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From: bobduff@world.std.com (Robert A Duff)
Subject: Re: Pointers
Message-ID: <D5Cnzx.BHr@world.std.com>
Organization: The World Public Access UNIX, Brookline, MA
References: <3jhj26$2er@gnat.cs.nyu.edu> <3jki04$9bj@theopolis.orl.mmc.com>
Date: Sun, 12 Mar 1995 23:02:21 GMT
Date: 1995-03-12T23:02:21+00:00
List-Id: <comp.lang.ada>

In article <3jki04$9bj@theopolis.orl.mmc.com>,
Bob Gilbert <rgilbert@orl.mmc.com> wrote:
>In my experience I have found several cases where the simple "for x use at .."
>will not work.  One problem is that with most comilers which support the 
>address clause, will perform a write to the memory location (initialization 
>I suppose) during elaboration.  This can cause problems with "read only" 
>addresses. ...

In Ada 95, you can turn off that behavior with a pragma Import.
See RM-B.1(38).

> ...In these situations I 
>had to resort to using access types, unchecked_conversion, and the knowledge
>that the comiler implements access types as addresses, to work around the 
>problem.  

You don't normally need to do that anymore, but if you ever *do* want to
deal with access values as addresses, use the
Address_To_Access_Conversions package -- you no longer need to make
*assumptions* about the representation of the access values.

- Bob