| 1 | // <variant> -*- C++ -*- |
|---|---|
| 2 | |
| 3 | // Copyright (C) 2016-2026 Free Software Foundation, Inc. |
| 4 | // |
| 5 | // This file is part of the GNU ISO C++ Library. This library is free |
| 6 | // software; you can redistribute it and/or modify it under the |
| 7 | // terms of the GNU General Public License as published by the |
| 8 | // Free Software Foundation; either version 3, or (at your option) |
| 9 | // any later version. |
| 10 | |
| 11 | // This library is distributed in the hope that it will be useful, |
| 12 | // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | // GNU General Public License for more details. |
| 15 | |
| 16 | // Under Section 7 of GPL version 3, you are granted additional |
| 17 | // permissions described in the GCC Runtime Library Exception, version |
| 18 | // 3.1, as published by the Free Software Foundation. |
| 19 | |
| 20 | // You should have received a copy of the GNU General Public License and |
| 21 | // a copy of the GCC Runtime Library Exception along with this program; |
| 22 | // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| 23 | // <http://www.gnu.org/licenses/>. |
| 24 | |
| 25 | /** @file variant |
| 26 | * This is the `<variant>` C++ Library header. |
| 27 | */ |
| 28 | |
| 29 | #ifndef _GLIBCXX_VARIANT |
| 30 | #define _GLIBCXX_VARIANT 1 |
| 31 | |
| 32 | #ifdef _GLIBCXX_SYSHDR |
| 33 | #pragma GCC system_header |
| 34 | #endif |
| 35 | |
| 36 | #define __glibcxx_want_freestanding_variant |
| 37 | #define __glibcxx_want_variant |
| 38 | #define __glibcxx_want_constrained_equality |
| 39 | #define __glibcxx_want_constexpr_exceptions |
| 40 | #include <bits/version.h> |
| 41 | |
| 42 | #ifdef __cpp_lib_variant // C++ >= 17 |
| 43 | #include <initializer_list> |
| 44 | #include <type_traits> |
| 45 | #include <bits/enable_special_members.h> |
| 46 | #include <bits/exception_defines.h> |
| 47 | #include <bits/functional_hash.h> |
| 48 | #include <bits/invoke.h> |
| 49 | #include <bits/monostate.h> |
| 50 | #include <bits/parse_numbers.h> // _Select_int |
| 51 | #include <bits/stl_iterator_base_funcs.h> |
| 52 | #include <bits/stl_construct.h> |
| 53 | #include <bits/utility.h> // in_place_index_t |
| 54 | #if __cplusplus >= 202002L |
| 55 | # include <concepts> |
| 56 | # include <compare> |
| 57 | #endif |
| 58 | |
| 59 | // C++ < 20 || __cpp_concepts < 202002L || __cpp_constexpr < 201811L |
| 60 | #if __cpp_lib_variant < 202106L |
| 61 | # include <ext/aligned_buffer.h> // Use __aligned_membuf for storage. |
| 62 | #endif |
| 63 | |
| 64 | namespace std _GLIBCXX_VISIBILITY(default) |
| 65 | { |
| 66 | _GLIBCXX_BEGIN_NAMESPACE_VERSION |
| 67 | |
| 68 | template<typename... _Types> class tuple; |
| 69 | template<typename... _Types> class variant; |
| 70 | |
| 71 | template<typename _Variant> |
| 72 | struct variant_size; |
| 73 | |
| 74 | template<typename _Variant> |
| 75 | struct variant_size<const _Variant> : variant_size<_Variant> {}; |
| 76 | |
| 77 | template<typename _Variant> |
| 78 | struct variant_size<volatile _Variant> : variant_size<_Variant> {}; |
| 79 | |
| 80 | template<typename _Variant> |
| 81 | struct variant_size<const volatile _Variant> : variant_size<_Variant> {}; |
| 82 | |
| 83 | template<typename... _Types> |
| 84 | struct variant_size<variant<_Types...>> |
| 85 | : std::integral_constant<size_t, sizeof...(_Types)> {}; |
| 86 | |
| 87 | template<typename _Variant> |
| 88 | inline constexpr size_t variant_size_v = variant_size<_Variant>::value; |
| 89 | |
| 90 | template<typename... _Types> |
| 91 | inline constexpr size_t |
| 92 | variant_size_v<variant<_Types...>> = sizeof...(_Types); |
| 93 | |
| 94 | template<typename... _Types> |
| 95 | inline constexpr size_t |
| 96 | variant_size_v<const variant<_Types...>> = sizeof...(_Types); |
| 97 | |
| 98 | template<size_t _Np, typename _Variant> |
| 99 | struct variant_alternative; |
| 100 | |
| 101 | template<size_t _Np, typename... _Types> |
| 102 | struct variant_alternative<_Np, variant<_Types...>> |
| 103 | { |
| 104 | static_assert(_Np < sizeof...(_Types)); |
| 105 | |
| 106 | using type = typename _Nth_type<_Np, _Types...>::type; |
| 107 | }; |
| 108 | |
| 109 | template<size_t _Np, typename _Variant> |
| 110 | using variant_alternative_t = |
| 111 | typename variant_alternative<_Np, _Variant>::type; |
| 112 | |
| 113 | template<size_t _Np, typename _Variant> |
| 114 | struct variant_alternative<_Np, const _Variant> |
| 115 | { using type = const variant_alternative_t<_Np, _Variant>; }; |
| 116 | |
| 117 | template<size_t _Np, typename _Variant> |
| 118 | struct variant_alternative<_Np, volatile _Variant> |
| 119 | { using type = volatile variant_alternative_t<_Np, _Variant>; }; |
| 120 | |
| 121 | template<size_t _Np, typename _Variant> |
| 122 | struct variant_alternative<_Np, const volatile _Variant> |
| 123 | { using type = const volatile variant_alternative_t<_Np, _Variant>; }; |
| 124 | |
| 125 | inline constexpr size_t variant_npos = -1; |
| 126 | |
| 127 | template<size_t _Np, typename... _Types> |
| 128 | constexpr variant_alternative_t<_Np, variant<_Types...>>& |
| 129 | get(variant<_Types...>&); |
| 130 | |
| 131 | template<size_t _Np, typename... _Types> |
| 132 | constexpr variant_alternative_t<_Np, variant<_Types...>>&& |
| 133 | get(variant<_Types...>&&); |
| 134 | |
| 135 | template<size_t _Np, typename... _Types> |
| 136 | constexpr variant_alternative_t<_Np, variant<_Types...>> const& |
| 137 | get(const variant<_Types...>&); |
| 138 | |
| 139 | template<size_t _Np, typename... _Types> |
| 140 | constexpr variant_alternative_t<_Np, variant<_Types...>> const&& |
| 141 | get(const variant<_Types...>&&); |
| 142 | |
| 143 | template<typename _Result_type, typename _Visitor, typename... _Variants> |
| 144 | constexpr decltype(auto) |
| 145 | __do_visit(_Visitor&& __visitor, _Variants&&... __variants); |
| 146 | |
| 147 | template <typename... _Types, typename _Tp> |
| 148 | _GLIBCXX20_CONSTEXPR |
| 149 | decltype(auto) |
| 150 | __variant_cast(_Tp&& __rhs) |
| 151 | { |
| 152 | if constexpr (is_lvalue_reference_v<_Tp>) |
| 153 | { |
| 154 | if constexpr (is_const_v<remove_reference_t<_Tp>>) |
| 155 | return static_cast<const variant<_Types...>&>(__rhs); |
| 156 | else |
| 157 | return static_cast<variant<_Types...>&>(__rhs); |
| 158 | } |
| 159 | else |
| 160 | return static_cast<variant<_Types...>&&>(__rhs); |
| 161 | } |
| 162 | |
| 163 | namespace __detail |
| 164 | { |
| 165 | namespace __variant |
| 166 | { |
| 167 | // used for raw visitation |
| 168 | struct __variant_cookie {}; |
| 169 | // used for raw visitation with indices passed in |
| 170 | struct __variant_idx_cookie { using type = __variant_idx_cookie; }; |
| 171 | // Used to enable deduction (and same-type checking) for std::visit: |
| 172 | template<typename _Tp> struct __deduce_visit_result { using type = _Tp; }; |
| 173 | |
| 174 | // Visit variants that might be valueless. |
| 175 | template<typename _Visitor, typename... _Variants> |
| 176 | constexpr void |
| 177 | __raw_visit(_Visitor&& __visitor, _Variants&&... __variants) |
| 178 | { |
| 179 | std::__do_visit<__variant_cookie>(std::forward<_Visitor>(__visitor), |
| 180 | std::forward<_Variants>(__variants)...); |
| 181 | } |
| 182 | |
| 183 | // Visit variants that might be valueless, passing indices to the visitor. |
| 184 | template<typename _Visitor, typename... _Variants> |
| 185 | constexpr void |
| 186 | __raw_idx_visit(_Visitor&& __visitor, _Variants&&... __variants) |
| 187 | { |
| 188 | std::__do_visit<__variant_idx_cookie>(std::forward<_Visitor>(__visitor), |
| 189 | std::forward<_Variants>(__variants)...); |
| 190 | } |
| 191 | |
| 192 | // The __as function templates implement the exposition-only "as-variant" |
| 193 | |
| 194 | template<typename... _Types> |
| 195 | constexpr std::variant<_Types...>& |
| 196 | __as(std::variant<_Types...>& __v) noexcept |
| 197 | { return __v; } |
| 198 | |
| 199 | template<typename... _Types> |
| 200 | constexpr const std::variant<_Types...>& |
| 201 | __as(const std::variant<_Types...>& __v) noexcept |
| 202 | { return __v; } |
| 203 | |
| 204 | template<typename... _Types> |
| 205 | constexpr std::variant<_Types...>&& |
| 206 | __as(std::variant<_Types...>&& __v) noexcept |
| 207 | { return std::move(__v); } |
| 208 | |
| 209 | template<typename... _Types> |
| 210 | constexpr const std::variant<_Types...>&& |
| 211 | __as(const std::variant<_Types...>&& __v) noexcept |
| 212 | { return std::move(__v); } |
| 213 | |
| 214 | #if (__cpp_lib_variant < 202106L) && defined(_GLIBCXX_USE_VARIANT_CXX17_OLD_ABI) |
| 215 | template<typename _Type, bool = std::is_trivially_destructible_v<_Type>> |
| 216 | struct _Uninitialized; |
| 217 | #else |
| 218 | template<typename _Type, bool /* unused */ = true> |
| 219 | struct _Uninitialized; |
| 220 | #endif |
| 221 | |
| 222 | // The primary template is used for trivially destructible types in C++17, |
| 223 | // and for all types in C++20. |
| 224 | template<typename _Type, bool> |
| 225 | struct _Uninitialized |
| 226 | { |
| 227 | template<typename... _Args> |
| 228 | constexpr |
| 229 | _Uninitialized(in_place_index_t<0>, _Args&&... __args) |
| 230 | : _M_storage(std::forward<_Args>(__args)...) |
| 231 | { } |
| 232 | |
| 233 | #if (__cpp_lib_variant < 202106L) && defined(_GLIBCXX_USE_VARIANT_CXX17_OLD_ABI) |
| 234 | constexpr const _Type& _M_get() const & noexcept |
| 235 | { return _M_storage; } |
| 236 | |
| 237 | constexpr _Type& _M_get() & noexcept |
| 238 | { return _M_storage; } |
| 239 | |
| 240 | constexpr const _Type&& _M_get() const && noexcept |
| 241 | { return std::move(_M_storage); } |
| 242 | |
| 243 | constexpr _Type&& _M_get() && noexcept |
| 244 | { return std::move(_M_storage); } |
| 245 | #endif |
| 246 | |
| 247 | _Type _M_storage; |
| 248 | }; |
| 249 | |
| 250 | #if (__cpp_lib_variant < 202106L) && defined(_GLIBCXX_USE_VARIANT_CXX17_OLD_ABI) |
| 251 | // This partial specialization is used for non-trivially destructible types |
| 252 | // in C++17. |
| 253 | template<typename _Type> |
| 254 | struct _Uninitialized<_Type, false> |
| 255 | { |
| 256 | template<typename... _Args> |
| 257 | constexpr |
| 258 | _Uninitialized(in_place_index_t<0>, _Args&&... __args) |
| 259 | { |
| 260 | ::new ((void*)std::addressof(_M_storage)) |
| 261 | _Type(std::forward<_Args>(__args)...); |
