include/future

// -*- C++ -*-
//===--------------------------- future -----------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_FUTURE
#define _LIBCPP_FUTURE

/*
 future synopsis

namespace std
{

enum class future_errc
{
 future_already_retrieved = 1,
 promise_already_satisfied,
 no_state,
 broken_promise
};

enum class launch
{
 async = 1,
 deferred = 2,
 any = async | deferred
};

enum class future_status
{
 ready,
 timeout,
 deferred
};

template <> struct is_error_code_enum<future_errc> : public true_type { };
error_code make_error_code(future_errc e) noexcept;
error_condition make_error_condition(future_errc e) noexcept;

const error_category& future_category() noexcept;

class future_error
 : public logic_error
{
public:
 future_error(error_code ec); // exposition only
 explicit future_error(future_errc); // C++17
 const error_code& code() const noexcept;
 const char* what() const noexcept;
};

template <class R>
class promise
{
public:
 promise();
 template <class Allocator>
 promise(allocator_arg_t, const Allocator& a);
 promise(promise&& rhs) noexcept;
 promise(const promise& rhs) = delete;
 ~promise();

 // assignment
 promise& operator=(promise&& rhs) noexcept;
 promise& operator=(const promise& rhs) = delete;
 void swap(promise& other) noexcept;

 // retrieving the result
 future<R> get_future();

 // setting the result
 void set_value(const R& r);
 void set_value(R&& r);
 void set_exception(exception_ptr p);

 // setting the result with deferred notification
 void set_value_at_thread_exit(const R& r);
 void set_value_at_thread_exit(R&& r);
 void set_exception_at_thread_exit(exception_ptr p);
};

template <class R>
class promise<R&>
{
public:
 promise();
 template <class Allocator>
 promise(allocator_arg_t, const Allocator& a);
 promise(promise&& rhs) noexcept;
 promise(const promise& rhs) = delete;
 ~promise();

 // assignment
 promise& operator=(promise&& rhs) noexcept;
 promise& operator=(const promise& rhs) = delete;
 void swap(promise& other) noexcept;

 // retrieving the result
 future<R&> get_future();

 // setting the result
 void set_value(R& r);
 void set_exception(exception_ptr p);

 // setting the result with deferred notification
 void set_value_at_thread_exit(R&);
 void set_exception_at_thread_exit(exception_ptr p);
};

template <>
class promise<void>
{
public:
 promise();
 template <class Allocator>
 promise(allocator_arg_t, const Allocator& a);
 promise(promise&& rhs) noexcept;
 promise(const promise& rhs) = delete;
 ~promise();

 // assignment
 promise& operator=(promise&& rhs) noexcept;
 promise& operator=(const promise& rhs) = delete;
 void swap(promise& other) noexcept;

 // retrieving the result
 future<void> get_future();

 // setting the result
 void set_value();
 void set_exception(exception_ptr p);

 // setting the result with deferred notification
 void set_value_at_thread_exit();
 void set_exception_at_thread_exit(exception_ptr p);
};

template <class R> void swap(promise<R>& x, promise<R>& y) noexcept;

template <class R, class Alloc>
 struct uses_allocator<promise<R>, Alloc> : public true_type {};

template <class R>
class future
{
public:
 future() noexcept;
 future(future&&) noexcept;
 future(const future& rhs) = delete;
 ~future();
 future& operator=(const future& rhs) = delete;
 future& operator=(future&&) noexcept;
 shared_future<R> share();

 // retrieving the value
 R get();

 // functions to check state
 bool valid() const noexcept;

 void wait() const;
 template <class Rep, class Period>
 future_status
 wait_for(const chrono::duration<Rep, Period>& rel_time) const;
 template <class Clock, class Duration>
 future_status
 wait_until(const chrono::time_point<Clock, Duration>& abs_time) const;
};

template <class R>
class future<R&>
{
public:
 future() noexcept;
 future(future&&) noexcept;
 future(const future& rhs) = delete;
 ~future();
 future& operator=(const future& rhs) = delete;
 future& operator=(future&&) noexcept;
 shared_future<R&> share();

 // retrieving the value
 R& get();

 // functions to check state
 bool valid() const noexcept;

 void wait() const;
 template <class Rep, class Period>
 future_status
 wait_for(const chrono::duration<Rep, Period>& rel_time) const;
 template <class Clock, class Duration>
 future_status
 wait_until(const chrono::time_point<Clock, Duration>& abs_time) const;
};

template <>
class future<void>
{
public:
 future() noexcept;
 future(future&&) noexcept;
 future(const future& rhs) = delete;
 ~future();
 future& operator=(const future& rhs) = delete;
 future& operator=(future&&) noexcept;
 shared_future<void> share();

 // retrieving the value
 void get();

 // functions to check state
 bool valid() const noexcept;

 void wait() const;
 template <class Rep, class Period>
 future_status
 wait_for(const chrono::duration<Rep, Period>& rel_time) const;
 template <class Clock, class Duration>
 future_status
 wait_until(const chrono::time_point<Clock, Duration>& abs_time) const;
};

template <class R>
class shared_future
{
public:
 shared_future() noexcept;
 shared_future(const shared_future& rhs);
 shared_future(future<R>&&) noexcept;
 shared_future(shared_future&& rhs) noexcept;
 ~shared_future();
 shared_future& operator=(const shared_future& rhs);
 shared_future& operator=(shared_future&& rhs) noexcept;

 // retrieving the value
 const R& get() const;

 // functions to check state
 bool valid() const noexcept;

 void wait() const;
 template <class Rep, class Period>
 future_status
 wait_for(const chrono::duration<Rep, Period>& rel_time) const;
 template <class Clock, class Duration>
 future_status
 wait_until(const chrono::time_point<Clock, Duration>& abs_time) const;
};

template <class R>
class shared_future<R&>
{
public:
 shared_future() noexcept;
 shared_future(const shared_future& rhs);
 shared_future(future<R&>&&) noexcept;
 shared_future(shared_future&& rhs) noexcept;
 ~shared_future();
 shared_future& operator=(const shared_future& rhs);
 shared_future& operator=(shared_future&& rhs) noexcept;

 // retrieving the value
 R& get() const;

 // functions to check state
 bool valid() const noexcept;

 void wait() const;
 template <class Rep, class Period>
 future_status
 wait_for(const chrono::duration<Rep, Period>& rel_time) const;
 template <class Clock, class Duration>
 future_status
 wait_until(const chrono::time_point<Clock, Duration>& abs_time) const;
};

template <>
class shared_future<void>
{
public:
 shared_future() noexcept;
 shared_future(const shared_future& rhs);
 shared_future(future<void>&&) noexcept;
 shared_future(shared_future&& rhs) noexcept;
 ~shared_future();
 shared_future& operator=(const shared_future& rhs);
 shared_future& operator=(shared_future&& rhs) noexcept;

 // retrieving the value
 void get() const;

 // functions to check state
 bool valid() const noexcept;

 void wait() const;
 template <class Rep, class Period>
 future_status
 wait_for(const chrono::duration<Rep, Period>& rel_time) const;
 template <class Clock, class Duration>
 future_status
 wait_until(const chrono::time_point<Clock, Duration>& abs_time) const;
};

template <class F, class... Args>
 future<typename result_of<typename decay<F>::type(typename decay<Args>::type...)>::type>
 async(F&& f, Args&&... args);

template <class F, class... Args>
 future<typename result_of<typename decay<F>::type(typename decay<Args>::type...)>::type>
 async(launch policy, F&& f, Args&&... args);

template <class> class packaged_task; // undefined

template <class R, class... ArgTypes>
class packaged_task<R(ArgTypes...)>
{
public:
 typedef R result_type; // extension

 // construction and destruction
 packaged_task() noexcept;
 template <class F>
 explicit packaged_task(F&& f);
 template <class F, class Allocator>
 packaged_task(allocator_arg_t, const Allocator& a, F&& f);
 ~packaged_task();

 // no copy
 packaged_task(const packaged_task&) = delete;
 packaged_task& operator=(const packaged_task&) = delete;

 // move support
 packaged_task(packaged_task&& other) noexcept;
 packaged_task& operator=(packaged_task&& other) noexcept;
 void swap(packaged_task& other) noexcept;

 bool valid() const noexcept;

 // result retrieval
 future<R> get_future();

 // execution
 void operator()(ArgTypes... );
 void make_ready_at_thread_exit(ArgTypes...);

 void reset();
};

template <class R>
 void swap(packaged_task<R(ArgTypes...)&, packaged_task<R(ArgTypes...)>&) noexcept;

template <class R, class Alloc> struct uses_allocator<packaged_task<R>, Alloc>;

} // std

*/

#include <__config>
#include <system_error>
#include <memory>
#include <chrono>
#include <exception>
#include <mutex>
#include <thread>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

#ifdef _LIBCPP_HAS_NO_THREADS
#error <future> is not supported on this single threaded system
#else // !_LIBCPP_HAS_NO_THREADS

