Re: Collation version tracking for macOS

On Thu, Jun 9, 2022 at 5:42 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I'm sure that Apple are indeed updating the UTF8 data behind
> their proprietary i18n APIs, but the libc APIs are mostly getting benign
> neglect.

As for how exactly they might be doing that, I don't know, but a bit
of light googling tells me that a private, headerless,
please-don't-call-me-directly copy of ICU arrived back in macOS
10.3[1]. I don't see it on my 12.4 system, but I also know that 12.x
started hiding system libraries completely (the linker is magic and
pulls libraries from some parallel dimension, there is no
/usr/lib/libSystem.B.dylib file on disk, and yet otool -L
<your_favourite_executable> references it).

It's a lovely client machine, but I don't know if anyone really runs
meaningful database server stuff on macOS. I think if I did I'd be
very keen to use ICU for everything directly, rather than trying to
unpick any of that and talk to Apple's API... I think the
how-to-support-multiple-ICUs subrant/subthread is a much more
interesting topic. I have no idea if the dlopen() concept I mentioned
is the right way forward, but FWIW the experimental patch I posted
seems to work just fine on a Mac, using multiple ICU libraries
installed by MacPorts, which might be useful to developers
contemplating that stuff.

[1] https://lists.apple.com/archives/xcode-users/2005/Jun/msg00633.html