libstdc++
future
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1// <future> -*- C++ -*-
2
3// Copyright (C) 2009-2020 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 __invoke_result<
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)
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
350 if (_M_is_deferred_future())
351 return future_status::deferred;
352
353 // Don't wait unless the relative time is greater than zero.
354 if (__rel > __rel.zero()
355 && _M_status._M_load_when_equal_for(_Status::__ready,
356 memory_order_acquire,
357 __rel))
358 {
359 // _GLIBCXX_RESOLVE_LIB_DEFECTS
360 // 2100. timed waiting functions must also join
361 // This call is a no-op by default except on an async future,
362 // in which case the async thread is joined. It's also not a
363 // no-op for a deferred future, but such a future will never
364 // reach this point because it returns future_status::deferred
365 // instead of waiting for the future to become ready (see
366 // above). Async futures synchronize in this call, so we need
367 // no further synchronization here.
368 _M_complete_async();
369
370 return future_status::ready;
371 }
372 return future_status::timeout;
373 }
374
375 template<typename _Clock, typename _Duration>
376 future_status
377 wait_until(const chrono::time_point<_Clock, _Duration>& __abs)
378 {
379#if __cplusplus > 201703L
380 static_assert(chrono::is_clock_v<_Clock>);
381#endif
382 // First, check if the future has been made ready. Use acquire MO
383 // to synchronize with the thread that made it ready.
384 if (_M_status._M_load(memory_order_acquire) == _Status::__ready)
385 return future_status::ready;
386
387 if (_M_is_deferred_future())
388 return future_status::deferred;
389
390 if (_M_status._M_load_when_equal_until(_Status::__ready,
391 memory_order_acquire,
392 __abs))
393 {
394 // _GLIBCXX_RESOLVE_LIB_DEFECTS
395 // 2100. timed waiting functions must also join
396 // See wait_for(...) above.
397 _M_complete_async();
398
399 return future_status::ready;
400 }
401 return future_status::timeout;
402 }
403
404 // Provide a result to the shared state and make it ready.
405 // Calls at most once: _M_result = __res();
406 void
407 _M_set_result(function<_Ptr_type()> __res, bool __ignore_failure = false)
408 {
409 bool __did_set = false;
410 // all calls to this function are serialized,
411 // side-effects of invoking __res only happen once
412 call_once(_M_once, &_State_baseV2::_M_do_set, this,
413 std::__addressof(__res), std::__addressof(__did_set));
414 if (__did_set)
415 // Use release MO to synchronize with observers of the ready state.
416 _M_status._M_store_notify_all(_Status::__ready,
417 memory_order_release);
418 else if (!__ignore_failure)
419 __throw_future_error(int(future_errc::promise_already_satisfied));
420 }
421
422 // Provide a result to the shared state but delay making it ready
423 // until the calling thread exits.
424 // Calls at most once: _M_result = __res();
425 void
426 _M_set_delayed_result(function<_Ptr_type()> __res,
427 weak_ptr<_State_baseV2> __self)
428 {
429 bool __did_set = false;
430 unique_ptr<_Make_ready> __mr{new _Make_ready};
431 // all calls to this function are serialized,
432 // side-effects of invoking __res only happen once
433 call_once(_M_once, &_State_baseV2::_M_do_set, this,
434 std::__addressof(__res), std::__addressof(__did_set));
435 if (!__did_set)
436 __throw_future_error(int(future_errc::promise_already_satisfied));
437 __mr->_M_shared_state = std::move(__self);
438 __mr->_M_set();
439 __mr.release();
440 }
441
442 // Abandon this shared state.
443 void
444 _M_break_promise(_Ptr_type __res)
445 {
446 if (static_cast<bool>(__res))
447 {
448 __res->_M_error =
449 make_exception_ptr(future_error(future_errc::broken_promise));
450 // This function is only called when the last asynchronous result
451 // provider is abandoning this shared state, so noone can be
452 // trying to make the shared state ready at the same time, and
453 // we can access _M_result directly instead of through call_once.
454 _M_result.swap(__res);
455 // Use release MO to synchronize with observers of the ready state.
456 _M_status._M_store_notify_all(_Status::__ready,
457 memory_order_release);
458 }
459 }
460
461 // Called when this object is first passed to a future.
462 void
463 _M_set_retrieved_flag()
464 {
465 if (_M_retrieved.test_and_set())
466 __throw_future_error(int(future_errc::future_already_retrieved));
467 }
468
469 template<typename _Res, typename _Arg>
470 struct _Setter;
471
472 // set lvalues
473 template<typename _Res, typename _Arg>
474 struct _Setter<_Res, _Arg&>
475 {
476 // check this is only used by promise<R>::set_value(const R&)
477 // or promise<R&>::set_value(R&)
478 static_assert(is_same<_Res, _Arg&>::value // promise<R&>
479 || is_same<const _Res, _Arg>::value, // promise<R>
480 "Invalid specialisation");
481
482 // Used by std::promise to copy construct the result.
483 typename promise<_Res>::_Ptr_type operator()() const
484 {
485 _M_promise->_M_storage->_M_set(*_M_arg);
486 return std::move(_M_promise->_M_storage);
487 }
488 promise<_Res>* _M_promise;
489 _Arg* _M_arg;
490 };
491
492 // set rvalues
493 template<typename _Res>
494 struct _Setter<_Res, _Res&&>
495 {
496 // Used by std::promise to move construct the result.
497 typename promise<_Res>::_Ptr_type operator()() const
498 {
499 _M_promise->_M_storage->_M_set(std::move(*_M_arg));
500 return std::move(_M_promise->_M_storage);
501 }
502 promise<_Res>* _M_promise;
503 _Res* _M_arg;
504 };
505
506 // set void
507 template<typename _Res>
508 struct _Setter<_Res, void>
509 {
510 static_assert(is_void<_Res>::value, "Only used for promise<void>");
511
512 typename promise<_Res>::_Ptr_type operator()() const
513 { return std::move(_M_promise->_M_storage); }
514
515 promise<_Res>* _M_promise;
516 };
517
518 struct __exception_ptr_tag { };
519
520 // set exceptions
521 template<typename _Res>
522 struct _Setter<_Res, __exception_ptr_tag>
523 {
524 // Used by std::promise to store an exception as the result.
