1// <variant> -*- C++ -*- 2 3// Copyright (C) 2016-2019 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 <type_traits> 37#include <utility> 38#include <bits/enable_special_members.h> 39#include <bits/functexcept.h> 40#include <bits/move.h> 41#include <bits/functional_hash.h> 42#include <bits/invoke.h> 43#include <ext/aligned_buffer.h> 44#include <bits/parse_numbers.h> 45#include <bits/stl_iterator_base_types.h> 46#include <bits/stl_iterator_base_funcs.h> 47#include <bits/stl_construct.h> 48 49namespace std _GLIBCXX_VISIBILITY(default) 50{ 51_GLIBCXX_BEGIN_NAMESPACE_VERSION 52 53namespace __detail 54{ 55namespace __variant 56{ 57 template<size_t _Np, typename... _Types> 58 struct _Nth_type; 59 60 template<size_t _Np, typename _First, typename... _Rest> 61 struct _Nth_type<_Np, _First, _Rest...> 62 : _Nth_type<_Np-1, _Rest...> { }; 63 64 template<typename _First, typename... _Rest> 65 struct _Nth_type<0, _First, _Rest...> 66 { using type = _First; }; 67 68} // namespace __variant 69} // namespace __detail 70 71#define __cpp_lib_variant 201606L 72 73 template<typename... _Types> class tuple; 74 template<typename... _Types> class variant; 75 template <typename> struct hash; 76 77 template<typename _Variant> 78 struct variant_size; 79 80 template<typename _Variant> 81 struct variant_size<const _Variant> : variant_size<_Variant> {}; 82 83 template<typename _Variant> 84 struct variant_size<volatile _Variant> : variant_size<_Variant> {}; 85 86 template<typename _Variant> 87 struct variant_size<const volatile _Variant> : variant_size<_Variant> {}; 88 89 template<typename... _Types> 90 struct variant_size<variant<_Types...>> 91 : std::integral_constant<size_t, sizeof...(_Types)> {}; 92 93 template<typename _Variant> 94 inline constexpr size_t variant_size_v = variant_size<_Variant>::value; 95 96 template<size_t _Np, typename _Variant> 97 struct variant_alternative; 98 99 template<size_t _Np, typename _First, typename... _Rest> 100 struct variant_alternative<_Np, variant<_First, _Rest...>> 101 : variant_alternative<_Np-1, variant<_Rest...>> {}; 102 103 template<typename _First, typename... _Rest> 104 struct variant_alternative<0, variant<_First, _Rest...>> 105 { using type = _First; }; 106 107 template<size_t _Np, typename _Variant> 108 using variant_alternative_t = 109 typename variant_alternative<_Np, _Variant>::type; 110 111 template<size_t _Np, typename _Variant> 112 struct variant_alternative<_Np, const _Variant> 113 { using type = add_const_t<variant_alternative_t<_Np, _Variant>>; }; 114 115 template<size_t _Np, typename _Variant> 116 struct variant_alternative<_Np, volatile _Variant> 117 { using type = add_volatile_t<variant_alternative_t<_Np, _Variant>>; }; 118 119 template<size_t _Np, typename _Variant> 120 struct variant_alternative<_Np, const volatile _Variant> 121 { using type = add_cv_t<variant_alternative_t<_Np, _Variant>>; }; 122 123 inline constexpr size_t variant_npos = -1; 124 125 template<size_t _Np, typename... _Types> 126 constexpr variant_alternative_t<_Np, variant<_Types...>>& 127 get(variant<_Types...>&); 128 129 template<size_t _Np, typename... _Types> 130 constexpr variant_alternative_t<_Np, variant<_Types...>>&& 131 get(variant<_Types...>&&); 132 133 template<size_t _Np, typename... _Types> 134 constexpr variant_alternative_t<_Np, variant<_Types...>> const& 135 get(const variant<_Types...>&); 136 137 template<size_t _Np, typename... _Types> 138 constexpr variant_alternative_t<_Np, variant<_Types...>> const&& 139 get(const variant<_Types...>&&); 140 141 template<bool __use_index=false, 142 bool __same_return_types = true, 143 typename _Visitor, typename... _Variants> 144 constexpr decltype(auto) 145 __do_visit(_Visitor&& __visitor, _Variants&&... __variants); 146 147 template <typename... _Types, typename _Tp> 148 decltype(auto) 149 __variant_cast(_Tp&& __rhs) 150 { 151 if constexpr (is_lvalue_reference_v<_Tp>) 152 { 153 if constexpr (is_const_v<remove_reference_t<_Tp>>) 154 return static_cast<const variant<_Types...>&>(__rhs); 155 else 156 return static_cast<variant<_Types...>&>(__rhs); 157 } 158 else 159 return static_cast<variant<_Types...>&&>(__rhs); 160 } 161 162namespace __detail 163{ 164namespace __variant 165{ 166 // Returns the first apparence of _Tp in _Types. 167 // Returns sizeof...(_Types) if _Tp is not in _Types. 168 template<typename _Tp, typename... _Types> 169 struct __index_of : std::integral_constant<size_t, 0> {}; 170 171 template<typename _Tp, typename... _Types> 172 inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value; 173 174 template<typename _Tp, typename _First, typename... _Rest> 175 struct __index_of<_Tp, _First, _Rest...> : 176 std::integral_constant<size_t, is_same_v<_Tp, _First> 177 ? 0 : __index_of_v<_Tp, _Rest...> + 1> {}; 178 179 // used for raw visitation 180 struct __variant_cookie {}; 181 // used for raw visitation with indices passed in 182 struct __variant_idx_cookie { using type = __variant_idx_cookie; }; 183 // a more explanatory name than 'true' 184 inline constexpr auto __visit_with_index = bool_constant<true>{}; 185 186 // _Uninitialized<T> is guaranteed to be a literal type, even if T is not. 187 // We have to do this, because [basic.types]p10.5.3 (n4606) is not implemented 188 // yet. When it's implemented, _Uninitialized<T> can be changed to the alias 189 // to T, therefore equivalent to being removed entirely. 190 // 191 // Another reason we may not want to remove _Uninitialzied<T> may be that, we 192 // want _Uninitialized<T> to be trivially destructible, no matter whether T 193 // is; but we will see. 194 template<typename _Type, bool = std::is_literal_type_v<_Type>> 195 struct _Uninitialized; 196 197 template<typename _Type> 198 struct _Uninitialized<_Type, true> 199 { 200 template<typename... _Args> 201 constexpr 202 _Uninitialized(in_place_index_t<0>, _Args&&... __args) 203 : _M_storage(std::forward<_Args>(__args)...) 204 { } 205 206 constexpr const _Type& _M_get() const & noexcept 207 { return _M_storage; } 208 209 constexpr _Type& _M_get() & noexcept 210 { return _M_storage; } 211 212 constexpr const _Type&& _M_get() const && noexcept 213 { return std::move(_M_storage); } 214 215 constexpr _Type&& _M_get() && noexcept 216 { return std::move(_M_storage); } 217 218 _Type _M_storage; 219 }; 220 221 template<typename _Type> 222 struct _Uninitialized<_Type, false> 223 { 224 template<typename... _Args> 225 constexpr 226 _Uninitialized(in_place_index_t<0>, _Args&&... __args) 227 { 228 ::new ((void*)std::addressof(_M_storage)) 229 _Type(std::forward<_Args>(__args)...); 230 } 231 232 const _Type& _M_get() const & noexcept 233 { return *_M_storage._M_ptr(); } 234 235 _Type& _M_get() & noexcept 236 { return *_M_storage._M_ptr(); } 237 238 const _Type&& _M_get() const && noexcept 239 { return std::move(*_M_storage._M_ptr()); } 240 241 _Type&& _M_get() && noexcept 242 { return std::move(*_M_storage._M_ptr()); } 243 244 __gnu_cxx::__aligned_membuf<_Type> _M_storage; 245 }; 246 247 template<typename _Union> 248 constexpr decltype(auto) 249 __get(in_place_index_t<0>, _Union&& __u) noexcept 250 { return std::forward<_Union>(__u)._M_first._M_get(); } 251 252 template<size_t _Np, typename _Union> 253 constexpr decltype(auto) 254 __get(in_place_index_t<_Np>, _Union&& __u) noexcept 255 { 256 return __variant::__get(in_place_index<_Np-1>, 257 std::forward<_Union>(__u)._M_rest); 258 } 259 260 // Returns the typed storage for __v. 261 template<size_t _Np, typename _Variant> 262 constexpr decltype(auto) 263 __get(_Variant&& __v) noexcept 264 { 265 return __variant::__get(std::in_place_index<_Np>, 266 std::forward<_Variant>(__v)._M_u); 267 } 268 269 template<typename... _Types> 270 struct _Traits 271 { 272 static constexpr bool _S_default_ctor = 273 is_default_constructible_v<typename _Nth_type<0, _Types...