std::atomic_flag_clear, std::atomic_flag_clear_explicit
From cppreference.com
| Defined in header <atomic>
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| 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) |
| 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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