1// <variant> -*- C++ -*- 2 3// Copyright (C) 2016-2018 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 201603 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 141namespace __detail 142{ 143namespace __variant 144{ 145 // Returns the first apparence of _Tp in _Types. 146 // Returns sizeof...(_Types) if _Tp is not in _Types. 147 template<typename _Tp, typename... _Types> 148 struct __index_of : std::integral_constant<size_t, 0> {}; 149 150 template<typename _Tp, typename... _Types> 151 inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value; 152 153 template<typename _Tp, typename _First, typename... _Rest> 154 struct __index_of<_Tp, _First, _Rest...> : 155 std::integral_constant<size_t, is_same_v<_Tp, _First> 156 ? 0 : __index_of_v<_Tp, _Rest...> + 1> {}; 157 158 // _Uninitialized<T> is guaranteed to be a literal type, even if T is not. 159 // We have to do this, because [basic.types]p10.5.3 (n4606) is not implemented 160 // yet. When it's implemented, _Uninitialized<T> can be changed to the alias 161 // to T, therefore equivalent to being removed entirely. 162 // 163 // Another reason we may not want to remove _Uninitialzied<T> may be that, we 164 // want _Uninitialized<T> to be trivially destructible, no matter whether T 165 // is; but we will see. 166 template<typename _Type, bool = std::is_literal_type_v<_Type>> 167 struct _Uninitialized; 168 169 template<typename _Type> 170 struct _Uninitialized<_Type, true> 171 { 172 template<typename... _Args> 173 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args) 174 : _M_storage(std::forward<_Args>(__args)...) 175 { } 176 177 constexpr const _Type& _M_get() const & 178 { return _M_storage; } 179 180 constexpr _Type& _M_get() & 181 { return _M_storage; } 182 183 constexpr const _Type&& _M_get() const && 184 { return std::move(_M_storage); } 185 186 constexpr _Type&& _M_get() && 187 { return std::move(_M_storage); } 188 189 _Type _M_storage; 190 }; 191 192 template<typename _Type> 193 struct _Uninitialized<_Type, false> 194 { 195 template<typename... _Args> 196 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args) 197 { ::new (&_M_storage) _Type(std::forward<_Args>(__args)...); } 198 199 const _Type& _M_get() const & 200 { return *_M_storage._M_ptr(); } 201 202 _Type& _M_get() & 203 { return *_M_storage._M_ptr(); } 204 205 const _Type&& _M_get() const && 206 { return std::move(*_M_storage._M_ptr()); } 207 208 _Type&& _M_get() && 209 { return std::move(*_M_storage._M_ptr()); } 210 211 __gnu_cxx::__aligned_membuf<_Type> _M_storage; 212 }; 213 214 template<typename _Ref> 215 _Ref __ref_cast(void* __ptr) 216 { 217 return static_cast<_Ref>(*static_cast<remove_reference_t<_Ref>*>(__ptr)); 218 } 219 220 template<typename _Union> 221 constexpr decltype(auto) __get(in_place_index_t<0>, _Union&& __u) 222 { return std::forward<_Union>(__u)._M_first._M_get(); } 223 224 template<size_t _Np, typename _Union> 225 constexpr decltype(auto) __get(in_place_index_t<_Np>, _Union&& __u) 226 { 227 return __variant::__get(in_place_index<_Np-1>, 228 std::forward<_Union>(__u)._M_rest); 229 } 230 231 // Returns the typed storage for __v. 232 template<size_t _Np, typename _Variant> 233 constexpr decltype(auto) __get(_Variant&& __v) 234 { 235 return __variant::__get(std::in_place_index<_Np>, 236 std::forward<_Variant>(__v)._M_u); 237 } 238 239 // Various functions as "vtable" entries, where those vtables are used by 240 // polymorphic operations. 241 template<typename _Lhs, typename _Rhs> 242 void 243 __erased_ctor(void* __lhs, void* __rhs) 244 { 245 using _Type = remove_reference_t<_Lhs>; 246 ::new (__lhs) _Type(__variant::__ref_cast<_Rhs>(__rhs)); 247 } 248 249 template<typename _Variant, size_t _Np> 250 void 251 __erased_dtor(_Variant&& __v) 252 { std::_Destroy(std::__addressof(__get<_Np>(__v))); } 253 254 template<typename _Lhs, typename _Rhs> 255 void 256 __erased_assign(void* __lhs, void* __rhs) 257 { 258 __variant::__ref_cast<_Lhs>(__lhs) = __variant::__ref_cast<_Rhs>(__rhs); 259 } 260 261 template<typename _Lhs, typename _Rhs> 262 void 263 __erased_swap(void* __lhs, void* __rhs) 264 { 265 using std::swap; 266 swap(__variant::__ref_cast<_Lhs>(__lhs), 267 __variant::__ref_cast<_Rhs>(__rhs)); 268 } 269 270#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \ 271 template<typename _Variant, size_t _Np> \ 272 constexpr bool \ 273 __erased_##__NAME(const _Variant& __lhs, const _Variant& __rhs) \ 274 { \ 275 return __variant::__get<_Np>(std::forward<_Variant>(__lhs)) \ 276 __OP __variant::__get<_Np>(std::forward<_Variant>(__rhs)); \ 277 } 278 279 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less) 280 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal) 281 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal) 282 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal) 283 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal) 284 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater) 285 286#undef _VARIANT_RELATION_FUNCTION_TEMPLATE 287 288 template<typename _Tp> 289 size_t 290 __erased_hash(void* __t) 291 { 292 return std::hash<remove_cv_t<remove_reference_t<_Tp>>>{}( 293 __variant::__ref_cast<_Tp>(__t)); 294 } 295 296 template<typename... _Types> 297 struct _Traits 298 { 299 static constexpr bool _S_default_ctor = 300 is_default_constructible_v<typename _Nth_type<0, _Types...