什么情况，帮忙找下错误



#include <stdio.h>
#define MAXNUM 100
#define NIL 0
typedef int elemtype;
typedef struct
{
 elemtype Stack[MAXNUM];
 int Top;        
}qstype;

void InitiateQStack(qstype *s)//初始化栈
{
 s->Top=-1;     
}
int PushQStack(qstype *s)//进栈
{
 elemtype x;
 if(s->Top>=MAXNUM-1) return 0;
 else
 {
  scanf("%d",&x);
  s->Stack[++(s->Top)]=x;
  return 1;   
 }
}

elemtype PopQStack(qstype *s)//出栈
{
 if(s->Top<0) return NIL;
 else return s->Stack[(s->Top)--];         
}
/*
elemtype GetTopQStack(qstype *s)
{
 if(s->Top<0) return NIL;
 else return s->Stack[s->Top];         
}*/

int main()
{
 qstype *p;
 InitiateQStack(p);
 if(PushQStack(p))
 {
  printf("%d\n",PopQStack(p));                  
 }   
 getchar();
 return 0;

}

I know 3q3q3q3q