| 262 | } |
| 263 | |
| 264 | const _Type& _M_get() const & noexcept |
| 265 | { return *_M_storage._M_ptr(); } |
| 266 | |
| 267 | _Type& _M_get() & noexcept |
| 268 | { return *_M_storage._M_ptr(); } |
| 269 | |
| 270 | const _Type&& _M_get() const && noexcept |
| 271 | { return std::move(*_M_storage._M_ptr()); } |
| 272 | |
| 273 | _Type&& _M_get() && noexcept |
| 274 | { return std::move(*_M_storage._M_ptr()); } |
| 275 | |
| 276 | __gnu_cxx::__aligned_membuf<_Type> _M_storage; |
| 277 | }; |
| 278 | |
| 279 | template<size_t _Np, typename _Union> |
| 280 | constexpr decltype(auto) |
| 281 | __get_n(_Union&& __u) noexcept |
| 282 | { |
| 283 | if constexpr (_Np == 0) |
| 284 | return std::forward<_Union>(__u)._M_first._M_get(); |
| 285 | else if constexpr (_Np == 1) |
| 286 | return std::forward<_Union>(__u)._M_rest._M_first._M_get(); |
| 287 | else if constexpr (_Np == 2) |
| 288 | return std::forward<_Union>(__u)._M_rest._M_rest._M_first._M_get(); |
| 289 | else |
| 290 | return __variant::__get_n<_Np - 3>( |
| 291 | std::forward<_Union>(__u)._M_rest._M_rest._M_rest); |
| 292 | } |
| 293 | #else // !_GLIBCXX_USE_VARIANT_CXX17_OLD_ABI |
| 294 | template<size_t _Np, typename _Union> |
| 295 | constexpr auto&& |
| 296 | __get_n(_Union&& __u) noexcept |
| 297 | { |
| 298 | if constexpr (_Np == 0) |
| 299 | return std::forward<_Union>(__u)._M_first._M_storage; |
| 300 | else if constexpr (_Np == 1) |
| 301 | return std::forward<_Union>(__u)._M_rest._M_first._M_storage; |
| 302 | else if constexpr (_Np == 2) |
| 303 | return std::forward<_Union>(__u)._M_rest._M_rest._M_first._M_storage; |
| 304 | else |
| 305 | return __variant::__get_n<_Np - 3>( |
| 306 | std::forward<_Union>(__u)._M_rest._M_rest._M_rest); |
| 307 | } |
| 308 | #endif // !_GLIBCXX_USE_VARIANT_CXX17_OLD_ABI |
| 309 | |
| 310 | // Returns the typed storage for __v. |
| 311 | template<size_t _Np, typename _Variant> |
| 312 | constexpr decltype(auto) |
| 313 | __get(_Variant&& __v) noexcept |
| 314 | { return __variant::__get_n<_Np>(std::forward<_Variant>(__v)._M_u); } |
| 315 | |
| 316 | // Gets the _Uninitialized to construct into for __u. |
| 317 | template<size_t _Np, typename _Union> |
| 318 | constexpr decltype(auto) |
| 319 | __construct_n(_Union& __u) noexcept |
| 320 | { |
| 321 | if constexpr (_Np == 0) |
| 322 | return &__u._M_first; |
| 323 | else if constexpr (_Np == 1) |
| 324 | { |
| 325 | std::_Construct(&__u._M_rest); |
| 326 | return &__u._M_rest._M_first; |
| 327 | } |
| 328 | else if constexpr (_Np == 2) |
| 329 | { |
| 330 | std::_Construct(&__u._M_rest); |
| 331 | std::_Construct(&__u._M_rest._M_rest); |
| 332 | return &__u._M_rest._M_rest._M_first; |
| 333 | } |
| 334 | else |
| 335 | { |
| 336 | std::_Construct(&__u._M_rest); |
| 337 | std::_Construct(&__u._M_rest._M_rest); |
| 338 | std::_Construct(&__u._M_rest._M_rest._M_rest); |
| 339 | return __variant::__construct_n<_Np - 3>(__u._M_rest._M_rest._M_rest); |
| 340 | } |
| 341 | } |
| 342 | |
| 343 | template<typename... _Types> |
| 344 | struct _Traits |
| 345 | { |
| 346 | static constexpr bool _S_default_ctor = |
| 347 | is_default_constructible_v<typename _Nth_type<0, _Types...>::type>; |
| 348 | static constexpr bool _S_copy_ctor = |
| 349 | (is_copy_constructible_v<_Types> && ...); |
| 350 | static constexpr bool _S_move_ctor = |
| 351 | (is_move_constructible_v<_Types> && ...); |
| 352 | static constexpr bool _S_copy_assign = |
| 353 | _S_copy_ctor |
| 354 | && (is_copy_assignable_v<_Types> && ...); |
| 355 | static constexpr bool _S_move_assign = |
| 356 | _S_move_ctor |
| 357 | && (is_move_assignable_v<_Types> && ...); |
| 358 | |
| 359 | static constexpr bool _S_trivial_dtor = |
| 360 | (is_trivially_destructible_v<_Types> && ...); |
| 361 | static constexpr bool _S_trivial_copy_ctor = |
| 362 | (is_trivially_copy_constructible_v<_Types> && ...); |
| 363 | static constexpr bool _S_trivial_move_ctor = |
| 364 | (is_trivially_move_constructible_v<_Types> && ...); |
| 365 | static constexpr bool _S_trivial_copy_assign = |
| 366 | _S_trivial_dtor && _S_trivial_copy_ctor |
| 367 | && (is_trivially_copy_assignable_v<_Types> && ...); |
| 368 | static constexpr bool _S_trivial_move_assign = |
| 369 | _S_trivial_dtor && _S_trivial_move_ctor |
| 370 | && (is_trivially_move_assignable_v<_Types> && ...); |
| 371 | |
| 372 | // The following nothrow traits are for non-trivial SMFs. Trivial SMFs |
| 373 | // are always nothrow. |
| 374 | static constexpr bool _S_nothrow_default_ctor = |
| 375 | is_nothrow_default_constructible_v< |
| 376 | typename _Nth_type<0, _Types...>::type>; |
| 377 | static constexpr bool _S_nothrow_copy_ctor = false; |
| 378 | static constexpr bool _S_nothrow_move_ctor = |
| 379 | (is_nothrow_move_constructible_v<_Types> && ...); |
| 380 | static constexpr bool _S_nothrow_copy_assign = false; |
| 381 | static constexpr bool _S_nothrow_move_assign = |
| 382 | _S_nothrow_move_ctor |
| 383 | && (is_nothrow_move_assignable_v<_Types> && ...); |
| 384 | }; |
| 385 | |
| 386 | // Defines members and ctors. |
| 387 | template<bool __trivially_destructible, typename... _Types> |
| 388 | union _Variadic_union |
| 389 | { |
| 390 | _Variadic_union() = default; |
| 391 | |
| 392 | template<size_t _Np, typename... _Args> |
| 393 | _Variadic_union(in_place_index_t<_Np>, _Args&&...) = delete; |
| 394 | }; |
| 395 | |
| 396 | template<typename _First, typename... _Rest> |
| 397 | union _Variadic_union<true, _First, _Rest...> |
| 398 | { |
| 399 | constexpr _Variadic_union() : _M_rest() { } |
| 400 | |
| 401 | template<typename... _Args> |
| 402 | constexpr |
| 403 | _Variadic_union(in_place_index_t<0>, _Args&&... __args) |
| 404 | : _M_first(in_place_index<0>, std::forward<_Args>(__args)...) |
| 405 | { } |
| 406 | |
| 407 | template<size_t _Np, typename... _Args> |
| 408 | constexpr |
| 409 | _Variadic_union(in_place_index_t<_Np>, _Args&&... __args) |
| 410 | : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...) |
| 411 | { } |
| 412 | |
| 413 | _Uninitialized<_First> _M_first; |
| 414 | _Variadic_union<true, _Rest...> _M_rest; |
| 415 | }; |
| 416 | |
| 417 | template<typename _First, typename... _Rest> |
| 418 | union _Variadic_union<false, _First, _Rest...> |
| 419 | { |
| 420 | constexpr _Variadic_union() : _M_rest() { } |
| 421 | |
| 422 | template<typename... _Args> |
| 423 | constexpr |
| 424 | _Variadic_union(in_place_index_t<0>, _Args&&... __args) |
| 425 | : _M_first(in_place_index<0>, std::forward<_Args>(__args)...) |
| 426 | { } |
| 427 | |
| 428 | template<size_t _Np, typename... _Args> |
| 429 | constexpr |
| 430 | _Variadic_union(in_place_index_t<_Np>, _Args&&... __args) |
| 431 | : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...) |
| 432 | { } |
| 433 | |
| 434 | _Variadic_union(const _Variadic_union&) = default; |
| 435 | _Variadic_union(_Variadic_union&&) = default; |
| 436 | _Variadic_union& operator=(const _Variadic_union&) = default; |
| 437 | _Variadic_union& operator=(_Variadic_union&&) = default; |
| 438 | |
| 439 | // If any alternative type is not trivially destructible then we need a |
| 440 | // user-provided destructor that does nothing. The active alternative |
| 441 | // will be destroyed by _Variant_storage::_M_reset() instead of here. |
| 442 | _GLIBCXX20_CONSTEXPR ~_Variadic_union() |
| 443 | { } |
| 444 | |
| 445 | _Uninitialized<_First> _M_first; |
| 446 | _Variadic_union<(is_trivially_destructible_v<_Rest> && ...), _Rest...> _M_rest; |
| 447 | }; |
| 448 | |
| 449 | // _Never_valueless_alt is true for variant alternatives that can |
| 450 | // always be placed in a variant without it becoming valueless. |
| 451 | |
| 452 | // For suitably-small, trivially copyable types we can create temporaries |
| 453 | // on the stack and then memcpy them into place. |
| 454 | template<typename _Tp> |
| 455 | struct _Never_valueless_alt |
| 456 | : __and_<bool_constant<sizeof(_Tp) <= 256>, is_trivially_copyable<_Tp>> |
| 457 | { }; |
| 458 | |
| 459 | // Specialize _Never_valueless_alt for other types which have a |
| 460 | // non-throwing and cheap move construction and move assignment operator, |
| 461 | // so that emplacing the type will provide the strong exception-safety |
| 462 | // guarantee, by creating and moving a temporary. |
| 463 | // Whether _Never_valueless_alt<T> is true or not affects the ABI of a |
| 464 | // variant using that alternative, so we can't change the value later! |
| 465 | |
| 466 | // True if every alternative in _Types... can be emplaced in a variant |
| 467 | // without it becoming valueless. If this is true, variant<_Types...> |
| 468 | // can never be valueless, which enables some minor optimizations. |
| 469 | template <typename... _Types> |
| 470 | constexpr bool __never_valueless() |
| 471 | { |
| 472 | return _Traits<_Types...>::_S_move_assign |
| 473 | && (_Never_valueless_alt<_Types>::value && ...); |
| 474 | } |
| 475 | |
| 476 | // Defines index and the dtor, possibly trivial. |
| 477 | template<bool __trivially_destructible, typename... _Types> |
| 478 | struct _Variant_storage; |
| 479 | |
| 480 | template <typename... _Types> |
| 481 | using __select_index = |
| 482 | typename __select_int::_Select_int_base<sizeof...(_Types), |
| 483 | unsigned char, |
| 484 | unsigned short>::type::value_type; |
| 485 | |
| 486 | template<typename... _Types> |
| 487 | struct _Variant_storage<false, _Types...> |
| 488 | { |
| 489 | constexpr |
| 490 | _Variant_storage() |
| 491 | : _M_index(static_cast<__index_type>(variant_npos)) |
| 492 | { } |
| 493 | |
| 494 | template<size_t _Np, typename... _Args> |
| 495 | constexpr |
| 496 | _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) |
| 497 | : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), |
| 498 | _M_index{_Np} |
| 499 | { } |
| 500 | |
| 501 | constexpr void |
| 502 | _M_reset() |
| 503 | { |
| 504 | if (!_M_valid()) [[__unlikely__]] |
| 505 | return; |
| 506 | |
| 507 | std::__do_visit<void>([](auto&& __this_mem) mutable |
| 508 | { |
| 509 | std::_Destroy(std::__addressof(__this_mem)); |
| 510 | }, __variant_cast<_Types...>(*this)); |
| 511 | |
| 512 | _M_index = static_cast<__index_type>(variant_npos); |
| 513 | } |
| 514 | |
| 515 | _GLIBCXX20_CONSTEXPR |
| 516 | ~_Variant_storage() |
| 517 | { _M_reset(); } |
| 518 | |
| 519 | constexpr bool |
| 520 | _M_valid() const noexcept |