>::type>; 301 static constexpr bool _S_copy_ctor = 302 (is_copy_constructible_v<_Types> && ...); 303 static constexpr bool _S_move_ctor = 304 (is_move_constructible_v<_Types> && ...); 305 static constexpr bool _S_copy_assign = 306 _S_copy_ctor && _S_move_ctor 307 && (is_copy_assignable_v<_Types> && ...); 308 static constexpr bool _S_move_assign = 309 _S_move_ctor 310 && (is_move_assignable_v<_Types> && ...); 311 312 static constexpr bool _S_trivial_dtor = 313 (is_trivially_destructible_v<_Types> && ...); 314 static constexpr bool _S_trivial_copy_ctor = 315 (is_trivially_copy_constructible_v<_Types> && ...); 316 static constexpr bool _S_trivial_move_ctor = 317 (is_trivially_move_constructible_v<_Types> && ...); 318 static constexpr bool _S_trivial_copy_assign = 319 _S_trivial_dtor && (is_trivially_copy_assignable_v<_Types> && ...); 320 static constexpr bool _S_trivial_move_assign = 321 _S_trivial_dtor && (is_trivially_move_assignable_v<_Types> && ...); 322 323 // The following nothrow traits are for non-trivial SMFs. Trivial SMFs 324 // are always nothrow. 325 static constexpr bool _S_nothrow_default_ctor = 326 is_nothrow_default_constructible_v< 327 typename _Nth_type<0, _Types...>::type>; 328 static constexpr bool _S_nothrow_copy_ctor = false; 329 static constexpr bool _S_nothrow_move_ctor = 330 (is_nothrow_move_constructible_v<_Types> && ...); 331 static constexpr bool _S_nothrow_copy_assign = false; 332 static constexpr bool _S_nothrow_move_assign = 333 _S_nothrow_move_ctor && (is_nothrow_move_assignable_v<_Types> && ...); 334 }; 335 336 // Defines members and ctors. 337 template<typename... _Types> 338 union _Variadic_union { }; 339 340 template<typename _First, typename... _Rest> 341 union _Variadic_union<_First, _Rest...> 342 { 343 constexpr _Variadic_union() : _M_rest() { } 344 345 template<typename... _Args> 346 constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args) 347 : _M_first(in_place_index<0>, std::forward<_Args>(__args)...) 348 { } 349 350 template<size_t _Np, typename... _Args> 351 constexpr _Variadic_union(in_place_index_t<_Np>, _Args&&... __args) 352 : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...) 353 { } 354 355 _Uninitialized<_First> _M_first; 356 _Variadic_union<_Rest...> _M_rest; 357 }; 358 359 // Defines index and the dtor, possibly trivial. 360 template<bool __trivially_destructible, typename... _Types> 361 struct _Variant_storage; 362 363 template <typename... _Types> 364 using __select_index = 365 typename __select_int::_Select_int_base<sizeof...(_Types) + 1, 366 unsigned char, 367 unsigned short>::type::value_type; 368 369 template<typename... _Types> 370 struct _Variant_storage<false, _Types...> 371 { 372 template<size_t... __indices> 373 static constexpr void (*_S_vtable[])(const _Variant_storage&) = 374 { &__erased_dtor<const _Variant_storage&, __indices>... }; 375 376 constexpr _Variant_storage() : _M_index(variant_npos) { } 377 378 template<size_t _Np, typename... _Args> 379 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) 380 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), 381 _M_index(_Np) 382 { } 383 384 template<size_t... __indices> 385 constexpr void _M_reset_impl(std::index_sequence<__indices...>) 386 { 387 if (_M_index != __index_type(variant_npos)) 388 _S_vtable<__indices...>[_M_index](*this); 389 } 390 391 void _M_reset() 392 { 393 _M_reset_impl(std::index_sequence_for<_Types...>{}); 394 _M_index = variant_npos; 395 } 396 397 ~_Variant_storage() 398 { _M_reset(); } 399 400 void* 401 _M_storage() const 402 { 403 return const_cast<void*>(static_cast<const void*>( 404 std::addressof(_M_u))); 405 } 406 407 constexpr bool 408 _M_valid() const noexcept 409 { 410 return this->_M_index != __index_type(variant_npos); 411 } 412 413 _Variadic_union<_Types...> _M_u; 414 using __index_type = __select_index<_Types...>; 415 __index_type _M_index; 416 }; 417 418 template<typename... _Types> 419 struct _Variant_storage<true, _Types...> 420 { 421 constexpr _Variant_storage() : _M_index(variant_npos) { } 422 423 template<size_t _Np, typename... _Args> 424 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args) 425 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...), 426 _M_index(_Np) 427 { } 428 429 void _M_reset() 430 { _M_index = variant_npos; } 431 432 void* 433 _M_storage() const 434 { 435 return const_cast<void*>(static_cast<const void*>( 436 std::addressof(_M_u))); 437 } 438 439 constexpr bool 440 _M_valid() const noexcept 441 { 442 return this->_M_index != __index_type(variant_npos); 443 } 444 445 _Variadic_union<_Types...> _M_u; 446 using __index_type = __select_index<_Types...>; 447 __index_type _M_index; 448 }; 449 450 template<typename... _Types> 451 using _Variant_storage_alias = 452 _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>; 453 454 // The following are (Copy|Move) (ctor|assign) layers for forwarding 455 // triviality and handling non-trivial SMF behaviors. 456 457 template<bool, typename... _Types> 458 struct _Copy_ctor_base : _Variant_storage_alias<_Types...> 459 { 460 using _Base = _Variant_storage_alias<_Types...>; 461 using _Base::_Base; 462 463 _Copy_ctor_base(const _Copy_ctor_base& __rhs) 464 noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor) 465 { 466 if (__rhs._M_valid()) 467 { 468 static constexpr void (*_S_vtable[])(void*, void*) = 469 { &__erased_ctor<_Types&, const _Types&>... }; 470 _S_vtable[__rhs._M_index](this->_M_storage(), __rhs._M_storage()); 471 this->_M_index = __rhs._M_index; 472 } 473 } 474 475 _Copy_ctor_base(_Copy_ctor_base&&) = default; 476 _Copy_ctor_base& operator=(const _Copy_ctor_base&) = default; 477 _Copy_ctor_base& operator=(_Copy_ctor_base&&) = default; 478 }; 479 480 template<typename... _Types> 481 struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...