Make vararray and restrict checks fail GCC 2.95.3's broken implementation.

configure.ac

@@ -51,15 +51,50 @@ AC_PROG_CC_C99
 AC_C_BIGENDIAN
 AC_C_CONST
 AC_C_INLINE
-AC_C_RESTRICT
+
+#Use a hacked up version of autoconf's AC_C_RESTRICT because it's not
+#strong enough a test to detect old buggy versions of GCC (e.g. 2.95.3)
+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, int * $ac_kw baz[]) {
+	return ip[0];
+       }]],
+      [[int s[1];
+	int * $ac_kw t = s;
+	t[0] = 0;
+	return foo(t, (void *)0)]])],
+      [ac_cv_c_restrict=$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 or
+   __restrict__, even though the corresponding Sun C compiler ends up with
+   "#define restrict _Restrict" or "#define restrict __restrict__" in the
+   previous line.  Perhaps some future version of Sun C++ will work with
+   restrict; if so, hopefully it defines __RESTRICT like Sun C does.  */
+#if defined __SUNPRO_CC && !defined __RESTRICT
+# define _Restrict
+# define __restrict__
+#endif])
+ case $ac_cv_c_restrict in
+   restrict) ;;
+   no) AC_DEFINE([restrict], []) ;;
+   *)  AC_DEFINE_UNQUOTED([restrict], [$ac_cv_c_restrict]) ;;
+ esac
 
 AC_DEFINE([OPUS_BUILD], [], [This is a build of OPUS])
 
 AC_MSG_CHECKING(for C99 variable-size arrays)
-AC_TRY_COMPILE( , [
-int foo=10;
-int array[foo];
-],
+AC_TRY_COMPILE( [], [static int x; char a[++x]; a[sizeof a - 1] = 0; int N; return a[0];],
 [has_var_arrays=yes;AC_DEFINE([VAR_ARRAYS], [], [Use C99 variable-size arrays])
 ],
 has_var_arrays=no