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Newsgroups: comp.lang.ada
Subject: Re: pragma Pack does not work on GNAT 5.01a for Redhat Linux.
From: Georg Bauhaus <rm.tsoh+bauhaus@maps.futureapps.de>
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Date: Tue, 19 Jun 2007 16:02:13 +0200
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Date: 2007-06-19T16:02:11+02:00
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On Tue, 2007-06-19 at 06:16 -0700, petter_fryklund@hotmail.com wrote:
> The Size of the following record is 112 on Linux, but 104 on Solaris.
> 
> type Something is record
>    A : Packed_16;
>    B : Packed_8;
>    C : Packed_8;
>    D : Packed_8;
>    E : Packed_32;
>    F : Packed_32;
> end record;
> pragma Pack (Something);
...
> and similar. Why is pragma Pack ignored?

I don't think pragma Pack is ignored, there are "should"s in the RM
and then alignment. You might need a rep spec, though. Does this work?

   -- assume word size of 32 bits, 4 bytes
   wordsize: constant := 4;

   for Something use record
      A  at 0*wordsize range 0 .. 15;
      B  at 0*wordsize range 16 .. 23;
      C  at 0*wordsize range 24 .. 31;
      D  at 3*wordsize range 0 .. 7;
      E  at 1*wordsize range 0 .. 31;
      F  at 2*wordsize range 0 .. 31;
   end record;

   for Something'Size use 104;