On Apr 4, 12:08 pm, Adam Beneschan <a...@[EMAIL PROTECTED]
> wrote:
> On Apr 4, 2:33 am, stefan-lu...@[EMAIL PROTECTED]
wrote:
>
>
>
> > Hi,
>
> > I have written a little program to demonstrate finalisation. The idea
is
> > to locally declare a singelton object of a class derived from
> > Ada.Finalization.Limited_Controlled, and to override the Finalize
method.
> > When the sigelton object leaves scope, Finalize than cleans up
whatever
> > needs to be cleaned up. At a first look this appeared to work nicely.
But
> > when done in a recursive subprogram, Finalize rather unexpectedly
seems to
> > always read the local parameters of the innermost scope.
>
> > Here is a test case:
>
> > ---begin fin_test_case.adb
>
> > with Ada.Text_IO, Ada.Finalization;
>
> > procedure Fin_Test_Case is
> > type Fin is new Ada.Finalization.Limited_Controlled with null
record;
>
> > procedure Do_Something (I: Natural) is
>
> > type My_Fin is new Fin with null record;
>
> > overriding procedure Finalize(Self: in out My_Fin) is
> > S: String := Natural'Image(I);
> > begin
> > Ada.Text_IO.Put_Line(" Do_Something Finalization " & S);
> > end Finalize;
>
> > Singleton: My_Fin;
>
> > begin -- Do_Something
> > Ada.Text_IO.Put_Line(" I = " & Natural'Image(I));
> > if I>0 then
> > Do_Something(I-1);
> > Do_Something(I-1);
> > end if;
> > end Do_Something;
>
> > begin
> > Ada.Text_IO.Put_Line("Start Do_Something (2)");
> > Do_Something(2);
> > Ada.Text_IO.Put_Line("Stop Do_Something (2)");
> > end Fin_Test_Case;
>
> > ---end fin_test_case.adb
>
> > This is what I got:
>
> > ---begin output
>
> > Start Do_Something (2)
> > I = 2
> > I = 1
> > I = 0
> > Do_Something Finalization 0
> > I = 0
> > Do_Something Finalization 0
> > Do_Something Finalization 0
> > I = 1
> > I = 0
> > Do_Something Finalization 0
> > I = 0
> > Do_Something Finalization 0
> > Do_Something Finalization 0
> > Do_Something Finalization 0
> > Stop Do_Something (2)
>
> > ---end output
>
> > Somehow, the local parameter I is always 0 when finalize is called.
What I
> > expected was the following:
>
> > ---begin expected output
>
> > Start Do_Something (2)
> > I = 2
> > I = 1
> > I = 0
> > Do_Something Finalization 0
> > I = 0
> > Do_Something Finalization 0
> > Do_Something Finalization 1
> > I = 1
> > I = 0
> > Do_Something Finalization 0
> > I = 0
> > Do_Something Finalization 0
> > Do_Something Finalization 1
> > Do_Something Finalization 2
> > Stop Do_Something (2)
>
> > ---end expected output
>
> > Now, is my expectation wrong? Or is this a compiler bug? I am using
> > GNAT GPL 2007 (20070405-41).
>
> This looks like a pretty clear compiler bug, especially since by the
> time Finalize is called by the outermost Do_Something, it's using, for
> the value of I, the parameter from a Do_Something call that is no
> longer active. It shouldn't be hard to modify this slightly, using
> (say) a string or record as a parameter to Do_Something, to create a
> test where utter garbage is displayed; then it would be clearer that
> this is a compiler bug.
>
> -- Adam
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