1// <future> -*- C++ -*-
2
3// Copyright (C) 2009-2018 Free Software Foundation, Inc.
4//
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)
9// any later version.
10
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.
15
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.
19
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/>.
24
25/** @file include/future
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_FUTURE
30#define _GLIBCXX_FUTURE 1
31
32#pragma GCC system_header
33
34#if __cplusplus < 201103L
35# include <bits/c++0x_warning.h>
36#else
37
38#include <mutex>
39#include <thread>
40#include <condition_variable>
41#include <system_error>
42#include <atomic>
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>
52
53namespace std _GLIBCXX_VISIBILITY(default)
54{
55_GLIBCXX_BEGIN_NAMESPACE_VERSION
56
57 /**
58 * @defgroup futures Futures
59 * @ingroup concurrency
60 *
61 * Classes for futures support.
62 * @{
63 */
64
65 /// Error code for futures
66 enum class future_errc
67 {
68 future_already_retrieved = 1,
69 promise_already_satisfied,
70 no_state,
71 broken_promise
72 };
73
74 /// Specialization.
75 template<>
76 struct is_error_code_enum<future_errc> : public true_type { };
77
78 /// Points to a statically-allocated object derived from error_category.
79 const error_category&
80 future_category() noexcept;
81
82 /// Overload for make_error_code.
83 inline error_code
84 make_error_code(future_errc __errc) noexcept
85 { return error_code(static_cast<int>(__errc), future_category()); }
86
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()); }
91
92 /**
93 * @brief Exception type thrown by futures.
94 * @ingroup exceptions
95 */
96 class future_error : public logic_error
97 {
98 public:
99 explicit
100 future_error(future_errc __errc)
101 : future_error(std::make_error_code(__errc))
102 { }
103
104 virtual ~future_error() noexcept;
105
106 virtual const char*
107 what() const noexcept;
108
109 const error_code&
110 code() const noexcept { return _M_code; }
111
112 private:
113 explicit
114 future_error(error_code __ec)
115 : logic_error("std::future_error: " + __ec.message()), _M_code(__ec)
116 { }
117
118 friend void __throw_future_error(int);
119
120 error_code _M_code;
121 };
122
123 // Forward declarations.
124 template<typename _Res>
125 class future;
126
127 template<typename _Res>
128 class shared_future;
129
130 template<typename _Signature>
131 class packaged_task;
132
133 template<typename _Res>
134 class promise;
135
136 /// Launch code for futures
137 enum class launch
138 {
139 async = 1,
140 deferred = 2
141 };
142
143 constexpr launch operator&(launch __x, launch __y)
144 {
145 return static_cast<launch>(
146 static_cast<int>(__x) & static_cast<int>(__y));
147 }
148
149 constexpr launch operator|(launch __x, launch __y)
150 {
151 return static_cast<launch>(
152 static_cast<int>(__x) | static_cast<int>(__y));
153 }
154
155 constexpr launch operator^(launch __x, launch __y)
156 {
157 return static_cast<launch>(
158 static_cast<int>(__x) ^ static_cast<int>(__y));
159 }
160
161 constexpr launch operator~(launch __x)
162 { return static_cast<launch>(~static_cast<int>(__x)); }
163
164 inline launch& operator&=(launch& __x, launch __y)
165 { return __x = __x & __y; }
166
167 inline launch& operator|=(launch& __x, launch __y)
168 { return __x = __x | __y; }
169
170 inline launch& operator^=(launch& __x, launch __y)
171 { return __x = __x ^ __y; }
172
173 /// Status code for futures
174 enum class future_status
175 {
176 ready,
177 timeout,
178 deferred
179 };
180
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;
186
187 template<typename _Fn, typename... _Args>
188 future<__async_result_of<_Fn, _Args...>>
189 async(launch __policy, _Fn&& __fn, _Args&&... __args);
190
191 template<typename _Fn, typename... _Args>
192 future<__async_result_of<_Fn, _Args...>>
193 async(_Fn&& __fn, _Args&&... __args);
194
195#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
196
197 /// Base class and enclosing scope.
198 struct __future_base
199 {
200 /// Base class for results.
201 struct _Result_base
202 {
203 exception_ptr _M_error;
204
205 _Result_base(const _Result_base&) = delete;
206 _Result_base& operator=(const _Result_base&) = delete;
207
208 // _M_destroy() allows derived classes to control deallocation
209 virtual void _M_destroy() = 0;
210
211 struct _Deleter
212 {
213 void operator()(_Result_base* __fr) const { __fr->_M_destroy(); }
214 };
215
216 protected:
217 _Result_base();
218 virtual ~_Result_base();
219 };
220
221 /// A unique_ptr for result objects.
222 template<typename _Res>
223 using _Ptr = unique_ptr<_Res, _Result_base::_Deleter>;
224
225 /// A result object that has storage for an object of type _Res.
226 template<typename _Res>
227 struct _Result : _Result_base
228 {
229 private:
230 __gnu_cxx::__aligned_buffer<_Res> _M_storage;
231 bool _M_initialized;
232
233 public:
234 typedef _Res result_type;
235
236 _Result() noexcept : _M_initialized() { }
237
238 ~_Result()
239 {
240 if (_M_initialized)
241 _M_value().~_Res();
242 }
243
244 // Return lvalue, future will add const or rvalue-reference
245 _Res&
246 _M_value() noexcept { return *_M_storage._M_ptr(); }
247
248 void
249 _M_set(const _Res& __res)
250 {
251 ::new (_M_storage._M_addr()) _Res(__res);
252 _M_initialized = true;
253 }
254
255 void
256 _M_set(_Res&& __res)
257 {
258 ::new (_M_storage._M_addr()) _Res(std::move(__res));
259 _M_initialized = true;
260 }
261
262 private:
263 void _M_destroy() { delete this; }
264 };
265
266 /// A result object that uses an allocator.
267 template<typename _Res, typename _Alloc>
268 struct _Result_alloc final : _Result<_Res>, _Alloc
269 {
270 using __allocator_type = __alloc_rebind<_Alloc, _Result_alloc>;
271
272 explicit
273 _Result_alloc(const _Alloc& __a) : _Result<_Res>(), _Alloc(__a)
274 { }
275
276 private:
277 void _M_destroy()
278 {
279 __allocator_type __a(*this);
280 __allocated_ptr<__allocator_type> __guard_ptr{ __a, this };
281 this->~_Result_alloc();
282 }
283 };
284
285 // Create a result object that uses an allocator.
286 template<typename _Res, typename _Allocator>
287 static _Ptr<_Result_alloc<_Res, _Allocator>>
288 _S_allocate_result(const _Allocator& __a)
289 {
290 using __result_type = _Result_alloc<_Res, _Allocator>;
291 typename __result_type::__allocator_type __a2(__a);
292 auto __guard = std::__allocate_guarded(__a2);
293 __result_type* __p = ::new((void*)__guard.get()) __result_type{__a};
294 __guard = nullptr;
295 return _Ptr<__result_type>(__p);
296 }
297
298 // Keep it simple for std::allocator.
