-extern bool rsa_public_encrypt(rsa_t *rsa, void *in, size_t len, void *out);
-extern bool rsa_private_decrypt(rsa_t *rsa, void *in, size_t len, void *out);
+extern bool rsa_public_encrypt(rsa_t *rsa, void *in, size_t len, void *out) __attribute__ ((__warn_unused_result__));
+extern bool rsa_private_decrypt(rsa_t *rsa, void *in, size_t len, void *out) __attribute__ ((__warn_unused_result__));