Editing Autoconf (section)

== Approach ==
Autoconf is similar to the Metaconfig package used by [[Perl]].  The [[imake]] system formerly used by the [[X Window System]] (up to X11R6.9) is closely related, but has a different philosophy.

The Autoconf approach to [[Porting|portability]] is to test for [[feature (software design)|feature]]s, not for [[Software versioning|versions]]. For example, the native C compiler on SunOS 4 did not support [[C (programming language)|ISO C]]. However, it is possible for the user or administrator to have installed an ISO C-compliant compiler.  A pure version-based approach would not detect the presence of the ISO C compiler, but a feature-testing approach would be able to discover the ISO C compiler the user had installed. The rationale of this approach is to gain the following advantages:

* the configure script can get reasonable results on newer or unknown systems
* it allows [[system administrator|administrator]]s to customize their machines and have the configure script take advantage of the customizations
* there is no need to keep track of minute details of versions, patch numbers, etc., to figure out whether a particular feature is supported or not

Autoconf provides extensive documentation around the non-portability of many POSIX shell constructs to older shells and bugs therein. It also provides M4SH, a macro-based replacement for shell syntax.<ref>{{cite web |title=Portable Shell |url=https://www.gnu.org/software/autoconf/manual/html_node/Portable-Shell.html |website=Autoconf |access-date=20 January 2020}}</ref>