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From: "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: Reference counter in smart pointers are not updated properly when
 used by multiple tasks
Date: Thu, 1 Feb 2018 21:12:37 +0100
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Xref: reader02.eternal-september.org comp.lang.ada:50262
Date: 2018-02-01T21:12:37+01:00
List-Id: <comp.lang.ada>

On 02/01/2018 08:37 PM, onox wrote:
> On Thursday, February 1, 2018 at 3:48:10 PM UTC+1, Jeffrey R. Carter wrote:
>> Set's parameter Free is an anonymous access-to-subprogram parameter; one is not
>> supposed to be able to assign those and call them later, but that is exactly
>> what this code does. Is this code legal? GNAT compiles it fine. If it is legal,
>> should it be?
> 
> I hope so. When I instantiate the Orka.Smart_Pointers package, I do not know how to free the Object_Type (access to an interface). Only when I call Set I know how to free the object (access to a tagged type implementing the interface).

AIUI, it should be illegal. Because Ada has nested subprograms, it's possible 
that the subprogram won't exist when you call it. To prevent that from happening 
is why named access-to-subprogram types are subject to accessibility checks. 
Anonymous access-to-subprogram parameters don't have such checks because you're 
not supposed to be able to copy them.

-- 
Jeff Carter
"My mind is aglow with whirling, transient nodes of
thought, careening through a cosmic vapor of invention."
Blazing Saddles
85