1 // <variant> -*- C++ -*-
3 // Copyright (C) 2016-2019 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 201606L
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(__variant::__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_cvref_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),
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 if constexpr ((is_trivially_copyable_v<_Types> && ...))
444 return this->_M_index != __index_type(variant_npos);
447 _Variadic_union<_Types...> _M_u;
448 using __index_type = __select_index<_Types...>;
449 __index_type _M_index;
452 template<typename... _Types>
453 using _Variant_storage_alias =
454 _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>;
456 // The following are (Copy|Move) (ctor|assign) layers for forwarding
457 // triviality and handling non-trivial SMF behaviors.
459 template<bool, typename... _Types>
460 struct _Copy_ctor_base : _Variant_storage_alias<_Types...>
462 using _Base = _Variant_storage_alias<_Types...>;
465 _Copy_ctor_base(const _Copy_ctor_base& __rhs)
466 noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor)
468 if (__rhs._M_valid())
470 static constexpr void (*_S_vtable[])(void*, void*) =
471 { &__erased_ctor<_Types&, const _Types&>... };
472 _S_vtable[__rhs._M_index](this->_M_storage(), __rhs._M_storage());
473 this->_M_index = __rhs._M_index;
477 _Copy_ctor_base(_Copy_ctor_base&&) = default;
478 _Copy_ctor_base& operator=(const _Copy_ctor_base&) = default;
479 _Copy_ctor_base& operator=(_Copy_ctor_base&&) = default;
482 template<typename... _Types>
483 struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...>
485 using _Base = _Variant_storage_alias<_Types...>;
489 template<typename... _Types>
490 using _Copy_ctor_alias =
491 _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>;
493 template<bool, typename... _Types>
494 struct _Move_ctor_base : _Copy_ctor_alias<_Types...>
496 using _Base = _Copy_ctor_alias<_Types...>;
499 _Move_ctor_base(_Move_ctor_base&& __rhs)
500 noexcept(_Traits<_Types...>::_S_nothrow_move_ctor)
502 if (__rhs._M_valid())
504 static constexpr void (*_S_vtable[])(void*, void*) =
505 { &__erased_ctor<_Types&, _Types&&>... };
506 _S_vtable[__rhs._M_index](this->_M_storage(), __rhs._M_storage());
507 this->_M_index = __rhs._M_index;
511 void _M_destructive_move(_Move_ctor_base&& __rhs)
513 this->~_Move_ctor_base();
516 ::new (this) _Move_ctor_base(std::move(__rhs));
520 this->_M_index = variant_npos;
521 __throw_exception_again;
525 _Move_ctor_base(const _Move_ctor_base&) = default;
526 _Move_ctor_base& operator=(const _Move_ctor_base&) = default;
527 _Move_ctor_base& operator=(_Move_ctor_base&&) = default;
530 template<typename... _Types>
531 struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...>
533 using _Base = _Copy_ctor_alias<_Types...>;
536 void _M_destructive_move(_Move_ctor_base&& __rhs)
538 this->~_Move_ctor_base();
539 ::new (this) _Move_ctor_base(std::move(__rhs));
543 template<typename... _Types>
544 using _Move_ctor_alias =
545 _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>;
547 template<bool, typename... _Types>
548 struct _Copy_assign_base : _Move_ctor_alias<_Types...>
550 using _Base = _Move_ctor_alias<_Types...>;
554 operator=(const _Copy_assign_base& __rhs)
555 noexcept(_Traits<_Types...>::_S_nothrow_copy_assign)
557 if (this->_M_index == __rhs._M_index)
559 if (__rhs._M_valid())
561 static constexpr void (*_S_vtable[])(void*, void*) =
562 { &__erased_assign<_Types&, const _Types&>... };
563 _S_vtable[__rhs._M_index](this->_M_storage(),
569 _Copy_assign_base __tmp(__rhs);
570 this->_M_destructive_move(std::move(__tmp));
572 __glibcxx_assert(this->_M_index == __rhs._M_index);
576 _Copy_assign_base(const _Copy_assign_base&) = default;
