Re: shifting bits

[Jeffrey Carter <spam@spam.com>]

Georg Bauhaus wrote:

> when I declare
> 
>    type month_type is range 1 .. 12;
>    for month_type'Size use 4;
> 
>    m: month_type := 1;
> 
> the compiler chooses 8 (following the rule
> "Object_Size must be 8, 16, 32, or multiple of 64"
> I guess.)
> 
>    TIO.put_line("m's size: " & Natural'image(m'size));
> 
> prints
> 
> m's size:  8

A specified 'Size effects the size in a packed composite type, but not 
for a stand-alone object. Try

type Month_List is array (Month_Type) of Month_Type;
pragma Pack (Month_List);

L : Month_List;

TIO.Put_Line ("L's size: " & Natural'image (L'Size) );

GNAT 3.15p/Win98 outputs

M's size:  8
L's size:  64

L has been padded to a multiple of 32, which is allowed because it's a 
stand-alone object, but is not 96, which is what you would get if each 
component were 8 bits.

-- 
Jeff Carter
"Now look, Col. Batguano, if that really is your name."
Dr. Strangelove
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