1// <variant> -*- C++ -*-
2
3// Copyright (C) 2016-2018 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file variant
26 * This is the <variant> C++ Library header.
27 */
28
29#ifndef _GLIBCXX_VARIANT
30#define _GLIBCXX_VARIANT 1
31
32#pragma GCC system_header
33
34#if __cplusplus >= 201703L
35
36#include <type_traits>
37#include <utility>
38#include <bits/enable_special_members.h>
39#include <bits/functexcept.h>
40#include <bits/move.h>
41#include <bits/functional_hash.h>
42#include <bits/invoke.h>
43#include <ext/aligned_buffer.h>
44#include <bits/parse_numbers.h>
45#include <bits/stl_iterator_base_types.h>
46#include <bits/stl_iterator_base_funcs.h>
47#include <bits/stl_construct.h>
48
49namespace std _GLIBCXX_VISIBILITY(default)
50{
51_GLIBCXX_BEGIN_NAMESPACE_VERSION
52
53namespace __detail
54{
55namespace __variant
56{
57 template<size_t _Np, typename... _Types>
58 struct _Nth_type;
59
60 template<size_t _Np, typename _First, typename... _Rest>
61 struct _Nth_type<_Np, _First, _Rest...>
62 : _Nth_type<_Np-1, _Rest...> { };
63
64 template<typename _First, typename... _Rest>
65 struct _Nth_type<0, _First, _Rest...>
66 { using type = _First; };
67
68} // namespace __variant
69} // namespace __detail
70
71#define __cpp_lib_variant 201603
72
73 template<typename... _Types> class tuple;
74 template<typename... _Types> class variant;
75 template <typename> struct hash;
76
77 template<typename _Variant>
78 struct variant_size;
79
80 template<typename _Variant>
81 struct variant_size<const _Variant> : variant_size<_Variant> {};
82
83 template<typename _Variant>
84 struct variant_size<volatile _Variant> : variant_size<_Variant> {};
85
86 template<typename _Variant>
87 struct variant_size<const volatile _Variant> : variant_size<_Variant> {};
88
89 template<typename... _Types>
90 struct variant_size<variant<_Types...>>
91 : std::integral_constant<size_t, sizeof...(_Types)> {};
92
93 template<typename _Variant>
94 inline constexpr size_t variant_size_v = variant_size<_Variant>::value;
95
96 template<size_t _Np, typename _Variant>
97 struct variant_alternative;
98
99 template<size_t _Np, typename _First, typename... _Rest>
100 struct variant_alternative<_Np, variant<_First, _Rest...>>
101 : variant_alternative<_Np-1, variant<_Rest...>> {};
102
103 template<typename _First, typename... _Rest>
104 struct variant_alternative<0, variant<_First, _Rest...>>
105 { using type = _First; };
106
107 template<size_t _Np, typename _Variant>
108 using variant_alternative_t =
109 typename variant_alternative<_Np, _Variant>::type;
110
111 template<size_t _Np, typename _Variant>
112 struct variant_alternative<_Np, const _Variant>
113 { using type = add_const_t<variant_alternative_t<_Np, _Variant>>; };
114
115 template<size_t _Np, typename _Variant>
116 struct variant_alternative<_Np, volatile _Variant>
117 { using type = add_volatile_t<variant_alternative_t<_Np, _Variant>>; };
118
119 template<size_t _Np, typename _Variant>
120 struct variant_alternative<_Np, const volatile _Variant>
121 { using type = add_cv_t<variant_alternative_t<_Np, _Variant>>; };
122
123 inline constexpr size_t variant_npos = -1;
124
125 template<size_t _Np, typename... _Types>
126 constexpr variant_alternative_t<_Np, variant<_Types...>>&
127 get(variant<_Types...>&);
128
129 template<size_t _Np, typename... _Types>
130 constexpr variant_alternative_t<_Np, variant<_Types...>>&&
131 get(variant<_Types...>&&);
132
133 template<size_t _Np, typename... _Types>
134 constexpr variant_alternative_t<_Np, variant<_Types...>> const&
135 get(const variant<_Types...>&);
136
137 template<size_t _Np, typename... _Types>
138 constexpr variant_alternative_t<_Np, variant<_Types...>> const&&
139 get(const variant<_Types...>&&);
140
141namespace __detail
142{
143namespace __variant
144{
145 // Returns the first apparence of _Tp in _Types.
146 // Returns sizeof...(_Types) if _Tp is not in _Types.
147 template<typename _Tp, typename... _Types>
148 struct __index_of : std::integral_constant<size_t, 0> {};
149
150 template<typename _Tp, typename... _Types>
151 inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value;
152
153 template<typename _Tp, typename _First, typename... _Rest>
154 struct __index_of<_Tp, _First, _Rest...> :
155 std::integral_constant<size_t, is_same_v<_Tp, _First>
156 ? 0 : __index_of_v<_Tp, _Rest...> + 1> {};
157
158 // _Uninitialized<T> is guaranteed to be a literal type, even if T is not.
159 // We have to do this, because [basic.types]p10.5.3 (n4606) is not implemented
160 // yet. When it's implemented, _Uninitialized<T> can be changed to the alias
161 // to T, therefore equivalent to being removed entirely.
162 //
163 // Another reason we may not want to remove _Uninitialzied<T> may be that, we
164 // want _Uninitialized<T> to be trivially destructible, no matter whether T
165 // is; but we will see.
166 template<typename _Type, bool = std::is_literal_type_v<_Type>>
167 struct _Uninitialized;
168
169 template<typename _Type>
170 struct _Uninitialized<_Type, true>
171 {
172 template<typename... _Args>
173 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
174 : _M_storage(std::forward<_Args>(__args)...)
