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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Bus error
Date: Thu, 28 Jun 2007 17:19:09 -0400
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Date: 2007-06-28T17:19:09-04:00
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Maciej Sobczak <see.my.homepage@gmail.com> writes:

> On 28 Cze, 03:58, Robert A Duff <bobd...@shell01.TheWorld.com> wrote:
>
>> > BTW - is it necessary to reveal in the public view that the type is
>> > tagged?
>>
>> No.  You can have an untagged private type whose full type is tagged.
>
> You mean - untagged *public*, I suppose?

Yeah, the terminology is confusing.  I mean:

    package P is
        type T is limited private;
    private
        type T is tagged limited ...;
    end P;

or:

    with Ada.Finalization; use Ada;
    package P is
        type T is limited private;
    private
        type T is new Finalization.Limited_Controlled with ...;
    end P;

Both of the above are legal.

>> > I cannot check it, because this time I get the explicit "GNAT BUG
>> > DETECTED".
>>
>> ...which requests that you send a bug report.
>
> I conclude that AdaCore guys read comp.lang.ada as well. :-)

Not really.  ;-)

I read it once in a while, but often not for months at a time.
Most AdaCore folks do not read comp.lang.ada at all.

And AdaCore certainly does not go looking for GNAT bugs on
comp.lang.ada.  If you want a bug fixed, you have to send
an official bug report.  And if you want it fixed fast,
or want AdaCore to answer your questions, you have to spend
money.

>> As to your original question, about an extension aggregate: I don't see
>> anything wrong with your code, and I do recall fixing a bug in that area
>> (extension aggregate of limited type with controlled parts returned from
>> build-in-place function) a month or so ago.  The bug fix will eventually
>> find its way into the public version of GNAT.
>
> That's a good news, really. I consider this feature (limited
> controlled with unknown discriminant) to be fundamental for correct
> handling of external resources and other "interesting" types. It is
> really a high time for this feature to get a wider adoption.

Right, but it's the Ada 2005 build-in-place function return stuff that
makes these really useful.  The bug we're talking about (assuming it
really is the same bug that I fixed, which I can't promise) was a
nasty interaction between build-in-place functions and controlled
types.

- Bob