> 482 { 483 using _Base = _Variant_storage_alias<_Types...>; 484 using _Base::_Base; 485 }; 486 487 template<typename... _Types> 488 using _Copy_ctor_alias = 489 _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>; 490 491 template<bool, typename... _Types> 492 struct _Move_ctor_base : _Copy_ctor_alias<_Types...> 493 { 494 using _Base = _Copy_ctor_alias<_Types...>; 495 using _Base::_Base; 496 497 _Move_ctor_base(_Move_ctor_base&& __rhs) 498 noexcept(_Traits<_Types...>::_S_nothrow_move_ctor) 499 { 500 if (__rhs._M_valid()) 501 { 502 static constexpr void (*_S_vtable[])(void*, void*) = 503 { &__erased_ctor<_Types&, _Types&&>... }; 504 _S_vtable[__rhs._M_index](this->_M_storage(), __rhs._M_storage()); 505 this->_M_index = __rhs._M_index; 506 } 507 } 508 509 _Move_ctor_base(const _Move_ctor_base&) = default; 510 _Move_ctor_base& operator=(const _Move_ctor_base&) = default; 511 _Move_ctor_base& operator=(_Move_ctor_base&&) = default; 512 }; 513 514 template<typename... _Types> 515 struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...> 516 { 517 using _Base = _Copy_ctor_alias<_Types...>; 518 using _Base::_Base; 519 }; 520 521 template<typename... _Types> 522 using _Move_ctor_alias = 523 _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>; 524 525 template<bool, typename... _Types> 526 struct _Copy_assign_base : _Move_ctor_alias<_Types...> 527 { 528 using _Base = _Move_ctor_alias<_Types...>; 529 using _Base::_Base; 530 531 _Copy_assign_base& 532 operator=(const _Copy_assign_base& __rhs) 533 noexcept(_Traits<_Types...>::_S_nothrow_copy_assign) 534 { 535 if (this->_M_index == __rhs._M_index) 536 { 537 if (__rhs._M_valid()) 538 { 539 static constexpr void (*_S_vtable[])(void*, void*) = 540 { &__erased_assign<_Types&, const _Types&>... }; 541 _S_vtable[__rhs._M_index](this->_M_storage(), __rhs._M_storage()); 542 } 543 } 544 else 545 { 546 _Copy_assign_base __tmp(__rhs); 547 this->~_Copy_assign_base(); 548 __try 549 { 550 ::new (this) _Copy_assign_base(std::move(__tmp)); 551 } 552 __catch (...) 553 { 554 this->_M_index = variant_npos; 555 __throw_exception_again; 556 } 557 } 558 __glibcxx_assert(this->_M_index == __rhs._M_index); 559 return *this; 560 } 561 562 _Copy_assign_base(const _Copy_assign_base&) = default; 563 _Copy_assign_base(_Copy_assign_base&&) = default; 564 _Copy_assign_base& operator=(_Copy_assign_base&&) = default; 565 }; 566 567 template<typename... _Types> 568 struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...> 569 { 570 using _Base = _Move_ctor_alias<_Types...>; 571 using _Base::_Base; 572 }; 573 574 template<typename... _Types> 575 using _Copy_assign_alias = 576 _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, 577 _Types...>; 578 579 template<bool, typename... _Types> 580 struct _Move_assign_base : _Copy_assign_alias<_Types...> 581 { 582 using _Base = _Copy_assign_alias<_Types...>; 583 using _Base::_Base; 584 585 void _M_destructive_move(_Move_assign_base&& __rhs) 586 { 587 this->~_Move_assign_base(); 588 __try 589 { 590 ::new (this) _Move_assign_base(std::move(__rhs)); 591 } 592 __catch (...) 593 { 594 this->_M_index = variant_npos; 595 __throw_exception_again; 596 } 597 } 598 599 _Move_assign_base& 600 operator=(_Move_assign_base&& __rhs) 601 noexcept(_Traits<_Types...>::_S_nothrow_move_assign) 602 { 603 if (this->_M_index == __rhs._M_index) 604 { 605 if (__rhs._M_valid()) 606 { 607 static constexpr void (*_S_vtable[])(void*, void*) = 608 { &__erased_assign<_Types&, _Types&&>... }; 609 _S_vtable[__rhs._M_index] 610 (this->_M_storage(), __rhs._M_storage()); 611 } 612 } 613 else 614 { 615 _Move_assign_base __tmp(std::move(__rhs)); 616 this->~_Move_assign_base(); 617 __try 618 { 619 ::new (this) _Move_assign_base(std::move(__tmp)); 620 } 621 __catch (...) 622 { 623 this->_M_index = variant_npos; 624 __throw_exception_again; 625 } 626 } 627 __glibcxx_assert(this->_M_index == __rhs._M_index); 628 return *this; 629 } 630 631 _Move_assign_base(const _Move_assign_base&) = default; 632 _Move_assign_base(_Move_assign_base&&) = default; 633 _Move_assign_base& operator=(const _Move_assign_base&) = default; 634 }; 635 636 template<typename... _Types> 637 struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...> 638 { 639 using _Base = _Copy_assign_alias<_Types...>; 640 using _Base::_Base; 641 }; 642 643 template<typename... _Types> 644 using _Move_assign_alias = 645 _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign, 646 _Types...>; 647 648 template<typename... _Types> 649 struct _Variant_base : _Move_assign_alias<_Types...> 650 { 651 using _Base = _Move_assign_alias<_Types...>; 652 653 constexpr 654 _Variant_base() 655 noexcept(_Traits<_Types...>::_S_nothrow_default_ctor) 656 : _Variant_base(in_place_index<0>) { } 657 658 template<size_t _Np, typename... _Args> 659 constexpr explicit 660 _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args) 661 : _Base(__i, std::forward<_Args>(__args)...) 662 { } 663 664 _Variant_base(const _Variant_base&) = default; 665 _Variant_base(_Variant_base&&) = default; 666 _Variant_base& operator=(const _Variant_base&) = default; 667 _Variant_base& operator=(_Variant_base&&) = default; 668 }; 669 670 // For how many times does _Tp appear in _Tuple? 671 template<typename _Tp, typename _Tuple> 672 struct __tuple_count; 673 674 template<typename _Tp, typename _Tuple> 675 inline constexpr size_t __tuple_count_v = 676 __tuple_count<_Tp, _Tuple>::value; 677 678 template<typename _Tp, typename... _Types> 679 struct __tuple_count<_Tp, tuple<_Types...