175 { }
176
177 constexpr const _Type& _M_get() const &
178 { return _M_storage; }
179
180 constexpr _Type& _M_get() &
181 { return _M_storage; }
182
183 constexpr const _Type&& _M_get() const &&
184 { return std::move(_M_storage); }
185
186 constexpr _Type&& _M_get() &&
187 { return std::move(_M_storage); }
188
189 _Type _M_storage;
190 };
191
192 template<typename _Type>
193 struct _Uninitialized<_Type, false>
194 {
195 template<typename... _Args>
196 constexpr _Uninitialized(in_place_index_t<0>, _Args&&... __args)
197 { ::new (&_M_storage) _Type(std::forward<_Args>(__args)...); }
198
199 const _Type& _M_get() const &
200 { return *_M_storage._M_ptr(); }
201
202 _Type& _M_get() &
203 { return *_M_storage._M_ptr(); }
204
205 const _Type&& _M_get() const &&
206 { return std::move(*_M_storage._M_ptr()); }
207
208 _Type&& _M_get() &&
209 { return std::move(*_M_storage._M_ptr()); }
210
211 __gnu_cxx::__aligned_membuf<_Type> _M_storage;
212 };
213
214 template<typename _Ref>
215 _Ref __ref_cast(void* __ptr)
216 {
217 return static_cast<_Ref>(*static_cast<remove_reference_t<_Ref>*>(__ptr));
218 }
219
220 template<typename _Union>
221 constexpr decltype(auto) __get(in_place_index_t<0>, _Union&& __u)
222 { return std::forward<_Union>(__u)._M_first._M_get(); }
223
224 template<size_t _Np, typename _Union>
225 constexpr decltype(auto) __get(in_place_index_t<_Np>, _Union&& __u)
226 {
227 return __variant::__get(in_place_index<_Np-1>,
228 std::forward<_Union>(__u)._M_rest);
229 }
230
231 // Returns the typed storage for __v.
232 template<size_t _Np, typename _Variant>
233 constexpr decltype(auto) __get(_Variant&& __v)
234 {
235 return __variant::__get(std::in_place_index<_Np>,
236 std::forward<_Variant>(__v)._M_u);
237 }
238
239 // Various functions as "vtable" entries, where those vtables are used by
240 // polymorphic operations.
241 template<typename _Lhs, typename _Rhs>
242 void
243 __erased_ctor(void* __lhs, void* __rhs)
244 {
245 using _Type = remove_reference_t<_Lhs>;
246 ::new (__lhs) _Type(__variant::__ref_cast<_Rhs>(__rhs));
247 }
248
249 template<typename _Variant, size_t _Np>
250 void
251 __erased_dtor(_Variant&& __v)
252 { std::_Destroy(std::__addressof(__variant::__get<_Np>(__v))); }
253
254 template<typename _Lhs, typename _Rhs>
255 void
256 __erased_assign(void* __lhs, void* __rhs)
257 {
258 __variant::__ref_cast<_Lhs>(__lhs) = __variant::__ref_cast<_Rhs>(__rhs);
259 }
260
261 template<typename _Lhs, typename _Rhs>
262 void
263 __erased_swap(void* __lhs, void* __rhs)
264 {
265 using std::swap;
266 swap(__variant::__ref_cast<_Lhs>(__lhs),
267 __variant::__ref_cast<_Rhs>(__rhs));
268 }
269
270#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
271 template<typename _Variant, size_t _Np> \
272 constexpr bool \
273 __erased_##__NAME(const _Variant& __lhs, const _Variant& __rhs) \
274 { \
275 return __variant::__get<_Np>(std::forward<_Variant>(__lhs)) \
276 __OP __variant::__get<_Np>(std::forward<_Variant>(__rhs)); \
277 }
278
279 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
280 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
281 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
282 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
283 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
284 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
285
286#undef _VARIANT_RELATION_FUNCTION_TEMPLATE
287
288 template<typename _Tp>
289 size_t
290 __erased_hash(void* __t)
291 {
292 return std::hash<remove_cv_t<remove_reference_t<_Tp>>>{}(
293 __variant::__ref_cast<_Tp>(__t));
294 }
295
296 template<typename... _Types>
297 struct _Traits
298 {
299 static constexpr bool _S_default_ctor =
300 is_default_constructible_v<typename _Nth_type<0, _Types...>::type>;
301 static constexpr bool _S_copy_ctor =
302 (is_copy_constructible_v<_Types> && ...);
303 static constexpr bool _S_move_ctor =
304 (is_move_constructible_v<_Types> && ...);
305 static constexpr bool _S_copy_assign =
306 _S_copy_ctor && _S_move_ctor
307 && (is_copy_assignable_v<_Types> && ...);
308 static constexpr bool _S_move_assign =
309 _S_move_ctor
310 && (is_move_assignable_v<_Types> && ...);
311
312 static constexpr bool _S_trivial_dtor =
313 (is_trivially_destructible_v<_Types> && ...);
314 static constexpr bool _S_trivial_copy_ctor =
315 (is_trivially_copy_constructible_v<_Types> && ...);
316 static constexpr bool _S_trivial_move_ctor =
317 (is_trivially_move_constructible_v<_Types> && ...);
318 static constexpr bool _S_trivial_copy_assign =
319 _S_trivial_dtor && (is_trivially_copy_assignable_v<_Types> && ...);
320 static constexpr bool _S_trivial_move_assign =
321 _S_trivial_dtor && (is_trivially_move_assignable_v<_Types> && ...);
322
323 // The following nothrow traits are for non-trivial SMFs. Trivial SMFs
324 // are always nothrow.
325 static constexpr bool _S_nothrow_default_ctor =
326 is_nothrow_default_constructible_v<
327 typename _Nth_type<0, _Types...>::type>;
328 static constexpr bool _S_nothrow_copy_ctor = false;
329 static constexpr bool _S_nothrow_move_ctor =
330 (is_nothrow_move_constructible_v<_Types> && ...);
331 static constexpr bool _S_nothrow_copy_assign = false;
332 static constexpr bool _S_nothrow_move_assign =
333 _S_nothrow_move_ctor && (is_nothrow_move_assignable_v<_Types> && ...);
334 };
335
336 // Defines members and ctors.
