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1#serial 1003
2dnl Copyright (C) 2003 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7# This macro can be removed once we can rely on Autoconf 2.57a or later,
8# since we can then use its AC_C_RESTRICT.
9
10# gl_C_RESTRICT
11# --------------
12# Determine whether the C/C++ compiler supports the "restrict" keyword
13# introduced in ANSI C99, or an equivalent. Do nothing if the compiler
14# accepts it. Otherwise, if the compiler supports an equivalent,
15# define "restrict" to be that. Here are some variants:
16# - GCC supports both __restrict and __restrict__
17# - older DEC Alpha C compilers support only __restrict
18# - _Restrict is the only spelling accepted by Sun WorkShop 6 update 2 C
19# Otherwise, define "restrict" to be empty.
20AC_DEFUN([gl_C_RESTRICT],
21[AC_CACHE_CHECK([for C/C++ restrict keyword], gl_cv_c_restrict,
22 [gl_cv_c_restrict=no
23 # Try the official restrict keyword, then gcc's __restrict, and
24 # the less common variants.
25 for ac_kw in restrict __restrict __restrict__ _Restrict; do
26 AC_COMPILE_IFELSE([AC_LANG_SOURCE(
27 [float * $ac_kw x;])],
28 [gl_cv_c_restrict=$ac_kw; break])
29 done
30 ])
31 case $gl_cv_c_restrict in
32 restrict) ;;
33 no) AC_DEFINE(restrict,,
34 [Define to equivalent of C99 restrict keyword, or to nothing if this
35 is not supported. Do not define if restrict is supported directly.]) ;;
36 *) AC_DEFINE_UNQUOTED(restrict, $gl_cv_c_restrict) ;;
37 esac
38])