1 // <variant> -*- C++ -*-
3 // Copyright (C) 2016 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/uses_allocator.h>
44 #include <bits/functional_hash.h>
46 namespace std _GLIBCXX_VISIBILITY(default)
48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
50 template<typename... _Types> class tuple;
51 template<typename... _Types> class variant;
52 template <typename> struct hash;
54 template<typename _Variant>
57 template<typename _Variant>
58 struct variant_size<const _Variant> : variant_size<_Variant> {};
60 template<typename _Variant>
61 struct variant_size<volatile _Variant> : variant_size<_Variant> {};
63 template<typename _Variant>
64 struct variant_size<const volatile _Variant> : variant_size<_Variant> {};
66 template<typename... _Types>
67 struct variant_size<variant<_Types...>>
68 : std::integral_constant<size_t, sizeof...(_Types)> {};
70 template<typename _Variant>
71 constexpr size_t variant_size_v = variant_size<_Variant>::value;
73 template<size_t _Np, typename _Variant>
74 struct variant_alternative;
76 template<size_t _Np, typename _First, typename... _Rest>
77 struct variant_alternative<_Np, variant<_First, _Rest...>>
78 : variant_alternative<_Np-1, variant<_Rest...>> {};
80 template<typename _First, typename... _Rest>
81 struct variant_alternative<0, variant<_First, _Rest...>>
82 { using type = _First; };
84 template<size_t _Np, typename _Variant>
85 using variant_alternative_t =
86 typename variant_alternative<_Np, _Variant>::type;
88 template<size_t _Np, typename _Variant>
89 struct variant_alternative<_Np, const _Variant>
90 { using type = add_const_t<variant_alternative_t<_Np, _Variant>>; };
92 template<size_t _Np, typename _Variant>
93 struct variant_alternative<_Np, volatile _Variant>
94 { using type = add_volatile_t<variant_alternative_t<_Np, _Variant>>; };
96 template<size_t _Np, typename _Variant>
97 struct variant_alternative<_Np, const volatile _Variant>
98 { using type = add_cv_t<variant_alternative_t<_Np, _Variant>>; };
100 constexpr size_t variant_npos = -1;
102 _GLIBCXX_END_NAMESPACE_VERSION
108 _GLIBCXX_BEGIN_NAMESPACE_VERSION
109 // Returns the first apparence of _Tp in _Types.
110 // Returns sizeof...(_Types) if _Tp is not in _Types.
111 template<typename _Tp, typename... _Types>
112 struct __index_of : std::integral_constant<size_t, 0> {};
114 template<typename _Tp, typename... _Types>
115 constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value;
117 template<typename _Tp, typename _First, typename... _Rest>
118 struct __index_of<_Tp, _First, _Rest...> :
119 std::integral_constant<size_t, is_same_v<_Tp, _First>
120 ? 0 : __index_of_v<_Tp, _Rest...> + 1> {};
122 // Extract _From's qualifiers and references and apply it to _To.
123 // __reserved_type_map<const int&, char> is const char&.
124 template<typename _From, typename _To>
125 struct __reserved_type_map_impl
126 { using type = _To; };
128 template<typename _From, typename _To>
129 using __reserved_type_map =
130 typename __reserved_type_map_impl<_From, _To>::type;
132 template<typename _From, typename _To>
133 struct __reserved_type_map_impl<_From&, _To>
134 { using type = add_lvalue_reference_t<__reserved_type_map<_From, _To>>; };
136 template<typename _From, typename _To>
137 struct __reserved_type_map_impl<_From&&, _To>
138 { using type = add_rvalue_reference_t<__reserved_type_map<_From, _To>>; };
140 template<typename _From, typename _To>
141 struct __reserved_type_map_impl<const _From, _To>
142 { using type = add_const_t<__reserved_type_map<_From, _To>>; };
144 template<typename _From, typename _To>
145 struct __reserved_type_map_impl<volatile _From, _To>
146 { using type = add_volatile_t<__reserved_type_map<_From, _To>>; };
148 template<typename _From, typename _To>
149 struct __reserved_type_map_impl<const volatile _From, _To>
150 { using type = add_cv_t<__reserved_type_map<_From, _To>>; };
152 // This abstraction might be useful for future features,
153 // e.g. boost::recursive_wrapper.
154 template<typename _Alternative>
155 using __storage = _Alternative;
157 template<typename _Type, bool __is_literal = std::is_literal_type_v<_Type>>
158 struct _Uninitialized;
160 template<typename _Type>
161 struct _Uninitialized<_Type, true>
163 constexpr _Uninitialized() = default;
165 template<typename... _Args>
166 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
167 : _M_storage(std::forward<_Args>(__args)...)
173 template<typename _Type>
174 struct _Uninitialized<_Type, false>
176 constexpr _Uninitialized() = default;
178 template<typename... _Args>
179 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
180 { ::new (&_M_storage) _Type(std::forward<_Args>(__args)...); }
182 typename std::aligned_storage<sizeof(_Type), alignof(_Type)>::type
186 // Given a qualified storage type, return the desired reference.
187 // For example, variant<int>&& stores the int as __storage<int>, and
188 // _Qualified_storage will be __storage<int>&&.
