} appear. This call
7687 to @code{gnatbind} generates the file @file{ada-control.c} containing
7688 the @code{adainit} and @code{adafinal} routines to be called before and
7689 after accessing the Ada units.
7693 @c ------------------------------------
7694 @node Linking Using gnatlink
7695 @chapter Linking Using @code{gnatlink}
7696 @c ------------------------------------
7700 This chapter discusses @code{gnatlink}, a tool that links
7701 an Ada program and builds an executable file. This utility
7702 invokes the system linker ^(via the @code{gcc} command)^^
7703 with a correct list of object files and library references.
7704 @code{gnatlink} automatically determines the list of files and
7705 references for the Ada part of a program. It uses the binder file
7706 generated by the @command{gnatbind} to determine this list.
7709 * Running gnatlink::
7710 * Switches for gnatlink::
7711 * Setting Stack Size from gnatlink::
7712 * Setting Heap Size from gnatlink::
7715 @node Running gnatlink
7716 @section Running @code{gnatlink}
7719 The form of the @code{gnatlink} command is
7722 $ gnatlink [@var{switches}] @var{mainprog}[.ali]
7723 [@var{non-Ada objects}] [@var{linker options}]
7727 The arguments of @code{gnatlink} (switches, main @file{ALI} file,
7729 or linker options) may be in any order, provided that no non-Ada object may
7730 be mistaken for a main @file{ALI} file.
7731 Any file name @file{F} without the @file{.ali}
7732 extension will be taken as the main @file{ALI} file if a file exists
7733 whose name is the concatenation of @file{F} and @file{.ali}.
7736 @file{@var{mainprog}.ali} references the ALI file of the main program.
7737 The @file{.ali} extension of this file can be omitted. From this
7738 reference, @code{gnatlink} locates the corresponding binder file
7739 @file{b~@var{mainprog}.adb} and, using the information in this file along
7740 with the list of non-Ada objects and linker options, constructs a
7741 linker command file to create the executable.
7743 The arguments other than the @code{gnatlink} switches and the main @file{ALI}
7744 file are passed to the linker uninterpreted.
7745 They typically include the names of
7746 object files for units written in other languages than Ada and any library
7747 references required to resolve references in any of these foreign language
7748 units, or in @code{Import} pragmas in any Ada units.
7750 @var{linker options} is an optional list of linker specific
7752 The default linker called by gnatlink is @var{gcc} which in
7753 turn calls the appropriate system linker.
7754 Standard options for the linker such as @option{-lmy_lib} or
7755 @option{-Ldir} can be added as is.
7756 For options that are not recognized by
7757 @var{gcc} as linker options, use the @var{gcc} switches @option{-Xlinker} or
7759 Refer to the GCC documentation for
7760 details. Here is an example showing how to generate a linker map:
7764 $ gnatlink my_prog -Wl,-Map,MAPFILE
7769 <<Need example for VMS>>
7772 Using @var{linker options} it is possible to set the program stack and
7773 heap size. See @ref{Setting Stack Size from gnatlink}, and
7774 @ref{Setting Heap Size from gnatlink}.
7776 @code{gnatlink} determines the list of objects required by the Ada
7777 program and prepends them to the list of objects passed to the linker.
7778 @code{gnatlink} also gathers any arguments set by the use of
7779 @code{pragma Linker_Options} and adds them to the list of arguments
7780 presented to the linker.
7783 @code{gnatlink} accepts the following types of extra files on the command
7784 line: objects (.OBJ), libraries (.OLB), sharable images (.EXE), and
7785 options files (.OPT). These are recognized and handled according to their
7789 @node Switches for gnatlink
7790 @section Switches for @code{gnatlink}
7793 The following switches are available with the @code{gnatlink} utility:
7798 @item ^-A^/BIND_FILE=ADA^
7799 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatlink})
7800 The binder has generated code in Ada. This is the default.
7802 @item ^-C^/BIND_FILE=C^
7803 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatlink})
7804 If instead of generating a file in Ada, the binder has generated one in
7805 C, then the linker needs to know about it. Use this switch to signal
7806 to @code{gnatlink} that the binder has generated C code rather than
7809 @item ^-f^/FORCE_OBJECT_FILE_LIST^
7810 @cindex Command line length
7811 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@code{gnatlink})
7812 On some targets, the command line length is limited, and @code{gnatlink}
7813 will generate a separate file for the linker if the list of object files
7815 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
7816 to be generated even if
7817 the limit is not exceeded. This is useful in some cases to deal with
7818 special situations where the command line length is exceeded.
7821 @cindex Debugging information, including
7822 @cindex @option{^-g^/DEBUG^} (@code{gnatlink})
7823 The option to include debugging information causes the Ada bind file (in
7824 other words, @file{b~@var{mainprog}.adb}) to be compiled with
7825 @option{^-g^/DEBUG^}.
7826 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
7827 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
7828 Without @option{^-g^/DEBUG^}, the binder removes these files by
7829 default. The same procedure apply if a C bind file was generated using
7830 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
7831 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
7833 @item ^-n^/NOCOMPILE^
7834 @cindex @option{^-n^/NOCOMPILE^} (@code{gnatlink})
7835 Do not compile the file generated by the binder. This may be used when
7836 a link is rerun with different options, but there is no need to recompile
7840 @cindex @option{^-v^/VERBOSE^} (@code{gnatlink})
7841 Causes additional information to be output, including a full list of the
7842 included object files. This switch option is most useful when you want
7843 to see what set of object files are being used in the link step.
7845 @item ^-v -v^/VERBOSE/VERBOSE^
7846 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@code{gnatlink})
7847 Very verbose mode. Requests that the compiler operate in verbose mode when
7848 it compiles the binder file, and that the system linker run in verbose mode.
7850 @item ^-o ^/EXECUTABLE=^@var{exec-name}
7851 @cindex @option{^-o^/EXECUTABLE^} (@code{gnatlink})
7852 @var{exec-name} specifies an alternate name for the generated
7853 executable program. If this switch is omitted, the executable has the same
7854 name as the main unit. For example, @code{gnatlink try.ali} creates
7855 an executable called @file{^try^TRY.EXE^}.
7858 @item -b @var{target}
7859 @cindex @option{-b} (@code{gnatlink})
7860 Compile your program to run on @var{target}, which is the name of a
7861 system configuration. You must have a GNAT cross-compiler built if
7862 @var{target} is not the same as your host system.
7865 @cindex @option{-B} (@code{gnatlink})
7866 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
7867 from @var{dir} instead of the default location. Only use this switch
7868 when multiple versions of the GNAT compiler are available. See the
7869 @code{gcc} manual page for further details. You would normally use the
7870 @option{-b} or @option{-V} switch instead.
7872 @item --GCC=@var{compiler_name}
7873 @cindex @option{--GCC=compiler_name} (@code{gnatlink})
7874 Program used for compiling the binder file. The default is
7875 `@code{gcc}'. You need to use quotes around @var{compiler_name} if
7876 @code{compiler_name} contains spaces or other separator characters. As
7877 an example @option{--GCC="foo -x -y"} will instruct @code{gnatlink} to use
7878 @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
7879 inserted after your command name. Thus in the above example the compiler
7880 command that will be used by @code{gnatlink} will be @code{foo -c -x -y}.
7881 If several @option{--GCC=compiler_name} are used, only the last
7882 @var{compiler_name} is taken into account. However, all the additional
7883 switches are also taken into account. Thus,
7884 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
7885 @option{--GCC="bar -x -y -z -t"}.
7887 @item --LINK=@var{name}
7888 @cindex @option{--LINK=} (@code{gnatlink})
7889 @var{name} is the name of the linker to be invoked. This is especially
7890 useful in mixed language programs since languages such as C++ require
7891 their own linker to be used. When this switch is omitted, the default
7892 name for the linker is (@file{gcc}). When this switch is used, the
7893 specified linker is called instead of (@file{gcc}) with exactly the same
7894 parameters that would have been passed to (@file{gcc}) so if the desired
7895 linker requires different parameters it is necessary to use a wrapper
7896 script that massages the parameters before invoking the real linker. It
7897 may be useful to control the exact invocation by using the verbose
7903 @item /DEBUG=TRACEBACK
7904 @cindex @code{/DEBUG=TRACEBACK} (@code{gnatlink})
7905 This qualifier causes sufficient information to be included in the
7906 executable file to allow a traceback, but does not include the full
7907 symbol information needed by the debugger.
7909 @item /IDENTIFICATION="<string>"
7910 @code{"<string>"} specifies the string to be stored in the image file
7911 identification field in the image header.
7912 It overrides any pragma @code{Ident} specified string.
7914 @item /NOINHIBIT-EXEC
7915 Generate the executable file even if there are linker warnings.
7917 @item /NOSTART_FILES
7918 Don't link in the object file containing the ``main'' transfer address.
7919 Used when linking with a foreign language main program compiled with a
7923 Prefer linking with object libraries over sharable images, even without
7929 @node Setting Stack Size from gnatlink
7930 @section Setting Stack Size from @code{gnatlink}
7933 Under Windows systems, it is possible to specify the program stack size from
7934 @code{gnatlink} using either:
7938 @item using @option{-Xlinker} linker option
7941 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
7944 This sets the stack reserve size to 0x10000 bytes and the stack commit
7945 size to 0x1000 bytes.
7947 @item using @option{-Wl} linker option
7950 $ gnatlink hello -Wl,--stack=0x1000000
7953 This sets the stack reserve size to 0x1000000 bytes. Note that with
7954 @option{-Wl} option it is not possible to set the stack commit size
7955 because the coma is a separator for this option.
7959 @node Setting Heap Size from gnatlink
7960 @section Setting Heap Size from @code{gnatlink}
7963 Under Windows systems, it is possible to specify the program heap size from
7964 @code{gnatlink} using either:
7968 @item using @option{-Xlinker} linker option
7971 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
7974 This sets the heap reserve size to 0x10000 bytes and the heap commit
7975 size to 0x1000 bytes.
7977 @item using @option{-Wl} linker option
7980 $ gnatlink hello -Wl,--heap=0x1000000
7983 This sets the heap reserve size to 0x1000000 bytes. Note that with
7984 @option{-Wl} option it is not possible to set the heap commit size
7985 because the coma is a separator for this option.
7989 @node The GNAT Make Program gnatmake
7990 @chapter The GNAT Make Program @code{gnatmake}
7994 * Running gnatmake::
7995 * Switches for gnatmake::
7996 * Mode Switches for gnatmake::
7997 * Notes on the Command Line::
7998 * How gnatmake Works::
7999 * Examples of gnatmake Usage::
8002 A typical development cycle when working on an Ada program consists of
8003 the following steps:
8007 Edit some sources to fix bugs.
8013 Compile all sources affected.
8023 The third step can be tricky, because not only do the modified files
8024 @cindex Dependency rules
8025 have to be compiled, but any files depending on these files must also be
8026 recompiled. The dependency rules in Ada can be quite complex, especially
8027 in the presence of overloading, @code{use} clauses, generics and inlined
8030 @code{gnatmake} automatically takes care of the third and fourth steps
8031 of this process. It determines which sources need to be compiled,
8032 compiles them, and binds and links the resulting object files.
8034 Unlike some other Ada make programs, the dependencies are always
8035 accurately recomputed from the new sources. The source based approach of
8036 the GNAT compilation model makes this possible. This means that if
8037 changes to the source program cause corresponding changes in
8038 dependencies, they will always be tracked exactly correctly by
8041 @node Running gnatmake
8042 @section Running @code{gnatmake}
8045 The usual form of the @code{gnatmake} command is
8048 $ gnatmake [@var{switches}] @var{file_name}
8049 [@var{file_names}] [@var{mode_switches}]
8053 The only required argument is one @var{file_name}, which specifies
8054 a compilation unit that is a main program. Several @var{file_names} can be
8055 specified: this will result in several executables being built.
8056 If @code{switches} are present, they can be placed before the first
8057 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
8058 If @var{mode_switches} are present, they must always be placed after
8059 the last @var{file_name} and all @code{switches}.
8061 If you are using standard file extensions (.adb and .ads), then the
8062 extension may be omitted from the @var{file_name} arguments. However, if
8063 you are using non-standard extensions, then it is required that the
8064 extension be given. A relative or absolute directory path can be
8065 specified in a @var{file_name}, in which case, the input source file will
8066 be searched for in the specified directory only. Otherwise, the input
8067 source file will first be searched in the directory where
8068 @code{gnatmake} was invoked and if it is not found, it will be search on
8069 the source path of the compiler as described in
8070 @ref{Search Paths and the Run-Time Library (RTL)}.
8072 All @code{gnatmake} output (except when you specify
8073 @option{^-M^/DEPENDENCIES_LIST^}) is to
8074 @file{stderr}. The output produced by the
8075 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
8078 @node Switches for gnatmake
8079 @section Switches for @code{gnatmake}
8082 You may specify any of the following switches to @code{gnatmake}:
8087 @item --GCC=@var{compiler_name}
8088 @cindex @option{--GCC=compiler_name} (@code{gnatmake})
8089 Program used for compiling. The default is `@code{gcc}'. You need to use
8090 quotes around @var{compiler_name} if @code{compiler_name} contains
8091 spaces or other separator characters. As an example @option{--GCC="foo -x
8092 -y"} will instruct @code{gnatmake} to use @code{foo -x -y} as your
8093 compiler. Note that switch @option{-c} is always inserted after your
8094 command name. Thus in the above example the compiler command that will
8095 be used by @code{gnatmake} will be @code{foo -c -x -y}.
8096 If several @option{--GCC=compiler_name} are used, only the last
8097 @var{compiler_name} is taken into account. However, all the additional
8098 switches are also taken into account. Thus,
8099 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8100 @option{--GCC="bar -x -y -z -t"}.
8102 @item --GNATBIND=@var{binder_name}
8103 @cindex @option{--GNATBIND=binder_name} (@code{gnatmake})
8104 Program used for binding. The default is `@code{gnatbind}'. You need to
8105 use quotes around @var{binder_name} if @var{binder_name} contains spaces
8106 or other separator characters. As an example @option{--GNATBIND="bar -x
8107 -y"} will instruct @code{gnatmake} to use @code{bar -x -y} as your
8108 binder. Binder switches that are normally appended by @code{gnatmake} to
8109 `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
8111 @item --GNATLINK=@var{linker_name}
8112 @cindex @option{--GNATLINK=linker_name} (@code{gnatmake})
8113 Program used for linking. The default is `@code{gnatlink}'. You need to
8114 use quotes around @var{linker_name} if @var{linker_name} contains spaces
8115 or other separator characters. As an example @option{--GNATLINK="lan -x
8116 -y"} will instruct @code{gnatmake} to use @code{lan -x -y} as your
8117 linker. Linker switches that are normally appended by @code{gnatmake} to
8118 `@code{gnatlink}' are now appended to the end of @code{lan -x -y}.
8122 @item ^-a^/ALL_FILES^
8123 @cindex @option{^-a^/ALL_FILES^} (@code{gnatmake})
8124 Consider all files in the make process, even the GNAT internal system
8125 files (for example, the predefined Ada library files), as well as any
8126 locked files. Locked files are files whose ALI file is write-protected.
8128 @code{gnatmake} does not check these files,
8129 because the assumption is that the GNAT internal files are properly up
8130 to date, and also that any write protected ALI files have been properly
8131 installed. Note that if there is an installation problem, such that one
8132 of these files is not up to date, it will be properly caught by the
8134 You may have to specify this switch if you are working on GNAT
8135 itself. The switch @option{^-a^/ALL_FILES^} is also useful
8136 in conjunction with @option{^-f^/FORCE_COMPILE^}
8137 if you need to recompile an entire application,
8138 including run-time files, using special configuration pragmas,
8139 such as a @code{Normalize_Scalars} pragma.
8142 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
8145 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
8148 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
8151 @item ^-b^/ACTIONS=BIND^
8152 @cindex @option{^-b^/ACTIONS=BIND^} (@code{gnatmake})
8153 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
8154 compilation and binding, but no link.
8155 Can be combined with @option{^-l^/ACTIONS=LINK^}
8156 to do binding and linking. When not combined with
8157 @option{^-c^/ACTIONS=COMPILE^}
8158 all the units in the closure of the main program must have been previously
8159 compiled and must be up to date. The root unit specified by @var{file_name}
8160 may be given without extension, with the source extension or, if no GNAT
8161 Project File is specified, with the ALI file extension.
8163 @item ^-c^/ACTIONS=COMPILE^
8164 @cindex @option{^-c^/ACTIONS=COMPILE^} (@code{gnatmake})
8165 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
8166 is also specified. Do not perform linking, except if both
8167 @option{^-b^/ACTIONS=BIND^} and
8168 @option{^-l^/ACTIONS=LINK^} are also specified.
8169 If the root unit specified by @var{file_name} is not a main unit, this is the
8170 default. Otherwise @code{gnatmake} will attempt binding and linking
8171 unless all objects are up to date and the executable is more recent than
8175 @cindex @option{^-C^/MAPPING^} (@code{gnatmake})
8176 Use a temporary mapping file. A mapping file is a way to communicate to the
8177 compiler two mappings: from unit names to file names (without any directory
8178 information) and from file names to path names (with full directory
8179 information). These mappings are used by the compiler to short-circuit the path
8180 search. When @code{gnatmake} is invoked with this switch, it will create
8181 a temporary mapping file, initially populated by the project manager,
8182 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
8183 Each invocation of the compiler will add the newly accessed sources to the
8184 mapping file. This will improve the source search during the next invocation
8187 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
8188 @cindex @option{^-C=^/USE_MAPPING^} (@code{gnatmake})
8189 Use a specific mapping file. The file, specified as a path name (absolute or
8190 relative) by this switch, should already exist, otherwise the switch is
8191 ineffective. The specified mapping file will be communicated to the compiler.
8192 This switch is not compatible with a project file
8193 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
8194 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
8196 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
8197 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatmake})
8198 Put all object files and ALI file in directory @var{dir}.
8199 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
8200 and ALI files go in the current working directory.
8202 This switch cannot be used when using a project file.
8206 @cindex @option{-eL} (@code{gnatmake})
8207 Follow all symbolic links when processing project files.
8210 @item ^-f^/FORCE_COMPILE^
8211 @cindex @option{^-f^/FORCE_COMPILE^} (@code{gnatmake})
8212 Force recompilations. Recompile all sources, even though some object
8213 files may be up to date, but don't recompile predefined or GNAT internal
8214 files or locked files (files with a write-protected ALI file),
8215 unless the @option{^-a^/ALL_FILES^} switch is also specified.
8217 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
8218 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatmake})
8219 When using project files, if some errors or warnings are detected during
8220 parsing and verbose mode is not in effect (no use of switch
8221 ^-v^/VERBOSE^), then error lines start with the full path name of the project
8222 file, rather than its simple file name.
8224 @item ^-i^/IN_PLACE^
8225 @cindex @option{^-i^/IN_PLACE^} (@code{gnatmake})
8226 In normal mode, @code{gnatmake} compiles all object files and ALI files
8227 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
8228 then instead object files and ALI files that already exist are overwritten
8229 in place. This means that once a large project is organized into separate
8230 directories in the desired manner, then @code{gnatmake} will automatically
8231 maintain and update this organization. If no ALI files are found on the
8232 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
8233 the new object and ALI files are created in the
8234 directory containing the source being compiled. If another organization
8235 is desired, where objects and sources are kept in different directories,
8236 a useful technique is to create dummy ALI files in the desired directories.
8237 When detecting such a dummy file, @code{gnatmake} will be forced to recompile
8238 the corresponding source file, and it will be put the resulting object
8239 and ALI files in the directory where it found the dummy file.
8241 @item ^-j^/PROCESSES=^@var{n}
8242 @cindex @option{^-j^/PROCESSES^} (@code{gnatmake})
8243 @cindex Parallel make
8244 Use @var{n} processes to carry out the (re)compilations. On a
8245 multiprocessor machine compilations will occur in parallel. In the
8246 event of compilation errors, messages from various compilations might
8247 get interspersed (but @code{gnatmake} will give you the full ordered
8248 list of failing compiles at the end). If this is problematic, rerun
8249 the make process with n set to 1 to get a clean list of messages.
8251 @item ^-k^/CONTINUE_ON_ERROR^
8252 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@code{gnatmake})
8253 Keep going. Continue as much as possible after a compilation error. To
8254 ease the programmer's task in case of compilation errors, the list of
8255 sources for which the compile fails is given when @code{gnatmake}
8258 If @code{gnatmake} is invoked with several @file{file_names} and with this
8259 switch, if there are compilation errors when building an executable,
8260 @code{gnatmake} will not attempt to build the following executables.
8262 @item ^-l^/ACTIONS=LINK^
8263 @cindex @option{^-l^/ACTIONS=LINK^} (@code{gnatmake})
8264 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
8265 and linking. Linking will not be performed if combined with
8266 @option{^-c^/ACTIONS=COMPILE^}
8267 but not with @option{^-b^/ACTIONS=BIND^}.
8268 When not combined with @option{^-b^/ACTIONS=BIND^}
8269 all the units in the closure of the main program must have been previously
8270 compiled and must be up to date, and the main program need to have been bound.
8271 The root unit specified by @var{file_name}
8272 may be given without extension, with the source extension or, if no GNAT
8273 Project File is specified, with the ALI file extension.
8275 @item ^-m^/MINIMAL_RECOMPILATION^
8276 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@code{gnatmake})
8277 Specifies that the minimum necessary amount of recompilations
8278 be performed. In this mode @code{gnatmake} ignores time
8279 stamp differences when the only
8280 modifications to a source file consist in adding/removing comments,
8281 empty lines, spaces or tabs. This means that if you have changed the
8282 comments in a source file or have simply reformatted it, using this
8283 switch will tell gnatmake not to recompile files that depend on it
8284 (provided other sources on which these files depend have undergone no
8285 semantic modifications). Note that the debugging information may be
8286 out of date with respect to the sources if the @option{-m} switch causes
8287 a compilation to be switched, so the use of this switch represents a
8288 trade-off between compilation time and accurate debugging information.
8290 @item ^-M^/DEPENDENCIES_LIST^
8291 @cindex Dependencies, producing list
8292 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@code{gnatmake})
8293 Check if all objects are up to date. If they are, output the object
8294 dependences to @file{stdout} in a form that can be directly exploited in
8295 a @file{Makefile}. By default, each source file is prefixed with its
8296 (relative or absolute) directory name. This name is whatever you
8297 specified in the various @option{^-aI^/SOURCE_SEARCH^}
8298 and @option{^-I^/SEARCH^} switches. If you use
8299 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
8300 @option{^-q^/QUIET^}
8301 (see below), only the source file names,
8302 without relative paths, are output. If you just specify the
8303 @option{^-M^/DEPENDENCIES_LIST^}
8304 switch, dependencies of the GNAT internal system files are omitted. This
8305 is typically what you want. If you also specify
8306 the @option{^-a^/ALL_FILES^} switch,
8307 dependencies of the GNAT internal files are also listed. Note that
8308 dependencies of the objects in external Ada libraries (see switch
8309 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
8312 @item ^-n^/DO_OBJECT_CHECK^
8313 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@code{gnatmake})
8314 Don't compile, bind, or link. Checks if all objects are up to date.
8315 If they are not, the full name of the first file that needs to be
8316 recompiled is printed.
8317 Repeated use of this option, followed by compiling the indicated source
8318 file, will eventually result in recompiling all required units.
8320 @item ^-o ^/EXECUTABLE=^@var{exec_name}
8321 @cindex @option{^-o^/EXECUTABLE^} (@code{gnatmake})
8322 Output executable name. The name of the final executable program will be
8323 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
8324 name for the executable will be the name of the input file in appropriate form
8325 for an executable file on the host system.
8327 This switch cannot be used when invoking @code{gnatmake} with several
8330 @item ^-P^/PROJECT_FILE=^@var{project}
8331 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatmake})
8332 Use project file @var{project}. Only one such switch can be used.
8333 See @ref{gnatmake and Project Files}.
8336 @cindex @option{^-q^/QUIET^} (@code{gnatmake})
8337 Quiet. When this flag is not set, the commands carried out by
8338 @code{gnatmake} are displayed.
8340 @item ^-s^/SWITCH_CHECK/^
8341 @cindex @option{^-s^/SWITCH_CHECK^} (@code{gnatmake})
8342 Recompile if compiler switches have changed since last compilation.
8343 All compiler switches but -I and -o are taken into account in the
8345 orders between different ``first letter'' switches are ignored, but
8346 orders between same switches are taken into account. For example,
8347 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
8348 is equivalent to @option{-O -g}.
8350 This switch is recommended when Integrated Preprocessing is used.
8353 @cindex @option{^-u^/UNIQUE^} (@code{gnatmake})
8354 Unique. Recompile at most the main files. It implies -c. Combined with
8355 -f, it is equivalent to calling the compiler directly. Note that using
8356 ^-u^/UNIQUE^ with a project file and no main has a special meaning
8357 (see @ref{Project Files and Main Subprograms}).
8359 @item ^-U^/ALL_PROJECTS^
8360 @cindex @option{^-U^/ALL_PROJECTS^} (@code{gnatmake})
8361 When used without a project file or with one or several mains on the command
8362 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
8363 on the command line, all sources of all project files are checked and compiled
8364 if not up to date, and libraries are rebuilt, if necessary.
8367 @cindex @option{^-v^/REASONS^} (@code{gnatmake})
8368 Verbose. Displays the reason for all recompilations @code{gnatmake}
8369 decides are necessary.
8371 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
8372 Indicates the verbosity of the parsing of GNAT project files.
8373 See @ref{Switches Related to Project Files}.
8375 @item ^-x^/NON_PROJECT_UNIT_COMPILATION^
8376 @cindex @option{^-x^/NON_PROJECT_UNIT_COMPILATION^} (@code{gnatmake})
8377 Indicates that sources that are not part of any Project File may be compiled.
8378 Normally, when using Project Files, only sources that are part of a Project
8379 File may be compile. When this switch is used, a source outside of all Project
8380 Files may be compiled. The ALI file and the object file will be put in the
8381 object directory of the main Project. The compilation switches used will only
8382 be those specified on the command line.
8384 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
8385 Indicates that external variable @var{name} has the value @var{value}.
8386 The Project Manager will use this value for occurrences of
8387 @code{external(name)} when parsing the project file.
8388 See @ref{Switches Related to Project Files}.
8391 @cindex @option{^-z^/NOMAIN^} (@code{gnatmake})
8392 No main subprogram. Bind and link the program even if the unit name
8393 given on the command line is a package name. The resulting executable
8394 will execute the elaboration routines of the package and its closure,
8395 then the finalization routines.
8398 @cindex @option{^-g^/DEBUG^} (@code{gnatmake})
8399 Enable debugging. This switch is simply passed to the compiler and to the
8405 @item @code{gcc} @asis{switches}
8407 Any uppercase or multi-character switch that is not a @code{gnatmake} switch
8408 is passed to @code{gcc} (e.g. @option{-O}, @option{-gnato,} etc.)
8411 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
8412 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
8413 automatically treated as a compiler switch, and passed on to all
8414 compilations that are carried out.
8419 Source and library search path switches:
8423 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
8424 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatmake})
8425 When looking for source files also look in directory @var{dir}.
8426 The order in which source files search is undertaken is
8427 described in @ref{Search Paths and the Run-Time Library (RTL)}.
8429 @item ^-aL^/SKIP_MISSING=^@var{dir}
8430 @cindex @option{^-aL^/SKIP_MISSING^} (@code{gnatmake})
8431 Consider @var{dir} as being an externally provided Ada library.
8432 Instructs @code{gnatmake} to skip compilation units whose @file{.ALI}
8433 files have been located in directory @var{dir}. This allows you to have
8434 missing bodies for the units in @var{dir} and to ignore out of date bodies
8435 for the same units. You still need to specify
8436 the location of the specs for these units by using the switches
8437 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
8438 or @option{^-I^/SEARCH=^@var{dir}}.
8439 Note: this switch is provided for compatibility with previous versions
8440 of @code{gnatmake}. The easier method of causing standard libraries
8441 to be excluded from consideration is to write-protect the corresponding
8444 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
8445 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatmake})
8446 When searching for library and object files, look in directory
8447 @var{dir}. The order in which library files are searched is described in
8448 @ref{Search Paths for gnatbind}.
8450 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
8451 @cindex Search paths, for @code{gnatmake}
8452 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@code{gnatmake})
8453 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
8454 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
8456 @item ^-I^/SEARCH=^@var{dir}
8457 @cindex @option{^-I^/SEARCH^} (@code{gnatmake})
8458 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
8459 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
8461 @item ^-I-^/NOCURRENT_DIRECTORY^
8462 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatmake})
8463 @cindex Source files, suppressing search
8464 Do not look for source files in the directory containing the source
8465 file named in the command line.
8466 Do not look for ALI or object files in the directory
8467 where @code{gnatmake} was invoked.
8469 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
8470 @cindex @option{^-L^/LIBRARY_SEARCH^} (@code{gnatmake})
8471 @cindex Linker libraries
8472 Add directory @var{dir} to the list of directories in which the linker
8473 will search for libraries. This is equivalent to
8474 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
8476 Furthermore, under Windows, the sources pointed to by the libraries path
8477 set in the registry are not searched for.
8481 @cindex @option{-nostdinc} (@code{gnatmake})
8482 Do not look for source files in the system default directory.
8485 @cindex @option{-nostdlib} (@code{gnatmake})
8486 Do not look for library files in the system default directory.
8488 @item --RTS=@var{rts-path}
8489 @cindex @option{--RTS} (@code{gnatmake})
8490 Specifies the default location of the runtime library. GNAT looks for the
8492 in the following directories, and stops as soon as a valid runtime is found
8493 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
8494 @file{ada_object_path} present):
8497 @item <current directory>/$rts_path
8499 @item <default-search-dir>/$rts_path
8501 @item <default-search-dir>/rts-$rts_path
8505 The selected path is handled like a normal RTS path.
8509 @node Mode Switches for gnatmake
8510 @section Mode Switches for @code{gnatmake}
8513 The mode switches (referred to as @code{mode_switches}) allow the
8514 inclusion of switches that are to be passed to the compiler itself, the
8515 binder or the linker. The effect of a mode switch is to cause all
8516 subsequent switches up to the end of the switch list, or up to the next
8517 mode switch, to be interpreted as switches to be passed on to the
8518 designated component of GNAT.
8522 @item -cargs @var{switches}
8523 @cindex @option{-cargs} (@code{gnatmake})
8524 Compiler switches. Here @var{switches} is a list of switches
8525 that are valid switches for @code{gcc}. They will be passed on to
8526 all compile steps performed by @code{gnatmake}.
8528 @item -bargs @var{switches}
8529 @cindex @option{-bargs} (@code{gnatmake})
8530 Binder switches. Here @var{switches} is a list of switches
8531 that are valid switches for @code{gnatbind}. They will be passed on to
8532 all bind steps performed by @code{gnatmake}.
8534 @item -largs @var{switches}
8535 @cindex @option{-largs} (@code{gnatmake})
8536 Linker switches. Here @var{switches} is a list of switches
8537 that are valid switches for @code{gnatlink}. They will be passed on to
8538 all link steps performed by @code{gnatmake}.
8540 @item -margs @var{switches}
8541 @cindex @option{-margs} (@code{gnatmake})
8542 Make switches. The switches are directly interpreted by @code{gnatmake},
8543 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
8547 @node Notes on the Command Line
8548 @section Notes on the Command Line
8551 This section contains some additional useful notes on the operation
8552 of the @code{gnatmake} command.
8556 @cindex Recompilation, by @code{gnatmake}
8557 If @code{gnatmake} finds no ALI files, it recompiles the main program
8558 and all other units required by the main program.
8559 This means that @code{gnatmake}
8560 can be used for the initial compile, as well as during subsequent steps of
8561 the development cycle.
8564 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
8565 is a subunit or body of a generic unit, @code{gnatmake} recompiles
8566 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
8570 In @code{gnatmake} the switch @option{^-I^/SEARCH^}
8571 is used to specify both source and
8572 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8573 instead if you just want to specify
8574 source paths only and @option{^-aO^/OBJECT_SEARCH^}
8575 if you want to specify library paths
8579 @code{gnatmake} examines both an ALI file and its corresponding object file
8580 for consistency. If an ALI is more recent than its corresponding object,
8581 or if the object file is missing, the corresponding source will be recompiled.
8582 Note that @code{gnatmake} expects an ALI and the corresponding object file
8583 to be in the same directory.
8586 @code{gnatmake} will ignore any files whose ALI file is write-protected.
8587 This may conveniently be used to exclude standard libraries from
8588 consideration and in particular it means that the use of the
8589 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
8590 unless @option{^-a^/ALL_FILES^} is also specified.
8593 @code{gnatmake} has been designed to make the use of Ada libraries
8594 particularly convenient. Assume you have an Ada library organized
8595 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
8596 of your Ada compilation units,
8597 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
8598 specs of these units, but no bodies. Then to compile a unit
8599 stored in @code{main.adb}, which uses this Ada library you would just type
8603 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
8606 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
8607 /SKIP_MISSING=@i{[OBJ_DIR]} main
8612 Using @code{gnatmake} along with the
8613 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
8614 switch provides a mechanism for avoiding unnecessary rcompilations. Using
8616 you can update the comments/format of your
8617 source files without having to recompile everything. Note, however, that
8618 adding or deleting lines in a source files may render its debugging
8619 info obsolete. If the file in question is a spec, the impact is rather
8620 limited, as that debugging info will only be useful during the
8621 elaboration phase of your program. For bodies the impact can be more
8622 significant. In all events, your debugger will warn you if a source file
8623 is more recent than the corresponding object, and alert you to the fact
8624 that the debugging information may be out of date.
8627 @node How gnatmake Works
8628 @section How @code{gnatmake} Works
8631 Generally @code{gnatmake} automatically performs all necessary
8632 recompilations and you don't need to worry about how it works. However,
8633 it may be useful to have some basic understanding of the @code{gnatmake}
8634 approach and in particular to understand how it uses the results of
8635 previous compilations without incorrectly depending on them.
8637 First a definition: an object file is considered @dfn{up to date} if the
8638 corresponding ALI file exists and its time stamp predates that of the
8639 object file and if all the source files listed in the
8640 dependency section of this ALI file have time stamps matching those in
8641 the ALI file. This means that neither the source file itself nor any
8642 files that it depends on have been modified, and hence there is no need
8643 to recompile this file.
8645 @code{gnatmake} works by first checking if the specified main unit is up
8646 to date. If so, no compilations are required for the main unit. If not,
8647 @code{gnatmake} compiles the main program to build a new ALI file that
8648 reflects the latest sources. Then the ALI file of the main unit is
8649 examined to find all the source files on which the main program depends,
8650 and @code{gnatmake} recursively applies the above procedure on all these files.
8652 This process ensures that @code{gnatmake} only trusts the dependencies
8653 in an existing ALI file if they are known to be correct. Otherwise it
8654 always recompiles to determine a new, guaranteed accurate set of
8655 dependencies. As a result the program is compiled ``upside down'' from what may
8656 be more familiar as the required order of compilation in some other Ada
8657 systems. In particular, clients are compiled before the units on which
8658 they depend. The ability of GNAT to compile in any order is critical in
8659 allowing an order of compilation to be chosen that guarantees that
8660 @code{gnatmake} will recompute a correct set of new dependencies if
8663 When invoking @code{gnatmake} with several @var{file_names}, if a unit is
8664 imported by several of the executables, it will be recompiled at most once.
8666 Note: when using non-standard naming conventions
8667 (See @ref{Using Other File Names}), changing through a configuration pragmas
8668 file the version of a source and invoking @code{gnatmake} to recompile may
8669 have no effect, if the previous version of the source is still accessible
8670 by @code{gnatmake}. It may be necessary to use the switch ^-f^/FORCE_COMPILE^.
8672 @node Examples of gnatmake Usage
8673 @section Examples of @code{gnatmake} Usage
8676 @item gnatmake hello.adb
8677 Compile all files necessary to bind and link the main program
8678 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
8679 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
8681 @item gnatmake main1 main2 main3
8682 Compile all files necessary to bind and link the main programs
8683 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
8684 (containing unit @code{Main2}) and @file{main3.adb}
8685 (containing unit @code{Main3}) and bind and link the resulting object files
8686 to generate three executable files @file{^main1^MAIN1.EXE^},
8687 @file{^main2^MAIN2.EXE^}
8688 and @file{^main3^MAIN3.EXE^}.
8691 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
8695 @item gnatmake Main_Unit /QUIET
8696 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
8697 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
8699 Compile all files necessary to bind and link the main program unit
8700 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
8701 be done with optimization level 2 and the order of elaboration will be
8702 listed by the binder. @code{gnatmake} will operate in quiet mode, not
8703 displaying commands it is executing.
8707 @c *************************
8708 @node Improving Performance
8709 @chapter Improving Performance
8710 @cindex Improving performance
8713 This chapter presents several topics related to program performance.
8714 It first describes some of the tradeoffs that need to be considered
8715 and some of the techniques for making your program run faster.
8716 It then documents the @command{gnatelim} tool, which can reduce
8717 the size of program executables.
8721 * Performance Considerations::
8722 * Reducing the Size of Ada Executables with gnatelim::
8727 @c *****************************
8728 @node Performance Considerations
8729 @section Performance Considerations
8732 The GNAT system provides a number of options that allow a trade-off
8737 performance of the generated code
8740 speed of compilation
8743 minimization of dependences and recompilation
8746 the degree of run-time checking.
8750 The defaults (if no options are selected) aim at improving the speed
8751 of compilation and minimizing dependences, at the expense of performance
8752 of the generated code:
8759 no inlining of subprogram calls
8762 all run-time checks enabled except overflow and elaboration checks
8766 These options are suitable for most program development purposes. This
8767 chapter describes how you can modify these choices, and also provides
8768 some guidelines on debugging optimized code.
8771 * Controlling Run-Time Checks::
8772 * Use of Restrictions::
8773 * Optimization Levels::
8774 * Debugging Optimized Code::
8775 * Inlining of Subprograms::
8776 * Optimization and Strict Aliasing::
8778 * Coverage Analysis::
8782 @node Controlling Run-Time Checks
8783 @subsection Controlling Run-Time Checks
8786 By default, GNAT generates all run-time checks, except arithmetic overflow
8787 checking for integer operations and checks for access before elaboration on
8788 subprogram calls. The latter are not required in default mode, because all
8789 necessary checking is done at compile time.
8790 @cindex @option{-gnatp} (@code{gcc})
8791 @cindex @option{-gnato} (@code{gcc})
8792 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
8793 be modified. @xref{Run-Time Checks}.
8795 Our experience is that the default is suitable for most development
8798 We treat integer overflow specially because these
8799 are quite expensive and in our experience are not as important as other
8800 run-time checks in the development process. Note that division by zero
8801 is not considered an overflow check, and divide by zero checks are
8802 generated where required by default.
8804 Elaboration checks are off by default, and also not needed by default, since
8805 GNAT uses a static elaboration analysis approach that avoids the need for
8806 run-time checking. This manual contains a full chapter discussing the issue
8807 of elaboration checks, and if the default is not satisfactory for your use,
8808 you should read this chapter.
8810 For validity checks, the minimal checks required by the Ada Reference
8811 Manual (for case statements and assignments to array elements) are on
8812 by default. These can be suppressed by use of the @option{-gnatVn} switch.
8813 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
8814 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
8815 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
8816 are also suppressed entirely if @option{-gnatp} is used.
8818 @cindex Overflow checks
8819 @cindex Checks, overflow
8822 @cindex pragma Suppress
8823 @cindex pragma Unsuppress
8824 Note that the setting of the switches controls the default setting of
8825 the checks. They may be modified using either @code{pragma Suppress} (to
8826 remove checks) or @code{pragma Unsuppress} (to add back suppressed
8827 checks) in the program source.
8829 @node Use of Restrictions
8830 @subsection Use of Restrictions
8833 The use of pragma Restrictions allows you to control which features are
8834 permitted in your program. Apart from the obvious point that if you avoid
8835 relatively expensive features like finalization (enforceable by the use
8836 of pragma Restrictions (No_Finalization), the use of this pragma does not
8837 affect the generated code in most cases.
8839 One notable exception to this rule is that the possibility of task abort
8840 results in some distributed overhead, particularly if finalization or
8841 exception handlers are used. The reason is that certain sections of code
8842 have to be marked as non-abortable.
8844 If you use neither the @code{abort} statement, nor asynchronous transfer
8845 of control (@code{select .. then abort}), then this distributed overhead
8846 is removed, which may have a general positive effect in improving
8847 overall performance. Especially code involving frequent use of tasking
8848 constructs and controlled types will show much improved performance.
8849 The relevant restrictions pragmas are
8852 pragma Restrictions (No_Abort_Statements);
8853 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
8857 It is recommended that these restriction pragmas be used if possible. Note
8858 that this also means that you can write code without worrying about the
8859 possibility of an immediate abort at any point.
8861 @node Optimization Levels
8862 @subsection Optimization Levels
8863 @cindex @option{^-O^/OPTIMIZE^} (@code{gcc})
8866 The default is optimization off. This results in the fastest compile
8867 times, but GNAT makes absolutely no attempt to optimize, and the
8868 generated programs are considerably larger and slower than when
8869 optimization is enabled. You can use the
8871 @option{-O@var{n}} switch, where @var{n} is an integer from 0 to 3,
8874 @code{OPTIMIZE} qualifier
8876 to @code{gcc} to control the optimization level:
8879 @item ^-O0^/OPTIMIZE=NONE^
8880 No optimization (the default);
8881 generates unoptimized code but has
8882 the fastest compilation time.
8884 @item ^-O1^/OPTIMIZE=SOME^
8885 Medium level optimization;
8886 optimizes reasonably well but does not
8887 degrade compilation time significantly.
8889 @item ^-O2^/OPTIMIZE=ALL^
8891 @itemx /OPTIMIZE=DEVELOPMENT
8894 generates highly optimized code and has
8895 the slowest compilation time.
8897 @item ^-O3^/OPTIMIZE=INLINING^
8898 Full optimization as in @option{-O2},
8899 and also attempts automatic inlining of small
8900 subprograms within a unit (@pxref{Inlining of Subprograms}).
8904 Higher optimization levels perform more global transformations on the
8905 program and apply more expensive analysis algorithms in order to generate
8906 faster and more compact code. The price in compilation time, and the
8907 resulting improvement in execution time,
8908 both depend on the particular application and the hardware environment.
8909 You should experiment to find the best level for your application.
8911 Since the precise set of optimizations done at each level will vary from
8912 release to release (and sometime from target to target), it is best to think
8913 of the optimization settings in general terms.
8914 The @cite{Using GNU GCC} manual contains details about
8915 ^the @option{-O} settings and a number of @option{-f} options that^how to^
8916 individually enable or disable specific optimizations.
8918 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
8919 been tested extensively at all optimization levels. There are some bugs
8920 which appear only with optimization turned on, but there have also been
8921 bugs which show up only in @emph{unoptimized} code. Selecting a lower
8922 level of optimization does not improve the reliability of the code
8923 generator, which in practice is highly reliable at all optimization
8926 Note regarding the use of @option{-O3}: The use of this optimization level
8927 is generally discouraged with GNAT, since it often results in larger
8928 executables which run more slowly. See further discussion of this point
8929 in @pxref{Inlining of Subprograms}.
8932 @node Debugging Optimized Code
8933 @subsection Debugging Optimized Code
8934 @cindex Debugging optimized code
8935 @cindex Optimization and debugging
8938 Although it is possible to do a reasonable amount of debugging at
8940 non-zero optimization levels,
8941 the higher the level the more likely that
8944 @option{/OPTIMIZE} settings other than @code{NONE},
8945 such settings will make it more likely that
8947 source-level constructs will have been eliminated by optimization.
8948 For example, if a loop is strength-reduced, the loop
8949 control variable may be completely eliminated and thus cannot be
8950 displayed in the debugger.
8951 This can only happen at @option{-O2} or @option{-O3}.
8952 Explicit temporary variables that you code might be eliminated at
8953 ^level^setting^ @option{-O1} or higher.
8955 The use of the @option{^-g^/DEBUG^} switch,
8956 @cindex @option{^-g^/DEBUG^} (@code{gcc})
8957 which is needed for source-level debugging,
8958 affects the size of the program executable on disk,
8959 and indeed the debugging information can be quite large.
8960 However, it has no effect on the generated code (and thus does not
8961 degrade performance)
8963 Since the compiler generates debugging tables for a compilation unit before
8964 it performs optimizations, the optimizing transformations may invalidate some
8965 of the debugging data. You therefore need to anticipate certain
8966 anomalous situations that may arise while debugging optimized code.
8967 These are the most common cases:
8971 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
8973 the PC bouncing back and forth in the code. This may result from any of
8974 the following optimizations:
8978 @i{Common subexpression elimination:} using a single instance of code for a
8979 quantity that the source computes several times. As a result you
8980 may not be able to stop on what looks like a statement.
8983 @i{Invariant code motion:} moving an expression that does not change within a
8984 loop, to the beginning of the loop.
8987 @i{Instruction scheduling:} moving instructions so as to
8988 overlap loads and stores (typically) with other code, or in
8989 general to move computations of values closer to their uses. Often
8990 this causes you to pass an assignment statement without the assignment
8991 happening and then later bounce back to the statement when the
8992 value is actually needed. Placing a breakpoint on a line of code
8993 and then stepping over it may, therefore, not always cause all the
8994 expected side-effects.
8998 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
8999 two identical pieces of code are merged and the program counter suddenly
9000 jumps to a statement that is not supposed to be executed, simply because
9001 it (and the code following) translates to the same thing as the code
9002 that @emph{was} supposed to be executed. This effect is typically seen in
9003 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
9004 a @code{break} in a C @code{^switch^switch^} statement.
9007 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
9008 There are various reasons for this effect:
9012 In a subprogram prologue, a parameter may not yet have been moved to its
9016 A variable may be dead, and its register re-used. This is
9017 probably the most common cause.
9020 As mentioned above, the assignment of a value to a variable may
9024 A variable may be eliminated entirely by value propagation or
9025 other means. In this case, GCC may incorrectly generate debugging
9026 information for the variable
9030 In general, when an unexpected value appears for a local variable or parameter
9031 you should first ascertain if that value was actually computed by
9032 your program, as opposed to being incorrectly reported by the debugger.
9034 array elements in an object designated by an access value
9035 are generally less of a problem, once you have ascertained that the access
9037 Typically, this means checking variables in the preceding code and in the
9038 calling subprogram to verify that the value observed is explainable from other
9039 values (one must apply the procedure recursively to those
9040 other values); or re-running the code and stopping a little earlier
9041 (perhaps before the call) and stepping to better see how the variable obtained
9042 the value in question; or continuing to step @emph{from} the point of the
9043 strange value to see if code motion had simply moved the variable's
9048 In light of such anomalies, a recommended technique is to use @option{-O0}
9049 early in the software development cycle, when extensive debugging capabilities
9050 are most needed, and then move to @option{-O1} and later @option{-O2} as
9051 the debugger becomes less critical.
9052 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
9053 a release management issue.
9055 Note that if you use @option{-g} you can then use the @command{strip} program
9056 on the resulting executable,
9057 which removes both debugging information and global symbols.
9061 @node Inlining of Subprograms
9062 @subsection Inlining of Subprograms
9065 A call to a subprogram in the current unit is inlined if all the
9066 following conditions are met:
9070 The optimization level is at least @option{-O1}.
9073 The called subprogram is suitable for inlining: It must be small enough
9074 and not contain nested subprograms or anything else that @code{gcc}
9075 cannot support in inlined subprograms.
9078 The call occurs after the definition of the body of the subprogram.
9081 @cindex pragma Inline
9083 Either @code{pragma Inline} applies to the subprogram or it is
9084 small and automatic inlining (optimization level @option{-O3}) is
9089 Calls to subprograms in @code{with}'ed units are normally not inlined.
9090 To achieve this level of inlining, the following conditions must all be
9095 The optimization level is at least @option{-O1}.
9098 The called subprogram is suitable for inlining: It must be small enough
9099 and not contain nested subprograms or anything else @code{gcc} cannot
9100 support in inlined subprograms.
9103 The call appears in a body (not in a package spec).
9106 There is a @code{pragma Inline} for the subprogram.
9109 @cindex @option{-gnatn} (@code{gcc})
9110 The @option{^-gnatn^/INLINE^} switch
9111 is used in the @code{gcc} command line
9114 Note that specifying the @option{-gnatn} switch causes additional
9115 compilation dependencies. Consider the following:
9117 @smallexample @c ada
9137 With the default behavior (no @option{-gnatn} switch specified), the
9138 compilation of the @code{Main} procedure depends only on its own source,
9139 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
9140 means that editing the body of @code{R} does not require recompiling
9143 On the other hand, the call @code{R.Q} is not inlined under these
9144 circumstances. If the @option{-gnatn} switch is present when @code{Main}
9145 is compiled, the call will be inlined if the body of @code{Q} is small
9146 enough, but now @code{Main} depends on the body of @code{R} in
9147 @file{r.adb} as well as on the spec. This means that if this body is edited,
9148 the main program must be recompiled. Note that this extra dependency
9149 occurs whether or not the call is in fact inlined by @code{gcc}.
9151 The use of front end inlining with @option{-gnatN} generates similar
9152 additional dependencies.
9154 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@code{gcc})
9155 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
9156 can be used to prevent
9157 all inlining. This switch overrides all other conditions and ensures
9158 that no inlining occurs. The extra dependences resulting from
9159 @option{-gnatn} will still be active, even if
9160 this switch is used to suppress the resulting inlining actions.
9162 Note regarding the use of @option{-O3}: There is no difference in inlining
9163 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
9164 pragma @code{Inline} assuming the use of @option{-gnatn}
9165 or @option{-gnatN} (the switches that activate inlining). If you have used
9166 pragma @code{Inline} in appropriate cases, then it is usually much better
9167 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
9168 in this case only has the effect of inlining subprograms you did not
9169 think should be inlined. We often find that the use of @option{-O3} slows
9170 down code by performing excessive inlining, leading to increased instruction
9171 cache pressure from the increased code size. So the bottom line here is
9172 that you should not automatically assume that @option{-O3} is better than
9173 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
9174 it actually improves performance.
9176 @node Optimization and Strict Aliasing
9177 @subsection Optimization and Strict Aliasing
9179 @cindex Strict Aliasing
9180 @cindex No_Strict_Aliasing
9183 The strong typing capabilities of Ada allow an optimizer to generate
9184 efficient code in situations where other languages would be forced to
9185 make worst case assumptions preventing such optimizations. Consider
9186 the following example:
9188 @smallexample @c ada
9191 type Int1 is new Integer;
9192 type Int2 is new Integer;
9193 type Int1A is access Int1;
9194 type Int2A is access Int2;
9201 for J in Data'Range loop
9202 if Data (J) = Int1V.all then
9203 Int2V.all := Int2V.all + 1;
9212 In this example, since the variable @code{Int1V} can only access objects
9213 of type @code{Int1}, and @code{Int2V} can only access objects of type
9214 @code{Int2}, there is no possibility that the assignment to
9215 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
9216 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
9217 for all iterations of the loop and avoid the extra memory reference
9218 required to dereference it each time through the loop.
9220 This kind of optimziation, called strict aliasing analysis, is
9221 triggered by specifying an optimization level of @option{-O2} or
9222 higher and allows @code{GNAT} to generate more efficient code
9223 when access values are involved.
9225 However, although this optimization is always correct in terms of
9226 the formal semantics of the Ada Reference Manual, difficulties can
9227 arise if features like @code{Unchecked_Conversion} are used to break
9228 the typing system. Consider the following complete program example:
9230 @smallexample @c ada
9233 type int1 is new integer;
9234 type int2 is new integer;
9235 type a1 is access int1;
9236 type a2 is access int2;
9241 function to_a2 (Input : a1) return a2;
9244 with Unchecked_Conversion;
9246 function to_a2 (Input : a1) return a2 is
9248 new Unchecked_Conversion (a1, a2);
9250 return to_a2u (Input);
9256 with Text_IO; use Text_IO;
9258 v1 : a1 := new int1;
9259 v2 : a2 := to_a2 (v1);
9263 put_line (int1'image (v1.all));
9269 This program prints out 0 in @code{-O0} or @code{-O1}
9270 mode, but it prints out 1 in @code{-O2} mode. That's
9271 because in strict aliasing mode, the compiler can and
9272 does assume that the assignment to @code{v2.all} could not
9273 affect the value of @code{v1.all}, since different types
9276 This behavior is not a case of non-conformance with the standard, since
9277 the Ada RM specifies that an unchecked conversion where the resulting
9278 bit pattern is not a correct value of the target type can result in an
9279 abnormal value and attempting to reference an abnormal value makes the
9280 execution of a program erroneous. That's the case here since the result
9281 does not point to an object of type @code{int2}. This means that the
9282 effect is entirely unpredictable.
9284 However, although that explanation may satisfy a language
9285 lawyer, in practice an applications programmer expects an
9286 unchecked conversion involving pointers to create true
9287 aliases and the behavior of printing 1 seems plain wrong.
9288 In this case, the strict aliasing optimization is unwelcome.
9290 Indeed the compiler recognizes this possibility, and the
9291 unchecked conversion generates a warning:
9294 p2.adb:5:07: warning: possible aliasing problem with type "a2"
9295 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
9296 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
9300 Unfortunately the problem is recognized when compiling the body of
9301 package @code{p2}, but the actual "bad" code is generated while
9302 compiling the body of @code{m} and this latter compilation does not see
9303 the suspicious @code{Unchecked_Conversion}.
9305 As implied by the warning message, there are approaches you can use to
9306 avoid the unwanted strict aliasing optimization in a case like this.
9308 One possibility is to simply avoid the use of @code{-O2}, but
9309 that is a bit drastic, since it throws away a number of useful
9310 optimizations that do not involve strict aliasing assumptions.
9312 A less drastic approach is to compile the program using the
9313 option @code{-fno-strict-aliasing}. Actually it is only the
9314 unit containing the dereferencing of the suspicious pointer
9315 that needs to be compiled. So in this case, if we compile
9316 unit @code{m} with this switch, then we get the expected
9317 value of zero printed. Analyzing which units might need
9318 the switch can be painful, so a more reasonable approach
9319 is to compile the entire program with options @code{-O2}
9320 and @code{-fno-strict-aliasing}. If the performance is
9321 satisfactory with this combination of options, then the
9322 advantage is that the entire issue of possible "wrong"
9323 optimization due to strict aliasing is avoided.
9325 To avoid the use of compiler switches, the configuration
9326 pragma @code{No_Strict_Aliasing} with no parameters may be
9327 used to specify that for all access types, the strict
9328 aliasing optimization should be suppressed.
9330 However, these approaches are still overkill, in that they causes
9331 all manipulations of all access values to be deoptimized. A more
9332 refined approach is to concentrate attention on the specific
9333 access type identified as problematic.
9335 First, if a careful analysis of uses of the pointer shows
9336 that there are no possible problematic references, then
9337 the warning can be suppressed by bracketing the
9338 instantiation of @code{Unchecked_Conversion} to turn
9341 @smallexample @c ada
9342 pragma Warnings (Off);
9344 new Unchecked_Conversion (a1, a2);
9345 pragma Warnings (On);
9349 Of course that approach is not appropriate for this particular
9350 example, since indeed there is a problematic reference. In this
9351 case we can take one of two other approaches.
9353 The first possibility is to move the instantiation of unchecked
9354 conversion to the unit in which the type is declared. In
9355 this example, we would move the instantiation of
9356 @code{Unchecked_Conversion} from the body of package
9357 @code{p2} to the spec of package @code{p1}. Now the
9358 warning disappears. That's because any use of the
9359 access type knows there is a suspicious unchecked
9360 conversion, and the strict aliasing optimization
9361 is automatically suppressed for the type.
9363 If it is not practical to move the unchecked conversion to the same unit
9364 in which the destination access type is declared (perhaps because the
9365 source type is not visible in that unit), you may use pragma
9366 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
9367 same declarative sequence as the declaration of the access type:
9369 @smallexample @c ada
9370 type a2 is access int2;
9371 pragma No_Strict_Aliasing (a2);
9375 Here again, the compiler now knows that the strict aliasing optimization
9376 should be suppressed for any reference to type @code{a2} and the
9377 expected behavior is obtained.
9379 Finally, note that although the compiler can generate warnings for
9380 simple cases of unchecked conversions, there are tricker and more
9381 indirect ways of creating type incorrect aliases which the compiler
9382 cannot detect. Examples are the use of address overlays and unchecked
9383 conversions involving composite types containing access types as
9384 components. In such cases, no warnings are generated, but there can
9385 still be aliasing problems. One safe coding practice is to forbid the
9386 use of address clauses for type overlaying, and to allow unchecked
9387 conversion only for primitive types. This is not really a significant
9388 restriction since any possible desired effect can be achieved by
9389 unchecked conversion of access values.
9392 @node Coverage Analysis
9393 @subsection Coverage Analysis
9396 GNAT supports the Digital Performance Coverage Analyzer (PCA), which allows
9397 the user to determine the distribution of execution time across a program,
9398 @pxref{Profiling} for details of usage.
9401 @node Reducing the Size of Ada Executables with gnatelim
9402 @section Reducing the Size of Ada Executables with @code{gnatelim}
9406 This section describes @command{gnatelim}, a tool which detects unused
9407 subprograms and helps the compiler to create a smaller executable for your
9412 * Running gnatelim::
9413 * Correcting the List of Eliminate Pragmas::
9414 * Making Your Executables Smaller::
9415 * Summary of the gnatelim Usage Cycle::
9418 @node About gnatelim
9419 @subsection About @code{gnatelim}
9422 When a program shares a set of Ada
9423 packages with other programs, it may happen that this program uses
9424 only a fraction of the subprograms defined in these packages. The code
9425 created for these unused subprograms increases the size of the executable.
9427 @code{gnatelim} tracks unused subprograms in an Ada program and
9428 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
9429 subprograms that are declared but never called. By placing the list of
9430 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
9431 recompiling your program, you may decrease the size of its executable,
9432 because the compiler will not generate the code for 'eliminated' subprograms.
9433 See GNAT Reference Manual for more information about this pragma.
9435 @code{gnatelim} needs as its input data the name of the main subprogram
9436 and a bind file for a main subprogram.
9438 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
9439 the main subprogram. @code{gnatelim} can work with both Ada and C
9440 bind files; when both are present, it uses the Ada bind file.
9441 The following commands will build the program and create the bind file:
9444 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
9445 $ gnatbind main_prog
9448 Note that @code{gnatelim} needs neither object nor ALI files.
9450 @node Running gnatelim
9451 @subsection Running @code{gnatelim}
9454 @code{gnatelim} has the following command-line interface:
9457 $ gnatelim [options] name
9461 @code{name} should be a name of a source file that contains the main subprogram
9462 of a program (partition).
9464 @code{gnatelim} has the following switches:
9469 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
9470 Quiet mode: by default @code{gnatelim} outputs to the standard error
9471 stream the number of program units left to be processed. This option turns
9475 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
9476 Verbose mode: @code{gnatelim} version information is printed as Ada
9477 comments to the standard output stream. Also, in addition to the number of
9478 program units left @code{gnatelim} will output the name of the current unit
9482 @cindex @option{^-a^/ALL^} (@command{gnatelim})
9483 Also look for subprograms from the GNAT run time that can be eliminated. Note
9484 that when @file{gnat.adc} is produced using this switch, the entire program
9485 must be recompiled with switch @option{^-a^/ALL_FILES^} to @code{gnatmake}.
9487 @item ^-I^/INCLUDE_DIRS=^@var{dir}
9488 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
9489 When looking for source files also look in directory @var{dir}. Specifying
9490 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
9491 sources in the current directory.
9493 @item ^-b^/BIND_FILE=^@var{bind_file}
9494 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
9495 Specifies @var{bind_file} as the bind file to process. If not set, the name
9496 of the bind file is computed from the full expanded Ada name
9497 of a main subprogram.
9499 @item ^-C^/CONFIG_FILE=^@var{config_file}
9500 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
9501 Specifies a file @var{config_file} that contains configuration pragmas. The
9502 file must be specified with full path.
9504 @item ^--GCC^/COMPILER^=@var{compiler_name}
9505 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
9506 Instructs @code{gnatelim} to use specific @code{gcc} compiler instead of one
9507 available on the path.
9509 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
9510 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
9511 Instructs @code{gnatelim} to use specific @code{gnatmake} instead of one
9512 available on the path.
9515 @cindex @option{-d@var{x}} (@command{gnatelim})
9516 Activate internal debugging switches. @var{x} is a letter or digit, or
9517 string of letters or digits, which specifies the type of debugging
9518 mode desired. Normally these are used only for internal development
9519 or system debugging purposes. You can find full documentation for these
9520 switches in the spec of the @code{Gnatelim} unit in the compiler
9521 source file @file{gnatelim.ads}.
9525 @code{gnatelim} sends its output to the standard output stream, and all the
9526 tracing and debug information is sent to the standard error stream.
9527 In order to produce a proper GNAT configuration file
9528 @file{gnat.adc}, redirection must be used:
9532 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
9535 $ gnatelim main_prog.adb > gnat.adc
9544 $ gnatelim main_prog.adb >> gnat.adc
9548 in order to append the @code{gnatelim} output to the existing contents of
9552 @node Correcting the List of Eliminate Pragmas
9553 @subsection Correcting the List of Eliminate Pragmas
9556 In some rare cases @code{gnatelim} may try to eliminate
9557 subprograms that are actually called in the program. In this case, the
9558 compiler will generate an error message of the form:
9561 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
9565 You will need to manually remove the wrong @code{Eliminate} pragmas from
9566 the @file{gnat.adc} file. You should recompile your program
9567 from scratch after that, because you need a consistent @file{gnat.adc} file
9568 during the entire compilation.
9571 @node Making Your Executables Smaller
9572 @subsection Making Your Executables Smaller
9575 In order to get a smaller executable for your program you now have to
9576 recompile the program completely with the new @file{gnat.adc} file
9577 created by @code{gnatelim} in your current directory:
9580 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
9584 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
9585 recompile everything
9586 with the set of pragmas @code{Eliminate} that you have obtained with
9587 @command{gnatelim}).
9589 Be aware that the set of @code{Eliminate} pragmas is specific to each
9590 program. It is not recommended to merge sets of @code{Eliminate}
9591 pragmas created for different programs in one @file{gnat.adc} file.
9593 @node Summary of the gnatelim Usage Cycle
9594 @subsection Summary of the gnatelim Usage Cycle
9597 Here is a quick summary of the steps to be taken in order to reduce
9598 the size of your executables with @code{gnatelim}. You may use
9599 other GNAT options to control the optimization level,
9600 to produce the debugging information, to set search path, etc.
9607 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
9608 $ gnatbind main_prog
9612 Generate a list of @code{Eliminate} pragmas
9615 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
9618 $ gnatelim main_prog >[>] gnat.adc
9623 Recompile the application
9626 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
9634 @c ********************************
9635 @node Renaming Files Using gnatchop
9636 @chapter Renaming Files Using @code{gnatchop}
9640 This chapter discusses how to handle files with multiple units by using
9641 the @code{gnatchop} utility. This utility is also useful in renaming
9642 files to meet the standard GNAT default file naming conventions.
9645 * Handling Files with Multiple Units::
9646 * Operating gnatchop in Compilation Mode::
9647 * Command Line for gnatchop::
9648 * Switches for gnatchop::
9649 * Examples of gnatchop Usage::
9652 @node Handling Files with Multiple Units
9653 @section Handling Files with Multiple Units
9656 The basic compilation model of GNAT requires that a file submitted to the
9657 compiler have only one unit and there be a strict correspondence
9658 between the file name and the unit name.
9660 The @code{gnatchop} utility allows both of these rules to be relaxed,
9661 allowing GNAT to process files which contain multiple compilation units
9662 and files with arbitrary file names. @code{gnatchop}
9663 reads the specified file and generates one or more output files,
9664 containing one unit per file. The unit and the file name correspond,
9665 as required by GNAT.
9667 If you want to permanently restructure a set of ``foreign'' files so that
9668 they match the GNAT rules, and do the remaining development using the
9669 GNAT structure, you can simply use @command{gnatchop} once, generate the
9670 new set of files and work with them from that point on.
9672 Alternatively, if you want to keep your files in the ``foreign'' format,
9673 perhaps to maintain compatibility with some other Ada compilation
9674 system, you can set up a procedure where you use @command{gnatchop} each
9675 time you compile, regarding the source files that it writes as temporary
9676 files that you throw away.
9679 @node Operating gnatchop in Compilation Mode
9680 @section Operating gnatchop in Compilation Mode
9683 The basic function of @code{gnatchop} is to take a file with multiple units
9684 and split it into separate files. The boundary between files is reasonably
9685 clear, except for the issue of comments and pragmas. In default mode, the
9686 rule is that any pragmas between units belong to the previous unit, except
9687 that configuration pragmas always belong to the following unit. Any comments
9688 belong to the following unit. These rules
9689 almost always result in the right choice of
9690 the split point without needing to mark it explicitly and most users will
9691 find this default to be what they want. In this default mode it is incorrect to
9692 submit a file containing only configuration pragmas, or one that ends in
9693 configuration pragmas, to @code{gnatchop}.
9695 However, using a special option to activate ``compilation mode'',
9697 can perform another function, which is to provide exactly the semantics
9698 required by the RM for handling of configuration pragmas in a compilation.
9699 In the absence of configuration pragmas (at the main file level), this
9700 option has no effect, but it causes such configuration pragmas to be handled
9701 in a quite different manner.
9703 First, in compilation mode, if @code{gnatchop} is given a file that consists of
9704 only configuration pragmas, then this file is appended to the
9705 @file{gnat.adc} file in the current directory. This behavior provides
9706 the required behavior described in the RM for the actions to be taken
9707 on submitting such a file to the compiler, namely that these pragmas
9708 should apply to all subsequent compilations in the same compilation
9709 environment. Using GNAT, the current directory, possibly containing a
9710 @file{gnat.adc} file is the representation
9711 of a compilation environment. For more information on the
9712 @file{gnat.adc} file, see the section on handling of configuration
9713 pragmas @pxref{Handling of Configuration Pragmas}.
9715 Second, in compilation mode, if @code{gnatchop}
9716 is given a file that starts with
9717 configuration pragmas, and contains one or more units, then these
9718 configuration pragmas are prepended to each of the chopped files. This
9719 behavior provides the required behavior described in the RM for the
9720 actions to be taken on compiling such a file, namely that the pragmas
9721 apply to all units in the compilation, but not to subsequently compiled
9724 Finally, if configuration pragmas appear between units, they are appended
9725 to the previous unit. This results in the previous unit being illegal,
9726 since the compiler does not accept configuration pragmas that follow
9727 a unit. This provides the required RM behavior that forbids configuration
9728 pragmas other than those preceding the first compilation unit of a
9731 For most purposes, @code{gnatchop} will be used in default mode. The
9732 compilation mode described above is used only if you need exactly
9733 accurate behavior with respect to compilations, and you have files
9734 that contain multiple units and configuration pragmas. In this
9735 circumstance the use of @code{gnatchop} with the compilation mode
9736 switch provides the required behavior, and is for example the mode
9737 in which GNAT processes the ACVC tests.
9739 @node Command Line for gnatchop
9740 @section Command Line for @code{gnatchop}
9743 The @code{gnatchop} command has the form:
9746 $ gnatchop switches @var{file name} [@var{file name} @var{file name} ...]
9751 The only required argument is the file name of the file to be chopped.
9752 There are no restrictions on the form of this file name. The file itself
9753 contains one or more Ada units, in normal GNAT format, concatenated
9754 together. As shown, more than one file may be presented to be chopped.
9756 When run in default mode, @code{gnatchop} generates one output file in
9757 the current directory for each unit in each of the files.
9759 @var{directory}, if specified, gives the name of the directory to which
9760 the output files will be written. If it is not specified, all files are
9761 written to the current directory.
9763 For example, given a
9764 file called @file{hellofiles} containing
9766 @smallexample @c ada
9771 with Text_IO; use Text_IO;
9784 $ gnatchop ^hellofiles^HELLOFILES.^
9788 generates two files in the current directory, one called
9789 @file{hello.ads} containing the single line that is the procedure spec,
9790 and the other called @file{hello.adb} containing the remaining text. The
9791 original file is not affected. The generated files can be compiled in
9795 When gnatchop is invoked on a file that is empty or that contains only empty
9796 lines and/or comments, gnatchop will not fail, but will not produce any
9799 For example, given a
9800 file called @file{toto.txt} containing
9802 @smallexample @c ada
9814 $ gnatchop ^toto.txt^TOT.TXT^
9818 will not produce any new file and will result in the following warnings:
9821 toto.txt:1:01: warning: empty file, contains no compilation units
9822 no compilation units found
9823 no source files written
9826 @node Switches for gnatchop
9827 @section Switches for @code{gnatchop}
9830 @command{gnatchop} recognizes the following switches:
9835 @item ^-c^/COMPILATION^
9836 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
9837 Causes @code{gnatchop} to operate in compilation mode, in which
9838 configuration pragmas are handled according to strict RM rules. See
9839 previous section for a full description of this mode.
9843 This passes the given @option{-gnatxxx} switch to @code{gnat} which is
9844 used to parse the given file. Not all @code{xxx} options make sense,
9845 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
9846 process a source file that uses Latin-2 coding for identifiers.
9850 Causes @code{gnatchop} to generate a brief help summary to the standard
9851 output file showing usage information.
9853 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
9854 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
9855 Limit generated file names to the specified number @code{mm}
9857 This is useful if the
9858 resulting set of files is required to be interoperable with systems
9859 which limit the length of file names.
9861 If no value is given, or
9862 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
9863 a default of 39, suitable for OpenVMS Alpha
9867 No space is allowed between the @option{-k} and the numeric value. The numeric
9868 value may be omitted in which case a default of @option{-k8},
9870 with DOS-like file systems, is used. If no @option{-k} switch
9872 there is no limit on the length of file names.
9875 @item ^-p^/PRESERVE^
9876 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
9877 Causes the file ^modification^creation^ time stamp of the input file to be
9878 preserved and used for the time stamp of the output file(s). This may be
9879 useful for preserving coherency of time stamps in an environment where
9880 @code{gnatchop} is used as part of a standard build process.
9883 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
9884 Causes output of informational messages indicating the set of generated
9885 files to be suppressed. Warnings and error messages are unaffected.
