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1 // <any> -*- C++ -*-
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2
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145
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3 // Copyright (C) 2014-2020 Free Software Foundation, Inc.
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111
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4 //
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5 // This file is part of the GNU ISO C++ Library. This library is free
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6 // software; you can redistribute it and/or modify it under the
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7 // terms of the GNU General Public License as published by the
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8 // Free Software Foundation; either version 3, or (at your option)
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9 // any later version.
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10
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11 // This library is distributed in the hope that it will be useful,
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12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 // GNU General Public License for more details.
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15
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16 // Under Section 7 of GPL version 3, you are granted additional
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17 // permissions described in the GCC Runtime Library Exception, version
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18 // 3.1, as published by the Free Software Foundation.
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19
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20 // You should have received a copy of the GNU General Public License and
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21 // a copy of the GCC Runtime Library Exception along with this program;
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22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 // <http://www.gnu.org/licenses/>.
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24
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25 /** @file include/any
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26 * This is a Standard C++ Library header.
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27 */
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28
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29 #ifndef _GLIBCXX_ANY
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30 #define _GLIBCXX_ANY 1
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31
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32 #pragma GCC system_header
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33
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34 #if __cplusplus >= 201703L
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35
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36 #include <typeinfo>
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37 #include <new>
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38 #include <utility>
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39 #include <type_traits>
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40
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41 namespace std _GLIBCXX_VISIBILITY(default)
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42 {
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43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
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44
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45 /**
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46 * @addtogroup utilities
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47 * @{
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48 */
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49
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50 /**
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51 * @brief Exception class thrown by a failed @c any_cast
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52 * @ingroup exceptions
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53 */
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54 class bad_any_cast : public bad_cast
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55 {
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56 public:
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57 virtual const char* what() const noexcept { return "bad any_cast"; }
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58 };
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59
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60 [[gnu::noreturn]] inline void __throw_bad_any_cast()
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61 {
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62 #if __cpp_exceptions
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63 throw bad_any_cast{};
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64 #else
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65 __builtin_abort();
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66 #endif
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67 }
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68
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145
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69 #define __cpp_lib_any 201606L
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111
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70
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71 /**
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72 * @brief A type-safe container of any type.
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131
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73 *
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111
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74 * An @c any object's state is either empty or it stores a contained object
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75 * of CopyConstructible type.
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76 */
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77 class any
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78 {
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79 // Holds either pointer to a heap object or the contained object itself.
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80 union _Storage
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81 {
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82 constexpr _Storage() : _M_ptr{nullptr} {}
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83
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84 // Prevent trivial copies of this type, buffer might hold a non-POD.
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85 _Storage(const _Storage&) = delete;
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86 _Storage& operator=(const _Storage&) = delete;
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87
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88 void* _M_ptr;
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89 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer;
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90 };
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91
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92 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>,
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93 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))
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94 && (alignof(_Tp) <= alignof(_Storage))>
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95 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>;
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96
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97 template<typename _Tp>
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98 struct _Manager_internal; // uses small-object optimization
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99
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100 template<typename _Tp>
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101 struct _Manager_external; // creates contained object on the heap
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102
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103 template<typename _Tp>
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104 using _Manager = conditional_t<_Internal<_Tp>::value,
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105 _Manager_internal<_Tp>,
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106 _Manager_external<_Tp>>;
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107
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108 template<typename _Tp, typename _Decayed = decay_t<_Tp>>
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109 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>;
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110
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111 /// Emplace with an object created from @p __args as the contained object.
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112 template <typename _Tp, typename... _Args,
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113 typename _Mgr = _Manager<_Tp>>
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114 void __do_emplace(_Args&&... __args)
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115 {
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116 reset();
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131
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117 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
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111
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118 _M_manager = &_Mgr::_S_manage;
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119 }
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120
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121 /// Emplace with an object created from @p __il and @p __args as
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122 /// the contained object.
