Q187983: BUG: IDE Crash with Compiled GlobalMultiUse
Article: Q187983
Product(s): Microsoft Visual Basic for Windows
Version(s):
Operating System(s):
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001
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The information in this article applies to:
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0
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SYMPTOMS
========
If the Terminate event of a GlobalMultiUse class calls a procedure in another
DLL, and if the same GlobalMultiUse class had previously called the same DLL,
then you receive an error and the IDE may crash.
With Visual Basic 5.0, you may receive one of the following errors:
Exception: privileged instruction (0xc0000096), Address: 0x00186a3a
-or-
VB5 caused an invalid page fault (or general page fault)
With Visual Basic 6.0, the IDE does not crash, but you may receive the following
error:
Run-time error '-2147418105 (80010007)':
Automation error
This error translates to:
"The callee (server [not server application]) is not available and
disappeared; all connections are invalid. The call may have executed."
CAUSE
=====
This problem can occur when the ActiveX components are not shut down in the
necessary order when your client application ends. For example, suppose your
client application uses two ActiveX DLLs (DLL1 and DLL2). If the Terminate event
of a class in DLL2 calls a procedure in DLL1, but DLL1 has been shut down before
DLL2, you can experience this problem because the procedure in DLL1 is
unavailable. The "Steps to Reproduce Behavior" section of this article
demonstrates this scenario and shows how to work around the problem by
controlling the order in which the two DLLs shut down.
STATUS
======
Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this bug and will post new
information here in the Microsoft Knowledge Base as it becomes available.
MORE INFORMATION
================
Steps to Reproduce Behavior
---------------------------
1. Start a new ActiveX DLL project and name the project P_DLL1.
2. Name its default module C_DLL1Globals and change its Instancing property to
GlobalMultiUse.
3. Add the following code to C_DLL1Globals:
Public Function DLL1_Function() As String
DLL1_Function = "Func1"
End Function
4. Add a second new ActiveX DLL project and name the project P_DLL2.
5. Name its default module C_DLL2Globals and change it's Instancing property to
GlobalMultiUse.
6. Add the following code to C_DLL2Globals:
Public Sub DLL2_FunctionWhichCallsDLL1_Function()
Dim s As String
s = DLL1_Function
End Sub
Public Property Get PublicObject() As C_PublicObject
Set PublicObject = M_Globals.PublicObject
End Property
7. Add a second Class Module to P_DLL2. Change the name to C_PublicObject and
change its Instancing property to PublicNotCreatable.
8. Add the following code to C_PublicObject:
Private m_Something As Integer
Private Sub Class_Terminate()
Dim s As String
s = DLL1_Function
End Sub
Public Property Let Something(ByVal vData As Integer)
m_Something = vData
End Property
9. Add a Standard Module to P_DLL2 and name it M_Globals.
10. To create a reference to P_DLL1, click References on the Project menu and
check P_DLL1.
11. Add the following code to M_Globals:
Private m_PublicObject As C_PublicObject
Public Property Get PublicObject() As C_PublicObject
If m_PublicObject Is Nothing Then
Set m_PublicObject = New C_PublicObject
End If
Set PublicObject = m_PublicObject
End Property
12. Add a Standard EXE project, and name the project GroupExe.
13. Name the default form frmGroupExe, and add a CommandButton to it.
14. Add the following code to frmGroupExe:
Private Sub Command1_Click()
DLL2_FunctionWhichCallsDLL1_Function
End Sub
Private Sub Form_Load()
PublicObject.Something = 1
End Sub
15. Save the project files.
16. Compile P_DLL1.dll and remove the P_DLL1 project from the project group by
choosing Remove Project from the File menu.
17. Compile P_DLL2.dll and remove the P_DLL2 project from the project group by
choosing Remove Project from the File menu.
18. In GroupExe, create a reference to P_DLL2.
19. Save your work.
NOTE: The next step will crash the IDE and you may lose your work if you do
not save it at this time.
20. Run GroupExe, click the CommandButton, and then exit GroupExe. Note that the
IDE crashes with one of the errors mentioned previously.
This problem occurs during the shut down process. If you were to trace the order
in which the classes in the two DLLs shut down, you would see the following
order of events:
C_DLL2Globals Terminate
C_DLL1Globals Terminate
C_PublicObject Terminate
The problem occurs when the Terminate event of C_PublicObject tries to call the
DLL1_Function, which is in the C_DLL1Globals object. Because the C_DLL1Globals
object has closed, the DLL1_Function cannot be called.
To work around this problem, make sure the C_PublicObject Terminate event occurs
while the C_DLL1Globals object is still available. To accomplish this task, put
code in the Terminate event of C_DLL2Globals that causes the C_PublicObject to
terminate. This will force the C_PublicObject Terminate event to fire before the
C_DLL1Globals object is closed. Here's the code modifications for the
workaround:
Put the following procedure in the M_Globals module of P_DLL2:
Public Sub ClosePublicObject
Set m_PublicObject = Nothing
End Sub
Next, add the following code to the C_DLL2Globals class:
Private Sub Class_Terminate()
ClosePublicObject
End Sub
Now, when C_DLL2Globals terminates, the ClosePublicObject procedure is run that
causes the C_PublicObject object to terminate. The new order of events during
shutdown is:
C_DLL2Globals Terminate
C_PublicObject Terminate
C_DLL1Globals Terminate
REFERENCES
==========
For more information about ActiveX component shutdown guidelines, please refer
to Appendix B: ActiveX Component Standards and Guidelines in the Visual Basic
Components Tools Guide
Additional query words: kbDSupport kbDSD gpf ipf kernel32.dll 0137:bff858c0 kbVBp500bug kbActiveX
kbClientServer kbVBp600bug kbVBp kbdsd kbDSupport
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Keywords : kbGrpDSVB
Technology : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Issue type : kbbug
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