#include<stdio.h>
#include<stdlib.h>      //include stdlib for malloc()

int *p1,*p2;      //make pointers global

void fun(void);     //No need to pass any arguments, as p1,p2 are global

int main(void)
{
    int s;
    fun();
    s=*p1 + *p2;

    printf("Sum= %d",s);
    return 0;
}

void fun(void)
{
    p1=malloc(sizeof(int));     //allocate memory to use it outside fun()
    p2=malloc(sizeof(int));
    *p1=3;
    *p2=5;
}