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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Issue with GNAT GPL 2009 and GtkAda
Newsgroups: comp.lang.ada
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Date: Wed, 24 Jun 2009 09:40:03 +0200
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Date: 2009-06-24T09:40:03+02:00
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On Tue, 23 Jun 2009 23:52:59 +0200, Damien Carbonne wrote:

> When compiling a program I had written to GNAT GPL 2009 on Linux and 
> Windows, I met a problem with the usage of Gtk.Tree_Model.Foreach.
> 
> I wrote a relatively small program (unfortunately, still quite long) 
> that reproduces the problem (attached in the end).
> 
> I wonder if this is a bug in
>     1) my program,
>     2) GtkAda or
>     3) GNAT GPL 2009.
> What surprises me is that it was quite hard to reproduce this problem.
> Most other examples I wrote with Foreach worked very well.
> I don't know how GNAT handles accessibility rules.
> I wonder if the problem is not related to the usage of Interfaces ?
> I did not try yet to change the program so that it can work, but other 
> examples I wrote were quite similar, except that they did not use 
> interfaces. I'll check, but do you have any idea on this issue ?

Well, it is difficult to say, I never used foreach. I do Gtk_Tree_Iter
instead. I looked briefly at the implementation of Foreach in GtkAda and
found nothing offending.

Interface should not be a problem. Run-time accessibility checks is always
a *huge* problem. If in doubt use Unchecked_Access everywhere. I know it is
disgusting, but so is the propagation of a Constraint_Error at run-time.

Other possible issues:

1. Types extending GtkAda types must be library-level

2. Text_IO shall not be used (may cause exception propagation at least on
some platforms, with a subsequent crash. Ada exceptions propagated through
Gtk almost certainly crash the program. You cannot catch them)

3. In your code there is no "unref" the model after Set_Model. Tree model
is not a widget, it must be explicitly unreferenced.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de