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std::atomic_ref<T>::exchange

From cppreference.com
< cpp‎ | atomic‎ | atomic ref
 
 
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value_type exchange( value_type desired,

                     std::memory_order order =

                         std::memory_order_seq_cst ) const noexcept;
(constexpr since C++26)

Atomically replaces the value of the referenced object with desired. The operation is a read-modify-write operation. Memory is affected according to the value of order.

This overload participates in overload resolution only if std::is_const_v<T> is false.

[edit] Parameters

desired - value to assign
order - memory order constraints to enforce

[edit] Return value

The value of the referenced object before the call.

[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 exchange was meaningless for const T constrained to accept only non-const T