std::experimental::make_exceptional_future

From cppreference.com
Defined in header <experimental/future>
template < class T >
future<T> make_exceptional_future(std::exception_ptr ex);
(1) (concurrency TS)
template < class T, class E >
future<T> make_exceptional_future(E ex);
(2) (concurrency TS)
1) Creates a shared state of type T that is immediately ready and stores the exception pointer ex, then return a future associated with that shared state, as if by promise<T> p; p.set_exception(ex); return p.get_future();. The behavior is undefined if ex is null.
2) Creates a shared state of type T that is immediately ready and stores an exception pointer created from ex, then return a future associated with that shared state, as if by promise<T> p; p.set_exception(std::make_exception_ptr(ex)); return p.get_future();

[edit] Return value

A future object associated with the shared state that was created.

[edit] See also

(concurrency TS)
produces a future that is ready immediately and holds the given value
(function template)