_LIBCPP_BEGIN_NAMESPACE_STD

//enum class future_errc
_LIBCPP_DECLARE_STRONG_ENUM(future_errc)
{
 future_already_retrieved = 1,
 promise_already_satisfied,
 no_state,
 broken_promise
};
_LIBCPP_DECLARE_STRONG_ENUM_EPILOG(future_errc)

template <>
struct _LIBCPP_TYPE_VIS_ONLY is_error_code_enum<future_errc> : public true_type {};

#ifdef _LIBCPP_HAS_NO_STRONG_ENUMS
template <>
struct _LIBCPP_TYPE_VIS_ONLY is_error_code_enum<future_errc::__lx> : public true_type { };
#endif

//enum class launch
_LIBCPP_DECLARE_STRONG_ENUM(launch)
{
 async = 1,
 deferred = 2,
 any = async | deferred
};
_LIBCPP_DECLARE_STRONG_ENUM_EPILOG(launch)

#ifndef _LIBCPP_HAS_NO_STRONG_ENUMS

#ifdef _LIBCXX_UNDERLYING_TYPE
typedef underlying_type<launch>::type __launch_underlying_type;
#else
typedef int __launch_underlying_type;
#endif

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
launch
operator&(launch __x, launch __y)
{
 return static_cast<launch>(static_cast<__launch_underlying_type>(__x) &
 static_cast<__launch_underlying_type>(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
launch
operator|(launch __x, launch __y)
{
 return static_cast<launch>(static_cast<__launch_underlying_type>(__x) |
 static_cast<__launch_underlying_type>(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
launch
operator^(launch __x, launch __y)
{
 return static_cast<launch>(static_cast<__launch_underlying_type>(__x) ^
 static_cast<__launch_underlying_type>(__y));
}

inline _LIBCPP_INLINE_VISIBILITY
_LIBCPP_CONSTEXPR
launch
operator~(launch __x)
{
 return static_cast<launch>(~static_cast<__launch_underlying_type>(__x) & 3);
}

inline _LIBCPP_INLINE_VISIBILITY
launch&
operator&=(launch& __x, launch __y)
{
 __x = __x & __y; return __x;
}

inline _LIBCPP_INLINE_VISIBILITY
launch&
operator|=(launch& __x, launch __y)
{
 __x = __x | __y; return __x;
}

inline _LIBCPP_INLINE_VISIBILITY
launch&
operator^=(launch& __x, launch __y)
{
 __x = __x ^ __y; return __x;
}

#endif // !_LIBCPP_HAS_NO_STRONG_ENUMS

//enum class future_status
_LIBCPP_DECLARE_STRONG_ENUM(future_status)
{
 ready,
 timeout,
 deferred
};
_LIBCPP_DECLARE_STRONG_ENUM_EPILOG(future_status)

_LIBCPP_FUNC_VIS
const error_category& future_category() _NOEXCEPT;

inline _LIBCPP_INLINE_VISIBILITY
error_code
make_error_code(future_errc __e) _NOEXCEPT
{
 return error_code(static_cast<int>(__e), future_category());
}

inline _LIBCPP_INLINE_VISIBILITY
error_condition
make_error_condition(future_errc __e) _NOEXCEPT
{
 return error_condition(static_cast<int>(__e), future_category());
}

class _LIBCPP_EXCEPTION_ABI future_error
 : public logic_error
{
 error_code __ec_;
public:
 future_error(error_code __ec);
#if _LIBCPP_STD_VERS > 14
 explicit future_error(future_errc _Ev) : logic_error(), __ec_(make_error_code(_Ev)) {}
#endif
 _LIBCPP_INLINE_VISIBILITY
 const error_code& code() const _NOEXCEPT {return __ec_;}

 virtual ~future_error() _NOEXCEPT;
};

_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
void __throw_future_error(future_errc _Ev)
{
#ifndef _LIBCPP_NO_EXCEPTIONS
 throw future_error(make_error_code(_Ev));
#else
 _VSTD::abort();
#endif
}

class _LIBCPP_TYPE_VIS __assoc_sub_state
 : public __shared_count
{
protected:
 exception_ptr __exception_;
 mutable mutex __mut_;
 mutable condition_variable __cv_;
 unsigned __state_;

 virtual void __on_zero_shared() _NOEXCEPT;
 void __sub_wait(unique_lock<mutex>& __lk);
public:
 enum
 {
 __constructed = 1,
 __future_attached = 2,
 ready = 4,
 deferred = 8
 };

 _LIBCPP_INLINE_VISIBILITY
 __assoc_sub_state() : __state_(0) {}

 _LIBCPP_INLINE_VISIBILITY
 bool __has_value() const
 {return (__state_ & __constructed) || (__exception_ != nullptr);}

 _LIBCPP_INLINE_VISIBILITY
 void __set_future_attached()
 {
 lock_guard<mutex> __lk(__mut_);
 __state_ |= __future_attached;
 }
 _LIBCPP_INLINE_VISIBILITY
 bool __has_future_attached() const {return (__state_ & __future_attached) != 0;}

 _LIBCPP_INLINE_VISIBILITY
 void __set_deferred() {__state_ |= deferred;}

 void __make_ready();
 _LIBCPP_INLINE_VISIBILITY
 bool __is_ready() const {return (__state_ & ready) != 0;}

 void set_value();
 void set_value_at_thread_exit();

 void set_exception(exception_ptr __p);
 void set_exception_at_thread_exit(exception_ptr __p);

 void copy();

 void wait();
 template <class _Rep, class _Period>
 future_status
 _LIBCPP_INLINE_VISIBILITY
 wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const;
 template <class _Clock, class _Duration>
 future_status
 wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const;

 virtual void __execute();
};

template <class _Clock, class _Duration>
future_status
__assoc_sub_state::wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const
{
 unique_lock<mutex> __lk(__mut_);
 if (__state_ & deferred)
 return future_status::deferred;
 while (!(__state_ & ready) && _Clock::now() < __abs_time)
 __cv_.wait_until(__lk, __abs_time);
 if (__state_ & ready)
 return future_status::ready;
 return future_status::timeout;
}

template <class _Rep, class _Period>
inline
future_status
__assoc_sub_state::wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const
{
 return wait_until(chrono::steady_clock::now() + __rel_time);
}

template <class _Rp>
class __assoc_state
 : public __assoc_sub_state
{
 typedef __assoc_sub_state base;
 typedef typename aligned_storage<sizeof(_Rp), alignment_of<_Rp>::value>::type _Up;
protected:
 _Up __value_;

 virtual void __on_zero_shared() _NOEXCEPT;
public:

 template <class _Arg>
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 void set_value(_Arg&& __arg);
#else
 void set_value(_Arg& __arg);
#endif

 template <class _Arg>
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 void set_value_at_thread_exit(_Arg&& __arg);
#else
 void set_value_at_thread_exit(_Arg& __arg);
#endif

 _Rp move();
 typename add_lvalue_reference<_Rp>::type copy();
};

template <class _Rp>
void
__assoc_state<_Rp>::__on_zero_shared() _NOEXCEPT
{
 if (this->__state_ & base::__constructed)
 reinterpret_cast<_Rp*>(&__value_)->~_Rp();
 delete this;
}

template <class _Rp>
template <class _Arg>
void
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__assoc_state<_Rp>::set_value(_Arg&& __arg)
#else
__assoc_state<_Rp>::set_value(_Arg& __arg)
#endif
{
 unique_lock<mutex> __lk(this->__mut_);
 if (this->__has_value())
 __throw_future_error(future_errc::promise_already_satisfied);
 ::new(&__value_) _Rp(_VSTD::forward<_Arg>(__arg));
 this->__state_ |= base::__constructed | base::ready;
 __cv_.notify_all();
}

template <class _Rp>
template <class _Arg>
void
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__assoc_state<_Rp>::set_value_at_thread_exit(_Arg&& __arg)
#else
__assoc_state<_Rp>::set_value_at_thread_exit(_Arg& __arg)
#endif
{
 unique_lock<mutex> __lk(this->__mut_);
 if (this->__has_value())
 __throw_future_error(future_errc::promise_already_satisfied);
 ::new(&__value_) _Rp(_VSTD::forward<_Arg>(__arg));
 this->__state_ |= base::__constructed;
 __thread_local_data()->__make_ready_at_thread_exit(this);
}

template <class _Rp>
_Rp
__assoc_state<_Rp>::move()
{
 unique_lock<mutex> __lk(this->__mut_);
 this->__sub_wait(__lk);
 if (this->__exception_ != nullptr)
 rethrow_exception(this->__exception_);
 return _VSTD::move(*reinterpret_cast<_Rp*>(&__value_));
}

template <class _Rp>
typename add_lvalue_reference<_Rp>::type
__assoc_state<_Rp>::copy()
{
 unique_lock<mutex> __lk(this->__mut_);
 this->__sub_wait(__lk);
 if (this->__exception_ != nullptr)
 rethrow_exception(this->__exception_);
 return *reinterpret_cast<_Rp*>(&__value_);
}

template <class _Rp>
class __assoc_state<_Rp&>
 : public __assoc_sub_state
{
 typedef __assoc_sub_state base;
 typedef _Rp* _Up;
protected:
 _Up __value_;

 virtual void __on_zero_shared() _NOEXCEPT;
public:

 void set_value(_Rp& __arg);
 void set_value_at_thread_exit(_Rp& __arg);

