72a9fd209b
PR libstdc++/93470 * include/bits/refwrap.h (reference_wrapper::operator()): Restrict static assertion to object types.
402 lines
13 KiB
C++
402 lines
13 KiB
C++
// Implementation of std::reference_wrapper -*- C++ -*-
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// Copyright (C) 2004-2020 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file include/bits/refwrap.h
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* This is an internal header file, included by other library headers.
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* Do not attempt to use it directly. @headername{functional}
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*/
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#ifndef _GLIBCXX_REFWRAP_H
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#define _GLIBCXX_REFWRAP_H 1
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#pragma GCC system_header
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#if __cplusplus < 201103L
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# include <bits/c++0x_warning.h>
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#else
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#include <bits/move.h>
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#include <bits/invoke.h>
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#include <bits/stl_function.h> // for unary_function and binary_function
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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/// @cond undocumented
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/**
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* Derives from @c unary_function or @c binary_function, or perhaps
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* nothing, depending on the number of arguments provided. The
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* primary template is the basis case, which derives nothing.
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*/
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template<typename _Res, typename... _ArgTypes>
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struct _Maybe_unary_or_binary_function { };
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/// Derives from @c unary_function, as appropriate.
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template<typename _Res, typename _T1>
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struct _Maybe_unary_or_binary_function<_Res, _T1>
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: std::unary_function<_T1, _Res> { };
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/// Derives from @c binary_function, as appropriate.
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template<typename _Res, typename _T1, typename _T2>
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struct _Maybe_unary_or_binary_function<_Res, _T1, _T2>
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: std::binary_function<_T1, _T2, _Res> { };
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template<typename _Signature>
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struct _Mem_fn_traits;
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template<typename _Res, typename _Class, typename... _ArgTypes>
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struct _Mem_fn_traits_base
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{
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using __result_type = _Res;
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using __maybe_type
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= _Maybe_unary_or_binary_function<_Res, _Class*, _ArgTypes...>;
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using __arity = integral_constant<size_t, sizeof...(_ArgTypes)>;
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};
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#define _GLIBCXX_MEM_FN_TRAITS2(_CV, _REF, _LVAL, _RVAL) \
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template<typename _Res, typename _Class, typename... _ArgTypes> \
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struct _Mem_fn_traits<_Res (_Class::*)(_ArgTypes...) _CV _REF> \
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: _Mem_fn_traits_base<_Res, _CV _Class, _ArgTypes...> \
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{ \
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using __vararg = false_type; \
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}; \
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template<typename _Res, typename _Class, typename... _ArgTypes> \
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struct _Mem_fn_traits<_Res (_Class::*)(_ArgTypes... ...) _CV _REF> \
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: _Mem_fn_traits_base<_Res, _CV _Class, _ArgTypes...> \
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{ \
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using __vararg = true_type; \
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};
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#define _GLIBCXX_MEM_FN_TRAITS(_REF, _LVAL, _RVAL) \
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_GLIBCXX_MEM_FN_TRAITS2( , _REF, _LVAL, _RVAL) \
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_GLIBCXX_MEM_FN_TRAITS2(const , _REF, _LVAL, _RVAL) \
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_GLIBCXX_MEM_FN_TRAITS2(volatile , _REF, _LVAL, _RVAL) \
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_GLIBCXX_MEM_FN_TRAITS2(const volatile, _REF, _LVAL, _RVAL)
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_GLIBCXX_MEM_FN_TRAITS( , true_type, true_type)
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_GLIBCXX_MEM_FN_TRAITS(&, true_type, false_type)
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_GLIBCXX_MEM_FN_TRAITS(&&, false_type, true_type)
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#if __cplusplus > 201402L
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_GLIBCXX_MEM_FN_TRAITS(noexcept, true_type, true_type)
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_GLIBCXX_MEM_FN_TRAITS(& noexcept, true_type, false_type)
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_GLIBCXX_MEM_FN_TRAITS(&& noexcept, false_type, true_type)
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#endif
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#undef _GLIBCXX_MEM_FN_TRAITS
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#undef _GLIBCXX_MEM_FN_TRAITS2
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/// If we have found a result_type, extract it.
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template<typename _Functor, typename = __void_t<>>
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struct _Maybe_get_result_type
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{ };
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template<typename _Functor>
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struct _Maybe_get_result_type<_Functor,
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__void_t<typename _Functor::result_type>>
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{ typedef typename _Functor::result_type result_type; };
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/**
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* Base class for any function object that has a weak result type, as
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* defined in 20.8.2 [func.require] of C++11.
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*/
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template<typename _Functor>
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struct _Weak_result_type_impl
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: _Maybe_get_result_type<_Functor>
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{ };
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/// Retrieve the result type for a function type.
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template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
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struct _Weak_result_type_impl<_Res(_ArgTypes...) _GLIBCXX_NOEXCEPT_QUAL>
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{ typedef _Res result_type; };
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/// Retrieve the result type for a varargs function type.
