SYNOPSIS

autoconf is a package for creating Bourne shell scripts to configure source code packages using templates and an `m4' macro package.

HISTORY

Autoconf was written chiefly by David Mackenzie, with input from many people, starting in 1991. When this page was started in 1997, the most recent releases (2.12 and 2.10) were used in hundreds of programs. Like the Perl-based dist, autoconf is essentially a library of useful tests that a developer can put together to ask questions about a system to determine which features it has. Both are customizable, but dist is not as widely used. Autoconf is simpler, easier to learn.

I have been using autoconf since June 1994, when Kevin Buettner started writing a configure script for vile. I started a script for my directory editor ded. at that time, as well. Both of these scripts differ philosophically from autoconf's design. The designer of autoconf decided that there should be two ways to generate C-style definitions:

as -D options in a makefile
as substitions for #undef in a template header file (e.g., config.h).

Autoconf is not design-neutral; sometimes this makes it awkward. Kevin chose a third alternative for vile, which we have kept because the first two options are unpalatable (the first because of tool limitations, and the second because it imposes unnecessary work on the maintainers, and maintaining the template is error-prone):

generate the header file directly from the definitions that are found during the configure process.

Since then, I've written simple configure scripts for several programs, as well as more complex scripts for a few (ncurses, tin, lynx, xterm).

PATCHES

I find these patches useful:

971222 simplify the way we generate the config.h file. This patch adds a parameter to AC_OUTPUT that tells it to use the definitions that it has built up to directly substitute into the template header, which can then be as simple as the single line
```
	@DEFS@
```
The new parameter ("sort" or "cat") tells autoconf how to process the generated definitions. I prefer to sort the definitions since it eases comparison of headers for different platforms. Using "cat", will generate the definitions in the order that the configure script defines them.
971222-emx a patch from Juan Jose Garcia Ripoll <worm@arrakis.es>, originally for autoconf 2.10, for an OS/2 EMX-specific version of autoconf.
971230 my own patch, for working around machines with limited environment space. AC_DIVERT_HELP splits long help messages into smaller pieces, which are emitted as a series of here-documents rather than attempt to keep their text in an environment variable. I use this macro to replace logic in autoconf's AC_ARG_ENABLE and AC_ARG_WITH, so it works without requiring you to change your configure.in or aclocal.m4 files.
This introduces a minor incompatibility: generating the here-document directly causes escaped quotes in the help-text to be displayed with the spurious backslashes. Once you have converted to this macro, you will probably want to cleanup the help message text.
autoconf 2.13 20030927 This is the most recent version of the autoconf 2.13 patch.
autoconf 2.13 20020210 EMX This is the most recent version of the autoconf 2.13 patch for EMX.
autoconf 2.52 20030208 This is a resync of the patch (not EMX) against autoconf 2.52 (lightly tested: autoconf 2.5x introduces a number of incompatibilities with autoconf 2.13). The patch also includes some fixes for minor bugs which were reported/ignored on the autoconf mailing list. Finally, it repairs some of the intentional incompatibilites.
autoconf 2.57 20030810 Even more lightly tested -- having noticed some new autoconf defects as I resync'd this patch, but unrelated to the patch.

Occasionally someone asks why I use autoconf 2.13 (actually the question should be why I maintain configure scripts which are compatible with 2.13). The autoconf group, rather than focusing on making a reliable product, is using ongoing development as a basis for experimentation. With some care, it is possible to construct configure.in files which are compatible between 2.13 and 2.5x. However, the standard response to reports of incompatibilities between the two is to blame 2.13 for "bugs" (ostensibly for quoting issues, but in fact on any issue without further analysis). Here is a recap of recent autoconf versions and release dates:

2.59 (2003-11-06) About nine months overdue (to repair 2.57). Design flaws such as its interdependence with automake are still not addressed.
2.58 (2003-11-04) Administrative blunder.
2.57 (2002-12-03) Back up to beta quality! Within a few weeks a handful of serious bugs were reported, making it less useful than 2.52.
2.56 (2002-11-15) Fixes an administrative blunder.
2.55 Dead on arrival.
2.54 (2002-09-13) Do not use: it was not tested with other "make" programs than GNU make.
2.53 (2002-03-18) Too many initial bug reports to bother with. Features incomplete support for OS/2 EMX.
2.52 (2001-07-18) Moderately stable (beta quality).
2.51 (2001-07-17) Dead on arrival. The changelog around 2.51 does not mention that the associated config.guess/config.sub had a syntax error (it wrote extra text to the output). This was silently fixed in the 2.52 version.
2.50 (2001-05-21) Do not use (alpha quality). It is compatible with 2.13 only for trivial configure.in's because the conventions for cached information were changed.

Generally the changelog of autoconf does not reflect the issues (serious defects and incompatibilities) reported on their mailing list.