菜鸟问题
//多线程时对该函数的调用是有加锁的
static void item_link_q(item *it) { /* item is the new head */
item **head, **tail; /* always true, warns: assert(it->slabs_clsid <= LARGEST_ID); */
assert((it->it_flags & ITEM_SLABBED) == 0);
head = &heads[it->slabs_clsid];
tail = &tails[it->slabs_clsid];
assert(it != *head);
assert((*head && *tail) || (*head == 0 && *tail == 0));
it->prev = 0;
it->next = *head;
if (it->next) it->next->prev = it;
*head = it;
if (*tail == 0) *tail = it;
sizes[it->slabs_clsid]++;
return;
}
请问此处声明为二级指针,但是我觉得声明一级指针为什么不可以呢?谢谢