189 template<typename _Qualified_storage>
191 __get_alternative(void* __ptr)
193 using _Storage = decay_t<_Qualified_storage>;
194 return __reserved_type_map<_Qualified_storage, _Storage>(
195 *static_cast<_Storage*>(__ptr));
198 // Various functions as "vtable" entries, where those vtables are used by
199 // polymorphic operations.
200 template<typename _Lhs, typename _Rhs>
202 __erased_ctor(void* __lhs, void* __rhs)
203 { ::new (__lhs) decay_t<_Lhs>(__get_alternative<_Rhs>(__rhs)); }
205 template<typename _Alloc, typename _Lhs, typename _Rhs>
207 __erased_use_alloc_ctor(const _Alloc& __a, void* __lhs, void* __rhs)
209 __uses_allocator_construct(__a, static_cast<decay_t<_Lhs>*>(__lhs),
210 __get_alternative<_Rhs>(__rhs));
213 // TODO: Find a potential chance to reuse this accross the project.
214 template<typename _Tp>
216 __erased_dtor(void* __ptr)
218 using _Storage = decay_t<_Tp>;
219 static_cast<_Storage*>(__ptr)->~_Storage();
222 template<typename _Lhs, typename _Rhs>
224 __erased_assign(void* __lhs, void* __rhs)
225 { __get_alternative<_Lhs>(__lhs) = __get_alternative<_Rhs>(__rhs); }
227 template<typename _Lhs, typename _Rhs>
229 __erased_swap(void* __lhs, void* __rhs)
232 swap(__get_alternative<_Lhs>(__lhs), __get_alternative<_Rhs>(__rhs));
235 template<typename _Lhs, typename _Rhs>
237 __erased_equal_to(void* __lhs, void* __rhs)
238 { return __get_alternative<_Lhs>(__lhs) == __get_alternative<_Rhs>(__rhs); }
240 template<typename _Lhs, typename _Rhs>
242 __erased_less_than(void* __lhs, void* __rhs)
243 { return __get_alternative<_Lhs>(__lhs) < __get_alternative<_Rhs>(__rhs); }
245 template<typename _Tp>
247 __erased_hash(void* __t)
248 { return std::hash<decay_t<_Tp>>{}(__get_alternative<_Tp>(__t)); }
250 template<typename... _Types>
251 struct _Variant_base;
253 template<typename... _Types>
254 struct _Variant_storage
255 { constexpr _Variant_storage() = default; };
257 // Use recursive unions to implement a trivially destructible variant.
258 template<typename _First, typename... _Rest>
259 struct _Variant_storage<_First, _Rest...>
261 constexpr _Variant_storage() = default;
263 template<size_t _Np, typename... _Args>
264 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
265 : _M_union(in_place_index<_Np>, std::forward<_Args>(__args)...)
268 ~_Variant_storage() = default;
273 return const_cast<void*>(
274 static_cast<const void*>(std::addressof(_M_union._M_first._M_storage)));
279 constexpr _Union() {};
281 template<typename... _Args>
282 constexpr _Union(in_place_index_t<0>, _Args&&... __args)
283 : _M_first(in_place_index<0>, std::forward<_Args>(__args)...)
286 template<size_t _Np, typename... _Args,
287 typename = enable_if_t<0 < _Np && _Np < sizeof...(_Rest) + 1>>
288 constexpr _Union(in_place_index_t<_Np>, _Args&&... __args)
289 : _M_rest(in_place_index<_Np - 1>, std::forward<_Args>(__args)...)
292 _Uninitialized<__storage<_First>> _M_first;
293 _Variant_storage<_Rest...> _M_rest;
297 template<typename _Derived, bool __is_trivially_destructible>
301 { static_cast<_Derived*>(this)->_M_destroy(); }
304 template<typename _Derived>
305 struct _Dtor_mixin<_Derived, true>
307 ~_Dtor_mixin() = default;
310 // Helps SFINAE on special member functions. Otherwise it can live in variant
312 template<typename... _Types>
313 struct _Variant_base :
314 _Variant_storage<_Types...>,
315 _Dtor_mixin<_Variant_base<_Types...>,
316 __and_<std::is_trivially_destructible<_Types>...>::value>
318 using _Storage = _Variant_storage<_Types...>;
322 noexcept(is_nothrow_default_constructible_v<
323 variant_alternative_t<0, variant<_Types...>>>)
324 : _Variant_base(in_place_index<0>) { }
326 _Variant_base(const _Variant_base& __rhs)
327 : _Storage(), _M_index(__rhs._M_index)
329 if (__rhs._M_valid())
331 static constexpr void (*_S_vtable[])(void*, void*) =
332 { &__erased_ctor<__storage<_Types>&,
333 const __storage<_Types>&>... };
334 _S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
338 _Variant_base(_Variant_base&& __rhs)
339 noexcept(__and_<is_nothrow_move_constructible<_Types>...>::value)
340 : _Storage(), _M_index(__rhs._M_index)
342 if (__rhs._M_valid())
344 static constexpr void (*_S_vtable[])(void*, void*) =
345 { &__erased_ctor<__storage<_Types>&, __storage<_Types>&&>... };
346 _S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
350 template<size_t _Np, typename... _Args>
352 _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
353 : _Storage(__i, std::forward<_Args>(__args)...), _M_index(_Np)