| 521 | { |
| 522 | if constexpr (__variant::__never_valueless<_Types...>()) |
| 523 | return true; |
| 524 | return this->_M_index != __index_type(variant_npos); |
| 525 | } |
| 526 | |
| 527 | _Variadic_union<false, _Types...> _M_u; |
| 528 | using __index_type = __select_index<_Types...>; |
| 529 | __index_type _M_index; |
| 530 | }; |
| 531 | |
| 532 | template<typename... _Types> |
| 533 | struct _Variant_storage<true, _Types...> |
| 534 | { |
| 535 | constexpr |
| 536 | _Variant_storage() |
| 537 | : _M_index(static_cast<__index_type>(variant_npos)) |
| 538 | { } |
| 539 | |
| 540 | template<size_t _Np, typename... _Args> |
| 541 | constexpr |
| 542 | _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) |
| 543 | : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), |
| 544 | _M_index{_Np} |
| 545 | { } |
| 546 | |
| 547 | constexpr void |
| 548 | _M_reset() noexcept |
| 549 | { _M_index = static_cast<__index_type>(variant_npos); } |
| 550 | |
| 551 | constexpr bool |
| 552 | _M_valid() const noexcept |
| 553 | { |
| 554 | if constexpr (__variant::__never_valueless<_Types...>()) |
| 555 | return true; |
| 556 | // It would be nice if we could just return true for -fno-exceptions. |
| 557 | // It's possible (but inadvisable) that a std::variant could become |
| 558 | // valueless in a translation unit compiled with -fexceptions and then |
| 559 | // be passed to functions compiled with -fno-exceptions. We would need |
| 560 | // some #ifdef _GLIBCXX_NO_EXCEPTIONS_GLOBALLY property to elide all |
| 561 | // checks for valueless_by_exception(). |
| 562 | return this->_M_index != static_cast<__index_type>(variant_npos); |
| 563 | } |
| 564 | |
| 565 | _Variadic_union<true, _Types...> _M_u; |
| 566 | using __index_type = __select_index<_Types...>; |
| 567 | __index_type _M_index; |
| 568 | }; |
| 569 | |
| 570 | // Implementation of v.emplace<N>(args...). |
| 571 | template<size_t _Np, bool _Triv, typename... _Types, typename... _Args> |
| 572 | _GLIBCXX20_CONSTEXPR |
| 573 | inline void |
| 574 | __emplace(_Variant_storage<_Triv, _Types...>& __v, _Args&&... __args) |
| 575 | { |
| 576 | __v._M_reset(); |
| 577 | auto* __addr = __variant::__construct_n<_Np>(__v._M_u); |
| 578 | std::_Construct(__addr, in_place_index<0>, |
| 579 | std::forward<_Args>(__args)...); |
| 580 | // Construction didn't throw, so can set the new index now: |
| 581 | __v._M_index = _Np; |
| 582 | } |
| 583 | |
| 584 | template<typename... _Types> |
| 585 | using _Variant_storage_alias = |
| 586 | _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>; |
| 587 | |
| 588 | // The following are (Copy|Move) (ctor|assign) layers for forwarding |
| 589 | // triviality and handling non-trivial SMF behaviors. |
| 590 | |
| 591 | template<bool, typename... _Types> |
| 592 | struct _Copy_ctor_base : _Variant_storage_alias<_Types...> |
| 593 | { |
| 594 | using _Base = _Variant_storage_alias<_Types...>; |
| 595 | using _Base::_Base; |
| 596 | |
| 597 | _GLIBCXX20_CONSTEXPR |
| 598 | _Copy_ctor_base(const _Copy_ctor_base& __rhs) |
| 599 | noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor) |
| 600 | { |
| 601 | __variant::__raw_idx_visit( |
| 602 | [this](auto&& __rhs_mem, auto __rhs_index) mutable |
| 603 | { |
| 604 | constexpr size_t __j = __rhs_index; |
| 605 | if constexpr (__j != variant_npos) |
| 606 | std::_Construct(std::__addressof(this->_M_u), |
| 607 | in_place_index<__j>, __rhs_mem); |
| 608 | }, __variant_cast<_Types...>(__rhs)); |
| 609 | this->_M_index = __rhs._M_index; |
| 610 | } |
| 611 | |
| 612 | _Copy_ctor_base(_Copy_ctor_base&&) = default; |
| 613 | _Copy_ctor_base& operator=(const _Copy_ctor_base&) = default; |
| 614 | _Copy_ctor_base& operator=(_Copy_ctor_base&&) = default; |
| 615 | }; |
| 616 | |
| 617 | template<typename... _Types> |
| 618 | struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...> |
| 619 | { |
| 620 | using _Base = _Variant_storage_alias<_Types...>; |
| 621 | using _Base::_Base; |
| 622 | }; |
| 623 | |
| 624 | template<typename... _Types> |
| 625 | using _Copy_ctor_alias = |
| 626 | _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>; |
| 627 | |
| 628 | template<bool, typename... _Types> |
| 629 | struct _Move_ctor_base : _Copy_ctor_alias<_Types...> |
| 630 | { |
| 631 | using _Base = _Copy_ctor_alias<_Types...>; |
| 632 | using _Base::_Base; |
| 633 | |
| 634 | _GLIBCXX20_CONSTEXPR |
| 635 | _Move_ctor_base(_Move_ctor_base&& __rhs) |
| 636 | noexcept(_Traits<_Types...>::_S_nothrow_move_ctor) |
| 637 | { |
| 638 | __variant::__raw_idx_visit( |
| 639 | [this](auto&& __rhs_mem, auto __rhs_index) mutable |
| 640 | { |
| 641 | constexpr size_t __j = __rhs_index; |
| 642 | if constexpr (__j != variant_npos) |
| 643 | std::_Construct(std::__addressof(this->_M_u), |
| 644 | in_place_index<__j>, |
| 645 | std::forward<decltype(__rhs_mem)>(__rhs_mem)); |
| 646 | }, __variant_cast<_Types...>(std::move(__rhs))); |
| 647 | this->_M_index = __rhs._M_index; |
| 648 | } |
| 649 | |
| 650 | _Move_ctor_base(const _Move_ctor_base&) = default; |
| 651 | _Move_ctor_base& operator=(const _Move_ctor_base&) = default; |
| 652 | _Move_ctor_base& operator=(_Move_ctor_base&&) = default; |
| 653 | }; |
| 654 | |
| 655 | template<typename... _Types> |
| 656 | struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...> |
| 657 | { |
| 658 | using _Base = _Copy_ctor_alias<_Types...>; |
| 659 | using _Base::_Base; |
| 660 | }; |
| 661 | |
| 662 | template<typename... _Types> |
| 663 | using _Move_ctor_alias = |
| 664 | _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>; |
| 665 | |
| 666 | template<bool, typename... _Types> |
| 667 | struct _Copy_assign_base : _Move_ctor_alias<_Types...> |
| 668 | { |
| 669 | using _Base = _Move_ctor_alias<_Types...>; |
| 670 | using _Base::_Base; |
| 671 | |
| 672 | _GLIBCXX20_CONSTEXPR |
| 673 | _Copy_assign_base& |
| 674 | operator=(const _Copy_assign_base& __rhs) |
| 675 | noexcept(_Traits<_Types...>::_S_nothrow_copy_assign) |
| 676 | { |
| 677 | __variant::__raw_idx_visit( |
| 678 | [this](auto&& __rhs_mem, auto __rhs_index) mutable |
| 679 | { |
| 680 | constexpr size_t __j = __rhs_index; |
| 681 | if constexpr (__j == variant_npos) |
| 682 | this->_M_reset(); // Make *this valueless. |
| 683 | else if (this->_M_index == __j) |
| 684 | __variant::__get<__j>(*this) = __rhs_mem; |
| 685 | else |
| 686 | { |
| 687 | using _Tj = typename _Nth_type<__j, _Types...>::type; |
| 688 | if constexpr (is_nothrow_copy_constructible_v<_Tj> |
| 689 | || !is_nothrow_move_constructible_v<_Tj>) |
| 690 | __variant::__emplace<__j>(*this, __rhs_mem); |
| 691 | else |
| 692 | { |
| 693 | using _Variant = variant<_Types...>; |
| 694 | _Variant& __self = __variant_cast<_Types...>(*this); |
| 695 | __self = _Variant(in_place_index<__j>, __rhs_mem); |
| 696 | } |
| 697 | } |
| 698 | }, __variant_cast<_Types...>(__rhs)); |
| 699 | return *this; |
| 700 | } |
| 701 | |
| 702 | _Copy_assign_base(const _Copy_assign_base&) = default; |
| 703 | _Copy_assign_base(_Copy_assign_base&&) = default; |
| 704 | _Copy_assign_base& operator=(_Copy_assign_base&&) = default; |
| 705 | }; |
| 706 | |
| 707 | template<typename... _Types> |
| 708 | struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...> |
| 709 | { |
| 710 | using _Base = _Move_ctor_alias<_Types...>; |
| 711 | using _Base::_Base; |
| 712 | }; |
| 713 | |
| 714 | template<typename... _Types> |
| 715 | using _Copy_assign_alias = |
| 716 | _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, _Types...>; |
| 717 | |
| 718 | template<bool, typename... _Types> |
| 719 | struct _Move_assign_base : _Copy_assign_alias<_Types...> |
| 720 | { |
| 721 | using _Base = _Copy_assign_alias<_Types...>; |
| 722 | using _Base::_Base; |
| 723 | |
| 724 | _GLIBCXX20_CONSTEXPR |
| 725 | _Move_assign_base& |
| 726 | operator=(_Move_assign_base&& __rhs) |
| 727 | noexcept(_Traits<_Types...>::_S_nothrow_move_assign) |
| 728 | { |
| 729 | __variant::__raw_idx_visit( |
| 730 | [this](auto&& __rhs_mem, auto __rhs_index) mutable |
| 731 | { |
| 732 | constexpr size_t __j = __rhs_index; |
| 733 | if constexpr (__j != variant_npos) |
| 734 | { |
| 735 | if (this->_M_index == __j) |
| 736 | __variant::__get<__j>(*this) = std::move(__rhs_mem); |
| 737 | else |
| 738 | { |
| 739 | using _Tj = typename _Nth_type<__j, _Types...>::type; |
| 740 | if constexpr (is_nothrow_move_constructible_v<_Tj>) |
| 741 | __variant::__emplace<__j>(*this, std::move(__rhs_mem)); |
| 742 | else |
| 743 | { |
| 744 | using _Variant = variant<_Types...>; |
| 745 | _Variant& __self = __variant_cast<_Types...>(*this); |
| 746 | __self.template emplace<__j>(std::move(__rhs_mem)); |
| 747 | } |
| 748 | } |
| 749 | } |
| 750 | else |
| 751 | this->_M_reset(); |
| 752 | }, __variant_cast<_Types...>(__rhs)); |
| 753 | return *this; |
| 754 | } |
| 755 | |
| 756 | _Move_assign_base(const _Move_assign_base&) = default; |
| 757 | _Move_assign_base(_Move_assign_base&&) = default; |
| 758 | _Move_assign_base& operator=(const _Move_assign_base&) = default; |
| 759 | }; |
| 760 | |
| 761 | template<typename... _Types> |
| 762 | struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...> |
| 763 | { |
| 764 | using _Base = _Copy_assign_alias<_Types...>; |
| 765 | using _Base::_Base; |
| 766 | }; |
| 767 | |
| 768 | template<typename... _Types> |
| 769 | using _Move_assign_alias = |
| 770 | _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign, _Types...>; |
| 771 | |
| 772 | template<typename... _Types> |
| 773 | struct _Variant_base : _Move_assign_alias<_Types...> |
| 774 | { |
| 775 | using _Base = _Move_assign_alias<_Types...>; |
| 776 | |
| 777 | constexpr |
| 778 | _Variant_base() noexcept(_Traits<_Types...>::_S_nothrow_default_ctor) |
| 779 | : _Variant_base(in_place_index<0>) { } |
| 780 | |
| 781 | template<size_t _Np, typename... _Args> |
| 782 | constexpr explicit |
| 783 | _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args) |
| 784 | : _Base(__i, std::forward<_Args>(__args)...) |
| 785 | { } |
| 786 | |
| 787 | _Variant_base(const _Variant_base&) = default; |
| 788 | _Variant_base(_Variant_base&&) = default; |
| 789 | _Variant_base& operator=(const _Variant_base&) = default; |
| 790 | _Variant_base& operator=(_Variant_base&&) = default; |
| 791 | }; |
| 792 | |
| 793 | template<typename _Tp, typename... _Types> |