337 template<typename... _Types>
338 union _Variadic_union { };
339
340 template<typename _First, typename... _Rest>
341 union _Variadic_union<_First, _Rest...>
342 {
343 constexpr _Variadic_union() : _M_rest() { }
344
345 template<typename... _Args>
346 constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args)
347 : _M_first(in_place_index<0>, std::forward<_Args>(__args)...)
348 { }
349
350 template<size_t _Np, typename... _Args>
351 constexpr _Variadic_union(in_place_index_t<_Np>, _Args&&... __args)
352 : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...)
353 { }
354
355 _Uninitialized<_First> _M_first;
356 _Variadic_union<_Rest...> _M_rest;
357 };
358
359 // Defines index and the dtor, possibly trivial.
360 template<bool __trivially_destructible, typename... _Types>
361 struct _Variant_storage;
362
363 template <typename... _Types>
364 using __select_index =
365 typename __select_int::_Select_int_base<sizeof...(_Types) + 1,
366 unsigned char,
367 unsigned short>::type::value_type;
368
369 template<typename... _Types>
370 struct _Variant_storage<false, _Types...>
371 {
372 template<size_t... __indices>
373 static constexpr void (*_S_vtable[])(const _Variant_storage&) =
374 { &__erased_dtor<const _Variant_storage&, __indices>... };
375
376 constexpr _Variant_storage() : _M_index(variant_npos) { }
377
378 template<size_t _Np, typename... _Args>
379 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
380 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
381 _M_index(_Np)
382 { }
383
384 template<size_t... __indices>
385 constexpr void _M_reset_impl(std::index_sequence<__indices...>)
386 {
387 if (_M_index != __index_type(variant_npos))
388 _S_vtable<__indices...>[_M_index](*this);
389 }
390
391 void _M_reset()
392 {
393 _M_reset_impl(std::index_sequence_for<_Types...>{});
394 _M_index = variant_npos;
395 }
396
397 ~_Variant_storage()
398 { _M_reset(); }
399
400 void*
401 _M_storage() const
402 {
403 return const_cast<void*>(static_cast<const void*>(
404 std::addressof(_M_u)));
405 }
406
407 constexpr bool
408 _M_valid() const noexcept
409 {
410 return this->_M_index != __index_type(variant_npos);
411 }
412
413 _Variadic_union<_Types...> _M_u;
414 using __index_type = __select_index<_Types...>;
415 __index_type _M_index;
416 };
417
418 template<typename... _Types>
419 struct _Variant_storage<true, _Types...>
420 {
421 constexpr _Variant_storage() : _M_index(variant_npos) { }
422
423 template<size_t _Np, typename... _Args>
424 constexpr _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
425 : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
426 _M_index(_Np)
427 { }
428
429 void _M_reset()
430 { _M_index = variant_npos; }
431
432 void*
433 _M_storage() const
434 {
435 return const_cast<void*>(static_cast<const void*>(
436 std::addressof(_M_u)));
437 }
438
439 constexpr bool
440 _M_valid() const noexcept
441 {
442 return this->_M_index != __index_type(variant_npos);
443 }
444
445 _Variadic_union<_Types...> _M_u;
446 using __index_type = __select_index<_Types...>;
447 __index_type _M_index;
448 };
449
450 template<typename... _Types>
451 using _Variant_storage_alias =
452 _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>;
453
454 // The following are (Copy|Move) (ctor|assign) layers for forwarding
455 // triviality and handling non-trivial SMF behaviors.
456
457 template<bool, typename... _Types>
458 struct _Copy_ctor_base : _Variant_storage_alias<_Types...>
459 {
460 using _Base = _Variant_storage_alias<_Types...>;
461 using _Base::_Base;
462
463 _Copy_ctor_base(const _Copy_ctor_base& __rhs)
464 noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor)
465 {
466 if (__rhs._M_valid())
467 {
468 static constexpr void (*_S_vtable[])(void*, void*) =
469 { &__erased_ctor<_Types&, const _Types&>... };
470 _S_vtable[__rhs._M_index](this->_M_storage(), __rhs._M_storage());
471 this->_M_index = __rhs._M_index;
472 }
473 }
474
475 _Copy_ctor_base(_Copy_ctor_base&&) = default;
476 _Copy_ctor_base& operator=(const _Copy_ctor_base&) = default;
477 _Copy_ctor_base& operator=(_Copy_ctor_base&&) = default;
478 };
479
480 template<typename... _Types>
481 struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...>
482 {
483 using _Base = _Variant_storage_alias<_Types...>;
484 using _Base::_Base;
485 };
486
487 template<typename... _Types>
488 using _Copy_ctor_alias =
489 _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>;
490
491 template<bool, typename... _Types>
492 struct _Move_ctor_base : _Copy_ctor_alias<_Types...>
493 {
494 using _Base = _Copy_ctor_alias<_Types...>;
495 using _Base::_Base;
496
497 _Move_ctor_base(_Move_ctor_base&& __rhs)
498 noexcept(_Traits<_Types...>::_S_nothrow_move_ctor)
499 {
500 if (__rhs._M_valid())
501 {
502 static constexpr void (*_S_vtable[])(void*, void*) =
503 { &__erased_ctor<_Types&, _Types&&>... };
504 _S_vtable[__rhs._M_index](this->_M_storage(), __rhs._M_storage());
505 this->_M_index = __rhs._M_index;
506 }
507 }
508
509 void _M_destructive_move(_Move_ctor_base&& __rhs)
510 {
511 this->~_Move_ctor_base();
512 __try
513 {
514 ::new (this) _Move_ctor_base(std::move(__rhs));
515 }
516 __catch (...)