525 typename promise<_Res>::_Ptr_type operator()() const
526 {
527 _M_promise->_M_storage->_M_error = *_M_ex;
528 return std::move(_M_promise->_M_storage);
529 }
530
531 promise<_Res>* _M_promise;
532 exception_ptr* _M_ex;
533 };
534
535 template<typename _Res, typename _Arg>
536 __attribute__((__always_inline__))
537 static _Setter<_Res, _Arg&&>
538 __setter(promise<_Res>* __prom, _Arg&& __arg) noexcept
539 {
540 return _Setter<_Res, _Arg&&>{ __prom, std::__addressof(__arg) };
541 }
542
543 template<typename _Res>
544 __attribute__((__always_inline__))
545 static _Setter<_Res, __exception_ptr_tag>
546 __setter(exception_ptr& __ex, promise<_Res>* __prom) noexcept
547 {
548 return _Setter<_Res, __exception_ptr_tag>{ __prom, &__ex };
549 }
550
551 template<typename _Res>
552 __attribute__((__always_inline__))
553 static _Setter<_Res, void>
554 __setter(promise<_Res>* __prom) noexcept
555 {
556 return _Setter<_Res, void>{ __prom };
557 }
558
559 template<typename _Tp>
560 static void
561 _S_check(const shared_ptr<_Tp>& __p)
562 {
563 if (!static_cast<bool>(__p))
564 __throw_future_error((int)future_errc::no_state);
565 }
566
567 private:
568 // The function invoked with std::call_once(_M_once, ...).
569 void
570 _M_do_set(function<_Ptr_type()>* __f, bool* __did_set)
571 {
572 _Ptr_type __res = (*__f)();
573 // Notify the caller that we did try to set; if we do not throw an
574 // exception, the caller will be aware that it did set (e.g., see
575 // _M_set_result).
576 *__did_set = true;
577 _M_result.swap(__res); // nothrow
578 }
579
580 // Wait for completion of async function.
581 virtual void _M_complete_async() { }
582
583 // Return true if state corresponds to a deferred function.
584 virtual bool _M_is_deferred_future() const { return false; }
585
586 struct _Make_ready final : __at_thread_exit_elt
587 {
588 weak_ptr<_State_baseV2> _M_shared_state;
589 static void _S_run(void*);
590 void _M_set();
591 };
592 };
593
594#ifdef _GLIBCXX_ASYNC_ABI_COMPAT
595 class _State_base;
596 class _Async_state_common;
597#else
598 using _State_base = _State_baseV2;
599 class _Async_state_commonV2;
600#endif
601
602 template<typename _BoundFn,
603 typename _Res = decltype(std::declval<_BoundFn&>()())>
604 class _Deferred_state;
605
606 template<typename _BoundFn,
607 typename _Res = decltype(std::declval<_BoundFn&>()())>
608 class _Async_state_impl;
609
610 template<typename _Signature>
611 class _Task_state_base;
612
613 template<typename _Fn, typename _Alloc, typename _Signature>
614 class _Task_state;
615
616 template<typename _BoundFn>
617 static std::shared_ptr<_State_base>
618 _S_make_deferred_state(_BoundFn&& __fn);
619
620 template<typename _BoundFn>
621 static std::shared_ptr<_State_base>
622 _S_make_async_state(_BoundFn&& __fn);
623
624 template<typename _Res_ptr, typename _Fn,
625 typename _Res = typename _Res_ptr::element_type::result_type>
626 struct _Task_setter;
627
628 template<typename _Res_ptr, typename _BoundFn>
629 static _Task_setter<_Res_ptr, _BoundFn>
630 _S_task_setter(_Res_ptr& __ptr, _BoundFn& __call)
631 {
632 return { std::__addressof(__ptr), std::__addressof(__call) };
633 }
634 };
635
636 /// Partial specialization for reference types.
637 template<typename _Res>
638 struct __future_base::_Result<_Res&> : __future_base::_Result_base
639 {
640 typedef _Res& result_type;
641
642 _Result() noexcept : _M_value_ptr() { }
643
644 void
645 _M_set(_Res& __res) noexcept
646 { _M_value_ptr = std::addressof(__res); }
647
648 _Res& _M_get() noexcept { return *_M_value_ptr; }
649
650 private:
651 _Res* _M_value_ptr;
652
653 void _M_destroy() { delete this; }
654 };
655
656 /// Explicit specialization for void.
657 template<>
658 struct __future_base::_Result<void> : __future_base::_Result_base
659 {
660 typedef void result_type;
661
662 private:
663 void _M_destroy() { delete this; }
664 };
665
666#ifndef _GLIBCXX_ASYNC_ABI_COMPAT
667
668 // Allow _Setter objects to be stored locally in std::function
669 template<typename _Res, typename _Arg>
670 struct __is_location_invariant
671 <__future_base::_State_base::_Setter<_Res, _Arg>>
672 : true_type { };
673
674 // Allow _Task_setter objects to be stored locally in std::function
675 template<typename _Res_ptr, typename _Fn, typename _Res>
676 struct __is_location_invariant
677 <__future_base::_Task_setter<_Res_ptr, _Fn, _Res>>
678 : true_type { };
679
680 /// Common implementation for future and shared_future.
681 template<typename _Res>
682 class __basic_future : public __future_base
683 {
684 protected:
685 typedef shared_ptr<_State_base> __state_type;
686 typedef __future_base::_Result<_Res>& __result_type;
687
688 private:
689 __state_type _M_state;
690
691 public:
692 // Disable copying.
