-extern rsa_t *rsa_generate(size_t bits, unsigned long exponent);
-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 rsa_t *rsa_generate(size_t bits, unsigned long exponent) __attribute__ ((__malloc__));
+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__));