356 template<typename _Alloc>
357 _Variant_base(const _Alloc& __a, const _Variant_base& __rhs)
358 : _Storage(), _M_index(__rhs._M_index)
360 if (__rhs._M_valid())
362 static constexpr void
363 (*_S_vtable[])(const _Alloc&, void*, void*) =
364 { &__erased_use_alloc_ctor<_Alloc, __storage<_Types>&,
365 const __storage<_Types>&>... };
366 _S_vtable[__rhs._M_index](__a, _M_storage(), __rhs._M_storage());
370 template<typename _Alloc>
371 _Variant_base(const _Alloc& __a, _Variant_base&& __rhs)
372 : _Storage(), _M_index(__rhs._M_index)
374 if (__rhs._M_valid())
376 static constexpr void
377 (*_S_vtable[])(const _Alloc&, void*, void*) =
378 { &__erased_use_alloc_ctor<_Alloc, __storage<_Types>&,
379 __storage<_Types>&&>... };
380 _S_vtable[__rhs._M_index](__a, _M_storage(), __rhs._M_storage());
384 template<typename _Alloc, size_t _Np, typename... _Args>
386 _Variant_base(const _Alloc& __a, in_place_index_t<_Np>,
388 : _Storage(), _M_index(_Np)
391 __storage<variant_alternative_t<_Np, variant<_Types...>>>;
392 __uses_allocator_construct(__a, static_cast<_Storage*>(_M_storage()),
393 std::forward<_Args>(__args)...);
394 __glibcxx_assert(_M_index == _Np);
398 operator=(const _Variant_base& __rhs)
400 if (_M_index == __rhs._M_index)
402 if (__rhs._M_valid())
404 static constexpr void (*_S_vtable[])(void*, void*) =
405 { &__erased_assign<__storage<_Types>&,
406 const __storage<_Types>&>... };
407 _S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
412 _Variant_base __tmp(__rhs);
413 this->~_Variant_base();
416 ::new (this) _Variant_base(std::move(__tmp));
420 _M_index = variant_npos;
421 __throw_exception_again;
424 __glibcxx_assert(_M_index == __rhs._M_index);
429 operator=(_Variant_base&& __rhs)
430 noexcept(__and_<is_nothrow_move_constructible<_Types>...,
431 is_nothrow_move_assignable<_Types>...>::value)
433 if (_M_index == __rhs._M_index)
435 if (__rhs._M_valid())
437 static constexpr void (*_S_vtable[])(void*, void*) =
438 { &__erased_assign<__storage<_Types>&,
439 __storage<_Types>&&>... };
440 _S_vtable[__rhs._M_index](_M_storage(), __rhs._M_storage());
445 this->~_Variant_base();
448 ::new (this) _Variant_base(std::move(__rhs));
452 _M_index = variant_npos;
453 __throw_exception_again;
463 static constexpr void (*_S_vtable[])(void*) =
464 { &__erased_dtor<__storage<_Types>&>... };
465 _S_vtable[this->_M_index](_M_storage());
471 { return _Storage::_M_storage(); }
474 _M_valid() const noexcept
475 { return _M_index != variant_npos; }
480 // For how many times does _Tp appear in _Tuple?
481 template<typename _Tp, typename _Tuple>
482 struct __tuple_count;
484 template<typename _Tp, typename _Tuple>
485 constexpr size_t __tuple_count_v = __tuple_count<_Tp, _Tuple>::value;
487 template<typename _Tp, typename... _Types>
488 struct __tuple_count<_Tp, tuple<_Types...>>
489 : integral_constant<size_t, 0> { };
491 template<typename _Tp, typename _First, typename... _Rest>
492 struct __tuple_count<_Tp, tuple<_First, _Rest...>>
495 __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { };
497 // TODO: Reuse this in <tuple> ?
498 template<typename _Tp, typename... _Types>
499 constexpr bool __exactly_once = __tuple_count_v<_Tp, tuple<_Types...>> == 1;
501 // Takes _Types and create an overloaded _S_fun for each type.
502 // If a type appears more than once in _Types, create only one overload.
503 template<typename... _Types>
504 struct __overload_set
505 { static void _S_fun(); };
507 template<typename _First, typename... _Rest>
508 struct __overload_set<_First, _Rest...> : __overload_set<_Rest...>
510 using __overload_set<_Rest...>::_S_fun;
511 static integral_constant<size_t, sizeof...(_Rest)> _S_fun(_First);
514 template<typename... _Rest>
515 struct __overload_set<void, _Rest...> : __overload_set<_Rest...>
517 using __overload_set<_Rest...>::_S_fun;
520 // Helper for variant(_Tp&&) and variant::operator=(_Tp&&).
521 // __accepted_index maps the arbitrary _Tp to an alternative type in _Variant.
522 template<typename _Tp, typename _Variant, typename = void>
523 struct __accepted_index
524 { static constexpr size_t value = variant_npos; };
526 template<typename _Tp, typename... _Types>
527 struct __accepted_index<
528 _Tp, variant<_Types...>,
529 decltype(__overload_set<_Types...>::_S_fun(std::declval<_Tp>()),
530 std::declval<void>())>
532 static constexpr size_t value = sizeof...(_Types) - 1
533 - decltype(__overload_set<_Types...>::
534 _S_fun(std::declval<_Tp>()))::value;
537 // Returns the raw storage for __v.