>::type>; 274 static constexpr bool _S_copy_ctor = 275 (is_copy_constructible_v<_Types> && ...); 276 static constexpr bool _S_move_ctor = 277 (is_move_constructible_v<_Types> && ...); 278 static constexpr bool _S_copy_assign = 279 _S_copy_ctor 280 && (is_copy_assignable_v<_Types> && ...); 281 static constexpr bool _S_move_assign = 282 _S_move_ctor 283 && (is_move_assignable_v<_Types> && ...); 284 285 static constexpr bool _S_trivial_dtor = 286 (is_trivially_destructible_v<_Types> && ...); 287 static constexpr bool _S_trivial_copy_ctor = 288 (is_trivially_copy_constructible_v<_Types> && ...); 289 static constexpr bool _S_trivial_move_ctor = 290 (is_trivially_move_constructible_v<_Types> && ...); 291 static constexpr bool _S_trivial_copy_assign = 292 _S_trivial_dtor && _S_trivial_copy_ctor 293 && (is_trivially_copy_assignable_v<_Types> && ...); 294 static constexpr bool _S_trivial_move_assign = 295 _S_trivial_dtor && _S_trivial_move_ctor 296 && (is_trivially_move_assignable_v<_Types> && ...); 297 298 // The following nothrow traits are for non-trivial SMFs. Trivial SMFs 299 // are always nothrow. 300 static constexpr bool _S_nothrow_default_ctor = 301 is_nothrow_default_constructible_v< 302 typename _Nth_type<0, _Types...>::type>; 303 static constexpr bool _S_nothrow_copy_ctor = false; 304 static constexpr bool _S_nothrow_move_ctor = 305 (is_nothrow_move_constructible_v<_Types> && ...); 306 static constexpr bool _S_nothrow_copy_assign = false; 307 static constexpr bool _S_nothrow_move_assign = 308 _S_nothrow_move_ctor 309 && (is_nothrow_move_assignable_v<_Types> && ...); 310 }; 311 312 // Defines members and ctors. 313 template<typename... _Types> 314 union _Variadic_union { }; 315 316 template<typename _First, typename... _Rest> 317 union _Variadic_union<_First, _Rest...> 318 { 319 constexpr _Variadic_union() : _M_rest() { } 320 321 template<typename... _Args> 322 constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args) 323 : _M_first(in_place_index<0>, std::forward<_Args>(__args)...) 324 { } 325 326 template<size_t _Np, typename... _Args> 327 constexpr _Variadic_union(in_place_index_t<_Np>, _Args&&... __args) 328 : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...) 329 { } 330 331 _Uninitialized<_First> _M_first; 332 _Variadic_union<_Rest...> _M_rest; 333 }; 334 335 // _Never_valueless_alt is true for variant alternatives that can 336 // always be placed in a variant without it becoming valueless. 337 338 // For suitably-small, trivially copyable types we can create temporaries 339 // on the stack and then memcpy them into place. 340 template<typename _Tp> 341 struct _Never_valueless_alt 342 : __and_<bool_constant<sizeof(_Tp) <= 256>, is_trivially_copyable<_Tp>> 343 { }; 344 345 // Specialize _Never_valueless_alt for other types which have a 346 // non-throwing and cheap move construction and move assignment operator, 347 // so that emplacing the type will provide the strong exception-safety 348 // guarantee, by creating and moving a temporary. 349 // Whether _Never_valueless_alt<T> is true or not affects the ABI of a 350 // variant using that alternative, so we can't change the value later! 351 352 // True if every alternative in _Types... can be emplaced in a variant 353 // without it becoming valueless. If this is true, variant<_Types...> 354 // can never be valueless, which enables some minor optimizations. 355 template <typename... _Types> 356 constexpr bool __never_valueless() 357 { 358 return _Traits<_Types...>::_S_move_assign 359 && (_Never_valueless_alt<_Types>::value && ...); 360 } 361 362 // Defines index and the dtor, possibly trivial. 363 template<bool __trivially_destructible, typename... _Types> 364 struct _Variant_storage; 365 366 template <typename... _Types> 367 using __select_index = 368 typename __select_int::_Select_int_base<sizeof...(_Types), 369 unsigned char, 370 unsigned short>::type::value_type; 371 372 template<typename... _Types> 373 struct _Variant_storage<false, _Types...> 374 { 375 constexpr _Variant_storage() : _M_index(variant_npos) { } 376 377 template<size_t _Np, typename... _Args> 378 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) 379 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), 380 _M_index(_Np) 381 { } 382 383 constexpr void _M_reset_impl() 384 { 385 __do_visit([](auto&& __this_mem) mutable 386 -> __detail::__variant::__variant_cookie 387 { 388 if constexpr (!is_same_v<remove_reference_t<decltype(__this_mem)>, 389 __variant_cookie>) 390 std::_Destroy(std::__addressof(__this_mem)); 391 return {}; 392 }, __variant_cast<_Types...>(*this)); 393 } 394 395 void _M_reset() 396 { 397 _M_reset_impl(); 398 _M_index = variant_npos; 399 } 400 401 ~_Variant_storage() 402 { _M_reset(); } 403 404 void* 405 _M_storage() const 406 { 407 return const_cast<void*>(static_cast<const void*>( 408 std::addressof(_M_u))); 409 } 410 411 constexpr bool 412 _M_valid() const noexcept 413 { 414 if constexpr (__never_valueless<_Types...>()) 415 return true; 416 return this->_M_index != __index_type(variant_npos); 417 } 418 419 _Variadic_union<_Types...> _M_u; 420 using __index_type = __select_index<_Types...>; 421 __index_type _M_index; 422 }; 423 424 template<typename... _Types> 425 struct _Variant_storage<true, _Types...> 426 { 427 constexpr _Variant_storage() : _M_index(variant_npos) { } 428 429 template<size_t _Np, typename... _Args> 430 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) 431 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), 432 _M_index(_Np) 433 { } 434 435 void _M_reset() 436 { _M_index = variant_npos; } 437 438 void* 439 _M_storage() const 440 { 441 return const_cast<void*>(static_cast<const void*>( 442 std::addressof(_M_u))); 443 } 444 445 constexpr bool 446 _M_valid() const noexcept 447 { 448 if constexpr (__never_valueless<_Types...>()) 449 return true; 450 return this->_M_index != __index_type(variant_npos); 451 } 452 453 _Variadic_union<_Types...> _M_u; 454 using __index_type = __select_index<_Types...>; 455 __index_type _M_index; 456 }; 457 458 template<typename... _Types> 459 using _Variant_storage_alias = 460 _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>; 461 462 template<typename _Tp, typename _Up> 463 void __variant_construct_single(_Tp&& __lhs, _Up&& __rhs_mem) 464 { 465 void* __storage = std::addressof(__lhs._M_u); 466 using _Type = remove_reference_t<decltype(__rhs_mem)>; 467 if constexpr (!is_same_v<_Type, __variant_cookie>) 468 ::new (__storage) 469 _Type(std::forward<decltype(__rhs_mem)>(__rhs_mem)); 470 } 471 472 template<typename... _Types, typename _Tp, typename _Up> 473 void __variant_construct(_Tp&& __lhs, _Up&& __rhs) 474 { 475 __lhs._M_index = __rhs._M_index; 476 __do_visit([&__lhs](auto&& __rhs_mem) mutable 477 -> __detail::__variant::__variant_cookie 478 { 479 __variant_construct_single(std::forward<_Tp>(__lhs), 480 std::forward<decltype(__rhs_mem)>(__rhs_mem)); 481 return {}; 482 }, __variant_cast<_Types...