1 // <variant> -*- C++ -*-
3 // Copyright (C) 2016-2018 Free Software Foundation, Inc.
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)
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.
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.
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/>.
26 * This is the <variant> C++ Library header.
29 #ifndef _GLIBCXX_VARIANT
30 #define _GLIBCXX_VARIANT 1
32 #pragma GCC system_header
34 #if __cplusplus >= 201703L
36 #include <type_traits>
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>
49 namespace std _GLIBCXX_VISIBILITY(default)
51 _GLIBCXX_BEGIN_NAMESPACE_VERSION
57 template<size_t _Np, typename... _Types>
60 template<size_t _Np, typename _First, typename... _Rest>
61 struct _Nth_type<_Np, _First, _Rest...>
62 : _Nth_type<_Np-1, _Rest...> { };
64 template<typename _First, typename... _Rest>
65 struct _Nth_type<0, _First, _Rest...>
66 { using type = _First; };
68 } // namespace __variant
69 } // namespace __detail
71 #define __cpp_lib_variant 201603
73 template<typename... _Types> class tuple;
74 template<typename... _Types> class variant;
75 template <typename> struct hash;
77 template<typename _Variant>
80 template<typename _Variant>
81 struct variant_size<const _Variant> : variant_size<_Variant> {};
83 template<typename _Variant>
84 struct variant_size<volatile _Variant> : variant_size<_Variant> {};
86 template<typename _Variant>
87 struct variant_size<const volatile _Variant> : variant_size<_Variant> {};
89 template<typename... _Types>
90 struct variant_size<variant<_Types...>>
91 : std::integral_constant<size_t, sizeof...(_Types)> {};
93 template<typename _Variant>
94 inline constexpr size_t variant_size_v = variant_size<_Variant>::value;
96 template<size_t _Np, typename _Variant>
97 struct variant_alternative;
99 template<size_t _Np, typename _First, typename... _Rest>
100 struct variant_alternative<_Np, variant<_First, _Rest...>>
101 : variant_alternative<_Np-1, variant<_Rest...>> {};
103 template<typename _First, typename... _Rest>
104 struct variant_alternative<0, variant<_First, _Rest...>>
105 { using type = _First; };
107 template<size_t _Np, typename _Variant>
108 using variant_alternative_t =
109 typename variant_alternative<_Np, _Variant>::type;
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>>; };
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>>; };
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>>; };
123 inline constexpr size_t variant_npos = -1;
125 template<size_t _Np, typename... _Types>
126 constexpr variant_alternative_t<_Np, variant<_Types...>>&
127 get(variant<_Types...>&);
129 template<size_t _Np, typename... _Types>
130 constexpr variant_alternative_t<_Np, variant<_Types...>>&&
131 get(variant<_Types...>&&);
133 template<size_t _Np, typename... _Types>
134 constexpr variant_alternative_t<_Np, variant<_Types...>> const&
135 get(const variant<_Types...>&);
137 template<size_t _Np, typename... _Types>
138 constexpr variant_alternative_t<_Np, variant<_Types...>> const&&
139 get(const variant<_Types...>&&);
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> {};
150 template<typename _Tp, typename... _Types>
151 inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value;
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> {};
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.
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;
169 template<typename _Type>
170 struct _Uninitialized<_Type, true>
172 template<typename... _Args>
173 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
174 : _M_storage(std::forward<_Args>(__args)...)
177 constexpr const _Type& _M_get() const &
178 { return _M_storage; }
180 constexpr _Type& _M_get() &
181 { return _M_storage; }
183 constexpr const _Type&& _M_get() const &&
184 { return std::move(_M_storage); }
186 constexpr _Type&& _M_get() &&
187 { return std::move(_M_storage); }
192 template<typename _Type>
193 struct _Uninitialized<_Type, false>
195 template<typename... _Args>
196 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
197 { ::new (&_M_storage) _Type(std::forward<_Args>(__args)...); }
199 const _Type& _M_get() const &
200 { return *_M_storage._M_ptr(); }
203 { return *_M_storage._M_ptr(); }
205 const _Type&& _M_get() const &&
206 { return std::move(*_M_storage._M_ptr()); }
209 { return std::move(*_M_storage._M_ptr()); }
211 __gnu_cxx::__aligned_membuf<_Type> _M_storage;
214 template<typename _Ref>
215 _Ref __ref_cast(void* __ptr)
217 return static_cast<_Ref>(*static_cast<remove_reference_t<_Ref>*>(__ptr));
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(); }
224 template<size_t _Np, typename _Union>
225 constexpr decltype(auto) __get(in_place_index_t<_Np>, _Union&& __u)
227 return __variant::__get(in_place_index<_Np-1>,
228 std::forward<_Union>(__u)._M_rest);
231 // Returns the typed storage for __v.
