From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,6339fea48a1b8cda
X-Google-Attributes: gid103376,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII
Path: 
 g2news1.google.com!postnews.google.com!c65g2000hsa.googlegroups.com!not-for-mail
From: richtmyer@cox.net
Newsgroups: comp.lang.ada
Subject: Re: Enumeration representation clause surprise.
Date: Thu, 12 Jun 2008 12:05:05 -0700 (PDT)
Organization: http://groups.google.com
Message-ID: 
 <770ae1af-b9fd-4c8a-915c-a5cb3ea8fc81@c65g2000hsa.googlegroups.com>
References: <g2odf9$3um$1@nntp.ilk.net>
NNTP-Posting-Host: 164.223.72.5
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
X-Trace: posting.google.com 1213297506 4900 127.0.0.1 (12 Jun 2008 19:05:06
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Thu, 12 Jun 2008 19:05:06 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: c65g2000hsa.googlegroups.com; posting-host=164.223.72.5;
	posting-account=Z7Cz1woAAAA0DPjSZK8wuaYD_ro5RKkK
User-Agent: G2/1.0
X-HTTP-UserAgent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1;
 .NET
	CLR 1.1.4322; .NET CLR 2.0.50727; InfoPath.1;
 .NET CLR 3.0.04506.30),gzip(gfe),gzip(gfe)
Xref: g2news1.google.com comp.lang.ada:676
Date: 2008-06-12T12:05:05-07:00
List-Id: <comp.lang.ada>

On Jun 11, 7:38=A0am, Markus Schoepflin <nos...@no.spam> wrote:
> Hello,
>
> please consider the following code snippet:

etc

-----
Interesting. I had been playing with a similar example, and have
modified it a bit
to present. What got me is the record type with length 1 but an object
with that
type that was length zero! (It compiles without any warnings).

------------------------------ test1.2.ada
--------------------------------------
--
-- GPS 4.2.1 (20080115) hosted on pentium-mingw32msv
-- GNAT GPL 2007 (20070405-41)
--
--  X_Type'size     =3D  31
--  X_Rec_Type'size =3D  32
--  X_Rec'size      =3D  32
--  Y_Rec_Type'size =3D  1
--  Y_Rec'size      =3D  8
--  X_Rec.X1        =3D  2147483647
--  Y_Rec.X1        =3D  2147483647

--  GPS Pro 4.1.1 (20070423) hosted on i686-pc-linux-gnu
--  GNAT Pro 6.1.1 (20080111-41)
--
--  X_Type'size     =3D  31
--  X_Rec_Type'size =3D  32
--  X_Rec'size      =3D  32
--  Y_Rec_Type'size =3D  1
--  Y_Rec'size      =3D  0             -- this object is smaller than
its type!
--  X_Rec.X1        =3D  2147483647
--  Y_Rec.X1        =3D  2147483647

-------------------------------------------------------------------------

with ada.exceptions;  use ada.exceptions;
with interfaces.c;
with text_io;   use text_io;
with unchecked_conversion;

procedure test1 is

   type X_Type is ( X );
   for x_type use (x =3D> 16#7FFF_FFFF#);

   type X_Rec_Type is
      Record
        X1 : X_Type;
      End Record;

   X_Rec : X_Rec_Type :=3D (X1 =3D> x);

   type Y_Rec_Type is
      Record
        X1 : X_Type;
      End Record;
   for Y_Rec_Type'size use 0;

   for Y_Rec_Type use
      Record
        X1 at 0 range 0 .. -1;                   -- Minus 1  !!
      End Record;

   Y_Rec : Y_Rec_Type :=3D (X1 =3D> X);

   function convert is new unchecked_conversion (X_type, natural);
begin

   put_line("X_Type'size     =3D " & X_Type'size'img);
   put_line("X_Rec_Type'size =3D " & X_Rec_Type'size'img);
   put_line("X_Rec'size      =3D " & X_Rec'size'img);
   put_line("Y_Rec_Type'size =3D " & Y_Rec_Type'size'img);
   put_line("Y_Rec'size      =3D " & Y_Rec'size'img);
   put_line("X_Rec.X1        =3D " & convert(X_Rec.X1)'img);
   put_line("Y_Rec.X1        =3D " & convert(Y_Rec.X1)'img);

end test1;