>(std::forward<_Up>(__rhs))); 483 } 484 485 // The following are (Copy|Move) (ctor|assign) layers for forwarding 486 // triviality and handling non-trivial SMF behaviors. 487 488 template<bool, typename... _Types> 489 struct _Copy_ctor_base : _Variant_storage_alias<_Types...> 490 { 491 using _Base = _Variant_storage_alias<_Types...>; 492 using _Base::_Base; 493 494 _Copy_ctor_base(const _Copy_ctor_base& __rhs) 495 noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor) 496 { 497 __variant_construct<_Types...>(*this, __rhs); 498 } 499 500 _Copy_ctor_base(_Copy_ctor_base&&) = default; 501 _Copy_ctor_base& operator=(const _Copy_ctor_base&) = default; 502 _Copy_ctor_base& operator=(_Copy_ctor_base&&) = default; 503 }; 504 505 template<typename... _Types> 506 struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...> 507 { 508 using _Base = _Variant_storage_alias<_Types...>; 509 using _Base::_Base; 510 }; 511 512 template<typename... _Types> 513 using _Copy_ctor_alias = 514 _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>; 515 516 template<bool, typename... _Types> 517 struct _Move_ctor_base : _Copy_ctor_alias<_Types...> 518 { 519 using _Base = _Copy_ctor_alias<_Types...>; 520 using _Base::_Base; 521 522 _Move_ctor_base(_Move_ctor_base&& __rhs) 523 noexcept(_Traits<_Types...>::_S_nothrow_move_ctor) 524 { 525 __variant_construct<_Types...>(*this, std::move(__rhs)); 526 } 527 528 template<typename _Up> 529 void _M_destructive_move(unsigned short __rhs_index, _Up&& __rhs) 530 { 531 this->_M_reset(); 532 __variant_construct_single(*this, std::forward<_Up>(__rhs)); 533 this->_M_index = __rhs_index; 534 } 535 536 template<typename _Up> 537 void _M_destructive_copy(unsigned short __rhs_index, const _Up& __rhs) 538 { 539 this->_M_reset(); 540 __variant_construct_single(*this, __rhs); 541 this->_M_index = __rhs_index; 542 } 543 544 _Move_ctor_base(const _Move_ctor_base&) = default; 545 _Move_ctor_base& operator=(const _Move_ctor_base&) = default; 546 _Move_ctor_base& operator=(_Move_ctor_base&&) = default; 547 }; 548 549 template<typename... _Types> 550 struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...> 551 { 552 using _Base = _Copy_ctor_alias<_Types...>; 553 using _Base::_Base; 554 555 template<typename _Up> 556 void _M_destructive_move(unsigned short __rhs_index, _Up&& __rhs) 557 { 558 this->_M_reset(); 559 __variant_construct_single(*this, std::forward<_Up>(__rhs)); 560 this->_M_index = __rhs_index; 561 } 562 563 template<typename _Up> 564 void _M_destructive_copy(unsigned short __rhs_index, const _Up& __rhs) 565 { 566 this->_M_reset(); 567 __variant_construct_single(*this, __rhs); 568 this->_M_index = __rhs_index; 569 } 570 }; 571 572 template<typename... _Types> 573 using _Move_ctor_alias = 574 _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>; 575 576 template<bool, typename... _Types> 577 struct _Copy_assign_base : _Move_ctor_alias<_Types...> 578 { 579 using _Base = _Move_ctor_alias<_Types...>; 580 using _Base::_Base; 581 582 _Copy_assign_base& 583 operator=(const _Copy_assign_base& __rhs) 584 noexcept(_Traits<_Types...>::_S_nothrow_copy_assign) 585 { 586 __do_visit<__visit_with_index>([this](auto&& __rhs_mem, 587 auto __rhs_index) mutable 588 -> __detail::__variant::__variant_idx_cookie 589 { 590 if constexpr (__rhs_index != variant_npos) 591 { 592 if (this->_M_index == __rhs_index) 593 __variant::__get<__rhs_index>(*this) = __rhs_mem; 594 else 595 { 596 using __rhs_type = __remove_cvref_t<decltype(__rhs_mem)>; 597 if constexpr (is_nothrow_copy_constructible_v<__rhs_type> 598 || !is_nothrow_move_constructible_v<__rhs_type>) 599 // The standard says this->emplace<__rhs_type>(__rhs_mem) 600 // should be used here, but _M_destructive_copy is 601 // equivalent in this case. Either copy construction 602 // doesn't throw, so _M_destructive_copy gives strong 603 // exception safety guarantee, or both copy construction 604 // and move construction can throw, so emplace only gives 605 // basic exception safety anyway. 606 this->_M_destructive_copy(__rhs_index, __rhs_mem); 607 else 608 __variant_cast<_Types...>(*this) 609 = variant<_Types...>(__rhs_mem); 610 } 611 } 612 else 613 this->_M_reset(); 614 return {}; 615 }, __variant_cast<_Types...>(__rhs)); 616 return *this; 617 } 618 619 _Copy_assign_base(const _Copy_assign_base&) = default; 620 _Copy_assign_base(_Copy_assign_base&&) = default; 621 _Copy_assign_base& operator=(_Copy_assign_base&&) = default; 622 }; 623 624 template<typename... _Types> 625 struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...> 626 { 627 using _Base = _Move_ctor_alias<_Types...>; 628 using _Base::_Base; 629 }; 630 631 template<typename... _Types> 632 using _Copy_assign_alias = 633 _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, _Types...>; 634 635 template<bool, typename... _Types> 636 struct _Move_assign_base : _Copy_assign_alias<_Types...> 637 { 638 using _Base = _Copy_assign_alias<_Types...>; 639 using _Base::_Base; 640 641 _Move_assign_base& 642 operator=(_Move_assign_base&& __rhs) 643 noexcept(_Traits<_Types...>::_S_nothrow_move_assign) 644 { 645 __do_visit<__visit_with_index>([this](auto&& __rhs_mem, 646 auto __rhs_index) mutable 647 -> __detail::__variant::__variant_idx_cookie 648 { 649 if constexpr (__rhs_index != variant_npos) 650 { 651 if (this->_M_index == __rhs_index) 652 __variant::__get<__rhs_index>(*this) = std::move(__rhs_mem); 653 else 654 __variant_cast<_Types...>(*this) 655 .template emplace<__rhs_index>(std::move(__rhs_mem)); 656 } 657 else 658 this->_M_reset(); 659 return {}; 660 }, __variant_cast<_Types...>(__rhs)); 661 return *this; 662 } 663 664 _Move_assign_base(const _Move_assign_base&) = default; 665 _Move_assign_base(_Move_assign_base&&) = default; 666 _Move_assign_base& operator=(const _Move_assign_base&) = default; 667 }; 668 669 template<typename... _Types> 670 struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...> 671 { 672 using _Base = _Copy_assign_alias<_Types...>; 673 using _Base::_Base; 674 }; 675 676 template<typename... _Types> 677 using _Move_assign_alias = 678 _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign, _Types...>; 679 680 template<typename... _Types> 681 struct _Variant_base : _Move_assign_alias<_Types...> 682 { 683 using _Base = _Move_assign_alias<_Types...>; 684 685 constexpr 686 _Variant_base() 687 noexcept(_Traits<_Types...>::_S_nothrow_default_ctor) 688 : _Variant_base(in_place_index<0>) { } 689 690 template<size_t _Np, typename... _Args> 691 constexpr explicit 692 _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args) 693 : _Base(__i, std::forward<_Args>(__args)...) 694 { } 695 696 _Variant_base(const _Variant_base&) = default; 697 _Variant_base(_Variant_base&&) = default; 698 _Variant_base& operator=(const _Variant_base&) = default; 699 _Variant_base& operator=(_Variant_base&&) = default; 700 }; 701 702 // For how many times does _Tp appear in _Tuple? 