299 template<typename _Res, typename _Tp>
300 static _Ptr<_Result<_Res>>
301 _S_allocate_result(const std::allocator<_Tp>& __a)
302 {
303 return _Ptr<_Result<_Res>>(new _Result<_Res>);
304 }
305
306 // Base class for various types of shared state created by an
307 // asynchronous provider (such as a std::promise) and shared with one
308 // or more associated futures.
309 class _State_baseV2
310 {
311 typedef _Ptr<_Result_base> _Ptr_type;
312
313 enum _Status : unsigned {
314 __not_ready,
315 __ready
316 };
317
318 _Ptr_type _M_result;
319 __atomic_futex_unsigned<> _M_status;
320 atomic_flag _M_retrieved = ATOMIC_FLAG_INIT;
321 once_flag _M_once;
322
323 public:
324 _State_baseV2() noexcept : _M_result(), _M_status(_Status::__not_ready)
325 { }
326 _State_baseV2(const _State_baseV2&) = delete;
327 _State_baseV2& operator=(const _State_baseV2&) = delete;
328 virtual ~_State_baseV2() = default;
329
330 _Result_base&
331 wait()
332 {
333 // Run any deferred function or join any asynchronous thread:
334 _M_complete_async();
335 // Acquire MO makes sure this synchronizes with the thread that made
336 // the future ready.
337 _M_status._M_load_when_equal(_Status::__ready, memory_order_acquire);
338 return *_M_result;
339 }
340
341 template<typename _Rep, typename _Period>
342 future_status
343 wait_for(const chrono::duration<_Rep, _Period>& __rel)
344 {
345 // First, check if the future has been made ready. Use acquire MO
346 // to synchronize with the thread that made it ready.
347 if (_M_status._M_load(memory_order_acquire) == _Status::__ready)
348 return future_status::ready;
349 if (_M_is_deferred_future())
350 return future_status::deferred;
351 if (_M_status._M_load_when_equal_for(_Status::__ready,
352 memory_order_acquire, __rel))
353 {
354 // _GLIBCXX_RESOLVE_LIB_DEFECTS
355 // 2100. timed waiting functions must also join
356 // This call is a no-op by default except on an async future,
357 // in which case the async thread is joined. It's also not a
358 // no-op for a deferred future, but such a future will never
359 // reach this point because it returns future_status::deferred
360 // instead of waiting for the future to become ready (see
361 // above). Async futures synchronize in this call, so we need
362 // no further synchronization here.
363 _M_complete_async();
364
365 return future_status::ready;
366 }
367 return future_status::timeout;
368 }
369
370 template<typename _Clock, typename _Duration>
371 future_status
372 wait_until(const chrono::time_point<_Clock, _Duration>& __abs)
373 {
374 // First, check if the future has been made ready. Use acquire MO
375 // to synchronize with the thread that made it ready.
376 if (_M_status._M_load(memory_order_acquire) == _Status::__ready)
377 return future_status::ready;
378 if (_M_is_deferred_future())
379 return future_status::deferred;
380 if (_M_status._M_load_when_equal_until(_Status::__ready,
381 memory_order_acquire, __abs))
382 {
383 // _GLIBCXX_RESOLVE_LIB_DEFECTS
384 // 2100. timed waiting functions must also join
385 // See wait_for(...) above.
386 _M_complete_async();
387
388 return future_status::ready;
389 }
390 return future_status::timeout;
391 }
392
393 // Provide a result to the shared state and make it ready.
394 // Calls at most once: _M_result = __res();
395 void
396 _M_set_result(function<_Ptr_type()> __res, bool __ignore_failure = false)
397 {
398 bool __did_set = false;
399 // all calls to this function are serialized,
400 // side-effects of invoking __res only happen once
401 call_once(_M_once, &_State_baseV2::_M_do_set, this,
402 std::__addressof(__res), std::__addressof(__did_set));
403 if (__did_set)
404 // Use release MO to synchronize with observers of the ready state.
405 _M_status._M_store_notify_all(_Status::__ready,
406 memory_order_release);
407 else if (!__ignore_failure)
408 __throw_future_error(int(future_errc::promise_already_satisfied));
409 }
410
411 // Provide a result to the shared state but delay making it ready
412 // until the calling thread exits.
413 // Calls at most once: _M_result = __res();
414 void
415 _M_set_delayed_result(function<_Ptr_type()> __res,
416 weak_ptr<_State_baseV2> __self)
417 {
418 bool __did_set = false;
419 unique_ptr<_Make_ready> __mr{new _Make_ready};
420 // all calls to this function are serialized,
421 // side-effects of invoking __res only happen once
422 call_once(_M_once, &_State_baseV2::_M_do_set, this,
423 std::__addressof(__res), std::__addressof(__did_set));
424 if (!__did_set)
425 __throw_future_error(int(future_errc::promise_already_satisfied));
426 __mr->_M_shared_state = std::move(__self);
427 __mr->_M_set();
428 __mr.release();
429 }
430
431 // Abandon this shared state.
432 void
433 _M_break_promise(_Ptr_type __res)
434 {
435 if (static_cast<bool>(__res))
436 {
437 __res->_M_error =
438 make_exception_ptr(future_error(future_errc::broken_promise));
439 // This function is only called when the last asynchronous result
440 // provider is abandoning this shared state, so noone can be
441 // trying to make the shared state ready at the same time, and
442 // we can access _M_result directly instead of through call_once.
443 _M_result.swap(__res);
444 // Use release MO to synchronize with observers of the ready state.
445 _M_status._M_store_notify_all(_Status::__ready,
446 memory_order_release);
447 }
448 }
449
450 // Called when this object is first passed to a future.
451 void
452 _M_set_retrieved_flag()
453 {
454 if (_M_retrieved.test_and_set())
455 __throw_future_error(int(future_errc::future_already_retrieved));
456 }
457
458 template<typename _Res, typename _Arg>
459 struct _Setter;
460
461 // set lvalues
462 template<typename _Res, typename _Arg>
463 struct _Setter<_Res, _Arg&>
464 {
465 // check this is only used by promise<R>::set_value(const R&)
466 // or promise<R&>::set_value(R&)
467 static_assert(is_same<_Res, _Arg&>::value // promise<R&>
468 || is_same<const _Res, _Arg>::value, // promise<R>
469 "Invalid specialisation");
470
471 // Used by std::promise to copy construct the result.
472 typename promise<_Res>::_Ptr_type operator()() const
473 {
474 _M_promise->_M_storage->_M_set(*_M_arg);
475 return std::move(_M_promise->_M_storage);
476 }
477 promise<_Res>* _M_promise;
478 _Arg* _M_arg;
479 };
480
481 // set rvalues
482 template<typename _Res>
483 struct _Setter<_Res, _Res&&>
484 {
485 // Used by std::promise to move construct the result.
