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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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.
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62 @c @itemize or @enumerate command.
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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
80 @setfilename gnat_ugn.info
83 @settitle GNAT User's Guide for Native Platforms / OpenVMS Alpha
84 @dircategory GNU Ada tools
86 * GNAT User's Guide (gnat_ugn_vms) for Native Platforms / OpenVMS Alpha
91 @settitle GNAT User's Guide for Native Platforms / Unix and Windows
93 * GNAT User's Guide (gnat_ugn_unw) for Native Platforms / Unix and Windows
97 @include gcc-common.texi
99 @setchapternewpage odd
104 Copyright @copyright{} 1995-2004, Free Software Foundation
106 Permission is granted to copy, distribute and/or modify this document
107 under the terms of the GNU Free Documentation License, Version 1.2
108 or any later version published by the Free Software Foundation;
109 with the Invariant Sections being ``GNU Free Documentation License'', with the
110 Front-Cover Texts being
112 ``GNAT User's Guide for Native Platforms / OpenVMS Alpha'',
115 ``GNAT User's Guide for Native Platforms / Unix and Windows'',
117 and with no Back-Cover Texts.
118 A copy of the license is included in the section entitled
119 ``GNU Free Documentation License''.
124 @title GNAT User's Guide
125 @center @titlefont{for Native Platforms}
130 @titlefont{@i{Unix and Windows}}
133 @titlefont{@i{OpenVMS Alpha}}
138 @subtitle GNAT, The GNU Ada 95 Compiler
139 @subtitle GCC version @value{version-GCC}
141 @author Ada Core Technologies, Inc.
144 @vskip 0pt plus 1filll
152 @node Top, About This Guide, (dir), (dir)
153 @top GNAT User's Guide
157 GNAT User's Guide for Native Platforms / OpenVMS Alpha
162 GNAT User's Guide for Native Platforms / Unix and Windows
166 GNAT, The GNU Ada 95 Compiler@*
167 GCC version @value{version-GCC}@*
170 Ada Core Technologies, Inc.@*
174 * Getting Started with GNAT::
175 * The GNAT Compilation Model::
176 * Compiling Using gcc::
177 * Binding Using gnatbind::
178 * Linking Using gnatlink::
179 * The GNAT Make Program gnatmake::
180 * Improving Performance::
181 * Renaming Files Using gnatchop::
182 * Configuration Pragmas::
183 * Handling Arbitrary File Naming Conventions Using gnatname::
184 * GNAT Project Manager::
185 * The Cross-Referencing Tools gnatxref and gnatfind::
186 * The GNAT Pretty-Printer gnatpp::
187 * File Name Krunching Using gnatkr::
188 * Preprocessing Using gnatprep::
190 * The GNAT Run-Time Library Builder gnatlbr::
192 * The GNAT Library Browser gnatls::
193 * Cleaning Up Using gnatclean::
195 * GNAT and Libraries::
196 * Using the GNU make Utility::
198 * Finding Memory Problems::
199 * Creating Sample Bodies Using gnatstub::
200 * Other Utility Programs::
201 * Running and Debugging Ada Programs::
203 * Compatibility with DEC Ada::
205 * Platform-Specific Information for the Run-Time Libraries::
206 * Example of Binder Output File::
207 * Elaboration Order Handling in GNAT::
209 * Compatibility and Porting Guide::
211 * Microsoft Windows Topics::
213 * GNU Free Documentation License::
216 --- The Detailed Node Listing ---
220 * What This Guide Contains::
221 * What You Should Know before Reading This Guide::
222 * Related Information::
225 Getting Started with GNAT
228 * Running a Simple Ada Program::
229 * Running a Program with Multiple Units::
230 * Using the gnatmake Utility::
232 * Editing with Emacs::
235 * Introduction to GPS::
236 * Introduction to Glide and GVD::
239 The GNAT Compilation Model
241 * Source Representation::
242 * Foreign Language Representation::
243 * File Naming Rules::
244 * Using Other File Names::
245 * Alternative File Naming Schemes::
246 * Generating Object Files::
247 * Source Dependencies::
248 * The Ada Library Information Files::
249 * Binding an Ada Program::
250 * Mixed Language Programming::
251 * Building Mixed Ada & C++ Programs::
252 * Comparison between GNAT and C/C++ Compilation Models::
253 * Comparison between GNAT and Conventional Ada Library Models::
255 * Placement of temporary files::
258 Foreign Language Representation
261 * Other 8-Bit Codes::
262 * Wide Character Encodings::
264 Compiling Ada Programs With gcc
266 * Compiling Programs::
268 * Search Paths and the Run-Time Library (RTL)::
269 * Order of Compilation Issues::
274 * Output and Error Message Control::
275 * Warning Message Control::
276 * Debugging and Assertion Control::
278 * Stack Overflow Checking::
279 * Validity Checking::
281 * Using gcc for Syntax Checking::
282 * Using gcc for Semantic Checking::
283 * Compiling Ada 83 Programs::
284 * Character Set Control::
285 * File Naming Control::
286 * Subprogram Inlining Control::
287 * Auxiliary Output Control::
288 * Debugging Control::
289 * Exception Handling Control::
290 * Units to Sources Mapping Files::
291 * Integrated Preprocessing::
296 Binding Ada Programs With gnatbind
299 * Switches for gnatbind::
300 * Command-Line Access::
301 * Search Paths for gnatbind::
302 * Examples of gnatbind Usage::
304 Switches for gnatbind
306 * Consistency-Checking Modes::
307 * Binder Error Message Control::
308 * Elaboration Control::
310 * Binding with Non-Ada Main Programs::
311 * Binding Programs with No Main Subprogram::
313 Linking Using gnatlink
316 * Switches for gnatlink::
317 * Setting Stack Size from gnatlink::
318 * Setting Heap Size from gnatlink::
320 The GNAT Make Program gnatmake
323 * Switches for gnatmake::
324 * Mode Switches for gnatmake::
325 * Notes on the Command Line::
326 * How gnatmake Works::
327 * Examples of gnatmake Usage::
330 Improving Performance
331 * Performance Considerations::
332 * Reducing the Size of Ada Executables with gnatelim::
334 Performance Considerations
335 * Controlling Run-Time Checks::
336 * Use of Restrictions::
337 * Optimization Levels::
338 * Debugging Optimized Code::
339 * Inlining of Subprograms::
340 * Optimization and Strict Aliasing::
342 * Coverage Analysis::
345 Reducing the Size of Ada Executables with gnatelim
348 * Correcting the List of Eliminate Pragmas::
349 * Making Your Executables Smaller::
350 * Summary of the gnatelim Usage Cycle::
352 Renaming Files Using gnatchop
354 * Handling Files with Multiple Units::
355 * Operating gnatchop in Compilation Mode::
356 * Command Line for gnatchop::
357 * Switches for gnatchop::
358 * Examples of gnatchop Usage::
360 Configuration Pragmas
362 * Handling of Configuration Pragmas::
363 * The Configuration Pragmas Files::
365 Handling Arbitrary File Naming Conventions Using gnatname
367 * Arbitrary File Naming Conventions::
369 * Switches for gnatname::
370 * Examples of gnatname Usage::
375 * Examples of Project Files::
376 * Project File Syntax::
377 * Objects and Sources in Project Files::
378 * Importing Projects::
379 * Project Extension::
380 * External References in Project Files::
381 * Packages in Project Files::
382 * Variables from Imported Projects::
385 * Using Third-Party Libraries through Projects::
386 * Stand-alone Library Projects::
387 * Switches Related to Project Files::
388 * Tools Supporting Project Files::
389 * An Extended Example::
390 * Project File Complete Syntax::
393 The Cross-Referencing Tools gnatxref and gnatfind
395 * gnatxref Switches::
396 * gnatfind Switches::
397 * Project Files for gnatxref and gnatfind::
398 * Regular Expressions in gnatfind and gnatxref::
399 * Examples of gnatxref Usage::
400 * Examples of gnatfind Usage::
403 The GNAT Pretty-Printer gnatpp
405 * Switches for gnatpp::
409 File Name Krunching Using gnatkr
414 * Examples of gnatkr Usage::
416 Preprocessing Using gnatprep
419 * Switches for gnatprep::
420 * Form of Definitions File::
421 * Form of Input Text for gnatprep::
424 The GNAT Run-Time Library Builder gnatlbr
427 * Switches for gnatlbr::
428 * Examples of gnatlbr Usage::
431 The GNAT Library Browser gnatls
434 * Switches for gnatls::
435 * Examples of gnatls Usage::
437 Cleaning Up Using gnatclean
439 * Running gnatclean::
440 * Switches for gnatclean::
441 * Examples of gnatclean Usage::
447 * Creating an Ada Library::
448 * Installing an Ada Library::
449 * Using an Ada Library::
450 * Creating an Ada Library to be Used in a Non-Ada Context::
451 * Rebuilding the GNAT Run-Time Library::
453 Using the GNU make Utility
455 * Using gnatmake in a Makefile::
456 * Automatically Creating a List of Directories::
457 * Generating the Command Line Switches::
458 * Overcoming Command Line Length Limits::
461 Finding Memory Problems
466 * The GNAT Debug Pool Facility::
472 * Switches for gnatmem::
473 * Example of gnatmem Usage::
476 The GNAT Debug Pool Facility
478 Creating Sample Bodies Using gnatstub
481 * Switches for gnatstub::
483 Other Utility Programs
485 * Using Other Utility Programs with GNAT::
486 * The External Symbol Naming Scheme of GNAT::
488 * Ada Mode for Glide::
490 * Converting Ada Files to html with gnathtml::
492 Running and Debugging Ada Programs
494 * The GNAT Debugger GDB::
496 * Introduction to GDB Commands::
497 * Using Ada Expressions::
498 * Calling User-Defined Subprograms::
499 * Using the Next Command in a Function::
502 * Debugging Generic Units::
503 * GNAT Abnormal Termination or Failure to Terminate::
504 * Naming Conventions for GNAT Source Files::
505 * Getting Internal Debugging Information::
513 Compatibility with DEC Ada
515 * Ada 95 Compatibility::
516 * Differences in the Definition of Package System::
517 * Language-Related Features::
518 * The Package STANDARD::
519 * The Package SYSTEM::
520 * Tasking and Task-Related Features::
521 * Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems::
522 * Pragmas and Pragma-Related Features::
523 * Library of Predefined Units::
525 * Main Program Definition::
526 * Implementation-Defined Attributes::
527 * Compiler and Run-Time Interfacing::
528 * Program Compilation and Library Management::
530 * Implementation Limits::
533 Language-Related Features
535 * Integer Types and Representations::
536 * Floating-Point Types and Representations::
537 * Pragmas Float_Representation and Long_Float::
538 * Fixed-Point Types and Representations::
539 * Record and Array Component Alignment::
541 * Other Representation Clauses::
543 Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
545 * Assigning Task IDs::
546 * Task IDs and Delays::
547 * Task-Related Pragmas::
548 * Scheduling and Task Priority::
550 * External Interrupts::
552 Pragmas and Pragma-Related Features
554 * Restrictions on the Pragma INLINE::
555 * Restrictions on the Pragma INTERFACE::
556 * Restrictions on the Pragma SYSTEM_NAME::
558 Library of Predefined Units
560 * Changes to DECLIB::
564 * Shared Libraries and Options Files::
568 Platform-Specific Information for the Run-Time Libraries
570 * Summary of Run-Time Configurations::
571 * Specifying a Run-Time Library::
572 * Choosing between Native and FSU Threads Libraries::
573 * Choosing the Scheduling Policy::
574 * Solaris-Specific Considerations::
575 * IRIX-Specific Considerations::
576 * Linux-Specific Considerations::
578 Example of Binder Output File
580 Elaboration Order Handling in GNAT
582 * Elaboration Code in Ada 95::
583 * Checking the Elaboration Order in Ada 95::
584 * Controlling the Elaboration Order in Ada 95::
585 * Controlling Elaboration in GNAT - Internal Calls::
586 * Controlling Elaboration in GNAT - External Calls::
587 * Default Behavior in GNAT - Ensuring Safety::
588 * Treatment of Pragma Elaborate::
589 * Elaboration Issues for Library Tasks::
590 * Mixing Elaboration Models::
591 * What to Do If the Default Elaboration Behavior Fails::
592 * Elaboration for Access-to-Subprogram Values::
593 * Summary of Procedures for Elaboration Control::
594 * Other Elaboration Order Considerations::
598 * Basic Assembler Syntax::
599 * A Simple Example of Inline Assembler::
600 * Output Variables in Inline Assembler::
601 * Input Variables in Inline Assembler::
602 * Inlining Inline Assembler Code::
603 * Other Asm Functionality::
604 * A Complete Example::
606 Compatibility and Porting Guide
608 * Compatibility with Ada 83::
609 * Implementation-dependent characteristics::
610 * Compatibility with DEC Ada 83::
611 * Compatibility with Other Ada 95 Systems::
612 * Representation Clauses::
615 Microsoft Windows Topics
617 * Using GNAT on Windows::
618 * CONSOLE and WINDOWS subsystems::
620 * Mixed-Language Programming on Windows::
621 * Windows Calling Conventions::
622 * Introduction to Dynamic Link Libraries (DLLs)::
623 * Using DLLs with GNAT::
624 * Building DLLs with GNAT::
625 * GNAT and Windows Resources::
627 * GNAT and COM/DCOM Objects::
635 @node About This Guide
636 @unnumbered About This Guide
640 This guide describes the use of of GNAT, a full language compiler for the Ada
641 95 programming language, implemented on HP OpenVMS Alpha platforms.
644 This guide describes the use of GNAT, a compiler and software development
645 toolset for the full Ada 95 programming language.
647 It describes the features of the compiler and tools, and details
648 how to use them to build Ada 95 applications.
651 * What This Guide Contains::
652 * What You Should Know before Reading This Guide::
653 * Related Information::
657 @node What This Guide Contains
658 @unnumberedsec What This Guide Contains
661 This guide contains the following chapters:
665 @ref{Getting Started with GNAT}, describes how to get started compiling
666 and running Ada programs with the GNAT Ada programming environment.
668 @ref{The GNAT Compilation Model}, describes the compilation model used
672 @ref{Compiling Using gcc}, describes how to compile
673 Ada programs with @code{gcc}, the Ada compiler.
676 @ref{Binding Using gnatbind}, describes how to
677 perform binding of Ada programs with @code{gnatbind}, the GNAT binding
681 @ref{Linking Using gnatlink},
682 describes @code{gnatlink}, a
683 program that provides for linking using the GNAT run-time library to
684 construct a program. @code{gnatlink} can also incorporate foreign language
685 object units into the executable.
688 @ref{The GNAT Make Program gnatmake}, describes @code{gnatmake}, a
689 utility that automatically determines the set of sources
690 needed by an Ada compilation unit, and executes the necessary compilations
694 @ref{Improving Performance}, shows various techniques for making your
695 Ada program run faster or take less space.
696 It discusses the effect of the compiler's optimization switch and
697 also describes the @command{gnatelim} tool.
700 @ref{Renaming Files Using gnatchop}, describes
701 @code{gnatchop}, a utility that allows you to preprocess a file that
702 contains Ada source code, and split it into one or more new files, one
703 for each compilation unit.
706 @ref{Configuration Pragmas}, describes the configuration pragmas
710 @ref{Handling Arbitrary File Naming Conventions Using gnatname},
711 shows how to override the default GNAT file naming conventions,
712 either for an individual unit or globally.
715 @ref{GNAT Project Manager}, describes how to use project files
716 to organize large projects.
719 @ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
720 @code{gnatxref} and @code{gnatfind}, two tools that provide an easy
721 way to navigate through sources.
724 @ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted
725 version of an Ada source file with control over casing, indentation,
726 comment placement, and other elements of program presentation style.
730 @ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
731 file name krunching utility, used to handle shortened
732 file names on operating systems with a limit on the length of names.
735 @ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
736 preprocessor utility that allows a single source file to be used to
737 generate multiple or parameterized source files, by means of macro
742 @ref{The GNAT Run-Time Library Builder gnatlbr}, describes @command{gnatlbr},
743 a tool for rebuilding the GNAT run time with user-supplied
744 configuration pragmas.
748 @ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
749 utility that displays information about compiled units, including dependences
750 on the corresponding sources files, and consistency of compilations.
753 @ref{Cleaning Up Using gnatclean}, describes @code{gnatclean}, a utility
754 to delete files that are produced by the compiler, binder and linker.
758 @ref{GNAT and Libraries}, describes the process of creating and using
759 Libraries with GNAT. It also describes how to recompile the GNAT run-time
763 @ref{Using the GNU make Utility}, describes some techniques for using
764 the GNAT toolset in Makefiles.
768 @ref{Finding Memory Problems}, describes
770 @command{gnatmem}, a utility that monitors dynamic allocation and deallocation
771 and helps detect ``memory leaks'', and
773 the GNAT Debug Pool facility, which helps detect incorrect memory references.
776 @ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
777 a utility that generates empty but compilable bodies for library units.
780 @ref{Other Utility Programs}, discusses several other GNAT utilities,
781 including @code{gnathtml}.
784 @ref{Running and Debugging Ada Programs}, describes how to run and debug
789 @ref{Compatibility with DEC Ada}, details the compatibility of GNAT with
790 DEC Ada 83 @footnote{``DEC Ada'' refers to the legacy product originally
791 developed by Digital Equipment Corporation and currently supported by HP.}
796 @ref{Platform-Specific Information for the Run-Time Libraries},
797 describes the various run-time
798 libraries supported by GNAT on various platforms and explains how to
799 choose a particular library.
802 @ref{Example of Binder Output File}, shows the source code for the binder
803 output file for a sample program.
806 @ref{Elaboration Order Handling in GNAT}, describes how GNAT helps
807 you deal with elaboration order issues.
810 @ref{Inline Assembler}, shows how to use the inline assembly facility
814 @ref{Compatibility and Porting Guide}, includes sections on compatibility
815 of GNAT with other Ada 83 and Ada 95 compilation systems, to assist
816 in porting code from other environments.
820 @ref{Microsoft Windows Topics}, presents information relevant to the
821 Microsoft Windows platform.
826 @c *************************************************
827 @node What You Should Know before Reading This Guide
828 @c *************************************************
829 @unnumberedsec What You Should Know before Reading This Guide
831 @cindex Ada 95 Language Reference Manual
833 This user's guide assumes that you are familiar with Ada 95 language, as
834 described in the International Standard ANSI/ISO/IEC-8652:1995, January
837 @node Related Information
838 @unnumberedsec Related Information
841 For further information about related tools, refer to the following
846 @cite{GNAT Reference Manual}, which contains all reference
847 material for the GNAT implementation of Ada 95.
851 @cite{Using the GNAT Programming System}, which describes the GPS
852 integrated development environment.
855 @cite{GNAT Programming System Tutorial}, which introduces the
856 main GPS features through examples.
860 @cite{Ada 95 Language Reference Manual}, which contains all reference
861 material for the Ada 95 programming language.
864 @cite{Debugging with GDB}
866 , located in the GNU:[DOCS] directory,
868 contains all details on the use of the GNU source-level debugger.
871 @cite{GNU Emacs Manual}
873 , located in the GNU:[DOCS] directory if the EMACS kit is installed,
875 contains full information on the extensible editor and programming
882 @unnumberedsec Conventions
884 @cindex Typographical conventions
887 Following are examples of the typographical and graphic conventions used
892 @code{Functions}, @code{utility program names}, @code{standard names},
899 @file{File Names}, @file{button names}, and @file{field names}.
908 [optional information or parameters]
911 Examples are described by text
913 and then shown this way.
918 Commands that are entered by the user are preceded in this manual by the
919 characters @w{``@code{$ }''} (dollar sign followed by space). If your system
920 uses this sequence as a prompt, then the commands will appear exactly as
921 you see them in the manual. If your system uses some other prompt, then
922 the command will appear with the @code{$} replaced by whatever prompt
923 character you are using.
926 Full file names are shown with the ``@code{/}'' character
927 as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}.
928 If you are using GNAT on a Windows platform, please note that
929 the ``@code{\}'' character should be used instead.
934 @c ****************************
935 @node Getting Started with GNAT
936 @chapter Getting Started with GNAT
939 This chapter describes some simple ways of using GNAT to build
940 executable Ada programs.
942 @ref{Running GNAT}, through @ref{Using the gnatmake Utility},
943 show how to use the command line environment.
944 @ref{Introduction to Glide and GVD}, provides a brief
945 introduction to the visually-oriented IDE for GNAT.
946 Supplementing Glide on some platforms is GPS, the
947 GNAT Programming System, which offers a richer graphical
948 ``look and feel'', enhanced configurability, support for
949 development in other programming language, comprehensive
950 browsing features, and many other capabilities.
951 For information on GPS please refer to
952 @cite{Using the GNAT Programming System}.
957 * Running a Simple Ada Program::
958 * Running a Program with Multiple Units::
959 * Using the gnatmake Utility::
961 * Editing with Emacs::
964 * Introduction to GPS::
965 * Introduction to Glide and GVD::
970 @section Running GNAT
973 Three steps are needed to create an executable file from an Ada source
978 The source file(s) must be compiled.
980 The file(s) must be bound using the GNAT binder.
982 All appropriate object files must be linked to produce an executable.
986 All three steps are most commonly handled by using the @code{gnatmake}
987 utility program that, given the name of the main program, automatically
988 performs the necessary compilation, binding and linking steps.
991 @node Running a Simple Ada Program
992 @section Running a Simple Ada Program
995 Any text editor may be used to prepare an Ada program.
998 used, the optional Ada mode may be helpful in laying out the program.
1001 program text is a normal text file. We will suppose in our initial
1002 example that you have used your editor to prepare the following
1003 standard format text file:
1005 @smallexample @c ada
1007 with Ada.Text_IO; use Ada.Text_IO;
1010 Put_Line ("Hello WORLD!");
1016 This file should be named @file{hello.adb}.
1017 With the normal default file naming conventions, GNAT requires
1019 contain a single compilation unit whose file name is the
1021 with periods replaced by hyphens; the
1022 extension is @file{ads} for a
1023 spec and @file{adb} for a body.
1024 You can override this default file naming convention by use of the
1025 special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
1026 Alternatively, if you want to rename your files according to this default
1027 convention, which is probably more convenient if you will be using GNAT
1028 for all your compilations, then the @code{gnatchop} utility
1029 can be used to generate correctly-named source files
1030 (@pxref{Renaming Files Using gnatchop}).
1032 You can compile the program using the following command (@code{$} is used
1033 as the command prompt in the examples in this document):
1040 @code{gcc} is the command used to run the compiler. This compiler is
1041 capable of compiling programs in several languages, including Ada 95 and
1042 C. It assumes that you have given it an Ada program if the file extension is
1043 either @file{.ads} or @file{.adb}, and it will then call
1044 the GNAT compiler to compile the specified file.
1047 The @option{-c} switch is required. It tells @command{gcc} to only do a
1048 compilation. (For C programs, @command{gcc} can also do linking, but this
1049 capability is not used directly for Ada programs, so the @option{-c}
1050 switch must always be present.)
1053 This compile command generates a file
1054 @file{hello.o}, which is the object
1055 file corresponding to your Ada program. It also generates
1056 an ``Ada Library Information'' file @file{hello.ali},
1057 which contains additional information used to check
1058 that an Ada program is consistent.
1059 To build an executable file,
1060 use @code{gnatbind} to bind the program
1061 and @code{gnatlink} to link it. The
1062 argument to both @code{gnatbind} and @code{gnatlink} is the name of the
1063 @file{ALI} file, but the default extension of @file{.ali} can
1064 be omitted. This means that in the most common case, the argument
1065 is simply the name of the main program:
1073 A simpler method of carrying out these steps is to use
1075 a master program that invokes all the required
1076 compilation, binding and linking tools in the correct order. In particular,
1077 @command{gnatmake} automatically recompiles any sources that have been
1078 modified since they were last compiled, or sources that depend
1079 on such modified sources, so that ``version skew'' is avoided.
1080 @cindex Version skew (avoided by @command{gnatmake})
1083 $ gnatmake hello.adb
1087 The result is an executable program called @file{hello}, which can be
1090 @c The following should be removed (BMB 2001-01-23)
1092 @c $ ^./hello^$ RUN HELLO^
1093 @c @end smallexample
1100 assuming that the current directory is on the search path
1101 for executable programs.
1104 and, if all has gone well, you will see
1111 appear in response to this command.
1114 @c ****************************************
1115 @node Running a Program with Multiple Units
1116 @section Running a Program with Multiple Units
1119 Consider a slightly more complicated example that has three files: a
1120 main program, and the spec and body of a package:
1122 @smallexample @c ada
1125 package Greetings is
1130 with Ada.Text_IO; use Ada.Text_IO;
1131 package body Greetings is
1134 Put_Line ("Hello WORLD!");
1137 procedure Goodbye is
1139 Put_Line ("Goodbye WORLD!");
1156 Following the one-unit-per-file rule, place this program in the
1157 following three separate files:
1161 spec of package @code{Greetings}
1164 body of package @code{Greetings}
1167 body of main program
1171 To build an executable version of
1172 this program, we could use four separate steps to compile, bind, and link
1173 the program, as follows:
1177 $ gcc -c greetings.adb
1183 Note that there is no required order of compilation when using GNAT.
1184 In particular it is perfectly fine to compile the main program first.
1185 Also, it is not necessary to compile package specs in the case where
1186 there is an accompanying body; you only need to compile the body. If you want
1187 to submit these files to the compiler for semantic checking and not code
1188 generation, then use the
1189 @option{-gnatc} switch:
1192 $ gcc -c greetings.ads -gnatc
1196 Although the compilation can be done in separate steps as in the
1197 above example, in practice it is almost always more convenient
1198 to use the @code{gnatmake} tool. All you need to know in this case
1199 is the name of the main program's source file. The effect of the above four
1200 commands can be achieved with a single one:
1203 $ gnatmake gmain.adb
1207 In the next section we discuss the advantages of using @code{gnatmake} in
1210 @c *****************************
1211 @node Using the gnatmake Utility
1212 @section Using the @command{gnatmake} Utility
1215 If you work on a program by compiling single components at a time using
1216 @code{gcc}, you typically keep track of the units you modify. In order to
1217 build a consistent system, you compile not only these units, but also any
1218 units that depend on the units you have modified.
1219 For example, in the preceding case,
1220 if you edit @file{gmain.adb}, you only need to recompile that file. But if
1221 you edit @file{greetings.ads}, you must recompile both
1222 @file{greetings.adb} and @file{gmain.adb}, because both files contain
1223 units that depend on @file{greetings.ads}.
1225 @code{gnatbind} will warn you if you forget one of these compilation
1226 steps, so that it is impossible to generate an inconsistent program as a
1227 result of forgetting to do a compilation. Nevertheless it is tedious and
1228 error-prone to keep track of dependencies among units.
1229 One approach to handle the dependency-bookkeeping is to use a
1230 makefile. However, makefiles present maintenance problems of their own:
1231 if the dependencies change as you change the program, you must make
1232 sure that the makefile is kept up-to-date manually, which is also an
1233 error-prone process.
1235 The @code{gnatmake} utility takes care of these details automatically.
1236 Invoke it using either one of the following forms:
1239 $ gnatmake gmain.adb
1240 $ gnatmake ^gmain^GMAIN^
1244 The argument is the name of the file containing the main program;
1245 you may omit the extension. @code{gnatmake}
1246 examines the environment, automatically recompiles any files that need
1247 recompiling, and binds and links the resulting set of object files,
1248 generating the executable file, @file{^gmain^GMAIN.EXE^}.
1249 In a large program, it
1250 can be extremely helpful to use @code{gnatmake}, because working out by hand
1251 what needs to be recompiled can be difficult.
1253 Note that @code{gnatmake}
1254 takes into account all the Ada 95 rules that
1255 establish dependencies among units. These include dependencies that result
1256 from inlining subprogram bodies, and from
1257 generic instantiation. Unlike some other
1258 Ada make tools, @code{gnatmake} does not rely on the dependencies that were
1259 found by the compiler on a previous compilation, which may possibly
1260 be wrong when sources change. @code{gnatmake} determines the exact set of
1261 dependencies from scratch each time it is run.
1264 @node Editing with Emacs
1265 @section Editing with Emacs
1269 Emacs is an extensible self-documenting text editor that is available in a
1270 separate VMSINSTAL kit.
1272 Invoke Emacs by typing @kbd{Emacs} at the command prompt. To get started,
1273 click on the Emacs Help menu and run the Emacs Tutorial.
1274 In a character cell terminal, Emacs help is invoked with @kbd{Ctrl-h} (also
1275 written as @kbd{C-h}), and the tutorial by @kbd{C-h t}.
1277 Documentation on Emacs and other tools is available in Emacs under the
1278 pull-down menu button: @code{Help - Info}. After selecting @code{Info},
1279 use the middle mouse button to select a topic (e.g. Emacs).
1281 In a character cell terminal, do @kbd{C-h i} to invoke info, and then @kbd{m}
1282 (stands for menu) followed by the menu item desired, as in @kbd{m Emacs}, to
1283 get to the Emacs manual.
1284 Help on Emacs is also available by typing @kbd{HELP EMACS} at the DCL command
1287 The tutorial is highly recommended in order to learn the intricacies of Emacs,
1288 which is sufficiently extensible to provide for a complete programming
1289 environment and shell for the sophisticated user.
1293 @node Introduction to GPS
1294 @section Introduction to GPS
1295 @cindex GPS (GNAT Programming System)
1296 @cindex GNAT Programming System (GPS)
1298 Although the command line interface (@command{gnatmake}, etc.) alone
1299 is sufficient, a graphical Interactive Development
1300 Environment can make it easier for you to compose, navigate, and debug
1301 programs. This section describes the main features of GPS
1302 (``GNAT Programming System''), the GNAT graphical IDE.
1303 You will see how to use GPS to build and debug an executable, and
1304 you will also learn some of the basics of the GNAT ``project'' facility.
1306 GPS enables you to do much more than is presented here;
1307 e.g., you can produce a call graph, interface to a third-party
1308 Version Control System, and inspect the generated assembly language
1310 Indeed, GPS also supports languages other than Ada.
1311 Such additional information, and an explanation of all of the GPS menu
1312 items. may be found in the on-line help, which includes
1313 a user's guide and a tutorial (these are also accessible from the GNAT
1317 * Building a New Program with GPS::
1318 * Simple Debugging with GPS::
1322 @node Building a New Program with GPS
1323 @subsection Building a New Program with GPS
1325 GPS invokes the GNAT compilation tools using information
1326 contained in a @emph{project} (also known as a @emph{project file}):
1327 a collection of properties such
1328 as source directories, identities of main subprograms, tool switches, etc.,
1329 and their associated values.
1330 (See @ref{GNAT Project Manager}, for details.)
1331 In order to run GPS, you will need to either create a new project
1332 or else open an existing one.
1334 This section will explain how you can use GPS to create a project,
1335 to associate Ada source files with a project, and to build and run
1339 @item @emph{Creating a project}
1341 Invoke GPS, either from the command line or the platform's IDE.
1342 After it starts, GPS will display a ``Welcome'' screen with three
1347 @code{Start with default project in directory}
1350 @code{Create new project with wizard}
1353 @code{Open existing project}
1357 Select @code{Create new project with wizard} and press @code{OK}.
1358 A new window will appear. In the text box labeled with
1359 @code{Enter the name of the project to create}, type @file{sample}
1360 as the project name.
1361 In the next box, browse to choose the directory in which you
1362 would like to create the project file.
1363 After selecting an appropriate directory, press @code{Forward}.
1365 A window will appear with the title
1366 @code{Version Control System Configuration}.
1367 Simply press @code{Forward}.
1369 A window will appear with the title
1370 @code{Please select the source directories for this project}.
1371 The directory that you specified for the project file will be selected
1372 by default as the one to use for sources; simply press @code{Forward}.
1374 A window will appear with the title
1375 @code{Please select the build directory for this project}.
1376 The directory that you specified for the project file will be selected
1377 by default for object files and executables;
1378 simply press @code{Forward}.
1380 A window will appear with the title
1381 @code{Please select the main units for this project}.
1382 You will supply this information later, after creating the source file.
1383 Simply press @code{Forward} for now.
1385 A window will appear with the title
1386 @code{Please select the switches to build the project}.
1387 Press @code{Apply}. This will create a project file named
1388 @file{sample.prj} in the directory that you had specified.
1390 @item @emph{Creating and saving the source file}
1392 After you create the new project, a GPS window will appear, which is
1393 partitioned into two main sections:
1397 A @emph{Workspace area}, initially greyed out, which you will use for
1398 creating and editing source files
1401 Directly below, a @emph{Messages area}, which initially displays a
1402 ``Welcome'' message.
1403 (If the Messages area is not visible, drag its border upward to expand it.)
1407 Select @code{File} on the menu bar, and then the @code{New} command.
1408 The Workspace area will become white, and you can now
1409 enter the source program explicitly.
1410 Type the following text
1412 @smallexample @c ada
1414 with Ada.Text_IO; use Ada.Text_IO;
1417 Put_Line("Hello from GPS!");
1423 Select @code{File}, then @code{Save As}, and enter the source file name
1425 The file will be saved in the same directory you specified as the
1426 location of the default project file.
1429 @item @emph{Updating the project file}
1431 You need to add the new source file to the project.
1433 the @code{Project} menu and then @code{Edit project properties}.
1434 Click the @code{Main files} tab on the left, and then the
1436 Choose @file{hello.adb} from the list, and press @code{Open}.
1437 The project settings window will reflect this action.
1440 @item @emph{Building and running the program}
1442 In the main GPS window, now choose the @code{Build} menu, then @code{Make},
1443 and select @file{hello.adb}.
1444 The Messages window will display the resulting invocations of @command{gcc},
1445 @command{gnatbind}, and @command{gnatlink}
1446 (reflecting the default switch settings from the
1447 project file that you created) and then a ``successful compilation/build''
1450 To run the program, choose the @code{Build} menu, then @code{Run}, and
1451 select @command{hello}.
1452 An @emph{Arguments Selection} window will appear.
1453 There are no command line arguments, so just click @code{OK}.
1455 The Messages window will now display the program's output (the string
1456 @code{Hello from GPS}), and at the bottom of the GPS window a status
1457 update is displayed (@code{Run: hello}).
1458 Close the GPS window (or select @code{File}, then @code{Exit}) to
1459 terminate this GPS session.
1464 @node Simple Debugging with GPS
1465 @subsection Simple Debugging with GPS
1467 This section illustrates basic debugging techniques (setting breakpoints,
1468 examining/modifying variables, single stepping).
1471 @item @emph{Opening a project}
1473 Start GPS and select @code{Open existing project}; browse to
1474 specify the project file @file{sample.prj} that you had created in the
1477 @item @emph{Creating a source file}
1479 Select @code{File}, then @code{New}, and type in the following program:
1481 @smallexample @c ada
1483 with Ada.Text_IO; use Ada.Text_IO;
1484 procedure Example is
1485 Line : String (1..80);
1488 Put_Line("Type a line of text at each prompt; an empty line to exit");
1492 Put_Line (Line (1..N) );
1500 Select @code{File}, then @code{Save as}, and enter the file name
1503 @item @emph{Updating the project file}
1505 Add @code{Example} as a new main unit for the project:
1508 Select @code{Project}, then @code{Edit Project Properties}.
1511 Select the @code{Main files} tab, click @code{Add}, then
1512 select the file @file{example.adb} from the list, and
1514 You will see the file name appear in the list of main units
1520 @item @emph{Building/running the executable}
1522 To build the executable
1523 select @code{Build}, then @code{Make}, and then choose @file{example.adb}.
1525 Run the program to see its effect (in the Messages area).
1526 Each line that you enter is displayed; an empty line will
1527 cause the loop to exit and the program to terminate.
1529 @item @emph{Debugging the program}
1531 Note that the @option{-g} switches to @command{gcc} and @command{gnatlink},
1532 which are required for debugging, are on by default when you create
1534 Thus unless you intentionally remove these settings, you will be able
1535 to debug any program that you develop using GPS.
1538 @item @emph{Initializing}
1540 Select @code{Debug}, then @code{Initialize}, then @file{example}
1542 @item @emph{Setting a breakpoint}
1544 After performing the initialization step, you will observe a small
1545 icon to the right of each line number.
1546 This serves as a toggle for breakpoints; clicking the icon will
1547 set a breakpoint at the corresponding line (the icon will change to
1548 a red circle with an ``x''), and clicking it again
1549 will remove the breakpoint / reset the icon.
1551 For purposes of this example, set a breakpoint at line 10 (the
1552 statement @code{Put_Line@ (Line@ (1..N));}
1554 @item @emph{Starting program execution}
1556 Select @code{Debug}, then @code{Run}. When the
1557 @code{Program Arguments} window appears, click @code{OK}.
1558 A console window will appear; enter some line of text,
1559 e.g. @code{abcde}, at the prompt.
1560 The program will pause execution when it gets to the
1561 breakpoint, and the corresponding line is highlighted.
1563 @item @emph{Examining a variable}
1565 Move the mouse over one of the occurrences of the variable @code{N}.
1566 You will see the value (5) displayed, in ``tool tip'' fashion.
1567 Right click on @code{N}, select @code{Debug}, then select @code{Display N}.
1568 You will see information about @code{N} appear in the @code{Debugger Data}
1569 pane, showing the value as 5.
1572 @item @emph{Assigning a new value to a variable}
1574 Right click on the @code{N} in the @code{Debugger Data} pane, and
1575 select @code{Set value of N}.
1576 When the input window appears, enter the value @code{4} and click
1578 This value does not automatically appear in the @code{Debugger Data}
1579 pane; to see it, right click again on the @code{N} in the
1580 @code{Debugger Data} pane and select @code{Update value}.
1581 The new value, 4, will appear in red.
1583 @item @emph{Single stepping}
1585 Select @code{Debug}, then @code{Next}.
1586 This will cause the next statement to be executed, in this case the
1587 call of @code{Put_Line} with the string slice.
1588 Notice in the console window that the displayed string is simply
1589 @code{abcd} and not @code{abcde} which you had entered.
1590 This is because the upper bound of the slice is now 4 rather than 5.
1592 @item @emph{Removing a breakpoint}
1594 Toggle the breakpoint icon at line 10.
1596 @item @emph{Resuming execution from a breakpoint}
1598 Select @code{Debug}, then @code{Continue}.
1599 The program will reach the next iteration of the loop, and
1600 wait for input after displaying the prompt.
1601 This time, just hit the @kbd{Enter} key.
1602 The value of @code{N} will be 0, and the program will terminate.
1603 The console window will disappear.
1608 @node Introduction to Glide and GVD
1609 @section Introduction to Glide and GVD
1613 This section describes the main features of Glide,
1614 a GNAT graphical IDE, and also shows how to use the basic commands in GVD,
1615 the GNU Visual Debugger.
1616 These tools may be present in addition to, or in place of, GPS on some
1618 Additional information on Glide and GVD may be found
1619 in the on-line help for these tools.
1622 * Building a New Program with Glide::
1623 * Simple Debugging with GVD::
1624 * Other Glide Features::
1627 @node Building a New Program with Glide
1628 @subsection Building a New Program with Glide
1630 The simplest way to invoke Glide is to enter @command{glide}
1631 at the command prompt. It will generally be useful to issue this
1632 as a background command, thus allowing you to continue using
1633 your command window for other purposes while Glide is running:
1640 Glide will start up with an initial screen displaying the top-level menu items
1641 as well as some other information. The menu selections are as follows
1643 @item @code{Buffers}
1654 For this introductory example, you will need to create a new Ada source file.
1655 First, select the @code{Files} menu. This will pop open a menu with around
1656 a dozen or so items. To create a file, select the @code{Open file...} choice.
1657 Depending on the platform, you may see a pop-up window where you can browse
1658 to an appropriate directory and then enter the file name, or else simply
1659 see a line at the bottom of the Glide window where you can likewise enter
1660 the file name. Note that in Glide, when you attempt to open a non-existent
1661 file, the effect is to create a file with that name. For this example enter
1662 @file{hello.adb} as the name of the file.
1664 A new buffer will now appear, occupying the entire Glide window,
1665 with the file name at the top. The menu selections are slightly different
1666 from the ones you saw on the opening screen; there is an @code{Entities} item,
1667 and in place of @code{Glide} there is now an @code{Ada} item. Glide uses
1668 the file extension to identify the source language, so @file{adb} indicates
1671 You will enter some of the source program lines explicitly,
1672 and use the syntax-oriented template mechanism to enter other lines.
1673 First, type the following text:
1675 with Ada.Text_IO; use Ada.Text_IO;
1681 Observe that Glide uses different colors to distinguish reserved words from
1682 identifiers. Also, after the @code{procedure Hello is} line, the cursor is
1683 automatically indented in anticipation of declarations. When you enter
1684 @code{begin}, Glide recognizes that there are no declarations and thus places
1685 @code{begin} flush left. But after the @code{begin} line the cursor is again
1686 indented, where the statement(s) will be placed.
1688 The main part of the program will be a @code{for} loop. Instead of entering
1689 the text explicitly, however, use a statement template. Select the @code{Ada}
1690 item on the top menu bar, move the mouse to the @code{Statements} item,
1691 and you will see a large selection of alternatives. Choose @code{for loop}.
1692 You will be prompted (at the bottom of the buffer) for a loop name;
1693 simply press the @key{Enter} key since a loop name is not needed.
1694 You should see the beginning of a @code{for} loop appear in the source
1695 program window. You will now be prompted for the name of the loop variable;
1696 enter a line with the identifier @code{ind} (lower case). Note that,
1697 by default, Glide capitalizes the name (you can override such behavior
1698 if you wish, although this is outside the scope of this introduction).
1699 Next, Glide prompts you for the loop range; enter a line containing
1700 @code{1..5} and you will see this also appear in the source program,
1701 together with the remaining elements of the @code{for} loop syntax.
1703 Next enter the statement (with an intentional error, a missing semicolon)
1704 that will form the body of the loop:
1706 Put_Line("Hello, World" & Integer'Image(I))
1710 Finally, type @code{end Hello;} as the last line in the program.
1711 Now save the file: choose the @code{File} menu item, and then the
1712 @code{Save buffer} selection. You will see a message at the bottom
1713 of the buffer confirming that the file has been saved.
1715 You are now ready to attempt to build the program. Select the @code{Ada}
1716 item from the top menu bar. Although we could choose simply to compile
1717 the file, we will instead attempt to do a build (which invokes
1718 @command{gnatmake}) since, if the compile is successful, we want to build
1719 an executable. Thus select @code{Ada build}. This will fail because of the
1720 compilation error, and you will notice that the Glide window has been split:
1721 the top window contains the source file, and the bottom window contains the
1722 output from the GNAT tools. Glide allows you to navigate from a compilation
1723 error to the source file position corresponding to the error: click the
1724 middle mouse button (or simultaneously press the left and right buttons,
1725 on a two-button mouse) on the diagnostic line in the tool window. The
1726 focus will shift to the source window, and the cursor will be positioned
1727 on the character at which the error was detected.
1729 Correct the error: type in a semicolon to terminate the statement.
1730 Although you can again save the file explicitly, you can also simply invoke
1731 @code{Ada} @result{} @code{Build} and you will be prompted to save the file.
1732 This time the build will succeed; the tool output window shows you the
1733 options that are supplied by default. The GNAT tools' output (e.g.
1734 object and ALI files, executable) will go in the directory from which
1737 To execute the program, choose @code{Ada} and then @code{Run}.
1738 You should see the program's output displayed in the bottom window:
1748 @node Simple Debugging with GVD
1749 @subsection Simple Debugging with GVD
1752 This section describes how to set breakpoints, examine/modify variables,
1753 and step through execution.
1755 In order to enable debugging, you need to pass the @option{-g} switch
1756 to both the compiler and to @command{gnatlink}. If you are using
1757 the command line, passing @option{-g} to @command{gnatmake} will have
1758 this effect. You can then launch GVD, e.g. on the @code{hello} program,
1759 by issuing the command:
1766 If you are using Glide, then @option{-g} is passed to the relevant tools
1767 by default when you do a build. Start the debugger by selecting the
1768 @code{Ada} menu item, and then @code{Debug}.
1770 GVD comes up in a multi-part window. One pane shows the names of files
1771 comprising your executable; another pane shows the source code of the current
1772 unit (initially your main subprogram), another pane shows the debugger output
1773 and user interactions, and the fourth pane (the data canvas at the top
1774 of the window) displays data objects that you have selected.
1776 To the left of the source file pane, you will notice green dots adjacent
1777 to some lines. These are lines for which object code exists and where
1778 breakpoints can thus be set. You set/reset a breakpoint by clicking
1779 the green dot. When a breakpoint is set, the dot is replaced by an @code{X}
1780 in a red circle. Clicking the circle toggles the breakpoint off,
1781 and the red circle is replaced by the green dot.
1783 For this example, set a breakpoint at the statement where @code{Put_Line}
1786 Start program execution by selecting the @code{Run} button on the top menu bar.
1787 (The @code{Start} button will also start your program, but it will
1788 cause program execution to break at the entry to your main subprogram.)
1789 Evidence of reaching the breakpoint will appear: the source file line will be
1790 highlighted, and the debugger interactions pane will display
1793 You can examine the values of variables in several ways. Move the mouse
1794 over an occurrence of @code{Ind} in the @code{for} loop, and you will see
1795 the value (now @code{1}) displayed. Alternatively, right-click on @code{Ind}
1796 and select @code{Display Ind}; a box showing the variable's name and value
1797 will appear in the data canvas.
1799 Although a loop index is a constant with respect to Ada semantics,
1800 you can change its value in the debugger. Right-click in the box
1801 for @code{Ind}, and select the @code{Set Value of Ind} item.
1802 Enter @code{2} as the new value, and press @command{OK}.
1803 The box for @code{Ind} shows the update.
1805 Press the @code{Step} button on the top menu bar; this will step through
1806 one line of program text (the invocation of @code{Put_Line}), and you can
1807 observe the effect of having modified @code{Ind} since the value displayed
1810 Remove the breakpoint, and resume execution by selecting the @code{Cont}
1811 button. You will see the remaining output lines displayed in the debugger
1812 interaction window, along with a message confirming normal program
1815 @node Other Glide Features
1816 @subsection Other Glide Features
1819 You may have observed that some of the menu selections contain abbreviations;
1820 e.g., @code{(C-x C-f)} for @code{Open file...} in the @code{Files} menu.
1821 These are @emph{shortcut keys} that you can use instead of selecting
1822 menu items. The @key{C} stands for @key{Ctrl}; thus @code{(C-x C-f)} means
1823 @key{Ctrl-x} followed by @key{Ctrl-f}, and this sequence can be used instead
1824 of selecting @code{Files} and then @code{Open file...}.
1826 To abort a Glide command, type @key{Ctrl-g}.
1828 If you want Glide to start with an existing source file, you can either
1829 launch Glide as above and then open the file via @code{Files} @result{}
1830 @code{Open file...}, or else simply pass the name of the source file
1831 on the command line:
1838 While you are using Glide, a number of @emph{buffers} exist.
1839 You create some explicitly; e.g., when you open/create a file.
1840 Others arise as an effect of the commands that you issue; e.g., the buffer
1841 containing the output of the tools invoked during a build. If a buffer
1842 is hidden, you can bring it into a visible window by first opening
1843 the @code{Buffers} menu and then selecting the desired entry.
1845 If a buffer occupies only part of the Glide screen and you want to expand it
1846 to fill the entire screen, then click in the buffer and then select
1847 @code{Files} @result{} @code{One Window}.
1849 If a window is occupied by one buffer and you want to split the window
1850 to bring up a second buffer, perform the following steps:
1852 @item Select @code{Files} @result{} @code{Split Window};
1853 this will produce two windows each of which holds the original buffer
1854 (these are not copies, but rather different views of the same buffer contents)
1856 @item With the focus in one of the windows,
1857 select the desired buffer from the @code{Buffers} menu
1861 To exit from Glide, choose @code{Files} @result{} @code{Exit}.
1864 @node The GNAT Compilation Model
1865 @chapter The GNAT Compilation Model
1866 @cindex GNAT compilation model
1867 @cindex Compilation model
1870 * Source Representation::
1871 * Foreign Language Representation::
1872 * File Naming Rules::
1873 * Using Other File Names::
1874 * Alternative File Naming Schemes::
1875 * Generating Object Files::
1876 * Source Dependencies::
1877 * The Ada Library Information Files::
1878 * Binding an Ada Program::
1879 * Mixed Language Programming::
1880 * Building Mixed Ada & C++ Programs::
1881 * Comparison between GNAT and C/C++ Compilation Models::
1882 * Comparison between GNAT and Conventional Ada Library Models::
1884 * Placement of temporary files::
1889 This chapter describes the compilation model used by GNAT. Although
1890 similar to that used by other languages, such as C and C++, this model
1891 is substantially different from the traditional Ada compilation models,
1892 which are based on a library. The model is initially described without
1893 reference to the library-based model. If you have not previously used an
1894 Ada compiler, you need only read the first part of this chapter. The
1895 last section describes and discusses the differences between the GNAT
1896 model and the traditional Ada compiler models. If you have used other
1897 Ada compilers, this section will help you to understand those
1898 differences, and the advantages of the GNAT model.
1900 @node Source Representation
1901 @section Source Representation
1905 Ada source programs are represented in standard text files, using
1906 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1907 7-bit ASCII set, plus additional characters used for
1908 representing foreign languages (@pxref{Foreign Language Representation}
1909 for support of non-USA character sets). The format effector characters
1910 are represented using their standard ASCII encodings, as follows:
1915 Vertical tab, @code{16#0B#}
1919 Horizontal tab, @code{16#09#}
1923 Carriage return, @code{16#0D#}
1927 Line feed, @code{16#0A#}
1931 Form feed, @code{16#0C#}
1935 Source files are in standard text file format. In addition, GNAT will
1936 recognize a wide variety of stream formats, in which the end of physical
1937 physical lines is marked by any of the following sequences:
1938 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1939 in accommodating files that are imported from other operating systems.
1941 @cindex End of source file
1942 @cindex Source file, end
1944 The end of a source file is normally represented by the physical end of
1945 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1946 recognized as signalling the end of the source file. Again, this is
1947 provided for compatibility with other operating systems where this
1948 code is used to represent the end of file.
1950 Each file contains a single Ada compilation unit, including any pragmas
1951 associated with the unit. For example, this means you must place a
1952 package declaration (a package @dfn{spec}) and the corresponding body in
1953 separate files. An Ada @dfn{compilation} (which is a sequence of
1954 compilation units) is represented using a sequence of files. Similarly,
1955 you will place each subunit or child unit in a separate file.
1957 @node Foreign Language Representation
1958 @section Foreign Language Representation
1961 GNAT supports the standard character sets defined in Ada 95 as well as
1962 several other non-standard character sets for use in localized versions
1963 of the compiler (@pxref{Character Set Control}).
1966 * Other 8-Bit Codes::
1967 * Wide Character Encodings::
1975 The basic character set is Latin-1. This character set is defined by ISO
1976 standard 8859, part 1. The lower half (character codes @code{16#00#}
1977 ... @code{16#7F#)} is identical to standard ASCII coding, but the upper half
1978 is used to represent additional characters. These include extended letters
1979 used by European languages, such as French accents, the vowels with umlauts
1980 used in German, and the extra letter A-ring used in Swedish.
1982 @findex Ada.Characters.Latin_1
1983 For a complete list of Latin-1 codes and their encodings, see the source
1984 file of library unit @code{Ada.Characters.Latin_1} in file
1985 @file{a-chlat1.ads}.
1986 You may use any of these extended characters freely in character or
1987 string literals. In addition, the extended characters that represent
1988 letters can be used in identifiers.
1990 @node Other 8-Bit Codes
1991 @subsection Other 8-Bit Codes
1994 GNAT also supports several other 8-bit coding schemes:
1997 @item ISO 8859-2 (Latin-2)
2000 Latin-2 letters allowed in identifiers, with uppercase and lowercase
2003 @item ISO 8859-3 (Latin-3)
2006 Latin-3 letters allowed in identifiers, with uppercase and lowercase
2009 @item ISO 8859-4 (Latin-4)
2012 Latin-4 letters allowed in identifiers, with uppercase and lowercase
2015 @item ISO 8859-5 (Cyrillic)
2018 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
2019 lowercase equivalence.
2021 @item ISO 8859-15 (Latin-9)
2024 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
2025 lowercase equivalence
2027 @item IBM PC (code page 437)
2028 @cindex code page 437
2029 This code page is the normal default for PCs in the U.S. It corresponds
2030 to the original IBM PC character set. This set has some, but not all, of
2031 the extended Latin-1 letters, but these letters do not have the same
2032 encoding as Latin-1. In this mode, these letters are allowed in
2033 identifiers with uppercase and lowercase equivalence.
2035 @item IBM PC (code page 850)
2036 @cindex code page 850
2037 This code page is a modification of 437 extended to include all the
2038 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
2039 mode, all these letters are allowed in identifiers with uppercase and
2040 lowercase equivalence.
2042 @item Full Upper 8-bit
2043 Any character in the range 80-FF allowed in identifiers, and all are
2044 considered distinct. In other words, there are no uppercase and lowercase
2045 equivalences in this range. This is useful in conjunction with
2046 certain encoding schemes used for some foreign character sets (e.g.
2047 the typical method of representing Chinese characters on the PC).
2050 No upper-half characters in the range 80-FF are allowed in identifiers.
2051 This gives Ada 83 compatibility for identifier names.
2055 For precise data on the encodings permitted, and the uppercase and lowercase
2056 equivalences that are recognized, see the file @file{csets.adb} in
2057 the GNAT compiler sources. You will need to obtain a full source release
2058 of GNAT to obtain this file.
2060 @node Wide Character Encodings
2061 @subsection Wide Character Encodings
2064 GNAT allows wide character codes to appear in character and string
2065 literals, and also optionally in identifiers, by means of the following
2066 possible encoding schemes:
2071 In this encoding, a wide character is represented by the following five
2079 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
2080 characters (using uppercase letters) of the wide character code. For
2081 example, ESC A345 is used to represent the wide character with code
2083 This scheme is compatible with use of the full Wide_Character set.
2085 @item Upper-Half Coding
2086 @cindex Upper-Half Coding
2087 The wide character with encoding @code{16#abcd#} where the upper bit is on
2088 (in other words, ``a'' is in the range 8-F) is represented as two bytes,
2089 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
2090 character, but is not required to be in the upper half. This method can
2091 be also used for shift-JIS or EUC, where the internal coding matches the
2094 @item Shift JIS Coding
2095 @cindex Shift JIS Coding
2096 A wide character is represented by a two-character sequence,
2098 @code{16#cd#}, with the restrictions described for upper-half encoding as
2099 described above. The internal character code is the corresponding JIS
2100 character according to the standard algorithm for Shift-JIS
2101 conversion. Only characters defined in the JIS code set table can be
2102 used with this encoding method.
2106 A wide character is represented by a two-character sequence
2108 @code{16#cd#}, with both characters being in the upper half. The internal
2109 character code is the corresponding JIS character according to the EUC
2110 encoding algorithm. Only characters defined in the JIS code set table
2111 can be used with this encoding method.
2114 A wide character is represented using
2115 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
2116 10646-1/Am.2. Depending on the character value, the representation
2117 is a one, two, or three byte sequence:
2122 16#0000#-16#007f#: 2#0xxxxxxx#
2123 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
2124 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
2129 where the xxx bits correspond to the left-padded bits of the
2130 16-bit character value. Note that all lower half ASCII characters
2131 are represented as ASCII bytes and all upper half characters and
2132 other wide characters are represented as sequences of upper-half
2133 (The full UTF-8 scheme allows for encoding 31-bit characters as
2134 6-byte sequences, but in this implementation, all UTF-8 sequences
2135 of four or more bytes length will be treated as illegal).
2136 @item Brackets Coding
2137 In this encoding, a wide character is represented by the following eight
2145 Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
2146 characters (using uppercase letters) of the wide character code. For
2147 example, [``A345''] is used to represent the wide character with code
2148 @code{16#A345#}. It is also possible (though not required) to use the
2149 Brackets coding for upper half characters. For example, the code
2150 @code{16#A3#} can be represented as @code{[``A3'']}.
2152 This scheme is compatible with use of the full Wide_Character set,
2153 and is also the method used for wide character encoding in the standard
2154 ACVC (Ada Compiler Validation Capability) test suite distributions.
2159 Note: Some of these coding schemes do not permit the full use of the
2160 Ada 95 character set. For example, neither Shift JIS, nor EUC allow the
2161 use of the upper half of the Latin-1 set.
2163 @node File Naming Rules
2164 @section File Naming Rules
2167 The default file name is determined by the name of the unit that the
2168 file contains. The name is formed by taking the full expanded name of
2169 the unit and replacing the separating dots with hyphens and using
2170 ^lowercase^uppercase^ for all letters.
2172 An exception arises if the file name generated by the above rules starts
2173 with one of the characters
2180 and the second character is a
2181 minus. In this case, the character ^tilde^dollar sign^ is used in place
2182 of the minus. The reason for this special rule is to avoid clashes with
2183 the standard names for child units of the packages System, Ada,
2184 Interfaces, and GNAT, which use the prefixes
2193 The file extension is @file{.ads} for a spec and
2194 @file{.adb} for a body. The following list shows some
2195 examples of these rules.
2202 @item arith_functions.ads
2203 Arith_Functions (package spec)
2204 @item arith_functions.adb
2205 Arith_Functions (package body)
2207 Func.Spec (child package spec)
2209 Func.Spec (child package body)
2211 Sub (subunit of Main)
2212 @item ^a~bad.adb^A$BAD.ADB^
2213 A.Bad (child package body)
2217 Following these rules can result in excessively long
2218 file names if corresponding
2219 unit names are long (for example, if child units or subunits are
2220 heavily nested). An option is available to shorten such long file names
2221 (called file name ``krunching''). This may be particularly useful when
2222 programs being developed with GNAT are to be used on operating systems
2223 with limited file name lengths. @xref{Using gnatkr}.
2225 Of course, no file shortening algorithm can guarantee uniqueness over
2226 all possible unit names; if file name krunching is used, it is your
2227 responsibility to ensure no name clashes occur. Alternatively you
2228 can specify the exact file names that you want used, as described
2229 in the next section. Finally, if your Ada programs are migrating from a
2230 compiler with a different naming convention, you can use the gnatchop
2231 utility to produce source files that follow the GNAT naming conventions.
2232 (For details @pxref{Renaming Files Using gnatchop}.)
2234 Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating
2235 systems, case is not significant. So for example on @code{Windows XP}
2236 if the canonical name is @code{main-sub.adb}, you can use the file name
2237 @code{Main-Sub.adb} instead. However, case is significant for other
2238 operating systems, so for example, if you want to use other than
2239 canonically cased file names on a Unix system, you need to follow
2240 the procedures described in the next section.
2242 @node Using Other File Names
2243 @section Using Other File Names
2247 In the previous section, we have described the default rules used by
2248 GNAT to determine the file name in which a given unit resides. It is
2249 often convenient to follow these default rules, and if you follow them,
2250 the compiler knows without being explicitly told where to find all
2253 However, in some cases, particularly when a program is imported from
2254 another Ada compiler environment, it may be more convenient for the
2255 programmer to specify which file names contain which units. GNAT allows
2256 arbitrary file names to be used by means of the Source_File_Name pragma.
2257 The form of this pragma is as shown in the following examples:
2258 @cindex Source_File_Name pragma
2260 @smallexample @c ada
2262 pragma Source_File_Name (My_Utilities.Stacks,
2263 Spec_File_Name => "myutilst_a.ada");
2264 pragma Source_File_name (My_Utilities.Stacks,
2265 Body_File_Name => "myutilst.ada");
2270 As shown in this example, the first argument for the pragma is the unit
2271 name (in this example a child unit). The second argument has the form
2272 of a named association. The identifier
2273 indicates whether the file name is for a spec or a body;
2274 the file name itself is given by a string literal.
2276 The source file name pragma is a configuration pragma, which means that
2277 normally it will be placed in the @file{gnat.adc}
2278 file used to hold configuration
2279 pragmas that apply to a complete compilation environment.
2280 For more details on how the @file{gnat.adc} file is created and used
2281 @pxref{Handling of Configuration Pragmas}
2282 @cindex @file{gnat.adc}
2285 GNAT allows completely arbitrary file names to be specified using the
2286 source file name pragma. However, if the file name specified has an
2287 extension other than @file{.ads} or @file{.adb} it is necessary to use
2288 a special syntax when compiling the file. The name in this case must be
2289 preceded by the special sequence @code{-x} followed by a space and the name
2290 of the language, here @code{ada}, as in:
2293 $ gcc -c -x ada peculiar_file_name.sim
2298 @code{gnatmake} handles non-standard file names in the usual manner (the
2299 non-standard file name for the main program is simply used as the
2300 argument to gnatmake). Note that if the extension is also non-standard,
2301 then it must be included in the gnatmake command, it may not be omitted.
2303 @node Alternative File Naming Schemes
2304 @section Alternative File Naming Schemes
2305 @cindex File naming schemes, alternative
2308 In the previous section, we described the use of the @code{Source_File_Name}
2309 pragma to allow arbitrary names to be assigned to individual source files.
2310 However, this approach requires one pragma for each file, and especially in
2311 large systems can result in very long @file{gnat.adc} files, and also create
2312 a maintenance problem.
2314 GNAT also provides a facility for specifying systematic file naming schemes
2315 other than the standard default naming scheme previously described. An
2316 alternative scheme for naming is specified by the use of
2317 @code{Source_File_Name} pragmas having the following format:
2318 @cindex Source_File_Name pragma
2320 @smallexample @c ada
2321 pragma Source_File_Name (
2322 Spec_File_Name => FILE_NAME_PATTERN
2323 [,Casing => CASING_SPEC]
2324 [,Dot_Replacement => STRING_LITERAL]);
2326 pragma Source_File_Name (
2327 Body_File_Name => FILE_NAME_PATTERN
2328 [,Casing => CASING_SPEC]
2329 [,Dot_Replacement => STRING_LITERAL]);
2331 pragma Source_File_Name (
2332 Subunit_File_Name => FILE_NAME_PATTERN
2333 [,Casing => CASING_SPEC]
2334 [,Dot_Replacement => STRING_LITERAL]);
2336 FILE_NAME_PATTERN ::= STRING_LITERAL
2337 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
2341 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
2342 It contains a single asterisk character, and the unit name is substituted
2343 systematically for this asterisk. The optional parameter
2344 @code{Casing} indicates
2345 whether the unit name is to be all upper-case letters, all lower-case letters,
2346 or mixed-case. If no
2347 @code{Casing} parameter is used, then the default is all
2348 ^lower-case^upper-case^.
2350 The optional @code{Dot_Replacement} string is used to replace any periods
2351 that occur in subunit or child unit names. If no @code{Dot_Replacement}
2352 argument is used then separating dots appear unchanged in the resulting
2354 Although the above syntax indicates that the
2355 @code{Casing} argument must appear
2356 before the @code{Dot_Replacement} argument, but it
2357 is also permissible to write these arguments in the opposite order.
2359 As indicated, it is possible to specify different naming schemes for
2360 bodies, specs, and subunits. Quite often the rule for subunits is the
2361 same as the rule for bodies, in which case, there is no need to give
2362 a separate @code{Subunit_File_Name} rule, and in this case the
2363 @code{Body_File_name} rule is used for subunits as well.
2365 The separate rule for subunits can also be used to implement the rather
2366 unusual case of a compilation environment (e.g. a single directory) which
2367 contains a subunit and a child unit with the same unit name. Although
2368 both units cannot appear in the same partition, the Ada Reference Manual
2369 allows (but does not require) the possibility of the two units coexisting
2370 in the same environment.
2372 The file name translation works in the following steps:
2377 If there is a specific @code{Source_File_Name} pragma for the given unit,
2378 then this is always used, and any general pattern rules are ignored.
2381 If there is a pattern type @code{Source_File_Name} pragma that applies to
2382 the unit, then the resulting file name will be used if the file exists. If
2383 more than one pattern matches, the latest one will be tried first, and the
2384 first attempt resulting in a reference to a file that exists will be used.
2387 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2388 for which the corresponding file exists, then the standard GNAT default
2389 naming rules are used.
2394 As an example of the use of this mechanism, consider a commonly used scheme
2395 in which file names are all lower case, with separating periods copied
2396 unchanged to the resulting file name, and specs end with @file{.1.ada}, and
2397 bodies end with @file{.2.ada}. GNAT will follow this scheme if the following
2400 @smallexample @c ada
2401 pragma Source_File_Name
2402 (Spec_File_Name => "*.1.ada");
2403 pragma Source_File_Name
2404 (Body_File_Name => "*.2.ada");
2408 The default GNAT scheme is actually implemented by providing the following
2409 default pragmas internally:
2411 @smallexample @c ada
2412 pragma Source_File_Name
2413 (Spec_File_Name => "*.ads", Dot_Replacement => "-");
2414 pragma Source_File_Name
2415 (Body_File_Name => "*.adb", Dot_Replacement => "-");
2419 Our final example implements a scheme typically used with one of the
2420 Ada 83 compilers, where the separator character for subunits was ``__''
2421 (two underscores), specs were identified by adding @file{_.ADA}, bodies
2422 by adding @file{.ADA}, and subunits by
2423 adding @file{.SEP}. All file names were
2424 upper case. Child units were not present of course since this was an
2425 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2426 the same double underscore separator for child units.
2428 @smallexample @c ada
2429 pragma Source_File_Name
2430 (Spec_File_Name => "*_.ADA",
2431 Dot_Replacement => "__",
2432 Casing = Uppercase);
2433 pragma Source_File_Name
2434 (Body_File_Name => "*.ADA",
2435 Dot_Replacement => "__",
2436 Casing = Uppercase);
2437 pragma Source_File_Name
2438 (Subunit_File_Name => "*.SEP",
2439 Dot_Replacement => "__",
2440 Casing = Uppercase);
2443 @node Generating Object Files
2444 @section Generating Object Files
2447 An Ada program consists of a set of source files, and the first step in
2448 compiling the program is to generate the corresponding object files.
2449 These are generated by compiling a subset of these source files.
2450 The files you need to compile are the following:
2454 If a package spec has no body, compile the package spec to produce the
2455 object file for the package.
2458 If a package has both a spec and a body, compile the body to produce the
2459 object file for the package. The source file for the package spec need
2460 not be compiled in this case because there is only one object file, which
2461 contains the code for both the spec and body of the package.
2464 For a subprogram, compile the subprogram body to produce the object file
2465 for the subprogram. The spec, if one is present, is as usual in a
2466 separate file, and need not be compiled.
2470 In the case of subunits, only compile the parent unit. A single object
2471 file is generated for the entire subunit tree, which includes all the
2475 Compile child units independently of their parent units
2476 (though, of course, the spec of all the ancestor unit must be present in order
2477 to compile a child unit).
2481 Compile generic units in the same manner as any other units. The object
2482 files in this case are small dummy files that contain at most the
2483 flag used for elaboration checking. This is because GNAT always handles generic
2484 instantiation by means of macro expansion. However, it is still necessary to
2485 compile generic units, for dependency checking and elaboration purposes.
2489 The preceding rules describe the set of files that must be compiled to
2490 generate the object files for a program. Each object file has the same
2491 name as the corresponding source file, except that the extension is
2494 You may wish to compile other files for the purpose of checking their
2495 syntactic and semantic correctness. For example, in the case where a
2496 package has a separate spec and body, you would not normally compile the
2497 spec. However, it is convenient in practice to compile the spec to make
2498 sure it is error-free before compiling clients of this spec, because such
2499 compilations will fail if there is an error in the spec.
2501 GNAT provides an option for compiling such files purely for the
2502 purposes of checking correctness; such compilations are not required as
2503 part of the process of building a program. To compile a file in this
2504 checking mode, use the @option{-gnatc} switch.
2506 @node Source Dependencies
2507 @section Source Dependencies
2510 A given object file clearly depends on the source file which is compiled
2511 to produce it. Here we are using @dfn{depends} in the sense of a typical
2512 @code{make} utility; in other words, an object file depends on a source
2513 file if changes to the source file require the object file to be
2515 In addition to this basic dependency, a given object may depend on
2516 additional source files as follows:
2520 If a file being compiled @code{with}'s a unit @var{X}, the object file
2521 depends on the file containing the spec of unit @var{X}. This includes
2522 files that are @code{with}'ed implicitly either because they are parents
2523 of @code{with}'ed child units or they are run-time units required by the
2524 language constructs used in a particular unit.
2527 If a file being compiled instantiates a library level generic unit, the
2528 object file depends on both the spec and body files for this generic
2532 If a file being compiled instantiates a generic unit defined within a
2533 package, the object file depends on the body file for the package as
2534 well as the spec file.
2538 @cindex @option{-gnatn} switch
2539 If a file being compiled contains a call to a subprogram for which
2540 pragma @code{Inline} applies and inlining is activated with the
2541 @option{-gnatn} switch, the object file depends on the file containing the
2542 body of this subprogram as well as on the file containing the spec. Note
2543 that for inlining to actually occur as a result of the use of this switch,
2544 it is necessary to compile in optimizing mode.
2546 @cindex @option{-gnatN} switch
2547 The use of @option{-gnatN} activates a more extensive inlining optimization
2548 that is performed by the front end of the compiler. This inlining does
2549 not require that the code generation be optimized. Like @option{-gnatn},
2550 the use of this switch generates additional dependencies.
2552 @option{-gnatN} automatically implies @option{-gnatn} so it is not necessary
2553 to specify both options.
2556 If an object file O depends on the proper body of a subunit through inlining
2557 or instantiation, it depends on the parent unit of the subunit. This means that
2558 any modification of the parent unit or one of its subunits affects the
2562 The object file for a parent unit depends on all its subunit body files.
2565 The previous two rules meant that for purposes of computing dependencies and
2566 recompilation, a body and all its subunits are treated as an indivisible whole.
2569 These rules are applied transitively: if unit @code{A} @code{with}'s
2570 unit @code{B}, whose elaboration calls an inlined procedure in package
2571 @code{C}, the object file for unit @code{A} will depend on the body of
2572 @code{C}, in file @file{c.adb}.
2574 The set of dependent files described by these rules includes all the
2575 files on which the unit is semantically dependent, as described in the
2576 Ada 95 Language Reference Manual. However, it is a superset of what the
2577 ARM describes, because it includes generic, inline, and subunit dependencies.
2579 An object file must be recreated by recompiling the corresponding source
2580 file if any of the source files on which it depends are modified. For
2581 example, if the @code{make} utility is used to control compilation,
2582 the rule for an Ada object file must mention all the source files on
2583 which the object file depends, according to the above definition.
2584 The determination of the necessary
2585 recompilations is done automatically when one uses @code{gnatmake}.
2588 @node The Ada Library Information Files
2589 @section The Ada Library Information Files
2590 @cindex Ada Library Information files
2591 @cindex @file{ALI} files
2594 Each compilation actually generates two output files. The first of these
2595 is the normal object file that has a @file{.o} extension. The second is a
2596 text file containing full dependency information. It has the same
2597 name as the source file, but an @file{.ali} extension.
2598 This file is known as the Ada Library Information (@file{ALI}) file.
2599 The following information is contained in the @file{ALI} file.
2603 Version information (indicates which version of GNAT was used to compile
2604 the unit(s) in question)
2607 Main program information (including priority and time slice settings,
2608 as well as the wide character encoding used during compilation).
2611 List of arguments used in the @code{gcc} command for the compilation
2614 Attributes of the unit, including configuration pragmas used, an indication
2615 of whether the compilation was successful, exception model used etc.
2618 A list of relevant restrictions applying to the unit (used for consistency)
2622 Categorization information (e.g. use of pragma @code{Pure}).
2625 Information on all @code{with}'ed units, including presence of
2626 @code{Elaborate} or @code{Elaborate_All} pragmas.
2629 Information from any @code{Linker_Options} pragmas used in the unit
2632 Information on the use of @code{Body_Version} or @code{Version}
2633 attributes in the unit.
2636 Dependency information. This is a list of files, together with
2637 time stamp and checksum information. These are files on which
2638 the unit depends in the sense that recompilation is required
2639 if any of these units are modified.
2642 Cross-reference data. Contains information on all entities referenced
2643 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
2644 provide cross-reference information.
2649 For a full detailed description of the format of the @file{ALI} file,
2650 see the source of the body of unit @code{Lib.Writ}, contained in file
2651 @file{lib-writ.adb} in the GNAT compiler sources.
2653 @node Binding an Ada Program
2654 @section Binding an Ada Program
2657 When using languages such as C and C++, once the source files have been
2658 compiled the only remaining step in building an executable program
2659 is linking the object modules together. This means that it is possible to
2660 link an inconsistent version of a program, in which two units have
2661 included different versions of the same header.
2663 The rules of Ada do not permit such an inconsistent program to be built.
2664 For example, if two clients have different versions of the same package,
2665 it is illegal to build a program containing these two clients.
2666 These rules are enforced by the GNAT binder, which also determines an
2667 elaboration order consistent with the Ada rules.
2669 The GNAT binder is run after all the object files for a program have
2670 been created. It is given the name of the main program unit, and from
2671 this it determines the set of units required by the program, by reading the
2672 corresponding ALI files. It generates error messages if the program is
2673 inconsistent or if no valid order of elaboration exists.
2675 If no errors are detected, the binder produces a main program, in Ada by
2676 default, that contains calls to the elaboration procedures of those
2677 compilation unit that require them, followed by
2678 a call to the main program. This Ada program is compiled to generate the
2679 object file for the main program. The name of
2680 the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
2681 @file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
2684 Finally, the linker is used to build the resulting executable program,
2685 using the object from the main program from the bind step as well as the
2686 object files for the Ada units of the program.
2688 @node Mixed Language Programming
2689 @section Mixed Language Programming
2690 @cindex Mixed Language Programming
2693 This section describes how to develop a mixed-language program,
2694 specifically one that comprises units in both Ada and C.
2697 * Interfacing to C::
2698 * Calling Conventions::
2701 @node Interfacing to C
2702 @subsection Interfacing to C
2704 Interfacing Ada with a foreign language such as C involves using
2705 compiler directives to import and/or export entity definitions in each
2706 language---using @code{extern} statements in C, for instance, and the
2707 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada. For
2708 a full treatment of these topics, read Appendix B, section 1 of the Ada
2709 95 Language Reference Manual.
2711 There are two ways to build a program using GNAT that contains some Ada
2712 sources and some foreign language sources, depending on whether or not
2713 the main subprogram is written in Ada. Here is a source example with
2714 the main subprogram in Ada:
2720 void print_num (int num)
2722 printf ("num is %d.\n", num);
2728 /* num_from_Ada is declared in my_main.adb */
2729 extern int num_from_Ada;
2733 return num_from_Ada;
2737 @smallexample @c ada
2739 procedure My_Main is
2741 -- Declare then export an Integer entity called num_from_Ada
2742 My_Num : Integer := 10;
2743 pragma Export (C, My_Num, "num_from_Ada");
2745 -- Declare an Ada function spec for Get_Num, then use
2746 -- C function get_num for the implementation.
2747 function Get_Num return Integer;
2748 pragma Import (C, Get_Num, "get_num");
2750 -- Declare an Ada procedure spec for Print_Num, then use
2751 -- C function print_num for the implementation.
2752 procedure Print_Num (Num : Integer);
2753 pragma Import (C, Print_Num, "print_num");
2756 Print_Num (Get_Num);
2762 To build this example, first compile the foreign language files to
2763 generate object files:
2770 Then, compile the Ada units to produce a set of object files and ALI
2773 gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
2777 Run the Ada binder on the Ada main program:
2779 gnatbind my_main.ali
2783 Link the Ada main program, the Ada objects and the other language
2786 gnatlink my_main.ali file1.o file2.o
2790 The last three steps can be grouped in a single command:
2792 gnatmake my_main.adb -largs file1.o file2.o
2795 @cindex Binder output file
2797 If the main program is in a language other than Ada, then you may have
2798 more than one entry point into the Ada subsystem. You must use a special
2799 binder option to generate callable routines that initialize and
2800 finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
2801 Calls to the initialization and finalization routines must be inserted
2802 in the main program, or some other appropriate point in the code. The
2803 call to initialize the Ada units must occur before the first Ada
2804 subprogram is called, and the call to finalize the Ada units must occur
2805 after the last Ada subprogram returns. The binder will place the
2806 initialization and finalization subprograms into the
2807 @file{b~@var{xxx}.adb} file where they can be accessed by your C
2808 sources. To illustrate, we have the following example:
2812 extern void adainit (void);
2813 extern void adafinal (void);
2814 extern int add (int, int);
2815 extern int sub (int, int);
2817 int main (int argc, char *argv[])
2823 /* Should print "21 + 7 = 28" */
2824 printf ("%d + %d = %d\n", a, b, add (a, b));
2825 /* Should print "21 - 7 = 14" */
2826 printf ("%d - %d = %d\n", a, b, sub (a, b));
2832 @smallexample @c ada
2835 function Add (A, B : Integer) return Integer;
2836 pragma Export (C, Add, "add");
2840 package body Unit1 is
2841 function Add (A, B : Integer) return Integer is
2849 function Sub (A, B : Integer) return Integer;
2850 pragma Export (C, Sub, "sub");
2854 package body Unit2 is
2855 function Sub (A, B : Integer) return Integer is
2864 The build procedure for this application is similar to the last
2865 example's. First, compile the foreign language files to generate object
2872 Next, compile the Ada units to produce a set of object files and ALI
2875 gnatmake ^-c^/ACTIONS=COMPILE^ unit1.adb
2876 gnatmake ^-c^/ACTIONS=COMPILE^ unit2.adb
2880 Run the Ada binder on every generated ALI file. Make sure to use the
2881 @option{-n} option to specify a foreign main program:
2883 gnatbind ^-n^/NOMAIN^ unit1.ali unit2.ali
2887 Link the Ada main program, the Ada objects and the foreign language
2888 objects. You need only list the last ALI file here:
2890 gnatlink unit2.ali main.o -o exec_file
2893 This procedure yields a binary executable called @file{exec_file}.
2896 @node Calling Conventions
2897 @subsection Calling Conventions
2898 @cindex Foreign Languages
2899 @cindex Calling Conventions
2900 GNAT follows standard calling sequence conventions and will thus interface
2901 to any other language that also follows these conventions. The following
2902 Convention identifiers are recognized by GNAT:
2905 @cindex Interfacing to Ada
2906 @cindex Other Ada compilers
2907 @cindex Convention Ada
2909 This indicates that the standard Ada calling sequence will be
2910 used and all Ada data items may be passed without any limitations in the
2911 case where GNAT is used to generate both the caller and callee. It is also
2912 possible to mix GNAT generated code and code generated by another Ada
2913 compiler. In this case, the data types should be restricted to simple
2914 cases, including primitive types. Whether complex data types can be passed
2915 depends on the situation. Probably it is safe to pass simple arrays, such
2916 as arrays of integers or floats. Records may or may not work, depending
2917 on whether both compilers lay them out identically. Complex structures
2918 involving variant records, access parameters, tasks, or protected types,
2919 are unlikely to be able to be passed.
2921 Note that in the case of GNAT running
2922 on a platform that supports DEC Ada 83, a higher degree of compatibility
2923 can be guaranteed, and in particular records are layed out in an identical
2924 manner in the two compilers. Note also that if output from two different
2925 compilers is mixed, the program is responsible for dealing with elaboration
2926 issues. Probably the safest approach is to write the main program in the
2927 version of Ada other than GNAT, so that it takes care of its own elaboration
2928 requirements, and then call the GNAT-generated adainit procedure to ensure
2929 elaboration of the GNAT components. Consult the documentation of the other
2930 Ada compiler for further details on elaboration.
2932 However, it is not possible to mix the tasking run time of GNAT and
2933 DEC Ada 83, All the tasking operations must either be entirely within
2934 GNAT compiled sections of the program, or entirely within DEC Ada 83
2935 compiled sections of the program.
2937 @cindex Interfacing to Assembly
2938 @cindex Convention Assembler
2940 Specifies assembler as the convention. In practice this has the
2941 same effect as convention Ada (but is not equivalent in the sense of being
2942 considered the same convention).
2944 @cindex Convention Asm
2947 Equivalent to Assembler.
2949 @cindex Interfacing to COBOL
2950 @cindex Convention COBOL
2953 Data will be passed according to the conventions described
2954 in section B.4 of the Ada 95 Reference Manual.
2957 @cindex Interfacing to C
2958 @cindex Convention C
2960 Data will be passed according to the conventions described
2961 in section B.3 of the Ada 95 Reference Manual.
2963 @findex C varargs function
2964 @cindex Intefacing to C varargs function
2965 @cindex varargs function intefacs
2966 @item C varargs function
2967 In C, @code{varargs} allows a function to take a variable number of
2968 arguments. There is no direct equivalent in this to Ada. One
2969 approach that can be used is to create a C wrapper for each
2970 different profile and then interface to this C wrapper. For
2971 example, to print an @code{int} value using @code{printf},
2972 create a C function @code{printfi} that takes two arguments, a
2973 pointer to a string and an int, and calls @code{printf}.
2974 Then in the Ada program, use pragma @code{Import} to
2975 interface to printfi.
2977 It may work on some platforms to directly interface to
2978 a @code{varargs} function by providing a specific Ada profile
2979 for a a particular call. However, this does not work on
2980 all platforms, since there is no guarantee that the
2981 calling sequence for a two argument normal C function
2982 is the same as for calling a @code{varargs} C function with
2983 the same two arguments.
2985 @cindex Convention Default
2990 @cindex Convention External
2996 @cindex Interfacing to C++
2997 @cindex Convention C++
2999 This stands for C++. For most purposes this is identical to C.
3000 See the separate description of the specialized GNAT pragmas relating to
3001 C++ interfacing for further details.
3004 @cindex Interfacing to Fortran
3005 @cindex Convention Fortran
3007 Data will be passed according to the conventions described
3008 in section B.5 of the Ada 95 Reference Manual.
3011 This applies to an intrinsic operation, as defined in the Ada 95
3012 Reference Manual. If a a pragma Import (Intrinsic) applies to a subprogram,
3013 this means that the body of the subprogram is provided by the compiler itself,
3014 usually by means of an efficient code sequence, and that the user does not
3015 supply an explicit body for it. In an application program, the pragma can
3016 only be applied to the following two sets of names, which the GNAT compiler
3021 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_-
3022 Arithmetic. The corresponding subprogram declaration must have
3023 two formal parameters. The
3024 first one must be a signed integer type or a modular type with a binary
3025 modulus, and the second parameter must be of type Natural.
3026 The return type must be the same as the type of the first argument. The size
3027 of this type can only be 8, 16, 32, or 64.
3028 @item binary arithmetic operators: ``+'', ``-'', ``*'', ``/''
3029 The corresponding operator declaration must have parameters and result type
3030 that have the same root numeric type (for example, all three are long_float
3031 types). This simplifies the definition of operations that use type checking
3032 to perform dimensional checks:
3034 @smallexample @c ada
3035 type Distance is new Long_Float;
3036 type Time is new Long_Float;
3037 type Velocity is new Long_Float;
3038 function "/" (D : Distance; T : Time)
3040 pragma Import (Intrinsic, "/");
3044 This common idiom is often programmed with a generic definition and an
3045 explicit body. The pragma makes it simpler to introduce such declarations.
3046 It incurs no overhead in compilation time or code size, because it is
3047 implemented as a single machine instruction.
3053 @cindex Convention Stdcall
3055 This is relevant only to NT/Win95 implementations of GNAT,
3056 and specifies that the Stdcall calling sequence will be used, as defined
3060 @cindex Convention DLL
3062 This is equivalent to Stdcall.
3065 @cindex Convention Win32
3067 This is equivalent to Stdcall.
3071 @cindex Convention Stubbed
3073 This is a special convention that indicates that the compiler
3074 should provide a stub body that raises @code{Program_Error}.
3078 GNAT additionally provides a useful pragma @code{Convention_Identifier}
3079 that can be used to parametrize conventions and allow additional synonyms
3080 to be specified. For example if you have legacy code in which the convention
3081 identifier Fortran77 was used for Fortran, you can use the configuration
3084 @smallexample @c ada
3085 pragma Convention_Identifier (Fortran77, Fortran);
3089 And from now on the identifier Fortran77 may be used as a convention
3090 identifier (for example in an @code{Import} pragma) with the same
3093 @node Building Mixed Ada & C++ Programs
3094 @section Building Mixed Ada & C++ Programs
3097 A programmer inexperienced with mixed-language development may find that
3098 building an application containing both Ada and C++ code can be a
3099 challenge. As a matter of fact, interfacing with C++ has not been
3100 standardized in the Ada 95 Reference Manual due to the immaturity of --
3101 and lack of standards for -- C++ at the time. This section gives a few
3102 hints that should make this task easier. The first section addresses
3103 the differences regarding interfacing with C. The second section
3104 looks into the delicate problem of linking the complete application from
3105 its Ada and C++ parts. The last section gives some hints on how the GNAT
3106 run time can be adapted in order to allow inter-language dispatching
3107 with a new C++ compiler.
3110 * Interfacing to C++::
3111 * Linking a Mixed C++ & Ada Program::
3112 * A Simple Example::
3113 * Adapting the Run Time to a New C++ Compiler::
3116 @node Interfacing to C++
3117 @subsection Interfacing to C++
3120 GNAT supports interfacing with C++ compilers generating code that is
3121 compatible with the standard Application Binary Interface of the given
3125 Interfacing can be done at 3 levels: simple data, subprograms, and
3126 classes. In the first two cases, GNAT offers a specific @var{Convention
3127 CPP} that behaves exactly like @var{Convention C}. Usually, C++ mangles
3128 the names of subprograms, and currently, GNAT does not provide any help
3129 to solve the demangling problem. This problem can be addressed in two
3133 by modifying the C++ code in order to force a C convention using
3134 the @code{extern "C"} syntax.
3137 by figuring out the mangled name and use it as the Link_Name argument of
3142 Interfacing at the class level can be achieved by using the GNAT specific
3143 pragmas such as @code{CPP_Class} and @code{CPP_Virtual}. See the GNAT
3144 Reference Manual for additional information.
3146 @node Linking a Mixed C++ & Ada Program
3147 @subsection Linking a Mixed C++ & Ada Program
3150 Usually the linker of the C++ development system must be used to link
3151 mixed applications because most C++ systems will resolve elaboration
3152 issues (such as calling constructors on global class instances)
3153 transparently during the link phase. GNAT has been adapted to ease the
3154 use of a foreign linker for the last phase. Three cases can be
3159 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
3160 The C++ linker can simply be called by using the C++ specific driver
3161 called @code{c++}. Note that this setup is not very common because it
3162 may involve recompiling the whole GCC tree from sources, which makes it
3163 harder to upgrade the compilation system for one language without
3164 destabilizing the other.
3169 $ gnatmake ada_unit -largs file1.o file2.o --LINK=c++
3173 Using GNAT and G++ from two different GCC installations: If both
3174 compilers are on the PATH, the previous method may be used. It is
3175 important to note that environment variables such as C_INCLUDE_PATH,
3176 GCC_EXEC_PREFIX, BINUTILS_ROOT, and GCC_ROOT will affect both compilers
3177 at the same time and may make one of the two compilers operate
3178 improperly if set during invocation of the wrong compiler. It is also
3179 very important that the linker uses the proper @file{libgcc.a} GCC
3180 library -- that is, the one from the C++ compiler installation. The
3181 implicit link command as suggested in the gnatmake command from the
3182 former example can be replaced by an explicit link command with the
3183 full-verbosity option in order to verify which library is used:
3186 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
3188 If there is a problem due to interfering environment variables, it can
3189 be worked around by using an intermediate script. The following example
3190 shows the proper script to use when GNAT has not been installed at its
3191 default location and g++ has been installed at its default location:
3199 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
3203 Using a non-GNU C++ compiler: The commands previously described can be
3204 used to insure that the C++ linker is used. Nonetheless, you need to add
3205 the path to libgcc explicitly, since some libraries needed by GNAT are
3206 located in this directory:
3211 CC $* `gcc -print-libgcc-file-name`
3212 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
3215 Where CC is the name of the non-GNU C++ compiler.
3219 @node A Simple Example
3220 @subsection A Simple Example
3222 The following example, provided as part of the GNAT examples, shows how
3223 to achieve procedural interfacing between Ada and C++ in both
3224 directions. The C++ class A has two methods. The first method is exported
3225 to Ada by the means of an extern C wrapper function. The second method
3226 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
3227 a limited record with a layout comparable to the C++ class. The Ada
3228 subprogram, in turn, calls the C++ method. So, starting from the C++
3229 main program, the process passes back and forth between the two
3233 Here are the compilation commands:
3235 $ gnatmake -c simple_cpp_interface
3238 $ gnatbind -n simple_cpp_interface
3239 $ gnatlink simple_cpp_interface -o cpp_main --LINK=$(CPLUSPLUS)
3240 -lstdc++ ex7.o cpp_main.o
3244 Here are the corresponding sources:
3252 void adainit (void);
3253 void adafinal (void);
3254 void method1 (A *t);
3276 class A : public Origin @{
3278 void method1 (void);
3279 virtual void method2 (int v);
3289 extern "C" @{ void ada_method2 (A *t, int v);@}
3291 void A::method1 (void)
3294 printf ("in A::method1, a_value = %d \n",a_value);
3298 void A::method2 (int v)
3300 ada_method2 (this, v);
3301 printf ("in A::method2, a_value = %d \n",a_value);
3308 printf ("in A::A, a_value = %d \n",a_value);
3312 @b{package} @b{body} Simple_Cpp_Interface @b{is}
3314 @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer) @b{is}
3318 @b{end} Ada_Method2;
3320 @b{end} Simple_Cpp_Interface;
3322 @b{package} Simple_Cpp_Interface @b{is}
3323 @b{type} A @b{is} @b{limited}
3328 @b{pragma} Convention (C, A);
3330 @b{procedure} Method1 (This : @b{in} @b{out} A);
3331 @b{pragma} Import (C, Method1);
3333 @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer);
3334 @b{pragma} Export (C, Ada_Method2);
3336 @b{end} Simple_Cpp_Interface;
3339 @node Adapting the Run Time to a New C++ Compiler
3340 @subsection Adapting the Run Time to a New C++ Compiler
3342 GNAT offers the capability to derive Ada 95 tagged types directly from
3343 preexisting C++ classes and . See ``Interfacing with C++'' in the
3344 @cite{GNAT Reference Manual}. The mechanism used by GNAT for achieving
3346 has been made user configurable through a GNAT library unit
3347 @code{Interfaces.CPP}. The default version of this file is adapted to
3348 the GNU C++ compiler. Internal knowledge of the virtual
3349 table layout used by the new C++ compiler is needed to configure
3350 properly this unit. The Interface of this unit is known by the compiler
3351 and cannot be changed except for the value of the constants defining the
3352 characteristics of the virtual table: CPP_DT_Prologue_Size, CPP_DT_Entry_Size,
3353 CPP_TSD_Prologue_Size, CPP_TSD_Entry_Size. Read comments in the source
3354 of this unit for more details.
3356 @node Comparison between GNAT and C/C++ Compilation Models
3357 @section Comparison between GNAT and C/C++ Compilation Models
3360 The GNAT model of compilation is close to the C and C++ models. You can
3361 think of Ada specs as corresponding to header files in C. As in C, you
3362 don't need to compile specs; they are compiled when they are used. The
3363 Ada @code{with} is similar in effect to the @code{#include} of a C
3366 One notable difference is that, in Ada, you may compile specs separately
3367 to check them for semantic and syntactic accuracy. This is not always
3368 possible with C headers because they are fragments of programs that have
3369 less specific syntactic or semantic rules.
3371 The other major difference is the requirement for running the binder,
3372 which performs two important functions. First, it checks for
3373 consistency. In C or C++, the only defense against assembling
3374 inconsistent programs lies outside the compiler, in a makefile, for
3375 example. The binder satisfies the Ada requirement that it be impossible
3376 to construct an inconsistent program when the compiler is used in normal
3379 @cindex Elaboration order control
3380 The other important function of the binder is to deal with elaboration
3381 issues. There are also elaboration issues in C++ that are handled
3382 automatically. This automatic handling has the advantage of being
3383 simpler to use, but the C++ programmer has no control over elaboration.
3384 Where @code{gnatbind} might complain there was no valid order of
3385 elaboration, a C++ compiler would simply construct a program that
3386 malfunctioned at run time.
3388 @node Comparison between GNAT and Conventional Ada Library Models
3389 @section Comparison between GNAT and Conventional Ada Library Models
3392 This section is intended to be useful to Ada programmers who have
3393 previously used an Ada compiler implementing the traditional Ada library
3394 model, as described in the Ada 95 Language Reference Manual. If you
3395 have not used such a system, please go on to the next section.
3397 @cindex GNAT library
3398 In GNAT, there is no @dfn{library} in the normal sense. Instead, the set of
3399 source files themselves acts as the library. Compiling Ada programs does
3400 not generate any centralized information, but rather an object file and
3401 a ALI file, which are of interest only to the binder and linker.
3402 In a traditional system, the compiler reads information not only from
3403 the source file being compiled, but also from the centralized library.
3404 This means that the effect of a compilation depends on what has been
3405 previously compiled. In particular:
3409 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3410 to the version of the unit most recently compiled into the library.
3413 Inlining is effective only if the necessary body has already been
3414 compiled into the library.
3417 Compiling a unit may obsolete other units in the library.
3421 In GNAT, compiling one unit never affects the compilation of any other
3422 units because the compiler reads only source files. Only changes to source
3423 files can affect the results of a compilation. In particular:
3427 When a unit is @code{with}'ed, the unit seen by the compiler corresponds
3428 to the source version of the unit that is currently accessible to the
3433 Inlining requires the appropriate source files for the package or
3434 subprogram bodies to be available to the compiler. Inlining is always
3435 effective, independent of the order in which units are complied.
3438 Compiling a unit never affects any other compilations. The editing of
3439 sources may cause previous compilations to be out of date if they
3440 depended on the source file being modified.
3444 The most important result of these differences is that order of compilation
3445 is never significant in GNAT. There is no situation in which one is
3446 required to do one compilation before another. What shows up as order of
3447 compilation requirements in the traditional Ada library becomes, in
3448 GNAT, simple source dependencies; in other words, there is only a set
3449 of rules saying what source files must be present when a file is
3453 @node Placement of temporary files
3454 @section Placement of temporary files
3455 @cindex Temporary files (user control over placement)
3458 GNAT creates temporary files in the directory designated by the environment
3459 variable @env{TMPDIR}.
3460 (See the HP @emph{C RTL Reference Manual} on the function @code{getenv()}
3461 for detailed information on how environment variables are resolved.
3462 For most users the easiest way to make use of this feature is to simply
3463 define @env{TMPDIR} as a job level logical name).
3464 For example, if you wish to use a Ramdisk (assuming DECRAM is installed)
3465 for compiler temporary files, then you can include something like the
3466 following command in your @file{LOGIN.COM} file:
3469 $ define/job TMPDIR "/disk$scratchram/000000/temp/"
3473 If @env{TMPDIR} is not defined, then GNAT uses the directory designated by
3474 @env{TMP}; if @env{TMP} is not defined, then GNAT uses the directory
3475 designated by @env{TEMP}.
3476 If none of these environment variables are defined then GNAT uses the
3477 directory designated by the logical name @code{SYS$SCRATCH:}
3478 (by default the user's home directory). If all else fails
3479 GNAT uses the current directory for temporary files.
3483 @c *************************
3484 @node Compiling Using gcc
3485 @chapter Compiling Using @code{gcc}
3488 This chapter discusses how to compile Ada programs using the @code{gcc}
3489 command. It also describes the set of switches
3490 that can be used to control the behavior of the compiler.
3492 * Compiling Programs::
3493 * Switches for gcc::
3494 * Search Paths and the Run-Time Library (RTL)::
3495 * Order of Compilation Issues::
3499 @node Compiling Programs
3500 @section Compiling Programs
3503 The first step in creating an executable program is to compile the units
3504 of the program using the @code{gcc} command. You must compile the
3509 the body file (@file{.adb}) for a library level subprogram or generic
3513 the spec file (@file{.ads}) for a library level package or generic
3514 package that has no body
3517 the body file (@file{.adb}) for a library level package
3518 or generic package that has a body
3523 You need @emph{not} compile the following files
3528 the spec of a library unit which has a body
3535 because they are compiled as part of compiling related units. GNAT
3537 when the corresponding body is compiled, and subunits when the parent is
3540 @cindex cannot generate code
3541 If you attempt to compile any of these files, you will get one of the
3542 following error messages (where fff is the name of the file you compiled):
3545 cannot generate code for file @var{fff} (package spec)
3546 to check package spec, use -gnatc
3548 cannot generate code for file @var{fff} (missing subunits)
3549 to check parent unit, use -gnatc
3551 cannot generate code for file @var{fff} (subprogram spec)
3552 to check subprogram spec, use -gnatc
3554 cannot generate code for file @var{fff} (subunit)
3555 to check subunit, use -gnatc
3559 As indicated by the above error messages, if you want to submit
3560 one of these files to the compiler to check for correct semantics
3561 without generating code, then use the @option{-gnatc} switch.
3563 The basic command for compiling a file containing an Ada unit is
3566 $ gcc -c [@var{switches}] @file{file name}
3570 where @var{file name} is the name of the Ada file (usually
3572 @file{.ads} for a spec or @file{.adb} for a body).
3575 @option{-c} switch to tell @code{gcc} to compile, but not link, the file.
3577 The result of a successful compilation is an object file, which has the
3578 same name as the source file but an extension of @file{.o} and an Ada
3579 Library Information (ALI) file, which also has the same name as the
3580 source file, but with @file{.ali} as the extension. GNAT creates these
3581 two output files in the current directory, but you may specify a source
3582 file in any directory using an absolute or relative path specification
3583 containing the directory information.
3586 @code{gcc} is actually a driver program that looks at the extensions of
3587 the file arguments and loads the appropriate compiler. For example, the
3588 GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
3589 These programs are in directories known to the driver program (in some
3590 configurations via environment variables you set), but need not be in
3591 your path. The @code{gcc} driver also calls the assembler and any other
3592 utilities needed to complete the generation of the required object
3595 It is possible to supply several file names on the same @code{gcc}
3596 command. This causes @code{gcc} to call the appropriate compiler for
3597 each file. For example, the following command lists three separate
3598 files to be compiled:
3601 $ gcc -c x.adb y.adb z.c
3605 calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
3606 @file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
3607 The compiler generates three object files @file{x.o}, @file{y.o} and
3608 @file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
3609 Ada compilations. Any switches apply to all the files ^listed,^listed.^
3612 @option{-gnat@var{x}} switches, which apply only to Ada compilations.
3615 @node Switches for gcc
3616 @section Switches for @code{gcc}
3619 The @code{gcc} command accepts switches that control the
3620 compilation process. These switches are fully described in this section.
3621 First we briefly list all the switches, in alphabetical order, then we
3622 describe the switches in more detail in functionally grouped sections.
3625 * Output and Error Message Control::
3626 * Warning Message Control::
3627 * Debugging and Assertion Control::
3629 * Stack Overflow Checking::
3630 * Validity Checking::
3632 * Using gcc for Syntax Checking::
3633 * Using gcc for Semantic Checking::
3634 * Compiling Ada 83 Programs::
3635 * Character Set Control::
3636 * File Naming Control::
3637 * Subprogram Inlining Control::
3638 * Auxiliary Output Control::
3639 * Debugging Control::
3640 * Exception Handling Control::
3641 * Units to Sources Mapping Files::
3642 * Integrated Preprocessing::
3651 @cindex @option{-b} (@code{gcc})
3652 @item -b @var{target}
3653 Compile your program to run on @var{target}, which is the name of a
3654 system configuration. You must have a GNAT cross-compiler built if
3655 @var{target} is not the same as your host system.
3658 @cindex @option{-B} (@code{gcc})
3659 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
3660 from @var{dir} instead of the default location. Only use this switch
3661 when multiple versions of the GNAT compiler are available. See the
3662 @code{gcc} manual page for further details. You would normally use the
3663 @option{-b} or @option{-V} switch instead.
3666 @cindex @option{-c} (@code{gcc})
3667 Compile. Always use this switch when compiling Ada programs.
3669 Note: for some other languages when using @code{gcc}, notably in
3670 the case of C and C++, it is possible to use
3671 use @code{gcc} without a @option{-c} switch to
3672 compile and link in one step. In the case of GNAT, you
3673 cannot use this approach, because the binder must be run
3674 and @code{gcc} cannot be used to run the GNAT binder.
3678 @cindex @option{-fno-inline} (@code{gcc})
3679 Suppresses all back-end inlining, even if other optimization or inlining
3681 This includes suppression of inlining that results
3682 from the use of the pragma @code{Inline_Always}.
3683 See also @option{-gnatn} and @option{-gnatN}.
3685 @item -fno-strict-aliasing
3686 @cindex @option{-fno-strict-aliasing} (@code{gcc})
3687 Causes the compiler to avoid assumptions regarding non-aliasing
3688 of objects of different types. See section
3689 @pxref{Optimization and Strict Aliasing} for details.
3692 @cindex @option{-fstack-check} (@code{gcc})
3693 Activates stack checking.
3694 See @ref{Stack Overflow Checking} for details of the use of this option.
3697 @cindex @option{^-g^/DEBUG^} (@code{gcc})
3698 Generate debugging information. This information is stored in the object
3699 file and copied from there to the final executable file by the linker,
3700 where it can be read by the debugger. You must use the
3701 @option{^-g^/DEBUG^} switch if you plan on using the debugger.
3704 @cindex @option{-gnat83} (@code{gcc})
3705 Enforce Ada 83 restrictions.
3708 @cindex @option{-gnata} (@code{gcc})
3709 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
3713 @cindex @option{-gnatA} (@code{gcc})
3714 Avoid processing @file{gnat.adc}. If a gnat.adc file is present,
3718 @cindex @option{-gnatb} (@code{gcc})
3719 Generate brief messages to @file{stderr} even if verbose mode set.
3722 @cindex @option{-gnatc} (@code{gcc})
3723 Check syntax and semantics only (no code generation attempted).
3726 @cindex @option{-gnatd} (@code{gcc})
3727 Specify debug options for the compiler. The string of characters after
3728 the @option{-gnatd} specify the specific debug options. The possible
3729 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
3730 compiler source file @file{debug.adb} for details of the implemented
3731 debug options. Certain debug options are relevant to applications
3732 programmers, and these are documented at appropriate points in this
3736 @cindex @option{-gnatD} (@code{gcc})
3737 Create expanded source files for source level debugging. This switch
3738 also suppress generation of cross-reference information
3739 (see @option{-gnatx}).
