BUG: Resource/Memory Leaks When Using MFC in a Static Library

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++, 32-bit Editions, versions 4.2, 5.0

SYMPTOMS

When you run an application that is built using MFC in a static library under NuMega's BoundsChecker or other utility designed to find resource and memory leaks, the following five leaks occur:

E:\MSDEV\MFC\SRC\afxtls.cpp(180): Memory leak; 256 bytes allocated by
GlobalAlloc in afxtls.cpp at line 180, HANDLE: 0x02850004

E:\MSDEV\MFC\SRC\afxtls.cpp(122): Resource leak: Allocated by TlsAlloc
in afxtls.cpp at line 122, HANDLE: 0x0000000A

E:\MSDEV\MFC\SRC\afxtls.cpp(126): Resource leak: Allocated by
InitializeCriticalSection in afxtls.cpp at line 126, HANDLE: 0x005045D4

E:\MSDEV\MFC\SRC\afxcrit.cpp(54): Resource leak: Allocated by
InitializeCriticalSection in afxcrit.cpp at line 52, HANDLE: 0x005047E0

E:\MSDEV\MFC\SRC\afxcrit.cpp(105): Resource leak: Allocated by
InitializeCriticalSection in afxcrit.cpp at line 103, HANDLE: 0x00504778

CAUSE

MFC is allocating these objects to implement Thread Local Storage (TLS) data for it's primary thread and to synchronize access to MFC global data and resources. MFC does not free these objects when the application exits.

RESOLUTION

Because these objects are allocated only once per process and should be freed by the operating system when the process terminates, you can safely ignore them.

You can also free these objects by calling AfxTermLocalData(), AfxCriticalTerm(), and AfxTlsRelease() in the termination code. The sample code below shows this method.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

The following sample code demonstrates how to work around this problem. You should place the code in a separate source file and then add it to the project.

Sample Code

   #include "stdafx.h"
   #ifndef _AFXDLL

   void AFXAPI AfxCriticalTerm();

   class _AFX_TERM_EXE_STATE
   {
   public:
      _AFX_TERM_EXE_STATE();
      ~_AFX_TERM_EXE_STATE();
   };

   _AFX_TERM_EXE_STATE::_AFX_TERM_EXE_STATE()
   {
      // Add a reference to Thread Local Storage data.
      AfxTlsAddRef();
   }

   _AFX_TERM_EXE_STATE::~_AFX_TERM_EXE_STATE()
   {
      // Terminate local data and critical sections.
      AfxTermLocalData(NULL, TRUE);
      AfxCriticalTerm();

      // Release the reference to Thread Local Storage data.
      AfxTlsRelease();
   }

   // Force initialization early.
   #pragma warning(disable: 4074)
   #pragma warning(disable: 4073)
   #pragma init_seg(lib)

   _AFX_TERM_EXE_STATE _afxTermExeState;
   #endif // !_AFXDLL 

© Microsoft Corporation 1997, All Rights Reserved.
Contributions by Kelly Marie Ward, Microsoft Corporation

Keywords          : kb3rdparty kbcode kbMFC kbVC420bug kbVC500bug 
Version           : WINNT:4.2,5.0
Platform          : winnt 
Issue type        : kbbug 

Last Reviewed: July 9, 1999