C++ Concurrency in Action, Second Edition

std::atomic_flag initialization with ATOMIC_FLAG_INIT

An instance of std::atomic_flag may be initialized using the ATOMIC_FLAG_INIT macro, in which case it’s initialized into the clear state. For objects of static storage duration, initialization shall be static initialization.

• Declaration

  #define ATOMIC_FLAG_INIT unspecified

• Usage

  std::atomic_flag flag=ATOMIC_FLAG_INIT;

• Effects Constructs a new std::atomic_flag object in the clear state.

• Throws Nothing.

std::atomic_flag::test_and_set member function

Atomically sets the flag and checks whether or not it was set.

• Declaration

  bool test_and_set(memory_order order = memory_order_seq_cst) volatile noexcept; bool test_and_set(memory_order order = memory_order_seq_cst) noexcept; ...