std::unique_lock::operator bool

From cppreference.com
explicit operator bool() const;
(since C++11)

Checks whether *this owns a locked mutex or not. Effectively calls owns_lock().

Contents

[edit] Parameters

(none)

[edit] Return value

true if *this has an associated mutex and has acquired ownership of it, false otherwise.

[edit] Exceptions

noexcept specification:  
noexcept
  (since C++11)

[edit] See also

tests whether the lock owns its associated mutex
(public member function)