Re: Binary files vs Portablity vs Ada

[Tucker Taft <stt@averstar.com>]

Ted Dennison wrote:
> 
> In article <7vvrin$gp9$1@nnrp1.deja.com>,
>   Robert Dewar <robert_dewar@my-deja.com> wrote:
> > In article <7vuto0$pv0$1@nnrp1.deja.com>,
> >   Ted Dennison <dennison@telepath.com> wrote:
> > > There's no reason to
> > > expect that your vendor would do something goofy with the data
> > > (like compress it or something), but there's nothing stopping
> > > them either.
> > There is specific implementation advice on this subject:
> 
> Perhaps. But advice is just that; advice. No guarantees. If you are
> trying to do something universally portable, you can't count on
> implementation advice.
> 
> > Now an implementation could conceivably refuse to follow this
> > implementation advice, but then it must document this fact:
> 
> That's only an issue if you have two particular implementations you want
> it to work between. But no one asked about portability between two
> particular compilers. The issue is portability in general.
> ...

It is always a bit frustrating to follow discussions like this
where people keep arguing about how this or that is not "guaranteed"
by the Ada RM, when other languages have far fewer guarantees to begin
with, and no strictly-obeyed standard and validation suite available.

Portability is not an absolute.  It is defined relative to the platforms
and compilers of interest.  The Ada RM tries to avoid overspecification,
partly because it is trying to handle any sort of target environment, with
storage elements varying from 8 bits each to 60 bits each. 

If you limit yourself to things which are "guaranteed" portable by
the RM, you will probably be disappointed.  If instead you concentrate
on localizing your target-specific assumptions, rather than spreading them
around, you use some common sense, and try your code on whatever compilers 
you have ready access to, you will probably be happier...

> T.E.D.

-- 
-Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA