添加变量导致的段错误

诚然，我是一个纯 C 新手，但这让我难住了。我正在研究链表实现以进行练习，并且通过简单地将变量添加到 split_node 函数中，我遇到了段错误：

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

struct Node {
    struct Node *child;
    char *content;
};

void print_list(struct Node node);
void split_node(struct Node *node, int position);

int main() {

    struct Node head, second, third;

    head.content = "first";
    second.content = "second";
    third.content = "i'm third";

    head.child = &second;
    second.child = &third;

    print_list(head);
    split_node(&head, 3);
    print_list(head);

    return 0;
}

void print_list(struct Node node) {
    printf("%s\n", node.content);
    if(node.child) print_list(*node.child);
}

    /*
    Split node into two nodes, with the first position characters of the node's content remaining with node, and the remainder being copied to the new node. (It doesn't yet truncate the first node's string, but does do the copy.)
    */
void split_node(struct Node *node, int position) {
    if(position >= strlen((*node).content)) return;
    struct Node newNode;
    newNode.child = (*node).child;
    (*node).child = &newNode;

    int length = (strlen((*node).content) - position);
    newNode.content = malloc(sizeof(char) * (length + 1));
    strncpy(newNode.content, (*node).content + sizeof(char) * position, length);
    newNode.content[length] = '\0';

    //int foo;
}

此代码编译（gcc -Wall -o list list.c）并运行良好：

$ ./list
first
second
i'm third
first
st
second
i'm third

但如果我取消评论int foo在......的最后split_node，编译并运行，我得到：

$ ./list
first
second
i'm third
first
st
Segmentation fault

gdb 给了我这个回溯：

#0  0x91d6ae70 in strlen ()
#1  0x91dd3126 in puts ()
#2  0x00001f21 in print_list (node={child = 0xbcec815b, content = 0x8b000000 <Address 0x8b000000 out of bounds>}) at list.c:41
#3  0x00001f3c in print_list (node={child = 0x8fe0154b, content = 0x1ff6 "i'm third"}) at list.c:42
#4  0x00001f3c in print_list (node={child = 0xbffff568, content = 0x1fef "second"}) at list.c:42
#5  0x00001f3c in print_list (node={child = 0xbffff570, content = 0x1fe9 "first"}) at list.c:42
#6  0x00001ee0 in main () at list.c:33

为什么添加变量定义会导致段错误？它似乎正在破坏新创建节点的内容指针。我很困惑;有什么帮助吗？

您需要动态分配节点（使用 malloc）。

正如您所看到的，您的新节点已在堆栈上声明。当 split 函数返回时，该新节点不再是有效内存。

添加变量会导致段错误，因为该变量会更改堆栈的布局，从而导致函数返回时行为略有不同。