693 __basic_future(const __basic_future&) = delete;
694 __basic_future& operator=(const __basic_future&) = delete;
695
696 bool
697 valid() const noexcept { return static_cast<bool>(_M_state); }
698
699 void
700 wait() const
701 {
702 _State_base::_S_check(_M_state);
703 _M_state->wait();
704 }
705
706 template<typename _Rep, typename _Period>
707 future_status
708 wait_for(const chrono::duration<_Rep, _Period>& __rel) const
709 {
710 _State_base::_S_check(_M_state);
711 return _M_state->wait_for(__rel);
712 }
713
714 template<typename _Clock, typename _Duration>
715 future_status
716 wait_until(const chrono::time_point<_Clock, _Duration>& __abs) const
717 {
718 _State_base::_S_check(_M_state);
719 return _M_state->wait_until(__abs);
720 }
721
722 protected:
723 /// Wait for the state to be ready and rethrow any stored exception
724 __result_type
725 _M_get_result() const
726 {
727 _State_base::_S_check(_M_state);
728 _Result_base& __res = _M_state->wait();
729 if (!(__res._M_error == 0))
730 rethrow_exception(__res._M_error);
731 return static_cast<__result_type>(__res);
732 }
733
734 void _M_swap(__basic_future& __that) noexcept
735 {
736 _M_state.swap(__that._M_state);
737 }
738
739 // Construction of a future by promise::get_future()
740 explicit
741 __basic_future(const __state_type& __state) : _M_state(__state)
742 {
743 _State_base::_S_check(_M_state);
744 _M_state->_M_set_retrieved_flag();
745 }
746
747 // Copy construction from a shared_future
748 explicit
749 __basic_future(const shared_future<_Res>&) noexcept;
750
751 // Move construction from a shared_future
752 explicit
753 __basic_future(shared_future<_Res>&&) noexcept;
754
755 // Move construction from a future
756 explicit
757 __basic_future(future<_Res>&&) noexcept;
758
759 constexpr __basic_future() noexcept : _M_state() { }
760
761 struct _Reset
762 {
763 explicit _Reset(__basic_future& __fut) noexcept : _M_fut(__fut) { }
764 ~_Reset() { _M_fut._M_state.reset(); }
765 __basic_future& _M_fut;
766 };
767 };
768
769
770 /// Primary template for future.
771 template<typename _Res>
772 class future : public __basic_future<_Res>
773 {
774 friend class promise<_Res>;
775 template<typename> friend class packaged_task;
776 template<typename _Fn, typename... _Args>
777 friend future<__async_result_of<_Fn, _Args...>>
778 async(launch, _Fn&&, _Args&&...);
779
780 typedef __basic_future<_Res> _Base_type;
781 typedef typename _Base_type::__state_type __state_type;
782
783 explicit
784 future(const __state_type& __state) : _Base_type(__state) { }
785
786 public:
787 constexpr future() noexcept : _Base_type() { }
788
789 /// Move constructor
790 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
791
792 // Disable copying
793 future(const future&) = delete;
794 future& operator=(const future&) = delete;
795
796 future& operator=(future&& __fut) noexcept
797 {
798 future(std::move(__fut))._M_swap(*this);
799 return *this;
800 }
801
802 /// Retrieving the value
803 _Res
804 get()
805 {
806 typename _Base_type::_Reset __reset(*this);
807 return std::move(this->_M_get_result()._M_value());
808 }
809
810 shared_future<_Res> share() noexcept;
811 };
812
813 /// Partial specialization for future<R&>
814 template<typename _Res>
815 class future<_Res&> : public __basic_future<_Res&>
816 {
817 friend class promise<_Res&>;
818 template<typename> friend class packaged_task;
819 template<typename _Fn, typename... _Args>
820 friend future<__async_result_of<_Fn, _Args...>>
821 async(launch, _Fn&&, _Args&&...);
822
823 typedef __basic_future<_Res&> _Base_type;
824 typedef typename _Base_type::__state_type __state_type;
825
826 explicit
827 future(const __state_type& __state) : _Base_type(__state) { }
828
829 public:
830 constexpr future() noexcept : _Base_type() { }
831
832 /// Move constructor
833 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
834
835 // Disable copying
836 future(const future&) = delete;
837 future& operator=(const future&) = delete;
838
839 future& operator=(future&& __fut) noexcept
840 {
841 future(std::move(__fut))._M_swap(*this);
842 return *this;
843 }
844
845 /// Retrieving the value
846 _Res&
847 get()
848 {
849 typename _Base_type::_Reset __reset(*this);
850 return this->_M_get_result()._M_get();
851 }
852
853 shared_future<_Res&> share() noexcept;
854 };
855
856 /// Explicit specialization for future<void>
857 template<>
858 class future<void> : public __basic_future<void>
859 {
860 friend class promise<void>;
861 template<typename> friend class packaged_task;
862 template<typename _Fn, typename... _Args>
863 friend future<__async_result_of<_Fn, _Args...>>
864 async(launch, _Fn&&, _Args&&...);
865
866 typedef __basic_future<void> _Base_type;
867 typedef typename _Base_type::__state_type __state_type;
868
869 explicit
870 future(const __state_type& __state) : _Base_type(__state) { }
871
872 public:
873 constexpr future() noexcept : _Base_type() { }
874
875 /// Move constructor
876 future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
877
878 // Disable copying
879 future(const future&) = delete;
880 future& operator=(const future&) = delete;
881
882 future& operator=(future&& __fut) noexcept
883 {
884 future(std::move(__fut))._M_swap(*this);
885 return *this;
886 }
887
888 /// Retrieving the value
889 void
890 get()
891 {
892 typename _Base_type::_Reset __reset(*this);
893 this->_M_get_result();
894 }
895
896 shared_future<void> share() noexcept;
897 };
898
899
900 /// Primary template for shared_future.
