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Diffstat (limited to 'aarch64-none-linux-gnu/include/c++/13.2.1/future')
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1 files changed, 1844 insertions, 0 deletions
diff --git a/aarch64-none-linux-gnu/include/c++/13.2.1/future b/aarch64-none-linux-gnu/include/c++/13.2.1/future new file mode 100644 index 0000000..95b413a --- /dev/null +++ b/aarch64-none-linux-gnu/include/c++/13.2.1/future @@ -0,0 +1,1844 @@ +// <future> -*- C++ -*- + +// Copyright (C) 2009-2023 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// Under Section 7 of GPL version 3, you are granted additional +// permissions described in the GCC Runtime Library Exception, version +// 3.1, as published by the Free Software Foundation. + +// You should have received a copy of the GNU General Public License and +// a copy of the GCC Runtime Library Exception along with this program; +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see +// <http://www.gnu.org/licenses/>. + +/** @file include/future + * This is a Standard C++ Library header. + */ + +#ifndef _GLIBCXX_FUTURE +#define _GLIBCXX_FUTURE 1 + +#pragma GCC system_header + +#include <bits/requires_hosted.h> // concurrency + +#if __cplusplus < 201103L +# include <bits/c++0x_warning.h> +#else + +#include <mutex> // call_once +#include <condition_variable> // __at_thread_exit_elt +#include <system_error> +#include <bits/atomic_base.h> // atomic_flag +#include <bits/allocated_ptr.h> +#include <bits/atomic_futex.h> +#include <bits/exception_defines.h> +#include <bits/invoke.h> +#include <bits/unique_ptr.h> +#include <bits/shared_ptr.h> +#include <bits/std_function.h> +#include <bits/std_thread.h> +#include <bits/uses_allocator.h> +#include <ext/aligned_buffer.h> + +namespace std _GLIBCXX_VISIBILITY(default) +{ +_GLIBCXX_BEGIN_NAMESPACE_VERSION + + /** + * @defgroup futures Futures + * @ingroup concurrency + * + * Futures and promises provide support for retrieving the result from + * an asynchronous function, e.g. one that is running in another thread. + * A `std::future` represents an asynchronous result that will become + * ready at some later time. A consumer can wait on a future until the + * result is ready to be accessed. + * + * @since C++11 + * @{ + */ + + /// Error code for futures + enum class future_errc + { + future_already_retrieved = 1, + promise_already_satisfied, + no_state, + broken_promise + }; + + /// Specialization that allows `future_errc` to convert to `error_code`. + template<> + struct is_error_code_enum<future_errc> : public true_type { }; + + /// Points to a statically-allocated object derived from error_category. + [[__nodiscard__, __gnu__::__const__]] + const error_category& + future_category() noexcept; + + /// Overload of make_error_code for `future_errc`. + [[__nodiscard__]] + inline error_code + make_error_code(future_errc __errc) noexcept + { return error_code(static_cast<int>(__errc), future_category()); } + + /// Overload of make_error_condition for `future_errc`. + [[__nodiscard__]] + inline error_condition + make_error_condition(future_errc __errc) noexcept + { return error_condition(static_cast<int>(__errc), future_category()); } + + /** + * @brief Exception type thrown by futures. + * @ingroup exceptions + * @since C++11 + */ + class future_error : public logic_error + { + public: + explicit + future_error(future_errc __errc) + : future_error(std::make_error_code(__errc)) + { } + + virtual ~future_error() noexcept; + + virtual const char* + what() const noexcept; + + const error_code& + code() const noexcept { return _M_code; } + + private: + explicit + future_error(error_code __ec) + : logic_error("std::future_error: " + __ec.message()), _M_code(__ec) + { } + + friend void __throw_future_error(int); + + error_code _M_code; + }; + + // Forward declarations. + template<typename _Res> + class future; + + template<typename _Res> + class shared_future; + + template<typename _Signature> + class packaged_task; + + template<typename _Res> + class promise; + + /// Launch code for futures + enum class launch + { + async = 1, + deferred = 2 + }; + + constexpr launch operator&(launch __x, launch __y) noexcept + { + return static_cast<launch>( + static_cast<int>(__x) & static_cast<int>(__y)); + } + + constexpr launch operator|(launch __x, launch __y) noexcept + { + return static_cast<launch>( + static_cast<int>(__x) | static_cast<int>(__y)); + } + + constexpr launch operator^(launch __x, launch __y) noexcept + { + return static_cast<launch>( + static_cast<int>(__x) ^ static_cast<int>(__y)); + } + + constexpr launch operator~(launch __x) noexcept + { return static_cast<launch>(~static_cast<int>(__x)); } + + inline launch& operator&=(launch& __x, launch __y) noexcept + { return __x = __x & __y; } + + inline launch& operator|=(launch& __x, launch __y) noexcept + { return __x = __x | __y; } + + inline launch& operator^=(launch& __x, launch __y) noexcept + { return __x = __x ^ __y; } + + /// Status code for futures + enum class future_status + { + ready, + timeout, + deferred + }; + + /// @cond undocumented + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2021. Further incorrect usages of result_of + template<typename _Fn, typename... _Args> + using __async_result_of = typename __invoke_result< + typename decay<_Fn>::type, typename decay<_Args>::type...>::type; + /// @endcond + + template<typename _Fn, typename... _Args> + future<__async_result_of<_Fn, _Args...>> + async(launch __policy, _Fn&& __fn, _Args&&... __args); + + template<typename _Fn, typename... _Args> + future<__async_result_of<_Fn, _Args...>> + async(_Fn&& __fn, _Args&&... __args); + +#if defined(_GLIBCXX_HAS_GTHREADS) + + /// @cond undocumented + + /// Base class and enclosing scope. + struct __future_base + { + /// Base class for results. + struct _Result_base + { + exception_ptr _M_error; + + _Result_base(const _Result_base&) = delete; + _Result_base& operator=(const _Result_base&) = delete; + + // _M_destroy() allows derived classes to control deallocation + virtual void _M_destroy() = 0; + + struct _Deleter + { + void operator()(_Result_base* __fr) const { __fr->_M_destroy(); } + }; + + protected: + _Result_base(); + virtual ~_Result_base(); + }; + + /// A unique_ptr for result objects. + template<typename _Res> + using _Ptr = unique_ptr<_Res, _Result_base::_Deleter>; + + /// A result object that has storage for an object of type _Res. + template<typename _Res> + struct _Result : _Result_base + { + private: + __gnu_cxx::__aligned_buffer<_Res> _M_storage; + bool _M_initialized; + + public: + typedef _Res result_type; + + _Result() noexcept : _M_initialized() { } + + ~_Result() + { + if (_M_initialized) + _M_value().~_Res(); + } + + // Return lvalue, future will add const or rvalue-reference + _Res& + _M_value() noexcept { return *_M_storage._M_ptr(); } + + void + _M_set(const _Res& __res) + { + ::new (_M_storage._M_addr()) _Res(__res); + _M_initialized = true; + } + + void + _M_set(_Res&& __res) + { + ::new (_M_storage._M_addr()) _Res(std::move(__res)); + _M_initialized = true; + } + + private: + void _M_destroy() { delete this; } + }; + + /// A result object that uses an allocator. + template<typename _Res, typename _Alloc> + struct _Result_alloc final : _Result<_Res>, _Alloc + { + using __allocator_type = __alloc_rebind<_Alloc, _Result_alloc>; + + explicit + _Result_alloc(const _Alloc& __a) : _Result<_Res>(), _Alloc(__a) + { } + + private: + void _M_destroy() + { + __allocator_type __a(*this); + __allocated_ptr<__allocator_type> __guard_ptr{ __a, this }; + this->~_Result_alloc(); + } + }; + + // Create a result object that uses an allocator. + template<typename _Res, typename _Allocator> + static _Ptr<_Result_alloc<_Res, _Allocator>> + _S_allocate_result(const _Allocator& __a) + { + using __result_type = _Result_alloc<_Res, _Allocator>; + typename __result_type::__allocator_type __a2(__a); + auto __guard = std::__allocate_guarded(__a2); + __result_type* __p = ::new((void*)__guard.get()) __result_type{__a}; + __guard = nullptr; + return _Ptr<__result_type>(__p); + } + + // Keep it simple for std::allocator. + template<typename _Res, typename _Tp> + static _Ptr<_Result<_Res>> + _S_allocate_result(const std::allocator<_Tp>& __a) + { + return _Ptr<_Result<_Res>>(new _Result<_Res>); + } + + // Base class for various types of shared state created by an + // asynchronous provider (such as a std::promise) and shared with one + // or more associated futures. + class _State_baseV2 + { + typedef _Ptr<_Result_base> _Ptr_type; + + enum _Status : unsigned { + __not_ready, + __ready + }; + + _Ptr_type _M_result; + __atomic_futex_unsigned<> _M_status; + atomic_flag _M_retrieved = ATOMIC_FLAG_INIT; + once_flag _M_once; + + public: + _State_baseV2() noexcept : _M_result(), _M_status(_Status::__not_ready) + { } + _State_baseV2(const _State_baseV2&) = delete; + _State_baseV2& operator=(const _State_baseV2&) = delete; + virtual ~_State_baseV2() = default; + + _Result_base& + wait() + { + // Run any deferred function or join any asynchronous thread: + _M_complete_async(); + // Acquire MO makes sure this synchronizes with the thread that made + // the future ready. + _M_status._M_load_when_equal(_Status::__ready, memory_order_acquire); + return *_M_result; + } + + template<typename _Rep, typename _Period> + future_status + wait_for(const chrono::duration<_Rep, _Period>& __rel) + { + // First, check if the future has been made ready. Use acquire MO + // to synchronize with the thread that made it ready. + if (_M_status._M_load(memory_order_acquire) == _Status::__ready) + return future_status::ready; + + if (_M_is_deferred_future()) + return future_status::deferred; + + // Don't wait unless the relative time is greater than zero. + if (__rel > __rel.zero() + && _M_status._M_load_when_equal_for(_Status::__ready, + memory_order_acquire, + __rel)) + { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2100. timed waiting functions must also join + // This call is a no-op by default except on an async future, + // in which case the async thread is joined. It's also not a + // no-op for a deferred future, but such a future will never + // reach this point because it returns future_status::deferred + // instead of waiting for the future to become ready (see + // above). Async futures synchronize in this call, so we need + // no further synchronization here. + _M_complete_async(); + + return future_status::ready; + } + return future_status::timeout; + } + + template<typename _Clock, typename _Duration> + future_status + wait_until(const chrono::time_point<_Clock, _Duration>& __abs) + { +#if __cplusplus > 201703L + static_assert(chrono::is_clock_v<_Clock>); +#endif + // First, check if the future has been made ready. Use acquire MO + // to synchronize with the thread that made it ready. + if (_M_status._M_load(memory_order_acquire) == _Status::__ready) + return future_status::ready; + + if (_M_is_deferred_future()) + return future_status::deferred; + + if (_M_status._M_load_when_equal_until(_Status::__ready, + memory_order_acquire, + __abs)) + { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2100. timed waiting functions must also join + // See wait_for(...) above. + _M_complete_async(); + + return future_status::ready; + } + return future_status::timeout; + } + + // Provide a result to the shared state and make it ready. + // Calls at most once: _M_result = __res(); + void + _M_set_result(function<_Ptr_type()> __res, bool __ignore_failure = false) + { + bool __did_set = false; + // all calls to this function are serialized, + // side-effects of invoking __res only happen once + call_once(_M_once, &_State_baseV2::_M_do_set, this, + std::__addressof(__res), std::__addressof(__did_set)); + if (__did_set) + // Use release MO to synchronize with observers of the ready state. + _M_status._M_store_notify_all(_Status::__ready, + memory_order_release); + else if (!__ignore_failure) + __throw_future_error(int(future_errc::promise_already_satisfied)); + } + + // Provide a result to the shared state but delay making it ready + // until the calling thread exits. + // Calls at most once: _M_result = __res(); + void + _M_set_delayed_result(function<_Ptr_type()> __res, + weak_ptr<_State_baseV2> __self) + { + bool __did_set = false; + unique_ptr<_Make_ready> __mr{new _Make_ready}; + // all calls to this function are serialized, + // side-effects of invoking __res only happen once + call_once(_M_once, &_State_baseV2::_M_do_set, this, + std::__addressof(__res), std::__addressof(__did_set)); + if (!