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73 lines
2.3 KiB
Plaintext
73 lines
2.3 KiB
Plaintext
# Check for variable-length arrays.
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# serial 6
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# From Paul Eggert
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# Copyright (C) 2001, 2009-2023 Free Software Foundation, Inc.
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# This file is free software; the Free Software Foundation
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# gives unlimited permission to copy and/or distribute it,
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# with or without modifications, as long as this notice is preserved.
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m4_version_prereq([2.70], [], [
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# AC_C_VARARRAYS
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# --------------
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# Check whether the C compiler supports variable-length arrays.
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AC_DEFUN([AC_C_VARARRAYS],
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[
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AC_CACHE_CHECK([for variable-length arrays],
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ac_cv_c_vararrays,
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[AC_EGREP_CPP([defined],
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[#ifdef __STDC_NO_VLA__
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defined
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#endif
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],
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[ac_cv_c_vararrays='no: __STDC_NO_VLA__ is defined'],
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[AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM(
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[[/* Test for VLA support. This test is partly inspired
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from examples in the C standard. Use at least two VLA
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functions to detect the GCC 3.4.3 bug described in:
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https://lists.gnu.org/archive/html/bug-gnulib/2014-08/msg00014.html
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*/
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#ifdef __STDC_NO_VLA__
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syntax error;
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#else
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extern int n;
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int B[100];
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int fvla (int m, int C[m][m]);
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int
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simple (int count, int all[static count])
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{
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return all[count - 1];
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}
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int
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fvla (int m, int C[m][m])
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{
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typedef int VLA[m][m];
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VLA x;
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int D[m];
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static int (*q)[m] = &B;
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int (*s)[n] = q;
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return C && &x[0][0] == &D[0] && &D[0] == s[0];
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}
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#endif
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]])],
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[ac_cv_c_vararrays=yes],
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[ac_cv_c_vararrays=no])])])
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if test "$ac_cv_c_vararrays" = yes; then
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dnl This is for compatibility with Autoconf 2.61-2.69.
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AC_DEFINE([HAVE_C_VARARRAYS], 1,
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[Define to 1 if C supports variable-length arrays.])
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elif test "$ac_cv_c_vararrays" = no; then
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AC_DEFINE([__STDC_NO_VLA__], 1,
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[Define to 1 if C does not support variable-length arrays, and
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if the compiler does not already define this.])
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fi
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])
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])
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