486 typename promise<_Res>::_Ptr_type operator()() const
487 {
488 _M_promise->_M_storage->_M_set(std::move(*_M_arg));
489 return std::move(_M_promise->_M_storage);
490 }
491 promise<_Res>* _M_promise;
492 _Res* _M_arg;
493 };
494
495 // set void
496 template<typename _Res>
497 struct _Setter<_Res, void>
498 {
499 static_assert(is_void<_Res>::value, "Only used for promise<void>");
500
501 typename promise<_Res>::_Ptr_type operator()() const
502 { return std::move(_M_promise->_M_storage); }
503
504 promise<_Res>* _M_promise;
505 };
506
507 struct __exception_ptr_tag { };
508
509 // set exceptions
510 template<typename _Res>
511 struct _Setter<_Res, __exception_ptr_tag>
512 {
513 // Used by std::promise to store an exception as the result.
514 typename promise<_Res>::_Ptr_type operator()() const
515 {
516 _M_promise->_M_storage->_M_error = *_M_ex;
517 return std::move(_M_promise->_M_storage);
518 }
519
520 promise<_Res>* _M_promise;
521 exception_ptr* _M_ex;
522 };
523
524 template<typename _Res, typename _Arg>
525 static _Setter<_Res, _Arg&&>
526 __setter(promise<_Res>* __prom, _Arg&& __arg)
527 {
528 _S_check(__prom->_M_future);
529 return _Setter<_Res, _Arg&&>{ __prom, std::__addressof(__arg) };
530 }
531
532 template<typename _Res>
533 static _Setter<_Res, __exception_ptr_tag>
534 __setter(exception_ptr& __ex, promise<_Res>* __prom)
535 {
536 _S_check(__prom->_M_future);
537 return _Setter<_Res, __exception_ptr_tag>{ __prom, &__ex };
538 }
539
540 template<typename _Res>
541 static _Setter<_Res, void>
542 __setter(promise<_Res>* __prom)
543 {
544 _S_check(__prom->_M_future);
545 return _Setter<_Res, void>{ __prom };
546 }
547
548 template<typename _Tp>
549 static void
550 _S_check(const shared_ptr<_Tp>& __p)
551 {
552 if (!static_cast<bool>(__p))
553 __throw_future_error((int)future_errc::no_state);
554 }
555
556 private:
557 // The function invoked with std::call_once(_M_once, ...).
558 void
559 _M_do_set(function<_Ptr_type()>* __f, bool* __did_set)
560 {
561 _Ptr_type __res = (*__f)();
562 // Notify the caller that we did try to set; if we do not throw an
563 // exception, the caller will be aware that it did set (e.g., see
564 // _M_set_result).
565 *__did_set = true;
566 _M_result.swap(__res); // nothrow
567 }
568
569 // Wait for completion of async function.
570 virtual void _M_complete_async() { }
571
572 // Return true if state corresponds to a deferred function.
573 virtual bool _M_is_deferred_future() const { return false; }
574
575 struct _Make_ready final : __at_thread_exit_elt
576 {
577 weak_ptr<_State_baseV2> _M_shared_state;
578 static void _S_run(void*);
579 void _M_set();
580 };
581 };
582
583#ifdef _GLIBCXX_ASYNC_ABI_COMPAT
584 class _State_base;
585 class _Async_state_common;
586#else
587 using _State_base = _State_baseV2;
588 class _Async_state_commonV2;
589#endif
590
591 template<typename _BoundFn,
592 typename _Res = decltype(std::declval<_BoundFn&>()())>
593 class _Deferred_state;
594
595 template<typename _BoundFn,
596 typename _Res = decltype(std::declval<_BoundFn&>()())>
597 class _Async_state_impl;
598
599 template<typename _Signature>
600 class _Task_state_base;
601
602 template<typename _Fn, typename _Alloc, typename _Signature>
603 class _Task_state;
604
605 template<typename _BoundFn>
606 static std::shared_ptr<_State_base>
607 _S_make_deferred_state(_BoundFn&& __fn);
608
609 template<typename _BoundFn>
610 static std::shared_ptr<_State_base>
611 _S_make_async_state(_BoundFn&& __fn);
612
613 template<typename _Res_ptr, typename _Fn,
614 typename _Res = typename _Res_ptr::element_type::result_type>
615 struct _Task_setter;
616
617 template<typename _Res_ptr, typename _BoundFn>
618 static _Task_setter<_Res_ptr, _BoundFn>
619 _S_task_setter(_Res_ptr& __ptr, _BoundFn& __call)
620 {
621 return { std::__addressof(__ptr), std::__addressof(__call) };
622 }
623 };
624
625 /// Partial specialization for reference types.
626 template<typename _Res>
627 struct __future_base::_Result<_Res&> : __future_base::_Result_base
628 {
629 typedef _Res& result_type;
630
631 _Result() noexcept : _M_value_ptr() { }
632
633 void
634 _M_set(_Res& __res) noexcept
635 { _M_value_ptr = std::addressof(__res); }
636
637 _Res& _M_get() noexcept { return *_M_value_ptr; }
638
639 private:
640 _Res* _M_value_ptr;
641
642 void _M_destroy() { delete this; }
643 };
644
645 /// Explicit specialization for void.
646 template<>
647 struct __future_base::_Result<void> : __future_base::_Result_base
648 {
649 typedef void result_type;
650
651 private:
652 void _M_destroy() { delete this; }
653 };
654
655#ifndef _GLIBCXX_ASYNC_ABI_COMPAT
656
657 // Allow _Setter objects to be stored locally in std::function
658 template<typename _Res, typename _Arg>
659 struct __is_location_invariant
660 <__future_base::_State_base::_Setter<_Res, _Arg>>
661 : true_type { };
662
663 // Allow _Task_setter objects to be stored locally in std::function
664 template<typename _Res_ptr, typename _Fn, typename _Res>
665 struct __is_location_invariant
666 <__future_base::_Task_setter<_Res_ptr, _Fn, _Res>>
667 : true_type { };
668
669 /// Common implementation for future and shared_future.
670 template<typename _Res>
671 class __basic_future : public __future_base
672 {
673 protected:
674 typedef shared_ptr<_State_base> __state_type;
675 typedef __future_base::_Result<_Res>& __result_type;
676
677 private:
678 __state_type _M_state;
679
680 public:
681 // Disable copying.