__did_set) + __throw_future_error(int(future_errc::promise_already_satisfied)); + __mr->_M_shared_state = std::move(__self); + __mr->_M_set(); + __mr.release(); + } + + // Abandon this shared state. + void + _M_break_promise(_Ptr_type __res) + { + if (static_cast<bool>(__res)) + { + __res->_M_error = + make_exception_ptr(future_error(future_errc::broken_promise)); + // This function is only called when the last asynchronous result + // provider is abandoning this shared state, so noone can be + // trying to make the shared state ready at the same time, and + // we can access _M_result directly instead of through call_once. + _M_result.swap(__res); + // Use release MO to synchronize with observers of the ready state. + _M_status._M_store_notify_all(_Status::__ready, + memory_order_release); + } + } + + // Called when this object is first passed to a future. + void + _M_set_retrieved_flag() + { + if (_M_retrieved.test_and_set()) + __throw_future_error(int(future_errc::future_already_retrieved)); + } + + template<typename _Res, typename _Arg> + struct _Setter; + + // set lvalues + template<typename _Res, typename _Arg> + struct _Setter<_Res, _Arg&> + { + // check this is only used by promise<R>::set_value(const R&) + // or promise<R&>::set_value(R&) + static_assert(is_same<_Res, _Arg&>::value // promise<R&> + || is_same<const _Res, _Arg>::value, // promise<R> + "Invalid specialisation"); + + // Used by std::promise to copy construct the result. + typename promise<_Res>::_Ptr_type operator()() const + { + _M_promise->_M_storage->_M_set(*_M_arg); + return std::move(_M_promise->_M_storage); + } + promise<_Res>* _M_promise; + _Arg* _M_arg; + }; + + // set rvalues + template<typename _Res> + struct _Setter<_Res, _Res&&> + { + // Used by std::promise to move construct the result. + typename promise<_Res>::_Ptr_type operator()() const + { + _M_promise->_M_storage->_M_set(std::move(*_M_arg)); + return std::move(_M_promise->_M_storage); + } + promise<_Res>* _M_promise; + _Res* _M_arg; + }; + + // set void + template<typename _Res> + struct _Setter<_Res, void> + { + static_assert(is_void<_Res>::value, "Only used for promise<void>"); + + typename promise<_Res>::_Ptr_type operator()() const + { return std::move(_M_promise->_M_storage); } + + promise<_Res>* _M_promise; + }; + + struct __exception_ptr_tag { }; + + // set exceptions + template<typename _Res> + struct _Setter<_Res, __exception_ptr_tag> + { + // Used by std::promise to store an exception as the result. + typename promise<_Res>::_Ptr_type operator()() const + { + _M_promise->_M_storage->_M_error = *_M_ex; + return std::move(_M_promise->_M_storage); + } + + promise<_Res>* _M_promise; + exception_ptr* _M_ex; + }; + + template<typename _Res, typename _Arg> + __attribute__((__always_inline__)) + static _Setter<_Res, _Arg&&> + __setter(promise<_Res>* __prom, _Arg&& __arg) noexcept + { + return _Setter<_Res, _Arg&&>{ __prom, std::__addressof(__arg) }; + } + + template<typename _Res> + __attribute__((__always_inline__)) + static _Setter<_Res, __exception_ptr_tag> + __setter(exception_ptr& __ex, promise<_Res>* __prom) noexcept + { + __glibcxx_assert(__ex != nullptr); // LWG 2276 + return _Setter<_Res, __exception_ptr_tag>{ __prom, &__ex }; + } + + template<typename _Res> + __attribute__((__always_inline__)) + static _Setter<_Res, void> + __setter(promise<_Res>* __prom) noexcept + { + return _Setter<_Res, void>{ __prom }; + } + + template<typename _Tp> + static void + _S_check(const shared_ptr<_Tp>& __p) + { + if (!static_cast<bool>(__p)) + __throw_future_error((int)future_errc::no_state); + } + + private: + // The function invoked with std::call_once(_M_once, ...). + void + _M_do_set(function<_Ptr_type()>* __f, bool* __did_set) + { + _Ptr_type __res = (*__f)(); + // Notify the caller that we did try to set; if we do not throw an + // exception, the caller will be aware that it did set (e.g., see + // _M_set_result). + *__did_set = true; + _M_result.swap(__res); // nothrow + } + + // Wait for completion of async function. + virtual void _M_complete_async() { } + + // Return true if state corresponds to a deferred function. + virtual bool _M_is_deferred_future() const { return false; } + + struct _Make_ready final : __at_thread_exit_elt + { + weak_ptr<_State_baseV2> _M_shared_state; + static void _S_run(void*); + void _M_set(); + }; + }; + +#ifdef _GLIBCXX_ASYNC_ABI_COMPAT + class _State_base; + class _Async_state_common; +#else + using _State_base = _State_baseV2; + class _Async_state_commonV2; +#endif + + template<typename _BoundFn, + typename _Res = decltype(std::declval<_BoundFn&>()())> + class _Deferred_state; + + template<typename _BoundFn, + typename _Res = decltype(std::declval<_BoundFn&>()())> + class _Async_state_impl; + + template<typename _Signature> + class _Task_state_base; + + template<typename _Fn, typename _Alloc, typename _Signature> + class _Task_state; + + template<typename _Res_ptr, typename _Fn, + typename _Res = typename _Res_ptr::element_type::result_type> + struct _Task_setter; + + template<typename _Res_ptr, typename _BoundFn> + static _Task_setter<_Res_ptr, _BoundFn> + _S_task_setter(_Res_ptr& __ptr, _BoundFn& __call) + { + return { std::__addressof(__ptr), std::__addressof(__call) }; + } + }; + + /// Partial specialization for reference types. + template<typename _Res> + struct __future_base::_Result<_Res&> : __future_base::_Result_base + { + typedef _Res& result_type; + + _Result() noexcept : _M_value_ptr() { } + + void + _M_set(_Res& __res) noexcept + { _M_value_ptr = std::addressof(__res); } + + _Res& _M_get() noexcept { return *_M_value_ptr; } + + private: + _Res* _M_value_ptr; + + void _M_destroy() { delete this; } + }; + + /// Explicit specialization for void. + template<> + struct __future_base::_Result<void> : __future_base::_Result_base + { + typedef void result_type; + + private: + void _M_destroy() { delete this; } + }; + + /// @endcond + +#ifndef _GLIBCXX_ASYNC_ABI_COMPAT + + /// @cond undocumented + // Allow _Setter objects to be stored locally in std::function + template<typename _Res, typename _Arg> + struct __is_location_invariant + <__future_base::_State_base::_Setter<_Res, _Arg>> + : true_type { }; + + // Allow _Task_setter objects to be stored locally in std::function + template<typename _Res_ptr, typename _Fn, typename _Res> + struct __is_location_invariant + <__future_base::_Task_setter<_Res_ptr, _Fn, _Res>> + : true_type { }; + /// @endcond + + /// Common implementation for future and shared_future. + template<typename _Res> + class __basic_future : public __future_base + { + protected: + typedef shared_ptr<_State_base> __state_type; + typedef __future_base::_Result<_Res>& __result_type; + + private: + __state_type _M_state; + + public: + // Disable copying. + __basic_future(const __basic_future&) = delete; + __basic_future& operator=(const __basic_future&) = delete; + + bool + valid() const noexcept { return static_cast<bool>(_M_state); } + + void + wait() const + { + _State_base::_S_check(_M_state); + _M_state->wait(); + } + + template<typename _Rep, typename _Period> + future_status + wait_for(const chrono::duration<_Rep, _Period>& __rel) const + { + _State_base::_S_check(_M_state); + return _M_state->wait_for(__rel); + } + + template<typename _Clock, typename _Duration> + future_status + wait_until(const chrono::time_point<_Clock, _Duration>& __abs) const + { + _State_base::_S_check(_M_state); + return _M_state->wait_until(__abs); + } + + protected: + /// Wait for the state to be ready and rethrow any stored exception + __result_type + _M_get_result() const + { + _State_base::_S_check(_M_state); + _Result_base& __res = _M_state->wait(); + if (!(__res._M_error == nullptr)) + rethrow_exception(__res._M_error); + return static_cast<__result_type>(__res); + } + + void _M_swap(__basic_future& __that) noexcept + { + _M_state.swap(__that._M_state); + } + + // Construction of a future by promise::get_future() + explicit + __basic_future(const __state_type& __state) : _M_state(__state) + { + _State_base::_S_check(_M_state); + _M_state->_M_set_retrieved_flag(); + } + + // Copy construction from a shared_future + explicit + __basic_future(const shared_future<_Res>&) noexcept; + + // Move construction from a shared_future + explicit + __basic_future(shared_future<_Res>&&) noexcept; + + // Move construction from a future + explicit + __basic_future(future<_Res>&&) noexcept; + + constexpr __basic_future() noexcept : _M_state() { } + + struct _Reset + { + explicit _Reset(__basic_future& __fut) noexcept : _M_fut(__fut) { } + ~_Reset() { _M_fut._M_state.reset(); } + __basic_future& _M_fut; + }; + }; + + + /// Primary template for future. + template<typename _Res> + class future : public __basic_future<_Res> + { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3458. Is shared_future intended to work with arrays or function types? + static_assert(!is_array<_Res>{}, "result type must not be an array"); + static_assert(!is_function<_Res>{}, "result type must not be a function"); + static_assert(is_destructible<_Res>{}, + "result type must be destructible"); + + friend class promise<_Res>; + template<typename> friend class packaged_task; + template<typename _Fn, typename... _Args> + friend future<__async_result_of<_Fn, _Args...>> + async(launch, _Fn&&, _Args&&...); + + typedef __basic_future<_Res> _Base_type; + typedef typename _Base_type::__state_type __state_type; + + explicit + future(const __state_type& __state) : _Base_type(__state) { } + + public: + constexpr future() noexcept : _Base_type() { } + + /// Move constructor + future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { } + + // Disable copying + future(const future&) = delete; + future& operator=(const future&) = delete; + + future& operator=(future&& __fut) noexcept + { + future(std::move(__fut))._M_swap(*this); + return *this; + } + + /// Retrieving the value + _Res + get() + { + typename _Base_type::_Reset __reset(*this); + return std::move(this->_M_get_result()._M_value()); + } + + shared_future<_Res> share() noexcept; + }; + + /// Partial specialization for future<R&> + template<typename _Res> + class future<_Res&> : public __basic_future<_Res&> + { + friend class promise<_Res&>; + template<typename> friend class packaged_task; + template<typename _Fn, typename... _Args> + friend future<__async_result_of<_Fn, _Args...>> + async(launch, _Fn&&, _Args&&...); + + typedef __basic_future<_Res&> _Base_type; + typedef typename _Base_type::__state_type __state_type; + + explicit + future(const __state_type& __state) : _Base_type(__state) { } + + public: + constexpr future() noexcept : _Base_type() { } + + /// Move constructor + future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { } + + // Disable copying + future(const future&) = delete; + future& operator=(const future&) = delete; + + future& operator=(future&& __fut) noexcept + { + future(std::move(__fut))._M_swap(*this); + return *this; + } + + /// Retrieving the value + _Res& + get() + { + typename _Base_type::_Reset __reset(*this); + return this->_M_get_result()._M_get(); + } + + shared_future<_Res&> share() noexcept; + }; + + /// Explicit specialization for future<void> + template<> + class future<void> : public __basic_future<void> + { + friend class promise<void>; + template<typename> friend class packaged_task; + template<typename _Fn, typename... _Args> + friend future<__async_result_of<_Fn, _Args...