1 // <future> -*- C++ -*-
3 // Copyright (C) 2009-2016 Free Software Foundation, Inc.
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
25 /** @file include/future
26 * This is a Standard C++ Library header.
29 #ifndef _GLIBCXX_FUTURE
30 #define _GLIBCXX_FUTURE 1
32 #pragma GCC system_header
34 #if __cplusplus < 201103L
35 # include <bits/c++0x_warning.h>
40 #include <condition_variable>
41 #include <system_error>
43 #include <bits/atomic_futex.h>
44 #include <bits/functexcept.h>
45 #include <bits/invoke.h>
46 #include <bits/unique_ptr.h>
47 #include <bits/shared_ptr.h>
48 #include <bits/std_function.h>
49 #include <bits/uses_allocator.h>
50 #include <bits/allocated_ptr.h>
51 #include <ext/aligned_buffer.h>
53 namespace std _GLIBCXX_VISIBILITY(default)
55 _GLIBCXX_BEGIN_NAMESPACE_VERSION
58 * @defgroup futures Futures
59 * @ingroup concurrency
61 * Classes for futures support.
65 /// Error code for futures
66 enum class future_errc
68 future_already_retrieved = 1,
69 promise_already_satisfied,
76 struct is_error_code_enum<future_errc> : public true_type { };
78 /// Points to a statically-allocated object derived from error_category.
80 future_category() noexcept;
82 /// Overload for make_error_code.
84 make_error_code(future_errc __errc) noexcept
85 { return error_code(static_cast<int>(__errc), future_category()); }
87 /// Overload for make_error_condition.
88 inline error_condition
89 make_error_condition(future_errc __errc) noexcept
90 { return error_condition(static_cast<int>(__errc), future_category()); }
93 * @brief Exception type thrown by futures.
96 class future_error : public logic_error
100 future_error(future_errc __errc)
101 : future_error(std::make_error_code(__errc))
104 virtual ~future_error() noexcept;
107 what() const noexcept;
110 code() const noexcept { return _M_code; }
114 future_error(error_code __ec)
115 : logic_error("std::future_error: " + __ec.message()), _M_code(__ec)
118 friend void __throw_future_error(int);
123 // Forward declarations.
124 template<typename _Res>
127 template<typename _Res>
130 template<typename _Signature>
133 template<typename _Res>
136 /// Launch code for futures
143 constexpr launch operator&(launch __x, launch __y)
145 return static_cast<launch>(
146 static_cast<int>(__x) & static_cast<int>(__y));
149 constexpr launch operator|(launch __x, launch __y)
151 return static_cast<launch>(
152 static_cast<int>(__x) | static_cast<int>(__y));
155 constexpr launch operator^(launch __x, launch __y)
157 return static_cast<launch>(
158 static_cast<int>(__x) ^ static_cast<int>(__y));
161 constexpr launch operator~(launch __x)
162 { return static_cast<launch>(~static_cast<int>(__x)); }
164 inline launch& operator&=(launch& __x, launch __y)
165 { return __x = __x & __y; }
167 inline launch& operator|=(launch& __x, launch __y)
168 { return __x = __x | __y; }
170 inline launch& operator^=(launch& __x, launch __y)
171 { return __x = __x ^ __y; }
173 /// Status code for futures
174 enum class future_status
181 // _GLIBCXX_RESOLVE_LIB_DEFECTS
182 // 2021. Further incorrect usages of result_of
183 template<typename _Fn, typename... _Args>
184 using __async_result_of = typename result_of<
185 typename decay<_Fn>::type(typename decay<_Args>::type...)>::type;
187 template<typename _Fn, typename... _Args>
188 future<__async_result_of<_Fn, _Args...>>
189 async(launch __policy, _Fn&& __fn, _Args&&... __args);
191 template<typename _Fn, typename... _Args>
192 future<__async_result_of<_Fn, _Args...>>
193 async(_Fn&& __fn, _Args&&... __args);
195 #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1) \
196 && (ATOMIC_INT_LOCK_FREE > 1)
198 /// Base class and enclosing scope.
201 /// Base class for results.
204 exception_ptr _M_error;
206 _Result_base(const _Result_base&) = delete;
207 _Result_base& operator=(const _Result_base&) = delete;
209 // _M_destroy() allows derived classes to control deallocation
210 virtual void _M_destroy() = 0;
214 void operator()(_Result_base* __fr) const { __fr->_M_destroy(); }
219 virtual ~_Result_base();
222 /// A unique_ptr for result objects.
223 template<typename _Res>
224 using _Ptr = unique_ptr<_Res, _Result_base::_Deleter>;
226 /// A result object that has storage for an object of type _Res.
227 template<typename _Res>
228 struct _Result : _Result_base
231 __gnu_cxx::__aligned_buffer<_Res> _M_storage;
235 typedef _Res result_type;
237 _Result() noexcept : _M_initialized() { }
245 // Return lvalue, future will add const or rvalue-reference
247 _M_value() noexcept { return *_M_storage._M_ptr(); }
250 _M_set(const _Res& __res)
252 ::new (_M_storage._M_addr()) _Res(__res);
253 _M_initialized = true;
259 ::new (_M_storage._M_addr()) _Res(std::move(__res));
260 _M_initialized = true;
264 void _M_destroy() { delete this; }
267 /// A result object that uses an allocator.
268 template<typename _Res, typename _Alloc>
269 struct _Result_alloc final : _Result<_Res>, _Alloc
271 using __allocator_type = __alloc_rebind<_Alloc, _Result_alloc>;
274 _Result_alloc(const _Alloc& __a) : _Result<_Res>(), _Alloc(__a)
280 __allocator_type __a(*this);
281 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
282 this->~_Result_alloc();
286 // Create a result object that uses an allocator.