538 template<typename _Variant>
539 void* __get_storage(_Variant&& __v)
540 { return __v._M_storage(); }
542 // Returns the reference to the desired alternative.
543 // It is as unsafe as a reinterpret_cast.
544 template<typename _Tp, typename _Variant>
545 decltype(auto) __access(_Variant&& __v)
547 return __get_alternative<__reserved_type_map<_Variant&&, __storage<_Tp>>>(
548 __get_storage(std::forward<_Variant>(__v)));
551 // A helper used to create variadic number of _To types.
552 template<typename _From, typename _To>
553 using _To_type = _To;
555 // Call the actual visitor.
556 // _Args are qualified storage types.
557 template<typename _Visitor, typename... _Args>
559 __visit_invoke(_Visitor&& __visitor, _To_type<_Args, void*>... __ptrs)
561 return std::forward<_Visitor>(__visitor)(
562 __get_alternative<_Args>(__ptrs)...);
565 // Used for storing multi-dimensional vtable.
566 template<typename _Tp, size_t... _Dimensions>
576 template<typename _Tp, size_t __first, size_t... __rest>
577 struct _Multi_array<_Tp, __first, __rest...>
579 template<typename... _Args>
581 _M_access(size_t __first_index, _Args... __rest_indices) const
582 { return _M_arr[__first_index]._M_access(__rest_indices...); }
584 _Multi_array<_Tp, __rest...> _M_arr[__first];
587 // Creates a multi-dimensional vtable recursively.
588 // _Variant_tuple is initially the input from visit(), and gets gradually
590 // _Arg_tuple is enumerated alternative sequence, represented by a
591 // qualified storage.
594 // visit([](auto, auto){},
595 // variant<int, char>(),
596 // variant<float, double, long double>())
597 // will trigger instantiations of:
598 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*), 2, 3>,
599 // tuple<variant<int, char>,
600 // variant<float, double, long double>>,
602 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*), 3>,
603 // tuple<variant<float, double, long double>>,
605 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
607 // tuple<int, float>>
608 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
610 // tuple<int, double>>
611 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
613 // tuple<int, long double>>
614 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*), 3>,
615 // tuple<variant<float, double, long double>>,
617 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
619 // tuple<char, float>>
620 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
622 // tuple<char, double>>
623 // __gen_vtable_impl<_Multi_array<void(*)(void*, void*)>,
625 // tuple<char, long double>>
626 // The returned multi-dimensional vtable can be fast accessed by the visitor
627 // using index calculation.
628 template<typename _Array_type, typename _Variant_tuple, typename _Arg_tuple>
629 struct __gen_vtable_impl;
631 template<typename _Array_type, typename _First, typename... _Rest,
633 struct __gen_vtable_impl<_Array_type, tuple<_First, _Rest...>,
636 static constexpr _Array_type
639 _Array_type __vtable{};
641 __vtable, make_index_sequence<variant_size_v<decay_t<_First>>>());
645 template<size_t... __indices>
646 static constexpr void
647 _S_apply_all_alts(_Array_type& __vtable, index_sequence<__indices...>)
648 { (_S_apply_single_alt<__indices>(__vtable._M_arr[__indices]), ...); }
650 template<size_t __index>
651 static constexpr void
652 _S_apply_single_alt(auto& __element)
654 using _Alternative = variant_alternative_t<__index, decay_t<_First>>;
655 using _Qualified_storage = __reserved_type_map<
656 _First, __storage<_Alternative>>;
657 __element = __gen_vtable_impl<
658 decay_t<decltype(__element)>, tuple<_Rest...>,
659 tuple<_Args..., _Qualified_storage>>::_S_apply();
663 template<typename _Result_type, typename _Visitor, typename... _Args>
664 struct __gen_vtable_impl<
665 _Multi_array<_Result_type (*)(_Visitor, _To_type<_Args, void*>...)>,
666 tuple<>, tuple<_Args...>>
669 _Multi_array<_Result_type (*)(_Visitor&&, _To_type<_Args, void*>...)>;
671 static constexpr auto
673 { return _Array_type{&__visit_invoke<_Visitor, _Args...>}; }
676 template<typename _Result_type, typename _Visitor, typename... _Variants>
680 _Result_type (*)(_Visitor&&, _To_type<_Variants, void*>...);
682 _Multi_array<_Func_ptr, variant_size_v<decay_t<_Variants>>...>;
684 static constexpr _Array_type
687 return __gen_vtable_impl<
688 _Array_type, tuple<_Variants...>, tuple<>>::_S_apply();
692 _GLIBCXX_END_NAMESPACE_VERSION
693 } // namespace __variant
694 } // namespace __detail
696 _GLIBCXX_BEGIN_NAMESPACE_VERSION
698 template<typename _Tp, typename... _Types>
699 inline constexpr bool holds_alternative(const variant<_Types...>& __v)
702 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
703 "T should occur for exactly once in alternatives");
704 return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>;
707 template<size_t _Np, typename... _Types>
708 variant_alternative_t<_Np, variant<_Types...>>&
709 get(variant<_Types...>&);
711 template<size_t _Np, typename... _Types>
712 variant_alternative_t<_Np, variant<_Types...>>&&
713 get(variant<_Types...>&&);
715 template<size_t _Np, typename... _Types>
716 variant_alternative_t<_Np, variant<_Types...>> const&
717 get(const variant<_Types...>&);
719 template<size_t _Np, typename... _Types>
720 variant_alternative_t<_Np, variant<_Types...>> const&&
721 get(const variant<_Types...>&&);
723 template<typename _Tp, typename... _Types>
724 inline _Tp& get(variant<_Types...>& __v)
726 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
727 "T should occur for exactly once in alternatives");
728 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
729 return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
