Crash bug in CDialog::DoModal

From:

=?Utf-8?B?U3JpdmF0c2FuICJWYXQiIFJhZ2hhdmFu?= <SrivatsanVatRaghavan@discussions.microsoft.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 24 Sep 2007 10:04:01 -0700

Message-ID:

<839D9A11-F4F4-4234-885C-D38D493AE2F1@microsoft.com>

Hi all,

this is related to a post i made last week.

To summarize i have a internal network monitoring app that we're currently
adding support for ups devices. So i have a popup modal message box
(using this class from codeproject ->
http://www.codeproject.com/dialog/MessageBoxDialog.asp) which tells the user
they have X seconds to shut everything down or the server will do it for
them.
This has a timeout and the [OK=X] button that gets updated via OnTimer.
the server can send a "all clear" packet and in that case i want to kill the
existing messagebox, and popup a new messagebox saying "all clear" with a
10second timeout.

This mostly works, but about 1/3 of the time i get a crash in DoModal after
the 2nd dialog box hits it timeout and disappears and i get a crash in
DoModal from the FIRST dialog box which causes my app to crash.

the code is below, while tryign to debug it i have this horrible feeling
it's cause it appears runmodalloop runs in seperate thread and my thread is
trying to delete the cdialog ptr from under mfc's feet.

void CFMainUIDlg::OnReportUPSDeviceAlert( const Socket1Packet &packet)
{
    BIT_ICD::STRUCT_REPORT_UPS_ALERT status;
    int length = sizeof(BIT_ICD::STRUCT_REPORT_UPS_ALERT);
    const char* body = packet.m_PacketBody.c_str();
    memcpy( &status, body, length);

    if( m_bKillMessageBox )
    {
        if(m_pDlgMessageBox)
        {
            Sleep(500);

            delete m_pDlgMessageBox;
            m_pDlgMessageBox = 0;
            m_bKillMessageBox = false;
        }
    }
    UI::ConnInfoIterator i = m_connections.find( status.IP );
    if ( i == m_connections.end() )
        return;
    BIT_ICD::UPSInfo ups;
    ups.eStatus = i->second->s.eUPSStatus;
    strncpy( ups.IP, i->first.c_str(), i->first.length() );
    strncpy( ups.sDeviceName, i->second->sPrettyName.c_str(),
i->second->sPrettyName.length() );

    UpdateTreeItem( ups );

    if ( !m_pDlgMessageBox )
    {
        if ( status.eStatus == BIT_ICD::UPS_POWER_LOSS )
        {
            CString upsName = i->second->sPrettyName.c_str();
            CString strTitle;
            strTitle.Format(UI::sUPSStatusMessagePowerLossAlertTitle.c_str(),
upsName.GetBuffer() );

            CString strMessage(UI::sUPSStatusMessagePowerLossAlertMessage.c_str());
            // Create a message box dialog.
            m_pDlgMessageBox = new CMessageBoxDialog(this, strMessage, strTitle,
MB_OK | MB_ICONEXCLAMATION);
            // Set the timeout for the message box.
            m_pDlgMessageBox->SetTimeout(status.iWaitingTime, false);
            // Display the dialog.
            INT_PTR nresult = m_pDlgMessageBox->DoModal();
            delete m_pDlgMessageBox;
            m_pDlgMessageBox = NULL;
        }
    }
    else
    {
        //dialog box exists, and we got an updated ups status. so we kill the box.
        if( ( status.eStatus == BIT_ICD::UPS_NORMAL) || (status.eStatus ==
BIT_ICD::UPS_CHARGING ) )
        {
            Sleep(500);
            //m_pDlgMessageBox->EndDialog( IDOK);
            m_bKillMessageBox = true;
            CMessageBoxDialog d(this,
UI::sUPSStatusMessagePowerRestoreMessage.c_str(),
                UI::sUPSStatusMessagePowerRestoreTitle.c_str(), MB_OK |
MB_ICONEXCLAMATION );
            d.SetTimeout( 10, false);
            int nResult = (int) d.DoModal();
        }
    }
}