3741 @item -gnatec=@var{path}
3742 @cindex @option{-gnatec} (@code{gcc})
3743 Specify a configuration pragma file
3745 (the equal sign is optional)
3747 (see @ref{The Configuration Pragmas Files}).
3749 @item ^-gnateD^/DATA_PREPROCESSING=^symbol[=value]
3750 @cindex @option{-gnateD} (@code{gcc})
3751 Defines a symbol, associated with value, for preprocessing.
3752 (see @ref{Integrated Preprocessing})
3755 @cindex @option{-gnatef} (@code{gcc})
3756 Display full source path name in brief error messages.
3758 @item -gnatem=@var{path}
3759 @cindex @option{-gnatem} (@code{gcc})
3760 Specify a mapping file
3762 (the equal sign is optional)
3764 (see @ref{Units to Sources Mapping Files}).
3766 @item -gnatep=@var{file}
3767 @cindex @option{-gnatep} (@code{gcc})
3768 Specify a preprocessing data file
3770 (the equal sign is optional)
3772 (see @ref{Integrated Preprocessing}).
3775 @cindex @option{-gnatE} (@code{gcc})
3776 Full dynamic elaboration checks.
3779 @cindex @option{-gnatf} (@code{gcc})
3780 Full errors. Multiple errors per line, all undefined references, do not
3781 attempt to suppress cascaded errors.
3784 @cindex @option{-gnatF} (@code{gcc})
3785 Externals names are folded to all uppercase.
3788 @cindex @option{-gnatg} (@code{gcc})
3789 Internal GNAT implementation mode. This should not be used for
3790 applications programs, it is intended only for use by the compiler
3791 and its run-time library. For documentation, see the GNAT sources.
3792 Note that @option{-gnatg} implies @option{-gnatwu} so that warnings
3793 are generated on unreferenced entities, and all warnings are treated
3797 @cindex @option{-gnatG} (@code{gcc})
3798 List generated expanded code in source form.
3800 @item ^-gnath^/HELP^
3801 @cindex @option{^-gnath^/HELP^} (@code{gcc})
3802 Output usage information. The output is written to @file{stdout}.
3804 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
3805 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@code{gcc})
3806 Identifier character set
3808 (@var{c}=1/2/3/4/8/9/p/f/n/w).
3811 For details of the possible selections for @var{c},
3812 see @xref{Character Set Control}.
3815 @item -gnatk=@var{n}
3816 @cindex @option{-gnatk} (@code{gcc})
3817 Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
3820 @cindex @option{-gnatl} (@code{gcc})
3821 Output full source listing with embedded error messages.
3824 @cindex @option{-gnatL} (@code{gcc})
3825 Use the longjmp/setjmp method for exception handling
3827 @item -gnatm=@var{n}
3828 @cindex @option{-gnatm} (@code{gcc})
3829 Limit number of detected error or warning messages to @var{n}
3830 where @var{n} is in the range 1..999_999. The default setting if
3831 no switch is given is 9999. Compilation is terminated if this
3835 @cindex @option{-gnatn} (@code{gcc})
3836 Activate inlining for subprograms for which
3837 pragma @code{inline} is specified. This inlining is performed
3838 by the GCC back-end.
3841 @cindex @option{-gnatN} (@code{gcc})
3842 Activate front end inlining for subprograms for which
3843 pragma @code{Inline} is specified. This inlining is performed
3844 by the front end and will be visible in the
3845 @option{-gnatG} output.
3846 In some cases, this has proved more effective than the back end
3847 inlining resulting from the use of
3850 @option{-gnatN} automatically implies
3851 @option{-gnatn} so it is not necessary
3852 to specify both options. There are a few cases that the back-end inlining
3853 catches that cannot be dealt with in the front-end.
3856 @cindex @option{-gnato} (@code{gcc})
3857 Enable numeric overflow checking (which is not normally enabled by
3858 default). Not that division by zero is a separate check that is not
3859 controlled by this switch (division by zero checking is on by default).
3862 @cindex @option{-gnatp} (@code{gcc})
3863 Suppress all checks.
3866 @cindex @option{-gnatP} (@code{gcc})
3867 Enable polling. This is required on some systems (notably Windows NT) to
3868 obtain asynchronous abort and asynchronous transfer of control capability.
3869 See the description of pragma Polling in the GNAT Reference Manual for
3873 @cindex @option{-gnatq} (@code{gcc})
3874 Don't quit; try semantics, even if parse errors.
3877 @cindex @option{-gnatQ} (@code{gcc})
3878 Don't quit; generate @file{ALI} and tree files even if illegalities.
3880 @item ^-gnatR[0/1/2/3[s]]^/REPRESENTATION_INFO^
3881 @cindex @option{-gnatR} (@code{gcc})
3882 Output representation information for declared types and objects.
3885 @cindex @option{-gnats} (@code{gcc})
3889 @cindex @option{-gnatS} (@code{gcc})
3890 Print package Standard.
3893 @cindex @option{-gnatt} (@code{gcc})
3894 Generate tree output file.
3896 @item ^-gnatT^/TABLE_MULTIPLIER=^@var{nnn}
3897 @cindex @option{^-gnatT^/TABLE_MULTIPLIER^} (@code{gcc})
3898 All compiler tables start at @var{nnn} times usual starting size.
3901 @cindex @option{-gnatu} (@code{gcc})
3902 List units for this compilation.
3905 @cindex @option{-gnatU} (@code{gcc})
3906 Tag all error messages with the unique string ``error:''
3909 @cindex @option{-gnatv} (@code{gcc})
3910 Verbose mode. Full error output with source lines to @file{stdout}.
3913 @cindex @option{-gnatV} (@code{gcc})
3914 Control level of validity checking. See separate section describing
3917 @item ^-gnatw@var{xxx}^/WARNINGS=(@var{option}[,...])^
3918 @cindex @option{^-gnatw^/WARNINGS^} (@code{gcc})
3920 ^@var{xxx} is a string of option letters that^the list of options^ denotes
3921 the exact warnings that
3922 are enabled or disabled. (see @ref{Warning Message Control})
3924 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
3925 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@code{gcc})
3926 Wide character encoding method
3928 (@var{e}=n/h/u/s/e/8).
3931 (@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
3935 @cindex @option{-gnatx} (@code{gcc})
3936 Suppress generation of cross-reference information.
3938 @item ^-gnaty^/STYLE_CHECKS=(option,option..)^
3939 @cindex @option{^-gnaty^/STYLE_CHECKS^} (@code{gcc})
3940 Enable built-in style checks. (see @ref{Style Checking})
3942 @item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
3943 @cindex @option{^-gnatz^/DISTRIBUTION_STUBS^} (@code{gcc})
3944 Distribution stub generation and compilation
3946 (@var{m}=r/c for receiver/caller stubs).
3949 (@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
3950 to be generated and compiled).
3954 Use the zero cost method for exception handling
3956 @item ^-I^/SEARCH=^@var{dir}
3957 @cindex @option{^-I^/SEARCH^} (@code{gcc})
3959 Direct GNAT to search the @var{dir} directory for source files needed by
3960 the current compilation
3961 (@pxref{Search Paths and the Run-Time Library (RTL)}).
3963 @item ^-I-^/NOCURRENT_DIRECTORY^
3964 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gcc})
3966 Except for the source file named in the command line, do not look for source
3967 files in the directory containing the source file named in the command line
3968 (@pxref{Search Paths and the Run-Time Library (RTL)}).
3972 @cindex @option{-mbig-switch} (@command{gcc})
3973 @cindex @code{case} statement (effect of @option{-mbig-switch} option)
3974 This standard gcc switch causes the compiler to use larger offsets in its
3975 jump table representation for @code{case} statements.
3976 This may result in less efficient code, but is sometimes necessary
3977 (for example on HP-UX targets)
3978 @cindex HP-UX and @option{-mbig-switch} option
3979 in order to compile large and/or nested @code{case} statements.
3982 @cindex @option{-o} (@code{gcc})
3983 This switch is used in @code{gcc} to redirect the generated object file
3984 and its associated ALI file. Beware of this switch with GNAT, because it may
3985 cause the object file and ALI file to have different names which in turn
3986 may confuse the binder and the linker.
3990 @cindex @option{-nostdinc} (@command{gcc})
3991 Inhibit the search of the default location for the GNAT Run Time
3992 Library (RTL) source files.
3995 @cindex @option{-nostdlib} (@command{gcc})
3996 Inhibit the search of the default location for the GNAT Run Time
3997 Library (RTL) ALI files.
4001 @cindex @option{-O} (@code{gcc})
4002 @var{n} controls the optimization level.
4006 No optimization, the default setting if no @option{-O} appears
4009 Normal optimization, the default if you specify @option{-O} without
4013 Extensive optimization
4016 Extensive optimization with automatic inlining of subprograms not
4017 specified by pragma @code{Inline}. This applies only to
4018 inlining within a unit. For details on control of inlining
4019 see @xref{Subprogram Inlining Control}.
4025 @cindex @option{/NOOPTIMIZE} (@code{GNAT COMPILE})
4026 Equivalent to @option{/OPTIMIZE=NONE}.
4027 This is the default behavior in the absence of an @option{/OPTMIZE}
4030 @item /OPTIMIZE[=(keyword[,...])]
4031 @cindex @option{/OPTIMIZE} (@code{GNAT COMPILE})
4032 Selects the level of optimization for your program. The supported
4033 keywords are as follows:
4036 Perform most optimizations, including those that
4038 This is the default if the @option{/OPTMIZE} qualifier is supplied
4039 without keyword options.
4042 Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
4045 Perform some optimizations, but omit ones that are costly.
4048 Same as @code{SOME}.
4051 Full optimization, and also attempt automatic inlining of small
4052 subprograms within a unit even when pragma @code{Inline}
4053 is not specified (@pxref{Inlining of Subprograms}).
4056 Try to unroll loops. This keyword may be specified together with
4057 any keyword above other than @code{NONE}. Loop unrolling
4058 usually, but not always, improves the performance of programs.
4063 @item -pass-exit-codes
4064 @cindex @option{-pass-exit-codes} (@code{gcc})
4065 Catch exit codes from the compiler and use the most meaningful as
4069 @item --RTS=@var{rts-path}
4070 @cindex @option{--RTS} (@code{gcc})
4071 Specifies the default location of the runtime library. Same meaning as the
4072 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
4075 @cindex @option{^-S^/ASM^} (@code{gcc})
4076 ^Used in place of @option{-c} to^Used to^
4077 cause the assembler source file to be
4078 generated, using @file{^.s^.S^} as the extension,
4079 instead of the object file.
4080 This may be useful if you need to examine the generated assembly code.
4083 @cindex @option{^-v^/VERBOSE^} (@code{gcc})
4084 Show commands generated by the @code{gcc} driver. Normally used only for
4085 debugging purposes or if you need to be sure what version of the
4086 compiler you are executing.
4090 @cindex @option{-V} (@code{gcc})
4091 Execute @var{ver} version of the compiler. This is the @code{gcc}
4092 version, not the GNAT version.
4098 You may combine a sequence of GNAT switches into a single switch. For
4099 example, the combined switch
4101 @cindex Combining GNAT switches
4107 is equivalent to specifying the following sequence of switches:
4110 -gnato -gnatf -gnati3
4115 @c NEED TO CHECK THIS FOR VMS
4118 The following restrictions apply to the combination of switches
4123 The switch @option{-gnatc} if combined with other switches must come
4124 first in the string.
4127 The switch @option{-gnats} if combined with other switches must come
4128 first in the string.
4132 @option{^-gnatz^/DISTRIBUTION_STUBS^}, @option{-gnatzc}, and @option{-gnatzr}
4133 may not be combined with any other switches.
4137 Once a ``y'' appears in the string (that is a use of the @option{-gnaty}
4138 switch), then all further characters in the switch are interpreted
4139 as style modifiers (see description of @option{-gnaty}).
4142 Once a ``d'' appears in the string (that is a use of the @option{-gnatd}
4143 switch), then all further characters in the switch are interpreted
4144 as debug flags (see description of @option{-gnatd}).
4147 Once a ``w'' appears in the string (that is a use of the @option{-gnatw}
4148 switch), then all further characters in the switch are interpreted
4149 as warning mode modifiers (see description of @option{-gnatw}).
4152 Once a ``V'' appears in the string (that is a use of the @option{-gnatV}
4153 switch), then all further characters in the switch are interpreted
4154 as validity checking options (see description of @option{-gnatV}).
4159 @node Output and Error Message Control
4160 @subsection Output and Error Message Control
4164 The standard default format for error messages is called ``brief format''.
4165 Brief format messages are written to @file{stderr} (the standard error
4166 file) and have the following form:
4169 e.adb:3:04: Incorrect spelling of keyword "function"
4170 e.adb:4:20: ";" should be "is"
4174 The first integer after the file name is the line number in the file,
4175 and the second integer is the column number within the line.
4176 @code{glide} can parse the error messages
4177 and point to the referenced character.
4178 The following switches provide control over the error message
4184 @cindex @option{-gnatv} (@code{gcc})
4187 The v stands for verbose.
4189 The effect of this setting is to write long-format error
4190 messages to @file{stdout} (the standard output file.
4191 The same program compiled with the
4192 @option{-gnatv} switch would generate:
4196 3. funcion X (Q : Integer)
4198 >>> Incorrect spelling of keyword "function"
4201 >>> ";" should be "is"
4206 The vertical bar indicates the location of the error, and the @samp{>>>}
4207 prefix can be used to search for error messages. When this switch is
4208 used the only source lines output are those with errors.
4211 @cindex @option{-gnatl} (@code{gcc})
4213 The @code{l} stands for list.
4215 This switch causes a full listing of
4216 the file to be generated. The output might look as follows:
4222 3. funcion X (Q : Integer)
4224 >>> Incorrect spelling of keyword "function"
4227 >>> ";" should be "is"
4239 When you specify the @option{-gnatv} or @option{-gnatl} switches and
4240 standard output is redirected, a brief summary is written to
4241 @file{stderr} (standard error) giving the number of error messages and
4242 warning messages generated.
4245 @cindex @option{-gnatU} (@code{gcc})
4246 This switch forces all error messages to be preceded by the unique
4247 string ``error:''. This means that error messages take a few more
4248 characters in space, but allows easy searching for and identification
4252 @cindex @option{-gnatb} (@code{gcc})
4254 The @code{b} stands for brief.
4256 This switch causes GNAT to generate the
4257 brief format error messages to @file{stderr} (the standard error
4258 file) as well as the verbose
4259 format message or full listing (which as usual is written to
4260 @file{stdout} (the standard output file).
4262 @item -gnatm^^=^@var{n}
4263 @cindex @option{-gnatm} (@code{gcc})
4265 The @code{m} stands for maximum.
4267 @var{n} is a decimal integer in the
4268 range of 1 to 999 and limits the number of error messages to be
4269 generated. For example, using @option{-gnatm2} might yield
4272 e.adb:3:04: Incorrect spelling of keyword "function"
4273 e.adb:5:35: missing ".."
4274 fatal error: maximum errors reached
4275 compilation abandoned
4279 @cindex @option{-gnatf} (@code{gcc})
4280 @cindex Error messages, suppressing
4282 The @code{f} stands for full.
4284 Normally, the compiler suppresses error messages that are likely to be
4285 redundant. This switch causes all error
4286 messages to be generated. In particular, in the case of
4287 references to undefined variables. If a given variable is referenced
4288 several times, the normal format of messages is
4290 e.adb:7:07: "V" is undefined (more references follow)
4294 where the parenthetical comment warns that there are additional
4295 references to the variable @code{V}. Compiling the same program with the
4296 @option{-gnatf} switch yields
4299 e.adb:7:07: "V" is undefined
4300 e.adb:8:07: "V" is undefined
4301 e.adb:8:12: "V" is undefined
4302 e.adb:8:16: "V" is undefined
4303 e.adb:9:07: "V" is undefined
4304 e.adb:9:12: "V" is undefined
4308 The @option{-gnatf} switch also generates additional information for
4309 some error messages. Some examples are:
4313 Full details on entities not available in high integrity mode
4315 Details on possibly non-portable unchecked conversion
4317 List possible interpretations for ambiguous calls
4319 Additional details on incorrect parameters
4324 @cindex @option{-gnatq} (@code{gcc})
4326 The @code{q} stands for quit (really ``don't quit'').
4328 In normal operation mode, the compiler first parses the program and
4329 determines if there are any syntax errors. If there are, appropriate
4330 error messages are generated and compilation is immediately terminated.
4332 GNAT to continue with semantic analysis even if syntax errors have been
4333 found. This may enable the detection of more errors in a single run. On
4334 the other hand, the semantic analyzer is more likely to encounter some
4335 internal fatal error when given a syntactically invalid tree.
4338 @cindex @option{-gnatQ} (@code{gcc})
4339 In normal operation mode, the @file{ALI} file is not generated if any
4340 illegalities are detected in the program. The use of @option{-gnatQ} forces
4341 generation of the @file{ALI} file. This file is marked as being in
4342 error, so it cannot be used for binding purposes, but it does contain
4343 reasonably complete cross-reference information, and thus may be useful
4344 for use by tools (e.g. semantic browsing tools or integrated development
4345 environments) that are driven from the @file{ALI} file. This switch
4346 implies @option{-gnatq}, since the semantic phase must be run to get a
4347 meaningful ALI file.
4349 In addition, if @option{-gnatt} is also specified, then the tree file is
4350 generated even if there are illegalities. It may be useful in this case
4351 to also specify @option{-gnatq} to ensure that full semantic processing
4352 occurs. The resulting tree file can be processed by ASIS, for the purpose
4353 of providing partial information about illegal units, but if the error
4354 causes the tree to be badly malformed, then ASIS may crash during the
4357 When @option{-gnatQ} is used and the generated @file{ALI} file is marked as
4358 being in error, @code{gnatmake} will attempt to recompile the source when it
4359 finds such an @file{ALI} file, including with switch @option{-gnatc}.
4361 Note that @option{-gnatQ} has no effect if @option{-gnats} is specified,
4362 since ALI files are never generated if @option{-gnats} is set.
4367 @node Warning Message Control
4368 @subsection Warning Message Control
4369 @cindex Warning messages
4371 In addition to error messages, which correspond to illegalities as defined
4372 in the Ada 95 Reference Manual, the compiler detects two kinds of warning
4375 First, the compiler considers some constructs suspicious and generates a
4376 warning message to alert you to a possible error. Second, if the
4377 compiler detects a situation that is sure to raise an exception at
4378 run time, it generates a warning message. The following shows an example
4379 of warning messages:
4381 e.adb:4:24: warning: creation of object may raise Storage_Error
4382 e.adb:10:17: warning: static value out of range
4383 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
4387 GNAT considers a large number of situations as appropriate
4388 for the generation of warning messages. As always, warnings are not
4389 definite indications of errors. For example, if you do an out-of-range
4390 assignment with the deliberate intention of raising a
4391 @code{Constraint_Error} exception, then the warning that may be
4392 issued does not indicate an error. Some of the situations for which GNAT
4393 issues warnings (at least some of the time) are given in the following
4394 list. This list is not complete, and new warnings are often added to
4395 subsequent versions of GNAT. The list is intended to give a general idea
4396 of the kinds of warnings that are generated.
4400 Possible infinitely recursive calls
4403 Out-of-range values being assigned
4406 Possible order of elaboration problems
4412 Fixed-point type declarations with a null range
4415 Variables that are never assigned a value
4418 Variables that are referenced before being initialized
4421 Task entries with no corresponding @code{accept} statement
4424 Duplicate accepts for the same task entry in a @code{select}
4427 Objects that take too much storage
4430 Unchecked conversion between types of differing sizes
4433 Missing @code{return} statement along some execution path in a function
4436 Incorrect (unrecognized) pragmas
4439 Incorrect external names
4442 Allocation from empty storage pool
4445 Potentially blocking operation in protected type
4448 Suspicious parenthesization of expressions
4451 Mismatching bounds in an aggregate
4454 Attempt to return local value by reference
4458 Premature instantiation of a generic body
4461 Attempt to pack aliased components
4464 Out of bounds array subscripts
4467 Wrong length on string assignment
4470 Violations of style rules if style checking is enabled
4473 Unused @code{with} clauses
4476 @code{Bit_Order} usage that does not have any effect
4479 @code{Standard.Duration} used to resolve universal fixed expression
4482 Dereference of possibly null value
4485 Declaration that is likely to cause storage error
4488 Internal GNAT unit @code{with}'ed by application unit
4491 Values known to be out of range at compile time
4494 Unreferenced labels and variables
4497 Address overlays that could clobber memory
4500 Unexpected initialization when address clause present
4503 Bad alignment for address clause
4506 Useless type conversions
4509 Redundant assignment statements and other redundant constructs
4512 Useless exception handlers
4515 Accidental hiding of name by child unit
4519 Access before elaboration detected at compile time
4522 A range in a @code{for} loop that is known to be null or might be null
4527 The following switches are available to control the handling of
4533 @emph{Activate all optional errors.}
4534 @cindex @option{-gnatwa} (@code{gcc})
4535 This switch activates most optional warning messages, see remaining list
4536 in this section for details on optional warning messages that can be
4537 individually controlled. The warnings that are not turned on by this
4539 @option{-gnatwd} (implicit dereferencing),
4540 @option{-gnatwh} (hiding),
4541 and @option{-gnatwl} (elaboration warnings).
4542 All other optional warnings are turned on.
4545 @emph{Suppress all optional errors.}
4546 @cindex @option{-gnatwA} (@code{gcc})
4547 This switch suppresses all optional warning messages, see remaining list
4548 in this section for details on optional warning messages that can be
4549 individually controlled.
4552 @emph{Activate warnings on conditionals.}
4553 @cindex @option{-gnatwc} (@code{gcc})
4554 @cindex Conditionals, constant
4555 This switch activates warnings for conditional expressions used in
4556 tests that are known to be True or False at compile time. The default
4557 is that such warnings are not generated.
4558 Note that this warning does
4559 not get issued for the use of boolean variables or constants whose
4560 values are known at compile time, since this is a standard technique
4561 for conditional compilation in Ada, and this would generate too many
4562 ``false positive'' warnings.
4563 This warning can also be turned on using @option{-gnatwa}.
4566 @emph{Suppress warnings on conditionals.}
4567 @cindex @option{-gnatwC} (@code{gcc})
4568 This switch suppresses warnings for conditional expressions used in
4569 tests that are known to be True or False at compile time.
4572 @emph{Activate warnings on implicit dereferencing.}
4573 @cindex @option{-gnatwd} (@code{gcc})
4574 If this switch is set, then the use of a prefix of an access type
4575 in an indexed component, slice, or selected component without an
4576 explicit @code{.all} will generate a warning. With this warning
4577 enabled, access checks occur only at points where an explicit
4578 @code{.all} appears in the source code (assuming no warnings are
4579 generated as a result of this switch). The default is that such
4580 warnings are not generated.
4581 Note that @option{-gnatwa} does not affect the setting of
4582 this warning option.
4585 @emph{Suppress warnings on implicit dereferencing.}
4586 @cindex @option{-gnatwD} (@code{gcc})
4587 @cindex Implicit dereferencing
4588 @cindex Dereferencing, implicit
4589 This switch suppresses warnings for implicit dereferences in
4590 indexed components, slices, and selected components.
4593 @emph{Treat warnings as errors.}
4594 @cindex @option{-gnatwe} (@code{gcc})
4595 @cindex Warnings, treat as error
4596 This switch causes warning messages to be treated as errors.
4597 The warning string still appears, but the warning messages are counted
4598 as errors, and prevent the generation of an object file.
4601 @emph{Activate warnings on unreferenced formals.}
4602 @cindex @option{-gnatwf} (@code{gcc})
4603 @cindex Formals, unreferenced
4604 This switch causes a warning to be generated if a formal parameter
4605 is not referenced in the body of the subprogram. This warning can
4606 also be turned on using @option{-gnatwa} or @option{-gnatwu}.
4609 @emph{Suppress warnings on unreferenced formals.}
4610 @cindex @option{-gnatwF} (@code{gcc})
4611 This switch suppresses warnings for unreferenced formal
4612 parameters. Note that the
4613 combination @option{-gnatwu} followed by @option{-gnatwF} has the
4614 effect of warning on unreferenced entities other than subprogram
4618 @emph{Activate warnings on unrecognized pragmas.}
4619 @cindex @option{-gnatwg} (@code{gcc})
4620 @cindex Pragmas, unrecognized
4621 This switch causes a warning to be generated if an unrecognized
4622 pragma is encountered. Apart from issuing this warning, the
4623 pragma is ignored and has no effect. This warning can
4624 also be turned on using @option{-gnatwa}. The default
4625 is that such warnings are issued (satisfying the Ada Reference
4626 Manual requirement that such warnings appear).
4629 @emph{Suppress warnings on unrecognized pragmas.}
4630 @cindex @option{-gnatwG} (@code{gcc})
4631 This switch suppresses warnings for unrecognized pragmas.
4634 @emph{Activate warnings on hiding.}
4635 @cindex @option{-gnatwh} (@code{gcc})
4636 @cindex Hiding of Declarations
4637 This switch activates warnings on hiding declarations.
4638 A declaration is considered hiding
4639 if it is for a non-overloadable entity, and it declares an entity with the
4640 same name as some other entity that is directly or use-visible. The default
4641 is that such warnings are not generated.
4642 Note that @option{-gnatwa} does not affect the setting of this warning option.
4645 @emph{Suppress warnings on hiding.}
4646 @cindex @option{-gnatwH} (@code{gcc})
4647 This switch suppresses warnings on hiding declarations.
4650 @emph{Activate warnings on implementation units.}
4651 @cindex @option{-gnatwi} (@code{gcc})
4652 This switch activates warnings for a @code{with} of an internal GNAT
4653 implementation unit, defined as any unit from the @code{Ada},
4654 @code{Interfaces}, @code{GNAT},
4655 ^^@code{DEC},^ or @code{System}
4656 hierarchies that is not
4657 documented in either the Ada Reference Manual or the GNAT
4658 Programmer's Reference Manual. Such units are intended only
4659 for internal implementation purposes and should not be @code{with}'ed
4660 by user programs. The default is that such warnings are generated
4661 This warning can also be turned on using @option{-gnatwa}.
4664 @emph{Disable warnings on implementation units.}
4665 @cindex @option{-gnatwI} (@code{gcc})
4666 This switch disables warnings for a @code{with} of an internal GNAT
4667 implementation unit.
4670 @emph{Activate warnings on obsolescent features (Annex J).}
4671 @cindex @option{-gnatwj} (@code{gcc})
4672 @cindex Features, obsolescent
4673 @cindex Obsolescent features
4674 If this warning option is activated, then warnings are generated for
4675 calls to subprograms marked with @code{pragma Obsolescent} and
4676 for use of features in Annex J of the Ada Reference Manual. In the
4677 case of Annex J, not all features are flagged. In particular use
4678 of the renamed packages (like @code{Text_IO}) and use of package
4679 @code{ASCII} are not flagged, since these are very common and
4680 would generate many annoying positive warnings. The default is that
4681 such warnings are not generated.
4684 @emph{Suppress warnings on obsolescent features (Annex J).}
4685 @cindex @option{-gnatwJ} (@code{gcc})
4686 This switch disables warnings on use of obsolescent features.
4689 @emph{Activate warnings on variables that could be constants.}
4690 @cindex @option{-gnatwk} (@code{gcc})
4691 This switch activates warnings for variables that are initialized but
4692 never modified, and then could be declared constants.
4695 @emph{Suppress warnings on variables that could be constants.}
4696 @cindex @option{-gnatwK} (@code{gcc})
4697 This switch disables warnings on variables that could be declared constants.
4700 @emph{Activate warnings for missing elaboration pragmas.}
4701 @cindex @option{-gnatwl} (@code{gcc})
4702 @cindex Elaboration, warnings
4703 This switch activates warnings on missing
4704 @code{pragma Elaborate_All} statements.
4705 See the section in this guide on elaboration checking for details on
4706 when such pragma should be used. Warnings are also generated if you
4707 are using the static mode of elaboration, and a @code{pragma Elaborate}
4708 is encountered. The default is that such warnings
4710 This warning is not automatically turned on by the use of @option{-gnatwa}.
4713 @emph{Suppress warnings for missing elaboration pragmas.}
4714 @cindex @option{-gnatwL} (@code{gcc})
4715 This switch suppresses warnings on missing pragma Elaborate_All statements.
4716 See the section in this guide on elaboration checking for details on
4717 when such pragma should be used.
4720 @emph{Activate warnings on modified but unreferenced variables.}
4721 @cindex @option{-gnatwm} (@code{gcc})
4722 This switch activates warnings for variables that are assigned (using
4723 an initialization value or with one or more assignment statements) but
4724 whose value is never read. The warning is suppressed for volatile
4725 variables and also for variables that are renamings of other variables
4726 or for which an address clause is given.
4727 This warning can also be turned on using @option{-gnatwa}.
4730 @emph{Disable warnings on modified but unreferenced variables.}
4731 @cindex @option{-gnatwM} (@code{gcc})
4732 This switch disables warnings for variables that are assigned or
4733 initialized, but never read.
4736 @emph{Set normal warnings mode.}
4737 @cindex @option{-gnatwn} (@code{gcc})
4738 This switch sets normal warning mode, in which enabled warnings are
4739 issued and treated as warnings rather than errors. This is the default
4740 mode. the switch @option{-gnatwn} can be used to cancel the effect of
4741 an explicit @option{-gnatws} or
4742 @option{-gnatwe}. It also cancels the effect of the
4743 implicit @option{-gnatwe} that is activated by the
4744 use of @option{-gnatg}.
4747 @emph{Activate warnings on address clause overlays.}
4748 @cindex @option{-gnatwo} (@code{gcc})
4749 @cindex Address Clauses, warnings
4750 This switch activates warnings for possibly unintended initialization
4751 effects of defining address clauses that cause one variable to overlap
4752 another. The default is that such warnings are generated.
4753 This warning can also be turned on using @option{-gnatwa}.
4756 @emph{Suppress warnings on address clause overlays.}
4757 @cindex @option{-gnatwO} (@code{gcc})
4758 This switch suppresses warnings on possibly unintended initialization
4759 effects of defining address clauses that cause one variable to overlap
4763 @emph{Activate warnings on ineffective pragma Inlines.}
4764 @cindex @option{-gnatwp} (@code{gcc})
4765 @cindex Inlining, warnings
4766 This switch activates warnings for failure of front end inlining
4767 (activated by @option{-gnatN}) to inline a particular call. There are
4768 many reasons for not being able to inline a call, including most
4769 commonly that the call is too complex to inline.
4770 This warning can also be turned on using @option{-gnatwa}.
4773 @emph{Suppress warnings on ineffective pragma Inlines.}
4774 @cindex @option{-gnatwP} (@code{gcc})
4775 This switch suppresses warnings on ineffective pragma Inlines. If the
4776 inlining mechanism cannot inline a call, it will simply ignore the
4780 @emph{Activate warnings on redundant constructs.}
4781 @cindex @option{-gnatwr} (@code{gcc})
4782 This switch activates warnings for redundant constructs. The following
4783 is the current list of constructs regarded as redundant:
4784 This warning can also be turned on using @option{-gnatwa}.
4788 Assignment of an item to itself.
4790 Type conversion that converts an expression to its own type.
4792 Use of the attribute @code{Base} where @code{typ'Base} is the same
4795 Use of pragma @code{Pack} when all components are placed by a record
4796 representation clause.
4798 Exception handler containing only a reraise statement (raise with no
4799 operand) which has no effect.
4801 Use of the operator abs on an operand that is known at compile time
4804 Use of an unnecessary extra level of parentheses (C-style) around conditions
4805 in @code{if} statements, @code{while} statements and @code{exit} statements.
4807 Comparison of boolean expressions to an explicit True value.
4811 @emph{Suppress warnings on redundant constructs.}
4812 @cindex @option{-gnatwR} (@code{gcc})
4813 This switch suppresses warnings for redundant constructs.
4816 @emph{Suppress all warnings.}
4817 @cindex @option{-gnatws} (@code{gcc})
4818 This switch completely suppresses the
4819 output of all warning messages from the GNAT front end.
4820 Note that it does not suppress warnings from the @code{gcc} back end.
4821 To suppress these back end warnings as well, use the switch @option{-w}
4822 in addition to @option{-gnatws}.
4825 @emph{Activate warnings on unused entities.}
4826 @cindex @option{-gnatwu} (@code{gcc})
4827 This switch activates warnings to be generated for entities that
4828 are declared but not referenced, and for units that are @code{with}'ed
4830 referenced. In the case of packages, a warning is also generated if
4831 no entities in the package are referenced. This means that if the package
4832 is referenced but the only references are in @code{use}
4833 clauses or @code{renames}
4834 declarations, a warning is still generated. A warning is also generated
4835 for a generic package that is @code{with}'ed but never instantiated.
4836 In the case where a package or subprogram body is compiled, and there
4837 is a @code{with} on the corresponding spec
4838 that is only referenced in the body,
4839 a warning is also generated, noting that the
4840 @code{with} can be moved to the body. The default is that
4841 such warnings are not generated.
4842 This switch also activates warnings on unreferenced formals
4843 (it is includes the effect of @option{-gnatwf}).
4844 This warning can also be turned on using @option{-gnatwa}.
4847 @emph{Suppress warnings on unused entities.}
4848 @cindex @option{-gnatwU} (@code{gcc})
4849 This switch suppresses warnings for unused entities and packages.
4850 It also turns off warnings on unreferenced formals (and thus includes
4851 the effect of @option{-gnatwF}).
4854 @emph{Activate warnings on unassigned variables.}
4855 @cindex @option{-gnatwv} (@code{gcc})
4856 @cindex Unassigned variable warnings
4857 This switch activates warnings for access to variables which
4858 may not be properly initialized. The default is that
4859 such warnings are generated.
4862 @emph{Suppress warnings on unassigned variables.}
4863 @cindex @option{-gnatwV} (@code{gcc})
4864 This switch suppresses warnings for access to variables which
4865 may not be properly initialized.
4868 @emph{Activate warnings on Export/Import pragmas.}
4869 @cindex @option{-gnatwx} (@code{gcc})
4870 @cindex Export/Import pragma warnings
4871 This switch activates warnings on Export/Import pragmas when
4872 the compiler detects a possible conflict between the Ada and
4873 foreign language calling sequences. For example, the use of
4874 default parameters in a convention C procedure is dubious
4875 because the C compiler cannot supply the proper default, so
4876 a warning is issued. The default is that such warnings are
4880 @emph{Suppress warnings on Export/Import pragmas.}
4881 @cindex @option{-gnatwX} (@code{gcc})
4882 This switch suppresses warnings on Export/Import pragmas.
4883 The sense of this is that you are telling the compiler that
4884 you know what you are doing in writing the pragma, and it
4885 should not complain at you.
4888 @emph{Activate warnings on unchecked conversions.}
4889 @cindex @option{-gnatwz} (@code{gcc})
4890 @cindex Unchecked_Conversion warnings
4891 This switch activates warnings for unchecked conversions
4892 where the types are known at compile time to have different
4894 is that such warnings are generated.
4897 @emph{Suppress warnings on unchecked conversions.}
4898 @cindex @option{-gnatwZ} (@code{gcc})
4899 This switch suppresses warnings for unchecked conversions
4900 where the types are known at compile time to have different
4903 @item ^-Wuninitialized^WARNINGS=UNINITIALIZED^
4904 @cindex @option{-Wuninitialized}
4905 The warnings controlled by the @option{-gnatw} switch are generated by the
4906 front end of the compiler. In some cases, the @option{^gcc^GCC^} back end
4907 can provide additional warnings. One such useful warning is provided by
4908 @option{^-Wuninitialized^WARNINGS=UNINITIALIZED^}. This must be used in
4909 conjunction with tunrning on optimization mode. This causes the flow
4910 analysis circuits of the back end optimizer to output additional
4911 warnings about uninitialized variables.
4913 @item ^-w^/NO_BACK_END_WARNINGS^
4915 This switch suppresses warnings from the @option{^gcc^GCC^} back end. It may
4916 be used in conjunction with @option{-gnatws} to ensure that all warnings
4917 are suppressed during the entire compilation process.
4923 A string of warning parameters can be used in the same parameter. For example:
4930 will turn on all optional warnings except for elaboration pragma warnings,
4931 and also specify that warnings should be treated as errors.
4933 When no switch @option{^-gnatw^/WARNINGS^} is used, this is equivalent to:
4959 @node Debugging and Assertion Control
4960 @subsection Debugging and Assertion Control
4964 @cindex @option{-gnata} (@code{gcc})
4970 The pragmas @code{Assert} and @code{Debug} normally have no effect and
4971 are ignored. This switch, where @samp{a} stands for assert, causes
4972 @code{Assert} and @code{Debug} pragmas to be activated.
4974 The pragmas have the form:
4978 @b{pragma} Assert (@var{Boolean-expression} [,
4979 @var{static-string-expression}])
4980 @b{pragma} Debug (@var{procedure call})
4985 The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
4986 If the result is @code{True}, the pragma has no effect (other than
4987 possible side effects from evaluating the expression). If the result is
4988 @code{False}, the exception @code{Assert_Failure} declared in the package
4989 @code{System.Assertions} is
4990 raised (passing @var{static-string-expression}, if present, as the
4991 message associated with the exception). If no string expression is
4992 given the default is a string giving the file name and line number
4995 The @code{Debug} pragma causes @var{procedure} to be called. Note that
4996 @code{pragma Debug} may appear within a declaration sequence, allowing
4997 debugging procedures to be called between declarations.
5000 @item /DEBUG[=debug-level]
5002 Specifies how much debugging information is to be included in
5003 the resulting object file where 'debug-level' is one of the following:
5006 Include both debugger symbol records and traceback
5008 This is the default setting.
5010 Include both debugger symbol records and traceback in
5013 Excludes both debugger symbol records and traceback
5014 the object file. Same as /NODEBUG.
5016 Includes only debugger symbol records in the object
5017 file. Note that this doesn't include traceback information.
5022 @node Validity Checking
5023 @subsection Validity Checking
5024 @findex Validity Checking
5027 The Ada 95 Reference Manual has specific requirements for checking
5028 for invalid values. In particular, RM 13.9.1 requires that the
5029 evaluation of invalid values (for example from unchecked conversions),
5030 not result in erroneous execution. In GNAT, the result of such an
5031 evaluation in normal default mode is to either use the value
5032 unmodified, or to raise Constraint_Error in those cases where use
5033 of the unmodified value would cause erroneous execution. The cases
5034 where unmodified values might lead to erroneous execution are case
5035 statements (where a wild jump might result from an invalid value),
5036 and subscripts on the left hand side (where memory corruption could
5037 occur as a result of an invalid value).
5039 The @option{-gnatV^@var{x}^^} switch allows more control over the validity
5042 The @code{x} argument is a string of letters that
5043 indicate validity checks that are performed or not performed in addition
5044 to the default checks described above.
5047 The options allowed for this qualifier
5048 indicate validity checks that are performed or not performed in addition
5049 to the default checks described above.
5056 @emph{All validity checks.}
5057 @cindex @option{-gnatVa} (@code{gcc})
5058 All validity checks are turned on.
5060 That is, @option{-gnatVa} is
5061 equivalent to @option{gnatVcdfimorst}.
5065 @emph{Validity checks for copies.}
5066 @cindex @option{-gnatVc} (@code{gcc})
5067 The right hand side of assignments, and the initializing values of
5068 object declarations are validity checked.
5071 @emph{Default (RM) validity checks.}
5072 @cindex @option{-gnatVd} (@code{gcc})
5073 Some validity checks are done by default following normal Ada semantics
5075 A check is done in case statements that the expression is within the range
5076 of the subtype. If it is not, Constraint_Error is raised.
5077 For assignments to array components, a check is done that the expression used
5078 as index is within the range. If it is not, Constraint_Error is raised.
5079 Both these validity checks may be turned off using switch @option{-gnatVD}.
5080 They are turned on by default. If @option{-gnatVD} is specified, a subsequent
5081 switch @option{-gnatVd} will leave the checks turned on.
5082 Switch @option{-gnatVD} should be used only if you are sure that all such
5083 expressions have valid values. If you use this switch and invalid values
5084 are present, then the program is erroneous, and wild jumps or memory
5085 overwriting may occur.
5088 @emph{Validity checks for floating-point values.}
5089 @cindex @option{-gnatVf} (@code{gcc})
5090 In the absence of this switch, validity checking occurs only for discrete
5091 values. If @option{-gnatVf} is specified, then validity checking also applies
5092 for floating-point values, and NaN's and infinities are considered invalid,
5093 as well as out of range values for constrained types. Note that this means
5094 that standard @code{IEEE} infinity mode is not allowed. The exact contexts
5095 in which floating-point values are checked depends on the setting of other
5096 options. For example,
5097 @option{^-gnatVif^VALIDITY_CHECKING=(IN_PARAMS,FLOATS)^} or
5098 @option{^-gnatVfi^VALIDITY_CHECKING=(FLOATS,IN_PARAMS)^}
5099 (the order does not matter) specifies that floating-point parameters of mode
5100 @code{in} should be validity checked.
5103 @emph{Validity checks for @code{in} mode parameters}
5104 @cindex @option{-gnatVi} (@code{gcc})
5105 Arguments for parameters of mode @code{in} are validity checked in function
5106 and procedure calls at the point of call.
5109 @emph{Validity checks for @code{in out} mode parameters.}
5110 @cindex @option{-gnatVm} (@code{gcc})
5111 Arguments for parameters of mode @code{in out} are validity checked in
5112 procedure calls at the point of call. The @code{'m'} here stands for
5113 modify, since this concerns parameters that can be modified by the call.
5114 Note that there is no specific option to test @code{out} parameters,
5115 but any reference within the subprogram will be tested in the usual
5116 manner, and if an invalid value is copied back, any reference to it
5117 will be subject to validity checking.
5120 @emph{No validity checks.}
5121 @cindex @option{-gnatVn} (@code{gcc})
5122 This switch turns off all validity checking, including the default checking
5123 for case statements and left hand side subscripts. Note that the use of
5124 the switch @option{-gnatp} suppresses all run-time checks, including
5125 validity checks, and thus implies @option{-gnatVn}. When this switch
5126 is used, it cancels any other @option{-gnatV} previously issued.
5129 @emph{Validity checks for operator and attribute operands.}
5130 @cindex @option{-gnatVo} (@code{gcc})
5131 Arguments for predefined operators and attributes are validity checked.
5132 This includes all operators in package @code{Standard},
5133 the shift operators defined as intrinsic in package @code{Interfaces}
5134 and operands for attributes such as @code{Pos}. Checks are also made
5135 on individual component values for composite comparisons.
5138 @emph{Validity checks for parameters.}
5139 @cindex @option{-gnatVp} (@code{gcc})
5140 This controls the treatment of parameters within a subprogram (as opposed
5141 to @option{-gnatVi} and @option{-gnatVm} which control validity testing
5142 of parameters on a call. If either of these call options is used, then
5143 normally an assumption is made within a subprogram that the input arguments
5144 have been validity checking at the point of call, and do not need checking
5145 again within a subprogram). If @option{-gnatVp} is set, then this assumption
5146 is not made, and parameters are not assumed to be valid, so their validity
5147 will be checked (or rechecked) within the subprogram.
5150 @emph{Validity checks for function returns.}
5151 @cindex @option{-gnatVr} (@code{gcc})
5152 The expression in @code{return} statements in functions is validity
5156 @emph{Validity checks for subscripts.}
5157 @cindex @option{-gnatVs} (@code{gcc})
5158 All subscripts expressions are checked for validity, whether they appear
5159 on the right side or left side (in default mode only left side subscripts
5160 are validity checked).
5163 @emph{Validity checks for tests.}
5164 @cindex @option{-gnatVt} (@code{gcc})
5165 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
5166 statements are checked, as well as guard expressions in entry calls.
5171 The @option{-gnatV} switch may be followed by
5172 ^a string of letters^a list of options^
5173 to turn on a series of validity checking options.
5175 @option{^-gnatVcr^/VALIDITY_CHECKING=(COPIES, RETURNS)^}
5176 specifies that in addition to the default validity checking, copies and
5177 function return expressions are to be validity checked.
5178 In order to make it easier
5179 to specify the desired combination of effects,
5181 the upper case letters @code{CDFIMORST} may
5182 be used to turn off the corresponding lower case option.
5185 the prefix @code{NO} on an option turns off the corresponding validity
5188 @item @code{NOCOPIES}
5189 @item @code{NODEFAULT}
5190 @item @code{NOFLOATS}
5191 @item @code{NOIN_PARAMS}
5192 @item @code{NOMOD_PARAMS}
5193 @item @code{NOOPERANDS}
5194 @item @code{NORETURNS}
5195 @item @code{NOSUBSCRIPTS}
5196 @item @code{NOTESTS}
5200 @option{^-gnatVaM^/VALIDITY_CHECKING=(ALL, NOMOD_PARAMS)^}
5201 turns on all validity checking options except for
5202 checking of @code{@b{in out}} procedure arguments.
5204 The specification of additional validity checking generates extra code (and
5205 in the case of @option{-gnatVa} the code expansion can be substantial.
5206 However, these additional checks can be very useful in detecting
5207 uninitialized variables, incorrect use of unchecked conversion, and other
5208 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
5209 is useful in conjunction with the extra validity checking, since this
5210 ensures that wherever possible uninitialized variables have invalid values.
5212 See also the pragma @code{Validity_Checks} which allows modification of
5213 the validity checking mode at the program source level, and also allows for
5214 temporary disabling of validity checks.
5217 @node Style Checking
5218 @subsection Style Checking
5219 @findex Style checking
5222 The @option{-gnaty^x^(option,option,...)^} switch
5223 @cindex @option{-gnaty} (@code{gcc})
5224 causes the compiler to
5225 enforce specified style rules. A limited set of style rules has been used
5226 in writing the GNAT sources themselves. This switch allows user programs
5227 to activate all or some of these checks. If the source program fails a
5228 specified style check, an appropriate warning message is given, preceded by
5229 the character sequence ``(style)''.
5231 @code{(option,option,...)} is a sequence of keywords
5234 The string @var{x} is a sequence of letters or digits
5236 indicating the particular style
5237 checks to be performed. The following checks are defined:
5242 @emph{Specify indentation level.}
5243 If a digit from 1-9 appears
5244 ^in the string after @option{-gnaty}^as an option for /STYLE_CHECKS^
5245 then proper indentation is checked, with the digit indicating the
5246 indentation level required.
5247 The general style of required indentation is as specified by
5248 the examples in the Ada Reference Manual. Full line comments must be
5249 aligned with the @code{--} starting on a column that is a multiple of
5250 the alignment level.
5253 @emph{Check attribute casing.}
5254 If the ^letter a^word ATTRIBUTE^ appears in the string after @option{-gnaty}
5255 then attribute names, including the case of keywords such as @code{digits}
5256 used as attributes names, must be written in mixed case, that is, the
5257 initial letter and any letter following an underscore must be uppercase.
5258 All other letters must be lowercase.
5261 @emph{Blanks not allowed at statement end.}
5262 If the ^letter b^word BLANKS^ appears in the string after @option{-gnaty} then
5263 trailing blanks are not allowed at the end of statements. The purpose of this
5264 rule, together with h (no horizontal tabs), is to enforce a canonical format
5265 for the use of blanks to separate source tokens.
5268 @emph{Check comments.}
5269 If the ^letter c^word COMMENTS^ appears in the string after @option{-gnaty}
5270 then comments must meet the following set of rules:
5275 The ``@code{--}'' that starts the column must either start in column one,
5276 or else at least one blank must precede this sequence.
5279 Comments that follow other tokens on a line must have at least one blank
5280 following the ``@code{--}'' at the start of the comment.
5283 Full line comments must have two blanks following the ``@code{--}'' that
5284 starts the comment, with the following exceptions.
5287 A line consisting only of the ``@code{--}'' characters, possibly preceded
5288 by blanks is permitted.
5291 A comment starting with ``@code{--x}'' where @code{x} is a special character
5293 This allows proper processing of the output generated by specialized tools
5294 including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK
5296 language (where ``@code{--#}'' is used). For the purposes of this rule, a
5297 special character is defined as being in one of the ASCII ranges
5298 @code{16#21#..16#2F#} or @code{16#3A#..16#3F#}.
5299 Note that this usage is not permitted
5300 in GNAT implementation units (i.e. when @option{-gnatg} is used).
5303 A line consisting entirely of minus signs, possibly preceded by blanks, is
5304 permitted. This allows the construction of box comments where lines of minus
5305 signs are used to form the top and bottom of the box.
5308 If a comment starts and ends with ``@code{--}'' is permitted as long as at
5309 least one blank follows the initial ``@code{--}''. Together with the preceding
5310 rule, this allows the construction of box comments, as shown in the following
5313 ---------------------------
5314 -- This is a box comment --
5315 -- with two text lines. --
5316 ---------------------------
5321 @emph{Check end/exit labels.}
5322 If the ^letter e^word END^ appears in the string after @option{-gnaty} then
5323 optional labels on @code{end} statements ending subprograms and on
5324 @code{exit} statements exiting named loops, are required to be present.
5327 @emph{No form feeds or vertical tabs.}
5328 If the ^letter f^word VTABS^ appears in the string after @option{-gnaty} then
5329 neither form feeds nor vertical tab characters are not permitted
5333 @emph{No horizontal tabs.}
5334 If the ^letter h^word HTABS^ appears in the string after @option{-gnaty} then
5335 horizontal tab characters are not permitted in the source text.
5336 Together with the b (no blanks at end of line) check, this
5337 enforces a canonical form for the use of blanks to separate
5341 @emph{Check if-then layout.}
5342 If the ^letter i^word IF_THEN^ appears in the string after @option{-gnaty},
5343 then the keyword @code{then} must appear either on the same
5344 line as corresponding @code{if}, or on a line on its own, lined
5345 up under the @code{if} with at least one non-blank line in between
5346 containing all or part of the condition to be tested.
5349 @emph{Check keyword casing.}
5350 If the ^letter k^word KEYWORD^ appears in the string after @option{-gnaty} then
5351 all keywords must be in lower case (with the exception of keywords
5352 such as @code{digits} used as attribute names to which this check
5356 @emph{Check layout.}
5357 If the ^letter l^word LAYOUT^ appears in the string after @option{-gnaty} then
5358 layout of statement and declaration constructs must follow the
5359 recommendations in the Ada Reference Manual, as indicated by the
5360 form of the syntax rules. For example an @code{else} keyword must
5361 be lined up with the corresponding @code{if} keyword.
5363 There are two respects in which the style rule enforced by this check
5364 option are more liberal than those in the Ada Reference Manual. First
5365 in the case of record declarations, it is permissible to put the
5366 @code{record} keyword on the same line as the @code{type} keyword, and
5367 then the @code{end} in @code{end record} must line up under @code{type}.
5368 For example, either of the following two layouts is acceptable:
5370 @smallexample @c ada
5386 Second, in the case of a block statement, a permitted alternative
5387 is to put the block label on the same line as the @code{declare} or
5388 @code{begin} keyword, and then line the @code{end} keyword up under
5389 the block label. For example both the following are permitted:
5391 @smallexample @c ada
5409 The same alternative format is allowed for loops. For example, both of
5410 the following are permitted:
5412 @smallexample @c ada
5414 Clear : while J < 10 loop
5425 @item ^m^LINE_LENGTH^
5426 @emph{Check maximum line length.}
5427 If the ^letter m^word LINE_LENGTH^ appears in the string after @option{-gnaty}
5428 then the length of source lines must not exceed 79 characters, including
5429 any trailing blanks. The value of 79 allows convenient display on an
5430 80 character wide device or window, allowing for possible special
5431 treatment of 80 character lines. Note that this count is of raw
5432 characters in the source text. This means that a tab character counts
5433 as one character in this count and a wide character sequence counts as
5434 several characters (however many are needed in the encoding).
5436 @item ^Mnnn^MAX_LENGTH=nnn^
5437 @emph{Set maximum line length.}
5438 If the sequence ^M^MAX_LENGTH=^nnn, where nnn is a decimal number, appears in
5439 the string after @option{-gnaty} then the length of lines must not exceed the
5442 @item ^n^STANDARD_CASING^
5443 @emph{Check casing of entities in Standard.}
5444 If the ^letter n^word STANDARD_CASING^ appears in the string
5445 after @option{-gnaty} then any identifier from Standard must be cased
5446 to match the presentation in the Ada Reference Manual (for example,
5447 @code{Integer} and @code{ASCII.NUL}).
5449 @item ^o^ORDERED_SUBPROGRAMS^
5450 @emph{Check order of subprogram bodies.}
5451 If the ^letter o^word ORDERED_SUBPROGRAMS^ appears in the string
5452 after @option{-gnaty} then all subprogram bodies in a given scope
5453 (e.g. a package body) must be in alphabetical order. The ordering
5454 rule uses normal Ada rules for comparing strings, ignoring casing
5455 of letters, except that if there is a trailing numeric suffix, then
5456 the value of this suffix is used in the ordering (e.g. Junk2 comes
5460 @emph{Check pragma casing.}
5461 If the ^letter p^word PRAGMA^ appears in the string after @option{-gnaty} then
5462 pragma names must be written in mixed case, that is, the
5463 initial letter and any letter following an underscore must be uppercase.
5464 All other letters must be lowercase.
5466 @item ^r^REFERENCES^
5467 @emph{Check references.}
5468 If the ^letter r^word REFERENCES^ appears in the string after @option{-gnaty}
5469 then all identifier references must be cased in the same way as the
5470 corresponding declaration. No specific casing style is imposed on
5471 identifiers. The only requirement is for consistency of references
5475 @emph{Check separate specs.}
5476 If the ^letter s^word SPECS^ appears in the string after @option{-gnaty} then
5477 separate declarations (``specs'') are required for subprograms (a
5478 body is not allowed to serve as its own declaration). The only
5479 exception is that parameterless library level procedures are
5480 not required to have a separate declaration. This exception covers
5481 the most frequent form of main program procedures.
5484 @emph{Check token spacing.}
5485 If the ^letter t^word TOKEN^ appears in the string after @option{-gnaty} then
5486 the following token spacing rules are enforced:
5491 The keywords @code{@b{abs}} and @code{@b{not}} must be followed by a space.
5494 The token @code{=>} must be surrounded by spaces.
5497 The token @code{<>} must be preceded by a space or a left parenthesis.
5500 Binary operators other than @code{**} must be surrounded by spaces.
5501 There is no restriction on the layout of the @code{**} binary operator.
5504 Colon must be surrounded by spaces.
5507 Colon-equal (assignment, initialization) must be surrounded by spaces.
5510 Comma must be the first non-blank character on the line, or be
5511 immediately preceded by a non-blank character, and must be followed
5515 If the token preceding a left parenthesis ends with a letter or digit, then
5516 a space must separate the two tokens.
5519 A right parenthesis must either be the first non-blank character on
5520 a line, or it must be preceded by a non-blank character.
5523 A semicolon must not be preceded by a space, and must not be followed by
5524 a non-blank character.
5527 A unary plus or minus may not be followed by a space.
5530 A vertical bar must be surrounded by spaces.
5534 In the above rules, appearing in column one is always permitted, that is,
5535 counts as meeting either a requirement for a required preceding space,
5536 or as meeting a requirement for no preceding space.
5538 Appearing at the end of a line is also always permitted, that is, counts
5539 as meeting either a requirement for a following space, or as meeting
5540 a requirement for no following space.
5545 If any of these style rules is violated, a message is generated giving
5546 details on the violation. The initial characters of such messages are
5547 always ``@code{(style)}''. Note that these messages are treated as warning
5548 messages, so they normally do not prevent the generation of an object
5549 file. The @option{-gnatwe} switch can be used to treat warning messages,
5550 including style messages, as fatal errors.
5554 @option{-gnaty} on its own (that is not
5555 followed by any letters or digits),
5556 is equivalent to @code{gnaty3abcefhiklmprst}, that is all checking
5557 options enabled with the exception of -gnatyo,
5560 /STYLE_CHECKS=ALL_BUILTIN enables all checking options with
5561 the exception of ORDERED_SUBPROGRAMS,
5563 with an indentation level of 3. This is the standard
5564 checking option that is used for the GNAT sources.
5573 clears any previously set style checks.
5575 @node Run-Time Checks
5576 @subsection Run-Time Checks
5577 @cindex Division by zero
5578 @cindex Access before elaboration
5579 @cindex Checks, division by zero
5580 @cindex Checks, access before elaboration
5583 If you compile with the default options, GNAT will insert many run-time
5584 checks into the compiled code, including code that performs range
5585 checking against constraints, but not arithmetic overflow checking for
5586 integer operations (including division by zero) or checks for access
5587 before elaboration on subprogram calls. All other run-time checks, as
5588 required by the Ada 95 Reference Manual, are generated by default.
5589 The following @code{gcc} switches refine this default behavior:
5594 @cindex @option{-gnatp} (@code{gcc})
5595 @cindex Suppressing checks
5596 @cindex Checks, suppressing
5598 Suppress all run-time checks as though @code{pragma Suppress (all_checks})
5599 had been present in the source. Validity checks are also suppressed (in
5600 other words @option{-gnatp} also implies @option{-gnatVn}.
5601 Use this switch to improve the performance
5602 of the code at the expense of safety in the presence of invalid data or
5606 @cindex @option{-gnato} (@code{gcc})
5607 @cindex Overflow checks
5608 @cindex Check, overflow
5609 Enables overflow checking for integer operations.
5610 This causes GNAT to generate slower and larger executable
5611 programs by adding code to check for overflow (resulting in raising
5612 @code{Constraint_Error} as required by standard Ada
5613 semantics). These overflow checks correspond to situations in which
5614 the true value of the result of an operation may be outside the base
5615 range of the result type. The following example shows the distinction:
5617 @smallexample @c ada
5618 X1 : Integer := Integer'Last;
5619 X2 : Integer range 1 .. 5 := 5;
5620 X3 : Integer := Integer'Last;
5621 X4 : Integer range 1 .. 5 := 5;
5622 F : Float := 2.0E+20;
5631 Here the first addition results in a value that is outside the base range
5632 of Integer, and hence requires an overflow check for detection of the
5633 constraint error. Thus the first assignment to @code{X1} raises a
5634 @code{Constraint_Error} exception only if @option{-gnato} is set.
5636 The second increment operation results in a violation
5637 of the explicit range constraint, and such range checks are always
5638 performed (unless specifically suppressed with a pragma @code{suppress}
5639 or the use of @option{-gnatp}).
5641 The two conversions of @code{F} both result in values that are outside
5642 the base range of type @code{Integer} and thus will raise
5643 @code{Constraint_Error} exceptions only if @option{-gnato} is used.
5644 The fact that the result of the second conversion is assigned to
5645 variable @code{X4} with a restricted range is irrelevant, since the problem
5646 is in the conversion, not the assignment.
5648 Basically the rule is that in the default mode (@option{-gnato} not
5649 used), the generated code assures that all integer variables stay
5650 within their declared ranges, or within the base range if there is
5651 no declared range. This prevents any serious problems like indexes
5652 out of range for array operations.
5654 What is not checked in default mode is an overflow that results in
5655 an in-range, but incorrect value. In the above example, the assignments
5656 to @code{X1}, @code{X2}, @code{X3} all give results that are within the
5657 range of the target variable, but the result is wrong in the sense that
5658 it is too large to be represented correctly. Typically the assignment
5659 to @code{X1} will result in wrap around to the largest negative number.
5660 The conversions of @code{F} will result in some @code{Integer} value
5661 and if that integer value is out of the @code{X4} range then the
5662 subsequent assignment would generate an exception.
5664 @findex Machine_Overflows
5665 Note that the @option{-gnato} switch does not affect the code generated
5666 for any floating-point operations; it applies only to integer
5668 For floating-point, GNAT has the @code{Machine_Overflows}
5669 attribute set to @code{False} and the normal mode of operation is to
5670 generate IEEE NaN and infinite values on overflow or invalid operations
5671 (such as dividing 0.0 by 0.0).
5673 The reason that we distinguish overflow checking from other kinds of
5674 range constraint checking is that a failure of an overflow check can
5675 generate an incorrect value, but cannot cause erroneous behavior. This
5676 is unlike the situation with a constraint check on an array subscript,
5677 where failure to perform the check can result in random memory description,
5678 or the range check on a case statement, where failure to perform the check
5679 can cause a wild jump.
5681 Note again that @option{-gnato} is off by default, so overflow checking is
5682 not performed in default mode. This means that out of the box, with the
5683 default settings, GNAT does not do all the checks expected from the
5684 language description in the Ada Reference Manual. If you want all constraint
5685 checks to be performed, as described in this Manual, then you must
5686 explicitly use the -gnato switch either on the @code{gnatmake} or
5690 @cindex @option{-gnatE} (@code{gcc})
5691 @cindex Elaboration checks
5692 @cindex Check, elaboration
5693 Enables dynamic checks for access-before-elaboration
5694 on subprogram calls and generic instantiations.
5695 For full details of the effect and use of this switch,
5696 @xref{Compiling Using gcc}.
5701 The setting of these switches only controls the default setting of the
5702 checks. You may modify them using either @code{Suppress} (to remove
5703 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
5706 @node Stack Overflow Checking
5707 @subsection Stack Overflow Checking
5708 @cindex Stack Overflow Checking
5709 @cindex -fstack-check
5712 For most operating systems, @code{gcc} does not perform stack overflow
5713 checking by default. This means that if the main environment task or
5714 some other task exceeds the available stack space, then unpredictable
5715 behavior will occur.
5717 To activate stack checking, compile all units with the gcc option
5718 @option{-fstack-check}. For example:
5721 gcc -c -fstack-check package1.adb
5725 Units compiled with this option will generate extra instructions to check
5726 that any use of the stack (for procedure calls or for declaring local
5727 variables in declare blocks) do not exceed the available stack space.
5728 If the space is exceeded, then a @code{Storage_Error} exception is raised.
5730 For declared tasks, the stack size is always controlled by the size
5731 given in an applicable @code{Storage_Size} pragma (or is set to
5732 the default size if no pragma is used.
5734 For the environment task, the stack size depends on
5735 system defaults and is unknown to the compiler. The stack
5736 may even dynamically grow on some systems, precluding the
5737 normal Ada semantics for stack overflow. In the worst case,
5738 unbounded stack usage, causes unbounded stack expansion
5739 resulting in the system running out of virtual memory.
5741 The stack checking may still work correctly if a fixed
5742 size stack is allocated, but this cannot be guaranteed.
5743 To ensure that a clean exception is signalled for stack
5744 overflow, set the environment variable
5745 @code{GNAT_STACK_LIMIT} to indicate the maximum
5746 stack area that can be used, as in:
5747 @cindex GNAT_STACK_LIMIT
5750 SET GNAT_STACK_LIMIT 1600
5754 The limit is given in kilobytes, so the above declaration would
5755 set the stack limit of the environment task to 1.6 megabytes.
5756 Note that the only purpose of this usage is to limit the amount
5757 of stack used by the environment task. If it is necessary to
5758 increase the amount of stack for the environment task, then this
5759 is an operating systems issue, and must be addressed with the
5760 appropriate operating systems commands.
5763 @node Using gcc for Syntax Checking
5764 @subsection Using @code{gcc} for Syntax Checking
5767 @cindex @option{-gnats} (@code{gcc})
5771 The @code{s} stands for ``syntax''.
5774 Run GNAT in syntax checking only mode. For
5775 example, the command
5778 $ gcc -c -gnats x.adb
5782 compiles file @file{x.adb} in syntax-check-only mode. You can check a
5783 series of files in a single command
5785 , and can use wild cards to specify such a group of files.
5786 Note that you must specify the @option{-c} (compile
5787 only) flag in addition to the @option{-gnats} flag.
5790 You may use other switches in conjunction with @option{-gnats}. In
5791 particular, @option{-gnatl} and @option{-gnatv} are useful to control the
5792 format of any generated error messages.
5794 When the source file is empty or contains only empty lines and/or comments,
5795 the output is a warning:
5798 $ gcc -c -gnats -x ada toto.txt
5799 toto.txt:1:01: warning: empty file, contains no compilation units
5803 Otherwise, the output is simply the error messages, if any. No object file or
5804 ALI file is generated by a syntax-only compilation. Also, no units other
5805 than the one specified are accessed. For example, if a unit @code{X}
5806 @code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
5807 check only mode does not access the source file containing unit
5810 @cindex Multiple units, syntax checking
5811 Normally, GNAT allows only a single unit in a source file. However, this
5812 restriction does not apply in syntax-check-only mode, and it is possible
5813 to check a file containing multiple compilation units concatenated
5814 together. This is primarily used by the @code{gnatchop} utility
5815 (@pxref{Renaming Files Using gnatchop}).
5819 @node Using gcc for Semantic Checking
5820 @subsection Using @code{gcc} for Semantic Checking
5823 @cindex @option{-gnatc} (@code{gcc})
5827 The @code{c} stands for ``check''.
5829 Causes the compiler to operate in semantic check mode,
5830 with full checking for all illegalities specified in the
5831 Ada 95 Reference Manual, but without generation of any object code
5832 (no object file is generated).
5834 Because dependent files must be accessed, you must follow the GNAT
5835 semantic restrictions on file structuring to operate in this mode:
5839 The needed source files must be accessible
5840 (@pxref{Search Paths and the Run-Time Library (RTL)}).
5843 Each file must contain only one compilation unit.
5846 The file name and unit name must match (@pxref{File Naming Rules}).
5849 The output consists of error messages as appropriate. No object file is
5850 generated. An @file{ALI} file is generated for use in the context of
5851 cross-reference tools, but this file is marked as not being suitable
5852 for binding (since no object file is generated).
5853 The checking corresponds exactly to the notion of
5854 legality in the Ada 95 Reference Manual.
5856 Any unit can be compiled in semantics-checking-only mode, including
5857 units that would not normally be compiled (subunits,
5858 and specifications where a separate body is present).
5861 @node Compiling Ada 83 Programs
5862 @subsection Compiling Ada 83 Programs
5864 @cindex Ada 83 compatibility
5866 @cindex @option{-gnat83} (@code{gcc})
5867 @cindex ACVC, Ada 83 tests
5870 Although GNAT is primarily an Ada 95 compiler, it accepts this switch to
5871 specify that an Ada 83 program is to be compiled in Ada 83 mode. If you specify
5872 this switch, GNAT rejects most Ada 95 extensions and applies Ada 83 semantics
5873 where this can be done easily.
5874 It is not possible to guarantee this switch does a perfect
5875 job; for example, some subtle tests, such as are
5876 found in earlier ACVC tests (and that have been removed from the ACATS suite
5877 for Ada 95), might not compile correctly.
5878 Nevertheless, this switch may be useful in some circumstances, for example
5879 where, due to contractual reasons, legacy code needs to be maintained
5880 using only Ada 83 features.
5882 With few exceptions (most notably the need to use @code{<>} on
5883 @cindex Generic formal parameters
5884 unconstrained generic formal parameters, the use of the new Ada 95
5885 reserved words, and the use of packages
5886 with optional bodies), it is not necessary to use the
5887 @option{-gnat83} switch when compiling Ada 83 programs, because, with rare
5888 exceptions, Ada 95 is upwardly compatible with Ada 83. This
5889 means that a correct Ada 83 program is usually also a correct Ada 95
5891 For further information, please refer to @ref{Compatibility and Porting Guide}.
5895 @node Character Set Control
5896 @subsection Character Set Control
5898 @item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
5899 @cindex @option{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@code{gcc})
5902 Normally GNAT recognizes the Latin-1 character set in source program
5903 identifiers, as described in the Ada 95 Reference Manual.
5905 GNAT to recognize alternate character sets in identifiers. @var{c} is a
5906 single character ^^or word^ indicating the character set, as follows:
5910 ISO 8859-1 (Latin-1) identifiers
5913 ISO 8859-2 (Latin-2) letters allowed in identifiers
5916 ISO 8859-3 (Latin-3) letters allowed in identifiers
5919 ISO 8859-4 (Latin-4) letters allowed in identifiers
5922 ISO 8859-5 (Cyrillic) letters allowed in identifiers
5925 ISO 8859-15 (Latin-9) letters allowed in identifiers
5928 IBM PC letters (code page 437) allowed in identifiers
5931 IBM PC letters (code page 850) allowed in identifiers
5933 @item ^f^FULL_UPPER^
5934 Full upper-half codes allowed in identifiers
5937 No upper-half codes allowed in identifiers
5940 Wide-character codes (that is, codes greater than 255)
5941 allowed in identifiers
5944 @xref{Foreign Language Representation}, for full details on the
5945 implementation of these character sets.
5947 @item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
5948 @cindex @option{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@code{gcc})
5949 Specify the method of encoding for wide characters.
5950 @var{e} is one of the following:
5955 Hex encoding (brackets coding also recognized)
5958 Upper half encoding (brackets encoding also recognized)
5961 Shift/JIS encoding (brackets encoding also recognized)
5964 EUC encoding (brackets encoding also recognized)
5967 UTF-8 encoding (brackets encoding also recognized)
5970 Brackets encoding only (default value)
5972 For full details on the these encoding
5973 methods see @xref{Wide Character Encodings}.
5974 Note that brackets coding is always accepted, even if one of the other
5975 options is specified, so for example @option{-gnatW8} specifies that both
5976 brackets and @code{UTF-8} encodings will be recognized. The units that are
5977 with'ed directly or indirectly will be scanned using the specified
5978 representation scheme, and so if one of the non-brackets scheme is
5979 used, it must be used consistently throughout the program. However,
5980 since brackets encoding is always recognized, it may be conveniently
5981 used in standard libraries, allowing these libraries to be used with
5982 any of the available coding schemes.
5983 scheme. If no @option{-gnatW?} parameter is present, then the default
5984 representation is Brackets encoding only.
5986 Note that the wide character representation that is specified (explicitly
5987 or by default) for the main program also acts as the default encoding used
5988 for Wide_Text_IO files if not specifically overridden by a WCEM form
5992 @node File Naming Control
5993 @subsection File Naming Control
5996 @item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
5997 @cindex @option{-gnatk} (@code{gcc})
5998 Activates file name ``krunching''. @var{n}, a decimal integer in the range
5999 1-999, indicates the maximum allowable length of a file name (not
6000 including the @file{.ads} or @file{.adb} extension). The default is not
6001 to enable file name krunching.
6003 For the source file naming rules, @xref{File Naming Rules}.
6007 @node Subprogram Inlining Control
6008 @subsection Subprogram Inlining Control
6013 @cindex @option{-gnatn} (@code{gcc})
6015 The @code{n} here is intended to suggest the first syllable of the
6018 GNAT recognizes and processes @code{Inline} pragmas. However, for the
6019 inlining to actually occur, optimization must be enabled. To enable
6020 inlining of subprograms specified by pragma @code{Inline},
6021 you must also specify this switch.
6022 In the absence of this switch, GNAT does not attempt
6023 inlining and does not need to access the bodies of
6024 subprograms for which @code{pragma Inline} is specified if they are not
6025 in the current unit.
6027 If you specify this switch the compiler will access these bodies,
6028 creating an extra source dependency for the resulting object file, and
6029 where possible, the call will be inlined.
6030 For further details on when inlining is possible
6031 see @xref{Inlining of Subprograms}.
6034 @cindex @option{-gnatN} (@code{gcc})
6035 The front end inlining activated by this switch is generally more extensive,
6036 and quite often more effective than the standard @option{-gnatn} inlining mode.
6037 It will also generate additional dependencies.
6039 @option{-gnatN} automatically implies @option{-gnatn} so it is not necessary
6040 to specify both options.
6043 @node Auxiliary Output Control
6044 @subsection Auxiliary Output Control
6048 @cindex @option{-gnatt} (@code{gcc})
6049 @cindex Writing internal trees
6050 @cindex Internal trees, writing to file
6051 Causes GNAT to write the internal tree for a unit to a file (with the
6052 extension @file{.adt}.
6053 This not normally required, but is used by separate analysis tools.
6055 these tools do the necessary compilations automatically, so you should
6056 not have to specify this switch in normal operation.
6059 @cindex @option{-gnatu} (@code{gcc})
6060 Print a list of units required by this compilation on @file{stdout}.
6061 The listing includes all units on which the unit being compiled depends
6062 either directly or indirectly.
6065 @item -pass-exit-codes
6066 @cindex @option{-pass-exit-codes} (@code{gcc})
6067 If this switch is not used, the exit code returned by @code{gcc} when
6068 compiling multiple files indicates whether all source files have
6069 been successfully used to generate object files or not.
6071 When @option{-pass-exit-codes} is used, @code{gcc} exits with an extended
6072 exit status and allows an integrated development environment to better
6073 react to a compilation failure. Those exit status are:
6077 There was an error in at least one source file.
6079 At least one source file did not generate an object file.
6081 The compiler died unexpectedly (internal error for example).
6083 An object file has been generated for every source file.
6088 @node Debugging Control
6089 @subsection Debugging Control
6093 @cindex Debugging options
6096 @cindex @option{-gnatd} (@code{gcc})
6097 Activate internal debugging switches. @var{x} is a letter or digit, or
6098 string of letters or digits, which specifies the type of debugging
6099 outputs desired. Normally these are used only for internal development
6100 or system debugging purposes. You can find full documentation for these
6101 switches in the body of the @code{Debug} unit in the compiler source
6102 file @file{debug.adb}.
6106 @cindex @option{-gnatG} (@code{gcc})
6107 This switch causes the compiler to generate auxiliary output containing
6108 a pseudo-source listing of the generated expanded code. Like most Ada
6109 compilers, GNAT works by first transforming the high level Ada code into
6110 lower level constructs. For example, tasking operations are transformed
6111 into calls to the tasking run-time routines. A unique capability of GNAT
6112 is to list this expanded code in a form very close to normal Ada source.
6113 This is very useful in understanding the implications of various Ada
6114 usage on the efficiency of the generated code. There are many cases in
6115 Ada (e.g. the use of controlled types), where simple Ada statements can
6116 generate a lot of run-time code. By using @option{-gnatG} you can identify
6117 these cases, and consider whether it may be desirable to modify the coding
6118 approach to improve efficiency.
6120 The format of the output is very similar to standard Ada source, and is
6121 easily understood by an Ada programmer. The following special syntactic
6122 additions correspond to low level features used in the generated code that
6123 do not have any exact analogies in pure Ada source form. The following
6124 is a partial list of these special constructions. See the specification
6125 of package @code{Sprint} in file @file{sprint.ads} for a full list.
6128 @item new @var{xxx} [storage_pool = @var{yyy}]
6129 Shows the storage pool being used for an allocator.
6131 @item at end @var{procedure-name};
6132 Shows the finalization (cleanup) procedure for a scope.
6134 @item (if @var{expr} then @var{expr} else @var{expr})
6135 Conditional expression equivalent to the @code{x?y:z} construction in C.
6137 @item @var{target}^^^(@var{source})
6138 A conversion with floating-point truncation instead of rounding.
6140 @item @var{target}?(@var{source})
6141 A conversion that bypasses normal Ada semantic checking. In particular
6142 enumeration types and fixed-point types are treated simply as integers.
6144 @item @var{target}?^^^(@var{source})
6145 Combines the above two cases.
6147 @item @var{x} #/ @var{y}
6148 @itemx @var{x} #mod @var{y}
6149 @itemx @var{x} #* @var{y}
6150 @itemx @var{x} #rem @var{y}
6151 A division or multiplication of fixed-point values which are treated as
6152 integers without any kind of scaling.
6154 @item free @var{expr} [storage_pool = @var{xxx}]
6155 Shows the storage pool associated with a @code{free} statement.
6157 @item freeze @var{typename} [@var{actions}]
6158 Shows the point at which @var{typename} is frozen, with possible
6159 associated actions to be performed at the freeze point.
6161 @item reference @var{itype}
6162 Reference (and hence definition) to internal type @var{itype}.
6164 @item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
6165 Intrinsic function call.
6167 @item @var{labelname} : label
6168 Declaration of label @var{labelname}.
6170 @item @var{expr} && @var{expr} && @var{expr} ... && @var{expr}
6171 A multiple concatenation (same effect as @var{expr} & @var{expr} &
6172 @var{expr}, but handled more efficiently).
6174 @item [constraint_error]
6175 Raise the @code{Constraint_Error} exception.
6177 @item @var{expression}'reference
6178 A pointer to the result of evaluating @var{expression}.
6180 @item @var{target-type}!(@var{source-expression})
6181 An unchecked conversion of @var{source-expression} to @var{target-type}.
6183 @item [@var{numerator}/@var{denominator}]
6184 Used to represent internal real literals (that) have no exact
6185 representation in base 2-16 (for example, the result of compile time
6186 evaluation of the expression 1.0/27.0).
6190 @cindex @option{-gnatD} (@code{gcc})
6191 When used in conjunction with @option{-gnatG}, this switch causes
6192 the expanded source, as described above for
6193 @option{-gnatG} to be written to files with names
6194 @file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
6195 instead of to the standard ooutput file. For
6196 example, if the source file name is @file{hello.adb}, then a file
6197 @file{^hello.adb.dg^HELLO.ADB_DG^} will be written. The debugging
6198 information generated by the @code{gcc} @option{^-g^/DEBUG^} switch
6199 will refer to the generated @file{^xxx.dg^XXX_DG^} file. This allows
6200 you to do source level debugging using the generated code which is
6201 sometimes useful for complex code, for example to find out exactly
6202 which part of a complex construction raised an exception. This switch
6203 also suppress generation of cross-reference information (see
6204 @option{-gnatx}) since otherwise the cross-reference information
6205 would refer to the @file{^.dg^.DG^} file, which would cause
6206 confusion since this is not the original source file.
6208 Note that @option{-gnatD} actually implies @option{-gnatG}
6209 automatically, so it is not necessary to give both options.
6210 In other words @option{-gnatD} is equivalent to @option{-gnatDG}).
6213 @item -gnatR[0|1|2|3[s]]
6214 @cindex @option{-gnatR} (@code{gcc})
6215 This switch controls output from the compiler of a listing showing
6216 representation information for declared types and objects. For
6217 @option{-gnatR0}, no information is output (equivalent to omitting
6218 the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
6219 so @option{-gnatR} with no parameter has the same effect), size and alignment
6220 information is listed for declared array and record types. For
6221 @option{-gnatR2}, size and alignment information is listed for all
6222 expression information for values that are computed at run time for
6223 variant records. These symbolic expressions have a mostly obvious
6224 format with #n being used to represent the value of the n'th
6225 discriminant. See source files @file{repinfo.ads/adb} in the
6226 @code{GNAT} sources for full details on the format of @option{-gnatR3}
6227 output. If the switch is followed by an s (e.g. @option{-gnatR2s}), then
6228 the output is to a file with the name @file{^file.rep^file_REP^} where
6229 file is the name of the corresponding source file.
6232 @item /REPRESENTATION_INFO
6233 @cindex @option{/REPRESENTATION_INFO} (@code{gcc})
6234 This qualifier controls output from the compiler of a listing showing
6235 representation information for declared types and objects. For
6236 @option{/REPRESENTATION_INFO=NONE}, no information is output
6237 (equivalent to omitting the @option{/REPRESENTATION_INFO} qualifier).
6238 @option{/REPRESENTATION_INFO} without option is equivalent to
6239 @option{/REPRESENTATION_INFO=ARRAYS}.
6240 For @option{/REPRESENTATION_INFO=ARRAYS}, size and alignment
6241 information is listed for declared array and record types. For
6242 @option{/REPRESENTATION_INFO=OBJECTS}, size and alignment information
6243 is listed for all expression information for values that are computed
6244 at run time for variant records. These symbolic expressions have a mostly
6245 obvious format with #n being used to represent the value of the n'th
6246 discriminant. See source files @file{REPINFO.ADS/ADB} in the
6247 @code{GNAT} sources for full details on the format of
6248 @option{/REPRESENTATION_INFO=SYMBOLIC} output.
6249 If _FILE is added at the end of an option
6250 (e.g. @option{/REPRESENTATION_INFO=ARRAYS_FILE}),
6251 then the output is to a file with the name @file{file_REP} where
6252 file is the name of the corresponding source file.
6256 @cindex @option{-gnatS} (@code{gcc})
6257 The use of the switch @option{-gnatS} for an
6258 Ada compilation will cause the compiler to output a
6259 representation of package Standard in a form very
6260 close to standard Ada. It is not quite possible to
6261 do this and remain entirely Standard (since new
6262 numeric base types cannot be created in standard
6263 Ada), but the output is easily
6264 readable to any Ada programmer, and is useful to
6265 determine the characteristics of target dependent
6266 types in package Standard.
6269 @cindex @option{-gnatx} (@code{gcc})
6270 Normally the compiler generates full cross-referencing information in
6271 the @file{ALI} file. This information is used by a number of tools,
6272 including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch
6273 suppresses this information. This saves some space and may slightly
6274 speed up compilation, but means that these tools cannot be used.
6277 @node Exception Handling Control
6278 @subsection Exception Handling Control
6281 GNAT uses two methods for handling exceptions at run-time. The
6282 @code{longjmp/setjmp} method saves the context when entering
6283 a frame with an exception handler. Then when an exception is
6284 raised, the context can be restored immediately, without the
6285 need for tracing stack frames. This method provides very fast
6286 exception propagation, but introduces significant overhead for
6287 the use of exception handlers, even if no exception is raised.
6289 The other approach is called ``zero cost'' exception handling.
6290 With this method, the compiler builds static tables to describe
6291 the exception ranges. No dynamic code is required when entering
6292 a frame containing an exception handler. When an exception is
6293 raised, the tables are used to control a back trace of the
6294 subprogram invocation stack to locate the required exception
6295 handler. This method has considerably poorer performance for
6296 the propagation of exceptions, but there is no overhead for
6297 exception handlers if no exception is raised.
6299 The following switches can be used to control which of the
6300 two exception handling methods is used.
6306 @cindex @option{-gnatL} (@code{gcc})
6307 This switch causes the longjmp/setjmp approach to be used
6308 for exception handling. If this is the default mechanism for the
6309 target (see below), then this has no effect. If the default
6310 mechanism for the target is zero cost exceptions, then
6311 this switch can be used to modify this default, but it must be
6312 used for all units in the partition, including all run-time
6313 library units. One way to achieve this is to use the
6314 @option{-a} and @option{-f} switches for @code{gnatmake}.
6315 This option is rarely used. One case in which it may be
6316 advantageous is if you have an application where exception
6317 raising is common and the overall performance of the
6318 application is improved by favoring exception propagation.
6321 @cindex @option{-gnatZ} (@code{gcc})
6322 @cindex Zero Cost Exceptions
6323 This switch causes the zero cost approach to be sed
6324 for exception handling. If this is the default mechanism for the
6325 target (see below), then this has no effect. If the default
6326 mechanism for the target is longjmp/setjmp exceptions, then
6327 this switch can be used to modify this default, but it must be
6328 used for all units in the partition, including all run-time
6329 library units. One way to achieve this is to use the
6330 @option{-a} and @option{-f} switches for @code{gnatmake}.
6331 This option can only be used if the zero cost approach
6332 is available for the target in use (see below).
6336 The @code{longjmp/setjmp} approach is available on all targets, but
6337 the @code{zero cost} approach is only available on selected targets.
6338 To determine whether zero cost exceptions can be used for a
6339 particular target, look at the private part of the file system.ads.
6340 Either @code{GCC_ZCX_Support} or @code{Front_End_ZCX_Support} must
6341 be True to use the zero cost approach. If both of these switches
6342 are set to False, this means that zero cost exception handling
6343 is not yet available for that target. The switch
6344 @code{ZCX_By_Default} indicates the default approach. If this
6345 switch is set to True, then the @code{zero cost} approach is
6348 @node Units to Sources Mapping Files
6349 @subsection Units to Sources Mapping Files
6353 @item -gnatem^^=^@var{path}
6354 @cindex @option{-gnatem} (@code{gcc})
6355 A mapping file is a way to communicate to the compiler two mappings:
6356 from unit names to file names (without any directory information) and from
6357 file names to path names (with full directory information). These mappings
6358 are used by the compiler to short-circuit the path search.
6360 The use of mapping files is not required for correct operation of the
6361 compiler, but mapping files can improve efficiency, particularly when
6362 sources are read over a slow network connection. In normal operation,
6363 you need not be concerned with the format or use of mapping files,
6364 and the @option{-gnatem} switch is not a switch that you would use
6365 explicitly. it is intended only for use by automatic tools such as
6366 @code{gnatmake} running under the project file facility. The
6367 description here of the format of mapping files is provided
6368 for completeness and for possible use by other tools.
6370 A mapping file is a sequence of sets of three lines. In each set,
6371 the first line is the unit name, in lower case, with ``@code{%s}''
6373 specifications and ``@code{%b}'' appended for bodies; the second line is the
6374 file name; and the third line is the path name.
6380 /gnat/project1/sources/main.2.ada
6383 When the switch @option{-gnatem} is specified, the compiler will create
6384 in memory the two mappings from the specified file. If there is any problem
6385 (non existent file, truncated file or duplicate entries), no mapping
6388 Several @option{-gnatem} switches may be specified; however, only the last
6389 one on the command line will be taken into account.
6391 When using a project file, @code{gnatmake} create a temporary mapping file
6392 and communicates it to the compiler using this switch.
6397 @node Integrated Preprocessing
6398 @subsection Integrated Preprocessing
6401 GNAT sources may be preprocessed immediately before compilation; the actual
6402 text of the source is not the text of the source file, but is derived from it
6403 through a process called preprocessing. Integrated preprocessing is specified
6404 through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep}
6405 indicates, through a text file, the preprocessing data to be used.
6406 @option{-gnateD} specifies or modifies the values of preprocessing symbol.
6409 It is recommended that @code{gnatmake} switch ^-s^/SWITCH_CHECK^ should be
6410 used when Integrated Preprocessing is used. The reason is that preprocessing
6411 with another Preprocessing Data file without changing the sources will
6412 not trigger recompilation without this switch.
6415 Note that @code{gnatmake} switch ^-m^/MINIMAL_RECOMPILATION^ will almost
6416 always trigger recompilation for sources that are preprocessed,
6417 because @code{gnatmake} cannot compute the checksum of the source after
6421 The actual preprocessing function is described in details in section
6422 @ref{Preprocessing Using gnatprep}. This section only describes how integrated
6423 preprocessing is triggered and parameterized.
6427 @item -gnatep=@var{file}
6428 @cindex @option{-gnatep} (@code{gcc})
6429 This switch indicates to the compiler the file name (without directory
6430 information) of the preprocessor data file to use. The preprocessor data file
6431 should be found in the source directories.
6434 A preprocessing data file is a text file with significant lines indicating
6435 how should be preprocessed either a specific source or all sources not
6436 mentioned in other lines. A significant line is a non empty, non comment line.
6437 Comments are similar to Ada comments.
6440 Each significant line starts with either a literal string or the character '*'.
6441 A literal string is the file name (without directory information) of the source
6442 to preprocess. A character '*' indicates the preprocessing for all the sources
6443 that are not specified explicitly on other lines (order of the lines is not
6444 significant). It is an error to have two lines with the same file name or two
6445 lines starting with the character '*'.
6448 After the file name or the character '*', another optional literal string
6449 indicating the file name of the definition file to be used for preprocessing.
6450 (see @ref{Form of Definitions File}. The definition files are found by the
6451 compiler in one of the source directories. In some cases, when compiling
6452 a source in a directory other than the current directory, if the definition
6453 file is in the current directory, it may be necessary to add the current
6454 directory as a source directory through switch ^-I.^/SEARCH=[]^, otherwise
6455 the compiler would not find the definition file.
6458 Then, optionally, ^switches^switches^ similar to those of @code{gnatprep} may
6459 be found. Those ^switches^switches^ are:
6464 Causes both preprocessor lines and the lines deleted by
6465 preprocessing to be replaced by blank lines, preserving the line number.
6466 This ^switch^switch^ is always implied; however, if specified after @option{-c}
6467 it cancels the effect of @option{-c}.
6470 Causes both preprocessor lines and the lines deleted
6471 by preprocessing to be retained as comments marked
6472 with the special string ``@code{--! }''.
6474 @item -Dsymbol=value
6475 Define or redefine a symbol, associated with value. A symbol is an Ada
6476 identifier, or an Ada reserved word, with the exception of @code{if},
6477 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
6478 @code{value} is either a literal string, an Ada identifier or any Ada reserved
6479 word. A symbol declared with this ^switch^switch^ replaces a symbol with the
6480 same name defined in a definition file.
6483 Causes a sorted list of symbol names and values to be
6484 listed on the standard output file.
6487 Causes undefined symbols to be treated as having the value @code{FALSE}
6489 of a preprocessor test. In the absence of this option, an undefined symbol in
6490 a @code{#if} or @code{#elsif} test will be treated as an error.
6495 Examples of valid lines in a preprocessor data file:
6498 "toto.adb" "prep.def" -u
6499 -- preprocess "toto.adb", using definition file "prep.def",
6500 -- undefined symbol are False.
6503 -- preprocess all other sources without a definition file;
6504 -- suppressed lined are commented; symbol VERSION has the value V101.
6506 "titi.adb" "prep2.def" -s
6507 -- preprocess "titi.adb", using definition file "prep2.def";
6508 -- list all symbols with their values.
6511 @item ^-gnateD^/DATA_PREPROCESSING=^symbol[=value]
6512 @cindex @option{-gnateD} (@code{gcc})
6513 Define or redefine a preprocessing symbol, associated with value. If no value
6514 is given on the command line, then the value of the symbol is @code{True}.
6515 A symbol is an identifier, following normal Ada (case-insensitive)
6516 rules for its syntax, and value is any sequence (including an empty sequence)
6517 of characters from the set (letters, digits, period, underline).
6518 Ada reserved words may be used as symbols, with the exceptions of @code{if},
6519 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
6522 A symbol declared with this ^switch^switch^ on the command line replaces a
6523 symbol with the same name either in a definition file or specified with a
6524 ^switch^switch^ -D in the preprocessor data file.
6527 This switch is similar to switch @option{^-D^/ASSOCIATE^} of @code{gnatprep}.
6533 @subsection Return Codes
6534 @cindex Return Codes
6535 @cindex @option{/RETURN_CODES=VMS}
6538 On VMS, GNAT compiled programs return POSIX-style codes by default,
6539 e.g. @option{/RETURN_CODES=POSIX}.
6541 To enable VMS style return codes, GNAT LINK with the option
6542 @option{/RETURN_CODES=VMS}. For example:
6545 GNAT LINK MYMAIN.ALI /RETURN_CODES=VMS
6549 Programs built with /RETURN_CODES=VMS are suitable to be called in
6550 VMS DCL scripts. Programs compiled with the default /RETURN_CODES=POSIX
6551 are suitable for spawning with appropriate GNAT RTL routines.
6556 @node Search Paths and the Run-Time Library (RTL)
6557 @section Search Paths and the Run-Time Library (RTL)
6560 With the GNAT source-based library system, the compiler must be able to
6561 find source files for units that are needed by the unit being compiled.
6562 Search paths are used to guide this process.
6564 The compiler compiles one source file whose name must be given
6565 explicitly on the command line. In other words, no searching is done
6566 for this file. To find all other source files that are needed (the most
6567 common being the specs of units), the compiler examines the following
6568 directories, in the following order:
6572 The directory containing the source file of the main unit being compiled
6573 (the file name on the command line).
6576 Each directory named by an @option{^-I^/SOURCE_SEARCH^} switch given on the
6577 @code{gcc} command line, in the order given.
6580 @findex ADA_INCLUDE_PATH
6581 Each of the directories listed in the value of the
6582 @code{ADA_INCLUDE_PATH} ^environment variable^logical name^.
6584 Construct this value
6585 exactly as the @code{PATH} environment variable: a list of directory
6586 names separated by colons (semicolons when working with the NT version).
6589 Normally, define this value as a logical name containing a comma separated
6590 list of directory names.
6592 This variable can also be defined by means of an environment string
6593 (an argument to the DEC C exec* set of functions).
6597 DEFINE ANOTHER_PATH FOO:[BAG]
6598 DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
6601 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
6602 first, followed by the standard Ada 95
6603 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
6604 If this is not redefined, the user will obtain the DEC Ada 83 IO packages
6605 (Text_IO, Sequential_IO, etc)
6606 instead of the Ada95 packages. Thus, in order to get the Ada 95
6607 packages by default, ADA_INCLUDE_PATH must be redefined.
6611 @findex ADA_PRJ_INCLUDE_FILE
6612 Each of the directories listed in the text file whose name is given
6613 by the @code{ADA_PRJ_INCLUDE_FILE} ^environment variable^logical name^.
6616 @code{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
6617 driver when project files are used. It should not normally be set
6621 The content of the @file{ada_source_path} file which is part of the GNAT
6622 installation tree and is used to store standard libraries such as the
6623 GNAT Run Time Library (RTL) source files.
6625 @ref{Installing an Ada Library}
6630 Specifying the switch @option{^-I-^/NOCURRENT_DIRECTORY^}
6631 inhibits the use of the directory
6632 containing the source file named in the command line. You can still
6633 have this directory on your search path, but in this case it must be
6634 explicitly requested with a @option{^-I^/SOURCE_SEARCH^} switch.
6636 Specifying the switch @option{-nostdinc}
6637 inhibits the search of the default location for the GNAT Run Time
6638 Library (RTL) source files.
6640 The compiler outputs its object files and ALI files in the current
6643 Caution: The object file can be redirected with the @option{-o} switch;
6644 however, @code{gcc} and @code{gnat1} have not been coordinated on this
6645 so the @file{ALI} file will not go to the right place. Therefore, you should
6646 avoid using the @option{-o} switch.
6650 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
6651 children make up the GNAT RTL, together with the simple @code{System.IO}
6652 package used in the @code{"Hello World"} example. The sources for these units
6653 are needed by the compiler and are kept together in one directory. Not
6654 all of the bodies are needed, but all of the sources are kept together
6655 anyway. In a normal installation, you need not specify these directory
6656 names when compiling or binding. Either the environment variables or
6657 the built-in defaults cause these files to be found.
6659 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
6660 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
6661 consisting of child units of @code{GNAT}. This is a collection of generally
6662 useful types, subprograms, etc. See the @cite{GNAT Reference Manual} for
6665 Besides simplifying access to the RTL, a major use of search paths is
6666 in compiling sources from multiple directories. This can make
6667 development environments much more flexible.
6670 @node Order of Compilation Issues
6671 @section Order of Compilation Issues
6674 If, in our earlier example, there was a spec for the @code{hello}
6675 procedure, it would be contained in the file @file{hello.ads}; yet this
6676 file would not have to be explicitly compiled. This is the result of the
6677 model we chose to implement library management. Some of the consequences
6678 of this model are as follows:
6682 There is no point in compiling specs (except for package
6683 specs with no bodies) because these are compiled as needed by clients. If
6684 you attempt a useless compilation, you will receive an error message.
6685 It is also useless to compile subunits because they are compiled as needed
6689 There are no order of compilation requirements: performing a
6690 compilation never obsoletes anything. The only way you can obsolete
6691 something and require recompilations is to modify one of the
6692 source files on which it depends.
6695 There is no library as such, apart from the ALI files
6696 (@pxref{The Ada Library Information Files}, for information on the format
6697 of these files). For now we find it convenient to create separate ALI files,
6698 but eventually the information therein may be incorporated into the object
6702 When you compile a unit, the source files for the specs of all units
6703 that it @code{with}'s, all its subunits, and the bodies of any generics it
6704 instantiates must be available (reachable by the search-paths mechanism
6705 described above), or you will receive a fatal error message.
6712 The following are some typical Ada compilation command line examples:
6715 @item $ gcc -c xyz.adb
6716 Compile body in file @file{xyz.adb} with all default options.
6719 @item $ gcc -c -O2 -gnata xyz-def.adb
6722 @item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
6725 Compile the child unit package in file @file{xyz-def.adb} with extensive
6726 optimizations, and pragma @code{Assert}/@code{Debug} statements
6729 @item $ gcc -c -gnatc abc-def.adb
6730 Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
6734 @node Binding Using gnatbind
6735 @chapter Binding Using @code{gnatbind}
6739 * Running gnatbind::
6740 * Switches for gnatbind::
6741 * Command-Line Access::
6742 * Search Paths for gnatbind::
6743 * Examples of gnatbind Usage::
6747 This chapter describes the GNAT binder, @code{gnatbind}, which is used
6748 to bind compiled GNAT objects. The @code{gnatbind} program performs
6749 four separate functions:
6753 Checks that a program is consistent, in accordance with the rules in
6754 Chapter 10 of the Ada 95 Reference Manual. In particular, error
6755 messages are generated if a program uses inconsistent versions of a
6759 Checks that an acceptable order of elaboration exists for the program
6760 and issues an error message if it cannot find an order of elaboration
6761 that satisfies the rules in Chapter 10 of the Ada 95 Language Manual.
6764 Generates a main program incorporating the given elaboration order.
6765 This program is a small Ada package (body and spec) that
6766 must be subsequently compiled
6767 using the GNAT compiler. The necessary compilation step is usually
6768 performed automatically by @code{gnatlink}. The two most important
6769 functions of this program
6770 are to call the elaboration routines of units in an appropriate order
6771 and to call the main program.
6774 Determines the set of object files required by the given main program.
6775 This information is output in the forms of comments in the generated program,
6776 to be read by the @code{gnatlink} utility used to link the Ada application.
6780 @node Running gnatbind
6781 @section Running @code{gnatbind}
6784 The form of the @code{gnatbind} command is
6787 $ gnatbind [@i{switches}] @i{mainprog}[.ali] [@i{switches}]
6791 where @file{@i{mainprog}.adb} is the Ada file containing the main program
6792 unit body. If no switches are specified, @code{gnatbind} constructs an Ada
6793 package in two files whose names are
6794 @file{b~@i{mainprog}.ads}, and @file{b~@i{mainprog}.adb}.
6795 For example, if given the
6796 parameter @file{hello.ali}, for a main program contained in file
6797 @file{hello.adb}, the binder output files would be @file{b~hello.ads}
6798 and @file{b~hello.adb}.
6800 When doing consistency checking, the binder takes into consideration
6801 any source files it can locate. For example, if the binder determines
6802 that the given main program requires the package @code{Pack}, whose
6804 file is @file{pack.ali} and whose corresponding source spec file is
6805 @file{pack.ads}, it attempts to locate the source file @file{pack.ads}
6806 (using the same search path conventions as previously described for the
6807 @code{gcc} command). If it can locate this source file, it checks that
6809 or source checksums of the source and its references to in @file{ALI} files
6810 match. In other words, any @file{ALI} files that mentions this spec must have
6811 resulted from compiling this version of the source file (or in the case
6812 where the source checksums match, a version close enough that the
6813 difference does not matter).
6815 @cindex Source files, use by binder
6816 The effect of this consistency checking, which includes source files, is
6817 that the binder ensures that the program is consistent with the latest
6818 version of the source files that can be located at bind time. Editing a
6819 source file without compiling files that depend on the source file cause
6820 error messages to be generated by the binder.
6822 For example, suppose you have a main program @file{hello.adb} and a
6823 package @code{P}, from file @file{p.ads} and you perform the following
6828 Enter @code{gcc -c hello.adb} to compile the main program.
6831 Enter @code{gcc -c p.ads} to compile package @code{P}.
6834 Edit file @file{p.ads}.
6837 Enter @code{gnatbind hello}.
6841 At this point, the file @file{p.ali} contains an out-of-date time stamp
6842 because the file @file{p.ads} has been edited. The attempt at binding
6843 fails, and the binder generates the following error messages:
6846 error: "hello.adb" must be recompiled ("p.ads" has been modified)
6847 error: "p.ads" has been modified and must be recompiled
6851 Now both files must be recompiled as indicated, and then the bind can
6852 succeed, generating a main program. You need not normally be concerned
6853 with the contents of this file, but for reference purposes a sample
6854 binder output file is given in @ref{Example of Binder Output File}.
6856 In most normal usage, the default mode of @command{gnatbind} which is to
6857 generate the main package in Ada, as described in the previous section.
6858 In particular, this means that any Ada programmer can read and understand
6859 the generated main program. It can also be debugged just like any other
6860 Ada code provided the @option{^-g^/DEBUG^} switch is used for
6861 @command{gnatbind} and @command{gnatlink}.
6863 However for some purposes it may be convenient to generate the main
6864 program in C rather than Ada. This may for example be helpful when you
6865 are generating a mixed language program with the main program in C. The
6866 GNAT compiler itself is an example.
6867 The use of the @option{^-C^/BIND_FILE=C^} switch
6868 for both @code{gnatbind} and @code{gnatlink} will cause the program to
6869 be generated in C (and compiled using the gnu C compiler).
6872 @node Switches for gnatbind
6873 @section Switches for @command{gnatbind}
6876 The following switches are available with @code{gnatbind}; details will
6877 be presented in subsequent sections.
6880 * Consistency-Checking Modes::
6881 * Binder Error Message Control::
6882 * Elaboration Control::
6884 * Binding with Non-Ada Main Programs::
6885 * Binding Programs with No Main Subprogram::
6890 @item ^-aO^/OBJECT_SEARCH^
6891 @cindex @option{^-aO^/OBJECT_SEARCH^} (@command{gnatbind})
6892 Specify directory to be searched for ALI files.
6894 @item ^-aI^/SOURCE_SEARCH^
6895 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
6896 Specify directory to be searched for source file.
6898 @item ^-A^/BIND_FILE=ADA^
6899 @cindex @option{^-A^/BIND_FILE=ADA^} (@command{gnatbind})
6900 Generate binder program in Ada (default)
6902 @item ^-b^/REPORT_ERRORS=BRIEF^
6903 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@command{gnatbind})
6904 Generate brief messages to @file{stderr} even if verbose mode set.
6906 @item ^-c^/NOOUTPUT^
6907 @cindex @option{^-c^/NOOUTPUT^} (@command{gnatbind})
6908 Check only, no generation of binder output file.
6910 @item ^-C^/BIND_FILE=C^
6911 @cindex @option{^-C^/BIND_FILE=C^} (@command{gnatbind})
6912 Generate binder program in C
6914 @item ^-e^/ELABORATION_DEPENDENCIES^
6915 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@command{gnatbind})
6916 Output complete list of elaboration-order dependencies.
6918 @item ^-E^/STORE_TRACEBACKS^
6919 @cindex @option{^-E^/STORE_TRACEBACKS^} (@command{gnatbind})
6920 Store tracebacks in exception occurrences when the target supports it.
6921 This is the default with the zero cost exception mechanism.
6923 @c The following may get moved to an appendix
6924 This option is currently supported on the following targets:
6925 all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
6927 See also the packages @code{GNAT.Traceback} and
6928 @code{GNAT.Traceback.Symbolic} for more information.
