Merge with gnulib.

(gl_C_RESTRICT): Renamed from ACX_C_RESTRICT.  All uses changed.
Rename cache vars to gl_cv_*.  Incorporate latest Autoconf CVS tricks.

1 files changed, 21 insertions, 16 deletions

diff --git a/m4/restrict.m4 b/m4/restrict.m4
index ca4f70f0b..634293892 100644
--- a/m4/restrict.m4
+++ b/m4/restrict.m4
@@ -1,28 +1,33 @@
-#serial 1001
-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
+#serial 1002
+# This macro can be removed once we can rely on Autoconf 2.57a or later,
+# since we can then use its AC_C_RESTRICT.
 
+# gl_C_RESTRICT
+# --------------
 # Determine whether the C/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/C++ restrict keyword], acx_cv_c_restrict,
-  [acx_cv_c_restrict=no
-   # Try the official restrict keyword, then gcc's __restrict__.
-   for acx_kw in restrict __restrict__; do
+# accepts it.  Otherwise, if the compiler supports an equivalent,
+# define "restrict" to be that.  Here are some variants:
+# - GCC supports both __restrict and __restrict__
+# - older DEC Alpha C compilers support only __restrict
+# - _Restrict is the only spelling accepted by Sun WorkShop 6 update 2 C
+# Otherwise, define "restrict" to be empty.
+AC_DEFUN([gl_C_RESTRICT],
+[AC_CACHE_CHECK([for C/C++ restrict keyword], gl_cv_c_restrict,
+  [gl_cv_c_restrict=no
+   # Try the official restrict keyword, then gcc's __restrict, and
+   # the less common variants.
+   for ac_kw in restrict __restrict __restrict__ _Restrict; do
      AC_COMPILE_IFELSE([AC_LANG_SOURCE(
-      [float * $acx_kw x;])],
-      [acx_cv_c_restrict=$acx_kw; break])
+      [float * $ac_kw x;])],
+      [gl_cv_c_restrict=$ac_kw; break])
    done
   ])
- case $acx_cv_c_restrict in
+ case $gl_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) ;;
+   *)  AC_DEFINE_UNQUOTED(restrict, $gl_cv_c_restrict) ;;
  esac
 ])