1 // <variant> -*- C++ -*-
3 // Copyright (C) 2016-2017 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 <= 201402L
35 # include <bits/c++17_warning.h>
38 #include <type_traits>
40 #include <bits/enable_special_members.h>
41 #include <bits/functexcept.h>
42 #include <bits/move.h>
43 #include <bits/functional_hash.h>
44 #include <bits/invoke.h>
45 #include <ext/aligned_buffer.h>
46 #include <bits/parse_numbers.h>
48 namespace std _GLIBCXX_VISIBILITY(default)
54 _GLIBCXX_BEGIN_NAMESPACE_VERSION
56 template<size_t _Np, typename... _Types>
59 template<size_t _Np, typename _First, typename... _Rest>
60 struct _Nth_type<_Np, _First, _Rest...>
61 : _Nth_type<_Np-1, _Rest...> { };
63 template<typename _First, typename... _Rest>
64 struct _Nth_type<0, _First, _Rest...>
65 { using type = _First; };
67 _GLIBCXX_END_NAMESPACE_VERSION
68 } // namespace __variant
69 } // namespace __detail
71 _GLIBCXX_BEGIN_NAMESPACE_VERSION
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...>&&);
141 _GLIBCXX_END_NAMESPACE_VERSION
147 _GLIBCXX_BEGIN_NAMESPACE_VERSION
148 // Returns the first apparence of _Tp in _Types.
149 // Returns sizeof...(_Types) if _Tp is not in _Types.
150 template<typename _Tp, typename... _Types>
151 struct __index_of : std::integral_constant<size_t, 0> {};
153 template<typename _Tp, typename... _Types>
154 inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value;
156 template<typename _Tp, typename _First, typename... _Rest>
157 struct __index_of<_Tp, _First, _Rest...> :
158 std::integral_constant<size_t, is_same_v<_Tp, _First>
159 ? 0 : __index_of_v<_Tp, _Rest...> + 1> {};
161 // _Uninitialized<T> is guaranteed to be a literal type, even if T is not.
162 // We have to do this, because [basic.types]p10.5.3 (n4606) is not implemented
163 // yet. When it's implemented, _Uninitialized<T> can be changed to the alias
164 // to T, therefore equivalent to being removed entirely.
166 // Another reason we may not want to remove _Uninitialzied<T> may be that, we
167 // want _Uninitialized<T> to be trivially destructible, no matter whether T
168 // is; but we will see.
169 template<typename _Type, bool = std::is_literal_type_v<_Type>>
170 struct _Uninitialized;
172 template<typename _Type>
173 struct _Uninitialized<_Type, true>
175 template<typename... _Args>
176 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
177 : _M_storage(std::forward<_Args>(__args)...)
180 constexpr const _Type& _M_get() const &
181 { return _M_storage; }
183 constexpr _Type& _M_get() &
184 { return _M_storage; }
186 constexpr const _Type&& _M_get() const &&
187 { return std::move(_M_storage); }
189 constexpr _Type&& _M_get() &&
190 { return std::move(_M_storage); }
195 template<typename _Type>
196 struct _Uninitialized<_Type, false>
198 template<typename... _Args>
199 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
200 { ::new (&_M_storage) _Type(std::forward<_Args>(__args)...); }
202 const _Type& _M_get() const &
203 { return *_M_storage._M_ptr(); }
206 { return *_M_storage._M_ptr(); }
208 const _Type&& _M_get() const &&
209 { return std::move(*_M_storage._M_ptr()); }
212 { return std::move(*_M_storage._M_ptr()); }
214 __gnu_cxx::__aligned_membuf<_Type> _M_storage;
217 template<typename _Ref>
218 _Ref __ref_cast(void* __ptr)
220 return static_cast<_Ref>(*static_cast<remove_reference_t<_Ref>*>(__ptr));
223 template<typename _Union>
224 constexpr decltype(auto) __get(in_place_index_t<0>, _Union&& __u)
225 { return std::forward<_Union>(__u)._M_first._M_get(); }
227 template<size_t _Np, typename _Union>
228 constexpr decltype(auto) __get(in_place_index_t<_Np>, _Union&& __u)
229 { return __get(in_place_index<_Np-1>, 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 __get(std::in_place_index<_Np>, std::forward<_Variant>(__v)._M_u);
238 // Various functions as "vtable" entries, where those vtables are used by
239 // polymorphic operations.
