libstdc++-v3/include/std/future

   1 // <future> -*- C++ -*-
   2
   3 // Copyright (C) 2009-2013 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 <functional>
  39 #include <mutex>
  40 #include <thread>
  41 #include <condition_variable>
  42 #include <system_error>
  43 #include <atomic>
  44 #include <bits/functexcept.h>
  45 #include <bits/unique_ptr.h>
  46 #include <bits/shared_ptr.h>
  47 #include <bits/uses_allocator.h>
  48 #include <bits/alloc_traits.h>
  49 #include <ext/aligned_buffer.h>
  50
  51 namespace std _GLIBCXX_VISIBILITY(default)
  52 {
  53 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  54
  55   /**
  56    * @defgroup futures Futures
  57    * @ingroup concurrency
  58    *
  59    * Classes for futures support.
  60    * @{
  61    */
  62
  63   /// Error code for futures
  64   enum class future_errc
  65   {
  66     future_already_retrieved = 1,
  67     promise_already_satisfied,
  68     no_state,
  69     broken_promise
  70   };
  71
  72   /// Specialization.
  73   template<>
  74     struct is_error_code_enum<future_errc> : public true_type { };
  75
  76   /// Points to a statically-allocated object derived from error_category.
  77   const error_category&
  78   future_category() noexcept;
  79
  80   /// Overload for make_error_code.
  81   inline error_code
  82   make_error_code(future_errc __errc) noexcept
  83   { return error_code(static_cast<int>(__errc), future_category()); }
  84
  85   /// Overload for make_error_condition.
  86   inline error_condition
  87   make_error_condition(future_errc __errc) noexcept
  88   { return error_condition(static_cast<int>(__errc), future_category()); }
  89
  90   /**
  91    *  @brief Exception type thrown by futures.
  92    *  @ingroup exceptions
  93    */
  94   class future_error : public logic_error
  95   {
  96     error_code                  _M_code;
  97
  98   public:
  99     explicit future_error(error_code __ec)
 100     : logic_error("std::future_error"), _M_code(__ec)
 101     { }
 102
 103     virtual ~future_error() noexcept;
 104
 105     virtual const char*
 106     what() const noexcept;
 107
 108     const error_code&
 109     code() const noexcept { return _M_code; }
 110   };
 111
 112   // Forward declarations.
 113   template<typename _Res>
 114     class future;
 115
 116   template<typename _Res>
 117     class shared_future;
 118
 119   template<typename _Signature>
 120     class packaged_task;
 121
 122   template<typename _Res>
 123     class promise;
 124
 125   /// Launch code for futures
 126   enum class launch
 127   {
 128     async = 1,
 129     deferred = 2
 130   };
 131
 132   constexpr launch operator&(launch __x, launch __y)
 133   {
 134     return static_cast<launch>(
 135         static_cast<int>(__x) & static_cast<int>(__y));
 136   }
 137
 138   constexpr launch operator|(launch __x, launch __y)
 139   {
 140     return static_cast<launch>(
 141         static_cast<int>(__x) | static_cast<int>(__y));
 142   }
 143
 144   constexpr launch operator^(launch __x, launch __y)
 145   {
 146     return static_cast<launch>(
 147         static_cast<int>(__x) ^ static_cast<int>(__y));
 148   }
 149
 150   constexpr launch operator~(launch __x)
 151   { return static_cast<launch>(~static_cast<int>(__x)); }
 152
 153   inline launch& operator&=(launch& __x, launch __y)
 154   { return __x = __x & __y; }
 155
 156   inline launch& operator|=(launch& __x, launch __y)
 157   { return __x = __x | __y; }
 158
 159   inline launch& operator^=(launch& __x, launch __y)
 160   { return __x = __x ^ __y; }
 161
 162   /// Status code for futures
 163   enum class future_status
 164   {
 165     ready,
 166     timeout,
 167     deferred
 168   };
 169
 170   template<typename _Fn, typename... _Args>
 171     future<typename result_of<_Fn(_Args...)>::type>
 172     async(launch __policy, _Fn&& __fn, _Args&&... __args);
 173
 174   template<typename _Fn, typename... _Args>
 175     future<typename result_of<_Fn(_Args...)>::type>
 176     async(_Fn&& __fn, _Args&&... __args);
 177
 178 #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1) \
 179   && (ATOMIC_INT_LOCK_FREE > 1)
 180
 181   /// Base class and enclosing scope.
 182   struct __future_base
 183   {
 184     /// Base class for results.
 185     struct _Result_base
 186     {
 187       exception_ptr             _M_error;
 188
 189       _Result_base(const _Result_base&) = delete;
 190       _Result_base& operator=(const _Result_base&) = delete;
 191
 192       // _M_destroy() allows derived classes to control deallocation
 193       virtual void _M_destroy() = 0;
 194
 195       struct _Deleter
 196       {
 197         void operator()(_Result_base* __fr) const { __fr->_M_destroy(); }
 198       };
 199
 200     protected:
 201       _Result_base();
 202       virtual ~_Result_base();
 203     };
 204
 205     /// Result.
 206     template<typename _Res>
 207       struct _Result : _Result_base
 208       {
 209       private:
 210         __gnu_cxx::__aligned_buffer<_Res>       _M_storage;
 211         bool                                    _M_initialized;
 212
 213       public:
 214         typedef _Res result_type;
 215
 216         _Result() noexcept : _M_initialized() { }
 217
 218         ~_Result()
 219         {
 220           if (_M_initialized)
 221             _M_value().~_Res();
 222         }
 223
 224         // Return lvalue, future will add const or rvalue-reference
 225         _Res&
 226         _M_value() noexcept { return *_M_storage._M_ptr(); }
 227
 228         void
 229         _M_set(const _Res& __res)
 230         {
 231           ::new (_M_storage._M_addr()) _Res(__res);
 232           _M_initialized = true;
 233         }
 234
 235         void
 236         _M_set(_Res&& __res)
 237         {
 238           ::new (_M_storage._M_addr()) _Res(std::move(__res));
 239           _M_initialized = true;
 240         }
 241
 242       private:
 243         void _M_destroy() { delete this; }
 244     };
 245
 246     /// A unique_ptr based on the instantiating type.
 247     template<typename _Res>
 248       using _Ptr = unique_ptr<_Res, _Result_base::_Deleter>;
 249
 250     /// Result_alloc.
