1// <variant> -*- C++ -*- 2 3// Copyright (C) 2016-2022 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#pragma GCC system_header 33 34#if __cplusplus >= 201703L 35 36#include <initializer_list> 37#include <type_traits> 38#include <bits/enable_special_members.h> 39#include <bits/exception_defines.h> 40#include <bits/functional_hash.h> 41#include <bits/invoke.h> 42#include <bits/parse_numbers.h> 43#include <bits/stl_iterator_base_types.h> 44#include <bits/stl_iterator_base_funcs.h> 45#include <bits/stl_construct.h> 46#include <bits/utility.h> // in_place_index_t 47#if __cplusplus >= 202002L 48# include <compare> 49#endif 50 51#if __cpp_concepts >= 202002L && __cpp_constexpr >= 201811L 52// P2231R1 constexpr needs constexpr unions and constrained destructors. 53# define __cpp_lib_variant 202106L 54#else 55# include <ext/aligned_buffer.h> // Use __aligned_membuf instead of union. 56# define __cpp_lib_variant 202102L 57#endif 58 59namespace std _GLIBCXX_VISIBILITY(default) 60{ 61_GLIBCXX_BEGIN_NAMESPACE_VERSION 62 63 template<typename... _Types> class tuple; 64 template<typename... _Types> class variant; 65 template <typename> struct hash; 66 67 template<typename _Variant> 68 struct variant_size; 69 70 template<typename _Variant> 71 struct variant_size<const _Variant> : variant_size<_Variant> {}; 72 73 template<typename _Variant> 74 struct variant_size<volatile _Variant> : variant_size<_Variant> {}; 75 76 template<typename _Variant> 77 struct variant_size<const volatile _Variant> : variant_size<_Variant> {}; 78 79 template<typename... _Types> 80 struct variant_size<variant<_Types...>> 81 : std::integral_constant<size_t, sizeof...(_Types)> {}; 82 83 template<typename _Variant> 84 inline constexpr size_t variant_size_v = variant_size<_Variant>::value; 85 86 template<typename... _Types> 87 inline constexpr size_t 88 variant_size_v<variant<_Types...>> = sizeof...(_Types); 89 90 template<typename... _Types> 91 inline constexpr size_t 92 variant_size_v<const variant<_Types...>> = sizeof...(_Types); 93 94 template<size_t _Np, typename _Variant> 95 struct variant_alternative; 96 97 template<size_t _Np, typename... _Types> 98 struct variant_alternative<_Np, variant<_Types...>> 99 { 100 static_assert(_Np < sizeof...(_Types)); 101 102 using type = typename _Nth_type<_Np, _Types...>::type; 103 }; 104 105 template<size_t _Np, typename _Variant> 106 using variant_alternative_t = 107 typename variant_alternative<_Np, _Variant>::type; 108 109 template<size_t _Np, typename _Variant> 110 struct variant_alternative<_Np, const _Variant> 111 { using type = add_const_t<variant_alternative_t<_Np, _Variant>>; }; 112 113 template<size_t _Np, typename _Variant> 114 struct variant_alternative<_Np, volatile _Variant> 115 { using type = add_volatile_t<variant_alternative_t<_Np, _Variant>>; }; 116 117 template<size_t _Np, typename _Variant> 118 struct variant_alternative<_Np, const volatile _Variant> 119 { using type = add_cv_t<variant_alternative_t<_Np, _Variant>>; }; 120 121 inline constexpr size_t variant_npos = -1; 122 123 template<size_t _Np, typename... _Types> 124 constexpr variant_alternative_t<_Np, variant<_Types...>>& 125 get(variant<_Types...>&); 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...>> const& 133 get(const 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<typename _Result_type, typename _Visitor, typename... _Variants> 140 constexpr decltype(auto) 141 __do_visit(_Visitor&& __visitor, _Variants&&... __variants); 142 143 template <typename... _Types, typename _Tp> 144 _GLIBCXX20_CONSTEXPR 145 decltype(auto) 146 __variant_cast(_Tp&& __rhs) 147 { 148 if constexpr (is_lvalue_reference_v<_Tp>) 149 { 150 if constexpr (is_const_v<remove_reference_t<_Tp>>) 151 return static_cast<const variant<_Types...>&>(__rhs); 152 else 153 return static_cast<variant<_Types...>&>(__rhs); 154 } 155 else 156 return static_cast<variant<_Types...>&&>(__rhs); 157 } 158 159namespace __detail 160{ 161namespace __variant 162{ 163 // used for raw visitation 164 struct __variant_cookie {}; 165 // used for raw visitation with indices passed in 166 struct __variant_idx_cookie { using type = __variant_idx_cookie; }; 167 // Used to enable deduction (and same-type checking) for std::visit: 168 template<typename _Tp> struct __deduce_visit_result { using type = _Tp; }; 169 170 // Visit variants that might be valueless. 171 template<typename _Visitor, typename... _Variants> 172 constexpr void 173 __raw_visit(_Visitor&& __visitor, _Variants&&... __variants) 174 { 175 std::__do_visit<__variant_cookie>(std::forward<_Visitor>(__visitor), 176 std::forward<_Variants>(__variants)...); 177 } 178 179 // Visit variants that might be valueless, passing indices to the visitor. 180 template<typename _Visitor, typename... _Variants> 181 constexpr void 182 __raw_idx_visit(_Visitor&& __visitor, _Variants&&... __variants) 183 { 184 std::__do_visit<__variant_idx_cookie>(std::forward<_Visitor>(__visitor), 185 std::forward<_Variants>(__variants)...); 186 } 187 188 // The __as function templates implement the exposition-only "as-variant" 189 190 template<typename... _Types> 191 constexpr std::variant<_Types...>& 192 __as(std::variant<_Types...>& __v) noexcept 193 { return __v; } 194 195 template<typename... _Types> 196 constexpr const std::variant<_Types...>& 197 __as(const std::variant<_Types...>& __v) noexcept 198 { return __v; } 199 200 template<typename... _Types> 201 constexpr std::variant<_Types...>&& 202 __as(std::variant<_Types...>&& __v) noexcept 203 { return std::move(__v); } 204 205 template<typename... _Types> 206 constexpr const std::variant<_Types...>&& 207 __as(const std::variant<_Types...>&& __v) noexcept 208 { return std::move(__v); } 209 210 // For C++17: 211 // _Uninitialized<T> is guaranteed to be a trivially destructible type, 212 // even if T is not. 213 // For C++20: 214 // _Uninitialized<T> is trivially destructible iff T is, so _Variant_union 215 // needs a constrained non-trivial destructor. 216 template<typename _Type, bool = std::is_trivially_destructible_v<_Type>> 217 struct _Uninitialized; 218 219 template<typename _Type> 220 struct _Uninitialized<_Type, true> 221 { 222 template<typename... _Args> 223 constexpr 224 _Uninitialized(in_place_index_t<0>, _Args&&... __args) 225 : _M_storage(std::forward<_Args>(__args)...) 226 { } 227 228 constexpr const _Type& _M_get() const & noexcept 229 { return _M_storage; } 230 231 constexpr _Type& _M_get() & noexcept 232 { return _M_storage; } 233 234 constexpr const _Type&& _M_get() const && noexcept 235 { return std::move(_M_storage); } 236 237 constexpr _Type&& _M_get() && noexcept 238 { return std::move(_M_storage); } 239 240 _Type _M_storage; 241 }; 242 243 template<typename _Type> 244 struct _Uninitialized<_Type, false> 245 { 246#if __cpp_lib_variant >= 202106L 247 template<typename... _Args> 248 constexpr 249 _Uninitialized(in_place_index_t<0>, _Args&&... __args) 250 : _M_storage(std::forward<_Args>(__args)...) 251 { } 252 253 constexpr ~_Uninitialized() { } 254 255 _Uninitialized(const _Uninitialized&) = default; 256 _Uninitialized(_Uninitialized&&) = default; 257 _Uninitialized& operator=(const _Uninitialized&) = default; 258 _Uninitialized& operator=(_Uninitialized&&) = default; 259 260 constexpr const _Type& _M_get() const & noexcept 261 { return _M_storage; } 262 263 constexpr _Type& _M_get() & noexcept 264 { return _M_storage; } 265 266 constexpr const _Type&& _M_get() const && noexcept 267 { return std::move(_M_storage); } 268 269 constexpr _Type&& _M_get() && noexcept 270 { return std::move(_M_storage); } 271 272 struct _Empty_byte { }; 273 274 union { 275 _Empty_byte _M_empty; 276 _Type _M_storage; 277 }; 278#else 279 template<typename... _Args> 280 constexpr 281 _Uninitialized(in_place_index_t<0>, _Args&&... __args) 282 { 283 ::new ((void*)std::addressof(_M_storage)) 284 _Type(std::forward<_Args>(__args)...); 285 } 286 287 const _Type& _M_get() const & noexcept 288 { return *_M_storage._M_ptr(); } 289 290 _Type& _M_get() & noexcept 291 { return *_M_storage._M_ptr(); } 292 293 const _Type&& _M_get() const && noexcept 294 { return std::move(*_M_storage._M_ptr()); } 295 296 _Type&& _M_get() && noexcept 297 { return std::move(*_M_storage._M_ptr()); } 298 299 __gnu_cxx::__aligned_membuf<_Type> _M_storage; 300#endif 301 }; 302 303 template<size_t _Np, typename _Union> 304 constexpr decltype(auto) 305 __get_n(_Union&& __u) noexcept 306 { 307 if constexpr (_Np == 0) 308 return std::forward<_Union>(__u)._M_first._M_get(); 309 else if constexpr (_Np == 1) 310 return std::forward<_Union>(__u)._M_rest._M_first._M_get(); 311 else if constexpr (_Np == 2) 312 return std::forward<_Union>(__u)._M_rest._M_rest._M_first._M_get(); 313 else 314 return __variant::__get_n<_Np - 3>( 315 std::forward<_Union>(__u)._M_rest._M_rest._M_rest); 316 } 317 318 // Returns the typed storage for __v. 319 template<size_t _Np, typename _Variant> 320 constexpr decltype(auto) 321 __get(_Variant&& __v) noexcept 322 { return __variant::__get_n<_Np>(std::forward<_Variant>(__v)._M_u); } 323 324 template<typename... _Types> 325 struct _Traits 326 { 327 static constexpr bool _S_default_ctor = 328 is_default_constructible_v<typename _Nth_type<0, _Types...