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std::atomic_ref<T>:: exchange

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atomic_ref::exchange
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Constants
value_type exchange ( value_type desired,

std:: memory_order order =

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

以原子操作将引用对象的值替换为 desired 。该操作属于读-改-写操作。内存访问顺序根据 order 参数值确定。

此重载仅当 std:: is_const_v < T > 为 false 时参与重载决议。

参数

desired - 要赋的值
order - 要强制执行的内存顺序约束

返回值

调用前被引用对象的值。

缺陷报告

下列行为变更缺陷报告被追溯应用于先前发布的C++标准。

缺陷报告 适用范围 发布时行为 修正后行为
LWG 3508
( P3323R1 ) 		C++20 exchange 对 const T 无意义 约束为仅接受非 const T