 251     template<typename _Res, typename _Alloc>
 252       struct _Result_alloc final : _Result<_Res>, _Alloc
 253       {
 254         typedef typename allocator_traits<_Alloc>::template
 255           rebind_alloc<_Result_alloc> __allocator_type;
 256
 257         explicit
 258         _Result_alloc(const _Alloc& __a) : _Result<_Res>(), _Alloc(__a)
 259         { }
 260
 261       private:
 262         void _M_destroy()
 263         {
 264           typedef allocator_traits<__allocator_type> __traits;
 265           __allocator_type __a(*this);
 266           __traits::destroy(__a, this);
 267           __traits::deallocate(__a, this, 1);
 268         }
 269       };
 270
 271     template<typename _Res, typename _Allocator>
 272       static _Ptr<_Result_alloc<_Res, _Allocator>>
 273       _S_allocate_result(const _Allocator& __a)
 274       {
 275         typedef _Result_alloc<_Res, _Allocator> __result_type;
 276         typedef allocator_traits<typename __result_type::__allocator_type>
 277           __traits;
 278         typename __traits::allocator_type __a2(__a);
 279         __result_type* __p = __traits::allocate(__a2, 1);
 280         __try
 281           {
 282             __traits::construct(__a2, __p, __a);
 283           }
 284         __catch(...)
 285           {
 286             __traits::deallocate(__a2, __p, 1);
 287             __throw_exception_again;
 288           }
 289         return _Ptr<__result_type>(__p);
 290       }
 291
 292     template<typename _Res, typename _Tp>
 293       static _Ptr<_Result<_Res>>
 294       _S_allocate_result(const std::allocator<_Tp>& __a)
 295       {
 296         return _Ptr<_Result<_Res>>(new _Result<_Res>);
 297       }
 298
 299     /// Base class for state between a promise and one or more
 300     /// associated futures.
 301     class _State_baseV2
 302     {
 303       typedef _Ptr<_Result_base> _Ptr_type;
 304
 305       _Ptr_type                 _M_result;
 306       mutex                     _M_mutex;
 307       condition_variable        _M_cond;
 308       atomic_flag               _M_retrieved;
 309       once_flag                 _M_once;
 310
 311     public:
 312       _State_baseV2() noexcept : _M_result(), _M_retrieved(ATOMIC_FLAG_INIT)
 313         { }
 314       _State_baseV2(const _State_baseV2&) = delete;
 315       _State_baseV2& operator=(const _State_baseV2&) = delete;
 316       virtual ~_State_baseV2() = default;
 317
 318       _Result_base&
 319       wait()
 320       {
 321         _M_complete_async();
 322         unique_lock<mutex> __lock(_M_mutex);
 323         _M_cond.wait(__lock, [&] { return _M_ready(); });
 324         return *_M_result;
 325       }
 326
 327       template<typename _Rep, typename _Period>
 328         future_status
 329         wait_for(const chrono::duration<_Rep, _Period>& __rel)
 330         {
 331           unique_lock<mutex> __lock(_M_mutex);
 332           if (_M_ready())
 333             return future_status::ready;
 334           if (_M_has_deferred())
 335             return future_status::deferred;
 336           if (_M_cond.wait_for(__lock, __rel, [&] { return _M_ready(); }))
 337             {
 338               // _GLIBCXX_RESOLVE_LIB_DEFECTS
 339               // 2100.  timed waiting functions must also join
 340               _M_complete_async();
 341               return future_status::ready;
 342             }
 343           return future_status::timeout;
 344         }
 345
 346       template<typename _Clock, typename _Duration>
 347         future_status
 348         wait_until(const chrono::time_point<_Clock, _Duration>& __abs)
 349         {
 350           unique_lock<mutex> __lock(_M_mutex);
 351           if (_M_ready())
 352             return future_status::ready;
 353           if (_M_has_deferred())
 354             return future_status::deferred;
 355           if (_M_cond.wait_until(__lock, __abs, [&] { return _M_ready(); }))
 356             {
 357               // _GLIBCXX_RESOLVE_LIB_DEFECTS
 358               // 2100.  timed waiting functions must also join
 359               _M_complete_async();
 360               return future_status::ready;
 361             }
 362           return future_status::timeout;
 363         }
 364
 365       void
 366       _M_set_result(function<_Ptr_type()> __res, bool __ignore_failure = false)
 367       {
 368         bool __set = __ignore_failure;
 369         // all calls to this function are serialized,
 370         // side-effects of invoking __res only happen once
 371         call_once(_M_once, &_State_baseV2::_M_do_set, this, ref(__res),
 372             ref(__set));
 373         if (!__set)
 374           __throw_future_error(int(future_errc::promise_already_satisfied));
 375       }
 376
 377       void
 378       _M_break_promise(_Ptr_type __res)
 379       {
 380         if (static_cast<bool>(__res))
 381           {
 382             error_code __ec(make_error_code(future_errc::broken_promise));
 383             __res->_M_error = make_exception_ptr(future_error(__ec));
 384             {
 385               lock_guard<mutex> __lock(_M_mutex);
 386               _M_result.swap(__res);
 387             }
 388             _M_cond.notify_all();
 389           }
 390       }
 391
 392       // Called when this object is passed to a future.