732 template<typename _Tp, typename... _Types>
733 inline _Tp&& get(variant<_Types...>&& __v)
735 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
736 "T should occur for exactly once in alternatives");
737 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
738 return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
742 template<typename _Tp, typename... _Types>
743 inline const _Tp& get(const 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...>>(__v);
751 template<typename _Tp, typename... _Types>
752 inline const _Tp&& get(const variant<_Types...>&& __v)
754 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
755 "T should occur for exactly once in alternatives");
756 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
757 return get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
761 template<size_t _Np, typename... _Types>
762 inline add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
763 get_if(variant<_Types...>* __ptr) noexcept
765 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
766 static_assert(_Np < sizeof...(_Types),
767 "The index should be in [0, number of alternatives)");
768 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void");
769 if (__ptr && __ptr->index() == _Np)
770 return &__detail::__variant::__access<_Alternative_type>(*__ptr);
774 template<size_t _Np, typename... _Types>
775 inline add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>>
776 get_if(const variant<_Types...>* __ptr) noexcept
778 using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
779 static_assert(_Np < sizeof...(_Types),
780 "The index should be in [0, number of alternatives)");
781 static_assert(!is_void_v<_Alternative_type>, "_Tp should not be void");
782 if (__ptr && __ptr->index() == _Np)
783 return &__detail::__variant::__access<_Alternative_type>(*__ptr);
787 template<typename _Tp, typename... _Types>
788 inline add_pointer_t<_Tp> get_if(variant<_Types...>* __ptr) noexcept
790 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
791 "T should occur for exactly once in alternatives");
792 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
793 return get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(__ptr);
796 template<typename _Tp, typename... _Types>
797 inline add_pointer_t<const _Tp> get_if(const variant<_Types...>* __ptr)
800 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
801 "T should occur for exactly once in alternatives");
802 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
803 return get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(__ptr);
806 template<typename... _Types>
807 bool operator==(const variant<_Types...>& __lhs,
808 const variant<_Types...>& __rhs)
810 if (__lhs.index() != __rhs.index())
813 if (__lhs.valueless_by_exception())
816 using __detail::__variant::__storage;
817 static constexpr bool (*_S_vtable[])(void*, void*) =
818 { &__detail::__variant::__erased_equal_to<
819 const __storage<_Types>&, const __storage<_Types>&>... };
820 return _S_vtable[__lhs.index()](
821 __detail::__variant::__get_storage(__lhs),
822 __detail::__variant::__get_storage(__rhs));
825 template<typename... _Types>
827 operator!=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
828 { return !(__lhs == __rhs); }
830 template<typename... _Types>
832 operator<(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
834 if (__lhs.index() < __rhs.index())
837 if (__lhs.index() > __rhs.index())
840 if (__lhs.valueless_by_exception())
843 using __detail::__variant::__storage;
844 static constexpr bool (*_S_vtable[])(void*, void*) =
845 { &__detail::__variant::__erased_less_than<
846 const __storage<_Types>&,
847 const __storage<_Types>&>... };
848 return _S_vtable[__lhs.index()](
849 __detail::__variant::__get_storage(__lhs),
850 __detail::__variant::__get_storage(__rhs));
853 template<typename... _Types>
855 operator>(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
856 { return __rhs < __lhs; }
858 template<typename... _Types>
860 operator<=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
861 { return !(__lhs > __rhs); }
863 template<typename... _Types>
865 operator>=(const variant<_Types...>& __lhs, const variant<_Types...>& __rhs)
866 { return !(__lhs < __rhs); }
868 template<typename _Visitor, typename... _Variants>
869 decltype(auto) visit(_Visitor&&, _Variants&&...);
871 struct monostate { };
873 constexpr bool operator<(monostate, monostate) noexcept
876 constexpr bool operator>(monostate, monostate) noexcept
879 constexpr bool operator<=(monostate, monostate) noexcept
882 constexpr bool operator>=(monostate, monostate) noexcept
885 constexpr bool operator==(monostate, monostate) noexcept
888 constexpr bool operator!=(monostate, monostate) noexcept
891 template<typename... _Types>
892 inline enable_if_t<__and_<is_move_constructible<_Types>...,
893 is_swappable<_Types>...>::value>
894 swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs)
895 noexcept(noexcept(__lhs.swap(__rhs)))
896 { __lhs.swap(__rhs); }
898 template<typename... _Types>
899 inline enable_if_t<!__and_<is_move_constructible<_Types>...,
900 is_swappable<_Types>...>::value>
901 swap(variant<_Types...>&, variant<_Types...>&) = delete;
903 class bad_variant_access : public exception
906 bad_variant_access() noexcept : _M_reason("Unknown reason") { }
907 const char* what() const noexcept override
908 { return _M_reason; }
911 bad_variant_access(const char* __reason) : _M_reason(__reason) { }
913 const char* _M_reason;
915 friend void __throw_bad_variant_access(const char* __what);
919 __throw_bad_variant_access(const char* __what)
920 { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); }
922 template<typename... _Types>
