member only of atomic<Integral> (C++11) and atomic<Floating> (C++20) template specializations | ||
(1) | ||
T operator+=( T arg ) noexcept; | ||
T operator+=( T arg ) volatile noexcept; | ||
member only of atomic<T*> template specialization | ||
(1) | ||
T* operator+=( std::ptrdiff_t arg ) noexcept; | ||
T* operator+=( std::ptrdiff_t arg ) volatile noexcept; | ||
member only of atomic<Integral> (C++11) and atomic<Floating> (C++20) template specializations | ||
(2) | ||
T operator-=( T arg ) noexcept; | ||
T operator-=( T arg ) volatile noexcept; | ||
member only of atomic<T*> template specialization | ||
(2) | ||
T* operator-=( std::ptrdiff_t arg ) noexcept; | ||
T* operator-=( std::ptrdiff_t arg ) volatile noexcept; | ||
member only of atomic<Integral> template specialization | ||
(3) | ||
T operator&=( T arg ) noexcept; | ||
T operator&=( T arg ) volatile noexcept; | ||
(4) | ||
T operator|=( T arg ) noexcept; | ||
T operator|=( T arg ) volatile noexcept; | ||
(5) | ||
T operator^=( T arg ) noexcept; | ||
T operator^=( T arg ) volatile noexcept; |
Atomically replaces the current value with the result of computation involving the previous value and arg
. The operation is read-modify-write operation.
fetch_add(arg)
+ arg.fetch_sub(arg)
- arg.fetch_and(arg)
& arg.fetch_or(arg)
| arg.fetch_xor(arg)
^ arg.For signed Integral
types, arithmetic is defined to use two’s complement representation. There are no undefined results.
For T*
types, the result may be an undefined address, but the operations otherwise have no undefined behavior. The program is ill-formed if T
is not an object type.
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 The volatile-qualified versions are deprecated if | (since C++20) |
arg | - | the argument for the arithmetic operation |
The resulting value (that is, the result of applying the corresponding binary operator to the value immediately preceding the effects of the corresponding member function in the modification order of *this
).
Unlike most compound assignment operators, the compound assignment operators for atomic types do not return a reference to their left-hand arguments. They return a copy of the stored value instead.
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR | Applied to | Behavior as published | Correct behavior |
---|---|---|---|
P0558R1 | C++11 | arithmetic permitted on pointers to cv void or function | made ill-formed |
increments or decrements the atomic value by one (public member function) |
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