Line data Source code
1 : // <variant> -*- C++ -*-
2 :
3 : // Copyright (C) 2016-2021 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 : #if __cplusplus > 201703L
49 : # include <compare>
50 : #endif
51 :
52 : namespace std _GLIBCXX_VISIBILITY(default)
53 : {
54 : _GLIBCXX_BEGIN_NAMESPACE_VERSION
55 :
56 : namespace __detail
57 : {
58 : namespace __variant
59 : {
60 : template<size_t _Np, typename... _Types>
61 : struct _Nth_type;
62 :
63 : template<size_t _Np, typename _First, typename... _Rest>
64 : struct _Nth_type<_Np, _First, _Rest...>
65 : : _Nth_type<_Np-1, _Rest...> { };
66 :
67 : template<typename _First, typename... _Rest>
68 : struct _Nth_type<0, _First, _Rest...>
69 : { using type = _First; };
70 :
71 : } // namespace __variant
72 : } // namespace __detail
73 :
74 : #define __cpp_lib_variant 202102L
75 :
76 : template<typename... _Types> class tuple;
77 : template<typename... _Types> class variant;
78 : template <typename> struct hash;
79 :
80 : template<typename _Variant>
81 : struct variant_size;
82 :
83 : template<typename _Variant>
84 : struct variant_size<const _Variant> : variant_size<_Variant> {};
85 :
86 : template<typename _Variant>
87 : struct variant_size<volatile _Variant> : variant_size<_Variant> {};
88 :
89 : template<typename _Variant>
90 : struct variant_size<const volatile _Variant> : variant_size<_Variant> {};
91 :
92 : template<typename... _Types>
93 : struct variant_size<variant<_Types...>>
94 : : std::integral_constant<size_t, sizeof...(_Types)> {};
95 :
96 : template<typename _Variant>
97 : inline constexpr size_t variant_size_v = variant_size<_Variant>::value;
98 :
99 : template<size_t _Np, typename _Variant>
100 : struct variant_alternative;
101 :
102 : template<size_t _Np, typename _First, typename... _Rest>
103 : struct variant_alternative<_Np, variant<_First, _Rest...>>
104 : : variant_alternative<_Np-1, variant<_Rest...>> {};
105 :
106 : template<typename _First, typename... _Rest>
107 : struct variant_alternative<0, variant<_First, _Rest...>>
108 : { using type = _First; };
109 :
110 : template<size_t _Np, typename _Variant>
111 : using variant_alternative_t =
112 : typename variant_alternative<_Np, _Variant>::type;
113 :
114 : template<size_t _Np, typename _Variant>
115 : struct variant_alternative<_Np, const _Variant>
116 : { using type = add_const_t<variant_alternative_t<_Np, _Variant>>; };
117 :
118 : template<size_t _Np, typename _Variant>
119 : struct variant_alternative<_Np, volatile _Variant>
120 : { using type = add_volatile_t<variant_alternative_t<_Np, _Variant>>; };
121 :
122 : template<size_t _Np, typename _Variant>
123 : struct variant_alternative<_Np, const volatile _Variant>
124 : { using type = add_cv_t<variant_alternative_t<_Np, _Variant>>; };
125 :
126 : inline constexpr size_t variant_npos = -1;
127 :
128 : template<size_t _Np, typename... _Types>
129 : constexpr variant_alternative_t<_Np, variant<_Types...>>&
130 : get(variant<_Types...>&);
131 :
132 : template<size_t _Np, typename... _Types>
133 : constexpr variant_alternative_t<_Np, variant<_Types...>>&&
134 : get(variant<_Types...>&&);
135 :
136 : template<size_t _Np, typename... _Types>
137 : constexpr variant_alternative_t<_Np, variant<_Types...>> const&
138 : get(const variant<_Types...>&);
139 :
140 : template<size_t _Np, typename... _Types>
141 : constexpr variant_alternative_t<_Np, variant<_Types...>> const&&
142 : get(const variant<_Types...>&&);
143 :
144 : template<typename _Result_type, typename _Visitor, typename... _Variants>
145 : constexpr decltype(auto)
146 : __do_visit(_Visitor&& __visitor, _Variants&&... __variants);
147 :
148 : template <typename... _Types, typename _Tp>
149 : decltype(auto)
150 4 : __variant_cast(_Tp&& __rhs)
151 : {
152 : if constexpr (is_lvalue_reference_v<_Tp>)
153 : {
154 : if constexpr (is_const_v<remove_reference_t<_Tp>>)
155 1 : return static_cast<const variant<_Types...>&>(__rhs);
156 : else
157 3 : return static_cast<variant<_Types...>&>(__rhs);
158 : }
159 : else
160 : return static_cast<variant<_Types...>&&>(__rhs);
161 : }
162 :
163 : namespace __detail
164 : {
165 : namespace __variant
166 : {
167 : // Returns the first appearance of _Tp in _Types.
168 : // Returns sizeof...(_Types) if _Tp is not in _Types.
169 : template<typename _Tp, typename... _Types>
170 : struct __index_of : std::integral_constant<size_t, 0> {};
171 :
172 : template<typename _Tp, typename... _Types>
173 : inline constexpr size_t __index_of_v = __index_of<_Tp, _Types...>::value;
174 :
175 : template<typename _Tp, typename _First, typename... _Rest>
176 : struct __index_of<_Tp, _First, _Rest...> :
177 : std::integral_constant<size_t, is_same_v<_Tp, _First>
178 : ? 0 : __index_of_v<_Tp, _Rest...> + 1> {};
179 :
180 : // used for raw visitation
181 : struct __variant_cookie {};
182 : // used for raw visitation with indices passed in
183 : struct __variant_idx_cookie { using type = __variant_idx_cookie; };
184 : // Used to enable deduction (and same-type checking) for std::visit:
185 : template<typename _Tp> struct __deduce_visit_result { using type = _Tp; };
186 :
187 : // Visit variants that might be valueless.
188 : template<typename _Visitor, typename... _Variants>
189 : constexpr void
190 1 : __raw_visit(_Visitor&& __visitor, _Variants&&... __variants)
191 : {
192 1 : std::__do_visit<__variant_cookie>(std::forward<_Visitor>(__visitor),
193 : std::forward<_Variants>(__variants)...);
194 1 : }
195 :
196 : // Visit variants that might be valueless, passing indices to the visitor.
197 : template<typename _Visitor, typename... _Variants>
198 : constexpr void
199 : __raw_idx_visit(_Visitor&& __visitor, _Variants&&... __variants)
200 : {
201 : std::__do_visit<__variant_idx_cookie>(std::forward<_Visitor>(__visitor),
202 : std::forward<_Variants>(__variants)...);
203 : }
204 :
205 : // The __as function templates implement the exposition-only "as-variant"
206 :
207 : template<typename... _Types>
208 : constexpr std::variant<_Types...>&
209 : __as(std::variant<_Types...>& __v) noexcept
210 : { return __v; }
211 :
212 : template<typename... _Types>
213 : constexpr const std::variant<_Types...>&
214 : __as(const std::variant<_Types...>& __v) noexcept
215 : { return __v; }
216 :
217 : template<typename... _Types>
218 : constexpr std::variant<_Types...>&&
219 : __as(std::variant<_Types...>&& __v) noexcept
220 : { return std::move(__v); }
221 :
222 : template<typename... _Types>
223 : constexpr const std::variant<_Types...>&&
224 : __as(const std::variant<_Types...>&& __v) noexcept
225 : { return std::move(__v); }
226 :
227 : // _Uninitialized<T> is guaranteed to be a trivially destructible type,
228 : // even if T is not.
229 : template<typename _Type, bool = std::is_trivially_destructible_v<_Type>>
230 : struct _Uninitialized;
231 :
232 : template<typename _Type>
233 : struct _Uninitialized<_Type, true>
234 : {
235 : template<typename... _Args>
236 : constexpr
237 1 : _Uninitialized(in_place_index_t<0>, _Args&&... __args)
238 : : _M_storage(std::forward<_Args>(__args)...)
239 1 : { }
240 :
241 0 : constexpr const _Type& _M_get() const & noexcept
242 0 : { return _M_storage; }
243 :
244 40 : constexpr _Type& _M_get() & noexcept
245 40 : { return _M_storage; }
246 :
247 : constexpr const _Type&& _M_get() const && noexcept
248 : { return std::move(_M_storage); }
249 :
250 : constexpr _Type&& _M_get() && noexcept
251 : { return std::move(_M_storage); }
252 :
253 : _Type _M_storage;
254 : };
255 :
256 : template<typename _Type>
257 : struct _Uninitialized<_Type, false>
258 : {
259 : template<typename... _Args>
260 : constexpr
261 : _Uninitialized(in_place_index_t<0>, _Args&&... __args)
262 : {
263 : ::new ((void*)std::addressof(_M_storage))
264 : _Type(std::forward<_Args>(__args)...);
265 : }
266 :
267 2 : const _Type& _M_get() const & noexcept
268 2 : { return *_M_storage._M_ptr(); }
269 :
270 4 : _Type& _M_get() & noexcept
271 4 : { return *_M_storage._M_ptr(); }
272 :
273 : const _Type&& _M_get() const && noexcept
274 : { return std::move(*_M_storage._M_ptr()); }
275 :
276 : _Type&& _M_get() && noexcept
277 : { return std::move(*_M_storage._M_ptr()); }
278 :
279 : __gnu_cxx::__aligned_membuf<_Type> _M_storage;
280 : };
281 :
282 : template<typename _Union>
283 : constexpr decltype(auto)
284 46 : __get(in_place_index_t<0>, _Union&& __u) noexcept
285 46 : { return std::forward<_Union>(__u)._M_first._M_get(); }
286 :
287 : template<size_t _Np, typename _Union>
288 : constexpr decltype(auto)
289 45 : __get(in_place_index_t<_Np>, _Union&& __u) noexcept
290 : {
291 45 : return __variant::__get(in_place_index<_Np-1>,
292 45 : std::forward<_Union>(__u)._M_rest);
293 : }
294 :
295 : // Returns the typed storage for __v.