232 template<size_t _Np, typename _Variant>
233 constexpr decltype(auto) __get(_Variant&& __v)
235 return __variant::__get(std::in_place_index<_Np>,
236 std::forward<_Variant>(__v)._M_u);
239 // Various functions as "vtable" entries, where those vtables are used by
240 // polymorphic operations.
241 template<typename _Lhs, typename _Rhs>
243 __erased_ctor(void* __lhs, void* __rhs)
245 using _Type = remove_reference_t<_Lhs>;
246 ::new (__lhs) _Type(__variant::__ref_cast<_Rhs>(__rhs));
249 template<typename _Variant, size_t _Np>
251 __erased_dtor(_Variant&& __v)
252 { std::_Destroy(std::__addressof(__get<_Np>(__v))); }
254 template<typename _Lhs, typename _Rhs>
256 __erased_assign(void* __lhs, void* __rhs)
258 __variant::__ref_cast<_Lhs>(__lhs) = __variant::__ref_cast<_Rhs>(__rhs);
261 template<typename _Lhs, typename _Rhs>
263 __erased_swap(void* __lhs, void* __rhs)
266 swap(__variant::__ref_cast<_Lhs>(__lhs),
267 __variant::__ref_cast<_Rhs>(__rhs));
270 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
271 template<typename _Variant, size_t _Np> \
273 __erased_##__NAME(const _Variant& __lhs, const _Variant& __rhs) \
275 return __variant::__get<_Np>(std::forward<_Variant>(__lhs)) \
276 __OP __variant::__get<_Np>(std::forward<_Variant>(__rhs)); \
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)
286 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
288 template<typename _Tp>
290 __erased_hash(void* __t)
292 return std::hash<remove_cv_t<remove_reference_t<_Tp>>>{}(
293 __variant::__ref_cast<_Tp>(__t));
296 template<typename... _Types>
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 =
310 && (is_move_assignable_v<_Types> && ...);
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> && ...);
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> && ...);
336 // Defines members and ctors.
337 template<typename... _Types>
338 union _Variadic_union { };
340 template<typename _First, typename... _Rest>
341 union _Variadic_union<_First, _Rest...>
343 constexpr _Variadic_union() : _M_rest() { }
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)...)
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)...)
355 _Uninitialized<_First> _M_first;
356 _Variadic_union<_Rest...> _M_rest;
359 // Defines index and the dtor, possibly trivial.
360 template<bool __trivially_destructible, typename... _Types>
361 struct _Variant_storage;
363 template <typename... _Types>
364 using __select_index =
365 typename __select_int::_Select_int_base<sizeof...(_Types) + 1,
367 unsigned short>::type::value_type;
369 template<typename... _Types>
370 struct _Variant_storage<false, _Types...>
372 template<size_t... __indices>
373 static constexpr void (*_S_vtable[])(const _Variant_storage&) =
374 { &__erased_dtor<const _Variant_storage&, __indices>... };
376 constexpr _Variant_storage() : _M_index(variant_npos) { }
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)...),
384 template<size_t... __indices>
385 constexpr void _M_reset_impl(std::index_sequence<__indices...>)
387 if (_M_index != __index_type(variant_npos))
388 _S_vtable<__indices...>[_M_index](*this);
393 _M_reset_impl(std::index_sequence_for<_Types...>{});
394 _M_index = variant_npos;
403 return const_cast<void*>(static_cast<const void*>(
404 std::addressof(_M_u)));
408 _M_valid() const noexcept
410 return this->_M_index != __index_type(variant_npos);
413 _Variadic_union<_Types...> _M_u;
414 using __index_type = __select_index<_Types...>;
415 __index_type _M_index;
418 template<typename... _Types>
419 struct _Variant_storage<true, _Types...>
421 constexpr _Variant_storage() : _M_index(variant_npos) { }
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)...),
430 { _M_index = variant_npos; }
435 return const_cast<void*>(static_cast<const void*>(
436 std::addressof(_M_u)));
440 _M_valid() const noexcept
442 return this->_M_index != __index_type(variant_npos);
445 _Variadic_union<_Types...> _M_u;
446 using __index_type = __select_index<_Types...>;
447 __index_type _M_index;
450 template<typename... _Types>
451 using _Variant_storage_alias =
452 _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>;
454 // The following are (Copy|Move) (ctor|assign) layers for forwarding
455 // triviality and handling non-trivial SMF behaviors.
