33 Thread support library [thread]

33.4 Mutual exclusion [thread.mutex]

33.4.4 Locks [thread.lock]

33.4.4.3 Class template unique_­lock [thread.lock.unique]

33.4.4.3.4 unique_­lock observers [thread.lock.unique.obs]

bool owns_lock() const noexcept;

explicit operator bool() const noexcept;

mutex_type *mutex() const noexcept;