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123 template <typename _Tp, typename _Up, typename... _Args,
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124 typename _Mgr = _Manager<_Tp>>
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125 void __do_emplace(initializer_list<_Up> __il, _Args&&... __args)
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126 {
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127 reset();
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131
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128 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
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111
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129 _M_manager = &_Mgr::_S_manage;
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130 }
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131
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132 public:
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133 // construct/destruct
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134
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135 /// Default constructor, creates an empty object.
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136 constexpr any() noexcept : _M_manager(nullptr) { }
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137
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138 /// Copy constructor, copies the state of @p __other
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139 any(const any& __other)
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140 {
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141 if (!__other.has_value())
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142 _M_manager = nullptr;
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143 else
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144 {
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145 _Arg __arg;
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146 __arg._M_any = this;
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147 __other._M_manager(_Op_clone, &__other, &__arg);
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148 }
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149 }
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150
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151 /**
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152 * @brief Move constructor, transfer the state from @p __other
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153 *
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154 * @post @c !__other.has_value() (this postcondition is a GNU extension)
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155 */
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156 any(any&& __other) noexcept
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157 {
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158 if (!__other.has_value())
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159 _M_manager = nullptr;
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160 else
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161 {
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162 _Arg __arg;
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163 __arg._M_any = this;
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164 __other._M_manager(_Op_xfer, &__other, &__arg);
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165 }
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166 }
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167
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168 template <typename _Res, typename _Tp, typename... _Args>
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169 using __any_constructible =
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170 enable_if<__and_<is_copy_constructible<_Tp>,
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171 is_constructible<_Tp, _Args...>>::value,
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172 _Res>;
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173
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174 template <typename _Tp, typename... _Args>
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175 using __any_constructible_t =
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176 typename __any_constructible<bool, _Tp, _Args...>::type;
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177
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178 /// Construct with a copy of @p __value as the contained object.
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179 template <typename _ValueType, typename _Tp = _Decay<_ValueType>,
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180 typename _Mgr = _Manager<_Tp>,
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181 __any_constructible_t<_Tp, _ValueType&&> = true,
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182 enable_if_t<!__is_in_place_type<_Tp>::value, bool> = true>
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183 any(_ValueType&& __value)
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184 : _M_manager(&_Mgr::_S_manage)
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185 {
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186 _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value));
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187 }
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188
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189 /// Construct with a copy of @p __value as the contained object.
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190 template <typename _ValueType, typename _Tp = _Decay<_ValueType>,
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191 typename _Mgr = _Manager<_Tp>,
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145
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192 enable_if_t<__and_v<is_copy_constructible<_Tp>,
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193 __not_<is_constructible<_Tp, _ValueType&&>>,
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194 __not_<__is_in_place_type<_Tp>>>,
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111
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195 bool> = false>
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196 any(_ValueType&& __value)
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197 : _M_manager(&_Mgr::_S_manage)
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198 {
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199 _Mgr::_S_create(_M_storage, __value);
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200 }
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201
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202 /// Construct with an object created from @p __args as the contained object.
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203 template <typename _ValueType, typename... _Args,
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204 typename _Tp = _Decay<_ValueType>,
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205 typename _Mgr = _Manager<_Tp>,
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206 __any_constructible_t<_Tp, _Args&&...> = false>
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207 explicit
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208 any(in_place_type_t<_ValueType>, _Args&&... __args)
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209 : _M_manager(&_Mgr::_S_manage)
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210 {
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211 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
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212 }
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213
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214 /// Construct with an object created from @p __il and @p __args as
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215 /// the contained object.
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216 template <typename _ValueType, typename _Up, typename... _Args,
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217 typename _Tp = _Decay<_ValueType>,
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218 typename _Mgr = _Manager<_Tp>,
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219 __any_constructible_t<_Tp, initializer_list<_Up>,
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220 _Args&&...> = false>
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221 explicit
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222 any(in_place_type_t<_ValueType>,
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223 initializer_list<_Up> __il, _Args&&... __args)
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224 : _M_manager(&_Mgr::_S_manage)
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225 {
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226 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
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227 }
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228
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229 /// Destructor, calls @c reset()
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230 ~any() { reset(); }
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231
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232 // assignments
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233
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234 /// Copy the state of another object.
