unique_lock::lock Method
Blocks the calling thread until the thread obtains ownership of the associated mutex.
void lock();
Remarks
If the stored mutex pointer is null, this method throws a system_error that has an error code of operation_not_permitted.
If the calling thread already owns the associated mutex, this method throws a system_error that has an error code of resource_deadlock_would_occur.
Otherwise, this method calls lock on the associated mutex and sets the internal thread ownership flag to true.
Requirements
Header: mutex
Namespace: std