诚然,我是一个纯 C 的新手,但这让我很难过。我正在研究一个链表实现以供练习,我通过简单地向 split_node 函数添加一个变量来得到一个段错误:
#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
但是如果我int foo
在结尾取消注释split_node
,编译并运行,我会得到:
$ ./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?