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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Default rep specs for record types - documented??
Date: Mon, 14 Nov 2005 21:14:14 +0000
Organization: Pushface
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Date: 2005-11-14T21:14:14+00:00
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Anonymous Coward <spam@spam.com> writes:

> As for records, I've imposed sizes on all my rep spec'd record
> types.  It would normally be needless, but to protect the maintainer
> from accidentally defining a partial rep spec as the operational
> spec grows, I've added a size spec so an error will be thrown at
> compile time.

Don't forget to consider alignment issues,especially as affected by
processor type; for instance, a GNAT Ada.Calendar.Time is 8 bytes
long, and has alignment of 4 bytes (the maximum) on x86 but alignment
of 8 bytes on PowerPC.

   with Ada.Calendar;
   package Align is
      type R is record
         B : Boolean;
         T : Ada.Calendar.Time;
      end record;
   end Align;

=>

   Representation information for unit Align (spec)
   ------------------------------------------------

   for R'Size use 128;
   for R'Alignment use 8;
   for R use record
      B at 0 range  0 ..  7;
      T at 8 range  0 .. 63;
   end record;