517 {
518 this->_M_index = variant_npos;
519 __throw_exception_again;
520 }
521 }
522
523 _Move_ctor_base(const _Move_ctor_base&) = default;
524 _Move_ctor_base& operator=(const _Move_ctor_base&) = default;
525 _Move_ctor_base& operator=(_Move_ctor_base&&) = default;
526 };
527
528 template<typename... _Types>
529 struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...>
530 {
531 using _Base = _Copy_ctor_alias<_Types...>;
532 using _Base::_Base;
533
534 void _M_destructive_move(_Move_ctor_base&& __rhs)
535 {
536 this->~_Move_ctor_base();
537 ::new (this) _Move_ctor_base(std::move(__rhs));
538 }
539 };
540
541 template<typename... _Types>
542 using _Move_ctor_alias =
543 _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>;
544
545 template<bool, typename... _Types>
546 struct _Copy_assign_base : _Move_ctor_alias<_Types...>
547 {
548 using _Base = _Move_ctor_alias<_Types...>;
549 using _Base::_Base;
550
551 _Copy_assign_base&
552 operator=(const _Copy_assign_base& __rhs)
553 noexcept(_Traits<_Types...>::_S_nothrow_copy_assign)
554 {
555 if (this->_M_index == __rhs._M_index)
556 {
557 if (__rhs._M_valid())
558 {
559 static constexpr void (*_S_vtable[])(void*, void*) =
560 { &__erased_assign<_Types&, const _Types&>... };
561 _S_vtable[__rhs._M_index](this->_M_storage(),
562 __rhs._M_storage());
563 }
564 }
565 else
566 {
567 _Copy_assign_base __tmp(__rhs);
568 this->_M_destructive_move(std::move(__tmp));
569 }
570 __glibcxx_assert(this->_M_index == __rhs._M_index);
571 return *this;
572 }
573
574 _Copy_assign_base(const _Copy_assign_base&) = default;
575 _Copy_assign_base(_Copy_assign_base&&) = default;
576 _Copy_assign_base& operator=(_Copy_assign_base&&) = default;
577 };
578
579 template<typename... _Types>
580 struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...>
581 {
582 using _Base = _Move_ctor_alias<_Types...>;
583 using _Base::_Base;
584 };
585
586 template<typename... _Types>
587 using _Copy_assign_alias =
588 _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign,
589 _Types...>;
590
591 template<bool, typename... _Types>
592 struct _Move_assign_base : _Copy_assign_alias<_Types...>
593 {
594 using _Base = _Copy_assign_alias<_Types...>;
595 using _Base::_Base;
596
597 _Move_assign_base&
598 operator=(_Move_assign_base&& __rhs)
599 noexcept(_Traits<_Types...>::_S_nothrow_move_assign)
600 {
601 if (this->_M_index == __rhs._M_index)
602 {
603 if (__rhs._M_valid())
604 {
605 static constexpr void (*_S_vtable[])(void*, void*) =
606 { &__erased_assign<_Types&, _Types&&>... };
607 _S_vtable[__rhs._M_index]
608 (this->_M_storage(), __rhs._M_storage());
609 }
610 }
611 else
612 {
613 _Move_assign_base __tmp(std::move(__rhs));
614 this->_M_destructive_move(std::move(__tmp));
615 }
616 __glibcxx_assert(this->_M_index == __rhs._M_index);
617 return *this;
618 }
619
620 _Move_assign_base(const _Move_assign_base&) = default;
621 _Move_assign_base(_Move_assign_base&&) = default;
622 _Move_assign_base& operator=(const _Move_assign_base&) = default;
623 };
624
625 template<typename... _Types>
626 struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...>
627 {
628 using _Base = _Copy_assign_alias<_Types...>;
629 using _Base::_Base;
630 };
631
632 template<typename... _Types>
633 using _Move_assign_alias =
634 _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign,
635 _Types...>;
636
637 template<typename... _Types>
638 struct _Variant_base : _Move_assign_alias<_Types...>
639 {
640 using _Base = _Move_assign_alias<_Types...>;
641
642 constexpr
643 _Variant_base()
644 noexcept(_Traits<_Types...>::_S_nothrow_default_ctor)
645 : _Variant_base(in_place_index<0>) { }
646
647 template<size_t _Np, typename... _Args>
648 constexpr explicit
649 _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
650 : _Base(__i, std::forward<_Args>(__args)...)
651 { }
652
653 _Variant_base(const _Variant_base&) = default;
654 _Variant_base(_Variant_base&&) = default;
655 _Variant_base& operator=(const _Variant_base&) = default;
656 _Variant_base& operator=(_Variant_base&&) = default;
657 };
658
659 // For how many times does _Tp appear in _Tuple?
660 template<typename _Tp, typename _Tuple>
661 struct __tuple_count;
662
663 template<typename _Tp, typename _Tuple>
664 inline constexpr size_t __tuple_count_v =
665 __tuple_count<_Tp, _Tuple>::value;
666
667 template<typename _Tp, typename... _Types>
668 struct __tuple_count<_Tp, tuple<_Types...>>
669 : integral_constant<size_t, 0> { };
670
671 template<typename _Tp, typename _First, typename... _Rest>
672 struct __tuple_count<_Tp, tuple<_First, _Rest...>>
673 : integral_constant<
674 size_t,
675 __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { };
676
677 // TODO: Reuse this in <tuple> ?
678 template<typename _Tp, typename... _Types>
679 inline constexpr bool __exactly_once =
680 __tuple_count_v<_Tp, tuple<_Types...>> == 1;
681
682 // Takes _Types and create an overloaded _S_fun for each type.
683 // If a type appears more than once in _Types, create only one overload.
684 template<typename... _Types>
685 struct __overload_set
686 { static void _S_fun(); };
687
688 template<typename _First, typename... _Rest>
689 struct __overload_set<_First, _Rest...> : __overload_set<_Rest...>
690 {
691 using __overload_set<_Rest...>::_S_fun;
692 static integral_constant<size_t, sizeof...(_Rest)> _S_fun(_First);
693 };
694
695 template<typename... _Rest>
696 struct __overload_set<void, _Rest...> : __overload_set<_Rest...>
697 {
698 using __overload_set<_Rest...>::_S_fun;
699 };
700
701 // Helper for variant(_Tp&&) and variant::operator=(_Tp&&).