457 template<bool, typename... _Types>
458 struct _Copy_ctor_base : _Variant_storage_alias<_Types...>
460 using _Base = _Variant_storage_alias<_Types...>;
463 _Copy_ctor_base(const _Copy_ctor_base& __rhs)
464 noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor)
466 if (__rhs._M_valid())
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;
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;
480 template<typename... _Types>
481 struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...>
483 using _Base = _Variant_storage_alias<_Types...>;
487 template<typename... _Types>
488 using _Copy_ctor_alias =
489 _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>;
491 template<bool, typename... _Types>
492 struct _Move_ctor_base : _Copy_ctor_alias<_Types...>
494 using _Base = _Copy_ctor_alias<_Types...>;
497 _Move_ctor_base(_Move_ctor_base&& __rhs)
498 noexcept(_Traits<_Types...>::_S_nothrow_move_ctor)
500 if (__rhs._M_valid())
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;
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;
514 template<typename... _Types>
515 struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...>
517 using _Base = _Copy_ctor_alias<_Types...>;
521 template<typename... _Types>
522 using _Move_ctor_alias =
523 _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>;
525 template<bool, typename... _Types>
526 struct _Copy_assign_base : _Move_ctor_alias<_Types...>
528 using _Base = _Move_ctor_alias<_Types...>;
532 operator=(const _Copy_assign_base& __rhs)
533 noexcept(_Traits<_Types...>::_S_nothrow_copy_assign)
535 if (this->_M_index == __rhs._M_index)
537 if (__rhs._M_valid())
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());
546 _Copy_assign_base __tmp(__rhs);
547 this->~_Copy_assign_base();
550 ::new (this) _Copy_assign_base(std::move(__tmp));
554 this->_M_index = variant_npos;
555 __throw_exception_again;
558 __glibcxx_assert(this->_M_index == __rhs._M_index);
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;
567 template<typename... _Types>
568 struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...>
570 using _Base = _Move_ctor_alias<_Types...>;
574 template<typename... _Types>
575 using _Copy_assign_alias =
576 _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign,
579 template<bool, typename... _Types>
580 struct _Move_assign_base : _Copy_assign_alias<_Types...>
582 using _Base = _Copy_assign_alias<_Types...>;
585 void _M_destructive_move(_Move_assign_base&& __rhs)
587 this->~_Move_assign_base();
590 ::new (this) _Move_assign_base(std::move(__rhs));
594 this->_M_index = variant_npos;
595 __throw_exception_again;
600 operator=(_Move_assign_base&& __rhs)
601 noexcept(_Traits<_Types...>::_S_nothrow_move_assign)
603 if (this->_M_index == __rhs._M_index)
605 if (__rhs._M_valid())
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());
615 _Move_assign_base __tmp(std::move(__rhs));
616 this->~_Move_assign_base();
619 ::new (this) _Move_assign_base(std::move(__tmp));
623 this->_M_index = variant_npos;
624 __throw_exception_again;
627 __glibcxx_assert(this->_M_index == __rhs._M_index);
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;
636 template<typename... _Types>
637 struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...>
639 using _Base = _Copy_assign_alias<_Types...>;
643 template<typename... _Types>
644 using _Move_assign_alias =
645 _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign,
648 template<typename... _Types>
649 struct _Variant_base : _Move_assign_alias<_Types...>
651 using _Base = _Move_assign_alias<_Types...>;
655 noexcept(_Traits<_Types...>::_S_nothrow_default_ctor)
656 : _Variant_base(in_place_index<0>) { }
658 template<size_t _Np, typename... _Args>
660 _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
661 : _Base(__i, std::forward<_Args>(__args)...)
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;
670 // For how many times does _Tp appear in _Tuple?