682 __basic_future(const __basic_future&) = delete;
683 __basic_future& operator=(const __basic_future&) = delete;
684
685 bool
686 valid() const noexcept { return static_cast<bool>(_M_state); }
687
688 void
689 wait() const
690 {
691 _State_base::_S_check(_M_state);
692 _M_state->wait();
693 }
694
695 template<typename _Rep, typename _Period>
696 future_status
697 wait_for(const chrono::duration<_Rep, _Period>& __rel) const
698 {
699 _State_base::_S_check(_M_state);
700 return _M_state->wait_for(__rel);
701 }
702
703 template<typename _Clock, typename _Duration>
704 future_status
705 wait_until(const chrono::time_point<_Clock, _Duration>& __abs) const
706 {
707 _State_base::_S_check(_M_state);
708 return _M_state->wait_until(__abs);
709 }
710
711 protected:
712 /// Wait for the state to be ready and rethrow any stored exception
713 __result_type
714 _M_get_result() const
715 {
716 _State_base::_S_check(_M_state);
717 _Result_base& __res = _M_state->wait();
718 if (!(__res._M_error == 0))
719 rethrow_exception(__res._M_error);
720 return static_cast<__result_type>(__res);
721 }
722
723 void _M_swap(__basic_future& __that) noexcept
724 {
725 _M_state.swap(__that._M_state);
726 }
727
728 // Construction of a future by promise::get_future()
729 explicit
730 __basic_future(const __state_type& __state) : _M_state(__state)
731 {
732 _State_base::_S_check(_M_state);
733 _M_state->_M_set_retrieved_flag();
734 }
735
736 // Copy construction from a shared_future
737 explicit
738 __basic_future(const shared_future<_Res>&) noexcept;
739
740 // Move construction from a shared_future
741 explicit
742 __basic_future(shared_future<_Res>&&) noexcept;
743
744 // Move construction from a future
745 explicit
746 __basic_future(future<_Res>&&) noexcept;
747
748 constexpr __basic_future() noexcept : _M_state() { }
749
750 struct _Reset
751 {
752 explicit _Reset(__basic_future& __fut) noexcept : _M_fut(__fut) { }
753 ~_Reset() { _M_fut._M_state.reset(); }
754 __basic_future& _M_fut;
755 };
756 };
757
758
759 /// Primary template for future.
760 template<typename _Res>
761 class future : public __basic_future<_Res>
762 {
763 friend class promise<_Res>;
764 template<typename> friend class packaged_task;
765 template<typename _Fn, typename... _Args>
766 friend future<__async_result_of<_Fn, _Args...>>
767 async(launch, _Fn&&, _Args&&...);
768
769 typedef __basic_future<_Res> _Base_type;
770 typedef typename _Base_type::__state_type __state_type;
771
772 explicit
773 future(const __state_type& __state) : _Base_type(__state) { }
774
775 public:
776 constexpr future() noexcept : _Base_type() { }
777
778 /// Move constructor
779 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
780
781 // Disable copying
782 future(const future&) = delete;
783 future& operator=(const future&) = delete;
784
785 future& operator=(future&& __fut) noexcept
786 {
787 future(std::move(__fut))._M_swap(*this);
788 return *this;
789 }
790
791 /// Retrieving the value
792 _Res
793 get()
794 {
795 typename _Base_type::_Reset __reset(*this);
796 return std::move(this->_M_get_result()._M_value());
797 }
798
799 shared_future<_Res> share() noexcept;
800 };
801
802 /// Partial specialization for future<R&>
803 template<typename _Res>
804 class future<_Res&> : public __basic_future<_Res&>
805 {
806 friend class promise<_Res&>;
807 template<typename> friend class packaged_task;
808 template<typename _Fn, typename... _Args>
809 friend future<__async_result_of<_Fn, _Args...>>
810 async(launch, _Fn&&, _Args&&...);
811
812 typedef __basic_future<_Res&> _Base_type;
813 typedef typename _Base_type::__state_type __state_type;
814
815 explicit
816 future(const __state_type& __state) : _Base_type(__state) { }
817
818 public:
819 constexpr future() noexcept : _Base_type() { }
820
821 /// Move constructor
822 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
823
824 // Disable copying
825 future(const future&) = delete;
826 future& operator=(const future&) = delete;
827
828 future& operator=(future&& __fut) noexcept
829 {
830 future(std::move(__fut))._M_swap(*this);
831 return *this;
832 }
833
834 /// Retrieving the value
835 _Res&
836 get()
837 {
838 typename _Base_type::_Reset __reset(*this);
839 return this->_M_get_result()._M_get();
840 }
841
842 shared_future<_Res&> share() noexcept;
843 };
844
845 /// Explicit specialization for future<void>
846 template<>
847 class future<void> : public __basic_future<void>
848 {
849 friend class promise<void>;
850 template<typename> friend class packaged_task;
851 template<typename _Fn, typename... _Args>
852 friend future<__async_result_of<_Fn, _Args...>>
853 async(launch, _Fn&&, _Args&&...);
854
855 typedef __basic_future<void> _Base_type;
856 typedef typename _Base_type::__state_type __state_type;
857
858 explicit
859 future(const __state_type& __state) : _Base_type(__state) { }
860
861 public:
862 constexpr future() noexcept : _Base_type() { }
863
864 /// Move constructor
865 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
866
867 // Disable copying
868 future(const future&) = delete;
869 future& operator=(const future&) = delete;
870
871 future& operator=(future&& __fut) noexcept
872 {
873 future(std::move(__fut))._M_swap(*this);
874 return *this;
875 }
876
877 /// Retrieving the value
878 void
879 get()
880 {
881 typename _Base_type::_Reset __reset(*this);
882 this->_M_get_result();
883 }
884
885 shared_future<void> share() noexcept;
886 };
887
888
889 /// Primary template for shared_future.
890 template<typename _Res>
891 class shared_future : public __basic_future<_Res>
892 {
893 typedef __basic_future<_Res> _Base_type;
894
895 public:
896 constexpr shared_future() noexcept : _Base_type() { }
897
898 /// Copy constructor
899 shared_future(const shared_future& __sf) noexcept : _Base_type(__sf) { }
900
901 /// Construct from a future rvalue
902 shared_future(future<_Res>&& __uf) noexcept
903 : _Base_type(std::move(__uf))
904 { }
905
906 /// Construct from a shared_future rvalue
907 shared_future(shared_future&& __sf) noexcept
908 : _Base_type(std::move(__sf))
909 { }
910
911 shared_future& operator=(const shared_future& __sf) noexcept
912 {
913 shared_future(__sf)._M_swap(*this);
914 return *this;
915 }
916
917 shared_future& operator=(shared_future&& __sf) noexcept
918 {
919 shared_future(std::move(__sf))._M_swap(*this);
920 return *this;
921 }
922
923 /// Retrieving the value
924 const _Res&
925 get() const { return this->_M_get_result()._M_value(); }
926 };
927
928 /// Partial specialization for shared_future<R&>
929 template<typename _Res>
930 class shared_future<_Res&> : public __basic_future<_Res&>
931 {
932 typedef __basic_future<_Res&> _Base_type;
933
934 public:
935 constexpr shared_future() noexcept : _Base_type() { }
936
937 /// Copy constructor
938 shared_future(const shared_future& __sf) : _Base_type(__sf) { }
939
940 /// Construct from a future rvalue
941 shared_future(future<_Res&>&& __uf) noexcept
942 : _Base_type(std::move(__uf))
943 { }
944
945 /// Construct from a shared_future rvalue
946 shared_future(shared_future&& __sf) noexcept
947 : _Base_type(std::move(__sf))
948 { }
949
950 shared_future& operator=(const shared_future& __sf)
951 {
952 shared_future(__sf)._M_swap(*this);
953 return *this;
954 }
955
956 shared_future& operator=(shared_future&& __sf) noexcept
957 {
958 shared_future(std::move(__sf))._M_swap(*this);
959 return *this;
960 }
961
962 /// Retrieving the value
963 _Res&
964 get() const { return this->_M_get_result()._M_get(); }
965 };
966
967 /// Explicit specialization for shared_future<void>
968 template<>
969 class shared_future<void> : public __basic_future<void>
970 {
971 typedef __basic_future<void> _Base_type;
972
973 public:
974 constexpr shared_future() noexcept : _Base_type() { }
975
976 /// Copy constructor
977 shared_future(const shared_future& __sf) : _Base_type(__sf) { }
978
979 /// Construct from a future rvalue
980 shared_future(future<void>&& __uf) noexcept
981 : _Base_type(std::move(__uf))
982 { }
983
984 /// Construct from a shared_future rvalue
985 shared_future(shared_future&& __sf) noexcept
986 : _Base_type(std::move(__sf))
987 { }
988
989 shared_future& operator=(const shared_future& __sf)
990 {
991 shared_future(__sf)._M_swap(*this);
992 return *this;
993 }
994
995 shared_future& operator=(shared_future&& __sf) noexcept
996 {
997 shared_future(std::move(__sf))._M_swap(*this);
998 return *this;
999 }
1000
1001 // Retrieving the value
1002 void
1003 get() const { this->_M_get_result(); }
1004 };
1005
1006 // Now we can define the protected __basic_future constructors.