296 : template<size_t _Np, typename _Variant>
297 : constexpr decltype(auto)
298 46 : __get(_Variant&& __v) noexcept
299 : {
300 46 : return __variant::__get(std::in_place_index<_Np>,
301 46 : std::forward<_Variant>(__v)._M_u);
302 : }
303 :
304 : template<typename... _Types>
305 : struct _Traits
306 : {
307 : static constexpr bool _S_default_ctor =
308 : is_default_constructible_v<typename _Nth_type<0, _Types...>::type>;
309 : static constexpr bool _S_copy_ctor =
310 : (is_copy_constructible_v<_Types> && ...);
311 : static constexpr bool _S_move_ctor =
312 : (is_move_constructible_v<_Types> && ...);
313 : static constexpr bool _S_copy_assign =
314 : _S_copy_ctor
315 : && (is_copy_assignable_v<_Types> && ...);
316 : static constexpr bool _S_move_assign =
317 : _S_move_ctor
318 : && (is_move_assignable_v<_Types> && ...);
319 :
320 : static constexpr bool _S_trivial_dtor =
321 : (is_trivially_destructible_v<_Types> && ...);
322 : static constexpr bool _S_trivial_copy_ctor =
323 : (is_trivially_copy_constructible_v<_Types> && ...);
324 : static constexpr bool _S_trivial_move_ctor =
325 : (is_trivially_move_constructible_v<_Types> && ...);
326 : static constexpr bool _S_trivial_copy_assign =
327 : _S_trivial_dtor && _S_trivial_copy_ctor
328 : && (is_trivially_copy_assignable_v<_Types> && ...);
329 : static constexpr bool _S_trivial_move_assign =
330 : _S_trivial_dtor && _S_trivial_move_ctor
331 : && (is_trivially_move_assignable_v<_Types> && ...);
332 :
333 : // The following nothrow traits are for non-trivial SMFs. Trivial SMFs
334 : // are always nothrow.
335 : static constexpr bool _S_nothrow_default_ctor =
336 : is_nothrow_default_constructible_v<
337 : typename _Nth_type<0, _Types...>::type>;
338 : static constexpr bool _S_nothrow_copy_ctor = false;
339 : static constexpr bool _S_nothrow_move_ctor =
340 : (is_nothrow_move_constructible_v<_Types> && ...);
341 : static constexpr bool _S_nothrow_copy_assign = false;
342 : static constexpr bool _S_nothrow_move_assign =
343 : _S_nothrow_move_ctor
344 : && (is_nothrow_move_assignable_v<_Types> && ...);
345 : };
346 :
347 : // Defines members and ctors.
348 : template<typename... _Types>
349 : union _Variadic_union { };
350 :
351 : template<typename _First, typename... _Rest>
352 : union _Variadic_union<_First, _Rest...>
353 : {
354 3 : constexpr _Variadic_union() : _M_rest() { }
355 :
356 : template<typename... _Args>
357 1 : constexpr _Variadic_union(in_place_index_t<0>, _Args&&... __args)
358 1 : : _M_first(in_place_index<0>, std::forward<_Args>(__args)...)
359 1 : { }
360 :
361 : template<size_t _Np, typename... _Args>
362 : constexpr _Variadic_union(in_place_index_t<_Np>, _Args&&... __args)
363 : : _M_rest(in_place_index<_Np-1>, std::forward<_Args>(__args)...)
364 : { }
365 :
366 : _Uninitialized<_First> _M_first;
367 : _Variadic_union<_Rest...> _M_rest;
368 : };
369 :
370 : // _Never_valueless_alt is true for variant alternatives that can
371 : // always be placed in a variant without it becoming valueless.
372 :
373 : // For suitably-small, trivially copyable types we can create temporaries
374 : // on the stack and then memcpy them into place.
375 : template<typename _Tp>
376 : struct _Never_valueless_alt
377 : : __and_<bool_constant<sizeof(_Tp) <= 256>, is_trivially_copyable<_Tp>>
378 : { };
379 :
380 : // Specialize _Never_valueless_alt for other types which have a
381 : // non-throwing and cheap move construction and move assignment operator,
382 : // so that emplacing the type will provide the strong exception-safety
383 : // guarantee, by creating and moving a temporary.
384 : // Whether _Never_valueless_alt<T> is true or not affects the ABI of a
385 : // variant using that alternative, so we can't change the value later!
386 :
387 : // True if every alternative in _Types... can be emplaced in a variant
388 : // without it becoming valueless. If this is true, variant<_Types...>
389 : // can never be valueless, which enables some minor optimizations.
390 : template <typename... _Types>
391 : constexpr bool __never_valueless()
392 : {
393 : return _Traits<_Types...>::_S_move_assign
394 : && (_Never_valueless_alt<_Types>::value && ...);
395 : }
396 :
397 : // Defines index and the dtor, possibly trivial.
398 : template<bool __trivially_destructible, typename... _Types>
399 : struct _Variant_storage;
400 :
401 : template <typename... _Types>
402 : using __select_index =
403 : typename __select_int::_Select_int_base<sizeof...(_Types),
404 : unsigned char,
405 : unsigned short>::type::value_type;
406 :
407 : template<typename... _Types>
408 : struct _Variant_storage<false, _Types...>
409 : {
410 : constexpr
411 1 : _Variant_storage()
412 1 : : _M_index(static_cast<__index_type>(variant_npos))
413 1 : { }
414 :
415 : template<size_t _Np, typename... _Args>
416 : constexpr
417 1 : _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
418 1 : : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
419 1 : _M_index{_Np}
420 1 : { }
421 :
422 3 : void _M_reset()
423 : {
424 3 : if (!_M_valid()) [[unlikely]]
425 0 : return;
426 :
427 9 : std::__do_visit<void>([](auto&& __this_mem) mutable
428 : {
429 3 : std::_Destroy(std::__addressof(__this_mem));
430 : }, __variant_cast<_Types...>(*this));
431 :
432 3 : _M_index = static_cast<__index_type>(variant_npos);
433 : }
434 :
435 2 : ~_Variant_storage()
436 2 : { _M_reset(); }
437 :
438 : constexpr bool
439 3 : _M_valid() const noexcept
440 : {
441 : if constexpr (__variant::__never_valueless<_Types...>())
442 : return true;
443 3 : return this->_M_index != __index_type(variant_npos);
444 : }
445 :
446 : _Variadic_union<_Types...> _M_u;
447 : using __index_type = __select_index<_Types...>;
448 : __index_type _M_index;
449 : };
450 :
451 : template<typename... _Types>
452 : struct _Variant_storage<true, _Types...>
453 : {
454 : constexpr
455 : _Variant_storage()
456 : : _M_index(static_cast<__index_type>(variant_npos))
457 : { }
458 :
459 : template<size_t _Np, typename... _Args>
460 : constexpr
461 : _Variant_storage(in_place_index_t<_Np>, _Args&&... __args)
462 : : _M_u(in_place_index<_Np>, std::forward<_Args>(__args)...),
463 : _M_index{_Np}
464 : { }
465 :
466 13 : void _M_reset() noexcept
467 13 : { _M_index = static_cast<__index_type>(variant_npos); }
468 :
469 : constexpr bool
470 0 : _M_valid() const noexcept
471 : {
472 : if constexpr (__variant::__never_valueless<_Types...>())
473 0 : return true;
474 : return this->_M_index != static_cast<__index_type>(variant_npos);
475 : }
476 :
477 : _Variadic_union<_Types...> _M_u;
478 : using __index_type = __select_index<_Types...>;
479 : __index_type _M_index;
480 : };
481 :
482 : template<typename... _Types>
483 : using _Variant_storage_alias =
484 : _Variant_storage<_Traits<_Types...>::_S_trivial_dtor, _Types...>;
485 :
486 : template<typename _Tp, typename _Up>
487 1 : void __variant_construct_single(_Tp&& __lhs, _Up&& __rhs_mem)
488 : {
489 1 : void* __storage = std::addressof(__lhs._M_u);
490 : using _Type = remove_reference_t<decltype(__rhs_mem)>;
491 : if constexpr (!is_same_v<_Type, __variant_cookie>)
492 1 : ::new (__storage)
493 1 : _Type(std::forward<decltype(__rhs_mem)>(__rhs_mem));
494 1 : }
495 :
496 : template<typename... _Types, typename _Tp, typename _Up>
497 1 : void __variant_construct(_Tp&& __lhs, _Up&& __rhs)
498 : {
499 1 : __lhs._M_index = __rhs._M_index;
500 4 : __variant::__raw_visit([&__lhs](auto&& __rhs_mem) mutable
501 : {
502 1 : __variant_construct_single(std::forward<_Tp>(__lhs),
503 : std::forward<decltype(__rhs_mem)>(__rhs_mem));
504 : }, __variant_cast<_Types...>(std::forward<_Up>(__rhs)));
505 1 : }
506 :
507 : // The following are (Copy|Move) (ctor|assign) layers for forwarding
508 : // triviality and handling non-trivial SMF behaviors.
