+# Compiler's language features.
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C/C++ restrict keyword" >&5
+$as_echo_n "checking for C/C++ restrict keyword... " >&6; }
+if ${ac_cv_c_restrict+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ ac_cv_c_restrict=no
+ # The order here caters to the fact that C++ does not require restrict.
+ for ac_kw in __restrict __restrict__ _Restrict restrict; do
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+typedef int * int_ptr;
+ int foo (int_ptr $ac_kw ip) {
+ return ip[0];
+ }
+int
+main ()
+{
+int s[1];
+ int * $ac_kw t = s;
+ t[0] = 0;
+ return foo(t)
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+ ac_cv_c_restrict=$ac_kw
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ test "$ac_cv_c_restrict" != no && break
+ done
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_c_restrict" >&5
+$as_echo "$ac_cv_c_restrict" >&6; }
+
+ case $ac_cv_c_restrict in
+ restrict) ;;
+ no) $as_echo "#define restrict /**/" >>confdefs.h
+ ;;
+ *) cat >>confdefs.h <<_ACEOF
+#define restrict $ac_cv_c_restrict
+_ACEOF
+ ;;
+ esac
+
+