>::type>; 329 static constexpr bool _S_copy_ctor = 330 (is_copy_constructible_v<_Types> && ...); 331 static constexpr bool _S_move_ctor = 332 (is_move_constructible_v<_Types> && ...); 333 static constexpr bool _S_copy_assign = 334 _S_copy_ctor 335 && (is_copy_assignable_v<_Types> && ...); 336 static constexpr bool _S_move_assign = 337 _S_move_ctor 338 && (is_move_assignable_v<_Types> && ...); 339 340 static constexpr bool _S_trivial_dtor = 341 (is_trivially_destructible_v<_Types> && ...); 342 static constexpr bool _S_trivial_copy_ctor = 343 (is_trivially_copy_constructible_v<_Types> && ...); 344 static constexpr bool _S_trivial_move_ctor = 345 (is_trivially_move_constructible_v<_Types> && ...); 346 static constexpr bool _S_trivial_copy_assign = 347 _S_trivial_dtor && _S_trivial_copy_ctor 348 && (is_trivially_copy_assignable_v<_Types> && ...); 349 static constexpr bool _S_trivial_move_assign = 350 _S_trivial_dtor && _S_trivial_move_ctor 351 && (is_trivially_move_assignable_v<_Types> && ...); 352 353 // The following nothrow traits are for non-trivial SMFs. Trivial SMFs 354 // are always nothrow. 355 static constexpr bool _S_nothrow_default_ctor = 356 is_nothrow_default_constructible_v< 357 typename _Nth_type<0, _Types...>::type>; 358 static constexpr bool _S_nothrow_copy_ctor = false; 359 static constexpr bool _S_nothrow_move_ctor = 360 (is_nothrow_move_constructible_v<_Types> && ...); 361 static constexpr bool _S_nothrow_copy_assign = false; 362 static constexpr bool _S_nothrow_move_assign = 363 _S_nothrow_move_ctor 364 && (is_nothrow_move_assignable_v<_Types> && ...); 365 }; 366 367 // Defines members and ctors. 368 template<typename... _Types> 369 union _Variadic_union 370 { 371 _Variadic_union() = default; 372 373 template<size_t _Np, typename... _Args> 374 _Variadic_union(in_place_index_t<_Np>, _Args&&...) = delete; 375 }; 376 377 template<typename _First, typename... _Rest> 378 union _Variadic_union<_First, _Rest...> 379 { 380 constexpr _Variadic_union() : _M_rest() { } 381 382 template<typename... _Args> 383 constexpr 384 _Variadic_union(in_place_index_t<0>, _Args&&... __args) 385 : _M_first(in_place_index<0>, std::forward<_Args>(__args)...) 386 { } 387 388 template<size_t _Np, typename... _Args> 389 constexpr 390 _Variadic_union(in_place_index_t<_Np>, _Args&&... __args) 391 : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...) 392 { } 393 394#if __cpp_lib_variant >= 202106L 395 _Variadic_union(const _Variadic_union&) = default; 396 _Variadic_union(_Variadic_union&&) = default; 397 _Variadic_union& operator=(const _Variadic_union&) = default; 398 _Variadic_union& operator=(_Variadic_union&&) = default; 399 400 ~_Variadic_union() = default; 401 402 constexpr ~_Variadic_union() 403 requires (!__has_trivial_destructor(_First)) 404 || (!__has_trivial_destructor(_Variadic_union<_Rest...>)) 405 { } 406#endif 407 408 _Uninitialized<_First> _M_first; 409 _Variadic_union<_Rest...> _M_rest; 410 }; 411 412 // _Never_valueless_alt is true for variant alternatives that can 413 // always be placed in a variant without it becoming valueless. 414 415 // For suitably-small, trivially copyable types we can create temporaries 416 // on the stack and then memcpy them into place. 417 template<typename _Tp> 418 struct _Never_valueless_alt 419 : __and_<bool_constant<sizeof(_Tp) <= 256>, is_trivially_copyable<_Tp>> 420 { }; 421 422 // Specialize _Never_valueless_alt for other types which have a 423 // non-throwing and cheap move construction and move assignment operator, 424 // so that emplacing the type will provide the strong exception-safety 425 // guarantee, by creating and moving a temporary. 426 // Whether _Never_valueless_alt<T> is true or not affects the ABI of a 427 // variant using that alternative, so we can't change the value later! 428 429 // True if every alternative in _Types... can be emplaced in a variant 430 // without it becoming valueless. If this is true, variant<_Types...> 431 // can never be valueless, which enables some minor optimizations. 432 template <typename... _Types> 433 constexpr bool __never_valueless() 434 { 435 return _Traits<_Types...>::_S_move_assign 436 && (_Never_valueless_alt<_Types>::value && ...); 437 } 438 439 // Defines index and the dtor, possibly trivial. 440 template<bool __trivially_destructible, typename... _Types> 441 struct _Variant_storage; 442 443 template <typename... _Types> 444 using __select_index = 445 typename __select_int::_Select_int_base<sizeof...(_Types), 446 unsigned char, 447 unsigned short>::type::value_type; 448 449 template<typename... _Types> 450 struct _Variant_storage<false, _Types...> 451 { 452 constexpr 453 _Variant_storage() 454 : _M_index(static_cast<__index_type>(variant_npos)) 455 { } 456 457 template<size_t _Np, typename... _Args> 458 constexpr 459 _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) 460 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), 461 _M_index{_Np} 462 { } 463 464 constexpr void 465 _M_reset() 466 { 467 if (!_M_valid()) [[unlikely]] 468 return; 469 470 std::__do_visit<void>([](auto&& __this_mem) mutable 471 { 472 std::_Destroy(std::__addressof(__this_mem)); 473 }, __variant_cast<_Types...>(*this)); 474 475 _M_index = static_cast<__index_type>(variant_npos); 476 } 477 478 _GLIBCXX20_CONSTEXPR 479 ~_Variant_storage() 480 { _M_reset(); } 481 482 constexpr bool 483 _M_valid() const noexcept 484 { 485 if constexpr (__variant::__never_valueless<_Types...>()) 486 return true; 487 return this->_M_index != __index_type(variant_npos); 488 } 489 490 _Variadic_union<_Types...> _M_u; 491 using __index_type = __select_index<_Types...>; 492 __index_type _M_index; 493 }; 494 495 template<typename... _Types> 496 struct _Variant_storage<true, _Types...> 497 { 498 constexpr 499 _Variant_storage() 500 : _M_index(static_cast<__index_type>(variant_npos)) 501 { } 502 503 template<size_t _Np, typename... _Args> 504 constexpr 505 _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) 506 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), 507 _M_index{_Np} 508 { } 509 510 constexpr void 511 _M_reset() noexcept 512 { _M_index = static_cast<__index_type>(variant_npos); } 513 514 constexpr bool 515 _M_valid() const noexcept 516 { 517 if constexpr (__variant::__never_valueless<_Types...>()) 518 return true; 519 // It would be nice if we could just return true for -fno-exceptions. 520 // It's possible (but inadvisable) that a std::variant could become 521 // valueless in a translation unit compiled with -fexceptions and then 522 // be passed to functions compiled with -fno-exceptions. We would need 523 // some #ifdef _GLIBCXX_NO_EXCEPTIONS_GLOBALLY property to elide all 524 // checks for valueless_by_exception(). 525 return this->_M_index != static_cast<__index_type>(variant_npos); 526 } 527 528 _Variadic_union<_Types...> _M_u; 529 using __index_type = __select_index<_Types...>; 530 __index_type _M_index; 531 }; 532 533 // Implementation of v.emplace<N>(args...). 534 template<size_t _Np, bool _Triv, typename... _Types, typename... _Args> 535 _GLIBCXX20_CONSTEXPR 536 inline void 537 __emplace(_Variant_storage<_Triv, _Types...