std::atomic_ref::operator+=,-= - cppreference.com (original) (raw)

Provided only when T is an arithmetic type other than cv bool or a pointer-to-object type
value_type operator+=( difference_type arg ) const noexcept;	(1)	(constexpr since C++26)
value_type operator-=( difference_type arg ) const noexcept;	(2)	(constexpr since C++26)

Atomically replaces the current value referenced by *_[ptr](../atomic%5Fref.html#ptr "cpp/atomic/atomic ref")_ with the result of computation involving the previous value and arg. These operations are read-modify-write operations.

operator+= performs atomic addition. Equivalent to return fetch_add(arg) + arg;.
operator-= performs atomic subtraction. Equivalent to return fetch_sub(arg) - arg;.

For signed integral types, arithmetic is defined to use two’s complement representation. There are no undefined results.
For floating-point types, the floating-point environment in effect may be different from the calling thread's floating-point environment. The operation need not be conform to the corresponding std::numeric_limits traits but is encouraged to do so. If the result is not a representable value for its type, the result is unspecified but the operation otherwise has no undefined behavior.
For pointer types, the result may be an undefined address, but the operation otherwise has no undefined behavior.
- If std::remove_pointer_t<T> is not a complete object type, the program is ill-formed.

These overloads participate in overload resolution only if std::is_const_v<T> is false.

[edit] Parameters

arg	-	the argument for the arithmetic operation

[edit] Return value

The resulting value (that is, the result of applying the corresponding binary operator to the value referenced by *_[ptr](../atomic%5Fref.html#ptr "cpp/atomic/atomic ref")_ immediately preceding the effects of the corresponding member function).

[edit] Notes

Unlike most compound assignment operators, the compound assignment operators for atomic_ref return a copy of the stored value instead of a reference to arg.

[edit] Example

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.