9887 @item ^-r^/REFERENCE^
9888 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
9889 @findex Source_Reference
9890 Generate @code{Source_Reference} pragmas. Use this switch if the output
9891 files are regarded as temporary and development is to be done in terms
9892 of the original unchopped file. This switch causes
9893 @code{Source_Reference} pragmas to be inserted into each of the
9894 generated files to refers back to the original file name and line number.
9895 The result is that all error messages refer back to the original
9897 In addition, the debugging information placed into the object file (when
9898 the @option{^-g^/DEBUG^} switch of @code{gcc} or @code{gnatmake} is specified)
9899 also refers back to this original file so that tools like profilers and
9900 debuggers will give information in terms of the original unchopped file.
9902 If the original file to be chopped itself contains
9903 a @code{Source_Reference}
9904 pragma referencing a third file, then gnatchop respects
9905 this pragma, and the generated @code{Source_Reference} pragmas
9906 in the chopped file refer to the original file, with appropriate
9907 line numbers. This is particularly useful when @code{gnatchop}
9908 is used in conjunction with @code{gnatprep} to compile files that
9909 contain preprocessing statements and multiple units.
9912 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
9913 Causes @code{gnatchop} to operate in verbose mode. The version
9914 number and copyright notice are output, as well as exact copies of
9915 the gnat1 commands spawned to obtain the chop control information.
9917 @item ^-w^/OVERWRITE^
9918 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
9919 Overwrite existing file names. Normally @code{gnatchop} regards it as a
9920 fatal error if there is already a file with the same name as a
9921 file it would otherwise output, in other words if the files to be
9922 chopped contain duplicated units. This switch bypasses this
9923 check, and causes all but the last instance of such duplicated
9924 units to be skipped.
9928 @cindex @option{--GCC=} (@code{gnatchop})
9929 Specify the path of the GNAT parser to be used. When this switch is used,
9930 no attempt is made to add the prefix to the GNAT parser executable.
9934 @node Examples of gnatchop Usage
9935 @section Examples of @code{gnatchop} Usage
9939 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
9942 @item gnatchop -w hello_s.ada prerelease/files
9945 Chops the source file @file{hello_s.ada}. The output files will be
9946 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
9948 files with matching names in that directory (no files in the current
9949 directory are modified).
9951 @item gnatchop ^archive^ARCHIVE.^
9952 Chops the source file @file{^archive^ARCHIVE.^}
9953 into the current directory. One
9954 useful application of @code{gnatchop} is in sending sets of sources
9955 around, for example in email messages. The required sources are simply
9956 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
9958 @code{gnatchop} is used at the other end to reconstitute the original
9961 @item gnatchop file1 file2 file3 direc
9962 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
9963 the resulting files in the directory @file{direc}. Note that if any units
9964 occur more than once anywhere within this set of files, an error message
9965 is generated, and no files are written. To override this check, use the
9966 @option{^-w^/OVERWRITE^} switch,
9967 in which case the last occurrence in the last file will
9968 be the one that is output, and earlier duplicate occurrences for a given
9969 unit will be skipped.
9972 @node Configuration Pragmas
9973 @chapter Configuration Pragmas
9974 @cindex Configuration pragmas
9975 @cindex Pragmas, configuration
9978 In Ada 95, configuration pragmas include those pragmas described as
9979 such in the Ada 95 Reference Manual, as well as
9980 implementation-dependent pragmas that are configuration pragmas. See the
9981 individual descriptions of pragmas in the GNAT Reference Manual for
9982 details on these additional GNAT-specific configuration pragmas. Most
9983 notably, the pragma @code{Source_File_Name}, which allows
9984 specifying non-default names for source files, is a configuration
9985 pragma. The following is a complete list of configuration pragmas
9986 recognized by @code{GNAT}:
9998 External_Name_Casing
9999 Float_Representation
10008 Propagate_Exceptions
10011 Restricted_Run_Time
10013 Restrictions_Warnings
10018 Task_Dispatching_Policy
10027 * Handling of Configuration Pragmas::
10028 * The Configuration Pragmas Files::
10031 @node Handling of Configuration Pragmas
10032 @section Handling of Configuration Pragmas
10034 Configuration pragmas may either appear at the start of a compilation
10035 unit, in which case they apply only to that unit, or they may apply to
10036 all compilations performed in a given compilation environment.
10038 GNAT also provides the @code{gnatchop} utility to provide an automatic
10039 way to handle configuration pragmas following the semantics for
10040 compilations (that is, files with multiple units), described in the RM.
10041 See section @pxref{Operating gnatchop in Compilation Mode} for details.
10042 However, for most purposes, it will be more convenient to edit the
10043 @file{gnat.adc} file that contains configuration pragmas directly,
10044 as described in the following section.
10046 @node The Configuration Pragmas Files
10047 @section The Configuration Pragmas Files
10048 @cindex @file{gnat.adc}
10051 In GNAT a compilation environment is defined by the current
10052 directory at the time that a compile command is given. This current
10053 directory is searched for a file whose name is @file{gnat.adc}. If
10054 this file is present, it is expected to contain one or more
10055 configuration pragmas that will be applied to the current compilation.
10056 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
10059 Configuration pragmas may be entered into the @file{gnat.adc} file
10060 either by running @code{gnatchop} on a source file that consists only of
10061 configuration pragmas, or more conveniently by
10062 direct editing of the @file{gnat.adc} file, which is a standard format
10065 In addition to @file{gnat.adc}, one additional file containing configuration
10066 pragmas may be applied to the current compilation using the switch
10067 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
10068 contains only configuration pragmas. These configuration pragmas are
10069 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
10070 is present and switch @option{-gnatA} is not used).
10072 It is allowed to specify several switches @option{-gnatec}, however only
10073 the last one on the command line will be taken into account.
10075 If you are using project file, a separate mechanism is provided using
10076 project attributes, see @ref{Specifying Configuration Pragmas} for more
10080 Of special interest to GNAT OpenVMS Alpha is the following
10081 configuration pragma:
10083 @smallexample @c ada
10085 pragma Extend_System (Aux_DEC);
10090 In the presence of this pragma, GNAT adds to the definition of the
10091 predefined package SYSTEM all the additional types and subprograms that are
10092 defined in DEC Ada. See @pxref{Compatibility with DEC Ada} for details.
10095 @node Handling Arbitrary File Naming Conventions Using gnatname
10096 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
10097 @cindex Arbitrary File Naming Conventions
10100 * Arbitrary File Naming Conventions::
10101 * Running gnatname::
10102 * Switches for gnatname::
10103 * Examples of gnatname Usage::
10106 @node Arbitrary File Naming Conventions
10107 @section Arbitrary File Naming Conventions
10110 The GNAT compiler must be able to know the source file name of a compilation
10111 unit. When using the standard GNAT default file naming conventions
10112 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
10113 does not need additional information.
10116 When the source file names do not follow the standard GNAT default file naming
10117 conventions, the GNAT compiler must be given additional information through
10118 a configuration pragmas file (see @ref{Configuration Pragmas})
10120 When the non standard file naming conventions are well-defined,
10121 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
10122 (see @ref{Alternative File Naming Schemes}) may be sufficient. However,
10123 if the file naming conventions are irregular or arbitrary, a number
10124 of pragma @code{Source_File_Name} for individual compilation units
10126 To help maintain the correspondence between compilation unit names and
10127 source file names within the compiler,
10128 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
10131 @node Running gnatname
10132 @section Running @code{gnatname}
10135 The usual form of the @code{gnatname} command is
10138 $ gnatname [@var{switches}] @var{naming_pattern} [@var{naming_patterns}]
10142 All of the arguments are optional. If invoked without any argument,
10143 @code{gnatname} will display its usage.
10146 When used with at least one naming pattern, @code{gnatname} will attempt to
10147 find all the compilation units in files that follow at least one of the
10148 naming patterns. To find these compilation units,
10149 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
10153 One or several Naming Patterns may be given as arguments to @code{gnatname}.
10154 Each Naming Pattern is enclosed between double quotes.
10155 A Naming Pattern is a regular expression similar to the wildcard patterns
10156 used in file names by the Unix shells or the DOS prompt.
10159 Examples of Naming Patterns are
10168 For a more complete description of the syntax of Naming Patterns,
10169 see the second kind of regular expressions described in @file{g-regexp.ads}
10170 (the ``Glob'' regular expressions).
10173 When invoked with no switches, @code{gnatname} will create a configuration
10174 pragmas file @file{gnat.adc} in the current working directory, with pragmas
10175 @code{Source_File_Name} for each file that contains a valid Ada unit.
10177 @node Switches for gnatname
10178 @section Switches for @code{gnatname}
10181 Switches for @code{gnatname} must precede any specified Naming Pattern.
10184 You may specify any of the following switches to @code{gnatname}:
10189 @item ^-c^/CONFIG_FILE=^@file{file}
10190 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
10191 Create a configuration pragmas file @file{file} (instead of the default
10194 There may be zero, one or more space between @option{-c} and
10197 @file{file} may include directory information. @file{file} must be
10198 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
10199 When a switch @option{^-c^/CONFIG_FILE^} is
10200 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
10202 @item ^-d^/SOURCE_DIRS=^@file{dir}
10203 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
10204 Look for source files in directory @file{dir}. There may be zero, one or more
10205 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
10206 When a switch @option{^-d^/SOURCE_DIRS^}
10207 is specified, the current working directory will not be searched for source
10208 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
10209 or @option{^-D^/DIR_FILES^} switch.
10210 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
10211 If @file{dir} is a relative path, it is relative to the directory of
10212 the configuration pragmas file specified with switch
10213 @option{^-c^/CONFIG_FILE^},
10214 or to the directory of the project file specified with switch
10215 @option{^-P^/PROJECT_FILE^} or,
10216 if neither switch @option{^-c^/CONFIG_FILE^}
10217 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
10218 current working directory. The directory
10219 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
10221 @item ^-D^/DIRS_FILE=^@file{file}
10222 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
10223 Look for source files in all directories listed in text file @file{file}.
10224 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
10226 @file{file} must be an existing, readable text file.
10227 Each non empty line in @file{file} must be a directory.
10228 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
10229 switches @option{^-d^/SOURCE_DIRS^} as there are non empty lines in
10232 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
10233 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
10234 Foreign patterns. Using this switch, it is possible to add sources of languages
10235 other than Ada to the list of sources of a project file.
10236 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
10239 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
10242 will look for Ada units in all files with the @file{.ada} extension,
10243 and will add to the list of file for project @file{prj.gpr} the C files
10244 with extension ".^c^C^".
10247 @cindex @option{^-h^/HELP^} (@code{gnatname})
10248 Output usage (help) information. The output is written to @file{stdout}.
10250 @item ^-P^/PROJECT_FILE=^@file{proj}
10251 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
10252 Create or update project file @file{proj}. There may be zero, one or more space
10253 between @option{-P} and @file{proj}. @file{proj} may include directory
10254 information. @file{proj} must be writable.
10255 There may be only one switch @option{^-P^/PROJECT_FILE^}.
10256 When a switch @option{^-P^/PROJECT_FILE^} is specified,
10257 no switch @option{^-c^/CONFIG_FILE^} may be specified.
10259 @item ^-v^/VERBOSE^
10260 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
10261 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
10262 This includes name of the file written, the name of the directories to search
10263 and, for each file in those directories whose name matches at least one of
10264 the Naming Patterns, an indication of whether the file contains a unit,
10265 and if so the name of the unit.
10267 @item ^-v -v^/VERBOSE /VERBOSE^
10268 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
10269 Very Verbose mode. In addition to the output produced in verbose mode,
10270 for each file in the searched directories whose name matches none of
10271 the Naming Patterns, an indication is given that there is no match.
10273 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
10274 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
10275 Excluded patterns. Using this switch, it is possible to exclude some files
10276 that would match the name patterns. For example,
10278 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
10281 will look for Ada units in all files with the @file{.ada} extension,
10282 except those whose names end with @file{_nt.ada}.
10286 @node Examples of gnatname Usage
10287 @section Examples of @code{gnatname} Usage
10291 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
10297 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
10302 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
10303 and be writable. In addition, the directory
10304 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
10305 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
10308 Note the optional spaces after @option{-c} and @option{-d}.
10313 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
10314 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
10317 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
10318 /EXCLUDED_PATTERN=*_nt_body.ada
10319 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
10320 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
10324 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
10325 even in conjunction with one or several switches
10326 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
10327 are used in this example.
10330 @c *****************************************
10331 @c * G N A T P r o j e c t M a n a g e r *
10332 @c *****************************************
10333 @node GNAT Project Manager
10334 @chapter GNAT Project Manager
10338 * Examples of Project Files::
10339 * Project File Syntax::
10340 * Objects and Sources in Project Files::
10341 * Importing Projects::
10342 * Project Extension::
10343 * External References in Project Files::
10344 * Packages in Project Files::
10345 * Variables from Imported Projects::
10347 * Library Projects::
10348 * Using Third-Party Libraries through Projects::
10349 * Stand-alone Library Projects::
10350 * Switches Related to Project Files::
10351 * Tools Supporting Project Files::
10352 * An Extended Example::
10353 * Project File Complete Syntax::
10356 @c ****************
10357 @c * Introduction *
10358 @c ****************
10361 @section Introduction
10364 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
10365 you to manage complex builds involving a number of source files, directories,
10366 and compilation options for different system configurations. In particular,
10367 project files allow you to specify:
10370 The directory or set of directories containing the source files, and/or the
10371 names of the specific source files themselves
10373 The directory in which the compiler's output
10374 (@file{ALI} files, object files, tree files) is to be placed
10376 The directory in which the executable programs is to be placed
10378 ^Switch^Switch^ settings for any of the project-enabled tools
10379 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
10380 @code{gnatfind}); you can apply these settings either globally or to individual
10383 The source files containing the main subprogram(s) to be built
10385 The source programming language(s) (currently Ada and/or C)
10387 Source file naming conventions; you can specify these either globally or for
10388 individual compilation units
10395 @node Project Files
10396 @subsection Project Files
10399 Project files are written in a syntax close to that of Ada, using familiar
10400 notions such as packages, context clauses, declarations, default values,
10401 assignments, and inheritance. Finally, project files can be built
10402 hierarchically from other project files, simplifying complex system
10403 integration and project reuse.
10405 A @dfn{project} is a specific set of values for various compilation properties.
10406 The settings for a given project are described by means of
10407 a @dfn{project file}, which is a text file written in an Ada-like syntax.
10408 Property values in project files are either strings or lists of strings.
10409 Properties that are not explicitly set receive default values. A project
10410 file may interrogate the values of @dfn{external variables} (user-defined
10411 command-line switches or environment variables), and it may specify property
10412 settings conditionally, based on the value of such variables.
10414 In simple cases, a project's source files depend only on other source files
10415 in the same project, or on the predefined libraries. (@emph{Dependence} is
10417 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
10418 the Project Manager also allows more sophisticated arrangements,
10419 where the source files in one project depend on source files in other
10423 One project can @emph{import} other projects containing needed source files.
10425 You can organize GNAT projects in a hierarchy: a @emph{child} project
10426 can extend a @emph{parent} project, inheriting the parent's source files and
10427 optionally overriding any of them with alternative versions
10431 More generally, the Project Manager lets you structure large development
10432 efforts into hierarchical subsystems, where build decisions are delegated
10433 to the subsystem level, and thus different compilation environments
10434 (^switch^switch^ settings) used for different subsystems.
10436 The Project Manager is invoked through the
10437 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
10438 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
10440 There may be zero, one or more spaces between @option{-P} and
10441 @option{@emph{projectfile}}.
10443 If you want to define (on the command line) an external variable that is
10444 queried by the project file, you must use the
10445 @option{^-X^/EXTERNAT_REFERENCE=^@emph{vbl}=@emph{value}} switch.
10446 The Project Manager parses and interprets the project file, and drives the
10447 invoked tool based on the project settings.
10449 The Project Manager supports a wide range of development strategies,
10450 for systems of all sizes. Here are some typical practices that are
10454 Using a common set of source files, but generating object files in different
10455 directories via different ^switch^switch^ settings
10457 Using a mostly-shared set of source files, but with different versions of
10462 The destination of an executable can be controlled inside a project file
10463 using the @option{^-o^-o^}
10465 In the absence of such a ^switch^switch^ either inside
10466 the project file or on the command line, any executable files generated by
10467 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
10468 in the project file. If no @code{Exec_Dir} is specified, they will be placed
10469 in the object directory of the project.
10471 You can use project files to achieve some of the effects of a source
10472 versioning system (for example, defining separate projects for
10473 the different sets of sources that comprise different releases) but the
10474 Project Manager is independent of any source configuration management tools
10475 that might be used by the developers.
10477 The next section introduces the main features of GNAT's project facility
10478 through a sequence of examples; subsequent sections will present the syntax
10479 and semantics in more detail. A more formal description of the project
10480 facility appears in the GNAT Reference Manual.
10482 @c *****************************
10483 @c * Examples of Project Files *
10484 @c *****************************
10486 @node Examples of Project Files
10487 @section Examples of Project Files
10489 This section illustrates some of the typical uses of project files and
10490 explains their basic structure and behavior.
10493 * Common Sources with Different ^Switches^Switches^ and Directories::
10494 * Using External Variables::
10495 * Importing Other Projects::
10496 * Extending a Project::
10499 @node Common Sources with Different ^Switches^Switches^ and Directories
10500 @subsection Common Sources with Different ^Switches^Switches^ and Directories
10504 * Specifying the Object Directory::
10505 * Specifying the Exec Directory::
10506 * Project File Packages::
10507 * Specifying ^Switch^Switch^ Settings::
10508 * Main Subprograms::
10509 * Executable File Names::
10510 * Source File Naming Conventions::
10511 * Source Language(s)::
10515 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
10516 @file{proc.adb} are in the @file{/common} directory. The file
10517 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
10518 package @code{Pack}. We want to compile these source files under two sets
10519 of ^switches^switches^:
10522 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
10523 and the @option{^-gnata^-gnata^},
10524 @option{^-gnato^-gnato^},
10525 and @option{^-gnatE^-gnatE^} switches to the
10526 compiler; the compiler's output is to appear in @file{/common/debug}
10528 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
10529 to the compiler; the compiler's output is to appear in @file{/common/release}
10533 The GNAT project files shown below, respectively @file{debug.gpr} and
10534 @file{release.gpr} in the @file{/common} directory, achieve these effects.
10547 ^/common/debug^[COMMON.DEBUG]^
10552 ^/common/release^[COMMON.RELEASE]^
10557 Here are the corresponding project files:
10559 @smallexample @c projectfile
10562 for Object_Dir use "debug";
10563 for Main use ("proc");
10566 for ^Default_Switches^Default_Switches^ ("Ada")
10568 for Executable ("proc.adb") use "proc1";
10573 package Compiler is
10574 for ^Default_Switches^Default_Switches^ ("Ada")
10575 use ("-fstack-check",
10578 "^-gnatE^-gnatE^");
10584 @smallexample @c projectfile
10587 for Object_Dir use "release";
10588 for Exec_Dir use ".";
10589 for Main use ("proc");
10591 package Compiler is
10592 for ^Default_Switches^Default_Switches^ ("Ada")
10600 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
10601 insensitive), and analogously the project defined by @file{release.gpr} is
10602 @code{"Release"}. For consistency the file should have the same name as the
10603 project, and the project file's extension should be @code{"gpr"}. These
10604 conventions are not required, but a warning is issued if they are not followed.
10606 If the current directory is @file{^/temp^[TEMP]^}, then the command
10608 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
10612 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
10613 as well as the @code{^proc1^PROC1.EXE^} executable,
10614 using the ^switch^switch^ settings defined in the project file.
10616 Likewise, the command
10618 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
10622 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
10623 and the @code{^proc^PROC.EXE^}
10624 executable in @file{^/common^[COMMON]^},
10625 using the ^switch^switch^ settings from the project file.
10628 @unnumberedsubsubsec Source Files
10631 If a project file does not explicitly specify a set of source directories or
10632 a set of source files, then by default the project's source files are the
10633 Ada source files in the project file directory. Thus @file{pack.ads},
10634 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
10636 @node Specifying the Object Directory
10637 @unnumberedsubsubsec Specifying the Object Directory
10640 Several project properties are modeled by Ada-style @emph{attributes};
10641 a property is defined by supplying the equivalent of an Ada attribute
10642 definition clause in the project file.
10643 A project's object directory is another such a property; the corresponding
10644 attribute is @code{Object_Dir}, and its value is also a string expression,
10645 specified either as absolute or relative. In the later case,
10646 it is relative to the project file directory. Thus the compiler's
10647 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
10648 (for the @code{Debug} project)
10649 and to @file{^/common/release^[COMMON.RELEASE]^}
10650 (for the @code{Release} project).
10651 If @code{Object_Dir} is not specified, then the default is the project file
10654 @node Specifying the Exec Directory
10655 @unnumberedsubsubsec Specifying the Exec Directory
10658 A project's exec directory is another property; the corresponding
10659 attribute is @code{Exec_Dir}, and its value is also a string expression,
10660 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
10661 then the default is the object directory (which may also be the project file
10662 directory if attribute @code{Object_Dir} is not specified). Thus the executable
10663 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
10664 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
10665 and in @file{^/common^[COMMON]^} for the @code{Release} project.
10667 @node Project File Packages
10668 @unnumberedsubsubsec Project File Packages
10671 A GNAT tool that is integrated with the Project Manager is modeled by a
10672 corresponding package in the project file. In the example above,
10673 The @code{Debug} project defines the packages @code{Builder}
10674 (for @command{gnatmake}) and @code{Compiler};
10675 the @code{Release} project defines only the @code{Compiler} package.
10677 The Ada-like package syntax is not to be taken literally. Although packages in
10678 project files bear a surface resemblance to packages in Ada source code, the
10679 notation is simply a way to convey a grouping of properties for a named
10680 entity. Indeed, the package names permitted in project files are restricted
10681 to a predefined set, corresponding to the project-aware tools, and the contents
10682 of packages are limited to a small set of constructs.
10683 The packages in the example above contain attribute definitions.
10685 @node Specifying ^Switch^Switch^ Settings
10686 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
10689 ^Switch^Switch^ settings for a project-aware tool can be specified through
10690 attributes in the package that corresponds to the tool.
10691 The example above illustrates one of the relevant attributes,
10692 @code{^Default_Switches^Default_Switches^}, which is defined in packages
10693 in both project files.
10694 Unlike simple attributes like @code{Source_Dirs},
10695 @code{^Default_Switches^Default_Switches^} is
10696 known as an @emph{associative array}. When you define this attribute, you must
10697 supply an ``index'' (a literal string), and the effect of the attribute
10698 definition is to set the value of the array at the specified index.
10699 For the @code{^Default_Switches^Default_Switches^} attribute,
10700 the index is a programming language (in our case, Ada),
10701 and the value specified (after @code{use}) must be a list
10702 of string expressions.
10704 The attributes permitted in project files are restricted to a predefined set.
10705 Some may appear at project level, others in packages.
10706 For any attribute that is an associative array, the index must always be a
10707 literal string, but the restrictions on this string (e.g., a file name or a
10708 language name) depend on the individual attribute.
10709 Also depending on the attribute, its specified value will need to be either a
10710 string or a string list.
10712 In the @code{Debug} project, we set the switches for two tools,
10713 @command{gnatmake} and the compiler, and thus we include the two corresponding
10714 packages; each package defines the @code{^Default_Switches^Default_Switches^}
10715 attribute with index @code{"Ada"}.
10716 Note that the package corresponding to
10717 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
10718 similar, but only includes the @code{Compiler} package.
10720 In project @code{Debug} above, the ^switches^switches^ starting with
10721 @option{-gnat} that are specified in package @code{Compiler}
10722 could have been placed in package @code{Builder}, since @command{gnatmake}
10723 transmits all such ^switches^switches^ to the compiler.
10725 @node Main Subprograms
10726 @unnumberedsubsubsec Main Subprograms
10729 One of the specifiable properties of a project is a list of files that contain
10730 main subprograms. This property is captured in the @code{Main} attribute,
10731 whose value is a list of strings. If a project defines the @code{Main}
10732 attribute, it is not necessary to identify the main subprogram(s) when
10733 invoking @command{gnatmake} (see @ref{gnatmake and Project Files}).
10735 @node Executable File Names
10736 @unnumberedsubsubsec Executable File Names
10739 By default, the executable file name corresponding to a main source is
10740 deducted from the main source file name. Through the attributes
10741 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
10742 it is possible to change this default.
10743 In project @code{Debug} above, the executable file name
10744 for main source @file{^proc.adb^PROC.ADB^} is
10745 @file{^proc1^PROC1.EXE^}.
10746 Attribute @code{Executable_Suffix}, when specified, may change the suffix
10747 of the the executable files, when no attribute @code{Executable} applies:
10748 its value replace the platform-specific executable suffix.
10749 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
10750 specify a non default executable file name when several mains are built at once
10751 in a single @command{gnatmake} command.
10753 @node Source File Naming Conventions
10754 @unnumberedsubsubsec Source File Naming Conventions
10757 Since the project files above do not specify any source file naming
10758 conventions, the GNAT defaults are used. The mechanism for defining source
10759 file naming conventions -- a package named @code{Naming} --
10760 is described below (@pxref{Naming Schemes}).
10762 @node Source Language(s)
10763 @unnumberedsubsubsec Source Language(s)
10766 Since the project files do not specify a @code{Languages} attribute, by
10767 default the GNAT tools assume that the language of the project file is Ada.
10768 More generally, a project can comprise source files
10769 in Ada, C, and/or other languages.
10771 @node Using External Variables
10772 @subsection Using External Variables
10775 Instead of supplying different project files for debug and release, we can
10776 define a single project file that queries an external variable (set either
10777 on the command line or via an ^environment variable^logical name^) in order to
10778 conditionally define the appropriate settings. Again, assume that the
10779 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
10780 located in directory @file{^/common^[COMMON]^}. The following project file,
10781 @file{build.gpr}, queries the external variable named @code{STYLE} and
10782 defines an object directory and ^switch^switch^ settings based on whether
10783 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
10784 the default is @code{"deb"}.
10786 @smallexample @c projectfile
10789 for Main use ("proc");
10791 type Style_Type is ("deb", "rel");
10792 Style : Style_Type := external ("STYLE", "deb");
10796 for Object_Dir use "debug";
10799 for Object_Dir use "release";
10800 for Exec_Dir use ".";
10809 for ^Default_Switches^Default_Switches^ ("Ada")
10811 for Executable ("proc") use "proc1";
10818 package Compiler is
10822 for ^Default_Switches^Default_Switches^ ("Ada")
10823 use ("^-gnata^-gnata^",
10825 "^-gnatE^-gnatE^");
10828 for ^Default_Switches^Default_Switches^ ("Ada")
10839 @code{Style_Type} is an example of a @emph{string type}, which is the project
10840 file analog of an Ada enumeration type but whose components are string literals
10841 rather than identifiers. @code{Style} is declared as a variable of this type.
10843 The form @code{external("STYLE", "deb")} is known as an
10844 @emph{external reference}; its first argument is the name of an
10845 @emph{external variable}, and the second argument is a default value to be
10846 used if the external variable doesn't exist. You can define an external
10847 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
10848 or you can use ^an environment variable^a logical name^
10849 as an external variable.
10851 Each @code{case} construct is expanded by the Project Manager based on the
10852 value of @code{Style}. Thus the command
10855 gnatmake -P/common/build.gpr -XSTYLE=deb
10861 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
10866 is equivalent to the @command{gnatmake} invocation using the project file
10867 @file{debug.gpr} in the earlier example. So is the command
10869 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
10873 since @code{"deb"} is the default for @code{STYLE}.
10879 gnatmake -P/common/build.gpr -XSTYLE=rel
10885 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
10890 is equivalent to the @command{gnatmake} invocation using the project file
10891 @file{release.gpr} in the earlier example.
10893 @node Importing Other Projects
10894 @subsection Importing Other Projects
10897 A compilation unit in a source file in one project may depend on compilation
10898 units in source files in other projects. To compile this unit under
10899 control of a project file, the
10900 dependent project must @emph{import} the projects containing the needed source
10902 This effect is obtained using syntax similar to an Ada @code{with} clause,
10903 but where @code{with}ed entities are strings that denote project files.
10905 As an example, suppose that the two projects @code{GUI_Proj} and
10906 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
10907 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
10908 and @file{^/comm^[COMM]^}, respectively.
10909 Suppose that the source files for @code{GUI_Proj} are
10910 @file{gui.ads} and @file{gui.adb}, and that the source files for
10911 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
10912 files is located in its respective project file directory. Schematically:
10931 We want to develop an application in directory @file{^/app^[APP]^} that
10932 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
10933 the corresponding project files (e.g. the ^switch^switch^ settings
10934 and object directory).
10935 Skeletal code for a main procedure might be something like the following:
10937 @smallexample @c ada
10940 procedure App_Main is
10949 Here is a project file, @file{app_proj.gpr}, that achieves the desired
10952 @smallexample @c projectfile
10954 with "/gui/gui_proj", "/comm/comm_proj";
10955 project App_Proj is
10956 for Main use ("app_main");
10962 Building an executable is achieved through the command:
10964 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
10967 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
10968 in the directory where @file{app_proj.gpr} resides.
10970 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
10971 (as illustrated above) the @code{with} clause can omit the extension.
10973 Our example specified an absolute path for each imported project file.
10974 Alternatively, the directory name of an imported object can be omitted
10978 The imported project file is in the same directory as the importing project
10981 You have defined ^an environment variable^a logical name^
10982 that includes the directory containing
10983 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
10984 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
10985 directory names separated by colons (semicolons on Windows).
10989 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
10990 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
10993 @smallexample @c projectfile
10995 with "gui_proj", "comm_proj";
10996 project App_Proj is
10997 for Main use ("app_main");
11003 Importing other projects can create ambiguities.
11004 For example, the same unit might be present in different imported projects, or
11005 it might be present in both the importing project and in an imported project.
11006 Both of these conditions are errors. Note that in the current version of
11007 the Project Manager, it is illegal to have an ambiguous unit even if the
11008 unit is never referenced by the importing project. This restriction may be
11009 relaxed in a future release.
11011 @node Extending a Project
11012 @subsection Extending a Project
11015 In large software systems it is common to have multiple
11016 implementations of a common interface; in Ada terms, multiple versions of a
11017 package body for the same specification. For example, one implementation
11018 might be safe for use in tasking programs, while another might only be used
11019 in sequential applications. This can be modeled in GNAT using the concept
11020 of @emph{project extension}. If one project (the ``child'') @emph{extends}
11021 another project (the ``parent'') then by default all source files of the
11022 parent project are inherited by the child, but the child project can
11023 override any of the parent's source files with new versions, and can also
11024 add new files. This facility is the project analog of a type extension in
11025 Object-Oriented Programming. Project hierarchies are permitted (a child
11026 project may be the parent of yet another project), and a project that
11027 inherits one project can also import other projects.
11029 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
11030 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
11031 @file{pack.adb}, and @file{proc.adb}:
11044 Note that the project file can simply be empty (that is, no attribute or
11045 package is defined):
11047 @smallexample @c projectfile
11049 project Seq_Proj is
11055 implying that its source files are all the Ada source files in the project
11058 Suppose we want to supply an alternate version of @file{pack.adb}, in
11059 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
11060 @file{pack.ads} and @file{proc.adb}. We can define a project
11061 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
11065 ^/tasking^[TASKING]^
11071 project Tasking_Proj extends "/seq/seq_proj" is
11077 The version of @file{pack.adb} used in a build depends on which project file
11080 Note that we could have obtained the desired behavior using project import
11081 rather than project inheritance; a @code{base} project would contain the
11082 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
11083 import @code{base} and add @file{pack.adb}, and likewise a tasking project
11084 would import @code{base} and add a different version of @file{pack.adb}. The
11085 choice depends on whether other sources in the original project need to be
11086 overridden. If they do, then project extension is necessary, otherwise,
11087 importing is sufficient.
11090 In a project file that extends another project file, it is possible to
11091 indicate that an inherited source is not part of the sources of the extending
11092 project. This is necessary sometimes when a package spec has been overloaded
11093 and no longer requires a body: in this case, it is necessary to indicate that
11094 the inherited body is not part of the sources of the project, otherwise there
11095 will be a compilation error when compiling the spec.
11097 For that purpose, the attribute @code{Locally_Removed_Files} is used.
11098 Its value is a string list: a list of file names.
11100 @smallexample @c @projectfile
11101 project B extends "a" is
11102 for Source_Files use ("pkg.ads");
11103 -- New spec of Pkg does not need a completion
11104 for Locally_Removed_Files use ("pkg.adb");
11108 Attribute @code{Locally_Removed_Files} may also be used to check if a source
11109 is still needed: if it is possible to build using @code{gnatmake} when such
11110 a source is put in attribute @code{Locally_Removed_Files} of a project P, then
11111 it is possible to remove the source completely from a system that includes
11114 @c ***********************
11115 @c * Project File Syntax *
11116 @c ***********************
11118 @node Project File Syntax
11119 @section Project File Syntax
11128 * Associative Array Attributes::
11129 * case Constructions::
11133 This section describes the structure of project files.
11135 A project may be an @emph{independent project}, entirely defined by a single
11136 project file. Any Ada source file in an independent project depends only
11137 on the predefined library and other Ada source files in the same project.
11140 A project may also @dfn{depend on} other projects, in either or both of
11141 the following ways:
11143 @item It may import any number of projects
11144 @item It may extend at most one other project
11148 The dependence relation is a directed acyclic graph (the subgraph reflecting
11149 the ``extends'' relation is a tree).
11151 A project's @dfn{immediate sources} are the source files directly defined by
11152 that project, either implicitly by residing in the project file's directory,
11153 or explicitly through any of the source-related attributes described below.
11154 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
11155 of @var{proj} together with the immediate sources (unless overridden) of any
11156 project on which @var{proj} depends (either directly or indirectly).
11159 @subsection Basic Syntax
11162 As seen in the earlier examples, project files have an Ada-like syntax.
11163 The minimal project file is:
11164 @smallexample @c projectfile
11173 The identifier @code{Empty} is the name of the project.
11174 This project name must be present after the reserved
11175 word @code{end} at the end of the project file, followed by a semi-colon.
11177 Any name in a project file, such as the project name or a variable name,
11178 has the same syntax as an Ada identifier.
11180 The reserved words of project files are the Ada reserved words plus
11181 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
11182 reserved words currently used in project file syntax are:
11210 Comments in project files have the same syntax as in Ada, two consecutives
11211 hyphens through the end of the line.
11214 @subsection Packages
11217 A project file may contain @emph{packages}. The name of a package must be one
11218 of the identifiers from the following list. A package
11219 with a given name may only appear once in a project file. Package names are
11220 case insensitive. The following package names are legal:
11236 @code{Cross_Reference}
11248 In its simplest form, a package may be empty:
11250 @smallexample @c projectfile
11260 A package may contain @emph{attribute declarations},
11261 @emph{variable declarations} and @emph{case constructions}, as will be
11264 When there is ambiguity between a project name and a package name,
11265 the name always designates the project. To avoid possible confusion, it is
11266 always a good idea to avoid naming a project with one of the
11267 names allowed for packages or any name that starts with @code{gnat}.
11270 @subsection Expressions
11273 An @emph{expression} is either a @emph{string expression} or a
11274 @emph{string list expression}.
11276 A @emph{string expression} is either a @emph{simple string expression} or a
11277 @emph{compound string expression}.
11279 A @emph{simple string expression} is one of the following:
11281 @item A literal string; e.g.@code{"comm/my_proj.gpr"}
11282 @item A string-valued variable reference (see @ref{Variables})
11283 @item A string-valued attribute reference (see @ref{Attributes})
11284 @item An external reference (see @ref{External References in Project Files})
11288 A @emph{compound string expression} is a concatenation of string expressions,
11289 using the operator @code{"&"}
11291 Path & "/" & File_Name & ".ads"
11295 A @emph{string list expression} is either a
11296 @emph{simple string list expression} or a
11297 @emph{compound string list expression}.
11299 A @emph{simple string list expression} is one of the following:
11301 @item A parenthesized list of zero or more string expressions,
11302 separated by commas
11304 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
11307 @item A string list-valued variable reference
11308 @item A string list-valued attribute reference
11312 A @emph{compound string list expression} is the concatenation (using
11313 @code{"&"}) of a simple string list expression and an expression. Note that
11314 each term in a compound string list expression, except the first, may be
11315 either a string expression or a string list expression.
11317 @smallexample @c projectfile
11319 File_Name_List := () & File_Name; -- One string in this list
11320 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
11322 Big_List := File_Name_List & Extended_File_Name_List;
11323 -- Concatenation of two string lists: three strings
11324 Illegal_List := "gnat.adc" & Extended_File_Name_List;
11325 -- Illegal: must start with a string list
11330 @subsection String Types
11333 A @emph{string type declaration} introduces a discrete set of string literals.
11334 If a string variable is declared to have this type, its value
11335 is restricted to the given set of literals.
11337 Here is an example of a string type declaration:
11339 @smallexample @c projectfile
11340 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
11344 Variables of a string type are called @emph{typed variables}; all other
11345 variables are called @emph{untyped variables}. Typed variables are
11346 particularly useful in @code{case} constructions, to support conditional
11347 attribute declarations.
11348 (see @ref{case Constructions}).
11350 The string literals in the list are case sensitive and must all be different.
11351 They may include any graphic characters allowed in Ada, including spaces.
11353 A string type may only be declared at the project level, not inside a package.
11355 A string type may be referenced by its name if it has been declared in the same
11356 project file, or by an expanded name whose prefix is the name of the project
11357 in which it is declared.
11360 @subsection Variables
11363 A variable may be declared at the project file level, or within a package.
11364 Here are some examples of variable declarations:
11366 @smallexample @c projectfile
11368 This_OS : OS := external ("OS"); -- a typed variable declaration
11369 That_OS := "GNU/Linux"; -- an untyped variable declaration
11374 The syntax of a @emph{typed variable declaration} is identical to the Ada
11375 syntax for an object declaration. By contrast, the syntax of an untyped
11376 variable declaration is identical to an Ada assignment statement. In fact,
11377 variable declarations in project files have some of the characteristics of
11378 an assignment, in that successive declarations for the same variable are
11379 allowed. Untyped variable declarations do establish the expected kind of the
11380 variable (string or string list), and successive declarations for it must
11381 respect the initial kind.
11384 A string variable declaration (typed or untyped) declares a variable
11385 whose value is a string. This variable may be used as a string expression.
11386 @smallexample @c projectfile
11387 File_Name := "readme.txt";
11388 Saved_File_Name := File_Name & ".saved";
11392 A string list variable declaration declares a variable whose value is a list
11393 of strings. The list may contain any number (zero or more) of strings.
11395 @smallexample @c projectfile
11397 List_With_One_Element := ("^-gnaty^-gnaty^");
11398 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
11399 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
11400 "pack2.ada", "util_.ada", "util.ada");
11404 The same typed variable may not be declared more than once at project level,
11405 and it may not be declared more than once in any package; it is in effect
11408 The same untyped variable may be declared several times. Declarations are
11409 elaborated in the order in which they appear, so the new value replaces
11410 the old one, and any subsequent reference to the variable uses the new value.
11411 However, as noted above, if a variable has been declared as a string, all
11413 declarations must give it a string value. Similarly, if a variable has
11414 been declared as a string list, all subsequent declarations
11415 must give it a string list value.
11417 A @emph{variable reference} may take several forms:
11420 @item The simple variable name, for a variable in the current package (if any)
11421 or in the current project
11422 @item An expanded name, whose prefix is a context name.
11426 A @emph{context} may be one of the following:
11429 @item The name of an existing package in the current project
11430 @item The name of an imported project of the current project
11431 @item The name of an ancestor project (i.e., a project extended by the current
11432 project, either directly or indirectly)
11433 @item An expanded name whose prefix is an imported/parent project name, and
11434 whose selector is a package name in that project.
11438 A variable reference may be used in an expression.
11441 @subsection Attributes
11444 A project (and its packages) may have @emph{attributes} that define
11445 the project's properties. Some attributes have values that are strings;
11446 others have values that are string lists.
11448 There are two categories of attributes: @emph{simple attributes}
11449 and @emph{associative arrays} (see @ref{Associative Array Attributes}).
11451 Legal project attribute names, and attribute names for each legal package are
11452 listed below. Attributes names are case-insensitive.
11454 The following attributes are defined on projects (all are simple attributes):
11456 @multitable @columnfractions .4 .3
11457 @item @emph{Attribute Name}
11459 @item @code{Source_Files}
11461 @item @code{Source_Dirs}
11463 @item @code{Source_List_File}
11465 @item @code{Object_Dir}
11467 @item @code{Exec_Dir}
11469 @item @code{Locally_Removed_Files}
11473 @item @code{Languages}
11475 @item @code{Main_Language}
11477 @item @code{Library_Dir}
11479 @item @code{Library_Name}
11481 @item @code{Library_Kind}
11483 @item @code{Library_Version}
11485 @item @code{Library_Interface}
11487 @item @code{Library_Auto_Init}
11489 @item @code{Library_Options}
11491 @item @code{Library_GCC}
11496 The following attributes are defined for package @code{Naming}
11497 (see @ref{Naming Schemes}):
11499 @multitable @columnfractions .4 .2 .2 .2
11500 @item Attribute Name @tab Category @tab Index @tab Value
11501 @item @code{Spec_Suffix}
11502 @tab associative array
11505 @item @code{Body_Suffix}
11506 @tab associative array
11509 @item @code{Separate_Suffix}
11510 @tab simple attribute
11513 @item @code{Casing}
11514 @tab simple attribute
11517 @item @code{Dot_Replacement}
11518 @tab simple attribute
11522 @tab associative array
11526 @tab associative array
11529 @item @code{Specification_Exceptions}
11530 @tab associative array
11533 @item @code{Implementation_Exceptions}
11534 @tab associative array
11540 The following attributes are defined for packages @code{Builder},
11541 @code{Compiler}, @code{Binder},
11542 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
11543 (see @ref{^Switches^Switches^ and Project Files}).
11545 @multitable @columnfractions .4 .2 .2 .2
11546 @item Attribute Name @tab Category @tab Index @tab Value
11547 @item @code{^Default_Switches^Default_Switches^}
11548 @tab associative array
11551 @item @code{^Switches^Switches^}
11552 @tab associative array
11558 In addition, package @code{Compiler} has a single string attribute
11559 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
11560 string attribute @code{Global_Configuration_Pragmas}.
11563 Each simple attribute has a default value: the empty string (for string-valued
11564 attributes) and the empty list (for string list-valued attributes).
11566 An attribute declaration defines a new value for an attribute.
11568 Examples of simple attribute declarations:
11570 @smallexample @c projectfile
11571 for Object_Dir use "objects";
11572 for Source_Dirs use ("units", "test/drivers");
11576 The syntax of a @dfn{simple attribute declaration} is similar to that of an
11577 attribute definition clause in Ada.
11579 Attributes references may be appear in expressions.
11580 The general form for such a reference is @code{<entity>'<attribute>}:
11581 Associative array attributes are functions. Associative
11582 array attribute references must have an argument that is a string literal.
11586 @smallexample @c projectfile
11588 Naming'Dot_Replacement
11589 Imported_Project'Source_Dirs
11590 Imported_Project.Naming'Casing
11591 Builder'^Default_Switches^Default_Switches^("Ada")
11595 The prefix of an attribute may be:
11597 @item @code{project} for an attribute of the current project
11598 @item The name of an existing package of the current project
11599 @item The name of an imported project
11600 @item The name of a parent project that is extended by the current project
11601 @item An expanded name whose prefix is imported/parent project name,
11602 and whose selector is a package name
11607 @smallexample @c projectfile
11610 for Source_Dirs use project'Source_Dirs & "units";
11611 for Source_Dirs use project'Source_Dirs & "test/drivers"
11617 In the first attribute declaration, initially the attribute @code{Source_Dirs}
11618 has the default value: an empty string list. After this declaration,
11619 @code{Source_Dirs} is a string list of one element: @code{"units"}.
11620 After the second attribute declaration @code{Source_Dirs} is a string list of
11621 two elements: @code{"units"} and @code{"test/drivers"}.
11623 Note: this example is for illustration only. In practice,
11624 the project file would contain only one attribute declaration:
11626 @smallexample @c projectfile
11627 for Source_Dirs use ("units", "test/drivers");
11630 @node Associative Array Attributes
11631 @subsection Associative Array Attributes
11634 Some attributes are defined as @emph{associative arrays}. An associative
11635 array may be regarded as a function that takes a string as a parameter
11636 and delivers a string or string list value as its result.
11638 Here are some examples of single associative array attribute associations:
11640 @smallexample @c projectfile
11641 for Body ("main") use "Main.ada";
11642 for ^Switches^Switches^ ("main.ada")
11644 "^-gnatv^-gnatv^");
11645 for ^Switches^Switches^ ("main.ada")
11646 use Builder'^Switches^Switches^ ("main.ada")
11651 Like untyped variables and simple attributes, associative array attributes
11652 may be declared several times. Each declaration supplies a new value for the
11653 attribute, and replaces the previous setting.
11656 An associative array attribute may be declared as a full associative array
11657 declaration, with the value of the same attribute in an imported or extended
11660 @smallexample @c projectfile
11662 for Default_Switches use Default.Builder'Default_Switches;
11667 In this example, @code{Default} must be either an project imported by the
11668 current project, or the project that the current project extends. If the
11669 attribute is in a package (in this case, in package @code{Builder}), the same
11670 package needs to be specified.
11673 A full associative array declaration replaces any other declaration for the
11674 attribute, including other full associative array declaration. Single
11675 associative array associations may be declare after a full associative
11676 declaration, modifying the value for a single association of the attribute.
11678 @node case Constructions
11679 @subsection @code{case} Constructions
11682 A @code{case} construction is used in a project file to effect conditional
11684 Here is a typical example:
11686 @smallexample @c projectfile
11689 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
11691 OS : OS_Type := external ("OS", "GNU/Linux");
11695 package Compiler is
11697 when "GNU/Linux" | "Unix" =>
11698 for ^Default_Switches^Default_Switches^ ("Ada")
11699 use ("^-gnath^-gnath^");
11701 for ^Default_Switches^Default_Switches^ ("Ada")
11702 use ("^-gnatP^-gnatP^");
11711 The syntax of a @code{case} construction is based on the Ada case statement
11712 (although there is no @code{null} construction for empty alternatives).
11714 The case expression must a typed string variable.
11715 Each alternative comprises the reserved word @code{when}, either a list of
11716 literal strings separated by the @code{"|"} character or the reserved word
11717 @code{others}, and the @code{"=>"} token.
11718 Each literal string must belong to the string type that is the type of the
11720 An @code{others} alternative, if present, must occur last.
11722 After each @code{=>}, there are zero or more constructions. The only
11723 constructions allowed in a case construction are other case constructions and
11724 attribute declarations. String type declarations, variable declarations and
11725 package declarations are not allowed.
11727 The value of the case variable is often given by an external reference
11728 (see @ref{External References in Project Files}).
11730 @c ****************************************
11731 @c * Objects and Sources in Project Files *
11732 @c ****************************************
11734 @node Objects and Sources in Project Files
11735 @section Objects and Sources in Project Files
11738 * Object Directory::
11740 * Source Directories::
11741 * Source File Names::
11745 Each project has exactly one object directory and one or more source
11746 directories. The source directories must contain at least one source file,
11747 unless the project file explicitly specifies that no source files are present
11748 (see @ref{Source File Names}).
11750 @node Object Directory
11751 @subsection Object Directory
11754 The object directory for a project is the directory containing the compiler's
11755 output (such as @file{ALI} files and object files) for the project's immediate
11758 The object directory is given by the value of the attribute @code{Object_Dir}
11759 in the project file.
11761 @smallexample @c projectfile
11762 for Object_Dir use "objects";
11766 The attribute @var{Object_Dir} has a string value, the path name of the object
11767 directory. The path name may be absolute or relative to the directory of the
11768 project file. This directory must already exist, and be readable and writable.
11770 By default, when the attribute @code{Object_Dir} is not given an explicit value
11771 or when its value is the empty string, the object directory is the same as the
11772 directory containing the project file.
11774 @node Exec Directory
11775 @subsection Exec Directory
11778 The exec directory for a project is the directory containing the executables
11779 for the project's main subprograms.
11781 The exec directory is given by the value of the attribute @code{Exec_Dir}
11782 in the project file.
11784 @smallexample @c projectfile
11785 for Exec_Dir use "executables";
11789 The attribute @var{Exec_Dir} has a string value, the path name of the exec
11790 directory. The path name may be absolute or relative to the directory of the
11791 project file. This directory must already exist, and be writable.
11793 By default, when the attribute @code{Exec_Dir} is not given an explicit value
11794 or when its value is the empty string, the exec directory is the same as the
11795 object directory of the project file.
11797 @node Source Directories
11798 @subsection Source Directories
11801 The source directories of a project are specified by the project file
11802 attribute @code{Source_Dirs}.
11804 This attribute's value is a string list. If the attribute is not given an
11805 explicit value, then there is only one source directory, the one where the
11806 project file resides.
11808 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
11811 @smallexample @c projectfile
11812 for Source_Dirs use ();
11816 indicates that the project contains no source files.
11818 Otherwise, each string in the string list designates one or more
11819 source directories.
11821 @smallexample @c projectfile
11822 for Source_Dirs use ("sources", "test/drivers");
11826 If a string in the list ends with @code{"/**"}, then the directory whose path
11827 name precedes the two asterisks, as well as all its subdirectories
11828 (recursively), are source directories.
11830 @smallexample @c projectfile
11831 for Source_Dirs use ("/system/sources/**");
11835 Here the directory @code{/system/sources} and all of its subdirectories
11836 (recursively) are source directories.
11838 To specify that the source directories are the directory of the project file
11839 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
11840 @smallexample @c projectfile
11841 for Source_Dirs use ("./**");
11845 Each of the source directories must exist and be readable.
11847 @node Source File Names
11848 @subsection Source File Names
11851 In a project that contains source files, their names may be specified by the
11852 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
11853 (a string). Source file names never include any directory information.
11855 If the attribute @code{Source_Files} is given an explicit value, then each
11856 element of the list is a source file name.
11858 @smallexample @c projectfile
11859 for Source_Files use ("main.adb");
11860 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
11864 If the attribute @code{Source_Files} is not given an explicit value,
11865 but the attribute @code{Source_List_File} is given a string value,
11866 then the source file names are contained in the text file whose path name
11867 (absolute or relative to the directory of the project file) is the
11868 value of the attribute @code{Source_List_File}.
11870 Each line in the file that is not empty or is not a comment
11871 contains a source file name.
11873 @smallexample @c projectfile
11874 for Source_List_File use "source_list.txt";
11878 By default, if neither the attribute @code{Source_Files} nor the attribute
11879 @code{Source_List_File} is given an explicit value, then each file in the
11880 source directories that conforms to the project's naming scheme
11881 (see @ref{Naming Schemes}) is an immediate source of the project.
11883 A warning is issued if both attributes @code{Source_Files} and
11884 @code{Source_List_File} are given explicit values. In this case, the attribute
11885 @code{Source_Files} prevails.
11887 Each source file name must be the name of one existing source file
11888 in one of the source directories.
11890 A @code{Source_Files} attribute whose value is an empty list
11891 indicates that there are no source files in the project.
11893 If the order of the source directories is known statically, that is if
11894 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
11895 be several files with the same source file name. In this case, only the file
11896 in the first directory is considered as an immediate source of the project
11897 file. If the order of the source directories is not known statically, it is
11898 an error to have several files with the same source file name.
11900 Projects can be specified to have no Ada source
11901 files: the value of (@code{Source_Dirs} or @code{Source_Files} may be an empty
11902 list, or the @code{"Ada"} may be absent from @code{Languages}:
11904 @smallexample @c projectfile
11905 for Source_Dirs use ();
11906 for Source_Files use ();
11907 for Languages use ("C", "C++");
11911 Otherwise, a project must contain at least one immediate source.
11913 Projects with no source files are useful as template packages
11914 (see @ref{Packages in Project Files}) for other projects; in particular to
11915 define a package @code{Naming} (see @ref{Naming Schemes}).
11917 @c ****************************
11918 @c * Importing Projects *
11919 @c ****************************
11921 @node Importing Projects
11922 @section Importing Projects
11925 An immediate source of a project P may depend on source files that
11926 are neither immediate sources of P nor in the predefined library.
11927 To get this effect, P must @emph{import} the projects that contain the needed
11930 @smallexample @c projectfile
11932 with "project1", "utilities.gpr";
11933 with "/namings/apex.gpr";
11940 As can be seen in this example, the syntax for importing projects is similar
11941 to the syntax for importing compilation units in Ada. However, project files
11942 use literal strings instead of names, and the @code{with} clause identifies
11943 project files rather than packages.
11945 Each literal string is the file name or path name (absolute or relative) of a
11946 project file. If a string is simply a file name, with no path, then its
11947 location is determined by the @emph{project path}:
11951 If the ^environment variable^logical name^ @env{ADA_PROJECT_PATH} exists,
11952 then the project path includes all the directories in this
11953 ^environment variable^logical name^, plus the directory of the project file.
11956 If the ^environment variable^logical name^ @env{ADA_PROJECT_PATH} does not
11957 exist, then the project path contains only one directory, namely the one where
11958 the project file is located.
11962 If a relative pathname is used, as in
11964 @smallexample @c projectfile
11969 then the path is relative to the directory where the importing project file is
11970 located. Any symbolic link will be fully resolved in the directory
11971 of the importing project file before the imported project file is examined.
11973 If the @code{with}'ed project file name does not have an extension,
11974 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
11975 then the file name as specified in the @code{with} clause (no extension) will
11976 be used. In the above example, if a file @code{project1.gpr} is found, then it
11977 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
11978 then it will be used; if neither file exists, this is an error.
11980 A warning is issued if the name of the project file does not match the
11981 name of the project; this check is case insensitive.
11983 Any source file that is an immediate source of the imported project can be
11984 used by the immediate sources of the importing project, transitively. Thus
11985 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
11986 sources of @code{A} may depend on the immediate sources of @code{C}, even if
11987 @code{A} does not import @code{C} explicitly. However, this is not recommended,
11988 because if and when @code{B} ceases to import @code{C}, some sources in
11989 @code{A} will no longer compile.
11991 A side effect of this capability is that normally cyclic dependencies are not
11992 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
11993 is not allowed to import @code{A}. However, there are cases when cyclic
11994 dependencies would be beneficial. For these cases, another form of import
11995 between projects exists, the @code{limited with}: a project @code{A} that
11996 imports a project @code{B} with a straigh @code{with} may also be imported,
11997 directly or indirectly, by @code{B} on the condition that imports from @code{B}
11998 to @code{A} include at least one @code{limited with}.
12000 @smallexample @c 0projectfile
12006 limited with "../a/a.gpr";
12014 limited with "../a/a.gpr";
12020 In the above legal example, there are two project cycles:
12023 @item A -> C -> D -> A
12027 In each of these cycle there is one @code{limited with}: import of @code{A}
12028 from @code{B} and import of @code{A} from @code{D}.
12030 The difference between straight @code{with} and @code{limited with} is that
12031 the name of a project imported with a @code{limited with} cannot be used in the
12032 project that imports it. In particular, its packages cannot be renamed and
12033 its variables cannot be referred to.
12035 An exception to the above rules for @code{limited with} is that for the main
12036 project specified to @command{gnatmake} or to the @command{GNAT} driver a
12037 @code{limited with} is equivalent to a straight @code{with}. For example,
12038 in the example above, projects @code{B} and @code{D} could not be main
12039 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
12040 each have a @code{limited with} that is the only one in a cycle of importing
12043 @c *********************
12044 @c * Project Extension *
12045 @c *********************
12047 @node Project Extension
12048 @section Project Extension
12051 During development of a large system, it is sometimes necessary to use
12052 modified versions of some of the source files, without changing the original
12053 sources. This can be achieved through the @emph{project extension} facility.
12055 @smallexample @c projectfile
12056 project Modified_Utilities extends "/baseline/utilities.gpr" is ...
12060 A project extension declaration introduces an extending project
12061 (the @emph{child}) and a project being extended (the @emph{parent}).
12063 By default, a child project inherits all the sources of its parent.
12064 However, inherited sources can be overridden: a unit in a parent is hidden
12065 by a unit of the same name in the child.
12067 Inherited sources are considered to be sources (but not immediate sources)
12068 of the child project; see @ref{Project File Syntax}.
12070 An inherited source file retains any switches specified in the parent project.
12072 For example if the project @code{Utilities} contains the specification and the
12073 body of an Ada package @code{Util_IO}, then the project
12074 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
12075 The original body of @code{Util_IO} will not be considered in program builds.
12076 However, the package specification will still be found in the project
12079 A child project can have only one parent but it may import any number of other
12082 A project is not allowed to import directly or indirectly at the same time a
12083 child project and any of its ancestors.
12085 @c ****************************************
12086 @c * External References in Project Files *
12087 @c ****************************************
12089 @node External References in Project Files
12090 @section External References in Project Files
12093 A project file may contain references to external variables; such references
12094 are called @emph{external references}.
12096 An external variable is either defined as part of the environment (an
12097 environment variable in Unix, for example) or else specified on the command
12098 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
12099 If both, then the command line value is used.
12101 The value of an external reference is obtained by means of the built-in
12102 function @code{external}, which returns a string value.
12103 This function has two forms:
12105 @item @code{external (external_variable_name)}
12106 @item @code{external (external_variable_name, default_value)}
12110 Each parameter must be a string literal. For example:
12112 @smallexample @c projectfile
12114 external ("OS", "GNU/Linux")
12118 In the form with one parameter, the function returns the value of
12119 the external variable given as parameter. If this name is not present in the
12120 environment, the function returns an empty string.
12122 In the form with two string parameters, the second argument is
12123 the value returned when the variable given as the first argument is not
12124 present in the environment. In the example above, if @code{"OS"} is not
12125 the name of ^an environment variable^a logical name^ and is not passed on
12126 the command line, then the returned value is @code{"GNU/Linux"}.
12128 An external reference may be part of a string expression or of a string
12129 list expression, and can therefore appear in a variable declaration or
12130 an attribute declaration.
12132 @smallexample @c projectfile
12134 type Mode_Type is ("Debug", "Release");
12135 Mode : Mode_Type := external ("MODE");
12142 @c *****************************
12143 @c * Packages in Project Files *
12144 @c *****************************
12146 @node Packages in Project Files
12147 @section Packages in Project Files
12150 A @emph{package} defines the settings for project-aware tools within a
12152 For each such tool one can declare a package; the names for these
12153 packages are preset (see @ref{Packages}).
12154 A package may contain variable declarations, attribute declarations, and case
12157 @smallexample @c projectfile
12160 package Builder is -- used by gnatmake
12161 for ^Default_Switches^Default_Switches^ ("Ada")
12170 The syntax of package declarations mimics that of package in Ada.
12172 Most of the packages have an attribute
12173 @code{^Default_Switches^Default_Switches^}.
12174 This attribute is an associative array, and its value is a string list.
12175 The index of the associative array is the name of a programming language (case
12176 insensitive). This attribute indicates the ^switch^switch^
12177 or ^switches^switches^ to be used
12178 with the corresponding tool.
12180 Some packages also have another attribute, @code{^Switches^Switches^},
12181 an associative array whose value is a string list.
12182 The index is the name of a source file.
12183 This attribute indicates the ^switch^switch^
12184 or ^switches^switches^ to be used by the corresponding
12185 tool when dealing with this specific file.
12187 Further information on these ^switch^switch^-related attributes is found in
12188 @ref{^Switches^Switches^ and Project Files}.
12190 A package may be declared as a @emph{renaming} of another package; e.g., from
12191 the project file for an imported project.
12193 @smallexample @c projectfile
12195 with "/global/apex.gpr";
12197 package Naming renames Apex.Naming;
12204 Packages that are renamed in other project files often come from project files
12205 that have no sources: they are just used as templates. Any modification in the
12206 template will be reflected automatically in all the project files that rename
12207 a package from the template.
12209 In addition to the tool-oriented packages, you can also declare a package
12210 named @code{Naming} to establish specialized source file naming conventions
12211 (see @ref{Naming Schemes}).
12213 @c ************************************
12214 @c * Variables from Imported Projects *
12215 @c ************************************
12217 @node Variables from Imported Projects
12218 @section Variables from Imported Projects
12221 An attribute or variable defined in an imported or parent project can
12222 be used in expressions in the importing / extending project.
12223 Such an attribute or variable is denoted by an expanded name whose prefix
12224 is either the name of the project or the expanded name of a package within
12227 @smallexample @c projectfile
12230 project Main extends "base" is
12231 Var1 := Imported.Var;
12232 Var2 := Base.Var & ".new";
12237 for ^Default_Switches^Default_Switches^ ("Ada")
12238 use Imported.Builder.Ada_^Switches^Switches^ &
12239 "^-gnatg^-gnatg^" &
12245 package Compiler is
12246 for ^Default_Switches^Default_Switches^ ("Ada")
12247 use Base.Compiler.Ada_^Switches^Switches^;
12258 The value of @code{Var1} is a copy of the variable @code{Var} defined
12259 in the project file @file{"imported.gpr"}
12261 the value of @code{Var2} is a copy of the value of variable @code{Var}
12262 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
12264 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
12265 @code{Builder} is a string list that includes in its value a copy of the value
12266 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
12267 in project file @file{imported.gpr} plus two new elements:
12268 @option{"^-gnatg^-gnatg^"}
12269 and @option{"^-v^-v^"};
12271 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
12272 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
12273 defined in the @code{Compiler} package in project file @file{base.gpr},
12274 the project being extended.
12277 @c ******************
12278 @c * Naming Schemes *
12279 @c ******************
12281 @node Naming Schemes
12282 @section Naming Schemes
12285 Sometimes an Ada software system is ported from a foreign compilation
12286 environment to GNAT, and the file names do not use the default GNAT
12287 conventions. Instead of changing all the file names (which for a variety
12288 of reasons might not be possible), you can define the relevant file
12289 naming scheme in the @code{Naming} package in your project file.
12292 Note that the use of pragmas described in @ref{Alternative
12293 File Naming Schemes} by mean of a configuration pragmas file is not
12294 supported when using project files. You must use the features described
12295 in this paragraph. You can however use specify other configuration
12296 pragmas (see @ref{Specifying Configuration Pragmas}).
12299 For example, the following
12300 package models the Apex file naming rules:
12302 @smallexample @c projectfile
12305 for Casing use "lowercase";
12306 for Dot_Replacement use ".";
12307 for Spec_Suffix ("Ada") use ".1.ada";
12308 for Body_Suffix ("Ada") use ".2.ada";
12315 For example, the following package models the DEC Ada file naming rules:
12317 @smallexample @c projectfile
12320 for Casing use "lowercase";
12321 for Dot_Replacement use "__";
12322 for Spec_Suffix ("Ada") use "_.^ada^ada^";
12323 for Body_Suffix ("Ada") use ".^ada^ada^";
12329 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
12330 names in lower case)
12334 You can define the following attributes in package @code{Naming}:
12339 This must be a string with one of the three values @code{"lowercase"},
12340 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
12343 If @var{Casing} is not specified, then the default is @code{"lowercase"}.
12345 @item @var{Dot_Replacement}
12346 This must be a string whose value satisfies the following conditions:
12349 @item It must not be empty
12350 @item It cannot start or end with an alphanumeric character
12351 @item It cannot be a single underscore
12352 @item It cannot start with an underscore followed by an alphanumeric
12353 @item It cannot contain a dot @code{'.'} except if the entire string
12358 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
12360 @item @var{Spec_Suffix}
12361 This is an associative array (indexed by the programming language name, case
12362 insensitive) whose value is a string that must satisfy the following
12366 @item It must not be empty
12367 @item It must include at least one dot
12370 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
12371 @code{"^.ads^.ADS^"}.
12373 @item @var{Body_Suffix}
12374 This is an associative array (indexed by the programming language name, case
12375 insensitive) whose value is a string that must satisfy the following
12379 @item It must not be empty
12380 @item It must include at least one dot
12381 @item It cannot end with the same string as @code{Spec_Suffix ("Ada")}
12384 If @code{Body_Suffix ("Ada")} is not specified, then the default is
12385 @code{"^.adb^.ADB^"}.
12387 @item @var{Separate_Suffix}
12388 This must be a string whose value satisfies the same conditions as
12389 @code{Body_Suffix}.
12392 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
12393 value as @code{Body_Suffix ("Ada")}.
12397 You can use the associative array attribute @code{Spec} to define
12398 the source file name for an individual Ada compilation unit's spec. The array
12399 index must be a string literal that identifies the Ada unit (case insensitive).
12400 The value of this attribute must be a string that identifies the file that
12401 contains this unit's spec (case sensitive or insensitive depending on the
12404 @smallexample @c projectfile
12405 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
12410 You can use the associative array attribute @code{Body} to
12411 define the source file name for an individual Ada compilation unit's body
12412 (possibly a subunit). The array index must be a string literal that identifies
12413 the Ada unit (case insensitive). The value of this attribute must be a string
12414 that identifies the file that contains this unit's body or subunit (case
12415 sensitive or insensitive depending on the operating system).
12417 @smallexample @c projectfile
12418 for Body ("MyPack.MyChild") use "mypack.mychild.body";
12422 @c ********************
12423 @c * Library Projects *
12424 @c ********************
12426 @node Library Projects
12427 @section Library Projects
12430 @emph{Library projects} are projects whose object code is placed in a library.
12431 (Note that this facility is not yet supported on all platforms)
12433 To create a library project, you need to define in its project file
12434 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
12435 Additionally, you may define the library-related attributes
12436 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
12437 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
12439 The @code{Library_Name} attribute has a string value. There is no restriction
12440 on the name of a library. It is the responsability of the developer to
12441 choose a name that will be accepted by the platform. It is recommanded to
12442 choose names that could be Ada identifiers; such names are almost guaranteed
12443 to be acceptable on all platforms.
12445 The @code{Library_Dir} attribute has a string value that designates the path
12446 (absolute or relative) of the directory where the library will reside.
12447 It must designate an existing directory, and this directory must be
12448 different from the project's object directory. It also needs to be writable.
12449 The directory should only be used for one library; the reason is that all
12450 files contained in this directory may be deleted by the Project Manager.
12452 If both @code{Library_Name} and @code{Library_Dir} are specified and
12453 are legal, then the project file defines a library project. The optional
12454 library-related attributes are checked only for such project files.
12456 The @code{Library_Kind} attribute has a string value that must be one of the
12457 following (case insensitive): @code{"static"}, @code{"dynamic"} or
12458 @code{"relocatable"} (which is a synonym for @code{"dynamic"}). If this
12459 attribute is not specified, the library is a static library, that is
12460 an archive of object files that can be potentially linked into an
12461 static executable. Otherwise, the library may be dynamic or
12462 relocatable, that is a library that is loaded only at the start of execution.
12464 If you need to build both a static and a dynamic library, you should use two
12465 different object directories, since in some cases some extra code needs to
12466 be generated for the latter. For such cases, it is recommended to either use
12467 two different project files, or a single one which uses external variables
12468 to indicate what kind of library should be build.
12470 The @code{Library_Version} attribute has a string value whose interpretation
12471 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
12472 used only for dynamic/relocatable libraries as the internal name of the
12473 library (the @code{"soname"}). If the library file name (built from the
12474 @code{Library_Name}) is different from the @code{Library_Version}, then the
12475 library file will be a symbolic link to the actual file whose name will be
12476 @code{Library_Version}.
12480 @smallexample @c projectfile
12486 for Library_Dir use "lib_dir";
12487 for Library_Name use "dummy";
12488 for Library_Kind use "relocatable";
12489 for Library_Version use "libdummy.so." & Version;
12496 Directory @file{lib_dir} will contain the internal library file whose name
12497 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
12498 @file{libdummy.so.1}.
12500 When @command{gnatmake} detects that a project file
12501 is a library project file, it will check all immediate sources of the project
12502 and rebuild the library if any of the sources have been recompiled.
12504 Standard project files can import library project files. In such cases,
12505 the libraries will only be rebuild if some of its sources are recompiled
12506 because they are in the closure of some other source in an importing project.
12507 Sources of the library project files that are not in such a closure will
12508 not be checked, unless the full library is checked, because one of its sources
12509 needs to be recompiled.
12511 For instance, assume the project file @code{A} imports the library project file
12512 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
12513 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
12514 @file{l2.ads}, @file{l2.adb}.
12516 If @file{l1.adb} has been modified, then the library associated with @code{L}
12517 will be rebuild when compiling all the immediate sources of @code{A} only
12518 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
12521 To be sure that all the sources in the library associated with @code{L} are
12522 up to date, and that all the sources of parject @code{A} are also up to date,
12523 the following two commands needs to be used:
12530 When a library is built or rebuilt, an attempt is made first to delete all
12531 files in the library directory.
12532 All @file{ALI} files will also be copied from the object directory to the
12533 library directory. To build executables, @command{gnatmake} will use the
12534 library rather than the individual object files.
12537 @c **********************************************
12538 @c * Using Third-Party Libraries through Projects
12539 @c **********************************************
12540 @node Using Third-Party Libraries through Projects
12541 @section Using Third-Party Libraries through Projects
12543 Whether you are exporting your own library to make it available to
12544 clients, or you are using a library provided by a third party, it is
12545 convenient to have project files that automatically set the correct
12546 command line switches for the compiler and linker.
12548 Such project files are very similar to the library project files;
12549 @xref{Library Projects}. The only difference is that you set the
12550 @code{Source_Dirs} and @code{Object_Dir} attribute so that they point to the
12551 directories where, respectively, the sources and the read-only ALI files have
12554 If you need to interface with a set of libraries, as opposed to a
12555 single one, you need to create one library project for each of the
12556 libraries. In addition, a top-level project that imports all these
12557 library projects should be provided, so that the user of your library
12558 has a single @code{with} clause to add to his own projects.
12560 For instance, let's assume you are providing two static libraries
12561 @file{liba.a} and @file{libb.a}. The user needs to link with
12562 both of these libraries. Each of these is associated with its
12563 own set of header files. Let's assume furthermore that all the
12564 header files for the two libraries have been installed in the same
12565 directory @file{headers}. The @file{ALI} files are found in the same
12566 @file{headers} directory.
