写string类遇到的问题

// wjbString.cpp: implementation of the CwjbString class.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "wjbString.h"

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

CwjbString::CwjbString()
{
    m_nLength = 0;
    m_pString = NULL;
}

CwjbString::CwjbString(char * pString)
{
    if(NULL != pString)
    {
        m_nLength = Strlen(pString);
        m_pString = new char[m_nLength + 1];
        Strcpy(m_pString, pString);
    }

}

CwjbString::CwjbString(CwjbString &r)
{
    m_nLength = r.m_nLength;
    m_pString = new char[m_nLength + 1];
    Strcpy(m_pString, r.m_pString);
}

CwjbString::~CwjbString()
{
    if(NULL != m_pString)
    {
        delete [] m_pString;
        m_pString = NULL;
    }
}

void CwjbString::SetString(const char *pString)
{
    delete [] m_pString;
    m_pString = NULL;
    m_nLength = Strlen(pString);
    m_pString = new char[m_nLength + 1];
    Strcpy(m_pString, pString);
}

char * CwjbString::GetString()
{
    return m_pString;
}

int CwjbString::GetLength()
{
    return m_nLength;
}

int CwjbString::Strlen(const char *pString)
{
    int nLength = 0;
    while('\0' != *pString++)
    {
        nLength++;
    }

    return nLength;
}

char * CwjbString::Strcpy(char *pString, const char *pString1)
{
    for(int i = 0; i <= Strlen(pString1); i++)
    {
        pString[i] = pString1[i];
    }
    return pString;
}

char * CwjbString::Strcat(char *pString, const char *pString1)
{
    char *pTemp = pString;
    while('\0' != *pTemp++)
        continue;
    while('\0' != (*pTemp++ = *pString1++))
        continue;

    return pString;
}

CwjbString& CwjbString::StrLink(const char *pString, const char *pString1)
{
    int n1 = Strlen(pString);
    int n2 = Strlen(pString1);
    m_pString = new char[n1+n2+1];
   
    int i;
    for(i = 0; i < n1; i++)
    {
        m_pString[i] = pString[i];
    }

    for(int j = 0; j <= n2; j++)
    {
        m_pString[i+j] = pString1[j];
    }
    m_nLength = n1 + n2;

    return *this;
}

CwjbString& CwjbString::operator = (const CwjbString& a)
{
    m_nLength = a.m_nLength;
    m_pString = new char[m_nLength + 1];
    Strcpy(m_pString, a.m_pString);

    return *this;
}

CwjbString& CwjbString::operator = (const char *pString)
{
    m_nLength = Strlen(pString);
    m_pString = new char[m_nLength + 1];
    Strcpy(m_pString, pString);

    return *this;
}

CwjbString CwjbString::operator + (const CwjbString& a)
{
    CwjbString Temp;
    Temp = Temp.StrLink(m_pString, a.m_pString);

    return Temp;
}

CwjbString CwjbString::operator + (const char *pString)
{
    CwjbString Temp;
    Temp = StrLink(m_pString, pString);
    return Temp;
}

CwjbString operator + (const char *pString , const CwjbString& a)
{
    CwjbString Temp;
    Temp = Temp.StrLink(pString, a.m_pString);
    return Temp;
}