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1This is Info file autoconf.info, produced by Makeinfo version 1.67 from
2the input file /home/bje/autoconf-2.13/autoconf.texi.
3
4START-INFO-DIR-ENTRY
5* Autoconf: (autoconf).         Create source code configuration scripts.
6END-INFO-DIR-ENTRY
7
8   Autoconf: Creating Automatic Configuration Scripts, by David
9MacKenzie.
10
11   This file documents the GNU Autoconf package for creating scripts to
12configure source code packages using templates and an `m4' macro
13package.
14
15   Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998 Free Software
16Foundation, Inc.
17
18   Permission is granted to make and distribute verbatim copies of this
19manual provided the copyright notice and this permission notice are
20preserved on all copies.
21
22   Permission is granted to copy and distribute modified versions of
23this manual under the conditions for verbatim copying, provided that
24the entire resulting derived work is distributed under the terms of a
25permission notice identical to this one.
26
27   Permission is granted to copy and distribute translations of this
28manual into another language, under the above conditions for modified
29versions, except that this permission notice may be stated in a
30translation approved by the Foundation.
31
32
33File: autoconf.info,  Node: Top,  Next: Introduction,  Prev: (dir),  Up: (dir)
34
35   This file documents the GNU Autoconf package for creating scripts to
36configure source code packages using templates and an `m4' macro
37package.  This is edition 2.13, for Autoconf version 2.13.
38
39* Menu:
40
41* Introduction::                Autoconf's purpose, strengths, and weaknesses.
42* Making configure Scripts::    How to organize and produce Autoconf scripts.
43* Setup::                       Initialization and output.
44* Existing Tests::              Macros that check for particular features.
45* Writing Tests::               How to write new feature checks.
46* Results::                     What to do with results from feature checks.
47* Writing Macros::              Adding new macros to Autoconf.
48* Manual Configuration::        Selecting features that can't be guessed.
49* Site Configuration::          Local defaults for `configure'.
50* Invoking configure::          How to use the Autoconf output.
51* Invoking config.status::      Recreating a configuration.
52* Questions::                   Questions about Autoconf, with answers.
53* Upgrading::                   Tips for upgrading from version 1.
54* History::                     History of Autoconf.
55* Old Macro Names::             Backward compatibility macros.
56* Environment Variable Index::  Index of environment variables used.
57* Output Variable Index::       Index of variables set in output files.
58* Preprocessor Symbol Index::   Index of C preprocessor symbols defined.
59* Macro Index::                 Index of Autoconf macros.
60
61 -- The Detailed Node Listing --
62
63Making `configure' Scripts
64
65* Writing configure.in::        What to put in an Autoconf input file.
66* Invoking autoscan::           Semi-automatic `configure.in' writing.
67* Invoking ifnames::            Listing the conditionals in source code.
68* Invoking autoconf::           How to create configuration scripts.
69* Invoking autoreconf::         Remaking multiple `configure' scripts.
70
71Initialization and Output Files
72
73* Input::                       Where Autoconf should find files.
74* Output::                      Creating output files.
75* Makefile Substitutions::      Using output variables in `Makefile's.
76* Configuration Headers::       Creating a configuration header file.
77* Subdirectories::              Configuring independent packages together.
78* Default Prefix::              Changing the default installation prefix.
79* Versions::                    Version numbers in `configure'.
80
81Substitutions in Makefiles
82
83* Preset Output Variables::     Output variables that are always set.
84* Build Directories::           Supporting multiple concurrent compiles.
85* Automatic Remaking::          Makefile rules for configuring.
86
87Configuration Header Files
88
89* Header Templates::            Input for the configuration headers.
90* Invoking autoheader::         How to create configuration templates.
91
92Existing Tests
93
94* Alternative Programs::        Selecting between alternative programs.
95* Libraries::                   Library archives that might be missing.
96* Library Functions::           C library functions that might be missing.
97* Header Files::                Header files that might be missing.
98* Structures::                  Structures or members that might be missing.
99* Typedefs::                    `typedef's that might be missing.
100* C Compiler Characteristics::
101* Fortran 77 Compiler Characteristics::
102* System Services::             Operating system services.
103* UNIX Variants::               Special kludges for specific UNIX variants.
104
105Alternative Programs
106
107* Particular Programs::         Special handling to find certain programs.
108* Generic Programs::            How to find other programs.
109
110Library Functions
111
112* Particular Functions::        Special handling to find certain functions.
113* Generic Functions::           How to find other functions.
114
115Header Files
116
117* Particular Headers::          Special handling to find certain headers.
118* Generic Headers::             How to find other headers.
119
120Typedefs
121
122* Particular Typedefs::         Special handling to find certain types.
123* Generic Typedefs::            How to find other types.
124
125Writing Tests
126
127* Examining Declarations::      Detecting header files and declarations.
128* Examining Syntax::            Detecting language syntax features.
129* Examining Libraries::         Detecting functions and global variables.
130* Run Time::                    Testing for run-time features.
131* Portable Shell::              Shell script portability pitfalls.
132* Testing Values and Files::    Checking strings and files.
133* Multiple Cases::              Tests for several possible values.
134* Language Choice::             Selecting which language to use for testing.
135
136Checking Run Time Behavior
137
138* Test Programs::               Running test programs.
139* Guidelines::                  General rules for writing test programs.
140* Test Functions::              Avoiding pitfalls in test programs.
141
142Results of Tests
143
144* Defining Symbols::            Defining C preprocessor symbols.
145* Setting Output Variables::    Replacing variables in output files.
146* Caching Results::             Speeding up subsequent `configure' runs.
147* Printing Messages::           Notifying users of progress or problems.
148
149Caching Results
150
151* Cache Variable Names::        Shell variables used in caches.
152* Cache Files::                 Files `configure' uses for caching.
153
154Writing Macros
155
156* Macro Definitions::           Basic format of an Autoconf macro.
157* Macro Names::                 What to call your new macros.
158* Quoting::                     Protecting macros from unwanted expansion.
159* Dependencies Between Macros::  What to do when macros depend on other macros.
160
161Dependencies Between Macros
162
163* Prerequisite Macros::         Ensuring required information.
164* Suggested Ordering::          Warning about possible ordering problems.
165* Obsolete Macros::             Warning about old ways of doing things.
166
167Manual Configuration
168
169* Specifying Names::            Specifying the system type.
170* Canonicalizing::              Getting the canonical system type.
171* System Type Variables::       Variables containing the system type.
172* Using System Type::           What to do with the system type.
173
174Site Configuration
175
176* External Software::           Working with other optional software.
177* Package Options::             Selecting optional features.
178* Site Details::                Configuring site details.
179* Transforming Names::          Changing program names when installing.
180* Site Defaults::               Giving `configure' local defaults.
181
182Transforming Program Names When Installing
183
184* Transformation Options::      `configure' options to transform names.
185* Transformation Examples::     Sample uses of transforming names.
186* Transformation Rules::        `Makefile' uses of transforming names.
187
188Running `configure' Scripts
189
190* Basic Installation::          Instructions for typical cases.
191* Compilers and Options::       Selecting compilers and optimization.
192* Multiple Architectures::      Compiling for multiple architectures at once.
193* Installation Names::          Installing in different directories.
194* Optional Features::           Selecting optional features.
195* System Type::                 Specifying the system type.
196* Sharing Defaults::            Setting site-wide defaults for `configure'.
197* Operation Controls::          Changing how `configure' runs.
198
199Questions About Autoconf
200
201* Distributing::                Distributing `configure' scripts.
202* Why GNU m4::                  Why not use the standard `m4'?
203* Bootstrapping::               Autoconf and GNU `m4' require each other?
204* Why Not Imake::               Why GNU uses `configure' instead of Imake.
205
206Upgrading From Version 1
207
208* Changed File Names::          Files you might rename.
209* Changed Makefiles::           New things to put in `Makefile.in'.
210* Changed Macros::              Macro calls you might replace.
211* Invoking autoupdate::         Replacing old macro names in `configure.in'.
212* Changed Results::             Changes in how to check test results.
213* Changed Macro Writing::       Better ways to write your own macros.
214
215History of Autoconf
216
217* Genesis::                     Prehistory and naming of `configure'.
218* Exodus::                      The plagues of `m4' and Perl.
219* Leviticus::                   The priestly code of portability arrives.
220* Numbers::                     Growth and contributors.
221* Deuteronomy::                 Approaching the promises of easy configuration.
222
223
224File: autoconf.info,  Node: Introduction,  Next: Making configure Scripts,  Prev: Top,  Up: Top
225
226Introduction
227************
228
229     A physicist, an engineer, and a computer scientist were
230     discussing the nature of God.  Surely a Physicist, said the
231     physicist, because early in the Creation, God made Light; and you
232     know, Maxwell's equations, the dual nature of electro-magnetic
233     waves, the relativist consequences... An Engineer!, said the
234     engineer, because before making Light, God split the Chaos into
235     Land and Water; it takes a hell of an engineer to handle that big
236     amount of mud, and orderly separation of solids from
237     liquids... The computer scientist shouted: And the Chaos,
238     where do you think it was coming from, hmm?
239     
240     ---Anonymous
241
242   Autoconf is a tool for producing shell scripts that automatically
243configure software source code packages to adapt to many kinds of
244UNIX-like systems.  The configuration scripts produced by Autoconf are
245independent of Autoconf when they are run, so their users do not need to
246have Autoconf.
247
248   The configuration scripts produced by Autoconf require no manual user
249intervention when run; they do not normally even need an argument
250specifying the system type.  Instead, they test for the presence of each
251feature that the software package they are for might need individually.
252(Before each check, they print a one-line message stating what they are
253checking for, so the user doesn't get too bored while waiting for the
254script to finish.)  As a result, they deal well with systems that are
255hybrids or customized from the more common UNIX variants.  There is no
256need to maintain files that list the features supported by each release
257of each variant of UNIX.
258
259   For each software package that Autoconf is used with, it creates a
260configuration script from a template file that lists the system
261features that the package needs or can use.  After the shell code to
262recognize and respond to a system feature has been written, Autoconf
263allows it to be shared by many software packages that can use (or need)
264that feature.  If it later turns out that the shell code needs
265adjustment for some reason, it needs to be changed in only one place;
266all of the configuration scripts can be regenerated automatically to
267take advantage of the updated code.
268
269   The Metaconfig package is similar in purpose to Autoconf, but the
270scripts it produces require manual user intervention, which is quite
271inconvenient when configuring large source trees.  Unlike Metaconfig
272scripts, Autoconf scripts can support cross-compiling, if some care is
273taken in writing them.
274
275   There are several jobs related to making portable software packages
276that Autoconf currently does not do.  Among these are automatically
277creating `Makefile' files with all of the standard targets, and
278supplying replacements for standard library functions and header files
279on systems that lack them.  Work is in progress to add those features in
280the future.
281
282   Autoconf imposes some restrictions on the names of macros used with
283`#ifdef' in C programs (*note Preprocessor Symbol Index::.).
284
285   Autoconf requires GNU `m4' in order to generate the scripts.  It
286uses features that some UNIX versions of `m4' do not have.  It also
287overflows internal limits of some versions of `m4', including GNU `m4'
2881.0.  You must use version 1.1 or later of GNU `m4'.  Using version 1.3
289or later will be much faster than 1.1 or 1.2.
290
291   *Note Upgrading::, for information about upgrading from version 1.
292*Note History::, for the story of Autoconf's development.  *Note
293Questions::, for answers to some common questions about Autoconf.
294
295   Mail suggestions and bug reports for Autoconf to
296`bug-gnu-utils@prep.ai.mit.edu'.  Please include the Autoconf version
297number, which you can get by running `autoconf --version'.
298
299
300File: autoconf.info,  Node: Making configure Scripts,  Next: Setup,  Prev: Introduction,  Up: Top
301
302Making `configure' Scripts
303**************************
304
305   The configuration scripts that Autoconf produces are by convention
306called `configure'.  When run, `configure' creates several files,
307replacing configuration parameters in them with appropriate values.
308The files that `configure' creates are:
309
310   * one or more `Makefile' files, one in each subdirectory of the
311     package (*note Makefile Substitutions::.);
312
313   * optionally, a C header file, the name of which is configurable,
314     containing `#define' directives (*note Configuration Headers::.);
315
316   * a shell script called `config.status' that, when run, will recreate
317     the files listed above (*note Invoking config.status::.);
318
319   * a shell script called `config.cache' that saves the results of
320     running many of the tests (*note Cache Files::.);
321
322   * a file called `config.log' containing any messages produced by
323     compilers, to help debugging if `configure' makes a mistake.
324
325   To create a `configure' script with Autoconf, you need to write an
326Autoconf input file `configure.in' and run `autoconf' on it.  If you
327write your own feature tests to supplement those that come with
328Autoconf, you might also write files called `aclocal.m4' and
329`acsite.m4'.  If you use a C header file to contain `#define'
330directives, you might also write `acconfig.h', and you will distribute
331the Autoconf-generated file `config.h.in' with the package.
332
333   Here is a diagram showing how the files that can be used in
334configuration are produced.  Programs that are executed are suffixed by
335`*'.  Optional files are enclosed in square brackets (`[]').
336`autoconf' and `autoheader' also read the installed Autoconf macro
337files (by reading `autoconf.m4').
338
339Files used in preparing a software package for distribution:
340     your source files --> [autoscan*] --> [configure.scan] --> configure.in
341     
342     configure.in --.   .------> autoconf* -----> configure
343                    +---+
344     [aclocal.m4] --+   `---.
345     [acsite.m4] ---'       |
346                            +--> [autoheader*] -> [config.h.in]
347     [acconfig.h] ----.     |
348                      +-----'
349     [config.h.top] --+
350     [config.h.bot] --'
351     
352     Makefile.in -------------------------------> Makefile.in
353
354Files used in configuring a software package:
355                            .-------------> config.cache
356     configure* ------------+-------------> config.log
357                            |
358     [config.h.in] -.       v            .-> [config.h] -.
359                    +--> config.status* -+               +--> make*
360     Makefile.in ---'                    `-> Makefile ---'
361
362* Menu:
363
364* Writing configure.in::        What to put in an Autoconf input file.
365* Invoking autoscan::           Semi-automatic `configure.in' writing.
366* Invoking ifnames::            Listing the conditionals in source code.
367* Invoking autoconf::           How to create configuration scripts.
368* Invoking autoreconf::         Remaking multiple `configure' scripts.
369
370
371File: autoconf.info,  Node: Writing configure.in,  Next: Invoking autoscan,  Prev: Making configure Scripts,  Up: Making configure Scripts
372
373Writing `configure.in'
374======================
375
376   To produce a `configure' script for a software package, create a
377file called `configure.in' that contains invocations of the Autoconf
378macros that test the system features your package needs or can use.
379Autoconf macros already exist to check for many features; see *Note
380Existing Tests::, for their descriptions.  For most other features, you
381can use Autoconf template macros to produce custom checks; see *Note
382Writing Tests::, for information about them.  For especially tricky or
383specialized features, `configure.in' might need to contain some
384hand-crafted shell commands.  The `autoscan' program can give you a
385good start in writing `configure.in' (*note Invoking autoscan::., for
386more information).
387
388   The order in which `configure.in' calls the Autoconf macros is not
389important, with a few exceptions.  Every `configure.in' must contain a
390call to `AC_INIT' before the checks, and a call to `AC_OUTPUT' at the
391end (*note Output::.).  Additionally, some macros rely on other macros
392having been called first, because they check previously set values of
393some variables to decide what to do.  These macros are noted in the
394individual descriptions (*note Existing Tests::.), and they also warn
395you when creating `configure' if they are called out of order.
396
397   To encourage consistency, here is a suggested order for calling the
398Autoconf macros.  Generally speaking, the things near the end of this
399list could depend on things earlier in it.  For example, library
400functions could be affected by typedefs and libraries.
401
402     `AC_INIT(FILE)'
403     checks for programs
404     checks for libraries
405     checks for header files
406     checks for typedefs
407     checks for structures
408     checks for compiler characteristics
409     checks for library functions
410     checks for system services
411     `AC_OUTPUT([FILE...])'
412
413   It is best to put each macro call on its own line in `configure.in'.
414Most of the macros don't add extra newlines; they rely on the newline
415after the macro call to terminate the commands.  This approach makes
416the generated `configure' script a little easier to read by not
417inserting lots of blank lines.  It is generally safe to set shell
418variables on the same line as a macro call, because the shell allows
419assignments without intervening newlines.
420
421   When calling macros that take arguments, there must not be any blank
422space between the macro name and the open parenthesis.  Arguments can be
423more than one line long if they are enclosed within the `m4' quote
424characters `[' and `]'.  If you have a long line such as a list of file
425names, you can generally use a backslash at the end of a line to
426continue it logically on the next line (this is implemented by the
427shell, not by anything special that Autoconf does).
428
429   Some macros handle two cases: what to do if the given condition is
430met, and what to do if the condition is not met.  In some places you
431might want to do something if a condition is true but do nothing if it's
432false, or vice versa.  To omit the true case, pass an empty value for
433the ACTION-IF-FOUND argument to the macro.  To omit the false case,
434omit the ACTION-IF-NOT-FOUND argument to the macro, including the comma
435before it.
436
437   You can include comments in `configure.in' files by starting them
438with the `m4' builtin macro `dnl', which discards text up through the
439next newline.  These comments do not appear in the generated
440`configure' scripts.  For example, it is helpful to begin
441`configure.in' files with a line like this:
442
443     dnl Process this file with autoconf to produce a configure script.
444
445
446File: autoconf.info,  Node: Invoking autoscan,  Next: Invoking ifnames,  Prev: Writing configure.in,  Up: Making configure Scripts
447
448Using `autoscan' to Create `configure.in'
449=========================================
450
451   The `autoscan' program can help you create a `configure.in' file for
452a software package.  `autoscan' examines source files in the directory
453tree rooted at a directory given as a command line argument, or the
454current directory if none is given.  It searches the source files for
455common portability problems and creates a file `configure.scan' which
456is a preliminary `configure.in' for that package.
457
458   You should manually examine `configure.scan' before renaming it to
459`configure.in'; it will probably need some adjustments.  Occasionally
460`autoscan' outputs a macro in the wrong order relative to another
461macro, so that `autoconf' produces a warning; you need to move such
462macros manually.  Also, if you want the package to use a configuration
463header file, you must add a call to `AC_CONFIG_HEADER' (*note
464Configuration Headers::.).  You might also have to change or add some
465`#if' directives to your program in order to make it work with Autoconf
466(*note Invoking ifnames::., for information about a program that can
467help with that job).
468
469   `autoscan' uses several data files, which are installed along with
470the distributed Autoconf macro files, to determine which macros to
471output when it finds particular symbols in a package's source files.
472These files all have the same format.  Each line consists of a symbol,
473whitespace, and the Autoconf macro to output if that symbol is
474encountered.  Lines starting with `#' are comments.
475
476   `autoscan' is only installed if you already have Perl installed.
477`autoscan' accepts the following options:
478
479`--help'
480     Print a summary of the command line options and exit.
481
482`--macrodir=DIR'
483     Look for the data files in directory DIR instead of the default
484     installation directory.  You can also set the `AC_MACRODIR'
485     environment variable to a directory; this option overrides the
486     environment variable.
487
488`--verbose'
489     Print the names of the files it examines and the potentially
490     interesting symbols it finds in them.  This output can be
491     voluminous.
492
493`--version'
494     Print the version number of Autoconf and exit.
495
496
497File: autoconf.info,  Node: Invoking ifnames,  Next: Invoking autoconf,  Prev: Invoking autoscan,  Up: Making configure Scripts
498
499Using `ifnames' to List Conditionals
500====================================
501
502   `ifnames' can help when writing a `configure.in' for a software
503package.  It prints the identifiers that the package already uses in C
504preprocessor conditionals.  If a package has already been set up to
505have some portability, this program can help you figure out what its
506`configure' needs to check for.  It may help fill in some gaps in a
507`configure.in' generated by `autoscan' (*note Invoking autoscan::.).
508
509   `ifnames' scans all of the C source files named on the command line
510(or the standard input, if none are given) and writes to the standard
511output a sorted list of all the identifiers that appear in those files
512in `#if', `#elif', `#ifdef', or `#ifndef' directives.  It prints each
513identifier on a line, followed by a space-separated list of the files
514in which that identifier occurs.
515
516`ifnames' accepts the following options:
517
518`--help'
519`-h'
520     Print a summary of the command line options and exit.
521
522`--macrodir=DIR'
523`-m DIR'
524     Look for the Autoconf macro files in directory DIR instead of the
525     default installation directory.  Only used to get the version
526     number.  You can also set the `AC_MACRODIR' environment variable
527     to a directory; this option overrides the environment variable.
528
529`--version'
530     Print the version number of Autoconf and exit.
531
532
533File: autoconf.info,  Node: Invoking autoconf,  Next: Invoking autoreconf,  Prev: Invoking ifnames,  Up: Making configure Scripts
534
535Using `autoconf' to Create `configure'
536======================================
537
538   To create `configure' from `configure.in', run the `autoconf'
539program with no arguments.  `autoconf' processes `configure.in' with
540the `m4' macro processor, using the Autoconf macros.  If you give
541`autoconf' an argument, it reads that file instead of `configure.in'
542and writes the configuration script to the standard output instead of
543to `configure'.  If you give `autoconf' the argument `-', it reads the
544standard input instead of `configure.in' and writes the configuration
545script on the standard output.
546
547   The Autoconf macros are defined in several files.  Some of the files
548are distributed with Autoconf; `autoconf' reads them first.  Then it
549looks for the optional file `acsite.m4' in the directory that contains
550the distributed Autoconf macro files, and for the optional file
551`aclocal.m4' in the current directory.  Those files can contain your
552site's or the package's own Autoconf macro definitions (*note Writing
553Macros::., for more information).  If a macro is defined in more than
554one of the files that `autoconf' reads, the last definition it reads
555overrides the earlier ones.
556
557   `autoconf' accepts the following options:
558
559`--help'
560`-h'
561     Print a summary of the command line options and exit.
562
563`--localdir=DIR'
564`-l DIR'
565     Look for the package file `aclocal.m4' in directory DIR instead of
566     in the current directory.
567
568`--macrodir=DIR'
569`-m DIR'
570     Look for the installed macro files in directory DIR.  You can also
571     set the `AC_MACRODIR' environment variable to a directory; this
572     option overrides the environment variable.
573
574`--version'
575     Print the version number of Autoconf and exit.
576
577
578File: autoconf.info,  Node: Invoking autoreconf,  Prev: Invoking autoconf,  Up: Making configure Scripts
579
580Using `autoreconf' to Update `configure' Scripts
581================================================
582
583   If you have a lot of Autoconf-generated `configure' scripts, the
584`autoreconf' program can save you some work.  It runs `autoconf' (and
585`autoheader', where appropriate) repeatedly to remake the Autoconf
586`configure' scripts and configuration header templates in the directory
587tree rooted at the current directory.  By default, it only remakes
588those files that are older than their `configure.in' or (if present)
589`aclocal.m4'.  Since `autoheader' does not change the timestamp of its
590output file if the file wouldn't be changing, this is not necessarily
591the minimum amount of work.  If you install a new version of Autoconf,
592you can make `autoreconf' remake *all* of the files by giving it the
593`--force' option.
594
595   If you give `autoreconf' the `--macrodir=DIR' or `--localdir=DIR'
596options, it passes them down to `autoconf' and `autoheader' (with
597relative paths adjusted properly).
598
599   `autoreconf' does not support having, in the same directory tree,
600both directories that are parts of a larger package (sharing
601`aclocal.m4' and `acconfig.h'), and directories that are independent
602packages (each with their own `aclocal.m4' and `acconfig.h').  It
603assumes that they are all part of the same package, if you use
604`--localdir', or that each directory is a separate package, if you
605don't use it.  This restriction may be removed in the future.
606
607   *Note Automatic Remaking::, for `Makefile' rules to automatically
608remake `configure' scripts when their source files change.  That method
609handles the timestamps of configuration header templates properly, but
610does not pass `--macrodir=DIR' or `--localdir=DIR'.
611
612`autoreconf' accepts the following options:
613
614`--help'
615`-h'
616     Print a summary of the command line options and exit.
617
618`--force'
619`-f'
620     Remake even `configure' scripts and configuration headers that are
621     newer than their input files (`configure.in' and, if present,
622     `aclocal.m4').
623
624`--localdir=DIR'
625`-l DIR'
626     Have `autoconf' and `autoheader' look for the package files
627     `aclocal.m4' and (`autoheader' only) `acconfig.h' (but not
628     `FILE.top' and `FILE.bot') in directory DIR instead of in the
629     directory containing each `configure.in'.
630
631`--macrodir=DIR'
632`-m DIR'
633     Look for the Autoconf macro files in directory DIR instead of the
634     default installation directory.  You can also set the `AC_MACRODIR'
635     environment variable to a directory; this option overrides the
636     environment variable.
637
638`--verbose'
639     Print the name of each directory where `autoreconf' runs
640     `autoconf' (and `autoheader', if appropriate).
641
642`--version'
643     Print the version number of Autoconf and exit.
644
645
646File: autoconf.info,  Node: Setup,  Next: Existing Tests,  Prev: Making configure Scripts,  Up: Top
647
648Initialization and Output Files
649*******************************
650
651   Autoconf-generated `configure' scripts need some information about
652how to initialize, such as how to find the package's source files; and
653about the output files to produce.  The following sections describe
654initialization and creating output files.
655
656* Menu:
657
658* Input::                       Where Autoconf should find files.
659* Output::                      Creating output files.
660* Makefile Substitutions::      Using output variables in `Makefile's.
661* Configuration Headers::       Creating a configuration header file.
662* Subdirectories::              Configuring independent packages together.
663* Default Prefix::              Changing the default installation prefix.
664* Versions::                    Version numbers in `configure'.
665
666
667File: autoconf.info,  Node: Input,  Next: Output,  Prev: Setup,  Up: Setup
668
669Finding `configure' Input
670=========================
671
672   Every `configure' script must call `AC_INIT' before doing anything
673else.  The only other required macro is `AC_OUTPUT' (*note Output::.).
674
675 - Macro: AC_INIT (UNIQUE-FILE-IN-SOURCE-DIR)
676     Process any command-line arguments and find the source code
677     directory.  UNIQUE-FILE-IN-SOURCE-DIR is some file that is in the
678     package's source directory; `configure' checks for this file's
679     existence to make sure that the directory that it is told contains
680     the source code in fact does.  Occasionally people accidentally
681     specify the wrong directory with `--srcdir'; this is a safety
682     check.  *Note Invoking configure::, for more information.
683
684   Packages that do manual configuration or use the `install' program
685might need to tell `configure' where to find some other shell scripts
686by calling `AC_CONFIG_AUX_DIR', though the default places it looks are
687correct for most cases.
688
689 - Macro: AC_CONFIG_AUX_DIR(DIR)
690     Use the `install-sh', `config.sub', `config.guess', and Cygnus
691     `configure' scripts that are in directory DIR.  These are
692     auxiliary files used in configuration.  DIR can be either absolute
693     or relative to `SRCDIR'.  The default is `SRCDIR' or `SRCDIR/..' or
694     `SRCDIR/../..', whichever is the first that contains `install-sh'.
695     The other files are not checked for, so that using
696     `AC_PROG_INSTALL' does not automatically require distributing the
697     other auxiliary files.  It checks for `install.sh' also, but that
698     name is obsolete because some `make' programs have a rule that
699     creates `install' from it if there is no `Makefile'.
700
701
702File: autoconf.info,  Node: Output,  Next: Makefile Substitutions,  Prev: Input,  Up: Setup
703
704Creating Output Files
705=====================
706
707   Every Autoconf-generated `configure' script must finish by calling
708`AC_OUTPUT'.  It is the macro that creates the `Makefile's and optional
709other files resulting from configuration.  The only other required
710macro is `AC_INIT' (*note Input::.).
711
712 - Macro: AC_OUTPUT ([FILE... [, EXTRA-CMDS [, INIT-CMDS]]])
713     Create output files.  Call this macro once, at the end of
714     `configure.in'.  The FILE... argument is a whitespace-separated
715     list of output files; it may be empty.  This macro creates each
716     file `FILE' by copying an input file (by default named `FILE.in'),
717     substituting the output variable values.  *Note Makefile
718     Substitutions::, for more information on using output variables.
719     *Note Setting Output Variables::, for more information on creating
720     them.  This macro creates the directory that the file is in if it
721     doesn't exist (but not the parents of that directory).  Usually,
722     `Makefile's are created this way, but other files, such as
723     `.gdbinit', can be specified as well.
724
725     If `AC_CONFIG_HEADER', `AC_LINK_FILES', or `AC_CONFIG_SUBDIRS' has
726     been called, this macro also creates the files named as their
727     arguments.
728
729     A typical call to `AC_OUTPUT' looks like this:
730          AC_OUTPUT(Makefile src/Makefile man/Makefile X/Imakefile)
731
732     You can override an input file name by appending to FILE a
733     colon-separated list of input files.  Examples:
734          AC_OUTPUT(Makefile:templates/top.mk lib/Makefile:templates/lib.mk)
735          AC_OUTPUT(Makefile:templates/vars.mk:Makefile.in:templates/rules.mk)
736     Doing this allows you to keep your file names acceptable to
737     MS-DOS, or to prepend and/or append boilerplate to the file.
738
739     If you pass EXTRA-CMDS, those commands will be inserted into
740     `config.status' to be run after all its other processing.  If
741     INIT-CMDS are given, they are inserted just before EXTRA-CMDS,
742     with shell variable, command, and backslash substitutions
743     performed on them in `configure'.  You can use INIT-CMDS to pass
744     variables from `configure' to the EXTRA-CMDS.  If
745     `AC_OUTPUT_COMMANDS' has been called, the commands given to it are
746     run just before the commands passed to this macro.
747
748 - Macro: AC_OUTPUT_COMMANDS (EXTRA-CMDS [, INIT-CMDS])
749     Specify additional shell commands to run at the end of
750     `config.status', and shell commands to initialize any variables
751     from `configure'.  This macro may be called multiple times.  Here
752     is an unrealistic example:
753
754          fubar=27
755          AC_OUTPUT_COMMANDS([echo this is extra $fubar, and so on.], fubar=$fubar)
756          AC_OUTPUT_COMMANDS([echo this is another, extra, bit], [echo init bit])
757
758   If you run `make' on subdirectories, you should run it using the
759`make' variable `MAKE'.  Most versions of `make' set `MAKE' to the name
760of the `make' program plus any options it was given.  (But many do not
761include in it the values of any variables set on the command line, so
762those are not passed on automatically.) Some old versions of `make' do
763not set this variable.  The following macro allows you to use it even
764with those versions.
765
766 - Macro: AC_PROG_MAKE_SET
767     If `make' predefines the variable `MAKE', define output variable
768     `SET_MAKE' to be empty.  Otherwise, define `SET_MAKE' to contain
769     `MAKE=make'.  Calls `AC_SUBST' for `SET_MAKE'.
770
771   To use this macro, place a line like this in each `Makefile.in' that
772runs `MAKE' on other directories:
773
774     @SET_MAKE@
775
776
777File: autoconf.info,  Node: Makefile Substitutions,  Next: Configuration Headers,  Prev: Output,  Up: Setup
778
779Substitutions in Makefiles
780==========================
781
782   Each subdirectory in a distribution that contains something to be
783compiled or installed should come with a file `Makefile.in', from which
784`configure' will create a `Makefile' in that directory.  To create a
785`Makefile', `configure' performs a simple variable substitution,
786replacing occurrences of `@VARIABLE@' in `Makefile.in' with the value
787that `configure' has determined for that variable.  Variables that are
788substituted into output files in this way are called "output
789variables".  They are ordinary shell variables that are set in
790`configure'.  To make `configure' substitute a particular variable into
791the output files, the macro `AC_SUBST' must be called with that
792variable name as an argument.  Any occurrences of `@VARIABLE@' for
793other variables are left unchanged.  *Note Setting Output Variables::,
794for more information on creating output variables with `AC_SUBST'.