577 _Copy_assign_base(_Copy_assign_base&&) = default;
578 _Copy_assign_base& operator=(_Copy_assign_base&&) = default;
581 template<typename... _Types>
582 struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...>
584 using _Base = _Move_ctor_alias<_Types...>;
588 template<typename... _Types>
589 using _Copy_assign_alias =
590 _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign,
593 template<bool, typename... _Types>
594 struct _Move_assign_base : _Copy_assign_alias<_Types...>
596 using _Base = _Copy_assign_alias<_Types...>;
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->_M_destructive_move(std::move(__tmp));
618 __glibcxx_assert(this->_M_index == __rhs._M_index);
622 _Move_assign_base(const _Move_assign_base&) = default;
623 _Move_assign_base(_Move_assign_base&&) = default;
624 _Move_assign_base& operator=(const _Move_assign_base&) = default;
627 template<typename... _Types>
628 struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...>
630 using _Base = _Copy_assign_alias<_Types...>;
634 template<typename... _Types>
635 using _Move_assign_alias =
636 _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign,
639 template<typename... _Types>
640 struct _Variant_base : _Move_assign_alias<_Types...>
642 using _Base = _Move_assign_alias<_Types...>;
646 noexcept(_Traits<_Types...>::_S_nothrow_default_ctor)
647 : _Variant_base(in_place_index<0>) { }
649 template<size_t _Np, typename... _Args>
651 _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
652 : _Base(__i, std::forward<_Args>(__args)...)
655 _Variant_base(const _Variant_base&) = default;
656 _Variant_base(_Variant_base&&) = default;
657 _Variant_base& operator=(const _Variant_base&) = default;
658 _Variant_base& operator=(_Variant_base&&) = default;
661 // For how many times does _Tp appear in _Tuple?
662 template<typename _Tp, typename _Tuple>
663 struct __tuple_count;
665 template<typename _Tp, typename _Tuple>
666 inline constexpr size_t __tuple_count_v =
667 __tuple_count<_Tp, _Tuple>::value;
669 template<typename _Tp, typename... _Types>
670 struct __tuple_count<_Tp, tuple<_Types...>>
671 : integral_constant<size_t, 0> { };
673 template<typename _Tp, typename _First, typename... _Rest>
674 struct __tuple_count<_Tp, tuple<_First, _Rest...>>
677 __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { };
679 // TODO: Reuse this in <tuple> ?
680 template<typename _Tp, typename... _Types>
681 inline constexpr bool __exactly_once =
682 __tuple_count_v<_Tp, tuple<_Types...>> == 1;
684 // Takes _Types and create an overloaded _S_fun for each type.
685 // If a type appears more than once in _Types, create only one overload.
686 template<typename... _Types>
687 struct __overload_set
688 { static void _S_fun(); };
690 template<typename _First, typename... _Rest>
691 struct __overload_set<_First, _Rest...> : __overload_set<_Rest...>
693 using __overload_set<_Rest...>::_S_fun;
694 static integral_constant<size_t, sizeof...(_Rest)> _S_fun(_First);
697 template<typename... _Rest>
698 struct __overload_set<void, _Rest...> : __overload_set<_Rest...>
700 using __overload_set<_Rest...>::_S_fun;
703 // Helper for variant(_Tp&&) and variant::operator=(_Tp&&).
704 // __accepted_index maps an arbitrary _Tp to an alternative type in _Variant
705 // (or to variant_npos).
706 template<typename _Tp, typename _Variant, typename = void>
707 struct __accepted_index
708 { static constexpr size_t value = variant_npos; };
710 template<typename _Tp, typename... _Types>
711 struct __accepted_index<
712 _Tp, variant<_Types...>,
713 void_t<decltype(__overload_set<_Types...>::_S_fun(std::declval<_Tp>()))>>
715 static constexpr size_t value = sizeof...(_Types) - 1
716 - decltype(__overload_set<_Types...>::
717 _S_fun(std::declval<_Tp>()))::value;
720 // Returns the raw storage for __v.