| 794 | inline constexpr bool __exactly_once |
| 795 | = std::__find_uniq_type_in_pack<_Tp, _Types...>() < sizeof...(_Types); |
| 796 | |
| 797 | // Helper used to check for valid conversions that don't involve narrowing. |
| 798 | template<typename _Ti> struct _Arr { _Ti _M_x[1]; }; |
| 799 | |
| 800 | // "Build an imaginary function FUN(Ti) for each alternative type Ti" |
| 801 | template<size_t _Ind, typename _Tp, typename _Ti, typename = void> |
| 802 | struct _Build_FUN |
| 803 | { |
| 804 | // This function means 'using _Build_FUN<I, T, Ti>::_S_fun;' is valid, |
| 805 | // but only static functions will be considered in the call below. |
| 806 | void _S_fun() = delete; |
| 807 | }; |
| 808 | |
| 809 | // "... for which Ti x[] = {std::forward<T>(t)}; is well-formed." |
| 810 | template<size_t _Ind, typename _Tp, typename _Ti> |
| 811 | struct _Build_FUN<_Ind, _Tp, _Ti, |
| 812 | void_t<decltype(_Arr<_Ti>{{std::declval<_Tp>()}})>> |
| 813 | { |
| 814 | // This is the FUN function for type _Ti, with index _Ind |
| 815 | static integral_constant<size_t, _Ind> _S_fun(_Ti); |
| 816 | }; |
| 817 | |
| 818 | template<typename _Tp, typename _Variant, |
| 819 | typename = make_index_sequence<variant_size_v<_Variant>>> |
| 820 | struct _Build_FUNs; |
| 821 | |
| 822 | template<typename _Tp, typename... _Ti, size_t... _Ind> |
| 823 | struct _Build_FUNs<_Tp, variant<_Ti...>, index_sequence<_Ind...>> |
| 824 | : _Build_FUN<_Ind, _Tp, _Ti>... |
| 825 | { |
| 826 | using _Build_FUN<_Ind, _Tp, _Ti>::_S_fun...; |
| 827 | }; |
| 828 | |
| 829 | // The index j of the overload FUN(Tj) selected by overload resolution |
| 830 | // for FUN(std::forward<_Tp>(t)) |
| 831 | template<typename _Tp, typename _Variant> |
| 832 | using _FUN_type |
| 833 | = decltype(_Build_FUNs<_Tp, _Variant>::_S_fun(std::declval<_Tp>())); |
| 834 | |
| 835 | // The index selected for FUN(std::forward<T>(t)), or variant_npos if none. |
| 836 | template<typename _Tp, typename _Variant, typename = void> |
| 837 | inline constexpr size_t |
| 838 | __accepted_index = variant_npos; |
| 839 | |
| 840 | template<typename _Tp, typename _Variant> |
| 841 | inline constexpr size_t |
| 842 | __accepted_index<_Tp, _Variant, void_t<_FUN_type<_Tp, _Variant>>> |
| 843 | = _FUN_type<_Tp, _Variant>::value; |
| 844 | |
| 845 | template<typename _Maybe_variant_cookie, typename _Variant, |
| 846 | typename = __remove_cvref_t<_Variant>> |
| 847 | inline constexpr bool |
| 848 | __extra_visit_slot_needed = false; |
| 849 | |
| 850 | template<typename _Var, typename... _Types> |
| 851 | inline constexpr bool |
| 852 | __extra_visit_slot_needed<__variant_cookie, _Var, variant<_Types...>> |
| 853 | = !__variant::__never_valueless<_Types...>(); |
| 854 | |
| 855 | template<typename _Var, typename... _Types> |
| 856 | inline constexpr bool |
| 857 | __extra_visit_slot_needed<__variant_idx_cookie, _Var, variant<_Types...>> |
| 858 | = !__variant::__never_valueless<_Types...>(); |
| 859 | |
| 860 | // Used for storing a multi-dimensional vtable. |
| 861 | template<typename _Tp, size_t... _Dimensions> |
| 862 | struct _Multi_array; |
| 863 | |
| 864 | // Partial specialization with rank zero, stores a single _Tp element. |
| 865 | template<typename _Tp> |
| 866 | struct _Multi_array<_Tp> |
| 867 | { |
| 868 | template<typename> |
| 869 | struct __untag_result |
| 870 | : false_type |
| 871 | { using element_type = _Tp; }; |
| 872 | |
| 873 | #pragma GCC diagnostic push |
| 874 | #pragma GCC diagnostic ignored "-Wignored-qualifiers" |
| 875 | template <typename... _Args> |
| 876 | struct __untag_result<const void(*)(_Args...)> |
| 877 | : false_type |
| 878 | { using element_type = void(*)(_Args...); }; |
| 879 | #pragma GCC diagnostic pop |
| 880 | |
| 881 | template <typename... _Args> |
| 882 | struct __untag_result<__variant_cookie(*)(_Args...)> |
| 883 | : false_type |
| 884 | { using element_type = void(*)(_Args...); }; |
| 885 | |
| 886 | template <typename... _Args> |
| 887 | struct __untag_result<__variant_idx_cookie(*)(_Args...)> |
| 888 | : false_type |
| 889 | { using element_type = void(*)(_Args...); }; |
| 890 | |
| 891 | template <typename _Res, typename... _Args> |
| 892 | struct __untag_result<__deduce_visit_result<_Res>(*)(_Args...)> |
| 893 | : true_type |
| 894 | { using element_type = _Res(*)(_Args...); }; |
| 895 | |
| 896 | using __result_is_deduced = __untag_result<_Tp>; |
| 897 | |
| 898 | constexpr const typename __untag_result<_Tp>::element_type& |
| 899 | _M_access() const |
| 900 | { return _M_data; } |
| 901 | |
| 902 | typename __untag_result<_Tp>::element_type _M_data; |
| 903 | }; |
| 904 | |
| 905 | // Partial specialization with rank >= 1. |
| 906 | template<typename _Ret, |
| 907 | typename _Visitor, |
| 908 | typename... _Variants, |
| 909 | size_t __first, size_t... __rest> |
| 910 | struct _Multi_array<_Ret(*)(_Visitor, _Variants...), __first, __rest...> |
| 911 | { |
| 912 | static constexpr size_t __index = |
| 913 | sizeof...(_Variants) - sizeof...(__rest) - 1; |
| 914 | |
| 915 | using _Variant = typename _Nth_type<__index, _Variants...>::type; |
| 916 | |
| 917 | static constexpr int __do_cookie = |
| 918 | __extra_visit_slot_needed<_Ret, _Variant> ? 1 : 0; |
| 919 | |
| 920 | using _Tp = _Ret(*)(_Visitor, _Variants...); |
| 921 | |
| 922 | template<typename... _Args> |
| 923 | constexpr decltype(auto) |
| 924 | _M_access(size_t __first_index, _Args... __rest_indices) const |
| 925 | { |
| 926 | return _M_arr[__first_index + __do_cookie] |
| 927 | ._M_access(__rest_indices...); |
| 928 | } |
| 929 | |
| 930 | _Multi_array<_Tp, __rest...> _M_arr[__first + __do_cookie]; |
| 931 | }; |
| 932 | |
| 933 | // Creates a multi-dimensional vtable recursively. |
| 934 | // |
| 935 | // For example, |
| 936 | // visit([](auto, auto){}, |
| 937 | // variant<int, char>(), // typedef'ed as V1 |
| 938 | // variant<float, double, long double>()) // typedef'ed as V2 |
| 939 | // will trigger instantiations of: |
| 940 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>, |
| 941 | // tuple<V1&&, V2&&>, std::index_sequence<>> |
| 942 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>, |
| 943 | // tuple<V1&&, V2&&>, std::index_sequence<0>> |
| 944 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, |
| 945 | // tuple<V1&&, V2&&>, std::index_sequence<0, 0>> |
| 946 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, |
| 947 | // tuple<V1&&, V2&&>, std::index_sequence<0, 1>> |
| 948 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, |
| 949 | // tuple<V1&&, V2&&>, std::index_sequence<0, 2>> |
| 950 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>, |
| 951 | // tuple<V1&&, V2&&>, std::index_sequence<1>> |
| 952 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, |
| 953 | // tuple<V1&&, V2&&>, std::index_sequence<1, 0>> |
| 954 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, |
| 955 | // tuple<V1&&, V2&&>, std::index_sequence<1, 1>> |
| 956 | // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, |
| 957 | // tuple<V1&&, V2&&>, std::index_sequence<1, 2>> |
| 958 | // The returned multi-dimensional vtable can be fast accessed by the visitor |
| 959 | // using index calculation. |
| 960 | template<typename _Array_type, typename _Index_seq> |
| 961 | struct __gen_vtable_impl; |
| 962 | |
| 963 | // Defines the _S_apply() member that returns a _Multi_array populated |
| 964 | // with function pointers that perform the visitation expressions e(m) |
| 965 | // for each valid pack of indexes into the variant types _Variants. |
| 966 | // |
| 967 | // This partial specialization builds up the index sequences by recursively |
| 968 | // calling _S_apply() on the next specialization of __gen_vtable_impl. |
| 969 | // The base case of the recursion defines the actual function pointers. |
| 970 | template<typename _Result_type, typename _Visitor, size_t... __dimensions, |
| 971 | typename... _Variants, size_t... __indices> |
| 972 | struct __gen_vtable_impl< |
| 973 | _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>, |
| 974 | std::index_sequence<__indices...>> |
| 975 | { |
| 976 | using _Next = |
| 977 | remove_reference_t<typename _Nth_type<sizeof...(__indices), |
| 978 | _Variants...>::type>; |
| 979 | using _Array_type = |
| 980 | _Multi_array<_Result_type (*)(_Visitor, _Variants...), |
| 981 | __dimensions...>; |
| 982 | |
| 983 | static constexpr _Array_type |
| 984 | _S_apply() |
| 985 | { |
| 986 | _Array_type __vtable{}; |
| 987 | _S_apply_all_alts( |
| 988 | __vtable, make_index_sequence<variant_size_v<_Next>>()); |
| 989 | return __vtable; |
| 990 | } |
| 991 | |
| 992 | template<size_t... __var_indices> |
| 993 | static constexpr void |
| 994 | _S_apply_all_alts(_Array_type& __vtable, |
| 995 | std::index_sequence<__var_indices...>) |
| 996 | { |
| 997 | if constexpr (__extra_visit_slot_needed<_Result_type, _Next>) |
| 998 | (_S_apply_single_alt<true, __var_indices>( |
| 999 | __vtable._M_arr[__var_indices + 1], |
| 1000 | &(__vtable._M_arr[0])), ...); |
| 1001 | else |
| 1002 | (_S_apply_single_alt<false, __var_indices>( |
| 1003 | __vtable._M_arr[__var_indices]), ...); |
| 1004 | } |
| 1005 | |
| 1006 | template<bool __do_cookie, size_t __index, typename _Tp> |
| 1007 | static constexpr void |
| 1008 | _S_apply_single_alt(_Tp& __element, _Tp* __cookie_element = nullptr) |
| 1009 | { |
| 1010 | if constexpr (__do_cookie) |
| 1011 | { |
| 1012 | __element = __gen_vtable_impl< |
| 1013 | _Tp, |
| 1014 | std::index_sequence<__indices..., __index>>::_S_apply(); |
| 1015 | *__cookie_element = __gen_vtable_impl< |
| 1016 | _Tp, |
| 1017 | std::index_sequence<__indices..., variant_npos>>::_S_apply(); |
| 1018 | } |
| 1019 | else |
| 1020 | { |
| 1021 | auto __tmp_element = __gen_vtable_impl< |
| 1022 | remove_reference_t<decltype(__element)>, |
| 1023 | std::index_sequence<__indices..., __index>>::_S_apply(); |
| 1024 | static_assert(is_same_v<_Tp, decltype(__tmp_element)>, |
| 1025 | "std::visit requires the visitor to have the same " |
| 1026 | "return type for all alternatives of a variant"); |
| 1027 | __element = __tmp_element; |
| 1028 | } |
| 1029 | } |
| 1030 | }; |
| 1031 | |
| 1032 | // This partial specialization is the base case for the recursion. |
| 1033 | // It populates a _Multi_array element with the address of a function |
| 1034 | // that invokes the visitor with the alternatives specified by __indices. |