 393       void
 394       _M_set_retrieved_flag()
 395       {
 396         if (_M_retrieved.test_and_set())
 397           __throw_future_error(int(future_errc::future_already_retrieved));
 398       }
 399
 400       template<typename _Res, typename _Arg>
 401         struct _Setter;
 402
 403       // set lvalues
 404       template<typename _Res, typename _Arg>
 405         struct _Setter<_Res, _Arg&>
 406         {
 407           // check this is only used by promise<R>::set_value(const R&)
 408           // or promise<R>::set_value(R&)
 409           static_assert(is_same<_Res, _Arg&>::value  // promise<R&>
 410               || is_same<const _Res, _Arg>::value,  // promise<R>
 411               "Invalid specialisation");
 412
 413           typename promise<_Res>::_Ptr_type operator()()
 414           {
 415             _State_baseV2::_S_check(_M_promise->_M_future);
 416             _M_promise->_M_storage->_M_set(_M_arg);
 417             return std::move(_M_promise->_M_storage);
 418           }
 419           promise<_Res>*    _M_promise;
 420           _Arg&             _M_arg;
 421         };
 422
 423       // set rvalues
 424       template<typename _Res>
 425         struct _Setter<_Res, _Res&&>
 426         {
 427           typename promise<_Res>::_Ptr_type operator()()
 428           {
 429             _State_baseV2::_S_check(_M_promise->_M_future);
 430             _M_promise->_M_storage->_M_set(std::move(_M_arg));
 431             return std::move(_M_promise->_M_storage);
 432           }
 433           promise<_Res>*    _M_promise;
 434           _Res&             _M_arg;
 435         };
 436
 437       struct __exception_ptr_tag { };
 438
 439       // set exceptions
 440       template<typename _Res>
 441         struct _Setter<_Res, __exception_ptr_tag>
 442         {
 443           typename promise<_Res>::_Ptr_type operator()()
 444           {
 445             _State_baseV2::_S_check(_M_promise->_M_future);
 446             _M_promise->_M_storage->_M_error = _M_ex;
 447             return std::move(_M_promise->_M_storage);
 448           }
 449
 450           promise<_Res>*   _M_promise;
 451           exception_ptr&    _M_ex;
 452         };
 453
 454       template<typename _Res, typename _Arg>
 455         static _Setter<_Res, _Arg&&>
 456         __setter(promise<_Res>* __prom, _Arg&& __arg)
 457         {
 458           return _Setter<_Res, _Arg&&>{ __prom, __arg };
 459         }
 460
 461       template<typename _Res>
 462         static _Setter<_Res, __exception_ptr_tag>
 463         __setter(exception_ptr& __ex, promise<_Res>* __prom)
 464         {
 465           return _Setter<_Res, __exception_ptr_tag>{ __prom, __ex };
 466         }
 467
 468       static _Setter<void, void>
 469       __setter(promise<void>* __prom);
 470
 471       template<typename _Tp>
 472         static void
 473         _S_check(const shared_ptr<_Tp>& __p)
 474         {
 475           if (!static_cast<bool>(__p))
 476             __throw_future_error((int)future_errc::no_state);
 477         }
 478
 479     private:
 480       void
 481       _M_do_set(function<_Ptr_type()>& __f, bool& __set)
 482       {
 483         _Ptr_type __res = __f();
 484         {
 485           lock_guard<mutex> __lock(_M_mutex);
 486           _M_result.swap(__res);
 487         }
 488         _M_cond.notify_all();
 489         __set = true;
 490       }
 491
 492       bool _M_ready() const noexcept { return static_cast<bool>(_M_result); }
 493
 494       // Wait for completion of async function.
 495       virtual void _M_complete_async() { }
 496
 497       // Return true if state contains a deferred function.
 498       virtual bool _M_has_deferred() const { return false; }
 499     };
 500
 501 #ifdef _GLIBCXX_ASYNC_ABI_COMPAT
 502     class _State_base;
 503     class _Async_state_common;
 504 #else
 505     using _State_base = _State_baseV2;
 506     class _Async_state_commonV2;
 507 #endif
 508
 509     template<typename _BoundFn, typename = typename _BoundFn::result_type>
 510       class _Deferred_state;
 511
 512     template<typename _BoundFn, typename = typename _BoundFn::result_type>
 513       class _Async_state_impl;
 514
 515     template<typename _Signature>
 516       class _Task_state_base;
 517
 518     template<typename _Fn, typename _Alloc, typename _Signature>
 519       class _Task_state;
 520
 521     template<typename _BoundFn>
 522       static std::shared_ptr<_State_base>
 523       _S_make_deferred_state(_BoundFn&& __fn);
 524
 525     template<typename _BoundFn>
 526       static std::shared_ptr<_State_base>
 527       _S_make_async_state(_BoundFn&& __fn);
 528
 529     template<typename _Res_ptr,
 530              typename _Res = typename _Res_ptr::element_type::result_type>
 531       struct _Task_setter;
 532
 533     template<typename _Res_ptr, typename _BoundFn>
 534       static _Task_setter<_Res_ptr>
 535       _S_task_setter(_Res_ptr& __ptr, _BoundFn&& __call)
 536       {
 537         return _Task_setter<_Res_ptr>{ __ptr, std::ref(__call) };
 538       }
 539   };
 540
 541   /// Partial specialization for reference types.
 542   template<typename _Res>
 543     struct __future_base::_Result<_Res&> : __future_base::_Result_base
 544     {
 545       typedef _Res& result_type;
 546
 547       _Result() noexcept : _M_value_ptr() { }
 548
 549       void _M_set(_Res& __res) noexcept { _M_value_ptr = &__res; }
 550
 551       _Res& _M_get() noexcept { return *_M_value_ptr; }
 552
 553     private:
 554       _Res*                     _M_value_ptr;
 555
 556       void _M_destroy() { delete this; }
 557     };
 558
 559   /// Explicit specialization for void.
 560   template<>
 561     struct __future_base::_Result<void> : __future_base::_Result_base
 562     {
 563       typedef void result_type;
 564
 565     private:
 566       void _M_destroy() { delete this; }
 567     };
 568
 569 #ifndef _GLIBCXX_ASYNC_ABI_COMPAT
 570
 571   /// Common implementation for future and shared_future.
 572   template<typename _Res>
 573     class __basic_future : public __future_base
 574     {
 575     protected:
 576       typedef shared_ptr<_State_base>           __state_type;
 577       typedef __future_base::_Result<_Res>&     __result_type;
 578
 579     private:
 580       __state_type              _M_state;
 581
 582     public:
 583       // Disable copying.