 _Rp& copy();
};

template <class _Rp>
void
__assoc_state<_Rp&>::__on_zero_shared() _NOEXCEPT
{
 delete this;
}

template <class _Rp>
void
__assoc_state<_Rp&>::set_value(_Rp& __arg)
{
 unique_lock<mutex> __lk(this->__mut_);
 if (this->__has_value())
 __throw_future_error(future_errc::promise_already_satisfied);
 __value_ = _VSTD::addressof(__arg);
 this->__state_ |= base::__constructed | base::ready;
 __cv_.notify_all();
}

template <class _Rp>
void
__assoc_state<_Rp&>::set_value_at_thread_exit(_Rp& __arg)
{
 unique_lock<mutex> __lk(this->__mut_);
 if (this->__has_value())
 __throw_future_error(future_errc::promise_already_satisfied);
 __value_ = _VSTD::addressof(__arg);
 this->__state_ |= base::__constructed;
 __thread_local_data()->__make_ready_at_thread_exit(this);
}

template <class _Rp>
_Rp&
__assoc_state<_Rp&>::copy()
{
 unique_lock<mutex> __lk(this->__mut_);
 this->__sub_wait(__lk);
 if (this->__exception_ != nullptr)
 rethrow_exception(this->__exception_);
 return *__value_;
}

template <class _Rp, class _Alloc>
class __assoc_state_alloc
 : public __assoc_state<_Rp>
{
 typedef __assoc_state<_Rp> base;
 _Alloc __alloc_;

 virtual void __on_zero_shared() _NOEXCEPT;
public:
 _LIBCPP_INLINE_VISIBILITY
 explicit __assoc_state_alloc(const _Alloc& __a)
 : __alloc_(__a) {}
};

template <class _Rp, class _Alloc>
void
__assoc_state_alloc<_Rp, _Alloc>::__on_zero_shared() _NOEXCEPT
{
 if (this->__state_ & base::__constructed)
 reinterpret_cast<_Rp*>(_VSTD::addressof(this->__value_))->~_Rp();
 typedef typename __allocator_traits_rebind<_Alloc, __assoc_state_alloc>::type _Al;
 typedef allocator_traits<_Al> _ATraits;
 typedef pointer_traits<typename _ATraits::pointer> _PTraits;
 _Al __a(__alloc_);
 this->~__assoc_state_alloc();
 __a.deallocate(_PTraits::pointer_to(*this), 1);
}

template <class _Rp, class _Alloc>
class __assoc_state_alloc<_Rp&, _Alloc>
 : public __assoc_state<_Rp&>
{
 typedef __assoc_state<_Rp&> base;
 _Alloc __alloc_;

 virtual void __on_zero_shared() _NOEXCEPT;
public:
 _LIBCPP_INLINE_VISIBILITY
 explicit __assoc_state_alloc(const _Alloc& __a)
 : __alloc_(__a) {}
};

template <class _Rp, class _Alloc>
void
__assoc_state_alloc<_Rp&, _Alloc>::__on_zero_shared() _NOEXCEPT
{
 typedef typename __allocator_traits_rebind<_Alloc, __assoc_state_alloc>::type _Al;
 typedef allocator_traits<_Al> _ATraits;
 typedef pointer_traits<typename _ATraits::pointer> _PTraits;
 _Al __a(__alloc_);
 this->~__assoc_state_alloc();
 __a.deallocate(_PTraits::pointer_to(*this), 1);
}

template <class _Alloc>
class __assoc_sub_state_alloc
 : public __assoc_sub_state
{
 typedef __assoc_sub_state base;
 _Alloc __alloc_;

 virtual void __on_zero_shared() _NOEXCEPT;
public:
 _LIBCPP_INLINE_VISIBILITY
 explicit __assoc_sub_state_alloc(const _Alloc& __a)
 : __alloc_(__a) {}
};

template <class _Alloc>
void
__assoc_sub_state_alloc<_Alloc>::__on_zero_shared() _NOEXCEPT
{
 typedef typename __allocator_traits_rebind<_Alloc, __assoc_sub_state_alloc>::type _Al;
 typedef allocator_traits<_Al> _ATraits;
 typedef pointer_traits<typename _ATraits::pointer> _PTraits;
 _Al __a(__alloc_);
 this->~__assoc_sub_state_alloc();
 __a.deallocate(_PTraits::pointer_to(*this), 1);
}

template <class _Rp, class _Fp>
class __deferred_assoc_state
 : public __assoc_state<_Rp>
{
 typedef __assoc_state<_Rp> base;

 _Fp __func_;

public:
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 explicit __deferred_assoc_state(_Fp&& __f);
#endif

 virtual void __execute();
};

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Rp, class _Fp>
inline
__deferred_assoc_state<_Rp, _Fp>::__deferred_assoc_state(_Fp&& __f)
 : __func_(_VSTD::forward<_Fp>(__f))
{
 this->__set_deferred();
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Rp, class _Fp>
void
__deferred_assoc_state<_Rp, _Fp>::__execute()
{
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 this->set_value(__func_());
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 this->set_exception(current_exception());
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template <class _Fp>
class __deferred_assoc_state<void, _Fp>
 : public __assoc_sub_state
{
 typedef __assoc_sub_state base;

 _Fp __func_;

public:
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 explicit __deferred_assoc_state(_Fp&& __f);
#endif

 virtual void __execute();
};

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Fp>
inline
__deferred_assoc_state<void, _Fp>::__deferred_assoc_state(_Fp&& __f)
 : __func_(_VSTD::forward<_Fp>(__f))
{
 this->__set_deferred();
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Fp>
void
__deferred_assoc_state<void, _Fp>::__execute()
{
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 __func_();
 this->set_value();
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 this->set_exception(current_exception());
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template <class _Rp, class _Fp>
class __async_assoc_state
 : public __assoc_state<_Rp>
{
 typedef __assoc_state<_Rp> base;

 _Fp __func_;

 virtual void __on_zero_shared() _NOEXCEPT;
public:
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 explicit __async_assoc_state(_Fp&& __f);
#endif

 virtual void __execute();
};

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Rp, class _Fp>
inline
__async_assoc_state<_Rp, _Fp>::__async_assoc_state(_Fp&& __f)
 : __func_(_VSTD::forward<_Fp>(__f))
{
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Rp, class _Fp>
void
__async_assoc_state<_Rp, _Fp>::__execute()
{
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 this->set_value(__func_());
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 this->set_exception(current_exception());
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template <class _Rp, class _Fp>
void
__async_assoc_state<_Rp, _Fp>::__on_zero_shared() _NOEXCEPT
{
 this->wait();
 base::__on_zero_shared();
}

template <class _Fp>
class __async_assoc_state<void, _Fp>
 : public __assoc_sub_state
{
 typedef __assoc_sub_state base;

 _Fp __func_;

 virtual void __on_zero_shared() _NOEXCEPT;
public:
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 explicit __async_assoc_state(_Fp&& __f);
#endif

 virtual void __execute();
};

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Fp>
inline
__async_assoc_state<void, _Fp>::__async_assoc_state(_Fp&& __f)
 : __func_(_VSTD::forward<_Fp>(__f))
{
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Fp>
void
__async_assoc_state<void, _Fp>::__execute()
{
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 __func_();
 this->set_value();
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 this->set_exception(current_exception());
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template <class _Fp>
void
__async_assoc_state<void, _Fp>::__on_zero_shared() _NOEXCEPT
{
 this->wait();
 base::__on_zero_shared();
}

template <class _Rp> class _LIBCPP_TYPE_VIS_ONLY promise;
template <class _Rp> class _LIBCPP_TYPE_VIS_ONLY shared_future;

// future

template <class _Rp> class _LIBCPP_TYPE_VIS_ONLY future;

template <class _Rp, class _Fp>
future<_Rp>
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__make_deferred_assoc_state(_Fp&& __f);
#else
__make_deferred_assoc_state(_Fp __f);
#endif

template <class _Rp, class _Fp>
future<_Rp>
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__make_async_assoc_state(_Fp&& __f);
#else
__make_async_assoc_state(_Fp __f);
#endif

template <class _Rp>
class _LIBCPP_TYPE_VIS_ONLY future
{
 __assoc_state<_Rp>* __state_;

 explicit future(__assoc_state<_Rp>* __state);

 template <class> friend class promise;
 template <class> friend class shared_future;

