FIX: Use of Implements and Public Constants Crashes Compiler (171489)


The information in this article applies to:

  • Microsoft Visual Basic Control Creation Edition for Windows 5.0
  • Microsoft Visual Basic Learning Edition for Windows 5.0
  • Microsoft Visual Basic Professional Edition for Windows 5.0
  • Microsoft Visual Basic Enterprise Edition for Windows 5.0
This article was previously published under Q171489

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:

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

For a list of the Visual Basic 5.0 bugs that were fixed in the Visual Studio 97 Service Pack 2, please see the following article in the Microsoft Knowledge Base:

171554 : 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:

    In Windows NT 4.0:
    The instruction at <address> referenced memory at <address>. The memory could not be read.[ASCII 148]
    In Windows 95, Windows 98, and Windows Me:
    VB5 has caused an invalid page fault in module VBA5.DLL at <address>
Modification Type:MajorLast Reviewed:12/10/2003
Keywords:kbbug kbfix kbVBp500fix kbVS97sp2fix KB171489
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