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#serial 1000
dnl based on acx_restrict.m4, from the GNU Autoconf Macro Archive at:
dnl http://www.gnu.org/software/ac-archive/htmldoc/acx_restrict.html
# Determine whether the C compiler supports the "restrict" keyword introduced
# in ANSI C99, or an equivalent. Do nothing if the compiler accepts it.
# Otherwise, if the compiler supports an equivalent (like gcc's __restrict__)
# define "restrict" to be that. Otherwise, define "restrict" to be empty.
AC_DEFUN([ACX_C_RESTRICT],
[AC_CACHE_CHECK([for C restrict keyword], acx_cv_c_restrict,
[acx_cv_c_restrict=no
# Try the official restrict keyword, then gcc's __restrict__, then
# SGI's __restrict. __restrict has slightly different semantics than
# restrict (it's a bit stronger, in that __restrict pointers can't
# overlap even with non __restrict pointers), but I think it should be
# okay under the circumstances where restrict is normally used.
for acx_kw in restrict __restrict__ __restrict; do
AC_COMPILE_IFELSE([AC_LANG_SOURCE(
[#ifndef __cplusplus
float * $acx_kw x;
#endif
])], [acx_cv_c_restrict=$acx_kw; break])
done
])
case $acx_cv_c_restrict in
restrict) ;;
no) AC_DEFINE(restrict,,
[Define to equivalent of C99 restrict keyword, or to nothing if this
is not supported. Do not define if restrict is supported directly.]) ;;
*) AC_DEFINE_UNQUOTED(restrict, $acx_cv_c_restrict) ;;
esac
])
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