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From: "Adam Beneschan" <adam@irvine.com>
Newsgroups: comp.lang.ada
Subject: Re: To collection (GNAT bug)
Date: 4 Oct 2006 10:18:47 -0700
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Date: 2006-10-04T10:18:47-07:00
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Dmitry A. Kazakov wrote:
> On Mon, 02 Oct 2006 09:06:42 -0400, Frank J. Lhota wrote:
>
> > Dmitry A. Kazakov wrote:
> >> On Sun, 01 Oct 2006 19:23:26 GMT, Jeffrey R. Carter wrote:
> >> However, I don't think that it was really the intended behavior in this
> >> case. [ If access String is a fat pointer, then Unchecked_Conversion should
> >> not be allowed at all. Otherwise it must honor the String's dope. ]
> >
> > I would agree that an unchecked conversion between an address and a fat
> > pointer (or any two types of different sizes, for that matter) should at
> > least trigger a warning.
>
> Well, actually, it gives a warning, that sizes are different.

Ummm, wait a minute.  If the sizes are different, why did you think
that the Unchecked_Conversion would be reversible?  I tried your
example on GNAT (Linux/x86), and it told me that X'Size=64 and
Addr'Size=32.  When you convert the 64-bit type to the 32-bit type, of
course you will lose some information that you won't recover when you
get it back.  It's mathematically impossible for this to be reversible.

                              -- Adam