240 template<typename _Lhs, typename _Rhs>
242 __erased_ctor(void* __lhs, void* __rhs)
243 { ::new (__lhs) remove_reference_t<_Lhs>(__ref_cast<_Rhs>(__rhs)); }
245 template<typename _Variant, size_t _Np>
247 __erased_dtor(_Variant&& __v)
249 auto&& __element = __get<_Np>(std::forward<_Variant>(__v));
250 using _Type = std::remove_reference_t<decltype(__element)>;
254 template<typename _Lhs, typename _Rhs>
256 __erased_assign(void* __lhs, void* __rhs)
257 { __ref_cast<_Lhs>(__lhs) = __ref_cast<_Rhs>(__rhs); }
259 template<typename _Lhs, typename _Rhs>
261 __erased_swap(void* __lhs, void* __rhs)
264 swap(__ref_cast<_Lhs>(__lhs), __ref_cast<_Rhs>(__rhs));
267 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
268 template<typename _Variant, size_t _Np> \
270 __erased_##__NAME(const _Variant& __lhs, const _Variant& __rhs) \
272 return __get<_Np>(std::forward<_Variant>(__lhs)) \
273 __OP __get<_Np>(std::forward<_Variant>(__rhs)); \
276 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
277 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
278 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
279 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
280 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
281 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
283 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
285 template<typename _Tp>
287 __erased_hash(void* __t)
289 return std::hash<remove_cv_t<remove_reference_t<_Tp>>>{}(
290 __ref_cast<_Tp>(__t));
293 // Defines members and ctors.
294 template<typename... _Types>
295 union _Variadic_union { };
297 template<typename _First, typename... _Rest>
298 union _Variadic_union<_First, _Rest...>
300 constexpr _Variadic_union() : _M_rest() { }
302 template<typename... _Args>
303 constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args)
304 : _M_first(in_place_index<0>, std::forward<_Args>(__args)...)
307 template<size_t _Np, typename... _Args>
308 constexpr _Variadic_union(in_place_index_t<_Np>, _Args&&... __args)
309 : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...)
312 _Uninitialized<_First> _M_first;
313 _Variadic_union<_Rest...> _M_rest;
316 // Defines index and the dtor, possibly trivial.
317 template<bool __trivially_destructible, typename... _Types>
318 struct _Variant_storage;
320 template <typename... _Types>
321 using __select_index =
322 typename __select_int::_Select_int_base<sizeof...(_Types)+1,
327 template<typename... _Types>
328 struct _Variant_storage<false, _Types...>
330 template<size_t... __indices>
331 static constexpr void (*_S_vtable[])(const _Variant_storage&) =
332 { &__erased_dtor<const _Variant_storage&, __indices>... };
334 constexpr _Variant_storage() : _M_index(variant_npos) { }
336 template<size_t _Np, typename... _Args>
337 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
338 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
342 template<size_t... __indices>
343 constexpr void _M_reset_impl(std::index_sequence<__indices...>)
345 if (_M_index != __index_type(variant_npos))
346 _S_vtable<__indices...>[_M_index](*this);
351 _M_reset_impl(std::index_sequence_for<_Types...>{});
352 _M_index = variant_npos;
358 _Variadic_union<_Types...> _M_u;
359 using __index_type = __select_index<_Types...>;
360 __index_type _M_index;
363 template<typename... _Types>
364 struct _Variant_storage<true, _Types...>
366 constexpr _Variant_storage() : _M_index(variant_npos) { }
368 template<size_t _Np, typename... _Args>
369 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
370 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
375 { _M_index = variant_npos; }
377 _Variadic_union<_Types...> _M_u;
378 using __index_type = __select_index<_Types...>;
379 __index_type _M_index;
382 // Helps SFINAE on special member functions. Otherwise it can live in variant
384 template<typename... _Types>
385 struct _Variant_base :
386 _Variant_storage<(std::is_trivially_destructible_v<_Types> && ...),
390 _Variant_storage<(std::is_trivially_destructible_v<_Types> && ...),
395 noexcept(is_nothrow_default_constructible_v<
396 variant_alternative_t<0, variant<_Types...>>>)
397 : _Variant_base(in_place_index<0>) { }
399 _Variant_base(const _Variant_base& __rhs)
401 if (__rhs._M_valid())
403 static constexpr void (*_S_vtable[])(void*, void*) =
404 { &__erased_ctor<_Types&, const _Types&>... };
405 _S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
406 this->_M_index = __rhs._M_index;
410 _Variant_base(_Variant_base&& __rhs)
411 noexcept((is_nothrow_move_constructible_v<_Types> && ...))
