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 1801