From: "Randy Brukardt" <randy@rrsoftware.com>
Subject: Re: Limited object by reference or access argument?
Date: Mon, 7 Aug 2017 18:31:41 -0500
Date: 2017-08-07T18:31:41-05:00 [thread overview]
Message-ID: <omat8u$sf7$1@franka.jacob-sparre.dk> (raw)
In-Reply-To: om88a9$1kis$1@gioia.aioe.org
"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.
next prev parent reply other threads:[~2017-08-07 23:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-06 21:16 Limited object by reference or access argument? Victor Porton
2017-08-06 22:01 ` Victor Porton
2017-08-06 23:21 ` Victor Porton
2017-08-07 0:35 ` Victor Porton
2017-08-07 23:31 ` Randy Brukardt [this message]
2017-08-07 14:10 ` Jere
2017-08-07 23:28 ` Randy Brukardt
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