287 template<typename _Res, typename _Allocator>
288 static _Ptr<_Result_alloc<_Res, _Allocator>>
289 _S_allocate_result(const _Allocator& __a)
291 using __result_type = _Result_alloc<_Res, _Allocator>;
292 typename __result_type::__allocator_type __a2(__a);
293 auto __guard = std::__allocate_guarded(__a2);
294 __result_type* __p = ::new((void*)__guard.get()) __result_type{__a};
296 return _Ptr<__result_type>(__p);
299 // Keep it simple for std::allocator.
300 template<typename _Res, typename _Tp>
301 static _Ptr<_Result<_Res>>
302 _S_allocate_result(const std::allocator<_Tp>& __a)
304 return _Ptr<_Result<_Res>>(new _Result<_Res>);
307 // Base class for various types of shared state created by an
308 // asynchronous provider (such as a std::promise) and shared with one
309 // or more associated futures.
312 typedef _Ptr<_Result_base> _Ptr_type;
314 enum _Status : unsigned {
320 __atomic_futex_unsigned<> _M_status;
321 atomic_flag _M_retrieved = ATOMIC_FLAG_INIT;
325 _State_baseV2() noexcept : _M_result(), _M_status(_Status::__not_ready)
327 _State_baseV2(const _State_baseV2&) = delete;
328 _State_baseV2& operator=(const _State_baseV2&) = delete;
329 virtual ~_State_baseV2() = default;
334 // Run any deferred function or join any asynchronous thread:
336 // Acquire MO makes sure this synchronizes with the thread that made
338 _M_status._M_load_when_equal(_Status::__ready, memory_order_acquire);
342 template<typename _Rep, typename _Period>
344 wait_for(const chrono::duration<_Rep, _Period>& __rel)
346 // First, check if the future has been made ready. Use acquire MO
347 // to synchronize with the thread that made it ready.
348 if (_M_status._M_load(memory_order_acquire) == _Status::__ready)
349 return future_status::ready;
350 if (_M_is_deferred_future())
351 return future_status::deferred;
352 if (_M_status._M_load_when_equal_for(_Status::__ready,
353 memory_order_acquire, __rel))
355 // _GLIBCXX_RESOLVE_LIB_DEFECTS
356 // 2100. timed waiting functions must also join
357 // This call is a no-op by default except on an async future,
358 // in which case the async thread is joined. It's also not a
359 // no-op for a deferred future, but such a future will never
360 // reach this point because it returns future_status::deferred
361 // instead of waiting for the future to become ready (see
362 // above). Async futures synchronize in this call, so we need
363 // no further synchronization here.
366 return future_status::ready;
368 return future_status::timeout;
371 template<typename _Clock, typename _Duration>
373 wait_until(const chrono::time_point<_Clock, _Duration>& __abs)
375 // First, check if the future has been made ready. Use acquire MO
376 // to synchronize with the thread that made it ready.
377 if (_M_status._M_load(memory_order_acquire) == _Status::__ready)
378 return future_status::ready;
379 if (_M_is_deferred_future())
380 return future_status::deferred;
381 if (_M_status._M_load_when_equal_until(_Status::__ready,
382 memory_order_acquire, __abs))
384 // _GLIBCXX_RESOLVE_LIB_DEFECTS
385 // 2100. timed waiting functions must also join
386 // See wait_for(...) above.
389 return future_status::ready;
391 return future_status::timeout;
394 // Provide a result to the shared state and make it ready.
395 // Calls at most once: _M_result = __res();
397 _M_set_result(function<_Ptr_type()> __res, bool __ignore_failure = false)
399 bool __did_set = false;
400 // all calls to this function are serialized,
401 // side-effects of invoking __res only happen once
402 call_once(_M_once, &_State_baseV2::_M_do_set, this,
403 std::__addressof(__res), std::__addressof(__did_set));
405 // Use release MO to synchronize with observers of the ready state.
406 _M_status._M_store_notify_all(_Status::__ready,
407 memory_order_release);
408 else if (!__ignore_failure)
409 __throw_future_error(int(future_errc::promise_already_satisfied));
412 // Provide a result to the shared state but delay making it ready
413 // until the calling thread exits.
414 // Calls at most once: _M_result = __res();
416 _M_set_delayed_result(function<_Ptr_type()> __res,
417 weak_ptr<_State_baseV2> __self)
419 bool __did_set = false;
420 unique_ptr<_Make_ready> __mr{new _Make_ready};
421 // all calls to this function are serialized,
422 // side-effects of invoking __res only happen once
423 call_once(_M_once, &_State_baseV2::_M_do_set, this,
424 std::__addressof(__res), std::__addressof(__did_set));
426 __throw_future_error(int(future_errc::promise_already_satisfied));
427 __mr->_M_shared_state = std::move(__self);
432 // Abandon this shared state.
434 _M_break_promise(_Ptr_type __res)
436 if (static_cast<bool>(__res))
439 make_exception_ptr(future_error(future_errc::broken_promise));
440 // This function is only called when the last asynchronous result
441 // provider is abandoning this shared state, so noone can be
442 // trying to make the shared state ready at the same time, and
443 // we can access _M_result directly instead of through call_once.
444 _M_result.swap(__res);
445 // Use release MO to synchronize with observers of the ready state.
446 _M_status._M_store_notify_all(_Status::__ready,
447 memory_order_release);
451 // Called when this object is first passed to a future.
453 _M_set_retrieved_flag()
455 if (_M_retrieved.test_and_set())
456 __throw_future_error(int(future_errc::future_already_retrieved));
459 template<typename _Res, typename _Arg>
463 template<typename _Res, typename _Arg>
464 struct _Setter<_Res, _Arg&>
466 // check this is only used by promise<R>::set_value(const R&)
467 // or promise<R&>::set_value(R&)
468 static_assert(is_same<_Res, _Arg&>::value // promise<R&>
469 || is_same<const _Res, _Arg>::value, // promise<R>
470 "Invalid specialisation");
472 // Used by std::promise to copy construct the result.
