这种联合的使用是严格一致的吗?

Given the code:

考虑到代码:

struct s1 {unsigned short x;};
struct s2 {unsigned short x;};
union s1s2 { struct s1 v1; struct s2 v2; };

static int read_s1x(struct s1 *p) { return p->x; }
static void write_s2x(struct s2 *p, int v) { p->x=v;}

int test(union s1s2 *p1, union s1s2 *p2, union s1s2 *p3)
{
  if (read_s1x(&p1->v1))
  {
    unsigned short temp;
    temp = p3->v1.x;
    p3->v2.x = temp;
    write_s2x(&p2->v2,1234);
    temp = p3->v2.x;
    p3->v1.x = temp;
  }
  return read_s1x(&p1->v1);
}
int test2(int x)
{
  union s1s2 q[2];
  q->v1.x = 4321;
  return test(q,q+x,q+x);
}
#include <stdio.h>
int main(void)
{
  printf("%d\n",test2(0));
}
struct s1 {unsigned