-#if !HAVE_SNPRINTF // GNU extension.
-int snprintf (char *str, size_t n, char const *format, ...);
+#if ! HAVE_MEMMEM /* GNU extension. */
+void *memmem (void const *haystack, int haystack_len,
+ void const *needle, int needle_len);
+#endif /* HAVE_MEMMEM */
+
+#if ! HAVE_MEMRCHR
+unsigned char *memrchr (unsigned char const *p, int n, char c);