Require an exact Autoconf version.

ChangeLog

@@ -1,3 +1,10 @@
+2012-11-02  Roland McGrath  <roland@hack.frob.com>
+
+	* aclocal.m4 (GLIBC_AUTOCONF_VERSION): New macro.
+	Check that AC_AUTOCONF_VERSION matches it and m4_fatal at
+	autoconf-time if not.
+	* configure.in: Remove AC_PREREQ.
+
 2012-11-02  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>
 
 	* sysdeps/powerpc/sys/platform/ppc.h (__ppc_get_timebase): Use

aclocal.m4

@@ -1,3 +1,13 @@
+dnl We require that everyone use exactly the same Autoconf version so that
+dnl the internal functions defined and used by the main configure script
+dnl match those expected by the fragments.
+m4_define([GLIBC_AUTOCONF_VERSION], [2.68])
+m4_if(m4_defn([AC_AUTOCONF_VERSION]), GLIBC_AUTOCONF_VERSION, [],
+      [m4_fatal(m4_flatten(
+Exactly version GLIBC_AUTOCONF_VERSION of Autoconf is required but you have
+m4_defn([AC_AUTOCONF_VERSION])
+), [63])])dnl
+dnl
 dnl We define the macro GLIBC_PROVIDES to do an AC_PROVIDE for each macro
 dnl which appears in configure.in before the sysdep configure scripts are run.
 dnl Each sysdep configure.in does GLIBC_PROVIDES first, to avoid any

configure.in

@@ -1,5 +1,5 @@
 dnl Process this file with autoconf to produce a configure script.
-AC_PREREQ(2.53)dnl		dnl Minimum Autoconf version required.
+dnl Note we do not use AC_PREREQ here!  See aclocal.m4 for what we use instead.
 AC_INIT([GNU C Library], [(see version.h)], [http://sourceware.org/bugzilla/], [glibc])
 AC_CONFIG_SRCDIR([include/features.h])
 AC_CONFIG_HEADERS([config.h])