>& __v, _Args&&... __args) 538 { 539 __v._M_reset(); 540 auto* __addr = std::__addressof(__variant::__get_n<_Np>(__v._M_u)); 541 std::_Construct(__addr, std::forward<_Args>(__args)...); 542 // Construction didn't throw, so can set the new index now: 543 __v._M_index = _Np; 544 } 545 546 template<typename... _Types> 547 using _Variant_storage_alias = 548 _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>; 549 550 // The following are (Copy|Move) (ctor|assign) layers for forwarding 551 // triviality and handling non-trivial SMF behaviors. 552 553 template<bool, typename... _Types> 554 struct _Copy_ctor_base : _Variant_storage_alias<_Types...> 555 { 556 using _Base = _Variant_storage_alias<_Types...>; 557 using _Base::_Base; 558 559 _GLIBCXX20_CONSTEXPR 560 _Copy_ctor_base(const _Copy_ctor_base& __rhs) 561 noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor) 562 { 563 __variant::__raw_idx_visit( 564 [this](auto&& __rhs_mem, auto __rhs_index) mutable 565 { 566 constexpr size_t __j = __rhs_index; 567 if constexpr (__j != variant_npos) 568 std::_Construct(std::__addressof(this->_M_u), 569 in_place_index<__j>, __rhs_mem); 570 }, __variant_cast<_Types...>(__rhs)); 571 this->_M_index = __rhs._M_index; 572 } 573 574 _Copy_ctor_base(_Copy_ctor_base&&) = default; 575 _Copy_ctor_base& operator=(const _Copy_ctor_base&) = default; 576 _Copy_ctor_base& operator=(_Copy_ctor_base&&) = default; 577 }; 578 579 template<typename... _Types> 580 struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...> 581 { 582 using _Base = _Variant_storage_alias<_Types...>; 583 using _Base::_Base; 584 }; 585 586 template<typename... _Types> 587 using _Copy_ctor_alias = 588 _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>; 589 590 template<bool, typename... _Types> 591 struct _Move_ctor_base : _Copy_ctor_alias<_Types...> 592 { 593 using _Base = _Copy_ctor_alias<_Types...>; 594 using _Base::_Base; 595 596 _GLIBCXX20_CONSTEXPR 597 _Move_ctor_base(_Move_ctor_base&& __rhs) 598 noexcept(_Traits<_Types...>::_S_nothrow_move_ctor) 599 { 600 __variant::__raw_idx_visit( 601 [this](auto&& __rhs_mem, auto __rhs_index) mutable 602 { 603 constexpr size_t __j = __rhs_index; 604 if constexpr (__j != variant_npos) 605 std::_Construct(std::__addressof(this->_M_u), 606 in_place_index<__j>, 607 std::forward<decltype(__rhs_mem)>(__rhs_mem)); 608 }, __variant_cast<_Types...>(std::move(__rhs))); 609 this->_M_index = __rhs._M_index; 610 } 611 612 _Move_ctor_base(const _Move_ctor_base&) = default; 613 _Move_ctor_base& operator=(const _Move_ctor_base&) = default; 614 _Move_ctor_base& operator=(_Move_ctor_base&&) = default; 615 }; 616 617 template<typename... _Types> 618 struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...> 619 { 620 using _Base = _Copy_ctor_alias<_Types...>; 621 using _Base::_Base; 622 }; 623 624 template<typename... _Types> 625 using _Move_ctor_alias = 626 _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>; 627 628 template<bool, typename... _Types> 629 struct _Copy_assign_base : _Move_ctor_alias<_Types...> 630 { 631 using _Base = _Move_ctor_alias<_Types...>; 632 using _Base::_Base; 633 634 _GLIBCXX20_CONSTEXPR 635 _Copy_assign_base& 636 operator=(const _Copy_assign_base& __rhs) 637 noexcept(_Traits<_Types...>::_S_nothrow_copy_assign) 638 { 639 __variant::__raw_idx_visit( 640 [this](auto&& __rhs_mem, auto __rhs_index) mutable 641 { 642 constexpr size_t __j = __rhs_index; 643 if constexpr (__j == variant_npos) 644 this->_M_reset(); // Make *this valueless. 645 else if (this->_M_index == __j) 646 __variant::__get<__j>(*this) = __rhs_mem; 647 else 648 { 649 using _Tj = typename _Nth_type<__j, _Types...>::type; 650 if constexpr (is_nothrow_copy_constructible_v<_Tj> 651 || !is_nothrow_move_constructible_v<_Tj>) 652 __variant::__emplace<__j>(*this, __rhs_mem); 653 else 654 { 655 using _Variant = variant<_Types...>; 656 _Variant& __self = __variant_cast<_Types...>(*this); 657 __self = _Variant(in_place_index<__j>, __rhs_mem); 658 } 659 } 660 }, __variant_cast<_Types...>(__rhs)); 661 return *this; 662 } 663 664 _Copy_assign_base(const _Copy_assign_base&) = default; 665 _Copy_assign_base(_Copy_assign_base&&) = default; 666 _Copy_assign_base& operator=(_Copy_assign_base&&) = default; 667 }; 668 669 template<typename... _Types> 670 struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...> 671 { 672 using _Base = _Move_ctor_alias<_Types...>; 673 using _Base::_Base; 674 }; 675 676 template<typename... _Types> 677 using _Copy_assign_alias = 678 _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, _Types...>; 679 680 template<bool, typename... _Types> 681 struct _Move_assign_base : _Copy_assign_alias<_Types...> 682 { 683 using _Base = _Copy_assign_alias<_Types...>; 684 using _Base::_Base; 685 686 _GLIBCXX20_CONSTEXPR 687 _Move_assign_base& 688 operator=(_Move_assign_base&& __rhs) 689 noexcept(_Traits<_Types...>::_S_nothrow_move_assign) 690 { 691 __variant::__raw_idx_visit( 692 [this](auto&& __rhs_mem, auto __rhs_index) mutable 693 { 694 constexpr size_t __j = __rhs_index; 695 if constexpr (__j != variant_npos) 696 { 697 if (this->_M_index == __j) 698 __variant::__get<__j>(*this) = std::move(__rhs_mem); 699 else 700 { 701 using _Tj = typename _Nth_type<__j, _Types...>::type; 702 if constexpr (is_nothrow_move_constructible_v<_Tj>) 703 __variant::__emplace<__j>(*this, std::move(__rhs_mem)); 704 else 705 { 706 using _Variant = variant<_Types...>; 707 _Variant& __self = __variant_cast<_Types...>(*this); 708 __self.template emplace<__j>(std::move(__rhs_mem)); 709 } 710 } 711 } 712 else 713 this->_M_reset(); 714 }, __variant_cast<_Types...>(__rhs)); 715 return *this; 716 } 717 718 _Move_assign_base(const _Move_assign_base&) = default; 719 _Move_assign_base(_Move_assign_base&&) = default; 720 _Move_assign_base& operator=(const _Move_assign_base&) = default; 721 }; 722 723 template<typename... _Types> 724 struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...> 725 { 726 using _Base = _Copy_assign_alias<_Types...>; 727 using _Base::_Base; 728 }; 729 730 template<typename... _Types> 731 using _Move_assign_alias = 732 _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign, _Types...>; 733 734 template<typename... _Types> 735 struct _Variant_base : _Move_assign_alias<_Types...> 736 { 737 using _Base = _Move_assign_alias<_Types...>; 738 739 constexpr 740 _Variant_base() noexcept(_Traits<_Types...>::_S_nothrow_default_ctor) 741 : _Variant_base(in_place_index<0>) { } 742 743 template<size_t _Np, typename... _Args> 744 constexpr explicit 745 _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args) 746 : _Base(__i, std::forward<_Args>(__args)...) 747 { } 748 749 _Variant_base(const _Variant_base&) = default; 750 _Variant_base(_Variant_base&&) = default; 751 _Variant_base& operator=(const _Variant_base&) = default; 752 _Variant_base& operator=(_Variant_base&&) = default; 753 }; 754 755 template<typename _Tp, typename... _Types> 756 inline constexpr bool __exactly_once 757 = std::__find_uniq_type_in_pack<_Tp, _Types...>() < sizeof...(_Types); 758 759 // Helper used to check for valid conversions that don't involve narrowing. 760 template<typename _Ti> struct _Arr { _Ti _M_x[1]; }; 761 762 // "Build an imaginary function FUN(Ti) for each alternative type Ti" 763 template<size_t _Ind, typename _Tp, typename _Ti, typename = void> 764 struct _Build_FUN 765 { 766 // This function means 'using _Build_FUN<I, T, Ti>::_S_fun;' is valid, 767 // but only static functions will be considered in the call below. 768 void _S_fun(); 769 }; 770 771 // "... for which Ti x[] = {std::forward<T>(t)}; is well-formed." 772 template<size_t _Ind, typename _Tp, typename _Ti> 773 struct _Build_FUN<_Ind, _Tp, _Ti, 774 void_t<decltype(_Arr<_Ti>{{std::declval<_Tp>()}})>> 775 { 776 // This is the FUN function for type _Ti, with index _Ind 777 static integral_constant<size_t, _Ind> _S_fun(_Ti); 778 }; 779 780 template<typename _Tp, typename _Variant, 781 typename = make_index_sequence<variant_size_v<_Variant>>> 782 struct _Build_FUNs; 783 784 template<typename _Tp, typename... _Ti, size_t... _Ind> 785 struct _Build_FUNs<_Tp, variant<_Ti...>, index_sequence<_Ind...>> 786 : _Build_FUN<_Ind, _Tp, _Ti>... 