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 template <class _R1, class _Fp>
 friend future<_R1> __make_deferred_assoc_state(_Fp&& __f);
 template <class _R1, class _Fp>
 friend future<_R1> __make_async_assoc_state(_Fp&& __f);
#else
 template <class _R1, class _Fp>
 friend future<_R1> __make_deferred_assoc_state(_Fp __f);
 template <class _R1, class _Fp>
 friend future<_R1> __make_async_assoc_state(_Fp __f);
#endif

public:
 _LIBCPP_INLINE_VISIBILITY
 future() _NOEXCEPT : __state_(nullptr) {}
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 future(future&& __rhs) _NOEXCEPT
 : __state_(__rhs.__state_) {__rhs.__state_ = nullptr;}
 future(const future&) = delete;
 future& operator=(const future&) = delete;
 _LIBCPP_INLINE_VISIBILITY
 future& operator=(future&& __rhs) _NOEXCEPT
 {
 future(std::move(__rhs)).swap(*this);
 return *this;
 }
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 future(const future&);
 future& operator=(const future&);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~future();
 _LIBCPP_INLINE_VISIBILITY
 shared_future<_Rp> share();

 // retrieving the value
 _Rp get();

 _LIBCPP_INLINE_VISIBILITY
 void swap(future& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // functions to check state
 _LIBCPP_INLINE_VISIBILITY
 bool valid() const _NOEXCEPT {return __state_ != nullptr;}

 _LIBCPP_INLINE_VISIBILITY
 void wait() const {__state_->wait();}
 template <class _Rep, class _Period>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const
 {return __state_->wait_for(__rel_time);}
 template <class _Clock, class _Duration>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const
 {return __state_->wait_until(__abs_time);}
};

template <class _Rp>
future<_Rp>::future(__assoc_state<_Rp>* __state)
 : __state_(__state)
{
 if (__state_->__has_future_attached())
 __throw_future_error(future_errc::future_already_retrieved);
 __state_->__add_shared();
 __state_->__set_future_attached();
}

struct __release_shared_count
{
 void operator()(__shared_count* p) {p->__release_shared();}
};

template <class _Rp>
future<_Rp>::~future()
{
 if (__state_)
 __state_->__release_shared();
}

template <class _Rp>
_Rp
future<_Rp>::get()
{
 unique_ptr<__shared_count, __release_shared_count> __(__state_);
 __assoc_state<_Rp>* __s = __state_;
 __state_ = nullptr;
 return __s->move();
}

template <class _Rp>
class _LIBCPP_TYPE_VIS_ONLY future<_Rp&>
{
 __assoc_state<_Rp&>* __state_;

 explicit future(__assoc_state<_Rp&>* __state);

 template <class> friend class promise;
 template <class> friend class shared_future;

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 template <class _R1, class _Fp>
 friend future<_R1> __make_deferred_assoc_state(_Fp&& __f);
 template <class _R1, class _Fp>
 friend future<_R1> __make_async_assoc_state(_Fp&& __f);
#else
 template <class _R1, class _Fp>
 friend future<_R1> __make_deferred_assoc_state(_Fp __f);
 template <class _R1, class _Fp>
 friend future<_R1> __make_async_assoc_state(_Fp __f);
#endif

public:
 _LIBCPP_INLINE_VISIBILITY
 future() _NOEXCEPT : __state_(nullptr) {}
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 future(future&& __rhs) _NOEXCEPT
 : __state_(__rhs.__state_) {__rhs.__state_ = nullptr;}
 future(const future&) = delete;
 future& operator=(const future&) = delete;
 _LIBCPP_INLINE_VISIBILITY
 future& operator=(future&& __rhs) _NOEXCEPT
 {
 future(std::move(__rhs)).swap(*this);
 return *this;
 }
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 future(const future&);
 future& operator=(const future&);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~future();
 _LIBCPP_INLINE_VISIBILITY
 shared_future<_Rp&> share();

 // retrieving the value
 _Rp& get();

 _LIBCPP_INLINE_VISIBILITY
 void swap(future& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // functions to check state
 _LIBCPP_INLINE_VISIBILITY
 bool valid() const _NOEXCEPT {return __state_ != nullptr;}

 _LIBCPP_INLINE_VISIBILITY
 void wait() const {__state_->wait();}
 template <class _Rep, class _Period>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const
 {return __state_->wait_for(__rel_time);}
 template <class _Clock, class _Duration>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const
 {return __state_->wait_until(__abs_time);}
};

template <class _Rp>
future<_Rp&>::future(__assoc_state<_Rp&>* __state)
 : __state_(__state)
{
 if (__state_->__has_future_attached())
 __throw_future_error(future_errc::future_already_retrieved);
 __state_->__add_shared();
 __state_->__set_future_attached();
}

template <class _Rp>
future<_Rp&>::~future()
{
 if (__state_)
 __state_->__release_shared();
}

template <class _Rp>
_Rp&
future<_Rp&>::get()
{
 unique_ptr<__shared_count, __release_shared_count> __(__state_);
 __assoc_state<_Rp&>* __s = __state_;
 __state_ = nullptr;
 return __s->copy();
}

template <>
class _LIBCPP_TYPE_VIS future<void>
{
 __assoc_sub_state* __state_;

 explicit future(__assoc_sub_state* __state);

 template <class> friend class promise;
 template <class> friend class shared_future;

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 template <class _R1, class _Fp>
 friend future<_R1> __make_deferred_assoc_state(_Fp&& __f);
 template <class _R1, class _Fp>
 friend future<_R1> __make_async_assoc_state(_Fp&& __f);
#else
 template <class _R1, class _Fp>
 friend future<_R1> __make_deferred_assoc_state(_Fp __f);
 template <class _R1, class _Fp>
 friend future<_R1> __make_async_assoc_state(_Fp __f);
#endif

public:
 _LIBCPP_INLINE_VISIBILITY
 future() _NOEXCEPT : __state_(nullptr) {}
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 future(future&& __rhs) _NOEXCEPT
 : __state_(__rhs.__state_) {__rhs.__state_ = nullptr;}
 future(const future&) = delete;
 future& operator=(const future&) = delete;
 _LIBCPP_INLINE_VISIBILITY
 future& operator=(future&& __rhs) _NOEXCEPT
 {
 future(std::move(__rhs)).swap(*this);
 return *this;
 }
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 future(const future&);
 future& operator=(const future&);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~future();
 _LIBCPP_INLINE_VISIBILITY
 shared_future<void> share();

 // retrieving the value
 void get();

 _LIBCPP_INLINE_VISIBILITY
 void swap(future& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // functions to check state
 _LIBCPP_INLINE_VISIBILITY
 bool valid() const _NOEXCEPT {return __state_ != nullptr;}

 _LIBCPP_INLINE_VISIBILITY
 void wait() const {__state_->wait();}
 template <class _Rep, class _Period>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const
 {return __state_->wait_for(__rel_time);}
 template <class _Clock, class _Duration>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const
 {return __state_->wait_until(__abs_time);}
};

template <class _Rp>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(future<_Rp>& __x, future<_Rp>& __y) _NOEXCEPT
{
 __x.swap(__y);
}

// promise<R>

template <class _Callable> class packaged_task;

template <class _Rp>
class _LIBCPP_TYPE_VIS_ONLY promise
{
 __assoc_state<_Rp>* __state_;

 _LIBCPP_INLINE_VISIBILITY
 explicit promise(nullptr_t) _NOEXCEPT : __state_(nullptr) {}

 template <class> friend class packaged_task;
public:
 promise();
 template <class _Alloc>
 promise(allocator_arg_t, const _Alloc& __a);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 promise(promise&& __rhs) _NOEXCEPT
 : __state_(__rhs.__state_) {__rhs.__state_ = nullptr;}
 promise(const promise& __rhs) = delete;
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 promise(const promise& __rhs);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~promise();

 // assignment
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 promise& operator=(promise&& __rhs) _NOEXCEPT
 {
 promise(std::move(__rhs)).swap(*this);
 return *this;
 }
 promise& operator=(const promise& __rhs) = delete;
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 promise& operator=(const promise& __rhs);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 void swap(promise& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // retrieving the result
 future<_Rp> get_future();

 // setting the result
 void set_value(const _Rp& __r);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 void set_value(_Rp&& __r);
#endif
 void set_exception(exception_ptr __p);