721 template<typename _Variant>
722 void* __get_storage(_Variant&& __v)
723 { return __v._M_storage(); }
725 // Used for storing multi-dimensional vtable.
726 template<typename _Tp, size_t... _Dimensions>
736 template<typename _Tp, size_t __first, size_t... __rest>
737 struct _Multi_array<_Tp, __first, __rest...>
739 template<typename... _Args>
741 _M_access(size_t __first_index, _Args... __rest_indices) const
742 { return _M_arr[__first_index]._M_access(__rest_indices...); }
744 _Multi_array<_Tp, __rest...> _M_arr[__first];
747 // Creates a multi-dimensional vtable recursively.
750 // visit([](auto, auto){},
751 // variant<int, char>(), // typedef'ed as V1
752 // variant<float, double, long double>()) // typedef'ed as V2
753 // will trigger instantiations of:
754 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>,
755 // tuple<V1&&, V2&&>, std::index_sequence<>>
756 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
757 // tuple<V1&&, V2&&>, std::index_sequence<0>>
758 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
759 // tuple<V1&&, V2&&>, std::index_sequence<0, 0>>
760 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
761 // tuple<V1&&, V2&&>, std::index_sequence<0, 1>>
762 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
763 // tuple<V1&&, V2&&>, std::index_sequence<0, 2>>
764 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
765 // tuple<V1&&, V2&&>, std::index_sequence<1>>
766 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
767 // tuple<V1&&, V2&&>, std::index_sequence<1, 0>>
768 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
769 // tuple<V1&&, V2&&>, std::index_sequence<1, 1>>
770 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
771 // tuple<V1&&, V2&&>, std::index_sequence<1, 2>>
772 // The returned multi-dimensional vtable can be fast accessed by the visitor
773 // using index calculation.
774 template<typename _Array_type, typename _Variant_tuple, typename _Index_seq>
775 struct __gen_vtable_impl;
777 template<typename _Result_type, typename _Visitor, size_t... __dimensions,
778 typename... _Variants, size_t... __indices>
779 struct __gen_vtable_impl<
780 _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>,
781 tuple<_Variants...>, std::index_sequence<__indices...>>
784 remove_reference_t<typename _Nth_type<sizeof...(__indices),
785 _Variants...>::type>;
787 _Multi_array<_Result_type (*)(_Visitor, _Variants...),
790 static constexpr _Array_type
793 _Array_type __vtable{};
795 __vtable, make_index_sequence<variant_size_v<_Next>>());
799 template<size_t... __var_indices>
800 static constexpr void
801 _S_apply_all_alts(_Array_type& __vtable,
802 std::index_sequence<__var_indices...>)
804 (_S_apply_single_alt<__var_indices>(
805 __vtable._M_arr[__var_indices]), ...);
808 template<size_t __index, typename _Tp>
809 static constexpr void
810 _S_apply_single_alt(_Tp& __element)
812 using _Alternative = variant_alternative_t<__index, _Next>;
813 __element = __gen_vtable_impl<
814 remove_reference_t<decltype(__element)>, tuple<_Variants...>,
815 std::index_sequence<__indices..., __index>>::_S_apply();
819 template<typename _Result_type, typename _Visitor, typename... _Variants,
821 struct __gen_vtable_impl<
822 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>,
823 tuple<_Variants...>, std::index_sequence<__indices...>>
826 _Multi_array<_Result_type (*)(_Visitor&&, _Variants...)>;
828 static constexpr decltype(auto)
829 __visit_invoke(_Visitor&& __visitor, _Variants... __vars)
831 return std::__invoke(std::forward<_Visitor>(__visitor),
832 __variant::__get<__indices>(std::forward<_Variants>(__vars))...);
835 static constexpr auto
837 { return _Array_type{&__visit_invoke}; }
840 template<typename _Result_type, typename _Visitor, typename... _Variants>
843 using _Func_ptr = _Result_type (*)(_Visitor&&, _Variants...);
845 _Multi_array<_Func_ptr,
846 variant_size_v<remove_reference_t<_Variants>>...>;
848 static constexpr _Array_type
851 return __gen_vtable_impl<_Array_type, tuple<_Variants...>,
852 std::index_sequence<>>::_S_apply();
855 static constexpr auto _S_vtable = _S_apply();
858 template<size_t _Np, typename _Tp>
859 struct _Base_dedup : public _Tp { };
861 template<typename _Variant, typename __indices>
862 struct _Variant_hash_base;
864 template<typename... _Types, size_t... __indices>
865 struct _Variant_hash_base<variant<_Types...>,
866 std::index_sequence<__indices...>>
867 : _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { };
869 } // namespace __variant
870 } // namespace __detail
872 template<typename _Tp, typename... _Types>
874 holds_alternative(const variant<_Types...>& __v) noexcept
876 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
877 "T should occur for exactly once in alternatives");
878 return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>;
881 template<typename _Tp, typename... _Types>
882 constexpr _Tp& get(variant<_Types...>& __v)
884 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
885 "T should occur for exactly once in alternatives");
886 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
887 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
890 template<typename _Tp, typename... _Types>
891 constexpr _Tp&& get(variant<_Types...>&& __v)
893 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
894 "T should occur for exactly once in alternatives");
895 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
896 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
900 template<typename _Tp, typename... _Types>
901 constexpr const _Tp& get(const variant<_Types...>& __v)
903 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
904 "T should occur for exactly once in alternatives");
905 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
906 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
909 template<typename _Tp, typename... _Types>
910 constexpr const _Tp&& get(const variant<_Types...>&& __v)
912 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
913 "T should occur for exactly once in alternatives");
914 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
915 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
919 template<size_t _Np, typename... _Types>
920 constexpr add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
921 get_if(variant<_Types...>* __ptr) noexcept
923 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
924 static_assert(_Np < sizeof...(_Types),
925 "The index should be in [0, number of alternatives)");
926 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void");
927 if (__ptr && __ptr->index() == _Np)
928 return &__detail::__variant::__get<_Np>(*__ptr);
932 template<size_t _Np, typename... _Types>
934 add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>>
935 get_if(const variant<_Types...>* __ptr) noexcept
937 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
938 static_assert(_Np < sizeof...(_Types),
939 "The index should be in [0, number of alternatives)");
940 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void");
941 if (__ptr && __ptr->index() == _Np)
942 return &__detail::__variant::__get<_Np>(*__ptr);
946 template<typename _Tp, typename... _Types>
947 constexpr add_pointer_t<_Tp>
948 get_if(variant<_Types...>* __ptr) noexcept
950 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
951 "T should occur for exactly once in alternatives");
952 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
953 return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(
957 template<typename _Tp, typename... _Types>
958 constexpr add_pointer_t<const _Tp>
959 get_if(const variant<_Types...>* __ptr)
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 struct monostate { };
971 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
972 template<typename... _Types> \
973 constexpr bool operator __OP(const variant<_Types...>& __lhs, \
974 const variant<_Types...>& __rhs) \
976 return __lhs._M_##__NAME(__rhs, std::index_sequence_for<_Types...>{}); \
979 constexpr bool operator __OP(monostate, monostate) noexcept \
982 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
983 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
984 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
985 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
986 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
987 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
989 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
991 template<typename _Visitor, typename... _Variants>
992 constexpr decltype(auto) visit(_Visitor&&, _Variants&&...);
994 template<typename... _Types>
995 inline enable_if_t<(is_move_constructible_v<_Types> && ...)
996 && (is_swappable_v<_Types> && ...)>
997 swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs)
998 noexcept(noexcept(__lhs.swap(__rhs)))
999 { __lhs.swap(__rhs); }
1001 template<typename... _Types>
1002 enable_if_t<!((is_move_constructible_v<_Types> && ...)
