CIRCLEQ_LAST
for ((var) = CIRCLEQ_LAST((head)); \
CIRCLEQ_LAST((head)) = (void *)(head); \
CIRCLEQ_LAST((head)) = (elm); \
if (CIRCLEQ_LAST((head)) == (void *)(head)) \
CIRCLEQ_LAST((head)) = (elm); \
CIRCLEQ_PREV((elm), field) = CIRCLEQ_LAST((head)); \
CIRCLEQ_NEXT(CIRCLEQ_LAST((head)), field) = (elm); \
CIRCLEQ_LAST((head)) = (elm); \
CIRCLEQ_LAST((head)) = CIRCLEQ_PREV((elm), field); \