12568 In this case, you should provide the following three projects:
12570 @smallexample @c projectfile
12572 with "liba", "libb";
12573 project My_Library is
12574 for Source_Dirs use ("headers");
12575 for Object_Dir use "headers";
12581 for Source_Dirs use ();
12582 for Library_Dir use "lib";
12583 for Library_Name use "a";
12584 for Library_Kind use "static";
12590 for Source_Dirs use ();
12591 for Library_Dir use "lib";
12592 for Library_Name use "b";
12593 for Library_Kind use "static";
12598 @c *******************************
12599 @c * Stand-alone Library Projects *
12600 @c *******************************
12602 @node Stand-alone Library Projects
12603 @section Stand-alone Library Projects
12606 A Stand-alone Library is a library that contains the necessary code to
12607 elaborate the Ada units that are included in the library. A Stand-alone
12608 Library is suitable to be used in an executable when the main is not
12609 in Ada. However, Stand-alone Libraries may also be used with an Ada main
12612 A Stand-alone Library Project is a Library Project where the library is
12613 a Stand-alone Library.
12615 To be a Stand-alone Library Project, in addition to the two attributes
12616 that make a project a Library Project (@code{Library_Name} and
12617 @code{Library_Dir}, see @ref{Library Projects}), the attribute
12618 @code{Library_Interface} must be defined.
12620 @smallexample @c projectfile
12622 for Library_Dir use "lib_dir";
12623 for Library_Name use "dummy";
12624 for Library_Interface use ("int1", "int1.child");
12628 Attribute @code{Library_Interface} has a non empty string list value,
12629 each string in the list designating a unit contained in an immediate source
12630 of the project file.
12632 When a Stand-alone Library is built, first the binder is invoked to build
12633 a package whose name depends on the library name
12634 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
12635 This binder-generated package includes initialization and
12636 finalization procedures whose
12637 names depend on the library name (dummyinit and dummyfinal in the example
12638 above). The object corresponding to this package is included in the library.
12640 A dynamic or relocatable Stand-alone Library is automatically initialized
12641 if automatic initialization of Stand-alone Libraries is supported on the
12642 platform and if attribute @code{Library_Auto_Init} is not specified or
12643 is specified with the value "true". A static Stand-alone Library is never
12644 automatically initialized.
12646 Single string attribute @code{Library_Auto_Init} may be specified with only
12647 two possible values: "false" or "true" (case-insensitive). Specifying
12648 "false" for attribute @code{Library_Auto_Init} will prevent automatic
12649 initialization of dynamic or relocatable libraries.
12651 When a non automatically initialized Stand-alone Library is used
12652 in an executable, its initialization procedure must be called before
12653 any service of the library is used.
12654 When the main subprogram is in Ada, it may mean that the initialization
12655 procedure has to be called during elaboration of another package.
12657 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
12658 (those that are listed in attribute @code{Library_Interface}) are copied to
12659 the Library Directory. As a consequence, only the Interface Units may be
12660 imported from Ada units outside of the library. If other units are imported,
12661 the binding phase will fail.
12663 When a Stand-Alone Library is bound, the switches that are specified in
12664 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
12665 used in the call to @command{gnatbind}.
12667 The string list attribute @code{Library_Options} may be used to specified
12668 additional switches to the call to @command{gcc} to link the library.
12670 The attribute @code{Library_Src_Dir}, may be specified for a
12671 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
12672 single string value. Its value must be the path (absolute or relative to the
12673 project directory) of an existing directory. This directory cannot be the
12674 object directory or one of the source directories, but it can be the same as
12675 the library directory. The sources of the Interface
12676 Units of the library, necessary to an Ada client of the library, will be
12677 copied to the designated directory, called Interface Copy directory.
12678 These sources includes the specs of the Interface Units, but they may also
12679 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
12680 are used, or when there is a generic units in the spec. Before the sources
12681 are copied to the Interface Copy directory, an attempt is made to delete all
12682 files in the Interface Copy directory.
12684 @c *************************************
12685 @c * Switches Related to Project Files *
12686 @c *************************************
12687 @node Switches Related to Project Files
12688 @section Switches Related to Project Files
12691 The following switches are used by GNAT tools that support project files:
12695 @item ^-P^/PROJECT_FILE=^@var{project}
12696 @cindex @option{^-P^/PROJECT_FILE^} (any tool supporting project files)
12697 Indicates the name of a project file. This project file will be parsed with
12698 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
12699 if any, and using the external references indicated
12700 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
12702 There may zero, one or more spaces between @option{-P} and @var{project}.
12706 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
12709 Since the Project Manager parses the project file only after all the switches
12710 on the command line are checked, the order of the switches
12711 @option{^-P^/PROJECT_FILE^},
12712 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
12713 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
12715 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
12716 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any tool supporting project files)
12717 Indicates that external variable @var{name} has the value @var{value}.
12718 The Project Manager will use this value for occurrences of
12719 @code{external(name)} when parsing the project file.
12723 If @var{name} or @var{value} includes a space, then @var{name=value} should be
12724 put between quotes.
12732 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
12733 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
12734 @var{name}, only the last one is used.
12737 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
12738 takes precedence over the value of the same name in the environment.
12740 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
12741 @cindex @code{^-vP^/MESSAGES_PROJECT_FILE^} (any tool supporting project files)
12742 @c Previous line uses code vs option command, to stay less than 80 chars
12743 Indicates the verbosity of the parsing of GNAT project files.
12746 @option{-vP0} means Default;
12747 @option{-vP1} means Medium;
12748 @option{-vP2} means High.
12752 There are three possible options for this qualifier: DEFAULT, MEDIUM and
12757 The default is ^Default^DEFAULT^: no output for syntactically correct
12760 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
12761 only the last one is used.
12765 @c **********************************
12766 @c * Tools Supporting Project Files *
12767 @c **********************************
12769 @node Tools Supporting Project Files
12770 @section Tools Supporting Project Files
12773 * gnatmake and Project Files::
12774 * The GNAT Driver and Project Files::
12776 * Glide and Project Files::
12780 @node gnatmake and Project Files
12781 @subsection gnatmake and Project Files
12784 This section covers several topics related to @command{gnatmake} and
12785 project files: defining ^switches^switches^ for @command{gnatmake}
12786 and for the tools that it invokes; specifying configuration pragmas;
12787 the use of the @code{Main} attribute; building and rebuilding library project
12791 * ^Switches^Switches^ and Project Files::
12792 * Specifying Configuration Pragmas::
12793 * Project Files and Main Subprograms::
12794 * Library Project Files::
12797 @node ^Switches^Switches^ and Project Files
12798 @subsubsection ^Switches^Switches^ and Project Files
12801 It is not currently possible to specify VMS style qualifiers in the project
12802 files; only Unix style ^switches^switches^ may be specified.
12806 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
12807 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
12808 attribute, a @code{^Switches^Switches^} attribute, or both;
12809 as their names imply, these ^switch^switch^-related
12810 attributes affect the ^switches^switches^ that are used for each of these GNAT
12812 @command{gnatmake} is invoked. As will be explained below, these
12813 component-specific ^switches^switches^ precede
12814 the ^switches^switches^ provided on the @command{gnatmake} command line.
12816 The @code{^Default_Switches^Default_Switches^} attribute is an associative
12817 array indexed by language name (case insensitive) whose value is a string list.
12820 @smallexample @c projectfile
12822 package Compiler is
12823 for ^Default_Switches^Default_Switches^ ("Ada")
12824 use ("^-gnaty^-gnaty^",
12831 The @code{^Switches^Switches^} attribute is also an associative array,
12832 indexed by a file name (which may or may not be case sensitive, depending
12833 on the operating system) whose value is a string list. For example:
12835 @smallexample @c projectfile
12838 for ^Switches^Switches^ ("main1.adb")
12840 for ^Switches^Switches^ ("main2.adb")
12847 For the @code{Builder} package, the file names must designate source files
12848 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
12849 file names must designate @file{ALI} or source files for main subprograms.
12850 In each case just the file name without an explicit extension is acceptable.
12852 For each tool used in a program build (@command{gnatmake}, the compiler, the
12853 binder, and the linker), the corresponding package @dfn{contributes} a set of
12854 ^switches^switches^ for each file on which the tool is invoked, based on the
12855 ^switch^switch^-related attributes defined in the package.
12856 In particular, the ^switches^switches^
12857 that each of these packages contributes for a given file @var{f} comprise:
12861 the value of attribute @code{^Switches^Switches^ (@var{f})},
12862 if it is specified in the package for the given file,
12864 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
12865 if it is specified in the package.
12869 If neither of these attributes is defined in the package, then the package does
12870 not contribute any ^switches^switches^ for the given file.
12872 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
12873 two sets, in the following order: those contributed for the file
12874 by the @code{Builder} package;
12875 and the switches passed on the command line.
12877 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
12878 the ^switches^switches^ passed to the tool comprise three sets,
12879 in the following order:
12883 the applicable ^switches^switches^ contributed for the file
12884 by the @code{Builder} package in the project file supplied on the command line;
12887 those contributed for the file by the package (in the relevant project file --
12888 see below) corresponding to the tool; and
12891 the applicable switches passed on the command line.
12895 The term @emph{applicable ^switches^switches^} reflects the fact that
12896 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
12897 tools, depending on the individual ^switch^switch^.
12899 @command{gnatmake} may invoke the compiler on source files from different
12900 projects. The Project Manager will use the appropriate project file to
12901 determine the @code{Compiler} package for each source file being compiled.
12902 Likewise for the @code{Binder} and @code{Linker} packages.
12904 As an example, consider the following package in a project file:
12906 @smallexample @c projectfile
12909 package Compiler is
12910 for ^Default_Switches^Default_Switches^ ("Ada")
12912 for ^Switches^Switches^ ("a.adb")
12914 for ^Switches^Switches^ ("b.adb")
12916 "^-gnaty^-gnaty^");
12923 If @command{gnatmake} is invoked with this project file, and it needs to
12924 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
12925 @file{a.adb} will be compiled with the ^switch^switch^
12926 @option{^-O1^-O1^},
12927 @file{b.adb} with ^switches^switches^
12929 and @option{^-gnaty^-gnaty^},
12930 and @file{c.adb} with @option{^-g^-g^}.
12932 The following example illustrates the ordering of the ^switches^switches^
12933 contributed by different packages:
12935 @smallexample @c projectfile
12939 for ^Switches^Switches^ ("main.adb")
12947 package Compiler is
12948 for ^Switches^Switches^ ("main.adb")
12956 If you issue the command:
12959 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
12963 then the compiler will be invoked on @file{main.adb} with the following
12964 sequence of ^switches^switches^
12967 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
12970 with the last @option{^-O^-O^}
12971 ^switch^switch^ having precedence over the earlier ones;
12972 several other ^switches^switches^
12973 (such as @option{^-c^-c^}) are added implicitly.
12975 The ^switches^switches^
12977 and @option{^-O1^-O1^} are contributed by package
12978 @code{Builder}, @option{^-O2^-O2^} is contributed
12979 by the package @code{Compiler}
12980 and @option{^-O0^-O0^} comes from the command line.
12982 The @option{^-g^-g^}
12983 ^switch^switch^ will also be passed in the invocation of
12984 @command{Gnatlink.}
12986 A final example illustrates switch contributions from packages in different
12989 @smallexample @c projectfile
12992 for Source_Files use ("pack.ads", "pack.adb");
12993 package Compiler is
12994 for ^Default_Switches^Default_Switches^ ("Ada")
12995 use ("^-gnata^-gnata^");
13003 for Source_Files use ("foo_main.adb", "bar_main.adb");
13005 for ^Switches^Switches^ ("foo_main.adb")
13013 -- Ada source file:
13015 procedure Foo_Main is
13023 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
13027 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
13028 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
13029 @option{^-gnato^-gnato^} (passed on the command line).
13030 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
13031 are @option{^-g^-g^} from @code{Proj4.Builder},
13032 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
13033 and @option{^-gnato^-gnato^} from the command line.
13036 When using @command{gnatmake} with project files, some ^switches^switches^ or
13037 arguments may be expressed as relative paths. As the working directory where
13038 compilation occurs may change, these relative paths are converted to absolute
13039 paths. For the ^switches^switches^ found in a project file, the relative paths
13040 are relative to the project file directory, for the switches on the command
13041 line, they are relative to the directory where @command{gnatmake} is invoked.
13042 The ^switches^switches^ for which this occurs are:
13048 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
13050 ^-o^-o^, object files specified in package @code{Linker} or after
13051 -largs on the command line). The exception to this rule is the ^switch^switch^
13052 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
13054 @node Specifying Configuration Pragmas
13055 @subsubsection Specifying Configuration Pragmas
13057 When using @command{gnatmake} with project files, if there exists a file
13058 @file{gnat.adc} that contains configuration pragmas, this file will be
13061 Configuration pragmas can be defined by means of the following attributes in
13062 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
13063 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
13065 Both these attributes are single string attributes. Their values is the path
13066 name of a file containing configuration pragmas. If a path name is relative,
13067 then it is relative to the project directory of the project file where the
13068 attribute is defined.
13070 When compiling a source, the configuration pragmas used are, in order,
13071 those listed in the file designated by attribute
13072 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
13073 project file, if it is specified, and those listed in the file designated by
13074 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
13075 the project file of the source, if it exists.
13077 @node Project Files and Main Subprograms
13078 @subsubsection Project Files and Main Subprograms
13081 When using a project file, you can invoke @command{gnatmake}
13082 with one or several main subprograms, by specifying their source files on the
13086 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
13090 Each of these needs to be a source file of the same project, except
13091 when the switch ^-u^/UNIQUE^ is used.
13094 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
13095 same project, one of the project in the tree rooted at the project specified
13096 on the command line. The package @code{Builder} of this common project, the
13097 "main project" is the one that is considered by @command{gnatmake}.
13100 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
13101 imported directly or indirectly by the project specified on the command line.
13102 Note that if such a source file is not part of the project specified on the
13103 command line, the ^switches^switches^ found in package @code{Builder} of the
13104 project specified on the command line, if any, that are transmitted
13105 to the compiler will still be used, not those found in the project file of
13109 When using a project file, you can also invoke @command{gnatmake} without
13110 explicitly specifying any main, and the effect depends on whether you have
13111 defined the @code{Main} attribute. This attribute has a string list value,
13112 where each element in the list is the name of a source file (the file
13113 extension is optional) that contains a unit that can be a main subprogram.
13115 If the @code{Main} attribute is defined in a project file as a non-empty
13116 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
13117 line, then invoking @command{gnatmake} with this project file but without any
13118 main on the command line is equivalent to invoking @command{gnatmake} with all
13119 the file names in the @code{Main} attribute on the command line.
13122 @smallexample @c projectfile
13125 for Main use ("main1", "main2", "main3");
13131 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
13133 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
13135 When the project attribute @code{Main} is not specified, or is specified
13136 as an empty string list, or when the switch @option{-u} is used on the command
13137 line, then invoking @command{gnatmake} with no main on the command line will
13138 result in all immediate sources of the project file being checked, and
13139 potentially recompiled. Depending on the presence of the switch @option{-u},
13140 sources from other project files on which the immediate sources of the main
13141 project file depend are also checked and potentially recompiled. In other
13142 words, the @option{-u} switch is applied to all of the immediate sources of the
13145 When no main is specified on the command line and attribute @code{Main} exists
13146 and includes several mains, or when several mains are specified on the
13147 command line, the default ^switches^switches^ in package @code{Builder} will
13148 be used for all mains, even if there are specific ^switches^switches^
13149 specified for one or several mains.
13151 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
13152 the specific ^switches^switches^ for each main, if they are specified.
13154 @node Library Project Files
13155 @subsubsection Library Project Files
13158 When @command{gnatmake} is invoked with a main project file that is a library
13159 project file, it is not allowed to specify one or more mains on the command
13163 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
13164 ^-l^/ACTION=LINK^ have special meanings.
13167 @item ^-b^/ACTION=BIND^ is only allowed for stand-alone libraries. It indicates
13168 to @command{gnatmake} that @command{gnatbind} should be invoked for the
13171 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
13172 to @command{gnatmake} that the binder generated file should be compiled
13173 (in the case of a stand-alone library) and that the library should be built.
13177 @node The GNAT Driver and Project Files
13178 @subsection The GNAT Driver and Project Files
13181 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
13183 @command{^gnatbind^gnatbind^},
13184 @command{^gnatfind^gnatfind^},
13185 @command{^gnatlink^gnatlink^},
13186 @command{^gnatls^gnatls^},
13187 @command{^gnatelim^gnatelim^},
13188 @command{^gnatpp^gnatpp^},
13189 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
13190 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
13191 They must be invoked through the @command{gnat} driver.
13193 The @command{gnat} driver is a front-end that accepts a number of commands and
13194 call the corresponding tool. It has been designed initially for VMS to convert
13195 VMS style qualifiers to Unix style switches, but it is now available to all
13196 the GNAT supported platforms.
13198 On non VMS platforms, the @command{gnat} driver accepts the following commands
13199 (case insensitive):
13203 BIND to invoke @command{^gnatbind^gnatbind^}
13205 CHOP to invoke @command{^gnatchop^gnatchop^}
13207 CLEAN to invoke @command{^gnatclean^gnatclean^}
13209 COMP or COMPILE to invoke the compiler
13211 ELIM to invoke @command{^gnatelim^gnatelim^}
13213 FIND to invoke @command{^gnatfind^gnatfind^}
13215 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
13217 LINK to invoke @command{^gnatlink^gnatlink^}
13219 LS or LIST to invoke @command{^gnatls^gnatls^}
13221 MAKE to invoke @command{^gnatmake^gnatmake^}
13223 NAME to invoke @command{^gnatname^gnatname^}
13225 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
13227 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
13229 STUB to invoke @command{^gnatstub^gnatstub^}
13231 XREF to invoke @command{^gnatxref^gnatxref^}
13235 Note that the compiler is invoked using the command
13236 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}.
13239 The command may be followed by switches and arguments for the invoked
13243 gnat bind -C main.ali
13249 Switches may also be put in text files, one switch per line, and the text
13250 files may be specified with their path name preceded by '@@'.
13253 gnat bind @@args.txt main.ali
13257 In addition, for command BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
13258 PP or PRETTY and XREF, the project file related switches
13259 (@option{^-P^/PROJECT_FILE^},
13260 @option{^-X^/EXTERNAL_REFERENCE^} and
13261 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
13262 the switches of the invoking tool.
13265 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
13266 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
13267 the immediate sources of the specified project file.
13270 For each of these commands, there is optionally a corresponding package
13271 in the main project.
13275 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
13278 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
13281 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
13284 package @code{Eliminate} for command ELIM (invoking
13285 @code{^gnatelim^gnatelim^})
13288 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
13291 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
13294 package @code{Pretty_Printer} for command PP or PRETTY
13295 (invoking @code{^gnatpp^gnatpp^})
13298 package @code{Cross_Reference} for command XREF (invoking
13299 @code{^gnatxref^gnatxref^})
13304 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
13305 a simple variable with a string list value. It contains ^switches^switches^
13306 for the invocation of @code{^gnatls^gnatls^}.
13308 @smallexample @c projectfile
13312 for ^Switches^Switches^
13321 All other packages have two attribute @code{^Switches^Switches^} and
13322 @code{^Default_Switches^Default_Switches^}.
13325 @code{^Switches^Switches^} is an associated array attribute, indexed by the
13326 source file name, that has a string list value: the ^switches^switches^ to be
13327 used when the tool corresponding to the package is invoked for the specific
13331 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
13332 indexed by the programming language that has a string list value.
13333 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
13334 ^switches^switches^ for the invocation of the tool corresponding
13335 to the package, except if a specific @code{^Switches^Switches^} attribute
13336 is specified for the source file.
13338 @smallexample @c projectfile
13342 for Source_Dirs use ("./**");
13345 for ^Switches^Switches^ use
13352 package Compiler is
13353 for ^Default_Switches^Default_Switches^ ("Ada")
13354 use ("^-gnatv^-gnatv^",
13355 "^-gnatwa^-gnatwa^");
13361 for ^Default_Switches^Default_Switches^ ("Ada")
13369 for ^Default_Switches^Default_Switches^ ("Ada")
13371 for ^Switches^Switches^ ("main.adb")
13380 for ^Default_Switches^Default_Switches^ ("Ada")
13387 package Cross_Reference is
13388 for ^Default_Switches^Default_Switches^ ("Ada")
13393 end Cross_Reference;
13399 With the above project file, commands such as
13402 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
13403 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
13404 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
13405 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
13406 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
13410 will set up the environment properly and invoke the tool with the switches
13411 found in the package corresponding to the tool:
13412 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
13413 except @code{^Switches^Switches^ ("main.adb")}
13414 for @code{^gnatlink^gnatlink^}.
13417 @node Glide and Project Files
13418 @subsection Glide and Project Files
13421 Glide will automatically recognize the @file{.gpr} extension for
13422 project files, and will
13423 convert them to its own internal format automatically. However, it
13424 doesn't provide a syntax-oriented editor for modifying these
13426 The project file will be loaded as text when you select the menu item
13427 @code{Ada} @result{} @code{Project} @result{} @code{Edit}.
13428 You can edit this text and save the @file{gpr} file;
13429 when you next select this project file in Glide it
13430 will be automatically reloaded.
13433 @c **********************
13434 @node An Extended Example
13435 @section An Extended Example
13438 Suppose that we have two programs, @var{prog1} and @var{prog2},
13439 whose sources are in corresponding directories. We would like
13440 to build them with a single @command{gnatmake} command, and we want to place
13441 their object files into @file{build} subdirectories of the source directories.
13442 Furthermore, we want to have to have two separate subdirectories
13443 in @file{build} -- @file{release} and @file{debug} -- which will contain
13444 the object files compiled with different set of compilation flags.
13446 In other words, we have the following structure:
13463 Here are the project files that we must place in a directory @file{main}
13464 to maintain this structure:
13468 @item We create a @code{Common} project with a package @code{Compiler} that
13469 specifies the compilation ^switches^switches^:
13474 @b{project} Common @b{is}
13476 @b{for} Source_Dirs @b{use} (); -- No source files
13480 @b{type} Build_Type @b{is} ("release", "debug");
13481 Build : Build_Type := External ("BUILD", "debug");
13484 @b{package} Compiler @b{is}
13485 @b{case} Build @b{is}
13486 @b{when} "release" =>
13487 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
13488 @b{use} ("^-O2^-O2^");
13489 @b{when} "debug" =>
13490 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
13491 @b{use} ("^-g^-g^");
13499 @item We create separate projects for the two programs:
13506 @b{project} Prog1 @b{is}
13508 @b{for} Source_Dirs @b{use} ("prog1");
13509 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
13511 @b{package} Compiler @b{renames} Common.Compiler;
13522 @b{project} Prog2 @b{is}
13524 @b{for} Source_Dirs @b{use} ("prog2");
13525 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
13527 @b{package} Compiler @b{renames} Common.Compiler;
13533 @item We create a wrapping project @code{Main}:
13542 @b{project} Main @b{is}
13544 @b{package} Compiler @b{renames} Common.Compiler;
13550 @item Finally we need to create a dummy procedure that @code{with}s (either
13551 explicitly or implicitly) all the sources of our two programs.
13556 Now we can build the programs using the command
13559 gnatmake ^-P^/PROJECT_FILE=^main dummy
13563 for the Debug mode, or
13567 gnatmake -Pmain -XBUILD=release
13573 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
13578 for the Release mode.
13580 @c ********************************
13581 @c * Project File Complete Syntax *
13582 @c ********************************
13584 @node Project File Complete Syntax
13585 @section Project File Complete Syntax
13589 context_clause project_declaration
13595 @b{with} path_name @{ , path_name @} ;
13600 project_declaration ::=
13601 simple_project_declaration | project_extension
13603 simple_project_declaration ::=
13604 @b{project} <project_>simple_name @b{is}
13605 @{declarative_item@}
13606 @b{end} <project_>simple_name;
13608 project_extension ::=
13609 @b{project} <project_>simple_name @b{extends} path_name @b{is}
13610 @{declarative_item@}
13611 @b{end} <project_>simple_name;
13613 declarative_item ::=
13614 package_declaration |
13615 typed_string_declaration |
13616 other_declarative_item
13618 package_declaration ::=
13619 package_specification | package_renaming
13621 package_specification ::=
13622 @b{package} package_identifier @b{is}
13623 @{simple_declarative_item@}
13624 @b{end} package_identifier ;
13626 package_identifier ::=
13627 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
13628 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
13629 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
13631 package_renaming ::==
13632 @b{package} package_identifier @b{renames}
13633 <project_>simple_name.package_identifier ;
13635 typed_string_declaration ::=
13636 @b{type} <typed_string_>_simple_name @b{is}
13637 ( string_literal @{, string_literal@} );
13639 other_declarative_item ::=
13640 attribute_declaration |
13641 typed_variable_declaration |
13642 variable_declaration |
13645 attribute_declaration ::=
13646 full_associative_array_declaration |
13647 @b{for} attribute_designator @b{use} expression ;
13649 full_associative_array_declaration ::=
13650 @b{for} <associative_array_attribute_>simple_name @b{use}
13651 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
13653 attribute_designator ::=
13654 <simple_attribute_>simple_name |
13655 <associative_array_attribute_>simple_name ( string_literal )
13657 typed_variable_declaration ::=
13658 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
13660 variable_declaration ::=
13661 <variable_>simple_name := expression;
13671 attribute_reference
13677 ( <string_>expression @{ , <string_>expression @} )
13680 @b{external} ( string_literal [, string_literal] )
13682 attribute_reference ::=
13683 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
13685 attribute_prefix ::=
13687 <project_>simple_name | package_identifier |
13688 <project_>simple_name . package_identifier
13690 case_construction ::=
13691 @b{case} <typed_variable_>name @b{is}
13696 @b{when} discrete_choice_list =>
13697 @{case_construction | attribute_declaration@}
13699 discrete_choice_list ::=
13700 string_literal @{| string_literal@} |
13704 simple_name @{. simple_name@}
13707 identifier (same as Ada)
13712 @node The Cross-Referencing Tools gnatxref and gnatfind
13713 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
13718 The compiler generates cross-referencing information (unless
13719 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
13720 This information indicates where in the source each entity is declared and
13721 referenced. Note that entities in package Standard are not included, but
13722 entities in all other predefined units are included in the output.
13724 Before using any of these two tools, you need to compile successfully your
13725 application, so that GNAT gets a chance to generate the cross-referencing
13728 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
13729 information to provide the user with the capability to easily locate the
13730 declaration and references to an entity. These tools are quite similar,
13731 the difference being that @code{gnatfind} is intended for locating
13732 definitions and/or references to a specified entity or entities, whereas
13733 @code{gnatxref} is oriented to generating a full report of all
13736 To use these tools, you must not compile your application using the
13737 @option{-gnatx} switch on the @file{gnatmake} command line
13738 (see @ref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
13739 information will not be generated.
13742 * gnatxref Switches::
13743 * gnatfind Switches::
13744 * Project Files for gnatxref and gnatfind::
13745 * Regular Expressions in gnatfind and gnatxref::
13746 * Examples of gnatxref Usage::
13747 * Examples of gnatfind Usage::
13750 @node gnatxref Switches
13751 @section @code{gnatxref} Switches
13754 The command invocation for @code{gnatxref} is:
13756 $ gnatxref [switches] sourcefile1 [sourcefile2 ...]
13763 @item sourcefile1, sourcefile2
13764 identifies the source files for which a report is to be generated. The
13765 ``with''ed units will be processed too. You must provide at least one file.
13767 These file names are considered to be regular expressions, so for instance
13768 specifying @file{source*.adb} is the same as giving every file in the current
13769 directory whose name starts with @file{source} and whose extension is
13772 You shouldn't specify any directory name, just base names. @command{gnatxref}
13773 and @command{gnatfind} will be able to locate these files by themselves using
13774 the source path. If you specify directories, no result is produced.
13779 The switches can be :
13782 @item ^-a^/ALL_FILES^
13783 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
13784 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
13785 the read-only files found in the library search path. Otherwise, these files
13786 will be ignored. This option can be used to protect Gnat sources or your own
13787 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
13788 much faster, and their output much smaller. Read-only here refers to access
13789 or permissions status in the file system for the current user.
13792 @cindex @option{-aIDIR} (@command{gnatxref})
13793 When looking for source files also look in directory DIR. The order in which
13794 source file search is undertaken is the same as for @file{gnatmake}.
13797 @cindex @option{-aODIR} (@command{gnatxref})
13798 When searching for library and object files, look in directory
13799 DIR. The order in which library files are searched is the same as for
13803 @cindex @option{-nostdinc} (@command{gnatxref})
13804 Do not look for sources in the system default directory.
13807 @cindex @option{-nostdlib} (@command{gnatxref})
13808 Do not look for library files in the system default directory.
13810 @item --RTS=@var{rts-path}
13811 @cindex @option{--RTS} (@command{gnatxref})
13812 Specifies the default location of the runtime library. Same meaning as the
13813 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
13815 @item ^-d^/DERIVED_TYPES^
13816 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
13817 If this switch is set @code{gnatxref} will output the parent type
13818 reference for each matching derived types.
13820 @item ^-f^/FULL_PATHNAME^
13821 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
13822 If this switch is set, the output file names will be preceded by their
13823 directory (if the file was found in the search path). If this switch is
13824 not set, the directory will not be printed.
13826 @item ^-g^/IGNORE_LOCALS^
13827 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
13828 If this switch is set, information is output only for library-level
13829 entities, ignoring local entities. The use of this switch may accelerate
13830 @code{gnatfind} and @code{gnatxref}.
13833 @cindex @option{-IDIR} (@command{gnatxref})
13834 Equivalent to @samp{-aODIR -aIDIR}.
13837 @cindex @option{-pFILE} (@command{gnatxref})
13838 Specify a project file to use @xref{Project Files}. These project files are
13839 the @file{.adp} files used by Glide. If you need to use the @file{.gpr}
13840 project files, you should use gnatxref through the GNAT driver
13841 (@command{gnat xref -Pproject}).
13843 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
13844 project file in the current directory.
13846 If a project file is either specified or found by the tools, then the content
13847 of the source directory and object directory lines are added as if they
13848 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
13849 and @samp{^-aO^OBJECT_SEARCH^}.
13851 Output only unused symbols. This may be really useful if you give your
13852 main compilation unit on the command line, as @code{gnatxref} will then
13853 display every unused entity and 'with'ed package.
13857 Instead of producing the default output, @code{gnatxref} will generate a
13858 @file{tags} file that can be used by vi. For examples how to use this
13859 feature, see @xref{Examples of gnatxref Usage}. The tags file is output
13860 to the standard output, thus you will have to redirect it to a file.
13866 All these switches may be in any order on the command line, and may even
13867 appear after the file names. They need not be separated by spaces, thus
13868 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
13869 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
13871 @node gnatfind Switches
13872 @section @code{gnatfind} Switches
13875 The command line for @code{gnatfind} is:
13878 $ gnatfind [switches] pattern[:sourcefile[:line[:column]]]
13887 An entity will be output only if it matches the regular expression found
13888 in @samp{pattern}, see @xref{Regular Expressions in gnatfind and gnatxref}.
13890 Omitting the pattern is equivalent to specifying @samp{*}, which
13891 will match any entity. Note that if you do not provide a pattern, you
13892 have to provide both a sourcefile and a line.
13894 Entity names are given in Latin-1, with uppercase/lowercase equivalence
13895 for matching purposes. At the current time there is no support for
13896 8-bit codes other than Latin-1, or for wide characters in identifiers.
13899 @code{gnatfind} will look for references, bodies or declarations
13900 of symbols referenced in @file{sourcefile}, at line @samp{line}
13901 and column @samp{column}. See @pxref{Examples of gnatfind Usage}
13902 for syntax examples.
13905 is a decimal integer identifying the line number containing
13906 the reference to the entity (or entities) to be located.
13909 is a decimal integer identifying the exact location on the
13910 line of the first character of the identifier for the
13911 entity reference. Columns are numbered from 1.
13913 @item file1 file2 ...
13914 The search will be restricted to these source files. If none are given, then
13915 the search will be done for every library file in the search path.
13916 These file must appear only after the pattern or sourcefile.
13918 These file names are considered to be regular expressions, so for instance
13919 specifying 'source*.adb' is the same as giving every file in the current
13920 directory whose name starts with 'source' and whose extension is 'adb'.
13922 The location of the spec of the entity will always be displayed, even if it
13923 isn't in one of file1, file2,... The occurrences of the entity in the
13924 separate units of the ones given on the command line will also be displayed.
13926 Note that if you specify at least one file in this part, @code{gnatfind} may
13927 sometimes not be able to find the body of the subprograms...
13932 At least one of 'sourcefile' or 'pattern' has to be present on
13935 The following switches are available:
13939 @item ^-a^/ALL_FILES^
13940 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
13941 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
13942 the read-only files found in the library search path. Otherwise, these files
13943 will be ignored. This option can be used to protect Gnat sources or your own
13944 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
13945 much faster, and their output much smaller. Read-only here refers to access
13946 or permission status in the file system for the current user.
13949 @cindex @option{-aIDIR} (@command{gnatfind})
13950 When looking for source files also look in directory DIR. The order in which
13951 source file search is undertaken is the same as for @file{gnatmake}.
13954 @cindex @option{-aODIR} (@command{gnatfind})
13955 When searching for library and object files, look in directory
13956 DIR. The order in which library files are searched is the same as for
13960 @cindex @option{-nostdinc} (@command{gnatfind})
13961 Do not look for sources in the system default directory.
13964 @cindex @option{-nostdlib} (@command{gnatfind})
13965 Do not look for library files in the system default directory.
13967 @item --RTS=@var{rts-path}
13968 @cindex @option{--RTS} (@command{gnatfind})
13969 Specifies the default location of the runtime library. Same meaning as the
13970 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
13972 @item ^-d^/DERIVED_TYPE_INFORMATION^
13973 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
13974 If this switch is set, then @code{gnatfind} will output the parent type
13975 reference for each matching derived types.
13977 @item ^-e^/EXPRESSIONS^
13978 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
13979 By default, @code{gnatfind} accept the simple regular expression set for
13980 @samp{pattern}. If this switch is set, then the pattern will be
13981 considered as full Unix-style regular expression.
13983 @item ^-f^/FULL_PATHNAME^
13984 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
13985 If this switch is set, the output file names will be preceded by their
13986 directory (if the file was found in the search path). If this switch is
13987 not set, the directory will not be printed.
13989 @item ^-g^/IGNORE_LOCALS^
13990 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
13991 If this switch is set, information is output only for library-level
13992 entities, ignoring local entities. The use of this switch may accelerate
13993 @code{gnatfind} and @code{gnatxref}.
13996 @cindex @option{-IDIR} (@command{gnatfind})
13997 Equivalent to @samp{-aODIR -aIDIR}.
14000 @cindex @option{-pFILE} (@command{gnatfind})
14001 Specify a project file (@pxref{Project Files}) to use.
14002 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
14003 project file in the current directory.
14005 If a project file is either specified or found by the tools, then the content
14006 of the source directory and object directory lines are added as if they
14007 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
14008 @samp{^-aO^/OBJECT_SEARCH^}.
14010 @item ^-r^/REFERENCES^
14011 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
14012 By default, @code{gnatfind} will output only the information about the
14013 declaration, body or type completion of the entities. If this switch is
14014 set, the @code{gnatfind} will locate every reference to the entities in
14015 the files specified on the command line (or in every file in the search
14016 path if no file is given on the command line).
14018 @item ^-s^/PRINT_LINES^
14019 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
14020 If this switch is set, then @code{gnatfind} will output the content
14021 of the Ada source file lines were the entity was found.
14023 @item ^-t^/TYPE_HIERARCHY^
14024 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
14025 If this switch is set, then @code{gnatfind} will output the type hierarchy for
14026 the specified type. It act like -d option but recursively from parent
14027 type to parent type. When this switch is set it is not possible to
14028 specify more than one file.
14033 All these switches may be in any order on the command line, and may even
14034 appear after the file names. They need not be separated by spaces, thus
14035 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
14036 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
14038 As stated previously, gnatfind will search in every directory in the
14039 search path. You can force it to look only in the current directory if
14040 you specify @code{*} at the end of the command line.
14042 @node Project Files for gnatxref and gnatfind
14043 @section Project Files for @command{gnatxref} and @command{gnatfind}
14046 Project files allow a programmer to specify how to compile its
14047 application, where to find sources, etc. These files are used
14049 primarily by the Glide Ada mode, but they can also be used
14052 @code{gnatxref} and @code{gnatfind}.
14054 A project file name must end with @file{.gpr}. If a single one is
14055 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
14056 extract the information from it. If multiple project files are found, none of
14057 them is read, and you have to use the @samp{-p} switch to specify the one
14060 The following lines can be included, even though most of them have default
14061 values which can be used in most cases.
14062 The lines can be entered in any order in the file.
14063 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
14064 each line. If you have multiple instances, only the last one is taken into
14069 [default: @code{"^./^[]^"}]
14070 specifies a directory where to look for source files. Multiple @code{src_dir}
14071 lines can be specified and they will be searched in the order they
14075 [default: @code{"^./^[]^"}]
14076 specifies a directory where to look for object and library files. Multiple
14077 @code{obj_dir} lines can be specified, and they will be searched in the order
14080 @item comp_opt=SWITCHES
14081 [default: @code{""}]
14082 creates a variable which can be referred to subsequently by using
14083 the @code{$@{comp_opt@}} notation. This is intended to store the default
14084 switches given to @command{gnatmake} and @command{gcc}.
14086 @item bind_opt=SWITCHES
14087 [default: @code{""}]
14088 creates a variable which can be referred to subsequently by using
14089 the @samp{$@{bind_opt@}} notation. This is intended to store the default
14090 switches given to @command{gnatbind}.
14092 @item link_opt=SWITCHES
14093 [default: @code{""}]
14094 creates a variable which can be referred to subsequently by using
14095 the @samp{$@{link_opt@}} notation. This is intended to store the default
14096 switches given to @command{gnatlink}.
14098 @item main=EXECUTABLE
14099 [default: @code{""}]
14100 specifies the name of the executable for the application. This variable can
14101 be referred to in the following lines by using the @samp{$@{main@}} notation.
14104 @item comp_cmd=COMMAND
14105 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
14108 @item comp_cmd=COMMAND
14109 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
14111 specifies the command used to compile a single file in the application.
14114 @item make_cmd=COMMAND
14115 [default: @code{"GNAT MAKE $@{main@}
14116 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
14117 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
14118 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
14121 @item make_cmd=COMMAND
14122 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
14123 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
14124 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
14126 specifies the command used to recompile the whole application.
14128 @item run_cmd=COMMAND
14129 [default: @code{"$@{main@}"}]
14130 specifies the command used to run the application.
14132 @item debug_cmd=COMMAND
14133 [default: @code{"gdb $@{main@}"}]
14134 specifies the command used to debug the application
14139 @command{gnatxref} and @command{gnatfind} only take into account the
14140 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
14142 @node Regular Expressions in gnatfind and gnatxref
14143 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
14146 As specified in the section about @command{gnatfind}, the pattern can be a
14147 regular expression. Actually, there are to set of regular expressions
14148 which are recognized by the program :
14151 @item globbing patterns
14152 These are the most usual regular expression. They are the same that you
14153 generally used in a Unix shell command line, or in a DOS session.
14155 Here is a more formal grammar :
14162 term ::= elmt -- matches elmt
14163 term ::= elmt elmt -- concatenation (elmt then elmt)
14164 term ::= * -- any string of 0 or more characters
14165 term ::= ? -- matches any character
14166 term ::= [char @{char@}] -- matches any character listed
14167 term ::= [char - char] -- matches any character in range
14171 @item full regular expression
14172 The second set of regular expressions is much more powerful. This is the
14173 type of regular expressions recognized by utilities such a @file{grep}.
14175 The following is the form of a regular expression, expressed in Ada
14176 reference manual style BNF is as follows
14183 regexp ::= term @{| term@} -- alternation (term or term ...)
14185 term ::= item @{item@} -- concatenation (item then item)
14187 item ::= elmt -- match elmt
14188 item ::= elmt * -- zero or more elmt's
14189 item ::= elmt + -- one or more elmt's
14190 item ::= elmt ? -- matches elmt or nothing
14193 elmt ::= nschar -- matches given character
14194 elmt ::= [nschar @{nschar@}] -- matches any character listed
14195 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
14196 elmt ::= [char - char] -- matches chars in given range
14197 elmt ::= \ char -- matches given character
14198 elmt ::= . -- matches any single character
14199 elmt ::= ( regexp ) -- parens used for grouping
14201 char ::= any character, including special characters
14202 nschar ::= any character except ()[].*+?^^^
14206 Following are a few examples :
14210 will match any of the two strings 'abcde' and 'fghi'.
14213 will match any string like 'abd', 'abcd', 'abccd', 'abcccd', and so on
14216 will match any string which has only lowercase characters in it (and at
14217 least one character
14222 @node Examples of gnatxref Usage
14223 @section Examples of @code{gnatxref} Usage
14225 @subsection General Usage
14228 For the following examples, we will consider the following units :
14230 @smallexample @c ada
14236 3: procedure Foo (B : in Integer);
14243 1: package body Main is
14244 2: procedure Foo (B : in Integer) is
14255 2: procedure Print (B : Integer);
14264 The first thing to do is to recompile your application (for instance, in
14265 that case just by doing a @samp{gnatmake main}, so that GNAT generates
14266 the cross-referencing information.
14267 You can then issue any of the following commands:
14269 @item gnatxref main.adb
14270 @code{gnatxref} generates cross-reference information for main.adb
14271 and every unit 'with'ed by main.adb.
14273 The output would be:
14281 Decl: main.ads 3:20
14282 Body: main.adb 2:20
14283 Ref: main.adb 4:13 5:13 6:19
14286 Ref: main.adb 6:8 7:8
14296 Decl: main.ads 3:15
14297 Body: main.adb 2:15
14300 Body: main.adb 1:14
14303 Ref: main.adb 6:12 7:12
14307 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
14308 its body is in main.adb, line 1, column 14 and is not referenced any where.
14310 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
14311 it referenced in main.adb, line 6 column 12 and line 7 column 12.
14313 @item gnatxref package1.adb package2.ads
14314 @code{gnatxref} will generates cross-reference information for
14315 package1.adb, package2.ads and any other package 'with'ed by any
14321 @subsection Using gnatxref with vi
14323 @code{gnatxref} can generate a tags file output, which can be used
14324 directly from @file{vi}. Note that the standard version of @file{vi}
14325 will not work properly with overloaded symbols. Consider using another
14326 free implementation of @file{vi}, such as @file{vim}.
14329 $ gnatxref -v gnatfind.adb > tags
14333 will generate the tags file for @code{gnatfind} itself (if the sources
14334 are in the search path!).
14336 From @file{vi}, you can then use the command @samp{:tag @i{entity}}
14337 (replacing @i{entity} by whatever you are looking for), and vi will
14338 display a new file with the corresponding declaration of entity.
14341 @node Examples of gnatfind Usage
14342 @section Examples of @code{gnatfind} Usage
14346 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
14347 Find declarations for all entities xyz referenced at least once in
14348 main.adb. The references are search in every library file in the search
14351 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
14354 The output will look like:
14356 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
14357 ^directory/^[directory]^main.adb:24:10: xyz <= body
14358 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
14362 that is to say, one of the entities xyz found in main.adb is declared at
14363 line 12 of main.ads (and its body is in main.adb), and another one is
14364 declared at line 45 of foo.ads
14366 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
14367 This is the same command as the previous one, instead @code{gnatfind} will
14368 display the content of the Ada source file lines.
14370 The output will look like:
14373 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
14375 ^directory/^[directory]^main.adb:24:10: xyz <= body
14377 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
14382 This can make it easier to find exactly the location your are looking
14385 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
14386 Find references to all entities containing an x that are
14387 referenced on line 123 of main.ads.
14388 The references will be searched only in main.ads and foo.adb.
14390 @item gnatfind main.ads:123
14391 Find declarations and bodies for all entities that are referenced on
14392 line 123 of main.ads.
14394 This is the same as @code{gnatfind "*":main.adb:123}.
14396 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
14397 Find the declaration for the entity referenced at column 45 in
14398 line 123 of file main.adb in directory mydir. Note that it
14399 is usual to omit the identifier name when the column is given,
14400 since the column position identifies a unique reference.
14402 The column has to be the beginning of the identifier, and should not
14403 point to any character in the middle of the identifier.
14408 @c *********************************
14409 @node The GNAT Pretty-Printer gnatpp
14410 @chapter The GNAT Pretty-Printer @command{gnatpp}
14412 @cindex Pretty-Printer
14415 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
14416 for source reformatting / pretty-printing.
14417 It takes an Ada source file as input and generates a reformatted
14419 You can specify various style directives via switches; e.g.,
14420 identifier case conventions, rules of indentation, and comment layout.
14422 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
14423 tree for the input source and thus requires the input to be syntactically and
14424 semantically legal.
14425 If this condition is not met, @command{gnatpp} will terminate with an
14426 error message; no output file will be generated.
14428 If the compilation unit
14429 contained in the input source depends semantically upon units located
14430 outside the current directory, you have to provide the source search path
14431 when invoking @command{gnatpp}, if these units are contained in files with
14432 names that do not follow the GNAT file naming rules, you have to provide
14433 the configuration file describing the corresponding naming scheme;
14434 see the description of the @command{gnatpp}
14435 switches below. Another possibility is to use a project file and to
14436 call @command{gnatpp} through the @command{gnat} driver
14438 The @command{gnatpp} command has the form
14441 $ gnatpp [@var{switches}] @var{filename}
14448 @var{switches} is an optional sequence of switches defining such properties as
14449 the formatting rules, the source search path, and the destination for the
14453 @var{filename} is the name (including the extension) of the source file to
14454 reformat; ``wildcards'' or several file names on the same gnatpp command are
14455 allowed. The file name may contain path information; it does not have to
14456 follow the GNAT file naming rules
14461 * Switches for gnatpp::
14462 * Formatting Rules::
14465 @node Switches for gnatpp
14466 @section Switches for @command{gnatpp}
14469 The following subsections describe the various switches accepted by
14470 @command{gnatpp}, organized by category.
14473 You specify a switch by supplying a name and generally also a value.
14474 In many cases the values for a switch with a given name are incompatible with
14476 (for example the switch that controls the casing of a reserved word may have
14477 exactly one value: upper case, lower case, or
14478 mixed case) and thus exactly one such switch can be in effect for an
14479 invocation of @command{gnatpp}.
14480 If more than one is supplied, the last one is used.
14481 However, some values for the same switch are mutually compatible.
14482 You may supply several such switches to @command{gnatpp}, but then
14483 each must be specified in full, with both the name and the value.
14484 Abbreviated forms (the name appearing once, followed by each value) are
14486 For example, to set
14487 the alignment of the assignment delimiter both in declarations and in
14488 assignment statements, you must write @option{-A2A3}
14489 (or @option{-A2 -A3}), but not @option{-A23}.
14493 In many cases the set of options for a given qualifier are incompatible with
14494 each other (for example the qualifier that controls the casing of a reserved
14495 word may have exactly one option, which specifies either upper case, lower
14496 case, or mixed case), and thus exactly one such option can be in effect for
14497 an invocation of @command{gnatpp}.
14498 If more than one is supplied, the last one is used.
14499 However, some qualifiers have options that are mutually compatible,
14500 and then you may then supply several such options when invoking
14504 In most cases, it is obvious whether or not the
14505 ^values for a switch with a given name^options for a given qualifier^
14506 are compatible with each other.
14507 When the semantics might not be evident, the summaries below explicitly
14508 indicate the effect.
14511 * Alignment Control::
14513 * Construct Layout Control::
14514 * General Text Layout Control::
14515 * Other Formatting Options::
14516 * Setting the Source Search Path::
14517 * Output File Control::
14518 * Other gnatpp Switches::
14522 @node Alignment Control
14523 @subsection Alignment Control
14524 @cindex Alignment control in @command{gnatpp}
14527 Programs can be easier to read if certain constructs are vertically aligned.
14528 By default all alignments are set ON.
14529 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
14530 OFF, and then use one or more of the other
14531 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
14532 to activate alignment for specific constructs.
14535 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
14539 Set all alignments to ON
14542 @item ^-A0^/ALIGN=OFF^
14543 Set all alignments to OFF
14545 @item ^-A1^/ALIGN=COLONS^
14546 Align @code{:} in declarations
14548 @item ^-A2^/ALIGN=DECLARATIONS^
14549 Align @code{:=} in initializations in declarations
14551 @item ^-A3^/ALIGN=STATEMENTS^
14552 Align @code{:=} in assignment statements
14554 @item ^-A4^/ALIGN=ARROWS^
14555 Align @code{=>} in associations
14559 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
14563 @node Casing Control
14564 @subsection Casing Control
14565 @cindex Casing control in @command{gnatpp}
14568 @command{gnatpp} allows you to specify the casing for reserved words,
14569 pragma names, attribute designators and identifiers.
14570 For identifiers you may define a
14571 general rule for name casing but also override this rule
14572 via a set of dictionary files.
14574 Three types of casing are supported: lower case, upper case, and mixed case.
14575 Lower and upper case are self-explanatory (but since some letters in
14576 Latin1 and other GNAT-supported character sets
14577 exist only in lower-case form, an upper case conversion will have no
14579 ``Mixed case'' means that the first letter, and also each letter immediately
14580 following an underscore, are converted to their uppercase forms;
14581 all the other letters are converted to their lowercase forms.
14584 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
14585 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
14586 Attribute designators are lower case
14588 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
14589 Attribute designators are upper case
14591 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
14592 Attribute designators are mixed case (this is the default)
14594 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
14595 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
14596 Keywords (technically, these are known in Ada as @emph{reserved words}) are
14597 lower case (this is the default)
14599 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
14600 Keywords are upper case
14602 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
14603 @item ^-nD^/NAME_CASING=AS_DECLARED^
14604 Name casing for defining occurrences are as they appear in the source file
14605 (this is the default)
14607 @item ^-nU^/NAME_CASING=UPPER_CASE^
14608 Names are in upper case
14610 @item ^-nL^/NAME_CASING=LOWER_CASE^
14611 Names are in lower case
14613 @item ^-nM^/NAME_CASING=MIXED_CASE^
14614 Names are in mixed case
14616 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
14617 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
14618 Pragma names are lower case
14620 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
14621 Pragma names are upper case
14623 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
14624 Pragma names are mixed case (this is the default)
14626 @item ^-D@var{file}^/DICTIONARY=@var{file}^
14627 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
14628 Use @var{file} as a @emph{dictionary file} that defines
14629 the casing for a set of specified names,
14630 thereby overriding the effect on these names by
14631 any explicit or implicit
14632 ^-n^/NAME_CASING^ switch.
14633 To supply more than one dictionary file,
14634 use ^several @option{-D} switches^a list of files as options^.
14637 @option{gnatpp} implicitly uses a @emph{default dictionary file}
14638 to define the casing for the Ada predefined names and
14639 the names declared in the GNAT libraries.
14641 @item ^-D-^/SPECIFIC_CASING^
14642 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
14643 Do not use the default dictionary file;
14644 instead, use the casing
14645 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
14650 The structure of a dictionary file, and details on the conventions
14651 used in the default dictionary file, are defined in @ref{Name Casing}.
14653 The @option{^-D-^/SPECIFIC_CASING^} and
14654 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
14658 @node Construct Layout Control
14659 @subsection Construct Layout Control
14660 @cindex Layout control in @command{gnatpp}
14663 This group of @command{gnatpp} switches controls the layout of comments and
14664 complex syntactic constructs. See @ref{Formatting Comments}, for details
14668 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
14669 @item ^-c0^/COMMENTS_LAYOUT=UNTOUCHED^
14670 All the comments remain unchanged
14672 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
14673 GNAT-style comment line indentation (this is the default).
14675 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
14676 Reference-manual comment line indentation.
14678 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
14679 GNAT-style comment beginning
14681 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
14682 Reformat comment blocks
14684 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
14685 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
14686 GNAT-style layout (this is the default)
14688 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
14691 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
14694 @item ^-notab^/NOTABS^
14695 All the VT characters are removed from the comment text. All the HT characters
14696 are expanded with the sequences of space characters to get to the next tab
14703 The @option{-c1} and @option{-c2} switches are incompatible.
14704 The @option{-c3} and @option{-c4} switches are compatible with each other and
14705 also with @option{-c1} and @option{-c2}. The @option{-c0} switch disables all
14706 the other comment formatting switches.
14708 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
14713 For the @option{/COMMENTS_LAYOUT} qualifier:
14716 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
14718 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
14719 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
14723 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
14724 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
14727 @node General Text Layout Control
14728 @subsection General Text Layout Control
14731 These switches allow control over line length and indentation.
14734 @item ^-M@i{nnn}^/LINE_LENGTH_MAX=@i{nnn}^
14735 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
14736 Maximum line length, @i{nnn} from 32 ..256, the default value is 79
14738 @item ^-i@i{nnn}^/INDENTATION_LEVEL=@i{nnn}^
14739 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
14740 Indentation level, @i{nnn} from 1 .. 9, the default value is 3
14742 @item ^-cl@i{nnn}^/CONTINUATION_INDENT=@i{nnn}^
14743 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
14744 Indentation level for continuation lines (relative to the line being
14745 continued), @i{nnn} from 1 .. 9.
14747 value is one less then the (normal) indentation level, unless the
14748 indentation is set to 1 (in which case the default value for continuation
14749 line indentation is also 1)
14753 @node Other Formatting Options
14754 @subsection Other Formatting Options
14757 These switches control the inclusion of missing end/exit labels, and
14758 the indentation level in @b{case} statements.
14761 @item ^-e^/NO_MISSED_LABELS^
14762 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
14763 Do not insert missing end/exit labels. An end label is the name of
14764 a construct that may optionally be repeated at the end of the
14765 construct's declaration;
14766 e.g., the names of packages, subprograms, and tasks.
14767 An exit label is the name of a loop that may appear as target
14768 of an exit statement within the loop.
14769 By default, @command{gnatpp} inserts these end/exit labels when
14770 they are absent from the original source. This option suppresses such
14771 insertion, so that the formatted source reflects the original.
14773 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
14774 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
14775 Insert a Form Feed character after a pragma Page.
14777 @item ^-T@i{nnn}^/MAX_INDENT=@i{nnn}^
14778 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
14779 Do not use an additional indentation level for @b{case} alternatives
14780 and variants if there are @i{nnn} or more (the default
14782 If @i{nnn} is 0, an additional indentation level is
14783 used for @b{case} alternatives and variants regardless of their number.
14786 @node Setting the Source Search Path
14787 @subsection Setting the Source Search Path
14790 To define the search path for the input source file, @command{gnatpp}
14791 uses the same switches as the GNAT compiler, with the same effects.
14794 @item ^-I^/SEARCH=^@var{dir}
14795 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
14796 The same as the corresponding gcc switch
14798 @item ^-I-^/NOCURRENT_DIRECTORY^
14799 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
14800 The same as the corresponding gcc switch
14802 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
14803 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
14804 The same as the corresponding gcc switch
14806 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
14807 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
14808 The same as the corresponding gcc switch
14813 @node Output File Control
14814 @subsection Output File Control
14817 By default the output is sent to the file whose name is obtained by appending
14818 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
14819 (if the file with this name already exists, it is unconditionally overwritten).
14820 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
14821 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
14823 The output may be redirected by the following switches:
14826 @item ^-pipe^/STANDARD_OUTPUT^
14827 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
14828 Send the output to @code{Standard_Output}
14830 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
14831 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
14832 Write the output into @var{output_file}.
14833 If @var{output_file} already exists, @command{gnatpp} terminates without
14834 reading or processing the input file.
14836 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
14837 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
14838 Write the output into @var{output_file}, overwriting the existing file
14839 (if one is present).
14841 @item ^-r^/REPLACE^
14842 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
14843 Replace the input source file with the reformatted output, and copy the
14844 original input source into the file whose name is obtained by appending the
14845 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
14846 If a file with this name already exists, @command{gnatpp} terminates without
14847 reading or processing the input file.
14849 @item ^-rf^/OVERRIDING_REPLACE^
14850 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
14851 Like @option{^-r^/REPLACE^} except that if the file with the specified name
14852 already exists, it is overwritten.
14854 @item ^-rnb^/NO_BACKUP^
14855 @cindex @option{^-rnb^/NO_BACKUP^} (@code{gnatpp})
14856 Replace the input source file with the reformatted output without
14857 creating any backup copy of the input source.
14861 Options @option{^-pipe^/STANDARD_OUTPUT^},
14862 @option{^-o^/OUTPUT^} and
14863 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
14864 contains only one file to reformat
14866 @node Other gnatpp Switches
14867 @subsection Other @code{gnatpp} Switches
14870 The additional @command{gnatpp} switches are defined in this subsection.
14873 @item ^-files @var{filename}^/FILES=@var{output_file}^
14874 @cindex @option{^-files^/FILES^} (@code{gnatpp})
14875 Take the argument source files from the specified file. This file should be an
14876 ordinary textual file containing file names separated by spaces or
14877 line breaks. You can use this switch more then once in the same call to
14878 @command{gnatpp}. You also can combine this switch with explicit list of
14881 @item ^-v^/VERBOSE^
14882 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
14884 @command{gnatpp} generates version information and then
14885 a trace of the actions it takes to produce or obtain the ASIS tree.
14887 @item ^-w^/WARNINGS^
14888 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
14890 @command{gnatpp} generates a warning whenever it can not provide
14891 a required layout in the result source.
14895 @node Formatting Rules
14896 @section Formatting Rules
14899 The following subsections show how @command{gnatpp} treats ``white space'',
14900 comments, program layout, and name casing.
14901 They provide the detailed descriptions of the switches shown above.
14904 * White Space and Empty Lines::
14905 * Formatting Comments::
14906 * Construct Layout::
14911 @node White Space and Empty Lines
14912 @subsection White Space and Empty Lines
14915 @command{gnatpp} does not have an option to control space characters.
14916 It will add or remove spaces according to the style illustrated by the
14917 examples in the @cite{Ada Reference Manual}.
14919 The only format effectors
14920 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
14921 that will appear in the output file are platform-specific line breaks,
14922 and also format effectors within (but not at the end of) comments.
14923 In particular, each horizontal tab character that is not inside
14924 a comment will be treated as a space and thus will appear in the
14925 output file as zero or more spaces depending on
14926 the reformatting of the line in which it appears.
14927 The only exception is a Form Feed character, which is inserted after a
14928 pragma @code{Page} when @option{-ff} is set.
14930 The output file will contain no lines with trailing ``white space'' (spaces,
14933 Empty lines in the original source are preserved
14934 only if they separate declarations or statements.
14935 In such contexts, a
14936 sequence of two or more empty lines is replaced by exactly one empty line.
14937 Note that a blank line will be removed if it separates two ``comment blocks''
14938 (a comment block is a sequence of whole-line comments).
14939 In order to preserve a visual separation between comment blocks, use an
14940 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
14941 Likewise, if for some reason you wish to have a sequence of empty lines,
14942 use a sequence of empty comments instead.
14945 @node Formatting Comments
14946 @subsection Formatting Comments
14949 Comments in Ada code are of two kinds:
14952 a @emph{whole-line comment}, which appears by itself (possibly preceded by
14953 ``white space'') on a line
14956 an @emph{end-of-line comment}, which follows some other Ada lexical element
14961 The indentation of a whole-line comment is that of either
14962 the preceding or following line in
14963 the formatted source, depending on switch settings as will be described below.
14965 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
14966 between the end of the preceding Ada lexical element and the beginning
14967 of the comment as appear in the original source,
14968 unless either the comment has to be split to
14969 satisfy the line length limitation, or else the next line contains a
14970 whole line comment that is considered a continuation of this end-of-line
14971 comment (because it starts at the same position).
14973 cases, the start of the end-of-line comment is moved right to the nearest
14974 multiple of the indentation level.
14975 This may result in a ``line overflow'' (the right-shifted comment extending
14976 beyond the maximum line length), in which case the comment is split as
14979 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
14980 (GNAT-style comment line indentation)
14981 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
14982 (reference-manual comment line indentation).
14983 With reference-manual style, a whole-line comment is indented as if it
14984 were a declaration or statement at the same place
14985 (i.e., according to the indentation of the preceding line(s)).
14986 With GNAT style, a whole-line comment that is immediately followed by an
14987 @b{if} or @b{case} statement alternative, a record variant, or the reserved
14988 word @b{begin}, is indented based on the construct that follows it.
14991 @smallexample @c ada
15003 Reference-manual indentation produces:
15005 @smallexample @c ada
15017 while GNAT-style indentation produces:
15019 @smallexample @c ada
15031 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
15032 (GNAT style comment beginning) has the following
15037 For each whole-line comment that does not end with two hyphens,
15038 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
15039 to ensure that there are at least two spaces between these hyphens and the
15040 first non-blank character of the comment.
15044 For an end-of-line comment, if in the original source the next line is a
15045 whole-line comment that starts at the same position
15046 as the end-of-line comment,
15047 then the whole-line comment (and all whole-line comments
15048 that follow it and that start at the same position)
15049 will start at this position in the output file.
15052 That is, if in the original source we have:
15054 @smallexample @c ada
15057 A := B + C; -- B must be in the range Low1..High1
15058 -- C must be in the range Low2..High2
15059 --B+C will be in the range Low1+Low2..High1+High2
15065 Then in the formatted source we get
15067 @smallexample @c ada
15070 A := B + C; -- B must be in the range Low1..High1
15071 -- C must be in the range Low2..High2
15072 -- B+C will be in the range Low1+Low2..High1+High2
15078 A comment that exceeds the line length limit will be split.
15080 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
15081 the line belongs to a reformattable block, splitting the line generates a
15082 @command{gnatpp} warning.
15083 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
15084 comments may be reformatted in typical
15085 word processor style (that is, moving words between lines and putting as
15086 many words in a line as possible).
15089 @node Construct Layout
15090 @subsection Construct Layout
15093 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
15094 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
15095 layout on the one hand, and uncompact layout
15096 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
15097 can be illustrated by the following examples:
15101 @multitable @columnfractions .5 .5
15102 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
15105 @smallexample @c ada
15112 @smallexample @c ada
15121 @smallexample @c ada
15129 @smallexample @c ada
15139 @smallexample @c ada
15140 Clear : for J in 1 .. 10 loop
15145 @smallexample @c ada
15147 for J in 1 .. 10 loop
15158 GNAT style, compact layout Uncompact layout
15160 type q is record type q is
15161 a : integer; record
15162 b : integer; a : integer;
15163 end record; b : integer;
15167 Block : declare Block :
15168 A : Integer := 3; declare
15169 begin A : Integer := 3;
15171 end Block; Proc (A, A);
15174 Clear : for J in 1 .. 10 loop Clear :
15175 A (J) := 0; for J in 1 .. 10 loop
15176 end loop Clear; A (J) := 0;
15183 A further difference between GNAT style layout and compact layout is that
15184 GNAT style layout inserts empty lines as separation for
15185 compound statements, return statements and bodies.
15189 @subsection Name Casing
15192 @command{gnatpp} always converts the usage occurrence of a (simple) name to
15193 the same casing as the corresponding defining identifier.
15195 You control the casing for defining occurrences via the
15196 @option{^-n^/NAME_CASING^} switch.
15198 With @option{-nD} (``as declared'', which is the default),
15201 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
15203 defining occurrences appear exactly as in the source file
15204 where they are declared.
15205 The other ^values for this switch^options for this qualifier^ ---
15206 @option{^-nU^UPPER_CASE^},
15207 @option{^-nL^LOWER_CASE^},
15208 @option{^-nM^MIXED_CASE^} ---
15210 ^upper, lower, or mixed case, respectively^the corresponding casing^.
15211 If @command{gnatpp} changes the casing of a defining
15212 occurrence, it analogously changes the casing of all the
15213 usage occurrences of this name.
15215 If the defining occurrence of a name is not in the source compilation unit
15216 currently being processed by @command{gnatpp}, the casing of each reference to
15217 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
15218 switch (subject to the dictionary file mechanism described below).
15219 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
15221 casing for the defining occurrence of the name.
15223 Some names may need to be spelled with casing conventions that are not
15224 covered by the upper-, lower-, and mixed-case transformations.
15225 You can arrange correct casing by placing such names in a
15226 @emph{dictionary file},
15227 and then supplying a @option{^-D^/DICTIONARY^} switch.
15228 The casing of names from dictionary files overrides
15229 any @option{^-n^/NAME_CASING^} switch.
15231 To handle the casing of Ada predefined names and the names from GNAT libraries,
15232 @command{gnatpp} assumes a default dictionary file.
15233 The name of each predefined entity is spelled with the same casing as is used
15234 for the entity in the @cite{Ada Reference Manual}.
15235 The name of each entity in the GNAT libraries is spelled with the same casing
15236 as is used in the declaration of that entity.
15238 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
15239 default dictionary file.
15240 Instead, the casing for predefined and GNAT-defined names will be established
15241 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
15242 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
15243 will appear as just shown,
15244 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
15245 To ensure that even such names are rendered in uppercase,
15246 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
15247 (or else, less conveniently, place these names in upper case in a dictionary
15250 A dictionary file is
15251 a plain text file; each line in this file can be either a blank line
15252 (containing only space characters and ASCII.HT characters), an Ada comment
15253 line, or the specification of exactly one @emph{casing schema}.
15255 A casing schema is a string that has the following syntax:
15259 @var{casing_schema} ::= @var{identifier} | [*]@var{simple_identifier}[*]
15261 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
15266 (The @code{[]} metanotation stands for an optional part;
15267 see @cite{Ada Reference Manual}, Section 2.3) for the definition of the
15268 @var{identifier} lexical element and the @var{letter_or_digit} category).
15270 The casing schema string can be followed by white space and/or an Ada-style
15271 comment; any amount of white space is allowed before the string.
15273 If a dictionary file is passed as
15275 the value of a @option{-D@var{file}} switch
15278 an option to the @option{/DICTIONARY} qualifier
15281 simple name and every identifier, @command{gnatpp} checks if the dictionary
15282 defines the casing for the name or for some of its parts (the term ``subword''
15283 is used below to denote the part of a name which is delimited by ``_'' or by
15284 the beginning or end of the word and which does not contain any ``_'' inside):
15288 if the whole name is in the dictionary, @command{gnatpp} uses for this name
15289 the casing defined by the dictionary; no subwords are checked for this word
15292 for the first subword (that is, for the subword preceding the leftmost
15293 ``_''), @command{gnatpp} checks if the dictionary contains the corresponding
15294 string of the form @code{@var{simple_identifier}*}, and if it does, the
15295 casing of this @var{simple_identifier} is used for this subword
15298 for the last subword (following the rightmost ``_'') @command{gnatpp}
15299 checks if the dictionary contains the corresponding string of the form
15300 @code{*@var{simple_identifier}}, and if it does, the casing of this
15301 @var{simple_identifier} is used for this subword
15304 for every intermediate subword (surrounded by two'_') @command{gnatpp} checks
15305 if the dictionary contains the corresponding string of the form
15306 @code{*@var{simple_identifier}*}, and if it does, the casing of this
15307 simple_identifier is used for this subword
15310 if more than one dictionary file is passed as @command{gnatpp} switches, each
15311 dictionary adds new casing exceptions and overrides all the existing casing
15312 exceptions set by the previous dictionaries
15315 when @command{gnatpp} checks if the word or subword is in the dictionary,
15316 this check is not case sensitive
15320 For example, suppose we have the following source to reformat:
15322 @smallexample @c ada
15325 name1 : integer := 1;
15326 name4_name3_name2 : integer := 2;
15327 name2_name3_name4 : Boolean;
15330 name2_name3_name4 := name4_name3_name2 > name1;
15336 And suppose we have two dictionaries:
15353 If @command{gnatpp} is called with the following switches:
15357 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
15360 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
15365 then we will get the following name casing in the @command{gnatpp} output:
15367 @smallexample @c ada
15370 NAME1 : Integer := 1;
15371 Name4_NAME3_NAME2 : integer := 2;
15372 Name2_NAME3_Name4 : Boolean;
15375 Name2_NAME3_Name4 := Name4_NAME3_NAME2 > NAME1;
15382 @c ***********************************
15383 @node File Name Krunching Using gnatkr
15384 @chapter File Name Krunching Using @code{gnatkr}
15388 This chapter discusses the method used by the compiler to shorten
15389 the default file names chosen for Ada units so that they do not
15390 exceed the maximum length permitted. It also describes the
15391 @code{gnatkr} utility that can be used to determine the result of
15392 applying this shortening.
15396 * Krunching Method::
15397 * Examples of gnatkr Usage::
15401 @section About @code{gnatkr}
15404 The default file naming rule in GNAT
15405 is that the file name must be derived from
15406 the unit name. The exact default rule is as follows:
15409 Take the unit name and replace all dots by hyphens.
15411 If such a replacement occurs in the
15412 second character position of a name, and the first character is
15413 ^a, g, s, or i^A, G, S, or I^ then replace the dot by the character
15414 ^~ (tilde)^$ (dollar sign)^
15415 instead of a minus.
15417 The reason for this exception is to avoid clashes
15418 with the standard names for children of System, Ada, Interfaces,
15419 and GNAT, which use the prefixes ^s- a- i- and g-^S- A- I- and G-^
15422 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
15423 switch of the compiler activates a ``krunching''
15424 circuit that limits file names to nn characters (where nn is a decimal
15425 integer). For example, using OpenVMS,
15426 where the maximum file name length is
15427 39, the value of nn is usually set to 39, but if you want to generate
15428 a set of files that would be usable if ported to a system with some
15429 different maximum file length, then a different value can be specified.
15430 The default value of 39 for OpenVMS need not be specified.
15432 The @code{gnatkr} utility can be used to determine the krunched name for
15433 a given file, when krunched to a specified maximum length.
15436 @section Using @code{gnatkr}
15439 The @code{gnatkr} command has the form
15443 $ gnatkr @var{name} [@var{length}]
15449 $ gnatkr @var{name} /COUNT=nn
15454 @var{name} is the uncrunched file name, derived from the name of the unit
15455 in the standard manner described in the previous section (i.e. in particular
15456 all dots are replaced by hyphens). The file name may or may not have an
15457 extension (defined as a suffix of the form period followed by arbitrary
15458 characters other than period). If an extension is present then it will
15459 be preserved in the output. For example, when krunching @file{hellofile.ads}
15460 to eight characters, the result will be hellofil.ads.
15462 Note: for compatibility with previous versions of @code{gnatkr} dots may
15463 appear in the name instead of hyphens, but the last dot will always be
15464 taken as the start of an extension. So if @code{gnatkr} is given an argument
15465 such as @file{Hello.World.adb} it will be treated exactly as if the first
15466 period had been a hyphen, and for example krunching to eight characters
15467 gives the result @file{hellworl.adb}.
15469 Note that the result is always all lower case (except on OpenVMS where it is
15470 all upper case). Characters of the other case are folded as required.
