std::atomic_flag::clear

 

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Atomic types atomic (C++11) atomic_ref (C++20) atomic_flag (C++11) Initialization of atomic types atomic_init (C++11)(deprecated in C++20) ATOMIC_VAR_INIT (C++11)(deprecated in C++20) ATOMIC_FLAG_INIT (C++11) Memory ordering memory_order (C++11) kill_dependency (C++11) atomic_thread_fence (C++11) atomic_signal_fence (C++11) Free functions for atomic operations 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) Free functions for atomic flags 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)

 

std::atomic_flag

Member functions

atomic_flag::atomic_flag

atomic_flag::operator=

atomic_flag::clear

atomic_flag::test_and_set

atomic_flag::test (C++20)

atomic_flag::wait (C++20)

atomic_flag::notify_one (C++20)

atomic_flag::notify_all (C++20)

 

Defined in header <atomic>
void clear( std::memory_order order =                 std::memory_order_seq_cst ) volatile noexcept;	(1)	(since C++11)
void clear( std::memory_order order =                 std::memory_order_seq_cst ) noexcept;	(2)	(since C++11)

Atomically changes the state of a std::atomic_flag to clear (false).

If order is one of std::memory_order_consume, std::memory_order_acquire and std::memory_order_acq_rel, the behavior is undefined.

Parameters

order

-

the memory synchronization ordering

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 2138	C++11	order could be std::memory_order_consume	the behavior is undefined in this case

See also

test_and_set	atomically sets the flag to true and obtains its previous value (public member function)
atomic_flag_clearatomic_flag_clear_explicit (C++11)(C++11)	atomically sets the value of the flag to false (function)
memory_order (C++11)	defines memory ordering constraints for the given atomic operation (enum)