Re: CWinThread, CFrameWnd and memory leak???
On Sat, 9 Feb 2008 07:21:14 -0800 (PST), ole.tetzschner@gmail.com wrote:
Hi
I guess it's just me being stupid, but I been googling and trying for
hours now and can't solve this problem myself.
The Problem is I have created a class (CmyUIthread) derived from
CWinThread, but when my test-app exit the compiler reports a memory
leak from a CFrameWnd object.
My test-app is just a dialog-app with 2 buttons. The first button just
create and starts the ui-thread:
m_p_thread = new CmyUIthread;
m_p_thread->CreateThread();
And the tread starts perfect :)
The second button stops the thread:
m_p_thread->PostThreadMessage( WM_QUIT,0,0);
And the thread stops :)
Use PostQuitMessage.
But when i quit my dlg-test-app the compiler reports the memory
leak???
I tried adding a third button that:
delete m_p_thread;
but this results in access violations.
The access violation occurs because you're relying on the auto-delete
behavior of CWinThread, which is a mistake. Go here for more:
http://members.cox.net/doug_web/threads.htm
CmyUIthread looks like this:
CmyUIthread::CmyUIthread()
{
}
CmyUIthread::~CmyUIthread()
{
}
BOOL CmyUIthread::InitInstance()
{
// TODO: perform and per-thread initialization here
CFrameWnd *wnd = new CFrameWnd;
wnd->Create( NULL, "myUIthread Window");
wnd->ShowWindow( SW_SHOW);
wnd->UpdateWindow();
m_pMainWnd = wnd;
return TRUE;
}
int CmyUIthread::ExitInstance()
{
// TODO: perform any per-thread cleanup here
return CWinThread::ExitInstance();
}
BEGIN_MESSAGE_MAP(CmyUIthread, CWinThread)
END_MESSAGE_MAP()
What is wrong??? do I miss some cleanup???
Why are you creating windows in a secondary thread? It's preferable to keep
all the windows in the primary thread, where issues like this don't occur.
If you are leaking a CFrameWnd object, it is due to the window not
receiving the WM_NCDESTROY message or you overriding it and not calling the
base version, which does "delete this". You should be able to set a
breakpoint in CFrameWnd::OnNcDestroy and verify it isn't being called. It
may be that you need to call DestroyWindow on it before exiting your
secondary thread. The tidier way would be to post WM_CLOSE, but it is
possible the frame window will decline to close, so you'd have to check
this before using PostQuitMessage.
--
Doug Harrison
Visual C++ MVP