6930 Note that on x86 ports, you must not use @option{-fomit-frame-pointer}
6934 @item ^-F^/FORCE_ELABS_FLAGS^
6935 @cindex @option{^-F^/FORCE_ELABS_FLAGS^} (@command{gnatbind})
6936 Force the checks of elaboration flags. @command{gnatbind} does not normally
6937 generate checks of elaboration flags for the main executable, except when
6938 a Stand-Alone Library is used. However, there are cases when this cannot be
6939 detected by gnatbind. An example is importing an interface of a Stand-Alone
6940 Library through a pragma Import and only specifying through a linker switch
6941 this Stand-Alone Library. This switch is used to guarantee that elaboration
6942 flag checks are generated.
6945 @cindex @option{^-h^/HELP^} (@command{gnatbind})
6946 Output usage (help) information
6949 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
6950 Specify directory to be searched for source and ALI files.
6952 @item ^-I-^/NOCURRENT_DIRECTORY^
6953 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@command{gnatbind})
6954 Do not look for sources in the current directory where @code{gnatbind} was
6955 invoked, and do not look for ALI files in the directory containing the
6956 ALI file named in the @code{gnatbind} command line.
6958 @item ^-l^/ORDER_OF_ELABORATION^
6959 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@command{gnatbind})
6960 Output chosen elaboration order.
6962 @item ^-Lxxx^/BUILD_LIBRARY=xxx^
6963 @cindex @option{^-L^/BUILD_LIBRARY^} (@command{gnatbind})
6964 Binds the units for library building. In this case the adainit and
6965 adafinal procedures (See @pxref{Binding with Non-Ada Main Programs})
6966 are renamed to ^xxxinit^XXXINIT^ and
6967 ^xxxfinal^XXXFINAL^.
6968 Implies ^-n^/NOCOMPILE^.
6970 (@pxref{GNAT and Libraries}, for more details.)
6973 On OpenVMS, these init and final procedures are exported in uppercase
6974 letters. For example if /BUILD_LIBRARY=toto is used, the exported name of
6975 the init procedure will be "TOTOINIT" and the exported name of the final
6976 procedure will be "TOTOFINAL".
6979 @item ^-Mxyz^/RENAME_MAIN=xyz^
6980 @cindex @option{^-M^/RENAME_MAIN^} (@command{gnatbind})
6981 Rename generated main program from main to xyz
6983 @item ^-m^/ERROR_LIMIT=^@var{n}
6984 @cindex @option{^-m^/ERROR_LIMIT^} (@command{gnatbind})
6985 Limit number of detected errors to @var{n}, where @var{n} is
6986 in the range 1..999_999. The default value if no switch is
6987 given is 9999. Binding is terminated if the limit is exceeded.
6989 Furthermore, under Windows, the sources pointed to by the libraries path
6990 set in the registry are not searched for.
6994 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
6998 @cindex @option{-nostdinc} (@command{gnatbind})
6999 Do not look for sources in the system default directory.
7002 @cindex @option{-nostdlib} (@command{gnatbind})
7003 Do not look for library files in the system default directory.
7005 @item --RTS=@var{rts-path}
7006 @cindex @option{--RTS} (@code{gnatbind})
7007 Specifies the default location of the runtime library. Same meaning as the
7008 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
7010 @item ^-o ^/OUTPUT=^@var{file}
7011 @cindex @option{^-o ^/OUTPUT^} (@command{gnatbind})
7012 Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
7013 Note that if this option is used, then linking must be done manually,
7014 gnatlink cannot be used.
7016 @item ^-O^/OBJECT_LIST^
7017 @cindex @option{^-O^/OBJECT_LIST^} (@command{gnatbind})
7020 @item ^-p^/PESSIMISTIC_ELABORATION^
7021 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@command{gnatbind})
7022 Pessimistic (worst-case) elaboration order
7024 @item ^-s^/READ_SOURCES=ALL^
7025 @cindex @option{^-s^/READ_SOURCES=ALL^} (@command{gnatbind})
7026 Require all source files to be present.
7028 @item ^-S@var{xxx}^/INITIALIZE_SCALARS=@var{xxx}^
7029 @cindex @option{^-S^/INITIALIZE_SCALARS^} (@command{gnatbind})
7030 Specifies the value to be used when detecting uninitialized scalar
7031 objects with pragma Initialize_Scalars.
7032 The @var{xxx} ^string specified with the switch^option^ may be either
7034 @item ``@option{^in^INVALID^}'' requesting an invalid value where possible
7035 @item ``@option{^lo^LOW^}'' for the lowest possible value
7036 possible, and the low
7037 @item ``@option{^hi^HIGH^}'' for the highest possible value
7038 @item ``@option{xx}'' for a value consisting of repeated bytes with the
7039 value 16#xx# (i.e. xx is a string of two hexadecimal digits).
7042 In addition, you can specify @option{-Sev} to indicate that the value is
7043 to be set at run time. In this case, the program will look for an environment
7044 @cindex GNAT_INIT_SCALARS
7045 variable of the form @code{GNAT_INIT_SCALARS=xx}, where xx is one
7046 of @option{in/lo/hi/xx} with the same meanings as above.
7047 If no environment variable is found, or if it does not have a valid value,
7048 then the default is @option{in} (invalid values).
7052 @cindex @option{-static} (@code{gnatbind})
7053 Link against a static GNAT run time.
7056 @cindex @option{-shared} (@code{gnatbind})
7057 Link against a shared GNAT run time when available.
7060 @item ^-t^/NOTIME_STAMP_CHECK^
7061 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7062 Tolerate time stamp and other consistency errors
7064 @item ^-T@var{n}^/TIME_SLICE=@var{n}^
7065 @cindex @option{^-T^/TIME_SLICE^} (@code{gnatbind})
7066 Set the time slice value to @var{n} milliseconds. If the system supports
7067 the specification of a specific time slice value, then the indicated value
7068 is used. If the system does not support specific time slice values, but
7069 does support some general notion of round-robin scheduling, then any
7070 non-zero value will activate round-robin scheduling.
7072 A value of zero is treated specially. It turns off time
7073 slicing, and in addition, indicates to the tasking run time that the
7074 semantics should match as closely as possible the Annex D
7075 requirements of the Ada RM, and in particular sets the default
7076 scheduling policy to @code{FIFO_Within_Priorities}.
7078 @item ^-v^/REPORT_ERRORS=VERBOSE^
7079 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7080 Verbose mode. Write error messages, header, summary output to
7085 @cindex @option{-w} (@code{gnatbind})
7086 Warning mode (@var{x}=s/e for suppress/treat as error)
7090 @item /WARNINGS=NORMAL
7091 @cindex @option{/WARNINGS} (@code{gnatbind})
7092 Normal warnings mode. Warnings are issued but ignored
7094 @item /WARNINGS=SUPPRESS
7095 @cindex @option{/WARNINGS} (@code{gnatbind})
7096 All warning messages are suppressed
7098 @item /WARNINGS=ERROR
7099 @cindex @option{/WARNINGS} (@code{gnatbind})
7100 Warning messages are treated as fatal errors
7103 @item ^-x^/READ_SOURCES=NONE^
7104 @cindex @option{^-x^/READ_SOURCES^} (@code{gnatbind})
7105 Exclude source files (check object consistency only).
7108 @item /READ_SOURCES=AVAILABLE
7109 @cindex @option{/READ_SOURCES} (@code{gnatbind})
7110 Default mode, in which sources are checked for consistency only if
7114 @item ^-z^/ZERO_MAIN^
7115 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7121 You may obtain this listing of switches by running @code{gnatbind} with
7126 @node Consistency-Checking Modes
7127 @subsection Consistency-Checking Modes
7130 As described earlier, by default @code{gnatbind} checks
7131 that object files are consistent with one another and are consistent
7132 with any source files it can locate. The following switches control binder
7137 @item ^-s^/READ_SOURCES=ALL^
7138 @cindex @option{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
7139 Require source files to be present. In this mode, the binder must be
7140 able to locate all source files that are referenced, in order to check
7141 their consistency. In normal mode, if a source file cannot be located it
7142 is simply ignored. If you specify this switch, a missing source
7145 @item ^-x^/READ_SOURCES=NONE^
7146 @cindex @option{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
7147 Exclude source files. In this mode, the binder only checks that ALI
7148 files are consistent with one another. Source files are not accessed.
7149 The binder runs faster in this mode, and there is still a guarantee that
7150 the resulting program is self-consistent.
7151 If a source file has been edited since it was last compiled, and you
7152 specify this switch, the binder will not detect that the object
7153 file is out of date with respect to the source file. Note that this is the
7154 mode that is automatically used by @code{gnatmake} because in this
7155 case the checking against sources has already been performed by
7156 @code{gnatmake} in the course of compilation (i.e. before binding).
7159 @item /READ_SOURCES=AVAILABLE
7160 @cindex @code{/READ_SOURCES=AVAILABLE} (@code{gnatbind})
7161 This is the default mode in which source files are checked if they are
7162 available, and ignored if they are not available.
7166 @node Binder Error Message Control
7167 @subsection Binder Error Message Control
7170 The following switches provide control over the generation of error
7171 messages from the binder:
7175 @item ^-v^/REPORT_ERRORS=VERBOSE^
7176 @cindex @option{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
7177 Verbose mode. In the normal mode, brief error messages are generated to
7178 @file{stderr}. If this switch is present, a header is written
7179 to @file{stdout} and any error messages are directed to @file{stdout}.
7180 All that is written to @file{stderr} is a brief summary message.
7182 @item ^-b^/REPORT_ERRORS=BRIEF^
7183 @cindex @option{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
7184 Generate brief error messages to @file{stderr} even if verbose mode is
7185 specified. This is relevant only when used with the
7186 @option{^-v^/REPORT_ERRORS=VERBOSE^} switch.
7190 @cindex @option{-m} (@code{gnatbind})
7191 Limits the number of error messages to @var{n}, a decimal integer in the
7192 range 1-999. The binder terminates immediately if this limit is reached.
7195 @cindex @option{-M} (@code{gnatbind})
7196 Renames the generated main program from @code{main} to @code{xxx}.
7197 This is useful in the case of some cross-building environments, where
7198 the actual main program is separate from the one generated
7202 @item ^-ws^/WARNINGS=SUPPRESS^
7203 @cindex @option{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
7205 Suppress all warning messages.
7207 @item ^-we^/WARNINGS=ERROR^
7208 @cindex @option{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
7209 Treat any warning messages as fatal errors.
7212 @item /WARNINGS=NORMAL
7213 Standard mode with warnings generated, but warnings do not get treated
7217 @item ^-t^/NOTIME_STAMP_CHECK^
7218 @cindex @option{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
7219 @cindex Time stamp checks, in binder
7220 @cindex Binder consistency checks
7221 @cindex Consistency checks, in binder
7222 The binder performs a number of consistency checks including:
7226 Check that time stamps of a given source unit are consistent
7228 Check that checksums of a given source unit are consistent
7230 Check that consistent versions of @code{GNAT} were used for compilation
7232 Check consistency of configuration pragmas as required
7236 Normally failure of such checks, in accordance with the consistency
7237 requirements of the Ada Reference Manual, causes error messages to be
7238 generated which abort the binder and prevent the output of a binder
7239 file and subsequent link to obtain an executable.
7241 The @option{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
7242 into warnings, so that
7243 binding and linking can continue to completion even in the presence of such
7244 errors. The result may be a failed link (due to missing symbols), or a
7245 non-functional executable which has undefined semantics.
7246 @emph{This means that
7247 @option{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
7251 @node Elaboration Control
7252 @subsection Elaboration Control
7255 The following switches provide additional control over the elaboration
7256 order. For full details see @xref{Elaboration Order Handling in GNAT}.
7259 @item ^-p^/PESSIMISTIC_ELABORATION^
7260 @cindex @option{^-p^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
7261 Normally the binder attempts to choose an elaboration order that is
7262 likely to minimize the likelihood of an elaboration order error resulting
7263 in raising a @code{Program_Error} exception. This switch reverses the
7264 action of the binder, and requests that it deliberately choose an order
7265 that is likely to maximize the likelihood of an elaboration error.
7266 This is useful in ensuring portability and avoiding dependence on
7267 accidental fortuitous elaboration ordering.
7269 Normally it only makes sense to use the @option{^-p^/PESSIMISTIC_ELABORATION^}
7271 elaboration checking is used (@option{-gnatE} switch used for compilation).
7272 This is because in the default static elaboration mode, all necessary
7273 @code{Elaborate_All} pragmas are implicitly inserted.
7274 These implicit pragmas are still respected by the binder in
7275 @option{^-p^/PESSIMISTIC_ELABORATION^} mode, so a
7276 safe elaboration order is assured.
7279 @node Output Control
7280 @subsection Output Control
7283 The following switches allow additional control over the output
7284 generated by the binder.
7289 @item ^-A^/BIND_FILE=ADA^
7290 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
7291 Generate binder program in Ada (default). The binder program is named
7292 @file{b~@var{mainprog}.adb} by default. This can be changed with
7293 @option{^-o^/OUTPUT^} @code{gnatbind} option.
7295 @item ^-c^/NOOUTPUT^
7296 @cindex @option{^-c^/NOOUTPUT^} (@code{gnatbind})
7297 Check only. Do not generate the binder output file. In this mode the
7298 binder performs all error checks but does not generate an output file.
7300 @item ^-C^/BIND_FILE=C^
7301 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatbind})
7302 Generate binder program in C. The binder program is named
7303 @file{b_@var{mainprog}.c}.
7304 This can be changed with @option{^-o^/OUTPUT^} @code{gnatbind}
7307 @item ^-e^/ELABORATION_DEPENDENCIES^
7308 @cindex @option{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
7309 Output complete list of elaboration-order dependencies, showing the
7310 reason for each dependency. This output can be rather extensive but may
7311 be useful in diagnosing problems with elaboration order. The output is
7312 written to @file{stdout}.
7315 @cindex @option{^-h^/HELP^} (@code{gnatbind})
7316 Output usage information. The output is written to @file{stdout}.
7318 @item ^-K^/LINKER_OPTION_LIST^
7319 @cindex @option{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
7320 Output linker options to @file{stdout}. Includes library search paths,
7321 contents of pragmas Ident and Linker_Options, and libraries added
7324 @item ^-l^/ORDER_OF_ELABORATION^
7325 @cindex @option{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
7326 Output chosen elaboration order. The output is written to @file{stdout}.
7328 @item ^-O^/OBJECT_LIST^
7329 @cindex @option{^-O^/OBJECT_LIST^} (@code{gnatbind})
7330 Output full names of all the object files that must be linked to provide
7331 the Ada component of the program. The output is written to @file{stdout}.
7332 This list includes the files explicitly supplied and referenced by the user
7333 as well as implicitly referenced run-time unit files. The latter are
7334 omitted if the corresponding units reside in shared libraries. The
7335 directory names for the run-time units depend on the system configuration.
7337 @item ^-o ^/OUTPUT=^@var{file}
7338 @cindex @option{^-o^/OUTPUT^} (@code{gnatbind})
7339 Set name of output file to @var{file} instead of the normal
7340 @file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
7341 binder generated body filename. In C mode you would normally give
7342 @var{file} an extension of @file{.c} because it will be a C source program.
7343 Note that if this option is used, then linking must be done manually.
7344 It is not possible to use gnatlink in this case, since it cannot locate
7347 @item ^-r^/RESTRICTION_LIST^
7348 @cindex @option{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
7349 Generate list of @code{pragma Restrictions} that could be applied to
7350 the current unit. This is useful for code audit purposes, and also may
7351 be used to improve code generation in some cases.
7355 @node Binding with Non-Ada Main Programs
7356 @subsection Binding with Non-Ada Main Programs
7359 In our description so far we have assumed that the main
7360 program is in Ada, and that the task of the binder is to generate a
7361 corresponding function @code{main} that invokes this Ada main
7362 program. GNAT also supports the building of executable programs where
7363 the main program is not in Ada, but some of the called routines are
7364 written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
7365 The following switch is used in this situation:
7369 @cindex @option{^-n^/NOMAIN^} (@code{gnatbind})
7370 No main program. The main program is not in Ada.
7374 In this case, most of the functions of the binder are still required,
7375 but instead of generating a main program, the binder generates a file
7376 containing the following callable routines:
7381 You must call this routine to initialize the Ada part of the program by
7382 calling the necessary elaboration routines. A call to @code{adainit} is
7383 required before the first call to an Ada subprogram.
7385 Note that it is assumed that the basic execution environment must be setup
7386 to be appropriate for Ada execution at the point where the first Ada
7387 subprogram is called. In particular, if the Ada code will do any
7388 floating-point operations, then the FPU must be setup in an appropriate
7389 manner. For the case of the x86, for example, full precision mode is
7390 required. The procedure GNAT.Float_Control.Reset may be used to ensure
7391 that the FPU is in the right state.
7395 You must call this routine to perform any library-level finalization
7396 required by the Ada subprograms. A call to @code{adafinal} is required
7397 after the last call to an Ada subprogram, and before the program
7402 If the @option{^-n^/NOMAIN^} switch
7403 @cindex @option{^-n^/NOMAIN^} (@command{gnatbind})
7404 @cindex Binder, multiple input files
7405 is given, more than one ALI file may appear on
7406 the command line for @code{gnatbind}. The normal @dfn{closure}
7407 calculation is performed for each of the specified units. Calculating
7408 the closure means finding out the set of units involved by tracing
7409 @code{with} references. The reason it is necessary to be able to
7410 specify more than one ALI file is that a given program may invoke two or
7411 more quite separate groups of Ada units.
7413 The binder takes the name of its output file from the last specified ALI
7414 file, unless overridden by the use of the @option{^-o file^/OUTPUT=file^}.
7415 @cindex @option{^-o^/OUTPUT^} (@command{gnatbind})
7416 The output is an Ada unit in source form that can
7417 be compiled with GNAT unless the -C switch is used in which case the
7418 output is a C source file, which must be compiled using the C compiler.
7419 This compilation occurs automatically as part of the @code{gnatlink}
7422 Currently the GNAT run time requires a FPU using 80 bits mode
7423 precision. Under targets where this is not the default it is required to
7424 call GNAT.Float_Control.Reset before using floating point numbers (this
7425 include float computation, float input and output) in the Ada code. A
7426 side effect is that this could be the wrong mode for the foreign code
7427 where floating point computation could be broken after this call.
7429 @node Binding Programs with No Main Subprogram
7430 @subsection Binding Programs with No Main Subprogram
7433 It is possible to have an Ada program which does not have a main
7434 subprogram. This program will call the elaboration routines of all the
7435 packages, then the finalization routines.
7437 The following switch is used to bind programs organized in this manner:
7440 @item ^-z^/ZERO_MAIN^
7441 @cindex @option{^-z^/ZERO_MAIN^} (@code{gnatbind})
7442 Normally the binder checks that the unit name given on the command line
7443 corresponds to a suitable main subprogram. When this switch is used,
7444 a list of ALI files can be given, and the execution of the program
7445 consists of elaboration of these units in an appropriate order.
7449 @node Command-Line Access
7450 @section Command-Line Access
7453 The package @code{Ada.Command_Line} provides access to the command-line
7454 arguments and program name. In order for this interface to operate
7455 correctly, the two variables
7467 are declared in one of the GNAT library routines. These variables must
7468 be set from the actual @code{argc} and @code{argv} values passed to the
7469 main program. With no @option{^n^/NOMAIN^} present, @code{gnatbind}
7470 generates the C main program to automatically set these variables.
7471 If the @option{^n^/NOMAIN^} switch is used, there is no automatic way to
7472 set these variables. If they are not set, the procedures in
7473 @code{Ada.Command_Line} will not be available, and any attempt to use
7474 them will raise @code{Constraint_Error}. If command line access is
7475 required, your main program must set @code{gnat_argc} and
7476 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
7480 @node Search Paths for gnatbind
7481 @section Search Paths for @code{gnatbind}
7484 The binder takes the name of an ALI file as its argument and needs to
7485 locate source files as well as other ALI files to verify object consistency.
7487 For source files, it follows exactly the same search rules as @code{gcc}
7488 (@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
7489 directories searched are:
7493 The directory containing the ALI file named in the command line, unless
7494 the switch @option{^-I-^/NOCURRENT_DIRECTORY^} is specified.
7497 All directories specified by @option{^-I^/SEARCH^}
7498 switches on the @code{gnatbind}
7499 command line, in the order given.
7502 @findex ADA_OBJECTS_PATH
7503 Each of the directories listed in the value of the
7504 @code{ADA_OBJECTS_PATH} ^environment variable^logical name^.
7506 Construct this value
7507 exactly as the @code{PATH} environment variable: a list of directory
7508 names separated by colons (semicolons when working with the NT version
7512 Normally, define this value as a logical name containing a comma separated
7513 list of directory names.
7515 This variable can also be defined by means of an environment string
7516 (an argument to the DEC C exec* set of functions).
7520 DEFINE ANOTHER_PATH FOO:[BAG]
7521 DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
7524 By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
7525 first, followed by the standard Ada 95
7526 libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
7527 If this is not redefined, the user will obtain the DEC Ada 83 IO packages
7528 (Text_IO, Sequential_IO, etc)
7529 instead of the Ada95 packages. Thus, in order to get the Ada 95
7530 packages by default, ADA_OBJECTS_PATH must be redefined.
7534 @findex ADA_PRJ_OBJECTS_FILE
7535 Each of the directories listed in the text file whose name is given
7536 by the @code{ADA_PRJ_OBJECTS_FILE} ^environment variable^logical name^.
7539 @code{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the ^gnat^GNAT^
7540 driver when project files are used. It should not normally be set
7544 The content of the @file{ada_object_path} file which is part of the GNAT
7545 installation tree and is used to store standard libraries such as the
7546 GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is
7549 @ref{Installing an Ada Library}
7554 In the binder the switch @option{^-I^/SEARCH^}
7555 @cindex @option{^-I^/SEARCH^} (@command{gnatbind})
7556 is used to specify both source and
7557 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
7558 @cindex @option{^-aI^/SOURCE_SEARCH^} (@command{gnatbind})
7559 instead if you want to specify
7560 source paths only, and @option{^-aO^/LIBRARY_SEARCH^}
7561 @cindex @option{^-aO^/LIBRARY_SEARCH^} (@command{gnatbind})
7562 if you want to specify library paths
7563 only. This means that for the binder
7564 @option{^-I^/SEARCH=^}@var{dir} is equivalent to
7565 @option{^-aI^/SOURCE_SEARCH=^}@var{dir}
7566 @option{^-aO^/OBJECT_SEARCH=^}@var{dir}.
7567 The binder generates the bind file (a C language source file) in the
7568 current working directory.
7574 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
7575 children make up the GNAT Run-Time Library, together with the package
7576 GNAT and its children, which contain a set of useful additional
7577 library functions provided by GNAT. The sources for these units are
7578 needed by the compiler and are kept together in one directory. The ALI
7579 files and object files generated by compiling the RTL are needed by the
7580 binder and the linker and are kept together in one directory, typically
7581 different from the directory containing the sources. In a normal
7582 installation, you need not specify these directory names when compiling
7583 or binding. Either the environment variables or the built-in defaults
7584 cause these files to be found.
7586 Besides simplifying access to the RTL, a major use of search paths is
7587 in compiling sources from multiple directories. This can make
7588 development environments much more flexible.
7590 @node Examples of gnatbind Usage
7591 @section Examples of @code{gnatbind} Usage
7594 This section contains a number of examples of using the GNAT binding
7595 utility @code{gnatbind}.
7598 @item gnatbind hello
7599 The main program @code{Hello} (source program in @file{hello.adb}) is
7600 bound using the standard switch settings. The generated main program is
7601 @file{b~hello.adb}. This is the normal, default use of the binder.
7604 @item gnatbind hello -o mainprog.adb
7607 @item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
7609 The main program @code{Hello} (source program in @file{hello.adb}) is
7610 bound using the standard switch settings. The generated main program is
7611 @file{mainprog.adb} with the associated spec in
7612 @file{mainprog.ads}. Note that you must specify the body here not the
7613 spec, in the case where the output is in Ada. Note that if this option
7614 is used, then linking must be done manually, since gnatlink will not
7615 be able to find the generated file.
7618 @item gnatbind main -C -o mainprog.c -x
7621 @item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
7623 The main program @code{Main} (source program in
7624 @file{main.adb}) is bound, excluding source files from the
7625 consistency checking, generating
7626 the file @file{mainprog.c}.
7629 @item gnatbind -x main_program -C -o mainprog.c
7630 This command is exactly the same as the previous example. Switches may
7631 appear anywhere in the command line, and single letter switches may be
7632 combined into a single switch.
7636 @item gnatbind -n math dbase -C -o ada-control.c
7639 @item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
7641 The main program is in a language other than Ada, but calls to
7642 subprograms in packages @code{Math} and @code{Dbase} appear. This call
7643 to @code{gnatbind} generates the file @file{ada-control.c} containing
7644 the @code{adainit} and @code{adafinal} routines to be called before and
7645 after accessing the Ada units.
7649 @c ------------------------------------
7650 @node Linking Using gnatlink
7651 @chapter Linking Using @code{gnatlink}
7652 @c ------------------------------------
7656 This chapter discusses @code{gnatlink}, a tool that links
7657 an Ada program and builds an executable file. This utility
7658 invokes the system linker ^(via the @code{gcc} command)^^
7659 with a correct list of object files and library references.
7660 @code{gnatlink} automatically determines the list of files and
7661 references for the Ada part of a program. It uses the binder file
7662 generated by the @command{gnatbind} to determine this list.
7665 * Running gnatlink::
7666 * Switches for gnatlink::
7667 * Setting Stack Size from gnatlink::
7668 * Setting Heap Size from gnatlink::
7671 @node Running gnatlink
7672 @section Running @code{gnatlink}
7675 The form of the @code{gnatlink} command is
7678 $ gnatlink [@var{switches}] @var{mainprog}[.ali]
7679 [@var{non-Ada objects}] [@var{linker options}]
7683 The arguments of @code{gnatlink} (switches, main @file{ALI} file,
7685 or linker options) may be in any order, provided that no non-Ada object may
7686 be mistaken for a main @file{ALI} file.
7687 Any file name @file{F} without the @file{.ali}
7688 extension will be taken as the main @file{ALI} file if a file exists
7689 whose name is the concatenation of @file{F} and @file{.ali}.
7692 @file{@var{mainprog}.ali} references the ALI file of the main program.
7693 The @file{.ali} extension of this file can be omitted. From this
7694 reference, @code{gnatlink} locates the corresponding binder file
7695 @file{b~@var{mainprog}.adb} and, using the information in this file along
7696 with the list of non-Ada objects and linker options, constructs a
7697 linker command file to create the executable.
7699 The arguments other than the @code{gnatlink} switches and the main @file{ALI}
7700 file are passed to the linker uninterpreted.
7701 They typically include the names of
7702 object files for units written in other languages than Ada and any library
7703 references required to resolve references in any of these foreign language
7704 units, or in @code{Import} pragmas in any Ada units.
7706 @var{linker options} is an optional list of linker specific
7708 The default linker called by gnatlink is @var{gcc} which in
7709 turn calls the appropriate system linker.
7710 Standard options for the linker such as @option{-lmy_lib} or
7711 @option{-Ldir} can be added as is.
7712 For options that are not recognized by
7713 @var{gcc} as linker options, use the @var{gcc} switches @option{-Xlinker} or
7715 Refer to the GCC documentation for
7716 details. Here is an example showing how to generate a linker map:
7720 $ gnatlink my_prog -Wl,-Map,MAPFILE
7725 <<Need example for VMS>>
7728 Using @var{linker options} it is possible to set the program stack and
7729 heap size. See @ref{Setting Stack Size from gnatlink}, and
7730 @ref{Setting Heap Size from gnatlink}.
7732 @code{gnatlink} determines the list of objects required by the Ada
7733 program and prepends them to the list of objects passed to the linker.
7734 @code{gnatlink} also gathers any arguments set by the use of
7735 @code{pragma Linker_Options} and adds them to the list of arguments
7736 presented to the linker.
7739 @code{gnatlink} accepts the following types of extra files on the command
7740 line: objects (.OBJ), libraries (.OLB), sharable images (.EXE), and
7741 options files (.OPT). These are recognized and handled according to their
7745 @node Switches for gnatlink
7746 @section Switches for @code{gnatlink}
7749 The following switches are available with the @code{gnatlink} utility:
7754 @item ^-A^/BIND_FILE=ADA^
7755 @cindex @option{^-A^/BIND_FILE=ADA^} (@code{gnatlink})
7756 The binder has generated code in Ada. This is the default.
7758 @item ^-C^/BIND_FILE=C^
7759 @cindex @option{^-C^/BIND_FILE=C^} (@code{gnatlink})
7760 If instead of generating a file in Ada, the binder has generated one in
7761 C, then the linker needs to know about it. Use this switch to signal
7762 to @code{gnatlink} that the binder has generated C code rather than
7765 @item ^-f^/FORCE_OBJECT_FILE_LIST^
7766 @cindex Command line length
7767 @cindex @option{^-f^/FORCE_OBJECT_FILE_LIST^} (@code{gnatlink})
7768 On some targets, the command line length is limited, and @code{gnatlink}
7769 will generate a separate file for the linker if the list of object files
7771 The @option{^-f^/FORCE_OBJECT_FILE_LIST^} switch forces this file
7772 to be generated even if
7773 the limit is not exceeded. This is useful in some cases to deal with
7774 special situations where the command line length is exceeded.
7777 @cindex Debugging information, including
7778 @cindex @option{^-g^/DEBUG^} (@code{gnatlink})
7779 The option to include debugging information causes the Ada bind file (in
7780 other words, @file{b~@var{mainprog}.adb}) to be compiled with
7781 @option{^-g^/DEBUG^}.
7782 In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
7783 @file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
7784 Without @option{^-g^/DEBUG^}, the binder removes these files by
7785 default. The same procedure apply if a C bind file was generated using
7786 @option{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames
7787 are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
7789 @item ^-n^/NOCOMPILE^
7790 @cindex @option{^-n^/NOCOMPILE^} (@code{gnatlink})
7791 Do not compile the file generated by the binder. This may be used when
7792 a link is rerun with different options, but there is no need to recompile
7796 @cindex @option{^-v^/VERBOSE^} (@code{gnatlink})
7797 Causes additional information to be output, including a full list of the
7798 included object files. This switch option is most useful when you want
7799 to see what set of object files are being used in the link step.
7801 @item ^-v -v^/VERBOSE/VERBOSE^
7802 @cindex @option{^-v -v^/VERBOSE/VERBOSE^} (@code{gnatlink})
7803 Very verbose mode. Requests that the compiler operate in verbose mode when
7804 it compiles the binder file, and that the system linker run in verbose mode.
7806 @item ^-o ^/EXECUTABLE=^@var{exec-name}
7807 @cindex @option{^-o^/EXECUTABLE^} (@code{gnatlink})
7808 @var{exec-name} specifies an alternate name for the generated
7809 executable program. If this switch is omitted, the executable has the same
7810 name as the main unit. For example, @code{gnatlink try.ali} creates
7811 an executable called @file{^try^TRY.EXE^}.
7814 @item -b @var{target}
7815 @cindex @option{-b} (@code{gnatlink})
7816 Compile your program to run on @var{target}, which is the name of a
7817 system configuration. You must have a GNAT cross-compiler built if
7818 @var{target} is not the same as your host system.
7821 @cindex @option{-B} (@code{gnatlink})
7822 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
7823 from @var{dir} instead of the default location. Only use this switch
7824 when multiple versions of the GNAT compiler are available. See the
7825 @code{gcc} manual page for further details. You would normally use the
7826 @option{-b} or @option{-V} switch instead.
7828 @item --GCC=@var{compiler_name}
7829 @cindex @option{--GCC=compiler_name} (@code{gnatlink})
7830 Program used for compiling the binder file. The default is
7831 `@code{gcc}'. You need to use quotes around @var{compiler_name} if
7832 @code{compiler_name} contains spaces or other separator characters. As
7833 an example @option{--GCC="foo -x -y"} will instruct @code{gnatlink} to use
7834 @code{foo -x -y} as your compiler. Note that switch @option{-c} is always
7835 inserted after your command name. Thus in the above example the compiler
7836 command that will be used by @code{gnatlink} will be @code{foo -c -x -y}.
7837 If several @option{--GCC=compiler_name} are used, only the last
7838 @var{compiler_name} is taken into account. However, all the additional
7839 switches are also taken into account. Thus,
7840 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
7841 @option{--GCC="bar -x -y -z -t"}.
7843 @item --LINK=@var{name}
7844 @cindex @option{--LINK=} (@code{gnatlink})
7845 @var{name} is the name of the linker to be invoked. This is especially
7846 useful in mixed language programs since languages such as C++ require
7847 their own linker to be used. When this switch is omitted, the default
7848 name for the linker is (@file{gcc}). When this switch is used, the
7849 specified linker is called instead of (@file{gcc}) with exactly the same
7850 parameters that would have been passed to (@file{gcc}) so if the desired
7851 linker requires different parameters it is necessary to use a wrapper
7852 script that massages the parameters before invoking the real linker. It
7853 may be useful to control the exact invocation by using the verbose
7859 @item /DEBUG=TRACEBACK
7860 @cindex @code{/DEBUG=TRACEBACK} (@code{gnatlink})
7861 This qualifier causes sufficient information to be included in the
7862 executable file to allow a traceback, but does not include the full
7863 symbol information needed by the debugger.
7865 @item /IDENTIFICATION="<string>"
7866 @code{"<string>"} specifies the string to be stored in the image file
7867 identification field in the image header.
7868 It overrides any pragma @code{Ident} specified string.
7870 @item /NOINHIBIT-EXEC
7871 Generate the executable file even if there are linker warnings.
7873 @item /NOSTART_FILES
7874 Don't link in the object file containing the ``main'' transfer address.
7875 Used when linking with a foreign language main program compiled with a
7879 Prefer linking with object libraries over sharable images, even without
7885 @node Setting Stack Size from gnatlink
7886 @section Setting Stack Size from @code{gnatlink}
7889 Under Windows systems, it is possible to specify the program stack size from
7890 @code{gnatlink} using either:
7894 @item using @option{-Xlinker} linker option
7897 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
7900 This sets the stack reserve size to 0x10000 bytes and the stack commit
7901 size to 0x1000 bytes.
7903 @item using @option{-Wl} linker option
7906 $ gnatlink hello -Wl,--stack=0x1000000
7909 This sets the stack reserve size to 0x1000000 bytes. Note that with
7910 @option{-Wl} option it is not possible to set the stack commit size
7911 because the coma is a separator for this option.
7915 @node Setting Heap Size from gnatlink
7916 @section Setting Heap Size from @code{gnatlink}
7919 Under Windows systems, it is possible to specify the program heap size from
7920 @code{gnatlink} using either:
7924 @item using @option{-Xlinker} linker option
7927 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
7930 This sets the heap reserve size to 0x10000 bytes and the heap commit
7931 size to 0x1000 bytes.
7933 @item using @option{-Wl} linker option
7936 $ gnatlink hello -Wl,--heap=0x1000000
7939 This sets the heap reserve size to 0x1000000 bytes. Note that with
7940 @option{-Wl} option it is not possible to set the heap commit size
7941 because the coma is a separator for this option.
7945 @node The GNAT Make Program gnatmake
7946 @chapter The GNAT Make Program @code{gnatmake}
7950 * Running gnatmake::
7951 * Switches for gnatmake::
7952 * Mode Switches for gnatmake::
7953 * Notes on the Command Line::
7954 * How gnatmake Works::
7955 * Examples of gnatmake Usage::
7958 A typical development cycle when working on an Ada program consists of
7959 the following steps:
7963 Edit some sources to fix bugs.
7969 Compile all sources affected.
7979 The third step can be tricky, because not only do the modified files
7980 @cindex Dependency rules
7981 have to be compiled, but any files depending on these files must also be
7982 recompiled. The dependency rules in Ada can be quite complex, especially
7983 in the presence of overloading, @code{use} clauses, generics and inlined
7986 @code{gnatmake} automatically takes care of the third and fourth steps
7987 of this process. It determines which sources need to be compiled,
7988 compiles them, and binds and links the resulting object files.
7990 Unlike some other Ada make programs, the dependencies are always
7991 accurately recomputed from the new sources. The source based approach of
7992 the GNAT compilation model makes this possible. This means that if
7993 changes to the source program cause corresponding changes in
7994 dependencies, they will always be tracked exactly correctly by
7997 @node Running gnatmake
7998 @section Running @code{gnatmake}
8001 The usual form of the @code{gnatmake} command is
8004 $ gnatmake [@var{switches}] @var{file_name}
8005 [@var{file_names}] [@var{mode_switches}]
8009 The only required argument is one @var{file_name}, which specifies
8010 a compilation unit that is a main program. Several @var{file_names} can be
8011 specified: this will result in several executables being built.
8012 If @code{switches} are present, they can be placed before the first
8013 @var{file_name}, between @var{file_names} or after the last @var{file_name}.
8014 If @var{mode_switches} are present, they must always be placed after
8015 the last @var{file_name} and all @code{switches}.
8017 If you are using standard file extensions (.adb and .ads), then the
8018 extension may be omitted from the @var{file_name} arguments. However, if
8019 you are using non-standard extensions, then it is required that the
8020 extension be given. A relative or absolute directory path can be
8021 specified in a @var{file_name}, in which case, the input source file will
8022 be searched for in the specified directory only. Otherwise, the input
8023 source file will first be searched in the directory where
8024 @code{gnatmake} was invoked and if it is not found, it will be search on
8025 the source path of the compiler as described in
8026 @ref{Search Paths and the Run-Time Library (RTL)}.
8028 All @code{gnatmake} output (except when you specify
8029 @option{^-M^/DEPENDENCIES_LIST^}) is to
8030 @file{stderr}. The output produced by the
8031 @option{^-M^/DEPENDENCIES_LIST^} switch is send to
8034 @node Switches for gnatmake
8035 @section Switches for @code{gnatmake}
8038 You may specify any of the following switches to @code{gnatmake}:
8043 @item --GCC=@var{compiler_name}
8044 @cindex @option{--GCC=compiler_name} (@code{gnatmake})
8045 Program used for compiling. The default is `@code{gcc}'. You need to use
8046 quotes around @var{compiler_name} if @code{compiler_name} contains
8047 spaces or other separator characters. As an example @option{--GCC="foo -x
8048 -y"} will instruct @code{gnatmake} to use @code{foo -x -y} as your
8049 compiler. Note that switch @option{-c} is always inserted after your
8050 command name. Thus in the above example the compiler command that will
8051 be used by @code{gnatmake} will be @code{foo -c -x -y}.
8052 If several @option{--GCC=compiler_name} are used, only the last
8053 @var{compiler_name} is taken into account. However, all the additional
8054 switches are also taken into account. Thus,
8055 @option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
8056 @option{--GCC="bar -x -y -z -t"}.
8058 @item --GNATBIND=@var{binder_name}
8059 @cindex @option{--GNATBIND=binder_name} (@code{gnatmake})
8060 Program used for binding. The default is `@code{gnatbind}'. You need to
8061 use quotes around @var{binder_name} if @var{binder_name} contains spaces
8062 or other separator characters. As an example @option{--GNATBIND="bar -x
8063 -y"} will instruct @code{gnatmake} to use @code{bar -x -y} as your
8064 binder. Binder switches that are normally appended by @code{gnatmake} to
8065 `@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
8067 @item --GNATLINK=@var{linker_name}
8068 @cindex @option{--GNATLINK=linker_name} (@code{gnatmake})
8069 Program used for linking. The default is `@code{gnatlink}'. You need to
8070 use quotes around @var{linker_name} if @var{linker_name} contains spaces
8071 or other separator characters. As an example @option{--GNATLINK="lan -x
8072 -y"} will instruct @code{gnatmake} to use @code{lan -x -y} as your
8073 linker. Linker switches that are normally appended by @code{gnatmake} to
8074 `@code{gnatlink}' are now appended to the end of @code{lan -x -y}.
8078 @item ^-a^/ALL_FILES^
8079 @cindex @option{^-a^/ALL_FILES^} (@code{gnatmake})
8080 Consider all files in the make process, even the GNAT internal system
8081 files (for example, the predefined Ada library files), as well as any
8082 locked files. Locked files are files whose ALI file is write-protected.
8084 @code{gnatmake} does not check these files,
8085 because the assumption is that the GNAT internal files are properly up
8086 to date, and also that any write protected ALI files have been properly
8087 installed. Note that if there is an installation problem, such that one
8088 of these files is not up to date, it will be properly caught by the
8090 You may have to specify this switch if you are working on GNAT
8091 itself. The switch @option{^-a^/ALL_FILES^} is also useful
8092 in conjunction with @option{^-f^/FORCE_COMPILE^}
8093 if you need to recompile an entire application,
8094 including run-time files, using special configuration pragmas,
8095 such as a @code{Normalize_Scalars} pragma.
8098 @code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
8101 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
8104 the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
8107 @item ^-b^/ACTIONS=BIND^
8108 @cindex @option{^-b^/ACTIONS=BIND^} (@code{gnatmake})
8109 Bind only. Can be combined with @option{^-c^/ACTIONS=COMPILE^} to do
8110 compilation and binding, but no link.
8111 Can be combined with @option{^-l^/ACTIONS=LINK^}
8112 to do binding and linking. When not combined with
8113 @option{^-c^/ACTIONS=COMPILE^}
8114 all the units in the closure of the main program must have been previously
8115 compiled and must be up to date. The root unit specified by @var{file_name}
8116 may be given without extension, with the source extension or, if no GNAT
8117 Project File is specified, with the ALI file extension.
8119 @item ^-c^/ACTIONS=COMPILE^
8120 @cindex @option{^-c^/ACTIONS=COMPILE^} (@code{gnatmake})
8121 Compile only. Do not perform binding, except when @option{^-b^/ACTIONS=BIND^}
8122 is also specified. Do not perform linking, except if both
8123 @option{^-b^/ACTIONS=BIND^} and
8124 @option{^-l^/ACTIONS=LINK^} are also specified.
8125 If the root unit specified by @var{file_name} is not a main unit, this is the
8126 default. Otherwise @code{gnatmake} will attempt binding and linking
8127 unless all objects are up to date and the executable is more recent than
8131 @cindex @option{^-C^/MAPPING^} (@code{gnatmake})
8132 Use a temporary mapping file. A mapping file is a way to communicate to the
8133 compiler two mappings: from unit names to file names (without any directory
8134 information) and from file names to path names (with full directory
8135 information). These mappings are used by the compiler to short-circuit the path
8136 search. When @code{gnatmake} is invoked with this switch, it will create
8137 a temporary mapping file, initially populated by the project manager,
8138 if @option{^-P^/PROJECT_FILE^} is used, otherwise initially empty.
8139 Each invocation of the compiler will add the newly accessed sources to the
8140 mapping file. This will improve the source search during the next invocation
8143 @item ^-C=^/USE_MAPPING_FILE=^@var{file}
8144 @cindex @option{^-C=^/USE_MAPPING^} (@code{gnatmake})
8145 Use a specific mapping file. The file, specified as a path name (absolute or
8146 relative) by this switch, should already exist, otherwise the switch is
8147 ineffective. The specified mapping file will be communicated to the compiler.
8148 This switch is not compatible with a project file
8149 (^-P^/PROJECT_FILE=^@var{file}) or with multiple compiling processes
8150 (^-j^/PROCESSES=^nnn, when nnn is greater than 1).
8152 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
8153 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatmake})
8154 Put all object files and ALI file in directory @var{dir}.
8155 If the @option{^-D^/DIRECTORY_OBJECTS^} switch is not used, all object files
8156 and ALI files go in the current working directory.
8158 This switch cannot be used when using a project file.
8162 @cindex @option{-eL} (@code{gnatmake})
8163 Follow all symbolic links when processing project files.
8166 @item ^-f^/FORCE_COMPILE^
8167 @cindex @option{^-f^/FORCE_COMPILE^} (@code{gnatmake})
8168 Force recompilations. Recompile all sources, even though some object
8169 files may be up to date, but don't recompile predefined or GNAT internal
8170 files or locked files (files with a write-protected ALI file),
8171 unless the @option{^-a^/ALL_FILES^} switch is also specified.
8173 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
8174 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatmake})
8175 When using project files, if some errors or warnings are detected during
8176 parsing and verbose mode is not in effect (no use of switch
8177 ^-v^/VERBOSE^), then error lines start with the full path name of the project
8178 file, rather than its simple file name.
8180 @item ^-i^/IN_PLACE^
8181 @cindex @option{^-i^/IN_PLACE^} (@code{gnatmake})
8182 In normal mode, @code{gnatmake} compiles all object files and ALI files
8183 into the current directory. If the @option{^-i^/IN_PLACE^} switch is used,
8184 then instead object files and ALI files that already exist are overwritten
8185 in place. This means that once a large project is organized into separate
8186 directories in the desired manner, then @code{gnatmake} will automatically
8187 maintain and update this organization. If no ALI files are found on the
8188 Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
8189 the new object and ALI files are created in the
8190 directory containing the source being compiled. If another organization
8191 is desired, where objects and sources are kept in different directories,
8192 a useful technique is to create dummy ALI files in the desired directories.
8193 When detecting such a dummy file, @code{gnatmake} will be forced to recompile
8194 the corresponding source file, and it will be put the resulting object
8195 and ALI files in the directory where it found the dummy file.
8197 @item ^-j^/PROCESSES=^@var{n}
8198 @cindex @option{^-j^/PROCESSES^} (@code{gnatmake})
8199 @cindex Parallel make
8200 Use @var{n} processes to carry out the (re)compilations. On a
8201 multiprocessor machine compilations will occur in parallel. In the
8202 event of compilation errors, messages from various compilations might
8203 get interspersed (but @code{gnatmake} will give you the full ordered
8204 list of failing compiles at the end). If this is problematic, rerun
8205 the make process with n set to 1 to get a clean list of messages.
8207 @item ^-k^/CONTINUE_ON_ERROR^
8208 @cindex @option{^-k^/CONTINUE_ON_ERROR^} (@code{gnatmake})
8209 Keep going. Continue as much as possible after a compilation error. To
8210 ease the programmer's task in case of compilation errors, the list of
8211 sources for which the compile fails is given when @code{gnatmake}
8214 If @code{gnatmake} is invoked with several @file{file_names} and with this
8215 switch, if there are compilation errors when building an executable,
8216 @code{gnatmake} will not attempt to build the following executables.
8218 @item ^-l^/ACTIONS=LINK^
8219 @cindex @option{^-l^/ACTIONS=LINK^} (@code{gnatmake})
8220 Link only. Can be combined with @option{^-b^/ACTIONS=BIND^} to binding
8221 and linking. Linking will not be performed if combined with
8222 @option{^-c^/ACTIONS=COMPILE^}
8223 but not with @option{^-b^/ACTIONS=BIND^}.
8224 When not combined with @option{^-b^/ACTIONS=BIND^}
8225 all the units in the closure of the main program must have been previously
8226 compiled and must be up to date, and the main program need to have been bound.
8227 The root unit specified by @var{file_name}
8228 may be given without extension, with the source extension or, if no GNAT
8229 Project File is specified, with the ALI file extension.
8231 @item ^-m^/MINIMAL_RECOMPILATION^
8232 @cindex @option{^-m^/MINIMAL_RECOMPILATION^} (@code{gnatmake})
8233 Specifies that the minimum necessary amount of recompilations
8234 be performed. In this mode @code{gnatmake} ignores time
8235 stamp differences when the only
8236 modifications to a source file consist in adding/removing comments,
8237 empty lines, spaces or tabs. This means that if you have changed the
8238 comments in a source file or have simply reformatted it, using this
8239 switch will tell gnatmake not to recompile files that depend on it
8240 (provided other sources on which these files depend have undergone no
8241 semantic modifications). Note that the debugging information may be
8242 out of date with respect to the sources if the @option{-m} switch causes
8243 a compilation to be switched, so the use of this switch represents a
8244 trade-off between compilation time and accurate debugging information.
8246 @item ^-M^/DEPENDENCIES_LIST^
8247 @cindex Dependencies, producing list
8248 @cindex @option{^-M^/DEPENDENCIES_LIST^} (@code{gnatmake})
8249 Check if all objects are up to date. If they are, output the object
8250 dependences to @file{stdout} in a form that can be directly exploited in
8251 a @file{Makefile}. By default, each source file is prefixed with its
8252 (relative or absolute) directory name. This name is whatever you
8253 specified in the various @option{^-aI^/SOURCE_SEARCH^}
8254 and @option{^-I^/SEARCH^} switches. If you use
8255 @code{gnatmake ^-M^/DEPENDENCIES_LIST^}
8256 @option{^-q^/QUIET^}
8257 (see below), only the source file names,
8258 without relative paths, are output. If you just specify the
8259 @option{^-M^/DEPENDENCIES_LIST^}
8260 switch, dependencies of the GNAT internal system files are omitted. This
8261 is typically what you want. If you also specify
8262 the @option{^-a^/ALL_FILES^} switch,
8263 dependencies of the GNAT internal files are also listed. Note that
8264 dependencies of the objects in external Ada libraries (see switch
8265 @option{^-aL^/SKIP_MISSING=^}@var{dir} in the following list)
8268 @item ^-n^/DO_OBJECT_CHECK^
8269 @cindex @option{^-n^/DO_OBJECT_CHECK^} (@code{gnatmake})
8270 Don't compile, bind, or link. Checks if all objects are up to date.
8271 If they are not, the full name of the first file that needs to be
8272 recompiled is printed.
8273 Repeated use of this option, followed by compiling the indicated source
8274 file, will eventually result in recompiling all required units.
8276 @item ^-o ^/EXECUTABLE=^@var{exec_name}
8277 @cindex @option{^-o^/EXECUTABLE^} (@code{gnatmake})
8278 Output executable name. The name of the final executable program will be
8279 @var{exec_name}. If the @option{^-o^/EXECUTABLE^} switch is omitted the default
8280 name for the executable will be the name of the input file in appropriate form
8281 for an executable file on the host system.
8283 This switch cannot be used when invoking @code{gnatmake} with several
8286 @item ^-P^/PROJECT_FILE=^@var{project}
8287 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatmake})
8288 Use project file @var{project}. Only one such switch can be used.
8289 See @ref{gnatmake and Project Files}.
8292 @cindex @option{^-q^/QUIET^} (@code{gnatmake})
8293 Quiet. When this flag is not set, the commands carried out by
8294 @code{gnatmake} are displayed.
8296 @item ^-s^/SWITCH_CHECK/^
8297 @cindex @option{^-s^/SWITCH_CHECK^} (@code{gnatmake})
8298 Recompile if compiler switches have changed since last compilation.
8299 All compiler switches but -I and -o are taken into account in the
8301 orders between different ``first letter'' switches are ignored, but
8302 orders between same switches are taken into account. For example,
8303 @option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O}
8304 is equivalent to @option{-O -g}.
8306 This switch is recommended when Integrated Preprocessing is used.
8309 @cindex @option{^-u^/UNIQUE^} (@code{gnatmake})
8310 Unique. Recompile at most the main files. It implies -c. Combined with
8311 -f, it is equivalent to calling the compiler directly. Note that using
8312 ^-u^/UNIQUE^ with a project file and no main has a special meaning
8313 (see @ref{Project Files and Main Subprograms}).
8315 @item ^-U^/ALL_PROJECTS^
8316 @cindex @option{^-U^/ALL_PROJECTS^} (@code{gnatmake})
8317 When used without a project file or with one or several mains on the command
8318 line, is equivalent to ^-u^/UNIQUE^. When used with a project file and no main
8319 on the command line, all sources of all project files are checked and compiled
8320 if not up to date, and libraries are rebuilt, if necessary.
8323 @cindex @option{^-v^/REASONS^} (@code{gnatmake})
8324 Verbose. Displays the reason for all recompilations @code{gnatmake}
8325 decides are necessary.
8327 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
8328 Indicates the verbosity of the parsing of GNAT project files.
8329 See @ref{Switches Related to Project Files}.
8331 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
8332 Indicates that external variable @var{name} has the value @var{value}.
8333 The Project Manager will use this value for occurrences of
8334 @code{external(name)} when parsing the project file.
8335 See @ref{Switches Related to Project Files}.
8338 @cindex @option{^-z^/NOMAIN^} (@code{gnatmake})
8339 No main subprogram. Bind and link the program even if the unit name
8340 given on the command line is a package name. The resulting executable
8341 will execute the elaboration routines of the package and its closure,
8342 then the finalization routines.
8345 @cindex @option{^-g^/DEBUG^} (@code{gnatmake})
8346 Enable debugging. This switch is simply passed to the compiler and to the
8352 @item @code{gcc} @asis{switches}
8354 Any uppercase or multi-character switch that is not a @code{gnatmake} switch
8355 is passed to @code{gcc} (e.g. @option{-O}, @option{-gnato,} etc.)
8358 Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
8359 but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
8360 automatically treated as a compiler switch, and passed on to all
8361 compilations that are carried out.
8366 Source and library search path switches:
8370 @item ^-aI^/SOURCE_SEARCH=^@var{dir}
8371 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatmake})
8372 When looking for source files also look in directory @var{dir}.
8373 The order in which source files search is undertaken is
8374 described in @ref{Search Paths and the Run-Time Library (RTL)}.
8376 @item ^-aL^/SKIP_MISSING=^@var{dir}
8377 @cindex @option{^-aL^/SKIP_MISSING^} (@code{gnatmake})
8378 Consider @var{dir} as being an externally provided Ada library.
8379 Instructs @code{gnatmake} to skip compilation units whose @file{.ALI}
8380 files have been located in directory @var{dir}. This allows you to have
8381 missing bodies for the units in @var{dir} and to ignore out of date bodies
8382 for the same units. You still need to specify
8383 the location of the specs for these units by using the switches
8384 @option{^-aI^/SOURCE_SEARCH=^@var{dir}}
8385 or @option{^-I^/SEARCH=^@var{dir}}.
8386 Note: this switch is provided for compatibility with previous versions
8387 of @code{gnatmake}. The easier method of causing standard libraries
8388 to be excluded from consideration is to write-protect the corresponding
8391 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
8392 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatmake})
8393 When searching for library and object files, look in directory
8394 @var{dir}. The order in which library files are searched is described in
8395 @ref{Search Paths for gnatbind}.
8397 @item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
8398 @cindex Search paths, for @code{gnatmake}
8399 @cindex @option{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@code{gnatmake})
8400 Equivalent to @option{^-aL^/SKIP_MISSING=^@var{dir}
8401 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
8403 @item ^-I^/SEARCH=^@var{dir}
8404 @cindex @option{^-I^/SEARCH^} (@code{gnatmake})
8405 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}
8406 ^-aI^/SOURCE_SEARCH=^@var{dir}}.
8408 @item ^-I-^/NOCURRENT_DIRECTORY^
8409 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatmake})
8410 @cindex Source files, suppressing search
8411 Do not look for source files in the directory containing the source
8412 file named in the command line.
8413 Do not look for ALI or object files in the directory
8414 where @code{gnatmake} was invoked.
8416 @item ^-L^/LIBRARY_SEARCH=^@var{dir}
8417 @cindex @option{^-L^/LIBRARY_SEARCH^} (@code{gnatmake})
8418 @cindex Linker libraries
8419 Add directory @var{dir} to the list of directories in which the linker
8420 will search for libraries. This is equivalent to
8421 @option{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
8423 Furthermore, under Windows, the sources pointed to by the libraries path
8424 set in the registry are not searched for.
8428 @cindex @option{-nostdinc} (@code{gnatmake})
8429 Do not look for source files in the system default directory.
8432 @cindex @option{-nostdlib} (@code{gnatmake})
8433 Do not look for library files in the system default directory.
8435 @item --RTS=@var{rts-path}
8436 @cindex @option{--RTS} (@code{gnatmake})
8437 Specifies the default location of the runtime library. GNAT looks for the
8439 in the following directories, and stops as soon as a valid runtime is found
8440 (@file{adainclude} or @file{ada_source_path}, and @file{adalib} or
8441 @file{ada_object_path} present):
8444 @item <current directory>/$rts_path
8446 @item <default-search-dir>/$rts_path
8448 @item <default-search-dir>/rts-$rts_path
8452 The selected path is handled like a normal RTS path.
8456 @node Mode Switches for gnatmake
8457 @section Mode Switches for @code{gnatmake}
8460 The mode switches (referred to as @code{mode_switches}) allow the
8461 inclusion of switches that are to be passed to the compiler itself, the
8462 binder or the linker. The effect of a mode switch is to cause all
8463 subsequent switches up to the end of the switch list, or up to the next
8464 mode switch, to be interpreted as switches to be passed on to the
8465 designated component of GNAT.
8469 @item -cargs @var{switches}
8470 @cindex @option{-cargs} (@code{gnatmake})
8471 Compiler switches. Here @var{switches} is a list of switches
8472 that are valid switches for @code{gcc}. They will be passed on to
8473 all compile steps performed by @code{gnatmake}.
8475 @item -bargs @var{switches}
8476 @cindex @option{-bargs} (@code{gnatmake})
8477 Binder switches. Here @var{switches} is a list of switches
8478 that are valid switches for @code{gnatbind}. They will be passed on to
8479 all bind steps performed by @code{gnatmake}.
8481 @item -largs @var{switches}
8482 @cindex @option{-largs} (@code{gnatmake})
8483 Linker switches. Here @var{switches} is a list of switches
8484 that are valid switches for @code{gnatlink}. They will be passed on to
8485 all link steps performed by @code{gnatmake}.
8487 @item -margs @var{switches}
8488 @cindex @option{-margs} (@code{gnatmake})
8489 Make switches. The switches are directly interpreted by @code{gnatmake},
8490 regardless of any previous occurrence of @option{-cargs}, @option{-bargs}
8494 @node Notes on the Command Line
8495 @section Notes on the Command Line
8498 This section contains some additional useful notes on the operation
8499 of the @code{gnatmake} command.
8503 @cindex Recompilation, by @code{gnatmake}
8504 If @code{gnatmake} finds no ALI files, it recompiles the main program
8505 and all other units required by the main program.
8506 This means that @code{gnatmake}
8507 can be used for the initial compile, as well as during subsequent steps of
8508 the development cycle.
8511 If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
8512 is a subunit or body of a generic unit, @code{gnatmake} recompiles
8513 @file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
8517 In @code{gnatmake} the switch @option{^-I^/SEARCH^}
8518 is used to specify both source and
8519 library file paths. Use @option{^-aI^/SOURCE_SEARCH^}
8520 instead if you just want to specify
8521 source paths only and @option{^-aO^/OBJECT_SEARCH^}
8522 if you want to specify library paths
8526 @code{gnatmake} examines both an ALI file and its corresponding object file
8527 for consistency. If an ALI is more recent than its corresponding object,
8528 or if the object file is missing, the corresponding source will be recompiled.
8529 Note that @code{gnatmake} expects an ALI and the corresponding object file
8530 to be in the same directory.
8533 @code{gnatmake} will ignore any files whose ALI file is write-protected.
8534 This may conveniently be used to exclude standard libraries from
8535 consideration and in particular it means that the use of the
8536 @option{^-f^/FORCE_COMPILE^} switch will not recompile these files
8537 unless @option{^-a^/ALL_FILES^} is also specified.
8540 @code{gnatmake} has been designed to make the use of Ada libraries
8541 particularly convenient. Assume you have an Ada library organized
8542 as follows: @i{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
8543 of your Ada compilation units,
8544 whereas @i{^include-dir^[INCLUDE_DIR]^} contains the
8545 specs of these units, but no bodies. Then to compile a unit
8546 stored in @code{main.adb}, which uses this Ada library you would just type
8550 $ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
8553 $ gnatmake /SOURCE_SEARCH=@i{[INCLUDE_DIR]}
8554 /SKIP_MISSING=@i{[OBJ_DIR]} main
8559 Using @code{gnatmake} along with the
8560 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
8561 switch provides a mechanism for avoiding unnecessary rcompilations. Using
8563 you can update the comments/format of your
8564 source files without having to recompile everything. Note, however, that
8565 adding or deleting lines in a source files may render its debugging
8566 info obsolete. If the file in question is a spec, the impact is rather
8567 limited, as that debugging info will only be useful during the
8568 elaboration phase of your program. For bodies the impact can be more
8569 significant. In all events, your debugger will warn you if a source file
8570 is more recent than the corresponding object, and alert you to the fact
8571 that the debugging information may be out of date.
8574 @node How gnatmake Works
8575 @section How @code{gnatmake} Works
8578 Generally @code{gnatmake} automatically performs all necessary
8579 recompilations and you don't need to worry about how it works. However,
8580 it may be useful to have some basic understanding of the @code{gnatmake}
8581 approach and in particular to understand how it uses the results of
8582 previous compilations without incorrectly depending on them.
8584 First a definition: an object file is considered @dfn{up to date} if the
8585 corresponding ALI file exists and its time stamp predates that of the
8586 object file and if all the source files listed in the
8587 dependency section of this ALI file have time stamps matching those in
8588 the ALI file. This means that neither the source file itself nor any
8589 files that it depends on have been modified, and hence there is no need
8590 to recompile this file.
8592 @code{gnatmake} works by first checking if the specified main unit is up
8593 to date. If so, no compilations are required for the main unit. If not,
8594 @code{gnatmake} compiles the main program to build a new ALI file that
8595 reflects the latest sources. Then the ALI file of the main unit is
8596 examined to find all the source files on which the main program depends,
8597 and @code{gnatmake} recursively applies the above procedure on all these files.
8599 This process ensures that @code{gnatmake} only trusts the dependencies
8600 in an existing ALI file if they are known to be correct. Otherwise it
8601 always recompiles to determine a new, guaranteed accurate set of
8602 dependencies. As a result the program is compiled ``upside down'' from what may
8603 be more familiar as the required order of compilation in some other Ada
8604 systems. In particular, clients are compiled before the units on which
8605 they depend. The ability of GNAT to compile in any order is critical in
8606 allowing an order of compilation to be chosen that guarantees that
8607 @code{gnatmake} will recompute a correct set of new dependencies if
8610 When invoking @code{gnatmake} with several @var{file_names}, if a unit is
8611 imported by several of the executables, it will be recompiled at most once.
8613 Note: when using non-standard naming conventions
8614 (See @ref{Using Other File Names}), changing through a configuration pragmas
8615 file the version of a source and invoking @code{gnatmake} to recompile may
8616 have no effect, if the previous version of the source is still accessible
8617 by @code{gnatmake}. It may be necessary to use the switch ^-f^/FORCE_COMPILE^.
8619 @node Examples of gnatmake Usage
8620 @section Examples of @code{gnatmake} Usage
8623 @item gnatmake hello.adb
8624 Compile all files necessary to bind and link the main program
8625 @file{hello.adb} (containing unit @code{Hello}) and bind and link the
8626 resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
8628 @item gnatmake main1 main2 main3
8629 Compile all files necessary to bind and link the main programs
8630 @file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
8631 (containing unit @code{Main2}) and @file{main3.adb}
8632 (containing unit @code{Main3}) and bind and link the resulting object files
8633 to generate three executable files @file{^main1^MAIN1.EXE^},
8634 @file{^main2^MAIN2.EXE^}
8635 and @file{^main3^MAIN3.EXE^}.
8638 @item gnatmake -q Main_Unit -cargs -O2 -bargs -l
8642 @item gnatmake Main_Unit /QUIET
8643 /COMPILER_QUALIFIERS /OPTIMIZE=ALL
8644 /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
8646 Compile all files necessary to bind and link the main program unit
8647 @code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
8648 be done with optimization level 2 and the order of elaboration will be
8649 listed by the binder. @code{gnatmake} will operate in quiet mode, not
8650 displaying commands it is executing.
8654 @c *************************
8655 @node Improving Performance
8656 @chapter Improving Performance
8657 @cindex Improving performance
8660 This chapter presents several topics related to program performance.
8661 It first describes some of the tradeoffs that need to be considered
8662 and some of the techniques for making your program run faster.
8663 It then documents the @command{gnatelim} tool, which can reduce
8664 the size of program executables.
8668 * Performance Considerations::
8669 * Reducing the Size of Ada Executables with gnatelim::
8674 @c *****************************
8675 @node Performance Considerations
8676 @section Performance Considerations
8679 The GNAT system provides a number of options that allow a trade-off
8684 performance of the generated code
8687 speed of compilation
8690 minimization of dependences and recompilation
8693 the degree of run-time checking.
8697 The defaults (if no options are selected) aim at improving the speed
8698 of compilation and minimizing dependences, at the expense of performance
8699 of the generated code:
8706 no inlining of subprogram calls
8709 all run-time checks enabled except overflow and elaboration checks
8713 These options are suitable for most program development purposes. This
8714 chapter describes how you can modify these choices, and also provides
8715 some guidelines on debugging optimized code.
8718 * Controlling Run-Time Checks::
8719 * Use of Restrictions::
8720 * Optimization Levels::
8721 * Debugging Optimized Code::
8722 * Inlining of Subprograms::
8723 * Optimization and Strict Aliasing::
8725 * Coverage Analysis::
8729 @node Controlling Run-Time Checks
8730 @subsection Controlling Run-Time Checks
8733 By default, GNAT generates all run-time checks, except arithmetic overflow
8734 checking for integer operations and checks for access before elaboration on
8735 subprogram calls. The latter are not required in default mode, because all
8736 necessary checking is done at compile time.
8737 @cindex @option{-gnatp} (@code{gcc})
8738 @cindex @option{-gnato} (@code{gcc})
8739 Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
8740 be modified. @xref{Run-Time Checks}.
8742 Our experience is that the default is suitable for most development
8745 We treat integer overflow specially because these
8746 are quite expensive and in our experience are not as important as other
8747 run-time checks in the development process. Note that division by zero
8748 is not considered an overflow check, and divide by zero checks are
8749 generated where required by default.
8751 Elaboration checks are off by default, and also not needed by default, since
8752 GNAT uses a static elaboration analysis approach that avoids the need for
8753 run-time checking. This manual contains a full chapter discussing the issue
8754 of elaboration checks, and if the default is not satisfactory for your use,
8755 you should read this chapter.
8757 For validity checks, the minimal checks required by the Ada Reference
8758 Manual (for case statements and assignments to array elements) are on
8759 by default. These can be suppressed by use of the @option{-gnatVn} switch.
8760 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
8761 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
8762 it may be reasonable to routinely use @option{-gnatVn}. Validity checks
8763 are also suppressed entirely if @option{-gnatp} is used.
8765 @cindex Overflow checks
8766 @cindex Checks, overflow
8769 @cindex pragma Suppress
8770 @cindex pragma Unsuppress
8771 Note that the setting of the switches controls the default setting of
8772 the checks. They may be modified using either @code{pragma Suppress} (to
8773 remove checks) or @code{pragma Unsuppress} (to add back suppressed
8774 checks) in the program source.
8776 @node Use of Restrictions
8777 @subsection Use of Restrictions
8780 The use of pragma Restrictions allows you to control which features are
8781 permitted in your program. Apart from the obvious point that if you avoid
8782 relatively expensive features like finalization (enforceable by the use
8783 of pragma Restrictions (No_Finalization), the use of this pragma does not
8784 affect the generated code in most cases.
8786 One notable exception to this rule is that the possibility of task abort
8787 results in some distributed overhead, particularly if finalization or
8788 exception handlers are used. The reason is that certain sections of code
8789 have to be marked as non-abortable.
8791 If you use neither the @code{abort} statement, nor asynchronous transfer
8792 of control (@code{select .. then abort}), then this distributed overhead
8793 is removed, which may have a general positive effect in improving
8794 overall performance. Especially code involving frequent use of tasking
8795 constructs and controlled types will show much improved performance.
8796 The relevant restrictions pragmas are
8799 pragma Restrictions (No_Abort_Statements);
8800 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
8804 It is recommended that these restriction pragmas be used if possible. Note
8805 that this also means that you can write code without worrying about the
8806 possibility of an immediate abort at any point.
8808 @node Optimization Levels
8809 @subsection Optimization Levels
8810 @cindex @option{^-O^/OPTIMIZE^} (@code{gcc})
8813 The default is optimization off. This results in the fastest compile
8814 times, but GNAT makes absolutely no attempt to optimize, and the
8815 generated programs are considerably larger and slower than when
8816 optimization is enabled. You can use the
8818 @option{-O@var{n}} switch, where @var{n} is an integer from 0 to 3,
8821 @code{OPTIMIZE} qualifier
8823 to @code{gcc} to control the optimization level:
8826 @item ^-O0^/OPTIMIZE=NONE^
8827 No optimization (the default);
8828 generates unoptimized code but has
8829 the fastest compilation time.
8831 @item ^-O1^/OPTIMIZE=SOME^
8832 Medium level optimization;
8833 optimizes reasonably well but does not
8834 degrade compilation time significantly.
8836 @item ^-O2^/OPTIMIZE=ALL^
8838 @itemx /OPTIMIZE=DEVELOPMENT
8841 generates highly optimized code and has
8842 the slowest compilation time.
8844 @item ^-O3^/OPTIMIZE=INLINING^
8845 Full optimization as in @option{-O2},
8846 and also attempts automatic inlining of small
8847 subprograms within a unit (@pxref{Inlining of Subprograms}).
8851 Higher optimization levels perform more global transformations on the
8852 program and apply more expensive analysis algorithms in order to generate
8853 faster and more compact code. The price in compilation time, and the
8854 resulting improvement in execution time,
8855 both depend on the particular application and the hardware environment.
8856 You should experiment to find the best level for your application.
8858 Since the precise set of optimizations done at each level will vary from
8859 release to release (and sometime from target to target), it is best to think
8860 of the optimization settings in general terms.
8861 The @cite{Using GNU GCC} manual contains details about
8862 ^the @option{-O} settings and a number of @option{-f} options that^how to^
8863 individually enable or disable specific optimizations.
8865 Unlike some other compilation systems, ^@command{gcc}^GNAT^ has
8866 been tested extensively at all optimization levels. There are some bugs
8867 which appear only with optimization turned on, but there have also been
8868 bugs which show up only in @emph{unoptimized} code. Selecting a lower
8869 level of optimization does not improve the reliability of the code
8870 generator, which in practice is highly reliable at all optimization
8873 Note regarding the use of @option{-O3}: The use of this optimization level
8874 is generally discouraged with GNAT, since it often results in larger
8875 executables which run more slowly. See further discussion of this point
8876 in @pxref{Inlining of Subprograms}.
8879 @node Debugging Optimized Code
8880 @subsection Debugging Optimized Code
8881 @cindex Debugging optimized code
8882 @cindex Optimization and debugging
8885 Although it is possible to do a reasonable amount of debugging at
8887 non-zero optimization levels,
8888 the higher the level the more likely that
8891 @option{/OPTIMIZE} settings other than @code{NONE},
8892 such settings will make it more likely that
8894 source-level constructs will have been eliminated by optimization.
8895 For example, if a loop is strength-reduced, the loop
8896 control variable may be completely eliminated and thus cannot be
8897 displayed in the debugger.
8898 This can only happen at @option{-O2} or @option{-O3}.
8899 Explicit temporary variables that you code might be eliminated at
8900 ^level^setting^ @option{-O1} or higher.
8902 The use of the @option{^-g^/DEBUG^} switch,
8903 @cindex @option{^-g^/DEBUG^} (@code{gcc})
8904 which is needed for source-level debugging,
8905 affects the size of the program executable on disk,
8906 and indeed the debugging information can be quite large.
8907 However, it has no effect on the generated code (and thus does not
8908 degrade performance)
8910 Since the compiler generates debugging tables for a compilation unit before
8911 it performs optimizations, the optimizing transformations may invalidate some
8912 of the debugging data. You therefore need to anticipate certain
8913 anomalous situations that may arise while debugging optimized code.
8914 These are the most common cases:
8918 @i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next}
8920 the PC bouncing back and forth in the code. This may result from any of
8921 the following optimizations:
8925 @i{Common subexpression elimination:} using a single instance of code for a
8926 quantity that the source computes several times. As a result you
8927 may not be able to stop on what looks like a statement.
8930 @i{Invariant code motion:} moving an expression that does not change within a
8931 loop, to the beginning of the loop.
8934 @i{Instruction scheduling:} moving instructions so as to
8935 overlap loads and stores (typically) with other code, or in
8936 general to move computations of values closer to their uses. Often
8937 this causes you to pass an assignment statement without the assignment
8938 happening and then later bounce back to the statement when the
8939 value is actually needed. Placing a breakpoint on a line of code
8940 and then stepping over it may, therefore, not always cause all the
8941 expected side-effects.
8945 @i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which
8946 two identical pieces of code are merged and the program counter suddenly
8947 jumps to a statement that is not supposed to be executed, simply because
8948 it (and the code following) translates to the same thing as the code
8949 that @emph{was} supposed to be executed. This effect is typically seen in
8950 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
8951 a @code{break} in a C @code{^switch^switch^} statement.
8954 @i{The ``roving variable'':} The symptom is an unexpected value in a variable.
8955 There are various reasons for this effect:
8959 In a subprogram prologue, a parameter may not yet have been moved to its
8963 A variable may be dead, and its register re-used. This is
8964 probably the most common cause.
8967 As mentioned above, the assignment of a value to a variable may
8971 A variable may be eliminated entirely by value propagation or
8972 other means. In this case, GCC may incorrectly generate debugging
8973 information for the variable
8977 In general, when an unexpected value appears for a local variable or parameter
8978 you should first ascertain if that value was actually computed by
8979 your program, as opposed to being incorrectly reported by the debugger.
8981 array elements in an object designated by an access value
8982 are generally less of a problem, once you have ascertained that the access
8984 Typically, this means checking variables in the preceding code and in the
8985 calling subprogram to verify that the value observed is explainable from other
8986 values (one must apply the procedure recursively to those
8987 other values); or re-running the code and stopping a little earlier
8988 (perhaps before the call) and stepping to better see how the variable obtained
8989 the value in question; or continuing to step @emph{from} the point of the
8990 strange value to see if code motion had simply moved the variable's
8995 In light of such anomalies, a recommended technique is to use @option{-O0}
8996 early in the software development cycle, when extensive debugging capabilities
8997 are most needed, and then move to @option{-O1} and later @option{-O2} as
8998 the debugger becomes less critical.
8999 Whether to use the @option{^-g^/DEBUG^} switch in the release version is
9000 a release management issue.
9002 Note that if you use @option{-g} you can then use the @command{strip} program
9003 on the resulting executable,
9004 which removes both debugging information and global symbols.
9008 @node Inlining of Subprograms
9009 @subsection Inlining of Subprograms
9012 A call to a subprogram in the current unit is inlined if all the
9013 following conditions are met:
9017 The optimization level is at least @option{-O1}.
9020 The called subprogram is suitable for inlining: It must be small enough
9021 and not contain nested subprograms or anything else that @code{gcc}
9022 cannot support in inlined subprograms.
9025 The call occurs after the definition of the body of the subprogram.
9028 @cindex pragma Inline
9030 Either @code{pragma Inline} applies to the subprogram or it is
9031 small and automatic inlining (optimization level @option{-O3}) is
9036 Calls to subprograms in @code{with}'ed units are normally not inlined.
9037 To achieve this level of inlining, the following conditions must all be
9042 The optimization level is at least @option{-O1}.
9045 The called subprogram is suitable for inlining: It must be small enough
9046 and not contain nested subprograms or anything else @code{gcc} cannot
9047 support in inlined subprograms.
9050 The call appears in a body (not in a package spec).
9053 There is a @code{pragma Inline} for the subprogram.
9056 @cindex @option{-gnatn} (@code{gcc})
9057 The @option{^-gnatn^/INLINE^} switch
9058 is used in the @code{gcc} command line
9061 Note that specifying the @option{-gnatn} switch causes additional
9062 compilation dependencies. Consider the following:
9064 @smallexample @c ada
9084 With the default behavior (no @option{-gnatn} switch specified), the
9085 compilation of the @code{Main} procedure depends only on its own source,
9086 @file{main.adb}, and the spec of the package in file @file{r.ads}. This
9087 means that editing the body of @code{R} does not require recompiling
9090 On the other hand, the call @code{R.Q} is not inlined under these
9091 circumstances. If the @option{-gnatn} switch is present when @code{Main}
9092 is compiled, the call will be inlined if the body of @code{Q} is small
9093 enough, but now @code{Main} depends on the body of @code{R} in
9094 @file{r.adb} as well as on the spec. This means that if this body is edited,
9095 the main program must be recompiled. Note that this extra dependency
9096 occurs whether or not the call is in fact inlined by @code{gcc}.
9098 The use of front end inlining with @option{-gnatN} generates similar
9099 additional dependencies.
9101 @cindex @option{^-fno-inline^/INLINE=SUPPRESS^} (@code{gcc})
9102 Note: The @option{^-fno-inline^/INLINE=SUPPRESS^} switch
9103 can be used to prevent
9104 all inlining. This switch overrides all other conditions and ensures
9105 that no inlining occurs. The extra dependences resulting from
9106 @option{-gnatn} will still be active, even if
9107 this switch is used to suppress the resulting inlining actions.
9109 Note regarding the use of @option{-O3}: There is no difference in inlining
9110 behavior between @option{-O2} and @option{-O3} for subprograms with an explicit
9111 pragma @code{Inline} assuming the use of @option{-gnatn}
9112 or @option{-gnatN} (the switches that activate inlining). If you have used
9113 pragma @code{Inline} in appropriate cases, then it is usually much better
9114 to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which
9115 in this case only has the effect of inlining subprograms you did not
9116 think should be inlined. We often find that the use of @option{-O3} slows
9117 down code by performing excessive inlining, leading to increased instruction
9118 cache pressure from the increased code size. So the bottom line here is
9119 that you should not automatically assume that @option{-O3} is better than
9120 @option{-O2}, and indeed you should use @option{-O3} only if tests show that
9121 it actually improves performance.
9123 @node Optimization and Strict Aliasing
9124 @subsection Optimization and Strict Aliasing
9126 @cindex Strict Aliasing
9127 @cindex No_Strict_Aliasing
9130 The strong typing capabilities of Ada allow an optimizer to generate
9131 efficient code in situations where other languages would be forced to
9132 make worst case assumptions preventing such optimizations. Consider
9133 the following example:
9135 @smallexample @c ada
9138 type Int1 is new Integer;
9139 type Int2 is new Integer;
9140 type Int1A is access Int1;
9141 type Int2A is access Int2;
9148 for J in Data'Range loop
9149 if Data (J) = Int1V.all then
9150 Int2V.all := Int2V.all + 1;
9159 In this example, since the variable @code{Int1V} can only access objects
9160 of type @code{Int1}, and @code{Int2V} can only access objects of type
9161 @code{Int2}, there is no possibility that the assignment to
9162 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
9163 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
9164 for all iterations of the loop and avoid the extra memory reference
9165 required to dereference it each time through the loop.
9167 This kind of optimziation, called strict aliasing analysis, is
9168 triggered by specifying an optimization level of @option{-O2} or
9169 higher and allows @code{GNAT} to generate more efficient code
9170 when access values are involved.
9172 However, although this optimization is always correct in terms of
9173 the formal semantics of the Ada Reference Manual, difficulties can
9174 arise if features like @code{Unchecked_Conversion} are used to break
9175 the typing system. Consider the following complete program example:
9177 @smallexample @c ada
9180 type int1 is new integer;
9181 type int2 is new integer;
9182 type a1 is access int1;
9183 type a2 is access int2;
9188 function to_a2 (Input : a1) return a2;
9191 with Unchecked_Conversion;
9193 function to_a2 (Input : a1) return a2 is
9195 new Unchecked_Conversion (a1, a2);
9197 return to_a2u (Input);
9203 with Text_IO; use Text_IO;
9205 v1 : a1 := new int1;
9206 v2 : a2 := to_a2 (v1);
9210 put_line (int1'image (v1.all));
9216 This program prints out 0 in @code{-O0} or @code{-O1}
9217 mode, but it prints out 1 in @code{-O2} mode. That's
9218 because in strict aliasing mode, the compiler can and
9219 does assume that the assignment to @code{v2.all} could not
9220 affect the value of @code{v1.all}, since different types
9223 This behavior is not a case of non-conformance with the standard, since
9224 the Ada RM specifies that an unchecked conversion where the resulting
9225 bit pattern is not a correct value of the target type can result in an
9226 abnormal value and attempting to reference an abnormal value makes the
9227 execution of a program erroneous. That's the case here since the result
9228 does not point to an object of type @code{int2}. This means that the
9229 effect is entirely unpredictable.
9231 However, although that explanation may satisfy a language
9232 lawyer, in practice an applications programmer expects an
9233 unchecked conversion involving pointers to create true
9234 aliases and the behavior of printing 1 seems plain wrong.
9235 In this case, the strict aliasing optimization is unwelcome.
9237 Indeed the compiler recognizes this possibility, and the
9238 unchecked conversion generates a warning:
9241 p2.adb:5:07: warning: possible aliasing problem with type "a2"
9242 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
9243 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
9247 Unfortunately the problem is recognized when compiling the body of
9248 package @code{p2}, but the actual "bad" code is generated while
9249 compiling the body of @code{m} and this latter compilation does not see
9250 the suspicious @code{Unchecked_Conversion}.
9252 As implied by the warning message, there are approaches you can use to
9253 avoid the unwanted strict aliasing optimization in a case like this.
9255 One possibility is to simply avoid the use of @code{-O2}, but
9256 that is a bit drastic, since it throws away a number of useful
9257 optimizations that do not involve strict aliasing assumptions.
9259 A less drastic approach is to compile the program using the
9260 option @code{-fno-strict-aliasing}. Actually it is only the
9261 unit containing the dereferencing of the suspicious pointer
9262 that needs to be compiled. So in this case, if we compile
9263 unit @code{m} with this switch, then we get the expected
9264 value of zero printed. Analyzing which units might need
9265 the switch can be painful, so a more reasonable approach
9266 is to compile the entire program with options @code{-O2}
9267 and @code{-fno-strict-aliasing}. If the performance is
9268 satisfactory with this combination of options, then the
9269 advantage is that the entire issue of possible "wrong"
9270 optimization due to strict aliasing is avoided.
9272 To avoid the use of compiler switches, the configuration
9273 pragma @code{No_Strict_Aliasing} with no parameters may be
9274 used to specify that for all access types, the strict
9275 aliasing optimization should be suppressed.
9277 However, these approaches are still overkill, in that they causes
9278 all manipulations of all access values to be deoptimized. A more
9279 refined approach is to concentrate attention on the specific
9280 access type identified as problematic.
9282 First, if a careful analysis of uses of the pointer shows
9283 that there are no possible problematic references, then
9284 the warning can be suppressed by bracketing the
9285 instantiation of @code{Unchecked_Conversion} to turn
9288 @smallexample @c ada
9289 pragma Warnings (Off);
9291 new Unchecked_Conversion (a1, a2);
9292 pragma Warnings (On);
9296 Of course that approach is not appropriate for this particular
9297 example, since indeed there is a problematic reference. In this
9298 case we can take one of two other approaches.
9300 The first possibility is to move the instantiation of unchecked
9301 conversion to the unit in which the type is declared. In
9302 this example, we would move the instantiation of
9303 @code{Unchecked_Conversion} from the body of package
9304 @code{p2} to the spec of package @code{p1}. Now the
9305 warning disappears. That's because any use of the
9306 access type knows there is a suspicious unchecked
9307 conversion, and the strict aliasing optimization
9308 is automatically suppressed for the type.
9310 If it is not practical to move the unchecked conversion to the same unit
9311 in which the destination access type is declared (perhaps because the
9312 source type is not visible in that unit), you may use pragma
9313 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
9314 same declarative sequence as the declaration of the access type:
9316 @smallexample @c ada
9317 type a2 is access int2;
9318 pragma No_Strict_Aliasing (a2);
9322 Here again, the compiler now knows that the strict aliasing optimization
9323 should be suppressed for any reference to type @code{a2} and the
9324 expected behavior is obtained.
9326 Finally, note that although the compiler can generate warnings for
9327 simple cases of unchecked conversions, there are tricker and more
9328 indirect ways of creating type incorrect aliases which the compiler
9329 cannot detect. Examples are the use of address overlays and unchecked
9330 conversions involving composite types containing access types as
9331 components. In such cases, no warnings are generated, but there can
9332 still be aliasing problems. One safe coding practice is to forbid the
9333 use of address clauses for type overlaying, and to allow unchecked
9334 conversion only for primitive types. This is not really a significant
9335 restriction since any possible desired effect can be achieved by
9336 unchecked conversion of access values.
9339 @node Coverage Analysis
9340 @subsection Coverage Analysis
9343 GNAT supports the Digital Performance Coverage Analyzer (PCA), which allows
9344 the user to determine the distribution of execution time across a program,
9345 @pxref{Profiling} for details of usage.
9348 @node Reducing the Size of Ada Executables with gnatelim
9349 @section Reducing the Size of Ada Executables with @code{gnatelim}
9353 This section describes @command{gnatelim}, a tool which detects unused
9354 subprograms and helps the compiler to create a smaller executable for your
9359 * Running gnatelim::
9360 * Correcting the List of Eliminate Pragmas::
9361 * Making Your Executables Smaller::
9362 * Summary of the gnatelim Usage Cycle::
9365 @node About gnatelim
9366 @subsection About @code{gnatelim}
9369 When a program shares a set of Ada
9370 packages with other programs, it may happen that this program uses
9371 only a fraction of the subprograms defined in these packages. The code
9372 created for these unused subprograms increases the size of the executable.
9374 @code{gnatelim} tracks unused subprograms in an Ada program and
9375 outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the
9376 subprograms that are declared but never called. By placing the list of
9377 @code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and
9378 recompiling your program, you may decrease the size of its executable,
9379 because the compiler will not generate the code for 'eliminated' subprograms.
9380 See GNAT Reference Manual for more information about this pragma.
9382 @code{gnatelim} needs as its input data the name of the main subprogram
9383 and a bind file for a main subprogram.
9385 To create a bind file for @code{gnatelim}, run @code{gnatbind} for
9386 the main subprogram. @code{gnatelim} can work with both Ada and C
9387 bind files; when both are present, it uses the Ada bind file.
9388 The following commands will build the program and create the bind file:
9391 $ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
9392 $ gnatbind main_prog
9395 Note that @code{gnatelim} needs neither object nor ALI files.
9397 @node Running gnatelim
9398 @subsection Running @code{gnatelim}
9401 @code{gnatelim} has the following command-line interface:
9404 $ gnatelim [options] name
9408 @code{name} should be a name of a source file that contains the main subprogram
9409 of a program (partition).
9411 @code{gnatelim} has the following switches:
9416 @cindex @option{^-q^/QUIET^} (@command{gnatelim})
9417 Quiet mode: by default @code{gnatelim} outputs to the standard error
9418 stream the number of program units left to be processed. This option turns
9422 @cindex @option{^-v^/VERBOSE^} (@command{gnatelim})
9423 Verbose mode: @code{gnatelim} version information is printed as Ada
9424 comments to the standard output stream. Also, in addition to the number of
9425 program units left @code{gnatelim} will output the name of the current unit
9429 @cindex @option{^-a^/ALL^} (@command{gnatelim})
9430 Also look for subprograms from the GNAT run time that can be eliminated. Note
9431 that when @file{gnat.adc} is produced using this switch, the entire program
9432 must be recompiled with switch @option{^-a^/ALL_FILES^} to @code{gnatmake}.
9434 @item ^-I^/INCLUDE_DIRS=^@var{dir}
9435 @cindex @option{^-I^/INCLUDE_DIRS^} (@command{gnatelim})
9436 When looking for source files also look in directory @var{dir}. Specifying
9437 @option{^-I-^/INCLUDE_DIRS=-^} instructs @code{gnatelim} not to look for
9438 sources in the current directory.
9440 @item ^-b^/BIND_FILE=^@var{bind_file}
9441 @cindex @option{^-b^/BIND_FILE^} (@command{gnatelim})
9442 Specifies @var{bind_file} as the bind file to process. If not set, the name
9443 of the bind file is computed from the full expanded Ada name
9444 of a main subprogram.
9446 @item ^-C^/CONFIG_FILE=^@var{config_file}
9447 @cindex @option{^-C^/CONFIG_FILE^} (@command{gnatelim})
9448 Specifies a file @var{config_file} that contains configuration pragmas. The
9449 file must be specified with full path.
9451 @item ^--GCC^/COMPILER^=@var{compiler_name}
9452 @cindex @option{^-GCC^/COMPILER^} (@command{gnatelim})
9453 Instructs @code{gnatelim} to use specific @code{gcc} compiler instead of one
9454 available on the path.
9456 @item ^--GNATMAKE^/GNATMAKE^=@var{gnatmake_name}
9457 @cindex @option{^--GNATMAKE^/GNATMAKE^} (@command{gnatelim})
9458 Instructs @code{gnatelim} to use specific @code{gnatmake} instead of one
9459 available on the path.
9462 @cindex @option{-d@var{x}} (@command{gnatelim})
9463 Activate internal debugging switches. @var{x} is a letter or digit, or
9464 string of letters or digits, which specifies the type of debugging
9465 mode desired. Normally these are used only for internal development
9466 or system debugging purposes. You can find full documentation for these
9467 switches in the spec of the @code{Gnatelim} unit in the compiler
9468 source file @file{gnatelim.ads}.
9472 @code{gnatelim} sends its output to the standard output stream, and all the
9473 tracing and debug information is sent to the standard error stream.
9474 In order to produce a proper GNAT configuration file
9475 @file{gnat.adc}, redirection must be used:
9479 $ PIPE GNAT ELIM MAIN_PROG.ADB > GNAT.ADC
9482 $ gnatelim main_prog.adb > gnat.adc
9491 $ gnatelim main_prog.adb >> gnat.adc
9495 in order to append the @code{gnatelim} output to the existing contents of
9499 @node Correcting the List of Eliminate Pragmas
9500 @subsection Correcting the List of Eliminate Pragmas
9503 In some rare cases @code{gnatelim} may try to eliminate
9504 subprograms that are actually called in the program. In this case, the
9505 compiler will generate an error message of the form:
9508 file.adb:106:07: cannot call eliminated subprogram "My_Prog"
9512 You will need to manually remove the wrong @code{Eliminate} pragmas from
9513 the @file{gnat.adc} file. You should recompile your program
9514 from scratch after that, because you need a consistent @file{gnat.adc} file
9515 during the entire compilation.
9518 @node Making Your Executables Smaller
9519 @subsection Making Your Executables Smaller
9522 In order to get a smaller executable for your program you now have to
9523 recompile the program completely with the new @file{gnat.adc} file
9524 created by @code{gnatelim} in your current directory:
9527 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
9531 (Use the @option{^-f^/FORCE_COMPILE^} option for @command{gnatmake} to
9532 recompile everything
9533 with the set of pragmas @code{Eliminate} that you have obtained with
9534 @command{gnatelim}).
9536 Be aware that the set of @code{Eliminate} pragmas is specific to each
9537 program. It is not recommended to merge sets of @code{Eliminate}
9538 pragmas created for different programs in one @file{gnat.adc} file.
9540 @node Summary of the gnatelim Usage Cycle
9541 @subsection Summary of the gnatelim Usage Cycle
9544 Here is a quick summary of the steps to be taken in order to reduce
9545 the size of your executables with @code{gnatelim}. You may use
9546 other GNAT options to control the optimization level,
9547 to produce the debugging information, to set search path, etc.
9554 $ gnatmake ^-c main_prog^/ACTIONS=COMPILE MAIN_PROG^
9555 $ gnatbind main_prog
9559 Generate a list of @code{Eliminate} pragmas
9562 $ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
9565 $ gnatelim main_prog >[>] gnat.adc
9570 Recompile the application
9573 $ gnatmake ^-f main_prog^/FORCE_COMPILE MAIN_PROG^
9581 @c ********************************
9582 @node Renaming Files Using gnatchop
9583 @chapter Renaming Files Using @code{gnatchop}
9587 This chapter discusses how to handle files with multiple units by using
9588 the @code{gnatchop} utility. This utility is also useful in renaming
9589 files to meet the standard GNAT default file naming conventions.
9592 * Handling Files with Multiple Units::
9593 * Operating gnatchop in Compilation Mode::
9594 * Command Line for gnatchop::
9595 * Switches for gnatchop::
9596 * Examples of gnatchop Usage::
9599 @node Handling Files with Multiple Units
9600 @section Handling Files with Multiple Units
9603 The basic compilation model of GNAT requires that a file submitted to the
9604 compiler have only one unit and there be a strict correspondence
9605 between the file name and the unit name.
9607 The @code{gnatchop} utility allows both of these rules to be relaxed,
9608 allowing GNAT to process files which contain multiple compilation units
9609 and files with arbitrary file names. @code{gnatchop}
9610 reads the specified file and generates one or more output files,
9611 containing one unit per file. The unit and the file name correspond,
9612 as required by GNAT.
9614 If you want to permanently restructure a set of ``foreign'' files so that
9615 they match the GNAT rules, and do the remaining development using the
9616 GNAT structure, you can simply use @command{gnatchop} once, generate the
9617 new set of files and work with them from that point on.
9619 Alternatively, if you want to keep your files in the ``foreign'' format,
9620 perhaps to maintain compatibility with some other Ada compilation
9621 system, you can set up a procedure where you use @command{gnatchop} each
9622 time you compile, regarding the source files that it writes as temporary
9623 files that you throw away.
9626 @node Operating gnatchop in Compilation Mode
9627 @section Operating gnatchop in Compilation Mode
9630 The basic function of @code{gnatchop} is to take a file with multiple units
9631 and split it into separate files. The boundary between files is reasonably
9632 clear, except for the issue of comments and pragmas. In default mode, the
9633 rule is that any pragmas between units belong to the previous unit, except
9634 that configuration pragmas always belong to the following unit. Any comments
9635 belong to the following unit. These rules
9636 almost always result in the right choice of
9637 the split point without needing to mark it explicitly and most users will
9638 find this default to be what they want. In this default mode it is incorrect to
9639 submit a file containing only configuration pragmas, or one that ends in
9640 configuration pragmas, to @code{gnatchop}.
9642 However, using a special option to activate ``compilation mode'',
9644 can perform another function, which is to provide exactly the semantics
9645 required by the RM for handling of configuration pragmas in a compilation.
9646 In the absence of configuration pragmas (at the main file level), this
9647 option has no effect, but it causes such configuration pragmas to be handled
9648 in a quite different manner.
9650 First, in compilation mode, if @code{gnatchop} is given a file that consists of
9651 only configuration pragmas, then this file is appended to the
9652 @file{gnat.adc} file in the current directory. This behavior provides
9653 the required behavior described in the RM for the actions to be taken
9654 on submitting such a file to the compiler, namely that these pragmas
9655 should apply to all subsequent compilations in the same compilation
9656 environment. Using GNAT, the current directory, possibly containing a
9657 @file{gnat.adc} file is the representation
9658 of a compilation environment. For more information on the
9659 @file{gnat.adc} file, see the section on handling of configuration
9660 pragmas @pxref{Handling of Configuration Pragmas}.
9662 Second, in compilation mode, if @code{gnatchop}
9663 is given a file that starts with
9664 configuration pragmas, and contains one or more units, then these
9665 configuration pragmas are prepended to each of the chopped files. This
9666 behavior provides the required behavior described in the RM for the
9667 actions to be taken on compiling such a file, namely that the pragmas
9668 apply to all units in the compilation, but not to subsequently compiled
9671 Finally, if configuration pragmas appear between units, they are appended
9672 to the previous unit. This results in the previous unit being illegal,
9673 since the compiler does not accept configuration pragmas that follow
9674 a unit. This provides the required RM behavior that forbids configuration
9675 pragmas other than those preceding the first compilation unit of a
9678 For most purposes, @code{gnatchop} will be used in default mode. The
9679 compilation mode described above is used only if you need exactly
9680 accurate behavior with respect to compilations, and you have files
9681 that contain multiple units and configuration pragmas. In this
9682 circumstance the use of @code{gnatchop} with the compilation mode
9683 switch provides the required behavior, and is for example the mode
9684 in which GNAT processes the ACVC tests.
9686 @node Command Line for gnatchop
9687 @section Command Line for @code{gnatchop}
9690 The @code{gnatchop} command has the form:
9693 $ gnatchop switches @var{file name} [@var{file name} @var{file name} ...]
9698 The only required argument is the file name of the file to be chopped.
9699 There are no restrictions on the form of this file name. The file itself
9700 contains one or more Ada units, in normal GNAT format, concatenated
9701 together. As shown, more than one file may be presented to be chopped.
9703 When run in default mode, @code{gnatchop} generates one output file in
9704 the current directory for each unit in each of the files.
9706 @var{directory}, if specified, gives the name of the directory to which
9707 the output files will be written. If it is not specified, all files are
9708 written to the current directory.
9710 For example, given a
9711 file called @file{hellofiles} containing
9713 @smallexample @c ada
9718 with Text_IO; use Text_IO;
9731 $ gnatchop ^hellofiles^HELLOFILES.^
9735 generates two files in the current directory, one called
9736 @file{hello.ads} containing the single line that is the procedure spec,
9737 and the other called @file{hello.adb} containing the remaining text. The
9738 original file is not affected. The generated files can be compiled in
9742 When gnatchop is invoked on a file that is empty or that contains only empty
9743 lines and/or comments, gnatchop will not fail, but will not produce any
9746 For example, given a
9747 file called @file{toto.txt} containing
9749 @smallexample @c ada
9761 $ gnatchop ^toto.txt^TOT.TXT^
9765 will not produce any new file and will result in the following warnings:
9768 toto.txt:1:01: warning: empty file, contains no compilation units
9769 no compilation units found
9770 no source files written
9773 @node Switches for gnatchop
9774 @section Switches for @code{gnatchop}
9777 @command{gnatchop} recognizes the following switches:
9782 @item ^-c^/COMPILATION^
9783 @cindex @option{^-c^/COMPILATION^} (@code{gnatchop})
9784 Causes @code{gnatchop} to operate in compilation mode, in which
9785 configuration pragmas are handled according to strict RM rules. See
9786 previous section for a full description of this mode.
9790 This passes the given @option{-gnatxxx} switch to @code{gnat} which is
9791 used to parse the given file. Not all @code{xxx} options make sense,
9792 but for example, the use of @option{-gnati2} allows @code{gnatchop} to
9793 process a source file that uses Latin-2 coding for identifiers.
9797 Causes @code{gnatchop} to generate a brief help summary to the standard
9798 output file showing usage information.
9800 @item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
9801 @cindex @option{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
9802 Limit generated file names to the specified number @code{mm}
9804 This is useful if the
9805 resulting set of files is required to be interoperable with systems
9806 which limit the length of file names.
9808 If no value is given, or
9809 if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
9810 a default of 39, suitable for OpenVMS Alpha
9814 No space is allowed between the @option{-k} and the numeric value. The numeric
9815 value may be omitted in which case a default of @option{-k8},
9817 with DOS-like file systems, is used. If no @option{-k} switch
9819 there is no limit on the length of file names.
9822 @item ^-p^/PRESERVE^
9823 @cindex @option{^-p^/PRESERVE^} (@code{gnatchop})
9824 Causes the file ^modification^creation^ time stamp of the input file to be
9825 preserved and used for the time stamp of the output file(s). This may be
9826 useful for preserving coherency of time stamps in an environment where
9827 @code{gnatchop} is used as part of a standard build process.
9830 @cindex @option{^-q^/QUIET^} (@code{gnatchop})
9831 Causes output of informational messages indicating the set of generated
9832 files to be suppressed. Warnings and error messages are unaffected.
9834 @item ^-r^/REFERENCE^
9835 @cindex @option{^-r^/REFERENCE^} (@code{gnatchop})
9836 @findex Source_Reference
9837 Generate @code{Source_Reference} pragmas. Use this switch if the output
9838 files are regarded as temporary and development is to be done in terms
9839 of the original unchopped file. This switch causes
9840 @code{Source_Reference} pragmas to be inserted into each of the
9841 generated files to refers back to the original file name and line number.
9842 The result is that all error messages refer back to the original
9844 In addition, the debugging information placed into the object file (when
9845 the @option{^-g^/DEBUG^} switch of @code{gcc} or @code{gnatmake} is specified)
9846 also refers back to this original file so that tools like profilers and
9847 debuggers will give information in terms of the original unchopped file.
9849 If the original file to be chopped itself contains
9850 a @code{Source_Reference}
9851 pragma referencing a third file, then gnatchop respects
9852 this pragma, and the generated @code{Source_Reference} pragmas
9853 in the chopped file refer to the original file, with appropriate
9854 line numbers. This is particularly useful when @code{gnatchop}
9855 is used in conjunction with @code{gnatprep} to compile files that
9856 contain preprocessing statements and multiple units.
9859 @cindex @option{^-v^/VERBOSE^} (@code{gnatchop})
9860 Causes @code{gnatchop} to operate in verbose mode. The version
9861 number and copyright notice are output, as well as exact copies of
9862 the gnat1 commands spawned to obtain the chop control information.
9864 @item ^-w^/OVERWRITE^
9865 @cindex @option{^-w^/OVERWRITE^} (@code{gnatchop})
9866 Overwrite existing file names. Normally @code{gnatchop} regards it as a
9867 fatal error if there is already a file with the same name as a
9868 file it would otherwise output, in other words if the files to be
9869 chopped contain duplicated units. This switch bypasses this
9870 check, and causes all but the last instance of such duplicated
9871 units to be skipped.
9875 @cindex @option{--GCC=} (@code{gnatchop})
9876 Specify the path of the GNAT parser to be used. When this switch is used,
9877 no attempt is made to add the prefix to the GNAT parser executable.
9881 @node Examples of gnatchop Usage
9882 @section Examples of @code{gnatchop} Usage
9886 @item gnatchop /OVERWRITE HELLO_S.ADA [PRERELEASE.FILES]
9889 @item gnatchop -w hello_s.ada prerelease/files
9892 Chops the source file @file{hello_s.ada}. The output files will be
9893 placed in the directory @file{^prerelease/files^[PRERELEASE.FILES]^},
9895 files with matching names in that directory (no files in the current
9896 directory are modified).
9898 @item gnatchop ^archive^ARCHIVE.^
9899 Chops the source file @file{^archive^ARCHIVE.^}
9900 into the current directory. One
9901 useful application of @code{gnatchop} is in sending sets of sources
9902 around, for example in email messages. The required sources are simply
9903 concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
9905 @code{gnatchop} is used at the other end to reconstitute the original
9908 @item gnatchop file1 file2 file3 direc
9909 Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
9910 the resulting files in the directory @file{direc}. Note that if any units
9911 occur more than once anywhere within this set of files, an error message
9912 is generated, and no files are written. To override this check, use the
9913 @option{^-w^/OVERWRITE^} switch,
9914 in which case the last occurrence in the last file will
9915 be the one that is output, and earlier duplicate occurrences for a given
9916 unit will be skipped.