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235 any& operator=(const any& __rhs)
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236 {
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237 *this = any(__rhs);
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238 return *this;
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239 }
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240
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241 /**
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242 * @brief Move assignment operator
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243 *
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244 * @post @c !__rhs.has_value() (not guaranteed for other implementations)
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245 */
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246 any& operator=(any&& __rhs) noexcept
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247 {
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248 if (!__rhs.has_value())
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249 reset();
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250 else if (this != &__rhs)
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251 {
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252 reset();
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253 _Arg __arg;
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254 __arg._M_any = this;
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255 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
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256 }
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257 return *this;
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258 }
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259
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260 /// Store a copy of @p __rhs as the contained object.
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261 template<typename _ValueType>
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262 enable_if_t<is_copy_constructible<_Decay<_ValueType>>::value, any&>
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263 operator=(_ValueType&& __rhs)
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264 {
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265 *this = any(std::forward<_ValueType>(__rhs));
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266 return *this;
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267 }
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268
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269 /// Emplace with an object created from @p __args as the contained object.
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270 template <typename _ValueType, typename... _Args>
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271 typename __any_constructible<_Decay<_ValueType>&,
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272 _Decay<_ValueType>, _Args&&...>::type
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273 emplace(_Args&&... __args)
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274 {
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131
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275 __do_emplace<_Decay<_ValueType>>(std::forward<_Args>(__args)...);
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111
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276 any::_Arg __arg;
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277 this->_M_manager(any::_Op_access, this, &__arg);
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278 return *static_cast<_Decay<_ValueType>*>(__arg._M_obj);
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279 }
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280
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281 /// Emplace with an object created from @p __il and @p __args as
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282 /// the contained object.
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283 template <typename _ValueType, typename _Up, typename... _Args>
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284 typename __any_constructible<_Decay<_ValueType>&,
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285 _Decay<_ValueType>,
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286 initializer_list<_Up>,
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287 _Args&&...>::type
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288 emplace(initializer_list<_Up> __il, _Args&&... __args)
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289 {
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131
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290 __do_emplace<_Decay<_ValueType>, _Up>(__il,
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291 std::forward<_Args>(__args)...);
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111
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292 any::_Arg __arg;
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293 this->_M_manager(any::_Op_access, this, &__arg);
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294 return *static_cast<_Decay<_ValueType>*>(__arg._M_obj);
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295 }
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296
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297 // modifiers
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298
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299 /// If not empty, destroy the contained object.
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300 void reset() noexcept
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301 {
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302 if (has_value())
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303 {
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304 _M_manager(_Op_destroy, this, nullptr);
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305 _M_manager = nullptr;
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306 }
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307 }
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308
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309 /// Exchange state with another object.
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310 void swap(any& __rhs) noexcept
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311 {
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312 if (!has_value() && !__rhs.has_value())
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313 return;
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314
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315 if (has_value() && __rhs.has_value())
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316 {
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317 if (this == &__rhs)
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318 return;
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319
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320 any __tmp;
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321 _Arg __arg;
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322 __arg._M_any = &__tmp;
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323 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
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324 __arg._M_any = &__rhs;
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325 _M_manager(_Op_xfer, this, &__arg);
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326 __arg._M_any = this;
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327 __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
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328 }
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329 else
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330 {
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331 any* __empty = !has_value() ? this : &__rhs;
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332 any* __full = !has_value() ? &__rhs : this;
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333 _Arg __arg;
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334 __arg._M_any = __empty;
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335 __full->_M_manager(_Op_xfer, __full, &__arg);
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336 }
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337 }
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338
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339 // observers
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340
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341 /// Reports whether there is a contained object or not.
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342 bool has_value() const noexcept { return _M_manager != nullptr; }
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343
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344 #if __cpp_rtti
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345 /// The @c typeid of the contained object, or @c typeid(void) if empty.
