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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Bus error
Date: Wed, 27 Jun 2007 21:58:49 -0400
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Date: 2007-06-27T21:58:49-04:00
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Maciej Sobczak <see.my.homepage@gmail.com> writes:

> On 27 Cze, 17:45, Georg Bauhaus <rm.tsoh+bauh...@maps.futureapps.de>
> wrote:
>> Procedure Make should be fine as the object returned is to be
>> built in place. (As per Bob Duff's "gems" on limited aggregates
>> and other sources.)

Thanks for mentioning the "gems", Georg.

> Except that those gems don't tell much about extension aggregates and
> even less about limited controlled.

There are a few more gems on this subject in the pipeline -- stay tuned.

http://www.adacore.com/category/developers-center/gems

> 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.
That means that clients cannot extend the type, but child packages can.

>... It is tagged only so that it can be controlled and since this
> is implementation detail,
> it should be private together with the extension.

Right.

> I cannot check it, because this time I get the explicit "GNAT BUG
> DETECTED".

...which requests that you send a bug report.  If you're not a supported
customer of AdaCore, and you send a bug report, it will eventually get
fixed (but it's lower priority than paying customers).

> Ideally, the public view should look like this:
>
> type T (<>) is limited private;
>
> With the private view unchanged. Is it possible? (assuming good
> compiler)

Yes, that's possible.  Assuming a bug-free compiler, of course. ;-).

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.

- Bob