topo_next_node
node = topo_next_node(root, root);
node = topo_next_node(root, node);
struct topo_node * topo_next_node(struct topo_node *top,
for (i = root; i != NULL; i = topo_next_node(root, i))
node = topo_next_node(root, node);
node = topo_next_node(root, node);
node = topo_next_node(root, node);
node = topo_next_node(root, node);
node = topo_next_node(root, node);