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template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
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struct _Weak_result_type_impl<_Res(_ArgTypes......) _GLIBCXX_NOEXCEPT_QUAL>
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{ typedef _Res result_type; };
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/// Retrieve the result type for a function pointer.
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template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
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struct _Weak_result_type_impl<_Res(*)(_ArgTypes...) _GLIBCXX_NOEXCEPT_QUAL>
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{ typedef _Res result_type; };
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/// Retrieve the result type for a varargs function pointer.
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template<typename _Res, typename... _ArgTypes _GLIBCXX_NOEXCEPT_PARM>
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struct
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_Weak_result_type_impl<_Res(*)(_ArgTypes......) _GLIBCXX_NOEXCEPT_QUAL>
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{ typedef _Res result_type; };
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// Let _Weak_result_type_impl perform the real work.
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template<typename _Functor,
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bool = is_member_function_pointer<_Functor>::value>
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struct _Weak_result_type_memfun
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: _Weak_result_type_impl<_Functor>
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{ };
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// A pointer to member function has a weak result type.
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template<typename _MemFunPtr>
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struct _Weak_result_type_memfun<_MemFunPtr, true>
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{
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using result_type = typename _Mem_fn_traits<_MemFunPtr>::__result_type;
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};
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// A pointer to data member doesn't have a weak result type.
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template<typename _Func, typename _Class>
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struct _Weak_result_type_memfun<_Func _Class::*, false>
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{ };
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/**
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* Strip top-level cv-qualifiers from the function object and let
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* _Weak_result_type_memfun perform the real work.
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*/
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template<typename _Functor>
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struct _Weak_result_type
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: _Weak_result_type_memfun<typename remove_cv<_Functor>::type>
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{ };
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#if __cplusplus <= 201703L
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// Detect nested argument_type.
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template<typename _Tp, typename = __void_t<>>
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struct _Refwrap_base_arg1
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{ };
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// Nested argument_type.
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template<typename _Tp>
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struct _Refwrap_base_arg1<_Tp,
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__void_t<typename _Tp::argument_type>>
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{
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typedef typename _Tp::argument_type argument_type;
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};
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// Detect nested first_argument_type and second_argument_type.
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template<typename _Tp, typename = __void_t<>>
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struct _Refwrap_base_arg2
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{ };
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// Nested first_argument_type and second_argument_type.
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template<typename _Tp>
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struct _Refwrap_base_arg2<_Tp,
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__void_t<typename _Tp::first_argument_type,
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typename _Tp::second_argument_type>>
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{
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typedef typename _Tp::first_argument_type first_argument_type;
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typedef typename _Tp::second_argument_type second_argument_type;
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};
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/**
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* Derives from unary_function or binary_function when it
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* can. Specializations handle all of the easy cases. The primary
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* template determines what to do with a class type, which may
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* derive from both unary_function and binary_function.
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*/
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template<typename _Tp>
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struct _Reference_wrapper_base
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: _Weak_result_type<_Tp>, _Refwrap_base_arg1<_Tp>, _Refwrap_base_arg2<_Tp>
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{ };
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// - a function type (unary)
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template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
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struct _Reference_wrapper_base<_Res(_T1) _GLIBCXX_NOEXCEPT_QUAL>
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: unary_function<_T1, _Res>
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{ };
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template<typename _Res, typename _T1>
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struct _Reference_wrapper_base<_Res(_T1) const>
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: unary_function<_T1, _Res>
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{ };
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template<typename _Res, typename _T1>
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struct _Reference_wrapper_base<_Res(_T1) volatile>
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: unary_function<_T1, _Res>
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{ };
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template<typename _Res, typename _T1>
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struct _Reference_wrapper_base<_Res(_T1) const volatile>
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: unary_function<_T1, _Res>
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{ };
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// - a function type (binary)
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template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
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struct _Reference_wrapper_base<_Res(_T1, _T2) _GLIBCXX_NOEXCEPT_QUAL>
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: binary_function<_T1, _T2, _Res>
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{ };
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template<typename _Res, typename _T1, typename _T2>
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struct _Reference_wrapper_base<_Res(_T1, _T2) const>
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: binary_function<_T1, _T2, _Res>
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{ };
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template<typename _Res, typename _T1, typename _T2>
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struct _Reference_wrapper_base<_Res(_T1, _T2) volatile>
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: binary_function<_T1, _T2, _Res>
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{ };
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template<typename _Res, typename _T1, typename _T2>
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struct _Reference_wrapper_base<_Res(_T1, _T2) const volatile>
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: binary_function<_T1, _T2, _Res>
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{ };
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// - a function pointer type (unary)
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template<typename _Res, typename _T1 _GLIBCXX_NOEXCEPT_PARM>
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struct _Reference_wrapper_base<_Res(*)(_T1) _GLIBCXX_NOEXCEPT_QUAL>
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: unary_function<_T1, _Res>
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{ };
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// - a function pointer type (binary)
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template<typename _Res, typename _T1, typename _T2 _GLIBCXX_NOEXCEPT_PARM>
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struct _Reference_wrapper_base<_Res(*)(_T1, _T2) _GLIBCXX_NOEXCEPT_QUAL>
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: binary_function<_T1, _T2, _Res>
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{ };
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template<typename _Tp, bool = is_member_function_pointer<_Tp>::value>
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struct _Reference_wrapper_base_memfun
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: _Reference_wrapper_base<_Tp>
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{ };
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template<typename _MemFunPtr>
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struct _Reference_wrapper_base_memfun<_MemFunPtr, true>
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: _Mem_fn_traits<_MemFunPtr>::__maybe_type
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{
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using result_type = typename _Mem_fn_traits<_MemFunPtr>::__result_type;
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};
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#endif // ! C++20
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/// @endcond
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/**
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* @brief Primary class template for reference_wrapper.
