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问题描述

好的,当我运行这段代码时,我遇到了分段错误:

Okay, when I run this code, I have a segmentation fault:

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define MAX 64

struct example {
    char *name;
};

int main()
{
    struct example *s = malloc (MAX);
    strcpy(s->name ,"Hello World!!");
    return !printf("%s
", s->name);
}

终端输出:

alshamlan@alshamlan-VGN-CR520E:/tmp/interview$ make q1
cc -Wall -g    q1.c   -o q1
alshamlan@alshamlan-VGN-CR520E:/tmp/interview$ ./q1
Segmentation fault (core dumped)
alshamlan@alshamlan-VGN-CR520E:/tmp/interview$ gedit q1.c

有人可以解释发生了什么吗?

Can someone explain what's going on?

推荐答案

你可能已经为你的结构体分配了内存,但没有为它的字符指针分配内存.

You may have allocated memory for your struct, but not for its character pointer.

您不能对未分配的内存执行 strcpy.你可以说

You can't perform a strcpy onto memory that isn't allocated. You could say

s->name = "Hello World";

改为.

或者,为您的 char 分配内存,然后执行复制.注意:我绝不认可以下代码是好的,只是它会起作用.

Alternatively, allocate memory for your char, and then perform the copying.NOTE: I in NO way endorse that the following code is good, just that it will work.

int main()
{
  struct example *s = malloc(MAX);
  s->name = malloc(MAX);
  strcpy(s->name ,"Hello World!!");
  return !printf("%s
", s->name);
}

这可能是一个更简洁的实现,但我仍然讨厌 C 风格的字符串


Here is perhaps a cleaner implementation, but I still hate C-style strings

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define KNOWN_GOOD_BUFFER_SIZE 64

typedef struct example {
  char *name;
} MyExample;

int main()
{
  MyExample *s = (MyExample*) malloc( sizeof(MyExample) );
  s->name = (char*) malloc(KNOWN_GOOD_BUFFER_SIZE);
  strcpy(s->name ,"Hello World!!");
  printf("%s
", s->name);
  free(s->name);
  free(s);
  return 0;
}

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08-19 20:45