From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00
	autolearn=unavailable autolearn_force=no version=3.4.4
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!nntp-feed.chiark.greenend.org.uk!ewrotcd!newsfeed.xs3.de!io.xs3.de!news.jacob-sparre.dk!franka.jacob-sparre.dk!pnx.dk!.POSTED.rrsoftware.com!not-for-mail
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: AI12-0218: What is the portable representation clause for
 processing IETF packets on little-endian machines?
Date: Fri, 11 May 2018 17:12:20 -0500
Organization: JSA Research & Innovation
Message-ID: <pd54g5$k0o$2@franka.jacob-sparre.dk>
References: <ec0145a4-9698-41f2-bc70-964dc1850e50@googlegroups.com>
 <9af47760-e731-4cb5-a1a0-d63e31019ce5@googlegroups.com>
 <877eob1cc6.fsf@nightsong.com>
 <c9986056-cc3d-432b-839d-fa226eb6e5f8@googlegroups.com>
 <flk0a3Fpvi4U1@mid.individual.net>
 <5c9b9f90-884f-4de7-8663-d39a67949f4f@googlegroups.com>
Injection-Date: Fri, 11 May 2018 22:12:21 -0000 (UTC)
Injection-Info: franka.jacob-sparre.dk;
 posting-host="rrsoftware.com:24.196.82.226";
	logging-data="20504"; mail-complaints-to="news@jacob-sparre.dk"
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2900.5931
X-RFC2646: Format=Flowed; Original
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.7246
Xref: reader02.eternal-september.org comp.lang.ada:52300
Date: 2018-05-11T17:12:20-05:00
List-Id: <comp.lang.ada>

"Dan'l Miller" <optikos@verizon.net> wrote in message 
news:5c9b9f90-884f-4de7-8663-d39a67949f4f@googlegroups.com...
>* on a per-processor, per-toolchain basis, selected via the conditional 
>compilation
>via the C preprocessor.  This selection (out of nonportable categorization) 
>is
>what accomplishes the portability.  Ada has no equivalent other than
>AI32-0218's/GNAT's solution.

The best way to do this in Ada is with different package bodies (and 
sometimes specs) for each target. That's how Janus/Ada is designed, and it 
works great. I know the GNAT project system even has facilities to make this 
happen automatically (by selecting the unit to compile based on a version 
id).

The problem is that existing version control systems cannot handle such 
designs properly. That was definitely true in the late 1980's (so I designed 
a wrapper around our version control to deal with this), and I haven't seen 
any that deal with it properly to date. (The main issue being that when a 
bug is fixed in one such package, you want a notification to check if the 
same is needed for the other versions. No version control that I'm aware of 
can handle this - they all seem focused on merging development for a single 
end-product.)

Shortcomings in version control are way outside of anything that the 
language can control. And using a sub-optimal design because ancillary tools 
are broken seems to be letting the tail wag the dog.

                 Randy.