473 typename promise<_Res>::_Ptr_type operator()() const
475 _State_baseV2::_S_check(_M_promise->_M_future);
476 _M_promise->_M_storage->_M_set(*_M_arg);
477 return std::move(_M_promise->_M_storage);
479 promise<_Res>* _M_promise;
484 template<typename _Res>
485 struct _Setter<_Res, _Res&&>
487 // Used by std::promise to move construct the result.
488 typename promise<_Res>::_Ptr_type operator()() const
490 _State_baseV2::_S_check(_M_promise->_M_future);
491 _M_promise->_M_storage->_M_set(std::move(*_M_arg));
492 return std::move(_M_promise->_M_storage);
494 promise<_Res>* _M_promise;
498 struct __exception_ptr_tag { };
501 template<typename _Res>
502 struct _Setter<_Res, __exception_ptr_tag>
504 // Used by std::promise to store an exception as the result.
505 typename promise<_Res>::_Ptr_type operator()() const
507 _State_baseV2::_S_check(_M_promise->_M_future);
508 _M_promise->_M_storage->_M_error = *_M_ex;
509 return std::move(_M_promise->_M_storage);
512 promise<_Res>* _M_promise;
513 exception_ptr* _M_ex;
516 template<typename _Res, typename _Arg>
517 static _Setter<_Res, _Arg&&>
518 __setter(promise<_Res>* __prom, _Arg&& __arg)
520 return _Setter<_Res, _Arg&&>{ __prom, std::__addressof(__arg) };
523 template<typename _Res>
524 static _Setter<_Res, __exception_ptr_tag>
525 __setter(exception_ptr& __ex, promise<_Res>* __prom)
527 return _Setter<_Res, __exception_ptr_tag>{ __prom, &__ex };
530 template<typename _Tp>
532 _S_check(const shared_ptr<_Tp>& __p)
534 if (!static_cast<bool>(__p))
535 __throw_future_error((int)future_errc::no_state);
539 // The function invoked with std::call_once(_M_once, ...).
541 _M_do_set(function<_Ptr_type()>* __f, bool* __did_set)
543 _Ptr_type __res = (*__f)();
544 // Notify the caller that we did try to set; if we do not throw an
545 // exception, the caller will be aware that it did set (e.g., see
548 _M_result.swap(__res); // nothrow
551 // Wait for completion of async function.
552 virtual void _M_complete_async() { }
554 // Return true if state corresponds to a deferred function.
555 virtual bool _M_is_deferred_future() const { return false; }
557 struct _Make_ready final : __at_thread_exit_elt
559 weak_ptr<_State_baseV2> _M_shared_state;
560 static void _S_run(void*);
565 #ifdef _GLIBCXX_ASYNC_ABI_COMPAT
567 class _Async_state_common;
569 using _State_base = _State_baseV2;
570 class _Async_state_commonV2;
573 template<typename _BoundFn,
574 typename _Res = decltype(std::declval<_BoundFn&>()())>
575 class _Deferred_state;
577 template<typename _BoundFn,
578 typename _Res = decltype(std::declval<_BoundFn&>()())>
579 class _Async_state_impl;
581 template<typename _Signature>
582 class _Task_state_base;
584 template<typename _Fn, typename _Alloc, typename _Signature>
587 template<typename _BoundFn>
588 static std::shared_ptr<_State_base>
589 _S_make_deferred_state(_BoundFn&& __fn);
591 template<typename _BoundFn>
592 static std::shared_ptr<_State_base>
593 _S_make_async_state(_BoundFn&& __fn);
595 template<typename _Res_ptr, typename _Fn,
596 typename _Res = typename _Res_ptr::element_type::result_type>
599 template<typename _Res_ptr, typename _BoundFn>
600 static _Task_setter<_Res_ptr, _BoundFn>
601 _S_task_setter(_Res_ptr& __ptr, _BoundFn& __call)
603 return { std::__addressof(__ptr), std::__addressof(__call) };
607 /// Partial specialization for reference types.
608 template<typename _Res>
609 struct __future_base::_Result<_Res&> : __future_base::_Result_base
611 typedef _Res& result_type;
613 _Result() noexcept : _M_value_ptr() { }
616 _M_set(_Res& __res) noexcept
617 { _M_value_ptr = std::addressof(__res); }
619 _Res& _M_get() noexcept { return *_M_value_ptr; }
624 void _M_destroy() { delete this; }
627 /// Explicit specialization for void.
629 struct __future_base::_Result<void> : __future_base::_Result_base
631 typedef void result_type;
634 void _M_destroy() { delete this; }
637 #ifndef _GLIBCXX_ASYNC_ABI_COMPAT
639 // Allow _Setter objects to be stored locally in std::function
640 template<typename _Res, typename _Arg>
641 struct __is_location_invariant
642 <__future_base::_State_base::_Setter<_Res, _Arg>>
645 // Allow _Task_setter objects to be stored locally in std::function
646 template<typename _Res_ptr, typename _Fn, typename _Res>
647 struct __is_location_invariant
648 <__future_base::_Task_setter<_Res_ptr, _Fn, _Res>>
651 /// Common implementation for future and shared_future.