413 if (__rhs._M_valid())
415 static constexpr void (*_S_vtable[])(void*, void*) =
416 { &__erased_ctor<_Types&, _Types&&>... };
417 _S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
418 this->_M_index = __rhs._M_index;
422 template<size_t _Np, typename... _Args>
424 _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
425 : _Storage(__i, std::forward<_Args>(__args)...)
429 operator=(const _Variant_base& __rhs)
431 if (this->_M_index == __rhs._M_index)
433 if (__rhs._M_valid())
435 static constexpr void (*_S_vtable[])(void*, void*) =
436 { &__erased_assign<_Types&, const _Types&>... };
437 _S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
442 _Variant_base __tmp(__rhs);
443 this->~_Variant_base();
446 ::new (this) _Variant_base(std::move(__tmp));
450 this->_M_index = variant_npos;
451 __throw_exception_again;
454 __glibcxx_assert(this->_M_index == __rhs._M_index);
458 void _M_destructive_move(_Variant_base&& __rhs)
460 this->~_Variant_base();
463 ::new (this) _Variant_base(std::move(__rhs));
467 this->_M_index = variant_npos;
468 __throw_exception_again;
473 operator=(_Variant_base&& __rhs)
474 noexcept((is_nothrow_move_constructible_v<_Types> && ...)
475 && (is_nothrow_move_assignable_v<_Types> && ...))
477 if (this->_M_index == __rhs._M_index)
479 if (__rhs._M_valid())
481 static constexpr void (*_S_vtable[])(void*, void*) =
482 { &__erased_assign<_Types&, _Types&&>... };
483 _S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
488 _M_destructive_move(std::move(__rhs));
496 return const_cast<void*>(static_cast<const void*>(
497 std::addressof(_Storage::_M_u)));
501 _M_valid() const noexcept
503 return this->_M_index !=
504 typename _Storage::__index_type(variant_npos);
508 // For how many times does _Tp appear in _Tuple?
509 template<typename _Tp, typename _Tuple>
510 struct __tuple_count;
512 template<typename _Tp, typename _Tuple>
513 inline constexpr size_t __tuple_count_v =
514 __tuple_count<_Tp, _Tuple>::value;
516 template<typename _Tp, typename... _Types>
517 struct __tuple_count<_Tp, tuple<_Types...>>
518 : integral_constant<size_t, 0> { };
520 template<typename _Tp, typename _First, typename... _Rest>
521 struct __tuple_count<_Tp, tuple<_First, _Rest...>>
524 __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { };
526 // TODO: Reuse this in <tuple> ?
527 template<typename _Tp, typename... _Types>
528 inline constexpr bool __exactly_once =
529 __tuple_count_v<_Tp, tuple<_Types...>> == 1;
531 // Takes _Types and create an overloaded _S_fun for each type.
532 // If a type appears more than once in _Types, create only one overload.
533 template<typename... _Types>
534 struct __overload_set
535 { static void _S_fun(); };
537 template<typename _First, typename... _Rest>
538 struct __overload_set<_First, _Rest...> : __overload_set<_Rest...>
540 using __overload_set<_Rest...>::_S_fun;
541 static integral_constant<size_t, sizeof...(_Rest)> _S_fun(_First);
544 template<typename... _Rest>
545 struct __overload_set<void, _Rest...> : __overload_set<_Rest...>
547 using __overload_set<_Rest...>::_S_fun;
550 // Helper for variant(_Tp&&) and variant::operator=(_Tp&&).
551 // __accepted_index maps the arbitrary _Tp to an alternative type in _Variant.
552 template<typename _Tp, typename _Variant, typename = void>
553 struct __accepted_index
554 { static constexpr size_t value = variant_npos; };
556 template<typename _Tp, typename... _Types>
557 struct __accepted_index<
558 _Tp, variant<_Types...>,
559 decltype(__overload_set<_Types...>::_S_fun(std::declval<_Tp>()),
560 std::declval<void>())>
562 static constexpr size_t value = sizeof...(_Types) - 1
563 - decltype(__overload_set<_Types...>::
564 _S_fun(std::declval<_Tp>()))::value;
567 // Returns the raw storage for __v.
568 template<typename _Variant>
569 void* __get_storage(_Variant&& __v)
570 { return __v._M_storage(); }
572 // Used for storing multi-dimensional vtable.
