std::cv_status
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   Defined in header  <condition_variable>
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|   enum class cv_status {     no_timeout,  | 
(since C++11) | |
The scoped enumeration std::cv_status describes whether a timed wait returned because of timeout or not.
std::cv_status is used by the wait_for and wait_until methods of std::condition_variable and std::condition_variable_any.
Member constants
| Constant | Explanation | 
  no_timeout
 | 
  the condition variable was awakened with notify_all, notify_one, or spuriously
 | 
  timeout
 | 
the condition variable was awakened by timeout expiration | 
See also
|    blocks the current thread until the condition variable is woken up or after the specified timeout duration   (public member function of std::condition_variable)  | |
|    blocks the current thread until the condition variable is woken up or after the specified timeout duration   (public member function of std::condition_variable_any)  | |
|    blocks the current thread until the condition variable is woken up or until specified time point has been reached   (public member function of std::condition_variable)  | |
|    blocks the current thread until the condition variable is woken up or until specified time point has been reached   (public member function of std::condition_variable_any)  |