-extern bool rsa_write_pem_public_key(rsa_t *rsa, FILE *fp);
-extern bool rsa_write_pem_private_key(rsa_t *rsa, FILE *fp);
+extern bool rsa_write_pem_public_key(rsa_t *rsa, FILE *fp) __attribute__ ((__warn_unused_result__));
+extern bool rsa_write_pem_private_key(rsa_t *rsa, FILE *fp) __attribute__ ((__warn_unused_result__));