>> 680 : integral_constant<size_t, 0> { }; 681 682 template<typename _Tp, typename _First, typename... _Rest> 683 struct __tuple_count<_Tp, tuple<_First, _Rest...>> 684 : integral_constant< 685 size_t, 686 __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { }; 687 688 // TODO: Reuse this in <tuple> ? 689 template<typename _Tp, typename... _Types> 690 inline constexpr bool __exactly_once = 691 __tuple_count_v<_Tp, tuple<_Types...>> == 1; 692 693 // Takes _Types and create an overloaded _S_fun for each type. 694 // If a type appears more than once in _Types, create only one overload. 695 template<typename... _Types> 696 struct __overload_set 697 { static void _S_fun(); }; 698 699 template<typename _First, typename... _Rest> 700 struct __overload_set<_First, _Rest...> : __overload_set<_Rest...> 701 { 702 using __overload_set<_Rest...>::_S_fun; 703 static integral_constant<size_t, sizeof...(_Rest)> _S_fun(_First); 704 }; 705 706 template<typename... _Rest> 707 struct __overload_set<void, _Rest...> : __overload_set<_Rest...> 708 { 709 using __overload_set<_Rest...>::_S_fun; 710 }; 711 712 // Helper for variant(_Tp&&) and variant::operator=(_Tp&&). 713 // __accepted_index maps the arbitrary _Tp to an alternative type in _Variant. 714 template<typename _Tp, typename _Variant, typename = void> 715 struct __accepted_index 716 { static constexpr size_t value = variant_npos; }; 717 718 template<typename _Tp, typename... _Types> 719 struct __accepted_index< 720 _Tp, variant<_Types...>, 721 decltype(__overload_set<_Types...>::_S_fun(std::declval<_Tp>()), 722 std::declval<void>())> 723 { 724 static constexpr size_t value = sizeof...(_Types) - 1 725 - decltype(__overload_set<_Types...>:: 726 _S_fun(std::declval<_Tp>()))::value; 727 }; 728 729 // Returns the raw storage for __v. 730 template<typename _Variant> 731 void* __get_storage(_Variant&& __v) 732 { return __v._M_storage(); } 733 734 // Used for storing multi-dimensional vtable. 735 template<typename _Tp, size_t... _Dimensions> 736 struct _Multi_array 737 { 738 constexpr const _Tp& 739 _M_access() const 740 { return _M_data; } 741 742 _Tp _M_data; 743 }; 744 745 template<typename _Tp, size_t __first, size_t... __rest> 746 struct _Multi_array<_Tp, __first, __rest...> 747 { 748 template<typename... _Args> 749 constexpr const _Tp& 750 _M_access(size_t __first_index, _Args... __rest_indices) const 751 { return _M_arr[__first_index]._M_access(__rest_indices...); } 752 753 _Multi_array<_Tp, __rest...> _M_arr[__first]; 754 }; 755 756 // Creates a multi-dimensional vtable recursively. 757 // 758 // For example, 759 // visit([](auto, auto){}, 760 // variant<int, char>(), // typedef'ed as V1 761 // variant<float, double, long double>()) // typedef'ed as V2 762 // will trigger instantiations of: 763 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>, 764 // tuple<V1&&, V2&&>, std::index_sequence<>> 765 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>, 766 // tuple<V1&&, V2&&>, std::index_sequence<0>> 767 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 768 // tuple<V1&&, V2&&>, std::index_sequence<0, 0>> 769 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 770 // tuple<V1&&, V2&&>, std::index_sequence<0, 1>> 771 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 772 // tuple<V1&&, V2&&>, std::index_sequence<0, 2>> 773 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>, 774 // tuple<V1&&, V2&&>, std::index_sequence<1>> 775 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 776 // tuple<V1&&, V2&&>, std::index_sequence<1, 0>> 777 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 778 // tuple<V1&&, V2&&>, std::index_sequence<1, 1>> 779 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>, 780 // tuple<V1&&, V2&&>, std::index_sequence<1, 2>> 781 // The returned multi-dimensional vtable can be fast accessed by the visitor 782 // using index calculation. 783 template<typename _Array_type, typename _Variant_tuple, typename _Index_seq> 784 struct __gen_vtable_impl; 785 786 template<typename _Result_type, typename _Visitor, size_t... __dimensions, 787 typename... _Variants, size_t... __indices> 788 struct __gen_vtable_impl< 789 _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>, 790 tuple<_Variants...>, std::index_sequence<__indices...>> 791 { 792 using _Next = 793 remove_reference_t<typename _Nth_type<sizeof...(__indices), 794 _Variants...>::type>; 795 using _Array_type = 796 _Multi_array<_Result_type (*)(_Visitor, _Variants...), 797 __dimensions...>; 798 799 static constexpr _Array_type 800 _S_apply() 801 { 802 _Array_type __vtable{}; 803 _S_apply_all_alts( 804 __vtable, make_index_sequence<variant_size_v<_Next>>()); 805 return __vtable; 806 } 807 808 template<size_t... __var_indices> 809 static constexpr void 810 _S_apply_all_alts(_Array_type& __vtable, 811 std::index_sequence<__var_indices...>) 812 { 813 (_S_apply_single_alt<__var_indices>( 814 __vtable._M_arr[__var_indices]), ...); 815 } 816 817 template<size_t __index, typename _Tp> 818 static constexpr void 819 _S_apply_single_alt(_Tp& __element) 820 { 821 using _Alternative = variant_alternative_t<__index, _Next>; 822 __element = __gen_vtable_impl< 823 remove_reference_t< 824 decltype(__element)>, tuple<_Variants...>, 825 std::index_sequence<__indices..., __index>>::_S_apply(); 826 } 827 }; 828 829 template<typename _Result_type, typename _Visitor, typename... _Variants, 830 size_t... __indices> 831 struct __gen_vtable_impl< 832 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>, 833 tuple<_Variants...