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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Limited object by reference or access argument?
Date: Mon, 7 Aug 2017 18:31:41 -0500
Organization: JSA Research & Innovation
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Date: 2017-08-07T18:31:41-05:00
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"Victor Porton" <porton@narod.ru> wrote in message 
news:om88a9$1kis$1@gioia.aioe.org...
...
>> It may work like this (in fact it is more complex):
>>
>> type World_Type is tagged limited
>>    record
>>       Handler: access BNode_ID_Handler'Class;
>>    end;
>>
>> procedure Set_Handler (World: World_Type;
>>                        Handler: BNode_ID_Handler'Class) is
>> begin
>>    World.Handler := Handler'Unchecked_Access;
>> end;

If you had written instead:

procedure Set_Handler (World: World_Type;
                        Handler: access BNode_ID_Handler'Class) is
begin
    World.Handler := Handler; -- (1)
end;

Program_Error will be raised at (1) if you passed a local object as a 
handler. Bob Duff calls that a "tripping hazard", and I agree. It's the sort 
of thing that gets by testing and only breaks at the worst possible time. 
Avoid anonymous access types!!

                                        Randy.