Microsoft KB Archive/168111

= FIX: #import Does Not Compensate for Gaps in vtable =

Article ID: 168111

Article Last Modified on 7/5/2005

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APPLIES TO


 * Microsoft Visual C++ 5.0 Enterprise Edition
 * Microsoft Visual C++ 5.0 Professional Edition

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This article was previously published under Q168111



SYMPTOMS
An access violation may occur when you #import a type library of a COM object that was produced by Visual Basic 5.0.



CAUSE
The compiler does not compensate for gaps in the vtable left by Visual Basic for properties that are Objects. The sample code below demonstrates this problem.



STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual Studio 97 Service Pack 1.

For additional information about the Visual Studio 97 Service Pack 1, please see the following article in the Microsoft Knowledge Base:

170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why



Steps to Reproduce Behavior
  Place the following Visual Basic code in a Class Module of an ActiveX DLL project: Option Explicit Public Obj As Object Public Val As Long Private Sub Class_Initialize Val = 2 End Sub  Make a native dll from the above code. In this example, it is named Test.dll and the Class Module is named TestClass.  Place the following code in a .cpp file: #import "test.dll" no_namespace void func {        _TestClassPtr p( __uuidof(TestClass) ); int i = p->Val; // 0xc0000005 here }                       

When the C++ code is executed, an access violation occurs on the commented line of code.

Keywords: kbbug kbfix kbvs97sp1fix kbcompiler KB168111

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