573 template<typename _Tp, size_t... _Dimensions>
583 template<typename _Tp, size_t __first, size_t... __rest>
584 struct _Multi_array<_Tp, __first, __rest...>
586 template<typename... _Args>
588 _M_access(size_t __first_index, _Args... __rest_indices) const
589 { return _M_arr[__first_index]._M_access(__rest_indices...); }
591 _Multi_array<_Tp, __rest...> _M_arr[__first];
594 // Creates a multi-dimensional vtable recursively.
597 // visit([](auto, auto){},
598 // variant<int, char>(), // typedef'ed as V1
599 // variant<float, double, long double>()) // typedef'ed as V2
600 // will trigger instantiations of:
601 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>,
602 // tuple<V1&&, V2&&>, std::index_sequence<>>
603 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
604 // tuple<V1&&, V2&&>, std::index_sequence<0>>
605 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
606 // tuple<V1&&, V2&&>, std::index_sequence<0, 0>>
607 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
608 // tuple<V1&&, V2&&>, std::index_sequence<0, 1>>
609 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
610 // tuple<V1&&, V2&&>, std::index_sequence<0, 2>>
611 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
612 // tuple<V1&&, V2&&>, std::index_sequence<1>>
613 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
614 // tuple<V1&&, V2&&>, std::index_sequence<1, 0>>
615 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
616 // tuple<V1&&, V2&&>, std::index_sequence<1, 1>>
617 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
618 // tuple<V1&&, V2&&>, std::index_sequence<1, 2>>
619 // The returned multi-dimensional vtable can be fast accessed by the visitor
620 // using index calculation.
621 template<typename _Array_type, typename _Variant_tuple, typename _Index_seq>
622 struct __gen_vtable_impl;
624 template<typename _Result_type, typename _Visitor, size_t... __dimensions,
625 typename... _Variants, size_t... __indices>
626 struct __gen_vtable_impl<
627 _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>,
628 tuple<_Variants...>, std::index_sequence<__indices...>>
631 remove_reference_t<typename _Nth_type<sizeof...(__indices),
632 _Variants...>::type>;
634 _Multi_array<_Result_type (*)(_Visitor, _Variants...),
637 static constexpr _Array_type
640 _Array_type __vtable{};
642 __vtable, make_index_sequence<variant_size_v<_Next>>());
646 template<size_t... __var_indices>
647 static constexpr void
648 _S_apply_all_alts(_Array_type& __vtable,
649 std::index_sequence<__var_indices...>)
651 (_S_apply_single_alt<__var_indices>(
652 __vtable._M_arr[__var_indices]), ...);
655 template<size_t __index, typename _Tp>
656 static constexpr void
657 _S_apply_single_alt(_Tp& __element)
659 using _Alternative = variant_alternative_t<__index, _Next>;
660 __element = __gen_vtable_impl<
662 decltype(__element)>, tuple<_Variants...>,
663 std::index_sequence<__indices..., __index>>::_S_apply();
667 template<typename _Result_type, typename _Visitor, typename... _Variants,
669 struct __gen_vtable_impl<
670 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>,
671 tuple<_Variants...>, std::index_sequence<__indices...>>
674 _Multi_array<_Result_type (*)(_Visitor&&, _Variants...)>;
677 static constexpr __visit_invoke(_Visitor&& __visitor, _Variants... __vars)
679 return __invoke(std::forward<_Visitor>(__visitor),
681 std::forward<_Variants>(__vars))...);
684 static constexpr auto
686 { return _Array_type{&__visit_invoke}; }
689 template<typename _Result_type, typename _Visitor, typename... _Variants>
692 using _Func_ptr = _Result_type (*)(_Visitor&&, _Variants...);
694 _Multi_array<_Func_ptr,
695 variant_size_v<remove_reference_t<_Variants>>...>;
697 static constexpr _Array_type
700 return __gen_vtable_impl<_Array_type, tuple<_Variants...>,
701 std::index_sequence<>>::_S_apply();
704 static constexpr auto _S_vtable = _S_apply();
707 template<size_t _Np, typename _Tp>
708 struct _Base_dedup : public _Tp { };
710 template<typename _Variant, typename __indices>
711 struct _Variant_hash_base;
713 template<typename... _Types, size_t... __indices>
714 struct _Variant_hash_base<variant<_Types...>,
715 std::index_sequence<__indices...>>
716 : _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { };
718 _GLIBCXX_END_NAMESPACE_VERSION
719 } // namespace __variant
720 } // namespace __detail
722 _GLIBCXX_BEGIN_NAMESPACE_VERSION
724 template<typename _Tp, typename... _Types>
725 inline constexpr bool holds_alternative(const variant<_Types...>& __v)
728 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
729 "T should occur for exactly once in alternatives");
730 return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>;
733 template<typename _Tp, typename... _Types>
734 constexpr inline _Tp& get(variant<_Types...>& __v)
736 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
737 "T should occur for exactly once in alternatives");
738 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
739 return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
742 template<typename _Tp, typename... _Types>