>, std::index_sequence<__indices...>> 834 { 835 using _Array_type = 836 _Multi_array<_Result_type (*)(_Visitor&&, _Variants...)>; 837 838 decltype(auto) 839 static constexpr __visit_invoke(_Visitor&& __visitor, _Variants... __vars) 840 { 841 return __invoke(std::forward<_Visitor>(__visitor), 842 std::get<__indices>( 843 std::forward<_Variants>(__vars))...); 844 } 845 846 static constexpr auto 847 _S_apply() 848 { return _Array_type{&__visit_invoke}; } 849 }; 850 851 template<typename _Result_type, typename _Visitor, typename... _Variants> 852 struct __gen_vtable 853 { 854 using _Func_ptr = _Result_type (*)(_Visitor&&, _Variants...); 855 using _Array_type = 856 _Multi_array<_Func_ptr, 857 variant_size_v<remove_reference_t<_Variants>>...>; 858 859 static constexpr _Array_type 860 _S_apply() 861 { 862 return __gen_vtable_impl<_Array_type, tuple<_Variants...>, 863 std::index_sequence<>>::_S_apply(); 864 } 865 866 static constexpr auto _S_vtable = _S_apply(); 867 }; 868 869 template<size_t _Np, typename _Tp> 870 struct _Base_dedup : public _Tp { }; 871 872 template<typename _Variant, typename __indices> 873 struct _Variant_hash_base; 874 875 template<typename... _Types, size_t... __indices> 876 struct _Variant_hash_base<variant<_Types...>, 877 std::index_sequence<__indices...>> 878 : _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { }; 879 880} // namespace __variant 881} // namespace __detail 882 883 template<typename _Tp, typename... _Types> 884 inline constexpr bool holds_alternative(const variant<_Types...>& __v) 885 noexcept 886 { 887 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 888 "T should occur for exactly once in alternatives"); 889 return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>; 890 } 891 892 template<typename _Tp, typename... _Types> 893 constexpr inline _Tp& get(variant<_Types...>& __v) 894 { 895 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 896 "T should occur for exactly once in alternatives"); 897 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 898 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v); 899 } 900 901 template<typename _Tp, typename... _Types> 902 constexpr inline _Tp&& get(variant<_Types...>&& __v) 903 { 904 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 905 "T should occur for exactly once in alternatives"); 906 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 907 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>( 908 std::move(__v)); 909 } 910 911 template<typename _Tp, typename... _Types> 912 constexpr inline const _Tp& get(const variant<_Types...>& __v) 913 { 914 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 915 "T should occur for exactly once in alternatives"); 916 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 917 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v); 918 } 919 920 template<typename _Tp, typename... _Types> 921 constexpr inline const _Tp&& get(const variant<_Types...>&& __v) 922 { 923 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 924 "T should occur for exactly once in alternatives"); 925 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 926 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>( 927 std::move(__v)); 928 } 929 930 template<size_t _Np, typename... _Types> 931 constexpr inline 932 add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>> 933 get_if(variant<_Types...>* __ptr) noexcept 934 { 935 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; 936 static_assert(_Np < sizeof...(_Types), 937 "The index should be in [0, number of alternatives)"); 938 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void"); 939 if (__ptr && __ptr->index() == _Np) 940 return &__detail::__variant::__get<_Np>(*__ptr); 941 return nullptr; 942 } 943 944 template<size_t _Np, typename... _Types> 945 constexpr inline 946 add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>> 947 get_if(const variant<_Types...>* __ptr) noexcept 948 { 949 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>; 950 static_assert(_Np < sizeof...(_Types), 951 "The index should be in [0, number of alternatives)"); 952 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void"); 953 if (__ptr && __ptr->index() == _Np) 954 return &__detail::__variant::__get<_Np>(*__ptr); 955 return nullptr; 956 } 957 958 template<typename _Tp, typename... _Types> 959 constexpr inline add_pointer_t<_Tp> 960 get_if(variant<_Types...>* __ptr) noexcept 961 { 962 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 963 "T should occur for exactly once in alternatives"); 964 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 965 return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>( 966 __ptr); 967 } 968 969 template<typename _Tp, typename... _Types> 970 constexpr inline add_pointer_t<const _Tp> 971 get_if(const variant<_Types...>* __ptr) 972 noexcept 973 { 974 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>, 975 "T should occur for exactly once in alternatives"); 976 static_assert(!is_void_v<_Tp>, "_Tp should not be void"); 977 return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>( 978 __ptr); 979 } 980 981 struct monostate { }; 982 983#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \ 984 template<typename... _Types> \ 985 constexpr bool operator __OP(const variant<_Types...>& __lhs, \ 986 const variant<_Types...