[libcxx-commits] [libcxx] [libc++] Allows any types of size 4 and 8 to use native platform ulock_wait (PR #161086)

[Louis Dionne via libcxx-commits]

================
@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: no-threads
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
----------------
ldionne wrote:

After investigating this with Hui, we were basically not able to reproduce this issue when back-deploying to macOS 26.1. We were also unable to reproduce this issue when back-deploying to macOS 15.6 on Hui's system, which is strange since the Github runners are using macOS 15.7 (and both have the same `libc++.dylib`). Hence, it seems like this only reproduces on Github runners. Consequently, I suggest we still add the test but mark it as `UNSUPPORTED` with a `TODO` when back-deploying on `macOS 15`. At the moment, I am not convinced of the value of investigating this failure all the way through: it could be extremely time consuming and might not even be something that actually happens on Apple hardware (I'm not familiar with Github-hosted runners but I'm not sure they use actual Apple hardware).

TLDR, this seems like a reasonable approach for now:

```
// TODO: This test (unreliably) fails when back-deploying to macOS 15. However,
//       we've only managed to observe the failure on the Github-provided CI
//       runners, which is suspicious.
// UNSUPPORTED: stdlib=system && target={{.+}}-apple-macosx15{{.*}}
```

Also note that when we update to `macOS 26` in the backdeployment CI, this test is going to start failing (if there's indeed a bug) -- at that point we might conclude that it wasn't a fluke and perhaps investigate this further.

https://github.com/llvm/llvm-project/pull/161086