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Date: Sat, 27 Jun 2009 14:25:58 +0200
From: Damien Carbonne <damien.carbonne@free.fr>
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Subject: Re: Issue with GNAT GPL 2009 and GtkAda
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Date: 2009-06-27T14:25:59+02:00
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Stephen Leake a �crit :
>>>
>>> ...
>> If what you say is true, why does the following example work fine
>> (using GNAT), without any compiler warning or execution error ?
> 
> Because the object being passed is explicitly labeled "aliased"; that
> means 'Access is allowed. See my other post from today.
> 
In the example, there is only one place where an object is explicitly 
declared and labeled "aliased" : in Main.
In signatures of P[123]M, X is not aliased (only in, out or in out modes).
There is no "aliased" key word in the bodies of corresponding procedures.

e.g.:
    procedure P1M (X : in out Base; Max_Depth : Positive) is
    begin
       Ada.Text_IO.Put_Line (Indent (Max_Depth) & "P1M" & Positive'Image 
(Max_Depth));
       if Max_Depth > 1 then
          P1A (X'Access, Max_Depth - 1); -- Here use of Access on a tyoe 
that is implicitely aliased
          X.P1A (Max_Depth - 1);
       end if;
    end P1M;
Nowhere X is explicitely declared aliased. It is only an "in out" tagged 
parameter. It is however possible to use X'Access, in my mind because X 
is tagged (and so passed by reference).

Do you mean that the fact that X is labeled "aliased" in Main is 
propagated everywhere it is used ? I would find this strange (and 
certainly needing a special support from compiler).

I really don't see the difference with the initial problem, where all 
types are tagged types or interfaces.