795
796   A software package that uses a `configure' script should be
797distributed with a file `Makefile.in', but no `Makefile'; that way, the
798user has to properly configure the package for the local system before
799compiling it.
800
801   *Note Makefile Conventions: (standards)Makefile Conventions, for
802more information on what to put in `Makefile's.
803
804* Menu:
805
806* Preset Output Variables::     Output variables that are always set.
807* Build Directories::           Supporting multiple concurrent compiles.
808* Automatic Remaking::          Makefile rules for configuring.
809
810
811File: autoconf.info,  Node: Preset Output Variables,  Next: Build Directories,  Prev: Makefile Substitutions,  Up: Makefile Substitutions
812
813Preset Output Variables
814-----------------------
815
816   Some output variables are preset by the Autoconf macros.  Some of the
817Autoconf macros set additional output variables, which are mentioned in
818the descriptions for those macros.  *Note Output Variable Index::, for a
819complete list of output variables.  Here is what each of the preset ones
820contains.  *Note Variables for Installation Directories:
821(standards)Directory Variables, for more information about the
822variables with names that end in `dir'.
823
824 - Variable: bindir
825     The directory for installing executables that users run.
826
827 - Variable: configure_input
828     A comment saying that the file was generated automatically by
829     `configure' and giving the name of the input file.  `AC_OUTPUT'
830     adds a comment line containing this variable to the top of every
831     `Makefile' it creates.  For other files, you should reference this
832     variable in a comment at the top of each input file.  For example,
833     an input shell script should begin like this:
834
835          #! /bin/sh
836          # @configure_input@
837
838     The presence of that line also reminds people editing the file
839     that it needs to be processed by `configure' in order to be used.
840
841 - Variable: datadir
842     The directory for installing read-only architecture-independent
843     data.
844
845 - Variable: exec_prefix
846     The installation prefix for architecture-dependent files.
847
848 - Variable: includedir
849     The directory for installing C header files.
850
851 - Variable: infodir
852     The directory for installing documentation in Info format.
853
854 - Variable: libdir
855     The directory for installing object code libraries.
856
857 - Variable: libexecdir
858     The directory for installing executables that other programs run.
859
860 - Variable: localstatedir
861     The directory for installing modifiable single-machine data.
862
863 - Variable: mandir
864     The top-level directory for installing documentation in man format.
865
866 - Variable: oldincludedir
867     The directory for installing C header files for non-gcc compilers.
868
869 - Variable: prefix
870     The installation prefix for architecture-independent files.
871
872 - Variable: sbindir
873     The directory for installing executables that system
874     administrators run.
875
876 - Variable: sharedstatedir
877     The directory for installing modifiable architecture-independent
878     data.
879
880 - Variable: srcdir
881     The directory that contains the source code for that `Makefile'.
882
883 - Variable: sysconfdir
884     The directory for installing read-only single-machine data.
885
886 - Variable: top_srcdir
887     The top-level source code directory for the package.  In the
888     top-level directory, this is the same as `srcdir'.
889
890 - Variable: CFLAGS
891     Debugging and optimization options for the C compiler.  If it is
892     not set in the environment when `configure' runs, the default
893     value is set when you call `AC_PROG_CC' (or empty if you don't).
894     `configure' uses this variable when compiling programs to test for
895     C features.
896
897 - Variable: CPPFLAGS
898     Header file search directory (`-IDIR') and any other miscellaneous
899     options for the C preprocessor and compiler.  If it is not set in
900     the environment when `configure' runs, the default value is empty.
901     `configure' uses this variable when compiling or preprocessing
902     programs to test for C features.
903
904 - Variable: CXXFLAGS
905     Debugging and optimization options for the C++ compiler.  If it is
906     not set in the environment when `configure' runs, the default
907     value is set when you call `AC_PROG_CXX' (or empty if you don't).
908     `configure' uses this variable when compiling programs to test for
909     C++ features.
910
911 - Variable: FFLAGS
912     Debugging and optimization options for the Fortran 77 compiler.
913     If it is not set in the environment when `configure' runs, the
914     default value is set when you call `AC_PROG_F77' (or empty if you
915     don't).  `configure' uses this variable when compiling programs to
916     test for Fortran 77 features.
917
918 - Variable: DEFS
919     `-D' options to pass to the C compiler.  If `AC_CONFIG_HEADER' is
920     called, `configure' replaces `@DEFS@' with `-DHAVE_CONFIG_H'
921     instead (*note Configuration Headers::.).  This variable is not
922     defined while `configure' is performing its tests, only when
923     creating the output files.  *Note Setting Output Variables::, for
924     how to check the results of previous tests.
925
926 - Variable: LDFLAGS
927     Stripping (`-s') and any other miscellaneous options for the
928     linker.  If it is not set in the environment when `configure' runs,
929     the default value is empty.  `configure' uses this variable when
930     linking programs to test for C features.
931
932 - Variable: LIBS
933     `-l' and `-L' options to pass to the linker.
934
935
936File: autoconf.info,  Node: Build Directories,  Next: Automatic Remaking,  Prev: Preset Output Variables,  Up: Makefile Substitutions
937
938Build Directories
939-----------------
940
941   You can support compiling a software package for several
942architectures simultaneously from the same copy of the source code.
943The object files for each architecture are kept in their own directory.
944
945   To support doing this, `make' uses the `VPATH' variable to find the
946files that are in the source directory.  GNU `make' and most other
947recent `make' programs can do this.  Older `make' programs do not
948support `VPATH'; when using them, the source code must be in the same
949directory as the object files.
950
951   To support `VPATH', each `Makefile.in' should contain two lines that
952look like:
953
954     srcdir = @srcdir@
955     VPATH = @srcdir@
956
957   Do not set `VPATH' to the value of another variable, for example
958`VPATH = $(srcdir)', because some versions of `make' do not do variable
959substitutions on the value of `VPATH'.
960
961   `configure' substitutes in the correct value for `srcdir' when it
962produces `Makefile'.
963
964   Do not use the `make' variable `$<', which expands to the pathname
965of the file in the source directory (found with `VPATH'), except in
966implicit rules.  (An implicit rule is one such as `.c.o', which tells
967how to create a `.o' file from a `.c' file.)  Some versions of `make'
968do not set `$<' in explicit rules; they expand it to an empty value.
969
970   Instead, `Makefile' command lines should always refer to source
971files by prefixing them with `$(srcdir)/'.  For example:
972
973     time.info: time.texinfo
974             $(MAKEINFO) $(srcdir)/time.texinfo
975
976
977File: autoconf.info,  Node: Automatic Remaking,  Prev: Build Directories,  Up: Makefile Substitutions
978
979Automatic Remaking
980------------------
981
982   You can put rules like the following in the top-level `Makefile.in'
983for a package to automatically update the configuration information when
984you change the configuration files.  This example includes all of the
985optional files, such as `aclocal.m4' and those related to configuration
986header files.  Omit from the `Makefile.in' rules any of these files
987that your package does not use.
988
989   The `${srcdir}/' prefix is included because of limitations in the
990`VPATH' mechanism.
991
992   The `stamp-' files are necessary because the timestamps of
993`config.h.in' and `config.h' will not be changed if remaking them does
994not change their contents.  This feature avoids unnecessary
995recompilation.  You should include the file `stamp-h.in' your package's
996distribution, so `make' will consider `config.h.in' up to date.  On
997some old BSD systems, `touch' or any command that results in an empty
998file does not update the timestamps, so use a command like `echo' as a
999workaround.
1000
1001     ${srcdir}/configure: configure.in aclocal.m4
1002             cd ${srcdir} && autoconf
1003     
1004     # autoheader might not change config.h.in, so touch a stamp file.
1005     ${srcdir}/config.h.in: stamp-h.in
1006     ${srcdir}/stamp-h.in: configure.in aclocal.m4 acconfig.h \
1007         config.h.top config.h.bot
1008             cd ${srcdir} && autoheader
1009             echo timestamp > ${srcdir}/stamp-h.in
1010     
1011     config.h: stamp-h
1012     stamp-h: config.h.in config.status
1013             ./config.status
1014     
1015     Makefile: Makefile.in config.status
1016             ./config.status
1017     
1018     config.status: configure
1019             ./config.status --recheck
1020
1021   In addition, you should pass `echo timestamp > stamp-h' in the
1022EXTRA-CMDS argument to `AC_OUTPUT', so `config.status' will ensure that
1023`config.h' is considered up to date.  *Note Output::, for more
1024information about `AC_OUTPUT'.
1025
1026   *Note Invoking config.status::, for more examples of handling
1027configuration-related dependencies.
1028
1029
1030File: autoconf.info,  Node: Configuration Headers,  Next: Subdirectories,  Prev: Makefile Substitutions,  Up: Setup
1031
1032Configuration Header Files
1033==========================
1034
1035   When a package tests more than a few C preprocessor symbols, the
1036command lines to pass `-D' options to the compiler can get quite long.
1037This causes two problems.  One is that the `make' output is hard to
1038visually scan for errors.  More seriously, the command lines can exceed
1039the length limits of some operating systems.  As an alternative to
1040passing `-D' options to the compiler, `configure' scripts can create a
1041C header file containing `#define' directives.  The `AC_CONFIG_HEADER'
1042macro selects this kind of output.  It should be called right after
1043`AC_INIT'.
1044
1045   The package should `#include' the configuration header file before
1046any other header files, to prevent inconsistencies in declarations (for
1047example, if it redefines `const').  Use `#include <config.h>' instead
1048of `#include "config.h"', and pass the C compiler a `-I.' option (or
1049`-I..'; whichever directory contains `config.h').  That way, even if
1050the source directory is configured itself (perhaps to make a
1051distribution), other build directories can also be configured without
1052finding the `config.h' from the source directory.
1053
1054 - Macro: AC_CONFIG_HEADER (HEADER-TO-CREATE ...)
1055     Make `AC_OUTPUT' create the file(s) in the whitespace-separated
1056     list HEADER-TO-CREATE containing C preprocessor `#define'
1057     statements, and replace `@DEFS@' in generated files with
1058     `-DHAVE_CONFIG_H' instead of the value of `DEFS'.  The usual name
1059     for HEADER-TO-CREATE is `config.h'.
1060
1061     If HEADER-TO-CREATE already exists and its contents are identical
1062     to what `AC_OUTPUT' would put in it, it is left alone.  Doing this
1063     allows some changes in configuration without needlessly causing
1064     object files that depend on the header file to be recompiled.
1065
1066     Usually the input file is named `HEADER-TO-CREATE.in'; however,
1067     you can override the input file name by appending to
1068     HEADER-TO-CREATE, a colon-separated list of input files.  Examples:
1069          AC_CONFIG_HEADER(defines.h:defines.hin)
1070          AC_CONFIG_HEADER(defines.h:defs.pre:defines.h.in:defs.post)
1071
1072     Doing this allows you to keep your file names acceptable to
1073     MS-DOS, or to prepend and/or append boilerplate to the file.
1074
1075* Menu:
1076
1077* Header Templates::            Input for the configuration headers.
1078* Invoking autoheader::         How to create configuration templates.
1079
1080
1081File: autoconf.info,  Node: Header Templates,  Next: Invoking autoheader,  Prev: Configuration Headers,  Up: Configuration Headers
1082
1083Configuration Header Templates
1084------------------------------
1085
1086   Your distribution should contain a template file that looks as you
1087want the final header file to look, including comments, with default
1088values in the `#define' statements.  For example, suppose your
1089`configure.in' makes these calls:
1090
1091     AC_CONFIG_HEADER(conf.h)
1092     AC_CHECK_HEADERS(unistd.h)
1093
1094Then you could have code like the following in `conf.h.in'.  On systems
1095that have `unistd.h', `configure' will change the 0 to a 1.  On other
1096systems, it will leave the line unchanged.
1097
1098     /* Define as 1 if you have unistd.h.  */
1099     #define HAVE_UNISTD_H 0
1100
1101   Alternately, if your code tests for configuration options using
1102`#ifdef' instead of `#if', a default value can be to `#undef' the
1103variable instead of to define it to a value.  On systems that have
1104`unistd.h', `configure' will change the second line to read `#define
1105HAVE_UNISTD_H 1'.  On other systems, it will comment that line out (in
1106case the system predefines that symbol).
1107
1108     /* Define if you have unistd.h.  */
1109     #undef HAVE_UNISTD_H
1110
1111
1112File: autoconf.info,  Node: Invoking autoheader,  Prev: Header Templates,  Up: Configuration Headers
1113
1114Using `autoheader' to Create `config.h.in'
1115------------------------------------------
1116
1117   The `autoheader' program can create a template file of C `#define'
1118statements for `configure' to use.  If `configure.in' invokes
1119`AC_CONFIG_HEADER(FILE)', `autoheader' creates `FILE.in'; if multiple
1120file arguments are given, the first one is used.  Otherwise,
1121`autoheader' creates `config.h.in'.
1122
1123   If you give `autoheader' an argument, it uses that file instead of
1124`configure.in' and writes the header file to the standard output
1125instead of to `config.h.in'.  If you give `autoheader' an argument of
1126`-', it reads the standard input instead of `configure.in' and writes
1127the header file to the standard output.
1128
1129   `autoheader' scans `configure.in' and figures out which C
1130preprocessor symbols it might define.  It copies comments and `#define'
1131and `#undef' statements from a file called `acconfig.h', which comes
1132with and is installed with Autoconf.  It also uses a file called
1133`acconfig.h' in the current directory, if present.  If you `AC_DEFINE'
1134any additional symbols, you must create that file with entries for
1135them.  For symbols defined by `AC_CHECK_HEADERS', `AC_CHECK_FUNCS',
1136`AC_CHECK_SIZEOF', or `AC_CHECK_LIB', `autoheader' generates comments
1137and `#undef' statements itself rather than copying them from a file,
1138since the possible symbols are effectively limitless.
1139
1140   The file that `autoheader' creates contains mainly `#define' and
1141`#undef' statements and their accompanying comments.  If `./acconfig.h'
1142contains the string `@TOP@', `autoheader' copies the lines before the
1143line containing `@TOP@' into the top of the file that it generates.
1144Similarly, if `./acconfig.h' contains the string `@BOTTOM@',
1145`autoheader' copies the lines after that line to the end of the file it
1146generates.  Either or both of those strings may be omitted.
1147
1148   An alternate way to produce the same effect is to create the files
1149`FILE.top' (typically `config.h.top') and/or `FILE.bot' in the current
1150directory.  If they exist, `autoheader' copies them to the beginning
1151and end, respectively, of its output.  Their use is discouraged because
1152they have file names that contain two periods, and so can not be stored
1153on MS-DOS; also, they are two more files to clutter up the directory.
1154But if you use the `--localdir=DIR' option to use an `acconfig.h' in
1155another directory, they give you a way to put custom boilerplate in each
1156individual `config.h.in'.
1157
1158   `autoheader' accepts the following options:
1159
1160`--help'
1161`-h'
1162     Print a summary of the command line options and exit.
1163
1164`--localdir=DIR'
1165`-l DIR'
1166     Look for the package files `aclocal.m4' and `acconfig.h' (but not
1167     `FILE.top' and `FILE.bot') in directory DIR instead of in the
1168     current directory.
1169
1170`--macrodir=DIR'
1171`-m DIR'
1172     Look for the installed macro files and `acconfig.h' in directory
1173     DIR.  You can also set the `AC_MACRODIR' environment variable to a
1174     directory; this option overrides the environment variable.
1175
1176`--version'
1177     Print the version number of Autoconf and exit.
1178
1179
1180File: autoconf.info,  Node: Subdirectories,  Next: Default Prefix,  Prev: Configuration Headers,  Up: Setup
1181
1182Configuring Other Packages in Subdirectories
1183============================================
1184
1185   In most situations, calling `AC_OUTPUT' is sufficient to produce
1186`Makefile's in subdirectories.  However, `configure' scripts that
1187control more than one independent package can use `AC_CONFIG_SUBDIRS'
1188to run `configure' scripts for other packages in subdirectories.
1189
1190 - Macro: AC_CONFIG_SUBDIRS (DIR ...)
1191     Make `AC_OUTPUT' run `configure' in each subdirectory DIR in the
1192     given whitespace-separated list.  If a given DIR is not found, no
1193     error is reported, so a `configure' script can configure whichever
1194     parts of a large source tree are present.  If a given DIR contains
1195     `configure.in' but no `configure', the Cygnus `configure' script
1196     found by `AC_CONFIG_AUXDIR' is used.
1197
1198     The subdirectory `configure' scripts are given the same command
1199     line options that were given to this `configure' script, with
1200     minor changes if needed (e.g., to adjust a relative path for the
1201     cache file or source directory).  This macro also sets the output
1202     variable `subdirs' to the list of directories `DIR ...'.
1203     `Makefile' rules can use this variable to determine which
1204     subdirectories to recurse into.  This macro may be called multiple
1205     times.
1206
1207
1208File: autoconf.info,  Node: Default Prefix,  Next: Versions,  Prev: Subdirectories,  Up: Setup
1209
1210Default Prefix
1211==============
1212
1213   By default, `configure' sets the prefix for files it installs to
1214`/usr/local'.  The user of `configure' can select a different prefix
1215using the `--prefix' and `--exec-prefix' options.  There are two ways
1216to change the default: when creating `configure', and when running it.
1217
1218   Some software packages might want to install in a directory besides
1219`/usr/local' by default.  To accomplish that, use the
1220`AC_PREFIX_DEFAULT' macro.
1221
1222 - Macro: AC_PREFIX_DEFAULT (PREFIX)
1223     Set the default installation prefix to PREFIX instead of
1224     `/usr/local'.
1225
1226   It may be convenient for users to have `configure' guess the
1227installation prefix from the location of a related program that they
1228have already installed.  If you wish to do that, you can call
1229`AC_PREFIX_PROGRAM'.
1230
1231 - Macro: AC_PREFIX_PROGRAM (PROGRAM)
1232     If the user did not specify an installation prefix (using the
1233     `--prefix' option), guess a value for it by looking for PROGRAM in
1234     `PATH', the way the shell does.  If PROGRAM is found, set the
1235     prefix to the parent of the directory containing PROGRAM;
1236     otherwise leave the prefix specified in `Makefile.in' unchanged.
1237     For example, if PROGRAM is `gcc' and the `PATH' contains
1238     `/usr/local/gnu/bin/gcc', set the prefix to `/usr/local/gnu'.
1239
1240
1241File: autoconf.info,  Node: Versions,  Prev: Default Prefix,  Up: Setup
1242
1243Version Numbers in `configure'
1244==============================
1245
1246   The following macros manage version numbers for `configure' scripts.
1247Using them is optional.
1248
1249 - Macro: AC_PREREQ (VERSION)
1250     Ensure that a recent enough version of Autoconf is being used.  If
1251     the version of Autoconf being used to create `configure' is earlier
1252     than VERSION, print an error message on the standard error output
1253     and do not create `configure'.  For example:
1254
1255          AC_PREREQ(1.8)
1256
1257     This macro is useful if your `configure.in' relies on non-obvious
1258     behavior that changed between Autoconf releases.  If it merely
1259     needs recently added macros, then `AC_PREREQ' is less useful,
1260     because the `autoconf' program already tells the user which macros
1261     are not found.  The same thing happens if `configure.in' is
1262     processed by a version of Autoconf older than when `AC_PREREQ' was
1263     added.
1264
1265 - Macro: AC_REVISION (REVISION-INFO)
1266     Copy revision stamp REVISION-INFO into the `configure' script,
1267     with any dollar signs or double-quotes removed.  This macro lets
1268     you put a revision stamp from `configure.in' into `configure'
1269     without RCS or CVS changing it when you check in `configure'.  That
1270     way, you can determine easily which revision of `configure.in' a
1271     particular `configure' corresponds to.
1272
1273     It is a good idea to call this macro before `AC_INIT' so that the
1274     revision number is near the top of both `configure.in' and
1275     `configure'.  To support doing that, the `AC_REVISION' output
1276     begins with `#! /bin/sh', like the normal start of a `configure'
1277     script does.
1278
1279     For example, this line in `configure.in':
1280
1281          AC_REVISION($Revision: 1.1.1.1 $)dnl
1282
1283     produces this in `configure':
1284
1285          #! /bin/sh
1286          # From configure.in Revision: 1.30
1287
1288
1289File: autoconf.info,  Node: Existing Tests,  Next: Writing Tests,  Prev: Setup,  Up: Top
1290
1291Existing Tests
1292**************
1293
1294   These macros test for particular system features that packages might
1295need or want to use.  If you need to test for a kind of feature that
1296none of these macros check for, you can probably do it by calling
1297primitive test macros with appropriate arguments (*note Writing
1298Tests::.).
1299
1300   These tests print messages telling the user which feature they're
1301checking for, and what they find.  They cache their results for future
1302`configure' runs (*note Caching Results::.).
1303
1304   Some of these macros set output variables.  *Note Makefile
1305Substitutions::, for how to get their values.  The phrase "define NAME"
1306is used below as a shorthand to mean "define C preprocessor symbol NAME
1307to the value 1".  *Note Defining Symbols::, for how to get those symbol
1308definitions into your program.
1309
1310* Menu:
1311
1312* Alternative Programs::        Selecting between alternative programs.
1313* Libraries::                   Library archives that might be missing.
1314* Library Functions::           C library functions that might be missing.
1315* Header Files::                Header files that might be missing.
1316* Structures::                  Structures or members that might be missing.
1317* Typedefs::                    `typedef's that might be missing.
1318* C Compiler Characteristics::
1319* Fortran 77 Compiler Characteristics::
1320* System Services::             Operating system services.
1321* UNIX Variants::               Special kludges for specific UNIX variants.
1322
1323
1324File: autoconf.info,  Node: Alternative Programs,  Next: Libraries,  Prev: Existing Tests,  Up: Existing Tests
1325
1326Alternative Programs
1327====================
1328
1329   These macros check for the presence or behavior of particular
1330programs.  They are used to choose between several alternative programs
1331and to decide what to do once one has been chosen.  If there is no
1332macro specifically defined to check for a program you need, and you
1333don't need to check for any special properties of it, then you can use
1334one of the general program check macros.
1335
1336* Menu:
1337
1338* Particular Programs::         Special handling to find certain programs.
1339* Generic Programs::            How to find other programs.
1340
1341
1342File: autoconf.info,  Node: Particular Programs,  Next: Generic Programs,  Prev: Alternative Programs,  Up: Alternative Programs
1343
1344Particular Program Checks
1345-------------------------
1346
1347   These macros check for particular programs--whether they exist, and
1348in some cases whether they support certain features.
1349
1350 - Macro: AC_DECL_YYTEXT
1351     Define `YYTEXT_POINTER' if `yytext' is a `char *' instead of a
1352     `char []'.  Also set output variable `LEX_OUTPUT_ROOT' to the base
1353     of the file name that the lexer generates; usually `lex.yy', but
1354     sometimes something else.  These results vary according to whether
1355     `lex' or `flex' is being used.
1356
1357 - Macro: AC_PROG_AWK
1358     Check for `mawk', `gawk', `nawk', and `awk', in that order, and
1359     set output variable `AWK' to the first one that it finds.  It
1360     tries `mawk' first because that is reported to be the fastest
1361     implementation.
1362
1363 - Macro: AC_PROG_CC
1364     Determine a C compiler to use.  If `CC' is not already set in the
1365     environment, check for `gcc', and use `cc' if that's not found.
1366     Set output variable `CC' to the name of the compiler found.
1367
1368     If using the GNU C compiler, set shell variable `GCC' to `yes',
1369     empty otherwise.  If output variable `CFLAGS' was not already set,
1370     set it to `-g -O2' for the GNU C compiler (`-O2' on systems where
1371     GCC does not accept `-g'), or `-g' for other compilers.
1372
1373     If the C compiler being used does not produce executables that can
1374     run on the system where `configure' is being run, set the shell
1375     variable `cross_compiling' to `yes', otherwise `no'.  In other
1376     words, this tests whether the build system type is different from
1377     the host system type (the target system type is irrelevant to this
1378     test).  *Note Manual Configuration::, for more on support for
1379     cross compiling.
1380
1381 - Macro: AC_PROG_CC_C_O
1382     If the C compiler does not accept the `-c' and `-o' options
1383     simultaneously, define `NO_MINUS_C_MINUS_O'.
1384
1385 - Macro: AC_PROG_CPP
1386     Set output variable `CPP' to a command that runs the C
1387     preprocessor.  If `$CC -E' doesn't work, it uses `/lib/cpp'.  It
1388     is only portable to run `CPP' on files with a `.c' extension.
1389
1390     If the current language is C (*note Language Choice::.), many of
1391     the specific test macros use the value of `CPP' indirectly by
1392     calling `AC_TRY_CPP', `AC_CHECK_HEADER', `AC_EGREP_HEADER', or
1393     `AC_EGREP_CPP'.
1394
1395 - Macro: AC_PROG_CXX
1396     Determine a C++ compiler to use.  Check if the environment variable
1397     `CXX' or `CCC' (in that order) is set; if so, set output variable
1398     `CXX' to its value.  Otherwise search for a C++ compiler under
1399     likely names (`c++', `g++', `gcc', `CC', `cxx', and `cc++').  If
1400     none of those checks succeed, as a last resort set `CXX' to `gcc'.
1401
1402     If using the GNU C++ compiler, set shell variable `GXX' to `yes',
1403     empty otherwise.  If output variable `CXXFLAGS' was not already
1404     set, set it to `-g -O2' for the GNU C++ compiler (`-O2' on systems
1405     where G++ does not accept `-g'), or `-g' for other compilers.
1406
1407     If the C++ compiler being used does not produce executables that
1408     can run on the system where `configure' is being run, set the shell
1409     variable `cross_compiling' to `yes', otherwise `no'.  In other
1410     words, this tests whether the build system type is different from
1411     the host system type (the target system type is irrelevant to this
1412     test).  *Note Manual Configuration::, for more on support for
1413     cross compiling.
1414
1415 - Macro: AC_PROG_CXXCPP
1416     Set output variable `CXXCPP' to a command that runs the C++
1417     preprocessor.  If `$CXX -E' doesn't work, it uses `/lib/cpp'.  It
1418     is only portable to run `CXXCPP' on files with a `.c', `.C', or
1419     `.cc' extension.
1420
1421     If the current language is C++ (*note Language Choice::.), many of
1422     the specific test macros use the value of `CXXCPP' indirectly by
1423     calling `AC_TRY_CPP', `AC_CHECK_HEADER', `AC_EGREP_HEADER', or
1424     `AC_EGREP_CPP'.
1425
1426 - Macro: AC_PROG_F77
1427     Determine a Fortran 77 compiler to use.  If `F77' is not already
1428     set in the environment, check for `g77', `f77' and `f2c', in that
1429     order.  Set the output variable `F77' to the name of the compiler
1430     found.
1431
1432     If using `g77' (the GNU Fortran 77 compiler), then `AC_PROG_F77'
1433     will set the shell variable `G77' to `yes', and empty otherwise.
1434     If the output variable `FFLAGS' was not already set in the
1435     environment, then set it to `-g -02' for `g77' (or `-O2' where
1436     `g77' does not accept `-g').  Otherwise, set `FFLAGS' to `-g' for
1437     all other Fortran 77 compilers.
1438
1439 - Macro: AC_PROG_F77_C_O
1440     Test if the Fortran 77 compiler accepts the options `-c' and `-o'
1441     simultaneously, and define `F77_NO_MINUS_C_MINUS_O' if it does not.
1442
1443 - Macro: AC_PROG_GCC_TRADITIONAL
1444     Add `-traditional' to output variable `CC' if using the GNU C
1445     compiler and `ioctl' does not work properly without
1446     `-traditional'.  That usually happens when the fixed header files
1447     have not been installed on an old system.  Since recent versions
1448     of the GNU C compiler fix the header files automatically when
1449     installed, this is becoming a less prevalent problem.
1450
1451 - Macro: AC_PROG_INSTALL
1452     Set output variable `INSTALL' to the path of a BSD compatible
1453     `install' program, if one is found in the current `PATH'.
1454     Otherwise, set `INSTALL' to `DIR/install-sh -c', checking the
1455     directories specified to `AC_CONFIG_AUX_DIR' (or its default
1456     directories) to determine DIR (*note Output::.).  Also set the
1457     variables `INSTALL_PROGRAM' and `INSTALL_SCRIPT' to `${INSTALL}'
1458     and `INSTALL_DATA' to `${INSTALL} -m 644'.
1459
1460     This macro screens out various instances of `install' known to not
1461     work.  It prefers to find a C program rather than a shell script,
1462     for speed.  Instead of `install-sh', it can also use `install.sh',
1463     but that name is obsolete because some `make' programs have a rule
1464     that creates `install' from it if there is no `Makefile'.
1465
1466     A copy of `install-sh' which you may use comes with Autoconf.  If
1467     you use `AC_PROG_INSTALL', you must include either `install-sh' or
1468     `install.sh' in your distribution, or `configure' will produce an
1469     error message saying it can't find them--even if the system you're
1470     on has a good `install' program.  This check is a safety measure
1471     to prevent you from accidentally leaving that file out, which
1472     would prevent your package from installing on systems that don't
1473     have a BSD-compatible `install' program.
1474
1475     If you need to use your own installation program because it has
1476     features not found in standard `install' programs, there is no
1477     reason to use `AC_PROG_INSTALL'; just put the pathname of your
1478     program into your `Makefile.in' files.
1479
1480 - Macro: AC_PROG_LEX
1481     If `flex' is found, set output variable `LEX' to `flex' and
1482     `LEXLIB' to `-lfl', if that library is in a standard place.
1483     Otherwise set `LEX' to `lex' and `LEXLIB' to `-ll'.
1484
1485 - Macro: AC_PROG_LN_S
1486     If `ln -s' works on the current filesystem (the operating system
1487     and filesystem support symbolic links), set output variable `LN_S'
1488     to `ln -s', otherwise set it to `ln'.
1489
1490     If the link is put in a directory other than the current
1491     directory, its meaning depends on whether `ln' or `ln -s' is used.
1492     To safely create links using `$(LN_S)', either find out which
1493     form is used and adjust the arguments, or always invoke `ln' in
1494     the directory where the link is to be created.
1495
1496     In other words, it does not work to do
1497          $(LN_S) foo /x/bar
1498
1499     Instead, do
1500
1501          (cd /x && $(LN_S) foo bar)
1502
1503 - Macro: AC_PROG_RANLIB
1504     Set output variable `RANLIB' to `ranlib' if `ranlib' is found,
1505     otherwise to `:' (do nothing).
1506
1507 - Macro: AC_PROG_YACC
1508     If `bison' is found, set output variable `YACC' to `bison -y'.
1509     Otherwise, if `byacc' is found, set `YACC' to `byacc'.  Otherwise
1510     set `YACC' to `yacc'.
1511
1512
1513File: autoconf.info,  Node: Generic Programs,  Prev: Particular Programs,  Up: Alternative Programs
1514
1515Generic Program and File Checks
1516-------------------------------
1517
1518   These macros are used to find programs not covered by the particular
1519test macros.  If you need to check the behavior of a program as well as
1520find out whether it is present, you have to write your own test for it
1521(*note Writing Tests::.).  By default, these macros use the environment
1522variable `PATH'.  If you need to check for a program that might not be
1523in the user's `PATH', you can pass a modified path to use instead, like
1524this:
1525
1526     AC_PATH_PROG(INETD, inetd, /usr/libexec/inetd,
1527       $PATH:/usr/libexec:/usr/sbin:/usr/etc:etc)
1528
1529 - Macro: AC_CHECK_FILE (FILE [, ACTION-IF-FOUND [,
1530          ACTION-IF-NOT-FOUND]])
1531     Check whether file FILE exists on the native system.  If it is
1532     found, execute ACTION-IF-FOUND, otherwise do ACTION-IF-NOT-FOUND,
1533     if given.
