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

  • Question

  • Hi,

    there seems to be a bug in vbscript.dll since cumulative update KB4524570. 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"


            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


    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...



    Sunday, January 26, 2020 10:48 AM


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