787 { 788 using _Build_FUN<_Ind, _Tp, _Ti>::_S_fun...; 789 }; 790 791 // The index j of the overload FUN(Tj) selected by overload resolution 792 // for FUN(std::forward<_Tp>(t)) 793 template<typename _Tp, typename _Variant> 794 using _FUN_type 795 = decltype(_Build_FUNs<_Tp, _Variant>::_S_fun(std::declval<_Tp>())); 796 797 // The index selected for FUN(std::forward<T>(t)), or variant_npos if none. 798 template<typename _Tp, typename _Variant, typename = void> 799 struct __accepted_index 800 : integral_constant<size_t, variant_npos> 801 { }; 802 803 template<typename _Tp, typename _Variant> 804 struct __accepted_index<_Tp, _Variant, void_t<_FUN_type<_Tp, _Variant>>> 805 : _FUN_type<_Tp, _Variant> 806 { }; 807 808 template <typename _Maybe_variant_cookie, typename _Variant> 809 struct _Extra_visit_slot_needed 810 { 811 template <typename> struct _Variant_never_valueless; 812 813 template <typename... _Types> 814 struct _Variant_never_valueless<variant<_Types...>> 815 : bool_constant<__variant::__never_valueless<_Types...>()> {}; 816 817 static constexpr bool value = 818 (is_same_v<_Maybe_variant_cookie, __variant_cookie> 819 || is_same_v<_Maybe_variant_cookie, __variant_idx_cookie>) 820 && !_Variant_never_valueless<__remove_cvref_t<_Variant>>::value; 821 }; 822 823 // Used for storing a multi-dimensional vtable. 824 template<typename _Tp, size_t... _Dimensions> 825 struct _Multi_array; 826 827 // Partial specialization with rank zero, stores a single _Tp element. 828 template<typename _Tp> 829 struct _Multi_array<_Tp> 830 { 831 template<typename> 832 struct __untag_result 833 : false_type 834 { using element_type = _Tp; }; 835 836 template <typename... _Args> 837 struct __untag_result<const void(*)(_Args...)> 838 : false_type 839 { using element_type = void(*)(_Args...); }; 840 841 template <typename... _Args> 842 struct __untag_result<__variant_cookie(*)(_Args...)> 843 : false_type 844 { using element_type = void(*)(_Args...); }; 845 846 template <typename... _Args> 847 struct __untag_result<__variant_idx_cookie(*)(_Args...)> 848 : false_type 849 { using element_type = void(*)(_Args...); }; 850 851 template <typename _Res, typename... _Args> 852 struct __untag_result<__deduce_visit_result<_Res>(*)(_Args...)> 853 : true_type 854 { using element_type = _Res(*)(_Args...); }; 855 856 using __result_is_deduced = __untag_result<_Tp>; 857 858 constexpr const typename __untag_result<_Tp>::element_type& 859 _M_access() const 860 { return _M_data; } 861 862 typename __untag_result<_Tp>::element_type _M_data; 863 }; 864 865 // Partial specialization with rank >= 1. 866 template<typename _Ret, 867 typename _Visitor, 868 typename... _Variants, 869 size_t __first, size_t... __rest> 870 struct _Multi_array<_Ret(*)(_Visitor, _Variants...), __first, __rest...> 871 { 872 static constexpr size_t __index = 873 sizeof...(_Variants) - sizeof...(__rest) - 1; 874 875 using _Variant = typename _Nth_type<__index, _Variants...>::type; 876 877 static constexpr int __do_cookie = 878 _Extra_visit_slot_needed<_Ret, _Variant>::value ? 1 : 0; 879 880 using _Tp = _Ret(*)(_Visitor, _Variants...); 881 882 template<typename... _Args> 883 constexpr decltype(auto) 884 _M_access(size_t __first_index, _Args... __rest_indices) const 885 { 886 return _M_arr[__first_index + __do_cookie] 887 ._M_access(__rest_indices...); 888 } 889 890 _Multi_array<_Tp, __rest...> _M_arr[__first + __do_cookie]; 891 }; 892 893 // Creates a multi-dimensional vtable recursively. 894 // 895 // For example, 896 // visit([](auto, auto){}, 897 // variant<int, char>(), // typedef'ed as V1 898 // variant<float, double, long double>()) // typedef'ed as V2 899 // will trigger instantiations of: 900 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>, 901 // tuple<V1&&, V2&&>, std::index_sequence<>> 902 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>, 903 // tuple<V1&&, V2&&>, std::index_sequence<0>> 904 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 905 // tuple<V1&&, V2&&>, std::index_sequence<0, 0>> 906 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 907 // tuple<V1&&, V2&&>, std::index_sequence<0, 1>> 908 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 909 // tuple<V1&&, V2&&>, std::index_sequence<0, 2>> 910 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>, 911 // tuple<V1&&, V2&&>, std::index_sequence<1>> 912 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 913 // tuple<V1&&, V2&&>, std::index_sequence<1, 0>> 914 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 915 // tuple<V1&&, V2&&>, std::index_sequence<1, 1>> 916 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 917 // tuple<V1&&, V2&&>, std::index_sequence<1, 2>> 918 // The returned multi-dimensional vtable can be fast accessed by the visitor 919 // using index calculation. 920 template<typename _Array_type, typename _Index_seq> 921 struct __gen_vtable_impl; 922 923 // Defines the _S_apply() member that returns a _Multi_array populated 924 // with function pointers that perform the visitation expressions e(m) 925 // for each valid pack of indexes into the variant types _Variants. 926 // 927 // This partial specialization builds up the index sequences by recursively 928 // calling _S_apply() on the next specialization of __gen_vtable_impl. 929 // The base case of the recursion defines the actual function pointers. 930 template<typename _Result_type, typename _Visitor, size_t... __dimensions, 931 typename... _Variants, size_t... __indices> 932 struct __gen_vtable_impl< 933 _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>, 934 std::index_sequence<__indices...>> 935 { 936 using _Next = 937 remove_reference_t<typename _Nth_type<sizeof...(__indices), 938 _Variants...>::type>; 939 using _Array_type = 940 _Multi_array<_Result_type (*)(_Visitor, _Variants...), 941 __dimensions...>; 942 943 static constexpr _Array_type 944 _S_apply() 945 { 946 _Array_type __vtable{}; 947 _S_apply_all_alts( 948 __vtable, make_index_sequence<variant_size_v<_Next>>()); 949 return __vtable; 950 } 951 952 template<size_t... __var_indices> 953 static constexpr void 954 _S_apply_all_alts(_Array_type& __vtable, 955 std::index_sequence<__var_indices...>) 956 { 957 if constexpr (_Extra_visit_slot_needed<_Result_type, _Next>::value) 958 (_S_apply_single_alt<true, __var_indices>( 959 __vtable._M_arr[__var_indices + 1], 960 &(__vtable._M_arr[0])), ...); 961 else 962 (_S_apply_single_alt<false, __var_indices>( 963 __vtable._M_arr[__var_indices]), ...); 964 } 965 966 template<bool __do_cookie, size_t __index, typename _Tp> 967 static constexpr void 968 _S_apply_single_alt(_Tp& __element, _Tp* __cookie_element = nullptr) 969 { 970 if constexpr (__do_cookie) 971 { 972 __element = __gen_vtable_impl< 973 _Tp, 974 std::index_sequence<__indices..., __index>>::_S_apply(); 975 *__cookie_element = __gen_vtable_impl< 976 _Tp, 977 std::index_sequence<__indices..., variant_npos>>::_S_apply(); 978 } 979 else 980 { 981 auto __tmp_element = __gen_vtable_impl< 982 remove_reference_t<decltype(__element)>, 983 std::index_sequence<__indices..., __index>>::_S_apply(); 984 static_assert(is_same_v<_Tp, decltype(__tmp_element)>, 985 "std::visit requires the visitor to have the same " 986 "return type for all alternatives of a variant"); 987 __element = __tmp_element; 988 } 989 } 990 }; 991 992 // This partial specialization is the base case for the recursion. 993 // It populates a _Multi_array element with the address of a function 994 // that invokes the visitor with the alternatives specified by __indices. 995 template<typename _Result_type, typename _Visitor, typename... _Variants, 996 size_t... __indices> 997 struct __gen_vtable_impl< 998 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>, 999 std::index_sequence<__indices...