- * If 'payload' is nonnull, on success '*payload' is initialized to the
- * error's payload, and on failure it is cleared. */
+ * If 'payload' is nonnull, on success '*payload' is initialized with a copy of
+ * the error's payload (copying is required because the payload is not properly
+ * aligned). The caller must free the payload (with ofpbuf_uninit()) when it
+ * is no longer needed. On failure, '*payload' is cleared. */