901 template<typename _Res>
902 class shared_future : public __basic_future<_Res>
903 {
904 typedef __basic_future<_Res> _Base_type;
905
906 public:
907 constexpr shared_future() noexcept : _Base_type() { }
908
909 /// Copy constructor
910 shared_future(const shared_future& __sf) noexcept : _Base_type(__sf) { }
911
912 /// Construct from a future rvalue
913 shared_future(future<_Res>&& __uf) noexcept
914 : _Base_type(std::move(__uf))
915 { }
916
917 /// Construct from a shared_future rvalue
918 shared_future(shared_future&& __sf) noexcept
919 : _Base_type(std::move(__sf))
920 { }
921
922 shared_future& operator=(const shared_future& __sf) noexcept
923 {
924 shared_future(__sf)._M_swap(*this);
925 return *this;
926 }
927
928 shared_future& operator=(shared_future&& __sf) noexcept
929 {
930 shared_future(std::move(__sf))._M_swap(*this);
931 return *this;
932 }
933
934 /// Retrieving the value
935 const _Res&
936 get() const { return this->_M_get_result()._M_value(); }
937 };
938
939 /// Partial specialization for shared_future<R&>
940 template<typename _Res>
941 class shared_future<_Res&> : public __basic_future<_Res&>
942 {
943 typedef __basic_future<_Res&> _Base_type;
944
945 public:
946 constexpr shared_future() noexcept : _Base_type() { }
947
948 /// Copy constructor
949 shared_future(const shared_future& __sf) : _Base_type(__sf) { }
950
951 /// Construct from a future rvalue
952 shared_future(future<_Res&>&& __uf) noexcept
953 : _Base_type(std::move(__uf))
954 { }
955
956 /// Construct from a shared_future rvalue
957 shared_future(shared_future&& __sf) noexcept
958 : _Base_type(std::move(__sf))
959 { }
960
961 shared_future& operator=(const shared_future& __sf)
962 {
963 shared_future(__sf)._M_swap(*this);
964 return *this;
965 }
966
967 shared_future& operator=(shared_future&& __sf) noexcept
968 {
969 shared_future(std::move(__sf))._M_swap(*this);
970 return *this;
971 }
972
973 /// Retrieving the value
974 _Res&
975 get() const { return this->_M_get_result()._M_get(); }
976 };
977
978 /// Explicit specialization for shared_future<void>
979 template<>
980 class shared_future<void> : public __basic_future<void>
981 {
982 typedef __basic_future<void> _Base_type;
983
984 public:
985 constexpr shared_future() noexcept : _Base_type() { }
986
987 /// Copy constructor
988 shared_future(const shared_future& __sf) : _Base_type(__sf) { }
989
990 /// Construct from a future rvalue
991 shared_future(future<void>&& __uf) noexcept
992 : _Base_type(std::move(__uf))
993 { }
994
995 /// Construct from a shared_future rvalue
996 shared_future(shared_future&& __sf) noexcept
997 : _Base_type(std::move(__sf))
998 { }
999
1000 shared_future& operator=(const shared_future& __sf)
1001 {
1002 shared_future(__sf)._M_swap(*this);
1003 return *this;
1004 }
1005
1006 shared_future& operator=(shared_future&& __sf) noexcept
1007 {
1008 shared_future(std::move(__sf))._M_swap(*this);
1009 return *this;
1010 }
1011
1012 // Retrieving the value
1013 void
1014 get() const { this->_M_get_result(); }
1015 };
1016
1017 // Now we can define the protected __basic_future constructors.
1018 template<typename _Res>
1019 inline __basic_future<_Res>::
1020 __basic_future(const shared_future<_Res>& __sf) noexcept
1021 : _M_state(__sf._M_state)
1022 { }
1023
1024 template<typename _Res>
1025 inline __basic_future<_Res>::
1026 __basic_future(shared_future<_Res>&& __sf) noexcept
1027 : _M_state(std::move(__sf._M_state))
1028 { }
1029
1030 template<typename _Res>
1031 inline __basic_future<_Res>::
1032 __basic_future(future<_Res>&& __uf) noexcept
1033 : _M_state(std::move(__uf._M_state))
1034 { }
1035
1036 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1037 // 2556. Wide contract for future::share()
1038 template<typename _Res>
1039 inline shared_future<_Res>
1040 future<_Res>::share() noexcept
1041 { return shared_future<_Res>(std::move(*this)); }
1042
1043 template<typename _Res>
1044 inline shared_future<_Res&>
1045 future<_Res&>::share() noexcept
1046 { return shared_future<_Res&>(std::move(*this)); }
1047
1048 inline shared_future<void>
1049 future<void>::share() noexcept
1050 { return shared_future<void>(std::move(*this)); }
1051
1052 /// Primary template for promise
1053 template<typename _Res>
1054 class promise
1055 {
1056 typedef __future_base::_State_base _State;
1057 typedef __future_base::_Result<_Res> _Res_type;
1058 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1059 template<typename, typename> friend class _State::_Setter;
1060 friend _State;
1061
1062 shared_ptr<_State> _M_future;
1063 _Ptr_type _M_storage;
1064
1065 public:
1066 promise()
1067 : _M_future(std::make_shared<_State>()),
1068 _M_storage(new _Res_type())
1069 { }
1070
1071 promise(promise&& __rhs) noexcept
