std::atomic<T>::operator+=,-=
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| Member functions | ||||
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(C++20)
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(C++20)
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(C++20)
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| Constants | ||||
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(C++17)
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| Specialized member functions | ||||
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Specialized for integral, floating-point (C++20) and pointer types |
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atomic::operator+=atomic::operator-= | ||||
| Specialized for integral and pointer types only | ||||
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(C++26)
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(C++26)
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| Specialized for integral types only | ||||
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member only of
atomic<Integral > specializationsand atomic<Floating > specializations(since C++20)
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T operator+=( T arg ) noexcept; |
(1) | (since C++11) |
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T operator+
=
( T arg )
volatile
noexcept
;
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(2) | (since C++11) |
T operator-=( T arg ) noexcept; |
(3) | (since C++11) |
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T operator-
=
( T arg )
volatile
noexcept
;
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(4) | (since C++11) |
member only of atomic<T*> partial specialization |
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T* operator+
=
(
std::ptrdiff_t arg )
noexcept
;
|
(5) | (since C++11) |
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T* operator+
=
(
std::ptrdiff_t arg )
volatile
noexcept
;
|
(6) | (since C++11) |
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T* operator-
=
(
std::ptrdiff_t arg )
noexcept
;
|
(7) | (since C++11) |
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T* operator-
=
(
std::ptrdiff_t arg )
volatile
noexcept
;
|
(8) | (since C++11) |
Atomically replaces the current value with the result of computation involving the previous value and arg. The operation is read-modify-write operation.
- operator+= performs atomic addition. Equivalent to return fetch_add(arg) + arg;
- operator-= performs atomic subtraction. Equivalent to return fetch_sub(arg) - arg;
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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 |
(since C++20) |
T is not a complete object type, the program is ill-formed.
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It is deprecated if std::atomic <T> :: is_always_lock_free is false and any volatile |
(since C++20) |
Parameters
| arg | - | the argument for the arithmetic operation |
Return value
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
Notes
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.
Defect reports
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 (possibly cv-qualified) void or function | made ill-formed |
See also
| atomically adds the argument to the value stored in the atomic object and obtains the value held previously (public member function) |
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| atomically subtracts the argument from the value stored in the atomic object and obtains the value held previously (public member function) |
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| increments or decrements the atomic value by one (public member function) |
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| performs bitwise AND, OR, XOR with the atomic value (public member function) |