9919 @node Configuration Pragmas
9920 @chapter Configuration Pragmas
9921 @cindex Configuration pragmas
9922 @cindex Pragmas, configuration
9925 In Ada 95, configuration pragmas include those pragmas described as
9926 such in the Ada 95 Reference Manual, as well as
9927 implementation-dependent pragmas that are configuration pragmas. See the
9928 individual descriptions of pragmas in the GNAT Reference Manual for
9929 details on these additional GNAT-specific configuration pragmas. Most
9930 notably, the pragma @code{Source_File_Name}, which allows
9931 specifying non-default names for source files, is a configuration
9932 pragma. The following is a complete list of configuration pragmas
9933 recognized by @code{GNAT}:
9945 External_Name_Casing
9946 Float_Representation
9953 Propagate_Exceptions
9962 Task_Dispatching_Policy
9971 * Handling of Configuration Pragmas::
9972 * The Configuration Pragmas Files::
9975 @node Handling of Configuration Pragmas
9976 @section Handling of Configuration Pragmas
9978 Configuration pragmas may either appear at the start of a compilation
9979 unit, in which case they apply only to that unit, or they may apply to
9980 all compilations performed in a given compilation environment.
9982 GNAT also provides the @code{gnatchop} utility to provide an automatic
9983 way to handle configuration pragmas following the semantics for
9984 compilations (that is, files with multiple units), described in the RM.
9985 See section @pxref{Operating gnatchop in Compilation Mode} for details.
9986 However, for most purposes, it will be more convenient to edit the
9987 @file{gnat.adc} file that contains configuration pragmas directly,
9988 as described in the following section.
9990 @node The Configuration Pragmas Files
9991 @section The Configuration Pragmas Files
9992 @cindex @file{gnat.adc}
9995 In GNAT a compilation environment is defined by the current
9996 directory at the time that a compile command is given. This current
9997 directory is searched for a file whose name is @file{gnat.adc}. If
9998 this file is present, it is expected to contain one or more
9999 configuration pragmas that will be applied to the current compilation.
10000 However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
10003 Configuration pragmas may be entered into the @file{gnat.adc} file
10004 either by running @code{gnatchop} on a source file that consists only of
10005 configuration pragmas, or more conveniently by
10006 direct editing of the @file{gnat.adc} file, which is a standard format
10009 In addition to @file{gnat.adc}, one additional file containing configuration
10010 pragmas may be applied to the current compilation using the switch
10011 @option{-gnatec}@var{path}. @var{path} must designate an existing file that
10012 contains only configuration pragmas. These configuration pragmas are
10013 in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
10014 is present and switch @option{-gnatA} is not used).
10016 It is allowed to specify several switches @option{-gnatec}, however only
10017 the last one on the command line will be taken into account.
10019 If you are using project file, a separate mechanism is provided using
10020 project attributes, see @ref{Specifying Configuration Pragmas} for more
10024 Of special interest to GNAT OpenVMS Alpha is the following
10025 configuration pragma:
10027 @smallexample @c ada
10029 pragma Extend_System (Aux_DEC);
10034 In the presence of this pragma, GNAT adds to the definition of the
10035 predefined package SYSTEM all the additional types and subprograms that are
10036 defined in DEC Ada. See @pxref{Compatibility with DEC Ada} for details.
10039 @node Handling Arbitrary File Naming Conventions Using gnatname
10040 @chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
10041 @cindex Arbitrary File Naming Conventions
10044 * Arbitrary File Naming Conventions::
10045 * Running gnatname::
10046 * Switches for gnatname::
10047 * Examples of gnatname Usage::
10050 @node Arbitrary File Naming Conventions
10051 @section Arbitrary File Naming Conventions
10054 The GNAT compiler must be able to know the source file name of a compilation
10055 unit. When using the standard GNAT default file naming conventions
10056 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
10057 does not need additional information.
10060 When the source file names do not follow the standard GNAT default file naming
10061 conventions, the GNAT compiler must be given additional information through
10062 a configuration pragmas file (see @ref{Configuration Pragmas})
10064 When the non standard file naming conventions are well-defined,
10065 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
10066 (see @ref{Alternative File Naming Schemes}) may be sufficient. However,
10067 if the file naming conventions are irregular or arbitrary, a number
10068 of pragma @code{Source_File_Name} for individual compilation units
10070 To help maintain the correspondence between compilation unit names and
10071 source file names within the compiler,
10072 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
10075 @node Running gnatname
10076 @section Running @code{gnatname}
10079 The usual form of the @code{gnatname} command is
10082 $ gnatname [@var{switches}] @var{naming_pattern} [@var{naming_patterns}]
10086 All of the arguments are optional. If invoked without any argument,
10087 @code{gnatname} will display its usage.
10090 When used with at least one naming pattern, @code{gnatname} will attempt to
10091 find all the compilation units in files that follow at least one of the
10092 naming patterns. To find these compilation units,
10093 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
10097 One or several Naming Patterns may be given as arguments to @code{gnatname}.
10098 Each Naming Pattern is enclosed between double quotes.
10099 A Naming Pattern is a regular expression similar to the wildcard patterns
10100 used in file names by the Unix shells or the DOS prompt.
10103 Examples of Naming Patterns are
10112 For a more complete description of the syntax of Naming Patterns,
10113 see the second kind of regular expressions described in @file{g-regexp.ads}
10114 (the ``Glob'' regular expressions).
10117 When invoked with no switches, @code{gnatname} will create a configuration
10118 pragmas file @file{gnat.adc} in the current working directory, with pragmas
10119 @code{Source_File_Name} for each file that contains a valid Ada unit.
10121 @node Switches for gnatname
10122 @section Switches for @code{gnatname}
10125 Switches for @code{gnatname} must precede any specified Naming Pattern.
10128 You may specify any of the following switches to @code{gnatname}:
10133 @item ^-c^/CONFIG_FILE=^@file{file}
10134 @cindex @option{^-c^/CONFIG_FILE^} (@code{gnatname})
10135 Create a configuration pragmas file @file{file} (instead of the default
10138 There may be zero, one or more space between @option{-c} and
10141 @file{file} may include directory information. @file{file} must be
10142 writable. There may be only one switch @option{^-c^/CONFIG_FILE^}.
10143 When a switch @option{^-c^/CONFIG_FILE^} is
10144 specified, no switch @option{^-P^/PROJECT_FILE^} may be specified (see below).
10146 @item ^-d^/SOURCE_DIRS=^@file{dir}
10147 @cindex @option{^-d^/SOURCE_DIRS^} (@code{gnatname})
10148 Look for source files in directory @file{dir}. There may be zero, one or more
10149 spaces between @option{^-d^/SOURCE_DIRS=^} and @file{dir}.
10150 When a switch @option{^-d^/SOURCE_DIRS^}
10151 is specified, the current working directory will not be searched for source
10152 files, unless it is explicitly specified with a @option{^-d^/SOURCE_DIRS^}
10153 or @option{^-D^/DIR_FILES^} switch.
10154 Several switches @option{^-d^/SOURCE_DIRS^} may be specified.
10155 If @file{dir} is a relative path, it is relative to the directory of
10156 the configuration pragmas file specified with switch
10157 @option{^-c^/CONFIG_FILE^},
10158 or to the directory of the project file specified with switch
10159 @option{^-P^/PROJECT_FILE^} or,
10160 if neither switch @option{^-c^/CONFIG_FILE^}
10161 nor switch @option{^-P^/PROJECT_FILE^} are specified, it is relative to the
10162 current working directory. The directory
10163 specified with switch @option{^-d^/SOURCE_DIRS^} must exist and be readable.
10165 @item ^-D^/DIRS_FILE=^@file{file}
10166 @cindex @option{^-D^/DIRS_FILE^} (@code{gnatname})
10167 Look for source files in all directories listed in text file @file{file}.
10168 There may be zero, one or more spaces between @option{^-D^/DIRS_FILE=^}
10170 @file{file} must be an existing, readable text file.
10171 Each non empty line in @file{file} must be a directory.
10172 Specifying switch @option{^-D^/DIRS_FILE^} is equivalent to specifying as many
10173 switches @option{^-d^/SOURCE_DIRS^} as there are non empty lines in
10176 @item ^-f^/FOREIGN_PATTERN=^@file{pattern}
10177 @cindex @option{^-f^/FOREIGN_PATTERN^} (@code{gnatname})
10178 Foreign patterns. Using this switch, it is possible to add sources of languages
10179 other than Ada to the list of sources of a project file.
10180 It is only useful if a ^-P^/PROJECT_FILE^ switch is used.
10183 gnatname ^-Pprj -f"*.c"^/PROJECT_FILE=PRJ /FOREIGN_PATTERN=*.C^ "*.ada"
10186 will look for Ada units in all files with the @file{.ada} extension,
10187 and will add to the list of file for project @file{prj.gpr} the C files
10188 with extension ".^c^C^".
10191 @cindex @option{^-h^/HELP^} (@code{gnatname})
10192 Output usage (help) information. The output is written to @file{stdout}.
10194 @item ^-P^/PROJECT_FILE=^@file{proj}
10195 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatname})
10196 Create or update project file @file{proj}. There may be zero, one or more space
10197 between @option{-P} and @file{proj}. @file{proj} may include directory
10198 information. @file{proj} must be writable.
10199 There may be only one switch @option{^-P^/PROJECT_FILE^}.
10200 When a switch @option{^-P^/PROJECT_FILE^} is specified,
10201 no switch @option{^-c^/CONFIG_FILE^} may be specified.
10203 @item ^-v^/VERBOSE^
10204 @cindex @option{^-v^/VERBOSE^} (@code{gnatname})
10205 Verbose mode. Output detailed explanation of behavior to @file{stdout}.
10206 This includes name of the file written, the name of the directories to search
10207 and, for each file in those directories whose name matches at least one of
10208 the Naming Patterns, an indication of whether the file contains a unit,
10209 and if so the name of the unit.
10211 @item ^-v -v^/VERBOSE /VERBOSE^
10212 @cindex @option{^-v -v^/VERBOSE /VERBOSE^} (@code{gnatname})
10213 Very Verbose mode. In addition to the output produced in verbose mode,
10214 for each file in the searched directories whose name matches none of
10215 the Naming Patterns, an indication is given that there is no match.
10217 @item ^-x^/EXCLUDED_PATTERN=^@file{pattern}
10218 @cindex @option{^-x^/EXCLUDED_PATTERN^} (@code{gnatname})
10219 Excluded patterns. Using this switch, it is possible to exclude some files
10220 that would match the name patterns. For example,
10222 gnatname ^-x "*_nt.ada"^/EXCLUDED_PATTERN=*_nt.ada^ "*.ada"
10225 will look for Ada units in all files with the @file{.ada} extension,
10226 except those whose names end with @file{_nt.ada}.
10230 @node Examples of gnatname Usage
10231 @section Examples of @code{gnatname} Usage
10235 $ gnatname /CONFIG_FILE=[HOME.ME]NAMES.ADC /SOURCE_DIRS=SOURCES "[a-z]*.ada*"
10241 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
10246 In this example, the directory @file{^/home/me^[HOME.ME]^} must already exist
10247 and be writable. In addition, the directory
10248 @file{^/home/me/sources^[HOME.ME.SOURCES]^} (specified by
10249 @option{^-d sources^/SOURCE_DIRS=SOURCES^}) must exist and be readable.
10252 Note the optional spaces after @option{-c} and @option{-d}.
10257 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
10258 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
10261 $ gnatname /PROJECT_FILE=[HOME.ME]PROJ
10262 /EXCLUDED_PATTERN=*_nt_body.ada
10263 /SOURCE_DIRS=(SOURCES,[SOURCES.PLUS])
10264 /DIRS_FILE=COMMON_DIRS.TXT "body_*" "spec_*"
10268 Note that several switches @option{^-d^/SOURCE_DIRS^} may be used,
10269 even in conjunction with one or several switches
10270 @option{^-D^/DIRS_FILE^}. Several Naming Patterns and one excluded pattern
10271 are used in this example.
10274 @c *****************************************
10275 @c * G N A T P r o j e c t M a n a g e r *
10276 @c *****************************************
10277 @node GNAT Project Manager
10278 @chapter GNAT Project Manager
10282 * Examples of Project Files::
10283 * Project File Syntax::
10284 * Objects and Sources in Project Files::
10285 * Importing Projects::
10286 * Project Extension::
10287 * External References in Project Files::
10288 * Packages in Project Files::
10289 * Variables from Imported Projects::
10291 * Library Projects::
10292 * Using Third-Party Libraries through Projects::
10293 * Stand-alone Library Projects::
10294 * Switches Related to Project Files::
10295 * Tools Supporting Project Files::
10296 * An Extended Example::
10297 * Project File Complete Syntax::
10300 @c ****************
10301 @c * Introduction *
10302 @c ****************
10305 @section Introduction
10308 This chapter describes GNAT's @emph{Project Manager}, a facility that allows
10309 you to manage complex builds involving a number of source files, directories,
10310 and compilation options for different system configurations. In particular,
10311 project files allow you to specify:
10314 The directory or set of directories containing the source files, and/or the
10315 names of the specific source files themselves
10317 The directory in which the compiler's output
10318 (@file{ALI} files, object files, tree files) is to be placed
10320 The directory in which the executable programs is to be placed
10322 ^Switch^Switch^ settings for any of the project-enabled tools
10323 (@command{gnatmake}, compiler, binder, linker, @code{gnatls}, @code{gnatxref},
10324 @code{gnatfind}); you can apply these settings either globally or to individual
10327 The source files containing the main subprogram(s) to be built
10329 The source programming language(s) (currently Ada and/or C)
10331 Source file naming conventions; you can specify these either globally or for
10332 individual compilation units
10339 @node Project Files
10340 @subsection Project Files
10343 Project files are written in a syntax close to that of Ada, using familiar
10344 notions such as packages, context clauses, declarations, default values,
10345 assignments, and inheritance. Finally, project files can be built
10346 hierarchically from other project files, simplifying complex system
10347 integration and project reuse.
10349 A @dfn{project} is a specific set of values for various compilation properties.
10350 The settings for a given project are described by means of
10351 a @dfn{project file}, which is a text file written in an Ada-like syntax.
10352 Property values in project files are either strings or lists of strings.
10353 Properties that are not explicitly set receive default values. A project
10354 file may interrogate the values of @dfn{external variables} (user-defined
10355 command-line switches or environment variables), and it may specify property
10356 settings conditionally, based on the value of such variables.
10358 In simple cases, a project's source files depend only on other source files
10359 in the same project, or on the predefined libraries. (@emph{Dependence} is
10361 the Ada technical sense; as in one Ada unit @code{with}ing another.) However,
10362 the Project Manager also allows more sophisticated arrangements,
10363 where the source files in one project depend on source files in other
10367 One project can @emph{import} other projects containing needed source files.
10369 You can organize GNAT projects in a hierarchy: a @emph{child} project
10370 can extend a @emph{parent} project, inheriting the parent's source files and
10371 optionally overriding any of them with alternative versions
10375 More generally, the Project Manager lets you structure large development
10376 efforts into hierarchical subsystems, where build decisions are delegated
10377 to the subsystem level, and thus different compilation environments
10378 (^switch^switch^ settings) used for different subsystems.
10380 The Project Manager is invoked through the
10381 @option{^-P^/PROJECT_FILE=^@emph{projectfile}}
10382 switch to @command{gnatmake} or to the @command{^gnat^GNAT^} front driver.
10384 There may be zero, one or more spaces between @option{-P} and
10385 @option{@emph{projectfile}}.
10387 If you want to define (on the command line) an external variable that is
10388 queried by the project file, you must use the
10389 @option{^-X^/EXTERNAT_REFERENCE=^@emph{vbl}=@emph{value}} switch.
10390 The Project Manager parses and interprets the project file, and drives the
10391 invoked tool based on the project settings.
10393 The Project Manager supports a wide range of development strategies,
10394 for systems of all sizes. Here are some typical practices that are
10398 Using a common set of source files, but generating object files in different
10399 directories via different ^switch^switch^ settings
10401 Using a mostly-shared set of source files, but with different versions of
10406 The destination of an executable can be controlled inside a project file
10407 using the @option{^-o^-o^}
10409 In the absence of such a ^switch^switch^ either inside
10410 the project file or on the command line, any executable files generated by
10411 @command{gnatmake} are placed in the directory @code{Exec_Dir} specified
10412 in the project file. If no @code{Exec_Dir} is specified, they will be placed
10413 in the object directory of the project.
10415 You can use project files to achieve some of the effects of a source
10416 versioning system (for example, defining separate projects for
10417 the different sets of sources that comprise different releases) but the
10418 Project Manager is independent of any source configuration management tools
10419 that might be used by the developers.
10421 The next section introduces the main features of GNAT's project facility
10422 through a sequence of examples; subsequent sections will present the syntax
10423 and semantics in more detail. A more formal description of the project
10424 facility appears in the GNAT Reference Manual.
10426 @c *****************************
10427 @c * Examples of Project Files *
10428 @c *****************************
10430 @node Examples of Project Files
10431 @section Examples of Project Files
10433 This section illustrates some of the typical uses of project files and
10434 explains their basic structure and behavior.
10437 * Common Sources with Different ^Switches^Switches^ and Directories::
10438 * Using External Variables::
10439 * Importing Other Projects::
10440 * Extending a Project::
10443 @node Common Sources with Different ^Switches^Switches^ and Directories
10444 @subsection Common Sources with Different ^Switches^Switches^ and Directories
10448 * Specifying the Object Directory::
10449 * Specifying the Exec Directory::
10450 * Project File Packages::
10451 * Specifying ^Switch^Switch^ Settings::
10452 * Main Subprograms::
10453 * Executable File Names::
10454 * Source File Naming Conventions::
10455 * Source Language(s)::
10459 Suppose that the Ada source files @file{pack.ads}, @file{pack.adb}, and
10460 @file{proc.adb} are in the @file{/common} directory. The file
10461 @file{proc.adb} contains an Ada main subprogram @code{Proc} that @code{with}s
10462 package @code{Pack}. We want to compile these source files under two sets
10463 of ^switches^switches^:
10466 When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
10467 and the @option{^-gnata^-gnata^},
10468 @option{^-gnato^-gnato^},
10469 and @option{^-gnatE^-gnatE^} switches to the
10470 compiler; the compiler's output is to appear in @file{/common/debug}
10472 When preparing a release version, we want to pass the @option{^-O2^O2^} switch
10473 to the compiler; the compiler's output is to appear in @file{/common/release}
10477 The GNAT project files shown below, respectively @file{debug.gpr} and
10478 @file{release.gpr} in the @file{/common} directory, achieve these effects.
10491 ^/common/debug^[COMMON.DEBUG]^
10496 ^/common/release^[COMMON.RELEASE]^
10501 Here are the corresponding project files:
10503 @smallexample @c projectfile
10506 for Object_Dir use "debug";
10507 for Main use ("proc");
10510 for ^Default_Switches^Default_Switches^ ("Ada")
10512 for Executable ("proc.adb") use "proc1";
10517 package Compiler is
10518 for ^Default_Switches^Default_Switches^ ("Ada")
10519 use ("-fstack-check",
10522 "^-gnatE^-gnatE^");
10528 @smallexample @c projectfile
10531 for Object_Dir use "release";
10532 for Exec_Dir use ".";
10533 for Main use ("proc");
10535 package Compiler is
10536 for ^Default_Switches^Default_Switches^ ("Ada")
10544 The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
10545 insensitive), and analogously the project defined by @file{release.gpr} is
10546 @code{"Release"}. For consistency the file should have the same name as the
10547 project, and the project file's extension should be @code{"gpr"}. These
10548 conventions are not required, but a warning is issued if they are not followed.
10550 If the current directory is @file{^/temp^[TEMP]^}, then the command
10552 gnatmake ^-P/common/debug.gpr^/PROJECT_FILE=[COMMON]DEBUG^
10556 generates object and ALI files in @file{^/common/debug^[COMMON.DEBUG]^},
10557 as well as the @code{^proc1^PROC1.EXE^} executable,
10558 using the ^switch^switch^ settings defined in the project file.
10560 Likewise, the command
10562 gnatmake ^-P/common/release.gpr^/PROJECT_FILE=[COMMON]RELEASE^
10566 generates object and ALI files in @file{^/common/release^[COMMON.RELEASE]^},
10567 and the @code{^proc^PROC.EXE^}
10568 executable in @file{^/common^[COMMON]^},
10569 using the ^switch^switch^ settings from the project file.
10572 @unnumberedsubsubsec Source Files
10575 If a project file does not explicitly specify a set of source directories or
10576 a set of source files, then by default the project's source files are the
10577 Ada source files in the project file directory. Thus @file{pack.ads},
10578 @file{pack.adb}, and @file{proc.adb} are the source files for both projects.
10580 @node Specifying the Object Directory
10581 @unnumberedsubsubsec Specifying the Object Directory
10584 Several project properties are modeled by Ada-style @emph{attributes};
10585 a property is defined by supplying the equivalent of an Ada attribute
10586 definition clause in the project file.
10587 A project's object directory is another such a property; the corresponding
10588 attribute is @code{Object_Dir}, and its value is also a string expression,
10589 specified either as absolute or relative. In the later case,
10590 it is relative to the project file directory. Thus the compiler's
10591 output is directed to @file{^/common/debug^[COMMON.DEBUG]^}
10592 (for the @code{Debug} project)
10593 and to @file{^/common/release^[COMMON.RELEASE]^}
10594 (for the @code{Release} project).
10595 If @code{Object_Dir} is not specified, then the default is the project file
10598 @node Specifying the Exec Directory
10599 @unnumberedsubsubsec Specifying the Exec Directory
10602 A project's exec directory is another property; the corresponding
10603 attribute is @code{Exec_Dir}, and its value is also a string expression,
10604 either specified as relative or absolute. If @code{Exec_Dir} is not specified,
10605 then the default is the object directory (which may also be the project file
10606 directory if attribute @code{Object_Dir} is not specified). Thus the executable
10607 is placed in @file{^/common/debug^[COMMON.DEBUG]^}
10608 for the @code{Debug} project (attribute @code{Exec_Dir} not specified)
10609 and in @file{^/common^[COMMON]^} for the @code{Release} project.
10611 @node Project File Packages
10612 @unnumberedsubsubsec Project File Packages
10615 A GNAT tool that is integrated with the Project Manager is modeled by a
10616 corresponding package in the project file. In the example above,
10617 The @code{Debug} project defines the packages @code{Builder}
10618 (for @command{gnatmake}) and @code{Compiler};
10619 the @code{Release} project defines only the @code{Compiler} package.
10621 The Ada-like package syntax is not to be taken literally. Although packages in
10622 project files bear a surface resemblance to packages in Ada source code, the
10623 notation is simply a way to convey a grouping of properties for a named
10624 entity. Indeed, the package names permitted in project files are restricted
10625 to a predefined set, corresponding to the project-aware tools, and the contents
10626 of packages are limited to a small set of constructs.
10627 The packages in the example above contain attribute definitions.
10629 @node Specifying ^Switch^Switch^ Settings
10630 @unnumberedsubsubsec Specifying ^Switch^Switch^ Settings
10633 ^Switch^Switch^ settings for a project-aware tool can be specified through
10634 attributes in the package that corresponds to the tool.
10635 The example above illustrates one of the relevant attributes,
10636 @code{^Default_Switches^Default_Switches^}, which is defined in packages
10637 in both project files.
10638 Unlike simple attributes like @code{Source_Dirs},
10639 @code{^Default_Switches^Default_Switches^} is
10640 known as an @emph{associative array}. When you define this attribute, you must
10641 supply an ``index'' (a literal string), and the effect of the attribute
10642 definition is to set the value of the array at the specified index.
10643 For the @code{^Default_Switches^Default_Switches^} attribute,
10644 the index is a programming language (in our case, Ada),
10645 and the value specified (after @code{use}) must be a list
10646 of string expressions.
10648 The attributes permitted in project files are restricted to a predefined set.
10649 Some may appear at project level, others in packages.
10650 For any attribute that is an associative array, the index must always be a
10651 literal string, but the restrictions on this string (e.g., a file name or a
10652 language name) depend on the individual attribute.
10653 Also depending on the attribute, its specified value will need to be either a
10654 string or a string list.
10656 In the @code{Debug} project, we set the switches for two tools,
10657 @command{gnatmake} and the compiler, and thus we include the two corresponding
10658 packages; each package defines the @code{^Default_Switches^Default_Switches^}
10659 attribute with index @code{"Ada"}.
10660 Note that the package corresponding to
10661 @command{gnatmake} is named @code{Builder}. The @code{Release} project is
10662 similar, but only includes the @code{Compiler} package.
10664 In project @code{Debug} above, the ^switches^switches^ starting with
10665 @option{-gnat} that are specified in package @code{Compiler}
10666 could have been placed in package @code{Builder}, since @command{gnatmake}
10667 transmits all such ^switches^switches^ to the compiler.
10669 @node Main Subprograms
10670 @unnumberedsubsubsec Main Subprograms
10673 One of the specifiable properties of a project is a list of files that contain
10674 main subprograms. This property is captured in the @code{Main} attribute,
10675 whose value is a list of strings. If a project defines the @code{Main}
10676 attribute, it is not necessary to identify the main subprogram(s) when
10677 invoking @command{gnatmake} (see @ref{gnatmake and Project Files}).
10679 @node Executable File Names
10680 @unnumberedsubsubsec Executable File Names
10683 By default, the executable file name corresponding to a main source is
10684 deducted from the main source file name. Through the attributes
10685 @code{Executable} and @code{Executable_Suffix} of package @code{Builder},
10686 it is possible to change this default.
10687 In project @code{Debug} above, the executable file name
10688 for main source @file{^proc.adb^PROC.ADB^} is
10689 @file{^proc1^PROC1.EXE^}.
10690 Attribute @code{Executable_Suffix}, when specified, may change the suffix
10691 of the the executable files, when no attribute @code{Executable} applies:
10692 its value replace the platform-specific executable suffix.
10693 Attributes @code{Executable} and @code{Executable_Suffix} are the only ways to
10694 specify a non default executable file name when several mains are built at once
10695 in a single @command{gnatmake} command.
10697 @node Source File Naming Conventions
10698 @unnumberedsubsubsec Source File Naming Conventions
10701 Since the project files above do not specify any source file naming
10702 conventions, the GNAT defaults are used. The mechanism for defining source
10703 file naming conventions -- a package named @code{Naming} --
10704 is described below (@pxref{Naming Schemes}).
10706 @node Source Language(s)
10707 @unnumberedsubsubsec Source Language(s)
10710 Since the project files do not specify a @code{Languages} attribute, by
10711 default the GNAT tools assume that the language of the project file is Ada.
10712 More generally, a project can comprise source files
10713 in Ada, C, and/or other languages.
10715 @node Using External Variables
10716 @subsection Using External Variables
10719 Instead of supplying different project files for debug and release, we can
10720 define a single project file that queries an external variable (set either
10721 on the command line or via an ^environment variable^logical name^) in order to
10722 conditionally define the appropriate settings. Again, assume that the
10723 source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
10724 located in directory @file{^/common^[COMMON]^}. The following project file,
10725 @file{build.gpr}, queries the external variable named @code{STYLE} and
10726 defines an object directory and ^switch^switch^ settings based on whether
10727 the value is @code{"deb"} (debug) or @code{"rel"} (release), and where
10728 the default is @code{"deb"}.
10730 @smallexample @c projectfile
10733 for Main use ("proc");
10735 type Style_Type is ("deb", "rel");
10736 Style : Style_Type := external ("STYLE", "deb");
10740 for Object_Dir use "debug";
10743 for Object_Dir use "release";
10744 for Exec_Dir use ".";
10753 for ^Default_Switches^Default_Switches^ ("Ada")
10755 for Executable ("proc") use "proc1";
10762 package Compiler is
10766 for ^Default_Switches^Default_Switches^ ("Ada")
10767 use ("^-gnata^-gnata^",
10769 "^-gnatE^-gnatE^");
10772 for ^Default_Switches^Default_Switches^ ("Ada")
10783 @code{Style_Type} is an example of a @emph{string type}, which is the project
10784 file analog of an Ada enumeration type but whose components are string literals
10785 rather than identifiers. @code{Style} is declared as a variable of this type.
10787 The form @code{external("STYLE", "deb")} is known as an
10788 @emph{external reference}; its first argument is the name of an
10789 @emph{external variable}, and the second argument is a default value to be
10790 used if the external variable doesn't exist. You can define an external
10791 variable on the command line via the @option{^-X^/EXTERNAL_REFERENCE^} switch,
10792 or you can use ^an environment variable^a logical name^
10793 as an external variable.
10795 Each @code{case} construct is expanded by the Project Manager based on the
10796 value of @code{Style}. Thus the command
10799 gnatmake -P/common/build.gpr -XSTYLE=deb
10805 gnatmake /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=deb
10810 is equivalent to the @command{gnatmake} invocation using the project file
10811 @file{debug.gpr} in the earlier example. So is the command
10813 gnatmake ^-P/common/build.gpr^/PROJECT_FILE=[COMMON]BUILD.GPR^
10817 since @code{"deb"} is the default for @code{STYLE}.
10823 gnatmake -P/common/build.gpr -XSTYLE=rel
10829 GNAT MAKE /PROJECT_FILE=[COMMON]BUILD.GPR /EXTERNAL_REFERENCE=STYLE=rel
10834 is equivalent to the @command{gnatmake} invocation using the project file
10835 @file{release.gpr} in the earlier example.
10837 @node Importing Other Projects
10838 @subsection Importing Other Projects
10841 A compilation unit in a source file in one project may depend on compilation
10842 units in source files in other projects. To compile this unit under
10843 control of a project file, the
10844 dependent project must @emph{import} the projects containing the needed source
10846 This effect is obtained using syntax similar to an Ada @code{with} clause,
10847 but where @code{with}ed entities are strings that denote project files.
10849 As an example, suppose that the two projects @code{GUI_Proj} and
10850 @code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
10851 @file{comm_proj.gpr} in directories @file{^/gui^[GUI]^}
10852 and @file{^/comm^[COMM]^}, respectively.
10853 Suppose that the source files for @code{GUI_Proj} are
10854 @file{gui.ads} and @file{gui.adb}, and that the source files for
10855 @code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, where each set of
10856 files is located in its respective project file directory. Schematically:
10875 We want to develop an application in directory @file{^/app^[APP]^} that
10876 @code{with} the packages @code{GUI} and @code{Comm}, using the properties of
10877 the corresponding project files (e.g. the ^switch^switch^ settings
10878 and object directory).
10879 Skeletal code for a main procedure might be something like the following:
10881 @smallexample @c ada
10884 procedure App_Main is
10893 Here is a project file, @file{app_proj.gpr}, that achieves the desired
10896 @smallexample @c projectfile
10898 with "/gui/gui_proj", "/comm/comm_proj";
10899 project App_Proj is
10900 for Main use ("app_main");
10906 Building an executable is achieved through the command:
10908 gnatmake ^-P/app/app_proj^/PROJECT_FILE=[APP]APP_PROJ^
10911 which will generate the @code{^app_main^APP_MAIN.EXE^} executable
10912 in the directory where @file{app_proj.gpr} resides.
10914 If an imported project file uses the standard extension (@code{^gpr^GPR^}) then
10915 (as illustrated above) the @code{with} clause can omit the extension.
10917 Our example specified an absolute path for each imported project file.
10918 Alternatively, the directory name of an imported object can be omitted
10922 The imported project file is in the same directory as the importing project
10925 You have defined ^an environment variable^a logical name^
10926 that includes the directory containing
10927 the needed project file. The syntax of @code{ADA_PROJECT_PATH} is the same as
10928 the syntax of @code{ADA_INCLUDE_PATH} and @code{ADA_OBJECTS_PATH}: a list of
10929 directory names separated by colons (semicolons on Windows).
10933 Thus, if we define @code{ADA_PROJECT_PATH} to include @file{^/gui^[GUI]^} and
10934 @file{^/comm^[COMM]^}, then our project file @file{app_proj.gpr} can be written
10937 @smallexample @c projectfile
10939 with "gui_proj", "comm_proj";
10940 project App_Proj is
10941 for Main use ("app_main");
10947 Importing other projects can create ambiguities.
10948 For example, the same unit might be present in different imported projects, or
10949 it might be present in both the importing project and in an imported project.
10950 Both of these conditions are errors. Note that in the current version of
10951 the Project Manager, it is illegal to have an ambiguous unit even if the
10952 unit is never referenced by the importing project. This restriction may be
10953 relaxed in a future release.
10955 @node Extending a Project
10956 @subsection Extending a Project
10959 In large software systems it is common to have multiple
10960 implementations of a common interface; in Ada terms, multiple versions of a
10961 package body for the same specification. For example, one implementation
10962 might be safe for use in tasking programs, while another might only be used
10963 in sequential applications. This can be modeled in GNAT using the concept
10964 of @emph{project extension}. If one project (the ``child'') @emph{extends}
10965 another project (the ``parent'') then by default all source files of the
10966 parent project are inherited by the child, but the child project can
10967 override any of the parent's source files with new versions, and can also
10968 add new files. This facility is the project analog of a type extension in
10969 Object-Oriented Programming. Project hierarchies are permitted (a child
10970 project may be the parent of yet another project), and a project that
10971 inherits one project can also import other projects.
10973 As an example, suppose that directory @file{^/seq^[SEQ]^} contains the project
10974 file @file{seq_proj.gpr} as well as the source files @file{pack.ads},
10975 @file{pack.adb}, and @file{proc.adb}:
10988 Note that the project file can simply be empty (that is, no attribute or
10989 package is defined):
10991 @smallexample @c projectfile
10993 project Seq_Proj is
10999 implying that its source files are all the Ada source files in the project
11002 Suppose we want to supply an alternate version of @file{pack.adb}, in
11003 directory @file{^/tasking^[TASKING]^}, but use the existing versions of
11004 @file{pack.ads} and @file{proc.adb}. We can define a project
11005 @code{Tasking_Proj} that inherits @code{Seq_Proj}:
11009 ^/tasking^[TASKING]^
11015 project Tasking_Proj extends "/seq/seq_proj" is
11021 The version of @file{pack.adb} used in a build depends on which project file
11024 Note that we could have obtained the desired behavior using project import
11025 rather than project inheritance; a @code{base} project would contain the
11026 sources for @file{pack.ads} and @file{proc.adb}, a sequential project would
11027 import @code{base} and add @file{pack.adb}, and likewise a tasking project
11028 would import @code{base} and add a different version of @file{pack.adb}. The
11029 choice depends on whether other sources in the original project need to be
11030 overridden. If they do, then project extension is necessary, otherwise,
11031 importing is sufficient.
11034 In a project file that extends another project file, it is possible to
11035 indicate that an inherited source is not part of the sources of the extending
11036 project. This is necessary sometimes when a package spec has been overloaded
11037 and no longer requires a body: in this case, it is necessary to indicate that
11038 the inherited body is not part of the sources of the project, otherwise there
11039 will be a compilation error when compiling the spec.
11041 For that purpose, the attribute @code{Locally_Removed_Files} is used.
11042 Its value is a string list: a list of file names.
11044 @smallexample @c @projectfile
11045 project B extends "a" is
11046 for Source_Files use ("pkg.ads");
11047 -- New spec of Pkg does not need a completion
11048 for Locally_Removed_Files use ("pkg.adb");
11052 Attribute @code{Locally_Removed_Files} may also be used to check if a source
11053 is still needed: if it is possible to build using @code{gnatmake} when such
11054 a source is put in attribute @code{Locally_Removed_Files} of a project P, then
11055 it is possible to remove the source completely from a system that includes
11058 @c ***********************
11059 @c * Project File Syntax *
11060 @c ***********************
11062 @node Project File Syntax
11063 @section Project File Syntax
11072 * Associative Array Attributes::
11073 * case Constructions::
11077 This section describes the structure of project files.
11079 A project may be an @emph{independent project}, entirely defined by a single
11080 project file. Any Ada source file in an independent project depends only
11081 on the predefined library and other Ada source files in the same project.
11084 A project may also @dfn{depend on} other projects, in either or both of
11085 the following ways:
11087 @item It may import any number of projects
11088 @item It may extend at most one other project
11092 The dependence relation is a directed acyclic graph (the subgraph reflecting
11093 the ``extends'' relation is a tree).
11095 A project's @dfn{immediate sources} are the source files directly defined by
11096 that project, either implicitly by residing in the project file's directory,
11097 or explicitly through any of the source-related attributes described below.
11098 More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
11099 of @var{proj} together with the immediate sources (unless overridden) of any
11100 project on which @var{proj} depends (either directly or indirectly).
11103 @subsection Basic Syntax
11106 As seen in the earlier examples, project files have an Ada-like syntax.
11107 The minimal project file is:
11108 @smallexample @c projectfile
11117 The identifier @code{Empty} is the name of the project.
11118 This project name must be present after the reserved
11119 word @code{end} at the end of the project file, followed by a semi-colon.
11121 Any name in a project file, such as the project name or a variable name,
11122 has the same syntax as an Ada identifier.
11124 The reserved words of project files are the Ada reserved words plus
11125 @code{extends}, @code{external}, and @code{project}. Note that the only Ada
11126 reserved words currently used in project file syntax are:
11154 Comments in project files have the same syntax as in Ada, two consecutives
11155 hyphens through the end of the line.
11158 @subsection Packages
11161 A project file may contain @emph{packages}. The name of a package must be one
11162 of the identifiers from the following list. A package
11163 with a given name may only appear once in a project file. Package names are
11164 case insensitive. The following package names are legal:
11180 @code{Cross_Reference}
11192 In its simplest form, a package may be empty:
11194 @smallexample @c projectfile
11204 A package may contain @emph{attribute declarations},
11205 @emph{variable declarations} and @emph{case constructions}, as will be
11208 When there is ambiguity between a project name and a package name,
11209 the name always designates the project. To avoid possible confusion, it is
11210 always a good idea to avoid naming a project with one of the
11211 names allowed for packages or any name that starts with @code{gnat}.
11214 @subsection Expressions
11217 An @emph{expression} is either a @emph{string expression} or a
11218 @emph{string list expression}.
11220 A @emph{string expression} is either a @emph{simple string expression} or a
11221 @emph{compound string expression}.
11223 A @emph{simple string expression} is one of the following:
11225 @item A literal string; e.g.@code{"comm/my_proj.gpr"}
11226 @item A string-valued variable reference (see @ref{Variables})
11227 @item A string-valued attribute reference (see @ref{Attributes})
11228 @item An external reference (see @ref{External References in Project Files})
11232 A @emph{compound string expression} is a concatenation of string expressions,
11233 using the operator @code{"&"}
11235 Path & "/" & File_Name & ".ads"
11239 A @emph{string list expression} is either a
11240 @emph{simple string list expression} or a
11241 @emph{compound string list expression}.
11243 A @emph{simple string list expression} is one of the following:
11245 @item A parenthesized list of zero or more string expressions,
11246 separated by commas
11248 File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
11251 @item A string list-valued variable reference
11252 @item A string list-valued attribute reference
11256 A @emph{compound string list expression} is the concatenation (using
11257 @code{"&"}) of a simple string list expression and an expression. Note that
11258 each term in a compound string list expression, except the first, may be
11259 either a string expression or a string list expression.
11261 @smallexample @c projectfile
11263 File_Name_List := () & File_Name; -- One string in this list
11264 Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
11266 Big_List := File_Name_List & Extended_File_Name_List;
11267 -- Concatenation of two string lists: three strings
11268 Illegal_List := "gnat.adc" & Extended_File_Name_List;
11269 -- Illegal: must start with a string list
11274 @subsection String Types
11277 A @emph{string type declaration} introduces a discrete set of string literals.
11278 If a string variable is declared to have this type, its value
11279 is restricted to the given set of literals.
11281 Here is an example of a string type declaration:
11283 @smallexample @c projectfile
11284 type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS");
11288 Variables of a string type are called @emph{typed variables}; all other
11289 variables are called @emph{untyped variables}. Typed variables are
11290 particularly useful in @code{case} constructions, to support conditional
11291 attribute declarations.
11292 (see @ref{case Constructions}).
11294 The string literals in the list are case sensitive and must all be different.
11295 They may include any graphic characters allowed in Ada, including spaces.
11297 A string type may only be declared at the project level, not inside a package.
11299 A string type may be referenced by its name if it has been declared in the same
11300 project file, or by an expanded name whose prefix is the name of the project
11301 in which it is declared.
11304 @subsection Variables
11307 A variable may be declared at the project file level, or within a package.
11308 Here are some examples of variable declarations:
11310 @smallexample @c projectfile
11312 This_OS : OS := external ("OS"); -- a typed variable declaration
11313 That_OS := "GNU/Linux"; -- an untyped variable declaration
11318 The syntax of a @emph{typed variable declaration} is identical to the Ada
11319 syntax for an object declaration. By contrast, the syntax of an untyped
11320 variable declaration is identical to an Ada assignment statement. In fact,
11321 variable declarations in project files have some of the characteristics of
11322 an assignment, in that successive declarations for the same variable are
11323 allowed. Untyped variable declarations do establish the expected kind of the
11324 variable (string or string list), and successive declarations for it must
11325 respect the initial kind.
11328 A string variable declaration (typed or untyped) declares a variable
11329 whose value is a string. This variable may be used as a string expression.
11330 @smallexample @c projectfile
11331 File_Name := "readme.txt";
11332 Saved_File_Name := File_Name & ".saved";
11336 A string list variable declaration declares a variable whose value is a list
11337 of strings. The list may contain any number (zero or more) of strings.
11339 @smallexample @c projectfile
11341 List_With_One_Element := ("^-gnaty^-gnaty^");
11342 List_With_Two_Elements := List_With_One_Element & "^-gnatg^-gnatg^";
11343 Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
11344 "pack2.ada", "util_.ada", "util.ada");
11348 The same typed variable may not be declared more than once at project level,
11349 and it may not be declared more than once in any package; it is in effect
11352 The same untyped variable may be declared several times. Declarations are
11353 elaborated in the order in which they appear, so the new value replaces
11354 the old one, and any subsequent reference to the variable uses the new value.
11355 However, as noted above, if a variable has been declared as a string, all
11357 declarations must give it a string value. Similarly, if a variable has
11358 been declared as a string list, all subsequent declarations
11359 must give it a string list value.
11361 A @emph{variable reference} may take several forms:
11364 @item The simple variable name, for a variable in the current package (if any)
11365 or in the current project
11366 @item An expanded name, whose prefix is a context name.
11370 A @emph{context} may be one of the following:
11373 @item The name of an existing package in the current project
11374 @item The name of an imported project of the current project
11375 @item The name of an ancestor project (i.e., a project extended by the current
11376 project, either directly or indirectly)
11377 @item An expanded name whose prefix is an imported/parent project name, and
11378 whose selector is a package name in that project.
11382 A variable reference may be used in an expression.
11385 @subsection Attributes
11388 A project (and its packages) may have @emph{attributes} that define
11389 the project's properties. Some attributes have values that are strings;
11390 others have values that are string lists.
11392 There are two categories of attributes: @emph{simple attributes}
11393 and @emph{associative arrays} (see @ref{Associative Array Attributes}).
11395 Legal project attribute names, and attribute names for each legal package are
11396 listed below. Attributes names are case-insensitive.
11398 The following attributes are defined on projects (all are simple attributes):
11400 @multitable @columnfractions .4 .3
11401 @item @emph{Attribute Name}
11403 @item @code{Source_Files}
11405 @item @code{Source_Dirs}
11407 @item @code{Source_List_File}
11409 @item @code{Object_Dir}
11411 @item @code{Exec_Dir}
11413 @item @code{Locally_Removed_Files}
11417 @item @code{Languages}
11419 @item @code{Main_Language}
11421 @item @code{Library_Dir}
11423 @item @code{Library_Name}
11425 @item @code{Library_Kind}
11427 @item @code{Library_Version}
11429 @item @code{Library_Interface}
11431 @item @code{Library_Auto_Init}
11433 @item @code{Library_Options}
11435 @item @code{Library_GCC}
11440 The following attributes are defined for package @code{Naming}
11441 (see @ref{Naming Schemes}):
11443 @multitable @columnfractions .4 .2 .2 .2
11444 @item Attribute Name @tab Category @tab Index @tab Value
11445 @item @code{Spec_Suffix}
11446 @tab associative array
11449 @item @code{Body_Suffix}
11450 @tab associative array
11453 @item @code{Separate_Suffix}
11454 @tab simple attribute
11457 @item @code{Casing}
11458 @tab simple attribute
11461 @item @code{Dot_Replacement}
11462 @tab simple attribute
11466 @tab associative array
11470 @tab associative array
11473 @item @code{Specification_Exceptions}
11474 @tab associative array
11477 @item @code{Implementation_Exceptions}
11478 @tab associative array
11484 The following attributes are defined for packages @code{Builder},
11485 @code{Compiler}, @code{Binder},
11486 @code{Linker}, @code{Cross_Reference}, and @code{Finder}
11487 (see @ref{^Switches^Switches^ and Project Files}).
11489 @multitable @columnfractions .4 .2 .2 .2
11490 @item Attribute Name @tab Category @tab Index @tab Value
11491 @item @code{^Default_Switches^Default_Switches^}
11492 @tab associative array
11495 @item @code{^Switches^Switches^}
11496 @tab associative array
11502 In addition, package @code{Compiler} has a single string attribute
11503 @code{Local_Configuration_Pragmas} and package @code{Builder} has a single
11504 string attribute @code{Global_Configuration_Pragmas}.
11507 Each simple attribute has a default value: the empty string (for string-valued
11508 attributes) and the empty list (for string list-valued attributes).
11510 An attribute declaration defines a new value for an attribute.
11512 Examples of simple attribute declarations:
11514 @smallexample @c projectfile
11515 for Object_Dir use "objects";
11516 for Source_Dirs use ("units", "test/drivers");
11520 The syntax of a @dfn{simple attribute declaration} is similar to that of an
11521 attribute definition clause in Ada.
11523 Attributes references may be appear in expressions.
11524 The general form for such a reference is @code{<entity>'<attribute>}:
11525 Associative array attributes are functions. Associative
11526 array attribute references must have an argument that is a string literal.
11530 @smallexample @c projectfile
11532 Naming'Dot_Replacement
11533 Imported_Project'Source_Dirs
11534 Imported_Project.Naming'Casing
11535 Builder'^Default_Switches^Default_Switches^("Ada")
11539 The prefix of an attribute may be:
11541 @item @code{project} for an attribute of the current project
11542 @item The name of an existing package of the current project
11543 @item The name of an imported project
11544 @item The name of a parent project that is extended by the current project
11545 @item An expanded name whose prefix is imported/parent project name,
11546 and whose selector is a package name
11551 @smallexample @c projectfile
11554 for Source_Dirs use project'Source_Dirs & "units";
11555 for Source_Dirs use project'Source_Dirs & "test/drivers"
11561 In the first attribute declaration, initially the attribute @code{Source_Dirs}
11562 has the default value: an empty string list. After this declaration,
11563 @code{Source_Dirs} is a string list of one element: @code{"units"}.
11564 After the second attribute declaration @code{Source_Dirs} is a string list of
11565 two elements: @code{"units"} and @code{"test/drivers"}.
11567 Note: this example is for illustration only. In practice,
11568 the project file would contain only one attribute declaration:
11570 @smallexample @c projectfile
11571 for Source_Dirs use ("units", "test/drivers");
11574 @node Associative Array Attributes
11575 @subsection Associative Array Attributes
11578 Some attributes are defined as @emph{associative arrays}. An associative
11579 array may be regarded as a function that takes a string as a parameter
11580 and delivers a string or string list value as its result.
11582 Here are some examples of single associative array attribute associations:
11584 @smallexample @c projectfile
11585 for Body ("main") use "Main.ada";
11586 for ^Switches^Switches^ ("main.ada")
11588 "^-gnatv^-gnatv^");
11589 for ^Switches^Switches^ ("main.ada")
11590 use Builder'^Switches^Switches^ ("main.ada")
11595 Like untyped variables and simple attributes, associative array attributes
11596 may be declared several times. Each declaration supplies a new value for the
11597 attribute, and replaces the previous setting.
11600 An associative array attribute may be declared as a full associative array
11601 declaration, with the value of the same attribute in an imported or extended
11604 @smallexample @c projectfile
11606 for Default_Switches use Default.Builder'Default_Switches;
11611 In this example, @code{Default} must be either an project imported by the
11612 current project, or the project that the current project extends. If the
11613 attribute is in a package (in this case, in package @code{Builder}), the same
11614 package needs to be specified.
11617 A full associative array declaration replaces any other declaration for the
11618 attribute, including other full associative array declaration. Single
11619 associative array associations may be declare after a full associative
11620 declaration, modifying the value for a single association of the attribute.
11622 @node case Constructions
11623 @subsection @code{case} Constructions
11626 A @code{case} construction is used in a project file to effect conditional
11628 Here is a typical example:
11630 @smallexample @c projectfile
11633 type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS");
11635 OS : OS_Type := external ("OS", "GNU/Linux");
11639 package Compiler is
11641 when "GNU/Linux" | "Unix" =>
11642 for ^Default_Switches^Default_Switches^ ("Ada")
11643 use ("^-gnath^-gnath^");
11645 for ^Default_Switches^Default_Switches^ ("Ada")
11646 use ("^-gnatP^-gnatP^");
11655 The syntax of a @code{case} construction is based on the Ada case statement
11656 (although there is no @code{null} construction for empty alternatives).
11658 The case expression must a typed string variable.
11659 Each alternative comprises the reserved word @code{when}, either a list of
11660 literal strings separated by the @code{"|"} character or the reserved word
11661 @code{others}, and the @code{"=>"} token.
11662 Each literal string must belong to the string type that is the type of the
11664 An @code{others} alternative, if present, must occur last.
11666 After each @code{=>}, there are zero or more constructions. The only
11667 constructions allowed in a case construction are other case constructions and
11668 attribute declarations. String type declarations, variable declarations and
11669 package declarations are not allowed.
11671 The value of the case variable is often given by an external reference
11672 (see @ref{External References in Project Files}).
11674 @c ****************************************
11675 @c * Objects and Sources in Project Files *
11676 @c ****************************************
11678 @node Objects and Sources in Project Files
11679 @section Objects and Sources in Project Files
11682 * Object Directory::
11684 * Source Directories::
11685 * Source File Names::
11689 Each project has exactly one object directory and one or more source
11690 directories. The source directories must contain at least one source file,
11691 unless the project file explicitly specifies that no source files are present
11692 (see @ref{Source File Names}).
11694 @node Object Directory
11695 @subsection Object Directory
11698 The object directory for a project is the directory containing the compiler's
11699 output (such as @file{ALI} files and object files) for the project's immediate
11702 The object directory is given by the value of the attribute @code{Object_Dir}
11703 in the project file.
11705 @smallexample @c projectfile
11706 for Object_Dir use "objects";
11710 The attribute @var{Object_Dir} has a string value, the path name of the object
11711 directory. The path name may be absolute or relative to the directory of the
11712 project file. This directory must already exist, and be readable and writable.
11714 By default, when the attribute @code{Object_Dir} is not given an explicit value
11715 or when its value is the empty string, the object directory is the same as the
11716 directory containing the project file.
11718 @node Exec Directory
11719 @subsection Exec Directory
11722 The exec directory for a project is the directory containing the executables
11723 for the project's main subprograms.
11725 The exec directory is given by the value of the attribute @code{Exec_Dir}
11726 in the project file.
11728 @smallexample @c projectfile
11729 for Exec_Dir use "executables";
11733 The attribute @var{Exec_Dir} has a string value, the path name of the exec
11734 directory. The path name may be absolute or relative to the directory of the
11735 project file. This directory must already exist, and be writable.
11737 By default, when the attribute @code{Exec_Dir} is not given an explicit value
11738 or when its value is the empty string, the exec directory is the same as the
11739 object directory of the project file.
11741 @node Source Directories
11742 @subsection Source Directories
11745 The source directories of a project are specified by the project file
11746 attribute @code{Source_Dirs}.
11748 This attribute's value is a string list. If the attribute is not given an
11749 explicit value, then there is only one source directory, the one where the
11750 project file resides.
11752 A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
11755 @smallexample @c projectfile
11756 for Source_Dirs use ();
11760 indicates that the project contains no source files.
11762 Otherwise, each string in the string list designates one or more
11763 source directories.
11765 @smallexample @c projectfile
11766 for Source_Dirs use ("sources", "test/drivers");
11770 If a string in the list ends with @code{"/**"}, then the directory whose path
11771 name precedes the two asterisks, as well as all its subdirectories
11772 (recursively), are source directories.
11774 @smallexample @c projectfile
11775 for Source_Dirs use ("/system/sources/**");
11779 Here the directory @code{/system/sources} and all of its subdirectories
11780 (recursively) are source directories.
11782 To specify that the source directories are the directory of the project file
11783 and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
11784 @smallexample @c projectfile
11785 for Source_Dirs use ("./**");
11789 Each of the source directories must exist and be readable.
11791 @node Source File Names
11792 @subsection Source File Names
11795 In a project that contains source files, their names may be specified by the
11796 attributes @code{Source_Files} (a string list) or @code{Source_List_File}
11797 (a string). Source file names never include any directory information.
11799 If the attribute @code{Source_Files} is given an explicit value, then each
11800 element of the list is a source file name.
11802 @smallexample @c projectfile
11803 for Source_Files use ("main.adb");
11804 for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
11808 If the attribute @code{Source_Files} is not given an explicit value,
11809 but the attribute @code{Source_List_File} is given a string value,
11810 then the source file names are contained in the text file whose path name
11811 (absolute or relative to the directory of the project file) is the
11812 value of the attribute @code{Source_List_File}.
11814 Each line in the file that is not empty or is not a comment
11815 contains a source file name.
11817 @smallexample @c projectfile
11818 for Source_List_File use "source_list.txt";
11822 By default, if neither the attribute @code{Source_Files} nor the attribute
11823 @code{Source_List_File} is given an explicit value, then each file in the
11824 source directories that conforms to the project's naming scheme
11825 (see @ref{Naming Schemes}) is an immediate source of the project.
11827 A warning is issued if both attributes @code{Source_Files} and
11828 @code{Source_List_File} are given explicit values. In this case, the attribute
11829 @code{Source_Files} prevails.
11831 Each source file name must be the name of one existing source file
11832 in one of the source directories.
11834 A @code{Source_Files} attribute whose value is an empty list
11835 indicates that there are no source files in the project.
11837 If the order of the source directories is known statically, that is if
11838 @code{"/**"} is not used in the string list @code{Source_Dirs}, then there may
11839 be several files with the same source file name. In this case, only the file
11840 in the first directory is considered as an immediate source of the project
11841 file. If the order of the source directories is not known statically, it is
11842 an error to have several files with the same source file name.
11844 Projects can be specified to have no Ada source
11845 files: the value of (@code{Source_Dirs} or @code{Source_Files} may be an empty
11846 list, or the @code{"Ada"} may be absent from @code{Languages}:
11848 @smallexample @c projectfile
11849 for Source_Dirs use ();
11850 for Source_Files use ();
11851 for Languages use ("C", "C++");
11855 Otherwise, a project must contain at least one immediate source.
11857 Projects with no source files are useful as template packages
11858 (see @ref{Packages in Project Files}) for other projects; in particular to
11859 define a package @code{Naming} (see @ref{Naming Schemes}).
11861 @c ****************************
11862 @c * Importing Projects *
11863 @c ****************************
11865 @node Importing Projects
11866 @section Importing Projects
11869 An immediate source of a project P may depend on source files that
11870 are neither immediate sources of P nor in the predefined library.
11871 To get this effect, P must @emph{import} the projects that contain the needed
11874 @smallexample @c projectfile
11876 with "project1", "utilities.gpr";
11877 with "/namings/apex.gpr";
11884 As can be seen in this example, the syntax for importing projects is similar
11885 to the syntax for importing compilation units in Ada. However, project files
11886 use literal strings instead of names, and the @code{with} clause identifies
11887 project files rather than packages.
11889 Each literal string is the file name or path name (absolute or relative) of a
11890 project file. If a string is simply a file name, with no path, then its
11891 location is determined by the @emph{project path}:
11895 If the ^environment variable^logical name^ @env{ADA_PROJECT_PATH} exists,
11896 then the project path includes all the directories in this
11897 ^environment variable^logical name^, plus the directory of the project file.
11900 If the ^environment variable^logical name^ @env{ADA_PROJECT_PATH} does not
11901 exist, then the project path contains only one directory, namely the one where
11902 the project file is located.
11906 If a relative pathname is used, as in
11908 @smallexample @c projectfile
11913 then the path is relative to the directory where the importing project file is
11914 located. Any symbolic link will be fully resolved in the directory
11915 of the importing project file before the imported project file is examined.
11917 If the @code{with}'ed project file name does not have an extension,
11918 the default is @file{^.gpr^.GPR^}. If a file with this extension is not found,
11919 then the file name as specified in the @code{with} clause (no extension) will
11920 be used. In the above example, if a file @code{project1.gpr} is found, then it
11921 will be used; otherwise, if a file @code{^project1^PROJECT1^} exists
11922 then it will be used; if neither file exists, this is an error.
11924 A warning is issued if the name of the project file does not match the
11925 name of the project; this check is case insensitive.
11927 Any source file that is an immediate source of the imported project can be
11928 used by the immediate sources of the importing project, transitively. Thus
11929 if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
11930 sources of @code{A} may depend on the immediate sources of @code{C}, even if
11931 @code{A} does not import @code{C} explicitly. However, this is not recommended,
11932 because if and when @code{B} ceases to import @code{C}, some sources in
11933 @code{A} will no longer compile.
11935 A side effect of this capability is that normally cyclic dependencies are not
11936 permitted: if @code{A} imports @code{B} (directly or indirectly) then @code{B}
11937 is not allowed to import @code{A}. However, there are cases when cyclic
11938 dependencies would be beneficial. For these cases, another form of import
11939 between projects exists, the @code{limited with}: a project @code{A} that
11940 imports a project @code{B} with a straigh @code{with} may also be imported,
11941 directly or indirectly, by @code{B} on the condition that imports from @code{B}
11942 to @code{A} include at least one @code{limited with}.
11944 @smallexample @c 0projectfile
11950 limited with "../a/a.gpr";
11958 limited with "../a/a.gpr";
11964 In the above legal example, there are two project cycles:
11967 @item A -> C -> D -> A
11971 In each of these cycle there is one @code{limited with}: import of @code{A}
11972 from @code{B} and import of @code{A} from @code{D}.
11974 The difference between straight @code{with} and @code{limited with} is that
11975 the name of a project imported with a @code{limited with} cannot be used in the
11976 project that imports it. In particular, its packages cannot be renamed and
11977 its variables cannot be referred to.
11979 An exception to the above rules for @code{limited with} is that for the main
11980 project specified to @command{gnatmake} or to the @command{GNAT} driver a
11981 @code{limited with} is equivalent to a straight @code{with}. For example,
11982 in the example above, projects @code{B} and @code{D} could not be main
11983 projects for @command{gnatmake} or to the @command{GNAT} driver, because they
11984 each have a @code{limited with} that is the only one in a cycle of importing
11987 @c *********************
11988 @c * Project Extension *
11989 @c *********************
11991 @node Project Extension
11992 @section Project Extension
11995 During development of a large system, it is sometimes necessary to use
11996 modified versions of some of the source files, without changing the original
11997 sources. This can be achieved through the @emph{project extension} facility.
11999 @smallexample @c projectfile
12000 project Modified_Utilities extends "/baseline/utilities.gpr" is ...
12004 A project extension declaration introduces an extending project
12005 (the @emph{child}) and a project being extended (the @emph{parent}).
12007 By default, a child project inherits all the sources of its parent.
12008 However, inherited sources can be overridden: a unit in a parent is hidden
12009 by a unit of the same name in the child.
12011 Inherited sources are considered to be sources (but not immediate sources)
12012 of the child project; see @ref{Project File Syntax}.
12014 An inherited source file retains any switches specified in the parent project.
12016 For example if the project @code{Utilities} contains the specification and the
12017 body of an Ada package @code{Util_IO}, then the project
12018 @code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
12019 The original body of @code{Util_IO} will not be considered in program builds.
12020 However, the package specification will still be found in the project
12023 A child project can have only one parent but it may import any number of other
12026 A project is not allowed to import directly or indirectly at the same time a
12027 child project and any of its ancestors.
12029 @c ****************************************
12030 @c * External References in Project Files *
12031 @c ****************************************
12033 @node External References in Project Files
12034 @section External References in Project Files
12037 A project file may contain references to external variables; such references
12038 are called @emph{external references}.
12040 An external variable is either defined as part of the environment (an
12041 environment variable in Unix, for example) or else specified on the command
12042 line via the @option{^-X^/EXTERNAL_REFERENCE=^@emph{vbl}=@emph{value}} switch.
12043 If both, then the command line value is used.
12045 The value of an external reference is obtained by means of the built-in
12046 function @code{external}, which returns a string value.
12047 This function has two forms:
12049 @item @code{external (external_variable_name)}
12050 @item @code{external (external_variable_name, default_value)}
12054 Each parameter must be a string literal. For example:
12056 @smallexample @c projectfile
12058 external ("OS", "GNU/Linux")
12062 In the form with one parameter, the function returns the value of
12063 the external variable given as parameter. If this name is not present in the
12064 environment, the function returns an empty string.
12066 In the form with two string parameters, the second argument is
12067 the value returned when the variable given as the first argument is not
12068 present in the environment. In the example above, if @code{"OS"} is not
12069 the name of ^an environment variable^a logical name^ and is not passed on
12070 the command line, then the returned value is @code{"GNU/Linux"}.
12072 An external reference may be part of a string expression or of a string
12073 list expression, and can therefore appear in a variable declaration or
12074 an attribute declaration.
12076 @smallexample @c projectfile
12078 type Mode_Type is ("Debug", "Release");
12079 Mode : Mode_Type := external ("MODE");
12086 @c *****************************
12087 @c * Packages in Project Files *
12088 @c *****************************
12090 @node Packages in Project Files
12091 @section Packages in Project Files
12094 A @emph{package} defines the settings for project-aware tools within a
12096 For each such tool one can declare a package; the names for these
12097 packages are preset (see @ref{Packages}).
12098 A package may contain variable declarations, attribute declarations, and case
12101 @smallexample @c projectfile
12104 package Builder is -- used by gnatmake
12105 for ^Default_Switches^Default_Switches^ ("Ada")
12114 The syntax of package declarations mimics that of package in Ada.
12116 Most of the packages have an attribute
12117 @code{^Default_Switches^Default_Switches^}.
12118 This attribute is an associative array, and its value is a string list.
12119 The index of the associative array is the name of a programming language (case
12120 insensitive). This attribute indicates the ^switch^switch^
12121 or ^switches^switches^ to be used
12122 with the corresponding tool.
12124 Some packages also have another attribute, @code{^Switches^Switches^},
12125 an associative array whose value is a string list.
12126 The index is the name of a source file.
12127 This attribute indicates the ^switch^switch^
12128 or ^switches^switches^ to be used by the corresponding
12129 tool when dealing with this specific file.
12131 Further information on these ^switch^switch^-related attributes is found in
12132 @ref{^Switches^Switches^ and Project Files}.
12134 A package may be declared as a @emph{renaming} of another package; e.g., from
12135 the project file for an imported project.
12137 @smallexample @c projectfile
12139 with "/global/apex.gpr";
12141 package Naming renames Apex.Naming;
12148 Packages that are renamed in other project files often come from project files
12149 that have no sources: they are just used as templates. Any modification in the
12150 template will be reflected automatically in all the project files that rename
12151 a package from the template.
12153 In addition to the tool-oriented packages, you can also declare a package
12154 named @code{Naming} to establish specialized source file naming conventions
12155 (see @ref{Naming Schemes}).
12157 @c ************************************
12158 @c * Variables from Imported Projects *
12159 @c ************************************
12161 @node Variables from Imported Projects
12162 @section Variables from Imported Projects
12165 An attribute or variable defined in an imported or parent project can
12166 be used in expressions in the importing / extending project.
12167 Such an attribute or variable is denoted by an expanded name whose prefix
12168 is either the name of the project or the expanded name of a package within
12171 @smallexample @c projectfile
12174 project Main extends "base" is
12175 Var1 := Imported.Var;
12176 Var2 := Base.Var & ".new";
12181 for ^Default_Switches^Default_Switches^ ("Ada")
12182 use Imported.Builder.Ada_^Switches^Switches^ &
12183 "^-gnatg^-gnatg^" &
12189 package Compiler is
12190 for ^Default_Switches^Default_Switches^ ("Ada")
12191 use Base.Compiler.Ada_^Switches^Switches^;
12202 The value of @code{Var1} is a copy of the variable @code{Var} defined
12203 in the project file @file{"imported.gpr"}
12205 the value of @code{Var2} is a copy of the value of variable @code{Var}
12206 defined in the project file @file{base.gpr}, concatenated with @code{".new"}
12208 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
12209 @code{Builder} is a string list that includes in its value a copy of the value
12210 of @code{Ada_^Switches^Switches^} defined in the @code{Builder} package
12211 in project file @file{imported.gpr} plus two new elements:
12212 @option{"^-gnatg^-gnatg^"}
12213 and @option{"^-v^-v^"};
12215 attribute @code{^Default_Switches^Default_Switches^ ("Ada")} in package
12216 @code{Compiler} is a copy of the variable @code{Ada_^Switches^Switches^}
12217 defined in the @code{Compiler} package in project file @file{base.gpr},
12218 the project being extended.
12221 @c ******************
12222 @c * Naming Schemes *
12223 @c ******************
12225 @node Naming Schemes
12226 @section Naming Schemes
12229 Sometimes an Ada software system is ported from a foreign compilation
12230 environment to GNAT, and the file names do not use the default GNAT
12231 conventions. Instead of changing all the file names (which for a variety
12232 of reasons might not be possible), you can define the relevant file
12233 naming scheme in the @code{Naming} package in your project file.
12236 Note that the use of pragmas described in @ref{Alternative
12237 File Naming Schemes} by mean of a configuration pragmas file is not
12238 supported when using project files. You must use the features described
12239 in this paragraph. You can however use specify other configuration
12240 pragmas (see @ref{Specifying Configuration Pragmas}).
12243 For example, the following
12244 package models the Apex file naming rules:
12246 @smallexample @c projectfile
12249 for Casing use "lowercase";
12250 for Dot_Replacement use ".";
12251 for Spec_Suffix ("Ada") use ".1.ada";
12252 for Body_Suffix ("Ada") use ".2.ada";
12259 For example, the following package models the DEC Ada file naming rules:
12261 @smallexample @c projectfile
12264 for Casing use "lowercase";
12265 for Dot_Replacement use "__";
12266 for Spec_Suffix ("Ada") use "_.^ada^ada^";
12267 for Body_Suffix ("Ada") use ".^ada^ada^";
12273 (Note that @code{Casing} is @code{"lowercase"} because GNAT gets the file
12274 names in lower case)
12278 You can define the following attributes in package @code{Naming}:
12283 This must be a string with one of the three values @code{"lowercase"},
12284 @code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
12287 If @var{Casing} is not specified, then the default is @code{"lowercase"}.
12289 @item @var{Dot_Replacement}
12290 This must be a string whose value satisfies the following conditions:
12293 @item It must not be empty
12294 @item It cannot start or end with an alphanumeric character
12295 @item It cannot be a single underscore
12296 @item It cannot start with an underscore followed by an alphanumeric
12297 @item It cannot contain a dot @code{'.'} except if the entire string
12302 If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
12304 @item @var{Spec_Suffix}
12305 This is an associative array (indexed by the programming language name, case
12306 insensitive) whose value is a string that must satisfy the following
12310 @item It must not be empty
12311 @item It must include at least one dot
12314 If @code{Spec_Suffix ("Ada")} is not specified, then the default is
12315 @code{"^.ads^.ADS^"}.
12317 @item @var{Body_Suffix}
12318 This is an associative array (indexed by the programming language name, case
12319 insensitive) whose value is a string that must satisfy the following
12323 @item It must not be empty
12324 @item It must include at least one dot
12325 @item It cannot end with the same string as @code{Spec_Suffix ("Ada")}
12328 If @code{Body_Suffix ("Ada")} is not specified, then the default is
12329 @code{"^.adb^.ADB^"}.
12331 @item @var{Separate_Suffix}
12332 This must be a string whose value satisfies the same conditions as
12333 @code{Body_Suffix}.
12336 If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
12337 value as @code{Body_Suffix ("Ada")}.
12341 You can use the associative array attribute @code{Spec} to define
12342 the source file name for an individual Ada compilation unit's spec. The array
12343 index must be a string literal that identifies the Ada unit (case insensitive).
12344 The value of this attribute must be a string that identifies the file that
12345 contains this unit's spec (case sensitive or insensitive depending on the
12348 @smallexample @c projectfile
12349 for Spec ("MyPack.MyChild") use "mypack.mychild.spec";
12354 You can use the associative array attribute @code{Body} to
12355 define the source file name for an individual Ada compilation unit's body
12356 (possibly a subunit). The array index must be a string literal that identifies
12357 the Ada unit (case insensitive). The value of this attribute must be a string
12358 that identifies the file that contains this unit's body or subunit (case
12359 sensitive or insensitive depending on the operating system).
12361 @smallexample @c projectfile
12362 for Body ("MyPack.MyChild") use "mypack.mychild.body";
12366 @c ********************
12367 @c * Library Projects *
12368 @c ********************
12370 @node Library Projects
12371 @section Library Projects
12374 @emph{Library projects} are projects whose object code is placed in a library.
12375 (Note that this facility is not yet supported on all platforms)
12377 To create a library project, you need to define in its project file
12378 two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
12379 Additionally, you may define the library-related attributes
12380 @code{Library_Kind}, @code{Library_Version}, @code{Library_Interface},
12381 @code{Library_Auto_Init}, @code{Library_Options} and @code{Library_GCC}.
12383 The @code{Library_Name} attribute has a string value. There is no restriction
12384 on the name of a library. It is the responsability of the developer to
12385 choose a name that will be accepted by the platform. It is recommanded to
12386 choose names that could be Ada identifiers; such names are almost guaranteed
12387 to be acceptable on all platforms.
12389 The @code{Library_Dir} attribute has a string value that designates the path
12390 (absolute or relative) of the directory where the library will reside.
12391 It must designate an existing directory, and this directory must be
12392 different from the project's object directory. It also needs to be writable.
12394 If both @code{Library_Name} and @code{Library_Dir} are specified and
12395 are legal, then the project file defines a library project. The optional
12396 library-related attributes are checked only for such project files.
12398 The @code{Library_Kind} attribute has a string value that must be one of the
12399 following (case insensitive): @code{"static"}, @code{"dynamic"} or
12400 @code{"relocatable"}. If this attribute is not specified, the library is a
12401 static library, that is an archive of object files that can be potentially
12402 linked into an static executable. Otherwise, the library may be dynamic or
12403 relocatable, that is a library that is loaded only at the start of execution.
12404 Depending on the operating system, there may or may not be a distinction
12405 between dynamic and relocatable libraries. For Unix and VMS Unix there is no
12408 If you need to build both a static and a dynamic library, you should use two
12409 different object directories, since in some cases some extra code needs to
12410 be generated for the latter. For such cases, it is recommended to either use
12411 two different project files, or a single one which uses external variables
12412 to indicate what kind of library should be build.
12414 The @code{Library_Version} attribute has a string value whose interpretation
12415 is platform dependent. It has no effect on VMS and Windows. On Unix, it is
12416 used only for dynamic/relocatable libraries as the internal name of the
12417 library (the @code{"soname"}). If the library file name (built from the
12418 @code{Library_Name}) is different from the @code{Library_Version}, then the
12419 library file will be a symbolic link to the actual file whose name will be
12420 @code{Library_Version}.
12424 @smallexample @c projectfile
12430 for Library_Dir use "lib_dir";
12431 for Library_Name use "dummy";
12432 for Library_Kind use "relocatable";
12433 for Library_Version use "libdummy.so." & Version;
12440 Directory @file{lib_dir} will contain the internal library file whose name
12441 will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
12442 @file{libdummy.so.1}.
12444 When @command{gnatmake} detects that a project file
12445 is a library project file, it will check all immediate sources of the project
12446 and rebuild the library if any of the sources have been recompiled.
12448 Standard project files can import library project files. In such cases,
12449 the libraries will only be rebuild if some of its sources are recompiled
12450 because they are in the closure of some other source in an importing project.
12451 Sources of the library project files that are not in such a closure will
12452 not be checked, unless the full library is checked, because one of its sources
12453 needs to be recompiled.
12455 For instance, assume the project file @code{A} imports the library project file
12456 @code{L}. The immediate sources of A are @file{a1.adb}, @file{a2.ads} and
12457 @file{a2.adb}. The immediate sources of L are @file{l1.ads}, @file{l1.adb},
12458 @file{l2.ads}, @file{l2.adb}.
12460 If @file{l1.adb} has been modified, then the library associated with @code{L}
12461 will be rebuild when compiling all the immediate sources of @code{A} only
12462 if @file{a1.ads}, @file{a2.ads} or @file{a2.adb} includes a statement
12465 To be sure that all the sources in the library associated with @code{L} are
12466 up to date, and that all the sources of parject @code{A} are also up to date,
12467 the following two commands needs to be used:
12474 When a library is built or rebuilt, an attempt is made first to delete all
12475 files in the library directory.
12476 All @file{ALI} files will also be copied from the object directory to the
12477 library directory. To build executables, @command{gnatmake} will use the
12478 library rather than the individual object files.
12481 @c **********************************************
12482 @c * Using Third-Party Libraries through Projects
12483 @c **********************************************
12484 @node Using Third-Party Libraries through Projects
12485 @section Using Third-Party Libraries through Projects
12487 Whether you are exporting your own library to make it available to
12488 clients, or you are using a library provided by a third party, it is
12489 convenient to have project files that automatically set the correct
12490 command line switches for the compiler and linker.
12492 Such project files are very similar to the library project files;
12493 @xref{Library Projects}. The only difference is that you set the
12494 @code{Source_Dirs} and @code{Object_Dir} attribute so that they point to the
12495 directories where, respectively, the sources and the read-only ALI files have
12498 If you need to interface with a set of libraries, as opposed to a
12499 single one, you need to create one library project for each of the
12500 libraries. In addition, a top-level project that imports all these
12501 library projects should be provided, so that the user of your library
12502 has a single @code{with} clause to add to his own projects.
12504 For instance, let's assume you are providing two static libraries
12505 @file{liba.a} and @file{libb.a}. The user needs to link with
12506 both of these libraries. Each of these is associated with its
12507 own set of header files. Let's assume furthermore that all the
12508 header files for the two libraries have been installed in the same
12509 directory @file{headers}. The @file{ALI} files are found in the same
12510 @file{headers} directory.
12512 In this case, you should provide the following three projects:
12514 @smallexample @c projectfile
12516 with "liba", "libb";
12517 project My_Library is
12518 for Source_Dirs use ("headers");
12519 for Object_Dir use "headers";
12525 for Source_Dirs use ();
12526 for Library_Dir use "lib";
12527 for Library_Name use "a";
12528 for Library_Kind use "static";
12534 for Source_Dirs use ();
12535 for Library_Dir use "lib";
12536 for Library_Name use "b";
12537 for Library_Kind use "static";
12542 @c *******************************
12543 @c * Stand-alone Library Projects *
12544 @c *******************************
12546 @node Stand-alone Library Projects
12547 @section Stand-alone Library Projects
12550 A Stand-alone Library is a library that contains the necessary code to
12551 elaborate the Ada units that are included in the library. A Stand-alone
12552 Library is suitable to be used in an executable when the main is not
12553 in Ada. However, Stand-alone Libraries may also be used with an Ada main
12556 A Stand-alone Library Project is a Library Project where the library is
12557 a Stand-alone Library.
12559 To be a Stand-alone Library Project, in addition to the two attributes
12560 that make a project a Library Project (@code{Library_Name} and
12561 @code{Library_Dir}, see @ref{Library Projects}), the attribute
12562 @code{Library_Interface} must be defined.
12564 @smallexample @c projectfile
12566 for Library_Dir use "lib_dir";
12567 for Library_Name use "dummy";
12568 for Library_Interface use ("int1", "int1.child");
12572 Attribute @code{Library_Interface} has a non empty string list value,
12573 each string in the list designating a unit contained in an immediate source
12574 of the project file.
12576 When a Stand-alone Library is built, first the binder is invoked to build
12577 a package whose name depends on the library name
12578 (^b~dummy.ads/b^B$DUMMY.ADS/B^ in the example above).
12579 This binder-generated package includes initialization and
12580 finalization procedures whose
12581 names depend on the library name (dummyinit and dummyfinal in the example
12582 above). The object corresponding to this package is included in the library.
12584 A dynamic or relocatable Stand-alone Library is automatically initialized
12585 if automatic initialization of Stand-alone Libraries is supported on the
12586 platform and if attribute @code{Library_Auto_Init} is not specified or
12587 is specified with the value "true". A static Stand-alone Library is never
12588 automatically initialized.
12590 Single string attribute @code{Library_Auto_Init} may be specified with only
12591 two possible values: "false" or "true" (case-insensitive). Specifying
12592 "false" for attribute @code{Library_Auto_Init} will prevent automatic
12593 initialization of dynamic or relocatable libraries.
12595 When a non automatically initialized Stand-alone Library is used
12596 in an executable, its initialization procedure must be called before
12597 any service of the library is used.
12598 When the main subprogram is in Ada, it may mean that the initialization
12599 procedure has to be called during elaboration of another package.
12601 For a Stand-Alone Library, only the @file{ALI} files of the Interface Units
12602 (those that are listed in attribute @code{Library_Interface}) are copied to
12603 the Library Directory. As a consequence, only the Interface Units may be
12604 imported from Ada units outside of the library. If other units are imported,
12605 the binding phase will fail.
12607 When a Stand-Alone Library is bound, the switches that are specified in
12608 the attribute @code{Default_Switches ("Ada")} in package @code{Binder} are
12609 used in the call to @command{gnatbind}.
12611 The string list attribute @code{Library_Options} may be used to specified
12612 additional switches to the call to @command{gcc} to link the library.
12614 The attribute @code{Library_Src_Dir}, may be specified for a
12615 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
12616 single string value. Its value must be the path (absolute or relative to the
12617 project directory) of an existing directory. This directory cannot be the
12618 object directory or one of the source directories, but it can be the same as
12619 the library directory. The sources of the Interface
12620 Units of the library, necessary to an Ada client of the library, will be
12621 copied to the designated directory, called Interface Copy directory.
12622 These sources includes the specs of the Interface Units, but they may also
12623 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
12624 are used, or when there is a generic units in the spec. Before the sources
12625 are copied to the Interface Copy directory, an attempt is made to delete all
12626 files in the Interface Copy directory.
12628 @c *************************************
12629 @c * Switches Related to Project Files *
12630 @c *************************************
12631 @node Switches Related to Project Files
12632 @section Switches Related to Project Files
12635 The following switches are used by GNAT tools that support project files:
12639 @item ^-P^/PROJECT_FILE=^@var{project}
12640 @cindex @option{^-P^/PROJECT_FILE^} (any tool supporting project files)
12641 Indicates the name of a project file. This project file will be parsed with
12642 the verbosity indicated by @option{^-vP^MESSAGE_PROJECT_FILES=^@emph{x}},
12643 if any, and using the external references indicated
12644 by @option{^-X^/EXTERNAL_REFERENCE^} switches, if any.
12646 There may zero, one or more spaces between @option{-P} and @var{project}.
12650 There must be only one @option{^-P^/PROJECT_FILE^} switch on the command line.
12653 Since the Project Manager parses the project file only after all the switches
12654 on the command line are checked, the order of the switches
12655 @option{^-P^/PROJECT_FILE^},
12656 @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}}
12657 or @option{^-X^/EXTERNAL_REFERENCE^} is not significant.
12659 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
12660 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (any tool supporting project files)
12661 Indicates that external variable @var{name} has the value @var{value}.
12662 The Project Manager will use this value for occurrences of
12663 @code{external(name)} when parsing the project file.
12667 If @var{name} or @var{value} includes a space, then @var{name=value} should be
12668 put between quotes.
12676 Several @option{^-X^/EXTERNAL_REFERENCE^} switches can be used simultaneously.
12677 If several @option{^-X^/EXTERNAL_REFERENCE^} switches specify the same
12678 @var{name}, only the last one is used.
12681 An external variable specified with a @option{^-X^/EXTERNAL_REFERENCE^} switch
12682 takes precedence over the value of the same name in the environment.
12684 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
12685 @cindex @code{^-vP^/MESSAGES_PROJECT_FILE^} (any tool supporting project files)
12686 @c Previous line uses code vs option command, to stay less than 80 chars
12687 Indicates the verbosity of the parsing of GNAT project files.
12690 @option{-vP0} means Default;
12691 @option{-vP1} means Medium;
12692 @option{-vP2} means High.
12696 There are three possible options for this qualifier: DEFAULT, MEDIUM and
12701 The default is ^Default^DEFAULT^: no output for syntactically correct
12704 If several @option{^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}} switches are present,
12705 only the last one is used.
12709 @c **********************************
12710 @c * Tools Supporting Project Files *
12711 @c **********************************
12713 @node Tools Supporting Project Files
12714 @section Tools Supporting Project Files
12717 * gnatmake and Project Files::
12718 * The GNAT Driver and Project Files::
12720 * Glide and Project Files::
12724 @node gnatmake and Project Files
12725 @subsection gnatmake and Project Files
12728 This section covers several topics related to @command{gnatmake} and
12729 project files: defining ^switches^switches^ for @command{gnatmake}
12730 and for the tools that it invokes; specifying configuration pragmas;
12731 the use of the @code{Main} attribute; building and rebuilding library project
12735 * ^Switches^Switches^ and Project Files::
12736 * Specifying Configuration Pragmas::
12737 * Project Files and Main Subprograms::
12738 * Library Project Files::
12741 @node ^Switches^Switches^ and Project Files
12742 @subsubsection ^Switches^Switches^ and Project Files
12745 It is not currently possible to specify VMS style qualifiers in the project
12746 files; only Unix style ^switches^switches^ may be specified.
12750 For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
12751 @code{Linker}, you can specify a @code{^Default_Switches^Default_Switches^}
12752 attribute, a @code{^Switches^Switches^} attribute, or both;
12753 as their names imply, these ^switch^switch^-related
12754 attributes affect the ^switches^switches^ that are used for each of these GNAT
12756 @command{gnatmake} is invoked. As will be explained below, these
12757 component-specific ^switches^switches^ precede
12758 the ^switches^switches^ provided on the @command{gnatmake} command line.
12760 The @code{^Default_Switches^Default_Switches^} attribute is an associative
12761 array indexed by language name (case insensitive) whose value is a string list.
12764 @smallexample @c projectfile
12766 package Compiler is
12767 for ^Default_Switches^Default_Switches^ ("Ada")
12768 use ("^-gnaty^-gnaty^",
12775 The @code{^Switches^Switches^} attribute is also an associative array,
12776 indexed by a file name (which may or may not be case sensitive, depending
12777 on the operating system) whose value is a string list. For example:
12779 @smallexample @c projectfile
12782 for ^Switches^Switches^ ("main1.adb")
12784 for ^Switches^Switches^ ("main2.adb")
12791 For the @code{Builder} package, the file names must designate source files
12792 for main subprograms. For the @code{Binder} and @code{Linker} packages, the
12793 file names must designate @file{ALI} or source files for main subprograms.
12794 In each case just the file name without an explicit extension is acceptable.
12796 For each tool used in a program build (@command{gnatmake}, the compiler, the
12797 binder, and the linker), the corresponding package @dfn{contributes} a set of
12798 ^switches^switches^ for each file on which the tool is invoked, based on the
12799 ^switch^switch^-related attributes defined in the package.
12800 In particular, the ^switches^switches^
12801 that each of these packages contributes for a given file @var{f} comprise:
12805 the value of attribute @code{^Switches^Switches^ (@var{f})},
12806 if it is specified in the package for the given file,
12808 otherwise, the value of @code{^Default_Switches^Default_Switches^ ("Ada")},
12809 if it is specified in the package.
12813 If neither of these attributes is defined in the package, then the package does
12814 not contribute any ^switches^switches^ for the given file.
12816 When @command{gnatmake} is invoked on a file, the ^switches^switches^ comprise
12817 two sets, in the following order: those contributed for the file
12818 by the @code{Builder} package;
12819 and the switches passed on the command line.
12821 When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
12822 the ^switches^switches^ passed to the tool comprise three sets,
12823 in the following order:
12827 the applicable ^switches^switches^ contributed for the file
12828 by the @code{Builder} package in the project file supplied on the command line;
12831 those contributed for the file by the package (in the relevant project file --
12832 see below) corresponding to the tool; and
12835 the applicable switches passed on the command line.
12839 The term @emph{applicable ^switches^switches^} reflects the fact that
12840 @command{gnatmake} ^switches^switches^ may or may not be passed to individual
12841 tools, depending on the individual ^switch^switch^.
12843 @command{gnatmake} may invoke the compiler on source files from different
12844 projects. The Project Manager will use the appropriate project file to
12845 determine the @code{Compiler} package for each source file being compiled.
12846 Likewise for the @code{Binder} and @code{Linker} packages.
12848 As an example, consider the following package in a project file:
12850 @smallexample @c projectfile
12853 package Compiler is
12854 for ^Default_Switches^Default_Switches^ ("Ada")
12856 for ^Switches^Switches^ ("a.adb")
12858 for ^Switches^Switches^ ("b.adb")
12860 "^-gnaty^-gnaty^");
12867 If @command{gnatmake} is invoked with this project file, and it needs to
12868 compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
12869 @file{a.adb} will be compiled with the ^switch^switch^
12870 @option{^-O1^-O1^},
12871 @file{b.adb} with ^switches^switches^
12873 and @option{^-gnaty^-gnaty^},
12874 and @file{c.adb} with @option{^-g^-g^}.
12876 The following example illustrates the ordering of the ^switches^switches^
12877 contributed by different packages:
12879 @smallexample @c projectfile
12883 for ^Switches^Switches^ ("main.adb")
12891 package Compiler is
12892 for ^Switches^Switches^ ("main.adb")
12900 If you issue the command:
12903 gnatmake ^-Pproj2^/PROJECT_FILE=PROJ2^ -O0 main
12907 then the compiler will be invoked on @file{main.adb} with the following
12908 sequence of ^switches^switches^
12911 ^-g -O1 -O2 -O0^-g -O1 -O2 -O0^
12914 with the last @option{^-O^-O^}
12915 ^switch^switch^ having precedence over the earlier ones;
12916 several other ^switches^switches^
12917 (such as @option{^-c^-c^}) are added implicitly.
12919 The ^switches^switches^
12921 and @option{^-O1^-O1^} are contributed by package
12922 @code{Builder}, @option{^-O2^-O2^} is contributed
12923 by the package @code{Compiler}
12924 and @option{^-O0^-O0^} comes from the command line.
12926 The @option{^-g^-g^}
12927 ^switch^switch^ will also be passed in the invocation of
12928 @command{Gnatlink.}
12930 A final example illustrates switch contributions from packages in different
12933 @smallexample @c projectfile
12936 for Source_Files use ("pack.ads", "pack.adb");
12937 package Compiler is
12938 for ^Default_Switches^Default_Switches^ ("Ada")
12939 use ("^-gnata^-gnata^");
12947 for Source_Files use ("foo_main.adb", "bar_main.adb");
12949 for ^Switches^Switches^ ("foo_main.adb")
12957 -- Ada source file:
12959 procedure Foo_Main is
12967 gnatmake ^-PProj4^/PROJECT_FILE=PROJ4^ foo_main.adb -cargs -gnato
12971 then the ^switches^switches^ passed to the compiler for @file{foo_main.adb} are
12972 @option{^-g^-g^} (contributed by the package @code{Proj4.Builder}) and
12973 @option{^-gnato^-gnato^} (passed on the command line).
12974 When the imported package @code{Pack} is compiled, the ^switches^switches^ used
12975 are @option{^-g^-g^} from @code{Proj4.Builder},
12976 @option{^-gnata^-gnata^} (contributed from package @code{Proj3.Compiler},
12977 and @option{^-gnato^-gnato^} from the command line.
12980 When using @command{gnatmake} with project files, some ^switches^switches^ or
12981 arguments may be expressed as relative paths. As the working directory where
12982 compilation occurs may change, these relative paths are converted to absolute
12983 paths. For the ^switches^switches^ found in a project file, the relative paths
12984 are relative to the project file directory, for the switches on the command
12985 line, they are relative to the directory where @command{gnatmake} is invoked.
12986 The ^switches^switches^ for which this occurs are:
12992 ^-aI^-aI^, as well as all arguments that are not switches (arguments to
12994 ^-o^-o^, object files specified in package @code{Linker} or after
12995 -largs on the command line). The exception to this rule is the ^switch^switch^
12996 ^--RTS=^--RTS=^ for which a relative path argument is never converted.
12998 @node Specifying Configuration Pragmas
12999 @subsubsection Specifying Configuration Pragmas
13001 When using @command{gnatmake} with project files, if there exists a file
13002 @file{gnat.adc} that contains configuration pragmas, this file will be
13005 Configuration pragmas can be defined by means of the following attributes in
13006 project files: @code{Global_Configuration_Pragmas} in package @code{Builder}
13007 and @code{Local_Configuration_Pragmas} in package @code{Compiler}.
13009 Both these attributes are single string attributes. Their values is the path
13010 name of a file containing configuration pragmas. If a path name is relative,
13011 then it is relative to the project directory of the project file where the
13012 attribute is defined.
13014 When compiling a source, the configuration pragmas used are, in order,
13015 those listed in the file designated by attribute
13016 @code{Global_Configuration_Pragmas} in package @code{Builder} of the main
13017 project file, if it is specified, and those listed in the file designated by
13018 attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of
13019 the project file of the source, if it exists.
13021 @node Project Files and Main Subprograms
13022 @subsubsection Project Files and Main Subprograms
13025 When using a project file, you can invoke @command{gnatmake}
13026 with one or several main subprograms, by specifying their source files on the
13030 gnatmake ^-P^/PROJECT_FILE=^prj main1 main2 main3
13034 Each of these needs to be a source file of the same project, except
13035 when the switch ^-u^/UNIQUE^ is used.
13038 When ^-u^/UNIQUE^ is not used, all the mains need to be sources of the
13039 same project, one of the project in the tree rooted at the project specified
13040 on the command line. The package @code{Builder} of this common project, the
13041 "main project" is the one that is considered by @command{gnatmake}.
13044 When ^-u^/UNIQUE^ is used, the specified source files may be in projects
13045 imported directly or indirectly by the project specified on the command line.
13046 Note that if such a source file is not part of the project specified on the
13047 command line, the ^switches^switches^ found in package @code{Builder} of the
13048 project specified on the command line, if any, that are transmitted
13049 to the compiler will still be used, not those found in the project file of
13053 When using a project file, you can also invoke @command{gnatmake} without
13054 explicitly specifying any main, and the effect depends on whether you have
13055 defined the @code{Main} attribute. This attribute has a string list value,
13056 where each element in the list is the name of a source file (the file
13057 extension is optional) that contains a unit that can be a main subprogram.
13059 If the @code{Main} attribute is defined in a project file as a non-empty
13060 string list and the switch @option{^-u^/UNIQUE^} is not used on the command
13061 line, then invoking @command{gnatmake} with this project file but without any
13062 main on the command line is equivalent to invoking @command{gnatmake} with all
13063 the file names in the @code{Main} attribute on the command line.
13066 @smallexample @c projectfile
13069 for Main use ("main1", "main2", "main3");
13075 With this project file, @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^"}
13077 @code{"gnatmake ^-Pprj^/PROJECT_FILE=PRJ^ main1 main2 main3"}.
13079 When the project attribute @code{Main} is not specified, or is specified
13080 as an empty string list, or when the switch @option{-u} is used on the command
13081 line, then invoking @command{gnatmake} with no main on the command line will
13082 result in all immediate sources of the project file being checked, and
13083 potentially recompiled. Depending on the presence of the switch @option{-u},
13084 sources from other project files on which the immediate sources of the main
13085 project file depend are also checked and potentially recompiled. In other
13086 words, the @option{-u} switch is applied to all of the immediate sources of the
13089 When no main is specified on the command line and attribute @code{Main} exists
13090 and includes several mains, or when several mains are specified on the
13091 command line, the default ^switches^switches^ in package @code{Builder} will
13092 be used for all mains, even if there are specific ^switches^switches^
13093 specified for one or several mains.
13095 But the ^switches^switches^ from package @code{Binder} or @code{Linker} will be
13096 the specific ^switches^switches^ for each main, if they are specified.
13098 @node Library Project Files
13099 @subsubsection Library Project Files
13102 When @command{gnatmake} is invoked with a main project file that is a library
13103 project file, it is not allowed to specify one or more mains on the command
13107 When a library project file is specified, switches ^-b^/ACTION=BIND^ and
13108 ^-l^/ACTION=LINK^ have special meanings.
13111 @item ^-b^/ACTION=BIND^ is only allwed for stand-alone libraries. It indicates
13112 to @command{gnatmake} that @command{gnatbind} should be invoked for the
13115 @item ^-l^/ACTION=LINK^ may be used for all library projects. It indicates
13116 to @command{gnatmake} that the binder generated file should be compiled
13117 (in the case of a stand-alone library) and that the library should be built.
13121 @node The GNAT Driver and Project Files
13122 @subsection The GNAT Driver and Project Files
13125 A number of GNAT tools, other than @command{^gnatmake^gnatmake^}
13127 @command{^gnatbind^gnatbind^},
13128 @command{^gnatfind^gnatfind^},
13129 @command{^gnatlink^gnatlink^},
13130 @command{^gnatls^gnatls^},
13131 @command{^gnatelim^gnatelim^},
13132 @command{^gnatpp^gnatpp^},
13133 and @command{^gnatxref^gnatxref^}. However, none of these tools can be invoked
13134 directly with a project file switch (@option{^-P^/PROJECT_FILE=^}).
13135 They must be invoked through the @command{gnat} driver.
13137 The @command{gnat} driver is a front-end that accepts a number of commands and
13138 call the corresponding tool. It has been designed initially for VMS to convert
13139 VMS style qualifiers to Unix style switches, but it is now available to all
13140 the GNAT supported platforms.
13142 On non VMS platforms, the @command{gnat} driver accepts the following commands
13143 (case insensitive):
13147 BIND to invoke @command{^gnatbind^gnatbind^}
13149 CHOP to invoke @command{^gnatchop^gnatchop^}
13151 CLEAN to invoke @command{^gnatclean^gnatclean^}
13153 COMP or COMPILE to invoke the compiler
13155 ELIM to invoke @command{^gnatelim^gnatelim^}
13157 FIND to invoke @command{^gnatfind^gnatfind^}
13159 KR or KRUNCH to invoke @command{^gnatkr^gnatkr^}
13161 LINK to invoke @command{^gnatlink^gnatlink^}
13163 LS or LIST to invoke @command{^gnatls^gnatls^}
13165 MAKE to invoke @command{^gnatmake^gnatmake^}
13167 NAME to invoke @command{^gnatname^gnatname^}
13169 PREP or PREPROCESS to invoke @command{^gnatprep^gnatprep^}
13171 PP or PRETTY to invoke @command{^gnatpp^gnatpp^}
13173 STUB to invoke @command{^gnatstub^gnatstub^}
13175 XREF to invoke @command{^gnatxref^gnatxref^}
13179 Note that the compiler is invoked using the command
13180 @command{^gnatmake -f -u -c^gnatmake -f -u -c^}.
13183 The command may be followed by switches and arguments for the invoked
13187 gnat bind -C main.ali
13193 Switches may also be put in text files, one switch per line, and the text
13194 files may be specified with their path name preceded by '@@'.
13197 gnat bind @@args.txt main.ali
13201 In addition, for command BIND, COMP or COMPILE, FIND, ELIM, LS or LIST, LINK,
13202 PP or PRETTY and XREF, the project file related switches
13203 (@option{^-P^/PROJECT_FILE^},
13204 @option{^-X^/EXTERNAL_REFERENCE^} and
13205 @option{^-vP^/MESSAGES_PROJECT_FILE=^x}) may be used in addition to
13206 the switches of the invoking tool.
13209 When GNAT PP or GNAT PRETTY is used with a project file, but with no source
13210 specified on the command line, it invokes @command{^gnatpp^gnatpp^} with all
13211 the immediate sources of the specified project file.
13214 For each of these commands, there is optionally a corresponding package
13215 in the main project.
13219 package @code{Binder} for command BIND (invoking @code{^gnatbind^gnatbind^})
13222 package @code{Compiler} for command COMP or COMPILE (invoking the compiler)
13225 package @code{Finder} for command FIND (invoking @code{^gnatfind^gnatfind^})
13228 package @code{Eliminate} for command ELIM (invoking
13229 @code{^gnatelim^gnatelim^})
13232 package @code{Gnatls} for command LS or LIST (invoking @code{^gnatls^gnatls^})
13235 package @code{Linker} for command LINK (invoking @code{^gnatlink^gnatlink^})
13238 package @code{Pretty_Printer} for command PP or PRETTY
13239 (invoking @code{^gnatpp^gnatpp^})
13242 package @code{Cross_Reference} for command XREF (invoking
13243 @code{^gnatxref^gnatxref^})
13248 Package @code{Gnatls} has a unique attribute @code{^Switches^Switches^},
13249 a simple variable with a string list value. It contains ^switches^switches^
13250 for the invocation of @code{^gnatls^gnatls^}.
13252 @smallexample @c projectfile
13256 for ^Switches^Switches^
13265 All other packages have two attribute @code{^Switches^Switches^} and
13266 @code{^Default_Switches^Default_Switches^}.
13269 @code{^Switches^Switches^} is an associated array attribute, indexed by the
13270 source file name, that has a string list value: the ^switches^switches^ to be
13271 used when the tool corresponding to the package is invoked for the specific
13275 @code{^Default_Switches^Default_Switches^} is an associative array attribute,
13276 indexed by the programming language that has a string list value.
13277 @code{^Default_Switches^Default_Switches^ ("Ada")} contains the
13278 ^switches^switches^ for the invocation of the tool corresponding
13279 to the package, except if a specific @code{^Switches^Switches^} attribute
13280 is specified for the source file.
13282 @smallexample @c projectfile
13286 for Source_Dirs use ("./**");
13289 for ^Switches^Switches^ use
13296 package Compiler is
13297 for ^Default_Switches^Default_Switches^ ("Ada")
13298 use ("^-gnatv^-gnatv^",
13299 "^-gnatwa^-gnatwa^");
13305 for ^Default_Switches^Default_Switches^ ("Ada")
13313 for ^Default_Switches^Default_Switches^ ("Ada")
13315 for ^Switches^Switches^ ("main.adb")
13324 for ^Default_Switches^Default_Switches^ ("Ada")
13331 package Cross_Reference is
13332 for ^Default_Switches^Default_Switches^ ("Ada")
13337 end Cross_Reference;
13343 With the above project file, commands such as
13346 ^gnat comp -Pproj main^GNAT COMP /PROJECT_FILE=PROJ MAIN^
13347 ^gnat ls -Pproj main^GNAT LIST /PROJECT_FILE=PROJ MAIN^
13348 ^gnat xref -Pproj main^GNAT XREF /PROJECT_FILE=PROJ MAIN^
13349 ^gnat bind -Pproj main.ali^GNAT BIND /PROJECT_FILE=PROJ MAIN.ALI^
13350 ^gnat link -Pproj main.ali^GNAT LINK /PROJECT_FILE=PROJ MAIN.ALI^
13354 will set up the environment properly and invoke the tool with the switches
13355 found in the package corresponding to the tool:
13356 @code{^Default_Switches^Default_Switches^ ("Ada")} for all tools,
13357 except @code{^Switches^Switches^ ("main.adb")}
13358 for @code{^gnatlink^gnatlink^}.
13361 @node Glide and Project Files
13362 @subsection Glide and Project Files
13365 Glide will automatically recognize the @file{.gpr} extension for
13366 project files, and will
13367 convert them to its own internal format automatically. However, it
13368 doesn't provide a syntax-oriented editor for modifying these
13370 The project file will be loaded as text when you select the menu item
13371 @code{Ada} @result{} @code{Project} @result{} @code{Edit}.
13372 You can edit this text and save the @file{gpr} file;
13373 when you next select this project file in Glide it
13374 will be automatically reloaded.
13377 @c **********************
13378 @node An Extended Example
13379 @section An Extended Example
13382 Suppose that we have two programs, @var{prog1} and @var{prog2},
13383 whose sources are in corresponding directories. We would like
13384 to build them with a single @command{gnatmake} command, and we want to place
13385 their object files into @file{build} subdirectories of the source directories.
13386 Furthermore, we want to have to have two separate subdirectories
13387 in @file{build} -- @file{release} and @file{debug} -- which will contain
13388 the object files compiled with different set of compilation flags.
13390 In other words, we have the following structure:
13407 Here are the project files that we must place in a directory @file{main}
13408 to maintain this structure:
13412 @item We create a @code{Common} project with a package @code{Compiler} that
13413 specifies the compilation ^switches^switches^:
13418 @b{project} Common @b{is}
13420 @b{for} Source_Dirs @b{use} (); -- No source files
13424 @b{type} Build_Type @b{is} ("release", "debug");
13425 Build : Build_Type := External ("BUILD", "debug");
13428 @b{package} Compiler @b{is}
13429 @b{case} Build @b{is}
13430 @b{when} "release" =>
13431 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
13432 @b{use} ("^-O2^-O2^");
13433 @b{when} "debug" =>
13434 @b{for} ^Default_Switches^Default_Switches^ ("Ada")
13435 @b{use} ("^-g^-g^");
13443 @item We create separate projects for the two programs:
13450 @b{project} Prog1 @b{is}
13452 @b{for} Source_Dirs @b{use} ("prog1");
13453 @b{for} Object_Dir @b{use} "prog1/build/" & Common.Build;
13455 @b{package} Compiler @b{renames} Common.Compiler;
13466 @b{project} Prog2 @b{is}
13468 @b{for} Source_Dirs @b{use} ("prog2");
13469 @b{for} Object_Dir @b{use} "prog2/build/" & Common.Build;
13471 @b{package} Compiler @b{renames} Common.Compiler;
13477 @item We create a wrapping project @code{Main}:
13486 @b{project} Main @b{is}
13488 @b{package} Compiler @b{renames} Common.Compiler;
13494 @item Finally we need to create a dummy procedure that @code{with}s (either
13495 explicitly or implicitly) all the sources of our two programs.
13500 Now we can build the programs using the command
13503 gnatmake ^-P^/PROJECT_FILE=^main dummy
13507 for the Debug mode, or
13511 gnatmake -Pmain -XBUILD=release
13517 GNAT MAKE /PROJECT_FILE=main /EXTERNAL_REFERENCE=BUILD=release
13522 for the Release mode.