>> + async(launch, _Fn&&, _Args&&...); + + typedef __basic_future<void> _Base_type; + typedef typename _Base_type::__state_type __state_type; + + explicit + future(const __state_type& __state) : _Base_type(__state) { } + + public: + constexpr future() noexcept : _Base_type() { } + + /// Move constructor + future(future&& __uf) noexcept : _Base_type(std::move(__uf)) { } + + // Disable copying + future(const future&) = delete; + future& operator=(const future&) = delete; + + future& operator=(future&& __fut) noexcept + { + future(std::move(__fut))._M_swap(*this); + return *this; + } + + /// Retrieving the value + void + get() + { + typename _Base_type::_Reset __reset(*this); + this->_M_get_result(); + } + + shared_future<void> share() noexcept; + }; + + + /// Primary template for shared_future. + template<typename _Res> + class shared_future : public __basic_future<_Res> + { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3458. Is shared_future intended to work with arrays or function types? + static_assert(!is_array<_Res>{}, "result type must not be an array"); + static_assert(!is_function<_Res>{}, "result type must not be a function"); + static_assert(is_destructible<_Res>{}, + "result type must be destructible"); + + typedef __basic_future<_Res> _Base_type; + + public: + constexpr shared_future() noexcept : _Base_type() { } + + /// Copy constructor + shared_future(const shared_future& __sf) noexcept : _Base_type(__sf) { } + + /// Construct from a future rvalue + shared_future(future<_Res>&& __uf) noexcept + : _Base_type(std::move(__uf)) + { } + + /// Construct from a shared_future rvalue + shared_future(shared_future&& __sf) noexcept + : _Base_type(std::move(__sf)) + { } + + shared_future& operator=(const shared_future& __sf) noexcept + { + shared_future(__sf)._M_swap(*this); + return *this; + } + + shared_future& operator=(shared_future&& __sf) noexcept + { + shared_future(std::move(__sf))._M_swap(*this); + return *this; + } + + /// Retrieving the value + const _Res& + get() const { return this->_M_get_result()._M_value(); } + }; + + /// Partial specialization for shared_future<R&> + template<typename _Res> + class shared_future<_Res&> : public __basic_future<_Res&> + { + typedef __basic_future<_Res&> _Base_type; + + public: + constexpr shared_future() noexcept : _Base_type() { } + + /// Copy constructor + shared_future(const shared_future& __sf) : _Base_type(__sf) { } + + /// Construct from a future rvalue + shared_future(future<_Res&>&& __uf) noexcept + : _Base_type(std::move(__uf)) + { } + + /// Construct from a shared_future rvalue + shared_future(shared_future&& __sf) noexcept + : _Base_type(std::move(__sf)) + { } + + shared_future& operator=(const shared_future& __sf) + { + shared_future(__sf)._M_swap(*this); + return *this; + } + + shared_future& operator=(shared_future&& __sf) noexcept + { + shared_future(std::move(__sf))._M_swap(*this); + return *this; + } + + /// Retrieving the value + _Res& + get() const { return this->_M_get_result()._M_get(); } + }; + + /// Explicit specialization for shared_future<void> + template<> + class shared_future<void> : public __basic_future<void> + { + typedef __basic_future<void> _Base_type; + + public: + constexpr shared_future() noexcept : _Base_type() { } + + /// Copy constructor + shared_future(const shared_future& __sf) : _Base_type(__sf) { } + + /// Construct from a future rvalue + shared_future(future<void>&& __uf) noexcept + : _Base_type(std::move(__uf)) + { } + + /// Construct from a shared_future rvalue + shared_future(shared_future&& __sf) noexcept + : _Base_type(std::move(__sf)) + { } + + shared_future& operator=(const shared_future& __sf) + { + shared_future(__sf)._M_swap(*this); + return *this; + } + + shared_future& operator=(shared_future&& __sf) noexcept + { + shared_future(std::move(__sf))._M_swap(*this); + return *this; + } + + // Retrieving the value + void + get() const { this->_M_get_result(); } + }; + + // Now we can define the protected __basic_future constructors. + template<typename _Res> + inline __basic_future<_Res>:: + __basic_future(const shared_future<_Res>& __sf) noexcept + : _M_state(__sf._M_state) + { } + + template<typename _Res> + inline __basic_future<_Res>:: + __basic_future(shared_future<_Res>&& __sf) noexcept + : _M_state(std::move(__sf._M_state)) + { } + + template<typename _Res> + inline __basic_future<_Res>:: + __basic_future(future<_Res>&& __uf) noexcept + : _M_state(std::move(__uf._M_state)) + { } + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2556. Wide contract for future::share() + template<typename _Res> + inline shared_future<_Res> + future<_Res>::share() noexcept + { return shared_future<_Res>(std::move(*this)); } + + template<typename _Res> + inline shared_future<_Res&> + future<_Res&>::share() noexcept + { return shared_future<_Res&>(std::move(*this)); } + + inline shared_future<void> + future<void>::share() noexcept + { return shared_future<void>(std::move(*this)); } + + /// Primary template for promise + template<typename _Res> + class promise + { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3466: Specify the requirements for promise/future/[...] consistently + static_assert(!is_array<_Res>{}, "result type must not be an array"); + static_assert(!is_function<_Res>{}, "result type must not be a function"); + static_assert(is_destructible<_Res>{}, + "result type must be destructible"); + + typedef __future_base::_State_base _State; + typedef __future_base::_Result<_Res> _Res_type; + typedef __future_base::_Ptr<_Res_type> _Ptr_type; + template<typename, typename> friend struct _State::_Setter; + friend _State; + + shared_ptr<_State> _M_future; + _Ptr_type _M_storage; + + public: + promise() + : _M_future(std::make_shared<_State>()), + _M_storage(new _Res_type()) + { } + + promise(promise&& __rhs) noexcept + : _M_future(std::move(__rhs._M_future)), + _M_storage(std::move(__rhs._M_storage)) + { } + + template<typename _Allocator> + promise(allocator_arg_t, const _Allocator& __a) + : _M_future(std::allocate_shared<_State>(__a)), + _M_storage(__future_base::_S_allocate_result<_Res>(__a)) + { } + + template<typename _Allocator> + promise(allocator_arg_t, const _Allocator&, promise&& __rhs) + : _M_future(std::move(__rhs._M_future)), + _M_storage(std::move(__rhs._M_storage)) + { } + + promise(const promise&) = delete; + + ~promise() + { + if (static_cast<bool>(_M_future) && !