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std::atomic_flag_test, std::atomic_flag_test_explicit

Defined in header <atomic> 
bool atomic_flag_test( const volatile std::atomic_flag* object ) noexcept;
 (1) (since C++20) 
bool atomic_flag_test( const std::atomic_flag* object ) noexcept;
 (2) (since C++20) 
bool atomic_flag_test_explicit( const volatile std::atomic_flag* object,
                                std::memory_order order ) noexcept;
 (3) (since C++20) 
bool atomic_flag_test_explicit( const std::atomic_flag* object,
                                std::memory_order order ) noexcept;
 (4) (since C++20)

Atomically reads the value of the *object and returns the value.

1,2) The memory synchronization order is std::memory_order_seq_cst.
3,4) The memory synchronization order is order.
If order is one of std::memory_order::release and std::memory_order::acq_rel, the behavior is undefined.

Parameters

object - pointer to the atomic_flag object to read
order - the memory synchronization ordering

Return value

The value atomically read.

Notes

Feature-test macro Value Std Feature
__cpp_lib_atomic_flag_test 201907L (C++20) std::atomic_flag::test

Example

See also

(C++20)
atomically returns the value of the flag
(public member function of std::atomic_flag)

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