743 constexpr inline _Tp&& get(variant<_Types...>&& __v)
745 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
746 "T should occur for exactly once in alternatives");
747 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
748 return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
752 template<typename _Tp, typename... _Types>
753 constexpr inline const _Tp& get(const variant<_Types...>& __v)
755 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
756 "T should occur for exactly once in alternatives");
757 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
758 return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
761 template<typename _Tp, typename... _Types>
762 constexpr inline const _Tp&& get(const variant<_Types...>&& __v)
764 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
765 "T should occur for exactly once in alternatives");
766 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
767 return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
771 template<size_t _Np, typename... _Types>
773 add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
774 get_if(variant<_Types...>* __ptr) noexcept
776 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
777 static_assert(_Np < sizeof...(_Types),
778 "The index should be in [0, number of alternatives)");
779 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void");
780 if (__ptr && __ptr->index() == _Np)
781 return &__detail::__variant::__get<_Np>(*__ptr);
785 template<size_t _Np, typename... _Types>
787 add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>>
788 get_if(const variant<_Types...>* __ptr) noexcept
790 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
791 static_assert(_Np < sizeof...(_Types),
792 "The index should be in [0, number of alternatives)");
793 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void");
794 if (__ptr && __ptr->index() == _Np)
795 return &__detail::__variant::__get<_Np>(*__ptr);
799 template<typename _Tp, typename... _Types>
800 constexpr inline add_pointer_t<_Tp>
801 get_if(variant<_Types...>* __ptr) noexcept
803 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
804 "T should occur for exactly once in alternatives");
805 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
806 return get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(__ptr);
809 template<typename _Tp, typename... _Types>
810 constexpr inline add_pointer_t<const _Tp>
811 get_if(const variant<_Types...>* __ptr)
814 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
815 "T should occur for exactly once in alternatives");
816 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
817 return get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(__ptr);
820 struct monostate { };
822 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
823 template<typename... _Types> \
824 constexpr bool operator __OP(const variant<_Types...>& __lhs, \
825 const variant<_Types...>& __rhs) \
827 return __lhs._M_##__NAME(__rhs, std::index_sequence_for<_Types...>{}); \
830 constexpr bool operator __OP(monostate, monostate) noexcept \
833 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
834 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
835 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
836 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
837 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
838 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
840 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
842 template<typename _Visitor, typename... _Variants>
843 constexpr decltype(auto) visit(_Visitor&&, _Variants&&...);
845 template<typename... _Types>
846 inline enable_if_t<(is_move_constructible_v<_Types> && ...)
847 && (is_swappable_v<_Types> && ...)>
848 swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs)
849 noexcept(noexcept(__lhs.swap(__rhs)))
850 { __lhs.swap(__rhs); }
852 template<typename... _Types>
853 enable_if_t<!((is_move_constructible_v<_Types> && ...)
854 && (is_swappable_v<_Types> && ...))>
855 swap(variant<_Types...>&, variant<_Types...>&) = delete;
857 class bad_variant_access : public exception
860 bad_variant_access() noexcept : _M_reason("Unknown reason") { }
861 const char* what() const noexcept override
862 { return _M_reason; }
865 bad_variant_access(const char* __reason) : _M_reason(__reason) { }
867 const char* _M_reason;
869 friend void __throw_bad_variant_access(const char* __what);
873 __throw_bad_variant_access(const char* __what)
874 { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); }
876 template<typename... _Types>
878 : private __detail::__variant::_Variant_base<_Types...>,
879 private _Enable_default_constructor<
880 is_default_constructible_v<
881 variant_alternative_t<0, variant<_Types...>>>, variant<_Types...>>,
882 private _Enable_copy_move<
883 (is_copy_constructible_v<_Types> && ...),
884 (is_copy_constructible_v<_Types> && ...)
885 && (is_move_constructible_v<_Types> && ...)
886 && (is_copy_assignable_v<_Types> && ...),
887 (is_move_constructible_v<_Types> && ...),
888 (is_move_constructible_v<_Types> && ...)
