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Autoconf

   This manual is for GNU Autoconf (version 2.59, 5 November 2003), a
package for creating scripts to configure source code packages using
templates and an M4 macro package.

   Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
2002, 2003 Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.1 or any later version published by the Free Software
     Foundation; with no Invariant Sections, with the Front-Cover texts
     being "A GNU Manual," and with the Back-Cover Texts as in (a)
     below.  A copy of the license is included in the section entitled
     "GNU Free Documentation License."

     (a) The FSF's Back-Cover Text is: "You have freedom to copy and
     modify this GNU Manual, like GNU software.  Copies published by
     the Free Software Foundation raise funds for GNU development."

Introduction	Autoconf's purpose, strengths, and weaknesses
The GNU Build System	A set of tools for portable software packages
Making configure Scripts	How to organize and produce Autoconf scripts
Setup	Initialization and output
Existing Tests	Macros that check for particular features
Writing Tests	How to write new feature checks
Results	What to do with results from feature checks
Programming in M4	Layers on top of which Autoconf is written
Writing Autoconf Macros	Adding new macros to Autoconf
Portable Shell	Shell script portability pitfalls
Manual Configuration	Selecting features that can't be guessed
Site Configuration	Local defaults for `configure'
Running configure Scripts	How to use the Autoconf output
config.status Invocation	Recreating a configuration
Obsolete Constructs	Kept for backward compatibility
Using Autotest	Creating portable test suites
FAQ	Frequent Autoconf Questions, with answers
History	History of Autoconf
Copying This Manual	How to make copies of this manual
Indices	Indices of symbols, concepts, etc.

The GNU Build System

Making `configure' Scripts

Writing `configure.ac'

Initialization and Output Files

Initializing configure	Option processing etc.
Notices	Copyright, version numbers in `configure'
Input	Where Autoconf should find files
Output	Outputting results from the configuration
Configuration Actions	Preparing the output based on results
Configuration Files	Creating output files
Makefile Substitutions	Using output variables in `Makefile's
Configuration Headers	Creating a configuration header file
Configuration Commands	Running arbitrary instantiation commands
Configuration Links	Links depending on the configuration
Subdirectories	Configuring independent packages together
Default Prefix	Changing the default installation prefix

Substitutions in Makefiles

Configuration Header Files

Existing Tests

Common Behavior	Macros' standard schemes
Alternative Programs	Selecting between alternative programs
Files	Checking for the existence of files
Libraries	Library archives that might be missing
Library Functions	C library functions that might be missing
Header Files	Header files that might be missing
Declarations	Declarations that may be missing
Structures	Structures or members that might be missing
Types	Types that might be missing
Compilers and Preprocessors	Checking for compiling programs
System Services	Operating system services
UNIX Variants	Special kludges for specific UNIX variants

Common Behavior

Alternative Programs

Library Functions

Header Files

Declarations

Structures

Types

Compilers and Preprocessors

Writing Tests

Writing Test Programs

Results of Tests

Caching Results

Programming in M4

M4 Quotation

Using `autom4te'

Programming in M4sugar

Writing Autoconf Macros

Dependencies Between Macros

Portable Shell Programming

Manual Configuration

Site Configuration

Transforming Program Names When Installing

Running `configure' Scripts

Obsolete Constructs

Upgrading From Version 1

Upgrading From Version 2.13

Generating Test Suites with Autotest

Using an Autotest Test Suite

Frequent Autoconf Questions, with answers

History of Autoconf

Copying This Manual

Indices

Automake	Escaping Makefile hell
Libtool	Building libraries portably
Pointers	More info on the GNU build system

Writing configure.ac	What to put in an Autoconf input file
autoscan Invocation	Semi-automatic `configure.ac' writing
ifnames Invocation	Listing the conditionals in source code
autoconf Invocation	How to create configuration scripts
autoreconf Invocation	Remaking multiple `configure' scripts

Shell Script Compiler	Autoconf as solution of a problem
Autoconf Language	Programming in Autoconf
configure.ac Layout	Standard organization of `configure.ac'

Preset Output Variables	Output variables that are always set
Installation Directory Variables	Other preset output variables
Build Directories	Supporting multiple concurrent compiles
Automatic Remaking	Makefile rules for configuring

Header Templates	Input for the configuration headers
autoheader Invocation	How to create configuration templates
Autoheader Macros	How to specify CPP templates

Standard Symbols	Symbols defined by the macros
Default Includes	Includes used by the generic macros

Particular Programs	Special handling to find certain programs
Generic Programs	How to find other programs

Function Portability	Pitfalls with usual functions
Particular Functions	Special handling to find certain functions
Generic Functions	How to find other functions

Header Portability	Collected knowledge on common headers
Particular Headers	Special handling to find certain headers
Generic Headers	How to find other headers

Particular Declarations	Macros to check for certain declarations
Generic Declarations	How to find other declarations

Particular Structures	Macros to check for certain structure members
Generic Structures	How to find other structure members

Particular Types	Special handling to find certain types
Generic Types	How to find other types

Specific Compiler Characteristics	Some portability issues
Generic Compiler Characteristics	Language independent tests and features
C Compiler	Checking its characteristics
C++ Compiler	Likewise
Fortran Compiler	Likewise

Language Choice	Selecting which language to use for testing
Writing Test Programs	Forging source files for compilers
Running the Preprocessor	Detecting preprocessor symbols
Running the Compiler	Detecting language or header features
Running the Linker	Detecting library features
Run Time	Testing for run-time features
Systemology	A zoology of operating systems
Multiple Cases	Tests for several possible values

