Re: Size and pack

[dewar@gnat.com (Robert Dewar)]

john.mccabe@emrad.com.nospam (John McCabe) wrote in message news:<3bc55c38.3322217@news.demon.co.uk>...
> Depends on the compiler. The example earlier...
> 
> >       for rx_header_data_packed use record       
> >          start_byte   at  0 range  0 ..  7;
> >          splitter     at  1 range  0 ..  7;
> >          command_byte at  2 range  0 ..  7;
> >          pad_byte_1   at  3 range  0 ..  7;
> >          log_num      at  4 range  0 .. 31;  -- Changed
> >          pad_byte_2   at  8 range  0 ..  7;  -- Changed
> >          end_byte     at  9 range  0 ..  7;
> >          lrc          at 10 range  0 ..  7;
> >       end record;
> 
> Could also be written as:
> for rx_header_data_packed use record       
>    start_byte   at 0 range   0 ..  7;
>    splitter     at 0 range   8 .. 15;
>    command_byte at 0 range  16 .. 23;
>    pad_byte_1   at 0 range  24 .. 31;
>    log_num      at 0 range  32 .. 63;
>    pad_byte_2   at 0 range  64 .. 71;
>    end_byte     at 0 range  72 .. 79;
>    lrc          at 0 range  80 .. 87;
> end record;
> 
> which would remove the possibility of confusion because 
> of different storage unit sizes.

This is FUD, the above rewriting accomplishes
nothing and is wholly undesirable. No confusion
arises in either case on a byte addressed machine,
and on a word addressed machine, neither form is
likely to give you what you want.