889 && (is_move_assignable_v<_Types> && ...),
893 static_assert(sizeof...(_Types) > 0,
894 "variant must have at least one alternative");
895 static_assert(!(std::is_reference_v<_Types> || ...),
896 "variant must have no reference alternative");
897 static_assert(!(std::is_void_v<_Types> || ...),
898 "variant must have no void alternative");
900 using _Base = __detail::__variant::_Variant_base<_Types...>;
901 using _Default_ctor_enabler =
902 _Enable_default_constructor<
903 is_default_constructible_v<
904 variant_alternative_t<0, variant<_Types...>>>, variant<_Types...>>;
906 template<typename _Tp>
907 static constexpr bool
908 __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>;
910 template<typename _Tp>
911 static constexpr size_t __accepted_index =
912 __detail::__variant::__accepted_index<_Tp&&, variant>::value;
914 template<size_t _Np, bool = _Np < sizeof...(_Types)>
915 struct __to_type_impl;
918 struct __to_type_impl<_Np, true>
919 { using type = variant_alternative_t<_Np, variant>; };
922 using __to_type = typename __to_type_impl<_Np>::type;
924 template<typename _Tp>
925 using __accepted_type = __to_type<__accepted_index<_Tp>>;
927 template<typename _Tp>
928 static constexpr size_t __index_of =
929 __detail::__variant::__index_of_v<_Tp, _Types...>;
933 noexcept(is_nothrow_default_constructible_v<__to_type<0>>) = default;
934 variant(const variant&) = default;
936 noexcept((is_nothrow_move_constructible_v<_Types> && ...)) = default;
938 template<typename _Tp,
939 typename = enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
940 && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>
941 && !is_same_v<decay_t<_Tp>, variant>>>
944 noexcept(is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
945 : variant(in_place_index<__accepted_index<_Tp&&>>, std::forward<_Tp>(__t))
946 { __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this)); }
948 template<typename _Tp, typename... _Args,
949 typename = enable_if_t<__exactly_once<_Tp>
950 && is_constructible_v<_Tp, _Args&&...>>>
952 variant(in_place_type_t<_Tp>, _Args&&... __args)
953 : variant(in_place_index<__index_of<_Tp>>, std::forward<_Args>(__args)...)
954 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
956 template<typename _Tp, typename _Up, typename... _Args,
957 typename = enable_if_t<__exactly_once<_Tp>
958 && is_constructible_v<
959 _Tp, initializer_list<_Up>&, _Args&&...>>>
961 variant(in_place_type_t<_Tp>, initializer_list<_Up> __il,
963 : variant(in_place_index<__index_of<_Tp>>, __il,
964 std::forward<_Args>(__args)...)
965 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
967 template<size_t _Np, typename... _Args,
968 typename = enable_if_t<
969 is_constructible_v<__to_type<_Np>, _Args&&...>>>
971 variant(in_place_index_t<_Np>, _Args&&... __args)
972 : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...),
973 _Default_ctor_enabler(_Enable_default_constructor_tag{})
974 { __glibcxx_assert(index() == _Np); }
976 template<size_t _Np, typename _Up, typename... _Args,
977 typename = enable_if_t<is_constructible_v<__to_type<_Np>,
978 initializer_list<_Up>&, _Args&&...>>>
980 variant(in_place_index_t<_Np>, initializer_list<_Up> __il,
982 : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...),
983 _Default_ctor_enabler(_Enable_default_constructor_tag{})
984 { __glibcxx_assert(index() == _Np); }
986 ~variant() = default;
988 variant& operator=(const variant&) = default;
989 variant& operator=(variant&&)
990 noexcept((is_nothrow_move_constructible_v<_Types> && ...)