Guidelines	General rules for writing test programs
Test Functions	Avoiding pitfalls in test programs
Generating Sources	Source program boilerplate

Cache Variable Names	Shell variables used in caches
Cache Files	Files `configure' uses for caching
Cache Checkpointing	Loading and saving the cache file

Active Characters	Characters that change the behavior of M4
One Macro Call	Quotation and one macro call
Quotation and Nested Macros	Macros calling macros
Changequote is Evil	Worse than INTERCAL: M4 + changequote
Quadrigraphs	Another way to escape special characters
Quotation Rule Of Thumb	One parenthesis, one quote

autom4te Invocation	A GNU M4 wrapper
Customizing autom4te	Customizing the Autoconf package

Redefined M4 Macros	M4 builtins changed in M4sugar
Evaluation Macros	More quotation and evaluation control
Forbidden Patterns	Catching unexpanded macros

Defining Symbols	Defining C preprocessor symbols
Setting Output Variables	Replacing variables in output files
Caching Results	Speeding up subsequent `configure' runs
Printing Messages	Notifying `configure' users

M4 Quotation	Protecting macros from unwanted expansion
Using autom4te	The Autoconf executables backbone
Programming in M4sugar	Convenient pure M4 macros
Programming in M4sh	Common shell Constructs

Macro Definitions	Basic format of an Autoconf macro
Macro Names	What to call your new macros
Reporting Messages	Notifying `autoconf' users
Dependencies Between Macros	What to do when macros depend on other macros
Obsoleting Macros	Warning about old ways of doing things
Coding Style	Writing Autoconf macros a` la Autoconf

Prerequisite Macros	Ensuring required information
Suggested Ordering	Warning about possible ordering problems

Shellology	A zoology of shells
Here-Documents	Quirks and tricks
File Descriptors	FDs and redirections
File System Conventions	File- and pathnames
Shell Substitutions	Variable and command expansions
Assignments	Varying side effects of assignments
Parentheses	Parentheses in shell scripts
Special Shell Variables	Variables you should not change
Limitations of Builtins	Portable use of not so portable /bin/sh
Limitations of Usual Tools	Portable use of portable tools
Limitations of Make	Portable Makefiles

Specifying Names	Specifying the system type
Canonicalizing	Getting the canonical system type
Using System Type	What to do with the system type

External Software	Working with other optional software
Package Options	Selecting optional features
Pretty Help Strings	Formatting help string
Site Details	Configuring site details
Transforming Names	Changing program names when installing
Site Defaults	Giving `configure' local defaults

Transformation Options	`configure' options to transform names
Transformation Examples	Sample uses of transforming names
Transformation Rules	`Makefile' uses of transforming names

Basic Installation	Instructions for typical cases
Compilers and Options	Selecting compilers and optimization
Multiple Architectures	Compiling for multiple architectures at once
Installation Names	Installing in different directories
Optional Features	Selecting optional features
System Type	Specifying the system type
Sharing Defaults	Setting site-wide defaults for `configure'
Defining Variables	Specifying the compiler etc.
configure Invocation	Changing how `configure' runs

Obsolete config.status Use	Different calling convention
acconfig.h	Additional entries in `config.h.in'
autoupdate Invocation	Automatic update of `configure.ac'
Obsolete Macros	Backward compatibility macros
Autoconf 1	Tips for upgrading your files
Autoconf 2.13	Some fresher tips

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Autoconf

Menu

Changed File Names	Files you might rename
Changed Makefiles	New things to put in `Makefile.in'
Changed Macros	Macro calls you might replace
Changed Results	Changes in how to check test results
Changed Macro Writing	Better ways to write your own macros

Changed Quotation	Broken code which used to work
New Macros	Interaction with foreign macros
Hosts and Cross-Compilation	Bugward compatibility kludges
AC_LIBOBJ vs LIBOBJS	LIBOBJS is a forbidden token
AC_FOO_IFELSE vs AC_TRY_FOO	A more generic scheme for testing sources

Using an Autotest Test Suite	Autotest and the user
Writing testsuite.at	Autotest macros
testsuite Invocation	Running `testsuite' scripts
Making testsuite Scripts	Using autom4te to create `testsuite'

testsuite Scripts	The concepts of Autotest
Autotest Logs	Their contents

Distributing	Distributing `configure' scripts
Why GNU m4	Why not use the standard M4?
Bootstrapping	Autoconf and GNU M4 require each other?
Why Not Imake	Why GNU uses `configure' instead of Imake
Defining Directories	Passing `datadir' to program
autom4te.cache	What is it? Can I remove it?
Present But Cannot Be Compiled	Compiler and Preprocessor Disagree

Genesis	Prehistory and naming of `configure'
Exodus	The plagues of M4 and Perl
Leviticus	The priestly code of portability arrives
Numbers	Growth and contributors
Deuteronomy	Approaching the promises of easy configuration

GNU Free Documentation License	License for copying this manual

Environment Variable Index	Index of environment variables used
Output Variable Index	Index of variables set in output files
Preprocessor Symbol Index	Index of C preprocessor symbols defined
Autoconf Macro Index	Index of Autoconf macros
M4 Macro Index	Index of M4, M4sugar, and M4sh macros
Autotest Macro Index	Index of Autotest macros
Program & Function Index	Index of those with portability problems
Concept Index	General index