13524 @c ********************************
13525 @c * Project File Complete Syntax *
13526 @c ********************************
13528 @node Project File Complete Syntax
13529 @section Project File Complete Syntax
13533 context_clause project_declaration
13539 @b{with} path_name @{ , path_name @} ;
13544 project_declaration ::=
13545 simple_project_declaration | project_extension
13547 simple_project_declaration ::=
13548 @b{project} <project_>simple_name @b{is}
13549 @{declarative_item@}
13550 @b{end} <project_>simple_name;
13552 project_extension ::=
13553 @b{project} <project_>simple_name @b{extends} path_name @b{is}
13554 @{declarative_item@}
13555 @b{end} <project_>simple_name;
13557 declarative_item ::=
13558 package_declaration |
13559 typed_string_declaration |
13560 other_declarative_item
13562 package_declaration ::=
13563 package_specification | package_renaming
13565 package_specification ::=
13566 @b{package} package_identifier @b{is}
13567 @{simple_declarative_item@}
13568 @b{end} package_identifier ;
13570 package_identifier ::=
13571 @code{Naming} | @code{Builder} | @code{Compiler} | @code{Binder} |
13572 @code{Linker} | @code{Finder} | @code{Cross_Reference} |
13573 @code{^gnatls^gnatls^} | @code{IDE} | @code{Pretty_Printer}
13575 package_renaming ::==
13576 @b{package} package_identifier @b{renames}
13577 <project_>simple_name.package_identifier ;
13579 typed_string_declaration ::=
13580 @b{type} <typed_string_>_simple_name @b{is}
13581 ( string_literal @{, string_literal@} );
13583 other_declarative_item ::=
13584 attribute_declaration |
13585 typed_variable_declaration |
13586 variable_declaration |
13589 attribute_declaration ::=
13590 full_associative_array_declaration |
13591 @b{for} attribute_designator @b{use} expression ;
13593 full_associative_array_declaration ::=
13594 @b{for} <associative_array_attribute_>simple_name @b{use}
13595 <project_>simple_name [ . <package_>simple_Name ] ' <attribute_>simple_name ;
13597 attribute_designator ::=
13598 <simple_attribute_>simple_name |
13599 <associative_array_attribute_>simple_name ( string_literal )
13601 typed_variable_declaration ::=
13602 <typed_variable_>simple_name : <typed_string_>name := string_expression ;
13604 variable_declaration ::=
13605 <variable_>simple_name := expression;
13615 attribute_reference
13621 ( <string_>expression @{ , <string_>expression @} )
13624 @b{external} ( string_literal [, string_literal] )
13626 attribute_reference ::=
13627 attribute_prefix ' <simple_attribute_>simple_name [ ( literal_string ) ]
13629 attribute_prefix ::=
13631 <project_>simple_name | package_identifier |
13632 <project_>simple_name . package_identifier
13634 case_construction ::=
13635 @b{case} <typed_variable_>name @b{is}
13640 @b{when} discrete_choice_list =>
13641 @{case_construction | attribute_declaration@}
13643 discrete_choice_list ::=
13644 string_literal @{| string_literal@} |
13648 simple_name @{. simple_name@}
13651 identifier (same as Ada)
13656 @node The Cross-Referencing Tools gnatxref and gnatfind
13657 @chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
13662 The compiler generates cross-referencing information (unless
13663 you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
13664 This information indicates where in the source each entity is declared and
13665 referenced. Note that entities in package Standard are not included, but
13666 entities in all other predefined units are included in the output.
13668 Before using any of these two tools, you need to compile successfully your
13669 application, so that GNAT gets a chance to generate the cross-referencing
13672 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
13673 information to provide the user with the capability to easily locate the
13674 declaration and references to an entity. These tools are quite similar,
13675 the difference being that @code{gnatfind} is intended for locating
13676 definitions and/or references to a specified entity or entities, whereas
13677 @code{gnatxref} is oriented to generating a full report of all
13680 To use these tools, you must not compile your application using the
13681 @option{-gnatx} switch on the @file{gnatmake} command line
13682 (see @ref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing
13683 information will not be generated.
13686 * gnatxref Switches::
13687 * gnatfind Switches::
13688 * Project Files for gnatxref and gnatfind::
13689 * Regular Expressions in gnatfind and gnatxref::
13690 * Examples of gnatxref Usage::
13691 * Examples of gnatfind Usage::
13694 @node gnatxref Switches
13695 @section @code{gnatxref} Switches
13698 The command invocation for @code{gnatxref} is:
13700 $ gnatxref [switches] sourcefile1 [sourcefile2 ...]
13707 @item sourcefile1, sourcefile2
13708 identifies the source files for which a report is to be generated. The
13709 ``with''ed units will be processed too. You must provide at least one file.
13711 These file names are considered to be regular expressions, so for instance
13712 specifying @file{source*.adb} is the same as giving every file in the current
13713 directory whose name starts with @file{source} and whose extension is
13719 The switches can be :
13722 @item ^-a^/ALL_FILES^
13723 @cindex @option{^-a^/ALL_FILES^} (@command{gnatxref})
13724 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
13725 the read-only files found in the library search path. Otherwise, these files
13726 will be ignored. This option can be used to protect Gnat sources or your own
13727 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
13728 much faster, and their output much smaller. Read-only here refers to access
13729 or permissions status in the file system for the current user.
13732 @cindex @option{-aIDIR} (@command{gnatxref})
13733 When looking for source files also look in directory DIR. The order in which
13734 source file search is undertaken is the same as for @file{gnatmake}.
13737 @cindex @option{-aODIR} (@command{gnatxref})
13738 When searching for library and object files, look in directory
13739 DIR. The order in which library files are searched is the same as for
13743 @cindex @option{-nostdinc} (@command{gnatxref})
13744 Do not look for sources in the system default directory.
13747 @cindex @option{-nostdlib} (@command{gnatxref})
13748 Do not look for library files in the system default directory.
13750 @item --RTS=@var{rts-path}
13751 @cindex @option{--RTS} (@command{gnatxref})
13752 Specifies the default location of the runtime library. Same meaning as the
13753 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
13755 @item ^-d^/DERIVED_TYPES^
13756 @cindex @option{^-d^/DERIVED_TYPES^} (@command{gnatxref})
13757 If this switch is set @code{gnatxref} will output the parent type
13758 reference for each matching derived types.
13760 @item ^-f^/FULL_PATHNAME^
13761 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatxref})
13762 If this switch is set, the output file names will be preceded by their
13763 directory (if the file was found in the search path). If this switch is
13764 not set, the directory will not be printed.
13766 @item ^-g^/IGNORE_LOCALS^
13767 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatxref})
13768 If this switch is set, information is output only for library-level
13769 entities, ignoring local entities. The use of this switch may accelerate
13770 @code{gnatfind} and @code{gnatxref}.
13773 @cindex @option{-IDIR} (@command{gnatxref})
13774 Equivalent to @samp{-aODIR -aIDIR}.
13777 @cindex @option{-pFILE} (@command{gnatxref})
13778 Specify a project file to use @xref{Project Files}. These project files are
13779 the @file{.adp} files used by Glide. If you need to use the @file{.gpr}
13780 project files, you should use gnatxref through the GNAT driver
13781 (@command{gnat xref -Pproject}).
13783 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
13784 project file in the current directory.
13786 If a project file is either specified or found by the tools, then the content
13787 of the source directory and object directory lines are added as if they
13788 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
13789 and @samp{^-aO^OBJECT_SEARCH^}.
13791 Output only unused symbols. This may be really useful if you give your
13792 main compilation unit on the command line, as @code{gnatxref} will then
13793 display every unused entity and 'with'ed package.
13797 Instead of producing the default output, @code{gnatxref} will generate a
13798 @file{tags} file that can be used by vi. For examples how to use this
13799 feature, see @xref{Examples of gnatxref Usage}. The tags file is output
13800 to the standard output, thus you will have to redirect it to a file.
13806 All these switches may be in any order on the command line, and may even
13807 appear after the file names. They need not be separated by spaces, thus
13808 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
13809 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
13811 @node gnatfind Switches
13812 @section @code{gnatfind} Switches
13815 The command line for @code{gnatfind} is:
13818 $ gnatfind [switches] pattern[:sourcefile[:line[:column]]]
13827 An entity will be output only if it matches the regular expression found
13828 in @samp{pattern}, see @xref{Regular Expressions in gnatfind and gnatxref}.
13830 Omitting the pattern is equivalent to specifying @samp{*}, which
13831 will match any entity. Note that if you do not provide a pattern, you
13832 have to provide both a sourcefile and a line.
13834 Entity names are given in Latin-1, with uppercase/lowercase equivalence
13835 for matching purposes. At the current time there is no support for
13836 8-bit codes other than Latin-1, or for wide characters in identifiers.
13839 @code{gnatfind} will look for references, bodies or declarations
13840 of symbols referenced in @file{sourcefile}, at line @samp{line}
13841 and column @samp{column}. See @pxref{Examples of gnatfind Usage}
13842 for syntax examples.
13845 is a decimal integer identifying the line number containing
13846 the reference to the entity (or entities) to be located.
13849 is a decimal integer identifying the exact location on the
13850 line of the first character of the identifier for the
13851 entity reference. Columns are numbered from 1.
13853 @item file1 file2 ...
13854 The search will be restricted to these source files. If none are given, then
13855 the search will be done for every library file in the search path.
13856 These file must appear only after the pattern or sourcefile.
13858 These file names are considered to be regular expressions, so for instance
13859 specifying 'source*.adb' is the same as giving every file in the current
13860 directory whose name starts with 'source' and whose extension is 'adb'.
13862 The location of the spec of the entity will always be displayed, even if it
13863 isn't in one of file1, file2,... The occurrences of the entity in the
13864 separate units of the ones given on the command line will also be displayed.
13866 Note that if you specify at least one file in this part, @code{gnatfind} may
13867 sometimes not be able to find the body of the subprograms...
13872 At least one of 'sourcefile' or 'pattern' has to be present on
13875 The following switches are available:
13879 @item ^-a^/ALL_FILES^
13880 @cindex @option{^-a^/ALL_FILES^} (@command{gnatfind})
13881 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
13882 the read-only files found in the library search path. Otherwise, these files
13883 will be ignored. This option can be used to protect Gnat sources or your own
13884 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
13885 much faster, and their output much smaller. Read-only here refers to access
13886 or permission status in the file system for the current user.
13889 @cindex @option{-aIDIR} (@command{gnatfind})
13890 When looking for source files also look in directory DIR. The order in which
13891 source file search is undertaken is the same as for @file{gnatmake}.
13894 @cindex @option{-aODIR} (@command{gnatfind})
13895 When searching for library and object files, look in directory
13896 DIR. The order in which library files are searched is the same as for
13900 @cindex @option{-nostdinc} (@command{gnatfind})
13901 Do not look for sources in the system default directory.
13904 @cindex @option{-nostdlib} (@command{gnatfind})
13905 Do not look for library files in the system default directory.
13907 @item --RTS=@var{rts-path}
13908 @cindex @option{--RTS} (@command{gnatfind})
13909 Specifies the default location of the runtime library. Same meaning as the
13910 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
13912 @item ^-d^/DERIVED_TYPE_INFORMATION^
13913 @cindex @option{^-d^/DERIVED_TYPE_INFORMATION^} (@code{gnatfind})
13914 If this switch is set, then @code{gnatfind} will output the parent type
13915 reference for each matching derived types.
13917 @item ^-e^/EXPRESSIONS^
13918 @cindex @option{^-e^/EXPRESSIONS^} (@command{gnatfind})
13919 By default, @code{gnatfind} accept the simple regular expression set for
13920 @samp{pattern}. If this switch is set, then the pattern will be
13921 considered as full Unix-style regular expression.
13923 @item ^-f^/FULL_PATHNAME^
13924 @cindex @option{^-f^/FULL_PATHNAME^} (@command{gnatfind})
13925 If this switch is set, the output file names will be preceded by their
13926 directory (if the file was found in the search path). If this switch is
13927 not set, the directory will not be printed.
13929 @item ^-g^/IGNORE_LOCALS^
13930 @cindex @option{^-g^/IGNORE_LOCALS^} (@command{gnatfind})
13931 If this switch is set, information is output only for library-level
13932 entities, ignoring local entities. The use of this switch may accelerate
13933 @code{gnatfind} and @code{gnatxref}.
13936 @cindex @option{-IDIR} (@command{gnatfind})
13937 Equivalent to @samp{-aODIR -aIDIR}.
13940 @cindex @option{-pFILE} (@command{gnatfind})
13941 Specify a project file (@pxref{Project Files}) to use.
13942 By default, @code{gnatxref} and @code{gnatfind} will try to locate a
13943 project file in the current directory.
13945 If a project file is either specified or found by the tools, then the content
13946 of the source directory and object directory lines are added as if they
13947 had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
13948 @samp{^-aO^/OBJECT_SEARCH^}.
13950 @item ^-r^/REFERENCES^
13951 @cindex @option{^-r^/REFERENCES^} (@command{gnatfind})
13952 By default, @code{gnatfind} will output only the information about the
13953 declaration, body or type completion of the entities. If this switch is
13954 set, the @code{gnatfind} will locate every reference to the entities in
13955 the files specified on the command line (or in every file in the search
13956 path if no file is given on the command line).
13958 @item ^-s^/PRINT_LINES^
13959 @cindex @option{^-s^/PRINT_LINES^} (@command{gnatfind})
13960 If this switch is set, then @code{gnatfind} will output the content
13961 of the Ada source file lines were the entity was found.
13963 @item ^-t^/TYPE_HIERARCHY^
13964 @cindex @option{^-t^/TYPE_HIERARCHY^} (@command{gnatfind})
13965 If this switch is set, then @code{gnatfind} will output the type hierarchy for
13966 the specified type. It act like -d option but recursively from parent
13967 type to parent type. When this switch is set it is not possible to
13968 specify more than one file.
13973 All these switches may be in any order on the command line, and may even
13974 appear after the file names. They need not be separated by spaces, thus
13975 you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
13976 @samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
13978 As stated previously, gnatfind will search in every directory in the
13979 search path. You can force it to look only in the current directory if
13980 you specify @code{*} at the end of the command line.
13982 @node Project Files for gnatxref and gnatfind
13983 @section Project Files for @command{gnatxref} and @command{gnatfind}
13986 Project files allow a programmer to specify how to compile its
13987 application, where to find sources, etc. These files are used
13989 primarily by the Glide Ada mode, but they can also be used
13992 @code{gnatxref} and @code{gnatfind}.
13994 A project file name must end with @file{.gpr}. If a single one is
13995 present in the current directory, then @code{gnatxref} and @code{gnatfind} will
13996 extract the information from it. If multiple project files are found, none of
13997 them is read, and you have to use the @samp{-p} switch to specify the one
14000 The following lines can be included, even though most of them have default
14001 values which can be used in most cases.
14002 The lines can be entered in any order in the file.
14003 Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of
14004 each line. If you have multiple instances, only the last one is taken into
14009 [default: @code{"^./^[]^"}]
14010 specifies a directory where to look for source files. Multiple @code{src_dir}
14011 lines can be specified and they will be searched in the order they
14015 [default: @code{"^./^[]^"}]
14016 specifies a directory where to look for object and library files. Multiple
14017 @code{obj_dir} lines can be specified, and they will be searched in the order
14020 @item comp_opt=SWITCHES
14021 [default: @code{""}]
14022 creates a variable which can be referred to subsequently by using
14023 the @code{$@{comp_opt@}} notation. This is intended to store the default
14024 switches given to @command{gnatmake} and @command{gcc}.
14026 @item bind_opt=SWITCHES
14027 [default: @code{""}]
14028 creates a variable which can be referred to subsequently by using
14029 the @samp{$@{bind_opt@}} notation. This is intended to store the default
14030 switches given to @command{gnatbind}.
14032 @item link_opt=SWITCHES
14033 [default: @code{""}]
14034 creates a variable which can be referred to subsequently by using
14035 the @samp{$@{link_opt@}} notation. This is intended to store the default
14036 switches given to @command{gnatlink}.
14038 @item main=EXECUTABLE
14039 [default: @code{""}]
14040 specifies the name of the executable for the application. This variable can
14041 be referred to in the following lines by using the @samp{$@{main@}} notation.
14044 @item comp_cmd=COMMAND
14045 [default: @code{"GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"}]
14048 @item comp_cmd=COMMAND
14049 [default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}]
14051 specifies the command used to compile a single file in the application.
14054 @item make_cmd=COMMAND
14055 [default: @code{"GNAT MAKE $@{main@}
14056 /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@}
14057 /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@}
14058 /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"}]
14061 @item make_cmd=COMMAND
14062 [default: @code{"gnatmake $@{main@} -aI$@{src_dir@}
14063 -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@}
14064 -bargs $@{bind_opt@} -largs $@{link_opt@}"}]
14066 specifies the command used to recompile the whole application.
14068 @item run_cmd=COMMAND
14069 [default: @code{"$@{main@}"}]
14070 specifies the command used to run the application.
14072 @item debug_cmd=COMMAND
14073 [default: @code{"gdb $@{main@}"}]
14074 specifies the command used to debug the application
14079 @command{gnatxref} and @command{gnatfind} only take into account the
14080 @code{src_dir} and @code{obj_dir} lines, and ignore the others.
14082 @node Regular Expressions in gnatfind and gnatxref
14083 @section Regular Expressions in @code{gnatfind} and @code{gnatxref}
14086 As specified in the section about @command{gnatfind}, the pattern can be a
14087 regular expression. Actually, there are to set of regular expressions
14088 which are recognized by the program :
14091 @item globbing patterns
14092 These are the most usual regular expression. They are the same that you
14093 generally used in a Unix shell command line, or in a DOS session.
14095 Here is a more formal grammar :
14102 term ::= elmt -- matches elmt
14103 term ::= elmt elmt -- concatenation (elmt then elmt)
14104 term ::= * -- any string of 0 or more characters
14105 term ::= ? -- matches any character
14106 term ::= [char @{char@}] -- matches any character listed
14107 term ::= [char - char] -- matches any character in range
14111 @item full regular expression
14112 The second set of regular expressions is much more powerful. This is the
14113 type of regular expressions recognized by utilities such a @file{grep}.
14115 The following is the form of a regular expression, expressed in Ada
14116 reference manual style BNF is as follows
14123 regexp ::= term @{| term@} -- alternation (term or term ...)
14125 term ::= item @{item@} -- concatenation (item then item)
14127 item ::= elmt -- match elmt
14128 item ::= elmt * -- zero or more elmt's
14129 item ::= elmt + -- one or more elmt's
14130 item ::= elmt ? -- matches elmt or nothing
14133 elmt ::= nschar -- matches given character
14134 elmt ::= [nschar @{nschar@}] -- matches any character listed
14135 elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
14136 elmt ::= [char - char] -- matches chars in given range
14137 elmt ::= \ char -- matches given character
14138 elmt ::= . -- matches any single character
14139 elmt ::= ( regexp ) -- parens used for grouping
14141 char ::= any character, including special characters
14142 nschar ::= any character except ()[].*+?^^^
14146 Following are a few examples :
14150 will match any of the two strings 'abcde' and 'fghi'.
14153 will match any string like 'abd', 'abcd', 'abccd', 'abcccd', and so on
14156 will match any string which has only lowercase characters in it (and at
14157 least one character
14162 @node Examples of gnatxref Usage
14163 @section Examples of @code{gnatxref} Usage
14165 @subsection General Usage
14168 For the following examples, we will consider the following units :
14170 @smallexample @c ada
14176 3: procedure Foo (B : in Integer);
14183 1: package body Main is
14184 2: procedure Foo (B : in Integer) is
14195 2: procedure Print (B : Integer);
14204 The first thing to do is to recompile your application (for instance, in
14205 that case just by doing a @samp{gnatmake main}, so that GNAT generates
14206 the cross-referencing information.
14207 You can then issue any of the following commands:
14209 @item gnatxref main.adb
14210 @code{gnatxref} generates cross-reference information for main.adb
14211 and every unit 'with'ed by main.adb.
14213 The output would be:
14221 Decl: main.ads 3:20
14222 Body: main.adb 2:20
14223 Ref: main.adb 4:13 5:13 6:19
14226 Ref: main.adb 6:8 7:8
14236 Decl: main.ads 3:15
14237 Body: main.adb 2:15
14240 Body: main.adb 1:14
14243 Ref: main.adb 6:12 7:12
14247 that is the entity @code{Main} is declared in main.ads, line 2, column 9,
14248 its body is in main.adb, line 1, column 14 and is not referenced any where.
14250 The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
14251 it referenced in main.adb, line 6 column 12 and line 7 column 12.
14253 @item gnatxref package1.adb package2.ads
14254 @code{gnatxref} will generates cross-reference information for
14255 package1.adb, package2.ads and any other package 'with'ed by any
14261 @subsection Using gnatxref with vi
14263 @code{gnatxref} can generate a tags file output, which can be used
14264 directly from @file{vi}. Note that the standard version of @file{vi}
14265 will not work properly with overloaded symbols. Consider using another
14266 free implementation of @file{vi}, such as @file{vim}.
14269 $ gnatxref -v gnatfind.adb > tags
14273 will generate the tags file for @code{gnatfind} itself (if the sources
14274 are in the search path!).
14276 From @file{vi}, you can then use the command @samp{:tag @i{entity}}
14277 (replacing @i{entity} by whatever you are looking for), and vi will
14278 display a new file with the corresponding declaration of entity.
14281 @node Examples of gnatfind Usage
14282 @section Examples of @code{gnatfind} Usage
14286 @item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
14287 Find declarations for all entities xyz referenced at least once in
14288 main.adb. The references are search in every library file in the search
14291 The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
14294 The output will look like:
14296 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
14297 ^directory/^[directory]^main.adb:24:10: xyz <= body
14298 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
14302 that is to say, one of the entities xyz found in main.adb is declared at
14303 line 12 of main.ads (and its body is in main.adb), and another one is
14304 declared at line 45 of foo.ads
14306 @item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
14307 This is the same command as the previous one, instead @code{gnatfind} will
14308 display the content of the Ada source file lines.
14310 The output will look like:
14313 ^directory/^[directory]^main.ads:106:14: xyz <= declaration
14315 ^directory/^[directory]^main.adb:24:10: xyz <= body
14317 ^directory/^[directory]^foo.ads:45:23: xyz <= declaration
14322 This can make it easier to find exactly the location your are looking
14325 @item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
14326 Find references to all entities containing an x that are
14327 referenced on line 123 of main.ads.
14328 The references will be searched only in main.ads and foo.adb.
14330 @item gnatfind main.ads:123
14331 Find declarations and bodies for all entities that are referenced on
14332 line 123 of main.ads.
14334 This is the same as @code{gnatfind "*":main.adb:123}.
14336 @item gnatfind ^mydir/^[mydir]^main.adb:123:45
14337 Find the declaration for the entity referenced at column 45 in
14338 line 123 of file main.adb in directory mydir. Note that it
14339 is usual to omit the identifier name when the column is given,
14340 since the column position identifies a unique reference.
14342 The column has to be the beginning of the identifier, and should not
14343 point to any character in the middle of the identifier.
14348 @c *********************************
14349 @node The GNAT Pretty-Printer gnatpp
14350 @chapter The GNAT Pretty-Printer @command{gnatpp}
14352 @cindex Pretty-Printer
14355 ^The @command{gnatpp} tool^GNAT PRETTY^ is an ASIS-based utility
14356 for source reformatting / pretty-printing.
14357 It takes an Ada source file as input and generates a reformatted
14359 You can specify various style directives via switches; e.g.,
14360 identifier case conventions, rules of indentation, and comment layout.
14362 To produce a reformatted file, @command{gnatpp} generates and uses the ASIS
14363 tree for the input source and thus requires the input to be syntactically and
14364 semantically legal.
14365 If this condition is not met, @command{gnatpp} will terminate with an
14366 error message; no output file will be generated.
14368 If the compilation unit
14369 contained in the input source depends semantically upon units located
14370 outside the current directory, you have to provide the source search path
14371 when invoking @command{gnatpp}; see the description of the @command{gnatpp}
14374 The @command{gnatpp} command has the form
14377 $ gnatpp [@var{switches}] @var{filename}
14384 @var{switches} is an optional sequence of switches defining such properties as
14385 the formatting rules, the source search path, and the destination for the
14389 @var{filename} is the name (including the extension) of the source file to
14390 reformat; ``wildcards'' or several file names on the same gnatpp command are
14391 allowed. The file name may contain path information; it does not have to follow
14392 the GNAT file naming rules
14397 * Switches for gnatpp::
14398 * Formatting Rules::
14401 @node Switches for gnatpp
14402 @section Switches for @command{gnatpp}
14405 The following subsections describe the various switches accepted by
14406 @command{gnatpp}, organized by category.
14409 You specify a switch by supplying a name and generally also a value.
14410 In many cases the values for a switch with a given name are incompatible with
14412 (for example the switch that controls the casing of a reserved word may have
14413 exactly one value: upper case, lower case, or
14414 mixed case) and thus exactly one such switch can be in effect for an
14415 invocation of @command{gnatpp}.
14416 If more than one is supplied, the last one is used.
14417 However, some values for the same switch are mutually compatible.
14418 You may supply several such switches to @command{gnatpp}, but then
14419 each must be specified in full, with both the name and the value.
14420 Abbreviated forms (the name appearing once, followed by each value) are
14422 For example, to set
14423 the alignment of the assignment delimiter both in declarations and in
14424 assignment statements, you must write @option{-A2A3}
14425 (or @option{-A2 -A3}), but not @option{-A23}.
14429 In many cases the set of options for a given qualifier are incompatible with
14430 each other (for example the qualifier that controls the casing of a reserved
14431 word may have exactly one option, which specifies either upper case, lower
14432 case, or mixed case), and thus exactly one such option can be in effect for
14433 an invocation of @command{gnatpp}.
14434 If more than one is supplied, the last one is used.
14435 However, some qualifiers have options that are mutually compatible,
14436 and then you may then supply several such options when invoking
14440 In most cases, it is obvious whether or not the
14441 ^values for a switch with a given name^options for a given qualifier^
14442 are compatible with each other.
14443 When the semantics might not be evident, the summaries below explicitly
14444 indicate the effect.
14447 * Alignment Control::
14449 * Construct Layout Control::
14450 * General Text Layout Control::
14451 * Other Formatting Options::
14452 * Setting the Source Search Path::
14453 * Output File Control::
14454 * Other gnatpp Switches::
14458 @node Alignment Control
14459 @subsection Alignment Control
14460 @cindex Alignment control in @command{gnatpp}
14463 Programs can be easier to read if certain constructs are vertically aligned.
14464 By default all alignments are set ON.
14465 Through the @option{^-A0^/ALIGN=OFF^} switch you may reset the default to
14466 OFF, and then use one or more of the other
14467 ^@option{-A@var{n}} switches^@option{/ALIGN} options^
14468 to activate alignment for specific constructs.
14471 @cindex @option{^-A@var{n}^/ALIGN^} (@command{gnatpp})
14475 Set all alignments to ON
14478 @item ^-A0^/ALIGN=OFF^
14479 Set all alignments to OFF
14481 @item ^-A1^/ALIGN=COLONS^
14482 Align @code{:} in declarations
14484 @item ^-A2^/ALIGN=DECLARATIONS^
14485 Align @code{:=} in initializations in declarations
14487 @item ^-A3^/ALIGN=STATEMENTS^
14488 Align @code{:=} in assignment statements
14490 @item ^-A4^/ALIGN=ARROWS^
14491 Align @code{=>} in associations
14495 The @option{^-A^/ALIGN^} switches are mutually compatible; any combination
14499 @node Casing Control
14500 @subsection Casing Control
14501 @cindex Casing control in @command{gnatpp}
14504 @command{gnatpp} allows you to specify the casing for reserved words,
14505 pragma names, attribute designators and identifiers.
14506 For identifiers you may define a
14507 general rule for name casing but also override this rule
14508 via a set of dictionary files.
14510 Three types of casing are supported: lower case, upper case, and mixed case.
14511 Lower and upper case are self-explanatory (but since some letters in
14512 Latin1 and other GNAT-supported character sets
14513 exist only in lower-case form, an upper case conversion will have no
14515 ``Mixed case'' means that the first letter, and also each letter immediately
14516 following an underscore, are converted to their uppercase forms;
14517 all the other letters are converted to their lowercase forms.
14520 @cindex @option{^-a@var{x}^/ATTRIBUTE^} (@command{gnatpp})
14521 @item ^-aL^/ATTRIBUTE_CASING=LOWER_CASE^
14522 Attribute designators are lower case
14524 @item ^-aU^/ATTRIBUTE_CASING=UPPER_CASE^
14525 Attribute designators are upper case
14527 @item ^-aM^/ATTRIBUTE_CASING=MIXED_CASE^
14528 Attribute designators are mixed case (this is the default)
14530 @cindex @option{^-k@var{x}^/KEYWORD_CASING^} (@command{gnatpp})
14531 @item ^-kL^/KEYWORD_CASING=LOWER_CASE^
14532 Keywords (technically, these are known in Ada as @emph{reserved words}) are
14533 lower case (this is the default)
14535 @item ^-kU^/KEYWORD_CASING=UPPER_CASE^
14536 Keywords are upper case
14538 @cindex @option{^-n@var{x}^/NAME_CASING^} (@command{gnatpp})
14539 @item ^-nD^/NAME_CASING=AS_DECLARED^
14540 Name casing for defining occurrences are as they appear in the source file
14541 (this is the default)
14543 @item ^-nU^/NAME_CASING=UPPER_CASE^
14544 Names are in upper case
14546 @item ^-nL^/NAME_CASING=LOWER_CASE^
14547 Names are in lower case
14549 @item ^-nM^/NAME_CASING=MIXED_CASE^
14550 Names are in mixed case
14552 @cindex @option{^-p@var{x}^/PRAGMA_CASING^} (@command{gnatpp})
14553 @item ^-pL^/PRAGMA_CASING=LOWER_CASE^
14554 Pragma names are lower case
14556 @item ^-pU^/PRAGMA_CASING=UPPER_CASE^
14557 Pragma names are upper case
14559 @item ^-pM^/PRAGMA_CASING=MIXED_CASE^
14560 Pragma names are mixed case (this is the default)
14562 @item ^-D@var{file}^/DICTIONARY=@var{file}^
14563 @cindex @option{^-D^/DICTIONARY^} (@command{gnatpp})
14564 Use @var{file} as a @emph{dictionary file} that defines
14565 the casing for a set of specified names,
14566 thereby overriding the effect on these names by
14567 any explicit or implicit
14568 ^-n^/NAME_CASING^ switch.
14569 To supply more than one dictionary file,
14570 use ^several @option{-D} switches^a list of files as options^.
14573 @option{gnatpp} implicitly uses a @emph{default dictionary file}
14574 to define the casing for the Ada predefined names and
14575 the names declared in the GNAT libraries.
14577 @item ^-D-^/SPECIFIC_CASING^
14578 @cindex @option{^-D-^/SPECIFIC_CASING^} (@command{gnatpp})
14579 Do not use the default dictionary file;
14580 instead, use the casing
14581 defined by a @option{^-n^/NAME_CASING^} switch and any explicit
14586 The structure of a dictionary file, and details on the conventions
14587 used in the default dictionary file, are defined in @ref{Name Casing}.
14589 The @option{^-D-^/SPECIFIC_CASING^} and
14590 @option{^-D@var{file}^/DICTIONARY=@var{file}^} switches are mutually
14594 @node Construct Layout Control
14595 @subsection Construct Layout Control
14596 @cindex Layout control in @command{gnatpp}
14599 This group of @command{gnatpp} switches controls the layout of comments and
14600 complex syntactic constructs. See @ref{Formatting Comments}, for details
14604 @cindex @option{^-c@var{n}^/COMMENTS_LAYOUT^} (@command{gnatpp})
14605 @item ^-c1^/COMMENTS_LAYOUT=DEFAULT^
14606 GNAT-style comment line indentation (this is the default).
14608 @item ^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^
14609 Reference-manual comment line indentation.
14611 @item ^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^
14612 GNAT-style comment beginning
14614 @item ^-c4^/COMMENTS_LAYOUT=REFORMAT^
14615 Reformat comment blocks
14617 @cindex @option{^-l@var{n}^/CONSTRUCT_LAYOUT^} (@command{gnatpp})
14618 @item ^-l1^/CONSTRUCT_LAYOUT=GNAT^
14619 GNAT-style layout (this is the default)
14621 @item ^-l2^/CONSTRUCT_LAYOUT=COMPACT^
14624 @item ^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^
14627 @item ^-notab^/NOTABS^
14628 All the VT characters are removed from the comment text. All the HT characters are
14629 expanded with the sequences of space characters to get to the next tab stops.
14635 The @option{-c1} and @option{-c2} switches are incompatible.
14636 The @option{-c3} and @option{-c4} switches are compatible with each other and
14637 also with @option{-c1} and @option{-c2}.
14639 The @option{-l1}, @option{-l2}, and @option{-l3} switches are incompatible.
14644 For the @option{/COMMENTS_LAYOUT} qualifier:
14647 The @option{DEFAULT} and @option{STANDARD_INDENT} options are incompatible.
14649 The @option{GNAT_BEGINNING} and @option{REFORMAT} options are compatible with
14650 each other and also with @option{DEFAULT} and @option{STANDARD_INDENT}.
14654 The @option{GNAT}, @option{COMPACT}, and @option{UNCOMPACT} options for the
14655 @option{/CONSTRUCT_LAYOUT} qualifier are incompatible.
14658 @node General Text Layout Control
14659 @subsection General Text Layout Control
14662 These switches allow control over line length and indentation.
14665 @item ^-M@i{nnn}^/LINE_LENGTH_MAX=@i{nnn}^
14666 @cindex @option{^-M^/LINE_LENGTH^} (@command{gnatpp})
14667 Maximum line length, @i{nnn} from 32 ..256, the default value is 79
14669 @item ^-i@i{nnn}^/INDENTATION_LEVEL=@i{nnn}^
14670 @cindex @option{^-i^/INDENTATION_LEVEL^} (@command{gnatpp})
14671 Indentation level, @i{nnn} from 1 .. 9, the default value is 3
14673 @item ^-cl@i{nnn}^/CONTINUATION_INDENT=@i{nnn}^
14674 @cindex @option{^-cl^/CONTINUATION_INDENT^} (@command{gnatpp})
14675 Indentation level for continuation lines (relative to the line being
14676 continued), @i{nnn} from 1 .. 9.
14678 value is one less then the (normal) indentation level, unless the
14679 indentation is set to 1 (in which case the default value for continuation
14680 line indentation is also 1)
14684 @node Other Formatting Options
14685 @subsection Other Formatting Options
14688 These switches control the inclusion of missing end/exit labels, and
14689 the indentation level in @b{case} statements.
14692 @item ^-e^/NO_MISSED_LABELS^
14693 @cindex @option{^-e^/NO_MISSED_LABELS^} (@command{gnatpp})
14694 Do not insert missing end/exit labels. An end label is the name of
14695 a construct that may optionally be repeated at the end of the
14696 construct's declaration;
14697 e.g., the names of packages, subprograms, and tasks.
14698 An exit label is the name of a loop that may appear as target
14699 of an exit statement within the loop.
14700 By default, @command{gnatpp} inserts these end/exit labels when
14701 they are absent from the original source. This option suppresses such
14702 insertion, so that the formatted source reflects the original.
14704 @item ^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^
14705 @cindex @option{^-ff^/FORM_FEED_AFTER_PRAGMA_PAGE^} (@command{gnatpp})
14706 Insert a Form Feed character after a pragma Page.
14708 @item ^-T@i{nnn}^/MAX_INDENT=@i{nnn}^
14709 @cindex @option{^-T^/MAX_INDENT^} (@command{gnatpp})
14710 Do not use an additional indentation level for @b{case} alternatives
14711 and variants if there are @i{nnn} or more (the default
14713 If @i{nnn} is 0, an additional indentation level is
14714 used for @b{case} alternatives and variants regardless of their number.
14717 @node Setting the Source Search Path
14718 @subsection Setting the Source Search Path
14721 To define the search path for the input source file, @command{gnatpp}
14722 uses the same switches as the GNAT compiler, with the same effects.
14725 @item ^-I^/SEARCH=^@var{dir}
14726 @cindex @option{^-I^/SEARCH^} (@code{gnatpp})
14727 The same as the corresponding gcc switch
14729 @item ^-I-^/NOCURRENT_DIRECTORY^
14730 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatpp})
14731 The same as the corresponding gcc switch
14733 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE^=@var{path}
14734 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@code{gnatpp})
14735 The same as the corresponding gcc switch
14737 @item ^--RTS^/RUNTIME_SYSTEM^=@var{path}
14738 @cindex @option{^--RTS^/RUNTIME_SYSTEM^} (@code{gnatpp})
14739 The same as the corresponding gcc switch
14744 @node Output File Control
14745 @subsection Output File Control
14748 By default the output is sent to the file whose name is obtained by appending
14749 the ^@file{.pp}^@file{$PP}^ suffix to the name of the input file
14750 (if the file with this name already exists, it is unconditionally overwritten).
14751 Thus if the input file is @file{^my_ada_proc.adb^MY_ADA_PROC.ADB^} then
14752 @command{gnatpp} will produce @file{^my_ada_proc.adb.pp^MY_ADA_PROC.ADB$PP^}
14754 The output may be redirected by the following switches:
14757 @item ^-pipe^/STANDARD_OUTPUT^
14758 @cindex @option{^-pipe^/STANDARD_OUTPUT^} (@code{gnatpp})
14759 Send the output to @code{Standard_Output}
14761 @item ^-o @var{output_file}^/OUTPUT=@var{output_file}^
14762 @cindex @option{^-o^/OUTPUT^} (@code{gnatpp})
14763 Write the output into @var{output_file}.
14764 If @var{output_file} already exists, @command{gnatpp} terminates without
14765 reading or processing the input file.
14767 @item ^-of ^/FORCED_OUTPUT=^@var{output_file}
14768 @cindex @option{^-of^/FORCED_OUTPUT^} (@code{gnatpp})
14769 Write the output into @var{output_file}, overwriting the existing file
14770 (if one is present).
14772 @item ^-r^/REPLACE^
14773 @cindex @option{^-r^/REPLACE^} (@code{gnatpp})
14774 Replace the input source file with the reformatted output, and copy the
14775 original input source into the file whose name is obtained by appending the
14776 ^@file{.npp}^@file{$NPP}^ suffix to the name of the input file.
14777 If a file with this name already exists, @command{gnatpp} terminates without
14778 reading or processing the input file.
14780 @item ^-rf^/OVERRIDING_REPLACE^
14781 @cindex @option{^-rf^/OVERRIDING_REPLACE^} (@code{gnatpp})
14782 Like @option{^-r^/REPLACE^} except that if the file with the specified name
14783 already exists, it is overwritten.
14787 Options @option{^-pipe^/STANDARD_OUTPUT^},
14788 @option{^-o^/OUTPUT^} and
14789 @option{^-of^/FORCED_OUTPUT^} are allowed only if the call to gnatpp
14790 contains only one file to reformat
14792 @node Other gnatpp Switches
14793 @subsection Other @code{gnatpp} Switches
14796 The additional @command{gnatpp} switches are defined in this subsection.
14799 @item ^-v^/VERBOSE^
14800 @cindex @option{^-v^/VERBOSE^} (@code{gnatpp})
14802 @command{gnatpp} generates version information and then
14803 a trace of the actions it takes to produce or obtain the ASIS tree.
14805 @item ^-w^/WARNINGS^
14806 @cindex @option{^-w^/WARNINGS^} (@code{gnatpp})
14808 @command{gnatpp} generates a warning whenever it can not provide
14809 a required layout in the result source.
14813 @node Formatting Rules
14814 @section Formatting Rules
14817 The following subsections show how @command{gnatpp} treats ``white space'',
14818 comments, program layout, and name casing.
14819 They provide the detailed descriptions of the switches shown above.
14822 * White Space and Empty Lines::
14823 * Formatting Comments::
14824 * Construct Layout::
14829 @node White Space and Empty Lines
14830 @subsection White Space and Empty Lines
14833 @command{gnatpp} does not have an option to control space characters.
14834 It will add or remove spaces according to the style illustrated by the
14835 examples in the @cite{Ada Reference Manual}.
14837 The only format effectors
14838 (see @cite{Ada Reference Manual}, paragraph 2.1(13))
14839 that will appear in the output file are platform-specific line breaks,
14840 and also format effectors within (but not at the end of) comments.
14841 In particular, each horizontal tab character that is not inside
14842 a comment will be treated as a space and thus will appear in the
14843 output file as zero or more spaces depending on
14844 the reformatting of the line in which it appears.
14845 The only exception is a Form Feed character, which is inserted after a
14846 pragma @code{Page} when @option{-ff} is set.
14848 The output file will contain no lines with trailing ``white space'' (spaces,
14851 Empty lines in the original source are preserved
14852 only if they separate declarations or statements.
14853 In such contexts, a
14854 sequence of two or more empty lines is replaced by exactly one empty line.
14855 Note that a blank line will be removed if it separates two ``comment blocks''
14856 (a comment block is a sequence of whole-line comments).
14857 In order to preserve a visual separation between comment blocks, use an
14858 ``empty comment'' (a line comprising only hyphens) rather than an empty line.
14859 Likewise, if for some reason you wish to have a sequence of empty lines,
14860 use a sequence of empty comments instead.
14863 @node Formatting Comments
14864 @subsection Formatting Comments
14867 Comments in Ada code are of two kinds:
14870 a @emph{whole-line comment}, which appears by itself (possibly preceded by
14871 ``white space'') on a line
14874 an @emph{end-of-line comment}, which follows some other Ada lexical element
14879 The indentation of a whole-line comment is that of either
14880 the preceding or following line in
14881 the formatted source, depending on switch settings as will be described below.
14883 For an end-of-line comment, @command{gnatpp} leaves the same number of spaces
14884 between the end of the preceding Ada lexical element and the beginning
14885 of the comment as appear in the original source,
14886 unless either the comment has to be split to
14887 satisfy the line length limitation, or else the next line contains a
14888 whole line comment that is considered a continuation of this end-of-line
14889 comment (because it starts at the same position).
14891 cases, the start of the end-of-line comment is moved right to the nearest
14892 multiple of the indentation level.
14893 This may result in a ``line overflow'' (the right-shifted comment extending
14894 beyond the maximum line length), in which case the comment is split as
14897 There is a difference between @option{^-c1^/COMMENTS_LAYOUT=DEFAULT^}
14898 (GNAT-style comment line indentation)
14899 and @option{^-c2^/COMMENTS_LAYOUT=STANDARD_INDENT^}
14900 (reference-manual comment line indentation).
14901 With reference-manual style, a whole-line comment is indented as if it
14902 were a declaration or statement at the same place
14903 (i.e., according to the indentation of the preceding line(s)).
14904 With GNAT style, a whole-line comment that is immediately followed by an
14905 @b{if} or @b{case} statement alternative, a record variant, or the reserved
14906 word @b{begin}, is indented based on the construct that follows it.
14909 @smallexample @c ada
14921 Reference-manual indentation produces:
14923 @smallexample @c ada
14935 while GNAT-style indentation produces:
14937 @smallexample @c ada
14949 The @option{^-c3^/COMMENTS_LAYOUT=GNAT_BEGINNING^} switch
14950 (GNAT style comment beginning) has the following
14955 For each whole-line comment that does not end with two hyphens,
14956 @command{gnatpp} inserts spaces if necessary after the starting two hyphens
14957 to ensure that there are at least two spaces between these hyphens and the
14958 first non-blank character of the comment.
14962 For an end-of-line comment, if in the original source the next line is a
14963 whole-line comment that starts at the same position
14964 as the end-of-line comment,
14965 then the whole-line comment (and all whole-line comments
14966 that follow it and that start at the same position)
14967 will start at this position in the output file.
14970 That is, if in the original source we have:
14972 @smallexample @c ada
14975 A := B + C; -- B must be in the range Low1..High1
14976 -- C must be in the range Low2..High2
14977 --B+C will be in the range Low1+Low2..High1+High2
14983 Then in the formatted source we get
14985 @smallexample @c ada
14988 A := B + C; -- B must be in the range Low1..High1
14989 -- C must be in the range Low2..High2
14990 -- B+C will be in the range Low1+Low2..High1+High2
14996 A comment that exceeds the line length limit will be split.
14998 @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} (reformat comment blocks) is set and
14999 the line belongs to a reformattable block, splitting the line generates a
15000 @command{gnatpp} warning.
15001 The @option{^-c4^/COMMENTS_LAYOUT=REFORMAT^} switch specifies that whole-line
15002 comments may be reformatted in typical
15003 word processor style (that is, moving words between lines and putting as
15004 many words in a line as possible).
15007 @node Construct Layout
15008 @subsection Construct Layout
15011 The difference between GNAT style @option{^-l1^/CONSTRUCT_LAYOUT=GNAT^}
15012 and compact @option{^-l2^/CONSTRUCT_LAYOUT=COMPACT^}
15013 layout on the one hand, and uncompact layout
15014 @option{^-l3^/CONSTRUCT_LAYOUT=UNCOMPACT^} on the other hand,
15015 can be illustrated by the following examples:
15019 @multitable @columnfractions .5 .5
15020 @item @i{GNAT style, compact layout} @tab @i{Uncompact layout}
15023 @smallexample @c ada
15030 @smallexample @c ada
15039 @smallexample @c ada
15047 @smallexample @c ada
15057 @smallexample @c ada
15058 Clear : for J in 1 .. 10 loop
15063 @smallexample @c ada
15065 for J in 1 .. 10 loop
15076 GNAT style, compact layout Uncompact layout
15078 type q is record type q is
15079 a : integer; record
15080 b : integer; a : integer;
15081 end record; b : integer;
15085 Block : declare Block :
15086 A : Integer := 3; declare
15087 begin A : Integer := 3;
15089 end Block; Proc (A, A);
15092 Clear : for J in 1 .. 10 loop Clear :
15093 A (J) := 0; for J in 1 .. 10 loop
15094 end loop Clear; A (J) := 0;
15101 A further difference between GNAT style layout and compact layout is that
15102 GNAT style layout inserts empty lines as separation for
15103 compound statements, return statements and bodies.
15107 @subsection Name Casing
15110 @command{gnatpp} always converts the usage occurrence of a (simple) name to
15111 the same casing as the corresponding defining identifier.
15113 You control the casing for defining occurrences via the
15114 @option{^-n^/NAME_CASING^} switch.
15116 With @option{-nD} (``as declared'', which is the default),
15119 With @option{/NAME_CASING=AS_DECLARED}, which is the default,
15121 defining occurrences appear exactly as in the source file
15122 where they are declared.
15123 The other ^values for this switch^options for this qualifier^ ---
15124 @option{^-nU^UPPER_CASE^},
15125 @option{^-nL^LOWER_CASE^},
15126 @option{^-nM^MIXED_CASE^} ---
15128 ^upper, lower, or mixed case, respectively^the corresponding casing^.
15129 If @command{gnatpp} changes the casing of a defining
15130 occurrence, it analogously changes the casing of all the
15131 usage occurrences of this name.
15133 If the defining occurrence of a name is not in the source compilation unit
15134 currently being processed by @command{gnatpp}, the casing of each reference to
15135 this name is changed according to the value of the @option{^-n^/NAME_CASING^}
15136 switch (subject to the dictionary file mechanism described below).
15137 Thus @command{gnatpp} acts as though the @option{^-n^/NAME_CASING^} switch
15139 casing for the defining occurrence of the name.
15141 Some names may need to be spelled with casing conventions that are not
15142 covered by the upper-, lower-, and mixed-case transformations.
15143 You can arrange correct casing by placing such names in a
15144 @emph{dictionary file},
15145 and then supplying a @option{^-D^/DICTIONARY^} switch.
15146 The casing of names from dictionary files overrides
15147 any @option{^-n^/NAME_CASING^} switch.
15149 To handle the casing of Ada predefined names and the names from GNAT libraries,
15150 @command{gnatpp} assumes a default dictionary file.
15151 The name of each predefined entity is spelled with the same casing as is used
15152 for the entity in the @cite{Ada Reference Manual}.
15153 The name of each entity in the GNAT libraries is spelled with the same casing
15154 as is used in the declaration of that entity.
15156 The @w{@option{^-D-^/SPECIFIC_CASING^}} switch suppresses the use of the
15157 default dictionary file.
15158 Instead, the casing for predefined and GNAT-defined names will be established
15159 by the @option{^-n^/NAME_CASING^} switch or explicit dictionary files.
15160 For example, by default the names @code{Ada.Text_IO} and @code{GNAT.OS_Lib}
15161 will appear as just shown,
15162 even in the presence of a @option{^-nU^/NAME_CASING=UPPER_CASE^} switch.
15163 To ensure that even such names are rendered in uppercase,
15164 additionally supply the @w{@option{^-D-^/SPECIFIC_CASING^}} switch
15165 (or else, less conveniently, place these names in upper case in a dictionary
15168 A dictionary file is
15169 a plain text file; each line in this file can be either a blank line
15170 (containing only space characters and ASCII.HT characters), an Ada comment
15171 line, or the specification of exactly one @emph{casing schema}.
15173 A casing schema is a string that has the following syntax:
15177 @var{casing_schema} ::= @var{identifier} | [*]@var{simple_identifier}[*]
15179 @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@}
15184 (The @code{[]} metanotation stands for an optional part;
15185 see @cite{Ada Reference Manual}, Section 2.3) for the definition of the
15186 @var{identifier} lexical element and the @var{letter_or_digit} category).
15188 The casing schema string can be followed by white space and/or an Ada-style
15189 comment; any amount of white space is allowed before the string.
15191 If a dictionary file is passed as
15193 the value of a @option{-D@var{file}} switch
15196 an option to the @option{/DICTIONARY} qualifier
15199 simple name and every identifier, @command{gnatpp} checks if the dictionary
15200 defines the casing for the name or for some of its parts (the term ``subword''
15201 is used below to denote the part of a name which is delimited by ``_'' or by
15202 the beginning or end of the word and which does not contain any ``_'' inside):
15206 if the whole name is in the dictionary, @command{gnatpp} uses for this name
15207 the casing defined by the dictionary; no subwords are checked for this word
15210 for the first subword (that is, for the subword preceding the leftmost
15211 ``_''), @command{gnatpp} checks if the dictionary contains the corresponding
15212 string of the form @code{@var{simple_identifier}*}, and if it does, the
15213 casing of this @var{simple_identifier} is used for this subword
15216 for the last subword (following the rightmost ``_'') @command{gnatpp}
15217 checks if the dictionary contains the corresponding string of the form
15218 @code{*@var{simple_identifier}}, and if it does, the casing of this
15219 @var{simple_identifier} is used for this subword
15222 for every intermediate subword (surrounded by two'_') @command{gnatpp} checks
15223 if the dictionary contains the corresponding string of the form
15224 @code{*@var{simple_identifier}*}, and if it does, the casing of this
15225 simple_identifier is used for this subword
15228 if more than one dictionary file is passed as @command{gnatpp} switches, each
15229 dictionary adds new casing exceptions and overrides all the existing casing
15230 exceptions set by the previous dictionaries
15233 when @command{gnatpp} checks if the word or subword is in the dictionary,
15234 this check is not case sensitive
15238 For example, suppose we have the following source to reformat:
15240 @smallexample @c ada
15243 name1 : integer := 1;
15244 name4_name3_name2 : integer := 2;
15245 name2_name3_name4 : Boolean;
15248 name2_name3_name4 := name4_name3_name2 > name1;
15254 And suppose we have two dictionaries:
15271 If @command{gnatpp} is called with the following switches:
15275 @command{gnatpp -nM -D dict1 -D dict2 test.adb}
15278 @command{gnatpp test.adb /NAME_CASING=MIXED_CASE /DICTIONARY=(dict1, dict2)}
15283 then we will get the following name casing in the @command{gnatpp} output:
15285 @smallexample @c ada
15288 NAME1 : Integer := 1;
15289 Name4_NAME3_NAME2 : integer := 2;
15290 Name2_NAME3_Name4 : Boolean;
15293 Name2_NAME3_Name4 := Name4_NAME3_NAME2 > NAME1;
15300 @c ***********************************
15301 @node File Name Krunching Using gnatkr
15302 @chapter File Name Krunching Using @code{gnatkr}
15306 This chapter discusses the method used by the compiler to shorten
15307 the default file names chosen for Ada units so that they do not
15308 exceed the maximum length permitted. It also describes the
15309 @code{gnatkr} utility that can be used to determine the result of
15310 applying this shortening.
15314 * Krunching Method::
15315 * Examples of gnatkr Usage::
15319 @section About @code{gnatkr}
15322 The default file naming rule in GNAT
15323 is that the file name must be derived from
15324 the unit name. The exact default rule is as follows:
15327 Take the unit name and replace all dots by hyphens.
15329 If such a replacement occurs in the
15330 second character position of a name, and the first character is
15331 ^a, g, s, or i^A, G, S, or I^ then replace the dot by the character
15332 ^~ (tilde)^$ (dollar sign)^
15333 instead of a minus.
15335 The reason for this exception is to avoid clashes
15336 with the standard names for children of System, Ada, Interfaces,
15337 and GNAT, which use the prefixes ^s- a- i- and g-^S- A- I- and G-^
15340 The @option{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
15341 switch of the compiler activates a ``krunching''
15342 circuit that limits file names to nn characters (where nn is a decimal
15343 integer). For example, using OpenVMS,
15344 where the maximum file name length is
15345 39, the value of nn is usually set to 39, but if you want to generate
15346 a set of files that would be usable if ported to a system with some
15347 different maximum file length, then a different value can be specified.
15348 The default value of 39 for OpenVMS need not be specified.
15350 The @code{gnatkr} utility can be used to determine the krunched name for
15351 a given file, when krunched to a specified maximum length.
15354 @section Using @code{gnatkr}
15357 The @code{gnatkr} command has the form
15361 $ gnatkr @var{name} [@var{length}]
15367 $ gnatkr @var{name} /COUNT=nn
15372 @var{name} is the uncrunched file name, derived from the name of the unit
15373 in the standard manner described in the previous section (i.e. in particular
15374 all dots are replaced by hyphens). The file name may or may not have an
15375 extension (defined as a suffix of the form period followed by arbitrary
15376 characters other than period). If an extension is present then it will
15377 be preserved in the output. For example, when krunching @file{hellofile.ads}
15378 to eight characters, the result will be hellofil.ads.
15380 Note: for compatibility with previous versions of @code{gnatkr} dots may
15381 appear in the name instead of hyphens, but the last dot will always be
15382 taken as the start of an extension. So if @code{gnatkr} is given an argument
15383 such as @file{Hello.World.adb} it will be treated exactly as if the first
15384 period had been a hyphen, and for example krunching to eight characters
15385 gives the result @file{hellworl.adb}.
15387 Note that the result is always all lower case (except on OpenVMS where it is
15388 all upper case). Characters of the other case are folded as required.
15390 @var{length} represents the length of the krunched name. The default
15391 when no argument is given is ^8^39^ characters. A length of zero stands for
15392 unlimited, in other words do not chop except for system files where the
15393 impled crunching length is always eight characters.
15396 The output is the krunched name. The output has an extension only if the
15397 original argument was a file name with an extension.
15399 @node Krunching Method
15400 @section Krunching Method
15403 The initial file name is determined by the name of the unit that the file
15404 contains. The name is formed by taking the full expanded name of the
15405 unit and replacing the separating dots with hyphens and
15406 using ^lowercase^uppercase^
15407 for all letters, except that a hyphen in the second character position is
15408 replaced by a ^tilde^dollar sign^ if the first character is
15409 ^a, i, g, or s^A, I, G, or S^.
15410 The extension is @code{.ads} for a
15411 specification and @code{.adb} for a body.
15412 Krunching does not affect the extension, but the file name is shortened to
15413 the specified length by following these rules:
15417 The name is divided into segments separated by hyphens, tildes or
15418 underscores and all hyphens, tildes, and underscores are
15419 eliminated. If this leaves the name short enough, we are done.
15422 If the name is too long, the longest segment is located (left-most
15423 if there are two of equal length), and shortened by dropping
15424 its last character. This is repeated until the name is short enough.
15426 As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
15427 to fit the name into 8 characters as required by some operating systems.
15430 our-strings-wide_fixed 22
15431 our strings wide fixed 19
15432 our string wide fixed 18
15433 our strin wide fixed 17
15434 our stri wide fixed 16
15435 our stri wide fixe 15
15436 our str wide fixe 14
15437 our str wid fixe 13
15443 Final file name: oustwifi.adb
15447 The file names for all predefined units are always krunched to eight
15448 characters. The krunching of these predefined units uses the following
15449 special prefix replacements:
15453 replaced by @file{^a^A^-}
15456 replaced by @file{^g^G^-}
15459 replaced by @file{^i^I^-}
15462 replaced by @file{^s^S^-}
15465 These system files have a hyphen in the second character position. That
15466 is why normal user files replace such a character with a
15467 ^tilde^dollar sign^, to
15468 avoid confusion with system file names.
15470 As an example of this special rule, consider
15471 @*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
15474 ada-strings-wide_fixed 22
15475 a- strings wide fixed 18
15476 a- string wide fixed 17
15477 a- strin wide fixed 16
15478 a- stri wide fixed 15
15479 a- stri wide fixe 14
15480 a- str wide fixe 13
15486 Final file name: a-stwifi.adb
15490 Of course no file shortening algorithm can guarantee uniqueness over all
15491 possible unit names, and if file name krunching is used then it is your
15492 responsibility to ensure that no name clashes occur. The utility
15493 program @code{gnatkr} is supplied for conveniently determining the
15494 krunched name of a file.
15496 @node Examples of gnatkr Usage
15497 @section Examples of @code{gnatkr} Usage
15504 $ gnatkr very_long_unit_name.ads --> velounna.ads
15505 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
15506 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
15507 $ gnatkr grandparent-parent-child --> grparchi
15509 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
15510 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
15513 @node Preprocessing Using gnatprep
15514 @chapter Preprocessing Using @code{gnatprep}
15518 The @code{gnatprep} utility provides
15519 a simple preprocessing capability for Ada programs.
15520 It is designed for use with GNAT, but is not dependent on any special
15525 * Switches for gnatprep::
15526 * Form of Definitions File::
15527 * Form of Input Text for gnatprep::
15530 @node Using gnatprep
15531 @section Using @code{gnatprep}
15534 To call @code{gnatprep} use
15537 $ gnatprep [-bcrsu] [-Dsymbol=value] infile outfile [deffile]
15544 is the full name of the input file, which is an Ada source
15545 file containing preprocessor directives.
15548 is the full name of the output file, which is an Ada source
15549 in standard Ada form. When used with GNAT, this file name will
15550 normally have an ads or adb suffix.
15553 is the full name of a text file containing definitions of
15554 symbols to be referenced by the preprocessor. This argument is
15555 optional, and can be replaced by the use of the @option{-D} switch.
15558 is an optional sequence of switches as described in the next section.
15561 @node Switches for gnatprep
15562 @section Switches for @code{gnatprep}
15567 @item ^-b^/BLANK_LINES^
15568 @cindex @option{^-b^/BLANK_LINES^} (@command{gnatprep})
15569 Causes both preprocessor lines and the lines deleted by
15570 preprocessing to be replaced by blank lines in the output source file,
15571 preserving line numbers in the output file.
15573 @item ^-c^/COMMENTS^
15574 @cindex @option{^-c^/COMMENTS^} (@command{gnatprep})
15575 Causes both preprocessor lines and the lines deleted
15576 by preprocessing to be retained in the output source as comments marked
15577 with the special string @code{"--! "}. This option will result in line numbers
15578 being preserved in the output file.
15580 @item ^-Dsymbol=value^/ASSOCIATE="symbol=value"^
15581 @cindex @option{^-D^/ASSOCIATE^} (@command{gnatprep})
15582 Defines a new symbol, associated with value. If no value is given on the
15583 command line, then symbol is considered to be @code{True}. This switch
15584 can be used in place of a definition file.
15588 @cindex @option{/REMOVE} (@command{gnatprep})
15589 This is the default setting which causes lines deleted by preprocessing
15590 to be entirely removed from the output file.
15593 @item ^-r^/REFERENCE^
15594 @cindex @option{^-r^/REFERENCE^} (@command{gnatprep})
15595 Causes a @code{Source_Reference} pragma to be generated that
15596 references the original input file, so that error messages will use
15597 the file name of this original file. The use of this switch implies
15598 that preprocessor lines are not to be removed from the file, so its
15599 use will force @option{^-b^/BLANK_LINES^} mode if
15600 @option{^-c^/COMMENTS^}
15601 has not been specified explicitly.
15603 Note that if the file to be preprocessed contains multiple units, then
15604 it will be necessary to @code{gnatchop} the output file from
15605 @code{gnatprep}. If a @code{Source_Reference} pragma is present
15606 in the preprocessed file, it will be respected by
15607 @code{gnatchop ^-r^/REFERENCE^}
15608 so that the final chopped files will correctly refer to the original
15609 input source file for @code{gnatprep}.
15611 @item ^-s^/SYMBOLS^
15612 @cindex @option{^-s^/SYMBOLS^} (@command{gnatprep})
15613 Causes a sorted list of symbol names and values to be
15614 listed on the standard output file.
15616 @item ^-u^/UNDEFINED^
15617 @cindex @option{^-u^/UNDEFINED^} (@command{gnatprep})
15618 Causes undefined symbols to be treated as having the value FALSE in the context
15619 of a preprocessor test. In the absence of this option, an undefined symbol in
15620 a @code{#if} or @code{#elsif} test will be treated as an error.
15626 Note: if neither @option{-b} nor @option{-c} is present,
15627 then preprocessor lines and
15628 deleted lines are completely removed from the output, unless -r is
15629 specified, in which case -b is assumed.
15632 @node Form of Definitions File
15633 @section Form of Definitions File
15636 The definitions file contains lines of the form
15643 where symbol is an identifier, following normal Ada (case-insensitive)
15644 rules for its syntax, and value is one of the following:
15648 Empty, corresponding to a null substitution
15650 A string literal using normal Ada syntax
15652 Any sequence of characters from the set
15653 (letters, digits, period, underline).
15657 Comment lines may also appear in the definitions file, starting with
15658 the usual @code{--},
15659 and comments may be added to the definitions lines.
15661 @node Form of Input Text for gnatprep
15662 @section Form of Input Text for @code{gnatprep}
15665 The input text may contain preprocessor conditional inclusion lines,
15666 as well as general symbol substitution sequences.
15668 The preprocessor conditional inclusion commands have the form
15673 #if @i{expression} [then]
15675 #elsif @i{expression} [then]
15677 #elsif @i{expression} [then]
15688 In this example, @i{expression} is defined by the following grammar:
15690 @i{expression} ::= <symbol>
15691 @i{expression} ::= <symbol> = "<value>"
15692 @i{expression} ::= <symbol> = <symbol>
15693 @i{expression} ::= <symbol> 'Defined
15694 @i{expression} ::= not @i{expression}
15695 @i{expression} ::= @i{expression} and @i{expression}
15696 @i{expression} ::= @i{expression} or @i{expression}
15697 @i{expression} ::= @i{expression} and then @i{expression}
15698 @i{expression} ::= @i{expression} or else @i{expression}
15699 @i{expression} ::= ( @i{expression} )
15703 For the first test (@i{expression} ::= <symbol>) the symbol must have
15704 either the value true or false, that is to say the right-hand of the
15705 symbol definition must be one of the (case-insensitive) literals
15706 @code{True} or @code{False}. If the value is true, then the
15707 corresponding lines are included, and if the value is false, they are
15710 The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
15711 the symbol has been defined in the definition file or by a @option{-D}
15712 switch on the command line. Otherwise, the test is false.
15714 The equality tests are case insensitive, as are all the preprocessor lines.
15716 If the symbol referenced is not defined in the symbol definitions file,
15717 then the effect depends on whether or not switch @option{-u}
15718 is specified. If so, then the symbol is treated as if it had the value
15719 false and the test fails. If this switch is not specified, then
15720 it is an error to reference an undefined symbol. It is also an error to
15721 reference a symbol that is defined with a value other than @code{True}
15724 The use of the @code{not} operator inverts the sense of this logical test, so
15725 that the lines are included only if the symbol is not defined.
15726 The @code{then} keyword is optional as shown
15728 The @code{#} must be the first non-blank character on a line, but
15729 otherwise the format is free form. Spaces or tabs may appear between
15730 the @code{#} and the keyword. The keywords and the symbols are case
15731 insensitive as in normal Ada code. Comments may be used on a
15732 preprocessor line, but other than that, no other tokens may appear on a
15733 preprocessor line. Any number of @code{elsif} clauses can be present,
15734 including none at all. The @code{else} is optional, as in Ada.
15736 The @code{#} marking the start of a preprocessor line must be the first
15737 non-blank character on the line, i.e. it must be preceded only by
15738 spaces or horizontal tabs.
15740 Symbol substitution outside of preprocessor lines is obtained by using
15748 anywhere within a source line, except in a comment or within a
15749 string literal. The identifier
15750 following the @code{$} must match one of the symbols defined in the symbol
15751 definition file, and the result is to substitute the value of the
15752 symbol in place of @code{$symbol} in the output file.
15754 Note that although the substitution of strings within a string literal
15755 is not possible, it is possible to have a symbol whose defined value is
15756 a string literal. So instead of setting XYZ to @code{hello} and writing:
15759 Header : String := "$XYZ";
15763 you should set XYZ to @code{"hello"} and write:
15766 Header : String := $XYZ;
15770 and then the substitution will occur as desired.
15773 @node The GNAT Run-Time Library Builder gnatlbr
15774 @chapter The GNAT Run-Time Library Builder @code{gnatlbr}
15776 @cindex Library builder
15779 @code{gnatlbr} is a tool for rebuilding the GNAT run time with user
15780 supplied configuration pragmas.
15783 * Running gnatlbr::
15784 * Switches for gnatlbr::
15785 * Examples of gnatlbr Usage::
15788 @node Running gnatlbr
15789 @section Running @code{gnatlbr}
15792 The @code{gnatlbr} command has the form
15795 $ GNAT LIBRARY /[CREATE | SET | DELETE]=directory [/CONFIG=file]
15798 @node Switches for gnatlbr
15799 @section Switches for @code{gnatlbr}
15802 @code{gnatlbr} recognizes the following switches:
15806 @item /CREATE=directory
15807 @cindex @code{/CREATE} (@code{gnatlbr})
15808 Create the new run-time library in the specified directory.
15810 @item /SET=directory
15811 @cindex @code{/SET} (@code{gnatlbr})
15812 Make the library in the specified directory the current run-time
15815 @item /DELETE=directory
15816 @cindex @code{/DELETE} (@code{gnatlbr})
15817 Delete the run-time library in the specified directory.
15820 @cindex @code{/CONFIG} (@code{gnatlbr})
15822 Use the configuration pragmas in the specified file when building
15826 Use the configuration pragmas in the specified file when compiling.
15830 @node Examples of gnatlbr Usage
15831 @section Example of @code{gnatlbr} Usage
15834 Contents of VAXFLOAT.ADC:
15835 pragma Float_Representation (VAX_Float);
15837 $ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
15839 GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
15844 @node The GNAT Library Browser gnatls
15845 @chapter The GNAT Library Browser @code{gnatls}
15847 @cindex Library browser
15850 @code{gnatls} is a tool that outputs information about compiled
15851 units. It gives the relationship between objects, unit names and source
15852 files. It can also be used to check the source dependencies of a unit
15853 as well as various characteristics.
15857 * Switches for gnatls::
15858 * Examples of gnatls Usage::
15861 @node Running gnatls
15862 @section Running @code{gnatls}
15865 The @code{gnatls} command has the form
15868 $ gnatls switches @var{object_or_ali_file}
15872 The main argument is the list of object or @file{ali} files
15873 (@pxref{The Ada Library Information Files})
15874 for which information is requested.
15876 In normal mode, without additional option, @code{gnatls} produces a
15877 four-column listing. Each line represents information for a specific
15878 object. The first column gives the full path of the object, the second
15879 column gives the name of the principal unit in this object, the third
15880 column gives the status of the source and the fourth column gives the
15881 full path of the source representing this unit.
15882 Here is a simple example of use:
15886 ^./^[]^demo1.o demo1 DIF demo1.adb
15887 ^./^[]^demo2.o demo2 OK demo2.adb
15888 ^./^[]^hello.o h1 OK hello.adb
15889 ^./^[]^instr-child.o instr.child MOK instr-child.adb
15890 ^./^[]^instr.o instr OK instr.adb
15891 ^./^[]^tef.o tef DIF tef.adb
15892 ^./^[]^text_io_example.o text_io_example OK text_io_example.adb
15893 ^./^[]^tgef.o tgef DIF tgef.adb
15897 The first line can be interpreted as follows: the main unit which is
15899 object file @file{demo1.o} is demo1, whose main source is in
15900 @file{demo1.adb}. Furthermore, the version of the source used for the
15901 compilation of demo1 has been modified (DIF). Each source file has a status
15902 qualifier which can be:
15905 @item OK (unchanged)
15906 The version of the source file used for the compilation of the
15907 specified unit corresponds exactly to the actual source file.
15909 @item MOK (slightly modified)
15910 The version of the source file used for the compilation of the
15911 specified unit differs from the actual source file but not enough to
15912 require recompilation. If you use gnatmake with the qualifier
15913 @option{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
15914 MOK will not be recompiled.
15916 @item DIF (modified)
15917 No version of the source found on the path corresponds to the source
15918 used to build this object.
15920 @item ??? (file not found)
15921 No source file was found for this unit.
15923 @item HID (hidden, unchanged version not first on PATH)
15924 The version of the source that corresponds exactly to the source used
15925 for compilation has been found on the path but it is hidden by another
15926 version of the same source that has been modified.
15930 @node Switches for gnatls
15931 @section Switches for @code{gnatls}
15934 @code{gnatls} recognizes the following switches:
15938 @item ^-a^/ALL_UNITS^
15939 @cindex @option{^-a^/ALL_UNITS^} (@code{gnatls})
15940 Consider all units, including those of the predefined Ada library.
15941 Especially useful with @option{^-d^/DEPENDENCIES^}.
15943 @item ^-d^/DEPENDENCIES^
15944 @cindex @option{^-d^/DEPENDENCIES^} (@code{gnatls})
15945 List sources from which specified units depend on.
15947 @item ^-h^/OUTPUT=OPTIONS^
15948 @cindex @option{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
15949 Output the list of options.
15951 @item ^-o^/OUTPUT=OBJECTS^
15952 @cindex @option{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
15953 Only output information about object files.
15955 @item ^-s^/OUTPUT=SOURCES^
15956 @cindex @option{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
15957 Only output information about source files.
15959 @item ^-u^/OUTPUT=UNITS^
15960 @cindex @option{^-u^/OUTPUT=UNITS^} (@code{gnatls})
15961 Only output information about compilation units.
15963 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
15964 @itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
15965 @itemx ^-I^/SEARCH=^@var{dir}
15966 @itemx ^-I-^/NOCURRENT_DIRECTORY^
15968 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatls})
15969 @cindex @option{^-aI^/SOURCE_SEARCH^} (@code{gnatls})
15970 @cindex @option{^-I^/SEARCH^} (@code{gnatls})
15971 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatls})
15972 Source path manipulation. Same meaning as the equivalent @code{gnatmake} flags
15973 (see @ref{Switches for gnatmake}).
15975 @item --RTS=@var{rts-path}
15976 @cindex @option{--RTS} (@code{gnatls})
15977 Specifies the default location of the runtime library. Same meaning as the
15978 equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
15980 @item ^-v^/OUTPUT=VERBOSE^
15981 @cindex @option{^-v^/OUTPUT=VERBOSE^} (@code{gnatls})
15982 Verbose mode. Output the complete source and object paths. Do not use
15983 the default column layout but instead use long format giving as much as
15984 information possible on each requested units, including special
15985 characteristics such as:
15988 @item Preelaborable
15989 The unit is preelaborable in the Ada 95 sense.
15992 No elaboration code has been produced by the compiler for this unit.
15995 The unit is pure in the Ada 95 sense.
15997 @item Elaborate_Body
15998 The unit contains a pragma Elaborate_Body.
16001 The unit contains a pragma Remote_Types.
16003 @item Shared_Passive
16004 The unit contains a pragma Shared_Passive.
16007 This unit is part of the predefined environment and cannot be modified
16010 @item Remote_Call_Interface
16011 The unit contains a pragma Remote_Call_Interface.
16017 @node Examples of gnatls Usage
16018 @section Example of @code{gnatls} Usage
16022 Example of using the verbose switch. Note how the source and
16023 object paths are affected by the -I switch.
16026 $ gnatls -v -I.. demo1.o
16028 GNATLS 3.10w (970212) Copyright 1999 Free Software Foundation, Inc.
16030 Source Search Path:
16031 <Current_Directory>
16033 /home/comar/local/adainclude/
16035 Object Search Path:
16036 <Current_Directory>
16038 /home/comar/local/lib/gcc-lib/mips-sni-sysv4/2.7.2/adalib/
16043 Kind => subprogram body
16044 Flags => No_Elab_Code
16045 Source => demo1.adb modified
16049 The following is an example of use of the dependency list.
16050 Note the use of the -s switch
16051 which gives a straight list of source files. This can be useful for
16052 building specialized scripts.
16055 $ gnatls -d demo2.o
16056 ./demo2.o demo2 OK demo2.adb
16062 $ gnatls -d -s -a demo1.o
16064 /home/comar/local/adainclude/ada.ads
16065 /home/comar/local/adainclude/a-finali.ads
16066 /home/comar/local/adainclude/a-filico.ads
16067 /home/comar/local/adainclude/a-stream.ads
16068 /home/comar/local/adainclude/a-tags.ads
16071 /home/comar/local/adainclude/gnat.ads
16072 /home/comar/local/adainclude/g-io.ads
16074 /home/comar/local/adainclude/system.ads
16075 /home/comar/local/adainclude/s-exctab.ads
16076 /home/comar/local/adainclude/s-finimp.ads
16077 /home/comar/local/adainclude/s-finroo.ads
16078 /home/comar/local/adainclude/s-secsta.ads
16079 /home/comar/local/adainclude/s-stalib.ads
16080 /home/comar/local/adainclude/s-stoele.ads
16081 /home/comar/local/adainclude/s-stratt.ads
16082 /home/comar/local/adainclude/s-tasoli.ads
16083 /home/comar/local/adainclude/s-unstyp.ads
16084 /home/comar/local/adainclude/unchconv.ads
16090 GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
16092 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
16093 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
16094 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
16095 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
16096 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
16100 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
16101 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
16103 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
16104 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
16105 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
16106 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
16107 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
16108 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
16109 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
16110 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
16111 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
16112 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
16113 GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
16117 @node Cleaning Up Using gnatclean
16118 @chapter Cleaning Up Using @code{gnatclean}
16120 @cindex Cleaning tool
16123 @code{gnatclean} is a tool that allows the deletion of files produced by the
16124 compiler, binder and linker, including ALI files, object files, tree files,
16125 expanded source files, library files, interface copy source files, binder
16126 generated files and executable files.
16129 * Running gnatclean::
16130 * Switches for gnatclean::
16131 * Examples of gnatclean Usage::
16134 @node Running gnatclean
16135 @section Running @code{gnatclean}
16138 The @code{gnatclean} command has the form:
16141 $ gnatclean switches @var{names}
16145 @var{names} is a list of source file names. Suffixes @code{.^ads^ADS^} and
16146 @code{^adb^ADB^} may be omitted. If a project file is specified using switch
16147 @code{^-P^/PROJECT_FILE=^}, then @var{names} may be completely omitted.
16150 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
16151 if switch @code{^-c^/COMPILER_FILES_ONLY^} is not specified, by the binder and
16152 the linker. In informative-only mode, specified by switch
16153 @code{^-n^/NODELETE^}, the list of files that would have been deleted in
16154 normal mode is listed, but no file is actually deleted.
16156 @node Switches for gnatclean
16157 @section Switches for @code{gnatclean}
16160 @code{gnatclean} recognizes the following switches:
16164 @item ^-c^/COMPILER_FILES_ONLY^
16165 @cindex @option{^-c^/COMPILER_FILES_ONLY^} (@code{gnatclean})
16166 Only attempt to delete the files produced by the compiler, not those produced
16167 by the binder or the linker. The files that are not to be deleted are library
16168 files, interface copy files, binder generated files and executable files.
16170 @item ^-D ^/DIRECTORY_OBJECTS=^@var{dir}
16171 @cindex @option{^-D^/DIRECTORY_OBJECTS^} (@code{gnatclean})
16172 Indicate that ALI and object files should normally be found in directory
16175 @item ^-F^/FULL_PATH_IN_BRIEF_MESSAGES^
16176 @cindex @option{^-F^/FULL_PATH_IN_BRIEF_MESSAGES^} (@code{gnatclean})
16177 When using project files, if some errors or warnings are detected during
16178 parsing and verbose mode is not in effect (no use of switch
16179 ^-v^/VERBOSE^), then error lines start with the full path name of the project
16180 file, rather than its simple file name.
16183 @cindex @option{^-h^/HELP^} (@code{gnatclean})
16184 Output a message explaining the usage of @code{^gnatclean^gnatclean^}.
16186 @item ^-n^/NODELETE^
16187 @cindex @option{^-n^/NODELETE^} (@code{gnatclean})
16188 Informative-only mode. Do not delete any files. Output the list of the files
16189 that would have been deleted if this switch was not specified.
16191 @item ^-P^/PROJECT_FILE=^@var{project}
16192 @cindex @option{^-P^/PROJECT_FILE^} (@code{gnatclean})
16193 Use project file @var{project}. Only one such switch can be used.
16194 When cleaning a project file, the files produced by the compilation of the
16195 immediate sources or inherited sources of the project files are to be
16196 deleted. This is not depending on the presence or not of executable names
16197 on the command line.
16200 @cindex @option{^-q^/QUIET^} (@code{gnatclean})
16201 Quiet output. If there are no error, do not ouuput anything, except in
16202 verbose mode (switch ^-v^/VERBOSE^) or in informative-only mode
16203 (switch ^-n^/NODELETE^).
16205 @item ^-r^/RECURSIVE^
16206 @cindex @option{^-r^/RECURSIVE^} (@code{gnatclean})
16207 When a project file is specified (using switch ^-P^/PROJECT_FILE=^),
16208 clean all imported and extended project files, recursively. If this switch
16209 is not specified, only the files related to the main project file are to be
16210 deleted. This switch has no effect if no project file is specified.
16212 @item ^-v^/VERBOSE^
16213 @cindex @option{^-v^/VERBOSE^} (@code{gnatclean})
16216 @item ^-vP^/MESSAGES_PROJECT_FILE=^@emph{x}
16217 @cindex @option{^-vP^/MESSAGES_PROJECT_FILE^} (@code{gnatclean})
16218 Indicates the verbosity of the parsing of GNAT project files.
16219 See @ref{Switches Related to Project Files}.
16221 @item ^-X^/EXTERNAL_REFERENCE=^@var{name=value}
16222 @cindex @option{^-X^/EXTERNAL_REFERENCE^} (@code{gnatclean})
16223 Indicates that external variable @var{name} has the value @var{value}.
16224 The Project Manager will use this value for occurrences of
16225 @code{external(name)} when parsing the project file.
16226 See @ref{Switches Related to Project Files}.
16228 @item ^-aO^/OBJECT_SEARCH=^@var{dir}
16229 @cindex @option{^-aO^/OBJECT_SEARCH^} (@code{gnatclean})
16230 When searching for ALI and object files, look in directory
16233 @item ^-I^/SEARCH=^@var{dir}
16234 @cindex @option{^-I^/SEARCH^} (@code{gnatclean})
16235 Equivalent to @option{^-aO^/OBJECT_SEARCH=^@var{dir}}.
16237 @item ^-I-^/NOCURRENT_DIRECTORY^
16238 @cindex @option{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatclean})
16239 @cindex Source files, suppressing search
16240 Do not look for ALI or object files in the directory
16241 where @code{gnatclean} was invoked.
16245 @node Examples of gnatclean Usage
16246 @section Examples of @code{gnatclean} Usage
16249 @node GNAT and Libraries
16250 @chapter GNAT and Libraries
16251 @cindex Library, building, installing
16254 This chapter addresses some of the issues related to building and using
16255 a library with GNAT. It also shows how the GNAT run-time library can be
16259 * Creating an Ada Library::
16260 * Installing an Ada Library::
16261 * Using an Ada Library::
16262 * Creating an Ada Library to be Used in a Non-Ada Context::
16263 * Rebuilding the GNAT Run-Time Library::
16266 @node Creating an Ada Library
16267 @section Creating an Ada Library
16270 In the GNAT environment, a library has two components:
16275 Compiled code and Ali files. See @ref{The Ada Library Information Files}.
16279 In order to use other packages @ref{The GNAT Compilation Model}
16280 requires a certain number of sources to be available to the compiler.
16282 sources required includes the specs of all the packages that make up the
16283 visible part of the library as well as all the sources upon which they
16284 depend. The bodies of all visible generic units must also be provided.
16286 Although it is not strictly mandatory, it is recommended that all sources
16287 needed to recompile the library be provided, so that the user can make
16288 full use of inter-unit inlining and source-level debugging. This can also
16289 make the situation easier for users that need to upgrade their compilation
16290 toolchain and thus need to recompile the library from sources.
16293 The compiled code can be provided in different ways. The simplest way is
16294 to provide directly the set of objects produced by the compiler during
16295 the compilation of the library. It is also possible to group the objects
16296 into an archive using whatever commands are provided by the operating
16297 system. Finally, it is also possible to create a shared library (see
16298 option -shared in the GCC manual).
16301 There are various possibilities for compiling the units that make up the
16302 library: for example with a Makefile @ref{Using the GNU make Utility},
16303 or with a conventional script.
16304 For simple libraries, it is also possible to create a
16305 dummy main program which depends upon all the packages that comprise the
16306 interface of the library. This dummy main program can then be given to
16307 gnatmake, in order to build all the necessary objects. Here is an example
16308 of such a dummy program and the generic commands used to build an
16309 archive or a shared library.
16311 @smallexample @c ada
16315 with My_Lib.Service1;
16316 with My_Lib.Service2;
16317 with My_Lib.Service3;
16318 procedure My_Lib_Dummy is
16325 # compiling the library
16326 $ gnatmake -c my_lib_dummy.adb
16328 # we don't need the dummy object itself
16329 $ rm my_lib_dummy.o my_lib_dummy.ali
16331 # create an archive with the remaining objects
16332 $ ar rc libmy_lib.a *.o
16333 # some systems may require "ranlib" to be run as well
16335 # or create a shared library
16336 $ gcc -shared -o libmy_lib.so *.o
16337 # some systems may require the code to have been compiled with -fPIC
16339 # remove the object files that are now in the library
16342 # Make the ALI files read-only so that gnatmake will not try to
16343 # regenerate the objects that are in the library
16349 When the objects are grouped in an archive or a shared library, the user
16350 needs to specify the desired library at link time, unless a pragma
16351 linker_options has been used in one of the sources:
16352 @smallexample @c ada
16353 pragma Linker_Options ("-lmy_lib");
16357 Please note that the library must have a name of the form libxxx.a or
16358 libxxx.so in order to be accessed by the directive -lxxx at link
16361 @node Installing an Ada Library
16362 @section Installing an Ada Library
16365 In the GNAT model, installing a library consists in copying into a specific
16366 location the files that make up this library. It is possible to install
16367 the sources in a different directory from the other files (ALI, objects,
16368 archives) since the source path and the object path can easily be
16369 specified separately.
16372 For general purpose libraries, it is possible for the system
16373 administrator to put those libraries in the default compiler paths. To
16374 achieve this, he must specify their location in the configuration files
16375 @file{ada_source_path} and @file{ada_object_path} that must be located in
16377 installation tree at the same place as the gcc spec file. The location of
16378 the gcc spec file can be determined as follows:
16384 The configuration files mentioned above have simple format: each line in them
16385 must contain one unique
16386 directory name. Those names are added to the corresponding path
16387 in their order of appearance in the file. The names can be either absolute
16388 or relative, in the latter case, they are relative to where theses files
16392 @file{ada_source_path} and @file{ada_object_path} might actually not be
16394 GNAT installation, in which case, GNAT will look for its run-time library in
16395 he directories @file{adainclude} for the sources and @file{adalib} for the
16396 objects and @file{ALI} files. When the files exist, the compiler does not
16397 look in @file{adainclude} and @file{adalib} at all, and thus the
16398 @file{ada_source_path} file
16399 must contain the location for the GNAT run-time sources (which can simply
16400 be @file{adainclude}). In the same way, the @file{ada_object_path} file must
16401 contain the location for the GNAT run-time objects (which can simply
16405 You can also specify a new default path to the runtime library at compilation
16406 time with the switch @option{--RTS=rts-path}. You can easily choose and change
16407 the runtime you want your program to be compiled with. This switch is
16408 recognized by gcc, gnatmake, gnatbind, gnatls, gnatfind and gnatxref.
16411 It is possible to install a library before or after the standard GNAT
16412 library, by reordering the lines in the configuration files. In general, a
16413 library must be installed before the GNAT library if it redefines
16416 @node Using an Ada Library
16417 @section Using an Ada Library
16420 In order to use a Ada library, you need to make sure that this
16421 library is on both your source and object path
16422 @ref{Search Paths and the Run-Time Library (RTL)}
16423 and @ref{Search Paths for gnatbind}. For
16424 instance, you can use the library @file{mylib} installed in
16425 @file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands:
16428 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
16433 This can be simplified down to the following:
16437 when the following conditions are met:
16440 @file{/dir/my_lib_src} has been added by the user to the environment
16441 variable @code{ADA_INCLUDE_PATH}, or by the administrator to the file
16442 @file{ada_source_path}
16444 @file{/dir/my_lib_obj} has been added by the user to the environment
16445 variable @code{ADA_OBJECTS_PATH}, or by the administrator to the file
16446 @file{ada_object_path}
16448 a pragma @code{Linker_Options}, as mentioned in @ref{Creating an Ada Library},
16449 has been added to the sources.
16453 @node Creating an Ada Library to be Used in a Non-Ada Context
16454 @section Creating an Ada Library to be Used in a Non-Ada Context
16457 The previous sections detailed how to create and install a library that
16458 was usable from an Ada main program. Using this library in a non-Ada
16459 context is not possible, because the elaboration of the library is
16460 automatically done as part of the main program elaboration.
16462 GNAT also provides the ability to build libraries that can be used both
16463 in an Ada and non-Ada context. This section describes how to build such
16464 a library, and then how to use it from a C program. The method for
16465 interfacing with the library from other languages such as Fortran for
16466 instance remains the same.
16468 @subsection Creating the Library
16471 @item Identify the units representing the interface of the library.
16473 Here is an example of simple library interface:
16475 @smallexample @c ada
16476 package Interface is
16478 procedure Do_Something;
16480 procedure Do_Something_Else;
16485 @item Use @code{pragma Export} or @code{pragma Convention} for the
16488 Our package @code{Interface} is then updated as follow:
16489 @smallexample @c ada
16490 package Interface is
16492 procedure Do_Something;
16493 pragma Export (C, Do_Something, "do_something");
16495 procedure Do_Something_Else;
16496 pragma Export (C, Do_Something_Else, "do_something_else");
16501 @item Compile all the units composing the library.
16503 @item Bind the library objects.
16505 This step is performed by invoking gnatbind with the @option{-L<prefix>}
16506 switch. @code{gnatbind} will then generate the library elaboration
16507 procedure (named @code{<prefix>init}) and the run-time finalization
16508 procedure (named @code{<prefix>final}).
16511 # generate the binder file in Ada
16512 $ gnatbind -Lmylib interface
16514 # generate the binder file in C
16515 $ gnatbind -C -Lmylib interface
16518 @item Compile the files generated by the binder
16521 $ gcc -c b~interface.adb
16524 @item Create the library;
16526 The procedure is identical to the procedure explained in
16527 @ref{Creating an Ada Library},
16528 except that @file{b~interface.o} needs to be added to
16529 the list of objects.
16532 # create an archive file
16533 $ ar cr libmylib.a b~interface.o <other object files>
16535 # create a shared library
16536 $ gcc -shared -o libmylib.so b~interface.o <other object files>
16539 @item Provide a ``foreign'' view of the library interface;
16541 The example below shows the content of @code{mylib_interface.h} (note
16542 that there is no rule for the naming of this file, any name can be used)
16544 /* the library elaboration procedure */
16545 extern void mylibinit (void);
16547 /* the library finalization procedure */
16548 extern void mylibfinal (void);
16550 /* the interface exported by the library */
16551 extern void do_something (void);
16552 extern void do_something_else (void);
16556 @subsection Using the Library
16559 Libraries built as explained above can be used from any program, provided
16560 that the elaboration procedures (named @code{mylibinit} in the previous
16561 example) are called before the library services are used. Any number of
16562 libraries can be used simultaneously, as long as the elaboration
16563 procedure of each library is called.
16565 Below is an example of C program that uses our @code{mylib} library.
16568 #include "mylib_interface.h"
16573 /* First, elaborate the library before using it */
16576 /* Main program, using the library exported entities */
16578 do_something_else ();
16580 /* Library finalization at the end of the program */
16587 Note that this same library can be used from an equivalent Ada main
16588 program. In addition, if the libraries are installed as detailed in
16589 @ref{Installing an Ada Library}, it is not necessary to invoke the
16590 library elaboration and finalization routines. The binder will ensure
16591 that this is done as part of the main program elaboration and
16592 finalization phases.
16594 @subsection The Finalization Phase
16597 Invoking any library finalization procedure generated by @code{gnatbind}
16598 shuts down the Ada run time permanently. Consequently, the finalization
16599 of all Ada libraries must be performed at the end of the program. No
16600 call to these libraries nor the Ada run time should be made past the
16601 finalization phase.
16603 @subsection Restrictions in Libraries
16606 The pragmas listed below should be used with caution inside libraries,
16607 as they can create incompatibilities with other Ada libraries:
16609 @item pragma @code{Locking_Policy}
16610 @item pragma @code{Queuing_Policy}
16611 @item pragma @code{Task_Dispatching_Policy}
16612 @item pragma @code{Unreserve_All_Interrupts}
16614 When using a library that contains such pragmas, the user must make sure
16615 that all libraries use the same pragmas with the same values. Otherwise,
16616 a @code{Program_Error} will
16617 be raised during the elaboration of the conflicting
16618 libraries. The usage of these pragmas and its consequences for the user
16619 should therefore be well documented.
16621 Similarly, the traceback in exception occurrences mechanism should be
16622 enabled or disabled in a consistent manner across all libraries.
16623 Otherwise, a Program_Error will be raised during the elaboration of the
16624 conflicting libraries.
16626 If the @code{'Version} and @code{'Body_Version}
16627 attributes are used inside a library, then it is necessary to
16628 perform a @code{gnatbind} step that mentions all @file{ALI} files in all
16629 libraries, so that version identifiers can be properly computed.
16630 In practice these attributes are rarely used, so this is unlikely
16631 to be a consideration.
16633 @node Rebuilding the GNAT Run-Time Library
16634 @section Rebuilding the GNAT Run-Time Library
16637 It may be useful to recompile the GNAT library in various contexts, the
16638 most important one being the use of partition-wide configuration pragmas
16639 such as Normalize_Scalar. A special Makefile called
16640 @code{Makefile.adalib} is provided to that effect and can be found in
16641 the directory containing the GNAT library. The location of this
16642 directory depends on the way the GNAT environment has been installed and can
16643 be determined by means of the command:
16650 The last entry in the object search path usually contains the
16651 gnat library. This Makefile contains its own documentation and in
16652 particular the set of instructions needed to rebuild a new library and
16655 @node Using the GNU make Utility
16656 @chapter Using the GNU @code{make} Utility
16660 This chapter offers some examples of makefiles that solve specific
16661 problems. It does not explain how to write a makefile (see the GNU make
16662 documentation), nor does it try to replace the @code{gnatmake} utility
16663 (@pxref{The GNAT Make Program gnatmake}).
16665 All the examples in this section are specific to the GNU version of
16666 make. Although @code{make} is a standard utility, and the basic language
16667 is the same, these examples use some advanced features found only in
16671 * Using gnatmake in a Makefile::
16672 * Automatically Creating a List of Directories::
16673 * Generating the Command Line Switches::
16674 * Overcoming Command Line Length Limits::
16677 @node Using gnatmake in a Makefile
16678 @section Using gnatmake in a Makefile
16683 Complex project organizations can be handled in a very powerful way by
16684 using GNU make combined with gnatmake. For instance, here is a Makefile
16685 which allows you to build each subsystem of a big project into a separate
16686 shared library. Such a makefile allows you to significantly reduce the link
16687 time of very big applications while maintaining full coherence at
16688 each step of the build process.
16690 The list of dependencies are handled automatically by
16691 @code{gnatmake}. The Makefile is simply used to call gnatmake in each of
16692 the appropriate directories.
16694 Note that you should also read the example on how to automatically
16695 create the list of directories
16696 (@pxref{Automatically Creating a List of Directories})
16697 which might help you in case your project has a lot of subdirectories.
16702 @font@heightrm=cmr8
16705 ## This Makefile is intended to be used with the following directory
16707 ## - The sources are split into a series of csc (computer software components)
16708 ## Each of these csc is put in its own directory.
16709 ## Their name are referenced by the directory names.
16710 ## They will be compiled into shared library (although this would also work
16711 ## with static libraries
16712 ## - The main program (and possibly other packages that do not belong to any
16713 ## csc is put in the top level directory (where the Makefile is).
16714 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
16715 ## \_ second_csc (sources) __ lib (will contain the library)
16717 ## Although this Makefile is build for shared library, it is easy to modify
16718 ## to build partial link objects instead (modify the lines with -shared and
16721 ## With this makefile, you can change any file in the system or add any new
16722 ## file, and everything will be recompiled correctly (only the relevant shared
16723 ## objects will be recompiled, and the main program will be re-linked).
16725 # The list of computer software component for your project. This might be
16726 # generated automatically.
16729 # Name of the main program (no extension)
16732 # If we need to build objects with -fPIC, uncomment the following line
16735 # The following variable should give the directory containing libgnat.so
16736 # You can get this directory through 'gnatls -v'. This is usually the last
16737 # directory in the Object_Path.
16740 # The directories for the libraries
16741 # (This macro expands the list of CSC to the list of shared libraries, you
16742 # could simply use the expanded form :
16743 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
16744 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
16746 $@{MAIN@}: objects $@{LIB_DIR@}
16747 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
16748 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
16751 # recompile the sources
16752 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
16754 # Note: In a future version of GNAT, the following commands will be simplified
16755 # by a new tool, gnatmlib
16757 mkdir -p $@{dir $@@ @}
16758 cd $@{dir $@@ @}; gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
16759 cd $@{dir $@@ @}; cp -f ../*.ali .
16761 # The dependencies for the modules
16762 # Note that we have to force the expansion of *.o, since in some cases
16763 # make won't be able to do it itself.
16764 aa/lib/libaa.so: $@{wildcard aa/*.o@}
16765 bb/lib/libbb.so: $@{wildcard bb/*.o@}
16766 cc/lib/libcc.so: $@{wildcard cc/*.o@}
16768 # Make sure all of the shared libraries are in the path before starting the
16771 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
16774 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
16775 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
16776 $@{RM@} $@{CSC_LIST:%=%/*.o@}
16777 $@{RM@} *.o *.ali $@{MAIN@}
16780 @node Automatically Creating a List of Directories
16781 @section Automatically Creating a List of Directories
16784 In most makefiles, you will have to specify a list of directories, and
16785 store it in a variable. For small projects, it is often easier to
16786 specify each of them by hand, since you then have full control over what
16787 is the proper order for these directories, which ones should be
16790 However, in larger projects, which might involve hundreds of
16791 subdirectories, it might be more convenient to generate this list
16794 The example below presents two methods. The first one, although less
16795 general, gives you more control over the list. It involves wildcard
16796 characters, that are automatically expanded by @code{make}. Its
16797 shortcoming is that you need to explicitly specify some of the
16798 organization of your project, such as for instance the directory tree
16799 depth, whether some directories are found in a separate tree,...
16801 The second method is the most general one. It requires an external
16802 program, called @code{find}, which is standard on all Unix systems. All
16803 the directories found under a given root directory will be added to the
16809 @font@heightrm=cmr8
16812 # The examples below are based on the following directory hierarchy:
16813 # All the directories can contain any number of files
16814 # ROOT_DIRECTORY -> a -> aa -> aaa
16817 # -> b -> ba -> baa
16820 # This Makefile creates a variable called DIRS, that can be reused any time
16821 # you need this list (see the other examples in this section)
16823 # The root of your project's directory hierarchy
16827 # First method: specify explicitly the list of directories
16828 # This allows you to specify any subset of all the directories you need.
16831 DIRS := a/aa/ a/ab/ b/ba/
16834 # Second method: use wildcards
16835 # Note that the argument(s) to wildcard below should end with a '/'.
16836 # Since wildcards also return file names, we have to filter them out
16837 # to avoid duplicate directory names.
16838 # We thus use make's @code{dir} and @code{sort} functions.
16839 # It sets DIRs to the following value (note that the directories aaa and baa
16840 # are not given, unless you change the arguments to wildcard).
16841 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
16844 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
16845 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
16848 # Third method: use an external program
16849 # This command is much faster if run on local disks, avoiding NFS slowdowns.
16850 # This is the most complete command: it sets DIRs to the following value:
16851 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
16854 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
16858 @node Generating the Command Line Switches
16859 @section Generating the Command Line Switches
16862 Once you have created the list of directories as explained in the
16863 previous section (@pxref{Automatically Creating a List of Directories}),
16864 you can easily generate the command line arguments to pass to gnatmake.
16866 For the sake of completeness, this example assumes that the source path
16867 is not the same as the object path, and that you have two separate lists
16871 # see "Automatically creating a list of directories" to create
16876 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
16877 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
16880 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
16883 @node Overcoming Command Line Length Limits
16884 @section Overcoming Command Line Length Limits
16887 One problem that might be encountered on big projects is that many
16888 operating systems limit the length of the command line. It is thus hard to give
16889 gnatmake the list of source and object directories.
16891 This example shows how you can set up environment variables, which will
16892 make @code{gnatmake} behave exactly as if the directories had been
16893 specified on the command line, but have a much higher length limit (or
16894 even none on most systems).
16896 It assumes that you have created a list of directories in your Makefile,
16897 using one of the methods presented in
16898 @ref{Automatically Creating a List of Directories}.
16899 For the sake of completeness, we assume that the object
16900 path (where the ALI files are found) is different from the sources patch.
16902 Note a small trick in the Makefile below: for efficiency reasons, we
16903 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
16904 expanded immediately by @code{make}. This way we overcome the standard
16905 make behavior which is to expand the variables only when they are
16908 On Windows, if you are using the standard Windows command shell, you must
16909 replace colons with semicolons in the assignments to these variables.
16914 @font@heightrm=cmr8
16917 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
16918 # This is the same thing as putting the -I arguments on the command line.
16919 # (the equivalent of using -aI on the command line would be to define
16920 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
16921 # You can of course have different values for these variables.
16923 # Note also that we need to keep the previous values of these variables, since
16924 # they might have been set before running 'make' to specify where the GNAT
16925 # library is installed.
16927 # see "Automatically creating a list of directories" to create these
16933 space:=$@{empty@} $@{empty@}
16934 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
16935 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
16936 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
16937 ADA_OBJECT_PATH += $@{OBJECT_LIST@}
16938 export ADA_INCLUDE_PATH
16939 export ADA_OBJECT_PATH
16947 @node Finding Memory Problems
16948 @chapter Finding Memory Problems
16951 This chapter describes
16953 the @command{gnatmem} tool, which can be used to track down
16954 ``memory leaks'', and
16956 the GNAT Debug Pool facility, which can be used to detect incorrect uses of
16957 access values (including ``dangling references'').
16961 * The gnatmem Tool::
16963 * The GNAT Debug Pool Facility::
16968 @node The gnatmem Tool
16969 @section The @command{gnatmem} Tool
16973 The @code{gnatmem} utility monitors dynamic allocation and
16974 deallocation activity in a program, and displays information about
16975 incorrect deallocations and possible sources of memory leaks.
16976 It provides three type of information:
16979 General information concerning memory management, such as the total
16980 number of allocations and deallocations, the amount of allocated
16981 memory and the high water mark, i.e. the largest amount of allocated
16982 memory in the course of program execution.
16985 Backtraces for all incorrect deallocations, that is to say deallocations
16986 which do not correspond to a valid allocation.
16989 Information on each allocation that is potentially the origin of a memory
16994 * Running gnatmem::
16995 * Switches for gnatmem::
16996 * Example of gnatmem Usage::
16999 @node Running gnatmem
17000 @subsection Running @code{gnatmem}
17003 @code{gnatmem} makes use of the output created by the special version of
17004 allocation and deallocation routines that record call information. This
17005 allows to obtain accurate dynamic memory usage history at a minimal cost to
17006 the execution speed. Note however, that @code{gnatmem} is not supported on
17007 all platforms (currently, it is supported on AIX, HP-UX, GNU/Linux x86,
17008 Solaris (sparc and x86) and Windows NT/2000/XP (x86).
17011 The @code{gnatmem} command has the form
17014 $ gnatmem [switches] user_program
17018 The program must have been linked with the instrumented version of the
17019 allocation and deallocation routines. This is done by linking with the
17020 @file{libgmem.a} library. For correct symbolic backtrace information,
17021 the user program should be compiled with debugging options
17022 @ref{Switches for gcc}. For example to build @file{my_program}:
17025 $ gnatmake -g my_program -largs -lgmem
17029 When running @file{my_program} the file @file{gmem.out} is produced. This file
17030 contains information about all allocations and deallocations done by the
17031 program. It is produced by the instrumented allocations and
17032 deallocations routines and will be used by @code{gnatmem}.
17035 Gnatmem must be supplied with the @file{gmem.out} file and the executable to
17036 examine. If the location of @file{gmem.out} file was not explicitly supplied by
17037 @code{-i} switch, gnatmem will assume that this file can be found in the
17038 current directory. For example, after you have executed @file{my_program},
17039 @file{gmem.out} can be analyzed by @code{gnatmem} using the command:
17042 $ gnatmem my_program
17046 This will produce the output with the following format:
17048 *************** debut cc
17050 $ gnatmem my_program
17054 Total number of allocations : 45
17055 Total number of deallocations : 6
17056 Final Water Mark (non freed mem) : 11.29 Kilobytes
17057 High Water Mark : 11.40 Kilobytes
17062 Allocation Root # 2
17063 -------------------
17064 Number of non freed allocations : 11
17065 Final Water Mark (non freed mem) : 1.16 Kilobytes
17066 High Water Mark : 1.27 Kilobytes
17068 my_program.adb:23 my_program.alloc
17074 The first block of output gives general information. In this case, the
17075 Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an
17076 Unchecked_Deallocation routine occurred.
17079 Subsequent paragraphs display information on all allocation roots.
17080 An allocation root is a specific point in the execution of the program
17081 that generates some dynamic allocation, such as a ``@code{@b{new}}''
17082 construct. This root is represented by an execution backtrace (or subprogram
17083 call stack). By default the backtrace depth for allocations roots is 1, so
17084 that a root corresponds exactly to a source location. The backtrace can
17085 be made deeper, to make the root more specific.