991 && (is_nothrow_move_assignable_v<_Types> && ...)) = default;
993 template<typename _Tp>
994 enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
995 && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>
996 && is_assignable_v<__accepted_type<_Tp&&>&, _Tp&&>
997 && !is_same_v<decay_t<_Tp>, variant>, variant&>
998 operator=(_Tp&& __rhs)
999 noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp&&>
1000 && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
1002 constexpr auto __index = __accepted_index<_Tp&&>;
1003 if (index() == __index)
1004 std::get<__index>(*this) = std::forward<_Tp>(__rhs);
1006 this->emplace<__index>(std::forward<_Tp>(__rhs));
1007 __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this));
1011 template<typename _Tp, typename... _Args>
1012 enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>,
1014 emplace(_Args&&... __args)
1017 this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...);
1018 __glibcxx_assert(holds_alternative<_Tp>(*this));
1022 template<typename _Tp, typename _Up, typename... _Args>
1023 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>
1024 && __exactly_once<_Tp>,
1026 emplace(initializer_list<_Up> __il, _Args&&... __args)
1029 this->emplace<__index_of<_Tp>>(__il,
1030 std::forward<_Args>(__args)...);
1031 __glibcxx_assert(holds_alternative<_Tp>(*this));
1035 template<size_t _Np, typename... _Args>
1036 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1038 variant_alternative_t<_Np, variant>&>
1039 emplace(_Args&&... __args)
1041 static_assert(_Np < sizeof...(_Types),
1042 "The index should be in [0, number of alternatives)");
1046 ::new (this) variant(in_place_index<_Np>,
1047 std::forward<_Args>(__args)...);
1051 this->_M_index = variant_npos;
1052 __throw_exception_again;
1054 __glibcxx_assert(index() == _Np);
1055 return std::get<_Np>(*this);
1058 template<size_t _Np, typename _Up, typename... _Args>
1059 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1060 initializer_list<_Up>&, _Args...>,
1061 variant_alternative_t<_Np, variant>&>
1062 emplace(initializer_list<_Up> __il, _Args&&... __args)
1064 static_assert(_Np < sizeof...(_Types),
1065 "The index should be in [0, number of alternatives)");
1069 ::new (this) variant(in_place_index<_Np>, __il,
1070 std::forward<_Args>(__args)...);
1074 this->_M_index = variant_npos;
1075 __throw_exception_again;
1077 __glibcxx_assert(index() == _Np);
1078 return std::get<_Np>(*this);
1081 constexpr bool valueless_by_exception() const noexcept
1082 { return !this->_M_valid(); }
1084 constexpr size_t index() const noexcept
1086 if (this->_M_index ==
1087 typename _Base::_Storage::__index_type(variant_npos))
1088 return variant_npos;
1089 return this->_M_index;
1093 swap(variant& __rhs)
1094 noexcept((__is_nothrow_swappable<_Types>::value && ...)
1095 && is_nothrow_move_constructible_v<variant>)
1097 if (this->index() == __rhs.index())
1099 if (this->_M_valid())
1101 static constexpr void (*_S_vtable[])(void*, void*) =
1102 { &__detail::__variant::__erased_swap<_Types&, _Types&>... };
1103 _S_vtable[__rhs._M_index](this->_M_storage(),
1104 __rhs._M_storage());
1107 else if (!this->_M_valid())
1109 this->_M_destructive_move(std::move(__rhs));
1112 else if (!__rhs._M_valid())
1114 __rhs._M_destructive_move(std::move(*this));
1119 auto __tmp = std::move(__rhs);
1120 __rhs._M_destructive_move(std::move(*this));
1121 this->_M_destructive_move(std::move(__tmp));
1126 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
1127 template<size_t... __indices> \
1128 static constexpr bool \
1129 (*_S_erased_##__NAME[])(const variant&, const variant&) = \
1130 { &__detail::__variant::__erased_##__NAME< \
1131 const variant&, __indices>... }; \
1132 template<size_t... __indices> \
1133 constexpr inline bool \
1134 _M_##__NAME(const variant& __rhs, \
1135 std::index_sequence<__indices...>) const \
1137 auto __lhs_index = this->index(); \
1138 auto __rhs_index = __rhs.index(); \
1139 if (__lhs_index != __rhs_index || valueless_by_exception()) \
1140 /* Modulo addition. */ \
1141 return __lhs_index + 1 __OP __rhs_index + 1; \
1142 return _S_erased_##__NAME<__indices...>[__lhs_index](*this, __rhs); \
1145 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
1146 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
1147 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
1148 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
1149 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
1150 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
1152 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1154 template<size_t _Np, typename _Vp>
