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From: fea <fea@gateway.net>
Subject: Re: Sun Ada 3.0 / 2.1.1
Date: 1999/05/24
Message-ID: <3748CEEB.9815A4F5@gateway.net>#1/1
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References: <37408CC0.5E601B20@sll.northrop.com>
 <TUF8qNRo#GA.209@newstoo.hiwaay.net>
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Newsgroups: comp.lang.ada
Date: 1999-05-24T00:00:00+00:00
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David C. Hoos, Sr. wrote:
> 
> Guy Calinsky <calinsky@sll.northrop.com> wrote in message
> news:37408CC0.5E601B20@sll.northrop.com...
> >
> > I have a requirement to upgrade my project's compiler from Sun Ada 2.1.1
> > to Sun Ada 3.0.
> > Easy enough, except that my application makes several calls to C
> > functions, passing floating point numbers.
> > Whereas my application worked fine under 2.1.1, the floating point
> > numbers are not mapping correctly between 3.0 and C and I get junk for
> > results.  Does anybody know why this is?
> > Sun and Rational are being difficult.
> >
> My guess would be that your code has interfaces to C based on types from
> the compiler's package Standard which have changed size.
> 
> For example, I remember that VADS on the SGI IRIX platform changed
> their type Float from 32-bit to 64-bit, and the Oracle interface was
> based on equating C float to VADS Float, and C double to VADS Long_Float.
> 
> You should have your own project-specific types of fixed size, to protect
> yourself from compiler changes.
>

My project had the same requirement as you do and encountered
the same problem.  David's guess is 100% correct.  In Sun 2.1.1
"Float" is the same size as "Long_Float."  In Sun 3.0, its size
changed to that of "Short_Float."

While the correct solution is to isolate the dependency with a 
user defined type, our project didn't have time in the schedule
for that.  We found all the instances of "Float," changed them
to "Long_Float," and everything, including our C interface,
worked fine and made the delivery.