17087 @node Switches for gnatmem
17088 @subsection Switches for @code{gnatmem}
17091 @code{gnatmem} recognizes the following switches:
17096 @cindex @option{-q} (@code{gnatmem})
17097 Quiet. Gives the minimum output needed to identify the origin of the
17098 memory leaks. Omits statistical information.
17101 @cindex @var{N} (@code{gnatmem})
17102 N is an integer literal (usually between 1 and 10) which controls the
17103 depth of the backtraces defining allocation root. The default value for
17104 N is 1. The deeper the backtrace, the more precise the localization of
17105 the root. Note that the total number of roots can depend on this
17106 parameter. This parameter must be specified @emph{before} the name of the
17107 executable to be analyzed, to avoid ambiguity.
17110 @cindex @option{-b} (@code{gnatmem})
17111 This switch has the same effect as just depth parameter.
17113 @item -i @var{file}
17114 @cindex @option{-i} (@code{gnatmem})
17115 Do the @code{gnatmem} processing starting from @file{file}, rather than
17116 @file{gmem.out} in the current directory.
17119 @cindex @option{-m} (@code{gnatmem})
17120 This switch causes @code{gnatmem} to mask the allocation roots that have less
17121 than n leaks. The default value is 1. Specifying the value of 0 will allow to
17122 examine even the roots that didn't result in leaks.
17125 @cindex @option{-s} (@code{gnatmem})
17126 This switch causes @code{gnatmem} to sort the allocation roots according to the
17127 specified order of sort criteria, each identified by a single letter. The
17128 currently supported criteria are @code{n, h, w} standing respectively for
17129 number of unfreed allocations, high watermark, and final watermark
17130 corresponding to a specific root. The default order is @code{nwh}.
17134 @node Example of gnatmem Usage
17135 @subsection Example of @code{gnatmem} Usage
17138 The following example shows the use of @code{gnatmem}
17139 on a simple memory-leaking program.
17140 Suppose that we have the following Ada program:
17142 @smallexample @c ada
17145 with Unchecked_Deallocation;
17146 procedure Test_Gm is
17148 type T is array (1..1000) of Integer;
17149 type Ptr is access T;
17150 procedure Free is new Unchecked_Deallocation (T, Ptr);
17153 procedure My_Alloc is
17158 procedure My_DeAlloc is
17166 for I in 1 .. 5 loop
17167 for J in I .. 5 loop
17178 The program needs to be compiled with debugging option and linked with
17179 @code{gmem} library:
17182 $ gnatmake -g test_gm -largs -lgmem
17186 Then we execute the program as usual:
17193 Then @code{gnatmem} is invoked simply with
17199 which produces the following output (result may vary on different platforms):
17204 Total number of allocations : 18
17205 Total number of deallocations : 5
17206 Final Water Mark (non freed mem) : 53.00 Kilobytes
17207 High Water Mark : 56.90 Kilobytes
17209 Allocation Root # 1
17210 -------------------
17211 Number of non freed allocations : 11
17212 Final Water Mark (non freed mem) : 42.97 Kilobytes
17213 High Water Mark : 46.88 Kilobytes
17215 test_gm.adb:11 test_gm.my_alloc
17217 Allocation Root # 2
17218 -------------------
17219 Number of non freed allocations : 1
17220 Final Water Mark (non freed mem) : 10.02 Kilobytes
17221 High Water Mark : 10.02 Kilobytes
17223 s-secsta.adb:81 system.secondary_stack.ss_init
17225 Allocation Root # 3
17226 -------------------
17227 Number of non freed allocations : 1
17228 Final Water Mark (non freed mem) : 12 Bytes
17229 High Water Mark : 12 Bytes
17231 s-secsta.adb:181 system.secondary_stack.ss_init
17235 Note that the GNAT run time contains itself a certain number of
17236 allocations that have no corresponding deallocation,
17237 as shown here for root #2 and root
17238 #3. This is a normal behavior when the number of non freed allocations
17239 is one, it allocates dynamic data structures that the run time needs for
17240 the complete lifetime of the program. Note also that there is only one
17241 allocation root in the user program with a single line back trace:
17242 test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
17243 program shows that 'My_Alloc' is called at 2 different points in the
17244 source (line 21 and line 24). If those two allocation roots need to be
17245 distinguished, the backtrace depth parameter can be used:
17248 $ gnatmem 3 test_gm
17252 which will give the following output:
17257 Total number of allocations : 18
17258 Total number of deallocations : 5
17259 Final Water Mark (non freed mem) : 53.00 Kilobytes
17260 High Water Mark : 56.90 Kilobytes
17262 Allocation Root # 1
17263 -------------------
17264 Number of non freed allocations : 10
17265 Final Water Mark (non freed mem) : 39.06 Kilobytes
17266 High Water Mark : 42.97 Kilobytes
17268 test_gm.adb:11 test_gm.my_alloc
17269 test_gm.adb:24 test_gm
17270 b_test_gm.c:52 main
17272 Allocation Root # 2
17273 -------------------
17274 Number of non freed allocations : 1
17275 Final Water Mark (non freed mem) : 10.02 Kilobytes
17276 High Water Mark : 10.02 Kilobytes
17278 s-secsta.adb:81 system.secondary_stack.ss_init
17279 s-secsta.adb:283 <system__secondary_stack___elabb>
17280 b_test_gm.c:33 adainit
17282 Allocation Root # 3
17283 -------------------
17284 Number of non freed allocations : 1
17285 Final Water Mark (non freed mem) : 3.91 Kilobytes
17286 High Water Mark : 3.91 Kilobytes
17288 test_gm.adb:11 test_gm.my_alloc
17289 test_gm.adb:21 test_gm
17290 b_test_gm.c:52 main
17292 Allocation Root # 4
17293 -------------------
17294 Number of non freed allocations : 1
17295 Final Water Mark (non freed mem) : 12 Bytes
17296 High Water Mark : 12 Bytes
17298 s-secsta.adb:181 system.secondary_stack.ss_init
17299 s-secsta.adb:283 <system__secondary_stack___elabb>
17300 b_test_gm.c:33 adainit
17304 The allocation root #1 of the first example has been split in 2 roots #1
17305 and #3 thanks to the more precise associated backtrace.
17310 @node The GNAT Debug Pool Facility
17311 @section The GNAT Debug Pool Facility
17313 @cindex storage, pool, memory corruption
17316 The use of unchecked deallocation and unchecked conversion can easily
17317 lead to incorrect memory references. The problems generated by such
17318 references are usually difficult to tackle because the symptoms can be
17319 very remote from the origin of the problem. In such cases, it is
17320 very helpful to detect the problem as early as possible. This is the
17321 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
17323 In order to use the GNAT specific debugging pool, the user must
17324 associate a debug pool object with each of the access types that may be
17325 related to suspected memory problems. See Ada Reference Manual 13.11.
17326 @smallexample @c ada
17327 type Ptr is access Some_Type;
17328 Pool : GNAT.Debug_Pools.Debug_Pool;
17329 for Ptr'Storage_Pool use Pool;
17333 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
17334 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
17335 allow the user to redefine allocation and deallocation strategies. They
17336 also provide a checkpoint for each dereference, through the use of
17337 the primitive operation @code{Dereference} which is implicitly called at
17338 each dereference of an access value.
17340 Once an access type has been associated with a debug pool, operations on
17341 values of the type may raise four distinct exceptions,
17342 which correspond to four potential kinds of memory corruption:
17345 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
17347 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
17349 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
17351 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
17355 For types associated with a Debug_Pool, dynamic allocation is performed using
17357 GNAT allocation routine. References to all allocated chunks of memory
17358 are kept in an internal dictionary.
17359 Several deallocation strategies are provided, whereupon the user can choose
17360 to release the memory to the system, keep it allocated for further invalid
17361 access checks, or fill it with an easily recognizable pattern for debug
17363 The memory pattern is the old IBM hexadecimal convention: @code{16#DEADBEEF#}.
17365 See the documentation in the file g-debpoo.ads for more information on the
17366 various strategies.
17368 Upon each dereference, a check is made that the access value denotes a
17369 properly allocated memory location. Here is a complete example of use of
17370 @code{Debug_Pools}, that includes typical instances of memory corruption:
17371 @smallexample @c ada
17375 with Gnat.Io; use Gnat.Io;
17376 with Unchecked_Deallocation;
17377 with Unchecked_Conversion;
17378 with GNAT.Debug_Pools;
17379 with System.Storage_Elements;
17380 with Ada.Exceptions; use Ada.Exceptions;
17381 procedure Debug_Pool_Test is
17383 type T is access Integer;
17384 type U is access all T;
17386 P : GNAT.Debug_Pools.Debug_Pool;
17387 for T'Storage_Pool use P;
17389 procedure Free is new Unchecked_Deallocation (Integer, T);
17390 function UC is new Unchecked_Conversion (U, T);
17393 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
17403 Put_Line (Integer'Image(B.all));
17405 when E : others => Put_Line ("raised: " & Exception_Name (E));
17410 when E : others => Put_Line ("raised: " & Exception_Name (E));
17414 Put_Line (Integer'Image(B.all));
17416 when E : others => Put_Line ("raised: " & Exception_Name (E));
17421 when E : others => Put_Line ("raised: " & Exception_Name (E));
17424 end Debug_Pool_Test;
17428 The debug pool mechanism provides the following precise diagnostics on the
17429 execution of this erroneous program:
17432 Total allocated bytes : 0
17433 Total deallocated bytes : 0
17434 Current Water Mark: 0
17438 Total allocated bytes : 8
17439 Total deallocated bytes : 0
17440 Current Water Mark: 8
17443 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
17444 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
17445 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
17446 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
17448 Total allocated bytes : 8
17449 Total deallocated bytes : 4
17450 Current Water Mark: 4
17455 @node Creating Sample Bodies Using gnatstub
17456 @chapter Creating Sample Bodies Using @command{gnatstub}
17460 @command{gnatstub} creates body stubs, that is, empty but compilable bodies
17461 for library unit declarations.
17463 To create a body stub, @command{gnatstub} has to compile the library
17464 unit declaration. Therefore, bodies can be created only for legal
17465 library units. Moreover, if a library unit depends semantically upon
17466 units located outside the current directory, you have to provide
17467 the source search path when calling @command{gnatstub}, see the description
17468 of @command{gnatstub} switches below.
17471 * Running gnatstub::
17472 * Switches for gnatstub::
17475 @node Running gnatstub
17476 @section Running @command{gnatstub}
17479 @command{gnatstub} has the command-line interface of the form
17482 $ gnatstub [switches] filename [directory]
17489 is the name of the source file that contains a library unit declaration
17490 for which a body must be created. The file name may contain the path
17492 The file name does not have to follow the GNAT file name conventions. If the
17494 does not follow GNAT file naming conventions, the name of the body file must
17496 explicitly as the value of the @option{^-o^/BODY=^@var{body-name}} option.
17497 If the file name follows the GNAT file naming
17498 conventions and the name of the body file is not provided,
17501 of the body file from the argument file name by replacing the @file{.ads}
17503 with the @file{.adb} suffix.
17506 indicates the directory in which the body stub is to be placed (the default
17511 is an optional sequence of switches as described in the next section
17514 @node Switches for gnatstub
17515 @section Switches for @command{gnatstub}
17521 @cindex @option{^-f^/FULL^} (@command{gnatstub})
17522 If the destination directory already contains a file with the name of the
17524 for the argument spec file, replace it with the generated body stub.
17526 @item ^-hs^/HEADER=SPEC^
17527 @cindex @option{^-hs^/HEADER=SPEC^} (@command{gnatstub})
17528 Put the comment header (i.e., all the comments preceding the
17529 compilation unit) from the source of the library unit declaration
17530 into the body stub.
17532 @item ^-hg^/HEADER=GENERAL^
17533 @cindex @option{^-hg^/HEADER=GENERAL^} (@command{gnatstub})
17534 Put a sample comment header into the body stub.
17538 @cindex @option{-IDIR} (@command{gnatstub})
17540 @cindex @option{-I-} (@command{gnatstub})
17543 @item /NOCURRENT_DIRECTORY
17544 @cindex @option{/NOCURRENT_DIRECTORY} (@command{gnatstub})
17546 ^These switches have ^This switch has^ the same meaning as in calls to
17548 ^They define ^It defines ^ the source search path in the call to
17549 @command{gcc} issued
17550 by @command{gnatstub} to compile an argument source file.
17552 @item ^-gnatec^/CONFIGURATION_PRAGMAS_FILE=^@var{PATH}
17553 @cindex @option{^-gnatec^/CONFIGURATION_PRAGMAS_FILE^} (@command{gnatstub})
17554 This switch has the same meaning as in calls to @command{gcc}.
17555 It defines the additional configuration file to be passed to the call to
17556 @command{gcc} issued
17557 by @command{gnatstub} to compile an argument source file.
17559 @item ^-gnatyM^/MAX_LINE_LENGTH=^@var{n}
17560 @cindex @option{^-gnatyM^/MAX_LINE_LENGTH^} (@command{gnatstub})
17561 (@var{n} is a non-negative integer). Set the maximum line length in the
17562 body stub to @var{n}; the default is 79. The maximum value that can be
17563 specified is 32767.
17565 @item ^-gnaty^/STYLE_CHECKS=^@var{n}
17566 @cindex @option{^-gnaty^/STYLE_CHECKS=^} (@command{gnatstub})
17567 (@var{n} is a non-negative integer from 1 to 9). Set the indentation level in
17568 the generated body sample to @var{n}.
17569 The default indentation is 3.
17571 @item ^-gnatyo^/ORDERED_SUBPROGRAMS^
17572 @cindex @option{^-gnato^/ORDERED_SUBPROGRAMS^} (@command{gnatstub})
17573 Order local bodies alphabetically. (By default local bodies are ordered
17574 in the same way as the corresponding local specs in the argument spec file.)
17576 @item ^-i^/INDENTATION=^@var{n}
17577 @cindex @option{^-i^/INDENTATION^} (@command{gnatstub})
17578 Same as @option{^-gnaty^/STYLE_CHECKS=^@var{n}}
17580 @item ^-k^/TREE_FILE=SAVE^
17581 @cindex @option{^-k^/TREE_FILE=SAVE^} (@command{gnatstub})
17582 Do not remove the tree file (i.e., the snapshot of the compiler internal
17583 structures used by @command{gnatstub}) after creating the body stub.
17585 @item ^-l^/LINE_LENGTH=^@var{n}
17586 @cindex @option{^-l^/LINE_LENGTH^} (@command{gnatstub})
17587 Same as @option{^-gnatyM^/MAX_LINE_LENGTH=^@var{n}}
17589 @item ^-o^/BODY=^@var{body-name}
17590 @cindex @option{^-o^/BODY^} (@command{gnatstub})
17591 Body file name. This should be set if the argument file name does not
17593 the GNAT file naming
17594 conventions. If this switch is omitted the default name for the body will be
17596 from the argument file name according to the GNAT file naming conventions.
17599 @cindex @option{^-q^/QUIET^} (@command{gnatstub})
17600 Quiet mode: do not generate a confirmation when a body is
17601 successfully created, and do not generate a message when a body is not
17605 @item ^-r^/TREE_FILE=REUSE^
17606 @cindex @option{^-r^/TREE_FILE=REUSE^} (@command{gnatstub})
17607 Reuse the tree file (if it exists) instead of creating it. Instead of
17608 creating the tree file for the library unit declaration, @command{gnatstub}
17609 tries to find it in the current directory and use it for creating
17610 a body. If the tree file is not found, no body is created. This option
17611 also implies @option{^-k^/SAVE^}, whether or not
17612 the latter is set explicitly.
17614 @item ^-t^/TREE_FILE=OVERWRITE^
17615 @cindex @option{^-t^/TREE_FILE=OVERWRITE^} (@command{gnatstub})
17616 Overwrite the existing tree file. If the current directory already
17617 contains the file which, according to the GNAT file naming rules should
17618 be considered as a tree file for the argument source file,
17620 will refuse to create the tree file needed to create a sample body
17621 unless this option is set.
17623 @item ^-v^/VERBOSE^
17624 @cindex @option{^-v^/VERBOSE^} (@command{gnatstub})
17625 Verbose mode: generate version information.
17630 @node Other Utility Programs
17631 @chapter Other Utility Programs
17634 This chapter discusses some other utility programs available in the Ada
17638 * Using Other Utility Programs with GNAT::
17639 * The External Symbol Naming Scheme of GNAT::
17641 * Ada Mode for Glide::
17643 * Converting Ada Files to html with gnathtml::
17644 * Installing gnathtml::
17651 @node Using Other Utility Programs with GNAT
17652 @section Using Other Utility Programs with GNAT
17655 The object files generated by GNAT are in standard system format and in
17656 particular the debugging information uses this format. This means
17657 programs generated by GNAT can be used with existing utilities that
17658 depend on these formats.
17661 In general, any utility program that works with C will also often work with
17662 Ada programs generated by GNAT. This includes software utilities such as
17663 gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
17667 @node The External Symbol Naming Scheme of GNAT
17668 @section The External Symbol Naming Scheme of GNAT
17671 In order to interpret the output from GNAT, when using tools that are
17672 originally intended for use with other languages, it is useful to
17673 understand the conventions used to generate link names from the Ada
17676 All link names are in all lowercase letters. With the exception of library
17677 procedure names, the mechanism used is simply to use the full expanded
17678 Ada name with dots replaced by double underscores. For example, suppose
17679 we have the following package spec:
17681 @smallexample @c ada
17692 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
17693 the corresponding link name is @code{qrs__mn}.
17695 Of course if a @code{pragma Export} is used this may be overridden:
17697 @smallexample @c ada
17702 pragma Export (Var1, C, External_Name => "var1_name");
17704 pragma Export (Var2, C, Link_Name => "var2_link_name");
17711 In this case, the link name for @var{Var1} is whatever link name the
17712 C compiler would assign for the C function @var{var1_name}. This typically
17713 would be either @var{var1_name} or @var{_var1_name}, depending on operating
17714 system conventions, but other possibilities exist. The link name for
17715 @var{Var2} is @var{var2_link_name}, and this is not operating system
17719 One exception occurs for library level procedures. A potential ambiguity
17720 arises between the required name @code{_main} for the C main program,
17721 and the name we would otherwise assign to an Ada library level procedure
17722 called @code{Main} (which might well not be the main program).
17724 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
17725 names. So if we have a library level procedure such as
17727 @smallexample @c ada
17730 procedure Hello (S : String);
17736 the external name of this procedure will be @var{_ada_hello}.
17739 @node Ada Mode for Glide
17740 @section Ada Mode for @code{Glide}
17741 @cindex Ada mode (for Glide)
17744 The Glide mode for programming in Ada (both Ada83 and Ada95) helps the
17745 user to understand and navigate existing code, and facilitates writing
17746 new code. It furthermore provides some utility functions for easier
17747 integration of standard Emacs features when programming in Ada.
17749 Its general features include:
17753 An Integrated Development Environment with functionality such as the
17758 ``Project files'' for configuration-specific aspects
17759 (e.g. directories and compilation options)
17762 Compiling and stepping through error messages.
17765 Running and debugging an applications within Glide.
17772 User configurability
17775 Some of the specific Ada mode features are:
17779 Functions for easy and quick stepping through Ada code
17782 Getting cross reference information for identifiers (e.g., finding a
17783 defining occurrence)
17786 Displaying an index menu of types and subprograms, allowing
17787 direct selection for browsing
17790 Automatic color highlighting of the various Ada entities
17793 Glide directly supports writing Ada code, via several facilities:
17797 Switching between spec and body files with possible
17798 autogeneration of body files
17801 Automatic formating of subprogram parameter lists
17804 Automatic indentation according to Ada syntax
17807 Automatic completion of identifiers
17810 Automatic (and configurable) casing of identifiers, keywords, and attributes
17813 Insertion of syntactic templates
17816 Block commenting / uncommenting
17820 For more information, please refer to the online documentation
17821 available in the @code{Glide} @result{} @code{Help} menu.
17825 @node Converting Ada Files to html with gnathtml
17826 @section Converting Ada Files to HTML with @code{gnathtml}
17829 This @code{Perl} script allows Ada source files to be browsed using
17830 standard Web browsers. For installation procedure, see the section
17831 @xref{Installing gnathtml}.
17833 Ada reserved keywords are highlighted in a bold font and Ada comments in
17834 a blue font. Unless your program was compiled with the gcc @option{-gnatx}
17835 switch to suppress the generation of cross-referencing information, user
17836 defined variables and types will appear in a different color; you will
17837 be able to click on any identifier and go to its declaration.
17839 The command line is as follow:
17841 $ perl gnathtml.pl [switches] ada-files
17845 You can pass it as many Ada files as you want. @code{gnathtml} will generate
17846 an html file for every ada file, and a global file called @file{index.htm}.
17847 This file is an index of every identifier defined in the files.
17849 The available switches are the following ones :
17853 @cindex @option{-83} (@code{gnathtml})
17854 Only the subset on the Ada 83 keywords will be highlighted, not the full
17855 Ada 95 keywords set.
17857 @item -cc @var{color}
17858 @cindex @option{-cc} (@code{gnathtml})
17859 This option allows you to change the color used for comments. The default
17860 value is green. The color argument can be any name accepted by html.
17863 @cindex @option{-d} (@code{gnathtml})
17864 If the ada files depend on some other files (using for instance the
17865 @code{with} command, the latter will also be converted to html.
17866 Only the files in the user project will be converted to html, not the files
17867 in the run-time library itself.
17870 @cindex @option{-D} (@code{gnathtml})
17871 This command is the same as @option{-d} above, but @command{gnathtml} will
17872 also look for files in the run-time library, and generate html files for them.
17874 @item -ext @var{extension}
17875 @cindex @option{-ext} (@code{gnathtml})
17876 This option allows you to change the extension of the generated HTML files.
17877 If you do not specify an extension, it will default to @file{htm}.
17880 @cindex @option{-f} (@code{gnathtml})
17881 By default, gnathtml will generate html links only for global entities
17882 ('with'ed units, global variables and types,...). If you specify the
17883 @option{-f} on the command line, then links will be generated for local
17886 @item -l @var{number}
17887 @cindex @option{-l} (@code{gnathtml})
17888 If this switch is provided and @var{number} is not 0, then @code{gnathtml}
17889 will number the html files every @var{number} line.
17892 @cindex @option{-I} (@code{gnathtml})
17893 Specify a directory to search for library files (@file{.ALI} files) and
17894 source files. You can provide several -I switches on the command line,
17895 and the directories will be parsed in the order of the command line.
17898 @cindex @option{-o} (@code{gnathtml})
17899 Specify the output directory for html files. By default, gnathtml will
17900 saved the generated html files in a subdirectory named @file{html/}.
17902 @item -p @var{file}
17903 @cindex @option{-p} (@code{gnathtml})
17904 If you are using Emacs and the most recent Emacs Ada mode, which provides
17905 a full Integrated Development Environment for compiling, checking,
17906 running and debugging applications, you may use @file{.gpr} files
17907 to give the directories where Emacs can find sources and object files.
17909 Using this switch, you can tell gnathtml to use these files. This allows
17910 you to get an html version of your application, even if it is spread
17911 over multiple directories.
17913 @item -sc @var{color}
17914 @cindex @option{-sc} (@code{gnathtml})
17915 This option allows you to change the color used for symbol definitions.
17916 The default value is red. The color argument can be any name accepted by html.
17918 @item -t @var{file}
17919 @cindex @option{-t} (@code{gnathtml})
17920 This switch provides the name of a file. This file contains a list of
17921 file names to be converted, and the effect is exactly as though they had
17922 appeared explicitly on the command line. This
17923 is the recommended way to work around the command line length limit on some
17928 @node Installing gnathtml
17929 @section Installing @code{gnathtml}
17932 @code{Perl} needs to be installed on your machine to run this script.
17933 @code{Perl} is freely available for almost every architecture and
17934 Operating System via the Internet.
17936 On Unix systems, you may want to modify the first line of the script
17937 @code{gnathtml}, to explicitly tell the Operating system where Perl
17938 is. The syntax of this line is :
17940 #!full_path_name_to_perl
17944 Alternatively, you may run the script using the following command line:
17947 $ perl gnathtml.pl [switches] files
17956 The GNAT distribution provides an Ada 95 template for the Digital Language
17957 Sensitive Editor (LSE), a component of DECset. In order to
17958 access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
17965 GNAT supports The Digital Performance Coverage Analyzer (PCA), a component
17966 of DECset. To use it proceed as outlined under ``HELP PCA'', except for running
17967 the collection phase with the /DEBUG qualifier.
17970 $ GNAT MAKE /DEBUG <PROGRAM_NAME>
17971 $ DEFINE LIB$DEBUG PCA$COLLECTOR
17972 $ RUN/DEBUG <PROGRAM_NAME>
17977 @node Running and Debugging Ada Programs
17978 @chapter Running and Debugging Ada Programs
17982 This chapter discusses how to debug Ada programs. An incorrect Ada program
17983 may be handled in three ways by the GNAT compiler:
17987 The illegality may be a violation of the static semantics of Ada. In
17988 that case GNAT diagnoses the constructs in the program that are illegal.
17989 It is then a straightforward matter for the user to modify those parts of
17993 The illegality may be a violation of the dynamic semantics of Ada. In
17994 that case the program compiles and executes, but may generate incorrect
17995 results, or may terminate abnormally with some exception.
17998 When presented with a program that contains convoluted errors, GNAT
17999 itself may terminate abnormally without providing full diagnostics on
18000 the incorrect user program.
18004 * The GNAT Debugger GDB::
18006 * Introduction to GDB Commands::
18007 * Using Ada Expressions::
18008 * Calling User-Defined Subprograms::
18009 * Using the Next Command in a Function::
18012 * Debugging Generic Units::
18013 * GNAT Abnormal Termination or Failure to Terminate::
18014 * Naming Conventions for GNAT Source Files::
18015 * Getting Internal Debugging Information::
18016 * Stack Traceback::
18022 @node The GNAT Debugger GDB
18023 @section The GNAT Debugger GDB
18026 @code{GDB} is a general purpose, platform-independent debugger that
18027 can be used to debug mixed-language programs compiled with @code{GCC},
18028 and in particular is capable of debugging Ada programs compiled with
18029 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
18030 complex Ada data structures.
18032 The manual @cite{Debugging with GDB}
18034 , located in the GNU:[DOCS] directory,
18036 contains full details on the usage of @code{GDB}, including a section on
18037 its usage on programs. This manual should be consulted for full
18038 details. The section that follows is a brief introduction to the
18039 philosophy and use of @code{GDB}.
18041 When GNAT programs are compiled, the compiler optionally writes debugging
18042 information into the generated object file, including information on
18043 line numbers, and on declared types and variables. This information is
18044 separate from the generated code. It makes the object files considerably
18045 larger, but it does not add to the size of the actual executable that
18046 will be loaded into memory, and has no impact on run-time performance. The
18047 generation of debug information is triggered by the use of the
18048 ^-g^/DEBUG^ switch in the gcc or gnatmake command used to carry out
18049 the compilations. It is important to emphasize that the use of these
18050 options does not change the generated code.
18052 The debugging information is written in standard system formats that
18053 are used by many tools, including debuggers and profilers. The format
18054 of the information is typically designed to describe C types and
18055 semantics, but GNAT implements a translation scheme which allows full
18056 details about Ada types and variables to be encoded into these
18057 standard C formats. Details of this encoding scheme may be found in
18058 the file exp_dbug.ads in the GNAT source distribution. However, the
18059 details of this encoding are, in general, of no interest to a user,
18060 since @code{GDB} automatically performs the necessary decoding.
18062 When a program is bound and linked, the debugging information is
18063 collected from the object files, and stored in the executable image of
18064 the program. Again, this process significantly increases the size of
18065 the generated executable file, but it does not increase the size of
18066 the executable program itself. Furthermore, if this program is run in
18067 the normal manner, it runs exactly as if the debug information were
18068 not present, and takes no more actual memory.
18070 However, if the program is run under control of @code{GDB}, the
18071 debugger is activated. The image of the program is loaded, at which
18072 point it is ready to run. If a run command is given, then the program
18073 will run exactly as it would have if @code{GDB} were not present. This
18074 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
18075 entirely non-intrusive until a breakpoint is encountered. If no
18076 breakpoint is ever hit, the program will run exactly as it would if no
18077 debugger were present. When a breakpoint is hit, @code{GDB} accesses
18078 the debugging information and can respond to user commands to inspect
18079 variables, and more generally to report on the state of execution.
18083 @section Running GDB
18086 The debugger can be launched directly and simply from @code{glide} or
18087 through its graphical interface: @code{gvd}. It can also be used
18088 directly in text mode. Here is described the basic use of @code{GDB}
18089 in text mode. All the commands described below can be used in the
18090 @code{gvd} console window even though there is usually other more
18091 graphical ways to achieve the same goals.
18095 The command to run the graphical interface of the debugger is
18102 The command to run @code{GDB} in text mode is
18105 $ ^gdb program^$ GDB PROGRAM^
18109 where @code{^program^PROGRAM^} is the name of the executable file. This
18110 activates the debugger and results in a prompt for debugger commands.
18111 The simplest command is simply @code{run}, which causes the program to run
18112 exactly as if the debugger were not present. The following section
18113 describes some of the additional commands that can be given to @code{GDB}.
18116 @c *******************************
18117 @node Introduction to GDB Commands
18118 @section Introduction to GDB Commands
18121 @code{GDB} contains a large repertoire of commands. The manual
18122 @cite{Debugging with GDB}
18124 , located in the GNU:[DOCS] directory,
18126 includes extensive documentation on the use
18127 of these commands, together with examples of their use. Furthermore,
18128 the command @var{help} invoked from within @code{GDB} activates a simple help
18129 facility which summarizes the available commands and their options.
18130 In this section we summarize a few of the most commonly
18131 used commands to give an idea of what @code{GDB} is about. You should create
18132 a simple program with debugging information and experiment with the use of
18133 these @code{GDB} commands on the program as you read through the
18137 @item set args @var{arguments}
18138 The @var{arguments} list above is a list of arguments to be passed to
18139 the program on a subsequent run command, just as though the arguments
18140 had been entered on a normal invocation of the program. The @code{set args}
18141 command is not needed if the program does not require arguments.
18144 The @code{run} command causes execution of the program to start from
18145 the beginning. If the program is already running, that is to say if
18146 you are currently positioned at a breakpoint, then a prompt will ask
18147 for confirmation that you want to abandon the current execution and
18150 @item breakpoint @var{location}
18151 The breakpoint command sets a breakpoint, that is to say a point at which
18152 execution will halt and @code{GDB} will await further
18153 commands. @var{location} is
18154 either a line number within a file, given in the format @code{file:linenumber},
18155 or it is the name of a subprogram. If you request that a breakpoint be set on
18156 a subprogram that is overloaded, a prompt will ask you to specify on which of
18157 those subprograms you want to breakpoint. You can also
18158 specify that all of them should be breakpointed. If the program is run
18159 and execution encounters the breakpoint, then the program
18160 stops and @code{GDB} signals that the breakpoint was encountered by
18161 printing the line of code before which the program is halted.
18163 @item breakpoint exception @var{name}
18164 A special form of the breakpoint command which breakpoints whenever
18165 exception @var{name} is raised.
18166 If @var{name} is omitted,
18167 then a breakpoint will occur when any exception is raised.
18169 @item print @var{expression}
18170 This will print the value of the given expression. Most simple
18171 Ada expression formats are properly handled by @code{GDB}, so the expression
18172 can contain function calls, variables, operators, and attribute references.
18175 Continues execution following a breakpoint, until the next breakpoint or the
18176 termination of the program.
18179 Executes a single line after a breakpoint. If the next statement
18180 is a subprogram call, execution continues into (the first statement of)
18181 the called subprogram.
18184 Executes a single line. If this line is a subprogram call, executes and
18185 returns from the call.
18188 Lists a few lines around the current source location. In practice, it
18189 is usually more convenient to have a separate edit window open with the
18190 relevant source file displayed. Successive applications of this command
18191 print subsequent lines. The command can be given an argument which is a
18192 line number, in which case it displays a few lines around the specified one.
18195 Displays a backtrace of the call chain. This command is typically
18196 used after a breakpoint has occurred, to examine the sequence of calls that
18197 leads to the current breakpoint. The display includes one line for each
18198 activation record (frame) corresponding to an active subprogram.
18201 At a breakpoint, @code{GDB} can display the values of variables local
18202 to the current frame. The command @code{up} can be used to
18203 examine the contents of other active frames, by moving the focus up
18204 the stack, that is to say from callee to caller, one frame at a time.
18207 Moves the focus of @code{GDB} down from the frame currently being
18208 examined to the frame of its callee (the reverse of the previous command),
18210 @item frame @var{n}
18211 Inspect the frame with the given number. The value 0 denotes the frame
18212 of the current breakpoint, that is to say the top of the call stack.
18216 The above list is a very short introduction to the commands that
18217 @code{GDB} provides. Important additional capabilities, including conditional
18218 breakpoints, the ability to execute command sequences on a breakpoint,
18219 the ability to debug at the machine instruction level and many other
18220 features are described in detail in @cite{Debugging with GDB}.
18221 Note that most commands can be abbreviated
18222 (for example, c for continue, bt for backtrace).
18224 @node Using Ada Expressions
18225 @section Using Ada Expressions
18226 @cindex Ada expressions
18229 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
18230 extensions. The philosophy behind the design of this subset is
18234 That @code{GDB} should provide basic literals and access to operations for
18235 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18236 leaving more sophisticated computations to subprograms written into the
18237 program (which therefore may be called from @code{GDB}).
18240 That type safety and strict adherence to Ada language restrictions
18241 are not particularly important to the @code{GDB} user.
18244 That brevity is important to the @code{GDB} user.
18247 Thus, for brevity, the debugger acts as if there were
18248 implicit @code{with} and @code{use} clauses in effect for all user-written
18249 packages, thus making it unnecessary to fully qualify most names with
18250 their packages, regardless of context. Where this causes ambiguity,
18251 @code{GDB} asks the user's intent.
18253 For details on the supported Ada syntax, see @cite{Debugging with GDB}.
18255 @node Calling User-Defined Subprograms
18256 @section Calling User-Defined Subprograms
18259 An important capability of @code{GDB} is the ability to call user-defined
18260 subprograms while debugging. This is achieved simply by entering
18261 a subprogram call statement in the form:
18264 call subprogram-name (parameters)
18268 The keyword @code{call} can be omitted in the normal case where the
18269 @code{subprogram-name} does not coincide with any of the predefined
18270 @code{GDB} commands.
18272 The effect is to invoke the given subprogram, passing it the
18273 list of parameters that is supplied. The parameters can be expressions and
18274 can include variables from the program being debugged. The
18275 subprogram must be defined
18276 at the library level within your program, and @code{GDB} will call the
18277 subprogram within the environment of your program execution (which
18278 means that the subprogram is free to access or even modify variables
18279 within your program).
18281 The most important use of this facility is in allowing the inclusion of
18282 debugging routines that are tailored to particular data structures
18283 in your program. Such debugging routines can be written to provide a suitably
18284 high-level description of an abstract type, rather than a low-level dump
18285 of its physical layout. After all, the standard
18286 @code{GDB print} command only knows the physical layout of your
18287 types, not their abstract meaning. Debugging routines can provide information
18288 at the desired semantic level and are thus enormously useful.
18290 For example, when debugging GNAT itself, it is crucial to have access to
18291 the contents of the tree nodes used to represent the program internally.
18292 But tree nodes are represented simply by an integer value (which in turn
18293 is an index into a table of nodes).
18294 Using the @code{print} command on a tree node would simply print this integer
18295 value, which is not very useful. But the PN routine (defined in file
18296 treepr.adb in the GNAT sources) takes a tree node as input, and displays
18297 a useful high level representation of the tree node, which includes the
18298 syntactic category of the node, its position in the source, the integers
18299 that denote descendant nodes and parent node, as well as varied
18300 semantic information. To study this example in more detail, you might want to
18301 look at the body of the PN procedure in the stated file.
18303 @node Using the Next Command in a Function
18304 @section Using the Next Command in a Function
18307 When you use the @code{next} command in a function, the current source
18308 location will advance to the next statement as usual. A special case
18309 arises in the case of a @code{return} statement.
18311 Part of the code for a return statement is the ``epilog'' of the function.
18312 This is the code that returns to the caller. There is only one copy of
18313 this epilog code, and it is typically associated with the last return
18314 statement in the function if there is more than one return. In some
18315 implementations, this epilog is associated with the first statement
18318 The result is that if you use the @code{next} command from a return
18319 statement that is not the last return statement of the function you
18320 may see a strange apparent jump to the last return statement or to
18321 the start of the function. You should simply ignore this odd jump.
18322 The value returned is always that from the first return statement
18323 that was stepped through.
18325 @node Ada Exceptions
18326 @section Breaking on Ada Exceptions
18330 You can set breakpoints that trip when your program raises
18331 selected exceptions.
18334 @item break exception
18335 Set a breakpoint that trips whenever (any task in the) program raises
18338 @item break exception @var{name}
18339 Set a breakpoint that trips whenever (any task in the) program raises
18340 the exception @var{name}.
18342 @item break exception unhandled
18343 Set a breakpoint that trips whenever (any task in the) program raises an
18344 exception for which there is no handler.
18346 @item info exceptions
18347 @itemx info exceptions @var{regexp}
18348 The @code{info exceptions} command permits the user to examine all defined
18349 exceptions within Ada programs. With a regular expression, @var{regexp}, as
18350 argument, prints out only those exceptions whose name matches @var{regexp}.
18358 @code{GDB} allows the following task-related commands:
18362 This command shows a list of current Ada tasks, as in the following example:
18369 ID TID P-ID Thread Pri State Name
18370 1 8088000 0 807e000 15 Child Activation Wait main_task
18371 2 80a4000 1 80ae000 15 Accept/Select Wait b
18372 3 809a800 1 80a4800 15 Child Activation Wait a
18373 * 4 80ae800 3 80b8000 15 Running c
18377 In this listing, the asterisk before the first task indicates it to be the
18378 currently running task. The first column lists the task ID that is used
18379 to refer to tasks in the following commands.
18381 @item break @var{linespec} task @var{taskid}
18382 @itemx break @var{linespec} task @var{taskid} if @dots{}
18383 @cindex Breakpoints and tasks
18384 These commands are like the @code{break @dots{} thread @dots{}}.
18385 @var{linespec} specifies source lines.
18387 Use the qualifier @samp{task @var{taskid}} with a breakpoint command
18388 to specify that you only want @code{GDB} to stop the program when a
18389 particular Ada task reaches this breakpoint. @var{taskid} is one of the
18390 numeric task identifiers assigned by @code{GDB}, shown in the first
18391 column of the @samp{info tasks} display.
18393 If you do not specify @samp{task @var{taskid}} when you set a
18394 breakpoint, the breakpoint applies to @emph{all} tasks of your
18397 You can use the @code{task} qualifier on conditional breakpoints as
18398 well; in this case, place @samp{task @var{taskid}} before the
18399 breakpoint condition (before the @code{if}).
18401 @item task @var{taskno}
18402 @cindex Task switching
18404 This command allows to switch to the task referred by @var{taskno}. In
18405 particular, This allows to browse the backtrace of the specified
18406 task. It is advised to switch back to the original task before
18407 continuing execution otherwise the scheduling of the program may be
18412 For more detailed information on the tasking support,
18413 see @cite{Debugging with GDB}.
18415 @node Debugging Generic Units
18416 @section Debugging Generic Units
18417 @cindex Debugging Generic Units
18421 GNAT always uses code expansion for generic instantiation. This means that
18422 each time an instantiation occurs, a complete copy of the original code is
18423 made, with appropriate substitutions of formals by actuals.
18425 It is not possible to refer to the original generic entities in
18426 @code{GDB}, but it is always possible to debug a particular instance of
18427 a generic, by using the appropriate expanded names. For example, if we have
18429 @smallexample @c ada
18434 generic package k is
18435 procedure kp (v1 : in out integer);
18439 procedure kp (v1 : in out integer) is
18445 package k1 is new k;
18446 package k2 is new k;
18448 var : integer := 1;
18461 Then to break on a call to procedure kp in the k2 instance, simply
18465 (gdb) break g.k2.kp
18469 When the breakpoint occurs, you can step through the code of the
18470 instance in the normal manner and examine the values of local variables, as for
18473 @node GNAT Abnormal Termination or Failure to Terminate
18474 @section GNAT Abnormal Termination or Failure to Terminate
18475 @cindex GNAT Abnormal Termination or Failure to Terminate
18478 When presented with programs that contain serious errors in syntax
18480 GNAT may on rare occasions experience problems in operation, such
18482 segmentation fault or illegal memory access, raising an internal
18483 exception, terminating abnormally, or failing to terminate at all.
18484 In such cases, you can activate
18485 various features of GNAT that can help you pinpoint the construct in your
18486 program that is the likely source of the problem.
18488 The following strategies are presented in increasing order of
18489 difficulty, corresponding to your experience in using GNAT and your
18490 familiarity with compiler internals.
18494 Run @code{gcc} with the @option{-gnatf}. This first
18495 switch causes all errors on a given line to be reported. In its absence,
18496 only the first error on a line is displayed.
18498 The @option{-gnatdO} switch causes errors to be displayed as soon as they
18499 are encountered, rather than after compilation is terminated. If GNAT
18500 terminates prematurely or goes into an infinite loop, the last error
18501 message displayed may help to pinpoint the culprit.
18504 Run @code{gcc} with the @option{^-v (verbose)^/VERBOSE^} switch. In this mode,
18505 @code{gcc} produces ongoing information about the progress of the
18506 compilation and provides the name of each procedure as code is
18507 generated. This switch allows you to find which Ada procedure was being
18508 compiled when it encountered a code generation problem.
18511 @cindex @option{-gnatdc} switch
18512 Run @code{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
18513 switch that does for the front-end what @option{^-v^VERBOSE^} does
18514 for the back end. The system prints the name of each unit,
18515 either a compilation unit or nested unit, as it is being analyzed.
18517 Finally, you can start
18518 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
18519 front-end of GNAT, and can be run independently (normally it is just
18520 called from @code{gcc}). You can use @code{gdb} on @code{gnat1} as you
18521 would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
18522 @code{where} command is the first line of attack; the variable
18523 @code{lineno} (seen by @code{print lineno}), used by the second phase of
18524 @code{gnat1} and by the @code{gcc} backend, indicates the source line at
18525 which the execution stopped, and @code{input_file name} indicates the name of
18529 @node Naming Conventions for GNAT Source Files
18530 @section Naming Conventions for GNAT Source Files
18533 In order to examine the workings of the GNAT system, the following
18534 brief description of its organization may be helpful:
18538 Files with prefix @file{^sc^SC^} contain the lexical scanner.
18541 All files prefixed with @file{^par^PAR^} are components of the parser. The
18542 numbers correspond to chapters of the Ada 95 Reference Manual. For example,
18543 parsing of select statements can be found in @file{par-ch9.adb}.
18546 All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
18547 numbers correspond to chapters of the Ada standard. For example, all
18548 issues involving context clauses can be found in @file{sem_ch10.adb}. In
18549 addition, some features of the language require sufficient special processing
18550 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
18551 dynamic dispatching, etc.
18554 All files prefixed with @file{^exp^EXP^} perform normalization and
18555 expansion of the intermediate representation (abstract syntax tree, or AST).
18556 these files use the same numbering scheme as the parser and semantics files.
18557 For example, the construction of record initialization procedures is done in
18558 @file{exp_ch3.adb}.
18561 The files prefixed with @file{^bind^BIND^} implement the binder, which
18562 verifies the consistency of the compilation, determines an order of
18563 elaboration, and generates the bind file.
18566 The files @file{atree.ads} and @file{atree.adb} detail the low-level
18567 data structures used by the front-end.
18570 The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
18571 the abstract syntax tree as produced by the parser.
18574 The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
18575 all entities, computed during semantic analysis.
18578 Library management issues are dealt with in files with prefix
18584 Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
18585 defined in Annex A.
18590 Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
18591 defined in Annex B.
18595 Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
18596 both language-defined children and GNAT run-time routines.
18600 Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
18601 general-purpose packages, fully documented in their specifications. All
18602 the other @file{.c} files are modifications of common @code{gcc} files.
18605 @node Getting Internal Debugging Information
18606 @section Getting Internal Debugging Information
18609 Most compilers have internal debugging switches and modes. GNAT
18610 does also, except GNAT internal debugging switches and modes are not
18611 secret. A summary and full description of all the compiler and binder
18612 debug flags are in the file @file{debug.adb}. You must obtain the
18613 sources of the compiler to see the full detailed effects of these flags.
18615 The switches that print the source of the program (reconstructed from
18616 the internal tree) are of general interest for user programs, as are the
18618 the full internal tree, and the entity table (the symbol table
18619 information). The reconstructed source provides a readable version of the
18620 program after the front-end has completed analysis and expansion,
18621 and is useful when studying the performance of specific constructs.
18622 For example, constraint checks are indicated, complex aggregates
18623 are replaced with loops and assignments, and tasking primitives
18624 are replaced with run-time calls.
18626 @node Stack Traceback
18627 @section Stack Traceback
18629 @cindex stack traceback
18630 @cindex stack unwinding
18633 Traceback is a mechanism to display the sequence of subprogram calls that
18634 leads to a specified execution point in a program. Often (but not always)
18635 the execution point is an instruction at which an exception has been raised.
18636 This mechanism is also known as @i{stack unwinding} because it obtains
18637 its information by scanning the run-time stack and recovering the activation
18638 records of all active subprograms. Stack unwinding is one of the most
18639 important tools for program debugging.
18641 The first entry stored in traceback corresponds to the deepest calling level,
18642 that is to say the subprogram currently executing the instruction
18643 from which we want to obtain the traceback.
18645 Note that there is no runtime performance penalty when stack traceback
18646 is enabled, and no exception is raised during program execution.
18649 * Non-Symbolic Traceback::
18650 * Symbolic Traceback::
18653 @node Non-Symbolic Traceback
18654 @subsection Non-Symbolic Traceback
18655 @cindex traceback, non-symbolic
18658 Note: this feature is not supported on all platforms. See
18659 @file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
18663 * Tracebacks From an Unhandled Exception::
18664 * Tracebacks From Exception Occurrences (non-symbolic)::
18665 * Tracebacks From Anywhere in a Program (non-symbolic)::
18668 @node Tracebacks From an Unhandled Exception
18669 @subsubsection Tracebacks From an Unhandled Exception
18672 A runtime non-symbolic traceback is a list of addresses of call instructions.
18673 To enable this feature you must use the @option{-E}
18674 @code{gnatbind}'s option. With this option a stack traceback is stored as part
18675 of exception information. You can retrieve this information using the
18676 @code{addr2line} tool.
18678 Here is a simple example:
18680 @smallexample @c ada
18686 raise Constraint_Error;
18701 $ gnatmake stb -bargs -E
18704 Execution terminated by unhandled exception
18705 Exception name: CONSTRAINT_ERROR
18707 Call stack traceback locations:
18708 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
18712 As we see the traceback lists a sequence of addresses for the unhandled
18713 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
18714 guess that this exception come from procedure P1. To translate these
18715 addresses into the source lines where the calls appear, the
18716 @code{addr2line} tool, described below, is invaluable. The use of this tool
18717 requires the program to be compiled with debug information.
18720 $ gnatmake -g stb -bargs -E
18723 Execution terminated by unhandled exception
18724 Exception name: CONSTRAINT_ERROR
18726 Call stack traceback locations:
18727 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
18729 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
18730 0x4011f1 0x77e892a4
18732 00401373 at d:/stb/stb.adb:5
18733 0040138B at d:/stb/stb.adb:10
18734 0040139C at d:/stb/stb.adb:14
18735 00401335 at d:/stb/b~stb.adb:104
18736 004011C4 at /build/.../crt1.c:200
18737 004011F1 at /build/.../crt1.c:222
18738 77E892A4 in ?? at ??:0
18742 The @code{addr2line} tool has several other useful options:
18746 to get the function name corresponding to any location
18748 @item --demangle=gnat
18749 to use the gnat decoding mode for the function names. Note that
18750 for binutils version 2.9.x the option is simply @option{--demangle}.
18754 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
18755 0x40139c 0x401335 0x4011c4 0x4011f1
18757 00401373 in stb.p1 at d:/stb/stb.adb:5
18758 0040138B in stb.p2 at d:/stb/stb.adb:10
18759 0040139C in stb at d:/stb/stb.adb:14
18760 00401335 in main at d:/stb/b~stb.adb:104
18761 004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
18762 004011F1 in <mainCRTStartup> at /build/.../crt1.c:222
18766 From this traceback we can see that the exception was raised in
18767 @file{stb.adb} at line 5, which was reached from a procedure call in
18768 @file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
18769 which contains the call to the main program.
18770 @pxref{Running gnatbind}. The remaining entries are assorted runtime routines,
18771 and the output will vary from platform to platform.
18773 It is also possible to use @code{GDB} with these traceback addresses to debug
18774 the program. For example, we can break at a given code location, as reported
18775 in the stack traceback:
18781 Furthermore, this feature is not implemented inside Windows DLL. Only
18782 the non-symbolic traceback is reported in this case.
18785 (gdb) break *0x401373
18786 Breakpoint 1 at 0x401373: file stb.adb, line 5.
18790 It is important to note that the stack traceback addresses
18791 do not change when debug information is included. This is particularly useful
18792 because it makes it possible to release software without debug information (to
18793 minimize object size), get a field report that includes a stack traceback
18794 whenever an internal bug occurs, and then be able to retrieve the sequence
18795 of calls with the same program compiled with debug information.
18797 @node Tracebacks From Exception Occurrences (non-symbolic)
18798 @subsubsection Tracebacks From Exception Occurrences
18801 Non-symbolic tracebacks are obtained by using the @option{-E} binder argument.
18802 The stack traceback is attached to the exception information string, and can
18803 be retrieved in an exception handler within the Ada program, by means of the
18804 Ada95 facilities defined in @code{Ada.Exceptions}. Here is a simple example:
18806 @smallexample @c ada
18808 with Ada.Exceptions;
18813 use Ada.Exceptions;
18821 Text_IO.Put_Line (Exception_Information (E));
18835 This program will output:
18840 Exception name: CONSTRAINT_ERROR
18841 Message: stb.adb:12
18842 Call stack traceback locations:
18843 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
18846 @node Tracebacks From Anywhere in a Program (non-symbolic)
18847 @subsubsection Tracebacks From Anywhere in a Program
18850 It is also possible to retrieve a stack traceback from anywhere in a
18851 program. For this you need to
18852 use the @code{GNAT.Traceback} API. This package includes a procedure called
18853 @code{Call_Chain} that computes a complete stack traceback, as well as useful
18854 display procedures described below. It is not necessary to use the
18855 @option{-E gnatbind} option in this case, because the stack traceback mechanism
18856 is invoked explicitly.
18859 In the following example we compute a traceback at a specific location in
18860 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
18861 convert addresses to strings:
18863 @smallexample @c ada
18865 with GNAT.Traceback;
18866 with GNAT.Debug_Utilities;
18872 use GNAT.Traceback;
18875 TB : Tracebacks_Array (1 .. 10);
18876 -- We are asking for a maximum of 10 stack frames.
18878 -- Len will receive the actual number of stack frames returned.
18880 Call_Chain (TB, Len);
18882 Text_IO.Put ("In STB.P1 : ");
18884 for K in 1 .. Len loop
18885 Text_IO.Put (Debug_Utilities.Image (TB (K)));
18906 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
18907 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
18911 You can then get further information by invoking the @code{addr2line}
18912 tool as described earlier (note that the hexadecimal addresses
18913 need to be specified in C format, with a leading ``0x'').
18916 @node Symbolic Traceback
18917 @subsection Symbolic Traceback
18918 @cindex traceback, symbolic
18921 A symbolic traceback is a stack traceback in which procedure names are
18922 associated with each code location.
18925 Note that this feature is not supported on all platforms. See
18926 @file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
18927 list of currently supported platforms.
18930 Note that the symbolic traceback requires that the program be compiled
18931 with debug information. If it is not compiled with debug information
18932 only the non-symbolic information will be valid.
18935 * Tracebacks From Exception Occurrences (symbolic)::
18936 * Tracebacks From Anywhere in a Program (symbolic)::
18939 @node Tracebacks From Exception Occurrences (symbolic)
18940 @subsubsection Tracebacks From Exception Occurrences
18942 @smallexample @c ada
18944 with GNAT.Traceback.Symbolic;
18950 raise Constraint_Error;
18967 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
18972 $ gnatmake -g .\stb -bargs -E -largs -lgnat -laddr2line -lintl
18975 0040149F in stb.p1 at stb.adb:8
18976 004014B7 in stb.p2 at stb.adb:13
18977 004014CF in stb.p3 at stb.adb:18
18978 004015DD in ada.stb at stb.adb:22
18979 00401461 in main at b~stb.adb:168
18980 004011C4 in __mingw_CRTStartup at crt1.c:200
18981 004011F1 in mainCRTStartup at crt1.c:222
18982 77E892A4 in ?? at ??:0
18986 In the above example the ``.\'' syntax in the @command{gnatmake} command
18987 is currently required by @command{addr2line} for files that are in
18988 the current working directory.
18989 Moreover, the exact sequence of linker options may vary from platform
18991 The above @option{-largs} section is for Windows platforms. By contrast,
18992 under Unix there is no need for the @option{-largs} section.
18993 Differences across platforms are due to details of linker implementation.
18995 @node Tracebacks From Anywhere in a Program (symbolic)
18996 @subsubsection Tracebacks From Anywhere in a Program
18999 It is possible to get a symbolic stack traceback
19000 from anywhere in a program, just as for non-symbolic tracebacks.
19001 The first step is to obtain a non-symbolic
19002 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
19003 information. Here is an example:
19005 @smallexample @c ada
19007 with GNAT.Traceback;
19008 with GNAT.Traceback.Symbolic;
19013 use GNAT.Traceback;
19014 use GNAT.Traceback.Symbolic;
19017 TB : Tracebacks_Array (1 .. 10);
19018 -- We are asking for a maximum of 10 stack frames.
19020 -- Len will receive the actual number of stack frames returned.
19022 Call_Chain (TB, Len);
19023 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
19037 @node Compatibility with DEC Ada
19038 @chapter Compatibility with DEC Ada
19039 @cindex Compatibility
19042 This section of the manual compares DEC Ada for OpenVMS Alpha and GNAT
19043 OpenVMS Alpha. GNAT achieves a high level of compatibility
19044 with DEC Ada, and it should generally be straightforward to port code
19045 from the DEC Ada environment to GNAT. However, there are a few language
19046 and implementation differences of which the user must be aware. These
19047 differences are discussed in this section. In
19048 addition, the operating environment and command structure for the
19049 compiler are different, and these differences are also discussed.
19051 Note that this discussion addresses specifically the implementation
19052 of Ada 83 for DIGITAL OpenVMS Alpha Systems. In cases where the implementation
19053 of DEC Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems,
19054 GNAT always follows the Alpha implementation.
19057 * Ada 95 Compatibility::
19058 * Differences in the Definition of Package System::
19059 * Language-Related Features::
19060 * The Package STANDARD::
19061 * The Package SYSTEM::
19062 * Tasking and Task-Related Features::
19063 * Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems::
19064 * Pragmas and Pragma-Related Features::
19065 * Library of Predefined Units::
19067 * Main Program Definition::
19068 * Implementation-Defined Attributes::
19069 * Compiler and Run-Time Interfacing::
19070 * Program Compilation and Library Management::
19072 * Implementation Limits::
19076 @node Ada 95 Compatibility
19077 @section Ada 95 Compatibility
19080 GNAT is an Ada 95 compiler, and DEC Ada is an Ada 83
19081 compiler. Ada 95 is almost completely upwards compatible
19082 with Ada 83, and therefore Ada 83 programs will compile
19083 and run under GNAT with
19084 no changes or only minor changes. The Ada 95 Reference
19085 Manual (ANSI/ISO/IEC-8652:1995) provides details on specific
19088 GNAT provides the switch /83 on the GNAT COMPILE command,
19089 as well as the pragma ADA_83, to force the compiler to
19090 operate in Ada 83 mode. This mode does not guarantee complete
19091 conformance to Ada 83, but in practice is sufficient to
19092 eliminate most sources of incompatibilities.
19093 In particular, it eliminates the recognition of the
19094 additional Ada 95 keywords, so that their use as identifiers
19095 in Ada83 program is legal, and handles the cases of packages
19096 with optional bodies, and generics that instantiate unconstrained
19097 types without the use of @code{(<>)}.
19099 @node Differences in the Definition of Package System
19100 @section Differences in the Definition of Package System
19103 Both the Ada 95 and Ada 83 reference manuals permit a compiler to add
19104 implementation-dependent declarations to package System. In normal mode,
19105 GNAT does not take advantage of this permission, and the version of System
19106 provided by GNAT exactly matches that in the Ada 95 Reference Manual.
19108 However, DEC Ada adds an extensive set of declarations to package System,
19109 as fully documented in the DEC Ada manuals. To minimize changes required
19110 for programs that make use of these extensions, GNAT provides the pragma
19111 Extend_System for extending the definition of package System. By using:
19113 @smallexample @c ada
19116 pragma Extend_System (Aux_DEC);
19122 The set of definitions in System is extended to include those in package
19123 @code{System.Aux_DEC}.
19124 These definitions are incorporated directly into package
19125 System, as though they had been declared there in the first place. For a
19126 list of the declarations added, see the specification of this package,
19127 which can be found in the file @code{s-auxdec.ads} in the GNAT library.
19128 The pragma Extend_System is a configuration pragma, which means that
19129 it can be placed in the file @file{gnat.adc}, so that it will automatically
19130 apply to all subsequent compilations. See the section on Configuration
19131 Pragmas for further details.
19133 An alternative approach that avoids the use of the non-standard
19134 Extend_System pragma is to add a context clause to the unit that
19135 references these facilities:
19137 @smallexample @c ada
19140 with System.Aux_DEC;
19141 use System.Aux_DEC;
19147 The effect is not quite semantically identical to incorporating
19148 the declarations directly into package @code{System},
19149 but most programs will not notice a difference
19150 unless they use prefix notation (e.g. @code{System.Integer_8})
19152 entities directly in package @code{System}.
19153 For units containing such references,
19154 the prefixes must either be removed, or the pragma @code{Extend_System}
19157 @node Language-Related Features
19158 @section Language-Related Features
19161 The following sections highlight differences in types,
19162 representations of types, operations, alignment, and
19166 * Integer Types and Representations::
19167 * Floating-Point Types and Representations::
19168 * Pragmas Float_Representation and Long_Float::
19169 * Fixed-Point Types and Representations::
19170 * Record and Array Component Alignment::
19171 * Address Clauses::
19172 * Other Representation Clauses::
19175 @node Integer Types and Representations
19176 @subsection Integer Types and Representations
19179 The set of predefined integer types is identical in DEC Ada and GNAT.
19180 Furthermore the representation of these integer types is also identical,
19181 including the capability of size clauses forcing biased representation.
19184 DEC Ada for OpenVMS Alpha systems has defined the
19185 following additional integer types in package System:
19206 When using GNAT, the first four of these types may be obtained from the
19207 standard Ada 95 package @code{Interfaces}.
19208 Alternatively, by use of the pragma
19209 @code{Extend_System}, identical
19210 declarations can be referenced directly in package @code{System}.
19211 On both GNAT and DEC Ada, the maximum integer size is 64 bits.
19213 @node Floating-Point Types and Representations
19214 @subsection Floating-Point Types and Representations
19215 @cindex Floating-Point types
19218 The set of predefined floating-point types is identical in DEC Ada and GNAT.
19219 Furthermore the representation of these floating-point
19220 types is also identical. One important difference is that the default
19221 representation for DEC Ada is VAX_Float, but the default representation
19224 Specific types may be declared to be VAX_Float or IEEE, using the pragma
19225 @code{Float_Representation} as described in the DEC Ada documentation.
19226 For example, the declarations:
19228 @smallexample @c ada
19231 type F_Float is digits 6;
19232 pragma Float_Representation (VAX_Float, F_Float);
19238 declare a type F_Float that will be represented in VAX_Float format.
19239 This set of declarations actually appears in System.Aux_DEC, which provides
19240 the full set of additional floating-point declarations provided in
19241 the DEC Ada version of package
19242 System. This and similar declarations may be accessed in a user program
19243 by using pragma @code{Extend_System}. The use of this
19244 pragma, and the related pragma @code{Long_Float} is described in further
19245 detail in the following section.
19247 @node Pragmas Float_Representation and Long_Float
19248 @subsection Pragmas Float_Representation and Long_Float
19251 DEC Ada provides the pragma @code{Float_Representation}, which
19252 acts as a program library switch to allow control over
19253 the internal representation chosen for the predefined
19254 floating-point types declared in the package @code{Standard}.
19255 The format of this pragma is as follows:
19260 @b{pragma} @code{Float_Representation}(VAX_Float | IEEE_Float);
19266 This pragma controls the representation of floating-point
19271 @code{VAX_Float} specifies that floating-point
19272 types are represented by default with the VAX hardware types
19273 F-floating, D-floating, G-floating. Note that the H-floating
19274 type is available only on DIGITAL Vax systems, and is not available
19275 in either DEC Ada or GNAT for Alpha systems.
19278 @code{IEEE_Float} specifies that floating-point
19279 types are represented by default with the IEEE single and
19280 double floating-point types.
19284 GNAT provides an identical implementation of the pragma
19285 @code{Float_Representation}, except that it functions as a
19286 configuration pragma, as defined by Ada 95. Note that the
19287 notion of configuration pragma corresponds closely to the
19288 DEC Ada notion of a program library switch.
19290 When no pragma is used in GNAT, the default is IEEE_Float, which is different
19291 from DEC Ada 83, where the default is VAX_Float. In addition, the
19292 predefined libraries in GNAT are built using IEEE_Float, so it is not
19293 advisable to change the format of numbers passed to standard library
19294 routines, and if necessary explicit type conversions may be needed.
19296 The use of IEEE_Float is recommended in GNAT since it is more efficient,
19297 and (given that it conforms to an international standard) potentially more
19298 portable. The situation in which VAX_Float may be useful is in interfacing
19299 to existing code and data that expects the use of VAX_Float. There are
19300 two possibilities here. If the requirement for the use of VAX_Float is
19301 localized, then the best approach is to use the predefined VAX_Float
19302 types in package @code{System}, as extended by
19303 @code{Extend_System}. For example, use @code{System.F_Float}
19304 to specify the 32-bit @code{F-Float} format.
19306 Alternatively, if an entire program depends heavily on the use of
19307 the @code{VAX_Float} and in particular assumes that the types in
19308 package @code{Standard} are in @code{Vax_Float} format, then it
19309 may be desirable to reconfigure GNAT to assume Vax_Float by default.
19310 This is done by using the GNAT LIBRARY command to rebuild the library, and
19311 then using the general form of the @code{Float_Representation}
19312 pragma to ensure that this default format is used throughout.
19313 The form of the GNAT LIBRARY command is:
19316 GNAT LIBRARY /CONFIG=@i{file} /CREATE=@i{directory}
19320 where @i{file} contains the new configuration pragmas
19321 and @i{directory} is the directory to be created to contain
19325 On OpenVMS systems, DEC Ada provides the pragma @code{Long_Float}
19326 to allow control over the internal representation chosen
19327 for the predefined type @code{Long_Float} and for floating-point
19328 type declarations with digits specified in the range 7 .. 15.
19329 The format of this pragma is as follows:
19331 @smallexample @c ada
19333 pragma Long_Float (D_FLOAT | G_FLOAT);
19337 @node Fixed-Point Types and Representations
19338 @subsection Fixed-Point Types and Representations
19341 On DEC Ada for OpenVMS Alpha systems, rounding is
19342 away from zero for both positive and negative numbers.
19343 Therefore, +0.5 rounds to 1 and -0.5 rounds to -1.
19345 On GNAT for OpenVMS Alpha, the results of operations
19346 on fixed-point types are in accordance with the Ada 95
19347 rules. In particular, results of operations on decimal
19348 fixed-point types are truncated.
19350 @node Record and Array Component Alignment
19351 @subsection Record and Array Component Alignment
19354 On DEC Ada for OpenVMS Alpha, all non composite components
19355 are aligned on natural boundaries. For example, 1-byte
19356 components are aligned on byte boundaries, 2-byte
19357 components on 2-byte boundaries, 4-byte components on 4-byte
19358 byte boundaries, and so on. The OpenVMS Alpha hardware
19359 runs more efficiently with naturally aligned data.
19361 ON GNAT for OpenVMS Alpha, alignment rules are compatible
19362 with DEC Ada for OpenVMS Alpha.
19364 @node Address Clauses
19365 @subsection Address Clauses
19368 In DEC Ada and GNAT, address clauses are supported for
19369 objects and imported subprograms.
19370 The predefined type @code{System.Address} is a private type
19371 in both compilers, with the same representation (it is simply
19372 a machine pointer). Addition, subtraction, and comparison
19373 operations are available in the standard Ada 95 package
19374 @code{System.Storage_Elements}, or in package @code{System}
19375 if it is extended to include @code{System.Aux_DEC} using a
19376 pragma @code{Extend_System} as previously described.
19378 Note that code that with's both this extended package @code{System}
19379 and the package @code{System.Storage_Elements} should not @code{use}
19380 both packages, or ambiguities will result. In general it is better
19381 not to mix these two sets of facilities. The Ada 95 package was
19382 designed specifically to provide the kind of features that DEC Ada
19383 adds directly to package @code{System}.
19385 GNAT is compatible with DEC Ada in its handling of address
19386 clauses, except for some limitations in
19387 the form of address clauses for composite objects with
19388 initialization. Such address clauses are easily replaced
19389 by the use of an explicitly-defined constant as described
19390 in the Ada 95 Reference Manual (13.1(22)). For example, the sequence
19393 @smallexample @c ada
19395 X, Y : Integer := Init_Func;
19396 Q : String (X .. Y) := "abc";
19398 for Q'Address use Compute_Address;
19403 will be rejected by GNAT, since the address cannot be computed at the time
19404 that Q is declared. To achieve the intended effect, write instead:
19406 @smallexample @c ada
19409 X, Y : Integer := Init_Func;
19410 Q_Address : constant Address := Compute_Address;
19411 Q : String (X .. Y) := "abc";
19413 for Q'Address use Q_Address;
19419 which will be accepted by GNAT (and other Ada 95 compilers), and is also
19420 backwards compatible with Ada 83. A fuller description of the restrictions
19421 on address specifications is found in the GNAT Reference Manual.
19423 @node Other Representation Clauses
19424 @subsection Other Representation Clauses
19427 GNAT supports in a compatible manner all the representation
19428 clauses supported by DEC Ada. In addition, it
19429 supports representation clause forms that are new in Ada 95
19430 including COMPONENT_SIZE and SIZE clauses for objects.
19432 @node The Package STANDARD
19433 @section The Package STANDARD
19436 The package STANDARD, as implemented by DEC Ada, is fully
19437 described in the Reference Manual for the Ada Programming
19438 Language (ANSI/MIL-STD-1815A-1983) and in the DEC Ada
19439 Language Reference Manual. As implemented by GNAT, the
19440 package STANDARD is described in the Ada 95 Reference
19443 In addition, DEC Ada supports the Latin-1 character set in
19444 the type CHARACTER. GNAT supports the Latin-1 character set
19445 in the type CHARACTER and also Unicode (ISO 10646 BMP) in
19446 the type WIDE_CHARACTER.
19448 The floating-point types supported by GNAT are those
19449 supported by DEC Ada, but defaults are different, and are controlled by
19450 pragmas. See @pxref{Floating-Point Types and Representations} for details.
19452 @node The Package SYSTEM
19453 @section The Package SYSTEM
19456 DEC Ada provides a system-specific version of the package
19457 SYSTEM for each platform on which the language ships.
19458 For the complete specification of the package SYSTEM, see
19459 Appendix F of the DEC Ada Language Reference Manual.
19461 On DEC Ada, the package SYSTEM includes the following conversion functions:
19463 @item TO_ADDRESS(INTEGER)
19465 @item TO_ADDRESS(UNSIGNED_LONGWORD)
19467 @item TO_ADDRESS(universal_integer)
19469 @item TO_INTEGER(ADDRESS)
19471 @item TO_UNSIGNED_LONGWORD(ADDRESS)
19473 @item Function IMPORT_VALUE return UNSIGNED_LONGWORD and the
19474 functions IMPORT_ADDRESS and IMPORT_LARGEST_VALUE
19478 By default, GNAT supplies a version of SYSTEM that matches
19479 the definition given in the Ada 95 Reference Manual.
19481 is a subset of the DIGITAL system definitions, which is as
19482 close as possible to the original definitions. The only difference
19483 is that the definition of SYSTEM_NAME is different:
19485 @smallexample @c ada
19488 type Name is (SYSTEM_NAME_GNAT);
19489 System_Name : constant Name := SYSTEM_NAME_GNAT;
19495 Also, GNAT adds the new Ada 95 declarations for
19496 BIT_ORDER and DEFAULT_BIT_ORDER.
19498 However, the use of the following pragma causes GNAT
19499 to extend the definition of package SYSTEM so that it
19500 encompasses the full set of DIGITAL-specific extensions,
19501 including the functions listed above:
19503 @smallexample @c ada
19505 pragma Extend_System (Aux_DEC);
19510 The pragma Extend_System is a configuration pragma that
19511 is most conveniently placed in the @file{gnat.adc} file. See the
19512 GNAT Reference Manual for further details.
19514 DEC Ada does not allow the recompilation of the package
19515 SYSTEM. Instead DEC Ada provides several pragmas (SYSTEM_
19516 NAME, STORAGE_UNIT, and MEMORY_SIZE) to modify values in
19517 the package SYSTEM. On OpenVMS Alpha systems, the pragma
19518 SYSTEM_NAME takes the enumeration literal OPENVMS_AXP as
19519 its single argument.
19521 GNAT does permit the recompilation of package SYSTEM using
19522 a special switch (@option{-gnatg}) and this switch can be used if
19523 it is necessary to modify the definitions in SYSTEM. GNAT does
19524 not permit the specification of SYSTEM_NAME, STORAGE_UNIT
19525 or MEMORY_SIZE by any other means.
19527 On GNAT systems, the pragma SYSTEM_NAME takes the
19528 enumeration literal SYSTEM_NAME_GNAT.
19530 The definitions provided by the use of
19532 @smallexample @c ada
19533 pragma Extend_System (AUX_Dec);
19537 are virtually identical to those provided by the DEC Ada 83 package
19538 System. One important difference is that the name of the TO_ADDRESS
19539 function for type UNSIGNED_LONGWORD is changed to TO_ADDRESS_LONG.
19540 See the GNAT Reference manual for a discussion of why this change was
19544 The version of TO_ADDRESS taking a universal integer argument is in fact
19545 an extension to Ada 83 not strictly compatible with the reference manual.
19546 In GNAT, we are constrained to be exactly compatible with the standard,
19547 and this means we cannot provide this capability. In DEC Ada 83, the
19548 point of this definition is to deal with a call like:
19550 @smallexample @c ada
19551 TO_ADDRESS (16#12777#);
19555 Normally, according to the Ada 83 standard, one would expect this to be
19556 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
19557 of TO_ADDRESS. However, in DEC Ada 83, there is no ambiguity, since the
19558 definition using universal_integer takes precedence.
19560 In GNAT, since the version with universal_integer cannot be supplied, it is
19561 not possible to be 100% compatible. Since there are many programs using
19562 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
19563 to change the name of the function in the UNSIGNED_LONGWORD case, so the
19564 declarations provided in the GNAT version of AUX_Dec are:
19566 @smallexample @c ada
19567 function To_Address (X : Integer) return Address;
19568 pragma Pure_Function (To_Address);
19570 function To_Address_Long (X : Unsigned_Longword) return Address;
19571 pragma Pure_Function (To_Address_Long);
19575 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
19576 change the name to TO_ADDRESS_LONG.
19578 @node Tasking and Task-Related Features
19579 @section Tasking and Task-Related Features
19582 The concepts relevant to a comparison of tasking on GNAT
19583 and on DEC Ada for OpenVMS Alpha systems are discussed in
19584 the following sections.
19586 For detailed information on concepts related to tasking in
19587 DEC Ada, see the DEC Ada Language Reference Manual and the
19588 relevant run-time reference manual.
19590 @node Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
19591 @section Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
19594 On OpenVMS Alpha systems, each Ada task (except a passive
19595 task) is implemented as a single stream of execution
19596 that is created and managed by the kernel. On these
19597 systems, DEC Ada tasking support is based on DECthreads,
19598 an implementation of the POSIX standard for threads.
19600 Although tasks are implemented as threads, all tasks in
19601 an Ada program are part of the same process. As a result,
19602 resources such as open files and virtual memory can be
19603 shared easily among tasks. Having all tasks in one process
19604 allows better integration with the programming environment
19605 (the shell and the debugger, for example).
19607 Also, on OpenVMS Alpha systems, DEC Ada tasks and foreign
19608 code that calls DECthreads routines can be used together.
19609 The interaction between Ada tasks and DECthreads routines
19610 can have some benefits. For example when on OpenVMS Alpha,
19611 DEC Ada can call C code that is already threaded.
19612 GNAT on OpenVMS Alpha uses the facilities of DECthreads,
19613 and Ada tasks are mapped to threads.
19616 * Assigning Task IDs::
19617 * Task IDs and Delays::
19618 * Task-Related Pragmas::
19619 * Scheduling and Task Priority::
19621 * External Interrupts::
19624 @node Assigning Task IDs
19625 @subsection Assigning Task IDs
19628 The DEC Ada Run-Time Library always assigns %TASK 1 to
19629 the environment task that executes the main program. On
19630 OpenVMS Alpha systems, %TASK 0 is often used for tasks
19631 that have been created but are not yet activated.
19633 On OpenVMS Alpha systems, task IDs are assigned at
19634 activation. On GNAT systems, task IDs are also assigned at
19635 task creation but do not have the same form or values as
19636 task ID values in DEC Ada. There is no null task, and the
19637 environment task does not have a specific task ID value.
19639 @node Task IDs and Delays
19640 @subsection Task IDs and Delays
19643 On OpenVMS Alpha systems, tasking delays are implemented
19644 using Timer System Services. The Task ID is used for the
19645 identification of the timer request (the REQIDT parameter).
19646 If Timers are used in the application take care not to use
19647 0 for the identification, because cancelling such a timer
19648 will cancel all timers and may lead to unpredictable results.
19650 @node Task-Related Pragmas
19651 @subsection Task-Related Pragmas
19654 Ada supplies the pragma TASK_STORAGE, which allows
19655 specification of the size of the guard area for a task
19656 stack. (The guard area forms an area of memory that has no
19657 read or write access and thus helps in the detection of
19658 stack overflow.) On OpenVMS Alpha systems, if the pragma
19659 TASK_STORAGE specifies a value of zero, a minimal guard
19660 area is created. In the absence of a pragma TASK_STORAGE, a default guard
19663 GNAT supplies the following task-related pragmas:
19668 This pragma appears within a task definition and
19669 applies to the task in which it appears. The argument
19670 must be of type SYSTEM.TASK_INFO.TASK_INFO_TYPE.
19674 GNAT implements pragma TASK_STORAGE in the same way as
19676 Both DEC Ada and GNAT supply the pragmas PASSIVE,
19677 SUPPRESS, and VOLATILE.
19679 @node Scheduling and Task Priority
19680 @subsection Scheduling and Task Priority
19683 DEC Ada implements the Ada language requirement that
19684 when two tasks are eligible for execution and they have
19685 different priorities, the lower priority task does not
19686 execute while the higher priority task is waiting. The DEC
19687 Ada Run-Time Library keeps a task running until either the
19688 task is suspended or a higher priority task becomes ready.
19690 On OpenVMS Alpha systems, the default strategy is round-
19691 robin with preemption. Tasks of equal priority take turns
19692 at the processor. A task is run for a certain period of
19693 time and then placed at the rear of the ready queue for
19694 its priority level.
19696 DEC Ada provides the implementation-defined pragma TIME_SLICE,
19697 which can be used to enable or disable round-robin
19698 scheduling of tasks with the same priority.
19699 See the relevant DEC Ada run-time reference manual for
19700 information on using the pragmas to control DEC Ada task
19703 GNAT follows the scheduling rules of Annex D (real-time
19704 Annex) of the Ada 95 Reference Manual. In general, this
19705 scheduling strategy is fully compatible with DEC Ada
19706 although it provides some additional constraints (as
19707 fully documented in Annex D).
19708 GNAT implements time slicing control in a manner compatible with
19709 DEC Ada 83, by means of the pragma Time_Slice, whose semantics are identical
19710 to the DEC Ada 83 pragma of the same name.
19711 Note that it is not possible to mix GNAT tasking and
19712 DEC Ada 83 tasking in the same program, since the two run times are
19715 @node The Task Stack
19716 @subsection The Task Stack
19719 In DEC Ada, a task stack is allocated each time a
19720 non passive task is activated. As soon as the task is
19721 terminated, the storage for the task stack is deallocated.
19722 If you specify a size of zero (bytes) with T'STORAGE_SIZE,
19723 a default stack size is used. Also, regardless of the size
19724 specified, some additional space is allocated for task
19725 management purposes. On OpenVMS Alpha systems, at least
19726 one page is allocated.
19728 GNAT handles task stacks in a similar manner. According to
19729 the Ada 95 rules, it provides the pragma STORAGE_SIZE as
19730 an alternative method for controlling the task stack size.
19731 The specification of the attribute T'STORAGE_SIZE is also
19732 supported in a manner compatible with DEC Ada.
19734 @node External Interrupts
19735 @subsection External Interrupts
19738 On DEC Ada, external interrupts can be associated with task entries.
19739 GNAT is compatible with DEC Ada in its handling of external interrupts.
19741 @node Pragmas and Pragma-Related Features
19742 @section Pragmas and Pragma-Related Features
19745 Both DEC Ada and GNAT supply all language-defined pragmas
19746 as specified by the Ada 83 standard. GNAT also supplies all
19747 language-defined pragmas specified in the Ada 95 Reference Manual.
19748 In addition, GNAT implements the implementation-defined pragmas
19754 @item COMMON_OBJECT
19756 @item COMPONENT_ALIGNMENT
19758 @item EXPORT_EXCEPTION
19760 @item EXPORT_FUNCTION
19762 @item EXPORT_OBJECT
19764 @item EXPORT_PROCEDURE
19766 @item EXPORT_VALUED_PROCEDURE
19768 @item FLOAT_REPRESENTATION
19772 @item IMPORT_EXCEPTION
19774 @item IMPORT_FUNCTION
19776 @item IMPORT_OBJECT
19778 @item IMPORT_PROCEDURE
19780 @item IMPORT_VALUED_PROCEDURE
19782 @item INLINE_GENERIC
19784 @item INTERFACE_NAME
19794 @item SHARE_GENERIC
19806 These pragmas are all fully implemented, with the exception of @code{Title},
19807 @code{Passive}, and @code{Share_Generic}, which are
19808 recognized, but which have no
19809 effect in GNAT. The effect of @code{Passive} may be obtained by the
19810 use of protected objects in Ada 95. In GNAT, all generics are inlined.
19812 Unlike DEC Ada, the GNAT 'EXPORT_@i{subprogram}' pragmas require
19813 a separate subprogram specification which must appear before the
19816 GNAT also supplies a number of implementation-defined pragmas as follows:
19818 @item C_PASS_BY_COPY
19820 @item EXTEND_SYSTEM
19822 @item SOURCE_FILE_NAME
19840 @item CPP_CONSTRUCTOR
19842 @item CPP_DESTRUCTOR
19852 @item LINKER_SECTION
19854 @item MACHINE_ATTRIBUTE
19858 @item PURE_FUNCTION
19860 @item SOURCE_REFERENCE
19864 @item UNCHECKED_UNION
19866 @item UNIMPLEMENTED_UNIT
19868 @item UNIVERSAL_DATA
19870 @item WEAK_EXTERNAL
19874 For full details on these GNAT implementation-defined pragmas, see
19875 the GNAT Reference Manual.
19878 * Restrictions on the Pragma INLINE::
19879 * Restrictions on the Pragma INTERFACE::
19880 * Restrictions on the Pragma SYSTEM_NAME::
19883 @node Restrictions on the Pragma INLINE
19884 @subsection Restrictions on the Pragma INLINE
19887 DEC Ada applies the following restrictions to the pragma INLINE:
19889 @item Parameters cannot be a task type.
19891 @item Function results cannot be task types, unconstrained
19892 array types, or unconstrained types with discriminants.
19894 @item Bodies cannot declare the following:
19896 @item Subprogram body or stub (imported subprogram is allowed)
19900 @item Generic declarations
19902 @item Instantiations
19906 @item Access types (types derived from access types allowed)
19908 @item Array or record types
19910 @item Dependent tasks
19912 @item Direct recursive calls of subprogram or containing
19913 subprogram, directly or via a renaming
19919 In GNAT, the only restriction on pragma INLINE is that the
19920 body must occur before the call if both are in the same
19921 unit, and the size must be appropriately small. There are
19922 no other specific restrictions which cause subprograms to
19923 be incapable of being inlined.
19925 @node Restrictions on the Pragma INTERFACE
19926 @subsection Restrictions on the Pragma INTERFACE
19929 The following lists and describes the restrictions on the
19930 pragma INTERFACE on DEC Ada and GNAT:
19932 @item Languages accepted: Ada, Bliss, C, Fortran, Default.
19933 Default is the default on OpenVMS Alpha systems.
19935 @item Parameter passing: Language specifies default
19936 mechanisms but can be overridden with an EXPORT pragma.
19939 @item Ada: Use internal Ada rules.
19941 @item Bliss, C: Parameters must be mode @code{in}; cannot be
19942 record or task type. Result cannot be a string, an
19943 array, or a record.
19945 @item Fortran: Parameters cannot be a task. Result cannot
19946 be a string, an array, or a record.
19951 GNAT is entirely upwards compatible with DEC Ada, and in addition allows
19952 record parameters for all languages.
19954 @node Restrictions on the Pragma SYSTEM_NAME
19955 @subsection Restrictions on the Pragma SYSTEM_NAME
19958 For DEC Ada for OpenVMS Alpha, the enumeration literal
19959 for the type NAME is OPENVMS_AXP. In GNAT, the enumeration
19960 literal for the type NAME is SYSTEM_NAME_GNAT.
19962 @node Library of Predefined Units
19963 @section Library of Predefined Units
19966 A library of predefined units is provided as part of the
19967 DEC Ada and GNAT implementations. DEC Ada does not provide
19968 the package MACHINE_CODE but instead recommends importing
19971 The GNAT versions of the DEC Ada Run-Time Library (ADA$PREDEFINED:)
19972 units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
19973 version. During GNAT installation, the DEC Ada Predefined
19974 Library units are copied into the GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
19975 (aka DECLIB) directory and patched to remove Ada 95 incompatibilities
19976 and to make them interoperable with GNAT, @pxref{Changes to DECLIB}
19979 The GNAT RTL is contained in
19980 the GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB] (aka ADALIB) directory and
19981 the default search path is set up to find DECLIB units in preference
19982 to ADALIB units with the same name (TEXT_IO, SEQUENTIAL_IO, and DIRECT_IO,
19985 However, it is possible to change the default so that the
19986 reverse is true, or even to mix them using child package
19987 notation. The DEC Ada 83 units are available as DEC.xxx where xxx
19988 is the package name, and the Ada units are available in the
19989 standard manner defined for Ada 95, that is to say as Ada.xxx. To
19990 change the default, set ADA_INCLUDE_PATH and ADA_OBJECTS_PATH
19991 appropriately. For example, to change the default to use the Ada95
19995 $ DEFINE ADA_INCLUDE_PATH GNU:[LIB.OPENVMS7_1.2_8_1.ADAINCLUDE],-
19996 GNU:[LIB.OPENVMS7_1.2_8_1.DECLIB]
19997 $ DEFINE ADA_OBJECTS_PATH GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB],-
19998 GNU:[LIB.OPENVMS7_1.2_8_1.DECLIB]
20002 * Changes to DECLIB::
20005 @node Changes to DECLIB
20006 @subsection Changes to DECLIB
20009 The changes made to the DEC Ada predefined library for GNAT and Ada 95
20010 compatibility are minor and include the following:
20013 @item Adjusting the location of pragmas and record representation
20014 clauses to obey Ada 95 rules
20016 @item Adding the proper notation to generic formal parameters
20017 that take unconstrained types in instantiation
20019 @item Adding pragma ELABORATE_BODY to package specifications
20020 that have package bodies not otherwise allowed
20022 @item Occurrences of the identifier @code{"PROTECTED"} are renamed to
20024 Currently these are found only in the STARLET package spec.
20028 None of the above changes is visible to users.
20034 On OpenVMS Alpha, DEC Ada provides the following strongly-typed bindings:
20037 @item Command Language Interpreter (CLI interface)
20039 @item DECtalk Run-Time Library (DTK interface)
20041 @item Librarian utility routines (LBR interface)
20043 @item General Purpose Run-Time Library (LIB interface)
20045 @item Math Run-Time Library (MTH interface)
20047 @item National Character Set Run-Time Library (NCS interface)
20049 @item Compiled Code Support Run-Time Library (OTS interface)
20051 @item Parallel Processing Run-Time Library (PPL interface)
20053 @item Screen Management Run-Time Library (SMG interface)
20055 @item Sort Run-Time Library (SOR interface)
20057 @item String Run-Time Library (STR interface)
20059 @item STARLET System Library
20062 @item X Window System Version 11R4 and 11R5 (X, XLIB interface)
20064 @item X Windows Toolkit (XT interface)
20066 @item X/Motif Version 1.1.3 and 1.2 (XM interface)
20070 GNAT provides implementations of these DEC bindings in the DECLIB directory.
20072 The X/Motif bindings used to build DECLIB are whatever versions are in the
20073 DEC Ada @file{ADA$PREDEFINED} directory with extension @file{.ADC}.
20074 The build script will
20075 automatically add a pragma Linker_Options to packages @code{Xm}, @code{Xt},
20077 causing the default X/Motif sharable image libraries to be linked in. This
20078 is done via options files named @file{xm.opt}, @file{xt.opt}, and
20079 @file{x_lib.opt} (also located in the @file{DECLIB} directory).
20081 It may be necessary to edit these options files to update or correct the
20082 library names if, for example, the newer X/Motif bindings from
20083 @file{ADA$EXAMPLES}
20084 had been (previous to installing GNAT) copied and renamed to supersede the
20085 default @file{ADA$PREDEFINED} versions.
20088 * Shared Libraries and Options Files::
20089 * Interfaces to C::
20092 @node Shared Libraries and Options Files
20093 @subsection Shared Libraries and Options Files
20096 When using the DEC Ada
20097 predefined X and Motif bindings, the linking with their sharable images is
20098 done automatically by @command{GNAT LINK}.
20099 When using other X and Motif bindings, you need
20100 to add the corresponding sharable images to the command line for
20101 @code{GNAT LINK}. When linking with shared libraries, or with
20102 @file{.OPT} files, you must
20103 also add them to the command line for @command{GNAT LINK}.
20105 A shared library to be used with GNAT is built in the same way as other
20106 libraries under VMS. The VMS Link command can be used in standard fashion.
20108 @node Interfaces to C
20109 @subsection Interfaces to C
20113 provides the following Ada types and operations:
20116 @item C types package (C_TYPES)
20118 @item C strings (C_TYPES.NULL_TERMINATED)
20120 @item Other_types (SHORT_INT)
20124 Interfacing to C with GNAT, one can use the above approach
20125 described for DEC Ada or the facilities of Annex B of
20126 the Ada 95 Reference Manual (packages INTERFACES.C,
20127 INTERFACES.C.STRINGS and INTERFACES.C.POINTERS). For more
20128 information, see the section ``Interfacing to C'' in the
20129 @cite{GNAT Reference Manual}.
20131 The @option{-gnatF} qualifier forces default and explicit
20132 @code{External_Name} parameters in pragmas Import and Export
20133 to be uppercased for compatibility with the default behavior
20134 of Compaq C. The qualifier has no effect on @code{Link_Name} parameters.
20136 @node Main Program Definition
20137 @section Main Program Definition
20140 The following section discusses differences in the
20141 definition of main programs on DEC Ada and GNAT.
20142 On DEC Ada, main programs are defined to meet the
20143 following conditions:
20145 @item Procedure with no formal parameters (returns 0 upon
20148 @item Procedure with no formal parameters (returns 42 when
20149 unhandled exceptions are raised)
20151 @item Function with no formal parameters whose returned value
20152 is of a discrete type
20154 @item Procedure with one OUT formal of a discrete type for
20155 which a specification of pragma EXPORT_VALUED_PROCEDURE is given.
20160 When declared with the pragma EXPORT_VALUED_PROCEDURE,
20161 a main function or main procedure returns a discrete
20162 value whose size is less than 64 bits (32 on VAX systems),
20163 the value is zero- or sign-extended as appropriate.
20164 On GNAT, main programs are defined as follows:
20166 @item Must be a non-generic, parameter-less subprogram that
20167 is either a procedure or function returning an Ada
20168 STANDARD.INTEGER (the predefined type)
20170 @item Cannot be a generic subprogram or an instantiation of a
20174 @node Implementation-Defined Attributes
20175 @section Implementation-Defined Attributes
20178 GNAT provides all DEC Ada implementation-defined
20181 @node Compiler and Run-Time Interfacing
20182 @section Compiler and Run-Time Interfacing
20185 DEC Ada provides the following ways to pass options to the linker
20188 @item /WAIT and /SUBMIT qualifiers
20190 @item /COMMAND qualifier
20192 @item /[NO]MAP qualifier
20194 @item /OUTPUT=file-spec
20196 @item /[NO]DEBUG and /[NO]TRACEBACK qualifiers
20200 To pass options to the linker, GNAT provides the following
20204 @item @option{/EXECUTABLE=exec-name}
20206 @item @option{/VERBOSE qualifier}
20208 @item @option{/[NO]DEBUG} and @option{/[NO]TRACEBACK} qualifiers
20212 For more information on these switches, see
20213 @ref{Switches for gnatlink}.
20214 In DEC Ada, the command-line switch @option{/OPTIMIZE} is available
20215 to control optimization. DEC Ada also supplies the
20218 @item @code{OPTIMIZE}
20220 @item @code{INLINE}
20222 @item @code{INLINE_GENERIC}
20224 @item @code{SUPPRESS_ALL}
20226 @item @code{PASSIVE}
20230 In GNAT, optimization is controlled strictly by command
20231 line parameters, as described in the corresponding section of this guide.
20232 The DIGITAL pragmas for control of optimization are
20233 recognized but ignored.
20235 Note that in GNAT, the default is optimization off, whereas in DEC Ada 83,
20236 the default is that optimization is turned on.
20238 @node Program Compilation and Library Management
20239 @section Program Compilation and Library Management
20242 DEC Ada and GNAT provide a comparable set of commands to
20243 build programs. DEC Ada also provides a program library,
20244 which is a concept that does not exist on GNAT. Instead,
20245 GNAT provides directories of sources that are compiled as
20248 The following table summarizes
20249 the DEC Ada commands and provides
20250 equivalent GNAT commands. In this table, some GNAT
20251 equivalents reflect the fact that GNAT does not use the
20252 concept of a program library. Instead, it uses a model
20253 in which collections of source and object files are used
20254 in a manner consistent with other languages like C and
20255 Fortran. Therefore, standard system file commands are used
20256 to manipulate these elements. Those GNAT commands are marked with
20258 Note that, unlike DEC Ada, none of the GNAT commands accepts wild cards.
20261 @multitable @columnfractions .35 .65
20263 @item @emph{DEC Ada Command}
20264 @tab @emph{GNAT Equivalent / Description}
20266 @item @command{ADA}
20267 @tab @command{GNAT COMPILE}@*
20268 Invokes the compiler to compile one or more Ada source files.
20270 @item @command{ACS ATTACH}@*
20271 @tab [No equivalent]@*
20272 Switches control of terminal from current process running the program
20275 @item @command{ACS CHECK}
20276 @tab @command{GNAT MAKE /DEPENDENCY_LIST}@*
20277 Forms the execution closure of one
20278 or more compiled units and checks completeness and currency.
20280 @item @command{ACS COMPILE}
20281 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
20282 Forms the execution closure of one or
20283 more specified units, checks completeness and currency,
20284 identifies units that have revised source files, compiles same,
20285 and recompiles units that are or will become obsolete.
20286 Also completes incomplete generic instantiations.
20288 @item @command{ACS COPY FOREIGN}
20290 Copies a foreign object file into the program library as a
20293 @item @command{ACS COPY UNIT}
20295 Copies a compiled unit from one program library to another.
20297 @item @command{ACS CREATE LIBRARY}
20298 @tab Create /directory (*)@*
20299 Creates a program library.
20301 @item @command{ACS CREATE SUBLIBRARY}
20302 @tab Create /directory (*)@*
20303 Creates a program sublibrary.
20305 @item @command{ACS DELETE LIBRARY}
20307 Deletes a program library and its contents.
20309 @item @command{ACS DELETE SUBLIBRARY}
20311 Deletes a program sublibrary and its contents.
20313 @item @command{ACS DELETE UNIT}
20314 @tab Delete file (*)@*
20315 On OpenVMS systems, deletes one or more compiled units from
20316 the current program library.
20318 @item @command{ACS DIRECTORY}
20319 @tab Directory (*)@*
20320 On OpenVMS systems, lists units contained in the current
20323 @item @command{ACS ENTER FOREIGN}
20325 Allows the import of a foreign body as an Ada library
20326 specification and enters a reference to a pointer.
20328 @item @command{ACS ENTER UNIT}
20330 Enters a reference (pointer) from the current program library to
20331 a unit compiled into another program library.
20333 @item @command{ACS EXIT}
20334 @tab [No equivalent]@*
20335 Exits from the program library manager.
20337 @item @command{ACS EXPORT}
20339 Creates an object file that contains system-specific object code
20340 for one or more units. With GNAT, object files can simply be copied
20341 into the desired directory.
20343 @item @command{ACS EXTRACT SOURCE}
20345 Allows access to the copied source file for each Ada compilation unit
20347 @item @command{ACS HELP}
20348 @tab @command{HELP GNAT}@*
20349 Provides online help.
20351 @item @command{ACS LINK}
20352 @tab @command{GNAT LINK}@*
20353 Links an object file containing Ada units into an executable file.
20355 @item @command{ACS LOAD}
20357 Loads (partially compiles) Ada units into the program library.
20358 Allows loading a program from a collection of files into a library
20359 without knowing the relationship among units.
20361 @item @command{ACS MERGE}
20363 Merges into the current program library, one or more units from
20364 another library where they were modified.
20366 @item @command{ACS RECOMPILE}
20367 @tab @command{GNAT MAKE /ACTIONS=COMPILE}@*
20368 Recompiles from external or copied source files any obsolete
20369 unit in the closure. Also, completes any incomplete generic
20372 @item @command{ACS REENTER}
20373 @tab @command{GNAT MAKE}@*
20374 Reenters current references to units compiled after last entered
20375 with the @command{ACS ENTER UNIT} command.
20377 @item @command{ACS SET LIBRARY}
20378 @tab Set default (*)@*
20379 Defines a program library to be the compilation context as well
20380 as the target library for compiler output and commands in general.
20382 @item @command{ACS SET PRAGMA}
20383 @tab Edit @file{gnat.adc} (*)@*
20384 Redefines specified values of the library characteristics
20385 @code{LONG_ FLOAT}, @code{MEMORY_SIZE}, @code{SYSTEM_NAME},
20386 and @code{Float_Representation}.
20388 @item @command{ACS SET SOURCE}
20389 @tab Define @code{ADA_INCLUDE_PATH} path (*)@*
20390 Defines the source file search list for the @command{ACS COMPILE} command.
20392 @item @command{ACS SHOW LIBRARY}
20393 @tab Directory (*)@*
20394 Lists information about one or more program libraries.
20396 @item @command{ACS SHOW PROGRAM}
20397 @tab [No equivalent]@*
20398 Lists information about the execution closure of one or
20399 more units in the program library.
20401 @item @command{ACS SHOW SOURCE}
20402 @tab Show logical @code{ADA_INCLUDE_PATH}@*
20403 Shows the source file search used when compiling units.
20405 @item @command{ACS SHOW VERSION}
20406 @tab Compile with @option{VERBOSE} option
20407 Displays the version number of the compiler and program library
20410 @item @command{ACS SPAWN}
20411 @tab [No equivalent]@*
20412 Creates a subprocess of the current process (same as @command{DCL SPAWN}
20415 @item @command{ACS VERIFY}
20416 @tab [No equivalent]@*
20417 Performs a series of consistency checks on a program library to
20418 determine whether the library structure and library files are in
20425 @section Input-Output
20428 On OpenVMS Alpha systems, DEC Ada uses OpenVMS Record
20429 Management Services (RMS) to perform operations on
20433 DEC Ada and GNAT predefine an identical set of input-
20434 output packages. To make the use of the
20435 generic TEXT_IO operations more convenient, DEC Ada
20436 provides predefined library packages that instantiate the
20437 integer and floating-point operations for the predefined
20438 integer and floating-point types as shown in the following table.
20440 @multitable @columnfractions .45 .55
20441 @item @emph{Package Name} @tab Instantiation
20443 @item @code{INTEGER_TEXT_IO}
20444 @tab @code{INTEGER_IO(INTEGER)}
20446 @item @code{SHORT_INTEGER_TEXT_IO}
20447 @tab @code{INTEGER_IO(SHORT_INTEGER)}
20449 @item @code{SHORT_SHORT_INTEGER_TEXT_IO}
20450 @tab @code{INTEGER_IO(SHORT_SHORT_INTEGER)}
20452 @item @code{FLOAT_TEXT_IO}
20453 @tab @code{FLOAT_IO(FLOAT)}
20455 @item @code{LONG_FLOAT_TEXT_IO}
20456 @tab @code{FLOAT_IO(LONG_FLOAT)}
20460 The DEC Ada predefined packages and their operations
20461 are implemented using OpenVMS Alpha files and input-
20462 output facilities. DEC Ada supports asynchronous input-
20463 output on OpenVMS Alpha. Familiarity with the following is
20466 @item RMS file organizations and access methods
20468 @item OpenVMS file specifications and directories
20470 @item OpenVMS File Definition Language (FDL)
20474 GNAT provides I/O facilities that are completely
20475 compatible with DEC Ada. The distribution includes the
20476 standard DEC Ada versions of all I/O packages, operating
20477 in a manner compatible with DEC Ada. In particular, the
20478 following packages are by default the DEC Ada (Ada 83)
20479 versions of these packages rather than the renamings
20480 suggested in annex J of the Ada 95 Reference Manual:
20482 @item @code{TEXT_IO}
20484 @item @code{SEQUENTIAL_IO}
20486 @item @code{DIRECT_IO}
20490 The use of the standard Ada 95 syntax for child packages (for
20491 example, @code{ADA.TEXT_IO}) retrieves the Ada 95 versions of these
20492 packages, as defined in the Ada 95 Reference Manual.
20493 GNAT provides DIGITAL-compatible predefined instantiations
20494 of the @code{TEXT_IO} packages, and also
20495 provides the standard predefined instantiations required
20496 by the Ada 95 Reference Manual.
20498 For further information on how GNAT interfaces to the file
20499 system or how I/O is implemented in programs written in
20500 mixed languages, see the chapter ``Implementation of the
20501 Standard I/O'' in the @cite{GNAT Reference Manual}.
20502 This chapter covers the following:
20504 @item Standard I/O packages
20506 @item @code{FORM} strings
20508 @item @code{ADA.DIRECT_IO}
20510 @item @code{ADA.SEQUENTIAL_IO}
20512 @item @code{ADA.TEXT_IO}
20514 @item Stream pointer positioning
20516 @item Reading and writing non-regular files
20518 @item @code{GET_IMMEDIATE}
20520 @item Treating @code{TEXT_IO} files as streams
20527 @node Implementation Limits
20528 @section Implementation Limits
20531 The following table lists implementation limits for DEC Ada
20533 @multitable @columnfractions .60 .20 .20
20535 @item @emph{Compilation Parameter}
20536 @tab @emph{DEC Ada}
20540 @item In a subprogram or entry declaration, maximum number of
20541 formal parameters that are of an unconstrained record type
20546 @item Maximum identifier length (number of characters)
20551 @item Maximum number of characters in a source line
20556 @item Maximum collection size (number of bytes)
20561 @item Maximum number of discriminants for a record type
20566 @item Maximum number of formal parameters in an entry or
20567 subprogram declaration
20572 @item Maximum number of dimensions in an array type
20577 @item Maximum number of library units and subunits in a compilation.
20582 @item Maximum number of library units and subunits in an execution.
20587 @item Maximum number of objects declared with the pragma @code{COMMON_OBJECT}
20588 or @code{PSECT_OBJECT}
20593 @item Maximum number of enumeration literals in an enumeration type
20599 @item Maximum number of lines in a source file
20604 @item Maximum number of bits in any object
20609 @item Maximum size of the static portion of a stack frame (approximate)
20620 @c **************************************
20621 @node Platform-Specific Information for the Run-Time Libraries
20622 @appendix Platform-Specific Information for the Run-Time Libraries
20623 @cindex Tasking and threads libraries
20624 @cindex Threads libraries and tasking
20625 @cindex Run-time libraries (platform-specific information)
20628 The GNAT run-time implementation
20629 may vary with respect to both the underlying threads library and
20630 the exception handling scheme.
20631 For threads support, one or more of the following are supplied:
20633 @item @b{native threads library}, a binding to the thread package from
20634 the underlying operating system
20636 @item @b{FSU threads library}, a binding to the Florida State University
20637 threads implementation, which complies fully with the requirements of Annex D
20639 @item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris
20640 POSIX thread package
20644 For exception handling, either or both of two models are supplied:
20646 @item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{
20647 Most programs should experience a substantial speed improvement by
20648 being compiled with a ZCX run-time.