671 template<typename _Tp, typename _Tuple>
672 struct __tuple_count;
674 template<typename _Tp, typename _Tuple>
675 inline constexpr size_t __tuple_count_v =
676 __tuple_count<_Tp, _Tuple>::value;
678 template<typename _Tp, typename... _Types>
679 struct __tuple_count<_Tp, tuple<_Types...>>
680 : integral_constant<size_t, 0> { };
682 template<typename _Tp, typename _First, typename... _Rest>
683 struct __tuple_count<_Tp, tuple<_First, _Rest...>>
686 __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { };
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;
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(); };
699 template<typename _First, typename... _Rest>
700 struct __overload_set<_First, _Rest...> : __overload_set<_Rest...>
702 using __overload_set<_Rest...>::_S_fun;
703 static integral_constant<size_t, sizeof...(_Rest)> _S_fun(_First);
706 template<typename... _Rest>
707 struct __overload_set<void, _Rest...> : __overload_set<_Rest...>
709 using __overload_set<_Rest...>::_S_fun;
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; };
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>())>
724 static constexpr size_t value = sizeof...(_Types) - 1
725 - decltype(__overload_set<_Types...>::
726 _S_fun(std::declval<_Tp>()))::value;
729 // Returns the raw storage for __v.
730 template<typename _Variant>
731 void* __get_storage(_Variant&& __v)
732 { return __v._M_storage(); }
734 // Used for storing multi-dimensional vtable.
735 template<typename _Tp, size_t... _Dimensions>
745 template<typename _Tp, size_t __first, size_t... __rest>
746 struct _Multi_array<_Tp, __first, __rest...>
748 template<typename... _Args>
750 _M_access(size_t __first_index, _Args... __rest_indices) const
751 { return _M_arr[__first_index]._M_access(__rest_indices...); }
753 _Multi_array<_Tp, __rest...> _M_arr[__first];
756 // Creates a multi-dimensional vtable recursively.
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;
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...>>
793 remove_reference_t<typename _Nth_type<sizeof...(__indices),
794 _Variants...>::type>;
796 _Multi_array<_Result_type (*)(_Visitor, _Variants...),
799 static constexpr _Array_type
802 _Array_type __vtable{};
804 __vtable, make_index_sequence<variant_size_v<_Next>>());
808 template<size_t... __var_indices>
809 static constexpr void
810 _S_apply_all_alts(_Array_type& __vtable,
811 std::index_sequence<__var_indices...>)
813 (_S_apply_single_alt<__var_indices>(
814 __vtable._M_arr[__var_indices]), ...);
817 template<size_t __index, typename _Tp>
818 static constexpr void
819 _S_apply_single_alt(_Tp& __element)
821 using _Alternative = variant_alternative_t<__index, _Next>;
822 __element = __gen_vtable_impl<
824 decltype(__element)>, tuple<_Variants...>,
825 std::index_sequence<__indices..., __index>>::_S_apply();
829 template<typename _Result_type, typename _Visitor, typename... _Variants,
831 struct __gen_vtable_impl<
832 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>,
833 tuple<_Variants...>, std::index_sequence<__indices...>>
836 _Multi_array<_Result_type (*)(_Visitor&&, _Variants...)>;
839 static constexpr __visit_invoke(_Visitor&& __visitor, _Variants... __vars)
841 return __invoke(std::forward<_Visitor>(__visitor),
843 std::forward<_Variants>(__vars))...);
846 static constexpr auto
848 { return _Array_type{&__visit_invoke}; }
851 template<typename _Result_type, typename _Visitor, typename... _Variants>
854 using _Func_ptr = _Result_type (*)(_Visitor&&, _Variants...);
856 _Multi_array<_Func_ptr,
857 variant_size_v<remove_reference_t<_Variants>>...>;
859 static constexpr _Array_type
862 return __gen_vtable_impl<_Array_type, tuple<_Variants...>,
863 std::index_sequence<>>::_S_apply();
866 static constexpr auto _S_vtable = _S_apply();
869 template<size_t _Np, typename _Tp>
870 struct _Base_dedup : public _Tp { };
872 template<typename _Variant, typename __indices>
873 struct _Variant_hash_base;
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>>>... { };
880 } // namespace __variant
881 } // namespace __detail
883 template<typename _Tp, typename... _Types>
884 inline constexpr bool holds_alternative(const variant<_Types...>& __v)
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...>;
892 template<typename _Tp, typename... _Types>
893 constexpr inline _Tp& get(variant<_Types...>& __v)
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);
901 template<typename _Tp, typename... _Types>
902 constexpr inline _Tp&& get(variant<_Types...>&& __v)
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...>>(
911 template<typename _Tp, typename... _Types>
912 constexpr inline const _Tp& get(const variant<_Types...>& __v)
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);
920 template<typename _Tp, typename... _Types>
921 constexpr inline const _Tp&& get(const variant<_Types...>&& __v)
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...>>(
930 template<size_t _Np, typename... _Types>
932 add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
933 get_if(variant<_Types...>* __ptr) noexcept
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);
944 template<size_t _Np, typename... _Types>
946 add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>>
947 get_if(const variant<_Types...>* __ptr) noexcept
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);
958 template<typename _Tp, typename... _Types>
959 constexpr inline add_pointer_t<_Tp>
960 get_if(variant<_Types...>* __ptr) noexcept
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...>>(
969 template<typename _Tp, typename... _Types>
