std::atomic::atomic (3) Linux Manual Page

std::atomic<T>::atomic – std::atomic<T>::atomic

Synopsis

atomic() noexcept = default;
(1)(since C++ 11)

    constexpr atomic(T desired) noexcept;
(2)(since C++ 11)

    atomic(const atomic &) = delete;
(3)(since C++ 11)

Constructs new atomic variable.
1) The default constructor is trivial: no initialization takes place other than zero_initialization of static and thread-local objects. std::atomic_init may be used to complete initialization.
2) Initializes the underlying value with desired. The initialization is not atomic.
3) Atomic variables are not CopyConstructible.

Parameters

desired – value to initialize with

Notes

The default-initialized std::atomic<T> does not contain a T object, and its only valid uses are destruction and initialization by std::atomic_init, see LWG_2334