_M_future.unique()) + _M_future->_M_break_promise(std::move(_M_storage)); + } + + // Assignment + promise& + operator=(promise&& __rhs) noexcept + { + promise(std::move(__rhs)).swap(*this); + return *this; + } + + promise& operator=(const promise&) = delete; + + void + swap(promise& __rhs) noexcept + { + _M_future.swap(__rhs._M_future); + _M_storage.swap(__rhs._M_storage); + } + + // Retrieving the result + future<_Res> + get_future() + { return future<_Res>(_M_future); } + + // Setting the result + void + set_value(const _Res& __r) + { _M_state()._M_set_result(_State::__setter(this, __r)); } + + void + set_value(_Res&& __r) + { _M_state()._M_set_result(_State::__setter(this, std::move(__r))); } + + void + set_exception(exception_ptr __p) + { _M_state()._M_set_result(_State::__setter(__p, this)); } + + void + set_value_at_thread_exit(const _Res& __r) + { + _M_state()._M_set_delayed_result(_State::__setter(this, __r), + _M_future); + } + + void + set_value_at_thread_exit(_Res&& __r) + { + _M_state()._M_set_delayed_result( + _State::__setter(this, std::move(__r)), _M_future); + } + + void + set_exception_at_thread_exit(exception_ptr __p) + { + _M_state()._M_set_delayed_result(_State::__setter(__p, this), + _M_future); + } + + private: + _State& + _M_state() + { + __future_base::_State_base::_S_check(_M_future); + return *_M_future; + } + }; + + template<typename _Res> + inline void + swap(promise<_Res>& __x, promise<_Res>& __y) noexcept + { __x.swap(__y); } + + template<typename _Res, typename _Alloc> + struct uses_allocator<promise<_Res>, _Alloc> + : public true_type { }; + + + /// Partial specialization for promise<R&> + template<typename _Res> + class promise<_Res&> + { + typedef __future_base::_State_base _State; + typedef __future_base::_Result<_Res&> _Res_type; + typedef __future_base::_Ptr<_Res_type> _Ptr_type; + template<typename, typename> friend struct _State::_Setter; + friend _State; + + shared_ptr<_State> _M_future; + _Ptr_type _M_storage; + + public: + promise() + : _M_future(std::make_shared<_State>()), + _M_storage(new _Res_type()) + { } + + promise(promise&& __rhs) noexcept + : _M_future(std::move(__rhs._M_future)), + _M_storage(std::move(__rhs._M_storage)) + { } + + template<typename _Allocator> + promise(allocator_arg_t, const _Allocator& __a) + : _M_future(std::allocate_shared<_State>(__a)), + _M_storage(__future_base::_S_allocate_result<_Res&>(__a)) + { } + + template<typename _Allocator> + promise(allocator_arg_t, const _Allocator&, promise&& __rhs) + : _M_future(std::move(__rhs._M_future)), + _M_storage(std::move(__rhs._M_storage)) + { } + + promise(const promise&) = delete; + + ~promise() + { + if (static_cast<bool>(_M_future) && !_M_future.unique()) + _M_future->_M_break_promise(std::move(_M_storage)); + } + + // Assignment + promise& + operator=(promise&& __rhs) noexcept + { + promise(std::move(__rhs)).swap(*this); + return *this; + } + + promise& operator=(const promise&) = delete; + + void + swap(promise& __rhs) noexcept + { + _M_future.swap(__rhs._M_future); + _M_storage.swap(__rhs._M_storage); + } + + // Retrieving the result + future<_Res&> + get_future() + { return future<_Res&>(_M_future); } + + // Setting the result + void + set_value(_Res& __r) + { _M_state()._M_set_result(_State::__setter(this, __r)); } + + void + set_exception(exception_ptr __p) + { _M_state()._M_set_result(_State::__setter(__p, this)); } + + void + set_value_at_thread_exit(_Res& __r) + { + _M_state()._M_set_delayed_result(_State::__setter(this, __r), + _M_future); + } + + void + set_exception_at_thread_exit(exception_ptr __p) + { + _M_state()._M_set_delayed_result(_State::__setter(__p, this), + _M_future); + } + + private: + _State& + _M_state() + { + __future_base::_State_base::_S_check(_M_future); + return *_M_future; + } + }; + + /// Explicit specialization for promise<void> + template<> + class promise<void> + { + typedef __future_base::_State_base _State; + typedef __future_base::_Result<void> _Res_type; + typedef __future_base::_Ptr<_Res_type> _Ptr_type; + template<typename, typename> friend struct _State::_Setter; + friend _State; + + shared_ptr<_State> _M_future; + _Ptr_type _M_storage; + + public: + promise() + : _M_future(std::make_shared<_State>()), + _M_storage(new _Res_type()) + { } + + promise(promise&& __rhs) noexcept + : _M_future(std::move(__rhs._M_future)), + _M_storage(std::move(__rhs._M_storage)) + { } + + template<typename _Allocator> + promise(allocator_arg_t, const _Allocator& __a) + : _M_future(std::allocate_shared<_State>(__a)), + _M_storage(__future_base::_S_allocate_result<void>(__a)) + { } + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2095. missing constructors needed for uses-allocator construction + template<typename _Allocator> + promise(allocator_arg_t, const _Allocator&, promise&& __rhs) + : _M_future(std::move(__rhs._M_future)), + _M_storage(std::move(__rhs._M_storage)) + { } + + promise(const promise&) = delete; + + ~promise() + { + if (static_cast<bool>(_M_future) && !_M_future.unique()) + _M_future->_M_break_promise(std::move(_M_storage)); + } + + // Assignment + promise& + operator=(promise&& __rhs) noexcept + { + promise(std::move(__rhs)).swap(*this); + return *this; + } + + promise& operator=(const promise&) = delete; + + void + swap(promise& __rhs) noexcept + { + _M_future.swap(__rhs._M_future); + _M_storage.swap(__rhs._M_storage); + } + + // Retrieving the result + future<void> + get_future() + { return future<void>(_M_future); } + + // Setting the result + void + set_value() + { _M_state()._M_set_result(_State::__setter(this)); } + + void + set_exception(exception_ptr __p) + { _M_state()._M_set_result(_State::__setter(__p, this)); } + + void + set_value_at_thread_exit() + { _M_state()._M_set_delayed_result(_State::__setter(this), _M_future); } + + void + set_exception_at_thread_exit(exception_ptr __p) + { + _M_state()._M_set_delayed_result(_State::__setter(__p, this), + _M_future); + } + + private: + _State& + _M_state() + { + __future_base::_State_base::_S_check(_M_future); + return *_M_future; + } + }; + + /// @cond undocumented + template<typename _Ptr_type, typename _Fn, typename _Res> + struct __future_base::_Task_setter + { + // Invoke the function and provide the result to the caller. + _Ptr_type operator()() const + { + __try + { + (*_M_result)->_M_set((*_M_fn)()); + } + __catch(const __cxxabiv1::__forced_unwind&) + { + __throw_exception_again; // will cause broken_promise + } + __catch(...) + { + (*_M_result)->_M_error = current_exception(); + } + return std::move(*_M_result); + } + _Ptr_type* _M_result; + _Fn* _M_fn; + }; + + template<typename _Ptr_type, typename _Fn> + struct __future_base::_Task_setter<_Ptr_type, _Fn, void> + { + _Ptr_type operator()() const + { + __try + { + (*_M_fn)(); + } + __catch(const __cxxabiv1::__forced_unwind&) + { + __throw_exception_again; // will cause broken_promise + } + __catch(...) + { + (*_M_result)->_M_error = current_exception(); + } + return std::move(*_M_result); + } + _Ptr_type* _M_result; + _Fn* _M_fn; + }; + + // Holds storage for a packaged_task's result. + template<typename _Res, typename... _Args> + struct __future_base::_Task_state_base<_Res(_Args...)