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std::atomic<T>::fetch_or

(since C++11)
(member only of atomic<Integral> template specialization)
T fetch_or( T arg, 
            std::memory_order order = std::memory_order_seq_cst ) noexcept;
T fetch_or( T arg, 
            std::memory_order order = std::memory_order_seq_cst ) volatile noexcept;

Atomically replaces the current value with the result of bitwise OR of the value and arg. The operation is read-modify-write operation. Memory is affected according to the value of order.

The volatile-qualified version is deprecated if std::atomic<T>::is_always_lock_free is false.

(since C++20)

Parameters

arg - the other argument of bitwise OR
order - memory order constraints to enforce

Return value

The value immediately preceding the effects of this function in the modification order of *this.

See also

(C++11)(C++11)
replaces the atomic object with the result of bitwise OR with a non-atomic argument and obtains the previous value of the atomic
(function template)

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