1534
1535 - Macro: AC_CHECK_FILES (FILES[, ACTION-IF-FOUND [,
1536          ACTION-IF-NOT-FOUND]])
1537     Executes `AC_CHECK_FILE' once for each file listed in FILES.
1538     Additionally, defines `HAVEFILE' for each file found, set to 1.
1539
1540 - Macro: AC_CHECK_PROG (VARIABLE, PROG-TO-CHECK-FOR, VALUE-IF-FOUND [,
1541          VALUE-IF-NOT-FOUND [, PATH, [ REJECT ]]])
1542     Check whether program PROG-TO-CHECK-FOR exists in `PATH'.  If it
1543     is found, set VARIABLE to VALUE-IF-FOUND, otherwise to
1544     VALUE-IF-NOT-FOUND, if given.  Always pass over REJECT (an
1545     absolute file name) even if it is the first found in the search
1546     path; in that case, set VARIABLE using the absolute file name of
1547     the PROG-TO-CHECK-FOR found that is not REJECT.  If VARIABLE was
1548     already set, do nothing.  Calls `AC_SUBST' for VARIABLE.
1549
1550 - Macro: AC_CHECK_PROGS (VARIABLE, PROGS-TO-CHECK-FOR [,
1551          VALUE-IF-NOT-FOUND [, PATH]])
1552     Check for each program in the whitespace-separated list
1553     PROGS-TO-CHECK-FOR exists in `PATH'.  If it is found, set VARIABLE
1554     to the name of that program.  Otherwise, continue checking the
1555     next program in the list.  If none of the programs in the list are
1556     found, set VARIABLE to VALUE-IF-NOT-FOUND; if VALUE-IF-NOT-FOUND
1557     is not specified, the value of VARIABLE is not changed.  Calls
1558     `AC_SUBST' for VARIABLE.
1559
1560 - Macro: AC_CHECK_TOOL (VARIABLE, PROG-TO-CHECK-FOR [,
1561          VALUE-IF-NOT-FOUND [, PATH]])
1562     Like `AC_CHECK_PROG', but first looks for PROG-TO-CHECK-FOR with a
1563     prefix of the host type as determined by `AC_CANONICAL_HOST',
1564     followed by a dash (*note Canonicalizing::.).  For example, if the
1565     user runs `configure --host=i386-gnu', then this call:
1566          AC_CHECK_TOOL(RANLIB, ranlib, :)
1567
1568     sets `RANLIB' to `i386-gnu-ranlib' if that program exists in
1569     `PATH', or to `ranlib' if that program exists in `PATH', or to `:'
1570     if neither program exists.
1571
1572 - Macro: AC_PATH_PROG (VARIABLE, PROG-TO-CHECK-FOR [,
1573          VALUE-IF-NOT-FOUND [, PATH]])
1574     Like `AC_CHECK_PROG', but set VARIABLE to the entire path of
1575     PROG-TO-CHECK-FOR if found.
1576
1577 - Macro: AC_PATH_PROGS (VARIABLE, PROGS-TO-CHECK-FOR [,
1578          VALUE-IF-NOT-FOUND [, PATH]])
1579     Like `AC_CHECK_PROGS', but if any of PROGS-TO-CHECK-FOR are found,
1580     set VARIABLE to the entire path of the program found.
1581
1582
1583File: autoconf.info,  Node: Libraries,  Next: Library Functions,  Prev: Alternative Programs,  Up: Existing Tests
1584
1585Library Files
1586=============
1587
1588   The following macros check for the presence of certain C, C++ or
1589Fortran 77 library archive files.
1590
1591 - Macro: AC_CHECK_LIB (LIBRARY, FUNCTION [, ACTION-IF-FOUND [,
1592          ACTION-IF-NOT-FOUND [, OTHER-LIBRARIES]]])
1593     Depending on the current language(*note Language Choice::.), try to
1594     ensure that the C, C++ or Fortran 77 function FUNCTION is
1595     available by checking whether a test program can be linked with the
1596     library LIBRARY to get the function.  LIBRARY is the base name of
1597     the library; e.g., to check for `-lmp', use `mp' as the LIBRARY
1598     argument.
1599
1600     ACTION-IF-FOUND is a list of shell commands to run if the link
1601     with the library succeeds; ACTION-IF-NOT-FOUND is a list of shell
1602     commands to run if the link fails.  If ACTION-IF-FOUND is not
1603     specified, the default action will add `-lLIBRARY' to `LIBS' and
1604     define `HAVE_LIBLIBRARY' (in all capitals).
1605
1606     If linking with LIBRARY results in unresolved symbols, which would
1607     be resolved by linking with additional libraries, give those
1608     libraries as the OTHER-LIBRARIES argument, separated by spaces:
1609     `-lXt -lX11'.  Otherwise this macro will fail to detect that
1610     LIBRARY is present, because linking the test program will always
1611     fail with unresolved symbols.
1612
1613 - Macro: AC_HAVE_LIBRARY (LIBRARY, [, ACTION-IF-FOUND [,
1614          ACTION-IF-NOT-FOUND [, OTHER-LIBRARIES]]])
1615     This macro is equivalent to calling `AC_CHECK_LIB' with a FUNCTION
1616     argument of `main'.  In addition, LIBRARY can be written as any of
1617     `foo', `-lfoo', or `libfoo.a'.  In all of those cases, the
1618     compiler is passed `-lfoo'.  However, LIBRARY can not be a shell
1619     variable; it must be a literal name.  This macro is considered
1620     obsolete.
1621
1622 - Macro: AC_SEARCH_LIBS (FUNCTION, SEARCH-LIBS [, ACTION-IF-FOUND [,
1623          ACTION-IF-NOT-FOUND [, OTHER-LIBRARIES]]])
1624     Search for a library defining FUNCTION, if it's not already
1625     available.  This equates to calling `AC_TRY_LINK_FUNC' first with
1626     no libraries, then for each library listed in SEARCH-LIBS.
1627
1628     If the function is found, run ACTION-IF-FOUND, otherwise run
1629     ACTION-IF-NOT-FOUND.
1630
1631     If linking with LIBRARY results in unresolved symbols, which would
1632     be resolved by linking with additional libraries, give those
1633     libraries as the OTHER-LIBRARIES argument, separated by spaces:
1634     `-lXt -lX11'.  Otherwise this macro will fail to detect that
1635     FUNCTION is present, because linking the test program will always
1636     fail with unresolved symbols.
1637
1638 - Macro: AC_SEARCH_LIBS (FUNCTION, SEARCH-LIBS[, ACTION-IF-FOUND [,
1639          ACTION-IF-NOT-FOUND]])
1640     This macro is equivalent to calling `AC_TRY_LINK_FUNC' once for
1641     each library listed in SEARCH-LIBS.  Add `-lLIBRARY' to `LIBS' for
1642     the first library found to contain FUNCTION, and execute
1643     ACTION-IF-FOUND.  Otherwise execute ACTION-IF-NOT-FOUND.
1644
1645
1646File: autoconf.info,  Node: Library Functions,  Next: Header Files,  Prev: Libraries,  Up: Existing Tests
1647
1648Library Functions
1649=================
1650
1651   The following macros check for particular C library functions.  If
1652there is no macro specifically defined to check for a function you need,
1653and you don't need to check for any special properties of it, then you
1654can use one of the general function check macros.
1655
1656* Menu:
1657
1658* Particular Functions::        Special handling to find certain functions.
1659* Generic Functions::           How to find other functions.
1660
1661
1662File: autoconf.info,  Node: Particular Functions,  Next: Generic Functions,  Prev: Library Functions,  Up: Library Functions
1663
1664Particular Function Checks
1665--------------------------
1666
1667   These macros check for particular C functions--whether they exist,
1668and in some cases how they respond when given certain arguments.
1669
1670 - Macro: AC_FUNC_ALLOCA
1671     Check how to get `alloca'.  Tries to get a builtin version by
1672     checking for `alloca.h' or the predefined C preprocessor macros
1673     `__GNUC__' and `_AIX'.  If this macro finds `alloca.h', it defines
1674     `HAVE_ALLOCA_H'.
1675
1676     If those attempts fail, it looks for the function in the standard C
1677     library.  If any of those methods succeed, it defines
1678     `HAVE_ALLOCA'.  Otherwise, it sets the output variable `ALLOCA' to
1679     `alloca.o' and defines `C_ALLOCA' (so programs can periodically
1680     call `alloca(0)' to garbage collect).  This variable is separate
1681     from `LIBOBJS' so multiple programs can share the value of
1682     `ALLOCA' without needing to create an actual library, in case only
1683     some of them use the code in `LIBOBJS'.
1684
1685     This macro does not try to get `alloca' from the System V R3
1686     `libPW' or the System V R4 `libucb' because those libraries
1687     contain some incompatible functions that cause trouble.  Some
1688     versions do not even contain `alloca' or contain a buggy version.
1689     If you still want to use their `alloca', use `ar' to extract
1690     `alloca.o' from them instead of compiling `alloca.c'.
1691
1692     Source files that use `alloca' should start with a piece of code
1693     like the following, to declare it properly.  In some versions of
1694     AIX, the declaration of `alloca' must precede everything else
1695     except for comments and preprocessor directives.  The `#pragma'
1696     directive is indented so that pre-ANSI C compilers will ignore it,
1697     rather than choke on it.
1698
1699          /* AIX requires this to be the first thing in the file.  */
1700          #ifndef __GNUC__
1701          # if HAVE_ALLOCA_H
1702          #  include <alloca.h>
1703          # else
1704          #  ifdef _AIX
1705           #pragma alloca
1706          #  else
1707          #   ifndef alloca /* predefined by HP cc +Olibcalls */
1708          char *alloca ();
1709          #   endif
1710          #  endif
1711          # endif
1712          #endif
1713
1714 - Macro: AC_FUNC_CLOSEDIR_VOID
1715     If the `closedir' function does not return a meaningful value,
1716     define `CLOSEDIR_VOID'.  Otherwise, callers ought to check its
1717     return value for an error indicator.
1718
1719 - Macro: AC_FUNC_FNMATCH
1720     If the `fnmatch' function is available and works (unlike the one on
1721     SunOS 5.4), define `HAVE_FNMATCH'.
1722
1723 - Macro: AC_FUNC_GETLOADAVG
1724     Check how to get the system load averages.  If the system has the
1725     `getloadavg' function, this macro defines `HAVE_GETLOADAVG', and
1726     adds to `LIBS' any libraries needed to get that function.
1727
1728     Otherwise, it adds `getloadavg.o' to the output variable
1729     `LIBOBJS', and possibly defines several other C preprocessor
1730     macros and output variables:
1731
1732       1. It defines `SVR4', `DGUX', `UMAX', or `UMAX4_3' if on those
1733          systems.
1734
1735       2. If it finds `nlist.h', it defines `NLIST_STRUCT'.
1736
1737       3. If `struct nlist' has an `n_un' member, it defines
1738          `NLIST_NAME_UNION'.
1739
1740       4. If compiling `getloadavg.c' defines `LDAV_PRIVILEGED',
1741          programs need to be installed specially on this system for
1742          `getloadavg' to work, and this macro defines
1743          `GETLOADAVG_PRIVILEGED'.
1744
1745       5. This macro sets the output variable `NEED_SETGID'.  The value
1746          is `true' if special installation is required, `false' if not.
1747          If `NEED_SETGID' is `true', this macro sets `KMEM_GROUP' to
1748          the name of the group that should own the installed program.
1749
1750 - Macro: AC_FUNC_GETMNTENT
1751     Check for `getmntent' in the `sun', `seq', and `gen' libraries,
1752     for Irix 4, PTX, and Unixware, respectively.  Then, if `getmntent'
1753     is available, define `HAVE_GETMNTENT'.
1754
1755 - Macro: AC_FUNC_GETPGRP
1756     If `getpgrp' takes no argument (the POSIX.1 version), define
1757     `GETPGRP_VOID'.  Otherwise, it is the BSD version, which takes a
1758     process ID as an argument.  This macro does not check whether
1759     `getpgrp' exists at all; if you need to work in that situation,
1760     first call `AC_CHECK_FUNC' for `getpgrp'.
1761
1762 - Macro: AC_FUNC_MEMCMP
1763     If the `memcmp' function is not available, or does not work on
1764     8-bit data (like the one on SunOS 4.1.3), add `memcmp.o' to output
1765     variable `LIBOBJS'.
1766
1767 - Macro: AC_FUNC_MMAP
1768     If the `mmap' function exists and works correctly, define
1769     `HAVE_MMAP'.  Only checks private fixed mapping of already-mapped
1770     memory.
1771
1772 - Macro: AC_FUNC_SELECT_ARGTYPES
1773     Determines the correct type to be passed to each of the `select'
1774     function's arguments, and defines those types in
1775     `SELECT_TYPE_ARG1', `SELECT_TYPE_ARG234', and `SELECT_TYPE_ARG5'
1776     respectively.  `SELECT_TYPE_ARG1' defaults to `int',
1777     `SELECT_TYPE_ARG234' defaults to `int *', and `SELECT_TYPE_ARG5'
1778     defaults to `struct timeval *'.
1779
1780 - Macro: AC_FUNC_SETPGRP
1781     If `setpgrp' takes no argument (the POSIX.1 version), define
1782     `SETPGRP_VOID'.  Otherwise, it is the BSD version, which takes two
1783     process ID as arguments.  This macro does not check whether
1784     `setpgrp' exists at all; if you need to work in that situation,
1785     first call `AC_CHECK_FUNC' for `setpgrp'.
1786
1787 - Macro: AC_FUNC_SETVBUF_REVERSED
1788     If `setvbuf' takes the buffering type as its second argument and
1789     the buffer pointer as the third, instead of the other way around,
1790     define `SETVBUF_REVERSED'.  This is the case on System V before
1791     release 3.
1792
1793 - Macro: AC_FUNC_STRCOLL
1794     If the `strcoll' function exists and works correctly, define
1795     `HAVE_STRCOLL'.  This does a bit more than
1796     `AC_CHECK_FUNCS(strcoll)', because some systems have incorrect
1797     definitions of `strcoll', which should not be used.
1798
1799 - Macro: AC_FUNC_STRFTIME
1800     Check for `strftime' in the `intl' library, for SCO UNIX.  Then,
1801     if `strftime' is available, define `HAVE_STRFTIME'.
1802
1803 - Macro: AC_FUNC_UTIME_NULL
1804     If `utime(FILE, NULL)' sets FILE's timestamp to the present,
1805     define `HAVE_UTIME_NULL'.
1806
1807 - Macro: AC_FUNC_VFORK
1808     If `vfork.h' is found, define `HAVE_VFORK_H'.  If a working
1809     `vfork' is not found, define `vfork' to be `fork'.  This macro
1810     checks for several known errors in implementations of `vfork' and
1811     considers the system to not have a working `vfork' if it detects
1812     any of them.  It is not considered to be an implementation error
1813     if a child's invocation of `signal' modifies the parent's signal
1814     handler, since child processes rarely change their signal handlers.
1815
1816 - Macro: AC_FUNC_VPRINTF
1817     If `vprintf' is found, define `HAVE_VPRINTF'.  Otherwise, if
1818     `_doprnt' is found, define `HAVE_DOPRNT'.  (If `vprintf' is
1819     available, you may assume that `vfprintf' and `vsprintf' are also
1820     available.)
1821
1822 - Macro: AC_FUNC_WAIT3
1823     If `wait3' is found and fills in the contents of its third argument
1824     (a `struct rusage *'), which HP-UX does not do, define
1825     `HAVE_WAIT3'.
1826
1827
1828File: autoconf.info,  Node: Generic Functions,  Prev: Particular Functions,  Up: Library Functions
1829
1830Generic Function Checks
1831-----------------------
1832
1833   These macros are used to find functions not covered by the particular
1834test macros.  If the functions might be in libraries other than the
1835default C library, first call `AC_CHECK_LIB' for those libraries.  If
1836you need to check the behavior of a function as well as find out
1837whether it is present, you have to write your own test for it (*note
1838Writing Tests::.).
1839
1840 - Macro: AC_CHECK_FUNC (FUNCTION, [ACTION-IF-FOUND [,
1841          ACTION-IF-NOT-FOUND]])
1842     If C function FUNCTION is available, run shell commands
1843     ACTION-IF-FOUND, otherwise ACTION-IF-NOT-FOUND.  If you just want
1844     to define a symbol if the function is available, consider using
1845     `AC_CHECK_FUNCS' instead.  This macro checks for functions with C
1846     linkage even when `AC_LANG_CPLUSPLUS' has been called, since C++ is
1847     more standardized than C is.  (*note Language Choice::., for more
1848     information about selecting the language for checks.)
1849
1850 - Macro: AC_CHECK_FUNCS (FUNCTION... [, ACTION-IF-FOUND [,
1851          ACTION-IF-NOT-FOUND]])
1852     For each given FUNCTION in the whitespace-separated argument list
1853     that is available, define `HAVE_FUNCTION' (in all capitals).  If
1854     ACTION-IF-FOUND is given, it is additional shell code to execute
1855     when one of the functions is found.  You can give it a value of
1856     `break' to break out of the loop on the first match.  If
1857     ACTION-IF-NOT-FOUND is given, it is executed when one of the
1858     functions is not found.
1859
1860 - Macro: AC_REPLACE_FUNCS (FUNCTION...)
1861     Like calling `AC_CHECK_FUNCS' using an ACTION-IF-NOT-FOUND that
1862     adds `FUNCTION.o' to the value of the output variable `LIBOBJS'.
1863     You can declare a function for which your replacement version is
1864     used by enclosing the prototype in `#ifndef HAVE_FUNCTION'.  If
1865     the system has the function, it probably declares it in a header
1866     file you should be including, so you shouldn't redeclare it, lest
1867     your declaration conflict.
1868
1869
1870File: autoconf.info,  Node: Header Files,  Next: Structures,  Prev: Library Functions,  Up: Existing Tests
1871
1872Header Files
1873============
1874
1875   The following macros check for the presence of certain C header
1876files.  If there is no macro specifically defined to check for a header
1877file you need, and you don't need to check for any special properties of
1878it, then you can use one of the general header file check macros.
1879
1880* Menu:
1881
1882* Particular Headers::          Special handling to find certain headers.
1883* Generic Headers::             How to find other headers.
1884
1885
1886File: autoconf.info,  Node: Particular Headers,  Next: Generic Headers,  Prev: Header Files,  Up: Header Files
1887
1888Particular Header Checks
1889------------------------
1890
1891   These macros check for particular system header files--whether they
1892exist, and in some cases whether they declare certain symbols.
1893
1894 - Macro: AC_DECL_SYS_SIGLIST
1895     Define `SYS_SIGLIST_DECLARED' if the variable `sys_siglist' is
1896     declared in a system header file, either `signal.h' or `unistd.h'.
1897
1898 - Macro: AC_DIR_HEADER
1899     Like calling `AC_HEADER_DIRENT' and `AC_FUNC_CLOSEDIR_VOID', but
1900     defines a different set of C preprocessor macros to indicate which
1901     header file is found.  This macro and the names it defines are
1902     considered obsolete.  The names it defines are:
1903
1904    `dirent.h'
1905          `DIRENT'
1906
1907    `sys/ndir.h'
1908          `SYSNDIR'
1909
1910    `sys/dir.h'
1911          `SYSDIR'
1912
1913    `ndir.h'
1914          `NDIR'
1915
1916     In addition, if the `closedir' function does not return a
1917     meaningful value, define `VOID_CLOSEDIR'.
1918
1919 - Macro: AC_HEADER_DIRENT
1920     Check for the following header files, and for the first one that is
1921     found and defines `DIR', define the listed C preprocessor macro:
1922
1923    `dirent.h'
1924          `HAVE_DIRENT_H'
1925
1926    `sys/ndir.h'
1927          `HAVE_SYS_NDIR_H'
1928
1929    `sys/dir.h'
1930          `HAVE_SYS_DIR_H'
1931
1932    `ndir.h'
1933          `HAVE_NDIR_H'
1934
1935     The directory library declarations in the source code should look
1936     something like the following:
1937
1938          #if HAVE_DIRENT_H
1939          # include <dirent.h>
1940          # define NAMLEN(dirent) strlen((dirent)->d_name)
1941          #else
1942          # define dirent direct
1943          # define NAMLEN(dirent) (dirent)->d_namlen
1944          # if HAVE_SYS_NDIR_H
1945          #  include <sys/ndir.h>
1946          # endif
1947          # if HAVE_SYS_DIR_H
1948          #  include <sys/dir.h>
1949          # endif
1950          # if HAVE_NDIR_H
1951          #  include <ndir.h>
1952          # endif
1953          #endif
1954
1955     Using the above declarations, the program would declare variables
1956     to be type `struct dirent', not `struct direct', and would access
1957     the length of a directory entry name by passing a pointer to a
1958     `struct dirent' to the `NAMLEN' macro.
1959
1960     This macro also checks for the SCO Xenix `dir' and `x' libraries.
1961
1962 - Macro: AC_HEADER_MAJOR
1963     If `sys/types.h' does not define `major', `minor', and `makedev',
1964     but `sys/mkdev.h' does, define `MAJOR_IN_MKDEV'; otherwise, if
1965     `sys/sysmacros.h' does, define `MAJOR_IN_SYSMACROS'.
1966
1967 - Macro: AC_HEADER_STDC
1968     Define `STDC_HEADERS' if the system has ANSI C header files.
1969     Specifically, this macro checks for `stdlib.h', `stdarg.h',
1970     `string.h', and `float.h'; if the system has those, it probably
1971     has the rest of the ANSI C header files.  This macro also checks
1972     whether `string.h' declares `memchr' (and thus presumably the
1973     other `mem' functions), whether `stdlib.h' declare `free' (and
1974     thus presumably `malloc' and other related functions), and whether
1975     the `ctype.h' macros work on characters with the high bit set, as
1976     ANSI C requires.
1977
1978     Use `STDC_HEADERS' instead of `__STDC__' to determine whether the
1979     system has ANSI-compliant header files (and probably C library
1980     functions) because many systems that have GCC do not have ANSI C
1981     header files.
1982
1983     On systems without ANSI C headers, there is so much variation that
1984     it is probably easier to declare the functions you use than to
1985     figure out exactly what the system header files declare.  Some
1986     systems contain a mix of functions ANSI and BSD; some are mostly
1987     ANSI but lack `memmove'; some define the BSD functions as macros in
1988     `string.h' or `strings.h'; some have only the BSD functions but
1989     `string.h'; some declare the memory functions in `memory.h', some
1990     in `string.h'; etc.  It is probably sufficient to check for one
1991     string function and one memory function; if the library has the
1992     ANSI versions of those then it probably has most of the others.
1993     If you put the following in `configure.in':
1994
1995          AC_HEADER_STDC
1996          AC_CHECK_FUNCS(strchr memcpy)
1997
1998     then, in your code, you can put declarations like this:
1999
2000          #if STDC_HEADERS
2001          # include <string.h>
2002          #else
2003          # ifndef HAVE_STRCHR
2004          #  define strchr index
2005          #  define strrchr rindex
2006          # endif
2007          char *strchr (), *strrchr ();
2008          # ifndef HAVE_MEMCPY
2009          #  define memcpy(d, s, n) bcopy ((s), (d), (n))
2010          #  define memmove(d, s, n) bcopy ((s), (d), (n))
2011          # endif
2012          #endif
2013
2014     If you use a function like `memchr', `memset', `strtok', or
2015     `strspn', which have no BSD equivalent, then macros won't suffice;
2016     you must provide an implementation of each function.  An easy way
2017     to incorporate your implementations only when needed (since the
2018     ones in system C libraries may be hand optimized) is to, taking
2019     `memchr' for example, put it in `memchr.c' and use
2020     `AC_REPLACE_FUNCS(memchr)'.
2021
2022 - Macro: AC_HEADER_SYS_WAIT
2023     If `sys/wait.h' exists and is compatible with POSIX.1, define
2024     `HAVE_SYS_WAIT_H'.  Incompatibility can occur if `sys/wait.h' does
2025     not exist, or if it uses the old BSD `union wait' instead of `int'
2026     to store a status value.  If `sys/wait.h' is not POSIX.1
2027     compatible, then instead of including it, define the POSIX.1
2028     macros with their usual interpretations.  Here is an example:
2029
2030          #include <sys/types.h>
2031          #if HAVE_SYS_WAIT_H
2032          # include <sys/wait.h>
2033          #endif
2034          #ifndef WEXITSTATUS
2035          # define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
2036          #endif
2037          #ifndef WIFEXITED
2038          # define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
2039          #endif
2040
2041 - Macro: AC_MEMORY_H
2042     Define `NEED_MEMORY_H' if `memcpy', `memcmp', etc. are not
2043     declared in `string.h' and `memory.h' exists.  This macro is
2044     obsolete; instead, use `AC_CHECK_HEADERS(memory.h)'.  See the
2045     example for `AC_HEADER_STDC'.
2046
2047 - Macro: AC_UNISTD_H
2048     Define `HAVE_UNISTD_H' if the system has `unistd.h'.  This macro
2049     is obsolete; instead, use `AC_CHECK_HEADERS(unistd.h)'.
2050
2051     The way to check if the system supports POSIX.1 is:
2052
2053          #if HAVE_UNISTD_H
2054          # include <sys/types.h>
2055          # include <unistd.h>
2056          #endif
2057         
2058          #ifdef _POSIX_VERSION
2059          /* Code for POSIX.1 systems.  */
2060          #endif
2061
2062     `_POSIX_VERSION' is defined when `unistd.h' is included on POSIX.1
2063     systems.  If there is no `unistd.h', it is definitely not a
2064     POSIX.1 system.  However, some non-POSIX.1 systems do have
2065     `unistd.h'.
2066
2067 - Macro: AC_USG
2068     Define `USG' if the system does not have `strings.h', `rindex',
2069     `bzero', etc.  This implies that it has `string.h', `strrchr',
2070     `memset', etc.
2071
2072     The symbol `USG' is obsolete.  Instead of this macro, see the
2073     example for `AC_HEADER_STDC'.
2074
2075
2076File: autoconf.info,  Node: Generic Headers,  Prev: Particular Headers,  Up: Header Files
2077
2078Generic Header Checks
2079---------------------
2080
2081   These macros are used to find system header files not covered by the
2082particular test macros.  If you need to check the contents of a header
2083as well as find out whether it is present, you have to write your own
2084test for it (*note Writing Tests::.).
2085
2086 - Macro: AC_CHECK_HEADER (HEADER-FILE, [ACTION-IF-FOUND [,
2087          ACTION-IF-NOT-FOUND]])
2088     If the system header file HEADER-FILE exists, execute shell
2089     commands ACTION-IF-FOUND, otherwise execute ACTION-IF-NOT-FOUND.
2090     If you just want to define a symbol if the header file is
2091     available, consider using `AC_CHECK_HEADERS' instead.
2092
2093 - Macro: AC_CHECK_HEADERS (HEADER-FILE... [, ACTION-IF-FOUND [,
2094          ACTION-IF-NOT-FOUND]])
2095     For each given system header file HEADER-FILE in the
2096     whitespace-separated argument list that exists, define
2097     `HAVE_HEADER-FILE' (in all capitals).  If ACTION-IF-FOUND is
2098     given, it is additional shell code to execute when one of the
2099     header files is found.  You can give it a value of `break' to
2100     break out of the loop on the first match.  If ACTION-IF-NOT-FOUND
2101     is given, it is executed when one of the header files is not found.
2102
2103
2104File: autoconf.info,  Node: Structures,  Next: Typedefs,  Prev: Header Files,  Up: Existing Tests
2105
2106Structures
2107==========
2108
2109   The following macros check for certain structures or structure
2110members.  To check structures not listed here, use `AC_EGREP_CPP'
2111(*note Examining Declarations::.) or `AC_TRY_COMPILE' (*note Examining
2112Syntax::.).
2113
2114 - Macro: AC_HEADER_STAT
2115     If the macros `S_ISDIR', `S_ISREG' et al. defined in `sys/stat.h'
2116     do not work properly (returning false positives), define
2117     `STAT_MACROS_BROKEN'.  This is the case on Tektronix UTekV, Amdahl
2118     UTS and Motorola System V/88.
2119
2120 - Macro: AC_HEADER_TIME
2121     If a program may include both `time.h' and `sys/time.h', define
2122     `TIME_WITH_SYS_TIME'.  On some older systems, `sys/time.h'
2123     includes `time.h', but `time.h' is not protected against multiple
2124     inclusion, so programs should not explicitly include both files.
2125     This macro is useful in programs that use, for example, `struct
2126     timeval' or `struct timezone' as well as `struct tm'.  It is best
2127     used in conjunction with `HAVE_SYS_TIME_H', which can be checked
2128     for using `AC_CHECK_HEADERS(sys/time.h)'.
2129
2130          #if TIME_WITH_SYS_TIME
2131          # include <sys/time.h>
2132          # include <time.h>
2133          #else
2134          # if HAVE_SYS_TIME_H
2135          #  include <sys/time.h>
2136          # else
2137          #  include <time.h>
2138          # endif
2139          #endif
2140
2141 - Macro: AC_STRUCT_ST_BLKSIZE
2142     If `struct stat' contains an `st_blksize' member, define
2143     `HAVE_ST_BLKSIZE'.
2144
2145 - Macro: AC_STRUCT_ST_BLOCKS
2146     If `struct stat' contains an `st_blocks' member, define
2147     `HAVE_ST_BLOCKS'.  Otherwise, add `fileblocks.o' to the output
2148     variable `LIBOBJS'.
2149
2150 - Macro: AC_STRUCT_ST_RDEV
2151     If `struct stat' contains an `st_rdev' member, define
2152     `HAVE_ST_RDEV'.
2153
2154 - Macro: AC_STRUCT_TM
2155     If `time.h' does not define `struct tm', define `TM_IN_SYS_TIME',
2156     which means that including `sys/time.h' had better define `struct
2157     tm'.
2158
2159 - Macro: AC_STRUCT_TIMEZONE
2160     Figure out how to get the current timezone.  If `struct tm' has a
2161     `tm_zone' member, define `HAVE_TM_ZONE'.  Otherwise, if the
2162     external array `tzname' is found, define `HAVE_TZNAME'.
2163
2164
2165File: autoconf.info,  Node: Typedefs,  Next: C Compiler Characteristics,  Prev: Structures,  Up: Existing Tests
2166
2167Typedefs
2168========
2169
2170   The following macros check for C typedefs.  If there is no macro
2171specifically defined to check for a typedef you need, and you don't need
2172to check for any special properties of it, then you can use a general
2173typedef check macro.
2174
2175* Menu:
2176
2177* Particular Typedefs::         Special handling to find certain types.
2178* Generic Typedefs::            How to find other types.
2179
2180
2181File: autoconf.info,  Node: Particular Typedefs,  Next: Generic Typedefs,  Prev: Typedefs,  Up: Typedefs
2182
2183Particular Typedef Checks
2184-------------------------
2185
2186   These macros check for particular C typedefs in `sys/types.h' and
2187`stdlib.h' (if it exists).
2188
2189 - Macro: AC_TYPE_GETGROUPS
2190     Define `GETGROUPS_T' to be whichever of `gid_t' or `int' is the
2191     base type of the array argument to `getgroups'.
2192
2193 - Macro: AC_TYPE_MODE_T
2194     If `mode_t' is not defined, define `mode_t' to be `int'.
2195
2196 - Macro: AC_TYPE_OFF_T
2197     If `off_t' is not defined, define `off_t' to be `long'.
2198
2199 - Macro: AC_TYPE_PID_T
2200     If `pid_t' is not defined, define `pid_t' to be `int'.
2201
2202 - Macro: AC_TYPE_SIGNAL
2203     If `signal.h' declares `signal' as returning a pointer to a
2204     function returning `void', define `RETSIGTYPE' to be `void';
2205     otherwise, define it to be `int'.