703 template<typename _Tp, typename _Tuple> 704 struct __tuple_count; 705 706 template<typename _Tp, typename _Tuple> 707 inline constexpr size_t __tuple_count_v = 708 __tuple_count<_Tp, _Tuple>::value; 709 710 template<typename _Tp, typename... _Types> 711 struct __tuple_count<_Tp, tuple<_Types...>> 712 : integral_constant<size_t, 0> { }; 713 714 template<typename _Tp, typename _First, typename... _Rest> 715 struct __tuple_count<_Tp, tuple<_First, _Rest...>> 716 : integral_constant< 717 size_t, 718 __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { }; 719 720 // TODO: Reuse this in <tuple> ? 721 template<typename _Tp, typename... _Types> 722 inline constexpr bool __exactly_once = 723 __tuple_count_v<_Tp, tuple<_Types...>> == 1; 724 725 // Takes _Types and create an overloaded _S_fun for each type. 726 // If a type appears more than once in _Types, create only one overload. 727 template<typename... _Types> 728 struct __overload_set 729 { static void _S_fun(); }; 730 731 template<typename _First, typename... _Rest> 732 struct __overload_set<_First, _Rest...> : __overload_set<_Rest...> 733 { 734 using __overload_set<_Rest...>::_S_fun; 735 static integral_constant<size_t, sizeof...(_Rest)> _S_fun(_First); 736 }; 737 738 template<typename... _Rest> 739 struct __overload_set<void, _Rest...> : __overload_set<_Rest...> 740 { 741 using __overload_set<_Rest...>::_S_fun; 742 }; 743 744 // Helper for variant(_Tp&&) and variant::operator=(_Tp&&). 745 // __accepted_index maps an arbitrary _Tp to an alternative type in _Variant 746 // (or to variant_npos). 747 template<typename _Tp, typename _Variant, typename = void> 748 struct __accepted_index 749 { static constexpr size_t value = variant_npos; }; 750 751 template<typename _Tp, typename... _Types> 752 struct __accepted_index< 753 _Tp, variant<_Types...>, 754 void_t<decltype(__overload_set<_Types...>::_S_fun(std::declval<_Tp>()))>> 755 { 756 static constexpr size_t value = sizeof...(_Types) - 1 757 - decltype(__overload_set<_Types...>:: 758 _S_fun(std::declval<_Tp>()))::value; 759 }; 760 761 // Returns the raw storage for __v. 762 template<typename _Variant> 763 void* __get_storage(_Variant&& __v) 764 { return __v._M_storage(); } 765 766 template <typename _Maybe_variant_cookie, typename _Variant> 767 struct _Extra_visit_slot_needed 768 { 769 template <typename> struct _Variant_never_valueless; 770 771 template <typename... _Types> 772 struct _Variant_never_valueless<variant<_Types...>> 773 : bool_constant<__never_valueless<_Types...>()> {}; 774 775 static constexpr bool value = 776 (is_same_v<_Maybe_variant_cookie, __variant_cookie> 777 || is_same_v<_Maybe_variant_cookie, __variant_idx_cookie>) 778 && !_Variant_never_valueless<__remove_cvref_t<_Variant>>::value; 779 }; 780 781 // Used for storing a multi-dimensional vtable. 782 template<typename _Tp, size_t... _Dimensions> 783 struct _Multi_array; 784 785 // Partial specialization with rank zero, stores a single _Tp element. 786 template<typename _Tp> 787 struct _Multi_array<_Tp> 788 { 789 constexpr const _Tp& 790 _M_access() const 791 { return _M_data; } 792 793 _Tp _M_data; 794 }; 795 796 // Partial specialization with rank >= 1. 797 template<typename _Ret, 798 typename _Visitor, 799 typename... _Variants, 800 size_t __first, size_t... __rest> 801 struct _Multi_array<_Ret(*)(_Visitor, _Variants...), __first, __rest...> 802 { 803 static constexpr size_t __index = 804 sizeof...(_Variants) - sizeof...(__rest) - 1; 805 806 using _Variant = typename _Nth_type<__index, _Variants...>::type; 807 808 static constexpr int __do_cookie = 809 _Extra_visit_slot_needed<_Ret, _Variant>::value ? 1 : 0; 810 811 using _Tp = _Ret(*)(_Visitor, _Variants...); 812 813 template<typename... _Args> 814 constexpr const _Tp& 815 _M_access(size_t __first_index, _Args... __rest_indices) const 816 { 817 return _M_arr[__first_index + __do_cookie] 818 ._M_access(__rest_indices...); 819 } 820 821 _Multi_array<_Tp, __rest...> _M_arr[__first + __do_cookie]; 822 }; 823 824 // Creates a multi-dimensional vtable recursively. 825 // 826 // The __same_return_types non-type template parameter specifies whether 827 // to enforce that all visitor invocations return the same type. This is 828 // required by std::visit but not std::visit<R>. 829 // 830 // For example, 831 // visit([](auto, auto){}, 832 // variant<int, char>(), // typedef'ed as V1 833 // variant<float, double, long double>()) // typedef'ed as V2 834 // will trigger instantiations of: 835 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&), 2, 3>, 836 // tuple<V1&&, V2&&>, std::index_sequence<>> 837 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&), 3>, 838 // tuple<V1&&, V2&&>, std::index_sequence<0>> 839 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&)>, 840 // tuple<V1&&, V2&&>, std::index_sequence<0, 0>> 841 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&)>, 842 // tuple<V1&&, V2&&>, std::index_sequence<0, 1>> 843 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&)>, 844 // tuple<V1&&, V2&&>, std::index_sequence<0, 2>> 845 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&), 3>, 846 // tuple<V1&&, V2&&>, std::index_sequence<1>> 847 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&)>, 848 // tuple<V1&&, V2&&>, std::index_sequence<1, 0>> 849 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&)>, 850 // tuple<V1&&, V2&&>, std::index_sequence<1, 1>> 851 // __gen_vtable_impl<true, _Multi_array<void(*)(V1&&, V2&&)>, 852 // tuple<V1&&, V2&&>, std::index_sequence<1, 2>> 853 // The returned multi-dimensional vtable can be fast accessed by the visitor 854 // using index calculation. 855 template<bool __same_return_types, 856 typename _Array_type, typename _Variant_tuple, typename _Index_seq> 857 struct __gen_vtable_impl; 858 859 // Defines the _S_apply() member that returns a _Multi_array populated 860 // with function pointers that perform the visitation expressions e(m) 861 // for each valid pack of indexes into the variant types _Variants. 862 // 863 // This partial specialization builds up the index sequences by recursively 864 // calling _S_apply() on the next specialization of __gen_vtable_impl. 865 // The base case of the recursion defines the actual function pointers. 866 template<bool __same_return_types, 867 typename _Result_type, typename _Visitor, size_t... __dimensions, 868 typename... _Variants, size_t... __indices> 869 struct __gen_vtable_impl< 870 __same_return_types, 871 _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>, 872 tuple<_Variants...>, std::index_sequence<__indices...>> 873 { 874 using _Next = 875 remove_reference_t<typename _Nth_type<sizeof...(__indices), 876 _Variants...>::type>; 877 using _Array_type = 878 _Multi_array<_Result_type (*)(_Visitor, _Variants...), 879 __dimensions...>; 880 881 static constexpr _Array_type 882 _S_apply() 883 { 884 _Array_type __vtable{}; 885 _S_apply_all_alts( 886 __vtable, make_index_sequence<variant_size_v<_Next>>()); 887 return __vtable; 888 } 889 890 template<size_t... __var_indices> 891 static constexpr void 892 _S_apply_all_alts(_Array_type& __vtable, 893 std::index_sequence<__var_indices...