15472 @var{length} represents the length of the krunched name. The default
15473 when no argument is given is ^8^39^ characters. A length of zero stands for
15474 unlimited, in other words do not chop except for system files where the
15475 impled crunching length is always eight characters.
15478 The output is the krunched name. The output has an extension only if the
15479 original argument was a file name with an extension.
15481 @node Krunching Method
15482 @section Krunching Method
15485 The initial file name is determined by the name of the unit that the file
15486 contains. The name is formed by taking the full expanded name of the
15487 unit and replacing the separating dots with hyphens and
15488 using ^lowercase^uppercase^
15489 for all letters, except that a hyphen in the second character position is
15490 replaced by a ^tilde^dollar sign^ if the first character is
15491 ^a, i, g, or s^A, I, G, or S^.
15492 The extension is @code{.ads} for a
15493 specification and @code{.adb} for a body.
15494 Krunching does not affect the extension, but the file name is shortened to
15495 the specified length by following these rules:
15499 The name is divided into segments separated by hyphens, tildes or
15500 underscores and all hyphens, tildes, and underscores are
15501 eliminated. If this leaves the name short enough, we are done.
15504 If the name is too long, the longest segment is located (left-most
15505 if there are two of equal length), and shortened by dropping
15506 its last character. This is repeated until the name is short enough.
15508 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
15509 to fit the name into 8 characters as required by some operating systems.
15512 our-strings-wide_fixed 22
15513 our strings wide fixed 19
15514 our string wide fixed 18
15515 our strin wide fixed 17
15516 our stri wide fixed 16
15517 our stri wide fixe 15
15518 our str wide fixe 14
15519 our str wid fixe 13
15525 Final file name: oustwifi.adb
15529 The file names for all predefined units are always krunched to eight
15530 characters. The krunching of these predefined units uses the following
15531 special prefix replacements:
15535 replaced by @file{^a^A^-}
15538 replaced by @file{^g^G^-}
15541 replaced by @file{^i^I^-}
15544 replaced by @file{^s^S^-}
15547 These system files have a hyphen in the second character position. That
15548 is why normal user files replace such a character with a
15549 ^tilde^dollar sign^, to
15550 avoid confusion with system file names.
15552 As an example of this special rule, consider
15553 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
15556 ada-strings-wide_fixed 22
15557 a- strings wide fixed 18
15558 a- string wide fixed 17
15559 a- strin wide fixed 16
15560 a- stri wide fixed 15
15561 a- stri wide fixe 14
15562 a- str wide fixe 13
15568 Final file name: a-stwifi.adb
15572 Of course no file shortening algorithm can guarantee uniqueness over all
15573 possible unit names, and if file name krunching is used then it is your
15574 responsibility to ensure that no name clashes occur. The utility
15575 program @code{gnatkr} is supplied for conveniently determining the
15576 krunched name of a file.
15578 @node Examples of gnatkr Usage
15579 @section Examples of @code{gnatkr} Usage
15586 $ gnatkr very_long_unit_name.ads --> velounna.ads
15587 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
15588 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
15589 $ gnatkr grandparent-parent-child --> grparchi
15591 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
15592 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
15595 @node Preprocessing Using gnatprep
15596 @chapter Preprocessing Using @code{gnatprep}
15600 The @code{gnatprep} utility provides
15601 a simple preprocessing capability for Ada programs.
15602 It is designed for use with GNAT, but is not dependent on any special
15607 * Switches for gnatprep::
15608 * Form of Definitions File::
15609 * Form of Input Text for gnatprep::
15612 @node Using gnatprep
15613 @section Using @code{gnatprep}
15616 To call @code{gnatprep} use
15619 $ gnatprep [-bcrsu] [-Dsymbol=value] infile outfile [deffile]
15626 is the full name of the input file, which is an Ada source
15627 file containing preprocessor directives.
15630 is the full name of the output file, which is an Ada source
15631 in standard Ada form. When used with GNAT, this file name will
15632 normally have an ads or adb suffix.
15635 is the full name of a text file containing definitions of
15636 symbols to be referenced by the preprocessor. This argument is
15637 optional, and can be replaced by the use of the @option{-D} switch.
15640 is an optional sequence of switches as described in the next section.
15643 @node Switches for gnatprep
15644 @section Switches for @code{gnatprep}
15649 @item ^-b^/BLANK_LINES^
15650 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
15651 Causes both preprocessor lines and the lines deleted by
15652 preprocessing to be replaced by blank lines in the output source file,
15653 preserving line numbers in the output file.
15655 @item ^-c^/COMMENTS^
15656 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
15657 Causes both preprocessor lines and the lines deleted
15658 by preprocessing to be retained in the output source as comments marked
15659 with the special string @code{"--! "}. This option will result in line numbers
15660 being preserved in the output file.
15662 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
15663 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
15664 Defines a new symbol, associated with value. If no value is given on the
15665 command line, then symbol is considered to be @code{True}. This switch
15666 can be used in place of a definition file.
15670 @cindex @option{/REMOVE} (@command{gnatprep})
15671 This is the default setting which causes lines deleted by preprocessing
15672 to be entirely removed from the output file.
15675 @item ^-r^/REFERENCE^
15676 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
15677 Causes a @code{Source_Reference} pragma to be generated that
15678 references the original input file, so that error messages will use
15679 the file name of this original file. The use of this switch implies
15680 that preprocessor lines are not to be removed from the file, so its
15681 use will force @option{^-b^/BLANK_LINES^} mode if
15682 @option{^-c^/COMMENTS^}
15683 has not been specified explicitly.
15685 Note that if the file to be preprocessed contains multiple units, then
15686 it will be necessary to @code{gnatchop} the output file from
15687 @code{gnatprep}. If a @code{Source_Reference} pragma is present
15688 in the preprocessed file, it will be respected by
15689 @code{gnatchop ^-r^/REFERENCE^}
15690 so that the final chopped files will correctly refer to the original
15691 input source file for @code{gnatprep}.
15693 @item ^-s^/SYMBOLS^
15694 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
15695 Causes a sorted list of symbol names and values to be
15696 listed on the standard output file.
15698 @item ^-u^/UNDEFINED^
15699 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
15700 Causes undefined symbols to be treated as having the value FALSE in the context
15701 of a preprocessor test. In the absence of this option, an undefined symbol in
15702 a @code{#if} or @code{#elsif} test will be treated as an error.
15708 Note: if neither @option{-b} nor @option{-c} is present,
15709 then preprocessor lines and
15710 deleted lines are completely removed from the output, unless -r is
15711 specified, in which case -b is assumed.
15714 @node Form of Definitions File
15715 @section Form of Definitions File
15718 The definitions file contains lines of the form
15725 where symbol is an identifier, following normal Ada (case-insensitive)
15726 rules for its syntax, and value is one of the following:
15730 Empty, corresponding to a null substitution
15732 A string literal using normal Ada syntax
15734 Any sequence of characters from the set
15735 (letters, digits, period, underline).
15739 Comment lines may also appear in the definitions file, starting with
15740 the usual @code{--},
15741 and comments may be added to the definitions lines.
15743 @node Form of Input Text for gnatprep
15744 @section Form of Input Text for @code{gnatprep}
15747 The input text may contain preprocessor conditional inclusion lines,
15748 as well as general symbol substitution sequences.
15750 The preprocessor conditional inclusion commands have the form
15755 #if @i{expression} [then]
15757 #elsif @i{expression} [then]
15759 #elsif @i{expression} [then]
15770 In this example, @i{expression} is defined by the following grammar:
15772 @i{expression} ::= <symbol>
15773 @i{expression} ::= <symbol> = "<value>"
15774 @i{expression} ::= <symbol> = <symbol>
15775 @i{expression} ::= <symbol> 'Defined
15776 @i{expression} ::= not @i{expression}
15777 @i{expression} ::= @i{expression} and @i{expression}
15778 @i{expression} ::= @i{expression} or @i{expression}
15779 @i{expression} ::= @i{expression} and then @i{expression}
15780 @i{expression} ::= @i{expression} or else @i{expression}
15781 @i{expression} ::= ( @i{expression} )
15785 For the first test (@i{expression} ::= <symbol>) the symbol must have
15786 either the value true or false, that is to say the right-hand of the
15787 symbol definition must be one of the (case-insensitive) literals
15788 @code{True} or @code{False}. If the value is true, then the
15789 corresponding lines are included, and if the value is false, they are
15792 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
15793 the symbol has been defined in the definition file or by a @option{-D}
15794 switch on the command line. Otherwise, the test is false.
15796 The equality tests are case insensitive, as are all the preprocessor lines.
15798 If the symbol referenced is not defined in the symbol definitions file,
15799 then the effect depends on whether or not switch @option{-u}
15800 is specified. If so, then the symbol is treated as if it had the value
15801 false and the test fails. If this switch is not specified, then
15802 it is an error to reference an undefined symbol. It is also an error to
15803 reference a symbol that is defined with a value other than @code{True}
15806 The use of the @code{not} operator inverts the sense of this logical test, so
15807 that the lines are included only if the symbol is not defined.
15808 The @code{then} keyword is optional as shown
15810 The @code{#} must be the first non-blank character on a line, but
15811 otherwise the format is free form. Spaces or tabs may appear between
15812 the @code{#} and the keyword. The keywords and the symbols are case
15813 insensitive as in normal Ada code. Comments may be used on a
15814 preprocessor line, but other than that, no other tokens may appear on a
15815 preprocessor line. Any number of @code{elsif} clauses can be present,
15816 including none at all. The @code{else} is optional, as in Ada.
15818 The @code{#} marking the start of a preprocessor line must be the first
15819 non-blank character on the line, i.e. it must be preceded only by
15820 spaces or horizontal tabs.
15822 Symbol substitution outside of preprocessor lines is obtained by using
15830 anywhere within a source line, except in a comment or within a
15831 string literal. The identifier
15832 following the @code{$} must match one of the symbols defined in the symbol
15833 definition file, and the result is to substitute the value of the
15834 symbol in place of @code{$symbol} in the output file.
15836 Note that although the substitution of strings within a string literal
15837 is not possible, it is possible to have a symbol whose defined value is
15838 a string literal. So instead of setting XYZ to @code{hello} and writing:
15841 Header : String := "$XYZ";
15845 you should set XYZ to @code{"hello"} and write:
15848 Header : String := $XYZ;
15852 and then the substitution will occur as desired.
15855 @node The GNAT Run-Time Library Builder gnatlbr
15856 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
15858 @cindex Library builder
15861 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
15862 supplied configuration pragmas.
15865 * Running gnatlbr::
15866 * Switches for gnatlbr::
15867 * Examples of gnatlbr Usage::
15870 @node Running gnatlbr
15871 @section Running @code{gnatlbr}
15874 The @code{gnatlbr} command has the form
15877 $ GNAT LIBRARY /[CREATE | SET | DELETE]=directory [/CONFIG=file]
15880 @node Switches for gnatlbr
15881 @section Switches for @code{gnatlbr}
15884 @code{gnatlbr} recognizes the following switches:
15888 @item /CREATE=directory
15889 @cindex @code{/CREATE} (@code{gnatlbr})
15890 Create the new run-time library in the specified directory.
15892 @item /SET=directory
15893 @cindex @code{/SET} (@code{gnatlbr})
15894 Make the library in the specified directory the current run-time
15897 @item /DELETE=directory
15898 @cindex @code{/DELETE} (@code{gnatlbr})
15899 Delete the run-time library in the specified directory.
15902 @cindex @code{/CONFIG} (@code{gnatlbr})
15904 Use the configuration pragmas in the specified file when building
15908 Use the configuration pragmas in the specified file when compiling.
15912 @node Examples of gnatlbr Usage
15913 @section Example of @code{gnatlbr} Usage
15916 Contents of VAXFLOAT.ADC:
15917 pragma Float_Representation (VAX_Float);
15919 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
15921 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
15926 @node The GNAT Library Browser gnatls
15927 @chapter The GNAT Library Browser @code{gnatls}
15929 @cindex Library browser
15932 @code{gnatls} is a tool that outputs information about compiled
15933 units. It gives the relationship between objects, unit names and source
15934 files. It can also be used to check the source dependencies of a unit
15935 as well as various characteristics.
15939 * Switches for gnatls::
15940 * Examples of gnatls Usage::
15943 @node Running gnatls
15944 @section Running @code{gnatls}
15947 The @code{gnatls} command has the form
15950 $ gnatls switches @var{object_or_ali_file}
15954 The main argument is the list of object or @file{ali} files
15955 (@pxref{The Ada Library Information Files})
15956 for which information is requested.
15958 In normal mode, without additional option, @code{gnatls} produces a
15959 four-column listing. Each line represents information for a specific
15960 object. The first column gives the full path of the object, the second
15961 column gives the name of the principal unit in this object, the third
15962 column gives the status of the source and the fourth column gives the
15963 full path of the source representing this unit.
15964 Here is a simple example of use:
15968 ^./^[]^demo1.o demo1 DIF demo1.adb
15969 ^./^[]^demo2.o demo2 OK demo2.adb
15970 ^./^[]^hello.o h1 OK hello.adb
15971 ^./^[]^instr-child.o instr.child MOK instr-child.adb
15972 ^./^[]^instr.o instr OK instr.adb
15973 ^./^[]^tef.o tef DIF tef.adb
15974 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
15975 ^./^[]^tgef.o tgef DIF tgef.adb
15979 The first line can be interpreted as follows: the main unit which is
15981 object file @file{demo1.o} is demo1, whose main source is in
15982 @file{demo1.adb}. Furthermore, the version of the source used for the
15983 compilation of demo1 has been modified (DIF). Each source file has a status
15984 qualifier which can be:
15987 @item OK (unchanged)
15988 The version of the source file used for the compilation of the
15989 specified unit corresponds exactly to the actual source file.
15991 @item MOK (slightly modified)
15992 The version of the source file used for the compilation of the
15993 specified unit differs from the actual source file but not enough to
15994 require recompilation. If you use gnatmake with the qualifier
15995 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
15996 MOK will not be recompiled.
15998 @item DIF (modified)
15999 No version of the source found on the path corresponds to the source
16000 used to build this object.
16002 @item ??? (file not found)
16003 No source file was found for this unit.
16005 @item HID (hidden, unchanged version not first on PATH)
16006 The version of the source that corresponds exactly to the source used
16007 for compilation has been found on the path but it is hidden by another
16008 version of the same source that has been modified.
16012 @node Switches for gnatls
16013 @section Switches for @code{gnatls}
16016 @code{gnatls} recognizes the following switches:
16020 @item ^-a^/ALL_UNITS^
16021 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
16022 Consider all units, including those of the predefined Ada library.
16023 Especially useful with @option{^-d^/DEPENDENCIES^}.
16025 @item ^-d^/DEPENDENCIES^
16026 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
16027 List sources from which specified units depend on.
16029 @item ^-h^/OUTPUT=OPTIONS^
16030 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
16031 Output the list of options.
16033 @item ^-o^/OUTPUT=OBJECTS^
16034 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
16035 Only output information about object files.
16037 @item ^-s^/OUTPUT=SOURCES^
16038 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
16039 Only output information about source files.
16041 @item ^-u^/OUTPUT=UNITS^
16042 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
16043 Only output information about compilation units.
16045 @item ^-files^/FILES^=@var{file}
16046 @cindex @option{^-files^/FILES^} (@code{gnatls})
16047 Take as arguments the files listed in text file @var{file}.
16048 Text file @var{file} may contain empty lines that are ignored.
16049 Each non empty line should contain the name of an existing file.
16050 Several such switches may be specified simultaneously.
16052 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
16053 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
16054 @itemx ^-I^/SEARCH=^@var{dir}
16055 @itemx ^-I-^/NOCURRENT_DIRECTORY^
16057 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
16058 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
16059 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
16060 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
16061 Source path manipulation. Same meaning as the equivalent @code{gnatmake} flags
16062 (see @ref{Switches for gnatmake}).
16064 @item --RTS=@var{rts-path}
16065 @cindex @option{--RTS} (@code{gnatls})
16066 Specifies the default location of the runtime library. Same meaning as the
16067 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
16069 @item ^-v^/OUTPUT=VERBOSE^
16070 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
16071 Verbose mode. Output the complete source and object paths. Do not use
16072 the default column layout but instead use long format giving as much as
16073 information possible on each requested units, including special
16074 characteristics such as:
16077 @item Preelaborable
16078 The unit is preelaborable in the Ada 95 sense.
16081 No elaboration code has been produced by the compiler for this unit.
16084 The unit is pure in the Ada 95 sense.
16086 @item Elaborate_Body
16087 The unit contains a pragma Elaborate_Body.
16090 The unit contains a pragma Remote_Types.
16092 @item Shared_Passive
16093 The unit contains a pragma Shared_Passive.
16096 This unit is part of the predefined environment and cannot be modified
16099 @item Remote_Call_Interface
16100 The unit contains a pragma Remote_Call_Interface.
16106 @node Examples of gnatls Usage
16107 @section Example of @code{gnatls} Usage
16111 Example of using the verbose switch. Note how the source and
16112 object paths are affected by the -I switch.
16115 $ gnatls -v -I.. demo1.o
16117 GNATLS 3.10w (970212) Copyright 1999 Free Software Foundation, Inc.
16119 Source Search Path:
16120 <Current_Directory>
16122 /home/comar/local/adainclude/
16124 Object Search Path:
16125 <Current_Directory>
16127 /home/comar/local/lib/gcc-lib/mips-sni-sysv4/2.7.2/adalib/
16132 Kind => subprogram body
16133 Flags => No_Elab_Code
16134 Source => demo1.adb modified
16138 The following is an example of use of the dependency list.
16139 Note the use of the -s switch
16140 which gives a straight list of source files. This can be useful for
16141 building specialized scripts.
16144 $ gnatls -d demo2.o
16145 ./demo2.o demo2 OK demo2.adb
16151 $ gnatls -d -s -a demo1.o
16153 /home/comar/local/adainclude/ada.ads
16154 /home/comar/local/adainclude/a-finali.ads
16155 /home/comar/local/adainclude/a-filico.ads
16156 /home/comar/local/adainclude/a-stream.ads
16157 /home/comar/local/adainclude/a-tags.ads
16160 /home/comar/local/adainclude/gnat.ads
16161 /home/comar/local/adainclude/g-io.ads
16163 /home/comar/local/adainclude/system.ads
16164 /home/comar/local/adainclude/s-exctab.ads
16165 /home/comar/local/adainclude/s-finimp.ads
16166 /home/comar/local/adainclude/s-finroo.ads
16167 /home/comar/local/adainclude/s-secsta.ads
16168 /home/comar/local/adainclude/s-stalib.ads
16169 /home/comar/local/adainclude/s-stoele.ads
16170 /home/comar/local/adainclude/s-stratt.ads
16171 /home/comar/local/adainclude/s-tasoli.ads
16172 /home/comar/local/adainclude/s-unstyp.ads
16173 /home/comar/local/adainclude/unchconv.ads
16179 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
16181 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
16182 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
16183 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
16184 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
16185 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
16189 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
16190 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
16192 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
16193 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
16194 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
16195 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
16196 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
16197 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
16198 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
16199 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
16200 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
16201 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
16202 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
16206 @node Cleaning Up Using gnatclean
16207 @chapter Cleaning Up Using @code{gnatclean}
16209 @cindex Cleaning tool
16212 @code{gnatclean} is a tool that allows the deletion of files produced by the
16213 compiler, binder and linker, including ALI files, object files, tree files,
16214 expanded source files, library files, interface copy source files, binder
16215 generated files and executable files.
16218 * Running gnatclean::
16219 * Switches for gnatclean::
16220 * Examples of gnatclean Usage::
16223 @node Running gnatclean
16224 @section Running @code{gnatclean}
16227 The @code{gnatclean} command has the form:
16230 $ gnatclean switches @var{names}
16234 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
16235 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
16236 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
16239 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
16240 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
16241 the linker. In informative-only mode, specified by switch
16242 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
16243 normal mode is listed, but no file is actually deleted.
16245 @node Switches for gnatclean
16246 @section Switches for @code{gnatclean}
16249 @code{gnatclean} recognizes the following switches:
16253 @item ^-c^/COMPILER_FILES_ONLY^
16254 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
16255 Only attempt to delete the files produced by the compiler, not those produced
16256 by the binder or the linker. The files that are not to be deleted are library
16257 files, interface copy files, binder generated files and executable files.
16259 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
16260 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
16261 Indicate that ALI and object files should normally be found in directory
16264 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
16265 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
16266 When using project files, if some errors or warnings are detected during
16267 parsing and verbose mode is not in effect (no use of switch
16268 ^-v^/VERBOSE^), then error lines start with the full path name of the project
16269 file, rather than its simple file name.
16272 @cindex @option{^-h^/HELP^} (@code{gnatclean})
16273 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
16275 @item ^-n^/NODELETE^
16276 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
16277 Informative-only mode. Do not delete any files. Output the list of the files
16278 that would have been deleted if this switch was not specified.
16280 @item ^-P^/PROJECT_FILE=^@var{project}
16281 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
16282 Use project file @var{project}. Only one such switch can be used.
16283 When cleaning a project file, the files produced by the compilation of the
16284 immediate sources or inherited sources of the project files are to be
16285 deleted. This is not depending on the presence or not of executable names
16286 on the command line.
16289 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
16290 Quiet output. If there are no error, do not ouuput anything, except in
16291 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
16292 (switch ^-n^/NODELETE^).
16294 @item ^-r^/RECURSIVE^
16295 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
16296 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
16297 clean all imported and extended project files, recursively. If this switch
16298 is not specified, only the files related to the main project file are to be
16299 deleted. This switch has no effect if no project file is specified.
16301 @item ^-v^/VERBOSE^
16302 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
16305 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
16306 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
16307 Indicates the verbosity of the parsing of GNAT project files.
16308 See @ref{Switches Related to Project Files}.
16310 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
16311 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
16312 Indicates that external variable @var{name} has the value @var{value}.
16313 The Project Manager will use this value for occurrences of
16314 @code{external(name)} when parsing the project file.
16315 See @ref{Switches Related to Project Files}.
16317 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
16318 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
16319 When searching for ALI and object files, look in directory
16322 @item ^-I^/SEARCH=^@var{dir}
16323 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
16324 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
16326 @item ^-I-^/NOCURRENT_DIRECTORY^
16327 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
16328 @cindex Source files, suppressing search
16329 Do not look for ALI or object files in the directory
16330 where @code{gnatclean} was invoked.
16334 @node Examples of gnatclean Usage
16335 @section Examples of @code{gnatclean} Usage
16338 @node GNAT and Libraries
16339 @chapter GNAT and Libraries
16340 @cindex Library, building, installing, using
16343 This chapter describes how to build and use
16344 libraries with GNAT, and also shows how to recompile the GNAT run-time library.
16345 You should be familiar with the
16346 Project Manager facility (see @ref{GNAT Project Manager}) before reading this
16350 * Introduction to Libraries in GNAT::
16351 * General Ada Libraries::
16352 * Stand-alone Ada Libraries::
16353 * Rebuilding the GNAT Run-Time Library::
16356 @node Introduction to Libraries in GNAT
16357 @section Introduction to Libraries in GNAT
16360 A library is, conceptually, a collection of objects which does not have its
16361 own main thread of execution, but rather provides certain services to the
16362 applications that use it. A library can be either statically linked with the
16363 application, in which case its code is directly included in the application,
16364 or, on platforms that support it, be dynamically linked, in which case
16365 its code is shared by all applications making use of this library.
16367 GNAT supports both types of libraries.
16368 In the static case, the compiled code can be provided in different ways.
16369 The simplest approach is to provide directly the
16370 set of objects resulting from compilation of the library source files.
16371 Alternatively, you can group the objects into an archive using whatever
16372 commands are provided by the operating system. For the latter case,
16373 the objects are grouped into a shared library.
16375 In the GNAT environment, a library has two types of components:
16380 Compiled code and @file{ALI} files.
16381 See @ref{The Ada Library Information Files}.
16385 A GNAT library may either completely expose its source files to the
16386 compilation context of the user's application.
16387 Alternatively, it may expose
16388 a limited subset of its source files, called @emph{interface units},
16389 in which case the library is referred to as a @emph{stand-alone library}
16390 (see @ref{Stand-alone Ada Libraries}). In addition, GNAT fully supports
16391 foreign libraries, which are only available in the object format.
16393 All compilation units comprising
16394 an application are elaborated, in an order partially defined by Ada language
16396 Where possible, GNAT provides facilities
16397 to ensure that compilation units of a library are automatically elaborated;
16398 however, there are cases where this must be responsibility of a user. This will
16399 be addressed in greater detail below.
16401 @node General Ada Libraries
16402 @section General Ada Libraries
16405 * Building the library::
16406 * Installing the library::
16407 * Using the library::
16410 @node Building the library
16411 @subsection Building the library
16414 The easiest way to build a library is to use the Project Manager,
16415 which supports a special type of projects called Library Projects
16416 (see @ref{Library Projects}).
16418 A project is considered a library project, when two project-level attributes
16419 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
16420 control different aspects of library configuration, additional optional
16421 project-level attributes can be specified:
16424 This attribute controls whether the library is to be static or shared
16426 @item Library_Version
16427 This attribute specifies what is the library version; this value is used
16428 during dynamic linking of shared libraries to determine if the currently
16429 installed versions of the binaries are compatible.
16431 @item Library_Options
16433 These attributes specify additional low-level options to be used during
16434 library generation, and redefine the actual application used to generate
16439 The GNAT Project Manager takes full care of the library maintenance task,
16440 including recompilation of the source files for which objects do not exist
16441 or are not up to date, assembly of the library archive, and installation of
16442 the library, i.e. copying associated source, object and @file{ALI} files
16443 to the specified location.
16445 It is not entirely trivial to correctly perform all the steps required to
16446 produce a library. We recommend that you use the GNAT Project Manager
16447 for this task. In special cases where this is not desired, the necessary
16448 steps are discussed below.
16450 There are various possibilities for compiling the units that make up the
16451 library: for example with a Makefile (see @ref{Using the GNU make Utility})
16452 or with a conventional script.
16453 For simple libraries, it is also possible to create a
16454 dummy main program which depends upon all the packages that comprise the
16455 interface of the library. This dummy main program can then be given to
16456 @command{gnatmake}, which will ensure that all necessary objects are built.
16458 After this task is accomplished, you should follow the standard procedure
16459 of the underlying operating system to produce the static or shared library.
16461 Here is an example of such a dummy program:
16462 @smallexample @c ada
16464 with My_Lib.Service1;
16465 with My_Lib.Service2;
16466 with My_Lib.Service3;
16467 procedure My_Lib_Dummy is
16475 Here are the generic commands that will build an archive or a shared library.
16478 # compiling the library
16479 $ gnatmake -c my_lib_dummy.adb
16481 # we don't need the dummy object itself
16482 $ rm my_lib_dummy.o my_lib_dummy.ali
16484 # create an archive with the remaining objects
16485 $ ar rc libmy_lib.a *.o
16486 # some systems may require "ranlib" to be run as well
16488 # or create a shared library
16489 $ gcc -shared -o libmy_lib.so *.o
16490 # some systems may require the code to have been compiled with -fPIC
16492 # remove the object files that are now in the library
16495 # Make the ALI files read-only so that gnatmake will not try to
16496 # regenerate the objects that are in the library
16501 Please note that the library must have a name of the form @file{libxxx.a} or
16502 @file{libxxx.so} in order to be accessed by the directive @option{-lxxx}
16505 @node Installing the library
16506 @subsection Installing the library
16509 In the GNAT model, installing a library consists in copying into a specific
16510 location the files that make up this library. When the library is built using
16511 projects, it is automatically installed in the location specified in the
16512 project by means of the attribute @code{Library_Dir},
16513 otherwise the user must specify the destination.
16514 GNAT also supports installing the sources in a
16515 different directory from the other files (@file{ALI}, objects, archives)
16516 since the source path and the object path can be specified separately.
16518 The system administrator can place general purpose libraries in the default
16519 compiler paths, by specifying the libraries' location in the configuration
16520 files @file{ada_source_path} and @file{ada_object_path}.
16521 These configuration files must be located in the GNAT
16522 installation tree at the same place as the gcc spec file. The location of
16523 the gcc spec file can be determined as follows:
16529 The configuration files mentioned above have a simple format: each line
16530 must contain one unique directory name.
16531 Those names are added to the corresponding path
16532 in their order of appearance in the file. The names can be either absolute
16533 or relative; in the latter case, they are relative to where theses files
16536 The files @file{ada_source_path} and @file{ada_object_path} might not be
16538 GNAT installation, in which case, GNAT will look for its run-time library in
16539 the directories @file{adainclude} (for the sources) and @file{adalib} (for the
16540 objects and @file{ALI} files). When the files exist, the compiler does not
16541 look in @file{adainclude} and @file{adalib}, and thus the
16542 @file{ada_source_path} file
16543 must contain the location for the GNAT run-time sources (which can simply
16544 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
16545 contain the location for the GNAT run-time objects (which can simply
16548 You can also specify a new default path to the run-time library at compilation
16549 time with the switch @option{--RTS=rts-path}. You can thus choose / change
16550 the run-time library you want your program to be compiled with. This switch is
16551 recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind},
16552 @command{gnatls}, @command{gnatfind} and @command{gnatxref}.
16554 It is possible to install a library before or after the standard GNAT
16555 library, by reordering the lines in the configuration files. In general, a
16556 library must be installed before the GNAT library if it redefines
16560 @node Using the library
16561 @subsection Using the library
16564 Once again, the project facility greatly simplifies the addition of libraries
16565 to the compilation. If the project file for an application lists a library
16566 project in its @code{with} clause, the Project Manager will ensure that the
16567 library files are consistent, and that they are considered during the
16568 compilation and linking of the application.
16570 Even if you have a third-party, non-Ada library, you can still use GNAT's
16571 Project Manager facility to provide a wrapper for it. The following project for
16572 example, when @code{with}ed in your main project, will link with the
16573 third-party library @file{liba.a}:
16575 @smallexample @c projectfile
16578 for Source_Dirs use ();
16579 for Library_Dir use "lib";
16580 for Library_Name use "a";
16581 for Library_Kind use "static";
16587 In order to use an Ada library manually, you need to make sure that this
16588 library is on both your source and object path
16589 (see @ref{Search Paths and the Run-Time Library (RTL)},
16590 and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped
16591 in an archive or a shared library, you need to specify the desired
16592 library at link time.
16594 For example, you can use the library @file{mylib} installed in
16595 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
16598 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
16603 This can be expressed more simply:
16608 when the following conditions are met:
16611 @file{/dir/my_lib_src} has been added by the user to the environment
16612 variable @code{ADA_INCLUDE_PATH}, or by the administrator to the file
16613 @file{ada_source_path}
16615 @file{/dir/my_lib_obj} has been added by the user to the environment
16616 variable @code{ADA_OBJECTS_PATH}, or by the administrator to the file
16617 @file{ada_object_path}
16619 a pragma @code{Linker_Options} has been added to one of the sources.
16622 @smallexample @c ada
16623 pragma Linker_Options ("-lmy_lib");
16628 @node Stand-alone Ada Libraries
16629 @section Stand-alone Ada Libraries
16630 @cindex Stand-alone library, building, using
16633 * Introduction to Stand-alone Libraries::
16634 * Building a Stand-alone Library::
16635 * Creating a Stand-alone Library to be used in a non-Ada context::
16636 * Restrictions in Stand-alone Libraries::
16639 @node Introduction to Stand-alone Libraries
16640 @subsection Introduction to Stand-alone Libraries
16643 A Stand-alone Library (SAL) is a library that contains the necessary code to
16644 elaborate the Ada units that are included in the library. In contrast with
16645 an ordinary library, which consists of all sources, objects and @file{ALI}
16647 library, a SAL may specify a restricted subset of compilation units
16648 to serve as a library interface. In this case, the fully
16649 self-sufficient set of files will normally consist of an objects
16650 archive, the sources of interface units' specs, and the @file{ALI}
16651 files of interface units.
16652 If an interface spec contains a generic unit or an inlined subprogram,
16654 source must also be provided; if the units that must be provided in the source
16655 form depend on other units, the source and @file{ALI} files of those must
16658 The main purpose of a SAL is to minimize the recompilation overhead of client
16659 applications when a new version of the library is installed. Specifically,
16660 if the interface sources have not changed, client applications do not need to
16661 be recompiled. If, furthermore, a SAL is provided in the shared form and its
16662 version, controlled by @code{Library_Version} attribute, is not changed,
16663 then the clients do not need to be relinked.
16665 SALs also allow the library providers to minimize the amount of library source
16666 text exposed to the clients. Such ``information hiding'' might be useful or
16667 necessary for various reasons.
16669 Stand-alone libraries are also well suited to be used in an executable whose
16670 main routine is not written in Ada.
16672 @node Building a Stand-alone Library
16673 @subsection Building a Stand-alone Library
16676 GNAT's Project facility provides a simple way of building and installing
16677 stand-alone libraries; see @ref{Stand-alone Library Projects}.
16678 To be a Stand-alone Library Project, in addition to the two attributes
16679 that make a project a Library Project (@code{Library_Name} and
16680 @code{Library_Dir}; see @ref{Library Projects}), the attribute
16681 @code{Library_Interface} must be defined. For example:
16683 @smallexample @c projectfile
16685 for Library_Dir use "lib_dir";
16686 for Library_Name use "dummy";
16687 for Library_Interface use ("int1", "int1.child");
16692 Attribute @code{Library_Interface} has a non empty string list value,
16693 each string in the list designating a unit contained in an immediate source
16694 of the project file.
16696 When a Stand-alone Library is built, first the binder is invoked to build
16697 a package whose name depends on the library name
16698 (@file{^b~dummy.ads/b^B$DUMMY.ADS/B^} in the example above).
16699 This binder-generated package includes initialization and
16700 finalization procedures whose
16701 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
16703 above). The object corresponding to this package is included in the library.
16705 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
16706 calling of these procedures if a static SAL is built, or if a shared SAL
16708 with the project-level attribute @code{Library_Auto_Init} set to
16711 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
16712 (those that are listed in attribute @code{Library_Interface}) are copied to
16713 the Library Directory. As a consequence, only the Interface Units may be
16714 imported from Ada units outside of the library. If other units are imported,
16715 the binding phase will fail.
16717 The attribute @code{Library_Src_Dir} may be specified for a
16718 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
16719 single string value. Its value must be the path (absolute or relative to the
16720 project directory) of an existing directory. This directory cannot be the
16721 object directory or one of the source directories, but it can be the same as
16722 the library directory. The sources of the Interface
16723 Units of the library that are needed by an Ada client of the library will be
16724 copied to the designated directory, called the Interface Copy directory.
16725 These sources includes the specs of the Interface Units, but they may also
16726 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
16727 are used, or when there is a generic unit in the spec. Before the sources
16728 are copied to the Interface Copy directory, an attempt is made to delete all
16729 files in the Interface Copy directory.
16731 Building stand-alone libraries by hand is somewhat tedious, but for those
16732 occasions when it is necessary here are the steps that you need to perform:
16735 Compile all library sources.
16738 Invoke the binder with the switch @option{-n} (No Ada main program),
16739 with all the @file{ALI} files of the interfaces, and
16740 with the switch @option{-L} to give specific names to the @code{init}
16741 and @code{final} procedures. For example:
16743 gnatbind -n int1.ali int2.ali -Lsal1
16747 Compile the binder generated file:
16753 Link the dynamic library with all the necessary object files,
16754 indicating to the linker the names of the @code{init} (and possibly
16755 @code{final}) procedures for automatic initialization (and finalization).
16756 The built library should be placed in a directory different from
16757 the object directory.
16760 Copy the @code{ALI} files of the interface to the library directory,
16761 add in this copy an indication that it is an interface to a SAL
16762 (i.e. add a word @option{SL} on the line in the @file{ALI} file that starts
16763 with letter ``P'') and make the modified copy of the @file{ALI} file
16768 Using SALs is not different from using other libraries
16769 (see @ref{Using the library}).
16771 @node Creating a Stand-alone Library to be used in a non-Ada context
16772 @subsection Creating a Stand-alone Library to be used in a non-Ada context
16775 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
16778 The only extra step required is to ensure that library interface subprograms
16779 are compatible with the main program, by means of @code{pragma Export}
16780 or @code{pragma Convention}.
16782 Here is an example of simple library interface for use with C main program:
16784 @smallexample @c ada
16785 package Interface is
16787 procedure Do_Something;
16788 pragma Export (C, Do_Something, "do_something");
16790 procedure Do_Something_Else;
16791 pragma Export (C, Do_Something_Else, "do_something_else");
16797 On the foreign language side, you must provide a ``foreign'' view of the
16798 library interface; remember that it should contain elaboration routines in
16799 addition to interface subprograms.
16801 The example below shows the content of @code{mylib_interface.h} (note
16802 that there is no rule for the naming of this file, any name can be used)
16804 /* the library elaboration procedure */
16805 extern void mylibinit (void);
16807 /* the library finalization procedure */
16808 extern void mylibfinal (void);
16810 /* the interface exported by the library */
16811 extern void do_something (void);
16812 extern void do_something_else (void);
16816 Libraries built as explained above can be used from any program, provided
16817 that the elaboration procedures (named @code{mylibinit} in the previous
16818 example) are called before the library services are used. Any number of
16819 libraries can be used simultaneously, as long as the elaboration
16820 procedure of each library is called.
16822 Below is an example of C program that uses the @code{mylib} library.
16825 #include "mylib_interface.h"
16830 /* First, elaborate the library before using it */
16833 /* Main program, using the library exported entities */
16835 do_something_else ();
16837 /* Library finalization at the end of the program */
16844 Note that invoking any library finalization procedure generated by
16845 @code{gnatbind} shuts down the Ada run-time environment.
16847 finalization of all Ada libraries must be performed at the end of the program.
16848 No call to these libraries nor to the Ada run-time library should be made
16849 after the finalization phase.
16851 @node Restrictions in Stand-alone Libraries
16852 @subsection Restrictions in Stand-alone Libraries
16855 The pragmas listed below should be used with caution inside libraries,
16856 as they can create incompatibilities with other Ada libraries:
16858 @item pragma @code{Locking_Policy}
16859 @item pragma @code{Queuing_Policy}
16860 @item pragma @code{Task_Dispatching_Policy}
16861 @item pragma @code{Unreserve_All_Interrupts}
16865 When using a library that contains such pragmas, the user must make sure
16866 that all libraries use the same pragmas with the same values. Otherwise,
16867 @code{Program_Error} will
16868 be raised during the elaboration of the conflicting
16869 libraries. The usage of these pragmas and its consequences for the user
16870 should therefore be well documented.
16872 Similarly, the traceback in the exception occurrence mechanism should be
16873 enabled or disabled in a consistent manner across all libraries.
16874 Otherwise, Program_Error will be raised during the elaboration of the
16875 conflicting libraries.
16877 If the @code{Version} or @code{Body_Version}
16878 attributes are used inside a library, then you need to
16879 perform a @code{gnatbind} step that specifies all @file{ALI} files in all
16880 libraries, so that version identifiers can be properly computed.
16881 In practice these attributes are rarely used, so this is unlikely
16882 to be a consideration.
16884 @node Rebuilding the GNAT Run-Time Library
16885 @section Rebuilding the GNAT Run-Time Library
16886 @cindex GNAT Run-Time Library, rebuilding
16889 It may be useful to recompile the GNAT library in various contexts, the
16890 most important one being the use of partition-wide configuration pragmas
16891 such as @code{Normalize_Scalars}. A special Makefile called
16892 @code{Makefile.adalib} is provided to that effect and can be found in
16893 the directory containing the GNAT library. The location of this
16894 directory depends on the way the GNAT environment has been installed and can
16895 be determined by means of the command:
16902 The last entry in the object search path usually contains the
16903 gnat library. This Makefile contains its own documentation and in
16904 particular the set of instructions needed to rebuild a new library and
16908 @node Using the GNU make Utility
16909 @chapter Using the GNU @code{make} Utility
16913 This chapter offers some examples of makefiles that solve specific
16914 problems. It does not explain how to write a makefile (see the GNU make
16915 documentation), nor does it try to replace the @code{gnatmake} utility
16916 (@pxref{The GNAT Make Program gnatmake}).
16918 All the examples in this section are specific to the GNU version of
16919 make. Although @code{make} is a standard utility, and the basic language
16920 is the same, these examples use some advanced features found only in
16924 * Using gnatmake in a Makefile::
16925 * Automatically Creating a List of Directories::
16926 * Generating the Command Line Switches::
16927 * Overcoming Command Line Length Limits::
16930 @node Using gnatmake in a Makefile
16931 @section Using gnatmake in a Makefile
16936 Complex project organizations can be handled in a very powerful way by
16937 using GNU make combined with gnatmake. For instance, here is a Makefile
16938 which allows you to build each subsystem of a big project into a separate
16939 shared library. Such a makefile allows you to significantly reduce the link
16940 time of very big applications while maintaining full coherence at
16941 each step of the build process.
16943 The list of dependencies are handled automatically by
16944 @code{gnatmake}. The Makefile is simply used to call gnatmake in each of
16945 the appropriate directories.
16947 Note that you should also read the example on how to automatically
16948 create the list of directories
16949 (@pxref{Automatically Creating a List of Directories})
16950 which might help you in case your project has a lot of subdirectories.
16955 @font@heightrm=cmr8
16958 ## This Makefile is intended to be used with the following directory
16960 ## - The sources are split into a series of csc (computer software components)
16961 ## Each of these csc is put in its own directory.
16962 ## Their name are referenced by the directory names.
16963 ## They will be compiled into shared library (although this would also work
16964 ## with static libraries
16965 ## - The main program (and possibly other packages that do not belong to any
16966 ## csc is put in the top level directory (where the Makefile is).
16967 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
16968 ## \_ second_csc (sources) __ lib (will contain the library)
16970 ## Although this Makefile is build for shared library, it is easy to modify
16971 ## to build partial link objects instead (modify the lines with -shared and
16974 ## With this makefile, you can change any file in the system or add any new
16975 ## file, and everything will be recompiled correctly (only the relevant shared
16976 ## objects will be recompiled, and the main program will be re-linked).
16978 # The list of computer software component for your project. This might be
16979 # generated automatically.
16982 # Name of the main program (no extension)
16985 # If we need to build objects with -fPIC, uncomment the following line
16988 # The following variable should give the directory containing libgnat.so
16989 # You can get this directory through 'gnatls -v'. This is usually the last
16990 # directory in the Object_Path.
16993 # The directories for the libraries
16994 # (This macro expands the list of CSC to the list of shared libraries, you
16995 # could simply use the expanded form :
16996 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
16997 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
16999 $@{MAIN@}: objects $@{LIB_DIR@}
17000 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
17001 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
17004 # recompile the sources
17005 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
17007 # Note: In a future version of GNAT, the following commands will be simplified
17008 # by a new tool, gnatmlib
17010 mkdir -p $@{dir $@@ @}
17011 cd $@{dir $@@ @}; gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
17012 cd $@{dir $@@ @}; cp -f ../*.ali .
17014 # The dependencies for the modules
17015 # Note that we have to force the expansion of *.o, since in some cases
17016 # make won't be able to do it itself.
17017 aa/lib/libaa.so: $@{wildcard aa/*.o@}
17018 bb/lib/libbb.so: $@{wildcard bb/*.o@}
17019 cc/lib/libcc.so: $@{wildcard cc/*.o@}
17021 # Make sure all of the shared libraries are in the path before starting the
17024 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
17027 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
17028 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
17029 $@{RM@} $@{CSC_LIST:%=%/*.o@}
17030 $@{RM@} *.o *.ali $@{MAIN@}
17033 @node Automatically Creating a List of Directories
17034 @section Automatically Creating a List of Directories
17037 In most makefiles, you will have to specify a list of directories, and
17038 store it in a variable. For small projects, it is often easier to
17039 specify each of them by hand, since you then have full control over what
17040 is the proper order for these directories, which ones should be
17043 However, in larger projects, which might involve hundreds of
17044 subdirectories, it might be more convenient to generate this list
17047 The example below presents two methods. The first one, although less
17048 general, gives you more control over the list. It involves wildcard
17049 characters, that are automatically expanded by @code{make}. Its
17050 shortcoming is that you need to explicitly specify some of the
17051 organization of your project, such as for instance the directory tree
17052 depth, whether some directories are found in a separate tree,...
17054 The second method is the most general one. It requires an external
17055 program, called @code{find}, which is standard on all Unix systems. All
17056 the directories found under a given root directory will be added to the
17062 @font@heightrm=cmr8
17065 # The examples below are based on the following directory hierarchy:
17066 # All the directories can contain any number of files
17067 # ROOT_DIRECTORY -> a -> aa -> aaa
17070 # -> b -> ba -> baa
17073 # This Makefile creates a variable called DIRS, that can be reused any time
17074 # you need this list (see the other examples in this section)
17076 # The root of your project's directory hierarchy
17080 # First method: specify explicitly the list of directories
17081 # This allows you to specify any subset of all the directories you need.
17084 DIRS := a/aa/ a/ab/ b/ba/
17087 # Second method: use wildcards
17088 # Note that the argument(s) to wildcard below should end with a '/'.
17089 # Since wildcards also return file names, we have to filter them out
17090 # to avoid duplicate directory names.
17091 # We thus use make's @code{dir} and @code{sort} functions.
17092 # It sets DIRs to the following value (note that the directories aaa and baa
17093 # are not given, unless you change the arguments to wildcard).
17094 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
17097 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
17098 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
17101 # Third method: use an external program
17102 # This command is much faster if run on local disks, avoiding NFS slowdowns.
17103 # This is the most complete command: it sets DIRs to the following value:
17104 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
17107 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
17111 @node Generating the Command Line Switches
17112 @section Generating the Command Line Switches
17115 Once you have created the list of directories as explained in the
17116 previous section (@pxref{Automatically Creating a List of Directories}),
17117 you can easily generate the command line arguments to pass to gnatmake.
17119 For the sake of completeness, this example assumes that the source path
17120 is not the same as the object path, and that you have two separate lists
17124 # see "Automatically creating a list of directories" to create
17129 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
17130 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
17133 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
17136 @node Overcoming Command Line Length Limits
17137 @section Overcoming Command Line Length Limits
17140 One problem that might be encountered on big projects is that many
17141 operating systems limit the length of the command line. It is thus hard to give
17142 gnatmake the list of source and object directories.
17144 This example shows how you can set up environment variables, which will
17145 make @code{gnatmake} behave exactly as if the directories had been
17146 specified on the command line, but have a much higher length limit (or
17147 even none on most systems).
17149 It assumes that you have created a list of directories in your Makefile,
17150 using one of the methods presented in
17151 @ref{Automatically Creating a List of Directories}.
17152 For the sake of completeness, we assume that the object
17153 path (where the ALI files are found) is different from the sources patch.
17155 Note a small trick in the Makefile below: for efficiency reasons, we
17156 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
17157 expanded immediately by @code{make}. This way we overcome the standard
17158 make behavior which is to expand the variables only when they are
17161 On Windows, if you are using the standard Windows command shell, you must
17162 replace colons with semicolons in the assignments to these variables.
17167 @font@heightrm=cmr8
17170 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
17171 # This is the same thing as putting the -I arguments on the command line.
17172 # (the equivalent of using -aI on the command line would be to define
17173 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
17174 # You can of course have different values for these variables.
17176 # Note also that we need to keep the previous values of these variables, since
17177 # they might have been set before running 'make' to specify where the GNAT
17178 # library is installed.
17180 # see "Automatically creating a list of directories" to create these
17186 space:=$@{empty@} $@{empty@}
17187 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
17188 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
17189 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
17190 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
17191 export ADA_INCLUDE_PATH
17192 export ADA_OBJECT_PATH
17200 @node Finding Memory Problems
17201 @chapter Finding Memory Problems
17204 This chapter describes
17206 the @command{gnatmem} tool, which can be used to track down
17207 ``memory leaks'', and
17209 the GNAT Debug Pool facility, which can be used to detect incorrect uses of
17210 access values (including ``dangling references'').
17214 * The gnatmem Tool::
17216 * The GNAT Debug Pool Facility::
17221 @node The gnatmem Tool
17222 @section The @command{gnatmem} Tool
17226 The @code{gnatmem} utility monitors dynamic allocation and
17227 deallocation activity in a program, and displays information about
17228 incorrect deallocations and possible sources of memory leaks.
17229 It provides three type of information:
17232 General information concerning memory management, such as the total
17233 number of allocations and deallocations, the amount of allocated
17234 memory and the high water mark, i.e. the largest amount of allocated
17235 memory in the course of program execution.
17238 Backtraces for all incorrect deallocations, that is to say deallocations
17239 which do not correspond to a valid allocation.
17242 Information on each allocation that is potentially the origin of a memory
17247 * Running gnatmem::
17248 * Switches for gnatmem::
17249 * Example of gnatmem Usage::
17252 @node Running gnatmem
17253 @subsection Running @code{gnatmem}
17256 @code{gnatmem} makes use of the output created by the special version of
17257 allocation and deallocation routines that record call information. This
17258 allows to obtain accurate dynamic memory usage history at a minimal cost to
17259 the execution speed. Note however, that @code{gnatmem} is not supported on
17260 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux x86,
17261 Solaris (sparc and x86) and Windows NT/2000/XP (x86).
17264 The @code{gnatmem} command has the form
17267 $ gnatmem [switches] user_program
17271 The program must have been linked with the instrumented version of the
17272 allocation and deallocation routines. This is done by linking with the
17273 @file{libgmem.a} library. For correct symbolic backtrace information,
17274 the user program should be compiled with debugging options
17275 @ref{Switches for gcc}. For example to build @file{my_program}:
17278 $ gnatmake -g my_program -largs -lgmem
17282 When running @file{my_program} the file @file{gmem.out} is produced. This file
17283 contains information about all allocations and deallocations done by the
17284 program. It is produced by the instrumented allocations and
17285 deallocations routines and will be used by @code{gnatmem}.
17288 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
17289 examine. If the location of @file{gmem.out} file was not explicitly supplied by
17290 @code{-i} switch, gnatmem will assume that this file can be found in the
17291 current directory. For example, after you have executed @file{my_program},
17292 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
17295 $ gnatmem my_program
17299 This will produce the output with the following format:
17301 *************** debut cc
17303 $ gnatmem my_program
17307 Total number of allocations : 45
17308 Total number of deallocations : 6
17309 Final Water Mark (non freed mem) : 11.29 Kilobytes
17310 High Water Mark : 11.40 Kilobytes
17315 Allocation Root # 2
17316 -------------------
17317 Number of non freed allocations : 11
17318 Final Water Mark (non freed mem) : 1.16 Kilobytes
17319 High Water Mark : 1.27 Kilobytes
17321 my_program.adb:23 my_program.alloc
17327 The first block of output gives general information. In this case, the
17328 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
17329 Unchecked_Deallocation routine occurred.
17332 Subsequent paragraphs display information on all allocation roots.
17333 An allocation root is a specific point in the execution of the program
17334 that generates some dynamic allocation, such as a ``@code{@b{new}}''
17335 construct. This root is represented by an execution backtrace (or subprogram
17336 call stack). By default the backtrace depth for allocations roots is 1, so
17337 that a root corresponds exactly to a source location. The backtrace can
17338 be made deeper, to make the root more specific.
17340 @node Switches for gnatmem
17341 @subsection Switches for @code{gnatmem}
17344 @code{gnatmem} recognizes the following switches:
17349 @cindex @option{-q} (@code{gnatmem})
17350 Quiet. Gives the minimum output needed to identify the origin of the
17351 memory leaks. Omits statistical information.
17354 @cindex @var{N} (@code{gnatmem})
17355 N is an integer literal (usually between 1 and 10) which controls the
17356 depth of the backtraces defining allocation root. The default value for
17357 N is 1. The deeper the backtrace, the more precise the localization of
17358 the root. Note that the total number of roots can depend on this
17359 parameter. This parameter must be specified @emph{before} the name of the
17360 executable to be analyzed, to avoid ambiguity.
17363 @cindex @option{-b} (@code{gnatmem})
17364 This switch has the same effect as just depth parameter.
17366 @item -i @var{file}
17367 @cindex @option{-i} (@code{gnatmem})
17368 Do the @code{gnatmem} processing starting from @file{file}, rather than
17369 @file{gmem.out} in the current directory.
17372 @cindex @option{-m} (@code{gnatmem})
17373 This switch causes @code{gnatmem} to mask the allocation roots that have less
17374 than n leaks. The default value is 1. Specifying the value of 0 will allow to
17375 examine even the roots that didn't result in leaks.
17378 @cindex @option{-s} (@code{gnatmem})
17379 This switch causes @code{gnatmem} to sort the allocation roots according to the
17380 specified order of sort criteria, each identified by a single letter. The
17381 currently supported criteria are @code{n, h, w} standing respectively for
17382 number of unfreed allocations, high watermark, and final watermark
17383 corresponding to a specific root. The default order is @code{nwh}.
17387 @node Example of gnatmem Usage
17388 @subsection Example of @code{gnatmem} Usage
17391 The following example shows the use of @code{gnatmem}
17392 on a simple memory-leaking program.
17393 Suppose that we have the following Ada program:
17395 @smallexample @c ada
17398 with Unchecked_Deallocation;
17399 procedure Test_Gm is
17401 type T is array (1..1000) of Integer;
17402 type Ptr is access T;
17403 procedure Free is new Unchecked_Deallocation (T, Ptr);
17406 procedure My_Alloc is
17411 procedure My_DeAlloc is
17419 for I in 1 .. 5 loop
17420 for J in I .. 5 loop
17431 The program needs to be compiled with debugging option and linked with
17432 @code{gmem} library:
17435 $ gnatmake -g test_gm -largs -lgmem
17439 Then we execute the program as usual:
17446 Then @code{gnatmem} is invoked simply with
17452 which produces the following output (result may vary on different platforms):
17457 Total number of allocations : 18
17458 Total number of deallocations : 5
17459 Final Water Mark (non freed mem) : 53.00 Kilobytes
17460 High Water Mark : 56.90 Kilobytes
17462 Allocation Root # 1
17463 -------------------
17464 Number of non freed allocations : 11
17465 Final Water Mark (non freed mem) : 42.97 Kilobytes
17466 High Water Mark : 46.88 Kilobytes
17468 test_gm.adb:11 test_gm.my_alloc
17470 Allocation Root # 2
17471 -------------------
17472 Number of non freed allocations : 1
17473 Final Water Mark (non freed mem) : 10.02 Kilobytes
17474 High Water Mark : 10.02 Kilobytes
17476 s-secsta.adb:81 system.secondary_stack.ss_init
17478 Allocation Root # 3
17479 -------------------
17480 Number of non freed allocations : 1
17481 Final Water Mark (non freed mem) : 12 Bytes
17482 High Water Mark : 12 Bytes
17484 s-secsta.adb:181 system.secondary_stack.ss_init
17488 Note that the GNAT run time contains itself a certain number of
17489 allocations that have no corresponding deallocation,
17490 as shown here for root #2 and root
17491 #3. This is a normal behavior when the number of non freed allocations
17492 is one, it allocates dynamic data structures that the run time needs for
17493 the complete lifetime of the program. Note also that there is only one
17494 allocation root in the user program with a single line back trace:
17495 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
17496 program shows that 'My_Alloc' is called at 2 different points in the
17497 source (line 21 and line 24). If those two allocation roots need to be
17498 distinguished, the backtrace depth parameter can be used:
17501 $ gnatmem 3 test_gm
17505 which will give the following output:
17510 Total number of allocations : 18
17511 Total number of deallocations : 5
17512 Final Water Mark (non freed mem) : 53.00 Kilobytes
17513 High Water Mark : 56.90 Kilobytes
17515 Allocation Root # 1
17516 -------------------
17517 Number of non freed allocations : 10
17518 Final Water Mark (non freed mem) : 39.06 Kilobytes
17519 High Water Mark : 42.97 Kilobytes
17521 test_gm.adb:11 test_gm.my_alloc
17522 test_gm.adb:24 test_gm
17523 b_test_gm.c:52 main
17525 Allocation Root # 2
17526 -------------------
17527 Number of non freed allocations : 1
17528 Final Water Mark (non freed mem) : 10.02 Kilobytes
17529 High Water Mark : 10.02 Kilobytes
17531 s-secsta.adb:81 system.secondary_stack.ss_init
17532 s-secsta.adb:283 <system__secondary_stack___elabb>
17533 b_test_gm.c:33 adainit
17535 Allocation Root # 3
17536 -------------------
17537 Number of non freed allocations : 1
17538 Final Water Mark (non freed mem) : 3.91 Kilobytes
17539 High Water Mark : 3.91 Kilobytes
17541 test_gm.adb:11 test_gm.my_alloc
17542 test_gm.adb:21 test_gm
17543 b_test_gm.c:52 main
17545 Allocation Root # 4
17546 -------------------
17547 Number of non freed allocations : 1
17548 Final Water Mark (non freed mem) : 12 Bytes
17549 High Water Mark : 12 Bytes
17551 s-secsta.adb:181 system.secondary_stack.ss_init
17552 s-secsta.adb:283 <system__secondary_stack___elabb>
17553 b_test_gm.c:33 adainit
17557 The allocation root #1 of the first example has been split in 2 roots #1
17558 and #3 thanks to the more precise associated backtrace.
17563 @node The GNAT Debug Pool Facility
17564 @section The GNAT Debug Pool Facility
17566 @cindex storage, pool, memory corruption
17569 The use of unchecked deallocation and unchecked conversion can easily
17570 lead to incorrect memory references. The problems generated by such
17571 references are usually difficult to tackle because the symptoms can be
17572 very remote from the origin of the problem. In such cases, it is
17573 very helpful to detect the problem as early as possible. This is the
17574 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
17576 In order to use the GNAT specific debugging pool, the user must
17577 associate a debug pool object with each of the access types that may be
17578 related to suspected memory problems. See Ada Reference Manual 13.11.
17579 @smallexample @c ada
17580 type Ptr is access Some_Type;
17581 Pool : GNAT.Debug_Pools.Debug_Pool;
17582 for Ptr'Storage_Pool use Pool;
17586 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
17587 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
17588 allow the user to redefine allocation and deallocation strategies. They
17589 also provide a checkpoint for each dereference, through the use of
17590 the primitive operation @code{Dereference} which is implicitly called at
17591 each dereference of an access value.
17593 Once an access type has been associated with a debug pool, operations on
17594 values of the type may raise four distinct exceptions,
17595 which correspond to four potential kinds of memory corruption:
17598 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
17600 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
17602 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
17604 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
17608 For types associated with a Debug_Pool, dynamic allocation is performed using
17610 GNAT allocation routine. References to all allocated chunks of memory
17611 are kept in an internal dictionary.
17612 Several deallocation strategies are provided, whereupon the user can choose
17613 to release the memory to the system, keep it allocated for further invalid
17614 access checks, or fill it with an easily recognizable pattern for debug
17616 The memory pattern is the old IBM hexadecimal convention: @code{16#DEADBEEF#}.
17618 See the documentation in the file g-debpoo.ads for more information on the
17619 various strategies.
17621 Upon each dereference, a check is made that the access value denotes a
17622 properly allocated memory location. Here is a complete example of use of
17623 @code{Debug_Pools}, that includes typical instances of memory corruption:
17624 @smallexample @c ada
17628 with Gnat.Io; use Gnat.Io;
17629 with Unchecked_Deallocation;
17630 with Unchecked_Conversion;
17631 with GNAT.Debug_Pools;
17632 with System.Storage_Elements;
17633 with Ada.Exceptions; use Ada.Exceptions;
17634 procedure Debug_Pool_Test is
17636 type T is access Integer;
17637 type U is access all T;
17639 P : GNAT.Debug_Pools.Debug_Pool;
17640 for T'Storage_Pool use P;
17642 procedure Free is new Unchecked_Deallocation (Integer, T);
17643 function UC is new Unchecked_Conversion (U, T);
17646 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
17656 Put_Line (Integer'Image(B.all));
17658 when E : others => Put_Line ("raised: " & Exception_Name (E));
17663 when E : others => Put_Line ("raised: " & Exception_Name (E));
17667 Put_Line (Integer'Image(B.all));
17669 when E : others => Put_Line ("raised: " & Exception_Name (E));
17674 when E : others => Put_Line ("raised: " & Exception_Name (E));
17677 end Debug_Pool_Test;
17681 The debug pool mechanism provides the following precise diagnostics on the
17682 execution of this erroneous program:
17685 Total allocated bytes : 0
17686 Total deallocated bytes : 0
17687 Current Water Mark: 0
17691 Total allocated bytes : 8
17692 Total deallocated bytes : 0
17693 Current Water Mark: 8
17696 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
17697 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
17698 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
17699 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
17701 Total allocated bytes : 8
17702 Total deallocated bytes : 4
17703 Current Water Mark: 4
17708 @node Creating Sample Bodies Using gnatstub
17709 @chapter Creating Sample Bodies Using @command{gnatstub}
17713 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
17714 for library unit declarations.
17716 To create a body stub, @command{gnatstub} has to compile the library
17717 unit declaration. Therefore, bodies can be created only for legal
17718 library units. Moreover, if a library unit depends semantically upon
17719 units located outside the current directory, you have to provide
17720 the source search path when calling @command{gnatstub}, see the description
17721 of @command{gnatstub} switches below.
17724 * Running gnatstub::
17725 * Switches for gnatstub::
17728 @node Running gnatstub
17729 @section Running @command{gnatstub}
17732 @command{gnatstub} has the command-line interface of the form
17735 $ gnatstub [switches] filename [directory]
17742 is the name of the source file that contains a library unit declaration
17743 for which a body must be created. The file name may contain the path
17745 The file name does not have to follow the GNAT file name conventions. If the
17747 does not follow GNAT file naming conventions, the name of the body file must
17749 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
17750 If the file name follows the GNAT file naming
17751 conventions and the name of the body file is not provided,
17754 of the body file from the argument file name by replacing the @file{.ads}
17756 with the @file{.adb} suffix.
17759 indicates the directory in which the body stub is to be placed (the default
17764 is an optional sequence of switches as described in the next section
17767 @node Switches for gnatstub
17768 @section Switches for @command{gnatstub}
17774 @cindex @option{^-f^/FULL^} (@command{gnatstub})
17775 If the destination directory already contains a file with the name of the
17777 for the argument spec file, replace it with the generated body stub.
17779 @item ^-hs^/HEADER=SPEC^
17780 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
17781 Put the comment header (i.e., all the comments preceding the
17782 compilation unit) from the source of the library unit declaration
17783 into the body stub.
17785 @item ^-hg^/HEADER=GENERAL^
17786 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
17787 Put a sample comment header into the body stub.
17791 @cindex @option{-IDIR} (@command{gnatstub})
17793 @cindex @option{-I-} (@command{gnatstub})
17796 @item /NOCURRENT_DIRECTORY
17797 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
17799 ^These switches have ^This switch has^ the same meaning as in calls to
17801 ^They define ^It defines ^ the source search path in the call to
17802 @command{gcc} issued
17803 by @command{gnatstub} to compile an argument source file.
17805 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
17806 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
17807 This switch has the same meaning as in calls to @command{gcc}.
17808 It defines the additional configuration file to be passed to the call to
17809 @command{gcc} issued
17810 by @command{gnatstub} to compile an argument source file.
17812 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
17813 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
17814 (@var{n} is a non-negative integer). Set the maximum line length in the
17815 body stub to @var{n}; the default is 79. The maximum value that can be
17816 specified is 32767. Note that in the special case of configuration
17817 pragma files, the maximum is always 32767 regardless of whether or
17818 not this switch appears.
17820 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
17821 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
17822 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
17823 the generated body sample to @var{n}.
17824 The default indentation is 3.
17826 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
17827 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
17828 Order local bodies alphabetically. (By default local bodies are ordered
17829 in the same way as the corresponding local specs in the argument spec file.)
17831 @item ^-i^/INDENTATION=^@var{n}
17832 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
17833 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
17835 @item ^-k^/TREE_FILE=SAVE^
17836 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
17837 Do not remove the tree file (i.e., the snapshot of the compiler internal
17838 structures used by @command{gnatstub}) after creating the body stub.
17840 @item ^-l^/LINE_LENGTH=^@var{n}
17841 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
17842 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
17844 @item ^-o^/BODY=^@var{body-name}
17845 @cindex @option{^-o^/BODY^} (@command{gnatstub})
17846 Body file name. This should be set if the argument file name does not
17848 the GNAT file naming
17849 conventions. If this switch is omitted the default name for the body will be
17851 from the argument file name according to the GNAT file naming conventions.
17854 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
17855 Quiet mode: do not generate a confirmation when a body is
17856 successfully created, and do not generate a message when a body is not
17860 @item ^-r^/TREE_FILE=REUSE^
17861 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
17862 Reuse the tree file (if it exists) instead of creating it. Instead of
17863 creating the tree file for the library unit declaration, @command{gnatstub}
17864 tries to find it in the current directory and use it for creating
17865 a body. If the tree file is not found, no body is created. This option
17866 also implies @option{^-k^/SAVE^}, whether or not
17867 the latter is set explicitly.
17869 @item ^-t^/TREE_FILE=OVERWRITE^
17870 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
17871 Overwrite the existing tree file. If the current directory already
17872 contains the file which, according to the GNAT file naming rules should
17873 be considered as a tree file for the argument source file,
17875 will refuse to create the tree file needed to create a sample body
17876 unless this option is set.
17878 @item ^-v^/VERBOSE^
17879 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
17880 Verbose mode: generate version information.
17885 @node Other Utility Programs
17886 @chapter Other Utility Programs
17889 This chapter discusses some other utility programs available in the Ada
17893 * Using Other Utility Programs with GNAT::
17894 * The External Symbol Naming Scheme of GNAT::
17896 * Ada Mode for Glide::
17898 * Converting Ada Files to html with gnathtml::
17899 * Installing gnathtml::
17906 @node Using Other Utility Programs with GNAT
17907 @section Using Other Utility Programs with GNAT
17910 The object files generated by GNAT are in standard system format and in
17911 particular the debugging information uses this format. This means
17912 programs generated by GNAT can be used with existing utilities that
17913 depend on these formats.
17916 In general, any utility program that works with C will also often work with
17917 Ada programs generated by GNAT. This includes software utilities such as
17918 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
17922 @node The External Symbol Naming Scheme of GNAT
17923 @section The External Symbol Naming Scheme of GNAT
17926 In order to interpret the output from GNAT, when using tools that are
17927 originally intended for use with other languages, it is useful to
17928 understand the conventions used to generate link names from the Ada
17931 All link names are in all lowercase letters. With the exception of library
17932 procedure names, the mechanism used is simply to use the full expanded
17933 Ada name with dots replaced by double underscores. For example, suppose
17934 we have the following package spec:
17936 @smallexample @c ada
17947 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
17948 the corresponding link name is @code{qrs__mn}.
17950 Of course if a @code{pragma Export} is used this may be overridden:
17952 @smallexample @c ada
17957 pragma Export (Var1, C, External_Name => "var1_name");
17959 pragma Export (Var2, C, Link_Name => "var2_link_name");
17966 In this case, the link name for @var{Var1} is whatever link name the
17967 C compiler would assign for the C function @var{var1_name}. This typically
17968 would be either @var{var1_name} or @var{_var1_name}, depending on operating
17969 system conventions, but other possibilities exist. The link name for
17970 @var{Var2} is @var{var2_link_name}, and this is not operating system
17974 One exception occurs for library level procedures. A potential ambiguity
17975 arises between the required name @code{_main} for the C main program,
17976 and the name we would otherwise assign to an Ada library level procedure
17977 called @code{Main} (which might well not be the main program).
17979 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
17980 names. So if we have a library level procedure such as
17982 @smallexample @c ada
17985 procedure Hello (S : String);
17991 the external name of this procedure will be @var{_ada_hello}.
17994 @node Ada Mode for Glide
17995 @section Ada Mode for @code{Glide}
17996 @cindex Ada mode (for Glide)
17999 The Glide mode for programming in Ada (both Ada83 and Ada95) helps the
18000 user to understand and navigate existing code, and facilitates writing
18001 new code. It furthermore provides some utility functions for easier
18002 integration of standard Emacs features when programming in Ada.
18004 Its general features include:
18008 An Integrated Development Environment with functionality such as the
18013 ``Project files'' for configuration-specific aspects
18014 (e.g. directories and compilation options)
18017 Compiling and stepping through error messages.
18020 Running and debugging an applications within Glide.
18027 User configurability
18030 Some of the specific Ada mode features are:
18034 Functions for easy and quick stepping through Ada code
18037 Getting cross reference information for identifiers (e.g., finding a
18038 defining occurrence)
18041 Displaying an index menu of types and subprograms, allowing
18042 direct selection for browsing
18045 Automatic color highlighting of the various Ada entities
18048 Glide directly supports writing Ada code, via several facilities:
18052 Switching between spec and body files with possible
18053 autogeneration of body files
18056 Automatic formating of subprogram parameter lists
18059 Automatic indentation according to Ada syntax
18062 Automatic completion of identifiers
18065 Automatic (and configurable) casing of identifiers, keywords, and attributes
18068 Insertion of syntactic templates
18071 Block commenting / uncommenting
18075 For more information, please refer to the online documentation
18076 available in the @code{Glide} @result{} @code{Help} menu.
18080 @node Converting Ada Files to html with gnathtml
18081 @section Converting Ada Files to HTML with @code{gnathtml}
18084 This @code{Perl} script allows Ada source files to be browsed using
18085 standard Web browsers. For installation procedure, see the section
18086 @xref{Installing gnathtml}.
18088 Ada reserved keywords are highlighted in a bold font and Ada comments in
18089 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
18090 switch to suppress the generation of cross-referencing information, user
18091 defined variables and types will appear in a different color; you will
18092 be able to click on any identifier and go to its declaration.
18094 The command line is as follow:
18096 $ perl gnathtml.pl [switches] ada-files
18100 You can pass it as many Ada files as you want. @code{gnathtml} will generate
18101 an html file for every ada file, and a global file called @file{index.htm}.
18102 This file is an index of every identifier defined in the files.
18104 The available switches are the following ones :
18108 @cindex @option{-83} (@code{gnathtml})
18109 Only the subset on the Ada 83 keywords will be highlighted, not the full
18110 Ada 95 keywords set.
18112 @item -cc @var{color}
18113 @cindex @option{-cc} (@code{gnathtml})
18114 This option allows you to change the color used for comments. The default
18115 value is green. The color argument can be any name accepted by html.
18118 @cindex @option{-d} (@code{gnathtml})
18119 If the ada files depend on some other files (using for instance the
18120 @code{with} command, the latter will also be converted to html.
18121 Only the files in the user project will be converted to html, not the files
18122 in the run-time library itself.