652 template<typename _Res>
653 class __basic_future : public __future_base
656 typedef shared_ptr<_State_base> __state_type;
657 typedef __future_base::_Result<_Res>& __result_type;
660 __state_type _M_state;
664 __basic_future(const __basic_future&) = delete;
665 __basic_future& operator=(const __basic_future&) = delete;
668 valid() const noexcept { return static_cast<bool>(_M_state); }
673 _State_base::_S_check(_M_state);
677 template<typename _Rep, typename _Period>
679 wait_for(const chrono::duration<_Rep, _Period>& __rel) const
681 _State_base::_S_check(_M_state);
682 return _M_state->wait_for(__rel);
685 template<typename _Clock, typename _Duration>
687 wait_until(const chrono::time_point<_Clock, _Duration>& __abs) const
689 _State_base::_S_check(_M_state);
690 return _M_state->wait_until(__abs);
694 /// Wait for the state to be ready and rethrow any stored exception
696 _M_get_result() const
698 _State_base::_S_check(_M_state);
699 _Result_base& __res = _M_state->wait();
700 if (!(__res._M_error == 0))
701 rethrow_exception(__res._M_error);
702 return static_cast<__result_type>(__res);
705 void _M_swap(__basic_future& __that) noexcept
707 _M_state.swap(__that._M_state);
710 // Construction of a future by promise::get_future()
712 __basic_future(const __state_type& __state) : _M_state(__state)
714 _State_base::_S_check(_M_state);
715 _M_state->_M_set_retrieved_flag();
718 // Copy construction from a shared_future
720 __basic_future(const shared_future<_Res>&) noexcept;
722 // Move construction from a shared_future
724 __basic_future(shared_future<_Res>&&) noexcept;
726 // Move construction from a future
728 __basic_future(future<_Res>&&) noexcept;
730 constexpr __basic_future() noexcept : _M_state() { }
734 explicit _Reset(__basic_future& __fut) noexcept : _M_fut(__fut) { }
735 ~_Reset() { _M_fut._M_state.reset(); }
736 __basic_future& _M_fut;
741 /// Primary template for future.
742 template<typename _Res>
743 class future : public __basic_future<_Res>
745 friend class promise<_Res>;
746 template<typename> friend class packaged_task;
747 template<typename _Fn, typename... _Args>
748 friend future<__async_result_of<_Fn, _Args...>>
749 async(launch, _Fn&&, _Args&&...);
751 typedef __basic_future<_Res> _Base_type;
752 typedef typename _Base_type::__state_type __state_type;
755 future(const __state_type& __state) : _Base_type(__state) { }
758 constexpr future() noexcept : _Base_type() { }
761 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
764 future(const future&) = delete;
765 future& operator=(const future&) = delete;
767 future& operator=(future&& __fut) noexcept
769 future(std::move(__fut))._M_swap(*this);
773 /// Retrieving the value
777 typename _Base_type::_Reset __reset(*this);
778 return std::move(this->_M_get_result()._M_value());
781 shared_future<_Res> share();
784 /// Partial specialization for future<R&>
785 template<typename _Res>
786 class future<_Res&> : public __basic_future<_Res&>
788 friend class promise<_Res&>;
789 template<typename> friend class packaged_task;
790 template<typename _Fn, typename... _Args>
791 friend future<__async_result_of<_Fn, _Args...>>
792 async(launch, _Fn&&, _Args&&...);
794 typedef __basic_future<_Res&> _Base_type;
795 typedef typename _Base_type::__state_type __state_type;
798 future(const __state_type& __state) : _Base_type(__state) { }
801 constexpr future() noexcept : _Base_type() { }
804 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
807 future(const future&) = delete;
808 future& operator=(const future&) = delete;
810 future& operator=(future&& __fut) noexcept
812 future(std::move(__fut))._M_swap(*this);
816 /// Retrieving the value
820 typename _Base_type::_Reset __reset(*this);
821 return this->_M_get_result()._M_get();
824 shared_future<_Res&> share();
827 /// Explicit specialization for future<void>
829 class future<void> : public __basic_future<void>
831 friend class promise<void>;
832 template<typename> friend class packaged_task;
833 template<typename _Fn, typename... _Args>
834 friend future<__async_result_of<_Fn, _Args...>>
835 async(launch, _Fn&&, _Args&&...);
837 typedef __basic_future<void> _Base_type;
838 typedef typename _Base_type::__state_type __state_type;
841 future(const __state_type& __state) : _Base_type(__state) { }
844 constexpr future() noexcept : _Base_type() { }
847 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
850 future(const future&) = delete;
851 future& operator=(const future&) = delete;
853 future& operator=(future&& __fut) noexcept
855 future(std::move(__fut))._M_swap(*this);
859 /// Retrieving the value
863 typename _Base_type::_Reset __reset(*this);
864 this->_M_get_result();
867 shared_future<void> share();
871 /// Primary template for shared_future.