>) 894 { 895 if constexpr (_Extra_visit_slot_needed<_Result_type, _Next>::value) 896 (_S_apply_single_alt<true, __var_indices>( 897 __vtable._M_arr[__var_indices + 1], 898 &(__vtable._M_arr[0])), ...); 899 else 900 (_S_apply_single_alt<false, __var_indices>( 901 __vtable._M_arr[__var_indices]), ...); 902 } 903 904 template<bool __do_cookie, size_t __index, typename _Tp> 905 static constexpr void 906 _S_apply_single_alt(_Tp& __element, _Tp* __cookie_element = nullptr) 907 { 908 using _Alternative = variant_alternative_t<__index, _Next>; 909 if constexpr (__do_cookie) 910 { 911 __element = __gen_vtable_impl< 912 __same_return_types, 913 _Tp, 914 tuple<_Variants...>, 915 std::index_sequence<__indices..., __index>>::_S_apply(); 916 *__cookie_element = __gen_vtable_impl< 917 __same_return_types, 918 _Tp, 919 tuple<_Variants...>, 920 std::index_sequence<__indices..., variant_npos>>::_S_apply(); 921 } 922 else 923 { 924 __element = __gen_vtable_impl< 925 __same_return_types, 926 remove_reference_t<decltype(__element)>, tuple<_Variants...>, 927 std::index_sequence<__indices..., __index>>::_S_apply(); 928 } 929 } 930 }; 931 932 // This partial specialization is the base case for the recursion. 933 // It populates a _Multi_array element with the address of a function 934 // that invokes the visitor with the alternatives specified by __indices. 935 template<bool __same_return_types, 936 typename _Result_type, typename _Visitor, typename... _Variants, 937 size_t... __indices> 938 struct __gen_vtable_impl< 939 __same_return_types, 940 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>, 941 tuple<_Variants...>, std::index_sequence<__indices...>> 942 { 943 using _Array_type = 944 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>; 945 946 template<size_t __index, typename _Variant> 947 static constexpr decltype(auto) 948 __element_by_index_or_cookie(_Variant&& __var) noexcept 949 { 950 if constexpr (__index != variant_npos) 951 return __variant::__get<__index>(std::forward<_Variant>(__var)); 952 else 953 return __variant_cookie{}; 954 } 955 956 static constexpr decltype(auto) 957 __visit_invoke_impl(_Visitor&& __visitor, _Variants... __vars) 958 { 959 // For raw visitation using indices, pass the indices to the visitor: 960 if constexpr (is_same_v<_Result_type, __variant_idx_cookie>) 961 return std::__invoke(std::forward<_Visitor>(__visitor), 962 __element_by_index_or_cookie<__indices>( 963 std::forward<_Variants>(__vars))..., 964 integral_constant<size_t, __indices>()...); 965 // For std::visit<cv void>, cast the result to void: 966 else if constexpr (!__same_return_types && 967 std::is_void_v<_Result_type>) 968 return (void)std::__invoke(std::forward<_Visitor>(__visitor), 969 __element_by_index_or_cookie<__indices>( 970 std::forward<_Variants>(__vars))...); 971 else 972 return std::__invoke(std::forward<_Visitor>(__visitor), 973 __element_by_index_or_cookie<__indices>( 974 std::forward<_Variants>(__vars))...); 975 } 976 977 static constexpr decltype(auto) 978 __do_visit_invoke(_Visitor&& __visitor, _Variants... __vars) 979 { 980 return __visit_invoke_impl(std::forward<_Visitor>(__visitor), 981 std::forward<_Variants>(__vars)...); 982 } 983 984 // Perform the implicit conversion to _Result_type for std::visit<R>. 985 static constexpr _Result_type 986 __do_visit_invoke_r(_Visitor&& __visitor, _Variants... __vars) 987 { 988 return __visit_invoke_impl(std::forward<_Visitor>(__visitor), 989 std::forward<_Variants>(__vars)...); 990 } 991 992 static constexpr decltype(auto) 993 __visit_invoke(_Visitor&& __visitor, _Variants... __vars) 994 { 995 if constexpr (__same_return_types) 996 return __do_visit_invoke(std::forward<_Visitor>(__visitor), 997 std::forward<_Variants>(__vars)...); 998 else 999 return __do_visit_invoke_r(std::forward<_Visitor>(__visitor), 1000 std::forward<_Variants>(__vars)...); 1001 } 1002 1003 static constexpr auto 1004 _S_apply() 1005 { return _Array_type{&__visit_invoke}; } 1006 }; 1007 1008 template<bool __same_return_types, 1009 typename _Result_type, typename _Visitor, typename... _Variants> 1010 struct __gen_vtable 1011 { 1012 using _Array_type = 1013 _Multi_array<_Result_type (*)(_Visitor, _Variants...), 1014 variant_size_v<remove_reference_t<_Variants>>...>; 1015 1016 static constexpr _Array_type _S_vtable 1017 = __gen_vtable_impl<__same_return_types, 1018 _Array_type, tuple<_Variants...>, 1019 std::index_sequence<>>::_S_apply(); 1020 }; 1021 1022 template<size_t _Np, typename _Tp> 1023 struct _Base_dedup : public _Tp { }; 1024 1025 template<typename _Variant, typename __indices> 1026 struct _Variant_hash_base; 1027 1028 template<typename... _Types, size_t... __indices> 1029 struct _Variant_hash_base<variant<_Types...>, 1030 std::index_sequence<__indices...>> 1031 : _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { }; 1032 1033} // namespace __variant 1034} // namespace __detail 1035 1036 template<size_t _Np, typename _Variant, typename... _Args> 1037 void __variant_construct_by_index(_Variant& __v, _Args&&... __args) 1038 { 1039 __v._M_index = _Np; 1040 auto&& __storage = __detail::__variant::__get<_Np>(__v); 1041 ::new ((void*)std::addressof(__storage)) 1042 remove_reference_t<decltype(__storage)> 1043 (std::forward<_Args>(__args)...); 1044 } 1045 1046 template<typename _Tp, typename... _Types> 1047 constexpr bool 1048 holds_alternative(const variant<_Types...>& __v) noexcept 1049 { 1050 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1051 "T should occur for exactly once in alternatives"); 1052 return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>; 1053 } 1054 1055 template<typename _Tp, typename... _Types> 1056 constexpr _Tp& get(variant<_Types...>& __v) 1057 { 1058 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1059 "T should occur for exactly once in alternatives"); 1060 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 1061 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v); 1062 } 1063 1064 template<typename _Tp, typename... _Types> 1065 constexpr _Tp&& get(variant<_Types...>&& __v) 1066 { 1067 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1068 "T should occur for exactly once in alternatives"); 1069 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 1070 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>( 1071 std::move(__v)); 1072 } 1073 1074 template<typename _Tp, typename... _Types> 1075 constexpr const _Tp& get(const variant<_Types...>& __v) 1076 { 1077 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1078 "T should occur for exactly once in alternatives"); 1079 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 1080 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v); 1081 } 1082 1083 template<typename _Tp, typename... _Types> 1084 constexpr const _Tp&& get(const variant<_Types...>&& __v) 1085 { 1086 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1087 "T should occur for exactly once in alternatives"); 1088 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 1089 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>( 1090 std::move(__v)); 1091 } 1092 1093 template<size_t _Np, typename... _Types> 1094 constexpr add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>> 1095 get_if(variant<_Types...>* __ptr) noexcept 1096 { 1097 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; 1098 static_assert(_Np < sizeof...