 584       __basic_future(const __basic_future&) = delete;
 585       __basic_future& operator=(const __basic_future&) = delete;
 586
 587       bool
 588       valid() const noexcept { return static_cast<bool>(_M_state); }
 589
 590       void
 591       wait() const
 592       {
 593         _State_base::_S_check(_M_state);
 594         _M_state->wait();
 595       }
 596
 597       template<typename _Rep, typename _Period>
 598         future_status
 599         wait_for(const chrono::duration<_Rep, _Period>& __rel) const
 600         {
 601           _State_base::_S_check(_M_state);
 602           return _M_state->wait_for(__rel);
 603         }
 604
 605       template<typename _Clock, typename _Duration>
 606         future_status
 607         wait_until(const chrono::time_point<_Clock, _Duration>& __abs) const
 608         {
 609           _State_base::_S_check(_M_state);
 610           return _M_state->wait_until(__abs);
 611         }
 612
 613     protected:
 614       /// Wait for the state to be ready and rethrow any stored exception
 615       __result_type
 616       _M_get_result() const
 617       {
 618         _State_base::_S_check(_M_state);
 619         _Result_base& __res = _M_state->wait();
 620         if (!(__res._M_error == 0))
 621           rethrow_exception(__res._M_error);
 622         return static_cast<__result_type>(__res);
 623       }
 624
 625       void _M_swap(__basic_future& __that) noexcept
 626       {
 627         _M_state.swap(__that._M_state);
 628       }
 629
 630       // Construction of a future by promise::get_future()
 631       explicit
 632       __basic_future(const __state_type& __state) : _M_state(__state)
 633       {
 634         _State_base::_S_check(_M_state);
 635         _M_state->_M_set_retrieved_flag();
 636       }
 637
 638       // Copy construction from a shared_future
 639       explicit
 640       __basic_future(const shared_future<_Res>&) noexcept;
 641
 642       // Move construction from a shared_future
 643       explicit
 644       __basic_future(shared_future<_Res>&&) noexcept;
 645
 646       // Move construction from a future
 647       explicit
 648       __basic_future(future<_Res>&&) noexcept;
 649
 650       constexpr __basic_future() noexcept : _M_state() { }
 651
 652       struct _Reset
 653       {
 654         explicit _Reset(__basic_future& __fut) noexcept : _M_fut(__fut) { }
 655         ~_Reset() { _M_fut._M_state.reset(); }
 656         __basic_future& _M_fut;
 657       };
 658     };
 659
 660
 661   /// Primary template for future.
 662   template<typename _Res>
 663     class future : public __basic_future<_Res>
 664     {
 665       friend class promise<_Res>;
 666       template<typename> friend class packaged_task;
 667       template<typename _Fn, typename... _Args>
 668         friend future<typename result_of<_Fn(_Args...)>::type>
 669         async(launch, _Fn&&, _Args&&...);
 670
 671       typedef __basic_future<_Res> _Base_type;
 672       typedef typename _Base_type::__state_type __state_type;
 673
 674       explicit
 675       future(const __state_type& __state) : _Base_type(__state) { }
 676
 677     public:
 678       constexpr future() noexcept : _Base_type() { }
 679
 680       /// Move constructor
 681       future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
 682
 683       // Disable copying
 684       future(const future&) = delete;
 685       future& operator=(const future&) = delete;
 686
 687       future& operator=(future&& __fut) noexcept
 688       {
 689         future(std::move(__fut))._M_swap(*this);
 690         return *this;
 691       }
 692
 693       /// Retrieving the value
 694       _Res
 695       get()
 696       {
 697         typename _Base_type::_Reset __reset(*this);
 698         return std::move(this->_M_get_result()._M_value());
 699       }
 700
 701       shared_future<_Res> share();
 702     };
 703
 704   /// Partial specialization for future<R&>
 705   template<typename _Res>
 706     class future<_Res&> : public __basic_future<_Res&>
 707     {
 708       friend class promise<_Res&>;
 709       template<typename> friend class packaged_task;
 710       template<typename _Fn, typename... _Args>
 711         friend future<typename result_of<_Fn(_Args...)>::type>
 712         async(launch, _Fn&&, _Args&&...);
 713
 714       typedef __basic_future<_Res&> _Base_type;
 715       typedef typename _Base_type::__state_type __state_type;
 716
 717       explicit
 718       future(const __state_type& __state) : _Base_type(__state) { }
 719
 720     public:
 721       constexpr future() noexcept : _Base_type() { }
 722
 723       /// Move constructor
 724       future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
 725
 726       // Disable copying
 727       future(const future&) = delete;
 728       future& operator=(const future&) = delete;
 729
 730       future& operator=(future&& __fut) noexcept
 731       {
 732         future(std::move(__fut))._M_swap(*this);
 733         return *this;
 734       }
 735
 736       /// Retrieving the value
 737       _Res&
 738       get()
 739       {
 740         typename _Base_type::_Reset __reset(*this);
 741         return this->_M_get_result()._M_get();
 742       }
 743
 744       shared_future<_Res&> share();
 745     };
 746
 747   /// Explicit specialization for future<void>
 748   template<>
 749     class future<void> : public __basic_future<void>
 750     {
 751       friend class promise<void>;
 752       template<typename> friend class packaged_task;
 753       template<typename _Fn, typename... _Args>
 754         friend future<typename result_of<_Fn(_Args...)>::type>
 755         async(launch, _Fn&&, _Args&&...);
 756
 757       typedef __basic_future<void> _Base_type;
 758       typedef typename _Base_type::__state_type __state_type;
 759
 760       explicit
 761       future(const __state_type& __state) : _Base_type(__state) { }
 762
 763     public:
 764       constexpr future() noexcept : _Base_type() { }
 765
 766       /// Move constructor
 767       future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { }
 768
 769       // Disable copying
 770       future(const future&) = delete;
 771       future& operator=(const future&) = delete;
 772
 773       future& operator=(future&& __fut) noexcept
 774       {
 775         future(std::move(__fut))._M_swap(*this);
 776         return *this;
 777       }
 778
 779       /// Retrieving the value
 780       void
 781       get()
 782       {
 783         typename _Base_type::_Reset __reset(*this);
 784         this->_M_get_result();
 785       }
 786
 787       shared_future<void> share();
 788     };
 789
 790
 791   /// Primary template for shared_future.