>& __rhs) \ 987 { \ 988 return __lhs._M_##__NAME(__rhs, std::index_sequence_for<_Types...>{}); \ 989 } \ 990\ 991 constexpr bool operator __OP(monostate, monostate) noexcept \ 992 { return 0 __OP 0; } 993 994 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less) 995 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal) 996 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal) 997 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal) 998 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal) 999 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater) 1000 1001#undef _VARIANT_RELATION_FUNCTION_TEMPLATE 1002 1003 template<typename _Visitor, typename... _Variants> 1004 constexpr decltype(auto) visit(_Visitor&&, _Variants&&...); 1005 1006 template<typename... _Types> 1007 inline enable_if_t<(is_move_constructible_v<_Types> && ...) 1008 && (is_swappable_v<_Types> && ...)> 1009 swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs) 1010 noexcept(noexcept(__lhs.swap(__rhs))) 1011 { __lhs.swap(__rhs); } 1012 1013 template<typename... _Types> 1014 enable_if_t<!((is_move_constructible_v<_Types> && ...) 1015 && (is_swappable_v<_Types> && ...))> 1016 swap(variant<_Types...>&, variant<_Types...>&) = delete; 1017 1018 class bad_variant_access : public exception 1019 { 1020 public: 1021 bad_variant_access() noexcept : _M_reason("Unknown reason") { } 1022 const char* what() const noexcept override 1023 { return _M_reason; } 1024 1025 private: 1026 bad_variant_access(const char* __reason) : _M_reason(__reason) { } 1027 1028 const char* _M_reason; 1029 1030 friend void __throw_bad_variant_access(const char* __what); 1031 }; 1032 1033 inline void 1034 __throw_bad_variant_access(const char* __what) 1035 { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); } 1036 1037 template<typename... _Types> 1038 class variant 1039 : private __detail::__variant::_Variant_base<_Types...>, 1040 private _Enable_default_constructor< 1041 __detail::__variant::_Traits<_Types...>::_S_default_ctor, 1042 variant<_Types...>>, 1043 private _Enable_copy_move< 1044 __detail::__variant::_Traits<_Types...>::_S_copy_ctor, 1045 __detail::__variant::_Traits<_Types...>::_S_copy_assign, 1046 __detail::__variant::_Traits<_Types...>::_S_move_ctor, 1047 __detail::__variant::_Traits<_Types...>::_S_move_assign, 1048 variant<_Types...>> 1049 { 1050 private: 1051 static_assert(sizeof...(_Types) > 0, 1052 "variant must have at least one alternative"); 1053 static_assert(!(std::is_reference_v<_Types> || ...), 1054 "variant must have no reference alternative"); 1055 static_assert(!(std::is_void_v<_Types> || ...), 1056 "variant must have no void alternative"); 1057 1058 using _Base = __detail::__variant::_Variant_base<_Types...>; 1059 using _Default_ctor_enabler = 1060 _Enable_default_constructor< 1061 __detail::__variant::_Traits<_Types...>::_S_default_ctor, 1062 variant<_Types...>>; 1063 1064 template<typename _Tp> 1065 static constexpr bool 1066 __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>; 1067 1068 template<typename _Tp> 1069 static constexpr size_t __accepted_index = 1070 __detail::__variant::__accepted_index<_Tp&&, variant>::value; 1071 1072 template<size_t _Np, bool = _Np < sizeof...(_Types)> 1073 struct __to_type_impl; 1074 1075 template<size_t _Np> 1076 struct __to_type_impl<_Np, true> 1077 { using type = variant_alternative_t<_Np, variant>; }; 1078 1079 template<size_t _Np> 1080 using __to_type = typename __to_type_impl<_Np>::type; 1081 1082 template<typename _Tp> 1083 using __accepted_type = __to_type<__accepted_index<_Tp>>; 1084 1085 template<typename _Tp> 1086 static constexpr size_t __index_of = 1087 __detail::__variant::__index_of_v<_Tp, _Types...>; 1088 1089 using _Traits = __detail::__variant::_Traits<_Types...>; 1090 1091 public: 1092 variant() = default; 1093 variant(const variant& __rhs) = default; 1094 variant(variant&&) = default; 1095 variant& operator=(const variant&) = default; 1096 variant& operator=(variant&&) = default; 1097 ~variant() = default; 1098 1099 template<typename _Tp, 1100 typename = enable_if_t<!is_same_v<decay_t<_Tp>, variant>>, 1101 typename = enable_if_t<(sizeof...(_Types)>0)>, 1102 typename = enable_if_t<__exactly_once<__accepted_type<_Tp&&>> 1103 && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>>> 1104 constexpr 1105 variant(_Tp&& __t) 1106 noexcept(is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>) 1107 : variant(in_place_index<__accepted_index<_Tp&&>>, 1108 std::forward<_Tp>(__t)) 1109 { __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this)); } 1110 1111 template<typename _Tp, typename... _Args, 1112 typename = enable_if_t<__exactly_once<_Tp> 1113 && is_constructible_v<_Tp, _Args&&...>>> 1114 constexpr explicit 1115 variant(in_place_type_t<_Tp>, _Args&&... __args) 1116 : variant(in_place_index<__index_of<_Tp>>, 1117 std::forward<_Args>(__args)...) 1118 { __glibcxx_assert(holds_alternative<_Tp>(*this)); } 1119 1120 template<typename _Tp, typename _Up, typename... _Args, 1121 typename = enable_if_t<__exactly_once<_Tp> 1122 && is_constructible_v< 1123 _Tp, initializer_list<_Up>&, _Args&&...>>> 1124 constexpr explicit 1125 variant(in_place_type_t<_Tp>, initializer_list<_Up> __il, 1126 _Args&&... __args) 1127 : variant(in_place_index<__index_of<_Tp>>, __il, 1128 std::forward<_Args>(__args)...) 1129 { __glibcxx_assert(holds_alternative<_Tp>(*this)); } 1130 1131 template<size_t _Np, typename... _Args, 1132 typename = enable_if_t< 1133 is_constructible_v<__to_type<_Np>, _Args&&...