(_Types), 1099 "The index should be in [0, number of alternatives)"); 1100 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void"); 1101 if (__ptr && __ptr->index() == _Np) 1102 return std::addressof(__detail::__variant::__get<_Np>(*__ptr)); 1103 return nullptr; 1104 } 1105 1106 template<size_t _Np, typename... _Types> 1107 constexpr 1108 add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>> 1109 get_if(const variant<_Types...>* __ptr) noexcept 1110 { 1111 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; 1112 static_assert(_Np < sizeof...(_Types), 1113 "The index should be in [0, number of alternatives)"); 1114 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void"); 1115 if (__ptr && __ptr->index() == _Np) 1116 return std::addressof(__detail::__variant::__get<_Np>(*__ptr)); 1117 return nullptr; 1118 } 1119 1120 template<typename _Tp, typename... _Types> 1121 constexpr add_pointer_t<_Tp> 1122 get_if(variant<_Types...>* __ptr) noexcept 1123 { 1124 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1125 "T should occur for exactly once in alternatives"); 1126 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 1127 return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>( 1128 __ptr); 1129 } 1130 1131 template<typename _Tp, typename... _Types> 1132 constexpr add_pointer_t<const _Tp> 1133 get_if(const variant<_Types...>* __ptr) noexcept 1134 { 1135 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 1136 "T should occur for exactly once in alternatives"); 1137 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 1138 return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>( 1139 __ptr); 1140 } 1141 1142 struct monostate { }; 1143 1144#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \ 1145 template<typename... _Types> \ 1146 constexpr bool operator __OP(const variant<_Types...>& __lhs, \ 1147 const variant<_Types...>& __rhs) \ 1148 { \ 1149 bool __ret = true; \ 1150 __do_visit<__detail::__variant::__visit_with_index>( \ 1151 [&__ret, &__lhs] \ 1152 (auto&& __rhs_mem, auto __rhs_index) mutable \ 1153 -> __detail::__variant::__variant_idx_cookie \ 1154 { \ 1155 if constexpr (__rhs_index != variant_npos) \ 1156 { \ 1157 if (__lhs.index() == __rhs_index) \ 1158 { \ 1159 auto& __this_mem = std::get<__rhs_index>(__lhs); \ 1160 __ret = __this_mem __OP __rhs_mem; \ 1161 } \ 1162 else \ 1163 __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \ 1164 } \ 1165 else \ 1166 __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \ 1167 return {}; \ 1168 }, __rhs); \ 1169 return __ret; \ 1170 } \ 1171\ 1172 constexpr bool operator __OP(monostate, monostate) noexcept \ 1173 { return 0 __OP 0; } 1174 1175 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less) 1176 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal) 1177 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal) 1178 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal) 1179 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal) 1180 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater) 1181 1182#undef _VARIANT_RELATION_FUNCTION_TEMPLATE 1183 1184 template<typename _Visitor, typename... _Variants> 1185 constexpr decltype(auto) visit(_Visitor&&, _Variants&&...); 1186 1187 template<typename... _Types> 1188 inline enable_if_t<(is_move_constructible_v<_Types> && ...) 1189 && (is_swappable_v<_Types> && ...)> 1190 swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs) 1191 noexcept(noexcept(__lhs.swap(__rhs))) 1192 { __lhs.swap(__rhs); } 1193 1194 template<typename... _Types> 1195 enable_if_t<!((is_move_constructible_v<_Types> && ...) 1196 && (is_swappable_v<_Types> && ...))> 1197 swap(variant<_Types...>&, variant<_Types...>&) = delete; 1198 1199 class bad_variant_access : public exception 1200 { 1201 public: 1202 bad_variant_access() noexcept : _M_reason("Unknown reason") { } 1203 const char* what() const noexcept override 1204 { return _M_reason; } 1205 1206 private: 1207 bad_variant_access(const char* __reason) : _M_reason(__reason) { } 1208 1209 const char* _M_reason; 1210 1211 friend void __throw_bad_variant_access(const char* __what); 1212 }; 1213 1214 inline void 1215 __throw_bad_variant_access(const char* __what) 1216 { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); } 1217 1218 template<typename... _Types> 1219 class variant 1220 : private __detail::__variant::_Variant_base<_Types...>, 1221 private _Enable_default_constructor< 1222 __detail::__variant::_Traits<_Types...>::_S_default_ctor, 1223 variant<_Types...>>, 1224 private _Enable_copy_move< 1225 __detail::__variant::_Traits<_Types...>::_S_copy_ctor, 1226 __detail::__variant::_Traits<_Types...>::_S_copy_assign, 1227 __detail::__variant::_Traits<_Types...>::_S_move_ctor, 1228 __detail::__variant::_Traits<_Types...>::_S_move_assign, 1229 variant<_Types...>> 1230 { 1231 private: 1232 template <typename... _UTypes, typename _Tp> 1233 friend decltype(auto) __variant_cast(_Tp&&); 1234 template<size_t _Np, typename _Variant, typename... _Args> 1235 friend void __variant_construct_by_index(_Variant& __v, 1236 _Args&&... __args); 1237 1238 static_assert(sizeof...(_Types) > 0, 1239 "variant must have at least one alternative"); 1240 static_assert(!(std::is_reference_v<_Types> || ...), 1241 "variant must have no reference alternative"); 1242 static_assert(!(std::is_void_v<_Types> || ...), 1243 "variant must have no void alternative"); 1244 1245 using _Base = __detail::__variant::_Variant_base<_Types...>; 1246 using _Default_ctor_enabler = 1247 _Enable_default_constructor< 1248 __detail::__variant::_Traits<_Types...>::_S_default_ctor, 1249 variant<_Types...>>; 1250 1251 template<typename _Tp> 1252 static constexpr bool __not_self 1253 = !is_same_v<__remove_cvref_t<_Tp>, variant>; 1254 1255 template<typename _Tp> 1256 static constexpr bool 1257 __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>; 1258 1259 template<typename _Tp> 1260 static constexpr size_t __accepted_index = 1261 __detail::__variant::__accepted_index<_Tp&&, variant>::value; 1262 1263 template<size_t _Np, typename = enable_if_t<(_Np < sizeof...(_Types))>> 1264 using __to_type = variant_alternative_t<_Np, variant>; 1265 1266 template<typename _Tp, typename = enable_if_t<__not_self<_Tp>>> 1267 using __accepted_type = __to_type<__accepted_index<_Tp>>; 1268 1269 template<typename _Tp> 1270 static constexpr size_t __index_of = 1271 __detail::__variant::__index_of_v<_Tp, _Types...>; 1272 1273 using _Traits = __detail::__variant::_Traits<_Types...>; 1274 1275 template<typename _Tp> 1276 struct __is_in_place_tag : false_type { }; 1277 template<typename _Tp> 1278 struct __is_in_place_tag<in_place_type_t<_Tp>> : true_type { }; 1279 template<size_t _Np> 1280 struct __is_in_place_tag<in_place_index_t<_Np>> : true_type { }; 1281 1282 template<typename _Tp> 1283 static constexpr bool __not_in_place_tag 1284 = !__is_in_place_tag<__remove_cvref_t<_Tp>>::value; 1285 1286 public: 1287 variant() = default; 1288 variant(const variant& __rhs) = default; 1289 variant(variant&&) = default; 1290 variant& operator=(const variant&) = default; 1291 variant& operator=(variant&&) = default; 1292 ~variant() = default; 1293 1294 template<typename _Tp, 1295 typename = enable_if_t<sizeof...