我使用的strcpy，malloc和结构时，可以有段故障（核心转储） [英] I have a segmentation fault (core dumped) when using strcpy, malloc, and struct

问题描述

好吧，当我运行这个code，我有一个分段错误：

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\n", s->name);
}

端子输出：

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

有人能解释这是怎么回事？

Can someone explain what's going on?

推荐答案

您可能已经分配的内存为你的结构，而不是它的字符指针。

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

您不能执行的strcpy到存储器上的未分配。你可以说

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

s->name = "Hello World"; 

代替。

另外，对于您的字符分配内存，然后再进行复制。
注意：我绝不赞同以下code是不错的，只是它会工作

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\n", s->name);
}

---

编辑：这也许是一个更清洁的实现，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\n", s->name);
  free(s->name);
  free(s);
  return 0;
}

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