924 : private __detail::__variant::_Variant_base<_Types...>,
925 private _Enable_default_constructor<
926 is_default_constructible_v<
927 variant_alternative_t<0, variant<_Types...>>>, variant<_Types...>>,
928 private _Enable_copy_move<
929 __and_<is_copy_constructible<_Types>...>::value,
930 __and_<is_copy_constructible<_Types>...,
931 is_move_constructible<_Types>...,
932 is_copy_assignable<_Types>...>::value,
933 __and_<is_move_constructible<_Types>...>::value,
934 __and_<is_move_constructible<_Types>...,
935 is_move_assignable<_Types>...>::value,
939 static_assert(sizeof...(_Types) > 0,
940 "variant must have at least one alternative");
941 static_assert(!(std::is_reference_v<_Types> || ...),
942 "variant must have no reference alternative");
943 static_assert(!(std::is_void_v<_Types> || ...),
944 "variant must have no void alternative");
946 using _Base = __detail::__variant::_Variant_base<_Types...>;
947 using _Default_ctor_enabler =
948 _Enable_default_constructor<
949 is_default_constructible_v<
950 variant_alternative_t<0, variant<_Types...>>>, variant<_Types...>>;
952 template<typename _Tp>
953 static constexpr bool
954 __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>;
956 template<typename _Tp>
957 static constexpr size_t __accepted_index =
958 __detail::__variant::__accepted_index<_Tp&&, variant>::value;
960 template<size_t _Np, bool = _Np < sizeof...(_Types)>
961 struct __to_type_impl;
964 struct __to_type_impl<_Np, true>
965 { using type = variant_alternative_t<_Np, variant>; };
968 using __to_type = typename __to_type_impl<_Np>::type;
970 template<typename _Tp>
971 using __accepted_type = __to_type<__accepted_index<_Tp>>;
973 template<typename _Tp>
974 using __storage = __detail::__variant::__storage<_Tp>;
976 template<typename _Tp>
977 static constexpr size_t __index_of =
978 __detail::__variant::__index_of_v<_Tp, _Types...>;
982 noexcept(is_nothrow_default_constructible_v<__to_type<0>>) = default;
983 variant(const variant&) = default;
986 is_nothrow_move_constructible<_Types>...>::value) = default;
988 template<typename _Tp,
989 typename = enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
990 && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>
991 && !is_same_v<decay_t<_Tp>, variant>>>
994 noexcept(is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
995 : variant(in_place_index<__accepted_index<_Tp&&>>, std::forward<_Tp>(__t))
996 { __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this)); }
998 template<typename _Tp, typename... _Args,
999 typename = enable_if_t<__exactly_once<_Tp>
1000 && is_constructible_v<_Tp, _Args&&...>>>
1002 variant(in_place_type_t<_Tp>, _Args&&... __args)
1003 : variant(in_place_index<__index_of<_Tp>>, std::forward<_Args>(__args)...)
1004 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
1006 template<typename _Tp, typename _Up, typename... _Args,
1007 typename = enable_if_t<__exactly_once<_Tp>
1008 && is_constructible_v<
1009 _Tp, initializer_list<_Up>&, _Args&&...>>>
1011 variant(in_place_type_t<_Tp>, initializer_list<_Up> __il,
1013 : variant(in_place_index<__index_of<_Tp>>, __il,
1014 std::forward<_Args>(__args)...)
1015 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
1017 template<size_t _Np, typename... _Args,
1018 typename = enable_if_t<
1019 is_constructible_v<__to_type<_Np>, _Args&&...>>>
1021 variant(in_place_index_t<_Np>, _Args&&... __args)
1022 : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...),
1023 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1024 { __glibcxx_assert(index() == _Np); }
1026 template<size_t _Np, typename _Up, typename... _Args,
1027 typename = enable_if_t<is_constructible_v<__to_type<_Np>,
1028 initializer_list<_Up>&, _Args&&...>>>
1030 variant(in_place_index_t<_Np>, initializer_list<_Up> __il,
1032 : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...),
1033 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1034 { __glibcxx_assert(index() == _Np); }
1036 template<typename _Alloc,
1037 typename = enable_if_t<
1038 __is_uses_allocator_constructible_v<__to_type<0>, _Alloc>>>
1039 variant(allocator_arg_t, const _Alloc& __a)
1040 : variant(allocator_arg, __a, in_place_index<0>)
1043 template<typename _Alloc,
1044 typename = enable_if_t<__and_<__is_uses_allocator_constructible<
1046 add_lvalue_reference_t<add_const_t<_Types>>>...>::value>>
1047 variant(allocator_arg_t, const _Alloc& __a, const variant& __rhs)
1048 : _Base(__a, __rhs),
1049 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1052 template<typename _Alloc,
1053 typename = enable_if_t<__and_<
1054 __is_uses_allocator_constructible<
1055 _Types, _Alloc, add_rvalue_reference_t<_Types>>...>::value>>
1056 variant(allocator_arg_t, const _Alloc& __a, variant&& __rhs)
1057 : _Base(__a, std::move(__rhs)),
1058 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1061 template<typename _Alloc, typename _Tp,
1062 typename = enable_if_t<
1063 __exactly_once<__accepted_type<_Tp&&>>
1064 && __is_uses_allocator_constructible_v<
1065 __accepted_type<_Tp&&>, _Alloc, _Tp&&>
1066 && !is_same_v<decay_t<_Tp>, variant>, variant&>>
1067 variant(allocator_arg_t, const _Alloc& __a, _Tp&& __t)
1068 : variant(allocator_arg, __a, in_place_index<__accepted_index<_Tp&&>>,
1069 std::forward<_Tp>(__t))
1070 { __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this)); }
1072 template<typename _Alloc, typename _Tp, typename... _Args,
1073 typename = enable_if_t<
1075 && __is_uses_allocator_constructible_v<
1076 _Tp, _Alloc, _Args&&...>>>
1077 variant(allocator_arg_t, const _Alloc& __a, in_place_type_t<_Tp>,
1079 : variant(allocator_arg, __a, in_place_index<__index_of<_Tp>>,
1080 std::forward<_Args>(__args)...)