2206
2207     Define signal handlers as returning type `RETSIGTYPE':
2208
2209          RETSIGTYPE
2210          hup_handler ()
2211          {
2212          ...
2213          }
2214
2215 - Macro: AC_TYPE_SIZE_T
2216     If `size_t' is not defined, define `size_t' to be `unsigned'.
2217
2218 - Macro: AC_TYPE_UID_T
2219     If `uid_t' is not defined, define `uid_t' to be `int' and `gid_t'
2220     to be `int'.
2221
2222
2223File: autoconf.info,  Node: Generic Typedefs,  Prev: Particular Typedefs,  Up: Typedefs
2224
2225Generic Typedef Checks
2226----------------------
2227
2228   This macro is used to check for typedefs not covered by the
2229particular test macros.
2230
2231 - Macro: AC_CHECK_TYPE (TYPE, DEFAULT)
2232     If the type TYPE is not defined in `sys/types.h', or `stdlib.h' or
2233     `stddef.h' if they exist, define it to be the C (or C++) builtin
2234     type DEFAULT; e.g., `short' or `unsigned'.
2235
2236
2237File: autoconf.info,  Node: C Compiler Characteristics,  Next: Fortran 77 Compiler Characteristics,  Prev: Typedefs,  Up: Existing Tests
2238
2239C Compiler Characteristics
2240==========================
2241
2242   The following macros check for C compiler or machine architecture
2243features.  To check for characteristics not listed here, use
2244`AC_TRY_COMPILE' (*note Examining Syntax::.) or `AC_TRY_RUN' (*note Run
2245Time::.)
2246
2247 - Macro: AC_C_BIGENDIAN
2248     If words are stored with the most significant byte first (like
2249     Motorola and SPARC, but not Intel and VAX, CPUs), define
2250     `WORDS_BIGENDIAN'.
2251
2252 - Macro: AC_C_CONST
2253     If the C compiler does not fully support the keyword `const',
2254     define `const' to be empty.  Some C compilers that do not define
2255     `__STDC__' do support `const'; some compilers that define
2256     `__STDC__' do not completely support `const'.  Programs can simply
2257     use `const' as if every C compiler supported it; for those that
2258     don't, the `Makefile' or configuration header file will define it
2259     as empty.
2260
2261 - Macro: AC_C_INLINE
2262     If the C compiler supports the keyword `inline', do nothing.
2263     Otherwise define `inline' to `__inline__' or `__inline' if it
2264     accepts one of those, otherwise define `inline' to be empty.
2265
2266 - Macro: AC_C_CHAR_UNSIGNED
2267     If the C type `char' is unsigned, define `__CHAR_UNSIGNED__',
2268     unless the C compiler predefines it.
2269
2270 - Macro: AC_C_LONG_DOUBLE
2271     If the C compiler supports the `long double' type, define
2272     `HAVE_LONG_DOUBLE'.  Some C compilers that do not define
2273     `__STDC__' do support the `long double' type; some compilers that
2274     define `__STDC__' do not support `long double'.
2275
2276 - Macro: AC_C_STRINGIZE
2277     If the C preprocessor supports the stringizing operator, define
2278     `HAVE_STRINGIZE'.  The stringizing operator is `#' and is found in
2279     macros such as this:
2280
2281          #define x(y) #y
2282
2283 - Macro: AC_CHECK_SIZEOF (TYPE [, CROSS-SIZE])
2284     Define `SIZEOF_UCTYPE' to be the size in bytes of the C (or C++)
2285     builtin type TYPE, e.g. `int' or `char *'.  If `type' is unknown
2286     to the compiler, it gets a size of 0.  UCTYPE is TYPE, with
2287     lowercase converted to uppercase, spaces changed to underscores,
2288     and asterisks changed to `P'.  If cross-compiling, the value
2289     CROSS-SIZE is used if given, otherwise `configure' exits with an
2290     error message.
2291
2292     For example, the call
2293          AC_CHECK_SIZEOF(int *)
2294
2295     defines `SIZEOF_INT_P' to be 8 on DEC Alpha AXP systems.
2296
2297 - Macro: AC_INT_16_BITS
2298     If the C type `int' is 16 bits wide, define `INT_16_BITS'.  This
2299     macro is obsolete; it is more general to use
2300     `AC_CHECK_SIZEOF(int)' instead.
2301
2302 - Macro: AC_LONG_64_BITS
2303     If the C type `long int' is 64 bits wide, define `LONG_64_BITS'.
2304     This macro is obsolete; it is more general to use
2305     `AC_CHECK_SIZEOF(long)' instead.
2306
2307
2308File: autoconf.info,  Node: Fortran 77 Compiler Characteristics,  Next: System Services,  Prev: C Compiler Characteristics,  Up: Existing Tests
2309
2310Fortran 77 Compiler Characteristics
2311===================================
2312
2313   The following macros check for Fortran 77 compiler characteristics.
2314To check for characteristics not listed here, use `AC_TRY_COMPILE'
2315(*note Examining Syntax::.) or `AC_TRY_RUN' (*note Run Time::.), making
2316sure to first set the current lanuage to Fortran 77 `AC_LANG_FORTRAN77'
2317(*note Language Choice::.).
2318
2319 - Macro: AC_F77_LIBRARY_LDFLAGS
2320     Determine the linker flags (e.g. `-L' and `-l') for the "Fortran
2321     77 intrinsic and run-time libraries" that are required to
2322     successfully link a Fortran 77 program or shared library.  The
2323     output variable `FLIBS' is set to these flags.
2324
2325     This macro is intended to be used in those situations when it is
2326     necessary to mix, e.g. C++ and Fortran 77 source code into a single
2327     program or shared library (*note Mixing Fortran 77 With C and C++:
2328     (automake)Mixing Fortran 77 With C and C++.).
2329
2330     For example, if object files from a C++ and Fortran 77 compiler
2331     must be linked together, then the C++ compiler/linker must be used
2332     for linking (since special C++-ish things need to happen at link
2333     time like calling global constructors, instantiating templates,
2334     enabling exception support, etc.).
2335
2336     However, the Fortran 77 intrinsic and run-time libraries must be
2337     linked in as well, but the C++ compiler/linker doesn't know by
2338     default how to add these Fortran 77 libraries.  Hence, the macro
2339     `AC_F77_LIBRARY_LDFLAGS' was created to determine these Fortran 77
2340     libraries.
2341
2342
2343File: autoconf.info,  Node: System Services,  Next: UNIX Variants,  Prev: Fortran 77 Compiler Characteristics,  Up: Existing Tests
2344
2345System Services
2346===============
2347
2348   The following macros check for operating system services or
2349capabilities.
2350
2351 - Macro: AC_CYGWIN
2352     Checks for the Cygwin environment.  If present, sets shell variable
2353     `CYGWIN' to `yes'.  If not present, sets `CYGWIN' to the empty
2354     string.
2355
2356 - Macro: AC_EXEEXT
2357     Defines substitute variable `EXEEXT' based on the output of the
2358     compiler, after .c, .o, and .obj files have been excluded.
2359     Typically set to empty string if Unix, `.exe' or `.EXE' if Win32.
2360
2361 - Macro: AC_OBJEXT
2362     Defines substitute variable `OBJEXT' based on the output of the
2363     compiler, after .c files have been excluded.  Typically set to
2364     `.o' if Unix, `.obj' if Win32.
2365
2366 - Macro: AC_MINGW32
2367     Checks for the MingW32 compiler environment.  If present, sets
2368     shell variable `MINGW32' to `yes'.  If not present, sets `MINGW32'
2369     to the empty string.
2370
2371 - Macro: AC_PATH_X
2372     Try to locate the X Window System include files and libraries.  If
2373     the user gave the command line options `--x-includes=DIR' and
2374     `--x-libraries=DIR', use those directories.  If either or both
2375     were not given, get the missing values by running `xmkmf' on a
2376     trivial `Imakefile' and examining the `Makefile' that it produces.
2377     If that fails (such as if `xmkmf' is not present), look for them
2378     in several directories where they often reside.  If either method
2379     is successful, set the shell variables `x_includes' and
2380     `x_libraries' to their locations, unless they are in directories
2381     the compiler searches by default.
2382
2383     If both methods fail, or the user gave the command line option
2384     `--without-x', set the shell variable `no_x' to `yes'; otherwise
2385     set it to the empty string.
2386
2387 - Macro: AC_PATH_XTRA
2388     An enhanced version of `AC_PATH_X'.  It adds the C compiler flags
2389     that X needs to output variable `X_CFLAGS', and the X linker flags
2390     to `X_LIBS'.  If X is not available, adds `-DX_DISPLAY_MISSING' to
2391     `X_CFLAGS'.
2392
2393     This macro also checks for special libraries that some systems
2394     need in order to compile X programs.  It adds any that the system
2395     needs to output variable `X_EXTRA_LIBS'.  And it checks for
2396     special X11R6 libraries that need to be linked with before
2397     `-lX11', and adds any found to the output variable `X_PRE_LIBS'.
2398
2399
2400 - Macro: AC_SYS_INTERPRETER
2401     Check whether the system supports starting scripts with a line of
2402     the form `#! /bin/csh' to select the interpreter to use for the
2403     script.  After running this macro, shell code in `configure.in'
2404     can check the shell variable `interpval'; it will be set to `yes'
2405     if the system supports `#!', `no' if not.
2406
2407 - Macro: AC_SYS_LONG_FILE_NAMES
2408     If the system supports file names longer than 14 characters, define
2409     `HAVE_LONG_FILE_NAMES'.
2410
2411 - Macro: AC_SYS_RESTARTABLE_SYSCALLS
2412     If the system automatically restarts a system call that is
2413     interrupted by a signal, define `HAVE_RESTARTABLE_SYSCALLS'.
2414
2415
2416File: autoconf.info,  Node: UNIX Variants,  Prev: System Services,  Up: Existing Tests
2417
2418UNIX Variants
2419=============
2420
2421   The following macros check for certain operating systems that need
2422special treatment for some programs, due to exceptional oddities in
2423their header files or libraries.  These macros are warts; they will be
2424replaced by a more systematic approach, based on the functions they make
2425available or the environments they provide.
2426
2427 - Macro: AC_AIX
2428     If on AIX, define `_ALL_SOURCE'.  Allows the use of some BSD
2429     functions.  Should be called before any macros that run the C
2430     compiler.
2431
2432 - Macro: AC_DYNIX_SEQ
2433     If on Dynix/PTX (Sequent UNIX), add `-lseq' to output variable
2434     `LIBS'.  This macro is obsolete; instead, use `AC_FUNC_GETMNTENT'.
2435
2436 - Macro: AC_IRIX_SUN
2437     If on IRIX (Silicon Graphics UNIX), add `-lsun' to output variable
2438     `LIBS'.  This macro is obsolete.  If you were using it to get
2439     `getmntent', use `AC_FUNC_GETMNTENT' instead.  If you used it for
2440     the NIS versions of the password and group functions, use
2441     `AC_CHECK_LIB(sun, getpwnam)'.
2442
2443 - Macro: AC_ISC_POSIX
2444     If on a POSIXized ISC UNIX, define `_POSIX_SOURCE' and add
2445     `-posix' (for the GNU C compiler) or `-Xp' (for other C compilers)
2446     to output variable `CC'.  This allows the use of POSIX facilities.
2447     Must be called after `AC_PROG_CC' and before any other macros
2448     that run the C compiler.
2449
2450 - Macro: AC_MINIX
2451     If on Minix, define `_MINIX' and `_POSIX_SOURCE' and define
2452     `_POSIX_1_SOURCE' to be 2.  This allows the use of POSIX
2453     facilities.  Should be called before any macros that run the C
2454     compiler.
2455
2456 - Macro: AC_SCO_INTL
2457     If on SCO UNIX, add `-lintl' to output variable `LIBS'.  This
2458     macro is obsolete; instead, use `AC_FUNC_STRFTIME'.
2459
2460 - Macro: AC_XENIX_DIR
2461     If on Xenix, add `-lx' to output variable `LIBS'.  Also, if
2462     `dirent.h' is being used, add `-ldir' to `LIBS'.  This macro is
2463     obsolete; use `AC_HEADER_DIRENT' instead.
2464
2465
2466File: autoconf.info,  Node: Writing Tests,  Next: Results,  Prev: Existing Tests,  Up: Top
2467
2468Writing Tests
2469*************
2470
2471   If the existing feature tests don't do something you need, you have
2472to write new ones.  These macros are the building blocks.  They provide
2473ways for other macros to check whether various kinds of features are
2474available and report the results.
2475
2476   This chapter contains some suggestions and some of the reasons why
2477the existing tests are written the way they are.  You can also learn a
2478lot about how to write Autoconf tests by looking at the existing ones.
2479If something goes wrong in one or more of the Autoconf tests, this
2480information can help you understand the assumptions behind them, which
2481might help you figure out how to best solve the problem.
2482
2483   These macros check the output of the C compiler system.  They do not
2484cache the results of their tests for future use (*note Caching
2485Results::.), because they don't know enough about the information they
2486are checking for to generate a cache variable name.  They also do not
2487print any messages, for the same reason.  The checks for particular
2488kinds of C features call these macros and do cache their results and
2489print messages about what they're checking for.
2490
2491   When you write a feature test that could be applicable to more than
2492one software package, the best thing to do is encapsulate it in a new
2493macro.  *Note Writing Macros::, for how to do that.
2494
2495* Menu:
2496
2497* Examining Declarations::      Detecting header files and declarations.
2498* Examining Syntax::            Detecting language syntax features.
2499* Examining Libraries::         Detecting functions and global variables.
2500* Run Time::                    Testing for run-time features.
2501* Portable Shell::              Shell script portability pitfalls.
2502* Testing Values and Files::    Checking strings and files.
2503* Multiple Cases::              Tests for several possible values.
2504* Language Choice::             Selecting which language to use for testing.
2505
2506
2507File: autoconf.info,  Node: Examining Declarations,  Next: Examining Syntax,  Prev: Writing Tests,  Up: Writing Tests
2508
2509Examining Declarations
2510======================
2511
2512   The macro `AC_TRY_CPP' is used to check whether particular header
2513files exist.  You can check for one at a time, or more than one if you
2514need several header files to all exist for some purpose.
2515
2516 - Macro: AC_TRY_CPP (INCLUDES, [ACTION-IF-TRUE [, ACTION-IF-FALSE]])
2517     INCLUDES is C or C++ `#include' statements and declarations, on
2518     which shell variable, backquote, and backslash substitutions are
2519     performed.  (Actually, it can be any C program, but other
2520     statements are probably not useful.)  If the preprocessor produces
2521     no error messages while processing it, run shell commands
2522     ACTION-IF-TRUE.  Otherwise run shell commands ACTION-IF-FALSE.
2523
2524     This macro uses `CPPFLAGS', but not `CFLAGS', because `-g', `-O',
2525     etc. are not valid options to many C preprocessors.
2526
2527   Here is how to find out whether a header file contains a particular
2528declaration, such as a typedef, a structure, a structure member, or a
2529function.  Use `AC_EGREP_HEADER' instead of running `grep' directly on
2530the header file; on some systems the symbol might be defined in another
2531header file that the file you are checking `#include's.
2532
2533 - Macro: AC_EGREP_HEADER (PATTERN, HEADER-FILE, ACTION-IF-FOUND [,
2534          ACTION-IF-NOT-FOUND])
2535     If the output of running the preprocessor on the system header file
2536     HEADER-FILE matches the `egrep' regular expression PATTERN,
2537     execute shell commands ACTION-IF-FOUND, otherwise execute
2538     ACTION-IF-NOT-FOUND.
2539
2540   To check for C preprocessor symbols, either defined by header files
2541or predefined by the C preprocessor, use `AC_EGREP_CPP'.  Here is an
2542example of the latter:
2543
2544     AC_EGREP_CPP(yes,
2545     [#ifdef _AIX
2546       yes
2547     #endif
2548     ], is_aix=yes, is_aix=no)
2549
2550 - Macro: AC_EGREP_CPP (PATTERN, PROGRAM, [ACTION-IF-FOUND [,
2551          ACTION-IF-NOT-FOUND]])
2552     PROGRAM is the text of a C or C++ program, on which shell
2553     variable, backquote, and backslash substitutions are performed.
2554     If the output of running the preprocessor on PROGRAM matches the
2555     `egrep' regular expression PATTERN, execute shell commands
2556     ACTION-IF-FOUND, otherwise execute ACTION-IF-NOT-FOUND.
2557
2558     This macro calls `AC_PROG_CPP' or `AC_PROG_CXXCPP' (depending on
2559     which language is current, *note Language Choice::.), if it hasn't
2560     been called already.
2561
2562
2563File: autoconf.info,  Node: Examining Syntax,  Next: Examining Libraries,  Prev: Examining Declarations,  Up: Writing Tests
2564
2565Examining Syntax
2566================
2567
2568   To check for a syntax feature of the C, C++ or Fortran 77 compiler,
2569such as whether it recognizes a certain keyword, use `AC_TRY_COMPILE' to
2570try to compile a small program that uses that feature.  You can also use
2571it to check for structures and structure members that are not present on
2572all systems.
2573
2574 - Macro: AC_TRY_COMPILE (INCLUDES, FUNCTION-BODY, [ACTION-IF-FOUND [,
2575          ACTION-IF-NOT-FOUND]])
2576     Create a C, C++ or Fortran 77 test program (depending on which
2577     language is current, *note Language Choice::.), to see whether a
2578     function whose body consists of FUNCTION-BODY can be compiled.
2579
2580     For C and C++, INCLUDES is any `#include' statements needed by the
2581     code in FUNCTION-BODY (INCLUDES will be ignored if the currently
2582     selected language is Fortran 77).  This macro also uses `CFLAGS'
2583     or `CXXFLAGS' if either C or C++ is the currently selected
2584     language, as well as `CPPFLAGS', when compiling.  If Fortran 77 is
2585     the currently selected language then `FFLAGS' will be used when
2586     compiling.
2587
2588     If the file compiles successfully, run shell commands
2589     ACTION-IF-FOUND, otherwise run ACTION-IF-NOT-FOUND.
2590
2591     This macro does not try to link; use `AC_TRY_LINK' if you need to
2592     do that (*note Examining Libraries::.).
2593
2594
2595File: autoconf.info,  Node: Examining Libraries,  Next: Run Time,  Prev: Examining Syntax,  Up: Writing Tests
2596
2597Examining Libraries
2598===================
2599
2600   To check for a library, a function, or a global variable, Autoconf
2601`configure' scripts try to compile and link a small program that uses
2602it.  This is unlike Metaconfig, which by default uses `nm' or `ar' on
2603the C library to try to figure out which functions are available.
2604Trying to link with the function is usually a more reliable approach
2605because it avoids dealing with the variations in the options and output
2606formats of `nm' and `ar' and in the location of the standard libraries.
2607It also allows configuring for cross-compilation or checking a
2608function's runtime behavior if needed.  On the other hand, it can be
2609slower than scanning the libraries once.
2610
2611   A few systems have linkers that do not return a failure exit status
2612when there are unresolved functions in the link.  This bug makes the
2613configuration scripts produced by Autoconf unusable on those systems.
2614However, some of them can be given options that make the exit status
2615correct.  This is a problem that Autoconf does not currently handle
2616automatically.  If users encounter this problem, they might be able to
2617solve it by setting `LDFLAGS' in the environment to pass whatever
2618options the linker needs (for example, `-Wl,-dn' on MIPS RISC/OS).
2619
2620   `AC_TRY_LINK' is used to compile test programs to test for functions
2621and global variables.  It is also used by `AC_CHECK_LIB' to check for
2622libraries (*note Libraries::.), by adding the library being checked for
2623to `LIBS' temporarily and trying to link a small program.
2624
2625 - Macro: AC_TRY_LINK (INCLUDES, FUNCTION-BODY, [ACTION-IF-FOUND [,
2626          ACTION-IF-NOT-FOUND]])
2627     Depending on the current language (*note Language Choice::.),
2628     create a test program to see whether a function whose body
2629     consists of FUNCTION-BODY can be compiled and linked.
2630
2631     For C and C++, INCLUDES is any `#include' statements needed by the
2632     code in FUNCTION-BODY (INCLUDES will be ignored if the currently
2633     selected language is Fortran 77).  This macro also uses `CFLAGS'
2634     or `CXXFLAGS' if either C or C++ is the currently selected
2635     language, as well as `CPPFLAGS', when compiling.  If Fortran 77 is
2636     the currently selected language then `FFLAGS' will be used when
2637     compiling.  However, both `LDFLAGS' and `LIBS' will be used during
2638     linking in all cases.
2639
2640     If the file compiles and links successfully, run shell commands
2641     ACTION-IF-FOUND, otherwise run ACTION-IF-NOT-FOUND.
2642
2643 - Macro: AC_TRY_LINK_FUNC (FUNCTION, [ACTION-IF-FOUND [,
2644          ACTION-IF-NOT-FOUND]])
2645     Depending on the current language (*note Language Choice::.),
2646     create a test program to see whether a program whose body consists
2647     of a prototype of and a call to FUNCTION can be compiled and
2648     linked.
2649
2650     If the file compiles and links successfully, run shell commands
2651     ACTION-IF-FOUND, otherwise run ACTION-IF-NOT-FOUND.
2652
2653 - Macro: AC_TRY_LINK_FUNC (FUNCTION, [ACTION-IF-FOUND [,
2654          ACTION-IF-NOT-FOUND]])
2655     Attempt to compile and link a small program that links with
2656     FUNCTION.  If the file compiles and links successfully, run shell
2657     commands ACTION-IF-FOUND, otherwise run ACTION-IF-NOT-FOUND.
2658
2659 - Macro: AC_COMPILE_CHECK (ECHO-TEXT, INCLUDES, FUNCTION-BODY,
2660          ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND])
2661     This is an obsolete version of `AC_TRY_LINK', with the addition
2662     that it prints `checking for ECHO-TEXT' to the standard output
2663     first, if ECHO-TEXT is non-empty.  Use `AC_MSG_CHECKING' and
2664     `AC_MSG_RESULT' instead to print messages (*note Printing
2665     Messages::.).
2666
2667
2668File: autoconf.info,  Node: Run Time,  Next: Portable Shell,  Prev: Examining Libraries,  Up: Writing Tests
2669
2670Checking Run Time Behavior
2671==========================
2672
2673   Sometimes you need to find out how a system performs at run time,
2674such as whether a given function has a certain capability or bug.  If
2675you can, make such checks when your program runs instead of when it is
2676configured.  You can check for things like the machine's endianness when
2677your program initializes itself.
2678
2679   If you really need to test for a run-time behavior while configuring,
2680you can write a test program to determine the result, and compile and
2681run it using `AC_TRY_RUN'.  Avoid running test programs if possible,
2682because using them prevents people from configuring your package for
2683cross-compiling.
2684
2685* Menu:
2686
2687* Test Programs::               Running test programs.
2688* Guidelines::                  General rules for writing test programs.
2689* Test Functions::              Avoiding pitfalls in test programs.
2690
2691
2692File: autoconf.info,  Node: Test Programs,  Next: Guidelines,  Prev: Run Time,  Up: Run Time
2693
2694Running Test Programs
2695---------------------
2696
2697   Use the following macro if you need to test run-time behavior of the
2698system while configuring.
2699
2700 - Macro: AC_TRY_RUN (PROGRAM, [ACTION-IF-TRUE [, ACTION-IF-FALSE [,
2701          ACTION-IF-CROSS-COMPILING]]])
2702     PROGRAM is the text of a C program, on which shell variable and
2703     backquote substitutions are performed.  If it compiles and links
2704     successfully and returns an exit status of 0 when executed, run
2705     shell commands ACTION-IF-TRUE.  Otherwise run shell commands
2706     ACTION-IF-FALSE; the exit status of the program is available in
2707     the shell variable `$?'.  This macro uses `CFLAGS' or `CXXFLAGS',
2708     `CPPFLAGS', `LDFLAGS', and `LIBS' when compiling.
2709
2710     If the C compiler being used does not produce executables that run
2711     on the system where `configure' is being run, then the test
2712     program is not run.  If the optional shell commands
2713     ACTION-IF-CROSS-COMPILING are given, they are run instead.
2714     Otherwise, `configure' prints an error message and exits.
2715
2716   Try to provide a pessimistic default value to use when
2717cross-compiling makes run-time tests impossible.  You do this by
2718passing the optional last argument to `AC_TRY_RUN'.  `autoconf' prints
2719a warning message when creating `configure' each time it encounters a
2720call to `AC_TRY_RUN' with no ACTION-IF-CROSS-COMPILING argument given.
2721You may ignore the warning, though users will not be able to configure
2722your package for cross-compiling.  A few of the macros distributed with
2723Autoconf produce this warning message.
2724
2725   To configure for cross-compiling you can also choose a value for
2726those parameters based on the canonical system name (*note Manual
2727Configuration::.).  Alternatively, set up a test results cache file with
2728the correct values for the target system (*note Caching Results::.).
2729
2730   To provide a default for calls of `AC_TRY_RUN' that are embedded in
2731other macros, including a few of the ones that come with Autoconf, you
2732can call `AC_PROG_CC' before running them.  Then, if the shell variable
2733`cross_compiling' is set to `yes', use an alternate method to get the
2734results instead of calling the macros.
2735
2736 - Macro: AC_C_CROSS
2737     This macro is obsolete; it does nothing.
2738
2739
2740File: autoconf.info,  Node: Guidelines,  Next: Test Functions,  Prev: Test Programs,  Up: Run Time
2741
2742Guidelines for Test Programs
2743----------------------------
2744
2745   Test programs should not write anything to the standard output.  They
2746should return 0 if the test succeeds, nonzero otherwise, so that success
2747can be distinguished easily from a core dump or other failure;
2748segmentation violations and other failures produce a nonzero exit
2749status.  Test programs should `exit', not `return', from `main',
2750because on some systems (old Suns, at least) the argument to `return'
2751in `main' is ignored.
2752
2753   Test programs can use `#if' or `#ifdef' to check the values of
2754preprocessor macros defined by tests that have already run.  For
2755example, if you call `AC_HEADER_STDC', then later on in `configure.in'
2756you can have a test program that includes an ANSI C header file
2757conditionally:
2758
2759     #if STDC_HEADERS
2760     # include <stdlib.h>
2761     #endif
2762
2763   If a test program needs to use or create a data file, give it a name
2764that starts with `conftest', such as `conftestdata'.  The `configure'
2765script cleans up by running `rm -rf conftest*' after running test
2766programs and if the script is interrupted.
2767
2768
2769File: autoconf.info,  Node: Test Functions,  Prev: Guidelines,  Up: Run Time
2770
2771Test Functions
2772--------------
2773
2774   Function declarations in test programs should have a prototype
2775conditionalized for C++.  In practice, though, test programs rarely need
2776functions that take arguments.
2777
2778     #ifdef __cplusplus
2779     foo(int i)
2780     #else
2781     foo(i) int i;
2782     #endif
2783
2784   Functions that test programs declare should also be conditionalized
2785for C++, which requires `extern "C"' prototypes.  Make sure to not
2786include any header files containing clashing prototypes.
2787
2788     #ifdef __cplusplus
2789     extern "C" void *malloc(size_t);
2790     #else
2791     char *malloc();
2792     #endif
2793
2794   If a test program calls a function with invalid parameters (just to
2795see whether it exists), organize the program to ensure that it never
2796invokes that function.  You can do this by calling it in another
2797function that is never invoked.  You can't do it by putting it after a
2798call to `exit', because GCC version 2 knows that `exit' never returns
2799and optimizes out any code that follows it in the same block.
2800
2801   If you include any header files, make sure to call the functions
2802relevant to them with the correct number of arguments, even if they are
2803just 0, to avoid compilation errors due to prototypes.  GCC version 2
2804has internal prototypes for several functions that it automatically
2805inlines; for example, `memcpy'.  To avoid errors when checking for
2806them, either pass them the correct number of arguments or redeclare them
2807with a different return type (such as `char').
2808
2809
2810File: autoconf.info,  Node: Portable Shell,  Next: Testing Values and Files,  Prev: Run Time,  Up: Writing Tests
2811
2812Portable Shell Programming
2813==========================
2814
2815   When writing your own checks, there are some shell script programming
2816techniques you should avoid in order to make your code portable.  The
2817Bourne shell and upward-compatible shells like Bash and the Korn shell
2818have evolved over the years, but to prevent trouble, do not take
2819advantage of features that were added after UNIX version 7, circa 1977.
2820You should not use shell functions, aliases, negated character classes,
2821or other features that are not found in all Bourne-compatible shells;
2822restrict yourself to the lowest common denominator.  Even `unset' is
2823not supported by all shells!  Also, include a space after the
2824exclamation point in interpreter specifications, like this:
2825     #! /usr/bin/perl
2826   If you omit the space before the path, then 4.2BSD based systems
2827(such as Sequent DYNIX) will ignore the line, because they interpret
2828`#! /' as a 4-byte magic number.
2829
2830   The set of external programs you should run in a `configure' script
2831is fairly small.  *Note Utilities in Makefiles: (standards)Utilities in
2832Makefiles, for the list.  This restriction allows users to start out
2833with a fairly small set of programs and build the rest, avoiding too
2834many interdependencies between packages.
2835
2836   Some of these external utilities have a portable subset of features,
2837as well; for example, don't rely on `ln' having a `-f' option or `cat'
2838having any options.  `sed' scripts should not contain comments or use
2839branch labels longer than 8 characters.  Don't use `grep -s' to
2840suppress output, because `grep -s' on System V does not suppress
2841output, only error messages.  Instead, redirect the standard output and
2842standard error (in case the file doesn't exist) of `grep' to
2843`/dev/null'.  Check the exit status of `grep' to determine whether it
2844found a match.
2845
2846
2847File: autoconf.info,  Node: Testing Values and Files,  Next: Multiple Cases,  Prev: Portable Shell,  Up: Writing Tests
2848
2849Testing Values and Files
2850========================
2851
2852   `configure' scripts need to test properties of many files and
2853strings.  Here are some portability problems to watch out for when doing
2854those tests.
2855
2856   The `test' program is the way to perform many file and string tests.
2857It is often invoked by the alternate name `[', but using that name in
2858Autoconf code is asking for trouble since it is an `m4' quote character.
2859
2860   If you need to make multiple checks using `test', combine them with
2861the shell operators `&&' and `||' instead of using the `test' operators
2862`-a' and `-o'.  On System V, the precedence of `-a' and `-o' is wrong
2863relative to the unary operators; consequently, POSIX does not specify
2864them, so using them is nonportable.  If you combine `&&' and `||' in
2865the same statement, keep in mind that they have equal precedence.
2866
2867   To enable `configure' scripts to support cross-compilation, they
2868shouldn't do anything that tests features of the host system instead of
2869the target system.  But occasionally you may find it necessary to check
2870whether some arbitrary file exists.  To do so, use `test -f' or `test
2871-r'.  Do not use `test -x', because 4.3BSD does not have it.
2872
2873   Another nonportable shell programming construction is
2874     VAR=${VAR:-VALUE}
2875
2876The intent is to set VAR to VALUE only if it is not already set, but if
2877VAR has any value, even the empty string, to leave it alone.  Old BSD
2878shells, including the Ultrix `sh', don't accept the colon, and complain
2879and die.  A portable equivalent is
2880     : ${VAR=VALUE}
2881
2882
2883File: autoconf.info,  Node: Multiple Cases,  Next: Language Choice,  Prev: Testing Values and Files,  Up: Writing Tests
2884
2885Multiple Cases
2886==============
2887
2888   Some operations are accomplished in several possible ways, depending
2889on the UNIX variant.  Checking for them essentially requires a "case
2890statement".  Autoconf does not directly provide one; however, it is
2891easy to simulate by using a shell variable to keep track of whether a
2892way to perform the operation has been found yet.