1155 friend constexpr decltype(auto) __detail::__variant::
1156 #if _GLIBCXX_INLINE_VERSION
1157 __7:: // Required due to PR c++/59256
1161 template<typename _Vp>
1162 friend void* __detail::__variant::
1163 #if _GLIBCXX_INLINE_VERSION
1164 __7:: // Required due to PR c++/59256
1166 __get_storage(_Vp&& __v);
1168 #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \
1169 template<typename... _Tp> \
1170 friend constexpr bool \
1171 operator __OP(const variant<_Tp...>& __lhs, \
1172 const variant<_Tp...>& __rhs);
1174 _VARIANT_RELATION_FUNCTION_TEMPLATE(<)
1175 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=)
1176 _VARIANT_RELATION_FUNCTION_TEMPLATE(==)
1177 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=)
1178 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=)
1179 _VARIANT_RELATION_FUNCTION_TEMPLATE(>)
1181 #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1184 template<size_t _Np, typename... _Types>
1185 constexpr variant_alternative_t<_Np, variant<_Types...>>&
1186 get(variant<_Types...>& __v)
1188 static_assert(_Np < sizeof...(_Types),
1189 "The index should be in [0, number of alternatives)");
1190 if (__v.index() != _Np)
1191 __throw_bad_variant_access("Unexpected index");
1192 return __detail::__variant::__get<_Np>(__v);
1195 template<size_t _Np, typename... _Types>
1196 constexpr variant_alternative_t<_Np, variant<_Types...>>&&
1197 get(variant<_Types...>&& __v)
1199 static_assert(_Np < sizeof...(_Types),
1200 "The index should be in [0, number of alternatives)");
1201 if (__v.index() != _Np)
1202 __throw_bad_variant_access("Unexpected index");
1203 return __detail::__variant::__get<_Np>(std::move(__v));
1206 template<size_t _Np, typename... _Types>
1207 constexpr const variant_alternative_t<_Np, variant<_Types...>>&
1208 get(const variant<_Types...>& __v)
1210 static_assert(_Np < sizeof...(_Types),
1211 "The index should be in [0, number of alternatives)");
1212 if (__v.index() != _Np)
1213 __throw_bad_variant_access("Unexpected index");
1214 return __detail::__variant::__get<_Np>(__v);
1217 template<size_t _Np, typename... _Types>
1218 constexpr const variant_alternative_t<_Np, variant<_Types...>>&&
1219 get(const variant<_Types...>&& __v)
1221 static_assert(_Np < sizeof...(_Types),
1222 "The index should be in [0, number of alternatives)");
1223 if (__v.index() != _Np)
1224 __throw_bad_variant_access("Unexpected index");
1225 return __detail::__variant::__get<_Np>(std::move(__v));
1228 template<typename _Visitor, typename... _Variants>
1229 constexpr decltype(auto)
1230 visit(_Visitor&& __visitor, _Variants&&... __variants)
1232 if ((__variants.valueless_by_exception() || ...))
1233 __throw_bad_variant_access("Unexpected index");
1235 using _Result_type =
1236 decltype(std::forward<_Visitor>(__visitor)(
1237 get<0>(std::forward<_Variants>(__variants))...));
1239 constexpr auto& __vtable = __detail::__variant::__gen_vtable<
1240 _Result_type, _Visitor&&, _Variants&&...>::_S_vtable;
1242 auto __func_ptr = __vtable._M_access(__variants.index()...);
1243 return (*__func_ptr)(std::forward<_Visitor>(__visitor),
1244 std::forward<_Variants>(__variants)...);
1247 template<bool, typename... _Types>
1248 struct __variant_hash_call_base_impl
1251 operator()(const variant<_Types...>& __t) const
1252 noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...))
1254 if (!__t.valueless_by_exception())
1256 namespace __edv = __detail::__variant;
1257 static constexpr size_t (*_S_vtable[])(void*) =
1258 { &__edv::__erased_hash<const _Types&>... };
1259 return hash<size_t>{}(__t.index())
1260 + _S_vtable[__t.index()](__edv::__get_storage(__t));
1262 return hash<size_t>{}(__t.index());
1266 template<typename... _Types>
1267 struct __variant_hash_call_base_impl<false, _Types...> {};
1269 template<typename... _Types>
1270 using __variant_hash_call_base =
1271 __variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>::
1272 __enable_hash_call &&...), _Types...>;
1274 template<typename... _Types>
1275 struct hash<variant<_Types...>>
1276 : private __detail::__variant::_Variant_hash_base<
1277 variant<_Types...>, std::index_sequence_for<_Types...>>,
1278 public __variant_hash_call_base<_Types...>
1280 using result_type = size_t;
1281 using argument_type = variant<_Types...>;
1285 struct hash<monostate>
1287 using result_type = size_t;
1288 using argument_type = monostate;
1291 operator()(const monostate& __t) const noexcept
1293 constexpr size_t __magic_monostate_hash = -7777;
1294 return __magic_monostate_hash;
1298 _GLIBCXX_END_NAMESPACE_VERSION
1303 #endif // _GLIBCXX_VARIANT