509 :
510 : template<bool, typename... _Types>
511 : struct _Copy_ctor_base : _Variant_storage_alias<_Types...>
512 : {
513 : using _Base = _Variant_storage_alias<_Types...>;
514 : using _Base::_Base;
515 :
516 1 : _Copy_ctor_base(const _Copy_ctor_base& __rhs)
517 : noexcept(_Traits<_Types...>::_S_nothrow_copy_ctor)
518 1 : {
519 1 : __variant_construct<_Types...>(*this, __rhs);
520 1 : }
521 :
522 : _Copy_ctor_base(_Copy_ctor_base&&) = default;
523 : _Copy_ctor_base& operator=(const _Copy_ctor_base&) = default;
524 : _Copy_ctor_base& operator=(_Copy_ctor_base&&) = default;
525 : };
526 :
527 : template<typename... _Types>
528 : struct _Copy_ctor_base<true, _Types...> : _Variant_storage_alias<_Types...>
529 : {
530 : using _Base = _Variant_storage_alias<_Types...>;
531 : using _Base::_Base;
532 : };
533 :
534 : template<typename... _Types>
535 : using _Copy_ctor_alias =
536 : _Copy_ctor_base<_Traits<_Types...>::_S_trivial_copy_ctor, _Types...>;
537 :
538 : template<bool, typename... _Types>
539 : struct _Move_ctor_base : _Copy_ctor_alias<_Types...>
540 : {
541 : using _Base = _Copy_ctor_alias<_Types...>;
542 : using _Base::_Base;
543 :
544 : _Move_ctor_base(_Move_ctor_base&& __rhs)
545 : noexcept(_Traits<_Types...>::_S_nothrow_move_ctor)
546 : {
547 : __variant_construct<_Types...>(*this, std::move(__rhs));
548 : }
549 :
550 : template<typename _Up>
551 : void _M_destructive_move(unsigned short __rhs_index, _Up&& __rhs)
552 : {
553 : this->_M_reset();
554 : __variant_construct_single(*this, std::forward<_Up>(__rhs));
555 : this->_M_index = __rhs_index;
556 : }
557 :
558 : template<typename _Up>
559 : void _M_destructive_copy(unsigned short __rhs_index, const _Up& __rhs)
560 : {
561 : this->_M_reset();
562 : __variant_construct_single(*this, __rhs);
563 : this->_M_index = __rhs_index;
564 : }
565 :
566 1 : _Move_ctor_base(const _Move_ctor_base&) = default;
567 : _Move_ctor_base& operator=(const _Move_ctor_base&) = default;
568 : _Move_ctor_base& operator=(_Move_ctor_base&&) = default;
569 : };
570 :
571 : template<typename... _Types>
572 : struct _Move_ctor_base<true, _Types...> : _Copy_ctor_alias<_Types...>
573 : {
574 : using _Base = _Copy_ctor_alias<_Types...>;
575 : using _Base::_Base;
576 :
577 : template<typename _Up>
578 : void _M_destructive_move(unsigned short __rhs_index, _Up&& __rhs)
579 : {
580 : this->_M_reset();
581 : __variant_construct_single(*this, std::forward<_Up>(__rhs));
582 : this->_M_index = __rhs_index;
583 : }
584 :
585 : template<typename _Up>
586 : void _M_destructive_copy(unsigned short __rhs_index, const _Up& __rhs)
587 : {
588 : this->_M_reset();
589 : __variant_construct_single(*this, __rhs);
590 : this->_M_index = __rhs_index;
591 : }
592 : };
593 :
594 : template<typename... _Types>
595 : using _Move_ctor_alias =
596 : _Move_ctor_base<_Traits<_Types...>::_S_trivial_move_ctor, _Types...>;
597 :
598 : template<bool, typename... _Types>
599 : struct _Copy_assign_base : _Move_ctor_alias<_Types...>
600 : {
601 : using _Base = _Move_ctor_alias<_Types...>;
602 : using _Base::_Base;
603 :
604 : _Copy_assign_base&
605 : operator=(const _Copy_assign_base& __rhs)
606 : noexcept(_Traits<_Types...>::_S_nothrow_copy_assign)
607 : {
608 : __variant::__raw_idx_visit(
609 : [this](auto&& __rhs_mem, auto __rhs_index) mutable
610 : {
611 : if constexpr (__rhs_index != variant_npos)
612 : {
613 : if (this->_M_index == __rhs_index)
614 : __variant::__get<__rhs_index>(*this) = __rhs_mem;
615 : else
616 : {
617 : using __rhs_type = __remove_cvref_t<decltype(__rhs_mem)>;
618 : if constexpr (is_nothrow_copy_constructible_v<__rhs_type>
619 : || !is_nothrow_move_constructible_v<__rhs_type>)
620 : // The standard says this->emplace<__rhs_type>(__rhs_mem)
621 : // should be used here, but _M_destructive_copy is
622 : // equivalent in this case. Either copy construction
623 : // doesn't throw, so _M_destructive_copy gives strong
624 : // exception safety guarantee, or both copy construction
625 : // and move construction can throw, so emplace only gives
626 : // basic exception safety anyway.
627 : this->_M_destructive_copy(__rhs_index, __rhs_mem);
628 : else
629 : __variant_cast<_Types...>(*this)
630 : = variant<_Types...>(std::in_place_index<__rhs_index>,
631 : __rhs_mem);
632 : }
633 : }
634 : else
635 : this->_M_reset();
636 : }, __variant_cast<_Types...>(__rhs));
637 : return *this;
638 : }
639 :
640 1 : _Copy_assign_base(const _Copy_assign_base&) = default;
641 : _Copy_assign_base(_Copy_assign_base&&) = default;
642 : _Copy_assign_base& operator=(_Copy_assign_base&&) = default;
643 : };
644 :
645 : template<typename... _Types>
646 : struct _Copy_assign_base<true, _Types...> : _Move_ctor_alias<_Types...>
647 : {
648 : using _Base = _Move_ctor_alias<_Types...>;
649 : using _Base::_Base;
650 : };
651 :
652 : template<typename... _Types>
653 : using _Copy_assign_alias =
654 : _Copy_assign_base<_Traits<_Types...>::_S_trivial_copy_assign, _Types...>;
655 :
656 : template<bool, typename... _Types>
657 : struct _Move_assign_base : _Copy_assign_alias<_Types...>
658 : {
659 : using _Base = _Copy_assign_alias<_Types...>;
660 : using _Base::_Base;
661 :
662 : _Move_assign_base&
663 : operator=(_Move_assign_base&& __rhs)
664 : noexcept(_Traits<_Types...>::_S_nothrow_move_assign)
665 : {
666 : __variant::__raw_idx_visit(
667 : [this](auto&& __rhs_mem, auto __rhs_index) mutable
668 : {
669 : if constexpr (__rhs_index != variant_npos)
670 : {
671 : if (this->_M_index == __rhs_index)
672 : __variant::__get<__rhs_index>(*this) = std::move(__rhs_mem);
673 : else
674 : __variant_cast<_Types...>(*this)
675 : .template emplace<__rhs_index>(std::move(__rhs_mem));
676 : }
677 : else
678 : this->_M_reset();
679 : }, __variant_cast<_Types...>(__rhs));
680 : return *this;
681 : }
682 :
683 1 : _Move_assign_base(const _Move_assign_base&) = default;
684 : _Move_assign_base(_Move_assign_base&&) = default;
685 : _Move_assign_base& operator=(const _Move_assign_base&) = default;
686 : };
687 :
688 : template<typename... _Types>
689 : struct _Move_assign_base<true, _Types...> : _Copy_assign_alias<_Types...>
690 : {
691 : using _Base = _Copy_assign_alias<_Types...>;
692 : using _Base::_Base;
693 : };
694 :
695 : template<typename... _Types>
696 : using _Move_assign_alias =
697 : _Move_assign_base<_Traits<_Types...>::_S_trivial_move_assign, _Types...>;
698 :
699 : template<typename... _Types>
700 : struct _Variant_base : _Move_assign_alias<_Types...>
701 : {
702 : using _Base = _Move_assign_alias<_Types...>;
703 :
704 : constexpr
705 1 : _Variant_base()
706 : noexcept(_Traits<_Types...>::_S_nothrow_default_ctor)
707 1 : : _Variant_base(in_place_index<0>) { }
708 :
709 : template<size_t _Np, typename... _Args>
710 : constexpr explicit
711 1 : _Variant_base(in_place_index_t<_Np> __i, _Args&&... __args)
712 1 : : _Base(__i, std::forward<_Args>(__args)...)
713 1 : { }
714 :
715 1 : _Variant_base(const _Variant_base&) = default;
716 : _Variant_base(_Variant_base&&) = default;
717 : _Variant_base& operator=(const _Variant_base&) = default;
718 : _Variant_base& operator=(_Variant_base&&) = default;
719 : };
720 :
721 : // For how many times does _Tp appear in _Tuple?
722 : template<typename _Tp, typename _Tuple>
723 : struct __tuple_count;
724 :
725 : template<typename _Tp, typename _Tuple>
726 : inline constexpr size_t __tuple_count_v =
727 : __tuple_count<_Tp, _Tuple>::value;
728 :
729 : template<typename _Tp, typename... _Types>
730 : struct __tuple_count<_Tp, tuple<_Types...>>
731 : : integral_constant<size_t, 0> { };
732 :
733 : template<typename _Tp, typename _First, typename... _Rest>
734 : struct __tuple_count<_Tp, tuple<_First, _Rest...>>
735 : : integral_constant<
736 : size_t,
737 : __tuple_count_v<_Tp, tuple<_Rest...>> + is_same_v<_Tp, _First>> { };
738 :
739 : // TODO: Reuse this in <tuple> ?
740 : template<typename _Tp, typename... _Types>
741 : inline constexpr bool __exactly_once =
742 : __tuple_count_v<_Tp, tuple<_Types...>> == 1;
743 :
744 : // Helper used to check for valid conversions that don't involve narrowing.
745 : template<typename _Ti> struct _Arr { _Ti _M_x[1]; };
746 :
747 : // "Build an imaginary function FUN(Ti) for each alternative type Ti"
748 : template<size_t _Ind, typename _Tp, typename _Ti, typename = void>
749 : struct _Build_FUN
750 : {
751 : // This function means 'using _Build_FUN<I, T, Ti>::_S_fun;' is valid,
752 : // but only static functions will be considered in the call below.