1072 : _M_future(std::move(__rhs._M_future)),
1073 _M_storage(std::move(__rhs._M_storage))
1074 { }
1075
1076 template<typename _Allocator>
1077 promise(allocator_arg_t, const _Allocator& __a)
1078 : _M_future(std::allocate_shared<_State>(__a)),
1079 _M_storage(__future_base::_S_allocate_result<_Res>(__a))
1080 { }
1081
1082 template<typename _Allocator>
1083 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1084 : _M_future(std::move(__rhs._M_future)),
1085 _M_storage(std::move(__rhs._M_storage))
1086 { }
1087
1088 promise(const promise&) = delete;
1089
1090 ~promise()
1091 {
1092 if (static_cast<bool>(_M_future) && !_M_future.unique())
1093 _M_future->_M_break_promise(std::move(_M_storage));
1094 }
1095
1096 // Assignment
1097 promise&
1098 operator=(promise&& __rhs) noexcept
1099 {
1100 promise(std::move(__rhs)).swap(*this);
1101 return *this;
1102 }
1103
1104 promise& operator=(const promise&) = delete;
1105
1106 void
1107 swap(promise& __rhs) noexcept
1108 {
1109 _M_future.swap(__rhs._M_future);
1110 _M_storage.swap(__rhs._M_storage);
1111 }
1112
1113 // Retrieving the result
1114 future<_Res>
1115 get_future()
1116 { return future<_Res>(_M_future); }
1117
1118 // Setting the result
1119 void
1120 set_value(const _Res& __r)
1121 { _M_state()._M_set_result(_State::__setter(this, __r)); }
1122
1123 void
1124 set_value(_Res&& __r)
1125 { _M_state()._M_set_result(_State::__setter(this, std::move(__r))); }
1126
1127 void
1128 set_exception(exception_ptr __p)
1129 { _M_state()._M_set_result(_State::__setter(__p, this)); }
1130
1131 void
1132 set_value_at_thread_exit(const _Res& __r)
1133 {
1134 _M_state()._M_set_delayed_result(_State::__setter(this, __r),
1135 _M_future);
1136 }
1137
1138 void
1139 set_value_at_thread_exit(_Res&& __r)
1140 {
1141 _M_state()._M_set_delayed_result(
1142 _State::__setter(this, std::move(__r)), _M_future);
1143 }
1144
1145 void
1146 set_exception_at_thread_exit(exception_ptr __p)
1147 {
1148 _M_state()._M_set_delayed_result(_State::__setter(__p, this),
1149 _M_future);
1150 }
1151
1152 private:
1153 _State&
1154 _M_state()
1155 {
1156 __future_base::_State_base::_S_check(_M_future);
1157 return *_M_future;
1158 }
1159 };
1160
1161 template<typename _Res>
1162 inline void
1163 swap(promise<_Res>& __x, promise<_Res>& __y) noexcept
1164 { __x.swap(__y); }
1165
1166 template<typename _Res, typename _Alloc>
1167 struct uses_allocator<promise<_Res>, _Alloc>
1168 : public true_type { };
1169
1170
1171 /// Partial specialization for promise<R&>
1172 template<typename _Res>
1173 class promise<_Res&>
1174 {
1175 typedef __future_base::_State_base _State;
1176 typedef __future_base::_Result<_Res&> _Res_type;
1177 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1178 template<typename, typename> friend class _State::_Setter;
1179 friend _State;
1180
1181 shared_ptr<_State> _M_future;
1182 _Ptr_type _M_storage;
1183
1184 public:
1185 promise()
1186 : _M_future(std::make_shared<_State>()),
1187 _M_storage(new _Res_type())
1188 { }
1189
1190 promise(promise&& __rhs) noexcept
1191 : _M_future(std::move(__rhs._M_future)),
1192 _M_storage(std::move(__rhs._M_storage))
1193 { }
1194
1195 template<typename _Allocator>
1196 promise(allocator_arg_t, const _Allocator& __a)
1197 : _M_future(std::allocate_shared<_State>(__a)),
1198 _M_storage(__future_base::_S_allocate_result<_Res&>(__a))
1199 { }
1200
1201 template<typename _Allocator>
1202 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1203 : _M_future(std::move(__rhs._M_future)),
1204 _M_storage(std::move(__rhs._M_storage))
1205 { }
1206
1207 promise(const promise&) = delete;
1208
1209 ~promise()
1210 {
1211 if (static_cast<bool>(_M_future) && !_M_future.unique())
1212 _M_future->_M_break_promise(std::move(_M_storage));
1213 }
1214
1215 // Assignment
1216 promise&
1217 operator=(promise&& __rhs) noexcept
1218 {
1219 promise(std::move(__rhs)).swap(*this);
1220 return *this;
1221 }
1222
1223 promise& operator=(const promise&) = delete;
1224
1225 void
1226 swap(promise& __rhs) noexcept
1227 {
1228 _M_future.swap(__rhs._M_future);
1229 _M_storage.swap(__rhs._M_storage);
1230 }
1231
1232 // Retrieving the result
1233 future<_Res&>
1234 get_future()
1235 { return future<_Res&>(_M_future); }
1236
1237 // Setting the result
1238 void
1239 set_value(_Res& __r)
1240 { _M_state()._M_set_result(_State::__setter(this, __r)); }
1241
1242 void
1243 set_exception(exception_ptr __p)
1244 { _M_state()._M_set_result(_State::__setter(__p, this)); }
1245
1246 void
1247 set_value_at_thread_exit(_Res& __r)
1248 {
1249 _M_state()._M_set_delayed_result(_State::__setter(this, __r),
1250 _M_future);
1251 }
1252
1253 void
1254 set_exception_at_thread_exit(exception_ptr __p)
1255 {
