Solved

Access violation when deleting CFrameWnd

Posted on 2006-11-02
9
661 Views
Last Modified: 2013-11-20
Ah hello.

I have the following code in a handler for a button on a dialog:

void CDialogAppDlg::OnBnClickedButton1()
{
      if ( m_pFrameWnd )
      {
            m_pFrameWnd->DestroyWindow();
            delete m_pFrameWnd;
      }

      m_pFrameWnd = new CFrameWnd();
      m_pFrameWnd->Create ( NULL, _T("Frame Window") );
      m_pFrameWnd->UpdateWindow();
      m_pFrameWnd->ShowWindow ( SW_SHOW );

}

Assume

CFrameWnd* m_pFrameWnd;

Now, I can click the button once and create the window, but if I click it again I get access violation when calling

m_pFrameWnd->DestroyWindow()

Strangely enough, if I just create the window once, then close the app, I get no memory leaks, which I would expect from

      m_pFrameWnd = new CFrameWnd();

What is going on ?

TIA
0
Comment
Question by:mrwad99
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 5
  • 4
9 Comments
 
LVL 48

Accepted Solution

by:
AlexFM earned 125 total points
ID: 17857559
CFrameWnd detetes itself in PostNCDestroy, it is enough to call DestroyWindow.
0
 
LVL 19

Author Comment

by:mrwad99
ID: 17857571
>> CFrameWnd detetes itself in PostNCDestroy

OK so that explains why I get no memory leaks

>> it is enough to call DestroyWindow.

I cannot call DestroyWindow, that is what crashes.  Or are you saying I don't need to ?

Thanks.
0
 
LVL 48

Expert Comment

by:AlexFM
ID: 17857611
How exactly does it crash?
Try this:

m_pFrameWnd->SendMessage(WM_CLOSE, 0, 0);
0
VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

 
LVL 19

Author Comment

by:mrwad99
ID: 17857635
Thanks.
0
 
LVL 19

Author Comment

by:mrwad99
ID: 17857638
>> How exactly does it crash?

Not sure what you were getting at there.  Can you elaborate ?

0
 
LVL 48

Expert Comment

by:AlexFM
ID: 17857724
Code line, message etc. - as usual. But I think it is enough to remove delete m_pFrameWnd line.
0
 
LVL 19

Author Comment

by:mrwad99
ID: 17857825
>> But I think it is enough to remove delete m_pFrameWnd line.

I have stepped though the code and found that I don't even need the

m_pFrameWnd->DestroyWindow(), as this gets called when I close the window via the 'X' button.  But I would need to call this if the user closes the dialog before the main window, otherwise I would get leaks.

Interestingly so, when I do close the dialog with the frame window still active, the frame window does go away, and I get the leak on

m_pFrameWnd = new CFrameWnd();

detected.

I assume the OS destroys the CFrameWnd, but still, I only get one call into

CWnd::DestroyWindow()

which is called for the modal dialog.  Not for the CFrameWnd...

Do you know why this is ?

(Sorry to go on after I have closed this, but I read your last comment a bit late)
0
 
LVL 48

Expert Comment

by:AlexFM
ID: 17857959
When you close dialog, application exits immediately. In this case possibly CFrameWnd is not deleted properly, because OnNCDestroy is not called, and there is memory leak. It is possible to debug this or read MFC code, but closing frame when dialog is closed fixes this problem in any case.
0
 
LVL 19

Author Comment

by:mrwad99
ID: 17858057
Thanks again :o)
0

Featured Post

Learn how to optimize MySQL for your business need

With the increasing importance of apps & networks in both business & personal interconnections, perfor. has become one of the key metrics of successful communication. This ebook is a hands-on business-case-driven guide to understanding MySQL query parameter tuning & database perf

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In this article, I'll describe -- and show pictures of -- some of the significant additions that have been made available to programmers in the MFC Feature Pack for Visual C++ 2008.  These same feature are in the MFC libraries that come with Visual …
Introduction: Hints for the grid button.  Nested classes, templated collections.  Squash that darned bug! Continuing from the sixth article about sudoku.   Open the project in visual studio. First we will finish with the SUD_SETVALUE messa…
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
This tutorial will teach you the special effect of super speed similar to the fictional character Wally West aka "The Flash" After Shake : http://www.videocopilot.net/presets/after_shake/ All lightning effects with instructions : http://www.mediaf…

622 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question