Implement RefUnwindSafe for atomic types

[apasel422]

Closes #37136

[rust-highfive]

r? @brson

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[alexcrichton]

@bors: r+

cc @rust-lang/libs

[bors]

📌 Commit da3b0b8 has been approved by alexcrichton

[ollie27]

It doesn't make much sense for this to be marked stable when AtomicI8 is still unstable. I think for the unstable types this should be #[unstable(feature = "integer_atomics", issue = "32976")] like the others impls for these types.

[apasel422]

Good catch. Updated.

[apasel422]

Should the impls be placed behind #[cfg(target_has_atomic = "x")]?

[alexcrichton]

@bors: r-

Should the impls be placed behind

Ah yes, indeed!

[apasel422]

As a side note, there are portions of the standard library that use atomics without the #[cfg(target_has_atomic = "x")] (most notably Arc and sync::mpsc). Should they be defined conditionally as well? Or does std assume/require their existence?

(Obviously not a change to make in this PR.)

[alexcrichton]

As a side note, there are portions of the standard library that use atomics without the #[cfg(target_has_atomic = "x")]

True yeah, this basically just means that libstd won't compile if AtomicUsize isn't available (intentional).

This seems like a mildly contentious topic on the associated issue, so I'm instead going to...

@rfcbot fcp merge

[rfcbot]

Team member @alexcrichton has proposed to merge this. The next step is review by the rest of the tagged teams:

• @BurntSushi
• @Kimundi
• @alexcrichton
• @aturon
• @brson
• @sfackler

No concerns currently listed.

Once these reviewers reach consensus, this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

psst @alexcrichton, I wasn't able to add the final-comment-period label, please do so.

[alexcrichton]

@bors: r+

[bors]

📌 Commit f832203 has been approved by alexcrichton

[bors]

⌛ Testing commit f832203 with merge 73f5cad...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-cargotest, auto-linux-64-cross-freebsd, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-opt, auto-mac-64-opt-rustbuild, auto-mac-cross-ios-opt, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-cargotest, auto-win-msvc-64-opt, auto-win-msvc-64-opt-rustbuild
Approved by: alexcrichton
Pushing 73f5cad to master...