<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/76807>76807</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [libc++] Hangs in std::condition_variable_any when used with std::stop_token
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          alexbatashev
      </td>
    </tr>
</table>

<pre>
    The following piece of code appears to work reliably and correctly (or at least the way that I expect it to work) with `libstdc++`, but sporadically hangs with the latest `libc++`:

```c++
#include <thread>
#include <stop_token>
#include <mutex>
#include <condition_variable>
#include <iostream>

class thread {
public:
    thread() {
 thread_ = std::jthread([this](std::stop_token st) {
            while (!st.stop_requested()) {
                std::unique_lock lock{m_};
 cv_.wait(lock, st, []{ return false; });
            }
 });
    }
private:
    std::mutex m_;
 std::condition_variable_any cv_;
    std::jthread thread_;
};

int main() {
    thread t;
    #ifdef _LIBCPP_VERSION
    std::cout << "libc++\n";
    #else
 std::cout << "libstdc++\n";
    #endif
}
```

Results with `libstdc++` and Clang 18. The process exits almost immediately with exit code 0.

`libc++` with Clang 18 commit d933b88b71b00461815667d7cd0bb2fecd8606db. Sometimes it works fine, but sometimes it would hang forever until the process is killed from outside.

I also tested with commit 7e186d366d6c7def0543acc255931f617e76dff0 with the same result.

https://godbolt.org/z/hjTheTnon

</pre>
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