一个有趣的问题

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

typedef struct {
    int a[2];
    double d;
} struct_t;

double fun(int i) {
    volatile struct_t s;
    s.d = 3.14;
    s.a[i] = 1073741824;
    return s.d;
}

int main(void)
{
    printf("%lf\n", fun(0));
    printf("%lf\n", fun(1));
    printf("%lf\n", fun(2));
    printf("%lf\n", fun(3));
    //printf("%lf\n", fun(4));
    
    system("pause");
    return 0;
}