急死了。。。。大神告诉我为什么程序会崩溃掉

/******************************************************************

#include<iostream>

#include"Mystack.h"

using namespace std;

Mystack::Mystack(int size)

{

m_iSize=size;

m_iTop=0;

char *m_pBuffer=new char[m_iSize];

}

Mystack::~Mystack()

{

delete[]m_pBuffer;

m_pBuffer=NULL;

}

bool Mystack::stackFull()

{

if(m_iTop==m_iSize)

{

return true;

}

return false;

}

bool Mystack::stackEmpty()

{

if(0==m_iTop)

{

return true;

}

return false;

}

int Mystack::stackLength()

{

return m_iTop;

}

void Mystack::clearStack()

{

m_iTop=0;

}

bool Mystack::Push(char element)

{

if(stackFull())

{

cout<<"栈已满"<<endl;

return false;

}

m_pBuffer[m_iTop]=element;

m_iTop++;

return true;

}

bool Mystack::Pop()

{

if(stackEmpty())

{

cout<<"栈已空"<<endl;

return false;

}

m_iTop--;

return true;

}

void Mystack::stackTravelse()

{

for(int i=0;i<m_iTop;i++)

{

cout<<m_pBuffer[i]<<" ";

}

cout<<endl;

}

**************************************************************/

/*************************************************************

#ifndef MYSTACK_H_

#define MYSTACK_H_

class Mystack

{

public:

Mystack(int size);

~Mystack();

bool stackFull();

bool stackEmpty();

int stackLength();

void clearStack();

bool Push(char element);

bool Pop();

void stackTravelse();

public:

char *m_pBuffer;

int m_iSize;

int m_iTop;

};

#endif

***************************************************************/

/**************************************************************

#include<iostream>

#include"Mystack.h"

using namespace std;

int main()

{

Mystack *pmystack=new Mystack(4);

delete pmystack;

pmystack=NULL;

return 0;

}

**********************************************/