1081 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
1083 template<typename _Alloc, typename _Tp, typename _Up, typename... _Args,
1084 typename = enable_if_t<
1086 && __is_uses_allocator_constructible_v<
1087 _Tp, _Alloc, initializer_list<_Up>&, _Args&&...>>>
1088 variant(allocator_arg_t, const _Alloc& __a, in_place_type_t<_Tp>,
1089 initializer_list<_Up> __il, _Args&&... __args)
1090 : variant(allocator_arg, __a, in_place_index<__index_of<_Tp>>, __il,
1091 std::forward<_Args>(__args)...)
1092 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
1094 template<typename _Alloc, size_t _Np, typename... _Args,
1095 typename = enable_if_t<
1096 __is_uses_allocator_constructible_v<
1097 __to_type<_Np>, _Alloc, _Args&&...>>>
1098 variant(allocator_arg_t, const _Alloc& __a, in_place_index_t<_Np>,
1100 : _Base(__a, in_place_index<_Np>, std::forward<_Args>(__args)...),
1101 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1102 { __glibcxx_assert(index() == _Np); }
1104 template<typename _Alloc, size_t _Np, typename _Up, typename... _Args,
1105 typename = enable_if_t<
1106 __is_uses_allocator_constructible_v<
1107 __to_type<_Np>, _Alloc, initializer_list<_Up>&, _Args&&...>>>
1108 variant(allocator_arg_t, const _Alloc& __a, in_place_index_t<_Np>,
1109 initializer_list<_Up> __il, _Args&&... __args)
1110 : _Base(__a, in_place_index<_Np>, __il, std::forward<_Args>(__args)...),
1111 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1112 { __glibcxx_assert(index() == _Np); }
1114 ~variant() = default;
1116 variant& operator=(const variant&) = default;
1117 variant& operator=(variant&&)
1118 noexcept(__and_<is_nothrow_move_constructible<_Types>...,
1119 is_nothrow_move_assignable<_Types>...>::value) = default;
1121 template<typename _Tp>
1122 enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
1123 && is_constructible_v<__accepted_type<_Tp&&>, _Tp&&>
1124 && is_assignable_v<__accepted_type<_Tp&&>&, _Tp&&>
1125 && !is_same_v<decay_t<_Tp>, variant>, variant&>
1126 operator=(_Tp&& __rhs)
1127 noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp&&>
1128 && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp&&>)
1130 constexpr auto __index = __accepted_index<_Tp&&>;
1131 if (index() == __index)
1132 std::get<__index>(*this) = std::forward<_Tp>(__rhs);
1134 this->emplace<__index>(std::forward<_Tp>(__rhs));
1135 __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this));
1139 template<typename _Tp, typename... _Args>
1140 void emplace(_Args&&... __args)
1142 static_assert(__exactly_once<_Tp>,
1143 "T should occur for exactly once in alternatives");
1144 this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...);
1145 __glibcxx_assert(holds_alternative<_Tp>(*this));
1148 template<typename _Tp, typename _Up, typename... _Args>
1149 void emplace(initializer_list<_Up> __il, _Args&&... __args)
1151 static_assert(__exactly_once<_Tp>,
1152 "T should occur for exactly once in alternatives");
1153 this->emplace<__index_of<_Tp>>(__il, std::forward<_Args>(__args)...);
1154 __glibcxx_assert(holds_alternative<_Tp>(*this));
1157 template<size_t _Np, typename... _Args>
1158 void emplace(_Args&&... __args)
1160 static_assert(_Np < sizeof...(_Types),
1161 "The index should be in [0, number of alternatives)");
1165 ::new (this) variant(in_place_index<_Np>,
1166 std::forward<_Args>(__args)...);
1170 this->_M_index = variant_npos;
1171 __throw_exception_again;
1173 __glibcxx_assert(index() == _Np);
1176 template<size_t _Np, typename _Up, typename... _Args>
1177 void emplace(initializer_list<_Up> __il, _Args&&... __args)
1179 static_assert(_Np < sizeof...(_Types),
1180 "The index should be in [0, number of alternatives)");
1184 ::new (this) variant(in_place_index<_Np>, __il,
1185 std::forward<_Args>(__args)...);
1189 this->_M_index = variant_npos;
1190 __throw_exception_again;
1192 __glibcxx_assert(index() == _Np);
1195 constexpr bool valueless_by_exception() const noexcept
1196 { return !this->_M_valid(); }
1198 constexpr size_t index() const noexcept
1199 { return this->_M_index; }
1202 swap(variant& __rhs)
1203 noexcept(__and_<__is_nothrow_swappable<_Types>...>::value
