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From: Adam Beneschan <adam@irvine.com>
Newsgroups: comp.lang.ada
Subject: Re: Enumeration representation clause surprise.
Date: Wed, 11 Jun 2008 07:58:44 -0700 (PDT)
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On Jun 11, 6:28 am, Samuel Tardieu <s...@rfc1149.net> wrote:
> Markus> This is exactly my point. I would have expected a compile time error
> Markus> for this impossible request.
>
> Markus> Representation clauses are (amongst other) meant to specify specific
> Markus> binary layouts for interfacing with the external world. Or am I
> Markus> mistaken here?
>
> I can't find anything in RM chapter 13 which either forbids or allows
> such a behaviour. I will submit a patch for GNAT which gives a new
> warning for this case:
>
>     11.       A1 at 0 range 0 .. 0; -- (*)
>                  |
>         >>> warning: component representation will be biased

This seems odd to me.  Having GNAT select a biased component in
Christoph's example makes some sense, since a compiler can choose any
representation it likes.  But in Markus' case, he specifically asked
for a certain representation for the enumeration types---should GNAT
take it upon itself to change that, and display a warning that doesn't
make it clear that it's disrespecting his request to have the
enumeration represented a certain way?

I dunno... maybe this would be acceptable to some, and apparently
Markus thinks it's OK, but ... it's just not what I would expect ...
I guess it's a subjective thing.

                                -- Adam