[clang-tidy] Add check to diagnose coroutine-hostile RAII objects (#68738)
This check detects **hostile-RAII** objects which should not **persist across a suspension point in a coroutine**. Some objects require that they be destroyed on the same thread that created them. Traditionally this requirement was often phrased as "must be a local variable", under the assumption that local variables always work this way. However this is incorrect with **C++20 coroutines**, since an intervening `co_await` may cause the coroutine to suspend and later be resumed on another thread. The lifetime of an object that requires being destroyed on the same thread must not encompass a `co_await` or `co_yield` point. If you create/destroy an object, you must do so without allowing the coroutine to suspend in the meantime. The check considers the following type as hostile: - **Scoped-lockable types**: A scoped-lockable object persisting across a suspension point is problematic as the lock held by this object could be unlocked by a different thread. This would be undefined behaviour. - Types belonging to a configurable **denylist**. ```cpp // Call some async API while holding a lock. const my::MutexLock l(&mu_); // Oops! The async Bar function may finish on a different // thread from the one that created the MutexLock object and therefore called // Mutex::Lock -- now Mutex::Unlock will be called on the wrong thread. co_await Bar(); ```
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