 792   template<typename _Res>
 793     class shared_future : public __basic_future<_Res>
 794     {
 795       typedef __basic_future<_Res> _Base_type;
 796
 797     public:
 798       constexpr shared_future() noexcept : _Base_type() { }
 799
 800       /// Copy constructor
 801       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
 802
 803       /// Construct from a future rvalue
 804       shared_future(future<_Res>&& __uf) noexcept
 805       : _Base_type(std::move(__uf))
 806       { }
 807
 808       /// Construct from a shared_future rvalue
 809       shared_future(shared_future&& __sf) noexcept
 810       : _Base_type(std::move(__sf))
 811       { }
 812
 813       shared_future& operator=(const shared_future& __sf)
 814       {
 815         shared_future(__sf)._M_swap(*this);
 816         return *this;
 817       }
 818
 819       shared_future& operator=(shared_future&& __sf) noexcept
 820       {
 821         shared_future(std::move(__sf))._M_swap(*this);
 822         return *this;
 823       }
 824
 825       /// Retrieving the value
 826       const _Res&
 827       get() const { return this->_M_get_result()._M_value(); }
 828     };
 829
 830   /// Partial specialization for shared_future<R&>
 831   template<typename _Res>
 832     class shared_future<_Res&> : public __basic_future<_Res&>
 833     {
 834       typedef __basic_future<_Res&>           _Base_type;
 835
 836     public:
 837       constexpr shared_future() noexcept : _Base_type() { }
 838
 839       /// Copy constructor
 840       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
 841
 842       /// Construct from a future rvalue
 843       shared_future(future<_Res&>&& __uf) noexcept
 844       : _Base_type(std::move(__uf))
 845       { }
 846
 847       /// Construct from a shared_future rvalue
 848       shared_future(shared_future&& __sf) noexcept
 849       : _Base_type(std::move(__sf))
 850       { }
 851
 852       shared_future& operator=(const shared_future& __sf)
 853       {
 854         shared_future(__sf)._M_swap(*this);
 855         return *this;
 856       }
 857
 858       shared_future& operator=(shared_future&& __sf) noexcept
 859       {
 860         shared_future(std::move(__sf))._M_swap(*this);
 861         return *this;
 862       }
 863
 864       /// Retrieving the value
 865       _Res&
 866       get() const { return this->_M_get_result()._M_get(); }
 867     };
 868
 869   /// Explicit specialization for shared_future<void>
 870   template<>
 871     class shared_future<void> : public __basic_future<void>
 872     {
 873       typedef __basic_future<void> _Base_type;
 874
 875     public:
 876       constexpr shared_future() noexcept : _Base_type() { }
 877
 878       /// Copy constructor
 879       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
 880
 881       /// Construct from a future rvalue
 882       shared_future(future<void>&& __uf) noexcept
 883       : _Base_type(std::move(__uf))
 884       { }
 885
 886       /// Construct from a shared_future rvalue
 887       shared_future(shared_future&& __sf) noexcept
 888       : _Base_type(std::move(__sf))
 889       { }
 890
 891       shared_future& operator=(const shared_future& __sf)
 892       {
 893         shared_future(__sf)._M_swap(*this);
 894         return *this;
 895       }
 896
 897       shared_future& operator=(shared_future&& __sf) noexcept
 898       {
 899         shared_future(std::move(__sf))._M_swap(*this);
 900         return *this;
 901       }
 902
 903       // Retrieving the value
 904       void
 905       get() const { this->_M_get_result(); }
 906     };
 907
 908   // Now we can define the protected __basic_future constructors.
 909   template<typename _Res>
 910     inline __basic_future<_Res>::
 911     __basic_future(const shared_future<_Res>& __sf) noexcept
 912     : _M_state(__sf._M_state)
 913     { }
 914
 915   template<typename _Res>
 916     inline __basic_future<_Res>::
 917     __basic_future(shared_future<_Res>&& __sf) noexcept
 918     : _M_state(std::move(__sf._M_state))
 919     { }
 920
 921   template<typename _Res>
 922     inline __basic_future<_Res>::
 923     __basic_future(future<_Res>&& __uf) noexcept
 924     : _M_state(std::move(__uf._M_state))
 925     { }
 926
 927   template<typename _Res>
 928     inline shared_future<_Res>
 929     future<_Res>::share()
 930     { return shared_future<_Res>(std::move(*this)); }
 931
 932   template<typename _Res>
 933     inline shared_future<_Res&>
 934     future<_Res&>::share()
 935     { return shared_future<_Res&>(std::move(*this)); }
 936
 937   inline shared_future<void>
 938   future<void>::share()
 939   { return shared_future<void>(std::move(*this)); }
 940
 941   /// Primary template for promise
 942   template<typename _Res>
 943     class promise
 944     {
 945       typedef __future_base::_State_base        _State;
 946       typedef __future_base::_Result<_Res>      _Res_type;
 947       typedef __future_base::_Ptr<_Res_type>    _Ptr_type;
 948       template<typename, typename> friend class _State::_Setter;
 949
 950       shared_ptr<_State>                        _M_future;
 951       _Ptr_type                                 _M_storage;
 952
 953     public:
 954       promise()
 955       : _M_future(std::make_shared<_State>()),
 956         _M_storage(new _Res_type())
 957       { }
 958
 959       promise(promise&& __rhs) noexcept
 960       : _M_future(std::move(__rhs._M_future)),
 961         _M_storage(std::move(__rhs._M_storage))
 962       { }
 963
 964       template<typename _Allocator>
 965         promise(allocator_arg_t, const _Allocator& __a)
 966         : _M_future(std::allocate_shared<_State>(__a)),
 967           _M_storage(__future_base::_S_allocate_result<_Res>(__a))
 968         { }
 969
 970       template<typename _Allocator>
 971         promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
 972         : _M_future(std::move(__rhs._M_future)),
 973           _M_storage(std::move(__rhs._M_storage))
 974         { }
 975
 976       promise(const promise&) = delete;
 977
 978       ~promise()
 979       {
 980         if (static_cast<bool>(_M_future) && !_M_future.unique())
 981           _M_future->_M_break_promise(std::move(_M_storage));
 982       }
 983
 984       // Assignment
 985       promise&
 986       operator=(promise&& __rhs) noexcept
 987       {
 988         promise(std::move(__rhs)).swap(*this);
 989         return *this;
 990       }
 991
 992       promise& operator=(const promise&) = delete;
 993
 994       void
 995       swap(promise& __rhs) noexcept
 996       {
 997         _M_future.swap(__rhs._M_future);
 998         _M_storage.swap(__rhs._M_storage);
 999       }
1000
1001       // Retrieving the result
1002       future<_Res>
1003       get_future()
1004       { return future<_Res>(_M_future); }
1005
1006       // Setting the result
1007       void
1008       set_value(const _Res& __r)
1009       {
1010         auto __setter = _State::__setter(this, __r);