872 template<typename _Res>
873 class shared_future : public __basic_future<_Res>
875 typedef __basic_future<_Res> _Base_type;
878 constexpr shared_future() noexcept : _Base_type() { }
881 shared_future(const shared_future& __sf) : _Base_type(__sf) { }
883 /// Construct from a future rvalue
884 shared_future(future<_Res>&& __uf) noexcept
885 : _Base_type(std::move(__uf))
888 /// Construct from a shared_future rvalue
889 shared_future(shared_future&& __sf) noexcept
890 : _Base_type(std::move(__sf))
893 shared_future& operator=(const shared_future& __sf)
895 shared_future(__sf)._M_swap(*this);
899 shared_future& operator=(shared_future&& __sf) noexcept
901 shared_future(std::move(__sf))._M_swap(*this);
905 /// Retrieving the value
907 get() const { return this->_M_get_result()._M_value(); }
910 /// Partial specialization for shared_future<R&>
911 template<typename _Res>
912 class shared_future<_Res&> : public __basic_future<_Res&>
914 typedef __basic_future<_Res&> _Base_type;
917 constexpr shared_future() noexcept : _Base_type() { }
920 shared_future(const shared_future& __sf) : _Base_type(__sf) { }
922 /// Construct from a future rvalue
923 shared_future(future<_Res&>&& __uf) noexcept
924 : _Base_type(std::move(__uf))
927 /// Construct from a shared_future rvalue
928 shared_future(shared_future&& __sf) noexcept
929 : _Base_type(std::move(__sf))
932 shared_future& operator=(const shared_future& __sf)
934 shared_future(__sf)._M_swap(*this);
938 shared_future& operator=(shared_future&& __sf) noexcept
940 shared_future(std::move(__sf))._M_swap(*this);
944 /// Retrieving the value
946 get() const { return this->_M_get_result()._M_get(); }
949 /// Explicit specialization for shared_future<void>
951 class shared_future<void> : public __basic_future<void>
953 typedef __basic_future<void> _Base_type;
956 constexpr shared_future() noexcept : _Base_type() { }
959 shared_future(const shared_future& __sf) : _Base_type(__sf) { }
961 /// Construct from a future rvalue
962 shared_future(future<void>&& __uf) noexcept
963 : _Base_type(std::move(__uf))
966 /// Construct from a shared_future rvalue
967 shared_future(shared_future&& __sf) noexcept
968 : _Base_type(std::move(__sf))
971 shared_future& operator=(const shared_future& __sf)
973 shared_future(__sf)._M_swap(*this);
977 shared_future& operator=(shared_future&& __sf) noexcept
979 shared_future(std::move(__sf))._M_swap(*this);
983 // Retrieving the value
985 get() const { this->_M_get_result(); }
988 // Now we can define the protected __basic_future constructors.
989 template<typename _Res>
990 inline __basic_future<_Res>::
991 __basic_future(const shared_future<_Res>& __sf) noexcept
992 : _M_state(__sf._M_state)
995 template<typename _Res>
996 inline __basic_future<_Res>::
997 __basic_future(shared_future<_Res>&& __sf) noexcept
998 : _M_state(std::move(__sf._M_state))
1001 template<typename _Res>
1002 inline __basic_future<_Res>::
1003 __basic_future(future<_Res>&& __uf) noexcept
1004 : _M_state(std::move(__uf._M_state))
1007 template<typename _Res>
1008 inline shared_future<_Res>
1009 future<_Res>::share()
1010 { return shared_future<_Res>(std::move(*this)); }
1012 template<typename _Res>
1013 inline shared_future<_Res&>
1014 future<_Res&>::share()
1015 { return shared_future<_Res&>(std::move(*this)); }
1017 inline shared_future<void>
1018 future<void>::share()
1019 { return shared_future<void>(std::move(*this)); }
1021 /// Primary template for promise
1022 template<typename _Res>
1025 typedef __future_base::_State_base _State;
1026 typedef __future_base::_Result<_Res> _Res_type;
1027 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1028 template<typename, typename> friend class _State::_Setter;
1030 shared_ptr<_State> _M_future;
1031 _Ptr_type _M_storage;
1035 : _M_future(std::make_shared<_State>()),
1036 _M_storage(new _Res_type())
1039 promise(promise&& __rhs) noexcept
1040 : _M_future(std::move(__rhs._M_future)),
1041 _M_storage(std::move(__rhs._M_storage))
1044 template<typename _Allocator>
1045 promise(allocator_arg_t, const _Allocator& __a)
1046 : _M_future(std::allocate_shared<_State>(__a)),
1047 _M_storage(__future_base::_S_allocate_result<_Res>(__a))
1050 template<typename _Allocator>
1051 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1052 : _M_future(std::move(__rhs._M_future)),
1053 _M_storage(std::move(__rhs._M_storage))
1056 promise(const promise&) = delete;
1060 if (static_cast<bool>(_M_future) && !_M_future.unique())
1061 _M_future->_M_break_promise(std::move(_M_storage));
1066 operator=(promise&& __rhs) noexcept
1068 promise(std::move(__rhs)).swap(*this);
1072 promise& operator=(const promise&) = delete;
1075 swap(promise& __rhs) noexcept
1077 _M_future.swap(__rhs._M_future);
1078 _M_storage.swap(__rhs._M_storage);
1081 // Retrieving the result
1084 { return future<_Res>(_M_future); }
1086 // Setting the result
1088 set_value(const _Res& __r)
1089 { _M_future->_M_set_result(_State::__setter(this, __r)); }
1092 set_value(_Res&& __r)
1093 { _M_future->_M_set_result(_State::__setter(this, std::move(__r))); }
1096 set_exception(exception_ptr __p)
1097 { _M_future->_M_set_result(_State::__setter(__p, this)); }
1100 set_value_at_thread_exit(const _Res& __r)
1102 _M_future->_M_set_delayed_result(_State::__setter(this, __r),
1107 set_value_at_thread_exit(_Res&& __r)
1109 _M_future->_M_set_delayed_result(
1110 _State::__setter(this, std::move(__r)), _M_future);
1114 set_exception_at_thread_exit(exception_ptr __p)
1116 _M_future->_M_set_delayed_result(_State::__setter(__p, this),
1121 template<typename _Res>
1123 swap(promise<_Res>& __x, promise<_Res>& __y) noexcept
