Backport glibc 2.34 fix to 3.07-4.12

[dra27]

With the release of Ubuntu 21.10 (Impish), we're starting to get (more) distros with Glibc 2.34+ and therefore ocaml/ocaml#10250 is biting. I think this is as with the GCC 10 changes - we need to back-port in opam-repository in order to keep old compilers building with newer distros.

I propose pushing ocaml/ocaml#10266 to the maintenance tips of the 4.10, 4.11 and 4.12 branches. The back-port to these versions is trivial. I'll aim to confirm this with @Octachron later and, assuming they get pushed upstream I'll amend this PR to point to ocaml/ocaml instead of dra27/ocaml.

I'm opening the draft for now in order to allow the cluster to test these packages.

I have not updated:

• alpha, beta, rc packages
• multicore 4.12 packages (cc. @ctk21 - this won't be a priority right now of course, but back-porting Dynamically allocate the alternate signal stack ocaml#10266 looked non-trivial when I just tried... it may of course be relatively fresh in your mind from the other direction for OCaml 5.00!)

The back-port to 4.09 and earlier is not as trivial: the machinery was changed in ocaml/ocaml#8670 to fix stack overflow in systhreads, so malloc'ing the alternate stack needs extricating from that. I intend to open a PR against 4.09 for that, just to allow (hopefully brief) review. Once that's merged to the 4.09 maintenance branch, I'd then aim to push that to previous branches and will then open another opam-repository PR like this one.

Patches prepared. Remaining tasks:

• Test opam source on all packages
• Test opam switch create on all the ocaml-base-compiler packages and the +options variants`
• Submit and review patches for pushing to ocaml/ocaml release branches
• Update packages to point to ocaml/ocaml instead of dra27/ocaml

[mseri]

pending upon ocaml/ocaml#10726

[cheese]

Also hope for 4.08

[Corfucinas]

Any ETA? I need to compile some deps using 4.12.1 on Ubuntu 21.04

[dra27]

@Corfucinas - you can temporarily add my branch, if it helps, with opam repo add dra27 'git+https://github.com/dra27/opam-repository.git#glibc-2.34-4.10+' which will pick these packages up.

In terms of ETA, the remaining upstream PR is slated for 4.14, so it should be no later than the first alpha of 4.14.0.

[fangyi-zhou]

Fedora 35 (released Nov 2021) also uses glibc 2.34
https://src.fedoraproject.org/rpms/glibc

[Leonidas-from-XIV]

pending upon ocaml/ocaml#10726

That PR has been merged now 🎉

[dra27]

This remote should be usable for anyone wishing to test compilers on Ubuntu 21.10+ etc.

[kit-ty-kate]

Closing temporarily (testing 300 compilers and their reverse dependencies is making the CI blow up). It’ll be reopened shortly I promise

[dra27]

Two updates:

• Patches for 3.07-3.11 incl. included inline, as the release branches on ocaml/ocaml need other things added for the patches to be reasonably carried there (affects ocaml-base-compiler and one old release of metaocaml)
• linting metadata copied from various releases - the only packages I left alone are the metaocaml variants, as I'm not sure what the values should be for those (@yallop?)

[yallop]

• linting metadata copied from various releases - the only packages I left alone are the metaocaml variants, as I'm not sure what the values should be for those (@yallop?)

See dra27#7.

[kit-ty-kate]

@dra27 is this PR ready?

[dra27]

Awaiting the patches being pushed to ocaml/ocaml (last task above). Hopefully tomorrow!

[dra27]

This PR should be good to go 🥳

[kit-ty-kate]

Thanks a lot!

[kit-ty-kate]

I believe this should be only LGPL-2.1-or-later WITH OCaml-LGPL-linking-exception but it doesn’t matter, we can always fix it later.