>>> 1134 constexpr explicit 1135 variant(in_place_index_t<_Np>, _Args&&... __args) 1136 : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...), 1137 _Default_ctor_enabler(_Enable_default_constructor_tag{}) 1138 { __glibcxx_assert(index() == _Np); } 1139 1140 template<size_t _Np, typename _Up, typename... _Args, 1141 typename = enable_if_t<is_constructible_v<__to_type<_Np>, 1142 initializer_list<_Up>&, _Args&&...>>> 1143 constexpr explicit 1144 variant(in_place_index_t<_Np>, initializer_list<_Up> __il, 1145 _Args&&... __args) 1146 : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...), 1147 _Default_ctor_enabler(_Enable_default_constructor_tag{}) 1148 { __glibcxx_assert(index() == _Np); } 1149 1150 template<typename _Tp> 1151 enable_if_t<__exactly_once<__accepted_type<_Tp&&>> 1152 && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&> 1153 && is_assignable_v<__accepted_type<_Tp&&>&, _Tp&&> 1154 && !is_same_v<decay_t<_Tp>, variant>, variant&> 1155 operator=(_Tp&& __rhs) 1156 noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp&&> 1157 && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>) 1158 { 1159 constexpr auto __index = __accepted_index<_Tp&&>; 1160 if (index() == __index) 1161 std::get<__index>(*this) = std::forward<_Tp>(__rhs); 1162 else 1163 this->emplace<__index>(std::forward<_Tp>(__rhs)); 1164 __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this)); 1165 return *this; 1166 } 1167 1168 template<typename _Tp, typename... _Args> 1169 enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>, 1170 _Tp&> 1171 emplace(_Args&&... __args) 1172 { 1173 auto& ret = 1174 this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...); 1175 __glibcxx_assert(holds_alternative<_Tp>(*this)); 1176 return ret; 1177 } 1178 1179 template<typename _Tp, typename _Up, typename... _Args> 1180 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...> 1181 && __exactly_once<_Tp>, 1182 _Tp&> 1183 emplace(initializer_list<_Up> __il, _Args&&... __args) 1184 { 1185 auto& ret = 1186 this->emplace<__index_of<_Tp>>(__il, 1187 std::forward<_Args>(__args)...); 1188 __glibcxx_assert(holds_alternative<_Tp>(*this)); 1189 return ret; 1190 } 1191 1192 template<size_t _Np, typename... _Args> 1193 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>, 1194 _Args...>, 1195 variant_alternative_t<_Np, variant>&> 1196 emplace(_Args&&... __args) 1197 { 1198 static_assert(_Np < sizeof...(_Types), 1199 "The index should be in [0, number of alternatives)"); 1200 this->~variant(); 1201 __try 1202 { 1203 ::new (this) variant(in_place_index<_Np>, 1204 std::forward<_Args>(__args)...); 1205 } 1206 __catch (...) 1207 { 1208 this->_M_index = variant_npos; 1209 __throw_exception_again; 1210 } 1211 __glibcxx_assert(index() == _Np); 1212 return std::get<_Np>(*this); 1213 } 1214 1215 template<size_t _Np, typename _Up, typename... _Args> 1216 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>, 1217 initializer_list<_Up>&, _Args...>, 1218 variant_alternative_t<_Np, variant>&> 1219 emplace(initializer_list<_Up> __il, _Args&&... __args) 1220 { 1221 static_assert(_Np < sizeof...(_Types), 1222 "The index should be in [0, number of alternatives)"); 1223 this->~variant(); 1224 __try 1225 { 1226 ::new (this) variant(in_place_index<_Np>, __il, 1227 std::forward<_Args>(__args)...); 1228 } 1229 __catch (...) 1230 { 1231 this->_M_index = variant_npos; 1232 __throw_exception_again; 1233 } 1234 __glibcxx_assert(index() == _Np); 1235 return std::get<_Np>(*this); 1236 } 1237 1238 constexpr bool valueless_by_exception() const noexcept 1239 { return !this->_M_valid(); } 1240 1241 constexpr size_t index() const noexcept 1242 { 1243 if (this->_M_index == 1244 typename _Base::__index_type(variant_npos)) 1245 return variant_npos; 1246 return this->_M_index; 1247 } 1248 1249 void 1250 swap(variant& __rhs) 1251 noexcept((__is_nothrow_swappable<_Types>::value && ...) 1252 && is_nothrow_move_constructible_v<variant>) 1253 { 1254 if (this->index() == __rhs.index()) 1255 { 1256 if (this->_M_valid()) 1257 { 1258 static constexpr void (*_S_vtable[])(void*, void*) = 1259 { &__detail::__variant::__erased_swap<_Types&, _Types&>... }; 1260 _S_vtable[__rhs._M_index](this->_M_storage(), 1261 __rhs._M_storage()); 1262 } 1263 } 1264 else if (!this->_M_valid()) 1265 { 1266 this->_M_destructive_move(std::move(__rhs)); 1267 __rhs._M_reset(); 1268 } 1269 else if (!__rhs._M_valid()) 1270 { 1271 __rhs._M_destructive_move(std::move(*this)); 1272 this->_M_reset(); 1273 } 1274 else 1275 { 1276 auto __tmp = std::move(__rhs); 1277 __rhs._M_destructive_move(std::move(*this)); 1278 this->_M_destructive_move(std::move(__tmp)); 1279 } 1280 } 1281 1282 private: 1283#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \ 1284 template<size_t... __indices> \ 1285 static constexpr bool \ 1286 (*_S_erased_##__NAME[])(const variant&, const variant&) = \ 1287 { &__detail::__variant::__erased_##__NAME< \ 1288 const variant&, __indices>... }; \ 1289 template<size_t... __indices> \ 1290 constexpr inline bool \ 1291 _M_##__NAME(const variant& __rhs, \ 1292 std::index_sequence<__indices...>) const \ 1293 { \ 1294 auto __lhs_index = this->index(); \ 1295 auto __rhs_index = __rhs.index(); \ 1296 if (__lhs_index != __rhs_index || valueless_by_exception()) \ 1297 /* Modulo addition. */ \ 1298 return __lhs_index + 1 __OP __rhs_index + 1; \ 1299 return _S_erased_##__NAME<__indices...