--- a/ChangeLog	Thu Aug 07 09:52:04 2014 -0700
+++ b/ChangeLog	Thu Aug 07 17:25:28 2014 -0700
@@ -1,3 +1,12 @@
+2014-08-07  Paul Eggert  <eggert@cs.ucla.edu>
+
+	vararrays: modernize AC_C_VARARRAYS for C11
+	This backports a change I recently made to Autoconf.
+	* m4/vararrays.m4 (AC_C_VARARRAYS): Define __STDC_NO_VLA__ if
+	VLAs are not supported, as this is what C11 does.  The old macro
+	HAVE_C_VARARRAYS is still defined if they are supported, but is
+	now obsolescent.  Also, check for VLA bug in GCC 3.4.3.
+
 2014-08-07  Alessandro Degano  <degano@cern.ch>  (tiny change)
 
 	relocatable-prog-wrapper: port gettext to OS X 10.8 + GCC 4.8.1

--- a/m4/vararrays.m4	Thu Aug 07 09:52:04 2014 -0700
+++ b/m4/vararrays.m4	Thu Aug 07 17:25:28 2014 -0700
@@ -1,6 +1,6 @@
 # Check for variable-length arrays.
 
-# serial 4
+# serial 5
 
 # From Paul Eggert
 
@@ -9,17 +9,60 @@
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
+# This is a copy of AC_C_VARARRAYS from a recent development version
+# of Autoconf.  It replaces Autoconf's version, or for pre-2.61 autoconf
+# it defines the macro that Autoconf lacks.
 AC_DEFUN([AC_C_VARARRAYS],
 [
   AC_CACHE_CHECK([for variable-length arrays],
     ac_cv_c_vararrays,
-    [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
-         [],
-         [[static int x; char a[++x]; a[sizeof a - 1] = 0; return a[0];]])],
-       ac_cv_c_vararrays=yes,
-       ac_cv_c_vararrays=no)])
-  if test $ac_cv_c_vararrays = yes; then
-    AC_DEFINE([HAVE_C_VARARRAYS], [1],
+    [AC_EGREP_CPP([defined],
+       [#ifdef __STDC_NO_VLA__
+	defined
+	#endif
+       ],
+       [ac_cv_c_vararrays='no: __STDC_NO_VLA__ is defined'],
+       [AC_COMPILE_IFELSE(
+	  [AC_LANG_PROGRAM(
+	     [[/* Test for VLA support.  This test is partly inspired
+		  from examples in the C standard.  Use at least two VLA
+		  functions to detect the GCC 3.4.3 bug described in:
+		  http://lists.gnu.org/archive/html/bug-gnulib/2014-08/msg00014.html
+		  */
+	       #ifdef __STDC_NO_VLA__
+		syntax error;
+	       #else
+		 extern int n;
+		 int B[100];
+		 int fvla (int m, int C[m][m]);
+
+		 int
+		 simple (int count, int all[static count])
+		 {
+		   return all[count - 1];
+		 }
+
+		 int
+		 fvla (int m, int C[m][m])
+		 {
+		   typedef int VLA[m][m];
+		   VLA x;
+		   int D[m];
+		   static int (*q)[m] = &B;
+		   int (*s)[n] = q;
+		   return C && &x[0][0] == &D[0] && &D[0] == s[0];
+		 }
+	       #endif
+	       ]])],
+	  [ac_cv_c_vararrays=yes],
+	  [ac_cv_c_vararrays=no])])])
+  if test "$ac_cv_c_vararrays" = yes; then
+    dnl This is for compatibility with Autoconf 2.61-2.69.
+    AC_DEFINE([HAVE_C_VARARRAYS], 1,
       [Define to 1 if C supports variable-length arrays.])
+  elif test "$ac_cv_c_vararrays" = no; then
+    AC_DEFINE([__STDC_NO_VLA__], 1,
+      [Define to 1 if C does not support variable-length arrays, and
+       if the compiler does not already define this.])
   fi
 ])