32 Concurrency support library [thread] (original) (raw)

32.10 Futures [futures]

32.10.2 Header synopsis [future.syn]

namespace std { enum class future_errc { broken_promise = implementation-defined,future_already_retrieved = implementation-defined,promise_already_satisfied = implementation-defined,no_state = implementation-defined };enum class launch : unspecified { async = unspecified,deferred = unspecified,implementation-defined };enum class future_status { ready,timeout,deferred };// [futures.errors], error handling template<> struct is_error_code_enum<future_errc> : public true_type { }; error_code make_error_code(future_errc e) noexcept; error_condition make_error_condition(future_errc e) noexcept;const error_category& future_category() noexcept;// [futures.future.error], class future_error class future_error;// [futures.promise], class template promise template<class R> class promise;template<class R> class promise<R&>;template<> class promise<void>;template<class R> void swap(promise<R>& x, promise<R>& y) noexcept;template<class R, class Alloc> struct uses_allocator<promise<R>, Alloc>;// [futures.unique.future], class template future template<class R> class future;template<class R> class future<R&>;template<> class future<void>;// [futures.shared.future], class template shared_future template<class R> class shared_future;template<class R> class shared_future<R&>;template<> class shared_future<void>;// [futures.task], class template packaged_task template<class> class packaged_task; // not defined template<class R, class... ArgTypes> class packaged_task<R(ArgTypes...)>;template<class R, class... ArgTypes> void swap(packaged_task<R(ArgTypes...)>&, packaged_task<R(ArgTypes...)>&) noexcept;// [futures.async], function template async template<class F, class... Args> future<invoke_result_t<decay_t<F>, decay_t<Args>...>> async(F&& f, Args&&... args);template<class F, class... Args> future<invoke_result_t<decay_t<F>, decay_t<Args>...>> async(launch policy, F&& f, Args&&... args);}

The enum type launch is a bitmask type ([bitmask.types]) with elements launch​::​async and launch​::​deferred.

[Note 1:

Implementations can provide bitmasks to specify restrictions on task interaction by functions launched by async() applicable to a corresponding subset of available launch policies.

Implementations can extend the behavior of the first overload of async() by adding their extensions to the launch policy under the “as if” rule.

— _end note_]

The enum values of future_errc are distinct and not zero.