1007 template<typename _Res>
1008 inline __basic_future<_Res>::
1009 __basic_future(const shared_future<_Res>& __sf) noexcept
1010 : _M_state(__sf._M_state)
1011 { }
1012
1013 template<typename _Res>
1014 inline __basic_future<_Res>::
1015 __basic_future(shared_future<_Res>&& __sf) noexcept
1016 : _M_state(std::move(__sf._M_state))
1017 { }
1018
1019 template<typename _Res>
1020 inline __basic_future<_Res>::
1021 __basic_future(future<_Res>&& __uf) noexcept
1022 : _M_state(std::move(__uf._M_state))
1023 { }
1024
1025 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1026 // 2556. Wide contract for future::share()
1027 template<typename _Res>
1028 inline shared_future<_Res>
1029 future<_Res>::share() noexcept
1030 { return shared_future<_Res>(std::move(*this)); }
1031
1032 template<typename _Res>
1033 inline shared_future<_Res&>
1034 future<_Res&>::share() noexcept
1035 { return shared_future<_Res&>(std::move(*this)); }
1036
1037 inline shared_future<void>
1038 future<void>::share() noexcept
1039 { return shared_future<void>(std::move(*this)); }
1040
1041 /// Primary template for promise
1042 template<typename _Res>
1043 class promise
1044 {
1045 typedef __future_base::_State_base _State;
1046 typedef __future_base::_Result<_Res> _Res_type;
1047 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1048 template<typename, typename> friend class _State::_Setter;
1049 friend _State;
1050
1051 shared_ptr<_State> _M_future;
1052 _Ptr_type _M_storage;
1053
1054 public:
1055 promise()
1056 : _M_future(std::make_shared<_State>()),
1057 _M_storage(new _Res_type())
1058 { }
1059
1060 promise(promise&& __rhs) noexcept
1061 : _M_future(std::move(__rhs._M_future)),
1062 _M_storage(std::move(__rhs._M_storage))
1063 { }
1064
1065 template<typename _Allocator>
1066 promise(allocator_arg_t, const _Allocator& __a)
1067 : _M_future(std::allocate_shared<_State>(__a)),
1068 _M_storage(__future_base::_S_allocate_result<_Res>(__a))
1069 { }
1070
1071 template<typename _Allocator>
1072 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1073 : _M_future(std::move(__rhs._M_future)),
1074 _M_storage(std::move(__rhs._M_storage))
1075 { }
1076
1077 promise(const promise&) = delete;
1078
1079 ~promise()
1080 {
1081 if (static_cast<bool>(_M_future) && !_M_future.unique())
1082 _M_future->_M_break_promise(std::move(_M_storage));
1083 }
1084
1085 // Assignment
1086 promise&
1087 operator=(promise&& __rhs) noexcept
1088 {
1089 promise(std::move(__rhs)).swap(*this);
1090 return *this;
1091 }
1092
1093 promise& operator=(const promise&) = delete;
1094
1095 void
1096 swap(promise& __rhs) noexcept
1097 {
1098 _M_future.swap(__rhs._M_future);
1099 _M_storage.swap(__rhs._M_storage);
1100 }
1101
1102 // Retrieving the result
1103 future<_Res>
1104 get_future()
1105 { return future<_Res>(_M_future); }
1106
1107 // Setting the result
1108 void
1109 set_value(const _Res& __r)
1110 { _M_future->_M_set_result(_State::__setter(this, __r)); }
1111
1112 void
1113 set_value(_Res&& __r)
1114 { _M_future->_M_set_result(_State::__setter(this, std::move(__r))); }
1115
1116 void
1117 set_exception(exception_ptr __p)
1118 { _M_future->_M_set_result(_State::__setter(__p, this)); }
1119
1120 void
1121 set_value_at_thread_exit(const _Res& __r)
1122 {
1123 _M_future->_M_set_delayed_result(_State::__setter(this, __r),
1124 _M_future);
1125 }
1126
1127 void
1128 set_value_at_thread_exit(_Res&& __r)
1129 {
1130 _M_future->_M_set_delayed_result(
1131 _State::__setter(this, std::move(__r)), _M_future);
1132 }
1133
1134 void
1135 set_exception_at_thread_exit(exception_ptr __p)
1136 {
1137 _M_future->_M_set_delayed_result(_State::__setter(__p, this),
1138 _M_future);
1139 }
1140 };
1141
1142 template<typename _Res>
1143 inline void
1144 swap(promise<_Res>& __x, promise<_Res>& __y) noexcept
1145 { __x.swap(__y); }
1146
1147 template<typename _Res, typename _Alloc>
1148 struct uses_allocator<promise<_Res>, _Alloc>
1149 : public true_type { };
1150
1151
1152 /// Partial specialization for promise<R&>
1153 template<typename _Res>
1154 class promise<_Res&>
1155 {
1156 typedef __future_base::_State_base _State;
1157 typedef __future_base::_Result<_Res&> _Res_type;
1158 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1159 template<typename, typename> friend class _State::_Setter;
1160 friend _State;
1161
1162 shared_ptr<_State> _M_future;
1163 _Ptr_type _M_storage;
1164
1165 public:
1166 promise()
1167 : _M_future(std::make_shared<_State>()),
1168 _M_storage(new _Res_type())
1169 { }
1170
1171 promise(promise&& __rhs) noexcept
1172 : _M_future(std::move(__rhs._M_future)),
1173 _M_storage(std::move(__rhs._M_storage))
1174 { }
1175
1176 template<typename _Allocator>
1177 promise(allocator_arg_t, const _Allocator& __a)
1178 : _M_future(std::allocate_shared<_State>(__a)),
1179 _M_storage(__future_base::_S_allocate_result<_Res&>(__a))
1180 { }
1181
1182 template<typename _Allocator>
1183 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1184 : _M_future(std::move(__rhs._M_future)),
1185 _M_storage(std::move(__rhs._M_storage))
1186 { }
1187
1188 promise(const promise&) = delete;
1189
1190 ~promise()