2893
2894   Here is an example that uses the shell variable `fstype' to keep
2895track of whether the remaining cases need to be checked.
2896
2897     AC_MSG_CHECKING(how to get filesystem type)
2898     fstype=no
2899     # The order of these tests is important.
2900     AC_TRY_CPP([#include <sys/statvfs.h>
2901     #include <sys/fstyp.h>], AC_DEFINE(FSTYPE_STATVFS) fstype=SVR4)
2902     if test $fstype = no; then
2903     AC_TRY_CPP([#include <sys/statfs.h>
2904     #include <sys/fstyp.h>], AC_DEFINE(FSTYPE_USG_STATFS) fstype=SVR3)
2905     fi
2906     if test $fstype = no; then
2907     AC_TRY_CPP([#include <sys/statfs.h>
2908     #include <sys/vmount.h>], AC_DEFINE(FSTYPE_AIX_STATFS) fstype=AIX)
2909     fi
2910     # (more cases omitted here)
2911     AC_MSG_RESULT($fstype)
2912
2913
2914File: autoconf.info,  Node: Language Choice,  Prev: Multiple Cases,  Up: Writing Tests
2915
2916Language Choice
2917===============
2918
2919   Packages that use both C and C++ need to test features of both
2920compilers.  Autoconf-generated `configure' scripts check for C features
2921by default.  The following macros determine which language's compiler
2922is used in tests that follow in `configure.in'.
2923
2924 - Macro: AC_LANG_C
2925     Do compilation tests using `CC' and `CPP' and use extension `.c'
2926     for test programs.  Set the shell variable `cross_compiling' to
2927     the value computed by `AC_PROG_CC' if it has been run, empty
2928     otherwise.
2929
2930 - Macro: AC_LANG_CPLUSPLUS
2931     Do compilation tests using `CXX' and `CXXCPP' and use extension
2932     `.C' for test programs.  Set the shell variable `cross_compiling'
2933     to the value computed by `AC_PROG_CXX' if it has been run, empty
2934     otherwise.
2935
2936 - Macro: AC_LANG_FORTRAN77
2937     Do compilation tests using `F77' and use extension `.f' for test
2938     programs.  Set the shell variable `cross_compiling' to the value
2939     computed by `AC_PROG_F77' if it has been run, empty otherwise.
2940
2941 - Macro: AC_LANG_SAVE
2942     Remember the current language (as set by `AC_LANG_C',
2943     `AC_LANG_CPLUSPLUS' or `AC_LANG_FORTRAN77') on a stack.  Does not
2944     change which language is current.  Use this macro and
2945     `AC_LANG_RESTORE' in macros that need to temporarily switch to a
2946     particular language.
2947
2948 - Macro: AC_LANG_RESTORE
2949     Select the language that is saved on the top of the stack, as set
2950     by `AC_LANG_SAVE', and remove it from the stack.  This macro is
2951     equivalent to either `AC_LANG_C', `AC_LANG_CPLUSPLUS' or
2952     `AC_LANG_FORTRAN77', whichever had been run most recently when
2953     `AC_LANG_SAVE' was last called.
2954
2955     Do not call this macro more times than `AC_LANG_SAVE'.
2956
2957 - Macro: AC_REQUIRE_CPP
2958     Ensure that whichever preprocessor would currently be used for
2959     tests has been found.  Calls `AC_REQUIRE' (*note Prerequisite
2960     Macros::.) with an argument of either `AC_PROG_CPP' or
2961     `AC_PROG_CXXCPP', depending on which language is current.
2962
2963
2964File: autoconf.info,  Node: Results,  Next: Writing Macros,  Prev: Writing Tests,  Up: Top
2965
2966Results of Tests
2967****************
2968
2969   Once `configure' has determined whether a feature exists, what can
2970it do to record that information?  There are four sorts of things it can
2971do: define a C preprocessor symbol, set a variable in the output files,
2972save the result in a cache file for future `configure' runs, and print
2973a message letting the user know the result of the test.
2974
2975* Menu:
2976
2977* Defining Symbols::            Defining C preprocessor symbols.
2978* Setting Output Variables::    Replacing variables in output files.
2979* Caching Results::             Speeding up subsequent `configure' runs.
2980* Printing Messages::           Notifying users of progress or problems.
2981
2982
2983File: autoconf.info,  Node: Defining Symbols,  Next: Setting Output Variables,  Prev: Results,  Up: Results
2984
2985Defining C Preprocessor Symbols
2986===============================
2987
2988   A common action to take in response to a feature test is to define a
2989C preprocessor symbol indicating the results of the test.  That is done
2990by calling `AC_DEFINE' or `AC_DEFINE_UNQUOTED'.
2991
2992   By default, `AC_OUTPUT' places the symbols defined by these macros
2993into the output variable `DEFS', which contains an option
2994`-DSYMBOL=VALUE' for each symbol defined.  Unlike in Autoconf version
29951, there is no variable `DEFS' defined while `configure' is running.
2996To check whether Autoconf macros have already defined a certain C
2997preprocessor symbol, test the value of the appropriate cache variable,
2998as in this example:
2999
3000     AC_CHECK_FUNC(vprintf, AC_DEFINE(HAVE_VPRINTF))
3001     if test "$ac_cv_func_vprintf" != yes; then
3002     AC_CHECK_FUNC(_doprnt, AC_DEFINE(HAVE_DOPRNT))
3003     fi
3004
3005   If `AC_CONFIG_HEADER' has been called, then instead of creating
3006`DEFS', `AC_OUTPUT' creates a header file by substituting the correct
3007values into `#define' statements in a template file.  *Note
3008Configuration Headers::, for more information about this kind of output.
3009
3010 - Macro: AC_DEFINE (VARIABLE [, VALUE [, DESCRIPTION]])
3011     Define C preprocessor variable VARIABLE.  If VALUE is given, set
3012     VARIABLE to that value (verbatim), otherwise set it to 1.  VALUE
3013     should not contain literal newlines, and if you are not using
3014     `AC_CONFIG_HEADER' it should not contain any `#' characters, as
3015     `make' tends to eat them.  To use a shell variable (which you need
3016     to do in order to define a value containing the `m4' quote
3017     characters `[' or `]'), use `AC_DEFINE_UNQUOTED' instead.
3018     DESCRIPTION is only useful if you are using `AC_CONFIG_HEADER'.
3019     In this case, DESCRIPTION is put into the generated `config.h.in'
3020     as the comment before the macro define; the macro need not be
3021     mentioned in `acconfig.h'.  The following example defines the C
3022     preprocessor variable `EQUATION' to be the string constant `"$a >
3023     $b"':
3024
3025          AC_DEFINE(EQUATION, "$a > $b")
3026
3027 - Macro: AC_DEFINE_UNQUOTED (VARIABLE [, VALUE [, DESCRIPTION]])
3028     Like `AC_DEFINE', but three shell expansions are
3029     performed--once--on VARIABLE and VALUE: variable expansion (`$'),
3030     command substitution (``'), and backslash escaping (`\').  Single
3031     and double quote characters in the value have no special meaning.
3032     Use this macro instead of `AC_DEFINE' when VARIABLE or VALUE is a
3033     shell variable.  Examples:
3034
3035          AC_DEFINE_UNQUOTED(config_machfile, "${machfile}")
3036          AC_DEFINE_UNQUOTED(GETGROUPS_T, $ac_cv_type_getgroups)
3037          AC_DEFINE_UNQUOTED(${ac_tr_hdr})
3038
3039   Due to the syntactical bizarreness of the Bourne shell, do not use
3040semicolons to separate `AC_DEFINE' or `AC_DEFINE_UNQUOTED' calls from
3041other macro calls or shell code; that can cause syntax errors in the
3042resulting `configure' script.  Use either spaces or newlines.  That is,
3043do this:
3044
3045     AC_CHECK_HEADER(elf.h, AC_DEFINE(SVR4) LIBS="$LIBS -lelf")
3046
3047or this:
3048
3049     AC_CHECK_HEADER(elf.h,
3050       AC_DEFINE(SVR4)
3051       LIBS="$LIBS -lelf")
3052
3053instead of this:
3054
3055     AC_CHECK_HEADER(elf.h, AC_DEFINE(SVR4); LIBS="$LIBS -lelf")
3056
3057
3058File: autoconf.info,  Node: Setting Output Variables,  Next: Caching Results,  Prev: Defining Symbols,  Up: Results
3059
3060Setting Output Variables
3061========================
3062
3063   One way to record the results of tests is to set "output variables",
3064which are shell variables whose values are substituted into files that
3065`configure' outputs.  The two macros below create new output variables.
3066*Note Preset Output Variables::, for a list of output variables that
3067are always available.
3068
3069 - Macro: AC_SUBST (VARIABLE)
3070     Create an output variable from a shell variable.  Make `AC_OUTPUT'
3071     substitute the variable VARIABLE into output files (typically one
3072     or more `Makefile's).  This means that `AC_OUTPUT' will replace
3073     instances of `@VARIABLE@' in input files with the value that the
3074     shell variable VARIABLE has when `AC_OUTPUT' is called.  The value
3075     of VARIABLE should not contain literal newlines.
3076
3077 - Macro: AC_SUBST_FILE (VARIABLE)
3078     Another way to create an output variable from a shell variable.
3079     Make `AC_OUTPUT' insert (without substitutions) the contents of
3080     the file named by shell variable VARIABLE into output files.  This
3081     means that `AC_OUTPUT' will replace instances of `@VARIABLE@' in
3082     output files (such as `Makefile.in') with the contents of the file
3083     that the shell variable VARIABLE names when `AC_OUTPUT' is called.
3084     Set the variable to `/dev/null' for cases that do not have a file
3085     to insert.
3086
3087     This macro is useful for inserting `Makefile' fragments containing
3088     special dependencies or other `make' directives for particular host
3089     or target types into `Makefile's.  For example, `configure.in'
3090     could contain:
3091
3092          AC_SUBST_FILE(host_frag)dnl
3093          host_frag=$srcdir/conf/sun4.mh
3094
3095     and then a `Makefile.in' could contain:
3096
3097          @host_frag@
3098
3099
3100File: autoconf.info,  Node: Caching Results,  Next: Printing Messages,  Prev: Setting Output Variables,  Up: Results
3101
3102Caching Results
3103===============
3104
3105   To avoid checking for the same features repeatedly in various
3106`configure' scripts (or repeated runs of one script), `configure' saves
3107the results of many of its checks in a "cache file".  If, when a
3108`configure' script runs, it finds a cache file, it reads from it the
3109results from previous runs and avoids rerunning those checks.  As a
3110result, `configure' can run much faster than if it had to perform all
3111of the checks every time.
3112
3113 - Macro: AC_CACHE_VAL (CACHE-ID, COMMANDS-TO-SET-IT)
3114     Ensure that the results of the check identified by CACHE-ID are
3115     available.  If the results of the check were in the cache file
3116     that was read, and `configure' was not given the `--quiet' or
3117     `--silent' option, print a message saying that the result was
3118     cached; otherwise, run the shell commands COMMANDS-TO-SET-IT.
3119     Those commands should have no side effects except for setting the
3120     variable CACHE-ID.  In particular, they should not call
3121     `AC_DEFINE'; the code that follows the call to `AC_CACHE_VAL'
3122     should do that, based on the cached value.  Also, they should not
3123     print any messages, for example with `AC_MSG_CHECKING'; do that
3124     before calling `AC_CACHE_VAL', so the messages are printed
3125     regardless of whether the results of the check are retrieved from
3126     the cache or determined by running the shell commands.  If the
3127     shell commands are run to determine the value, the value will be
3128     saved in the cache file just before `configure' creates its output
3129     files.  *Note Cache Variable Names::, for how to choose the name
3130     of the CACHE-ID variable.
3131
3132 - Macro: AC_CACHE_CHECK (MESSAGE, CACHE-ID, COMMANDS)
3133     A wrapper for `AC_CACHE_VAL' that takes care of printing the
3134     messages.  This macro provides a convenient shorthand for the most
3135     common way to use these macros.  It calls `AC_MSG_CHECKING' for
3136     MESSAGE, then `AC_CACHE_VAL' with the CACHE-ID and COMMANDS
3137     arguments, and `AC_MSG_RESULT' with CACHE-ID.
3138
3139 - Macro: AC_CACHE_LOAD
3140     Loads values from existing cache file, or creates a new cache file
3141     if a cache file is not found.  Called automatically from `AC_INIT'.
3142
3143 - Macro: AC_CACHE_SAVE
3144     Flushes all cached values to the cache file.  Called automatically
3145     from `AC_OUTPUT', but it can be quite useful to call
3146     `AC_CACHE_SAVE' at key points in configure.in.  Doing so
3147     checkpoints the cache in case of an early configure script abort.
3148
3149* Menu:
3150
3151* Cache Variable Names::        Shell variables used in caches.
3152* Cache Files::                 Files `configure' uses for caching.
3153
3154
3155File: autoconf.info,  Node: Cache Variable Names,  Next: Cache Files,  Prev: Caching Results,  Up: Caching Results
3156
3157Cache Variable Names
3158--------------------
3159
3160   The names of cache variables should have the following format:
3161
3162     PACKAGE-PREFIX_cv_VALUE-TYPE_SPECIFIC-VALUE[_ADDITIONAL-OPTIONS]
3163
3164for example, `ac_cv_header_stat_broken' or
3165`ac_cv_prog_gcc_traditional'.  The parts of the variable name are:
3166
3167PACKAGE-PREFIX
3168     An abbreviation for your package or organization; the same prefix
3169     you begin local Autoconf macros with, except lowercase by
3170     convention.  For cache values used by the distributed Autoconf
3171     macros, this value is `ac'.
3172
3173`_cv_'
3174     Indicates that this shell variable is a cache value.
3175
3176VALUE-TYPE
3177     A convention for classifying cache values, to produce a rational
3178     naming system.  The values used in Autoconf are listed in *Note
3179     Macro Names::.
3180
3181SPECIFIC-VALUE
3182     Which member of the class of cache values this test applies to.
3183     For example, which function (`alloca'), program (`gcc'), or output
3184     variable (`INSTALL').
3185
3186ADDITIONAL-OPTIONS
3187     Any particular behavior of the specific member that this test
3188     applies to.  For example, `broken' or `set'.  This part of the
3189     name may be omitted if it does not apply.
3190
3191   The values assigned to cache variables may not contain newlines.
3192Usually, their values will be boolean (`yes' or `no') or the names of
3193files or functions; so this is not an important restriction.
3194
3195
3196File: autoconf.info,  Node: Cache Files,  Prev: Cache Variable Names,  Up: Caching Results
3197
3198Cache Files
3199-----------
3200
3201   A cache file is a shell script that caches the results of configure
3202tests run on one system so they can be shared between configure scripts
3203and configure runs.  It is not useful on other systems.  If its contents
3204are invalid for some reason, the user may delete or edit it.
3205
3206   By default, configure uses `./config.cache' as the cache file,
3207creating it if it does not exist already.  `configure' accepts the
3208`--cache-file=FILE' option to use a different cache file; that is what
3209`configure' does when it calls `configure' scripts in subdirectories,
3210so they share the cache.  *Note Subdirectories::, for information on
3211configuring subdirectories with the `AC_CONFIG_SUBDIRS' macro.
3212
3213   Giving `--cache-file=/dev/null' disables caching, for debugging
3214`configure'.  `config.status' only pays attention to the cache file if
3215it is given the `--recheck' option, which makes it rerun `configure'.
3216If you are anticipating a long debugging period, you can also disable
3217cache loading and saving for a `configure' script by redefining the
3218cache macros at the start of `configure.in':
3219
3220     define([AC_CACHE_LOAD], )dnl
3221     define([AC_CACHE_SAVE], )dnl
3222     AC_INIT(whatever)
3223      ... rest of configure.in ...
3224
3225   It is wrong to try to distribute cache files for particular system
3226types.  There is too much room for error in doing that, and too much
3227administrative overhead in maintaining them.  For any features that
3228can't be guessed automatically, use the standard method of the canonical
3229system type and linking files (*note Manual Configuration::.).
3230
3231   The cache file on a particular system will gradually accumulate
3232whenever someone runs a `configure' script; it will be initially
3233nonexistent.  Running `configure' merges the new cache results with the
3234existing cache file.  The site initialization script can specify a
3235site-wide cache file to use instead of the default, to make it work
3236transparently, as long as the same C compiler is used every time (*note
3237Site Defaults::.).
3238
3239   If your configure script, or a macro called from configure.in,
3240happens to abort the configure process, it may be useful to checkpoint
3241the cache a few times at key points.  Doing so will reduce the amount
3242of time it takes to re-run the configure script with (hopefully) the
3243error that caused the previous abort corrected.
3244
3245      ... AC_INIT, etc. ...
3246     dnl checks for programs
3247     AC_PROG_CC
3248     AC_PROG_GCC_TRADITIONAL
3249      ... more program checks ...
3250     AC_CACHE_SAVE
3251     
3252     dnl checks for libraries
3253     AC_CHECK_LIB(nsl, gethostbyname)
3254     AC_CHECK_LIB(socket, connect)
3255      ... more lib checks ...
3256     AC_CACHE_SAVE
3257     
3258     dnl Might abort...
3259     AM_PATH_GTK(1.0.2, , exit 1)
3260     AM_PATH_GTKMM(0.9.5, , exit 1)
3261
3262
3263File: autoconf.info,  Node: Printing Messages,  Prev: Caching Results,  Up: Results
3264
3265Printing Messages
3266=================
3267
3268   `configure' scripts need to give users running them several kinds of
3269information.  The following macros print messages in ways appropriate
3270for each kind.  The arguments to all of them get enclosed in shell
3271double quotes, so the shell performs variable and backquote substitution
3272on them.  You can print a message containing a comma by quoting the
3273message with the `m4' quote characters:
3274
3275     AC_MSG_RESULT([never mind, I found the BASIC compiler])
3276
3277   These macros are all wrappers around the `echo' shell command.
3278`configure' scripts should rarely need to run `echo' directly to print
3279messages for the user.  Using these macros makes it easy to change how
3280and when each kind of message is printed; such changes need only be
3281made to the macro definitions, and all of the callers change
3282automatically.
3283
3284 - Macro: AC_MSG_CHECKING (FEATURE-DESCRIPTION)
3285     Notify the user that `configure' is checking for a particular
3286     feature.  This macro prints a message that starts with `checking '
3287     and ends with `...' and no newline.  It must be followed by a call
3288     to `AC_MSG_RESULT' to print the result of the check and the
3289     newline.  The FEATURE-DESCRIPTION should be something like
3290     `whether the Fortran compiler accepts C++ comments' or `for c89'.
3291
3292     This macro prints nothing if `configure' is run with the `--quiet'
3293     or `--silent' option.
3294
3295 - Macro: AC_MSG_RESULT (RESULT-DESCRIPTION)
3296     Notify the user of the results of a check.  RESULT-DESCRIPTION is
3297     almost always the value of the cache variable for the check,
3298     typically `yes', `no', or a file name.  This macro should follow a
3299     call to `AC_MSG_CHECKING', and the RESULT-DESCRIPTION should be
3300     the completion of the message printed by the call to
3301     `AC_MSG_CHECKING'.
3302
3303     This macro prints nothing if `configure' is run with the `--quiet'
3304     or `--silent' option.
3305
3306 - Macro: AC_MSG_ERROR (ERROR-DESCRIPTION)
3307     Notify the user of an error that prevents `configure' from
3308     completing.  This macro prints an error message on the standard
3309     error output and exits `configure' with a nonzero status.
3310     ERROR-DESCRIPTION should be something like `invalid value $HOME
3311     for \$HOME'.
3312
3313 - Macro: AC_MSG_WARN (PROBLEM-DESCRIPTION)
3314     Notify the `configure' user of a possible problem.  This macro
3315     prints the message on the standard error output; `configure'
3316     continues running afterward, so macros that call `AC_MSG_WARN'
3317     should provide a default (back-up) behavior for the situations
3318     they warn about.  PROBLEM-DESCRIPTION should be something like `ln
3319     -s seems to make hard links'.
3320
3321   The following two macros are an obsolete alternative to
3322`AC_MSG_CHECKING' and `AC_MSG_RESULT'.
3323
3324 - Macro: AC_CHECKING (FEATURE-DESCRIPTION)
3325     This macro is similar to `AC_MSG_CHECKING', except that it prints a
3326     newline after the FEATURE-DESCRIPTION.  It is useful mainly to
3327     print a general description of the overall purpose of a group of
3328     feature checks, e.g.,
3329
3330          AC_CHECKING(if stack overflow is detectable)
3331
3332 - Macro: AC_VERBOSE (RESULT-DESCRIPTION)
3333     This macro is similar to `AC_MSG_RESULT', except that it is meant
3334     to follow a call to `AC_CHECKING' instead of `AC_MSG_CHECKING'; it
3335     starts the message it prints with a tab.  It is considered
3336     obsolete.
3337
3338
3339File: autoconf.info,  Node: Writing Macros,  Next: Manual Configuration,  Prev: Results,  Up: Top
3340
3341Writing Macros
3342**************
3343
3344   When you write a feature test that could be applicable to more than
3345one software package, the best thing to do is encapsulate it in a new
3346macro.  Here are some instructions and guidelines for writing Autoconf
3347macros.
3348
3349* Menu:
3350
3351* Macro Definitions::           Basic format of an Autoconf macro.
3352* Macro Names::                 What to call your new macros.
3353* Quoting::                     Protecting macros from unwanted expansion.
3354* Dependencies Between Macros::  What to do when macros depend on other macros.
3355
3356
3357File: autoconf.info,  Node: Macro Definitions,  Next: Macro Names,  Prev: Writing Macros,  Up: Writing Macros
3358
3359Macro Definitions
3360=================
3361
3362   Autoconf macros are defined using the `AC_DEFUN' macro, which is
3363similar to the `m4' builtin `define' macro.  In addition to defining a
3364macro, `AC_DEFUN' adds to it some code which is used to constrain the
3365order in which macros are called (*note Prerequisite Macros::.).
3366
3367   An Autoconf macro definition looks like this:
3368
3369     AC_DEFUN(MACRO-NAME, [MACRO-BODY])
3370
3371The square brackets here do not indicate optional text: they should
3372literally be present in the macro definition to avoid macro expansion
3373problems (*note Quoting::.).  You can refer to any arguments passed to
3374the macro as `$1', `$2', etc.
3375
3376   To introduce comments in `m4', use the `m4' builtin `dnl'; it causes
3377`m4' to discard the text through the next newline.  It is not needed
3378between macro definitions in `acsite.m4' and `aclocal.m4', because all
3379output is discarded until `AC_INIT' is called.
3380
3381   *Note How to define new macros: (m4.info)Definitions, for more
3382complete information on writing `m4' macros.
3383
3384
3385File: autoconf.info,  Node: Macro Names,  Next: Quoting,  Prev: Macro Definitions,  Up: Writing Macros
3386
3387Macro Names
3388===========
3389
3390   All of the Autoconf macros have all-uppercase names starting with
3391`AC_' to prevent them from accidentally conflicting with other text.
3392All shell variables that they use for internal purposes have
3393mostly-lowercase names starting with `ac_'.  To ensure that your macros
3394don't conflict with present or future Autoconf macros, you should
3395prefix your own macro names and any shell variables they use with some
3396other sequence.  Possibilities include your initials, or an abbreviation
3397for the name of your organization or software package.
3398
3399   Most of the Autoconf macros' names follow a structured naming
3400convention that indicates the kind of feature check by the name.  The
3401macro names consist of several words, separated by underscores, going
3402from most general to most specific.   The names of their cache
3403variables use the same convention (*note Cache Variable Names::., for
3404more information on them).
3405
3406   The first word of the name after `AC_' usually tells the category of
3407feature being tested.  Here are the categories used in Autoconf for
3408specific test macros, the kind of macro that you are more likely to
3409write.  They are also used for cache variables, in all-lowercase.  Use
3410them where applicable; where they're not, invent your own categories.
3411
3412`C'
3413     C language builtin features.
3414
3415`DECL'
3416     Declarations of C variables in header files.
3417
3418`FUNC'
3419     Functions in libraries.
3420
3421`GROUP'
3422     UNIX group owners of files.
3423
3424`HEADER'
3425     Header files.
3426
3427`LIB'
3428     C libraries.
3429
3430`PATH'
3431     The full path names to files, including programs.
3432
3433`PROG'
3434     The base names of programs.
3435
3436`STRUCT'
3437     Definitions of C structures in header files.
3438
3439`SYS'
3440     Operating system features.
3441
3442`TYPE'
3443     C builtin or declared types.
3444
3445`VAR'
3446     C variables in libraries.
3447
3448   After the category comes the name of the particular feature being
3449tested.  Any further words in the macro name indicate particular aspects
3450of the feature.  For example, `AC_FUNC_UTIME_NULL' checks the behavior
3451of the `utime' function when called with a `NULL' pointer.
3452
3453   A macro that is an internal subroutine of another macro should have a
3454name that starts with the name of that other macro, followed by one or
3455more words saying what the internal macro does.  For example,
3456`AC_PATH_X' has internal macros `AC_PATH_X_XMKMF' and
3457`AC_PATH_X_DIRECT'.
3458
3459
3460File: autoconf.info,  Node: Quoting,  Next: Dependencies Between Macros,  Prev: Macro Names,  Up: Writing Macros
3461
3462Quoting
3463=======
3464
3465   Macros that are called by other macros are evaluated by `m4' several
3466times; each evaluation might require another layer of quotes to prevent
3467unwanted expansions of macros or `m4' builtins, such as `define' and
3468`$1'.  Quotes are also required around macro arguments that contain
3469commas, since commas separate the arguments from each other.  It's a
3470good idea to quote any macro arguments that contain newlines or calls
3471to other macros, as well.
3472
3473   Autoconf changes the `m4' quote characters from the default ``' and
3474`'' to `[' and `]', because many of the macros use ``' and `'',
3475mismatched.  However, in a few places the macros need to use brackets
3476(usually in C program text or regular expressions).  In those places,
3477they use the `m4' builtin command `changequote' to temporarily change
3478the quote characters to `<<' and `>>'.  (Sometimes, if they don't need
3479to quote anything, they disable quoting entirely instead by setting the
3480quote characters to empty strings.)  Here is an example:
3481
3482     AC_TRY_LINK(
3483     changequote(<<, >>)dnl
3484     <<#include <time.h>
3485     #ifndef tzname /* For SGI.  */
3486     extern char *tzname[]; /* RS6000 and others reject char **tzname.  */
3487     #endif>>,
3488     changequote([, ])dnl
3489     [atoi(*tzname);], ac_cv_var_tzname=yes, ac_cv_var_tzname=no)
3490
3491   When you create a `configure' script using newly written macros,
3492examine it carefully to check whether you need to add more quotes in
3493your macros.  If one or more words have disappeared in the `m4' output,
3494you need more quotes.  When in doubt, quote.
3495
3496   However, it's also possible to put on too many layers of quotes.  If
3497this happens, the resulting `configure' script will contain unexpanded
3498macros.  The `autoconf' program checks for this problem by doing `grep
3499AC_ configure'.
3500
3501
3502File: autoconf.info,  Node: Dependencies Between Macros,  Prev: Quoting,  Up: Writing Macros
3503
3504Dependencies Between Macros
3505===========================
3506
3507   Some Autoconf macros depend on other macros having been called first
3508in order to work correctly.  Autoconf provides a way to ensure that
3509certain macros are called if needed and a way to warn the user if
3510macros are called in an order that might cause incorrect operation.
3511
3512* Menu:
3513
3514* Prerequisite Macros::         Ensuring required information.
3515* Suggested Ordering::          Warning about possible ordering problems.
3516* Obsolete Macros::             Warning about old ways of doing things.
3517
3518
3519File: autoconf.info,  Node: Prerequisite Macros,  Next: Suggested Ordering,  Prev: Dependencies Between Macros,  Up: Dependencies Between Macros
3520
3521Prerequisite Macros
3522-------------------
3523
3524   A macro that you write might need to use values that have previously
3525been computed by other macros.  For example, `AC_DECL_YYTEXT' examines
3526the output of `flex' or `lex', so it depends on `AC_PROG_LEX' having
3527been called first to set the shell variable `LEX'.
3528
3529   Rather than forcing the user of the macros to keep track of the
3530dependencies between them, you can use the `AC_REQUIRE' macro to do it
3531automatically.  `AC_REQUIRE' can ensure that a macro is only called if
3532it is needed, and only called once.
3533
3534 - Macro: AC_REQUIRE (MACRO-NAME)
3535     If the `m4' macro MACRO-NAME has not already been called, call it
3536     (without any arguments).  Make sure to quote MACRO-NAME with
3537     square brackets.  MACRO-NAME must have been defined using
3538     `AC_DEFUN' or else contain a call to `AC_PROVIDE' to indicate that
3539     it has been called.
3540
3541   An alternative to using `AC_DEFUN' is to use `define' and call
3542`AC_PROVIDE'.  Because this technique does not prevent nested messages,
3543it is considered obsolete.
3544
3545 - Macro: AC_PROVIDE (THIS-MACRO-NAME)
3546     Record the fact that THIS-MACRO-NAME has been called.
3547     THIS-MACRO-NAME should be the name of the macro that is calling
3548     `AC_PROVIDE'.  An easy way to get it is from the `m4' builtin
3549     variable `$0', like this:
3550
3551          AC_PROVIDE([$0])
3552
3553
3554File: autoconf.info,  Node: Suggested Ordering,  Next: Obsolete Macros,  Prev: Prerequisite Macros,  Up: Dependencies Between Macros
3555
3556Suggested Ordering
3557------------------
3558
3559   Some macros should be run before another macro if both are called,
3560but neither *requires* that the other be called.  For example, a macro
3561that changes the behavior of the C compiler should be called before any
3562macros that run the C compiler.  Many of these dependencies are noted in
3563the documentation.
3564
3565   Autoconf provides the `AC_BEFORE' macro to warn users when macros
3566with this kind of dependency appear out of order in a `configure.in'
3567file.  The warning occurs when creating `configure' from
3568`configure.in', not when running `configure'.  For example,
3569`AC_PROG_CPP' checks whether the C compiler can run the C preprocessor
3570when given the `-E' option.  It should therefore be called after any
3571macros that change which C compiler is being used, such as
3572`AC_PROG_CC'.  So `AC_PROG_CC' contains:
3573
3574     AC_BEFORE([$0], [AC_PROG_CPP])dnl
3575
3576This warns the user if a call to `AC_PROG_CPP' has already occurred
3577when `AC_PROG_CC' is called.
3578
3579 - Macro: AC_BEFORE (THIS-MACRO-NAME, CALLED-MACRO-NAME)
3580     Make `m4' print a warning message on the standard error output if
3581     CALLED-MACRO-NAME has already been called.  THIS-MACRO-NAME should
3582     be the name of the macro that is calling `AC_BEFORE'.  The macro
3583     CALLED-MACRO-NAME must have been defined using `AC_DEFUN' or else
3584     contain a call to `AC_PROVIDE' to indicate that it has been called.
