std::atomic_flag - Man Page

constexpr atomic_flag (bool __i) noexcept
atomic_flag (const atomic_flag &)=delete
void clear (memory_order __m=memory_order_seq_cst) noexcept
void clear (memory_order __m=memory_order_seq_cst) volatile noexcept
atomic_flag & operator= (const atomic_flag &) volatile=delete
atomic_flag & operator= (const atomic_flag &)=delete
bool test_and_set (memory_order __m=memory_order_seq_cst) noexcept
bool test_and_set (memory_order __m=memory_order_seq_cst) volatile noexcept

__atomic_flag_data_type _M_i