linux c指针理解

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

#define SS 1234567


void fun(int*p1,int a)
{
    //a为局部变量，函数执行完内存就释放，p1也就为NULL
     p1 = &a;
}

int main()
{


   int *p;
   p = (int*)malloc(sizeof(int));//加这句打印结果为0，不加打印段错误

   int c = 12;
   fun(p,c);
   printf("*p = %d\n",*p);
   return 0;
}