1256 _M_state()._M_set_delayed_result(_State::__setter(__p, this),
1257 _M_future);
1258 }
1259
1260 private:
1261 _State&
1262 _M_state()
1263 {
1264 __future_base::_State_base::_S_check(_M_future);
1265 return *_M_future;
1266 }
1267 };
1268
1269 /// Explicit specialization for promise<void>
1270 template<>
1271 class promise<void>
1272 {
1273 typedef __future_base::_State_base _State;
1274 typedef __future_base::_Result<void> _Res_type;
1275 typedef __future_base::_Ptr<_Res_type> _Ptr_type;
1276 template<typename, typename> friend class _State::_Setter;
1277 friend _State;
1278
1279 shared_ptr<_State> _M_future;
1280 _Ptr_type _M_storage;
1281
1282 public:
1283 promise()
1284 : _M_future(std::make_shared<_State>()),
1285 _M_storage(new _Res_type())
1286 { }
1287
1288 promise(promise&& __rhs) noexcept
1289 : _M_future(std::move(__rhs._M_future)),
1290 _M_storage(std::move(__rhs._M_storage))
1291 { }
1292
1293 template<typename _Allocator>
1294 promise(allocator_arg_t, const _Allocator& __a)
1295 : _M_future(std::allocate_shared<_State>(__a)),
1296 _M_storage(__future_base::_S_allocate_result<void>(__a))
1297 { }
1298
1299 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1300 // 2095. missing constructors needed for uses-allocator construction
1301 template<typename _Allocator>
1302 promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1303 : _M_future(std::move(__rhs._M_future)),
1304 _M_storage(std::move(__rhs._M_storage))
1305 { }
1306
1307 promise(const promise&) = delete;
1308
1309 ~promise()
1310 {
1311 if (static_cast<bool>(_M_future) && !_M_future.unique())
1312 _M_future->_M_break_promise(std::move(_M_storage));
1313 }
1314
1315 // Assignment
1316 promise&
1317 operator=(promise&& __rhs) noexcept
1318 {
1319 promise(std::move(__rhs)).swap(*this);
1320 return *this;
1321 }
1322
1323 promise& operator=(const promise&) = delete;
1324
1325 void
1326 swap(promise& __rhs) noexcept
1327 {
1328 _M_future.swap(__rhs._M_future);
1329 _M_storage.swap(__rhs._M_storage);
1330 }
1331
1332 // Retrieving the result
1333 future<void>
1334 get_future()
1335 { return future<void>(_M_future); }
1336
1337 // Setting the result
1338 void
1339 set_value()
1340 { _M_state()._M_set_result(_State::__setter(this)); }
1341
1342 void
1343 set_exception(exception_ptr __p)
1344 { _M_state()._M_set_result(_State::__setter(__p, this)); }
1345
1346 void
1347 set_value_at_thread_exit()
1348 { _M_state()._M_set_delayed_result(_State::__setter(this), _M_future); }
1349
1350 void
1351 set_exception_at_thread_exit(exception_ptr __p)
1352 {
1353 _M_state()._M_set_delayed_result(_State::__setter(__p, this),
1354 _M_future);
1355 }
1356
1357 private:
1358 _State&
1359 _M_state()
1360 {
1361 __future_base::_State_base::_S_check(_M_future);
1362 return *_M_future;
1363 }
1364 };
1365
1366 template<typename _Ptr_type, typename _Fn, typename _Res>
1367 struct __future_base::_Task_setter
1368 {
1369 // Invoke the function and provide the result to the caller.
1370 _Ptr_type operator()() const
1371 {
1372 __try
1373 {
1374 (*_M_result)->_M_set((*_M_fn)());
1375 }
1376 __catch(const __cxxabiv1::__forced_unwind&)
1377 {
1378 __throw_exception_again; // will cause broken_promise
1379 }
1380 __catch(...)
1381 {
1382 (*_M_result)->_M_error = current_exception();
1383 }
1384 return std::move(*_M_result);
1385 }
1386 _Ptr_type* _M_result;
1387 _Fn* _M_fn;
1388 };
1389
1390 template<typename _Ptr_type, typename _Fn>
1391 struct __future_base::_Task_setter<_Ptr_type, _Fn, void>
1392 {
1393 _Ptr_type operator()() const
1394 {
1395 __try
1396 {
1397 (*_M_fn)();
1398 }
1399 __catch(const __cxxabiv1::__forced_unwind&)
1400 {
1401 __throw_exception_again; // will cause broken_promise
1402 }
1403 __catch(...)
1404 {
1405 (*_M_result)->_M_error = current_exception();
1406 }
1407 return std::move(*_M_result);
1408 }
1409 _Ptr_type* _M_result;
1410 _Fn* _M_fn;
1411 };
1412
1413 // Holds storage for a packaged_task's result.
1414 template<typename _Res, typename... _Args>
1415 struct __future_base::_Task_state_base<_Res(_Args...)>
1416 : __future_base::_State_base
1417 {
1418 typedef _Res _Res_type;
1419
1420 template<typename _Alloc>
1421 _Task_state_base(const _Alloc& __a)
1422 : _M_result(_S_allocate_result<_Res>(__a))
1423 { }
1424
1425 // Invoke the stored task and make the state ready.
1426 virtual void
1427 _M_run(_Args&&... __args) = 0;
1428
1429 // Invoke the stored task and make the state ready at thread exit.
1430 virtual void
1431 _M_run_delayed(_Args&&... __args, weak_ptr<_State_base>) = 0;
1432
1433 virtual shared_ptr<_Task_state_base>
1434 _M_reset() = 0;
1435
1436 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1437 _Ptr_type _M_result;
1438 };
1439
1440 // Holds a packaged_task's stored task.
