PRB: "Warning: Calling DestroyWindow in CWnd::~CWnd" Message (105081)
The information in this article applies to:
- The Microsoft Foundation Classes (MFC), when used with:
- Microsoft Visual C++, 32-bit Professional Edition
- Microsoft Visual C++, 32-bit Enterprise Edition
- Microsoft Visual C++, 32-bit Learning Edition
This article was previously published under Q105081 SYMPTOMS
The following warnings are displayed when a debug version of a program is
executed and TRACE() diagnostics are enabled:
Warning: calling DestroyWindow in CWnd::~CWnd
OnDestroy or PostNcDestroy in derived class will not be called
CAUSE
The above warnings are displayed by the CWnd::~CWnd() destructor.
The warnings indicate the following:
- The programmer has most likely called "delete" on a CWnd object
rather than DestroyWindow().
- An object derived from CWnd is not performing a DestroyWindow()
call in its destructor.
- Because the DestroyWindow() call is executed in the destructor
for CWnd, only the CWnd portion of the CWnd-derived object is
remaining when the DestroyWindow() is called. Thus, if you have
a CWnd-derived object and receive this warning, the derived
object's virtual functions will not exist and the CWnd functions
will be called instead.
RESOLUTION
MFC Technote #17 contains more information on how to properly destroy a
Window object and states the following cardinal rule:
To destroy a C++ Windows object, use DestroyWindow, not "delete".
Also, examining CWnd::~CWnd() will reveal that the foremost task of the
destructor is to ensure that the associated Windows window object has been
destroyed. If a program calls DestroyWindow() before the CWnd destructor
is called, the m_hWnd data member will be NULL, the TRACE0() messages will
not occur, and DestroyWindow() will not be called in CWnd::~CWnd().
| Modification Type: | Major | Last Reviewed: | 12/1/2003 |
|---|
| Keywords: | kbprb kbWndw KB105081 |
|---|
|