3585
3586
3587File: autoconf.info,  Node: Obsolete Macros,  Prev: Suggested Ordering,  Up: Dependencies Between Macros
3588
3589Obsolete Macros
3590---------------
3591
3592   Configuration and portability technology has evolved over the years.
3593Often better ways of solving a particular problem are developed, or
3594ad-hoc approaches are systematized.  This process has occurred in many
3595parts of Autoconf.  One result is that some of the macros are now
3596considered "obsolete"; they still work, but are no longer considered
3597the best thing to do.  Autoconf provides the `AC_OBSOLETE' macro to
3598warn users producing `configure' scripts when they use obsolete macros,
3599to encourage them to modernize.  A sample call is:
3600
3601     AC_OBSOLETE([$0], [; use AC_CHECK_HEADERS(unistd.h) instead])dnl
3602
3603 - Macro: AC_OBSOLETE (THIS-MACRO-NAME [, SUGGESTION])
3604     Make `m4' print a message on the standard error output warning that
3605     THIS-MACRO-NAME is obsolete, and giving the file and line number
3606     where it was called.  THIS-MACRO-NAME should be the name of the
3607     macro that is calling `AC_OBSOLETE'.  If SUGGESTION is given, it
3608     is printed at the end of the warning message; for example, it can
3609     be a suggestion for what to use instead of THIS-MACRO-NAME.
3610
3611
3612File: autoconf.info,  Node: Manual Configuration,  Next: Site Configuration,  Prev: Writing Macros,  Up: Top
3613
3614Manual Configuration
3615********************
3616
3617   A few kinds of features can't be guessed automatically by running
3618test programs.  For example, the details of the object file format, or
3619special options that need to be passed to the compiler or linker.  You
3620can check for such features using ad-hoc means, such as having
3621`configure' check the output of the `uname' program, or looking for
3622libraries that are unique to particular systems.  However, Autoconf
3623provides a uniform method for handling unguessable features.
3624
3625* Menu:
3626
3627* Specifying Names::            Specifying the system type.
3628* Canonicalizing::              Getting the canonical system type.
3629* System Type Variables::       Variables containing the system type.
3630* Using System Type::           What to do with the system type.
3631
3632
3633File: autoconf.info,  Node: Specifying Names,  Next: Canonicalizing,  Prev: Manual Configuration,  Up: Manual Configuration
3634
3635Specifying the System Type
3636==========================
3637
3638   Like other GNU `configure' scripts, Autoconf-generated `configure'
3639scripts can make decisions based on a canonical name for the system
3640type, which has the form:
3641
3642     CPU-COMPANY-SYSTEM
3643
3644   `configure' can usually guess the canonical name for the type of
3645system it's running on.  To do so it runs a script called
3646`config.guess', which derives the name using the `uname' command or
3647symbols predefined by the C preprocessor.
3648
3649   Alternately, the user can specify the system type with command line
3650arguments to `configure'.  Doing so is necessary when cross-compiling.
3651In the most complex case of cross-compiling, three system types are
3652involved.  The options to specify them are:
3653
3654`--build=BUILD-TYPE'
3655     the type of system on which the package is being configured and
3656     compiled (rarely needed);
3657
3658`--host=HOST-TYPE'
3659     the type of system on which the package will run;
3660
3661`--target=TARGET-TYPE'
3662     the type of system for which any compiler tools in the package will
3663     produce code.
3664
3665If the user gives `configure' a non-option argument, it is used as the
3666default for the host, target, and build system types if the user does
3667not specify them explicitly with options.  The target and build types
3668default to the host type if it is given and they are not.  If you are
3669cross-compiling, you still have to specify the names of the cross-tools
3670you use, in particular the C compiler, on the `configure' command line,
3671e.g.,
3672
3673     CC=m68k-coff-gcc configure --target=m68k-coff
3674
3675   `configure' recognizes short aliases for many system types; for
3676example, `decstation' can be given on the command line instead of
3677`mips-dec-ultrix4.2'.  `configure' runs a script called `config.sub' to
3678canonicalize system type aliases.
3679
3680
3681File: autoconf.info,  Node: Canonicalizing,  Next: System Type Variables,  Prev: Specifying Names,  Up: Manual Configuration
3682
3683Getting the Canonical System Type
3684=================================
3685
3686   The following macros make the system type available to `configure'
3687scripts.  They run the shell script `config.guess' to determine any
3688values for the host, target, and build types that they need and the user
3689did not specify on the command line.  They run `config.sub' to
3690canonicalize any aliases the user gave.  If you use these macros, you
3691must distribute those two shell scripts along with your source code.
3692*Note Output::, for information about the `AC_CONFIG_AUX_DIR' macro
3693which you can use to control which directory `configure' looks for
3694those scripts in.  If you do not use either of these macros,
3695`configure' ignores any `--host', `--target', and `--build' options
3696given to it.
3697
3698 - Macro: AC_CANONICAL_SYSTEM
3699     Determine the system type and set output variables to the names of
3700     the canonical system types.  *Note System Type Variables::, for
3701     details about the variables this macro sets.
3702
3703 - Macro: AC_CANONICAL_HOST
3704     Perform only the subset of `AC_CANONICAL_SYSTEM' relevant to the
3705     host type.  This is all that is needed for programs that are not
3706     part of a compiler toolchain.
3707
3708 - Macro: AC_VALIDATE_CACHED_SYSTEM_TUPLE (CMD)
3709     If the cache file is inconsistent with the current host, target
3710     and build system types, execute CMD or print a default error
3711     message.
3712
3713
3714File: autoconf.info,  Node: System Type Variables,  Next: Using System Type,  Prev: Canonicalizing,  Up: Manual Configuration
3715
3716System Type Variables
3717=====================
3718
3719   After calling `AC_CANONICAL_SYSTEM', the following output variables
3720contain the system type information.  After `AC_CANONICAL_HOST', only
3721the `host' variables below are set.
3722
3723``build', `host', `target''
3724     the canonical system names;
3725
3726``build_alias', `host_alias', `target_alias''
3727     the names the user specified, or the canonical names if
3728     `config.guess' was used;
3729
3730``build_cpu', `build_vendor', `build_os''
3731``host_cpu', `host_vendor', `host_os''
3732``target_cpu', `target_vendor', `target_os''
3733     the individual parts of the canonical names (for convenience).
3734
3735
3736File: autoconf.info,  Node: Using System Type,  Prev: System Type Variables,  Up: Manual Configuration
3737
3738Using the System Type
3739=====================
3740
3741   How do you use a canonical system type?  Usually, you use it in one
3742or more `case' statements in `configure.in' to select system-specific C
3743files.  Then link those files, which have names based on the system
3744name, to generic names, such as `host.h' or `target.c'.  The `case'
3745statement patterns can use shell wildcards to group several cases
3746together, like in this fragment:
3747
3748     case "$target" in
3749     i386-*-mach* | i386-*-gnu*) obj_format=aout emulation=mach bfd_gas=yes ;;
3750     i960-*-bout) obj_format=bout ;;
3751     esac
3752
3753 - Macro: AC_LINK_FILES (SOURCE..., DEST...)
3754     Make `AC_OUTPUT' link each of the existing files SOURCE to the
3755     corresponding link name DEST.  Makes a symbolic link if possible,
3756     otherwise a hard link.  The DEST and SOURCE names should be
3757     relative to the top level source or build directory.  This macro
3758     may be called multiple times.
3759
3760     For example, this call:
3761
3762          AC_LINK_FILES(config/${machine}.h config/${obj_format}.h, host.h object.h)
3763
3764     creates in the current directory `host.h', which is a link to
3765     `SRCDIR/config/${machine}.h', and `object.h', which is a link to
3766     `SRCDIR/config/${obj_format}.h'.
3767
3768   You can also use the host system type to find cross-compilation
3769tools.  *Note Generic Programs::, for information about the
3770`AC_CHECK_TOOL' macro which does that.
3771
3772
3773File: autoconf.info,  Node: Site Configuration,  Next: Invoking configure,  Prev: Manual Configuration,  Up: Top
3774
3775Site Configuration
3776******************
3777
3778   `configure' scripts support several kinds of local configuration
3779decisions.  There are ways for users to specify where external software
3780packages are, include or exclude optional features, install programs
3781under modified names, and set default values for `configure' options.
3782
3783* Menu:
3784
3785* External Software::           Working with other optional software.
3786* Package Options::             Selecting optional features.
3787* Site Details::                Configuring site details.
3788* Transforming Names::          Changing program names when installing.
3789* Site Defaults::               Giving `configure' local defaults.
3790
3791
3792File: autoconf.info,  Node: External Software,  Next: Package Options,  Prev: Site Configuration,  Up: Site Configuration
3793
3794Working With External Software
3795==============================
3796
3797   Some packages require, or can optionally use, other software packages
3798which are already installed.  The user can give `configure' command
3799line options to specify which such external software to use.  The
3800options have one of these forms:
3801
3802     --with-PACKAGE[=ARG]
3803     --without-PACKAGE
3804
3805   For example, `--with-gnu-ld' means work with the GNU linker instead
3806of some other linker.  `--with-x' means work with The X Window System.
3807
3808   The user can give an argument by following the package name with `='
3809and the argument.  Giving an argument of `no' is for packages that are
3810used by default; it says to *not* use the package.  An argument that is
3811neither `yes' nor `no' could include a name or number of a version of
3812the other package, to specify more precisely which other package this
3813program is supposed to work with.  If no argument is given, it defaults
3814to `yes'.  `--without-PACKAGE' is equivalent to `--with-PACKAGE=no'.
3815
3816   `configure' scripts do not complain about `--with-PACKAGE' options
3817that they do not support.  This behavior permits configuring a source
3818tree containing multiple packages with a top-level `configure' script
3819when the packages support different options, without spurious error
3820messages about options that some of the packages support.  An
3821unfortunate side effect is that option spelling errors are not
3822diagnosed.  No better approach to this problem has been suggested so
3823far.
3824
3825   For each external software package that may be used, `configure.in'
3826should call `AC_ARG_WITH' to detect whether the `configure' user asked
3827to use it.  Whether each package is used or not by default, and which
3828arguments are valid, is up to you.
3829
3830 - Macro: AC_ARG_WITH (PACKAGE, HELP-STRING [, ACTION-IF-GIVEN [,
3831          ACTION-IF-NOT-GIVEN]])
3832     If the user gave `configure' the option `--with-PACKAGE' or
3833     `--without-PACKAGE', run shell commands ACTION-IF-GIVEN.  If
3834     neither option was given, run shell commands ACTION-IF-NOT-GIVEN.
3835     The name PACKAGE indicates another software package that this
3836     program should work with.  It should consist only of alphanumeric
3837     characters and dashes.
3838
3839     The option's argument is available to the shell commands
3840     ACTION-IF-GIVEN in the shell variable `withval', which is actually
3841     just the value of the shell variable `with_PACKAGE', with any `-'
3842     characters changed into `_'.  You may use that variable instead,
3843     if you wish.
3844
3845     The argument HELP-STRING is a description of the option which
3846     looks like this:
3847            --with-readline         support fancy command line editing
3848
3849     HELP-STRING may be more than one line long, if more detail is
3850     needed.  Just make sure the columns line up in `configure --help'.
3851     Avoid tabs in the help string.  You'll need to enclose it in `['
3852     and `]' in order to produce the leading spaces.
3853
3854 - Macro: AC_WITH (PACKAGE, ACTION-IF-GIVEN [, ACTION-IF-NOT-GIVEN])
3855     This is an obsolete version of `AC_ARG_WITH' that does not support
3856     providing a help string.
3857
3858
3859File: autoconf.info,  Node: Package Options,  Next: Site Details,  Prev: External Software,  Up: Site Configuration
3860
3861Choosing Package Options
3862========================
3863
3864   If a software package has optional compile-time features, the user
3865can give `configure' command line options to specify whether to compile
3866them.  The options have one of these forms:
3867
3868     --enable-FEATURE[=ARG]
3869     --disable-FEATURE
3870
3871   These options allow users to choose which optional features to build
3872and install.  `--enable-FEATURE' options should never make a feature
3873behave differently or cause one feature to replace another.  They
3874should only cause parts of the program to be built rather than left out.
3875
3876   The user can give an argument by following the feature name with `='
3877and the argument.  Giving an argument of `no' requests that the feature
3878*not* be made available.  A feature with an argument looks like
3879`--enable-debug=stabs'.  If no argument is given, it defaults to `yes'.
3880`--disable-FEATURE' is equivalent to `--enable-FEATURE=no'.
3881
3882   `configure' scripts do not complain about `--enable-FEATURE' options
3883that they do not support.  This behavior permits configuring a source
3884tree containing multiple packages with a top-level `configure' script
3885when the packages support different options, without spurious error
3886messages about options that some of the packages support.  An
3887unfortunate side effect is that option spelling errors are not
3888diagnosed.  No better approach to this problem has been suggested so
3889far.
3890
3891   For each optional feature, `configure.in' should call
3892`AC_ARG_ENABLE' to detect whether the `configure' user asked to include
3893it.  Whether each feature is included or not by default, and which
3894arguments are valid, is up to you.
3895
3896 - Macro: AC_ARG_ENABLE (FEATURE, HELP-STRING [, ACTION-IF-GIVEN [,
3897          ACTION-IF-NOT-GIVEN]])
3898     If the user gave `configure' the option `--enable-FEATURE' or
3899     `--disable-FEATURE', run shell commands ACTION-IF-GIVEN.  If
3900     neither option was given, run shell commands ACTION-IF-NOT-GIVEN.
3901     The name FEATURE indicates an optional user-level facility.  It
3902     should consist only of alphanumeric characters and dashes.
3903
3904     The option's argument is available to the shell commands
3905     ACTION-IF-GIVEN in the shell variable `enableval', which is
3906     actually just the value of the shell variable `enable_FEATURE',
3907     with any `-' characters changed into `_'.  You may use that
3908     variable instead, if you wish.  The HELP-STRING argument is like
3909     that of `AC_ARG_WITH' (*note External Software::.).
3910
3911 - Macro: AC_ENABLE (FEATURE, ACTION-IF-GIVEN [, ACTION-IF-NOT-GIVEN])
3912     This is an obsolete version of `AC_ARG_ENABLE' that does not
3913     support providing a help string.
3914
3915
3916File: autoconf.info,  Node: Site Details,  Next: Transforming Names,  Prev: Package Options,  Up: Site Configuration
3917
3918Configuring Site Details
3919========================
3920
3921   Some software packages require complex site-specific information.
3922Some examples are host names to use for certain services, company
3923names, and email addresses to contact.  Since some configuration
3924scripts generated by Metaconfig ask for such information interactively,
3925people sometimes wonder how to get that information in
3926Autoconf-generated configuration scripts, which aren't interactive.
3927
3928   Such site configuration information should be put in a file that is
3929edited *only by users*, not by programs.  The location of the file can
3930either be based on the `prefix' variable, or be a standard location
3931such as the user's home directory.  It could even be specified by an
3932environment variable.  The programs should examine that file at run
3933time, rather than at compile time.  Run time configuration is more
3934convenient for users and makes the configuration process simpler than
3935getting the information while configuring.  *Note Variables for
3936Installation Directories: (standards)Directory Variables, for more
3937information on where to put data files.
3938
3939
3940File: autoconf.info,  Node: Transforming Names,  Next: Site Defaults,  Prev: Site Details,  Up: Site Configuration
3941
3942Transforming Program Names When Installing
3943==========================================
3944
3945   Autoconf supports changing the names of programs when installing
3946them.  In order to use these transformations, `configure.in' must call
3947the macro `AC_ARG_PROGRAM'.
3948
3949 - Macro: AC_ARG_PROGRAM
3950     Place in output variable `program_transform_name' a sequence of
3951     `sed' commands for changing the names of installed programs.
3952
3953     If any of the options described below are given to `configure',
3954     program names are transformed accordingly.  Otherwise, if
3955     `AC_CANONICAL_SYSTEM' has been called and a `--target' value is
3956     given that differs from the host type (specified with `--host' or
3957     defaulted by `config.sub'), the target type followed by a dash is
3958     used as a prefix.  Otherwise, no program name transformation is
3959     done.
3960
3961* Menu:
3962
3963* Transformation Options::      `configure' options to transform names.
3964* Transformation Examples::     Sample uses of transforming names.
3965* Transformation Rules::        `Makefile' uses of transforming names.
3966
3967
3968File: autoconf.info,  Node: Transformation Options,  Next: Transformation Examples,  Prev: Transforming Names,  Up: Transforming Names
3969
3970Transformation Options
3971----------------------
3972
3973   You can specify name transformations by giving `configure' these
3974command line options:
3975
3976`--program-prefix=PREFIX'
3977     prepend PREFIX to the names;
3978
3979`--program-suffix=SUFFIX'
3980     append SUFFIX to the names;
3981
3982`--program-transform-name=EXPRESSION'
3983     perform `sed' substitution EXPRESSION on the names.
3984
3985
3986File: autoconf.info,  Node: Transformation Examples,  Next: Transformation Rules,  Prev: Transformation Options,  Up: Transforming Names
3987
3988Transformation Examples
3989-----------------------
3990
3991   These transformations are useful with programs that can be part of a
3992cross-compilation development environment.  For example, a
3993cross-assembler running on a Sun 4 configured with
3994`--target=i960-vxworks' is normally installed as `i960-vxworks-as',
3995rather than `as', which could be confused with a native Sun 4 assembler.
3996
3997   You can force a program name to begin with `g', if you don't want
3998GNU programs installed on your system to shadow other programs with the
3999same name.  For example, if you configure GNU `diff' with
4000`--program-prefix=g', then when you run `make install' it is installed
4001as `/usr/local/bin/gdiff'.
4002
4003   As a more sophisticated example, you could use
4004     --program-transform-name='s/^/g/; s/^gg/g/; s/^gless/less/'
4005
4006to prepend `g' to most of the program names in a source tree, excepting
4007those like `gdb' that already have one and those like `less' and
4008`lesskey' that aren't GNU programs.  (That is assuming that you have a
4009source tree containing those programs that is set up to use this
4010feature.)
4011
4012   One way to install multiple versions of some programs simultaneously
4013is to append a version number to the name of one or both.  For example,
4014if you want to keep Autoconf version 1 around for awhile, you can
4015configure Autoconf version 2 using `--program-suffix=2' to install the
4016programs as `/usr/local/bin/autoconf2', `/usr/local/bin/autoheader2',
4017etc.
4018
4019
4020File: autoconf.info,  Node: Transformation Rules,  Prev: Transformation Examples,  Up: Transforming Names
4021
4022Transformation Rules
4023--------------------
4024
4025   Here is how to use the variable `program_transform_name' in a
4026`Makefile.in':
4027
4028     transform=@program_transform_name@
4029     install: all
4030             $(INSTALL_PROGRAM) myprog $(bindir)/`echo myprog|sed '$(transform)'`
4031     
4032     uninstall:
4033             rm -f $(bindir)/`echo myprog|sed '$(transform)'`
4034
4035If you have more than one program to install, you can do it in a loop:
4036
4037     PROGRAMS=cp ls rm
4038     install:
4039             for p in $(PROGRAMS); do \
4040               $(INSTALL_PROGRAM) $$p $(bindir)/`echo $$p|sed '$(transform)'`; \
4041             done
4042     
4043     uninstall:
4044             for p in $(PROGRAMS); do \
4045               rm -f $(bindir)/`echo $$p|sed '$(transform)'`; \
4046             done
4047
4048   Whether to do the transformations on documentation files (Texinfo or
4049`man') is a tricky question; there seems to be no perfect answer, due
4050to the several reasons for name transforming.  Documentation is not
4051usually particular to a specific architecture, and Texinfo files do not
4052conflict with system documentation.  But they might conflict with
4053earlier versions of the same files, and `man' pages sometimes do
4054conflict with system documentation.  As a compromise, it is probably
4055best to do name transformations on `man' pages but not on Texinfo
4056manuals.
4057
4058
4059File: autoconf.info,  Node: Site Defaults,  Prev: Transforming Names,  Up: Site Configuration
4060
4061Setting Site Defaults
4062=====================
4063
4064   Autoconf-generated `configure' scripts allow your site to provide
4065default values for some configuration values.  You do this by creating
4066site- and system-wide initialization files.
4067
4068   If the environment variable `CONFIG_SITE' is set, `configure' uses
4069its value as the name of a shell script to read.  Otherwise, it reads
4070the shell script `PREFIX/share/config.site' if it exists, then
4071`PREFIX/etc/config.site' if it exists.  Thus, settings in
4072machine-specific files override those in machine-independent ones in
4073case of conflict.
4074
4075   Site files can be arbitrary shell scripts, but only certain kinds of
4076code are really appropriate to be in them.  Because `configure' reads
4077any cache file after it has read any site files, a site file can define
4078a default cache file to be shared between all Autoconf-generated
4079`configure' scripts run on that system.  If you set a default cache
4080file in a site file, it is a good idea to also set the output variable
4081`CC' in that site file, because the cache file is only valid for a
4082particular compiler, but many systems have several available.
4083
4084   You can examine or override the value set by a command line option to
4085`configure' in a site file; options set shell variables that have the
4086same names as the options, with any dashes turned into underscores.
4087The exceptions are that `--without-' and `--disable-' options are like
4088giving the corresponding `--with-' or `--enable-' option and the value
4089`no'.  Thus, `--cache-file=localcache' sets the variable `cache_file'
4090to the value `localcache'; `--enable-warnings=no' or
4091`--disable-warnings' sets the variable `enable_warnings' to the value
4092`no'; `--prefix=/usr' sets the variable `prefix' to the value `/usr';
4093etc.
4094
4095   Site files are also good places to set default values for other
4096output variables, such as `CFLAGS', if you need to give them non-default
4097values: anything you would normally do, repetitively, on the command
4098line.  If you use non-default values for PREFIX or EXEC_PREFIX
4099(wherever you locate the site file), you can set them in the site file
4100if you specify it with the `CONFIG_SITE' environment variable.
4101
4102   You can set some cache values in the site file itself.  Doing this is
4103useful if you are cross-compiling, so it is impossible to check features
4104that require running a test program.  You could "prime the cache" by
4105setting those values correctly for that system in
4106`PREFIX/etc/config.site'.  To find out the names of the cache variables
4107you need to set, look for shell variables with `_cv_' in their names in
4108the affected `configure' scripts, or in the Autoconf `m4' source code
4109for those macros.
4110
4111   The cache file is careful to not override any variables set in the
4112site files.  Similarly, you should not override command-line options in
4113the site files.  Your code should check that variables such as `prefix'
4114and `cache_file' have their default values (as set near the top of
4115`configure') before changing them.
4116
4117   Here is a sample file `/usr/share/local/gnu/share/config.site'.  The
4118command `configure --prefix=/usr/share/local/gnu' would read this file
4119(if `CONFIG_SITE' is not set to a different file).
4120
4121     # config.site for configure
4122     #
4123     # Change some defaults.
4124     test "$prefix" = NONE && prefix=/usr/share/local/gnu
4125     test "$exec_prefix" = NONE && exec_prefix=/usr/local/gnu
4126     test "$sharedstatedir" = '${prefix}/com' && sharedstatedir=/var
4127     test "$localstatedir" = '${prefix}/var' && localstatedir=/var
4128     #
4129     # Give Autoconf 2.x generated configure scripts a shared default
4130     # cache file for feature test results, architecture-specific.
4131     if test "$cache_file" = ./config.cache; then
4132       cache_file="$prefix/var/config.cache"
4133       # A cache file is only valid for one C compiler.
4134       CC=gcc
4135     fi
4136
4137
4138File: autoconf.info,  Node: Invoking configure,  Next: Invoking config.status,  Prev: Site Configuration,  Up: Top
4139
4140Running `configure' Scripts
4141***************************
4142
4143   Below are instructions on how to configure a package that uses a
4144`configure' script, suitable for inclusion as an `INSTALL' file in the
4145package.  A plain-text version of `INSTALL' which you may use comes
4146with Autoconf.
4147
4148* Menu:
4149
4150* Basic Installation::          Instructions for typical cases.
4151* Compilers and Options::       Selecting compilers and optimization.
4152* Multiple Architectures::      Compiling for multiple architectures at once.
4153* Installation Names::          Installing in different directories.
4154* Optional Features::           Selecting optional features.
4155* System Type::                 Specifying the system type.
4156* Sharing Defaults::            Setting site-wide defaults for `configure'.
4157* Operation Controls::          Changing how `configure' runs.
4158
4159
4160File: autoconf.info,  Node: Basic Installation,  Next: Compilers and Options,  Up: Invoking configure
4161
4162Basic Installation
4163==================
4164
4165   These are generic installation instructions.
4166
4167   The `configure' shell script attempts to guess correct values for
4168various system-dependent variables used during compilation.  It uses
4169those values to create a `Makefile' in each directory of the package.
4170It may also create one or more `.h' files containing system-dependent
4171definitions.  Finally, it creates a shell script `config.status' that
4172you can run in the future to recreate the current configuration, a file
4173`config.cache' that saves the results of its tests to speed up
4174reconfiguring, and a file `config.log' containing compiler output
4175(useful mainly for debugging `configure').
4176
4177   If you need to do unusual things to compile the package, please try
4178to figure out how `configure' could check whether to do them, and mail
4179diffs or instructions to the address given in the `README' so they can
4180be considered for the next release.  If at some point `config.cache'
4181contains results you don't want to keep, you may remove or edit it.
4182
4183   The file `configure.in' is used to create `configure' by a program
4184called `autoconf'.  You only need `configure.in' if you want to change
4185it or regenerate `configure' using a newer version of `autoconf'.
4186
4187The simplest way to compile this package is:
4188
4189  1. `cd' to the directory containing the package's source code and type
4190     `./configure' to configure the package for your system.  If you're
4191     using `csh' on an old version of System V, you might need to type
4192     `sh ./configure' instead to prevent `csh' from trying to execute
4193     `configure' itself.
4194
4195     Running `configure' takes awhile.  While running, it prints some
4196     messages telling which features it is checking for.
4197
4198  2. Type `make' to compile the package.
4199
4200  3. Optionally, type `make check' to run any self-tests that come with
4201     the package.
4202
4203  4. Type `make install' to install the programs and any data files and
4204     documentation.
4205
4206  5. You can remove the program binaries and object files from the
4207     source code directory by typing `make clean'.  To also remove the
4208     files that `configure' created (so you can compile the package for
4209     a different kind of computer), type `make distclean'.  There is
4210     also a `make maintainer-clean' target, but that is intended mainly
4211     for the package's developers.  If you use it, you may have to get
4212     all sorts of other programs in order to regenerate files that came
4213     with the distribution.
4214
4215
4216File: autoconf.info,  Node: Compilers and Options,  Next: Multiple Architectures,  Prev: Basic Installation,  Up: Invoking configure
4217
4218Compilers and Options
4219=====================
4220
4221   Some systems require unusual options for compilation or linking that
4222the `configure' script does not know about.  You can give `configure'
4223initial values for variables by setting them in the environment.  Using
4224a Bourne-compatible shell, you can do that on the command line like
4225this:
4226     CC=c89 CFLAGS=-O2 LIBS=-lposix ./configure
4227
4228Or on systems that have the `env' program, you can do it like this:
4229     env CPPFLAGS=-I/usr/local/include LDFLAGS=-s ./configure
4230
4231
4232File: autoconf.info,  Node: Multiple Architectures,  Next: Installation Names,  Prev: Compilers and Options,  Up: Invoking configure
4233
4234Compiling For Multiple Architectures
4235====================================
4236
4237   You can compile the package for more than one kind of computer at the
4238same time, by placing the object files for each architecture in their
4239own directory.  To do this, you must use a version of `make' that
4240supports the `VPATH' variable, such as GNU `make'.  `cd' to the
4241directory where you want the object files and executables to go and run
4242the `configure' script.  `configure' automatically checks for the
4243source code in the directory that `configure' is in and in `..'.
4244
4245   If you have to use a `make' that does not supports the `VPATH'
4246variable, you have to compile the package for one architecture at a time
4247in the source code directory.  After you have installed the package for
4248one architecture, use `make distclean' before reconfiguring for another
4249architecture.
4250
4251
4252File: autoconf.info,  Node: Installation Names,  Next: Optional Features,  Prev: Multiple Architectures,  Up: Invoking configure
4253
4254Installation Names
4255==================
4256
4257   By default, `make install' will install the package's files in
4258`/usr/local/bin', `/usr/local/man', etc.  You can specify an
4259installation prefix other than `/usr/local' by giving `configure' the
4260option `--prefix=PATH'.
4261
4262   You can specify separate installation prefixes for
4263architecture-specific files and architecture-independent files.  If you
4264give `configure' the option `--exec-prefix=PATH', the package will use
4265PATH as the prefix for installing programs and libraries.
4266Documentation and other data files will still use the regular prefix.
4267
4268   In addition, if you use an unusual directory layout you can give
4269options like `--bindir=PATH' to specify different values for particular
4270kinds of files.  Run `configure --help' for a list of the directories
4271you can set and what kinds of files go in them.
4272
4273   If the package supports it, you can cause programs to be installed
4274with an extra prefix or suffix on their names by giving `configure' the
4275option `--program-prefix=PREFIX' or `--program-suffix=SUFFIX'.
4276
4277
4278File: autoconf.info,  Node: Optional Features,  Next: System Type,  Prev: Installation Names,  Up: Invoking configure
4279
4280Optional Features
4281=================
4282
4283   Some packages pay attention to `--enable-FEATURE' options to
4284`configure', where FEATURE indicates an optional part of the package.
4285They may also pay attention to `--with-PACKAGE' options, where PACKAGE
4286is something like `gnu-as' or `x' (for the X Window System).  The
4287`README' should mention any `--enable-' and `--with-' options that the
4288package recognizes.
4289
4290   For packages that use the X Window System, `configure' can usually
4291find the X include and library files automatically, but if it doesn't,
4292you can use the `configure' options `--x-includes=DIR' and
4293`--x-libraries=DIR' to specify their locations.
4294
4295
4296File: autoconf.info,  Node: System Type,  Next: Sharing Defaults,  Prev: Optional Features,  Up: Invoking configure
4297
4298Specifying the System Type
4299==========================
4300
4301   There may be some features `configure' can not figure out
4302automatically, but needs to determine by the type of host the package
4303will run on.  Usually `configure' can figure that out, but if it prints
4304a message saying it can not guess the host type, give it the
4305`--host=TYPE' option.  TYPE can either be a short name for the system
4306type, such as `sun4', or a canonical name with three fields:
4307     CPU-COMPANY-SYSTEM
4308
4309See the file `config.sub' for the possible values of each field.  If
4310`config.sub' isn't included in this package, then this package doesn't
4311need to know the host type.
4312
4313   If you are building compiler tools for cross-compiling, you can also
4314use the `--target=TYPE' option to select the type of system they will
4315produce code for and the `--build=TYPE' option to select the type of
4316system on which you are compiling the package.
4317
4318
4319File: autoconf.info,  Node: Sharing Defaults,  Next: Operation Controls,  Prev: System Type,  Up: Invoking configure
4320
4321Sharing Defaults
4322================
4323
4324   If you want to set default values for `configure' scripts to share,
4325you can create a site shell script called `config.site' that gives
4326default values for variables like `CC', `cache_file', and `prefix'.
4327`configure' looks for `PREFIX/share/config.site' if it exists, then
4328`PREFIX/etc/config.site' if it exists.  Or, you can set the
4329`CONFIG_SITE' environment variable to the location of the site script.
4330A warning: not all `configure' scripts look for a site script.
4331
4332
4333File: autoconf.info,  Node: Operation Controls,  Prev: Sharing Defaults,  Up: Invoking configure
4334
4335Operation Controls
4336==================
4337
4338   `configure' recognizes the following options to control how it
4339operates.
4340
4341`--cache-file=FILE'
4342     Use and save the results of the tests in FILE instead of
4343     `./config.cache'.  Set FILE to `/dev/null' to disable caching, for
4344     debugging `configure'.
4345
4346`--help'
4347     Print a summary of the options to `configure', and exit.
4348
4349`--quiet'
4350`--silent'
4351`-q'
4352     Do not print messages saying which checks are being made.  To
4353     suppress all normal output, redirect it to `/dev/null' (any error
4354     messages will still be shown).
4355
4356`--srcdir=DIR'
4357     Look for the package's source code in directory DIR.  Usually
4358     `configure' can determine that directory automatically.
4359
4360`--version'
4361     Print the version of Autoconf used to generate the `configure'
4362     script, and exit.