702 // __accepted_index maps the arbitrary _Tp to an alternative type in _Variant.
703 template<typename _Tp, typename _Variant, typename = void>
704 struct __accepted_index
705 { static constexpr size_t value = variant_npos; };
706
707 template<typename _Tp, typename... _Types>
708 struct __accepted_index<
709 _Tp, variant<_Types...>,
710 decltype(__overload_set<_Types...>::_S_fun(std::declval<_Tp>()),
711 std::declval<void>())>
712 {
713 static constexpr size_t value = sizeof...(_Types) - 1
714 - decltype(__overload_set<_Types...>::
715 _S_fun(std::declval<_Tp>()))::value;
716 };
717
718 // Returns the raw storage for __v.
719 template<typename _Variant>
720 void* __get_storage(_Variant&& __v)
721 { return __v._M_storage(); }
722
723 // Used for storing multi-dimensional vtable.
724 template<typename _Tp, size_t... _Dimensions>
725 struct _Multi_array
726 {
727 constexpr const _Tp&
728 _M_access() const
729 { return _M_data; }
730
731 _Tp _M_data;
732 };
733
734 template<typename _Tp, size_t __first, size_t... __rest>
735 struct _Multi_array<_Tp, __first, __rest...>
736 {
737 template<typename... _Args>
738 constexpr const _Tp&
739 _M_access(size_t __first_index, _Args... __rest_indices) const
740 { return _M_arr[__first_index]._M_access(__rest_indices...); }
741
742 _Multi_array<_Tp, __rest...> _M_arr[__first];
743 };
744
745 // Creates a multi-dimensional vtable recursively.
746 //
747 // For example,
748 // visit([](auto, auto){},
749 // variant<int, char>(), // typedef'ed as V1
750 // variant<float, double, long double>()) // typedef'ed as V2
751 // will trigger instantiations of:
752 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>,
753 // tuple<V1&&, V2&&>, std::index_sequence<>>
754 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
755 // tuple<V1&&, V2&&>, std::index_sequence<0>>
756 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
757 // tuple<V1&&, V2&&>, std::index_sequence<0, 0>>
758 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
759 // tuple<V1&&, V2&&>, std::index_sequence<0, 1>>
760 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
761 // tuple<V1&&, V2&&>, std::index_sequence<0, 2>>
762 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
763 // tuple<V1&&, V2&&>, std::index_sequence<1>>
764 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
765 // tuple<V1&&, V2&&>, std::index_sequence<1, 0>>
766 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
767 // tuple<V1&&, V2&&>, std::index_sequence<1, 1>>
768 // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
769 // tuple<V1&&, V2&&>, std::index_sequence<1, 2>>
770 // The returned multi-dimensional vtable can be fast accessed by the visitor
771 // using index calculation.
772 template<typename _Array_type, typename _Variant_tuple, typename _Index_seq>
773 struct __gen_vtable_impl;
774
775 template<typename _Result_type, typename _Visitor, size_t... __dimensions,
776 typename... _Variants, size_t... __indices>
777 struct __gen_vtable_impl<
778 _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>,
779 tuple<_Variants...>, std::index_sequence<__indices...>>
780 {
781 using _Next =
782 remove_reference_t<typename _Nth_type<sizeof...(__indices),
783 _Variants...>::type>;
784 using _Array_type =
785 _Multi_array<_Result_type (*)(_Visitor, _Variants...),
786 __dimensions...>;
787
788 static constexpr _Array_type
789 _S_apply()
790 {
791 _Array_type __vtable{};
792 _S_apply_all_alts(
793 __vtable, make_index_sequence<variant_size_v<_Next>>());
794 return __vtable;
795 }
796
797 template<size_t... __var_indices>
798 static constexpr void
799 _S_apply_all_alts(_Array_type& __vtable,
800 std::index_sequence<__var_indices...>)
801 {
802 (_S_apply_single_alt<__var_indices>(
803 __vtable._M_arr[__var_indices]), ...);
804 }
805
806 template<size_t __index, typename _Tp>
807 static constexpr void
808 _S_apply_single_alt(_Tp& __element)
809 {
810 using _Alternative = variant_alternative_t<__index, _Next>;
811 __element = __gen_vtable_impl<
812 remove_reference_t<
813 decltype(__element)>, tuple<_Variants...>,
814 std::index_sequence<__indices..., __index>>::_S_apply();
815 }
816 };
817
818 template<typename _Result_type, typename _Visitor, typename... _Variants,
819 size_t... __indices>
820 struct __gen_vtable_impl<
821 _Multi_array<_Result_type (*)(_Visitor, _Variants...)>,
822 tuple<_Variants...>, std::index_sequence<__indices...>>
823 {
824 using _Array_type =
825 _Multi_array<_Result_type (*)(_Visitor&&, _Variants...)>;
826
827 decltype(auto)
828 static constexpr __visit_invoke(_Visitor&& __visitor, _Variants... __vars)
829 {
830 return std::__invoke(std::forward<_Visitor>(__visitor),
831 std::get<__indices>(std::forward<_Variants>(__vars))...);
832 }
833
834 static constexpr auto
835 _S_apply()
836 { return _Array_type{&__visit_invoke}; }
837 };
838
839 template<typename _Result_type, typename _Visitor, typename... _Variants>
840 struct __gen_vtable
841 {
842 using _Func_ptr = _Result_type (*)(_Visitor&&, _Variants...);
843 using _Array_type =
844 _Multi_array<_Func_ptr,
845 variant_size_v<remove_reference_t<_Variants>>...>;
846
847 static constexpr _Array_type
848 _S_apply()
849 {
850 return __gen_vtable_impl<_Array_type, tuple<_Variants...>,
851 std::index_sequence<>>::_S_apply();
852 }
853
854 static constexpr auto _S_vtable = _S_apply();
855 };
856
857 template<size_t _Np, typename _Tp>
858 struct _Base_dedup : public _Tp { };
859
860 template<typename _Variant, typename __indices>
861 struct _Variant_hash_base;
862
863 template<typename... _Types, size_t... __indices>
864 struct _Variant_hash_base<variant<_Types...>,
865 std::index_sequence<__indices...>>
866 : _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { };
867
868} // namespace __variant
869} // namespace __detail
870
871 template<typename _Tp, typename... _Types>
872 inline constexpr bool holds_alternative(const variant<_Types...>& __v)
873 noexcept
874 {
