Refine definition of mcontext_t on x86_64-unknown-linux-musl

[nmattia]

Fixes #1553

I've inlined the links I used for defining constants and fields, although they pretty much map to the changes introduced in ac7f0fa and ae06c2b.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @gnzlbg (or someone else) soon.

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[gnzlbg]

@bors: r+

Thanks!

[bors]

📌 Commit e691d94 has been approved by gnzlbg

[bors]

⌛ Testing commit e691d94 with merge 6dae870...

[bors]

☀️ Test successful - checks-cirrus-freebsd-10, checks-cirrus-freebsd-11, checks-cirrus-freebsd-12, status-azure
Approved by: gnzlbg
Pushing 6dae870 to master...

[nmattia]

@gnzlbg thanks for the quick response! When should we expect a release on crates.io? This would help us tremendously!

[gnzlbg]

I personally would prefer to do so after rust-lang/rust#65469 is merged. That PR is green but apparently blocked by rust-lang/rust#65251 which is being merged right now. The risk of producing new releases of libc in the meantime is that we might have to yank them if upgrading rust discovers newer issues.

I'd say let's wait 24h and see if the situation resolves by itself, which it often does, and if it doesn't, then please ping me again here and I'll re-evaluate whether we maybe just do a new release to unblock work on your side or not. If it resolves by itself and I do a new release I will ping you here instead.

In the meantime, please use a git dependency on libc master if you want to already use this. The cargo book explains how to patch dependencies if you don't want to modify your Cargo.toml.

[nmattia]

here's the ping @gnzlbg ! rust-lang/rust#65251 is in and it looks like rust-lang/rust#65469 is ready as well, though bors didn't perform the merge.

Unfortunately we can't patch, as the dependency is then treated as a local crate and we treat warnings as errors.

[gnzlbg]

Thanks for the ping, yes everything looks green on their side, so I've released 0.2.65. If something unlikely were to fail on their side, we can always release 0.2.66 with a fix.

[nmattia]

Thanks a bunch!