test_flag_and_insert(&info->explore_queue, c, TOPO_WALK_EXPLORED);
test_flag_and_insert(&info->indegree_queue, c, TOPO_WALK_INDEGREE);
test_flag_and_insert(&info->explore_queue, c, TOPO_WALK_EXPLORED);
test_flag_and_insert(&info->indegree_queue, c, TOPO_WALK_INDEGREE);