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