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* @ingroup functors
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*/
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template<typename _Tp>
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class reference_wrapper
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#if __cplusplus <= 201703L
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// In C++20 std::reference_wrapper<T> allows T to be incomplete,
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// so checking for nested types could result in ODR violations.
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: public _Reference_wrapper_base_memfun<typename remove_cv<_Tp>::type>
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#endif
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{
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_Tp* _M_data;
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_GLIBCXX20_CONSTEXPR
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static _Tp* _S_fun(_Tp& __r) noexcept { return std::__addressof(__r); }
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static void _S_fun(_Tp&&) = delete;
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template<typename _Up, typename _Up2 = __remove_cvref_t<_Up>>
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using __not_same
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= typename enable_if<!is_same<reference_wrapper, _Up2>::value>::type;
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public:
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typedef _Tp type;
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// _GLIBCXX_RESOLVE_LIB_DEFECTS
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// 2993. reference_wrapper<T> conversion from T&&
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// 3041. Unnecessary decay in reference_wrapper
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template<typename _Up, typename = __not_same<_Up>, typename
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= decltype(reference_wrapper::_S_fun(std::declval<_Up>()))>
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_GLIBCXX20_CONSTEXPR
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reference_wrapper(_Up&& __uref)
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noexcept(noexcept(reference_wrapper::_S_fun(std::declval<_Up>())))
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: _M_data(reference_wrapper::_S_fun(std::forward<_Up>(__uref)))
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{ }
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reference_wrapper(const reference_wrapper&) = default;
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reference_wrapper&
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operator=(const reference_wrapper&) = default;
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_GLIBCXX20_CONSTEXPR
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operator _Tp&() const noexcept
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{ return this->get(); }
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_GLIBCXX20_CONSTEXPR
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_Tp&
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get() const noexcept
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{ return *_M_data; }
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template<typename... _Args>
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_GLIBCXX20_CONSTEXPR
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typename result_of<_Tp&(_Args&&...)>::type
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operator()(_Args&&... __args) const
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{
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#if __cplusplus > 201703L
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if constexpr (is_object_v<type>)
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static_assert(sizeof(type), "type must be complete");
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#endif
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return std::__invoke(get(), std::forward<_Args>(__args)...);
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}
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};
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#if __cpp_deduction_guides
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template<typename _Tp>
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reference_wrapper(_Tp&) -> reference_wrapper<_Tp>;
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#endif
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/// @relates reference_wrapper @{
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/// Denotes a reference should be taken to a variable.
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template<typename _Tp>
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_GLIBCXX20_CONSTEXPR
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inline reference_wrapper<_Tp>
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ref(_Tp& __t) noexcept
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{ return reference_wrapper<_Tp>(__t); }
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/// Denotes a const reference should be taken to a variable.
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template<typename _Tp>
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_GLIBCXX20_CONSTEXPR
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inline reference_wrapper<const _Tp>
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cref(const _Tp& __t) noexcept
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{ return reference_wrapper<const _Tp>(__t); }
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template<typename _Tp>
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void ref(const _Tp&&) = delete;
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template<typename _Tp>
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void cref(const _Tp&&) = delete;
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/// std::ref overload to prevent wrapping a reference_wrapper
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template<typename _Tp>
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_GLIBCXX20_CONSTEXPR
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inline reference_wrapper<_Tp>
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ref(reference_wrapper<_Tp> __t) noexcept
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{ return __t; }
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/// std::cref overload to prevent wrapping a reference_wrapper
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template<typename _Tp>
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_GLIBCXX20_CONSTEXPR
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inline reference_wrapper<const _Tp>
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cref(reference_wrapper<_Tp> __t) noexcept
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{ return { __t.get() }; }
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// @}
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace std
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#endif // C++11
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#endif // _GLIBCXX_REFWRAP_H
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