875 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
876 "T should occur for exactly once in alternatives");
877 return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>;
878 }
879
880 template<typename _Tp, typename... _Types>
881 constexpr inline _Tp& get(variant<_Types...>& __v)
882 {
883 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
884 "T should occur for exactly once in alternatives");
885 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
886 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
887 }
888
889 template<typename _Tp, typename... _Types>
890 constexpr inline _Tp&& get(variant<_Types...>&& __v)
891 {
892 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
893 "T should occur for exactly once in alternatives");
894 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
895 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
896 std::move(__v));
897 }
898
899 template<typename _Tp, typename... _Types>
900 constexpr inline const _Tp& get(const variant<_Types...>& __v)
901 {
902 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
903 "T should occur for exactly once in alternatives");
904 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
905 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
906 }
907
908 template<typename _Tp, typename... _Types>
909 constexpr inline const _Tp&& get(const variant<_Types...>&& __v)
910 {
911 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
912 "T should occur for exactly once in alternatives");
913 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
914 return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
915 std::move(__v));
916 }
917
918 template<size_t _Np, typename... _Types>
919 constexpr inline
920 add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
921 get_if(variant<_Types...>* __ptr) noexcept
922 {
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);
929 return nullptr;
930 }
931
932 template<size_t _Np, typename... _Types>
933 constexpr inline
934 add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>>
935 get_if(const variant<_Types...>* __ptr) noexcept
936 {
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);
943 return nullptr;
944 }
945
946 template<typename _Tp, typename... _Types>
947 constexpr inline add_pointer_t<_Tp>
948 get_if(variant<_Types...>* __ptr) noexcept
949 {
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...>>(
954 __ptr);
955 }
956
957 template<typename _Tp, typename... _Types>
958 constexpr inline add_pointer_t<const _Tp>
959 get_if(const variant<_Types...>* __ptr)
960 noexcept
961 {
962 static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
963 "T should occur for exactly once in alternatives");
964 static_assert(!is_void_v<_Tp>, "_Tp should not be void");
965 return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(
966 __ptr);
967 }
968
969 struct monostate { };
970
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) \
975 { \
976 return __lhs._M_##__NAME(__rhs, std::index_sequence_for<_Types...>{}); \
977 } \
978\
979 constexpr bool operator __OP(monostate, monostate) noexcept \
980 { return 0 __OP 0; }
981
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)
988
989#undef _VARIANT_RELATION_FUNCTION_TEMPLATE
990
991 template<typename _Visitor, typename... _Variants>
992 constexpr decltype(auto) visit(_Visitor&&, _Variants&&...);
993
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); }
1000
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;
1005
1006 class bad_variant_access : public exception
1007 {
1008 public:
1009 bad_variant_access() noexcept : _M_reason("Unknown reason") { }
1010 const char* what() const noexcept override
1011 { return _M_reason; }
1012
1013 private:
1014 bad_variant_access(const char* __reason) : _M_reason(__reason) { }
1015
1016 const char* _M_reason;
1017
1018 friend void __throw_bad_variant_access(const char* __what);
1019 };
1020
1021 inline void
1022 __throw_bad_variant_access(const char* __what)
1023 { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); }
1024
1025 template<typename... _Types>
1026 class variant
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,
1036 variant<_Types...>>
1037 {
1038 private:
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");
1045
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...>>;
1051
1052 template<typename _Tp>
1053 static constexpr bool
1054 __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>;
1055
1056 template<typename _Tp>
1057 static constexpr size_t __accepted_index =
1058 __detail::__variant::__accepted_index<_Tp&&, variant>::value;
1059
1060 template<size_t _Np, bool = _Np < sizeof...(_Types)>
1061 struct __to_type_impl;
1062
1063 template<size_t _Np>
1064 struct __to_type_impl<_Np, true>
1065 { using type = variant_alternative_t<_Np, variant>; };
1066
1067 template<size_t _Np>
1068 using __to_type = typename __to_type_impl<_Np>::type;
1069
1070 template<typename _Tp>
1071 using __accepted_type = __to_type<__accepted_index<_Tp>>;
1072
1073 template<typename _Tp>
1074 static constexpr size_t __index_of =
1075 __detail::__variant::__index_of_v<_Tp, _Types...>;
1076
1077 using _Traits = __detail::__variant::_Traits<_Types...>;
1078
1079 public:
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;
1086
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&&>>>
1092 constexpr
1093 variant(_Tp&& __t)
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)); }
1098
1099 template<typename _Tp, typename... _Args,
1100 typename = enable_if_t<__exactly_once<_Tp>
1101 && is_constructible_v<_Tp, _Args&&...>>>
1102 constexpr explicit
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)); }
1107
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&&...>>>
1112 constexpr explicit
1113 variant(in_place_type_t<_Tp>, initializer_list<_Up> __il,
1114 _Args&&... __args)
1115 : variant(in_place_index<__index_of<_Tp>>, __il,
1116 std::forward<_Args>(__args)...)