1441 template<typename _Fn, typename _Alloc, typename _Res, typename... _Args>
1442 struct __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)> final
1443 : __future_base::_Task_state_base<_Res(_Args...)>
1444 {
1445 template<typename _Fn2>
1446 _Task_state(_Fn2&& __fn, const _Alloc& __a)
1447 : _Task_state_base<_Res(_Args...)>(__a),
1448 _M_impl(std::forward<_Fn2>(__fn), __a)
1449 { }
1450
1451 private:
1452 virtual void
1453 _M_run(_Args&&... __args)
1454 {
1455 auto __boundfn = [&] () -> _Res {
1456 return std::__invoke_r<_Res>(_M_impl._M_fn,
1457 std::forward<_Args>(__args)...);
1458 };
1459 this->_M_set_result(_S_task_setter(this->_M_result, __boundfn));
1460 }
1461
1462 virtual void
1463 _M_run_delayed(_Args&&... __args, weak_ptr<_State_base> __self)
1464 {
1465 auto __boundfn = [&] () -> _Res {
1466 return std::__invoke_r<_Res>(_M_impl._M_fn,
1467 std::forward<_Args>(__args)...);
1468 };
1469 this->_M_set_delayed_result(_S_task_setter(this->_M_result, __boundfn),
1470 std::move(__self));
1471 }
1472
1473 virtual shared_ptr<_Task_state_base<_Res(_Args...)>>
1474 _M_reset();
1475
1476 struct _Impl : _Alloc
1477 {
1478 template<typename _Fn2>
1479 _Impl(_Fn2&& __fn, const _Alloc& __a)
1480 : _Alloc(__a), _M_fn(std::forward<_Fn2>(__fn)) { }
1481 _Fn _M_fn;
1482 } _M_impl;
1483 };
1484
1485 template<typename _Signature, typename _Fn,
1486 typename _Alloc = std::allocator<int>>
1487 static shared_ptr<__future_base::_Task_state_base<_Signature>>
1488 __create_task_state(_Fn&& __fn, const _Alloc& __a = _Alloc())
1489 {
1490 typedef typename decay<_Fn>::type _Fn2;
1491 typedef __future_base::_Task_state<_Fn2, _Alloc, _Signature> _State;
1492 return std::allocate_shared<_State>(__a, std::forward<_Fn>(__fn), __a);
1493 }
1494
1495 template<typename _Fn, typename _Alloc, typename _Res, typename... _Args>
1496 shared_ptr<__future_base::_Task_state_base<_Res(_Args...)>>
1497 __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)>::_M_reset()
1498 {
1499 return __create_task_state<_Res(_Args...)>(std::move(_M_impl._M_fn),
1500 static_cast<_Alloc&>(_M_impl));
1501 }
1502
1503 /// packaged_task
1504 template<typename _Res, typename... _ArgTypes>
1505 class packaged_task<_Res(_ArgTypes...)>
1506 {
1507 typedef __future_base::_Task_state_base<_Res(_ArgTypes...)> _State_type;
1508 shared_ptr<_State_type> _M_state;
1509
1510 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1511 // 3039. Unnecessary decay in thread and packaged_task
1512 template<typename _Fn, typename _Fn2 = __remove_cvref_t<_Fn>>
1513 using __not_same
1514 = typename enable_if<!is_same<packaged_task, _Fn2>::value>::type;
1515
1516 public:
1517 // Construction and destruction
1518 packaged_task() noexcept { }
1519
1520 template<typename _Fn, typename = __not_same<_Fn>>
1521 explicit
1522 packaged_task(_Fn&& __fn)
1523 : _M_state(
1524 __create_task_state<_Res(_ArgTypes...)>(std::forward<_Fn>(__fn)))
1525 { }
1526
1527#if __cplusplus < 201703L
1528 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1529 // 2097. packaged_task constructors should be constrained
1530 // 2407. [this constructor should not be] explicit
1531 // 2921. packaged_task and type-erased allocators
1532 template<typename _Fn, typename _Alloc, typename = __not_same<_Fn>>
1533 packaged_task(allocator_arg_t, const _Alloc& __a, _Fn&& __fn)
1534 : _M_state(__create_task_state<_Res(_ArgTypes...)>(
1535 std::forward<_Fn>(__fn), __a))
1536 { }
1537
1538 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1539 // 2095. missing constructors needed for uses-allocator construction
1540 template<typename _Allocator>
1541 packaged_task(allocator_arg_t, const _Allocator& __a) noexcept
1542 { }
1543
1544 template<typename _Allocator>
1545 packaged_task(allocator_arg_t, const _Allocator&,
1546 const packaged_task&) = delete;
1547
1548 template<typename _Allocator>
1549 packaged_task(allocator_arg_t, const _Allocator&,
1550 packaged_task&& __other) noexcept
1551 { this->swap(__other); }
1552#endif
1553
1554 ~packaged_task()
1555 {
1556 if (static_cast<bool>(_M_state) && !_M_state.unique())
1557 _M_state->_M_break_promise(std::move(_M_state->_M_result));
1558 }
1559
1560 // No copy
1561 packaged_task(const packaged_task&) = delete;
1562 packaged_task& operator=(const packaged_task&) = delete;
1563
1564 // Move support
1565 packaged_task(packaged_task&& __other) noexcept
1566 { this->swap(__other); }
1567
1568 packaged_task& operator=(packaged_task&& __other) noexcept
1569 {
1570 packaged_task(std::move(__other)).swap(*this);
1571 return *this;
1572 }
1573
1574 void
1575 swap(packaged_task& __other) noexcept
1576 { _M_state.swap(__other._M_state); }
1577
1578 bool
1579 valid() const noexcept
1580 { return static_cast<bool>(_M_state); }
1581
1582 // Result retrieval
1583 future<_Res>
1584 get_future()
1585 { return future<_Res>(_M_state); }
1586
1587 // Execution
1588 void
1589 operator()(_ArgTypes... __args)
1590 {
1591 __future_base::_State_base::_S_check(_M_state);
1592 _M_state->_M_run(std::forward<_ArgTypes>(__args)...);
1593 }
1594
1595 void
1596 make_ready_at_thread_exit(_ArgTypes... __args)
1597 {
1598 __future_base::_State_base::_S_check(_M_state);
1599 _M_state->_M_run_delayed(std::forward<_ArgTypes>(__args)..., _M_state);
1600 }
1601
1602 void
1603 reset()
1604 {
1605 __future_base::_State_base::_S_check(_M_state);
1606 packaged_task __tmp;
1607 __tmp._M_state = _M_state;
1608 _M_state = _M_state->_M_reset();
1609 }
1610 };
1611
1612 /// swap
1613 template<typename _Res, typename... _ArgTypes>
1614 inline void
1615 swap(packaged_task<_Res(_ArgTypes...)>& __x,
1616 packaged_task<_Res(_ArgTypes...)>& __y) noexcept
1617 { __x.swap(__y); }
1618
1619#if __cplusplus < 201703L
1620 // _GLIBCXX_RESOLVE_LIB_DEFECTS
1621 // 2976. Dangling uses_allocator specialization for packaged_task
1622 template<typename _Res, typename _Alloc>
1623 struct uses_allocator<packaged_task<_Res>, _Alloc>
1624 : public true_type { };
1625#endif
1626
1627 // Shared state created by std::async().
1628 // Holds a deferred function and storage for its result.
1629 template<typename _BoundFn, typename _Res>
1630 class __future_base::_Deferred_state final
1631 : public __future_base::_State_base
1632 {
1633 public:
1634 explicit
1635 _Deferred_state(_BoundFn&& __fn)
1636 : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
1637 { }
1638
1639 private:
1640 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1641 _Ptr_type _M_result;
1642 _BoundFn _M_fn;
1643
1644 // Run the deferred function.
