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From: Thomas Munro <thomas.munro@gmail.com>
Date: Wed, 30 Nov 2022 13:54:26 +1300
Message-ID: 
 <CA+hUKGJSBPXRzxkM4f5rLr02z_CWJSPb9VuPtk0t4P4QayGraA@mail.gmail.com>
Subject: Re: Collation version tracking for macOS
To: Jeff Davis <pgsql@j-davis.com>
Cc: Robert Haas <robertmhaas@gmail.com>,
	Peter Eisentraut <peter.eisentraut@enterprisedb.com>,
	Jeremy Schneider <schneider@ardentperf.com>, Peter Geoghegan <pg@bowt.ie>,
	"Finnerty, Jim" <jfinnert@amazon.com>, "Nasby, Jim" <nasbyj@amazon.com>,
 Tom Lane <tgl@sss.pgh.pa.us>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
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On Wed, Nov 30, 2022 at 1:25 PM Jeff Davis <pgsql@j-davis.com> wrote:
> On Wed, 2022-11-30 at 10:52 +1300, Thomas Munro wrote:
> > On Wed, Nov 30, 2022 at 8:38 AM Jeff Davis <pgsql@j-davis.com> wrote:
> > > On Tue, 2022-11-29 at 10:46 -0800, Jeff Davis wrote:
> > > https://unicode-org.atlassian.net/browse/ICU-22216
> >
> > I'm no expert on loader/linker arcana but I have a feeling this is a
> > dead end.  It's an ancient Unix or at least elf-era Unix convention
> > that SONAMEs have major versions only, because major versions are the
> > basis of ABI stability.
>
> It's possible that it's more a problem of how they are doing it: the
> specific version is coming from a dependency rather than the library
> itself. The results are surprising, so I figured it's worth a report.
> Let's see what they say.
>
> Regardless, even if they did make a change, it's not going to help us
> anytime soon. We can't rely on any scheme that involves multiple minor
> versions for a single major version being installed at once. That means
> that, if you create a collation depending on ICU X.Y, and then it gets
> upgraded to X.(Y+1), and you create another collation depending on that
> library version, you are stuck.

Mainstream package maintainers aren't going to let that happen anyway
as discussed, so this would always be a fairly specialised concern.
Maybe someone in our community would be motivated to publish a repo
full of mutant packages that don't conflict with each other and that
have specially modified DT_NEEDED, or are rolled into one single
library so the DT_NEEDED problem goes away.