970 constexpr inline add_pointer_t<const _Tp>
971 get_if(const variant<_Types...>* __ptr)
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...>>(
981 struct monostate { };
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) \
988 return __lhs._M_##__NAME(__rhs, std::index_sequence_for<_Types...>{}); \
991 constexpr bool operator __OP(monostate, monostate) noexcept \
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)
1001 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1003 template<typename _Visitor, typename... _Variants>
1004 constexpr decltype(auto) visit(_Visitor&&, _Variants&&...);
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); }
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;
1018 class bad_variant_access : public exception
1021 bad_variant_access() noexcept : _M_reason("Unknown reason") { }
1022 const char* what() const noexcept override
1023 { return _M_reason; }
1026 bad_variant_access(const char* __reason) : _M_reason(__reason) { }
1028 const char* _M_reason;
1030 friend void __throw_bad_variant_access(const char* __what);
1034 __throw_bad_variant_access(const char* __what)
1035 { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); }
1037 template<typename... _Types>
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,
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");
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...>>;
1064 template<typename _Tp>
1065 static constexpr bool
1066 __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>;
1068 template<typename _Tp>
1069 static constexpr size_t __accepted_index =
1070 __detail::__variant::__accepted_index<_Tp&&, variant>::value;
1072 template<size_t _Np, bool = _Np < sizeof...(_Types)>
1073 struct __to_type_impl;
1075 template<size_t _Np>
1076 struct __to_type_impl<_Np, true>
1077 { using type = variant_alternative_t<_Np, variant>; };
1079 template<size_t _Np>
1080 using __to_type = typename __to_type_impl<_Np>::type;
1082 template<typename _Tp>
1083 using __accepted_type = __to_type<__accepted_index<_Tp>>;
1085 template<typename _Tp>
1086 static constexpr size_t __index_of =
1087 __detail::__variant::__index_of_v<_Tp, _Types...>;
1089 using _Traits = __detail::__variant::_Traits<_Types...>;
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;
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&&>>>
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)); }
1111 template<typename _Tp, typename... _Args,
1112 typename = enable_if_t<__exactly_once<_Tp>
1113 && is_constructible_v<_Tp, _Args&&...>>>
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)); }
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&&...>>>
1125 variant(in_place_type_t<_Tp>, initializer_list<_Up> __il,
1127 : variant(in_place_index<__index_of<_Tp>>, __il,
1128 std::forward<_Args>(__args)...)
1129 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
1131 template<size_t _Np, typename... _Args,
1132 typename = enable_if_t<
1133 is_constructible_v<__to_type<_Np>, _Args&&...>>>
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); }
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&&...>>>
1144 variant(in_place_index_t<_Np>, initializer_list<_Up> __il,
1146 : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...),
1147 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1148 { __glibcxx_assert(index() == _Np); }
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&&>)
1159 constexpr auto __index = __accepted_index<_Tp&&>;
1160 if (index() == __index)
1161 std::get<__index>(*this) = std::forward<_Tp>(__rhs);
1163 this->emplace<__index>(std::forward<_Tp>(__rhs));
1164 __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this));
1168 template<typename _Tp, typename... _Args>
1169 enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>,
1171 emplace(_Args&&... __args)
1174 this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...);
1175 __glibcxx_assert(holds_alternative<_Tp>(*this));
1179 template<typename _Tp, typename _Up, typename... _Args>
1180 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>
1181 && __exactly_once<_Tp>,
1183 emplace(initializer_list<_Up> __il, _Args&&... __args)
1186 this->emplace<__index_of<_Tp>>(__il,
1187 std::forward<_Args>(__args)...);
1188 __glibcxx_assert(holds_alternative<_Tp>(*this));
1192 template<size_t _Np, typename... _Args>
1193 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1195 variant_alternative_t<_Np, variant>&>
1196 emplace(_Args&&... __args)
1198 static_assert(_Np < sizeof...(_Types),
1199 "The index should be in [0, number of alternatives)");
1203 ::new (this) variant(in_place_index<_Np>,
1204 std::forward<_Args>(__args)...);
1208 this->_M_index = variant_npos;
1209 __throw_exception_again;
1211 __glibcxx_assert(index() == _Np);
1212 return std::get<_Np>(*this);
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)
1221 static_assert(_Np < sizeof...(_Types),
1222 "The index should be in [0, number of alternatives)");
1226 ::new (this) variant(in_place_index<_Np>, __il,
1227 std::forward<_Args>(__args)...);
1231 this->_M_index = variant_npos;
1232 __throw_exception_again;
1234 __glibcxx_assert(index() == _Np);
1235 return std::get<_Np>(*this);
1238 constexpr bool valueless_by_exception() const noexcept
1239 { return !this->_M_valid(); }
1241 constexpr size_t index() const noexcept
1243 if (this->_M_index ==
1244 typename _Base::__index_type(variant_npos))
1245 return variant_npos;
1246 return this->_M_index;
1250 swap(variant& __rhs)
1251 noexcept((__is_nothrow_swappable<_Types>::value && ...)
