PRB: ASSERT(hbrBtnFace != NULL) In AuxData.cpp

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

SYMPTOMS

An ASSERT can occur when a non-MFC application tries to load, free, and again load an MFC Regular DLL. The assert occurs in the Auxdata.cpp file as a result of a failed call to GetSysColorBrush. The specific code is:

   hbrBtnFace = ::GetSysColorBrush(COLOR_BTNFACE);
   ASSERT(hbrBtnFace != NULL); 

CAUSE

User32.dll leaks resources, which causes ::GetSysColorBrush to fail.

RESOLUTION

If a non-MFC application intends to load and free a Regular DLL, make sure that User32.dll is not also being unloaded when FreeLibrary is used to free the DLL. To do so, you can call LoadLibrary to load User32.dll once in the application, before the application loads and frees the Regular DLL.

STATUS

Microsoft is researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

In its initialization process, MFC loads User32.dll. The ASSERT occurs when the Regular DLL is the only module in an application that uses User32.dll (including the application). If this application loads, frees, and again loads this DLL, the ASSERT occurs because User32.dll does not free all of its resources when it is unloaded.

As a result, the data table used to store the value for the symbol COLOR_BTNFACE is corrupted. When the Regular DLL is loaded for the second time, GetSysColorBrush returns NULL.

REFERENCES

For additional information, please see the following articles in the Microsoft Knowledge Base:

Q184807 BUG: User32.dll Leaks Memory

Q171145 PRB: Resource Leaks in System Components

© Microsoft Corporation 1998, All Rights Reserved.
Contributions by Isaac L. Varon, Microsoft Corporation

Additional query words: GDI kbDLL kbKernBase kbMFC kbVC500

Keywords :
Version : winnt:5.0
Platform : winnt
Issue type : kbprb