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From: malaise@magic.fr
Newsgroups: comp.lang.ada
Subject: Re: Extending a type and Finalization
Date: Fri, 5 Jun 2009 04:29:36 -0700 (PDT)
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Date: 2009-06-05T04:29:36-07:00
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On 4 juin, 21:33, Adam Beneschan <a...@irvine.com> wrote:


> In addition to making an individual component a Limited_Controlled
> type, you can use trickery using access discriminants to allow the
> Initialize and Finalize routines to access the entire record.
I have done that and it works (at least it compiles). Thank's.

> However, if it's possible to go back and change P.T to make it a type
> derived from Limited_Controlled, that would be preferable, I think.
> The default Initialize and Finalize routines will be null, so doing
> this shouldn't change the semantics of the rest of the program any,
> although it will add some overhead.
I face a problem when doing that, despite it should be
straightforward!.

I declare P.T as "new Ada.Finalization.Controlled with record ..." and
I don't define Finalize for it.
Then in Pp I declare Tt as "new P.T with record ..." and I declare an
overriding procedure Finalize (V : in out Tt) and its body in Pp body.
It does not compile, with error: 'subprogram "Finalize" is not
overriding'

Same if I define in P a Finalize for T.

Any idea?

------------------------------
with Ada.Finalization;
package P is
  type T is tagged private;
private
  type T is new Ada.Finalization.Controlled with record
    I : Integer;
  end record;
end P;

with P;
package Pp is
  type Tt is tagged private;
private
  type Tt is new P.T with record
    Ii : Integer;
  end record;
  overriding procedure Finalize (V : in out Tt);
end Pp;

package body Pp is
  overriding procedure Finalize (V : in out Tt) is
  begin
    null;
  end Finalize;
end Pp;