std::shared_future

template <class T> shared_future;template <class R&> shared_future<R&>; // specialization : T is a reference type (R&)template <> shared_future<void>; // specialization : T is void

Shared future

A shared_future object behaves like a future object, except that it can be copied, and that more than one shared_future can share ownership over their end of a shared state. They also allow the value in the shared state to be retrieved multiple times once ready.

shared_future objects can be implicitly converted from future objects (see its constructor ), or explicitly obtained by calling future::share . In both cases, the future object from which it is obtained transfers its association with the shared state to the shared_future and becomes itself non-valid .

The lifetime of the shared state lasts at least until the last object with which it is associated is destroyed. Retrieving the value from a shared_future (with member get ) does not release its ownership over the shared state (unlike with futures ). Therefore, if associated to shared_future objects, the shared state can survive the object from which it was obtained in the first place (if any).

Member functions

(constructor): Construct shared_future (public member function)

(destructor): Destroy shared_future (public member function)

operator=: Assign shared future (public member function)

get: Get value (public member function)

valid: Check for valid shared state (public member function)

wait: Wait for ready (public member function)

wait_for: Wait for ready during time span (public member function)

wait_until: Wait for ready until time point (public member function)

Template specializations

Two specific shared_future specializations are declared in <future> :

1
2

template <class R&> shared_future<R&>; // specialization : T is a reference type (R&)
template <> shared_future<void>; // specialization : T is void

They operate in the same way as the unspecialized template, except for the return value of their shared_future::get member function.

classes

enum classes

functions

member functions

std::shared_future

Member functions

Template specializations