c - fread 错误 - 段错误

Question

这是我的代码文件名filewrite.c

#include<stdio.h>
#include <stdlib.h>
void main()
{

    int *p; 
    *p = 5;
    FILE *fp1 = fopen("sample.txt","w");
    fwrite(&p,sizeof(int),1,fp1);
    fclose(fp1);

    printf("\n Value of p written into the file is :%d \n",*p);

 int *q;
 FILE *fp2 = fopen("sample.txt","r");
 fread(&q,sizeof(int),1,fp2);
 fclose(fp2);

 printf("\n Value of q read from the file is :%d \n",*q);

 }

Linux 终端上看到的输出:

$>gcc -o filewrite.o filewrite.c

$>filewrite.o

$>Segmentation fault (core dumped)

我可以看到写出的文件sample.txt。但无法理解为什么会有核心转储。

Answer 1

你需要改变

fread(&q,sizeof(int),1,fp2);

至

fread(q,sizeof(int),1,fp2);

fread 的第一个参数是 void *，并且您向它传递一个指向 int 的指针

<小时/>

并且，为指针分配内存p

int *p;
p = malloc(sizeof(int));

同样适用于q

int *q;
q = malloc(sizeof(int));