>> 1000 { 1001 using _Array_type = 1002 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>; 1003 1004 template<size_t __index, typename _Variant> 1005 static constexpr decltype(auto) 1006 __element_by_index_or_cookie(_Variant&& __var) noexcept 1007 { 1008 if constexpr (__index != variant_npos) 1009 return __variant::__get<__index>(std::forward<_Variant>(__var)); 1010 else 1011 return __variant_cookie{}; 1012 } 1013 1014 static constexpr decltype(auto) 1015 __visit_invoke(_Visitor&& __visitor, _Variants... __vars) 1016 { 1017 if constexpr (is_same_v<_Result_type, __variant_idx_cookie>) 1018 // For raw visitation using indices, pass the indices to the visitor 1019 // and discard the return value: 1020 std::__invoke(std::forward<_Visitor>(__visitor), 1021 __element_by_index_or_cookie<__indices>( 1022 std::forward<_Variants>(__vars))..., 1023 integral_constant<size_t, __indices>()...); 1024 else if constexpr (is_same_v<_Result_type, __variant_cookie>) 1025 // For raw visitation without indices, and discard the return value: 1026 std::__invoke(std::forward<_Visitor>(__visitor), 1027 __element_by_index_or_cookie<__indices>( 1028 std::forward<_Variants>(__vars))...); 1029 else if constexpr (_Array_type::__result_is_deduced::value) 1030 // For the usual std::visit case deduce the return value: 1031 return std::__invoke(std::forward<_Visitor>(__visitor), 1032 __element_by_index_or_cookie<__indices>( 1033 std::forward<_Variants>(__vars))...); 1034 else // for std::visit<R> use INVOKE<R> 1035 return std::__invoke_r<_Result_type>( 1036 std::forward<_Visitor>(__visitor), 1037 __variant::__get<__indices>(std::forward<_Variants>(__vars))...); 1038 } 1039 1040 static constexpr auto 1041 _S_apply() 1042 { 1043 if constexpr (_Array_type::__result_is_deduced::value) 1044 { 1045 constexpr bool __visit_ret_type_mismatch = 1046 !is_same_v<typename _Result_type::type, 1047 decltype(__visit_invoke(std::declval<_Visitor>(), 1048 std::declval<_Variants>()...))>; 1049 if constexpr (__visit_ret_type_mismatch) 1050 { 1051 struct __cannot_match {}; 1052 return __cannot_match{}; 1053 } 1054 else 1055 return _Array_type{&__visit_invoke}; 1056 } 1057 else 1058 return _Array_type{&__visit_invoke}; 1059 } 1060 }; 1061 1062 template<typename _Result_type, typename _Visitor, typename... _Variants> 1063 struct __gen_vtable 1064 { 1065 using _Array_type = 1066 _Multi_array<_Result_type (*)(_Visitor, _Variants...), 1067 variant_size_v<remove_reference_t<_Variants>>...>; 1068 1069 static constexpr _Array_type _S_vtable 1070 = __gen_vtable_impl<_Array_type, std::index_sequence<>>::_S_apply(); 1071 }; 1072 1073 template<size_t _Np, typename _Tp> 1074 struct _Base_dedup : public _Tp { }; 1075 1076 template<typename _Variant, typename __indices> 1077 struct _Variant_hash_base; 1078 1079 template<typename... _Types, size_t... __indices> 1080 struct _Variant_hash_base<variant<_Types...>, 1081 std::index_sequence<__indices...>> 1082 : _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { }; 1083 1084 // Equivalent to decltype(get<_Np>(as-variant(declval<_Variant>()))) 1085 template<size_t _Np, typename _Variant, 1086 typename _AsV = decltype(__variant::__as(std::declval<_Variant>())), 1087 typename _Tp = variant_alternative_t<_Np, remove_reference_t<_AsV>>> 1088 using __get_t 1089 = __conditional_t<is_lvalue_reference_v<_Variant>, _Tp&, _Tp&&>; 1090 1091 // Return type of std::visit. 1092 template<typename _Visitor, typename... _Variants> 1093 using __visit_result_t 1094 = invoke_result_t<_Visitor, __get_t<0, _Variants>...>; 1095 1096 template<typename _Tp, typename... _Types> 1097 constexpr inline bool __same_types = (is_same_v<_Tp, _Types> && ...); 1098 1099 template <typename _Visitor, typename _Variant, size_t... _Idxs> 1100 constexpr bool __check_visitor_results(std::index_sequence<_Idxs...>) 1101 { 1102 return __same_types< 1103 invoke_result_t<_Visitor, __get_t<_Idxs, _Variant>>... 1104 >; 1105 } 1106 1107} // namespace __variant 1108} // namespace __detail 1109 1110 template<typename _Tp, typename... _Types> 1111 constexpr bool 1112 holds_alternative(const variant<_Types...>& __v) noexcept 1113 { 1114 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1115 "T must occur exactly once in alternatives"); 1116 return __v.index() == std::__find_uniq_type_in_pack<_Tp, _Types...>(); 1117 } 1118 1119 template<typename _Tp, typename... _Types> 1120 constexpr _Tp& 1121 get(variant<_Types...>& __v) 1122 { 1123 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1124 "T must occur exactly once in alternatives"); 1125 static_assert(!is_void_v<_Tp>, "_Tp must not be void"); 1126 constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); 1127 return std::get<__n>(__v); 1128 } 1129 1130 template<typename _Tp, typename... _Types> 1131 constexpr _Tp&& 1132 get(variant<_Types...>&& __v) 1133 { 1134 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1135 "T must occur exactly once in alternatives"); 1136 static_assert(!is_void_v<_Tp>, "_Tp must not be void"); 1137 constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); 1138 return std::get<__n>(std::move(__v)); 1139 } 1140 1141 template<typename _Tp, typename... _Types> 1142 constexpr const _Tp& 1143 get(const variant<_Types...>& __v) 1144 { 1145 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1146 "T must occur exactly once in alternatives"); 1147 static_assert(!is_void_v<_Tp>, "_Tp must not be void"); 1148 constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); 1149 return std::get<__n>(__v); 1150 } 1151 1152 template<typename _Tp, typename... _Types> 1153 constexpr const _Tp&& 1154 get(const variant<_Types...>&& __v) 1155 { 1156 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1157 "T must occur exactly once in alternatives"); 1158 static_assert(!is_void_v<_Tp>, "_Tp must not be void"); 1159 constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); 1160 return std::get<__n>(std::move(__v)); 1161 } 1162 1163 template<size_t _Np, typename... _Types> 1164 constexpr add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>> 1165 get_if(variant<_Types...>* __ptr) noexcept 1166 { 1167 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; 1168 static_assert(_Np < sizeof...(_Types), 1169 "The index must be in [0, number of alternatives)"); 1170 static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void"); 1171 if (__ptr && __ptr->index() == _Np) 1172 return std::addressof(__detail::__variant::__get<_Np>(*__ptr)); 1173 return nullptr; 1174 } 1175 1176 template<size_t _Np, typename... _Types> 1177 constexpr 1178 add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>> 1179 get_if(const variant<_Types...>* __ptr) noexcept 1180 { 1181 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; 1182 static_assert(_Np < sizeof...(_Types), 1183 "The index must be in [0, number of alternatives)"); 1184 static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void"); 1185 if (__ptr && __ptr->index() == _Np) 1186 return std::addressof(__detail::__variant::__get<_Np>(*__ptr)); 1187 return nullptr; 1188 } 1189 1190 template<typename _Tp, typename... _Types> 1191 constexpr add_pointer_t<_Tp> 1192 get_if(variant<_Types...>* __ptr) noexcept 1193 { 1194 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1195 "T must occur exactly once in alternatives"); 1196 static_assert(!is_void_v<_Tp>, "_Tp must not be void"); 1197 constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); 1198 return std::get_if<__n>(__ptr); 1199 } 1200 1201 template<typename _Tp, typename... _Types> 1202 constexpr add_pointer_t<const _Tp> 1203 get_if(const variant<_Types...>* __ptr) noexcept 1204 { 1205 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1206 "T must occur exactly once in alternatives"); 1207 static_assert(!is_void_v<_Tp>, "_Tp must not be void"); 1208 constexpr size_t __n = std::__find_uniq_type_in_pack<_Tp, _Types...>(); 1209 return std::get_if<__n>(__ptr); 1210 } 1211 1212 struct monostate { }; 1213 1214#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \ 1215 template<typename... _Types> \ 1216 constexpr bool operator __OP(const variant<_Types...>& __lhs, \ 1217 const variant<_Types...