 // setting the result with deferred notification
 void set_value_at_thread_exit(const _Rp& __r);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 void set_value_at_thread_exit(_Rp&& __r);
#endif
 void set_exception_at_thread_exit(exception_ptr __p);
};

template <class _Rp>
promise<_Rp>::promise()
 : __state_(new __assoc_state<_Rp>)
{
}

template <class _Rp>
template <class _Alloc>
promise<_Rp>::promise(allocator_arg_t, const _Alloc& __a0)
{
 typedef __assoc_state_alloc<_Rp, _Alloc> _State;
 typedef typename __allocator_traits_rebind<_Alloc, _State>::type _A2;
 typedef __allocator_destructor<_A2> _D2;
 _A2 __a(__a0);
 unique_ptr<_State, _D2> __hold(__a.allocate(1), _D2(__a, 1));
 ::new(static_cast<void*>(_VSTD::addressof(*__hold.get()))) _State(__a0);
 __state_ = _VSTD::addressof(*__hold.release());
}

template <class _Rp>
promise<_Rp>::~promise()
{
 if (__state_)
 {
 if (!__state_->__has_value() && __state_->use_count() > 1)
 __state_->set_exception(make_exception_ptr(
 future_error(make_error_code(future_errc::broken_promise))
 ));
 __state_->__release_shared();
 }
}

template <class _Rp>
future<_Rp>
promise<_Rp>::get_future()
{
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 return future<_Rp>(__state_);
}

template <class _Rp>
void
promise<_Rp>::set_value(const _Rp& __r)
{
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_value(__r);
}

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Rp>
void
promise<_Rp>::set_value(_Rp&& __r)
{
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_value(_VSTD::move(__r));
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Rp>
void
promise<_Rp>::set_exception(exception_ptr __p)
{
 _LIBCPP_ASSERT( __p != nullptr, "promise::set_exception: received nullptr" );
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_exception(__p);
}

template <class _Rp>
void
promise<_Rp>::set_value_at_thread_exit(const _Rp& __r)
{
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_value_at_thread_exit(__r);
}

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Rp>
void
promise<_Rp>::set_value_at_thread_exit(_Rp&& __r)
{
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_value_at_thread_exit(_VSTD::move(__r));
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

template <class _Rp>
void
promise<_Rp>::set_exception_at_thread_exit(exception_ptr __p)
{
 _LIBCPP_ASSERT( __p != nullptr, "promise::set_exception_at_thread_exit: received nullptr" );
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_exception_at_thread_exit(__p);
}

// promise<R&>

template <class _Rp>
class _LIBCPP_TYPE_VIS_ONLY promise<_Rp&>
{
 __assoc_state<_Rp&>* __state_;

 _LIBCPP_INLINE_VISIBILITY
 explicit promise(nullptr_t) _NOEXCEPT : __state_(nullptr) {}

 template <class> friend class packaged_task;

public:
 promise();
 template <class _Allocator>
 promise(allocator_arg_t, const _Allocator& __a);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 promise(promise&& __rhs) _NOEXCEPT
 : __state_(__rhs.__state_) {__rhs.__state_ = nullptr;}
 promise(const promise& __rhs) = delete;
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 promise(const promise& __rhs);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~promise();

 // assignment
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 promise& operator=(promise&& __rhs) _NOEXCEPT
 {
 promise(std::move(__rhs)).swap(*this);
 return *this;
 }
 promise& operator=(const promise& __rhs) = delete;
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 promise& operator=(const promise& __rhs);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 void swap(promise& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // retrieving the result
 future<_Rp&> get_future();

 // setting the result
 void set_value(_Rp& __r);
 void set_exception(exception_ptr __p);

 // setting the result with deferred notification
 void set_value_at_thread_exit(_Rp&);
 void set_exception_at_thread_exit(exception_ptr __p);
};

template <class _Rp>
promise<_Rp&>::promise()
 : __state_(new __assoc_state<_Rp&>)
{
}

template <class _Rp>
template <class _Alloc>
promise<_Rp&>::promise(allocator_arg_t, const _Alloc& __a0)
{
 typedef __assoc_state_alloc<_Rp&, _Alloc> _State;
 typedef typename __allocator_traits_rebind<_Alloc, _State>::type _A2;
 typedef __allocator_destructor<_A2> _D2;
 _A2 __a(__a0);
 unique_ptr<_State, _D2> __hold(__a.allocate(1), _D2(__a, 1));
 ::new(static_cast<void*>(_VSTD::addressof(*__hold.get()))) _State(__a0);
 __state_ = _VSTD::addressof(*__hold.release());
}

template <class _Rp>
promise<_Rp&>::~promise()
{
 if (__state_)
 {
 if (!__state_->__has_value() && __state_->use_count() > 1)
 __state_->set_exception(make_exception_ptr(
 future_error(make_error_code(future_errc::broken_promise))
 ));
 __state_->__release_shared();
 }
}

template <class _Rp>
future<_Rp&>
promise<_Rp&>::get_future()
{
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 return future<_Rp&>(__state_);
}

template <class _Rp>
void
promise<_Rp&>::set_value(_Rp& __r)
{
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_value(__r);
}

template <class _Rp>
void
promise<_Rp&>::set_exception(exception_ptr __p)
{
 _LIBCPP_ASSERT( __p != nullptr, "promise::set_exception: received nullptr" );
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_exception(__p);
}

template <class _Rp>
void
promise<_Rp&>::set_value_at_thread_exit(_Rp& __r)
{
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_value_at_thread_exit(__r);
}

template <class _Rp>
void
promise<_Rp&>::set_exception_at_thread_exit(exception_ptr __p)
{
 _LIBCPP_ASSERT( __p != nullptr, "promise::set_exception_at_thread_exit: received nullptr" );
 if (__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 __state_->set_exception_at_thread_exit(__p);
}

// promise<void>

template <>
class _LIBCPP_TYPE_VIS promise<void>
{
 __assoc_sub_state* __state_;

 _LIBCPP_INLINE_VISIBILITY
 explicit promise(nullptr_t) _NOEXCEPT : __state_(nullptr) {}

 template <class> friend class packaged_task;

public:
 promise();
 template <class _Allocator>
 promise(allocator_arg_t, const _Allocator& __a);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 promise(promise&& __rhs) _NOEXCEPT
 : __state_(__rhs.__state_) {__rhs.__state_ = nullptr;}
 promise(const promise& __rhs) = delete;
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 promise(const promise& __rhs);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~promise();

 // assignment
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 promise& operator=(promise&& __rhs) _NOEXCEPT
 {
 promise(std::move(__rhs)).swap(*this);
 return *this;
 }
 promise& operator=(const promise& __rhs) = delete;
#else // _LIBCPP_HAS_NO_RVALUE_REFERENCES
private:
 promise& operator=(const promise& __rhs);
public:
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 void swap(promise& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // retrieving the result
 future<void> get_future();

 // setting the result
 void set_value();
 void set_exception(exception_ptr __p);

 // setting the result with deferred notification
 void set_value_at_thread_exit();
 void set_exception_at_thread_exit(exception_ptr __p);
};

template <class _Alloc>
promise<void>::promise(allocator_arg_t, const _Alloc& __a0)
{
 typedef __assoc_sub_state_alloc<_Alloc> _State;
 typedef typename __allocator_traits_rebind<_Alloc, _State>::type _A2;
 typedef __allocator_destructor<_A2> _D2;
 _A2 __a(__a0);
 unique_ptr<_State, _D2> __hold(__a.allocate(1), _D2(__a, 1));
 ::new(static_cast<void*>(_VSTD::addressof(*__hold.get()))) _State(__a0);
 __state_ = _VSTD::addressof(*__hold.release());
}

template <class _Rp>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(promise<_Rp>& __x, promise<_Rp>& __y) _NOEXCEPT
{
 __x.swap(__y);
}

template <class _Rp, class _Alloc>
 struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<promise<_Rp>, _Alloc>
 : public true_type {};

#ifndef _LIBCPP_HAS_NO_VARIADICS

// packaged_task

template<class _Fp> class __packaged_task_base;

template<class _Rp, class ..._ArgTypes>
class __packaged_task_base<_Rp(_ArgTypes...)>
{
 __packaged_task_base(const __packaged_task_base&);
 __packaged_task_base& operator=(const __packaged_task_base&);
public:
 _LIBCPP_INLINE_VISIBILITY
 __packaged_task_base() {}
 _LIBCPP_INLINE_VISIBILITY
 virtual ~__packaged_task_base() {}
 virtual void __move_to(__packaged_task_base*) _NOEXCEPT = 0;
 virtual void destroy() = 0;
 virtual void destroy_deallocate() = 0;
 virtual _Rp operator()(_ArgTypes&& ...) = 0;
};

template<class _FD, class _Alloc, class _FB> class __packaged_task_func;

template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
class __packaged_task_func<_Fp, _Alloc, _Rp(_ArgTypes...)>
 : public __packaged_task_base<_Rp(_ArgTypes...)>
{
 __compressed_pair<_Fp, _Alloc> __f_;
public:
 _LIBCPP_INLINE_VISIBILITY
 explicit __packaged_task_func(const _Fp& __f) : __f_(__f) {}
 _LIBCPP_INLINE_VISIBILITY
 explicit __packaged_task_func(_Fp&& __f) : __f_(_VSTD::move(__f)) {}
 _LIBCPP_INLINE_VISIBILITY
 __packaged_task_func(const _Fp& __f, const _Alloc& __a)
 : __f_(__f, __a) {}
 _LIBCPP_INLINE_VISIBILITY
 __packaged_task_func(_Fp&& __f, const _Alloc& __a)
 : __f_(_VSTD::move(__f), __a) {}
 virtual void __move_to(__packaged_task_base<_Rp(_ArgTypes...)>*) _NOEXCEPT;
 virtual void destroy();
 virtual void destroy_deallocate();
 virtual _Rp operator()(_ArgTypes&& ... __args);
};

