list_coll_offset
return list_coll_offset((struct sort_list_item **)ss1,
return list_coll_offset(ss1, ss2, N); \
int list_coll_offset(struct sort_list_item **ss1, struct sort_list_item **ss2, size_t offset);
if (list_coll_offset(&(sl->tosort[0]), &(sl->tosort[1]),