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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Best representation for spares
Date: Fri, 14 Feb 2014 09:19:20 +0000
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Date: 2014-02-14T09:19:20+00:00
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"Rego, P." <pvrego@gmail.com> writes:

> using this kind of definitions, the compiler warns (correctly) me
>    warning: 29-bit gap before component "AUX_ENABLES"

I'd much prefer to fill this space. And, on the whole, better with zeros
(unless, of course, 'unused' means 'don't even write to this bit').

Something like

   type Zero_Bit is range 0 .. 0;
   type Zero_Bits is array (Positive range <>) of Zero_Bit;
   for Zero_Bits'Component_Size use 1;

   type Auxiliary_Interrupt_Status_Type is
      record
         Mini_Uart_IRQ : Boolean;
         SPI_1_IRQ     : Boolean;
         SPI_2_IRQ     : Boolean;
         Spare         : Zero_Bits (3 .. 31);
      end record;
   pragma Pack (Auxiliary_Interrupt_Status_Type);
   for Auxiliary_Interrupt_Status_Type'Size use 32;