Re: Size and pack

[Jeffrey Carter <jrcarter@acm.org>]

Smark wrote:
> 
> <tmoran@acm.org> wrote in message
> news:8b7C7.72629$gT6.36974049@news1.rdc1.sfba.home.com...
> > >As you indicated in another post, neither pragma pack nor a rep clause
> > >gives you what you want.  This is because neither of these will violate
> > >the alignment rules for a given type.
> >   I seem to have missed the previous post, so I don't know what the
> > problem is.  The following code works just fine - isn't it what you want?
> >     type Rx_Header_Data is
> >        record
> >           Start_Byte   : Character := Latin_1.STX;
> >           Splitter     : Character;
> >           Command_Byte : Character;
> >           Pad_Byte_1   : Character;
> >           Pad_Byte_2   : Character;
> >           Log_Num      : Interfaces.C.Long;
> >           End_Byte     : Character := Latin_1.ETX;
> >           LRC          : Character;
> >        end record;
> >     for Rx_Header_Data 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;
> >           Pad_Byte_2   at 4 range 0 .. 7;
> >           Log_Num      at 5 range 0 .. 31;
> >           End_Byte     at 9 range 0 .. 7;
> >           LRC          at 10 range 0 .. 7;
> >        end record;
> >     for Rx_Header_Data'size use 8*11;
> 
> The problem was that this rep clause will not work, because Log_Num must
> be aligned to a 4-byte boundary.  Some compilers will silently ignore your
> rep clause, I believe GNAT will tell you it can't do it.

You don't seem to be paying attention. He said, "[This] code works just
fine". That probably means he tested it. I have compiled and linked it
with GNAT 3.13p/Win98 without any problem.

On what compiler/target did your test reject this rep clause? 

-- 
Jeff Carter
"I wave my private parts at your aunties."
Monty Python & the Holy Grail