1117 { __glibcxx_assert(holds_alternative<_Tp>(*this)); }
1118
1119 template<size_t _Np, typename... _Args,
1120 typename = enable_if_t<
1121 is_constructible_v<__to_type<_Np>, _Args&&...>>>
1122 constexpr explicit
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); }
1127
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&&...>>>
1131 constexpr explicit
1132 variant(in_place_index_t<_Np>, initializer_list<_Up> __il,
1133 _Args&&... __args)
1134 : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...),
1135 _Default_ctor_enabler(_Enable_default_constructor_tag{})
1136 { __glibcxx_assert(index() == _Np); }
1137
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&&>)
1146 {
1147 constexpr auto __index = __accepted_index<_Tp&&>;
1148 if (index() == __index)
1149 std::get<__index>(*this) = std::forward<_Tp>(__rhs);
1150 else
1151 this->emplace<__index>(std::forward<_Tp>(__rhs));
1152 __glibcxx_assert(holds_alternative<__accepted_type<_Tp&&>>(*this));
1153 return *this;
1154 }
1155
1156 template<typename _Tp, typename... _Args>
1157 enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>,
1158 _Tp&>
1159 emplace(_Args&&... __args)
1160 {
1161 auto& ret =
1162 this->emplace<__index_of<_Tp>>(std::forward<_Args>(__args)...);
1163 __glibcxx_assert(holds_alternative<_Tp>(*this));
1164 return ret;
1165 }
1166
1167 template<typename _Tp, typename _Up, typename... _Args>
1168 enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>
1169 && __exactly_once<_Tp>,
1170 _Tp&>
1171 emplace(initializer_list<_Up> __il, _Args&&... __args)
1172 {
1173 auto& ret =
1174 this->emplace<__index_of<_Tp>>(__il,
1175 std::forward<_Args>(__args)...);
1176 __glibcxx_assert(holds_alternative<_Tp>(*this));
1177 return ret;
1178 }
1179
1180 template<size_t _Np, typename... _Args>
1181 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1182 _Args...>,
1183 variant_alternative_t<_Np, variant>&>
1184 emplace(_Args&&... __args)
1185 {
1186 static_assert(_Np < sizeof...(_Types),
1187 "The index should be in [0, number of alternatives)");
1188 this->~variant();
1189 __try
1190 {
1191 ::new (this) variant(in_place_index<_Np>,
1192 std::forward<_Args>(__args)...);
1193 }
1194 __catch (...)
1195 {
1196 this->_M_index = variant_npos;
1197 __throw_exception_again;
1198 }
1199 __glibcxx_assert(index() == _Np);
1200 return std::get<_Np>(*this);
1201 }
1202
1203 template<size_t _Np, typename _Up, typename... _Args>
1204 enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1205 initializer_list<_Up>&, _Args...>,
1206 variant_alternative_t<_Np, variant>&>
1207 emplace(initializer_list<_Up> __il, _Args&&... __args)
1208 {
1209 static_assert(_Np < sizeof...(_Types),
1210 "The index should be in [0, number of alternatives)");
1211 this->~variant();
1212 __try
1213 {
1214 ::new (this) variant(in_place_index<_Np>, __il,
1215 std::forward<_Args>(__args)...);
1216 }
1217 __catch (...)
1218 {
1219 this->_M_index = variant_npos;
1220 __throw_exception_again;
1221 }
1222 __glibcxx_assert(index() == _Np);
1223 return std::get<_Np>(*this);
1224 }
1225
1226 constexpr bool valueless_by_exception() const noexcept
1227 { return !this->_M_valid(); }
1228
1229 constexpr size_t index() const noexcept
1230 {
1231 if (this->_M_index ==
1232 typename _Base::__index_type(variant_npos))
1233 return variant_npos;
1234 return this->_M_index;
1235 }
1236
1237 void
1238 swap(variant& __rhs)
1239 noexcept((__is_nothrow_swappable<_Types>::value && ...)
1240 && is_nothrow_move_constructible_v<variant>)
1241 {
1242 if (this->index() == __rhs.index())
1243 {
1244 if (this->_M_valid())
1245 {
1246 static constexpr void (*_S_vtable[])(void*, void*) =
1247 { &__detail::__variant::__erased_swap<_Types&, _Types&>... };
1248 _S_vtable[__rhs._M_index](this->_M_storage(),
1249 __rhs._M_storage());
1250 }
1251 }
1252 else if (!this->_M_valid())
1253 {
1254 this->_M_destructive_move(std::move(__rhs));
1255 __rhs._M_reset();
1256 }
1257 else if (!__rhs._M_valid())
1258 {
1259 __rhs._M_destructive_move(std::move(*this));
1260 this->_M_reset();
1261 }
1262 else
1263 {
1264 auto __tmp = std::move(__rhs);
1265 __rhs._M_destructive_move(std::move(*this));
1266 this->_M_destructive_move(std::move(__tmp));
1267 }
1268 }
1269
1270 private:
1271#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
1272 template<size_t... __indices> \
1273 static constexpr bool \
1274 (*_S_erased_##__NAME[])(const variant&, const variant&) = \
1275 { &__detail::__variant::__erased_##__NAME< \
1276 const variant&, __indices>... }; \
1277 template<size_t... __indices> \
1278 constexpr inline bool \
1279 _M_##__NAME(const variant& __rhs, \
1280 std::index_sequence<__indices...>) const \
1281 { \
1282 auto __lhs_index = this->index(); \
1283 auto __rhs_index = __rhs.index(); \
1284 if (__lhs_index != __rhs_index || valueless_by_exception()) \
1285 /* Modulo addition. */ \
1286 return __lhs_index + 1 __OP __rhs_index + 1; \
1287 return _S_erased_##__NAME<__indices...>[__lhs_index](*this, __rhs); \
1288 }
1289
1290 _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
1291 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
1292 _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
1293 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
1294 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
