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-rw-r--r--gl/m4/vararrays.m472
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1# Check for variable-length arrays.
2
3# serial 6
4
5# From Paul Eggert
6
7# Copyright (C) 2001, 2009-2023 Free Software Foundation, Inc.
8# This file is free software; the Free Software Foundation
9# gives unlimited permission to copy and/or distribute it,
10# with or without modifications, as long as this notice is preserved.
11
12m4_version_prereq([2.70], [], [
13
14# AC_C_VARARRAYS
15# --------------
16# Check whether the C compiler supports variable-length arrays.
17AC_DEFUN([AC_C_VARARRAYS],
18[
19 AC_CACHE_CHECK([for variable-length arrays],
20 ac_cv_c_vararrays,
21 [AC_EGREP_CPP([defined],
22 [#ifdef __STDC_NO_VLA__
23 defined
24 #endif
25 ],
26 [ac_cv_c_vararrays='no: __STDC_NO_VLA__ is defined'],
27 [AC_COMPILE_IFELSE(
28 [AC_LANG_PROGRAM(
29 [[/* Test for VLA support. This test is partly inspired
30 from examples in the C standard. Use at least two VLA
31 functions to detect the GCC 3.4.3 bug described in:
32 https://lists.gnu.org/archive/html/bug-gnulib/2014-08/msg00014.html
33 */
34 #ifdef __STDC_NO_VLA__
35 syntax error;
36 #else
37 extern int n;
38 int B[100];
39 int fvla (int m, int C[m][m]);
40
41 int
42 simple (int count, int all[static count])
43 {
44 return all[count - 1];
45 }
46
47 int
48 fvla (int m, int C[m][m])
49 {
50 typedef int VLA[m][m];
51 VLA x;
52 int D[m];
53 static int (*q)[m] = &B;
54 int (*s)[n] = q;
55 return C && &x[0][0] == &D[0] && &D[0] == s[0];
56 }
57 #endif
58 ]])],
59 [ac_cv_c_vararrays=yes],
60 [ac_cv_c_vararrays=no])])])
61 if test "$ac_cv_c_vararrays" = yes; then
62 dnl This is for compatibility with Autoconf 2.61-2.69.
63 AC_DEFINE([HAVE_C_VARARRAYS], 1,
64 [Define to 1 if C supports variable-length arrays.])
65 elif test "$ac_cv_c_vararrays" = no; then
66 AC_DEFINE([__STDC_NO_VLA__], 1,
67 [Define to 1 if C does not support variable-length arrays, and
68 if the compiler does not already define this.])
69 fi
70])
71
72])