1126 template<typename _Res, typename _Alloc>
1127 struct uses_allocator<promise<_Res>, _Alloc>
1128 : public true_type { };
1131 /// Partial specialization for promise<R&>
1132 template<typename _Res>
1133 class promise<_Res&>
1135 typedef __future_base::_State_base _State;
1136 typedef __future_base::_Result<_Res&> _Res_type;
1137 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1138 template<typename, typename> friend class _State::_Setter;
1140 shared_ptr<_State> _M_future;
1141 _Ptr_type _M_storage;
1145 : _M_future(std::make_shared<_State>()),
1146 _M_storage(new _Res_type())
1149 promise(promise&& __rhs) noexcept
1150 : _M_future(std::move(__rhs._M_future)),
1151 _M_storage(std::move(__rhs._M_storage))
1154 template<typename _Allocator>
1155 promise(allocator_arg_t, const _Allocator& __a)
1156 : _M_future(std::allocate_shared<_State>(__a)),
1157 _M_storage(__future_base::_S_allocate_result<_Res&>(__a))
1160 template<typename _Allocator>
1161 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1162 : _M_future(std::move(__rhs._M_future)),
1163 _M_storage(std::move(__rhs._M_storage))
1166 promise(const promise&) = delete;
1170 if (static_cast<bool>(_M_future) && !_M_future.unique())
1171 _M_future->_M_break_promise(std::move(_M_storage));
1176 operator=(promise&& __rhs) noexcept
1178 promise(std::move(__rhs)).swap(*this);
1182 promise& operator=(const promise&) = delete;
1185 swap(promise& __rhs) noexcept
1187 _M_future.swap(__rhs._M_future);
1188 _M_storage.swap(__rhs._M_storage);
1191 // Retrieving the result
1194 { return future<_Res&>(_M_future); }
1196 // Setting the result
1198 set_value(_Res& __r)
1199 { _M_future->_M_set_result(_State::__setter(this, __r)); }
1202 set_exception(exception_ptr __p)
1203 { _M_future->_M_set_result(_State::__setter(__p, this)); }
1206 set_value_at_thread_exit(_Res& __r)
1208 _M_future->_M_set_delayed_result(_State::__setter(this, __r),
1213 set_exception_at_thread_exit(exception_ptr __p)
1215 _M_future->_M_set_delayed_result(_State::__setter(__p, this),
1220 /// Explicit specialization for promise<void>
1224 typedef __future_base::_State_base _State;
1225 typedef __future_base::_Result<void> _Res_type;
1226 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1227 template<typename, typename> friend class _State::_Setter;
1229 shared_ptr<_State> _M_future;
1230 _Ptr_type _M_storage;
1234 : _M_future(std::make_shared<_State>()),
1235 _M_storage(new _Res_type())
1238 promise(promise&& __rhs) noexcept
1239 : _M_future(std::move(__rhs._M_future)),
1240 _M_storage(std::move(__rhs._M_storage))
1243 template<typename _Allocator>
1244 promise(allocator_arg_t, const _Allocator& __a)
1245 : _M_future(std::allocate_shared<_State>(__a)),
1246 _M_storage(__future_base::_S_allocate_result<void>(__a))
1249 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1250 // 2095. missing constructors needed for uses-allocator construction
1251 template<typename _Allocator>
1252 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1253 : _M_future(std::move(__rhs._M_future)),
1254 _M_storage(std::move(__rhs._M_storage))
1257 promise(const promise&) = delete;
1261 if (static_cast<bool>(_M_future) && !_M_future.unique())
1262 _M_future->_M_break_promise(std::move(_M_storage));
1267 operator=(promise&& __rhs) noexcept
1269 promise(std::move(__rhs)).swap(*this);
1273 promise& operator=(const promise&) = delete;
1276 swap(promise& __rhs) noexcept
1278 _M_future.swap(__rhs._M_future);
1279 _M_storage.swap(__rhs._M_storage);
1282 // Retrieving the result
1285 { return future<void>(_M_future); }
1287 // Setting the result
1291 set_exception(exception_ptr __p)
1292 { _M_future->_M_set_result(_State::__setter(__p, this)); }
1295 set_value_at_thread_exit();
1298 set_exception_at_thread_exit(exception_ptr __p)
1300 _M_future->_M_set_delayed_result(_State::__setter(__p, this),
1307 struct __future_base::_State_base::_Setter<void, void>
1309 promise<void>::_Ptr_type operator()() const
1311 _State_base::_S_check(_M_promise->_M_future);
1312 return std::move(_M_promise->_M_storage);
1315 promise<void>* _M_promise;
1319 promise<void>::set_value()
1320 { _M_future->_M_set_result(_State::_Setter<void, void>{ this }); }
1323 promise<void>::set_value_at_thread_exit()
1325 _M_future->_M_set_delayed_result(_State::_Setter<void, void>{this},
1329 template<typename _Ptr_type, typename _Fn, typename _Res>
1330 struct __future_base::_Task_setter
1332 // Invoke the function and provide the result to the caller.
1333 _Ptr_type operator()() const
1337 (*_M_result)->_M_set((*_M_fn)());
1339 __catch(const __cxxabiv1::__forced_unwind&)
1341 __throw_exception_again; // will cause broken_promise
1345 (*_M_result)->_M_error = current_exception();
1347 return std::move(*_M_result);
1349 _Ptr_type* _M_result;
1353 template<typename _Ptr_type, typename _Fn>
1354 struct __future_base::_Task_setter<_Ptr_type, _Fn, void>
1356 _Ptr_type operator()() const
1362 __catch(const __cxxabiv1::__forced_unwind&)
1364 __throw_exception_again; // will cause broken_promise
1368 (*_M_result)->_M_error = current_exception();
1370 return std::move(*_M_result);
1372 _Ptr_type* _M_result;
1376 // Holds storage for a packaged_task's result.
1377 template<typename _Res, typename... _Args>
1378 struct __future_base::_Task_state_base<_Res(_Args...)>
1379 : __future_base::_State_base
1381 typedef _Res _Res_type;
1383 template<typename _Alloc>
1384 _Task_state_base(const _Alloc& __a)
1385 : _M_result(_S_allocate_result<_Res>(__a))
1388 // Invoke the stored task and make the state ready.
1390 _M_run(_Args&&... __args) = 0;
1392 // Invoke the stored task and make the state ready at thread exit.