1645 virtual void
1646 _M_complete_async()
1647 {
1648 // Multiple threads can call a waiting function on the future and
1649 // reach this point at the same time. The call_once in _M_set_result
1650 // ensures only the first one run the deferred function, stores the
1651 // result in _M_result, swaps that with the base _M_result and makes
1652 // the state ready. Tell _M_set_result to ignore failure so all later
1653 // calls do nothing.
1654 _M_set_result(_S_task_setter(_M_result, _M_fn), true);
1655 }
1656
1657 // Caller should check whether the state is ready first, because this
1658 // function will return true even after the deferred function has run.
1659 virtual bool _M_is_deferred_future() const { return true; }
1660 };
1661
1662 // Common functionality hoisted out of the _Async_state_impl template.
1663 class __future_base::_Async_state_commonV2
1664 : public __future_base::_State_base
1665 {
1666 protected:
1667 ~_Async_state_commonV2() = default;
1668
1669 // Make waiting functions block until the thread completes, as if joined.
1670 //
1671 // This function is used by wait() to satisfy the first requirement below
1672 // and by wait_for() / wait_until() to satisfy the second.
1673 //
1674 // [futures.async]:
1675 //
1676 // - a call to a waiting function on an asynchronous return object that
1677 // shares the shared state created by this async call shall block until
1678 // the associated thread has completed, as if joined, or else time out.
1679 //
1680 // - the associated thread completion synchronizes with the return from
1681 // the first function that successfully detects the ready status of the
1682 // shared state or with the return from the last function that releases
1683 // the shared state, whichever happens first.
1684 virtual void _M_complete_async() { _M_join(); }
1685
1686 void _M_join() { std::call_once(_M_once, &thread::join, &_M_thread); }
1687
1688 thread _M_thread;
1689 once_flag _M_once;
1690 };
1691
1692 // Shared state created by std::async().
1693 // Starts a new thread that runs a function and makes the shared state ready.
1694 template<typename _BoundFn, typename _Res>
1695 class __future_base::_Async_state_impl final
1696 : public __future_base::_Async_state_commonV2
1697 {
1698 public:
1699 explicit
1700 _Async_state_impl(_BoundFn&& __fn)
1701 : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
1702 {
1703 _M_thread = std::thread{ [this] {
1704 __try
1705 {
1706 _M_set_result(_S_task_setter(_M_result, _M_fn));
1707 }
1708 __catch (const __cxxabiv1::__forced_unwind&)
1709 {
1710 // make the shared state ready on thread cancellation
1711 if (static_cast<bool>(_M_result))
1712 this->_M_break_promise(std::move(_M_result));
1713 __throw_exception_again;
1714 }
1715 } };
1716 }
1717
1718 // Must not destroy _M_result and _M_fn until the thread finishes.
1719 // Call join() directly rather than through _M_join() because no other
1720 // thread can be referring to this state if it is being destroyed.
1721 ~_Async_state_impl() { if (_M_thread.joinable()) _M_thread.join(); }
1722
1723 private:
1724 typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1725 _Ptr_type _M_result;
1726 _BoundFn _M_fn;
1727 };
1728
1729 template<typename _BoundFn>
1730 inline std::shared_ptr<__future_base::_State_base>
1731 __future_base::_S_make_deferred_state(_BoundFn&& __fn)
1732 {
1733 typedef typename remove_reference<_BoundFn>::type __fn_type;
1734 typedef _Deferred_state<__fn_type> __state_type;
1735 return std::make_shared<__state_type>(std::move(__fn));
1736 }
1737
1738 template<typename _BoundFn>
1739 inline std::shared_ptr<__future_base::_State_base>
1740 __future_base::_S_make_async_state(_BoundFn&& __fn)
1741 {
1742 typedef typename remove_reference<_BoundFn>::type __fn_type;
1743 typedef _Async_state_impl<__fn_type> __state_type;
1744 return std::make_shared<__state_type>(std::move(__fn));
1745 }
1746
1747
1748 /// async
1749 template<typename _Fn, typename... _Args>
1750 _GLIBCXX_NODISCARD future<__async_result_of<_Fn, _Args...>>
1751 async(launch __policy, _Fn&& __fn, _Args&&... __args)
1752 {
1753 std::shared_ptr<__future_base::_State_base> __state;
1754 if ((__policy & launch::async) == launch::async)
1755 {
1756 __try
1757 {
1758 __state = __future_base::_S_make_async_state(
1759 std::thread::__make_invoker(std::forward<_Fn>(__fn),
1760 std::forward<_Args>(__args)...)
1761 );
1762 }
1763#if __cpp_exceptions
1764 catch(const system_error& __e)
1765 {
1766 if (__e.code() != errc::resource_unavailable_try_again
1767 || (__policy & launch::deferred) != launch::deferred)
1768 throw;
1769 }
1770#endif
1771 }
1772 if (!__state)
1773 {
1774 __state = __future_base::_S_make_deferred_state(
1775 std::thread::__make_invoker(std::forward<_Fn>(__fn),
1776 std::forward<_Args>(__args)...));
1777 }
1778 return future<__async_result_of<_Fn, _Args...>>(__state);
1779 }
1780
1781 /// async, potential overload
1782 template<typename _Fn, typename... _Args>
1783 _GLIBCXX_NODISCARD inline future<__async_result_of<_Fn, _Args...>>
1784 async(_Fn&& __fn, _Args&&... __args)
1785 {
1786 return std::async(launch::async|launch::deferred,
1787 std::forward<_Fn>(__fn),
1788 std::forward<_Args>(__args)...);
1789 }
1790
1791#endif // _GLIBCXX_ASYNC_ABI_COMPAT
1792#endif // _GLIBCXX_HAS_GTHREADS
1793
1794 /// @} group futures
1795_GLIBCXX_END_NAMESPACE_VERSION
1796} // namespace
1797
1798#endif // C++11
1799
1800#endif // _GLIBCXX_FUTURE