std:: atomic_flag_clear, std:: atomic_flag_clear_explicit

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atomic_flag_clear atomic_flag_clear_explicit
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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.

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

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