>[__lhs_index](*this, __rhs); \ 1300 } 1301 1302 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less) 1303 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal) 1304 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal) 1305 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal) 1306 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal) 1307 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater) 1308 1309#undef _VARIANT_RELATION_FUNCTION_TEMPLATE 1310 1311#ifdef __clang__ 1312 public: 1313 using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852 1314 private: 1315#endif 1316 1317 template<size_t _Np, typename _Vp> 1318 friend constexpr decltype(auto) __detail::__variant::__get(_Vp&& __v); 1319 1320 template<typename _Vp> 1321 friend void* __detail::__variant::__get_storage(_Vp&& __v); 1322 1323#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \ 1324 template<typename... _Tp> \ 1325 friend constexpr bool \ 1326 operator __OP(const variant<_Tp...>& __lhs, \ 1327 const variant<_Tp...>& __rhs); 1328 1329 _VARIANT_RELATION_FUNCTION_TEMPLATE(<) 1330 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=) 1331 _VARIANT_RELATION_FUNCTION_TEMPLATE(==) 1332 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=) 1333 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=) 1334 _VARIANT_RELATION_FUNCTION_TEMPLATE(>) 1335 1336#undef _VARIANT_RELATION_FUNCTION_TEMPLATE 1337 }; 1338 1339 template<size_t _Np, typename... _Types> 1340 constexpr variant_alternative_t<_Np, variant<_Types...>>& 1341 get(variant<_Types...>& __v) 1342 { 1343 static_assert(_Np < sizeof...(_Types), 1344 "The index should be in [0, number of alternatives)"); 1345 if (__v.index() != _Np) 1346 __throw_bad_variant_access("Unexpected index"); 1347 return __detail::__variant::__get<_Np>(__v); 1348 } 1349 1350 template<size_t _Np, typename... _Types> 1351 constexpr variant_alternative_t<_Np, variant<_Types...>>&& 1352 get(variant<_Types...>&& __v) 1353 { 1354 static_assert(_Np < sizeof...(_Types), 1355 "The index should be in [0, number of alternatives)"); 1356 if (__v.index() != _Np) 1357 __throw_bad_variant_access("Unexpected index"); 1358 return __detail::__variant::__get<_Np>(std::move(__v)); 1359 } 1360 1361 template<size_t _Np, typename... _Types> 1362 constexpr const variant_alternative_t<_Np, variant<_Types...>>& 1363 get(const variant<_Types...>& __v) 1364 { 1365 static_assert(_Np < sizeof...(_Types), 1366 "The index should be in [0, number of alternatives)"); 1367 if (__v.index() != _Np) 1368 __throw_bad_variant_access("Unexpected index"); 1369 return __detail::__variant::__get<_Np>(__v); 1370 } 1371 1372 template<size_t _Np, typename... _Types> 1373 constexpr const variant_alternative_t<_Np, variant<_Types...>>&& 1374 get(const variant<_Types...>&& __v) 1375 { 1376 static_assert(_Np < sizeof...(_Types), 1377 "The index should be in [0, number of alternatives)"); 1378 if (__v.index() != _Np) 1379 __throw_bad_variant_access("Unexpected index"); 1380 return __detail::__variant::__get<_Np>(std::move(__v)); 1381 } 1382 1383 template<typename _Visitor, typename... _Variants> 1384 constexpr decltype(auto) 1385 visit(_Visitor&& __visitor, _Variants&&... __variants) 1386 { 1387 if ((__variants.valueless_by_exception() || ...)) 1388 __throw_bad_variant_access("Unexpected index"); 1389 1390 using _Result_type = 1391 decltype(std::forward<_Visitor>(__visitor)( 1392 get<0>(std::forward<_Variants>(__variants))...)); 1393 1394 constexpr auto& __vtable = __detail::__variant::__gen_vtable< 1395 _Result_type, _Visitor&&, _Variants&&...>::_S_vtable; 1396 1397 auto __func_ptr = __vtable._M_access(__variants.index()...); 1398 return (*__func_ptr)(std::forward<_Visitor>(__visitor), 1399 std::forward<_Variants>(__variants)...); 1400 } 1401 1402 template<bool, typename... _Types> 1403 struct __variant_hash_call_base_impl 1404 { 1405 size_t 1406 operator()(const variant<_Types...>& __t) const 1407 noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...)) 1408 { 1409 if (!__t.valueless_by_exception()) 1410 { 1411 namespace __edv = __detail::__variant; 1412 static constexpr size_t (*_S_vtable[])(void*) = 1413 { &__edv::__erased_hash<const _Types&>... }; 1414 return hash<size_t>{}(__t.index()) 1415 + _S_vtable[__t.index()](__edv::__get_storage(__t)); 1416 } 1417 return hash<size_t>{}(__t.index()); 1418 } 1419 }; 1420 1421 template<typename... _Types> 1422 struct __variant_hash_call_base_impl<false, _Types...> {}; 1423 1424 template<typename... _Types> 1425 using __variant_hash_call_base = 1426 __variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>:: 1427 __enable_hash_call &&...), _Types...>; 1428 1429 template<typename... _Types> 1430 struct hash<variant<_Types...>> 1431 : private __detail::__variant::_Variant_hash_base< 1432 variant<_Types...>, std::index_sequence_for<_Types...>>, 1433 public __variant_hash_call_base<_Types...> 1434 { 1435 using result_type [[__deprecated__]] = size_t; 1436 using argument_type [[__deprecated__]] = variant<_Types...>; 1437 }; 1438 1439 template<> 1440 struct hash<monostate> 1441 { 1442 using result_type [[__deprecated__]] = size_t; 1443 using argument_type [[__deprecated__]] = monostate; 1444 1445 size_t 1446 operator()(const monostate& __t) const noexcept 1447 { 1448 constexpr size_t __magic_monostate_hash = -7777; 1449 return __magic_monostate_hash; 1450 } 1451 }; 1452 1453 template<typename... _Types> 1454 struct __is_fast_hash<hash<variant<_Types...>>> 1455 : bool_constant<(__is_fast_hash<_Types>::value && ...)> 1456 { }; 1457 1458_GLIBCXX_END_NAMESPACE_VERSION 1459} // namespace std 1460 1461#endif // C++17 1462 1463#endif // _GLIBCXX_VARIANT 1464