-extern bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *outdata) __attribute__((__warn_unused_result__));
-extern bool digest_verify(digest_t *digest, const void *indata, size_t inlen, const void *digestdata) __attribute__((__warn_unused_result__));
-extern bool digest_set_key(digest_t *digest, const void *key, size_t len) __attribute__((__warn_unused_result__));
-extern int digest_get_nid(const digest_t *digest);
+extern bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *outdata) ATTR_WARN_UNUSED;
+extern bool digest_verify(digest_t *digest, const void *indata, size_t inlen, const void *digestdata) ATTR_WARN_UNUSED;
+extern bool digest_set_key(digest_t *digest, const void *key, size_t len) ATTR_WARN_UNUSED;
+extern nid_t digest_get_nid(const digest_t *digest);