[libcxx-commits] [libcxx] [libc++] Use public os_sync API instead of private __ulock on newer Apple platforms (PR #182947)

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Bbn08 wrote:

@H-G-Hristov Thanks for the heads up, I'm aware of the previous revert the issue there was an unconditional include of the header. This PR guards the include behind `_LIBCPP_USE_OS_SYNC`, which is only defined when the deployment target is macOS 14.4+ / iOS 17.4+, so older SDKs won't try to include the header at all. Also added `Fixes #146142` to the description.
As for the AIX CI failure, it looks unrelated to this PR all new code is guarded behind `defined(__APPLE__)`, so the AIX build follows exactly the same code path as before. The two CI runs also failed on different sub-checks (32-bit vs 64-bit), which suggests bot flakiness rather than a regression. Happy to be corrected if I'm missing something though, let me know what you think.

https://github.com/llvm/llvm-project/pull/182947