1003 && (is_swappable_v<_Types> && ...))>
1004 swap(variant<_Types...>&, variant<_Types...>&) = delete;
1006 class bad_variant_access : public exception
1009 bad_variant_access() noexcept : _M_reason("Unknown reason") { }
1010 const char* what() const noexcept override
1011 { return _M_reason; }
1014 bad_variant_access(const char* __reason) : _M_reason(__reason) { }
1016 const char* _M_reason;
1018 friend void __throw_bad_variant_access(const char* __what);
1022 __throw_bad_variant_access(const char* __what)
1023 { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); }
1025 template<typename... _Types>
1027 : private __detail::__variant::_Variant_base<_Types...>,
1028 private _Enable_default_constructor<
1029 __detail::__variant::_Traits<_Types...>::_S_default_ctor,
1030 variant<_Types...>>,
1031 private _Enable_copy_move<
1032 __detail::__variant::_Traits<_Types...>::_S_copy_ctor,
1033 __detail::__variant::_Traits<_Types...>::_S_copy_assign,
1034 __detail::__variant::_Traits<_Types...>::_S_move_ctor,
1035 __detail::__variant::_Traits<_Types...>::_S_move_assign,
1039 static_assert(sizeof...(_Types) > 0,
1040 "variant must have at least one alternative");
1041 static_assert(!(std::is_reference_v<_Types> || ...),
1042 "variant must have no reference alternative");
1043 static_assert(!(std::is_void_v<_Types> || ...),
1044 "variant must have no void alternative");
1046 using _Base = __detail::__variant::_Variant_base<_Types...>;
1047 using _Default_ctor_enabler =
1048 _Enable_default_constructor<
1049 __detail::__variant::_Traits<_Types...>::_S_default_ctor,
1050 variant<_Types...>>;
1052 template<typename _Tp>
1053 static constexpr bool
1054 __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>;
1056 template<typename _Tp>
1057 static constexpr size_t __accepted_index =
1058 __detail::__variant::__accepted_index<_Tp&&, variant>::value;
1060 template<size_t _Np, bool = _Np < sizeof...(_Types)>
1061 struct __to_type_impl;
1063 template<size_t _Np>
1064 struct __to_type_impl<_Np, true>
1065 { using type = variant_alternative_t<_Np, variant>; };
1067 template<size_t _Np>
1068 using __to_type = typename __to_type_impl<_Np>::type;
1070 template<typename _Tp>
1071 using __accepted_type = __to_type<__accepted_index<_Tp>>;
1073 template<typename _Tp>
1074 static constexpr size_t __index_of =
1075 __detail::__variant::__index_of_v<_Tp, _Types...>;
1077 using _Traits = __detail::__variant::_Traits<_Types...>;
1080 variant() = default;
1081 variant(const variant& __rhs) = default;
1082 variant(variant&&) = default;
1083 variant& operator=(const variant&) = default;
1084 variant& operator=(variant&&) = default;
1085 ~variant() = default;
1087 template<typename _Tp,
1088 typename = enable_if_t<!is_same_v<decay_t<_Tp>, variant>>,
1089 typename = enable_if_t<(sizeof...(_Types)>0)>,
1090 typename = enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
1091 && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>>>
1094 noexcept(is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
1095 : variant(in_place_index<__accepted_index<_Tp&&>>,
1096 std::forward<_Tp>(__t))
1097 { __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this)); }
1099 template<typename _Tp, typename... _Args,
1100 typename = enable_if_t<__exactly_once<_Tp>
1101 && is_constructible_v<_Tp, _Args&&...>>>
1103 variant(in_place_type_t<_Tp>, _Args&&... __args)
1104 : variant(in_place_index<__index_of<_Tp>>,
1105 std::forward<_Args>(__args)...)
1106 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
1108 template<typename _Tp, typename _Up, typename... _Args,
1109 typename = enable_if_t<__exactly_once<_Tp>
1110 && is_constructible_v<
1111 _Tp, initializer_list<_Up>&, _Args&&...>>>
1113 variant(in_place_type_t<_Tp>, initializer_list<_Up> __il,
1115 : variant(in_place_index<__index_of<_Tp>>, __il,
1116 std::forward<_Args>(__args)...)