18125 @cindex @option{-D} (@code{gnathtml})
18126 This command is the same as @option{-d} above, but @command{gnathtml} will
18127 also look for files in the run-time library, and generate html files for them.
18129 @item -ext @var{extension}
18130 @cindex @option{-ext} (@code{gnathtml})
18131 This option allows you to change the extension of the generated HTML files.
18132 If you do not specify an extension, it will default to @file{htm}.
18135 @cindex @option{-f} (@code{gnathtml})
18136 By default, gnathtml will generate html links only for global entities
18137 ('with'ed units, global variables and types,...). If you specify the
18138 @option{-f} on the command line, then links will be generated for local
18141 @item -l @var{number}
18142 @cindex @option{-l} (@code{gnathtml})
18143 If this switch is provided and @var{number} is not 0, then @code{gnathtml}
18144 will number the html files every @var{number} line.
18147 @cindex @option{-I} (@code{gnathtml})
18148 Specify a directory to search for library files (@file{.ALI} files) and
18149 source files. You can provide several -I switches on the command line,
18150 and the directories will be parsed in the order of the command line.
18153 @cindex @option{-o} (@code{gnathtml})
18154 Specify the output directory for html files. By default, gnathtml will
18155 saved the generated html files in a subdirectory named @file{html/}.
18157 @item -p @var{file}
18158 @cindex @option{-p} (@code{gnathtml})
18159 If you are using Emacs and the most recent Emacs Ada mode, which provides
18160 a full Integrated Development Environment for compiling, checking,
18161 running and debugging applications, you may use @file{.gpr} files
18162 to give the directories where Emacs can find sources and object files.
18164 Using this switch, you can tell gnathtml to use these files. This allows
18165 you to get an html version of your application, even if it is spread
18166 over multiple directories.
18168 @item -sc @var{color}
18169 @cindex @option{-sc} (@code{gnathtml})
18170 This option allows you to change the color used for symbol definitions.
18171 The default value is red. The color argument can be any name accepted by html.
18173 @item -t @var{file}
18174 @cindex @option{-t} (@code{gnathtml})
18175 This switch provides the name of a file. This file contains a list of
18176 file names to be converted, and the effect is exactly as though they had
18177 appeared explicitly on the command line. This
18178 is the recommended way to work around the command line length limit on some
18183 @node Installing gnathtml
18184 @section Installing @code{gnathtml}
18187 @code{Perl} needs to be installed on your machine to run this script.
18188 @code{Perl} is freely available for almost every architecture and
18189 Operating System via the Internet.
18191 On Unix systems, you may want to modify the first line of the script
18192 @code{gnathtml}, to explicitly tell the Operating system where Perl
18193 is. The syntax of this line is :
18195 #!full_path_name_to_perl
18199 Alternatively, you may run the script using the following command line:
18202 $ perl gnathtml.pl [switches] files
18211 The GNAT distribution provides an Ada 95 template for the Digital Language
18212 Sensitive Editor (LSE), a component of DECset. In order to
18213 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
18220 GNAT supports The Digital Performance Coverage Analyzer (PCA), a component
18221 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
18222 the collection phase with the /DEBUG qualifier.
18225 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
18226 $ DEFINE LIB$DEBUG PCA$COLLECTOR
18227 $ RUN/DEBUG <PROGRAM_NAME>
18232 @node Running and Debugging Ada Programs
18233 @chapter Running and Debugging Ada Programs
18237 This chapter discusses how to debug Ada programs. An incorrect Ada program
18238 may be handled in three ways by the GNAT compiler:
18242 The illegality may be a violation of the static semantics of Ada. In
18243 that case GNAT diagnoses the constructs in the program that are illegal.
18244 It is then a straightforward matter for the user to modify those parts of
18248 The illegality may be a violation of the dynamic semantics of Ada. In
18249 that case the program compiles and executes, but may generate incorrect
18250 results, or may terminate abnormally with some exception.
18253 When presented with a program that contains convoluted errors, GNAT
18254 itself may terminate abnormally without providing full diagnostics on
18255 the incorrect user program.
18259 * The GNAT Debugger GDB::
18261 * Introduction to GDB Commands::
18262 * Using Ada Expressions::
18263 * Calling User-Defined Subprograms::
18264 * Using the Next Command in a Function::
18267 * Debugging Generic Units::
18268 * GNAT Abnormal Termination or Failure to Terminate::
18269 * Naming Conventions for GNAT Source Files::
18270 * Getting Internal Debugging Information::
18271 * Stack Traceback::
18277 @node The GNAT Debugger GDB
18278 @section The GNAT Debugger GDB
18281 @code{GDB} is a general purpose, platform-independent debugger that
18282 can be used to debug mixed-language programs compiled with @code{GCC},
18283 and in particular is capable of debugging Ada programs compiled with
18284 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
18285 complex Ada data structures.
18287 The manual @cite{Debugging with GDB}
18289 , located in the GNU:[DOCS] directory,
18291 contains full details on the usage of @code{GDB}, including a section on
18292 its usage on programs. This manual should be consulted for full
18293 details. The section that follows is a brief introduction to the
18294 philosophy and use of @code{GDB}.
18296 When GNAT programs are compiled, the compiler optionally writes debugging
18297 information into the generated object file, including information on
18298 line numbers, and on declared types and variables. This information is
18299 separate from the generated code. It makes the object files considerably
18300 larger, but it does not add to the size of the actual executable that
18301 will be loaded into memory, and has no impact on run-time performance. The
18302 generation of debug information is triggered by the use of the
18303 ^-g^/DEBUG^ switch in the gcc or gnatmake command used to carry out
18304 the compilations. It is important to emphasize that the use of these
18305 options does not change the generated code.
18307 The debugging information is written in standard system formats that
18308 are used by many tools, including debuggers and profilers. The format
18309 of the information is typically designed to describe C types and
18310 semantics, but GNAT implements a translation scheme which allows full
18311 details about Ada types and variables to be encoded into these
18312 standard C formats. Details of this encoding scheme may be found in
18313 the file exp_dbug.ads in the GNAT source distribution. However, the
18314 details of this encoding are, in general, of no interest to a user,
18315 since @code{GDB} automatically performs the necessary decoding.
18317 When a program is bound and linked, the debugging information is
18318 collected from the object files, and stored in the executable image of
18319 the program. Again, this process significantly increases the size of
18320 the generated executable file, but it does not increase the size of
18321 the executable program itself. Furthermore, if this program is run in
18322 the normal manner, it runs exactly as if the debug information were
18323 not present, and takes no more actual memory.
18325 However, if the program is run under control of @code{GDB}, the
18326 debugger is activated. The image of the program is loaded, at which
18327 point it is ready to run. If a run command is given, then the program
18328 will run exactly as it would have if @code{GDB} were not present. This
18329 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
18330 entirely non-intrusive until a breakpoint is encountered. If no
18331 breakpoint is ever hit, the program will run exactly as it would if no
18332 debugger were present. When a breakpoint is hit, @code{GDB} accesses
18333 the debugging information and can respond to user commands to inspect
18334 variables, and more generally to report on the state of execution.
18338 @section Running GDB
18341 The debugger can be launched directly and simply from @code{glide} or
18342 through its graphical interface: @code{gvd}. It can also be used
18343 directly in text mode. Here is described the basic use of @code{GDB}
18344 in text mode. All the commands described below can be used in the
18345 @code{gvd} console window even though there is usually other more
18346 graphical ways to achieve the same goals.
18350 The command to run the graphical interface of the debugger is
18357 The command to run @code{GDB} in text mode is
18360 $ ^gdb program^$ GDB PROGRAM^
18364 where @code{^program^PROGRAM^} is the name of the executable file. This
18365 activates the debugger and results in a prompt for debugger commands.
18366 The simplest command is simply @code{run}, which causes the program to run
18367 exactly as if the debugger were not present. The following section
18368 describes some of the additional commands that can be given to @code{GDB}.
18371 @c *******************************
18372 @node Introduction to GDB Commands
18373 @section Introduction to GDB Commands
18376 @code{GDB} contains a large repertoire of commands. The manual
18377 @cite{Debugging with GDB}
18379 , located in the GNU:[DOCS] directory,
18381 includes extensive documentation on the use
18382 of these commands, together with examples of their use. Furthermore,
18383 the command @var{help} invoked from within @code{GDB} activates a simple help
18384 facility which summarizes the available commands and their options.
18385 In this section we summarize a few of the most commonly
18386 used commands to give an idea of what @code{GDB} is about. You should create
18387 a simple program with debugging information and experiment with the use of
18388 these @code{GDB} commands on the program as you read through the
18392 @item set args @var{arguments}
18393 The @var{arguments} list above is a list of arguments to be passed to
18394 the program on a subsequent run command, just as though the arguments
18395 had been entered on a normal invocation of the program. The @code{set args}
18396 command is not needed if the program does not require arguments.
18399 The @code{run} command causes execution of the program to start from
18400 the beginning. If the program is already running, that is to say if
18401 you are currently positioned at a breakpoint, then a prompt will ask
18402 for confirmation that you want to abandon the current execution and
18405 @item breakpoint @var{location}
18406 The breakpoint command sets a breakpoint, that is to say a point at which
18407 execution will halt and @code{GDB} will await further
18408 commands. @var{location} is
18409 either a line number within a file, given in the format @code{file:linenumber},
18410 or it is the name of a subprogram. If you request that a breakpoint be set on
18411 a subprogram that is overloaded, a prompt will ask you to specify on which of
18412 those subprograms you want to breakpoint. You can also
18413 specify that all of them should be breakpointed. If the program is run
18414 and execution encounters the breakpoint, then the program
18415 stops and @code{GDB} signals that the breakpoint was encountered by
18416 printing the line of code before which the program is halted.
18418 @item breakpoint exception @var{name}
18419 A special form of the breakpoint command which breakpoints whenever
18420 exception @var{name} is raised.
18421 If @var{name} is omitted,
18422 then a breakpoint will occur when any exception is raised.
18424 @item print @var{expression}
18425 This will print the value of the given expression. Most simple
18426 Ada expression formats are properly handled by @code{GDB}, so the expression
18427 can contain function calls, variables, operators, and attribute references.
18430 Continues execution following a breakpoint, until the next breakpoint or the
18431 termination of the program.
18434 Executes a single line after a breakpoint. If the next statement
18435 is a subprogram call, execution continues into (the first statement of)
18436 the called subprogram.
18439 Executes a single line. If this line is a subprogram call, executes and
18440 returns from the call.
18443 Lists a few lines around the current source location. In practice, it
18444 is usually more convenient to have a separate edit window open with the
18445 relevant source file displayed. Successive applications of this command
18446 print subsequent lines. The command can be given an argument which is a
18447 line number, in which case it displays a few lines around the specified one.
18450 Displays a backtrace of the call chain. This command is typically
18451 used after a breakpoint has occurred, to examine the sequence of calls that
18452 leads to the current breakpoint. The display includes one line for each
18453 activation record (frame) corresponding to an active subprogram.
18456 At a breakpoint, @code{GDB} can display the values of variables local
18457 to the current frame. The command @code{up} can be used to
18458 examine the contents of other active frames, by moving the focus up
18459 the stack, that is to say from callee to caller, one frame at a time.
18462 Moves the focus of @code{GDB} down from the frame currently being
18463 examined to the frame of its callee (the reverse of the previous command),
18465 @item frame @var{n}
18466 Inspect the frame with the given number. The value 0 denotes the frame
18467 of the current breakpoint, that is to say the top of the call stack.
18471 The above list is a very short introduction to the commands that
18472 @code{GDB} provides. Important additional capabilities, including conditional
18473 breakpoints, the ability to execute command sequences on a breakpoint,
18474 the ability to debug at the machine instruction level and many other
18475 features are described in detail in @cite{Debugging with GDB}.
18476 Note that most commands can be abbreviated
18477 (for example, c for continue, bt for backtrace).
18479 @node Using Ada Expressions
18480 @section Using Ada Expressions
18481 @cindex Ada expressions
18484 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
18485 extensions. The philosophy behind the design of this subset is
18489 That @code{GDB} should provide basic literals and access to operations for
18490 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18491 leaving more sophisticated computations to subprograms written into the
18492 program (which therefore may be called from @code{GDB}).
18495 That type safety and strict adherence to Ada language restrictions
18496 are not particularly important to the @code{GDB} user.
18499 That brevity is important to the @code{GDB} user.
18502 Thus, for brevity, the debugger acts as if there were
18503 implicit @code{with} and @code{use} clauses in effect for all user-written
18504 packages, thus making it unnecessary to fully qualify most names with
18505 their packages, regardless of context. Where this causes ambiguity,
18506 @code{GDB} asks the user's intent.
18508 For details on the supported Ada syntax, see @cite{Debugging with GDB}.
18510 @node Calling User-Defined Subprograms
18511 @section Calling User-Defined Subprograms
18514 An important capability of @code{GDB} is the ability to call user-defined
18515 subprograms while debugging. This is achieved simply by entering
18516 a subprogram call statement in the form:
18519 call subprogram-name (parameters)
18523 The keyword @code{call} can be omitted in the normal case where the
18524 @code{subprogram-name} does not coincide with any of the predefined
18525 @code{GDB} commands.
18527 The effect is to invoke the given subprogram, passing it the
18528 list of parameters that is supplied. The parameters can be expressions and
18529 can include variables from the program being debugged. The
18530 subprogram must be defined
18531 at the library level within your program, and @code{GDB} will call the
18532 subprogram within the environment of your program execution (which
18533 means that the subprogram is free to access or even modify variables
18534 within your program).
18536 The most important use of this facility is in allowing the inclusion of
18537 debugging routines that are tailored to particular data structures
18538 in your program. Such debugging routines can be written to provide a suitably
18539 high-level description of an abstract type, rather than a low-level dump
18540 of its physical layout. After all, the standard
18541 @code{GDB print} command only knows the physical layout of your
18542 types, not their abstract meaning. Debugging routines can provide information
18543 at the desired semantic level and are thus enormously useful.
18545 For example, when debugging GNAT itself, it is crucial to have access to
18546 the contents of the tree nodes used to represent the program internally.
18547 But tree nodes are represented simply by an integer value (which in turn
18548 is an index into a table of nodes).
18549 Using the @code{print} command on a tree node would simply print this integer
18550 value, which is not very useful. But the PN routine (defined in file
18551 treepr.adb in the GNAT sources) takes a tree node as input, and displays
18552 a useful high level representation of the tree node, which includes the
18553 syntactic category of the node, its position in the source, the integers
18554 that denote descendant nodes and parent node, as well as varied
18555 semantic information. To study this example in more detail, you might want to
18556 look at the body of the PN procedure in the stated file.
18558 @node Using the Next Command in a Function
18559 @section Using the Next Command in a Function
18562 When you use the @code{next} command in a function, the current source
18563 location will advance to the next statement as usual. A special case
18564 arises in the case of a @code{return} statement.
18566 Part of the code for a return statement is the ``epilog'' of the function.
18567 This is the code that returns to the caller. There is only one copy of
18568 this epilog code, and it is typically associated with the last return
18569 statement in the function if there is more than one return. In some
18570 implementations, this epilog is associated with the first statement
18573 The result is that if you use the @code{next} command from a return
18574 statement that is not the last return statement of the function you
18575 may see a strange apparent jump to the last return statement or to
18576 the start of the function. You should simply ignore this odd jump.
18577 The value returned is always that from the first return statement
18578 that was stepped through.
18580 @node Ada Exceptions
18581 @section Breaking on Ada Exceptions
18585 You can set breakpoints that trip when your program raises
18586 selected exceptions.
18589 @item break exception
18590 Set a breakpoint that trips whenever (any task in the) program raises
18593 @item break exception @var{name}
18594 Set a breakpoint that trips whenever (any task in the) program raises
18595 the exception @var{name}.
18597 @item break exception unhandled
18598 Set a breakpoint that trips whenever (any task in the) program raises an
18599 exception for which there is no handler.
18601 @item info exceptions
18602 @itemx info exceptions @var{regexp}
18603 The @code{info exceptions} command permits the user to examine all defined
18604 exceptions within Ada programs. With a regular expression, @var{regexp}, as
18605 argument, prints out only those exceptions whose name matches @var{regexp}.
18613 @code{GDB} allows the following task-related commands:
18617 This command shows a list of current Ada tasks, as in the following example:
18624 ID TID P-ID Thread Pri State Name
18625 1 8088000 0 807e000 15 Child Activation Wait main_task
18626 2 80a4000 1 80ae000 15 Accept/Select Wait b
18627 3 809a800 1 80a4800 15 Child Activation Wait a
18628 * 4 80ae800 3 80b8000 15 Running c
18632 In this listing, the asterisk before the first task indicates it to be the
18633 currently running task. The first column lists the task ID that is used
18634 to refer to tasks in the following commands.
18636 @item break @var{linespec} task @var{taskid}
18637 @itemx break @var{linespec} task @var{taskid} if @dots{}
18638 @cindex Breakpoints and tasks
18639 These commands are like the @code{break @dots{} thread @dots{}}.
18640 @var{linespec} specifies source lines.
18642 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
18643 to specify that you only want @code{GDB} to stop the program when a
18644 particular Ada task reaches this breakpoint. @var{taskid} is one of the
18645 numeric task identifiers assigned by @code{GDB}, shown in the first
18646 column of the @samp{info tasks} display.
18648 If you do not specify @samp{task @var{taskid}} when you set a
18649 breakpoint, the breakpoint applies to @emph{all} tasks of your
18652 You can use the @code{task} qualifier on conditional breakpoints as
18653 well; in this case, place @samp{task @var{taskid}} before the
18654 breakpoint condition (before the @code{if}).
18656 @item task @var{taskno}
18657 @cindex Task switching
18659 This command allows to switch to the task referred by @var{taskno}. In
18660 particular, This allows to browse the backtrace of the specified
18661 task. It is advised to switch back to the original task before
18662 continuing execution otherwise the scheduling of the program may be
18667 For more detailed information on the tasking support,
18668 see @cite{Debugging with GDB}.
18670 @node Debugging Generic Units
18671 @section Debugging Generic Units
18672 @cindex Debugging Generic Units
18676 GNAT always uses code expansion for generic instantiation. This means that
18677 each time an instantiation occurs, a complete copy of the original code is
18678 made, with appropriate substitutions of formals by actuals.
18680 It is not possible to refer to the original generic entities in
18681 @code{GDB}, but it is always possible to debug a particular instance of
18682 a generic, by using the appropriate expanded names. For example, if we have
18684 @smallexample @c ada
18689 generic package k is
18690 procedure kp (v1 : in out integer);
18694 procedure kp (v1 : in out integer) is
18700 package k1 is new k;
18701 package k2 is new k;
18703 var : integer := 1;
18716 Then to break on a call to procedure kp in the k2 instance, simply
18720 (gdb) break g.k2.kp
18724 When the breakpoint occurs, you can step through the code of the
18725 instance in the normal manner and examine the values of local variables, as for
18728 @node GNAT Abnormal Termination or Failure to Terminate
18729 @section GNAT Abnormal Termination or Failure to Terminate
18730 @cindex GNAT Abnormal Termination or Failure to Terminate
18733 When presented with programs that contain serious errors in syntax
18735 GNAT may on rare occasions experience problems in operation, such
18737 segmentation fault or illegal memory access, raising an internal
18738 exception, terminating abnormally, or failing to terminate at all.
18739 In such cases, you can activate
18740 various features of GNAT that can help you pinpoint the construct in your
18741 program that is the likely source of the problem.
18743 The following strategies are presented in increasing order of
18744 difficulty, corresponding to your experience in using GNAT and your
18745 familiarity with compiler internals.
18749 Run @code{gcc} with the @option{-gnatf}. This first
18750 switch causes all errors on a given line to be reported. In its absence,
18751 only the first error on a line is displayed.
18753 The @option{-gnatdO} switch causes errors to be displayed as soon as they
18754 are encountered, rather than after compilation is terminated. If GNAT
18755 terminates prematurely or goes into an infinite loop, the last error
18756 message displayed may help to pinpoint the culprit.
18759 Run @code{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this mode,
18760 @code{gcc} produces ongoing information about the progress of the
18761 compilation and provides the name of each procedure as code is
18762 generated. This switch allows you to find which Ada procedure was being
18763 compiled when it encountered a code generation problem.
18766 @cindex @option{-gnatdc} switch
18767 Run @code{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
18768 switch that does for the front-end what @option{^-v^VERBOSE^} does
18769 for the back end. The system prints the name of each unit,
18770 either a compilation unit or nested unit, as it is being analyzed.
18772 Finally, you can start
18773 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
18774 front-end of GNAT, and can be run independently (normally it is just
18775 called from @code{gcc}). You can use @code{gdb} on @code{gnat1} as you
18776 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
18777 @code{where} command is the first line of attack; the variable
18778 @code{lineno} (seen by @code{print lineno}), used by the second phase of
18779 @code{gnat1} and by the @code{gcc} backend, indicates the source line at
18780 which the execution stopped, and @code{input_file name} indicates the name of
18784 @node Naming Conventions for GNAT Source Files
18785 @section Naming Conventions for GNAT Source Files
18788 In order to examine the workings of the GNAT system, the following
18789 brief description of its organization may be helpful:
18793 Files with prefix @file{^sc^SC^} contain the lexical scanner.
18796 All files prefixed with @file{^par^PAR^} are components of the parser. The
18797 numbers correspond to chapters of the Ada 95 Reference Manual. For example,
18798 parsing of select statements can be found in @file{par-ch9.adb}.
18801 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
18802 numbers correspond to chapters of the Ada standard. For example, all
18803 issues involving context clauses can be found in @file{sem_ch10.adb}. In
18804 addition, some features of the language require sufficient special processing
18805 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
18806 dynamic dispatching, etc.
18809 All files prefixed with @file{^exp^EXP^} perform normalization and
18810 expansion of the intermediate representation (abstract syntax tree, or AST).
18811 these files use the same numbering scheme as the parser and semantics files.
18812 For example, the construction of record initialization procedures is done in
18813 @file{exp_ch3.adb}.
18816 The files prefixed with @file{^bind^BIND^} implement the binder, which
18817 verifies the consistency of the compilation, determines an order of
18818 elaboration, and generates the bind file.
18821 The files @file{atree.ads} and @file{atree.adb} detail the low-level
18822 data structures used by the front-end.
18825 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
18826 the abstract syntax tree as produced by the parser.
18829 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
18830 all entities, computed during semantic analysis.
18833 Library management issues are dealt with in files with prefix
18839 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
18840 defined in Annex A.
18845 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
18846 defined in Annex B.
18850 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
18851 both language-defined children and GNAT run-time routines.
18855 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
18856 general-purpose packages, fully documented in their specifications. All
18857 the other @file{.c} files are modifications of common @code{gcc} files.
18860 @node Getting Internal Debugging Information
18861 @section Getting Internal Debugging Information
18864 Most compilers have internal debugging switches and modes. GNAT
18865 does also, except GNAT internal debugging switches and modes are not
18866 secret. A summary and full description of all the compiler and binder
18867 debug flags are in the file @file{debug.adb}. You must obtain the
18868 sources of the compiler to see the full detailed effects of these flags.
18870 The switches that print the source of the program (reconstructed from
18871 the internal tree) are of general interest for user programs, as are the
18873 the full internal tree, and the entity table (the symbol table
18874 information). The reconstructed source provides a readable version of the
18875 program after the front-end has completed analysis and expansion,
18876 and is useful when studying the performance of specific constructs.
18877 For example, constraint checks are indicated, complex aggregates
18878 are replaced with loops and assignments, and tasking primitives
18879 are replaced with run-time calls.
18881 @node Stack Traceback
18882 @section Stack Traceback
18884 @cindex stack traceback
18885 @cindex stack unwinding
18888 Traceback is a mechanism to display the sequence of subprogram calls that
18889 leads to a specified execution point in a program. Often (but not always)
18890 the execution point is an instruction at which an exception has been raised.
18891 This mechanism is also known as @i{stack unwinding} because it obtains
18892 its information by scanning the run-time stack and recovering the activation
18893 records of all active subprograms. Stack unwinding is one of the most
18894 important tools for program debugging.
18896 The first entry stored in traceback corresponds to the deepest calling level,
18897 that is to say the subprogram currently executing the instruction
18898 from which we want to obtain the traceback.
18900 Note that there is no runtime performance penalty when stack traceback
18901 is enabled, and no exception is raised during program execution.
18904 * Non-Symbolic Traceback::
18905 * Symbolic Traceback::
18908 @node Non-Symbolic Traceback
18909 @subsection Non-Symbolic Traceback
18910 @cindex traceback, non-symbolic
18913 Note: this feature is not supported on all platforms. See
18914 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
18918 * Tracebacks From an Unhandled Exception::
18919 * Tracebacks From Exception Occurrences (non-symbolic)::
18920 * Tracebacks From Anywhere in a Program (non-symbolic)::
18923 @node Tracebacks From an Unhandled Exception
18924 @subsubsection Tracebacks From an Unhandled Exception
18927 A runtime non-symbolic traceback is a list of addresses of call instructions.
18928 To enable this feature you must use the @option{-E}
18929 @code{gnatbind}'s option. With this option a stack traceback is stored as part
18930 of exception information. You can retrieve this information using the
18931 @code{addr2line} tool.
18933 Here is a simple example:
18935 @smallexample @c ada
18941 raise Constraint_Error;
18956 $ gnatmake stb -bargs -E
18959 Execution terminated by unhandled exception
18960 Exception name: CONSTRAINT_ERROR
18962 Call stack traceback locations:
18963 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
18967 As we see the traceback lists a sequence of addresses for the unhandled
18968 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
18969 guess that this exception come from procedure P1. To translate these
18970 addresses into the source lines where the calls appear, the
18971 @code{addr2line} tool, described below, is invaluable. The use of this tool
18972 requires the program to be compiled with debug information.
18975 $ gnatmake -g stb -bargs -E
18978 Execution terminated by unhandled exception
18979 Exception name: CONSTRAINT_ERROR
18981 Call stack traceback locations:
18982 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
18984 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
18985 0x4011f1 0x77e892a4
18987 00401373 at d:/stb/stb.adb:5
18988 0040138B at d:/stb/stb.adb:10
18989 0040139C at d:/stb/stb.adb:14
18990 00401335 at d:/stb/b~stb.adb:104
18991 004011C4 at /build/.../crt1.c:200
18992 004011F1 at /build/.../crt1.c:222
18993 77E892A4 in ?? at ??:0
18997 The @code{addr2line} tool has several other useful options:
19001 to get the function name corresponding to any location
19003 @item --demangle=gnat
19004 to use the gnat decoding mode for the function names. Note that
19005 for binutils version 2.9.x the option is simply @option{--demangle}.
19009 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
19010 0x40139c 0x401335 0x4011c4 0x4011f1
19012 00401373 in stb.p1 at d:/stb/stb.adb:5
19013 0040138B in stb.p2 at d:/stb/stb.adb:10
19014 0040139C in stb at d:/stb/stb.adb:14
19015 00401335 in main at d:/stb/b~stb.adb:104
19016 004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
19017 004011F1 in <mainCRTStartup> at /build/.../crt1.c:222
19021 From this traceback we can see that the exception was raised in
19022 @file{stb.adb} at line 5, which was reached from a procedure call in
19023 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
19024 which contains the call to the main program.
19025 @pxref{Running gnatbind}. The remaining entries are assorted runtime routines,
19026 and the output will vary from platform to platform.
19028 It is also possible to use @code{GDB} with these traceback addresses to debug
19029 the program. For example, we can break at a given code location, as reported
19030 in the stack traceback:
19036 Furthermore, this feature is not implemented inside Windows DLL. Only
19037 the non-symbolic traceback is reported in this case.
19040 (gdb) break *0x401373
19041 Breakpoint 1 at 0x401373: file stb.adb, line 5.
19045 It is important to note that the stack traceback addresses
19046 do not change when debug information is included. This is particularly useful
19047 because it makes it possible to release software without debug information (to
19048 minimize object size), get a field report that includes a stack traceback
19049 whenever an internal bug occurs, and then be able to retrieve the sequence
19050 of calls with the same program compiled with debug information.
19052 @node Tracebacks From Exception Occurrences (non-symbolic)
19053 @subsubsection Tracebacks From Exception Occurrences
19056 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
19057 The stack traceback is attached to the exception information string, and can
19058 be retrieved in an exception handler within the Ada program, by means of the
19059 Ada95 facilities defined in @code{Ada.Exceptions}. Here is a simple example:
19061 @smallexample @c ada
19063 with Ada.Exceptions;
19068 use Ada.Exceptions;
19076 Text_IO.Put_Line (Exception_Information (E));
19090 This program will output:
19095 Exception name: CONSTRAINT_ERROR
19096 Message: stb.adb:12
19097 Call stack traceback locations:
19098 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
19101 @node Tracebacks From Anywhere in a Program (non-symbolic)
19102 @subsubsection Tracebacks From Anywhere in a Program
19105 It is also possible to retrieve a stack traceback from anywhere in a
19106 program. For this you need to
19107 use the @code{GNAT.Traceback} API. This package includes a procedure called
19108 @code{Call_Chain} that computes a complete stack traceback, as well as useful
19109 display procedures described below. It is not necessary to use the
19110 @option{-E gnatbind} option in this case, because the stack traceback mechanism
19111 is invoked explicitly.
19114 In the following example we compute a traceback at a specific location in
19115 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
19116 convert addresses to strings:
19118 @smallexample @c ada
19120 with GNAT.Traceback;
19121 with GNAT.Debug_Utilities;
19127 use GNAT.Traceback;
19130 TB : Tracebacks_Array (1 .. 10);
19131 -- We are asking for a maximum of 10 stack frames.
19133 -- Len will receive the actual number of stack frames returned.
19135 Call_Chain (TB, Len);
19137 Text_IO.Put ("In STB.P1 : ");
19139 for K in 1 .. Len loop
19140 Text_IO.Put (Debug_Utilities.Image (TB (K)));
19161 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
19162 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
19166 You can then get further information by invoking the @code{addr2line}
19167 tool as described earlier (note that the hexadecimal addresses
19168 need to be specified in C format, with a leading ``0x'').
19171 @node Symbolic Traceback
19172 @subsection Symbolic Traceback
19173 @cindex traceback, symbolic
19176 A symbolic traceback is a stack traceback in which procedure names are
19177 associated with each code location.
19180 Note that this feature is not supported on all platforms. See
19181 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
19182 list of currently supported platforms.
19185 Note that the symbolic traceback requires that the program be compiled
19186 with debug information. If it is not compiled with debug information
19187 only the non-symbolic information will be valid.
19190 * Tracebacks From Exception Occurrences (symbolic)::
19191 * Tracebacks From Anywhere in a Program (symbolic)::
19194 @node Tracebacks From Exception Occurrences (symbolic)
19195 @subsubsection Tracebacks From Exception Occurrences
19197 @smallexample @c ada
19199 with GNAT.Traceback.Symbolic;
19205 raise Constraint_Error;
19222 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
19227 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
19230 0040149F in stb.p1 at stb.adb:8
19231 004014B7 in stb.p2 at stb.adb:13
19232 004014CF in stb.p3 at stb.adb:18
19233 004015DD in ada.stb at stb.adb:22
19234 00401461 in main at b~stb.adb:168
19235 004011C4 in __mingw_CRTStartup at crt1.c:200
19236 004011F1 in mainCRTStartup at crt1.c:222
19237 77E892A4 in ?? at ??:0
19241 In the above example the ``.\'' syntax in the @command{gnatmake} command
19242 is currently required by @command{addr2line} for files that are in
19243 the current working directory.
19244 Moreover, the exact sequence of linker options may vary from platform
19246 The above @option{-largs} section is for Windows platforms. By contrast,
19247 under Unix there is no need for the @option{-largs} section.
19248 Differences across platforms are due to details of linker implementation.
19250 @node Tracebacks From Anywhere in a Program (symbolic)
19251 @subsubsection Tracebacks From Anywhere in a Program
19254 It is possible to get a symbolic stack traceback
19255 from anywhere in a program, just as for non-symbolic tracebacks.
19256 The first step is to obtain a non-symbolic
19257 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
19258 information. Here is an example:
19260 @smallexample @c ada
19262 with GNAT.Traceback;
19263 with GNAT.Traceback.Symbolic;
19268 use GNAT.Traceback;
19269 use GNAT.Traceback.Symbolic;
19272 TB : Tracebacks_Array (1 .. 10);
19273 -- We are asking for a maximum of 10 stack frames.
19275 -- Len will receive the actual number of stack frames returned.
19277 Call_Chain (TB, Len);
19278 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
19292 @node Compatibility with DEC Ada
19293 @chapter Compatibility with DEC Ada
19294 @cindex Compatibility
19297 This section of the manual compares DEC Ada for OpenVMS Alpha and GNAT
19298 OpenVMS Alpha. GNAT achieves a high level of compatibility
19299 with DEC Ada, and it should generally be straightforward to port code
19300 from the DEC Ada environment to GNAT. However, there are a few language
19301 and implementation differences of which the user must be aware. These
19302 differences are discussed in this section. In
19303 addition, the operating environment and command structure for the
19304 compiler are different, and these differences are also discussed.
19306 Note that this discussion addresses specifically the implementation
19307 of Ada 83 for DIGITAL OpenVMS Alpha Systems. In cases where the implementation
19308 of DEC Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
19309 GNAT always follows the Alpha implementation.
19312 * Ada 95 Compatibility::
19313 * Differences in the Definition of Package System::
19314 * Language-Related Features::
19315 * The Package STANDARD::
19316 * The Package SYSTEM::
19317 * Tasking and Task-Related Features::
19318 * Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems::
19319 * Pragmas and Pragma-Related Features::
19320 * Library of Predefined Units::
19322 * Main Program Definition::
19323 * Implementation-Defined Attributes::
19324 * Compiler and Run-Time Interfacing::
19325 * Program Compilation and Library Management::
19327 * Implementation Limits::
19331 @node Ada 95 Compatibility
19332 @section Ada 95 Compatibility
19335 GNAT is an Ada 95 compiler, and DEC Ada is an Ada 83
19336 compiler. Ada 95 is almost completely upwards compatible
19337 with Ada 83, and therefore Ada 83 programs will compile
19338 and run under GNAT with
19339 no changes or only minor changes. The Ada 95 Reference
19340 Manual (ANSI/ISO/IEC-8652:1995) provides details on specific
19343 GNAT provides the switch /83 on the GNAT COMPILE command,
19344 as well as the pragma ADA_83, to force the compiler to
19345 operate in Ada 83 mode. This mode does not guarantee complete
19346 conformance to Ada 83, but in practice is sufficient to
19347 eliminate most sources of incompatibilities.
19348 In particular, it eliminates the recognition of the
19349 additional Ada 95 keywords, so that their use as identifiers
19350 in Ada83 program is legal, and handles the cases of packages
19351 with optional bodies, and generics that instantiate unconstrained
19352 types without the use of @code{(<>)}.
19354 @node Differences in the Definition of Package System
19355 @section Differences in the Definition of Package System
19358 Both the Ada 95 and Ada 83 reference manuals permit a compiler to add
19359 implementation-dependent declarations to package System. In normal mode,
19360 GNAT does not take advantage of this permission, and the version of System
19361 provided by GNAT exactly matches that in the Ada 95 Reference Manual.
19363 However, DEC Ada adds an extensive set of declarations to package System,
19364 as fully documented in the DEC Ada manuals. To minimize changes required
19365 for programs that make use of these extensions, GNAT provides the pragma
19366 Extend_System for extending the definition of package System. By using:
19368 @smallexample @c ada
19371 pragma Extend_System (Aux_DEC);
19377 The set of definitions in System is extended to include those in package
19378 @code{System.Aux_DEC}.
19379 These definitions are incorporated directly into package
19380 System, as though they had been declared there in the first place. For a
19381 list of the declarations added, see the specification of this package,
19382 which can be found in the file @code{s-auxdec.ads} in the GNAT library.
19383 The pragma Extend_System is a configuration pragma, which means that
19384 it can be placed in the file @file{gnat.adc}, so that it will automatically
19385 apply to all subsequent compilations. See the section on Configuration
19386 Pragmas for further details.
19388 An alternative approach that avoids the use of the non-standard
19389 Extend_System pragma is to add a context clause to the unit that
19390 references these facilities:
19392 @smallexample @c ada
19395 with System.Aux_DEC;
19396 use System.Aux_DEC;
19402 The effect is not quite semantically identical to incorporating
19403 the declarations directly into package @code{System},
19404 but most programs will not notice a difference
19405 unless they use prefix notation (e.g. @code{System.Integer_8})
19407 entities directly in package @code{System}.
19408 For units containing such references,
19409 the prefixes must either be removed, or the pragma @code{Extend_System}
19412 @node Language-Related Features
19413 @section Language-Related Features
19416 The following sections highlight differences in types,
19417 representations of types, operations, alignment, and
19421 * Integer Types and Representations::
19422 * Floating-Point Types and Representations::
19423 * Pragmas Float_Representation and Long_Float::
19424 * Fixed-Point Types and Representations::
19425 * Record and Array Component Alignment::
19426 * Address Clauses::
19427 * Other Representation Clauses::
19430 @node Integer Types and Representations
19431 @subsection Integer Types and Representations
19434 The set of predefined integer types is identical in DEC Ada and GNAT.
19435 Furthermore the representation of these integer types is also identical,
19436 including the capability of size clauses forcing biased representation.
19439 DEC Ada for OpenVMS Alpha systems has defined the
19440 following additional integer types in package System:
19461 When using GNAT, the first four of these types may be obtained from the
19462 standard Ada 95 package @code{Interfaces}.
19463 Alternatively, by use of the pragma
19464 @code{Extend_System}, identical
19465 declarations can be referenced directly in package @code{System}.
19466 On both GNAT and DEC Ada, the maximum integer size is 64 bits.
19468 @node Floating-Point Types and Representations
19469 @subsection Floating-Point Types and Representations
19470 @cindex Floating-Point types
19473 The set of predefined floating-point types is identical in DEC Ada and GNAT.
19474 Furthermore the representation of these floating-point
19475 types is also identical. One important difference is that the default
19476 representation for DEC Ada is VAX_Float, but the default representation
19479 Specific types may be declared to be VAX_Float or IEEE, using the pragma
19480 @code{Float_Representation} as described in the DEC Ada documentation.
19481 For example, the declarations:
19483 @smallexample @c ada
19486 type F_Float is digits 6;
19487 pragma Float_Representation (VAX_Float, F_Float);
19493 declare a type F_Float that will be represented in VAX_Float format.
19494 This set of declarations actually appears in System.Aux_DEC, which provides
19495 the full set of additional floating-point declarations provided in
19496 the DEC Ada version of package
19497 System. This and similar declarations may be accessed in a user program
19498 by using pragma @code{Extend_System}. The use of this
19499 pragma, and the related pragma @code{Long_Float} is described in further
19500 detail in the following section.
19502 @node Pragmas Float_Representation and Long_Float
19503 @subsection Pragmas Float_Representation and Long_Float
19506 DEC Ada provides the pragma @code{Float_Representation}, which
19507 acts as a program library switch to allow control over
19508 the internal representation chosen for the predefined
19509 floating-point types declared in the package @code{Standard}.
19510 The format of this pragma is as follows:
19515 @b{pragma} @code{Float_Representation}(VAX_Float | IEEE_Float);
19521 This pragma controls the representation of floating-point
19526 @code{VAX_Float} specifies that floating-point
19527 types are represented by default with the VAX hardware types
19528 F-floating, D-floating, G-floating. Note that the H-floating
19529 type is available only on DIGITAL Vax systems, and is not available
19530 in either DEC Ada or GNAT for Alpha systems.
19533 @code{IEEE_Float} specifies that floating-point
19534 types are represented by default with the IEEE single and
19535 double floating-point types.
19539 GNAT provides an identical implementation of the pragma
19540 @code{Float_Representation}, except that it functions as a
19541 configuration pragma, as defined by Ada 95. Note that the
19542 notion of configuration pragma corresponds closely to the
19543 DEC Ada notion of a program library switch.
19545 When no pragma is used in GNAT, the default is IEEE_Float, which is different
19546 from DEC Ada 83, where the default is VAX_Float. In addition, the
19547 predefined libraries in GNAT are built using IEEE_Float, so it is not
19548 advisable to change the format of numbers passed to standard library
19549 routines, and if necessary explicit type conversions may be needed.
19551 The use of IEEE_Float is recommended in GNAT since it is more efficient,
19552 and (given that it conforms to an international standard) potentially more
19553 portable. The situation in which VAX_Float may be useful is in interfacing
19554 to existing code and data that expects the use of VAX_Float. There are
19555 two possibilities here. If the requirement for the use of VAX_Float is
19556 localized, then the best approach is to use the predefined VAX_Float
19557 types in package @code{System}, as extended by
19558 @code{Extend_System}. For example, use @code{System.F_Float}
19559 to specify the 32-bit @code{F-Float} format.
19561 Alternatively, if an entire program depends heavily on the use of
19562 the @code{VAX_Float} and in particular assumes that the types in
19563 package @code{Standard} are in @code{Vax_Float} format, then it
19564 may be desirable to reconfigure GNAT to assume Vax_Float by default.
19565 This is done by using the GNAT LIBRARY command to rebuild the library, and
19566 then using the general form of the @code{Float_Representation}
19567 pragma to ensure that this default format is used throughout.
19568 The form of the GNAT LIBRARY command is:
19571 GNAT LIBRARY /CONFIG=@i{file} /CREATE=@i{directory}
19575 where @i{file} contains the new configuration pragmas
19576 and @i{directory} is the directory to be created to contain
19580 On OpenVMS systems, DEC Ada provides the pragma @code{Long_Float}
19581 to allow control over the internal representation chosen
19582 for the predefined type @code{Long_Float} and for floating-point
19583 type declarations with digits specified in the range 7 .. 15.
19584 The format of this pragma is as follows:
19586 @smallexample @c ada
19588 pragma Long_Float (D_FLOAT | G_FLOAT);
19592 @node Fixed-Point Types and Representations
19593 @subsection Fixed-Point Types and Representations
19596 On DEC Ada for OpenVMS Alpha systems, rounding is
19597 away from zero for both positive and negative numbers.
19598 Therefore, +0.5 rounds to 1 and -0.5 rounds to -1.
19600 On GNAT for OpenVMS Alpha, the results of operations
19601 on fixed-point types are in accordance with the Ada 95
19602 rules. In particular, results of operations on decimal
19603 fixed-point types are truncated.
19605 @node Record and Array Component Alignment
19606 @subsection Record and Array Component Alignment
19609 On DEC Ada for OpenVMS Alpha, all non composite components
19610 are aligned on natural boundaries. For example, 1-byte
19611 components are aligned on byte boundaries, 2-byte
19612 components on 2-byte boundaries, 4-byte components on 4-byte
19613 byte boundaries, and so on. The OpenVMS Alpha hardware
19614 runs more efficiently with naturally aligned data.
19616 ON GNAT for OpenVMS Alpha, alignment rules are compatible
19617 with DEC Ada for OpenVMS Alpha.
19619 @node Address Clauses
19620 @subsection Address Clauses
19623 In DEC Ada and GNAT, address clauses are supported for
19624 objects and imported subprograms.
19625 The predefined type @code{System.Address} is a private type
19626 in both compilers, with the same representation (it is simply
19627 a machine pointer). Addition, subtraction, and comparison
19628 operations are available in the standard Ada 95 package
19629 @code{System.Storage_Elements}, or in package @code{System}
19630 if it is extended to include @code{System.Aux_DEC} using a
19631 pragma @code{Extend_System} as previously described.
19633 Note that code that with's both this extended package @code{System}
19634 and the package @code{System.Storage_Elements} should not @code{use}
19635 both packages, or ambiguities will result. In general it is better
19636 not to mix these two sets of facilities. The Ada 95 package was
19637 designed specifically to provide the kind of features that DEC Ada
19638 adds directly to package @code{System}.
19640 GNAT is compatible with DEC Ada in its handling of address
19641 clauses, except for some limitations in
19642 the form of address clauses for composite objects with
19643 initialization. Such address clauses are easily replaced
19644 by the use of an explicitly-defined constant as described
19645 in the Ada 95 Reference Manual (13.1(22)). For example, the sequence
19648 @smallexample @c ada
19650 X, Y : Integer := Init_Func;
19651 Q : String (X .. Y) := "abc";
19653 for Q'Address use Compute_Address;
19658 will be rejected by GNAT, since the address cannot be computed at the time
19659 that Q is declared. To achieve the intended effect, write instead:
19661 @smallexample @c ada
19664 X, Y : Integer := Init_Func;
19665 Q_Address : constant Address := Compute_Address;
19666 Q : String (X .. Y) := "abc";
19668 for Q'Address use Q_Address;
19674 which will be accepted by GNAT (and other Ada 95 compilers), and is also
19675 backwards compatible with Ada 83. A fuller description of the restrictions
19676 on address specifications is found in the GNAT Reference Manual.
19678 @node Other Representation Clauses
19679 @subsection Other Representation Clauses
19682 GNAT supports in a compatible manner all the representation
19683 clauses supported by DEC Ada. In addition, it
19684 supports representation clause forms that are new in Ada 95
19685 including COMPONENT_SIZE and SIZE clauses for objects.
19687 @node The Package STANDARD
19688 @section The Package STANDARD
19691 The package STANDARD, as implemented by DEC Ada, is fully
19692 described in the Reference Manual for the Ada Programming
19693 Language (ANSI/MIL-STD-1815A-1983) and in the DEC Ada
19694 Language Reference Manual. As implemented by GNAT, the
19695 package STANDARD is described in the Ada 95 Reference
19698 In addition, DEC Ada supports the Latin-1 character set in
19699 the type CHARACTER. GNAT supports the Latin-1 character set
19700 in the type CHARACTER and also Unicode (ISO 10646 BMP) in
19701 the type WIDE_CHARACTER.
19703 The floating-point types supported by GNAT are those
19704 supported by DEC Ada, but defaults are different, and are controlled by
19705 pragmas. See @pxref{Floating-Point Types and Representations} for details.
19707 @node The Package SYSTEM
19708 @section The Package SYSTEM
19711 DEC Ada provides a system-specific version of the package
19712 SYSTEM for each platform on which the language ships.
19713 For the complete specification of the package SYSTEM, see
19714 Appendix F of the DEC Ada Language Reference Manual.
19716 On DEC Ada, the package SYSTEM includes the following conversion functions:
19718 @item TO_ADDRESS(INTEGER)
19720 @item TO_ADDRESS(UNSIGNED_LONGWORD)
19722 @item TO_ADDRESS(universal_integer)
19724 @item TO_INTEGER(ADDRESS)
19726 @item TO_UNSIGNED_LONGWORD(ADDRESS)
19728 @item Function IMPORT_VALUE return UNSIGNED_LONGWORD and the
19729 functions IMPORT_ADDRESS and IMPORT_LARGEST_VALUE
19733 By default, GNAT supplies a version of SYSTEM that matches
19734 the definition given in the Ada 95 Reference Manual.
19736 is a subset of the DIGITAL system definitions, which is as
19737 close as possible to the original definitions. The only difference
19738 is that the definition of SYSTEM_NAME is different:
19740 @smallexample @c ada
19743 type Name is (SYSTEM_NAME_GNAT);
19744 System_Name : constant Name := SYSTEM_NAME_GNAT;
19750 Also, GNAT adds the new Ada 95 declarations for
19751 BIT_ORDER and DEFAULT_BIT_ORDER.
19753 However, the use of the following pragma causes GNAT
19754 to extend the definition of package SYSTEM so that it
19755 encompasses the full set of DIGITAL-specific extensions,
19756 including the functions listed above:
19758 @smallexample @c ada
19760 pragma Extend_System (Aux_DEC);
19765 The pragma Extend_System is a configuration pragma that
19766 is most conveniently placed in the @file{gnat.adc} file. See the
19767 GNAT Reference Manual for further details.
19769 DEC Ada does not allow the recompilation of the package
19770 SYSTEM. Instead DEC Ada provides several pragmas (SYSTEM_
19771 NAME, STORAGE_UNIT, and MEMORY_SIZE) to modify values in
19772 the package SYSTEM. On OpenVMS Alpha systems, the pragma
19773 SYSTEM_NAME takes the enumeration literal OPENVMS_AXP as
19774 its single argument.
19776 GNAT does permit the recompilation of package SYSTEM using
19777 a special switch (@option{-gnatg}) and this switch can be used if
19778 it is necessary to modify the definitions in SYSTEM. GNAT does
19779 not permit the specification of SYSTEM_NAME, STORAGE_UNIT
19780 or MEMORY_SIZE by any other means.
19782 On GNAT systems, the pragma SYSTEM_NAME takes the
19783 enumeration literal SYSTEM_NAME_GNAT.
19785 The definitions provided by the use of
19787 @smallexample @c ada
19788 pragma Extend_System (AUX_Dec);
19792 are virtually identical to those provided by the DEC Ada 83 package
19793 System. One important difference is that the name of the TO_ADDRESS
19794 function for type UNSIGNED_LONGWORD is changed to TO_ADDRESS_LONG.
19795 See the GNAT Reference manual for a discussion of why this change was
19799 The version of TO_ADDRESS taking a universal integer argument is in fact
19800 an extension to Ada 83 not strictly compatible with the reference manual.
19801 In GNAT, we are constrained to be exactly compatible with the standard,
19802 and this means we cannot provide this capability. In DEC Ada 83, the
19803 point of this definition is to deal with a call like:
19805 @smallexample @c ada
19806 TO_ADDRESS (16#12777#);
19810 Normally, according to the Ada 83 standard, one would expect this to be
19811 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
19812 of TO_ADDRESS. However, in DEC Ada 83, there is no ambiguity, since the
19813 definition using universal_integer takes precedence.
19815 In GNAT, since the version with universal_integer cannot be supplied, it is
19816 not possible to be 100% compatible. Since there are many programs using
19817 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
19818 to change the name of the function in the UNSIGNED_LONGWORD case, so the
19819 declarations provided in the GNAT version of AUX_Dec are:
19821 @smallexample @c ada
19822 function To_Address (X : Integer) return Address;
19823 pragma Pure_Function (To_Address);
19825 function To_Address_Long (X : Unsigned_Longword) return Address;
19826 pragma Pure_Function (To_Address_Long);
19830 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
19831 change the name to TO_ADDRESS_LONG.
19833 @node Tasking and Task-Related Features
19834 @section Tasking and Task-Related Features
19837 The concepts relevant to a comparison of tasking on GNAT
19838 and on DEC Ada for OpenVMS Alpha systems are discussed in
19839 the following sections.
19841 For detailed information on concepts related to tasking in
19842 DEC Ada, see the DEC Ada Language Reference Manual and the
19843 relevant run-time reference manual.
19845 @node Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
19846 @section Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
19849 On OpenVMS Alpha systems, each Ada task (except a passive
19850 task) is implemented as a single stream of execution
19851 that is created and managed by the kernel. On these
19852 systems, DEC Ada tasking support is based on DECthreads,
19853 an implementation of the POSIX standard for threads.
19855 Although tasks are implemented as threads, all tasks in
19856 an Ada program are part of the same process. As a result,
19857 resources such as open files and virtual memory can be
19858 shared easily among tasks. Having all tasks in one process
19859 allows better integration with the programming environment
19860 (the shell and the debugger, for example).
19862 Also, on OpenVMS Alpha systems, DEC Ada tasks and foreign
19863 code that calls DECthreads routines can be used together.
19864 The interaction between Ada tasks and DECthreads routines
19865 can have some benefits. For example when on OpenVMS Alpha,
19866 DEC Ada can call C code that is already threaded.
19867 GNAT on OpenVMS Alpha uses the facilities of DECthreads,
19868 and Ada tasks are mapped to threads.
19871 * Assigning Task IDs::
19872 * Task IDs and Delays::
19873 * Task-Related Pragmas::
19874 * Scheduling and Task Priority::
19876 * External Interrupts::
19879 @node Assigning Task IDs
19880 @subsection Assigning Task IDs
19883 The DEC Ada Run-Time Library always assigns %TASK 1 to
19884 the environment task that executes the main program. On
19885 OpenVMS Alpha systems, %TASK 0 is often used for tasks
19886 that have been created but are not yet activated.
19888 On OpenVMS Alpha systems, task IDs are assigned at
19889 activation. On GNAT systems, task IDs are also assigned at
19890 task creation but do not have the same form or values as
19891 task ID values in DEC Ada. There is no null task, and the
19892 environment task does not have a specific task ID value.
19894 @node Task IDs and Delays
19895 @subsection Task IDs and Delays
19898 On OpenVMS Alpha systems, tasking delays are implemented
19899 using Timer System Services. The Task ID is used for the
19900 identification of the timer request (the REQIDT parameter).
19901 If Timers are used in the application take care not to use
19902 0 for the identification, because cancelling such a timer
19903 will cancel all timers and may lead to unpredictable results.
19905 @node Task-Related Pragmas
19906 @subsection Task-Related Pragmas
19909 Ada supplies the pragma TASK_STORAGE, which allows
19910 specification of the size of the guard area for a task
19911 stack. (The guard area forms an area of memory that has no
19912 read or write access and thus helps in the detection of
19913 stack overflow.) On OpenVMS Alpha systems, if the pragma
19914 TASK_STORAGE specifies a value of zero, a minimal guard
19915 area is created. In the absence of a pragma TASK_STORAGE, a default guard
19918 GNAT supplies the following task-related pragmas:
19923 This pragma appears within a task definition and
19924 applies to the task in which it appears. The argument
19925 must be of type SYSTEM.TASK_INFO.TASK_INFO_TYPE.
19929 GNAT implements pragma TASK_STORAGE in the same way as
19931 Both DEC Ada and GNAT supply the pragmas PASSIVE,
19932 SUPPRESS, and VOLATILE.
19934 @node Scheduling and Task Priority
19935 @subsection Scheduling and Task Priority
19938 DEC Ada implements the Ada language requirement that
19939 when two tasks are eligible for execution and they have
19940 different priorities, the lower priority task does not
19941 execute while the higher priority task is waiting. The DEC
19942 Ada Run-Time Library keeps a task running until either the
19943 task is suspended or a higher priority task becomes ready.
19945 On OpenVMS Alpha systems, the default strategy is round-
19946 robin with preemption. Tasks of equal priority take turns
19947 at the processor. A task is run for a certain period of
19948 time and then placed at the rear of the ready queue for
19949 its priority level.
19951 DEC Ada provides the implementation-defined pragma TIME_SLICE,
19952 which can be used to enable or disable round-robin
19953 scheduling of tasks with the same priority.
19954 See the relevant DEC Ada run-time reference manual for
19955 information on using the pragmas to control DEC Ada task
19958 GNAT follows the scheduling rules of Annex D (real-time
19959 Annex) of the Ada 95 Reference Manual. In general, this
19960 scheduling strategy is fully compatible with DEC Ada
19961 although it provides some additional constraints (as
19962 fully documented in Annex D).
19963 GNAT implements time slicing control in a manner compatible with
19964 DEC Ada 83, by means of the pragma Time_Slice, whose semantics are identical
19965 to the DEC Ada 83 pragma of the same name.
19966 Note that it is not possible to mix GNAT tasking and
19967 DEC Ada 83 tasking in the same program, since the two run times are
19970 @node The Task Stack
19971 @subsection The Task Stack
19974 In DEC Ada, a task stack is allocated each time a
19975 non passive task is activated. As soon as the task is
19976 terminated, the storage for the task stack is deallocated.
19977 If you specify a size of zero (bytes) with T'STORAGE_SIZE,
19978 a default stack size is used. Also, regardless of the size
19979 specified, some additional space is allocated for task
19980 management purposes. On OpenVMS Alpha systems, at least
19981 one page is allocated.
19983 GNAT handles task stacks in a similar manner. According to
19984 the Ada 95 rules, it provides the pragma STORAGE_SIZE as
19985 an alternative method for controlling the task stack size.
19986 The specification of the attribute T'STORAGE_SIZE is also
19987 supported in a manner compatible with DEC Ada.
19989 @node External Interrupts
19990 @subsection External Interrupts
19993 On DEC Ada, external interrupts can be associated with task entries.
19994 GNAT is compatible with DEC Ada in its handling of external interrupts.
19996 @node Pragmas and Pragma-Related Features
19997 @section Pragmas and Pragma-Related Features
20000 Both DEC Ada and GNAT supply all language-defined pragmas
20001 as specified by the Ada 83 standard. GNAT also supplies all
20002 language-defined pragmas specified in the Ada 95 Reference Manual.
20003 In addition, GNAT implements the implementation-defined pragmas
20009 @item COMMON_OBJECT
20011 @item COMPONENT_ALIGNMENT
20013 @item EXPORT_EXCEPTION
20015 @item EXPORT_FUNCTION
20017 @item EXPORT_OBJECT
20019 @item EXPORT_PROCEDURE
20021 @item EXPORT_VALUED_PROCEDURE
20023 @item FLOAT_REPRESENTATION
20027 @item IMPORT_EXCEPTION
20029 @item IMPORT_FUNCTION
20031 @item IMPORT_OBJECT
20033 @item IMPORT_PROCEDURE
20035 @item IMPORT_VALUED_PROCEDURE
20037 @item INLINE_GENERIC
20039 @item INTERFACE_NAME
20049 @item SHARE_GENERIC
20061 These pragmas are all fully implemented, with the exception of @code{Title},
20062 @code{Passive}, and @code{Share_Generic}, which are
20063 recognized, but which have no
20064 effect in GNAT. The effect of @code{Passive} may be obtained by the
20065 use of protected objects in Ada 95. In GNAT, all generics are inlined.
20067 Unlike DEC Ada, the GNAT 'EXPORT_@i{subprogram}' pragmas require
20068 a separate subprogram specification which must appear before the
20071 GNAT also supplies a number of implementation-defined pragmas as follows:
20073 @item C_PASS_BY_COPY
20075 @item EXTEND_SYSTEM
20077 @item SOURCE_FILE_NAME
20095 @item CPP_CONSTRUCTOR
20097 @item CPP_DESTRUCTOR
20107 @item LINKER_SECTION
20109 @item MACHINE_ATTRIBUTE
20113 @item PURE_FUNCTION
20115 @item SOURCE_REFERENCE
20119 @item UNCHECKED_UNION
20121 @item UNIMPLEMENTED_UNIT
20123 @item UNIVERSAL_DATA
20125 @item WEAK_EXTERNAL
20129 For full details on these GNAT implementation-defined pragmas, see
20130 the GNAT Reference Manual.
20133 * Restrictions on the Pragma INLINE::
20134 * Restrictions on the Pragma INTERFACE::
20135 * Restrictions on the Pragma SYSTEM_NAME::
20138 @node Restrictions on the Pragma INLINE
20139 @subsection Restrictions on the Pragma INLINE
20142 DEC Ada applies the following restrictions to the pragma INLINE:
20144 @item Parameters cannot be a task type.
20146 @item Function results cannot be task types, unconstrained
20147 array types, or unconstrained types with discriminants.
20149 @item Bodies cannot declare the following:
20151 @item Subprogram body or stub (imported subprogram is allowed)
20155 @item Generic declarations
20157 @item Instantiations
20161 @item Access types (types derived from access types allowed)
20163 @item Array or record types
20165 @item Dependent tasks
20167 @item Direct recursive calls of subprogram or containing
20168 subprogram, directly or via a renaming
20174 In GNAT, the only restriction on pragma INLINE is that the
20175 body must occur before the call if both are in the same
20176 unit, and the size must be appropriately small. There are
20177 no other specific restrictions which cause subprograms to
20178 be incapable of being inlined.
20180 @node Restrictions on the Pragma INTERFACE
20181 @subsection Restrictions on the Pragma INTERFACE
20184 The following lists and describes the restrictions on the
20185 pragma INTERFACE on DEC Ada and GNAT:
20187 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
20188 Default is the default on OpenVMS Alpha systems.
20190 @item Parameter passing: Language specifies default
20191 mechanisms but can be overridden with an EXPORT pragma.
20194 @item Ada: Use internal Ada rules.
20196 @item Bliss, C: Parameters must be mode @code{in}; cannot be
20197 record or task type. Result cannot be a string, an
20198 array, or a record.
20200 @item Fortran: Parameters cannot be a task. Result cannot
20201 be a string, an array, or a record.
20206 GNAT is entirely upwards compatible with DEC Ada, and in addition allows
20207 record parameters for all languages.
20209 @node Restrictions on the Pragma SYSTEM_NAME
20210 @subsection Restrictions on the Pragma SYSTEM_NAME
20213 For DEC Ada for OpenVMS Alpha, the enumeration literal
20214 for the type NAME is OPENVMS_AXP. In GNAT, the enumeration
20215 literal for the type NAME is SYSTEM_NAME_GNAT.
20217 @node Library of Predefined Units
20218 @section Library of Predefined Units
20221 A library of predefined units is provided as part of the
20222 DEC Ada and GNAT implementations. DEC Ada does not provide
20223 the package MACHINE_CODE but instead recommends importing
20226 The GNAT versions of the DEC Ada Run-Time Library (ADA$PREDEFINED:)
20227 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
20228 version. During GNAT installation, the DEC Ada Predefined
20229 Library units are copied into the GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
20230 (aka DECLIB) directory and patched to remove Ada 95 incompatibilities
20231 and to make them interoperable with GNAT, @pxref{Changes to DECLIB}
20234 The GNAT RTL is contained in
20235 the GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB] (aka ADALIB) directory and
20236 the default search path is set up to find DECLIB units in preference
20237 to ADALIB units with the same name (TEXT_IO, SEQUENTIAL_IO, and DIRECT_IO,
20240 However, it is possible to change the default so that the
20241 reverse is true, or even to mix them using child package
20242 notation. The DEC Ada 83 units are available as DEC.xxx where xxx
20243 is the package name, and the Ada units are available in the
20244 standard manner defined for Ada 95, that is to say as Ada.xxx. To
20245 change the default, set ADA_INCLUDE_PATH and ADA_OBJECTS_PATH
20246 appropriately. For example, to change the default to use the Ada95
20250 $ DEFINE ADA_INCLUDE_PATH GNU:[LIB.OPENVMS7_1.2_8_1.ADAINCLUDE],-
20251 GNU:[LIB.OPENVMS7_1.2_8_1.DECLIB]
20252 $ DEFINE ADA_OBJECTS_PATH GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB],-
20253 GNU:[LIB.OPENVMS7_1.2_8_1.DECLIB]
20257 * Changes to DECLIB::
20260 @node Changes to DECLIB
20261 @subsection Changes to DECLIB
20264 The changes made to the DEC Ada predefined library for GNAT and Ada 95
20265 compatibility are minor and include the following:
20268 @item Adjusting the location of pragmas and record representation
20269 clauses to obey Ada 95 rules
20271 @item Adding the proper notation to generic formal parameters
20272 that take unconstrained types in instantiation
20274 @item Adding pragma ELABORATE_BODY to package specifications
20275 that have package bodies not otherwise allowed
20277 @item Occurrences of the identifier @code{"PROTECTED"} are renamed to
20279 Currently these are found only in the STARLET package spec.
20283 None of the above changes is visible to users.
20289 On OpenVMS Alpha, DEC Ada provides the following strongly-typed bindings:
20292 @item Command Language Interpreter (CLI interface)
20294 @item DECtalk Run-Time Library (DTK interface)
20296 @item Librarian utility routines (LBR interface)
20298 @item General Purpose Run-Time Library (LIB interface)
20300 @item Math Run-Time Library (MTH interface)
20302 @item National Character Set Run-Time Library (NCS interface)
20304 @item Compiled Code Support Run-Time Library (OTS interface)
20306 @item Parallel Processing Run-Time Library (PPL interface)
20308 @item Screen Management Run-Time Library (SMG interface)
20310 @item Sort Run-Time Library (SOR interface)
20312 @item String Run-Time Library (STR interface)
20314 @item STARLET System Library
20317 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
20319 @item X Windows Toolkit (XT interface)
20321 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
20325 GNAT provides implementations of these DEC bindings in the DECLIB directory.
20327 The X/Motif bindings used to build DECLIB are whatever versions are in the
20328 DEC Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
20329 The build script will
20330 automatically add a pragma Linker_Options to packages @code{Xm}, @code{Xt},
20332 causing the default X/Motif sharable image libraries to be linked in. This
20333 is done via options files named @file{xm.opt}, @file{xt.opt}, and
20334 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
20336 It may be necessary to edit these options files to update or correct the
20337 library names if, for example, the newer X/Motif bindings from
20338 @file{ADA$EXAMPLES}
20339 had been (previous to installing GNAT) copied and renamed to supersede the
20340 default @file{ADA$PREDEFINED} versions.
20343 * Shared Libraries and Options Files::
20344 * Interfaces to C::
20347 @node Shared Libraries and Options Files
20348 @subsection Shared Libraries and Options Files
20351 When using the DEC Ada
20352 predefined X and Motif bindings, the linking with their sharable images is
20353 done automatically by @command{GNAT LINK}.
20354 When using other X and Motif bindings, you need
20355 to add the corresponding sharable images to the command line for
20356 @code{GNAT LINK}. When linking with shared libraries, or with
20357 @file{.OPT} files, you must
20358 also add them to the command line for @command{GNAT LINK}.
20360 A shared library to be used with GNAT is built in the same way as other
20361 libraries under VMS. The VMS Link command can be used in standard fashion.
20363 @node Interfaces to C
20364 @subsection Interfaces to C
20368 provides the following Ada types and operations:
20371 @item C types package (C_TYPES)
20373 @item C strings (C_TYPES.NULL_TERMINATED)
20375 @item Other_types (SHORT_INT)
20379 Interfacing to C with GNAT, one can use the above approach
20380 described for DEC Ada or the facilities of Annex B of
20381 the Ada 95 Reference Manual (packages INTERFACES.C,
20382 INTERFACES.C.STRINGS and INTERFACES.C.POINTERS). For more
20383 information, see the section ``Interfacing to C'' in the
20384 @cite{GNAT Reference Manual}.
20386 The @option{-gnatF} qualifier forces default and explicit
20387 @code{External_Name} parameters in pragmas Import and Export
20388 to be uppercased for compatibility with the default behavior
20389 of Compaq C. The qualifier has no effect on @code{Link_Name} parameters.
20391 @node Main Program Definition
20392 @section Main Program Definition
20395 The following section discusses differences in the
20396 definition of main programs on DEC Ada and GNAT.
20397 On DEC Ada, main programs are defined to meet the
20398 following conditions:
20400 @item Procedure with no formal parameters (returns 0 upon
20403 @item Procedure with no formal parameters (returns 42 when
20404 unhandled exceptions are raised)
20406 @item Function with no formal parameters whose returned value
20407 is of a discrete type
20409 @item Procedure with one OUT formal of a discrete type for
20410 which a specification of pragma EXPORT_VALUED_PROCEDURE is given.
20415 When declared with the pragma EXPORT_VALUED_PROCEDURE,
20416 a main function or main procedure returns a discrete
20417 value whose size is less than 64 bits (32 on VAX systems),
20418 the value is zero- or sign-extended as appropriate.
20419 On GNAT, main programs are defined as follows:
20421 @item Must be a non-generic, parameter-less subprogram that
20422 is either a procedure or function returning an Ada
20423 STANDARD.INTEGER (the predefined type)
20425 @item Cannot be a generic subprogram or an instantiation of a
20429 @node Implementation-Defined Attributes
20430 @section Implementation-Defined Attributes
20433 GNAT provides all DEC Ada implementation-defined
20436 @node Compiler and Run-Time Interfacing
20437 @section Compiler and Run-Time Interfacing
20440 DEC Ada provides the following ways to pass options to the linker
20443 @item /WAIT and /SUBMIT qualifiers
20445 @item /COMMAND qualifier
20447 @item /[NO]MAP qualifier
20449 @item /OUTPUT=file-spec
20451 @item /[NO]DEBUG and /[NO]TRACEBACK qualifiers
20455 To pass options to the linker, GNAT provides the following
20459 @item @option{/EXECUTABLE=exec-name}
20461 @item @option{/VERBOSE qualifier}
20463 @item @option{/[NO]DEBUG} and @option{/[NO]TRACEBACK} qualifiers
20467 For more information on these switches, see
20468 @ref{Switches for gnatlink}.
20469 In DEC Ada, the command-line switch @option{/OPTIMIZE} is available
20470 to control optimization. DEC Ada also supplies the
20473 @item @code{OPTIMIZE}
20475 @item @code{INLINE}
20477 @item @code{INLINE_GENERIC}
20479 @item @code{SUPPRESS_ALL}
20481 @item @code{PASSIVE}
20485 In GNAT, optimization is controlled strictly by command
20486 line parameters, as described in the corresponding section of this guide.
20487 The DIGITAL pragmas for control of optimization are
20488 recognized but ignored.
20490 Note that in GNAT, the default is optimization off, whereas in DEC Ada 83,
20491 the default is that optimization is turned on.
20493 @node Program Compilation and Library Management
20494 @section Program Compilation and Library Management
20497 DEC Ada and GNAT provide a comparable set of commands to
20498 build programs. DEC Ada also provides a program library,
20499 which is a concept that does not exist on GNAT. Instead,
20500 GNAT provides directories of sources that are compiled as
20503 The following table summarizes
20504 the DEC Ada commands and provides
20505 equivalent GNAT commands. In this table, some GNAT
20506 equivalents reflect the fact that GNAT does not use the
20507 concept of a program library. Instead, it uses a model
20508 in which collections of source and object files are used
20509 in a manner consistent with other languages like C and
20510 Fortran. Therefore, standard system file commands are used
20511 to manipulate these elements. Those GNAT commands are marked with
20513 Note that, unlike DEC Ada, none of the GNAT commands accepts wild cards.
20516 @multitable @columnfractions .35 .65
20518 @item @emph{DEC Ada Command}
20519 @tab @emph{GNAT Equivalent / Description}
20521 @item @command{ADA}
20522 @tab @command{GNAT COMPILE}@*
20523 Invokes the compiler to compile one or more Ada source files.
20525 @item @command{ACS ATTACH}@*
20526 @tab [No equivalent]@*
20527 Switches control of terminal from current process running the program
20530 @item @command{ACS CHECK}
20531 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
20532 Forms the execution closure of one
20533 or more compiled units and checks completeness and currency.
20535 @item @command{ACS COMPILE}
20536 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
20537 Forms the execution closure of one or
20538 more specified units, checks completeness and currency,
20539 identifies units that have revised source files, compiles same,
20540 and recompiles units that are or will become obsolete.
