-extern int xwrite (int sock, const void *buf, size_t len);
-extern int xread (int sock, void *buf, size_t len);
+extern int xwrite (int sock, const void *buf, size_t len)
+ __attribute__((__warn_unused_result__));
+extern int xread (int sock, void *buf, size_t len)
+ __attribute__((__warn_unused_result__));