std::atomic<T>::is_always_lock_free

static constexpr bool is_always_lock_free = /implementation-defined/;		(C++17 起)

如果此原子型別始終是無鎖的，則為 true，如果它從不或有時無鎖，則為 false。

此常量的值與宏 ATOMIC_xxx_LOCK_FREE（如果已定義）、成員函式 is_lock_free 和非成員函式 std::atomic_is_lock_free 保持一致。

此靜態成員常量沒有等效的非成員函式，因為非成員函式接受原子型別的指標，因此在常量表達式中不太有用。

特性測試宏	值	標準	特性
`__cpp_lib_atomic_is_always_lock_free`	`201603L`	(C++17)	`constexpr atomic<T>::is_always_lock_free`

is_lock_free	檢查原子物件是否為無鎖 (public 成員函式) [編輯]
atomic_is_lock_free (C++11)	檢查原子型別的操作是否是無鎖的 (函式模板) [編輯]

成員函式
atomic::atomic
atomic::operator=
atomic::is_lock_free
atomic::store
atomic::load
atomic::operator T
atomic::exchange
atomic::compare_exchange_strongatomic::compare_exchange_weak
atomic::wait (C++20)
atomic::notify_one (C++20)
atomic::notify_all (C++20)
常量
atomic::is_always_lock_free (C++17)
Specialized member functions
Specialized for integral, floating-point (C++20) and pointer types
atomic::fetch_add
atomic::fetch_sub
atomic::operator+=atomic::operator-=
Specialized for integral and pointer types only
atomic::fetch_max (C++26)
atomic::fetch_min (C++26)
atomic::operator++atomic::operator++(int)atomic::operator--atomic::operator--(int)
Specialized for integral types only
atomic::fetch_and
atomic::fetch_or
atomic::fetch_xor
atomic::operator&=atomic::operator\|=atomic::operator^=