1295 _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
1296
1297#undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1298
1299#ifdef __clang__
1300 public:
1301 using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852
1302 private:
1303#endif
1304
1305 template<size_t _Np, typename _Vp>
1306 friend constexpr decltype(auto) __detail::__variant::__get(_Vp&& __v);
1307
1308 template<typename _Vp>
1309 friend void* __detail::__variant::__get_storage(_Vp&& __v);
1310
1311#define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \
1312 template<typename... _Tp> \
1313 friend constexpr bool \
1314 operator __OP(const variant<_Tp...>& __lhs, \
1315 const variant<_Tp...>& __rhs);
1316
1317 _VARIANT_RELATION_FUNCTION_TEMPLATE(<)
1318 _VARIANT_RELATION_FUNCTION_TEMPLATE(<=)
1319 _VARIANT_RELATION_FUNCTION_TEMPLATE(==)
1320 _VARIANT_RELATION_FUNCTION_TEMPLATE(!=)
1321 _VARIANT_RELATION_FUNCTION_TEMPLATE(>=)
1322 _VARIANT_RELATION_FUNCTION_TEMPLATE(>)
1323
1324#undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1325 };
1326
1327 template<size_t _Np, typename... _Types>
1328 constexpr variant_alternative_t<_Np, variant<_Types...>>&
1329 get(variant<_Types...>& __v)
1330 {
1331 static_assert(_Np < sizeof...(_Types),
1332 "The index should be in [0, number of alternatives)");
1333 if (__v.index() != _Np)
1334 __throw_bad_variant_access("Unexpected index");
1335 return __detail::__variant::__get<_Np>(__v);
1336 }
1337
1338 template<size_t _Np, typename... _Types>
1339 constexpr variant_alternative_t<_Np, variant<_Types...>>&&
1340 get(variant<_Types...>&& __v)
1341 {
1342 static_assert(_Np < sizeof...(_Types),
1343 "The index should be in [0, number of alternatives)");
1344 if (__v.index() != _Np)
1345 __throw_bad_variant_access("Unexpected index");
1346 return __detail::__variant::__get<_Np>(std::move(__v));
1347 }
1348
1349 template<size_t _Np, typename... _Types>
1350 constexpr const variant_alternative_t<_Np, variant<_Types...>>&
1351 get(const variant<_Types...>& __v)
1352 {
1353 static_assert(_Np < sizeof...(_Types),
1354 "The index should be in [0, number of alternatives)");
1355 if (__v.index() != _Np)
1356 __throw_bad_variant_access("Unexpected index");
1357 return __detail::__variant::__get<_Np>(__v);
1358 }
1359
1360 template<size_t _Np, typename... _Types>
1361 constexpr const variant_alternative_t<_Np, variant<_Types...>>&&
1362 get(const variant<_Types...>&& __v)
1363 {
1364 static_assert(_Np < sizeof...(_Types),
1365 "The index should be in [0, number of alternatives)");
1366 if (__v.index() != _Np)
1367 __throw_bad_variant_access("Unexpected index");
1368 return __detail::__variant::__get<_Np>(std::move(__v));
1369 }
1370
1371 template<typename _Visitor, typename... _Variants>
1372 constexpr decltype(auto)
1373 visit(_Visitor&& __visitor, _Variants&&... __variants)
1374 {
1375 if ((__variants.valueless_by_exception() || ...))
1376 __throw_bad_variant_access("Unexpected index");
1377
1378 using _Result_type =
1379 decltype(std::forward<_Visitor>(__visitor)(
1380 std::get<0>(std::forward<_Variants>(__variants))...));
1381
1382 constexpr auto& __vtable = __detail::__variant::__gen_vtable<
1383 _Result_type, _Visitor&&, _Variants&&...>::_S_vtable;
1384
1385 auto __func_ptr = __vtable._M_access(__variants.index()...);
1386 return (*__func_ptr)(std::forward<_Visitor>(__visitor),
1387 std::forward<_Variants>(__variants)...);
1388 }
1389
1390 template<bool, typename... _Types>
1391 struct __variant_hash_call_base_impl
1392 {
1393 size_t
1394 operator()(const variant<_Types...>& __t) const
1395 noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...))
1396 {
1397 if (!__t.valueless_by_exception())
1398 {
1399 namespace __edv = __detail::__variant;
1400 static constexpr size_t (*_S_vtable[])(void*) =
1401 { &__edv::__erased_hash<const _Types&>... };
1402 return hash<size_t>{}(__t.index())
1403 + _S_vtable[__t.index()](__edv::__get_storage(__t));
1404 }
1405 return hash<size_t>{}(__t.index());
1406 }
1407 };
1408
1409 template<typename... _Types>
1410 struct __variant_hash_call_base_impl<false, _Types...> {};
1411
1412 template<typename... _Types>
1413 using __variant_hash_call_base =
1414 __variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>::
1415 __enable_hash_call &&...), _Types...>;
1416
1417 template<typename... _Types>
1418 struct hash<variant<_Types...>>
1419 : private __detail::__variant::_Variant_hash_base<
1420 variant<_Types...>, std::index_sequence_for<_Types...>>,
1421 public __variant_hash_call_base<_Types...>
1422 {
1423 using result_type [[__deprecated__]] = size_t;
1424 using argument_type [[__deprecated__]] = variant<_Types...>;
1425 };
1426
1427 template<>
1428 struct hash<monostate>
1429 {
1430 using result_type [[__deprecated__]] = size_t;
1431 using argument_type [[__deprecated__]] = monostate;
1432
1433 size_t
1434 operator()(const monostate& __t) const noexcept
1435 {
1436 constexpr size_t __magic_monostate_hash = -7777;
1437 return __magic_monostate_hash;
1438 }
1439 };
1440
1441 template<typename... _Types>
1442 struct __is_fast_hash<hash<variant<_Types...>>>
1443 : bool_constant<(__is_fast_hash<_Types>::value && ...)>
1444 { };
1445
1446_GLIBCXX_END_NAMESPACE_VERSION
1447} // namespace std
1448
1449#endif // C++17
1450
1451#endif // _GLIBCXX_VARIANT
1452