20541 Also completes incomplete generic instantiations.
20543 @item @command{ACS COPY FOREIGN}
20545 Copies a foreign object file into the program library as a
20548 @item @command{ACS COPY UNIT}
20550 Copies a compiled unit from one program library to another.
20552 @item @command{ACS CREATE LIBRARY}
20553 @tab Create /directory (*)@*
20554 Creates a program library.
20556 @item @command{ACS CREATE SUBLIBRARY}
20557 @tab Create /directory (*)@*
20558 Creates a program sublibrary.
20560 @item @command{ACS DELETE LIBRARY}
20562 Deletes a program library and its contents.
20564 @item @command{ACS DELETE SUBLIBRARY}
20566 Deletes a program sublibrary and its contents.
20568 @item @command{ACS DELETE UNIT}
20569 @tab Delete file (*)@*
20570 On OpenVMS systems, deletes one or more compiled units from
20571 the current program library.
20573 @item @command{ACS DIRECTORY}
20574 @tab Directory (*)@*
20575 On OpenVMS systems, lists units contained in the current
20578 @item @command{ACS ENTER FOREIGN}
20580 Allows the import of a foreign body as an Ada library
20581 specification and enters a reference to a pointer.
20583 @item @command{ACS ENTER UNIT}
20585 Enters a reference (pointer) from the current program library to
20586 a unit compiled into another program library.
20588 @item @command{ACS EXIT}
20589 @tab [No equivalent]@*
20590 Exits from the program library manager.
20592 @item @command{ACS EXPORT}
20594 Creates an object file that contains system-specific object code
20595 for one or more units. With GNAT, object files can simply be copied
20596 into the desired directory.
20598 @item @command{ACS EXTRACT SOURCE}
20600 Allows access to the copied source file for each Ada compilation unit
20602 @item @command{ACS HELP}
20603 @tab @command{HELP GNAT}@*
20604 Provides online help.
20606 @item @command{ACS LINK}
20607 @tab @command{GNAT LINK}@*
20608 Links an object file containing Ada units into an executable file.
20610 @item @command{ACS LOAD}
20612 Loads (partially compiles) Ada units into the program library.
20613 Allows loading a program from a collection of files into a library
20614 without knowing the relationship among units.
20616 @item @command{ACS MERGE}
20618 Merges into the current program library, one or more units from
20619 another library where they were modified.
20621 @item @command{ACS RECOMPILE}
20622 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
20623 Recompiles from external or copied source files any obsolete
20624 unit in the closure. Also, completes any incomplete generic
20627 @item @command{ACS REENTER}
20628 @tab @command{GNAT MAKE}@*
20629 Reenters current references to units compiled after last entered
20630 with the @command{ACS ENTER UNIT} command.
20632 @item @command{ACS SET LIBRARY}
20633 @tab Set default (*)@*
20634 Defines a program library to be the compilation context as well
20635 as the target library for compiler output and commands in general.
20637 @item @command{ACS SET PRAGMA}
20638 @tab Edit @file{gnat.adc} (*)@*
20639 Redefines specified values of the library characteristics
20640 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
20641 and @code{Float_Representation}.
20643 @item @command{ACS SET SOURCE}
20644 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
20645 Defines the source file search list for the @command{ACS COMPILE} command.
20647 @item @command{ACS SHOW LIBRARY}
20648 @tab Directory (*)@*
20649 Lists information about one or more program libraries.
20651 @item @command{ACS SHOW PROGRAM}
20652 @tab [No equivalent]@*
20653 Lists information about the execution closure of one or
20654 more units in the program library.
20656 @item @command{ACS SHOW SOURCE}
20657 @tab Show logical @code{ADA_INCLUDE_PATH}@*
20658 Shows the source file search used when compiling units.
20660 @item @command{ACS SHOW VERSION}
20661 @tab Compile with @option{VERBOSE} option
20662 Displays the version number of the compiler and program library
20665 @item @command{ACS SPAWN}
20666 @tab [No equivalent]@*
20667 Creates a subprocess of the current process (same as @command{DCL SPAWN}
20670 @item @command{ACS VERIFY}
20671 @tab [No equivalent]@*
20672 Performs a series of consistency checks on a program library to
20673 determine whether the library structure and library files are in
20680 @section Input-Output
20683 On OpenVMS Alpha systems, DEC Ada uses OpenVMS Record
20684 Management Services (RMS) to perform operations on
20688 DEC Ada and GNAT predefine an identical set of input-
20689 output packages. To make the use of the
20690 generic TEXT_IO operations more convenient, DEC Ada
20691 provides predefined library packages that instantiate the
20692 integer and floating-point operations for the predefined
20693 integer and floating-point types as shown in the following table.
20695 @multitable @columnfractions .45 .55
20696 @item @emph{Package Name} @tab Instantiation
20698 @item @code{INTEGER_TEXT_IO}
20699 @tab @code{INTEGER_IO(INTEGER)}
20701 @item @code{SHORT_INTEGER_TEXT_IO}
20702 @tab @code{INTEGER_IO(SHORT_INTEGER)}
20704 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
20705 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
20707 @item @code{FLOAT_TEXT_IO}
20708 @tab @code{FLOAT_IO(FLOAT)}
20710 @item @code{LONG_FLOAT_TEXT_IO}
20711 @tab @code{FLOAT_IO(LONG_FLOAT)}
20715 The DEC Ada predefined packages and their operations
20716 are implemented using OpenVMS Alpha files and input-
20717 output facilities. DEC Ada supports asynchronous input-
20718 output on OpenVMS Alpha. Familiarity with the following is
20721 @item RMS file organizations and access methods
20723 @item OpenVMS file specifications and directories
20725 @item OpenVMS File Definition Language (FDL)
20729 GNAT provides I/O facilities that are completely
20730 compatible with DEC Ada. The distribution includes the
20731 standard DEC Ada versions of all I/O packages, operating
20732 in a manner compatible with DEC Ada. In particular, the
20733 following packages are by default the DEC Ada (Ada 83)
20734 versions of these packages rather than the renamings
20735 suggested in annex J of the Ada 95 Reference Manual:
20737 @item @code{TEXT_IO}
20739 @item @code{SEQUENTIAL_IO}
20741 @item @code{DIRECT_IO}
20745 The use of the standard Ada 95 syntax for child packages (for
20746 example, @code{ADA.TEXT_IO}) retrieves the Ada 95 versions of these
20747 packages, as defined in the Ada 95 Reference Manual.
20748 GNAT provides DIGITAL-compatible predefined instantiations
20749 of the @code{TEXT_IO} packages, and also
20750 provides the standard predefined instantiations required
20751 by the Ada 95 Reference Manual.
20753 For further information on how GNAT interfaces to the file
20754 system or how I/O is implemented in programs written in
20755 mixed languages, see the chapter ``Implementation of the
20756 Standard I/O'' in the @cite{GNAT Reference Manual}.
20757 This chapter covers the following:
20759 @item Standard I/O packages
20761 @item @code{FORM} strings
20763 @item @code{ADA.DIRECT_IO}
20765 @item @code{ADA.SEQUENTIAL_IO}
20767 @item @code{ADA.TEXT_IO}
20769 @item Stream pointer positioning
20771 @item Reading and writing non-regular files
20773 @item @code{GET_IMMEDIATE}
20775 @item Treating @code{TEXT_IO} files as streams
20782 @node Implementation Limits
20783 @section Implementation Limits
20786 The following table lists implementation limits for DEC Ada
20788 @multitable @columnfractions .60 .20 .20
20790 @item @emph{Compilation Parameter}
20791 @tab @emph{DEC Ada}
20795 @item In a subprogram or entry declaration, maximum number of
20796 formal parameters that are of an unconstrained record type
20801 @item Maximum identifier length (number of characters)
20806 @item Maximum number of characters in a source line
20811 @item Maximum collection size (number of bytes)
20816 @item Maximum number of discriminants for a record type
20821 @item Maximum number of formal parameters in an entry or
20822 subprogram declaration
20827 @item Maximum number of dimensions in an array type
20832 @item Maximum number of library units and subunits in a compilation.
20837 @item Maximum number of library units and subunits in an execution.
20842 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
20843 or @code{PSECT_OBJECT}
20848 @item Maximum number of enumeration literals in an enumeration type
20854 @item Maximum number of lines in a source file
20859 @item Maximum number of bits in any object
20864 @item Maximum size of the static portion of a stack frame (approximate)
20875 @c **************************************
20876 @node Platform-Specific Information for the Run-Time Libraries
20877 @appendix Platform-Specific Information for the Run-Time Libraries
20878 @cindex Tasking and threads libraries
20879 @cindex Threads libraries and tasking
20880 @cindex Run-time libraries (platform-specific information)
20883 The GNAT run-time implementation
20884 may vary with respect to both the underlying threads library and
20885 the exception handling scheme.
20886 For threads support, one or more of the following are supplied:
20888 @item @b{native threads library}, a binding to the thread package from
20889 the underlying operating system
20891 @item @b{FSU threads library}, a binding to the Florida State University
20892 threads implementation, which complies fully with the requirements of Annex D
20894 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
20895 POSIX thread package
20899 For exception handling, either or both of two models are supplied:
20901 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
20902 Most programs should experience a substantial speed improvement by
20903 being compiled with a ZCX run-time.
20904 This is especially true for
20905 tasking applications or applications with many exception handlers.}
20906 @cindex Zero-Cost Exceptions
20907 @cindex ZCX (Zero-Cost Exceptions)
20908 which uses binder-generated tables that
20909 are interrogated at run time to locate a handler
20911 @item @b{setjmp / longjmp} (``SJLJ''),
20912 @cindex setjmp/longjmp Exception Model
20913 @cindex SJLJ (setjmp/longjmp Exception Model)
20914 which uses dynamically-set data to establish
20915 the set of handlers
20919 This appendix summarizes which combinations of threads and exception support
20920 are supplied on various GNAT platforms.
20921 It then shows how to select a particular library either
20922 permanently or temporarily,
20923 explains the properties of (and tradeoffs among) the various threads
20924 libraries, and provides some additional
20925 information about several specific platforms.
20928 * Summary of Run-Time Configurations::
20929 * Specifying a Run-Time Library::
20930 * Choosing between Native and FSU Threads Libraries::
20931 * Choosing the Scheduling Policy::
20932 * Solaris-Specific Considerations::
20933 * IRIX-Specific Considerations::
20934 * Linux-Specific Considerations::
20935 * AIX-Specific Considerations::
20939 @node Summary of Run-Time Configurations
20940 @section Summary of Run-Time Configurations
20943 @multitable @columnfractions .30 .70
20944 @item @b{alpha-openvms}
20945 @item @code{@ @ }@i{rts-native (default)}
20946 @item @code{@ @ @ @ }Tasking @tab native VMS threads
20947 @item @code{@ @ @ @ }Exceptions @tab ZCX
20950 @item @code{@ @ }@i{rts-native (default)}
20951 @item @code{@ @ @ @ }Tasking @tab native HP threads library
20952 @item @code{@ @ @ @ }Exceptions @tab ZCX
20954 @item @code{@ @ }@i{rts-sjlj}
20955 @item @code{@ @ @ @ }Tasking @tab native HP threads library
20956 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20958 @item @b{sparc-solaris} @tab
20959 @item @code{@ @ }@i{rts-native (default)}
20960 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
20961 @item @code{@ @ @ @ }Exceptions @tab ZCX
20963 @item @code{@ @ }@i{rts-fsu} @tab
20964 @item @code{@ @ @ @ }Tasking @tab FSU threads library
20965 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20967 @item @code{@ @ }@i{rts-m64}
20968 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
20969 @item @code{@ @ @ @ }Exceptions @tab ZCX
20970 @item @code{@ @ @ @ }Constraints @tab Use only when compiling in 64-bit mode;
20971 @item @tab Use only on Solaris 8 or later.
20972 @item @tab @xref{Building and Debugging 64-bit Applications}, for details.
20974 @item @code{@ @ }@i{rts-pthread}
20975 @item @code{@ @ @ @ }Tasking @tab pthreads library
20976 @item @code{@ @ @ @ }Exceptions @tab ZCX
20978 @item @code{@ @ }@i{rts-sjlj}
20979 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
20980 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20982 @item @b{x86-linux}
20983 @item @code{@ @ }@i{rts-native (default)}
20984 @item @code{@ @ @ @ }Tasking @tab LinuxThread library
20985 @item @code{@ @ @ @ }Exceptions @tab ZCX
20987 @item @code{@ @ }@i{rts-fsu}
20988 @item @code{@ @ @ @ }Tasking @tab FSU threads library
20989 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20991 @item @code{@ @ }@i{rts-sjlj}
20992 @item @code{@ @ @ @ }Tasking @tab LinuxThread library
20993 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20995 @item @b{x86-windows}
20996 @item @code{@ @ }@i{rts-native (default)}
20997 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
20998 @item @code{@ @ @ @ }Exceptions @tab SJLJ
21004 @node Specifying a Run-Time Library
21005 @section Specifying a Run-Time Library
21008 The @file{adainclude} subdirectory containing the sources of the GNAT
21009 run-time library, and the @file{adalib} subdirectory containing the
21010 @file{ALI} files and the static and/or shared GNAT library, are located
21011 in the gcc target-dependent area:
21014 target=$prefix/lib/gcc-lib/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
21018 As indicated above, on some platforms several run-time libraries are supplied.
21019 These libraries are installed in the target dependent area and
21020 contain a complete source and binary subdirectory. The detailed description
21021 below explains the differences between the different libraries in terms of
21022 their thread support.
21024 The default run-time library (when GNAT is installed) is @emph{rts-native}.
21025 This default run time is selected by the means of soft links.
21026 For example on x86-linux:
21032 +--- adainclude----------+
21034 +--- adalib-----------+ |
21036 +--- rts-native | |
21038 | +--- adainclude <---+
21040 | +--- adalib <----+
21057 If the @i{rts-fsu} library is to be selected on a permanent basis,
21058 these soft links can be modified with the following commands:
21062 $ rm -f adainclude adalib
21063 $ ln -s rts-fsu/adainclude adainclude
21064 $ ln -s rts-fsu/adalib adalib
21068 Alternatively, you can specify @file{rts-fsu/adainclude} in the file
21069 @file{$target/ada_source_path} and @file{rts-fsu/adalib} in
21070 @file{$target/ada_object_path}.
21072 Selecting another run-time library temporarily can be
21073 achieved by the regular mechanism for GNAT object or source path selection:
21077 Set the environment variables:
21080 $ ADA_INCLUDE_PATH=$target/rts-fsu/adainclude:$ADA_INCLUDE_PATH
21081 $ ADA_OBJECTS_PATH=$target/rts-fsu/adalib:$ADA_OBJECTS_PATH
21082 $ export ADA_INCLUDE_PATH ADA_OBJECTS_PATH
21086 Use @option{-aI$target/rts-fsu/adainclude}
21087 and @option{-aO$target/rts-fsu/adalib}
21088 on the @command{gnatmake} command line
21091 Use the switch @option{--RTS}; e.g., @option{--RTS=fsu}
21092 @cindex @option{--RTS} option
21096 You can similarly switch to @emph{rts-sjlj}.
21098 @node Choosing between Native and FSU Threads Libraries
21099 @section Choosing between Native and FSU Threads Libraries
21100 @cindex Native threads library
21101 @cindex FSU threads library
21104 Some GNAT implementations offer a choice between
21105 native threads and FSU threads.
21109 The @emph{native threads} library correspond to the standard system threads
21110 implementation (e.g. LinuxThreads on GNU/Linux,
21111 @cindex LinuxThreads library
21112 POSIX threads on AIX, or
21113 Solaris threads on Solaris). When this option is chosen, GNAT provides
21114 a full and accurate implementation of the core language tasking model
21115 as described in Chapter 9 of the Ada Reference Manual,
21116 but might not (and probably does not) implement
21117 the exact semantics as specified in @w{Annex D} (the Real-Time Systems Annex).
21118 @cindex Annex D (Real-Time Systems Annex) compliance
21119 @cindex Real-Time Systems Annex compliance
21120 Indeed, the reason that a choice of libraries is offered
21121 on a given target is because some of the
21122 ACATS tests for @w{Annex D} fail using the native threads library.
21123 As far as possible, this library is implemented
21124 in accordance with Ada semantics (e.g., modifying priorities as required
21125 to simulate ceiling locking),
21126 but there are often slight inaccuracies, most often in the area of
21127 absolutely respecting the priority rules on a single
21129 Moreover, it is not possible in general to define the exact behavior,
21130 because the native threads implementations
21131 are not well enough documented.
21133 On systems where the @code{SCHED_FIFO} POSIX scheduling policy is supported,
21134 @cindex POSIX scheduling policies
21135 @cindex @code{SCHED_FIFO} scheduling policy
21136 native threads will provide a behavior very close to the @w{Annex D}
21137 requirements (i.e., a run-till-blocked scheduler with fixed priorities), but
21138 on some systems (in particular GNU/Linux and Solaris), you need to have root
21139 privileges to use the @code{SCHED_FIFO} policy.
21142 The @emph{FSU threads} library provides a completely accurate implementation
21144 Thus, operating with this library, GNAT is 100% compliant with both the core
21145 and all @w{Annex D}
21147 The formal validations for implementations offering
21148 a choice of threads packages are always carried out using the FSU
21153 From these considerations, it might seem that FSU threads are the
21155 but that is by no means always the case. The FSU threads package
21156 operates with all Ada tasks appearing to the system to be a single
21157 thread. This is often considerably more efficient than operating
21158 with separate threads, since for example, switching between tasks
21159 can be accomplished without the (in some cases considerable)
21160 overhead of a context switch between two system threads. However,
21161 it means that you may well lose concurrency at the system
21162 level. Notably, some system operations (such as I/O) may block all
21163 tasks in a program and not just the calling task. More
21164 significantly, the FSU threads approach likely means you cannot
21165 take advantage of multiple processors, since for this you need
21166 separate threads (or even separate processes) to operate on
21167 different processors.
21169 For most programs, the native threads library is
21170 usually the better choice. Use the FSU threads if absolute
21171 conformance to @w{Annex D} is important for your application, or if
21172 you find that the improved efficiency of FSU threads is significant to you.
21174 Note also that to take full advantage of Florist and Glade, it is highly
21175 recommended that you use native threads.
21178 @node Choosing the Scheduling Policy
21179 @section Choosing the Scheduling Policy
21182 When using a POSIX threads implementation, you have a choice of several
21183 scheduling policies: @code{SCHED_FIFO},
21184 @cindex @code{SCHED_FIFO} scheduling policy
21186 @cindex @code{SCHED_RR} scheduling policy
21187 and @code{SCHED_OTHER}.
21188 @cindex @code{SCHED_OTHER} scheduling policy
21189 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
21190 or @code{SCHED_RR} requires special (e.g., root) privileges.
21192 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
21194 @cindex @code{SCHED_FIFO} scheduling policy
21195 you can use one of the following:
21199 @code{pragma Time_Slice (0.0)}
21200 @cindex pragma Time_Slice
21202 the corresponding binder option @option{-T0}
21203 @cindex @option{-T0} option
21205 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
21206 @cindex pragma Task_Dispatching_Policy
21210 To specify @code{SCHED_RR},
21211 @cindex @code{SCHED_RR} scheduling policy
21212 you should use @code{pragma Time_Slice} with a
21213 value greater than @code{0.0}, or else use the corresponding @option{-T}
21218 @node Solaris-Specific Considerations
21219 @section Solaris-Specific Considerations
21220 @cindex Solaris Sparc threads libraries
21223 This section addresses some topics related to the various threads libraries
21224 on Sparc Solaris and then provides some information on building and
21225 debugging 64-bit applications.
21228 * Solaris Threads Issues::
21229 * Building and Debugging 64-bit Applications::
21233 @node Solaris Threads Issues
21234 @subsection Solaris Threads Issues
21237 Starting with version 3.14, GNAT under Solaris comes with a new tasking
21238 run-time library based on POSIX threads --- @emph{rts-pthread}.
21239 @cindex rts-pthread threads library
21240 This run-time library has the advantage of being mostly shared across all
21241 POSIX-compliant thread implementations, and it also provides under
21242 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
21243 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
21244 and @code{PTHREAD_PRIO_PROTECT}
21245 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
21246 semantics that can be selected using the predefined pragma
21247 @code{Locking_Policy}
21248 @cindex pragma Locking_Policy (under rts-pthread)
21250 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
21251 @cindex @code{Inheritance_Locking} (under rts-pthread)
21252 @cindex @code{Ceiling_Locking} (under rts-pthread)
21254 As explained above, the native run-time library is based on the Solaris thread
21255 library (@code{libthread}) and is the default library.
21256 The FSU run-time library is based on the FSU threads.
21257 @cindex FSU threads library
21259 Starting with Solaris 2.5.1, when the Solaris threads library is used
21260 (this is the default), programs
21261 compiled with GNAT can automatically take advantage of
21262 and can thus execute on multiple processors.
21263 The user can alternatively specify a processor on which the program should run
21264 to emulate a single-processor system. The multiprocessor / uniprocessor choice
21266 setting the environment variable @code{GNAT_PROCESSOR}
21267 @cindex @code{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
21268 to one of the following:
21272 Use the default configuration (run the program on all
21273 available processors) - this is the same as having
21274 @code{GNAT_PROCESSOR} unset
21277 Let the run-time implementation choose one processor and run the program on
21280 @item 0 .. Last_Proc
21281 Run the program on the specified processor.
21282 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
21283 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
21287 @node Building and Debugging 64-bit Applications
21288 @subsection Building and Debugging 64-bit Applications
21291 In a 64-bit application, all the sources involved must be compiled with the
21292 @option{-m64} command-line option, and a specific GNAT library (compiled with
21293 this option) is required.
21294 The easiest way to build a 64bit application is to add
21295 @option{-m64 --RTS=m64} to the @command{gnatmake} flags.
21297 To debug these applications, dwarf-2 debug information is required, so you
21298 have to add @option{-gdwarf-2} to your gnatmake arguments.
21299 In addition, a special
21300 version of gdb, called @command{gdb64}, needs to be used.
21302 To summarize, building and debugging a ``Hello World'' program in 64-bit mode
21306 $ gnatmake -m64 -gdwarf-2 --RTS=m64 hello.adb
21312 @node IRIX-Specific Considerations
21313 @section IRIX-Specific Considerations
21314 @cindex IRIX thread library
21317 On SGI IRIX, the thread library depends on which compiler is used.
21318 The @emph{o32 ABI} compiler comes with a run-time library based on the
21319 user-level @code{athread}
21320 library. Thus kernel-level capabilities such as nonblocking system
21321 calls or time slicing can only be achieved reliably by specifying different
21322 @code{sprocs} via the pragma @code{Task_Info}
21323 @cindex pragma Task_Info (and IRIX threads)
21325 @code{System.Task_Info} package.
21326 @cindex @code{System.Task_Info} package (and IRIX threads)
21327 See the @cite{GNAT Reference Manual} for further information.
21329 The @emph{n32 ABI} compiler comes with a run-time library based on the
21330 kernel POSIX threads and thus does not have the limitations mentioned above.
21333 @node Linux-Specific Considerations
21334 @section Linux-Specific Considerations
21335 @cindex Linux threads libraries
21338 The default thread library under GNU/Linux has the following disadvantages
21339 compared to other native thread libraries:
21342 @item The size of the task's stack is limited to 2 megabytes.
21343 @item The signal model is not POSIX compliant, which means that to send a
21344 signal to the process, you need to send the signal to all threads,
21345 e.g. by using @code{killpg()}.
21348 @node AIX-Specific Considerations
21349 @section AIX-Specific Considerations
21350 @cindex AIX resolver library
21353 On AIX, the resolver library initializes some internal structure on
21354 the first call to @code{get*by*} functions, which are used to implement
21355 @code{GNAT.Sockets.Get_Host_By_Name} and
21356 @code{GNAT.Sockets.Get_Host_By_Addrss}.
21357 If such initialization occurs within an Ada task, and the stack size for
21358 the task is the default size, a stack overflow may occur.
21360 To avoid this overflow, the user should either ensure that the first call
21361 to @code{GNAT.Sockets.Get_Host_By_Name} or
21362 @code{GNAT.Sockets.Get_Host_By_Addrss}
21363 occurs in the environment task, or use @code{pragma Storage_Size} to
21364 specify a sufficiently large size for the stack of the task that contains
21367 @c *******************************
21368 @node Example of Binder Output File
21369 @appendix Example of Binder Output File
21372 This Appendix displays the source code for @command{gnatbind}'s output
21373 file generated for a simple ``Hello World'' program.
21374 Comments have been added for clarification purposes.
21377 @smallexample @c adanocomment
21381 -- The package is called Ada_Main unless this name is actually used
21382 -- as a unit name in the partition, in which case some other unique
21386 package ada_main is
21388 Elab_Final_Code : Integer;
21389 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
21391 -- The main program saves the parameters (argument count,
21392 -- argument values, environment pointer) in global variables
21393 -- for later access by other units including
21394 -- Ada.Command_Line.
21396 gnat_argc : Integer;
21397 gnat_argv : System.Address;
21398 gnat_envp : System.Address;
21400 -- The actual variables are stored in a library routine. This
21401 -- is useful for some shared library situations, where there
21402 -- are problems if variables are not in the library.
21404 pragma Import (C, gnat_argc);
21405 pragma Import (C, gnat_argv);
21406 pragma Import (C, gnat_envp);
21408 -- The exit status is similarly an external location
21410 gnat_exit_status : Integer;
21411 pragma Import (C, gnat_exit_status);
21413 GNAT_Version : constant String :=
21414 "GNAT Version: 3.15w (20010315)";
21415 pragma Export (C, GNAT_Version, "__gnat_version");
21417 -- This is the generated adafinal routine that performs
21418 -- finalization at the end of execution. In the case where
21419 -- Ada is the main program, this main program makes a call
21420 -- to adafinal at program termination.
21422 procedure adafinal;
21423 pragma Export (C, adafinal, "adafinal");
21425 -- This is the generated adainit routine that performs
21426 -- initialization at the start of execution. In the case
21427 -- where Ada is the main program, this main program makes
21428 -- a call to adainit at program startup.
21431 pragma Export (C, adainit, "adainit");
21433 -- This routine is called at the start of execution. It is
21434 -- a dummy routine that is used by the debugger to breakpoint
21435 -- at the start of execution.
21437 procedure Break_Start;
21438 pragma Import (C, Break_Start, "__gnat_break_start");
21440 -- This is the actual generated main program (it would be
21441 -- suppressed if the no main program switch were used). As
21442 -- required by standard system conventions, this program has
21443 -- the external name main.
21447 argv : System.Address;
21448 envp : System.Address)
21450 pragma Export (C, main, "main");
21452 -- The following set of constants give the version
21453 -- identification values for every unit in the bound
21454 -- partition. This identification is computed from all
21455 -- dependent semantic units, and corresponds to the
21456 -- string that would be returned by use of the
21457 -- Body_Version or Version attributes.
21459 type Version_32 is mod 2 ** 32;
21460 u00001 : constant Version_32 := 16#7880BEB3#;
21461 u00002 : constant Version_32 := 16#0D24CBD0#;
21462 u00003 : constant Version_32 := 16#3283DBEB#;
21463 u00004 : constant Version_32 := 16#2359F9ED#;
21464 u00005 : constant Version_32 := 16#664FB847#;
21465 u00006 : constant Version_32 := 16#68E803DF#;
21466 u00007 : constant Version_32 := 16#5572E604#;
21467 u00008 : constant Version_32 := 16#46B173D8#;
21468 u00009 : constant Version_32 := 16#156A40CF#;
21469 u00010 : constant Version_32 := 16#033DABE0#;
21470 u00011 : constant Version_32 := 16#6AB38FEA#;
21471 u00012 : constant Version_32 := 16#22B6217D#;
21472 u00013 : constant Version_32 := 16#68A22947#;
21473 u00014 : constant Version_32 := 16#18CC4A56#;
21474 u00015 : constant Version_32 := 16#08258E1B#;
21475 u00016 : constant Version_32 := 16#367D5222#;
21476 u00017 : constant Version_32 := 16#20C9ECA4#;
21477 u00018 : constant Version_32 := 16#50D32CB6#;
21478 u00019 : constant Version_32 := 16#39A8BB77#;
21479 u00020 : constant Version_32 := 16#5CF8FA2B#;
21480 u00021 : constant Version_32 := 16#2F1EB794#;
21481 u00022 : constant Version_32 := 16#31AB6444#;
21482 u00023 : constant Version_32 := 16#1574B6E9#;
21483 u00024 : constant Version_32 := 16#5109C189#;
21484 u00025 : constant Version_32 := 16#56D770CD#;
21485 u00026 : constant Version_32 := 16#02F9DE3D#;
21486 u00027 : constant Version_32 := 16#08AB6B2C#;
21487 u00028 : constant Version_32 := 16#3FA37670#;
21488 u00029 : constant Version_32 := 16#476457A0#;
21489 u00030 : constant Version_32 := 16#731E1B6E#;
21490 u00031 : constant Version_32 := 16#23C2E789#;
21491 u00032 : constant Version_32 := 16#0F1BD6A1#;
21492 u00033 : constant Version_32 := 16#7C25DE96#;
21493 u00034 : constant Version_32 := 16#39ADFFA2#;
21494 u00035 : constant Version_32 := 16#571DE3E7#;
21495 u00036 : constant Version_32 := 16#5EB646AB#;
21496 u00037 : constant Version_32 := 16#4249379B#;
21497 u00038 : constant Version_32 := 16#0357E00A#;
21498 u00039 : constant Version_32 := 16#3784FB72#;
21499 u00040 : constant Version_32 := 16#2E723019#;
21500 u00041 : constant Version_32 := 16#623358EA#;
21501 u00042 : constant Version_32 := 16#107F9465#;
21502 u00043 : constant Version_32 := 16#6843F68A#;
21503 u00044 : constant Version_32 := 16#63305874#;
21504 u00045 : constant Version_32 := 16#31E56CE1#;
21505 u00046 : constant Version_32 := 16#02917970#;
21506 u00047 : constant Version_32 := 16#6CCBA70E#;
21507 u00048 : constant Version_32 := 16#41CD4204#;
21508 u00049 : constant Version_32 := 16#572E3F58#;
21509 u00050 : constant Version_32 := 16#20729FF5#;
21510 u00051 : constant Version_32 := 16#1D4F93E8#;
21511 u00052 : constant Version_32 := 16#30B2EC3D#;
21512 u00053 : constant Version_32 := 16#34054F96#;
21513 u00054 : constant Version_32 := 16#5A199860#;
21514 u00055 : constant Version_32 := 16#0E7F912B#;
21515 u00056 : constant Version_32 := 16#5760634A#;
21516 u00057 : constant Version_32 := 16#5D851835#;
21518 -- The following Export pragmas export the version numbers
21519 -- with symbolic names ending in B (for body) or S
21520 -- (for spec) so that they can be located in a link. The
21521 -- information provided here is sufficient to track down
21522 -- the exact versions of units used in a given build.
21524 pragma Export (C, u00001, "helloB");
21525 pragma Export (C, u00002, "system__standard_libraryB");
21526 pragma Export (C, u00003, "system__standard_libraryS");
21527 pragma Export (C, u00004, "adaS");
21528 pragma Export (C, u00005, "ada__text_ioB");
21529 pragma Export (C, u00006, "ada__text_ioS");
21530 pragma Export (C, u00007, "ada__exceptionsB");
21531 pragma Export (C, u00008, "ada__exceptionsS");
21532 pragma Export (C, u00009, "gnatS");
21533 pragma Export (C, u00010, "gnat__heap_sort_aB");
21534 pragma Export (C, u00011, "gnat__heap_sort_aS");
21535 pragma Export (C, u00012, "systemS");
21536 pragma Export (C, u00013, "system__exception_tableB");
21537 pragma Export (C, u00014, "system__exception_tableS");
21538 pragma Export (C, u00015, "gnat__htableB");
21539 pragma Export (C, u00016, "gnat__htableS");
21540 pragma Export (C, u00017, "system__exceptionsS");
21541 pragma Export (C, u00018, "system__machine_state_operationsB");
21542 pragma Export (C, u00019, "system__machine_state_operationsS");
21543 pragma Export (C, u00020, "system__machine_codeS");
21544 pragma Export (C, u00021, "system__storage_elementsB");
21545 pragma Export (C, u00022, "system__storage_elementsS");
21546 pragma Export (C, u00023, "system__secondary_stackB");
21547 pragma Export (C, u00024, "system__secondary_stackS");
21548 pragma Export (C, u00025, "system__parametersB");
21549 pragma Export (C, u00026, "system__parametersS");
21550 pragma Export (C, u00027, "system__soft_linksB");
21551 pragma Export (C, u00028, "system__soft_linksS");
21552 pragma Export (C, u00029, "system__stack_checkingB");
21553 pragma Export (C, u00030, "system__stack_checkingS");
21554 pragma Export (C, u00031, "system__tracebackB");
21555 pragma Export (C, u00032, "system__tracebackS");
21556 pragma Export (C, u00033, "ada__streamsS");
21557 pragma Export (C, u00034, "ada__tagsB");
21558 pragma Export (C, u00035, "ada__tagsS");
21559 pragma Export (C, u00036, "system__string_opsB");
21560 pragma Export (C, u00037, "system__string_opsS");
21561 pragma Export (C, u00038, "interfacesS");
21562 pragma Export (C, u00039, "interfaces__c_streamsB");
21563 pragma Export (C, u00040, "interfaces__c_streamsS");
21564 pragma Export (C, u00041, "system__file_ioB");
21565 pragma Export (C, u00042, "system__file_ioS");
21566 pragma Export (C, u00043, "ada__finalizationB");
21567 pragma Export (C, u00044, "ada__finalizationS");
21568 pragma Export (C, u00045, "system__finalization_rootB");
21569 pragma Export (C, u00046, "system__finalization_rootS");
21570 pragma Export (C, u00047, "system__finalization_implementationB");
21571 pragma Export (C, u00048, "system__finalization_implementationS");
21572 pragma Export (C, u00049, "system__string_ops_concat_3B");
21573 pragma Export (C, u00050, "system__string_ops_concat_3S");
21574 pragma Export (C, u00051, "system__stream_attributesB");
21575 pragma Export (C, u00052, "system__stream_attributesS");
21576 pragma Export (C, u00053, "ada__io_exceptionsS");
21577 pragma Export (C, u00054, "system__unsigned_typesS");
21578 pragma Export (C, u00055, "system__file_control_blockS");
21579 pragma Export (C, u00056, "ada__finalization__list_controllerB");
21580 pragma Export (C, u00057, "ada__finalization__list_controllerS");
21582 -- BEGIN ELABORATION ORDER
21585 -- gnat.heap_sort_a (spec)
21586 -- gnat.heap_sort_a (body)
21587 -- gnat.htable (spec)
21588 -- gnat.htable (body)
21589 -- interfaces (spec)
21591 -- system.machine_code (spec)
21592 -- system.parameters (spec)
21593 -- system.parameters (body)
21594 -- interfaces.c_streams (spec)
21595 -- interfaces.c_streams (body)
21596 -- system.standard_library (spec)
21597 -- ada.exceptions (spec)
21598 -- system.exception_table (spec)
21599 -- system.exception_table (body)
21600 -- ada.io_exceptions (spec)
21601 -- system.exceptions (spec)
21602 -- system.storage_elements (spec)
21603 -- system.storage_elements (body)
21604 -- system.machine_state_operations (spec)
21605 -- system.machine_state_operations (body)
21606 -- system.secondary_stack (spec)
21607 -- system.stack_checking (spec)
21608 -- system.soft_links (spec)
21609 -- system.soft_links (body)
21610 -- system.stack_checking (body)
21611 -- system.secondary_stack (body)
21612 -- system.standard_library (body)
21613 -- system.string_ops (spec)
21614 -- system.string_ops (body)
21617 -- ada.streams (spec)
21618 -- system.finalization_root (spec)
21619 -- system.finalization_root (body)
21620 -- system.string_ops_concat_3 (spec)
21621 -- system.string_ops_concat_3 (body)
21622 -- system.traceback (spec)
21623 -- system.traceback (body)
21624 -- ada.exceptions (body)
21625 -- system.unsigned_types (spec)
21626 -- system.stream_attributes (spec)
21627 -- system.stream_attributes (body)
21628 -- system.finalization_implementation (spec)
21629 -- system.finalization_implementation (body)
21630 -- ada.finalization (spec)
21631 -- ada.finalization (body)
21632 -- ada.finalization.list_controller (spec)
21633 -- ada.finalization.list_controller (body)
21634 -- system.file_control_block (spec)
21635 -- system.file_io (spec)
21636 -- system.file_io (body)
21637 -- ada.text_io (spec)
21638 -- ada.text_io (body)
21640 -- END ELABORATION ORDER
21644 -- The following source file name pragmas allow the generated file
21645 -- names to be unique for different main programs. They are needed
21646 -- since the package name will always be Ada_Main.
21648 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
21649 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
21651 -- Generated package body for Ada_Main starts here
21653 package body ada_main is
21655 -- The actual finalization is performed by calling the
21656 -- library routine in System.Standard_Library.Adafinal
21658 procedure Do_Finalize;
21659 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
21666 procedure adainit is
21668 -- These booleans are set to True once the associated unit has
21669 -- been elaborated. It is also used to avoid elaborating the
21670 -- same unit twice.
21673 pragma Import (Ada, E040, "interfaces__c_streams_E");
21676 pragma Import (Ada, E008, "ada__exceptions_E");
21679 pragma Import (Ada, E014, "system__exception_table_E");
21682 pragma Import (Ada, E053, "ada__io_exceptions_E");
21685 pragma Import (Ada, E017, "system__exceptions_E");
21688 pragma Import (Ada, E024, "system__secondary_stack_E");
21691 pragma Import (Ada, E030, "system__stack_checking_E");
21694 pragma Import (Ada, E028, "system__soft_links_E");
21697 pragma Import (Ada, E035, "ada__tags_E");
21700 pragma Import (Ada, E033, "ada__streams_E");
21703 pragma Import (Ada, E046, "system__finalization_root_E");
21706 pragma Import (Ada, E048, "system__finalization_implementation_E");
21709 pragma Import (Ada, E044, "ada__finalization_E");
21712 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
21715 pragma Import (Ada, E055, "system__file_control_block_E");
21718 pragma Import (Ada, E042, "system__file_io_E");
21721 pragma Import (Ada, E006, "ada__text_io_E");
21723 -- Set_Globals is a library routine that stores away the
21724 -- value of the indicated set of global values in global
21725 -- variables within the library.
21727 procedure Set_Globals
21728 (Main_Priority : Integer;
21729 Time_Slice_Value : Integer;
21730 WC_Encoding : Character;
21731 Locking_Policy : Character;
21732 Queuing_Policy : Character;
21733 Task_Dispatching_Policy : Character;
21734 Adafinal : System.Address;
21735 Unreserve_All_Interrupts : Integer;
21736 Exception_Tracebacks : Integer);
21737 @findex __gnat_set_globals
21738 pragma Import (C, Set_Globals, "__gnat_set_globals");
21740 -- SDP_Table_Build is a library routine used to build the
21741 -- exception tables. See unit Ada.Exceptions in files
21742 -- a-except.ads/adb for full details of how zero cost
21743 -- exception handling works. This procedure, the call to
21744 -- it, and the two following tables are all omitted if the
21745 -- build is in longjmp/setjump exception mode.
21747 @findex SDP_Table_Build
21748 @findex Zero Cost Exceptions
21749 procedure SDP_Table_Build
21750 (SDP_Addresses : System.Address;
21751 SDP_Count : Natural;
21752 Elab_Addresses : System.Address;
21753 Elab_Addr_Count : Natural);
21754 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
21756 -- Table of Unit_Exception_Table addresses. Used for zero
21757 -- cost exception handling to build the top level table.
21759 ST : aliased constant array (1 .. 23) of System.Address := (
21761 Ada.Text_Io'UET_Address,
21762 Ada.Exceptions'UET_Address,
21763 Gnat.Heap_Sort_A'UET_Address,
21764 System.Exception_Table'UET_Address,
21765 System.Machine_State_Operations'UET_Address,
21766 System.Secondary_Stack'UET_Address,
21767 System.Parameters'UET_Address,
21768 System.Soft_Links'UET_Address,
21769 System.Stack_Checking'UET_Address,
21770 System.Traceback'UET_Address,
21771 Ada.Streams'UET_Address,
21772 Ada.Tags'UET_Address,
21773 System.String_Ops'UET_Address,
21774 Interfaces.C_Streams'UET_Address,
21775 System.File_Io'UET_Address,
21776 Ada.Finalization'UET_Address,
21777 System.Finalization_Root'UET_Address,
21778 System.Finalization_Implementation'UET_Address,
21779 System.String_Ops_Concat_3'UET_Address,
21780 System.Stream_Attributes'UET_Address,
21781 System.File_Control_Block'UET_Address,
21782 Ada.Finalization.List_Controller'UET_Address);
21784 -- Table of addresses of elaboration routines. Used for
21785 -- zero cost exception handling to make sure these
21786 -- addresses are included in the top level procedure
21789 EA : aliased constant array (1 .. 23) of System.Address := (
21790 adainit'Code_Address,
21791 Do_Finalize'Code_Address,
21792 Ada.Exceptions'Elab_Spec'Address,
21793 System.Exceptions'Elab_Spec'Address,
21794 Interfaces.C_Streams'Elab_Spec'Address,
21795 System.Exception_Table'Elab_Body'Address,
21796 Ada.Io_Exceptions'Elab_Spec'Address,
21797 System.Stack_Checking'Elab_Spec'Address,
21798 System.Soft_Links'Elab_Body'Address,
21799 System.Secondary_Stack'Elab_Body'Address,
21800 Ada.Tags'Elab_Spec'Address,
21801 Ada.Tags'Elab_Body'Address,
21802 Ada.Streams'Elab_Spec'Address,
21803 System.Finalization_Root'Elab_Spec'Address,
21804 Ada.Exceptions'Elab_Body'Address,
21805 System.Finalization_Implementation'Elab_Spec'Address,
21806 System.Finalization_Implementation'Elab_Body'Address,
21807 Ada.Finalization'Elab_Spec'Address,
21808 Ada.Finalization.List_Controller'Elab_Spec'Address,
21809 System.File_Control_Block'Elab_Spec'Address,
21810 System.File_Io'Elab_Body'Address,
21811 Ada.Text_Io'Elab_Spec'Address,
21812 Ada.Text_Io'Elab_Body'Address);
21814 -- Start of processing for adainit
21818 -- Call SDP_Table_Build to build the top level procedure
21819 -- table for zero cost exception handling (omitted in
21820 -- longjmp/setjump mode).
21822 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
21824 -- Call Set_Globals to record various information for
21825 -- this partition. The values are derived by the binder
21826 -- from information stored in the ali files by the compiler.
21828 @findex __gnat_set_globals
21830 (Main_Priority => -1,
21831 -- Priority of main program, -1 if no pragma Priority used
21833 Time_Slice_Value => -1,
21834 -- Time slice from Time_Slice pragma, -1 if none used
21836 WC_Encoding => 'b',
21837 -- Wide_Character encoding used, default is brackets
21839 Locking_Policy => ' ',
21840 -- Locking_Policy used, default of space means not
21841 -- specified, otherwise it is the first character of
21842 -- the policy name.
21844 Queuing_Policy => ' ',
21845 -- Queuing_Policy used, default of space means not
21846 -- specified, otherwise it is the first character of
21847 -- the policy name.
21849 Task_Dispatching_Policy => ' ',
21850 -- Task_Dispatching_Policy used, default of space means
21851 -- not specified, otherwise first character of the
21854 Adafinal => System.Null_Address,
21855 -- Address of Adafinal routine, not used anymore
21857 Unreserve_All_Interrupts => 0,
21858 -- Set true if pragma Unreserve_All_Interrupts was used
21860 Exception_Tracebacks => 0);
21861 -- Indicates if exception tracebacks are enabled
21863 Elab_Final_Code := 1;
21865 -- Now we have the elaboration calls for all units in the partition.
21866 -- The Elab_Spec and Elab_Body attributes generate references to the
21867 -- implicit elaboration procedures generated by the compiler for
21868 -- each unit that requires elaboration.
21871 Interfaces.C_Streams'Elab_Spec;
21875 Ada.Exceptions'Elab_Spec;
21878 System.Exception_Table'Elab_Body;
21882 Ada.Io_Exceptions'Elab_Spec;
21886 System.Exceptions'Elab_Spec;
21890 System.Stack_Checking'Elab_Spec;
21893 System.Soft_Links'Elab_Body;
21898 System.Secondary_Stack'Elab_Body;
21902 Ada.Tags'Elab_Spec;
21905 Ada.Tags'Elab_Body;
21909 Ada.Streams'Elab_Spec;
21913 System.Finalization_Root'Elab_Spec;
21917 Ada.Exceptions'Elab_Body;
21921 System.Finalization_Implementation'Elab_Spec;
21924 System.Finalization_Implementation'Elab_Body;
21928 Ada.Finalization'Elab_Spec;
21932 Ada.Finalization.List_Controller'Elab_Spec;
21936 System.File_Control_Block'Elab_Spec;
21940 System.File_Io'Elab_Body;
21944 Ada.Text_Io'Elab_Spec;
21947 Ada.Text_Io'Elab_Body;
21951 Elab_Final_Code := 0;
21959 procedure adafinal is
21968 -- main is actually a function, as in the ANSI C standard,
21969 -- defined to return the exit status. The three parameters
21970 -- are the argument count, argument values and environment
21973 @findex Main Program
21976 argv : System.Address;
21977 envp : System.Address)
21980 -- The initialize routine performs low level system
21981 -- initialization using a standard library routine which
21982 -- sets up signal handling and performs any other
21983 -- required setup. The routine can be found in file
21986 @findex __gnat_initialize
21987 procedure initialize;
21988 pragma Import (C, initialize, "__gnat_initialize");
21990 -- The finalize routine performs low level system
21991 -- finalization using a standard library routine. The
21992 -- routine is found in file a-final.c and in the standard
21993 -- distribution is a dummy routine that does nothing, so
21994 -- really this is a hook for special user finalization.
21996 @findex __gnat_finalize
21997 procedure finalize;
21998 pragma Import (C, finalize, "__gnat_finalize");
22000 -- We get to the main program of the partition by using
22001 -- pragma Import because if we try to with the unit and
22002 -- call it Ada style, then not only do we waste time
22003 -- recompiling it, but also, we don't really know the right
22004 -- switches (e.g. identifier character set) to be used
22007 procedure Ada_Main_Program;
22008 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
22010 -- Start of processing for main
22013 -- Save global variables
22019 -- Call low level system initialization
22023 -- Call our generated Ada initialization routine
22027 -- This is the point at which we want the debugger to get
22032 -- Now we call the main program of the partition
22036 -- Perform Ada finalization
22040 -- Perform low level system finalization
22044 -- Return the proper exit status
22045 return (gnat_exit_status);
22048 -- This section is entirely comments, so it has no effect on the
22049 -- compilation of the Ada_Main package. It provides the list of
22050 -- object files and linker options, as well as some standard
22051 -- libraries needed for the link. The gnatlink utility parses
22052 -- this b~hello.adb file to read these comment lines to generate
22053 -- the appropriate command line arguments for the call to the
22054 -- system linker. The BEGIN/END lines are used for sentinels for
22055 -- this parsing operation.
22057 -- The exact file names will of course depend on the environment,
22058 -- host/target and location of files on the host system.
22060 @findex Object file list
22061 -- BEGIN Object file/option list
22064 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
22065 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
22066 -- END Object file/option list
22072 The Ada code in the above example is exactly what is generated by the
22073 binder. We have added comments to more clearly indicate the function
22074 of each part of the generated @code{Ada_Main} package.
22076 The code is standard Ada in all respects, and can be processed by any
22077 tools that handle Ada. In particular, it is possible to use the debugger
22078 in Ada mode to debug the generated @code{Ada_Main} package. For example,
22079 suppose that for reasons that you do not understand, your program is crashing
22080 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
22081 you can place a breakpoint on the call:
22083 @smallexample @c ada
22084 Ada.Text_Io'Elab_Body;
22088 and trace the elaboration routine for this package to find out where
22089 the problem might be (more usually of course you would be debugging
22090 elaboration code in your own application).
22093 @node Elaboration Order Handling in GNAT
22094 @appendix Elaboration Order Handling in GNAT
22095 @cindex Order of elaboration
22096 @cindex Elaboration control
22099 * Elaboration Code in Ada 95::
22100 * Checking the Elaboration Order in Ada 95::
22101 * Controlling the Elaboration Order in Ada 95::
22102 * Controlling Elaboration in GNAT - Internal Calls::
22103 * Controlling Elaboration in GNAT - External Calls::
22104 * Default Behavior in GNAT - Ensuring Safety::
22105 * Treatment of Pragma Elaborate::
22106 * Elaboration Issues for Library Tasks::
22107 * Mixing Elaboration Models::
22108 * What to Do If the Default Elaboration Behavior Fails::
22109 * Elaboration for Access-to-Subprogram Values::
22110 * Summary of Procedures for Elaboration Control::
22111 * Other Elaboration Order Considerations::
22115 This chapter describes the handling of elaboration code in Ada 95 and
22116 in GNAT, and discusses how the order of elaboration of program units can
22117 be controlled in GNAT, either automatically or with explicit programming
22120 @node Elaboration Code in Ada 95
22121 @section Elaboration Code in Ada 95
22124 Ada 95 provides rather general mechanisms for executing code at elaboration
22125 time, that is to say before the main program starts executing. Such code arises
22129 @item Initializers for variables.
22130 Variables declared at the library level, in package specs or bodies, can
22131 require initialization that is performed at elaboration time, as in:
22132 @smallexample @c ada
22134 Sqrt_Half : Float := Sqrt (0.5);
22138 @item Package initialization code
22139 Code in a @code{BEGIN-END} section at the outer level of a package body is
22140 executed as part of the package body elaboration code.
22142 @item Library level task allocators
22143 Tasks that are declared using task allocators at the library level
22144 start executing immediately and hence can execute at elaboration time.
22148 Subprogram calls are possible in any of these contexts, which means that
22149 any arbitrary part of the program may be executed as part of the elaboration
22150 code. It is even possible to write a program which does all its work at
22151 elaboration time, with a null main program, although stylistically this
22152 would usually be considered an inappropriate way to structure
22155 An important concern arises in the context of elaboration code:
22156 we have to be sure that it is executed in an appropriate order. What we
22157 have is a series of elaboration code sections, potentially one section
22158 for each unit in the program. It is important that these execute
22159 in the correct order. Correctness here means that, taking the above
22160 example of the declaration of @code{Sqrt_Half},
22161 if some other piece of
22162 elaboration code references @code{Sqrt_Half},
22163 then it must run after the
22164 section of elaboration code that contains the declaration of
22167 There would never be any order of elaboration problem if we made a rule
22168 that whenever you @code{with} a unit, you must elaborate both the spec and body
22169 of that unit before elaborating the unit doing the @code{with}'ing:
22171 @smallexample @c ada
22175 package Unit_2 is ...
22181 would require that both the body and spec of @code{Unit_1} be elaborated
22182 before the spec of @code{Unit_2}. However, a rule like that would be far too
22183 restrictive. In particular, it would make it impossible to have routines
22184 in separate packages that were mutually recursive.
22186 You might think that a clever enough compiler could look at the actual
22187 elaboration code and determine an appropriate correct order of elaboration,
22188 but in the general case, this is not possible. Consider the following
22191 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
22193 the variable @code{Sqrt_1}, which is declared in the elaboration code
22194 of the body of @code{Unit_1}:
22196 @smallexample @c ada
22198 Sqrt_1 : Float := Sqrt (0.1);
22203 The elaboration code of the body of @code{Unit_1} also contains:
22205 @smallexample @c ada
22208 if expression_1 = 1 then
22209 Q := Unit_2.Func_2;
22216 @code{Unit_2} is exactly parallel,
22217 it has a procedure @code{Func_2} that references
22218 the variable @code{Sqrt_2}, which is declared in the elaboration code of
22219 the body @code{Unit_2}:
22221 @smallexample @c ada
22223 Sqrt_2 : Float := Sqrt (0.1);
22228 The elaboration code of the body of @code{Unit_2} also contains:
22230 @smallexample @c ada
22233 if expression_2 = 2 then
22234 Q := Unit_1.Func_1;
22241 Now the question is, which of the following orders of elaboration is
22266 If you carefully analyze the flow here, you will see that you cannot tell
22267 at compile time the answer to this question.
22268 If @code{expression_1} is not equal to 1,
22269 and @code{expression_2} is not equal to 2,
22270 then either order is acceptable, because neither of the function calls is
22271 executed. If both tests evaluate to true, then neither order is acceptable
22272 and in fact there is no correct order.
22274 If one of the two expressions is true, and the other is false, then one
22275 of the above orders is correct, and the other is incorrect. For example,
22276 if @code{expression_1} = 1 and @code{expression_2} /= 2,
22277 then the call to @code{Func_2}
22278 will occur, but not the call to @code{Func_1.}
22279 This means that it is essential
22280 to elaborate the body of @code{Unit_1} before
22281 the body of @code{Unit_2}, so the first
22282 order of elaboration is correct and the second is wrong.
22284 By making @code{expression_1} and @code{expression_2}
22285 depend on input data, or perhaps
22286 the time of day, we can make it impossible for the compiler or binder
22287 to figure out which of these expressions will be true, and hence it
22288 is impossible to guarantee a safe order of elaboration at run time.
22290 @node Checking the Elaboration Order in Ada 95
22291 @section Checking the Elaboration Order in Ada 95
22294 In some languages that involve the same kind of elaboration problems,
22295 e.g. Java and C++, the programmer is expected to worry about these
22296 ordering problems himself, and it is common to
22297 write a program in which an incorrect elaboration order gives
22298 surprising results, because it references variables before they
22300 Ada 95 is designed to be a safe language, and a programmer-beware approach is
22301 clearly not sufficient. Consequently, the language provides three lines
22305 @item Standard rules
22306 Some standard rules restrict the possible choice of elaboration
22307 order. In particular, if you @code{with} a unit, then its spec is always
22308 elaborated before the unit doing the @code{with}. Similarly, a parent
22309 spec is always elaborated before the child spec, and finally
22310 a spec is always elaborated before its corresponding body.
22312 @item Dynamic elaboration checks
22313 @cindex Elaboration checks
22314 @cindex Checks, elaboration
22315 Dynamic checks are made at run time, so that if some entity is accessed
22316 before it is elaborated (typically by means of a subprogram call)
22317 then the exception (@code{Program_Error}) is raised.
22319 @item Elaboration control
22320 Facilities are provided for the programmer to specify the desired order
22324 Let's look at these facilities in more detail. First, the rules for
22325 dynamic checking. One possible rule would be simply to say that the
22326 exception is raised if you access a variable which has not yet been
22327 elaborated. The trouble with this approach is that it could require
22328 expensive checks on every variable reference. Instead Ada 95 has two
22329 rules which are a little more restrictive, but easier to check, and
22333 @item Restrictions on calls
22334 A subprogram can only be called at elaboration time if its body
22335 has been elaborated. The rules for elaboration given above guarantee
22336 that the spec of the subprogram has been elaborated before the
22337 call, but not the body. If this rule is violated, then the
22338 exception @code{Program_Error} is raised.
22340 @item Restrictions on instantiations
22341 A generic unit can only be instantiated if the body of the generic
22342 unit has been elaborated. Again, the rules for elaboration given above
22343 guarantee that the spec of the generic unit has been elaborated
22344 before the instantiation, but not the body. If this rule is
22345 violated, then the exception @code{Program_Error} is raised.
22349 The idea is that if the body has been elaborated, then any variables
22350 it references must have been elaborated; by checking for the body being
22351 elaborated we guarantee that none of its references causes any
22352 trouble. As we noted above, this is a little too restrictive, because a
22353 subprogram that has no non-local references in its body may in fact be safe
22354 to call. However, it really would be unsafe to rely on this, because
22355 it would mean that the caller was aware of details of the implementation
22356 in the body. This goes against the basic tenets of Ada.
22358 A plausible implementation can be described as follows.
22359 A Boolean variable is associated with each subprogram
22360 and each generic unit. This variable is initialized to False, and is set to
22361 True at the point body is elaborated. Every call or instantiation checks the
22362 variable, and raises @code{Program_Error} if the variable is False.
22364 Note that one might think that it would be good enough to have one Boolean
22365 variable for each package, but that would not deal with cases of trying
22366 to call a body in the same package as the call
22367 that has not been elaborated yet.
22368 Of course a compiler may be able to do enough analysis to optimize away
22369 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
22370 does such optimizations, but still the easiest conceptual model is to
22371 think of there being one variable per subprogram.
22373 @node Controlling the Elaboration Order in Ada 95
22374 @section Controlling the Elaboration Order in Ada 95
22377 In the previous section we discussed the rules in Ada 95 which ensure
22378 that @code{Program_Error} is raised if an incorrect elaboration order is
22379 chosen. This prevents erroneous executions, but we need mechanisms to
22380 specify a correct execution and avoid the exception altogether.
22381 To achieve this, Ada 95 provides a number of features for controlling
22382 the order of elaboration. We discuss these features in this section.
22384 First, there are several ways of indicating to the compiler that a given
22385 unit has no elaboration problems:
22388 @item packages that do not require a body
22389 In Ada 95, a library package that does not require a body does not permit
22390 a body. This means that if we have a such a package, as in:
22392 @smallexample @c ada
22395 package Definitions is
22397 type m is new integer;
22399 type a is array (1 .. 10) of m;
22400 type b is array (1 .. 20) of m;
22408 A package that @code{with}'s @code{Definitions} may safely instantiate
22409 @code{Definitions.Subp} because the compiler can determine that there
22410 definitely is no package body to worry about in this case
22413 @cindex pragma Pure
22415 Places sufficient restrictions on a unit to guarantee that
22416 no call to any subprogram in the unit can result in an
22417 elaboration problem. This means that the compiler does not need
22418 to worry about the point of elaboration of such units, and in
22419 particular, does not need to check any calls to any subprograms
22422 @item pragma Preelaborate
22423 @findex Preelaborate
22424 @cindex pragma Preelaborate
22425 This pragma places slightly less stringent restrictions on a unit than
22427 but these restrictions are still sufficient to ensure that there
22428 are no elaboration problems with any calls to the unit.
22430 @item pragma Elaborate_Body
22431 @findex Elaborate_Body
22432 @cindex pragma Elaborate_Body
22433 This pragma requires that the body of a unit be elaborated immediately
22434 after its spec. Suppose a unit @code{A} has such a pragma,
22435 and unit @code{B} does
22436 a @code{with} of unit @code{A}. Recall that the standard rules require
22437 the spec of unit @code{A}
22438 to be elaborated before the @code{with}'ing unit; given the pragma in
22439 @code{A}, we also know that the body of @code{A}
22440 will be elaborated before @code{B}, so
22441 that calls to @code{A} are safe and do not need a check.
22446 unlike pragma @code{Pure} and pragma @code{Preelaborate},
22448 @code{Elaborate_Body} does not guarantee that the program is
22449 free of elaboration problems, because it may not be possible
22450 to satisfy the requested elaboration order.
22451 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
22453 marks @code{Unit_1} as @code{Elaborate_Body},
22454 and not @code{Unit_2,} then the order of
22455 elaboration will be:
22467 Now that means that the call to @code{Func_1} in @code{Unit_2}
22468 need not be checked,
22469 it must be safe. But the call to @code{Func_2} in
22470 @code{Unit_1} may still fail if
22471 @code{Expression_1} is equal to 1,
22472 and the programmer must still take
22473 responsibility for this not being the case.
22475 If all units carry a pragma @code{Elaborate_Body}, then all problems are
22476 eliminated, except for calls entirely within a body, which are
22477 in any case fully under programmer control. However, using the pragma
22478 everywhere is not always possible.
22479 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
22480 we marked both of them as having pragma @code{Elaborate_Body}, then
22481 clearly there would be no possible elaboration order.
22483 The above pragmas allow a server to guarantee safe use by clients, and
22484 clearly this is the preferable approach. Consequently a good rule in
22485 Ada 95 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
22486 and if this is not possible,
22487 mark them as @code{Elaborate_Body} if possible.
22488 As we have seen, there are situations where neither of these
22489 three pragmas can be used.
22490 So we also provide methods for clients to control the
22491 order of elaboration of the servers on which they depend:
22494 @item pragma Elaborate (unit)
22496 @cindex pragma Elaborate
22497 This pragma is placed in the context clause, after a @code{with} clause,
22498 and it requires that the body of the named unit be elaborated before
22499 the unit in which the pragma occurs. The idea is to use this pragma
22500 if the current unit calls at elaboration time, directly or indirectly,
22501 some subprogram in the named unit.
22503 @item pragma Elaborate_All (unit)
22504 @findex Elaborate_All
22505 @cindex pragma Elaborate_All
22506 This is a stronger version of the Elaborate pragma. Consider the
22510 Unit A @code{with}'s unit B and calls B.Func in elab code
22511 Unit B @code{with}'s unit C, and B.Func calls C.Func
22515 Now if we put a pragma @code{Elaborate (B)}
22516 in unit @code{A}, this ensures that the
22517 body of @code{B} is elaborated before the call, but not the
22518 body of @code{C}, so
22519 the call to @code{C.Func} could still cause @code{Program_Error} to
22522 The effect of a pragma @code{Elaborate_All} is stronger, it requires
22523 not only that the body of the named unit be elaborated before the
22524 unit doing the @code{with}, but also the bodies of all units that the
22525 named unit uses, following @code{with} links transitively. For example,
22526 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
22528 not only that the body of @code{B} be elaborated before @code{A},
22530 body of @code{C}, because @code{B} @code{with}'s @code{C}.
22534 We are now in a position to give a usage rule in Ada 95 for avoiding
22535 elaboration problems, at least if dynamic dispatching and access to
22536 subprogram values are not used. We will handle these cases separately
22539 The rule is simple. If a unit has elaboration code that can directly or
22540 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
22541 a generic unit in a @code{with}'ed unit,
22542 then if the @code{with}'ed unit does not have
22543 pragma @code{Pure} or @code{Preelaborate}, then the client should have
22544 a pragma @code{Elaborate_All}
22545 for the @code{with}'ed unit. By following this rule a client is
22546 assured that calls can be made without risk of an exception.
22547 If this rule is not followed, then a program may be in one of four
22551 @item No order exists
22552 No order of elaboration exists which follows the rules, taking into
22553 account any @code{Elaborate}, @code{Elaborate_All},
22554 or @code{Elaborate_Body} pragmas. In
22555 this case, an Ada 95 compiler must diagnose the situation at bind
22556 time, and refuse to build an executable program.
22558 @item One or more orders exist, all incorrect
22559 One or more acceptable elaboration orders exists, and all of them
22560 generate an elaboration order problem. In this case, the binder
22561 can build an executable program, but @code{Program_Error} will be raised
22562 when the program is run.
22564 @item Several orders exist, some right, some incorrect
22565 One or more acceptable elaboration orders exists, and some of them
22566 work, and some do not. The programmer has not controlled
22567 the order of elaboration, so the binder may or may not pick one of
22568 the correct orders, and the program may or may not raise an
22569 exception when it is run. This is the worst case, because it means
22570 that the program may fail when moved to another compiler, or even
22571 another version of the same compiler.
22573 @item One or more orders exists, all correct
22574 One ore more acceptable elaboration orders exist, and all of them
22575 work. In this case the program runs successfully. This state of
22576 affairs can be guaranteed by following the rule we gave above, but
22577 may be true even if the rule is not followed.
22581 Note that one additional advantage of following our Elaborate_All rule
22582 is that the program continues to stay in the ideal (all orders OK) state
22583 even if maintenance
22584 changes some bodies of some subprograms. Conversely, if a program that does
22585 not follow this rule happens to be safe at some point, this state of affairs
22586 may deteriorate silently as a result of maintenance changes.
22588 You may have noticed that the above discussion did not mention
22589 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
22590 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
22591 code in the body makes calls to some other unit, so it is still necessary
22592 to use @code{Elaborate_All} on such units.
22594 @node Controlling Elaboration in GNAT - Internal Calls
22595 @section Controlling Elaboration in GNAT - Internal Calls
22598 In the case of internal calls, i.e. calls within a single package, the
22599 programmer has full control over the order of elaboration, and it is up
22600 to the programmer to elaborate declarations in an appropriate order. For
22603 @smallexample @c ada
22606 function One return Float;
22610 function One return Float is
22619 will obviously raise @code{Program_Error} at run time, because function
22620 One will be called before its body is elaborated. In this case GNAT will
22621 generate a warning that the call will raise @code{Program_Error}:
22627 2. function One return Float;
22629 4. Q : Float := One;
22631 >>> warning: cannot call "One" before body is elaborated
22632 >>> warning: Program_Error will be raised at run time
22635 6. function One return Float is
22648 Note that in this particular case, it is likely that the call is safe, because
22649 the function @code{One} does not access any global variables.
22650 Nevertheless in Ada 95, we do not want the validity of the check to depend on
22651 the contents of the body (think about the separate compilation case), so this
22652 is still wrong, as we discussed in the previous sections.
22654 The error is easily corrected by rearranging the declarations so that the
22655 body of One appears before the declaration containing the call
22656 (note that in Ada 95,
22657 declarations can appear in any order, so there is no restriction that
22658 would prevent this reordering, and if we write:
22660 @smallexample @c ada
22663 function One return Float;
22665 function One return Float is
22676 then all is well, no warning is generated, and no
22677 @code{Program_Error} exception
22679 Things are more complicated when a chain of subprograms is executed:
22681 @smallexample @c ada
22684 function A return Integer;
22685 function B return Integer;
22686 function C return Integer;
22688 function B return Integer is begin return A; end;
22689 function C return Integer is begin return B; end;
22693 function A return Integer is begin return 1; end;
22699 Now the call to @code{C}
22700 at elaboration time in the declaration of @code{X} is correct, because
22701 the body of @code{C} is already elaborated,
22702 and the call to @code{B} within the body of
22703 @code{C} is correct, but the call
22704 to @code{A} within the body of @code{B} is incorrect, because the body
22705 of @code{A} has not been elaborated, so @code{Program_Error}
22706 will be raised on the call to @code{A}.
22707 In this case GNAT will generate a
22708 warning that @code{Program_Error} may be
22709 raised at the point of the call. Let's look at the warning:
22715 2. function A return Integer;
22716 3. function B return Integer;
22717 4. function C return Integer;
22719 6. function B return Integer is begin return A; end;
22721 >>> warning: call to "A" before body is elaborated may
22722 raise Program_Error
22723 >>> warning: "B" called at line 7
22724 >>> warning: "C" called at line 9
22726 7. function C return Integer is begin return B; end;
22728 9. X : Integer := C;
22730 11. function A return Integer is begin return 1; end;
22740 Note that the message here says ``may raise'', instead of the direct case,
22741 where the message says ``will be raised''. That's because whether
22743 actually called depends in general on run-time flow of control.
22744 For example, if the body of @code{B} said
22746 @smallexample @c ada
22749 function B return Integer is
22751 if some-condition-depending-on-input-data then
22762 then we could not know until run time whether the incorrect call to A would
22763 actually occur, so @code{Program_Error} might
22764 or might not be raised. It is possible for a compiler to
22765 do a better job of analyzing bodies, to
22766 determine whether or not @code{Program_Error}
22767 might be raised, but it certainly
22768 couldn't do a perfect job (that would require solving the halting problem
22769 and is provably impossible), and because this is a warning anyway, it does
22770 not seem worth the effort to do the analysis. Cases in which it
22771 would be relevant are rare.
22773 In practice, warnings of either of the forms given
22774 above will usually correspond to
22775 real errors, and should be examined carefully and eliminated.
22776 In the rare case where a warning is bogus, it can be suppressed by any of
22777 the following methods:
22781 Compile with the @option{-gnatws} switch set
22784 Suppress @code{Elaboration_Check} for the called subprogram
22787 Use pragma @code{Warnings_Off} to turn warnings off for the call
22791 For the internal elaboration check case,
22792 GNAT by default generates the
22793 necessary run-time checks to ensure
22794 that @code{Program_Error} is raised if any
22795 call fails an elaboration check. Of course this can only happen if a
22796 warning has been issued as described above. The use of pragma
22797 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
22798 some of these checks, meaning that it may be possible (but is not
22799 guaranteed) for a program to be able to call a subprogram whose body
22800 is not yet elaborated, without raising a @code{Program_Error} exception.
22802 @node Controlling Elaboration in GNAT - External Calls
22803 @section Controlling Elaboration in GNAT - External Calls
22806 The previous section discussed the case in which the execution of a
22807 particular thread of elaboration code occurred entirely within a
22808 single unit. This is the easy case to handle, because a programmer
22809 has direct and total control over the order of elaboration, and
22810 furthermore, checks need only be generated in cases which are rare
22811 and which the compiler can easily detect.
22812 The situation is more complex when separate compilation is taken into account.
22813 Consider the following:
22815 @smallexample @c ada
22819 function Sqrt (Arg : Float) return Float;
22822 package body Math is
22823 function Sqrt (Arg : Float) return Float is
22832 X : Float := Math.Sqrt (0.5);
22845 where @code{Main} is the main program. When this program is executed, the
22846 elaboration code must first be executed, and one of the jobs of the
22847 binder is to determine the order in which the units of a program are
22848 to be elaborated. In this case we have four units: the spec and body
22850 the spec of @code{Stuff} and the body of @code{Main}).
22851 In what order should the four separate sections of elaboration code
22854 There are some restrictions in the order of elaboration that the binder
22855 can choose. In particular, if unit U has a @code{with}
22856 for a package @code{X}, then you
22857 are assured that the spec of @code{X}
22858 is elaborated before U , but you are
22859 not assured that the body of @code{X}
22860 is elaborated before U.
22861 This means that in the above case, the binder is allowed to choose the
22872 but that's not good, because now the call to @code{Math.Sqrt}
22873 that happens during
22874 the elaboration of the @code{Stuff}
22875 spec happens before the body of @code{Math.Sqrt} is
22876 elaborated, and hence causes @code{Program_Error} exception to be raised.
22877 At first glance, one might say that the binder is misbehaving, because
22878 obviously you want to elaborate the body of something you @code{with}
22880 that is not a general rule that can be followed in all cases. Consider
22882 @smallexample @c ada
22890 package body Y is ...
22893 package body X is ...
22899 This is a common arrangement, and, apart from the order of elaboration
22900 problems that might arise in connection with elaboration code, this works fine.
22901 A rule that says that you must first elaborate the body of anything you
22902 @code{with} cannot work in this case:
22903 the body of @code{X} @code{with}'s @code{Y},
22904 which means you would have to
22905 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
22907 you have to elaborate the body of @code{X} first, but ... and we have a
22908 loop that cannot be broken.
