Autoconf Reference Guide - 1 Introduction

A physicist, an engineer, and a computer scientist were discussing the

nature of God. “Surely a Physicist,” said the physicist, “because

early in the Creation, God made Light; and you know, Maxwell's

equations, the dual nature of electromagnetic waves, the relativistic

consequences...” “An Engineer!,” said the engineer, “because

before making Light, God split the Chaos into Land and Water; it takes a

hell of an engineer to handle that big amount of mud, and orderly

separation of solids from liquids...” The computer scientist

shouted: “And the Chaos, where do you think it was coming from, hmm?”

—Anonymous

Autoconf is a tool for producing shell scripts that automatically configure software source code packages to adapt to many kinds of Posix-like systems. The configuration scripts produced by Autoconf are independent of Autoconf when they are run, so their users do not need to have Autoconf.

The configuration scripts produced by Autoconf require no manual user intervention when run; they do not normally even need an argument specifying the system type. Instead, they individually test for the presence of each feature that the software package they are for might need. (Before each check, they print a one-line message stating what they are checking for, so the user doesn't get too bored while waiting for the script to finish.) As a result, they deal well with systems that are hybrids or customized from the more common Posix variants. There is no need to maintain files that list the features supported by each release of each variant of Posix.

For each software package that Autoconf is used with, it creates a configuration script from a template file that lists the system features that the package needs or can use. After the shell code to recognize and respond to a system feature has been written, Autoconf allows it to be shared by many software packages that can use (or need) that feature. If it later turns out that the shell code needs adjustment for some reason, it needs to be changed in only one place; all of the configuration scripts can be regenerated automatically to take advantage of the updated code.

The Metaconfig package is similar in purpose to Autoconf, but the scripts it produces require manual user intervention, which is quite inconvenient when configuring large source trees. Unlike Metaconfig scripts, Autoconf scripts can support cross-compiling, if some care is taken in writing them.

Autoconf does not solve all problems related to making portable software packages—for a more complete solution, it should be used in concert with other GNU build tools like Automake and Libtool. These other tools take on jobs like the creation of a portable, recursive makefile with all of the standard targets, linking of shared libraries, and so on. See The GNU Build System, for more information.

Autoconf imposes some restrictions on the names of macros used with #if in C programs (see Preprocessor Symbol Index).

Autoconf requires GNU M4 in order to generate the scripts. It uses features that some versions of M4, including GNU M4 1.3, do not have. You should use version 1.4.4 or later of GNU M4.

See Autoconf 1, for information about upgrading from version 1. See History, for the story of Autoconf's development. See FAQ, for answers to some common questions about Autoconf.

See the Autoconf web page for up-to-date information, details on the mailing lists, pointers to a list of known bugs, etc.

If possible, first check that your bug is not already solved in current development versions, and that it has not been reported yet. Be sure to include all the needed information and a short configure.ac that demonstrates the problem.

Autoconf's development tree is accessible via anonymous CVS; see the Autoconf Summary for details. Patches relative to the current CVS version can be sent for review to the Autoconf Patches mailing list. Past patches are archived.

Because of its mission, the Autoconf package itself includes only a set of often-used macros that have already demonstrated their usefulness. Nevertheless, if you wish to share your macros, or find existing ones, see the Autoconf Macro Archive, which is kindly run by Peter Simons.