20649 This is especially true for
20650 tasking applications or applications with many exception handlers.}
20651 @cindex Zero-Cost Exceptions
20652 @cindex ZCX (Zero-Cost Exceptions)
20653 which uses binder-generated tables that
20654 are interrogated at run time to locate a handler
20656 @item @b{setjmp / longjmp} (``SJLJ''),
20657 @cindex setjmp/longjmp Exception Model
20658 @cindex SJLJ (setjmp/longjmp Exception Model)
20659 which uses dynamically-set data to establish
20660 the set of handlers
20664 This appendix summarizes which combinations of threads and exception support
20665 are supplied on various GNAT platforms.
20666 It then shows how to select a particular library either
20667 permanently or temporarily,
20668 explains the properties of (and tradeoffs among) the various threads
20669 libraries, and provides some additional
20670 information about several specific platforms.
20673 * Summary of Run-Time Configurations::
20674 * Specifying a Run-Time Library::
20675 * Choosing between Native and FSU Threads Libraries::
20676 * Choosing the Scheduling Policy::
20677 * Solaris-Specific Considerations::
20678 * IRIX-Specific Considerations::
20679 * Linux-Specific Considerations::
20683 @node Summary of Run-Time Configurations
20684 @section Summary of Run-Time Configurations
20687 @multitable @columnfractions .30 .70
20688 @item @b{alpha-openvms}
20689 @item @code{@ @ }@i{rts-native (default)}
20690 @item @code{@ @ @ @ }Tasking @tab native VMS threads
20691 @item @code{@ @ @ @ }Exceptions @tab ZCX
20694 @item @code{@ @ }@i{rts-native (default)}
20695 @item @code{@ @ @ @ }Tasking @tab native HP threads library
20696 @item @code{@ @ @ @ }Exceptions @tab ZCX
20698 @item @code{@ @ }@i{rts-sjlj}
20699 @item @code{@ @ @ @ }Tasking @tab native HP threads library
20700 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20702 @item @b{sparc-solaris} @tab
20703 @item @code{@ @ }@i{rts-native (default)}
20704 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
20705 @item @code{@ @ @ @ }Exceptions @tab ZCX
20707 @item @code{@ @ }@i{rts-fsu} @tab
20708 @item @code{@ @ @ @ }Tasking @tab FSU threads library
20709 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20711 @item @code{@ @ }@i{rts-m64}
20712 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
20713 @item @code{@ @ @ @ }Exceptions @tab ZCX
20714 @item @code{@ @ @ @ }Constraints @tab Use only when compiling in 64-bit mode;
20715 @item @tab Use only on Solaris 8 or later.
20716 @item @tab @xref{Building and Debugging 64-bit Applications}, for details.
20718 @item @code{@ @ }@i{rts-pthread}
20719 @item @code{@ @ @ @ }Tasking @tab pthreads library
20720 @item @code{@ @ @ @ }Exceptions @tab ZCX
20722 @item @code{@ @ }@i{rts-sjlj}
20723 @item @code{@ @ @ @ }Tasking @tab native Solaris threads library
20724 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20726 @item @b{x86-linux}
20727 @item @code{@ @ }@i{rts-native (default)}
20728 @item @code{@ @ @ @ }Tasking @tab LinuxThread library
20729 @item @code{@ @ @ @ }Exceptions @tab ZCX
20731 @item @code{@ @ }@i{rts-fsu}
20732 @item @code{@ @ @ @ }Tasking @tab FSU threads library
20733 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20735 @item @code{@ @ }@i{rts-sjlj}
20736 @item @code{@ @ @ @ }Tasking @tab LinuxThread library
20737 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20739 @item @b{x86-windows}
20740 @item @code{@ @ }@i{rts-native (default)}
20741 @item @code{@ @ @ @ }Tasking @tab native Win32 threads
20742 @item @code{@ @ @ @ }Exceptions @tab SJLJ
20748 @node Specifying a Run-Time Library
20749 @section Specifying a Run-Time Library
20752 The @file{adainclude} subdirectory containing the sources of the GNAT
20753 run-time library, and the @file{adalib} subdirectory containing the
20754 @file{ALI} files and the static and/or shared GNAT library, are located
20755 in the gcc target-dependent area:
20758 target=$prefix/lib/gcc-lib/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/
20762 As indicated above, on some platforms several run-time libraries are supplied.
20763 These libraries are installed in the target dependent area and
20764 contain a complete source and binary subdirectory. The detailed description
20765 below explains the differences between the different libraries in terms of
20766 their thread support.
20768 The default run-time library (when GNAT is installed) is @emph{rts-native}.
20769 This default run time is selected by the means of soft links.
20770 For example on x86-linux:
20776 +--- adainclude----------+
20778 +--- adalib-----------+ |
20780 +--- rts-native | |
20782 | +--- adainclude <---+
20784 | +--- adalib <----+
20801 If the @i{rts-fsu} library is to be selected on a permanent basis,
20802 these soft links can be modified with the following commands:
20806 $ rm -f adainclude adalib
20807 $ ln -s rts-fsu/adainclude adainclude
20808 $ ln -s rts-fsu/adalib adalib
20812 Alternatively, you can specify @file{rts-fsu/adainclude} in the file
20813 @file{$target/ada_source_path} and @file{rts-fsu/adalib} in
20814 @file{$target/ada_object_path}.
20816 Selecting another run-time library temporarily can be
20817 achieved by the regular mechanism for GNAT object or source path selection:
20821 Set the environment variables:
20824 $ ADA_INCLUDE_PATH=$target/rts-fsu/adainclude:$ADA_INCLUDE_PATH
20825 $ ADA_OBJECTS_PATH=$target/rts-fsu/adalib:$ADA_OBJECTS_PATH
20826 $ export ADA_INCLUDE_PATH ADA_OBJECTS_PATH
20830 Use @option{-aI$target/rts-fsu/adainclude}
20831 and @option{-aO$target/rts-fsu/adalib}
20832 on the @command{gnatmake} command line
20835 Use the switch @option{--RTS}; e.g., @option{--RTS=fsu}
20836 @cindex @option{--RTS} option
20840 You can similarly switch to @emph{rts-sjlj}.
20842 @node Choosing between Native and FSU Threads Libraries
20843 @section Choosing between Native and FSU Threads Libraries
20844 @cindex Native threads library
20845 @cindex FSU threads library
20848 Some GNAT implementations offer a choice between
20849 native threads and FSU threads.
20853 The @emph{native threads} library correspond to the standard system threads
20854 implementation (e.g. LinuxThreads on GNU/Linux,
20855 @cindex LinuxThreads library
20856 POSIX threads on AIX, or
20857 Solaris threads on Solaris). When this option is chosen, GNAT provides
20858 a full and accurate implementation of the core language tasking model
20859 as described in Chapter 9 of the Ada Reference Manual,
20860 but might not (and probably does not) implement
20861 the exact semantics as specified in @w{Annex D} (the Real-Time Systems Annex).
20862 @cindex Annex D (Real-Time Systems Annex) compliance
20863 @cindex Real-Time Systems Annex compliance
20864 Indeed, the reason that a choice of libraries is offered
20865 on a given target is because some of the
20866 ACATS tests for @w{Annex D} fail using the native threads library.
20867 As far as possible, this library is implemented
20868 in accordance with Ada semantics (e.g., modifying priorities as required
20869 to simulate ceiling locking),
20870 but there are often slight inaccuracies, most often in the area of
20871 absolutely respecting the priority rules on a single
20873 Moreover, it is not possible in general to define the exact behavior,
20874 because the native threads implementations
20875 are not well enough documented.
20877 On systems where the @code{SCHED_FIFO} POSIX scheduling policy is supported,
20878 @cindex POSIX scheduling policies
20879 @cindex @code{SCHED_FIFO} scheduling policy
20880 native threads will provide a behavior very close to the @w{Annex D}
20881 requirements (i.e., a run-till-blocked scheduler with fixed priorities), but
20882 on some systems (in particular GNU/Linux and Solaris), you need to have root
20883 privileges to use the @code{SCHED_FIFO} policy.
20886 The @emph{FSU threads} library provides a completely accurate implementation
20888 Thus, operating with this library, GNAT is 100% compliant with both the core
20889 and all @w{Annex D}
20891 The formal validations for implementations offering
20892 a choice of threads packages are always carried out using the FSU
20897 From these considerations, it might seem that FSU threads are the
20899 but that is by no means always the case. The FSU threads package
20900 operates with all Ada tasks appearing to the system to be a single
20901 thread. This is often considerably more efficient than operating
20902 with separate threads, since for example, switching between tasks
20903 can be accomplished without the (in some cases considerable)
20904 overhead of a context switch between two system threads. However,
20905 it means that you may well lose concurrency at the system
20906 level. Notably, some system operations (such as I/O) may block all
20907 tasks in a program and not just the calling task. More
20908 significantly, the FSU threads approach likely means you cannot
20909 take advantage of multiple processors, since for this you need
20910 separate threads (or even separate processes) to operate on
20911 different processors.
20913 For most programs, the native threads library is
20914 usually the better choice. Use the FSU threads if absolute
20915 conformance to @w{Annex D} is important for your application, or if
20916 you find that the improved efficiency of FSU threads is significant to you.
20918 Note also that to take full advantage of Florist and Glade, it is highly
20919 recommended that you use native threads.
20922 @node Choosing the Scheduling Policy
20923 @section Choosing the Scheduling Policy
20926 When using a POSIX threads implementation, you have a choice of several
20927 scheduling policies: @code{SCHED_FIFO},
20928 @cindex @code{SCHED_FIFO} scheduling policy
20930 @cindex @code{SCHED_RR} scheduling policy
20931 and @code{SCHED_OTHER}.
20932 @cindex @code{SCHED_OTHER} scheduling policy
20933 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
20934 or @code{SCHED_RR} requires special (e.g., root) privileges.
20936 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
20938 @cindex @code{SCHED_FIFO} scheduling policy
20939 you can use one of the following:
20943 @code{pragma Time_Slice (0.0)}
20944 @cindex pragma Time_Slice
20946 the corresponding binder option @option{-T0}
20947 @cindex @option{-T0} option
20949 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
20950 @cindex pragma Task_Dispatching_Policy
20954 To specify @code{SCHED_RR},
20955 @cindex @code{SCHED_RR} scheduling policy
20956 you should use @code{pragma Time_Slice} with a
20957 value greater than @code{0.0}, or else use the corresponding @option{-T}
20962 @node Solaris-Specific Considerations
20963 @section Solaris-Specific Considerations
20964 @cindex Solaris Sparc threads libraries
20967 This section addresses some topics related to the various threads libraries
20968 on Sparc Solaris and then provides some information on building and
20969 debugging 64-bit applications.
20972 * Solaris Threads Issues::
20973 * Building and Debugging 64-bit Applications::
20977 @node Solaris Threads Issues
20978 @subsection Solaris Threads Issues
20981 Starting with version 3.14, GNAT under Solaris comes with a new tasking
20982 run-time library based on POSIX threads --- @emph{rts-pthread}.
20983 @cindex rts-pthread threads library
20984 This run-time library has the advantage of being mostly shared across all
20985 POSIX-compliant thread implementations, and it also provides under
20986 @w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT}
20987 @cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread)
20988 and @code{PTHREAD_PRIO_PROTECT}
20989 @cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread)
20990 semantics that can be selected using the predefined pragma
20991 @code{Locking_Policy}
20992 @cindex pragma Locking_Policy (under rts-pthread)
20994 @code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy.
20995 @cindex @code{Inheritance_Locking} (under rts-pthread)
20996 @cindex @code{Ceiling_Locking} (under rts-pthread)
20998 As explained above, the native run-time library is based on the Solaris thread
20999 library (@code{libthread}) and is the default library.
21000 The FSU run-time library is based on the FSU threads.
21001 @cindex FSU threads library
21003 Starting with Solaris 2.5.1, when the Solaris threads library is used
21004 (this is the default), programs
21005 compiled with GNAT can automatically take advantage of
21006 and can thus execute on multiple processors.
21007 The user can alternatively specify a processor on which the program should run
21008 to emulate a single-processor system. The multiprocessor / uniprocessor choice
21010 setting the environment variable @code{GNAT_PROCESSOR}
21011 @cindex @code{GNAT_PROCESSOR} environment variable (on Sparc Solaris)
21012 to one of the following:
21016 Use the default configuration (run the program on all
21017 available processors) - this is the same as having
21018 @code{GNAT_PROCESSOR} unset
21021 Let the run-time implementation choose one processor and run the program on
21024 @item 0 .. Last_Proc
21025 Run the program on the specified processor.
21026 @code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1}
21027 (where @code{_SC_NPROCESSORS_CONF} is a system variable).
21031 @node Building and Debugging 64-bit Applications
21032 @subsection Building and Debugging 64-bit Applications
21035 In a 64-bit application, all the sources involved must be compiled with the
21036 @option{-m64} command-line option, and a specific GNAT library (compiled with
21037 this option) is required.
21038 The easiest way to build a 64bit application is to add
21039 @option{-m64 --RTS=m64} to the @command{gnatmake} flags.
21041 To debug these applications, dwarf-2 debug information is required, so you
21042 have to add @option{-gdwarf-2} to your gnatmake arguments.
21043 In addition, a special
21044 version of gdb, called @command{gdb64}, needs to be used.
21046 To summarize, building and debugging a ``Hello World'' program in 64-bit mode
21050 $ gnatmake -m64 -gdwarf-2 --RTS=m64 hello.adb
21056 @node IRIX-Specific Considerations
21057 @section IRIX-Specific Considerations
21058 @cindex IRIX thread library
21061 On SGI IRIX, the thread library depends on which compiler is used.
21062 The @emph{o32 ABI} compiler comes with a run-time library based on the
21063 user-level @code{athread}
21064 library. Thus kernel-level capabilities such as nonblocking system
21065 calls or time slicing can only be achieved reliably by specifying different
21066 @code{sprocs} via the pragma @code{Task_Info}
21067 @cindex pragma Task_Info (and IRIX threads)
21069 @code{System.Task_Info} package.
21070 @cindex @code{System.Task_Info} package (and IRIX threads)
21071 See the @cite{GNAT Reference Manual} for further information.
21073 The @emph{n32 ABI} compiler comes with a run-time library based on the
21074 kernel POSIX threads and thus does not have the limitations mentioned above.
21077 @node Linux-Specific Considerations
21078 @section Linux-Specific Considerations
21079 @cindex Linux threads libraries
21082 The default thread library under GNU/Linux has the following disadvantages
21083 compared to other native thread libraries:
21086 @item The size of the task's stack is limited to 2 megabytes.
21087 @item The signal model is not POSIX compliant, which means that to send a
21088 signal to the process, you need to send the signal to all threads,
21089 e.g. by using @code{killpg()}.
21094 @c *******************************
21095 @node Example of Binder Output File
21096 @appendix Example of Binder Output File
21099 This Appendix displays the source code for @command{gnatbind}'s output
21100 file generated for a simple ``Hello World'' program.
21101 Comments have been added for clarification purposes.
21104 @smallexample @c adanocomment
21108 -- The package is called Ada_Main unless this name is actually used
21109 -- as a unit name in the partition, in which case some other unique
21113 package ada_main is
21115 Elab_Final_Code : Integer;
21116 pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
21118 -- The main program saves the parameters (argument count,
21119 -- argument values, environment pointer) in global variables
21120 -- for later access by other units including
21121 -- Ada.Command_Line.
21123 gnat_argc : Integer;
21124 gnat_argv : System.Address;
21125 gnat_envp : System.Address;
21127 -- The actual variables are stored in a library routine. This
21128 -- is useful for some shared library situations, where there
21129 -- are problems if variables are not in the library.
21131 pragma Import (C, gnat_argc);
21132 pragma Import (C, gnat_argv);
21133 pragma Import (C, gnat_envp);
21135 -- The exit status is similarly an external location
21137 gnat_exit_status : Integer;
21138 pragma Import (C, gnat_exit_status);
21140 GNAT_Version : constant String :=
21141 "GNAT Version: 3.15w (20010315)";
21142 pragma Export (C, GNAT_Version, "__gnat_version");
21144 -- This is the generated adafinal routine that performs
21145 -- finalization at the end of execution. In the case where
21146 -- Ada is the main program, this main program makes a call
21147 -- to adafinal at program termination.
21149 procedure adafinal;
21150 pragma Export (C, adafinal, "adafinal");
21152 -- This is the generated adainit routine that performs
21153 -- initialization at the start of execution. In the case
21154 -- where Ada is the main program, this main program makes
21155 -- a call to adainit at program startup.
21158 pragma Export (C, adainit, "adainit");
21160 -- This routine is called at the start of execution. It is
21161 -- a dummy routine that is used by the debugger to breakpoint
21162 -- at the start of execution.
21164 procedure Break_Start;
21165 pragma Import (C, Break_Start, "__gnat_break_start");
21167 -- This is the actual generated main program (it would be
21168 -- suppressed if the no main program switch were used). As
21169 -- required by standard system conventions, this program has
21170 -- the external name main.
21174 argv : System.Address;
21175 envp : System.Address)
21177 pragma Export (C, main, "main");
21179 -- The following set of constants give the version
21180 -- identification values for every unit in the bound
21181 -- partition. This identification is computed from all
21182 -- dependent semantic units, and corresponds to the
21183 -- string that would be returned by use of the
21184 -- Body_Version or Version attributes.
21186 type Version_32 is mod 2 ** 32;
21187 u00001 : constant Version_32 := 16#7880BEB3#;
21188 u00002 : constant Version_32 := 16#0D24CBD0#;
21189 u00003 : constant Version_32 := 16#3283DBEB#;
21190 u00004 : constant Version_32 := 16#2359F9ED#;
21191 u00005 : constant Version_32 := 16#664FB847#;
21192 u00006 : constant Version_32 := 16#68E803DF#;
21193 u00007 : constant Version_32 := 16#5572E604#;
21194 u00008 : constant Version_32 := 16#46B173D8#;
21195 u00009 : constant Version_32 := 16#156A40CF#;
21196 u00010 : constant Version_32 := 16#033DABE0#;
21197 u00011 : constant Version_32 := 16#6AB38FEA#;
21198 u00012 : constant Version_32 := 16#22B6217D#;
21199 u00013 : constant Version_32 := 16#68A22947#;
21200 u00014 : constant Version_32 := 16#18CC4A56#;
21201 u00015 : constant Version_32 := 16#08258E1B#;
21202 u00016 : constant Version_32 := 16#367D5222#;
21203 u00017 : constant Version_32 := 16#20C9ECA4#;
21204 u00018 : constant Version_32 := 16#50D32CB6#;
21205 u00019 : constant Version_32 := 16#39A8BB77#;
21206 u00020 : constant Version_32 := 16#5CF8FA2B#;
21207 u00021 : constant Version_32 := 16#2F1EB794#;
21208 u00022 : constant Version_32 := 16#31AB6444#;
21209 u00023 : constant Version_32 := 16#1574B6E9#;
21210 u00024 : constant Version_32 := 16#5109C189#;
21211 u00025 : constant Version_32 := 16#56D770CD#;
21212 u00026 : constant Version_32 := 16#02F9DE3D#;
21213 u00027 : constant Version_32 := 16#08AB6B2C#;
21214 u00028 : constant Version_32 := 16#3FA37670#;
21215 u00029 : constant Version_32 := 16#476457A0#;
21216 u00030 : constant Version_32 := 16#731E1B6E#;
21217 u00031 : constant Version_32 := 16#23C2E789#;
21218 u00032 : constant Version_32 := 16#0F1BD6A1#;
21219 u00033 : constant Version_32 := 16#7C25DE96#;
21220 u00034 : constant Version_32 := 16#39ADFFA2#;
21221 u00035 : constant Version_32 := 16#571DE3E7#;
21222 u00036 : constant Version_32 := 16#5EB646AB#;
21223 u00037 : constant Version_32 := 16#4249379B#;
21224 u00038 : constant Version_32 := 16#0357E00A#;
21225 u00039 : constant Version_32 := 16#3784FB72#;
21226 u00040 : constant Version_32 := 16#2E723019#;
21227 u00041 : constant Version_32 := 16#623358EA#;
21228 u00042 : constant Version_32 := 16#107F9465#;
21229 u00043 : constant Version_32 := 16#6843F68A#;
21230 u00044 : constant Version_32 := 16#63305874#;
21231 u00045 : constant Version_32 := 16#31E56CE1#;
21232 u00046 : constant Version_32 := 16#02917970#;
21233 u00047 : constant Version_32 := 16#6CCBA70E#;
21234 u00048 : constant Version_32 := 16#41CD4204#;
21235 u00049 : constant Version_32 := 16#572E3F58#;
21236 u00050 : constant Version_32 := 16#20729FF5#;
21237 u00051 : constant Version_32 := 16#1D4F93E8#;
21238 u00052 : constant Version_32 := 16#30B2EC3D#;
21239 u00053 : constant Version_32 := 16#34054F96#;
21240 u00054 : constant Version_32 := 16#5A199860#;
21241 u00055 : constant Version_32 := 16#0E7F912B#;
21242 u00056 : constant Version_32 := 16#5760634A#;
21243 u00057 : constant Version_32 := 16#5D851835#;
21245 -- The following Export pragmas export the version numbers
21246 -- with symbolic names ending in B (for body) or S
21247 -- (for spec) so that they can be located in a link. The
21248 -- information provided here is sufficient to track down
21249 -- the exact versions of units used in a given build.
21251 pragma Export (C, u00001, "helloB");
21252 pragma Export (C, u00002, "system__standard_libraryB");
21253 pragma Export (C, u00003, "system__standard_libraryS");
21254 pragma Export (C, u00004, "adaS");
21255 pragma Export (C, u00005, "ada__text_ioB");
21256 pragma Export (C, u00006, "ada__text_ioS");
21257 pragma Export (C, u00007, "ada__exceptionsB");
21258 pragma Export (C, u00008, "ada__exceptionsS");
21259 pragma Export (C, u00009, "gnatS");
21260 pragma Export (C, u00010, "gnat__heap_sort_aB");
21261 pragma Export (C, u00011, "gnat__heap_sort_aS");
21262 pragma Export (C, u00012, "systemS");
21263 pragma Export (C, u00013, "system__exception_tableB");
21264 pragma Export (C, u00014, "system__exception_tableS");
21265 pragma Export (C, u00015, "gnat__htableB");
21266 pragma Export (C, u00016, "gnat__htableS");
21267 pragma Export (C, u00017, "system__exceptionsS");
21268 pragma Export (C, u00018, "system__machine_state_operationsB");
21269 pragma Export (C, u00019, "system__machine_state_operationsS");
21270 pragma Export (C, u00020, "system__machine_codeS");
21271 pragma Export (C, u00021, "system__storage_elementsB");
21272 pragma Export (C, u00022, "system__storage_elementsS");
21273 pragma Export (C, u00023, "system__secondary_stackB");
21274 pragma Export (C, u00024, "system__secondary_stackS");
21275 pragma Export (C, u00025, "system__parametersB");
21276 pragma Export (C, u00026, "system__parametersS");
21277 pragma Export (C, u00027, "system__soft_linksB");
21278 pragma Export (C, u00028, "system__soft_linksS");
21279 pragma Export (C, u00029, "system__stack_checkingB");
21280 pragma Export (C, u00030, "system__stack_checkingS");
21281 pragma Export (C, u00031, "system__tracebackB");
21282 pragma Export (C, u00032, "system__tracebackS");
21283 pragma Export (C, u00033, "ada__streamsS");
21284 pragma Export (C, u00034, "ada__tagsB");
21285 pragma Export (C, u00035, "ada__tagsS");
21286 pragma Export (C, u00036, "system__string_opsB");
21287 pragma Export (C, u00037, "system__string_opsS");
21288 pragma Export (C, u00038, "interfacesS");
21289 pragma Export (C, u00039, "interfaces__c_streamsB");
21290 pragma Export (C, u00040, "interfaces__c_streamsS");
21291 pragma Export (C, u00041, "system__file_ioB");
21292 pragma Export (C, u00042, "system__file_ioS");
21293 pragma Export (C, u00043, "ada__finalizationB");
21294 pragma Export (C, u00044, "ada__finalizationS");
21295 pragma Export (C, u00045, "system__finalization_rootB");
21296 pragma Export (C, u00046, "system__finalization_rootS");
21297 pragma Export (C, u00047, "system__finalization_implementationB");
21298 pragma Export (C, u00048, "system__finalization_implementationS");
21299 pragma Export (C, u00049, "system__string_ops_concat_3B");
21300 pragma Export (C, u00050, "system__string_ops_concat_3S");
21301 pragma Export (C, u00051, "system__stream_attributesB");
21302 pragma Export (C, u00052, "system__stream_attributesS");
21303 pragma Export (C, u00053, "ada__io_exceptionsS");
21304 pragma Export (C, u00054, "system__unsigned_typesS");
21305 pragma Export (C, u00055, "system__file_control_blockS");
21306 pragma Export (C, u00056, "ada__finalization__list_controllerB");
21307 pragma Export (C, u00057, "ada__finalization__list_controllerS");
21309 -- BEGIN ELABORATION ORDER
21312 -- gnat.heap_sort_a (spec)
21313 -- gnat.heap_sort_a (body)
21314 -- gnat.htable (spec)
21315 -- gnat.htable (body)
21316 -- interfaces (spec)
21318 -- system.machine_code (spec)
21319 -- system.parameters (spec)
21320 -- system.parameters (body)
21321 -- interfaces.c_streams (spec)
21322 -- interfaces.c_streams (body)
21323 -- system.standard_library (spec)
21324 -- ada.exceptions (spec)
21325 -- system.exception_table (spec)
21326 -- system.exception_table (body)
21327 -- ada.io_exceptions (spec)
21328 -- system.exceptions (spec)
21329 -- system.storage_elements (spec)
21330 -- system.storage_elements (body)
21331 -- system.machine_state_operations (spec)
21332 -- system.machine_state_operations (body)
21333 -- system.secondary_stack (spec)
21334 -- system.stack_checking (spec)
21335 -- system.soft_links (spec)
21336 -- system.soft_links (body)
21337 -- system.stack_checking (body)
21338 -- system.secondary_stack (body)
21339 -- system.standard_library (body)
21340 -- system.string_ops (spec)
21341 -- system.string_ops (body)
21344 -- ada.streams (spec)
21345 -- system.finalization_root (spec)
21346 -- system.finalization_root (body)
21347 -- system.string_ops_concat_3 (spec)
21348 -- system.string_ops_concat_3 (body)
21349 -- system.traceback (spec)
21350 -- system.traceback (body)
21351 -- ada.exceptions (body)
21352 -- system.unsigned_types (spec)
21353 -- system.stream_attributes (spec)
21354 -- system.stream_attributes (body)
21355 -- system.finalization_implementation (spec)
21356 -- system.finalization_implementation (body)
21357 -- ada.finalization (spec)
21358 -- ada.finalization (body)
21359 -- ada.finalization.list_controller (spec)
21360 -- ada.finalization.list_controller (body)
21361 -- system.file_control_block (spec)
21362 -- system.file_io (spec)
21363 -- system.file_io (body)
21364 -- ada.text_io (spec)
21365 -- ada.text_io (body)
21367 -- END ELABORATION ORDER
21371 -- The following source file name pragmas allow the generated file
21372 -- names to be unique for different main programs. They are needed
21373 -- since the package name will always be Ada_Main.
21375 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
21376 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
21378 -- Generated package body for Ada_Main starts here
21380 package body ada_main is
21382 -- The actual finalization is performed by calling the
21383 -- library routine in System.Standard_Library.Adafinal
21385 procedure Do_Finalize;
21386 pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
21393 procedure adainit is
21395 -- These booleans are set to True once the associated unit has
21396 -- been elaborated. It is also used to avoid elaborating the
21397 -- same unit twice.
21400 pragma Import (Ada, E040, "interfaces__c_streams_E");
21403 pragma Import (Ada, E008, "ada__exceptions_E");
21406 pragma Import (Ada, E014, "system__exception_table_E");
21409 pragma Import (Ada, E053, "ada__io_exceptions_E");
21412 pragma Import (Ada, E017, "system__exceptions_E");
21415 pragma Import (Ada, E024, "system__secondary_stack_E");
21418 pragma Import (Ada, E030, "system__stack_checking_E");
21421 pragma Import (Ada, E028, "system__soft_links_E");
21424 pragma Import (Ada, E035, "ada__tags_E");
21427 pragma Import (Ada, E033, "ada__streams_E");
21430 pragma Import (Ada, E046, "system__finalization_root_E");
21433 pragma Import (Ada, E048, "system__finalization_implementation_E");
21436 pragma Import (Ada, E044, "ada__finalization_E");
21439 pragma Import (Ada, E057, "ada__finalization__list_controller_E");
21442 pragma Import (Ada, E055, "system__file_control_block_E");
21445 pragma Import (Ada, E042, "system__file_io_E");
21448 pragma Import (Ada, E006, "ada__text_io_E");
21450 -- Set_Globals is a library routine that stores away the
21451 -- value of the indicated set of global values in global
21452 -- variables within the library.
21454 procedure Set_Globals
21455 (Main_Priority : Integer;
21456 Time_Slice_Value : Integer;
21457 WC_Encoding : Character;
21458 Locking_Policy : Character;
21459 Queuing_Policy : Character;
21460 Task_Dispatching_Policy : Character;
21461 Adafinal : System.Address;
21462 Unreserve_All_Interrupts : Integer;
21463 Exception_Tracebacks : Integer);
21464 @findex __gnat_set_globals
21465 pragma Import (C, Set_Globals, "__gnat_set_globals");
21467 -- SDP_Table_Build is a library routine used to build the
21468 -- exception tables. See unit Ada.Exceptions in files
21469 -- a-except.ads/adb for full details of how zero cost
21470 -- exception handling works. This procedure, the call to
21471 -- it, and the two following tables are all omitted if the
21472 -- build is in longjmp/setjump exception mode.
21474 @findex SDP_Table_Build
21475 @findex Zero Cost Exceptions
21476 procedure SDP_Table_Build
21477 (SDP_Addresses : System.Address;
21478 SDP_Count : Natural;
21479 Elab_Addresses : System.Address;
21480 Elab_Addr_Count : Natural);
21481 pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
21483 -- Table of Unit_Exception_Table addresses. Used for zero
21484 -- cost exception handling to build the top level table.
21486 ST : aliased constant array (1 .. 23) of System.Address := (
21488 Ada.Text_Io'UET_Address,
21489 Ada.Exceptions'UET_Address,
21490 Gnat.Heap_Sort_A'UET_Address,
21491 System.Exception_Table'UET_Address,
21492 System.Machine_State_Operations'UET_Address,
21493 System.Secondary_Stack'UET_Address,
21494 System.Parameters'UET_Address,
21495 System.Soft_Links'UET_Address,
21496 System.Stack_Checking'UET_Address,
21497 System.Traceback'UET_Address,
21498 Ada.Streams'UET_Address,
21499 Ada.Tags'UET_Address,
21500 System.String_Ops'UET_Address,
21501 Interfaces.C_Streams'UET_Address,
21502 System.File_Io'UET_Address,
21503 Ada.Finalization'UET_Address,
21504 System.Finalization_Root'UET_Address,
21505 System.Finalization_Implementation'UET_Address,
21506 System.String_Ops_Concat_3'UET_Address,
21507 System.Stream_Attributes'UET_Address,
21508 System.File_Control_Block'UET_Address,
21509 Ada.Finalization.List_Controller'UET_Address);
21511 -- Table of addresses of elaboration routines. Used for
21512 -- zero cost exception handling to make sure these
21513 -- addresses are included in the top level procedure
21516 EA : aliased constant array (1 .. 23) of System.Address := (
21517 adainit'Code_Address,
21518 Do_Finalize'Code_Address,
21519 Ada.Exceptions'Elab_Spec'Address,
21520 System.Exceptions'Elab_Spec'Address,
21521 Interfaces.C_Streams'Elab_Spec'Address,
21522 System.Exception_Table'Elab_Body'Address,
21523 Ada.Io_Exceptions'Elab_Spec'Address,
21524 System.Stack_Checking'Elab_Spec'Address,
21525 System.Soft_Links'Elab_Body'Address,
21526 System.Secondary_Stack'Elab_Body'Address,
21527 Ada.Tags'Elab_Spec'Address,
21528 Ada.Tags'Elab_Body'Address,
21529 Ada.Streams'Elab_Spec'Address,
21530 System.Finalization_Root'Elab_Spec'Address,
21531 Ada.Exceptions'Elab_Body'Address,
21532 System.Finalization_Implementation'Elab_Spec'Address,
21533 System.Finalization_Implementation'Elab_Body'Address,
21534 Ada.Finalization'Elab_Spec'Address,
21535 Ada.Finalization.List_Controller'Elab_Spec'Address,
21536 System.File_Control_Block'Elab_Spec'Address,
21537 System.File_Io'Elab_Body'Address,
21538 Ada.Text_Io'Elab_Spec'Address,
21539 Ada.Text_Io'Elab_Body'Address);
21541 -- Start of processing for adainit
21545 -- Call SDP_Table_Build to build the top level procedure
21546 -- table for zero cost exception handling (omitted in
21547 -- longjmp/setjump mode).
21549 SDP_Table_Build (ST'Address, 23, EA'Address, 23);
21551 -- Call Set_Globals to record various information for
21552 -- this partition. The values are derived by the binder
21553 -- from information stored in the ali files by the compiler.
21555 @findex __gnat_set_globals
21557 (Main_Priority => -1,
21558 -- Priority of main program, -1 if no pragma Priority used
21560 Time_Slice_Value => -1,
21561 -- Time slice from Time_Slice pragma, -1 if none used
21563 WC_Encoding => 'b',
21564 -- Wide_Character encoding used, default is brackets
21566 Locking_Policy => ' ',
21567 -- Locking_Policy used, default of space means not
21568 -- specified, otherwise it is the first character of
21569 -- the policy name.
21571 Queuing_Policy => ' ',
21572 -- Queuing_Policy used, default of space means not
21573 -- specified, otherwise it is the first character of
21574 -- the policy name.
21576 Task_Dispatching_Policy => ' ',
21577 -- Task_Dispatching_Policy used, default of space means
21578 -- not specified, otherwise first character of the
21581 Adafinal => System.Null_Address,
21582 -- Address of Adafinal routine, not used anymore
21584 Unreserve_All_Interrupts => 0,
21585 -- Set true if pragma Unreserve_All_Interrupts was used
21587 Exception_Tracebacks => 0);
21588 -- Indicates if exception tracebacks are enabled
21590 Elab_Final_Code := 1;
21592 -- Now we have the elaboration calls for all units in the partition.
21593 -- The Elab_Spec and Elab_Body attributes generate references to the
21594 -- implicit elaboration procedures generated by the compiler for
21595 -- each unit that requires elaboration.
21598 Interfaces.C_Streams'Elab_Spec;
21602 Ada.Exceptions'Elab_Spec;
21605 System.Exception_Table'Elab_Body;
21609 Ada.Io_Exceptions'Elab_Spec;
21613 System.Exceptions'Elab_Spec;
21617 System.Stack_Checking'Elab_Spec;
21620 System.Soft_Links'Elab_Body;
21625 System.Secondary_Stack'Elab_Body;
21629 Ada.Tags'Elab_Spec;
21632 Ada.Tags'Elab_Body;
21636 Ada.Streams'Elab_Spec;
21640 System.Finalization_Root'Elab_Spec;
21644 Ada.Exceptions'Elab_Body;
21648 System.Finalization_Implementation'Elab_Spec;
21651 System.Finalization_Implementation'Elab_Body;
21655 Ada.Finalization'Elab_Spec;
21659 Ada.Finalization.List_Controller'Elab_Spec;
21663 System.File_Control_Block'Elab_Spec;
21667 System.File_Io'Elab_Body;
21671 Ada.Text_Io'Elab_Spec;
21674 Ada.Text_Io'Elab_Body;
21678 Elab_Final_Code := 0;
21686 procedure adafinal is
21695 -- main is actually a function, as in the ANSI C standard,
21696 -- defined to return the exit status. The three parameters
21697 -- are the argument count, argument values and environment
21700 @findex Main Program
21703 argv : System.Address;
21704 envp : System.Address)
21707 -- The initialize routine performs low level system
21708 -- initialization using a standard library routine which
21709 -- sets up signal handling and performs any other
21710 -- required setup. The routine can be found in file
21713 @findex __gnat_initialize
21714 procedure initialize;
21715 pragma Import (C, initialize, "__gnat_initialize");
21717 -- The finalize routine performs low level system
21718 -- finalization using a standard library routine. The
21719 -- routine is found in file a-final.c and in the standard
21720 -- distribution is a dummy routine that does nothing, so
21721 -- really this is a hook for special user finalization.
21723 @findex __gnat_finalize
21724 procedure finalize;
21725 pragma Import (C, finalize, "__gnat_finalize");
21727 -- We get to the main program of the partition by using
21728 -- pragma Import because if we try to with the unit and
21729 -- call it Ada style, then not only do we waste time
21730 -- recompiling it, but also, we don't really know the right
21731 -- switches (e.g. identifier character set) to be used
21734 procedure Ada_Main_Program;
21735 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
21737 -- Start of processing for main
21740 -- Save global variables
21746 -- Call low level system initialization
21750 -- Call our generated Ada initialization routine
21754 -- This is the point at which we want the debugger to get
21759 -- Now we call the main program of the partition
21763 -- Perform Ada finalization
21767 -- Perform low level system finalization
21771 -- Return the proper exit status
21772 return (gnat_exit_status);
21775 -- This section is entirely comments, so it has no effect on the
21776 -- compilation of the Ada_Main package. It provides the list of
21777 -- object files and linker options, as well as some standard
21778 -- libraries needed for the link. The gnatlink utility parses
21779 -- this b~hello.adb file to read these comment lines to generate
21780 -- the appropriate command line arguments for the call to the
21781 -- system linker. The BEGIN/END lines are used for sentinels for
21782 -- this parsing operation.
21784 -- The exact file names will of course depend on the environment,
21785 -- host/target and location of files on the host system.
21787 @findex Object file list
21788 -- BEGIN Object file/option list
21791 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
21792 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
21793 -- END Object file/option list
21799 The Ada code in the above example is exactly what is generated by the
21800 binder. We have added comments to more clearly indicate the function
21801 of each part of the generated @code{Ada_Main} package.
21803 The code is standard Ada in all respects, and can be processed by any
21804 tools that handle Ada. In particular, it is possible to use the debugger
21805 in Ada mode to debug the generated @code{Ada_Main} package. For example,
21806 suppose that for reasons that you do not understand, your program is crashing
21807 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
21808 you can place a breakpoint on the call:
21810 @smallexample @c ada
21811 Ada.Text_Io'Elab_Body;
21815 and trace the elaboration routine for this package to find out where
21816 the problem might be (more usually of course you would be debugging
21817 elaboration code in your own application).
21820 @node Elaboration Order Handling in GNAT
21821 @appendix Elaboration Order Handling in GNAT
21822 @cindex Order of elaboration
21823 @cindex Elaboration control
21826 * Elaboration Code in Ada 95::
21827 * Checking the Elaboration Order in Ada 95::
21828 * Controlling the Elaboration Order in Ada 95::
21829 * Controlling Elaboration in GNAT - Internal Calls::
21830 * Controlling Elaboration in GNAT - External Calls::
21831 * Default Behavior in GNAT - Ensuring Safety::
21832 * Treatment of Pragma Elaborate::
21833 * Elaboration Issues for Library Tasks::
21834 * Mixing Elaboration Models::
21835 * What to Do If the Default Elaboration Behavior Fails::
21836 * Elaboration for Access-to-Subprogram Values::
21837 * Summary of Procedures for Elaboration Control::
21838 * Other Elaboration Order Considerations::
21842 This chapter describes the handling of elaboration code in Ada 95 and
21843 in GNAT, and discusses how the order of elaboration of program units can
21844 be controlled in GNAT, either automatically or with explicit programming
21847 @node Elaboration Code in Ada 95
21848 @section Elaboration Code in Ada 95
21851 Ada 95 provides rather general mechanisms for executing code at elaboration
21852 time, that is to say before the main program starts executing. Such code arises
21856 @item Initializers for variables.
21857 Variables declared at the library level, in package specs or bodies, can
21858 require initialization that is performed at elaboration time, as in:
21859 @smallexample @c ada
21861 Sqrt_Half : Float := Sqrt (0.5);
21865 @item Package initialization code
21866 Code in a @code{BEGIN-END} section at the outer level of a package body is
21867 executed as part of the package body elaboration code.
21869 @item Library level task allocators
21870 Tasks that are declared using task allocators at the library level
21871 start executing immediately and hence can execute at elaboration time.
21875 Subprogram calls are possible in any of these contexts, which means that
21876 any arbitrary part of the program may be executed as part of the elaboration
21877 code. It is even possible to write a program which does all its work at
21878 elaboration time, with a null main program, although stylistically this
21879 would usually be considered an inappropriate way to structure
21882 An important concern arises in the context of elaboration code:
21883 we have to be sure that it is executed in an appropriate order. What we
21884 have is a series of elaboration code sections, potentially one section
21885 for each unit in the program. It is important that these execute
21886 in the correct order. Correctness here means that, taking the above
21887 example of the declaration of @code{Sqrt_Half},
21888 if some other piece of
21889 elaboration code references @code{Sqrt_Half},
21890 then it must run after the
21891 section of elaboration code that contains the declaration of
21894 There would never be any order of elaboration problem if we made a rule
21895 that whenever you @code{with} a unit, you must elaborate both the spec and body
21896 of that unit before elaborating the unit doing the @code{with}'ing:
21898 @smallexample @c ada
21902 package Unit_2 is ...
21908 would require that both the body and spec of @code{Unit_1} be elaborated
21909 before the spec of @code{Unit_2}. However, a rule like that would be far too
21910 restrictive. In particular, it would make it impossible to have routines
21911 in separate packages that were mutually recursive.
21913 You might think that a clever enough compiler could look at the actual
21914 elaboration code and determine an appropriate correct order of elaboration,
21915 but in the general case, this is not possible. Consider the following
21918 In the body of @code{Unit_1}, we have a procedure @code{Func_1}
21920 the variable @code{Sqrt_1}, which is declared in the elaboration code
21921 of the body of @code{Unit_1}:
21923 @smallexample @c ada
21925 Sqrt_1 : Float := Sqrt (0.1);
21930 The elaboration code of the body of @code{Unit_1} also contains:
21932 @smallexample @c ada
21935 if expression_1 = 1 then
21936 Q := Unit_2.Func_2;
21943 @code{Unit_2} is exactly parallel,
21944 it has a procedure @code{Func_2} that references
21945 the variable @code{Sqrt_2}, which is declared in the elaboration code of
21946 the body @code{Unit_2}:
21948 @smallexample @c ada
21950 Sqrt_2 : Float := Sqrt (0.1);
21955 The elaboration code of the body of @code{Unit_2} also contains:
21957 @smallexample @c ada
21960 if expression_2 = 2 then
21961 Q := Unit_1.Func_1;
21968 Now the question is, which of the following orders of elaboration is
21993 If you carefully analyze the flow here, you will see that you cannot tell
21994 at compile time the answer to this question.
21995 If @code{expression_1} is not equal to 1,
21996 and @code{expression_2} is not equal to 2,
21997 then either order is acceptable, because neither of the function calls is
21998 executed. If both tests evaluate to true, then neither order is acceptable
21999 and in fact there is no correct order.
22001 If one of the two expressions is true, and the other is false, then one
22002 of the above orders is correct, and the other is incorrect. For example,
22003 if @code{expression_1} = 1 and @code{expression_2} /= 2,
22004 then the call to @code{Func_2}
22005 will occur, but not the call to @code{Func_1.}
22006 This means that it is essential
22007 to elaborate the body of @code{Unit_1} before
22008 the body of @code{Unit_2}, so the first
22009 order of elaboration is correct and the second is wrong.
22011 By making @code{expression_1} and @code{expression_2}
22012 depend on input data, or perhaps
22013 the time of day, we can make it impossible for the compiler or binder
22014 to figure out which of these expressions will be true, and hence it
22015 is impossible to guarantee a safe order of elaboration at run time.
22017 @node Checking the Elaboration Order in Ada 95
22018 @section Checking the Elaboration Order in Ada 95
22021 In some languages that involve the same kind of elaboration problems,
22022 e.g. Java and C++, the programmer is expected to worry about these
22023 ordering problems himself, and it is common to
22024 write a program in which an incorrect elaboration order gives
22025 surprising results, because it references variables before they
22027 Ada 95 is designed to be a safe language, and a programmer-beware approach is
22028 clearly not sufficient. Consequently, the language provides three lines
22032 @item Standard rules
22033 Some standard rules restrict the possible choice of elaboration
22034 order. In particular, if you @code{with} a unit, then its spec is always
22035 elaborated before the unit doing the @code{with}. Similarly, a parent
22036 spec is always elaborated before the child spec, and finally
22037 a spec is always elaborated before its corresponding body.
22039 @item Dynamic elaboration checks
22040 @cindex Elaboration checks
22041 @cindex Checks, elaboration
22042 Dynamic checks are made at run time, so that if some entity is accessed
22043 before it is elaborated (typically by means of a subprogram call)
22044 then the exception (@code{Program_Error}) is raised.
22046 @item Elaboration control
22047 Facilities are provided for the programmer to specify the desired order
22051 Let's look at these facilities in more detail. First, the rules for
22052 dynamic checking. One possible rule would be simply to say that the
22053 exception is raised if you access a variable which has not yet been
22054 elaborated. The trouble with this approach is that it could require
22055 expensive checks on every variable reference. Instead Ada 95 has two
22056 rules which are a little more restrictive, but easier to check, and
22060 @item Restrictions on calls
22061 A subprogram can only be called at elaboration time if its body
22062 has been elaborated. The rules for elaboration given above guarantee
22063 that the spec of the subprogram has been elaborated before the
22064 call, but not the body. If this rule is violated, then the
22065 exception @code{Program_Error} is raised.
22067 @item Restrictions on instantiations
22068 A generic unit can only be instantiated if the body of the generic
22069 unit has been elaborated. Again, the rules for elaboration given above
22070 guarantee that the spec of the generic unit has been elaborated
22071 before the instantiation, but not the body. If this rule is
22072 violated, then the exception @code{Program_Error} is raised.
22076 The idea is that if the body has been elaborated, then any variables
22077 it references must have been elaborated; by checking for the body being
22078 elaborated we guarantee that none of its references causes any
22079 trouble. As we noted above, this is a little too restrictive, because a
22080 subprogram that has no non-local references in its body may in fact be safe
22081 to call. However, it really would be unsafe to rely on this, because
22082 it would mean that the caller was aware of details of the implementation
22083 in the body. This goes against the basic tenets of Ada.
22085 A plausible implementation can be described as follows.
22086 A Boolean variable is associated with each subprogram
22087 and each generic unit. This variable is initialized to False, and is set to
22088 True at the point body is elaborated. Every call or instantiation checks the
22089 variable, and raises @code{Program_Error} if the variable is False.
22091 Note that one might think that it would be good enough to have one Boolean
22092 variable for each package, but that would not deal with cases of trying
22093 to call a body in the same package as the call
22094 that has not been elaborated yet.
22095 Of course a compiler may be able to do enough analysis to optimize away
22096 some of the Boolean variables as unnecessary, and @code{GNAT} indeed
22097 does such optimizations, but still the easiest conceptual model is to
22098 think of there being one variable per subprogram.
22100 @node Controlling the Elaboration Order in Ada 95
22101 @section Controlling the Elaboration Order in Ada 95
22104 In the previous section we discussed the rules in Ada 95 which ensure
22105 that @code{Program_Error} is raised if an incorrect elaboration order is
22106 chosen. This prevents erroneous executions, but we need mechanisms to
22107 specify a correct execution and avoid the exception altogether.
22108 To achieve this, Ada 95 provides a number of features for controlling
22109 the order of elaboration. We discuss these features in this section.
22111 First, there are several ways of indicating to the compiler that a given
22112 unit has no elaboration problems:
22115 @item packages that do not require a body
22116 In Ada 95, a library package that does not require a body does not permit
22117 a body. This means that if we have a such a package, as in:
22119 @smallexample @c ada
22122 package Definitions is
22124 type m is new integer;
22126 type a is array (1 .. 10) of m;
22127 type b is array (1 .. 20) of m;
22135 A package that @code{with}'s @code{Definitions} may safely instantiate
22136 @code{Definitions.Subp} because the compiler can determine that there
22137 definitely is no package body to worry about in this case
22140 @cindex pragma Pure
22142 Places sufficient restrictions on a unit to guarantee that
22143 no call to any subprogram in the unit can result in an
22144 elaboration problem. This means that the compiler does not need
22145 to worry about the point of elaboration of such units, and in
22146 particular, does not need to check any calls to any subprograms
22149 @item pragma Preelaborate
22150 @findex Preelaborate
22151 @cindex pragma Preelaborate
22152 This pragma places slightly less stringent restrictions on a unit than
22154 but these restrictions are still sufficient to ensure that there
22155 are no elaboration problems with any calls to the unit.
22157 @item pragma Elaborate_Body
22158 @findex Elaborate_Body
22159 @cindex pragma Elaborate_Body
22160 This pragma requires that the body of a unit be elaborated immediately
22161 after its spec. Suppose a unit @code{A} has such a pragma,
22162 and unit @code{B} does
22163 a @code{with} of unit @code{A}. Recall that the standard rules require
22164 the spec of unit @code{A}
22165 to be elaborated before the @code{with}'ing unit; given the pragma in
22166 @code{A}, we also know that the body of @code{A}
22167 will be elaborated before @code{B}, so
22168 that calls to @code{A} are safe and do not need a check.
22173 unlike pragma @code{Pure} and pragma @code{Preelaborate},
22175 @code{Elaborate_Body} does not guarantee that the program is
22176 free of elaboration problems, because it may not be possible
22177 to satisfy the requested elaboration order.
22178 Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
22180 marks @code{Unit_1} as @code{Elaborate_Body},
22181 and not @code{Unit_2,} then the order of
22182 elaboration will be:
22194 Now that means that the call to @code{Func_1} in @code{Unit_2}
22195 need not be checked,
22196 it must be safe. But the call to @code{Func_2} in
22197 @code{Unit_1} may still fail if
22198 @code{Expression_1} is equal to 1,
22199 and the programmer must still take
22200 responsibility for this not being the case.
22202 If all units carry a pragma @code{Elaborate_Body}, then all problems are
22203 eliminated, except for calls entirely within a body, which are
22204 in any case fully under programmer control. However, using the pragma
22205 everywhere is not always possible.
22206 In particular, for our @code{Unit_1}/@code{Unit_2} example, if
22207 we marked both of them as having pragma @code{Elaborate_Body}, then
22208 clearly there would be no possible elaboration order.
22210 The above pragmas allow a server to guarantee safe use by clients, and
22211 clearly this is the preferable approach. Consequently a good rule in
22212 Ada 95 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
22213 and if this is not possible,
22214 mark them as @code{Elaborate_Body} if possible.
22215 As we have seen, there are situations where neither of these
22216 three pragmas can be used.
22217 So we also provide methods for clients to control the
22218 order of elaboration of the servers on which they depend:
22221 @item pragma Elaborate (unit)
22223 @cindex pragma Elaborate
22224 This pragma is placed in the context clause, after a @code{with} clause,
22225 and it requires that the body of the named unit be elaborated before
22226 the unit in which the pragma occurs. The idea is to use this pragma
22227 if the current unit calls at elaboration time, directly or indirectly,
22228 some subprogram in the named unit.
22230 @item pragma Elaborate_All (unit)
22231 @findex Elaborate_All
22232 @cindex pragma Elaborate_All
22233 This is a stronger version of the Elaborate pragma. Consider the
22237 Unit A @code{with}'s unit B and calls B.Func in elab code
22238 Unit B @code{with}'s unit C, and B.Func calls C.Func
22242 Now if we put a pragma @code{Elaborate (B)}
22243 in unit @code{A}, this ensures that the
22244 body of @code{B} is elaborated before the call, but not the
22245 body of @code{C}, so
22246 the call to @code{C.Func} could still cause @code{Program_Error} to
22249 The effect of a pragma @code{Elaborate_All} is stronger, it requires
22250 not only that the body of the named unit be elaborated before the
22251 unit doing the @code{with}, but also the bodies of all units that the
22252 named unit uses, following @code{with} links transitively. For example,
22253 if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
22255 not only that the body of @code{B} be elaborated before @code{A},
22257 body of @code{C}, because @code{B} @code{with}'s @code{C}.
22261 We are now in a position to give a usage rule in Ada 95 for avoiding
22262 elaboration problems, at least if dynamic dispatching and access to
22263 subprogram values are not used. We will handle these cases separately
22266 The rule is simple. If a unit has elaboration code that can directly or
22267 indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
22268 a generic unit in a @code{with}'ed unit,
22269 then if the @code{with}'ed unit does not have
22270 pragma @code{Pure} or @code{Preelaborate}, then the client should have
22271 a pragma @code{Elaborate_All}
22272 for the @code{with}'ed unit. By following this rule a client is
22273 assured that calls can be made without risk of an exception.
22274 If this rule is not followed, then a program may be in one of four
22278 @item No order exists
22279 No order of elaboration exists which follows the rules, taking into
22280 account any @code{Elaborate}, @code{Elaborate_All},
22281 or @code{Elaborate_Body} pragmas. In
22282 this case, an Ada 95 compiler must diagnose the situation at bind
22283 time, and refuse to build an executable program.
22285 @item One or more orders exist, all incorrect
22286 One or more acceptable elaboration orders exists, and all of them
22287 generate an elaboration order problem. In this case, the binder
22288 can build an executable program, but @code{Program_Error} will be raised
22289 when the program is run.
22291 @item Several orders exist, some right, some incorrect
22292 One or more acceptable elaboration orders exists, and some of them
22293 work, and some do not. The programmer has not controlled
22294 the order of elaboration, so the binder may or may not pick one of
22295 the correct orders, and the program may or may not raise an
22296 exception when it is run. This is the worst case, because it means
22297 that the program may fail when moved to another compiler, or even
22298 another version of the same compiler.
22300 @item One or more orders exists, all correct
22301 One ore more acceptable elaboration orders exist, and all of them
22302 work. In this case the program runs successfully. This state of
22303 affairs can be guaranteed by following the rule we gave above, but
22304 may be true even if the rule is not followed.
22308 Note that one additional advantage of following our Elaborate_All rule
22309 is that the program continues to stay in the ideal (all orders OK) state
22310 even if maintenance
22311 changes some bodies of some subprograms. Conversely, if a program that does
22312 not follow this rule happens to be safe at some point, this state of affairs
22313 may deteriorate silently as a result of maintenance changes.
22315 You may have noticed that the above discussion did not mention
22316 the use of @code{Elaborate_Body}. This was a deliberate omission. If you
22317 @code{with} an @code{Elaborate_Body} unit, it still may be the case that
22318 code in the body makes calls to some other unit, so it is still necessary
22319 to use @code{Elaborate_All} on such units.
22321 @node Controlling Elaboration in GNAT - Internal Calls
22322 @section Controlling Elaboration in GNAT - Internal Calls
22325 In the case of internal calls, i.e. calls within a single package, the
22326 programmer has full control over the order of elaboration, and it is up
22327 to the programmer to elaborate declarations in an appropriate order. For
22330 @smallexample @c ada
22333 function One return Float;
22337 function One return Float is
22346 will obviously raise @code{Program_Error} at run time, because function
22347 One will be called before its body is elaborated. In this case GNAT will
22348 generate a warning that the call will raise @code{Program_Error}:
22354 2. function One return Float;
22356 4. Q : Float := One;
22358 >>> warning: cannot call "One" before body is elaborated
22359 >>> warning: Program_Error will be raised at run time
22362 6. function One return Float is
22375 Note that in this particular case, it is likely that the call is safe, because
22376 the function @code{One} does not access any global variables.
22377 Nevertheless in Ada 95, we do not want the validity of the check to depend on
22378 the contents of the body (think about the separate compilation case), so this
22379 is still wrong, as we discussed in the previous sections.
22381 The error is easily corrected by rearranging the declarations so that the
22382 body of One appears before the declaration containing the call
22383 (note that in Ada 95,
22384 declarations can appear in any order, so there is no restriction that
22385 would prevent this reordering, and if we write:
22387 @smallexample @c ada
22390 function One return Float;
22392 function One return Float is
22403 then all is well, no warning is generated, and no
22404 @code{Program_Error} exception
22406 Things are more complicated when a chain of subprograms is executed:
22408 @smallexample @c ada
22411 function A return Integer;
22412 function B return Integer;
22413 function C return Integer;
22415 function B return Integer is begin return A; end;
22416 function C return Integer is begin return B; end;
22420 function A return Integer is begin return 1; end;
22426 Now the call to @code{C}
22427 at elaboration time in the declaration of @code{X} is correct, because
22428 the body of @code{C} is already elaborated,
22429 and the call to @code{B} within the body of
22430 @code{C} is correct, but the call
22431 to @code{A} within the body of @code{B} is incorrect, because the body
22432 of @code{A} has not been elaborated, so @code{Program_Error}
22433 will be raised on the call to @code{A}.
22434 In this case GNAT will generate a
22435 warning that @code{Program_Error} may be
22436 raised at the point of the call. Let's look at the warning:
22442 2. function A return Integer;
22443 3. function B return Integer;
22444 4. function C return Integer;
22446 6. function B return Integer is begin return A; end;
22448 >>> warning: call to "A" before body is elaborated may
22449 raise Program_Error
22450 >>> warning: "B" called at line 7
22451 >>> warning: "C" called at line 9
22453 7. function C return Integer is begin return B; end;
22455 9. X : Integer := C;
22457 11. function A return Integer is begin return 1; end;
22467 Note that the message here says ``may raise'', instead of the direct case,
22468 where the message says ``will be raised''. That's because whether
22470 actually called depends in general on run-time flow of control.
22471 For example, if the body of @code{B} said
22473 @smallexample @c ada
22476 function B return Integer is
22478 if some-condition-depending-on-input-data then
22489 then we could not know until run time whether the incorrect call to A would
22490 actually occur, so @code{Program_Error} might
22491 or might not be raised. It is possible for a compiler to
22492 do a better job of analyzing bodies, to
22493 determine whether or not @code{Program_Error}
22494 might be raised, but it certainly
22495 couldn't do a perfect job (that would require solving the halting problem
22496 and is provably impossible), and because this is a warning anyway, it does
22497 not seem worth the effort to do the analysis. Cases in which it
22498 would be relevant are rare.
22500 In practice, warnings of either of the forms given
22501 above will usually correspond to
22502 real errors, and should be examined carefully and eliminated.
22503 In the rare case where a warning is bogus, it can be suppressed by any of
22504 the following methods:
22508 Compile with the @option{-gnatws} switch set
22511 Suppress @code{Elaboration_Check} for the called subprogram
22514 Use pragma @code{Warnings_Off} to turn warnings off for the call
22518 For the internal elaboration check case,
22519 GNAT by default generates the
22520 necessary run-time checks to ensure
22521 that @code{Program_Error} is raised if any
22522 call fails an elaboration check. Of course this can only happen if a
22523 warning has been issued as described above. The use of pragma
22524 @code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress
22525 some of these checks, meaning that it may be possible (but is not
22526 guaranteed) for a program to be able to call a subprogram whose body
22527 is not yet elaborated, without raising a @code{Program_Error} exception.
22529 @node Controlling Elaboration in GNAT - External Calls
22530 @section Controlling Elaboration in GNAT - External Calls
22533 The previous section discussed the case in which the execution of a
22534 particular thread of elaboration code occurred entirely within a
22535 single unit. This is the easy case to handle, because a programmer
22536 has direct and total control over the order of elaboration, and
22537 furthermore, checks need only be generated in cases which are rare
22538 and which the compiler can easily detect.
22539 The situation is more complex when separate compilation is taken into account.
22540 Consider the following:
22542 @smallexample @c ada
22546 function Sqrt (Arg : Float) return Float;
22549 package body Math is
22550 function Sqrt (Arg : Float) return Float is
22559 X : Float := Math.Sqrt (0.5);
22572 where @code{Main} is the main program. When this program is executed, the
22573 elaboration code must first be executed, and one of the jobs of the
22574 binder is to determine the order in which the units of a program are
22575 to be elaborated. In this case we have four units: the spec and body
22577 the spec of @code{Stuff} and the body of @code{Main}).
22578 In what order should the four separate sections of elaboration code
22581 There are some restrictions in the order of elaboration that the binder
22582 can choose. In particular, if unit U has a @code{with}
22583 for a package @code{X}, then you
22584 are assured that the spec of @code{X}
22585 is elaborated before U , but you are
22586 not assured that the body of @code{X}
22587 is elaborated before U.
22588 This means that in the above case, the binder is allowed to choose the
22599 but that's not good, because now the call to @code{Math.Sqrt}
22600 that happens during
22601 the elaboration of the @code{Stuff}
22602 spec happens before the body of @code{Math.Sqrt} is
22603 elaborated, and hence causes @code{Program_Error} exception to be raised.
22604 At first glance, one might say that the binder is misbehaving, because
22605 obviously you want to elaborate the body of something you @code{with}
22607 that is not a general rule that can be followed in all cases. Consider
22609 @smallexample @c ada
22617 package body Y is ...
22620 package body X is ...
22626 This is a common arrangement, and, apart from the order of elaboration
22627 problems that might arise in connection with elaboration code, this works fine.
22628 A rule that says that you must first elaborate the body of anything you
22629 @code{with} cannot work in this case:
22630 the body of @code{X} @code{with}'s @code{Y},
22631 which means you would have to
22632 elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
22634 you have to elaborate the body of @code{X} first, but ... and we have a
22635 loop that cannot be broken.
22637 It is true that the binder can in many cases guess an order of elaboration
22638 that is unlikely to cause a @code{Program_Error}
22639 exception to be raised, and it tries to do so (in the
22640 above example of @code{Math/Stuff/Spec}, the GNAT binder will
22642 elaborate the body of @code{Math} right after its spec, so all will be well).
22644 However, a program that blindly relies on the binder to be helpful can
22645 get into trouble, as we discussed in the previous sections, so
22647 provides a number of facilities for assisting the programmer in
22648 developing programs that are robust with respect to elaboration order.
22650 @node Default Behavior in GNAT - Ensuring Safety
22651 @section Default Behavior in GNAT - Ensuring Safety
22654 The default behavior in GNAT ensures elaboration safety. In its
22655 default mode GNAT implements the
22656 rule we previously described as the right approach. Let's restate it:
22660 @emph{If a unit has elaboration code that can directly or indirectly make a
22661 call to a subprogram in a @code{with}'ed unit, or instantiate a generic unit
22662 in a @code{with}'ed unit, then if the @code{with}'ed unit
22663 does not have pragma @code{Pure} or
22664 @code{Preelaborate}, then the client should have an
22665 @code{Elaborate_All} for the @code{with}'ed unit.}
22669 By following this rule a client is assured that calls and instantiations
22670 can be made without risk of an exception.
22672 In this mode GNAT traces all calls that are potentially made from
22673 elaboration code, and puts in any missing implicit @code{Elaborate_All}
22675 The advantage of this approach is that no elaboration problems
22676 are possible if the binder can find an elaboration order that is
22677 consistent with these implicit @code{Elaborate_All} pragmas. The
22678 disadvantage of this approach is that no such order may exist.
22680 If the binder does not generate any diagnostics, then it means that it
22681 has found an elaboration order that is guaranteed to be safe. However,
22682 the binder may still be relying on implicitly generated
22683 @code{Elaborate_All} pragmas so portability to other compilers than
22684 GNAT is not guaranteed.
22686 If it is important to guarantee portability, then the compilations should
22689 (warn on elaboration problems) switch. This will cause warning messages
22690 to be generated indicating the missing @code{Elaborate_All} pragmas.
22691 Consider the following source program:
22693 @smallexample @c ada
22698 m : integer := k.r;
22705 where it is clear that there
22706 should be a pragma @code{Elaborate_All}
22707 for unit @code{k}. An implicit pragma will be generated, and it is
22708 likely that the binder will be able to honor it. However, if you want
22709 to port this program to some other Ada compiler than GNAT.
22710 it is safer to include the pragma explicitly in the source. If this
22711 unit is compiled with the
22713 switch, then the compiler outputs a warning:
22720 3. m : integer := k.r;
22722 >>> warning: call to "r" may raise Program_Error
22723 >>> warning: missing pragma Elaborate_All for "k"
22731 and these warnings can be used as a guide for supplying manually
22732 the missing pragmas. It is usually a bad idea to use this warning
22733 option during development. That's because it will warn you when
22734 you need to put in a pragma, but cannot warn you when it is time
22735 to take it out. So the use of pragma Elaborate_All may lead to
22736 unnecessary dependencies and even false circularities.
22738 This default mode is more restrictive than the Ada Reference
22739 Manual, and it is possible to construct programs which will compile
22740 using the dynamic model described there, but will run into a
22741 circularity using the safer static model we have described.
22743 Of course any Ada compiler must be able to operate in a mode
22744 consistent with the requirements of the Ada Reference Manual,
22745 and in particular must have the capability of implementing the
22746 standard dynamic model of elaboration with run-time checks.
22748 In GNAT, this standard mode can be achieved either by the use of
22749 the @option{-gnatE} switch on the compiler (@code{gcc} or @code{gnatmake})
22750 command, or by the use of the configuration pragma:
22752 @smallexample @c ada
22753 pragma Elaboration_Checks (RM);
22757 Either approach will cause the unit affected to be compiled using the
22758 standard dynamic run-time elaboration checks described in the Ada
22759 Reference Manual. The static model is generally preferable, since it
22760 is clearly safer to rely on compile and link time checks rather than
22761 run-time checks. However, in the case of legacy code, it may be
22762 difficult to meet the requirements of the static model. This
22763 issue is further discussed in
22764 @ref{What to Do If the Default Elaboration Behavior Fails}.
22766 Note that the static model provides a strict subset of the allowed
22767 behavior and programs of the Ada Reference Manual, so if you do
22768 adhere to the static model and no circularities exist,
22769 then you are assured that your program will
22770 work using the dynamic model, providing that you remove any
22771 pragma Elaborate statements from the source.
22773 @node Treatment of Pragma Elaborate
22774 @section Treatment of Pragma Elaborate
22775 @cindex Pragma Elaborate
22778 The use of @code{pragma Elaborate}
22779 should generally be avoided in Ada 95 programs.
22780 The reason for this is that there is no guarantee that transitive calls
22781 will be properly handled. Indeed at one point, this pragma was placed
22782 in Annex J (Obsolescent Features), on the grounds that it is never useful.
22784 Now that's a bit restrictive. In practice, the case in which
22785 @code{pragma Elaborate} is useful is when the caller knows that there
22786 are no transitive calls, or that the called unit contains all necessary
22787 transitive @code{pragma Elaborate} statements, and legacy code often
22788 contains such uses.
22790 Strictly speaking the static mode in GNAT should ignore such pragmas,
22791 since there is no assurance at compile time that the necessary safety
22792 conditions are met. In practice, this would cause GNAT to be incompatible
22793 with correctly written Ada 83 code that had all necessary
22794 @code{pragma Elaborate} statements in place. Consequently, we made the
22795 decision that GNAT in its default mode will believe that if it encounters
22796 a @code{pragma Elaborate} then the programmer knows what they are doing,
22797 and it will trust that no elaboration errors can occur.
22799 The result of this decision is two-fold. First to be safe using the
22800 static mode, you should remove all @code{pragma Elaborate} statements.
22801 Second, when fixing circularities in existing code, you can selectively
22802 use @code{pragma Elaborate} statements to convince the static mode of
22803 GNAT that it need not generate an implicit @code{pragma Elaborate_All}
22806 When using the static mode with @option{-gnatwl}, any use of
22807 @code{pragma Elaborate} will generate a warning about possible
22810 @node Elaboration Issues for Library Tasks
22811 @section Elaboration Issues for Library Tasks
22812 @cindex Library tasks, elaboration issues
22813 @cindex Elaboration of library tasks
22816 In this section we examine special elaboration issues that arise for
22817 programs that declare library level tasks.
22819 Generally the model of execution of an Ada program is that all units are
22820 elaborated, and then execution of the program starts. However, the
22821 declaration of library tasks definitely does not fit this model. The
22822 reason for this is that library tasks start as soon as they are declared
22823 (more precisely, as soon as the statement part of the enclosing package
22824 body is reached), that is to say before elaboration
22825 of the program is complete. This means that if such a task calls a
22826 subprogram, or an entry in another task, the callee may or may not be
22827 elaborated yet, and in the standard
22828 Reference Manual model of dynamic elaboration checks, you can even
22829 get timing dependent Program_Error exceptions, since there can be
22830 a race between the elaboration code and the task code.
22832 The static model of elaboration in GNAT seeks to avoid all such
22833 dynamic behavior, by being conservative, and the conservative
22834 approach in this particular case is to assume that all the code
22835 in a task body is potentially executed at elaboration time if
22836 a task is declared at the library level.
22838 This can definitely result in unexpected circularities. Consider
22839 the following example
22841 @smallexample @c ada
22847 type My_Int is new Integer;
22849 function Ident (M : My_Int) return My_Int;
22853 package body Decls is
22854 task body Lib_Task is
22860 function Ident (M : My_Int) return My_Int is
22868 procedure Put_Val (Arg : Decls.My_Int);
22872 package body Utils is
22873 procedure Put_Val (Arg : Decls.My_Int) is
22875 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
22882 Decls.Lib_Task.Start;
22887 If the above example is compiled in the default static elaboration
22888 mode, then a circularity occurs. The circularity comes from the call
22889 @code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
22890 this call occurs in elaboration code, we need an implicit pragma
22891 @code{Elaborate_All} for @code{Utils}. This means that not only must
22892 the spec and body of @code{Utils} be elaborated before the body
22893 of @code{Decls}, but also the spec and body of any unit that is
22894 @code{with'ed} by the body of @code{Utils} must also be elaborated before
22895 the body of @code{Decls}. This is the transitive implication of
22896 pragma @code{Elaborate_All} and it makes sense, because in general
22897 the body of @code{Put_Val} might have a call to something in a
22898 @code{with'ed} unit.
22900 In this case, the body of Utils (actually its spec) @code{with's}
22901 @code{Decls}. Unfortunately this means that the body of @code{Decls}
22902 must be elaborated before itself, in case there is a call from the
22903 body of @code{Utils}.
22905 Here is the exact chain of events we are worrying about:
22909 In the body of @code{Decls} a call is made from within the body of a library
22910 task to a subprogram in the package @code{Utils}. Since this call may
22911 occur at elaboration time (given that the task is activated at elaboration
22912 time), we have to assume the worst, i.e. that the
22913 call does happen at elaboration time.
22916 This means that the body and spec of @code{Util} must be elaborated before
22917 the body of @code{Decls} so that this call does not cause an access before
22921 Within the body of @code{Util}, specifically within the body of
22922 @code{Util.Put_Val} there may be calls to any unit @code{with}'ed
22926 One such @code{with}'ed package is package @code{Decls}, so there
22927 might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
22928 In fact there is such a call in this example, but we would have to
22929 assume that there was such a call even if it were not there, since
22930 we are not supposed to write the body of @code{Decls} knowing what
22931 is in the body of @code{Utils}; certainly in the case of the
22932 static elaboration model, the compiler does not know what is in
22933 other bodies and must assume the worst.
22936 This means that the spec and body of @code{Decls} must also be
22937 elaborated before we elaborate the unit containing the call, but
22938 that unit is @code{Decls}! This means that the body of @code{Decls}
22939 must be elaborated before itself, and that's a circularity.
22943 Indeed, if you add an explicit pragma Elaborate_All for @code{Utils} in
22944 the body of @code{Decls} you will get a true Ada Reference Manual
22945 circularity that makes the program illegal.
22947 In practice, we have found that problems with the static model of
22948 elaboration in existing code often arise from library tasks, so
22949 we must address this particular situation.
22951 Note that if we compile and run the program above, using the dynamic model of
22952 elaboration (that is to say use the @option{-gnatE} switch),
22953 then it compiles, binds,
22954 links, and runs, printing the expected result of 2. Therefore in some sense
22955 the circularity here is only apparent, and we need to capture
22956 the properties of this program that distinguish it from other library-level
22957 tasks that have real elaboration problems.
22959 We have four possible answers to this question:
22964 Use the dynamic model of elaboration.
22966 If we use the @option{-gnatE} switch, then as noted above, the program works.
22967 Why is this? If we examine the task body, it is apparent that the task cannot
22969 @code{accept} statement until after elaboration has been completed, because
22970 the corresponding entry call comes from the main program, not earlier.
22971 This is why the dynamic model works here. But that's really giving
22972 up on a precise analysis, and we prefer to take this approach only if we cannot
22974 problem in any other manner. So let us examine two ways to reorganize
22975 the program to avoid the potential elaboration problem.
22978 Split library tasks into separate packages.
22980 Write separate packages, so that library tasks are isolated from
22981 other declarations as much as possible. Let us look at a variation on
22984 @smallexample @c ada
22992 package body Decls1 is
22993 task body Lib_Task is
23001 type My_Int is new Integer;
23002 function Ident (M : My_Int) return My_Int;
23006 package body Decls2 is
23007 function Ident (M : My_Int) return My_Int is
23015 procedure Put_Val (Arg : Decls2.My_Int);
23019 package body Utils is
23020 procedure Put_Val (Arg : Decls2.My_Int) is
23022 Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
23029 Decls1.Lib_Task.Start;
23034 All we have done is to split @code{Decls} into two packages, one
23035 containing the library task, and one containing everything else. Now
23036 there is no cycle, and the program compiles, binds, links and executes
23037 using the default static model of elaboration.
23040 Declare separate task types.
23042 A significant part of the problem arises because of the use of the
23043 single task declaration form. This means that the elaboration of
23044 the task type, and the elaboration of the task itself (i.e. the
23045 creation of the task) happen at the same time. A good rule
23046 of style in Ada 95 is to always create explicit task types. By
23047 following the additional step of placing task objects in separate
23048 packages from the task type declaration, many elaboration problems
23049 are avoided. Here is another modified example of the example program:
23051 @smallexample @c ada
23053 task type Lib_Task_Type is
23057 type My_Int is new Integer;
23059 function Ident (M : My_Int) return My_Int;
23063 package body Decls is
23064 task body Lib_Task_Type is
23070 function Ident (M : My_Int) return My_Int is
23078 procedure Put_Val (Arg : Decls.My_Int);
23082 package body Utils is
23083 procedure Put_Val (Arg : Decls.My_Int) is
23085 Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
23091 Lib_Task : Decls.Lib_Task_Type;
23097 Declst.Lib_Task.Start;
23102 What we have done here is to replace the @code{task} declaration in
23103 package @code{Decls} with a @code{task type} declaration. Then we
23104 introduce a separate package @code{Declst} to contain the actual
23105 task object. This separates the elaboration issues for
23106 the @code{task type}
23107 declaration, which causes no trouble, from the elaboration issues
23108 of the task object, which is also unproblematic, since it is now independent
23109 of the elaboration of @code{Utils}.
23110 This separation of concerns also corresponds to
23111 a generally sound engineering principle of separating declarations
23112 from instances. This version of the program also compiles, binds, links,
23113 and executes, generating the expected output.
23116 Use No_Entry_Calls_In_Elaboration_Code restriction.
23117 @cindex No_Entry_Calls_In_Elaboration_Code
23119 The previous two approaches described how a program can be restructured
23120 to avoid the special problems caused by library task bodies. in practice,
23121 however, such restructuring may be difficult to apply to existing legacy code,
23122 so we must consider solutions that do not require massive rewriting.
23124 Let us consider more carefully why our original sample program works
23125 under the dynamic model of elaboration. The reason is that the code
23126 in the task body blocks immediately on the @code{accept}
23127 statement. Now of course there is nothing to prohibit elaboration
23128 code from making entry calls (for example from another library level task),
23129 so we cannot tell in isolation that
23130 the task will not execute the accept statement during elaboration.
23132 However, in practice it is very unusual to see elaboration code
23133 make any entry calls, and the pattern of tasks starting
23134 at elaboration time and then immediately blocking on @code{accept} or
23135 @code{select} statements is very common. What this means is that
23136 the compiler is being too pessimistic when it analyzes the
23137 whole package body as though it might be executed at elaboration
23140 If we know that the elaboration code contains no entry calls, (a very safe
23141 assumption most of the time, that could almost be made the default
23142 behavior), then we can compile all units of the program under control
23143 of the following configuration pragma:
23146 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
23150 This pragma can be placed in the @file{gnat.adc} file in the usual
23151 manner. If we take our original unmodified program and compile it
23152 in the presence of a @file{gnat.adc} containing the above pragma,
23153 then once again, we can compile, bind, link, and execute, obtaining
23154 the expected result. In the presence of this pragma, the compiler does
23155 not trace calls in a task body, that appear after the first @code{accept}
23156 or @code{select} statement, and therefore does not report a potential
23157 circularity in the original program.
23159 The compiler will check to the extent it can that the above
23160 restriction is not violated, but it is not always possible to do a
23161 complete check at compile time, so it is important to use this
23162 pragma only if the stated restriction is in fact met, that is to say
23163 no task receives an entry call before elaboration of all units is completed.
23167 @node Mixing Elaboration Models
23168 @section Mixing Elaboration Models
23170 So far, we have assumed that the entire program is either compiled
23171 using the dynamic model or static model, ensuring consistency. It
23172 is possible to mix the two models, but rules have to be followed
23173 if this mixing is done to ensure that elaboration checks are not
23176 The basic rule is that @emph{a unit compiled with the static model cannot
23177 be @code{with'ed} by a unit compiled with the dynamic model}. The
23178 reason for this is that in the static model, a unit assumes that
23179 its clients guarantee to use (the equivalent of) pragma
23180 @code{Elaborate_All} so that no elaboration checks are required
23181 in inner subprograms, and this assumption is violated if the
23182 client is compiled with dynamic checks.
23184 The precise rule is as follows. A unit that is compiled with dynamic
23185 checks can only @code{with} a unit that meets at least one of the
23186 following criteria:
23191 The @code{with'ed} unit is itself compiled with dynamic elaboration
23192 checks (that is with the @option{-gnatE} switch.
23195 The @code{with'ed} unit is an internal GNAT implementation unit from
23196 the System, Interfaces, Ada, or GNAT hierarchies.
23199 The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
23202 The @code{with'ing} unit (that is the client) has an explicit pragma
23203 @code{Elaborate_All} for the @code{with'ed} unit.
23208 If this rule is violated, that is if a unit with dynamic elaboration
23209 checks @code{with's} a unit that does not meet one of the above four
23210 criteria, then the binder (@code{gnatbind}) will issue a warning
23211 similar to that in the following example:
23214 warning: "x.ads" has dynamic elaboration checks and with's
23215 warning: "y.ads" which has static elaboration checks
23219 These warnings indicate that the rule has been violated, and that as a result
23220 elaboration checks may be missed in the resulting executable file.
23221 This warning may be suppressed using the @option{-ws} binder switch
23222 in the usual manner.
23224 One useful application of this mixing rule is in the case of a subsystem
23225 which does not itself @code{with} units from the remainder of the
23226 application. In this case, the entire subsystem can be compiled with
23227 dynamic checks to resolve a circularity in the subsystem, while
23228 allowing the main application that uses this subsystem to be compiled
23229 using the more reliable default static model.
23231 @node What to Do If the Default Elaboration Behavior Fails
23232 @section What to Do If the Default Elaboration Behavior Fails
23235 If the binder cannot find an acceptable order, it outputs detailed
23236 diagnostics. For example:
23242 error: elaboration circularity detected
23243 info: "proc (body)" must be elaborated before "pack (body)"
23244 info: reason: Elaborate_All probably needed in unit "pack (body)"
23245 info: recompile "pack (body)" with -gnatwl
23246 info: for full details
23247 info: "proc (body)"
23248 info: is needed by its spec:
23249 info: "proc (spec)"
23250 info: which is withed by:
23251 info: "pack (body)"
23252 info: "pack (body)" must be elaborated before "proc (body)"
23253 info: reason: pragma Elaborate in unit "proc (body)"
23259 In this case we have a cycle that the binder cannot break. On the one
23260 hand, there is an explicit pragma Elaborate in @code{proc} for
23261 @code{pack}. This means that the body of @code{pack} must be elaborated
23262 before the body of @code{proc}. On the other hand, there is elaboration
23263 code in @code{pack} that calls a subprogram in @code{proc}. This means
23264 that for maximum safety, there should really be a pragma
23265 Elaborate_All in @code{pack} for @code{proc} which would require that
23266 the body of @code{proc} be elaborated before the body of
23267 @code{pack}. Clearly both requirements cannot be satisfied.
23268 Faced with a circularity of this kind, you have three different options.
23271 @item Fix the program
23272 The most desirable option from the point of view of long-term maintenance
23273 is to rearrange the program so that the elaboration problems are avoided.
23274 One useful technique is to place the elaboration code into separate
23275 child packages. Another is to move some of the initialization code to
23276 explicitly called subprograms, where the program controls the order
23277 of initialization explicitly. Although this is the most desirable option,
23278 it may be impractical and involve too much modification, especially in
23279 the case of complex legacy code.
23281 @item Perform dynamic checks
23282 If the compilations are done using the
23284 (dynamic elaboration check) switch, then GNAT behaves in
23285 a quite different manner. Dynamic checks are generated for all calls
23286 that could possibly result in raising an exception. With this switch,
23287 the compiler does not generate implicit @code{Elaborate_All} pragmas.
23288 The behavior then is exactly as specified in the Ada 95 Reference Manual.
23289 The binder will generate an executable program that may or may not
23290 raise @code{Program_Error}, and then it is the programmer's job to ensure
23291 that it does not raise an exception. Note that it is important to
23292 compile all units with the switch, it cannot be used selectively.
23294 @item Suppress checks
23295 The drawback of dynamic checks is that they generate a
23296 significant overhead at run time, both in space and time. If you
23297 are absolutely sure that your program cannot raise any elaboration
23298 exceptions, and you still want to use the dynamic elaboration model,
23299 then you can use the configuration pragma
23300 @code{Suppress (Elaboration_Check)} to suppress all such checks. For
23301 example this pragma could be placed in the @file{gnat.adc} file.
23303 @item Suppress checks selectively
23304 When you know that certain calls in elaboration code cannot possibly
23305 lead to an elaboration error, and the binder nevertheless generates warnings
23306 on those calls and inserts Elaborate_All pragmas that lead to elaboration
23307 circularities, it is possible to remove those warnings locally and obtain
23308 a program that will bind. Clearly this can be unsafe, and it is the
23309 responsibility of the programmer to make sure that the resulting program has
23310 no elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can
23311 be used with different granularity to suppress warnings and break
23312 elaboration circularities:
23316 Place the pragma that names the called subprogram in the declarative part
23317 that contains the call.
23320 Place the pragma in the declarative part, without naming an entity. This
23321 disables warnings on all calls in the corresponding declarative region.
23324 Place the pragma in the package spec that declares the called subprogram,
23325 and name the subprogram. This disables warnings on all elaboration calls to
23329 Place the pragma in the package spec that declares the called subprogram,
23330 without naming any entity. This disables warnings on all elaboration calls to
23331 all subprograms declared in this spec.
23333 @item Use Pragma Elaborate
23334 As previously described in section @xref{Treatment of Pragma Elaborate},
23335 GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly
23336 that no elaboration checks are required on calls to the designated unit.
23337 There may be cases in which the caller knows that no transitive calls
23338 can occur, so that a @code{pragma Elaborate} will be sufficient in a
23339 case where @code{pragma Elaborate_All} would cause a circularity.
23343 These five cases are listed in order of decreasing safety, and therefore
23344 require increasing programmer care in their application. Consider the
23347 @smallexample @c adanocomment
23349 function F1 return Integer;
23354 function F2 return Integer;
23355 function Pure (x : integer) return integer;
23356 -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
23357 -- pragma Suppress (Elaboration_Check); -- (4)
23361 package body Pack1 is
23362 function F1 return Integer is
23366 Val : integer := Pack2.Pure (11); -- Elab. call (1)
23369 -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
23370 -- pragma Suppress(Elaboration_Check); -- (2)
23372 X1 := Pack2.F2 + 1; -- Elab. call (2)
23377 package body Pack2 is
23378 function F2 return Integer is
23382 function Pure (x : integer) return integer is
23384 return x ** 3 - 3 * x;
23388 with Pack1, Ada.Text_IO;
23391 Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
23394 In the absence of any pragmas, an attempt to bind this program produces
23395 the following diagnostics:
23401 error: elaboration circularity detected
23402 info: "pack1 (body)" must be elaborated before "pack1 (body)"
23403 info: reason: Elaborate_All probably needed in unit "pack1 (body)"
23404 info: recompile "pack1 (body)" with -gnatwl for full details
23405 info: "pack1 (body)"
23406 info: must be elaborated along with its spec:
23407 info: "pack1 (spec)"
23408 info: which is withed by:
23409 info: "pack2 (body)"
23410 info: which must be elaborated along with its spec:
23411 info: "pack2 (spec)"
23412 info: which is withed by:
23413 info: "pack1 (body)"
23416 The sources of the circularity are the two calls to @code{Pack2.Pure} and
23417 @code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
23418 F2 is safe, even though F2 calls F1, because the call appears after the
23419 elaboration of the body of F1. Therefore the pragma (1) is safe, and will
23420 remove the warning on the call. It is also possible to use pragma (2)
23421 because there are no other potentially unsafe calls in the block.
23424 The call to @code{Pure} is safe because this function does not depend on the
23425 state of @code{Pack2}. Therefore any call to this function is safe, and it
23426 is correct to place pragma (3) in the corresponding package spec.
23429 Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
23430 warnings on all calls to functions declared therein. Note that this is not
23431 necessarily safe, and requires more detailed examination of the subprogram
23432 bodies involved. In particular, a call to @code{F2} requires that @code{F1}
23433 be already elaborated.
23437 It is hard to generalize on which of these four approaches should be
23438 taken. Obviously if it is possible to fix the program so that the default
23439 treatment works, this is preferable, but this may not always be practical.
23440 It is certainly simple enough to use
23442 but the danger in this case is that, even if the GNAT binder
23443 finds a correct elaboration order, it may not always do so,
23444 and certainly a binder from another Ada compiler might not. A
23445 combination of testing and analysis (for which the warnings generated
23448 switch can be useful) must be used to ensure that the program is free
23449 of errors. One switch that is useful in this testing is the
23450 @option{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
23453 Normally the binder tries to find an order that has the best chance of
23454 of avoiding elaboration problems. With this switch, the binder
23455 plays a devil's advocate role, and tries to choose the order that
23456 has the best chance of failing. If your program works even with this
23457 switch, then it has a better chance of being error free, but this is still
23460 For an example of this approach in action, consider the C-tests (executable
23461 tests) from the ACVC suite. If these are compiled and run with the default
23462 treatment, then all but one of them succeed without generating any error
23463 diagnostics from the binder. However, there is one test that fails, and
23464 this is not surprising, because the whole point of this test is to ensure
23465 that the compiler can handle cases where it is impossible to determine
23466 a correct order statically, and it checks that an exception is indeed
23467 raised at run time.
23469 This one test must be compiled and run using the
23471 switch, and then it passes. Alternatively, the entire suite can
23472 be run using this switch. It is never wrong to run with the dynamic
23473 elaboration switch if your code is correct, and we assume that the
23474 C-tests are indeed correct (it is less efficient, but efficiency is
23475 not a factor in running the ACVC tests.)
23477 @node Elaboration for Access-to-Subprogram Values
23478 @section Elaboration for Access-to-Subprogram Values
23479 @cindex Access-to-subprogram
23482 The introduction of access-to-subprogram types in Ada 95 complicates
23483 the handling of elaboration. The trouble is that it becomes
23484 impossible to tell at compile time which procedure
23485 is being called. This means that it is not possible for the binder
23486 to analyze the elaboration requirements in this case.
23488 If at the point at which the access value is created
23489 (i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
23490 the body of the subprogram is
23491 known to have been elaborated, then the access value is safe, and its use
23492 does not require a check. This may be achieved by appropriate arrangement
23493 of the order of declarations if the subprogram is in the current unit,
23494 or, if the subprogram is in another unit, by using pragma
23495 @code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
23496 on the referenced unit.
23498 If the referenced body is not known to have been elaborated at the point
23499 the access value is created, then any use of the access value must do a
23500 dynamic check, and this dynamic check will fail and raise a
23501 @code{Program_Error} exception if the body has not been elaborated yet.
23502 GNAT will generate the necessary checks, and in addition, if the
23504 switch is set, will generate warnings that such checks are required.
23506 The use of dynamic dispatching for tagged types similarly generates
23507 a requirement for dynamic checks, and premature calls to any primitive
23508 operation of a tagged type before the body of the operation has been
23509 elaborated, will result in the raising of @code{Program_Error}.
23511 @node Summary of Procedures for Elaboration Control
23512 @section Summary of Procedures for Elaboration Control
23513 @cindex Elaboration control
23516 First, compile your program with the default options, using none of
23517 the special elaboration control switches. If the binder successfully
23518 binds your program, then you can be confident that, apart from issues
23519 raised by the use of access-to-subprogram types and dynamic dispatching,
23520 the program is free of elaboration errors. If it is important that the
23521 program be portable, then use the
23523 switch to generate warnings about missing @code{Elaborate_All}
23524 pragmas, and supply the missing pragmas.
23526 If the program fails to bind using the default static elaboration
23527 handling, then you can fix the program to eliminate the binder
23528 message, or recompile the entire program with the
23529 @option{-gnatE} switch to generate dynamic elaboration checks,
23530 and, if you are sure there really are no elaboration problems,
23531 use a global pragma @code{Suppress (Elaboration_Check)}.
23533 @node Other Elaboration Order Considerations
23534 @section Other Elaboration Order Considerations
23536 This section has been entirely concerned with the issue of finding a valid
23537 elaboration order, as defined by the Ada Reference Manual. In a case
23538 where several elaboration orders are valid, the task is to find one
23539 of the possible valid elaboration orders (and the static model in GNAT
23540 will ensure that this is achieved).
23542 The purpose of the elaboration rules in the Ada Reference Manual is to
23543 make sure that no entity is accessed before it has been elaborated. For
23544 a subprogram, this means that the spec and body must have been elaborated
23545 before the subprogram is called. For an object, this means that the object
23546 must have been elaborated before its value is read or written. A violation
23547 of either of these two requirements is an access before elaboration order,
23548 and this section has been all about avoiding such errors.
23550 In the case where more than one order of elaboration is possible, in the
23551 sense that access before elaboration errors are avoided, then any one of
23552 the orders is ``correct'' in the sense that it meets the requirements of
23553 the Ada Reference Manual, and no such error occurs.
23555 However, it may be the case for a given program, that there are
23556 constraints on the order of elaboration that come not from consideration
23557 of avoiding elaboration errors, but rather from extra-lingual logic
23558 requirements. Consider this example:
23560 @smallexample @c ada
23561 with Init_Constants;
23562 package Constants is
23567 package Init_Constants is
23568 procedure P; -- require a body
23569 end Init_Constants;
23572 package body Init_Constants is
23573 procedure P is begin null; end;
23577 end Init_Constants;
23581 Z : Integer := Constants.X + Constants.Y;
23585 with Text_IO; use Text_IO;
23588 Put_Line (Calc.Z'Img);
23593 In this example, there is more than one valid order of elaboration. For
23594 example both the following are correct orders:
23597 Init_Constants spec
23600 Init_Constants body
23605 Init_Constants spec
23606 Init_Constants body
23613 There is no language rule to prefer one or the other, both are correct
23614 from an order of elaboration point of view. But the programmatic effects
23615 of the two orders are very different. In the first, the elaboration routine
23616 of @code{Calc} initializes @code{Z} to zero, and then the main program
23617 runs with this value of zero. But in the second order, the elaboration
23618 routine of @code{Calc} runs after the body of Init_Constants has set
23619 @code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
23622 One could perhaps by applying pretty clever non-artificial intelligence
23623 to the situation guess that it is more likely that the second order of
23624 elaboration is the one desired, but there is no formal linguistic reason
23625 to prefer one over the other. In fact in this particular case, GNAT will
23626 prefer the second order, because of the rule that bodies are elaborated
23627 as soon as possible, but it's just luck that this is what was wanted
23628 (if indeed the second order was preferred).
23630 If the program cares about the order of elaboration routines in a case like
23631 this, it is important to specify the order required. In this particular
23632 case, that could have been achieved by adding to the spec of Calc:
23634 @smallexample @c ada
23635 pragma Elaborate_All (Constants);
23639 which requires that the body (if any) and spec of @code{Constants},
23640 as well as the body and spec of any unit @code{with}'ed by
23641 @code{Constants} be elaborated before @code{Calc} is elaborated.
23643 Clearly no automatic method can always guess which alternative you require,
23644 and if you are working with legacy code that had constraints of this kind
23645 which were not properly specified by adding @code{Elaborate} or
23646 @code{Elaborate_All} pragmas, then indeed it is possible that two different
23647 compilers can choose different orders.
23649 The @code{gnatbind}
23650 @option{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
23651 out problems. This switch causes bodies to be elaborated as late as possible
23652 instead of as early as possible. In the example above, it would have forced
23653 the choice of the first elaboration order. If you get different results
23654 when using this switch, and particularly if one set of results is right,
23655 and one is wrong as far as you are concerned, it shows that you have some
23656 missing @code{Elaborate} pragmas. For the example above, we have the
23660 gnatmake -f -q main
23663 gnatmake -f -q main -bargs -p
23669 It is of course quite unlikely that both these results are correct, so
23670 it is up to you in a case like this to investigate the source of the
23671 difference, by looking at the two elaboration orders that are chosen,
23672 and figuring out which is correct, and then adding the necessary
23673 @code{Elaborate_All} pragmas to ensure the desired order.
23676 @node Inline Assembler
23677 @appendix Inline Assembler
23680 If you need to write low-level software that interacts directly
23681 with the hardware, Ada provides two ways to incorporate assembly
23682 language code into your program. First, you can import and invoke
23683 external routines written in assembly language, an Ada feature fully
23684 supported by GNAT. However, for small sections of code it may be simpler
23685 or more efficient to include assembly language statements directly
23686 in your Ada source program, using the facilities of the implementation-defined
23687 package @code{System.Machine_Code}, which incorporates the gcc
23688 Inline Assembler. The Inline Assembler approach offers a number of advantages,
23689 including the following:
23692 @item No need to use non-Ada tools
23693 @item Consistent interface over different targets
23694 @item Automatic usage of the proper calling conventions
23695 @item Access to Ada constants and variables
23696 @item Definition of intrinsic routines
23697 @item Possibility of inlining a subprogram comprising assembler code
23698 @item Code optimizer can take Inline Assembler code into account
23701 This chapter presents a series of examples to show you how to use
23702 the Inline Assembler. Although it focuses on the Intel x86,
23703 the general approach applies also to other processors.
23704 It is assumed that you are familiar with Ada
23705 and with assembly language programming.
23708 * Basic Assembler Syntax::
23709 * A Simple Example of Inline Assembler::
23710 * Output Variables in Inline Assembler::
23711 * Input Variables in Inline Assembler::
23712 * Inlining Inline Assembler Code::
23713 * Other Asm Functionality::
23714 * A Complete Example::
23717 @c ---------------------------------------------------------------------------
23718 @node Basic Assembler Syntax
23719 @section Basic Assembler Syntax
23722 The assembler used by GNAT and gcc is based not on the Intel assembly
23723 language, but rather on a language that descends from the AT&T Unix
23724 assembler @emph{as} (and which is often referred to as ``AT&T syntax'').
23725 The following table summarizes the main features of @emph{as} syntax
23726 and points out the differences from the Intel conventions.
23727 See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
23728 pre-processor) documentation for further information.
23731 @item Register names
23732 gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
23734 Intel: No extra punctuation; for example @code{eax}
23736 @item Immediate operand
23737 gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
23739 Intel: No extra punctuation; for example @code{4}
23742 gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
23744 Intel: No extra punctuation; for example @code{loc}
23746 @item Memory contents
23747 gcc / @emph{as}: No extra punctuation; for example @code{loc}
23749 Intel: Square brackets; for example @code{[loc]}
23751 @item Register contents
23752 gcc / @emph{as}: Parentheses; for example @code{(%eax)}
23754 Intel: Square brackets; for example @code{[eax]}
23756 @item Hexadecimal numbers
23757 gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
23759 Intel: Trailing ``h''; for example @code{A0h}
23762 gcc / @emph{as}: Explicit in op code; for example @code{movw} to move
23765 Intel: Implicit, deduced by assembler; for example @code{mov}
23767 @item Instruction repetition
23768 gcc / @emph{as}: Split into two lines; for example
23774 Intel: Keep on one line; for example @code{rep stosl}
23776 @item Order of operands
23777 gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
23779 Intel: Destination first; for example @code{mov eax, 4}
23782 @c ---------------------------------------------------------------------------
23783 @node A Simple Example of Inline Assembler
23784 @section A Simple Example of Inline Assembler
23787 The following example will generate a single assembly language statement,
23788 @code{nop}, which does nothing. Despite its lack of run-time effect,
23789 the example will be useful in illustrating the basics of
23790 the Inline Assembler facility.
23792 @smallexample @c ada
23794 with System.Machine_Code; use System.Machine_Code;
23795 procedure Nothing is
23802 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
23803 here it takes one parameter, a @emph{template string} that must be a static
23804 expression and that will form the generated instruction.
23805 @code{Asm} may be regarded as a compile-time procedure that parses
23806 the template string and additional parameters (none here),
23807 from which it generates a sequence of assembly language instructions.
23809 The examples in this chapter will illustrate several of the forms
23810 for invoking @code{Asm}; a complete specification of the syntax
23811 is found in the @cite{GNAT Reference Manual}.
23813 Under the standard GNAT conventions, the @code{Nothing} procedure
23814 should be in a file named @file{nothing.adb}.
23815 You can build the executable in the usual way:
23819 However, the interesting aspect of this example is not its run-time behavior
23820 but rather the generated assembly code.
23821 To see this output, invoke the compiler as follows:
23823 gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
23825 where the options are:
23829 compile only (no bind or link)
23831 generate assembler listing
23832 @item -fomit-frame-pointer
23833 do not set up separate stack frames
23835 do not add runtime checks
23838 This gives a human-readable assembler version of the code. The resulting
23839 file will have the same name as the Ada source file, but with a @code{.s}
23840 extension. In our example, the file @file{nothing.s} has the following
23845 .file "nothing.adb"
23847 ___gnu_compiled_ada:
23850 .globl __ada_nothing
23862 The assembly code you included is clearly indicated by
23863 the compiler, between the @code{#APP} and @code{#NO_APP}
23864 delimiters. The character before the 'APP' and 'NOAPP'
23865 can differ on different targets. For example, GNU/Linux uses '#APP' while
23866 on NT you will see '/APP'.
23868 If you make a mistake in your assembler code (such as using the
23869 wrong size modifier, or using a wrong operand for the instruction) GNAT
23870 will report this error in a temporary file, which will be deleted when
23871 the compilation is finished. Generating an assembler file will help
23872 in such cases, since you can assemble this file separately using the
23873 @emph{as} assembler that comes with gcc.
23875 Assembling the file using the command
23878 as @file{nothing.s}
23881 will give you error messages whose lines correspond to the assembler
23882 input file, so you can easily find and correct any mistakes you made.
23883 If there are no errors, @emph{as} will generate an object file
23884 @file{nothing.out}.
23886 @c ---------------------------------------------------------------------------
23887 @node Output Variables in Inline Assembler
23888 @section Output Variables in Inline Assembler
23891 The examples in this section, showing how to access the processor flags,
23892 illustrate how to specify the destination operands for assembly language
23895 @smallexample @c ada
23897 with Interfaces; use Interfaces;
23898 with Ada.Text_IO; use Ada.Text_IO;
23899 with System.Machine_Code; use System.Machine_Code;
23900 procedure Get_Flags is
23901 Flags : Unsigned_32;
23904 Asm ("pushfl" & LF & HT & -- push flags on stack
23905 "popl %%eax" & LF & HT & -- load eax with flags
23906 "movl %%eax, %0", -- store flags in variable
23907 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
23908 Put_Line ("Flags register:" & Flags'Img);
23913 In order to have a nicely aligned assembly listing, we have separated
23914 multiple assembler statements in the Asm template string with linefeed
23915 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
23916 The resulting section of the assembly output file is:
23923 movl %eax, -40(%ebp)
23928 It would have been legal to write the Asm invocation as:
23931 Asm ("pushfl popl %%eax movl %%eax, %0")
23934 but in the generated assembler file, this would come out as:
23938 pushfl popl %eax movl %eax, -40(%ebp)
23942 which is not so convenient for the human reader.
23944 We use Ada comments
23945 at the end of each line to explain what the assembler instructions
23946 actually do. This is a useful convention.
23948 When writing Inline Assembler instructions, you need to precede each register
23949 and variable name with a percent sign. Since the assembler already requires
23950 a percent sign at the beginning of a register name, you need two consecutive
23951 percent signs for such names in the Asm template string, thus @code{%%eax}.
23952 In the generated assembly code, one of the percent signs will be stripped off.
23954 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
23955 variables: operands you later define using @code{Input} or @code{Output}
23956 parameters to @code{Asm}.
23957 An output variable is illustrated in
23958 the third statement in the Asm template string:
23962 The intent is to store the contents of the eax register in a variable that can
23963 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
23964 necessarily work, since the compiler might optimize by using a register
23965 to hold Flags, and the expansion of the @code{movl} instruction would not be
23966 aware of this optimization. The solution is not to store the result directly
23967 but rather to advise the compiler to choose the correct operand form;
23968 that is the purpose of the @code{%0} output variable.
23970 Information about the output variable is supplied in the @code{Outputs}
23971 parameter to @code{Asm}:
23973 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
23976 The output is defined by the @code{Asm_Output} attribute of the target type;
23977 the general format is
23979 Type'Asm_Output (constraint_string, variable_name)
23982 The constraint string directs the compiler how
23983 to store/access the associated variable. In the example
23985 Unsigned_32'Asm_Output ("=m", Flags);
23987 the @code{"m"} (memory) constraint tells the compiler that the variable
23988 @code{Flags} should be stored in a memory variable, thus preventing
23989 the optimizer from keeping it in a register. In contrast,
23991 Unsigned_32'Asm_Output ("=r", Flags);
23993 uses the @code{"r"} (register) constraint, telling the compiler to
23994 store the variable in a register.
23996 If the constraint is preceded by the equal character (@strong{=}), it tells
23997 the compiler that the variable will be used to store data into it.
23999 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
24000 allowing the optimizer to choose whatever it deems best.
