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From: Pascal MALAISE <malaise@magic.fr>
Subject: Re: GNAT Opinions
Date: 1999/01/04
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choboy@calspan.com wrote:
> I'm looking for opinions from people
> who may have used GNAT in a large-scale development effort such as ours or
> perhaps did some trade studies that resulted in a GNAT go/no-go decision.

Knowing that Verdix products will soon not be supported (on Digital Unix
at least)
and considering the price of the APEX package, we are starting a similar
study.
At present, this is just a study which involves a double migration, from
DU 4.0 to Linux and from Verdix to Gnat (in 95 mode).

For the compiler quality, nothing to say, except that 
- gnat compiling policy is restrictive, and despite the *nice* gnatchop,
it is difficult to maintain both versions with unique sources. It is
difficult
to insert gnat compilation within an existing (and Verdix oriented) ada
CASE 
environment.
- gnat reliability, as a compiler, looks good. It better detects unused
and
non initialized variables. No compiler bugs have been detected so far.
- gnat has some (specific or ada 95?) constraints on representation
clauses
which have to be defined before the usage of the type which forbids to
put
them in private parts, by instance.

For the scale and progress of our study, 
- we migrate the middleware (which is mainly in C with ADA interfaces)
- we migrate a demonstration program in Ada 83 to Gnat in 95
- everything compiles so far, but no attempt hs been made to run the
result,
which tempers my remark about gnat reliability, but we forsee to achieve
the migration by the end of Feb.
- we don't use Ada Core Tech support

As a conclusion, so far so good. This migration does not raise more
problems
than other migration (to decada or Aonix).

-- 
Pascal MALAISE
(priv) mailto:malaise@magic.fr
(prof) mailto:malaise@fr.airsysatm.thomson-csf.com