4363
4364`configure' also accepts some other, not widely useful, options.
4365
4366
4367File: autoconf.info,  Node: Invoking config.status,  Next: Questions,  Prev: Invoking configure,  Up: Top
4368
4369Recreating a Configuration
4370**************************
4371
4372   The `configure' script creates a file named `config.status' which
4373describes which configuration options were specified when the package
4374was last configured.  This file is a shell script which, if run, will
4375recreate the same configuration.
4376
4377   You can give `config.status' the `--recheck' option to update
4378itself.  This option is useful if you change `configure', so that the
4379results of some tests might be different from the previous run.  The
4380`--recheck' option re-runs `configure' with the same arguments you used
4381before, plus the `--no-create' option, which prevent `configure' from
4382running `config.status' and creating `Makefile' and other files, and
4383the `--no-recursion' option, which prevents `configure' from running
4384other `configure' scripts in subdirectories.  (This is so other
4385`Makefile' rules can run `config.status' when it changes; *note
4386Automatic Remaking::., for an example).
4387
4388   `config.status' also accepts the options `--help', which prints a
4389summary of the options to `config.status', and `--version', which
4390prints the version of Autoconf used to create the `configure' script
4391that generated `config.status'.
4392
4393   `config.status' checks several optional environment variables that
4394can alter its behavior:
4395
4396 - Variable: CONFIG_SHELL
4397     The shell with which to run `configure' for the `--recheck'
4398     option.  It must be Bourne-compatible.  The default is `/bin/sh'.
4399
4400 - Variable: CONFIG_STATUS
4401     The file name to use for the shell script that records the
4402     configuration.  The default is `./config.status'.  This variable is
4403     useful when one package uses parts of another and the `configure'
4404     scripts shouldn't be merged because they are maintained separately.
4405
4406   The following variables provide one way for separately distributed
4407packages to share the values computed by `configure'.  Doing so can be
4408useful if some of the packages need a superset of the features that one
4409of them, perhaps a common library, does.  These variables allow a
4410`config.status' file to create files other than the ones that its
4411`configure.in' specifies, so it can be used for a different package.
4412
4413 - Variable: CONFIG_FILES
4414     The files in which to perform `@VARIABLE@' substitutions.  The
4415     default is the arguments given to `AC_OUTPUT' in `configure.in'.
4416
4417 - Variable: CONFIG_HEADERS
4418     The files in which to substitute C `#define' statements.  The
4419     default is the arguments given to `AC_CONFIG_HEADER'; if that
4420     macro was not called, `config.status' ignores this variable.
4421
4422   These variables also allow you to write `Makefile' rules that
4423regenerate only some of the files.  For example, in the dependencies
4424given above (*note Automatic Remaking::.), `config.status' is run twice
4425when `configure.in' has changed.  If that bothers you, you can make
4426each run only regenerate the files for that rule:
4427
4428     config.h: stamp-h
4429     stamp-h: config.h.in config.status
4430             CONFIG_FILES= CONFIG_HEADERS=config.h ./config.status
4431             echo > stamp-h
4432     
4433     Makefile: Makefile.in config.status
4434             CONFIG_FILES=Makefile CONFIG_HEADERS= ./config.status
4435
4436(If `configure.in' does not call `AC_CONFIG_HEADER', there is no need
4437to set `CONFIG_HEADERS' in the `make' rules.)
4438
4439
4440File: autoconf.info,  Node: Questions,  Next: Upgrading,  Prev: Invoking config.status,  Up: Top
4441
4442Questions About Autoconf
4443************************
4444
4445   Several questions about Autoconf come up occasionally.  Here some of
4446them are addressed.
4447
4448* Menu:
4449
4450* Distributing::                Distributing `configure' scripts.
4451* Why GNU m4::                  Why not use the standard `m4'?
4452* Bootstrapping::               Autoconf and GNU `m4' require each other?
4453* Why Not Imake::               Why GNU uses `configure' instead of Imake.
4454
4455
4456File: autoconf.info,  Node: Distributing,  Next: Why GNU m4,  Prev: Questions,  Up: Questions
4457
4458Distributing `configure' Scripts
4459================================
4460
4461     What are the restrictions on distributing `configure'
4462     scripts that Autoconf generates?  How does that affect my
4463     programs that use them?
4464
4465   There are no restrictions on how the configuration scripts that
4466Autoconf produces may be distributed or used.  In Autoconf version 1,
4467they were covered by the GNU General Public License.  We still
4468encourage software authors to distribute their work under terms like
4469those of the GPL, but doing so is not required to use Autoconf.
4470
4471   Of the other files that might be used with `configure',
4472`config.h.in' is under whatever copyright you use for your
4473`configure.in', since it is derived from that file and from the public
4474domain file `acconfig.h'.  `config.sub' and `config.guess' have an
4475exception to the GPL when they are used with an Autoconf-generated
4476`configure' script, which permits you to distribute them under the same
4477terms as the rest of your package.  `install-sh' is from the X
4478Consortium and is not copyrighted.
4479
4480
4481File: autoconf.info,  Node: Why GNU m4,  Next: Bootstrapping,  Prev: Distributing,  Up: Questions
4482
4483Why Require GNU `m4'?
4484=====================
4485
4486     Why does Autoconf require GNU `m4'?
4487
4488   Many `m4' implementations have hard-coded limitations on the size
4489and number of macros, which Autoconf exceeds.  They also lack several
4490builtin macros that it would be difficult to get along without in a
4491sophisticated application like Autoconf, including:
4492
4493     builtin
4494     indir
4495     patsubst
4496     __file__
4497     __line__
4498
4499   Since only software maintainers need to use Autoconf, and since GNU
4500`m4' is simple to configure and install, it seems reasonable to require
4501GNU `m4' to be installed also.  Many maintainers of GNU and other free
4502software already have most of the GNU utilities installed, since they
4503prefer them.
4504
4505
4506File: autoconf.info,  Node: Bootstrapping,  Next: Why Not Imake,  Prev: Why GNU m4,  Up: Questions
4507
4508How Can I Bootstrap?
4509====================
4510
4511     If Autoconf requires GNU `m4' and GNU `m4' has an
4512     Autoconf `configure' script, how do I bootstrap?  It seems
4513     like a chicken and egg problem!
4514
4515   This is a misunderstanding.  Although GNU `m4' does come with a
4516`configure' script produced by Autoconf, Autoconf is not required in
4517order to run the script and install GNU `m4'.  Autoconf is only
4518required if you want to change the `m4' `configure' script, which few
4519people have to do (mainly its maintainer).
4520
4521
4522File: autoconf.info,  Node: Why Not Imake,  Prev: Bootstrapping,  Up: Questions
4523
4524Why Not Imake?
4525==============
4526
4527     Why not use Imake instead of `configure' scripts?
4528
4529   Several people have written addressing this question, so I include
4530adaptations of their explanations here.
4531
4532   The following answer is based on one written by Richard Pixley:
4533
4534   Autoconf generated scripts frequently work on machines which it has
4535never been set up to handle before.  That is, it does a good job of
4536inferring a configuration for a new system.  Imake cannot do this.
4537
4538   Imake uses a common database of host specific data.  For X11, this
4539makes sense because the distribution is made as a collection of tools,
4540by one central authority who has control over the database.
4541
4542   GNU tools are not released this way.  Each GNU tool has a maintainer;
4543these maintainers are scattered across the world.  Using a common
4544database would be a maintenance nightmare.  Autoconf may appear to be
4545this kind of database, but in fact it is not.  Instead of listing host
4546dependencies, it lists program requirements.
4547
4548   If you view the GNU suite as a collection of native tools, then the
4549problems are similar.  But the GNU development tools can be configured
4550as cross tools in almost any host+target permutation.  All of these
4551configurations can be installed concurrently.  They can even be
4552configured to share host independent files across hosts.  Imake doesn't
4553address these issues.
4554
4555   Imake templates are a form of standardization.  The GNU coding
4556standards address the same issues without necessarily imposing the same
4557restrictions.
4558
4559   Here is some further explanation, written by Per Bothner:
4560
4561   One of the advantages of Imake is that it easy to generate large
4562Makefiles using `cpp''s `#include' and macro mechanisms.  However,
4563`cpp' is not programmable: it has limited conditional facilities, and
4564no looping.  And `cpp' cannot inspect its environment.
4565
4566   All of these problems are solved by using `sh' instead of `cpp'.
4567The shell is fully programmable, has macro substitution, can execute
4568(or source) other shell scripts, and can inspect its environment.
4569
4570   Paul Eggert elaborates more:
4571
4572   With Autoconf, installers need not assume that Imake itself is
4573already installed and working well.  This may not seem like much of an
4574advantage to people who are accustomed to Imake.  But on many hosts
4575Imake is not installed or the default installation is not working well,
4576and requiring Imake to install a package hinders the acceptance of that
4577package on those hosts.  For example, the Imake template and
4578configuration files might not be installed properly on a host, or the
4579Imake build procedure might wrongly assume that all source files are in
4580one big directory tree, or the Imake configuration might assume one
4581compiler whereas the package or the installer needs to use another, or
4582there might be a version mismatch between the Imake expected by the
4583package and the Imake supported by the host.  These problems are much
4584rarer with Autoconf, where each package comes with its own independent
4585configuration processor.
4586
4587   Also, Imake often suffers from unexpected interactions between
4588`make' and the installer's C preprocessor.  The fundamental problem
4589here is that the C preprocessor was designed to preprocess C programs,
4590not `Makefile's.  This is much less of a problem with Autoconf, which
4591uses the general-purpose preprocessor `m4', and where the package's
4592author (rather than the installer) does the preprocessing in a standard
4593way.
4594
4595   Finally, Mark Eichin notes:
4596
4597   Imake isn't all that extensible, either.  In order to add new
4598features to Imake, you need to provide your own project template, and
4599duplicate most of the features of the existing one.  This means that
4600for a sophisticated project, using the vendor-provided Imake templates
4601fails to provide any leverage--since they don't cover anything that
4602your own project needs (unless it is an X11 program).
4603
4604   On the other side, though:
4605
4606   The one advantage that Imake has over `configure': `Imakefile's tend
4607to be much shorter (likewise, less redundant) than `Makefile.in's.
4608There is a fix to this, however--at least for the Kerberos V5 tree,
4609we've modified things to call in common `post.in' and `pre.in'
4610`Makefile' fragments for the entire tree.  This means that a lot of
4611common things don't have to be duplicated, even though they normally
4612are in `configure' setups.
4613
4614
4615File: autoconf.info,  Node: Upgrading,  Next: History,  Prev: Questions,  Up: Top
4616
4617Upgrading From Version 1
4618************************
4619
4620   Autoconf version 2 is mostly backward compatible with version 1.
4621However, it introduces better ways to do some things, and doesn't
4622support some of the ugly things in version 1.  So, depending on how
4623sophisticated your `configure.in' files are, you might have to do some
4624manual work in order to upgrade to version 2.  This chapter points out
4625some problems to watch for when upgrading.  Also, perhaps your
4626`configure' scripts could benefit from some of the new features in
4627version 2; the changes are summarized in the file `NEWS' in the
4628Autoconf distribution.
4629
4630   First, make sure you have GNU `m4' version 1.1 or higher installed,
4631preferably 1.3 or higher.  Versions before 1.1 have bugs that prevent
4632them from working with Autoconf version 2.  Versions 1.3 and later are
4633much faster than earlier versions, because as of version 1.3, GNU `m4'
4634has a more efficient implementation of diversions and can freeze its
4635internal state in a file that it can read back quickly.
4636
4637* Menu:
4638
4639* Changed File Names::          Files you might rename.
4640* Changed Makefiles::           New things to put in `Makefile.in'.
4641* Changed Macros::              Macro calls you might replace.
4642* Invoking autoupdate::         Replacing old macro names in `configure.in'.
4643* Changed Results::             Changes in how to check test results.
4644* Changed Macro Writing::       Better ways to write your own macros.
4645
4646
4647File: autoconf.info,  Node: Changed File Names,  Next: Changed Makefiles,  Prev: Upgrading,  Up: Upgrading
4648
4649Changed File Names
4650==================
4651
4652   If you have an `aclocal.m4' installed with Autoconf (as opposed to
4653in a particular package's source directory), you must rename it to
4654`acsite.m4'.  *Note Invoking autoconf::.
4655
4656   If you distribute `install.sh' with your package, rename it to
4657`install-sh' so `make' builtin rules won't inadvertently create a file
4658called `install' from it.  `AC_PROG_INSTALL' looks for the script under
4659both names, but it is best to use the new name.
4660
4661   If you were using `config.h.top' or `config.h.bot', you still can,
4662but you will have less clutter if you merge them into `acconfig.h'.
4663*Note Invoking autoheader::.
4664
4665
4666File: autoconf.info,  Node: Changed Makefiles,  Next: Changed Macros,  Prev: Changed File Names,  Up: Upgrading
4667
4668Changed Makefiles
4669=================
4670
4671   Add `@CFLAGS@', `@CPPFLAGS@', and `@LDFLAGS@' in your `Makefile.in'
4672files, so they can take advantage of the values of those variables in
4673the environment when `configure' is run.  Doing this isn't necessary,
4674but it's a convenience for users.
4675
4676   Also add `@configure_input@' in a comment to each non-`Makefile'
4677input file for `AC_OUTPUT', so that the output files will contain a
4678comment saying they were produced by `configure'.  Automatically
4679selecting the right comment syntax for all the kinds of files that
4680people call `AC_OUTPUT' on became too much work.
4681
4682   Add `config.log' and `config.cache' to the list of files you remove
4683in `distclean' targets.
4684
4685   If you have the following in `Makefile.in':
4686
4687     prefix = /usr/local
4688     exec_prefix = ${prefix}
4689
4690you must change it to:
4691
4692     prefix = @prefix@
4693     exec_prefix = @exec_prefix@
4694
4695The old behavior of replacing those variables without `@' characters
4696around them has been removed.
4697
4698
4699File: autoconf.info,  Node: Changed Macros,  Next: Invoking autoupdate,  Prev: Changed Makefiles,  Up: Upgrading
4700
4701Changed Macros
4702==============
4703
4704   Many of the macros were renamed in Autoconf version 2.  You can still
4705use the old names, but the new ones are clearer, and it's easier to find
4706the documentation for them.  *Note Old Macro Names::, for a table
4707showing the new names for the old macros.  Use the `autoupdate' program
4708to convert your `configure.in' to using the new macro names.  *Note
4709Invoking autoupdate::.
4710
4711   Some macros have been superseded by similar ones that do the job
4712better, but are not call-compatible.  If you get warnings about calling
4713obsolete macros while running `autoconf', you may safely ignore them,
4714but your `configure' script will generally work better if you follow
4715the advice it prints about what to replace the obsolete macros with.  In
4716particular, the mechanism for reporting the results of tests has
4717changed.  If you were using `echo' or `AC_VERBOSE' (perhaps via
4718`AC_COMPILE_CHECK'), your `configure' script's output will look better
4719if you switch to `AC_MSG_CHECKING' and `AC_MSG_RESULT'.  *Note Printing
4720Messages::.  Those macros work best in conjunction with cache
4721variables.  *Note Caching Results::.
4722
4723
4724File: autoconf.info,  Node: Invoking autoupdate,  Next: Changed Results,  Prev: Changed Macros,  Up: Upgrading
4725
4726Using `autoupdate' to Modernize `configure'
4727===========================================
4728
4729   The `autoupdate' program updates a `configure.in' file that calls
4730Autoconf macros by their old names to use the current macro names.  In
4731version 2 of Autoconf, most of the macros were renamed to use a more
4732uniform and descriptive naming scheme.  *Note Macro Names::, for a
4733description of the new scheme.  Although the old names still work
4734(*note Old Macro Names::., for a list of the old macro names and the
4735corresponding new names), you can make your `configure.in' files more
4736readable and make it easier to use the current Autoconf documentation
4737if you update them to use the new macro names.
4738
4739   If given no arguments, `autoupdate' updates `configure.in', backing
4740up the original version with the suffix `~' (or the value of the
4741environment variable `SIMPLE_BACKUP_SUFFIX', if that is set).  If you
4742give `autoupdate' an argument, it reads that file instead of
4743`configure.in' and writes the updated file to the standard output.
4744
4745`autoupdate' accepts the following options:
4746
4747`--help'
4748`-h'
4749     Print a summary of the command line options and exit.
4750
4751`--macrodir=DIR'
4752`-m DIR'
4753     Look for the Autoconf macro files in directory DIR instead of the
4754     default installation directory.  You can also set the `AC_MACRODIR'
4755     environment variable to a directory; this option overrides the
4756     environment variable.
4757
4758`--version'
4759     Print the version number of `autoupdate' and exit.
4760
4761
4762File: autoconf.info,  Node: Changed Results,  Next: Changed Macro Writing,  Prev: Invoking autoupdate,  Up: Upgrading
4763
4764Changed Results
4765===============
4766
4767   If you were checking the results of previous tests by examining the
4768shell variable `DEFS', you need to switch to checking the values of the
4769cache variables for those tests.  `DEFS' no longer exists while
4770`configure' is running; it is only created when generating output
4771files.  This difference from version 1 is because properly quoting the
4772contents of that variable turned out to be too cumbersome and
4773inefficient to do every time `AC_DEFINE' is called.  *Note Cache
4774Variable Names::.
4775
4776   For example, here is a `configure.in' fragment written for Autoconf
4777version 1:
4778
4779     AC_HAVE_FUNCS(syslog)
4780     case "$DEFS" in
4781     *-DHAVE_SYSLOG*) ;;
4782     *) # syslog is not in the default libraries.  See if it's in some other.
4783       saved_LIBS="$LIBS"
4784       for lib in bsd socket inet; do
4785         AC_CHECKING(for syslog in -l$lib)
4786         LIBS="$saved_LIBS -l$lib"
4787         AC_HAVE_FUNCS(syslog)
4788         case "$DEFS" in
4789         *-DHAVE_SYSLOG*) break ;;
4790         *) ;;
4791         esac
4792         LIBS="$saved_LIBS"
4793       done ;;
4794     esac
4795
4796   Here is a way to write it for version 2:
4797
4798     AC_CHECK_FUNCS(syslog)
4799     if test $ac_cv_func_syslog = no; then
4800       # syslog is not in the default libraries.  See if it's in some other.
4801       for lib in bsd socket inet; do
4802         AC_CHECK_LIB($lib, syslog, [AC_DEFINE(HAVE_SYSLOG)
4803           LIBS="$LIBS $lib"; break])
4804       done
4805     fi
4806
4807   If you were working around bugs in `AC_DEFINE_UNQUOTED' by adding
4808backslashes before quotes, you need to remove them.  It now works
4809predictably, and does not treat quotes (except backquotes) specially.
4810*Note Setting Output Variables::.
4811
4812   All of the boolean shell variables set by Autoconf macros now use
4813`yes' for the true value.  Most of them use `no' for false, though for
4814backward compatibility some use the empty string instead.  If you were
4815relying on a shell variable being set to something like 1 or `t' for
4816true, you need to change your tests.
4817
4818
4819File: autoconf.info,  Node: Changed Macro Writing,  Prev: Changed Results,  Up: Upgrading
4820
4821Changed Macro Writing
4822=====================
4823
4824   When defining your own macros, you should now use `AC_DEFUN' instead
4825of `define'.  `AC_DEFUN' automatically calls `AC_PROVIDE' and ensures
4826that macros called via `AC_REQUIRE' do not interrupt other macros, to
4827prevent nested `checking...' messages on the screen.  There's no actual
4828harm in continuing to use the older way, but it's less convenient and
4829attractive.  *Note Macro Definitions::.
4830
4831   You probably looked at the macros that came with Autoconf as a guide
4832for how to do things.  It would be a good idea to take a look at the new
4833versions of them, as the style is somewhat improved and they take
4834advantage of some new features.
4835
4836   If you were doing tricky things with undocumented Autoconf internals
4837(macros, variables, diversions), check whether you need to change
4838anything to account for changes that have been made.  Perhaps you can
4839even use an officially supported technique in version 2 instead of
4840kludging.  Or perhaps not.
4841
4842   To speed up your locally written feature tests, add caching to them.
4843See whether any of your tests are of general enough usefulness to
4844encapsulate into macros that you can share.
4845
4846
4847File: autoconf.info,  Node: History,  Next: Old Macro Names,  Prev: Upgrading,  Up: Top
4848
4849History of Autoconf
4850*******************
4851
4852   You may be wondering, Why was Autoconf originally written?  How did
4853it get into its present form?  (Why does it look like gorilla spit?)  If
4854you're not wondering, then this chapter contains no information useful
4855to you, and you might as well skip it.  If you *are* wondering, then
4856let there be light...
4857
4858* Menu:
4859
4860* Genesis::                     Prehistory and naming of `configure'.
4861* Exodus::                      The plagues of `m4' and Perl.
4862* Leviticus::                   The priestly code of portability arrives.
4863* Numbers::                     Growth and contributors.
4864* Deuteronomy::                 Approaching the promises of easy configuration.
4865
4866
4867File: autoconf.info,  Node: Genesis,  Next: Exodus,  Prev: History,  Up: History
4868
4869Genesis
4870=======
4871
4872   In June 1991 I was maintaining many of the GNU utilities for the Free
4873Software Foundation.  As they were ported to more platforms and more
4874programs were added, the number of `-D' options that users had to
4875select in the `Makefile' (around 20) became burdensome.  Especially for
4876me--I had to test each new release on a bunch of different systems.  So
4877I wrote a little shell script to guess some of the correct settings for
4878the fileutils package, and released it as part of fileutils 2.0.  That
4879`configure' script worked well enough that the next month I adapted it
4880(by hand) to create similar `configure' scripts for several other GNU
4881utilities packages.  Brian Berliner also adapted one of my scripts for
4882his CVS revision control system.
4883
4884   Later that summer, I learned that Richard Stallman and Richard Pixley
4885were developing similar scripts to use in the GNU compiler tools; so I
4886adapted my `configure' scripts to support their evolving interface:
4887using the file name `Makefile.in' as the templates; adding `+srcdir',
4888the first option (of many); and creating `config.status' files.
4889
4890
4891File: autoconf.info,  Node: Exodus,  Next: Leviticus,  Prev: Genesis,  Up: History
4892
4893Exodus
4894======
4895
4896   As I got feedback from users, I incorporated many improvements, using
4897Emacs to search and replace, cut and paste, similar changes in each of
4898the scripts.  As I adapted more GNU utilities packages to use
4899`configure' scripts, updating them all by hand became impractical.
4900Rich Murphey, the maintainer of the GNU graphics utilities, sent me mail
4901saying that the `configure' scripts were great, and asking if I had a
4902tool for generating them that I could send him.  No, I thought, but I
4903should!  So I started to work out how to generate them.  And the
4904journey from the slavery of hand-written `configure' scripts to the
4905abundance and ease of Autoconf began.
4906
4907   Cygnus `configure', which was being developed at around that time,
4908is table driven; it is meant to deal mainly with a discrete number of
4909system types with a small number of mainly unguessable features (such as
4910details of the object file format).  The automatic configuration system
4911that Brian Fox had developed for Bash takes a similar approach.  For
4912general use, it seems to me a hopeless cause to try to maintain an
4913up-to-date database of which features each variant of each operating
4914system has.  It's easier and more reliable to check for most features on
4915the fly--especially on hybrid systems that people have hacked on
4916locally or that have patches from vendors installed.
4917
4918   I considered using an architecture similar to that of Cygnus
4919`configure', where there is a single `configure' script that reads
4920pieces of `configure.in' when run.  But I didn't want to have to
4921distribute all of the feature tests with every package, so I settled on
4922having a different `configure' made from each `configure.in' by a
4923preprocessor.  That approach also offered more control and flexibility.
4924
4925   I looked briefly into using the Metaconfig package, by Larry Wall,
4926Harlan Stenn, and Raphael Manfredi, but I decided not to for several
4927reasons.  The `Configure' scripts it produces are interactive, which I
4928find quite inconvenient; I didn't like the ways it checked for some
4929features (such as library functions); I didn't know that it was still
4930being maintained, and the `Configure' scripts I had seen didn't work on
4931many modern systems (such as System V R4 and NeXT); it wasn't very
4932flexible in what it could do in response to a feature's presence or
4933absence; I found it confusing to learn; and it was too big and complex
4934for my needs (I didn't realize then how much Autoconf would eventually
4935have to grow).
4936
4937   I considered using Perl to generate my style of `configure' scripts,
4938but decided that `m4' was better suited to the job of simple textual
4939substitutions: it gets in the way less, because output is implicit.
4940Plus, everyone already has it.  (Initially I didn't rely on the GNU
4941extensions to `m4'.)  Also, some of my friends at the University of
4942Maryland had recently been putting `m4' front ends on several programs,
4943including `tvtwm', and I was interested in trying out a new language.
4944
4945
4946File: autoconf.info,  Node: Leviticus,  Next: Numbers,  Prev: Exodus,  Up: History
4947
4948Leviticus
4949=========
4950
4951   Since my `configure' scripts determine the system's capabilities
4952automatically, with no interactive user intervention, I decided to call
4953the program that generates them Autoconfig.  But with a version number
4954tacked on, that name would be too long for old UNIX file systems, so I
4955shortened it to Autoconf.
4956
4957   In the fall of 1991 I called together a group of fellow questers
4958after the Holy Grail of portability (er, that is, alpha testers) to
4959give me feedback as I encapsulated pieces of my handwritten scripts in
4960`m4' macros and continued to add features and improve the techniques
4961used in the checks.  Prominent among the testers were Franc,ois Pinard,
4962who came up with the idea of making an `autoconf' shell script to run
4963`m4' and check for unresolved macro calls; Richard Pixley, who
4964suggested running the compiler instead of searching the file system to
4965find include files and symbols, for more accurate results; Karl Berry,
4966who got Autoconf to configure TeX and added the macro index to the
4967documentation; and Ian Taylor, who added support for creating a C
4968header file as an alternative to putting `-D' options in a `Makefile',
4969so he could use Autoconf for his UUCP package.  The alpha testers
4970cheerfully adjusted their files again and again as the names and
4971calling conventions of the Autoconf macros changed from release to
4972release.  They all contributed many specific checks, great ideas, and
4973bug fixes.
4974
4975
4976File: autoconf.info,  Node: Numbers,  Next: Deuteronomy,  Prev: Leviticus,  Up: History
4977
4978Numbers
4979=======
4980
4981   In July 1992, after months of alpha testing, I released Autoconf 1.0,
4982and converted many GNU packages to use it.  I was surprised by how
4983positive the reaction to it was.  More people started using it than I
4984could keep track of, including people working on software that wasn't
4985part of the GNU Project (such as TCL, FSP, and Kerberos V5).  Autoconf
4986continued to improve rapidly, as many people using the `configure'
4987scripts reported problems they encountered.
4988
4989   Autoconf turned out to be a good torture test for `m4'
4990implementations.  UNIX `m4' started to dump core because of the length
4991of the macros that Autoconf defined, and several bugs showed up in GNU
4992`m4' as well.  Eventually, we realized that we needed to use some
4993features that only GNU `m4' has.  4.3BSD `m4', in particular, has an
4994impoverished set of builtin macros; the System V version is better, but
4995still doesn't provide everything we need.
4996
4997   More development occurred as people put Autoconf under more stresses
4998(and to uses I hadn't anticipated).  Karl Berry added checks for X11.
4999david zuhn contributed C++ support.  Franc,ois Pinard made it diagnose
5000invalid arguments.  Jim Blandy bravely coerced it into configuring GNU
5001Emacs, laying the groundwork for several later improvements.  Roland
5002McGrath got it to configure the GNU C Library, wrote the `autoheader'
5003script to automate the creation of C header file templates, and added a
5004`--verbose' option to `configure'.  Noah Friedman added the
5005`--macrodir' option and `AC_MACRODIR' environment variable.  (He also
5006coined the term "autoconfiscate" to mean "adapt a software package to
5007use Autoconf".)  Roland and Noah improved the quoting protection in
5008`AC_DEFINE' and fixed many bugs, especially when I got sick of dealing
5009with portability problems from February through June, 1993.
5010
5011
5012File: autoconf.info,  Node: Deuteronomy,  Prev: Numbers,  Up: History
5013
5014Deuteronomy
5015===========
5016
5017   A long wish list for major features had accumulated, and the effect
5018of several years of patching by various people had left some residual
5019cruft.  In April 1994, while working for Cygnus Support, I began a major
5020revision of Autoconf.  I added most of the features of the Cygnus
5021`configure' that Autoconf had lacked, largely by adapting the relevant
5022parts of Cygnus `configure' with the help of david zuhn and Ken
5023Raeburn.  These features include support for using `config.sub',
5024`config.guess', `--host', and `--target'; making links to files; and
5025running `configure' scripts in subdirectories.  Adding these features
5026enabled Ken to convert GNU `as', and Rob Savoye to convert DejaGNU, to
5027using Autoconf.
5028
5029   I added more features in response to other peoples' requests.  Many
5030people had asked for `configure' scripts to share the results of the
5031checks between runs, because (particularly when configuring a large
5032source tree, like Cygnus does) they were frustratingly slow.  Mike
5033Haertel suggested adding site-specific initialization scripts.  People
5034distributing software that had to unpack on MS-DOS asked for a way to
5035override the `.in' extension on the file names, which produced file
5036names like `config.h.in' containing two dots.  Jim Avera did an
5037extensive examination of the problems with quoting in `AC_DEFINE' and
5038`AC_SUBST'; his insights led to significant improvements.  Richard
5039Stallman asked that compiler output be sent to `config.log' instead of
5040`/dev/null', to help people debug the Emacs `configure' script.
5041
5042   I made some other changes because of my dissatisfaction with the
5043quality of the program.  I made the messages showing results of the
5044checks less ambiguous, always printing a result.  I regularized the
5045names of the macros and cleaned up coding style inconsistencies.  I
5046added some auxiliary utilities that I had developed to help convert
5047source code packages to use Autoconf.  With the help of Franc,ois
5048Pinard, I made the macros not interrupt each others' messages.  (That
5049feature revealed some performance bottlenecks in GNU `m4', which he
5050hastily corrected!) I reorganized the documentation around problems
5051people want to solve.  And I began a testsuite, because experience had
5052shown that Autoconf has a pronounced tendency to regress when we change
5053it.
5054
5055   Again, several alpha testers gave invaluable feedback, especially
5056Franc,ois Pinard, Jim Meyering, Karl Berry, Rob Savoye, Ken Raeburn,
5057and Mark Eichin.
5058
5059   Finally, version 2.0 was ready.  And there was much rejoicing.  (And
5060I have free time again.  I think.  Yeah, right.)
5061
5062
5063File: autoconf.info,  Node: Old Macro Names,  Next: Environment Variable Index,  Prev: History,  Up: Top
5064
5065Old Macro Names
5066***************
5067
5068   In version 2 of Autoconf, most of the macros were renamed to use a
5069more uniform and descriptive naming scheme.  Here are the old names of
5070the macros that were renamed, followed by the current names of those
5071macros.  Although the old names are still accepted by the `autoconf'
5072program for backward compatibility, the old names are considered
5073obsolete.  *Note Macro Names::, for a description of the new naming
5074scheme.
