c - 链接列表和大小为 4 的无效读取

Question

我一直在实现一个链表来清除我的开发技能上的锈迹，但在我删除中间元素的测试中注意到 valgrind 报告大小为 4 的无效读取。

==1197== Invalid read of size 4
==1197==    at 0x804885C: main (list.c:135)
==1197==  Address 0x426e76c is 4 bytes inside a block of size 12 free'd
==1197==    at 0x40257ED: free (vg_replace_malloc.c:366)
==1197==    by 0x804875E: list_remove (list.c:112)
==1197==    by 0x8048857: main (list.c:137)

触发这个的主要代码是:

    for (iter = l2->head; iter; iter = iter->next) {
            if (iter->n >= 10 && iter->n <= 14)
                    list_remove(l2, iter);

删除函数是:

void list_remove(struct list *list, struct node *node)
{
        if (node == list->head && node == list->tail) {
                list->head = list->tail = NULL;
        }
        else if (node == list->head) {
                list->head = node->next;
                list->head->prev = NULL;
        }
        else if (node == list->tail) {
                list->tail = node->prev;
                list->tail = NULL;
        }
        else  {
                struct node *prev, *next;
                prev = node->prev;
                next = node->next;
                prev->next = next;
                next->prev = prev;
        }

        free(node);
}

知道我可能做错了什么吗？

Answer 1

您正在释放循环中的值，然后取消引用它以获取其“下一个”指针。您需要一个临时值才能正确执行此操作:

    for (iter = l2->head; iter; iter = next) {
            next = iter->next;
            if (iter->n >= 10 && iter->n <= 14)
                    list_remove(l2, iter);
    }