1011         _M_future->_M_set_result(std::move(__setter));
1012       }
1013
1014       void
1015       set_value(_Res&& __r)
1016       {
1017         auto __setter = _State::__setter(this, std::move(__r));
1018         _M_future->_M_set_result(std::move(__setter));
1019       }
1020
1021       void
1022       set_exception(exception_ptr __p)
1023       {
1024         auto __setter = _State::__setter(__p, this);
1025         _M_future->_M_set_result(std::move(__setter));
1026       }
1027     };
1028
1029   template<typename _Res>
1030     inline void
1031     swap(promise<_Res>& __x, promise<_Res>& __y) noexcept
1032     { __x.swap(__y); }
1033
1034   template<typename _Res, typename _Alloc>
1035     struct uses_allocator<promise<_Res>, _Alloc>
1036     : public true_type { };
1037
1038
1039   /// Partial specialization for promise<R&>
1040   template<typename _Res>
1041     class promise<_Res&>
1042     {
1043       typedef __future_base::_State_base        _State;
1044       typedef __future_base::_Result<_Res&>     _Res_type;
1045       typedef __future_base::_Ptr<_Res_type>    _Ptr_type;
1046       template<typename, typename> friend class _State::_Setter;
1047
1048       shared_ptr<_State>                        _M_future;
1049       _Ptr_type                                 _M_storage;
1050
1051     public:
1052       promise()
1053       : _M_future(std::make_shared<_State>()),
1054         _M_storage(new _Res_type())
1055       { }
1056
1057       promise(promise&& __rhs) noexcept
1058       : _M_future(std::move(__rhs._M_future)),
1059         _M_storage(std::move(__rhs._M_storage))
1060       { }
1061
1062       template<typename _Allocator>
1063         promise(allocator_arg_t, const _Allocator& __a)
1064         : _M_future(std::allocate_shared<_State>(__a)),
1065           _M_storage(__future_base::_S_allocate_result<_Res&>(__a))
1066         { }
1067
1068       template<typename _Allocator>
1069         promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1070         : _M_future(std::move(__rhs._M_future)),
1071           _M_storage(std::move(__rhs._M_storage))
1072         { }
1073
1074       promise(const promise&) = delete;
1075
1076       ~promise()
1077       {
1078         if (static_cast<bool>(_M_future) && !_M_future.unique())
1079           _M_future->_M_break_promise(std::move(_M_storage));
1080       }
1081
1082       // Assignment
1083       promise&
1084       operator=(promise&& __rhs) noexcept
1085       {
1086         promise(std::move(__rhs)).swap(*this);
1087         return *this;
1088       }
1089
1090       promise& operator=(const promise&) = delete;
1091
1092       void
1093       swap(promise& __rhs) noexcept
1094       {
1095         _M_future.swap(__rhs._M_future);
1096         _M_storage.swap(__rhs._M_storage);
1097       }
1098
1099       // Retrieving the result
1100       future<_Res&>
1101       get_future()
1102       { return future<_Res&>(_M_future); }
1103
1104       // Setting the result
1105       void
1106       set_value(_Res& __r)
1107       {
1108         auto __setter = _State::__setter(this, __r);
1109         _M_future->_M_set_result(std::move(__setter));
1110       }
1111
1112       void
1113       set_exception(exception_ptr __p)
1114       {
1115         auto __setter = _State::__setter(__p, this);
1116         _M_future->_M_set_result(std::move(__setter));
1117       }
1118     };
1119
1120   /// Explicit specialization for promise<void>
1121   template<>
1122     class promise<void>
1123     {
1124       typedef __future_base::_State_base        _State;
1125       typedef __future_base::_Result<void>      _Res_type;
1126       typedef __future_base::_Ptr<_Res_type>    _Ptr_type;
1127       template<typename, typename> friend class _State::_Setter;
1128
1129       shared_ptr<_State>                        _M_future;
1130       _Ptr_type                                 _M_storage;
1131
1132     public:
1133       promise()
1134       : _M_future(std::make_shared<_State>()),
1135         _M_storage(new _Res_type())
1136       { }
1137
1138       promise(promise&& __rhs) noexcept
1139       : _M_future(std::move(__rhs._M_future)),
1140         _M_storage(std::move(__rhs._M_storage))
1141       { }
1142
1143       template<typename _Allocator>
1144         promise(allocator_arg_t, const _Allocator& __a)
1145         : _M_future(std::allocate_shared<_State>(__a)),
1146           _M_storage(__future_base::_S_allocate_result<void>(__a))
1147         { }
1148
1149       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1150       // 2095.  missing constructors needed for uses-allocator construction
1151       template<typename _Allocator>
1152         promise(allocator_arg_t, const _Allocator&, promise&& __rhs)
1153         : _M_future(std::move(__rhs._M_future)),
1154           _M_storage(std::move(__rhs._M_storage))
1155         { }
1156
1157       promise(const promise&) = delete;
1158
1159       ~promise()
1160       {
1161         if (static_cast<bool>(_M_future) && !_M_future.unique())
1162           _M_future->_M_break_promise(std::move(_M_storage));
1163       }
1164
1165       // Assignment
1166       promise&
1167       operator=(promise&& __rhs) noexcept
1168       {
1169         promise(std::move(__rhs)).swap(*this);
1170         return *this;
1171       }
1172
1173       promise& operator=(const promise&) = delete;
1174
1175       void
1176       swap(promise& __rhs) noexcept
1177       {
1178         _M_future.swap(__rhs._M_future);
1179         _M_storage.swap(__rhs._M_storage);
1180       }
1181
1182       // Retrieving the result
1183       future<void>
1184       get_future()
1185       { return future<void>(_M_future); }
1186
1187       // Setting the result
1188       void set_value();
1189
1190       void
1191       set_exception(exception_ptr __p)
1192       {
1193         auto __setter = _State::__setter(__p, this);
1194         _M_future->_M_set_result(std::move(__setter));
1195       }
1196     };
1197
1198   // set void
1199   template<>
1200     struct __future_base::_State_base::_Setter<void, void>
1201     {
1202       promise<void>::_Ptr_type operator()()
1203       {
1204         _State_base::_S_check(_M_promise->_M_future);
1205         return std::move(_M_promise->_M_storage);
1206       }
1207
1208       promise<void>*    _M_promise;
1209     };
1210
1211   inline __future_base::_State_base::_Setter<void, void>
1212   __future_base::_State_base::__setter(promise<void>* __prom)
1213   {
1214     return _Setter<void, void>{ __prom };
1215   }
1216
1217   inline void
1218   promise<void>::set_value()
1219   {
1220     auto __setter = _State::__setter(this);
1221     _M_future->_M_set_result(std::move(__setter));
1222   }
1223
1224
1225   template<typename _Ptr_type, typename _Res>
1226     struct __future_base::_Task_setter
1227     {
1228       _Ptr_type operator()()
1229       {
1230         __try
1231           {
1232             _M_result->_M_set(_M_fn());
1233           }
1234         __catch(...)