753 : void _S_fun();
754 : };
755 :
756 : // "... for which Ti x[] = {std::forward<T>(t)}; is well-formed."
757 : template<size_t _Ind, typename _Tp, typename _Ti>
758 : struct _Build_FUN<_Ind, _Tp, _Ti,
759 : void_t<decltype(_Arr<_Ti>{{std::declval<_Tp>()}})>>
760 : {
761 : // This is the FUN function for type _Ti, with index _Ind
762 : static integral_constant<size_t, _Ind> _S_fun(_Ti);
763 : };
764 :
765 : template<typename _Tp, typename _Variant,
766 : typename = make_index_sequence<variant_size_v<_Variant>>>
767 : struct _Build_FUNs;
768 :
769 : template<typename _Tp, typename... _Ti, size_t... _Ind>
770 : struct _Build_FUNs<_Tp, variant<_Ti...>, index_sequence<_Ind...>>
771 : : _Build_FUN<_Ind, _Tp, _Ti>...
772 : {
773 : using _Build_FUN<_Ind, _Tp, _Ti>::_S_fun...;
774 : };
775 :
776 : // The index j of the overload FUN(Tj) selected by overload resolution
777 : // for FUN(std::forward<_Tp>(t))
778 : template<typename _Tp, typename _Variant>
779 : using _FUN_type
780 : = decltype(_Build_FUNs<_Tp, _Variant>::_S_fun(std::declval<_Tp>()));
781 :
782 : // The index selected for FUN(std::forward<T>(t)), or variant_npos if none.
783 : template<typename _Tp, typename _Variant, typename = void>
784 : struct __accepted_index
785 : : integral_constant<size_t, variant_npos>
786 : { };
787 :
788 : template<typename _Tp, typename _Variant>
789 : struct __accepted_index<_Tp, _Variant, void_t<_FUN_type<_Tp, _Variant>>>
790 : : _FUN_type<_Tp, _Variant>
791 : { };
792 :
793 : template <typename _Maybe_variant_cookie, typename _Variant>
794 : struct _Extra_visit_slot_needed
795 : {
796 : template <typename> struct _Variant_never_valueless;
797 :
798 : template <typename... _Types>
799 : struct _Variant_never_valueless<variant<_Types...>>
800 : : bool_constant<__variant::__never_valueless<_Types...>()> {};
801 :
802 : static constexpr bool value =
803 : (is_same_v<_Maybe_variant_cookie, __variant_cookie>
804 : || is_same_v<_Maybe_variant_cookie, __variant_idx_cookie>)
805 : && !_Variant_never_valueless<__remove_cvref_t<_Variant>>::value;
806 : };
807 :
808 : // Used for storing a multi-dimensional vtable.
809 : template<typename _Tp, size_t... _Dimensions>
810 : struct _Multi_array;
811 :
812 : // Partial specialization with rank zero, stores a single _Tp element.
813 : template<typename _Tp>
814 : struct _Multi_array<_Tp>
815 : {
816 : template<typename>
817 : struct __untag_result
818 : : false_type
819 : { using element_type = _Tp; };
820 :
821 : template <typename... _Args>
822 : struct __untag_result<const void(*)(_Args...)>
823 : : false_type
824 : { using element_type = void(*)(_Args...); };
825 :
826 : template <typename... _Args>
827 : struct __untag_result<__variant_cookie(*)(_Args...)>
828 : : false_type
829 : { using element_type = void(*)(_Args...); };
830 :
831 : template <typename... _Args>
832 : struct __untag_result<__variant_idx_cookie(*)(_Args...)>
833 : : false_type
834 : { using element_type = void(*)(_Args...); };
835 :
836 : template <typename _Res, typename... _Args>
837 : struct __untag_result<__deduce_visit_result<_Res>(*)(_Args...)>
838 : : true_type
839 : { using element_type = _Res(*)(_Args...); };
840 :
841 : using __result_is_deduced = __untag_result<_Tp>;
842 :
843 : constexpr const typename __untag_result<_Tp>::element_type&
844 4 : _M_access() const
845 4 : { return _M_data; }
846 :
847 : typename __untag_result<_Tp>::element_type _M_data;
848 : };
849 :
850 : // Partial specialization with rank >= 1.
851 : template<typename _Ret,
852 : typename _Visitor,
853 : typename... _Variants,
854 : size_t __first, size_t... __rest>
855 : struct _Multi_array<_Ret(*)(_Visitor, _Variants...), __first, __rest...>
856 : {
857 : static constexpr size_t __index =
858 : sizeof...(_Variants) - sizeof...(__rest) - 1;
859 :
860 : using _Variant = typename _Nth_type<__index, _Variants...>::type;
861 :
862 : static constexpr int __do_cookie =
863 : _Extra_visit_slot_needed<_Ret, _Variant>::value ? 1 : 0;
864 :
865 : using _Tp = _Ret(*)(_Visitor, _Variants...);
866 :
867 : template<typename... _Args>
868 : constexpr decltype(auto)
869 4 : _M_access(size_t __first_index, _Args... __rest_indices) const
870 : {
871 1 : return _M_arr[__first_index + __do_cookie]
872 4 : ._M_access(__rest_indices...);
873 : }
874 :
875 : _Multi_array<_Tp, __rest...> _M_arr[__first + __do_cookie];
876 : };
877 :
878 : // Creates a multi-dimensional vtable recursively.
879 : //
880 : // For example,
881 : // visit([](auto, auto){},
882 : // variant<int, char>(), // typedef'ed as V1
883 : // variant<float, double, long double>()) // typedef'ed as V2
884 : // will trigger instantiations of:
885 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 2, 3>,
886 : // tuple<V1&&, V2&&>, std::index_sequence<>>
887 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
888 : // tuple<V1&&, V2&&>, std::index_sequence<0>>
889 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
890 : // tuple<V1&&, V2&&>, std::index_sequence<0, 0>>
891 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
892 : // tuple<V1&&, V2&&>, std::index_sequence<0, 1>>
893 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
894 : // tuple<V1&&, V2&&>, std::index_sequence<0, 2>>
895 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&), 3>,
896 : // tuple<V1&&, V2&&>, std::index_sequence<1>>
897 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
898 : // tuple<V1&&, V2&&>, std::index_sequence<1, 0>>
899 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
900 : // tuple<V1&&, V2&&>, std::index_sequence<1, 1>>
901 : // __gen_vtable_impl<_Multi_array<void(*)(V1&&, V2&&)>,
902 : // tuple<V1&&, V2&&>, std::index_sequence<1, 2>>
903 : // The returned multi-dimensional vtable can be fast accessed by the visitor
904 : // using index calculation.
905 : template<typename _Array_type, typename _Index_seq>
906 : struct __gen_vtable_impl;
907 :
908 : // Defines the _S_apply() member that returns a _Multi_array populated
909 : // with function pointers that perform the visitation expressions e(m)
910 : // for each valid pack of indexes into the variant types _Variants.
911 : //
912 : // This partial specialization builds up the index sequences by recursively
913 : // calling _S_apply() on the next specialization of __gen_vtable_impl.
914 : // The base case of the recursion defines the actual function pointers.
915 : template<typename _Result_type, typename _Visitor, size_t... __dimensions,
916 : typename... _Variants, size_t... __indices>
917 : struct __gen_vtable_impl<
918 : _Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>,
919 : std::index_sequence<__indices...>>
920 : {
921 : using _Next =
922 : remove_reference_t<typename _Nth_type<sizeof...(__indices),
923 : _Variants...>::type>;
924 : using _Array_type =
925 : _Multi_array<_Result_type (*)(_Visitor, _Variants...),
926 : __dimensions...>;
927 :
928 : static constexpr _Array_type
929 : _S_apply()
930 : {
931 : _Array_type __vtable{};
932 : _S_apply_all_alts(
933 : __vtable, make_index_sequence<variant_size_v<_Next>>());
934 : return __vtable;
935 : }
936 :
937 : template<size_t... __var_indices>
938 : static constexpr void
939 : _S_apply_all_alts(_Array_type& __vtable,
940 : std::index_sequence<__var_indices...>)
941 : {
942 : if constexpr (_Extra_visit_slot_needed<_Result_type, _Next>::value)
943 : (_S_apply_single_alt<true, __var_indices>(
944 : __vtable._M_arr[__var_indices + 1],
945 : &(__vtable._M_arr[0])), ...);
946 : else
947 : (_S_apply_single_alt<false, __var_indices>(
948 : __vtable._M_arr[__var_indices]), ...);
949 : }
950 :
951 : template<bool __do_cookie, size_t __index, typename _Tp>
952 : static constexpr void
953 : _S_apply_single_alt(_Tp& __element, _Tp* __cookie_element = nullptr)
954 : {
955 : if constexpr (__do_cookie)
956 : {
957 : __element = __gen_vtable_impl<
958 : _Tp,
959 : std::index_sequence<__indices..., __index>>::_S_apply();
960 : *__cookie_element = __gen_vtable_impl<
961 : _Tp,
962 : std::index_sequence<__indices..., variant_npos>>::_S_apply();
963 : }
964 : else
965 : {
966 : auto __tmp_element = __gen_vtable_impl<
967 : remove_reference_t<decltype(__element)>,
968 : std::index_sequence<__indices..., __index>>::_S_apply();
969 : static_assert(is_same_v<_Tp, decltype(__tmp_element)>,
970 : "std::visit requires the visitor to have the same "
971 : "return type for all alternatives of a variant");
972 : __element = __tmp_element;
973 : }
974 : }
975 : };
976 :
977 : // This partial specialization is the base case for the recursion.
978 : // It populates a _Multi_array element with the address of a function
979 : // that invokes the visitor with the alternatives specified by __indices.