| 1035 | template<typename _Result_type, typename _Visitor, typename... _Variants, |
| 1036 | size_t... __indices> |
| 1037 | struct __gen_vtable_impl< |
| 1038 | _Multi_array<_Result_type (*)(_Visitor, _Variants...)>, |
| 1039 | std::index_sequence<__indices...>> |
| 1040 | { |
| 1041 | using _Array_type = |
| 1042 | _Multi_array<_Result_type (*)(_Visitor, _Variants...)>; |
| 1043 | |
| 1044 | template<size_t __index, typename _Variant> |
| 1045 | static constexpr decltype(auto) |
| 1046 | __element_by_index_or_cookie(_Variant&& __var) noexcept |
| 1047 | { |
| 1048 | if constexpr (__index != variant_npos) |
| 1049 | return __variant::__get<__index>(std::forward<_Variant>(__var)); |
| 1050 | else |
| 1051 | return __variant_cookie{}; |
| 1052 | } |
| 1053 | |
| 1054 | static constexpr decltype(auto) |
| 1055 | __visit_invoke(_Visitor&& __visitor, _Variants... __vars) |
| 1056 | { |
| 1057 | if constexpr (is_same_v<_Result_type, __variant_idx_cookie>) |
| 1058 | // For raw visitation using indices, pass the indices to the visitor |
| 1059 | // and discard the return value: |
| 1060 | std::__invoke(std::forward<_Visitor>(__visitor), |
| 1061 | __element_by_index_or_cookie<__indices>( |
| 1062 | std::forward<_Variants>(__vars))..., |
| 1063 | integral_constant<size_t, __indices>()...); |
| 1064 | else if constexpr (is_same_v<_Result_type, __variant_cookie>) |
| 1065 | // For raw visitation without indices, and discard the return value: |
| 1066 | std::__invoke(std::forward<_Visitor>(__visitor), |
| 1067 | __element_by_index_or_cookie<__indices>( |
| 1068 | std::forward<_Variants>(__vars))...); |
| 1069 | else if constexpr (_Array_type::__result_is_deduced::value) |
| 1070 | // For the usual std::visit case deduce the return value: |
| 1071 | return std::__invoke(std::forward<_Visitor>(__visitor), |
| 1072 | __element_by_index_or_cookie<__indices>( |
| 1073 | std::forward<_Variants>(__vars))...); |
| 1074 | else // for std::visit<R> use INVOKE<R> |
| 1075 | return std::__invoke_r<_Result_type>( |
| 1076 | std::forward<_Visitor>(__visitor), |
| 1077 | __variant::__get<__indices>(std::forward<_Variants>(__vars))...); |
| 1078 | } |
| 1079 | |
| 1080 | static constexpr auto |
| 1081 | _S_apply() |
| 1082 | { |
| 1083 | if constexpr (_Array_type::__result_is_deduced::value) |
| 1084 | { |
| 1085 | constexpr bool __visit_ret_type_mismatch = |
| 1086 | !is_same_v<typename _Result_type::type, |
| 1087 | decltype(__visit_invoke(visitor: std::declval<_Visitor>(), |
| 1088 | vars: std::declval<_Variants>()...))>; |
| 1089 | if constexpr (__visit_ret_type_mismatch) |
| 1090 | { |
| 1091 | struct __cannot_match {}; |
| 1092 | return __cannot_match{}; |
| 1093 | } |
| 1094 | else |
| 1095 | return _Array_type{&__visit_invoke}; |
| 1096 | } |
| 1097 | else |
| 1098 | return _Array_type{&__visit_invoke}; |
| 1099 | } |
| 1100 | }; |
| 1101 | |
| 1102 | template<typename _Result_type, typename _Visitor, typename... _Variants> |
| 1103 | struct __gen_vtable |
| 1104 | { |
| 1105 | using _Array_type = |
| 1106 | _Multi_array<_Result_type (*)(_Visitor, _Variants...), |
| 1107 | variant_size_v<remove_reference_t<_Variants>>...>; |
| 1108 | |
| 1109 | static constexpr _Array_type _S_vtable |
| 1110 | = __gen_vtable_impl<_Array_type, std::index_sequence<>>::_S_apply(); |
| 1111 | }; |
| 1112 | |
| 1113 | #if ! _GLIBCXX_INLINE_VERSION |
| 1114 | template<size_t _Nm, typename _Tp> |
| 1115 | struct _Base_dedup : public _Tp { }; |
| 1116 | |
| 1117 | template<typename _Variant, typename __indices> |
| 1118 | struct _Variant_hash_base; |
| 1119 | |
| 1120 | template<typename... _Types, size_t... __indices> |
| 1121 | struct _Variant_hash_base<variant<_Types...>, |
| 1122 | std::index_sequence<__indices...>> |
| 1123 | : _Base_dedup<__indices, __hash_empty_base<remove_const_t<_Types>>>... |
| 1124 | { }; |
| 1125 | #endif |
| 1126 | |
| 1127 | // Equivalent to decltype(get<_Np>(as-variant(declval<_Variant>()))) |
| 1128 | template<size_t _Np, typename _Variant, |
| 1129 | typename _AsV = decltype(__variant::__as(std::declval<_Variant>())), |
| 1130 | typename _Tp = variant_alternative_t<_Np, remove_reference_t<_AsV>>> |
| 1131 | using __get_t |
| 1132 | = __conditional_t<is_lvalue_reference_v<_Variant>, _Tp&, _Tp&&>; |
| 1133 | |
| 1134 | // Return type of std::visit. |
| 1135 | template<typename _Visitor, typename... _Variants> |
| 1136 | using __visit_result_t |
| 1137 | = invoke_result_t<_Visitor, __get_t<0, _Variants>...>; |
| 1138 | |
| 1139 | template<typename _Tp, typename... _Types> |
| 1140 | constexpr inline bool __same_types = (is_same_v<_Tp, _Types> && ...); |
| 1141 | |
| 1142 | template <typename _Visitor, typename _Variant, size_t... _Idxs> |
| 1143 | constexpr bool __check_visitor_results(std::index_sequence<_Idxs...>) |
| 1144 | { |
| 1145 | return __same_types< |
| 1146 | invoke_result_t<_Visitor, __get_t<_Idxs, _Variant>>... |
| 1147 | >; |
| 1148 | } |
| 1149 | |
| 1150 | } // namespace __variant |
| 1151 | } // namespace __detail |
| 1152 | |
| 1153 | template<typename _Tp, typename... _Types> |
| 1154 | constexpr bool |
| 1155 | holds_alternative(const variant<_Types...>& __v) noexcept |
| 1156 | { |
| 1157 | static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, |
| 1158 | "T must occur exactly once in alternatives"); |
| 1159 | return __v.index() == std::__find_uniq_type_in_pack<_Tp, _Types...>(); |
| 1160 | } |
| 1161 | |
| 1162 | template<typename _Tp, typename... _Types> |
| 1163 | constexpr _Tp& |
| 1164 | get(variant<_Types...>& __v) |
| 1165 | { |
| 1166 | static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, |
| 1167 | "T must occur exactly once in alternatives"); |
| 1168 | constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); |
| 1169 | return std::get<__n>(__v); |
| 1170 | } |
| 1171 | |
| 1172 | template<typename _Tp, typename... _Types> |
| 1173 | constexpr _Tp&& |
| 1174 | get(variant<_Types...>&& __v) |
| 1175 | { |
| 1176 | static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, |
| 1177 | "T must occur exactly once in alternatives"); |
| 1178 | constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); |
| 1179 | return std::get<__n>(std::move(__v)); |
| 1180 | } |
| 1181 | |
| 1182 | template<typename _Tp, typename... _Types> |
| 1183 | constexpr const _Tp& |
| 1184 | get(const variant<_Types...>& __v) |
| 1185 | { |
| 1186 | static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, |
| 1187 | "T must occur exactly once in alternatives"); |
| 1188 | constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); |
| 1189 | return std::get<__n>(__v); |
| 1190 | } |
| 1191 | |
| 1192 | template<typename _Tp, typename... _Types> |
| 1193 | constexpr const _Tp&& |
| 1194 | get(const variant<_Types...>&& __v) |
| 1195 | { |
| 1196 | static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, |
| 1197 | "T must occur exactly once in alternatives"); |
| 1198 | constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); |
| 1199 | return std::get<__n>(std::move(__v)); |
| 1200 | } |
| 1201 | |
| 1202 | template<size_t _Np, typename... _Types> |
| 1203 | constexpr add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>> |
| 1204 | get_if(variant<_Types...>* __ptr) noexcept |
| 1205 | { |
| 1206 | using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; |
| 1207 | static_assert(_Np < sizeof...(_Types), |
| 1208 | "The index must be in [0, number of alternatives)"); |
| 1209 | static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void"); |
| 1210 | if (__ptr && __ptr->index() == _Np) |
| 1211 | return std::addressof(__detail::__variant::__get<_Np>(*__ptr)); |
| 1212 | return nullptr; |
| 1213 | } |
| 1214 | |
| 1215 | template<size_t _Np, typename... _Types> |
| 1216 | constexpr |
| 1217 | add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>> |
| 1218 | get_if(const variant<_Types...>* __ptr) noexcept |
| 1219 | { |
| 1220 | using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; |
| 1221 | static_assert(_Np < sizeof...(_Types), |
| 1222 | "The index must be in [0, number of alternatives)"); |
| 1223 | static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void"); |
| 1224 | if (__ptr && __ptr->index() == _Np) |
| 1225 | return std::addressof(__detail::__variant::__get<_Np>(*__ptr)); |
| 1226 | return nullptr; |
| 1227 | } |
| 1228 | |
| 1229 | template<typename _Tp, typename... _Types> |
| 1230 | constexpr add_pointer_t<_Tp> |
| 1231 | get_if(variant<_Types...>* __ptr) noexcept |
| 1232 | { |
| 1233 | static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, |
| 1234 | "T must occur exactly once in alternatives"); |
| 1235 | static_assert(!is_void_v<_Tp>, "_Tp must not be void"); |
| 1236 | constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); |
| 1237 | return std::get_if<__n>(__ptr); |
| 1238 | } |
| 1239 | |
| 1240 | template<typename _Tp, typename... _Types> |
| 1241 | constexpr add_pointer_t<const _Tp> |
| 1242 | get_if(const variant<_Types...>* __ptr) noexcept |
| 1243 | { |
| 1244 | static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, |
| 1245 | "T must occur exactly once in alternatives"); |
| 1246 | static_assert(!is_void_v<_Tp>, "_Tp must not be void"); |
| 1247 | constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); |
| 1248 | return std::get_if<__n>(__ptr); |
| 1249 | } |
| 1250 | |
| 1251 | namespace __detail::__variant |
| 1252 | { |
| 1253 | template<typename _Ret, typename _Vp, typename _Op> |
| 1254 | constexpr _Ret |
| 1255 | __compare(_Ret __ret, const _Vp& __lhs, const _Vp& __rhs, _Op __op) |
| 1256 | { |
| 1257 | __variant::__raw_idx_visit( |
| 1258 | [&__ret, &__lhs, __op] (auto&& __rhs_mem, auto __rhs_index) mutable |
| 1259 | { |
| 1260 | if constexpr (__rhs_index != variant_npos) |
| 1261 | { |
| 1262 | if (__lhs.index() == __rhs_index.value) |
| 1263 | { |
| 1264 | auto& __this_mem = std::get<__rhs_index>(__lhs); |
| 1265 | __ret = __op(__this_mem, __rhs_mem); |
| 1266 | return; |
| 1267 | } |
| 1268 | } |
| 1269 | __ret = __op(__lhs.index() + 1, __rhs_index + 1); |
| 1270 | }, __rhs); |
| 1271 | return __ret; |
| 1272 | } |
| 1273 | } // namespace __detail::__variant |
| 1274 | |
| 1275 | template<typename... _Types> |
| 1276 | #if __cpp_lib_concepts |
| 1277 | requires ((requires (const _Types& __t) { |