1394 _M_run_delayed(_Args&&... __args, weak_ptr<_State_base>) = 0;
1396 virtual shared_ptr<_Task_state_base>
1399 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1400 _Ptr_type _M_result;
1403 // Holds a packaged_task's stored task.
1404 template<typename _Fn, typename _Alloc, typename _Res, typename... _Args>
1405 struct __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)> final
1406 : __future_base::_Task_state_base<_Res(_Args...)>
1408 template<typename _Fn2>
1409 _Task_state(_Fn2&& __fn, const _Alloc& __a)
1410 : _Task_state_base<_Res(_Args...)>(__a),
1411 _M_impl(std::forward<_Fn2>(__fn), __a)
1416 _M_run(_Args&&... __args)
1418 auto __boundfn = [&] () -> typename result_of<_Fn(_Args&&...)>::type {
1419 return std::__invoke(_M_impl._M_fn, std::forward<_Args>(__args)...);
1421 this->_M_set_result(_S_task_setter(this->_M_result, __boundfn));
1425 _M_run_delayed(_Args&&... __args, weak_ptr<_State_base> __self)
1427 auto __boundfn = [&] () -> typename result_of<_Fn(_Args&&...)>::type {
1428 return std::__invoke(_M_impl._M_fn, std::forward<_Args>(__args)...);
1430 this->_M_set_delayed_result(_S_task_setter(this->_M_result, __boundfn),
1434 virtual shared_ptr<_Task_state_base<_Res(_Args...)>>
1437 struct _Impl : _Alloc
1439 template<typename _Fn2>
1440 _Impl(_Fn2&& __fn, const _Alloc& __a)
1441 : _Alloc(__a), _M_fn(std::forward<_Fn2>(__fn)) { }
1446 template<typename _Signature, typename _Fn, typename _Alloc>
1447 static shared_ptr<__future_base::_Task_state_base<_Signature>>
1448 __create_task_state(_Fn&& __fn, const _Alloc& __a)
1450 typedef typename decay<_Fn>::type _Fn2;
1451 typedef __future_base::_Task_state<_Fn2, _Alloc, _Signature> _State;
1452 return std::allocate_shared<_State>(__a, std::forward<_Fn>(__fn), __a);
1455 template<typename _Fn, typename _Alloc, typename _Res, typename... _Args>
1456 shared_ptr<__future_base::_Task_state_base<_Res(_Args...)>>
1457 __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)>::_M_reset()
1459 return __create_task_state<_Res(_Args...)>(std::move(_M_impl._M_fn),
1460 static_cast<_Alloc&>(_M_impl));
1463 template<typename _Task, typename _Fn, bool
1464 = is_same<_Task, typename decay<_Fn>::type>::value>
1465 struct __constrain_pkgdtask
1466 { typedef void __type; };
1468 template<typename _Task, typename _Fn>
1469 struct __constrain_pkgdtask<_Task, _Fn, true>
1473 template<typename _Res, typename... _ArgTypes>
1474 class packaged_task<_Res(_ArgTypes...)>
1476 typedef __future_base::_Task_state_base<_Res(_ArgTypes...)> _State_type;
1477 shared_ptr<_State_type> _M_state;
1480 // Construction and destruction
1481 packaged_task() noexcept { }
1483 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1484 // 2095. missing constructors needed for uses-allocator construction
1485 template<typename _Allocator>
1486 packaged_task(allocator_arg_t, const _Allocator& __a) noexcept
1489 template<typename _Fn, typename = typename
1490 __constrain_pkgdtask<packaged_task, _Fn>::__type>
1492 packaged_task(_Fn&& __fn)
1493 : packaged_task(allocator_arg, std::allocator<int>(),
1494 std::forward<_Fn>(__fn))
1497 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1498 // 2097. packaged_task constructors should be constrained
1499 // 2407. [this constructor should not be] explicit
1500 template<typename _Fn, typename _Alloc, typename = typename
1501 __constrain_pkgdtask<packaged_task, _Fn>::__type>
1502 packaged_task(allocator_arg_t, const _Alloc& __a, _Fn&& __fn)
1503 : _M_state(__create_task_state<_Res(_ArgTypes...)>(
1504 std::forward<_Fn>(__fn), __a))
1509 if (static_cast<bool>(_M_state) && !_M_state.unique())
1510 _M_state->_M_break_promise(std::move(_M_state->_M_result));
1514 packaged_task(const packaged_task&) = delete;
1515 packaged_task& operator=(const packaged_task&) = delete;
1517 template<typename _Allocator>
1518 packaged_task(allocator_arg_t, const _Allocator&,
1519 const packaged_task&) = delete;
1522 packaged_task(packaged_task&& __other) noexcept
1523 { this->swap(__other); }
1525 template<typename _Allocator>
1526 packaged_task(allocator_arg_t, const _Allocator&,
1527 packaged_task&& __other) noexcept
1528 { this->swap(__other); }
1530 packaged_task& operator=(packaged_task&& __other) noexcept
1532 packaged_task(std::move(__other)).swap(*this);
1537 swap(packaged_task& __other) noexcept
1538 { _M_state.swap(__other._M_state); }
1541 valid() const noexcept
1542 { return static_cast<bool>(_M_state); }
1547 { return future<_Res>(_M_state); }
1551 operator()(_ArgTypes... __args)
1553 __future_base::_State_base::_S_check(_M_state);
1554 _M_state->_M_run(std::forward<_ArgTypes>(__args)...);
1558 make_ready_at_thread_exit(_ArgTypes... __args)
1560 __future_base::_State_base::_S_check(_M_state);
1561 _M_state->_M_run_delayed(std::forward<_ArgTypes>(__args)..., _M_state);
1567 __future_base::_State_base::_S_check(_M_state);
1568 packaged_task __tmp;
1569 __tmp._M_state = _M_state;
1570 _M_state = _M_state->_M_reset();
1575 template<typename _Res, typename... _ArgTypes>
1577 swap(packaged_task<_Res(_ArgTypes...)>& __x,
1578 packaged_task<_Res(_ArgTypes...)>& __y) noexcept
1581 template<typename _Res, typename _Alloc>
1582 struct uses_allocator<packaged_task<_Res>, _Alloc>
1583 : public true_type { };
1586 // Shared state created by std::async().