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346 const type_info& type() const noexcept
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347 {
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348 if (!has_value())
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349 return typeid(void);
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350 _Arg __arg;
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351 _M_manager(_Op_get_type_info, this, &__arg);
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352 return *__arg._M_typeinfo;
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353 }
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354 #endif
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355
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356 template<typename _Tp>
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357 static constexpr bool __is_valid_cast()
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358 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
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359
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360 private:
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361 enum _Op {
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362 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer
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363 };
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364
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365 union _Arg
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366 {
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367 void* _M_obj;
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368 const std::type_info* _M_typeinfo;
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369 any* _M_any;
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370 };
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371
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372 void (*_M_manager)(_Op, const any*, _Arg*);
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373 _Storage _M_storage;
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374
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375 template<typename _Tp>
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376 friend void* __any_caster(const any* __any);
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377
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378 // Manage in-place contained object.
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379 template<typename _Tp>
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380 struct _Manager_internal
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381 {
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382 static void
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383 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
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384
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385 template<typename _Up>
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386 static void
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387 _S_create(_Storage& __storage, _Up&& __value)
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388 {
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389 void* __addr = &__storage._M_buffer;
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390 ::new (__addr) _Tp(std::forward<_Up>(__value));
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391 }
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392
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393 template<typename... _Args>
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394 static void
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395 _S_create(_Storage& __storage, _Args&&... __args)
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396 {
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397 void* __addr = &__storage._M_buffer;
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398 ::new (__addr) _Tp(std::forward<_Args>(__args)...);
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399 }
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400 };
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401
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402 // Manage external contained object.
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403 template<typename _Tp>
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404 struct _Manager_external
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405 {
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406 static void
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407 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
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408
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409 template<typename _Up>
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410 static void
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411 _S_create(_Storage& __storage, _Up&& __value)
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412 {
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413 __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
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414 }
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415 template<typename... _Args>
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416 static void
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417 _S_create(_Storage& __storage, _Args&&... __args)
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418 {
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419 __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...);
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420 }
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421 };
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422 };
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423
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424 /// Exchange the states of two @c any objects.
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425 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
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426
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427 /// Create an any holding a @c _Tp constructed from @c __args.
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428 template <typename _Tp, typename... _Args>
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429 any make_any(_Args&&... __args)
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430 {
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431 return any(in_place_type<_Tp>, std::forward<_Args>(__args)...);
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432 }
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433
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434 /// Create an any holding a @c _Tp constructed from @c __il and @c __args.
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435 template <typename _Tp, typename _Up, typename... _Args>
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436 any make_any(initializer_list<_Up> __il, _Args&&... __args)
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437 {
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438 return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...);
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439 }
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440
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441 /**
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442 * @brief Access the contained object.
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443 *
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444 * @tparam _ValueType A const-reference or CopyConstructible type.
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445 * @param __any The object to access.
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446 * @return The contained object.
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447 * @throw bad_any_cast If <code>
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448 * __any.type() != typeid(remove_reference_t<_ValueType>)
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449 * </code>
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450 */
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451 template<typename _ValueType>
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452 inline _ValueType any_cast(const any& __any)
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453 {
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131
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454 using _Up = __remove_cvref_t<_ValueType>;
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111
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455 static_assert(any::__is_valid_cast<_ValueType>(),
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456 "Template argument must be a reference or CopyConstructible type");
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131
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457 static_assert(is_constructible_v<_ValueType, const _Up&>,
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458 "Template argument must be constructible from a const value.");
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459 auto __p = any_cast<_Up>(&__any);
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111
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460 if (__p)
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461 return static_cast<_ValueType>(*__p);
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462 __throw_bad_any_cast();
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463 }
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464
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465 /**
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466 * @brief Access the contained object.
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467 *
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468 * @tparam _ValueType A reference or CopyConstructible type.
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469 * @param __any The object to access.
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470 * @return The contained object.
