NAME¶

std::atomic_flag_clear,std::atomic_flag_clear_explicit - std::atomic_flag_clear,std::atomic_flag_clear_explicit

Synopsis¶

Defined in header <atomic>
void atomic_flag_clear( volatile std::atomic_flag* obj ) noexcept; (1) (since C++11)
void atomic_flag_clear( std::atomic_flag* obj ) noexcept; (2) (since C++11)
void atomic_flag_clear_explicit( volatile std::atomic_flag* obj,
std::memory_order order ) (3) (since C++11)
noexcept;
void atomic_flag_clear_explicit( std::atomic_flag* obj,
std::memory_order order ) (4) (since C++11)
noexcept;

Atomically changes the state of the std::atomic_flag pointed to by obj to clear
(false).

1,2) The memory synchronization ordering is std::memory_order_seq_cst.
3,4) The memory synchronization ordering is order.
If order is one of std::memory_order_consume, std::memory_order_acquire and
std::memory_order_acq_rel, the behavior is undefined.

Parameters¶

obj - pointer to std::atomic_flag to access
order - the memory synchronization ordering

Notes¶

std::atomic_flag_clear and std::atomic_flag_clear_explicit can be implemented as
obj->clear() and obj->clear(order) respectively.

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¶

atomic_flag the lock-free boolean atomic type
(C++11) (class)
atomic_flag_test_and_set atomically sets the flag to true and returns its
atomic_flag_test_and_set_explicit previous value
(C++11) (function)
(C++11)
memory_order defines memory ordering constraints for the given
(C++11) atomic operation
(enum)
C documentation for
atomic_flag_clear,
atomic_flag_clear_explicit