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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Problem with Position of the enumeration Type
Date: Wed, 23 Jan 2019 22:35:42 +0000
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Date: 2019-01-23T22:35:42+00:00
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Niklas Holsti <niklas.holsti@tidorum.invalid> writes:

> Such rules also commonly say that such types should not be used as
> array index types, because of the possible introduction of gaps in the
> array representations.

Not, it seems, with GNAT:

   $ cat gappy.adb
   with Ada.Text_IO; use Ada.Text_IO;
   procedure Gappy is
      type E_Test is (Pos10, Pos11, Pos12, Pos13, Pos14);
      for E_Test use (Pos10 => 100,
                      Pos11 => 110,
                      Pos12 => 120,
                      Pos13 => 130,
                      Pos14 => 255);
      type Arr is array (E_Test) of Integer;
   begin
      Put_Line ("Arr's size is"
                  & Arr'Max_Size_In_Storage_Elements'Img
                  & " bytes.");
   end Gappy;
   
   $ gnatmake -f gappy
   gcc -c gappy.adb
   gnatbind -x gappy.ali
   gnatlink gappy.ali

   $ ./gappy
   Arr's size is 20 bytes.

I'd think any other behaviour would be unreasonable (though I can't see
any statement about it in the ARM).