+/* These states are used to mark the grammar graph when freeing, to
+ * detect loop. */
+enum ec_node_free_state {
+ EC_NODE_FREE_STATE_NONE,
+ EC_NODE_FREE_STATE_TRAVERSED,
+ EC_NODE_FREE_STATE_FREEABLE,
+ EC_NODE_FREE_STATE_NOT_FREEABLE,
+ EC_NODE_FREE_STATE_FREEING,
+};
+
+/**
+ * The grammar node structure.
+ */