980 : template<typename _Result_type, typename _Visitor, typename... _Variants,
981 : size_t... __indices>
982 : struct __gen_vtable_impl<
983 : _Multi_array<_Result_type (*)(_Visitor, _Variants...)>,
984 : std::index_sequence<__indices...>>
985 : {
986 : using _Array_type =
987 : _Multi_array<_Result_type (*)(_Visitor, _Variants...)>;
988 :
989 : template<size_t __index, typename _Variant>
990 : static constexpr decltype(auto)
991 1 : __element_by_index_or_cookie(_Variant&& __var) noexcept
992 : {
993 : if constexpr (__index != variant_npos)
994 1 : return __variant::__get<__index>(std::forward<_Variant>(__var));
995 : else
996 0 : return __variant_cookie{};
997 : }
998 :
999 : static constexpr decltype(auto)
1000 4 : __visit_invoke(_Visitor&& __visitor, _Variants... __vars)
1001 : {
1002 : if constexpr (is_same_v<_Result_type, __variant_idx_cookie>)
1003 : // For raw visitation using indices, pass the indices to the visitor
1004 : // and discard the return value:
1005 : std::__invoke(std::forward<_Visitor>(__visitor),
1006 : __element_by_index_or_cookie<__indices>(
1007 : std::forward<_Variants>(__vars))...,
1008 : integral_constant<size_t, __indices>()...);
1009 : else if constexpr (is_same_v<_Result_type, __variant_cookie>)
1010 : // For raw visitation without indices, and discard the return value:
1011 1 : std::__invoke(std::forward<_Visitor>(__visitor),
1012 0 : __element_by_index_or_cookie<__indices>(
1013 : std::forward<_Variants>(__vars))...);
1014 : else if constexpr (_Array_type::__result_is_deduced::value)
1015 : // For the usual std::visit case deduce the return value:
1016 : return std::__invoke(std::forward<_Visitor>(__visitor),
1017 : __element_by_index_or_cookie<__indices>(
1018 : std::forward<_Variants>(__vars))...);
1019 : else // for std::visit<R> use INVOKE<R>
1020 3 : return std::__invoke_r<_Result_type>(
1021 : std::forward<_Visitor>(__visitor),
1022 3 : __variant::__get<__indices>(std::forward<_Variants>(__vars))...);
1023 1 : }
1024 :
1025 : static constexpr auto
1026 : _S_apply()
1027 : {
1028 : if constexpr (_Array_type::__result_is_deduced::value)
1029 : {
1030 : constexpr bool __visit_ret_type_mismatch =
1031 : !is_same_v<typename _Result_type::type,
1032 : decltype(__visit_invoke(std::declval<_Visitor>(),
1033 : std::declval<_Variants>()...))>;
1034 : if constexpr (__visit_ret_type_mismatch)
1035 : {
1036 : struct __cannot_match {};
1037 : return __cannot_match{};
1038 : }
1039 : else
1040 : return _Array_type{&__visit_invoke};
1041 : }
1042 : else
1043 : return _Array_type{&__visit_invoke};
1044 : }
1045 : };
1046 :
1047 : template<typename _Result_type, typename _Visitor, typename... _Variants>
1048 : struct __gen_vtable
1049 : {
1050 : using _Array_type =
1051 : _Multi_array<_Result_type (*)(_Visitor, _Variants...),
1052 : variant_size_v<remove_reference_t<_Variants>>...>;
1053 :
1054 : static constexpr _Array_type _S_vtable
1055 : = __gen_vtable_impl<_Array_type, std::index_sequence<>>::_S_apply();
1056 : };
1057 :
1058 : template<size_t _Np, typename _Tp>
1059 : struct _Base_dedup : public _Tp { };
1060 :
1061 : template<typename _Variant, typename __indices>
1062 : struct _Variant_hash_base;
1063 :
1064 : template<typename... _Types, size_t... __indices>
1065 : struct _Variant_hash_base<variant<_Types...>,
1066 : std::index_sequence<__indices...>>
1067 : : _Base_dedup<__indices, __poison_hash<remove_const_t<_Types>>>... { };
1068 :
1069 : // Equivalent to decltype(get<_Np>(as-variant(declval<_Variant>())))
1070 : template<size_t _Np, typename _Variant,
1071 : typename _AsV = decltype(__variant::__as(std::declval<_Variant>())),
1072 : typename _Tp = variant_alternative_t<_Np, remove_reference_t<_AsV>>>
1073 : using __get_t
1074 : = conditional_t<is_lvalue_reference_v<_Variant>, _Tp&, _Tp&&>;
1075 :
1076 : // Return type of std::visit.
1077 : template<typename _Visitor, typename... _Variants>
1078 : using __visit_result_t
1079 : = invoke_result_t<_Visitor, __get_t<0, _Variants>...>;
1080 :
1081 : template<typename _Tp, typename... _Types>
1082 : constexpr inline bool __same_types = (is_same_v<_Tp, _Types> && ...);
1083 :
1084 : template <typename _Visitor, typename _Variant, size_t... _Idxs>
1085 : constexpr bool __check_visitor_results(std::index_sequence<_Idxs...>)
1086 : {
1087 : return __same_types<
1088 : invoke_result_t<_Visitor, __get_t<_Idxs, _Variant>>...
1089 : >;
1090 : }
1091 :
1092 : template<size_t _Np, typename _Variant, typename... _Args>
1093 : inline void
1094 14 : __construct_by_index(_Variant& __v, _Args&&... __args)
1095 : {
1096 14 : auto&& __storage = __detail::__variant::__get<_Np>(__v);
1097 14 : ::new ((void*)std::addressof(__storage))
1098 : remove_reference_t<decltype(__storage)>
1099 14 : (std::forward<_Args>(__args)...);
1100 : // Construction didn't throw, so can set the new index now:
1101 14 : __v._M_index = _Np;
1102 14 : }
1103 :
1104 : } // namespace __variant
1105 : } // namespace __detail
1106 :
1107 : template<typename _Tp, typename... _Types>
1108 : constexpr bool
1109 52 : holds_alternative(const variant<_Types...>& __v) noexcept
1110 : {
1111 : static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
1112 : "T must occur exactly once in alternatives");
1113 52 : return __v.index() == __detail::__variant::__index_of_v<_Tp, _Types...>;
1114 : }
1115 :
1116 : template<typename _Tp, typename... _Types>
1117 13 : constexpr _Tp& get(variant<_Types...>& __v)
1118 : {
1119 : static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
1120 : "T must occur exactly once in alternatives");
1121 : static_assert(!is_void_v<_Tp>, "_Tp must not be void");
1122 13 : return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
1123 : }
1124 :
1125 : template<typename _Tp, typename... _Types>
1126 : constexpr _Tp&& get(variant<_Types...>&& __v)
1127 : {
1128 : static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
1129 : "T must occur exactly once in alternatives");
1130 : static_assert(!is_void_v<_Tp>, "_Tp must not be void");
1131 : return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
1132 : std::move(__v));
1133 : }
1134 :
1135 : template<typename _Tp, typename... _Types>
1136 : constexpr const _Tp& get(const variant<_Types...>& __v)
1137 : {
1138 : static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
1139 : "T must occur exactly once in alternatives");
1140 : static_assert(!is_void_v<_Tp>, "_Tp must not be void");
1141 : return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(__v);
1142 : }
1143 :
1144 : template<typename _Tp, typename... _Types>
1145 : constexpr const _Tp&& get(const variant<_Types...>&& __v)
1146 : {
1147 : static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
1148 : "T must occur exactly once in alternatives");
1149 : static_assert(!is_void_v<_Tp>, "_Tp must not be void");
1150 : return std::get<__detail::__variant::__index_of_v<_Tp, _Types...>>(
1151 : std::move(__v));
1152 : }
1153 :
1154 : template<size_t _Np, typename... _Types>
1155 : constexpr add_pointer_t<variant_alternative_t<_Np, variant<_Types...>>>
1156 : get_if(variant<_Types...>* __ptr) noexcept
1157 : {
1158 : using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
1159 : static_assert(_Np < sizeof...(_Types),
1160 : "The index must be in [0, number of alternatives)");
1161 : static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void");
1162 : if (__ptr && __ptr->index() == _Np)
1163 : return std::addressof(__detail::__variant::__get<_Np>(*__ptr));
1164 : return nullptr;
1165 : }
1166 :
1167 : template<size_t _Np, typename... _Types>
1168 : constexpr
1169 : add_pointer_t<const variant_alternative_t<_Np, variant<_Types...>>>
1170 1 : get_if(const variant<_Types...>* __ptr) noexcept
1171 : {
1172 : using _Alternative_type = variant_alternative_t<_Np, variant<_Types...>>;
1173 : static_assert(_Np < sizeof...(_Types),
1174 : "The index must be in [0, number of alternatives)");
1175 : static_assert(!is_void_v<_Alternative_type>, "_Tp must not be void");
1176 1 : if (__ptr && __ptr->index() == _Np)
1177 1 : return std::addressof(__detail::__variant::__get<_Np>(*__ptr));
1178 0 : return nullptr;
1179 : }
1180 :
1181 : template<typename _Tp, typename... _Types>
1182 : constexpr add_pointer_t<_Tp>
1183 : get_if(variant<_Types...>* __ptr) noexcept
1184 : {
1185 : static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
1186 : "T must occur exactly once in alternatives");
1187 : static_assert(!is_void_v<_Tp>, "_Tp must not be void");
1188 : return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(
1189 : __ptr);
1190 : }
1191 :
1192 : template<typename _Tp, typename... _Types>
1193 : constexpr add_pointer_t<const _Tp>
1194 1 : get_if(const variant<_Types...>* __ptr) noexcept
1195 : {
1196 : static_assert(__detail::__variant::__exactly_once<_Tp, _Types...>,
1197 : "T must occur exactly once in alternatives");
1198 : static_assert(!is_void_v<_Tp>, "_Tp must not be void");
1199 1 : return std::get_if<__detail::__variant::__index_of_v<_Tp, _Types...>>(
1200 1 : __ptr);
1201 : }
1202 :
1203 : struct monostate { };
1204 :
1205 : #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP, __NAME) \
1206 : template<typename... _Types> \
1207 : constexpr bool operator __OP(const variant<_Types...>& __lhs, \
1208 : const variant<_Types...>& __rhs) \
1209 : { \
1210 : bool __ret = true; \
1211 : __detail::__variant::__raw_idx_visit( \
1212 : [&__ret, &__lhs] (auto&& __rhs_mem, auto __rhs_index) mutable \
1213 : { \
1214 : if constexpr (__rhs_index != variant_npos) \
1215 : { \
1216 : if (__lhs.index() == __rhs_index) \
1217 : { \
1218 : auto& __this_mem = std::get<__rhs_index>(__lhs); \
1219 : __ret = __this_mem __OP __rhs_mem; \
1220 : } \
1221 : else \
1222 : __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \
1223 : } \
1224 : else \
1225 : __ret = (__lhs.index() + 1) __OP (__rhs_index + 1); \
1226 : }, __rhs); \
1227 : return __ret; \
1228 : }
1229 :
1230 : _VARIANT_RELATION_FUNCTION_TEMPLATE(<, less)
1231 : _VARIANT_RELATION_FUNCTION_TEMPLATE(<=, less_equal)
1232 : _VARIANT_RELATION_FUNCTION_TEMPLATE(==, equal)
1233 : _VARIANT_RELATION_FUNCTION_TEMPLATE(!=, not_equal)
1234 : _VARIANT_RELATION_FUNCTION_TEMPLATE(>=, greater_equal)
1235 : _VARIANT_RELATION_FUNCTION_TEMPLATE(>, greater)
1236 :
1237 : #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1238 :
1239 : constexpr bool operator==(monostate, monostate) noexcept { return true; }
1240 :
1241 : #ifdef __cpp_lib_three_way_comparison
1242 : template<typename... _Types>
1243 : requires (three_way_comparable<_Types> && ...)