template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
void
__packaged_task_func<_Fp, _Alloc, _Rp(_ArgTypes...)>::__move_to(
 __packaged_task_base<_Rp(_ArgTypes...)>* __p) _NOEXCEPT
{
 ::new (__p) __packaged_task_func(_VSTD::move(__f_.first()), _VSTD::move(__f_.second()));
}

template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
void
__packaged_task_func<_Fp, _Alloc, _Rp(_ArgTypes...)>::destroy()
{
 __f_.~__compressed_pair<_Fp, _Alloc>();
}

template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
void
__packaged_task_func<_Fp, _Alloc, _Rp(_ArgTypes...)>::destroy_deallocate()
{
 typedef typename __allocator_traits_rebind<_Alloc, __packaged_task_func>::type _Ap;
 typedef allocator_traits<_Ap> _ATraits;
 typedef pointer_traits<typename _ATraits::pointer> _PTraits;
 _Ap __a(__f_.second());
 __f_.~__compressed_pair<_Fp, _Alloc>();
 __a.deallocate(_PTraits::pointer_to(*this), 1);
}

template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
_Rp
__packaged_task_func<_Fp, _Alloc, _Rp(_ArgTypes...)>::operator()(_ArgTypes&& ... __arg)
{
 return __invoke(__f_.first(), _VSTD::forward<_ArgTypes>(__arg)...);
}

template <class _Callable> class __packaged_task_function;

template<class _Rp, class ..._ArgTypes>
class __packaged_task_function<_Rp(_ArgTypes...)>
{
 typedef __packaged_task_base<_Rp(_ArgTypes...)> __base;
 typename aligned_storage<3*sizeof(void*)>::type __buf_;
 __base* __f_;

public:
 typedef _Rp result_type;

 // construct/copy/destroy:
 _LIBCPP_INLINE_VISIBILITY
 __packaged_task_function() _NOEXCEPT : __f_(nullptr) {}
 template<class _Fp>
 __packaged_task_function(_Fp&& __f);
 template<class _Fp, class _Alloc>
 __packaged_task_function(allocator_arg_t, const _Alloc& __a, _Fp&& __f);

 __packaged_task_function(__packaged_task_function&&) _NOEXCEPT;
 __packaged_task_function& operator=(__packaged_task_function&&) _NOEXCEPT;

 __packaged_task_function(const __packaged_task_function&) = delete;
 __packaged_task_function& operator=(const __packaged_task_function&) = delete;

 ~__packaged_task_function();

 void swap(__packaged_task_function&) _NOEXCEPT;

 _LIBCPP_INLINE_VISIBILITY
 _Rp operator()(_ArgTypes...) const;
};

template<class _Rp, class ..._ArgTypes>
__packaged_task_function<_Rp(_ArgTypes...)>::__packaged_task_function(__packaged_task_function&& __f) _NOEXCEPT
{
 if (__f.__f_ == nullptr)
 __f_ = nullptr;
 else if (__f.__f_ == (__base*)&__f.__buf_)
 {
 __f_ = (__base*)&__buf_;
 __f.__f_->__move_to(__f_);
 }
 else
 {
 __f_ = __f.__f_;
 __f.__f_ = nullptr;
 }
}

template<class _Rp, class ..._ArgTypes>
template <class _Fp>
__packaged_task_function<_Rp(_ArgTypes...)>::__packaged_task_function(_Fp&& __f)
 : __f_(nullptr)
{
 typedef typename remove_reference<typename decay<_Fp>::type>::type _FR;
 typedef __packaged_task_func<_FR, allocator<_FR>, _Rp(_ArgTypes...)> _FF;
 if (sizeof(_FF) <= sizeof(__buf_))
 {
 __f_ = (__base*)&__buf_;
 ::new (__f_) _FF(_VSTD::forward<_Fp>(__f));
 }
 else
 {
 typedef allocator<_FF> _Ap;
 _Ap __a;
 typedef __allocator_destructor<_Ap> _Dp;
 unique_ptr<__base, _Dp> __hold(__a.allocate(1), _Dp(__a, 1));
 ::new (__hold.get()) _FF(_VSTD::forward<_Fp>(__f), allocator<_FR>(__a));
 __f_ = __hold.release();
 }
}

template<class _Rp, class ..._ArgTypes>
template <class _Fp, class _Alloc>
__packaged_task_function<_Rp(_ArgTypes...)>::__packaged_task_function(
 allocator_arg_t, const _Alloc& __a0, _Fp&& __f)
 : __f_(nullptr)
{
 typedef typename remove_reference<typename decay<_Fp>::type>::type _FR;
 typedef __packaged_task_func<_FR, _Alloc, _Rp(_ArgTypes...)> _FF;
 if (sizeof(_FF) <= sizeof(__buf_))
 {
 __f_ = (__base*)&__buf_;
 ::new (__f_) _FF(_VSTD::forward<_Fp>(__f));
 }
 else
 {
 typedef typename __allocator_traits_rebind<_Alloc, _FF>::type _Ap;
 _Ap __a(__a0);
 typedef __allocator_destructor<_Ap> _Dp;
 unique_ptr<__base, _Dp> __hold(__a.allocate(1), _Dp(__a, 1));
 ::new (static_cast<void*>(_VSTD::addressof(*__hold.get())))
 _FF(_VSTD::forward<_Fp>(__f), _Alloc(__a));
 __f_ = _VSTD::addressof(*__hold.release());
 }
}

template<class _Rp, class ..._ArgTypes>
__packaged_task_function<_Rp(_ArgTypes...)>&
__packaged_task_function<_Rp(_ArgTypes...)>::operator=(__packaged_task_function&& __f) _NOEXCEPT
{
 if (__f_ == (__base*)&__buf_)
 __f_->destroy();
 else if (__f_)
 __f_->destroy_deallocate();
 __f_ = nullptr;
 if (__f.__f_ == nullptr)
 __f_ = nullptr;
 else if (__f.__f_ == (__base*)&__f.__buf_)
 {
 __f_ = (__base*)&__buf_;
 __f.__f_->__move_to(__f_);
 }
 else
 {
 __f_ = __f.__f_;
 __f.__f_ = nullptr;
 }
 return *this;
}

template<class _Rp, class ..._ArgTypes>
__packaged_task_function<_Rp(_ArgTypes...)>::~__packaged_task_function()
{
 if (__f_ == (__base*)&__buf_)
 __f_->destroy();
 else if (__f_)
 __f_->destroy_deallocate();
}

template<class _Rp, class ..._ArgTypes>
void
__packaged_task_function<_Rp(_ArgTypes...)>::swap(__packaged_task_function& __f) _NOEXCEPT
{
 if (__f_ == (__base*)&__buf_ && __f.__f_ == (__base*)&__f.__buf_)
 {
 typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
 __base* __t = (__base*)&__tempbuf;
 __f_->__move_to(__t);
 __f_->destroy();
 __f_ = nullptr;
 __f.__f_->__move_to((__base*)&__buf_);
 __f.__f_->destroy();
 __f.__f_ = nullptr;
 __f_ = (__base*)&__buf_;
 __t->__move_to((__base*)&__f.__buf_);
 __t->destroy();
 __f.__f_ = (__base*)&__f.__buf_;
 }
 else if (__f_ == (__base*)&__buf_)
 {
 __f_->__move_to((__base*)&__f.__buf_);
 __f_->destroy();
 __f_ = __f.__f_;
 __f.__f_ = (__base*)&__f.__buf_;
 }
 else if (__f.__f_ == (__base*)&__f.__buf_)
 {
 __f.__f_->__move_to((__base*)&__buf_);
 __f.__f_->destroy();
 __f.__f_ = __f_;
 __f_ = (__base*)&__buf_;
 }
 else
 _VSTD::swap(__f_, __f.__f_);
}

template<class _Rp, class ..._ArgTypes>
inline
_Rp
__packaged_task_function<_Rp(_ArgTypes...)>::operator()(_ArgTypes... __arg) const
{
 return (*__f_)(_VSTD::forward<_ArgTypes>(__arg)...);
}

template<class _Rp, class ..._ArgTypes>
class _LIBCPP_TYPE_VIS_ONLY packaged_task<_Rp(_ArgTypes...)>
{
public:
 typedef _Rp result_type; // extension

private:
 __packaged_task_function<result_type(_ArgTypes...)> __f_;
 promise<result_type> __p_;

public:
 // construction and destruction
 _LIBCPP_INLINE_VISIBILITY
 packaged_task() _NOEXCEPT : __p_(nullptr) {}
 template <class _Fp,
 class = typename enable_if
 <
 !is_same<
 typename decay<_Fp>::type, 
 packaged_task
 >::value
 >::type
 >
 _LIBCPP_INLINE_VISIBILITY
 explicit packaged_task(_Fp&& __f) : __f_(_VSTD::forward<_Fp>(__f)) {}
 template <class _Fp, class _Allocator,
 class = typename enable_if
 <
 !is_same<
 typename decay<_Fp>::type, 
 packaged_task
 >::value
 >::type
 >
 _LIBCPP_INLINE_VISIBILITY
 packaged_task(allocator_arg_t, const _Allocator& __a, _Fp&& __f)
 : __f_(allocator_arg, __a, _VSTD::forward<_Fp>(__f)),
 __p_(allocator_arg, __a) {}
 // ~packaged_task() = default;