1235           {
1236             _M_result->_M_error = current_exception();
1237           }
1238         return std::move(_M_result);
1239       }
1240       _Ptr_type&                _M_result;
1241       std::function<_Res()>     _M_fn;
1242     };
1243
1244   template<typename _Ptr_type>
1245     struct __future_base::_Task_setter<_Ptr_type, void>
1246     {
1247       _Ptr_type operator()()
1248       {
1249         __try
1250           {
1251             _M_fn();
1252           }
1253         __catch(...)
1254           {
1255             _M_result->_M_error = current_exception();
1256           }
1257         return std::move(_M_result);
1258       }
1259       _Ptr_type&                _M_result;
1260       std::function<void()>     _M_fn;
1261     };
1262
1263   template<typename _Res, typename... _Args>
1264     struct __future_base::_Task_state_base<_Res(_Args...)>
1265     : __future_base::_State_base
1266     {
1267       typedef _Res _Res_type;
1268
1269       template<typename _Alloc>
1270         _Task_state_base(const _Alloc& __a)
1271         : _M_result(_S_allocate_result<_Res>(__a))
1272         { }
1273
1274       virtual void
1275       _M_run(_Args... __args) = 0;
1276
1277       virtual shared_ptr<_Task_state_base>
1278       _M_reset() = 0;
1279
1280       typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1281       _Ptr_type _M_result;
1282     };
1283
1284   template<typename _Fn, typename _Alloc, typename _Res, typename... _Args>
1285     struct __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)> final
1286     : __future_base::_Task_state_base<_Res(_Args...)>
1287     {
1288       _Task_state(_Fn&& __fn, const _Alloc& __a)
1289       : _Task_state_base<_Res(_Args...)>(__a), _M_impl(std::move(__fn), __a)
1290       { }
1291
1292     private:
1293       virtual void
1294       _M_run(_Args... __args)
1295       {
1296         // bound arguments decay so wrap lvalue references
1297         auto __boundfn = std::__bind_simple(std::ref(_M_impl._M_fn),
1298             _S_maybe_wrap_ref(std::forward<_Args>(__args))...);
1299         auto __setter = _S_task_setter(this->_M_result, std::move(__boundfn));
1300         this->_M_set_result(std::move(__setter));
1301       }
1302
1303       virtual shared_ptr<_Task_state_base<_Res(_Args...)>>
1304       _M_reset();
1305
1306       template<typename _Tp>
1307         static reference_wrapper<_Tp>
1308         _S_maybe_wrap_ref(_Tp& __t)
1309         { return std::ref(__t); }
1310
1311       template<typename _Tp>
1312         static
1313         typename enable_if<!is_lvalue_reference<_Tp>::value, _Tp>::type&&
1314         _S_maybe_wrap_ref(_Tp&& __t)
1315         { return std::forward<_Tp>(__t); }
1316
1317       struct _Impl : _Alloc
1318       {
1319         _Impl(_Fn&& __fn, const _Alloc& __a)
1320           : _Alloc(__a), _M_fn(std::move(__fn)) { }
1321         _Fn _M_fn;
1322       } _M_impl;
1323     };
1324
1325     template<typename _Signature, typename _Fn, typename _Alloc>
1326       static shared_ptr<__future_base::_Task_state_base<_Signature>>
1327       __create_task_state(_Fn&& __fn, const _Alloc& __a)
1328       {
1329         typedef __future_base::_Task_state<_Fn, _Alloc, _Signature> _State;
1330         return std::allocate_shared<_State>(__a, std::move(__fn), __a);
1331       }
1332
1333   template<typename _Fn, typename _Alloc, typename _Res, typename... _Args>
1334     shared_ptr<__future_base::_Task_state_base<_Res(_Args...)>>
1335     __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)>::_M_reset()
1336     {
1337       return __create_task_state<_Res(_Args...)>(std::move(_M_impl._M_fn),
1338                                                  static_cast<_Alloc&>(_M_impl));
1339     }
1340
1341   template<typename _Task, typename _Fn, bool
1342            = is_same<_Task, typename decay<_Fn>::type>::value>
1343     struct __constrain_pkgdtask
1344     { typedef void __type; };
1345
1346   template<typename _Task, typename _Fn>
1347     struct __constrain_pkgdtask<_Task, _Fn, true>
1348     { };
1349
1350   /// packaged_task
1351   template<typename _Res, typename... _ArgTypes>
1352     class packaged_task<_Res(_ArgTypes...)>
1353     {
1354       typedef __future_base::_Task_state_base<_Res(_ArgTypes...)> _State_type;
1355       shared_ptr<_State_type>                   _M_state;
1356
1357     public:
1358       // Construction and destruction
1359       packaged_task() noexcept { }
1360
1361       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1362       // 2095.  missing constructors needed for uses-allocator construction
1363       template<typename _Allocator>
1364         packaged_task(allocator_arg_t, const _Allocator& __a) noexcept
1365         { }
1366
1367       template<typename _Fn, typename = typename
1368                __constrain_pkgdtask<packaged_task, _Fn>::__type>
1369         explicit
1370         packaged_task(_Fn&& __fn)
1371         : packaged_task(allocator_arg, std::allocator<int>(), std::move(__fn))
1372         { }
1373
1374       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1375       // 2097.  packaged_task constructors should be constrained
1376       template<typename _Fn, typename _Alloc, typename = typename
1377                __constrain_pkgdtask<packaged_task, _Fn>::__type>
1378         explicit
1379         packaged_task(allocator_arg_t, const _Alloc& __a, _Fn&& __fn)
1380         : _M_state(__create_task_state<_Res(_ArgTypes...)>(
1381                     std::forward<_Fn>(__fn), __a))
1382         { }
1383
1384       ~packaged_task()
1385       {
1386         if (static_cast<bool>(_M_state) && !_M_state.unique())
1387           _M_state->_M_break_promise(std::move(_M_state->_M_result));
1388       }
1389
1390       // No copy
1391       packaged_task(const packaged_task&) = delete;
1392       packaged_task& operator=(const packaged_task&) = delete;
1393
1394       template<typename _Allocator>
1395         packaged_task(allocator_arg_t, const _Allocator&,
1396                       const packaged_task&) = delete;
1397