1204 && is_nothrow_move_assignable_v<variant>)
1206 if (this->index() == __rhs.index())
1208 if (this->_M_valid())
1210 static constexpr void (*_S_vtable[])(void*, void*) =
1211 { &__detail::__variant::__erased_swap<
1212 __storage<_Types>&, __storage<_Types>&>... };
1213 _S_vtable[__rhs._M_index](this->_M_storage(),
1214 __rhs._M_storage());
1217 else if (!this->_M_valid())
1219 *this = std::move(__rhs);
1221 else if (!__rhs._M_valid())
1223 __rhs = std::move(*this);
1227 auto __tmp = std::move(__rhs);
1228 __rhs = std::move(*this);
1229 *this = std::move(__tmp);
1233 template<typename _Vp>
1234 friend void* __detail::__variant::
1235 #if _GLIBCXX_INLINE_VERSION
1236 __7:: // Required due to PR c++/59256
1238 __get_storage(_Vp&& __v);
1241 template<size_t _Np, typename... _Types>
1242 variant_alternative_t<_Np, variant<_Types...>>&
1243 get(variant<_Types...>& __v)
1245 static_assert(_Np < sizeof...(_Types),
1246 "The index should be in [0, number of alternatives)");
1247 if (__v.index() != _Np)
1248 __throw_bad_variant_access("Unexpected index");
1249 return __detail::__variant::__access<
1250 variant_alternative_t<_Np, variant<_Types...>>>(__v);
1253 template<size_t _Np, typename... _Types>
1254 variant_alternative_t<_Np, variant<_Types...>>&&
1255 get(variant<_Types...>&& __v)
1257 static_assert(_Np < sizeof...(_Types),
1258 "The index should be in [0, number of alternatives)");
1259 if (__v.index() != _Np)
1260 __throw_bad_variant_access("Unexpected index");
1261 return __detail::__variant::__access<
1262 variant_alternative_t<_Np, variant<_Types...>>>(std::move(__v));
1265 template<size_t _Np, typename... _Types>
1266 const variant_alternative_t<_Np, variant<_Types...>>&
1267 get(const variant<_Types...>& __v)
1269 static_assert(_Np < sizeof...(_Types),
1270 "The index should be in [0, number of alternatives)");
1271 if (__v.index() != _Np)
1272 __throw_bad_variant_access("Unexpected index");
1273 return __detail::__variant::__access<
1274 variant_alternative_t<_Np, variant<_Types...>>>(__v);
1277 template<size_t _Np, typename... _Types>
1278 const variant_alternative_t<_Np, variant<_Types...>>&&
1279 get(const variant<_Types...>&& __v)
1281 static_assert(_Np < sizeof...(_Types),
1282 "The index should be in [0, number of alternatives)");
1283 if (__v.index() != _Np)
1284 __throw_bad_variant_access("Unexpected index");
1285 return __detail::__variant::__access<
1286 variant_alternative_t<_Np, variant<_Types...>>>(std::move(__v));
1289 template<typename _Visitor, typename... _Variants>
1291 visit(_Visitor&& __visitor, _Variants&&... __variants)
1293 using _Result_type =
1294 decltype(std::forward<_Visitor>(__visitor)(get<0>(__variants)...));
1295 static constexpr auto _S_vtable =
1296 __detail::__variant::__gen_vtable<
1297 _Result_type, _Visitor&&, _Variants&&...>::_S_apply();
1298 auto __func_ptr = _S_vtable._M_access(__variants.index()...);
1299 return (*__func_ptr)(std::forward<_Visitor>(__visitor),
1300 __detail::__variant::__get_storage(__variants)...);
1303 template<typename... _Types, typename _Alloc>
1304 struct uses_allocator<variant<_Types...>, _Alloc>
1307 template<typename... _Types>
1308 struct hash<variant<_Types...>>
1309 : private __poison_hash<remove_const_t<_Types>>...
1311 using result_type = size_t;
1312 using argument_type = variant<_Types...>;
1315 operator()(const variant<_Types...>& __t) const
1316 noexcept((... && noexcept(hash<decay_t<_Types>>{}(std::declval<_Types>()))))
1318 if (!__t.valueless_by_exception())
1320 namespace __edv = __detail::__variant;
1321 static constexpr size_t (*_S_vtable[])(void*) =
1322 { &__edv::__erased_hash<const __edv::__storage<_Types>&>... };
1323 return hash<size_t>{}(__t.index())
1324 + _S_vtable[__t.index()](__edv::__get_storage(__t));
1326 return hash<size_t>{}(__t.index());
1331 struct hash<monostate>
1333 using result_type = size_t;
1334 using argument_type = monostate;
1337 operator()(const monostate& __t) const noexcept
1339 constexpr size_t __magic_monostate_hash = -7777;
1340 return __magic_monostate_hash;
1344 _GLIBCXX_END_NAMESPACE_VERSION
1349 #endif // _GLIBCXX_VARIANT