 // no copy
 packaged_task(const packaged_task&) = delete;
 packaged_task& operator=(const packaged_task&) = delete;

 // move support
 _LIBCPP_INLINE_VISIBILITY
 packaged_task(packaged_task&& __other) _NOEXCEPT
 : __f_(_VSTD::move(__other.__f_)), __p_(_VSTD::move(__other.__p_)) {}
 _LIBCPP_INLINE_VISIBILITY
 packaged_task& operator=(packaged_task&& __other) _NOEXCEPT
 {
 __f_ = _VSTD::move(__other.__f_);
 __p_ = _VSTD::move(__other.__p_);
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY
 void swap(packaged_task& __other) _NOEXCEPT
 {
 __f_.swap(__other.__f_);
 __p_.swap(__other.__p_);
 }

 _LIBCPP_INLINE_VISIBILITY
 bool valid() const _NOEXCEPT {return __p_.__state_ != nullptr;}

 // result retrieval
 _LIBCPP_INLINE_VISIBILITY
 future<result_type> get_future() {return __p_.get_future();}

 // execution
 void operator()(_ArgTypes... __args);
 void make_ready_at_thread_exit(_ArgTypes... __args);

 void reset();
};

template<class _Rp, class ..._ArgTypes>
void
packaged_task<_Rp(_ArgTypes...)>::operator()(_ArgTypes... __args)
{
 if (__p_.__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 if (__p_.__state_->__has_value())
 __throw_future_error(future_errc::promise_already_satisfied);
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 __p_.set_value(__f_(_VSTD::forward<_ArgTypes>(__args)...));
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 __p_.set_exception(current_exception());
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template<class _Rp, class ..._ArgTypes>
void
packaged_task<_Rp(_ArgTypes...)>::make_ready_at_thread_exit(_ArgTypes... __args)
{
 if (__p_.__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 if (__p_.__state_->__has_value())
 __throw_future_error(future_errc::promise_already_satisfied);
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 __p_.set_value_at_thread_exit(__f_(_VSTD::forward<_ArgTypes>(__args)...));
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 __p_.set_exception_at_thread_exit(current_exception());
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template<class _Rp, class ..._ArgTypes>
void
packaged_task<_Rp(_ArgTypes...)>::reset()
{
 if (!valid())
 __throw_future_error(future_errc::no_state);
 __p_ = promise<result_type>();
}

template<class ..._ArgTypes>
class _LIBCPP_TYPE_VIS_ONLY packaged_task<void(_ArgTypes...)>
{
public:
 typedef void result_type; // extension

private:
 __packaged_task_function<result_type(_ArgTypes...)> __f_;
 promise<result_type> __p_;

public:
 // construction and destruction
 _LIBCPP_INLINE_VISIBILITY
 packaged_task() _NOEXCEPT : __p_(nullptr) {}
 template <class _Fp,
 class = typename enable_if
 <
 !is_same<
 typename decay<_Fp>::type, 
 packaged_task
 >::value
 >::type
 >
 _LIBCPP_INLINE_VISIBILITY
 explicit packaged_task(_Fp&& __f) : __f_(_VSTD::forward<_Fp>(__f)) {}
 template <class _Fp, class _Allocator,
 class = typename enable_if
 <
 !is_same<
 typename decay<_Fp>::type, 
 packaged_task
 >::value
 >::type
 > 
 _LIBCPP_INLINE_VISIBILITY
 packaged_task(allocator_arg_t, const _Allocator& __a, _Fp&& __f)
 : __f_(allocator_arg, __a, _VSTD::forward<_Fp>(__f)),
 __p_(allocator_arg, __a) {}
 // ~packaged_task() = default;

 // no copy
 packaged_task(const packaged_task&) = delete;
 packaged_task& operator=(const packaged_task&) = delete;

 // move support
 _LIBCPP_INLINE_VISIBILITY
 packaged_task(packaged_task&& __other) _NOEXCEPT
 : __f_(_VSTD::move(__other.__f_)), __p_(_VSTD::move(__other.__p_)) {}
 _LIBCPP_INLINE_VISIBILITY
 packaged_task& operator=(packaged_task&& __other) _NOEXCEPT
 {
 __f_ = _VSTD::move(__other.__f_);
 __p_ = _VSTD::move(__other.__p_);
 return *this;
 }
 _LIBCPP_INLINE_VISIBILITY
 void swap(packaged_task& __other) _NOEXCEPT
 {
 __f_.swap(__other.__f_);
 __p_.swap(__other.__p_);
 }

 _LIBCPP_INLINE_VISIBILITY
 bool valid() const _NOEXCEPT {return __p_.__state_ != nullptr;}

 // result retrieval
 _LIBCPP_INLINE_VISIBILITY
 future<result_type> get_future() {return __p_.get_future();}

 // execution
 void operator()(_ArgTypes... __args);
 void make_ready_at_thread_exit(_ArgTypes... __args);

 void reset();
};

template<class ..._ArgTypes>
void
packaged_task<void(_ArgTypes...)>::operator()(_ArgTypes... __args)
{
 if (__p_.__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 if (__p_.__state_->__has_value())
 __throw_future_error(future_errc::promise_already_satisfied);
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 __f_(_VSTD::forward<_ArgTypes>(__args)...);
 __p_.set_value();
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 __p_.set_exception(current_exception());
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template<class ..._ArgTypes>
void
packaged_task<void(_ArgTypes...)>::make_ready_at_thread_exit(_ArgTypes... __args)
{
 if (__p_.__state_ == nullptr)
 __throw_future_error(future_errc::no_state);
 if (__p_.__state_->__has_value())
 __throw_future_error(future_errc::promise_already_satisfied);
#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif // _LIBCPP_NO_EXCEPTIONS
 __f_(_VSTD::forward<_ArgTypes>(__args)...);
 __p_.set_value_at_thread_exit();
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch (...)
 {
 __p_.set_exception_at_thread_exit(current_exception());
 }
#endif // _LIBCPP_NO_EXCEPTIONS
}

template<class ..._ArgTypes>
void
packaged_task<void(_ArgTypes...)>::reset()
{
 if (!valid())
 __throw_future_error(future_errc::no_state);
 __p_ = promise<result_type>();
}

template <class _Callable>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(packaged_task<_Callable>& __x, packaged_task<_Callable>& __y) _NOEXCEPT
{
 __x.swap(__y);
}

template <class _Callable, class _Alloc>
struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<packaged_task<_Callable>, _Alloc>
 : public true_type {};

template <class _Rp, class _Fp>
future<_Rp>
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__make_deferred_assoc_state(_Fp&& __f)
#else
__make_deferred_assoc_state(_Fp __f)
#endif
{
 unique_ptr<__deferred_assoc_state<_Rp, _Fp>, __release_shared_count>
 __h(new __deferred_assoc_state<_Rp, _Fp>(_VSTD::forward<_Fp>(__f)));
 return future<_Rp>(__h.get());
}

template <class _Rp, class _Fp>
future<_Rp>
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
__make_async_assoc_state(_Fp&& __f)
#else
__make_async_assoc_state(_Fp __f)
#endif
{
 unique_ptr<__async_assoc_state<_Rp, _Fp>, __release_shared_count>
 __h(new __async_assoc_state<_Rp, _Fp>(_VSTD::forward<_Fp>(__f)));
 _VSTD::thread(&__async_assoc_state<_Rp, _Fp>::__execute, __h.get()).detach();
 return future<_Rp>(__h.get());
}

template <class _Fp, class... _Args>
class __async_func
{
 tuple<_Fp, _Args...> __f_;

public:
 typedef typename __invoke_of<_Fp, _Args...>::type _Rp;

 _LIBCPP_INLINE_VISIBILITY
 explicit __async_func(_Fp&& __f, _Args&&... __args)
 : __f_(_VSTD::move(__f), _VSTD::move(__args)...) {}

 _LIBCPP_INLINE_VISIBILITY
 __async_func(__async_func&& __f) : __f_(_VSTD::move(__f.__f_)) {}

