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);