1244 : constexpr
1245 : common_comparison_category_t<compare_three_way_result_t<_Types>...>
1246 : operator<=>(const variant<_Types...>& __v, const variant<_Types...>& __w)
1247 : {
1248 : common_comparison_category_t<compare_three_way_result_t<_Types>...> __ret
1249 : = strong_ordering::equal;
1250 :
1251 : __detail::__variant::__raw_idx_visit(
1252 : [&__ret, &__v] (auto&& __w_mem, auto __w_index) mutable
1253 : {
1254 : if constexpr (__w_index != variant_npos)
1255 : {
1256 : if (__v.index() == __w_index)
1257 : {
1258 : auto& __this_mem = std::get<__w_index>(__v);
1259 : __ret = __this_mem <=> __w_mem;
1260 : return;
1261 : }
1262 : }
1263 : __ret = (__v.index() + 1) <=> (__w_index + 1);
1264 : }, __w);
1265 : return __ret;
1266 : }
1267 :
1268 : constexpr strong_ordering
1269 : operator<=>(monostate, monostate) noexcept { return strong_ordering::equal; }
1270 : #else
1271 : constexpr bool operator!=(monostate, monostate) noexcept { return false; }
1272 : constexpr bool operator<(monostate, monostate) noexcept { return false; }
1273 : constexpr bool operator>(monostate, monostate) noexcept { return false; }
1274 : constexpr bool operator<=(monostate, monostate) noexcept { return true; }
1275 : constexpr bool operator>=(monostate, monostate) noexcept { return true; }
1276 : #endif
1277 :
1278 : template<typename _Visitor, typename... _Variants>
1279 : constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...>
1280 : visit(_Visitor&&, _Variants&&...);
1281 :
1282 : template<typename... _Types>
1283 : inline enable_if_t<(is_move_constructible_v<_Types> && ...)
1284 : && (is_swappable_v<_Types> && ...)>
1285 : swap(variant<_Types...>& __lhs, variant<_Types...>& __rhs)
1286 : noexcept(noexcept(__lhs.swap(__rhs)))
1287 : { __lhs.swap(__rhs); }
1288 :
1289 : template<typename... _Types>
1290 : enable_if_t<!((is_move_constructible_v<_Types> && ...)
1291 : && (is_swappable_v<_Types> && ...))>
1292 : swap(variant<_Types...>&, variant<_Types...>&) = delete;
1293 :
1294 : class bad_variant_access : public exception
1295 : {
1296 : public:
1297 : bad_variant_access() noexcept { }
1298 :
1299 0 : const char* what() const noexcept override
1300 0 : { return _M_reason; }
1301 :
1302 : private:
1303 0 : bad_variant_access(const char* __reason) noexcept : _M_reason(__reason) { }
1304 :
1305 : // Must point to a string with static storage duration:
1306 : const char* _M_reason = "bad variant access";
1307 :
1308 : friend void __throw_bad_variant_access(const char* __what);
1309 : };
1310 :
1311 : // Must only be called with a string literal
1312 : inline void
1313 0 : __throw_bad_variant_access(const char* __what)
1314 0 : { _GLIBCXX_THROW_OR_ABORT(bad_variant_access(__what)); }
1315 :
1316 : inline void
1317 0 : __throw_bad_variant_access(bool __valueless)
1318 : {
1319 0 : if (__valueless) [[__unlikely__]]
1320 0 : __throw_bad_variant_access("std::get: variant is valueless");
1321 : else
1322 0 : __throw_bad_variant_access("std::get: wrong index for variant");
1323 0 : }
1324 :
1325 : template<typename... _Types>
1326 : class variant
1327 : : private __detail::__variant::_Variant_base<_Types...>,
1328 : private _Enable_default_constructor<
1329 : __detail::__variant::_Traits<_Types...>::_S_default_ctor,
1330 : variant<_Types...>>,
1331 : private _Enable_copy_move<
1332 : __detail::__variant::_Traits<_Types...>::_S_copy_ctor,
1333 : __detail::__variant::_Traits<_Types...>::_S_copy_assign,
1334 : __detail::__variant::_Traits<_Types...>::_S_move_ctor,
1335 : __detail::__variant::_Traits<_Types...>::_S_move_assign,
1336 : variant<_Types...>>
1337 : {
1338 : private:
1339 : template <typename... _UTypes, typename _Tp>
1340 : friend decltype(auto) __variant_cast(_Tp&&);
1341 : template<size_t _Np, typename _Variant, typename... _Args>
1342 : friend void
1343 : __detail::__variant::__construct_by_index(_Variant& __v,
1344 : _Args&&... __args);
1345 :
1346 : static_assert(sizeof...(_Types) > 0,
1347 : "variant must have at least one alternative");
1348 : static_assert(!(std::is_reference_v<_Types> || ...),
1349 : "variant must have no reference alternative");
1350 : static_assert(!(std::is_void_v<_Types> || ...),
1351 : "variant must have no void alternative");
1352 :
1353 : using _Base = __detail::__variant::_Variant_base<_Types...>;
1354 : using _Default_ctor_enabler =
1355 : _Enable_default_constructor<
1356 : __detail::__variant::_Traits<_Types...>::_S_default_ctor,
1357 : variant<_Types...>>;
1358 :
1359 : template<typename _Tp>
1360 : static constexpr bool __not_self
1361 : = !is_same_v<__remove_cvref_t<_Tp>, variant>;
1362 :
1363 : template<typename _Tp>
1364 : static constexpr bool
1365 : __exactly_once = __detail::__variant::__exactly_once<_Tp, _Types...>;
1366 :
1367 : template<typename _Tp>
1368 : static constexpr size_t __accepted_index
1369 : = __detail::__variant::__accepted_index<_Tp, variant>::value;
1370 :
1371 : template<size_t _Np, typename = enable_if_t<(_Np < sizeof...(_Types))>>
1372 : using __to_type = variant_alternative_t<_Np, variant>;
1373 :
1374 : template<typename _Tp, typename = enable_if_t<__not_self<_Tp>>>
1375 : using __accepted_type = __to_type<__accepted_index<_Tp>>;
1376 :
1377 : template<typename _Tp>
1378 : static constexpr size_t __index_of =
1379 : __detail::__variant::__index_of_v<_Tp, _Types...>;
1380 :
1381 : using _Traits = __detail::__variant::_Traits<_Types...>;
1382 :
1383 : template<typename _Tp>
1384 : struct __is_in_place_tag : false_type { };
1385 : template<typename _Tp>
1386 : struct __is_in_place_tag<in_place_type_t<_Tp>> : true_type { };
1387 : template<size_t _Np>
1388 : struct __is_in_place_tag<in_place_index_t<_Np>> : true_type { };
1389 :
1390 : template<typename _Tp>
1391 : static constexpr bool __not_in_place_tag
1392 : = !__is_in_place_tag<__remove_cvref_t<_Tp>>::value;
1393 :
1394 : public:
1395 1 : variant() = default;
1396 1 : variant(const variant& __rhs) = default;
1397 : variant(variant&&) = default;
1398 : variant& operator=(const variant&) = default;
1399 : variant& operator=(variant&&) = default;
1400 2 : ~variant() = default;
1401 :
1402 : template<typename _Tp,
1403 : typename = enable_if_t<sizeof...(_Types) != 0>,
1404 : typename = enable_if_t<__not_in_place_tag<_Tp>>,
1405 : typename _Tj = __accepted_type<_Tp&&>,
1406 : typename = enable_if_t<__exactly_once<_Tj>
1407 : && is_constructible_v<_Tj, _Tp>>>
1408 : constexpr
1409 : variant(_Tp&& __t)
1410 : noexcept(is_nothrow_constructible_v<_Tj, _Tp>)
1411 : : variant(in_place_index<__accepted_index<_Tp>>,
1412 : std::forward<_Tp>(__t))
1413 : { }
1414 :
1415 : template<typename _Tp, typename... _Args,
1416 : typename = enable_if_t<__exactly_once<_Tp>
1417 : && is_constructible_v<_Tp, _Args...>>>
1418 : constexpr explicit
1419 : variant(in_place_type_t<_Tp>, _Args&&... __args)
1420 : : variant(in_place_index<__index_of<_Tp>>,
1421 : std::forward<_Args>(__args)...)