1191 {
1192 if (static_cast<bool>(_M_future) && !_M_future.unique())
1193 _M_future->_M_break_promise(std::move(_M_storage));
1194 }
1195
1196 // Assignment
1197 promise&
1198 operator=(promise&& __rhs) noexcept
1199 {
1200 promise(std::move(__rhs)).swap(*this);
1201 return *this;
1202 }
1203
1204 promise& operator=(const promise&) = delete;
1205
1206 void
1207 swap(promise& __rhs) noexcept
1208 {
1209 _M_future.swap(__rhs._M_future);
1210 _M_storage.swap(__rhs._M_storage);
1211 }
1212
1213 // Retrieving the result
1214 future<_Res&>
1215 get_future()
1216 { return future<_Res&>(_M_future); }
1217
1218 // Setting the result
1219 void
1220 set_value(_Res& __r)
1221 { _M_future->_M_set_result(_State::__setter(this, __r)); }
1222
1223 void
1224 set_exception(exception_ptr __p)
1225 { _M_future->_M_set_result(_State::__setter(__p, this)); }
1226
1227 void
1228 set_value_at_thread_exit(_Res& __r)
1229 {
1230 _M_future->_M_set_delayed_result(_State::__setter(this, __r),
1231 _M_future);
1232 }
1233
1234 void
1235 set_exception_at_thread_exit(exception_ptr __p)
1236 {
1237 _M_future->_M_set_delayed_result(_State::__setter(__p, this),
1238 _M_future);
1239 }
1240 };
1241
1242 /// Explicit specialization for promise<void>
1243 template<>
1244 class promise<void>
1245 {
1246 typedef __future_base::_State_base _State;
1247 typedef __future_base::_Result<void> _Res_type;
1248 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1249 template<typename, typename> friend class _State::_Setter;
1250 friend _State;
1251
1252 shared_ptr<_State> _M_future;
1253 _Ptr_type _M_storage;
1254
1255 public:
1256 promise()
1257 : _M_future(std::make_shared<_State>()),
1258 _M_storage(new _Res_type())
1259 { }
1260
1261 promise(promise&& __rhs) noexcept
1262 : _M_future(std::move(__rhs._M_future)),
1263 _M_storage(std::move(__rhs._M_storage))
1264 { }
1265
1266 template<typename _Allocator>
1267 promise(allocator_arg_t, const _Allocator& __a)
1268 : _M_future(std::allocate_shared<_State>(__a)),
1269 _M_storage(__future_base::_S_allocate_result<void>(__a))
1270 { }
1271
1272 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1273 // 2095. missing constructors needed for uses-allocator construction
1274 template<typename _Allocator>
1275 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1276 : _M_future(std::move(__rhs._M_future)),
1277 _M_storage(std::move(__rhs._M_storage))
1278 { }
1279
1280 promise(const promise&) = delete;
1281
1282 ~promise()
1283 {
1284 if (static_cast<bool>(_M_future) && !_M_future.unique())
1285 _M_future->_M_break_promise(std::move(_M_storage));
1286 }
1287
1288 // Assignment
1289 promise&
1290 operator=(promise&& __rhs) noexcept
1291 {
1292 promise(std::move(__rhs)).swap(*this);
1293 return *this;
1294 }
1295
1296 promise& operator=(const promise&) = delete;
1297
1298 void
1299 swap(promise& __rhs) noexcept
1300 {
1301 _M_future.swap(__rhs._M_future);
1302 _M_storage.swap(__rhs._M_storage);
1303 }
1304
1305 // Retrieving the result
1306 future<void>
1307 get_future()
1308 { return future<void>(_M_future); }
1309
1310 // Setting the result
1311 void
1312 set_value()
1313 { _M_future->_M_set_result(_State::__setter(this)); }
1314
1315 void
1316 set_exception(exception_ptr __p)
1317 { _M_future->_M_set_result(_State::__setter(__p, this)); }
1318
1319 void
1320 set_value_at_thread_exit()
1321 { _M_future->_M_set_delayed_result(_State::__setter(this), _M_future); }
1322
1323 void
1324 set_exception_at_thread_exit(exception_ptr __p)
1325 {
1326 _M_future->_M_set_delayed_result(_State::__setter(__p, this),
1327 _M_future);
1328 }
1329 };
1330
1331 template<typename _Ptr_type, typename _Fn, typename _Res>
1332 struct __future_base::_Task_setter
1333 {
1334 // Invoke the function and provide the result to the caller.
1335 _Ptr_type operator()() const
1336 {
1337 __try
1338 {
1339 (*_M_result)->_M_set((*_M_fn)());
1340 }
1341 __catch(const __cxxabiv1::__forced_unwind&)
1342 {
1343 __throw_exception_again; // will cause broken_promise
1344 }
1345 __catch(...)
1346 {
1347 (*_M_result)->_M_error = current_exception();
1348 }
1349 return std::move(*_M_result);
1350 }
1351 _Ptr_type* _M_result;
1352 _Fn* _M_fn;
1353 };
1354
1355 template<typename _Ptr_type, typename _Fn>
1356 struct __future_base::_Task_setter<_Ptr_type, _Fn, void>
1357 {
1358 _Ptr_type operator()() const
1359 {
1360 __try
1361 {
1362 (*_M_fn)();
1363 }
1364 __catch(const __cxxabiv1::__forced_unwind&)
1365 {
1366 __throw_exception_again; // will cause broken_promise
1367 }
1368 __catch(...)
1369 {
1370 (*_M_result)->_M_error = current_exception();
1371 }
1372 return std::move(*_M_result);
1373 }
1374 _Ptr_type* _M_result;
1375 _Fn* _M_fn;
1376 };
1377
1378 // Holds storage for a packaged_task's result.
1379 template<typename _Res, typename... _Args>
1380 struct __future_base::_Task_state_base<_Res(_Args...)>
1381 : __future_base::_State_base
1382 {
1383 typedef _Res _Res_type;
1384
1385 template<typename _Alloc>
1386 _Task_state_base(const _Alloc& __a)
1387 : _M_result(_S_allocate_result<_Res>(__a))
1388 { }
1389
1390 // Invoke the stored task and make the state ready.
