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Date: Fri, 26 Jun 2009 18:29:11 +0200
From: Damien Carbonne <damien.carbonne@free.fr>
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Subject: Re: Issue with GNAT GPL 2009 and GtkAda
References: <4A414EBB.8060204@free.fr> <uk532lyzd.fsf@stephe-leake.org>
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Date: 2009-06-26T18:29:12+02:00
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Niklas Holsti a �crit :
>  > Damien Carbonne <damien.carbonne@free.fr> writes:
>  >>
>  >>    type Listener is interface;
>  >>    procedure Process (L : in out Listener) is abstract;
>  ...
>  >>    type Base is tagged null record;
>  ...
>  >>    type Derived is new Base and Listener with null record;
>  >>    overriding procedure Process (D : in out Derived);
>  >>
> 
> Stephen Leake wrote:
>> The problem is clear here.
>>
>> "D : in out Derived" is allowed to create a copy of the actual
>> parameter.
> 
> Huh? Do you mean that this "D" parameter may be passed by copy? But 
> "Derived" is a tagged type, and tagged types are passed by reference, 
> not by copy. Or so I thought.
> 
I also thought that tagged types were always passed by reference, 
whatever the mode (in, out, in out) is.
I'll have to read Ada RM !
If this is true, it means that using in/out/in out modes is almost 
impossible in the code I write if this code must be mixed with code from 
third party libraries (like GtkAda) that use access almost everywhere. sad.