FIX: Use of Implements and Public Constants Crashes Compiler

• Microsoft Visual Basic Control Creation, Learning, Professional, and Enterprise Editions for Windows, version 5.0

SYMPTOMS

Using the IMPLEMENTS statement in a private class that is implementing another private class in the same project can cause a compiler error if public module level constants used by the implemented class are not located in the same .BAS file. This error occurs whether the code is compiled to p-code or native code. It does not occur while running in the IDE.

RESOLUTION

To work around this behavior, declare all public module level constants used by an implemented class in the same .BAS file.

In the sample below, if LF_FACESIZE is declared in the same module as the other public module level constants (in Module1 rather than Module2), then the error does not occur.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been fixed in Visual Studio 97 Service Pack 2.

For more information on the Visual Studio 97 Service Pack 2, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q170365
   TITLE     : INFO: Visual Studio 97 Service Packs - What, Where, and Why

   ARTICLE-ID: Q171554
   TITLE     : INFO: Visual Basic 5.0 Fixes in Visual Studio 97
               Service Pack 2

MORE INFORMATION

1. Start a new Standard EXE project.

2. Add a new module (Module1) and add the following code:

         Public Type tFont
            Color As Long
            Angle As Integer
            Bold As Byte
            Italic As Byte
            Underline As Byte
            StrikeOut As Byte
            PointSize As Single
            Name As String * LF_FACESIZE
         End Type
   
   

3. Add another module (Module2) to the project and add the following code:

         Global Const LF_FACESIZE As Long = 32
   

4. Add a third module (Module3) to the project and add the following code:

         Sub Main()
   
         End Sub
   
   

5. Add a class (Class1) to the project and add the following code:

         Private mtWindowProps As tFont
   

         Public Property Let BorderStyle(nNewValue As Integer)
         End Property
   

         Public Property Get BorderStyle() As Integer
         End Property
   

6. Add a second class (Class2) to the project and add the following code:

         Implements Class1
   

         Private Property Get Class1_BorderStyle() As Integer
         End Property
   

         Private Property Let Class1_BorderStyle(RHS As Integer)
         End Property
   

7. Compile the project, using either p-code or native code. You should get an Application Error:

   "The instruction at <address> referenced memory at <address>. The memory could not be read.” (Windows NT4)

   -or-

   "VB5 has caused an invalid page fault in module VBA5.DLL at <address>" (Windows95)

Keywords          : vb5all VS97FixlistSP3 VS97FixlistSP2 VB5FixlistSP2
Version           : 5.0
Platform          : WINDOWS
Issue type        : kbbug
Solution Type     : kbfix kbservicepack