1 files changed, 38 insertions, 0 deletions

diff --git a/m4/restrict.m4 b/m4/restrict.m4
new file mode 100644
index 00000000..1f3bbb92
--- /dev/null
+++ b/m4/restrict.m4
@@ -0,0 +1,38 @@
+#serial 1003
+dnl Copyright (C) 2003 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# 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,
+# 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 * $ac_kw x;])],
+      [gl_cv_c_restrict=$ac_kw; break])
+   done
+  ])
+ 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, $gl_cv_c_restrict) ;;
+ esac
+])