> + : __future_base::_State_base + { + typedef _Res _Res_type; + + template<typename _Alloc> + _Task_state_base(const _Alloc& __a) + : _M_result(_S_allocate_result<_Res>(__a)) + { } + + // Invoke the stored task and make the state ready. + virtual void + _M_run(_Args&&... __args) = 0; + + // Invoke the stored task and make the state ready at thread exit. + virtual void + _M_run_delayed(_Args&&... __args, weak_ptr<_State_base>) = 0; + + virtual shared_ptr<_Task_state_base> + _M_reset() = 0; + + typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type; + _Ptr_type _M_result; + }; + + // Holds a packaged_task's stored task. + template<typename _Fn, typename _Alloc, typename _Res, typename... _Args> + struct __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)> final + : __future_base::_Task_state_base<_Res(_Args...)> + { + template<typename _Fn2> + _Task_state(_Fn2&& __fn, const _Alloc& __a) + : _Task_state_base<_Res(_Args...)>(__a), + _M_impl(std::forward<_Fn2>(__fn), __a) + { } + + private: + virtual void + _M_run(_Args&&... __args) + { + auto __boundfn = [&] () -> _Res { + return std::__invoke_r<_Res>(_M_impl._M_fn, + std::forward<_Args>(__args)...); + }; + this->_M_set_result(_S_task_setter(this->_M_result, __boundfn)); + } + + virtual void + _M_run_delayed(_Args&&... __args, weak_ptr<_State_base> __self) + { + auto __boundfn = [&] () -> _Res { + return std::__invoke_r<_Res>(_M_impl._M_fn, + std::forward<_Args>(__args)...); + }; + this->_M_set_delayed_result(_S_task_setter(this->_M_result, __boundfn), + std::move(__self)); + } + + virtual shared_ptr<_Task_state_base<_Res(_Args...)>> + _M_reset(); + + struct _Impl : _Alloc + { + template<typename _Fn2> + _Impl(_Fn2&& __fn, const _Alloc& __a) + : _Alloc(__a), _M_fn(std::forward<_Fn2>(__fn)) { } + _Fn _M_fn; + } _M_impl; + }; + + template<typename _Signature, typename _Fn, + typename _Alloc = std::allocator<int>> + static shared_ptr<__future_base::_Task_state_base<_Signature>> + __create_task_state(_Fn&& __fn, const _Alloc& __a = _Alloc()) + { + typedef typename decay<_Fn>::type _Fn2; + typedef __future_base::_Task_state<_Fn2, _Alloc, _Signature> _State; + return std::allocate_shared<_State>(__a, std::forward<_Fn>(__fn), __a); + } + + template<typename _Fn, typename _Alloc, typename _Res, typename... _Args> + shared_ptr<__future_base::_Task_state_base<_Res(_Args...)>> + __future_base::_Task_state<_Fn, _Alloc, _Res(_Args...)>::_M_reset() + { + return __create_task_state<_Res(_Args...)>(std::move(_M_impl._M_fn), + static_cast<_Alloc&>(_M_impl)); + } + /// @endcond + + /// packaged_task + template<typename _Res, typename... _ArgTypes> + class packaged_task<_Res(_ArgTypes...)> + { + typedef __future_base::_Task_state_base<_Res(_ArgTypes...)> _State_type; + shared_ptr<_State_type> _M_state; + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3039. Unnecessary decay in thread and packaged_task + template<typename _Fn, typename _Fn2 = __remove_cvref_t<_Fn>> + using __not_same + = typename enable_if<!is_same<packaged_task, _Fn2>::value>::type; + + public: + // Construction and destruction + packaged_task() noexcept { } + + template<typename _Fn, typename = __not_same<_Fn>> + explicit + packaged_task(_Fn&& __fn) + : _M_state( + __create_task_state<_Res(_ArgTypes...)>(std::forward<_Fn>(__fn))) + { } + +#if __cplusplus < 201703L + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2097. packaged_task constructors should be constrained + // 2407. [this constructor should not be] explicit + // 2921. packaged_task and type-erased allocators + template<typename _Fn, typename _Alloc, typename = __not_same<_Fn>> + packaged_task(allocator_arg_t, const _Alloc& __a, _Fn&& __fn) + : _M_state(__create_task_state<_Res(_ArgTypes...)>( + std::forward<_Fn>(__fn), __a)) + { } + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2095. missing constructors needed for uses-allocator construction + template<typename _Allocator> + packaged_task(allocator_arg_t, const _Allocator& __a) noexcept + { } + + template<typename _Allocator> + packaged_task(allocator_arg_t, const _Allocator&, + const packaged_task&) = delete; + + template<typename _Allocator> + packaged_task(allocator_arg_t, const _Allocator&, + packaged_task&& __other) noexcept + { this->swap(__other); } +#endif + + ~packaged_task() + { + if (static_cast<bool>(_M_state) && !_M_state.unique()) + _M_state->_M_break_promise(std::move(_M_state->_M_result)); + } + + // No copy + packaged_task(const packaged_task&) = delete; + packaged_task& operator=(const packaged_task&) = delete; + + // Move support + packaged_task(packaged_task&& __other) noexcept + { this->swap(__other); } + + packaged_task& operator=(packaged_task&& __other) noexcept + { + packaged_task(std::move(__other)).swap(*this); + return *this; + } + + void + swap(packaged_task& __other) noexcept + { _M_state.swap(__other._M_state); } + + bool + valid() const noexcept + { return static_cast<bool>(_M_state); } + + // Result retrieval + future<_Res> + get_future() + { return future<_Res>(_M_state); } + + // Execution + void + operator()(_ArgTypes... __args) + { + __future_base::_State_base::_S_check(_M_state); + _M_state->_M_run(std::forward<_ArgTypes>(__args)...); + } + + void + make_ready_at_thread_exit(_ArgTypes... __args) + { + __future_base::_State_base::_S_check(_M_state); + _M_state->_M_run_delayed(std::forward<_ArgTypes>(__args)..., _M_state); + } + + void + reset() + { + __future_base::_State_base::_S_check(_M_state); + packaged_task __tmp; + __tmp._M_state = _M_state; + _M_state = _M_state->_M_reset(); + } + }; + + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3117. Missing packaged_task deduction guides +#if __cpp_deduction_guides >= 201606 + template<typename _Res, typename... _ArgTypes> + packaged_task(_Res(*)(_ArgTypes...)) -> packaged_task<_Res(_ArgTypes...)