24002 There are a fairly large number of constraints, but the ones that are
24003 most useful (for the Intel x86 processor) are the following:
24009 global (i.e. can be stored anywhere)
24027 use one of eax, ebx, ecx or edx
24029 use one of eax, ebx, ecx, edx, esi or edi
24032 The full set of constraints is described in the gcc and @emph{as}
24033 documentation; note that it is possible to combine certain constraints
24034 in one constraint string.
24036 You specify the association of an output variable with an assembler operand
24037 through the @code{%}@emph{n} notation, where @emph{n} is a non-negative
24039 @smallexample @c ada
24041 Asm ("pushfl" & LF & HT & -- push flags on stack
24042 "popl %%eax" & LF & HT & -- load eax with flags
24043 "movl %%eax, %0", -- store flags in variable
24044 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24048 @code{%0} will be replaced in the expanded code by the appropriate operand,
24050 the compiler decided for the @code{Flags} variable.
24052 In general, you may have any number of output variables:
24055 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
24057 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
24058 of @code{Asm_Output} attributes
24062 @smallexample @c ada
24064 Asm ("movl %%eax, %0" & LF & HT &
24065 "movl %%ebx, %1" & LF & HT &
24067 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
24068 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
24069 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
24073 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
24074 in the Ada program.
24076 As a variation on the @code{Get_Flags} example, we can use the constraints
24077 string to direct the compiler to store the eax register into the @code{Flags}
24078 variable, instead of including the store instruction explicitly in the
24079 @code{Asm} template string:
24081 @smallexample @c ada
24083 with Interfaces; use Interfaces;
24084 with Ada.Text_IO; use Ada.Text_IO;
24085 with System.Machine_Code; use System.Machine_Code;
24086 procedure Get_Flags_2 is
24087 Flags : Unsigned_32;
24090 Asm ("pushfl" & LF & HT & -- push flags on stack
24091 "popl %%eax", -- save flags in eax
24092 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
24093 Put_Line ("Flags register:" & Flags'Img);
24099 The @code{"a"} constraint tells the compiler that the @code{Flags}
24100 variable will come from the eax register. Here is the resulting code:
24108 movl %eax,-40(%ebp)
24113 The compiler generated the store of eax into Flags after
24114 expanding the assembler code.
24116 Actually, there was no need to pop the flags into the eax register;
24117 more simply, we could just pop the flags directly into the program variable:
24119 @smallexample @c ada
24121 with Interfaces; use Interfaces;
24122 with Ada.Text_IO; use Ada.Text_IO;
24123 with System.Machine_Code; use System.Machine_Code;
24124 procedure Get_Flags_3 is
24125 Flags : Unsigned_32;
24128 Asm ("pushfl" & LF & HT & -- push flags on stack
24129 "pop %0", -- save flags in Flags
24130 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
24131 Put_Line ("Flags register:" & Flags'Img);
24136 @c ---------------------------------------------------------------------------
24137 @node Input Variables in Inline Assembler
24138 @section Input Variables in Inline Assembler
24141 The example in this section illustrates how to specify the source operands
24142 for assembly language statements.
24143 The program simply increments its input value by 1:
24145 @smallexample @c ada
24147 with Interfaces; use Interfaces;
24148 with Ada.Text_IO; use Ada.Text_IO;
24149 with System.Machine_Code; use System.Machine_Code;
24150 procedure Increment is
24152 function Incr (Value : Unsigned_32) return Unsigned_32 is
24153 Result : Unsigned_32;
24156 Inputs => Unsigned_32'Asm_Input ("a", Value),
24157 Outputs => Unsigned_32'Asm_Output ("=a", Result));
24161 Value : Unsigned_32;
24165 Put_Line ("Value before is" & Value'Img);
24166 Value := Incr (Value);
24167 Put_Line ("Value after is" & Value'Img);
24172 The @code{Outputs} parameter to @code{Asm} specifies
24173 that the result will be in the eax register and that it is to be stored
24174 in the @code{Result} variable.
24176 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
24177 but with an @code{Asm_Input} attribute.
24178 The @code{"="} constraint, indicating an output value, is not present.
24180 You can have multiple input variables, in the same way that you can have more
24181 than one output variable.
24183 The parameter count (%0, %1) etc, now starts at the first input
24184 statement, and continues with the output statements.
24185 When both parameters use the same variable, the
24186 compiler will treat them as the same %n operand, which is the case here.
24188 Just as the @code{Outputs} parameter causes the register to be stored into the
24189 target variable after execution of the assembler statements, so does the
24190 @code{Inputs} parameter cause its variable to be loaded into the register
24191 before execution of the assembler statements.
24193 Thus the effect of the @code{Asm} invocation is:
24195 @item load the 32-bit value of @code{Value} into eax
24196 @item execute the @code{incl %eax} instruction
24197 @item store the contents of eax into the @code{Result} variable
24200 The resulting assembler file (with @option{-O2} optimization) contains:
24203 _increment__incr.1:
24216 @c ---------------------------------------------------------------------------
24217 @node Inlining Inline Assembler Code
24218 @section Inlining Inline Assembler Code
24221 For a short subprogram such as the @code{Incr} function in the previous
24222 section, the overhead of the call and return (creating / deleting the stack
24223 frame) can be significant, compared to the amount of code in the subprogram
24224 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
24225 which directs the compiler to expand invocations of the subprogram at the
24226 point(s) of call, instead of setting up a stack frame for out-of-line calls.
24227 Here is the resulting program:
24229 @smallexample @c ada
24231 with Interfaces; use Interfaces;
24232 with Ada.Text_IO; use Ada.Text_IO;
24233 with System.Machine_Code; use System.Machine_Code;
24234 procedure Increment_2 is
24236 function Incr (Value : Unsigned_32) return Unsigned_32 is
24237 Result : Unsigned_32;
24240 Inputs => Unsigned_32'Asm_Input ("a", Value),
24241 Outputs => Unsigned_32'Asm_Output ("=a", Result));
24244 pragma Inline (Increment);
24246 Value : Unsigned_32;
24250 Put_Line ("Value before is" & Value'Img);
24251 Value := Increment (Value);
24252 Put_Line ("Value after is" & Value'Img);
24257 Compile the program with both optimization (@option{-O2}) and inlining
24258 enabled (@option{-gnatpn} instead of @option{-gnatp}).
24260 The @code{Incr} function is still compiled as usual, but at the
24261 point in @code{Increment} where our function used to be called:
24266 call _increment__incr.1
24271 the code for the function body directly appears:
24284 thus saving the overhead of stack frame setup and an out-of-line call.
24286 @c ---------------------------------------------------------------------------
24287 @node Other Asm Functionality
24288 @section Other @code{Asm} Functionality
24291 This section describes two important parameters to the @code{Asm}
24292 procedure: @code{Clobber}, which identifies register usage;
24293 and @code{Volatile}, which inhibits unwanted optimizations.
24296 * The Clobber Parameter::
24297 * The Volatile Parameter::
24300 @c ---------------------------------------------------------------------------
24301 @node The Clobber Parameter
24302 @subsection The @code{Clobber} Parameter
24305 One of the dangers of intermixing assembly language and a compiled language
24306 such as Ada is that the compiler needs to be aware of which registers are
24307 being used by the assembly code. In some cases, such as the earlier examples,
24308 the constraint string is sufficient to indicate register usage (e.g.,
24310 the eax register). But more generally, the compiler needs an explicit
24311 identification of the registers that are used by the Inline Assembly
24314 Using a register that the compiler doesn't know about
24315 could be a side effect of an instruction (like @code{mull}
24316 storing its result in both eax and edx).
24317 It can also arise from explicit register usage in your
24318 assembly code; for example:
24321 Asm ("movl %0, %%ebx" & LF & HT &
24323 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24324 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
24328 where the compiler (since it does not analyze the @code{Asm} template string)
24329 does not know you are using the ebx register.
24331 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
24332 to identify the registers that will be used by your assembly code:
24336 Asm ("movl %0, %%ebx" & LF & HT &
24338 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24339 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
24344 The Clobber parameter is a static string expression specifying the
24345 register(s) you are using. Note that register names are @emph{not} prefixed
24346 by a percent sign. Also, if more than one register is used then their names
24347 are separated by commas; e.g., @code{"eax, ebx"}
24349 The @code{Clobber} parameter has several additional uses:
24351 @item Use ``register'' name @code{cc} to indicate that flags might have changed
24352 @item Use ``register'' name @code{memory} if you changed a memory location
24355 @c ---------------------------------------------------------------------------
24356 @node The Volatile Parameter
24357 @subsection The @code{Volatile} Parameter
24358 @cindex Volatile parameter
24361 Compiler optimizations in the presence of Inline Assembler may sometimes have
24362 unwanted effects. For example, when an @code{Asm} invocation with an input
24363 variable is inside a loop, the compiler might move the loading of the input
24364 variable outside the loop, regarding it as a one-time initialization.
24366 If this effect is not desired, you can disable such optimizations by setting
24367 the @code{Volatile} parameter to @code{True}; for example:
24369 @smallexample @c ada
24371 Asm ("movl %0, %%ebx" & LF & HT &
24373 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
24374 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
24380 By default, @code{Volatile} is set to @code{False} unless there is no
24381 @code{Outputs} parameter.
24383 Although setting @code{Volatile} to @code{True} prevents unwanted
24384 optimizations, it will also disable other optimizations that might be
24385 important for efficiency. In general, you should set @code{Volatile}
24386 to @code{True} only if the compiler's optimizations have created
24389 @c ---------------------------------------------------------------------------
24390 @node A Complete Example
24391 @section A Complete Example
24394 This section contains a complete program illustrating a realistic usage
24395 of GNAT's Inline Assembler capabilities. It comprises a main procedure
24396 @code{Check_CPU} and a package @code{Intel_CPU}.
24397 The package declares a collection of functions that detect the properties
24398 of the 32-bit x86 processor that is running the program.
24399 The main procedure invokes these functions and displays the information.
24401 The Intel_CPU package could be enhanced by adding functions to
24402 detect the type of x386 co-processor, the processor caching options and
24403 special operations such as the SIMD extensions.
24405 Although the Intel_CPU package has been written for 32-bit Intel
24406 compatible CPUs, it is OS neutral. It has been tested on DOS,
24407 Windows/NT and GNU/Linux.
24410 * Check_CPU Procedure::
24411 * Intel_CPU Package Specification::
24412 * Intel_CPU Package Body::
24415 @c ---------------------------------------------------------------------------
24416 @node Check_CPU Procedure
24417 @subsection @code{Check_CPU} Procedure
24418 @cindex Check_CPU procedure
24420 @smallexample @c adanocomment
24421 ---------------------------------------------------------------------
24423 -- Uses the Intel_CPU package to identify the CPU the program is --
24424 -- running on, and some of the features it supports. --
24426 ---------------------------------------------------------------------
24428 with Intel_CPU; -- Intel CPU detection functions
24429 with Ada.Text_IO; -- Standard text I/O
24430 with Ada.Command_Line; -- To set the exit status
24432 procedure Check_CPU is
24434 Type_Found : Boolean := False;
24435 -- Flag to indicate that processor was identified
24437 Features : Intel_CPU.Processor_Features;
24438 -- The processor features
24440 Signature : Intel_CPU.Processor_Signature;
24441 -- The processor type signature
24445 -----------------------------------
24446 -- Display the program banner. --
24447 -----------------------------------
24449 Ada.Text_IO.Put_Line (Ada.Command_Line.Command_Name &
24450 ": check Intel CPU version and features, v1.0");
24451 Ada.Text_IO.Put_Line ("distribute freely, but no warranty whatsoever");
24452 Ada.Text_IO.New_Line;
24454 -----------------------------------------------------------------------
24455 -- We can safely start with the assumption that we are on at least --
24456 -- a x386 processor. If the CPUID instruction is present, then we --
24457 -- have a later processor type. --
24458 -----------------------------------------------------------------------
24460 if Intel_CPU.Has_CPUID = False then
24462 -- No CPUID instruction, so we assume this is indeed a x386
24463 -- processor. We can still check if it has a FP co-processor.
24464 if Intel_CPU.Has_FPU then
24465 Ada.Text_IO.Put_Line
24466 ("x386-type processor with a FP co-processor");
24468 Ada.Text_IO.Put_Line
24469 ("x386-type processor without a FP co-processor");
24470 end if; -- check for FPU
24473 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
24476 end if; -- check for CPUID
24478 -----------------------------------------------------------------------
24479 -- If CPUID is supported, check if this is a true Intel processor, --
24480 -- if it is not, display a warning. --
24481 -----------------------------------------------------------------------
24483 if Intel_CPU.Vendor_ID /= Intel_CPU.Intel_Processor then
24484 Ada.Text_IO.Put_Line ("*** This is a Intel compatible processor");
24485 Ada.Text_IO.Put_Line ("*** Some information may be incorrect");
24486 end if; -- check if Intel
24488 ----------------------------------------------------------------------
24489 -- With the CPUID instruction present, we can assume at least a --
24490 -- x486 processor. If the CPUID support level is < 1 then we have --
24491 -- to leave it at that. --
24492 ----------------------------------------------------------------------
24494 if Intel_CPU.CPUID_Level < 1 then
24496 -- Ok, this is a x486 processor. we still can get the Vendor ID
24497 Ada.Text_IO.Put_Line ("x486-type processor");
24498 Ada.Text_IO.Put_Line ("Vendor ID is " & Intel_CPU.Vendor_ID);
24500 -- We can also check if there is a FPU present
24501 if Intel_CPU.Has_FPU then
24502 Ada.Text_IO.Put_Line ("Floating-Point support");
24504 Ada.Text_IO.Put_Line ("No Floating-Point support");
24505 end if; -- check for FPU
24508 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
24511 end if; -- check CPUID level
24513 ---------------------------------------------------------------------
24514 -- With a CPUID level of 1 we can use the processor signature to --
24515 -- determine it's exact type. --
24516 ---------------------------------------------------------------------
24518 Signature := Intel_CPU.Signature;
24520 ----------------------------------------------------------------------
24521 -- Ok, now we go into a lot of messy comparisons to get the --
24522 -- processor type. For clarity, no attememt to try to optimize the --
24523 -- comparisons has been made. Note that since Intel_CPU does not --
24524 -- support getting cache info, we cannot distinguish between P5 --
24525 -- and Celeron types yet. --
24526 ----------------------------------------------------------------------
24529 if Signature.Processor_Type = 2#00# and
24530 Signature.Family = 2#0100# and
24531 Signature.Model = 2#0100# then
24532 Type_Found := True;
24533 Ada.Text_IO.Put_Line ("x486SL processor");
24536 -- x486DX2 Write-Back
24537 if Signature.Processor_Type = 2#00# and
24538 Signature.Family = 2#0100# and
24539 Signature.Model = 2#0111# then
24540 Type_Found := True;
24541 Ada.Text_IO.Put_Line ("Write-Back Enhanced x486DX2 processor");
24545 if Signature.Processor_Type = 2#00# and
24546 Signature.Family = 2#0100# and
24547 Signature.Model = 2#1000# then
24548 Type_Found := True;
24549 Ada.Text_IO.Put_Line ("x486DX4 processor");
24552 -- x486DX4 Overdrive
24553 if Signature.Processor_Type = 2#01# and
24554 Signature.Family = 2#0100# and
24555 Signature.Model = 2#1000# then
24556 Type_Found := True;
24557 Ada.Text_IO.Put_Line ("x486DX4 OverDrive processor");
24560 -- Pentium (60, 66)
24561 if Signature.Processor_Type = 2#00# and
24562 Signature.Family = 2#0101# and
24563 Signature.Model = 2#0001# then
24564 Type_Found := True;
24565 Ada.Text_IO.Put_Line ("Pentium processor (60, 66)");
24568 -- Pentium (75, 90, 100, 120, 133, 150, 166, 200)
24569 if Signature.Processor_Type = 2#00# and
24570 Signature.Family = 2#0101# and
24571 Signature.Model = 2#0010# then
24572 Type_Found := True;
24573 Ada.Text_IO.Put_Line
24574 ("Pentium processor (75, 90, 100, 120, 133, 150, 166, 200)");
24577 -- Pentium OverDrive (60, 66)
24578 if Signature.Processor_Type = 2#01# and
24579 Signature.Family = 2#0101# and
24580 Signature.Model = 2#0001# then
24581 Type_Found := True;
24582 Ada.Text_IO.Put_Line ("Pentium OverDrive processor (60, 66)");
24585 -- Pentium OverDrive (75, 90, 100, 120, 133, 150, 166, 200)
24586 if Signature.Processor_Type = 2#01# and
24587 Signature.Family = 2#0101# and
24588 Signature.Model = 2#0010# then
24589 Type_Found := True;
24590 Ada.Text_IO.Put_Line
24591 ("Pentium OverDrive cpu (75, 90, 100, 120, 133, 150, 166, 200)");
24594 -- Pentium OverDrive processor for x486 processor-based systems
24595 if Signature.Processor_Type = 2#01# and
24596 Signature.Family = 2#0101# and
24597 Signature.Model = 2#0011# then
24598 Type_Found := True;
24599 Ada.Text_IO.Put_Line
24600 ("Pentium OverDrive processor for x486 processor-based systems");
24603 -- Pentium processor with MMX technology (166, 200)
24604 if Signature.Processor_Type = 2#00# and
24605 Signature.Family = 2#0101# and
24606 Signature.Model = 2#0100# then
24607 Type_Found := True;
24608 Ada.Text_IO.Put_Line
24609 ("Pentium processor with MMX technology (166, 200)");
24612 -- Pentium OverDrive with MMX for Pentium (75, 90, 100, 120, 133)
24613 if Signature.Processor_Type = 2#01# and
24614 Signature.Family = 2#0101# and
24615 Signature.Model = 2#0100# then
24616 Type_Found := True;
24617 Ada.Text_IO.Put_Line
24618 ("Pentium OverDrive processor with MMX " &
24619 "technology for Pentium processor (75, 90, 100, 120, 133)");
24622 -- Pentium Pro processor
24623 if Signature.Processor_Type = 2#00# and
24624 Signature.Family = 2#0110# and
24625 Signature.Model = 2#0001# then
24626 Type_Found := True;
24627 Ada.Text_IO.Put_Line ("Pentium Pro processor");
24630 -- Pentium II processor, model 3
24631 if Signature.Processor_Type = 2#00# and
24632 Signature.Family = 2#0110# and
24633 Signature.Model = 2#0011# then
24634 Type_Found := True;
24635 Ada.Text_IO.Put_Line ("Pentium II processor, model 3");
24638 -- Pentium II processor, model 5 or Celeron processor
24639 if Signature.Processor_Type = 2#00# and
24640 Signature.Family = 2#0110# and
24641 Signature.Model = 2#0101# then
24642 Type_Found := True;
24643 Ada.Text_IO.Put_Line
24644 ("Pentium II processor, model 5 or Celeron processor");
24647 -- Pentium Pro OverDrive processor
24648 if Signature.Processor_Type = 2#01# and
24649 Signature.Family = 2#0110# and
24650 Signature.Model = 2#0011# then
24651 Type_Found := True;
24652 Ada.Text_IO.Put_Line ("Pentium Pro OverDrive processor");
24655 -- If no type recognized, we have an unknown. Display what
24657 if Type_Found = False then
24658 Ada.Text_IO.Put_Line ("Unknown processor");
24661 -----------------------------------------
24662 -- Display processor stepping level. --
24663 -----------------------------------------
24665 Ada.Text_IO.Put_Line ("Stepping level:" & Signature.Stepping'Img);
24667 ---------------------------------
24668 -- Display vendor ID string. --
24669 ---------------------------------
24671 Ada.Text_IO.Put_Line ("Vendor ID: " & Intel_CPU.Vendor_ID);
24673 ------------------------------------
24674 -- Get the processors features. --
24675 ------------------------------------
24677 Features := Intel_CPU.Features;
24679 -----------------------------
24680 -- Check for a FPU unit. --
24681 -----------------------------
24683 if Features.FPU = True then
24684 Ada.Text_IO.Put_Line ("Floating-Point unit available");
24686 Ada.Text_IO.Put_Line ("no Floating-Point unit");
24687 end if; -- check for FPU
24689 --------------------------------
24690 -- List processor features. --
24691 --------------------------------
24693 Ada.Text_IO.Put_Line ("Supported features: ");
24695 -- Virtual Mode Extension
24696 if Features.VME = True then
24697 Ada.Text_IO.Put_Line (" VME - Virtual Mode Extension");
24700 -- Debugging Extension
24701 if Features.DE = True then
24702 Ada.Text_IO.Put_Line (" DE - Debugging Extension");
24705 -- Page Size Extension
24706 if Features.PSE = True then
24707 Ada.Text_IO.Put_Line (" PSE - Page Size Extension");
24710 -- Time Stamp Counter
24711 if Features.TSC = True then
24712 Ada.Text_IO.Put_Line (" TSC - Time Stamp Counter");
24715 -- Model Specific Registers
24716 if Features.MSR = True then
24717 Ada.Text_IO.Put_Line (" MSR - Model Specific Registers");
24720 -- Physical Address Extension
24721 if Features.PAE = True then
24722 Ada.Text_IO.Put_Line (" PAE - Physical Address Extension");
24725 -- Machine Check Extension
24726 if Features.MCE = True then
24727 Ada.Text_IO.Put_Line (" MCE - Machine Check Extension");
24730 -- CMPXCHG8 instruction supported
24731 if Features.CX8 = True then
24732 Ada.Text_IO.Put_Line (" CX8 - CMPXCHG8 instruction");
24735 -- on-chip APIC hardware support
24736 if Features.APIC = True then
24737 Ada.Text_IO.Put_Line (" APIC - on-chip APIC hardware support");
24740 -- Fast System Call
24741 if Features.SEP = True then
24742 Ada.Text_IO.Put_Line (" SEP - Fast System Call");
24745 -- Memory Type Range Registers
24746 if Features.MTRR = True then
24747 Ada.Text_IO.Put_Line (" MTTR - Memory Type Range Registers");
24750 -- Page Global Enable
24751 if Features.PGE = True then
24752 Ada.Text_IO.Put_Line (" PGE - Page Global Enable");
24755 -- Machine Check Architecture
24756 if Features.MCA = True then
24757 Ada.Text_IO.Put_Line (" MCA - Machine Check Architecture");
24760 -- Conditional Move Instruction Supported
24761 if Features.CMOV = True then
24762 Ada.Text_IO.Put_Line
24763 (" CMOV - Conditional Move Instruction Supported");
24766 -- Page Attribute Table
24767 if Features.PAT = True then
24768 Ada.Text_IO.Put_Line (" PAT - Page Attribute Table");
24771 -- 36-bit Page Size Extension
24772 if Features.PSE_36 = True then
24773 Ada.Text_IO.Put_Line (" PSE_36 - 36-bit Page Size Extension");
24776 -- MMX technology supported
24777 if Features.MMX = True then
24778 Ada.Text_IO.Put_Line (" MMX - MMX technology supported");
24781 -- Fast FP Save and Restore
24782 if Features.FXSR = True then
24783 Ada.Text_IO.Put_Line (" FXSR - Fast FP Save and Restore");
24786 ---------------------
24787 -- Program done. --
24788 ---------------------
24790 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
24795 Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Failure);
24801 @c ---------------------------------------------------------------------------
24802 @node Intel_CPU Package Specification
24803 @subsection @code{Intel_CPU} Package Specification
24804 @cindex Intel_CPU package specification
24806 @smallexample @c adanocomment
24807 -------------------------------------------------------------------------
24809 -- file: intel_cpu.ads --
24811 -- ********************************************* --
24812 -- * WARNING: for 32-bit Intel processors only * --
24813 -- ********************************************* --
24815 -- This package contains a number of subprograms that are useful in --
24816 -- determining the Intel x86 CPU (and the features it supports) on --
24817 -- which the program is running. --
24819 -- The package is based upon the information given in the Intel --
24820 -- Application Note AP-485: "Intel Processor Identification and the --
24821 -- CPUID Instruction" as of April 1998. This application note can be --
24822 -- found on www.intel.com. --
24824 -- It currently deals with 32-bit processors only, will not detect --
24825 -- features added after april 1998, and does not guarantee proper --
24826 -- results on Intel-compatible processors. --
24828 -- Cache info and x386 fpu type detection are not supported. --
24830 -- This package does not use any privileged instructions, so should --
24831 -- work on any OS running on a 32-bit Intel processor. --
24833 -------------------------------------------------------------------------
24835 with Interfaces; use Interfaces;
24836 -- for using unsigned types
24838 with System.Machine_Code; use System.Machine_Code;
24839 -- for using inline assembler code
24841 with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
24842 -- for inserting control characters
24844 package Intel_CPU is
24846 ----------------------
24847 -- Processor bits --
24848 ----------------------
24850 subtype Num_Bits is Natural range 0 .. 31;
24851 -- the number of processor bits (32)
24853 --------------------------
24854 -- Processor register --
24855 --------------------------
24857 -- define a processor register type for easy access to
24858 -- the individual bits
24860 type Processor_Register is array (Num_Bits) of Boolean;
24861 pragma Pack (Processor_Register);
24862 for Processor_Register'Size use 32;
24864 -------------------------
24865 -- Unsigned register --
24866 -------------------------
24868 -- define a processor register type for easy access to
24869 -- the individual bytes
24871 type Unsigned_Register is
24879 for Unsigned_Register use
24881 L1 at 0 range 0 .. 7;
24882 H1 at 0 range 8 .. 15;
24883 L2 at 0 range 16 .. 23;
24884 H2 at 0 range 24 .. 31;
24887 for Unsigned_Register'Size use 32;
24889 ---------------------------------
24890 -- Intel processor vendor ID --
24891 ---------------------------------
24893 Intel_Processor : constant String (1 .. 12) := "GenuineIntel";
24894 -- indicates an Intel manufactured processor
24896 ------------------------------------
24897 -- Processor signature register --
24898 ------------------------------------
24900 -- a register type to hold the processor signature
24902 type Processor_Signature is
24904 Stepping : Natural range 0 .. 15;
24905 Model : Natural range 0 .. 15;
24906 Family : Natural range 0 .. 15;
24907 Processor_Type : Natural range 0 .. 3;
24908 Reserved : Natural range 0 .. 262143;
24911 for Processor_Signature use
24913 Stepping at 0 range 0 .. 3;
24914 Model at 0 range 4 .. 7;
24915 Family at 0 range 8 .. 11;
24916 Processor_Type at 0 range 12 .. 13;
24917 Reserved at 0 range 14 .. 31;
24920 for Processor_Signature'Size use 32;
24922 -----------------------------------
24923 -- Processor features register --
24924 -----------------------------------
24926 -- a processor register to hold the processor feature flags
24928 type Processor_Features is
24930 FPU : Boolean; -- floating point unit on chip
24931 VME : Boolean; -- virtual mode extension
24932 DE : Boolean; -- debugging extension
24933 PSE : Boolean; -- page size extension
24934 TSC : Boolean; -- time stamp counter
24935 MSR : Boolean; -- model specific registers
24936 PAE : Boolean; -- physical address extension
24937 MCE : Boolean; -- machine check extension
24938 CX8 : Boolean; -- cmpxchg8 instruction
24939 APIC : Boolean; -- on-chip apic hardware
24940 Res_1 : Boolean; -- reserved for extensions
24941 SEP : Boolean; -- fast system call
24942 MTRR : Boolean; -- memory type range registers
24943 PGE : Boolean; -- page global enable
24944 MCA : Boolean; -- machine check architecture
24945 CMOV : Boolean; -- conditional move supported
24946 PAT : Boolean; -- page attribute table
24947 PSE_36 : Boolean; -- 36-bit page size extension
24948 Res_2 : Natural range 0 .. 31; -- reserved for extensions
24949 MMX : Boolean; -- MMX technology supported
24950 FXSR : Boolean; -- fast FP save and restore
24951 Res_3 : Natural range 0 .. 127; -- reserved for extensions
24954 for Processor_Features use
24956 FPU at 0 range 0 .. 0;
24957 VME at 0 range 1 .. 1;
24958 DE at 0 range 2 .. 2;
24959 PSE at 0 range 3 .. 3;
24960 TSC at 0 range 4 .. 4;
24961 MSR at 0 range 5 .. 5;
24962 PAE at 0 range 6 .. 6;
24963 MCE at 0 range 7 .. 7;
24964 CX8 at 0 range 8 .. 8;
24965 APIC at 0 range 9 .. 9;
24966 Res_1 at 0 range 10 .. 10;
24967 SEP at 0 range 11 .. 11;
24968 MTRR at 0 range 12 .. 12;
24969 PGE at 0 range 13 .. 13;
24970 MCA at 0 range 14 .. 14;
24971 CMOV at 0 range 15 .. 15;
24972 PAT at 0 range 16 .. 16;
24973 PSE_36 at 0 range 17 .. 17;
24974 Res_2 at 0 range 18 .. 22;
24975 MMX at 0 range 23 .. 23;
24976 FXSR at 0 range 24 .. 24;
24977 Res_3 at 0 range 25 .. 31;
24980 for Processor_Features'Size use 32;
24982 -------------------
24984 -------------------
24986 function Has_FPU return Boolean;
24987 -- return True if a FPU is found
24988 -- use only if CPUID is not supported
24990 function Has_CPUID return Boolean;
24991 -- return True if the processor supports the CPUID instruction
24993 function CPUID_Level return Natural;
24994 -- return the CPUID support level (0, 1 or 2)
24995 -- can only be called if the CPUID instruction is supported
24997 function Vendor_ID return String;
24998 -- return the processor vendor identification string
24999 -- can only be called if the CPUID instruction is supported
25001 function Signature return Processor_Signature;
25002 -- return the processor signature
25003 -- can only be called if the CPUID instruction is supported
25005 function Features return Processor_Features;
25006 -- return the processors features
25007 -- can only be called if the CPUID instruction is supported
25011 ------------------------
25012 -- EFLAGS bit names --
25013 ------------------------
25015 ID_Flag : constant Num_Bits := 21;
25021 @c ---------------------------------------------------------------------------
25022 @node Intel_CPU Package Body
25023 @subsection @code{Intel_CPU} Package Body
25024 @cindex Intel_CPU package body
25026 @smallexample @c adanocomment
25027 package body Intel_CPU is
25029 ---------------------------
25030 -- Detect FPU presence --
25031 ---------------------------
25033 -- There is a FPU present if we can set values to the FPU Status
25034 -- and Control Words.
25036 function Has_FPU return Boolean is
25038 Register : Unsigned_16;
25039 -- processor register to store a word
25043 -- check if we can change the status word
25046 -- the assembler code
25047 "finit" & LF & HT & -- reset status word
25048 "movw $0x5A5A, %%ax" & LF & HT & -- set value status word
25049 "fnstsw %0" & LF & HT & -- save status word
25050 "movw %%ax, %0", -- store status word
25052 -- output stored in Register
25053 -- register must be a memory location
25054 Outputs => Unsigned_16'Asm_output ("=m", Register),
25056 -- tell compiler that we used eax
25059 -- if the status word is zero, there is no FPU
25060 if Register = 0 then
25061 return False; -- no status word
25062 end if; -- check status word value
25064 -- check if we can get the control word
25067 -- the assembler code
25068 "fnstcw %0", -- save the control word
25070 -- output into Register
25071 -- register must be a memory location
25072 Outputs => Unsigned_16'Asm_output ("=m", Register));
25074 -- check the relevant bits
25075 if (Register and 16#103F#) /= 16#003F# then
25076 return False; -- no control word
25077 end if; -- check control word value
25084 --------------------------------
25085 -- Detect CPUID instruction --
25086 --------------------------------
25088 -- The processor supports the CPUID instruction if it is possible
25089 -- to change the value of ID flag bit in the EFLAGS register.
25091 function Has_CPUID return Boolean is
25093 Original_Flags, Modified_Flags : Processor_Register;
25094 -- EFLAG contents before and after changing the ID flag
25098 -- try flipping the ID flag in the EFLAGS register
25101 -- the assembler code
25102 "pushfl" & LF & HT & -- push EFLAGS on stack
25103 "pop %%eax" & LF & HT & -- pop EFLAGS into eax
25104 "movl %%eax, %0" & LF & HT & -- save EFLAGS content
25105 "xor $0x200000, %%eax" & LF & HT & -- flip ID flag
25106 "push %%eax" & LF & HT & -- push EFLAGS on stack
25107 "popfl" & LF & HT & -- load EFLAGS register
25108 "pushfl" & LF & HT & -- push EFLAGS on stack
25109 "pop %1", -- save EFLAGS content
25111 -- output values, may be anything
25112 -- Original_Flags is %0
25113 -- Modified_Flags is %1
25115 (Processor_Register'Asm_output ("=g", Original_Flags),
25116 Processor_Register'Asm_output ("=g", Modified_Flags)),
25118 -- tell compiler eax is destroyed
25121 -- check if CPUID is supported
25122 if Original_Flags(ID_Flag) /= Modified_Flags(ID_Flag) then
25123 return True; -- ID flag was modified
25125 return False; -- ID flag unchanged
25126 end if; -- check for CPUID
25130 -------------------------------
25131 -- Get CPUID support level --
25132 -------------------------------
25134 function CPUID_Level return Natural is
25136 Level : Unsigned_32;
25137 -- returned support level
25141 -- execute CPUID, storing the results in the Level register
25144 -- the assembler code
25145 "cpuid", -- execute CPUID
25147 -- zero is stored in eax
25148 -- returning the support level in eax
25149 Inputs => Unsigned_32'Asm_input ("a", 0),
25151 -- eax is stored in Level
25152 Outputs => Unsigned_32'Asm_output ("=a", Level),
25154 -- tell compiler ebx, ecx and edx registers are destroyed
25155 Clobber => "ebx, ecx, edx");
25157 -- return the support level
25158 return Natural (Level);
25162 --------------------------------
25163 -- Get CPU Vendor ID String --
25164 --------------------------------
25166 -- The vendor ID string is returned in the ebx, ecx and edx register
25167 -- after executing the CPUID instruction with eax set to zero.
25168 -- In case of a true Intel processor the string returned is
25171 function Vendor_ID return String is
25173 Ebx, Ecx, Edx : Unsigned_Register;
25174 -- registers containing the vendor ID string
25176 Vendor_ID : String (1 .. 12);
25177 -- the vendor ID string
25181 -- execute CPUID, storing the results in the processor registers
25184 -- the assembler code
25185 "cpuid", -- execute CPUID
25187 -- zero stored in eax
25188 -- vendor ID string returned in ebx, ecx and edx
25189 Inputs => Unsigned_32'Asm_input ("a", 0),
25191 -- ebx is stored in Ebx
25192 -- ecx is stored in Ecx
25193 -- edx is stored in Edx
25194 Outputs => (Unsigned_Register'Asm_output ("=b", Ebx),
25195 Unsigned_Register'Asm_output ("=c", Ecx),
25196 Unsigned_Register'Asm_output ("=d", Edx)));
25198 -- now build the vendor ID string
25199 Vendor_ID( 1) := Character'Val (Ebx.L1);
25200 Vendor_ID( 2) := Character'Val (Ebx.H1);
25201 Vendor_ID( 3) := Character'Val (Ebx.L2);
25202 Vendor_ID( 4) := Character'Val (Ebx.H2);
25203 Vendor_ID( 5) := Character'Val (Edx.L1);
25204 Vendor_ID( 6) := Character'Val (Edx.H1);
25205 Vendor_ID( 7) := Character'Val (Edx.L2);
25206 Vendor_ID( 8) := Character'Val (Edx.H2);
25207 Vendor_ID( 9) := Character'Val (Ecx.L1);
25208 Vendor_ID(10) := Character'Val (Ecx.H1);
25209 Vendor_ID(11) := Character'Val (Ecx.L2);
25210 Vendor_ID(12) := Character'Val (Ecx.H2);
25217 -------------------------------
25218 -- Get processor signature --
25219 -------------------------------
25221 function Signature return Processor_Signature is
25223 Result : Processor_Signature;
25224 -- processor signature returned
25228 -- execute CPUID, storing the results in the Result variable
25231 -- the assembler code
25232 "cpuid", -- execute CPUID
25234 -- one is stored in eax
25235 -- processor signature returned in eax
25236 Inputs => Unsigned_32'Asm_input ("a", 1),
25238 -- eax is stored in Result
25239 Outputs => Processor_Signature'Asm_output ("=a", Result),
25241 -- tell compiler that ebx, ecx and edx are also destroyed
25242 Clobber => "ebx, ecx, edx");
25244 -- return processor signature
25249 ------------------------------
25250 -- Get processor features --
25251 ------------------------------
25253 function Features return Processor_Features is
25255 Result : Processor_Features;
25256 -- processor features returned
25260 -- execute CPUID, storing the results in the Result variable
25263 -- the assembler code
25264 "cpuid", -- execute CPUID
25266 -- one stored in eax
25267 -- processor features returned in edx
25268 Inputs => Unsigned_32'Asm_input ("a", 1),
25270 -- edx is stored in Result
25271 Outputs => Processor_Features'Asm_output ("=d", Result),
25273 -- tell compiler that ebx and ecx are also destroyed
25274 Clobber => "ebx, ecx");
25276 -- return processor signature
25283 @c END OF INLINE ASSEMBLER CHAPTER
25284 @c ===============================
25288 @c ***********************************
25289 @c * Compatibility and Porting Guide *
25290 @c ***********************************
25291 @node Compatibility and Porting Guide
25292 @appendix Compatibility and Porting Guide
25295 This chapter describes the compatibility issues that may arise between
25296 GNAT and other Ada 83 and Ada 95 compilation systems, and shows how GNAT
25297 can expedite porting
25298 applications developed in other Ada environments.
25301 * Compatibility with Ada 83::
25302 * Implementation-dependent characteristics::
25303 * Compatibility with DEC Ada 83::
25304 * Compatibility with Other Ada 95 Systems::
25305 * Representation Clauses::
25308 @node Compatibility with Ada 83
25309 @section Compatibility with Ada 83
25310 @cindex Compatibility (between Ada 83 and Ada 95)
25313 Ada 95 is designed to be highly upwards compatible with Ada 83. In
25314 particular, the design intention is that the difficulties associated
25315 with moving from Ada 83 to Ada 95 should be no greater than those
25316 that occur when moving from one Ada 83 system to another.
25318 However, there are a number of points at which there are minor
25319 incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains
25320 full details of these issues,
25321 and should be consulted for a complete treatment.
25323 following subsections treat the most likely issues to be encountered.
25326 * Legal Ada 83 programs that are illegal in Ada 95::
25327 * More deterministic semantics::
25328 * Changed semantics::
25329 * Other language compatibility issues::
25332 @node Legal Ada 83 programs that are illegal in Ada 95
25333 @subsection Legal Ada 83 programs that are illegal in Ada 95
25336 @item Character literals
25337 Some uses of character literals are ambiguous. Since Ada 95 has introduced
25338 @code{Wide_Character} as a new predefined character type, some uses of
25339 character literals that were legal in Ada 83 are illegal in Ada 95.
25341 @smallexample @c ada
25342 for Char in 'A' .. 'Z' loop ... end loop;
25345 The problem is that @code{'A'} and @code{'Z'} could be from either
25346 @code{Character} or @code{Wide_Character}. The simplest correction
25347 is to make the type explicit; e.g.:
25348 @smallexample @c ada
25349 for Char in Character range 'A' .. 'Z' loop ... end loop;
25352 @item New reserved words
25353 The identifiers @code{abstract}, @code{aliased}, @code{protected},
25354 @code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95.
25355 Existing Ada 83 code using any of these identifiers must be edited to
25356 use some alternative name.
25358 @item Freezing rules
25359 The rules in Ada 95 are slightly different with regard to the point at
25360 which entities are frozen, and representation pragmas and clauses are
25361 not permitted past the freeze point. This shows up most typically in
25362 the form of an error message complaining that a representation item
25363 appears too late, and the appropriate corrective action is to move
25364 the item nearer to the declaration of the entity to which it refers.
25366 A particular case is that representation pragmas
25369 extended DEC Ada 83 compatibility pragmas such as @code{Export_Procedure})
25371 cannot be applied to a subprogram body. If necessary, a separate subprogram
25372 declaration must be introduced to which the pragma can be applied.
25374 @item Optional bodies for library packages
25375 In Ada 83, a package that did not require a package body was nevertheless
25376 allowed to have one. This lead to certain surprises in compiling large
25377 systems (situations in which the body could be unexpectedly ignored by the
25378 binder). In Ada 95, if a package does not require a body then it is not
25379 permitted to have a body. To fix this problem, simply remove a redundant
25380 body if it is empty, or, if it is non-empty, introduce a dummy declaration
25381 into the spec that makes the body required. One approach is to add a private
25382 part to the package declaration (if necessary), and define a parameterless
25383 procedure called @code{Requires_Body}, which must then be given a dummy
25384 procedure body in the package body, which then becomes required.
25385 Another approach (assuming that this does not introduce elaboration
25386 circularities) is to add an @code{Elaborate_Body} pragma to the package spec,
25387 since one effect of this pragma is to require the presence of a package body.
25389 @item @code{Numeric_Error} is now the same as @code{Constraint_Error}
25390 In Ada 95, the exception @code{Numeric_Error} is a renaming of
25391 @code{Constraint_Error}.
25392 This means that it is illegal to have separate exception handlers for
25393 the two exceptions. The fix is simply to remove the handler for the
25394 @code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise
25395 @code{Constraint_Error} in place of @code{Numeric_Error} in all cases).
25397 @item Indefinite subtypes in generics
25398 In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String})
25399 as the actual for a generic formal private type, but then the instantiation
25400 would be illegal if there were any instances of declarations of variables
25401 of this type in the generic body. In Ada 95, to avoid this clear violation
25402 of the methodological principle known as the ``contract model'',
25403 the generic declaration explicitly indicates whether
25404 or not such instantiations are permitted. If a generic formal parameter
25405 has explicit unknown discriminants, indicated by using @code{(<>)} after the
25406 type name, then it can be instantiated with indefinite types, but no
25407 stand-alone variables can be declared of this type. Any attempt to declare
25408 such a variable will result in an illegality at the time the generic is
25409 declared. If the @code{(<>)} notation is not used, then it is illegal
25410 to instantiate the generic with an indefinite type.
25411 This is the potential incompatibility issue when porting Ada 83 code to Ada 95.
25412 It will show up as a compile time error, and
25413 the fix is usually simply to add the @code{(<>)} to the generic declaration.
25416 @node More deterministic semantics
25417 @subsection More deterministic semantics
25421 Conversions from real types to integer types round away from 0. In Ada 83
25422 the conversion Integer(2.5) could deliver either 2 or 3 as its value. This
25423 implementation freedom was intended to support unbiased rounding in
25424 statistical applications, but in practice it interfered with portability.
25425 In Ada 95 the conversion semantics are unambiguous, and rounding away from 0
25426 is required. Numeric code may be affected by this change in semantics.
25427 Note, though, that this issue is no worse than already existed in Ada 83
25428 when porting code from one vendor to another.
25431 The Real-Time Annex introduces a set of policies that define the behavior of
25432 features that were implementation dependent in Ada 83, such as the order in
25433 which open select branches are executed.
25436 @node Changed semantics
25437 @subsection Changed semantics
25440 The worst kind of incompatibility is one where a program that is legal in
25441 Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not
25442 possible in Ada 83. Fortunately this is extremely rare, but the one
25443 situation that you should be alert to is the change in the predefined type
25444 @code{Character} from 7-bit ASCII to 8-bit Latin-1.
25447 @item range of @code{Character}
25448 The range of @code{Standard.Character} is now the full 256 characters
25449 of Latin-1, whereas in most Ada 83 implementations it was restricted
25450 to 128 characters. Although some of the effects of
25451 this change will be manifest in compile-time rejection of legal
25452 Ada 83 programs it is possible for a working Ada 83 program to have
25453 a different effect in Ada 95, one that was not permitted in Ada 83.
25454 As an example, the expression
25455 @code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now
25456 delivers @code{255} as its value.
25457 In general, you should look at the logic of any
25458 character-processing Ada 83 program and see whether it needs to be adapted
25459 to work correctly with Latin-1. Note that the predefined Ada 95 API has a
25460 character handling package that may be relevant if code needs to be adapted
25461 to account for the additional Latin-1 elements.
25462 The desirable fix is to
25463 modify the program to accommodate the full character set, but in some cases
25464 it may be convenient to define a subtype or derived type of Character that
25465 covers only the restricted range.
25469 @node Other language compatibility issues
25470 @subsection Other language compatibility issues
25472 @item @option{-gnat83 switch}
25473 All implementations of GNAT provide a switch that causes GNAT to operate
25474 in Ada 83 mode. In this mode, some but not all compatibility problems
25475 of the type described above are handled automatically. For example, the
25476 new Ada 95 reserved words are treated simply as identifiers as in Ada 83.
25478 in practice, it is usually advisable to make the necessary modifications
25479 to the program to remove the need for using this switch.
25480 See @ref{Compiling Ada 83 Programs}.
25482 @item Support for removed Ada 83 pragmas and attributes
25483 A number of pragmas and attributes from Ada 83 have been removed from Ada 95,
25484 generally because they have been replaced by other mechanisms. Ada 95
25485 compilers are allowed, but not required, to implement these missing
25486 elements. In contrast with some other Ada 95 compilers, GNAT implements all
25487 such pragmas and attributes, eliminating this compatibility concern. These
25488 include @code{pragma Interface} and the floating point type attributes
25489 (@code{Emax}, @code{Mantissa}, etc.), among other items.
25493 @node Implementation-dependent characteristics
25494 @section Implementation-dependent characteristics
25496 Although the Ada language defines the semantics of each construct as
25497 precisely as practical, in some situations (for example for reasons of
25498 efficiency, or where the effect is heavily dependent on the host or target
25499 platform) the implementation is allowed some freedom. In porting Ada 83
25500 code to GNAT, you need to be aware of whether / how the existing code
25501 exercised such implementation dependencies. Such characteristics fall into
25502 several categories, and GNAT offers specific support in assisting the
25503 transition from certain Ada 83 compilers.
25506 * Implementation-defined pragmas::
25507 * Implementation-defined attributes::
25509 * Elaboration order::
25510 * Target-specific aspects::
25514 @node Implementation-defined pragmas
25515 @subsection Implementation-defined pragmas
25518 Ada compilers are allowed to supplement the language-defined pragmas, and
25519 these are a potential source of non-portability. All GNAT-defined pragmas
25520 are described in the GNAT Reference Manual, and these include several that
25521 are specifically intended to correspond to other vendors' Ada 83 pragmas.
25522 For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful.
25524 compatibility with DEC Ada 83, GNAT supplies the pragmas
25525 @code{Extend_System}, @code{Ident}, @code{Inline_Generic},
25526 @code{Interface_Name}, @code{Passive}, @code{Suppress_All},
25527 and @code{Volatile}.
25528 Other relevant pragmas include @code{External} and @code{Link_With}.
25529 Some vendor-specific
25530 Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are
25532 avoiding compiler rejection of units that contain such pragmas; they are not
25533 relevant in a GNAT context and hence are not otherwise implemented.
25535 @node Implementation-defined attributes
25536 @subsection Implementation-defined attributes
25538 Analogous to pragmas, the set of attributes may be extended by an
25539 implementation. All GNAT-defined attributes are described in the
25540 @cite{GNAT Reference Manual}, and these include several that are specifically
25542 to correspond to other vendors' Ada 83 attributes. For migrating from VADS,
25543 the attribute @code{VADS_Size} may be useful. For compatibility with DEC
25544 Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and
25548 @subsection Libraries
25550 Vendors may supply libraries to supplement the standard Ada API. If Ada 83
25551 code uses vendor-specific libraries then there are several ways to manage
25555 If the source code for the libraries (specifications and bodies) are
25556 available, then the libraries can be migrated in the same way as the
25559 If the source code for the specifications but not the bodies are
25560 available, then you can reimplement the bodies.
25562 Some new Ada 95 features obviate the need for library support. For
25563 example most Ada 83 vendors supplied a package for unsigned integers. The
25564 Ada 95 modular type feature is the preferred way to handle this need, so
25565 instead of migrating or reimplementing the unsigned integer package it may
25566 be preferable to retrofit the application using modular types.
25569 @node Elaboration order
25570 @subsection Elaboration order
25572 The implementation can choose any elaboration order consistent with the unit
25573 dependency relationship. This freedom means that some orders can result in
25574 Program_Error being raised due to an ``Access Before Elaboration'': an attempt
25575 to invoke a subprogram its body has been elaborated, or to instantiate a
25576 generic before the generic body has been elaborated. By default GNAT
25577 attempts to choose a safe order (one that will not encounter access before
25578 elaboration problems) by implicitly inserting Elaborate_All pragmas where
25579 needed. However, this can lead to the creation of elaboration circularities
25580 and a resulting rejection of the program by gnatbind. This issue is
25581 thoroughly described in @ref{Elaboration Order Handling in GNAT}.
25582 In brief, there are several
25583 ways to deal with this situation:
25587 Modify the program to eliminate the circularities, e.g. by moving
25588 elaboration-time code into explicitly-invoked procedures
25590 Constrain the elaboration order by including explicit @code{Elaborate_Body} or
25591 @code{Elaborate} pragmas, and then inhibit the generation of implicit
25592 @code{Elaborate_All}
25593 pragmas either globally (as an effect of the @option{-gnatE} switch) or locally
25594 (by selectively suppressing elaboration checks via pragma
25595 @code{Suppress(Elaboration_Check)} when it is safe to do so).
25598 @node Target-specific aspects
25599 @subsection Target-specific aspects
25601 Low-level applications need to deal with machine addresses, data
25602 representations, interfacing with assembler code, and similar issues. If
25603 such an Ada 83 application is being ported to different target hardware (for
25604 example where the byte endianness has changed) then you will need to
25605 carefully examine the program logic; the porting effort will heavily depend
25606 on the robustness of the original design. Moreover, Ada 95 is sometimes
25607 incompatible with typical Ada 83 compiler practices regarding implicit
25608 packing, the meaning of the Size attribute, and the size of access values.
25609 GNAT's approach to these issues is described in @ref{Representation Clauses}.
25612 @node Compatibility with Other Ada 95 Systems
25613 @section Compatibility with Other Ada 95 Systems
25616 Providing that programs avoid the use of implementation dependent and
25617 implementation defined features of Ada 95, as documented in the Ada 95
25618 reference manual, there should be a high degree of portability between
25619 GNAT and other Ada 95 systems. The following are specific items which
25620 have proved troublesome in moving GNAT programs to other Ada 95
25621 compilers, but do not affect porting code to GNAT@.
25624 @item Ada 83 Pragmas and Attributes
25625 Ada 95 compilers are allowed, but not required, to implement the missing
25626 Ada 83 pragmas and attributes that are no longer defined in Ada 95.
25627 GNAT implements all such pragmas and attributes, eliminating this as
25628 a compatibility concern, but some other Ada 95 compilers reject these
25629 pragmas and attributes.
25631 @item Special-needs Annexes
25632 GNAT implements the full set of special needs annexes. At the
25633 current time, it is the only Ada 95 compiler to do so. This means that
25634 programs making use of these features may not be portable to other Ada
25635 95 compilation systems.
25637 @item Representation Clauses
25638 Some other Ada 95 compilers implement only the minimal set of
25639 representation clauses required by the Ada 95 reference manual. GNAT goes
25640 far beyond this minimal set, as described in the next section.
25643 @node Representation Clauses
25644 @section Representation Clauses
25647 The Ada 83 reference manual was quite vague in describing both the minimal
25648 required implementation of representation clauses, and also their precise
25649 effects. The Ada 95 reference manual is much more explicit, but the minimal
25650 set of capabilities required in Ada 95 is quite limited.
25652 GNAT implements the full required set of capabilities described in the
25653 Ada 95 reference manual, but also goes much beyond this, and in particular
25654 an effort has been made to be compatible with existing Ada 83 usage to the
25655 greatest extent possible.
25657 A few cases exist in which Ada 83 compiler behavior is incompatible with
25658 requirements in the Ada 95 reference manual. These are instances of
25659 intentional or accidental dependence on specific implementation dependent
25660 characteristics of these Ada 83 compilers. The following is a list of
25661 the cases most likely to arise in existing legacy Ada 83 code.
25664 @item Implicit Packing
25665 Some Ada 83 compilers allowed a Size specification to cause implicit
25666 packing of an array or record. This could cause expensive implicit
25667 conversions for change of representation in the presence of derived
25668 types, and the Ada design intends to avoid this possibility.
25669 Subsequent AI's were issued to make it clear that such implicit
25670 change of representation in response to a Size clause is inadvisable,
25671 and this recommendation is represented explicitly in the Ada 95 RM
25672 as implementation advice that is followed by GNAT@.
25673 The problem will show up as an error
25674 message rejecting the size clause. The fix is simply to provide
25675 the explicit pragma @code{Pack}, or for more fine tuned control, provide
25676 a Component_Size clause.
25678 @item Meaning of Size Attribute
25679 The Size attribute in Ada 95 for discrete types is defined as being the
25680 minimal number of bits required to hold values of the type. For example,
25681 on a 32-bit machine, the size of Natural will typically be 31 and not
25682 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and
25683 some 32 in this situation. This problem will usually show up as a compile
25684 time error, but not always. It is a good idea to check all uses of the
25685 'Size attribute when porting Ada 83 code. The GNAT specific attribute
25686 Object_Size can provide a useful way of duplicating the behavior of
25687 some Ada 83 compiler systems.
25689 @item Size of Access Types
25690 A common assumption in Ada 83 code is that an access type is in fact a pointer,
25691 and that therefore it will be the same size as a System.Address value. This
25692 assumption is true for GNAT in most cases with one exception. For the case of
25693 a pointer to an unconstrained array type (where the bounds may vary from one
25694 value of the access type to another), the default is to use a ``fat pointer'',
25695 which is represented as two separate pointers, one to the bounds, and one to
25696 the array. This representation has a number of advantages, including improved
25697 efficiency. However, it may cause some difficulties in porting existing Ada 83
25698 code which makes the assumption that, for example, pointers fit in 32 bits on
25699 a machine with 32-bit addressing.
25701 To get around this problem, GNAT also permits the use of ``thin pointers'' for
25702 access types in this case (where the designated type is an unconstrained array
25703 type). These thin pointers are indeed the same size as a System.Address value.
25704 To specify a thin pointer, use a size clause for the type, for example:
25706 @smallexample @c ada
25707 type X is access all String;
25708 for X'Size use Standard'Address_Size;
25712 which will cause the type X to be represented using a single pointer.
25713 When using this representation, the bounds are right behind the array.
25714 This representation is slightly less efficient, and does not allow quite
25715 such flexibility in the use of foreign pointers or in using the
25716 Unrestricted_Access attribute to create pointers to non-aliased objects.
25717 But for any standard portable use of the access type it will work in
25718 a functionally correct manner and allow porting of existing code.
25719 Note that another way of forcing a thin pointer representation
25720 is to use a component size clause for the element size in an array,
25721 or a record representation clause for an access field in a record.
25724 @node Compatibility with DEC Ada 83
25725 @section Compatibility with DEC Ada 83
25728 The VMS version of GNAT fully implements all the pragmas and attributes
25729 provided by DEC Ada 83, as well as providing the standard DEC Ada 83
25730 libraries, including Starlet. In addition, data layouts and parameter
25731 passing conventions are highly compatible. This means that porting
25732 existing DEC Ada 83 code to GNAT in VMS systems should be easier than
25733 most other porting efforts. The following are some of the most
25734 significant differences between GNAT and DEC Ada 83.
25737 @item Default floating-point representation
25738 In GNAT, the default floating-point format is IEEE, whereas in DEC Ada 83,
25739 it is VMS format. GNAT does implement the necessary pragmas
25740 (Long_Float, Float_Representation) for changing this default.
25743 The package System in GNAT exactly corresponds to the definition in the
25744 Ada 95 reference manual, which means that it excludes many of the
25745 DEC Ada 83 extensions. However, a separate package Aux_DEC is provided
25746 that contains the additional definitions, and a special pragma,
25747 Extend_System allows this package to be treated transparently as an
25748 extension of package System.
25751 The definitions provided by Aux_DEC are exactly compatible with those
25752 in the DEC Ada 83 version of System, with one exception.
25753 DEC Ada provides the following declarations:
25755 @smallexample @c ada
25756 TO_ADDRESS (INTEGER)
25757 TO_ADDRESS (UNSIGNED_LONGWORD)
25758 TO_ADDRESS (universal_integer)
25762 The version of TO_ADDRESS taking a universal integer argument is in fact
25763 an extension to Ada 83 not strictly compatible with the reference manual.
25764 In GNAT, we are constrained to be exactly compatible with the standard,
25765 and this means we cannot provide this capability. In DEC Ada 83, the
25766 point of this definition is to deal with a call like:
25768 @smallexample @c ada
25769 TO_ADDRESS (16#12777#);
25773 Normally, according to the Ada 83 standard, one would expect this to be
25774 ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
25775 of TO_ADDRESS@. However, in DEC Ada 83, there is no ambiguity, since the
25776 definition using universal_integer takes precedence.
25778 In GNAT, since the version with universal_integer cannot be supplied, it is
25779 not possible to be 100% compatible. Since there are many programs using
25780 numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
25781 to change the name of the function in the UNSIGNED_LONGWORD case, so the
25782 declarations provided in the GNAT version of AUX_Dec are:
25784 @smallexample @c ada
25785 function To_Address (X : Integer) return Address;
25786 pragma Pure_Function (To_Address);
25788 function To_Address_Long (X : Unsigned_Longword)
25790 pragma Pure_Function (To_Address_Long);
25794 This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
25795 change the name to TO_ADDRESS_LONG@.
25797 @item Task_Id values
25798 The Task_Id values assigned will be different in the two systems, and GNAT
25799 does not provide a specified value for the Task_Id of the environment task,
25800 which in GNAT is treated like any other declared task.
25803 For full details on these and other less significant compatibility issues,
25804 see appendix E of the Digital publication entitled @cite{DEC Ada, Technical
25805 Overview and Comparison on DIGITAL Platforms}.
25807 For GNAT running on other than VMS systems, all the DEC Ada 83 pragmas and
25808 attributes are recognized, although only a subset of them can sensibly
25809 be implemented. The description of pragmas in this reference manual
25810 indicates whether or not they are applicable to non-VMS systems.
25815 @node Microsoft Windows Topics
25816 @appendix Microsoft Windows Topics
25822 This chapter describes topics that are specific to the Microsoft Windows
25823 platforms (NT, 2000, and XP Professional).
25826 * Using GNAT on Windows::
25827 * Using a network installation of GNAT::
25828 * CONSOLE and WINDOWS subsystems::
25829 * Temporary Files::
25830 * Mixed-Language Programming on Windows::
25831 * Windows Calling Conventions::
25832 * Introduction to Dynamic Link Libraries (DLLs)::
25833 * Using DLLs with GNAT::
25834 * Building DLLs with GNAT::
25835 * GNAT and Windows Resources::
25836 * Debugging a DLL::
25837 * GNAT and COM/DCOM Objects::
25840 @node Using GNAT on Windows
25841 @section Using GNAT on Windows
25844 One of the strengths of the GNAT technology is that its tool set
25845 (@code{gcc}, @code{gnatbind}, @code{gnatlink}, @code{gnatmake}, the
25846 @code{gdb} debugger, etc.) is used in the same way regardless of the
25849 On Windows this tool set is complemented by a number of Microsoft-specific
25850 tools that have been provided to facilitate interoperability with Windows
25851 when this is required. With these tools:
25856 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
25860 You can use any Dynamically Linked Library (DLL) in your Ada code (both
25861 relocatable and non-relocatable DLLs are supported).
25864 You can build Ada DLLs for use in other applications. These applications
25865 can be written in a language other than Ada (e.g., C, C++, etc). Again both
25866 relocatable and non-relocatable Ada DLLs are supported.
25869 You can include Windows resources in your Ada application.
25872 You can use or create COM/DCOM objects.
25876 Immediately below are listed all known general GNAT-for-Windows restrictions.
25877 Other restrictions about specific features like Windows Resources and DLLs
25878 are listed in separate sections below.
25883 It is not possible to use @code{GetLastError} and @code{SetLastError}
25884 when tasking, protected records, or exceptions are used. In these
25885 cases, in order to implement Ada semantics, the GNAT run-time system
25886 calls certain Win32 routines that set the last error variable to 0 upon
25887 success. It should be possible to use @code{GetLastError} and
25888 @code{SetLastError} when tasking, protected record, and exception
25889 features are not used, but it is not guaranteed to work.
25892 It is not possible to link against Microsoft libraries except for
25893 import libraries. The library must be built to be compatible with
25894 @file{MSVCRT.LIB} (/MD Microsoft compiler option), @file{LIBC.LIB} and
25895 @file{LIBCMT.LIB} (/ML or /MT Microsoft compiler options) are known to
25896 not be compatible with the GNAT runtime. Even if the library is
25897 compatible with @file{MSVCRT.LIB} it is not guaranteed to work.
25900 When the compilation environment is located on FAT32 drives, users may
25901 experience recompilations of the source files that have not changed if
25902 Daylight Saving Time (DST) state has changed since the last time files
25903 were compiled. NTFS drives do not have this problem.
25906 No components of the GNAT toolset use any entries in the Windows
25907 registry. The only entries that can be created are file associations and
25908 PATH settings, provided the user has chosen to create them at installation
25909 time, as well as some minimal book-keeping information needed to correctly
25910 uninstall or integrate different GNAT products.
25913 @node Using a network installation of GNAT
25914 @section Using a network installation of GNAT
25917 Make sure the system on which GNAT is installed is accessible from the
25918 current machine, i.e. the install location is shared over the network.
25919 Shared resources are accessed on Windows by means of UNC paths, which
25920 have the format @code{\\server\sharename\path}
25922 In order to use such a network installation, simply add the UNC path of the
25923 @file{bin} directory of your GNAT installation in front of your PATH. For
25924 example, if GNAT is installed in @file{\GNAT} directory of a share location
25925 called @file{c-drive} on a machine @file{LOKI}, the following command will
25928 @code{@ @ @ path \\loki\c-drive\gnat\bin;%path%}
25930 Be aware that every compilation using the network installation results in the
25931 transfer of large amounts of data across the network and will likely cause
25932 serious performance penalty.
25934 @node CONSOLE and WINDOWS subsystems
25935 @section CONSOLE and WINDOWS subsystems
25936 @cindex CONSOLE Subsystem
25937 @cindex WINDOWS Subsystem
25941 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
25942 (which is the default subsystem) will always create a console when
25943 launching the application. This is not something desirable when the
25944 application has a Windows GUI. To get rid of this console the
25945 application must be using the @code{WINDOWS} subsystem. To do so
25946 the @option{-mwindows} linker option must be specified.
25949 $ gnatmake winprog -largs -mwindows
25952 @node Temporary Files
25953 @section Temporary Files
25954 @cindex Temporary files
25957 It is possible to control where temporary files gets created by setting
25958 the TMP environment variable. The file will be created:
25961 @item Under the directory pointed to by the TMP environment variable if
25962 this directory exists.
25964 @item Under c:\temp, if the TMP environment variable is not set (or not
25965 pointing to a directory) and if this directory exists.
25967 @item Under the current working directory otherwise.
25971 This allows you to determine exactly where the temporary
25972 file will be created. This is particularly useful in networked
25973 environments where you may not have write access to some
25976 @node Mixed-Language Programming on Windows
25977 @section Mixed-Language Programming on Windows
25980 Developing pure Ada applications on Windows is no different than on
25981 other GNAT-supported platforms. However, when developing or porting an
25982 application that contains a mix of Ada and C/C++, the choice of your
25983 Windows C/C++ development environment conditions your overall
25984 interoperability strategy.
25986 If you use @code{gcc} to compile the non-Ada part of your application,
25987 there are no Windows-specific restrictions that affect the overall
25988 interoperability with your Ada code. If you plan to use
25989 Microsoft tools (e.g. Microsoft Visual C/C++), you should be aware of
25990 the following limitations:
25994 You cannot link your Ada code with an object or library generated with
25995 Microsoft tools if these use the @code{.tls} section (Thread Local
25996 Storage section) since the GNAT linker does not yet support this section.
25999 You cannot link your Ada code with an object or library generated with
26000 Microsoft tools if these use I/O routines other than those provided in
26001 the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
26002 uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
26003 libraries can cause a conflict with @code{msvcrt.dll} services. For
26004 instance Visual C++ I/O stream routines conflict with those in
26009 If you do want to use the Microsoft tools for your non-Ada code and hit one
26010 of the above limitations, you have two choices:
26014 Encapsulate your non Ada code in a DLL to be linked with your Ada
26015 application. In this case, use the Microsoft or whatever environment to
26016 build the DLL and use GNAT to build your executable
26017 (@pxref{Using DLLs with GNAT}).
26020 Or you can encapsulate your Ada code in a DLL to be linked with the
26021 other part of your application. In this case, use GNAT to build the DLL
26022 (@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
26023 environment to build your executable.
26026 @node Windows Calling Conventions
26027 @section Windows Calling Conventions
26032 * C Calling Convention::
26033 * Stdcall Calling Convention::
26034 * DLL Calling Convention::
26038 When a subprogram @code{F} (caller) calls a subprogram @code{G}
26039 (callee), there are several ways to push @code{G}'s parameters on the
26040 stack and there are several possible scenarios to clean up the stack
26041 upon @code{G}'s return. A calling convention is an agreed upon software
26042 protocol whereby the responsibilities between the caller (@code{F}) and
26043 the callee (@code{G}) are clearly defined. Several calling conventions
26044 are available for Windows:
26048 @code{C} (Microsoft defined)
26051 @code{Stdcall} (Microsoft defined)
26054 @code{DLL} (GNAT specific)
26057 @node C Calling Convention
26058 @subsection @code{C} Calling Convention
26061 This is the default calling convention used when interfacing to C/C++
26062 routines compiled with either @code{gcc} or Microsoft Visual C++.
26064 In the @code{C} calling convention subprogram parameters are pushed on the
26065 stack by the caller from right to left. The caller itself is in charge of
26066 cleaning up the stack after the call. In addition, the name of a routine
26067 with @code{C} calling convention is mangled by adding a leading underscore.
26069 The name to use on the Ada side when importing (or exporting) a routine
26070 with @code{C} calling convention is the name of the routine. For
26071 instance the C function:
26074 int get_val (long);
26078 should be imported from Ada as follows:
26080 @smallexample @c ada
26082 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26083 pragma Import (C, Get_Val, External_Name => "get_val");
26088 Note that in this particular case the @code{External_Name} parameter could
26089 have been omitted since, when missing, this parameter is taken to be the
26090 name of the Ada entity in lower case. When the @code{Link_Name} parameter
26091 is missing, as in the above example, this parameter is set to be the
26092 @code{External_Name} with a leading underscore.
26094 When importing a variable defined in C, you should always use the @code{C}
26095 calling convention unless the object containing the variable is part of a
26096 DLL (in which case you should use the @code{DLL} calling convention,
26097 @pxref{DLL Calling Convention}).
26099 @node Stdcall Calling Convention
26100 @subsection @code{Stdcall} Calling Convention
26103 This convention, which was the calling convention used for Pascal
26104 programs, is used by Microsoft for all the routines in the Win32 API for
26105 efficiency reasons. It must be used to import any routine for which this
26106 convention was specified.
26108 In the @code{Stdcall} calling convention subprogram parameters are pushed
26109 on the stack by the caller from right to left. The callee (and not the
26110 caller) is in charge of cleaning the stack on routine exit. In addition,
26111 the name of a routine with @code{Stdcall} calling convention is mangled by
26112 adding a leading underscore (as for the @code{C} calling convention) and a
26113 trailing @code{@@}@code{@i{nn}}, where @i{nn} is the overall size (in
26114 bytes) of the parameters passed to the routine.
26116 The name to use on the Ada side when importing a C routine with a
26117 @code{Stdcall} calling convention is the name of the C routine. The leading
26118 underscore and trailing @code{@@}@code{@i{nn}} are added automatically by
26119 the compiler. For instance the Win32 function:
26122 @b{APIENTRY} int get_val (long);
26126 should be imported from Ada as follows:
26128 @smallexample @c ada
26130 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26131 pragma Import (Stdcall, Get_Val);
26132 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
26137 As for the @code{C} calling convention, when the @code{External_Name}
26138 parameter is missing, it is taken to be the name of the Ada entity in lower
26139 case. If instead of writing the above import pragma you write:
26141 @smallexample @c ada
26143 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26144 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
26149 then the imported routine is @code{_retrieve_val@@4}. However, if instead
26150 of specifying the @code{External_Name} parameter you specify the
26151 @code{Link_Name} as in the following example:
26153 @smallexample @c ada
26155 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
26156 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
26161 then the imported routine is @code{retrieve_val@@4}, that is, there is no
26162 trailing underscore but the appropriate @code{@@}@code{@i{nn}} is always
26163 added at the end of the @code{Link_Name} by the compiler.
26166 Note, that in some special cases a DLL's entry point name lacks a trailing
26167 @code{@@}@code{@i{nn}} while the exported name generated for a call has it.
26168 The @code{gnatdll} tool, which creates the import library for the DLL, is able
26169 to handle those cases (see the description of the switches in
26170 @pxref{Using gnatdll} section).
26172 @node DLL Calling Convention
26173 @subsection @code{DLL} Calling Convention
26176 This convention, which is GNAT-specific, must be used when you want to
26177 import in Ada a variables defined in a DLL. For functions and procedures
26178 this convention is equivalent to the @code{Stdcall} convention. As an
26179 example, if a DLL contains a variable defined as:
26186 then, to access this variable from Ada you should write:
26188 @smallexample @c ada
26190 My_Var : Interfaces.C.int;
26191 pragma Import (DLL, My_Var);
26195 The remarks concerning the @code{External_Name} and @code{Link_Name}
26196 parameters given in the previous sections equally apply to the @code{DLL}
26197 calling convention.
26199 @node Introduction to Dynamic Link Libraries (DLLs)
26200 @section Introduction to Dynamic Link Libraries (DLLs)
26204 A Dynamically Linked Library (DLL) is a library that can be shared by
26205 several applications running under Windows. A DLL can contain any number of
26206 routines and variables.
26208 One advantage of DLLs is that you can change and enhance them without
26209 forcing all the applications that depend on them to be relinked or
26210 recompiled. However, you should be aware than all calls to DLL routines are
26211 slower since, as you will understand below, such calls are indirect.
26213 To illustrate the remainder of this section, suppose that an application
26214 wants to use the services of a DLL @file{API.dll}. To use the services
26215 provided by @file{API.dll} you must statically link against an import
26216 library which contains a jump table with an entry for each routine and
26217 variable exported by the DLL. In the Microsoft world this import library is
26218 called @file{API.lib}. When using GNAT this import library is called either
26219 @file{libAPI.a} or @file{libapi.a} (names are case insensitive).
26221 After you have statically linked your application with the import library
26222 and you run your application, here is what happens:
26226 Your application is loaded into memory.
26229 The DLL @file{API.dll} is mapped into the address space of your
26230 application. This means that:
26234 The DLL will use the stack of the calling thread.
26237 The DLL will use the virtual address space of the calling process.
26240 The DLL will allocate memory from the virtual address space of the calling
26244 Handles (pointers) can be safely exchanged between routines in the DLL
26245 routines and routines in the application using the DLL.
26249 The entries in the @file{libAPI.a} or @file{API.lib} jump table which is
26250 part of your application are initialized with the addresses of the routines
26251 and variables in @file{API.dll}.
26254 If present in @file{API.dll}, routines @code{DllMain} or
26255 @code{DllMainCRTStartup} are invoked. These routines typically contain
26256 the initialization code needed for the well-being of the routines and
26257 variables exported by the DLL.
26261 There is an additional point which is worth mentioning. In the Windows
26262 world there are two kind of DLLs: relocatable and non-relocatable
26263 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
26264 in the target application address space. If the addresses of two
26265 non-relocatable DLLs overlap and these happen to be used by the same
26266 application, a conflict will occur and the application will run
26267 incorrectly. Hence, when possible, it is always preferable to use and
26268 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
26269 supported by GNAT. Note that the @option{-s} linker option (see GNU Linker
26270 User's Guide) removes the debugging symbols from the DLL but the DLL can
26271 still be relocated.
26273 As a side note, an interesting difference between Microsoft DLLs and
26274 Unix shared libraries, is the fact that on most Unix systems all public
26275 routines are exported by default in a Unix shared library, while under
26276 Windows the exported routines must be listed explicitly in a definition
26277 file (@pxref{The Definition File}).
26279 @node Using DLLs with GNAT
26280 @section Using DLLs with GNAT
26283 * Creating an Ada Spec for the DLL Services::
26284 * Creating an Import Library::
26288 To use the services of a DLL, say @file{API.dll}, in your Ada application
26293 The Ada spec for the routines and/or variables you want to access in
26294 @file{API.dll}. If not available this Ada spec must be built from the C/C++
26295 header files provided with the DLL.
26298 The import library (@file{libAPI.a} or @file{API.lib}). As previously
26299 mentioned an import library is a statically linked library containing the
26300 import table which will be filled at load time to point to the actual
26301 @file{API.dll} routines. Sometimes you don't have an import library for the
26302 DLL you want to use. The following sections will explain how to build one.
26305 The actual DLL, @file{API.dll}.
26309 Once you have all the above, to compile an Ada application that uses the
26310 services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
26311 you simply issue the command
26314 $ gnatmake my_ada_app -largs -lAPI
26318 The argument @option{-largs -lAPI} at the end of the @code{gnatmake} command
26319 tells the GNAT linker to look first for a library named @file{API.lib}
26320 (Microsoft-style name) and if not found for a library named @file{libAPI.a}
26321 (GNAT-style name). Note that if the Ada package spec for @file{API.dll}
26322 contains the following pragma
26324 @smallexample @c ada
26325 pragma Linker_Options ("-lAPI");
26329 you do not have to add @option{-largs -lAPI} at the end of the @code{gnatmake}
26332 If any one of the items above is missing you will have to create it
26333 yourself. The following sections explain how to do so using as an
26334 example a fictitious DLL called @file{API.dll}.
26336 @node Creating an Ada Spec for the DLL Services
26337 @subsection Creating an Ada Spec for the DLL Services
26340 A DLL typically comes with a C/C++ header file which provides the
26341 definitions of the routines and variables exported by the DLL. The Ada
26342 equivalent of this header file is a package spec that contains definitions
26343 for the imported entities. If the DLL you intend to use does not come with
26344 an Ada spec you have to generate one such spec yourself. For example if
26345 the header file of @file{API.dll} is a file @file{api.h} containing the
26346 following two definitions:
26358 then the equivalent Ada spec could be:
26360 @smallexample @c ada
26363 with Interfaces.C.Strings;
26368 function Get (Str : C.Strings.Chars_Ptr) return C.int;
26371 pragma Import (C, Get);
26372 pragma Import (DLL, Some_Var);
26379 Note that a variable is @strong{always imported with a DLL convention}. A
26380 function can have @code{C}, @code{Stdcall} or @code{DLL} convention. For
26381 subprograms, the @code{DLL} convention is a synonym of @code{Stdcall}
26382 (@pxref{Windows Calling Conventions}).
26384 @node Creating an Import Library
26385 @subsection Creating an Import Library
26386 @cindex Import library
26389 * The Definition File::
26390 * GNAT-Style Import Library::
26391 * Microsoft-Style Import Library::
26395 If a Microsoft-style import library @file{API.lib} or a GNAT-style
26396 import library @file{libAPI.a} is available with @file{API.dll} you
26397 can skip this section. Otherwise read on.
26399 @node The Definition File
26400 @subsubsection The Definition File
26401 @cindex Definition file
26405 As previously mentioned, and unlike Unix systems, the list of symbols
26406 that are exported from a DLL must be provided explicitly in Windows.
26407 The main goal of a definition file is precisely that: list the symbols
26408 exported by a DLL. A definition file (usually a file with a @code{.def}
26409 suffix) has the following structure:
26415 [DESCRIPTION @i{string}]
26425 @item LIBRARY @i{name}
26426 This section, which is optional, gives the name of the DLL.
26428 @item DESCRIPTION @i{string}
26429 This section, which is optional, gives a description string that will be
26430 embedded in the import library.
26433 This section gives the list of exported symbols (procedures, functions or
26434 variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
26435 section of @file{API.def} looks like:
26449 Note that you must specify the correct suffix (@code{@@}@code{@i{nn}})
26450 (@pxref{Windows Calling Conventions}) for a Stdcall
26451 calling convention function in the exported symbols list.
26454 There can actually be other sections in a definition file, but these
26455 sections are not relevant to the discussion at hand.
26457 @node GNAT-Style Import Library
26458 @subsubsection GNAT-Style Import Library
26461 To create a static import library from @file{API.dll} with the GNAT tools
26462 you should proceed as follows:
26466 Create the definition file @file{API.def} (@pxref{The Definition File}).
26467 For that use the @code{dll2def} tool as follows:
26470 $ dll2def API.dll > API.def
26474 @code{dll2def} is a very simple tool: it takes as input a DLL and prints
26475 to standard output the list of entry points in the DLL. Note that if
26476 some routines in the DLL have the @code{Stdcall} convention
26477 (@pxref{Windows Calling Conventions}) with stripped @code{@@}@i{nn}
26478 suffix then you'll have to edit @file{api.def} to add it.
26481 Here are some hints to find the right @code{@@}@i{nn} suffix.
26485 If you have the Microsoft import library (.lib), it is possible to get
26486 the right symbols by using Microsoft @code{dumpbin} tool (see the
26487 corresponding Microsoft documentation for further details).
26490 $ dumpbin /exports api.lib
26494 If you have a message about a missing symbol at link time the compiler
26495 tells you what symbol is expected. You just have to go back to the
26496 definition file and add the right suffix.
26500 Build the import library @code{libAPI.a}, using @code{gnatdll}
26501 (@pxref{Using gnatdll}) as follows:
26504 $ gnatdll -e API.def -d API.dll
26508 @code{gnatdll} takes as input a definition file @file{API.def} and the
26509 name of the DLL containing the services listed in the definition file
26510 @file{API.dll}. The name of the static import library generated is
26511 computed from the name of the definition file as follows: if the
26512 definition file name is @i{xyz}@code{.def}, the import library name will
26513 be @code{lib}@i{xyz}@code{.a}. Note that in the previous example option
26514 @option{-e} could have been removed because the name of the definition
26515 file (before the ``@code{.def}'' suffix) is the same as the name of the
26516 DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
26519 @node Microsoft-Style Import Library
26520 @subsubsection Microsoft-Style Import Library
26523 With GNAT you can either use a GNAT-style or Microsoft-style import
26524 library. A Microsoft import library is needed only if you plan to make an
26525 Ada DLL available to applications developed with Microsoft
26526 tools (@pxref{Mixed-Language Programming on Windows}).
26528 To create a Microsoft-style import library for @file{API.dll} you
26529 should proceed as follows:
26533 Create the definition file @file{API.def} from the DLL. For this use either
26534 the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
26535 tool (see the corresponding Microsoft documentation for further details).
26538 Build the actual import library using Microsoft's @code{lib} utility:
26541 $ lib -machine:IX86 -def:API.def -out:API.lib
26545 If you use the above command the definition file @file{API.def} must
26546 contain a line giving the name of the DLL:
26553 See the Microsoft documentation for further details about the usage of
26557 @node Building DLLs with GNAT
26558 @section Building DLLs with GNAT
26559 @cindex DLLs, building
26562 * Limitations When Using Ada DLLs from Ada::
26563 * Exporting Ada Entities::
26564 * Ada DLLs and Elaboration::
26565 * Ada DLLs and Finalization::
26566 * Creating a Spec for Ada DLLs::
26567 * Creating the Definition File::
26572 This section explains how to build DLLs containing Ada code. These DLLs
26573 will be referred to as Ada DLLs in the remainder of this section.
26575 The steps required to build an Ada DLL that is to be used by Ada as well as
26576 non-Ada applications are as follows:
26580 You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
26581 @code{Stdcall} calling convention to avoid any Ada name mangling for the
26582 entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
26583 skip this step if you plan to use the Ada DLL only from Ada applications.
26586 Your Ada code must export an initialization routine which calls the routine
26587 @code{adainit} generated by @code{gnatbind} to perform the elaboration of
26588 the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
26589 routine exported by the Ada DLL must be invoked by the clients of the DLL
26590 to initialize the DLL.
26593 When useful, the DLL should also export a finalization routine which calls
26594 routine @code{adafinal} generated by @code{gnatbind} to perform the
26595 finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
26596 The finalization routine exported by the Ada DLL must be invoked by the
26597 clients of the DLL when the DLL services are no further needed.
26600 You must provide a spec for the services exported by the Ada DLL in each
26601 of the programming languages to which you plan to make the DLL available.
26604 You must provide a definition file listing the exported entities
26605 (@pxref{The Definition File}).
26608 Finally you must use @code{gnatdll} to produce the DLL and the import
26609 library (@pxref{Using gnatdll}).
26613 Note that a relocatable DLL stripped using the @code{strip} binutils
26614 tool will not be relocatable anymore. To build a DLL without debug
26615 information pass @code{-largs -s} to @code{gnatdll}.
26617 @node Limitations When Using Ada DLLs from Ada
26618 @subsection Limitations When Using Ada DLLs from Ada
26621 When using Ada DLLs from Ada applications there is a limitation users
26622 should be aware of. Because on Windows the GNAT run time is not in a DLL of
26623 its own, each Ada DLL includes a part of the GNAT run time. Specifically,
26624 each Ada DLL includes the services of the GNAT run time that are necessary
26625 to the Ada code inside the DLL. As a result, when an Ada program uses an
26626 Ada DLL there are two independent GNAT run times: one in the Ada DLL and
26627 one in the main program.
26629 It is therefore not possible to exchange GNAT run-time objects between the
26630 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
26631 handles (e.g. @code{Text_IO.File_Type}), tasks types, protected objects
26634 It is completely safe to exchange plain elementary, array or record types,
26635 Windows object handles, etc.
26637 @node Exporting Ada Entities
26638 @subsection Exporting Ada Entities
26639 @cindex Export table
26642 Building a DLL is a way to encapsulate a set of services usable from any
26643 application. As a result, the Ada entities exported by a DLL should be
26644 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
26645 any Ada name mangling. Please note that the @code{Stdcall} convention
26646 should only be used for subprograms, not for variables. As an example here
26647 is an Ada package @code{API}, spec and body, exporting two procedures, a
26648 function, and a variable:
26650 @smallexample @c ada
26653 with Interfaces.C; use Interfaces;
26655 Count : C.int := 0;
26656 function Factorial (Val : C.int) return C.int;
26658 procedure Initialize_API;
26659 procedure Finalize_API;
26660 -- Initialization & Finalization routines. More in the next section.
26662 pragma Export (C, Initialize_API);
26663 pragma Export (C, Finalize_API);
26664 pragma Export (C, Count);
26665 pragma Export (C, Factorial);
26671 @smallexample @c ada
26674 package body API is
26675 function Factorial (Val : C.int) return C.int is
26678 Count := Count + 1;
26679 for K in 1 .. Val loop
26685 procedure Initialize_API is
26687 pragma Import (C, Adainit);
26690 end Initialize_API;
26692 procedure Finalize_API is
26693 procedure Adafinal;
26694 pragma Import (C, Adafinal);
26704 If the Ada DLL you are building will only be used by Ada applications
26705 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
26706 convention. As an example, the previous package could be written as
26709 @smallexample @c ada
26713 Count : Integer := 0;
26714 function Factorial (Val : Integer) return Integer;
26716 procedure Initialize_API;
26717 procedure Finalize_API;
26718 -- Initialization and Finalization routines.
26724 @smallexample @c ada
26727 package body API is
26728 function Factorial (Val : Integer) return Integer is
26729 Fact : Integer := 1;
26731 Count := Count + 1;
26732 for K in 1 .. Val loop
26739 -- The remainder of this package body is unchanged.
26746 Note that if you do not export the Ada entities with a @code{C} or
26747 @code{Stdcall} convention you will have to provide the mangled Ada names
26748 in the definition file of the Ada DLL
26749 (@pxref{Creating the Definition File}).
26751 @node Ada DLLs and Elaboration
26752 @subsection Ada DLLs and Elaboration
26753 @cindex DLLs and elaboration
26756 The DLL that you are building contains your Ada code as well as all the
26757 routines in the Ada library that are needed by it. The first thing a
26758 user of your DLL must do is elaborate the Ada code
26759 (@pxref{Elaboration Order Handling in GNAT}).
26761 To achieve this you must export an initialization routine
26762 (@code{Initialize_API} in the previous example), which must be invoked
26763 before using any of the DLL services. This elaboration routine must call
26764 the Ada elaboration routine @code{adainit} generated by the GNAT binder
26765 (@pxref{Binding with Non-Ada Main Programs}). See the body of
26766 @code{Initialize_Api} for an example. Note that the GNAT binder is
26767 automatically invoked during the DLL build process by the @code{gnatdll}
26768 tool (@pxref{Using gnatdll}).
26770 When a DLL is loaded, Windows systematically invokes a routine called
26771 @code{DllMain}. It would therefore be possible to call @code{adainit}
26772 directly from @code{DllMain} without having to provide an explicit
26773 initialization routine. Unfortunately, it is not possible to call
26774 @code{adainit} from the @code{DllMain} if your program has library level
26775 tasks because access to the @code{DllMain} entry point is serialized by
26776 the system (that is, only a single thread can execute ``through'' it at a
26777 time), which means that the GNAT run time will deadlock waiting for the
26778 newly created task to complete its initialization.
26780 @node Ada DLLs and Finalization
26781 @subsection Ada DLLs and Finalization
26782 @cindex DLLs and finalization
26785 When the services of an Ada DLL are no longer needed, the client code should
26786 invoke the DLL finalization routine, if available. The DLL finalization
26787 routine is in charge of releasing all resources acquired by the DLL. In the
26788 case of the Ada code contained in the DLL, this is achieved by calling
26789 routine @code{adafinal} generated by the GNAT binder
26790 (@pxref{Binding with Non-Ada Main Programs}).
26791 See the body of @code{Finalize_Api} for an
26792 example. As already pointed out the GNAT binder is automatically invoked
26793 during the DLL build process by the @code{gnatdll} tool
26794 (@pxref{Using gnatdll}).
26796 @node Creating a Spec for Ada DLLs
26797 @subsection Creating a Spec for Ada DLLs
26800 To use the services exported by the Ada DLL from another programming
26801 language (e.g. C), you have to translate the specs of the exported Ada
26802 entities in that language. For instance in the case of @code{API.dll},
26803 the corresponding C header file could look like:
26808 extern int *_imp__count;
26809 #define count (*_imp__count)
26810 int factorial (int);
26816 It is important to understand that when building an Ada DLL to be used by
26817 other Ada applications, you need two different specs for the packages
26818 contained in the DLL: one for building the DLL and the other for using
26819 the DLL. This is because the @code{DLL} calling convention is needed to
26820 use a variable defined in a DLL, but when building the DLL, the variable
26821 must have either the @code{Ada} or @code{C} calling convention. As an
26822 example consider a DLL comprising the following package @code{API}:
26824 @smallexample @c ada
26828 Count : Integer := 0;
26830 -- Remainder of the package omitted.
26837 After producing a DLL containing package @code{API}, the spec that
26838 must be used to import @code{API.Count} from Ada code outside of the
26841 @smallexample @c ada
26846 pragma Import (DLL, Count);
26852 @node Creating the Definition File
26853 @subsection Creating the Definition File
26856 The definition file is the last file needed to build the DLL. It lists
26857 the exported symbols. As an example, the definition file for a DLL
26858 containing only package @code{API} (where all the entities are exported
26859 with a @code{C} calling convention) is:
26874 If the @code{C} calling convention is missing from package @code{API},
26875 then the definition file contains the mangled Ada names of the above
26876 entities, which in this case are:
26885 api__initialize_api
26890 @node Using gnatdll
26891 @subsection Using @code{gnatdll}
26895 * gnatdll Example::
26896 * gnatdll behind the Scenes::
26901 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
26902 and non-Ada sources that make up your DLL have been compiled.
26903 @code{gnatdll} is actually in charge of two distinct tasks: build the
26904 static import library for the DLL and the actual DLL. The form of the
26905 @code{gnatdll} command is
26909 $ gnatdll [@var{switches}] @var{list-of-files} [-largs @var{opts}]
26914 where @i{list-of-files} is a list of ALI and object files. The object
26915 file list must be the exact list of objects corresponding to the non-Ada
26916 sources whose services are to be included in the DLL. The ALI file list
26917 must be the exact list of ALI files for the corresponding Ada sources
26918 whose services are to be included in the DLL. If @i{list-of-files} is
26919 missing, only the static import library is generated.
26922 You may specify any of the following switches to @code{gnatdll}:
26925 @item -a[@var{address}]
26926 @cindex @option{-a} (@code{gnatdll})
26927 Build a non-relocatable DLL at @var{address}. If @var{address} is not
26928 specified the default address @var{0x11000000} will be used. By default,
26929 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
26930 advise the reader to build relocatable DLL.
26932 @item -b @var{address}
26933 @cindex @option{-b} (@code{gnatdll})
26934 Set the relocatable DLL base address. By default the address is
26937 @item -bargs @var{opts}
26938 @cindex @option{-bargs} (@code{gnatdll})
26939 Binder options. Pass @var{opts} to the binder.
26941 @item -d @var{dllfile}
26942 @cindex @option{-d} (@code{gnatdll})
26943 @var{dllfile} is the name of the DLL. This switch must be present for
26944 @code{gnatdll} to do anything. The name of the generated import library is
26945 obtained algorithmically from @var{dllfile} as shown in the following
26946 example: if @var{dllfile} is @code{xyz.dll}, the import library name is
26947 @code{libxyz.a}. The name of the definition file to use (if not specified
26948 by option @option{-e}) is obtained algorithmically from @var{dllfile}
26949 as shown in the following example:
26950 if @var{dllfile} is @code{xyz.dll}, the definition
26951 file used is @code{xyz.def}.
26953 @item -e @var{deffile}
26954 @cindex @option{-e} (@code{gnatdll})
26955 @var{deffile} is the name of the definition file.
26958 @cindex @option{-g} (@code{gnatdll})
26959 Generate debugging information. This information is stored in the object
26960 file and copied from there to the final DLL file by the linker,
26961 where it can be read by the debugger. You must use the
26962 @option{-g} switch if you plan on using the debugger or the symbolic
26966 @cindex @option{-h} (@code{gnatdll})
26967 Help mode. Displays @code{gnatdll} switch usage information.
26970 @cindex @option{-I} (@code{gnatdll})
26971 Direct @code{gnatdll} to search the @var{dir} directory for source and
26972 object files needed to build the DLL.
26973 (@pxref{Search Paths and the Run-Time Library (RTL)}).
26976 @cindex @option{-k} (@code{gnatdll})
26977 Removes the @code{@@}@i{nn} suffix from the import library's exported
26978 names. You must specified this option if you want to use a
26979 @code{Stdcall} function in a DLL for which the @code{@@}@i{nn} suffix
26980 has been removed. This is the case for most of the Windows NT DLL for
26981 example. This option has no effect when @option{-n} option is specified.
26983 @item -l @var{file}
26984 @cindex @option{-l} (@code{gnatdll})
26985 The list of ALI and object files used to build the DLL are listed in
26986 @var{file}, instead of being given in the command line. Each line in
26987 @var{file} contains the name of an ALI or object file.
26990 @cindex @option{-n} (@code{gnatdll})
26991 No Import. Do not create the import library.
26994 @cindex @option{-q} (@code{gnatdll})
26995 Quiet mode. Do not display unnecessary messages.
26998 @cindex @option{-v} (@code{gnatdll})
26999 Verbose mode. Display extra information.
27001 @item -largs @var{opts}
27002 @cindex @option{-largs} (@code{gnatdll})
27003 Linker options. Pass @var{opts} to the linker.
27006 @node gnatdll Example
27007 @subsubsection @code{gnatdll} Example
27010 As an example the command to build a relocatable DLL from @file{api.adb}
27011 once @file{api.adb} has been compiled and @file{api.def} created is
27014 $ gnatdll -d api.dll api.ali
27018 The above command creates two files: @file{libapi.a} (the import
27019 library) and @file{api.dll} (the actual DLL). If you want to create
27020 only the DLL, just type:
27023 $ gnatdll -d api.dll -n api.ali
27027 Alternatively if you want to create just the import library, type:
27030 $ gnatdll -d api.dll
27033 @node gnatdll behind the Scenes
27034 @subsubsection @code{gnatdll} behind the Scenes
27037 This section details the steps involved in creating a DLL. @code{gnatdll}
27038 does these steps for you. Unless you are interested in understanding what
27039 goes on behind the scenes, you should skip this section.
27041 We use the previous example of a DLL containing the Ada package @code{API},
27042 to illustrate the steps necessary to build a DLL. The starting point is a
27043 set of objects that will make up the DLL and the corresponding ALI
27044 files. In the case of this example this means that @file{api.o} and
27045 @file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
27050 @code{gnatdll} builds the base file (@file{api.base}). A base file gives
27051 the information necessary to generate relocation information for the
27057 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
27062 In addition to the base file, the @code{gnatlink} command generates an
27063 output file @file{api.jnk} which can be discarded. The @option{-mdll} switch
27064 asks @code{gnatlink} to generate the routines @code{DllMain} and
27065 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
27066 is loaded into memory.
27069 @code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
27070 export table (@file{api.exp}). The export table contains the relocation
27071 information in a form which can be used during the final link to ensure
27072 that the Windows loader is able to place the DLL anywhere in memory.
27076 $ dlltool --dllname api.dll --def api.def --base-file api.base \
27077 --output-exp api.exp
27082 @code{gnatdll} builds the base file using the new export table. Note that
27083 @code{gnatbind} must be called once again since the binder generated file
27084 has been deleted during the previous call to @code{gnatlink}.
27089 $ gnatlink api -o api.jnk api.exp -mdll
27090 -Wl,--base-file,api.base
27095 @code{gnatdll} builds the new export table using the new base file and
27096 generates the DLL import library @file{libAPI.a}.
27100 $ dlltool --dllname api.dll --def api.def --base-file api.base \
27101 --output-exp api.exp --output-lib libAPI.a
27106 Finally @code{gnatdll} builds the relocatable DLL using the final export
27112 $ gnatlink api api.exp -o api.dll -mdll
27117 @node Using dlltool
27118 @subsubsection Using @code{dlltool}
27121 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
27122 DLLs and static import libraries. This section summarizes the most
27123 common @code{dlltool} switches. The form of the @code{dlltool} command
27127 $ dlltool [@var{switches}]
27131 @code{dlltool} switches include:
27134 @item --base-file @var{basefile}
27135 @cindex @option{--base-file} (@command{dlltool})
27136 Read the base file @var{basefile} generated by the linker. This switch
27137 is used to create a relocatable DLL.
27139 @item --def @var{deffile}
27140 @cindex @option{--def} (@command{dlltool})
27141 Read the definition file.
27143 @item --dllname @var{name}
27144 @cindex @option{--dllname} (@command{dlltool})
27145 Gives the name of the DLL. This switch is used to embed the name of the
27146 DLL in the static import library generated by @code{dlltool} with switch
27147 @option{--output-lib}.
27150 @cindex @option{-k} (@command{dlltool})
27151 Kill @code{@@}@i{nn} from exported names
27152 (@pxref{Windows Calling Conventions}
27153 for a discussion about @code{Stdcall}-style symbols.
27156 @cindex @option{--help} (@command{dlltool})
27157 Prints the @code{dlltool} switches with a concise description.
27159 @item --output-exp @var{exportfile}
27160 @cindex @option{--output-exp} (@command{dlltool})
27161 Generate an export file @var{exportfile}. The export file contains the
27162 export table (list of symbols in the DLL) and is used to create the DLL.
27164 @item --output-lib @i{libfile}
27165 @cindex @option{--output-lib} (@command{dlltool})
27166 Generate a static import library @var{libfile}.
27169 @cindex @option{-v} (@command{dlltool})
27172 @item --as @i{assembler-name}
27173 @cindex @option{--as} (@command{dlltool})
27174 Use @i{assembler-name} as the assembler. The default is @code{as}.
27177 @node GNAT and Windows Resources
27178 @section GNAT and Windows Resources
27179 @cindex Resources, windows
27182 * Building Resources::
27183 * Compiling Resources::
27184 * Using Resources::
27188 Resources are an easy way to add Windows specific objects to your
27189 application. The objects that can be added as resources include:
27218 This section explains how to build, compile and use resources.
27220 @node Building Resources
27221 @subsection Building Resources
27222 @cindex Resources, building
27225 A resource file is an ASCII file. By convention resource files have an
27226 @file{.rc} extension.
27227 The easiest way to build a resource file is to use Microsoft tools
27228 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
27229 @code{dlgedit.exe} to build dialogs.
27230 It is always possible to build an @file{.rc} file yourself by writing a
27233 It is not our objective to explain how to write a resource file. A
27234 complete description of the resource script language can be found in the
27235 Microsoft documentation.
27237 @node Compiling Resources
27238 @subsection Compiling Resources
27241 @cindex Resources, compiling
27244 This section describes how to build a GNAT-compatible (COFF) object file
27245 containing the resources. This is done using the Resource Compiler
27246 @code{windres} as follows:
27249 $ windres -i myres.rc -o myres.o
27253 By default @code{windres} will run @code{gcc} to preprocess the @file{.rc}
27254 file. You can specify an alternate preprocessor (usually named
27255 @file{cpp.exe}) using the @code{windres} @option{--preprocessor}
27256 parameter. A list of all possible options may be obtained by entering
27257 the command @code{windres} @option{--help}.
27259 It is also possible to use the Microsoft resource compiler @code{rc.exe}
27260 to produce a @file{.res} file (binary resource file). See the
27261 corresponding Microsoft documentation for further details. In this case
27262 you need to use @code{windres} to translate the @file{.res} file to a
27263 GNAT-compatible object file as follows:
27266 $ windres -i myres.res -o myres.o
27269 @node Using Resources
27270 @subsection Using Resources
27271 @cindex Resources, using
27274 To include the resource file in your program just add the
27275 GNAT-compatible object file for the resource(s) to the linker
27276 arguments. With @code{gnatmake} this is done by using the @option{-largs}
27280 $ gnatmake myprog -largs myres.o
27283 @node Debugging a DLL
27284 @section Debugging a DLL
27285 @cindex DLL debugging
27288 * Program and DLL Both Built with GCC/GNAT::
27289 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
27293 Debugging a DLL is similar to debugging a standard program. But
27294 we have to deal with two different executable parts: the DLL and the
27295 program that uses it. We have the following four possibilities:
27299 The program and the DLL are built with @code{GCC/GNAT}.
27301 The program is built with foreign tools and the DLL is built with
27304 The program is built with @code{GCC/GNAT} and the DLL is built with
27310 In this section we address only cases one and two above.
27311 There is no point in trying to debug
27312 a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
27313 information in it. To do so you must use a debugger compatible with the
27314 tools suite used to build the DLL.
27316 @node Program and DLL Both Built with GCC/GNAT
27317 @subsection Program and DLL Both Built with GCC/GNAT
27320 This is the simplest case. Both the DLL and the program have @code{GDB}
27321 compatible debugging information. It is then possible to break anywhere in
27322 the process. Let's suppose here that the main procedure is named
27323 @code{ada_main} and that in the DLL there is an entry point named
27327 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
27328 program must have been built with the debugging information (see GNAT -g
27329 switch). Here are the step-by-step instructions for debugging it:
27332 @item Launch @code{GDB} on the main program.
27338 @item Break on the main procedure and run the program.
27341 (gdb) break ada_main
27346 This step is required to be able to set a breakpoint inside the DLL. As long
27347 as the program is not run, the DLL is not loaded. This has the
27348 consequence that the DLL debugging information is also not loaded, so it is not
27349 possible to set a breakpoint in the DLL.
27351 @item Set a breakpoint inside the DLL
27354 (gdb) break ada_dll
27361 At this stage a breakpoint is set inside the DLL. From there on
27362 you can use the standard approach to debug the whole program
27363 (@pxref{Running and Debugging Ada Programs}).
27365 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT
27366 @subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
27369 * Debugging the DLL Directly::
27370 * Attaching to a Running Process::
27374 In this case things are slightly more complex because it is not possible to
27375 start the main program and then break at the beginning to load the DLL and the
27376 associated DLL debugging information. It is not possible to break at the
27377 beginning of the program because there is no @code{GDB} debugging information,
27378 and therefore there is no direct way of getting initial control. This
27379 section addresses this issue by describing some methods that can be used
27380 to break somewhere in the DLL to debug it.
27383 First suppose that the main procedure is named @code{main} (this is for
27384 example some C code built with Microsoft Visual C) and that there is a
27385 DLL named @code{test.dll} containing an Ada entry point named
27389 The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
27390 been built with debugging information (see GNAT -g option).
27392 @node Debugging the DLL Directly
27393 @subsubsection Debugging the DLL Directly
27397 Launch the debugger on the DLL.
27403 @item Set a breakpoint on a DLL subroutine.
27406 (gdb) break ada_dll
27410 Specify the executable file to @code{GDB}.
27413 (gdb) exec-file main.exe
27424 This will run the program until it reaches the breakpoint that has been
27425 set. From that point you can use the standard way to debug a program
27426 as described in (@pxref{Running and Debugging Ada Programs}).
27431 It is also possible to debug the DLL by attaching to a running process.
27433 @node Attaching to a Running Process
27434 @subsubsection Attaching to a Running Process
27435 @cindex DLL debugging, attach to process
27438 With @code{GDB} it is always possible to debug a running process by
27439 attaching to it. It is possible to debug a DLL this way. The limitation
27440 of this approach is that the DLL must run long enough to perform the
27441 attach operation. It may be useful for instance to insert a time wasting
27442 loop in the code of the DLL to meet this criterion.
27446 @item Launch the main program @file{main.exe}.
27452 @item Use the Windows @i{Task Manager} to find the process ID. Let's say
27453 that the process PID for @file{main.exe} is 208.
27461 @item Attach to the running process to be debugged.
27467 @item Load the process debugging information.
27470 (gdb) symbol-file main.exe
27473 @item Break somewhere in the DLL.
27476 (gdb) break ada_dll
27479 @item Continue process execution.
27488 This last step will resume the process execution, and stop at
27489 the breakpoint we have set. From there you can use the standard
27490 approach to debug a program as described in
27491 (@pxref{Running and Debugging Ada Programs}).
27493 @node GNAT and COM/DCOM Objects
27494 @section GNAT and COM/DCOM Objects
27499 This section is temporarily left blank.
27504 @c **********************************
27505 @c * GNU Free Documentation License *
27506 @c **********************************
27508 @c GNU Free Documentation License
27510 @node Index,,GNU Free Documentation License, Top
27516 @c Put table of contents at end, otherwise it precedes the "title page" in
27517 @c the .txt version
27518 @c Edit the pdf file to move the contents to the beginning, after the title