#include <stdio.h>
#include <stdlib.h>
struct str{
    int t;
    char v;
};

union uni{
    int t;
    char v;
}u;

int g = 15;

void fun(int* xp){
    void (*f) (int*) = fun;

    struct str s = {1, 'a'};
    union uni *up = (union uni *) malloc(sizeof(union uni));
    int *ip[2] = {xp, &g};
    up->v = s.v + 1;

    printf("\n%p\n",&g);
    printf("ip = %p, *ip = %p, **ip = %d\n", ip, *ip, **ip);
    printf("ip+1 = %p, ip[1] = %p, *ip[1] = %d\n", ip+1, ip[1], *ip[1]);
    printf("&s.v = %p, s.v = '%c'\n", &s.v, s.v);
    printf("&up->v = %p, up->v = '%c'\n", &up->v, up->v);
    printf("&up->t = %p, up->t = '%c'\n", &up->t, up->t);
    printf("f = %p\n", f);

    if (--(*xp) > 0)
    f(xp);

}
int main(){
    int x = 2;
    fun(&x);
    return 0;
}

运行结果

0x100008020
ip = 0x7ffeefbff340, ip = 0x7ffeefbff378, ip = 2
ip+1 = 0x7ffeefbff348, ip[1] = 0x100008020, ip[1] = 15
&s.v = 0x7ffeefbff32c, s.v = ‘a’
&up->v = 0x105b398d0, up->v = ‘b’
&up->t = 0x105b398d0, up->t = ‘b’
f = 0x100003d10

0x100008020
ip = 0x7ffeefbff2c0, ip = 0x7ffeefbff378, ip = 1
ip+1 = 0x7ffeefbff2c8, ip[1] = 0x100008020, ip[1] = 15
&s.v = 0x7ffeefbff2ac, s.v = ‘a’
&up->v = 0x105835870, up->v = ‘b’
&up->t = 0x105835870, up->t = ‘b’
f = 0x100003d10