Chapter 55: std::atomics

Section 55.1: atomic types

Each instantiation and full specialization of the std::atomic template defines an atomic type. If one thread writes to an atomic object while another thread reads from it, the behavior is well-defined (see memory model for details on data races)

In addition, accesses to atomic objects may establish inter-thread synchronization and order non-atomic memory accesses as specified by std::memory_order.

std::atomic may be instantiated with any TriviallyCopyable type T. std::atomic is neither copyable nor movable.

The standard library provides specializations of the std::atomic template for the following types:

1.One full specialization for the type bool and its typedef name is defined that is treated as a non-specialized std::atomic<T> except that it has standard layout, trivial default constructor, trivial destructors, and supports aggregate initialization syntax:

Typedef name Full specialization

std::atomic_bool std::atomic<bool>

2)Full specializations and typedefs for integral types, as follows:

std::atomic_int_least8_t std::atomic<std::int_least8_t> std::atomic_uint_least8_t std::atomic<std::uint_least8_t>

std::atomic_int_least16_t std::atomic<std::int_least16_t>

std::atomic_uint_least16_t std::atomic<std::uint_least16_t>

std::atomic_int_least32_t std::atomic<std::int_least32_t>

std::atomic_uint_least32_t std::atomic<std::uint_least32_t>

std::atomic_int_least64_t std::atomic<std::int_least64_t>

std::atomic_uint_least64_t std::atomic<std::uint_least64_t>

std::atomic_int_fast8_t std::atomic<std::int_fast8_t>

std::atomic_uint_fast8_t std::atomic<std::uint_fast8_t>

std::atomic_int_fast16_t std::atomic<std::int_fast16_t>

std::atomic_uint_fast16_t std::atomic<std::uint_fast16_t>

std::atomic_int_fast32_t std::atomic<std::int_fast32_t>

std::atomic_uint_fast32_t std::atomic<std::uint_fast32_t>

std::atomic_int_fast64_t std::atomic<std::int_fast64_t>

std::atomic_uint_fast64_t std::atomic<std::uint_fast64_t>

std::atomic_intptr_t std::atomic<std::intptr_t>

std::atomic_uintptr_t std::atomic<std::uintptr_t>

std::atomic_size_t std::atomic<std::size_t>

std::atomic_ptrdiff_t std::atomic<std::ptrdiff_t>

std::atomic_intmax_t std::atomic<std::intmax_t>

std::atomic_uintmax_t std::atomic<std::uintmax_t>

Simple example of using std::atomic_int

int main ()

{

std::thread first (print_foo); std::thread second (set_foo,10); first.join();

//second.join(); return 0;

}

//output: foo: 10