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From: "David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>
Subject: Re: Problem with representation clause
Date: 1997/12/09
Message-ID: <66jcrm$q7o$1@polo.advicom.net>#1/1
X-Deja-AN: 296573275
References: <66gvas$pmp@remus.rutgers.edu>
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Organization: ADViCOM -- Advanced Internet Communications
Newsgroups: comp.lang.ada
Date: 1997-12-09T00:00:00+00:00
List-Id: <comp.lang.ada>


Hi

The problem would seem to be the implementation advice given in the Ada95
LRM
13.2(9), viz.:

For a packed array type, if the component subtype's Size is less than or
equal to the word size, and Component_Size is not specified for the type,
Component_Size should be less than or equal to the Size of the component
subtype, rounded up to the nearest factor of the word size.

So the solution would seem to be to use a two-dimensional array of your
two-bit components --

i.e. :
   type Global_Integrity_Array_2 is array( Slot_Number, Slot_Number ) of
Measurement_Status_Value;
   pragma Pack(Global_Integrity_Array_2);

The gnat compiler gives this array a size of 1152 bits.

Fabrizio Castrotorres wrote in message <66gvas$pmp@remus.rutgers.edu>...
>Hi,
>
>Given the code:
>-- START CODE
>
>
>   type Measurement_Status_Value is range -2 .. 1;
>   for  Measurement_Status_Value'Size use 2;
>
>   type Slot_Number is range 0 .. 23;
>
>   type Integrity_Data is array (Slot_Number) of Measurement_Status_Value;
>   For Integrity_Data'Size use 24*2;   -- REPRESENTATION 1
>   pragma Pack(Integrity_Data);
>
>   type Global_Integrity_Array is array( Slot_Number ) of Integrity_Data;
>   For Global_Integrity_Array'Size use 24*48;  -- REPRESENTATION 2
>   pragma Pack(Global_Integrity_Array);
>
>-- END CODE
>
>The GNAT ADA 95 compiler (the one with the graphical user interface for
NT/95)
>lets th file compile fine. The problem comes when I try to build the main
>module which uses this package specification (no body). It
>gives me the following error message:
>
>size for "Global_Integrity_Array" too small, minimun allowed is 1536
>
>
>The size I specified is             24*(24*2) = 1152 bits
>The size the compiler requires is   24*(32*2) = 1536 bits
>
>Is there a pragma I overlooked, specification I can write/correct, or
command
>line switch I need, in order to fix this ?
>
>Please reply to fcastrot@ccmail.avionics.itt.com
>
>Thanks
>