1 // -*- C++ -*- 2 //===----------------------------------------------------------------------===// 3 // 4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 // See https://llvm.org/LICENSE.txt for license information. 6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 11 #define _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 12 13 #include <__compare/synth_three_way.h> 14 #include <__concepts/convertible_to.h> 15 #include <__config> 16 #include <__functional/weak_result_type.h> 17 #include <__memory/addressof.h> 18 #include <__type_traits/common_reference.h> 19 #include <__type_traits/desugars_to.h> 20 #include <__type_traits/enable_if.h> 21 #include <__type_traits/invoke.h> 22 #include <__type_traits/is_const.h> 23 #include <__type_traits/is_core_convertible.h> 24 #include <__type_traits/is_same.h> 25 #include <__type_traits/is_specialization.h> 26 #include <__type_traits/remove_cvref.h> 27 #include <__type_traits/void_t.h> 28 #include <__utility/declval.h> 29 #include <__utility/forward.h> 30 31 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 32 # pragma GCC system_header 33 #endif 34 35 _LIBCPP_BEGIN_NAMESPACE_STD 36 37 template <class _Tp> 38 class reference_wrapper : public __weak_result_type<_Tp> { 39 public: 40 // types 41 typedef _Tp type; 42 43 private: 44 type* __f_; 45 46 static void __fun(_Tp&) _NOEXCEPT; 47 static void __fun(_Tp&&) = delete; // NOLINT(modernize-use-equals-delete) ; This is llvm.org/PR54276 48 49 public: 50 template <class _Up, 51 class = __void_t<decltype(__fun(std::declval<_Up>()))>, 52 __enable_if_t<!is_same<__remove_cvref_t<_Up>, reference_wrapper>::value, int> = 0> 53 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper(_Up&& __u) 54 _NOEXCEPT_(noexcept(__fun(std::declval<_Up>()))) { 55 type& __f = static_cast<_Up&&>(__u); 56 __f_ = std::addressof(__f); 57 } 58 59 // access 60 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 operator type&() const _NOEXCEPT { return *__f_; } 61 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 type& get() const _NOEXCEPT { return *__f_; } 62 63 // invoke 64 template <class... _ArgTypes> 65 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __invoke_result_t<type&, _ArgTypes...> 66 operator()(_ArgTypes&&... __args) const 67 #if _LIBCPP_STD_VER >= 17 68 // Since is_nothrow_invocable requires C++17 LWG3764 is not backported 69 // to earlier versions. 70 noexcept(is_nothrow_invocable_v<_Tp&, _ArgTypes...>) 71 #endif 72 { 73 return std::__invoke(get(), std::forward<_ArgTypes>(__args)...); 74 } 75 76 #if _LIBCPP_STD_VER >= 26 77 78 // [refwrap.comparisons], comparisons 79 80 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, reference_wrapper __y) 81 requires requires { 82 { __x.get() == __y.get() } -> __core_convertible_to<bool>; 83 } 84 { 85 return __x.get() == __y.get(); 86 } 87 88 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, const _Tp& __y) 89 requires requires { 90 { __x.get() == __y } -> __core_convertible_to<bool>; 91 } 92 { 93 return __x.get() == __y; 94 } 95 96 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(reference_wrapper __x, reference_wrapper<const _Tp> __y) 97 requires(!is_const_v<_Tp>) && requires { 98 { __x.get() == __y.get() } -> __core_convertible_to<bool>; 99 } 100 { 101 return __x.get() == __y.get(); 102 } 103 104 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, reference_wrapper __y) 105 requires requires { std::__synth_three_way(__x.get(), __y.get()); } 106 { 107 return std::__synth_three_way(__x.get(), __y.get()); 108 } 109 110 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, const _Tp& __y) 111 requires requires { std::__synth_three_way(__x.get(), __y); } 112 { 113 return std::__synth_three_way(__x.get(), __y); 114 } 115 116 _LIBCPP_HIDE_FROM_ABI friend constexpr auto operator<=>(reference_wrapper __x, reference_wrapper<const _Tp> __y) 117 requires(!is_const_v<_Tp>) && requires { std::__synth_three_way(__x.get(), __y.get()); } 118 { 119 return std::__synth_three_way(__x.get(), __y.get()); 120 } 121 122 #endif // _LIBCPP_STD_VER >= 26 123 }; 124 125 #if _LIBCPP_STD_VER >= 17 126 template <class _Tp> 127 reference_wrapper(_Tp&) -> reference_wrapper<_Tp>; 128 #endif 129 130 template <class _Tp> 131 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp> ref(_Tp& __t) _NOEXCEPT { 132 return reference_wrapper<_Tp>(__t); 133 } 134 135 template <class _Tp> 136 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<_Tp> 137 ref(reference_wrapper<_Tp> __t) _NOEXCEPT { 138 return __t; 139 } 140 141 template <class _Tp> 142 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp> cref(const _Tp& __t) _NOEXCEPT { 143 return reference_wrapper<const _Tp>(__t); 144 } 145 146 template <class _Tp> 147 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 reference_wrapper<const _Tp> 148 cref(reference_wrapper<_Tp> __t) _NOEXCEPT { 149 return __t; 150 } 151 152 template <class _Tp> 153 void ref(const _Tp&&) = delete; 154 template <class _Tp> 155 void cref(const _Tp&&) = delete; 156 157 // Let desugars-to pass through std::reference_wrapper 158 template <class _CanonicalTag, class _Operation, class... _Args> 159 inline const bool __desugars_to_v<_CanonicalTag, reference_wrapper<_Operation>, _Args...> = 160 __desugars_to_v<_CanonicalTag, _Operation, _Args...>; 161 162 #if _LIBCPP_STD_VER >= 20 163 164 template <class _Tp> 165 inline constexpr bool __is_ref_wrapper = __is_specialization_v<_Tp, reference_wrapper>; 166 167 template <class _Rp, class _Tp, class _RpQual, class _TpQual> 168 concept __ref_wrap_common_reference_exists_with = __is_ref_wrapper<_Rp> && requires { 169 typename common_reference_t<typename _Rp::type&, _TpQual>; 170 } && convertible_to<_RpQual, common_reference_t<typename _Rp::type&, _TpQual>>; 171 172 template <class _Rp, class _Tp, template <class> class _RpQual, template <class> class _TpQual> 173 requires(__ref_wrap_common_reference_exists_with<_Rp, _Tp, _RpQual<_Rp>, _TpQual<_Tp>> && 174 !__ref_wrap_common_reference_exists_with<_Tp, _Rp, _TpQual<_Tp>, _RpQual<_Rp>>) 175 struct basic_common_reference<_Rp, _Tp, _RpQual, _TpQual> { 176 using type _LIBCPP_NODEBUG = common_reference_t<typename _Rp::type&, _TpQual<_Tp>>; 177 }; 178 179 template <class _Tp, class _Rp, template <class> class _TpQual, template <class> class _RpQual> 180 requires(__ref_wrap_common_reference_exists_with<_Rp, _Tp, _RpQual<_Rp>, _TpQual<_Tp>> && 181 !__ref_wrap_common_reference_exists_with<_Tp, _Rp, _TpQual<_Tp>, _RpQual<_Rp>>) 182 struct basic_common_reference<_Tp, _Rp, _TpQual, _RpQual> { 183 using type _LIBCPP_NODEBUG = common_reference_t<typename _Rp::type&, _TpQual<_Tp>>; 184 }; 185 186 #endif // _LIBCPP_STD_VER >= 20 187 188 _LIBCPP_END_NAMESPACE_STD 189 190 #endif // _LIBCPP___FUNCTIONAL_REFERENCE_WRAPPER_H 191