link_top
link = list_entry(link_top(graph), typeof(*link), list);
link_top(graph) = link_top(graph)->next;
link_top(graph) = link_top(graph)->next;
link_top(graph) = link_top(graph)->next;
link_top(graph) = link_top(graph)->next;
while (link_top(graph) != &stack_top(graph)->links)