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471 * @throw bad_any_cast If <code>
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472 * __any.type() != typeid(remove_reference_t<_ValueType>)
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473 * </code>
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474 *
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475 * @{
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476 */
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477 template<typename _ValueType>
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478 inline _ValueType any_cast(any& __any)
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479 {
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131
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480 using _Up = __remove_cvref_t<_ValueType>;
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111
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481 static_assert(any::__is_valid_cast<_ValueType>(),
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482 "Template argument must be a reference or CopyConstructible type");
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131
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483 static_assert(is_constructible_v<_ValueType, _Up&>,
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484 "Template argument must be constructible from an lvalue.");
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485 auto __p = any_cast<_Up>(&__any);
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111
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486 if (__p)
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487 return static_cast<_ValueType>(*__p);
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488 __throw_bad_any_cast();
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489 }
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490
|
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131
|
491 template<typename _ValueType>
|
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111
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492 inline _ValueType any_cast(any&& __any)
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493 {
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131
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494 using _Up = __remove_cvref_t<_ValueType>;
|
|
111
|
495 static_assert(any::__is_valid_cast<_ValueType>(),
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|
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496 "Template argument must be a reference or CopyConstructible type");
|
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131
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497 static_assert(is_constructible_v<_ValueType, _Up>,
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|
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498 "Template argument must be constructible from an rvalue.");
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|
|
499 auto __p = any_cast<_Up>(&__any);
|
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111
|
500 if (__p)
|
|
|
501 return static_cast<_ValueType>(std::move(*__p));
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|
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502 __throw_bad_any_cast();
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|
|
503 }
|
|
|
504 // @}
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|
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505
|
|
145
|
506 /// @cond undocumented
|
|
111
|
507 template<typename _Tp>
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|
|
508 void* __any_caster(const any* __any)
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|
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509 {
|
|
145
|
510 // any_cast<T> returns non-null if __any->type() == typeid(T) and
|
|
|
511 // typeid(T) ignores cv-qualifiers so remove them:
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|
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512 using _Up = remove_cv_t<_Tp>;
|
|
|
513 // The contained value has a decayed type, so if decay_t<U> is not U,
|
|
|
514 // then it's not possible to have a contained value of type U:
|
|
|
515 if constexpr (!is_same_v<decay_t<_Up>, _Up>)
|
|
|
516 return nullptr;
|
|
|
517 // Only copy constructible types can be used for contained values:
|
|
|
518 else if constexpr (!is_copy_constructible_v<_Up>)
|
|
|
519 return nullptr;
|
|
|
520 // First try comparing function addresses, which works without RTTI
|
|
|
521 else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage
|
|
|
522 #if __cpp_rtti
|
|
|
523 || __any->type() == typeid(_Tp)
|
|
|
524 #endif
|
|
|
525 )
|
|
111
|
526 {
|
|
145
|
527 any::_Arg __arg;
|
|
|
528 __any->_M_manager(any::_Op_access, __any, &__arg);
|
|
|
529 return __arg._M_obj;
|
|
111
|
530 }
|
|
|
531 return nullptr;
|
|
|
532 }
|
|
145
|
533 /// @endcond
|
|
111
|
534
|
|
|
535 /**
|
|
|
536 * @brief Access the contained object.
|
|
|
537 *
|
|
|
538 * @tparam _ValueType The type of the contained object.
|
|
|
539 * @param __any A pointer to the object to access.
|
|
|
540 * @return The address of the contained object if <code>
|
|
|
541 * __any != nullptr && __any.type() == typeid(_ValueType)
|
|
|
542 * </code>, otherwise a null pointer.
