CI: include next upcoming LTS Ubuntu release

[marxin]

No description provided.

[marxin]

@davidlattimore Can you please take a look at the new linker-diff failures?

[davidlattimore]

Looks like GNU ld now uses VER_NDX_LOCAL for undefined symbols without a version rather than VER_NDX_GLOBAL. This appears to be from this commit. This later change is also related.

LLD still emits VER_NDX_GLOBAL for undefined symbols without a version.

Maskray's blog post on symbol versioning has this to say:

• Index 0 is called VER_NDX_LOCAL (misleading name, should have been VER_NDX_NONE). For defined symbols, the binding of the symbol will be changed to STB_LOCAL.
• Index 1 is called VER_NDX_GLOBAL. It has no special effect and is used for unversioned symbols.
• Index 2 to 0xffef are used for user defined versions.

The spec doesn't seem to really say which is correct for undefined symbols. It just says:

VER_NDX_LOCAL 0 - The symbol is private, and is not available outside this object.
VER_NDX_GLOBAL 1 - The symbol is globally available (ie the base or default version).

I guess maybe it doesn't matter which is used, so perhaps we should change linker-diff to treat them as the same, at least for undefined symbols.

The other option would be enable LLD for all affected tests, although there are quite a few.

[davidlattimore]

I've created #1424 to make linker-diff ignore the difference. Feel free to merge that PR if you like. With that PR, the tests now pass for me on a 26.04 docker image.

[davidlattimore]

LGTM once the tests are passing. Do you think we should remove some older ubuntu platforms? I'm no longer developing on 22.04, so I'd be happy to remove that unless folks think we still need it for some reason.

[marxin]

I'm no longer developing on 22.04, so I'd be happy to remove that unless folks think we still need it for some reason.
Good idea - I welcome that.

Anyway, thanks for the investigation related to the symbol versioning.

[LeoniePhiline]

Debian Bookworm only provides glibc 2.36, while new wild-linker builds now require glibc 2.39.

Would you recommend users of Debian oldstable use the musl builds, or is there any chance you could consider providing backward compatibility?

[davidlattimore]

Thanks for bringing that to our attention @LeoniePhiline. I've raised #1490. We'll ensure that the next release has lower glibc requirements for our release builds. In the meantime, if you have a rust toolchain installed, I'd probably suggest cargo install wild-linker. The musl build would also be fine.