VC中利用ODBC链接access中的问题

if (GetData()->nRefs > 1 || nMinBufLength > GetData()->nAllocLength)
我编程的时候，在access中增加一列数据，运行VC，报错，显示上面buf出错，怎么修改。
LPTSTR CString::GetBuffer(int nMinBufLength)
{
    ASSERT(nMinBufLength >= 0);

    if (GetData()->nRefs > 1 || nMinBufLength > GetData()->nAllocLength)
    {
#ifdef _DEBUG
        // give a warning in case locked string becomes unlocked
        if (GetData() != _afxDataNil && GetData()->nRefs < 0)
            TRACE0("Warning: GetBuffer on locked CString creates unlocked CString!\n");
#endif
        // we have to grow the buffer
        CStringData* pOldData = GetData();
        int nOldLen = GetData()->nDataLength;   // AllocBuffer will tromp it
        if (nMinBufLength < nOldLen)
            nMinBufLength = nOldLen;
        AllocBuffer(nMinBufLength);
        memcpy(m_pchData, pOldData->data(), (nOldLen+1)*sizeof(TCHAR));
        GetData()->nDataLength = nOldLen;
        CString::Release(pOldData);
    }
    ASSERT(GetData()->nRefs <= 1);

    // return a pointer to the character storage for this string
    ASSERT(m_pchData != NULL);
    return m_pchData;


}