1117 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
1119 template<size_t _Np, typename... _Args,
1120 typename = enable_if_t<
1121 is_constructible_v<__to_type<_Np>, _Args&&...>>>
1123 variant(in_place_index_t<_Np>, _Args&&... __args)
1124 : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...),
1125 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1126 { __glibcxx_assert(index() == _Np); }
1128 template<size_t _Np, typename _Up, typename... _Args,
1129 typename = enable_if_t<is_constructible_v<__to_type<_Np>,
1130 initializer_list<_Up>&, _Args&&...>>>
1132 variant(in_place_index_t<_Np>, initializer_list<_Up> __il,
1134 : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...),
1135 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1136 { __glibcxx_assert(index() == _Np); }
1138 template<typename _Tp>
1139 enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
1140 && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>
1141 && is_assignable_v<__accepted_type<_Tp&&>&, _Tp&&>
1142 && !is_same_v<decay_t<_Tp>, variant>, variant&>
1143 operator=(_Tp&& __rhs)
1144 noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp&&>
1145 && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
1147 constexpr auto __index = __accepted_index<_Tp&&>;
1148 if (index() == __index)
1149 std::get<__index>(*this) = std::forward<_Tp>(__rhs);
1151 this->emplace<__index>(std::forward<_Tp>(__rhs));
1152 __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this));
1156 template<typename _Tp, typename... _Args>
1157 enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>,
1159 emplace(_Args&&... __args)
1162 this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...);
1163 __glibcxx_assert(holds_alternative<_Tp>(*this));
1167 template<typename _Tp, typename _Up, typename... _Args>
1168 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>
1169 && __exactly_once<_Tp>,
1171 emplace(initializer_list<_Up> __il, _Args&&... __args)
1174 this->emplace<__index_of<_Tp>>(__il,
1175 std::forward<_Args>(__args)...);
1176 __glibcxx_assert(holds_alternative<_Tp>(*this));
1180 template<size_t _Np, typename... _Args>
1181 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1183 variant_alternative_t<_Np, variant>&>
1184 emplace(_Args&&... __args)
1186 static_assert(_Np < sizeof...(_Types),
1187 "The index should be in [0, number of alternatives)");
1189 using type = variant_alternative_t<_Np, variant>;
1190 // If constructing the value can throw but move assigning it can't,
1191 // construct in a temporary and then move assign from it. This gives
1192 // the strong exception safety guarantee, ensuring we never become
1194 if constexpr (is_trivially_copyable_v<type>
1195 && !is_nothrow_constructible_v<type, _Args...>)
1197 // If move assignment cannot throw then we can provide the
1198 // strong exception safety guarantee, and never become valueless.
1199 variant __tmp(in_place_index<_Np>,
1200 std::forward<_Args>(__args)...);
1201 *this = std::move(__tmp);
1202 return std::get<_Np>(*this);
1208 ::new (this) variant(in_place_index<_Np>,
1209 std::forward<_Args>(__args)...);
1213 this->_M_index = variant_npos;
1214 __throw_exception_again;
1216 __glibcxx_assert(index() == _Np);
1217 return std::get<_Np>(*this);
1220 template<size_t _Np, typename _Up, typename... _Args>
1221 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1222 initializer_list<_Up>&, _Args...>,
1223 variant_alternative_t<_Np, variant>&>
1224 emplace(initializer_list<_Up> __il, _Args&&... __args)
1226 static_assert(_Np < sizeof...(_Types),
1227 "The index should be in [0, number of alternatives)");
1229 using type = variant_alternative_t<_Np, variant>;
1230 if constexpr (is_trivially_copyable_v<type>
1231 && !is_nothrow_constructible_v<type, initializer_list<_Up>,
1234 // If move assignment cannot throw then we can provide the
1235 // strong exception safety guarantee, and never become valueless.
