28 #if ENABLE_EXTRA_CHECKS    32 #define DLIST_FIELDS(name) \    35 #define DLIST_FOREACH(prefix, list, p) \    36     for (p = prefix ## _ ## first(list); p != NULL; p = prefix ## _ ## next(list, p))    40     assert(!ring_item->next && !ring_item->prev);
    41     ring_pos->next->prev = ring_item;
    42     ring_item->prev = ring_pos;
    43     ring_item->next = ring_pos->next;
    44     ring_pos->next = ring_item;
    45     assert(ring_item->next && ring_item->prev);