1587 // Holds a deferred function and storage for its result.
1588 template<typename _BoundFn, typename _Res>
1589 class __future_base::_Deferred_state final
1590 : public __future_base::_State_base
1594 _Deferred_state(_BoundFn&& __fn)
1595 : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
1599 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1600 _Ptr_type _M_result;
1603 // Run the deferred function.
1607 // Multiple threads can call a waiting function on the future and
1608 // reach this point at the same time. The call_once in _M_set_result
1609 // ensures only the first one run the deferred function, stores the
1610 // result in _M_result, swaps that with the base _M_result and makes
1611 // the state ready. Tell _M_set_result to ignore failure so all later
1612 // calls do nothing.
1613 _M_set_result(_S_task_setter(_M_result, _M_fn), true);
1616 // Caller should check whether the state is ready first, because this
1617 // function will return true even after the deferred function has run.
1618 virtual bool _M_is_deferred_future() const { return true; }
1621 // Common functionality hoisted out of the _Async_state_impl template.
1622 class __future_base::_Async_state_commonV2
1623 : public __future_base::_State_base
1626 ~_Async_state_commonV2() = default;
1628 // Make waiting functions block until the thread completes, as if joined.
1630 // This function is used by wait() to satisfy the first requirement below
1631 // and by wait_for() / wait_until() to satisfy the second.
1635 // — a call to a waiting function on an asynchronous return object that
1636 // shares the shared state created by this async call shall block until
1637 // the associated thread has completed, as if joined, or else time out.
1639 // — the associated thread completion synchronizes with the return from
1640 // the first function that successfully detects the ready status of the
1641 // shared state or with the return from the last function that releases
1642 // the shared state, whichever happens first.
1643 virtual void _M_complete_async() { _M_join(); }
1645 void _M_join() { std::call_once(_M_once, &thread::join, &_M_thread); }
1651 // Shared state created by std::async().
1652 // Starts a new thread that runs a function and makes the shared state ready.
1653 template<typename _BoundFn, typename _Res>
1654 class __future_base::_Async_state_impl final
1655 : public __future_base::_Async_state_commonV2
1659 _Async_state_impl(_BoundFn&& __fn)
1660 : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
1662 _M_thread = std::thread{ [this] {
1665 _M_set_result(_S_task_setter(_M_result, _M_fn));
1667 __catch (const __cxxabiv1::__forced_unwind&)
1669 // make the shared state ready on thread cancellation
1670 if (static_cast<bool>(_M_result))
1671 this->_M_break_promise(std::move(_M_result));
1672 __throw_exception_again;
1677 // Must not destroy _M_result and _M_fn until the thread finishes.
1678 // Call join() directly rather than through _M_join() because no other
1679 // thread can be referring to this state if it is being destroyed.
1680 ~_Async_state_impl() { if (_M_thread.joinable()) _M_thread.join(); }
1683 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1684 _Ptr_type _M_result;
1688 template<typename _BoundFn>
1689 inline std::shared_ptr<__future_base::_State_base>
1690 __future_base::_S_make_deferred_state(_BoundFn&& __fn)
1692 typedef typename remove_reference<_BoundFn>::type __fn_type;
1693 typedef _Deferred_state<__fn_type> __state_type;
1694 return std::make_shared<__state_type>(std::move(__fn));
1697 template<typename _BoundFn>
1698 inline std::shared_ptr<__future_base::_State_base>
1699 __future_base::_S_make_async_state(_BoundFn&& __fn)
1701 typedef typename remove_reference<_BoundFn>::type __fn_type;
1702 typedef _Async_state_impl<__fn_type> __state_type;
1703 return std::make_shared<__state_type>(std::move(__fn));
1708 template<typename _Fn, typename... _Args>
1709 future<__async_result_of<_Fn, _Args...>>
1710 async(launch __policy, _Fn&& __fn, _Args&&... __args)
1712 std::shared_ptr<__future_base::_State_base> __state;
1713 if ((__policy & launch::async) == launch::async)
1717 __state = __future_base::_S_make_async_state(
1718 std::thread::__make_invoker(std::forward<_Fn>(__fn),
1719 std::forward<_Args>(__args)...)
1722 #if __cpp_exceptions
1723 catch(const system_error& __e)
1725 if (__e.code() != errc::resource_unavailable_try_again
1726 || (__policy & launch::deferred) != launch::deferred)
1733 __state = __future_base::_S_make_deferred_state(
1734 std::thread::__make_invoker(std::forward<_Fn>(__fn),
1735 std::forward<_Args>(__args)...));
1737 return future<__async_result_of<_Fn, _Args...>>(__state);
1740 /// async, potential overload
1741 template<typename _Fn, typename... _Args>
1742 inline future<__async_result_of<_Fn, _Args...>>
1743 async(_Fn&& __fn, _Args&&... __args)
1745 return std::async(launch::async|launch::deferred,
1746 std::forward<_Fn>(__fn),
1747 std::forward<_Args>(__args)...);
1750 #endif // _GLIBCXX_ASYNC_ABI_COMPAT
1751 #endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
1752 // && ATOMIC_INT_LOCK_FREE
1755 _GLIBCXX_END_NAMESPACE_VERSION
1760 #endif // _GLIBCXX_FUTURE