1398       // Move support
1399       packaged_task(packaged_task&& __other) noexcept
1400       { this->swap(__other); }
1401
1402       template<typename _Allocator>
1403         packaged_task(allocator_arg_t, const _Allocator&,
1404                       packaged_task&& __other) noexcept
1405         { this->swap(__other); }
1406
1407       packaged_task& operator=(packaged_task&& __other) noexcept
1408       {
1409         packaged_task(std::move(__other)).swap(*this);
1410         return *this;
1411       }
1412
1413       void
1414       swap(packaged_task& __other) noexcept
1415       { _M_state.swap(__other._M_state); }
1416
1417       bool
1418       valid() const noexcept
1419       { return static_cast<bool>(_M_state); }
1420
1421       // Result retrieval
1422       future<_Res>
1423       get_future()
1424       { return future<_Res>(_M_state); }
1425
1426       // Execution
1427       void
1428       operator()(_ArgTypes... __args)
1429       {
1430         __future_base::_State_base::_S_check(_M_state);
1431         _M_state->_M_run(std::forward<_ArgTypes>(__args)...);
1432       }
1433
1434       void
1435       reset()
1436       {
1437         __future_base::_State_base::_S_check(_M_state);
1438         packaged_task __tmp;
1439         __tmp._M_state = _M_state;
1440         _M_state = _M_state->_M_reset();
1441       }
1442     };
1443
1444   /// swap
1445   template<typename _Res, typename... _ArgTypes>
1446     inline void
1447     swap(packaged_task<_Res(_ArgTypes...)>& __x,
1448          packaged_task<_Res(_ArgTypes...)>& __y) noexcept
1449     { __x.swap(__y); }
1450
1451   template<typename _Res, typename _Alloc>
1452     struct uses_allocator<packaged_task<_Res>, _Alloc>
1453     : public true_type { };
1454
1455
1456   template<typename _BoundFn, typename _Res>
1457     class __future_base::_Deferred_state final
1458     : public __future_base::_State_base
1459     {
1460     public:
1461       explicit
1462       _Deferred_state(_BoundFn&& __fn)
1463       : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
1464       { }
1465
1466     private:
1467       typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1468       _Ptr_type _M_result;
1469       _BoundFn _M_fn;
1470
1471       // Run the deferred function.
1472       virtual void
1473       _M_complete_async()
1474       {
1475         // safe to call multiple times so ignore failure
1476         _M_set_result(_S_task_setter(_M_result, _M_fn), true);
1477       }
1478
1479       virtual bool
1480       _M_has_deferred() const { return static_cast<bool>(_M_result); }
1481     };
1482
1483   class __future_base::_Async_state_commonV2
1484     : public __future_base::_State_base
1485   {
1486   protected:
1487     ~_Async_state_commonV2() = default;
1488
1489     // Make waiting functions block until the thread completes, as if joined.
1490     virtual void _M_complete_async() { _M_join(); }
1491
1492     void _M_join() { std::call_once(_M_once, &thread::join, ref(_M_thread)); }
1493
1494     thread _M_thread;
1495     once_flag _M_once;
1496   };
1497
1498   template<typename _BoundFn, typename _Res>
1499     class __future_base::_Async_state_impl final
1500     : public __future_base::_Async_state_commonV2
1501     {
1502     public:
1503       explicit
1504       _Async_state_impl(_BoundFn&& __fn)
1505       : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
1506       {
1507         _M_thread = std::thread{ [this] {
1508           _M_set_result(_S_task_setter(_M_result, _M_fn));
1509         } };
1510       }
1511
1512       ~_Async_state_impl() { _M_join(); }
1513
1514     private:
1515       typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type;
1516       _Ptr_type _M_result;
1517       _BoundFn _M_fn;
1518     };
1519
1520   template<typename _BoundFn>
1521     inline std::shared_ptr<__future_base::_State_base>
1522     __future_base::_S_make_deferred_state(_BoundFn&& __fn)
1523     {
1524       typedef typename remove_reference<_BoundFn>::type __fn_type;
1525       typedef _Deferred_state<__fn_type> __state_type;
1526       return std::make_shared<__state_type>(std::move(__fn));
1527     }
1528
1529   template<typename _BoundFn>
1530     inline std::shared_ptr<__future_base::_State_base>
1531     __future_base::_S_make_async_state(_BoundFn&& __fn)
1532     {
1533       typedef typename remove_reference<_BoundFn>::type __fn_type;
1534       typedef _Async_state_impl<__fn_type> __state_type;
1535       return std::make_shared<__state_type>(std::move(__fn));
1536     }
1537
1538
1539   /// async
1540   template<typename _Fn, typename... _Args>
1541     future<typename result_of<_Fn(_Args...)>::type>
1542     async(launch __policy, _Fn&& __fn, _Args&&... __args)
1543     {
1544       typedef typename result_of<_Fn(_Args...)>::type result_type;
1545       std::shared_ptr<__future_base::_State_base> __state;
1546       if ((__policy & (launch::async|launch::deferred)) == launch::async)
1547         {
1548           __state = __future_base::_S_make_async_state(std::__bind_simple(
1549               std::forward<_Fn>(__fn), std::forward<_Args>(__args)...));
1550         }
1551       else
1552         {
1553           __state = __future_base::_S_make_deferred_state(std::__bind_simple(
1554               std::forward<_Fn>(__fn), std::forward<_Args>(__args)...));
1555         }
1556       return future<result_type>(__state);
1557     }
1558
1559   /// async, potential overload
1560   template<typename _Fn, typename... _Args>
1561     inline future<typename result_of<_Fn(_Args...)>::type>
1562     async(_Fn&& __fn, _Args&&... __args)
1563     {
1564       return async(launch::async|launch::deferred, std::forward<_Fn>(__fn),
1565                    std::forward<_Args>(__args)...);
1566     }
1567
1568 #endif // _GLIBCXX_ASYNC_ABI_COMPAT
1569 #endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
1570        // && ATOMIC_INT_LOCK_FREE
1571
1572   // @} group futures
1573 _GLIBCXX_END_NAMESPACE_VERSION
1574 } // namespace
1575
1576 #endif // C++11
1577
1578 #endif // _GLIBCXX_FUTURE