c - 为什么在以下 C 代码中出现段错误

Question

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

struct a1 {
    int value ;
};

struct cf {
   struct a1 *a1;
   int val;
};

main(){

   struct cf *cf = malloc(sizeof(struct cf));

   cf->a1->value = 45;
   printf("cf->a1->value = %d \n",cf->a1->value);

}

当我试图执行此 C 代码时，我遇到了段错误(核心已转储)!

Answer 1

原因是您正在为 cf 而不是为 a1 分配所需的内存。你必须做类似的事情

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

struct a1 {
    int value ;
};

struct cf {
   struct a1 *a1;
   int val;
};

main(){

   struct cf *cf = malloc(sizeof(struct cf));
   cf->a1 = malloc(sizeof(struct a1));
   cf->a1->value = 45;
   printf("cf->a1->value = %d \n",cf->a1->value);

}