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From: Simon Wright <simon.j.wright@mac.com>
Newsgroups: comp.lang.ada
Subject: Re: pragma Pack does not work on GNAT 5.01a for Redhat Linux.
Date: Sun, 01 Jul 2007 11:57:10 +0100
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Date: 2007-07-01T11:57:10+01:00
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Ole-Hjalmar Kristensen <ole-hjalmar.kristensen@substitute_employer_here.com> writes:

>>>>>> "SW" == Simon Wright <simon.j.wright@mac.com> writes:

You seem to have snipped the last bit that I actually did say ..

>     SW> "Bob Spooner" <rls19@psu.edu> writes:
>     >> "Simon Wright" <simon.j.wright@mac.com> wrote in message 
>     >> news:m2hcp2e4fv.fsf@mac.com...
>     >>> 
>     >>> There's always a price to pay, of course; the packing isn't
>     >>> dense, and it can be quite a challenge to work out what
>     >>> bytes are actually being sent (eg, if you find yourself
>     >>> having to talk to C after all).
>     >> 
>     >> Yes, XDR takes care of things like endianness, etc. that
>     >> otherwise get in the way, but as you point out, there's
>     >> always a price to be paid for generality. In some cases it
>     >> looks like it even will take care of differing floating point
>     >> representations, although I wonder about out of range
>     >> problems when converting. Isn't there an XDR library for C? I
>     >> know that there is one for Fortran. I would think that as
>     >> long as you have an XDR library for the language with which
>     >> you need to communicate, you wouldn't have to decode the
>     >> bytes yourself; or have I misunderstood what you are saying?
>
> C has had XDR and RPC at least since 1987. Try man xdr or man rpcgen
> on any unix box.

True but not helpful if one side of the interface is implemented in
Ada and the other side uses just C and sockets (and you are on the Ada
side with no influence on the protocol). VxWorks both sides would
probably add to the fun.

I realise I didn't note these extra influences in my original remarks ..