std::unique_lock<Mutex>::operator=
| unique_lock& operator=( unique_lock&& other ) noexcept; |
(since C++11) | |
Move assignment operator. Equivalent to unique_lock{std::move(other)}.swap(*this); return *this;.
If other is the same object as *this, there is no effect. Otherwise, if prior to the call *this has an associated mutex and has acquired ownership of it, the mutex is unlocked.
Contents |
[edit] Parameters
| other | - | another unique_lock to replace the state with
|
[edit] Return value
*this
[edit] Notes
With a recursive mutex it is possible for both *this and other to own the same mutex before the assignment. In this case, *this will own the mutex after the assignment and other will not.
The move assignment possibly raises undefined behavior. For example, when *this is constructed with std::adopt_lock, but the calling thread does not have the ownership of the associated mutex, the ownership of the associated mutex cannot be properly released.
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 2104 | C++11 | the move assignment operator was noexcept but could have undefined behavior | noexcept removed |
| LWG 4172 | C++11 | LWG2104 removed noexcept self-move-assignment of unique_lock was incorrectly specified
|
noexcept restored respecified as no-op |
