std::packaged_task<R(Args...)>::valid - cppreference.com

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并发支持库

线程

thread

(C++11)

jthread

(C++20)

hardware_destructive_interference_sizehardware_constructive_interference_size

(C++17)(C++17)

this_thread 命名空间

get_id (C++11)
yield (C++11)

sleep_for (C++11)
sleep_until (C++11)

协作式取消

stop_token (C++20)
inplace_stop_token (C++26)
never_stop_token (C++26)
stop_source (C++20)
inplace_stop_source (C++26)
stop_callback (C++20)

inplace_stop_callback (C++26)
stop_callback_for_t (C++26)
stoppable_token (C++26)
unstoppable_token (C++26)
stoppable-source (C++26)
stoppable-callback-for (C++26)

互斥

mutex (C++11)
recursive_mutex (C++11)
shared_mutex (C++17)

timed_mutex (C++11)
recursive_timed_mutex (C++11)
shared_timed_mutex (C++14)

通用锁管理

lock (C++11)
lock_guard (C++11)
scoped_lock (C++17)
unique_lock (C++11)
shared_lock (C++14)
once_flag (C++11)
call_once (C++11)

try_lock (C++11)
defer_locktry_to_lockadopt_lockdefer_lock_ttry_to_lock_tadopt_lock_t (C++11)(C++11)(C++11)(C++11)(C++11)(C++11)

条件变量

condition_variable

(C++11)

condition_variable_any

(C++11)

notify_all_at_thread_exit

(C++11)

cv_status

(C++11)

信号量

counting_semaphorebinary_semaphore

(C++20)(C++20)

(C++20)

(C++20)

promise (C++11)
future (C++11)
shared_future (C++11)
packaged_task (C++11)
async (C++11)

launch (C++11)
future_status (C++11)
future_error (C++11)
future_category (C++11)
future_errc (C++11)

安全回收

读-复制-更新机制

rcu_obj_base (C++26)
rcu_domain (C++26)
rcu_default_domain (C++26)

rcu_synchronize (C++26)
rcu_barrier (C++26)
rcu_retire (C++26)

风险指针

hazard_pointer_obj_base

(C++26)

hazard_pointer

(C++26)

make_hazard_pointer

(C++26)

原子类型
atomic (C++11)
atomic_ref (C++20)
atomic_flag (C++11)
原子类型的初始化
atomic_init (C++11)(C++20 弃用)
ATOMIC_VAR_INIT (C++11)(C++20 弃用)
ATOMIC_FLAG_INIT (C++11)
内存定序
memory_order (C++11)
kill_dependency (C++11)(C++26 弃用)
atomic_thread_fence (C++11)
atomic_signal_fence (C++11)
原子操作的自由函数
atomic_storeatomic_store_explicit (C++11)(C++11)
atomic_loadatomic_load_explicit (C++11)(C++11)
atomic_exchangeatomic_exchange_explicit (C++11)(C++11)
atomic_compare_exchange_weakatomic_compare_exchange_weak_explicitatomic_compare_exchange_strongatomic_compare_exchange_strong_explicit (C++11)(C++11)(C++11)(C++11)
atomic_fetch_addatomic_fetch_add_explicit (C++11)(C++11)
atomic_fetch_subatomic_fetch_sub_explicit (C++11)(C++11)
atomic_fetch_andatomic_fetch_and_explicit (C++11)(C++11)
atomic_fetch_oratomic_fetch_or_explicit (C++11)(C++11)
atomic_fetch_xoratomic_fetch_xor_explicit (C++11)(C++11)
atomic_fetch_maxatomic_fetch_max_explicit (C++26)(C++26)
atomic_fetch_minatomic_fetch_min_explicit (C++26)(C++26)
atomic_is_lock_free (C++11)
atomic_waitatomic_wait_explicit (C++20)(C++20)
atomic_notify_one (C++20)
atomic_notify_all (C++20)
原子标志的自由函数
atomic_flag_test_and_setatomic_flag_test_and_set_explicit (C++11)(C++11)
atomic_flag_clearatomic_flag_clear_explicit (C++11)(C++11)
atomic_flag_testatomic_flag_test_explicit (C++20)(C++20)
atomic_flag_waitatomic_flag_wait_explicit (C++20)(C++20)
atomic_flag_notify_one (C++20)
atomic_flag_notify_all (C++20)

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std::packaged_task

成员函数
packaged_task::packaged_task
packaged_task::~packaged_task
packaged_task::operator=
packaged_task::valid
packaged_task::swap
获取结果
packaged_task::get_future
执行
packaged_task::operator()
packaged_task::make_ready_at_thread_exit
packaged_task::reset
非成员函数
swap(std::packaged_task)
辅助类
uses_allocator<std::packaged_task> (C++17 前)
推导指引(C++17)

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bool valid() const noexcept;		(C++11 起)

检查 *this 是否拥有共享状态。

参数

（无）

返回值

若 *this 拥有共享状态则为 true，否则为 false。