From: dewar@gnat.com
Subject: Re: "out" or "access"
Date: 1998/10/31
Date: 1998-10-31T00:00:00+00:00 [thread overview]
Message-ID: <71dpa3$d76$1@nnrp1.dejanews.com> (raw)
In-Reply-To: wccpvb9vh0k.fsf@world.std.com
In article <wccpvb9vh0k.fsf@world.std.com>,
Robert A Duff <bobduff@world.std.com> wrote:
> Matthew Heaney <matthew_heaney@acm.org> writes:
>
> > The RM also recommends that implementations "deliver a useful result"
> > when you take the O'Address of a by-reference type (tagged types,
> > limited types) passed as a subprogram parameter. That's why
> > Sys.Addr_To_Acc_Conv can be used to work around this problem.
>
> I don't understand why you want to use 'Address at all.
> My earlier suggestion was to use 'Unchecked_Access.
> It has the same problem with possible dangling references,
> but at least it doesn't throw type checking completely out
> the window, as 'Address does.
Note that Unchecked_Access still has restrictions which can be annoying, it
cannot be applied to parameters for example, because it still requires the
object to be aliased. In GNAT, the Unrestricted_Access attribute can be used
anywhere 'Address is usable, and is comparable in effect, except that strong
typing of the resulting pointer is retained.
Robert Dewar
Ada Core Technologies
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next prev parent reply other threads:[~1998-10-31 0:00 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-10-21 0:00 "out" or "access" =:-) Vincent
1998-10-21 0:00 ` dennison
1998-10-21 0:00 ` Tucker Taft
1998-10-22 0:00 ` Pascal Obry
1998-10-29 0:00 ` Robert A Duff
1998-10-29 0:00 ` Matthew Heaney
1998-10-29 0:00 ` Robert A Duff
1998-10-30 0:00 ` dennison
1998-10-30 0:00 ` Matthew Heaney
1998-10-30 0:00 ` Robert A Duff
1998-10-31 0:00 ` dewar [this message]
1998-10-31 0:00 ` Matthew Heaney
1998-10-31 0:00 ` Matthew Heaney
1998-11-01 0:00 ` Robert A Duff
1998-11-01 0:00 ` Matthew Heaney
1998-11-01 0:00 ` Robert A Duff
1998-11-02 0:00 ` Matthew Heaney
1998-11-03 0:00 ` Simon Wright
1998-11-16 0:00 ` Matthew Heaney
1998-10-21 0:00 ` Jeff Carter
1998-10-21 0:00 ` Pat Rogers
1998-10-21 0:00 ` Martin C. Carlisle
1998-10-22 0:00 ` Pat Rogers
1998-10-22 0:00 ` Robert A Duff
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