1391 virtual void
1392 _M_run(_Args&&... __args) = 0;
1393
1394 // Invoke the stored task and make the state ready at thread exit.
1395 virtual void
1396 _M_run_delayed(_Args&&... __args, weak_ptr<_State_base>) = 0;
1397
1398 virtual shared_ptr<_Task_state_base>
1399 _M_reset() = 0;
1400
1401 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1402 _Ptr_type _M_result;
1403 };
1404
1405 // Holds a packaged_task's stored task.
1406 template<typename _Fn, typename _Alloc, typename _Res, typename... _Args>
1407 struct __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)> final
1408 : __future_base::_Task_state_base<_Res(_Args...)>
1409 {
1410 template<typename _Fn2>
1411 _Task_state(_Fn2&& __fn, const _Alloc& __a)
1412 : _Task_state_base<_Res(_Args...)>(__a),
1413 _M_impl(std::forward<_Fn2>(__fn), __a)
1414 { }
1415
1416 private:
1417 virtual void
1418 _M_run(_Args&&... __args)
1419 {
1420 auto __boundfn = [&] () -> typename result_of<_Fn&(_Args&&...)>::type {
1421 return std::__invoke(_M_impl._M_fn, std::forward<_Args>(__args)...);
1422 };
1423 this->_M_set_result(_S_task_setter(this->_M_result, __boundfn));
1424 }
1425
1426 virtual void
1427 _M_run_delayed(_Args&&... __args, weak_ptr<_State_base> __self)
1428 {
1429 auto __boundfn = [&] () -> typename result_of<_Fn&(_Args&&...)>::type {
1430 return std::__invoke(_M_impl._M_fn, std::forward<_Args>(__args)...);
1431 };
1432 this->_M_set_delayed_result(_S_task_setter(this->_M_result, __boundfn),
1433 std::move(__self));
1434 }
1435
1436 virtual shared_ptr<_Task_state_base<_Res(_Args...)>>
1437 _M_reset();
1438
1439 struct _Impl : _Alloc
1440 {
1441 template<typename _Fn2>
1442 _Impl(_Fn2&& __fn, const _Alloc& __a)
1443 : _Alloc(__a), _M_fn(std::forward<_Fn2>(__fn)) { }
1444 _Fn _M_fn;
1445 } _M_impl;
1446 };
1447
1448 template<typename _Signature, typename _Fn, typename _Alloc>
1449 static shared_ptr<__future_base::_Task_state_base<_Signature>>
1450 __create_task_state(_Fn&& __fn, const _Alloc& __a)
1451 {
1452 typedef typename decay<_Fn>::type _Fn2;
1453 typedef __future_base::_Task_state<_Fn2, _Alloc, _Signature> _State;
1454 return std::allocate_shared<_State>(__a, std::forward<_Fn>(__fn), __a);
1455 }
1456
1457 template<typename _Fn, typename _Alloc, typename _Res, typename... _Args>
1458 shared_ptr<__future_base::_Task_state_base<_Res(_Args...)>>
1459 __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)>::_M_reset()
1460 {
1461 return __create_task_state<_Res(_Args...)>(std::move(_M_impl._M_fn),
1462 static_cast<_Alloc&>(_M_impl));
1463 }
1464
1465 template<typename _Task, typename _Fn, bool
1466 = is_same<_Task, typename decay<_Fn>::type>::value>
1467 struct __constrain_pkgdtask
1468 { typedef void __type; };
1469
1470 template<typename _Task, typename _Fn>
1471 struct __constrain_pkgdtask<_Task, _Fn, true>
1472 { };
1473
1474 /// packaged_task
1475 template<typename _Res, typename... _ArgTypes>
1476 class packaged_task<_Res(_ArgTypes...)>
1477 {
1478 typedef __future_base::_Task_state_base<_Res(_ArgTypes...)> _State_type;
1479 shared_ptr<_State_type> _M_state;
1480
1481 public:
1482 // Construction and destruction
1483 packaged_task() noexcept { }
1484
1485 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1486 // 2095. missing constructors needed for uses-allocator construction
1487 template<typename _Allocator>
1488 packaged_task(allocator_arg_t, const _Allocator& __a) noexcept
1489 { }
1490
1491 template<typename _Fn, typename = typename
1492 __constrain_pkgdtask<packaged_task, _Fn>::__type>
1493 explicit
1494 packaged_task(_Fn&& __fn)
1495 : packaged_task(allocator_arg, std::allocator<int>(),
1496 std::forward<_Fn>(__fn))
1497 { }
1498
1499 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1500 // 2097. packaged_task constructors should be constrained
1501 // 2407. [this constructor should not be] explicit
1502 template<typename _Fn, typename _Alloc, typename = typename
1503 __constrain_pkgdtask<packaged_task, _Fn>::__type>
1504 packaged_task(allocator_arg_t, const _Alloc& __a, _Fn&& __fn)
1505 : _M_state(__create_task_state<_Res(_ArgTypes...)>(
1506 std::forward<_Fn>(__fn), __a))
1507 { }
1508
1509 ~packaged_task()
1510 {
1511 if (static_cast<bool>(_M_state) && !_M_state.unique())
1512 _M_state->_M_break_promise(std::move(_M_state->_M_result));
1513 }
1514
1515 // No copy
1516 packaged_task(const packaged_task&) = delete;
1517 packaged_task& operator=(const packaged_task&) = delete;
1518
1519 template<typename _Allocator>
1520 packaged_task(allocator_arg_t, const _Allocator&,
1521 const packaged_task&) = delete;
1522
1523 // Move support
1524 packaged_task(packaged_task&& __other) noexcept
1525 { this->swap(__other); }
1526
1527 template<typename _Allocator>
1528 packaged_task(allocator_arg_t, const _Allocator&,
1529 packaged_task&& __other) noexcept
1530 { this->swap(__other); }
1531
1532 packaged_task& operator=(packaged_task&& __other) noexcept
1533 {
1534 packaged_task(std::move(__other)).swap(*this);
1535 return *this;
1536 }
1537
1538 void
1539 swap(packaged_task& __other) noexcept
1540 { _M_state.swap(__other._M_state); }
1541
1542 bool
1543 valid() const noexcept
1544 { return static_cast<bool>(_M_state); }
1545
1546 // Result retrieval
1547 future<_Res>
1548 get_future()
1549 { return future<_Res>(_M_state); }
1550
1551 // Execution
1552 void
1553 operator()(_ArgTypes... __args)
1554 {
1555 __future_base::_State_base::_S_check(_M_state);
1556 _M_state->_M_run(std::forward<_ArgTypes>(__args)...);
1557 }
1558
1559 void
1560 make_ready_at_thread_exit(_ArgTypes... __args)
1561 {
1562 __future_base::_State_base::_S_check(_M_state);
1563 _M_state->_M_run_delayed(std::forward<_ArgTypes>(__args)..., _M_state);
1564 }
1565
1566 void
1567 reset()
1568 {
1569 __future_base::_State_base::_S_check(_M_state);
1570 packaged_task __tmp;
1571 __tmp._M_state = _M_state;
1572 _M_state = _M_state->_M_reset();
1573 }
1574 };
1575
1576 /// swap
1577 template<typename _Res, typename... _ArgTypes>
1578 inline void
1579 swap(packaged_task<_Res(_ArgTypes...)>& __x,
1580 packaged_task<_Res(_ArgTypes...)>& __y) noexcept
1581 { __x.swap(__y); }
1582
1583 template<typename _Res, typename _Alloc>
1584 struct uses_allocator<packaged_task<_Res>, _Alloc>
1585 : public true_type { };
1586
1587
1588 // Shared state created by std::async().
