std::atomic_ref::operator++,++(int),--,--(int) - cppreference.com (original) (raw)
| Provided only when T is an integral type other than cv bool or a pointer-to-object type | ||
|---|---|---|
| value_type operator++() const noexcept; | (1) | (since C++20) |
| value_type operator++( int ) const noexcept; | (2) | (since C++20) |
| value_type operator--() const noexcept; | (3) | (since C++20) |
| value_type operator--( int ) const noexcept; | (4) | (since C++20) |
Atomically increments or decrements the current value of the referenced object. These operations are read-modify-write operations.
Performs atomic pre-increment. Equivalent to return fetch_add(1) + 1;.
Performs atomic post-increment. Equivalent to return fetch_add(1);.
Performs atomic pre-decrement. Equivalent to return fetch_sub(1) - 1;
Performs atomic post-decrement. Equivalent to return fetch_sub(1);.
- For signed integral types, arithmetic is defined to use two’s complement representation. There are no undefined results.
- For pointer-to-object types, the result may be an undefined address, but the operations otherwise have no undefined behavior. The program is ill-formed if std::remove_pointer_t<T> is not a complete object type.
These overloads participate in overload resolution only if std::is_const_v<T> is false.
[edit] Return value
1,3) The value of the referenced object after the modification.
2,4) The value of the referenced object before the modification.
[edit] Notes
Unlike most pre-increment and pre-decrement operators, the pre-increment and pre-decrement operators for atomic_ref do not return a reference to the modified object. They return a copy of the stored value instead.
[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 3508(P3323R1) | C++20 | increment and decrement operators were meaningless for const T | constrained to accept only non-const T |
[edit] See also
| | atomically adds the argument to the value stored in the referenced object and obtains the value held previously (public member function) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | atomically subtracts the argument from the value stored in the referenced object and obtains the value held previously (public member function) [edit] | | | atomically adds to or subtracts from the referenced value (public member function) [edit] | | | atomically performs bitwise AND, OR, XOR with the referenced value (public member function) [edit] |