5075
5076`AC_ALLOCA'
5077     `AC_FUNC_ALLOCA'
5078
5079`AC_ARG_ARRAY'
5080     removed because of limited usefulness
5081
5082`AC_CHAR_UNSIGNED'
5083     `AC_C_CHAR_UNSIGNED'
5084
5085`AC_CONST'
5086     `AC_C_CONST'
5087
5088`AC_CROSS_CHECK'
5089     `AC_C_CROSS'
5090
5091`AC_ERROR'
5092     `AC_MSG_ERROR'
5093
5094`AC_FIND_X'
5095     `AC_PATH_X'
5096
5097`AC_FIND_XTRA'
5098     `AC_PATH_XTRA'
5099
5100`AC_FUNC_CHECK'
5101     `AC_CHECK_FUNC'
5102
5103`AC_GCC_TRADITIONAL'
5104     `AC_PROG_GCC_TRADITIONAL'
5105
5106`AC_GETGROUPS_T'
5107     `AC_TYPE_GETGROUPS'
5108
5109`AC_GETLOADAVG'
5110     `AC_FUNC_GETLOADAVG'
5111
5112`AC_HAVE_FUNCS'
5113     `AC_CHECK_FUNCS'
5114
5115`AC_HAVE_HEADERS'
5116     `AC_CHECK_HEADERS'
5117
5118`AC_HAVE_POUNDBANG'
5119     `AC_SYS_INTERPRETER' (different calling convention)
5120
5121`AC_HEADER_CHECK'
5122     `AC_CHECK_HEADER'
5123
5124`AC_HEADER_EGREP'
5125     `AC_EGREP_HEADER'
5126
5127`AC_INLINE'
5128     `AC_C_INLINE'
5129
5130`AC_LN_S'
5131     `AC_PROG_LN_S'
5132
5133`AC_LONG_DOUBLE'
5134     `AC_C_LONG_DOUBLE'
5135
5136`AC_LONG_FILE_NAMES'
5137     `AC_SYS_LONG_FILE_NAMES'
5138
5139`AC_MAJOR_HEADER'
5140     `AC_HEADER_MAJOR'
5141
5142`AC_MINUS_C_MINUS_O'
5143     `AC_PROG_CC_C_O'
5144
5145`AC_MMAP'
5146     `AC_FUNC_MMAP'
5147
5148`AC_MODE_T'
5149     `AC_TYPE_MODE_T'
5150
5151`AC_OFF_T'
5152     `AC_TYPE_OFF_T'
5153
5154`AC_PID_T'
5155     `AC_TYPE_PID_T'
5156
5157`AC_PREFIX'
5158     `AC_PREFIX_PROGRAM'
5159
5160`AC_PROGRAMS_CHECK'
5161     `AC_CHECK_PROGS'
5162
5163`AC_PROGRAMS_PATH'
5164     `AC_PATH_PROGS'
5165
5166`AC_PROGRAM_CHECK'
5167     `AC_CHECK_PROG'
5168
5169`AC_PROGRAM_EGREP'
5170     `AC_EGREP_CPP'
5171
5172`AC_PROGRAM_PATH'
5173     `AC_PATH_PROG'
5174
5175`AC_REMOTE_TAPE'
5176     removed because of limited usefulness
5177
5178`AC_RESTARTABLE_SYSCALLS'
5179     `AC_SYS_RESTARTABLE_SYSCALLS'
5180
5181`AC_RETSIGTYPE'
5182     `AC_TYPE_SIGNAL'
5183
5184`AC_RSH'
5185     removed because of limited usefulness
5186
5187`AC_SETVBUF_REVERSED'
5188     `AC_FUNC_SETVBUF_REVERSED'
5189
5190`AC_SET_MAKE'
5191     `AC_PROG_MAKE_SET'
5192
5193`AC_SIZEOF_TYPE'
5194     `AC_CHECK_SIZEOF'
5195
5196`AC_SIZE_T'
5197     `AC_TYPE_SIZE_T'
5198
5199`AC_STAT_MACROS_BROKEN'
5200     `AC_HEADER_STAT'
5201
5202`AC_STDC_HEADERS'
5203     `AC_HEADER_STDC'
5204
5205`AC_STRCOLL'
5206     `AC_FUNC_STRCOLL'
5207
5208`AC_ST_BLKSIZE'
5209     `AC_STRUCT_ST_BLKSIZE'
5210
5211`AC_ST_BLOCKS'
5212     `AC_STRUCT_ST_BLOCKS'
5213
5214`AC_ST_RDEV'
5215     `AC_STRUCT_ST_RDEV'
5216
5217`AC_SYS_SIGLIST_DECLARED'
5218     `AC_DECL_SYS_SIGLIST'
5219
5220`AC_TEST_CPP'
5221     `AC_TRY_CPP'
5222
5223`AC_TEST_PROGRAM'
5224     `AC_TRY_RUN'
5225
5226`AC_TIMEZONE'
5227     `AC_STRUCT_TIMEZONE'
5228
5229`AC_TIME_WITH_SYS_TIME'
5230     `AC_HEADER_TIME'
5231
5232`AC_UID_T'
5233     `AC_TYPE_UID_T'
5234
5235`AC_UTIME_NULL'
5236     `AC_FUNC_UTIME_NULL'
5237
5238`AC_VFORK'
5239     `AC_FUNC_VFORK'
5240
5241`AC_VPRINTF'
5242     `AC_FUNC_VPRINTF'
5243
5244`AC_WAIT3'
5245     `AC_FUNC_WAIT3'
5246
5247`AC_WARN'
5248     `AC_MSG_WARN'
5249
5250`AC_WORDS_BIGENDIAN'
5251     `AC_C_BIGENDIAN'
5252
5253`AC_YYTEXT_POINTER'
5254     `AC_DECL_YYTEXT'
5255
5256
5257File: autoconf.info,  Node: Environment Variable Index,  Next: Output Variable Index,  Prev: Old Macro Names,  Up: Top
5258
5259Environment Variable Index
5260**************************
5261
5262   This is an alphabetical list of the environment variables that
5263Autoconf checks.
5264
5265* Menu:
5266
5267* AC_MACRODIR <1>:                       Invoking autoupdate.
5268* AC_MACRODIR <2>:                       Invoking autoheader.
5269* AC_MACRODIR <3>:                       Invoking autoreconf.
5270* AC_MACRODIR <4>:                       Invoking autoconf.
5271* AC_MACRODIR <5>:                       Invoking ifnames.
5272* AC_MACRODIR:                           Invoking autoscan.
5273* CONFIG_FILES:                          Invoking config.status.
5274* CONFIG_HEADERS:                        Invoking config.status.
5275* CONFIG_SHELL:                          Invoking config.status.
5276* CONFIG_SITE:                           Site Defaults.
5277* CONFIG_STATUS:                         Invoking config.status.
5278* SIMPLE_BACKUP_SUFFIX:                  Invoking autoupdate.
5279
5280
5281File: autoconf.info,  Node: Output Variable Index,  Next: Preprocessor Symbol Index,  Prev: Environment Variable Index,  Up: Top
5282
5283Output Variable Index
5284*********************
5285
5286   This is an alphabetical list of the variables that Autoconf can
5287substitute into files that it creates, typically one or more
5288`Makefile's.  *Note Setting Output Variables::, for more information on
5289how this is done.
5290
5291* Menu:
5292
5293* ALLOCA:                                Particular Functions.
5294* AWK:                                   Particular Programs.
5295* bindir:                                Preset Output Variables.
5296* build:                                 System Type Variables.
5297* build_alias:                           System Type Variables.
5298* build_cpu:                             System Type Variables.
5299* build_os:                              System Type Variables.
5300* build_vendor:                          System Type Variables.
5301* CC <1>:                                UNIX Variants.
5302* CC:                                    Particular Programs.
5303* CFLAGS <1>:                            Particular Programs.
5304* CFLAGS:                                Preset Output Variables.
5305* configure_input:                       Preset Output Variables.
5306* CPP:                                   Particular Programs.
5307* CPPFLAGS:                              Preset Output Variables.
5308* CXX:                                   Particular Programs.
5309* CXXCPP:                                Particular Programs.
5310* CXXFLAGS <1>:                          Particular Programs.
5311* CXXFLAGS:                              Preset Output Variables.
5312* datadir:                               Preset Output Variables.
5313* DEFS:                                  Preset Output Variables.
5314* exec_prefix:                           Preset Output Variables.
5315* EXEEXT:                                System Services.
5316* F77:                                   Particular Programs.
5317* FFLAGS <1>:                            Particular Programs.
5318* FFLAGS:                                Preset Output Variables.
5319* FLIBS:                                 Fortran 77 Compiler Characteristics.
5320* host:                                  System Type Variables.
5321* host_alias:                            System Type Variables.
5322* host_cpu:                              System Type Variables.
5323* host_os:                               System Type Variables.
5324* host_vendor:                           System Type Variables.
5325* includedir:                            Preset Output Variables.
5326* infodir:                               Preset Output Variables.
5327* INSTALL:                               Particular Programs.
5328* INSTALL_DATA:                          Particular Programs.
5329* INSTALL_PROGRAM:                       Particular Programs.
5330* INSTALL_SCRIPT:                        Particular Programs.
5331* KMEM_GROUP:                            Particular Functions.
5332* LDFLAGS:                               Preset Output Variables.
5333* LEX:                                   Particular Programs.
5334* LEX_OUTPUT_ROOT:                       Particular Programs.
5335* LEXLIB:                                Particular Programs.
5336* libdir:                                Preset Output Variables.
5337* libexecdir:                            Preset Output Variables.
5338* LIBOBJS <1>:                           Structures.
5339* LIBOBJS <2>:                           Generic Functions.
5340* LIBOBJS:                               Particular Functions.
5341* LIBS <1>:                              UNIX Variants.
5342* LIBS:                                  Preset Output Variables.
5343* LN_S:                                  Particular Programs.
5344* localstatedir:                         Preset Output Variables.
5345* mandir:                                Preset Output Variables.
5346* NEED_SETGID:                           Particular Functions.
5347* OBJEXT:                                System Services.
5348* oldincludedir:                         Preset Output Variables.
5349* prefix:                                Preset Output Variables.
5350* program_transform_name:                Transforming Names.
5351* RANLIB:                                Particular Programs.
5352* sbindir:                               Preset Output Variables.
5353* SET_MAKE:                              Output.
5354* sharedstatedir:                        Preset Output Variables.
5355* srcdir:                                Preset Output Variables.
5356* subdirs:                               Subdirectories.
5357* sysconfdir:                            Preset Output Variables.
5358* target:                                System Type Variables.
5359* target_alias:                          System Type Variables.
5360* target_cpu:                            System Type Variables.
5361* target_os:                             System Type Variables.
5362* target_vendor:                         System Type Variables.
5363* top_srcdir:                            Preset Output Variables.
5364* X_CFLAGS:                              System Services.
5365* X_EXTRA_LIBS:                          System Services.
5366* X_LIBS:                                System Services.
5367* X_PRE_LIBS:                            System Services.
5368* YACC:                                  Particular Programs.
5369
5370
5371File: autoconf.info,  Node: Preprocessor Symbol Index,  Next: Macro Index,  Prev: Output Variable Index,  Up: Top
5372
5373Preprocessor Symbol Index
5374*************************
5375
5376   This is an alphabetical list of the C preprocessor symbols that the
5377Autoconf macros define.  To work with Autoconf, C source code needs to
5378use these names in `#if' directives.
5379
5380* Menu:
5381
5382* __CHAR_UNSIGNED__:                     C Compiler Characteristics.
5383* _ALL_SOURCE:                           UNIX Variants.
5384* _MINIX:                                UNIX Variants.
5385* _POSIX_1_SOURCE:                       UNIX Variants.
5386* _POSIX_SOURCE:                         UNIX Variants.
5387* _POSIX_VERSION:                        Particular Headers.
5388* C_ALLOCA:                              Particular Functions.
5389* CLOSEDIR_VOID:                         Particular Functions.
5390* const:                                 C Compiler Characteristics.
5391* DGUX:                                  Particular Functions.
5392* DIRENT:                                Particular Headers.
5393* F77_NO_MINUS_C_MINUS_O:                Particular Programs.
5394* GETGROUPS_T:                           Particular Typedefs.
5395* GETLODAVG_PRIVILEGED:                  Particular Functions.
5396* GETPGRP_VOID:                          Particular Functions.
5397* gid_t:                                 Particular Typedefs.
5398* HAVE_ALLOCA_H:                         Particular Functions.
5399* HAVE_CONFIG_H:                         Configuration Headers.
5400* HAVE_DIRENT_H:                         Particular Headers.
5401* HAVE_DOPRNT:                           Particular Functions.
5402* HAVE_FUNCTION:                         Generic Functions.
5403* HAVE_GETMNTENT:                        Particular Functions.
5404* HAVE_HEADER:                           Generic Headers.
5405* HAVE_LONG_DOUBLE:                      C Compiler Characteristics.
5406* HAVE_LONG_FILE_NAMES:                  System Services.
5407* HAVE_MMAP:                             Particular Functions.
5408* HAVE_NDIR_H:                           Particular Headers.
5409* HAVE_RESTARTABLE_SYSCALLS:             System Services.
5410* HAVE_ST_BLKSIZE:                       Structures.
5411* HAVE_ST_BLOCKS:                        Structures.
5412* HAVE_ST_RDEV:                          Structures.
5413* HAVE_STRCOLL:                          Particular Functions.
5414* HAVE_STRFTIME:                         Particular Functions.
5415* HAVE_STRINGIZE:                        C Compiler Characteristics.
5416* HAVE_SYS_DIR_H:                        Particular Headers.
5417* HAVE_SYS_NDIR_H:                       Particular Headers.
5418* HAVE_SYS_WAIT_H:                       Particular Headers.
5419* HAVE_TM_ZONE:                          Structures.
5420* HAVE_TZNAME:                           Structures.
5421* HAVE_UNISTD_H:                         Particular Headers.
5422* HAVE_UTIME_NULL:                       Particular Functions.
5423* HAVE_VFORK_H:                          Particular Functions.
5424* HAVE_VPRINTF:                          Particular Functions.
5425* HAVE_WAIT3:                            Particular Functions.
5426* inline:                                C Compiler Characteristics.
5427* INT_16_BITS:                           C Compiler Characteristics.
5428* LONG_64_BITS:                          C Compiler Characteristics.
5429* MAJOR_IN_MKDEV:                        Particular Headers.
5430* MAJOR_IN_SYSMACROS:                    Particular Headers.
5431* mode_t:                                Particular Typedefs.
5432* NDIR:                                  Particular Headers.
5433* NEED_MEMORY_H:                         Particular Headers.
5434* NEED_SETGID:                           Particular Functions.
5435* NLIST_NAME_UNION:                      Particular Functions.
5436* NLIST_STRUCT:                          Particular Functions.
5437* NO_MINUS_C_MINUS_O:                    Particular Programs.
5438* off_t:                                 Particular Typedefs.
5439* pid_t:                                 Particular Typedefs.
5440* RETSIGTYPE:                            Particular Typedefs.
5441* SELECT_TYPE_ARG1:                      Particular Functions.
5442* SELECT_TYPE_ARG234:                    Particular Functions.
5443* SELECT_TYPE_ARG5:                      Particular Functions.
5444* SETPGRP_VOID:                          Particular Functions.
5445* SETVBUF_REVERSED:                      Particular Functions.
5446* size_t:                                Particular Typedefs.
5447* STDC_HEADERS:                          Particular Headers.
5448* SVR4:                                  Particular Functions.
5449* SYS_SIGLIST_DECLARED:                  Particular Headers.
5450* SYSDIR:                                Particular Headers.
5451* SYSNDIR:                               Particular Headers.
5452* TIME_WITH_SYS_TIME:                    Structures.
5453* TM_IN_SYS_TIME:                        Structures.
5454* uid_t:                                 Particular Typedefs.
5455* UMAX:                                  Particular Functions.
5456* UMAX4_3:                               Particular Functions.
5457* USG:                                   Particular Headers.
5458* vfork:                                 Particular Functions.
5459* VOID_CLOSEDIR:                         Particular Headers.
5460* WORDS_BIGENDIAN:                       C Compiler Characteristics.
5461* YYTEXT_POINTER:                        Particular Programs.
5462
5463
5464File: autoconf.info,  Node: Macro Index,  Prev: Preprocessor Symbol Index,  Up: Top
5465
5466Macro Index
5467***********
5468
5469   This is an alphabetical list of the Autoconf macros.  To make the
5470list easier to use, the macros are listed without their preceding `AC_'.
5471
5472* Menu:
5473
5474* AIX:                                   UNIX Variants.
5475* ALLOCA:                                Old Macro Names.
5476* ARG_ARRAY:                             Old Macro Names.
5477* ARG_ENABLE:                            Package Options.
5478* ARG_PROGRAM:                           Transforming Names.
5479* ARG_WITH:                              External Software.
5480* BEFORE:                                Suggested Ordering.
5481* C_BIGENDIAN:                           C Compiler Characteristics.
5482* C_CHAR_UNSIGNED:                       C Compiler Characteristics.
5483* C_CONST:                               C Compiler Characteristics.
5484* C_CROSS:                               Test Programs.
5485* C_INLINE:                              C Compiler Characteristics.
5486* C_LONG_DOUBLE:                         C Compiler Characteristics.
5487* C_STRINGIZE:                           C Compiler Characteristics.
5488* CACHE_CHECK:                           Caching Results.
5489* CACHE_LOAD:                            Caching Results.
5490* CACHE_SAVE:                            Caching Results.
5491* CACHE_VAL:                             Caching Results.
5492* CANONICAL_HOST:                        Canonicalizing.
5493* CANONICAL_SYSTEM:                      Canonicalizing.
5494* CHAR_UNSIGNED:                         Old Macro Names.
5495* CHECK_FILE:                            Generic Programs.
5496* CHECK_FILES:                           Generic Programs.
5497* CHECK_FUNC:                            Generic Functions.
5498* CHECK_FUNCS:                           Generic Functions.
5499* CHECK_HEADER:                          Generic Headers.
5500* CHECK_HEADERS:                         Generic Headers.
5501* CHECK_LIB:                             Libraries.
5502* CHECK_PROG:                            Generic Programs.
5503* CHECK_PROGS:                           Generic Programs.
5504* CHECK_SIZEOF:                          C Compiler Characteristics.
5505* CHECK_TOOL:                            Generic Programs.
5506* CHECK_TYPE:                            Generic Typedefs.
5507* CHECKING:                              Printing Messages.
5508* COMPILE_CHECK:                         Examining Libraries.
5509* CONFIG_AUX_DIR:                        Input.
5510* CONFIG_HEADER:                         Configuration Headers.
5511* CONFIG_SUBDIRS:                        Subdirectories.
5512* CONST:                                 Old Macro Names.
5513* CROSS_CHECK:                           Old Macro Names.
5514* CYGWIN:                                System Services.
5515* DECL_SYS_SIGLIST:                      Particular Headers.
5516* DECL_YYTEXT:                           Particular Programs.
5517* DEFINE:                                Defining Symbols.
5518* DEFINE_UNQUOTED:                       Defining Symbols.
5519* DEFUN:                                 Macro Definitions.
5520* DIR_HEADER:                            Particular Headers.
5521* DYNIX_SEQ:                             UNIX Variants.
5522* EGREP_CPP:                             Examining Declarations.
5523* EGREP_HEADER:                          Examining Declarations.
5524* ENABLE:                                Package Options.
5525* ERROR:                                 Old Macro Names.
5526* EXEEXT:                                System Services.
5527* F77_LIBRARY_LDFLAGS:                   Fortran 77 Compiler Characteristics.
5528* FIND_X:                                Old Macro Names.
5529* FIND_XTRA:                             Old Macro Names.
5530* FUNC_ALLOCA:                           Particular Functions.
5531* FUNC_CHECK:                            Old Macro Names.
5532* FUNC_CLOSEDIR_VOID:                    Particular Functions.
5533* FUNC_FNMATCH:                          Particular Functions.
5534* FUNC_GETLOADAVG:                       Particular Functions.
5535* FUNC_GETMNTENT:                        Particular Functions.
5536* FUNC_GETPGRP:                          Particular Functions.
5537* FUNC_MEMCMP:                           Particular Functions.
5538* FUNC_MMAP:                             Particular Functions.
5539* FUNC_SELECT_ARGTYPES:                  Particular Functions.
5540* FUNC_SETPGRP:                          Particular Functions.
5541* FUNC_SETVBUF_REVERSED:                 Particular Functions.
5542* FUNC_STRCOLL:                          Particular Functions.
5543* FUNC_STRFTIME:                         Particular Functions.
5544* FUNC_UTIME_NULL:                       Particular Functions.
5545* FUNC_VFORK:                            Particular Functions.
5546* FUNC_VPRINTF:                          Particular Functions.
5547* FUNC_WAIT3:                            Particular Functions.
5548* GCC_TRADITIONAL:                       Old Macro Names.
5549* GETGROUPS_T:                           Old Macro Names.
5550* GETLOADAVG:                            Old Macro Names.
5551* HAVE_FUNCS:                            Old Macro Names.
5552* HAVE_HEADERS:                          Old Macro Names.
5553* HAVE_LIBRARY:                          Libraries.
5554* HAVE_POUNDBANG:                        Old Macro Names.
5555* HEADER_CHECK:                          Old Macro Names.
5556* HEADER_DIRENT:                         Particular Headers.
5557* HEADER_EGREP:                          Old Macro Names.
5558* HEADER_MAJOR:                          Particular Headers.
5559* HEADER_STAT:                           Structures.
5560* HEADER_STDC:                           Particular Headers.
5561* HEADER_SYS_WAIT:                       Particular Headers.
5562* HEADER_TIME:                           Structures.
5563* INIT:                                  Input.
5564* INLINE:                                Old Macro Names.
5565* INT_16_BITS:                           C Compiler Characteristics.
5566* IRIX_SUN:                              UNIX Variants.
5567* ISC_POSIX:                             UNIX Variants.
5568* LANG_C:                                Language Choice.
5569* LANG_CPLUSPLUS:                        Language Choice.
5570* LANG_FORTRAN77:                        Language Choice.
5571* LANG_RESTORE:                          Language Choice.
5572* LANG_SAVE:                             Language Choice.
5573* LINK_FILES:                            Using System Type.
5574* LN_S:                                  Old Macro Names.
5575* LONG_64_BITS:                          C Compiler Characteristics.
5576* LONG_DOUBLE:                           Old Macro Names.
5577* LONG_FILE_NAMES:                       Old Macro Names.
5578* MAJOR_HEADER:                          Old Macro Names.
5579* MEMORY_H:                              Particular Headers.
5580* MINGW32:                               System Services.
5581* MINIX:                                 UNIX Variants.
5582* MINUS_C_MINUS_O:                       Old Macro Names.
5583* MMAP:                                  Old Macro Names.
5584* MODE_T:                                Old Macro Names.
5585* MSG_CHECKING:                          Printing Messages.
5586* MSG_ERROR:                             Printing Messages.
5587* MSG_RESULT:                            Printing Messages.
5588* MSG_WARN:                              Printing Messages.
5589* OBJEXT:                                System Services.
5590* OBSOLETE:                              Obsolete Macros.
5591* OFF_T:                                 Old Macro Names.
5592* OUTPUT:                                Output.
5593* PATH_PROG:                             Generic Programs.
5594* PATH_PROGS:                            Generic Programs.
5595* PATH_X:                                System Services.
5596* PATH_XTRA:                             System Services.
5597* PID_T:                                 Old Macro Names.
5598* PREFIX:                                Old Macro Names.
5599* PREFIX_PROGRAM:                        Default Prefix.
5600* PREREQ:                                Versions.
5601* PROG_AWK:                              Particular Programs.
5602* PROG_CC:                               Particular Programs.
5603* PROG_CC_C_O:                           Particular Programs.
5604* PROG_CPP:                              Particular Programs.
5605* PROG_CXX:                              Particular Programs.
5606* PROG_CXXCPP:                           Particular Programs.
5607* PROG_F77_C_O:                          Particular Programs.
5608* PROG_FORTRAN:                          Particular Programs.
5609* PROG_GCC_TRADITIONAL:                  Particular Programs.
5610* PROG_INSTALL:                          Particular Programs.
5611* PROG_LEX:                              Particular Programs.
5612* PROG_LN_S:                             Particular Programs.
5613* PROG_MAKE_SET:                         Output.
5614* PROG_RANLIB:                           Particular Programs.
5615* PROG_YACC:                             Particular Programs.
5616* PROGRAM_CHECK:                         Old Macro Names.
5617* PROGRAM_EGREP:                         Old Macro Names.
5618* PROGRAM_PATH:                          Old Macro Names.
5619* PROGRAMS_CHECK:                        Old Macro Names.
5620* PROGRAMS_PATH:                         Old Macro Names.
5621* PROVIDE:                               Prerequisite Macros.
5622* REMOTE_TAPE:                           Old Macro Names.
5623* REPLACE_FUNCS:                         Generic Functions.
5624* REQUIRE:                               Prerequisite Macros.
5625* REQUIRE_CPP:                           Language Choice.
5626* RESTARTABLE_SYSCALLS:                  Old Macro Names.
5627* RETSIGTYPE:                            Old Macro Names.
5628* REVISION:                              Versions.
5629* RSH:                                   Old Macro Names.
5630* SCO_INTL:                              UNIX Variants.
5631* SEARCH_LIBS:                           Libraries.
5632* SET_MAKE:                              Old Macro Names.
5633* SETVBUF_REVERSED:                      Old Macro Names.
5634* SIZE_T:                                Old Macro Names.
5635* SIZEOF_TYPE:                           Old Macro Names.
5636* ST_BLKSIZE:                            Old Macro Names.
5637* ST_BLOCKS:                             Old Macro Names.
5638* ST_RDEV:                               Old Macro Names.
5639* STAT_MACROS_BROKEN <1>:                Old Macro Names.
5640* STAT_MACROS_BROKEN:                    Structures.
5641* STDC_HEADERS:                          Old Macro Names.
5642* STRCOLL:                               Old Macro Names.
5643* STRUCT_ST_BLKSIZE:                     Structures.
5644* STRUCT_ST_BLOCKS:                      Structures.
5645* STRUCT_ST_RDEV:                        Structures.
5646* STRUCT_TIMEZONE:                       Structures.
5647* STRUCT_TM:                             Structures.
5648* SUBST:                                 Setting Output Variables.
5649* SUBST_FILE:                            Setting Output Variables.
5650* SYS_INTERPRETER:                       System Services.
5651* SYS_LONG_FILE_NAMES:                   System Services.
5652* SYS_RESTARTABLE_SYSCALLS:              System Services.
5653* SYS_SIGLIST_DECLARED:                  Old Macro Names.
5654* TEST_CPP:                              Old Macro Names.
5655* TEST_PROGRAM:                          Old Macro Names.
5656* TIME_WITH_SYS_TIME:                    Old Macro Names.
5657* TIMEZONE:                              Old Macro Names.
5658* TRY_COMPILE:                           Examining Syntax.
5659* TRY_CPP:                               Examining Declarations.
5660* TRY_LINK:                              Examining Libraries.
5661* TRY_LINK_FUNC:                         Examining Libraries.
5662* TRY_RUN:                               Test Programs.
5663* TYPE_GETGROUPS:                        Particular Typedefs.
5664* TYPE_MODE_T:                           Particular Typedefs.
5665* TYPE_OFF_T:                            Particular Typedefs.
5666* TYPE_PID_T:                            Particular Typedefs.
5667* TYPE_SIGNAL:                           Particular Typedefs.
5668* TYPE_SIZE_T:                           Particular Typedefs.
5669* TYPE_UID_T:                            Particular Typedefs.
5670* UID_T:                                 Old Macro Names.
5671* UNISTD_H:                              Particular Headers.
5672* USG:                                   Particular Headers.
5673* UTIME_NULL:                            Old Macro Names.
5674* VALIDATE_CACHED_SYSTEM_TUPLE:          Canonicalizing.
5675* VERBOSE:                               Printing Messages.
5676* VFORK:                                 Old Macro Names.
5677* VPRINTF:                               Old Macro Names.
5678* WAIT3:                                 Old Macro Names.
5679* WARN:                                  Old Macro Names.
5680* WITH:                                  External Software.
5681* WORDS_BIGENDIAN:                       Old Macro Names.
5682* XENIX_DIR:                             UNIX Variants.
5683* YYTEXT_POINTER:                        Old Macro Names.
5684
5685
5686
5687Tag Table:
5688Node: Top1209
5689Node: Introduction9711
5690Node: Making configure Scripts13551
5691Node: Writing configure.in16632
5692Node: Invoking autoscan20365
5693Node: Invoking ifnames22670
5694Node: Invoking autoconf24160
5695Node: Invoking autoreconf25998
5696Node: Setup28834
5697Node: Input29739
5698Node: Output31476
5699Node: Makefile Substitutions35113
5700Node: Preset Output Variables36716
5701Node: Build Directories41585
5702Node: Automatic Remaking43218
5703Node: Configuration Headers45304
5704Node: Header Templates47818
5705Node: Invoking autoheader49027
5706Node: Subdirectories52175
5707Node: Default Prefix53570
5708Node: Versions54974
5709Node: Existing Tests56878
5710Node: Alternative Programs58426
5711Node: Particular Programs59113
5712Node: Generic Programs67165
5713Node: Libraries70471
5714Node: Library Functions73545
5715Node: Particular Functions74103
5716Node: Generic Functions81297
5717Node: Header Files83401
5718Node: Particular Headers83960
5719Node: Generic Headers90952
5720Node: Structures92254
5721Node: Typedefs94491
5722Node: Particular Typedefs94997
5723Node: Generic Typedefs96214
5724Node: C Compiler Characteristics96671
5725Node: Fortran 77 Compiler Characteristics99542
5726Node: System Services101245
5727Node: UNIX Variants104381
5728Node: Writing Tests106400
5729Node: Examining Declarations108393
5730Node: Examining Syntax110885
5731Node: Examining Libraries112330
5732Node: Run Time116040
5733Node: Test Programs117028
5734Node: Guidelines119356
5735Node: Test Functions120545
5736Node: Portable Shell122088
5737Node: Testing Values and Files124020
5738Node: Multiple Cases125675
5739Node: Language Choice126873
5740Node: Results128975
5741Node: Defining Symbols129737
5742Node: Setting Output Variables133033
5743Node: Caching Results134879
5744Node: Cache Variable Names137625
5745Node: Cache Files139109
5746Node: Printing Messages141946
5747Node: Writing Macros145394
5748Node: Macro Definitions146041
5749Node: Macro Names147169
5750Node: Quoting149620
5751Node: Dependencies Between Macros151522
5752Node: Prerequisite Macros152169
5753Node: Suggested Ordering153660
5754Node: Obsolete Macros155190
5755Node: Manual Configuration156414
5756Node: Specifying Names157313
5757Node: Canonicalizing159214
5758Node: System Type Variables160726
5759Node: Using System Type161473
5760Node: Site Configuration162967
5761Node: External Software163740
5762Node: Package Options166943
5763Node: Site Details169690
5764Node: Transforming Names170913
5765Node: Transformation Options172091
5766Node: Transformation Examples172584
5767Node: Transformation Rules174152
5768Node: Site Defaults175561
5769Node: Invoking configure179467
5770Node: Basic Installation180416
5771Node: Compilers and Options182996
5772Node: Multiple Architectures183645
5773Node: Installation Names184631
5774Node: Optional Features185815
5775Node: System Type186585
5776Node: Sharing Defaults187607
5777Node: Operation Controls188231
5778Node: Invoking config.status189217
5779Node: Questions192605
5780Node: Distributing193137
5781Node: Why GNU m4194281
5782Node: Bootstrapping195094
5783Node: Why Not Imake195710
5784Node: Upgrading200119
5785Node: Changed File Names201640
5786Node: Changed Makefiles202394
5787Node: Changed Macros203490
5788Node: Invoking autoupdate204737
5789Node: Changed Results206328
5790Node: Changed Macro Writing208430
5791Node: History209693
5792Node: Genesis210485
5793Node: Exodus211674
5794Node: Leviticus214723
5795Node: Numbers216246
5796Node: Deuteronomy218162
5797Node: Old Macro Names220826
5798Node: Environment Variable Index223875
5799Node: Output Variable Index224889
5800Node: Preprocessor Symbol Index230087
5801Node: Macro Index235373
5802
5803End Tag Table
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