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From: nickroberts@ukf.net (Nick Roberts)
Newsgroups: comp.lang.ada
Subject: Re: System.Address'Size - not a static integer expression?
Date: Mon, 08 Apr 2002 00:43:55 GMT
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Date: 2002-04-08T00:43:55+00:00
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On 6 Mar 2002 09:57:38 -0800, vgodunko@vipmail.ru (Vadim Godunko) strongly
typed:

>9     type T is record
>10       P : System.Address := System.Null_Address;
>11    end record;
>12    for T'Size use System.Address'Size;

Others will tell you GNAT is correct (this is not allowed).

Perhaps it might be helpful to analyse a little more deeply why you wrote
this code in the first place.

Presumably you wanted to say "I want this type to be the same size as
System.Address". This is apparently a fairly reasonable requirement, since
T only contains a System.Address.

However, think again. If the compiler really needs to put some extra
information into the record, then it needs it, and the 'for T'Size ...'
clause will simply cause the compilation to fail. If the compiler doesn't
need to put any extra information in, it won't!

So, in conclusion, I think that probably you never needed the
representation clause in the first place.

I think it might be fair to suggest that quite often the reason why someone
gets tangled up with a representation clause (or pragma) is because they
are using it inappropriately.

All the best,

-- 
Nick Roberts