| 1278 | { __t == __t } -> convertible_to<bool>; }) && ...) |
| 1279 | #endif |
| 1280 | constexpr bool |
| 1281 | operator== [[nodiscard]] (const variant<_Types...>& __lhs, |
| 1282 | const variant<_Types...>& __rhs) |
| 1283 | { |
| 1284 | namespace __variant = __detail::__variant; |
| 1285 | return __variant::__compare(true, __lhs, __rhs, |
| 1286 | [](auto&& __l, auto&& __r) -> bool { |
| 1287 | return __l == __r; |
| 1288 | }); |
| 1289 | } |
| 1290 | |
| 1291 | template<typename... _Types> |
| 1292 | #if __cpp_lib_concepts |
| 1293 | requires ((requires (const _Types& __t) { |
| 1294 | { __t != __t } -> convertible_to<bool>; }) && ...) |
| 1295 | #endif |
| 1296 | constexpr bool |
| 1297 | operator!= [[nodiscard]] (const variant<_Types...>& __lhs, |
| 1298 | const variant<_Types...>& __rhs) |
| 1299 | { |
| 1300 | namespace __variant = __detail::__variant; |
| 1301 | return __variant::__compare(true, __lhs, __rhs, |
| 1302 | [](auto&& __l, auto&& __r) -> bool { |
| 1303 | return __l != __r; |
| 1304 | }); |
| 1305 | } |
| 1306 | |
| 1307 | template<typename... _Types> |
| 1308 | #if __cpp_lib_concepts |
| 1309 | requires ((requires (const _Types& __t) { |
| 1310 | { __t < __t } -> convertible_to<bool>; }) && ...) |
| 1311 | #endif |
| 1312 | constexpr bool |
| 1313 | operator< [[nodiscard]] (const variant<_Types...>& __lhs, |
| 1314 | const variant<_Types...>& __rhs) |
| 1315 | { |
| 1316 | namespace __variant = __detail::__variant; |
| 1317 | return __variant::__compare(true, __lhs, __rhs, |
| 1318 | [](auto&& __l, auto&& __r) -> bool { |
| 1319 | return __l < __r; |
| 1320 | }); |
| 1321 | } |
| 1322 | |
| 1323 | template<typename... _Types> |
| 1324 | #if __cpp_lib_concepts |
| 1325 | requires ((requires (const _Types& __t) { |
| 1326 | { __t <= __t } -> convertible_to<bool>; }) && ...) |
| 1327 | #endif |
| 1328 | constexpr bool |
| 1329 | operator<= [[nodiscard]] (const variant<_Types...>& __lhs, |
| 1330 | const variant<_Types...>& __rhs) |
| 1331 | { |
| 1332 | namespace __variant = __detail::__variant; |
| 1333 | return __variant::__compare(true, __lhs, __rhs, |
| 1334 | [](auto&& __l, auto&& __r) -> bool { |
| 1335 | return __l <= __r; |
| 1336 | }); |
| 1337 | } |
| 1338 | |
| 1339 | template<typename... _Types> |
| 1340 | #if __cpp_lib_concepts |
| 1341 | requires ((requires (const _Types& __t) { |
| 1342 | { __t > __t } -> convertible_to<bool>; }) && ...) |
| 1343 | #endif |
| 1344 | constexpr bool |
| 1345 | operator> [[nodiscard]] (const variant<_Types...>& __lhs, |
| 1346 | const variant<_Types...>& __rhs) |
| 1347 | { |
| 1348 | namespace __variant = __detail::__variant; |
| 1349 | return __variant::__compare(true, __lhs, __rhs, |
| 1350 | [](auto&& __l, auto&& __r) -> bool { |
| 1351 | return __l > __r; |
| 1352 | }); |
| 1353 | } |
| 1354 | |
| 1355 | template<typename... _Types> |
| 1356 | #if __cpp_lib_concepts |
| 1357 | requires ((requires (const _Types& __t) { |
| 1358 | { __t >= __t } -> convertible_to<bool>; }) && ...) |
| 1359 | #endif |
| 1360 | constexpr bool |
| 1361 | operator>= [[nodiscard]] (const variant<_Types...>& __lhs, |
| 1362 | const variant<_Types...>& __rhs) |
| 1363 | { |
| 1364 | namespace __variant = __detail::__variant; |
| 1365 | return __variant::__compare(true, __lhs, __rhs, |
| 1366 | [](auto&& __l, auto&& __r) -> bool { |
| 1367 | return __l >= __r; |
| 1368 | }); |
| 1369 | } |
| 1370 | |
| 1371 | #ifdef __cpp_lib_three_way_comparison |
| 1372 | template<typename... _Types> |
| 1373 | requires (three_way_comparable<_Types> && ...) |
| 1374 | constexpr |
| 1375 | common_comparison_category_t<compare_three_way_result_t<_Types>...> |
| 1376 | operator<=>(const variant<_Types...>& __v, const variant<_Types...>& __w) |
| 1377 | { |
| 1378 | common_comparison_category_t<compare_three_way_result_t<_Types>...> __ret |
| 1379 | = strong_ordering::equal; |
| 1380 | namespace __variant = __detail::__variant; |
| 1381 | return __variant::__compare(__ret, __v, __w, |
| 1382 | [](auto&& __l, auto&& __r) { |
| 1383 | return __l <=> __r; |
| 1384 | }); |
| 1385 | } |
| 1386 | #endif |
| 1387 | |
| 1388 | template<typename _Visitor, typename... _Variants> |
| 1389 | constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...> |
| 1390 | visit(_Visitor&&, _Variants&&...); |
| 1391 | |
| 1392 | #if __cplusplus > 201703L |
| 1393 | template<typename _Res, typename _Visitor, typename... _Variants> |
| 1394 | constexpr _Res |
| 1395 | visit(_Visitor&&, _Variants&&...); |
| 1396 | #endif |
| 1397 | |
| 1398 | template<typename... _Types> |
| 1399 | _GLIBCXX20_CONSTEXPR |
| 1400 | inline enable_if_t<(is_move_constructible_v<_Types> && ...) |
| 1401 | && (is_swappable_v<_Types> && ...)> |
| 1402 | swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs) |
| 1403 | noexcept(noexcept(__lhs.swap(__rhs))) |
| 1404 | { __lhs.swap(__rhs); } |
| 1405 | |
| 1406 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
| 1407 | // 2766. Swapping non-swappable types |
| 1408 | template<typename... _Types> |
| 1409 | enable_if_t<!((is_move_constructible_v<_Types> && ...) |
| 1410 | && (is_swappable_v<_Types> && ...))> |
| 1411 | swap(variant<_Types...>&, variant<_Types...>&) = delete; |
| 1412 | |
| 1413 | #if __cpp_lib_constexpr_exceptions >= 202502L |
| 1414 | #define _GLIBCXX_CONSTEXPR_BAD_VARIANT_ACCESS constexpr |
| 1415 | #else |
| 1416 | #define _GLIBCXX_CONSTEXPR_BAD_VARIANT_ACCESS |
| 1417 | #endif |
| 1418 | [[noreturn]] _GLIBCXX_CONSTEXPR_BAD_VARIANT_ACCESS void |
| 1419 | __throw_bad_variant_access(unsigned); |
| 1420 | |
| 1421 | class bad_variant_access : public exception |
| 1422 | { |
| 1423 | public: |
| 1424 | _GLIBCXX_CONSTEXPR_BAD_VARIANT_ACCESS bad_variant_access() noexcept { } |
| 1425 | |
| 1426 | _GLIBCXX_CONSTEXPR_BAD_VARIANT_ACCESS const char* what() |
| 1427 | const noexcept override |
| 1428 | { return _M_reason; } |
| 1429 | |
| 1430 | private: |
| 1431 | // Must only be called with a string literal |
| 1432 | _GLIBCXX_CONSTEXPR_BAD_VARIANT_ACCESS |
| 1433 | bad_variant_access(const char* __reason) noexcept : _M_reason(__reason) { } |
| 1434 | |
| 1435 | // Must point to a string with static storage duration: |
| 1436 | const char* _M_reason = "bad variant access"; |
| 1437 | |
| 1438 | friend _GLIBCXX_CONSTEXPR_BAD_VARIANT_ACCESS void |
| 1439 | __throw_bad_variant_access([[maybe_unused]] unsigned __n) |
| 1440 | { |
| 1441 | [[maybe_unused]] static constexpr const char* __reasons[] = { |
| 1442 | "std::get: wrong index for variant", |
| 1443 | "std::get: variant is valueless", |
| 1444 | "std::visit: variant is valueless", |
| 1445 | "std::visit<R>: variant is valueless", |
| 1446 | }; |
| 1447 | _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__reasons[__n % 4u])); |
| 1448 | } |
| 1449 | #undef _GLIBCXX_CONSTEXPR_BAD_VARIANT_ACCESS |
| 1450 | }; |
| 1451 | |
| 1452 | template<typename... _Types> |
| 1453 | class variant |
| 1454 | : private __detail::__variant::_Variant_base<_Types...>, |
| 1455 | private _Enable_copy_move< |
| 1456 | __detail::__variant::_Traits<_Types...>::_S_copy_ctor, |
| 1457 | __detail::__variant::_Traits<_Types...>::_S_copy_assign, |
| 1458 | __detail::__variant::_Traits<_Types...>::_S_move_ctor, |
| 1459 | __detail::__variant::_Traits<_Types...>::_S_move_assign, |
| 1460 | variant<_Types...>> |
| 1461 | { |
| 1462 | private: |
| 1463 | template <typename... _UTypes, typename _Tp> |
| 1464 | friend _GLIBCXX20_CONSTEXPR decltype(auto) |
| 1465 | __variant_cast(_Tp&&); |
| 1466 | |
| 1467 | static_assert(sizeof...(_Types) > 0, |
| 1468 | "variant must have at least one alternative"); |
| 1469 | static_assert(((std::is_object_v<_Types> && !is_array_v<_Types>) && ...), |
| 1470 | "variant alternatives must be non-array object types"); |
| 1471 | |
| 1472 | using _Base = __detail::__variant::_Variant_base<_Types...>; |
| 1473 | |
| 1474 | template<typename _Tp> |
| 1475 | static constexpr bool __not_self |
| 1476 | = !is_same_v<__remove_cvref_t<_Tp>, variant>; |
| 1477 | |
| 1478 | template<typename _Tp> |
| 1479 | static constexpr bool |
| 1480 | __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>; |
| 1481 | |
| 1482 | template<typename _Tp> |
| 1483 | static constexpr size_t __accepted_index |
| 1484 | = __detail::__variant::__accepted_index<_Tp, variant>; |
| 1485 | |
| 1486 | template<size_t _Np, typename = enable_if_t<(_Np < sizeof...(_Types))>> |
| 1487 | using __to_type = typename _Nth_type<_Np, _Types...>::type; |
| 1488 | |
| 1489 | template<typename _Tp, typename = enable_if_t<__not_self<_Tp>>> |
| 1490 | using __accepted_type = __to_type<__accepted_index<_Tp>>; |
| 1491 | |
| 1492 | template<typename _Tp> |
| 1493 | static constexpr size_t __index_of |
| 1494 | = std::__find_uniq_type_in_pack<_Tp, _Types...>(); |
| 1495 | |
| 1496 | using _Traits = __detail::__variant::_Traits<_Types...>; |
| 1497 | |
| 1498 | template<typename _Tp> |
| 1499 | static constexpr bool __not_in_place_tag |
| 1500 | = !__is_in_place_type_v<__remove_cvref_t<_Tp>> |
| 1501 | && !__is_in_place_index_v<__remove_cvref_t<_Tp>>; |
| 1502 | |
| 1503 | public: |
| 1504 | #if __cpp_concepts |
| 1505 | variant() requires is_default_constructible_v<__to_type<0>> = default; |
| 1506 | #else |
| 1507 | template<typename _Tp0 = __to_type<0>, |
| 1508 | typename = enable_if_t<is_default_constructible_v<_Tp0>>> |
| 1509 | constexpr |
| 1510 | variant() noexcept(is_nothrow_default_constructible_v<__to_type<0>>) |
| 1511 | { } |
| 1512 | #endif |
| 1513 | |
| 1514 | variant(const variant& __rhs) = default; |
| 1515 | variant(variant&&) = default; |
| 1516 | variant& operator=(const variant&) = default; |
| 1517 | variant& operator=(variant&&) = default; |
| 1518 | _GLIBCXX20_CONSTEXPR ~variant() = default; |
| 1519 | |
| 1520 | template<typename _Tp, |
| 1521 | typename = enable_if_t<sizeof...(_Types) != 0>, |
| 1522 | typename = enable_if_t<__not_in_place_tag<_Tp>>, |
| 1523 | typename _Tj = __accepted_type<_Tp&&>, |
| 1524 | typename = enable_if_t<__exactly_once<_Tj> |
| 1525 | && is_constructible_v<_Tj, _Tp>>> |
| 1526 | constexpr |
| 1527 | variant(_Tp&& __t) |
| 1528 | noexcept(is_nothrow_constructible_v<_Tj, _Tp>) |
| 1529 | : variant(in_place_index<__accepted_index<_Tp>>, |
| 1530 | std::forward<_Tp>(__t)) |
| 1531 | { } |
| 1532 | |
| 1533 | template<typename _Tp, typename... _Args, |
| 1534 | typename = enable_if_t<__exactly_once<_Tp> |