1589 // Holds a deferred function and storage for its result.
1590 template<typename _BoundFn, typename _Res>
1591 class __future_base::_Deferred_state final
1592 : public __future_base::_State_base
1593 {
1594 public:
1595 explicit
1596 _Deferred_state(_BoundFn&& __fn)
1597 : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
1598 { }
1599
1600 private:
1601 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1602 _Ptr_type _M_result;
1603 _BoundFn _M_fn;
1604
1605 // Run the deferred function.
1606 virtual void
1607 _M_complete_async()
1608 {
1609 // Multiple threads can call a waiting function on the future and
1610 // reach this point at the same time. The call_once in _M_set_result
1611 // ensures only the first one run the deferred function, stores the
1612 // result in _M_result, swaps that with the base _M_result and makes
1613 // the state ready. Tell _M_set_result to ignore failure so all later
1614 // calls do nothing.
1615 _M_set_result(_S_task_setter(_M_result, _M_fn), true);
1616 }
1617
1618 // Caller should check whether the state is ready first, because this
1619 // function will return true even after the deferred function has run.
1620 virtual bool _M_is_deferred_future() const { return true; }
1621 };
1622
1623 // Common functionality hoisted out of the _Async_state_impl template.
1624 class __future_base::_Async_state_commonV2
1625 : public __future_base::_State_base
1626 {
1627 protected:
1628 ~_Async_state_commonV2() = default;
1629
1630 // Make waiting functions block until the thread completes, as if joined.
1631 //
1632 // This function is used by wait() to satisfy the first requirement below
1633 // and by wait_for() / wait_until() to satisfy the second.
1634 //
1635 // [futures.async]:
1636 //
1637 // — a call to a waiting function on an asynchronous return object that
1638 // shares the shared state created by this async call shall block until
1639 // the associated thread has completed, as if joined, or else time out.
1640 //
1641 // — the associated thread completion synchronizes with the return from
1642 // the first function that successfully detects the ready status of the
1643 // shared state or with the return from the last function that releases
1644 // the shared state, whichever happens first.
1645 virtual void _M_complete_async() { _M_join(); }
1646
1647 void _M_join() { std::call_once(_M_once, &thread::join, &_M_thread); }
1648
1649 thread _M_thread;
1650 once_flag _M_once;
1651 };
1652
1653 // Shared state created by std::async().
1654 // Starts a new thread that runs a function and makes the shared state ready.
1655 template<typename _BoundFn, typename _Res>
1656 class __future_base::_Async_state_impl final
1657 : public __future_base::_Async_state_commonV2
1658 {
1659 public:
1660 explicit
1661 _Async_state_impl(_BoundFn&& __fn)
1662 : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
1663 {
1664 _M_thread = std::thread{ [this] {
1665 __try
1666 {
1667 _M_set_result(_S_task_setter(_M_result, _M_fn));
1668 }
1669 __catch (const __cxxabiv1::__forced_unwind&)
1670 {
1671 // make the shared state ready on thread cancellation
1672 if (static_cast<bool>(_M_result))
1673 this->_M_break_promise(std::move(_M_result));
1674 __throw_exception_again;
1675 }
1676 } };
1677 }
1678
1679 // Must not destroy _M_result and _M_fn until the thread finishes.
1680 // Call join() directly rather than through _M_join() because no other
1681 // thread can be referring to this state if it is being destroyed.
1682 ~_Async_state_impl() { if (_M_thread.joinable()) _M_thread.join(); }
1683
1684 private:
1685 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1686 _Ptr_type _M_result;
1687 _BoundFn _M_fn;
1688 };
1689
1690 template<typename _BoundFn>
1691 inline std::shared_ptr<__future_base::_State_base>
1692 __future_base::_S_make_deferred_state(_BoundFn&& __fn)
1693 {
1694 typedef typename remove_reference<_BoundFn>::type __fn_type;
1695 typedef _Deferred_state<__fn_type> __state_type;
1696 return std::make_shared<__state_type>(std::move(__fn));
1697 }
1698
1699 template<typename _BoundFn>
1700 inline std::shared_ptr<__future_base::_State_base>
1701 __future_base::_S_make_async_state(_BoundFn&& __fn)
1702 {
1703 typedef typename remove_reference<_BoundFn>::type __fn_type;
1704 typedef _Async_state_impl<__fn_type> __state_type;
1705 return std::make_shared<__state_type>(std::move(__fn));
1706 }
1707
1708
1709 /// async
1710 template<typename _Fn, typename... _Args>
1711 future<__async_result_of<_Fn, _Args...>>
1712 async(launch __policy, _Fn&& __fn, _Args&&... __args)
1713 {
1714 std::shared_ptr<__future_base::_State_base> __state;
1715 if ((__policy & launch::async) == launch::async)
1716 {
1717 __try
1718 {
1719 __state = __future_base::_S_make_async_state(
1720 std::thread::__make_invoker(std::forward<_Fn>(__fn),
1721 std::forward<_Args>(__args)...)
1722 );
1723 }
1724#if __cpp_exceptions
1725 catch(const system_error& __e)
1726 {
1727 if (__e.code() != errc::resource_unavailable_try_again
1728 || (__policy & launch::deferred) != launch::deferred)
1729 throw;
1730 }
1731#endif
1732 }
1733 if (!__state)
1734 {
1735 __state = __future_base::_S_make_deferred_state(
1736 std::thread::__make_invoker(std::forward<_Fn>(__fn),
1737 std::forward<_Args>(__args)...));
1738 }
1739 return future<__async_result_of<_Fn, _Args...>>(__state);
1740 }
1741
1742 /// async, potential overload
1743 template<typename _Fn, typename... _Args>
1744 inline future<__async_result_of<_Fn, _Args...>>
1745 async(_Fn&& __fn, _Args&&... __args)
1746 {
1747 return std::async(launch::async|launch::deferred,
1748 std::forward<_Fn>(__fn),
1749 std::forward<_Args>(__args)...);
1750 }
1751
1752#endif // _GLIBCXX_ASYNC_ABI_COMPAT
1753#endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
1754
1755 // @} group futures
1756_GLIBCXX_END_NAMESPACE_VERSION
1757} // namespace
1758
1759#endif // C++11
1760
1761#endif // _GLIBCXX_FUTURE
1762