实现链表时指针的奇怪问题 [英] Odd problem with pointer while implementing a linked list

问题描述

我正在尝试在 C 中实现一个链表，并且我想将头节点存储在一个单独的结构中.但是，每当我添加另一个节点时，头节点似乎都会以某种方式重新分配.

I'm trying to implement a linked list in C, and I want to store the head node in a separate struct. However, it seems like the head node is being reassigned somehow whenever I add another node.

#include <stdio.h>
#include <stdlib.h>

struct BC_node {
    struct BC_node *next;
    void *data;
};
struct BC_list {
    struct BC_node *head;
    struct BC_node *tail;
};

void
BC_list_push(struct BC_list *list, void *data)
{
    struct BC_node *node = calloc(1, sizeof(struct BC_node));

    if (list->head != NULL)
        printf("head: %d
", *((int *) (list->head)->data));

    node->next = NULL;
    node->data = data;
    if (list->head == NULL) {
        printf("head is null.
");
        list->head = node;
    }
    if (list->tail != NULL) {
        (list->tail)->next = node;
    }
    list->tail = node;

    printf("head: %d
", *((int *) (list->head)->data));
}

int
main(void)
{
    int i;
    struct BC_list *list = calloc(1, sizeof(struct BC_list));

    list->head = NULL;
    list->tail = NULL;
    for (i = 0; i < 3; i++)
        BC_list_push(list, &i);
    return 0;
}

输出:

head is null.
head: 0
head: 1
head: 1
head: 2
head: 2

推荐答案

你的 data 成员只是一个指向 main 变量 i 的指针>，因此当您打印 *data 时，您只会看到该轮循环中计数器的值.您所有的节点都具有相同的数据值！

Your data member is just a pointer to the variable i in main, so when you print *data you just see the value of the counter during that round of the loop. All your nodes have the same data value!

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