 _Rp operator()()
 {
 typedef typename __make_tuple_indices<1+sizeof...(_Args), 1>::type _Index;
 return __execute(_Index());
 }
private:
 template <size_t ..._Indices>
 _Rp
 __execute(__tuple_indices<_Indices...>)
 {
 return __invoke(_VSTD::move(_VSTD::get<0>(__f_)), _VSTD::move(_VSTD::get<_Indices>(__f_))...);
 }
};

inline _LIBCPP_INLINE_VISIBILITY bool __does_policy_contain(launch __policy, launch __value )
{ return (int(__policy) & int(__value)) != 0; }

template <class _Fp, class... _Args>
future<typename __invoke_of<typename decay<_Fp>::type, typename decay<_Args>::type...>::type>
async(launch __policy, _Fp&& __f, _Args&&... __args)
{
 typedef __async_func<typename decay<_Fp>::type, typename decay<_Args>::type...> _BF;
 typedef typename _BF::_Rp _Rp;

#ifndef _LIBCPP_NO_EXCEPTIONS
 try
 {
#endif
 if (__does_policy_contain(__policy, launch::async))
 return _VSTD::__make_async_assoc_state<_Rp>(_BF(__decay_copy(_VSTD::forward<_Fp>(__f)),
 __decay_copy(_VSTD::forward<_Args>(__args))...));
#ifndef _LIBCPP_NO_EXCEPTIONS
 }
 catch ( ... ) { if (__policy == launch::async) throw ; }
#endif

 if (__does_policy_contain(__policy, launch::deferred))
 return _VSTD::__make_deferred_assoc_state<_Rp>(_BF(__decay_copy(_VSTD::forward<_Fp>(__f)),
 __decay_copy(_VSTD::forward<_Args>(__args))...));
 return future<_Rp>{};
}

template <class _Fp, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
future<typename __invoke_of<typename decay<_Fp>::type, typename decay<_Args>::type...>::type>
async(_Fp&& __f, _Args&&... __args)
{
 return _VSTD::async(launch::any, _VSTD::forward<_Fp>(__f),
 _VSTD::forward<_Args>(__args)...);
}

#endif // _LIBCPP_HAS_NO_VARIADICS

// shared_future

template <class _Rp>
class _LIBCPP_TYPE_VIS_ONLY shared_future
{
 __assoc_state<_Rp>* __state_;

public:
 _LIBCPP_INLINE_VISIBILITY
 shared_future() _NOEXCEPT : __state_(nullptr) {}
 _LIBCPP_INLINE_VISIBILITY
 shared_future(const shared_future& __rhs) _NOEXCEPT : __state_(__rhs.__state_)
 {if (__state_) __state_->__add_shared();}
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 shared_future(future<_Rp>&& __f) _NOEXCEPT : __state_(__f.__state_)
 {__f.__state_ = nullptr;}
 _LIBCPP_INLINE_VISIBILITY
 shared_future(shared_future&& __rhs) _NOEXCEPT : __state_(__rhs.__state_)
 {__rhs.__state_ = nullptr;}
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~shared_future();
 shared_future& operator=(const shared_future& __rhs) _NOEXCEPT;
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 shared_future& operator=(shared_future&& __rhs) _NOEXCEPT
 {
 shared_future(std::move(__rhs)).swap(*this);
 return *this;
 }
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

 // retrieving the value
 _LIBCPP_INLINE_VISIBILITY
 const _Rp& get() const {return __state_->copy();}

 _LIBCPP_INLINE_VISIBILITY
 void swap(shared_future& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // functions to check state
 _LIBCPP_INLINE_VISIBILITY
 bool valid() const _NOEXCEPT {return __state_ != nullptr;}

 _LIBCPP_INLINE_VISIBILITY
 void wait() const {__state_->wait();}
 template <class _Rep, class _Period>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const
 {return __state_->wait_for(__rel_time);}
 template <class _Clock, class _Duration>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const
 {return __state_->wait_until(__abs_time);}
};

template <class _Rp>
shared_future<_Rp>::~shared_future()
{
 if (__state_)
 __state_->__release_shared();
}

template <class _Rp>
shared_future<_Rp>&
shared_future<_Rp>::operator=(const shared_future& __rhs) _NOEXCEPT
{
 if (__rhs.__state_)
 __rhs.__state_->__add_shared();
 if (__state_)
 __state_->__release_shared();
 __state_ = __rhs.__state_;
 return *this;
}

template <class _Rp>
class _LIBCPP_TYPE_VIS_ONLY shared_future<_Rp&>
{
 __assoc_state<_Rp&>* __state_;

public:
 _LIBCPP_INLINE_VISIBILITY
 shared_future() _NOEXCEPT : __state_(nullptr) {}
 _LIBCPP_INLINE_VISIBILITY
 shared_future(const shared_future& __rhs) : __state_(__rhs.__state_)
 {if (__state_) __state_->__add_shared();}
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 shared_future(future<_Rp&>&& __f) _NOEXCEPT : __state_(__f.__state_)
 {__f.__state_ = nullptr;}
 _LIBCPP_INLINE_VISIBILITY
 shared_future(shared_future&& __rhs) _NOEXCEPT : __state_(__rhs.__state_)
 {__rhs.__state_ = nullptr;}
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~shared_future();
 shared_future& operator=(const shared_future& __rhs);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 shared_future& operator=(shared_future&& __rhs) _NOEXCEPT
 {
 shared_future(std::move(__rhs)).swap(*this);
 return *this;
 }
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

 // retrieving the value
 _LIBCPP_INLINE_VISIBILITY
 _Rp& get() const {return __state_->copy();}

 _LIBCPP_INLINE_VISIBILITY
 void swap(shared_future& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // functions to check state
 _LIBCPP_INLINE_VISIBILITY
 bool valid() const _NOEXCEPT {return __state_ != nullptr;}

 _LIBCPP_INLINE_VISIBILITY
 void wait() const {__state_->wait();}
 template <class _Rep, class _Period>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const
 {return __state_->wait_for(__rel_time);}
 template <class _Clock, class _Duration>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const
 {return __state_->wait_until(__abs_time);}
};

template <class _Rp>
shared_future<_Rp&>::~shared_future()
{
 if (__state_)
 __state_->__release_shared();
}

template <class _Rp>
shared_future<_Rp&>&
shared_future<_Rp&>::operator=(const shared_future& __rhs)
{
 if (__rhs.__state_)
 __rhs.__state_->__add_shared();
 if (__state_)
 __state_->__release_shared();
 __state_ = __rhs.__state_;
 return *this;
}

template <>
class _LIBCPP_TYPE_VIS shared_future<void>
{
 __assoc_sub_state* __state_;

public:
 _LIBCPP_INLINE_VISIBILITY
 shared_future() _NOEXCEPT : __state_(nullptr) {}
 _LIBCPP_INLINE_VISIBILITY
 shared_future(const shared_future& __rhs) : __state_(__rhs.__state_)
 {if (__state_) __state_->__add_shared();}
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 shared_future(future<void>&& __f) _NOEXCEPT : __state_(__f.__state_)
 {__f.__state_ = nullptr;}
 _LIBCPP_INLINE_VISIBILITY
 shared_future(shared_future&& __rhs) _NOEXCEPT : __state_(__rhs.__state_)
 {__rhs.__state_ = nullptr;}
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 ~shared_future();
 shared_future& operator=(const shared_future& __rhs);
#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 _LIBCPP_INLINE_VISIBILITY
 shared_future& operator=(shared_future&& __rhs) _NOEXCEPT
 {
 shared_future(std::move(__rhs)).swap(*this);
 return *this;
 }
#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

 // retrieving the value
 _LIBCPP_INLINE_VISIBILITY
 void get() const {__state_->copy();}

 _LIBCPP_INLINE_VISIBILITY
 void swap(shared_future& __rhs) _NOEXCEPT {_VSTD::swap(__state_, __rhs.__state_);}

 // functions to check state
 _LIBCPP_INLINE_VISIBILITY
 bool valid() const _NOEXCEPT {return __state_ != nullptr;}

 _LIBCPP_INLINE_VISIBILITY
 void wait() const {__state_->wait();}
 template <class _Rep, class _Period>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const
 {return __state_->wait_for(__rel_time);}
 template <class _Clock, class _Duration>
 _LIBCPP_INLINE_VISIBILITY
 future_status
 wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const
 {return __state_->wait_until(__abs_time);}
};

template <class _Rp>
inline _LIBCPP_INLINE_VISIBILITY
void
swap(shared_future<_Rp>& __x, shared_future<_Rp>& __y) _NOEXCEPT
{
 __x.swap(__y);
}

template <class _Rp>
inline
shared_future<_Rp>
future<_Rp>::share()
{
 return shared_future<_Rp>(_VSTD::move(*this));
}

template <class _Rp>
inline
shared_future<_Rp&>
future<_Rp&>::share()
{
 return shared_future<_Rp&>(_VSTD::move(*this));
}

#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES

inline
shared_future<void>
future<void>::share()
{
 return shared_future<void>(_VSTD::move(*this));
}

#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES

_LIBCPP_END_NAMESPACE_STD

#endif // !_LIBCPP_HAS_NO_THREADS

#endif // _LIBCPP_FUTURE