>& __rhs) \ 1218 { \ 1219 bool __ret = true; \ 1220 __detail::__variant::__raw_idx_visit( \ 1221 [&__ret, &__lhs] (auto&& __rhs_mem, auto __rhs_index) mutable \ 1222 { \ 1223 if constexpr (__rhs_index != variant_npos) \ 1224 { \ 1225 if (__lhs.index() == __rhs_index) \ 1226 { \ 1227 auto& __this_mem = std::get<__rhs_index>(__lhs); \ 1228 __ret = __this_mem __OP __rhs_mem; \ 1229 } \ 1230 else \ 1231 __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \ 1232 } \ 1233 else \ 1234 __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \ 1235 }, __rhs); \ 1236 return __ret; \ 1237 } 1238 1239 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less) 1240 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal) 1241 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal) 1242 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal) 1243 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal) 1244 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater) 1245 1246#undef _VARIANT_RELATION_FUNCTION_TEMPLATE 1247 1248 constexpr bool operator==(monostate, monostate) noexcept { return true; } 1249 1250#ifdef __cpp_lib_three_way_comparison 1251 template<typename... _Types> 1252 requires (three_way_comparable<_Types> && ...) 1253 constexpr 1254 common_comparison_category_t<compare_three_way_result_t<_Types>...> 1255 operator<=>(const variant<_Types...>& __v, const variant<_Types...>& __w) 1256 { 1257 common_comparison_category_t<compare_three_way_result_t<_Types>...> __ret 1258 = strong_ordering::equal; 1259 1260 __detail::__variant::__raw_idx_visit( 1261 [&__ret, &__v] (auto&& __w_mem, auto __w_index) mutable 1262 { 1263 if constexpr (__w_index != variant_npos) 1264 { 1265 if (__v.index() == __w_index) 1266 { 1267 auto& __this_mem = std::get<__w_index>(__v); 1268 __ret = __this_mem <=> __w_mem; 1269 return; 1270 } 1271 } 1272 __ret = (__v.index() + 1) <=> (__w_index + 1); 1273 }, __w); 1274 return __ret; 1275 } 1276 1277 constexpr strong_ordering 1278 operator<=>(monostate, monostate) noexcept { return strong_ordering::equal; } 1279#else 1280 constexpr bool operator!=(monostate, monostate) noexcept { return false; } 1281 constexpr bool operator<(monostate, monostate) noexcept { return false; } 1282 constexpr bool operator>(monostate, monostate) noexcept { return false; } 1283 constexpr bool operator<=(monostate, monostate) noexcept { return true; } 1284 constexpr bool operator>=(monostate, monostate) noexcept { return true; } 1285#endif 1286 1287 template<typename _Visitor, typename... _Variants> 1288 constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...> 1289 visit(_Visitor&&, _Variants&&...); 1290 1291 template<typename... _Types> 1292 _GLIBCXX20_CONSTEXPR 1293 inline enable_if_t<(is_move_constructible_v<_Types> && ...) 1294 && (is_swappable_v<_Types> && ...)> 1295 swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs) 1296 noexcept(noexcept(__lhs.swap(__rhs))) 1297 { __lhs.swap(__rhs); } 1298 1299 template<typename... _Types> 1300 enable_if_t<!((is_move_constructible_v<_Types> && ...) 1301 && (is_swappable_v<_Types> && ...))> 1302 swap(variant<_Types...>&, variant<_Types...>&) = delete; 1303 1304 class bad_variant_access : public exception 1305 { 1306 public: 1307 bad_variant_access() noexcept { } 1308 1309 const char* what() const noexcept override 1310 { return _M_reason; } 1311 1312 private: 1313 bad_variant_access(const char* __reason) noexcept : _M_reason(__reason) { } 1314 1315 // Must point to a string with static storage duration: 1316 const char* _M_reason = "bad variant access"; 1317 1318 friend void __throw_bad_variant_access(const char* __what); 1319 }; 1320 1321 // Must only be called with a string literal 1322 inline void 1323 __throw_bad_variant_access(const char* __what) 1324 { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); } 1325 1326 inline void 1327 __throw_bad_variant_access(bool __valueless) 1328 { 1329 if (__valueless) [[__unlikely__]] 1330 __throw_bad_variant_access("std::get: variant is valueless"); 1331 else 1332 __throw_bad_variant_access("std::get: wrong index for variant"); 1333 } 1334 1335 template<typename... _Types> 1336 class variant 1337 : private __detail::__variant::_Variant_base<_Types...>, 1338 private _Enable_default_constructor< 1339 __detail::__variant::_Traits<_Types...>::_S_default_ctor, 1340 variant<_Types...>>, 1341 private _Enable_copy_move< 1342 __detail::__variant::_Traits<_Types...>::_S_copy_ctor, 1343 __detail::__variant::_Traits<_Types...>::_S_copy_assign, 1344 __detail::__variant::_Traits<_Types...>::_S_move_ctor, 1345 __detail::__variant::_Traits<_Types...>::_S_move_assign, 1346 variant<_Types...>> 1347 { 1348 private: 1349 template <typename... _UTypes, typename _Tp> 1350 friend _GLIBCXX20_CONSTEXPR decltype(auto) 1351 __variant_cast(_Tp&&); 1352 1353 static_assert(sizeof...(_Types) > 0, 1354 "variant must have at least one alternative"); 1355 static_assert(!(std::is_reference_v<_Types> || ...), 1356 "variant must have no reference alternative"); 1357 static_assert(!(std::is_void_v<_Types> || ...), 1358 "variant must have no void alternative"); 1359 1360 using _Base = __detail::__variant::_Variant_base<_Types...>; 1361 using _Default_ctor_enabler = 1362 _Enable_default_constructor< 1363 __detail::__variant::_Traits<_Types...>::_S_default_ctor, 1364 variant<_Types...>>; 1365 1366 template<typename _Tp> 1367 static constexpr bool __not_self 1368 = !is_same_v<__remove_cvref_t<_Tp>, variant>; 1369 1370 template<typename _Tp> 1371 static constexpr bool 1372 __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>; 1373 1374 template<typename _Tp> 1375 static constexpr size_t __accepted_index 1376 = __detail::__variant::__accepted_index<_Tp, variant>::value; 1377 1378 template<size_t _Np, typename = enable_if_t<(_Np < sizeof...(_Types))>> 1379 using __to_type = typename _Nth_type<_Np, _Types...>::type; 1380 1381 template<typename _Tp, typename = enable_if_t<__not_self<_Tp>>> 1382 using __accepted_type = __to_type<__accepted_index<_Tp>>; 1383 1384 template<typename _Tp> 1385 static constexpr size_t __index_of 1386 = std::__find_uniq_type_in_pack<_Tp, _Types...>(); 1387 1388 using _Traits = __detail::__variant::_Traits<_Types...>; 1389 1390 template<typename _Tp> 1391 struct __is_in_place_tag : false_type { }; 1392 template<typename _Tp> 1393 struct __is_in_place_tag<in_place_type_t<_Tp>> : true_type { }; 1394 template<size_t _Np> 1395 struct __is_in_place_tag<in_place_index_t<_Np>> : true_type { }; 1396 1397 template<typename _Tp> 1398 static constexpr bool __not_in_place_tag 1399 = !__is_in_place_tag<__remove_cvref_t<_Tp>>::value; 1400 1401 public: 1402 variant() = default; 1403 variant(const variant& __rhs) = default; 1404 variant(variant&&) = default; 1405 variant& operator=(const variant&) = default; 1406 variant& operator=(variant&&) = default; 1407 _GLIBCXX20_CONSTEXPR ~variant() = default; 1408 1409 template<typename _Tp, 1410 typename = enable_if_t<sizeof...(_Types) != 0>, 1411 typename = enable_if_t<__not_in_place_tag<_Tp>>, 1412 typename _Tj = __accepted_type<_Tp&&>, 1413 typename = enable_if_t<__exactly_once<_Tj> 1414 && is_constructible_v<_Tj, _Tp>>> 1415 constexpr 1416 variant(_Tp&& __t) 1417 noexcept(is_nothrow_constructible_v<_Tj, _Tp>) 1418 : variant(in_place_index<__accepted_index<_Tp>>, 1419 std::forward<_Tp>(__t)) 1420 { } 1421 1422 template<typename _Tp, typename... _Args, 1423 typename = enable_if_t<__exactly_once<_Tp> 1424 && is_constructible_v<_Tp, _Args...>>> 1425 constexpr explicit 1426 variant(in_place_type_t<_Tp>, _Args&&... __args) 1427 : variant(in_place_index<__index_of<_Tp>>, 1428 std::forward<_Args>(__args)...) 1429 { } 1430 1431 template<typename _Tp, typename _Up, typename... _Args, 1432 typename = enable_if_t<__exactly_once<_Tp> 1433 && is_constructible_v<_Tp, 1434 initializer_list<_Up>&, _Args...>>> 1435 constexpr explicit 1436 variant(in_place_type_t<_Tp>, initializer_list<_Up> __il, 1437 _Args&&... __args) 1438 : variant(in_place_index<__index_of<_Tp>>, __il, 1439 std::forward<_Args>(__args)...) 1440 { } 1441 1442 template<size_t _Np, typename... _Args, 1443 typename _Tp = __to_type<_Np>, 1444 typename = enable_if_t<is_constructible_v<_Tp, _Args...>>> 1445 constexpr explicit 1446 variant(in_place_index_t<_Np>, _Args&&... __args) 1447 : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...), 1448 _Default_ctor_enabler(_Enable_default_constructor_tag{}) 1449 { } 1450 1451 template<size_t _Np, typename _Up, typename... _Args, 1452 typename _Tp = __to_type<_Np>, 1453 typename = enable_if_t<is_constructible_v<_Tp, 1454 initializer_list<_Up>&, 1455 _Args...