[libcxx-commits] [libcxx] [libc++] Fix `std::atomic::wait` ulock wait UL_COMPARE_AND_WAIT64 (PR #92783)

[Louis Dionne via libcxx-commits]

================
@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// 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: c++03, c++11, c++14, c++17
+// UNSUPPORTED: no-threads
+// XFAIL: availability-synchronization_library-missing
+// XFAIL: !has-64-bit-atomics
+
+#include <atomic>
+#include <cassert>
+
+#include "test_macros.h"
+
+void test_85107() {
+  if constexpr (sizeof(std::__cxx_contention_t) == 8) {
+    // https://github.com/llvm/llvm-project/issues/85107
+    // [libc++] atomic_wait uses UL_COMPARE_AND_WAIT when it should use UL_COMPARE_AND_WAIT64 on Darwin
+    constexpr std::__cxx_contention_t old_val = 0;
+    constexpr std::__cxx_contention_t new_val = old_val + (1l << 32);
+    std::__cxx_atomic_contention_t ct(new_val);
+    std::__libcpp_atomic_wait(&ct, old_val);
----------------
ldionne wrote:

```suggestion
    std::__libcpp_atomic_wait(&ct, old_val); // this will hang forever if the bug is present
```

https://github.com/llvm/llvm-project/pull/92783