1422 : { }
1423 :
1424 : template<typename _Tp, typename _Up, typename... _Args,
1425 : typename = enable_if_t<__exactly_once<_Tp>
1426 : && is_constructible_v<_Tp,
1427 : initializer_list<_Up>&, _Args...>>>
1428 : constexpr explicit
1429 : variant(in_place_type_t<_Tp>, initializer_list<_Up> __il,
1430 : _Args&&... __args)
1431 : : variant(in_place_index<__index_of<_Tp>>, __il,
1432 : std::forward<_Args>(__args)...)
1433 : { }
1434 :
1435 : template<size_t _Np, typename... _Args,
1436 : typename _Tp = __to_type<_Np>,
1437 : typename = enable_if_t<is_constructible_v<_Tp, _Args...>>>
1438 : constexpr explicit
1439 : variant(in_place_index_t<_Np>, _Args&&... __args)
1440 : : _Base(in_place_index<_Np>, std::forward<_Args>(__args)...),
1441 : _Default_ctor_enabler(_Enable_default_constructor_tag{})
1442 : { }
1443 :
1444 : template<size_t _Np, typename _Up, typename... _Args,
1445 : typename _Tp = __to_type<_Np>,
1446 : typename = enable_if_t<is_constructible_v<_Tp,
1447 : initializer_list<_Up>&,
1448 : _Args...>>>
1449 : constexpr explicit
1450 : variant(in_place_index_t<_Np>, initializer_list<_Up> __il,
1451 : _Args&&... __args)
1452 : : _Base(in_place_index<_Np>, __il, std::forward<_Args>(__args)...),
1453 : _Default_ctor_enabler(_Enable_default_constructor_tag{})
1454 : { }
1455 :
1456 : template<typename _Tp>
1457 : enable_if_t<__exactly_once<__accepted_type<_Tp&&>>
1458 : && is_constructible_v<__accepted_type<_Tp&&>, _Tp>
1459 : && is_assignable_v<__accepted_type<_Tp&&>&, _Tp>,
1460 : variant&>
1461 14 : operator=(_Tp&& __rhs)
1462 : noexcept(is_nothrow_assignable_v<__accepted_type<_Tp&&>&, _Tp>
1463 : && is_nothrow_constructible_v<__accepted_type<_Tp&&>, _Tp>)
1464 : {
1465 14 : constexpr auto __index = __accepted_index<_Tp>;
1466 14 : if (index() == __index)
1467 0 : std::get<__index>(*this) = std::forward<_Tp>(__rhs);
1468 : else
1469 : {
1470 : using _Tj = __accepted_type<_Tp&&>;
1471 : if constexpr (is_nothrow_constructible_v<_Tj, _Tp>
1472 : || !is_nothrow_move_constructible_v<_Tj>)
1473 14 : this->emplace<__index>(std::forward<_Tp>(__rhs));
1474 : else
1475 : // _GLIBCXX_RESOLVE_LIB_DEFECTS
1476 : // 3585. converting assignment with immovable alternative
1477 : this->emplace<__index>(_Tj(std::forward<_Tp>(__rhs)));
1478 : }
1479 14 : return *this;
1480 : }
1481 :
1482 : template<typename _Tp, typename... _Args>
1483 : enable_if_t<is_constructible_v<_Tp, _Args...> && __exactly_once<_Tp>,
1484 : _Tp&>
1485 : emplace(_Args&&... __args)
1486 : {
1487 : constexpr size_t __index = __index_of<_Tp>;
1488 : return this->emplace<__index>(std::forward<_Args>(__args)...);
1489 : }
1490 :
1491 : template<typename _Tp, typename _Up, typename... _Args>
1492 : enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>
1493 : && __exactly_once<_Tp>,
1494 : _Tp&>
1495 : emplace(initializer_list<_Up> __il, _Args&&... __args)
1496 : {
1497 : constexpr size_t __index = __index_of<_Tp>;
1498 : return this->emplace<__index>(__il, std::forward<_Args>(__args)...);
1499 : }
1500 :
1501 : template<size_t _Np, typename... _Args>
1502 : enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1503 : _Args...>,
1504 : variant_alternative_t<_Np, variant>&>
1505 14 : emplace(_Args&&... __args)
1506 : {
1507 : static_assert(_Np < sizeof...(_Types),
1508 : "The index must be in [0, number of alternatives)");
1509 : using type = variant_alternative_t<_Np, variant>;
1510 : namespace __variant = std::__detail::__variant;
1511 : // Provide the strong exception-safety guarantee when possible,
1512 : // to avoid becoming valueless.
1513 : if constexpr (is_nothrow_constructible_v<type, _Args...>)
1514 : {
1515 14 : this->_M_reset();
1516 14 : __variant::__construct_by_index<_Np>(*this,
1517 : std::forward<_Args>(__args)...);
1518 : }
1519 : else if constexpr (is_scalar_v<type>)
1520 : {
1521 : // This might invoke a potentially-throwing conversion operator:
1522 : const type __tmp(std::forward<_Args>(__args)...);
1523 : // But these steps won't throw:
1524 : this->_M_reset();
1525 : __variant::__construct_by_index<_Np>(*this, __tmp);
1526 : }
1527 : else if constexpr (__variant::_Never_valueless_alt<type>()
1528 : && _Traits::_S_move_assign)
1529 : {
1530 : // This construction might throw:
1531 : variant __tmp(in_place_index<_Np>,
1532 : std::forward<_Args>(__args)...);
1533 : // But _Never_valueless_alt<type> means this won't:
1534 : *this = std::move(__tmp);
1535 : }
1536 : else
1537 : {
1538 : // This case only provides the basic exception-safety guarantee,
1539 : // i.e. the variant can become valueless.
1540 : this->_M_reset();
1541 : __variant::__construct_by_index<_Np>(*this,
1542 : std::forward<_Args>(__args)...);
1543 : }
1544 14 : return std::get<_Np>(*this);
1545 : }
1546 :
1547 : template<size_t _Np, typename _Up, typename... _Args>
1548 : enable_if_t<is_constructible_v<variant_alternative_t<_Np, variant>,
1549 : initializer_list<_Up>&, _Args...>,
1550 : variant_alternative_t<_Np, variant>&>
1551 : emplace(initializer_list<_Up> __il, _Args&&... __args)
1552 : {
1553 : static_assert(_Np < sizeof...(_Types),
1554 : "The index must be in [0, number of alternatives)");
1555 : using type = variant_alternative_t<_Np, variant>;
1556 : namespace __variant = std::__detail::__variant;
1557 : // Provide the strong exception-safety guarantee when possible,
1558 : // to avoid becoming valueless.
1559 : if constexpr (is_nothrow_constructible_v<type,
1560 : initializer_list<_Up>&,
1561 : _Args...>)
1562 : {
1563 : this->_M_reset();
1564 : __variant::__construct_by_index<_Np>(*this, __il,
1565 : std::forward<_Args>(__args)...);
1566 : }
1567 : else if constexpr (__variant::_Never_valueless_alt<type>()
1568 : && _Traits::_S_move_assign)
1569 : {
1570 : // This construction might throw:
1571 : variant __tmp(in_place_index<_Np>, __il,
1572 : std::forward<_Args>(__args)...);
1573 : // But _Never_valueless_alt<type> means this won't:
1574 : *this = std::move(__tmp);
1575 : }
1576 : else
1577 : {
1578 : // This case only provides the basic exception-safety guarantee,
1579 : // i.e. the variant can become valueless.
1580 : this->_M_reset();
1581 : __variant::__construct_by_index<_Np>(*this, __il,
1582 : std::forward<_Args>(__args)...);
1583 : }
1584 : return std::get<_Np>(*this);
1585 : }
1586 :
1587 0 : constexpr bool valueless_by_exception() const noexcept
1588 0 : { return !this->_M_valid(); }
1589 :
1590 98 : constexpr size_t index() const noexcept
1591 : {
1592 : using __index_type = typename _Base::__index_type;
1593 : if constexpr (__detail::__variant::__never_valueless<_Types...>())
1594 91 : return this->_M_index;
1595 : else if constexpr (sizeof...(_Types) <= __index_type(-1) / 2)
1596 7 : return make_signed_t<__index_type>(this->_M_index);
1597 : else
1598 : return size_t(__index_type(this->_M_index + 1)) - 1;
1599 : }
1600 :
1601 : void
1602 : swap(variant& __rhs)
1603 : noexcept((__is_nothrow_swappable<_Types>::value && ...)
