FIX: Unregistering ATL Server Causes Access Violation

ID: Q194180

The information in this article applies to:

The Microsoft Active Template Library (ATL) 3.0, used with:
- Microsoft Visual C++, 32-bit Editions, version 6.0

SYMPTOMS

Unregistering an ATL DLL or .exe file that was built with a version of Visual C++ prior to 6.0 might result in an access violation when Atl.dll (version 3.00.8168) that ships with Visual C++6.0 is installed on the machine.

Running "REGSVR32.EXE /U" to unregister an ATL DLL might display the following error message:

DllUnregisterServer in <component.dll> failed. Return code was: 0xc0000005

Running an ATL .exe file with the "/Unregserver" switch may display a dialog box titled "OleMainThreadWndName: <server.exe> - Application Error", with the following error message:

The instruction at 0x00000000 referenced memory at 0x00000000. The memory could not be read.

The ATL server has to be of build type Release MinSize or Unicode Release MinSize.

CAUSE

In the version of Atl.dll that comes with Visual C++ 6.0, the _ATL_OBJMAP_ENTRY structure has an additional member called "pfnGetCategoryMap". During unregistration, AtlModuleUnregisterServerEx() tries to access this member, which does not exist for ATL servers built prior to Visual C++ 6.0, and the access violation occurs.

RESOLUTION

To work around this problem, use one of the following options:

Rebuild your server with Release MinDependency. This statically links in all the code that was in Atl.dll, so your server isn't dependent on it.

Rebuild your server with Visual C++ 6.0.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:

Q194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why

Q194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed

Additional query words:

Keywords : kberrmsg kbservicepack kbActiveX kbCOMt kbRegistry kbVC600bug kbATL300 kbATL300bug kbVS600sp2 kbfaq kbVS600SP1 kbVS600sp3fix kbGrpMFCATL
Version : WINDOWS:3.0
Platform : WINDOWS
Issue type : kbbug