1252 && is_nothrow_move_constructible_v<variant>)
1254 if (this->index() == __rhs.index())
1256 if (this->_M_valid())
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());
1264 else if (!this->_M_valid())
1266 this->_M_destructive_move(std::move(__rhs));
1269 else if (!__rhs._M_valid())
1271 __rhs._M_destructive_move(std::move(*this));
1276 auto __tmp = std::move(__rhs);
1277 __rhs._M_destructive_move(std::move(*this));
1278 this->_M_destructive_move(std::move(__tmp));
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 \
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); \
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)
1309 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1313 using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852
1317 template<size_t _Np, typename _Vp>
1318 friend constexpr decltype(auto) __detail::__variant::__get(_Vp&& __v);
1320 template<typename _Vp>
1321 friend void* __detail::__variant::__get_storage(_Vp&& __v);
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);
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(>)
1336 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1339 template<size_t _Np, typename... _Types>
1340 constexpr variant_alternative_t<_Np, variant<_Types...>>&
1341 get(variant<_Types...>& __v)
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);
1350 template<size_t _Np, typename... _Types>
1351 constexpr variant_alternative_t<_Np, variant<_Types...>>&&
1352 get(variant<_Types...>&& __v)
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));
1361 template<size_t _Np, typename... _Types>
1362 constexpr const variant_alternative_t<_Np, variant<_Types...>>&
1363 get(const variant<_Types...>& __v)
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);
1372 template<size_t _Np, typename... _Types>
1373 constexpr const variant_alternative_t<_Np, variant<_Types...>>&&
1374 get(const variant<_Types...>&& __v)
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));
1383 template<typename _Visitor, typename... _Variants>
1384 constexpr decltype(auto)
1385 visit(_Visitor&& __visitor, _Variants&&... __variants)
1387 if ((__variants.valueless_by_exception() || ...))
1388 __throw_bad_variant_access("Unexpected index");
1390 using _Result_type =
1391 decltype(std::forward<_Visitor>(__visitor)(
1392 get<0>(std::forward<_Variants>(__variants))...));
1394 constexpr auto& __vtable = __detail::__variant::__gen_vtable<
1395 _Result_type, _Visitor&&, _Variants&&...>::_S_vtable;
1397 auto __func_ptr = __vtable._M_access(__variants.index()...);
1398 return (*__func_ptr)(std::forward<_Visitor>(__visitor),
1399 std::forward<_Variants>(__variants)...);
1402 template<bool, typename... _Types>
1403 struct __variant_hash_call_base_impl
1406 operator()(const variant<_Types...>& __t) const
1407 noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...))
1409 if (!__t.valueless_by_exception())
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));
1417 return hash<size_t>{}(__t.index());
1421 template<typename... _Types>
1422 struct __variant_hash_call_base_impl<false, _Types...> {};
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...>;
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...>
1435 using result_type [[__deprecated__]] = size_t;
1436 using argument_type [[__deprecated__]] = variant<_Types...>;
1440 struct hash<monostate>
1442 using result_type [[__deprecated__]] = size_t;
1443 using argument_type [[__deprecated__]] = monostate;
1446 operator()(const monostate& __t) const noexcept
1448 constexpr size_t __magic_monostate_hash = -7777;
1449 return __magic_monostate_hash;
1453 template<typename... _Types>
1454 struct __is_fast_hash<hash<variant<_Types...>>>
1455 : bool_constant<(__is_fast_hash<_Types>::value && ...)>
1458 _GLIBCXX_END_NAMESPACE_VERSION
1463 #endif // _GLIBCXX_VARIANT