# Check for variable-length arrays.

# serial 5

# From Paul Eggert

# Copyright (C) 2001, 2009-2017 Free Software Foundation, Inc.

# This file is free software; the Free Software Foundation

# 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_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

])