22910 It is true that the binder can in many cases guess an order of elaboration
22911 that is unlikely to cause a @code{Program_Error}
22912 exception to be raised, and it tries to do so (in the
22913 above example of @code{Math/Stuff/Spec}, the GNAT binder will
22915 elaborate the body of @code{Math} right after its spec, so all will be well).
22917 However, a program that blindly relies on the binder to be helpful can
22918 get into trouble, as we discussed in the previous sections, so
22920 provides a number of facilities for assisting the programmer in
22921 developing programs that are robust with respect to elaboration order.
22923 @node Default Behavior in GNAT - Ensuring Safety
22924 @section Default Behavior in GNAT - Ensuring Safety
22927 The default behavior in GNAT ensures elaboration safety. In its
22928 default mode GNAT implements the
22929 rule we previously described as the right approach. Let's restate it:
22933 @emph{If a unit has elaboration code that can directly or indirectly make a
22934 call to a subprogram in a @code{with}'ed unit, or instantiate a generic unit
22935 in a @code{with}'ed unit, then if the @code{with}'ed unit
22936 does not have pragma @code{Pure} or
22937 @code{Preelaborate}, then the client should have an
22938 @code{Elaborate_All} for the @code{with}'ed unit.}
22942 By following this rule a client is assured that calls and instantiations
22943 can be made without risk of an exception.
22945 In this mode GNAT traces all calls that are potentially made from
22946 elaboration code, and puts in any missing implicit @code{Elaborate_All}
22948 The advantage of this approach is that no elaboration problems
22949 are possible if the binder can find an elaboration order that is
22950 consistent with these implicit @code{Elaborate_All} pragmas. The
22951 disadvantage of this approach is that no such order may exist.
22953 If the binder does not generate any diagnostics, then it means that it
22954 has found an elaboration order that is guaranteed to be safe. However,
22955 the binder may still be relying on implicitly generated
22956 @code{Elaborate_All} pragmas so portability to other compilers than
22957 GNAT is not guaranteed.
22959 If it is important to guarantee portability, then the compilations should
22962 (warn on elaboration problems) switch. This will cause warning messages
22963 to be generated indicating the missing @code{Elaborate_All} pragmas.
22964 Consider the following source program:
22966 @smallexample @c ada
22971 m : integer := k.r;
22978 where it is clear that there
22979 should be a pragma @code{Elaborate_All}
22980 for unit @code{k}. An implicit pragma will be generated, and it is
22981 likely that the binder will be able to honor it. However, if you want
22982 to port this program to some other Ada compiler than GNAT.
22983 it is safer to include the pragma explicitly in the source. If this
22984 unit is compiled with the
22986 switch, then the compiler outputs a warning:
22993 3. m : integer := k.r;
22995 >>> warning: call to "r" may raise Program_Error
22996 >>> warning: missing pragma Elaborate_All for "k"
23004 and these warnings can be used as a guide for supplying manually
23005 the missing pragmas. It is usually a bad idea to use this warning
23006 option during development. That's because it will warn you when
23007 you need to put in a pragma, but cannot warn you when it is time
23008 to take it out. So the use of pragma Elaborate_All may lead to
23009 unnecessary dependencies and even false circularities.
23011 This default mode is more restrictive than the Ada Reference
23012 Manual, and it is possible to construct programs which will compile
23013 using the dynamic model described there, but will run into a
23014 circularity using the safer static model we have described.
23016 Of course any Ada compiler must be able to operate in a mode
23017 consistent with the requirements of the Ada Reference Manual,
23018 and in particular must have the capability of implementing the
23019 standard dynamic model of elaboration with run-time checks.
23021 In GNAT, this standard mode can be achieved either by the use of
23022 the @option{-gnatE} switch on the compiler (@code{gcc} or @code{gnatmake})
23023 command, or by the use of the configuration pragma:
23025 @smallexample @c ada
23026 pragma Elaboration_Checks (RM);
23030 Either approach will cause the unit affected to be compiled using the
23031 standard dynamic run-time elaboration checks described in the Ada
23032 Reference Manual. The static model is generally preferable, since it
23033 is clearly safer to rely on compile and link time checks rather than
23034 run-time checks. However, in the case of legacy code, it may be
23035 difficult to meet the requirements of the static model. This
23036 issue is further discussed in
23037 @ref{What to Do If the Default Elaboration Behavior Fails}.
23039 Note that the static model provides a strict subset of the allowed
23040 behavior and programs of the Ada Reference Manual, so if you do
23041 adhere to the static model and no circularities exist,
23042 then you are assured that your program will
23043 work using the dynamic model, providing that you remove any
23044 pragma Elaborate statements from the source.
23046 @node Treatment of Pragma Elaborate
23047 @section Treatment of Pragma Elaborate
23048 @cindex Pragma Elaborate
23051 The use of @code{pragma Elaborate}
23052 should generally be avoided in Ada 95 programs.
23053 The reason for this is that there is no guarantee that transitive calls
23054 will be properly handled. Indeed at one point, this pragma was placed
23055 in Annex J (Obsolescent Features), on the grounds that it is never useful.
23057 Now that's a bit restrictive. In practice, the case in which
23058 @code{pragma Elaborate} is useful is when the caller knows that there
23059 are no transitive calls, or that the called unit contains all necessary
23060 transitive @code{pragma Elaborate} statements, and legacy code often
23061 contains such uses.
23063 Strictly speaking the static mode in GNAT should ignore such pragmas,
23064 since there is no assurance at compile time that the necessary safety
23065 conditions are met. In practice, this would cause GNAT to be incompatible
23066 with correctly written Ada 83 code that had all necessary
23067 @code{pragma Elaborate} statements in place. Consequently, we made the
23068 decision that GNAT in its default mode will believe that if it encounters
23069 a @code{pragma Elaborate} then the programmer knows what they are doing,
23070 and it will trust that no elaboration errors can occur.
23072 The result of this decision is two-fold. First to be safe using the
23073 static mode, you should remove all @code{pragma Elaborate} statements.
23074 Second, when fixing circularities in existing code, you can selectively
23075 use @code{pragma Elaborate} statements to convince the static mode of
23076 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
23079 When using the static mode with @option{-gnatwl}, any use of
23080 @code{pragma Elaborate} will generate a warning about possible
23083 @node Elaboration Issues for Library Tasks
23084 @section Elaboration Issues for Library Tasks
23085 @cindex Library tasks, elaboration issues
23086 @cindex Elaboration of library tasks
23089 In this section we examine special elaboration issues that arise for
23090 programs that declare library level tasks.
23092 Generally the model of execution of an Ada program is that all units are
23093 elaborated, and then execution of the program starts. However, the
23094 declaration of library tasks definitely does not fit this model. The
23095 reason for this is that library tasks start as soon as they are declared
23096 (more precisely, as soon as the statement part of the enclosing package
23097 body is reached), that is to say before elaboration
23098 of the program is complete. This means that if such a task calls a
23099 subprogram, or an entry in another task, the callee may or may not be
23100 elaborated yet, and in the standard
23101 Reference Manual model of dynamic elaboration checks, you can even
23102 get timing dependent Program_Error exceptions, since there can be
23103 a race between the elaboration code and the task code.
23105 The static model of elaboration in GNAT seeks to avoid all such
23106 dynamic behavior, by being conservative, and the conservative
23107 approach in this particular case is to assume that all the code
23108 in a task body is potentially executed at elaboration time if
23109 a task is declared at the library level.
23111 This can definitely result in unexpected circularities. Consider
23112 the following example
23114 @smallexample @c ada
23120 type My_Int is new Integer;
23122 function Ident (M : My_Int) return My_Int;
23126 package body Decls is
23127 task body Lib_Task is
23133 function Ident (M : My_Int) return My_Int is
23141 procedure Put_Val (Arg : Decls.My_Int);
23145 package body Utils is
23146 procedure Put_Val (Arg : Decls.My_Int) is
23148 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
23155 Decls.Lib_Task.Start;
23160 If the above example is compiled in the default static elaboration
23161 mode, then a circularity occurs. The circularity comes from the call
23162 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
23163 this call occurs in elaboration code, we need an implicit pragma
23164 @code{Elaborate_All} for @code{Utils}. This means that not only must
23165 the spec and body of @code{Utils} be elaborated before the body
23166 of @code{Decls}, but also the spec and body of any unit that is
23167 @code{with'ed} by the body of @code{Utils} must also be elaborated before
23168 the body of @code{Decls}. This is the transitive implication of
23169 pragma @code{Elaborate_All} and it makes sense, because in general
23170 the body of @code{Put_Val} might have a call to something in a
23171 @code{with'ed} unit.
23173 In this case, the body of Utils (actually its spec) @code{with's}
23174 @code{Decls}. Unfortunately this means that the body of @code{Decls}
23175 must be elaborated before itself, in case there is a call from the
23176 body of @code{Utils}.
23178 Here is the exact chain of events we are worrying about:
23182 In the body of @code{Decls} a call is made from within the body of a library
23183 task to a subprogram in the package @code{Utils}. Since this call may
23184 occur at elaboration time (given that the task is activated at elaboration
23185 time), we have to assume the worst, i.e. that the
23186 call does happen at elaboration time.
23189 This means that the body and spec of @code{Util} must be elaborated before
23190 the body of @code{Decls} so that this call does not cause an access before
23194 Within the body of @code{Util}, specifically within the body of
23195 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
23199 One such @code{with}'ed package is package @code{Decls}, so there
23200 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
23201 In fact there is such a call in this example, but we would have to
23202 assume that there was such a call even if it were not there, since
23203 we are not supposed to write the body of @code{Decls} knowing what
23204 is in the body of @code{Utils}; certainly in the case of the
23205 static elaboration model, the compiler does not know what is in
23206 other bodies and must assume the worst.
23209 This means that the spec and body of @code{Decls} must also be
23210 elaborated before we elaborate the unit containing the call, but
23211 that unit is @code{Decls}! This means that the body of @code{Decls}
23212 must be elaborated before itself, and that's a circularity.
23216 Indeed, if you add an explicit pragma Elaborate_All for @code{Utils} in
23217 the body of @code{Decls} you will get a true Ada Reference Manual
23218 circularity that makes the program illegal.
23220 In practice, we have found that problems with the static model of
23221 elaboration in existing code often arise from library tasks, so
23222 we must address this particular situation.
23224 Note that if we compile and run the program above, using the dynamic model of
23225 elaboration (that is to say use the @option{-gnatE} switch),
23226 then it compiles, binds,
23227 links, and runs, printing the expected result of 2. Therefore in some sense
23228 the circularity here is only apparent, and we need to capture
23229 the properties of this program that distinguish it from other library-level
23230 tasks that have real elaboration problems.
23232 We have four possible answers to this question:
23237 Use the dynamic model of elaboration.
23239 If we use the @option{-gnatE} switch, then as noted above, the program works.
23240 Why is this? If we examine the task body, it is apparent that the task cannot
23242 @code{accept} statement until after elaboration has been completed, because
23243 the corresponding entry call comes from the main program, not earlier.
23244 This is why the dynamic model works here. But that's really giving
23245 up on a precise analysis, and we prefer to take this approach only if we cannot
23247 problem in any other manner. So let us examine two ways to reorganize
23248 the program to avoid the potential elaboration problem.
23251 Split library tasks into separate packages.
23253 Write separate packages, so that library tasks are isolated from
23254 other declarations as much as possible. Let us look at a variation on
23257 @smallexample @c ada
23265 package body Decls1 is
23266 task body Lib_Task is
23274 type My_Int is new Integer;
23275 function Ident (M : My_Int) return My_Int;
23279 package body Decls2 is
23280 function Ident (M : My_Int) return My_Int is
23288 procedure Put_Val (Arg : Decls2.My_Int);
23292 package body Utils is
23293 procedure Put_Val (Arg : Decls2.My_Int) is
23295 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
23302 Decls1.Lib_Task.Start;
23307 All we have done is to split @code{Decls} into two packages, one
23308 containing the library task, and one containing everything else. Now
23309 there is no cycle, and the program compiles, binds, links and executes
23310 using the default static model of elaboration.
23313 Declare separate task types.
23315 A significant part of the problem arises because of the use of the
23316 single task declaration form. This means that the elaboration of
23317 the task type, and the elaboration of the task itself (i.e. the
23318 creation of the task) happen at the same time. A good rule
23319 of style in Ada 95 is to always create explicit task types. By
23320 following the additional step of placing task objects in separate
23321 packages from the task type declaration, many elaboration problems
23322 are avoided. Here is another modified example of the example program:
23324 @smallexample @c ada
23326 task type Lib_Task_Type is
23330 type My_Int is new Integer;
23332 function Ident (M : My_Int) return My_Int;
23336 package body Decls is
23337 task body Lib_Task_Type is
23343 function Ident (M : My_Int) return My_Int is
23351 procedure Put_Val (Arg : Decls.My_Int);
23355 package body Utils is
23356 procedure Put_Val (Arg : Decls.My_Int) is
23358 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
23364 Lib_Task : Decls.Lib_Task_Type;
23370 Declst.Lib_Task.Start;
23375 What we have done here is to replace the @code{task} declaration in
23376 package @code{Decls} with a @code{task type} declaration. Then we
23377 introduce a separate package @code{Declst} to contain the actual
23378 task object. This separates the elaboration issues for
23379 the @code{task type}
23380 declaration, which causes no trouble, from the elaboration issues
23381 of the task object, which is also unproblematic, since it is now independent
23382 of the elaboration of @code{Utils}.
23383 This separation of concerns also corresponds to
23384 a generally sound engineering principle of separating declarations
23385 from instances. This version of the program also compiles, binds, links,
23386 and executes, generating the expected output.
23389 Use No_Entry_Calls_In_Elaboration_Code restriction.
23390 @cindex No_Entry_Calls_In_Elaboration_Code
23392 The previous two approaches described how a program can be restructured
23393 to avoid the special problems caused by library task bodies. in practice,
23394 however, such restructuring may be difficult to apply to existing legacy code,
23395 so we must consider solutions that do not require massive rewriting.
23397 Let us consider more carefully why our original sample program works
23398 under the dynamic model of elaboration. The reason is that the code
23399 in the task body blocks immediately on the @code{accept}
23400 statement. Now of course there is nothing to prohibit elaboration
23401 code from making entry calls (for example from another library level task),
23402 so we cannot tell in isolation that
23403 the task will not execute the accept statement during elaboration.
23405 However, in practice it is very unusual to see elaboration code
23406 make any entry calls, and the pattern of tasks starting
23407 at elaboration time and then immediately blocking on @code{accept} or
23408 @code{select} statements is very common. What this means is that
23409 the compiler is being too pessimistic when it analyzes the
23410 whole package body as though it might be executed at elaboration
23413 If we know that the elaboration code contains no entry calls, (a very safe
23414 assumption most of the time, that could almost be made the default
23415 behavior), then we can compile all units of the program under control
23416 of the following configuration pragma:
23419 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
23423 This pragma can be placed in the @file{gnat.adc} file in the usual
23424 manner. If we take our original unmodified program and compile it
23425 in the presence of a @file{gnat.adc} containing the above pragma,
23426 then once again, we can compile, bind, link, and execute, obtaining
23427 the expected result. In the presence of this pragma, the compiler does
23428 not trace calls in a task body, that appear after the first @code{accept}
23429 or @code{select} statement, and therefore does not report a potential
23430 circularity in the original program.
23432 The compiler will check to the extent it can that the above
23433 restriction is not violated, but it is not always possible to do a
23434 complete check at compile time, so it is important to use this
23435 pragma only if the stated restriction is in fact met, that is to say
23436 no task receives an entry call before elaboration of all units is completed.
23440 @node Mixing Elaboration Models
23441 @section Mixing Elaboration Models
23443 So far, we have assumed that the entire program is either compiled
23444 using the dynamic model or static model, ensuring consistency. It
23445 is possible to mix the two models, but rules have to be followed
23446 if this mixing is done to ensure that elaboration checks are not
23449 The basic rule is that @emph{a unit compiled with the static model cannot
23450 be @code{with'ed} by a unit compiled with the dynamic model}. The
23451 reason for this is that in the static model, a unit assumes that
23452 its clients guarantee to use (the equivalent of) pragma
23453 @code{Elaborate_All} so that no elaboration checks are required
23454 in inner subprograms, and this assumption is violated if the
23455 client is compiled with dynamic checks.
23457 The precise rule is as follows. A unit that is compiled with dynamic
23458 checks can only @code{with} a unit that meets at least one of the
23459 following criteria:
23464 The @code{with'ed} unit is itself compiled with dynamic elaboration
23465 checks (that is with the @option{-gnatE} switch.
23468 The @code{with'ed} unit is an internal GNAT implementation unit from
23469 the System, Interfaces, Ada, or GNAT hierarchies.
23472 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
23475 The @code{with'ing} unit (that is the client) has an explicit pragma
23476 @code{Elaborate_All} for the @code{with'ed} unit.
23481 If this rule is violated, that is if a unit with dynamic elaboration
23482 checks @code{with's} a unit that does not meet one of the above four
23483 criteria, then the binder (@code{gnatbind}) will issue a warning
23484 similar to that in the following example:
23487 warning: "x.ads" has dynamic elaboration checks and with's
23488 warning: "y.ads" which has static elaboration checks
23492 These warnings indicate that the rule has been violated, and that as a result
23493 elaboration checks may be missed in the resulting executable file.
23494 This warning may be suppressed using the @option{-ws} binder switch
23495 in the usual manner.
23497 One useful application of this mixing rule is in the case of a subsystem
23498 which does not itself @code{with} units from the remainder of the
23499 application. In this case, the entire subsystem can be compiled with
23500 dynamic checks to resolve a circularity in the subsystem, while
23501 allowing the main application that uses this subsystem to be compiled
23502 using the more reliable default static model.
23504 @node What to Do If the Default Elaboration Behavior Fails
23505 @section What to Do If the Default Elaboration Behavior Fails
23508 If the binder cannot find an acceptable order, it outputs detailed
23509 diagnostics. For example:
23515 error: elaboration circularity detected
23516 info: "proc (body)" must be elaborated before "pack (body)"
23517 info: reason: Elaborate_All probably needed in unit "pack (body)"
23518 info: recompile "pack (body)" with -gnatwl
23519 info: for full details
23520 info: "proc (body)"
23521 info: is needed by its spec:
23522 info: "proc (spec)"
23523 info: which is withed by:
23524 info: "pack (body)"
23525 info: "pack (body)" must be elaborated before "proc (body)"
23526 info: reason: pragma Elaborate in unit "proc (body)"
23532 In this case we have a cycle that the binder cannot break. On the one
23533 hand, there is an explicit pragma Elaborate in @code{proc} for
23534 @code{pack}. This means that the body of @code{pack} must be elaborated
23535 before the body of @code{proc}. On the other hand, there is elaboration
23536 code in @code{pack} that calls a subprogram in @code{proc}. This means
23537 that for maximum safety, there should really be a pragma
23538 Elaborate_All in @code{pack} for @code{proc} which would require that
23539 the body of @code{proc} be elaborated before the body of
23540 @code{pack}. Clearly both requirements cannot be satisfied.
23541 Faced with a circularity of this kind, you have three different options.
23544 @item Fix the program
23545 The most desirable option from the point of view of long-term maintenance
23546 is to rearrange the program so that the elaboration problems are avoided.
23547 One useful technique is to place the elaboration code into separate
23548 child packages. Another is to move some of the initialization code to
23549 explicitly called subprograms, where the program controls the order
23550 of initialization explicitly. Although this is the most desirable option,
23551 it may be impractical and involve too much modification, especially in
23552 the case of complex legacy code.
23554 @item Perform dynamic checks
23555 If the compilations are done using the
23557 (dynamic elaboration check) switch, then GNAT behaves in
23558 a quite different manner. Dynamic checks are generated for all calls
23559 that could possibly result in raising an exception. With this switch,
23560 the compiler does not generate implicit @code{Elaborate_All} pragmas.
23561 The behavior then is exactly as specified in the Ada 95 Reference Manual.
23562 The binder will generate an executable program that may or may not
23563 raise @code{Program_Error}, and then it is the programmer's job to ensure
23564 that it does not raise an exception. Note that it is important to
23565 compile all units with the switch, it cannot be used selectively.
23567 @item Suppress checks
23568 The drawback of dynamic checks is that they generate a
23569 significant overhead at run time, both in space and time. If you
23570 are absolutely sure that your program cannot raise any elaboration
23571 exceptions, and you still want to use the dynamic elaboration model,
23572 then you can use the configuration pragma
23573 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
23574 example this pragma could be placed in the @file{gnat.adc} file.
23576 @item Suppress checks selectively
23577 When you know that certain calls in elaboration code cannot possibly
23578 lead to an elaboration error, and the binder nevertheless generates warnings
23579 on those calls and inserts Elaborate_All pragmas that lead to elaboration
23580 circularities, it is possible to remove those warnings locally and obtain
23581 a program that will bind. Clearly this can be unsafe, and it is the
23582 responsibility of the programmer to make sure that the resulting program has
23583 no elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can
23584 be used with different granularity to suppress warnings and break
23585 elaboration circularities:
23589 Place the pragma that names the called subprogram in the declarative part
23590 that contains the call.
23593 Place the pragma in the declarative part, without naming an entity. This
23594 disables warnings on all calls in the corresponding declarative region.
23597 Place the pragma in the package spec that declares the called subprogram,
23598 and name the subprogram. This disables warnings on all elaboration calls to
23602 Place the pragma in the package spec that declares the called subprogram,
23603 without naming any entity. This disables warnings on all elaboration calls to
23604 all subprograms declared in this spec.
23606 @item Use Pragma Elaborate
23607 As previously described in section @xref{Treatment of Pragma Elaborate},
23608 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
23609 that no elaboration checks are required on calls to the designated unit.
23610 There may be cases in which the caller knows that no transitive calls
23611 can occur, so that a @code{pragma Elaborate} will be sufficient in a
23612 case where @code{pragma Elaborate_All} would cause a circularity.
23616 These five cases are listed in order of decreasing safety, and therefore
23617 require increasing programmer care in their application. Consider the
23620 @smallexample @c adanocomment
23622 function F1 return Integer;
23627 function F2 return Integer;
23628 function Pure (x : integer) return integer;
23629 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
23630 -- pragma Suppress (Elaboration_Check); -- (4)
23634 package body Pack1 is
23635 function F1 return Integer is
23639 Val : integer := Pack2.Pure (11); -- Elab. call (1)
23642 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
23643 -- pragma Suppress(Elaboration_Check); -- (2)
23645 X1 := Pack2.F2 + 1; -- Elab. call (2)
23650 package body Pack2 is
23651 function F2 return Integer is
23655 function Pure (x : integer) return integer is
23657 return x ** 3 - 3 * x;
23661 with Pack1, Ada.Text_IO;
23664 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
23667 In the absence of any pragmas, an attempt to bind this program produces
23668 the following diagnostics:
23674 error: elaboration circularity detected
23675 info: "pack1 (body)" must be elaborated before "pack1 (body)"
23676 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
23677 info: recompile "pack1 (body)" with -gnatwl for full details
23678 info: "pack1 (body)"
23679 info: must be elaborated along with its spec:
23680 info: "pack1 (spec)"
23681 info: which is withed by:
23682 info: "pack2 (body)"
23683 info: which must be elaborated along with its spec:
23684 info: "pack2 (spec)"
23685 info: which is withed by:
23686 info: "pack1 (body)"
23689 The sources of the circularity are the two calls to @code{Pack2.Pure} and
23690 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
23691 F2 is safe, even though F2 calls F1, because the call appears after the
23692 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
23693 remove the warning on the call. It is also possible to use pragma (2)
23694 because there are no other potentially unsafe calls in the block.
23697 The call to @code{Pure} is safe because this function does not depend on the
23698 state of @code{Pack2}. Therefore any call to this function is safe, and it
23699 is correct to place pragma (3) in the corresponding package spec.
23702 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
23703 warnings on all calls to functions declared therein. Note that this is not
23704 necessarily safe, and requires more detailed examination of the subprogram
23705 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
23706 be already elaborated.
23710 It is hard to generalize on which of these four approaches should be
23711 taken. Obviously if it is possible to fix the program so that the default
23712 treatment works, this is preferable, but this may not always be practical.
23713 It is certainly simple enough to use
23715 but the danger in this case is that, even if the GNAT binder
23716 finds a correct elaboration order, it may not always do so,
23717 and certainly a binder from another Ada compiler might not. A
23718 combination of testing and analysis (for which the warnings generated
23721 switch can be useful) must be used to ensure that the program is free
23722 of errors. One switch that is useful in this testing is the
23723 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
23726 Normally the binder tries to find an order that has the best chance of
23727 of avoiding elaboration problems. With this switch, the binder
23728 plays a devil's advocate role, and tries to choose the order that
23729 has the best chance of failing. If your program works even with this
23730 switch, then it has a better chance of being error free, but this is still
23733 For an example of this approach in action, consider the C-tests (executable
23734 tests) from the ACVC suite. If these are compiled and run with the default
23735 treatment, then all but one of them succeed without generating any error
23736 diagnostics from the binder. However, there is one test that fails, and
23737 this is not surprising, because the whole point of this test is to ensure
23738 that the compiler can handle cases where it is impossible to determine
23739 a correct order statically, and it checks that an exception is indeed
23740 raised at run time.
23742 This one test must be compiled and run using the
23744 switch, and then it passes. Alternatively, the entire suite can
23745 be run using this switch. It is never wrong to run with the dynamic
23746 elaboration switch if your code is correct, and we assume that the
23747 C-tests are indeed correct (it is less efficient, but efficiency is
23748 not a factor in running the ACVC tests.)
23750 @node Elaboration for Access-to-Subprogram Values
23751 @section Elaboration for Access-to-Subprogram Values
23752 @cindex Access-to-subprogram
23755 The introduction of access-to-subprogram types in Ada 95 complicates
23756 the handling of elaboration. The trouble is that it becomes
23757 impossible to tell at compile time which procedure
23758 is being called. This means that it is not possible for the binder
23759 to analyze the elaboration requirements in this case.
23761 If at the point at which the access value is created
23762 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
23763 the body of the subprogram is
23764 known to have been elaborated, then the access value is safe, and its use
23765 does not require a check. This may be achieved by appropriate arrangement
23766 of the order of declarations if the subprogram is in the current unit,
23767 or, if the subprogram is in another unit, by using pragma
23768 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
23769 on the referenced unit.
23771 If the referenced body is not known to have been elaborated at the point
23772 the access value is created, then any use of the access value must do a
23773 dynamic check, and this dynamic check will fail and raise a
23774 @code{Program_Error} exception if the body has not been elaborated yet.
23775 GNAT will generate the necessary checks, and in addition, if the
23777 switch is set, will generate warnings that such checks are required.
23779 The use of dynamic dispatching for tagged types similarly generates
23780 a requirement for dynamic checks, and premature calls to any primitive
23781 operation of a tagged type before the body of the operation has been
23782 elaborated, will result in the raising of @code{Program_Error}.
23784 @node Summary of Procedures for Elaboration Control
23785 @section Summary of Procedures for Elaboration Control
23786 @cindex Elaboration control
23789 First, compile your program with the default options, using none of
23790 the special elaboration control switches. If the binder successfully
23791 binds your program, then you can be confident that, apart from issues
23792 raised by the use of access-to-subprogram types and dynamic dispatching,
23793 the program is free of elaboration errors. If it is important that the
23794 program be portable, then use the
23796 switch to generate warnings about missing @code{Elaborate_All}
23797 pragmas, and supply the missing pragmas.
23799 If the program fails to bind using the default static elaboration
23800 handling, then you can fix the program to eliminate the binder
23801 message, or recompile the entire program with the
23802 @option{-gnatE} switch to generate dynamic elaboration checks,
23803 and, if you are sure there really are no elaboration problems,
23804 use a global pragma @code{Suppress (Elaboration_Check)}.
23806 @node Other Elaboration Order Considerations
23807 @section Other Elaboration Order Considerations
23809 This section has been entirely concerned with the issue of finding a valid
23810 elaboration order, as defined by the Ada Reference Manual. In a case
23811 where several elaboration orders are valid, the task is to find one
23812 of the possible valid elaboration orders (and the static model in GNAT
23813 will ensure that this is achieved).
23815 The purpose of the elaboration rules in the Ada Reference Manual is to
23816 make sure that no entity is accessed before it has been elaborated. For
23817 a subprogram, this means that the spec and body must have been elaborated
23818 before the subprogram is called. For an object, this means that the object
23819 must have been elaborated before its value is read or written. A violation
23820 of either of these two requirements is an access before elaboration order,
23821 and this section has been all about avoiding such errors.
23823 In the case where more than one order of elaboration is possible, in the
23824 sense that access before elaboration errors are avoided, then any one of
23825 the orders is ``correct'' in the sense that it meets the requirements of
23826 the Ada Reference Manual, and no such error occurs.
23828 However, it may be the case for a given program, that there are
23829 constraints on the order of elaboration that come not from consideration
23830 of avoiding elaboration errors, but rather from extra-lingual logic
23831 requirements. Consider this example:
23833 @smallexample @c ada
23834 with Init_Constants;
23835 package Constants is
23840 package Init_Constants is
23841 procedure P; -- require a body
23842 end Init_Constants;
23845 package body Init_Constants is
23846 procedure P is begin null; end;
23850 end Init_Constants;
23854 Z : Integer := Constants.X + Constants.Y;
23858 with Text_IO; use Text_IO;
23861 Put_Line (Calc.Z'Img);
23866 In this example, there is more than one valid order of elaboration. For
23867 example both the following are correct orders:
23870 Init_Constants spec
23873 Init_Constants body
23878 Init_Constants spec
23879 Init_Constants body
23886 There is no language rule to prefer one or the other, both are correct
23887 from an order of elaboration point of view. But the programmatic effects
23888 of the two orders are very different. In the first, the elaboration routine
23889 of @code{Calc} initializes @code{Z} to zero, and then the main program
23890 runs with this value of zero. But in the second order, the elaboration
23891 routine of @code{Calc} runs after the body of Init_Constants has set
23892 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
23895 One could perhaps by applying pretty clever non-artificial intelligence
23896 to the situation guess that it is more likely that the second order of
23897 elaboration is the one desired, but there is no formal linguistic reason
23898 to prefer one over the other. In fact in this particular case, GNAT will
23899 prefer the second order, because of the rule that bodies are elaborated
23900 as soon as possible, but it's just luck that this is what was wanted
23901 (if indeed the second order was preferred).
23903 If the program cares about the order of elaboration routines in a case like
23904 this, it is important to specify the order required. In this particular
23905 case, that could have been achieved by adding to the spec of Calc:
23907 @smallexample @c ada
23908 pragma Elaborate_All (Constants);
23912 which requires that the body (if any) and spec of @code{Constants},
23913 as well as the body and spec of any unit @code{with}'ed by
23914 @code{Constants} be elaborated before @code{Calc} is elaborated.
23916 Clearly no automatic method can always guess which alternative you require,
23917 and if you are working with legacy code that had constraints of this kind
23918 which were not properly specified by adding @code{Elaborate} or
23919 @code{Elaborate_All} pragmas, then indeed it is possible that two different
23920 compilers can choose different orders.
23922 The @code{gnatbind}
23923 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
23924 out problems. This switch causes bodies to be elaborated as late as possible
23925 instead of as early as possible. In the example above, it would have forced
23926 the choice of the first elaboration order. If you get different results
23927 when using this switch, and particularly if one set of results is right,
23928 and one is wrong as far as you are concerned, it shows that you have some
23929 missing @code{Elaborate} pragmas. For the example above, we have the
23933 gnatmake -f -q main
23936 gnatmake -f -q main -bargs -p
23942 It is of course quite unlikely that both these results are correct, so
23943 it is up to you in a case like this to investigate the source of the
23944 difference, by looking at the two elaboration orders that are chosen,
23945 and figuring out which is correct, and then adding the necessary
23946 @code{Elaborate_All} pragmas to ensure the desired order.
23949 @node Inline Assembler
23950 @appendix Inline Assembler
23953 If you need to write low-level software that interacts directly
23954 with the hardware, Ada provides two ways to incorporate assembly
23955 language code into your program. First, you can import and invoke
23956 external routines written in assembly language, an Ada feature fully
23957 supported by GNAT. However, for small sections of code it may be simpler
23958 or more efficient to include assembly language statements directly
23959 in your Ada source program, using the facilities of the implementation-defined
23960 package @code{System.Machine_Code}, which incorporates the gcc
23961 Inline Assembler. The Inline Assembler approach offers a number of advantages,
23962 including the following:
23965 @item No need to use non-Ada tools
23966 @item Consistent interface over different targets
23967 @item Automatic usage of the proper calling conventions
23968 @item Access to Ada constants and variables
23969 @item Definition of intrinsic routines
23970 @item Possibility of inlining a subprogram comprising assembler code
23971 @item Code optimizer can take Inline Assembler code into account
23974 This chapter presents a series of examples to show you how to use
23975 the Inline Assembler. Although it focuses on the Intel x86,
23976 the general approach applies also to other processors.
23977 It is assumed that you are familiar with Ada
23978 and with assembly language programming.
23981 * Basic Assembler Syntax::
23982 * A Simple Example of Inline Assembler::
23983 * Output Variables in Inline Assembler::
23984 * Input Variables in Inline Assembler::
23985 * Inlining Inline Assembler Code::
23986 * Other Asm Functionality::
23987 * A Complete Example::
23990 @c ---------------------------------------------------------------------------
23991 @node Basic Assembler Syntax
23992 @section Basic Assembler Syntax
23995 The assembler used by GNAT and gcc is based not on the Intel assembly
23996 language, but rather on a language that descends from the AT&T Unix
23997 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
23998 The following table summarizes the main features of @emph{as} syntax
23999 and points out the differences from the Intel conventions.
24000 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
24001 pre-processor) documentation for further information.
24004 @item Register names
24005 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
24007 Intel: No extra punctuation; for example @code{eax}
24009 @item Immediate operand
24010 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
24012 Intel: No extra punctuation; for example @code{4}
24015 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
24017 Intel: No extra punctuation; for example @code{loc}
24019 @item Memory contents
24020 gcc / @emph{as}: No extra punctuation; for example @code{loc}
24022 Intel: Square brackets; for example @code{[loc]}
24024 @item Register contents
24025 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
24027 Intel: Square brackets; for example @code{[eax]}
24029 @item Hexadecimal numbers
24030 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
24032 Intel: Trailing ``h''; for example @code{A0h}
24035 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
24038 Intel: Implicit, deduced by assembler; for example @code{mov}
24040 @item Instruction repetition
24041 gcc / @emph{as}: Split into two lines; for example
24047 Intel: Keep on one line; for example @code{rep stosl}
24049 @item Order of operands
24050 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
24052 Intel: Destination first; for example @code{mov eax, 4}
24055 @c ---------------------------------------------------------------------------
24056 @node A Simple Example of Inline Assembler
24057 @section A Simple Example of Inline Assembler
24060 The following example will generate a single assembly language statement,
24061 @code{nop}, which does nothing. Despite its lack of run-time effect,
24062 the example will be useful in illustrating the basics of
24063 the Inline Assembler facility.
24065 @smallexample @c ada
24067 with System.Machine_Code; use System.Machine_Code;
24068 procedure Nothing is
24075 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
24076 here it takes one parameter, a @emph{template string} that must be a static
24077 expression and that will form the generated instruction.
24078 @code{Asm} may be regarded as a compile-time procedure that parses
24079 the template string and additional parameters (none here),
24080 from which it generates a sequence of assembly language instructions.
24082 The examples in this chapter will illustrate several of the forms
24083 for invoking @code{Asm}; a complete specification of the syntax
24084 is found in the @cite{GNAT Reference Manual}.
24086 Under the standard GNAT conventions, the @code{Nothing} procedure
24087 should be in a file named @file{nothing.adb}.
24088 You can build the executable in the usual way:
24092 However, the interesting aspect of this example is not its run-time behavior
24093 but rather the generated assembly code.
24094 To see this output, invoke the compiler as follows:
24096 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
24098 where the options are:
24102 compile only (no bind or link)
24104 generate assembler listing
24105 @item -fomit-frame-pointer
24106 do not set up separate stack frames
24108 do not add runtime checks
24111 This gives a human-readable assembler version of the code. The resulting
24112 file will have the same name as the Ada source file, but with a @code{.s}
24113 extension. In our example, the file @file{nothing.s} has the following
24118 .file "nothing.adb"
24120 ___gnu_compiled_ada:
24123 .globl __ada_nothing
24135 The assembly code you included is clearly indicated by
24136 the compiler, between the @code{#APP} and @code{#NO_APP}
24137 delimiters. The character before the 'APP' and 'NOAPP'
24138 can differ on different targets. For example, GNU/Linux uses '#APP' while
24139 on NT you will see '/APP'.
24141 If you make a mistake in your assembler code (such as using the
24142 wrong size modifier, or using a wrong operand for the instruction) GNAT
24143 will report this error in a temporary file, which will be deleted when
24144 the compilation is finished. Generating an assembler file will help
24145 in such cases, since you can assemble this file separately using the
24146 @emph{as} assembler that comes with gcc.
24148 Assembling the file using the command
24151 as @file{nothing.s}
24154 will give you error messages whose lines correspond to the assembler
24155 input file, so you can easily find and correct any mistakes you made.
24156 If there are no errors, @emph{as} will generate an object file
24157 @file{nothing.out}.
24159 @c ---------------------------------------------------------------------------
24160 @node Output Variables in Inline Assembler
24161 @section Output Variables in Inline Assembler
24164 The examples in this section, showing how to access the processor flags,
24165 illustrate how to specify the destination operands for assembly language
24168 @smallexample @c ada
24170 with Interfaces; use Interfaces;
24171 with Ada.Text_IO; use Ada.Text_IO;
24172 with System.Machine_Code; use System.Machine_Code;
24173 procedure Get_Flags is
24174 Flags : Unsigned_32;
24177 Asm ("pushfl" & LF & HT & -- push flags on stack
24178 "popl %%eax" & LF & HT & -- load eax with flags
24179 "movl %%eax, %0", -- store flags in variable
24180 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24181 Put_Line ("Flags register:" & Flags'Img);
24186 In order to have a nicely aligned assembly listing, we have separated
24187 multiple assembler statements in the Asm template string with linefeed
24188 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
24189 The resulting section of the assembly output file is:
24196 movl %eax, -40(%ebp)
24201 It would have been legal to write the Asm invocation as:
24204 Asm ("pushfl popl %%eax movl %%eax, %0")
24207 but in the generated assembler file, this would come out as:
24211 pushfl popl %eax movl %eax, -40(%ebp)
24215 which is not so convenient for the human reader.
24217 We use Ada comments
24218 at the end of each line to explain what the assembler instructions
24219 actually do. This is a useful convention.
24221 When writing Inline Assembler instructions, you need to precede each register
24222 and variable name with a percent sign. Since the assembler already requires
24223 a percent sign at the beginning of a register name, you need two consecutive
24224 percent signs for such names in the Asm template string, thus @code{%%eax}.
24225 In the generated assembly code, one of the percent signs will be stripped off.
24227 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
24228 variables: operands you later define using @code{Input} or @code{Output}
24229 parameters to @code{Asm}.
24230 An output variable is illustrated in
24231 the third statement in the Asm template string:
24235 The intent is to store the contents of the eax register in a variable that can
24236 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
24237 necessarily work, since the compiler might optimize by using a register
24238 to hold Flags, and the expansion of the @code{movl} instruction would not be
24239 aware of this optimization. The solution is not to store the result directly
24240 but rather to advise the compiler to choose the correct operand form;
24241 that is the purpose of the @code{%0} output variable.
24243 Information about the output variable is supplied in the @code{Outputs}
24244 parameter to @code{Asm}:
24246 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24249 The output is defined by the @code{Asm_Output} attribute of the target type;
24250 the general format is
24252 Type'Asm_Output (constraint_string, variable_name)
24255 The constraint string directs the compiler how
24256 to store/access the associated variable. In the example
24258 Unsigned_32'Asm_Output ("=m", Flags);
24260 the @code{"m"} (memory) constraint tells the compiler that the variable
24261 @code{Flags} should be stored in a memory variable, thus preventing
24262 the optimizer from keeping it in a register. In contrast,
24264 Unsigned_32'Asm_Output ("=r", Flags);
24266 uses the @code{"r"} (register) constraint, telling the compiler to
24267 store the variable in a register.
24269 If the constraint is preceded by the equal character (@strong{=}), it tells
24270 the compiler that the variable will be used to store data into it.
24272 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
24273 allowing the optimizer to choose whatever it deems best.
24275 There are a fairly large number of constraints, but the ones that are
24276 most useful (for the Intel x86 processor) are the following:
24282 global (i.e. can be stored anywhere)
24300 use one of eax, ebx, ecx or edx
24302 use one of eax, ebx, ecx, edx, esi or edi
24305 The full set of constraints is described in the gcc and @emph{as}
24306 documentation; note that it is possible to combine certain constraints
24307 in one constraint string.
24309 You specify the association of an output variable with an assembler operand
24310 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
24312 @smallexample @c ada
24314 Asm ("pushfl" & LF & HT & -- push flags on stack
24315 "popl %%eax" & LF & HT & -- load eax with flags
24316 "movl %%eax, %0", -- store flags in variable
24317 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24321 @code{%0} will be replaced in the expanded code by the appropriate operand,
24323 the compiler decided for the @code{Flags} variable.
24325 In general, you may have any number of output variables:
24328 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
24330 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
24331 of @code{Asm_Output} attributes
24335 @smallexample @c ada
24337 Asm ("movl %%eax, %0" & LF & HT &
24338 "movl %%ebx, %1" & LF & HT &
24340 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
24341 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
24342 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
24346 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
24347 in the Ada program.
24349 As a variation on the @code{Get_Flags} example, we can use the constraints
24350 string to direct the compiler to store the eax register into the @code{Flags}
24351 variable, instead of including the store instruction explicitly in the
24352 @code{Asm} template string:
24354 @smallexample @c ada
24356 with Interfaces; use Interfaces;
24357 with Ada.Text_IO; use Ada.Text_IO;
24358 with System.Machine_Code; use System.Machine_Code;
24359 procedure Get_Flags_2 is
24360 Flags : Unsigned_32;
24363 Asm ("pushfl" & LF & HT & -- push flags on stack
24364 "popl %%eax", -- save flags in eax
24365 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
24366 Put_Line ("Flags register:" & Flags'Img);
24372 The @code{"a"} constraint tells the compiler that the @code{Flags}
24373 variable will come from the eax register. Here is the resulting code:
24381 movl %eax,-40(%ebp)
24386 The compiler generated the store of eax into Flags after
24387 expanding the assembler code.
24389 Actually, there was no need to pop the flags into the eax register;
24390 more simply, we could just pop the flags directly into the program variable:
24392 @smallexample @c ada
24394 with Interfaces; use Interfaces;
24395 with Ada.Text_IO; use Ada.Text_IO;
24396 with System.Machine_Code; use System.Machine_Code;
24397 procedure Get_Flags_3 is
24398 Flags : Unsigned_32;
24401 Asm ("pushfl" & LF & HT & -- push flags on stack
24402 "pop %0", -- save flags in Flags
24403 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24404 Put_Line ("Flags register:" & Flags'Img);
24409 @c ---------------------------------------------------------------------------
24410 @node Input Variables in Inline Assembler
24411 @section Input Variables in Inline Assembler
24414 The example in this section illustrates how to specify the source operands
24415 for assembly language statements.
24416 The program simply increments its input value by 1:
24418 @smallexample @c ada
24420 with Interfaces; use Interfaces;
24421 with Ada.Text_IO; use Ada.Text_IO;
24422 with System.Machine_Code; use System.Machine_Code;
24423 procedure Increment is
24425 function Incr (Value : Unsigned_32) return Unsigned_32 is
24426 Result : Unsigned_32;
24429 Inputs => Unsigned_32'Asm_Input ("a", Value),
24430 Outputs => Unsigned_32'Asm_Output ("=a", Result));
24434 Value : Unsigned_32;
24438 Put_Line ("Value before is" & Value'Img);
24439 Value := Incr (Value);
24440 Put_Line ("Value after is" & Value'Img);
24445 The @code{Outputs} parameter to @code{Asm} specifies
24446 that the result will be in the eax register and that it is to be stored
24447 in the @code{Result} variable.
24449 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
24450 but with an @code{Asm_Input} attribute.
24451 The @code{"="} constraint, indicating an output value, is not present.
24453 You can have multiple input variables, in the same way that you can have more
24454 than one output variable.
24456 The parameter count (%0, %1) etc, now starts at the first input
24457 statement, and continues with the output statements.
24458 When both parameters use the same variable, the
24459 compiler will treat them as the same %n operand, which is the case here.
24461 Just as the @code{Outputs} parameter causes the register to be stored into the
24462 target variable after execution of the assembler statements, so does the
24463 @code{Inputs} parameter cause its variable to be loaded into the register
24464 before execution of the assembler statements.
24466 Thus the effect of the @code{Asm} invocation is:
24468 @item load the 32-bit value of @code{Value} into eax
24469 @item execute the @code{incl %eax} instruction
24470 @item store the contents of eax into the @code{Result} variable
24473 The resulting assembler file (with @option{-O2} optimization) contains:
24476 _increment__incr.1:
24489 @c ---------------------------------------------------------------------------
24490 @node Inlining Inline Assembler Code
24491 @section Inlining Inline Assembler Code
24494 For a short subprogram such as the @code{Incr} function in the previous
24495 section, the overhead of the call and return (creating / deleting the stack
24496 frame) can be significant, compared to the amount of code in the subprogram
24497 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
24498 which directs the compiler to expand invocations of the subprogram at the
24499 point(s) of call, instead of setting up a stack frame for out-of-line calls.
24500 Here is the resulting program:
24502 @smallexample @c ada
24504 with Interfaces; use Interfaces;
24505 with Ada.Text_IO; use Ada.Text_IO;
24506 with System.Machine_Code; use System.Machine_Code;
24507 procedure Increment_2 is
24509 function Incr (Value : Unsigned_32) return Unsigned_32 is
24510 Result : Unsigned_32;
24513 Inputs => Unsigned_32'Asm_Input ("a", Value),
24514 Outputs => Unsigned_32'Asm_Output ("=a", Result));
24517 pragma Inline (Increment);
24519 Value : Unsigned_32;
24523 Put_Line ("Value before is" & Value'Img);
24524 Value := Increment (Value);
24525 Put_Line ("Value after is" & Value'Img);
24530 Compile the program with both optimization (@option{-O2}) and inlining
24531 enabled (@option{-gnatpn} instead of @option{-gnatp}).
24533 The @code{Incr} function is still compiled as usual, but at the
24534 point in @code{Increment} where our function used to be called:
24539 call _increment__incr.1
24544 the code for the function body directly appears:
24557 thus saving the overhead of stack frame setup and an out-of-line call.
24559 @c ---------------------------------------------------------------------------
24560 @node Other Asm Functionality
24561 @section Other @code{Asm} Functionality
24564 This section describes two important parameters to the @code{Asm}
24565 procedure: @code{Clobber}, which identifies register usage;
24566 and @code{Volatile}, which inhibits unwanted optimizations.
24569 * The Clobber Parameter::
24570 * The Volatile Parameter::
24573 @c ---------------------------------------------------------------------------
24574 @node The Clobber Parameter
24575 @subsection The @code{Clobber} Parameter
24578 One of the dangers of intermixing assembly language and a compiled language
24579 such as Ada is that the compiler needs to be aware of which registers are
24580 being used by the assembly code. In some cases, such as the earlier examples,
24581 the constraint string is sufficient to indicate register usage (e.g.,
24583 the eax register). But more generally, the compiler needs an explicit
24584 identification of the registers that are used by the Inline Assembly
24587 Using a register that the compiler doesn't know about
24588 could be a side effect of an instruction (like @code{mull}
24589 storing its result in both eax and edx).
24590 It can also arise from explicit register usage in your
24591 assembly code; for example:
24594 Asm ("movl %0, %%ebx" & LF & HT &
24596 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24597 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
24601 where the compiler (since it does not analyze the @code{Asm} template string)
24602 does not know you are using the ebx register.
24604 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
24605 to identify the registers that will be used by your assembly code:
24609 Asm ("movl %0, %%ebx" & LF & HT &
24611 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24612 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
24617 The Clobber parameter is a static string expression specifying the
24618 register(s) you are using. Note that register names are @emph{not} prefixed
24619 by a percent sign. Also, if more than one register is used then their names
24620 are separated by commas; e.g., @code{"eax, ebx"}
24622 The @code{Clobber} parameter has several additional uses:
24624 @item Use ``register'' name @code{cc} to indicate that flags might have changed
24625 @item Use ``register'' name @code{memory} if you changed a memory location
24628 @c ---------------------------------------------------------------------------
24629 @node The Volatile Parameter
24630 @subsection The @code{Volatile} Parameter
24631 @cindex Volatile parameter
24634 Compiler optimizations in the presence of Inline Assembler may sometimes have
24635 unwanted effects. For example, when an @code{Asm} invocation with an input
24636 variable is inside a loop, the compiler might move the loading of the input
24637 variable outside the loop, regarding it as a one-time initialization.
24639 If this effect is not desired, you can disable such optimizations by setting
24640 the @code{Volatile} parameter to @code{True}; for example:
24642 @smallexample @c ada
24644 Asm ("movl %0, %%ebx" & LF & HT &
24646 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24647 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
24653 By default, @code{Volatile} is set to @code{False} unless there is no
24654 @code{Outputs} parameter.
24656 Although setting @code{Volatile} to @code{True} prevents unwanted
24657 optimizations, it will also disable other optimizations that might be
24658 important for efficiency. In general, you should set @code{Volatile}
24659 to @code{True} only if the compiler's optimizations have created
24662 @c ---------------------------------------------------------------------------
24663 @node A Complete Example
24664 @section A Complete Example
24667 This section contains a complete program illustrating a realistic usage
24668 of GNAT's Inline Assembler capabilities. It comprises a main procedure
24669 @code{Check_CPU} and a package @code{Intel_CPU}.
24670 The package declares a collection of functions that detect the properties
24671 of the 32-bit x86 processor that is running the program.
24672 The main procedure invokes these functions and displays the information.
24674 The Intel_CPU package could be enhanced by adding functions to
24675 detect the type of x386 co-processor, the processor caching options and
24676 special operations such as the SIMD extensions.
24678 Although the Intel_CPU package has been written for 32-bit Intel
24679 compatible CPUs, it is OS neutral. It has been tested on DOS,
24680 Windows/NT and GNU/Linux.
24683 * Check_CPU Procedure::
24684 * Intel_CPU Package Specification::
24685 * Intel_CPU Package Body::
24688 @c ---------------------------------------------------------------------------
24689 @node Check_CPU Procedure
24690 @subsection @code{Check_CPU} Procedure
24691 @cindex Check_CPU procedure
24693 @smallexample @c adanocomment
24694 ---------------------------------------------------------------------
24696 -- Uses the Intel_CPU package to identify the CPU the program is --
24697 -- running on, and some of the features it supports. --
24699 ---------------------------------------------------------------------
24701 with Intel_CPU; -- Intel CPU detection functions
24702 with Ada.Text_IO; -- Standard text I/O
24703 with Ada.Command_Line; -- To set the exit status
24705 procedure Check_CPU is
24707 Type_Found : Boolean := False;
24708 -- Flag to indicate that processor was identified
24710 Features : Intel_CPU.Processor_Features;
24711 -- The processor features
24713 Signature : Intel_CPU.Processor_Signature;
24714 -- The processor type signature
24718 -----------------------------------
24719 -- Display the program banner. --
24720 -----------------------------------
24722 Ada.Text_IO.Put_Line (Ada.Command_Line.Command_Name &
24723 ": check Intel CPU version and features, v1.0");
24724 Ada.Text_IO.Put_Line ("distribute freely, but no warranty whatsoever");
24725 Ada.Text_IO.New_Line;
24727 -----------------------------------------------------------------------
24728 -- We can safely start with the assumption that we are on at least --
24729 -- a x386 processor. If the CPUID instruction is present, then we --
24730 -- have a later processor type. --
24731 -----------------------------------------------------------------------
24733 if Intel_CPU.Has_CPUID = False then
24735 -- No CPUID instruction, so we assume this is indeed a x386
24736 -- processor. We can still check if it has a FP co-processor.
24737 if Intel_CPU.Has_FPU then
24738 Ada.Text_IO.Put_Line
24739 ("x386-type processor with a FP co-processor");
24741 Ada.Text_IO.Put_Line
24742 ("x386-type processor without a FP co-processor");
24743 end if; -- check for FPU
24746 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
24749 end if; -- check for CPUID
24751 -----------------------------------------------------------------------
24752 -- If CPUID is supported, check if this is a true Intel processor, --
24753 -- if it is not, display a warning. --
24754 -----------------------------------------------------------------------
24756 if Intel_CPU.Vendor_ID /= Intel_CPU.Intel_Processor then
24757 Ada.Text_IO.Put_Line ("*** This is a Intel compatible processor");
24758 Ada.Text_IO.Put_Line ("*** Some information may be incorrect");
24759 end if; -- check if Intel
24761 ----------------------------------------------------------------------
24762 -- With the CPUID instruction present, we can assume at least a --
24763 -- x486 processor. If the CPUID support level is < 1 then we have --
24764 -- to leave it at that. --
24765 ----------------------------------------------------------------------
24767 if Intel_CPU.CPUID_Level < 1 then
24769 -- Ok, this is a x486 processor. we still can get the Vendor ID
24770 Ada.Text_IO.Put_Line ("x486-type processor");
24771 Ada.Text_IO.Put_Line ("Vendor ID is " & Intel_CPU.Vendor_ID);
24773 -- We can also check if there is a FPU present
24774 if Intel_CPU.Has_FPU then
24775 Ada.Text_IO.Put_Line ("Floating-Point support");
24777 Ada.Text_IO.Put_Line ("No Floating-Point support");
24778 end if; -- check for FPU
24781 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
24784 end if; -- check CPUID level
24786 ---------------------------------------------------------------------
24787 -- With a CPUID level of 1 we can use the processor signature to --
24788 -- determine it's exact type. --
24789 ---------------------------------------------------------------------
24791 Signature := Intel_CPU.Signature;
24793 ----------------------------------------------------------------------
24794 -- Ok, now we go into a lot of messy comparisons to get the --
24795 -- processor type. For clarity, no attememt to try to optimize the --
24796 -- comparisons has been made. Note that since Intel_CPU does not --
24797 -- support getting cache info, we cannot distinguish between P5 --
24798 -- and Celeron types yet. --
24799 ----------------------------------------------------------------------
24802 if Signature.Processor_Type = 2#00# and
24803 Signature.Family = 2#0100# and
24804 Signature.Model = 2#0100# then
24805 Type_Found := True;
24806 Ada.Text_IO.Put_Line ("x486SL processor");
24809 -- x486DX2 Write-Back
24810 if Signature.Processor_Type = 2#00# and
24811 Signature.Family = 2#0100# and
24812 Signature.Model = 2#0111# then
24813 Type_Found := True;
24814 Ada.Text_IO.Put_Line ("Write-Back Enhanced x486DX2 processor");
24818 if Signature.Processor_Type = 2#00# and
24819 Signature.Family = 2#0100# and
24820 Signature.Model = 2#1000# then
24821 Type_Found := True;
24822 Ada.Text_IO.Put_Line ("x486DX4 processor");
24825 -- x486DX4 Overdrive
24826 if Signature.Processor_Type = 2#01# and
24827 Signature.Family = 2#0100# and
24828 Signature.Model = 2#1000# then
24829 Type_Found := True;
24830 Ada.Text_IO.Put_Line ("x486DX4 OverDrive processor");
24833 -- Pentium (60, 66)
24834 if Signature.Processor_Type = 2#00# and
24835 Signature.Family = 2#0101# and
24836 Signature.Model = 2#0001# then
24837 Type_Found := True;
24838 Ada.Text_IO.Put_Line ("Pentium processor (60, 66)");
24841 -- Pentium (75, 90, 100, 120, 133, 150, 166, 200)
24842 if Signature.Processor_Type = 2#00# and
24843 Signature.Family = 2#0101# and
24844 Signature.Model = 2#0010# then
24845 Type_Found := True;
24846 Ada.Text_IO.Put_Line
24847 ("Pentium processor (75, 90, 100, 120, 133, 150, 166, 200)");
24850 -- Pentium OverDrive (60, 66)
24851 if Signature.Processor_Type = 2#01# and
24852 Signature.Family = 2#0101# and
24853 Signature.Model = 2#0001# then
24854 Type_Found := True;
24855 Ada.Text_IO.Put_Line ("Pentium OverDrive processor (60, 66)");
24858 -- Pentium OverDrive (75, 90, 100, 120, 133, 150, 166, 200)
24859 if Signature.Processor_Type = 2#01# and
24860 Signature.Family = 2#0101# and
24861 Signature.Model = 2#0010# then
24862 Type_Found := True;
24863 Ada.Text_IO.Put_Line
24864 ("Pentium OverDrive cpu (75, 90, 100, 120, 133, 150, 166, 200)");
24867 -- Pentium OverDrive processor for x486 processor-based systems
24868 if Signature.Processor_Type = 2#01# and
24869 Signature.Family = 2#0101# and
24870 Signature.Model = 2#0011# then
24871 Type_Found := True;
24872 Ada.Text_IO.Put_Line
24873 ("Pentium OverDrive processor for x486 processor-based systems");
24876 -- Pentium processor with MMX technology (166, 200)
24877 if Signature.Processor_Type = 2#00# and
24878 Signature.Family = 2#0101# and
24879 Signature.Model = 2#0100# then
24880 Type_Found := True;
24881 Ada.Text_IO.Put_Line
24882 ("Pentium processor with MMX technology (166, 200)");
24885 -- Pentium OverDrive with MMX for Pentium (75, 90, 100, 120, 133)
24886 if Signature.Processor_Type = 2#01# and
24887 Signature.Family = 2#0101# and
24888 Signature.Model = 2#0100# then
24889 Type_Found := True;
24890 Ada.Text_IO.Put_Line
24891 ("Pentium OverDrive processor with MMX " &
24892 "technology for Pentium processor (75, 90, 100, 120, 133)");
24895 -- Pentium Pro processor
24896 if Signature.Processor_Type = 2#00# and
24897 Signature.Family = 2#0110# and
24898 Signature.Model = 2#0001# then
24899 Type_Found := True;
24900 Ada.Text_IO.Put_Line ("Pentium Pro processor");
24903 -- Pentium II processor, model 3
24904 if Signature.Processor_Type = 2#00# and
24905 Signature.Family = 2#0110# and
24906 Signature.Model = 2#0011# then
24907 Type_Found := True;
24908 Ada.Text_IO.Put_Line ("Pentium II processor, model 3");
24911 -- Pentium II processor, model 5 or Celeron processor
24912 if Signature.Processor_Type = 2#00# and
24913 Signature.Family = 2#0110# and
24914 Signature.Model = 2#0101# then
24915 Type_Found := True;
24916 Ada.Text_IO.Put_Line
24917 ("Pentium II processor, model 5 or Celeron processor");
24920 -- Pentium Pro OverDrive processor
24921 if Signature.Processor_Type = 2#01# and
24922 Signature.Family = 2#0110# and
24923 Signature.Model = 2#0011# then
24924 Type_Found := True;
24925 Ada.Text_IO.Put_Line ("Pentium Pro OverDrive processor");
24928 -- If no type recognized, we have an unknown. Display what
24930 if Type_Found = False then
24931 Ada.Text_IO.Put_Line ("Unknown processor");
24934 -----------------------------------------
24935 -- Display processor stepping level. --
24936 -----------------------------------------
24938 Ada.Text_IO.Put_Line ("Stepping level:" & Signature.Stepping'Img);
24940 ---------------------------------
24941 -- Display vendor ID string. --
24942 ---------------------------------
24944 Ada.Text_IO.Put_Line ("Vendor ID: " & Intel_CPU.Vendor_ID);
24946 ------------------------------------
24947 -- Get the processors features. --
24948 ------------------------------------
24950 Features := Intel_CPU.Features;
24952 -----------------------------
24953 -- Check for a FPU unit. --
24954 -----------------------------
24956 if Features.FPU = True then
24957 Ada.Text_IO.Put_Line ("Floating-Point unit available");
24959 Ada.Text_IO.Put_Line ("no Floating-Point unit");
24960 end if; -- check for FPU
24962 --------------------------------
24963 -- List processor features. --
24964 --------------------------------
24966 Ada.Text_IO.Put_Line ("Supported features: ");
24968 -- Virtual Mode Extension
24969 if Features.VME = True then
24970 Ada.Text_IO.Put_Line (" VME - Virtual Mode Extension");
24973 -- Debugging Extension
24974 if Features.DE = True then
24975 Ada.Text_IO.Put_Line (" DE - Debugging Extension");
24978 -- Page Size Extension
24979 if Features.PSE = True then
24980 Ada.Text_IO.Put_Line (" PSE - Page Size Extension");
24983 -- Time Stamp Counter
24984 if Features.TSC = True then
24985 Ada.Text_IO.Put_Line (" TSC - Time Stamp Counter");
24988 -- Model Specific Registers
24989 if Features.MSR = True then
24990 Ada.Text_IO.Put_Line (" MSR - Model Specific Registers");
24993 -- Physical Address Extension
24994 if Features.PAE = True then
24995 Ada.Text_IO.Put_Line (" PAE - Physical Address Extension");
24998 -- Machine Check Extension
24999 if Features.MCE = True then
25000 Ada.Text_IO.Put_Line (" MCE - Machine Check Extension");
25003 -- CMPXCHG8 instruction supported
25004 if Features.CX8 = True then
25005 Ada.Text_IO.Put_Line (" CX8 - CMPXCHG8 instruction");
25008 -- on-chip APIC hardware support
25009 if Features.APIC = True then
25010 Ada.Text_IO.Put_Line (" APIC - on-chip APIC hardware support");
25013 -- Fast System Call
25014 if Features.SEP = True then
25015 Ada.Text_IO.Put_Line (" SEP - Fast System Call");
25018 -- Memory Type Range Registers
25019 if Features.MTRR = True then
25020 Ada.Text_IO.Put_Line (" MTTR - Memory Type Range Registers");
25023 -- Page Global Enable
25024 if Features.PGE = True then
25025 Ada.Text_IO.Put_Line (" PGE - Page Global Enable");
25028 -- Machine Check Architecture
25029 if Features.MCA = True then
25030 Ada.Text_IO.Put_Line (" MCA - Machine Check Architecture");
25033 -- Conditional Move Instruction Supported
25034 if Features.CMOV = True then
25035 Ada.Text_IO.Put_Line
25036 (" CMOV - Conditional Move Instruction Supported");
25039 -- Page Attribute Table
25040 if Features.PAT = True then
25041 Ada.Text_IO.Put_Line (" PAT - Page Attribute Table");
25044 -- 36-bit Page Size Extension
25045 if Features.PSE_36 = True then
25046 Ada.Text_IO.Put_Line (" PSE_36 - 36-bit Page Size Extension");
25049 -- MMX technology supported
25050 if Features.MMX = True then
25051 Ada.Text_IO.Put_Line (" MMX - MMX technology supported");
25054 -- Fast FP Save and Restore
25055 if Features.FXSR = True then
25056 Ada.Text_IO.Put_Line (" FXSR - Fast FP Save and Restore");
25059 ---------------------
25060 -- Program done. --
25061 ---------------------
25063 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
25068 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Failure);
25074 @c ---------------------------------------------------------------------------
25075 @node Intel_CPU Package Specification
25076 @subsection @code{Intel_CPU} Package Specification
25077 @cindex Intel_CPU package specification
25079 @smallexample @c adanocomment
25080 -------------------------------------------------------------------------
25082 -- file: intel_cpu.ads --
25084 -- ********************************************* --
25085 -- * WARNING: for 32-bit Intel processors only * --
25086 -- ********************************************* --
25088 -- This package contains a number of subprograms that are useful in --
25089 -- determining the Intel x86 CPU (and the features it supports) on --
25090 -- which the program is running. --
25092 -- The package is based upon the information given in the Intel --
25093 -- Application Note AP-485: "Intel Processor Identification and the --
25094 -- CPUID Instruction" as of April 1998. This application note can be --
25095 -- found on www.intel.com. --
25097 -- It currently deals with 32-bit processors only, will not detect --
25098 -- features added after april 1998, and does not guarantee proper --
25099 -- results on Intel-compatible processors. --
25101 -- Cache info and x386 fpu type detection are not supported. --
25103 -- This package does not use any privileged instructions, so should --
25104 -- work on any OS running on a 32-bit Intel processor. --
25106 -------------------------------------------------------------------------
25108 with Interfaces; use Interfaces;
25109 -- for using unsigned types
25111 with System.Machine_Code; use System.Machine_Code;
25112 -- for using inline assembler code
25114 with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
25115 -- for inserting control characters
25117 package Intel_CPU is
25119 ----------------------
25120 -- Processor bits --
25121 ----------------------
25123 subtype Num_Bits is Natural range 0 .. 31;
25124 -- the number of processor bits (32)
25126 --------------------------
25127 -- Processor register --
25128 --------------------------
25130 -- define a processor register type for easy access to
25131 -- the individual bits
25133 type Processor_Register is array (Num_Bits) of Boolean;
25134 pragma Pack (Processor_Register);
25135 for Processor_Register'Size use 32;
25137 -------------------------
25138 -- Unsigned register --
25139 -------------------------
25141 -- define a processor register type for easy access to
25142 -- the individual bytes
25144 type Unsigned_Register is
25152 for Unsigned_Register use
25154 L1 at 0 range 0 .. 7;
25155 H1 at 0 range 8 .. 15;
25156 L2 at 0 range 16 .. 23;
25157 H2 at 0 range 24 .. 31;
25160 for Unsigned_Register'Size use 32;
25162 ---------------------------------
25163 -- Intel processor vendor ID --
25164 ---------------------------------
25166 Intel_Processor : constant String (1 .. 12) := "GenuineIntel";
25167 -- indicates an Intel manufactured processor
25169 ------------------------------------
25170 -- Processor signature register --
25171 ------------------------------------
25173 -- a register type to hold the processor signature
25175 type Processor_Signature is
25177 Stepping : Natural range 0 .. 15;
25178 Model : Natural range 0 .. 15;
25179 Family : Natural range 0 .. 15;
25180 Processor_Type : Natural range 0 .. 3;
25181 Reserved : Natural range 0 .. 262143;
25184 for Processor_Signature use
25186 Stepping at 0 range 0 .. 3;
25187 Model at 0 range 4 .. 7;
25188 Family at 0 range 8 .. 11;
25189 Processor_Type at 0 range 12 .. 13;
25190 Reserved at 0 range 14 .. 31;
25193 for Processor_Signature'Size use 32;
25195 -----------------------------------
25196 -- Processor features register --
25197 -----------------------------------
25199 -- a processor register to hold the processor feature flags
25201 type Processor_Features is
25203 FPU : Boolean; -- floating point unit on chip
25204 VME : Boolean; -- virtual mode extension
25205 DE : Boolean; -- debugging extension
25206 PSE : Boolean; -- page size extension
25207 TSC : Boolean; -- time stamp counter
25208 MSR : Boolean; -- model specific registers
25209 PAE : Boolean; -- physical address extension
25210 MCE : Boolean; -- machine check extension
25211 CX8 : Boolean; -- cmpxchg8 instruction
25212 APIC : Boolean; -- on-chip apic hardware
25213 Res_1 : Boolean; -- reserved for extensions
25214 SEP : Boolean; -- fast system call
25215 MTRR : Boolean; -- memory type range registers
25216 PGE : Boolean; -- page global enable
25217 MCA : Boolean; -- machine check architecture
25218 CMOV : Boolean; -- conditional move supported
25219 PAT : Boolean; -- page attribute table
25220 PSE_36 : Boolean; -- 36-bit page size extension
25221 Res_2 : Natural range 0 .. 31; -- reserved for extensions
25222 MMX : Boolean; -- MMX technology supported
25223 FXSR : Boolean; -- fast FP save and restore
25224 Res_3 : Natural range 0 .. 127; -- reserved for extensions
25227 for Processor_Features use
25229 FPU at 0 range 0 .. 0;
25230 VME at 0 range 1 .. 1;
25231 DE at 0 range 2 .. 2;
25232 PSE at 0 range 3 .. 3;
25233 TSC at 0 range 4 .. 4;
25234 MSR at 0 range 5 .. 5;
25235 PAE at 0 range 6 .. 6;
25236 MCE at 0 range 7 .. 7;
25237 CX8 at 0 range 8 .. 8;
25238 APIC at 0 range 9 .. 9;
25239 Res_1 at 0 range 10 .. 10;
25240 SEP at 0 range 11 .. 11;
25241 MTRR at 0 range 12 .. 12;
25242 PGE at 0 range 13 .. 13;
25243 MCA at 0 range 14 .. 14;
25244 CMOV at 0 range 15 .. 15;
25245 PAT at 0 range 16 .. 16;
25246 PSE_36 at 0 range 17 .. 17;
25247 Res_2 at 0 range 18 .. 22;
25248 MMX at 0 range 23 .. 23;
25249 FXSR at 0 range 24 .. 24;
25250 Res_3 at 0 range 25 .. 31;
25253 for Processor_Features'Size use 32;
25255 -------------------
25257 -------------------
25259 function Has_FPU return Boolean;
25260 -- return True if a FPU is found
25261 -- use only if CPUID is not supported
25263 function Has_CPUID return Boolean;
25264 -- return True if the processor supports the CPUID instruction
25266 function CPUID_Level return Natural;
25267 -- return the CPUID support level (0, 1 or 2)
25268 -- can only be called if the CPUID instruction is supported
25270 function Vendor_ID return String;
25271 -- return the processor vendor identification string
25272 -- can only be called if the CPUID instruction is supported
25274 function Signature return Processor_Signature;
25275 -- return the processor signature
25276 -- can only be called if the CPUID instruction is supported
25278 function Features return Processor_Features;
25279 -- return the processors features
25280 -- can only be called if the CPUID instruction is supported
25284 ------------------------
25285 -- EFLAGS bit names --
25286 ------------------------
25288 ID_Flag : constant Num_Bits := 21;
25294 @c ---------------------------------------------------------------------------
25295 @node Intel_CPU Package Body
25296 @subsection @code{Intel_CPU} Package Body
25297 @cindex Intel_CPU package body
25299 @smallexample @c adanocomment
25300 package body Intel_CPU is
25302 ---------------------------
25303 -- Detect FPU presence --
25304 ---------------------------
25306 -- There is a FPU present if we can set values to the FPU Status
25307 -- and Control Words.
