You receive error messages in an MFC application when you upgrade from an earlier version of Visual C++ to Visual C++ 4.2 or a later version

This article was previously published under Q154744
This article has been archived. It is offered "as is" and will no longer be updated.
SYMPTOMS
The error below may occur in an MFC application where one of the following is assigned a value by the programmer:
   CWinApp::m_pszAppName   CWinApp::m_pszRegistryKey   CWinApp::m_pszExeName   CWinApp::m_pszHelpFilePath   CWinApp::m_pszProfileName					
The following error is displayed in a message box:
   Debug Assertion failed   Program: my.exe   File: dbgheap.c   Line: 1017   Expression:_BLOCK_TYPE_IS_VALID(pHead->nBlockUse)					
In Microsoft Visual C++ 6.0, the following error is displayed in a message box:
   Debug Assertion failed   Program: my.exe   File: dbgheap.c   Line: 1011   Expression: _CrtIsValidHelpPointer(pUserData)					
You may see this error when you upgrade from an earlier version of Visual C++ to Visual C++ versions 4.2 or later.
CAUSE
The CWinApp destructor in MFC included with Visual C++ 4.2 and later now frees the data assigned to the member variables shown above by passing the pointer to the free() function. Doing this prevents memory leaks, which would occur if an MFC regular DLL were dynamically loaded and unloaded.
STATUS
This behavior is by design.
RESOLUTION
If you assign a value to m_pszAppName, m_pszRegistryKey, m_pszExeName, m_pszHelpFilePath, or m_pszProfileName, the data must be dynamically allocated on the heap. You may want to use the _tcsdup() run-time library function to do this.

Also, free the memory associated with the current pointer before assigning a new value. Here is an example:
   // First free the string that was allocated by MFC in the startup   // of CWinApp. The string is allocated before InitInstance is   // called.   free((void*)m_pszProfileName);   // Change the name of the .INI file--CWinApp destructor will free   // the memory.   m_pszProfileName=_tcsdup(_T("d:\\somedir\\myini.ini"));				
4.10 port porting strdup
Properties

Article ID: 154744 - Last Review: 02/28/2014 04:16:22 - Revision: 4.1

Microsoft Foundation Class Library 4.2

  • kbnosurvey kbarchive kberrmsg kbtshoot kbprb KB154744
Feedback