>>> 1456 constexpr explicit 1457 variant(in_place_index_t<_Np>, initializer_list<_Up> __il, 1458 _Args&&... __args) 1459 : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...), 1460 _Default_ctor_enabler(_Enable_default_constructor_tag{}) 1461 { } 1462 1463 template<typename _Tp> 1464 _GLIBCXX20_CONSTEXPR 1465 enable_if_t<__exactly_once<__accepted_type<_Tp&&>> 1466 && is_constructible_v<__accepted_type<_Tp&&>, _Tp> 1467 && is_assignable_v<__accepted_type<_Tp&&>&, _Tp>, 1468 variant&> 1469 operator=(_Tp&& __rhs) 1470 noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp> 1471 && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp>) 1472 { 1473 constexpr auto __index = __accepted_index<_Tp>; 1474 if (index() == __index) 1475 std::get<__index>(*this) = std::forward<_Tp>(__rhs); 1476 else 1477 { 1478 using _Tj = __accepted_type<_Tp&&>; 1479 if constexpr (is_nothrow_constructible_v<_Tj, _Tp> 1480 || !is_nothrow_move_constructible_v<_Tj>) 1481 this->emplace<__index>(std::forward<_Tp>(__rhs)); 1482 else 1483 // _GLIBCXX_RESOLVE_LIB_DEFECTS 1484 // 3585. converting assignment with immovable alternative 1485 this->emplace<__index>(_Tj(std::forward<_Tp>(__rhs))); 1486 } 1487 return *this; 1488 } 1489 1490 template<typename _Tp, typename... _Args> 1491 _GLIBCXX20_CONSTEXPR 1492 enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>, 1493 _Tp&> 1494 emplace(_Args&&... __args) 1495 { 1496 constexpr size_t __index = __index_of<_Tp>; 1497 return this->emplace<__index>(std::forward<_Args>(__args)...); 1498 } 1499 1500 template<typename _Tp, typename _Up, typename... _Args> 1501 _GLIBCXX20_CONSTEXPR 1502 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...> 1503 && __exactly_once<_Tp>, 1504 _Tp&> 1505 emplace(initializer_list<_Up> __il, _Args&&... __args) 1506 { 1507 constexpr size_t __index = __index_of<_Tp>; 1508 return this->emplace<__index>(__il, std::forward<_Args>(__args)...); 1509 } 1510 1511 template<size_t _Np, typename... _Args> 1512 _GLIBCXX20_CONSTEXPR 1513 enable_if_t<is_constructible_v<__to_type<_Np>, _Args...>, 1514 __to_type<_Np>&> 1515 emplace(_Args&&... __args) 1516 { 1517 namespace __variant = std::__detail::__variant; 1518 using type = typename _Nth_type<_Np, _Types...>::type; 1519 // Provide the strong exception-safety guarantee when possible, 1520 // to avoid becoming valueless. 1521 if constexpr (is_nothrow_constructible_v<type, _Args...>) 1522 { 1523 __variant::__emplace<_Np>(*this, std::forward<_Args>(__args)...); 1524 } 1525 else if constexpr (is_scalar_v<type>) 1526 { 1527 // This might invoke a potentially-throwing conversion operator: 1528 const type __tmp(std::forward<_Args>(__args)...); 1529 // But this won't throw: 1530 __variant::__emplace<_Np>(*this, __tmp); 1531 } 1532 else if constexpr (__variant::_Never_valueless_alt<type>() 1533 && _Traits::_S_move_assign) 1534 { 1535 // This construction might throw: 1536 variant __tmp(in_place_index<_Np>, 1537 std::forward<_Args>(__args)...); 1538 // But _Never_valueless_alt<type> means this won't: 1539 *this = std::move(__tmp); 1540 } 1541 else 1542 { 1543 // This case only provides the basic exception-safety guarantee, 1544 // i.e. the variant can become valueless. 1545 __variant::__emplace<_Np>(*this, std::forward<_Args>(__args)...); 1546 } 1547 return std::get<_Np>(*this); 1548 } 1549 1550 template<size_t _Np, typename _Up, typename... _Args> 1551 _GLIBCXX20_CONSTEXPR 1552 enable_if_t<is_constructible_v<__to_type<_Np>, 1553 initializer_list<_Up>&, _Args...>, 1554 __to_type<_Np>&> 1555 emplace(initializer_list<_Up> __il, _Args&&... __args) 1556 { 1557 namespace __variant = std::__detail::__variant; 1558 using type = typename _Nth_type<_Np, _Types...>::type; 1559 // Provide the strong exception-safety guarantee when possible, 1560 // to avoid becoming valueless. 1561 if constexpr (is_nothrow_constructible_v<type, 1562 initializer_list<_Up>&, 1563 _Args...>) 1564 { 1565 __variant::__emplace<_Np>(*this, __il, 1566 std::forward<_Args>(__args)...); 1567 } 1568 else if constexpr (__variant::_Never_valueless_alt<type>() 1569 && _Traits::_S_move_assign) 1570 { 1571 // This construction might throw: 1572 variant __tmp(in_place_index<_Np>, __il, 1573 std::forward<_Args>(__args)...); 1574 // But _Never_valueless_alt<type> means this won't: 1575 *this = std::move(__tmp); 1576 } 1577 else 1578 { 1579 // This case only provides the basic exception-safety guarantee, 1580 // i.e. the variant can become valueless. 1581 __variant::__emplace<_Np>(*this, __il, 1582 std::forward<_Args>(__args)...); 1583 } 1584 return std::get<_Np>(*this); 1585 } 1586 1587 template<size_t _Np, typename... _Args> 1588 enable_if_t<!(_Np < sizeof...(_Types))> emplace(_Args&&...) = delete; 1589 1590 template<typename _Tp, typename... _Args> 1591 enable_if_t<!__exactly_once<_Tp>> emplace(_Args&&...) = delete; 1592 1593 constexpr bool valueless_by_exception() const noexcept 1594 { return !this->_M_valid(); } 1595 1596 constexpr size_t index() const noexcept 1597 { 1598 using __index_type = typename _Base::__index_type; 1599 if constexpr (__detail::__variant::__never_valueless<_Types...>()) 1600 return this->_M_index; 1601 else if constexpr (sizeof...(_Types) <= __index_type(-1) / 2) 1602 return make_signed_t<__index_type>(this->_M_index); 1603 else 1604 return size_t(__index_type(this->_M_index + 1)) - 1; 1605 } 1606 1607 _GLIBCXX20_CONSTEXPR 1608 void 1609 swap(variant& __rhs) 1610 noexcept((__is_nothrow_swappable<_Types>::value && ...) 1611 && is_nothrow_move_constructible_v<variant>) 1612 { 1613 static_assert((is_move_constructible_v<_Types> && ...)); 1614 1615 // Handle this here to simplify the visitation. 1616 if (__rhs.valueless_by_exception()) [[__unlikely__]] 1617 { 1618 if (!this->valueless_by_exception()) [[__likely__]] 1619 __rhs.swap(*this); 1620 return; 1621 } 1622 1623 namespace __variant = __detail::__variant; 1624 1625 __variant::__raw_idx_visit( 1626 [this, &__rhs](auto&& __rhs_mem, auto __rhs_index) mutable 1627 { 1628 constexpr size_t __j = __rhs_index; 1629 if constexpr (__j != variant_npos) 1630 { 1631 if (this->index() == __j) 1632 { 1633 using std::swap; 1634 swap(std::get<__j>(*this), __rhs_mem); 1635 } 1636 else 1637 { 1638 auto __tmp(std::move(__rhs_mem)); 1639 1640 if constexpr (_Traits::_S_trivial_move_assign) 1641 __rhs = std::move(*this); 1642 else 1643 __variant::__raw_idx_visit( 1644 [&__rhs](auto&& __this_mem, auto __this_index) mutable 1645 { 1646 constexpr size_t __k = __this_index; 1647 if constexpr (__k != variant_npos) 1648 __variant::__emplace<__k>(__rhs, 1649 std::move(__this_mem)); 1650 }, *this); 1651 1652 __variant::__emplace<__j>(*this, std::move(__tmp)); 1653 } 1654 } 1655 }, __rhs); 1656 } 1657 1658#if defined(__clang__) && __clang_major__ <= 7 1659 public: 1660 using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852 1661#endif 1662 1663 private: 1664 template<size_t _Np, typename _Vp> 1665 friend constexpr decltype(auto) 1666 __detail::__variant::__get(_Vp&& __v) noexcept; 1667 1668#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \ 1669 template<typename... _Tp> \ 1670 friend constexpr bool \ 1671 operator __OP(const variant<_Tp...>& __lhs, \ 1672 const variant<_Tp...>& __rhs); 1673 1674 _VARIANT_RELATION_FUNCTION_TEMPLATE(<) 1675 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=) 1676 _VARIANT_RELATION_FUNCTION_TEMPLATE(==) 1677 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=) 1678 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=) 1679 _VARIANT_RELATION_FUNCTION_TEMPLATE(>) 1680 1681#undef _VARIANT_RELATION_FUNCTION_TEMPLATE 1682 }; 1683 1684 template<size_t _Np, typename... _Types> 1685 constexpr variant_alternative_t<_Np, variant<_Types...>>& 1686 get(variant<_Types...>& __v) 1687 { 1688 static_assert(_Np < sizeof...(_Types), 1689 "The index must be in [0, number of alternatives)"); 1690 if (__v.index() != _Np) 1691 __throw_bad_variant_access(__v.valueless_by_exception()); 1692 return __detail::__variant::__get<_Np>(__v); 1693 } 1694 1695 template<size_t _Np, typename... _Types> 1696 constexpr variant_alternative_t<_Np, variant<_Types...>>&& 1697 get(variant<_Types...>&& __v) 1698 { 1699 static_assert(_Np < sizeof...