>; + + template<typename _Fun, typename _Signature + = __function_guide_t<_Fun, decltype(&_Fun::operator())>> + packaged_task(_Fun) -> packaged_task<_Signature>; +#endif + + /// swap + template<typename _Res, typename... _ArgTypes> + inline void + swap(packaged_task<_Res(_ArgTypes...)>& __x, + packaged_task<_Res(_ArgTypes...)>& __y) noexcept + { __x.swap(__y); } + +#if __cplusplus < 201703L + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 2976. Dangling uses_allocator specialization for packaged_task + template<typename _Res, typename _Alloc> + struct uses_allocator<packaged_task<_Res>, _Alloc> + : public true_type { }; +#endif + + /// @cond undocumented + + // Shared state created by std::async(). + // Holds a deferred function and storage for its result. + template<typename _BoundFn, typename _Res> + class __future_base::_Deferred_state final + : public __future_base::_State_base + { + public: + template<typename... _Args> + explicit + _Deferred_state(_Args&&... __args) + : _M_result(new _Result<_Res>()), + _M_fn(std::forward<_Args>(__args)...) + { } + + private: + typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type; + _Ptr_type _M_result; + _BoundFn _M_fn; + + // Run the deferred function. + virtual void + _M_complete_async() + { + // Multiple threads can call a waiting function on the future and + // reach this point at the same time. The call_once in _M_set_result + // ensures only the first one run the deferred function, stores the + // result in _M_result, swaps that with the base _M_result and makes + // the state ready. Tell _M_set_result to ignore failure so all later + // calls do nothing. + _M_set_result(_S_task_setter(_M_result, _M_fn), true); + } + + // Caller should check whether the state is ready first, because this + // function will return true even after the deferred function has run. + virtual bool _M_is_deferred_future() const { return true; } + }; + + // Common functionality hoisted out of the _Async_state_impl template. + class __future_base::_Async_state_commonV2 + : public __future_base::_State_base + { + protected: + ~_Async_state_commonV2() = default; + + // Make waiting functions block until the thread completes, as if joined. + // + // This function is used by wait() to satisfy the first requirement below + // and by wait_for() / wait_until() to satisfy the second. + // + // [futures.async]: + // + // - a call to a waiting function on an asynchronous return object that + // shares the shared state created by this async call shall block until + // the associated thread has completed, as if joined, or else time out. + // + // - the associated thread completion synchronizes with the return from + // the first function that successfully detects the ready status of the + // shared state or with the return from the last function that releases + // the shared state, whichever happens first. + virtual void _M_complete_async() { _M_join(); } + + void _M_join() { std::call_once(_M_once, &thread::join, &_M_thread); } + + thread _M_thread; + once_flag _M_once; + }; + + // Shared state created by std::async(). + // Starts a new thread that runs a function and makes the shared state ready. + template<typename _BoundFn, typename _Res> + class __future_base::_Async_state_impl final + : public __future_base::_Async_state_commonV2 + { + public: + template<typename... _Args> + explicit + _Async_state_impl(_Args&&... __args) + : _M_result(new _Result<_Res>()), + _M_fn(std::forward<_Args>(__args)...) + { + _M_thread = std::thread{&_Async_state_impl::_M_run, this}; + } + + // Must not destroy _M_result and _M_fn until the thread finishes. + // Call join() directly rather than through _M_join() because no other + // thread can be referring to this state if it is being destroyed. + ~_Async_state_impl() + { + if (_M_thread.joinable()) + _M_thread.join(); + } + + private: + void + _M_run() + { + __try + { + _M_set_result(_S_task_setter(_M_result, _M_fn)); + } + __catch (const __cxxabiv1::__forced_unwind&) + { + // make the shared state ready on thread cancellation + if (static_cast<bool>(_M_result)) + this->_M_break_promise(std::move(_M_result)); + __throw_exception_again; + } + } + + typedef __future_base::_Ptr<_Result<_Res>> _Ptr_type; + _Ptr_type _M_result; + _BoundFn _M_fn; + }; + /// @endcond + + /// async + template<typename _Fn, typename... _Args> + _GLIBCXX_NODISCARD future<__async_result_of<_Fn, _Args...>> + async(launch __policy, _Fn&& __fn, _Args&&... __args) + { + using _Wr = std::thread::_Call_wrapper<_Fn, _Args...>; + using _As = __future_base::_Async_state_impl<_Wr>; + using _Ds = __future_base::_Deferred_state<_Wr>; + + std::shared_ptr<__future_base::_State_base> __state; + if ((__policy & launch::async) == launch::async) + { + __try + { + __state = std::make_shared<_As>(std::forward<_Fn>(__fn), + std::forward<_Args>(__args)...); + } +#if __cpp_exceptions + catch(const system_error& __e) + { + if (__e.code() != errc::resource_unavailable_try_again + || (__policy & launch::deferred) != launch::deferred) + throw; + } +#endif + } + if (!__state) + { + __state = std::make_shared<_Ds>(std::forward<_Fn>(__fn), + std::forward<_Args>(__args)...); + } + return future<__async_result_of<_Fn, _Args...>>(std::move(__state)); + } + + /// async, potential overload + template<typename _Fn, typename... _Args> + _GLIBCXX_NODISCARD inline future<__async_result_of<_Fn, _Args...>> + async(_Fn&& __fn, _Args&&... __args) + { + return std::async(launch::async|launch::deferred, + std::forward<_Fn>(__fn), + std::forward<_Args>(__args)...); + } + +#endif // _GLIBCXX_ASYNC_ABI_COMPAT +#endif // _GLIBCXX_HAS_GTHREADS + + /// @} group futures +_GLIBCXX_END_NAMESPACE_VERSION +} // namespace + +#endif // C++11 + +#endif // _GLIBCXX_FUTURE |