25309 function Has_FPU return Boolean is
25311 Register : Unsigned_16;
25312 -- processor register to store a word
25316 -- check if we can change the status word
25319 -- the assembler code
25320 "finit" & LF & HT & -- reset status word
25321 "movw $0x5A5A, %%ax" & LF & HT & -- set value status word
25322 "fnstsw %0" & LF & HT & -- save status word
25323 "movw %%ax, %0", -- store status word
25325 -- output stored in Register
25326 -- register must be a memory location
25327 Outputs => Unsigned_16'Asm_output ("=m", Register),
25329 -- tell compiler that we used eax
25332 -- if the status word is zero, there is no FPU
25333 if Register = 0 then
25334 return False; -- no status word
25335 end if; -- check status word value
25337 -- check if we can get the control word
25340 -- the assembler code
25341 "fnstcw %0", -- save the control word
25343 -- output into Register
25344 -- register must be a memory location
25345 Outputs => Unsigned_16'Asm_output ("=m", Register));
25347 -- check the relevant bits
25348 if (Register and 16#103F#) /= 16#003F# then
25349 return False; -- no control word
25350 end if; -- check control word value
25357 --------------------------------
25358 -- Detect CPUID instruction --
25359 --------------------------------
25361 -- The processor supports the CPUID instruction if it is possible
25362 -- to change the value of ID flag bit in the EFLAGS register.
25364 function Has_CPUID return Boolean is
25366 Original_Flags, Modified_Flags : Processor_Register;
25367 -- EFLAG contents before and after changing the ID flag
25371 -- try flipping the ID flag in the EFLAGS register
25374 -- the assembler code
25375 "pushfl" & LF & HT & -- push EFLAGS on stack
25376 "pop %%eax" & LF & HT & -- pop EFLAGS into eax
25377 "movl %%eax, %0" & LF & HT & -- save EFLAGS content
25378 "xor $0x200000, %%eax" & LF & HT & -- flip ID flag
25379 "push %%eax" & LF & HT & -- push EFLAGS on stack
25380 "popfl" & LF & HT & -- load EFLAGS register
25381 "pushfl" & LF & HT & -- push EFLAGS on stack
25382 "pop %1", -- save EFLAGS content
25384 -- output values, may be anything
25385 -- Original_Flags is %0
25386 -- Modified_Flags is %1
25388 (Processor_Register'Asm_output ("=g", Original_Flags),
25389 Processor_Register'Asm_output ("=g", Modified_Flags)),
25391 -- tell compiler eax is destroyed
25394 -- check if CPUID is supported
25395 if Original_Flags(ID_Flag) /= Modified_Flags(ID_Flag) then
25396 return True; -- ID flag was modified
25398 return False; -- ID flag unchanged
25399 end if; -- check for CPUID
25403 -------------------------------
25404 -- Get CPUID support level --
25405 -------------------------------
25407 function CPUID_Level return Natural is
25409 Level : Unsigned_32;
25410 -- returned support level
25414 -- execute CPUID, storing the results in the Level register
25417 -- the assembler code
25418 "cpuid", -- execute CPUID
25420 -- zero is stored in eax
25421 -- returning the support level in eax
25422 Inputs => Unsigned_32'Asm_input ("a", 0),
25424 -- eax is stored in Level
25425 Outputs => Unsigned_32'Asm_output ("=a", Level),
25427 -- tell compiler ebx, ecx and edx registers are destroyed
25428 Clobber => "ebx, ecx, edx");
25430 -- return the support level
25431 return Natural (Level);
25435 --------------------------------
25436 -- Get CPU Vendor ID String --
25437 --------------------------------
25439 -- The vendor ID string is returned in the ebx, ecx and edx register
25440 -- after executing the CPUID instruction with eax set to zero.
25441 -- In case of a true Intel processor the string returned is
25444 function Vendor_ID return String is
25446 Ebx, Ecx, Edx : Unsigned_Register;
25447 -- registers containing the vendor ID string
25449 Vendor_ID : String (1 .. 12);
25450 -- the vendor ID string
25454 -- execute CPUID, storing the results in the processor registers
25457 -- the assembler code
25458 "cpuid", -- execute CPUID
25460 -- zero stored in eax
25461 -- vendor ID string returned in ebx, ecx and edx
25462 Inputs => Unsigned_32'Asm_input ("a", 0),
25464 -- ebx is stored in Ebx
25465 -- ecx is stored in Ecx
25466 -- edx is stored in Edx
25467 Outputs => (Unsigned_Register'Asm_output ("=b", Ebx),
25468 Unsigned_Register'Asm_output ("=c", Ecx),
25469 Unsigned_Register'Asm_output ("=d", Edx)));
25471 -- now build the vendor ID string
25472 Vendor_ID( 1) := Character'Val (Ebx.L1);
25473 Vendor_ID( 2) := Character'Val (Ebx.H1);
25474 Vendor_ID( 3) := Character'Val (Ebx.L2);
25475 Vendor_ID( 4) := Character'Val (Ebx.H2);
25476 Vendor_ID( 5) := Character'Val (Edx.L1);
25477 Vendor_ID( 6) := Character'Val (Edx.H1);
25478 Vendor_ID( 7) := Character'Val (Edx.L2);
25479 Vendor_ID( 8) := Character'Val (Edx.H2);
25480 Vendor_ID( 9) := Character'Val (Ecx.L1);
25481 Vendor_ID(10) := Character'Val (Ecx.H1);
25482 Vendor_ID(11) := Character'Val (Ecx.L2);
25483 Vendor_ID(12) := Character'Val (Ecx.H2);
25490 -------------------------------
25491 -- Get processor signature --
25492 -------------------------------
25494 function Signature return Processor_Signature is
25496 Result : Processor_Signature;
25497 -- processor signature returned
25501 -- execute CPUID, storing the results in the Result variable
25504 -- the assembler code
25505 "cpuid", -- execute CPUID
25507 -- one is stored in eax
25508 -- processor signature returned in eax
25509 Inputs => Unsigned_32'Asm_input ("a", 1),
25511 -- eax is stored in Result
25512 Outputs => Processor_Signature'Asm_output ("=a", Result),
25514 -- tell compiler that ebx, ecx and edx are also destroyed
25515 Clobber => "ebx, ecx, edx");
25517 -- return processor signature
25522 ------------------------------
25523 -- Get processor features --
25524 ------------------------------
25526 function Features return Processor_Features is
25528 Result : Processor_Features;
25529 -- processor features returned
25533 -- execute CPUID, storing the results in the Result variable
25536 -- the assembler code
25537 "cpuid", -- execute CPUID
25539 -- one stored in eax
25540 -- processor features returned in edx
25541 Inputs => Unsigned_32'Asm_input ("a", 1),
25543 -- edx is stored in Result
25544 Outputs => Processor_Features'Asm_output ("=d", Result),
25546 -- tell compiler that ebx and ecx are also destroyed
25547 Clobber => "ebx, ecx");
25549 -- return processor signature
25556 @c END OF INLINE ASSEMBLER CHAPTER
25557 @c ===============================
25561 @c ***********************************
25562 @c * Compatibility and Porting Guide *
25563 @c ***********************************
25564 @node Compatibility and Porting Guide
25565 @appendix Compatibility and Porting Guide
25568 This chapter describes the compatibility issues that may arise between
25569 GNAT and other Ada 83 and Ada 95 compilation systems, and shows how GNAT
25570 can expedite porting
25571 applications developed in other Ada environments.
25574 * Compatibility with Ada 83::
25575 * Implementation-dependent characteristics::
25576 * Compatibility with DEC Ada 83::
25577 * Compatibility with Other Ada 95 Systems::
25578 * Representation Clauses::
25581 @node Compatibility with Ada 83
25582 @section Compatibility with Ada 83
25583 @cindex Compatibility (between Ada 83 and Ada 95)
25586 Ada 95 is designed to be highly upwards compatible with Ada 83. In
25587 particular, the design intention is that the difficulties associated
25588 with moving from Ada 83 to Ada 95 should be no greater than those
25589 that occur when moving from one Ada 83 system to another.
25591 However, there are a number of points at which there are minor
25592 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
25593 full details of these issues,
25594 and should be consulted for a complete treatment.
25596 following subsections treat the most likely issues to be encountered.
25599 * Legal Ada 83 programs that are illegal in Ada 95::
25600 * More deterministic semantics::
25601 * Changed semantics::
25602 * Other language compatibility issues::
25605 @node Legal Ada 83 programs that are illegal in Ada 95
25606 @subsection Legal Ada 83 programs that are illegal in Ada 95
25609 @item Character literals
25610 Some uses of character literals are ambiguous. Since Ada 95 has introduced
25611 @code{Wide_Character} as a new predefined character type, some uses of
25612 character literals that were legal in Ada 83 are illegal in Ada 95.
25614 @smallexample @c ada
25615 for Char in 'A' .. 'Z' loop ... end loop;
25618 The problem is that @code{'A'} and @code{'Z'} could be from either
25619 @code{Character} or @code{Wide_Character}. The simplest correction
25620 is to make the type explicit; e.g.:
25621 @smallexample @c ada
25622 for Char in Character range 'A' .. 'Z' loop ... end loop;
25625 @item New reserved words
25626 The identifiers @code{abstract}, @code{aliased}, @code{protected},
25627 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
25628 Existing Ada 83 code using any of these identifiers must be edited to
25629 use some alternative name.
25631 @item Freezing rules
25632 The rules in Ada 95 are slightly different with regard to the point at
25633 which entities are frozen, and representation pragmas and clauses are
25634 not permitted past the freeze point. This shows up most typically in
25635 the form of an error message complaining that a representation item
25636 appears too late, and the appropriate corrective action is to move
25637 the item nearer to the declaration of the entity to which it refers.
25639 A particular case is that representation pragmas
25642 extended DEC Ada 83 compatibility pragmas such as @code{Export_Procedure})
25644 cannot be applied to a subprogram body. If necessary, a separate subprogram
25645 declaration must be introduced to which the pragma can be applied.
25647 @item Optional bodies for library packages
25648 In Ada 83, a package that did not require a package body was nevertheless
25649 allowed to have one. This lead to certain surprises in compiling large
25650 systems (situations in which the body could be unexpectedly ignored by the
25651 binder). In Ada 95, if a package does not require a body then it is not
25652 permitted to have a body. To fix this problem, simply remove a redundant
25653 body if it is empty, or, if it is non-empty, introduce a dummy declaration
25654 into the spec that makes the body required. One approach is to add a private
25655 part to the package declaration (if necessary), and define a parameterless
25656 procedure called @code{Requires_Body}, which must then be given a dummy
25657 procedure body in the package body, which then becomes required.
25658 Another approach (assuming that this does not introduce elaboration
25659 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
25660 since one effect of this pragma is to require the presence of a package body.
25662 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
25663 In Ada 95, the exception @code{Numeric_Error} is a renaming of
25664 @code{Constraint_Error}.
25665 This means that it is illegal to have separate exception handlers for
25666 the two exceptions. The fix is simply to remove the handler for the
25667 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
25668 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
25670 @item Indefinite subtypes in generics
25671 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
25672 as the actual for a generic formal private type, but then the instantiation
25673 would be illegal if there were any instances of declarations of variables
25674 of this type in the generic body. In Ada 95, to avoid this clear violation
25675 of the methodological principle known as the ``contract model'',
25676 the generic declaration explicitly indicates whether
25677 or not such instantiations are permitted. If a generic formal parameter
25678 has explicit unknown discriminants, indicated by using @code{(<>)} after the
25679 type name, then it can be instantiated with indefinite types, but no
25680 stand-alone variables can be declared of this type. Any attempt to declare
25681 such a variable will result in an illegality at the time the generic is
25682 declared. If the @code{(<>)} notation is not used, then it is illegal
25683 to instantiate the generic with an indefinite type.
25684 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
25685 It will show up as a compile time error, and
25686 the fix is usually simply to add the @code{(<>)} to the generic declaration.
25689 @node More deterministic semantics
25690 @subsection More deterministic semantics
25694 Conversions from real types to integer types round away from 0. In Ada 83
25695 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
25696 implementation freedom was intended to support unbiased rounding in
25697 statistical applications, but in practice it interfered with portability.
25698 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
25699 is required. Numeric code may be affected by this change in semantics.
25700 Note, though, that this issue is no worse than already existed in Ada 83
25701 when porting code from one vendor to another.
25704 The Real-Time Annex introduces a set of policies that define the behavior of
25705 features that were implementation dependent in Ada 83, such as the order in
25706 which open select branches are executed.
25709 @node Changed semantics
25710 @subsection Changed semantics
25713 The worst kind of incompatibility is one where a program that is legal in
25714 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
25715 possible in Ada 83. Fortunately this is extremely rare, but the one
25716 situation that you should be alert to is the change in the predefined type
25717 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
25720 @item range of @code{Character}
25721 The range of @code{Standard.Character} is now the full 256 characters
25722 of Latin-1, whereas in most Ada 83 implementations it was restricted
25723 to 128 characters. Although some of the effects of
25724 this change will be manifest in compile-time rejection of legal
25725 Ada 83 programs it is possible for a working Ada 83 program to have
25726 a different effect in Ada 95, one that was not permitted in Ada 83.
25727 As an example, the expression
25728 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
25729 delivers @code{255} as its value.
25730 In general, you should look at the logic of any
25731 character-processing Ada 83 program and see whether it needs to be adapted
25732 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
25733 character handling package that may be relevant if code needs to be adapted
25734 to account for the additional Latin-1 elements.
25735 The desirable fix is to
25736 modify the program to accommodate the full character set, but in some cases
25737 it may be convenient to define a subtype or derived type of Character that
25738 covers only the restricted range.
25742 @node Other language compatibility issues
25743 @subsection Other language compatibility issues
25745 @item @option{-gnat83 switch}
25746 All implementations of GNAT provide a switch that causes GNAT to operate
25747 in Ada 83 mode. In this mode, some but not all compatibility problems
25748 of the type described above are handled automatically. For example, the
25749 new Ada 95 reserved words are treated simply as identifiers as in Ada 83.
25751 in practice, it is usually advisable to make the necessary modifications
25752 to the program to remove the need for using this switch.
25753 See @ref{Compiling Ada 83 Programs}.
25755 @item Support for removed Ada 83 pragmas and attributes
25756 A number of pragmas and attributes from Ada 83 have been removed from Ada 95,
25757 generally because they have been replaced by other mechanisms. Ada 95
25758 compilers are allowed, but not required, to implement these missing
25759 elements. In contrast with some other Ada 95 compilers, GNAT implements all
25760 such pragmas and attributes, eliminating this compatibility concern. These
25761 include @code{pragma Interface} and the floating point type attributes
25762 (@code{Emax}, @code{Mantissa}, etc.), among other items.
25766 @node Implementation-dependent characteristics
25767 @section Implementation-dependent characteristics
25769 Although the Ada language defines the semantics of each construct as
25770 precisely as practical, in some situations (for example for reasons of
25771 efficiency, or where the effect is heavily dependent on the host or target
25772 platform) the implementation is allowed some freedom. In porting Ada 83
25773 code to GNAT, you need to be aware of whether / how the existing code
25774 exercised such implementation dependencies. Such characteristics fall into
25775 several categories, and GNAT offers specific support in assisting the
25776 transition from certain Ada 83 compilers.
25779 * Implementation-defined pragmas::
25780 * Implementation-defined attributes::
25782 * Elaboration order::
25783 * Target-specific aspects::
25787 @node Implementation-defined pragmas
25788 @subsection Implementation-defined pragmas
25791 Ada compilers are allowed to supplement the language-defined pragmas, and
25792 these are a potential source of non-portability. All GNAT-defined pragmas
25793 are described in the GNAT Reference Manual, and these include several that
25794 are specifically intended to correspond to other vendors' Ada 83 pragmas.
25795 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
25797 compatibility with DEC Ada 83, GNAT supplies the pragmas
25798 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
25799 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
25800 and @code{Volatile}.
25801 Other relevant pragmas include @code{External} and @code{Link_With}.
25802 Some vendor-specific
25803 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
25805 avoiding compiler rejection of units that contain such pragmas; they are not
25806 relevant in a GNAT context and hence are not otherwise implemented.
25808 @node Implementation-defined attributes
25809 @subsection Implementation-defined attributes
25811 Analogous to pragmas, the set of attributes may be extended by an
25812 implementation. All GNAT-defined attributes are described in the
25813 @cite{GNAT Reference Manual}, and these include several that are specifically
25815 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
25816 the attribute @code{VADS_Size} may be useful. For compatibility with DEC
25817 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
25821 @subsection Libraries
25823 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
25824 code uses vendor-specific libraries then there are several ways to manage
25828 If the source code for the libraries (specifications and bodies) are
25829 available, then the libraries can be migrated in the same way as the
25832 If the source code for the specifications but not the bodies are
25833 available, then you can reimplement the bodies.
25835 Some new Ada 95 features obviate the need for library support. For
25836 example most Ada 83 vendors supplied a package for unsigned integers. The
25837 Ada 95 modular type feature is the preferred way to handle this need, so
25838 instead of migrating or reimplementing the unsigned integer package it may
25839 be preferable to retrofit the application using modular types.
25842 @node Elaboration order
25843 @subsection Elaboration order
25845 The implementation can choose any elaboration order consistent with the unit
25846 dependency relationship. This freedom means that some orders can result in
25847 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
25848 to invoke a subprogram its body has been elaborated, or to instantiate a
25849 generic before the generic body has been elaborated. By default GNAT
25850 attempts to choose a safe order (one that will not encounter access before
25851 elaboration problems) by implicitly inserting Elaborate_All pragmas where
25852 needed. However, this can lead to the creation of elaboration circularities
25853 and a resulting rejection of the program by gnatbind. This issue is
25854 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
25855 In brief, there are several
25856 ways to deal with this situation:
25860 Modify the program to eliminate the circularities, e.g. by moving
25861 elaboration-time code into explicitly-invoked procedures
25863 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
25864 @code{Elaborate} pragmas, and then inhibit the generation of implicit
25865 @code{Elaborate_All}
25866 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
25867 (by selectively suppressing elaboration checks via pragma
25868 @code{Suppress(Elaboration_Check)} when it is safe to do so).
25871 @node Target-specific aspects
25872 @subsection Target-specific aspects
25874 Low-level applications need to deal with machine addresses, data
25875 representations, interfacing with assembler code, and similar issues. If
25876 such an Ada 83 application is being ported to different target hardware (for
25877 example where the byte endianness has changed) then you will need to
25878 carefully examine the program logic; the porting effort will heavily depend
25879 on the robustness of the original design. Moreover, Ada 95 is sometimes
25880 incompatible with typical Ada 83 compiler practices regarding implicit
25881 packing, the meaning of the Size attribute, and the size of access values.
25882 GNAT's approach to these issues is described in @ref{Representation Clauses}.
25885 @node Compatibility with Other Ada 95 Systems
25886 @section Compatibility with Other Ada 95 Systems
25889 Providing that programs avoid the use of implementation dependent and
25890 implementation defined features of Ada 95, as documented in the Ada 95
25891 reference manual, there should be a high degree of portability between
25892 GNAT and other Ada 95 systems. The following are specific items which
25893 have proved troublesome in moving GNAT programs to other Ada 95
25894 compilers, but do not affect porting code to GNAT@.
25897 @item Ada 83 Pragmas and Attributes
25898 Ada 95 compilers are allowed, but not required, to implement the missing
25899 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
25900 GNAT implements all such pragmas and attributes, eliminating this as
25901 a compatibility concern, but some other Ada 95 compilers reject these
25902 pragmas and attributes.
25904 @item Special-needs Annexes
25905 GNAT implements the full set of special needs annexes. At the
25906 current time, it is the only Ada 95 compiler to do so. This means that
25907 programs making use of these features may not be portable to other Ada
25908 95 compilation systems.
25910 @item Representation Clauses
25911 Some other Ada 95 compilers implement only the minimal set of
25912 representation clauses required by the Ada 95 reference manual. GNAT goes
25913 far beyond this minimal set, as described in the next section.
25916 @node Representation Clauses
25917 @section Representation Clauses
25920 The Ada 83 reference manual was quite vague in describing both the minimal
25921 required implementation of representation clauses, and also their precise
25922 effects. The Ada 95 reference manual is much more explicit, but the minimal
25923 set of capabilities required in Ada 95 is quite limited.
25925 GNAT implements the full required set of capabilities described in the
25926 Ada 95 reference manual, but also goes much beyond this, and in particular
25927 an effort has been made to be compatible with existing Ada 83 usage to the
25928 greatest extent possible.
25930 A few cases exist in which Ada 83 compiler behavior is incompatible with
25931 requirements in the Ada 95 reference manual. These are instances of
25932 intentional or accidental dependence on specific implementation dependent
25933 characteristics of these Ada 83 compilers. The following is a list of
25934 the cases most likely to arise in existing legacy Ada 83 code.
25937 @item Implicit Packing
25938 Some Ada 83 compilers allowed a Size specification to cause implicit
25939 packing of an array or record. This could cause expensive implicit
25940 conversions for change of representation in the presence of derived
25941 types, and the Ada design intends to avoid this possibility.
25942 Subsequent AI's were issued to make it clear that such implicit
25943 change of representation in response to a Size clause is inadvisable,
25944 and this recommendation is represented explicitly in the Ada 95 RM
25945 as implementation advice that is followed by GNAT@.
25946 The problem will show up as an error
25947 message rejecting the size clause. The fix is simply to provide
25948 the explicit pragma @code{Pack}, or for more fine tuned control, provide
25949 a Component_Size clause.
25951 @item Meaning of Size Attribute
25952 The Size attribute in Ada 95 for discrete types is defined as being the
25953 minimal number of bits required to hold values of the type. For example,
25954 on a 32-bit machine, the size of Natural will typically be 31 and not
25955 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
25956 some 32 in this situation. This problem will usually show up as a compile
25957 time error, but not always. It is a good idea to check all uses of the
25958 'Size attribute when porting Ada 83 code. The GNAT specific attribute
25959 Object_Size can provide a useful way of duplicating the behavior of
25960 some Ada 83 compiler systems.
25962 @item Size of Access Types
25963 A common assumption in Ada 83 code is that an access type is in fact a pointer,
25964 and that therefore it will be the same size as a System.Address value. This
25965 assumption is true for GNAT in most cases with one exception. For the case of
25966 a pointer to an unconstrained array type (where the bounds may vary from one
25967 value of the access type to another), the default is to use a ``fat pointer'',
25968 which is represented as two separate pointers, one to the bounds, and one to
25969 the array. This representation has a number of advantages, including improved
25970 efficiency. However, it may cause some difficulties in porting existing Ada 83
25971 code which makes the assumption that, for example, pointers fit in 32 bits on
25972 a machine with 32-bit addressing.
25974 To get around this problem, GNAT also permits the use of ``thin pointers'' for
25975 access types in this case (where the designated type is an unconstrained array
25976 type). These thin pointers are indeed the same size as a System.Address value.
25977 To specify a thin pointer, use a size clause for the type, for example:
25979 @smallexample @c ada
25980 type X is access all String;
25981 for X'Size use Standard'Address_Size;
25985 which will cause the type X to be represented using a single pointer.
25986 When using this representation, the bounds are right behind the array.
25987 This representation is slightly less efficient, and does not allow quite
25988 such flexibility in the use of foreign pointers or in using the
25989 Unrestricted_Access attribute to create pointers to non-aliased objects.
25990 But for any standard portable use of the access type it will work in
25991 a functionally correct manner and allow porting of existing code.
25992 Note that another way of forcing a thin pointer representation
25993 is to use a component size clause for the element size in an array,
25994 or a record representation clause for an access field in a record.
25997 @node Compatibility with DEC Ada 83
25998 @section Compatibility with DEC Ada 83
26001 The VMS version of GNAT fully implements all the pragmas and attributes
26002 provided by DEC Ada 83, as well as providing the standard DEC Ada 83
26003 libraries, including Starlet. In addition, data layouts and parameter
26004 passing conventions are highly compatible. This means that porting
26005 existing DEC Ada 83 code to GNAT in VMS systems should be easier than
26006 most other porting efforts. The following are some of the most
26007 significant differences between GNAT and DEC Ada 83.
26010 @item Default floating-point representation
26011 In GNAT, the default floating-point format is IEEE, whereas in DEC Ada 83,
26012 it is VMS format. GNAT does implement the necessary pragmas
26013 (Long_Float, Float_Representation) for changing this default.
26016 The package System in GNAT exactly corresponds to the definition in the
26017 Ada 95 reference manual, which means that it excludes many of the
26018 DEC Ada 83 extensions. However, a separate package Aux_DEC is provided
26019 that contains the additional definitions, and a special pragma,
26020 Extend_System allows this package to be treated transparently as an
26021 extension of package System.
26024 The definitions provided by Aux_DEC are exactly compatible with those
26025 in the DEC Ada 83 version of System, with one exception.
26026 DEC Ada provides the following declarations:
26028 @smallexample @c ada
26029 TO_ADDRESS (INTEGER)
26030 TO_ADDRESS (UNSIGNED_LONGWORD)
26031 TO_ADDRESS (universal_integer)
26035 The version of TO_ADDRESS taking a universal integer argument is in fact
26036 an extension to Ada 83 not strictly compatible with the reference manual.
26037 In GNAT, we are constrained to be exactly compatible with the standard,
26038 and this means we cannot provide this capability. In DEC Ada 83, the
26039 point of this definition is to deal with a call like:
26041 @smallexample @c ada
26042 TO_ADDRESS (16#12777#);
26046 Normally, according to the Ada 83 standard, one would expect this to be
26047 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
26048 of TO_ADDRESS@. However, in DEC Ada 83, there is no ambiguity, since the
26049 definition using universal_integer takes precedence.
26051 In GNAT, since the version with universal_integer cannot be supplied, it is
26052 not possible to be 100% compatible. Since there are many programs using
26053 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
26054 to change the name of the function in the UNSIGNED_LONGWORD case, so the
26055 declarations provided in the GNAT version of AUX_Dec are:
26057 @smallexample @c ada
26058 function To_Address (X : Integer) return Address;
26059 pragma Pure_Function (To_Address);
26061 function To_Address_Long (X : Unsigned_Longword)
26063 pragma Pure_Function (To_Address_Long);
26067 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
26068 change the name to TO_ADDRESS_LONG@.
26070 @item Task_Id values
26071 The Task_Id values assigned will be different in the two systems, and GNAT
26072 does not provide a specified value for the Task_Id of the environment task,
26073 which in GNAT is treated like any other declared task.
26076 For full details on these and other less significant compatibility issues,
26077 see appendix E of the Digital publication entitled @cite{DEC Ada, Technical
26078 Overview and Comparison on DIGITAL Platforms}.
26080 For GNAT running on other than VMS systems, all the DEC Ada 83 pragmas and
26081 attributes are recognized, although only a subset of them can sensibly
26082 be implemented. The description of pragmas in this reference manual
26083 indicates whether or not they are applicable to non-VMS systems.
26088 @node Microsoft Windows Topics
26089 @appendix Microsoft Windows Topics
26095 This chapter describes topics that are specific to the Microsoft Windows
26096 platforms (NT, 2000, and XP Professional).
26099 * Using GNAT on Windows::
26100 * Using a network installation of GNAT::
26101 * CONSOLE and WINDOWS subsystems::
26102 * Temporary Files::
26103 * Mixed-Language Programming on Windows::
26104 * Windows Calling Conventions::
26105 * Introduction to Dynamic Link Libraries (DLLs)::
26106 * Using DLLs with GNAT::
26107 * Building DLLs with GNAT::
26108 * GNAT and Windows Resources::
26109 * Debugging a DLL::
26110 * GNAT and COM/DCOM Objects::
26113 @node Using GNAT on Windows
26114 @section Using GNAT on Windows
26117 One of the strengths of the GNAT technology is that its tool set
26118 (@code{gcc}, @code{gnatbind}, @code{gnatlink}, @code{gnatmake}, the
26119 @code{gdb} debugger, etc.) is used in the same way regardless of the
26122 On Windows this tool set is complemented by a number of Microsoft-specific
26123 tools that have been provided to facilitate interoperability with Windows
26124 when this is required. With these tools:
26129 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
26133 You can use any Dynamically Linked Library (DLL) in your Ada code (both
26134 relocatable and non-relocatable DLLs are supported).
26137 You can build Ada DLLs for use in other applications. These applications
26138 can be written in a language other than Ada (e.g., C, C++, etc). Again both
26139 relocatable and non-relocatable Ada DLLs are supported.
26142 You can include Windows resources in your Ada application.
26145 You can use or create COM/DCOM objects.
26149 Immediately below are listed all known general GNAT-for-Windows restrictions.
26150 Other restrictions about specific features like Windows Resources and DLLs
26151 are listed in separate sections below.
26156 It is not possible to use @code{GetLastError} and @code{SetLastError}
26157 when tasking, protected records, or exceptions are used. In these
26158 cases, in order to implement Ada semantics, the GNAT run-time system
26159 calls certain Win32 routines that set the last error variable to 0 upon
26160 success. It should be possible to use @code{GetLastError} and
26161 @code{SetLastError} when tasking, protected record, and exception
26162 features are not used, but it is not guaranteed to work.
26165 It is not possible to link against Microsoft libraries except for
26166 import libraries. The library must be built to be compatible with
26167 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
26168 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
26169 not be compatible with the GNAT runtime. Even if the library is
26170 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
26173 When the compilation environment is located on FAT32 drives, users may
26174 experience recompilations of the source files that have not changed if
26175 Daylight Saving Time (DST) state has changed since the last time files
26176 were compiled. NTFS drives do not have this problem.
26179 No components of the GNAT toolset use any entries in the Windows
26180 registry. The only entries that can be created are file associations and
26181 PATH settings, provided the user has chosen to create them at installation
26182 time, as well as some minimal book-keeping information needed to correctly
26183 uninstall or integrate different GNAT products.
26186 @node Using a network installation of GNAT
26187 @section Using a network installation of GNAT
26190 Make sure the system on which GNAT is installed is accessible from the
26191 current machine, i.e. the install location is shared over the network.
26192 Shared resources are accessed on Windows by means of UNC paths, which
26193 have the format @code{\\server\sharename\path}
26195 In order to use such a network installation, simply add the UNC path of the
26196 @file{bin} directory of your GNAT installation in front of your PATH. For
26197 example, if GNAT is installed in @file{\GNAT} directory of a share location
26198 called @file{c-drive} on a machine @file{LOKI}, the following command will
26201 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
26203 Be aware that every compilation using the network installation results in the
26204 transfer of large amounts of data across the network and will likely cause
26205 serious performance penalty.
26207 @node CONSOLE and WINDOWS subsystems
26208 @section CONSOLE and WINDOWS subsystems
26209 @cindex CONSOLE Subsystem
26210 @cindex WINDOWS Subsystem
26214 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
26215 (which is the default subsystem) will always create a console when
26216 launching the application. This is not something desirable when the
26217 application has a Windows GUI. To get rid of this console the
26218 application must be using the @code{WINDOWS} subsystem. To do so
26219 the @option{-mwindows} linker option must be specified.
26222 $ gnatmake winprog -largs -mwindows
26225 @node Temporary Files
26226 @section Temporary Files
26227 @cindex Temporary files
26230 It is possible to control where temporary files gets created by setting
26231 the TMP environment variable. The file will be created:
26234 @item Under the directory pointed to by the TMP environment variable if
26235 this directory exists.
26237 @item Under c:\temp, if the TMP environment variable is not set (or not
26238 pointing to a directory) and if this directory exists.
26240 @item Under the current working directory otherwise.
26244 This allows you to determine exactly where the temporary
26245 file will be created. This is particularly useful in networked
26246 environments where you may not have write access to some
26249 @node Mixed-Language Programming on Windows
26250 @section Mixed-Language Programming on Windows
26253 Developing pure Ada applications on Windows is no different than on
26254 other GNAT-supported platforms. However, when developing or porting an
26255 application that contains a mix of Ada and C/C++, the choice of your
26256 Windows C/C++ development environment conditions your overall
26257 interoperability strategy.
26259 If you use @code{gcc} to compile the non-Ada part of your application,
26260 there are no Windows-specific restrictions that affect the overall
26261 interoperability with your Ada code. If you plan to use
26262 Microsoft tools (e.g. Microsoft Visual C/C++), you should be aware of
26263 the following limitations:
26267 You cannot link your Ada code with an object or library generated with
26268 Microsoft tools if these use the @code{.tls} section (Thread Local
26269 Storage section) since the GNAT linker does not yet support this section.
26272 You cannot link your Ada code with an object or library generated with
26273 Microsoft tools if these use I/O routines other than those provided in
26274 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
26275 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
26276 libraries can cause a conflict with @code{msvcrt.dll} services. For
26277 instance Visual C++ I/O stream routines conflict with those in
26282 If you do want to use the Microsoft tools for your non-Ada code and hit one
26283 of the above limitations, you have two choices:
26287 Encapsulate your non Ada code in a DLL to be linked with your Ada
26288 application. In this case, use the Microsoft or whatever environment to
26289 build the DLL and use GNAT to build your executable
26290 (@pxref{Using DLLs with GNAT}).
26293 Or you can encapsulate your Ada code in a DLL to be linked with the
26294 other part of your application. In this case, use GNAT to build the DLL
26295 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
26296 environment to build your executable.
26299 @node Windows Calling Conventions
26300 @section Windows Calling Conventions
26305 * C Calling Convention::
26306 * Stdcall Calling Convention::
26307 * DLL Calling Convention::
26311 When a subprogram @code{F} (caller) calls a subprogram @code{G}
26312 (callee), there are several ways to push @code{G}'s parameters on the
26313 stack and there are several possible scenarios to clean up the stack
26314 upon @code{G}'s return. A calling convention is an agreed upon software
26315 protocol whereby the responsibilities between the caller (@code{F}) and
26316 the callee (@code{G}) are clearly defined. Several calling conventions
26317 are available for Windows:
26321 @code{C} (Microsoft defined)
26324 @code{Stdcall} (Microsoft defined)
26327 @code{DLL} (GNAT specific)
26330 @node C Calling Convention
26331 @subsection @code{C} Calling Convention
26334 This is the default calling convention used when interfacing to C/C++
26335 routines compiled with either @code{gcc} or Microsoft Visual C++.
26337 In the @code{C} calling convention subprogram parameters are pushed on the
26338 stack by the caller from right to left. The caller itself is in charge of
26339 cleaning up the stack after the call. In addition, the name of a routine
26340 with @code{C} calling convention is mangled by adding a leading underscore.
26342 The name to use on the Ada side when importing (or exporting) a routine
26343 with @code{C} calling convention is the name of the routine. For
26344 instance the C function:
26347 int get_val (long);
26351 should be imported from Ada as follows:
26353 @smallexample @c ada
26355 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26356 pragma Import (C, Get_Val, External_Name => "get_val");
26361 Note that in this particular case the @code{External_Name} parameter could
26362 have been omitted since, when missing, this parameter is taken to be the
26363 name of the Ada entity in lower case. When the @code{Link_Name} parameter
26364 is missing, as in the above example, this parameter is set to be the
26365 @code{External_Name} with a leading underscore.
26367 When importing a variable defined in C, you should always use the @code{C}
26368 calling convention unless the object containing the variable is part of a
26369 DLL (in which case you should use the @code{DLL} calling convention,
26370 @pxref{DLL Calling Convention}).
26372 @node Stdcall Calling Convention
26373 @subsection @code{Stdcall} Calling Convention
26376 This convention, which was the calling convention used for Pascal
26377 programs, is used by Microsoft for all the routines in the Win32 API for
26378 efficiency reasons. It must be used to import any routine for which this
26379 convention was specified.
26381 In the @code{Stdcall} calling convention subprogram parameters are pushed
26382 on the stack by the caller from right to left. The callee (and not the
26383 caller) is in charge of cleaning the stack on routine exit. In addition,
26384 the name of a routine with @code{Stdcall} calling convention is mangled by
26385 adding a leading underscore (as for the @code{C} calling convention) and a
26386 trailing @code{@@}@code{@i{nn}}, where @i{nn} is the overall size (in
26387 bytes) of the parameters passed to the routine.
26389 The name to use on the Ada side when importing a C routine with a
26390 @code{Stdcall} calling convention is the name of the C routine. The leading
26391 underscore and trailing @code{@@}@code{@i{nn}} are added automatically by
26392 the compiler. For instance the Win32 function:
26395 @b{APIENTRY} int get_val (long);
26399 should be imported from Ada as follows:
26401 @smallexample @c ada
26403 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26404 pragma Import (Stdcall, Get_Val);
26405 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
26410 As for the @code{C} calling convention, when the @code{External_Name}
26411 parameter is missing, it is taken to be the name of the Ada entity in lower
26412 case. If instead of writing the above import pragma you write:
26414 @smallexample @c ada
26416 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26417 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
26422 then the imported routine is @code{_retrieve_val@@4}. However, if instead
26423 of specifying the @code{External_Name} parameter you specify the
26424 @code{Link_Name} as in the following example:
26426 @smallexample @c ada
26428 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26429 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
26434 then the imported routine is @code{retrieve_val@@4}, that is, there is no
26435 trailing underscore but the appropriate @code{@@}@code{@i{nn}} is always
26436 added at the end of the @code{Link_Name} by the compiler.
26439 Note, that in some special cases a DLL's entry point name lacks a trailing
26440 @code{@@}@code{@i{nn}} while the exported name generated for a call has it.
26441 The @code{gnatdll} tool, which creates the import library for the DLL, is able
26442 to handle those cases (see the description of the switches in
26443 @pxref{Using gnatdll} section).
26445 @node DLL Calling Convention
26446 @subsection @code{DLL} Calling Convention
26449 This convention, which is GNAT-specific, must be used when you want to
26450 import in Ada a variables defined in a DLL. For functions and procedures
26451 this convention is equivalent to the @code{Stdcall} convention. As an
26452 example, if a DLL contains a variable defined as:
26459 then, to access this variable from Ada you should write:
26461 @smallexample @c ada
26463 My_Var : Interfaces.C.int;
26464 pragma Import (DLL, My_Var);
26468 The remarks concerning the @code{External_Name} and @code{Link_Name}
26469 parameters given in the previous sections equally apply to the @code{DLL}
26470 calling convention.
26472 @node Introduction to Dynamic Link Libraries (DLLs)
26473 @section Introduction to Dynamic Link Libraries (DLLs)
26477 A Dynamically Linked Library (DLL) is a library that can be shared by
26478 several applications running under Windows. A DLL can contain any number of
26479 routines and variables.
26481 One advantage of DLLs is that you can change and enhance them without
26482 forcing all the applications that depend on them to be relinked or
26483 recompiled. However, you should be aware than all calls to DLL routines are
26484 slower since, as you will understand below, such calls are indirect.
26486 To illustrate the remainder of this section, suppose that an application
26487 wants to use the services of a DLL @file{API.dll}. To use the services
26488 provided by @file{API.dll} you must statically link against an import
26489 library which contains a jump table with an entry for each routine and
26490 variable exported by the DLL. In the Microsoft world this import library is
26491 called @file{API.lib}. When using GNAT this import library is called either
26492 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
26494 After you have statically linked your application with the import library
26495 and you run your application, here is what happens:
26499 Your application is loaded into memory.
26502 The DLL @file{API.dll} is mapped into the address space of your
26503 application. This means that:
26507 The DLL will use the stack of the calling thread.
26510 The DLL will use the virtual address space of the calling process.
26513 The DLL will allocate memory from the virtual address space of the calling
26517 Handles (pointers) can be safely exchanged between routines in the DLL
26518 routines and routines in the application using the DLL.
26522 The entries in the @file{libAPI.a} or @file{API.lib} jump table which is
26523 part of your application are initialized with the addresses of the routines
26524 and variables in @file{API.dll}.
26527 If present in @file{API.dll}, routines @code{DllMain} or
26528 @code{DllMainCRTStartup} are invoked. These routines typically contain
26529 the initialization code needed for the well-being of the routines and
26530 variables exported by the DLL.
26534 There is an additional point which is worth mentioning. In the Windows
26535 world there are two kind of DLLs: relocatable and non-relocatable
26536 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
26537 in the target application address space. If the addresses of two
26538 non-relocatable DLLs overlap and these happen to be used by the same
26539 application, a conflict will occur and the application will run
26540 incorrectly. Hence, when possible, it is always preferable to use and
26541 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
26542 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
26543 User's Guide) removes the debugging symbols from the DLL but the DLL can
26544 still be relocated.
26546 As a side note, an interesting difference between Microsoft DLLs and
26547 Unix shared libraries, is the fact that on most Unix systems all public
26548 routines are exported by default in a Unix shared library, while under
26549 Windows the exported routines must be listed explicitly in a definition
26550 file (@pxref{The Definition File}).
26552 @node Using DLLs with GNAT
26553 @section Using DLLs with GNAT
26556 * Creating an Ada Spec for the DLL Services::
26557 * Creating an Import Library::
26561 To use the services of a DLL, say @file{API.dll}, in your Ada application
26566 The Ada spec for the routines and/or variables you want to access in
26567 @file{API.dll}. If not available this Ada spec must be built from the C/C++
26568 header files provided with the DLL.
26571 The import library (@file{libAPI.a} or @file{API.lib}). As previously
26572 mentioned an import library is a statically linked library containing the
26573 import table which will be filled at load time to point to the actual
26574 @file{API.dll} routines. Sometimes you don't have an import library for the
26575 DLL you want to use. The following sections will explain how to build one.
26578 The actual DLL, @file{API.dll}.
26582 Once you have all the above, to compile an Ada application that uses the
26583 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
26584 you simply issue the command
26587 $ gnatmake my_ada_app -largs -lAPI
26591 The argument @option{-largs -lAPI} at the end of the @code{gnatmake} command
26592 tells the GNAT linker to look first for a library named @file{API.lib}
26593 (Microsoft-style name) and if not found for a library named @file{libAPI.a}
26594 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
26595 contains the following pragma
26597 @smallexample @c ada
26598 pragma Linker_Options ("-lAPI");
26602 you do not have to add @option{-largs -lAPI} at the end of the @code{gnatmake}
26605 If any one of the items above is missing you will have to create it
26606 yourself. The following sections explain how to do so using as an
26607 example a fictitious DLL called @file{API.dll}.
26609 @node Creating an Ada Spec for the DLL Services
26610 @subsection Creating an Ada Spec for the DLL Services
26613 A DLL typically comes with a C/C++ header file which provides the
26614 definitions of the routines and variables exported by the DLL. The Ada
26615 equivalent of this header file is a package spec that contains definitions
26616 for the imported entities. If the DLL you intend to use does not come with
26617 an Ada spec you have to generate one such spec yourself. For example if
26618 the header file of @file{API.dll} is a file @file{api.h} containing the
26619 following two definitions:
26631 then the equivalent Ada spec could be:
26633 @smallexample @c ada
26636 with Interfaces.C.Strings;
26641 function Get (Str : C.Strings.Chars_Ptr) return C.int;
26644 pragma Import (C, Get);
26645 pragma Import (DLL, Some_Var);
26652 Note that a variable is @strong{always imported with a DLL convention}. A
26653 function can have @code{C}, @code{Stdcall} or @code{DLL} convention. For
26654 subprograms, the @code{DLL} convention is a synonym of @code{Stdcall}
26655 (@pxref{Windows Calling Conventions}).
26657 @node Creating an Import Library
26658 @subsection Creating an Import Library
26659 @cindex Import library
26662 * The Definition File::
26663 * GNAT-Style Import Library::
26664 * Microsoft-Style Import Library::
26668 If a Microsoft-style import library @file{API.lib} or a GNAT-style
26669 import library @file{libAPI.a} is available with @file{API.dll} you
26670 can skip this section. Otherwise read on.
26672 @node The Definition File
26673 @subsubsection The Definition File
26674 @cindex Definition file
26678 As previously mentioned, and unlike Unix systems, the list of symbols
26679 that are exported from a DLL must be provided explicitly in Windows.
26680 The main goal of a definition file is precisely that: list the symbols
26681 exported by a DLL. A definition file (usually a file with a @code{.def}
26682 suffix) has the following structure:
26688 [DESCRIPTION @i{string}]
26698 @item LIBRARY @i{name}
26699 This section, which is optional, gives the name of the DLL.
26701 @item DESCRIPTION @i{string}
26702 This section, which is optional, gives a description string that will be
26703 embedded in the import library.
26706 This section gives the list of exported symbols (procedures, functions or
26707 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
26708 section of @file{API.def} looks like:
26722 Note that you must specify the correct suffix (@code{@@}@code{@i{nn}})
26723 (@pxref{Windows Calling Conventions}) for a Stdcall
26724 calling convention function in the exported symbols list.
26727 There can actually be other sections in a definition file, but these
26728 sections are not relevant to the discussion at hand.
26730 @node GNAT-Style Import Library
26731 @subsubsection GNAT-Style Import Library
26734 To create a static import library from @file{API.dll} with the GNAT tools
26735 you should proceed as follows:
26739 Create the definition file @file{API.def} (@pxref{The Definition File}).
26740 For that use the @code{dll2def} tool as follows:
26743 $ dll2def API.dll > API.def
26747 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
26748 to standard output the list of entry points in the DLL. Note that if
26749 some routines in the DLL have the @code{Stdcall} convention
26750 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@i{nn}
26751 suffix then you'll have to edit @file{api.def} to add it, and specify
26752 @code{-k} to @code{gnatdll} when creating the import library.
26755 Here are some hints to find the right @code{@@}@i{nn} suffix.
26759 If you have the Microsoft import library (.lib), it is possible to get
26760 the right symbols by using Microsoft @code{dumpbin} tool (see the
26761 corresponding Microsoft documentation for further details).
26764 $ dumpbin /exports api.lib
26768 If you have a message about a missing symbol at link time the compiler
26769 tells you what symbol is expected. You just have to go back to the
26770 definition file and add the right suffix.
26774 Build the import library @code{libAPI.a}, using @code{gnatdll}
26775 (@pxref{Using gnatdll}) as follows:
26778 $ gnatdll -e API.def -d API.dll
26782 @code{gnatdll} takes as input a definition file @file{API.def} and the
26783 name of the DLL containing the services listed in the definition file
26784 @file{API.dll}. The name of the static import library generated is
26785 computed from the name of the definition file as follows: if the
26786 definition file name is @i{xyz}@code{.def}, the import library name will
26787 be @code{lib}@i{xyz}@code{.a}. Note that in the previous example option
26788 @option{-e} could have been removed because the name of the definition
26789 file (before the ``@code{.def}'' suffix) is the same as the name of the
26790 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
26793 @node Microsoft-Style Import Library
26794 @subsubsection Microsoft-Style Import Library
26797 With GNAT you can either use a GNAT-style or Microsoft-style import
26798 library. A Microsoft import library is needed only if you plan to make an
26799 Ada DLL available to applications developed with Microsoft
26800 tools (@pxref{Mixed-Language Programming on Windows}).
26802 To create a Microsoft-style import library for @file{API.dll} you
26803 should proceed as follows:
26807 Create the definition file @file{API.def} from the DLL. For this use either
26808 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
26809 tool (see the corresponding Microsoft documentation for further details).
26812 Build the actual import library using Microsoft's @code{lib} utility:
26815 $ lib -machine:IX86 -def:API.def -out:API.lib
26819 If you use the above command the definition file @file{API.def} must
26820 contain a line giving the name of the DLL:
26827 See the Microsoft documentation for further details about the usage of
26831 @node Building DLLs with GNAT
26832 @section Building DLLs with GNAT
26833 @cindex DLLs, building
26836 * Limitations When Using Ada DLLs from Ada::
26837 * Exporting Ada Entities::
26838 * Ada DLLs and Elaboration::
26839 * Ada DLLs and Finalization::
26840 * Creating a Spec for Ada DLLs::
26841 * Creating the Definition File::
26846 This section explains how to build DLLs containing Ada code. These DLLs
26847 will be referred to as Ada DLLs in the remainder of this section.
26849 The steps required to build an Ada DLL that is to be used by Ada as well as
26850 non-Ada applications are as follows:
26854 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
26855 @code{Stdcall} calling convention to avoid any Ada name mangling for the
26856 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
26857 skip this step if you plan to use the Ada DLL only from Ada applications.
26860 Your Ada code must export an initialization routine which calls the routine
26861 @code{adainit} generated by @code{gnatbind} to perform the elaboration of
26862 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
26863 routine exported by the Ada DLL must be invoked by the clients of the DLL
26864 to initialize the DLL.
26867 When useful, the DLL should also export a finalization routine which calls
26868 routine @code{adafinal} generated by @code{gnatbind} to perform the
26869 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
26870 The finalization routine exported by the Ada DLL must be invoked by the
26871 clients of the DLL when the DLL services are no further needed.
26874 You must provide a spec for the services exported by the Ada DLL in each
26875 of the programming languages to which you plan to make the DLL available.
26878 You must provide a definition file listing the exported entities
26879 (@pxref{The Definition File}).
26882 Finally you must use @code{gnatdll} to produce the DLL and the import
26883 library (@pxref{Using gnatdll}).
26887 Note that a relocatable DLL stripped using the @code{strip} binutils
26888 tool will not be relocatable anymore. To build a DLL without debug
26889 information pass @code{-largs -s} to @code{gnatdll}.
26891 @node Limitations When Using Ada DLLs from Ada
26892 @subsection Limitations When Using Ada DLLs from Ada
26895 When using Ada DLLs from Ada applications there is a limitation users
26896 should be aware of. Because on Windows the GNAT run time is not in a DLL of
26897 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
26898 each Ada DLL includes the services of the GNAT run time that are necessary
26899 to the Ada code inside the DLL. As a result, when an Ada program uses an
26900 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
26901 one in the main program.
26903 It is therefore not possible to exchange GNAT run-time objects between the
26904 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
26905 handles (e.g. @code{Text_IO.File_Type}), tasks types, protected objects
26908 It is completely safe to exchange plain elementary, array or record types,
26909 Windows object handles, etc.
26911 @node Exporting Ada Entities
26912 @subsection Exporting Ada Entities
26913 @cindex Export table
26916 Building a DLL is a way to encapsulate a set of services usable from any
26917 application. As a result, the Ada entities exported by a DLL should be
26918 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
26919 any Ada name mangling. Please note that the @code{Stdcall} convention
26920 should only be used for subprograms, not for variables. As an example here
26921 is an Ada package @code{API}, spec and body, exporting two procedures, a
26922 function, and a variable:
26924 @smallexample @c ada
26927 with Interfaces.C; use Interfaces;
26929 Count : C.int := 0;
26930 function Factorial (Val : C.int) return C.int;
26932 procedure Initialize_API;
26933 procedure Finalize_API;
26934 -- Initialization & Finalization routines. More in the next section.
26936 pragma Export (C, Initialize_API);
26937 pragma Export (C, Finalize_API);
26938 pragma Export (C, Count);
26939 pragma Export (C, Factorial);
26945 @smallexample @c ada
26948 package body API is
26949 function Factorial (Val : C.int) return C.int is
26952 Count := Count + 1;
26953 for K in 1 .. Val loop
26959 procedure Initialize_API is
26961 pragma Import (C, Adainit);
26964 end Initialize_API;
26966 procedure Finalize_API is
26967 procedure Adafinal;
26968 pragma Import (C, Adafinal);
26978 If the Ada DLL you are building will only be used by Ada applications
26979 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
26980 convention. As an example, the previous package could be written as
26983 @smallexample @c ada
26987 Count : Integer := 0;
26988 function Factorial (Val : Integer) return Integer;
26990 procedure Initialize_API;
26991 procedure Finalize_API;
26992 -- Initialization and Finalization routines.
26998 @smallexample @c ada
27001 package body API is
27002 function Factorial (Val : Integer) return Integer is
27003 Fact : Integer := 1;
27005 Count := Count + 1;
27006 for K in 1 .. Val loop
27013 -- The remainder of this package body is unchanged.
27020 Note that if you do not export the Ada entities with a @code{C} or
27021 @code{Stdcall} convention you will have to provide the mangled Ada names
27022 in the definition file of the Ada DLL
27023 (@pxref{Creating the Definition File}).
27025 @node Ada DLLs and Elaboration
27026 @subsection Ada DLLs and Elaboration
27027 @cindex DLLs and elaboration
27030 The DLL that you are building contains your Ada code as well as all the
27031 routines in the Ada library that are needed by it. The first thing a
27032 user of your DLL must do is elaborate the Ada code
27033 (@pxref{Elaboration Order Handling in GNAT}).
27035 To achieve this you must export an initialization routine
27036 (@code{Initialize_API} in the previous example), which must be invoked
27037 before using any of the DLL services. This elaboration routine must call
27038 the Ada elaboration routine @code{adainit} generated by the GNAT binder
27039 (@pxref{Binding with Non-Ada Main Programs}). See the body of
27040 @code{Initialize_Api} for an example. Note that the GNAT binder is
27041 automatically invoked during the DLL build process by the @code{gnatdll}
27042 tool (@pxref{Using gnatdll}).
27044 When a DLL is loaded, Windows systematically invokes a routine called
27045 @code{DllMain}. It would therefore be possible to call @code{adainit}
27046 directly from @code{DllMain} without having to provide an explicit
27047 initialization routine. Unfortunately, it is not possible to call
27048 @code{adainit} from the @code{DllMain} if your program has library level
27049 tasks because access to the @code{DllMain} entry point is serialized by
27050 the system (that is, only a single thread can execute ``through'' it at a
27051 time), which means that the GNAT run time will deadlock waiting for the
27052 newly created task to complete its initialization.
27054 @node Ada DLLs and Finalization
27055 @subsection Ada DLLs and Finalization
27056 @cindex DLLs and finalization
27059 When the services of an Ada DLL are no longer needed, the client code should
27060 invoke the DLL finalization routine, if available. The DLL finalization
27061 routine is in charge of releasing all resources acquired by the DLL. In the
27062 case of the Ada code contained in the DLL, this is achieved by calling
27063 routine @code{adafinal} generated by the GNAT binder
27064 (@pxref{Binding with Non-Ada Main Programs}).
27065 See the body of @code{Finalize_Api} for an
27066 example. As already pointed out the GNAT binder is automatically invoked
27067 during the DLL build process by the @code{gnatdll} tool
27068 (@pxref{Using gnatdll}).
27070 @node Creating a Spec for Ada DLLs
27071 @subsection Creating a Spec for Ada DLLs
27074 To use the services exported by the Ada DLL from another programming
27075 language (e.g. C), you have to translate the specs of the exported Ada
27076 entities in that language. For instance in the case of @code{API.dll},
27077 the corresponding C header file could look like:
27082 extern int *_imp__count;
27083 #define count (*_imp__count)
27084 int factorial (int);
27090 It is important to understand that when building an Ada DLL to be used by
27091 other Ada applications, you need two different specs for the packages
27092 contained in the DLL: one for building the DLL and the other for using
27093 the DLL. This is because the @code{DLL} calling convention is needed to
27094 use a variable defined in a DLL, but when building the DLL, the variable
27095 must have either the @code{Ada} or @code{C} calling convention. As an
27096 example consider a DLL comprising the following package @code{API}:
27098 @smallexample @c ada
27102 Count : Integer := 0;
27104 -- Remainder of the package omitted.
27111 After producing a DLL containing package @code{API}, the spec that
27112 must be used to import @code{API.Count} from Ada code outside of the
27115 @smallexample @c ada
27120 pragma Import (DLL, Count);
27126 @node Creating the Definition File
27127 @subsection Creating the Definition File
27130 The definition file is the last file needed to build the DLL. It lists
27131 the exported symbols. As an example, the definition file for a DLL
27132 containing only package @code{API} (where all the entities are exported
27133 with a @code{C} calling convention) is:
27148 If the @code{C} calling convention is missing from package @code{API},
27149 then the definition file contains the mangled Ada names of the above
27150 entities, which in this case are:
27159 api__initialize_api
27164 @node Using gnatdll
27165 @subsection Using @code{gnatdll}
27169 * gnatdll Example::
27170 * gnatdll behind the Scenes::
27175 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
27176 and non-Ada sources that make up your DLL have been compiled.
27177 @code{gnatdll} is actually in charge of two distinct tasks: build the
27178 static import library for the DLL and the actual DLL. The form of the
27179 @code{gnatdll} command is
27183 $ gnatdll [@var{switches}] @var{list-of-files} [-largs @var{opts}]
27188 where @i{list-of-files} is a list of ALI and object files. The object
27189 file list must be the exact list of objects corresponding to the non-Ada
27190 sources whose services are to be included in the DLL. The ALI file list
27191 must be the exact list of ALI files for the corresponding Ada sources
27192 whose services are to be included in the DLL. If @i{list-of-files} is
27193 missing, only the static import library is generated.
27196 You may specify any of the following switches to @code{gnatdll}:
27199 @item -a[@var{address}]
27200 @cindex @option{-a} (@code{gnatdll})
27201 Build a non-relocatable DLL at @var{address}. If @var{address} is not
27202 specified the default address @var{0x11000000} will be used. By default,
27203 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
27204 advise the reader to build relocatable DLL.
27206 @item -b @var{address}
27207 @cindex @option{-b} (@code{gnatdll})
27208 Set the relocatable DLL base address. By default the address is
27211 @item -bargs @var{opts}
27212 @cindex @option{-bargs} (@code{gnatdll})
27213 Binder options. Pass @var{opts} to the binder.
27215 @item -d @var{dllfile}
27216 @cindex @option{-d} (@code{gnatdll})
27217 @var{dllfile} is the name of the DLL. This switch must be present for
27218 @code{gnatdll} to do anything. The name of the generated import library is
27219 obtained algorithmically from @var{dllfile} as shown in the following
27220 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
27221 @code{libxyz.a}. The name of the definition file to use (if not specified
27222 by option @option{-e}) is obtained algorithmically from @var{dllfile}
27223 as shown in the following example:
27224 if @var{dllfile} is @code{xyz.dll}, the definition
27225 file used is @code{xyz.def}.
27227 @item -e @var{deffile}
27228 @cindex @option{-e} (@code{gnatdll})
27229 @var{deffile} is the name of the definition file.
27232 @cindex @option{-g} (@code{gnatdll})
27233 Generate debugging information. This information is stored in the object
27234 file and copied from there to the final DLL file by the linker,
27235 where it can be read by the debugger. You must use the
27236 @option{-g} switch if you plan on using the debugger or the symbolic
27240 @cindex @option{-h} (@code{gnatdll})
27241 Help mode. Displays @code{gnatdll} switch usage information.
27244 @cindex @option{-I} (@code{gnatdll})
27245 Direct @code{gnatdll} to search the @var{dir} directory for source and
27246 object files needed to build the DLL.
27247 (@pxref{Search Paths and the Run-Time Library (RTL)}).
27250 @cindex @option{-k} (@code{gnatdll})
27251 Removes the @code{@@}@i{nn} suffix from the import library's exported
27252 names, but keeps them for the link names. You must specify this
27253 option if you want to use a @code{Stdcall} function in a DLL for which
27254 the @code{@@}@i{nn} suffix has been removed. This is the case for most
27255 of the Windows NT DLL for example. This option has no effect when
27256 @option{-n} option is specified.
27258 @item -l @var{file}
27259 @cindex @option{-l} (@code{gnatdll})
27260 The list of ALI and object files used to build the DLL are listed in
27261 @var{file}, instead of being given in the command line. Each line in
27262 @var{file} contains the name of an ALI or object file.
27265 @cindex @option{-n} (@code{gnatdll})
27266 No Import. Do not create the import library.
27269 @cindex @option{-q} (@code{gnatdll})
27270 Quiet mode. Do not display unnecessary messages.
27273 @cindex @option{-v} (@code{gnatdll})
27274 Verbose mode. Display extra information.
27276 @item -largs @var{opts}
27277 @cindex @option{-largs} (@code{gnatdll})
27278 Linker options. Pass @var{opts} to the linker.
27281 @node gnatdll Example
27282 @subsubsection @code{gnatdll} Example
27285 As an example the command to build a relocatable DLL from @file{api.adb}
27286 once @file{api.adb} has been compiled and @file{api.def} created is
27289 $ gnatdll -d api.dll api.ali
27293 The above command creates two files: @file{libapi.a} (the import
27294 library) and @file{api.dll} (the actual DLL). If you want to create
27295 only the DLL, just type:
27298 $ gnatdll -d api.dll -n api.ali
27302 Alternatively if you want to create just the import library, type:
27305 $ gnatdll -d api.dll
27308 @node gnatdll behind the Scenes
27309 @subsubsection @code{gnatdll} behind the Scenes
27312 This section details the steps involved in creating a DLL. @code{gnatdll}
27313 does these steps for you. Unless you are interested in understanding what
27314 goes on behind the scenes, you should skip this section.
27316 We use the previous example of a DLL containing the Ada package @code{API},
27317 to illustrate the steps necessary to build a DLL. The starting point is a
27318 set of objects that will make up the DLL and the corresponding ALI
27319 files. In the case of this example this means that @file{api.o} and
27320 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
27325 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
27326 the information necessary to generate relocation information for the
27332 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
27337 In addition to the base file, the @code{gnatlink} command generates an
27338 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
27339 asks @code{gnatlink} to generate the routines @code{DllMain} and
27340 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
27341 is loaded into memory.
27344 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
27345 export table (@file{api.exp}). The export table contains the relocation
27346 information in a form which can be used during the final link to ensure
27347 that the Windows loader is able to place the DLL anywhere in memory.
27351 $ dlltool --dllname api.dll --def api.def --base-file api.base \
27352 --output-exp api.exp
27357 @code{gnatdll} builds the base file using the new export table. Note that
27358 @code{gnatbind} must be called once again since the binder generated file
27359 has been deleted during the previous call to @code{gnatlink}.
27364 $ gnatlink api -o api.jnk api.exp -mdll
27365 -Wl,--base-file,api.base
27370 @code{gnatdll} builds the new export table using the new base file and
27371 generates the DLL import library @file{libAPI.a}.
27375 $ dlltool --dllname api.dll --def api.def --base-file api.base \
27376 --output-exp api.exp --output-lib libAPI.a
27381 Finally @code{gnatdll} builds the relocatable DLL using the final export
27387 $ gnatlink api api.exp -o api.dll -mdll
27392 @node Using dlltool
27393 @subsubsection Using @code{dlltool}
27396 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
27397 DLLs and static import libraries. This section summarizes the most
27398 common @code{dlltool} switches. The form of the @code{dlltool} command
27402 $ dlltool [@var{switches}]
27406 @code{dlltool} switches include:
27409 @item --base-file @var{basefile}
27410 @cindex @option{--base-file} (@command{dlltool})
27411 Read the base file @var{basefile} generated by the linker. This switch
27412 is used to create a relocatable DLL.
27414 @item --def @var{deffile}
27415 @cindex @option{--def} (@command{dlltool})
27416 Read the definition file.
27418 @item --dllname @var{name}
27419 @cindex @option{--dllname} (@command{dlltool})
27420 Gives the name of the DLL. This switch is used to embed the name of the
27421 DLL in the static import library generated by @code{dlltool} with switch
27422 @option{--output-lib}.
27425 @cindex @option{-k} (@command{dlltool})
27426 Kill @code{@@}@i{nn} from exported names
27427 (@pxref{Windows Calling Conventions}
27428 for a discussion about @code{Stdcall}-style symbols.
27431 @cindex @option{--help} (@command{dlltool})
27432 Prints the @code{dlltool} switches with a concise description.
27434 @item --output-exp @var{exportfile}
27435 @cindex @option{--output-exp} (@command{dlltool})
27436 Generate an export file @var{exportfile}. The export file contains the
27437 export table (list of symbols in the DLL) and is used to create the DLL.
27439 @item --output-lib @i{libfile}
27440 @cindex @option{--output-lib} (@command{dlltool})
27441 Generate a static import library @var{libfile}.
27444 @cindex @option{-v} (@command{dlltool})
27447 @item --as @i{assembler-name}
27448 @cindex @option{--as} (@command{dlltool})
27449 Use @i{assembler-name} as the assembler. The default is @code{as}.
27452 @node GNAT and Windows Resources
27453 @section GNAT and Windows Resources
27454 @cindex Resources, windows
27457 * Building Resources::
27458 * Compiling Resources::
27459 * Using Resources::
27463 Resources are an easy way to add Windows specific objects to your
27464 application. The objects that can be added as resources include:
27493 This section explains how to build, compile and use resources.
27495 @node Building Resources
27496 @subsection Building Resources
27497 @cindex Resources, building
27500 A resource file is an ASCII file. By convention resource files have an
27501 @file{.rc} extension.
27502 The easiest way to build a resource file is to use Microsoft tools
27503 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
27504 @code{dlgedit.exe} to build dialogs.
27505 It is always possible to build an @file{.rc} file yourself by writing a
27508 It is not our objective to explain how to write a resource file. A
27509 complete description of the resource script language can be found in the
27510 Microsoft documentation.
27512 @node Compiling Resources
27513 @subsection Compiling Resources
27516 @cindex Resources, compiling
27519 This section describes how to build a GNAT-compatible (COFF) object file
27520 containing the resources. This is done using the Resource Compiler
27521 @code{windres} as follows:
27524 $ windres -i myres.rc -o myres.o
27528 By default @code{windres} will run @code{gcc} to preprocess the @file{.rc}
27529 file. You can specify an alternate preprocessor (usually named
27530 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
27531 parameter. A list of all possible options may be obtained by entering
27532 the command @code{windres} @option{--help}.
27534 It is also possible to use the Microsoft resource compiler @code{rc.exe}
27535 to produce a @file{.res} file (binary resource file). See the
27536 corresponding Microsoft documentation for further details. In this case
27537 you need to use @code{windres} to translate the @file{.res} file to a
27538 GNAT-compatible object file as follows:
27541 $ windres -i myres.res -o myres.o
27544 @node Using Resources
27545 @subsection Using Resources
27546 @cindex Resources, using
27549 To include the resource file in your program just add the
27550 GNAT-compatible object file for the resource(s) to the linker
27551 arguments. With @code{gnatmake} this is done by using the @option{-largs}
27555 $ gnatmake myprog -largs myres.o
27558 @node Debugging a DLL
27559 @section Debugging a DLL
27560 @cindex DLL debugging
27563 * Program and DLL Both Built with GCC/GNAT::
27564 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
27568 Debugging a DLL is similar to debugging a standard program. But
27569 we have to deal with two different executable parts: the DLL and the
27570 program that uses it. We have the following four possibilities:
27574 The program and the DLL are built with @code{GCC/GNAT}.
27576 The program is built with foreign tools and the DLL is built with
27579 The program is built with @code{GCC/GNAT} and the DLL is built with
27585 In this section we address only cases one and two above.
27586 There is no point in trying to debug
27587 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
27588 information in it. To do so you must use a debugger compatible with the
27589 tools suite used to build the DLL.
27591 @node Program and DLL Both Built with GCC/GNAT
27592 @subsection Program and DLL Both Built with GCC/GNAT
27595 This is the simplest case. Both the DLL and the program have @code{GDB}
27596 compatible debugging information. It is then possible to break anywhere in
27597 the process. Let's suppose here that the main procedure is named
27598 @code{ada_main} and that in the DLL there is an entry point named
27602 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
27603 program must have been built with the debugging information (see GNAT -g
27604 switch). Here are the step-by-step instructions for debugging it:
27607 @item Launch @code{GDB} on the main program.
27613 @item Break on the main procedure and run the program.
27616 (gdb) break ada_main
27621 This step is required to be able to set a breakpoint inside the DLL. As long
27622 as the program is not run, the DLL is not loaded. This has the
27623 consequence that the DLL debugging information is also not loaded, so it is not
27624 possible to set a breakpoint in the DLL.
27626 @item Set a breakpoint inside the DLL
27629 (gdb) break ada_dll
27636 At this stage a breakpoint is set inside the DLL. From there on
27637 you can use the standard approach to debug the whole program
27638 (@pxref{Running and Debugging Ada Programs}).
27640 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
27641 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
27644 * Debugging the DLL Directly::
27645 * Attaching to a Running Process::
27649 In this case things are slightly more complex because it is not possible to
27650 start the main program and then break at the beginning to load the DLL and the
27651 associated DLL debugging information. It is not possible to break at the
27652 beginning of the program because there is no @code{GDB} debugging information,
27653 and therefore there is no direct way of getting initial control. This
27654 section addresses this issue by describing some methods that can be used
27655 to break somewhere in the DLL to debug it.
27658 First suppose that the main procedure is named @code{main} (this is for
27659 example some C code built with Microsoft Visual C) and that there is a
27660 DLL named @code{test.dll} containing an Ada entry point named
27664 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
27665 been built with debugging information (see GNAT -g option).
27667 @node Debugging the DLL Directly
27668 @subsubsection Debugging the DLL Directly
27672 Launch the debugger on the DLL.
27678 @item Set a breakpoint on a DLL subroutine.
27681 (gdb) break ada_dll
27685 Specify the executable file to @code{GDB}.
27688 (gdb) exec-file main.exe
27699 This will run the program until it reaches the breakpoint that has been
27700 set. From that point you can use the standard way to debug a program
27701 as described in (@pxref{Running and Debugging Ada Programs}).
27706 It is also possible to debug the DLL by attaching to a running process.
27708 @node Attaching to a Running Process
27709 @subsubsection Attaching to a Running Process
27710 @cindex DLL debugging, attach to process
27713 With @code{GDB} it is always possible to debug a running process by
27714 attaching to it. It is possible to debug a DLL this way. The limitation
27715 of this approach is that the DLL must run long enough to perform the
27716 attach operation. It may be useful for instance to insert a time wasting
27717 loop in the code of the DLL to meet this criterion.
27721 @item Launch the main program @file{main.exe}.
27727 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
27728 that the process PID for @file{main.exe} is 208.
27736 @item Attach to the running process to be debugged.
27742 @item Load the process debugging information.
27745 (gdb) symbol-file main.exe
27748 @item Break somewhere in the DLL.
27751 (gdb) break ada_dll
27754 @item Continue process execution.
27763 This last step will resume the process execution, and stop at
27764 the breakpoint we have set. From there you can use the standard
27765 approach to debug a program as described in
27766 (@pxref{Running and Debugging Ada Programs}).
27768 @node GNAT and COM/DCOM Objects
27769 @section GNAT and COM/DCOM Objects
27774 This section is temporarily left blank.
27779 @c **********************************
27780 @c * GNU Free Documentation License *
27781 @c **********************************
27783 @c GNU Free Documentation License
27785 @node Index,,GNU Free Documentation License, Top
27791 @c Put table of contents at end, otherwise it precedes the "title page" in
27792 @c the .txt version
27793 @c Edit the pdf file to move the contents to the beginning, after the title