BUG: Freeing Resource DLLs in ExitInstance Causes Error

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++, 32-bit Editions, versions 5.0, 6.0

SYMPTOMS

In Windows 95, calling FreeLibrary() on the resource DLLs in the ExitInstance() function of the COleControl-derived class causes an application error.

CAUSE

This is a bug in Windows 95. When FreeLibrary() is called on resource DLLs, Windows 95 is running through the chain of DLLs in that process and looking for other DLLs that have a zero reference count. This causes other DLLs to be unloaded too soon.

RESOLUTION

Move the FreeLibrary() calls to the destructor function of the COleControl-derived class.

STATUS

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

MORE INFORMATION

Steps to Reproduce Behavior

1. Use Control Wizard to generate an ActiveX control project.



2. Create a non-MFC resource-ONLY DLL. Make sure you specify the /NOENTRY switch in the Project, Settings dialog box.



3. Call LoadLibrary in InitInstance() of the control's CWinApp-derived class.



4. Call FreeLIbrary in ExitInstance() of the control's CWinApp-derived class.



5. Build the resource-ONLY DLL and the ActiveX control projects. Make sure the .dll file is being placed in the same directory as the .ocx file.



6. At the MS-DOS prompt, change to the directory where both the .ocx and .dll files are found. Type "REGSVR32 mycontrol.OCX".

REFERENCES

(c) Microsoft Corporation 1999, All Rights Reserved. Contributions by Yeong-Kah Tam, Microsoft Corporation.

Additional query words: ocx

Keywords : kbole kbDLL kbMFC kbVC kbVC500bug kbVC600bug kbWinOS95bug
Version : winnt:5.0,6.0
Platform : winnt
Issue type : kbbug