|
|
|
543 *
|
|
|
544 * @{
|
|
|
545 */
|
|
|
546 template<typename _ValueType>
|
|
|
547 inline const _ValueType* any_cast(const any* __any) noexcept
|
|
|
548 {
|
|
145
|
549 if constexpr (is_object_v<_ValueType>)
|
|
|
550 if (__any)
|
|
|
551 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
|
|
111
|
552 return nullptr;
|
|
|
553 }
|
|
|
554
|
|
|
555 template<typename _ValueType>
|
|
|
556 inline _ValueType* any_cast(any* __any) noexcept
|
|
|
557 {
|
|
145
|
558 if constexpr (is_object_v<_ValueType>)
|
|
|
559 if (__any)
|
|
|
560 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
|
|
111
|
561 return nullptr;
|
|
|
562 }
|
|
|
563 // @}
|
|
|
564
|
|
|
565 template<typename _Tp>
|
|
|
566 void
|
|
|
567 any::_Manager_internal<_Tp>::
|
|
|
568 _S_manage(_Op __which, const any* __any, _Arg* __arg)
|
|
|
569 {
|
|
|
570 // The contained object is in _M_storage._M_buffer
|
|
|
571 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
|
|
|
572 switch (__which)
|
|
|
573 {
|
|
|
574 case _Op_access:
|
|
|
575 __arg->_M_obj = const_cast<_Tp*>(__ptr);
|
|
|
576 break;
|
|
|
577 case _Op_get_type_info:
|
|
|
578 #if __cpp_rtti
|
|
|
579 __arg->_M_typeinfo = &typeid(_Tp);
|
|
|
580 #endif
|
|
|
581 break;
|
|
|
582 case _Op_clone:
|
|
|
583 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
|
|
|
584 __arg->_M_any->_M_manager = __any->_M_manager;
|
|
|
585 break;
|
|
|
586 case _Op_destroy:
|
|
|
587 __ptr->~_Tp();
|
|
|
588 break;
|
|
|
589 case _Op_xfer:
|
|
|
590 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp
|
|
|
591 (std::move(*const_cast<_Tp*>(__ptr)));
|
|
|
592 __ptr->~_Tp();
|
|
|
593 __arg->_M_any->_M_manager = __any->_M_manager;
|
|
|
594 const_cast<any*>(__any)->_M_manager = nullptr;
|
|
|
595 break;
|
|
|
596 }
|
|
|
597 }
|
|
|
598
|
|
|
599 template<typename _Tp>
|
|
|
600 void
|
|
|
601 any::_Manager_external<_Tp>::
|
|
|
602 _S_manage(_Op __which, const any* __any, _Arg* __arg)
|
|
|
603 {
|
|
|
604 // The contained object is *_M_storage._M_ptr
|
|
|
605 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
|
|
|
606 switch (__which)
|
|
|
607 {
|
|
|
608 case _Op_access:
|
|
|
609 __arg->_M_obj = const_cast<_Tp*>(__ptr);
|
|
|
610 break;
|
|
|
611 case _Op_get_type_info:
|
|
|
612 #if __cpp_rtti
|
|
|
613 __arg->_M_typeinfo = &typeid(_Tp);
|
|
|
614 #endif
|
|
|
615 break;
|
|
|
616 case _Op_clone:
|
|
|
617 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
|
|
|
618 __arg->_M_any->_M_manager = __any->_M_manager;
|
|
|
619 break;
|
|
|
620 case _Op_destroy:
|
|
|
621 delete __ptr;
|
|
|
622 break;
|
|
|
623 case _Op_xfer:
|
|
|
624 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr;
|
|
|
625 __arg->_M_any->_M_manager = __any->_M_manager;
|
|
|
626 const_cast<any*>(__any)->_M_manager = nullptr;
|
|
|
627 break;
|
|
|
628 }
|
|
|
629 }
|
|
|
630
|
|
|
631 /// @}
|
|
131
|
632
|
|
145
|
633 namespace __detail::__variant
|
|
|
634 {
|
|
|
635 template<typename> struct _Never_valueless_alt; // see <variant>
|
|
|
636
|
|
|
637 // Provide the strong exception-safety guarantee when emplacing an
|
|
|
638 // any into a variant.
|
|
|
639 template<>
|
|
|
640 struct _Never_valueless_alt<std::any>
|
|
|
641 : std::true_type
|
|
|
642 { };
|
|
|
643 } // namespace __detail::__variant
|
|
|
644
|
|
111
|
645 _GLIBCXX_END_NAMESPACE_VERSION
|
|
|
646 } // namespace std
|
|
|
647
|
|
145
|
648 #endif // C++17
|
|
111
|
649 #endif // _GLIBCXX_ANY
|
