DOCUMENT:Q184332 07-MAY-2001 [vbwin] TITLE :FIX: UserControl in VB4 or VC++ 5.0 Container Causes IPF on Exit PRODUCT :Microsoft Visual Basic for Windows PROD/VER::4.0,5.0 OPER/SYS: KEYWORDS:kbCRT kbCtrlCreate kbVBp kbVBp400bug kbVBp500bug kbVC500bug kbGrpDSVB ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Visual Basic Learning Edition for Windows, version 5.0 - Microsoft Visual Basic Professional Edition for Windows, version 5.0 - Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 - Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0 - Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0 - Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 ------------------------------------------------------------------------------- SYMPTOMS ======== An application compiled in Visual Basic 4.0 or Visual C++ 5.0 generates an "Invalid Page Fault in MSVBVM50.DLL" error when the application is closed. CAUSE ===== This error can occur in the following situation: - The Visual Basic 4.0 or Visual C++ 5.0 application contains a UserControl created in Visual Basic 5.0. -and- - The UserControl contains a Class that creates a reference to the UserControl. -and- - You are running Windows 95 or Windows 98. RESOLUTION ========== To work around this problem, use the ObjPtr function in combination with the CopyMemory API call to create the UserControl reference in the Class Module. The steps to complete the workaround are listed in the MORE INFORMATION section of this article. STATUS ====== Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This problem was corrected in Windows 2000. MORE INFORMATION ================ WARNING: One or more of the following functions are discussed in this article; VarPtr, VarPtrArray, VarPtrStringArray, StrPtr, ObjPtr. These functions are not supported by Microsoft Technical Support. They are not documented in the Visual Basic documentation and are provided in this Knowledge Base article "as is." Microsoft does not guarantee that they will be available in future releases of Visual Basic. Steps to Reproduce Behavior 1. Start a new ActiveX Control project in Visual Basic 5.0. 2. Name the project "passcontrol." 3. Add a Class Module to the project. 4. Add the following code to Class1: Private mycontrol As passcontrol.UserControl1 Friend Sub passSelf(obj As passcontrol.UserControl1) Set mycontrol = obj mycontrol.SayHello End Sub Private Sub Class_Terminate() Set mycontrol = Nothing End Sub 5. Add the following code to UserControl1: Private myclass As New passcontrol.Class1 Private Sub UserControl_Initialize() myclass.passSelf Me End Sub Friend Sub SayHello() MsgBox "Hello!" End Sub 6. On the File menu, click "Make Passcontrol.ocx" to build the control. 7. Create a new project in Visual Basic 4.0 (32-bit) or Visual C++ 5.0. 8. Add Passcontrol.ocx to your project's form. 9. Compile (or build) the Visual Basic or Visual C++ application. 10. Run the application on a computer running Windows 95, Windows 98, or Windows Me. 11. Exit the application. You should receive the error " caused an Invalid Page Fault in Module MSVBVM50.DLL." WARNING: If you reproduce this problem, it is advisable to restart the computer you are testing on after you receive the error. Passcontrol.ocx is locked by the system, and any attempt to manipulate this file causes your computer to freeze. Workaround In the Class Module, substitute the following code: Private Declare Sub CopyMemory _ Lib "kernel32" Alias "RtlMoveMemory" _ (pDest As Any, _ pSrc As Any, _ ByVal ByteLen As Long) Private mycontrol As passcontrol.UserControl1 Friend Sub passSelf(ByVal ptrobj As Long) CopyMemory mycontrol, ptrobj, 4 mycontrol.SayHello End Sub Private Sub Class_Terminate() Set mycontrol = Nothing End Sub In the UserControl, substitute the following code: Private myclass As New passcontrol.Class1 Private Sub UserControl_Initialize() myclass.passSelf ObjPtr(Me) End Sub Friend Sub SayHello() MsgBox "Hello!" End Sub Additional query words: VC++ C++ user control activex ocx ====================================================================== Keywords : kbCRT kbCtrlCreate kbVBp kbVBp400bug kbVBp500bug kbVC500bug kbGrpDSVB Technology : kbVCsearch kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB500 kbVB400Search kbVB400 kbVC500 kbVC32bitSearch kbVC500Search Version : :4.0,5.0 Issue type : kbbug Solution Type : kbfix ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2001.