(_Types) != 0>, 1296 typename = enable_if_t<__not_in_place_tag<_Tp>>, 1297 typename _Tj = __accepted_type<_Tp&&>, 1298 typename = enable_if_t<__exactly_once<_Tj> 1299 && is_constructible_v<_Tj, _Tp>>> 1300 constexpr 1301 variant(_Tp&& __t) 1302 noexcept(is_nothrow_constructible_v<_Tj, _Tp>) 1303 : variant(in_place_index<__accepted_index<_Tp&&>>, 1304 std::forward<_Tp>(__t)) 1305 { } 1306 1307 template<typename _Tp, typename... _Args, 1308 typename = enable_if_t<__exactly_once<_Tp> 1309 && is_constructible_v<_Tp, _Args...>>> 1310 constexpr explicit 1311 variant(in_place_type_t<_Tp>, _Args&&... __args) 1312 : variant(in_place_index<__index_of<_Tp>>, 1313 std::forward<_Args>(__args)...) 1314 { } 1315 1316 template<typename _Tp, typename _Up, typename... _Args, 1317 typename = enable_if_t<__exactly_once<_Tp> 1318 && is_constructible_v<_Tp, 1319 initializer_list<_Up>&, _Args...>>> 1320 constexpr explicit 1321 variant(in_place_type_t<_Tp>, initializer_list<_Up> __il, 1322 _Args&&... __args) 1323 : variant(in_place_index<__index_of<_Tp>>, __il, 1324 std::forward<_Args>(__args)...) 1325 { } 1326 1327 template<size_t _Np, typename... _Args, 1328 typename _Tp = __to_type<_Np>, 1329 typename = enable_if_t<is_constructible_v<_Tp, _Args...>>> 1330 constexpr explicit 1331 variant(in_place_index_t<_Np>, _Args&&... __args) 1332 : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...), 1333 _Default_ctor_enabler(_Enable_default_constructor_tag{}) 1334 { } 1335 1336 template<size_t _Np, typename _Up, typename... _Args, 1337 typename _Tp = __to_type<_Np>, 1338 typename = enable_if_t<is_constructible_v<_Tp, 1339 initializer_list<_Up>&, 1340 _Args...>>> 1341 constexpr explicit 1342 variant(in_place_index_t<_Np>, initializer_list<_Up> __il, 1343 _Args&&... __args) 1344 : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...), 1345 _Default_ctor_enabler(_Enable_default_constructor_tag{}) 1346 { } 1347 1348 template<typename _Tp> 1349 enable_if_t<__exactly_once<__accepted_type<_Tp&&>> 1350 && is_constructible_v<__accepted_type<_Tp&&>, _Tp> 1351 && is_assignable_v<__accepted_type<_Tp&&>&, _Tp>, 1352 variant&> 1353 operator=(_Tp&& __rhs) 1354 noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp> 1355 && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp>) 1356 { 1357 constexpr auto __index = __accepted_index<_Tp&&>; 1358 if (index() == __index) 1359 std::get<__index>(*this) = std::forward<_Tp>(__rhs); 1360 else 1361 { 1362 using _Tj = __accepted_type<_Tp&&>; 1363 if constexpr (is_nothrow_constructible_v<_Tj, _Tp> 1364 || !is_nothrow_move_constructible_v<_Tj>) 1365 this->emplace<__index>(std::forward<_Tp>(__rhs)); 1366 else 1367 operator=(variant(std::forward<_Tp>(__rhs))); 1368 } 1369 return *this; 1370 } 1371 1372 template<typename _Tp, typename... _Args> 1373 enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>, 1374 _Tp&> 1375 emplace(_Args&&... __args) 1376 { 1377 constexpr size_t __index = __index_of<_Tp>; 1378 return this->emplace<__index>(std::forward<_Args>(__args)...); 1379 } 1380 1381 template<typename _Tp, typename _Up, typename... _Args> 1382 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...> 1383 && __exactly_once<_Tp>, 1384 _Tp&> 1385 emplace(initializer_list<_Up> __il, _Args&&... __args) 1386 { 1387 constexpr size_t __index = __index_of<_Tp>; 1388 return this->emplace<__index>(__il, std::forward<_Args>(__args)...); 1389 } 1390 1391 template<size_t _Np, typename... _Args> 1392 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>, 1393 _Args...>, 1394 variant_alternative_t<_Np, variant>&> 1395 emplace(_Args&&... __args) 1396 { 1397 static_assert(_Np < sizeof...(_Types), 1398 "The index should be in [0, number of alternatives)"); 1399 using type = variant_alternative_t<_Np, variant>; 1400 // Provide the strong exception-safety guarantee when possible, 1401 // to avoid becoming valueless. 1402 if constexpr (is_nothrow_constructible_v<type, _Args...>) 1403 { 1404 this->_M_reset(); 1405 __variant_construct_by_index<_Np>(*this, 1406 std::forward<_Args>(__args)...); 1407 } 1408 else if constexpr (is_scalar_v<type>) 1409 { 1410 // This might invoke a potentially-throwing conversion operator: 1411 const type __tmp(std::forward<_Args>(__args)...); 1412 // But these steps won't throw: 1413 this->_M_reset(); 1414 __variant_construct_by_index<_Np>(*this, __tmp); 1415 } 1416 else if constexpr (__detail::__variant::_Never_valueless_alt<type>() 1417 && _Traits::_S_move_assign) 1418 { 1419 // This construction might throw: 1420 variant __tmp(in_place_index<_Np>, 1421 std::forward<_Args>(__args)...); 1422 // But _Never_valueless_alt<type> means this won't: 1423 *this = std::move(__tmp); 1424 } 1425 else 1426 { 1427 // This case only provides the basic exception-safety guarantee, 1428 // i.e. the variant can become valueless. 1429 this->_M_reset(); 1430 __try 1431 { 1432 __variant_construct_by_index<_Np>(*this, 1433 std::forward<_Args>(__args)...); 1434 } 1435 __catch (...) 1436 { 1437 this->_M_index = variant_npos; 1438 __throw_exception_again; 1439 } 1440 } 1441 return std::get<_Np>(*this); 1442 } 1443 1444 template<size_t _Np, typename _Up, typename... _Args> 1445 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>, 1446 initializer_list<_Up>&, _Args...>, 1447 variant_alternative_t<_Np, variant>&> 1448 emplace(initializer_list<_Up> __il, _Args&&... __args) 1449 { 1450 static_assert(_Np < sizeof...(_Types), 1451 "The index should be in [0, number of alternatives)"); 1452 using type = variant_alternative_t<_Np, variant>; 1453 // Provide the strong exception-safety guarantee when possible, 1454 // to avoid becoming valueless. 1455 if constexpr (is_nothrow_constructible_v<type, 1456 initializer_list<_Up>&, 1457 _Args...>) 1458 { 1459 this->_M_reset(); 1460 __variant_construct_by_index<_Np>(*this, __il, 1461 std::forward<_Args>(__args)...); 1462 } 1463 else if constexpr (__detail::__variant::_Never_valueless_alt<type>() 1464 && _Traits::_S_move_assign) 1465 { 1466 // This construction might throw: 1467 variant __tmp(in_place_index<_Np>, __il, 1468 std::forward<_Args>(__args)...); 1469 // But _Never_valueless_alt<type> means this won't: 1470 *this = std::move(__tmp); 1471 } 1472 else 1473 { 1474 // This case only provides the basic exception-safety guarantee, 1475 // i.e. the variant can become valueless. 1476 this->_M_reset(); 1477 __try 1478 { 1479 __variant_construct_by_index<_Np>(*this, __il, 1480 std::forward<_Args>(__args)...); 1481 } 1482 __catch (...) 1483 { 1484 this->_M_index = variant_npos; 1485 __throw_exception_again; 1486 } 1487 } 1488 return std::get<_Np>(*this); 1489 } 1490 1491 constexpr bool valueless_by_exception() const noexcept 1492 { return !this->_M_valid(); } 1493 1494 constexpr size_t index() const noexcept 1495 { 1496 if (this->_M_index == 1497 typename _Base::__index_type(variant_npos)) 1498 return variant_npos; 1499 return this->_M_index; 1500 } 1501 1502 void 1503 swap(variant& __rhs) 1504 noexcept((__is_nothrow_swappable<_Types>::value && ...) 