--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2007-10-26  Bruno Haible  <bruno@clisp.org>
+
+	* m4/gnulib-common.m4 (AC_C_RESTRICT): New overriding definition,
+	borrowed from autoconf.
+
 2007-10-26  Bruno Haible  <bruno@clisp.org>
 
 	* lib/strerror.c (rpl_strerror): Return "Unknown error ..." also if

--- a/m4/gnulib-common.m4
+++ b/m4/gnulib-common.m4
@@ -1,4 +1,4 @@
-# gnulib-common.m4 serial 2
+# gnulib-common.m4 serial 3
 dnl Copyright (C) 2007 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -20,3 +20,46 @@
     [AC_REQUIRE([AM_PROG_MKDIR_P])dnl defined by automake
      MKDIR_P='$(mkdir_p)'
      AC_SUBST([MKDIR_P])])])
+
+# AC_C_RESTRICT
+# This definition overrides the AC_C_RESTRICT macro from autoconf 2.60..2.61,
+# so that mixed use of GNU C and GNU C++ and mixed use of Sun C and Sun C++
+# works.
+# This definition can be removed once autoconf >= 2.62 can be assumed.
+AC_DEFUN([AC_C_RESTRICT],
+[AC_CACHE_CHECK([for C/C++ restrict keyword], ac_cv_c_restrict,
+  [ac_cv_c_restrict=no
+   # The order here caters to the fact that C++ does not require restrict.
+   for ac_kw in __restrict __restrict__ _Restrict restrict; do
+     AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+      [[typedef int * int_ptr;
+	int foo (int_ptr $ac_kw ip) {
+	return ip[0];
+       }]],
+      [[int s[1];
+	int * $ac_kw t = s;
+	t[0] = 0;
+	return foo(t)]])],
+      [ac_cv_c_restrict=$ac_kw])
+     test "$ac_cv_c_restrict" != no && break
+   done
+  ])
+ AH_VERBATIM([restrict],
+[/* Define to the equivalent of the C99 'restrict' keyword, or to
+   nothing if this is not supported.  Do not define if restrict is
+   supported directly.  */
+#undef restrict
+/* Work around a bug in Sun C++: it does not support _Restrict, even
+   though the corresponding Sun C compiler does, which causes
+   "#define restrict _Restrict" in the previous line.  Perhaps some future
+   version of Sun C++ will work with _Restrict; if so, it'll probably
+   define __RESTRICT, just as Sun C does.  */
+#if defined __SUNPRO_CC && !defined __RESTRICT
+# define _Restrict
+#endif])
+ case $ac_cv_c_restrict in
+   restrict) ;;
+   no) AC_DEFINE([restrict], []) ;;
+   *)  AC_DEFINE_UNQUOTED([restrict], [$ac_cv_c_restrict]) ;;
+ esac
+])