1236 variant __tmp(in_place_index<_Np>, __il,
1237 std::forward<_Args>(__args)...);
1238 *this = std::move(__tmp);
1239 return std::get<_Np>(*this);
1245 ::new (this) variant(in_place_index<_Np>, __il,
1246 std::forward<_Args>(__args)...);
1250 this->_M_index = variant_npos;
1251 __throw_exception_again;
1253 __glibcxx_assert(index() == _Np);
1254 return std::get<_Np>(*this);
1257 constexpr bool valueless_by_exception() const noexcept
1258 { return !this->_M_valid(); }
1260 constexpr size_t index() const noexcept
1262 if (this->_M_index ==
1263 typename _Base::__index_type(variant_npos))
1264 return variant_npos;
1265 return this->_M_index;
1269 swap(variant& __rhs)
1270 noexcept((__is_nothrow_swappable<_Types>::value && ...)
1271 && is_nothrow_move_constructible_v<variant>)
1273 if (this->index() == __rhs.index())
1275 if (this->_M_valid())
1277 static constexpr void (*_S_vtable[])(void*, void*) =
1278 { &__detail::__variant::__erased_swap<_Types&, _Types&>... };
1279 _S_vtable[__rhs._M_index](this->_M_storage(),
1280 __rhs._M_storage());
1283 else if (!this->_M_valid())
1285 this->_M_destructive_move(std::move(__rhs));
1288 else if (!__rhs._M_valid())
1290 __rhs._M_destructive_move(std::move(*this));
1295 auto __tmp = std::move(__rhs);
1296 __rhs._M_destructive_move(std::move(*this));
1297 this->_M_destructive_move(std::move(__tmp));
1302 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
1303 template<size_t... __indices> \
1304 static constexpr bool \
1305 (*_S_erased_##__NAME[])(const variant&, const variant&) = \
1306 { &__detail::__variant::__erased_##__NAME< \
1307 const variant&, __indices>... }; \
1308 template<size_t... __indices> \
1310 _M_##__NAME(const variant& __rhs, \
1311 std::index_sequence<__indices...>) const \
1313 auto __lhs_index = this->index(); \
1314 auto __rhs_index = __rhs.index(); \
1315 if (__lhs_index != __rhs_index || valueless_by_exception()) \
1316 /* Modulo addition. */ \
1317 return __lhs_index + 1 __OP __rhs_index + 1; \
1318 return _S_erased_##__NAME<__indices...>[__lhs_index](*this, __rhs); \
1321 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
1322 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
1323 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
1324 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
1325 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
1326 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
1328 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1330 #if defined(__clang__) && __clang_major__ <= 7
1332 using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852
1336 template<size_t _Np, typename _Vp>
1337 friend constexpr decltype(auto) __detail::__variant::__get(_Vp&& __v);
1339 template<typename _Vp>
1340 friend void* __detail::__variant::__get_storage(_Vp&& __v);
1342 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \
1343 template<typename... _Tp> \
1344 friend constexpr bool \
1345 operator __OP(const variant<_Tp...>& __lhs, \
1346 const variant<_Tp...>& __rhs);
1348 _VARIANT_RELATION_FUNCTION_TEMPLATE(<)
1349 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=)
1350 _VARIANT_RELATION_FUNCTION_TEMPLATE(==)
1351 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=)
1352 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=)
1353 _VARIANT_RELATION_FUNCTION_TEMPLATE(>)
1355 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1358 template<size_t _Np, typename... _Types>
1359 constexpr variant_alternative_t<_Np, variant<_Types...>>&
1360 get(variant<_Types...>& __v)
1362 static_assert(_Np < sizeof...(_Types),
1363 "The index should be in [0, number of alternatives)");
