autoconf: Versioning
1
1 4.2 Dealing with Autoconf versions
1 ==================================
1
1 The following optional macros can be used to help choose the minimum
1 version of Autoconf that can successfully compile a given
1 `configure.ac'.
1
1 -- Macro: AC_PREREQ (VERSION)
1 Ensure that a recent enough version of Autoconf is being used. If
1 the version of Autoconf being used to create `configure' is
1 earlier than VERSION, print an error message to the standard error
1 output and exit with failure (exit status is 63). For example:
1
1 AC_PREREQ([2.69])
1
1 This macro may be used before `AC_INIT'.
1
1 -- Macro: AC_AUTOCONF_VERSION
1 This macro was introduced in Autoconf 2.62. It identifies the
1 version of Autoconf that is currently parsing the input file, in a
11 format suitable for `m4_version_compare' (⇒
m4_version_compare); in other words, for this release of
1 Autoconf, its value is `2.69'. One potential use of this macro is
1 for writing conditional fallbacks based on when a feature was
1 added to Autoconf, rather than using `AC_PREREQ' to require the
1 newer version of Autoconf. However, remember that the Autoconf
1 philosophy favors feature checks over version checks.
1
1 You should not expand this macro directly; use
1 `m4_defn([AC_AUTOCONF_VERSION])' instead. This is because some
1 users might have a beta version of Autoconf installed, with
1 arbitrary letters included in its version string. This means it
1 is possible for the version string to contain the name of a
1 defined macro, such that expanding `AC_AUTOCONF_VERSION' would
1 trigger the expansion of that macro during rescanning, and change
1 the version string to be different than what you intended to check.
1