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188.8.131.52 (2001/07/26) C_Support @ ac-archive-0.5.39
Steven G. Johnson <firstname.lastname@example.org>
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 ])