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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: pragma Pack vs. Convention C, portability issue?
Date: Thu, 10 Jan 2008 22:20:37 -0600
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Date: 2008-01-10T22:20:37-06:00
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"okellogg" <okellogg@freenet.de> wrote in message
news:a244cc70-8735-468d-a0ad-b2b659b6d58e@v67g2000hse.googlegroups.com...
> -- File: main.adb
> -- Can we portably rely on pragma Pack taking precedence
> -- over Convention C?

The ARG has argued similar questions as part of AI05-0012. And when I say
argue, I meant it -- this was one of the most contentious issues that I can
remember in the ARG. About all we were able to agree on was that the
Implementation Advice for Pack requires things that are impossible. It got
bad enough that we tabled the AI completely; we're not planning to try to
resolve it in the near future.

One of the points of contention was that "best efforts" packing is good
enough (even when the IA says something else). Another point of contention
is whether the pragma should be rejected if "best efforts" packing causes
none at all.

Moral: avoid Pack for anything where the representation matters to
portability. Use 'Component_Size instead.

                                 Randy.