vbscript.dll class_terminate bug since KB4524570 (November 12, 2019) Windows 10 1903

Question

Hi,

there seems to be a bug in vbscript.dll since cumulative update 4524570. When I create a instance of a class inside a class member function and assign it to a local variable the instance is not directly destroyed when this member function is left as it was before this update. See the following example code:

Option Explicit

Class CTest

    Sub Class_Initialize

        WScript.Echo Timer & ": CTest::Class_Initialize()"

    End Sub

    Sub Class_Terminate

        WScript.Echo Timer & ": CTest::Class_Terminate()"

    End Sub

End Class

Class CFoo

    Sub Work

        WScript.Echo Timer & ": CFoo::Work() started"

        DoWork

        WSCript.Sleep 3000

        WScript.Echo Timer & ": CFoo::Work() done"

    End Sub

    Sub DoWork

        WScript.Echo Timer & ": CFoo::DoWork() started"

        Dim obj

        Set obj= New CTest

        WScript.Echo Timer & ": CFoo::DoWork() done, CTest::Class_Terminate() should be called now without delay"

    End Sub

End Class

Dim objFoo

Set objFoo= New CFoo

objFoo.Work

WScript.Echo Timer & ": objFoo.Work() done"

When executing using cscript.exe the following output is generated:

80547,52: CFoo::Work() started

80547,52: CFoo::DoWork() started

80547,52: CTest::Class_Initialize()

80547,52: CFoo::DoWork() done, CTest::Class_Terminate() should be called now without delay

80550,52: CFoo::Work() done

80550,52: CTest::Class_Terminate()

80550,53: objFoo.Work() done

When executing with a prior version of vbscript.dll the output looks correct like this:

79971,76: CFoo::Work() started

79971,76: CFoo::DoWork() started

79971,76: CTest::Class_Initialize()

79971,76: CFoo::DoWork() done, CTest::Class_Terminate() should be called now without delay

79971,76: CTest::Class_Terminate()

79974,76: CFoo::Work() done

79974,76: objFoo.Work() done

I think this will lead to problems in any kind of code that count on the fact that objects referenced by local variables are destroyed when the scope is left.

The same bug is there on Windows 7 since KB4524535 (November 12, 2019 (Monthly Rollup)).

Is there any reason for this change in this behavior? I hope there will be a bugfix for this soon...

Regards,

Steffen.

Answer 1

I have asked a similar question on Stack Overflow

We identified another KB for our out-of-memory issue but at the root it looks like the same problem.

Regards,

Lieven