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From: Brian Courtney <bcourtn@hercii.mar.lmco.com>
Newsgroups: comp.lang.ada
Subject: Re: Green Hiils AdaMULTI 2000 -> Motorola Coldfire
Date: Thu, 11 Jan 2001 09:44:37 -0500
Organization: Lockheed Martin Corporation
Message-ID: <3A5DC6D5.5A8446D8@hercii.mar.lmco.com>
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Date: 2001-01-11T09:44:37-05:00
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We recently ported a 200,000+ sloc app (MIPS) from Ada83 (Aonix)
to GHS Ada95 as part of an evaluation of the AdaMULTI2000
environment.  The only problem we experienced was not
with the compiler/environment, rather some bad assumptions
made by the original developers about the size of subtypes.
NOTE: The language does not require objects of a subtype to
be the same size as objects of the parent type.  As you
might expect, the two compilers implemented this differently.
The Aonix Ada83 compiler would preserve the size of subtypes
from the parent type and the GHS Ada95 compiler would not (it
seemed to chose the smallest size possible based on the range
of the subtype).  Either implementation is allowed by the language.

A misunderstanding by the developers, or an oversight in the
language? Either way, this issue has plagued more than one
project, so it may be something you want to be on the lookout for.
I've used XDAda in the past, but can't recall its behavior.  In any
event, the moral of the story is "don't assume the size of a subtype".

Hope this helps,

Brian Courtney

Mark Fisher wrote:

> I am currently getting to grips with the Green Hills `AdaMULTI`
> compiler/environment
> using the Coldfire MCF5307 processor.
>
> In the coming weeks I am doing some risk reduction which is
> being ported from XDAda (83) / Motorola 68020.
>
> Any tips for a new AdaMULTI user? In particular are there known
> weaknesses/problems
> that I should steer clear of?
>
> Many thanks
>
> Mark