compare_exchange_weak采用兩個Ordering參數來說明此操作的內存順序。success說明了與current比較成功時發生的讀取-修改-寫入操作所需的順序。failure說明了比較失敗時發生的加載操作所需的順序。使用Acquire作為成功排序使存儲成為此操作的一部分Relaxed,並使用Release使成功加載Relaxed。失敗排序隻能是SeqCst、Acquire或...
>::type storage;staticstd::atomic<int> flag;while(flag <2) {// all threads spin until the object is properly initializedintexpected =0;if(flag.compare_exchange_weak(expected,1)) {// only one thread succeeds at the compare_exchange.try{ ::new(&storage) my_type; }catch(...) {// I...
compare_exchange_weak函数直接比较所包含值的物理内容，这可能导致使用(如果底层类型有填充位、陷阱值或相...
2.3.1compare_exchange_weak boolcompare_exchange_weak(T& expected, T val, memory_order sync = memory_order_seq_cst)volatilenoexcept; boolcompare_exchange_weak(T& expected, T val, memory_order sync = memory_order_seq_cst)noexcept; boolcompare_exchange_weak(T& expected, T val, memory_order s...
atomic_compare_exchange 分为两个版本 atomic_compare_exchange_strong 和 atomic_compare_exchange_weak,语义如下 boolatomic_compare_exchange(volatileA *obj, C*expected, C desired, memory_order succ, memory_order fail ); { fence_before(succ);//fence 1if(*obj ==expected) ...
bool compare_exchange_weak( Ty& Exp, Ty Value, memory_order Order1, memory_order Order2 ) volatile _NOEXCEPT; bool compare_exchange_weak( Ty& Exp, Ty Value, memory_order Order1, memory_order Order2 ) _NOEXCEPT; bool compare_exchange_weak( Ty& Exp, Ty Value, memory_order Order1 = me...
Atomically sets the value to newValue if the current value, referred to as the <em>witness value</em>, == expectedValue, with memory effects as specified by VarHandle#compareAndExchangeAcquire.
template <class Ty> inline bool atomic_compare_exchange_weak_explicit( volatile atomic<Ty> *Atom, Ty *Exp, Ty Value, memory_order Order1, memory_order Order2 ) _NOEXCEPT; template <class Ty> inline bool atomic_compare_exchange_weak_explicit( atomic<Ty> *Atom, Ty *Exp, Ty Value, memory...
在头文件<stdatomic.h>中定义_Bool atomic_compare_exchange_strong(volatile A * obj,C * expected,C desired);(1)(自C11以来)_Bool atomic_compare_exchange_weak(volatile A * obj,C * expected,C desired);(2)(自C11以来)_Bool atomic_compare_exchange_strong_explicit(volatile A * obj,C *...
Prototypes boolA::compare_exchange_weak(C&expected,Cdesired, memory_ordersuccess, memory_orderfailure) volatile noexcept; boolA::compare_exchange_weak(C&expected,Cdesired, memory_ordersuccess, memory_orderfailure) noexcept; boolA::compare_exchange_weak(C&expected,Cdesired, memory_orderorder= memory_or...