#include<stdio.h>
#include<malloc.h>
struct P
{
    int x,y;
};
typedef struct PO
{
    struct P * s;
    struct PO  *next;
}LinkP;
void main()
{
    LinkP  * A ;      
    A=(LinkP *)malloc(sizeof(LinkP));
    A->s->x=2;
    A->s->y=3;
    A->next=NULL;
    printf("<%d,%d>\n",A->s->x,A->s->y);
}
为什么运行时会出现错误呢？