| 1535 | && is_constructible_v<_Tp, _Args...>>> |
| 1536 | constexpr explicit |
| 1537 | variant(in_place_type_t<_Tp>, _Args&&... __args) |
| 1538 | : variant(in_place_index<__index_of<_Tp>>, |
| 1539 | std::forward<_Args>(__args)...) |
| 1540 | { } |
| 1541 | |
| 1542 | template<typename _Tp, typename _Up, typename... _Args, |
| 1543 | typename = enable_if_t<__exactly_once<_Tp> |
| 1544 | && is_constructible_v<_Tp, |
| 1545 | initializer_list<_Up>&, _Args...>>> |
| 1546 | constexpr explicit |
| 1547 | variant(in_place_type_t<_Tp>, initializer_list<_Up> __il, |
| 1548 | _Args&&... __args) |
| 1549 | : variant(in_place_index<__index_of<_Tp>>, __il, |
| 1550 | std::forward<_Args>(__args)...) |
| 1551 | { } |
| 1552 | |
| 1553 | template<size_t _Np, typename... _Args, |
| 1554 | typename _Tp = __to_type<_Np>, |
| 1555 | typename = enable_if_t<is_constructible_v<_Tp, _Args...>>> |
| 1556 | constexpr explicit |
| 1557 | variant(in_place_index_t<_Np>, _Args&&... __args) |
| 1558 | : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...) |
| 1559 | { } |
| 1560 | |
| 1561 | template<size_t _Np, typename _Up, typename... _Args, |
| 1562 | typename _Tp = __to_type<_Np>, |
| 1563 | typename = enable_if_t<is_constructible_v<_Tp, |
| 1564 | initializer_list<_Up>&, |
| 1565 | _Args...>>> |
| 1566 | constexpr explicit |
| 1567 | variant(in_place_index_t<_Np>, initializer_list<_Up> __il, |
| 1568 | _Args&&... __args) |
| 1569 | : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...) |
| 1570 | { } |
| 1571 | |
| 1572 | template<typename _Tp> |
| 1573 | _GLIBCXX20_CONSTEXPR |
| 1574 | enable_if_t<__exactly_once<__accepted_type<_Tp&&>> |
| 1575 | && is_constructible_v<__accepted_type<_Tp&&>, _Tp> |
| 1576 | && is_assignable_v<__accepted_type<_Tp&&>&, _Tp>, |
| 1577 | variant&> |
| 1578 | operator=(_Tp&& __rhs) |
| 1579 | noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp> |
| 1580 | && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp>) |
| 1581 | { |
| 1582 | constexpr auto __index = __accepted_index<_Tp>; |
| 1583 | if (index() == __index) |
| 1584 | std::get<__index>(*this) = std::forward<_Tp>(__rhs); |
| 1585 | else |
| 1586 | { |
| 1587 | using _Tj = __accepted_type<_Tp&&>; |
| 1588 | if constexpr (is_nothrow_constructible_v<_Tj, _Tp> |
| 1589 | || !is_nothrow_move_constructible_v<_Tj>) |
| 1590 | this->emplace<__index>(std::forward<_Tp>(__rhs)); |
| 1591 | else |
| 1592 | // _GLIBCXX_RESOLVE_LIB_DEFECTS |
| 1593 | // 3585. converting assignment with immovable alternative |
| 1594 | this->emplace<__index>(_Tj(std::forward<_Tp>(__rhs))); |
| 1595 | } |
| 1596 | return *this; |
| 1597 | } |
| 1598 | |
| 1599 | template<typename _Tp, typename... _Args> |
| 1600 | _GLIBCXX20_CONSTEXPR |
| 1601 | enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>, |
| 1602 | _Tp&> |
| 1603 | emplace(_Args&&... __args) |
| 1604 | { |
| 1605 | constexpr size_t __index = __index_of<_Tp>; |
| 1606 | return this->emplace<__index>(std::forward<_Args>(__args)...); |
| 1607 | } |
| 1608 | |
| 1609 | template<typename _Tp, typename _Up, typename... _Args> |
| 1610 | _GLIBCXX20_CONSTEXPR |
| 1611 | enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...> |
| 1612 | && __exactly_once<_Tp>, |
| 1613 | _Tp&> |
| 1614 | emplace(initializer_list<_Up> __il, _Args&&... __args) |
| 1615 | { |
| 1616 | constexpr size_t __index = __index_of<_Tp>; |
| 1617 | return this->emplace<__index>(__il, std::forward<_Args>(__args)...); |
| 1618 | } |
| 1619 | |
| 1620 | template<size_t _Np, typename... _Args> |
| 1621 | _GLIBCXX20_CONSTEXPR |
| 1622 | enable_if_t<is_constructible_v<__to_type<_Np>, _Args...>, |
| 1623 | __to_type<_Np>&> |
| 1624 | emplace(_Args&&... __args) |
| 1625 | { |
| 1626 | namespace __variant = std::__detail::__variant; |
| 1627 | using type = typename _Nth_type<_Np, _Types...>::type; |
| 1628 | // Provide the strong exception-safety guarantee when possible, |
| 1629 | // to avoid becoming valueless. |
| 1630 | if constexpr (is_nothrow_constructible_v<type, _Args...>) |
| 1631 | { |
| 1632 | __variant::__emplace<_Np>(*this, std::forward<_Args>(__args)...); |
| 1633 | } |
| 1634 | else if constexpr (is_scalar_v<type>) |
| 1635 | { |
| 1636 | // This might invoke a potentially-throwing conversion operator: |
| 1637 | const type __tmp(std::forward<_Args>(__args)...); |
| 1638 | // But this won't throw: |
| 1639 | __variant::__emplace<_Np>(*this, __tmp); |
| 1640 | } |
| 1641 | else if constexpr (__variant::_Never_valueless_alt<type>() |
| 1642 | && _Traits::_S_move_assign) |
| 1643 | { |
| 1644 | // This construction might throw: |
| 1645 | variant __tmp(in_place_index<_Np>, |
| 1646 | std::forward<_Args>(__args)...); |
| 1647 | // But _Never_valueless_alt<type> means this won't: |
| 1648 | *this = std::move(__tmp); |
| 1649 | } |
| 1650 | else |
| 1651 | { |
| 1652 | // This case only provides the basic exception-safety guarantee, |
| 1653 | // i.e. the variant can become valueless. |
| 1654 | __variant::__emplace<_Np>(*this, std::forward<_Args>(__args)...); |
| 1655 | } |
| 1656 | return std::get<_Np>(*this); |
| 1657 | } |
| 1658 | |
| 1659 | template<size_t _Np, typename _Up, typename... _Args> |
| 1660 | _GLIBCXX20_CONSTEXPR |
| 1661 | enable_if_t<is_constructible_v<__to_type<_Np>, |
| 1662 | initializer_list<_Up>&, _Args...>, |
| 1663 | __to_type<_Np>&> |
| 1664 | emplace(initializer_list<_Up> __il, _Args&&... __args) |
| 1665 | { |
| 1666 | namespace __variant = std::__detail::__variant; |
| 1667 | using type = typename _Nth_type<_Np, _Types...>::type; |
| 1668 | // Provide the strong exception-safety guarantee when possible, |
| 1669 | // to avoid becoming valueless. |
| 1670 | if constexpr (is_nothrow_constructible_v<type, |
| 1671 | initializer_list<_Up>&, |
| 1672 | _Args...>) |
| 1673 | { |
| 1674 | __variant::__emplace<_Np>(*this, __il, |
| 1675 | std::forward<_Args>(__args)...); |
| 1676 | } |
| 1677 | else if constexpr (__variant::_Never_valueless_alt<type>() |
| 1678 | && _Traits::_S_move_assign) |
| 1679 | { |
| 1680 | // This construction might throw: |
| 1681 | variant __tmp(in_place_index<_Np>, __il, |
| 1682 | std::forward<_Args>(__args)...); |
| 1683 | // But _Never_valueless_alt<type> means this won't: |
| 1684 | *this = std::move(__tmp); |
| 1685 | } |
| 1686 | else |
| 1687 | { |
| 1688 | // This case only provides the basic exception-safety guarantee, |
| 1689 | // i.e. the variant can become valueless. |
| 1690 | __variant::__emplace<_Np>(*this, __il, |
| 1691 | std::forward<_Args>(__args)...); |
| 1692 | } |
| 1693 | return std::get<_Np>(*this); |
| 1694 | } |
| 1695 | |
| 1696 | template<size_t _Np, typename... _Args> |
| 1697 | enable_if_t<!(_Np < sizeof...(_Types))> emplace(_Args&&...) = delete; |
| 1698 | |
| 1699 | template<typename _Tp, typename... _Args> |
| 1700 | enable_if_t<!__exactly_once<_Tp>> emplace(_Args&&...) = delete; |
| 1701 | |
| 1702 | constexpr bool valueless_by_exception() const noexcept |
| 1703 | { return !this->_M_valid(); } |
| 1704 | |
| 1705 | constexpr size_t index() const noexcept |
| 1706 | { |
| 1707 | using __index_type = typename _Base::__index_type; |
| 1708 | if constexpr (__detail::__variant::__never_valueless<_Types...>()) |
| 1709 | return this->_M_index; |
| 1710 | else if constexpr (sizeof...(_Types) <= __index_type(-1) / 2) |
| 1711 | return make_signed_t<__index_type>(this->_M_index); |
| 1712 | else |
| 1713 | return size_t(__index_type(this->_M_index + 1)) - 1; |
| 1714 | } |
| 1715 | |
| 1716 | _GLIBCXX20_CONSTEXPR |
| 1717 | void |
| 1718 | swap(variant& __rhs) |
| 1719 | noexcept((__is_nothrow_swappable<_Types>::value && ...) |
| 1720 | && is_nothrow_move_constructible_v<variant>) |
| 1721 | { |
| 1722 | static_assert((is_move_constructible_v<_Types> && ...)); |
| 1723 | |
| 1724 | // Handle this here to simplify the visitation. |
| 1725 | if (__rhs.valueless_by_exception()) [[__unlikely__]] |
| 1726 | { |
| 1727 | if (!this->valueless_by_exception()) [[__likely__]] |
| 1728 | __rhs.swap(rhs&: *this); |
| 1729 | return; |
| 1730 | } |
| 1731 | |
| 1732 | namespace __variant = __detail::__variant; |
| 1733 | |
| 1734 | __variant::__raw_idx_visit( |
| 1735 | [this, &__rhs](auto&& __rhs_mem, auto __rhs_index) mutable |
| 1736 | { |
| 1737 | constexpr size_t __j = __rhs_index; |
| 1738 | if constexpr (__j != variant_npos) |
| 1739 | { |
| 1740 | if (this->index() == __j) |
| 1741 | { |
| 1742 | using std::swap; |
| 1743 | swap(std::get<__j>(*this), __rhs_mem); |
| 1744 | } |
| 1745 | else |
| 1746 | { |
| 1747 | auto __tmp(std::move(__rhs_mem)); |
| 1748 | |
| 1749 | if constexpr (_Traits::_S_trivial_move_assign) |
| 1750 | __rhs = std::move(*this); |
| 1751 | else |
| 1752 | __variant::__raw_idx_visit( |
| 1753 | [&__rhs](auto&& __this_mem, auto __this_index) mutable |
| 1754 | { |
| 1755 | constexpr size_t __k = __this_index; |
| 1756 | if constexpr (__k != variant_npos) |
| 1757 | __variant::__emplace<__k>(__rhs, |
| 1758 | std::move(__this_mem)); |
| 1759 | }, *this); |
| 1760 | |
| 1761 | __variant::__emplace<__j>(*this, std::move(__tmp)); |
| 1762 | } |
| 1763 | } |
| 1764 | }, __rhs); |
| 1765 | } |
| 1766 | |
| 1767 | #if __cpp_lib_variant >= 202306L // >= C++26 |
| 1768 | // [variant.visit], visitation |
| 1769 | |
| 1770 | /** Simple visitation for a single variant |
| 1771 | * |
| 1772 | * To visit a single variant you can use `var.visit(visitor)` |
| 1773 | * instead of `std::visit(visitor, var)`. |
| 1774 | * |
| 1775 | * @since C++26 |
| 1776 | */ |
| 1777 | template<int = 0, typename _Self, typename _Visitor> |
| 1778 | constexpr decltype(auto) |
| 1779 | visit(this _Self&& __self, _Visitor&& __vis) |
| 1780 | { |
| 1781 | using _CVar = __conditional_t<is_const_v<remove_reference_t<_Self>>, |
| 1782 | const variant, variant>; |
| 1783 | using _Var = __conditional_t<is_rvalue_reference_v<_Self&&>, |
| 1784 | _CVar&&, _CVar&>; |
| 1785 | return std::visit(std::forward<_Visitor>(__vis), (_Var)__self); |
| 1786 | } |
| 1787 | |
| 1788 | /** Simple visitation for a single variant, with explicit return type |
| 1789 | * |
| 1790 | * To visit a single variant you can use `var.visit<R>(visitor)` |
| 1791 | * instead of `std::visit<R>(visitor, var)`. |
| 1792 | * |
| 1793 | * @since C++26 |
| 1794 | */ |
| 1795 | template<typename _Res, typename _Self, typename _Visitor> |
| 1796 | constexpr _Res |