1604 : && is_nothrow_move_constructible_v<variant>)
1605 : {
1606 : __detail::__variant::__raw_idx_visit(
1607 : [this, &__rhs](auto&& __rhs_mem, auto __rhs_index) mutable
1608 : {
1609 : if constexpr (__rhs_index != variant_npos)
1610 : {
1611 : if (this->index() == __rhs_index)
1612 : {
1613 : auto& __this_mem =
1614 : std::get<__rhs_index>(*this);
1615 : using std::swap;
1616 : swap(__this_mem, __rhs_mem);
1617 : }
1618 : else
1619 : {
1620 : if (!this->valueless_by_exception()) [[__likely__]]
1621 : {
1622 : auto __tmp(std::move(__rhs_mem));
1623 : __rhs = std::move(*this);
1624 : this->_M_destructive_move(__rhs_index,
1625 : std::move(__tmp));
1626 : }
1627 : else
1628 : {
1629 : this->_M_destructive_move(__rhs_index,
1630 : std::move(__rhs_mem));
1631 : __rhs._M_reset();
1632 : }
1633 : }
1634 : }
1635 : else
1636 : {
1637 : if (!this->valueless_by_exception()) [[__likely__]]
1638 : {
1639 : __rhs = std::move(*this);
1640 : this->_M_reset();
1641 : }
1642 : }
1643 : }, __rhs);
1644 : }
1645 :
1646 : private:
1647 :
1648 : #if defined(__clang__) && __clang_major__ <= 7
1649 : public:
1650 : using _Base::_M_u; // See https://bugs.llvm.org/show_bug.cgi?id=31852
1651 : private:
1652 : #endif
1653 :
1654 : template<size_t _Np, typename _Vp>
1655 : friend constexpr decltype(auto)
1656 : __detail::__variant::__get(_Vp&& __v) noexcept;
1657 :
1658 : #define _VARIANT_RELATION_FUNCTION_TEMPLATE(__OP) \
1659 : template<typename... _Tp> \
1660 : friend constexpr bool \
1661 : operator __OP(const variant<_Tp...>& __lhs, \
1662 : const variant<_Tp...>& __rhs);
1663 :
1664 : _VARIANT_RELATION_FUNCTION_TEMPLATE(<)
1665 : _VARIANT_RELATION_FUNCTION_TEMPLATE(<=)
1666 : _VARIANT_RELATION_FUNCTION_TEMPLATE(==)
1667 : _VARIANT_RELATION_FUNCTION_TEMPLATE(!=)
1668 : _VARIANT_RELATION_FUNCTION_TEMPLATE(>=)
1669 : _VARIANT_RELATION_FUNCTION_TEMPLATE(>)
1670 :
1671 : #undef _VARIANT_RELATION_FUNCTION_TEMPLATE
1672 : };
1673 :
1674 : template<size_t _Np, typename... _Types>
1675 : constexpr variant_alternative_t<_Np, variant<_Types...>>&
1676 27 : get(variant<_Types...>& __v)
1677 : {
1678 : static_assert(_Np < sizeof...(_Types),
1679 : "The index must be in [0, number of alternatives)");
1680 27 : if (__v.index() != _Np)
1681 0 : __throw_bad_variant_access(__v.valueless_by_exception());
1682 27 : return __detail::__variant::__get<_Np>(__v);
1683 : }
1684 :
1685 : template<size_t _Np, typename... _Types>
1686 : constexpr variant_alternative_t<_Np, variant<_Types...>>&&
1687 : get(variant<_Types...>&& __v)
1688 : {
1689 : static_assert(_Np < sizeof...(_Types),
1690 : "The index must be in [0, number of alternatives)");
1691 : if (__v.index() != _Np)
1692 : __throw_bad_variant_access(__v.valueless_by_exception());
1693 : return __detail::__variant::__get<_Np>(std::move(__v));
1694 : }
1695 :
1696 : template<size_t _Np, typename... _Types>
1697 : constexpr const variant_alternative_t<_Np, variant<_Types...>>&
1698 : get(const variant<_Types...>& __v)
1699 : {
1700 : static_assert(_Np < sizeof...(_Types),
1701 : "The index must be in [0, number of alternatives)");
1702 : if (__v.index() != _Np)
1703 : __throw_bad_variant_access(__v.valueless_by_exception());
1704 : return __detail::__variant::__get<_Np>(__v);
1705 : }
1706 :
1707 : template<size_t _Np, typename... _Types>
1708 : constexpr const variant_alternative_t<_Np, variant<_Types...>>&&
1709 : get(const variant<_Types...>&& __v)
1710 : {
1711 : static_assert(_Np < sizeof...(_Types),
1712 : "The index must be in [0, number of alternatives)");
1713 : if (__v.index() != _Np)
1714 : __throw_bad_variant_access(__v.valueless_by_exception());
1715 : return __detail::__variant::__get<_Np>(std::move(__v));
1716 : }
1717 :
1718 : /// @cond undocumented
1719 : template<typename _Result_type, typename _Visitor, typename... _Variants>
1720 : constexpr decltype(auto)
1721 4 : __do_visit(_Visitor&& __visitor, _Variants&&... __variants)
1722 : {
1723 4 : constexpr auto& __vtable = __detail::__variant::__gen_vtable<
1724 : _Result_type, _Visitor&&, _Variants&&...>::_S_vtable;
1725 :
1726 4 : auto __func_ptr = __vtable._M_access(__variants.index()...);
1727 4 : return (*__func_ptr)(std::forward<_Visitor>(__visitor),
1728 4 : std::forward<_Variants>(__variants)...);
1729 : }
1730 : /// @endcond
1731 :
1732 : template<typename _Visitor, typename... _Variants>
1733 : constexpr __detail::__variant::__visit_result_t<_Visitor, _Variants...>
1734 : visit(_Visitor&& __visitor, _Variants&&... __variants)
1735 : {
1736 : namespace __variant = std::__detail::__variant;
1737 :
1738 : if ((__variant::__as(__variants).valueless_by_exception() || ...))
1739 : __throw_bad_variant_access("std::visit: variant is valueless");
1740 :
1741 : using _Result_type
1742 : = __detail::__variant::__visit_result_t<_Visitor, _Variants...>;
1743 :
1744 : using _Tag = __detail::__variant::__deduce_visit_result<_Result_type>;
1745 :
1746 : if constexpr (sizeof...(_Variants) == 1)
1747 : {
1748 : using _Vp = decltype(__variant::__as(std::declval<_Variants>()...));
1749 :
1750 : constexpr bool __visit_rettypes_match = __detail::__variant::
1751 : __check_visitor_results<_Visitor, _Vp>(
1752 : make_index_sequence<variant_size_v<remove_reference_t<_Vp>>>());
1753 : if constexpr (!__visit_rettypes_match)
1754 : {
1755 : static_assert(__visit_rettypes_match,
1756 : "std::visit requires the visitor to have the same "
1757 : "return type for all alternatives of a variant");
1758 : return;
1759 : }
1760 : else
1761 : return std::__do_visit<_Tag>(
1762 : std::forward<_Visitor>(__visitor),
1763 : static_cast<_Vp>(__variants)...);
1764 : }
1765 : else
1766 : return std::__do_visit<_Tag>(
1767 : std::forward<_Visitor>(__visitor),
1768 : __variant::__as(std::forward<_Variants>(__variants))...);
1769 : }
1770 :
1771 : #if __cplusplus > 201703L
1772 : template<typename _Res, typename _Visitor, typename... _Variants>
1773 : constexpr _Res
1774 : visit(_Visitor&& __visitor, _Variants&&... __variants)
1775 : {
1776 : namespace __variant = std::__detail::__variant;
1777 :
1778 : if ((__variant::__as(__variants).valueless_by_exception() || ...))
1779 : __throw_bad_variant_access("std::visit<R>: variant is valueless");
1780 :
1781 : return std::__do_visit<_Res>(std::forward<_Visitor>(__visitor),
1782 : __variant::__as(std::forward<_Variants>(__variants))...);
1783 : }
1784 : #endif
1785 :
1786 : /// @cond undocumented
1787 : template<bool, typename... _Types>
1788 : struct __variant_hash_call_base_impl
1789 : {
1790 : size_t
1791 : operator()(const variant<_Types...>& __t) const
1792 : noexcept((is_nothrow_invocable_v<hash<decay_t<_Types>>, _Types> && ...))
1793 : {
1794 : size_t __ret;
1795 : __detail::__variant::__raw_visit(
1796 : [&__t, &__ret](auto&& __t_mem) mutable
1797 : {
1798 : using _Type = __remove_cvref_t<decltype(__t_mem)>;
1799 : if constexpr (!is_same_v<_Type,
1800 : __detail::__variant::__variant_cookie>)
1801 : __ret = std::hash<size_t>{}(__t.index())
1802 : + std::hash<_Type>{}(__t_mem);
1803 : else
1804 : __ret = std::hash<size_t>{}(__t.index());
1805 : }, __t);
1806 : return __ret;
1807 : }
1808 : };
1809 :
1810 : template<typename... _Types>
1811 : struct __variant_hash_call_base_impl<false, _Types...> {};
1812 :
1813 : template<typename... _Types>
1814 : using __variant_hash_call_base =
1815 : __variant_hash_call_base_impl<(__poison_hash<remove_const_t<_Types>>::
1816 : __enable_hash_call &&...), _Types...>;
1817 : /// @endcond
1818 :
1819 : template<typename... _Types>
1820 : struct hash<variant<_Types...>>
1821 : : private __detail::__variant::_Variant_hash_base<
1822 : variant<_Types...>, std::index_sequence_for<_Types...>>,
1823 : public __variant_hash_call_base<_Types...>
1824 : {
1825 : using result_type [[__deprecated__]] = size_t;
1826 : using argument_type [[__deprecated__]] = variant<_Types...>;
1827 : };
1828 :
1829 : template<>
1830 : struct hash<monostate>
1831 : {
1832 : using result_type [[__deprecated__]] = size_t;
1833 : using argument_type [[__deprecated__]] = monostate;
1834 :
1835 : size_t
1836 : operator()(const monostate&) const noexcept
1837 : {
1838 : constexpr size_t __magic_monostate_hash = -7777;
1839 : return __magic_monostate_hash;
1840 : }
1841 : };
1842 :
1843 : template<typename... _Types>
1844 : struct __is_fast_hash<hash<variant<_Types...>>>
1845 : : bool_constant<(__is_fast_hash<_Types>::value && ...)>
1846 : { };
1847 :
1848 : _GLIBCXX_END_NAMESPACE_VERSION
1849 : } // namespace std
1850 :
1851 : #endif // C++17
1852 :
1853 : #endif // _GLIBCXX_VARIANT
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