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std::atomic_flag_clear, std::atomic_flag_clear_explicit

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< cpp‎ | atomic
 
 
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atomic_flag_clearatomic_flag_clear_explicit
(C++11)(C++11)
 
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 ) noexcept;
(3) (since C++11)
void atomic_flag_clear_explicit( std::atomic_flag* obj,
                                 std::memory_order order ) noexcept;
(4) (since C++11)

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.

Contents

[edit] Parameters

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

[edit] Notes

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

[edit] 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

[edit] See also

the lock-free boolean atomic type
(class) [edit]
atomically sets the flag to true and returns its previous value
(function) [edit]
defines memory ordering constraints for the given atomic operation
(enum) [edit]
C documentation for atomic_flag_clear, atomic_flag_clear_explicit