Steven G. Johnson <stevenj@alum.mit.edu>
GPLWithACException
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cryp.to ac-archive's Obsoleted (obsoleted)
This macro determines whether the C compiler supports the
"restrict" keyword introduced in ANSI C99, or an equivalent. Does
nothing if the compiler accepts the keyword. Otherwise, if the
compiler supports an equivalent (like gcc's __restrict__) defines
"restrict" to be that. Otherwise, defines "restrict" to be empty.
AC_DEFUN([ACX_C_RESTRICT],
[AC_CACHE_CHECK([for C restrict keyword], acx_cv_c_restrict,
[acx_cv_c_restrict=unsupported
AC_LANG_SAVE
AC_LANG_C
# 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_TRY_COMPILE([], [float * $acx_kw x;], [acx_cv_c_restrict=$acx_kw; break])
done
AC_LANG_RESTORE
])
if test "$acx_cv_c_restrict" != "restrict"; then
acx_kw="$acx_cv_c_restrict"
if test "$acx_kw" = unsupported; then acx_kw=""; fi
AC_DEFINE_UNQUOTED(restrict, $acx_kw, [Define to equivalent of C99 restrict keyword, or to nothing if this is not supported. Do not define if restrict is supported directly.])
fi
])