第一次发帖，请问一个C++有关问题！

第一次发帖，请教一个C++问题！！！
先贴代码：
[code=C/C++][/code]
#include<iostream>
#include<string>
#include <cassert>

using namespace std;

static int SMALL_FOOD = 1;
static int BIG_FOOD = 2;
static int WEST = 3;
static int EAST = 4;

struct _Visitor;
//
typedef struct _Tofu
{
int type;
void (*eat)(struct _Tofu* pTofu,struct _Visitor* pVisitor);
}Tofu;

//
typedef struct _Visitor
{
int region;
void (*process)(struct _Tofu* pTofu,struct _Visitor* pVisitor);
}Visitor;

void eat(struct _Tofu* pTofu,struct _Visitor* pVisitor)
{
assert(pTofu != NULL && pVisitor != NULL);
pVisitor->process(pTofu,pVisitor);
}

void process(struct _Tofu* pTofu,struct _Visitor* pVisitor)
{
assert(NULL != pTofu && NULL != pVisitor);

if( (pTofu->type == SMALL_FOOD && pVisitor->region == WEST) ||
(pTofu->type == BIG_FOOD && pVisitor->region == EAST) )
{
cout<<"I like this food !\n";
return;
}

cout<<"I do not like this food ! \n";
}
int main()
{
Visitor* pVis;
pVis->region = EAST;//请问这个为什么有问题，编译通过，运行出错！
//
Visitor vis;  
vis.region = EAST; //没问题
return 0;
}



[解决办法]
Visitor* pVis； 声明了 但是没初始化，没分配空间
[解决办法]
Visitor* pVis;
明显指针没有初始化，指向了不可写区域，导致出错