| 1797 | visit(this _Self&& __self, _Visitor&& __vis) |
| 1798 | { |
| 1799 | using _CVar = __conditional_t<is_const_v<remove_reference_t<_Self>>, |
| 1800 | const variant, variant>; |
| 1801 | using _Var = __conditional_t<is_rvalue_reference_v<_Self&&>, |
| 1802 | _CVar&&, _CVar&>; |
| 1803 | return std::visit<_Res>(std::forward<_Visitor>(__vis), (_Var)__self); |
| 1804 | } |
| 1805 | #endif |
| 1806 | |
| 1807 | private: |
| 1808 | template<size_t _Np, typename _Vp> |
| 1809 | friend constexpr decltype(auto) |
| 1810 | __detail::__variant::__get(_Vp&& __v) noexcept; |
| 1811 | }; |
| 1812 | |
| 1813 | template<size_t _Np, typename... _Types> |
| 1814 | constexpr variant_alternative_t<_Np, variant<_Types...>>& |
| 1815 | get(variant<_Types...>& __v) |
| 1816 | { |
| 1817 | static_assert(_Np < sizeof...(_Types), |
| 1818 | "The index must be in [0, number of alternatives)"); |
| 1819 | if (__v.index() != _Np) |
| 1820 | __throw_bad_variant_access(__v.valueless_by_exception()); |
| 1821 | return __detail::__variant::__get<_Np>(__v); |
| 1822 | } |
| 1823 | |
| 1824 | template<size_t _Np, typename... _Types> |
| 1825 | constexpr variant_alternative_t<_Np, variant<_Types...>>&& |
| 1826 | get(variant<_Types...>&& __v) |
| 1827 | { |
| 1828 | static_assert(_Np < sizeof...(_Types), |
| 1829 | "The index must be in [0, number of alternatives)"); |
| 1830 | if (__v.index() != _Np) |
| 1831 | __throw_bad_variant_access(__v.valueless_by_exception()); |
| 1832 | return __detail::__variant::__get<_Np>(std::move(__v)); |
| 1833 | } |
| 1834 | |
| 1835 | template<size_t _Np, typename... _Types> |
| 1836 | constexpr const variant_alternative_t<_Np, variant<_Types...>>& |
| 1837 | get(const variant<_Types...>& __v) |
| 1838 | { |
| 1839 | static_assert(_Np < sizeof...(_Types), |
| 1840 | "The index must be in [0, number of alternatives)"); |
| 1841 | if (__v.index() != _Np) |
| 1842 | __throw_bad_variant_access(__v.valueless_by_exception()); |
| 1843 | return __detail::__variant::__get<_Np>(__v); |
| 1844 | } |
| 1845 | |
| 1846 | template<size_t _Np, typename... _Types> |
| 1847 | constexpr const variant_alternative_t<_Np, variant<_Types...>>&& |
| 1848 | get(const variant<_Types...>&& __v) |
| 1849 | { |
| 1850 | static_assert(_Np < sizeof...(_Types), |
| 1851 | "The index must be in [0, number of alternatives)"); |
| 1852 | if (__v.index() != _Np) |
| 1853 | __throw_bad_variant_access(__v.valueless_by_exception()); |
| 1854 | return __detail::__variant::__get<_Np>(std::move(__v)); |
| 1855 | } |
| 1856 | |
| 1857 | /// @cond undocumented |
| 1858 | template<typename _Result_type, typename _Visitor, typename... _Variants> |
| 1859 | constexpr decltype(auto) |
| 1860 | __do_visit(_Visitor&& __visitor, _Variants&&... __variants) |
| 1861 | { |
| 1862 | // Get the silly case of visiting no variants out of the way first. |
| 1863 | if constexpr (sizeof...(_Variants) == 0) |
| 1864 | { |
| 1865 | if constexpr (is_void_v<_Result_type>) |
| 1866 | return (void) std::forward<_Visitor>(__visitor)(); |
| 1867 | else |
| 1868 | return std::forward<_Visitor>(__visitor)(); |
| 1869 | } |
| 1870 | else |
| 1871 | { |
| 1872 | constexpr size_t __max = 11; // "These go to eleven." |
| 1873 | |
| 1874 | // The type of the first variant in the pack. |
| 1875 | using _V0 = typename _Nth_type<0, _Variants...>::type; |
| 1876 | // The number of alternatives in that first variant. |
| 1877 | constexpr auto __n = variant_size_v<remove_reference_t<_V0>>; |
| 1878 | |
| 1879 | if constexpr (sizeof...(_Variants) > 1 || __n > __max) |
| 1880 | { |
| 1881 | // Use a jump table for the general case. |
| 1882 | constexpr auto& __vtable = __detail::__variant::__gen_vtable< |
| 1883 | _Result_type, _Visitor&&, _Variants&&...>::_S_vtable; |
| 1884 | |
| 1885 | auto __func_ptr = __vtable._M_access(__variants.index()...); |
| 1886 | return (*__func_ptr)(std::forward<_Visitor>(__visitor), |
| 1887 | std::forward<_Variants>(__variants)...); |
| 1888 | } |
| 1889 | else // We have a single variant with a small number of alternatives. |
| 1890 | { |
| 1891 | // A name for the first variant in the pack. |
| 1892 | _V0& __v0 |
| 1893 | = [](_V0& __v, ...) -> _V0& { return __v; }(__variants...); |
| 1894 | |
| 1895 | using __detail::__variant::_Multi_array; |
| 1896 | using __detail::__variant::__gen_vtable_impl; |
| 1897 | using _Ma = _Multi_array<_Result_type (*)(_Visitor&&, _V0&&)>; |
| 1898 | |
| 1899 | #ifdef _GLIBCXX_DEBUG |
| 1900 | # define _GLIBCXX_VISIT_UNREACHABLE __builtin_trap |
| 1901 | #else |
| 1902 | # define _GLIBCXX_VISIT_UNREACHABLE __builtin_unreachable |
| 1903 | #endif |
| 1904 | |
| 1905 | #define _GLIBCXX_VISIT_CASE(N) \ |
| 1906 | case N: \ |
| 1907 | { \ |
| 1908 | if constexpr (N < __n) \ |
| 1909 | { \ |
| 1910 | return __gen_vtable_impl<_Ma, index_sequence<N>>:: \ |
| 1911 | __visit_invoke(std::forward<_Visitor>(__visitor), \ |
| 1912 | std::forward<_V0>(__v0)); \ |
| 1913 | } \ |
| 1914 | else _GLIBCXX_VISIT_UNREACHABLE(); \ |
| 1915 | } |
| 1916 | |
| 1917 | switch (__v0.index()) |
| 1918 | { |
| 1919 | _GLIBCXX_VISIT_CASE(0) |
| 1920 | _GLIBCXX_VISIT_CASE(1) |
| 1921 | _GLIBCXX_VISIT_CASE(2) |
| 1922 | _GLIBCXX_VISIT_CASE(3) |
| 1923 | _GLIBCXX_VISIT_CASE(4) |
| 1924 | _GLIBCXX_VISIT_CASE(5) |
| 1925 | _GLIBCXX_VISIT_CASE(6) |
| 1926 | _GLIBCXX_VISIT_CASE(7) |
| 1927 | _GLIBCXX_VISIT_CASE(8) |
| 1928 | _GLIBCXX_VISIT_CASE(9) |
| 1929 | _GLIBCXX_VISIT_CASE(10) |
| 1930 | case variant_npos: |
| 1931 | using __detail::__variant::__variant_idx_cookie; |
| 1932 | using __detail::__variant::__variant_cookie; |
| 1933 | if constexpr (is_same_v<_Result_type, __variant_idx_cookie> |
| 1934 | || is_same_v<_Result_type, __variant_cookie>) |
| 1935 | { |
| 1936 | using _Npos = index_sequence<variant_npos>; |
| 1937 | return __gen_vtable_impl<_Ma, _Npos>:: |
| 1938 | __visit_invoke(std::forward<_Visitor>(__visitor), |
| 1939 | std::forward<_V0>(__v0)); |
| 1940 | } |
| 1941 | else |
| 1942 | _GLIBCXX_VISIT_UNREACHABLE(); |
| 1943 | default: |
| 1944 | _GLIBCXX_VISIT_UNREACHABLE(); |
| 1945 | } |
| 1946 | #undef _GLIBCXX_VISIT_CASE |
| 1947 | #undef _GLIBCXX_VISIT_UNREACHABLE |
| 1948 | } |
| 1949 | } |
| 1950 | } |
| 1951 | /// @endcond |
| 1952 | |
| 1953 | template<typename _Visitor, typename... _Variants> |
| 1954 | constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...> |
| 1955 | visit(_Visitor&& __visitor, _Variants&&... __variants) |
| 1956 | { |
| 1957 | namespace __variant = std::__detail::__variant; |
| 1958 | |
| 1959 | if ((__variant::__as(__variants).valueless_by_exception() || ...)) |
| 1960 | __throw_bad_variant_access(2); |
| 1961 | |
| 1962 | using _Result_type |
| 1963 | = __detail::__variant::__visit_result_t<_Visitor, _Variants...>; |
| 1964 | |
| 1965 | using _Tag = __detail::__variant::__deduce_visit_result<_Result_type>; |
| 1966 | |
| 1967 | if constexpr (sizeof...(_Variants) == 1) |
| 1968 | { |
| 1969 | using _Vp = decltype(__variant::__as(std::declval<_Variants>()...)); |
| 1970 | |
| 1971 | constexpr bool __visit_rettypes_match = __detail::__variant:: |
| 1972 | __check_visitor_results<_Visitor, _Vp>( |
| 1973 | make_index_sequence<variant_size_v<remove_reference_t<_Vp>>>()); |
| 1974 | if constexpr (!__visit_rettypes_match) |
| 1975 | { |
| 1976 | static_assert(__visit_rettypes_match, |
| 1977 | "std::visit requires the visitor to have the same " |
| 1978 | "return type for all alternatives of a variant"); |
| 1979 | return; |
| 1980 | } |
| 1981 | else |
| 1982 | return std::__do_visit<_Tag>( |
| 1983 | std::forward<_Visitor>(__visitor), |
| 1984 | static_cast<_Vp>(__variants)...); |
| 1985 | } |
| 1986 | else |
| 1987 | return std::__do_visit<_Tag>( |
| 1988 | std::forward<_Visitor>(__visitor), |
| 1989 | __variant::__as(std::forward<_Variants>(__variants))...); |
| 1990 | } |
| 1991 | |
| 1992 | #if __cplusplus > 201703L |
| 1993 | template<typename _Res, typename _Visitor, typename... _Variants> |
| 1994 | constexpr _Res |
| 1995 | visit(_Visitor&& __visitor, _Variants&&... __variants) |
| 1996 | { |
| 1997 | namespace __variant = std::__detail::__variant; |
| 1998 | |
| 1999 | if ((__variant::__as(__variants).valueless_by_exception() || ...)) |
| 2000 | __throw_bad_variant_access(3); |
| 2001 | |
| 2002 | return std::__do_visit<_Res>(std::forward<_Visitor>(__visitor), |
| 2003 | __variant::__as(std::forward<_Variants>(__variants))...); |
| 2004 | } |
| 2005 | #endif |
| 2006 | |
| 2007 | /// @cond undocumented |
| 2008 | template<typename... _Types> |
| 2009 | struct __variant_hash |
| 2010 | { |
| 2011 | #if __cplusplus < 202002L |
| 2012 | using result_type [[__deprecated__]] = size_t; |
| 2013 | using argument_type [[__deprecated__]] = variant<_Types...>; |
| 2014 | #endif |
| 2015 | |
| 2016 | size_t |
| 2017 | operator()(const variant<_Types...>& __t) const |
| 2018 | noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...)) |
| 2019 | { |
| 2020 | size_t __ret; |
| 2021 | __detail::__variant::__raw_visit( |
| 2022 | [&__t, &__ret](auto&& __t_mem) mutable |
| 2023 | { |
| 2024 | using _Type = __remove_cvref_t<decltype(__t_mem)>; |
| 2025 | if constexpr (!is_same_v<_Type, |
| 2026 | __detail::__variant::__variant_cookie>) |
| 2027 | __ret = std::hash<size_t>{}(__t.index()) |
| 2028 | + std::hash<_Type>{}(__t_mem); |
| 2029 | else |
| 2030 | __ret = std::hash<size_t>{}(__t.index()); |
| 2031 | }, __t); |
| 2032 | return __ret; |
| 2033 | } |
| 2034 | }; |
| 2035 | /// @endcond |
| 2036 | |
| 2037 | template<typename... _Types> |
| 2038 | struct hash<variant<_Types...>> |
| 2039 | : __conditional_t<(__is_hash_enabled_for<remove_const_t<_Types>> && ...), |
| 2040 | __variant_hash<_Types...>, |
| 2041 | __hash_not_enabled<variant<_Types...>>> |
| 2042 | #if ! _GLIBCXX_INLINE_VERSION |
| 2043 | , __detail::__variant::_Variant_hash_base<variant<_Types...>, |
| 2044 | index_sequence_for<_Types...>> |
| 2045 | #endif |
| 2046 | { }; |
| 2047 | |
| 2048 | template<typename... _Types> |
| 2049 | struct __is_fast_hash<hash<variant<_Types...>>> |
| 2050 | : bool_constant<(__is_fast_hash<_Types>::value && ...)> |
| 2051 | { }; |
| 2052 | |
| 2053 | _GLIBCXX_END_NAMESPACE_VERSION |
| 2054 | } // namespace std |
| 2055 | |
| 2056 | #endif // __cpp_lib_variant |
| 2057 | #endif // _GLIBCXX_VARIANT |
| 2058 |
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