(_Types), 1700 "The index must be in [0, number of alternatives)"); 1701 if (__v.index() != _Np) 1702 __throw_bad_variant_access(__v.valueless_by_exception()); 1703 return __detail::__variant::__get<_Np>(std::move(__v)); 1704 } 1705 1706 template<size_t _Np, typename... _Types> 1707 constexpr const variant_alternative_t<_Np, variant<_Types...>>& 1708 get(const variant<_Types...>& __v) 1709 { 1710 static_assert(_Np < sizeof...(_Types), 1711 "The index must be in [0, number of alternatives)"); 1712 if (__v.index() != _Np) 1713 __throw_bad_variant_access(__v.valueless_by_exception()); 1714 return __detail::__variant::__get<_Np>(__v); 1715 } 1716 1717 template<size_t _Np, typename... _Types> 1718 constexpr const variant_alternative_t<_Np, variant<_Types...>>&& 1719 get(const variant<_Types...>&& __v) 1720 { 1721 static_assert(_Np < sizeof...(_Types), 1722 "The index must be in [0, number of alternatives)"); 1723 if (__v.index() != _Np) 1724 __throw_bad_variant_access(__v.valueless_by_exception()); 1725 return __detail::__variant::__get<_Np>(std::move(__v)); 1726 } 1727 1728 /// @cond undocumented 1729 template<typename _Result_type, typename _Visitor, typename... _Variants> 1730 constexpr decltype(auto) 1731 __do_visit(_Visitor&& __visitor, _Variants&&... __variants) 1732 { 1733 // Get the silly case of visiting no variants out of the way first. 1734 if constexpr (sizeof...(_Variants) == 0) 1735 { 1736 if constexpr (is_void_v<_Result_type>) 1737 return (void) std::forward<_Visitor>(__visitor)(); 1738 else 1739 return std::forward<_Visitor>(__visitor)(); 1740 } 1741 else 1742 { 1743 constexpr size_t __max = 11; // "These go to eleven." 1744 1745 // The type of the first variant in the pack. 1746 using _V0 = typename _Nth_type<0, _Variants...>::type; 1747 // The number of alternatives in that first variant. 1748 constexpr auto __n = variant_size_v<remove_reference_t<_V0>>; 1749 1750 if constexpr (sizeof...(_Variants) > 1 || __n > __max) 1751 { 1752 // Use a jump table for the general case. 1753 constexpr auto& __vtable = __detail::__variant::__gen_vtable< 1754 _Result_type, _Visitor&&, _Variants&&...>::_S_vtable; 1755 1756 auto __func_ptr = __vtable._M_access(__variants.index()...); 1757 return (*__func_ptr)(std::forward<_Visitor>(__visitor), 1758 std::forward<_Variants>(__variants)...); 1759 } 1760 else // We have a single variant with a small number of alternatives. 1761 { 1762 // A name for the first variant in the pack. 1763 _V0& __v0 1764 = [](_V0& __v, ...) -> _V0& { return __v; }(__variants...); 1765 1766 using __detail::__variant::_Multi_array; 1767 using __detail::__variant::__gen_vtable_impl; 1768 using _Ma = _Multi_array<_Result_type (*)(_Visitor&&, _V0&&)>; 1769 1770#ifdef _GLIBCXX_DEBUG 1771# define _GLIBCXX_VISIT_UNREACHABLE __builtin_trap 1772#else 1773# define _GLIBCXX_VISIT_UNREACHABLE __builtin_unreachable 1774#endif 1775 1776#define _GLIBCXX_VISIT_CASE(N) \ 1777 case N: \ 1778 { \ 1779 if constexpr (N < __n) \ 1780 { \ 1781 return __gen_vtable_impl<_Ma, index_sequence<N>>:: \ 1782 __visit_invoke(std::forward<_Visitor>(__visitor), \ 1783 std::forward<_V0>(__v0)); \ 1784 } \ 1785 else _GLIBCXX_VISIT_UNREACHABLE(); \ 1786 } 1787 1788 switch (__v0.index()) 1789 { 1790 _GLIBCXX_VISIT_CASE(0) 1791 _GLIBCXX_VISIT_CASE(1) 1792 _GLIBCXX_VISIT_CASE(2) 1793 _GLIBCXX_VISIT_CASE(3) 1794 _GLIBCXX_VISIT_CASE(4) 1795 _GLIBCXX_VISIT_CASE(5) 1796 _GLIBCXX_VISIT_CASE(6) 1797 _GLIBCXX_VISIT_CASE(7) 1798 _GLIBCXX_VISIT_CASE(8) 1799 _GLIBCXX_VISIT_CASE(9) 1800 _GLIBCXX_VISIT_CASE(10) 1801 case variant_npos: 1802 using __detail::__variant::__variant_idx_cookie; 1803 using __detail::__variant::__variant_cookie; 1804 if constexpr (is_same_v<_Result_type, __variant_idx_cookie> 1805 || is_same_v<_Result_type, __variant_cookie>) 1806 { 1807 using _Npos = index_sequence<variant_npos>; 1808 return __gen_vtable_impl<_Ma, _Npos>:: 1809 __visit_invoke(std::forward<_Visitor>(__visitor), 1810 std::forward<_V0>(__v0)); 1811 } 1812 else 1813 _GLIBCXX_VISIT_UNREACHABLE(); 1814 default: 1815 _GLIBCXX_VISIT_UNREACHABLE(); 1816 } 1817#undef _GLIBCXX_VISIT_CASE 1818#undef _GLIBCXX_VISIT_UNREACHABLE 1819 } 1820 } 1821 } 1822 /// @endcond 1823 1824 template<typename _Visitor, typename... _Variants> 1825 constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...> 1826 visit(_Visitor&& __visitor, _Variants&&... __variants) 1827 { 1828 namespace __variant = std::__detail::__variant; 1829 1830 if ((__variant::__as(__variants).valueless_by_exception() || ...)) 1831 __throw_bad_variant_access("std::visit: variant is valueless"); 1832 1833 using _Result_type 1834 = __detail::__variant::__visit_result_t<_Visitor, _Variants...>; 1835 1836 using _Tag = __detail::__variant::__deduce_visit_result<_Result_type>; 1837 1838 if constexpr (sizeof...(_Variants) == 1) 1839 { 1840 using _Vp = decltype(__variant::__as(std::declval<_Variants>()...)); 1841 1842 constexpr bool __visit_rettypes_match = __detail::__variant:: 1843 __check_visitor_results<_Visitor, _Vp>( 1844 make_index_sequence<variant_size_v<remove_reference_t<_Vp>>>()); 1845 if constexpr (!__visit_rettypes_match) 1846 { 1847 static_assert(__visit_rettypes_match, 1848 "std::visit requires the visitor to have the same " 1849 "return type for all alternatives of a variant"); 1850 return; 1851 } 1852 else 1853 return std::__do_visit<_Tag>( 1854 std::forward<_Visitor>(__visitor), 1855 static_cast<_Vp>(__variants)...); 1856 } 1857 else 1858 return std::__do_visit<_Tag>( 1859 std::forward<_Visitor>(__visitor), 1860 __variant::__as(std::forward<_Variants>(__variants))...); 1861 } 1862 1863#if __cplusplus > 201703L 1864 template<typename _Res, typename _Visitor, typename... _Variants> 1865 constexpr _Res 1866 visit(_Visitor&& __visitor, _Variants&&... __variants) 1867 { 1868 namespace __variant = std::__detail::__variant; 1869 1870 if ((__variant::__as(__variants).valueless_by_exception() || ...)) 1871 __throw_bad_variant_access("std::visit<R>: variant is valueless"); 1872 1873 return std::__do_visit<_Res>(std::forward<_Visitor>(__visitor), 1874 __variant::__as(std::forward<_Variants>(__variants))...); 1875 } 1876#endif 1877 1878 /// @cond undocumented 1879 template<bool, typename... _Types> 1880 struct __variant_hash_call_base_impl 1881 { 1882 size_t 1883 operator()(const variant<_Types...>& __t) const 1884 noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...)) 1885 { 1886 size_t __ret; 1887 __detail::__variant::__raw_visit( 1888 [&__t, &__ret](auto&& __t_mem) mutable 1889 { 1890 using _Type = __remove_cvref_t<decltype(__t_mem)>; 1891 if constexpr (!is_same_v<_Type, 1892 __detail::__variant::__variant_cookie>) 1893 __ret = std::hash<size_t>{}(__t.index()) 1894 + std::hash<_Type>{}(__t_mem); 1895 else 1896 __ret = std::hash<size_t>{}(__t.index()); 1897 }, __t); 1898 return __ret; 1899 } 1900 }; 1901 1902 template<typename... _Types> 1903 struct __variant_hash_call_base_impl<false, _Types...> {}; 1904 1905 template<typename... _Types> 1906 using __variant_hash_call_base = 1907 __variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>:: 1908 __enable_hash_call &&...), _Types...>; 1909 /// @endcond 1910 1911 template<typename... _Types> 1912 struct hash<variant<_Types...>> 1913 : private __detail::__variant::_Variant_hash_base< 1914 variant<_Types...>, std::index_sequence_for<_Types...>>, 1915 public __variant_hash_call_base<_Types...> 1916 { 1917 using result_type [[__deprecated__]] = size_t; 1918 using argument_type [[__deprecated__]] = variant<_Types...>; 1919 }; 1920 1921 template<> 1922 struct hash<monostate> 1923 { 1924 using result_type [[__deprecated__]] = size_t; 1925 using argument_type [[__deprecated__]] = monostate; 1926 1927 size_t 1928 operator()(const monostate&) const noexcept 1929 { 1930 constexpr size_t __magic_monostate_hash = -7777; 1931 return __magic_monostate_hash; 1932 } 1933 }; 1934 1935 template<typename... _Types> 1936 struct __is_fast_hash<hash<variant<_Types...>>> 1937 : bool_constant<(__is_fast_hash<_Types>::value && ...)> 1938 { }; 1939 1940_GLIBCXX_END_NAMESPACE_VERSION 1941} // namespace std 1942 1943#endif // C++17 1944 1945#endif // _GLIBCXX_VARIANT 1946