1505 && is_nothrow_move_constructible_v<variant>) 1506 { 1507 __do_visit<__detail::__variant::__visit_with_index>( 1508 [this, &__rhs](auto&& __rhs_mem, 1509 auto __rhs_index) mutable 1510 -> __detail::__variant::__variant_idx_cookie 1511 { 1512 if constexpr (__rhs_index != variant_npos) 1513 { 1514 if (this->index() == __rhs_index) 1515 { 1516 auto& __this_mem = 1517 std::get<__rhs_index>(*this); 1518 using std::swap; 1519 swap(__this_mem, __rhs_mem); 1520 } 1521 else 1522 { 1523 if (this->index() != variant_npos) 1524 { 1525 auto __tmp(std::move(__rhs_mem)); 1526 __rhs = std::move(*this); 1527 this->_M_destructive_move(__rhs_index, 1528 std::move(__tmp)); 1529 } 1530 else 1531 { 1532 this->_M_destructive_move(__rhs_index, 1533 std::move(__rhs_mem)); 1534 __rhs._M_reset(); 1535 } 1536 } 1537 } 1538 else 1539 { 1540 if (this->index() != variant_npos) 1541 { 1542 __rhs = std::move(*this); 1543 this->_M_reset(); 1544 } 1545 } 1546 return {}; 1547 }, __rhs); 1548 } 1549 1550 private: 1551 1552#if defined(__clang__) && __clang_major__ <= 7 1553 public: 1554 using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852 1555 private: 1556#endif 1557 1558 template<size_t _Np, typename _Vp> 1559 friend constexpr decltype(auto) 1560 __detail::__variant::__get(_Vp&& __v) noexcept; 1561 1562 template<typename _Vp> 1563 friend void* __detail::__variant::__get_storage(_Vp&& __v); 1564 1565#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \ 1566 template<typename... _Tp> \ 1567 friend constexpr bool \ 1568 operator __OP(const variant<_Tp...>& __lhs, \ 1569 const variant<_Tp...>& __rhs); 1570 1571 _VARIANT_RELATION_FUNCTION_TEMPLATE(<) 1572 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=) 1573 _VARIANT_RELATION_FUNCTION_TEMPLATE(==) 1574 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=) 1575 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=) 1576 _VARIANT_RELATION_FUNCTION_TEMPLATE(>) 1577 1578#undef _VARIANT_RELATION_FUNCTION_TEMPLATE 1579 }; 1580 1581 template<size_t _Np, typename... _Types> 1582 constexpr variant_alternative_t<_Np, variant<_Types...>>& 1583 get(variant<_Types...>& __v) 1584 { 1585 static_assert(_Np < sizeof...(_Types), 1586 "The index should be in [0, number of alternatives)"); 1587 if (__v.index() != _Np) 1588 __throw_bad_variant_access("Unexpected index"); 1589 return __detail::__variant::__get<_Np>(__v); 1590 } 1591 1592 template<size_t _Np, typename... _Types> 1593 constexpr variant_alternative_t<_Np, variant<_Types...>>&& 1594 get(variant<_Types...>&& __v) 1595 { 1596 static_assert(_Np < sizeof...(_Types), 1597 "The index should be in [0, number of alternatives)"); 1598 if (__v.index() != _Np) 1599 __throw_bad_variant_access("Unexpected index"); 1600 return __detail::__variant::__get<_Np>(std::move(__v)); 1601 } 1602 1603 template<size_t _Np, typename... _Types> 1604 constexpr const variant_alternative_t<_Np, variant<_Types...>>& 1605 get(const variant<_Types...>& __v) 1606 { 1607 static_assert(_Np < sizeof...(_Types), 1608 "The index should be in [0, number of alternatives)"); 1609 if (__v.index() != _Np) 1610 __throw_bad_variant_access("Unexpected index"); 1611 return __detail::__variant::__get<_Np>(__v); 1612 } 1613 1614 template<size_t _Np, typename... _Types> 1615 constexpr const variant_alternative_t<_Np, variant<_Types...>>&& 1616 get(const variant<_Types...>&& __v) 1617 { 1618 static_assert(_Np < sizeof...(_Types), 1619 "The index should be in [0, number of alternatives)"); 1620 if (__v.index() != _Np) 1621 __throw_bad_variant_access("Unexpected index"); 1622 return __detail::__variant::__get<_Np>(std::move(__v)); 1623 } 1624 1625 template<bool __use_index, 1626 bool __same_return_types, 1627 typename _Visitor, typename... _Variants> 1628 constexpr decltype(auto) 1629 __do_visit(_Visitor&& __visitor, _Variants&&... __variants) 1630 { 1631 using _Deduced_type = std::invoke_result<_Visitor, 1632 decltype(std::get<0>(std::declval<_Variants>()))...>; 1633 1634 using _Result_type = typename std::conditional_t<__use_index, 1635 __detail::__variant::__variant_idx_cookie, 1636 _Deduced_type>::type; 1637 1638 constexpr auto& __vtable = __detail::__variant::__gen_vtable< 1639 __same_return_types, 1640 _Result_type, _Visitor&&, _Variants&&...>::_S_vtable; 1641 1642 auto __func_ptr = __vtable._M_access(__variants.index()...); 1643 return (*__func_ptr)(std::forward<_Visitor>(__visitor), 1644 std::forward<_Variants>(__variants)...); 1645 } 1646 1647 template<typename _Visitor, typename... _Variants> 1648 constexpr decltype(auto) 1649 visit(_Visitor&& __visitor, _Variants&&... __variants) 1650 { 1651 if ((__variants.valueless_by_exception() || ...)) 1652 __throw_bad_variant_access("Unexpected index"); 1653 1654 return __do_visit(std::forward<_Visitor>(__visitor), 1655 std::forward<_Variants>(__variants)...); 1656 } 1657 1658#if __cplusplus > 201703L 1659 template<typename _Res, typename _Visitor, typename... _Variants> 1660 constexpr _Res 1661 visit(_Visitor&& __visitor, _Variants&&... __variants) 1662 { 1663 if ((__variants.valueless_by_exception() || ...)) 1664 __throw_bad_variant_access("Unexpected index"); 1665 1666 if constexpr (std::is_void_v<_Res>) 1667 (void) __do_visit<false, false>(std::forward<_Visitor>(__visitor), 1668 std::forward<_Variants>(__variants)...); 1669 else 1670 return __do_visit<false, false>(std::forward<_Visitor>(__visitor), 1671 std::forward<_Variants>(__variants)...); 1672 } 1673#endif 1674 1675 template<bool, typename... _Types> 1676 struct __variant_hash_call_base_impl 1677 { 1678 size_t 1679 operator()(const variant<_Types...>& __t) const 1680 noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...)) 1681 { 1682 size_t __ret; 1683 __do_visit([&__t, &__ret](auto&& __t_mem) mutable 1684 -> __detail::__variant::__variant_cookie 1685 { 1686 using _Type = __remove_cvref_t<decltype(__t_mem)>; 1687 if constexpr (!is_same_v<_Type, 1688 __detail::__variant::__variant_cookie>) 1689 __ret = std::hash<size_t>{}(__t.index()) 1690 + std::hash<_Type>{}(__t_mem); 1691 else 1692 __ret = std::hash<size_t>{}(__t.index()); 1693 return {}; 1694 }, __t); 1695 return __ret; 1696 } 1697 }; 1698 1699 template<typename... _Types> 1700 struct __variant_hash_call_base_impl<false, _Types...> {}; 1701 1702 template<typename... _Types> 1703 using __variant_hash_call_base = 1704 __variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>:: 1705 __enable_hash_call &&...), _Types...>; 1706 1707 template<typename... _Types> 1708 struct hash<variant<_Types...>> 1709 : private __detail::__variant::_Variant_hash_base< 1710 variant<_Types...>, std::index_sequence_for<_Types...>>, 1711 public __variant_hash_call_base<_Types...> 1712 { 1713 using result_type [[__deprecated__]] = size_t; 1714 using argument_type [[__deprecated__]] = variant<_Types...>; 1715 }; 1716 1717 template<> 1718 struct hash<monostate> 1719 { 1720 using result_type [[__deprecated__]] = size_t; 1721 using argument_type [[__deprecated__]] = monostate; 1722 1723 size_t 1724 operator()(const monostate& __t) const noexcept 1725 { 1726 constexpr size_t __magic_monostate_hash = -7777; 1727 return __magic_monostate_hash; 1728 } 1729 }; 1730 1731 template<typename... _Types> 1732 struct __is_fast_hash<hash<variant<_Types...>>> 1733 : bool_constant<(__is_fast_hash<_Types>::value && ...)> 1734 { }; 1735 1736_GLIBCXX_END_NAMESPACE_VERSION 1737} // namespace std 1738 1739#endif // C++17 1740 1741#endif // _GLIBCXX_VARIANT 1742