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# vararrays.m4
# serial 6
dnl Copyright (C) 2001, 2009-2024 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
# Check for variable-length arrays.
# From Paul Eggert
m4_version_prereq([2.70], [], [
# AC_C_VARARRAYS
# --------------
# Check whether the C compiler supports variable-length arrays.
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:
https://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
])
])
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