1364 if (__v.index() != _Np)
1365 __throw_bad_variant_access("Unexpected index");
1366 return __detail::__variant::__get<_Np>(__v);
1369 template<size_t _Np, typename... _Types>
1370 constexpr variant_alternative_t<_Np, variant<_Types...>>&&
1371 get(variant<_Types...>&& __v)
1373 static_assert(_Np < sizeof...(_Types),
1374 "The index should be in [0, number of alternatives)");
1375 if (__v.index() != _Np)
1376 __throw_bad_variant_access("Unexpected index");
1377 return __detail::__variant::__get<_Np>(std::move(__v));
1380 template<size_t _Np, typename... _Types>
1381 constexpr const variant_alternative_t<_Np, variant<_Types...>>&
1382 get(const variant<_Types...>& __v)
1384 static_assert(_Np < sizeof...(_Types),
1385 "The index should be in [0, number of alternatives)");
1386 if (__v.index() != _Np)
1387 __throw_bad_variant_access("Unexpected index");
1388 return __detail::__variant::__get<_Np>(__v);
1391 template<size_t _Np, typename... _Types>
1392 constexpr const variant_alternative_t<_Np, variant<_Types...>>&&
1393 get(const variant<_Types...>&& __v)
1395 static_assert(_Np < sizeof...(_Types),
1396 "The index should be in [0, number of alternatives)");
1397 if (__v.index() != _Np)
1398 __throw_bad_variant_access("Unexpected index");
1399 return __detail::__variant::__get<_Np>(std::move(__v));
1402 template<typename _Visitor, typename... _Variants>
1403 constexpr decltype(auto)
1404 visit(_Visitor&& __visitor, _Variants&&... __variants)
1406 if ((__variants.valueless_by_exception() || ...))
1407 __throw_bad_variant_access("Unexpected index");
1409 using _Result_type =
1410 decltype(std::forward<_Visitor>(__visitor)(
1411 std::get<0>(std::forward<_Variants>(__variants))...));
1413 constexpr auto& __vtable = __detail::__variant::__gen_vtable<
1414 _Result_type, _Visitor&&, _Variants&&...>::_S_vtable;
1416 auto __func_ptr = __vtable._M_access(__variants.index()...);
1417 return (*__func_ptr)(std::forward<_Visitor>(__visitor),
1418 std::forward<_Variants>(__variants)...);
1421 template<bool, typename... _Types>
1422 struct __variant_hash_call_base_impl
1425 operator()(const variant<_Types...>& __t) const
1426 noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...))
1428 if (!__t.valueless_by_exception())
1430 namespace __edv = __detail::__variant;
1431 static constexpr size_t (*_S_vtable[])(void*) =
1432 { &__edv::__erased_hash<const _Types&>... };
1433 return hash<size_t>{}(__t.index())
1434 + _S_vtable[__t.index()](__edv::__get_storage(__t));
1436 return hash<size_t>{}(__t.index());
1440 template<typename... _Types>
1441 struct __variant_hash_call_base_impl<false, _Types...> {};
1443 template<typename... _Types>
1444 using __variant_hash_call_base =
1445 __variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>::
1446 __enable_hash_call &&...), _Types...>;
1448 template<typename... _Types>
1449 struct hash<variant<_Types...>>
1450 : private __detail::__variant::_Variant_hash_base<
1451 variant<_Types...>, std::index_sequence_for<_Types...>>,
1452 public __variant_hash_call_base<_Types...>
1454 using result_type [[__deprecated__]] = size_t;
1455 using argument_type [[__deprecated__]] = variant<_Types...>;
1459 struct hash<monostate>
1461 using result_type [[__deprecated__]] = size_t;
1462 using argument_type [[__deprecated__]] = monostate;
1465 operator()(const monostate& __t) const noexcept
1467 constexpr size_t __magic_monostate_hash = -7777;
1468 return __magic_monostate_hash;
1472 template<typename... _Types>
1473 struct __is_fast_hash<hash<variant<_Types...>>>
1474 : bool_constant<(__is_fast_hash<_Types>::value && ...)>
1477 _GLIBCXX_END_NAMESPACE_VERSION
1482 #endif // _GLIBCXX_VARIANT